US3623721A

US3623721A - Means for overcoming fan-out in lithographic press

Info

Publication number: US3623721A
Application number: US869565A
Authority: US
Inventors: Walter S Smith
Original assignee: North American Rockwell Corp
Current assignee: Boeing North American Inc
Priority date: 1969-10-27
Filing date: 1969-10-27
Publication date: 1971-11-30
Anticipated expiration: 1988-11-30
Also published as: GB1257447A; FR2066812A5; CH530867A; JPS495925B1

Abstract

An infeed gripper mechanism including an oscillated transfer assembly for transferring a sheet from a feed table to a constantly running impression cylinder by means of a series of gripper pads which grip the leading edge of the sheet and which are biased into aligned reference position. Fixed but adjustable stops are provided on the frame in the path of movement of the gripper pad mounting means for displacing certain of the pads from reference position so that the pads occupy an arcuate, or bowed, locus upon gripping the sheet. Subsequent restoration of the pads to reference position upon leaving the stops thus imparts a reverse bow to the leading edge of the sheet to overcome fan-out at the trailing edge. In the preferred embodiment, the pad mounting means is in the form of a pad bar to which all of the pads are secured and which is deformed into bowed shape upon obstruction by the fixed stops. Also in the preferred embodiment each of the fixed stops is in the form of a lever having a stop surface adjusted by a manually rotated positioning screw and with an overpowered spring effectively in series to protect against damage or breakage in the event a foreign object is interposed.

Description

ilnite States Patent [72] Inventor Walter S. Smith Naperville, Ill.

[21] Appl. No. 869,565

[22] Filed Oct. 27, 1969 [45] Patented Nov. 30, 1971 [73] Assignee North American Rockwell Corporation Pittsburgh, Pa.

[54] MEANS FOR OVERCOMING FAN-OUT IN Primary E.raminer-Joseph Wegbreit Attorney-Wolfe. Hubbard. Leydig, Voit and Osann ABSTRACT: An infeed gripper mechanism including an oscillated transfer assembly for transferring a sheet from a feed table to a constantly running impression cylinder by means of a series of gripper pads which grip the leading edge of the sheet and which are biased into aligned reference position. Fixed but adjustable stops are provided on the frame in the path of movement of the gripper pad mounting means for displacing certain of the pads from reference position so that the pads occupy an arcuate, or bowed, locus upon gripping the sheet. Subsequent restoration of the pads to reference position upon leaving the stops thus imparts a reverse bow to the leading edge of the sheet to overcome fan-out at the trailing edge. In the preferred embodiment, the pad mounting means is in the form of a pad bar to which all of the pads are secured and which is deformed into bowed shape upon obstruction by the fixed stops. Also in the preferred embodiment each of the fixed stops is in the form of a lever having a stop surface adjusted by a manually rotated positioning screw and with an overpowered spring effectively in series to protect against damage or breakage in the event a foreign object is interposed.

PATENTEU mwso I971 SHEET 1 BF 5 R mm n NS .A as M, n m... mM W M J M J,

IIII I vii PATENTEDHUV30I97I 3,623,721

sum 2 or 5 TZMMH AXIS a TNVENTR WALTER SSMWH ,VM LMM Arrvs.

PATENTEDNMBOIQ?! 3,623.72].

SHEET '4 UF 5 LC 1062 so 92 [08'3 92 INVENTOR WALTER 5. SMITH A'I'TYS.

MEANS FOR OVERCOMING FAN-OUT IN LITHOGRAPHIC PRESS In multicolor printing misregister sometimes occurs by reason of a phenomenon known as fan-out. Fan-out is the change in' the lateral dimension of the sheet as it passes through the press, believed to be caused by the absorption of moisture from the dampening units combined with the ironing effect of the cylinders causing the sheet to expand laterally, particularly at the trailing portion. This condition can be largely overcome by imparting an artificial curvature, or bow, to the leading edge of the sheet. One common expedient for bowing the leading edge is to arrange the front register guides in a bowed configuration and to force the sheet into conformation with the guides. This has the disadvantage that the drive-up rollers or the like, employed to force the sheet against the guides, tend to leave marks on the sheet. Alternative schemes to achieve bowing by offsetting the gripper pads on the impression cylinder have been expensive and have not lent themselves to adjustment while the press is in operation.

