US2597169A - Hydraulic press in which the thrust of the ram and the reaction of the slide bar areequalized - Google Patents

Description

May 20, 1952 A K NowAK 2,597,169

HYDRAULIC PRESS IN WHICH. THE THRUST OF THE RAM ANDl THE REACTION OF' THE SLIDE BAR ARE, EQUALIZED Filed Aug. 2l, 1947 4 Sheets-Sheet l ifi/9J f7 2 Raoucma 80 REI-'EF VALVE y I 48 l f 26 87 76 Ill y ff-J9 May 20, 1952 l A, K, NOWAK 2,597,169

HYDRAUL. RESS IN WHICH THE THRUST THE RAM AND THE CTION OF THE SLIDE 'BAR AR QUALI Filed Aug. 21, 1947 4 eets-Sheet 2 May 20, 1952 A. K NowAKI 2,597,169Y

HYDRAULIC PRESS IN WHICH' THE THRUST OF' THE RAM AND THE REACTION OF THE SLIDE BAR ARE EQUALIZED Filed Aug. 21, 1947 4 Sheets-Sheet 3 l Egg-7 Ill' l 7 'x Il O 27 28 2 f4 r l 0 23 A a O I A. K. NOWAK HYDRAULIC PRESS IN WHICH THE THRUST OF' THE RAM AND THE REACTION OF THE SLIDE BAR ARE EQUALIZED Filed Aug. 2l, 1947 4 Sheets-Sheet 4.

driving plunger II in the cylinder I2. In consequence, the two plungers I I and have the same cross sectional area, and hence the same displacement. The two cylinders I2 and I4 and their connecting pipe I9 form a closed hydraulic system, and the xed stroke and displacement of the plunger I I in cylinder I2, mechanically actuated by eccentric 9, will cause identical displacement in cylinder I4 and identical stroke of the plunger 20 and the press head 2l.

It is axiomatic in hydraulics that the pressure in every part of a closed system is the same. The force exerted by a hydraulic plunger is the cross sectional area of the plunger multiplied by the pressure per square inch. Therefore, the force i of plunger II is the same as plunger 2S; and, since these two plungers are equi-distant from the axis ofthe pin I5, the two forces balance each other. The pin is consequently subjected to a vertical upward acting force equal to the sum of the two forces. By strengthening the bearings I6 of pin I5 with heavy bars 22 (Fig. 6), welded to the side plates 2 vand 3, and extending them to their lower ends, distortion of the side Yplates is completely eliminated, and the guides 2 3 of the press head 2| are maintained in precise alignment.

On top of the cylinder I4 is an air cylinder 24 with its piston 25 and crosshead 26. Two pullback rods 21 are fastened to the crosshead, and support on their lower ends the ears 28 of the press head 2 I. Air cylinder 24 is supplied by .pipe 29 with air pressure of 70 pounds per square inch, giving its piston a continuous tendency to remain in its upper position, and hence the press head is continuously pulled upward.

During the down stroke of plunger Il, the air piston 25 can raise the press head 2l and plunger 20 only at the rate at which the down movement of the plunger II permits the filling of the cylinder. Thus, the movement of plunger 20 and press head 2I is perfectly harmonious, the beginning and end of the upper and lower ends of the stroke gradually approaching zero velocity from the maximum at midstroke.

The air pipe 29 is supplied with a check valve 33 to prevent air ow out of the air cylinder 24, and thus causes intensification of the air pressure in the cylinder due to the additional compression effected .by the down movement of the piston 2'5. The construction of the air cylinder 24 and the piston 25 is such as to limit this additional compression'to a ratio of 2:1. Thus, the air pressure at the bottom of the stroke will be approximately 140 pounds per square inch, which is desirable to effect the stripping of the work from the die.

It will be apparent from the description that the working plunger and the press head have exactly the same reciprocating stroke as the driving plunger II.

