US2380153A - Hydraulic draw press - Google Patents

Description

July in, 1945. R. E. DAVIS v 2,380,153

HYDRAULIC DRAW PRESS Filed April 30. 1941 2 Sheets-Sheet 1 INVHVTOR.

I Lssggoals --H -|;HAHD E. III/was.

July 10, 1945. R. E. DAVIS HYDRAULIC DRAW PRESS Filed April 30, 1941 2 Sheets-Sheet 2 1J5in M SSW A }A 14 A; 9

I J L 4 I08 j I09 3 INVENTOR. RICHARD E. DAVIS W ATTORNEK Patented July 10, 1945 UNITED STATES caries 35 mmuucpnawranss ilt'tnielc":'ml?,';idislisz poratlon of Wisconsin pplication April so, 1541; Sbl'lflihihifilzllfi'l 12 Claims.

This invention relates to hydraulic presses oi the type employed for forming or drawing work pieces or blanks into desired shapes, and it is Particularly pted to Dresses 0! large capacity, a

A press of the type to which the invention relates in particular is provided with a die arranged in a stationary position, a movable die carried by at least one main hydraulic motor and adapted to cooperate with a stationary die to form or draw a work piece or blank into a desired shape, and a draw ring carried by a plurality of hydraulic clamping motors and adapted to press a marginal portion or the blank against a stationary abutment such as marginal portion of the stationary die. The movable die and the ram oi the main motor are ordinarily advanced at high speed until the die is close to or engages the the blank, the clamping motors are energized and cause the ring to clamp the blank against the abutment, then the main motor is energized and slowly advances the movable die to force the blank into or over the stationary die to perform the forming or drawing operation, and then the movable die and the draw ring are retracted, thereby completing a cycle 01 operation During the forming or drawing operation, a prede- FIZZ-1 1 3 EOJEBB/IIIIDEUGVIW' showing the pies men al: e m

tlon dlfl a valvesi' f Q 'm 1 'For-thepurpose or ilius'tration the; v 'tion har he mli ad w w f i s i "pressthe platen? I Eidraw'ririg'oi which arerapid travers vi we bit sw atshirts to be-incarnate umvenuou'mcy be matured "in southern or pwamflsttmg ea r s cum" enha ces wen I1 steam raw e f! of which h nna traversed by, auxiliary motors and} the terms used herein to denote As shown, the press'hasalpw'er ste icnaryjted fixed a) the press frame which. Sm 11th of conventional construction, snn'rorms ndiia t or the present invention, not been ,1 l1stratedbut it is to; be undrstoddlihat, the platen andjthe termined pressure is maintained in each'clamping motor which necessitates wasting power.

The present invention has as an object to provide a press of the above character that will operate at high speed and will exert large pressing forces with a minimum loss of power.

Another object is to provide a press that is positive and precise in operation.

Other objects and advantages will appear from the description hereinafter given of a press in' which the invention is embodied.

According to the invention in its general aspect and as ordinarily embodied in a downward acting press, the movable die and the draw ring are rapidly advanced by gravity until the ring is about to engage the blank, then liquid from a large pump energizes the clamping motors and causes them to press the draw ring against the blank, the large pump continues to deliver liquid dra re sta y see e t a thatallstatioriary partsjarilxed simtiol a v ow r, 'di 'ii l has a hat pdrtion to pro idesigwment. for supporting awork piece etailing; and

which coordinates with n er die i'orm draw bla k inio? a d s r to the clamping motors until pump pressure exceeds a predetermined value and then the pressure in the clamping motor is maintained by a small pump and the liquid discharged by the large pump is directed to the main motor and causes it to advance the movable die to perform the drawing or forming operation.

The invention is exemplified by the press shown schematically in the accompanying drawings in which the views are as follows:

' time; by aisl- Upper diejjl is carried; by aplate'nt is cylinder 1 and which ecnn ted a flma'wrlphe i s aj lm tv me fixes r r w r he Wiih, and e e dln's be e th a e h tl lanse or'a plurality or flanges l2 extending in ard it m and fixed to or iormed integral with a drawring i which er'ttends dplaten 5 directly abpve the marginal portion oflowerjdie 2,.

Draw ring a is dat d o be pr ss d new r 'l vi ff s bt m. t mm H W'br'v qh r sten d jw i is and'extend, respectively, into srsne rm iindjers' I5 an is; e press chosen for tion is ordinal-11y providedwith at least six clamping motors which are'divided into pairs and'each pair is controlled by a valve it having a valve communication between an admission port It and two distributing ports and 2" formed therein.

Since the clamping motors are identical both as i to structure and function and are controlled by identical valves, only one pair of motors has been shown.

The press is powered by a large capacity pump which is reversible and a much smaller capacity pump 26 which draws liquid from a surge tank 21 and discharges into a channel 28. Pump 26 is oi the type that will deliver liquid at its maximum adjusted rate until the pressure created by it reaches apredetermined maximum and then it will automatically reduce its displacement until it is delivering lust sufllclent liquid to maintain that maximum pressure constant.

