US2799499A - Pneumatic sheet separating and feeding apparatus - Google Patents

Description

y 16, 1951 J. R. PERRY EIAL 2,799,499

. PNEUMATIC SHEET SEPARATING AND FEEDING APPARATUS Filed Dec. 11, 1953 3 Sheets-Sheet. 1

n Y// ///1 y/////J II INVENTORS v JOHN R. PERRY ATTORNEYS y 957 J. R. PERRY EI'AL PNEUMATIC SHEET SEPARATING AND FEEDING APPARATUS Filed Dec. 11, 1955 3 Sheets-Sheet 2 uvwszvrons JOHN R. PERRY LEO c. WILLIAMS ATTORNEYS July 16, 1957 J. R. PERRY ETAL PNEUMATIC SHEET SEPARATING AND FEEDING APPARATUS 3 Sheets-Sheet 3 Filed Dec.

INVENTORS JOHN R. PERRY LEO C. WILLIAMS flm and ATTORNEYS United States Patent Ofifice 2,799,499 Patented July 16, 1957 PNEUMATIC SHEET SEPARATIN G AND FEEDING APPARATUS John R. Perry and Leo C. Williams, Pearl River, N. Y.,

assignors, by mesne assignments, to Miehle-Goss- Dexter, Incorporated, a corporation of Delaware Application December 11, 1953, Serial No. 397,726

25 Claims. (Cl. 271-26) This invention relates to sheet feeders and more particularly to sheet separating mechanisms thereof employed to separate the sheets one after another from a pile or supply of sheets carried on the feeder preparatory to forwarding of the sheets from said pile or supply.

The present invention while capable of use in sheet by sheet feeders is particularly adapted for embodiment in stream feeders, or in combination stream and sheet by sheet feeders, wherein the sheets are advanced in lapped relation or singly one after another from a pile or supply to a printing press or other instrumentality with which the feeder is associated.

One object of the present invention is to provide an improved sheet feeder which Will effectively and reliably feed sheets of paper and other similar thin and relatively light and flexible material, as well as sheets of cardboard and other similar stiff and relatively thick and heavy material, one after another from the top of a supply thereof and present said sheets to conveying means for movement by the latter to a printing press or other machine acting on such sheets.

Another object of the invention is to provide a sheet feeder having sheet separating mechanisms, including suction devices novelly constructed so as to provide for limited downward movement thereof toward the top of the sheet pile or supply when handling paper and other similar thin and relatively light sheets, and unlimited downward movement thereof when handling cardboard and other similar stiff and relatively thick and heavy sheets, whereby handling of such sheets in said feeder is made possible and practical, and accurate separation and feeding thereof singly is assured.

Another object is to provide an improved sheet feeder of the above character having sheet separating mechanisms, including novel suction devices of the pneumatically actuated cylinder and piston type which will effectively lift paper as well as cardboard sheets from the top of a pile or supply thereof at opposite corner portions of said sheets and transversely stretch said corner portions for further accurate action of other sheet handling devices on the sheets.

Another object is to provide an improved sheet separating mechanism which may be incorporated in existing well-known paper sheet feeders to advantageously and successfully enable the handling of cardboard sheets also therein, and in existing well-known cardboard sheet feeders to advantageously and successfully enable the handling of paper sheets also therein.

The above and further objects and novel features of the present invention will more fully appear from the following detail description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the pur pose of illustration only, and are not intended as a definition of the limits of the invention.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a vertical longitudinal sectional view of a sheet feeder embodying sheet separating mechanisms constructed in accordance with the present invention, said view being taken substantially on the line 11 of Fig. 2;

Fig. 2 is a fragmentary top plan view of the feeder shown in Fig. 1, with portions of certain of the parts thereof. broken away for purposes of clearer illustration;

Fig. 3 is an enlarged side elevational view, partly in section, of the sheet separating mechanism shown in Fig. 1, with portions of certain of the parts thereof broken away for purposes of clearer illustration;

Fig. 4 is a horizontal sectional view substantially on the line 44 of Fig. 3;

Fig. 5 is a rear elevational view of the sheet separating mechanism shown in Fig. 3;

Fig. 6 is a vertical transverse sectional view of the pneumatic sheet lifting and stretching device shown in Figs. 3, 4 and 5, said view being taken on the line 66 of Fig. 3 and showing said device as it is arranged or adjusted for action upon cardboard and similar stiff and thick sheets;

Fig. 7 is a rear elevational view, partly in section, of the pneumatic sheet lifting and stretching device with certain of the parts having portions thereof broken away for purposes of clearer illustration, showing said device as it is arranged or adjusted for action upon paper and similar thin and flexible sheets; and

Fig. 8 is a detail top plan view, on an enlarged scale, of the pneumatically operated piston embodied in the suction sheet lifting and stretching device.

Referring to the drawings, 10 and 11 (Figs. 1 and 2) indicate the side frames of a sheet feeder of the pile type on which are mounted the various movable parts of said feeder, as well as certain stationary parts thereof. Disposed at both sides of the feeder are two cables 12 and 13 having corresponding ends thereof connected to winding drums 14 which are fixed on opposite ends of a shaft 15 that extends transversely of the feeder and is journalled in suitable bearings in the frames 10 and 11. From the drums 14 the cables 12 and 13 extend upwardly and pass over sheaves 16 journalled on the frames 10 and 11. From the sheaves 16 the cables 12 extend downwardly and have their lower free ends connected to the front ends of side bars 17 of a pile elevator including said cables and the cables 13. From the sheaves 16 the cables 13 pass over and around sheaves 18 journalled on the frames 10 and 11. From the sheaves 18 the cables 13 extend downwardly and have their lower free ends connected to the rear ends of the side bars 17. The side bars 17 are adapted to receive and support a pile board 19 and a pile 20 of paper, cardboard or other sheets of a similar character.

The elevator may be lowered to load it, and raised to bring the top of the pile 20 thereon to proper feeding position by any suitable means for these purposes connected with the drum shaft 15. Shaft 15 is then intermittently rotated in the usual manner by any well-known means to maintain the top of the pile 20 at the proper level as the sheets are fed therefrom in succession by means for this purpose to be hereinafter described. During step by step upward movement of the elevator, the pile of sheets 20 is guided at the front thereof by an apron or plate 21 (Fig. 1) secured in any suitable manner to the frames 10 and 11. The construction of the pile elevator and its operation for pile loading and sheet feeding purposes are well understood in the art and since the elevator per se forms no part of the present invention, further description thereof is believed to be unnecessary.

In accordance with the present invention, sheet separating mechanisms of novel construction are provided which are capable of successfully and reliably separating cardboard and other similar stiff and relatively thick and heavy sheets as well as paper and other similar flexible and relatively light and thin sheets, thus providing a sheet feeder which is more efficient than present feeders which are designed in accordance with the type of material to be handled therein and wherein sheet separating mechanisms of different designs are employed for paper and cardboard sheets in order to obtain satisfactory separation and feeding of such sheets at the present day high operating speeds.

