US2922459A - Material handling means - Google Patents

Description

E. R. BEEBE MATERIAL HANDLING MEANS Jan. 26, 1960 4 Sheets-Sheet 1 Filed NOV. 27. 1956 E. R. BEEBE MATERIAL HANDLING MEANS 4 Sheets-Sheet 2 INVENTOR. [172272622 Efieebe,

Jan. 26, 1960 Filed Nov. 27. 1956 Jan. 26, 1960 E. R. BEEBE 2,922,459

MATERIAL HANDLING MEANS Filed Nov. 27. 1956 4 Sheets-Sheet 3 IN V EN TOR.

Jan. 26, 1960 E. R. BEEBE 2,922,459

, MATERIAL HANDLING MEANS Filed Nov. 27. 1956 4 Sheets-Sheet 4 EXHAUST "-0 IN V EN TOR.

United States Patent HANDLING MEANS; V m t-R-Bs e, Ch a o 1 a i no o s & 0 mean 913 2X Ch c eqil l-i qtas a b of aw re Application November 27, 1956, Serial No. 624,682

1. ns. 71- ==z.1)

he n n ion e ates. en a o m l nd n means and it has particular relation to such means for use with mechanical presses employed for forming a flange along one edge of a, metallic sheet.

Among the objects, or this invention are: To provide sheet during the forming operation tending to raise theuniormed portion there'ofi as. a control for both the raising and the lowering. oi the sheet and its support;

to prevent the. raising of the sheet and support except on intended operation oi the elevating mechanism; to. employ air pressure means for raising and lowering the sheet and support; to provide such a ratio betweenthe.

t l volume f h s a e QPP JPi y he om r s air and the volume of the space through which a piston. connected to the sheet support moves. that the force. exerted on the support varies as a function of the angle to which il iq t $W l 9 exha s e. r i ni the air pressure means. when it exceeds a predetermined pressure; and. to. provide fortsupporting. the sheet and swinging the. same. about close to the bending axis and additional support means. movable with. respect to the sheet support and. swinging about an axisbelow the bending axis.

Other objects of this inventionwill, in part, be obvious and in part appear hereinafter.

This invention isdisclosed in the embodiment thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement ofparts. that will; be exemplified in the construction hereinafter setforth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention reference can be had to the fol-- lowing detailed description, taken together with the ac-.

companying drawings, in which:

Figure l is a view, in side elevation, of a portion of the material handling means in which this invention is incorporated and showing somewhat diagrammatically the application thereof to a conventional mechanical press;

Figure 2 is a vertical sectional view taken generally'along the line 2--2 of Figure 1;

Figure? is a vertical sectional view taken generally along the 3.3 of Eigure 1 and at anenlarged scale;

4 a vertical sectional view. or the balance adjusting means;

Figure 5 is asectionalview taken generally along the 2,922,459 Patented Jan. 26, 1960 ine 5- o F r 3: and snow g. the. s n a1.a.. an en lime atbani sbamsm;

e s b .5. anemia si elev tio n n enlarged sq i iq ma aise u nism show 1 11 81 7 5, h cover being removed in order to show the. details of construction; and

figure 7 u t ates i grammat cally ce t th mecnamcal d. e c l. m tu es embod ed n is vention.

fin n w t ra tiqulat y Fi ure 1. qt r edrawings, it will be observed that the reference character llldes: n e lly me baaieat press. o onvent on construction ich i den ified he a t. s. a p es brake h p e 10 s emu ated. o apply g a sun stamial. b nd ts. for n h et bi. me al; uch. as eet: s e having a mqls gssq item 9 4,-" and a er. for b d n he a as. part eg a ly. or. end n a flang 89 e ge- EQ aisrii nb e Imp ss. w n des, an pr wh shi mess d. o. be, mou t d 0 t Suitable p d ubni. u h. as]?! lac Q onc t em.- bedd n h st ma. .Mpynted an. he. apron. 1 is a; a on or l v'veL ie. tt a 1. underneath. a mo bl n pp d al-" hibh s. attaa edt n a e a. heet. for n n a an naqu ed e etebt. twill. be Observed hat efmatins a es, .1 t e ies nd. 13. generally form right angles so that the flange along as t ne sheet 14 arta iae tq be b n at i ht angles thereto. Other angular ties can be iormed by, suitable configuration of the mating sp facesoi the dies, 12 and 13. '4 k When the sheet 14-is. of relatively... short length, it a i p e m te to end h flan e; When t s takes.

