US3833213A

US3833213A - Means for overcoming fan-out in lithograph press

Info

Publication number: US3833213A
Application number: US00244387A
Authority: US
Inventors: W Smith
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1972-04-17
Filing date: 1972-04-17
Publication date: 1974-09-03
Anticipated expiration: 1991-09-03

Abstract

An infeed mechanism including an oscillating transfer assembly for gripping the straight leading edge of a sheet in a sheet-fed press and for transferring it to grippers on a rotating cylinder in a bowed condition in order to overcome the tendency for the trailing portion of the sheet to spread or fan-out as it is acted upon by the press cylinders. The transfer assembly has gripper pads which are in general alinement but which are moved into the locus of a bow during a stroke of swinging movement for progressively deforming the leading edge of the sheet into a bow from the time that the sheet is engaged to the time that the sheet is released to the grippers on the rotating cylinder. In the preferred embodiment the gripper pads on the transfer assembly are mounted upon a pad bar which is progressively bowed in one direction as the transfer assembly is swung into its sheet pick-up position and then progressively restored to its straight position and into a bow of opposite direction as the transfer assembly is swung to the position where the sheet is released to the grippers on the constantly rotating cylinder. Means are provided for varying the amount of bow in the bar including levers on the transfer assembly which are actuated by a cam and cam follower which move relatively to one another as the transfer assembly swings back and forth.

Description

United States Paten 1191 Smith Sept. 3, 1974 MEANS FOR OVERCOMING FAN-OUT IN LITHOGRAPH PRESS Walter S. Smith, Naperville, Ill.

[73] Assignee: Rockwell International Corporation,

Pittsburgh, Pa.

[22] Filed: Apr. 17, 1972 [21] Appl. No.: 244,387

[75] Inventor:

Primary ExaminerEvon C. Blunk Assistant ExaminerBruce l-I. Stoner, Jr.

[57] ABSTRACT An infeed mechanism including an oscillating transfer assembly for gripping the straight leading edge of a sheet in a sheet-fed press and for transferring it to grippers on a rotating cylinder in a bowed condition in order to overcome the tendency for the trailing portion of the sheet to spread or fan-out as it is acted upon by the press cylinders. The transfer assembly has gripper pads which are in general alinement but which are moved into the locus of a bow during a stroke of swinging movement for progressively deforming the leading edge of the sheet into a bow from the time that the sheet is engaged to the time that the sheet is released to the grippers on the rotating cylinder. ln the preferred embodiment the gripper pads on the transfer assembly are mounted upon a pad bar which is progressively bowed in one direction as the transfer assembly is swung into its sheet pick-up position and then progressively restored to its straight position and into a bow of opposite direction as the transfer assem- 9 Claims, 16 Drawing Figures .SMITH J N+ WALTERS 3 I PATENTEO 35? 31974 a v Q3 A TYS;

PAIENIEMEP 3mm MET 30$ 4 lavas-ran WALTER 8. 8mm

Atty;

j l7 Iuvsuron WALTER '5. SMITH MEANS FOR OVERCOMING FAN-OUT IN LITHOGRAPH PRESS It is an object of the present invention to provide an infeed mechanism for a rotary sheet-fed printing press in which the oscillating transfer assembly has a set of gripper pads for gripping the straight leading edge of the sheet and for progressively deforming the leading edge into a bowed condition as the sheet is swung toward the point where the sheet is released to grippers on an associated constantly rotating cylinder. It is a more specific object of the invention to provide a transfer assembly having bar-mounted gripper pads and in which means are provided for gradually or progressively deforming the bar to vary the bowed condition of the bar as the transfer assembly is swung between its sheet engaging and sheet releasing positions. The arrangement is thus distinguished over prior bowing arrangements having a pad bar and in which the pad bar is bent into a bowed configuration as a result of engaging adjustable stops at the limit of its swinging movement. Consequently it is an object of the invention to provide an infeed mechanism in which the bowing and pick-up functions occur smoothly and quietly and which may be operated at high press speeds.

It is a related object to provide an infeed mechanism for a rotary sheet-fed printing press which is highly versatile, permitting any desired degree or direction of bowing, which is easily adjustable, and which, once adjusted, reliably retains its adjustment over long press runs. It is a general object to provide an infeed mechanism which is of inherently economical construction and which operates reliably, with minimum maintenance, 'over long periods of time.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a front view of a pad bar assembly in accordance with the present invention looking along line I-l in FIG. 3.