These sheet separating mechanisms, indicated generally at 22 and 23 (Figs. 1 and 2), are located adjacent the rear corners of the pile of sheets and they effectively serve to preliminarily separate opposite rear corner portions of the topmost sheet on the pile from the next or underlying sheet, and to lift each topmost sheet at its separated corner portions and stretch the same in a direction transversely to the feeding direction, whereby the entire rear edge or rear edge portions of each topmost sheet, in turn, are raised and straightened to insure accurate engagement by sheet forwarding devices and accurate feeding of the sheets singly and successively from the top of the pile. The sheet separating mechanisms 22 and 23 are constructed one right-hand and the other left-hand, and since the constructions of said mechanisms are otherwise identical, a description of one will suflice for both.

As shown particularly in Figs. 3 to 8, the sheet separating mechanism at each rear corner of the pile of sheets 20 preferably comprises a bracket 24 which is slidably mounted on two parallel tubular cross shafts 25 and 26 to enable adjustment of said mechanism transversely of the feeder to accommodate sheets of different widths and to locate the same at the desired position with respect to its operation upon rear corner portions of the sheets at the top of the pile 20. The bracket 24 is secured in the desired position of adjustment thereof along the tubular shafts 25, 26 by a jam screw 27 threaded in said bracket and engaging the shaft 26. The tubular shafts 25, 26 are closed at their opposite ends to provide a vacuum conduit and an air supply conduit, respectively, and are secured at said ends in brackets 28 (Figs. 1 and 2) which are slidably mounted on the feeder frames 10 and 11 to enable adjustment of the sheet separating mechanisms 22 and 23 as a unit longitudinally of the feeder to accommodate sheets of different lengths.

The bracket 24 is provided in the outer surface thereof with a vertically extending U-shaped groove 29 (Figs. 3 and 4) and slidably engaged in said groove is a vertically disposed square bar 30 which projects above and below said bracket. The bar 30 is externally threaded at the upper end thereof and has threaded thereon an adjusting nut 31 by means of which said bar and parts carried thereby to be presently described may be vertically adjusted relative to the bracket 24 to desired positions with respect to the top of the pile of sheets 20. The nut 31 holds the bar 30 against sliding downward movement and permits free slidable upward movement of said bar and parts carried thereby so that if some portion of the pile of sheets should accidentally engage the same, they can move upwardly without damage thereto as the elevator rises. The bar 30 is held against outward lateral displacement from the bracket 24 by a cover plate 32 which is bolted or otherwise suitably secured to said bracket.

The bar 30 is suitably constructed to support adjacent the lower end thereof, as at 33 (Figs. 3 and 5), a short horizontal square bar 34 (Figs. 3, 4 and 5) which extends along the rear face of the pile of sheets 20. This bar 34 has welded or otherwise suitably secured to the inner end thereof a short vertically disposed blow pipe 35 which is closed at the lower end thereof and is provided with air jet means in the form of a thin slot or orifice 36. The slot 36 is directed forwardly through the wall portion of the pipe 35 facing the rear face of the pile of sheets and extends vertically of said pipe and crosswise or vertically of the plane of the sheets in the pile. Slidably engaged over and adjustable along the horizontal blow-pipe-carrying-bar 34 is a holder 37 provided with a vertically disposed elongated opening 38 to receive said bar therein. The holder 37 is further provided with another vertically extending elongated opening 39 which is disposed at right angles to the opening 38 so as to slidably and adjustably receive therein a second short horizontal square bar 40. This bar 40 is disposed below and at right angles to the bar 34 and extends from the holder 37 along the adjacent side face of the pile of sheets 20. The bar 40 has welded or otherwise suitably secured to the forward end thereof a short vertically disposed blow pipe 41, like blow pipe 35, which is closed at the lower end thereof and is provided with air jet means in the form of a thin slot or orifice 42. This slot 42 is directed laterally through the wall portion of the pipe 41 facing the side face of the pile of sheets and, like the slot 36 in pipe 35, extends vertically of the pipe 41 and crosswise or vertically of the plane of the sheets in the pile. The holder 37 is releasably clamped to the bar 34 and the bar 40 is, in turn, releasably clamped against said holder and the bar 34 by a jam screw 43 threaded in the holder and engaging the bar 34.

The slots 36 and 42 in the blow pipes 35 and 41, respectively, are thin enough so that sufficient pressure can be maintained in said pipes to give strong jets of air issuing from said slots. The slots 36 and 42 are preferably of a length such that when the pipes 35 and 41 are properly located vertically with respect to the normal feeding level of the top of the pile of sheets 20, the lower ends of the air jets issuing therefrom engage a plurality of the top sheets in the pile and the level of the upper ends of said air jets is above said pile level depending upon the extent of sheet separation desired. The sheet separating mechanisms 22 and 23 thus include and provide two air jet means comprising the blow pipes 35 and slots 36 at the rear and adjacent the rear corners of the pile of sheets 20, and one air jet means comprising the blow pipe 41 and slot 42 at each side and adjacent said corners of said pile. In the normal operating positions of the sheet separating mechanisms 22 and 23, the angularly related blow pipes 35 and 41 at each rear corner of the pile of sheets 20 are located approximately three inches in from said corner and approximately threequarters of an inch away from the rear and side faces of said pile. However, the spacing of the blow pipes 35, 41 from the edges and rear corners of the sheets, the velocity of the air jets, the relative positions of the jets below and above the level of the top of the pile of sheets, and other factors are dependent largely upon the weight and character of the sheets being handled in the feeder. When handling stiff and relatively thick and heavy sheets such as cardboard, for example, a heavier blast of air is necessary and desirable and this may be obtained by increasing the pressure in the air lines and hence at the jets and/or moving the blow pipes 35, 41 closer to the edges of the sheets. When handling thin, flexible, and relatively light sheets such as paper, for example, a lighter air blast is required and this may be obtained by decreasing the pressure in the air lines and hence at the jets and/or moving the blow pipes 35, 41 farther away from the edges of the sheets. The tendency of the sheets to stick together is also a factor which bears upon the blast and the location of the air jets and because of the great number of different kinds of sheets that may now be handled in the feeder, the strength of the air jets and their location for best results can be determined only by trial.

Air under pressure is delivered to the blow pipes 35 and 41 at predetermined intervals in timed relation with the operation of suction devices to be hereinafter described, and for this purpose, the blow pipes 35, 41 have connected therewith corresponding ends of flexible conduits 44 (Figs. 2 to 5) the opposite ends of which are connected to the air pressure side of a rotary valve mechanism 45 which is disposed centrally between the feeder frames and 11 and is mounted on and supported by the tubular shafts and 26. This valve mechanism 45 is of the type disclosed in the United States Patent No. 2,233,934, granted March 4, 1941, to Headley Townsend Backhouse, and needs no detail description herein. The valve mechanism 45 appropriately communicates with the tubular shafts 25 and 26 which are, in turn, connected in any suitable manner with the vacuum side and air pressure side, respectively, of a vacuum and air pump (not shown). The valve mechanism 45 is driven by suitable gearing (not shown) from a cam shaft 46 to control the delivery of air under pressure to the blow pipes and 41, and the making and breaking of vacuum in suction sheet separating, lifting, stretching and forwarding devices to be hereinafter described. The cam shaft 46 extends transversely of the feeder and is journalled in suitable bearings in the end brackets 28 and in the separator brackets 24, and is driven in any suitable manner from the printing press or any other suitable source of power to make one revolution for each cycle of operation of the feeder.

