US2622397A

US2622397A - Hydraulic transmission for press rams

Info

Publication number: US2622397A
Application number: US770033A
Authority: US
Inventors: Nowak Alois Karl
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-08-22
Filing date: 1947-08-22
Publication date: 1952-12-23
Anticipated expiration: 1969-12-23

Description

Dec. 23, 1952 A. K. NowAK 2,622,397

HYDRAULIC TRANSMISSION FOR PRESS RAMs Filed Aug. 22, 1947 5 Sheets-Sheet l gnam/am Dec. 23, 1952 A. K. NowAK HYDRAULIC TRANSMISSION FOR PRESS RAMS 5 Sheets-Sheet 2 Filed Aug. 22, 1947 Dec. 23, 1952 A. K. NOWAK HYDRAULIC TRANSMISSION FOR PRESS RAMS Filed Aug. 22, 1947 5 Sheets-Sheet 3 Dec. 23, 1952 A. K. NowAK HYDRAULIC TRANSMISSION RoR PRESS RAMs 5 Sheets-Sheet 4 Filed Aug. 22, 1947 vof vii

QmIm/n/SZ @lfm/M @am Dec. 23, 1952 A. K. NowAK 2,622,397

HYDRAULIC TRANSMISSION FOR PRESS RAMS Filed Aug. 22, 194'? 5 Sheets-Sheet 5 woRK 6"APPRoAcH APPRocH PRESSING# sLow RETURN STROKE CYCLE CURVE PRESS wrm 6" srnoKE EccENTRlc OPERATING wlw-134)' DRAW J WM Patented Dec. 23, i952 f f- 2,6229397 PATEN-'1* OFFICE 2,522,397- HYDRAULIC TRANsMIssroN Bonnasses RAMs Aloisy Karl Nowak; Evanstuuu,y Ill. Aupliesiion August 2?, 19437, .Seriell Vlvo- W010i? ITCIaimis. (Clt (iQ-52) l 2; This mention relates" borrower presseseno transmission forming e very importent oertof rineipellobieetsltomeilse aliiizseos el; this invention Tite hydraulic transmission (Fig. l) L; E The eccentric strap 25 drives a ram 26 in a tending through a stuffing box 29 inthe lower end o f the cylinder opposite to the rain 2B. The

Y .i connectionfbetween the strap andthe ram inpressule Control: and U0 provide e pressured 19, cludes a wrist pi 3o'. in the interests of. com- Pefofi, @t lplmm Qf, 12h@ ql WLU pactness, the ram is made hollow, as indicated 28 in the telesccping relation indicated in the drawing."

Associated with the main cylinder are auxiliary cylinders i32V and 3,3,"one at each side of the main cylinder and each equipped with a piston 341extending through the 'corresponding stufing box 35'in the Vlower lend of the cylinder.' All of the cylinders are made 'fast yin the bottom of the crown/l2, as dia'grarnmatically illustrated at '35. The ram'ii has across-sectional areaequal to thefs'urn of the crosssectional' areas of the DiS ioss'ahd 34! 9 l l f Thelvver ends of the three pistons are suit- Fle 4 1s a transverse s etlon 011 the Ilot-24:19; ably 'se'ured t6 a cycle veuve block Amin "tum i .1.; secured to and within the slide la. 5 -eum The main piston has a longitudinal bore 4l f. ne] and the auxiliary pistons each have a similar longitudinal-bore 4 2. Ihe cycle valve block has a.v longitudinal passage 43 connected by end branches with therespective longitudinal bores 42 of the auxiliary pistons. The valve block also has a longitudinal passage 4 5 in communication With the longitudinal bore 4l 0 5 the mainpiston.

The passages 6 3 and 45 are separated a nartition 546l having `two valved passageways Wd 4,8 lcolin.estilos the passages .4 3 and 55 trolled by spring seated valves.

swaywr t presenteren isessswiees iseluees. .e as bed lll right lsideJgJieces IU, and n ,crownv 112.

The separation volpe (Fig. n4)

The separation valve controls .the vpassage 41, and has for its function to permit or prevent communication between the main cylinder and the auxiliary cylinders at different phases of the cycleof operation. The valvebody 50 cooperates with a sest 51 :in thepessose ,472 "It hoefelsone die 5 2 extending .in opposite ydirreti ris and ebnneefeo with Pistons. .ssd so ,erlifisefs'ooi eo 55 `formed ntherelvefll @killen ololoos. es of the main passages i3 end A51 The historie esendsareof equel'isrea'butthe slorsilfefo2 eistends beyond the piston 54 in a shank 5'lmpff'issine mainv cylinder 21 having a main piston`28 exo' at 3l, to receive the upper portion of the piston 3 through a stuffing box 58 and out of the cylinder 58.

A passage 60 running lengthwise to the valve spindle 52 maintains co-mmunication between the cylinders 55 and 56 on opposite sides of the pistons 53 and 54 and a crosswise passage 6I connects to the passage 50 with the passage 45, which, in turn, is in communication with the main cylinder. From this, it follows that whatever hydraulic pressure per square inch exists in the main cylinder will be transmitted to the cylinders 55 and 55 on opposite sides of the pistons 53 and 54. Those pistons are of equal cross section, but, because of the shank 51, they present unequal areas to the hydraulic pressure, and hence there is a tendency for the piston 53 to prevail over the piston 54 and open the separation valve. This tendency is resisted by a spring 61 in the cylinder 56 beneath the piston 54, and is, under appropriate conditions, to hold the valve closed.