Adjustment of the press head Working practice, however, demands an -adjustment of the press head 2l up or down for various heights of die sets placed between press head 2i and press bed I. It is an important feature of this invention that the adjustment of the press head may be effected by varying the volume of fluid in the closed hydraulic system consisting of the cylinders I2 and I4 and the connecting pipe I9. Increasing the fluid in the system will lower the press head, and decreasing the fluid in the system will raise it, and by control of the increase or decrease an exceedingly fine adjustment may be had.

An auxiliary motor 3l drives a small pump 32 having its intake connected by pipe 33 with an overhead tank 31% (Fig. 1). A discharge pipe 35 of the pump is divided into two branches 3S and 3'1. The branch 33 is equipped with a check valve 3S, and leads directly to the upper end of the cylinder I2. The check valve permits flow away from the pump to the cylinder but checks any tendency to flow in the reverse direction. The branch 3? is fitted with a globe valve i0 and is connected to the pipe 33. By opening the valve 43, the pump will discharge through the pipes 35, 3l, and 33 back into the tank while the check valve 38 prevents any flow of nuid through the pipe 3S from the cylinder I2.

A pipe 4I, fitted with a globe valve 42, connects the branch pipes 3G and 37, so that by opening the valve 42 uid may escape from the cylinder 2 through the port 39, pipe 36, pipe 37, and pipe 33 to the tank. Another pipe 43 parallel to the pipe 4I is connected to the pipes 36 and 31 and fitted with a pressure release valve 44. In the event the pump 32 is running and the valves and 42 are closed, the pump discharge will pass through the pipe 35, check valve 38, pipe 43,

' through relief valve lli into pipes 31. and 36, and

thence to the tank 3.

It will be apparent from this arrangement that the volume of uid in the closed hydraulic system can be changed at will, even when the press V'is operating; that is, the main motorv driving the eccentric and both plungers'll and 2B reciprocating. By closing valve 40 and opening valve E2, the distance between the bed I and the working face of the presshead -2I (when the press head is atthe bottom ofthe stroke) will increase. By. closing valves 453., and 132,` that distance will decrease. By closing valve d2 and opening valve AI), the distance Will remain xed.

If some operation to be performed on the press requires a gradual but continuous approach of the press head 2l toward the press bed I at the end of each stroke,that may be readily .accomplished by continuous discharge of the pump 32 into the hydraulic system. During each stroke, the pump delivers a fixed amount of Yuid into the cylinder I2, and the following stroke will thus be advanced toward the bed by that amount.

Fixing the adjustment of the rpress head In conventional stamping operations for which this pressl is primarily intended, this distance, which is called in the trade shunt height, is fixed for a given die set and product. The press head is adjusted for the required shut height, and is then iixed for the production run with this die set.

With the stufling boxes of the cylinders I2 and I4 absolutely tight and no leaks whatever in the communicating pipe I3, the volume of fluid would remain the same, and consequently the shut height would remain the same. The adjustment of the system above described would therefore be sufficient to accomplish-the desired result. However, in actual practice the packing in the stuffing boxes Wears, and gradually increasing losses of fluid will result. And any loss of fluid, no mat.- ter how minute, will increase the shut height, and thus impair the resulting product andrequire. the continuous attention of the operator.

lower' vportions enlarged and fdrilledto receive pins for turning them. The upper portions are threaded Von the 'outside and screwed into the ears 14'6 of cylinder I4. JamY nuts 411 are'jprovide'd to prevent any change Vin the position of the stop sleeves 45 after the adjustment has been made-. Pull back rods 217 pass through and are guidedv by the stop sleeves 45.

Whenv the shut height of a givenrdi'e set'vhas been adjusted f hydraulically with theY pump 3| and the valvesfll and42, the stop sleeves are then set in such va manner that the upper surfaces of the ears 28 of the v'press head 2l just contact the lower surfaces -o'f the stop sleeves when the press head 2]- is at 'the-end of its up stroke. The jam nuts 41 are then tightened to make this setting permanent. Such a fixed setting will make 4the Volume -df-'the vhydraulic system permanent, and any leakagev o'f uid during any stroke of vthe plunger Il will produce a vacuum in the system which will automatically cause the control valve 48 to replenish the lost liquid.

