US2797074A - Operating controls for print-drying apparatus - Google Patents

Description

June 25, 1957 J. H. FLYNN 2,797,074 OPERATING CONTROLS FOR PRINT-DRYING APPARATUS Filed April 28. 1955 s Sheets-Shet- 2 Livea June 25, 195.7 J. H. FLYNN 2,797,074

OPERATING CONTROLS FOR PRINT-DRYING APPARATUS Filed April 28, 195s s Sheets-Sheet s INVENTOR. Jo/J/YHFZ 27 J. H. FLYNN June 25; 1957 OPERATING CONTROLS FOR PRINT-DRYING APPARATUS Filed April 28, 1955 6 Sheets-Sheet 4 June- 25, 1957 J. FLYNN OPERATING CONTROLS FOR PRINT-DRYING APPARATUS Filed April 28, 1955 6 Sheets-Sheet 5 INVENTOR. 0/2/7165 F2 22 .7

' Hirer/761 June 25, 1957 J. H. FLYNN 2,797,074

OPERATING CONTROLS FOR Pam-DRYING APPARATUS Filed April 2E3, 1955 s SheetS Sheet s INVENTOR.

United States Patent OPERATING CONTROLS FOR PRINT-DRYING APPARATUS John H. Flynn, New Rochelle, N. Y; Application April 28, 1955, Serial No. 504,453

21 Claims. (Cl. 2633) the latter passes through a restricted drying zone at the same high speed at which it travels through a modern printing press and at which a readily perceptible air layer clings to and travels with the web. Thus, a perceptible air layer will cling to a web traveling at even moderate speed, say in the neighborhood of 400 feet per minute, and this air layer will not only increase in height and density, but also cling ever more tenaciously to the web, as the web speed increases and approaches present-day maximum web speeds in the neighborhood of 2000 feet per minute achieved in recently developed printing presses. In accordance with my aforementioned method, a printed web is, on its emergence from a printing press and While traveling at the same high speed as through the latter,

directed past a sheet of flame of such high velocity and heat intensity that the same will drive through the clinging air layer on the web and actually contact the printed face thereof and drive the volatiles from the printed ink and into the immediately reforming air layer on the web in which a part of the volatiles will burn off and the remainder become entrapped. Shortly after the subjection of the traveling web to the flame, the air layer clinging to the printed face thereof is with the remaining entrapped volatiles therein separated or lifted from the web by any suitable means, such as a driving air jet or knife directed against the printed web face generally counter to the web travel.

Another copending application of mine, Serial No. 504,452, filed April 28, 1955, discloses apparatus in which printed ink on a traveling web' may be dried efiiciently and reliably in accordance with my aforementioned method. This drying apparatus includes among its operating devices not only the aforementioned gas burner and an air manifold that provides the aforementioned air knife, but also an ignition electrode for the burner and valves for controlling the flow of a combustible mixture and air to the burner and manifold, respectively.

It is the primary aim and object of the present invention to provide for the aforementioned operating devices of my drying apparatus operating controls which not only render the apparatus entirely safe in operation, especially from the potential dangers springing from leaking gas or accumulated burner gas in the apparatus, but also protect a printed web passing through the apparatus from being scorched or burned by the flame from the burner.

It is another object of the present invention to arrange the aforementioned operating controls so that they are automatic in action, and more especially self-responsive in action to predetermined safety and danger signal conditions, thereby to eliminate in their performance all possible human error and obtain maximum assurance of safe operation of the drying apparatus.

It is a further object of the present invention to arrange the aforementioned operating controls so that they will, for a start of an operating run of the drying apparatus, perform automatically in successive order in cyclic fashion as rapidly as the various prescribed safety conditions for their performance are met by the apparatus, yet each of these controls will, at the start or during an operating run of the apparatus, individually detect immediately the particular danger signal condition to which it is also to respond, and act to prevent this danger signal condition from ever developing into a truly dangerous condition, thereby not only obtaining a full start of an operating run of the apparatus in the shortest possible time consistent with safe operation of the latter, but also achieving immediate detection of and safe control over any danger signal condition by the respective operating control at the start or during an operating run of the apparatus.

Another object of the present invention is to provide for my aforementioned drying apparatus operating controls which permit ignition of the burner flame by sparks from an ignition electrode only after an exhaust fan has purged the apparatus for a predetermined length of time and while it continues to purge it of any possible dangerous accumulation of combustible gas therein, and even then only after a printed web from an associated printing press has been extended through the apparatus and has reached a safe speed, preferably its normal running speed through the press, at which it will be neither scorched nor burned by the burner flame.

It is a further object of the present invention to provide trols which, despite the aforementioned continued purge by the exhaust fan of the apparatus and the attainment of a safe web speed therein, will prevent operation of the ignition electrode unless an air compressor is in operation and puts out compressed air adapted for the air knife from the manifold and also to draw non-compressed gas from a Zero-pressure governor and mix therewith in a flow mixer to form a combustible air-gas mixture for the burner, thereby to eliminate ignition failure due to inoperation of the compressor as one possible source.

Another object of the present invention is to provide for my aforementioned drying apparatus operating controls which cause operation of the ignition electrode and simultaneous opening of a normally spring-closed valve for trode and thereby terminate its spark production, but

will also simultaneously permit spring-closure of the afore mentioned gas valve, if during a predetermined safety period, from the time the electrode becomes operative or should become operative and the gas valve opens or should open, ignition failure should prevail from any cause whatever, such as breakdown or malfunction of the electrode itself or its circuit, or lack of a combustible mixture at the burner due to lack of gas at the very source 7 or failure of the gas valve to open at all or at the proper time, or due to a defective conduit orlconduits for the gas and air media, for instance, thereby to prevent under any circumstances the creation of a potentially dangerous condition in the apparatus from undue accumulation of non-ignited burner gas therein despite continued operation of the exhaust fan, or prolonged ineffective spark production by the electrode in case no combustible mixture, or only an amount thereof inadequate for ignition, should reach the burner within the time period allotted for ignition.

It is another object of the present invention to provide for my aforementioned drying apparatus operating controls which are adjustable to vary within predetermined limits the duration of the aforementioned safety period during which the ignition electrode produces sparks, or should produce sparks, before the electrode is deenergized and the gas valve permitted to close in case of ignition failure from any cause whatever, thereby to permit variation of the time necessary for starting the apparatus into full operation at maximum rapidity despite regulatable variations in the volumetric flow rate of the combustible mixture to the burner for different required operating conditions of the apparatus.

It is a further object of the present invention to provide for my aforementioned drying apparatus operating controls which will deenergize the ignition electrode and terminate spark production by the latter immediately on detection of the ignited burner flame by a flame rod, thereby to require the electrode to produce sparks for no longer period than is absolutely necessary.

Another object of the present invention is to provide for my aforementioned drying apparatus operating controls which on ignition failure throughout the aforementioned safety period or on extinction or bad fluttering of the ignited burner flame from any cause whatever during operation of the apparatus, and for automatic closure of the aforementioned gas valve in either of these events, will open a switch which, for reclosure of the circuit of th ignition electrode and re-opening of the gas valve for re-ignition of the burner flame, must be manually reclosed, but cannot be re-closed until a predetermined time interval has elapsed during which the aforementioned ex-.

haust fan has thoroughly purged the apparatus of all possible combustible matter, thereby not only giving immediate notice to attending personnel that something is wrong with the burner operation and personal attention is required for restarting the same, but also preventing a restart of the burner operation until the apparatus is entirely safe from any danger of explosion.

It is another object of the present invention to provide for my aforementioned drying apparatus operating controls which, on breakage or undue slackening of a printed web or slow-down of the same below the aforementioned safe speed on its course through the apparatus, or on failure of the aforementioned compressor to deliver compressed air at any time during operation of the apparatus, will also permit spring-closure of the aforementioned gas valve, but will not cause opening of the aforementioned switch, thereby to recondition the operating controls for their immediate normal cyclic performance to bring about restoration of the operation of the apparatus as soon as the condition responsible for the valve closure has'been rectified.