In order to avoid unnecessary loss of power, channel 28 is normally connected through a bypass valve 29 to a drain channel 3' which discharges into surge tank 21. Valve 20 has a valve plunger Ii fitted in its casing to control communicatlon between channels 2! and ll and between channel 28 and a port 32 to which all of the clampin cylinders ii and I5 ar connected as will presently be explained. Plunger II is norextensive use. Since such a pump is shown and described in application Patent No. 2,269,778, it is deemed sufllcient to state herein that it is controlled by two solenoids 3i and 38, that its displacement and delivery will be reduced to zero when both solenoids are deenergized, that it will deliver liquid into one and have liquid returned to it through the other or two branched channels "and 38 when one or the other or the two solenoids is energized, and that any deficiency or excess in the liquid returned to the pump 2! i compensated for by liquid drawn from or discharged into surge tank 21.

Communication between pump 25 and tank 21 is controlled by a differential valve 3! arranged in a bore 40 which communicates at or near its center with tank 21 through a check valve II and a low pressure resistance valve 0. Branches of channels 31 and I8 communicate with bore I at opposite sides of its center and are connected.

respectively, by channels I! and Il to opposite ends oi bore It.

The arrangement is such that, when the pressure is higher in one than in the other of channels I1 and 3!, liquid will flow from the high pressure channel through channel 43 or Q! to the end of bore II and shift differential valve ll in a direction to cause it to block the end of the high pressure channel and uncover the end of the low pressure channel so that liquid cannot escape from the high pressure channel into tank 21 but liquid may be discharged from the low pressure channel into tank 11 through resistance valve 42, or pump 25 may draw liquid from tank 21 through check valve I.

Pump 25 is employed to control the speed of platen 5 and draw ring I 3 during gravitational descent thereof. to supply liquid to the clamping motors at the end or the gr vitational descent to enable them to force ring l3 against blank 3, to supply liquid to main motor Bl to enable it to perform the pressing operation, and to supply liquid to the pull back motors to enable them to raise platen 5 and ring ll.

nee les.

In order that pump 25 may energize the clamping motors, channel I! is connected to port is in valve l8 and ports it and Ill thereof are connected by channels SI and SI to cylinders II and I5 respectively.

In order that pump 25 may control the rapid traverse descent of platen 5 and in order that it may supply liquid to the pull back motors to cause them to raise platen 5, a channel ii has one of its ends connected to the lower ends of both of cylinders II and It and its other end connected to channel 3| through a check valve 52, a resistance valve 53 and a blocking valve 5| which when open bypasses valves 52 and i3. Blocking valve 54 has a. valve member or plunger 5 arranged in its casing to control communication between two annular groovw or ports 58 and 51 which are formed therein and have channels 38 and Il connected thereto respectively. a spring II for urging plunger SI to the position shown in Fig. l and normally keeping valve it closed, and a solenoid 59 for moving plunger 55 to the position shown in Fig. 5 to open valve 54.

The arrangement is such that, when pump 25 is adjusted to discharge liquid into channel 88. the liquid may ilow freely through check valve I2 or through blocking valve 5| if it is open and then flow through channel II to the lower ends of cylinders ll d ii and cause pistons 9 and 9 toraisep landdrawringll.

When pump 26 is idle, valve 5| is closed and platen 5 and draw ring I! are supported in their upper positions by liquid which is trapped in the lower ends of cylinders ii and ll for the reason that the pressure required to open resistance valve 53 is higher than the pressure required to enable pistons 9 and O'to support the weight of platen i and draw ring it.

When pump 25 is adjusted to discharge liquid into channel 31, valve 54 is open and pump 25 will draw liquid throughchannel 88, valve 84 and channel 5| from cylinders II and Ill and permit platen i and draw ring it to descend by gravity at a rapid traverse rate. That is, pump 25 will meter the outflow from cylinders II and ill and thereby govern the rate at which platen l and ring I! descend.

Platen l and ring l3 will descend at rapid traverse rate until ring II is about to engage blank land then valve ii is closed which will momentarily arrestdownward movement of platen I and draw ring I! for the reason that liquid can then escape from cylinders It and It only through resistance valve 53.

During this time, pump II has been delivering liquid through channel 11, valve it and channels 5. and II to all of the clamp ng linders I! and ii but the total volume supplied to cylinders I! and I! is insumcient to keep them filled. However, suiilcient additional liquid to keep cylinders I! and I5 fllled is supplied thereto from tank 21 as will presently be explained.

As soon as valve it closes and arrests the gravitational descent of ring II. the liquid delivered by pump 2! to cylinders I5 and ii will create pressure therein and cause rams it and itto move ring I! downward against blank 3 and will then create sufllcient additional pressure to cause cylinder i5 r i may be adjusted independently of the pressure in any other clamping cylinder, each clamping motor is provided wi'thRa-separate pressure regulating'unit. shown, motor l'L-l 5 is provided with a untt consisting of two oppositely opening resistance valves 60 and il which may be simultaneously adjusted to vary the resistance thereof inversely to each other by rotating and adjusting screw 52 but the sum of the resistances of the two valves remains constant and the pressure required to open both valves simultaneously is greater than the maximum pressure that pump 26 can create.