When air under pressure is delivered to the blow pipes 35 and 41 and issues therefrom through the slots 36 and 42, respectively, as strong thin elongated jets of air, said jets impinge against the rear and side edges of the sheets in the pile 20 at points contiguous the rear corners thereof and the air enters under pressure between a plurality of the uppermost sheets in said pile. The air from the jets so projected under pressure into the pile from two angularly related directions intermingles or intersects at a point inwardly from the rear and side edges of the sheets contiguous the rear corners thereof and produces between the sheets cddying or whirling currents of air which turbinate toward said edges. The opposite rear corner portions of the sheets thus acted upon by the jets of air will, as shown in broken lines in Fig. 7, raise or fluff-up and become separated one from another in a progressive manner beginning with the lowermost sheet and ending with the uppermost sheet, with the minimum amount of separation being between the lowermost sheet and the next overlying sheet, and the maximum amount of separation being between the top sheet and the next underlying sheet. It is to be noted that the described mounting for the blow pipes 35 and 41 further provides for upward movement thereof by the pile board 19 when the pile of sheets 20 thereon is depleted, thus enabling continued action of the air jets on the sheets until said pile is completely exhausted.

When the jets of air contiguous the rear corners of the pile of sheets 20 have preliminarily separated the top sheet at its rear opposite corners as described, said sheet is further separated and lifted from the pile by its separated rear corner portions and stretched in a direction transversely to the feeding direction by two sheet separating devices of the suction type located adjacent the rear corners of the pile and which are actuated in opposite directions by vacuum or suction to engage and lift the sheet, and away from each other by cam means to stretch said sheet. When handling paper and other thin, flexible and relatively light sheets, the stretching of each sheet raises and straightens the entire rear edge thereof for accurate engagement by sheet forwarding devices, and when handling cardboard and other stifif, thick and relatively heavy sheets, the stretching of each sheet straightens at least opposite corner portions of said sheet to en able accurate engagement of said sheet forwarding devices with the sheet at said corner portions. The suction sheet separating devices are novelly constructed so as to provide for unlimited downward movement thereof when handling cardboard and other similar stilf and heavy sheets whereby said devices will engage such sheets under pneumatic pressure and firmly grip the same for accurate and reliable lifting and stretching purposes, and limited downward movement thereof when handling paper and other similar thin and light sheets whereby said devices will engage such sheets at their separated levels and grip the same substantially without pressure thereon and without depressing the separated corner portions of such lighter sheets back onto the pile, thus always assuring that the top sheet alone and that single sheets only are lifted by said devices.

These suction sheet separating, lifting and stretching devices, indicated generally at 47 (Figs. 3 to 7) are component parts of the sheet separating mechanisms 22 and 23 and, hence, are carried by and movable with the brackets 24 of said mechanisms. The suction sheet separating devices 47 are identical as respects their construction, mounting and operation and a description of one of said devices will therefore be sufficient for both of the same. As herein shown, each suction sheet separating device 47 preferably comprises a cylinder 48 having a mounting head 49 at the upper end thereof which is pressed on and over said cylinder and is further secured thereto in any suitable manner such as by brazing as indicated at 50. The head 49 is formed with a journal 51 which is disposed at right angles to the cylinder 48 and is rotatably mounted in a suitable bearing 52 provided on the bracket 24 and which extends in the direction of feed of the sheets and is so disposed that the axis thereof is slightly inclined downwardly from the horizontal and forwardly with respect to the direction of feed of the sheets from the top of the pile, as shown in Fig. 3. Accordingly, the cylinders 48, through mounting of the heads 49 in the bearings 52 on the brackets 24, are correspondingly inclined upwardly and forwardly from the top of the pile of sheets 20 and toward the front of the feeder, as shown in Fig. 3, for a purpose to appear hereinafter. Axial forward displacement of each cylinder 48 from the respective bracket 24 is prevented by a washer 53 which is pinned and bolted to the journal 51 of the respective mounting head 49.

Each cylinder 48 is closed at its upper end by a cap 54 (Figs. 3, 5 and 6) which is bolted or otherwise suitably secured to the mounting head 49. The cylinder 48 is closed at the lower end thereof by a cap 55 (Fig. 6) which is disposed within said cylinder and is secured thereto by machine screws 56 or the like. Disposed within the cylinder 48 is a relatively large diameter piston stem 57 which is fitted for sliding vertical movement in the lower cap 55 of said cylinder and projects downwardly through said cap beyond the same. Fitted for sliding vertical movement in the cylinder 48 and formed integrally with the stem 57 at the upper end thereof is a relatively thin piston head 58 having a relatively thin upwardly projecting skirt 59. The stem 57 is formed with an annular passage 60 of a relatively large diameter extending axially therethrough for a major portion of the length thereof beginning at the lower end and ending a short distance from the piston head 58 thereby forming in the stem an internal annular shoulder 61 adjacent the upper end thereof. The passage 60 opens outwardly through the lower end of the stem 57 and communicates at the upper end thereof with lower portions of a plurality of axially extending passages 62 (Figs. 6 and 8) of a relatively small diameter which are equally spaced around the passage 60 and open outwardly at the upper ends thereof through the piston head 58. The piston stem 57 is provided adjacent the upper end thereof with two diametrically opposite radially extending passages 63 of a small diameter for establishing communication between the passage 60 and the interior portion of the cylinder 48 below the piston head 58.

Fixed on the lower projecting end of the stem 57 is a rubber suction cup 64 provided with a duct 65 (Fig. 6) connecting said cup with the passage 60 through the lower open end of the latter. The cup 64 is held against axial displacement from the stem 57 by suitable annular teeth 66 formed on the lower end of said stem. Surrounding the piston stem 57 and interposed between the piston head 58 and the lower cap 55 of the cylinder 48 is a light coil compression spring 67 which is adapted to hold the relatively light piston head 58, piston stem 57 and suction cup 64 in their normally raised full line positions when no vacuum is created in the cylinder 48. The cylinder 48 has secured therein adjacent the lower end thereof a tubular fitting 68 which communicates with the interior of said cylinder through a suitable passage 69 formed in the lower cylinder cap 55. The fittings 68 on the cylinders 48 have attached thereto corresponding ends of flexible conduits 70 the opposite ends of which are connected to the vacuum side of the valve mechanism 45, whereby vacuum is created and broken at predetermined intervals in the cylinders 48 to cause the suction cups 64 to engage, grip, lift and release each sheet.