When the hydraulic pressure in the main cylinder 21 reaches a predetermined amount, acting on the piston 53, it overcomes the resistance of spring 61 and opens the separation valve, thereby establishing communication between the main and auxiliary cylinders.

In one embodiment that has been found satisfactory, the power of the spring 61 is 10% above the hydraulic pressure created in the main cylinder when the pull-back force of the air pistons I4 is applied to the piston 28 only.

Opening the separation valve with. air pressure The shank 51, which projects through the stuing box 58, becomes a piston rod 58 for a piston 69 in an air cylinder 10 supplied by pipe 1|. By admitting suicient air pressure to the cylinder 1B, the separation valve will be open against the resistance of the spring 61, thus establishing free communication between the main and auxiliary cylinders. Conversely, by exhausting the air from the cylinder 10, the spring 61 will close the separation valve and cut off communication between the main and auxiliary cylinders.

The make-up valve The make-up valve controls the passage 48 through the partition 46. The head I2 of the make-up valve closes with a seat 13 under the pressure of a spring 14, wound about a. shank 15 and compressed between a spider 16 and an end wall 11 of a cylinder 18. Whenever the hydraulic pressure in the auxiliary cylinders is greater than in the main cylinder by a predetermined amount, it opens the make-up valve against the resistance of spring 14. In one embodiment that has been found satisfactory, the force of spring 14 is 10% above the hydraulic pressure generated in the auxiliary cylinders when the entire pullback force of the pist-ons I4 is applied to the auxiliary pistons 34.

Air control for the make-up valve The shank 15 of the make-up valve is reduced at 80, passes a stufng box 8| and becomes the piston rod of a piston 82 and an air cylinder 83, receiving compressed air from a pipe 84. By admitting sufcient compressed air to the cylinder 83, the make-up valve is opened; and, conversely, by exhausting air from the cylinder 83 the make-up valve is allowed to close under the action of spring 14.

21 Slide limit stops (Fig. l)

The slide I3 has arms 35 at each side, and directly above each arm is a stationary bracket 86 equipped with a threaded pin 81 having an enlarged head 88 at the bottom to form a stop against Which the corresponding arm 85 cornes to rest in the upper position of the slide. The pins being threaded into the brackets, the positions of the stops are readily adjustable. They are held in adjustment by lock nuts 89.

Filling and by-pass valve and press-ure relief valve (Fig. 5)

tions and also with a pressure relief valve -to protect the system against excessive pressure.

The upper end of lthe auxiliary cylinder 3 2 is open at 90, and over this open end are bolted 25,* a flange 9| and a valve housing 92, the latter" having wide ports 93 communicating with the reservoir of hydraulic iluid. The flange 9| is' y Y upper end or head 91 projecting into the valve housing 92. Y

The valve is urged toward its seat 94 by a compression spring 98 held against the shoulder 99 by spring retainer |00 threaded onto a sleeve I0|, which, in turn, is threaded onto the head 91 of the valve 95.

When the piston 34 in the cylinder 32 de#A scends, it produces a partial vacuum within that cylinder, and the atmospheric pressure in the reservoir compresses the spring 98 and opens the valve 95, permitting the hydraulic fluid to flow into the cylinder 32 and supply the vacuum. In this way, the valve performs the oilice of lling the system. In another way, it serves as a bypass to permit the hydraulic fluid to ilow freely back and forth between the system andthe reservoir.

The valve 95 is hollow, and its lower portion y or limiting valve |03, and provided with relief channels |04 above the seating line which com`- municate with drilled holes or passages |05 through the lling and by-pass valve 95.

Aligned with the sleeve |0Il and abutting against its top end is a valve spindle |06 having in its lower end a cylinder |01 for a lapped piston sleeve |08, force fitted over a reduced end |09 of a valve stem I|0 against a spring washer III, and a valve spring II2 is compressed between that washer and the upper end of the valve 95. The valve spindle |06 extends upwardly into a hydraulic cylinder II4, and is solid above the cylinder |01 formed in its lower portion, and the cylinder I I 4 is provided with spaced stuffing boxes I I5 fitted to the valve spindle. In the intermediate portion, the valve spindle |06 and the cylinder II4 are undercut to form a chamber I I8, and the spindle is perforated at II1. The chamber I I6 is connected by a pipe IIB with the lower end of the main cylinder 21.

When the hydraulic pressure in the main cylinder ,'21 increases to a predetermined amount, it istransmitted through the pipe I I8 into the undercut portion I I6, acts on the differential areas between the upper and lower portions of the valve spindle |06, and holds itrmly lin its up position.

lIfiftlie same. time, this pressure is transmitted through the holes ||1 into: the cylinderY |01j formed in thelower portion of the. valve spindle ari'daetson the pistonsleeve |08. The i diameter of' thisf sleeve is slightly larger than the effective area of the relief valve |03, and the net force created by the hydraulic pressure is on the differential area. When this force overbalances the spring II2, the relief valve will open and hydraiilic.` uid will exhaust through the drilled openings: |'in the ports 93 into the reservoir, relieving' thepressure in the system.. Since maxi` mum pressure canbe'g'enera'ted in theu main cylinder 21 only Wheniallfthehydraulic cylinders are communicatingy through the separation' valve 50, the'f'pressure will be relieved in all hydraulic cylinders by the opening' of the relief valve |63. 'Rhei-instant the pressureinthe cylinders drops below t'he'maximuzn predeterminedl amount, the spring ||2A will .closev the relief valve.

