US3071999A

US3071999A - Cut-off control apparatus

Info

Publication number: US3071999A
Application number: US769678A
Authority: US
Inventors: Harry F Thorn
Original assignee: Koppers Co Inc
Current assignee: Beazer East Inc
Priority date: 1958-10-27
Filing date: 1958-10-27
Publication date: 1963-01-08
Anticipated expiration: 1980-01-08

Description

Jan. 8, 1963 H. F. THQRN 1' CUT-oFF coNTRoL APPARATUS 3 Sheets-Sheet 1 Filed Oct. 27, 1958 Jan. 8, 1963 H. F. THoRN 3,071,999

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Jan. 8, 1963 H. F. THoRN 3,071,999

' CUT-OFF CONTROL APPARATUS Filed Oct. 27, 1958 3 Sheets-Sheet 5 14 143 c-ff TT 75A CS1/PFU 5w LL/156 L i@ Ncnnououuou 76 7? 162 INVENTOR.

BY 7d? E noz/ELE aA c/rEk GEN. ARMA Tlf/PE' ArrOE/VEKSZ United States Patent Ofiice 3,071,999 Patented Jan. 8, 1963.

3,071,999 CUT-GFF CONTROL APPARATUS I Harry F. Thorn, Trenton, NJ., assignor, by mesne assignments, to Koppers Company, Inc., Pittsburgh, Pa., a corporation of Delaware Filed Oct. 27, 1958, Ser. No. 769,678 7 Claims. (Ci. 8.3-76) This invention pertains to apparatus for the production of corrugated paperboard and the like in the form of a continuously produced moving web which is slit to width and cut to length into sheets as formed, and more especially to methods and apparatus for automatically maintaining the sheet length of cutting within extremely close tolerances.

In the manufacture of corrugated paperboard, the continuous length of board as progressively fed forwardly from the double facer, usually passes first through a slitter-scorer which is adjustable to slit the board longitudinally into continuous side by side strips of Selected widths, these strips then passing through a cut-oli which is adjustable to sever them transversely intoblanks of different selected lengths.

To enable blanks of different lengths to be sheared by the cut-off, it has long been the practice to `interpose a variable speed transmission, e.g., a Reeves drive, between the cut-off and the driving mechanism, the cut-off being connected to the output shaft o f the variable speed transmission. By adjustment of the variable speedtransmission the cut-Off is caused to cut at longer or shorter intervals and thereby produce longer or shorter blanks.

To conform the rate of travel of the cut-off knives at :the time `of cut to the rate of travel of the board, under different settings of the variable speed transmission, it also has long been customary to interpose lbetween the variable speed transmission and the cut-olf knives, ad-

justable crank mechanism or other mechanism capable of causing the cutting knives to move at different speeds in different phases of their cycle, this mechanism being adjusted to keep the cutting speed from varying with different lengths of cut. The two adjustments for length of cut and cutting speed are made coordinately and simultaneously while the machine is running, so that whenever the cutoff is adjusted to a different length of cut, the motion modifying mechanism is shifted as needed to keep the cutting speed substantially equal to the rate of travel of the board. The U.S. patents to G. W. Swift, Jr., 1,951,536, 1,997,608, 2,059,412; Morrison 2,215,762; H. W. Bruker 2,244,673; H. W. Bruker and F. W. Overton 2,316,221, may be referred to as illustrative of machines of the character above briefly described.

Cut-ott controlk apparatus of the above character, as heretofore known and used, depends for its accuracy upon constancy in relationship between the speed of operation of the double facer and the resulting speed of travel of the board, and also upon constancy in the speed ratios between the input and output shafts of the variable speed transmission in its various settings for different lengths of cut. It has long been known that objectionable inaccuracies or variances in the length of cut have been caused 4by deviations in the above factors from constancy, but such inaccuracies in the length of cut have persisted for many years.

The present invention aims primarily to provide cut-off control apparatus by which inaccuracies in length of cut, as caused by variances in the yfeed of material being cut, or in the speed ratios secured by the Reeves drive, may be automatically compensated for to secure substantially uniform length of cut for any given setting of the machine. In accordance with the invention, one tachometer is activated by the advancing web to be cut as the latter passes into the cut-olf, so as to be directly and immediately responsive to the fluctuations in the speed of feed of the web. A second tachometeris similarly related lto the output shaft of the Reeves drive so as to respond immediately to any fluctuations in speed of the latter. The outputs' of the two tachometers are then integrated, and the resultant thereof utilized as a control factor which determines the setting of the positioning mechanism which jointly shifts the Reeves drive and the mechanism which controls the cutting speed. The above control factor is adjusted according to the length of blank desired to be cut, and once the control apparatus has been set for a particular length of cut, fluctuations either in the speed of feed of the web to be cut or in the speed ratio of the Reeves drive will be reflected through the control apparatus to cause the latter to immediately shift the abovementioned positioning mechanism as needed to correct for such iiuctuation-s. Further objects and advantages of the invention will be in part obvious and in part specifically referred to in the description hereinafter contained which, taken in conjunction with the accompanying drawings, discloses a preferred form of cut-oli control apparatus capable of functioning in accordance with the inven-- tion; the disclosure, however, should be considered as merely illustrative of the invention in its broader aspects.

