US2587076A

US2587076A - Punch press

Info

Publication number: US2587076A
Application number: US38916A
Authority: US
Inventors: Verson John; Kassnel Nick
Original assignee: Verson Allsteel Press Co
Current assignee: Verson Allsteel Press Co
Priority date: 1948-07-15
Filing date: 1948-07-15
Publication date: 1952-02-26
Anticipated expiration: 1969-02-26

Description

Feb. 26, 1952 v so ET AL 2,587,076

' PUNCH PRESS Filed July 15, 1948 8 Sheets-Sheet l zlbm Feb. 26, 1952 y s ET AL 2,587,076

PUNCH PRESS Fild July 15, 1948 8 Sheets-Sheet 4 1952 J. VERSON ET AL 7,07

I I PUNCH PRESS Filed July 15, 1948 8 Sheets-Sheet 5 Feb. 26, VERSON ET AL PUNCH PRESS Filed July 15, 1948 8 Sheets-Sheet e 3a 2 ZZZ/ Feb. 26, J. VERSQN ET AL PUNCH PRESS Filed July 15, 1948 8 Shets-Sheet 7 Feb. 26, J, \IIERSQIN ET AL PUNCH PRESS Filed July 15, 1948 8 Sheets-Sheet s Patented F eb. 26, 1952 PUNCH PRESS John Verson and Nick Kassnel, Chicago, 11]., assignors to Verson Allsteel Press Company, Chicago, 111., a. corporation of Delaware Application July 15, 1948, Serial No. 38,916

9 Claims. 1

The present invention relates to presses for drawing and forming sheet metal, and in particular to a novel convertible press that may be operated as single acting or double acting.

It has been difficult to obtain versatility in the design of metal working presses due to their large size, engineering problems encountered and the complexity of their operating and controlling mechanisms. These difiiculties are enhanced in combination presses, that is, presses wherein the drawing or blanking is performed mechanically and the work holding is performed hydraulically. And even further diificulties are encountered when it is desired to embody mechanical drawing with hydraulic blank holding in a convertible press which can be operated as a single action press and also as a double action press.

It is, therefore, the principal object of the present invention to provide a novel combination mechanical and hydraulic metal working press which can be operated either single acting or double acting.

Another object is to provide an improved combination single action and double action press which is operated fully mechanically when single I acting.

Another object is to provide a novel combination single action and double action press which is mechanically and hydraulically actuated when operated double acting.

A further object is to provide an improved combination single and double action press which provides complete control over the timing of the blank holding cycle. 7

Still another object is to provide an improved single and double action press wherein the timing of the blank holding cycle is accomplished from the work cycle. 7 i

Another object is to provide an improved combination single and double action press which may readily be changed to double acting from single acting and to single acting from double acting. l 4

Another object is to provide a novel-single and double acting press which when operated single acting has a work slide which is composed of the blank holder slide and the work slide of the 7 double action press.

Another object is to provide a novel interlock between the work and blank holder slides of a press so that these two slides may, if desired, be reciprocated in unison. I

Another object is to provide a novel combination singleand double acting press which when operated singleacting utilizes only the main or 2 work slide with the blank holder slide locked in its inoperative position.

And another object is to provide a novel combination single and double action press which when operated single acting may use either a work slide composed of the usual work slide locked to the blank holder slide or only the work slide with the blank holder slide locked in it inoperative position. I

And a further object is to provide a novel convertible single and double action press wherein the independent mechanism for reciprocating the blank holder slide is rendered inoperative when the press is operated single acting.

And still anotherobject is to provide a novel convertible single and double action press having a hydraulic system for effecting the blank holding operation when the press is operated double acting and incorporating means whereby the hydraulic pistons are disconnected from the blank holder slide and are locked in their cylinders when the press is operated single acting.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a frontelevational view of a press embodying the present invention;

'Fig. 2 is a side elevational view of the press and may be considered as being taken along the line 2-2 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is. an enlarged elevational view of the mechanical drive for the work slide or main platen;

Fig. 4 is an enlarged cross-sectional plan view showing constructional details, of the work and blank holder slides and may be considered as being taken substantially along the line 4-4 of Fig. 1, looking in the direction of the arrows;

Fig. 5 is a detailed sectional View of the interlock between the work slide and the blank holder slide, illustrating the locked position;

Fig. 6 is a detailed sectional view of the interlock between the work slide and the blank holder slide illustrating the unlocked position:

Fig. '7 is a detailed View showing a typical connection between a blank holder slide piston and the blank holder and illustrating the means for locking the blank holder slide piston to the crown of the press when the press is operated as single acting;

Fig. 8 is a diagrammatic view of a representative portion of the hydraulic control circuit and a typical electrical circuit illustrating the circuit components in top rest position;

Fig. 9 is a diagrammatic view similar to Fig. 8, illustrating the circuit components immediately after the start button has been pressed and the blank holder slide is in the rapid advance stage of its cycle;

Fig. 10 is a diagrammatic view similar to Fig. 8 illustrating the circuit components when the press has developed pressing speed and is in the drawing or forming portion of the press cycle; and

Fig. 11 is a diagrammatic view similar to Fig. 8 illustrating the circuit components after the press has reversed itself and the work andblank holder slides are being restored to the rest position.

General organization Referring primarily to Figs. 1 and 2, the press is shown as comprising a crown and a bed 22 interconnected by end columns 24; a bolster plate 28 is supported upon the press bed 22. The crown and bed are tied together by the conventional tie rods 28 by meansof whichthe press frame is prestr-essed; A mechanical drive mechanism 30 is mounted in theecrown 20 as are the blank holding cylinder-piston combinations 32 of which there are six in the embodiment of the press shown in this patent application. The mechanical drive 30 is suitably secured to a work slide or main platen 34 and the cylinder-piston combinations 32 may likewise be suitably and removably secured to a blank holder slide 36.

