US3893664A

US3893664A - Stock feeder for printing press

Info

Publication number: US3893664A
Application number: US381352A
Authority: US
Inventors: Elmer R Thomsen
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-07-20
Filing date: 1973-07-20
Publication date: 1975-07-08
Anticipated expiration: 1992-07-08

Abstract

A stock feeder for an offset printing press has vacuum suckers arranged below a stack of stock, like envelopes, with the suckers being swung curvilinearly into and out of engagement with the lowermost envelope in the stack in order to feed it from the stack into the press. The suckers have an initial twisting motion after they grip the lowermost envelope before lowering it from the stack, and thereby separating it from the stack without disturbing the next uppermost envelope. As the edge only of the envelope is twisted downward and yet does not lower the body of the envelope, two purposes are accomplished. First, the vacuum between the first and second sheet is broken and second, the edge of the envelope has been released from resting on the inwardly turned leaf springs. As the suckers start their downward motion, a pressure roll swings toward the envelope and contacts the envelope on the upper side when the suckers have moved downward about three-fourths of their travel and at which point the suction or vacuum from the vacuum pump of the press is released. The pressure roller then continues rearward toward the rubber feed roll until it clamps the envelope against the feed roll so as to positively advance it into a set of pull-out rolls and thence into the press.

Description

United States Patent [1 1 Thomsen STOCK FEEDER FOR PRINTING PRESS Elmer R. Thomsen, 1021 NE. 135th Ave., Portland, Oreg. 97230 [22] Filed: July 20, I973 [21] Appl. No.: 381,352

[76] Inventor:

'rimary Examiner-Richard A. Schacher ssistant Examiner-Bruce H. Stoner, Jr. ttorney, Agent, or Firm-Edward F. Connors 14 1 July 8,1975

[57] ABSTRACT A stock feeder for an offset printing press has vacuum suckers arranged below a stack of stock, like envelopes, with the suckers being swung curvilinearly into and out of engagement with the lowermost envelope in the stack in order to feed it from the stack into the press. The suckers have an initial twisting motion after they grip the lowermost envelope before lowering it from the stack, and thereby separating it from the stack without disturbing the next uppermost envelope. As the edge only of the envelope is twisted downward and yet does not lower the body of the envelope, two purposes are accomplished. First, the vacuum between the first and second sheet is broken and second, the edge of the envelope has been released from resting on the inwardly turned leaf springs. As the suckers start their downward motion, a pressure roll swings toward the envelope and contacts the envelope on the upper side when the suckers have moved downward about three-fourths of their travel and at which point the suction or vacuum from the vacuum pump of the press is released. The pressure roller then continues rearward toward the rubber feed roll until it clamps the envelope against the feed roll so as to positively advance it into a set of pull-out rolls and thence into the press.

8 Claims, 12 Drawing Figures 1 STOCK FEEDER FOR PRINTING PRESS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally appertains to improvements in apparatus for removing flexible sheets in consecutive order from a stack and especially to new and novel improvements in apparatus for feeding individual sheets from the bottom of a stack of such sheets to a sheet handling machine.

The present invention relates to new and novel improvements in feeders for feeding stock to an offset printing press or letter press.

2. State of the Prior Art Since the feeder of the present invention has been developed for use with printing presses for feeding stock, like envelopes, to the press such environment will be retained in relation to the description of the background of the feeder.

In normal operation in feeding stock in the Multilith press, the stock is placed in the feeder at the rear end of the press. The top sheet is then lifted by suckers or vacuum cups and brought forward into feed rolls and then fed to the printing cylinder by tapes. It is obvious that the primary drawback of such feeding arrangement is that it is necessary to stop the press in order to replenish the stock, which is placed in the stock hopper of the feeder from the top.

In view of this drawback, there have been many attempts to feed the stock from the bottom of the stack by engaging the lowermost sheet in the stack with a suction means and gripping the sheet to pull it downwardly away from the stack.

One example of an apparatus for feeding individual sheets from the bottom of a stack of such sheets to a sheet handling machine is shown in U.S. Pat. No. 3,093,371, issued June 11, 1963. In such patent, a suction means is disposed beneath the stack of sheets and is swung curvilinearly into and out of engagement with the lowermost sheet in the stack. In its initial engagement with the lowermost sheet, the suction means grasps the sheet and draws the latter straight downwardly as the suction means commences its downward swinging movement away from the stack. A rod arrangement cooperates with the suction means to move in and out of supporting relation with the stack in consort with the engagement of the lowermost sheet in the stack by the suction means. And in such manner, an attempt is made to prevent the next uppermost sheet in the stack from being pulled downwardly by the suction means as it moves the lowermost sheet down away from the stack.

In U.S. Pat. No. 3,172,655, issued Mar. 9, 1965, a suction nozzle is mounted for swinging movement on a horizontally transverse axis below a stack of sheets and is moved upwardly to grip the lowermost sheet. Cooperating with the suction nozzle in its downward swinging movement away from the stack is a blank separator having a laterally projecting tongue provided with an opening for discharging an air jet. When the suction nozzle moves downwardly carrying the engaged marginal edge portion of the lowermost sheet away from the stack, the tongue moves inwardly between the engaged sheet and the next uppermost sheet and discharges an air jet between the sheet so as to prevent the next uppermost sheet from being pulled downwardly by the suction nozzle.

In U.S. Pat. No. 3,071,369, issued Jan. 1, 1963, a suction cup is disposed below a stack of flexible sheets and is actuated by a cam means so as to be moved in a substantially direct up and down movement toward and away from the stack. In such patent, there is a rapid initial retracting movement of the suction cup due to a bellows arrangement in cooperation with the cam means. Such is intended to effect a quick jerking downward movement of the suction cup and thereby realize an efficient removal of only one sheet from the stack.

In U.S. Pat. No. 3,658,319, issued Apr. 25, 1972, an arrangement of rocking side suckers and a central sucker is provided wherein the central sucker operates to engage the lowermost sheet while, at the same time, a blower nozzle forces air between the gripped sheet and the next uppermost sheet to assist in forming a gap between the engaged sheet and the next sheet thereabove. A separator tongue then is swung into the gap between the engaged sheet and the next sheet thereabove and the side suckers operate with a time delay relative to the start of suction of the central sucker and engage the engaged sheet to complete the downward pulling movement of the sheet away from the stack.