The suction sheet separating devices 47 located adjacent the rear corners of the pile of sheets and constructed and mounted as thus far described, will effectively and reliably lift cardboard and other relatively stiff and heavy sheets from the top of a pile thereof. In the operation of the suction devices 47 on cardboard and similar stiff sheets, when vacuum is created in the conduits 70, which is timed to occur while the upper rear corner portions of the pile of such sheets are being acted upon by the jets of air issuing from the blow pipes and 41, vacuum is likewise created in the lower ends of the cylinders 48 through the fittings 68 and passages 69. Vacuum so created in the lower ends of the cylinders 48 and beneath the piston heads 58 causes said heads, the piston stems 57 and the suction cups 64 to move downwardly and rearwardly with unlimited movement, compressing the springs 67, until said suction cups engage the rear corner portions of the top cardboard or other similar stiff sheet on the pile under vacuum pressure sufficient to press said corner portions against said pile and thereby form a good seal between the same and the suction cups, as shown in broken lines in Fig. 6. The vacuum in the cylinders 48 also draws air through the passages 63, 62 and and the ducts in the suction cups 64. However, the passages 63 are small enough so that this air infiltration does not reduce the vacuum pressure materially and, hence, sufiicient vacuum pressure is created upon the lower sides of the piston heads 58 so that the latter and the suction cups 64 move downwardly against the tension of the springs 67 and said cups engage the sheet under pressure, as described. No vacuum or substantially no vacuum is created above the piston heads 58 because the ducts 65 in the suction cups 64 are open to atmosphere.

When, however, the suction cups 64 are sealed by the sheet, vacuum is also created in the cylinder portions above the piston heads 58 and in the passages 60 and 65 in the piston stems 57 and suction cups 64, respectively, through the passages 63 and 62. Through the relatively large diameters of the piston stems 57 there is now a relatively large differential in vacuum effect above and below the piston heads 58, and the latter, the stems 57, the suction cups 64, and the rear corner portions of the sheet now firmly gripped by vacuum by said cups are lifted upwardly and forwardly by vacuum regardless of, but augmented somewhat by, the expanding action of the springs 67. Due to the forward inclination of the suction devices 47, the corner portions of the sheet when lifted by said devices are drawn toward the front of the pile, thereby exerting a forward pushing action on the sheet so that it is held against the pile plate 21 and prevented from sliding rearwardly on and possibly displacing the next or underlying sheet.

Immediately after the suction devices 47 have lifted the topmost cardboard or other similar stiff sheet at its rear corner portions from the pile as above-described,

the supply of compressed air to the blow pipes 35 and 41 is discontinued through continued rotation of the valve mechanism 45, and said suction devices while gripping said sheet are moved outwardly away from each other toward the sides of the pile so as to transversely stretch the sheet sufficiently to straighten and raise at least portions of said sheet inwardly of the suction devices 47 for accurate engagement by sheet forwarding devices to be hereinafter described. For this purpose, each sheet separating mechanism 22 and 23 includes a cam 71 (Figs. 3, 4 and 5) which is mounted on the cam shaft 46 and is drivably connected to said shaft by a key fixed in said cam and slidably engaged in a suitable keyway formed in and extending along the shaft. The cam 71 is disposed between the separator bracket 24 and the cover plate 32 thereon and, hence, said cam may be adjusted along the shaft 46 by and with said bracket without disturbing its operating position and the driving connection with said shaft, The cam 71 engages a roller 72 journalled on one arm 73 of a vertically disposed bell crank 74 which is pivotally mounted at 75 between and on the bracket 24 and cover plate 32. The other arm 76 of the bell crank 74 projects downwardly and has pivotally connected therewith as at 77 the rear end of an adjustable connecting link 78. The front end of the link 78 is pivotally connected as at 79 with one arm 80 of a horizontally disposed bell crank 81 which is pivotally mounted at 82 on the bracket 24. The other arm 83 of the bell crank 81 projects forwardly of the bracket 24 inwardly of the respective suction device 47 and carries at the free end thereof an adjustable contact member 84 in the form of a headed screw which is threaded in a suitable threaded opening in said arm and is held in adjusted positions by a lock nut 85 threaded thereon. The contact member or screw 84 is arranged to engage the head of the one of the screws 56 on the cylinder 48 of the associated suction device 47. The suction device 47 is yieldingly urged inwardly about its pivotal axis 51 toward the bell-crank arm 83 by a coil extension spring 86 having one end thereof connected as at 87 to the lower end of the cylinder 48 of said suction device and the opposite end connected as at 88 to the bracket 24. The spring 86 also serves to yieldingly urge the roller 72 toward and into engagement with the cam 71.

It will thus be apparent that the inward swinging movement of the suction devices 47 about their pivotal axes 51 by the springs 86 is limited through engagement of the rollers 72 with the low parts of the cams 71 and engagement of said suction devices with the contact members 84, and that such engagement of the rollers 72 and suction devices 47 locates said suction devices in their normal inward sheet engaging and lifting positions. It will also be apparent that the outward swinging movement of the suction devices 47 about their pivotal axes 51 is a positive action effected by the earns 71 through engagement of the high parts of said cams with the rollers 72 and engagement of the contact members 84 with said suction devices, whereby stretching of cardboard and other similar stiff and heavy sheets transversely to the feeding direction by the suction devices 47 as and for the purpose above described may be effectively and reliably accomplished. It will further be apparent that by adjusting the contact members 84 and varying the length of the connecting links 78, the suction devices 47 in their normal inward sheet engaging and lifting positions may be adjusted about their pivotal axes 51 from a straight up and down position to an upwardly and inwardly inclined position, as shown in Fig. 5, which latter position is preferred when handling cardboard and similar stiff and heavy sheets in the feeder, whereby the rear corner portions of such sheets are drawn inwardly toward each other as well as forwardly by the suction devices 47, thus in effect peeling the top sheet from the one therebelow and insuring that said suction devices will effectively and reliably separate such sheets and only one sheet at a time from the top of the pile 20.

After the uppermost cardboard or other relatively stiff sheet has been gripped, lifted and stretched by the suction devices 47, as hereinbefore described, and while blasts of air are directed forwardly beneath said sheet through blow pipes (not shown), the sheet is transferred to sheet forwarding devices indicated generally at 89 (Figs. 1 and 2), whereupon said sheet is released by the suction devices 47 and forwarded by said forwarding devices and said forwardly directed air blasts from the top of the pile 20 to conveyor means indicated generally at 90. The sheet forwarding devices 89 may be of any type, but as herein shown they are of the suction type and located at the rear of the pile of sheets 20 and close to the suction sheet separating devices 47 so that the lifted uppermost sheet is effectively gripped thereby in the region of the stretched portions thereof. The suction sheet forwarding devices 89 are carried by arms 91 fixed on a transversely extending rock shaft 92 which is journalled in suitable hearings in the end brackets 28. The shaft 92 is actuated from the cam shaft 46 by suitable connections (not shown) to swing the suction sheet forwarding devices 89 rearwardly to the broken line positions thereof shown in Fig. 2 to grip the lifted and stretched sheet, and then forwardly to forward said sheet from the pile and deliver the same to the conveyor 90. The making and breaking of vacuum in the suction sheet forwarding devices 89 is effected at proper intervals to cause the same to grip and release each lifted and forwarded sheet. For this purpose, the suction sheet forwarding devices 89 have connected there with corresponding ends of flexible conduits 93 the opposite ends of which are connected with the vacuum side of the valve mechanism 45. After the sheet is delivered to the conveyor 90 by the suction sheet forwarding devices 89, the latter are released from the sheet and returned for action on the next lifted and stretched sheet.