The blank holder slide is actuated when the press is operated as double acting by a hydraulic circuit 38 illustrated diagrammatically in Figs. 8 to 11. The hydraulic circuit includes solenoid operated elements which are controlled from an electrical circuit 4!! similarly diagrammatically illustrated in Figs. 8 to 11. These figures, for simplicity of illustration, show a hydraulic circuit having only three cylinders, but it is understood that any number of cylinders may be employed. Likewise, the electrical circuit is merely typical of any suitable electrical circuit that may be used in conjunction with the particular hydraulic circuit. v

Blank holder slide Referring particularly to Figs. 1 and 4, it will be observed that the blank holder slide 36 is guided on gibs 44, adjustably bolted to the columns 24. The blank holder slide 36 comprises a pair of end wall forming members 46, a rear wall 48, front wall 50, and top and

bottom plates

52 and 54, respectively. The blank holder slide is hollow and is formed with openings in the top and bottom plates through which the work slide 34 may move relative to the blank holder slide (Fig. 4). The work slide 34 is slidable on suitable adjustable gibs 58 carried by the blank holder slide 36. These gibs 53 are sufliciently long to permit the Work slide 34 to be guided thereby when the press is operated single acting with the blank holder slide 36 stationary.

The top plate 52 of the blank holder slide 36 is formed at the corners as indicated by the dash-dot lines in Fig. 4 with arcuate projections 68 to accommodate blank holder pistons 62. At the front and rear the top plate 52 is formed with smaller arcuate projections 64 to form places in which to secure blank holder piston rods 66. 70

Since the top plate 52 carries all of the load transmitted from the blank holder piston-cylinder combinations 32 to the blank holder .slide, it is additionally braced by suitable plates 68 which may be welded to the outer faces of the 4 blank

holder slide walls

48 and 50 and to the under side of the top plate 52.

A typical connection between a blank holder piston and the blank holder slide 36 is illustrated in detail in Fig. '7. Inasmuch as this connection is substantially the same whether it is for one of the blank holder .pistons 52 or for a blank holder connecting rod 66 only one such connection will be described.

When the press is operated single acting with the blank holder slide 36 locked to the work slide 34 for movement therewith, it is essential that the mechanical drive not be hampered by the fluid which otherwise would be trapped in the cylinders 10 and 14. Such trapped fluid would impose a nonproductive load on the work slide with the blank holder slide interlocked with the work slide. The nonproductive load can be removed from the work slide by disconnecting the pistons 62 and theconnecting rods 65 fromthe blank holder slide 36, but then these pistons and piston rods must be securedout of the path of the reciprocating blank holder slide which then is a part of the work slide. j

The structure for holding the pistons and connecting rods out of the path of the reciprocating blank holder slide is shown in detail in Fig. 7, which is taken with reference to one of the pistons 62 and cylinders 'lil. At the lower end of the cylinder I9 is a packing gland 16 held against displacement by a retainer ringflfl. The retainer ring '18 is secured in position by an annulus which is bolted to the lower open end of the cylinder it by means of 'aplurality of machine screws 82 extending through holes 83.

The lower end of the piston 62 is formed with a reduced portion having a threaded stem 84 which is adapted to be threaded into an annulus 85. The annulus 86 is removably secured by means of machine screws 88, extending through suitable holes 89, to the upper plate 52 of the blank holder slide 36. The annulus 86 is provided with a second set of holes 90 having enlarged openings 92 to accommodate the heads of the screws which are arranged so as to coincide with tapped openings 94 in the annulus 80. There are six of each of the

holes

83, 94 and 89, 99; and these holes are arranged alternately in the two

annuli

80 and 86.

When it is desired to operate the press as single acting, the screws 88 are removed from the upper wall 52 of the blank holder slide and the annulus 86 is moved upwardly against the lower face of the annulus 80. The screws 88 are in- 5 serted through the openings 98 and into the tapped openings 94 in the annulus 80 and by drawing the screws 88 up tight the annulus will be drawn against the annulus 8i! and the piston 62 locked within the cylinder 79. The 0 piston is thus prevented from slipping downwardly into the path of the reciprocating blank holder slide 36.

At other times when the press is operated single acting the blank holder slide may be held in its 65 upper or rest position by the fluid trapped below the piston heads 12 in the cylinders 14. In these circumstances it is not necessary to lock the pistons 62 to the press crown as they do not interfere with the mechanical reciprocation of the main slide 34 which is guided by the gibs 58 in the stationary hollow blank holder slide 38.

Interlock between the slides Under certain circumstances when it is desired 5 to operate the press as single acting, the blank locked and unlocked positions, respectively, in

Figs. and 6. The interlock comprises a pin 98 which extends through openings I00 and I02, respectively, in adjacent walls of the blank holder slide 36 and work slide 34. In the locked position the pin 98 is secured by means of a generally diamond shaped head piece I04 and bolts I06 to the wall 60 of the blank holder slide 36, and the pin 98 extends through the aligned openings I00 and I02 insuring that when the work slide 34 is reciprocated the blank holder slide is similarly reciprocated.

In unlocked position the bolts I06 are withdrawn from the tapped openings in the wall 50, permitting the withdrawal of the pin 98 from the opening I62. After the pin 98 has been withdrawn so that it no longer extends into the opening I02 it is turned through 90 so that the diamond shaped plate I64 has its long axis extending vertically and the bolt holes adjacent the more acute ends of the plate I04 coincide with tapped openings in bottom plate 54 of the blank holder and a block I08 which is welded to the wall 50 of the blank holder slide. The block I08 is of such size that when the inner face of the plate I04 bears against the blocks outer face, the inner end of the pin 98 is free of the work slide 34. The pin 98 is secured in the unlocked position by screwing the bolts I04 into tapped openings in the lower wall 54 and block I08.

Mechanical drive The mechanical drive 30 is most clearly shown in Figs. 3 and 2, and includes an electric motor indicated generally by the reference character IIO. The motor H0 drives a fly wheel II2 by means of a multiple belt pulley I I4. The fly wheel II2 has associated therewith a suitable air operated combination brake and clutch II6 which is controlled by a solenoid operated air valve I I1 (Figs. 8 to 11). The fly wheel and combination brake and clutch are mounted upon a shaft II8 which has a spur gear I20 secured to its outer end; the spur gear I20 intermeshing with an intermediate large gear I22 mounted upon and keyed to a stub shaft I24; the stub shaft has secured to it for rotation therewith a spur gear I26. The intermediate gear I22 meshes with a similarly sized second intermediate gear I28 which is mounted for rotation with a shaft I30 which has secured to it a spur gear I32 similar to the spur gear I26. The spur gears I32 and I26 drive a pair of bull gears I34 in opposite rotational directions as indicated by the arrows in Fig. 3.