It is therefore, an object of the present invention to provide an infeed mechanism for a sheet-fed press in which the degree of bowing is achieved with precision and consistency without risk of marking or other damage to the sheet and which permits the degree of bowing to be varied to achieve exact register with the press in operation.

It is another object of the invention to provide an infeed mechanism for a sheet-fed press which is inherently durable and maintenance free, which is simple to use and adjust, and which avoids possibility of damage in the event a foreign object becomes obstructively interposed between the stop surfaces.

It is yet another object to provide a transfer assembly which is highly versatile and which may be adjusted to overcome any condition related to fan-out, such as negative fan-out, as that term is subsequently defined.

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 view in elevation of a transfer assembly constructed in accordance with the invention, in section for the purpose of foreshortening;

FIG. 2 is a fragmentary section taken along the line 2-2 in FIG. 1;

FIG. 3 is a vertical section taken along the line 3-3 in FIG.

FIG. 4 is a fragmentary section based upon FIG. 3 but showing transfer of the sheet to the impression cylinder;

FIG. 5 is a section taken along the line 5-5 in FIG. 1;

FIG. 6 is a fragmentary section looking along the line 6-6 in FIG. 5;

FIG. 7 is a fragmentary section showing a gripper pad and cooperating gripper finger;

FIG. 8 is a fragmentary section looking along the line 8-8 in FIG. 1;

FIG. 9 is a fragmentary section looking along the line 9-9 in FIG. 8;

FIG. 10 is a fragmentary section taken along the line 10-10 in FIG. 1;

FIG. 11 is a fragmentary section looking along the line 11- II in FIG. 10;

FIG. 12 is a fragmentary top view looking along the line 12-12 and showing the cluster of adjusting knobs.

FIG. 13 is a fragment showing a pillow on the pad bar as it is swung downwardly from minimum to maximum radius condition incident to obstruction with a stop;

FIG. 14 is a diagram of a sheet in contact with the front register guides;

FIG. 14a is a diagram showing the bowing of the pad bar on striking of the fixed stops; and

FIG. 14b is a diagram similar to FIG. 14a but showing restoration of the pad bar to straight reference condition to impart reverse bowing to the leading edge of the sheet.

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 invention.

Turning now to the drawings and particularly to FIGS. 1-5, there is disclosed a portion of a sheet-fed lithograph press having a frame [0 and a feed table 11 onto which sheets are fed, one by one, from left to right as viewed in the drawings, against front register stops 13. The latter are mounted upon a shaft 14. A typical sheet, indicated at 15, has a leading edge 16, lateral edges l7, l8, 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 transfer in proper phase relation to grippers on a constantly rotating impression cylinder. The front register stops are physically separate from the table'll, 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 including a transversely extending supporting shaft 31 which is mounted for oscillating movement, imparted by arms 32, in frame plates 33 only one of which is shown (FIG. 3) and which in turn are supported upon pedestal structure 34. A stop 35 limits the movement of the transfer assembly and defines its position at the time of pickup.

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, following which the transfer assembly decelerates and reverses its movement to return to the pickup position shown in FIG. 3. The means for oscillating the shaft 31 are not included within the scope of the present invention and reference may be made to the prior art for typical oscillating drives such, for example, as that shown in prior U.S. Pat. No. 1,764,104.

In accordance with present invention, a plurality of gripper pads are provided on the transfer assembly, each of the gripper pads having gripper pad mounting means biased against reference stops on the transfer assembly so as to normally occupy an aligned reference position but having provision for a small amount of retreating movement. Mounted on the frame in the path of movement of the gripper pad mounting means are a series of fixed but differentially adjustable stops so arranged that when the stops are encountered the gripper pads are moved out of aligned position to an arcuate or bowed locus for gripping the leading edge of the sheet, thereby imparting a bow of opposite curvature to the leading edge of the sheet when the transfer assembly swings away from the fixed stops and as the gripper pad mounting means resumes a condition of alignment determined by the reference stops.

More specifically in accordance with the invention, a plurality of gripper pads are provided mounted along a gripper pad bar which is normally straight, biased to a reference position, but which is mounted for localized retreating movement with respect to the transfer assembly so that, upon engaging the adjusted configuration of fixed stops, the gripper pad bar is bowed to hold the gripper pad in correspondingly bowed configuration during the time of gripping. A moment later, when the transfer assembly moves away from the fixed stops, the bar resumes its straight, reference position so as to deform the leading edge of the sheet into a slight bow for the purpose of overcoming fan-out at the trailing edge of the sheet.