The conveyor 90 is of well-known construction and includes a feed roller 94, cooperating pressure rollers 95 and a series of endless tapes 96. The conveyor 90 is driven continuously by any suitable source of power connected therewith, either at slow speed to enable lapping of the sheets thereon and to advance a stream of the lapped sheets to a printing press or other machine, or at fast speed to advance the sheets singly in spaced relation to said press or machine, as well understood in the art.

Thus far the foregoing description has related mostly to the construction, mounting and operation of the sheet separating mechanisms 22 and 23, and the use of said mechanisms in connection with the handling of cardboard and other similar stiff and relatively thick and heavy sheets successfully in the feeder. The efficiency of a sheet feeder depends upon the many different kinds of sheet material that it can capably and successfully handle. In accordance with another aspect of the present invention, the sheet separating mechanisms 22 and 23 are constructed so that paper and other similar thin, light and flexible sheets may also be successfully handled in the feeder without any change in the mode of operation of said mechanisms, i. e., the rear corner portions of the paper and the like sheets are preliminarily separated by the jets of air issuing from the blow pipes 35 and 41, the sheets are gripped and lifted at the separated rear corner portions thereof by the suction devices 47 and stretched in a direction transversely to the feeding direction by said suction devices, and the lifted and stretched 5. sets are taken by the suction devices 89 in the region of the retched portions thereof and forwarded from the pile, all as above described in connection with the handling of cardboard and other similar stiff sheets.

In the handling of paper and other thin, light and flexible sheets successfully in the feeder, the suction sheet separating, lifting and stretching devices 47 are preferably adjusted about their pivotal axes 51 to a substantial straight up and down position, as shown in Fig. 7, through the medium of the contact members 84 and connecting links 78 as hereinbefore described, but may be inclined toward each other if deemed necessary or desirable. Also, the suction devices 47 are so controlled by means to be presently described, that the downward sheet engaging movement of the suction cups 64 is limited to the separated levels of the winded rear corner portions of the top sheet, whereby said corner sheet portions will be gripped by said suction cups at said levels and will not be depressed back onto the pile and lifting of the top sheet only is thereby assured. Additionally, the outward sheet stretching movement of the suction devices 47 may be varied as necessary or required depending on the slack or sag in the lifted sheet whereby stretching of the entire rear edge of said sheet may be effectively achieved without tearing the thin sheet. When handling paper and similar thin sheets in the feeder, the suction sheet forwarding devices 89 are also preferably spaced evenly across the width of the pile so that the stretched rear edge of the lifted sheet will be gripped by said suction devices at spaced points along said edge and thereby obtain better control of the thin sheet.

As herein shown, the extent of downward movement of the suction cups 64 and the extent of outward swinging movement of the suction devices 47 is preferably controlled by the following elements which form permanent parts of the sheet separating mechanisms 22 and 23 and are constructed, mounted and utilized as follows. Disposed within the tubular piston stem 57 of each suction device 47 and below the internal annular shoulder 61 on said stem is an annular abutment member or stop 97 (Figs. 4, 6 and 7) which is of a diameter slightly less than the diameter of the passage 60 in the stem so as to avoid sliding contact of said stem therewith, and is pro vided in and around the peripheral surface thereof with a series of axially extending arcuate grooves or slots 98 so as to allow for unobstructed and sufficient flow of air through the passage 60 for the purposes hereinbefore described. The stop 97 is concentrically secured to or formed integrally with a small diameter rod 99 which extends upwardly from said stop and outwardly beyond the upper cylinder cap 54 through suitable axially aligned clearance openings 100 and 101 formed in said cap and the piston head 58 and piston stem 57, respectively. The upper end portion of the rod 99 is externally threaded and projects through a spacer sleeve 102 which is interposed between the cylinder cap 54 and a conventional self-locking adjusting nut 103 threaded on said rod. The rod 99 has suitably secured thereto at the extreme upper end thereof a knurled nut 104 by means of which said rod may be manually held against rotation when the nut 103 is manually rotated to different positions along the rod by a wrench or the like.

It will thus appear that downward axial movement of the stop 97 and rod 99 is limited through engagement of the nut 103 with the sleeve 102, and that said stop and rod are free to move upwardly should the piston stem 57 and piston head 58 upon upward sheet lifting movement thereof frictionally grip the stop or rod for some reason. Under normal conditions and during the normal operation of the feeder, no movement is imparted to the stop 97 and rod 99 by the piston stem 57 and piston head 58. It is to be noted that the axial spacing of the ports 63 in the piston stem 57 from the shoulder 61 in said stem is slightly greater than the thickness of the stop 97 and, hence, said stop when engaged by said shoulder as hereinafter described, will not in any way affect the effective vacuum actuation of the piston stem 57 and piston head 58 and the effective vacuum gripping action of the suction cups 64 on the sheet. It will further appear that the position of the stop 97 axially with respect to the piston stem 57 may be conveniently adjusted by simply rotating the nut 103.

When handling cardboard and other relatively stiff and heavy sheets in the feeder and unlimited downward move- 11 ment of the suction cups 64 is desired as hereinbefore described, the stops 97 through rotation of the nuts 103 in one direction are each lowered to the position thereof shown in Fig. 6, wherein it will be noted that said stop is spaced from the normal uppermost position of the shoulder 61 on the piston stem 57 a distance in excess of the distance between the normal feeding level of the top of the pile 20 and the suction cup 64 in its normal raised position and in excess of the maximum downward movement of the suction cup required for said suction cup to effectively engage, grip and lift the top sheet from said pile. Under these conditions, upon downward movement of the piston stems 57, piston heads 58 and suction cups 64, the shoulders 61 on said stems will not engage the stops 97 and the stems, heads and suction cups will unobstructively continue to move downwardly until said suction cups engage the top sheet of the pile and press said sheet under vacuum pressure against said pile to form an effective seal between the same and the sheet, as hereinbefore described, at which time vacuum is created in the suction cups through the grooves 98 in the stops 97.

