US3451247A - Apparatus for forming sheet metal - Google Patents

Description

June 24, 1969 K. 1.. MILTENBERGER 3,451.,247

APPARATUS FOR FORMING SHEET METAL Sheet of 8 Filed April 12, 1967 BY I Z June 1969 K. L. MILTENBERGER APPARATUS FOR FORMING SHEET METAL Sheet 2 of 8 Filed April 12, 1967 I N V E NTOR. Mmvazzazz BY 2 Z I I Afidi/VE/ June 24, 1969 1.. MILTENBERGER 3,451,247

APPARATUS FOR FORMING SHEET METAL Sheet Filed April 12, 1967 June24, 1969 K. I... MILTENBERGER 3,451,247

APPARATUS FOR FORMING SHEET METAL Filed April 12, 1967 Sheet 4 of 8 a 7g 6% m0 /0 /20 ma My 1 1 g. Z- I f r w/25 m 77azA/0 June 24, 1969 K. 1.. MILTENBERGER I 3,451,247

APPARATUS FOR FORMING SHEET METAL Filed April 12, 1967 Sheet 5 of s Arramvzfl June 24, 1969 K, 1.. MILTENBERGER 3,451,247

APPARATUS FOR FORMING SHEET METAL Sheet Filed April 12, 1967 i\ mw Q xmwv June 1969 K. MILTENBERGER 3,451,247

APPARATUS FOR FORMING SHEET METAL Filed April 12, 1967 Sheet 3 of 8 gya 27/ 274 25 ass-2% 27J a 270 772 252 I NVENTOR. ,m z/ ZMm/Jaae United States Patent 3,451,247 APPARATUS FOR FORMING SHEET METAL Kenneth L. Miltenberger, Lakewood, Calif., assignor, by

mesne assignments, to McDonnell Douglas Corporation, Santa Monica, Calif., a corporation of Maryland Filed Apr. 12, 1967, Ser. No. 630,452 Int. Cl. B21d 45/00, 43/ 18, 43/00 US. Cl. 72346 12 Claims ABSTRACT OF THE DISCLOSURE Background of the invention This invention lies in the field of hydraulic sheet metal forming presses and deals with improvements in efficiently delivering workpieces to the forming zone of a press and removing them therefrom. It is directed particularly to the combination of a hydraulic forming press with a reload station for the exchange of blank workpieces for formed workpieces, a conveyor system for moving the workpieces to the desired locations, and transfer mechanism for handling workpieces at the various locations, and to novel details of the various components. The components cooperate to make it possible to supply workpieces to the press and remove them as rapidly as the press can be cycled regardless of the nature or complexity of the workloads.

Various types of presses have been used for producing formed sheet metal parts. When large numbers of identical parts are to be made, a draw type press with fixed tooling is usually preferred. Such a press is not suitable for short runs of many different parts. In most cases such parts are processed in a press having a rigid generally fiat horizontal bed on which one or more form blocks carrying blank workpieces may be laid. A head is located above the bed and carries a large elastomeric pad which overlies the bed and is forced toward it to form the workpieces on the form blocks. The head may be vertically movable by fluid pressure to force the pad toward the bed, or it may have a set position and the pad may be forced down by a hydraulically expansible container carried by the head.

Some of the hydraulic presses mentioned above have rather slow operating cycles and it is possible to keep them supplied with work by the use of one or two work tables or pallets which may be loaded at leisure and moved into and out of the press manually or automatically. Some of the newer versions of these hydraulic presses have very fast operating cycles, at least one having a cycle of only about twenty seconds. To make full use of such a press it is necessary to have a comparatively large number of work-holding pallets and workmen to reload them. To properly handle these pallets, various conveyor systems have been devised which are fairly satisfactory but still have drawbacks, such as insertion of a new pallet being delayed by removal of the previous one, and faster-loading pallets in a series being delayed by slower-loading pallets.

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Summary of the invention The present invention solves the above problems and provides a complete metal forming apparatus which can operate as rapidly as the cycle of the press will permit, is efficient in the amount of equipment and floor space needed, and is very convenient in all aspects and very easy to operate. Generally stated, the apparatus includes a press which has a rigid flat bed and a head which is vertically movable from an open position to a closed position immediately over the bed, on which a pallet with form blocks and workpieces is located. An elastomeric pad carried by the head is forced down toward the bed by fluid pressure in an expansible container also carried by the head. The vertical separating pressure is resisted by a pair of clamp rings which move laterally to grip flanges on the margins of the press bed and head. When the clamp rings are separated laterally, the head is raised and the press is open at two opposite sides.