It is a further object of the present invention to provide 7 for my. aforementioned drying apparatus operating controls which, on breakdown or malfunction of the afore mentioned exhaust fan at any time during a start of an operation or during normal operation of the apparatus,

In the accompanying drawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

Fig. 1 is a longitudinal section through print-drying apparatus having operating controls which embody the present invention;

Fig. 2 is a cross-section through the apparatus, taken substantially on the line 22 of Fig. 1;

Fig. 3 is a top plan view of the conduit arrangement and some operating controls of the apparatus;

Fig. 4 is a fragmentary side elevation of the apparatus with its conduit arrangement and some of its operating controls, as viewed in the direction of the arrow 4 in Fig. 3; and

Figs. 5 to 10, inclusive, are wiring diagrams of the electrically actuated operating controls of the apparatus under different operating conditions.

Referring to the drawings, and more particularly to Figs. 1 and 2 thereof, the reference numeral 20 designates print-drying apparatus comprising a housing 22 having end walls 24, side walls 26, a bottom wall 28 and a top wall 30. The walls of the housing 22 may be made of any suitable heat-resistant sheet material, and the housing is on the outside preferably provided with a sheet metal lining 32. The housing 22 may be supported at its bottom on suitable rails 23 which, in turn, may be mounted on upright frames 25 and 27 (Figs. 1 to 4).

The end walls 24 of the housing 22 are substantially throughout their widths provided with lead-in and lead-out apertures 34 and 36, respectively, which define in the housing a longitudinal through-passage 38 for a printed web w or the like. The housing 22 is also provided with a transverse partition 40 which extends substantially to the web passage 38 therein and defines in the housing a front chamber 42 and a rear chamber 44. Suitably mounted in the front chamber 42 is a high-capacity burner 46 which extends throughout the width of the housing 22 and has ports 48 arranged to direct a flame F of high velocity and heat intensity against the adjacent printed face 1 of a guided web w in the passage 38. Suitably mounted at 47 on the burner 46 is a holder 49 for an ignition electrode 51 which on energization produces sparks for the ignition of a combustible mixture at the burner. Also suitably mounted on the burner, as at 53, is a holder 55 for a flame rod 57 the function of which will be described hereinafter.

The housing 22 is further provided with a transverse baffle 50 which slants from above the burner 46 to the lower end of the partition 40 and defines in the front chamber 42 a trapless duct 52 leading to the rear chamber .44 for the escape thereinto of the hot gases and combusdirection of the arrow 58 (Fig. l), i. e. counter to the will'shut off all power from the latter, thereby to require complete recycling of. the controls as in a normal start of the operation of the apparatus, including initial purging of the latter prior to ignition of the burner flame, when normal operation of the exhaust fan has been restored.

Other objects and advantages will appear to those skilled in the art from the followi g, considered in conjunction with the accompanying drawings.

feeding direction of the web w in the passage 38, in order to cool the web.

Suitably mounted in the rear chamber .44 and extending substantially throughout the width of the latter is an air manifold 60 having an outlet port 62 arranged for the discharge of compressed air in a sheet or knife K inclined to the guided web w in the passage 38 and forming therewith an acute angle pointing toward the front chamber 42. In accordance with my aforementioned inkdrying method, the air knife K is adapted to lift from the web w an air layer and entrapped ink volatiles therein which at the elected feeding speed of the web will cling to the latter.

The rear chamber 44 is at the top and next to the end wall 24 of the housing 22 provided with an exhaust port 66 which through a conduit 68 is in communication with an exhaust fan 70. In order to achieve least impeded aficionxhaust through the port 66 of the hot gases and combus- Itin products from the duct 52, of the counter-flowing cooling air from the duct 56, and of the air knife K from the manifold 60 and air layer lifted thereby from the traveling web w, the baflie 54 in the housing 22 is continued in the offset fashion indicated at 72 to a point above the manifold 60 so as to form a restricted passage 74 to an exhaust chamber 76 which is in direct communication with the exhaust fan 70 through the port 66 and conduit 68, and the housing 22 is further provided. with another transverse baffle 78 which is spaced from the paritition 40 and forms therewith a duct 80 extending from close proximity with the guided web w in the passage 38 toward the restricted exhaust passage 74. The baflle 78 effectively separates the hot gases and combustion products drawn from the duct 52 through the duct 80 from the counter-flowing cooling air and from the air knife and air layer lifted thereby from the traveling web, in the very region in which they would clash head-on and impede their exhaust, and instead leads them in substantially parallel path to compel them to flow beyond this baflle as nearly as possible uni-directionally toward and into the restricted exhaust passage 74. On the other hand, the extension of the duct 56 over the manifold 60 in the offset fashion indicated at 72 serves to prevent any appreciable clash between the counter-flowing cooling air therein and the air knife and air layer lifted thereby from the traveling web, and instead compels them into substantially parallel paths toward and into the restricted exhaust passage 74. To regulate the draft in the duct 80, there is provided a damper 82 which is turnable from the outside of the housing 22. A similar damper 84 may be turned from the outside of the housing 22 for regulation of the draft in the exhaust passage 74. The housing 22 of the apparatus is at least on one side preferably provided with hinged doors 75 (Fig. 4) which may be opened for access to the interior of the apparatus for any purpose whatever.

The exhaust conduit 68 is in communication with the intake 86 of the fan housing 88 in which the fan 70 operates. The fan housing 88, which is provided with an outlet 90, is at its front wall 92 suitably supported on spaced side walls 94 of an upright frame 96 having a base plate 98 mounted at 100 on the top wall 30 of the housing 22 of the apparatus. The fan shaft 102. may suitably be journaled in bearings 104 and 106 on the front wall 92 of the fan housing 88 and on a platform 108 thereon, respectively. The forward end of the fan shaft 102 carries a pulley 110 which through a belt 112 is drivingly connected with a pulley 114 on the shaft 116 of a motor 118 on the base plate 98 of the frame 96.

The apparatus described so far is essentially like that more fully shown and described in my aforementioned copending application Serial No. 504,452, filed April 28, 1955. The present apparatus has also provisions for 4 supplying the burner 46 with a combustible gas-air mixture and the manifold 66 with compressed air. To this end, there is provided an air compressor 120 (Figs. 3 and 4) which through a conduit 122 and T fitting 124 is connected with branch conduits 126 and 128 that are in communication with the burner 46 and manifold 60, respectively. To the same end, there is further provided a conduit 130 which leads from a suitable source of compressed gas to a Venturi-type gas-air mixer 132 interposed in the air branch conduit 126. Successively interposed in the gas conduit 130 are, in this instance, a manual shutoff valve 133, an electric diaphragm valve 134, a gas pressure governor 136 and a solenoid valve 138. The diaphragm valve 134 is of a well-known type, having a diaphragm chamber (not shown) and a relay [to be described, of which the former is subjected to the compressed gas in the line 130 to close the valve when the relay is deenergized, and is shut off from the compressed gas and vented to the atmosphere to cause opening of the valve when the relay is energized. The gas pressure governor 136 is of conventional construction, being regu- 6 latable to let gas escape therefrom at substantially zero pressure. The solenoid valve 138 is a conventional spring-actuated quick-closure valve which is opened on energization of a relay to be described.

When the compressor is operating, the same will put out compressed air which will flow through the conduit 122 and thence through the branch conduits 126 and 128 to the burner 46 and air manifold 60, respectively. Assuming that the diaphragm and solenoid valves 134 and 138 are open, the compressed air flowing through the gasair mixer 132 will by typical Venturi action draw zeropressure gas from the governor 136 and mix therewith to form a combustible gas-air mixture which may be ignited into the flame F by sparks from the ignition electrode 51 as it emerges from the burner 46.