Resistance valve 50 has its inlet connected to cylinder I5, as by being connected to channel 50. and its outlet connected to tank 21 by a channel 63. Resistance valve 5| has its inlet connected by a channel 64 to port 32 in bypass valve 29 and its outlet connected to channel 58. In order that clamping cylinder l5 may be supplied with liquid from tank 21 when draw ring I3 is moved downward at rapid traverse speed. channel 53 is connected to channel 50 through a check valve 65 which permits liquid to flow from channel fii'into channel 50 but prevents flow in the opposite direction.

The pressure regulating unit for each of the other clamping cylinders is identical to and connected in the same manner as the above described unit. Consequently. a description thereof is unnecessary, the corresponding parts of the unit for cylinder l5 being indicated by corresponding reference numerals with the exponent a added thereto. While only two pressure regulating un ts have been shown connected to port 32 in bypass valve 25, it is to be understood that all of the pressure units are connected thereto.

Each resistance valve 50 or 60' is adjusted to open at a pressure slightly higher than the ressure desired in the clamping cylinder to which it s connected, and each resistance valve Bl or iii is so adjusted that the drop in pressure ther across is equal to the difference between the pressure desired in the clamping cylinder associated therewith and the maximum pressure created by pump 26.

For example, if a pressure of 2200# per sq. in. were desired in cylinder l5 and pump 26 were adjusted to create a max mum pressure of 25001: per sq. in., resistance valve 5| would be adiusted to close at 3001* and resistance valve 60 would be adjusted to open at about 221011. Then. if the pressure in cylinder l5 should be too low when bypass valve 29 is opened. liquid from pump 26 would flow through channel 28, valve 29 and channel 64 to resistance valve 5i and open it and then flow therethrough arid through channel in to cylinder l5 until the pressure th'erein reached 2200# at which time valve Bl would close. If the pressure in cylinder i5 should become too high for any reason. valve iii would open and ermit liquid to escape therefrom until the pressure therein was reduced to 22l0#.

Since the drop in pressure across each res stance valve 5| or Si is equal to the difference between the pressure created by pump 26 and the ressure in the clamping cylinder l5 or Li assoc ated with that valve, the pressure in each clampng cvlln ler is independent of the pressure in any other clamping cylinder.

During gravitational descent of platen 5. rar" cylinder 1 is kept filled with liquid suppli d thereto from tank 21 under the control of a sur e valve In which is arranged in a valve casing li connected to cylinder 1. Valve 'iil controls communication between cylinder I and. a channel 12 which connects oneend ofcasing llrto -tanlilh andbetween cylinder and a port I: which is-connected tochannel 31 by channelii.

Surge valve I0 is adapted to be shifted to one are connected in parallel and open in oppositev directions.

In order that cylinders l5 and i5 may be dis- V connected from pump 25 after pressure has been created therein and before pump 25 delivers liqu d to ram cylinder 1, valve It has its left end con-' nected by a channel BI to channel 18 intermediate the ends thereof and, in order that pressure may be maintained in cylinders i5 and l5 until after ram 5 has stripped die 5- from the article into which blank 3 was formed, valve l6 has its right end connected by a channel 82 to channel 38 through a hold-down valve 83 and a check valve 84.

Valve 53 has a plunger 85 arranged in its casing to control communication between two ports 85 and 8! to which channels 38 and 82 are connected respectively. Plunger 85 is urged to the position shown in Fig. l by a spring ill and it is adapted to be shifted by a solenoid 89 to the position shown in Fig. 6. I

The arrangement is such that. when platen 5 and draw ring l3 descend by gravity, surge valve I0 is in the position shown in Fig 1 and liquid flows freely from tank 21 through channel 12 and surge valve casing II to ram cflinder 1 and from tank 21 through channels 63 and 63, check valves 65 and 65 to cylinders i5 and I5 to keep cylinders I. I5 and I5 filled with liquid.

When draw ring I3 meets the work, pump 25 creates pressure in cylinders l5 and l5 until the pressure becomes high enough to open resistance valve and then liquid will flow through channels 31 and Hi and resistance valve 80 into chinnel 18. Since the force required to move surge valve 10 is greater than the force required to move plunger I! of valve iii. the liquid'will first flow from channel 18 through channel 8| to the left end of valve l5 and shift it plunger i! to the position shown in Fig. 4 to block communication between pump 25 and cylinders I5 and i5, and plunger I! will eject liquid from the right end of valve i5 through channel 82 and check valve Bl into channel 38. As soon as plunger I1 is shifted. pressure will rise enough to enable the liquid in channel 18 to enter cylinder 16 and cause piston 15 to shift surge valve I5 tothe position shown in Fig. 3. liquid being expelled by piston 15 from the right end of cylinder 16 through channel 11 into channel 38.

Moving surge valve 10 to the position shown in Fig. 3 blocks communication between cylinder i and channel I2 and opens communication between cylinder 1 and port 13 so that liquid from pump 25 may flow through channels 31 and I4 and surge valve casing H to cylinder 1 and cause ram 6 to move platen 5 downward.