FIG. 2 is a top view of thestructure looking along line 2-2 in FIG. 1.

FIG. 3 is a vertical section taken'through the transfer assembly along the line 33 in FIG. 2.

FIG. 3a is an enlarged cross section taken through the pad bar and showing the feedtable and shaft which operates the gripper fingers.

FIG. 3b is a fragmentary bottom view lookingalong the line 3b3b in FIG. 3

FIG. 4 is a simplified section similar to FIG. 3 but showing transfer of a sheet to the constantly running cylinder.

FIG. 5 is a side view of a central supporting bracket looking along line 5-5 in FIG. 2.

FIG. 6 is a transverse section along line 66 of FIG. 2 and showing one support bracket for the pad bar control lever.

FIG. 7 is a transverse section taken along line 77 of FIG. 2 and showing the other support bracket for the pad bar control lever.

FIG. 8 is a plan view of a cam supporting bracket.

FIGS. 9, 9a and 9b are stop motion views showing the travel of the cam follower along the cam.

FIGS. 10, 10a and 10b are stop motion views showing the progressive deformation of the pad bar andthe sheet which is transported by the pad bar.

While the invention'has been described in connection with a preferred embodiment, it will be understood that I do not intend to limit the invention to the particular embodiment shown but intend on the contrary to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.

Turning now to the drawings and particularly to FIGS. 1-5, there is disclosed a portionof a sheet-fed lithograph press having a frame 10 (see also FIG. 8) and a feed table I I (FIG. 3a) onto which sheets are fed, one by one, from left to right as viewed in the drawings, against front register stops I3. The latter are mounted upon a shaft 14. A typical sheet, indicated at I5, has a straight leading edge 16,

lateral edges

17,18 and a trailing edge 19. The front register stops 13 are provided for the purpose of accurately defining the position of the leading edge of the sheet in readiness for pick-up in proper phase relation for transfer'to grippers on a constantly rotating impression cylinder. Thefront register stops are physically separate from the table 11, and it will be understood that they may be separately adjusted forwardly or backwardly with respect to the length dimension of the sheet or skewed slightly as desired.

For the purpose of picking up a stationary sheet at the leading edge and for accelerating it to press speed an oscillating transfer assembly 30 is provided formed of a cylindrical drumlike member 31 having

end members

33, 34 and with

journals

35, 36 on the cylinder axis, which journals are mounted in suitable hearings in the press frame 10 for oscillation back and forth. The transfer assembly 30 swings from the position shown in FIG. 3,. where the stationary sheet is gripped, to the position shown in FIG. 4 where the sheet has accelerated to press" speed and at which point transfer takes place to a set of grippers 41 mounted upon a constantly rotating impression cylinder 40. After a certain amount of overtravel, the transfer assembly decelerates and reverses its movement to return to the pick-up position shown in FIG. 3. The means for oscillating the assembly 30 is not included within the scope of the present invention, and reference may be made to the prior art for typical oscillating drive such, for example, as that shown in prior patent 1,764,104.

For the purpose of gripping the leading edge of a sheet a pad bar 50 is provided having a series of gripper pads including a set of central gripper pads 51 and a' set of gripper pads 52 at the opposite ends of the bar. Taking a gripper pad 51 by way of example (FIG. 3a) it has an anchoring portion 56, a sheet engaging pad surface 57 and an angled entry leg 58' for guiding the leading edge 16 of the sheet into position for gripping. Cooperating with sets of

pads

51, 52 are sets of

gripper fingers

61, 62 which are mounted upon a shaft 60. Means not shown but well understood by those skilled in the art are provided for imparting rocking movement to the shaft 60 whereby the gripper fingers thereon are caused to grip a sheet when the transfer assembly is in the position of pick up shown :in FIG. 3 and release the sheet immediately following transfer shown in FIG. 4. It is one of the features of the present construction that the pad surface '57 on each of the pads is roughened whereas the gripping surface on each of the cooperating

fingers

61, 62 is smooth. Thus when the pad bar 50 flexes or bows, as will be discussed, the leading edge of the sheet will move with the pads, and slip relative to the fingers.