In the various feeders, as disclosed in the above patents which are exemplary of the prior art, the sheet that is engaged by the suction means is pulled directly downwardly as the suction means swings away from the stack or moves downwardly from the stack. Whether the suction means swings curvilinearly or moves in a substantially rectilinear path beneath the stack and regardless of any mechanical means provided to operate in sonsort with the downwardly moving suction means. there is still no reliable arrangement provided whereby it can be assured that only one sheet will be removed at a time. In all such patented devices, there exists the possibility of two sheets being removed from the stack at the same time. This is true even where there are attempts to provide mechanical separators between the engaged sheet and the next sheet or to provide air means for blowing between the sheets so as to separate the sheet engaged by the suction means and the next sheet thereabove in the stack.

None of the known bottom feeders operate with such degree of reliability that the possibility of double feeding is obviated. And yet, this malfunctioning is the most troublesome one, especially in feeding stock to a printing press.

SUMMARY OF THE INVENTION An important feature of the present invention resides in the provision of a unique system of suckers in a sheet feeder mechanism whereby the removal of one sheet at a time is positively ensured. Thus, it is a primary object of the present invention to provide a very novel and unique method and apparatus of sheet separation in a feeder. In accordance with the present invention, the suckers contact the lowermost sheet in a stack, but before they start a downward motion in gripping the sheet andpulling the sheet away from the stack, the gripped edge of the sheet is twisted downward while at the same time, because of the twisting action, it is pulled off leaf springs or the like which support or carry the leading edge of the pile or stack.

It has been found in prior practice, regardless of various mechanical arrangements such as disclosed in the aforesaid patents, that double sheet feeding does occur. This is especially true in feeding heavy stock, such as card stock, wherein the cards lie close together and as the first card is pulled away it also pulls the second card downwardly because of the vacuum action between the first and second cards. Such dougle sheet feeding is overcome by the present invention wherein the suckers in contacting the lowermost sheet have a revolving motion before lowering. Because of such revolving mo tion, the suckers twist the edge of the sheet and thereby separate the edge of the engaged sheet from the next sheet thereabove.

Because the sheet is merely twisted and then pulled downward off the leaf spring carriers, heavy material such as card stock, booklets, etc. can be fed.

If the stock had to be moved rearward and off a solid ledge, a buckle in the sheet would have to occur. Stiff and heavy material could not then be fed. In this invention the sheet does not buckle and therefore very heavy material can be fed.

The suckers are in the form of suction cups provided on a hollow manifold rod arranged transversely of the stack and rotatably journaled at its ends in a pair of supporting arms, which are pivoted on a parallel shaft that has one of its outer ends provided with a bell crank having a cam roller which is engaged by a cam on a reciprocating slide. The sucker manifold is retained in a raised position by spring means and is moved downwardly, against the urgement of the spring means, by the positive action of the cam in engaging the roller and rotating the crank to cause the arms to swing downwardly away from the stack. Prior to the downward movement of the arms, the manifold rod is rotated. Thus, as the suction cups contact the sheet, just before they start the downward motion under the impetus of the supporting arms, the initial downward movement of the arms is reacted to and resisted by the restraining lever to cause the manifold to commence a rotary counter-clockwise motion. The manifold is moved rearward while in its rotating action to prevent the sheet from being pulled forward. If the manifold merely rotated on its journals without moving rearward, the sheet would then be pulled forward because the suckers would be compelled to move forward. Because of the motion of the manifold, the axis or joint of pivot is actually center of the top of the suckers. Such rotary motion will cause the suction cups engaging the leading edge of the engaged sheet to twist sudh edge downwardly away from the next sheet thereabove.

The manifold or suction rod is connected by a flexible tube to the conventional vacuum tube of the printing press which has a valve means that controls the timing of the supply of vacuum to the manifold rod. Such a press is well-known in the art; for example, the A. B. Dick offset press manufactured by the A. B. Dick Co. of Chicago, Illinois and the Chief l5 and Itek presses manufactured by American Type Founders of Louisville, Kentucky.

The operation of the suckers is timed so that the vacuum sucks the sheet at the high point of the suckers in relation to the stack and is released just before the suckers are at the low point in regard to their downward movement below the stack of sheets.

The cam carrying slide is mounted on the feeder frame alongside the stock hopper for forward and rearward sliding movement under the control of a feeder linkage from the printing press. Such slide also carries another cam which is adapted to engage a roller provided on the end of a bell crank for a pressure roll which operates in coordinated relation with the suckers and in cooperation with a feed roll. The feed roll is rotated through a gearing in relation with the operating mechanism of the press so that it is rotated in time relation therewith with the normal pull-out rolls of the feeder.

The pressure roll is retained in a normally inoperative position out of engagement with the sheet and away from its relation with the feed roll by means of a cam which compels the pressure roll forward and away from the feed roll. The pressure roll is returned to the feed roll by means of a spring. As the cam moves forward, the roller of the bell crank drops off the cam and permits the pressure roller to move rearward by spring action to contact the feed roll.

When the slide is in its rearward position, the sucker rod will rise and the suckers will contact the lowermost sheet with the bell crank being in high position. With the suckers at the high point, they are in contact with the lowermost sheet. At this point, the vacuum is engaged in the valve of the press and the slide is in its most rearward position. As the slide is pulled forward by the lever actuating mechanism from the press, the suckers carrying the sheet are pulled downward toward the rubber feed roller. Before the suckers move downwardly, they are rotated counter-clockwise so as to twist the edge of the engaged sheet away from the stack and thereby break the suction between the engaged sheet and the next uppermost sheet. The suckers have a revolving motion before lowering so as to separate the edge of the engaged sheet from the next above sheet. Since the sheets are separated at the edge, the vacuum which normally exists between the superimposed sheet is broken and atmospheric air enters between the sheets.

As the suckers carrying the sheet are pulled downwardly by the action of the arms being swung by the cam rod which is rotated under the positive action of the engaged bell crank that is being swung downwardly by the forwardly reciprocating cam slide, the engaged sheet is moved down toward the feed roll. Before the sheet contacts the feed roll, the pressure roll is moved, under the spring urgement, into a position above the sheet and then, as the sheet contacts the feed roll, the pressure roll squeezes the sheet against the feed roll and causes the sheet to be impelled towards the normal pull-out rolls. The suckers remain in a down position because the cam slide is still in positive engagement with the roller on the bell crank and holds them down until the sheet has cleared.

When the sheet has traveled about seven inches, the pressure roll then lifts off the sheet because the cam slide starts its rearward action and engages the roller on the bell crank of the pressure roll and cause the bell crank to be swung downwardly. At this same time, the roller on the bell crank for the suction rod is free to move upwardly under the spring urgement into a notched-out portion in the cam slide provided in advance of the cam segment thereon that is adapted to engage the bell crank roller. Thus, the suckers are swung upwardly to contact the next sheet to be engaged.