To speed the replacement of workloads in the press, a loading station is provided at the front or first side of the press and an unloading station is provided at the rear or second side of the press. Transfer mechanism at the loading station pushes the pallet which is on the press bed to discharge it to the unloading station and at the same time pushes the succeeding pallet from the loading station on to the press bed. Because of this straight through action, the succeeding pallet does not have to be held in an out of the way place while the previous pallet is being removed from the press and dispatched to a reloading area.

A conveyor system has a supply section to deliver reloaded pallets to the loading station and a return section to receive pallets of processed parts from the unloading station. The delivery end of the return section and the receiving end of the supply section are remote from the press and define an exchange zone, this part of the return section preferably being arranged in spaced parallel relation beneath the corresponding part of the supply section. At the exchange zone there are a plurality of reload stations, usually varying between two and eight. Each reload station includes a reload table where a selected pallet is' located temporarily while a workman removes formed parts from one or more form blocks carried by the pallet and replaces them with blank workpieces from a convenient storage rack.

In order to achieve maximum utilization of the press, a distinct, selected pallet having certain form blocks thereon is assigned to each workman and he has a rack of blanks for these form blocks. His selected pallet is de- 'tected and discharged from the return section of the conveyor system only to his particular reload station and reload table, and as soon as he reloads all of the form blocks with blank workpieces he may immediately transfer his pallet to the return section of the conveyor system without regard to the rate of progress of any of the other workmen. Since each reload table is independently accessible to both sections of the conveyor, it is apparent that one workman may reload a few large form blocks in a half minute while another workman may require several minutes to reload a large number of small form blocks, and yet the fast reload is not held back by the slow reload. Also, the order in which the pallets return from the press will not cause any delay. The number of reload stations used at one time may be readily adjusted to provide an average number of loads per minute just equal to the capacity of the press.

Brief description 0 the drawings Various other advantages and features of novelty will become apparent as the description proceeds in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a hydraulic metal forming press particularly suited for use in the combination of the invention;

FIG. 2 is a perspective view of the complete apparatus of the invention;

FIG. 3 is a schematic plan view of the apparatus of FIG. 2;

FIG. 4 is a schematic view in elevation of part of the apparatus of FIG. 3;

FIG. 5 is a schematic end view in elevation of the conveyor system and reload station of FIG. 3;

FIG. 6 is a schematic plan view of the return section of the conveyor system at a reload station;

FIG. 7 is a schematic view in elevation of a portion of the return section of FIG. 6 with the detection means to identify selected pallets;

FIG. 8 is a schematic side elevational view of the press, loading station, and transfer mechanism;

FIG. 9 is a schematic plan view of the apparatus of FIG. 8;

FIG. 10 is a schematic side elevational view of the press and the unloading station and its transfer mechan1sm;

FIG. 11 is a schematic plan view of the apparatus of FIG. 10;

FIG. 12 is a schematic view in side elevation of the transfer mechanism of the unloading station;

FIG. 13 is a schematic plan view of a modified form of the apparatus; and

FIG. 14 is a schematic view in side elevation of a portion of the conveyor system and the roller drive means therefor.

Description of the preferred embodiments A hydraulic press which is particularly suitable for incorporation in the apparatus of the invention is illustrated in FIG. 1, and generally comprises a base 10 on which is mounted a press bed 12 having a circular plan- =form, the margin 14 overhanging the pedestal 16 to form a flange. A head 18 is carried by arm 20 which is pivoted at 22 to the base and is raised and lowered by hydraulic servornotors 24. The head includes a rigid backing member 26 to which is connected a stress ring 28 forming a cavity in which is located an elastomeric member 30. Between members 26 and 30 is located an expansible fluid container including a plate 32 and an elastic diaphragm 34. When the head is in juxtaposition to the press bed, hydraulic fluid at high pressure is supplied through line 36 to distend diaphragm 34 and force member 30 toward the press bed to apply forming pressure to one or more sheet metal blanks on form blocks which are lodged on the press bed in known manner. Clamp rings 38 engage the flange portions of the press bed and the head to resist the separating pressure produced during the forming operation. When they are separated by hydraulic servo motors 40 as shown in FIG. 1, the press is open at the front and rear, or opposite sides, making it particularly suitable for loading and unloading in accordance with the invention.

