US2362205A - Method and mechanism for feeding sheets to printing machines - Google Patents

Description

Nov. 7, 1944. w. F. HUCK METHOD AND MECHANISM FOR FEEDING SHEETS TO PRINTING MACHINES Filed Sept. 26, 1941 4 Sheets-Sheet l INVENTOR NOV. 7, 1944. w c 2,362,205

METHOD AND MECHANISM FOR FEEDING SHEETS TO PRINTING MACHINES Filed Sept. 26, 1941 4 Sheets-Sheet 2 llll l Maw INVENTOR ATTORNEY Nov. 1, 1944. w. k 2,362,205

METHOD AND MECHANISM FOR FEEDING SHEETS T0 PRINTING MACHINES Filed Sept. 26, 1941 4 Sheeis-Sheet 3 I ENTOR INVZ ATTORNEY W. F. HUCK Nov; 7, 1944.

METHOD AND MECHANISM FOR FEEDING SHEETS TO PRINTING MACHINES Filed Sept. 26, 1941 4 Sheets-Sheet 4 W I INVENTOR ATTORNEY Patented Nov. 7, 1944 METHOD AND MECHANISM FOR FEEDING SHEETS TO PRINTING MACHINES William F. Huck, Richmond Hill, N. Y., assignmto R. Hoe & Co., Inc., New York, N. Y., a corporation of New York Application September 26, 1941, Serial No. 412.488

19 Claims.

This invention relates to feeding mechanism for rotary printing machines, and more particularly to mechanism of this type adapted for feeding sheets of metal or other relatively rigid material tothe printing cylinders of planographic or other printing machines.

In feeding sheets of tin plate, this being a use to which the invention herein disclosed has a wide application, it is usual to forward the sheets along guides fomiing a feed table of the machine, and into registered position by means of pushers which engage the rear edge of the sheet and move it forward until its forward edge reaches stops that align it in proper registered position. It has heretofore been the practice to make the feed table along which the sheets are forwarded substantially fiat, and with such construction when the sheet meets the stops, continued pressure of the pushers tends to cause the sheet to buckle transversely, a certain portion of the sheet between the forward and rear edges being raised from the feed table along which it is being moved. This difliculty is avoided by forming the feed table as herein shown, with a curvature which causes the leading edge of the sheet to beraised as it moves forward toward the stops, and pusher fingers which'engage the rear or trailing edge of the sheet are arranged to raise this edge from the feed table. By thus bending the sheet upward a greater pressure can be applied by the pushers and greater accuracy of register obtained, because with the sheet thus curved pressure between the front stops and the pushers can not raise a mid-section of the sheet similarly urged sidewise by a side register mechanism, which presses on one side edge of the sheet to move it into engagement with a stop on the opposite side of the machine. It is found that the slight curvature of the sheet, resulting from the use of a curved feed table, materially stiffens the sheet transversely and effectively prevents buckling due to pressure on the side guides.

Due to the stifiening of a sheet being forwarded, a machine arranged as herein disclosed can successfully handle and accurately register sheets of a much lighter gauge than is possible with conventional machines having flat feed tables.

In printing machines of this kind, the leading edge of each sheet must arrive at a certain position at a time when grippers carried on an impression cylinder are in position to engage the leading edge of the sheet. The sheet is carried by pusher mechanism which has pusher fingers that propel the sheet to the sheet-taking grippers inaccurate timed relation. In order to insure that the leading edge of the sheet arrives at sheet-taking position at the same time the grippers reach this position, the pusher mechanism must be made adjustable to accommodate sheets of various lengths.

It is therefore an object of this invention to provide a sheet feeding mechanism in which each sheet travels through an arcuate path of travel on its way to sheet receiving position, so that the sheet is bent slightly by raising its leading portion, thus stiffening it and avoiding a tendency of the sheet to buckle upwardly when subjected to pressure by the pushers.

Another object of this inve. tion is to provide a sheet feeding mechanism in which the sheet travels upon arcuate sheet guides which are arranged to bend the leading portion of the sheet upwardly, so that the sheet is forced downward- 1y against the guides by pressure which is exerted on the leading and trailing edges of the sheet.