When pump 25 is reversed. plunger 85 of blocking valve ill is in the position shown in Fig. 6 so that the liquid discharged by pump 25 cannot shift plunger II of valve I5 but will flow through channels 38 and H to cylinder 15 and cause piston 15 to shift surge valve III to the position and channels 50 and Ell shown in Fig. l to open cylinder I to channel I2 and to block the end of channel It. Piston I will eject liquid from cylinder I6 through channel II, check valve 19 and channel H into channel 31.

The electric circuit An electric circuit which may be employed for controlling the press is shown in Fig. 2 in which the numerals 90 and 9| represent two sides of a power line from which current for energizing the several solenoids is supplied thereto under the control of various switches.

As shown, solenoids 35 and 35 which control pump 25 are controlled, respectively, by two magnetic switches or contactors A and B. contactor A includes three normally open switches A A and A, a normally closed switch A and a magnet A" which when energized will open switch A and close switches A, A and A. Contactor B includes two normally open switches 13 and l? and a magnet 13 which when energized will close switches 13' and B".

Solenoid 95 has one end of its winding connected by a conductor 92 to one terminal of switch A the other terminal of which is connected by a conductor 93 to power conductor 90. The other end of the winding of solenoid 35 is connectedby a conductor 04 to one terminal of switch A the other terminal of which is connected by a conductor95 to power conductor 9i.

contactor A is controlled by a normally closed stop switch Si, a normally open starting switch S2 and either by a normally closed limit switch LSI, which is opened when platen 5 reaches a given point in its down stroke, or a normally closed pressure responsive switch PSI which opens when the pressure in ram cylinder I reaches a predetermined maximum. As shown, pressure switch PSI is subjected to the pressure in cylinder I as by being connected thereto through surge valve casing II and limit switch LSI is arranged in a stationary position and an arm 96 on platen 5 has an actuator 91 so located thereon that it will open switchLSl when platen 5 reaches a given point in its down stroke, such as when die I has completed its operation upon blank 9.

While for the purpose of illustration pressure switch PSI has been shown connected directly to surge valve casing II so that it is subjected to the full pressure created in cylinder I, in practice a low pressure switch is employed and connected to surge valve casing II through a high pressure resistance valve, so that the switch is subjectedto only a low pressure, and a check valve is provided to permit liquid to escape from the pressure switch when the pressure in ram cylinder 1 drops to a low value.

The winding of magnet A has one end thereof connected to power conductor 90 by a conductor IM and the other end thereof to one terminal of starting switch S2 by a conductor I02. The other terminal of switch S2 is connected by a conductor I09 to one terminal of stop switch SI the other terminal of which is connected to conductor Si by a conductor I00. Conductor I02 is connected by a conductor I05 to one terminal of switch A the other terminal of which is connected by a conductor I05 to one terminal of limit switch LSI and to one terminal 01' pressure switch PSI. The other terminals of switches PSI and LSI are adapted to be connected to conductor I00 by a selector switch which may be adiusted to connect either of these switches into the circuit and to simultaneously cut the other switch out of circuit.

conductor 95 is connected, a second contact connected by a conductor I00 to one end of the winding of solenoid 39 the other end of which is connected to conductor 90, a third contact connected by a conductor I09 to one end 01' the winding of magnet 1? the other end of which is connected to conductor 90 by a conductor H0, and a fourth contact connected byra conductor III to one terminal of switch A the other terminal of which is connected to conductor I03 by a conductor I I2 so that, when switches A and LS2 are closed, magnet B and solenoid 34 will be energized.

Solenoid 36 has one end of its winding connected to conductor 90 by ,a conductor H5 and the other end thereof connected by a conductor H6 to one terminal of switch B the other terminal of which has conductor I09 connected thereto. Switch B has one of its terminals connected to conductor I03 by a conductor III and its other terminal connected to conductor III by a conductor I I8.

Solenoid 59 is controlled in part by contactor A and in part by a normally closed limit switch LS3 which is opened just before draw ring I3 engages blank 3. As shown, limit switch LS9 is arranged in a stationary position and operated by an actuator I I9 carried by draw ring 13. Solenoid 59 has one end of its winding connected to conductor 92 and the other end thereof connected by a conductor I20 to one terminal of limit switch LS3 the other terminal of which has conductor 94 connected thereto.

Solenoid 09 is controlled by a normally closed limit switch LS4 which is opened when platen 5 approaches the end of its up stroke. As s own, limit switch LS4 is arranged in a stationary position and operated by an actuator I2I carried by arm 95 on platen 5. Solenoid 09 has one end of its winding connected to conductor and the other end thereof connected by a conductor I22 to one terminal of limit switch LS4 the other terminal of which is connected to conductor 9| by a conductor I23.

Operation with the parts in the positions shown and pumps Hand 25' running, pump 25 is at zero stroke so that no liquid is delivered thereby, pump 25 is discharging freely through valve 29 into tank 27, and platen 5 and draw ring I3 are being held in their upper positions by the liquid trapped in the lower ends of pull back cylinders I0 and I0 by valve 55 being closed.

To start a cycle of operation, switch S2 is closed to establish a circuit (9Illl4SI-I03S2 |02-A -l0I-90) to energize magnet A which will close switches A A and A and open switch A.