More particularly to invention comprises in its essentials, an idler roll engaging the web, and on the shaft of which is mounted the armature of a tachometer generator for generating a voltage proportional to the rate of lineal displacement of the web. The armature of a second tachometer generator is carried by a shaft driven -by the outputpshaft of the Reeves drive for generating a second voltage proportional to the rotative speed yofthat shaft; In accordance with one modification of the invention, these tachometers designated herein as the line tachometer for that driven by the web, and the cutter follow tachometer for that driven by the Reeves drive, are connected in series additive relation in a closed circuit containing a Calibrating rheostat in series with the lines tachometer and sheet length adjusting rheostats in series with :the cutter follow tachometer and with the fixed arm of a Vernier potentiometer connected therebetween. T apoff connections to the input of an amplifier are taken from between the tachometers and from Athe variable arm or tapping point of the potentiometer, respectively, thus to comprise a form of electrical bridge circuit, the potential difference between the tapping points of which, in operation of the apparatus, will be zero only if the total resistance in each leg of the bridge between the tapping points is proportional to the voltage generated by the tachometer in that leg, since the current flow in the closed circuit is lthe same throughout for the condition of balance. And since the voltages generated by the line and cutter follow tachometers are proportional to the lineal speed of travel of the web and the speed of rotation of the Reeves drive output shaft, respectively, the condition of Ibalance attains only when the ratio of these speeds expressed in angular speed of the tachometer shafts, is equal to the ratio of totalV resistance in the respective legs of the bridge. -If these rati-os are not the same, an unbalance voltage will be .generated across the bridge points, the direction and magnitude of which will be determined by the discrepancy of these ratios and on which is larger, and which is impressed on'the amplifier input.

The amplifier output is extended through additional stages of amplication to the main field winding of a D.C. generator provided with an oppositely poled auxiliary tield winding, the latter energized from a constant voltage source. The generator armature is electrically v connected to the armature ofv a reversible D.C. motor, which is geared to the adjusting shaftsof the crank mo` tion and the -Reeves drive. This motor is referred to herein as the shifter motor and the generator as the shifter generator for reasons which will become apparent below.

The amplifier output current is initially so adjusted with no voltage impressed on its input, that the current flow in lthe main field Winding of the generator is equal to the constant current flow in the oppositely poled and separately energized auxiliary field winding, thus to reduce the magnetic flux in the generator field to zero, so that for this condition, no voltage is produced in the generator armature for actuation of the shift motor.

In the operation of the apparatus, therefore, any unbalance voltage produced across the bridge points as above explained, and impressed thence on the amplifier input, will produce a net current fiow and resulting net magnetic flux in the generator field in the direction of, and in magnitude proportional to, the unbalance voltage impressed on the amplifier input. The net vflux thu-s produced in the generator field will generate in the armature a` corresponding voltage of amplified magnitude, sufficient to actuate the shifter motor -in direction and amount such as to restore the bridge to a condition of balance by appropriate adjustments of the adjusting shafts of the Reeves drive and crank motion.

The apparatus is adjusted to cut the web into `sheets of a preselected length by appropriate setting of the sheet length rheostats in the bridge circuit, the Calibrating resistance and the potentiometer having been preset in an initial over-all calibration of the apparatus. Thus the setting of the sheet length rheostats determines the ratio of total resistance in the bridge legs, respectively, and thereby determines the ratio of the voltages generated by the tachometers at which the bridge will be balanced. This in turn determines the ratio of lineal speed of the web to the rotative speed of the Reeves output shaft drive at which this condition occurs. On switching the apparatus to automatic operation, therefore, with the web being fed at an appropriate speed as discussed below, the shifter motor will be actuated as above explained until the bridge is balanced, and the proper speed ratio between the web feed and the Reeves output shaft, thereby established and maintained.

The invention in its preferred embodiment involves a number of additional refinements, which will be explained with reference to the accompanying drawings, wherein:

, FIG. 1 is a yschematic and diagrammatic showing of the mechanical and electrical circuit components of the basic embodiment of the invention as above described;

FIG. 2 is an electrical circuit layout of a modi-fied portion of the electrical system of FIG. 1, embodying various refinements and improvements over the basic circuit of FIG. 1 as will be discussed; and

FIG. 3 is a diagrammatic layout of a control panel and appurtenant electrical circuits for controlling the Ioperation of the FIGS. l and 2 embodiments.

Referring to FIG. l, the corrugated web emerging `from the double facer 11, is fed forward in the direction of the arrow by driven pull rolls 12, which `feed the web through the slitter 13, which longitudinally slits the web into appropriate Widths, the web thus slit being fed thence between the driven pull rolls 12, and thence through the cutter 14 provided with axially extending knife blades |15 which cut the slitted web into appropriate length.

The cutter-s which are geared together as described in the aforesaid Bruker et al. Patent 2,316,221, for example, are driven over a shaft 19 from a crank motion 2G preferably of the construction described in said patent, which in turn is driven from a Reeves drive 21, the output shaft 22 of which drives the input shaft 24 of the crank motion through intermeshing gears 23a-23C, inc., a pair of which are keyed to said shafts, respectively, as shown. The Reeves input shaft 25 is driven from a D.C. motor 26 through intermeshing gears 27-29, inc., a pair of which are keyed, respectively, to the motor shaft 29a and shaft 25 of the Reeves drive. Other forms of drive may of course be substituted such as link belts engaging pinions on the respective shafts referred to.