One of the bull gears I34 is shown in detail and is mounted upon a shaft I36. An eccentric I38 is formed on or secured to one face of the bull gear I34 and drives a connecting rod I40. The connecting rod I40 includes the conventional split bearing I42, and part I44 is secured in position by means of the bolt and nut combination I46. The lower end of the connecting rod I40 is pivotally secured by means of the pin I48 to an adjustable thrust bearing mech- 6 brake I54 is provided for coaction with the fly wheel II2 to brake the action of the fly wheel II2 when it is desired to bring the wheel to a stop after a press run and sooner than it would stop by expending its stored up energy.

Hydraulic circuits The control circuits will be described with particular reference to Figs. 8 to ll wherein the component parts of the press and the control circuit are diagrammatically illustrated at different stages of the press cycle when the press is being operated as double acting. These illustrations are diagrammatic and the parts may not be properly proportioned as to size relative one to the other. In these figures, those parts of the hydraulic circuit and the electrical circuit which are operative during different stages of the cycle are indicated in heavier lines than the inoperative parts of the circuit. This will become apparent as the description of these parts pro gresses.

Fluid for the hydraulic circuit is obtained from a tank I60 which is located in the crown of the press. Fluid is circulated from the tank I60 by means of a hydraulic pump I62 having its inlets connected to the tank by inlet pipes I64 and having its outlets connected to conduits I66 and I68.

The hydraulic circuit is primarily controlled by a spring centered, solenoid controlled, pilot operated four-way valve I10. This valve shown is of the type manufactured by Vickers, Inc., of Detroit, Michigan, and is illustrated in U. S. Pat. No. 2,307,544. A pilot pump I16 supplies fluid for operation of the valve I10 and has its inlet connected by means of a pipe I18 to the tank I60 and has its outlet connected by means of a pipe I to the valve I10. A variable pressure relief valve I82 having a spill conduit I84 is inserted in the conduit I80 between the pump I16 and valve I10. Solenoids I12 and I14 control pilot valves I86 and I88, respectively, which in turn control the flow of fluid from the pump I16 to operate the four-way valve I10. A return conduit I90 is connected to the outlets from the pilot valves I86 and I88 and leads to the tank I60. The valve I10 has four ports, one port being connected to conduit I92 through which fluid under pressure from the double pump I68 enters the four-way valve I10. A second port is connected by a conduit I94 to the tank I60 and returns fluid to the tank I60 either while the press is at rest position, during which time no fluid under pressure is furnished to the cylinders or while the press is being run through the work phase of the cycle. The functions of and connections to the other two ports I96 and I98 will be explained in detail hereinafter.

Conduit I66 is connected to an unloading valve 200 which in turn is connected to a check valve 202 by a conduit 204 and to the tank by conduit 206. It likewise is connected to a relief valve 208 by conduit 2I0. The unloading valve is set at 900 p. s. i. The pressure relief valve is also connected to the conduit 206 which returns to the tank I60. The check valve 202 and pressure relief valve 208 are connected to the conduit I92, the former by a conduit '2I2.

During the work portion of the cycle fluid flows from the four-way valve I10- through the port I98 into a conduit 2-I4 which is connected to a pressure reducing valve 2I6 which is in turn connected through a conduit 2I8 to a port at the upper end of the cylinder 14 and above 7 the piston 12. The conduit 2| 4 also is connected to a variable sequence valve 226 which isconnected to a pair of pressure reducing valves 222 by a branched conduit 224. Each pressurev reducing valve 222 has its outlet connected to an unloading valve 226 by a conduit 228, and the unloading valve 226 is connected by a conduit 236 to the upper end of the cylinder 10. The pressure reducing valves 2I6 and 222 are connected by conduits 232 containing shut-off valves 234 and variable pressure relief valves 326 to a return conduit 238 which leads to the tank I66. Also connected to the pressure reducing. valves 2i6 and 222 are pressure indicating. gauges 240 which are protected by means of shut-oft valves check valve 246 and by branch conduits 248. The

branch conduits 248 are connected to the conduits 2I8 and 236 at or just ahead of the inlet port to the cylinders 16 and 14.

The unloading valves 226 are connected by means of conduits 256 to a return conduit 252 leading to the tank I66. The variable sequence valve 226 is connected to spill excess fluid to the conduit 252 through a conduit 254-. For a reason which will be apparent hereinafter, the conduit 224 connecting the sequence valve 226 with the reducing valve 222 is connected through a check valve 256 back to the sequence valve 226 for ridding the hydraulic circuit of excess fluid.

The conduit H4 is connected by a conduit 256 to a pressure operated unloading valve 266. The

unloading valve has its inlet connected by means of a conduit 262 to a port at the lower end of the cylinder 74 and regulates the back pressure against the piston 12 during such times as the press is being driven through the work portion of its cycle. The outlet from the unloading valve 266 is connected by means of. a conduit 264 to the port I96 of the four-way valve I76. This port iii) 39 is also connected by means of a conduit 266 containing check valve 268 to a second inlet to i the unloading valve 266, the conduit 266 being directly to the tank I66 by a conduit 216, the other outlet being connected to the tank I60 by a conduit 273 containing a solenoid operated valve 286 which when opened vents the valve 214 to allow the latter to open.

The reducin valve 2I6 is bypassed by a conduit 232 connected to the conduits 2I4 and 2I8 and containing a check valve 284.

e specific constructions of the unloading valve 266, the pressure reducing valve 2I6, the variable sequence valve 2 20, the pressure reducing valves 222, the unloading valve 226 and the unloading valve 266 are not part of the present invention and these valves may be of a type manufactured by Vickers, Inc., Detroit, Michigan. Specifically the unloading valve 296 may be of a type illustrated in U. S. Patent No. 2,260,824; the pressure reducing valves H6 and 222- may be of a type illustrated in U. S. Patent No. Re. 21,529,

illustrated in U. S. Patent No. 2,104,780 (Fig. 2).

These last three named patents are all owned by Vickers, Incorporated, as assignee of the inven-- Electrical circuit The various solenoids which have been referred to in discussing the organization of the hydraulic control system are in turn operated by the electrical circuit 46 which has heretofore been referred to only generally. A typical circuit is shown in Figs. 8 to 11 and is of the type wherein the control relays and switches are operated at a low voltage and the current for operating. the solenoids in the control circuit is of a higher voltage.

