US3463082A - Offset printing machine with wiping sheet for removing ink from blanket cylinder - Google Patents

Description

Aug. 26, 1969 H. KUFEIQ 3,463,082

OFFSET PRINTING MACHINE WITH WIPING SHEET FOR REMOVING INK FROM BLANKET CYLINDER Filed April 5,' 1966 3 Sheets-Sheet 1 Fig] ,8a 18. 79 2] i 77 2069a -O 20a L /9 o 23 a 33 9.25 seb 3359 31a 336 `4 sbgbovw' I W13? 7erir l L39 R I 4g l Il, I 24e 36e m4 2% m 2 4l \l \\`30 36d 7 a f '0l 3.23.1 43 .38 ,4d 24a 4 24h 9b \;`2\92 73 l ,l 9 27 l 23 29 42 z: f

IN V EN TOR.

HELMUT KUFER Aug. 26, 1969 H. KUFf-:R 3,453L032 OFFSET PRINTING MACHINE WTH WPING SHEET FOR REMOVING v INK FROM BJANKFT CYLINDER Filed Aprilia, 1966 5 Sheets-Sheet 2 INVENTOR.

HELMUT KAUFER Aug. 26, 1969 H, KUFER 3,463,082

OFFSET PRINTING MACHINE WITH wIPING SHEET FOR REMOVING INK FROM BLANKET CYLINDER Filed April 5, 1966 3 'Sheets-Sheet 3 INVENTOR.

H11-LMU? KUFER BY Mum! ff/iw United States Patent O 3,463,082 FFSET PRINTING MACHINE WITH WIPING SHEET FOR REMOVING INK FROM BLAN- KET CYLINDER Helmut Kufer, Metzkausen/uber Mettmann, Germany,

assigner to Agfa-Gevaert Aktiengesellschaft, Leverkusen, Germany Filed Apr. 5, 1966, Ser. No. 540,291 Claims priority, application Germany, Apr. 15, 1965,

rat. Cl. B411? 9/08, 13/24 U.S. Cl. lill-144 18 Claims ABSTRACT F THE DISCLOSURE The present invention relates to offset printing machines in general, and more particularly to improvements in cleaning or wiping devices for removing ink from the blanket of the rubber blanket cylinder in an offset printing machine. Still more particularly, the invention relates to improvements in wiping or cleaning devices for rubber blanket cylinders which are especially suited for use in comparatively small offset printing machines of the type normally employed in oices and similarestablishments to produce relatively small numbers or stacks of printed copies.

It is well known that the blanket of the rubber blanket cylinder in an offset printing machine must be cleaned to remove remaining ink prior to insertion of a 'fresh master sheet. Proper cleaning of the blanket takes up considerable time; in fact, such cleaning can take up an interval of time which is a multiple of the time required to produce a relatively small number of printed copies.

Accordingly, it is an important object of the present invention to provide an improved offset printing machine wherein the removal of ink from the exposed surface of the blanket of a rubber blanket cylinder requires very little time and wherein such removal can take place immediately after the printing operation is completed so that the still wet or moist ink can be removed without resorting to solvents.

Another object of the invention is to provide the improved machine with a novel foil which can be used as a master sheet, as a wiping device for the blanket, and as a back support for fresh copy sheets during actual printing.

A further object of the invention is to provide the improved offset printing machine with a foil of the just outlined characteristics and to provide the foil with very simple and reliable anchoring means to facilitate its attachment to or disconnection from suitable clamping devices on the master cylinder of the machine.

An additional object of the instant invention is to provide the offset printing machine with a very simple but reliable and compact control unit which can be readily manipulated by semiskilled persons and which can convert the machine from printing to wiping or vice versa.

A concomitant object of the invention is to provide the offset printing machine with a novel master cylinder which, in addition to being capable of transferring ink to the blanket, is also capable of carrying a wiping de- Mice vice for the blanket and of serving as a back support for fresh copy s'heets during printing.

Still another object of the invention is to provide the machine with a wiping device for the blanket of the rubber blanket cylinder and to construct and mount the wiping device in such a way that it can also perform at least one additional important function, particularly of serving as a back support for fresh copy sheets during actual printing or as a back support during writing or otherwise applying images to the master sheet.

A further object of the invention is to provide an offset printing machine wherein the wiping device for the blllanket can be caused to switch places with the master s eet.

Brieily stated, one feature of my invention resides in the provision of an offset printing machine which cornprises a rotary rubber blanket cylinder, a rotary master cylinder and platen unit which may comprise a single cylinder or a separate master cylinder and a separate platen cylinder and whose purpose is to respectively transfer inked images to and to constitute a back support for the blanket cylinder, an image-transferring master sheet, a cleaning or wiping sheet for removing ink from the blanket of the blanket cylinder, and clamping means detachably securing the sheets to the aforementioned unit.

In accordance with a more specific feature of my invention, the unit can comprise a single cylinder and the clamping means then comprises two clamping devices provided on such single cylinder. The two sheets are then preferably combined into a single foil which can be applied around the periphery of the single cylinder in such a way that both sheets remain exposed or that one of the sheets is withdrawn into the interior of the single cylinder when the other sheet is exposed or vice versa. The machine further preferably comprises suitable control means including selector means for moving the blanket cylinder into contact with the one or the other sheet, depending upon whether the machine is set for printing or for cleaning of the blanket on the blanket cylinder. The wiping sheet may also serve as a back support for fresh copy sheets at the time such copy sheets are being fed into and pass through the bite between the blanket cylinder and the cylinder which carries the wiping sheet.