The press of FIG. 1 is shown in FIGS. 2, 3 and 4 incorporated into the remainder of the apparatus of the invention including a conveyor system having a supply section 42 and a return section 44. The delivery end of the supply section is adjacent to loading station 46 and the receiving end of the return section is adjacent to unloading station 48. Their respective receiving and delivery ends are remote from the press and define an exchange zone 50. At the exchange zone are two or more reload stations 52, 54, each having a reload table 56, 58. Pallets 60, in the form of disks, travel from the reload stations to the loading station 46 on conveyor supply section 42 on rollers 62, at least some of which are driven by contact with one or more belts 64 in a manner to be described later. Preferably at least two sections 66 and 68 of the rollers are independently actuated in order that they may remain stationary and accumulate pallets for the loading station while other rollers continue to rotate.

After processing, pallets 60 are discharged to unloading station 48 which transfers them to the gravity portion of return section 44. When they reach the horizontal portion of section 44 they are conveyed by live rollers until they reach their appropriate reload stations 52 or 54. They are then transferred by means later described to elevator sections 70 or 72 and thence to reload tables 56 or 58 where the formed parts are removed and replaced by new blanks. The sequence is completed by transporting the reloaded pallets across transport sections 74 or 76 to section 42 for return to the loading station.

A power unit 78 supplies hydraulic fluid at high pressure to operate the press and compressed air for various servo motors throughout the apparatus. An electrical console 80 is provided to supply power where needed and to directly control various operations which are not automatically actuated. Electrical conduits 82, 84, 86 and 88 extend from the console respectively to the power unit, unloading station, loading station, and bus 90 which provides electric power for various operations along the conveyor system.

It is, of course, essential that each pallet return to its original reload station because the necessary blanks for reloading the pallet are available only to the workman at that station. Therefore, each pallet has a distinctive index formation for cooperation with detection means. As previously noted, all of the pallets are in the form of disks and they are all of the same diameter which is substantially the same as the width of the conveyor sections between side rails so that the disks at all times during their travel will be located with their centers on the center line of the conveyor section. Each pallet is provided on its bottom or lower side with a concentric annular groove 92 which may be about an inch wide and an eighth to a quarter inch deep. All of the pallets belonging to one station have a groove of the same radius, which is measurably diiferent from the radius of the groove in any other pallet. Since the pallets presently being used are 39 inches in diameter the radii of the grooves may differ by several inches if desired.

As will be seen by reference to FIGS. 6 and 7, the detection and identification means comprise a pair of switch actuators 94 and 96 adjacent to each reload station, provided with sensors 98 and 100. The actuators are pivoted to the conveyor structure at 102 and 104 and their lower ends are adapted to contact switches 106 and 108. They are provided with load springs 110 and 112 and stops 114 and 116 so that they are biased to an inoperative position in which the tips of the sensors lie slightly above the upper plane of rollers 118. It will be seen in FIG. 6 that sensor 98 is located laterally of the center line of the conveyor a distance equal to the radius of groove 92 and that sensor is on the center line of the conveyor and onward of sensor 98 a distance equal to the radius of the pallet.

With this arrangement, as viewed in FIG. 6, pallet 60 approaches from the left. When its leading edge reaches sensor 98, it depresses it to the extent necessary for the sensor to pass under the bottom of the pallet. This motion is sutficient to cause the lower end of actuator '94 to contact switch 106 and pass beyond it to the dotted line position. As the pallet advances, sensor 98 will enter groove 92 and the lower end of the actuator will close switch 106. Since the relative movement of the sensor is along a tangent of the groove and the sensor is considerably narrower than the groove, the switch will remain closed during several inches of travel of the pallet. The sensor 98 will still be in the groove when sensor 100 is depressed by the leading edge of the pallet, closing switch 108 and cornpleting a series circuit through the two switches by way of conductor 120.