The current for the electric circuit is obtained from the line 366, 362 which may be a source of 440 volt 60 cycle current. The line 366 is connected to the primary of a step down transformer 364 by a conductor 386 containing a master switch 336 which preferably is of the knife type. Closing of the switch 338 conditions the electrical circuit for operation. The other end of the primary of the transformer 364 is connected by a conductor 3I6 to one terminal of a normally closed thermostatic overload switch BIZ which is in turn connected to the line 302. In some installations it may be desirable to combine the switches 308 and 3I2 into one master control and overload responsive switch.

Solenoid 3M controlling the air valve In for the combination air operated clutch and brake H6 is connected by conductor 3I6 to the conductor 366 and by conductor 3I8 to one terminal of a normally open switch 326. The other terminal of the normally open switch 326 is connected to a heater coil 322 arranged opposite the thermostatic switch 3I2. The heater coil 322 is connected through the thermostatic switch 3| 2 to the line 362.

The secondary of the transformer 304 is connected to

conductors

324 and 326. The conductor 324 contains a manually operable emergency disconnect switch 328.

The switches in the electrical circuit are under the master control of three

cams

336, 332, and 334 which operate, respectively, switches 336, 338 and 346. The cams are mounted on a camshaft 335 and make one complete revolution for every complete cycle of the press; the cams are thus synchronized to the operation of the main slide 34. The switches 336 and 333 are closed at the start of a press cycle while the switch 340 is open. The fixed contacts of the

switches

336, 338 are directly connected to the conductor 324. Switch 336 is connected by a conductor 342 to a pair of manuall operable start switches 344- and 346. Arranged in parallel with the

switches

344 and 346 is a holding circuit switch 348. The

switches

344, 346 and 343 are connected to

relays

350 and 352; the relay 356 is connected by conductor 353 to the conductor 326, and the relay 352 is connected by conductor 355 containing the normally closed switch 353 to the conductor 326.

Closing the start switches 344 and 346 energizes the

relays

356 and 352. Energization of the relay 356 closes the switch 348 and a switch 354 which is in series via the conductor 356 with a relay 353 and a time delay switch 360. The switch 360 is of the type including a time delay closing device of the dashpot type and made by the Cutler-Hammer Company of Milwaukee, Wisconsin.

Energization of the relay 352 moves the switch 360 toward closed position, but actual closing of this switch does not take place until after a predetermined time interval has passed. The relay 352 also actuates

switches

362 and 364 to'closed position. Switch 362 is parallel with the switch 360 through a manually operable switch 366.

Switch 366 and switch 368 in the conductor 324 are shown in Figs. 3 to 11 in the position in which they are set when the press is operated as a double acting press. They are moved to their alternate position when the press is to be operated as single acting.

With the circuit as shown in Figs. 8 to 11, it will be observed that the relay 358 is not energized until after the switch 360 closes, even though the switch 354 is closed immediately upon energization of the relay 350. When, however, the circuit to the relay 358 is closed, the latter closes switch 320, energizing the circuit to the solenoid 3I4, and also closes the switch 310 in the conductor 312. This conductor 312 including

switches

338 and 310 connects relay 358 to conductor 324 through a circuit in parallel with the previously described circuit and is, therefore, a holding circuit for the relay 358.

I Closing the switch 364 which is connected by conductor 314 to the conductor 324 and by a con ductor 316 to relay 318 energizes this relay through a normally closed slow-down position limit switch 380. Energization of the solenoid 318 moves switch 382 to the closed position. One terminal of switch 382 is connected to conductor 384 which is in turn connected to the line 302 through the bimetal thermostatic switch 3| 2. The other terminal of the switch 382 is connected by a conductor 385to solenoid 386 the opposite end of which is connected by conductor 388 to the conductor 306. The circuit which energizes the solenoid 386 is line 300, switch 308, conductor 306, conductor 388, solenoid 386, conductor 385, switch 382, conductor 384, bimetal switch 3l2, and line 302.

When energized the solenoid 386 opens the venting valve 280 so that this valve vents the valve 214 to allow the free flow of fluid through the valve 214 and conduit 216 to the tank I60. The circuit is thus in the energized position which is shown in Fig. 9 wherein the blank holder slide is advancing rapidly toward the bed of the press under the influence of gravity.

The conductor 316 is connected by a conductor 390 to a conductor 392 leading to relay 394 which is in turn connected by a conductor 396 with the switch 350. Thus when the switch 364 is closed, the relay 304 is energized through the circuit from the conductor 324 through conductor 314, switch 364,

conductors

316, 390, 392, relay 304, conductor 396, switch 359, conductor 326 and secondary of the transformer 304. Upon energization the relay 394 closes the three

switches

398, 400 and 402. The switch 398 is in a holding circuit to the relay 394 and is in parallel with the switch 364 having one terminal connected to the conductor 314 by a conductor 404 and having its other terminal connected to the conductor 392.

Closing of the switch 402 conditions the circuit to relay 406, the function of which will be described hereinafter.

Switch 400 is connected by a conductor 408 to the conductor 384 and by conductor M0 to the solenoid I12 which is connected by conductor 4I2 tothe conductor 306. The solenoid I12 is energized through the following circuit: line 300, switch 308, conductor 306, conductor 4I 2, solenoid 10 I12, conductor 4 I 0, switch 400, conductor 408, conductor 384, bimetal switch 3I2 and line 302.

The solenoid I12 controls the operation of the pilot valve I86 to allow fluid under pressure from the pump I16 to shift the valve I10 to connect the inlet conduit I92 with the port I08 which is connected to the conduit 2I4 whereby fluid is supplied to the upper ends of the cylinders 10 and 14.

When the blankholder slide starts its downward movement, top position limit switch 4I4 closes. One terminal of the limit switch 4M is connected to the conductor 326, and the other terminal is connected directly to the relay 406. The relay 406 is also connected by a conductor M6 to one terminal of the switch 402 which has its other terminal connected by conductor M8 to the cam-operated switch 340. The camoperated switch 340, which is open during most of the press cycle, is connected to the conductor 324. Closing of the switch 402 by the relay 394 and the closing of the top position limit switch by the movement of the blank holder slide away from its uppermost position conditions the circuit through the normally open switch 340 for energization upon closing of this switch later in the press cycle.

As the blank holder slide moves toward and just before encountering the work, it trips the slow-down position limit switch 380 to open it, thus breaking the circuit to the relay 318 to open the switch 382. Opening of the switch 382 deenergizes the circuit to the previously energized solenoid 386, and the valve 200 is closed thereby shutting off the free flow of fluid to the tank I60.