Such coordinated movements of the suckers and the pressure roll are effected by the cam slide which has cam segments that engage the rollers on the bell cranks for each of the components, namely, the sucker rod and the pressure roll.

Another important object of the present invention is to provide means for retaining forward edge portions of the sheets in the stack as the lowermost sheet is being separated therefrom. Depending upon the nature of the sheet material, that is with respect to its weight, softness or evenness, various mechanical means may be provided and the provision thereof constitutes another feature of the present invention.

Such means engages the leading edge of the stock being carried and comprises the inwardly turned lower ends of leaf springs which are vertically mounted at the front of the stock hopper and have their lower inwardly turned ends disposed in the open space at the bottom of the hopper through which open space the suckers are adapted to move in engaging the front edge portion of the sheets in the stack.

In another instance, needle screws are moved inwardly to contact the leading edge of the lowermost sheet in the stack and such is very helpful in running card stock especially.

In other instances, the springs may be used alone by backing out the needle screw so that they do not contact the stock. And in other circumstances, the springs may be put out of use by turning them outwardly of the hopper so that they are not in vertical position to have their lower ends engage the stock.

With some types of stock, both the springs and the needle screws may be simultaneously used.

Another important object of the present invention is to provide means for controlling the height of the suckers. The purpose of this is that because of the type of stock, or paper or sheet material or the condition thereof, it is desirable to lower or raise the suckers for better contact with the sheet.

To realize such adjustment, an offset rod is journalled between the walls of the hopper rearwardly and below the pivoted ends of the supporting arms for the sucker tube. Such offset rod has eccentric ends and the rod is pivoted to a threaded adjustment rod which is attached to a cross bar between the sides of the hopper frame at the rear thereof. By adjusting the threaded screw, the offset rod is rotated which will, due to its eccentric journalling, raise and lower it below the pivoted ends of the arms. Such ends are pivoted to blocks fixed on the cam rod and the arms have cut-outs whereby they can be bodily moved on their pivots relative to the anchoring blocks to which they are pivoted and by means of which they are attached to the actuating rod for effecting an upward and downward swinging movement of the sucker rod.

Another important object of the present invention is to provide means for delaying the rise of the suckers under the impetus of the cam slide. This is especially useful depending upon the length of the stock, as for example in feeding long envelopes.

The rise of the suckers is delayed by effecting a delay in the rise in the bell crank and this is carried out by means of a pair of cooperating levers which are adapted to be hooked together and which are under spring urgement in being retained in their hooked together relation but which can be spread apart as the cam slide moves forwardly. One of the levers has a cam edge that is in advance of the cam segment that is provided to contact the roller on the bell crank for the sucker rod and, therefore, the initial contact of such lever effects a delay in the real contact of the cam slide with the roller on the bell crank, whereby the rise of the sucker rod is delayed.

Another important object of the present invention is to provide a simple, compact and very practical feeder mechanism for feeding flexible sheet material in a true one by one fashion regardless of the nature thereof and irrespective of the apparatus to which such material is fed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view of the feeder of the present invention.

FIG. 2 is a top plan view thereof.

FIG. 3 is a longitudinal vertical sectional view taken substantially on line 3-3 of FIG. 2 and showing the suckers their highest positions and in engagement with the lowermost sheet in the stack.

FIG. 4 is a view similar to FIG. 3 showing the suckers on their way down and the pressure roller in a position about to engage the pulled down sheet.

FIG. 5 is a view similar to FIGS. 3 and 4 but showing the suckers in their lowermost position and showing the pressure roll engaged with the sheet and holding the sheet onto the feed roll with the sheet being advanced by the feed roll to the pull-out rolls that are driven by the press.

FIG. 6 is a side elevational view, similar to FIG. 1, but showing the suckers in a down position and the pressure roll engaging the sheet and holding the sheet on the feed roll.

FIG. 7 is an exploded perspective view of the suckers, the pressure roll and the adjustment rod for varying the effective height of the suckers.

FIG. 8 is a side elevational view, similar to FIGS. I and 6, and showing the suckers beginning the downard stroke.

FIGS. 9, l0 and 11 are pictorial and somewhat diagrammatic views, showing the action of the suckers in effecting a rearward twist of the engaged sheet with the suckers effecting an initial rotating action before they start their downward swinging movement away from the stack so as to realize the rearward twist of the sheet and, consequently, the effective separation of the engaged sheet from the stack so as to break the vacuum existing between the engaged sheet and the next uppermost sheet in the stack.

FIG. 12 is a fragmentary perspective showing of the restraining leverage arrangement between the sucker rod which is rotatably journalled in the outer ends of the pivoted supporting and actuating arms and the frame of the feeder.

DESCRIPTION OF THE PREFERRED EMBODIMENT For exemplary purposes, the sheet feeder 10 is shown in the accompanying drawings in structural and operational association with an offset printing press 12, such as one of the conventional presses described in the foregoing. Since such press is conventional and wellknown in the art, the press is only fragmentarily shown in FIG. 2. The frame I4 of the feeder 10 is attached to the press by having its

side plates

16 and 18 mounted on the press frame in a position, as shown in FIG. 6. For this purpose, the transversely spaced and

parallel side plates

16 and 18 are provided with apertured mounting feet 20 that are adapted to be anchored by bolts on the press frame.

The press 12 is provided with a feeder operating linkage 20a, as shown in FIG. 6, and such feeder linkage, which is standard equipment on the press, is adapted to actuate the operating mechanism of the feeder 10, as will be described. The feeder I is positioned at the feed or front end of the press and has its outlet end 22 disposed above the conventional feed tapes 24 of the press which tapes carrying the sheets fed from the feeder under the conventional sheet riders and into the printing cylinders of the press, as will be well appreciated by those skilled in the art.

The feeder is provided with a bottom plate 26 that is mounted between the side plates and which provides the bottom of a supply hopper 28 within which the sheets of stock, such as the illustrated envelopes 30, are disposed. The envelopes are piled in a stack within the hopper and are fed from underneath the pile or stack in one by one consecutive fashion. The hopper is composed of a front plate 32 and a complementary upstanding rear plate 34. The rear plate 34 is adjustable forwardly and rearwardly between the side plates and by mounting adjustment means on the bottom plate 26.