Alternatively, the machine may comprise a unit which is composed of two cylinders, namely a master cylinder which carries the master sheet and a platen cylinder which carries the wiping sheet. When the machine is in actual use to print images on copy sheets, the blanket receives inked images from the master sheet and the platen cylinder (and more particularly the wiping sheet thereon) serves as a back support for such fresh copy sheets. In order to clean the blanket, the master sheet is moved away from contact with the blanket and the feed of fresh copy sheets is interrupted so that the wiping sheet automatically removes all surplus ink from the exposed surface of the blanket.

The novel features which are considered as characteristic of the invention are aet forth in particular in the appended claims. The improved offset printing machine itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawings, in which:

FIG. l is a partly elevational and partly vertical sectional view of an offset printing which embodies one form of my invention, the section being taken in the direction of arrows as seen from the line I-I of FIG. 2;

FIG. 2 is a fragmentary horizontal section substantially 3 as seen in the direction of arrows from the line II-II of FIG. 1;

FIG. 3 is a fragmentary vertical section through a portion of a modified offset printing machine wherein the wiping sheet is carried by a platen cylinder;

FIG. 4 is a transverse section through a master cylinder which is provided with means for selectively exposing the master sheet or the wiping sheet;

FIG. 5 is a similar transverse section through a further master cylinder and illustrates the foil prior to attachment of the master sheet to the corresponding clamping device;

FIG. 6 is a similar section and illustrates the foil in fully applied position with the master sheet exposed; and

FIG. 7 is a similar section but showing the wiping sheet in exposed position.

Referring irst to FIGS. l and 2, there is shown an off* set printing machine comprising a frame 1 which supports a rotary shaft 2 for a unit including a single combined master, cleaning or wiping and platen cylinder 4, hereinafter called master cylinder. A diametral pin 3 connects the master cylinder with the shaft 2 so that the parts 2 and 4 rotate as a unit. The master cylinder 4 is provided with clamping devices 5 and 6 for a combined master and wiping or cleaning foil 7, the latter being applied around the periphery of the master cylinder and being composed of two portions or sheets 7a and 7b. The master sheet 7a is indicated by broken lines and its impression surface serves as a carrier of the image which is to be transferred to the rubber blanket 12 of a second or rubber blanket cylinder 11. The sheet 7b serves as a cleaning or wiping device and is indicated by a corrugated or undulate line because its exposed surface is rather rough. The clamping devices 5 and 6 may be of the well known type, for example, each such clamping device may comprise a spring biased anchor bar which is provided with hooked projections extending into openings provided therefor in the scalloped edge portions of the sheet 7a and 7b. It will be noted that the clamping devices 5 and 6 are accommodated in a recess provided in the periphery of and extending in parallelism with the axis of the master cylinder 4. The length of the foil 7 and the combined width of clamping devices 5, 6 together approximate the circumferential length of the cylinder 4.

The frame 1 further supports a second shaft 8 which is parallel with the shaft 2 and carries one end of each of two rocker arms or holders 9 whose other ends carry the shaft 10 of the rubber blanket cylinder 11. The latter carries the aforementioned blanket 12 whose edges are held by suitable clamping devices of known design. As shown in FIG. l, the blanket 12 is wrapped around the cylinder 11 and its clamped edge portions extend into an axially parallel recess provided in the periphery of the cylinder 11. The diameter of the rubber blanket cylinder 11 equals half the diameter of the master cylinder 4. The holders 9 are biased by springs 13 which tend to rock them in a counter-clockwise direction, as viewed in FIG. 1, so that the blanket 12 is normally urged against the foil 7 on the cylinder 4. FIG. 1 merely shows one of the holders 9 and a single spring 13.

One end face of the cylinder 4 carries a specially congurated face cam 14 whose endless cam groove comprises a first arcuate portion 14a which is more remote from the shaft 2 and a second arcuate portion 14b which is nearer to the shaft 2. The cam 14 forms part of a control assembly. The two cam groove portions 14a, 14b are connected with each other by two intermediate groove portions 14C, 14d which serve to guide a pin-shaped follower 15 in such a way that the latter can rapidly move from the groove portion 14a into the groove portion 14b or vice versa without being subjected to excessive shocks. The cam groove portions 14a and 14b are respectively coextensive (more or less) with the sheets 7a and 7b of the foil 7 on the master cylinder 4. As stated before, the configuration of the intermediate cam groove portions 14C, 14d is such that the follower 15 can rapidly advance from the groove portion 14a to the groove portion 14b or vice versa, i.e., in response to a relatively small angular displacement of the master cylinder 4.