A further object of this invention is to provide a sheet feeding mechanism in which the sheet is propelled along arcuate sheet guides which are arranged to bend the leading portion of the sheet upwardly to thus dispose the sheet in an arcof relatively great radius about an axis which is disposed transversely of the direction of travel of the sheet, so that the sheet is forced downwardly against the guides by pressure that may be exerted on the trailing edge of the sheet by the propelling mechanism, and on the leading edge of the sheet by the front guide or stop of the grippers, the arcuate disposition of the sheet reinforcing it against lateral stresses to thereby prevent buckling of the sheet that may be ordinarily caused by the lateral stress exerted on the side edge of the sheet by the conventional side registering mechanism.

An additional object of this invention is to provide a sheet feeding mechanism in which each sheet is propelled by a pusher mechanism through a path of travel in such relation that the leading edge of the sheet arrives at a given point at a, predetermined time to be taken by the grippers of the sheet receiving cylinder, .the pushing mechanism incorporating adjustable means so that sheets of various sizes may be fed in accurate timed relation to the gripper mechanism of the sheet receiving cylinder.

Another object of this invention is to provide a sheet feeding mechanism for a printing machine in which the sheets are fed from sheet receiving position on a feed table along arcuate guide members which define an arcuate path of travel which curves upwardly as'it approaches the cooperable printing cylinders, the printing cylinders being arranged with their bite portions positioned immediately adjacent the discharge terminal of the arcuate guide members and disposed in tangential relation thereto, so that a plurality of printing machines may be arranged in tandem relation with the discharge terminal of one machine being disposed immediately adjacent the sheet receiving portion of the feed table of the adjacent machine in order that printed sheets from one machine may be directly discharged on the feed table of the next machine.

It is also an object of this invention to provide a sheet feeding mechanism of generally improved construction and arrangement, whereby the device will be simple, durable, and inexpensive in construction, as well as convenient, practical, serviceable and efficient in its use.

With the foregoing and other objects in view, which will appear as the description proceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it

being understood that various changes in forms,

proportion and minor details of construction may be made within the scope of the claims without departing from the spirit or sacrificing any advantages of the invention.

For a complete disclosure of the invention, a detailed description thereof will now be given in connection with the accompanying drawings forming a part of the specification; wherein:

Figure 1 is a fragmental longitudinal vertical sectional view taken through a planographic offset printing machine, showing the invention applied thereto;

Figure 2 is a fragmental plan view of the sheet feeding mechanism of the printing machine;

Figure 3 is a fragmental vertical sectional view, taken on a line 33 of Figure 2, parts being omitted to more clearly show the invention; and

Figure 4 is a diagrammatic view depicting a plurality of printing machines incorporating this invention, the machines being arranged in tandem relation.

Referring to the drawings in which similar reference characters designate corresponding parts, there is depicted an impression'cylinder ll) of a metal printing or decorating machine, and this cylinder is operably supported by a shaft i which is rotatably mounted in the usual bearings supportedby the machine frame. Inasmuch as the printing machine frame and cylinder bearings are of conventional construction, they have not been illustrated in this application.

A blanket or form cylinder l2 of the usual construction is rotatably mounted for cooperative relation with the impression cylinder I0, and the axis of the blanket cylinder I2 is located to one side of a vertical plane passing through the axis of the impression cylinder III, as best seen in Figure 4. The reason for disposing the axis of the blanket cylinder |2 to one side of a vertical plane which passes through the axis of the impression cylinder I! will be hereinafter set forth.

The impression cylinder ID has a gripper shaft i3 mounted for rotary or rocking movement therein, and this shaft has an arm i5 keyed or otherwise secured thereto. The arm l5 extends radially from the shaft |3 and rotatably supports a roller i6 at its outer terminal. Gripper arms or brackets I! are keyed or otherwise secured to the shaft l3, and the outer terminal of each gripper bracket I1 rigidly supports a sheetgripper l8. A cylindrical aperture 20 is formed in the outer terminals of each gripper arm or bracket for the sliding reception of a cylindrical stem 2| of a front sheet stop or member 22. The stem 2| has a reduced extension 23 which is slidably received in a cylindrical aperture 25 formed in the gripper arm or bracket ll. A helical spring 26 surrounds the reduced extension 23 of the stem 2| of the stop 22, and one terminal of this spring engages an end wall of the cylindrical aperture 25 and its opposed terminal engages the stem 2| of the stop 22 to thereby normally bias or stress the stop 22 for outward movement. The terminal of the reduced stem 23 which is remote from the stop 22 is provided with threads 21, and this threaded portion 21 is engaged by a threaded nut 28. By rotating the nut 28, the stop 22 may be drawn inwardly against the tension of the helical extension spring 23 to thereby permit the adjustment of the stop 22 relative to the gripper bracket l1 and gripper ill, for reasons to be hereinafter disclosed.