In carrying out the present invention the pad bar 50 is rigidly mounted with respect tothe cylinder 31 at its center and is mounted at its ends for limited movement in a peripheral direction relative to the cylinder. Thus, referring to FIGS. 1 and 2, the central portion of the bar is mounted upon brackets 71 which are secured to pads 72 which are welded to the cylinder 31 in depending position. Secured to the brackets 71' are supports 73 which are bolted to the bar by bolts 74. Extending through the

members

71, 73 is a registering opening 75 in which a roller bearing 76 is fitted, the shaft 60, which mounts the

fingers

61, 62, extending through the central race. A total of two of such fixed bracket assemblies are used in the central position, corresponding numerals being used to designate corresponding parts.

While the central portion of the pad'bar 50 is fixed with respect to the transfer assembly by

brackets

71, 73, the endsof the pad bar are not positively anchored but are mounted for slight relative or floating movement with respect to the assembly. Thus, adjacent each end of the bar 50 is a bracket 80 which is secured to the cylinder 31 and which mounts a bolt 81 having a washer. 82 and collar 83, the collar extending through a clearance opening 84 in the bar and the length of the collar being such as to provide forward and

back clearance

85, 86. To provide support for the end of the bar in the radial direction, however, a spring plate 87 of rectangular configuration is used, the outer end of which is securely clamped to the bracket 80 and the inner end of which is clamped to the bar by a pair of cap screws 88.

To provide additional support for the bar 50 at points intermediate the center and the ends of the bar, brackets 91 are provided mounted ,upon respective pads 92 and each carrying a support 93 having a bolt 94, the head of which extends into a clearance opening 95 formed in the bar. Radial support is provided by a spring plate 96 of rectangular shape which is secured to the support 93 at the center and the ends of which are clamped to the bar by

cap screws

97, 98. Corresponding structure is used at the corresponding offcenter location.

Since the spring plates 87 and 96 have a high degree of rigidity in the radial direction they support the bar 50 against possible deflection by centrifugal force and yet enable the bar to bow freely, in the peripheral sense, in one direction or the other. The bar is sufficiently thin so that a reasonable force suffices to produce the slight bending required.

In accordance with the present invention a cam and cam follower are provided between the movable portions of the bar (in this case the ends) and the frame of the machine, for operation progressively during a stroke of oscillating movement, so that the sheet is gripped with the pads occupying a first bowed locus and released to the constantly rotating cylinder with the pads occupying a second bowed locus with the leading edge of the sheet being progressively deformed into abow. In the present instance the cam, indicated at 100, has an arcuate inner surface 101-l04 which is engaged by a cam follower in the form of a roller 105, on a pin 106, the cam surface being arcuately disposed about the axis of the transfer assembly and so arranged that the cam follower roller is cammed radiallyinward as the transfer'ass'embly rocks to its limit of clockwise movement. For transmitting the movement of the cam follower roller a lever 110 is provided which has an upwardly extending arm 11], which is curved to follow the contour of the drum 31, and a short downwardly extending arm 112, making the lever of dog-leg shape.

Extending through the bend of the dog-leg is a transverse pivot pin 113 which is journaled in alined bearings 114, 115. The pin 113 is held in place by a clamping member 116 in the form of an elongated lug which is scalloped out as indicated at 117 and which is threaded and provided with a nut 118.at its outer end. Tightening the nut 118 draws the lug 116 endwise, thereby clamping the pin tightly in position.

For transmitting the motion of the lever to the pad bar, a bracket 120 is provided in the form of a clevis (FIG. 3b) having sides 121, 122 which embrace the lower end 112 of the lever 110, the bracket being secured to the end of the bar by means of a bolt 123. To hold the lower end of the lever captive in the clevis, and to permit relative rocking movement, a bearing 125 is provided having a central opening 126 through which the shaft 60 which mounts the

cyclical fingers

61, 62, extends. An annular clearance space 127 is provided between the shaft 60 and the inner race of the bearing 125 so that limited movement of the bracket 120 may occur without any necessity for bending the shaft 60.

In order to maintain the cam follower roller 105 bottomed on the cam surface a spring 130 is used which is held in place by a first. pin 131 near the tip of the lever and by a second pin 132 which isfastened to an anchoring pad 133- on the drum 31.