The hopper further includes side plates 36 which are positioned between the front and

back plates

32 and 34, respectively, and which can be moved apart or to gether so as to accommodate stock of various widths. As shown in FIG. 2, the hopper side plates 36 are slidably mounted in a slot 38 in the bottom plate 26 between the

frame plates

16 and 18 by virtue of slide blocks 40 that carry thumb screws 42 for locking the plates in set positions along the extent of the cross-bar 38.

As shown in FIGS. 3-5, the bottom plate 26 of the hopper 28 terminates rearwardly of the front plate 32 so that a feeding space 44 is provided. The front terminating edge 46 of the bottom plate is inclined downwardly to provide a pull-off surface for the envelopes to slide on as they are being pulled downwardly from the stack.

A sucker rod 48, which is in the form of a hollow manifold. is provided with suckers 50, which are in the form of vacuum cups, and which are spaced along the extent of the sucker rod that is adapted to be operatively movable within the feeding space 44. The sucker rod is connected by a flexible tube 52 to the normal vacuum system of the printing press 12, which, as will be understood by those skilled in the art, has a valve means that is operated in time relation with the movements of the sucker rod in relation to the stack of envelopes.

As shown more particularly in FIG. 7 the sucker rod 48 has its end portions 54 rotatably journaled in the forward ends 56 of operating arms 58 which support the sucker rod and which move the same in a curvilinear path of movement relative to the overhead stack of envelopes. The arms 58 are provided with enlarged rear mounting ends 60 that are pivoted by pivot pins 62 in clevises 64 which integrally depend from blocks 66. The blocks 66 are sleeved onto an actuating rod 68 and are held in fixed positions by set screws 70.

The actuating rod 68 is provided at one end with a bell crank 72 that has a cam roller 74 provided thereon. The bell crank 72 with the cam roller 74 is disposed ex teriorly of the side plate 18 and is adapted to be engaged by a cam segment 76 provided on a slide plate 78 that is slidably mounted on the outer face of the frame side plate 18 for reciprocating backward and forward movement under the actuation of the press linkage 20a, as shown in FIG. 6, for example.

The end portion 54a of the sucker rod projects beyond the adjacent mounting and supporting arm 58 and is fixed to a link 780 by a pin 79. The link 78a is pivoted to a link 80, as shown in FIGS. 7 and I2. The link 80 is attached by a pivot pin 82 to an anchoring sleeve 84 which is fixed to the frame side plate 18 and projects inwardly therefrom. The

links

780 and 80 constitute a restraining linkage which secures the sucker rod 48 to the frame in a manner so as to effect the initial rearward revolving or rotating motion of the sucker rod before the sucker rod is moved downwardly under the actuation of the arms 58 in the manner as shown in FIGS. 3-5.

The downward swinging movement of the sucker rod is controlled by the arms 58 under the action of the bell crank 72 and the cam segment 76 of the slide plate 78. The operating and supporting arms 58 for the sucker rod are also provided with spring biasing means which is in the form of coil springs 86 that are anchored to depending lugs 88 on the rear end portion 60 of each of the arms 58 and to a cross bar 880 on the frame.

The end of coil springs 86a are fixed to depending pins 90 on a cross rod 92 and to the frame bar 880. The rod 92 is rotatably journaled transversely between the

side plates

16 and 18 of the feeder frame and swingably supports a pressure roll 94. The pressure roll 94 is provided at its ends with mounting sleeves 96 that receive threaded adjustment rods 98 which are positioned through vertical openings in the rod 92 and are held in adjusted fixed positions thereby by locking nuts 99. In this fashion, the height of the pressure roll 94 can be adjusted. And more particularly, the position of the pressure roll in relation to a feed roll 100 can be controlled.

As shown in FIGS. 3-5, the feed roll 100, which is preferably formed from rubber, is rotatably journaled between the

side plates

16 and 18 of the feeder frame 14 and is positioned below and slightly rearwardly of the feeding space 44 from the hopper 28. The pressure roll 94 is adapted to cooperate therewith in holding a sheet thereagainst after the sheet has been lowered from the stack by the sucker rod 48. The feed roll is rotated in a counterclockwise direction by a gearing 102 which also drives a pair of pull-out rolls 104 in a counterclockwise direction and at the same rate of rotation as the feed roll 100, as shown in FIGS. 3-5.

The pull-out rolls 104 are disposed in cooperating relation one above the other and are adapted to receive therebetween the pulled-off sheet which is given its initial forward impetus relative to the nip between the pull-out rolls by the feed roll 100 with the pressure roll serving to hold the sheet onto the feed roll so that it is frictionally engaged with and moved forward by the feed roll 100 as can be appreciated from a consideration of FIG. 5.

The gear means 102 assures a proper rotation between the feed roll 100 and the pull-out rolls 104 which advance the sheet to the tapes 24 of the printing press. The gearing I02 is driven by gearing from the printing press so as to assure the proper rotary speed between the pull-out rolls and the sheet riders and printing cylinders of the press with the sheets being fed onto the types and under the sheet riders and then into the printing cylinders, as will be well understood by those skilled in the art.

The pressure roll 94 is swung into a sheet clamping relation with the feed roll 100 by the action of the spring means 86a and is retained in a position away from the feed roll, as shown in FIG. 3, by the action of the slide mechanism 78 which operates on a roller 106 that is provided on a bell crank 108 which is disposed exteriorly of the frame plate 18 and which is connected by a pin 110 with one end of the pressure roll supporting rod 92. The center gear in the gearing 102 between the gears for the pull-out rolls 104 and the feed roll 100 is rotatably journaled on one end of the rod 92 internally at the inner face of the frame plate 16, as shown in FIGS. 2 and 7.

Depending upon the particular type of stock, such as the nature of the material, for example, the softness. unevenness, or the like, various methods are provided for sheet separation and for retention, in this regard, of the forward edges of the lowermost envelope in the stack as the pulled out envelope is being lowered from the stack by the suckers 50.

As best shown in FIGS. 3-5, the leading edge of the bottom envelope 30b in the stack after the preceding envelope 30a has been pulled down from the stack by the suckers 50 is retained by various means. Thus, spring bars 112, like flat clock springs, are vertically oriented on the outside of the front wall 32 of the hopper means and are held in vertical positions thereon by pins 114. The free lower end portions project downwardly below the end of the front wall and are inturned towards the stack so that the inturned end portions 116 can engage and retain the leading edge of the bottommost sheet 30b in the stack 30.