A third shaft 14, fixed to the frame 1, supports a roller-shaped applicator 17 which forms part of an inking unit and serves as a means for distributing coloring matter (hereinafter called ink for short) along the periphery of a coating or inking roller 21 which can come in direct contact with the master sheet 7a. The applicator 17 can receive ink from a withdrawing roller 18 through the intermediary of a rockable ductor roller 19 mounted on a rocker arm 19a. The ductor roller 19 is located in the space between the applicator 17 and withdrawing roller 18, and the latter is driven to withdraw ink from a fountain or source 18a. The rate at which the ductor roller 19 can transfer ink from the withdrawing roller 18 to the applicator 17 is adjustable in a manner not forming part of the present invention. The applicator 17 is in rolling contact with a moistening or wetting roller 33 which forms part of a wetting unit and draws a film of liquid from a source or tank 32 to apply such film of liquid over the layer of ink which is transferred by the ductor roller 19. The shaft 16 for the applicator 17 supports two swingable levers or carriers 20 (only one shown in FIG. l) which are provided with aligned elongated slots 20a for the shaft of the inking roller 21 so that the latter can reciprocate toward and away from the shaft 16. The shaft of the inking roller 21 is biased by springs 22 which maintain the periphery of the inking roller 21 in permanent contact with the periphery of the applicator 17. The free ends of the carriers 20 are biased by springs 23 which tend to maintain the inking roller 21 in permanent rolling contact with the master sheet 7 on the cylinder 4.

The follower 15 is mounted on a motion transmitting lever 24 which is rockable on a pin 25 fixed to the frame 1. This motion transmitting lever 24 is coupled with a push rod 26 by means of a pivot pin 26a which extends through a lug 24a of the lever 24. The push rod 26 is also coupled with a rockable lever or link 69 having a projection 69a engaging one of the carriers 20 and serving to move the inking roller 21 away from the master cylinder 4 as soon as the follower 15 enters the cam groove portion 14a, i.e., as soon as the wiping sheet 7b travels below the inking roller. In this way, the push rod 26 and link 69 prevent transfer of ink to the wiping sheet 7b.

The lever 24 is provided with two cam faces 24b, 24e which are disposed at the opposite sides of the pivot pin 25 and each of which can be engaged by the free end of a regulating link 27 forming part of a selector unit and being pivotally connected with an intermediate portion of one of the holders 9. The selector unit further comprises a connecting link 28 which is articulately coupled to an intermediate portion of the regulating link 27 and to one arm 29a of a three-armed selector lever 29 rockable on a frame-supported pin 30. Another arm 31 of the selector lever 29 has a knob-like index 31a which can be moved by hand into registry with one of a series of graduations D, V, N and R provided on the frame 1. Furthermore, the index 31a is slidable in an arcuate guide slot 31b of the frame 1. In the illustrated position, the index 31a registers with the graduation V which means that the machine is set for preinking of the master sheet 7a. The regulating link 27 engages the cam face 24o of the motion transmitting lever 24. Therefore, the blanket 12 of the cylinder 11 will move into contact with the master sheet 7a of the foil 7 during each revolution of the master cylinder 4. Also, the blanket 12 will move away from the wiping sheet 7b during each revolution of the master cylinder 4. On the other hand, the inking roller 21 moves into engagement with the master sheet 7a during each revolution of the master cylinder 4 so that the image on the sheet 7a transfers ink to the exposed surface of the blanket 12 during each revolution of the master cylinder 4. In other words, all of the symbols carried by the sheet 7a are reproduced on the exposed surface of the blanket 12.

The frame 1 further supports two guide pins 34, 35 which extend into elongated guide slots 36a, 36b of a slide 36 forming part of a feed unit. The slide 36 is biased by a spring 37 which tends to move it in a direction to the left, as viewed in FIG. 1. A guide 36C of the slide 36 accommodates a portion of a reciprocable arm 36d also forming part of the sheet feeding unit which latter further comprises a sheet advancing or feeding roll 38. A pusher or trip 39 carried by the right-hand portion of the slide 36 can engage the arm 24d of the motion transmitting lever 24. The trip 39 is mounted on a pivot pin 40 of the slide 36 and is rockable about the pin 40 by a link 41 which is articulately coupled to the arm 29h of the selector lever 29.

If the index 31a of the selector lever 29 is moved into registry with the graduation D on the frame 1, the machine is set for printing. The trip 39 then engages the arm 24d of the motion transmitting lever 24 and, at the same time, the regulating link 27 is rocked in a clockwise direction, as viewed in FIG. 1, and moves beyond (to the right of) the cam face 24C. Therefore, the blanket 12 of the cylinder 11 remains in continuous contact with the foil 7, i.e., not only with the master sheet 7a but also with the wiping sheet 7b. Also, and since the trip 39 on the slide 36 engages the arm 24d of the motion transmitting lever 24, the slide 36 is caused to move in a direction to the right whenever the lever 24 is rocked in a clockwise direction, i.e., whenever the follower 15 moves from the cam groove portion 14a into the cam groove portion 14b. Therefore, the advancing roll 38 shifts the topmost copy sheet 43 of the stack on the supporting platform or table 42 in a direction to the right and advances such topmost sheet into the bite between the cylinders 4 and 11, namely, between the foil 7 and blanket 12. In such position of the index 31a, the wiping sheet 7b merely serves as a platen or back support for fresh copy sheets 43 during printing. The blanket 12 transfers printed matter to the underside of the thus advanced copy sheet 43 and thereupon advances the properly imprinted copy sheet into a receiving rack or collector here shown as an inclined tray 44.