The control valve The control valve 48, shown in the large sectieni-Fig. 5), is mounted on top of the cylinder i12, which is open to give access ofthe vfluid to v'the valve. The control valve casing includes a heavy flange 49, a valve seat 55 which guides and seats the hollow valve body 5l, the upper portion of which is threaded for screwing on the sleeve 52, and theupper part of the sleeve is also threaded for screwingv into the spring plate 53. This assembly is` enclosed in casing 54 having a lower flange which, together with the heavy disk 4Q,- is

secured to the cylinder I-2 by bolts 55.

superimposed on the Valve casing 54 in perfe'ctalignment with it is an air cylinder 56with an a-ir piston 5l and closing cap 58 provided with a portv 55. The air cylinder below the piston 5'! has a .port 6l). Fastened to the air piston El? by'meansof a bolt 6l is a packing cap 52 which4 is tightly threaded into a hollow stem' 63 coniining and compressing packing 54. The lower part of the stem 63 is guided in the spring plate. 531 and labuts against thevupper surface of the sleeve 52. A spring 55 is placed between the valve seat 50 and the spring plate' 53.

The lower part of the air cylinder 'con'tains astung leo-x for the hollowv stem 53 consisting Uffa-gland ring 65, bronze guides 5l, and 'com'- pressionA packing 58; Thisl stuing bok" safely separates thev air cylinder 56' from thevalve housing and: prevents any possible leakage between the two.

Placed in thev center oi1v the hollow valve' 5l', sleeve 52, and hollowstem 63 is a small valve 78 seating on the valve part 5l and extending upward' as stem ll is slightly enlarged to form a piston '12, which is lappedl into the hollow part 63 forming Va fluid seal. Below' the piston head 7.22' visv a washer 13. Between this washer' 'F3 and the valve part 5I is a spring 14'. The valve lil, stern ll, andY piston head l2 have a continuous holel for transferring the fluid pressure Withi'nthe cylinder |2` to above the piston head l2. The'valve 'lohas vdirectly under its 'seat' the re'- lieved section 15, which coincides with a drilled port 'l-'I in the valve'l.

Thev control valve serves several purposes asma 'filling-` valve rorfreplenish-ing lostnuid from 6 the lsystern: and, third, byl manual. operation it can lbe used to s'ta'r't and s't'op the 'presslhead The positions of the parts in those threes-'operationsare'shown in Figs. V2, -3, ande.

The control value' as a 'safety vulve' The hydraulic system of the -pressfrnayrbe designed for a maximum Vpressure-for example, `3,000 pounds per 'square inch. If 'that 'pressure is reached in the hydraulic system, it will beeX erted through the holefl-5 in the valve 110 toabove the piston l2. Thal-...piston has a slightly larger area than the seated 'area o'fvalve lll. This difference in area, multiplied by 3,000, rgivesthe total vvforce on the'piston head 'l2 ltending to 'fo-'ree 'the valve 'Iii ori the seat 5l. The spring -14 made to -bala'n'c'e' 'tlatforce-v lshould the pressure of 3,000 pounds pers'q'uare inch be. exceeded, the force on the piston head l2 will overbalanceithe spring 14,'and the'v'alve l0 will leave th'e-seati 5 I and permit uid to escape through the relieved portion 'I6 and hole 'll into the valve 'casing' `'54, and thence through port A65 'into the tank 34. Since the maximum pressure occurs usual-ly'in the last half inch ofthe down stroke, this'comparatively small valve willfully protectthe'equipment against overloading.