The reduced end |09 of the relief valve stem Hllexten'dsfu'pwardly above the face of the piston sleeve |08-to within a small distance from. the lv'v'er faceI of the solid portion' of the valve spindle |06'.`v

- When compressed air is admitted to cylinder |2| above the piston |20 at the saineV time, air is exhausted below the piston |26. Separation valve islpen, and the hydraulic system has a pressure above aY predetermined amount, this pressure acting on the differential area of the upperfand lower portion of valve spindle |96 in the chamber I|6H will overbalancev the downwardl force of the piston |20.

When the pressure in the hydraulic systemdiminishes` below a predetermined amount, the separation valve will close, and at the same time by' means of pipe I|8 the pressure in chamber H6'v will also diminish to' this predetermined amount.. The downward force of piston |26 will overbalance this diminished hydraulic pressure acting on the differential area in valve spindle |06in chamber IIB, and the piston |20 and valve spindle |06.will move downward. The solid portiorioff the latter will strike the upper reduced end |09 of the relief valve stem IIO, compress valvevspring |I2, and unseat the relief valve |03, thus relieving the hydraulic pressure in the cylinder.- The piston |20 and valve spindle |66 will continue the downward movement until the lowery face of the hollow portion of the valve spindle |06 strikes the open end of the sleeve I'0|, thereby compressing the valve spring 98, and unseating the filling and by-pass valve 95, thereby establishing free communication between the auxiliary cylinder 32 and the reservoir.

When the compressed air in the cylinder I2| above the piston |20 is exhausted through port |33; vcompressed air'will simultaneously be admitted intof the. chamber' below piston; I 2-Ilin cylinder I2I.y through' port |-33`a,. and .this will litt? the piston |203` and. valve spindle; |66, and; the: valve spring Strand' I|2 Willclo'se the ii'llingand;

by-passV valve and the pressure relief. valine'.V

the rod and cam bar downwardly..r

One of thearms 8-6 cooperating with. the limit stops 80' is provided with an adjusting screwv |46 rotatable byV the.A handwh'eel |41 to adjust it to the proper height within thepathy determined point in the up stroke* of the slideA I3 and disengageita'tthe same point/in the: down stroke of the slide.`

The hydraulic pilot cylinder |236' is connected to a valve block |48 by a pipefIiiEJ.- The' valvel block |49 is equipped. with a balanced checl valve |5I, permitting free flow ofi exhaust from.

the cylinder |36 into thel pipev |I8i'but blocking' any now in the opposite direction. It is also equipped with a balancedpressure relief'valve: |52, which permits flow from the*A pipe ||8 into the cylinder |36 only when a predetermined pressure prevails in the pipe Il8`fbut blocks any now when the pressure is less than the predetermined amount, and also blocks any flow The slide adjustment (Fig. 3)

Mounted on the crown I2 is a small motor |60 driving a rotary pump I6'I with asuction pipe |62 extending into the fluid space of the reservoir and a discharge pipe |63' connectedto the inlet port of a solenoid operated three-way valve |64. The outlet of this valve isv connected with the pipe IIS, and through it withV the main cylinder 21. The exhaust port |65 of thevalve |64 leads back to the reservoir. The two solenoids |66 and |61 are connected with switches operated by push buttons'l and |69.

When the button ispressed, the solenoid |61 will shift the valve-to connect the pipes |63 and IIS, and the pump will then deliver fluid into the pipe |I8 and the main cylinder 21, thereby forcing the slide I3 toward the bed. When the button |458- is pressed, the solenoid |66 connects to pipes |I0 and |65 and allows hydraulic uid to escape from the cylinder 21 to the fluid reservoir, and the slide increases its distance from the bed. This arrangement is used in adjusting the distance between the slide I3 and the bed to the required height for various sets of tools. Springs normally hold the valve |64 in mid position.

Slow-down arrangement (Figs. 2 and 4) During' the approach portion of the down stroke, the slide I3 moves at three times the speed of the ram 26. If this speed should be maintained until the tool engages the workpiece, the blow would be harsh. For that reason, it is desirable to change the speed of the approach portion of the down stroke into the speed 'of the drawing or pressing portion of that stroke just prior to contact of the tool with the work piece.

.The pull-back cylinders |5 are supplied with compressed air by pipe |13. A small branch pipe |1| connects the supply pipe |10 with the inlet port of a solenoid operated three-way valve |12 through a telescoping joint |13. The solenoid valve is controlled by limit switch |14 mounted on the arm 85 of the slide alongside the valve. The outlet port of the valve |12 is connected by a pipe |15 with the air cylinder 10 of the separation valve 5D. A stationary bar |16, carried by the side frame is equipped with an adjustable cam |11 for cooperation with the limit switch |14. By adjusting this cam to operate the limit switch |14 just before the tool on the slide strikes the Work piece, the solenoid valve is operated to admit air to the cylinder 13 and open the separation valve in time to slow the approach speed down to the drawing speed before the tool actually strikes the work piece, as hereafter explained. After the cam passes the limit switch, the valve exhausts the air from the cylinder |10 and leaves the further operation of the crycle to the hydraulic forces involved.

Elimination of the clutch (Fig. 2)

It is sometimes desirable, and in many cases entirely practical, to eliminate the air clutch 2| connecting the flywheel drive with the eccentric drive. This is accomplished by a special control for the filling and by-pass valve 95 and the make-up valve 12.

For this purpose, air is taken from the supply pipe |10 through a small pipe |88 to a telescoping joint |8I connected to the inlet port of a solenoid operated three-way valve |82 on another arm of the slide I3. The outlet port of the valve 82 is connected by a pipe |83 with the cylinder 83 of the make-up valve 12.