place. and the movable or upper die 13 performs the nd g pera n. e. l ge h ah. o b bent. swung p rdly ou h m n e. f. for example. d. e em n n p t 'b he sh et ike i e s. wi h ou fp e Since e an e sja s nled. o be formed at a 90- angle... When the sheet 14 is rela: tively long, for example. is 6 to. 8 or 1Q feet long, the m n g P'Q b it t. be swunaun a dly hrough the requiredlangleinprder to maintainlthe proper relationship between the flange and the remaining p of the sheet. Although some attempts have h' n made in the past. to provide a solution tothe problem of hane tiling the remaining portion of' the sheet under the secir cumstances when it is relatively long, the principal method employed has. been to use the services of p or three human op erators who manually liftthe rein n ing portion of the sheet'through the requiredangle lower it after thebending operation has been comple d p This has been costlyv in time of. the operators require and has been rnore or less dangerous. The presenting vention is addressed particularly to the, provision of means for mechanically handling the remaining portion of'the sheet during and after the bending operation It, will be understood that the, sheet 14 is variable in size and in so characterizing it it is intended to refer to not only to the dimensions butalso to the weight oi. the, sheet. I

Associated with the mechanical press, 10. in a suitable manner (not shown) is a stop 15' which limits the posttion of the sheet 14- between, the dies 12 and, 13 and determines the width ofthe flange to be bent as will be understood readily. The upper die 13' is moved down; wardly in response to the operation, of a suitable mannal control, such as the depressionof a foot pedal lo is mounted on a shaft :17; that rotatesto; eflectthe desiredcontrol operation Associated wtih the foot pedal 16 is an arm; 18 which controls the operation of'a ped switch.19 the function of which will he set forth here: inafter.

It is desirable that the sheet '14 be supported for move;

ment about the axis of bending and that there be a minimum of movement between the sheet and its support in order to avoid injury to its surface. For this purpose a pair of rider members 22 are provided. As shown more clearly in Figures 2 and 3 of the'drawings'the rider members 22 may be in the form of channels with the side flanges extending downwardly. At their forward ends the rider members 22 are provided with cars 23 which are pivoted at 24 about a horizontal axis that is located adjacent the bending axis of the sheet 14 as determined by the cooperating dies 12 and 13; The pivot axis 24 is provided on fulcrum blocks 25 which are securely mounted on the apron 11 adjacent the stationary or lower die 12. g i A Provision is made for swinging the rider. members 22 upwardly and controlling the return movement thereof to the horizontal position shown in Figure l of the drawings through the agency of a mainframe that is indicated, generally, at 26. The frame 26 is formed of a combination of tubular construction and rolled struc-,

tural members. It will be understood that other members can be employed as may be'desired, the particular construction being for illustrative purposes The main frame '26 may include tubular frame members 27 which extend horizontally when the frame 26 is in the lowermost position. The frame members 27 carry rollers 28 which readily permit relative movement between the main frame 26 and the rider members 22 as the combination is swung upwardly by means tobe described in order to permit the remaining portion of the sheet 14 to follow the bending operation. Depending from the forward ends of the tubular frame members 27 are channel frame members 29 that are interconnected by an angle cross member 30. The various frame members are secured together preferably by. welding. Extending forwardly from the frame members 29 arehorizontal frame members 31 and inclined frame members 32. It will be observed that the frame members 31 and 32 are pivoted at 33 about a horizontal axis on fulcrum blocks 34. The horizontal axis through the pivots 33 is positioned laterally of and below the bending axis between the dies 12 and 13. Anarm 35 is carried by one of the frame members 32 forcontrolling the operation of a lock disconnect switch 36 the function of which will be described hereinafter.

Provision is made for swinging the remaining portion of the sheet 14 upwardly through a corresponding movement of the rider members 22 and main frame 26. In accordance with this invention air pressure means, shown generally at 39 in Figures 1, 2 and 7 of the drawings, is employed. The air pressure-means 39 includes an air cylinder 40 which is pivotally mounted at its lower end about a horizontal axis 41 on a suitable ear 42 that is supported on the same foundation that supports the mechanical press 10. A piston 43 is slidable within the cylinder 40 and a piston rod 44 is connected thereto and extends out of the upper end for connection to the main frame 26.