If selector switch SSI is adjusted to connect limit switch LSI in circuit as shown, closing switch A establishes a circuit (9II0l-Sl I03 SSIl.SI-I05A*l05I02A-I0l- 90) to keep magnet A energized and switches A, A and A closed and switch A open.

Closing switches A and A establishes a circuit (0093A -823594A 9 I) to energize solenoid 35 which will adjust pump 25 to cause it to draw liquid from channel 88 and charge it into channel 31.

Closing switches A and A also establishes a circuit (9| s: A 92-I0-l2II-B3ll- AMI-9|) to n rgize solenoid I! which will shift plunger II of valve Il to the position shown in Fig. to bypass resistancevalve II.

Platen I, draw ring II andthe parts connected thereto will then descend by gravity and pistons 9 and swill expel liquid from cylinders in and I0- through channel II, valve II and channel II to the intake of pump 2I. The pressure created by the weight of the platen and associated parts extends through channel II and holds differential valve 29 in its right hand position so that the liquid discharged from cylinders Ill and Il must pass through pump 28 which meters the flow and thereby permits platen I and ring I! to descend at a rapid but controlled rate.

As platen I and ring it move downward, actuators ill and l2i will move out of engagement with limit switches LS2 and ms and permit them to close. Closing limit switch LS4 establishes a circuit (9089l2218ll2I-8|l to energize solenoid is which will shift plunger BI of valve 83 to the position shown in Fig. 6 so that valve is will not be operated when pump 25 is reversed as will presently be explained.

Closing switch LS2 establishes a circuit (Il- I4-ill8-LS2lI-lll) to energize solenoid 34 which will shift plunger ll of valve 20 to the position shown in Fig. I and then the liquid discharged by pump 26 will flow through channel 2!, valve 29, channels I. and I4, resistance valves BI and il and channels III and Ill to cylinders II and ii. At the same time the liquid discharged by pump II is flowing through channel 11, valve I6 and channels II and II to cylinders II and II but the liquid discharged by both pumps is insuiiicient to keep cylinders II and II filled during the rapid traverse descent of platen I and ring II. However, additional liquid flows from tank 21 through channels 63 and II, check valves and II- and channels II and II to cylinders II and II- to keep them filled. ram cylinder I being kept filled with liquid which flows thereto from tank 21 through channel 12 and surge valve casing II as previously explained.

Platen I and ring it will continue downward at rapid traverse speed until Just before ring it engages blank 3 and then actuator Ill opens limit switch LS3 to deenergiae solenoid II which permits spring II to close valve I4 so that the liquid expelled from cylinders II and II- by pistons I and 9 must pass through resistance valve 53. Since the pressure required to open valve II is greater than the pressure required to enable pistons I and l to support platen I, closing valve I4 causes the rapid downward movement of platen I to be checked.

Pump II will then tend to discharge through resistance valve 42 which will cause pressure to rise, extend through channel 43 and shift difierential valve is toward the left to block communication between channel 21 and tank 21 so that the entire output of pump 2I will enter clamping cylinders II and li and cause rams l4 and Il to move ring II and platen I downward at reduced speed. v

Ring II and platen I will continue downward at reduced speed until ring II engages blank I and pump 26 will continue to deliver liquid to the clamping ylinders until the pressure therein becomes high enough to cause ce valve II to open and permit liquid to iiow therethrough dis into channel II. This liquid will first now through channels Ill and 8| to valve It andshift its plunger I! to the position shown in Fig. 4 and then the liquid will flow to cylinder 16 and cause piston II to shift surge valve It to the po-.

sltion shown in Fig. 3.

Valve plunger II when shifted blocks communication between channel 31 and channels I0 and I0" so that no more liquid can be delivered from pump 26 to cylinders l5 and l5 but pump 26 continues to deliver liquid thereto and to maintain in each clamping cylinder at pressure which is determined by the adjustment of the resistance valve unit connected thereto and which is independent of the pressure in any other clamping cylinder. If the pressure in any clamping cylinders is too low, liquid from pump 28 will ilow through channel 28, valve 29 and channel 64 or 84', resistance valve II or GI and channel Ill or II to that cylinder and increase the pressure therein to a value equal to the difl'erence between the pressure created by pump 26 and the drop in pressure across the. resistance valve 6! or II connected to that cylinder. If the pressure in any clamping cylinder is too high, liquid will escape therefrom through channel III or III, resistance valve or 60- snd channel 68 or 63' into tank 21 until the pressure in that cylinder has been reduced to the value detemiined by the adjustment of resistance valve III 01' I0.

Surge valve ll when shifted blocks communication between ram cylinder 7 and tank 21 and opens communication between cylinder 1 and channel 14 so that, since valve i6 is new blocking communication between channel 31 and channels II and It. all of the liquid discharged by pump 2I will flow through channels 31 and H and surge valve casing H to cylinder 1 and cause ram t to move platen I downward at slow speed and force die I into die 2 to form or draw blank 3 into a desired shape. I

Ram 8 will continue downward at slow speed until the forming or drawing operation is completed at which time actuator 91 opens limit switch Isl. If selector switch SSI is in the position shown, opening switch LSI will break the circuit through magnet A. If selector switch SSl is adjusted to connect pressure switch PSI into the circuit, pump 25 will continue to deliver liquid to ram cylinder 1 until the pressure therein becomes high enough to cause pressure switch PSI to open and break the circuit through magnet A". In either case, magnet A is deepergized and permits switches A A and A to open and switch A to close.

