US2616265A - Means for adjusting fluid motor elements to maintain synchronized movement - Google Patents

Description

MEANS FOR ADJUS'TIIIIG FLUID MOTOR ELEMENTS TO MAINTAIN SYNCHRONIZED MOVEMENT Filed Aug. 24, 1949 INVENTOR. AOBERTC. W/L50N BY www L m i ATTORNEY Patented Nov. 4, 1952 MEANS FOR ADJUSTING FLUID MOTOR ELE- MENTS TO MOVEMENT MAINTAIN SYNCHRONIZED Robert C. Wilson, Warren, Ohio Application August 24, 1949, Serial No. 112,043

9 Claims.

My invention relates to means for adjusting an element or elements and has for its principal object to provide new and improved means of this character.

The invention has particular application to means for causing to move in unison, or according to some convenient ratio of motions, or alignthe position in accordance with that ratio, two or more hydraulically operated pistons (or cylinders) for the purpose of performing some useful work or function, regardless of the relative amount of axial load within the capacity of the means and which is applied to each at a given instant, and which load is substantially stationary, resists motion of the pistons, or is the means by which motion is produced and against which the pistons, singly or in combination, act as resistance.

Generally, my invention comprises connecting hydraulic pistons in a hydraulic system in series relationship, that is, using the motion of one of the pistons, which, itself, may or may not do other useful work, to move fluid affecting the movement of the other of the pistons, so that the latter piston or pistons move in whatever ratio exists between it (or them) and the first named piston, and further comprises means for compensating the efiect of variables by adding or removing fluid from the supply of the latter piston or pistons.

My invention has great application in industry, and for example, but by no means as limitations, my invention may be used in the hydraulic system of a press for advancing or retracting the press platen, and including means for preventing, within practicable close limits, one end of the platen from lagging behind or preceding the other end, to compensate for unequal loading of the platen. My invention may also be used in combination with a system for raising or lowering a long sheet piler table, especially where the length of the sheet or position of the pile on the table varies considerably. Further, my invention may be used to obtain accurate adjustment of motion or position of separate pieces when one of such pieces is caused to move. It will be appreciated that many other applications, not herein specifically mentioned, are possible. In the drawing accompanying this specification, and forming a part of this application, there is shown, for purposes of illustration, an embodiment which my invention may assume, and in this drawing:

Figure 1 is a generally schematic view of a hydraulic system showing an embodiment of my invention, and

Figure 2 is a fragmentary view of a detail of construction shown in Figure 1.

Referring to the drawing, the embodiment herein shown to disclose the invention is applied to a hydraulic system for a downclosing press, although it will be appreciated that such application is for illustration purposes only.

The press herein shown comprises a movable platen I2 and a stationary bed or bolster surface 5!, the platen, in this instance, being moved by two pistons 4 and B which are connected to the platen in any suitable manner. Fluid under pressure for the purpose of operating the system may be provided from a suitable source [3, such as a fluid pump or fluid supply system.

A conduit 2 leads from the fluid source l3 to the top of the cylinder of the piston 4, and a conduit i I leads from the fluid source to the bot tom of the cylinder of the piston 8, the connections being so constructed and arranged that either conduit may be a supply line or a return line for fluid, depending upon the direction of travel of the platen. A source of auxiliary fluid pressure I is available at all times while the fluid source I3 is operating, and this auxiliary supply has a minimum pressure sufiicient to be applied to support the platen and articles attached thereto against the force of gravity.

In advancing the platen l2 toward the bolster surface 5!, suitable valve means (not shown) are shifted so that fluid under pressure from the source 13 is delivered through the conduit 2 to the space 3 of the cylinder for th piston The piston E is movable in a cylinder to provide an effective diameter D1, and fluid pressure against the piston causes it to move downwardly in its cylinder. The piston rod 69 is of smaller diameter, D2, than the piston 4, and as this piston moves downwardly the annular space 5 below the piston is decreased in cubic content, thus displacing fluid therein through a conduit 8 to the cylinder for piston 8, to cause this piston to move downwardly. For purposes of this description, the piston 4 will be referred to as the master piston and the piston 8 will be referred to as the servant piston.

In the case (as in the embodiment herein shown) where it is desired that the master and servant pistons move substantially each an identical amount, the cross-sectional area of the annular space 5 is equal to the effective area of the piston 8 having an effective diameter D3. Thus, for all practical purposes, and disregarding variables such as fluid compressibility, leakage, elasticity of materials, and the like, downward movement of the piston i will effect corresponding and equal movement of the piston 8. Mathematically the diameters relate as follows: D1 -D2 :D3

During stationary periods or motion downward, the platen and connected parts are pre- 3 vented from falling of their ownweight by fluid compressed in the annular space 9 in the cylinder below the piston 8 and by resulting pressure in the amuiarsp 'ce 5 in the cylinder below the piston 4. Pressure in the space 9 is main tained. by a relief valve section of a counterbalance or foot valve In. The valve l6 may be of any available commercial; constructionv and accordingly need not be ii'escribed detail.