A cam 30 is rigidly secured to the machine frame, not shown, and this cam is provided with a projection 3| which operably engages the roller iii to thus open and close the grippers l8 in accurate timed relation to the movement of the leading edge of the sheet to be fed to the grippers, as will be more fully explained hereinafter.

A plurality of endless belts 33 are trained about a drive roller 35 (Figure 2) which is rotatably mounted in suitable bearings supported by the feeder frame 36. The belts 33 extend forwardly, or in a direction towards the printing cylinders, from the drive roller 35, and they are trained about pulleys 31, which are rotatably mounted in brackets 38 carried by a cross member or brace 40 of the feeder frame.

The upper reach of each belt is supported by a slat or strap 4| which extends longitudinally along the feeder frame from a point adjacent the drive roller 35 to the guide pulleys 31. The slats 4| are rigidly supported on the frame of the sheet feeder, and each slat, in turn, supports the upper reach of a belt 33 so that it will not sag or yield under the weight of the feeding sheets.

A sprocket 42 is secured to one terminal of the shaft of the drive roller 35, and this sprocket is engaged by a conventional drive chain 43. The chain 43 extends forwardly from the sprocket 42 and is trained around a drive sprocket 45. The drive sprocket 45 is secured to a gear 44 which is driven by means hereinafter described. The sheets S which are to be fed to the printing cylinders ill and I2, are placed on the feed belts 33 either by hand or by means of an automatic feeder of known construction. Each sheet is carried forwardly by the feed belts 33 which ride over the rigid supporting slats 4|. As each sheet S reaches the forward terminal of its movement on the belts 33, it is engaged by pusher mechanism hereinafter described, which propels the sllaieet until its leading edge is taken by the gripp rs Each pusher mechanism includes "a carriage 46 supported by rollers 41 which run along longitudinally extending tracks 48 supported by cross braces 46 and 56 and other components, not shown, of the feeder frame 36. The carriage 46 has a rocking member which is mounted for pivotal movement about the axis of the shaft 52 of the frontsupport rollers 41. The rocking member 5| has a link 53 pivotally secured thereto at a point remote from the shaft 52, as indicated at 54, and this link extends rearwardly from its pivotal point 54 through an abutment 51 that extends upwardly from the carriage 46. A helical spring 55 surrounds the link 53, and one ter-' minal of the spring 55 engages the abutment 51. A stop or limit nut 56 is threadedly secured to the outer terminal of the link 53, and this nut engages the abutment 51 to limit the forward movement of the rocking member about its pivot 52. A pusher finger 66 is carried by and extends upwardly from the rocking member 5|, and this pusher finger is adapted to engage the trailing edge of the sheet S, as will be more fully explained hereinafter.

Each carriage 46 is secured to an endless chain 6| of which four are shown trained around drive sprockets 62. The drive sprockets 62 are keyed or otherwise secured to a drive shaft 63 that extends transversely across the frame of the sheet feeding mechanism and is rotatably mounted in suitable bearings 65,supported by the feeder frame 36. Cams or guide plates 66 are supported by the cross brace 56, and these cams are located at each side of each sprocket 62. Each rocking member 5| carries spaced rollers 61 which are located to engage thecams 66 as the carriage 46 passes downwardly around the drive sprocket 62. As the carriage passes downwardly around the sprocket 62, the rollers 61 engage the outer edges 68 of the cams 66 to thereby rock the pusher fingers 66 rearwardly away from the sheet.