Opening switch A prevents magnet A from being energized and again closing switches A, A" and A when limit switch LSI or .pressure switch PSI closes. Opening switches A and A deenerglzes solenoid II which causes pump 25 to be adjusted to zero displacement.

In practice, operation of limit switch LSI or pressure switch PSI causes the displacement of pump 2I to be reduced to zero and a. valve to be shifted to reduce the pressure in ram cylinder 1 to a given value and then a pressure responsive switch operates to energize solenoid 38 so that the pressure in cylinder 1 is reduced before reversal takes place, as described in Patent No. 2,337,848 but, since reducing the pressure in the ram cylinder before reversal takes place forms no part of the present invention, the press has been shown provided with simplified electric and bydraulic circuits and the electric circuit so arranged that closins switch A establishes a circuit on platen 5 engages flange through channels ill and 50, valve (9lIllSIlu3-l l2 A! l i-I.B2lfl9- B -il-90) to energize magnet B which will close switches B and B.

Closing switch 13 establishes a circuit (9l llllSilli3ll|-B' llBHl-LS2N9 B -lili80) to keep magnet 12 energized and switches B and B closed. Closing switch B establishes a circuit (9i-l|i4S|-i03B -l lfi 36-5-58) to energize solenoid 38 which will cause pump 25 to be adjusted to deliver liquid into channel 38.

Since the liquid discharged by pump 25 cannot raise platen until surge valve Ill is shifted, it first flows through channel I and shifts differential valve 38 to the position shown in Fig. 1, then it flows through channels 38 and 11 to cylinder 16 and causes piston II to shift surge valve to the position shown in Fig. 1 to disconnect ram cylinder 1 from channel ll and connect it to channel 12, and then it flows through channel 38, check valve 52 and channel UI to cylinders ill and i0 and causes pistons 9 and 9 to raise platen I. As platen 5 moves upward, ram I expels liquid freely from cylinder 1 through surge valve casing II and channel 12 into tank 21.

Pump it continues to maintain the selected pressures in the clamping cylinders to enable rams l4 and II to hold ring I! firmly against the work until after platen 5 has been raised high enough to free die 4 from the work. Before flange ii on platen 5 engages flange I: on rin l3. actuator [2| opens limit switch LS4 to deenergize solenoid 88 which permits spring 88 to shift plunger 85 of valve 83 to the position shown in Fig. l and then liquid flows from channel 38 through valve 83 and channel 82 to the right end of valve l8 and shifts its plunger H to the position shown in Fig. 1.

After valve It has been shifted, the flange II I! on ring I: and causes ring I 3 to move upward and the clamping rams to expel liquid from the clamping cylinders l8 and channel 31 to the intake or pump 25, the liquid in excess of pump requirements being exhausted through resistance valve 4! into tank TI.

Pressure responsive switch PSI will close as soon as the displacement of pump 25 is reduced to zero and limit switch LSI will close as soon as platen 5 starts upward but neither will establish a circuit at this time for the reason that switch A opened as soon as the active switch PSI or LSI was opened. Limit switch LS3 will close Just after ring it starts upward but it will not establish a circuit for the reason that switches A and A were previously opened.

Platen 5 and ring I! will continue upward until actuator llll opens limit switch L8! to dee ergize solenoid 84 and magnet B Deenergizing solenoid ll permits valve to open and bypass pump 26. Deenergizing magnet B permits switches B and 13 to open and deenerglze solenoid 38 which will cause pump to be adjusted to zero stroke and the press to come to rest with the parts in the positions shown in Figs. 1 and 2 and the controls in position to start another cycle of operation when starting switch 5; is again closed, the platen and associated parts being held up by liquid trapped in cylinders II and III- by valves 52, "and 84. Opening limit switch LS2 also deenerglzes solenoid I4 and permits valve 2! to open and bypass pump 28.

If liquid should leak from cylinders 10 and'lfl and permit the platen and associated parts to desclld. switch LSI would close as soon as ring I! descended a very short distance. Closing switch LS2 would establish a circuit (IL-IM- Sl-liiI-l l2 A*- lllLS2lIis-B --i I0- to energize magnet B which would close switches B and B and establish a, circuit (98- IM-SI-IIISBI "-36-! 15-98) to energize solenoid 38 which would cause pump 25 to be adjusted to deliver liquid into channel 38 and thereby cause platen 5 and associated parts to be raised until actuator llil again opened limit switch LSI to deenergize magnet B and solenoid 3B and stop the press as previously explained.

The press disclosed herein may be modified in various ways without departing from the scope of the invention which is hereby claimed as follows:

1. In a hydraulic press having a main motor for forcing a die against a work piece, a clamping motor for forcing a clamping member against said work piece and auxiliary motor means for retracting said die, the combination of a main pump for energizing said main motor, an auxiliary pump for energizing said clamping motor, means for directing the output of both pumps to said clamping motor to create pressure therein, means responsive to said pressure reaching a given value for diverting the output of said main pump only to said main motor means for diverting the output of said main pump from said main motor to said auxiliary motor means to retract said die, and means responsive to said die being retracted through a limited distance for connecting said auxiliary pump and said clamping motors to discharge.