Suflice it is to say that the valve meaning fr' fluid flow from the conduit ll into the annular space 9, but prevents, except by leakage, fluid flow from the annular space s andinto the .conduit ll until after a predetermined"fluidprs sure is reached in space S. The valve is so set as to open at a pressurewhich is slightly higher than the'pressure resulting from, the weightof the parts acting upon. the effective, cross-sec,- tional area of space 9,. Thus, to movethe. p aten l2 downwardly even against no platen resistance requires a positive pressure in cylinder, space 3 which in. turn increases. the positive pressure in spaces 5, land. 9. sufiicient to openvalve l0. Accordingly, a partial 'vacuum which ordinarily would falsify the volume of spaces. 5. and l, and conduit 6 is avoided.

In moving the platen I2 inatdirection. away from the work and toward its openrest position and, also for compensating for leakage so as. to maintain the platen initslres t position, the valve controlling fluid flow through conduits fixandul-l is shifted so that fluid under pressure issupplied through conduit H, and the valve 1 i1. provides free passage of such fluid-tothe annular space 9 below the piston 8-. When sufiicient pressure is exerted in the space 9, the piston-8 is. moved upwardly, moving its corresponding endofthe platen. Also, as the piston 8--moves upwardly, the space I is decreased in cubic content and fluid is displacedfrom this space and flows through conduit t-to the annular space 5 below the piston 4, and as a result the piston 4 is moved upwardly in unison with the piston 8, and that end of'the platen to which the piston this connected is also movedupwardly. Duringthis operation, fluid is displacedf-rom space-3 above the piston 4 and flows through conduit 2, which is either connected'to pump intake or tea reservoir or drain. Thus, it willbeappreciatedthat the functions of the master piston 4 and servant piston 8-are reversible, depending uponwhether the platen is to be lowered-orv lifted.

The foregoing means andmethodpreferably are used in cooperation with a means to add or remove fluid from space 7 when necessary to maintain the platen parallel to the bolster plate within the desired degree of accuracy. A simple example of such an application might bethe foregoing means combined with a manually operated valve to add or remove fluid from space I by the skill of the operator observing the efiect on the work.

For the purpose of detecting the efiect on the angular position of the platen as caused by such variables as leakage, fluid compressibility, elasticity of parts, and the like, my inventionprovides an indicating means, one embodiment of which will now be described. I

Secured to one end of a stationary bed or bolster plate 25,- in any suitable manner, as, for example, by a pin passing through a bracket 25, is an accurately cut spur-gear toothrack' iii-of a desired length. The rack l4-is inmesh'with an accurately. cut spur-gear I5, proper rack and gear engagement being held in any suitable man 4 ner, such as by a back-up roll. Fixed rotatably with the gear I5 is a suitably rigid shaft l6 which is mounted in spaced bearing brackets I! carriedvby the platen l2. r v

A spur gar l8; similar to the gear I5, is secured to the opposite end of the shaft for rotation therewith. The gear I8 meshes with a spurgear rack 19 which is similar to the rack I4. 'lfhe rack; la however, has a rod section l9a which has-asliding bearing fit with a bearing blockjfl secured to the bolster plate 5| so as to hold the rack 19 to longitudinal reciprocable, movement, The top of rack 19 may also move in direction generally parallel to the axis of the shaft I6, since the bearing block 20 has pin engagement with a, supporting block 2| secured; to the bolster, plate; 5 Aback-up roller t; en a e the ea l i i ce he a nd maintains it in proper; meshing relationship with the gear l8.

Secured to the I rodsection l 9a,; of; the rack l9 isa. pair of spaced apart collars I 24 and 2 5, each of. which m yb adius e e on -ihe n $6 193 [9a and, held; in desired adjustment by means of set-screws, The, collars, 2 4 and 25 respectively carry adjustable. screws 24c and 255a. The bearin block; Zia-carries a pair of electricaldimit switchesfli, and; 23,- each having an operating stern in line with a respective screw; 24a, 25a,

Thus. by. means w n c q ars,- 5 and: I8, at any given instant, gear teeth on both racks are always at; the v same position relative tathe p a e .plane rentho gh h an a been shifted with respect to the bolsterplate. sians s h plat n vI mo v nddgwn a-plane-initi ll s bl sh by the in of ea mesh and by; the, positionof the adjusting screws 24a, 25a with respectgto the limit switches 22f, 2 3, neither limitswitch stemw-illbe operated byan adjusting screw,,