The speed ratio between the Reeves drive input shaft 25 and its output shaft 22 is adjustable by means of the shaft 31, which adjusts the relative spacing of the Reeves drive pulleys, and which is geared through gears 32, 33, to the shaft 34 of a direct current motor 35 comprising the above-mentioned shifter motor. Likewise, the actuation of the crank motion 2i), is adjustable by means of a shaft 36 geared by means of pinion 37 to the motor driven pinion 33. The speed adjusting shifter motor 35 may be automatically actuated over an electrical circuit 33 as hereinafter explained. Or it may be actuated under manual control by the alternating current motor 39, by means of belt 49 passing about the pulleys 41 and 42 keyed, respectively, to the shafts of

motors

39 and 35. The motor is a reversible motor, which is actuatable under control of manually depressed push-buttons 43, to drive motor 39 clockwise or counterclockwise, as desired, for adjusting the ratio of the Reeves drive and crank motion in either direction to a desired extent.

Mounted on an extension 24a of shaft 24 of the crank motion drive, is the armature of a tachometer generator 45, which thus generates a voltage proportional to the speed at which shaft 24 is driven from the output shaft 22 of the Reeves drive. Riding on the web 10` is an idler roll 46 provided with an extension shaft 47, on which is mounted the armature of a second tachometer generator 48, for generating a voltage proportional to the speed of rotation of roll 46.

The

tachometer generators

45 and 48 are connected in series additive relation in a closed

electrical circuit

100, 161, which includes in series with the tachometers, re-j spectively, the adjustable resistances 49 and 5t), between which is connected the fixed arm of a potentiometer `'51 having an adjustable arm 51a variably tapped thereto at A as shown. At a point B between the tachorneters 45 and 48, a connection 52 is tapped off. Another connection 53 is connected to the variable tapping arm 51a of the potentiometer 51.

Connections

52 and 53 extend to the input of an amplifier 54 for impressing thereon any differences of potential arising between the tapping points A and B, of the electrical bridge formed between these tapping points by the series connected

tachometers

45, 48, resistors 49, 5@ and potentiometer 51. Connection 53 extends to the input control grid on the amplifier while grounded connection 52 extends to the grounded cathode system. Amplifier 54 is energized from a power pack 54a, supplied from a 6() cycle A C. source 54b.

Bridged across the output of the amplifier 54 in series, is the fixed arm of a potentiometer 56 and a resistor 57. The variable arm 58 of the potentiometer 56 is connected through an adjustable resistance 59 and thence through a fixed resistance 60 of about 1 megohm, to the input control grid connection 61 of a second D.C. amplifier 62, the opposite or cathode input connection 63, of which is connected to the grounded output connection l64 of ampliner 54. An equalizing resistor 65 is connected between the variable potentiometer arm 51a and the input connection 61 to amplifier 62. Amplifier 62 is energized from a power pack 62a, connected to a 6()l cycle A C. source 66.

The output of amplifier 62 is connected to the control winding of a phase shift bridge 65, which is energized from the alternating current source 66, which source also energizes a grid controlled thyratron rectifier 67, to which the output of the phase shift bridge is connected as shown, for regulating the rectier or direct current output of the thyratron rectifier in accordance with the magnitude output current of the D C. amplifier 62. Connected to the output of the thyratron rectifier over leads 69, is the main field winding 70, of a direct current generator 71, provided with an oppositely poled auxiliary field winding 72. Armature 73 is driven by an A.C. motor 73a, as discussed below. This is the above-mentioned shifter generator.

The auxiliary generator winding 72 is connected in series 45 with an adjustable resistance 73h, to the output 74 of a second thyratron rectifier 75, .energizing over inputconnections 76 from the alternating current source 66. The thyratron rectifier 75 supplies current at substantially constant output voltage to the auxiliary field winding 72 of the `generator 71. The output of the generator armature 73 is connected over leads 38 to the armature of the shifter motor 35, the field winding of which is energized over leads 38a connected to the output of thyratron 75, as at 38b.

, Amplifier 54 may be of the type in .which when no voltage is impressed upon its input, its output lead 55 will be maintained at zero potential with respect to ground, in which event no voltage would be impressed on the amplifier 62 for the condition of balance across bridge points A-B. In this event the phase shift bridge 65 will be so adjusted initially that the output current from the thyratron rectifier 67, which traverses the main generator field coil 70, will be equal and opposite to that supplied from thyratron rectifier 75 to the auxiliary field coil 72, as indicated by the arrows I-1 and I-2, so that the resultant magnetic field produced by the main and auxiliary generatorwindings 70 and 72, will be zero for the condition of zero voltage between the bridge points A and B. n

Alternatively, amplifier 54 may be of the type that with zero voltage impressed upon its input, a constant current flows in the output through the resistor 57 and fixed potentiometer arm 56. With an amplifier of this type the `variable potentiometer arm 58 is initially adjusted in conjunction with the phase shift bridge, again so that the current flowing in the lmain generator field winding 70 is equal and opposite to that supplied to the auxiliary winding 72. 'I'hus for either type of amplifier aforesaid, no voltage will be generated by the generator armature 73 so long as a condition of balance or zero difference of potential exists between the bridge points A and B.

