US 3565422 A
Description (OCR text may contain errors)
11.36, 26, 26 (SUE), 27, 28, 29, 30, 31, 62 (B);
O United States Patent 13,565,422
 Inventors William B. McCain, [5 6] References Cited Hinsdale; UNITED STATES PATENTS [211 App] No $27 33 2,693,957 11/1954 Welsh 27l/62(B) 3,087,721 4 1963 M 22 Filed Apr. 11,1969 270/54  patented 23 97 Pnmary Examiner-Andres Nielsen  Assignee McCain Manufacturing Corporation Attorney -K1nzer1 D & Zlckert Chieago,lll.
 SIGNATURE MACHINES ABSTRACT- A machine includin g means for transferrmg 10 Claims 10 Drawing signatures or like flexible sheets of paper from a hopper to an  U.S. Cl 271/36, extractor is so constructed that a portion of each such sheet to 27 l/ 11 be extracted from the hopper is delivered to and located tem-  Int. Cl B65h 3/06 porarily in a holding position between the magazine and the  Field of Search 271/5, extractor; subsequently the extractor picks up the sheet at temporary holding position and extracts the sheet entirely from the hopper.
; PATENIEDFEB23 197i SHEET 1 OF 4 Inventor .m 3 w cl.. 8 nmum 55M". mnmn m .mh mh w W K u.
PATENTED H823 |sn SHEET 3 OF 4 luv 2 ate r's William B.MCain John Balla.
' SHEET u UF 4 l I I W Inventors William. B. M Coin.
John Ballo. 5g .Dm & 2W
H'Hornea s 1 SIGNATUREMACHINES This invention relates to a signature machine in which flexible sheets, such as signatures, are delivered from a hopper to an extracting means in the form of a cylinder or drum.
In a known form of signature gathering machine, feed means in the-form of one or more sucker fingers applies suction to the so-called backbone (fold) of a folded sheet constituting a signature fora book, and partly withdraws the signature from the hopper in which it is initially located, at the same time presenting the backbone of the signature in position to be picked up by a gripper on a rotatable cylinder incidental to using the cylinder to feed the signature to some other station in the machine, for example, to a register station from whence the signature may be further transported to a conveyor. One form of such machine is illustrated in FIG. of McCain U.S. Pat. No. 3,087,721, although the orientation of the structure in that instance is somewhat different from that disclosed in the present instance.
in a single cycle of rotation. The main 'object of the'presen't invention is to utilize this capacity which is otherwise wasted, and at the same time to realize a higher production rate for the machine.
More specifically, it is an object of the present invention to interpose between the hopper and the cylinder a signature positioning means which receives each signature from a c'yclically operable primary delivery means and holds each signature in a temporary holding position at which it is picked up by a gripper on the cylinder.
Thus, under the present invention, and as a stated object, there is a primary delivery means to withdraw a portion of each leading signature from the hopper, and the signature as thus withdrawn is delivered through a very short path to the signature positioning means where it isg'merely held in position to he grabbed by a gripper on the cylinder.
The primary feeder or delivery means of the present machine only withdraws a portion of each signature from the hopper; it does not present a signature to the cylinder gripper, which is the role of the signature positioning means. The operating path of the delivery means is thus shortened, in effect, and it returns to the hopper while the backbone of the signature last withdrawn from the hopper is being retained in temporary holding position adjacent the path of the gripper on the extracting cylinder. Then, while the delivery means is on the threshold of withdrawing a portion of the next signature from the hopper, the previous signature, in holding position, is grabbed by a gripper for transfer to the extracting cylinder which completely extracts the signature from the hopper, and while this transfer is taking place the delivery means delivers the backbone of the next signature'to the positioning means, constituting another object of the invention.
Timing is therefore importannand another object of the present invention is to time all operations on the basis of cylinder rotation. More specifically in this regard, another ob I ject of the present invention is to associate timing means with rotation of the cylinder, such timing means being effective to synchronize and correlate operation of both the signature delivery means and the signature positioning means to operation of the grippers carried by he cylinder, and a related object is to enable the delivery means and the positioning means to be effective on the signatures through suction, established and disestablished by valve means rotatable with the cylinder.
Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illus tration, show a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles.
Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention.