As each sheet S reaches the limit of its forward movement along the belts 33, it then engages and is guided through the remainder of its movement from the belts 33 to the grippers I6 of the printing cylinders by arcuate sheet guides 16 which are supported by cross braces 1| and 12 of the feeder frame 36. Each sheet guide 16 extends horizontally forwardly a short distance from its rear support 12, and then the guide is curved upwardly, as indicated in Figure 1. Each sheet guide 16 is curved upwardly continuously from its horizontal portion through a radius or radii of relatively great length about an axis or axes which is ,or are disposed transversely of the direction of travel of the sheet. The reason for the arcuate guides will be more fully explained hereinafter. The forward terminal of each sheet guide 16 extends between portions of the impression cylinder I6 and blanket cylinder I2 to sheet taking location, at which location the grippers I6 take the sheet and convey it to the bite of the printing cylinders. As each sheet approaches the grippers I6, it passes below front fingers 13 of usual construction which operate to hold down the leading edge of the sheet S as it travels along the arcuate sheet guide 16. Each sheet must present its leading edge tothe grippers I8 at exactly the time the grippers I6 are actuated by the cam 36 to grip the sheet and the time of arrival of the leading edge of the sheet at the grippers I6 is determined by the position of the pusher fingers 66' at this instant. Printing machines "of this character are required to print sheets of various lengths, therefore, some provision must be made for adjusting the'pusher with relation to the sheet taking position of the grippers in order that the leading edge of the sheet may arrive at the grippers at the sheet taking time.

In order to provide this required adjustment, a pinion 15 (Figure 3) is loosely mounted on a countershaft 16 which is rotatably supported by anti-friction bearings 11 and 16. The bearing unit 11 is supported by the feeder frame 36, and the bearing unit 18 is supported by a gear housng 66 which is secured to the frame 36. The bearing 16 engages the hub portion of the pinion 15, thereby rotatably supporting the countershaft 16, but it is to be understood that these bearings may be located to directly engage the countershaft if preferred. The pinion 15 has a gear 8| keyed or otherwise secured thereto, as indicated at 62, so that the gear 6| rotates with the pinion 15. The gear 6| is driven through an idler gear 19 that meshes with the gear 44 which, in turn, is driven by a gear 69 secured to a shaft 69a. The shaft 69a is rotated in timed relation with the printing cylinders I6 and I2, preferably in accordance with the usual practice, by means of gears and shafting, not shown;

A collar 63 is keyed or otherwise secured to the countershaft 16, as indicated at 65, to secure the collar against rotation relative to the countershaft 16, butto permit axial movement of the collar on the countershaft. This collar is located on the countershaft 16 at one side of the loose pinion and gears '15 and 6|, and a bell-shaped clutch member 66 is keyed or otherwise secured to the countershaft 16, as indicated at 81, to secure the clutch member against rotary motion relative to the shaft 16. A gear 66 is keyed or otherwise secured to the countershaft 16, as indicated at 96, to secure the gear 88 against rotation relative to the shaft, and the gear 68 is held against longitudinal movement on the shaft by a locking member or nut 9|. The terminal of the countershaft 16 on which the collar 83 is located is threaded, as indicated at 92, for the reception of a nut 93 having radially-disposed wrench-receiving apertures formed therein for the reception of the inner terminal of a pin wrench 96, for a purpose to be hereinafter disclosed. Similar radially-disposed wrench-receiving apertures 91 are formed in the collar 63 for the reception of the inner terminal of the pin wrench 96. Thepurpose of this will also be explained hereinafter. A disc or dial 14 is pinnedor otherwise secured to the pinion 15 to rotate therewith, and this dial is provided on its outer face with radially-disposed index marks which are calibrated to indicate the correct position of the pusher mechanism for each size sheet. An index or pointer 84 extends radially from the collar 63, and this pointer cooperates with the calibrated index marks on the dial 14 so that the relative angular position of the pinion 15 and the countershaft 16 may be accurately indicated to determine the relative position'of the pusher fingers 66.

The pinion 15 meshes with a gear I66 which drives a cam shaft I6I having cams I62 to actuate the conventional side guides, and inasmuch as the side guides are of well known construction and form no part of this invention, they have not been disclosed in this application. An idler gear I63 meshes with the gear 66, and this idler gear in turn meshes with a gear I64 carried by the sprocket drive shaft 63. Thus, it is seen that rotation of the gear 86 imparts rotary movement to the sprocket shaft 63, and consequently, the sprocket 62 to propel the pusher carriage 45 through the instrumentality of the chain 6|.