Thus, referring to the drawings, a gripper pad bar 50 is provided having bolted, or otherwise secured along its length, gripper pads indicated at 5 155 (see FIGS. I to 3). Taking a gripper pad 51 by way of example (FIG. 7), 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 the pads 51-55 is a set of gripper fingers 61-65 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 gripper finger shaft 60 for gripping the sheet when the transfer assembly is in the position of pickup shown in FIG. 3 and for releasing the sheet immediately following transfer shown in FIG. 4. It is one of the features of the present invention tat the pad surface 57 on each of the pads is roughened whereas the gripping surface on each of the cooperating fingers 61-65 is smooth. Thus when the pad bar 50 leaves the fixed stops, which permits restoration to its straight or reference condition, the leading edge of the sheet tends to follow the pads and relative slippage takes place at the smooth end s of the fingers.

For the purpose of supporting shaft 60, as well as the pad bar 50, for bodily oscillation by shaft 31, a bracket is provided at each end of the shaft. Such brackets, bifurcated at the lower end, are indicated at 71, 72 in FIGS. 1 and 2. Mounted between the bifurcations at the left-hand end is a supporting lever 73 (see also FIG. having a central opening for admitting the shaft 60 and having a forwardly projecting arm 74 which mounts the bar 50 as well as a rearwardly projecting arm 75. Similarly, at the opposite end of the shaft 60, is a mounting lever 76 mounted between the bifurcations of bracket 72 and having a forwardly projecting arm 77 and a rearwardly projecting am 78. Mounted at the rear ends of the

arms

75, 78 are rollers 79 which are engaged by suitable cams so that after the sheet has been deposited in the grippers on the impression cylinder, the pad bar 50 and its associated pads and gripper fingers may be swung inwardly toward the axis of the shaft 31 in an upwardly tucked position so as to avoid interference with elements on the impression cylinder or interference with the trailing portion of the sheet during the return movement of the transfer assembly. However, the specific cam surfaces for acting upon the rollers 79 are outside of the scope of the present invention and, except as will be discussed in connection with FIG. 13, the position of the pad bar 50, with respect to the oscillating support shaft 31, may be assumed to be defined by a set of limit stops indicated at 80 in FIG. 5.

In the above paragraphs, mention has been made of the means for supporting the finger operating shaft 60, and the pad bar 50, at the ends. Anns are additionally provided on the support shaft 31 for supporting the shaft 60 and pad bar 50 at two more central, evenly spaced positions. Thus, referring to FIGS. 2 and 8, a bracket 91 is mounted upon the shaft 31 in supporting engagement with shaft 60. Straddling the lower end of bracket 91 is a forwardly extending arm 92 of clevis shape having a transverse opening for receiving the shaft 60. A second bracket 93 (FIG. 2) secured to the shaft 31 provides support for shaft 60 and has an arm 94 of clevis shape similar to arm 92. In summary, then, the bar 50 is supported at its ends upon

arms

74, 77 and is supported centrally upon evenly spaced

arms

92, 94.

Mention will now be made of the manner in which the bar 50 is supported in a normal straight reference position while permitting localized retreating movement of the bar, with respect to its supporting arms, to deform the bar into arcuate or bowed shape, upon the striking of fixed but adjustable stops. The manner is which the left-hand end of the bar 50 is supported on the arm 74 (see FIGS. 2 and 5), will first be discussed. The bar, at its left-hand end, is penetrated by a bolt which threads into the arm 74. Under the bolt head, in addition to a lockwasher, is a restraining washer 102, the back surface 103 of which serves as a reference stop. Surrounding the shank of the bolt 101 is a square spacer 104 having a length L which is somewhat greater than the thickness W of the bar 50, thereby to define a clearance space 105 behind the bar. It might be mentioned, also that the square spacer 104, instead of directly engaging the surfaces in the bar, engages a square opening cut into an annular insert 106 which is provided for antiwear purposes. For urging the engaged end of the bar 50 into a normal seated position against the reference stop surface 103, on the backside of the washer, a pair of

springs

107, 108 are provided. These springs are conveniently recessed into the arm 74 and, while appearing of relatively light construction, are nevertheless sufficiently strong to keep the bar seated on the reference surface until intentional unseating by the adjacent striking of a fixed stop. For the purpose of additionally supporting the bar in the course of its limited lateral movement, a pin 109 is provided which is force fitted into the arm 74 and which has a flat formed on its upper side as a bearing surface.