The circuit is completed through conductors 122 and 124 and a power source, to an actuator 126, FIG. 5, which supplies compressed air to servomotor 128. Roller track assembly 130 is pivotally mounted to the structure at 132 and is pivotally connected at 134 to the piston rod 136 of the servo motor. In inoperative position the assembly lies just below the upper plane of rollers 118. When the servo motor is actuated, it raises the left end of the assembly, as viewed in FIG. 5, and the entire assembly rises above the roller plane at an angle, picks up the pallet, and transfers it to the reload station.

As will be apparent from FIG. 6, pallet 138 passes the first reload station without triggering its roller track assembly because groove 140 is of smaller radius and sensor 98 does not enter the groove. Sensor 142 however will enter groove 140 and Will act with sensor 144 to cause the transfer of pallet 138 into the second reload station. If the positions of the two sets of sensors were reversed they would still react correctly because the sensor closer to the center line would enter and leave the larger radius groove at times when its cooperating sensor was not depressed.

Returning to FIG. 5, when the pallet 60 is discharged to its reload station it rolls onto elevator section 72 and its leading edge contacts switch 146. This action triggers actuator 148 which delivers compressed air to servo motor 150 which raises elevator section 72, guided by guide rods 152, to the level of the supply conveyor, and the pallet is then rolled onto reload table 58. The workman then removes the formed parts from the form blocks and replaces them with blanks and moves the reloaded pallet across transport section 76 onto the supply conveyor sectlon for return to the press.

The loading station and its transfer mechanlsm are illustrated in FIGS. 8 and 9, in which extension 154 of base carries a plurality of guides 156. Platform 158 is provided with guide rods 160 which are mounted for sliding movement in guides 156, and the platform 1s movable from its solid line position forward to the dotted line position adjacent to the press bed 12 by servomotor 159. The platform carries a plurality of ball transfer rollers 161 to facilitate movement of pallets 60 onto the platform from the supply section of the conveyor and then laterally onto the press bed.

A support plate 162 is mounted on platform 158 by standards 164 and carries depending guides 166 near 1ts forward end and depending bosses 168 near its rear end. Tubular guide rods 170 are slidingly mounted in guides 166 and telescope over interior guide rods 172 anchored in bosses 168. Guide rods 170 carry pusher foot 174 at their rear end and bar 176 at their forward end, the bar in turn pivotally carrying pusher foot 178. The bar 1s moved fore and aft by servo motor 180. Bar 176 is provided with a central boss 182 and side stop members 184. Pusher foot 178 is provided with a pair of rearwardly extending ears 186 which span boss 1'82 and are connected thereto by pivot pin 188. Clevis 190 is rigidly mounted on foot 178 and pivotally connected at 192 to piston rod 194 of servo motor 196. The latter is pivotally mounted on bar 176 by clevis 198. Operation of servo motor 196 swings foot 178 upwardly about pivot pin 188 to a sufiicient extent to clear a form block and its workpiece resting on a pallet.

The operation of the transfer mechanism takes place in two stages. In the first stage, servo motor 159 is actuated to move platform 158 together with all the elements mounted thereon forward toward the press until the forward edge of the platform is in juxtaposition with the near edge of the press bed as indicated by dotted lines in FIGS. 8 and 9. It will be seen that at this time the pallet to be loaded actually overlies the edge of the press bed and pusher foot 178 is very close to the pallet to be discharged. Servo motor 180 is now actuated and pressure feet 174 and 178 move forward with respect to the platform. As indicated in FIG. 9 in dotted lines, foot 178 moves almost entirely across the press bed and pushes the posit the succeeding pallet concentrically on the press be The pusher feet are now tron with respect to the of the retraction retracted to their original posiplatform, but at the beginning movement servomotor 196 is actuated to swing foot 178 upwardly so that it will pass back over the form block and workpiece now on the press bed without interference. When this step of retraction is completed, the platform itself is retracted to its original position shown in solid lines and is ready to receive the next pallet from the supply section of the conveyor.

The construction and operation of the unloading station are schematically depicted in FIGS. 10, 11 and 12. Transfer means to shift a discharged pallet to the receiving end of the return section of the conveyor system takes the form of a pair of side plates 200, 202 secured in verti cal spaced parallelism to structural members 204, 206 rlgidly attached to base 10. The side plates extend perpendicular to the direction of movement of the pallets received from the press and carry between them a belt 208 mounted on a series of pulleys arranged to provide a belt conveyor surface elevated slightly above the edges of the side plates and actuated to transfer pallets laterally of their direction of movement from the press bed to the un loading station.