In operation, the sheets S are placed one at a time on the feed belts 83, either by hand or preferably by means of an automatic feeder. Each sheet S is carried forwardly by the belts 83 toward the printing cylinders l8 and I2 until the pusher fingers 88 rise behind the sheet and engaging and lifting its trailing edge. These pusher fingers 80 then propel the sheet forwardly along the arcuate sheet guides 18, and as the sheet moves along these guides its leading portion is bent upwardly so that the sheet conforms to the arcuate path defined by the arcuate guides 10, and its trailing portion also is bent upward by the pusher fingers 88. By thus lifting both the leading and trailing edges of the sheet, it is bent transversely to its path of travel, the arrangement preferably being such that a sheet of the maximum thickness that the machine is designed to print will be curved to about the same extent as when it is supported only at its leading and trailing edges.

In this condition, the sheet S is prevented from buckling transversely, due to longitudinal pressure on its front and rear edges by the front sheet stop 22 and the pusher fingers 88 respectively, and is strengthened transversely so that it resists the tendency of the conventional side registering device, not shown, to buckle the sheet in the direction of its travel. The pusher mechanism operates in timed relation with the impression cylinder gripper mechanism, so that the leading edge of the sheet reaches sheet taking position at the same time the gripper mechanism reaches its sheet gripping position. When the sheet S reaches its sheet gripping position, its leading edge engages the stop 22. The adjusting springs 26 of the stops 22 are strong enough to resist the tendency of the pusher fingers 80 to push the sheet forward, so that the stops 22 momentarily hold the sheet until the grippers |8 close. As the grippers l8 close. they move downwardly and rearwardly about their pivot l8, thus tending to push the sheet rearwardly against the resiliently mounted pusher fingers 88. This action exerts a stress on both the forward and trailing terminals of the sheet, but inasmuch as the sheet is held in arcuate disposition by the arcuate guide 18, such stress tends to force the sheet downwardly against the guides 18 to thus insure the accurate positioning of the sheet on the guides preparatory to the final closing action of the grippers I8. After the sheet is taken by the grippers l8, the pusher fingers follow the sheet forwardly a short distance until the rollers 81 of the rockingmembers engage the cams 88 to thereby rock the pusher fingers 88 rearwardly away from the trailing edge of the sheet as the pusher carriage 48 moves downwardly around the sprocket 62.

This action is repeated as long as sheets of the same sizeare being conveyed to the printing cylinders, but if sheets of a different size are to be printedgthen the propelling mechanism for the pusher carriage 48 must be adjusted so that the pusher fingers 88 will convey the leading edge of the new size sheet to the sheet taking position at the :instant the grippers close to take the sheet. Thislradjusting mechanism is best seen in Figure'3, and-in its drive condition, the tightened nut 83 forces the outer edge 88a of the clutch member fleagainst the annular face 8la of the gear 8| tot-hereby frictionally lock these members so that tlfifiyzrotate together. When it is desired to adjust the mechanism to accommodate sheets of a different length. then the pin wrench 98 is inserted ;aperture 85 of the locking nut 98, and the nut is manipulated to release or unscrew it. In this releasing of the clutch components, the outer annular surface 881: of the bellshaped clutch member 88 is released from binding engagement with the annular surface 8|a of the gear 8|, so that the pinion l8 and gear 8| are free to rotate relative to the countershaft l8 and clutch member 88. Now the pin wrench 88 is inserted into an aperture 81 of the collar 83 so that the collar 88, countershait l8, clutch member 88, and gear 88 may be rotated in unison by rotating the collar 83. The rotation of the gear 88 moves the pusher carriage 48 to a new or adjusted position through the instrumentality of the interposed gears I03, I84, shaft 83, sprocket 82, and chain 8|. While the countershaft I8 is being moved to effect the adjustment of the pusher carriage 48, the pinion l5, gear 8| and the remaining drive gears of the machine remain stationary. After the adjustment has been made, the nut 83 is again tightened, thus forcing the annular surface 88a of the clutch member 88 into frictional engagement with the annularclutch surface 8: of the gear 8|. Now the gear 8| and clutch member 88 rotate in unison to thus drive the pusher carriage 48 to convey the new sheets to the gripper mechanism. In making this adjustment, the operator knowing the size of the required new sheets may readily determine the correct position of the drive components by observing the relative angular positions of the index marks on the calibrated dial it, and the pointer or index 88.