The velocity and heat intensity of the burner flame F may be regulated for any particular print-drying operation by manipulating a gas ratio valve 139 in the gas conduit (Fig. 4) and a manual valve 140 in the air branch conduit 126 to the burner. Similarly, the velocity and expanse of the air knife K may be regulated by manipulating a manual valve 142 in the air branch conduit 128 to the manifold 60.

The web w is, in the present instance (Fig. 4), guided over rolls 146 and between successive pairs of powerdriven printing and back-up rolls 148, 150 in the previously described frame 25, thence over guide rolls 152 and 154 which direct the web in a predetermined path through the passage 38 in the drying apparatus 20, and finally over another guide roll 156 and between power-driven rolls 158 which-under suitable control feed the Web w forward at such a rate that the latter is kept uniformly taut on its run through the drying apparatus. The guide rolls 152 and 154 may conveniently be journaled in the frame 25 and the support rails 23, respectively, while the remaining guide roll 156 may suitably be journaled in the previously described frame 27. The printing rolls 148 apply the printing to be dried to the adjacent face f of the web w, and these printing rolls are supplied with printing ink from conventional ink rollers 160. The web w is within the confines of the passage 38 in the drying apparatus preferably further guided over a roller 162 so as not to be torn or caused to flutter under the impact of the air knife K. The roller 162 may be journaled in in accordance with my aforementioned ink-drying meth-' od, the printed web travels in its guided path through the passage 38 at the same speed at which it travels between the printing and back-up rolls 148, 150. At this travel speed of the web w a readily perceptible air layer will cling to the latter, as previously explained, and the flame F from the burner 46 must have sufiicient velocity or drive to cut through this air layer and actually contact the printed web face 1 in order to be at all effective in driving the volatiles from theprinted ink primarily into the quickly reforming air layer on the web. The air knife K subsequently lifts the clinging air layer and therein entrapped residue of the driven-off volatiles from the traveling web w, the exhaust fan 70 all the while drawing from the apparatus the hot gases'and combustion products from the front chamber 42 and the air from the knife K and air layer lifted thereby from the web, and also inducing a flow of atmospheric air through the duct 56 counter to the travel of the web to relieve the latter of any latent heat and expedite the final setting of the printed ink.

In view of the high velocity and high heat-intensity of the burner flame F and the requirement that the same actually contact the web w, it is obvious that highly reliable controls for the burner operation are imperative in order to prevent burning or even the slightest scorching of the web at the start of or during a normal printdrying operation of the apparatus. Equally imperative from a safety standpoint are reliable controls which, inf

the burner from any cause whateverorextinction ofthe burner flame at any time, will assuredly prevent any dangerous accumulation of the highly combustible gas-air mixture in the apparatus. In order that these specific, as well as other, potentially dangerous conditions may never arise, the following controls are provided which have cyclic relationship with each other as described hereinafter.

- Thus, in order that the ignition electrode 51 may be at all energized for spark production to start a printdrying operation, it is imperative that sub-atmospheric pressure prevailsin the'exhaust conduit 68, meaning that the fan 70 must operate to purge the housing 22 of all intended matter. This is accomplished by a vacuumtype switch 170 which, in the present instance, is associted with the fan housing- 88 (Fig. 1) Before permitting energization of the ignition electrode 51, it is further imperative that the printed Web w not'only extends in itsguided path through the passage 38 in the apparatus so, as to be within operating reach of the subsequently issuingburner flame, but also travels at a safe speed at which it will be neither burned nor scorched by the burner flame. This is accomplished by a web switch 172 and a centrifugal switch 174 (Figs. 3 and 4). Furthermore, before permitting energization of the ignition electrode 51:, it is also imperative that the compressor 120 operates and puts out compressed air to assure the delivery of a combustible gas-air mixture to the burner 46 as soon as the gas valves 134 and 138 are opened in a manner described hereinafter. This is accomplished by a pressureresponsive switch 176 which isassociated with the air conduit 122 (Figs. 3 and 4). To carry the safety factor in starting a print-drying operation even further, energization of the ignition electrode 51 will not be permitted even if all the aforementioned conditions are met, unless the exhaust fan '70 has first purged the apparatus for a predetermined safe time period during which any possible dangerous accumulation of explosive gases therein has assuredly been removed. This is accomplished by a timer switch 178' (Fig. 5);

The aforementioned switches 170, 178, 172, 176 and 174, all of which are normally open, are closed as follows. Thus, the vacuum switch 170 (Figs. 1 and 5) is closed when the operation of the fan 70 creates'subatmospheric pressure in the fan housing 83. The timer.

switch 173. (Fig. 5) is closed after a predetermined period of operation of a timer 188 to be described. The web switch 172 (Figs 4 and 5) is closed by a web w if extending in its predetermined path in the passage 38 through the drying apparatus. The pressure switch 176 (Figs. 3 to 5) is closed by super-atmospheric pressure in the air conduit 122, and this is only possible if the air compressor 120 operates. Finally, the centrifugal switch 174 (Figs. 3 to 5) is closed when the printing and back-up rolls 148, 154ifeed the web w at normal printing speed. This is accomplished by a suitable brancholf from, the main drive of the printing and back-up rolls 148. and 150, including a gear box 182 the output shaft 184 of which carries a pulley 186 which through a belt 188. is drivingly connected with a pulley 190 on ashaft 192 of the centrifugal switch 174 (Figs, 3 and 4). Since the centrifugal switch 174 may be entirely conventional in its construction and operation, it is deemed sufficient to explain that this switch will be closed when its. shaft 192 reaches a certain speed corresponding to the normal travel speed of the web w imparted to it by the'printing and back-up rolls 148, 159. I

The switches 170, 178, 172, 176 and 174, once closed under thedescribed conditions, close a first energizing circuit for the aforementioned relays of the gas valves 134-. and 138. and for the ignition electrode 51 in order to supply the burner 46with combustible gas-air mixture and causespark production by the ignition electrode for igniting the gas-air mixture at the burner and establish the burner'flame F. This first circuit will now be de-- scribed with reference to Figs. 7 and 8, of which Fig. 8 illustrates the'spec ific part of the circuit in a panel structure indicated only in dot-and-dash lines in Fig. 7 and identified by the-reference numeral 194 therein. In order readily to trace the correct connections between the parts of the present first circuit, and also parts of other circuits to be described, in Figs. 7 and 8, respectively-, the panel structure 194 is provided with terminals 196 marked if-2, 3, 5, 6, *T," F and G.

The first circuit abovementioned, which is shown open in Figs. 5 and6 and closed in Figs. 7 and 8, includes any suitable A. C. power source from one side of which extends a lead 198 to the terminal 196 marked 6. Interposed in this lead 198 and in series connection with each other therein are a manually operative main switch 200, the described vacuum, timer, web, pressure and centrifugal switches 170, 178, 172, 176 and 174, respectively, and a manual switch 202. This first circuit is continued from terminal 6 to terminal 3 via a lead 284 (Fig. 8), and from terminal 3 via a lead 286 (Fig. 7) which at 208 continues in parallel branches 210 and 212 of which the latter continues to a return lead 214 to the other side of the power source. The branch 210 divides into further branches 216 and 218 which connect the relays 220 and 222 of the diaphragm and solenoid gas valves 134 and 138 respectively, in parallel with each other, and join at- 224 with a lead 226 that is connected with the return lead 214. interposed in the other branch 212 is the primary coil 228 of a step-up transformer 230 of which the secondary coil 232 is at one end suitably grounded at 234 and is at its other end connected by a lead 236 with the iginition electrode 51.