When handling paper and other thin, light and flexible sheets in the feeder and limited downward movement of the suction cups 64 is desired as hereinbefore described, the stops 97 through rotation of the nuts 103 in the opposite direction are each raised to the position thereof shown in Fig. 7, so that said stop is spaced from the nor mal uppermost position of the shoulder 61 on the piston stem 57 a distance less than the distance between the normal feeding level of the top of the pile 20 and the suction cup 64 and substantially equal to the distance between said suction cup and the level occupied by the air separated rear corner portion of the top sheet on said pile. Under these conditions, upon downward movement of the piston stems 57, piston heads 58 and suction cups 64, the shoulders 61 on said stems will engage the stops 7 when said suction cups substantially reach the separated levels of the rear corner portions of the top sheet, as shown in broken lines in Fig. 7, whereupon the suction cups are stopped against further downward movement and the corner portions of the sheet are attracted to and gripped by vacuum by said suction cups without depressing said corner sheet portions back onto the pile, thus assuring that the top sheet alone and that only a single sheet is engaged, gripped and lifted by the suction devices 47. In order to alleviate shock and to reduce noise to a minimum upon engagement of the rapidly moving piston stems 57 with the stops 97, cushion discs or washers 105 (Fig. 6) are preferably interposed between the spacer sleeves 102. and the cylinder caps 54. It will be understood that when handling paper and other thin, light and flexible sheets, the stops 97 may occupy different axial positions with respect to the piston stems 57 and also with respect to each other depending on stock conditions, the type of material, and the degree of separation effected by the air jet blow pipes 35 and 41. The nuts 103 provide for adjusting of the stops 97 to any desired axial positions and this may be finely regulated by said nuts even while the feeder is in operation, thus avoiding loss of time and production.

Disposed exteriorly of the cover plate 32 on the bracket 24 of each sheet separating mechanism 22 and 23 is a bell crank lever 106 (Figs. 3, 4 and 5) which is pivotally mounted at 75 on said bracket. This bell crank lever 106 has a forwardly projecting arm 107 and a downwardly projecting arm 108 which is formed at the lower end thereof with another arm 109 which projects inwardly therefrom into the path of forward swinging movement of the arm 76 of bell crank 74. The arm 107 of bell crank 106 is arranged to engage an adjustable abutment member 110 in the form of a machine screw which is threaded in a suitable threaded opening in a block 111 and is held in adjusted positions by a lock nut 112 threaded thereon. The block 111 is bolted or otherwise suitably secured to the cover plate 32. The arm 107 12 of bell crank 106 is continuously urged toward the abutment member or screw and yieldingly engaged with said abutment member by a light coil compression spring 113 having one end thereof engaging against said arm and the opposite end engaging against a shoulder or shelf on the block 111.

When handling cardboard and other similar stiff sheets in the feeder, each bell crank 106 is adjusted by means of the abutment member 110 to the full line position thereof shown in Fig. 3, wherein it will be noted that the arm :09 of said bell crank is disposed clear of the maximum forward swinging movement of the bell-crank-arm 76, and, hence, the roller 72 on bell-crank-arm 73 may follow the full drop of the cam 71 and maximum outward sheet stretching swinging movement will be imparted to the suction device 47 by said cam upon continued rotation of the latter and engagement of the high part thereof with said roller, as hereinbefore described. On some types of cardboard and other similar stiff sheets, it might be necessary or desirable to eliminate the sheet stretching action of the suction devices 47, and this may be conveniently accomplished by simply adjusting each bell crank 106 by means of the abutment member 110 in a counter-clockwise direction, as viewed in Fig. 3, to a position such that the arm 109 of said bell crank will engage the bell-crank-arm 76 when the roller 72 on the bell-crank-arm 73 is engaged with the high part of the cam 71. Under these conditions, the rollers 72 will be prevented by the bell cranks 106 from following the low parts of the earns 71 to enable return movement of the suction devices 47 by the springs 86 and subsequent outward movement of said suction devices by said cams, thus rendering the suction devices ineffective to stretch the sheet. It is to be noted that when the bell cranks 103 are adjusted as aforesaid to discontinue the sheet stretching operation of the suction devices 47, said suction devices, through engagement of the high parts of the earns 71 with the rollers 72, will be disposed at an increased angle in their outermost sheet stretching positions and may be left in said positions for effective sheet lifting operation or reset, if desired or necessary to a lesser angle by simply adjusting the contact members 84 and the connecting links 78.

It will thus be apparent that when handling paper and other thin, light and flexible sheets in the feeder, the extent of outward movement of the suction devices 47 to insure proper stretching of such sheets without tearing the same may be accurately controlled, as desired, by adjusting the bell cranks 106 from the position thereof shown in Fig. 3 toward the bell cranks 74 to various positions with respect to the bell-crank-arms 76. It will also be apparent that by virtue of the bell cranks 106, the sheet stretching operation of the suction devices 47 may be controlled as desired or required in accordance with the type of material being handled, and such that said stretching operation may be effected solely by one or the other of the suction devices 47, or by both of said suction devices through equal or unequal outward movements thereof. Additionally, by virtue of the adjustable contact members 84 and connecting links 78, the angle of inward inclination of the suction devices 47 in their normal sheet engaging and lifting positions may be adjusted as desired or required in accordance with the type of material being handled and the action of said suction devices on such material. Also, by virtue of the adjustable stops 97, the extent of downward movement of the suction cups 64 may be regulated as desired or required in accordance with the type of material being handled.

The operation of the sheet feeder embodying the pres ent invention will be clearly understood from the foregoing description, and while said description and the accompanying drawings set forth with more or less particularity one embodiment of the invention, it is to be expressly understood that said invention is not limited to said embodiment. Various changes may be made therein, particularly in the design and arrangement of the parts illustrated, without departing from the spirit and scope of the invention, as will now be apparent to those skilled in the art. The suction sheet lifting and stretching devices may, for example, be also embodied in continuous types of sheet feeders wherein the sheets are fed one after another from the top of a fanned-out bank of sheets. For a definition of the limits of the invention, reference is had primarily to the appended claims.

What is claimed is:

1. In a sheet feeder, means for separating sheets successively from the top of a supply thereof and comprising, a pair of transversely spaced vacuum sheet separators arranged above the supply of sheets and reciprocated pneumatically toward and away from said supply to grip the topmost sheet and lift said sheet from said supply, means supporting said vacuum sheet separators for pivotal movement about fixed axes extending in the direction of feed of the sheets, cam means for swinging said vacuum sheet separators by a positive action outwardly away from each other about said axes while gripping the sheet to stretch said sheet, resilient means for swinging said vacuum sheet separators inwardly toward each other about said axes after the sheet is stretched and released thereby to return said sheet separators to their original sheet gripping and lifting positions, and adjustable means for varying the extent of downward movement of the pneumatically reciprocated vacuum sheet separators toward the top of the supply of sheets independently of each other.

2. A sheet feeder as defined in claim 1, comprising adjustable means for varying the extent of outward movement of the pneumatically reciprocated vacuum sheet separators by the cam means independently of each other and thereby varying the sheet stretching action of said sheet separators.