The variable resistance 50 in the bridge leg 100, is the sheet length adjusting rheostat, while variable resistance 49 in bridge leg 101 is the calibrating resistance. Potentiometer 51, 51a is the Vernier potentiometer, above mentioned. Resistance 50 provides the sheet length setting for automatic operation when the control circuit is switched on while the web is being fed at an appropriate minimum speed as discussed below. When automatic operation is thus initiated, the bridge A--B will in general be unbalanced, to apply an unbalance voltage to the input of amplifier 54. This will produce a proportional change in current flow throughthe generator main field winding 70, either an increase or a decrease, depending n the direction of uubalance of the bridge A-B. There will accordingly result a net magnetic flux in the generator vfield of apolarity corresponding to the bridge unbalance and of proportional magnitude. In consequence, a corresponding voltage will be generated in the generator armature which is applied over leads 38 to the shifter motor 35 armature. The shifter motor is thus energized in the direction to balance the bridge by adjustment in speed of the Reeves drive output shaft 22 until the voltage generated by the cutter tachometer `45 bears a ratio to that generated by the line tachometer 4S, corresponding to the ratio of total resistance between the bridge points A-B in the

opposite legs

100, 101 of the bridge, respectively, i.e., that containing tachometer 48 and that containing tachometer 45.

Once the bridge is balanced by the shifter motor in the manner explained, it will be de-energized and remain so until a further unbalance occurs, as for example by slippage of the strip between pull rolls 12, thus slowing down tachometer 48, whereupon motor 35 would again be energized, as above explained, to readjust the Reeves drive until the correct voltage ratio between the tachometers is restored.

FIG. 2 shows the electrical portion of the FIG. 1 control system more in detail, and as including various modifications and refinements for minimizing hunting and for otherwise improving over-all performance. Referring to FIG. 2, the bridge 'circuit A--B contains in leg 100 in series with the cutter follow tachometer 45, a current limiting or ballast resistor 102 and sheet length adjusting rheostats 103, 104; and contains in leg 101 in series with the line speed tachometer 48, a ballast resistor 105`and a sheet length calibration rheostat 106. 'Ihe fixed arm of the Vernier potentiometer 51 is connected between

rheostats

104 and 106.

As in FIG. l, the bridge point A of FIG. 2 is connected from the variable potentiometer arm 51a, over a lead 53 and thence through a resistor 109 to the control grid of an amplifier stage 110. The opposite bridge point B is connected over a lead 52 to the grounded input terminal of this amplifier stage. 'Ihe upper output of amplifier stage 110 is connected to the input of a second amplifier stage 111, over

connections

111a and 111b, having interposed therein a resistance 111C for purposes hereinafter explained.

Amplifiers

110 and 111 comprise a two-stage-amplifier for increasing the sensitivity of the apparatus tovoltage changes across the bridge points A-B. A preferred form of amplifier for each of the

stages

110 and 111 is that pr0- duced by George A. Philbrick Researchers, Inc., Boston, Massachusetts, under their designation Model KZ-X Operational Amplifier as supplemented by their Model KZ-P Stabilizing Amplifier, as described in their circulars so designated. Any standard form of amplifier may, however, be employed, having adequate sensitivity.

As in FIG. l, the output of the second amplifier stage 111 is bridged by fixed resistance 57in series vwith the fixed arm of potentiometer 56, the variable arm 58 of which is connected over. lead 61 through rheostat 59, thence through the fixed isolating resistor 60', thence through contacts D-1 and a current limiter 112 as discussed below, and thence to the input control grid of the D.C. amplifier 62, which is the like numbered amplifier of FIG. 1. The lower or grounded output lead 64 of amplifier stage 111, is connected over lead 52, as shown, to the opposite input terminal of the D.C. amplifier 62. The portion of the output of amplifier 111 which is irnpressed on the input to amplifier 62, is as above explained, that applied between the Variable arm 58 of potentiometer 56 and ground.

'I'he electrical circuit of FIG. 2 embodies various antihunt circuits for minimizing hunting of the apparatus in automatically adjusting to a balance as above explained with reference to FIG. l. One of these anti-hunt circuits which is disposed in the output of the amplifier stage 111,

includes the condenser 113 connected between the upper terminal of resistor 57 and the lower terminal of the isolating resistor 60'. This condenser in conjunction with the resistance bridging the same which includes resistor 57 and the rheostat 59 and also in conjunction with the internal resistance of the amplifier output, provides an anti-hunt time constant circuit which controls the rate at which the output of the amplifier stage responds to an unbalance voltage developed across the bridge points AB for applying a correcting potential to the input lead 61 of the amplifier 62. The time constant of this circuit may be adjusted by adjustment of the rheostat 59. The effect of this time constant circuit is to slow down the rate at which a potential variation occurring on the output lead 55 of amplifier 111 is applied to the input lead 61 of amplifier 62, this of course being dependent upon the magnitude of condenser 113 in relation to the resistances aforesaid connected thereto, iny a manner well understood in the art.