' It appears from Figs. 7 and 8 that the aforementioned first circuit is closed on automatic closure of the vacuum, timer, web, pressure and centrifugal switches 170, 178, 172, 176 and 174, respectively, and preceding manual closure of the-main switch 209 and switch 202, in which case the diaphragm and solenoid valves 134 and 138 will be opened and the ignition electrode 51 will produce sparks toignite the combustible gas-air mixture as soon as it emerges from the burner 46, the latter being suitably grounded at 238 to complete the energizing circuit of the ignition electrode 51. I

It has previously been explained that the aforementioned first'circuit cannot be closed unless the vacuum, timer, web, pressure and centrifugal switches 170, 178, 172, 176 and 174 are closed. The automatic closure of the vacuum, web, pressure and centrifugal switches 170, 172, 176 and 174, respectfully, under certain conditions has been explained previously, and the closure of the normally open timer switch 178 will now be explained. The normally open timer switch 178 (Fig. 5) is closed by the timer 180 which, in the present instance, comprises a synchronous motor 240, a timing element 242 driven thereby and being in the exemplary form of a gear, a follower 244 which is fioatingly pivoted in a slot 246 in a fixed support 248 and normally urged by a spring 250 into a retracted position, and a relay 252 in cooperative relation with the follower 244. When the relay 252 is deenergized, a spring 254 urges the follower 244 against a stop pin 256, in which case the latch end 258 of the follower is retracted from interlock with the teeth of the timing element 242. The relay 252, being by leads 260 and 262 connected in series with the main switch 200 and vacuum switch and in parallel with the rest of the described first circuit, will be deenergized when either of these switches is open. Hence, even if the main switch 200 should be left in closed position when the apparatus is idle, the relay 252 will be deenergized when the vacuum switch 170 is open in consequence of non-operation of the exhaust fan 70, with the result that the follower 244 is in its retracted position with its latch end 258 withdrawn from. theteeth of the timing element 242. 'However, as soon as under the aforementioned conditions the circuit of the fan motor 118 is closed by a conventional switch (not shown), the relay 252 will be energized and react with the follower 244 in bringing the latch end 258 of the latter into coupling interlock with the teeth of the timing element 242 against the tendency of the spring 254 to retract the follower end 258 from interlock with the timing element. The circuit of the timing motor 240 is closed simultaneously with the energization of the relay 252, this being due to the fact that the motor is connected in parallel with the relay 252 by means of a lead 266 which has interposed in series connection with the motor a normally closed motor switch 268 that is ganged with the timer switch. Accordingly, as soon as the relay 252 is energized and the latch end 258 of the follower 244 drawn into coupling relation with the timing element 242, the synchronous timer motor 240 will operate and turn the timing element which, in turn, will gradually depress the follower 244 until after the lapse of a predetermined time period the insulating end of the latter opens the motor switch 268 and simultaneously closes the timer switch 178 (Fig. 7). The circuit of the timer motor 240 is now open, but the relay 252 remains energized to retain the latch end 258 of the follower 244 in coupling relation with the nonbacking timing element 242 and thereby retain the follower in its depressed position in which it will hold the motor switch 268 open and the timer switch 178 closed as long as the relay 252 remains energized.

It follows from the preceding description that, for a start of a print-drying operation of the instant apparatus and before a combustible gas-air mixture will be delivered to the burner 46 and sparks will be produced by the ignition electrode 51, the web w must not only extend in its predetermined path through the apparatus but also travel at a safe predetermined speed, the air compressor 120 must be in operation, and the exhaust fan must not only be in operation but must have been in continuous operation for a predetermined time period, before the aforementioned first circuit will be closed. While this first circuit safeguards against the dangers of accumulation of combustible gas in the apparatus due to malfunction or breakdown of the exhaust fan, burning or scorching of the web by the burner flame due to deviation of the web from its guided path from any cause whatever, such as breakage or excessive fluttering of the same, for instance, or due to slow-down of the traveling web below its safe speed or stoppage of the same, and failure to supply the burner with a proper gas-air mixture and the manifold with compressed air-for the air knife due to malfunction or breakdown of the air compressor or a leak or leaks in the air conduits, this first circuit does not safeguard against the dangers of .excessive and prolonged accumulation of combustible gasair mixture in the apparatus beyond the capacity of the exhaust fan to remove it therefrom in case the iginition electrode fails to spark for any reason whatever. It is principally for this latter reason that the aforementioned first circuit is merely a starting circuit, and that a holding circuit for the valve relays 220 and 222, but not for the ignition electrode 51, is provided Which will be closed on establishment of the flame F at the burner, but which will not be closed when the starting circuit is opened, by an electric control device to be described, after a predetermined time period during which no flame is established at the burner.

The electric control device just mentioned comprises a normally open control switch 272 interposed in the lead 204 of the aforementioned starting circuit (Figs. 6, 8 and and an associated relay 274 which, on energization, closes the control switch 272. Hence, the starting circuit of .the gas valve relays 220 and 222 and of ignition electrode 51 will not be closed unless the control switch 272 is closed on energization of the relay 274. The relay 274 has a starting circuit which has for its current 10 source the output of the secondary coil 276 of a stepdown transformer 278 the primary coil 280 of which is in said first described starting circuit of the gas valve relays and ignition electrode connected in series with the main switch 280, and a vacuum, timer, web, pressure and centrifugal switches 70, 178, 172, 176 and 174, respectively, and in parallel with the rest of the circuit via a lead 282 that crosses the terminal marked 2 and joins the return lead 7214 (Figs. 7 and 8). The starting circuit of the relay 274, shown closed and in heavy lines in Figs. 7 and 8, includes the secondary transformer coil 276, a lead 284 with an interposed resistance 286, a normally closed switch 288, a lead .290 which extends across one of the terminals marked T, a normally open switch 292, a lead 294 which extends across the other terminal marked T, a warp-type switch 296, a lead 298, relay 272 and a lead 300. The normally open switch 292 (Fig. 7) is closed by a relay 302 when the latter is energized on closing the press switch (not shown) which in this instance controls the drive of the printing and back-up rolls 148, (Fig. 4).

Assuming that the printing press is running and the switch 292 is closed in consequence thereof, and assuming further that the warp switch 296 is closed, it follows from Figs. 7 and 8 that current will flow in the described starting circuit of the relay 274 immediately on current flow through the primary transformer coil 280 in the described starting circuit of the gas valve relays and ignition electrode, with the result that the relay 274 becomes energized and closes the switch 272 to carry the current in the latter circuit to the terminal marked 3 and therebeyond to the gas valve relays 220, 222 and ignition electrode 51.

Let it now be assumed that after closure of the starting circuit of the valve relays 220, 222 and ignition electrode 51 no flame will be established at the burner 46, due to malfunction of either gas valve 134 or 138 or malfunction or breakdown of the ignition electrode 51, for instance, then the switch 296 will after a predetermined safety time period warp out and open the described starting circuit of the relay 274, thereby permitting opening of the control switch 272 and, hence, causing cut-off of the gas valve relays 220, 222 and ignition electrode 51 from their current source. The delayed warp-out of the switch 296 under these conditions is achieved by the interposition in the starting circuit of the relay 274 of the described resistance 286 which accounts for a current flow in this circuit that will cause the bimetallic blade 304 of the warp switch 296 to bend and thereby disconnect from the fixed contact 306 of this switch after closure of this starting circuit for the aforementioned safety time period, say 15 seconds, for instance. When thus being bent out of engagement with the switch contact 306, the bimetallic blade 304 will cam a spring-urged plunger 308 out of the way and move to the other side of the latter to be held thereby out of engagement with the switch contact 306 even after cooling off and recovering its straight form, thus requiring for re-closure of the warp switch manual depression of a button 310 in order to force the bimetallic blade 304 past the spring-urged plunger 308 and into reengagement with the switch contact 306.