In the drawings: 7
FIG. 1 is a perspective view of the portion of a machine incorporating the present invention; 7
FIG. 2 is a side elevation of the machine showing certain control elements;
.FIG. 3 is a'perspective view of the rear of the machine as seen in FIG. 1;
FIG. 4 is another perspective at the rear of the machine;
FIGS. 5 and 6 are detail views showing actuating a structure for the grippers on the cylinder;
FIG. 7 is a detail view of valve means; and
FIGS. 7A, 7B and 7C are views taken on lines 7A-7A, 7B-7Band 7C-7C of FIG. 7.
The. machine of V the present invention includes a supply hopper or magazine presenting a forwardly inclined front plate 10 and side plates 12, FIG. 2 (plates removed from FIG. 1) enabling a plurality of.-signatures S in the form of folded sheets to be stacked one against another andinclined against the front plate with the folded sides or socalled backbones in alowermost position engaged with endless bands 13, FIG. 1, which travel in a forward direction as shown by arrows in FIG. 1 to press the signatures against the front plate. The supply hopper as thus defined is located between a pair of side plates 14A and 148, FIG. I, constituting a part of the main supporting frame of the machine. There is a great deal of separation between the lower end of the front plate 12 and the bottom of the hopper as will be apparent in FIG. 2, and through the opening thus afforded the signatures are withdrawn one by one for transfer to a so-called extracting cylinder defined by a pair of rotary discs 15, FIG. 3. l
The general orientation or disposition of the supply hopper with respect to the extracting cylinder may vary in actual practice, depending upon the specifications ofthe manufacturer or the specifications of the customer, particularly in terms of subsequent handling of the signature after it has been transferred to the extracting cylinder, and in this connection reference may be made to US. Pat. No. 3,087,721 for a distinctive environment involving a supply hopper and related extracting cylinder of a signature gathering machine.
The present invention is concerned primarily with increasing the rate or production, using the full capacity of standard sized discs 15 so that at least three grippers 21 thereon, FIG. 6, may be utilized, which has not heretofore been possible to the best of our knowledge. In fact, an extracting cylinderpresenting only two grippers of the specific form embraced by the present disclosure, operating adjacent the supply hopper for signatures, has been prevalent in the art for many years.
. While a manifestation of the invention is represented by three grippers on the extracting cylinder, the invention is not merely that because the problem was to find a way by which it would be possible to present signatures at a rapid rate to the cylinder grippers; Thus, the addition of the third gripper increases the cylinder capacity by 50 percent. If the rotary speed of the cylinder is to be maintained constant compared to the two-gripper situation formerly prevailing, this means that signatures must be moved out of the hopper at a 50 percent increase in rate.
Before describing in detail the distinctive structure and functional characteristics of the present invention, it is appropriate to consider the known construction and operation of the gripper fingers zl carried by the discs 15. Each such finger and its associated parts are identical, and attention is now directed to FIG. 4 wherein it will be observed that each finge'r' or gripper 21 is normally in an open position with respect to a fiat anvil or plate 24 This is the condition prevailing at the time a gripper finger is approaching the backbone of the signature adjacent the supply hopper, but the concurrent event is that the gripper finger is then to be oscillated to a closed position to clamp the backbone of the signature to the opposed anvil surface 24. It will be appreciated that this is an accurately timed operation as will be apparent from the description to follow.
As noted above, there are three gripper fingers associated with each disc 15, constituting the extracting cylinder. There is a gripper finger on one disc directly opposite and paired with an identical gripper finger on the other disc as shown in FIG. 4. Each gripper finger, FIG. 4 is supported by a bracket 25 which in turn is clamped to a rock shaft 26 carried by and extending between the discs 15. The supporting shaft 26 extends parallel to the main shaft 30 to which the discs 15 are keyed or otherwise affixed for rotation therewith. Thus, .rotation of the shaft 30 is effective to rotate the discs 15, and the shaft 26 which carries the gripper finger assemblies is carried along in a planetary sense.
Two additional rock shafts each supporting a pair of gripper fingers 21 are likewise carried by the discs 15, and these rock shafts are identified as 26A and 26B in FIG. 4.
A third disc 31 is carried by shaft 30, FIG. 3, and this disc carries means including gears for oscillating the shafts as 26 which support the grippers, as will be described.