In some instances, additional retainers and separators will be desired and, for this reason, needle screws 118 are adjustably supported in threaded bores in a cross bar 120 fixed between the

frame plates

16 and 18 and are rotatable therein so that their needle points 122 can be positioned beneath the leading edge of the bottom envelope 30b in the stack 30, as shown in FIGS. 3S.

The springs 112 and needle screws 118 may be conjointly employed depending upon the nature of the stock. In such instance, the springs will be left in the vertical positions, as shown in FIGS. 3-5, and the needle screws will be rotated until their inner pointed ends 122 just touch the stock.

The spring bars 112 are disposed adjacent the ends of the front plate and they may be put out of use by swinging them upwardly and outwardly so that they will not be in operative positions. Then, only the needle screws 118 will be used.

Accordingly, it can be seen that there are three means of sheet separation for supporting the leading edge of the bottom sheet of the stock. Such supporting means serves as means to help to separate the sheets since it works in conjunction with the suckers 50 to hold the next succeeding sheet 30b in the stack as the bottommost sheet 30a is being pulled therefrom by the downwardly moving suckers 50.

Means is provided for adjusting the effective or working height of the suckers 50. As shown in FIGS. 2, 3 and 7, an offset rod 124 is provided with eccentric ends 126 which are rotatably journaled in the

frame side plates

16 and 18 with the offset rod underlying the rear end portions 60 of the mounting arms. The end portions 60 are provided with slots 128 that accommodate the sup porting blocks 66 with the end portions 60 being free to be moved about the pivots 62 relative to the blocks 66 by virtue of the slots 128. Such movement is effected by rotating the offset rod 124. For this purpose, an adjustment rod 130 is pivotally attached, as at 131, to the offset rod and the adjustment rod extends rearwardly and is provided with a threaded end portion 132 that extends through a bore 134 in a bar 136 which is fixed between the frame side plates [6 and I8. A knurled knob 138 is threaded onto the end portion 132 and bears against the cross bar 136. The adjustment rod 130 has a fixed collar 140 against which one end of a coil spring 142 coiled about the rod bears with the other end of the spring bearing against the cross bar 136. As can be appreciated, manual rotation of the knob 138 will cause the adjustment rod to be moved axially longitudinally of the feeder frame and will result in an effective clockwise or counterclockwise rotary movement of the offset rod I24. By virtue of the eccentric mounting of such offset rod 124, it will rise up against or move down from the end portions 60 of the sucker rod supporting arms 58 and cause the arms to be moved up or down in respect to their supporting blocks 66 on the supporting and operating rod 68. This will cause the sucker rod to be moved to higher or lower effective heights. Such action will be governed by the type of stock or the condition thereof, for example. The necessity to lower or raise the suckers 50 is dictated by the need for better contact thereof with the sheets of stock in the stack.

As shown in FIGS. 1, 6 and 8, the slide plate 78 is provided with longitudinally extending slots 144 and 146 which form trackways that slide on guide pins I48 and 150 that are fastened to the exterior of the side plate 18 of the feeder frame. The slide plate 78 is provided with the cam segment 76 that engages the roller 74 of the crank lever 72 and which effects the downward swinging movement of the arms 58 that produces the downward swinging action of the sucker rod 48 that is shown in its downward movements in detail in FIGS. 3-5. The slide plate also has a cam member 152 that acts on the roller 106 for the bell crank 108 of the pressure roll 94.

For a better understanding of the operation of the feeder, attention is first directed to FIGS. 1, 6 and 8 which show the sequence of events in relation to the slide plate and the bell cranks 72 and 108 for the sucker rod 48 and for the pressure roll 94.

With reference to FIG. 8, it will be noted that the slide plate 78 is starting forward and that the suckers 50 are in their upper position and are beginning the downward stroke with the cam segment 76 engaging the upper roller 74 and causing the crank lever 72 to be swung downwardly in a counterclockwise direction. Continuing to FIG. 6, it can be seen that the sucker rod 48 is in its down position and would be held in such position because the cam segment 76 is seated over the roller 74 on the bell crank 72 which would hold the sucker rod 48 in a down position. In FIG. 1, the sucker rod is shown in its uppermost position to which it has been urged by the spring means 86 since the cam segment 76 has moved rearwardly to permit the crank lever 72 to ride up to its uppermost position.

The cam segment 152 has an upwardly and rearwardly inclined rear edge 154 and a straight bottom edge 156. The bottom edge acts on the roller 106 to hold the pressure roll 94 in its inoperative position, as shown in FIG. 3. As the slide plate 78 moves forwardly the roller 106 is allowed to travel up the inclined cam face I54 and this permits the springs 86a to be active to swing the pressure roll into engagement with the feed roll 100, as shown in FIGS. 4 and 5.

When the slide plate 78 moves rearwardly the cam segment I52 will act on the roller I06 to cause the pressure roll to be swung back to its inoperative position, as shown in FIG. 3. And, as the slide plate 78 moves rearwardly, the roller 74 for the bell crank 72 of the sucker rod actuating mechanism will be allowed to move upwardly under the action of the springs 86 and thus will allow the sucker rod 48 to move to its uppermost position where the suckers 50 will engage the underside of the front edge portion of the lowermost envelope in the stack, as shown in FIG. 3.

Thus, when the slide plate 78 is in its forward position toward the delivery end of the feeder 10, the suckers 50 are down and the pressure roll 94 is against the rubber feed roll 100, as shown in FIG. 5. As the slide plate 78 is reciprocated rearwardly by the operating linkage a from the printing press, the suckers 50 will rise and will contact the underside of the lowermost envelope a in the stack, as shown in FIG. 3. With the suckers 50 in the high position, they contact the underside of the front edge portion of the envelope 30a. At this point, the vacuum is engaged in the printing press valve and the slide plate 78 is in its most rearward position.

As the slide plate is pulled forwardly on the guide pins I48 and 150 by the press operating linkage 20a, the cam segment 76 will engage the roller 74 and, through the crank lever 72 and the rod 68 and the arms 58, will start the suckers 50 in their down position. As the arms 58 start downwardly to swing the sucker rod 48 in the downward curvilinear movement, the initial downward swinging action of the arms 58 will result in a constraining or restraining action on the sucker rod produced by the

links

78 and 80 and this will cause the sucker rod 48 to effect a rearward revolving motion. Such rearward revolving motion will produce a twisting action and will effect an initial twisting of the front edge of the envelope or sheet 300 as shown in FIG. 10.