After the venting valve 280 has been closed any further flow of fluid from the cylinder 14 is through the unloading valve 260 and a back pressure is built against the blank holder slide which is moved downwardly by the fluid under pressure which it receives from the double pump I62 through the conduit 2I4. The arrows in Fig. 10 show the direction in which the fluid is flowing and. also the parts of the hydraulic and electric circuit which are energized during the "down pressing portion of the press cycle.

When the pressing operation has been completed, the properly timed cam 334 closes the' switch 340 to energize the circuit to the relay 406. Energization of the relay 406 closes switches .420 and 422 and opens switch 359. The switch 420 has one terminal connected to a conductor 424 which is connected to the switch 368 and thus to conductor 324, and has its other terminal connected by a conductor 426 to the conductor M6. The switch 420 is thus in the holding circuit which is in parallel with the

switches

340 and 402 and even though these switches may open subsequently, the holding circuit will maintain the. relay 406 in energized condition. The switch422 is connected by conductor 428 to the conductor 384 and by a conductor 430 to the solenoid I14. The other end of the solenoid I 14 is connected to the conductor 4I2 which connects it to the conductor 306. Closing the switch 422, therefore, energizes the solenoid I14 through the following circuit: line 300, switch 308, conductor 306, conductor 4I2, solenoid I14, conductor- 430, switch 422,'conductor 428, conductor 384, thermostatic bimetal switch 3I2 and line 302.

Simultaneously with the closing of the

switches

420 and 422, the relay 406 opens the switch 359 to break the circuit to the

relays

352 and 394.

Breaking the circuit to the relay 352 opens the

switches

369, 362 and 364. However, the relay 338, in series with switch 368, is continued energized through its holding circuit. Breaking the circuit to the relay 364 opens

switches

398, 406 and 482. Since the switch 420 is in parallel with switch 492, the circuit to the relay 486 remains complete. Opening the switch 398 breaks the holding circuit to the relay 384, and opening the switch 488 breaks the circuit to the solenoid I12.

Since the solenoid I12 is deenergized and solenoid I14 is energized, the pilot valve I88 is actuated to connect the hydraulic circuit through the valve I39 as shown in Fig. 11 wherein the inlet from the conduit N2 is connected to the port I96 and fluid is pumped through the

conduits

264, 266 and 262 to the lower inlet of cylinder 14 to move the blank holder slide 36 toward the uppermost position.

The circuit conditions shown in Fig. 11 continue until the blank holder slide is restored to its uppermost position, when the top position limit switch M4 is tripped open to break the circuit to the relay 486. Previously, however,

cams

338 and 332 had sequentially opened their switches 336 and 333, respectively, to break the circuit to the

relays

358 and 358 thereby to condition the circuit for another operating cycle.

Operation of pressSingZe acting When the press is to be operated as single acting with the work and blank holder slides inter locked, the blank holder slide 36 is disconnected from the pistons 62 and connecting rods 66 as has previously been described, and the pistons 62 and connecting rods 66 are locked against the lower ends of the cylinders and 14. The blank holder slide 36 is then mechanically connected to the work slide 34 by means of the interlocks 96 of which there are four.

In the electrical circuit the switches 366 and 368 are moved to their positions opposite from those shown in Figs. 8 to 11. Switch 366., therefore, short circuits the time delay switch 366 through the switch 362, and switch 368 is opened and renders inoperative that part of the circuit containing the position limit switches 389 and 4M, cam operated switch 348 and

relays

394, 318 and 406.

Inasmuch as none of the hydraulic circuit has to be used during the operation of the press as single acting, none of the solenoids I12, 114 or 386 are energized. However, the solenoid 3I4 must be energized, as it controls the air valve I I1 controlling the supply of air to the air operated combination clutch and brake I I6.

The master switch 388 is closed to condition the control circuit for operation, and then the start switches 344 and 346 are closed to energize the relays B and 352. Energization of the relay 350 closes the switch 348 to. the holding circuit for the relays 3 56 and 352 and also closes the switch 354 in series with the relay 358. The relay 352 closes the

switches

368, 362 and 364. Inasmuch as switch 369 is short circuited by the switch 362 through the switch 366, there is no time delay and the relay 358 is energized immediately. The relay 358 closes the

switches

310 and 320. Closing of the switch 326 completes the circuit to the solenoid SM and air under pressure is supplied immediately to the clutch I I6 to cause P it to engage the flywheel H2. Since the switch 364 is in the inoperative part of the circuit whether it is closed or not is immaterial.

As the press cycle nears its end the cam 338 opens the switch 336 to break the circuit 10 1 1? a

switches

348 and 362. This deenergizes the

relays

358 and 352, which in turn open the switch 348 in the holding circuit, and switches 354, 362, 368 .and 364. However, the circuit to the relay 358 remains complete through the holding circuit containing the

switches

338 and 318, and this circuit is not broken until immediately prior to the end of the press cycle, when the cam 332 opens the switch 338. This breaks the circuit to the relay 358 to open the

switches

318 and 326. It will be noted that the operation of the switches 336 and 33.8 is arranged so that the switch 336 will close before the end of the press cycle, and the switch 338 is closed immediately upon the termination of a press cycle.

When it is-desired to operate the press single acting without interlocking the slides as under the conditions just described, the switches 366 and 368 are moved to the single acting position. The hydraulic circuit is rendered inoperative except to maintain the blank holder slide 36 in its upper or rest position. Also the adjustable gibs 44 might be tightened against the blank holder slide 36 to brake the slide against any tendency to move as the work slide 34 is reciprocated. The

pistons 62 and 66-12 remain connected to the slide 36, and the interlock connection is not made. Operation of the press is initiated by pressing the button to close the start switches 344 and 346. The operation of the press continues-as described in the immediately preceding paragraphs-with the work slide 34 reciprocating on the gibs 58 in the blank holder slide 36.

It is within the skill of those versed in this art to arrange this circuit so that the press will run continuously without the necessity of pressing the start button each time.

Operation of press-Double acting When it is desired to operate the press as double acting, the blank holder slide 36 must be connected to the pistons 62 and connecting rods 66, and then the interlock between the blank holder slide 36 and the main slide or work platen 34 is disconnected by withdrawing the pin 98 from the hole I82 in the wall of the blank holder slide 34. The pin in its withdrawn position is rotated from the position shown in Fig. 1, and then fastened to the blank holder slide 36 by means of the screws I94 (Fig. 6). When these operations have been completed (assuming that they were necessary from a previous single acting operation) the blank holder slide 36 will be independent of .the work slide 34 and the blank holder slide will be held in its uppermost or rest posi tion by the hydraulic circuit which is in the condition shown in Fig. 8.