Pulleys 210, 212 and 214 extend between side plates 200 and 202 and, as best seen in FIG. 12, support the belt in a horizontal plane to receive and move a pallet in the desired direction. Pulleys 216 likewise extend between the side plates 200 and 202, and the belt is so threaded over all of the pulleys as to provide two deep depressions or troughs 218, and the side plates are out way at 220 to provide clearance for the roller track means which receives the pallets from the press. Pulley 210 is driven by motor 211 by means of a chain drive.

The roller track means comprises two track sections 222 connected to each other, as in FIG. 11, by cross braces 224 and 226, each track section carrying a plurality of rollers 228. In FIG. 12 and in the solid line position of FIG. 10 the roller tracks are in retracted position and their rollers lie below the plane of the belt. Referring particularly to FIG. 10, it will be seen that the left, or remote, ends of track section 222 have depending side plates 229, each carrying a support roller 230 and a safety roller 232. The support roller rides on the upper surface of track 234, which is in the form of a horizontally extending flange, and the safety roller engages the under surface of track 234 to prevent unintentional displacement of the track sections. It will be noted that the extreme outer end of track 234 has an inclined upper surface 236 on which roller 230 rests when the track section is fully retracted in the solid line position.

As stated above, when it is fully retracted, the track section is horizontal and slightly below the level of belt 208. The forward end of the track section is pivotally connected at 238 to crank arm 240 which in turn is pivotal- 1y mounted at 242 on block 244. The lower end of the crank arm which extends below pivot 242 is pivotally connected to the end of extension 246, which in turn is connected to servomotor 248 by piston rod 250.

When the time arrives for a pallet 60 to be discharged to the unloading station, piston rod 250 is retracted, swinging crank arm 240 clockwise. This movement not only moves the track section forward but also raises it. At the same time roller 230 at the rear rides up the inclined portion 236 of track 240 and then moves forward on the horizontal portion. The crank arm produces more rise than the inclined portion 236 and consequently the track section is inclined to the left as viewed in FIG. 10, the foremost roller 228 being just level with press bed 12. When pusher foot 178 moves fully forward as previously described it pushes pallet 60 almost entirely ontotrack sections 222 and, since they are inclined, the

pallet will continue until it strikes stop 252. Piston rod 250 is now extended, crank arm 240 rotates counterclockwise to the full line position, and roller 230 returns to inclined portion 236, causing the track section to retract below the belt level. It therefore deposits the pallet on the belt and the latter transfers it to the receiving end of the return section of the conveyor.

It is sometimes desirable because of the loading rates of the workpieces on the pallets or because of limitations on floor space or arrangement to extend the conveyor system laterally of the press to each side. Such a modified arrangement is shown in FIG. 13 which schematically depicts an arrangement similar to that of FIG. 3 but with a second conveyor system comprising supply section 254 and return section 256 extending opposite to sections 42 and 44.

In order to route all of the pallets back to their original reload stations the detection system of FIGS. 6 and 7 may be used at the unloading station. In one form, belt 208 is replaced by two separate belts 258 and 260, leaving a clear area extending laterally of the direction of discharge movement of the pallet from the press and located at a distance of half the diameter of the pallet from the stop 262. A switch 264 is mounted on stop 262 to be closed by the contact of the pallet leading edge. A pair of sensors 266 and 268, for example, are located in the lateral clear space between the belts, each sensor being laterally spaced the proper distance to identify a particular selected pallet. As shown, sensor 266 enters the groove in pallet 60, closing a switch, not shown, which is in series with switch 264. When the two switches are closed simultaneously a circuit is completed through a directional switch for the belt motor 211, causing it and belts 258 and 260 to rotate in a direction to transfer pallet 60 to section 256. If, on the other hand, the groove in pallet 60 were to match sensor 268, the combination with switch 264 could be used to transfer the pallet to section 44. Obviously there may be several sensors for transfer in each direction.

