US2579094A

US2579094A - Stacking apparatus

Info

Publication number: US2579094A
Application number: US673792A
Authority: US
Inventors: Rooksby William Holdsworth
Original assignee: Turners Asbestos Cement Co Ltd
Current assignee: Turners Asbestos Cement Co Ltd
Priority date: 1945-06-08
Filing date: 1946-06-01
Publication date: 1951-12-18
Anticipated expiration: 1968-12-18

Description

Dec. 18, 1951 w, ROQKSBY 2,579,094

' STACK-ING APPARATUS Filed. June 1, 1946 5 Sheets-Sheet l Inventor By i 2 20 U A Altor'ney.

Dec. 18, 1951 w, H, ROOKSBY 2,579,094

STACKING APPARATUS 5 Sheets-Sheet 2 Filed June l, 1946 Q 1 n l A gt 0 .I

[F L. 51 0 r\ 0 0 8 {if Inventor llorney.

Dec. 18, 1951 w. H. ROOKSBY 2,579,094

STACKING APPARATUS Filed June 1, .1946 5 Sheets-Sheet 5 D D 48 I Inventor Sim, 62W,

A ttorney.

W. H. ROOKSBY STACKING APPARATUS Dec. 18, 1951,

5 Sheets-Sheet 4 Filed June 1, 1946 Inventor Dec. 18; 1951 w, oo s 2,579,094

STACKING APPARATUS Filed June 1, 1946 5 Sheets-Sheet 5 Attorney- Patented Dec. 18, 1951 UNITED STATS PATENT OFFICE v STACKING APPARATUS William Holdsworth Rooksby, Trafiord Park, Manchester, England, assignor to Turners Asbestos Cement Company Limited, Spotland, Rochdale, England, a British company Application June 1, 1946, Serial No. 67 3,7 92 In Great Britain June 8, 1945 15 Claims. (Cl. 271-84) This invention relates to apparatus for stack- When the apparatus is being used for forming ing sheets, particularly plastic sheets of asbestosa stack of wet asbestos-cement sheets intercement. leavecl with templates, the sheets are delivered Asbestos-cement sheets are plastic when they one by one to a fixed point on one side of the are first made and are usually allowed to set berocking axis and the apparatus is then operated tween metal templates. The sheets and temto rock the framefirst to lower the suction deplates are built into a stack, either mechanivice onto the sheet and then in the reverse dically or manually, and allowed to rest until the rection to carry it to the other side of the rocking sheets have hardened enough to be removed from axis, where the stack is built up. In building the the interleaving templates. Care must be taken stack the templates can be put in position manunot to damage the plastic sheets while they are ally, but I prefer to provide a second suction debeing built into a stack and one way of hanvice and rocking frameworkin between a stack dling them involves the use of a suction box of templates and the'stacking position of the first which has openings in its undersurface and is lowdevice. By this means a stack can be built up erecl onto each sheet in turn. When the suction l5 rapidly with a minimum of labour and without box is in contact with a sheet the operator moves any risk of damage to the plastic sheets.

a valve to put the interior of the box under par- In order that the invention may be clearly untial vacuum and then moves the box to a stackderstood and readily carried into effect, the preing position. On the arrival of the box and sheet ferred form of apparatus will now be described in this position the operator restores the pressure :30 by way of example with reference to the accominside the box so that the sheet ceases to stick panying drawings, in which:

to the underside of the box, which is then moved Figure 1 is a diagram of part of a plant emaway again by the operator, leaving the sheet bebodying two of the apparatus; hind. To build up a stack, interleaving tem- Figure 2 isa plan and Figure 3 a side elevation plates must be introduced, and these may be put (D 57 S Of e pp imposition manually or by a similar suction ap- Figure 4 is an end elevation of the apparatus paratus. The whole procedure involves a number seen from the left of Figure 2;

of manual operations and accordingly takes a Figure 5 is an end elevation looking from the relatively long time. right of Figure 2;

An object of this invention is to provide an im- Figure 6 is a section through the suction deproved apparatus comprisin a suction box or vice on the line VI-VI in Figure 2; other suction device for building up a stack of Figure '7 is a fragmentary section through the sheets automatically. suction device on a much enlarged scale;

Another object is to control a stacking mech- Figure Sis an operational diagram; anism so that the stack is madetruly vertical. Figure 9 is an electrical circuit diagram; and