Similar structure is provided for supporting the pad bar at a total of four regions of support. Thus in FIG. 10, which shows the structure along the section line 10-l0, and in FIG. 11, which is based thereon, corresponding parts are indicated by corresponding reference numerals with the addition of subscript a. Thus a spacer 104a surrounding a bolt 1010 provides clearance a, with the bar being pressed against the reference surface 103a, on the backside of the washer, by biasing springs 107a, 108a. At a third point of support of the pad bar shown in FIG. 8, and corresponding to section line 8- 8 in FIG. 1, a bolt 101b, penetrating spacer 104b, secures the bar to arm 92 with clearance indicated at 105b, other corresponding parts being indicated by corresponding reference numerals with the addition of subscript b Finally, at its righthand end, the pad bar is supported by a bolt 101C and the construction is a substantial duplicate of that previously described in connection with FIGS. 5 and 6.

To prevent the bowing of the bar 50, as it strikes the fixed stops to be described, from causing binding at the spacers, the inserts 106 are machined out to provide lateral clearance as indicated at 110 in FIG. 6 and as indicated at 110a in FIG. 1 1. No side clearance is however provided for spacer 104b in FIGS. 8 and 9. In the case of the spacer associated with the bolt 101e, lateral clearance is provided adjacent the spacer but on the right-hand instead of the left-hand side.

In accordance with the present invention, fixed stops are provided adjacent the respective ends of the pad bar 50 for the purpose of engaging the pad bar and to deform the locus of the pads into arcuate or bowed shape as described. A typical one of the fixed, but adjustable stop structures is shown in FIG. 3, as viewed along section line 3-3 in FIG. 1. The stop is in the form of the stop lever having a lower or stop arm 121 and an upper or positionable arm 122, the lever, overall, being of dogleg shape and centrally pivoted at a horizontal pin 123. The ends of the pin 123 are mounted in a vertical bracket 124 having spaced walls secured to a transversely extending bridging member 125 of fairly massive hollow construction. The bridging member 125 is rigidly mounted on brackets 126 at the respective ends thereof, the brackets being secured to side plates 33 mounted on pedestals 34 previously referred to.

For positioning the stop 120 a manually operated positioning screw 130 is provided which is threaded as indicated at 131 and which has an adjusting knob 132 which in turned backwardly or forwardly to position the tip 133 which engages the backside of the portion 122 of the stop member. In order to maintain the stop member in contact with the tip of the adjusting screw, in the face of normal loading, and for protecting the stop assembly and the parts which engage it, a strong spring 135 is interposed between the lower end of the stop member and the frame 124 in which it is mounted. The spring is effectively preloaded so that it is strong enough not to yield in the face of normally developed impact pressure but yieldable in the event that a foreign object should for some reason become interposed between the stop and the bar.

For providing a smooth wear surface on the pad bar and for minimizing impact at the stop 120, the bar has secured thereto a pillow block 136 of progressive thickness to achieve final consuming action. As already stated, the bar 50, in addition to its oscillatory swinging movement is rocked upwardly about the center of the shaft 60 (see FIG. 5) in timed relation to the bodily movement to provide clearance. Thus when the gripper pads have completed transfer and bar 50 is undergoing return movement, the bar is tucked upwardly. The final movement of the pad bar is movement radially downward from the shaft 31 as the fixed stop 120 is engaged and just prior to gripping the leading edge of the sheet. During such downward movement, the stop 120 is engaged first at a radius r1. With subsequent wiping movement of the pillow block, final positioning occurs at the radius r2. This reduces impact with the fixed stop since, instead of imparting a hammer blow to the stop, the pillow only lightly engages the stop 120 and then wipes or crowns" its way quietly to final position.

Corresponding stop structure is provided at two other stop positions, one at the center and the other at the opposite end of the pad bar. Referring to the adjustable stop at the center position of the bar, parts corresponding to those described in FIG. 3 are employed, where applicable, with the addition of subscript a. Thus a stop lever 120a is used having an upper portion 122a, and pivoted about a horizontal pin 123a mounted in a vertical frame 1240, which is secured to the bridging member 125. To position the upper end of the stop member 120a, an adjusting screw 130a is provided having a thread 131a and a tip 133a. However, instead of mounting the knob 132a directly upon the threaded screw 1300, an auxiliary shaft 136 is provided in a more accessible location (see FIG. 12), the two shafts being coupled together by a sprocket chain 137 trained about sprockets 138, I39.