When the follower 15 moves from the cam groove portion 14b into the cam groove portion 14a, the motion transmitting lever 24 is rocked in a counterclockwise direction, as viewed in FIG. 1, whereby the spring 37 is free to retract the slide 36 in a direction to the left and back to its starting position. The slide 36 remains in such starting position during the entire interval in the course of which the follower 15 travels in the ca-m groove por tion 14a. Thus, no copy sheet 43 can be fed during such interval so that the blanket 12 on the cylinder 11 can roll along the master sheet 7a and the latter applies thereto ink to replace ink which was removed during printing of the preceding copy sheet.

If the inking of the blanket 12 and the production of printed copy sheets 43a is to be terminated or interrupted, the index 31a will be shifted into registry with the graduation N whereby the regulating link 27 engages a median cam face 24e of the lever 24 which is located between the cam faces 24b, 24C. The position of the cam face 24e is such that its portions perform negligible radial movements with reference to the pin 25 when the motion transmitting lever 24 is rocked in response to travel of the follower 15 in the composite cam groove of the face cam 14. The distance between the cam face 24e and the pin 25 is selected in such a way that, when the cam face 24e is engaged by the upper end portion of the regulating link 27, the latter holds the blanket 12 out of contact with the foil 7, i.e., the holder 9 is rocked in a counterclockwise direction. At the same time, the arm 29h of the selector lever lifts the link 41 so that the latter maintains the trip 39 out of contact with the arm 24d of the lever 24 whereby the slide 36 remains in its starting position and the roll 38 cannot feed fresh copy sheets 43 into the bite between the cylinders 4 and 11.

If the operator moves the index 31a into registry with the graduation R (wiping or cleaning), the regulating link 27 is moved into engagement with the cam face 24b of the lever 24. Consequently, the blanket 12 is moved away from the foil 7 (master sheet 7a) when the follower 15 enters the cam groove portion 14a but will engage the wiping sheet 7b when the follower 15 enters the cam groove portion 14h. In other words, during each revolution of the master cylinder 4, the blanket 12 comes into rolling Contact with the wiping sheet 7b but not with the master sheet '7a. When the index 31a is shifted from registry with the graduation N into registry with the graduation R, the trip 39 is rocked in a clockwise direction, as viewed in FIG. l, and moves even farther away from the arm 24d of the lever 24 so that the feed unit including the slide 36 and roll 38 remains idle. As the master cylinder 4 continues to rotate, all remaining ink on the exposed surface of the blanket 12 is rapidly transferred onto the exposed surface of the wiping sheet 7b so that the blanket 12 is rapidly cleaned.

FIG. 2 shows that the front end portion of the shaft 2 for the master cylinder 4 extends beyond the frame 1 and carries a manually operable manipulating member in the form of a hand wheel 45 which is secured thereto by a radial pin 46, A screw 47 serves to hold the hand wheel 45 `against excessive axial movement away from the shaft 2. The pin 46 extends into and is slidable in an axially parallel peripheral groove 2a of the shaft 2. The hand wheel 45 has some freedom of axial move-ment with reference to the shaft 2 and is biased in a direction toward the frame 1 by a corrugated annular dished spring 47 interposed between the head of the screw 47 and the hub of the hand wheel. This hub carries a first clawed clutch element 45a which is biased by the spring 48 into motion receiving engagement with a complementary clawed clutch element 50a provided on a gear 50, the latter being rotatably supported by the shaft 2 between the frame 1 and the adjoining end portion of the master cylinder 4. The gear 50 serves to provide a driving connection between the cylinders 4, 11 and its teeth 50b mesh with the teeth of :a complementary driver gear (not shown) on the shaft lll of the cylinder 11 to insure that the two cylinders rotate at the same peripheral speed. The diameter of the pitch circle of the gear 50 equals the diameter of the master cylinder 4, and the same holds true for the driver gear and cylinder 11. If the operator decides to pull the hand wheel 45 `against the bias of the spring 43, i.e., in a direction indicated in FIG. 2 by arrow A, the clutch elements 45a, 50a are disengaged from each other and the driving connection between the cylinders 4, 11 is terminated. The hand wheel 45 can be utilized to change the angular position of the master cylinder 4 with reference to the cylinder 11 so that the operator can readily move different portions of the wiping sheet 7b into contact with different portions of the exposed surface on the blanket 12 to thereby insure complete removal of ink from the blanket. For example, the cylinder 11 may be rotated at a constant speed by a drive including an electric motor or another suitable prime mover, :and the operator will manipulate the hand wheel 45 to respectively disengage and reengage the gear 50 with the driver gear on the shaft 10, such reengagement taking place subsequent to angular displacement of the cylinder 4 with reference to the cylinder 11. Actually, the operator must only pull the hand wheel 45 in the direction of the arrow A because the angular position of the cylinder 11 (which is driven) changes automatically as soon as the clutch including the elements 45a, 50a is rendered ineffective. Also, the person in charge need not fear that he would accidentally reengage the cylinders 4, 11 in an angular position in which the blanket 12 would come into contact with the master Sheet 7a because the follower 15 remains in the groove of the cam 14 and thus automatically prevents direct contact between the sheet 7a and blanket 12. The same holds true for the inking roller 21 which is invariably lifted away from the cylinder 4 as soon as the follower 1S leaves the cam groove portion 14b to enter the cam groove portion 14a.