For the purpose of mounting the bearings 114 and 115, a bearing mounting assembly (FIGS. 6 and 7) is provided having bearing blocks 141, 142. The bearing block 141 is mounted upon the transfer cylinder 31 by means of bolts 143 which are threaded into a pad 144 welded or otherwise secured to the cylinder 31. The bearing block 142 is essentially a mirror image of block 141 and it is secured by bolts 145 to a similar pad 146 welded to the cylinder 31. The bearing blocks each have a groove 147 to fit over tongues 148 on the

respective pads

144 and 146 for alinement purposes and, when initially assembled,'the blocks are adjusted axially relative to each other to remove all looseness or play in the bearings before they are bolted in position. Corresponding structure isemployed at the opposite end of the bar 50, operating in synchronism, and the same reference numerals have been used.

For the purpose of defining a reference position for the transfer assembly and'the central gripper pads 51 at the center of the bar 50 and which are effectively fixed to the assembly, the

end plates

33, 34 are extended upwardly as shown in profile in FIG. 3, terminatingin stops 150 which strike respective stops 151 fixed with respect to the frame. The degree of bow which is imparted to the leading edge of the sheet therefore depends upon the locus of the gripper pads when the transfer assembly is in its reference position, at the time that the gripper fingers are closed, as well as upon the subsequent bowing movement of the pad bar during its swing intothe position where the sheet is transferred to the grippers on the constantly rotating companion cylinder.

In operation, then, as the cam follower is swung on the transfer assembly, from the region 103, through the region 102 to the region 101 of the cam surface, i.e.,

to the position shown in FIG. 3, inward crowding of the follower roller causes the lever 110 to rock about the axis of the pivot pin 113 through a small angle in the counterclockwise direction to retract the associated end of the bar so that the bar is bowed to place the pads thereon in the locus of a bow in readiness for gripping the straight leading edge of the sheet.

Further in accordance with the invention the arcuate surface l0ll04 of the cam 100 is formed so as to be concentric with the axis of oscillation of cylinder 31 to define a neutral condition in which the bar. 50 is straight, yet capable of cocking adjustment in either direction about a central pivot axis to vary both the amount and direction of bow in the locus of the gripper pads which the cam controls. Thus the cam 100, which is in the present construction of boomerang profile is pivoted for cocking adjustment about a pin 160, mounting a bearing 161, which is secured to'the end of a bracket 162 (FIG. 8) mounted upon one of the stationary'end frame members of the press. For the purpose of imparting minute cocking adjustment to the cam member in one direction or the other, a manual control 170 is provided in a form of an adjusting shaft 171 having a shallow thread 172 which is screwed into a threaded support 173, the degree of advancementof the thread being manually controllable by a knob 174. Rotation of the knob is limited to a useful range, in the present instance slightly less than.360, by a pin 175 on I the shaft which engages a stop pin 176. The support 173, into which the shaft is screwed, is supported on a bracket 177 .in the form of a flat, horizontally extending rigid plate which is firmly secured to the frame10 on the press.

Arranged in the path of movement of the adjusting shaft 171 is a bell crank 180 having a first leg 181 and a second leg 182 pivoted about a central axis 183. The leg 182 of the bell crank is pinned at 184 to a drop link 185, the lower end of which is pinned at 186 to one end of the cam member. For removing from the linkage system any possible looseness or play, a stiff spring 187 is interposed between the stationary bracket 177 and the cam. The spring is centered about a pin 188 on the cam and engages, at its upper end, a threadedly adjustable seat member 189 which permits adjustment of the spring pressure. The spring force is sufficiently great so that the spring maintains the bell crank firmly seated against the adjusting screw regardless of the normally encountered variations in reaction pressure between the cam follower and the cam. The force originating in the take-up spring 187 also has the effect of removing any endwise play in the tread 172 of the adjusting shaft 171 so that even the minutest amount of adjusting movement of the knob 174 results in an accurately corresponding degree of cocking movement of the cam.

Corresponding adjusting structure, in a mirror image, is employed for the cam 100 at the opposite end of the transfer assembly. Because of the complete take-up of the play at both ends, corresponding movements of the adjusting knobs can be expected to produce corresponding amounts of bow in the locus of the gripper pads mounted on the pad bar.