. Referring to Figures 1 and 4, it will be observed that as each sheet travels forwardly along the,

arcuate sheet guides III, the forward portion of the sheet is bent upwardly above the general horizontal plane in which the sheet receiving portion of the feed table is located, and the sheet is delivered from the printing cylinders in this elevated plane. In addition to strengthening the sheet against buckling under transverse stresses and also insuring that the sheet is held down against the arcuate guides 18 when subjected-to longitudinal stresses, there is also an advantage in elevating the sheet prior to the printing operation, because after the sheet is printed, it is discharged in a plane above the sheet receiving portion of the feed mechanism so that the printed sheet may be discharged directly onto the receiving terminal of an immediately adjacent feed table without the intervention of automatic feeding instrumentalities. By this arrangement, a plurality of printing machines may be disposed in tandem relation so that the printed product from one machine may be received directly by the sheet receiving portion of the feed table of an immediately adjacent machine Figure 4. Inasmuch as the portions of the arcuate sheet guides I8 which are disposed toward the printing cylinders are curved upwardly, the printing cylinders are preferably arranged so that they are disposed in tangential relation to the immediately adjacent portions of the sheet guides 18. This disposition of the impression cylinder [0 and blanket or form cylinder l2 causes the axis of the form cylinder I! to be positioned inwardly to one side of a vertical plane that passes through the axis of the lower or impression cyiinde II. By this arrangement, the upper or blanket cylinder I2 is disposed away from the sheet receiving portionof the feed table of the adjacent machine, thus permitting the machines to be positioned immediately adjacent each other'without interfering with the printing operation of the machines. r,

It will be understood that the invention herein disclosed may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being had to the claims rather than to the foregoing description to indicate the scope of the invention.

What I claim is:

1. The method of feeding metal sheets to a printing machine which consists in upwardly bending the leading portion of each sheet about an axis or axes disposed transversely of the direction of travel of the sheet towards sheet gripping position, and exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition towards sheet gripping position to thereby laterally stiffen the sheet against buckling.

2. The method of feeding metal sheets to a printing machine which consists in passing an unconfined sheet over arcuate sheet guides which support the sheet as it travels toward sheet gripping position, the guides being curved about an axis or axes located above the guides .and disposed transversely of the direction of travel of the sheet towards sheet gripping position to thereby upwardly bend the sheet, exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition towards sheet gripping position on the arcuate sheet guides to thereby force the sheet downwardly against the arcuate guides to laterally stiffen it.

3. The method of feeding metal sheets to a printing machine, which consists in raising one of the edges of each sheet to bend it transversely of its direction of travel as it is forwarded towards sheet gripping position, and exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition towards sheet gripping position to thereby laterally stiflen the sheet against buckling.

4. The method of feeding metal sheets to a printing machine, which consists in lifting the trailing edge of each sheet to bend it about an axis or axes disposed transversely of the direction of travel of the sheet while the sheet is being forwarded towards sheet gripping position, and exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition towards sheet gripping position to 1thereby laterally stiffen the sheet against bucking.

5. The method of feeding metal sheets along a sheet guide to a printing machine, which consists in lifting the trailing edge of each sheet to bend it transversely of its direction of travel and exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet while it is being forwarded in an unconfined path towards sheet gripping position in bent condition, to thereby force the portion of the sheet between the trailing and leading edges downwardly against the guide.

6. The method of feeding metal sheets to a printing machine which consists in upwardly bending the leading portion of each sheet about an axis or axes disposed transversely of the direction of travel of the sheet by passing the sheet over upwardly turned arcuate guides as the sheet travels in an unconfined path towards sheet gripping. osition to thereby laterally stiffen the sheet against buckling when the lateral edges of the sheet are subjected to inward lateral stresses, exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition on the arcuate sheet guides to thereby force the sheet downwardly against the arcuate guides.