2. In a hydraulic press having a main motor for forcing a die against a. work piece and a pinrality of clamping motors for forcing a clamping member against said work piece, the combination of a large capacity high pressure main pump for energizing said main motor, a constant pressure auxiliary pump for energizing said clamping motors, means for directing the output of both pumps to said clamping motors to create pressure therein, means responsive to said pressure reaching a given value for diverting the output of said main pump to said main motor. and means connected between said auxiliary pump and each clamping motor for enabling said an!- iliary pump to maintain in that motor a pressure independent of the pressure in any other motor.

3. In a hydraulic press having a main motor for forcing a die against a work piece, a clamping motor for forcing a clamping member against said work piece and a surge tank, the combinatics. of a large capacity high pressure main pump for energizing said main motor, an auxiliary pump for energizing said clamping motor, means for directing the output of both pumps to said clamping motor, means for causing said die and said member to advance toward said work piece at rapid traverse speed, means for directing liqold from said tank to said motors during rapid traverse advance of said die and said member. means responsive to said die and said member reaching a given point for checking said rapid traverse advance and thereby causing saidbumps to create pressure in said clamping motor, and means responsive to said pressure reaching a given value for blocking communication between said motors and said tank and (or diverting the output of said main pump only'to said main motor.

4. In a hydraulic press having a main motor for forcing a die against a work piece, a plurality working ch'amber of clamping motors for forcing a clamping member against said work piece and a surge tank. the combination of a. large capacity high pressure main pump for energizing said main motor, a constant pressure aumliary pump for energizing said clamping motors, means for directing the output of both pumps to said clamping motors, means for causing sald die and said member to advance toward said work piece at rapid traverse speed, means for directing liquid from said tank to said motors during rapid traverse advance of said die and said member. means responsive to said die and said member reaching a given point for checking said rapid traverse advance and thereby causing said pumps to create pressure in said clamping motors, means responsive to said pressure reaching a given value for blocking communication between said motors and said tank and for diverting the output of said main pump to said main motor, and means connected between said auxiliary pump and each clamping motor for enabling said auxiliary pump to maintain in that motor a pressure independent oi the pressure in any other motor.

5. In a downward actinghydraulic press having main motor means for forcing a die against a work piece and retracting it therefrom and including a working chamber and a return chamber, a clamping motor for forcing a clamping member against said work piece and a surge tank, the combination of a large capacity high pressure main pump for energizing said main motor means, an auxiliary pump for energizins said clamping motor, means for directing the output of both pumps to said clamping motor, a resistance valve connected to said return chamber to resist the discharge of liquid therefrom and having sumcient resistance to prevent gravitational descent of said die, valve means for bypassing said resistance valve, means for openinfl said valve means to bypass liquid around said resistance valve and thereby permit free advance of said die at rapid traverse speed, means for directin liquid from said tank to said working chamber during rapid traverse advance of said die, means responsive to said die reaching a given point for closing said bypass valve means to cause said pumps to create pressure in said clamping motor, and means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output of said main pump only to said working chamber.

6. In a downward acting hydraulic press having main motor means for forcing a die against a work piece and retracting it therefrom and including a working chamber and a return chamber, a plurality of clamping motors'ior forcing a clamping member against said work piece and a surge tank, the combination of a large capacity' high pressure main pump for energizing said main motor means, a constant pressure auxiliary pump for energizing said clamping motors, means for directing the output of both pumps to said clamping motors, a resistance valve connected to said return chamber to resist the discharge of liquid therefrom and having suilicient resistance to prevent gravitational descent of said die, valve means tor bypassing said resistance valve, means for opening said valve means to bypass liquid around said resistance valve and thereby permit tree advance of said die at rapid traverse speed, means for directing liquid from said tank to said uri rapid traverse advance of said die, means responsive to said die reaching a given point for closing said bypass valve means to cause said pumps to create pressure in said clamping motors, means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output of said main pump to said working chamber, and means connected between said auxiliary pump and each clamping motor for enabling said auxiliary pump to maintain in that motor a pressure independent of the pressure in any other motor.

7. In a downward acting hydraulic press having main motor means for forcing a die against a work piece and retracting it therefrom and including a working chamber and a return chamber, a clamping motor for forcing a clamping member against said work piece and a surge tank, the combination of a large capacity high pressure main pump for energizing said main motor means, an auxiliary pump for energizing said clamping motor, means 101' directing the output at both pumps to said clamping motor, a resistance valve connected to said return chamber to resist the discharge of liquid therefrom and having suflicient resistance to prevent gravitational descent of said die and said member, valve means for bymassing aid resistance valve, means for opening said valve means to bypass liquid around said resistance valve and thereby permit gravitational descent of said die,

means for directing liquid from said tank to said working chamber and to said clamping motor during gravitational descent of ,said die, means responsive to said die and said member reaching a given point for closing said bypass valve means to check said gravitational descent and thereby cause said pumps to create pressure in said clamping motors, and means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output or said main pump only to said working chamber.