As best shown in FIG. 3, in which the parts are rotated in a slightly different position compared to FIG. 4 to reveal further details of construction, the rock shaft 26 is provided at its right-hand end, outboard of disc 31, with a pinion gear 32, meshed with a segment gear 33, and this same feature prevails with respect to the rock shafts 26A and 2613. Each such segment gear 33 is pivotally supported on a stub shaft 34, FIG. 6, supported on the right-hand side of disc 31 as viewed in FIG. 3 (see FIG. and is biased by a spring 35 anchored at one end to a pin 36 on the segment gear and at the opposite end to a projecting ear 38 on a hub element 39 keyed to the disc 31 for rotation therewith. This arrangement prevails for each segment gear.
Each segment gear as 33 has a cam follower 40 thereon located between the pivotal mounting of the segment gear and the end thereof having the gear teeth 33T. The cam followers, of which there are three, one for each of the segment gears, are adapted to travel in a revolving sense, about and in contact with a stationary cam 41, FIG. 6, mounted on the inside face of the side plate 14A, and the general contour of this cam presents a long lobe 41L and a shorter dwell 41D, FIG. 6.
Each spring 35 is effective, wen the follower 40 rides on the cam dwell 41D to pivot the segment gear inward toward the axis of disc 16 imparting rotation to the pinion 32, FIG. 6, causing the gripper finger 21 to pivot in a closing direction toward the related anvil 24. This action takes place at a time when a signature as S1, FIG. 2, is in temporary holding position, whereupon the two activated fingers 21 (one on each disc grab the backbone of the thus positioned signature and transfer the signature from holding position to the cylinder. Continued rotation of the cylinder carries the signature along until the cam follower of each of the activated gripper fingers encounters the lobe 41L of the cam 41, FIG. 6, whereupon each corresponding segment gear is oscillated in a direction opposite to that induced initially by the spring 35, manifest in an opening movement of the gripper finger which releases the signature. The release point will vary depending upon the part or station in the machine to which the signature is to be released.
Referring now to FIG. 1, signature delivery means in the form of a bar 50 extends across the front of the supply hopper in position to bear against the forward margin of the backbone of the forwardmost signature in the supply hopper. The delivery bar is hollow and presents on its operative face a plurality of elongated openings 51. The hollow bar 50 is provided with nipples 52, FIGS. 1 and 2, which lead to the slots 51 and to which suction (negative air pressure) is communicated through means including conduits 53, FIG. 2.
Means as hereinafter described are afforded to cyclically oscillate the bar 50 along a substantially reciprocal path so that the leading signature held along its backbone by suction prevailing at the openings 51 will be withdrawn from the supply hopper forwardly or to the right as viewed in FIG. 2 incidental to delivering this signature to a temporary positioning means which maintains the signature in a temporary holding position where it will be grabbed by an activated set of gripper fingers 21 as above described.
The precise manner in which the' signature deliver bar or am 50 is cyclically operated will be described in detail below, but it may first be observed that the delivery means is effective to partially withdraw from the hopper a signature S1, FIG. 2, and to present it to the signature positioning means which preferably take the form of a plurality of suction cups 55 located immediately in front of the bar 50 and interposed between the delivery bar 50 and thediscs 15 representing the extracting cylinder. Thus it will be seen that the operating path of the delivery bar 50 between the bottom of the hopper and the signature positioning cups 55 is quite short. Advantageously, the cups 55 are themselves cyclically operated in unison over a very short reciprocal path as will now be described.
Each suction cup 55 is secured to an adapter 56, FIG. 1, presenting an interior passage which communicates negative pressure to the related cup, and this passage in turn communicates with a conduit 57 which also in effect suspends the cup in proper position at the station, FIG. 2, where a signature delivered by the bar 50 is to be held in position to be picked up by the cylinder gripper means. Each conduit 57 in turn communicates with a bore 58, FIG. 2, presented by a bracket 59, and each bracket 59 is secured to a hollow shaft 60 in an airtight fit about an opening therein by which suction supplied to the shaft 60 is communicated to the suction cup.
The shaft 60 thus serves to both support the signature positioning means and to enable suction to be communicated thereto.
Shaft 60, FIGS. 1 and 4, extends between and is supported in the side plates 14A and 148 for slight rocking motion, and such motion is imparted to shaft 60 by an arm 61, FIG. 2, secured to the right-hand end thereof as it would be viewed in FIG. 1. Arm 61 is operated by means including a cam 63, FIGS. 2 and 3, synchronized to the extracting cylinder by virtue of being mounted in the shaft 30.