3. A sheet feeder as defined in claim 1, comprising adjustable means movable to one position for preventing outward movement of the pneumatically reciprocated vacuum sheet separators by the cam means independently of each other and to other positions to vary the extent of outward movement of said sheet separators by said cam means independently of each other, whereby the stretching of the sheet may be selectively discontinued or effected solely by either one of said sheet separators or by both of said sheet separators through equal or unequal outward movements thereof.

4. In a sheet feeder, means for separating sheets one after another from the top of a supply thereof and comprising, a pair of vacuum sheet separators arranged above the supply of sheets and reciprocated by vacuum toward and away from said supply to grip the topmost sheet at transversely spaced points and lift said sheet from said supply, means supporting said vacuum sheet separators for pivotal movement about fixed axes extending in the direction of feed of the sheets, driven rotary cam means for swinging said vacuum sheet separators by a positive action outwardly away from each other about said axes while gripping the sheet to stretch said sheet, resilient means under the control of said cam means for swinging said vacuum sheet separators inwardly toward each other about said axes after the sheet is stretched and released thereby to return said sheet separators to their original sheet gripping and lifting positions, and adjustable means for varying the extent of downward movement of the vacuum reciprocated vacuum sheet separators toward the top of the supply of sheets independently of each other.

5. A sheet feeder as defined in claim 4 wherein the pivotal axes of the vacuum reciprocated vacuum sheet separators are inclined downwardly from the horizontal and forwardly with respect to the direction of feed of the sheets so that said sheet separators are correspondingly inclined forwardly from the vertical, whereby the sheet is drawn upwardly and forwardly when lifted by said sheet separators.

6. A sheet feeder as defined in claim 4, comprising adjustable means for varying the extent of outward move ment of the vacuum reciprocated vacuum sheet separators by the cam means independently of each other and thereby varying the sheet stretching action of said sheet separators.

7. A sheet feeder as defined in claim 4 wherein the vacuum reciprocated vacuum sheet separators in their normal inward sheet engaging and lifting positions are inclined upwardly and inwardly from the top of the sheet supply toward each other so that the portions of the sheet gripped by said sheet separators are drawn upwardly and inwardly when lifted by said sheet separators.

8. In a sheet feeder, mean for separating sheets successively from the top of a supply thereof and comprising, a pair of vacuum sheet separators arranged above the supply and reciprocated pneumatically toward and away from said supply to grip the topmost sheet at transversely spaced points and lift said sheet from said supply, means supporting said vacuum sheet separators for pivotal movement about fixed axes extending in the direction of feed of the sheets, a pair of driven rotary cams having high and low parts, connections between said cams and said vacuum sheet separators and including rollers engaged by the high parts of said cams for swinging said vacuum sheet separators outwardly away from each other about said axes while gripping the sheet to stretch said sheet, resilient means under the control of said cams for swinging said vacuum sheet separators inwardly toward each other about said axes after the sheet is stretched and released thereby to return said sheet separators to their normal inward sheet gripping and lifting positions determined through engagement of said rollers with the low parts of said cams, and adjustable means for varying the extent of downward movement of the pneumatically reciprocated vacuum sheet separators towards the top of the supply of sheets independently of each other.

9. A sheet feeder as defined in claim 8 wherein the connections between the cams and the pneumatically reciprocated vacuum sheet separators include adjustable elements which provide for angular adjustment of said sheet separators about their pivotal axes relative to each other to various angular positions with respect to the top of the supply of sheets.

10. A sheet feeder as defined in claim 8, comprising adjustable means associated with said connections for varying the effective action of the high parts of said cams and thereby varying the extent of outward movement of said vacuum sheet separators by said cams.

11. A sheet feeder as defined in claim 8 wherein the pivotal axes of the pneumatically reciprocated vacuum sheet separators are inclined downwardly from the horizontal and forwardly with respect to the direction of feed of the sheets so that said sheet separators are correspondingly inclined forwardly from the vertical, whereby the sheet is drawn upwardly and forwardly when lifted by said sheet separators.

12. In a sheet feeder, means for separating sheets one after another from the top of a supply thereof and comprising, a pair of transversely spaced cylinders arranged above the supply of sheets, means supporting said cylinders for pivotal movement about fixed axes extending in the direction of feed of the sheets, piston type suction means in said cylinders and reciprocal relative to said cylinders toward and away from said supply to grip the topmost sheet and lift said sheet from said supply, a pair of driven rotary cams having high and low parts, connections between said cams and said cylinders and actuated by the high parts of said cams for swinging said cylinders and therewith said suction means outwardly away from each other about said axes to stretch the sheet gripped by said suction means, said connections comprising a pair of pivotally mounted bell cranks having rollers on corresponding arms thereof engaging said earns, a pair of other pivotally mounted bell cranks having corresponding arms thereof engaging said cylinders, and links connecting the other arms of said first-named bell cranks with the other arms of said other bell cranks, biasing means acting upon said cylinders and at all times urging the same toward and into engagement with the said corresponding arms of said other bell cranks to thus swing said cylinders and said suction means inwardly toward each other about said axes to their normal inward positions determined through engagement of said rollers with the low parts of said cams, and adjustable means carried by said cylinders and arranged to be engaged by said suction means for varying the extent of downward movement of said suction means towards the top of the supply of sheets.

13. A sheet feeder as defined in claim 12 wherein said links are adjustable as to the effective lengths thereof so as to provide for angular adjustment of the cylinders and suction means about said axes relative to each other to various angular positions with respect to the top of the supply of sheets.

14. A sheet feeder as defined in claim 12, comprising contact members adjustably carried by the said corresponding arms of said other bell cranks and interposed between said arms and said cylinders and engaging the latter, said contact members providing for angular adjustment of said cylinders about their pivotal axes relative to each other to various angular positions with respect to the top of the supply of sheets.

15. A sheet feeder as defined in claim 12, comprising adjustable means associated with one of said pairs of hell cranks and movable to one position for preventing movement of said rollers into the low parts of said cams and to other positions for varying the extent of movcment of said rollers into said cam parts.

16. A sheet feeder as defined in claim 12 wherein the pivotal axes of said cylinders are inclined downwardly from the horizontal and forwardly with respect to the direction of feed of the sheets so that said cylinders and said suction means are correspondingly inclined forwardly from the vertical.

17. In a sheet feeder, a pair of transversely spaced cylinders, vacuum sheet separating elements having hollow piston stems extending into said cylinders and provided therein with piston heads, means for reciprocating said vacuum sheet separating elements relative to said cylinders toward and away from the top of a supply of sheets to cause said vacuum sheet separating elements to grip the topmost sheet and lift said sheet from said supply, abutment means carried by said cylinders and extending into said hollow piston stems for engagement by the latter to limit the downward movement of said vacuum sheet separating elements, and means for adjusting said abutment means to various positions axially of said hollow piston stems to vary the extent of downward movement of said vacuum sheet separating elements.