Let it now be assumed that in the normal course of events flame will be established at the burner before the lapse of the aforementioned safety time period after which the switch 296 would warp out, such flame establishment will bring about immediate closure of a holding circuit of the relay 274 and opening of the starting circuit thereof. As explained more fully hereinafter, closure of this holding circuit of the relay 274 is imperative in order to effect closure of the holding circuit of the gas valve relays 220, 222. As shown in heavy lines in Figs. 9 and 10, the holding circuit of the relay 274 includes at least part of the secondary transformer coil 276 (Fig. 10), a lead 314, a normally open control switch 316, a lead 318, a

. 11 a normally open control switch 320, a lead 322, the lead 290 across one of the terminals marked T (Fig. 9), switch 292, lead 294across the other terminal marked T, warp switch 296 (Fig. lead 298, relay 274 and lead 300. This holding circuit will be closed when the control switch 316 is closed on energization of another relay 324 immediately on flame establishment at the burner as will be described more fully hereinafter, the other control switch 320 in this holding circuit being held closed by the energized relay 274.

Energization of the relay 324 on flame establishment at the burner is achieved by a rectifier network generally indicated at 326 (Figs. 6, 8 and 10), which may be of the type shown and described in a circular published in 1952 by the Minneapolis-Honeywell Regulator Company, and entitled W124 Protectoglo Instruction. Since this specific rectifier network does not form any part of the present invention, it is deemed suflicient to explain that if the same is supplied with A. C. current it will convert it into D. C. current, but not until a flame electrode circuit to be described is closed. A. C. current is supplied to the rectifier network 326 through a secondary coil 328 of a step-down transformer 330 the primary coil 332 of which is through leads 334, 336 and the leads 282 and 214 connected with the A. C. current source of the apparatus when the main switch 200 is closed. Hence, A. C. current is supplied to the rectifier network 326 whenever the main switch 200 is closed.

The aforementioned flame electrode circuit, shown closed in heavy lines in Figs. 9 and 10, includes part of the rectifier network 326, a lead 338, a normally open control switch 340, a lead 342 which extends across the terminal marked F, the flame rod or electrode 57, the flame F at the burner 46, the burner itself and a lead 344 which extends across the terminal marked G. The control switch 340 is held closed by the energized relay 274, the control switch 346 being to this end ganged with the control switches 272 and 320. It follows from the preceding that the burner flame F, as soon as established, will close the described flame electrode circuit and cause immediate conversion of the applied A. C. current in the rectifier network 326 into D. C. current which is then immediately applied to the relay 324 through leads 346 and 343. A micro-arnmeter 349 may be connected in the flame electrode circuit to indicate the current flow therein.

It follows from the preceding that the previously described starting and holding circuits of the relay 274 are opened and closed, respectively, when the ganged control switches 28% and 316 are opened and closed, respectively, on energization of the relay 324, and energization of the latter occurs immediately on flame establishment at the burner, as explained. Since the described holding circuit of the relay 274 is devoid of the resistance 286 and further includes, in the present instance, only part of the secondary transformer coil 276, the current flow in this holding circuit is inadequate to warp out the switch 296, so that the latter remains closed as long as the burner flame is sustained and plays against the flame rod or electrode 57. However, should flame failure occur at the burner from any cause other than deliberate opening of the previously mentioned press switch or of the main switch 200, or should the burner flame flutter so badly as to lose contact with the flame rod or electrode 57, the described flame electrode circuit will be opened, with the result that the ganged control switches 316 and 288 will be permitted to open and close, respectively, and reestablish the described starting circuit of the relay 274 with ensuing timely warp-out of the switch 296 and consequential deenergization of the gas valve relays 220 and 222 and, hence, closure of the gas valves 134 andi38.

Ganged with the control switches 316 and 288 is another normally opencontrol switch 350 fora relay 352 which, on energization, opens a normally closed switch 354 in the branch 212 of the described starting circuit of the gas valve relays 220, 222 and ignition electrode 51.

Opening of the switch 354 brings about deenergization of the ignition electrode immediately on flame establishment at the burner. To this end, the previously described lead 204, which carries current as long as the main switch 20% and the vacuum, timer, web, pressure and centrifugal switches 170, 178, 172, 176 and 174 are closed, is connected through a lead 356 with one side of the switch 350 the other side of which is connected through a lead 358 across the terminal marked 5 with one end of the relay 352 the other end of which is through a lead 360 connected with the return lead 214. Accordingly, the ignition electrode 51 ceases spark production immediately on flame establishment at the burner, this being due to the opening of the switch 354 on the described closure of the switch 350 by the energized relay 324 as a direct result of the burner flame establishment.

The holding circuit to be described of the gas valve relays 220 and 222 is necessitated by the provision in the described starting circuit thereof of a normally closed limit switch 362 which, at any start of a print-drying operation of the apparatus, will open in any event, and in consequence open this starting circuit to the extent of causing deenergization of these gas valve relays and of the ignition electrode 51, after a predetermined time lapse from the closure of this starting circuit. This limit switch 362 is presettable so as to open after a variable time interval which at any rate is shorter than the waiting period for burner flame establishment permitted by the warp switch 296. The limit switch 362 comprises, in the present instance, flxed contacts 364 and 366 which are interposed in the lead 206 and normally bridged by a spring-urged conductive blade 368 to close the switch. Associated with the blade 368 is a plunger 370 which is slidable in a dashpot 372 having a vent 374. The plunger 370 is normally urged by a spring 376 into a depressed or inoperative position in which the same is seated against an adjustable stop 378 (Fig. 7) and in which a collar 380 on the plunger is spaced from the blade 368. Cooperating with the plunger 370 is a relay 332 which is connected across the previously described leads 206 and 360. Hence, the relay 382 will become energized immediately on closure of the starting circuit of the gas valve relays 220, 222 and ignition electrode 51, and will draw the plunger 370 upwardly from its inoperative position at a rate controlled by the dashpot 372, with the result that the collar 380 on the plunger 370 will raise the blade 368 from engagement with the contacts 364 and 366 and open the switch 362 after a time interval determined by the setting of the stop 378. if for any reason no flame is established at the burner 46 during this time interval, say 3 to 5 seconds, for instance, the relays 220 and 222 of the gas valves 134 and 138 will be cut off from their current source and these valves will then be permitted to close, and the ignition electrode 51 will likewise be cut oif from its current source. The warp switch 296 will then take over (Fig. 8) and warp out after a longer time period for which it is designed, say 15 seconds, for instance, requiring thereafter manual resetting of this warp switch in order to carry current again to the gas valve relays 220 and 222 and to the ignition electrode for a renewed start of a print-drying operation of the apparatus. Under these circumstances, the relay 382 remains energized and, hence, locks the plunger 370 in its switch-opening position (Fig. 9) until the switch 296 warps out. The limit switch 362 will thereupon be restored to its normally closed position before the warp switch 296 can be manually re-closed.

Since the limit switch 362 is connected in the described starting circuit of the valve relays 220, 222 and ignition electrode 51, and will open in any event, as explained, it is imperative that a holding circuit for these valve relays take over after flame establishmentat the burner in order to sustain the flame with a continuous supply of gas-air mixture. heavy lines in Figs. 9'and 10, includes one side of the aforementioned A. C. power source, lead 198 with the This holding circuit, which 'is shown closed in I terminal marked 5,:a lead=384,' thebladeand fixed contact 386 and 388 of a switch 390 having another fixed contact 392, a lead 3%, lead 21tl,the branching leads 216 and ZN-Which connect thev gas- valve relays 220 and 222 in parallel with each other, lead '226 and return lead 21410 the other side of the A.C.1power source. This holding circuit is closed immediately'on flame establishment at the burner 446. To this end, the burner-flame responsive energization of the'relayi324causes closure of the control switch 35%} (Fig.10). T the same end, establishment of the burner flame causes closure of the blade and contact 886,388 of the. control switch 390 under the control of a relay 3%. The relay 396 is initially energized on closure of a starting circuit thereof which includes the lead 334 that carries currentas'soonas the burner flame is established, the 'normallyclose'd blade and contact 386, 392 of the control switch 390, a lead 398, relay 396, a lead 406 and the return lead 214. (Fig.7) .On initial energization of the relay 396 in this fashion, a normally open control switch-402, ganged to the blade .386 of switch 390, is closed and the blade 386 and contact 388 of the switch 6% are also closed (Fig.=-9). -Closure of the blade 386 and contact 383 of the switch 390 closes the described holding circuit of the gas valve relays 220 and 222, while closure of the control switch 402closes a holding circuit for the relay396 including the current-carrying lead 206, a lead 4M, switch-402, a lead 466, lead 398, relay396, lead 469 and return lead 214.