Cam 63 is provided with three short lobes 64, and in the course of a single cycle of shaft 30 each lobe 64 strikes a cam follower 66, FIG. 3, carried by an operating arm 68. Ann 68 is pivotally supported for rocking motion on a stub shaft 70 projecting from the side plate 14B, FIG. 3, and its follower 66 is normally urged into contact with cam-63 by a spring 71, FIG. 3. Thus, spring 71 at one end is anchored to a pin 72 on the upper end of the operating arm 68 and at the opposite end is anchored to a pin 73 projecting from the side plate 143.
A motion transmitting link 75 is pivotally connected at one end, FIG. 3, to the arm 68, the point of connection lying between the pin 72 and the pivotal axis of arm 68 presented by shaft 70. The opposite end of link 75, FIG. 2, is pivotally connected to the lower end of the arm 61 which is fast on shaft 60. It will be apparent from FIG. 2 that each time a cam lobe 64 strikes the follower 66, arm 68 is rocked counterclockwise manifest in a slight amount of clockwise motion imparted to the rock shaft 60. This shifts the assembly of cups 55 slightly to the left, FIG. 2, toward the delivery bar 50. Suction prevails in shaft 60 at this time, and concurrently the delivery bar, as
will be described, is reciprocated to the right toward the cups 55 to deliver thereto the backbone'of a signature, partially withdrawn from the hopper. Suction in bar 50 is then interrupted, and the suction cups 55 take the signature. As the effective lobe 64 falls off the follower 66, spring 71 takes over and the signature positioning means 55 shifts slightly back to home" position to hold the backbone of the signature, S1, in the temporary holding position, FIG. 2, thereb y presenting the partially withdrawn signature to the approaching cylinder gripper.
This slight to-and-fro motion of the signature positioning means occurs three times in each cycle of revolution of shaft 30, accordingly as three signatures are to be extracted from the hopper in each cycle of revolution.
The delivery bar 50 is alsoreciprocated three times ineach cycle of operation, and again a cam onshaft 30 is used to.
second cam 80, FIG. 2, is secured to shaft30. Cam 80. has
three lobes 81 and an equal number of dwells 82 related to a cam follower 85 carried at the lower end of a linkoperating arm 86. Arm 86 is pivotally mounted on shaft 70, and its follower 85 is held against cam 80 by a spring 88, FIG. 3, anchored at one end to the pin 73 and at its opposite end to a pin 89 at the upper end of arm 86. A motion transmitting link 90. at one end is pivotally connectedto arm186 and at the opposite end, FIG. 2, is pivotally connected to an operating arm 91 serving to reciprocate the delivery bar 50. Arm 91- is pivotally supportedon a stub). shaft. 92 extending inwardfrom the frameside plate 14B. 1
It will be observed that-when a cam dwell 82 is-presented to the follower 85, spring 88 'is effective to. rock arm 86 clockwise, FIG. 2, reciprocating link 90 and arm 91 to the. right. This motion of "link 90 andarm 9 11}, ,through the connections to be described, also shiftsthedeliverybar 50.to the right, advancing the backbone of: the leading. signaturein the hopper to the signature positioning means 55 which at this.- time is shifted tolthe left (cam lobe 64 strikes follower 66)'to' receive the backbone of the signature being delivered from the hopper. Thus, the delivery bar 50 andpositioning cups 55, are correlated'and synchronized by their cams 63 and]80.to the cycle of-the gripper cylinder.
'I'he deliverybar 50 at its left-hand end as' viewed inFlG; 1.- is carried-at the lowerendof an arm95 andlis similarly supported at the opposite end on the lowerend of arm 91', FIG. 2. The arm 95 is secured to a rock shaft 9 7, projecting inward relative to the side frame plate 14A, and shaft 97'is rocked-by anarm 98 in turn clamped to a motionitransmitting bar'99.. The bar 99. extends across the hopper-as shown inFlG'. l and its right-hand end is carried at the upperend' 'of arm 91, FIG. 2, so that reciprocal movement of link 90.;willbe manifest in. corresponding rocking motion of bar99. i
. Establishment and. disestablishment of suction-in thecon: duits connected to the delivery bar 50 and the shaft 60' which carries the signature positioning means is controlled by a valve assembly 100, FIG. 7.. Thisvalvc assembly includes a slotted valve disc 101 connected by pins 102. to a pilot disc 103 in tum-secured to shaft as by setscrews 104;
Thus it will be seen that valve disc" 10]. rotates withthe cylinder means which carry the gripperfingers 21.