At the third fixed stop position, at the right-hand end of the pad bar as viewed in FIG. 2, a similar fixed stop assembly is provided with corresponding reference numerals for identification with the addition of subscript b. Thus a stop 120b is used having an upper portion l22b and mounted in a frame or bracket 12 3b for engagement by an adjusting screw 13% having a thread 1311b and a knob l32b. The knob is mounted on a shaft 13612 (FIG. 12) which is coupled to the shaft 13% by a sprocket chain 1137b trained around sprockets 138b, I39b. The threads 13!, 131a, and 13112 are preferably left-hand threads for psychological purposes, so that right-hand rotation of the knob is effective to advance the stops incrementally into obstructing position. The adjusting knobs are not only grouped for easy access, but they may be provided with calibrated scales for directly indicating the position of the stops which they are associated. Because of the relatively massive nature of the fixed stop mechanisms, the stops and their associated linkages may be expected to retain calibration with a high order of accuracy over a long press lift.

The operation of the mechanism discussed above may be reviewed in connection with FIGS. 14, 14a and 14b:

A sheet 15 is fed onto the feed table 11 into contact with front register guides 13. It will be assumed that the sheet, being subject to fan-out, has a fan-out dimension, corresponding to the distance between the side edges 17, 18. It will be assumed further that the desired width of the sheet, for accurate register, corresponds to that between the dot-

dash outline

17a, 18a.

When the transfer assembly is bodily swung to its pick-up position, defined by stop 35, and illustrated in FIG. 3 and FIG. 14a, the pad bar is engaged by the fixed tops 120, 12012 in the two end positions, causing the pad bar to bent away from the reference surfaces into arcuate or bowed shape against the restoring force of the bar and the associated biasing springs. For the type of bowing shown in FIG. 140, the central stop 120a may be completely backed off. With the pads formed into a bowed locus, the sheet is clamped from the underside against the roughened pad surfaces 57 by fingers 61. The front register guides swing downwardly to clear of the edge of the sheet.

A moment later when the transfer assembly swings to the right toward the FIG. 4 position, the pad bar 50 leaves the fixed stops pennitting the bar to return to its straight reference position illustrated in FIG. 14b. The pads, being roughened, carry with them the leading edge portion of the sheet during the restoring movement, imparting a bow of opposite curvature to the leading edge 16 of the sheet and with relative slippage taking place at the smooth-surfaced gripper fingers. The width dimensions between 17, 18 and 17a, 18a now correspond, as shown in 14b, to compensate for, and overcome, the tendency toward fan-out. The bowed shape of the leading edge is retained by the grippers in the impression cylinders following the transfer.

In the above discussion it has been assumed that it is conventional fan-out which is to be taken care of, that is, the condition where the trailing edge of the sheet tends to be too wide because of the wetting and subsequent ironing as the sheet passes through the press. This might be referred to for convenience as positive fan-out. However it is one of the features of the present construction that it is capable of producing a correction in the opposite direction, that is, where the trailing edge of the sheet is, for some reason, narrower than desired and which condition might be referred to as negative fan-out. To take care of this condition the central stop a may be advanced and the side stops 120, 12%, retracted so that the pad bar undergoes opposite curvature from that shown in FIG. 14a and so that, upon resumption of the straight condition, a concave rather than convex curvature is imparted to the leading edge 16 of the sheet.

While the stops 120, 120a and 120k are shown as levers of the first class it will be apparent to one skilled in the art that, with slight modification of the structure, levers of the second or third class could be used as well.

It will be clear that the objects of the invention have been amply fulfilled. The sheet is maintained free of roller markings and the adjustment may be varied conveniently and with precision as the press continues to operate.