Under normal circumstances, where it is desired to impart a convex bow to the leading edge of a sheet for overcoming fan-out,,the cam 100 is adjusted by rotating the adjusting shaft so as to rock the bell crank 180 counterclockwise, cocking the cam'clockwise from its neutral position so that the cam occupies the position shown, greatly exaggerated for clarity, in FIG. 9. When the transfer assembly 30 is rocked to its reference position, defined by the

stops

150, 151, for pick-up, the cam follower occupies the position 101 on the cam surface in which the follower is pressed radially inward against the force of the spring 130, causing the levers at the ends of the bar to rock slightly counterclockwise, pulling upon the ends of the bar 50, so that the bar, and the

gripper pads

51, 52 which are mounted thereon, as well as the intermediate gripper pads. occupy a convexly bowed locus at the time that the gripper fingers are closed against the pads. as shown in FIG. 10. This closure, of itself, does not deform the leading edge of the sheet. However, when the transfer assembly begins to swing counterclockwise, relative movement occurs between the cam followers and the respective cams, advancing the followers to the region 102 of the cam surface, alined with the pins 160 which support the cam members. By reason of the alinement, the region 102 is a neutral region, which is unaffected by the cocking of the cam member. As the cam followers proceed to the neutral position, they are moved radially outward by follow-up expansion of the spring 130, causing the pad bar to be restored to its straight condition as shown in FIG. 10a. This causes the gripper pads 52 at the ends of the bar to move relatively in the direction of the sheet so that the lateral edges of the sheet retreat slightly, accompanied by convex bowing at the leading edge.

. As the transfer assembly swings further in the counterclockwise direction the follower roller 105 proceeds from the neutral point 102 to the position 103 corresponding to release of the sheet to the grippers on the constantly running cylinder. Such movement, from 102 to 103, is accompanied by an additional movement of the follower roller radially outward with respect to the transfer cylinder, which results in clockwise relative rocking of the levers 110 and pushing of the pad bar 50 by supports at each end. This forms the pad bar In short, it will be seen that one-half of the bowing of the leading edge of the sheet occurs during the first half of the swing, until the pad bar at mid-point occupies its straight condition, the other half occurring during the final portion of the swing until the pad bar is bowed in its opposite direction. This enables maximum antifanout effect with a minimum deflection of the pad bar from its neutral condition. It is to be noted that the leading edge of the sheet is deformed from its straight condition to its bowed condition progressively during the time that it is being transported, enabling the entire sheet to be gradually accommodated to the convexity at the leading edge over the entire transport stroke.

The bowing is accomplished both smoothly and gradually and the structure i-sithus distinguished over prior structures where the bowing is controlled by stops which deflect the pad bar to the required extent during the final movement of the transfer assembly into its reference pick-up position. The transfer assembly then overtravels to the to the position 104 on the cam 100 to clear" the gripper fingers. Upon the return stroke of swinging movement the sequence automatically reverses. i

While it is one of the features of the Construction that the locus of the pads changes gradually from bowing in one direction to bowing in the opposite direction over the transport stroke, it will be apparent that the invention is not limited'thereto and the invention may be practiced with bowing of the pad bar in a single direction only. For example, by moving the lever pivot pin 160 from the position shown in FIG. 3 to position'101 on the cam surface, the sheet may be picked up with the pad bar in its straight condition, and all of the bow ing movement may be imparted to the sheet by bowing of the bar in the direction shown in FIG. 10b. Conversely, the pivot pin 160 may be moved into alinement with the portion of the surface 103 of the cam, whereupon'the pad barwill be bowed, as shown in FIG. 10, at the time of pick-up and straightened, as shown in FIG. 10a at the time'of transfer to the grippers on the constant rotating cylinder.

Also while it is one of the features of the present con struction that the

gripper pads

51, 52 are distributed at the central and end positions on a continuous supporting bar, it will be apparent to one skilled in the art that the invention, in one of its aspects, is not limited to use of a bowed bar and that the gripper pads 52 may be separately mounted for individual peripheral movement and directlycoupled to the lower end of the lever 110 for direct positioning by the latter. For example, the pads 52 might be mounted as slides in peripherally extending ways for, limited forward and backward movement without departing from the invention. Alternatively, the gripper pads might be mounted on a radial arm secured to the cylinder 31 and having sufficient flexibility so as to permit limited movement, under the control of lever 110, in the peripheral direction.

Also, while means have been shown for anchoring the central portion of the bar 50 and imparting limited relative movement to' the ends, the invention is not limited thereto and, if desired, the ends of the bar may be relatively fixed, as regards movement in the peripheral direction, to the transfer assembly, while the central portion of the bar is floatingly mounted and movable by a single lever such as the lever 110 disclosed in the drawings.

As used herein the term sheet register guides refers to any means for holding and positioning the straight leading edge of the sheet for pick-up by the gripper pads.