In the electrical circuits the switches 366 and 368 are set in the positions shown in Figs. 8 to 11.

Fig. 8 illustrates the hydraulic circuit in the rest position of the press. A column of hydraulic fluid is trapped on the under side of the piston 12 and is prevented from escaping by the

closed valves

214 and 268. Even though the motor or motors operating the pumps I62 and I16 are running, these pumps are doing no work, as the fluid from the pump I62 is circulated through the conduits I68 and 2I2 to the conduit I92 through the four-way valve I18 to the return conduit I94. Pump I16 circulates fluid through the variable pressure relief valve I82 and the pilot valves I86 and I88 and the return conduit I98. This circulation of fluid is shown by the arrows in Fig. 8.

When it is desired to operate the press, the

,master control switch 388 is closed and the but- 13 ton or buttons controllings the start"

switches

344 and 346 are pressed, manually closing these switches. The switch 368 energizes the circuit between the lines 366, 362, through the primary of the transformer 364. Closing the

switches

344 and 346 energizes the circuit through the secondary of the transformer to the

relays

356 and 352. The relay 356 closes the

switches

348 and 354. Switch 348, in parallel with the

switches

344 and 346, energizes a holding circuit to the two

relays

356 and 352, preventing their deenergization upon release and opening of the

switches

344 and 346. Closing of the switch 354 conditions the circuit to the relay 358 which is not energized immediately because there is a time delay mechanism incorporated in the switch 366.

The relay 352 immediately closes

switches

362 and 364 and slowly closes switch 366 through the previously mentioned time delay mechanism. Closing of the switch 3'64. however, completes the circuit through the relay 318 to close the switch 382 which is in series with the solenoid 386 controlling operation of the venting valve 286.

When the solenoid 386 is energized the valve 286 is opened and a small amount of fluid is allowed to pass through the conduit 218 to the tank I60 (Fig. 9). The opening of valve 286 vents the pressure relief valve 214 which opens and fluid flows from the cylinder 14 to the tank I66 through the conduit 216. The speed with which this fluid is allowed to flow from the lower part of the cylinder 14 is regulated by the adjustable metering valve 212 in series with the valve 214. The press is in the free fall or rapid advance stage of the cycle wherein the blank holder slide is moving rapidly toward the work and is exhausting hydraulic fluid from beneath the piston 12 through the conduit 262 leading to the valve 214 via the pressure resistance regulator valve 212. Fluid is supplied to the upper ends of the cylinders 16 and 14 through the conduit 244 including the check valve 246 and the branch conduits 248.

Simultaneously with the energization of the relay 318, the circuit to the relay 394 was closed. Energization of the relay 394 closes the switches 398, 466 and 462. Switch 368 is in a holding circuit which is in parallel with the switch 364 and prevents the deenergization of the relay 394 even though the circuit to the relay 318 be broken. Switch 462 is in a circuit to the relay 466 and closes merely to condition this circuit for future energization. The switch 466 is in series in the circuit containing the solenoid I12 controlling the flow of fluid to the pilot valve I86, and clos ing of this switch 466 energizes the circuit to the solenoid I12. The solenoid I12 operates the pilot valve I86 so that fluid is supplied to the main four-way valve I 16 to shift it so as to connect the conduit I92 with the conduit 2| 4 through the port I98. When the circuit is in this condition the fluid is supplied from the pump I62 through the conduits indicated by the arrows to the conduit 2I4 which is connected to the sequence valve 226 and to the pressure reducing valve 2 I 6. Fluid flows from the pressure reducing valve 2I6 through the conduit 2I8 to the upper end of the cylinder 14 above the piston 12. Thus fluid is flowing in the circuit which subsequently will supply fluid for the blank holding pressure, and the circuit is conditioned for the blank holding operation while the blank holder slide is in a free fall toward the press bed.

Inasmuch as the initial movement of the blank holder slide is somewhat slower than the move- 14- ment of the mechanically driven work platen toward the press, the switch 366 of the time-delay character is provided in the electrical circuit 46. After a predetermined interval of time has elapsed following the circuit energization just described, the switch 366 will close to energize the circuit to the relay 368 which closes the switches 316 i and 326. Closing of the switch 316 energizes the holding circuit to the relay 358 through the switch 338, which circuit is in parallel with the

switches

336, 366 and 354. ergizes the circuit to the solenoid 3I4 operating the air valve II1 which controls the supply-of air to the press clutch I I6. When the clutch H6 is engaged the mechanical drive for the work slide is rendered operative to send the work slide 34 through its work cycle which movement is not interrupted until the cycle has been completed.

Fig. 10 illustrates the hydraulic and electrical circuits during the forming or work producing portion of the press cycle. Just prior to the commencement of this portion of the cycle the blank holder slide 36 had tripped the slow-down limit switch 386 to break the circuit to the solenoid 318. This opened the switch 382 thereby deenergizing the solenoid 386 and closing the valve 286. When the valve 286 has been closed, flow of fluid through the conduit 216 will be stopped because valve 214 closes and the fluid is returned to the tank I66 through the circuit which will be described immediately hereinafter.

By the time the work producing stage of the press cycle has been reached the pressure of the fluid from the pump I 62 through the conduit I92, main valve I16 and the conduit 2 I4 has increased considerably so that a substantial pressure is built up in the cylinder 14 above the piston 12. This increased pressure likewise has tripped the sequence valve 226 so that fluid flows through the conduit 224, the pressure reducing valves 222 and the unloadin valves 226 to the cylinders 16 so as to supply blank holding pressure to the pistons 62. Fluid under pressure continues to supply pressure to the piston 12. The blank holding pressure holds the work against the die member which rests upon the press bed. Excess fluid is returned to the tank from the sequence valve 226 through the

conduits

254 and 252. Since the valves 2I6 and 222 are pressure reducing valves, excess fluid from these valves must be disposed of and is exhausted through the conduits 232, pressure relief valves 236 and return conduit 238.