Another pipe |86 leads to the inlet port of a solenoid operated four-way air valve |81, one

The main shaft 23 for the eccentric 24 is equipped with a cam |88 engaging a limit switch |89 just prior to the instant that the eccentric 24 and the slide I3 reach the top position. Two push buttons and I9| with their switches are mounted on the control panel of the press and are wired in series with the limit switch |89. Button |98 energizes the solenoids on-valves |82 and |81, and button ISI de-energizes them. Pressing the button |98 produces no effect until the cam |88 strikes the limit switch |88, but then the make-up valve 'I2 andthe lling and ley-pass valve 95 are opened instantly, permitting free flow between the hydraulic cylinders and the reservoir. The slide I3 is arrested at top position, where it is held by the pull-back pistons I4, and the hydraulic fluid merely surges back and forth into and out of the reservoir as the ram reciprocates in the main cylinder 21. Pressing the button |9| de-energizes the solenoid valves, allows the valve 12 and 95 to close, and the operation of the press is resumed at the next down stroke of the ram 28.

Operation When the press is idle, the air clutch 2| is open, the motor and flywheel with shaft 20 may' be rotating, but the main shaft 23 and the eccentric 24 are standing still with the ram 26 in the main cylinder 21 in top position.

The pull-baci: pistons I4 in the cylinders I5 hold the tool carrying slide |3 in top position against the heads 88 of the pins 81, those pins having been adjusted to give the proper clearance between the faces of the slide I3 and the bed I8. The main and auxiliary pistons are all in top position.

The adjusting screw |46 holds the cam rod |43 with its cam |42 in top position, in which the roller |4| is engaged with the cam |42 and is holding the piston valve |34 in position to connect the ring port |35 with the cylinder connection |33 and the exhaust port |32 and at the same time ring port |35a with the other cylinder connection |33a and the supply port |3|. This valve setting connects the air supply I 3| through channel |23 with the chamber below piston |20 and connects the chamber above piston |28 with the air exhaust |32. rThe valve springs 98 and ||2 are holding the filling and by-pass valve 95 and the pressure relief valve |83 in closed position.

The hydraulic uids in the entire system of cylinders and valves is free from pressure because the pull-back force of the pistons |4 is taken entirely by the frame through engagement of the arms 85 with the heads 88 of the pins 81. The separation and make-up valves in the valve block 48 are closed. s v

The operation of the press is started by pressing a push button on the control panel to engage the air friction clutch 2|, start the countershaft 28 in rotation to drive the mainshaft through the gearing 22, and startv theeccentric and the ram on their downwardstroke.

The iiuid displacement in the main cylinder 21 caused by the downward movement of the ram 26 is locked wtihin the cylinder 21 because both the separation and make-up valves in the valve blocks 48 are closed. The total displacement caused by the ram is therefore communicated to the main piston 28 and through it to the slide I3, which starts its downward movement against the pull-back force of the pistons |4 in the cylinders I5. This creates a hydraulic pressure in the main cylinder 21 equal to the pullback force divided by the cross-sectional area of the main piston 28.

The cross-sectional area of the ram 26 is equal to the sum of the cross-sectional areas of the main piston 28 and the auxiliary pistons 34, or three times the cross-sectional area of the main piston 28. Consequently, since the displacement of the piston 28 must equal the displacement of the ram 26, the piston and the slide I3 must move three times as fast as the ram and three times the distance of the ram. This means that, when the ram moves downwardly one inch, the main piston Vand the slide |3 must move downwardly three inches.

The auxiliary pistons 34 in the auxiliary cylinateniese? draulic uid to flow fromk the reservoir into the auxiliaryl cylinder' 32 yandA through' the' passages 4'3 and 44 in the valve block 40 intoV the auxiliary cylinder 33, nlling the two'cylinders continuously as' the slide proceeds downwardly ythrough the vapproach portionof the stroke.

The tool carried by the" slide I3 strikesv the metal't'o be worked, andresista'n'ce" against further movement is encountered. The' force: re'- quired for'further downward movement manifests itself as an increase'in hydraulic pressure in the main cylinder 21, and when that increase reaches a predetermined amount" .above the prevailing pressure` of the previous'momenti' it overbal'ance's the valve' spring 61, and' thesparation' valve 50 opens, providing' communication between'the pass-ages' 43 and'i45 in the'valve block and hence between the main cylinder 21` and the

auxiliary cylinders

32 and 33 through' their bored r'vi'stonsjSli.r The opening'of thesep'arationvalve terminates the vacuum or suctionin the auxiliary cylinders instantaneously, and the illling and bY- pass Valve 95 closes immediately, therebyv block-- ing the now between the auxiliary cylinder 32 and the' reservoir.

During this initial downward movement ofthe slide I3, adjusting screw' |46 andv with it therod |43' and the earn' block |42 move` downwardly untilthe collar' |45 comes torest' against the stationary bracket 86" and the cam' I '42. has released the roller |4I on `the bent" rocking 'arm' |381 The ram 26 continues downwardly, but its displacement is now distributed equally to the three cylinders; and, since its displacement equals the total displacement' or the main yand auxiliary pistons, the slide moves downwardly `at the same' speed and for the same distance as the ram.

The further downward movement of the tool carried' by the slide deforme the metal being worked and meets increasing' resistance; This is 'continually being. overbalanced by the dri-.ven eccentric 24' through the ram 2B, which` increases the hydraulic pressure in the three cylinders'. This pressure is transmitted from the main cylinder' 2'1 through the pipe I I8" tothe chamber formedfby the undercut I I'in thefvalvespindle HIE within the cylinder I I4vr and to the relief' .fa'lv'el i52in thevalve block |49..