7. The method of printing metal sheets which consists in arranging in tandem relation a plurality of printing machines each having cooperable printing cylinders and sheet feeding mechanism for the cylinders, the sheet feeding mechanism having a sheet receiving portion, upwardly bending the leading portion of each sheet about an axis or axes disposed transversely of the direction of travel of the sheet along the sheet feeding mechanism of one machine towards its printing cylinders, so that the sheet is presented to the bite of the printing cylinders at a point positioned above the plane in which the sheet receiving portion of the sheet feeding mechanism is located, and discharging the printed sheet from the bite of the printing cylinder directly onto the sheet receiving portion of the sheet feeding mechanism of the next printing machine.

8. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feedtable along which sheets are fed to the printing cylinders, the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby upwardly bend the leading portion of the sheet aboutan axis or axes disposed transversely of the direction of travel of the sheet towards the printing cylinders, and exerting forward and rearward longitudinal pressure against the trailing and leading edges of the sheet when it is moving in upwardly bent condition towards sheet grippin position to thereby stiffen the sheet to resist upward buckling away from the arcuate guides when the lateral edges of the sheet are subiected to lateral stresses.

9. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which sheets are fed to the printing cylinders, the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby upwardly bend the leading portion of the sheet about an axis or axes disposed transversely of the direction of travel of the sheet towards the printing cylinders, a yieldable pusher member for engaging the trailing edge of the sheet to propel it along the arcuate guides to the printing cylinders, grippers carried by a printing cylinder for engaging the leading edge of the sheet, the arcuate bending of the sheet on the arcuate guides causing the sheet to be so disposed as to resist upward buckling when the pusher mechanism and the gripper mechanism subjects the trailing and leading edges of the sheet to longitudinal stresses.

10. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the. sheet guide surface of the feed table along which sheets are fed to the printing cylinders, the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby bend upwardly the leading portions of the sheets about an axis or axes disposed transversely of the direction of travel of the sheets towards the printing cylinders, gripper members pivotally secured to one of the printing cylinders, sheet stops carried by the gripper members, the gripper members and sheet stops moving against the direction of travel of the sheet as the gripper members are moved to closed or sheet taking position, yieldable pusher members for engaging the trailing edge of each sheet to propel it along the arcuate guides to the printing cylinders, the arcuate disposition of the sheet on the arcuate guides causing the sheet to be forced downwardly into engagement with the arcuate guides when rearward and forward longitudinal stresses are exerted on the leadin and trailing edges of the sheet by the sheet stop and yieldable pusher members.

11. A plurality of printing machines arranged in tandem relation, each machine including a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which the sheets are fed to the printing cylinders, the'portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby upwardly bend the leading portion of each sheet about an axis or axes disposed transversely of the direction of travel of the sheet, the bite of the cooperable cylinders of each printing machine being located immediately adjacent the discharge terminals of the arcuate guides and above the plane in which the sheet receiving portions of the guide tables are located, with. the printing cylinders arranged in tangential relation to the discharge terminals of the arcuate guides, the upward bending of each sheet as it approaches the cooperable printing cylinders so positioning the sheet that it is discharged directly from the bite of the cooperable printing cylinders of one machine directly onto the feed table of the next printing machine.

12. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which sheets are fed to the printing cylinders, the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby bend upwardly the leading portion of each sheet about an axis or axes disposed transversely of the direction of travel of the sheet towards the printing cylinders, sheet grippers operably supported by one of the printing cylinders, and pusher members for engaging the trailing edge of each sheet to propel it along the arcuate guides in accurate timed relation to the gripper members, mechanism for driving the pusher members, and 'adjusting means operably interposed between the pusher members and their drive mechanism so that the location of the pusher members relative to the sheet grippers may be varied to accommodate sheets of various lengths.

13. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table along which the sheets are fed to the printing cylinders, pusher mechanism for propelling the sheets along the feed table,

drive mechanism for driving the pusher mechanism, the drive mechanism having drive components driven by any suitable source of power, a clutch having a first clutch member, a second clutch member rotatably driven by the drive components and independently rotatable relative to the first clutch member, one clutch member being axially movable relative to the other in order to move the clutch members to and from frictional engagement, driven components driven by the second clutch member and operably connected with the pusher mechanism to impart movement thereto for propelling the sheets to the printing cylinders, and means for moving one clutch member axially to and from frictional engagement with the other thereby controlling the clutch mechanism so that the driven components may be adjusted relative to the drive components.

14. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table along which the sheets are fed to the printing cylinders, pusher mechanism for propelling the sheets along the feed table, drive mechanism for driving the pusher mechanism, the drive mechanism including a countershaft, a gear and pinion loosely mounted on the countershaft, the gear and pinion rotating as a unit, means for driving the gear and pinion from any suitable source of power, a clutch face formed on the gear, a clutch member rotatable with the countershaft and having a clutch surface for engagement with the clutch surface of the gear, means for operably connecting the countershaft with the pusher mechanism so that rotation of the countershaft imparts movement to the pusher mechanism to propel the sheets along the feed table to the printing cylinders, and means for forcing the clutch surface of the gear and the clutch surface of the clutch member into frictional engagement so that rotation of the gear imparts rotation to the clutch member and countershaft to thereby drive the pusher mechanism, and means for releasing the frictional engagement between the clutch surface of the clutch member and the clutch surface of the gear so that the pusher mechanism may be adjusted relative to the drive mechanism by moving the clutch member and countershaft relative the pinion and gear. a

15. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which sheets are fed to the printing cylinders, the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby bend upwardly the leading portion of the sheet about an axis or axes disposed transversely of the direction of travel of the sheet, a yieldable pusher member for engaging the trailing edge of the sheet to'propel it along the arcuate guides to the printing cylinders, the arcuate bending of the sheet on the arcuate guides stiffening the sheet laterally to resist upward buckling of the sheet away from the arcuate guides when the lateral edges of the sheet are subjected to lateral stresses and when the pusher mechanism subjects the trailing edge of the sheet to longitudinal stress.

16. In a sheet feeding mechanism for a printing machine, cooperable printing cylinders, a feed table, arcuate guide members located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which sheets are fed to the printing cylinders,

the portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby bend upwardly the leading portion of the sheet about an axis or axes disposed transversely of the direction of travel of the sheet toward the printing cylinders, the cooperable printing cylinders being disposed in tangential relation to adjacent portions of the arcuate guides with their bite portions located immediately adjacent the terminals of the arcuate guides.

17. In a sheet feeding mechanism for a printing machine having cooperable printing cylinders, a feed table, arcuate guides located adjacent the printing cylinders and forming a portion of the sheet guide surface of the feed table along which sheets are fed to the printing cylinders, the

portions of the arcuate guides which are disposed towards the printing cylinders being curved upwardly to thereby bend upwardly the leading portion of the sheet about an axis oraxes disposed transversely of the direction of travel of the sheet towards the printing cylinders, gripper members carried by one of the cylinders, sheet stops supported by the gripper members, yieldable pusher members for engaging the trailing edge of the sheet to propel it along the arcuate guides to the printing cylinders, the arcuate bending of the sheet on the arcuate guides causing the sheet to be forced downwardly into engagement with the arcuate guides when longitudinal stresses are exerted on the leading and trailing edges of the sheet by the-sheet stops and pusher members.

18. In a mechanism for feeding flexible sheets to cooperating printing cylinders of a printing machine, a sheet guide positioned to direct a flexible sheet to the cylinder, the guide being upwardly curved to curve the sheet so that its intermediate portion will be lower than the intermediate portion of. a plane intersecting and parallel with the leading and trailing edges of the sheet, and movable pusher mechanism adapted to engage the trailing edge of the sheet with sufficient force to overcome the friction between the sheet and the guide and push the sheet forwardly along the guide thereby pressing the sheet into conformity with the guide to stifien the sheet.

19. In a mechanism for feeding flexible sheets to cooperating printing cylinders of a printing machine, a sheet guide curved substantially throughout its length with its forward terminal located uppermost and positioned to direct a flexible sheet forwardly to the cylinders, and a mov able pusher mechanism for engaging the trailing edge of the sheet with sufficient force to overcome the friction between the sheet and the guide to push the sheet forwardly along the guide thereby supplementing the action of gravity in forcing the sheet into conformity with the curved guide to stiffen the sheet against upward buckling on the guide.

WILLIAM F. HUCK.

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