'A further object is to provide an apparatus Figure 10 is a Section Similar o u e 7 which, once started, will perform a complete through another form of suction device. cycle of operations automatically and return to The pla t s wn in F g e 1 C p s s WO a rest position. lifting and stacking apparatus Aand B arranged In this invention the suction device is carried 40 t ld up a s a of fia as st sm nt sheets by and mounted to swing in a frame which itself i t l av d t fiat templates. on a trolley C- is mounted to rock about a horizontal axis and The ts e a d to the appa atus A on which .serves to move the suction device from by 0118 y an erm ntly oving endless 0011-, one side of the axis to the other. Now as the ev D which halts e it has brought a s eet stack builds up the release position will become E into e position Shown in Figure e Sh t successively higher and the suction device, if unis then a ed by he apparatus A and transsuccessively smaller horizontal distance from the Similarly transferred one y one from a trolley axis of rotation ofthe frame at the moment of F to t trolleyc y the apparatus release. Accordingly means are provided for e app A and B e e t l in P constraining the suction device to travel in a verciple and are both connected to a suction pump tical path once it has arrived at a given point G. The sheet lifter A is shown in detail in Figin. the course of its descending movement, ures 2 to 7. It includes a suction box 2 which Then, of course, the stack is built up beneath that hangs from a frame 3 which can be rocked po nt, V through rather more than by a shaft 4 car constrained laterally, would accordingly be at a ferred by it to the trolley C. The templates are 'moving each sheet.

ried in bearings on pedestals 6. At each operation the box is lowered onto a sheet on the conveyor D and engages it by suction, and the frame is then rocked to bring the box and sheet above the trolley C, lower the sheet onto the trolley and release it by breaking the vacuum in the box. Finally the box is moved back to its starting position.

The box 2 is rectangular and shallow, its bottom 8 being secured to its lid 9 by bolts I0 and being formed with a large number of small openings II. The underside ofthe bottom 8 is flat and covered by wire gauze 6|] clamped between the sides of the box and plates BI and this gauze is in turn covered by Hessian 62 held by barbs 63 which extend out from the plates 6|. The Hessian and gauze serve to prevent the plastic asbestos-cement from being drawn into the holes H by the suction. A relatively large opening l2 is made in the middle of the lid 9 and receives the end of a flexible pipe l3 through which suction can be applied to the interior of the box.

The frame 3 is composed of two radial arms l4, each keyed to the shaft 4 and furnished with a counterweight l5, and a hollow rod l6 passing through eyes in the ends of the arms l4. The rod l6 can turn-in these eyes and two short radial arms H are keyed to it, each arm forming a pivot mounting for one of two cross-heads l8 which form part of the suspension support for the suction box 2. Each cross-head 3 comprises two plates l9 united by pins 2|] as well as by a pivot pin 2| which passes through the associated arm l1. At each end of the cross-head the plates IQ'embrace a guide block 22; Posts 23 pivoted to the lid 9 of the suction box 2 project upwards through bores in the blocks 22 and are surrounded by springs 24 held by bolts 25 above the blocks. This construction results both in the suction box being freely suspended from the frame 3 and being free to slide vertically on the posts 23 relatively to the cross-heads I8. Accordingly when the frame 3 is rocked, the axis of the rod |6-will travel through an arc of a circle and the suction box 2 will move with the rod IE but will hang vertically throughout.

The whole apparatus is designed to operate automatically and it is most convenient to make the frame 3 rock through the same angle in This is permitted by the lost-motion connection constituted by the crossheads l8 and posts 23, since as the stack builds up on the trolley C and a sheet comes into contact with the top of it the cross-heads 3 will move downwards over the posts 23 while the frame 3 completes its stroke.

If desired the suction boxes 2 may be hung by chains from the ends of the short arms H.

In the rest position of the frame 3 the arms M are nearly vertical.