A stationarymanifold disc 107 is s'upport'edin a stationary. position on a collar 108 located on'the inside faceof the frame side plate 14B as viewed in FIG. 3. Spring elements (not shown) are mounted on the pins 102 to press disc 101 into airtight engagement with the manifold 107.
As shown in FIG. 7B, the rotary valve disc 101 is provided along an outer radius .with a series of three elongated arcuate slots 110 controlling the establishment of suctionin-theconduits 53 connected to the suction bar 50. The slots 110, FIG;
. 7, are open at the side of the disc- 101 which engages the manifold 107, and this is equally true of a radially inner setofthree valve slots 112 adapted to establish suction in the con- 1 duit which supplies shaft 60.
The disc 101 in the course of the operationof the machine rotates past disc 107, which, as shown in FIG. 7A, is provided with an opening 115 in a radialposition alignedwith the slots in the valve disc 101, and this is ,equally trueof a second openingilfi. In the description to follow, itshould be-visualized that the slotted face of disc ltllas-seen in FIG. 7B will .be
; juxtaposed (mirror image) on the face of the manifold 107', as
shown in-FIG 7A. Opening communicates with a nipple 117 which receives vacuum from the source, and opening. 116 communicates with anipple 118 which delivers vacuum to the conduits as 53 which communicate. with the slots 51 inthe signature delivery bar 50.. The leading end'of aslot 110 is identified by the refererice character LE in FIG. 7B. Thus, as
i the valve disc 101-presents the leading end portion ofaslot' 110 to couple or span the openings 1.15 and116, vacu,um is established in the delivery bar, and the timing and-proportioning is such that vacuum is thus established in the cycle phase when the delivery bar 50iis to transfer the backbone of a signature from the hopper to the signature positioning means 55. On the other hand, when disc 101 has rotated to such an extentthat the trailing endTE of a slot 110 passes opening 115,
transmission of vacuum to the delivery bar is interrupted, and this circumstance prevails'until the next slot 110 iseffective to recouple openings 115 and 116. The intervening periodv of lapsed vacuum inbar 50 corresponds to the, positioning cups 55 holding a signature receivedfrom the delivery bar.
The radial inner slots 112 which control vacuum to the suction cups 55 are effective in asimilar fashion. Thus, the manifolddiscl07 includes another set of openings 120 and 121 which-are radially. inwardzcompared to the location of the openings 115 and 116. Opening 120 communicates with a. passage in disc 107 in communication with a nipple 122 which receives vacuumfrqm the source and opening 121 communicates with an internallpassage in disc 1.0.7'in turn connected toa nipple 123 adapted .to :be connected to the conduit which.
The .valving slots 1'12: in=the-valve disc 101'are on the radius. of the opening of 120and 121 just as the valving slots 1-12are' onthe radius of the openings 115 and 116. When the leading endportion LE'of av valve slot 112 couples openings 120 and 121, vacuum isestablished for the. suction cups 55 whereby the. suction cups 55- hold the signature in the temporary holding position as describedlabove. On the. other hand, when the trailing end TE of a-slotl 12 .moves pastopening 12.0, delivery:
of vacuum to the suction cups 55 is interrupted, andthis is. timed to o ccur'when the grippers 21 are effective to-grab a signature at the temporary-holding station, completely extracting the signaturefrom .thehopper.
Insofar as concerns the valving of suction,.it will be ap preciated thattlie. basic :requirements are. simply that vacuum be-disestablished'inthe delivery bar 50.wiien.it presents the backbone of. the'signature'to the suction cups 55 where suc.-. tion is established as a concurrent event; that suction. be reestablished in th e delivery bar 50 at the end of its return stroke to the hopper and maintained until the'terminationof itsdelivery stroke, and that suction be disestablishedin the suction cups 55 when the grippers 21 become active atthe temporary holdingstation to transfer-a signature to'the ex-- tracting cylinder. Atmospheric pressure, characteristicofdisestablishment of vacuum,is communicated to the slots 51 of the signature deliverybar and to the interior ofshaft 60 by two exhaust portsand 131, FIG. 7A, respectively on theradius. of the slots. lloandzthe radius of the slots 112'. The propor tioning is such that aslot'1101is in communication-with the exhaust port. 130 for-a brief-period prior to. the nexttrailingslot 110 being effective to couple the openings 115 and 116. A similar state prevails with respect to the. exhaust port 131 effective to communicate atmospheric pressure. tothe interior of shaft 60-when the cylinder grippersll. become active to take a signature from thepositioning means 55. The conduits. which communicate atmospheric pressure from the exhaust ports to the delivery bar and shaft 60 are not shown.