18. A suction sheet handling device comprising, a cylinder, reciprocal piston means in said cylinder, said piston means including a hollow piston stern projecting outwardly beyond one end of said cylinder and having within the same a shoulder facing said cylinder end, a suction cup secured to the outwardly projecting end of said piston stem for gripping a sheet and moving the same toward said cylinder upon reciprocation of said piston means. an abutment member disposed within said piston stem for limiting the movement of said suction cup away from said cylinder through engagement of said shoulder with said abutment member, and means adjustably carried by said cylinder and connected to said abutment member for adjusting the latter to various positions axially of said piston stem and thereby varying the extent of movement of said suction cup away from the cylinder.

19. A suction sheet handling device comprising, a cylinder closed at both ends thereof, a piston head in said cylinder and reciprocated by vacuum and normally disposed adjacent one end of said cylinder, a piston stem on said piston head and extending therefrom through and beyond the opposite end of said cylinder, a sheet gripping suction cup secured to the outwardly projecting end of said piston stem, said piston stem having an annular passage extending axially therethrough and an internal annular shoulder facing said opposite end of said cylinder, said passage communicating with said suction cup and with the interior portion of said cylinder between the said one end thereof and said piston head, an annular abutment member disposed within said passage for limiting projecting movement of said piston stem from said cylinder through engagement of said shoulder therewith, said abutment member having a plurality of passages extending axially therethrough which provide for evacuation of said piston stem passage and said suction cup, and a rod adjustably carried by said cylinder and connected to said abutment member for adjusting the latter to various positions axially of said piston stem and thereby varying the extent of projecting movement of said piston stem.

20. A suction sheet handling device comprising, a cylinder, a cap closing one end of said cylinder, another cap closing the other end of said cylinder, a piston head reciprocal in said cylinder and normally disposed adjacent one of asid caps, a piston stem on said piston head and extending therefrom through and beyond the other of said caps, a sheet gripping suction cup secured to the outwardly projecting end of said piston stern, said piston stem having an annular passage extending axially therethrough and an internal annular shoulder facing said suction cup, said passage communicating with said suction cup and with the interior portion of said cylinder between the said one of said caps and said piston head, said cylinder having a passage therein for establishing communication between a source of vacuum and the interior portion of said cylinder between the said other of said caps and said piston head, said piston stem having a radially extending port therein for establishing communication between said cylinder portions through said piston stem passage, an annular abutment member disposed Within said piston stern passage for limiting projecting movement of said piston stem from said cylinder through engagement of said shoulder therewith, said abutment member having a plurality of passages extending axially therethrough which provide for flow of air through said piston stern passage, and a rod adjustably carried by the said one of said caps and connected to said abutment member for adjusting the latter to various positions axially of said piston stem and thereby varying the extent of projecting movement of said piston stem.

21. A suction sheet handling device comprising, a cylinder, a cap closing one end of said cylinder, another cap closing the other end of said cylinder, a piston head reciprocal in said cylinder and normally disposed adjacent one of said caps, a piston stem on said piston head and extending therefrom through and beyond the other of said caps, a sheet gripping suction cup secured to the outwardly projecting end of said piston stem, said piston stem having an axially extending annular passage therein communicating with said suction cup and terminating at a point spaced axially from said piston head, said piston stem having therein a plurality of axially extending passages spaced around and communicating with said annular passage and opening outwardly through said piston head, said cylinder having a passage therein for establishing communication between a source of vacuum and the interior portion of said cylinder between the said other of said caps and said piston head, said piston stern having a radially extending port therein for estab- 17 lishing communication between said cylinder portion and said piston stem passage and said plurality of passages, an annular abutment member disposed in said piston stem passage for limiting projecting movement of said piston stem from said cylinder through engagement of said piston stem therewith, said abutment member having a plurality of passages extending axially therethrough to at all times enable evacuation of said piston stem passage, and a rod adjustably carried by the said one of said caps and connected to said abutment member for adjusting the latter to various positions axially of said piston stem and thereby varying the extent of projecting movement of said piston stem.

22. In a sheet feeder, means for separating sheets successively from the top of a supply thereof and comprising, a pair of transversely spaced vacuum sheet sepa rators arranged above the supply of sheets and reciprocated pneumatically toward and away from said supply to grip the topmost sheet and lift said sheet from said supply, means supporting said vacuum sheet separators for pivotal movement about fixed axes extending in the direction of feed of the sheets, cam means for swinging said vacuum sheet separators by a positive action outwardly away from each other about said axes while gripping the sheet to stretch said sheet, resilient means for swinging said vacuum sheet separators inwardly toward each other about said axes after the sheet is stretched and released thereby to return said sheet separators to their original sheet gripping and lifting positions, and adjustable means for varying the extent of outward movement of said vacuum sheet separators by said cam means independently of each other and thereby varying the sheet stretching action of said sheet separators.

23. A sheet feeder as defined in claim 22 wherein said adjustable means is movable to one position for preventing outward movement of the vacuum sheet separators by the cam means independently of each other and to other positions to vary the extent of outward movement of said sheet separators by said cam means independently of each other, whereby the stretching of the sheet may be selectively discontinued or effected solely by either one of said sheet separators or by both of said sheet separators through equal or unequal outward movements thereof.

24. In a sheet feeder, means for separating sheets successively from the top of a supply thereof and comprising, a pair of vacuum sheet separators arranged above the supply and reciprocated pneumatically toward and away from said supply to grip the topmost sheet at transversely spaced points and lift said sheet from said supply, means supporting said vacuum sheet separators for pivotal movement about fixed axes extending in the direction of feed of the sheets, a pair of driven rotary cams having high and low parts, connections between said cams and said vacuum sheet separators and including rollers engaged the high parts of said cams for swinging said vacuum sheet separators outwardly away from each other about said axes while gripping the sheet to stretch said sheet, resilient means under the control of said cams for swinging said vacuum sheet separators inwardly toward each other about said axes after the sheet is stretched and released thereby to return said sheet separators to their normal inward sheet gripping and lifting positions determined through engagement of said rollers with the low parts of said cams, and adjustable means associated with said connections for varying the effective action of the high parts of said cams and thereby varying the extent of outward movement of said vacuum sheet separators by said cams.

25. A sheet feeder as defined in claim 24 wherein said connections comprise a pair of pivotally mounted bell cranks having said rollers journalled on corresponding arms thereof, a pair of other pivotally mounted bell cranks having corresponding arms thereof acting on said vacuum sheet separators, and links connecting the other arms of said first-named bell cranks with the other arms of said other bell cranks, said resilient means comprise a pair of coil extension springs having corresponding ends thereof connected to said corresponding arms of said other bell cranks and other ends connected to said vacuum sheet separators, and said adjustable means is associated with one of said pairs of bell cranks.

References Cited in the file of this patent UNITED STATES PATENTS 1,475,621 Christophel Nov. 27, 1923 2,080,010 Rowlands May 11, 1937 2,389,480 Baker Nov. 20, 1945 2,402,442 Perry June 18, 1946 2,434,530 Williams Jan. 13, 1948

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