It will be realised that the stack built up on the trolley must be truly vertical and means are therefore provided for constraining the suction box pivot 2| to move in a vertical plane soon after it has begun its descent on either side of the apparatus. These means are two link-and-cam mechanisms, one close to each end of the shaft 4. In each mechanism there is a link keyed at one end to the rod I6 and pivotally connected at the other end to a second link 3|. This link 3| is slotted at 32 and theshaft 4 passes through the slot, so that the link 3| can both turn around and slide over the shaft 4. At its slotted end the link 3| is provided with one of a pair of camand-follower members, the other of which is fixed. The movable member is a roller 33 carried by a pin 34 fixed in the end of the link 3| and the fixed member is a cam plate 35 secured to the adjacent pedestal 6 and having cam surfaces 33 at each end. In effect the two links 35 and 3| and the corresponding main frame arm [4 at each side of the apparatus together form a triangle and as the shaft 4 turns this triangle turns about the axis of the shaft, the slotted link 3| sliding over the shaft 4 as a result of the engagement of the roller 33 with the cam surfaces 36 on the plate 35 when the arm l4 has turned through about 45 from its vertical position. When the arm is moving through at an angle of about 45 on each side of the vertical, the roller 33 travels below and clear of the cam plate 35. When the arm I4 is about 45 from the vertical the roller strikes the cam surface in question (if the arm is moving downwards) or leaves it (if the arm is moving upwards), but so long as the roller is in engagement with a cam surface 33 the free end of the slotted link 3| is constrained in its movement and the end of the link 3|! moves with it. The link 33 therefore rocks the rod l6, and this causes the shaft arms H to rock corrspondingly and to maintain the pivots 2| for the cross-heads |8 in a single vertical plane. This operation is diagrammatically illustrated in Figure 8.

The shaft 4 is driven by a reversible electric motor 40 through gear wheels 42. The drive is started electrically through a starting switch 43 (see Figure 9). Once the motor '40 has started to run it causes the apparatus to perform a cycle of operations, the drive being controlled by

switches

44, 45 and 46. The

switches

44 and 45 serve to reverse the motor 40 when the frame 3 reaches the ends of its travel, and they are actuated by a traveller 41 which is threaded over a rotary threaded rod 48 within a complementary tube 49 which prevents it from turning on or with the rod 48. The rod is mounted in bearings 5| in a housing 5|] in which the

switches

44 and 45 are also mounted and is driven through chains '52 and 53 and a layshaft 54 from the shaft of the motor 40. As a result the traveller 41 moves along the rod first in one direction and then the other, serving to reverse the motor 40 (and so its own direction of travel) each time it engages one of the

switches

44 and 45.

' The switch 46 is actuated as the arms |4 pass through their vertical position by a roller 64 on an arm 65 which is keyed to the shaft 4, and it serves to stop the apparatus with the arms hi just beyond their vertical position during the return movement from the deposition of a sheet on the stack.

Turning now to Figure 9, the motor is provided with forward and reverse contactor starters I0 and 7| respectively, the switch 43 being connected to the starting contacts 72 in the forward starter l3. When the motor is started it runs inthe forward direction regardless of whether the switch 43 remains closed or not, since each starter includes a maintaining circuit of the usual kind (not shown in Figure 9). The motor runs until the switch 44 is actuated by the traveller 41, at which time the mechanism has lowered the suction box 2 onto the sheet on the conveyor D. The switch embodies normally closed contacts 73 which are connected to the stopping contacts 14 of the starter l0 and which are opened to break the maintaining circuit and so stop the motor. The switch 44 also embodies normally open contacts 15 connected to the startingcontacts 16 of the'starter ll, so that the motor is started in the reverse direction. The motor runs in thereverse direction, the suction box 2 carrying the sheet E with it, until the switch 45 is engaged by the traveller 41. In the course of this movement of the mechanism the switch 46 is actuated. This is a normally closed switch with its contacts in series with the contacts 13, and since it is immaterial whether the circuit through the contacts I4 is broken or not when the motor is running in the reverse direction this actuation of the switch 46 does not affect the operation. The actuation of the switch 45, however, serves, in the same way as the switch 44, to reverse the motor,contacts 18 com nected to the stopping contacts 11 in the starter H being opened and contacts 19 connectedto the starting contacts 12 being closed. The motor 40 therefore reverses the mechanism, which has now deposited the sheet E on the trolley C. When the switch 48 is actuated during this travel of the mechanism the circuit containing the contacts 14 is opened and the motor and mechanism are stopped. The momentum of the moving parts carries the roller 64 just clear of the switch 46 before the mechanism stops. The switch 46 resets itself by spring action immediately after being actuated. The

switches

44 and 45 are reset by the traveller 41 when it reverses.

The application of suction to the box 2- is controlled by two valves 80 and 8|, the valve 80 being placed in a pipe 82 which leads to the suction pump G and which also leads through a pipe83 to a union 84 on the end of the hollow rod Hi. The suction connection is completed by a union 85 which puts the interior of the rod Is in communication with the flexible pipe l3. The valve 8| is placed in a pipe 38 which branches from the pipe 82 and leads to the atmosphere. The valves 80 and 8| cooperate with valve seats 87 and 88 respectively and are mechanically united by a rod 89 which forms the armature of a solenoid 9t and is urged to the right, as seen in Figure 3, by a spring $1. Normally the valve 80 closes on its seat 8'! and the valve BI is off its seat 88, but when the solenoid is energised the valve '80 is moved off its seat and the valve 8| is moved onto its seat.