In order to facilitate a checkof the performance of the major control aggregates of the-drying apparatus and afford ready detection of non-performance or malfunction 193 and 214, will indicate, when lighted, the presence of an available current source forthe apparatus when the main switch 2tl0 is closed, but will indicate, when not lighted, the absence of available current. Another light bulb 41%, also connected across the leads 198 and 214 and in series with the vacuum and timer switches 170 and 178, respectively, will indicate, when lighted, satisfactory performance of the exhaust fan 70 and termination of the purge of the apparatus under the control of the timer 180, but will indicate, when not lighted for a period longer than this purge time, either non-performance or malfunction of the exhaust'fan 70 or non-performance or malfunction of the timerilSl), or both.

Another light bulb 412, also connected across the leads 198 and 214 and in series with the vacuum, timer, web, pressure and centrifugal switches 170, 178,172, 176 and 174, respectively, will indicate, when lighted together with the bulbs 4% and 41d, correct disposition of a printed web in the apparatus in its predetermined path therethrough and travel of the web at a safe speed, also satisfactory performance of the air compressor 120, but will indicate, when not lighted while the bulbs 408 and 410 are lighted, wrong web disposition in the apparatus or no travel of the web or travel of the same below a safe speed, or non-performance or malfunction of the air compressor.

Another light bulb 414, connected in parallel with the primary coil 228 of the ignition transformer 230, will indicate, when lighted, poweravailable to the ignition electrode 51, but will indicate, when not lighted while the bulbs 408,410 and 412 are lighted, the absence of such power for the ignition electrode.

Finally, another lightbulb 416, connected in parallel with the relay 222 of the quick-closure gas valve 1%, will indicate, when lighted, that the valve is open and gas airamixture-shouldreach the burner 46 unless no gas is available to this'valve, but will indicate,-when not lighted 'whileithe bulbs see, 410 and 512 are lighted, that the valveis closedwhen it should be open.

The signal bulbs "thii tltl, 412, 41 i and 416, aswell as the -micro-ammeter 34) may, for convenient observation, bemounted on a door 418 of a control box 420 on -::the frame-2'7 (Figs. 3 and 4). Also mounted on this :d'oorf41 8 for convenient manipulation may be the switches Asalready explained, the present print-drying appaoperation and put out compressed air. In thus compelling the apparatusto comply with these conditions before the gas valvesarepermitte'd to open and the ignition electrode ispermittedto produce sparks, much is alieady achieved. toward assuringsafe operation of the apparatus. Further than that,-t-he aforementioned control circuit with the warp :switch-296permits initial opening of the 25 gas valves l34and 1-38 and-spark production by the electrode "fil'for a limited time only even after the aforementioned safety conditions concerning the purging of .the apparatuspthe disposition-and travel of the web and the operation of the air-compressor have been complied with. Thus, incase of ignition failure at the burner from anycause whatever, the-gasvalves 134 and 138 will be re-closed and thelignition electrode 51 deenergized in any :eventafter thei-lapse'of the safe time period allowed by the .limit switch 362. iMoreover,-the gas valve relays 220, 222:and ignition :electrode 51, once deenergized on ignition failure :atlthe burner, cannot be reenergized until the warp switch 2% warps out and is re-closedmanually. Hence, since any attempted restart of the-burner flame after preceding ignition failure involves the performance of a manual:taslgxnamely re-closure of the warp switch 295, it is .obvious :that each single occurrence of ignition failure is unmistakably brought to the attention of operating personnel for immediate correction of the cause of the ignition failure. Furthermore, due to'the simultaneous energization ofthe gas valve relays'22t), 222 and of the ignition 'electrode5 lat the start of an operation of .the print-drying apparatus, thespa'rks from the electrode controls will act immediately and reliably to forestall the developmentof any of these dangerous conditions. These controls are equally effective in anticipating and forestalling the development of any of these dangerous conditions at any time during an operation of the print-drying apparatus. Thus, if during operation of the apparatus the exhaust fan 70 should for any reason cease to purge the apparatus of the gases and combustion products therein, or should the printed web from any cause whatever deviate from its predetermined path through the apparatus or slowdown below its predetermined safe speed or stop altogether, or should the air compressor for any reason cease to' put out compressed air for the burner 46 and manifold 69, the gas valve relays 220, 222 will irnmediately be deenergized and the gas valves 134 and 138 will close in consequence and thus bring about immediate extinction of the burner flame F. This is due to the fact that under any of these adverse conditions the respective detecting switch will open and thereby cut off the power from the primary coil 280 of the step-down 15 transformer 278, meaning that the relay 274 will be deenergized and the control switch 272 opened in consequence, thereby opening the described holding circuit of the gas valve relays 220 and 222, as will be readily understood. As soon as the adverse condition which caused interruption of the operation of the print-drying apparatus is corrected and the respective detecting switch closed in consequence thereof, the gas valve relays 220 and 222 and the ignition electrode 51 will be reenergized the same as at any start of an operation of the apparatus, except that the present start will not be delayed for the duration of the usual purge period if the main switch 200 and the control switch (not shown) for the fan motor 118 were left closed during the correction of the adverse .condition. However, if the main switch 200 or the control switch for the fan motor 118 is opened for the correction of this adverse condition, then reenergization of the gas valve relays 220, 222 and of the ignition electrode 51 must await the end of the purging period of the apparatus under the control of the timer 180. On the other hand, if during an operation of the print-drying apparatus flame failure or malfunction should occur for any reason whatever, the described flame electrode circuit will immediately be interrupted, with the result that the relay 324 will be deenergized to permit opening of the control switch 350 and, hence, cut-off of the power from the gas valve relays 220 and 222 and consequential closure of the gas valves 134 and 138.

The invention may be carried out in other specific ways than those herein set forth without departing from the spirit and essential characteristics of the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency 1. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame. from the burner, the combination of a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normally closed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; normally inoperative first and second devices for opening said valve and for igniting gas-air mixture from the burner, respectively; control means including :a vacuum switch in said exhaust passage and a pressure switch in said conduit, said control means being operative only on establishment of sub-atmospheric pressure in said exhaust passage and of certain super-atmospheric pressure in said conduit and on travel of a web in said path at a speed above a predetermined minimum for rendering said devices operative; and means operative on flame establishment at the burner for causing said control means to render said second device inoperative.

2. In print-drying apparatus having a chamber with an exhaust passage, 2. burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of normally inoperative first and second devices for supplying said burner with combustible gas and for igniting gas from the burner, respectively; electrical control means adapted, when connected with a current source, to render said devices operative; means including a vacuum switch in said exhaust passage and being operative only on maintenance of sub-atmospheric pressure in said exhaust passage for a predetermined time period and on travel of a web in said path at a speed above a predetermined minimum for connecting said control means with a current source; and means operative on flame establishment at the burner for causing said control means to render said second device inoperative.

3. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of normally inoperative first and second devices for supplying said burner with combustible gas and for igniting gas from the burner, respectively; first and second electrical controls adapted, when connected with a current source, to render said first and second devices respectively, operative; first means operative only on maintenance of sub-atmospheric pressure in said exhaust passage for a predetermined time period and on travel of a web in said path at a speed above a predetermined minimum for connecting said controls with a current source for another predetermined time period only; and other means operative on flame establishment at the burner and continued maintenance of sub-atmospheric pressure in said exhaust passage and travel of said web in said path at a speed above a predetermined minimum for establishing a holding connection between said first control and said current source and disconnecting said second control from said current source.