The details of the connection of the piston rod 44 to the main frame 26 are illustrated more clearly in Figure 2. There it will be observed that a fitting 45 is threaded on the upper end of the piston rod 44 and is secured by a transverse pin 46 to a central portion 47 of a lift yoke as indicated, generally, at 48. The yoke48 includes a pair of depending arms 49 which are pivotally connected at 50 near their lower ends to the lower ends of the channel frame members 29. It will be understood that, as air pressure is applied to the piston 43, the piston rod moves upwardly and carries with it the yoke 48. The upward thrust is applied through the channel frame mentbers 29 to the main frame 26 which swings around the axis through the pivots 33 and causes the rider members 22 to swing conjointly therewith about the horizontal axis through the pivots 24. As this conjoint movement takes place, because of the spacing of the axes through the pivots 24 and 33, the rider members 22 move outwardly along the rollers 28-- during the upward movement and move inwardly during the downward movement. During such operation the air pressure means 39 pivots about the axis 41 to the extent required to permit the movement of the main frame 26, rider members 22 and sheet 14.

It is desirable. that the volume of theair pressure means 39 be relatively large as compared to the volume in the air cylinder 40 through which the piston 43 moves. The reason for this is to permit a reduction in the thrust applied to the main frame 26 as it swings upwardly with the reduction varying as the cosine of the angle through which the main frame 26 is swung." This makes it possible to substantially balance the main frame 26, rider members 22 and the sheet 14 carried thereby in any position between the horizontal position and the fully raised position without varyingthe amount of air initially measured into the air pressure means 39 by the automatic loading feature described hereinafter. For this purpose, instead of employing a long cylinder 40, an accumulator cylinder 51 is provided and is connected, as" shown in Figure 7, to the air cylinder'40. The accumulator cylinder 51 preferably is mounted to move conjointly with the air cylinder 40.

Air under pressure is supplied to the accumulator chamber 51 through a flexible connection 52 from a conduit 53 and the supply is controlled by an air intake valve 54 from an air supply pipe 55. It will'be understood that the pipe or conduit 55 is connected'to a suitable source of air under pressure. The operation of the air intake valve 54- is controlled by an operating solenoid 56 in a manner to be described hereinafter. The air is exhausted from the accumulator cylinder 51 and air cylinder 40 through an air exhaust valve 57 to a discharge conduit 58. An operating solenoid'59 controls the operation of the air exhaust valve 57 and the operation thereof will be set forth hereinafter.

It is desirable that the outer end of the main frame 26 be supported in the horizontal position. For this purpose a support frame or stand, shown generally at 62 in Figure l, is provided. The support frame or stand 62 may include frame uprights 63in the form of tubular members interconnected; as shown in Figure 3, by a cross member 64. Adjustable supports 65 carried by the upper ends of the frameuprights 63 and cooperating with the ends of a cross member 66, forming a part of the main frame 26, serve to limit the downward movement of the latter as desired.

It is desirable to provide an adjustment for the balance of the main frame '26'and'rider members 22' in accordance with the size of'the sheet 14 that is to be operated on. For this purpose balance adjusting means, shown generally at 67, is mounted on the cross member 64. The details of construction of the balance adjusting means 67 are shown more clearly in Figure 4 of the drawings. 7 a

The balance adjusting means 67 includes a housing 68 that is carried by the cross member 64 of the support frame or stand 62. Within the housing 68 is a coil compression spring 69 that reacts against a plunger 70 at its upper end which, in turn, bears against the underside of the cross member 66 of the main frame26. The tension of the spring 69 can be adjusted by an adjusting screw 71. By varying the tension on the spring 69, the upward thrust exerted by the plunger 79 on the main frame 26 can be varied to effect a corresponding variation in the upward thrust required to be applied by the air pressure means 39 thereby providing the required amount of force to balance the force-of gravity exerted downwardly on the main frame 26, rider members 22 and sheet 14 carried thereby which varies as the cosine of the angle through which the main frame 26 moves from thehoripressure means 39 provision is made for controlling the energization of the operating solenoid; 56- associated' with the air intake valve 54. For this purpose a down limit switch72 is mounted on' the cross'mem ber 64 of the support frame or stand-'- 62. It is arranged to be operated by the main frame 26, particularly by the cross member 66 thereof engaging the switch, as shown in Figure 3, to hold the contacts thereof in the closed position, As soon as suflicient air pressure is applied to the air pressure means 39 to lift the main frame 26 slightly with the aid of the spring 69 in the balance adjusting means 67 and-react ing against the force of gravity, the contacts Of'lfhlS' switch are opened and the circuit to the operating solenoid 56 is opened, as will be set forth hereinafter, to permit the valve- 54 to close andprevent further application of= air to the air pressure means 39.