8. In a downward acting hydraulic press having main motor means for forcing a die against a work piece and retracting it therefrom and including a working chamber and a return chamber, a plurality of clamping motors for forcing a clamping member against said work piece and a surge tank, the combination of a large capacity high ressure main pump for energizing said main motor means, a constant pressure auxiliary pump for energizing said clamping motors, means for directing the output of both pumps to said clamping motors, a resistance valve connected to said return chamber to resist the discharge of liquid therefrom and having sufiicient resistance to prevent gravitational descent of said die and said member, valve means for byaid resistance valve, means for opening said valve means to bypass liquid around saidresistance valve and thereby permit gravitational descent 0! said die, means for directing liquid from said tank to said working chamber and to said clamping motors during gravitational descent oi said die. means responsive to said die and said member reaching a given point for closing said bypass valve means to check said gavitational descent and thereby cause said pumps to create pressure in said clamping motors, means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output of said main pump to said working chamber, and means connected between said auxiliary pump and each clamping motor for enabling said auxiliary pump to maintain in that motor a pressure independent of the pressure in any other motor.

9. In a downward acting hydraulic press having main motor means for forcing a die against a work piece and retracting it therefrom and including a working chamber and a return chamher, a clamping motor for forcing a clamping member against said work piece and a surge tank, the combination of a reversible main pump for energizing said main motor means, an auxiliary pump for energizing said clamp g motor, means for directing the output of both pumps-"to said clamping motor, means for connecting said return chamber to the intake of said main pump including a resistance valve having suflicient resistance to prevent liquid from being expelled from said return chamber by the weight of said die and the parts movable therewith and valve means for bypassing said resistance valve, means for opening said valve means to bypass liquid around said resistance valve and thereby permit said die and said member to descend by gravity as fast as said main pump draws liquid from said return chamber, means for directing liquid from said tank to said working chamber during gravitational descent of said die, means responsive to said die and said member reaching a given point for closing said bypass valve means to check said gravitational descent and thereby cause said pumps to create pressure in said clamping motor, and means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output of said main pump only to said working chamber.

10. In a downward acting hydraulic press having main motor means for forcing a die against a workpiece and retracting it therefrom and including a working chamber and a return chamber, a plurality of clamping motors for forcing a clamping member against said work piece and a surge tank, the combination of a reversible main pump for energizing said main motor means, a constant pressure auxiliary pump for energizing said clamping motors, means for directing the output of both pumps to said clamping motors, means for connecting said return chamber to-the intake or said main pump including a resistance valve having suiiicient resistance to prevent liquid from being expelled from said return chamber by the weight of said die and the parts movable therewith and valve means for bypassing said resistance valve, means for opening said valve means to bypass liquid around said resistance valve and thereby permit said die and said member to descend by gravity as fast as said main pump draws liquid from said return chamber, means for directing liquid from said tank to said working chamber and to said clamping motors during gravitational descent of said die, means responsive to said die and said member reaching a given point for closing said bypass valve means to check said gravitational descent and thereby cause said pumps to create pressure in said clamping motors, means responsive to said pressure reaching a given value for blocking communication between said working chamber and said tank and for diverting the output of said main pump to said working chamber, and means connected between saidauxiliary pump and each clamping motor for enabling said auxiliary pump to maintain in that motor a pressure independent of the pressure in any other motor.

11. In a hydraulic press having a main motor for forcing a die against a Work piece, a clamping motor for forcing a clamping member against said work piece and a surge tank, the combination of a large capacity high pressure main pump for energizing said main motor, an auxiliary pump for energizing said clamping motor, means for connecting said main motor to said main pump and to said tank selectively including an initially open surge valve adapted when open to block communication between said main motor and said main pump and to provide communication be-,

tween said main motor and said tank, means for directing the output of said auxiliary pump to said clamping motor, means including an initially open control valve for directing the output of said main pump to said clamping motor to create pressure therein, means for closing said control valve to stop delivery of liquid from said main pump to said clamping motor, and means for shifting said surge valve to direct the output of said main pump to said main motor and simultaneously block communication between said tank and said main motor, said last two means being operated'in response to the pressure created by said main pump reaching a given valve.

12. In a hydraulic press having a main motor for forcing a die against a work piece, a plurality of clamping motors for forcing a clamping member against said work piece and a surge tank, the combination of a large capacity high pressure main pump for energizing said main motor, a constant pressure auxiliary pump for energizing said clamping motors, means for connecting said main motor to said main pump and to said tank selectively including an initially open surge valve adapted when open to block communication between said main motor and said main pump and to provide communication between said main motor and said tank, means for directing the output of said auxiliary pump to said clamping motors, means including an initially open control valve for directing the output of said main pump to said clamping motors to create pressure therein, means for closing said control valve to stop delivery of liquid from said main pump to said clamping motors, means for shifting said surge valve to direct the output or said main pump to said main motor and simultaneously block communication between said tank and said main motor, said last two means being operated in response to the pressure created by said main pump reaching a given value, and means connected between said auxiliary pump and each clamping motor for enabling said auxiliary pump to maintain in that motor a pressure independent of the pressure in any other motor.

RICHARD E. DAVIS.

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