4. In print-drying apparatus having a burner and means for feeding a continuous printed web in a predetermined path past the burner with the printed web face in contacting relation with a flame therefrom, the combination of a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normally closed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gas-air mixture from the burner; an energizing circuit for said relay and device having a first branch including three normally-open first switches in series with each other, and a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normallyclosed second switch in series with said device, said first switches being closed by certain super-atmospheric pressure in said conduit, by a web in said path, and on attainrnent by said feeding means of a certain operating speed, respectively; a second relay adapted, when energized, to open said second switch and thereby cause deenergization of said device; and means operative on flame establishment at said burner for energizing said second relay.

5. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; an energizing circuit'for said devices having a first branch including three normally-open first switches in series with each other, and a second branch in series with said first branch and connecting said devices in parallel with each other and including a normally-closed second .switch in series with said second device, said first switches for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normally-closed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gas-air mixture from the burner; an energizing circuit for said relay and device having a first branch including four normally-open first switches in series with each other, and a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normally-closed second switch in series with said device, said first switches being closed by sub-atmospheric pressure in said exhaust passage, by certain super-atmospheric pressure in said conduit, by a web in said path, and on attainment by said feeding means of a certain operating speed, respectively; a second relay adapted, when energized, to open said second switch and thereby cause deenergization of said device; and means operative on flame establishment at said burner for energizing said second relay.

7. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; an energizing circuit for said devices having a first branch including normally-open first, second, third and fourth switches in series with each other, and a second branch in series with said first branch and connecting said devices in parallel with each other and including a normallyclosed fifth switch in series with said second device, said first, third and fourth switches being closed by subatmospheric pressure in said exhaust passage, by a web in said path, and on attainment by said feeding means of a certain operating speed, respectively; a normally-closed sixth switch ganged with said second switch; an electric timer having a timing element and being adapted, when energized, to operate said element; means including a first relay and being operative on energization of the latter to open and close said sixth and second switches, respectively, after operation of said timer element for a predetermined period, and retain said sixth and second switches in their respective open and closed positions;

an energizing circuit for said timer and relay having a first branch including said first switch in series with said relay and a second branch connecting said timer in parallel with said relay and including said sixth switch in series with said timer; a second relay adapted, when energized, to open said fifth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said second relay.

8. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the

combination of a conduit providing communication be tween a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a nor-' mally closedvalve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gas-air mixture from the burner; an energizing circuit for said relay and device having a first branch including normally-open first, second, third, fourth and fifth switches in series with each other, and a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normally-closed sixth switch in serieis with said device, said first, third, fourth and fifth switches being closed by sub-atmospheric pressure in said exhaust passage, by a web in said path, by certain super-atmospheric pressure in said conduit, and on attainment by said feeding means of a certain operating speed, respectively; a normallyclosed seventh switch ganged with said second switch; an electric timer having a timing element and being adapted, when energized,rto operate said element; means including a second relay and being operative on energization of the latter to open and close said seventh and second switches, respectively, after operation of said timer element for a predetermined period, and retain said seventh and second switches in their respective open.

and closed positions; an energizing circuit for said timer and second relay having a first branch including said first switch in series with said second relay and a second branch connecting said timer in parallel with said second relay and including said seventh switch in series with said timer; a third relay adapted, when energized, to open said sixth switch and thereby cause deenergization of said device; and means operative on flame estblishment at said burner for energizing said third relay.

9. In print-drying apparatus having a burner and means for feeding a continuous printed web in a predetermined path past the burner with the printed web face in contacting relation with a flame therefrom, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; an energizing circuit for said devices having a first branch including normally-open first, second, and third switches in series with each other, a second branchin series with said first branch and connecting said devices in parallel with each other and including a normally-closedrfourth switch in series with said second device, and a third branch including theprimary coil of a step-down transformer in series with said first and second switches and in parallel with the rest of said circuit, said first and second switches, being closed by a web in said path and on attainment by said feeding means of a certain operating speed, respectively; a first relay adapted, when energized, to close said third switch; a starting circuit for said relay including the secondary coil of said transformer, a normally-closed fifth switch, and a safety switch in series with each other and with said relay, said safety switch being of the warp-type so as to open on current flow for a predetermined time period in said starting circuit, when closed, and requiring manual re-closure; a holding circuit for said relay including at least part of said secondary transformer coil, a normally-open sixth switch ganged with said fifth switch, and said safety switch in series witheach other and with said relay, the current flowing in said holding circuit, when closed, being insufiicient to open said safety switch; a second relay adapted, when energized, to close said sixth switch and open said fifth switch; a third relay adapted, when energized, to open said fourth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said second and third relays.

10. The combination in print-drying apparatus as set forth in claim 9, further comprising a chamber in which said burner is located and which has an exhaust passage and a through-passage for a web in said predetermined path, and said energizing circuit further includes in said first branch a normally-open seventh switch in series with said first, second and third switches and in parallel with the rest of said energizing circuit, and said seventh switch being closed by sub-atmospheric pressure in said exhaust passage.

11. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means 19 for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the .combinatiouof a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normally-closed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gas-air mixture from the burner; an energizing circuit f-or'said relay and device having a first branch including normallyopen first, second, third, fourth and fifth switches in series with each other, a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normally-closed sixth switch in series with said device, and a third branch including the primary coil of a step-down transformer in series with said first, second, third and fourth switches and in parallel with the rest of said circuit, said first, second, third and fourth switches being closed by subatmospheric pressure in said exhaust passage, by a web in said path, by certain super-atmospheric pressure in said conduit, and on attainment by said feeding means of a certain operating speed, respectively; 'a second relay adapted, when energized, to close said fifth switch; a starting circuit for said second relay including the secondary coil of said transformer, a normally-closed seventh switch, and a safety switch in series with each other and with said second relay, said safety switch being of the warp-type so as to open on current flow for a predetermined time period in said starting circuit, when closed, and requiring manual re-closure; a holding circuit for said second relay including at least part of said secondary transformer coil, a normally-open eighth switch ganged with said seventh switch, and said safety switch in series with each other and with said second relay, the current flowing in said holding circuit, when closed, being insufficient to open said safety switch; a third relay adapted,

when energized, to close said eighth switch and open saidseventh switch; a fourth relay adapted, when energized, to open said sixth switch and thereby cause deenergization of said device; and means operative on flame establishment at said burner for energizing said third and fourth relays.

12. In print drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; an energizing circuit for said devices having a first branch including normally-open first, second, third, fourth and fifth switches in series with each other, a second branch in series with said first branch and connecting said devices in parallel with each other and including a normallyclosed sixth switch in series with said second device, and a third branch including the primary coil of a step-down transformer in series with said first, second, third and fourth switches and in parallel with the rest of said circuit, said first, third and fourth switches being closed by subatmospheric pressure in said exhaust passage, by a web in said path, and on attainment by said feeding means of a certain operating speed, respectively; a normally-closed seventh switch ganged with said second switch; an electric timer having a timing element and being adapted, when energized, to operate said element; means including a first relay and being operative on energization of the latter to open and close said seventh and second switches, respectively, after operation of said timer element for a predetermined period, and retain said seventh and second switches in their respective open and closed positions; an energizing circuit for said timer and relay having a first branch including said first switch in series with said relay and a second branch connecting said timer in parallel with said relay and including said seventh switch in series with said timer; a second relay adapted, when energized, to close said fifth switch; a starting circuit for said relay including the secondary coil of said transformer, a normally-closed eighth switch, and a safety switch in series with each other and with said second relay, said safety switch being of the warp-type so as to open on current flow for a predetermined time period in said starting circuit, when closed, and requiring manual re-closure; a holding circuit for said second relay including at least part of said secondary transformer coil, 21 normally-open ninth switch ganged with said eighth switch, and said safety switch in series with each other and with said second relay, the current flowing in said holding circuit, when closed, being insufiicient to open said safety switch; a third relay adapted, when energized, to close said ninth switch and open said eighth switch; a fourth relay adapted, when energized, to open said sixth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said third and fourth relays.