I claim as my invention:

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 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 the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounted thereon, the pads having respective coacting gripper fingers, means including reference stops on the transfer assembly spaced along said par pad for establishing a reference position for the war with respect to the assembly while permitting localized retreating movement away from reference position, biasing springs on the transfer assembly spaced along said pad bar for baising the pad bar against the reference stops, means for defining the limit of movement of the transfer assembly, a series of fixed but adjustable stops on the frame in the path of movement of the pad bar, the pad bar being of relatively thin construction so that upon encountering the fixed stops the pad bar is slightly bowed to position the gripper pads in a locus of the bow, means for closing the gripper fingers for gripping the leading edge of the sheet so that when the transfer assembly reverses its movement, drawing the pad bar from engagement with the fixed stops, the pad bar is free to straighten to its reference position to impart a bow of reverse curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

2. A 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 the rotating cylinder, said transfer assembly having a plurality of gripper pads having mounting means therefor supported for limited movement, the pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing an aligned reference position for the pads while permitting localized retreatment movement away from reference position, biasing springs on the transfer assembly for biasing the pad mounting means against the reference stops, means for defining the limit of movement of the transfer assembly, and a series of fixed but adjustable stops on the frame in the path of movement of the pad mounting means so that upon encountering the fixed stops the pads are positioned in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet in the locus of a bow and so that when the transfer assembly reverses its movement, drawing the pad mounting means from engagement with the fixed stops, the pads are free to resume the reference posifion thereby to impart a bow of reverse curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

3. The combination as claimed in claim 2 in which each pad has a roughened surface and each cooperating gripper finger has a smooth surface to permit relative movement between the sheet and the gripper incident to restorative movement of the pad mounting means to reference position as bowing is imparting to the leading edge of the sheet.

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 bone by one, 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 the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounted thereon, the pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing a reference position for the bar with respect to the assembly while permitting localized retreating movement away from reference position, means for biasing the pad bar against the reference stops, means for defining the limit of movement of the transfer assembly, a pair of fixed but adjustable stops on the frame in the path of movement of the respective ends of the pad bar, the pad bar being of relatively thin construction so that upon the ends thereof encountering the fixed stops the pad bar is bowed to position the gripper pads in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet so that when the transfer assembly reverses its movement the pad bar is free to straighten in reference position to impart a bow of reverse curvature to the leading edge of the sheet for compensation of fan-out at the trailing edge.

5, The combination as claimed in claim 4 in which three fixed stops are provided, one atthe center of the bar and the remaining two at the ends, the stop at the center being differentially adjustable with respect to the stops at the ends in order to impart either a concave or convex bow to the leading edge of the sheet thereby to compensate for either positive or negative fan-out.

6. The combination as claimed in claim 4 in which bolts penetrating the pad bar are provided for securing the pad bar, such bolts are being surrounded by spacers having an axial length which is thicker than the pad bar to provide a limited amount of lateral lost motion with respect to the reference stops and in which the biasing springs are located adjacent the bolts for taking up the lost motion by pressing the pad bar against the reference stops, the biasing springs being sufficiently strong so as to maintain the pad bar seated against the reference stops at positions remote from the points of engagement of the fixed stops.

7. An infeed gripper 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 of transfer to the grippers on the rotating cylinder, said transfer assembly including a plurality of gripper pads having mounting means supported on the assembly, the gripper pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing an aligned reference position for the pads while permitting a small amount of localized retreating movement away from the reference position, biasing springs on the transfer assembly for biasing the pad mounting means against the reference stops, means for defining the limit of movement of the transfer assembly, and a series of fixed but adjustable stops on the frame in the path of movement of the pad mounting means, each of said fixed but adjustable stops having a threaded adjusting screw mounted on the frame for adjusting the stops so that upon closure of the gripper fingers the leading edge of the sheet is gripped in the locus of a bow and so that when the assembly reverses its movement, thereby storing the pad mounting means to reference position, a bow of reverse curvature is imparted to the leading edge of the sheet for compensation of fan-out at the trailing edge.

8. The combination as claimed in claim 7 in which each of the fixed stops has a preloaded spring effectively connected in series for maintaining the stop in its manually adjusted position but capable of yielding in the event a foreign object becomes interposed between the fixed stop and the pad mounting means.

9. The combination as claimed in claim 7 in which each of the fixed stops is in the form of a lever having a stop surface at one end and a threaded manually operated positioning screw at the other end and including a strong spring for maintaining the lever seated with respect to the screw during normal operation of the stop but which is capable of yielding upon interposition of a foreign object at the stop surface.