A reactance pressure of about p. s. i. against the blank holder slide is obtained by the unloading valve 266 through which the fluid from the lower end of the cylinder 14 flows during this portion of the press cycle. The unloading valve is actuated to connect the conduit 262 with the conduit 264 leading to the port I96 of the main valve I16 by the pressure in the conduit 214 as transmitted to the valve 266 through the conduit 258. The port I96 is connected through the valve I16 with the drain conduit I94 leading to the tank I66. The fluid thus flows from the bottom of the cylinder 14 through the conduit 262, unloading valve 266, conduit 264, port I96, valve I16 and drain conduit I94.

Since the work slide 34 is crank driven it is mechanically reversed in its direction of movement after the eccentric I38 has been rotated from the position shown in Fig. 3. The blank holder slide 36 preferably continues the blank holding operation for an interval after termination of the forming operation to allow Closing the switch 326 en- 15 the work slide to strip its die from the work. Proper timing of this added holding operation is obtained by timing the cam 334 relative to the work slide cycle since the camshaft 335 is driven in synchronism with the work slide 34.

Referring to Fig. 11., there are shown the circuits in operative condition to restore the blank holder slide 33 to the normal or rest position. This part of the press cycle is under the influence of the timed cam 334 which on further counterclockwise rotation closes the switch 340 to engage the circuit to the relay 496. Energize.- tion of the relay 486 closes the switches 429 and 422. The switch 420 is in parallel with the switches 348 and M6 and closes the holding circuit for the relay 488. Opening the switch 359 breaks the circuit to the relay 334 to open the switches 393, 436 and 452. Opening the switch breaks the circuit to the solenoid I'I2, which permits release of holding pressure from the pilotvalve I86 and the centering of the spool in the four-way valve ITO. It is noted, however, that the energization of relay 486 closes the switch 422 in circuit to the solenoid I74. The solenoid I14 then moves the pilot valve I88 so as to connect the operating fluid from the pump I76 to shift the valve I'Hl so as to connect the conduit I92 through the valve I'IG with the port H36 and to connect the port I98 through the valve Il'fl with drain conduit I94. The hydraulic fiuid from the pump 262 is thus used to restore the blank holder side 33 to its uppermost position. The fluid'fiows from the pump I52 to the conduit I92 through the valve no, port N35, conduit 2G4, check valve "268 in the conduit 266, unloading valve 260, conduit 282 to the inlet at the lower end of the cylinder '14 and below the piston i2. Forcing of fluid under pressure through this circuit moves the piston 12 upwardly, and since the piston rod "53 is connected to the blank holder slide 35 as are the pistons 62, the three or six pistons, as the case may be, are moved upwardly and evacuate the fluid from the upper ends oi all the cylinders 70 and 14.

The fluid is forced from the upper end of the cylinder 74 through the conduit 2 I8, conduit 282, check valve 284, conduit 2I4, port I98, valve I?!) and drain conduit I94. The fluid is forced from the cylinders '0 through the conduits 239, unloading valves 225, conductors 2150 and drain conduit 252 which returns it .to the tank I59. This latter circuit is conditioned by fluid under pressure in conduit 21B actuating the unloading nlves to interconnect the

conduits

230 and 250. While the work slide .34 and-the blank holder lide 35 are being restored to "their uppermost positions, the

timing cams

33B, 332 and 334 continue their counterclockwise rotation. The timing cam 334 first opens theswitch 340 so as to condition the electrical circuit foranother cycle of operation. Then the timing cam 33.0 opens the switch 335 which deenergizes the holding circuit, including switch 348, for the relay35ll. Deenergization of the relay 35!! opens the

switches

348 and 354 likewise to condition the electrical circuit for a second or successive cycle of operation. .At approximately the same time, and timed to coincide with the return of the work slide to its rest position, the cam 332 opens the switch 338 to deenergize the relay 358. This opens the switches 370' and 320, thereby breaking the holding circuit to the relay 358 and breaking the circuit to the solenoid 3I4 thereby to close the valve controlling the supply of air under pressure to the air operated clutch H6.

When the blank holder slide 36 reaches its ill uppermostv position it trips the top position limit switch 4I4 which opens "the circuit to the relay 405, thereby opening the switches 42% and 422 and closing the switch 359. Closing the switch 35:3, however, does not energize either the relay 352 or the relay 358 inasmuch as the direct circuits to these relays have already been broken and conditioned for successive operation. Opening of the switch 420 breaks the holding circuit to the relay 406, maintaining it in deenergized condition when the top position limit switch 4M closes upon a successive operation of the press. Opening the switch 422 breaks the circuit to the solenoid I14. Since the valve H0 is of the selfcentering type, its valve spool is centered and the conduit I92 is connected directly through the valve I!!! to the conduit I94 and the fluid which is circulated from the pump I82 merely flows through the valve I10 without the use of any substantial pressure.

From the foregoing description it has been demonstrated that the objectives claimed for the present invention have been met. It is within the skill of those well versed in this art to make modifications and variations in this invention without deparitng from the spirit and scope thereof.

What is claimed as new and desired to be secured by United States Letters Patent is:

l. A convertible single and doube acting press comprising a work slide, means for reciprocating said'wor'k slide, a blank holder slide, hydraulic means separate from said work slide reciprocating means for reciprocating said blank holder slide, said hydraulic means including a cylinder, 2. piston 'reciprocable in said cylinder, means removably connecting said piston to said blank holder slide when the press is operated double acting, said last named means being adapted to secure said piston to said cylinder when the press is operated single acting, and means for con trollably supplying fluid under pressure to said cylinder to reciprocate said blank holder slide, manually removable means to interlock said blank holder slide with said work slide so that they may move in unison when the press is operated single acting, and manually operable selector means for rendering said fluid supplying means operative or inoperative during such time as the press is operated double acting or single acting. respectively.

2. A convertible single and double acting press comprising a work slide, means for reciprocating said work slide, a blank holder slide, hydraulic means for reciprocating said blank holder slide. said hydraulic means including a cylinder, 2. piston reciprocable in said cylinder, means removably connecting said piston to said blank holder slide when the press is operated double acting, a source of fluid under pressure, and controllable means connecting said source of fluid under pressure to said cylinder, and electrical means having means synchronized with the reciprocation of said work slide for actuating said controllable means, said electrical means including manually operable selector switch means for rendering a portion of said electrical means and all of said controllable means inoperative during such time as the press is operated single acting.