It is desirable that meansbe provided for preventing the upward swinging movement ofthe sheet 1 4, rider members 22 and main frame 26. A mechanical latch mechanism, shown generally at 73, in Figures 5, 6 and-7, isprovided for this purpose. The latch mechanism 73 is mounted on a support member '74 which is carried by the cross member 64 forming a part of thesupport frame or stand 62. It cooperates with a detent 7-5 which is carried by the cross member 66 that forms a partof the main frame 26. Cooperating with the detent: 75 isa movable latch 76 which, as shown more clearly in Figure 6, is slidably mounted in an opening7-7'in a block 78 which is carried by the support member- 74.

The fit of the latch 76 in the opening 77 is relatively loose for the purpose of permitting the former to moveupwardly in the latter to eifecta control function whichwill be described presently. A transversely extending pin 79 is carried by the latch 76 and, when the latch 76 is withdrawn under normal operating conditions, the pin 79 interfits with a slot 80 in the block 73. However, should the latch 76 be raised upwardly as permitted by the loose fit in the opening 77, the pin 79 will not register with the slot 80 and thus will prevent movement of the latch 76 to the unlatched position.

The latch 76 is biased to the latched position by a coil compression springSl which reacts between itand a stationary plate 82 that is carried by the-support member 74. A shaft 83 is connected to the latch'76 and extends through the spring 81 and through the plate 82 for connection to an armature 84 which is arranged to be attracted by a solenoid 85 which is illustrated as a winding in Figure 7 of the drawings. A suitablecover 86 is provided, as shown in Figure 5, for enclosing the latch mechanism 73. i

It has been pointed out hereinbefore that the air exhaust valve 57 is opened under certain circumstances. For this purpose an up limit switch, shown generally at 87, is provided. As shown in Figure 7 the up limit switch 87 is provided with normally open contacts87a and normally closed contacts 87b. These contacts are operated by a plunger 88 which extends through anopening 89in the block 78, Figure 6, whereits lower end is positioned inthe path of upward movement of the latch 76. In the event that the airpressurevrises to such an extent in the air pressure means 39 thatthe main frame.

26 is liftedsntficientlyfar to-cause the detent '75 to lift the latch 76, then the up limit switch 87 is operatedzfromone position toan alternate position foreffecting; the energization of the operating solenoid 59- associated withthe air exhaust valve 57.

The several switches previously referred to are connected in an electrical system as shown in Figure 7. This system also includesa control relay that is indicated, generally, at 90 and is provided with an operating wind: ing 9 0w, normallyopen contacts 90a and;90 b and'nor mally closed contacts 90c. The system also includesa transferswitch, shown generally at 91,- which includes contaets.9la and 91m for either automatic or manual operation as. will appear hereinafter. In addition there spam is an exhaust switch 92 that is arrang ed to be manually operated and a-fill switch 93: that likewise isarranged to? be manually operated, The electricalsystem can be energized f-rom-auy suitable source of 'current such as 110 voltcycle; source which; maybe applied across conductors 9 and 95 through a suitable switch 96.

In describing theoperation: of the material handling means disclosed herein, it will'beassumedthat the switch 96 is-closed= to energize. conductors-"94 and 95- and that the-transfer-switch 91 is in the automatieposition with contacts 91a closed: Further it will. beassumed that a sheet-14 has been placed onthe rider members 22 as shown in. Figure 1 with the lefthancl end abutting the stop 15*.

The fill switch 92 is depressed momentarily to efiect the operation of the control=relay90. The circuit for accomplishing this can be traced from energized conductor 94-. through the normally-closedv contacts of the down limitswitch72, contactsof the fill switch 93, operating winding w to energized conductor-; Asa result of theenergization of winding9tlw a holdingcircuit is completedtatcontacts 9011 through contacts 91a and the fill switch. 93. need be held in the depressed condition no longer.

As a result of the operation of the control relay 90 a circuit is completed for'energizing the operating solenoid 56 of'the. air. intake valve54: This circuit can be traced from energized conductor 94 contacts of the down limitswitch 72, solenoid 5'6, contacts 90a to energized conductor 95.