For further minimizing hunting, a condenser 107 in series With rheostat 108, is bridged across the cutter tachometer 45, and a connection 114 tapped off from between them and extended through rheostat 115 and resistance 116 in series to the amplifier 62 input lead 61 at point 117. Thus should the voltage across tachometer 45 vary suddenly due to a change in speed or from any other causes, the rate at which the full effect of this change is impressed between the bridge points A--B will be reduced by the initial shunting action of the condenser 107 charging or discharging in series with the resistance of rheostat 108. In addition to this, it will be noted that the potential at point 114a of the resistance capacity circuit, is impressed over connection 114 and through resistance 65 onto bridge point A in a direction to oppose the potential imposed thereon with respect to point B, by the voltage change across the tachometer 45. By reason of both of these effects, a change in voltage generated by tachometer 45 due to a sudden change in speed, etc., will build up more slowly as an unbalance voltage between bridge points A-B and the input to amplifier 62, than otherwise in the absence of the anti-hunt circuits above discussed.

In order further to stabilize the system against hunting, a portion of the voltage generated in the generator, armature 73 due to an unbalance voltage originating across bridge points A-B, is impressed across the input to amplifier 62 in opposite polarity to that impressed thereon by the output of amplifier 111 as a result of the unbalance -in the bridge circuit. Thus the generator is connected between lead 52 and point 119. Bridged in series across it are a resistance 120, the fixed arm of a potentiometer 121 and a resistance 122. The variable arm 123 of the potentiometer 121, is connected through a rheostat 124 and thence in series through a high resistance 125 of about 1 megohm, and over connection 126 to the amplifier control grid input lead 61 at point 127. With this arrangement, any voltage generated in the generator armature will produce a fiow of current through the resistances 120-122, inc., bridging it, the portion of the voltage drop across which, occurring between connection 52 and the tapping point of the variable potentiometer arm 123, is impressed via leads 52 and 126, 61 across the input of amplifier 62. This feed-back voltage from the generator is impressed on amplifier 52 in a polarity opposite to that impressed thereon by the output of amplifier 111, as the result of a voltage difference developing across the bridge points AB. This feedback voltage tends to slow down the rate-of-change at which such voltage difference appears as a correcting voltage across the input to amplifier 62 for automatically rebalancing the bridge.

In order to control the rate at which the generator feedback voltage is impressed on the amplifier, a condenser 127 is connected from point 119 to a point between rheostat 124 and resistance 125. The condenser is thus bridged by the resistance in series comprising the rheostat 124, a variable portion of the xed arm of potentiometer 121 and resistance 120. The time constant of the resistance capacity circuit thus traced is adjusted by means of rheostat 124.

Assuming a time at which the generator is generating no voltage, condenser 127 will be fully discharged. If now a voltage appears across the generator armature as the result of an unbalance voltage across the bridge A--B, the full generator voltage will initially be impressed through condenser 127 and resistance 125 and between

leads

52 and 126, across the input tov amplifier 62, thus for the instant to minimize to the maximum extent, the effect of the correcting voltage applied from amplifier 111. However, as condenser 127 charges up, the fraction of the total voltage of the generator armature applied as a feed-back to amplifier 62, will decrease to that comprising, as above stated, the voltage drop between lead 52 and the variable arm 123 of the potentiometer.

The armature 128 of the shifter motor, in series with a protective fuse resistance 129 and contacts D-Z as explained below, is bridged between the generator terminal 119 and the variable arm 130 of a potentiometer 131 of a few ohms resistance, to serve as a ballast resistance in the thus formed closed circuit containing the generator and motor armatures.

In order to limit the maximum current flow in the motor-generator circuit, a connection 132 extends from the variable arm of the potentiometer 131, to one input terminal of a current limiter 133, the opposite input terminal of which is connected to lead 61, and thence over lead 126 and through potentiometer 121 and resistance 122 to lead 52, connected to the opposite terminal of the fixed arm of potentiometer 131 as shown. g

Should an excess voltage develop the bridge points A-B, the second amplifier stage 111 would become overloaded. To prevent this, circuit connections are provided which automatically bypass the first amplifier stage 110, under these conditions. These comprise a connection 135 from the input lead 53 to amplifier stage 110, having connected therebetween and a connection 136, a condenser 137, shunted by a resistance 138, in series with a two-way rectifier 139. The connection 136 extends to the upper output lead 111a of amplifier stage 110, and also through resistance 111e to the input lead 111b of amplier stage 111.

The rectifier 139 has a breakdown voltage such as to transmit at a potential applied to the input lead 53 of amplifier stage 11o that would overload amplifier stage 111. When this occurs the rectifier 139 breaks down and the potential on lead 53 is applied through resistance 138 and rectifier 139 to the input of amplifier stage 111 via resistance 111e and connection 111b. This effectively bypasses amplifier stage 110 inasmuch as when rectifier 139 is thus conducting, the high potential output lead of amplifier stage 110 is conductively connected back to its input lead 53 via the rectifier circuit.

As the potential builds up initially on input lead 53', condenser 137 charges up to breakdown voltage of rectifier 139, and thereupon discharges through the rectifier to effect the breakdown. Once breakdown is thus effected, the rectifier remains conductive down to a much lower minimum potential, as is well understood, before it again becomes non-conducting. The condenser 137 in conjunction with the resistance 138 functions as an integrator circuit which accumulates potential until the breakdown voltage of the rectifier is reached. A high resistance 140 of about 2 megohms is bridged between the input and output connections 111e and 55 of amplifier stage 111 to prevent blocking of the input control grid of this amplifier stage.

Bridged across the shifter generator armature 73 is a relay I in series with a resistance 14061, shunted by normally closed back contacts I-1 of a relay .T which is in turn bridged across the generator armature in series with a resistance 140b. This equipment will be explained below with reference to FIG. 3.