10. 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 the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounting thereon, the pads having respective coacting gripper fingers, means for radially retracting the pad bar following transfer of the sheet and for radially projecting the bar to working position upon completing a cycle of transferring movement, means including reference stops on the transfer assembly spaced along said pad bar for establishing a reference position for the bar with respect to the assembly while permitting localized retreating movement away from reference position, biasing springs on the transfer assembly spaced along said pad bar for biasing the pad bar against the reference stops, means for defining the limit of movement of the transfer assembly, a series of fixed but adjustable stops on the frame in the path of movement of the pad bar, the pad bar being of relatively thin construction and having pillow blocks thereon of tapering thickness for engaging the fixed stops so that upon encountering the fixed stops the pillow block is radially projected with wiping action against the stops crowding the pad bar into a bowed position so that the gripper pads lie in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet so that when the assembly reverses its movement, drawing the pad bar from engagement with the fixed stops, the pad bar is free to straighten in reference position to impart a bow of reverse curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

11. An infeed mechanism for transferring sheets from a position of rest on a support to grippers ona constantly rotating cylinder comprising an oscillatable transfer assembly having a series of gripper fingers and coacting pads for gripping a sheet on said support, accelerating the sheet to cylinder speed and transferring the sheet to the cylinder grippers, mounting means for said pads including an axially extending resilient member for normally maintaining the pads in a reference plane extending transverse to the path of the sheets, means for oscillating the transfer assembly between a sheet engaging position with respect to said support and a transfer point with respect to the cylinder, adjustable stop means located in the path of said resilient member adjacent said support, said stop means being adjustable to intercept and variably displace local portions of the resilient member from the reference plane while the transfer assembly is in the sheet engaging position to thereby temporarily displace the pads into the locus of a bow, and means for actuating the gripper fingers to grip a sheet while the pads are so displaced so that a predetermined bow is imparted to the leading edge of the sheet as the pads return to said reference plane upon movement of the transfer assembly away from said stop means.

12. An infeed mechanism for a rotary, sheet-fed printing press comprising in combination, an oscillatable transfer assembly having a series of gripper pads and coacting gripper fingers for gripping the leading edge of a sheet at rest on a feed table and accelerating said sheet to press speed for transfer to grippers on a constantly rotating cylinder, means for oscillating the transfer assembly between a sheet gripping position adjacent the feed table and a sheet transfer position adjacent the cylinder, means mounting said gripper pads on the transfer assembly including an axially disposed flexible bar for normally maintaining the pads in a predetermined reference plane extending transverse to the path of the sheets, at least one fixed but adjustable stop located in the path of said bar adjacent the feed table, said stop being adjustable to intercept and variably displace a local portion of said bar from the said reference plane as the transfer assembly moves to the sheet gripping position to thereby temporarily place the gripper pads thereon in the locus of a bow, and means for actuating the gripper fingers to grip the leading edge of a sheet while the gripper pads are so displaced so that upon movement of the transfer assembly away from said stop, the flexible bar and therewith said pads will return to the reference plane and thereby impart a bow to the leading edge of the sheet.

*h i l 1 I3! PO-IOSO Patent No.

Inventor(s) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated November 30, 1971 WALTER S. SMITH It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 22,

Column Column Column before "degree" insert ---desired--.

line 12, change "crowns" to read "crowds";

line 47,

line

line change "tops" to read "stops".

line change "par pad" to read "pad bar";

change "war" to read "bar";

28, change "bone" to read "one";

line 63, delete "are" line 5, change "of" to read "for";

line 50, change "mounting" to read "mounted".

Signed and sealed this 1 8th day of July 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissioner of Patents

Claims

2. A 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 the rotating cylinder, said transfer assembly having a plurality of gripper pads having mounting means therefor supported for limited movement, the pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing an aligned reference position for the pads while permitting localized retreatment movement away from reference position, biasing springs on the transfer assembly for biasing the pad mounting means against the reference stops, means for defining the limit of movement of the transfer assembly, and a series of fixed but adjustable stops on the frame in the path of movement of the pad mounting means so that upon encountering the fixed stops the pads are positioned in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet in the loCus of a bow and so that when the transfer assembly reverses its movement, drawing the pad mounting means from engagement with the fixed stops, the pads are free to resume the reference position thereby to impart a bow of reverse curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

3. The combination as claimed in claim 2 in which each pad has a roughened surface and each cooperating gripper finger has a smooth surface to permit relative movement between the sheet and the gripper incident to restorative movement of the pad mounting means to reference position as bowing is imparted to the leading edge of the sheet.