As. aresult of the opening of the air intake valve 54,

air under pressure is appliedto the accumulator cylinder 51 and air cylinder 40. Whensuflicient air pressure is developed within the air cylinder), the piston 43 is moved upwardly tolift the sheet 14, rider members 22 and main. frame26. Only a slight upward movement of. the main frame 26:talres place until the contacts'of the. down. limit switch 72 are opened. As a result the holding. circuit. for the. winding 90w is opened and the controtrelay 90 is deenergized] Contacts 90a open and the solenoid 561isdeenergizedresulting in closureof airintake valve 54. V i

It will. be unders'toodthat the amount of air pressure:

admitted into the. air-cylinder- 40*for liftingthe main frame 26 sufiiciently to open the contacts of the down limit switch 72: can be adjusted by-thebalance adjusting means67. This is accomplished by varying the tension in the spring 69:by the adjusting'screw -71.

The system now is in condition forperforming the bending operation on the sheet 14. For this purpose the operator depresses the foot pedal 16. One result OfthlS operation is to operate the mechanicalpress iii and cause the movable or upper die 13 to move downwardlyas indicated by the-arrow 97 in Figure Such operation is conventional and need not be described further. At the time that the foot pedal 16 is depressed thecontacts of pedal switch 19 are closed to complete a circuit forenergizmg the. solenoid 85 associated with the latch mechanism 73; This circuit can be traced from the 'energized'conductor 94-th'rough normally closed contacts 87b, contacts of the pedal switch 19, solenoid 85, normally closed contacts of-locle disconnect switch 36, normally losedcontacts 900 to conductor 95. As a result the latch 76 is withdrawn from the path of the detent 75 and the main frame 26 then is free to swing As the movable or upper die 13moves downwardly to'engage the-sheet 14- for performing the bending operation, a portion indicated at" 98 of the sheet 14 tends to be ralsedso that the portion of the sheet adjacent the stationary orlower die 12 can conform to the shape of axis of the bend which of this surface. it will the bendingsurface 99'about the isindicatedat 100- at the nadir beunderstood tha t the upward force; applied to the sheet 14 as indicated at 98 reduces the downward force exthrough the normally closed 7 erted by the sheet 14 against the piston 43. As a result, the air pressure which is trapped in the air cylinder 40 and accumulator cylinder 51 is permitted to raise the frame 26. Previously the upward force exerted by the air pressure within the air cylinder 40 had been balanced by the force of gravity acting on the sheet 14, rider members 22 and main frame 26 Some of that force is de: creased, as described, by the upward'thrust applied to the portion 98 of the sheet 14 as the bending operation progresses. 1 Consequently the remaining portion of the sheet 14, rider members 22 and, main frame 26, are swung upwardly as the air in the air cylinder 40 and accumulator cylinder 51 expands. The upward force exerted by the air pressure decreases as the air expands. However, the downward force of gravity applied to the sheet 14, rider members 22 and main frame 26 varies as the cosine of the angle through which they are swung so that the system generally remains, in balanceexcept as unbalanced by the upward thrust applied to theportion 98 of the sheet 14. The upward movement of the remaining portion of the sheet ,14, rider members 22 and main frame 26 continues until they occupy a position parallel to the right hand side of the bending surface 99 of the stationary or lower die 12. Where .a 90 bend is formed in the sheet 14, this corresponds to a move ment through about 45 for the remaining portion of the sheet 14, rider members 22 and main frame 26.

As soon as the bending operation is completed, no further upward thrust is applied to theportion98 of the sheet 14, Consequently, the only forces acting are the force of gravity acting downwardly on the sheet 1.4, rider members 22 and main frame 26 and the force exerted: by. the air pressure in the air pressure means 39. acting up--.

wardly. The relationship is such that the downwardly acting force exceeds the upwardly acting force, and, as a result, the sheet 14, rider members 22 and main frame 26 are biased downwardly by a force equalto the difference between the oppositely acting forces after the upper die 13 has been retracted, to a position completely out of engagement with the sheet 14. Theaforernentioned difference is adjustable by the previouslytdescribed adjustment means 67. The return of these parts to the horizontal position is cushioned by theair pressure means 39.

It is pointed out that, as the main frame26iis swung upwardly the contacts of the lock disconnect switch 36 are opened and the previously traced circuit for energizing the solenoid 85 of the latch mechanism 73 is opened. The spring81 then returns therlatch 76 to the position shown in Figure 7 so that, when the,detent 75 is moved downwardly, it rides over the inclined latching surface 101 to displace the latch. and permit the return of the main frame 26 to the horizontal position. As soon as the latch 76 is disengaged by the detent 75, the former is urged to the latching position by the spring81.