In some operations, itis verydesirable to `have `a short pressure dwell on the bottom ofth'e stroke. The safety valve arrangement `may `be used to accomplish this. By over-adjusting the press head somewhat downwardly, the 'dies will be bottomed before the plunger Il has completed its stroke. The excess fluid of Vthe Vremaining stroke will pass through thevalve 'i0 in the manplenishing Valve. The spring 65 balances'thesum total weight of the valves l@ and 5i, sleeve 52, valve stem 'l l, piston head l2, washer 13, spring le, and spring plate 53, .plus the pressure in the tank VSli multiplied by the effective area of vthe valve 5i. In the event the hydraulic system `is short of oil, a vacuum will occur, and the pressure differential between the tankfl and the fluid system willoverbalance thel spring 65 and'rnov'e the valve 5l. ofi `its lseatand permit the tlid'to pass --from the tank 34 .into the system. A's'soon as the system islledlandthe vacuum'. eliminatedl the vbalance is restoredv and thespring if'w'ill close the valve 5lv again,v

The. control calce 'as a liu-'ross volte. for starting and stopping Fig. @shows the Valve acting as "a by-passvvtlve' for stopping and starting the press head.

The piston 5lof the: air cylinderA 55 is nor:- mally in the up position due to theconstant pressure of 15 pounds per square inchmaintained underneath the piston because the port 60 connected through the pipe i8 with the upper part of the tank 3d, which receives its air supplyffrom thepipe i8 through a reducing valve i235. The safety valve 8l limits this pressure to 15 pounds per square inch. With the valve 'i0 closed, the hydraulic system is closed, and the reciprocating plunger i I 'will cause reciprocation'of the plunger 20, andthe fluid will surge through the communiel eating pipe AI 5. Y

vThe 'drive' shaft l' at one vend vllas keyed to it aj cam 82 having a short projecting lug'` '(Figif') which actuated theoperating 'leveri of "a twowith it the hollow stem 63 and cap x52.Y

way air ValveV 84, which is known as a quick-asa-wink, made by Ross Valve Mfg. Co. of Troy, New York.

One port of the valve 84 is connected by a pipe 85 with the operating Valve 89, and the other port is connected by pipe 81 with pipe 1S, which is connected with the port 50 of the air cylinder 56 by the branch line 88. The cam 82 is keyed to the shaft .1 in such a manner that the valve 84 is open for the instant the plunger Il passes through the bottom of its stroke.

Manually operated air valve 'I'he operating air Valve 89 is a three-way inanually operated type, and has an air supply port 90 and exhaust port BI. Placing the operating lever y92 of the valve 89 into starting position will connect the pressure supply port 90 with the port and pipe 85. The instant the plunger I I reaches the next bottom position of the stroke and the plunger 20 with its press head 2| reaches the tcp position, the lug on the cam 82 will for that instant open the air valve 84 and allow air to flow throughpipes 81 and 88 into the cylinder 55, thereby depressing the piston 51 and through the hollow stem 63 in the sleeve 52 open the valve 5 I. On the following upstroke, the displacement of the plunger II will pass through the valve seat 50 into the valve housing 54, valve port 69, pipe 93, and through its hole 94 into the tank On the down stroke, the iiuid will return from the tank in a similar manner into the cylinder I2. On subsequent strokes, the iiuid will surge back and forth between the cylinder i2 and tank 34. In the meantime, plunger 223 and press head 2| remain in their upper position. By placing the operating lever 92 of valve 85 in starting position, the exhaust port 9i will be connected with the valve 814 through the pipe 85. The instant the plunger II reaches the next bottom position of the stroke, the lug on the cam 32 will exhaust the air pressure in the cylinder 5S through the pipes- 81 and 8S.

The air pressure used in this control is 'l0 pounds per square inch. With the air cylinder 56 exhausted, the constant air pressure of 15 pounds will immediately lift the piston 51 and The spring v|55 will close the valve 5|, thereby closing thesystem andon the following upstroke of the plunger I| the displacement will again pass into the cylinder I4 and cause the down stroke of the plunger Y and the press head 2|. This control can be arranged for single stroke operationor for repeat stroking. Instead.v of hand control, foot pedal operation may be provided.

For the purpose of inclining the press, two pedestals 94 with pivots 95, one on each side of the press, are provided. The entire press is supported by those pivots, and by means of a slide block 96 engaging lug 08 and screw 91 the press can be inclined. By inserting pins 99 in holes |00, the inclined position may be locked. Other means may obviously be used for inclining the press. Y I Alternative value and pipe arrangement for auxiary pump Fig. 9 shows an alternative valve and pipe arrangement for use in connection with the auxiliary fluid pump 32. The pipe delivers to branch pipes I0| and |02 through a piston valve 8 and the by-pass is fittedV with the globe valve |06 and a relief Valve |01.