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 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 including an axially extending pad bar having a plurality of gripper pads mounted thereon, the pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing a reference position for the bar with respect to the assembly while permitting localized retreating movement away from reference position, means for biasing the pad bar against the reference stops, means for defining the limit of movement of the transfer assembly, a pair of fixed but adjustable stops on the frame in the path of movement of the respective ends of the pad bar, the pad bar being of relatively thin construction so that upon the ends thereof encountering the fixed stops the pad bar is bowed to position the gripper pads in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet so that when the transfer assembly reverses its movement the pad bar is free to straighten in reference position to impart a bow of reverse curvature to the leading edge of the sheet for compensation of fan-out at the trailing edge.

5. The combination as claimed in claim 4 in which three fixed stops are provided, one at the center of the bar and the remaining two at the ends, the stop at the center being differentially adjustable with respect to the stops at the ends in order to impart either a concave or convex bow to the leading edge of the sheet thereby to compensate for either positive or negative fan-out.

6. The combination as claimed in claim 4 in which bolts penetrating the pad bar are provided for securing the pad bar, such bolts being surrounded by spacers having an axial length which is thicker than the pad bar to provide a limited amount of lateral lost motion with respect to the reference stops and in which the biasing springs are located adjacent the bolts for taking up the lost motion by pressing the pad bar against the reference stops, the biasing springs being sufficiently strong so as to maintain the pad bar seated against the reference stops at positions remote from the points of engagement of the fixed stops.

7. An infeed gripper 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 the rotating cylinder, said transfer assembly including a plurality of gripper pads having mounting means supported on the assembly, the gripper pads having respective coacting gripper fingers, means including reference stops on the transfer assembly for establishing an aligned reference position for the pads while permitting a small amount of localized retreating movement away from the reference position, biasing springs on the transfer assembly for biasing the pad mounting means against the reference stops, means for defining the limit of movement of the transfer assembly, and a series of fixed but adjustable stops on the frame in the path of movement of the pad mounting means, each of said fixed but adjustable stops having a threaded adjusting screw mounted on the frame for adjusting the stops so that upon closure of the gripper fingers the leading edge of the sheet is gripped in the locus of a bow and so that when the assembly reverses its movement, thereby restoring the pad mounting means to reference position, a bow of reverse curvature is imparted to the leading edge of the sheet for compensation of fan-out at the trailing edge.

10. 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 the rotating cylinder, said transfer assembly including an axially extending pad bar having a plurality of gripper pads mounted thereon, the pads having respective coacting gripper fingers, means for radially retracting the pad bar following transfer of the sheet and for radially projecting the bar to working position upon completing a cycle of transferring movement, means including reference stops on the transfer assembly spaced along said pad bar for establishing a reference position for the bar with respect to the assembly while permitting localized retreating movement away from reference position, biasing springs on the transfer assembly spaced along said pad bar for biasing the pad bar against the reference stops, means for defining the limit of movement of the transfer assembly, a series of fixed but adjustable stops on the frame in the path of movement of the pad bar, the pad bar being of relatively thin construction and having pillow blocks thereon of tapering thickness for engaging the fixed stops so that upon encountering the fixed stops the pillow block is radially projected with wiping action against the stops crowding the pad bar into a bowed position so that the gripper pads lie in the locus of a bow, means for closing the gripper fingers for gripping the leading edge of the sheet so that when the assembly reverses its movement, drawing the pad bar from engagement with the fixed stops, the pad bar is free to straighten in reference position to impart a bow of reverse curvature to the leading edge of the sheet for compensation for fan-out at the trailing edge.

11. An infeed mechanism for transferring sheets from a position of rest on a support to grippers on a constantly rotating cylinder comprising an oscillatable transfer assembly having a series of gripper fingers and coacting pads for gripping a sheet on said support, accelerating the sheet to cylinder speed and transferring the sheet to the cylinder grippers, mounting means for said pads including an axially extending resilient member for normally maintaining the pads in a reference plane extending transverse to the path of the sheets, means for oscillating the transfer assembly between a sheet engaging position with respect to said support and a transfer point with respect to the cylinder, adjustable stop means located in the path of said resilient member adjacent said support, said stop means being adjustable to intercept and variably displace local portions of the resilient member from the reference plane while the transfer assembly is in the sheet engaging position to thereby temporarily displace the pads into the locus of a bow, and means for actuating the gripper fingers to grip a sheet while the pads are so displaced so that a predetermined bow is imparted to the leading edge of the sheet as the pads return to said reference plane upon movement of the transfer assembly away from said stop means.