FIG. 3 illustrates diagrammatically the essential electrical circuit components of a control panel for the automatic regulating system of FIG. 1 as modified by FIG. 2. Referring to FIGS. l and 3, the thyratron rectifiers 67, 75, the phase shift bridge 67, and the power packs 54a and 62a, which energize the

D.C. amplifiers

54 and 62, are energized from individual phases of a three-phase source of power supplied over leads 143, FIG. 3,

components

62a, 65, 67 and 75, through a transformer 144, having input leads 145, connected to one of the phases, as at 146. Power pack 54a is connected over input leads 54h, to another ofthe phases, as at 148, FIG. 3.

A relay C connected in a start-stop circuit 149, controls through its normally open front contacts C-2, connection of power supplied over the input leads 143, to

circuits

146, 148, and to motor 73a, FIG. l, which drives the shifter generator armature, as well as motor which drives the armature 151 of the double facer generator which in turn drives the double facer motor 26, FIG. l; and also connects power to various blower motors not shown.

As shown in FIG. 3, the thyratron rectifier 75 supplies a direct current output voltage V41, over leads 152, 153, to the shunt field 154, of the shifter motor 35, FIG. 1, and also to the auxiliary field winding 72, of the shifter generator 71, FIG. 1. Rectifier 75 also supplies .a direct current output `voltage V-2, over leads 152, 155, to the control panel signaling and control circuits as discussed below.

Over-all energization of the system is initiated by depressing the start button 156, to energize the C relay which locks up through its front contacts C2 bridged across the start switch contacts, and also closes its front contacts C-1 to connect the input power leads 143 to the various components above mentioned. A time delay of about 45 seconds is required for the electronic panels thus energized to warm up.

Following the time delay, the selector switch 154, may be operated from its manual position as shown, to the automatic position shown dotted. This prepares a cir cuit over connection 160, bridging the power leads 152, 155, for energizing the D relayk to connect in the automatic regulating system of FIGS. 1 and 2 through closure of its D-1, D-2 contacts, FIG. 2. It will be observed, however, that connection 160, contains in series, the normally open lfront contacts F-1, G-1 and H-1 of relays F, Gand H, FIG. 3. i

The H relay which is contained in the thyratron rectier circuit 75, energizes to close contacts H-l as soon as the rectifier has warmed up. Relay F which is connected over lead 161 between the power leads 152, 155 through normally closed contacts I-1 of the I relay, FIG. 2, operates as soon as adequate minimum voltage is supplied to these power leads from rectifier 75. Relay G is tapped across a portion of a resistance 162 which isconnected via'leads 163 across the armature 15'1 of the double facer generator. This is a minimum Voltage operated relay which does not operate until generator 151 is supplying suicient power to motor 26, to drive the double facer at suiiicient speed to allow shifting of the sheet lengths cut from web 15, FIG. 1, without damage. This speed is about 90 feet per minute of travel of the web.

Accordingly, with the selector switch 154 in the automatic position, the speed of motor 26 can be increased to this proper operating minimum, by adjusting the field strength of generator 151, whereupon the G relayl will operate to close its contacts G-1, thereby to complete the circuit over lead 160 for energizing the D relay. The D relay thereupon operates and locks through its front cont-acts D-3 bridging contacts F-I of the F relay, and also closes its contacts D-1, D-2, FIG. 2, to connect in the automatic regulating system for operation. It also closes its front contacts D-4 on the control panel, FIG. 3, to

light the automatic on lamp 163, which is connected in lead 164 bridging the power leads through D-4 relay contacts. Operation of this lamp provides an indication to the operator that the automatic regulating system is now connected for operation.

A second pilot lamp 165 -is connected in lead 166 bridged between the power leads through normally closed contacts F-2 and D-5 in parallel of the F and D relays, respectively. The lighting of this lamp which is designated automatic operating, signals the operator that the automatic regulating system has not yet completed adjusting the sheet length in accordance with the setting of the sheet length rheostats 103, 104, FIG. 2, and that the shifter motor 128 is running to eect this adjustment. As above pointed out, at this stage of operation the D relay is actuated so that its D45 contacts .are open. However, lamp 165 may still be energized by the shunt path through the normally closed contacts F-2 of the F relay provided this'relay is released at this stage. y

The operating circuit for the F relay is through the back contacts I-1 of fthe I relay, which, Ias above explained, is bridged across the shifter generator armature in series with resistance 140e s'hunted by the back contacts I-l of the I relay, which in turn is bridged across the shifter generator armature in series with resistance 1401;. So long as the shifter generatory armature is supplying sucient voltage to energize the shifter motor, relays I and I will be energized, the former to open its back contacts I-1 and thus release the F relay, and thereby energize lamp 165 through the F-l back contacts of the F relay. Conversely, when the shifter generator voltage falls below the operating valaue for the shifter motor, relays I and I will release, relay F will be energized and lamp 165 extinguished. Relay J is merely ancillary Vto relay I for providing a current limitingV holding circuit for the latter through resistance a when relay I is operated.

Accordingly, `the lighting of the automatic on signal lamp advises the operator when the automatic regulating system is connected in for operation, while the lighting of the automatic operating signal lamp 163, advises the operator that the system is operating and adjusting the sheet length. When lamp 165 is thereafter extinguished, leaving lamp 163 lit, the operator knows that the automatic regulating system is'operating and that the sheet length has been set to the desired point.