It must be understood that when the cam roll 74 is in the highest position, the shaft 68 has rotated clockwise, causing the clevices 64 to arrive at their most forward position. In this position a gap is created between block 66 and gap of arm 58. The suckers are now in their most forward position. As the cam roll is forced down by the cam 76, the clevices are rotated clockwise, pulling the arms 58 rearward until the gap closes.

The arms 58 and sucker rod are prevented from moving downward because of the resistance of the spring 86. Clearing this action. the sucker rod has moved rearward while the suckers have remained in the original position except for having rotated 23 in a twisting motion. Then the gap having closed, the arms must move downward because of the continuing rotary action of the rod 68 and clevices 64.

The initial rotational motion of the sucker rod 48 will rotate or twist the leading edge of the envelope 30a in such a fashion that the edge will separate from the envelope 30b immediately above it in the stack, as shown in FIGS. 3 and 10. The envelope 30a remains otherwise in its original position without being pulled forward. As the sucker rod 48 rotates and at the same time moves backward, the normal vacuum between the envelopes 30a and 30b is broken and when the sucker rod has moved back about a quarter of an inch, the timing is such that the arms 58 will then start the downward mol 2 tion of the sucker rod 48, as shown in FIGS. 4 and 11.

As the sucker rod 48 moves downwardly to the position of FIG. 4, the slide plate 78 has moved forwardly to the extent that the roller 106 is now free to roll up the edge 154 so as to enable the pressure roll 94, under the spring action 86A, to start moving toward the feed roll 100, as shown in FIG. 4.

The extreme forward movement of the slide plate 78 will permit the pressure roll 94 to move to its final position, as shown in FIG. 5, wherein it will hold the envelope 30a against the feed roll I00. The feed roll will frictionally move the envelope 30a forwardly to the nip between the pullout rolls I04 and the pulllout rolls will grasp the sheet and feed it onto the pullout 24 and to the printing press cylinders.

With regard to the slide plate 78 in its action on the roller 74 of the sucker rod assembly, it is sometimes desirable to delay the rise of the suckers 50. This may be desirable in the instance of feeding long envelopes or long sheets of types of stock. To effect such delay a slide arm 158 is disposed on the outer face of the slide 78 and is mounted by slots 16] on pins 160 for horizontal sliding movement. The arm has a front free end with a vertical cam edge 162 that is disposed in advance of the cam segment 76, as shown clearly in FIG. 8. A catch I64 is pivoted on a pin 166 above the arm 158 and the catch and the arm have interlocking hook ends 168 and 170. A spring 172 is connected between the arm and the catch and serves to urge the hook ends into interlocking engagement, as shown in FIG. 8.

When the slide plate starts its forward movement, the cam edge 162 of the arm will first engage the roller 74 but this will not result in a downward movement of the roller because the arm 158 will slide rearward with the spring 172 giving way to the crank lever 70 and permitting the ends 168 and to break away and thus elongate the arm. In this respect, the arm 158 will slide rearwardly since the pins 160 are mounted in the slots in the arm, as shown in FIG. 8. Thus, the arm can slide rearwardly to the position shown in FIG. 1 with the catch and the arm in the open position. When the slide plate has moved to its rearward position, the spring 162 will be active to cause the two parts to be interlocked again, as shown in FIG. 6.

A locking lever 176 is pivoted as at 178 and is adapted to swing down and to engage the spring retaining pin 174 on the arm for the purpose of holding the arm in an open position, as shown in FIG I. When held in such position, the catch and the arm will be in a spread apart position, as shown in FIG. 1 and the arm will be inactive. Thus, such mechanism can be rendered inactive when running short envelopes or similar short stock.

In FIG. 1 of the drawings, the cam or slide plate 78 has moved rearward to nearly its maximum, with the slide arm 158 in its most forward position. With the slide arm in this position, the raise of the suckers has been delayed so the longer sheet may clear before the suckers raise. Now as the cam plate 78 moves rearward to its extreme position, the roller 74 raises slightly higher and therefore raises the arm and disengages the lock as shown in FIG. 2. In this position the suckers have raised to their highest level.

Now as the cam plate 78 moves forward, the roller 74 contacts the arm I58, holding it in this position as the cam plate moves. The bevel of the cam on the cam plate contacts the roller, forcing it downward and therefore lowering the sucker bar. When the roller 74 has reached its lowest point and having forced the arm 158 rearward, as shown in FIG. 1, the slide then moves forward by the spring action to again lock in position with the catch 164. The arm 158 can move forward as its lower surface is slightly higher than the surface of the slide or cam plate 74.

While the preferred embodiment of the present invention has been illustrated in the accompanying drawings and described herein, it can be appreciated that other means can be provided for effecting the movement of the sucker rod and for realizing the coordinated movements of the sucker rod and the pressure roll.

In this respect, while the invention has been described and illustrated in connection with feeding envelopes to an offset printing press, it is obvious that this is merely one environment for the feeder. For the feeder can be utilized in other environments where sheet material is fed to a sheet handling machine, regardless of the nature of the material or the type and nature of the machine or mechanism.

Thus, the foregoing description and the accomapanying drawings are merely exemplary of one form of and one environment for the present invention which is only limited by the scope and spirit of the appended claims.

What is claimed is:

l. A feeder for flexible sheet material comprising: a hopper means for receiving and supporting a plurality of flexible sheets in a stack; a vacuum gripping means movably disposed under said stack and adapted to engage a marginal edge portion of the lowermost sheet in the stack; means for initially moving said gripping means in a twisting motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets; means after cessation of the operation of the foregoing means and consequent completion of the twisting action for moving said gripping means downwardly away from the stack with the sheet held thereby and thus lowering the sheet from the stack; means for engaging the edge portion of the next lowermost sheet in the stack and thus assisting in the separation of the sheets and also retaining the stack properly within the hopper means as the engaged sheet is lowered from the stack; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder; means for returning the gripping means upwardly back into engagement with the next lowermost sheet in the stack, said gripping means including a sucker rod constituting a manifold and having a plurality of suction cup s constituting suckers mounted therein in communication therewith; means connecting the sucker rod to a vacuum source; said means for moving the gripping means downwardly from the stack including a pair of arms mounted for vertical swinging movement, and a rod supporting and actuating said arms and said sucker rod being carried by the arms, said sucker rod being rotatably journaled in the arms and said means for initially moving the gripping means in a twisting motion including a constraining linkage connected to the sucker rod and to a fixed point so as to cause the sucker rod to rotate counterclockwise as the arms first attempt to move it down away from the stack and spring means connected to said arms to prevent the sucker rod from lowering until the twisting action is completed and constituting the means for returning the gripping means to its raised position with the suction cups engaging the next lower most sheet in the stack.