As long as the same sheet 14 remains, on the rider members 22, it is unnecessary to provide additional air under pressure to the air pressure means 39; All that is required is for the successive operation and release of the foot pedal 16 to cause the mechanical press.10 to go through a complete stroke and for the remaining portion of the sheet 14 to be raised and lowered during and after the bending operation, respectively, as described.

After all of the bending operations have been performed on the sheet 14, it is removed from the rider members 22. The downwardly exerted force is reduced to an extent equal to the mass ofthe sheet and, as a result, the air pressure in the air pressure means 39 tends to swing the main frame 22 upwardly, The detent, 75 then engages the under side of the latchg76 and moves it upwardly. This movement is transmitted through the plunger 88 to the upper limit switch 87. Contact members 87b are opened to open any possible energizing circuit to the solenoid 85. As a further precaution, as

pointed out hereinbefore, thepin 79 is provided on the latch 76 so that, when it is raised, as just described, the latch 76 could not be withdrawn to-the unlatched position even if the solenoid might inadvertently be energized.

A further result of the operation of the up limit switch 87 is to close contacts 87a and complete a circuit for energizing the operating solenoid 59 of the air exhaust valve 57. This circuit can be traced from the energized conductor 94 through contacts 87a, solenoid 59, to energized conductor 95. On opening of the air exhaust valve 57, the air pressure applied to the air pressure means 39 is released through the discharge conduit 58 to the atmosphere. The air pressure is not discharged fully but only to an extent sufficient to permit the force of gravity to overcome the force exerted on the piston 43. Under these circumstances the detent 75 no longer holds the latch 76 in the elevated position and contacts 87:: are opened to open the previously traced energized circuit for the solenoid 59.

On the application of another sheet 14 to the rider members 22, the fill switch 93 is again depressed and the foregoing cycle of operation is repeated.

In the event that it is desired to operate the system manually, the transfer switch 91 is operated to close contacts 91m. Under these conditions, it is necessary to hold the fill switch 93 in the closed position until sufficient air pressure is developed in the air pressure means 39 to open the contacts of the down limit switch 72. In other words, the control relay 90 is not automatically held energized since it is not possible to complete the holding circuit to the contacts 902; for the reason that the contacts 91a are open.

The air pressure means 39 can be exhausted completely by depressing the exhaust switch 92 under the assumed conditions and holding the same closed. The circuit for energizing the operating solenoid 59 of the air exhaust valve 57 by operation of the exhaust switch 92 can be traced from the energized conductor 94 through contacts 91m, contacts of exhaust switch 92, solenoid 59 to the energized conductor 95.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

What is claimed as new is:

1. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet accompanied by application of force tending to raise the remaining portion of the sheet, sheet hoisting means comprising, frame means pivotally supported to swing about a horizontal axis below the bending surface of said stationary die, sheet support means movably carried by said frame means and pivotally supported to swing about a horizontal axis in close proximity to said bending surface of said stationary die, and means for conjointly moving said frame means and said sheet sup port means upwardly as the bending operation is performed to support the unbent portion of the sheet during such operation.

2. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of. a metallic sheet accompanied by application of force tending to raise the remaining portion of the sheet, sheet hoisting means comprising, frame means pivotally supported to swing about a horizontal axis below the bending surface of said stationary die, sheet support means movably carried by said frame means and pivotally supported to swing about a horizontal axis in close proximity to said bending surface of said stationary die, and means for. conjointly moving said frame means and said sheet support means upwardly as the bending operation is performed with a force varying: as the cosine of the angle through which .said framemeansismoved and lessthanthat-s required to.,.overcome. the; force: of: gravity. acting:

the'reonnand 'on said sheet support .meansnand said :sheet whereby,- wherhthe. bendingeoperationis, completed and the-first mentioned forceismolonger. applied, the. return to .the initial: posit-iontunder. the; forceof gravity;v of saidraise the remaining. portion of. the. sheet, sheet hoisting means comprising, meansior supporting vsait'lisheentoswing thersame upwardly generally about:-the. bendingaxis thereof, and means formoving said: supporting means.

upwardly as the. bending. operation is performedwitha constantly; applied force. which is. less 1 than. that: required to; overcome the force. of-gra-vity. actington said supporting-i means and. sheet. whereby, when. the. bending opera-. tioniisicompleted; and: the first mentioned: force is no.

longer applied, the return to. the initialtpositiom under the force of gravity. of said. supportingmeansand sheet.

is Qushioned by thesecond mentioned force.