13. In print-drying apparatus having a burner and means for feeding a continuous printed web in a predetermined path past the burner with the printed web face in contacting relation with a flame therefrom, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; a starting circuit for said devices having a first branch including normally-open first and second switches and a normallyclosed third switch in series with each other, and a second branch in series with said first branch and connecting said devices in parallel and including a normally-closed fourth switch in series with said second device, said first and second switches being closed by a web in said path and on attainment by said feeding means of a certain operating speed, respectively; an instrumentality including a first relay and adapted, on energization of the latter, to open said third switch after a predetermined time period and hold the sameopen, said relay being connected in said circuit in series with said first and second switches and in parallel with the rest of said circuit; a holding circuit for said first device including said first and second switches and normally-open fifth and sixth switches in series with each other and with said first device; second and third relays adapted, when energized, to close said fifth and sixth switches, respectively; a fourth relay adapted, when'energized, to open said fourth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said second, third and fourth relays.

14. The combination in print-drying apparatus as set forth in claim 13, in which said instrumentality is presettable to vary the duration of said time period.

15. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gasand ignite gas from the burner, respectively; a starting circuit for said devices having a first branch including normally-open first, second and third switches and a normally-closed fourth switch in series with each other, and a second branch in series with said first branch and connecting said devices in parallel with each other and including a normally-closed fifth switch in series with said second device, said first, second and third switches being closed by sub-atmospheric pressure in said exhaust passage, by a web in said path, and on .attainment by said feeding means of a certain operating speed, respectively; an .instrumentality including a first relay and adapted, on

ass-rant 21 energization of the latter, to open said fourth switch after a predetermined time period and hold the same open, said relay being connected in said circuit in series with said first, second and third switches and in parallel with the rest of said circuit; a holding circ 't for said first device including said first, second and third switches and normally-open sixth and seventh switches in series with each other and with said first device; second and third relays adapted, when energized, to close said sixth and seventh switches, respectively; a fourth relay adapted, when energized, to open sa'd fifth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said second, third and fourth relays.

16. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normallyclosed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gasair mixture from the burner; a starting circuit for said relay and device having a first branch including normallyopen first, second, third and fourth switches and a normally-closed fifth switch in series with each other, and a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normally-closed sixth switch in series with said device, said first, second, third and fourth switches being closed by sub-atmospheric pressure in said exhaust passage, by a web in said path, by certain super-atmospheric pressure in said conduit, and on attainment by said feeding means of a certain operating speed, respectively; an instrumentality including a second relay and adapted, on energization of the latter, to open said fifth switch after a predetermined time period and hold the same open, said second relay being connected in said circuit in series with said first, second, third and fourth switches and in parallel with the rest of said circuit; a holding circuit for said first relay including said first, second, third and fourth switches and normally-open seventh and eighth switches in series with each other and with said first relay; third and fourth relays adapted, when energized, to close said seventh and eighth switches, respectively; a fifth relay adapted, when energized, to open said sixth switch and thereby cause deenergization of said device; and means operative on flame establishment at said burner for energizing said third, fourth and fifth relays.

17. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite gas from the burner, respectively; a starting circuit for said devices having a first branch including normally-open first, second, third and fourth switches and a normally-closed fifth switch in series with each other, and a second branch in series with said first branch and connecting ,said devices in parallel with each other and including a normally-closed sixth switch in series with said second device, said first, third and fourth switches being closed by sub-atmospheric pressure in said exhaust passage, by a web in said path, and on attainment by said feeding means of a certain operating speed, respectively; a normally-closed seventh switch ganged with said second switch; an electric timer having a timing element and being adapted, when energized, to operate said element;

'22 means including a first relay and being operative on energization of the latter to open and close said seventh and second switches, respectively, after operation of said timer element for a predetermined period, and retain said seventh and second switches in their respective open and closed positions; an energizing circuit for said timer and relay having a first branch including said first switch in series with said relay and a second branch connecting said timer in parallel with said relay and including said seventh switch in series with said timer; an instrumentality including a second relay and adapted, on energization of the latter, to open said fifth switch after a predetermined time period and hold the same open, said second relay being connected in said starting circuit in series with said first, second, third and fourth switches and in parallel with the rest of said starting circuit; a holding circuit for said first device including said first, second, third and fourth switches and normally-open eighth and ninth 'switches in series with each other and with said first device; third and fourth relays adapted, when energized, to close said eighth and ninth switches, respectively; a fifth relay adapted, when energized, to open said sixth switch and thereby cause deenergization of said second device; and means operative on flame establishment at said burner for energizing said third, fourth and fifth relays.

18. In print-drying apparatus having a chamber with an exhaust passage, a burner in the chamber and means for feeding a continuous printed web in a predetermined path through the chamber with the printed web face in contacting relation with a flame from the burner, the combination of a conduit providing communication between a source of compressed air and the burner and having a Venturi-type gas-air mixer interposed; a normally-closed valve adapted, when open, to provide communication between a low-pressure gas source and said mixer; a first relay adapted, when energized, to open said valve; an electric device adapted, when energized, to ignite gas-air mixture from the burner; a starting circuit for said relay and device having a first branch including normally-open first, second, third, fourth and fifth switches and a normally-closed sixth switch in series with each other, and a second branch in series with said first branch and connecting said relay and device in parallel with each other and including a normally-closed seventh switch in series with said device, said first, third, fourth and fifth switches being closed by sub-atmospheric pressure in said exhaust chamber, by a web in said path, by certain super-atmospheric pressure in said conduit, and on attainment by said feeding means of a certain operating speed, respectively; a normally-closed eighth switch ganged with said second switch; an electric timer having a timing element and being adapted, when energized, to operate said element; means including a second relay and being operative on energization of the latter to open and close said eighth and second switches, respectively, after operation of said timer element for a predetermined period, and retain said eighth and second switches in their respective open and closed positions; an energizing circuit for said timer and second relay having a first branch including said first switch in series with said second relay and a second branch connecting said timer in parallel with said second relay and including said eighth switch in series with said timer; an instrumentality including a third relay and adapted, on energization of the latter, to open said sixth switch after a predetermined time period and hold the same open, said third relay being connected in said starting circuit in series with said first, second, third,

fourth and fifth switches and in parallel with the rest of said starting circuit; a holding circuit for said first relay including said first, second, third, fourth and fifth switches and normally-open ninth and tenth switches in series with each other and with said first relay; fourth and fifth relays adapted, when energized, to close said ninth and tenth switches, respectively; a sixth relay adapted, when energized, to open said seventh switch and thereby cause deenergization of said device; and means operative on flame establishment at said burner for energizing said fourth, fifth and sixth relays.

19. In print-drying apparatus having a burner and means for feeding a continuous printed web in a predetermined path past the burner with the printed web face in contacting relation with a flame therefrom, the combination of first and second electric devices adapted, when energized, to supply said burner with combustible gas and ignite 'gas from the burner, respectively; a first starting circuit for said devices having a first branch including normally-open first, second and third switches and a normally-closed fourth switch in series with each other, a second branch in series with said first branch and connecting said devices in parallel with each other and including a normally-closed fifth switch in series with said second device, and a third branch including the primary coil of a step-down transformer in series with said first and second switches and in parallel with the rest of said safety switch and a normally-closed sixth switch in series with each other and with said relay, said safety switch being of the warp-type part of said secondary transformer coil, said safety switch and a normally-open seventh switch in series with each other and with said relay, the current flowing in said holding circuit, when closed,

circuit for said first device including said first, second and third switches and normally-open eighth and ninth ond device; and means operative at said burner for energizing said relays.

20. The combination in print-drying appaartus as set f th in claim 19, in which said instrumentality is presettable to vary the duration References Cited in the file of this patent UNITED STATES PATENTS 2,288,129 Feldhausen et al June 30, 1942

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