A very important advantage of the machine shown in FIGS. l and 2 is that cleaning or wiping of the blanket 12 requires very little time and also that the wiping sheet 7b can be reused as often as desired, i.e., as long as the foil 7 remains attached to the master cylinder 4. All that an operator has to do is to shift the selector lever 29 to a position in which the index 31a registers with the graduation R and the wiping operation proceeds in a fully automatic way while the feed of fresh copy sheets 43 and the transfer of ink to the master sheet 7a remain interrupted. The selector lever 29 may be shifted while the machine is in actual use so that the transition from printing to wiping or vice versa can be effected without necessitating any manipulation of control elements which start or arrest the prime mover of the machine. The wiping sheet 7b is expendable and may be produced at low cost lbecause it need not meet any special requirements excepting that it should be capable of collecting ink which remains on the exposed surface of the blanket 12. Thus, whenever the master sheet 7a is to be discarded or replaced by another master sheet, the wiping sheet 7b is discarded with the master sheet. Due to the fact that the improved machine can accommodate a foil 7 which in part serves as a master sheet and in part as a wiping sheet for the blanket 12, the machine need not be equipped with any other cleaning or wiping devices so that its dimensions may be reduced considerably. Furthermore, and since the cleaning or wiping operation can begin as soon as the printing of a selected number of fresh copy sheets 43 is completed, the wiping sheet 7b can remove ink which is still wet or moist so that such removal can take place without resorting to solvents which are necessary in many presently known types of Offset printing machines wherein ink remaining on the blanket is allowed to harden. All that is necessary is to construct the control system of the machine (including the drive for the cylinders 4, 11 and the assembly of levers, links, slides, trips and similar elements shown in FIGS. 1 and 2) in such a way that the wiping operation can be started immediately following completion of a printing operation. Thus, all that is necessary is to control movements of the cylinder 11 toward and away from the foil 7 in such a way that the cylinder 11 can move into repeated contact with the wiping sheet 7b but is held out of contact with the master sheet 7a. It is further clear that the length of the wiping sheet 7b need not equal the length of the master sheet 7a. However, it is advisable to utilize a wiping sheet having a certain minimum length in order to make sure that the material of the wiping sheet can remove all such ink which remains on the blanket 12 upon completed printing of crowded images onto copy sheets 43, i.e., When the image transferred onto the blanket 12 occupies a substantial percentage of its exposed surface.

The fact that the wiping sheet 7b can serve as a back support for the blanket 12 when the latter transfers an image onto a freshly admitted copy sheet 43 is not detrimental for the quality of prints. As a matter of fact, and since the material of the wiping sheet 7b is preferably of felt-like consistency, this wiping sheet constitutes a more satisfactory back support than a metallic body such as is employed in many presently known small offset printing machines.

The effective length of the wiping sheet 7b is shown as being at least equal to the effective length of the master sheet 7a, i.e., the wiping sheet can be brought into ink removing contact with all such portions of the blanket 12 which come into contact with the master sheet. Therefore, it normally suffices to bring the 'blanket 12 into repeated rolling contact with the sheet 7b whereby the latter reliably removes all surplus ink from the exposed surface of the blanket, especially if the wiping action follows the printing operation without delay. The manually operable wheel 45 will be manipulated only as a precautionary measure or when the operator notes that some ink continues to adhere to the blanket 12 after the cylinders 4, 11 have performed several revolutions subsequent to movement of the index 31a into registry with the graduation R.

In the event that the improved offset printing machine comprises a separate platen cylinder, i.e., that the wiping sheet 7b need not act as a back support, a cleaning action between the exposed surface of the wiping sheet 7b and the exposed surface of the blanket can be achieved by constructing the master cylinder 4 in such a way that the portion of this cylinder which carries the sheet 7b has a different radius than that of the pitch circle of the gear 50. The difference between the two radii equals the thickness of the sheet 7b. In such a modified machine, the platen cylinder will be rocked to operative position and the feed unit will Ibe rendered operative when the index 31a registers with the graduation V. The cleaning or wiping operation will take place when the index 31a registers with the graduation R.

FIG. 3 illustrates a portion of a further offset printing machine which comprises a rubber blanket cylinder 63 and a platen cylinder or back support 64. The latter is provided with two releasable clamping devices 65, 66 for a wiping sheet 67 which surrounds the major part of the peripheral surface of the cylinder 64. This cylinder 64 is also formed with a recess or cutout which extends between the clamping devices 65, 66 and accommodates a conventional paper gripper 68. FIG. l shows that the cylinder 11 carries a similar gripper. The gripper 68 of FIG. 3 is rockable in synchronism with rotation of the cylinder 64 and with operation of the feed unit so that it can grip the leading edge of the topmost fresh copy sheet 43 when the latter is advanced from the table 42 by the feed roll 38. For example, the gripper 63 may be permanently biased by a spring and may be controlled by a suitable fixed cam in a manner well known from the art of offset printing machines. Its purpose is to draw the copy sheets 43 through the bite between the cylinders 63, 64 and to release each freshly printed sheet 43a in good time so that such printed sheets 43a can accumulate in the tray 4-4.