When. the pressure reaches a predetermined amount (hydraulic pressure .generated whenthe entire pull-back. force is applied to themain piston 23 plus 50%) the relief valve |52' opens and allows the hydraulic fluid to pass through the pipe |53' into the cylinder' |33' and shift the reciprocating piston valve |34 to the right` (it being free tom'ove as the cam |42 is outo'f the' way of th'e roller |41)v rinto a position connecting air supply` I3`I` with cylinder connection |33, thereby admitting compressed airl into the chamber above piston I2il, and at the same time. connecting air exhaust |52 with the port I33a and channel |23, thereby exhausting the compressed yair in the chamber below piston in cylinder |21.. The force of" that piston thus created is greatly overbalanced by hydraulic pressure in the chamber formed by the undercut I I6 .and the holes, I |.1,.'so that no movement of the spindle ||l|i takes place.

The slide and tooll continue downwardly until the'e'ccentriehasrevolved 18d-degrees from the start, when'the lowest'poitfisreached; at' which the worked meter has? conformed to the contours of'l the; tools. At this point,v the hydraulic pressure hasl increased' to'v they highest limit, and the frame' structure'- ishighly stressed. Further movement of: the'v-eccentric raises 'the ram 26` in thewrn'aii'i'cylinder` 21- in a gradual manner, thereby graduallyL relieving the'V hydraulic pressure in the; main4v 'and auxiliary cylinders and also the v'stress'i'n thelpress'frame structure until the pressurehas decreased'to an amount"(total pull-back frce'of the"pistons"- I4 divided bythe sum ofi the areas-ofthe three-pistons, or theare'a'4 of the ram, plusn 101%); During this'gradual'decline in pressure; it'-v passes" a valuea (totalpullbackv force divided-by' the'area; ofthepistonZB plus-10%); at which point the'valve' spring '61 seats the separation valve 5U andcutsofcommunication between the pa's'sfavge's'

vv

43 and 45; thei'ebyseparating the main' cylinder 2"!l fromlthe; auxiliary cylinders 32 and 33';

Simultaneously, the force on' the' differential area between the-"upper landVv lbwer' portions of the valve spindlf'l |36 v in the-cylinder I`I4Ihasdecreased inlike'A manner, and' is overbalanced by the'A force' of the-air pressure on the area :above the piston |20, and: thatv pistonI with'its-spindle I 0E moves downwardly intoV contact with the upper 'end I''ilof-the'valve stem' IIO, overcoming spring' I` I 2f an'dopeni'ngthe relief val-vel I 03; thereby establishing -arestrictedcommunication between thevauiiiliary' cylinders and the reservoir and-relieving'the hydraulic pressure in them.

Thief-downward movement',l of'I the piston |20 and thespindlei |03 continues; yand the lower end of the latter' pushes down* the'v sleeve IOI, compressing" the valve spring 23 and openingv the filling and"fby--p'assz valve `l95, thereby establishing free'communicatienbetween the auxiliary cylin ders and thereservoir. The downward movement of therpisto'nf" |20 isA limitedby the stop provided inthe cylinder |211'.

This operation of the valves 951 and |031 is effectedveryquickly; and they` remain-open as long astheair pressure in the cylinder |2I above the pistonI I 20 prevails.-

'Ihram 26 inither main cylinder 21 with the slide andthe three pistons` now move' upwardlyi Thehydraul-ic pressure in the-main cylinderl 21 is theftotal pull-back' force of'thepistons I4 di'- videdby ktlf-ie cross'e'ctionai area `of the pistons 28k and the displacement off that' piston must equa-lj theidisplacement of? theV ram 25. Because the area fof* the pistonv and ram' are inthe ratio of'l'zb", the pisten 28 moves three times the speed and three' times" thedistance-the ram 2G moves. Thus, when the ram rises one-inch, the' piston 28 and the'sl'ide` willrise threeinches. The-displacements" of the two' auxiliary cylinders'- are rforced through Vtheilling and bypassvalve 95 intothereservoir.

11 raising piston |20 and valve spindle I 06, relieving the pressure on the springs II2 and 93, and permitting the lling and by-pass valve 95 and the pressure relief valve |03 to close.

The adjusting screw |40 is set to cause the exhaust of air above the piston |20 and have the iilling and by-pass valve 95 and pressure, relief valve I 03 close when the slide passes through the point a distance from its topposition equal to the length of the pressing portion of the stroke, the valves S and |03 being closed and the separation Valve 50 blocking communication between the main and auxiliary cylinders. The uid in those cylinders is locked while the ram 26 continues upward, thereby producing a partial Vacuum or suction. The hydraulic pressure in the

auxiliary cylinders

32 and 33 is the total pullback force of the pistons I4 divided by the combined area of the auxiliary pistons 34; and this pressure, acting in the passage 43 of the valve block 40, overbalances the make-up Valve spring 'I4 and opens the make-up valve 12, permitting the hydraulic uid in the auxiliary cylinders to iiow into the main cylinder. The upward movement of the ram and the flow of the fluid continues until the slides strike the heads 88 of the pins 37 in the stationary brackets 86. This ends one stroke cycle with the press being in the initial position before the cycle started.