As mentioned above in connection with FIG. 3, some or all of the conveyor rollers may be live, or driven, and they may be independently driven in large or small groups. For example, in FIG. 3, sections 66 and 68 of the rollers are desirably independently driven so that they may be held stationary at will to accumulate several loaded pallets adjacent to the loading station of the press.

FIG. 14 illustrates in schematic form a roller driving system suitable for the above purpose. A conveyor structure includes a base 270, end plate 272, and side rail 274 carrying conveyor rollers 276 for rotation. A belt 278 extends horizontally with one pass in proximity to rollers 276. It is carried on drive roller 280 and another roller, not shown, and the drive roller is driven by motor 282 through belt 284. Idler rollers 286 are mounted for rotation on a rail 288 which is provided with inclined slots 290. Side rail 274 carries pins 292 which engage slots 290 to support rail 288. As the latter is shifted horizontally in opposite directions as indicated by the arrows, it rises and falls, changing the position of rollers 286 with respect to belt 278.

When rail 288 is lowered, belt 278 sags sufiiciently to clear rollers 276 and they will remain stationary even if the belt is moving. When it is desired to positively drive rollers 276, rail 288 is moved to the left which causes it to rise and bring idler rollers 286 into contact with belt 278. They are actually raised to such a position that the belt cannot pass in a straight horizontal line between rollers 276 and 286. The serpentine path brings the belt into positive driving contact with rollers 276. This system is particularly useful when it is desired to use a long single drive belt and at the same time control several short sections of rollers independently.

In the system as presented, it is assumed that most phases of the various operations are to be controlled by the operator at the main console 80 adjacent to the loading station, or by the reload workmen using small auxiliary consoles. However, it is apparent that the system can be substantially fully automated if desired by the use of snap switches, limit switches, tape controls, etc.

The use of round pallets and a round press bed is particularly advantageous because it obviates the necessity of orienting the pallets at any stage in the operation. The circular planform also makes possible the coding formations which have been described. It should be noted that an important advantage of the system is that two or more pallets may be assigned to each reload station and used in the system at the same time without confusion or delay because of the coding arrangement and the fact that pallets can be placed on the supply section at random.

It will be apparent to those skilled in the art that various changes may be made in the construction and arrangement of parts as disclosed without departing from the spirit of the invention, and it is intended that all such changes shall be embraced within the scope of the following claims.

I claim:

1. Apparatus for forming sheet metal work-pieces to predetermined shapes, comprising: a hydraulic press having a rigid bed and a forming head; said bed being adapted to receive a pallet carrying at least one form block of predetermined shape with a sheet metal workpiece thereon; said forming head including a rigid backing member and an elastomeric member carried thereby and adapted to be forced by fluid pressure toward said bed and pallet to form the workpiece on the form block; said press being open at opposite sides at least on occasion for loading and discharge of pallets; a loading station at a first side of said press and an unloading station at the second side of said press; a conveyor system including a supply section having a receiving end remote from said press and a delivery end adjacent to said loading station, and a return section having a delivery end remote from said press and a receiving end adjacent to said unloading station; the receiving end of the supply section and the delivery end of the return section being adjacent to each other and defining an exchange zone; a plurality of reload tables at said exchange zone, each independently connected to said sections to receive selected pallets from the return section and discharge them to the supply section; means at the exchange zone to identify and divert selected pallets from the return section to each reload table; means to transport pallets from each reload table to the supply section; transfer mechanism at said loading station adapted to discharge a pallet from the press bed to the unloading station and to transfer a succeeding pallet from the loading station to the press bed; and transfer means at the unloading station to forward pallets to the adjacent end of the return section.

2. Apparatus as claimed in claim 1; and, in addition thereto, a second conveyor system of the same type extending away from the press in a second direction; and means at the unloading station to identify and divert selected pallets to each of the return sections of the conveyor systems.

3. Apparatus as claimed in claim 1; said press bed being circular in planform; and a plurality of pallets for use in the press; each pallet being circular in planform to obviate the necessity of orienting it for travel through the press or throughout the conveyor system.

4. Apparatus as claimed in claim 1; the supply section of the conveyor system being provided with load-supporting rollers throughout its length; at least some of said rollers being power driven to move the pallets from the exchange zone to the loading station; at least one group of said rollers at the delivery end being operable independently of the others to remain stationary and provide temporary storage for loaded pallets adjacent to the loading station while the other rollers are being driven.