When the nking of the blanket 63a on the cylinder 63 and the feed of fresh copy sheets 43 is interrupted in a manner as described in connection with FIGS. 1 and 2, the remaining ink may be rapidly removed from the exposed surface of the blanket 63a by repeated contact with the exposed surface of the wiping sheet 67. Such removal of remaining ink can be completed in response to a few revolutions of the cylinders 63, 64.

The cleaning or wiping effect may be improved considerably if the shaft 64a of the platen cylinder 64 carries a clutch which can be disengaged by a readily accessible hand wheel similar to the hand wheel 45 of FIGS. l and 2 in order to change the angular position of the cylinder 64 with reference to the cylinder 63. The two cylinders are normally coupled for rotation at the same peripheral speed and the just mentioned clutch enables the operator to change the angular position of the cylinder 64 by equal or nearly equal increments to move different surface portions of the blanket 63a into contact with different portions of the exposed surface on the wiping sheet 67. The cylinder 63 may be driven at a constant speed by a drive including an electric motor, a hand crank or another suitable prime mover.

In order to avoid damage to the blanket 63a, the recess between the clamping devices 65, 66 should be deep enough to accommodate the gripper 68 in each of the latters angular positions, i.e., this gripper 68 should not extend beyond the outline of the cylinder 64. It is equally possible to provide a control system which automatically increases the the distance between the cylinders 63, 64 when the gripper 68 approaches the blanket 63a. Itis further important to ultimately recouple the cylinders 63, 64 in such angular positions that the operation of the gripper 68 is again synchronized with the operation of the feed unit including the advancing roll 38. This can be readily achieved by resorting to a conventional one-tooth clutch which insures accurate engagement of its elements only when the cylinders 63, 64 are moved to desired angular positions with reference to each other.

Otherwise, the operation of the offset printing machine shown in FIG. 3 is analogous to that of the previously described machines. Of course, the master cylinder of this machine need not carry a wiping sheet 7b. A very irnportant advantage of the embodiment shown in FIG. 3 is that the wiping sheet 67 can constitute an exceptionally satisfactory back support for the copy sheets 43 which are being fed into the bite between the cylinders 63, 64. Also, the cleaning or wiping operation can be initiated in a very simple and time-saving manner. All that is necessary is to interrupt the feed of fresh copy sheets 43 whereby the exposed surface of the blanket 63a is free to come in direct Contact with the wiping sheet 67.

FIG. 4 shows a further master cylinder 52 which can replace the master cylinder 4 of FIGS. l and 2. This master cylinder carries a modified foil 7 having a master sheet 7a and a wiping or cleaning sheet 7b. The interior of the cylinder 52 is hollow and accommodates two clamping devices in the form of collecting drums or reels 5l, 53. The drum 51 is provided with an axially parallel peripheral clamping groove 51a which receives and retains one edge portion of the wiping sheet 7b. The axially parallel peripheral clamping groove 53a of the drum 53 receives and retains one edge portion of the master sheet 7a. The drum 53 is normally held against rotation in one direction (namely, in a direction to pay out the master sheet 7a') by a one-way clutch including a ratchet wheel 54 and a pawl 55. A similar one-way clutch including a ratchet wheel 56 and a pawl 57 holds the drum 51 against rotation in a sense to pay out the wiping sheet 7b'. ln the illustrated position, the wiping sheet 7b extends along the entire circumference of the master cylinder 52. If the master sheet 7a is to be moved to operative position, the operator disengages the pawl 55 from the ratchet wheel 54 and the drum 51 is rotated by means of a knob or the like (not shown) in a sense to collect the wiping sheet 7b whereby the latter unwinds the master sheet 7a and causes it to surround the periphery of the drum 52. In other words, in order to switch from transfer of ink from the master sheet 7a' to the non-illustrated blanket over to cleaning of the blanket by means of the wiping sheet 7b' or vice versa, the operator manipulates the one-way clutch 54, 55 or 56, 57 and thereupon rotates the drum 51 or 53 in a sense to collect the sheet 7a or the sheet 7b. While the solution shown in FIG. 4 requires additional manual work, it brings about considerable simplification of the control arrangement in the offset printing machine because the rubber blanket cylinder need not be moved away from the master cylinder 52.

The diameter of the master cylinder S2 can be the same as that of the cooperating rubber blanket cylinder, not shown. The machine which embodies the master cylinder 52 need not be provided with a special control system. All that is needed to start a cleaning operation is to arrest the drive and to thereupon manipulate the one-way clutch 54, 55 so that the wiping sheet 7b can be moved to operative position as actually shown in FIG. 4, i.e., that the wiping sheet surrounds the cylinder 52. The drive is thereupon started anew and the cleaning operation begins in a fully automatic way. It is clear that the driving connection between the blanket cylinder and the master cylinder 52 of FIG. 4 can also include a manually engageable or disengageable clutch to allow for placing selected portions of the wiping sheet 7b into contact with selected portions of the blanket in the same way as described in connection CTI l0 with the clutch 45a, 50a of FIG. 2. The prime mover of the machine is preferably coupled with the blanket cylinder and the aforementioned clutch transmits rotary motion to the master cylinder 52.