When the press is adjusted for single cycle operation, the slide I3, just before contacting the heads 88, trips a limit switch, which de-energizes the solenoid operated air valve and opens the clutch 2 l .i This stops the eccentric and the slide while the moto-r and flywheel continue rotating. From the above description of the operating cycle, it will be seen that the slide has a variable stroke. When the slide encounters no work resistance-that is, when the press is operated idly without a set of tools-the separation valve remains closed and the entire displacement of the ram 23 changes into displacement of the main piston 28. The strokes of the piston 28 and the slide I3 are therefore three times the stroke of the ram 26. Hence, if the eccentric stroke is six inches, the slide stroke is eighteen inches. But, if the slide should encounter resistance at the very start of the stroke, the separation valve would immediately open communication between the main and auxiliary cylinders, f

and the displacement of the ram 26 through its entire stroke of six inches would distribute itself equally among the three cylinders and give the slide a stroke of six inches. In between those limits of six inches minimumand 18 inches maximum, any length of stroke can be'produced by placing the point of contact of the slide tool with length of the stroke of the slide.

Each down stroke consists of an approach stroke plus the pressing stroke o r drawing stroke. The latter requires the equivalent length of stroke of the ram and eccentric. The length of the approach stroke is three times the remaining length of the ram and eccentric. The approach stroke must be long enough to allow the removal of the work piece from between the work engaging tools. A In the conventional, presently used press, the length of the stroke of the slide is ixed, land is the equivalentV of the stroke of the driving crank or ecccentric, commonly inches. This difference in the stroke of the eccentric of 10 inches on the conventional, presently used press and y-6 inches on the press of this invention is the crux of it. This diierence in eccentric represents a the workpiece in the proper relation to the total- .very substantial saving in the cost of ,construction of the press, amounting to a great deal in large presses with long strokes. For instance, a conventional press with a crank or eccentric of liZ-inch stroke can be replaced by this invention with a crank or eccentric of 27-inch stroke, or a difference of 15 inches.

Increase in number of stroke cycles per minute But moreiznportant than the saving in cost of construction just mentioned and perhaps the most important feature of the invention is that it increases the number of stroke cycles per minute beyond anything possible with conventional types of presses.

In the conventional press having a crank or eccentric stroke of v10 inches, the work angle is 72 30 as compared with a press embodying the present invention having an eccentric stroke of 6 inches and a work angle of 104 30'.

Each metal used in forming Work pieces in presses has its own definite limit ofwspeed in inches per minute at which it may be deformed by the tools without rupturing. Higher speeds than this limit will tear the metal and spoil the Work piece. f

Assuming a conventional press with a 10-inch stroke operates at 12 stroke cycles per minute, based on the pressing speed for theparticular material, then the Work angle of 72 30' is made in approximately one second. Since'the limit of Working speed must be maintained, the work angle of 104 30' of the press embodying the present invention must be made in the same interval of one second. This means that the eccentric of such a press makes onerevolution or one complete stroke in 3.5 seconds, or operates with a speed of 17 strokes perminute as compared with 12 strokes per minute for the con ventional press, an increase of 40%.

There are, however, pressing operations in which the labor cost involved precludes the possibility of taking advantage of this increased number of strokes per minute. But another advantage may be had by running the press embodying this invention at the same number of strokes per minute as the conventional press. Under these conditions, the work angle of 104 30 will be made at the same angular speed as the work angle of 72 30 of the conventional press, or in 1.44 seconds, or an increase of worktime of about 44%.

It is the general experience of men in the lindustry that the slower the pressing speed, the

betterlthe formation of the work piece and the smaller the percentage of loss due to rejects. Consequently, the press of this invention. running at the same number of strokes per minute as the conventional press, will' maintain the production rate but give better results and' fewer rejects.

Advantage of the improved slide adjustment .13 u vai. press; embodying,`r the". present. invention,4 but having, a. fifinchxeccentric f with a: maximum' shut heightpof leiv inches,.has` a minimum; shut height of inches withoutany adjustment;

Theadjusting mechanism ofi theffconventional press; consists of aheavyscrewor screws between the'. slide .andi the. drivingdevice.. They must. ybe constructed. toy resist the.- full. pressure of. the machine, and'` theaindus-tryrequires presses.l from ai capacityof` 75. tons to. manyhundreds or even thousands of' tons, which. makes the adjusting mechanism very7` costly. As. comparedawith this, adjustment'wi-th. the presentv invention is made by the simple means described heretofore under the heading The Slide Adjustment. Increasing. the volumef of fluid; iny the hydraulic system. decreasesY the shut height. Decreasing thevolume increases" the shut height;` andY the increase and decrease are controlledzentirely by the push.` buttons Hi8- and 1.69. The adgustmentnot. only provides for; quick and very-,y accuratesetting of.. the shuti height; to conform to af tool set, butv controls the maximum pressure produced on-a:to.ol. set and provides for a; dwell of. pressure onthe work.-` piece at the bottomrof the stroke. y

Fine pressure cmitroll A press' embodying the present invention should. be' equipped withV a hydraulic pressure gauge 2'00 connected" to the hydraulic systemfor instance, by aA pipe 213i' lea-'ding' to the pipe Hdl or some.l other part-Ain communication with the; interior' of.` the main cylinder 2T. Such a gauge indicates the pressure prevailing' in the system and'. the totalpressure generated inthe -l contrast, the' operator of'` the: press"v embodying i the; presentzinvention: merely: has; totobservethe pressure gauge tand operate one or both. of thepush; buttons: le@ and' i155. toiv make the pres sure delivered.'exactlyl what is desired; Het can der this:y whilethe: press is:. operating'. Introducing' a* pressure dwelling period' at the bottom cfa stroke It welk-known; that. af time interval. of steady pressure .onthe work pieceaiter it: is: pressedsets thef.vork metal and; permits Ythe internal stresses tc.- arrangeftheinselvesf in a. balanced: condition. Workpieces formed inthatzmanner havefthef-.true and-=accrnfate contours ofv the tools withoutfiwarps or other. undesirable:deformations; The-conventionafl press has no; means' ior-producing: such a dwell,v Consequently, the work piecesfrequently have t'o'be fitted by hand.