Referring to FIG. 2, an additional set of sheet length adjusting and Calibrating legs containing resistors like 102404, inc., and 10S-106, inc., may be connected in parallel thereto, respectively, if desired, to allow the operator to set up the sheet length for the next operation, while a lirst sheet length is being cut. Provision ffor this is made on the -operating panel of FIG. 3, by the sheet length selector switch 170, operable to either of two positions for operation as

sheet length

1 or 2, as the case may be. Relays K and L are energized in the respective positions of the select-or switch over leads 171, 172, respectively. These relays have `front contacts K1 and L-1 in

connections

173 and 174, respectively, for

lighting lamps

175 or 176 to indicate which sheet length is lbeing run. In FIG. 2, the bridge oircuitis modied t-o incorporate this addition by inserting normally open contacts K-Z for relay K at points X-X of of FIG. 2, and by connecting in parallel to resistors 102-104, inc., and 105-106, inc., of FIG. 2, similar connections for the second sheet length setting having normally open Ycontacts L-Z for the relay interposed therein at points corresponding to X-X.

I-f the line speed o-f the web 15, FIG. l, falls below about 90 feet per minute, the automatic pilot light 163 will be extinguished by release of the D relay ydue to re lease of the G relay. This will require use of the manual sheet length adjustment provided by the pushbutton actuated motor 39, of FIG. l.

Reference to the control apparatus as applied to a cutoff produc-ing blanks of selected length, should be understood as comprehending other cutting, impressing and like tools operating periodically upon continuously fed material and where it is desired to correct irregularities in the period of frequency of operation of the tool as caused by irregularities in the feed of the material or in the speed at which the tool is driven, or both, insofar as the operating conditions and requirements are analogous to those met with in respect to cutois, and with'- in the range of equivalents afforded by the prior art. It should also 'be understood that changes may be -rnade in the above disclosed form of control apparatus without departing from the invention in its broader aspects, within the scope of the appended claims.

What is claimed is:

1. Cutoi or like Iapparatus of the character described `having means for progressively feeding thereto a web of matenial at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, -a periodically operating tool in `driven relation to said loutput shaft, a pair of tachorneters in direct idriven relation to said web and out put shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said adjusting mechanism to restore said ratio, said `means including a closed electrical circuit containing resistances in series with the voltage outputs of said tachometers, respectively, a pair of connections extending, respectively, from a point between said tachometer outputs .and a point of said resistance, and actuating means selectively responsive to the polarity and magnitude of a difference of potential arising between said connections for so actuating said adjusting mechanism.

2. Cuto or like 'apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rot-ary speed ratio of the output to the input shaft, means for ydriving the input shaft at a substantially constant speed, a periodically operating tool in -driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said ladjusting mechanism to restore sai-d ratio, said means including a closed electrical circuit containing resistances in series with the voltage outputs of said tachometers, respectively, a pair of connections extending, respectively, from a point between said tachometer outputs .and a point of said resistance, and actuating means selectively responsive to the polarity and magnitude of a ditference of potenti-al arising between said connections for so actuating said adjusting mechanism, said actuating means including -a reversible motor, `and means driven thereby 'for actuating said adjusting mechanism in direction and extent in accordance with the direction and extent of rotation o-f said motor.

3. Cutotf or like apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, a periodically operating tool in driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said adjusting mechanism to restore said ratio, said means including a closed electrical circuit `containing a pair of adjustableresistances in series with the 'voltage outputs of said tachometers, respectively, and said circuit also containing a fixed resistance, a pair of connections extending, respectively, from a point of said resistance and a point displaced therefrom having the same potential when said tachometer speeds conform to said preselected ratio, and actuating means responsive to the polarity and magnitude of a difference of potential arising between said connections for so actuating said adjusting mechanism.

4. Cutoff or like apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, a periodically operating tool in driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said adjusting mechanism to restore said ratio, said means including a closed electrical circuit containing a pair of adjustable resistances in series with the voltage outputs of said tachometers, respectively, and

said circuit also containing a iixed resistance, a pair of connections extending, respectively, from a point of said resistance and a point displaced therefrom having the same potential when said tachometer speeds conform to said preselected ratio, and actuating means responsive to the polarity and magnitude of a difference of potential arising between said connections for so actuating said adjusting mechanism, said actuating means including a reversible motor, and means driven thereby for actuating said adjusting mechanism in direction and extent in accordance with the direction and extent of rotation of Said motor.

5. Cutoff or like apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, a periodically operating tool in driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said adjusting mechanism to restore said ratio, said means including a closed electrical circuit containing a pair of adjustable resistances in series with the voltage outputs of said tachometers, respectively, and said circuit also containing a fixed resistance, a pair of connections extending, respectively, from a point between said tachometers to a point of said resistance, and actuating means responsibe to the polarity and magnitude of a difference of potential arising between said connections for actuating said adjusting mechanism.

6. Cutolf or like apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, a periodically operating tool in driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preselected ratio for actuating said adjusting mechanism to restore said ratio, said means including a closed electrical circuit containing a pair of adjustable resistances in series with the voltage outputs of said tachometers, respectively, and said circuit also containing a fixed resistance, a pair of connections extending, respectively, from a point between said tachometers to a point of said resistance, and actuating means responsive to the polarity and magnitude of a diiference of potential arising between said connections for actuating said adjusting mechanism, said actuating means including a reversible motor, and means driven thereby for actuating said adjusting mechanism in direction and extent in accordance with the direction and extent of rotation of said motor.