A convertible single and double acting press comprising a work slide, means for reciprocating said work slide, a blank holder slide, hydraulic means separate from said work slide reciprocating means for reciprocating said blank holder slide, means for removably connecting a part of said hydraulic means with said blank holder slide work slide reciprocating means and said hy-" draulic means so thatsaid blank holder slide is L reciprocated in synchronism with said work slide, said electrical control means includingmanually operable selector switch means for rendering a part of 's'aid electrical control means and said" hydraulic means operativeor inoperative during such time as the press is operateddouble acting or single acting, respectively, and removablemeans to interlock said work slide and said blank holder slide so that both said slides may be reciprocated in unison when the pressis operated single acting. 4., A convertible single and double acting press comprising a Work slide, means'for reciprocating said work slide, av blank holder slide, a cylinderpiston combination having a fixed part and a movable part, means for removably securing said movable part to said blank holder slide when the press is operated double actingand for removably securing said movable part to said fixed part when the press is operated single acting, a source of fluid under pressure including a fluid tank, valve means controllably connecting said source of fluid with said cylinder-piston combination when the press is operated double acting, a conduit including a second valve means connecting said cylinder-piston combination with said tank, and electric circuit means for actuating both said valve means and for controlling the operation of said work slide reciprocating means, said electric circuit means including means timed to the movement of the blank holder slide toward the work to actuate said second valve means to closed position to slow down said movement and to enable a holding pressure to be build up in said cylinderpiston combination and including means synchronized with the reciprocation of the work slide to actuate said first valve means to release the blank holding pressure and to enable said source of fluid under pressure to restore said blank holder to the start position, said electric circuit means including manually operable selector switch means for rendering both said valve means inoperative when the press is operated single acting.

5. A convertible single and double acting metal working press comprising a work slide, means for reciprocating said work slide, a blank holder slide, a cylinder-piston combination having a fixed part and a movable part, means for removably securing said movable part to said blank holder slide when the press is operated double acting and for removably securing said movable part to said fixed part when the press is operated single acting, a source of fluid under pressure including a fluid tank, valve means controllably connecting said source of fluid under pressure with said cylinder-piston combination to reciprocate said blank holder slide under pressure and to supply fluid under pressure for a blank holding operation, a conduit containing a second valve means connecting said cylinder-piston combination directly to said tank, other conduit means connecting another party of said cylinder piston combination directly to said tank, electric circuit means for actuating both said valve means and for controlling the operation of said work slide reciprocating means, said electric circuit means containing means timed to the movement of said blank holder slide toward the work to actuate said second valve means to closed position to slow down said movement and to enable a holding pressure to be built up in said cylinderpiston combination and including means synchronized with the reciprocation of the work slide to actuate said first valve means to release the blank holding pressure and to enable said source of fluid under pressure to restore said blank holder to the start position, said other --conduit means conveying fluid to and from said cylinder-piston combination during non-holding portion of the blank holder cycle, said other conduit means including means preventing inadvertent release of the holding pressure, and said electric circuit means including tmanually operable selector switch means for rendering both said valve means inoperative when the press is operated single acting.

6. A metal working press comprising a work -'slide, means for reciprocating said work slide, a

blank holder slide, hydraulic means for reciproeating said blank holder slide, said hydraulic means comprising a source of fluid, a fixed cylinder, a piston reciprocable in said cylinder and secured to said blank holder slide, means for transferring fluid under pressure from said fluid source to one end of said cylinder to urge said piston and said blank holder slide toward the work under pressure, main valve means associated with said transferring means for controlling the flow of fluid to said cylinder, conduit means connecting said end of said cylinder with said fluid source, a valve in said conduit to prevent fluid flow from said cylinder to said fluid source, second conduit means connecting the other end of said cylinder with said fluid source, controllable valve means in said second conduit means, third conduit means connecting said second end of said cylinder with said fluid source through said main valve means, an unloading valve in said third conduit means, means timed with the movement of the blank holder slide to actuate said controllable valve means to stop fluid flow through said second conduit means, and means timed with the work cycle of the press to control said main valve means whereby said hydraulic means reciprocates said blank holder slide and applies a holding pressure thereto.

7. In a convertible single and double acting press the combination of a reciprocable work slide, a reciprocable blank holder slide, said blank holder slide having an opening extending vertically therethrough through which said work slide is reciprocable, alignable openings in adjacent walls of said slides, a pin having a shank adapted to extend through said openings when aligned to interlock said slides for reciprocation in unison, said pin having an elongated head with at least one aperture therethrough, a block secured to and standing out from the outer face of said blank holder slide wall adjacent said wall opening therein, and means for securing said pin head in a first radial position to said block so that said shank projects into the wall opening in only said blank holder slide and for securing said pin head in a second radial position directly to the wall of said blank holder slide so that said shank projects through said blank holder slide wall opening and into said work slide wall opening.

8. In a convertible single and double acting press, the combination of a reciprocable work slide, a reciprocable blank holder slide, and means for reciprocating said blank holder slide, said means including a hydraulic cylinder and a piston reciprocable therein, a mounting annulus secured to and carried by said piston outside of 19 said cylinder, meansremo'vably securing said annulus to said blank holder slide when the press is operated double acting, said annulus being adapted to be secured to said cylinder thereby to prevent reciprocation of said piston in said cylinder when the press is operated single acting, manually operable means for rendering said hydraulic means inoperative when the press is operated single acting, and removable means to interlock said work slide and said blank holder slide so that both slides may be reciprocated in unison.

9. In a convertible single and double acting press, the combination of a reciprocable work slide, a reciprocable blank holder slide, hydraulic means for reciprocating said blank holder slide, said hydraulic means including a hydraulic cylinder and a piston reciprocable therein, means removably securing said piston to said blank holder slide, said last named means being adapted,

20 interlock said work slide" and said blank holder slide 50- that both slides may be reciproeated in unison. 7

JOHN VERSQN.v NICK KASSN-EL.

REFERENCES" CITED 7 The following references are of record in the file of this patent:

UNITED STATES PATE- NTS Number Name Date 538,013 Cushxn'an Apr. 23,1895 1,263,401 Fraser Apr. 23, 1918 1,891,121 Thores'on -a Dec. 13., 1932 2,143,429 Auble Jan. 10, 1939 2,219,385 Ernst Oct. 29, 1940 2,305,336 Williamson Dec. 15, 1942 2,323,410 Muller July 6, 1943 2,460,612 Vers'on Feb. 1, 1949 FOREIGN PATENTS Number Country Date 25,954 Austria of 1906