The. present` invention makes it possible to introduce-av'pressure :dwelling` period aty thebot tom ofythe strokeup 'to-30 eccentric. angle with@ out interrupting thestrolze-cye-le.. The. operator sirnpiyadjusts ther top position of/ the slide to bring it to res-t against the stops 3dK before the eccentric and/ram. reachedrtheir top' positiens.t Toe-additional movement'oftheram cre'- atesfa partial vacuum'or: suction, whichV is-satis.- ned with fluid admitted: through. the lling and by-parss valvelr.- Gn the next downistroke, this additional. il-uid bringsthe slide to-the'bottomaofv 514 itsr travel beforethe yrarrnreaches; the..- bottonr. of itsstrolre and producesthe dwellwhilezthiszaddie tional'fluid'isexhausted fromthe system through the pressurefrelief valve, during. Whichthe'itools are hei dV pressed against: the work. piece;

Relieving a jammed press Vlhenlthel workingfstrolze oi a press absorbsthe energyof a ny-wheel excessively tosuch arr-extent thatv the circuit breakerscut off` the power; the press with its entire structure is severely overestressed'; To free the pressfrom sucha condition is' alengthy and costly procedure; Frequently the dies and tie-rodsfmust be torch-cut. With a stresser theepresentv invention, when-al jamoccurs itl may-be' relieved in'a matter of secondsbyioperiati-ng the push button-control to `decrease Athe fluid in the system; f

The gistV of the invention lies' in introducing betweenI the drive with axedstroke-and the slide ahydraulic transmis-sion includ-ing means for delivering dierent portions of'thedi'splacement of the ram to' the piston-during different-'portions oi thestroke. Theabovementioned and other advantages are nherentin this feature.

The embodiment here used for illustration; inciuding'onefmainand two auxiliary cylinders; appears to Jbe the bestffor wide presses* and heavy duty; bluteng-ineers will readily` design other embodiments vforparticular conditions and-to2 suit personal preferencesl inW-hich the number'off cyl'- ind'ers their arrangement and relative si-'zeef pistons will be varied: Some will prefer to-use but a' sine-le cylinder for tirera-m and a piston connected withy the slide. Otherswill" prefer to use one or more auxiliarycylnders: T-hefprin ci'ples here illustratedreadi-ly l'endthernselves-to those and other variations,

Whathave here been-called separationvalve fnialie-upivalve etc., areso called becauseiofithe arrangement in this embodiment.` In other embodiments, they may he merely valves.

I claim:

l'. Irrapress, a slide', a mechanical' drive'hav'- ing a fixed stroke and a hydraulic transmission for transmittingforce through a uidbetween the slide andv the drive including a ram operated by said drive', main' andiauxiliary cylinders With'pi'stons, a. iui'd connection between the ram'v and main cylinder, a .fluid reservoir, a fluid" connection between the cylinders; a fluid connection between the auxiliary cylinder and' the reservoir.,v and spring seated .valves .for controlling/fluid communication through". said connectons,.the.val`ve. in

' the reservoir connection permitting ii'uid. flow from the reservoir tothe auxiliary. cylind'enwhen the pressure. or. the. auxiliary cylinder is. belowthatof'thereservoir by a predeterminedlamount, and' the valve. inA thev cylinder connectionsper.- mitting flow from. the main-.cylinder tothe. auxf iliary cylinder. upon.. a.. predetermined excess:` of. pressure in the main.cylinder.

2. In a press, aslide, amechanical. drivezha-ving. a, xed stroke .and a. hydrauliotransmission for transmitting. force throughv a fiuidzbetween the slide andthe drive.. including a .ramoperated by said drive, mainand. auxiliary cylinders-with;

pistons, a-iuid connection betweenthe-.ranfr and maincylinder, afiuidreservoir, a' fluid coimecsA tion .between the cylinders, a spring seated valve for said connection yielding to pressure in the. main cylinder, a second spring seated valvei for'- said connection. yieldingyto pressusefin anzauxiliary cy1inder a. iiuid. connectionL between the auxiliary cylinder and the reservoir, a spring seated valve for said last mentioned connection yielding to vacuum in said auxiliary cylinder, and means to open said last mentioned valve in response to pressure developed in said main cylinder.

3. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with pistons, a fluid connection between the ram and main cylinder, a fluid reservoir, a fluid connection between the cylinders, a spring seated valve closing said fluid connection during the approach movement of the slide and automatically opened by increased pressure in the main cylinder, a fluid connection between an auxiliary cylinder and the reservoir, and a spring seated valve for said last mentioned connection yielding to vacuum in said auxiliary cylinder and to pressure in said main cylinder.

4. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the v slide and the drive including a ram operated by said drive, main and auxiliary cylinders with pistons, the area of the ram being equal to the combined areas of the pistons, a fluid connection between said ram and main cylinder, a fluid l reservoir, a. uid connection between the cylinders, a fluid connection between an auxiliary cylinder and the reservoir, and spring seated valves for said connections, the valve in the reservoir connection permitting fluid flow from the reservoir to the auxiliary cylinder when the pressure of the auxiliary cylinder is below that of the reservoir by a predetermined amount, and the valve in the cylinder connections permitting flow from the main cylinder to the auxiliary cylinder upon a predetermined excess of pressure in the main cylinder.

5. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with a piston in each, a fluid connection between the ram and main cylinder, a fluid connection between the cylinders, and means for closing the connection during the approach movement of the slide and opening the connection during the drawing movement of the slide.

.6. In a press, a slide, a mechanical drive having a xed stroke at least the draw portion of which approximates simple harmonic motion and a hydraulic transmission between the slide and the drive including automatic means for positively moving the slide at a speed in excess of the drive during the approach portion of the stroke, and then moving the slide at a slow speed and with substantially harmonic motion during the draw portion of the stroke.

'7. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with a piston in each, a fluid connection between the ram and main cylinder, and means for delivering all the displacement of the ram against the main piston during the approach movement of .the slide and against all the pistons during the drawing movement of the slide.

8. In a press, a slide, a mechanical drive having Cil a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with pistons, a fluid connection between the ram and main cylinder, a fluid reservoir, a fluid connection between the cylinders, a fluid connection between an auxiliary cylinder and the reservoir, and automatic separation and make-up valves for said connection, said separation valve adapted to control fluid connection from the main cylinder to the auxiliary cylinder in response to a predetermined pressure differential therebetween.

9. In a press, a slide, a mechanical drive having a xed stroke and a hydraulic transmission for transmitting force through a, fluid between the slide and the drive including a main cylinder, a main piston, a ram in the main cylinder operated by said drive, a fluid connection between the ram and the main cylinder, auxiliary cylinders, an auxiliary piston in each auxiliary cylinder, a fluid connection between the main cylinder and the auxiliary cylinder, and means for blocking communication between the main cylinder and the auxiliary cylinders during the approach movement of the slide and connecting tnem during the drawing movement of the slide.

10. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders, a fluid connection between the ram and main cylinder, a hollow piston in each, a valve block connecting the hollow pistons, and automatic separation and make-up valves in the valve block, said separation valve adapted to control fluid communication between said main and auxiliary cylinders.

l1. In a press, a slide, a mechanical drive having a fixed stroke and a. hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders, a fluid connection between the ram and main cylinder, a hollow piston in each, a valve block connecting the hollow pistons, a fluid connection in the block for the main piston, a fluid connection in the block for the auxiliary pistons, and automatic separation and make-up valves in the block for said connections, said separation valve adapted to control fluid communication between said main and auxiliary cylinders.

12. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders, a fluid connection between said ram and main cylinder, a hollow piston in each, a valve block connecting the hollow pistons, a fluid connection in the block for the main piston, a fluid connection in the block for the auxiliary pistons, automatic separation and make-up valves in the block for said connections, and means for operating said valves, said separation valve adapted to control fluid communication between said main and auxiliary cylinders.

13. In a press, a slide, a mechanical drive having a i'lxed stroke and a hydraulic transmission for transmitting force through a fluid betweenthe slide and the drive including a ram operated `by said drive, a cylinder, a piston in the cylinder, a fluid connection between the ram and the cyl- 17 inder, a fluid reservoir, a pump, uid connections, and valve means to direct the fluid from the pump to the cylinder and from the cylinder to the reservoir.

14. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, a cylinder, a piston in the cylinder, a fluid connection between the ram and the cylinder, a fluid reservoir, a pump, fluid connections, valve means to direct the fluid from the pump to the cylinder and from the cylinder to the reservoir, and push button controls for said valve means.

15. In a press, a slide, a mechanical drive having a xed stroke and a hydraulic transmission for transmitting force through a uid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with a piston in each, a iluid connection between said ram and main cylinder, means for driving all the displacement of the ram against the main piston during the approach movement of the slide including a fluid connection between the cylinders, a separation valve automatically closing the connection, and means for opening the valve toward the end of the approach movement.

16. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a ram operated by said drive, main and auxiliary cylinders with pistons, a fluid connection between the ram and main cylinder, a fluid reservoir, a fluid connection between the cylinders, a spring seated valve for said connection yielding to pressure in the main cylinder, a fluid connection between an auxiliary cylinder and the reservoir, a spring seated valve for said last mentioned connection yielding to Vacuum in said auxiliary cylinder and to pressure in said main cylinder, and adjustable means for stopping the upward travel of the slide before the ram reaches the top of its stroke.

17. In a press, a slide, a mechanical drive having a fixed stroke and a hydraulic transmission for transmitting force through a fluid between the slide and the drive including a cylinder, a ram in the cylinder connected with the drive, a fluid connection between the ram and cylinder, a piston connected with the slide, and means including valves for delivering different portions of the displacement of the ram to the piston during dierent portions of the stroke.

ALOIS KARL NOWAK.

REFERENCES CITED The following references are of record in the 111e of this patent:

UNITED STATES PATENTS Number' Name Date 133,543 Robertson Dec. 3, 1872 214,574 McGowan Apr. 22, 1879 429,667 Webb June 10, 1890 933,010 Wilzin Aug. 31, 1909 1,429,665 Wood Sept. 19, 1922 1,690,398 Bollinger Nov. 6, 1928 1,939,886 Ferris Dec. 19, 1933 1,980,514 Ferris Nov. 13, 1934 2,075,235 Sciaky Mar. 30, 1937 2,128,152 MacMillin Aug. 23, 1938 2,407,957 Hull-Ryde Sept. 17, 1946