The piston Valve is shown in section in Figs. 10, 11, and 12. It includes a casing |08 having threaded nipples to receive the ends of the pipes 35', IOI, and |02. It is hollow and mounted to slide therein is a piston Valve |09 having heads I|0 and III and a central bore |I2 connected with ports I3 and I0.

The valve proper I 09 is shifted by stems II5 and IIS equipped with knobs |I1 and |I8 and urged to a normal position, shown in Fig. 11, by springs I9 compressed by caps |20.

The arrows in Figs. 10, l1, and 12 indicate the ow of the uid. With the parts inthe position shown in Fig. 10, the press head will be adjusted downwardly, while with the parts in the position shown in Fig. 12, it will be adjusted upwardly; and with the parts in the position shown in Fig. l1, the output of the pump is lay-passed back to the supply tank 3B.

No values impede the flow in the hydraulic system 1n the invention here disclosed, the force` of a single mechanically driven plunger is transthere is no valve to impede the flow between the plungers. The uid surges back and forth freely. The Valves used in the press are auxiliary, separate from the system-one, to limit the pressure to that for which the press was designed; to replenish the iiuid reduced by loss; three, to control the surge to start or stop the press; and, four, to vary the Volume of fluid to adjust the press.

Specific examples 7,040 pounds at the end of the down stroke. This force will create a hydraulic pressure on the plungers of pounds per square inch minimum and 250 pounds per square inch maximum.

The safety feature or pressure relief feature of the control valve 48 is performed by the small check valve 10. As previously stated, the effective area of the lower portion or head of, this valve is somewhat smaller than the area of the piston 12 carried by the upper end of thevalve stem 1I and lapped into the cylinder 63. Assume the diameter of the head of the small check valve 10 to be 1 and the diameter of the piston 12 to be le", the difference in area is .1012 square inch. The passage 15 through the small check valve transmits the pressure of the hydraulic system to the cylinder 83 above the piston 12. Assume a maximum pressure desired in the systeinof 3500 pounds per square inch, the maximum force of the piston head pushing the valve open is the diierence in area multiplied by 3500 or 3,54 pounds. Thisforce lis balanced by the Valve, 51 acting as azby-pass for starting, and= stopping press '1 'Assumingthe diameter :ofthe seated,` part of the valve 5| to be 3" and the outside diameter of the sleeve or hollow spindle 63 to be 21/2", the differential area will be 2.16 s'iuare inches.

Due to the timing valve 84, the opening and closing of the valve 5| can only take place during the up stroke of the press head or the down stroke of the eccentric. During this period, the prevailing hydraulic pressure, as previously shown, is 125 pounds minimum or 250 pounds maximum. This pressure is exerted on the under side of the valve 5| and causes a total upward pressure of 884 pounds. Counteracting is the downward force caused in the valve housing on the differential area at the prevailing tank pressure of pounds per square inch, or a total of 32.4 pounds. There isan additional upward for-ce caused by the outer spring 65 of approximately 45 pounds. The press head dwells against the adjusting nuts at the top of its stroke. During this dwell, the reaction to the hydraulic upward force is taken up by the frame of the press through the adjusting screws or sleeves 45, so that the only upward pressure against the valve 5| is the net force existing in the valve housing, which is 12.6 pounds. This is the force to be balanced by the air piston 51 on the control valve. The diameter of the piston is assumed as 5, and the air pressure is therefore .64 pounds per square inch. To this must be added the constant pressure of 15 pounds per square inch prevailing under the piston 51, which makes the required pressure for opening the valve at least 15.6 pounds per square inch. Actually, the required pressure will be somewhat less than 15.6 pounds per square inch, since the eiective area of the lower face of piston 51 acted on by the tank pressure is less than the effective area of the upper face of the piston 51. Because very snappy action in opening the valve is desired, a pressure of pounds is used. When the air is exhausted out of the cylinder 56, the constant pressure of 15 pounds per square inch beneath the piston Will raise it, and the sleeve or spindle 63 fastened to it. Since this force is 295 pounds, it is sufficient to pull this sleeve through the stuning box. The valve 5| will be closed by the spring 65.