Referring finally to FIGS. 5 to 7, there is shown another master cylinder 59 which is provided with an axially parallel recess or cutout 59a. The cylinder 59 is mounted on a shaft 58 which also carries a cylindrical core 60 performing the function of drums S1, 53 shown in FIG. 4. The core 60 is mounted on the shaft 58 and is provided with two axially parallel clamping devices 61, 62 for a foil 7". The clamping devices 61, 62 are accessible through the cutout 59a when the core 60 is rotated (by a suitable handgrip means, not shown) to assuem the angular position shown in FIG. 5. One edge portion of the wiping sheet 7b" is then attached to the clamping device 61 and the core 60 is rotated through a full revolution in a direction indicated by the arrow B. This moves the sheet 7b into the annular clearance or gap between the cylinder 59 and drum 6o so that the sheet 7b" is fully concealed whereas the master sheet 7a remains exposed and can be wrapped around the periphery of the cylinder 59 (see the arrow C in FIG. S). Once the free edge portion of the master sheet 7a is attached to the clamping device 62, the master cylinder 59 assumes the position shown in FIG. 6y and the master sheet 7a is ready to transfer an image to the non-illustrated blanket.

Prior to wiping of the blanket, the core 60 is rotated in the direction indicated by the arrow D (see FIG. 7) whereby the clamping device 62 retracts the master sheet 7a" into the annular gap between the parts 59, 60 and exposes the wiping sheet 7b so that the latter is ready to wipe olf ink from the exposed surface of the blanket. It will be seen that the solution shown in FIGS. 5 to 7 is analogous to the solution of FIG. 4, i.e., the master cylinder 52 or 59 is provided with means (51, 53 or 60) flr selectively concealing the master sheet or the wiping s eet.

In order to convolute the master sheet 7a of FIG. 5 onto the exposed surface of the master cylinder 59, the cylinder 59 and the core 60 may be rotated as a unit in a counterclockwise direction. A very important advantage 0f the structure shown in FIGS. 5 to 7 is that the core 60 may be equipped with conventional clamping devices. Furthermore, a single revolution of the core 60 with reference to the cylinder S9, or vice versa, suffices to expose the sheet 7a" or 7b. Therefore, such core can be readily coupled to a rather simple control device (not shown) which automatically exposes the wiping sheet 7b" when the printing operation is completed and which can automatically retract the wiping sheet when the printing operation begins. Such a control device can turn the core 60 with reference to the cylinder 59 while the offset printing machine is in actual use.

The foil 7, 7 or 7 is preferably dirnensioned in such a way that the area of the master sheet 7a, 7a' or 7a" at least approximates the area of the wiping sheet 7b, 7b or 7b. The two sheets can be separated from each other by a fold 7c shown, for example, in FIG. 4. The free transverse edge portions of the sheets 7a, 7b or 7a', '7b' or 7a, 7b are preferably provided with anchoring means to facilitate their attachment to suitable clamping devices. The anchoring means may be constituted by openings provided in such edge portions or each such edge portion may be thickened or otherwise reinforced by a rib or bead to be readily held by a conventional clamping device.

The foil 7, 7' or 7" may be made of a single piece of paper or synthetic plastic so that the two sheets 7a, 7b or 7a', 7b or 7a", 7b form an integral unit. That portion of such integral unit which constitutes the master sheets (7a, '7a' or 7a") is provided with one or more coats of a material adapted to receive ink from the inking roller or rollers 21.

Alternatively, the foil may be assembled of two separate sheets which are bonded to each other, for example, by adhesive, by welding, by riveting or in another suitable way. That portion of such composite foil which constitutes the master sheet may be made up of surface-treated aluminum, plastic sheet stock or paper. The other portion which constitutes the wiping sheet may be made up mainly of roughened synthetic plastic stock, roughened textile, absorbent textile, paper or other suitable sheet material.

The provision of a one-piece (composite or integral) foil 7, 7 or 7" has been found to be of considerable advantage because it can be readily attached to a cylinder 4, 52 or 59 by resorting to a single pair of clamping devices 5, 6 or 51, 53 or 6l, 62. Of course, and as shown in FIG. 3, it is equally possible to utilize a tirst set of clamping devices 65, 66 for the wiping sheet 67 and to utilize a second set of clamping devices to secure the master sheet (not shown) to the master cylinder of the machine illustrated in FIG. 3.

The improved foil may be produced at low cost in any desired size or shape so that it can be readily fitted on different types of offset printing machines. Its edges can be retained by resorting to conventional clamping devices. In fact, a single clamping device may suce to clamp both edge portions of a foil in an offset printing machine. If the image on the master sheet 7a, 7a or 7a is formed in a typewriter, the foil 7, 7 or 7 is folded in half so that the wiping sheet 7b, 7b' or 7b" is located behind the master sheet and provides a higly satisfactory back support during typing. In fact, and since the wiping sheet is often of substantially felt-like consistency, it serves as an exceptionally satisfactory back support which insures that the outline of each character or symbol is impressed into the master sheet with unexpectedly satisfactory accuracy.