4:.In1 combination. with armechanical pressi having a.

downwardly, movable die and a; cooperating stationary die foryforming a flange alongone edge of'a metallic sheet: accompanied by. application of, force. tending to. raise-the remaining. portion. Off the sheet, sheet. hoisting means; comprising, means for. supporting saidsheet to. swing the same upwardly generally. about. the bending thereof, means for moving. said supporting means upwardly asthe bending operation is. performed with a eflnstantly applied force which varies as the cosine of the; ngle through. which. the same is. swung. and which is less thanthat. requiredtp overcome theforce ofgravity acting, on said: supporting means. and: sheet. whereby,

when, the bending operation is completed and. the. first. mentionedforce is. no longer applied, the return tothe. initial. position; unden the force of gravity. of saidv sup.-. porting means and; sheet. is ;cushioned by the. second: men-.

tioned force, and means. independent of the. means-for applying said' second mentionediforce. for-varying the.

nit ali mean hereon required: to functionas. aforesaid.

5. In combination. with. a mechanical. press having a downwardly movable die and a. cooperating.- stationary die for forming a flange along one edge of a metallic sheet accompanied by application of force tending to raise the remaining portion of the sheet, sheet hoisting means comprising, means for supporting said sheet to swing the samev upwardlyv generally about the bending agtis thereof; and. air pressure. operating means disposed below said sheet and reacting upwardly against said supporting means for moving the same upwardly as the bending; operation. is. performed. with. a constantly applied force which cushions the return of said supporting means and sheet to said initial position under the influence of gravity after the bending operation has been completed and the first mentioned force is no longer applied.

6. The invention as set forth in claim 5 wherein the air pressure operating means comprises an air cylinder and a piston slidable therein with the volume of the former being substantially greater'than the volume of the space therein through which said piston moves.

7. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet accompanied by application of force tending to raise the remaining portion of the sheet, sheet hoisting means comprising, means for supporting said sheet to swing the same upwardly generally about the bending axis thereof, air pressure operating means disposed below said sheet and reacting upwardly against said supporting means for moving the same upwardly as the bending operation is performed with a constantly applied force .whichvaries. asthetcosine of? the angular. displace-.. ment.ofqsaidasupporting means. from its initial position and;which cushions the.return..ofsaid supportinglmeans.

andnsheetto said; initial positiomunder theinfiuence-of: gravity.- after. the bending operation, has been completed: and thefirst mentioned'forceis no longer applied, and; means independent of said air pressure operating means.

for varying. the initialr amount of" force. required to-.be exerted thereby to-function. as aforesaid:

8. In combinationwitha mechanical press. havinga. downwardly-movable. die and a cooperating stationary die for forming a. flange along one edge of a. metallic sheet accompanied by application of forcetending. to

raise the. remaiuingportion of the sheet, sheet hoisting. means comprising, means. for. supporting said sheet to swing the same; upwardly generally about the. bending.

axis thereof; air pressure. operating means disposed: below. said sheet and reacting upwardly against said supporting means. formatting the sa'rneupwardly'as the bending operation isperformed with a constantly appliedforce which varies as the cosine. of the angular displacement of said supporting, means from itsinitial position and whichcushions-thereturm of said supporting means and sheet: to said initial position under the influence of gravity after, the bending. operation has been completed: and. the first mentionediforce is no longer applied, and means cooperating .withsaid air pressure operating meansfor. limiting: the.initial=valueof the force exerted there by, when thesamereachesa value determined principally bythe force ofrg-ravity acting on said. supporting means andw sheet.

9. In combination withaa mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet; accompanied byapplication of force tending to raise the remaining portion of: the sheet sheet hoisting means comprisingjmeans for supporting said sheet to swing the same upwardly generally about-the bending axis thereof; means for. moving said supporting means'up wardly. as. the bending operation is performed with a constantly applied. force which is. less than that required to overcome the. force of-gravity acting on said sup porting means and sheet whereby, when the bending first.- mentioned force is" operation is completedand the no longer,- applied; the. returnto the initial position under the forceof: gravity of said supporting means and sheet:

is I cushioned; by the second mentioned; force.