I claim as my invention:

I. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of an advancing sheet, a transfer assembly having means oscillating the same for picking up the straight leading edge of the sheet at the register guides and accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounted therealong, the pads having respective coacting gripper fingers, the pad bar being secured at its center to the transfer assembly and mounted for limited movement in the peripheral direction at its ends, means for defining the limit of movement of the transfer assembly to establish a reference position for the bar, means for closing the gripper fingers on the pads at the limit position for gripping the leading edge of the sheet, cam members mounted on the frame at the ends of the transfer assembly and presenting respective arcuate cam surfaces which are substantially concentric with the axis of oscillation, cam followers coupled to the ends'of the pad bar for engaging the respective cam surfaces, each of the cam members being positionable to define a neutral position for the cam follower at which the pad bar is substantially straight and having provision for precise cocking adjustment so that the bar is bowed in one direction at the time of gripping the leading edge of the sheet and bowed in the opposite direction at the time the sheet is released to the grippers of the constantly rotating cylinder thereby to progressively deform the leading edge of the sheet from a straight condition to a bowed condition for transfer to the cylinder grippers to compensate for fan-out at the trailing edge.

2. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the straight leading edge of an advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of generally alined gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having respective coacting gripper fingers, means for defining the limit of movement of the transfer assembly to momentarily position the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting in either direction from the straight condition into a bowed locus, cam and cam follower means interposed between the shifting means and the frame to produce progressive relative movement of the shifting means over a stroke of oscillation of the transfer assembly, the cam being so contoured as to cause the locus of the gripper pads to be bowed in one direction at the time of gripping the leading edge of the sheet and to be bowed in the other direction at the time that the sheet is released to the grippers on the constantly rotating cylinder thereby to deform the leading edge of the sheet from the straight condition to a bowed condition for compensation for fan-out-at the trailing edge.

3. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of aligned fining the limit of movementof the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shift-' ing the same with respect to the assembly so that the pads occupya bowed locus at the instant of gripping, cam means on the frame adjustably mounted with respect to the frame for varying the maximum throw of the cam and thereby varying the curvature of the locus of the pads at the instant of gripping, said cam means having a cam surface extending arcuately about-the transfer assembly, cam follower means coupledto the shifting means for engaging the camrneans, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement'of the pads progressively into straight position as the transfer assembly reverses its movement, thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

4. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheetsfed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transto bow in the opposite direction at the instant of transfer of the sheet to the rotating cylinder.

5. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leadingedge of the advancing sheet, a transfer assembly having means for oscillating the same for picking upthe straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a-s'eries of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly and being concentric with the axis of oscillation of the transfer assembly to provide zero throwof the cam follower and in which adjusting means are provided for'adjustably fer assembly having means for oscillating the same for I center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly,

said pads having coacting gripper fingers, means for defining the limit of movement of the transfer. assembly for momentarily positioning the said one set of pads-in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted -on the transfer assembly for limited relative movement in the peripheral direction ahd having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus atthe instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that, the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge, the cam means being so shaped as to cause the locus of the gripper 'pads to bow in one direction at the instant of gripping the sheet and cocking the cam means to produce a desired degree and direction of bowing of the locus of the gripper pads at the respective gripping and release of the sheet, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallowthrow and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position'as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge-of the sheet for compensation for fan out at the trailing edge. 1

1 6. An infeed mechanism for arotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of frontregister guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to thegrippers on the rotating cylinder, .said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, saidpads having coacting gripper fingers, means for defining the limit of movement, of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly, for limited relative movement in the peripheral direction andhaving means for shifting the same with respect to the assemblyso that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly and being substantially concentric with the axis of oscillating movement of the transfer assembly, said cam means being centrally pivoted with means including an adjusting screw for rocking the cam means about the pivot in one direction or the other, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

7. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylindercomprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and'positioning the leading edge of the advancing sheet, a transfer assembly havingv means for oscillating the same for pickingup the straight leading edge of' the sheet at the register guides and for accelerating the sheet to press register guides and accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having respective sets of gripper pads at the center and at the ends in general alinement with one another, the pads having coacting gripper fingers, means for closing the gripper fingers on the pads to grip the-leading edge of the sheet, at least one set of the pads being movable through a small displacement relative to the transfer assembly and having means for shifting the pads relative to the assembly so that the padsoccupy a bowed locus at the instant of gripping, means including a cam follower on the transfer assembly and a cam on the frame for operating the shifting means, a spring on the transfer assembly for maintaining the cam follower at all times in firm contact with the surface of the cam, the cam having a cam surface which is substantially concentric with the speed for transfer to the grippers on the rotatingcylinder, -said transfer assembly having a series of aligned gripper pads including respective sets of pads-at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly, cam follower means coupled'to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge, said gripper pads each having a roughened surface and each coacting gripper finger having a smooth surface so that the sheet tends to move with the pad andrelative to the finger to put the leading edge of the sheet into bowed configuration.

8. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the straight leading edge of an advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the axis of oscillating movement of the transfer assembly and having means for supporting the same for cooking movement thereby to determine the throw of the cam follower, a manually operated adjusting linkage coupled to the cam for holding it in a desired position of adjustment, and means including a strong spring for constant take-up of any play in the linkage means.

9. An infeed-mechanism for a rotary sheet-fed printing press for feeding sheetsto grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the register guides and for accelerating the sheet to'press speed for transfer to the grippers on arotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads thereon in general alinement including a central set and a set at the respective ends of the bar, at least one of the sets being movable through a small displacement in a peripheral direction relative to the transfer assembly so that the pads occupy a bowed locus, thepad bar having supporting levers in its regions of movement, each of the levers beingof dog-leg-shape centrally pivoted to the transfer assembly and having a radially extending arm for engaging the bar and a peripherally extending arm having a cam follower mounted at theend thereof, cam members on the framerespectively alined with the cam followers and each having-an arcuate inwardly facing surface on-which the associated cam follower rides, springs on the transferassembly for pressing the cam followers against the cam surfaces, the cam members being pivoted to the frame aboutvan axis parallel to the axis of oscillation, manual adjusting linkage for cocking each cam member into an adjustedposition thereby to determine the amount of throw of the cam and hence the amount of bowing'imparted to the locus' of the pads, means for constantly stressing the cam member thereby to take up any play in the adjustinglinkage, means for establishing the limit of movement of the transfer assembly to define a reference position for pick-up, and means for closing the gripper fingers on the pads to grip the leading edge of the sheet at the reference-position so that when the transfer assembly reverses its movement the change in the curvature of the locus of the gripper pads imparts a bow to the leading edge of the sheet for compensation for fan-out at the trailing edge. a a j"

Claims

1. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of an advancing sheet, a transfer assembly having means oscillating the same for picking up the straight leading edge of the sheet at the register guides and accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounted therealong, the pads having respective coacting gripper fingers, the pad bar being secured at its center to the transfer assembly and mounted for limited movement in the peripheral direction at its ends, means for defining the limit of movement of the transfer assembly to establish a reference position for the bar, means for closing the gripper fingers on the pads at the limit position for gripping the leading edge of the sheet, cam members mounted on the frame at the ends of the transfer assembly and presenting respective arcuate cam surfaces which are substantially concentric with the axis of oscillation, cam followers coupled to the ends of the pad bar for engaging the respective cam surfaces, each of the cam members being positionable to define a neutral position for the cam follower at which the pad bar is substantially straight and having provision for precise cocking adjustment so that the bar is bowed in one direction at the time of gripping the leading edge of the sheet and bowed in the opposite direction at the time the sheet is released to the grippers of the constantly rotating cylinder thereby to progressively deform the leading edge of the sheet from a straight condition to a bowed condition for transfer to the cylinder grippers to compensate for fan-out at the trailing edge.

2. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the straight leading edge of an advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of generally alined gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having respective coacting gripper fingers, means for defining the limit of movement of the transfer assembly to momentarily position thE said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting in either direction from the straight condition into a bowed locus, cam and cam follower means interposed between the shifting means and the frame to produce progressive relative movement of the shifting means over a stroke of oscillation of the transfer assembly, the cam being so contoured as to cause the locus of the gripper pads to be bowed in one direction at the time of gripping the leading edge of the sheet and to be bowed in the other direction at the time that the sheet is released to the grippers on the constantly rotating cylinder thereby to deform the leading edge of the sheet from the straight condition to a bowed condition for compensation for fan-out at the trailing edge.

3. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame adjustably mounted with respect to the frame for varying the maximum throw of the cam and thereby varying the curvature of the locus of the pads at the instant of gripping, said cam means having a cam surface extending arcuately about the transfer assembly, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement, thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

4. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one sEt of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction ahd having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge, the cam means being so shaped as to cause the locus of the gripper pads to bow in one direction at the instant of gripping the sheet and to bow in the opposite direction at the instant of transfer of the sheet to the rotating cylinder.

5. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly and being concentric with the axis of oscillation of the transfer assembly to provide zero throw of the cam follower and in which adjusting means are provided for adjustably cocking the cam means to produce a desired degree and direction of bowing of the locus of the gripper pads at the respective gripping and release of the sheet, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan out at the trailing edge.

6. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotatIng cylinder, said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly and being substantially concentric with the axis of oscillating movement of the transfer assembly, said cam means being centrally pivoted with means including an adjusting screw for rocking the cam means about the pivot in one direction or the other, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

7. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the straight leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having a series of aligned gripper pads including respective sets of pads at the center and at the ends of the transfer assembly, at least one set of the pads being fixed to the transfer assembly, said pads having coacting gripper fingers, means for defining the limit of movement of the transfer assembly for momentarily positioning the said one set of pads in a reference gripping position, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, the other set of gripper pads being mounted on the transfer assembly for limited relative movement in the peripheral direction and having means for shifting the same with respect to the assembly so that the pads occupy a bowed locus at the instant of gripping, cam means on the frame having a cam surface extending arcuately about the transfer assembly, cam follower means coupled to the shifting means for engaging the cam means, the cam surface having a shallow throw and being of such contour that the pads are moved into a bowed locus progressively with movement of the transfer assembly toward the reference position followed by movement of the pads progressively into straight position as the transfer assembly reverses its movement thereby to impart a bow of opposite curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge, said gripper pads each having a roughened surface and each coacting gripper finger having a smooth surface so that the sheet tends to move with the pad and relative to the finger to put the leading edge of the sheet into bowed configuration.

8. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the straight leading edge of an advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the register guides and accelerating the sheet to press speed for transfer to the grippers on the rotating cylinder, said transfer assembly having respective sets of gripper pads at the center and at the ends in general alinement with one another, the pads having coacting gripper fingers, means for closing the gripper fingers on the pads to grip the leading edge of the sheet, at least one set of the pads being movable through a small displacement relative to the transfer assembly and having means for shifting the pads relative to the assembly so that the pads occupy a bowed locus at the instant of gripping, means including a cam follower on the transfer assembly and a cam on the frame for operating the shifting means, a spring on the transfer assembly for maintaining the cam follower at all times in firm contact with the surface of the cam, the cam having a cam surface which is substantially concentric with the axis of oscillating movement of the transfer assembly and having means for supporting the same for cocking movement thereby to determine the throw of the cam follower, a manually operated adjusting linkage coupled to the cam for holding it in a desired position of adjustment, and means including a strong spring for constant take-up of any play in the linkage means.

9. An infeed mechanism for a rotary sheet-fed printing press for feeding sheets to grippers on a constantly rotating cylinder comprising, in combination, a frame including a feed table for receiving sheets fed one by one, a set of front register guides for engaging and positioning the leading edge of the advancing sheet, a transfer assembly having means for oscillating the same for picking up the leading edge of the sheet at the register guides and for accelerating the sheet to press speed for transfer to the grippers on a rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads thereon in general alinement including a central set and a set at the respective ends of the bar, at least one of the sets being movable through a small displacement in a peripheral direction relative to the transfer assembly so that the pads occupy a bowed locus, the pad bar having supporting levers in its regions of movement, each of the levers being of dog-leg shape centrally pivoted to the transfer assembly and having a radially extending arm for engaging the bar and a peripherally extending arm having a cam follower mounted at the end thereof, cam members on the frame respectively alined with the cam followers and each having an arcuate inwardly facing surface on which the associated cam follower rides, springs on the transfer assembly for pressing the cam followers against the cam surfaces, the cam members being pivoted to the frame about an axis parallel to the axis of oscillation, manual adjusting linkage for cocking each cam member into an adjusted position thereby to determine the amount of throw of the cam and hence the amount of bowing imparted to the locus of the pads, means for constantly stressing the cam member thereby to take up any play in the adjusting linkage, means for establishing the limit of movement of the transfer assembly to define a reference position for pick-up, and means for closing the gripper fingers on the pads to grip the leading edge of the sheet at the reference position so that when the transfer assembly reverses its movement the change in the curvature of the locus of the gripper pads imparts a bow to the leading edge of the sheet for compensation for fan-out at the trailing edge.