7. Cutoff or like apparatus of the character described having means for progressively feeding thereto a web of material at substantially constant speed, a variable speed transmission having output and input shafts and mechanism for adjusting the rotary speed ratio of the output to the input shaft, means for driving the input shaft at a substantially constant speed, a periodically operating tool in driven relation to said output shaft, a pair of tachometers in direct driven relation to said web and output 'i i shaft, respectively, means responsive to variations in the relative speeds of rotation of said tachometers from a preserected ratio for actuating said adjusting mechanism to restore said ratio, said means including a closed electrical circuit containing a pair of adjustable resistances in series with the voltage outputs of said tachometers, respectively,

and said circuit also containing a xed resistance, a pair Y of connections extending, respectively, from a point of said resistance and a point displaced therefrom having the same potential when said tachometer speeds conform to said preselected ratio, and actuating means selectively responsive to the polarity and magnitude of a difference of potential arising between said connections for so actuating said adjusting mechanism, said actuating means comprising a direct current amplier having an input to which said connections extend, and an output, a generator having an armature and main and auxiliary field windings, means connecting said main eld winding to said amplier output and said auxiliary eld winding to a direct current source of opposite polarity, means for driving said generator armature, and a reversible motor responsive to the generator output for selectively actuating the adjusting mechanism of said variable speed transmission in accordance with the direction and extent of rotation of said motor.

References Cited in the le of this patent UNITED STATES PATENTS 1,954,132 Iverson Apr. 10, 1934 1,991,083 Dean Feb. 12, 1935 2,023,243 Rhea et al Dec. 3, 1935 2,187,091 Morgan Ian. 16, 1940 2,298,877 Edwards et al Oct. 13, 1942 2,425,484 Murrah sAug. 12, 1947 2,580,959 Ropp Jan. 1, 1952 2,634,811 Schaelchlin Apr. 14, 1953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3O7l,999 January 8, 1963 Harry F. Thorn It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4, line 67, for .,Drectifer" read rectified column 5, line 2, for "energizing" read energized column 8, line Il, after develop insert across line 35,

after v'tom insert the column l0, line 8, for "vallaue" read value line 39, strike o ut "of", second Occurrence;

column l2, line 3l, for ,"responsibe" read responsive signed and Sealed'nhis 29th day of october 1963,

(SEAL) Attest:

ERNEST Wb SWIDER EDWIN Le* REYNOLDS Attesting Officer A@ i n@ Commissioner of Patents UNITED STATES PATENT oEEICE CERTIFICATE OF CGRRECTION Patent No. 3O7l999 January 8, 1963 Harry F. Thorn It is hereby certified that error' appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 7 for U"rectifier" read rectified column 5Y line 2 for "energizing" read energized column 8q line ll after "developo' insert across line 35, after 'to" insert m the column lO line 8, for "valaue" read value M; line 39 strike out "of'H1 second occurrence; column l2V line 3lY for 'responsibe" read responsive Signed and sealed` this 29th day of October 1963.

(SEAL) Attest:

ERNEST w SWTDEE @Wm L MILES Attesting Officer A@ i n@ Commissioner of Patents

Claims

1. CUTOFF OR LIKE APPARATUS OF THE CHARACTER DESCRIBED HAVING MEANS FOR PROGRESSIVELY FEEDING THERETO A WEB OF MATERIAL AT SUBSTANTIALLY CONSTANT SPEED, A VARIABLE SPEED TRANSMISSION HAVING OUTPUT AND INPUT SHAFTS AND MECHANISM FOR ADJUSTING THE ROTARY SPEED RATIO OF THE OUTPUT TO THE INPUT SHAFT, MEANS FOR DRIVING THE INPUT SHAFT AT A SUBSTANTIALLY CONSTANT SPEED, A PERIODICALLY OPERATING TOOL IN DRIVEN RELATION TO SAID OUTPUT SHAFT, A PAIR OF TACHOMETERS IN DIRECT DRIVEN RELATION TO SAID WEB AND OUTPUT SHAFT, RESPECTIVELY, MEANS RESPONSIVE TO VARIATIONS IN THE RELATIVE SPEEDS OF ROTATION OF SAID TACHOMETERS FROM A PRESELECTED RATIO FOR ACTUATING SAID ADJUSTING MECHANISM TO RESTORE SAID RATIO, SAID MEANS INCLUDING A CLOSED ELECTRICAL CIRCUIT CONTAINING RESISTANCES IN SERIES WITH THE VOLTAGE OUTPUTS OF SAID TACHOMETERS, RESPECTIVELY, A PAIR OF CONNECTIONS EXTENDING, RESPECTIVELY, FROM A POINT BETWEEN SAID TACHOMETER OUTPUTS AND A POINT OF SAID RESISTANCE, AND ACTUATING MEANS SELECTIVELY RESPONSIVE TO THE POLARITY AND MAGNITUDE OF A DIFFERENCE OF POTENTIAL ARISING BETWEEN SAID CONNECTIONS FOR SO ACTUATING SAID ADJUSTING MECHANISM.