The operation of the solenoid 96 is controlled by the

switches

44 and 45. connected to a source of direct current 92 through normally open contacts 93 in the switch 44, the circuit being completed by normally closed contacts 94 in the switch 45 and a holding solenoid 96, so that momentary actuation of the switch 44 energises both solenoids and completes a holding circuit through contacts 91, the contacts 94 and both solenoids. This holding circuit is broken when the contacts 94 are opened as a result of the actuation of the switch 45.

The main switch 43 may be manually operated, but preferably is automatically operated by a connection with the intermittently moving conveyor in the manner described in application Serial No. 673,793 of even date herewith.

The two apparatus A and B are operated in alternating fashion so that when the apparatus A has put a sheet on the trolley C and moved back to its rest position the apparatus B operates to put a template on the sheet. To start the apparatus B automatically additional contacts (not shown) are provided in the switch 45, the closing of these contacts serving to start the'apparatus B in the same way as the switch 43 .starts the apparatus A.

The solenoid 96 is The onl difference between the apparatus A and B is that a different form of suction device is used. Instead of using a suction box with holes in its bottom, a' device I00 (see Figure 10) with an open bottom'and a rubber strip IDI projecting downwards around the whole of its lower edge is'used. To prevent the flat templates which are lifted by this device from being deformed by the suction, circular bosses 102 are provided to act as abutments for the templates. I Although the apparatus shown is particularly suitable for handling asbestos-cement sheets in the plastic state it is useful for moving sheets of any kind, and these may be of corrugated'or other shape provided that the undersideof the suction box is correspondingly shaped. Naturally if a stack of corrugated sheets withv interleaved templates is being formed the templates are corrugated to match the sheets. i q

It will be observed that the constraining means shown serve to make theasuction box travel in a vertical path duringits initial upward movement also. This is important when a corrugated sheet is being lifted from a cor-, rugated surface as any lateral movement of the sheet in relation to the surface before the corrugations were clear of one another would damage the sheet.

I claim:

1. An apparatus for forming a stack of asbestos cement sheets comprising a suction device carried by and mounted to swing ina frame, means pivotally supporting said frame to rock about a fixed horizontal-axis, mechanism connected to the frame to rock same about said axis thereby to move the suction device from one side of the axis to the other, means constraining the suction device to travel in a vertical path once it has reached a predetermined point in its descending movement to put asheet on the stack,-whereby the stack is built up vertically, and a lost motion connection between said frame and suction device Whereby said frame can continue to move downwardly after descent of said suction device has been halted due to said device coming to rest on the top of the stack. 7

2. An apparatus according to claim 1 in which the suction device is suspended from the frame to hang vertically throughout the rocking movements of the frame. I 1

'3. An apparatus according to claim 1 in which the means for constraining the suction device to travel in a vertical path comprises a cam controlled linkagein'cluding a slotted link-mounted both to slide across-and turn around the horizontal axis of the frame.

4. An apparatus according to claim 3 in whic the frame comprises radial arms rocked by an operating shaft, a rod carried by said arms parallel to said shaft, auxiliary arms rigid with said rod carrying said suction box, and in which the linkage comprisesa link fixed at oneend to the rod and pivoted atthe other end to the slotted link, the latter being mounted to slide over and turn around the operating shaft.

5. Apparatus for stacking asbestos cement sheets, comprising a stationary base, a frame pivotally mounted on said base to swing about a fixed horizontal axis, drive mechanism including a prime mover connected to said frame and operative to swing the frame back and forth about said axis in regular cycles, said frame having a free end effective to travel in an arc over said. axis from one side of the axis. to the other as-the frame swings, said drive mechan'ism including means to automatically halt and reverse the movement of said frame when said free end thereof reaches a predetermined point at each side ofsaid axis, a suction device carried by .the free end of said frame, mechanism operative during a predetermined portion of the descent of saidnfree endon one side of the axis to shift said suction devicelaterally relative said free end at a rate to maintain said device in a vertical path during ,suchdescent, said mechanism comprising a cam element and a thrust element coacting therewith, one of said elementsbeing stationary andthe other mounted to move with said frame, and said other element having operative connection with said de: vice for'shifting same laterally;