Valve 51 acting as a replenishing calce for keeping the system constantly filled The outer spring 65 balances the weight of all the inner valve Darts, assumed to be 9.63 pounds plus tank pressure in the valve housing of 32.4 pounds, or a total of 42 pounds. Should at any time fluid be lost from the system, a vacuum will be instantly created, which opens this valve and lls the cylinder from the tank. The instant the system is filled, the vacuum is broken and the valve closes again. This arrangement permits the sleeves 45 to be over-adjusted downwardly, producing a vacuum in the system at the top of the up stroke with the resultant slightly over filling of the hydraulic system, and the result, at

',"10 the bottom of the stroke o-f a dwell, during which the excess hydraulicfluid ofthe system will be exhaustedthrough the valve10.

Constant gauge indication V'of ypressure In theconventional press',- the accuracy of the adjustment depends upon the skill and judgment of .the operator, and `there isno way to determine 3 readily:` what pressure is being exertedby the press. .'Toovercome this difficulty, theimproved rpress here disclosed is provided with# at, lconveniently located, hydraulicfpressure. gauge" connected withthe.closedzhydraulic ssystem so that the pressure per square inch can be observed directly and adjusted by the valve and pipe arrangement of the auxiliary pump.

In Fig. 1, the gauge |50 is shown connected directly to the branch pipe 31, and in Fig. 9 to the branch |65. But these are mere suggestions, and other connections will be readily made to suit particular conditions or personal preference.

I claim.:

1. In a pre-s, a Work bed, a slide movable toward and away from the bed, a frame having an upright portion provided with a connecting block at its upper end, a hydraulic power-transmitting device having a driving piston and cylinder mounted on one side of said upright portion and a substantially parallel driven piston and cylinder mounted on the opposite side thereof, a fluid connection between said cylinders, an eccentric mechanical drive for the driving piston to impart substantially simple harmonic motion to such piston and through the iluid connection with the driven piston to impart similar motion to that piston, and means connecting the driven piston to the slide, said cylinders being rigidly associated with the connecting block and of such cross-sectional area and so spaced from said upright portion of the frame that the moments exerted on the connecting block by said driving and driven cylinders and pistons are substantially equal and opposite, thereby substantially eliminating bending stresses from being developed in said upright portion of the frame during the press operation.

2. A press as set forth in claim l, including means to adjust the amount of fluid in said uid connection, said last named means including a fluid pump and valved passageways associated therewith for enabling the pump to add to or subtract from the amount of fluid in said fluid connection.

3. A press as set forth in claim 1, in which means are provided for adjustably fixing the shut height of the driven piston, and valve means are provided in said fluid connection to automatically regulate the amount of fluid in said connection to properly accommodate the selected shut height.

4. A press as set forth in claim 1 in which means are provided to adjust the amount of uid in said iluid connection While the press is '1n operation.

5. A press as set forth in claim 1 in which means are provided to adjust the amount of uid in said uid connection, said last named means including a valve responsive to pressure in said fluid connection for maintaining such pressure within prescribed limits.

ALOIS KARL NOW'AK.

(References cn following page) REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date Nagel et a1. Jan. 28, 1913 Lewis June 15, 1920 Wood Sept. 19, 1922 10 Ferris Dec. 19, 1933 Lapointe May 1, 1934 Ferris Nov. 13, 1934 Number 2,014,162

Number 12 A Name Y Date Benedek Sept. 10, 1935 Sciaky Mar. 30, 1937 Smith Dec. 31, 1940 Pocock et a1. Sept. 15, 1942 Blair May 7, 1946 Stevens Aug. 19, 1947 FOREIGN PATENTS Country Date Great Britain June 10, 1924 Great Britain 1 June 25, 1945

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