2. A feeder for flexible sheet material comprising; a hopper means for receiving and supporting a plurality of flexible sheets in a stack; a vacuum gripping means movably disposed under said stack and adapted to engage a marginal edge portion of the lowermost sheet in the stack; means for initially moving said gripping means in a twisting motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets; means after cessation of the operation of the foregoing means and consequent completion of the twisting action for moving said gripping means downwardly away from the stack with the sheet held thereby and thus lowering the sheet from the stack; means for engaging the edge portion of the next lowermost sheet in the stack and thus assisting in the separation of the sheets and also retaining the stack properly within the hopper means as the engaged sheet is lowered from the stack; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder; means for returning the gripping means upwardly back into engagement with the next lowermost sheet in the stack, said gripping means including a sucker rod constituting a manifold and having a plurality of suction cups constituting suck ers mounted therein in communication therewith; means connecting the sucker rod to a vacuum source; said means for moving the gripping means downwardly from the stack including a pair of arms mounted for vertical swinging movement and a rod supporting and actuating said arms and said sucker rod being carried by the arms and including means engaging the supporting rod for the arms of the gripping means for adjusting the effective height of the gripping means relative to the stack.

3. For use with a printing press having a vacuum means and having a feed linkage, a feeder for feeding stock to the press comprising; hopper means for supporting the stock in a stack; vacuum gripping means movably disposed under said stack and having means connecting it to the source of vacuum on the printing press with said gripping means being adapted to engage a marginal edge portion of the lowermost sheet of stock in the stock; means actuated by the printing press feed linkage for moving said gripping means downwardly away from the stack with the gripping means geing in communication with the vacuum means on the press and with the sheet held thereby so as to lower the sheet from the stack; means responsive to said foregoing moving means for initially twisting said gripping means in a revolving motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets prior to the downward movement of said gripping means which downward movement is initiated and carried out only upon completion of the initial twisting action; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder to the printing press, said conveying means being actuated by the printing press in timed relation with the operation of the press; means for moving the gripping means upwardly back into engagement with the next lowermost sheet in the stack after the removed sheet is delivered to the conveying means; said conveying means including a feed roll driven by the press and onto which the sheet is lowered by the gripping means and a pressure roll adapted to clampingly hold the sheet against the feed roll and means for moving said pressure roll into and out of clamping relation with the feed roll in timed relation with the movement of the gripping means; said last means including a rotatable rod, means connecting the pressure roll to said rod in spaced parallel and adjustable relation therewith. means actuated by the press linkage for rotating the rod in one direction to hold the pressure roll out of engagement with the feed roll and spring means connected between a fixed point and the rotatable rod and operative upon the deactivation of said foregoing means to swing the pressure roll into clamping relation with the feed roll.

4. The invention of claim 3 wherein said means for moving said gripping means downwardly away from the stack includes a rotating rod having a bell crank, a reciprocating cam means driven by the press feed linkage and adapted to engage the crank for rotating the rod, a pair of arms carried by the rod and on which the gripping means is mounted, said gripping means including a sucker rod having a plurality of suckers, said sucker rod being rotatably journaled in the arms and said means for initially moving said gripping means in a twisting motion including a restraining linkage pivotally connected between the rod and a fixed point, said link age reacting to the downward movement of the arms to effect an initial twisting motion of the sucker rod.

5. The invention of claim 4 including means engaging the rod carrying the arms for the sucker rod for raising and lowering the effective height of the sucker rod in relation to the stack.

6. The invention of claim 4 wherein said reciprocating cam means is provided with means for delaying the rise of the sucker rod which means may be selectively employed in the instance of feeding longer sheets so as to permit such sheets to be clear of the conveying means before the spring means returns the sucker rod to its raised position.

7. The invention of claim 3 wherein a reciprocating cam means is driven by the press feed linkage, said conveying means including a feed roll on which the removed sheet is placed by the gripping means, a pressure roll, means mounting the pressure roll for bodily movement relative to the feed roll, means connecting the pressure roll to the cam means so it can be held thereby out of engagement with the feed roll and spring means connected between a fixed point and the mounting means for the pressure roll for moving it into en gagement of the feed roll after the removed sheet has been delivered thereto by the gripping means, a rotat' able rod having a bell crank engaged by the cam means so as to rotate the rod, a pair of arms carried by the rod and supporting the gripping means, said arms being swung downwardly by the cam means to move the gripping means downwardly and said twisting means including restraining means pivotally connected between the gripping means and a fixed point and reacting to the initial downward movement of the arms to effect the initial twisting action of the gripping means and said means for moving the gripping means upwardly back into engagement with the stack including springs connected between the arms and a fixed point, said springs also functioning to prevent the gripping means from lowering until the twisting motion is concluded.

8. A feeder for flexible sheet material comprising; a hopper means for receiving and supporting a plurality of flexible sheets in a stack; a vacuum gripping means movably disposed under said stack and adapted to engage a marginal edge portion of the lowermost sheet in the stack; means for initially moving said gripping means in a twisting motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets; means after cessation of the operation of the foregoing means and consequent completion of the twisting action for moving said gripping means downwardly away from the stack with the sheet held thereby and thus lowering the sheet from the stack; means for engaging the edge portion of the next lowermost sheet in the stack and thus assisting in the separation of the sheets and also retaining the stack properly within the hopper means as the engaged sheet is lowered from the stack; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder; means for returning the gripping means upwardly back into engagement with the next lowermost sheet in the stack; said conveying means including a rotating feeed roll on which the sheet is deposited by the gripping means, a pressure roll operable to clamp the sheet against the feed roll, a pair of rotating pull-out rolls into the nip of which the sheet is fed by the feed roll, means operating in consort and timed relation with the means for moving the gripping means for moving the pressure roll into and out of sheet clamping relation with the feed roll, said last means including spring means connected to the pressure roll for swinging the pressure roll into sheet clamping relation with the feed roll, said means for moving the gripping means downwardly including a cam slide mechanism driven in a rectilinearly reciprocating path, said pressure roll having a crank means, a roller carried by the crank means and engaged by the cam slide mechanism to hold the pressure roll away from the feed roll in opposition to the action of the spring means until the gripping means has been moved to its lowermost position with the removed sheet, said rod for the arms of the gripping means having the arms pivotally connected thereto and said rod having a crank end, a roller on the crank end engaged by the cam slide mechanism which swings the arms downwardly while maintaining the pressure roll in its position out of contact with the feed roll until the gripping means delivers the removed sheet to the feed roll.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,893,664 Dated July 1975 Inv nto ELMER R. THOMSEN It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 3, line 51, change "stock" to stack-;

line 52, change "geing" to -being-.