6. Apparatus for stacking asbestos. cemen sheets, comprising a pivotal frame, means for rockingthe frame about a fixed horizontal axis, said frame having a free end adapted during such rockingtotravel .in an arc over said axis from one side of theaxis to the other, parallel armspivoted to the free end of the frame, a suction device swingably depending from the free ends of said arms, mechanism operative duringa predetermined portion of the descent of said free end on one side of the axis tonturn said arms relative said frame at a rate to maintain'said suction device in a vertical path durin the descent, said mechanism comprising a cam element and a thrust element coacting therewith, one of said elements being stationary, and the other element being-mounted to move with said frame and having operative connec-- tion with one of said arms.

LApparatus for stackingasbestos cement sheets, comprising a support, a frame pivotally mounted on the support to rock about a horizontalaxis, a rod carried by the frame parallel to the axis, motor driven'mechanism connected to-the frame for rocking same thereby to movesaid rod inan-arcfrom one side of the axis-to the other, limit switches controlling the motor. for automatically reversing said mechanism when said rod reaches a predetermined position on either side of said axis, a suction device carried by said rod, mechanism operative during a predetermined portion of the descent of the rod to shift said suction device laterally relative the rod at a rate maintaining said device in a vertical path, an intermittently operated conveyor for carrying the asbestos cement sheets to a predetermined station adjacent said support, and a switch controlled by the conveyor for periodically initiating the operation .of said motor driven mechanism.

8. Apparatus for stacking sheets, comprising a stationary base, a primary frame pivotally mounted on said base to swing about a fixed horizontal axis, said frame having a free end spaced from said axis, means for swinging the frame about said axis so that said free end travels in an are over said axis back and forth from one side of the axis to the other, said frame being rigid whereby the free end thereof always remains at a fixed distance from said axis and, during said travel, moves in a true circle concentric with said axis, a secondary frame pivotally mounted on the free end of said primary frame to turn about an axis parallel to said first axis, a depending suction device pivotally mounted on said secondary frame to swing freely about a third axis parallel tobut spaced laterally from said second axis, and mechanism operative during a predetermined portion of the descent of the free end of said primary frame on one side ofsaid first axis to turn said secondary frame about said second axis at a rate to maintain said third axis in a vertical path during the, descent.

, 9. Apparatus for stacking sheets comprising a stationary base, a primary frame pivotally mountedon said base to swing about a fixed horizontalaxis, said frame having a free end spaced fromzsaid axis, means for swinging the frame about said axis so that said free end travels in an are over said axis back and forth from one side of the axis to the other, said frame being rigid whereby the free end thereof always remains at a fixed distance from said axis and, during said travel, moves in a true circle concentric with said axis, a secondary frame pivotally mounted on the free end of said primary frame to turn about an axis parallel to said first axis, a link having an,elongated slot therein with a guide in the slot fixedlypositioned at said first axis, the end of said link being connected to said secondary frame whereby it travels with said secondary frame as the same is carried back and forth by the primary frame, cam means to cause said link to shift axially as it turns about said guide and thus turn said secondary frame about said second axis, and a depending suction device pivotally mounted on said secondary frame to swing freely about a thirdaxis parallel to but spaced laterally from said second axis.

10. Apparatus for stacking sheets, comprising a stationary base, a frame pivotally mounted on said base to swing about a fixed horizontal axis, drive mechanism including a prime mover connected to said frame andoperative to swing the frame back and forth about said axis in regular cycles, said frame having a free end effective to travel in an are over said axis from one side of the axis to the other as the frame swings, said drive mechanism including means to automatically halt and reverse the movement of said frame. when said free, end thereof reaches a predetermined point on each side of said axis, a secondary frame pivotally mounted on the free end of said primar frame to turn about an axis parallel to said first axis, a depending suction device pivotally mounted on said secondary frame to-swing freely about a third axis parallel to but spaced laterally from said second axis, and mechanism operative durin a predetermined portion of the descent of the free end of the primary frame on one side of said first axis to turn said secondary frame about said second axis at a rate to maintain said third axis in a vertical path during the descent.