A foil wherein the two sheets form an integral unit made of a single sheet of paper or plastic is Often preferred in the production of a relatively small number of copies, for example, in an office. As stated before, that portion of the foil which is to form the master sheet is coated and otherwise treated to be capable of taking ink and of transferring images to the rubber blanket cylinder. The other portion which is to constitute the wiping sheet remains roughened so that it can readily remove ink from the blanket cylinder. Foils of plastic are often preferred because they do not leave any bres on the surface of the blanket cylinder.

It is also within the scope of my invention to provide the machine with an automatic, semiautomatic or manually operable sprinkling or moistening device which applies a suitable cleaning liquid onto the wiping sheet 7b, 67, 7b' or 7b after each contact with the blanket cylinder or at less frequent intervals. If provided, such a moistening device constitutes an optional feature of the machine because the material of the wiping sheet can be readily selected in such a way that the latter can remove from the blanket all traces of ink without the assistance from a special cleaning medium.

What is claimed as new and desired to be protected by Letters Patent is:

1. In an offset printing machine, a rotary rubber blanket cylinder; a rotary master cylinder and platen unit for respectively transferring ink images to and for constituting a back support for said blanket cylinder, said unit comprising a sin gle cylinder; an image transferring master sheet; a wiping sheet for removing ink from said blanket cylinder, said sheets together forming a single foil which surrounds the periphery of said single cylinder; and clamping means detachably securing said foil to said unit, comprising two clamping devices associated with said single cylinder.

2. A structure as set forth in claim 1, wherein the length of said foil and the combined width of said clamping devices together approximate the circumferential length of said single cylinder.

3. A structure as set forth in claim 1, wherein the diameter of said blanket cylinder approximates half the diameter of said single cylinder and wherein said wiping sheet rolls along and constitutes a back support for said blanket cylinder subsequent to transfer of an image onto the exposed surface of said blanket cylinder by said master sheet.

4. A structure as set forth in claim 3, further comprisin inking means inluding an inking roller movable toward and away from said foil, holder means for moving said blanket cylinder toward and away from said foil, and control means including carrier means for moving said inking roller against said master sheet in response to rotation of said single cylinder and selector means for moving said blanket cylinder against one of said sheets.

5. A structure as set forth in Claim 4, wherein said selector means comprises a selector m-ember movable between a plurality of positions in one of which said blanket cylinder engages only with said master sheet and in another of which said blanket cylinder engages only with said wiping sheet.

6. A structure as set forth in claim 5, further comprising a feed for supplying fresh copy sheets into the bite between said blanket cylinder and said single cylinder, said control means including a device for operating said feed and said selector member being movable to a third position in which said feed is operative and said blanket cylinder continuously bears against said foil.

7. A structure as set forth in claim 5, wherein said selector member is movable to a further position in which it maintains said blanket cylinder away from both sheets of said foil.

8. A structure as set forth in claim 5, wherein said control means further comprises a cam provided on said single cylinder and having two portions respectively associated with said master sheet and said wiping sheet, a rockable motion transmitting lever having a follower arranged to track said cam portions in response to rotation of said single cylinder and to thereby rock said lever, said lever having a plurality of cam faces, and a regulating member coupled with said holder means and movable by said selector member into and from engagement with selected cam faces on said lever to thereby determine the position of said blanket cylinder with reference to said single cylinder.

9. A structure as set forth in claim 8, further comprising a feed for supplying clean copy sheets into the bite between said blanket cylinder and said single cylinder, said feed being coupled with said selector member and being arranged to terminate the supplying of copy sheets when said selector member is moved to a position in which said regulating member is disengaged from said cam faces.

10. A structure as set forth in claim 8, wherein said lever is provided with three cam faces and is pivotable about a fixed pivot axis, two of said cam faces being disposed at the opposite sides of said axis and the third cam face being located between said two cam faces.

11. A structure as set forth in claim 1, wherein said single cylinder comprises two portions having different radii, one 0f said portions being surrounded by said master sheet and the other of said portions being surrounded by said wiping sheet.

12. A structure as set forth in claim 11, further comprising a pair of normally meshing gears, one of said geais being coaxial with and having the same pitch diameter as the diameter of said blanket cylinder, the other of said gears being coaxial with said single cylinder and having the same pitch radius as the radius of said one portion.

13. A structure as set forth in claim 1, further comprising a drive for said blanket cylinder and clutch means for selectively coupling said single cylinder with said drive.

14. A structure as set forth in claim 13, further comprising manually operated means for manipulating Said clutch means.

15. A structure as set forth in claim 1, wherein said single cylinder is hollow and said clamping devices are provided in the interior of said single cylinder.

16. A structure as set forth in claim 15, wherein each of said clamping devices comprises a reel for respectively collecting or paying out one of said sheets.

17. A structure as set forth in claim 16, wherein the length of said foil exceeds the circumferential length of said single cylinder.

18. A structure as set forth in claim 15, further comprising a core rotatably received in said single cylinder, said clamping devices being provided on said core an said single cylinder having a cutout through which portions of said sheets extend, one of said sheets being withdrawable into said single cylinder in response to angular displacement of said core in one direction and the other of said sheets being Withdrawable into said single cylinder in response to angular displacement of said core in the other direction.

References Cited ROBERT E. PULFREY, Primary Examiner I. REED FISHER, Assistant Examiner U.S. Cl. X.R. lOl-232, 351, 425

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