1,9, In cprnbinationwitha mechanical press. having a dQ QW TQlY BWQblQ- d and a. cooperating. stationary die for; forming,v a flange. along oneedge. of a metallic sheet: accompanied, by, application of. force tending to raise the remaining portion of the sheet, sheethoisting means, comprising, means for supporting. said. sheet to swing; the. same. upwardly generally about: the bending axis thereof, means for moving said supporting means upwardly as the bending operation is performed with a constantly applied force which varies as the cosine of the angle through which the same is swung and which is less than that required to overcome the force of gravity acting on said supporting r..eans and sheet whereby, when the bending operation is completed and the first mentioned force is no longer applied, the return to the initial position under the force of gravity of said supporting means and sheet is cushioned by the second mentioned force, and locking means cooperating with said supporting means for preventing upward movement thereof in the event that said second mentioned force exceeds a predetermined value.

11. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet, sheet hoisting means comprising, means for supporting said sheet independently of said die, means for pivotally mounting said sheet supporting means to swing about a horizontal axis in close proximity to said bending surface of said stationary die, air pressure operating means connected to said sheet supporting means, and means connected to said air cylinder for controlling the supply of air under pressure thereto and the discharge of air therefrom. I

12. In combination with a mechanical press having a downwardly movable. die and a cooperating stationarydie for forming a flange along one edge of a metallic sheet, sheet hoisting means comprising, means for supporting said sheet, means for pivotally mounting said sheet supporting means to swing about a horizontal axis in close proximity to said bending surface of said stationary die, air pressure operating means connected to said sheet sup orting means, means connected to said air cylinder for controlling the supply of air under pressure thereto and the discharge of air therefrom, and adjustable means cooperating with said sheet supporting means to apply a variable upward thrust thereto to accommodate sheets of different size.

13. In combination With a mechanical press having a downwardly movable die and'a cooperating stationary die for forming a flange along'one edge of a metallic sheet, sheet hoisting means comprising, means for supporting said sheet, means for pivotally mounting said sheet supporting means to swing about a horizontal axis in close proximity to said bending surface of said stationary die, air pressure operating means connected to said sheet supporting means, means connected to said air cylinder for controlling the supply of air under pressure thereto and the discharge of air therefrom, and means cooperating with said air cylinder control means for limiting the air pressure applied thereto to a value determined principally by the force of gravity acting on said sheet supporting means and sheet.

14. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet, sheet hoisting means comprising, a main frame, means for pivotally supporting said main frame to swing about a horizontal axis below the bending surface of said stationary die, means for supporting said sheet movably supported on said main frame, means for pivotally supporting said sheet supporting means to swing about a horizontal axis in close proximity to said bending surface of said stationary die, air pressure operating means including an air cylinder having a piston slidable therein and operatively connected to said main frame, and means connected to said air cylinder for controlling the supply of air under pressure thereto and the discharge of air therefrom.

15. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet, sheet hoisting means comprising, a main frame, means for pivotally supporting said main frame'to swing about a horizontal axis below the bending surface of said stationary die, means movably supported on'said main frame for supporting said sheet, means for pivotally supporting said rider means to swing about a horizontal axis in close proximity to said bending surface of said stationary die; air pressure operating means including an air cylinder having a piston slidable therein and operatively connected to said main frame, and an electrically operated air intake valve connected to said air cylinder for controlling the supply of air under pressure thereto; fill switch means connected to effect the operation of said air intake valve to apply an upward thrust to said main frame and said rider means and sheet carried thereby, down limit switch means connected to effect closure of said .air intake valve on predetermined upward movement of said main frame, and frame balance adjusting means including a coil compression spn'ng'reacting at one end against a plunger engaging said main frame in its lowermost position and having an adjusting screw reacting against the other end.

16. In combination with a mechanical press having a downwardly movable die and a cooperating stationary die for forming a flange along one edge of a metallic sheet accompanied by application of force tending to raise the remaining portion of the sheet, sheet hoisting means comprising, a main frame, means for pivotally supporting said main frame to swing about a horizontal axis below the bending surface of said stationary die, rider means movably supported on said main frame for supporting said sheet, means for pivotally supporting said rider means to swing about a horizontal axis in close proximity to said bending surface of said stationary die, air pressure operating means including an air cylinder having a piston slidable therein and operatively connected to said main frame, and an electrically operated air intake valve connected to said air cylinder for controlling the supply of air under pressure thereto; fill switch means connected to effect the operation of said air intake valve to apply an upward thrust to said main frame and said rider means and sheet carried thereby, and down limit switch means connected to effect closure of said air intake valve on predetermined upward movement of said main frame.

References Cited in the file of this patent UNITED STATES PATENTS

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