11. Apparatus for stacking asbestos. cement sheets, comprising a stationary base, a frame pivotally mounted on said base to swing about a fixed horizontal axis, drive mechanism in,- cluding a prime mover connected to said frame and operative to swing the frame back and forth about said axis in regular cycles, said frame having a free end effective to travel in an are over said axis from one side of the axis to the other as the frame swings, said drive mechanism including means to automatically halt and reverse the movement of said frame when the free end thereof reaches a predetermined point at each side of said axis, a support carried by the free end of the frame, mechanismoperative as said free end approaches one of said predetermined points to shift said support laterally relative to said free end at a rate to maintain said support in a vertical path during descent; a suction device below said support connected to and carried by said support, the connection between said support and suction device constructed and arranged to provide lost motion between the two such that the vertical descent of said support can continue after the descent of the suction device has halted.

12. Apparatus for stacking asbestos cement sheets, comprising a stationary base, a primary frame mounted on said base to swing about a fixed horizontal axis, said frame having a free end spaced from said axis, means for swinging the frame about said axis so that said free end travels in an are over said axis back and forth from one side of the axis to the other, said frame being rigid whereby the free end thereof always remains at a fixed distance from said axis and, during said travel, moves in a true circle concentric with said axis, a secondary frame mounted on the 'free end of said first frame for lateral movement relative to said free end, mechanism operative during a predetermined portion of the descent of said free end on one side of the axis to shift said secondary frame laterally relative to said free end at a rate to maintain said secondary frame in a predetermined vertical path during such descent, a depending suction device below said secondary frame connected to and carried by said secondary frame, the connection between said secondary frame and said suction device constructed and arranged to provide vertical-lost motion between the two such that the vertical descent of said secondary frame can continue after the descent of the suction device has halted.

13. Apparatus for stacking asbestos cement sheets, comprising a stationary base, a primary frame mounted on said base to swing about a fixed horizontal axis, said frame having a free end spaced from said axis, means for swinging the frame about said axis so that said free end travels in an are over said axis back and forth from one side of the axis to the other, said frame being rigid whereby the free end thereof always remains at a fixed distance from said axis and, during said travel, moves in a true circle concentric with said axis, a secondary frame mounted on the free end of said first frame for lateral movement relative to said free end, mechanism operative during a predetermined portion of the descent of said free endon one side of said axis to shift said secondary frame laterally relative to said free end at a rate to maintain said secondary frame in a predetermined vertical path during such descent, said mechanism comprising a cam element and a thrust element coacting therewith, one of said elements being stationary, the other of said elements being mounted to move with said primary frame and 10 having operative connection with said secondary frame for shifting same laterally, a depending suction device below said secondary frame connected to and carried by said secondary frame, the connection between said secondary frame and said suction device constructed and arranged to provide vertical lost motion between the two such that the vertical descent of said secondary frame can continue after the descent of the suction device has halted.

14. Apparatus for stacking asbestos cement sheets, comprising a stationary base, a primary frame mounted on said base to swing about a fixed horizontal axis, said frame having a free end spaced from said axis, means for swinging the frame about said axis so that said free end travels in an are over said axis back and forth from one side of the axis to the other, said frame being rigid whereby the free end thereof always remains at a fixed distance from said axis and, during said travel, moves in a true circle concentric with said axis, a secondary frame mounted on the free end of said first frame for lateral movement relative to said free end, mechanism operative during a predetermined portion of the descent of said free end on one side of the axis to shift said secondary frame laterally relative to said free end at a rate to maintain said secondary frame in a predetermined vertical path during such descent, said mechanism comprising an elongated link disposed crosswise of said axis and operatively connected to said sec ondary frame, said link mounted both to swing about said axis with said primary frame and also r to slide endwise across the axis, and a cam acting on said link as it swings about said axis for sliding the link endwise to shift said secondary frame, and a depending suction device below said secondary frame connected to and carried by the secondary frame.

15. Apparatus as in claim 14 wherein said cam is stationary and said link contains an elongated slot with a guide therein fixedly positioned at said horizontal axis,

WILLIAM HOLDSWORTH ROOKSBY.

REFERENCES CITED The following references are of record in the file of this patent:

/ UNITED STATES PATENTS Number Name Date 493,476 Burr Mar. 14, 1893 571,699 Sinclair Nov. 17, 1896 696,186 Orlofi" Mar. 25, 1902 940,497 Bean Nov. 16, 1909 1,428,716 Smith et a1. Sept. 12, 1922 1,554,429 Hasselquist Sept. 22, 1925 2,170,025 Jordhoy Aug. 22, 1939 2,224,802 Speiss Dec. 10, 1940 2,295,055 Rupp et al. Sept. 8, 1942