5. Apparatus for sequentially forming a series of sheet metal workpieces to predetermined shapes, comprising:

a hydraulic press having a rigid bed and a forming head; said bed being adapted to receive a pallet carrying at least one form block of predetermined shape with a sheet metal workpiece thereon; said press being open at opposite sides at least on occasion for loading and discharge of pallets; a loading station at a first side of said press and an unloading station at the second side of said press; said loading station comprising a platform at the height of the press bed and adjacent thereto and adapted to receive successive loaded pallets from the supply section of a conveyor system; and transfer mechanism at said loading station including a first pusher foot at the edge of said platform adjacent to the press bed and a second pusher foot at the edge of said platform remote from the press bed, said first and second feet being adapted to respectively engage the margins of the pallet on the press bed and the pallet on the platform; and means to move said feet in unison toward the press and over the press bed a sufiicient distance to discharge the pallet from the press bed to the unloading station and to deliver the succeeding pallet from the platform to the press bed.

6. Apparatus as claimed in claim and means to raise the first foot to provide vertical clearance between it and the succeeding loaded pallet during the return stroke of the transfer mechanism.

7. Apparatus as claimed in claim 5; said loading station further comprising a base; said platform being mounted on said base for movement toward and away from the press; and said pusher feet being mounted on said platform for movement with and with respect to said platform; and means to move said platform a predetermined distance toward said press bed.

8. Apparatus as claimed in claim 5; said unloading station being provided with transfer means to deliver pallets to the return section of a conveyor system, and with roller track means movable toward and away from said press bed to receive each pallet and deposit it on said transfer means.

9. Apparatus as claimed in claim 8; said transfer means comprising a power driven belt traveling in part in a horizontal plane; said roller track means being movable to a position below said plane to release each pallet to said belt.

10. A system for selectively returning formed workpieces to their original reload stations, comprising: a return section of a conveyor system having a receiving end at a forming press and a delivery end defining an exchange zone, and provided with spaced rollers along its length to transport workloads; a plurality of reload stations at said exchange zone; an individual pallet for each reload station adapted to carry form blocks with workpieces thereon; each pallet bearing an index formation distinct from that of any other pallet; a diverter adjacent to each reload station adapted to transfer a selected pallet from the conveyor section to the appropriate reload station; and detection means adjacent to each reload station adapted to identify a selected pallet by its index formation and activate the diverter.

11. A system as claimed in claim 10; each pallet being in the form of a disk having a diameter substantially equal to the width of the conveyor section to insure that the center of the disk will be on the longitudinal center line of the conveyor at all points in its travel; each disk bearing in its bottom surface a concentric groove having a radius measurably different from the radius of the groove in any other disk; said detection means comprising a pair of switches and a pair of vertically movable switch actuators adjacent to each reload station; a first actuator of each pair being located laterally of the center line of the conveyor a distance equal to the radius of the groove in the selected disk to be intercepted and at such height that it will close its respective switch when it enters the groove in the selected disk; the second actuator of the pair being located on the center line of the conveyor and onward of the first actuator a distance equal to the radius of the disk and at such height that it will close its respective switch when it is depressed by the leading edge of the disk; said switches being connected to each other and to the diverter in series to cause activation of the diverter only upon simultaneous closure of both switches.

12. A system as claim in claim 10; each diverter comprising a roller track assembly arranged between rollers of the conveyor and movable between a first, inoperative, position slightly below the plane of the conveyor rollers and a second, operative, position above said rollers and inclined toward its respective reload station; and power means to raise said assembly to said second position to lift a selected pallet off the conveyor rollers and transport it to said reload station; said power means being activated by its associated detection means.

References Cited UNITED STATES PATENTS 2,600,038 6/1952 Whale-y 2l4l1 X 2,848,968 8/1956 Novak 72419 X 3,126,938 3/1964 McCoy 72419 X 3,149,736 9/1964 Austin et a1 19885 X 3,184,030 5/1965 Ludwig 19885 X 3,250,377 5/1966 Minichello et al 198-38 3,376,982 4/1968 Hutchinson 2141l MILTON S. MEHR, Primary Examiner.

US. Cl. X.R.

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