It will-be-seen-from the foregoing that:and in accordance with-the present inventionthree signatures can beextracted. by thegrippers 21 carried by the discs 15in a single-cycle orrevolution where heretofore the discs 15.0nly extracted twosignatures. This is made possible by holding a signature ata temporary holding position by the suction cups 55- during the, interval that.the.delivery.-bar isreturning to. the hopper incidental-to delivering the next signature: Thus, the delivery:
bar need not-be delayed to await the arrival of a gripper, or
viewed. another way, the interposition ofthe positioning.
means 55 enables the delivery bar, in terms of time, .to-return.
same shaft becomes a convenient means for timing the response of vacuum to the phasing of the grippers 21, the delivery bar 50 and the positioning cups 55. Of course, it will be appreciated that suction as a positive force does not exist, only negative air pressure, but nonetheless the common term is itself used in scientific parlance.
Hence, while we have illustrated and described a preferred embodiment of our invention, it is to be understood that this is capable of variation and modification within the purview of the following claims.
1. In a cyclically operable signature machine where signatures or like flexible sheets are to be transferred from a supply hopper to a rotary cylinder, cyclically operable signature delivery means interposed between said hopper and said cylinder and effective in successive cycles of the machine to withdraw a portion of each leading signature in the hopper and deliver it to a positioning means, signature positioning means interposed between said cylinder and said delivery means for receiving the delivered portion of the signature from the delivery means while holding that signature in temporary holding position immediately adjacent said cylinder, and a plurality of signature grippers arranged successively about the cylinder and each effective to grab and transfer to the cylinder a signature at its temporary holding position.
2. A machine according to claim 1 in which there are timing means synchronized with the cylinder to time and correlate operation of the delivery means to the operation of the grippers.
3. A machine according to claim 1 in which the delivery means moves along a path between the signature positioning means and the leading signature in the hopper and applies suction to each leading signature in the hopper to withdraw said portion of the signature from the hopper, and in which the signature positioning means holds each signature in holding position by suction.
4. A machine according to claim 3 in which suction is established and disestablished by rotary valve means rotatable with the cylinder.
5. A machine according to claim 4 in which there are timing means synchronized with the cylinder to time and correlate operation of the delivery means to the operation of the grippers.
6. A machine according to claim 3 in which the grippers are carried on shafts supported by the cylinder for rotation therewith, and means to oscillate the shafts in timed sequence to render the grippers effective to both grab a signature and release the signature.
7. In a cyclically operable signature machine where signatures or like flexible sheets are to be transferred one by one from a supply hopper to means supporting grippers which accept the transferred signatures, which means travel along a predetermined path and at a predetermined speed adjacent the hopper, cyclically operable delivery means at the front of the hopper and effective in successive cycles of the machine to withdraw a portion of each such sheet in the hopper and deliver it to a positioning means, and positioning means interposed between the delivery means and the means supporting the grippers for receiving the delivered portion of the sheet and holding it in a temporary holding position at which position it is picked up by one of said grippers.
8. A machine according to claim 7 in which the delivery means is oscillatable in opposed directions along a path between the hopper and the positioning means, and in which timing means synchronized to the movement of the gripper supporting means controls oscillation of the delivery means.
9. A machine according to claim 8 in which the delivery means is adapted to apply suction to the sheet in the hopper incidental to delivering the sheet to the positioning means, and valve means synchronized to the movement of the gripper supporting means to disestablish suction when a sheet is delivered to the positioning means and to reestablish suction when the deliveR means returns to the hopper for the next sheet,
10. machine according to c arm 9 in which the positioning means is adapted to hold the sheet at temporary holding position by suction and in which said valve means is effective to disestablish suction supplied to the positioning means when a gripper is in position to pick up a sheet at temporary holding position.