Claim 8, line 35, change "feeed" to -feed.

Signed and Scaled this sixteenth Day Of September1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (nmmlssivm'r ufParenrs and Trademarks

Claims

1. A feeder for flexible sheet material comprising: a hopper means for receiving and supporting a plurality of flexible sheets in a stack; a vacuum gripping means movably disposed under said stack and adapted to engage a marginal edge portion of the lowermost sheet in the stack; means for initially moving said gripping means in a twisting motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets; means after cessation of the operation of the foregoing means and consequent completion of the twisting action for moving said gripping means downwardly away from the stack with the sheet held thereby and thus lowering the sheet from the stack; means for engaging the edge portion of the next lowermost sheet in the stack and thus assisting in the separation of the sheets and also retaining the stack properly within the hopper means as the engaged sheet is lowered from the stack; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder; means for returning the gripping means upwardly back into engagement with the next lowermost sheet in the stack, said gripping means including a sucker rod constituting a manifold and having a plurality of suction cups constituting suckers mounted therein in communication therewith; means connecting the sucker rod to a vacuum source; said means for moving the gripping means downwardly from the stack including a pair of arms mounted for vertical swinging movement, and a rod supporting and actuating said arms and said sucker rod being carried by the arms, said sucker rod being rotatably journaled in the arms and said means for initially moving the gripping means in a twisting motion including a constraining linkage connected to the sucker rod and to a fixed point so as to cause the sucker rod to rotate counterclockwise as the arms first attempt to move it down away from the stack and spring means connected to said arms to prevent the sucker rod from lowering until the twisting action is completed and constituting the means for returning the gripping means to its raised position with the suction cups engaging the next lower most sheet in the stack.

2. A feeder for flexible sheet material comprising; a hopper means for receiving and supporting a plurality of flexible sheets in a stack; a vacuum gripping means movably disposed under said stack and adapted to engage a marginal edge portion of the lowermost sheet in the stack; means for initially moving said gripping means in a twisting motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets; means after cessation of the operation of the foregoing means and consequent completion of the twisting action for moving said gripping means downwardly away from the stack with the sheet held thereby and thus lowering the sheet from the stack; means for engaging the edge portion of the next lowermost sheet in the stack and thus assisting in the separation of the sheets and also retaining the stack properly within the hopper means as the enGaged sheet is lowered from the stack; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder; means for returning the gripping means upwardly back into engagement with the next lowermost sheet in the stack, said gripping means including a sucker rod constituting a manifold and having a plurality of suction cups constituting suckers mounted therein in communication therewith; means connecting the sucker rod to a vacuum source; said means for moving the gripping means downwardly from the stack including a pair of arms mounted for vertical swinging movement and a rod supporting and actuating said arms and said sucker rod being carried by the arms and including means engaging the supporting rod for the arms of the gripping means for adjusting the effective height of the gripping means relative to the stack.

3. For use with a printing press having a vacuum means and having a feed linkage, a feeder for feeding stock to the press comprising; hopper means for supporting the stock in a stack; vacuum gripping means movably disposed under said stack and having means connecting it to the source of vacuum on the printing press with said gripping means being adapted to engage a marginal edge portion of the lowermost sheet of stock in the stock; means actuated by the printing press feed linkage for moving said gripping means downwardly away from the stack with the gripping means geing in communication with the vacuum means on the press and with the sheet held thereby so as to lower the sheet from the stack; means responsive to said foregoing moving means for initially twisting said gripping means in a revolving motion while it is engaged with the lowermost sheet so as to twist the engaged sheet off of the stack and thereby separate such sheet from the next uppermost sheet in the stack and consequently break the vacuum between such sheets prior to the downward movement of said gripping means which downward movement is initiated and carried out only upon completion of the initial twisting action; a conveying means to which the sheet is delivered by the gripping means for conveying the sheet from the feeder to the printing press, said conveying means being actuated by the printing press in timed relation with the operation of the press; means for moving the gripping means upwardly back into engagement with the next lowermost sheet in the stack after the removed sheet is delivered to the conveying means; said conveying means including a feed roll driven by the press and onto which the sheet is lowered by the gripping means and a pressure roll adapted to clampingly hold the sheet against the feed roll and means for moving said pressure roll into and out of clamping relation with the feed roll in timed relation with the movement of the gripping means; said last means including a rotatable rod, means connecting the pressure roll to said rod in spaced parallel and adjustable relation therewith, means actuated by the press linkage for rotating the rod in one direction to hold the pressure roll out of engagement with the feed roll and spring means connected between a fixed point and the rotatable rod and operative upon the deactivation of said foregoing means to swing the pressure roll into clamping relation with the feed roll.

4. The invention of claim 3 wherein said means for moving said gripping means downwardly away from the stack includes a rotating rod having a bell crank, a reciprocating cam means driven by the press feed linkage and adapted to engage the crank for rotating the rod, a pair of arms carried by the rod and on which the gripping means is mounted, said gripping means including a sucker rod having a plurality of suckers, said sucker rod being rotatably journaled in the arms and said means for initially moving said gripping means in a twisting motion including a restraining linkage pivotally connected between the rod and a fixed point, said linkage reacting to the downward movement of the arms to effect an initiaL twisting motion of the sucker rod.

7. The invention of claim 3 wherein a reciprocating cam means is driven by the press feed linkage, said conveying means including a feed roll on which the removed sheet is placed by the gripping means, a pressure roll, means mounting the pressure roll for bodily movement relative to the feed roll, means connecting the pressure roll to the cam means so it can be held thereby out of engagement with the feed roll and spring means connected between a fixed point and the mounting means for the pressure roll for moving it into engagement of the feed roll after the removed sheet has been delivered thereto by the gripping means, a rotatable rod having a bell crank engaged by the cam means so as to rotate the rod, a pair of arms carried by the rod and supporting the gripping means, said arms being swung downwardly by the cam means to move the gripping means downwardly and said twisting means including restraining means pivotally connected between the gripping means and a fixed point and reacting to the initial downward movement of the arms to effect the initial twisting action of the gripping means and said means for moving the gripping means upwardly back into engagement with the stack including springs connected between the arms and a fixed point, said springs also functioning to prevent the gripping means from lowering until the twisting motion is concluded.