If, for example, theleft hand; end (with reference tothe drawing) of the platen; I2 began to, precede the; right hand end duringadvance: mer t, of the platen lg, or-ifthe left hand end lags the right hand end whilelreturning, Or would tend to drop while at rest, the rack l9 would belowered acorrespondingamount through eneasement. with the gear [8, and the adjusting screw 25a. would be, moved into engagement with the operating stemoflimit switch 2-3;to effect operation of this limitswitch. Y Onthe. other hand, if the righthand end of the, platenprecededthe leftv hand end during advancement of theplaten, orif it lagged during retraction or tended "to; fall, the rack I 9, would be. moved ,upwardly to bring adjusting .screw 24a into, operating. engagement with the stemof limit switch 22.

It will be appreciated that instead of, limit switches2'2, 2 3,, suitable valves, or mechanical indicators maybe usedfor cooperation with the respective adjusting screwsl24e, 2511. Operation of .thetlimit switches (orval'ves and the like) may actuate a correction means as later described 'ora signalling devicetoindicate to an operator that the..platen. lZis-notrunning according to a desired angular-relation with-respect to the bolster .plate 51; so. that the operator may make necessary adjustments, either mechanically. or l'rydraulically.v

In the present embodiment, the-limitswitches provide forautomatic compensation when the platen is not running. indesired angular relation with respect to. the bolster plate,- and w for. this purpose when the left side of the platen is lower than the right side, the limit switch 23, operated by this condition, is electrically connected to energize the solenoid 3|a of a normally closed solenoid-operated spring-returned two-way valve 3| and so permit flow of fluid under pressure through conduit 30 and 33 to the cylinder of servant piston 8. When the right side of the platen is lower than the left side, limit switch 22 operated by this condition is electrically connected to energize the solenoid 43a of normally closed solenoid-operated spring-returned two-way valve 43 and so permit flow of fluid from the cylinder of servant piston 8 through conduits 33 and 45. The conduit 45 for the present time may be considered a drain conduit. A needle valve 42 or other means for controlling flow is preferably interposed in conduit 33 leading to solenoid valve 43, and a similar needle valve 32 or flow control valve is preferably interposed in conduit 30 leading from solenoid valve 3|. is convenient to assume that the check valve 44, solenoid valve 430, needle valve 420, check valve 440, and conduit 450 are non-existent.

For purposes of the description of the means and methods up to this point, it may be assumed that conduit 30 is connected to a source of fluid under a pressure higher than that in space of the cylinder of servant piston 8, so that if the platen is rotated to effect operating of limit switch 23, the solenoid valve 3| will be opened to permit fluid to pass through conduits 3D, 33 to the space '1 above the servant iston 8, and this servant piston will be urged downwardly a sufficiently greater amount than the master piston 4, or the master piston will be urged upwardly as the case may be, so that the platen |2 will be realigned. As soon as the platen is re-aligned the operating stem of limit switch 23 will be disengaged from adjusting screw a and the valve 3| closed. In the event the platen I2 is oppositely rotated sufficiently to operate the limit switch 22, the valve 43 will be opened so that pressure fluid from the space 1 above the servant piston 8 may flow through conduit 33 to drain, or to be used by other mechanism, whereby fluid volume in the space 1 will be reduced sufficiently to allow either the servant piston 8 to move upwardly or the master piston 4 to move downwardly a sufficient amount to re-align platen l2, and, thus, to stop flow by releasing stem of limit switch 22 which closes valve 43. By means of multiple limit switches operated successively, or a rheostat or the like in combination with multiple valves, or a variable orifice valve, fine and coarse rates of fluid addition or removal may be had. That is to say, if only slight misalignment occurs only a small amount of fluid would be necessary for a fine correction, whereas if large misalignment occurred then a correspondingly large amount of fluid would be necessary for coarse correction.

For general applications and especially where the loading on the platen changes to some unpredictable position at substantially every stroke, the foregoing described methods and means would suffice.

In the present embodiment, the higher-pressure fluid for conduit is provided by a pressure intensifier 4n. As herein shown, the annular space 400. of the intensifier cylinder 38 is connected by conduit 4| to conduit 30 through a check valve 29. The intensifier 4|! is charged when not in use from an auxiliary pressure line 21, the pressure of which is sufficient to be used by valve 3| in maintaining the rest position of For the present it the platen and its connected parts against gravity. Check valves 28 and 56 prevent the escape of fluid under pressure developed in space 40a to regions which at the time may be of lower pressure.

The intensifier 40 includes a piston 31 working in a cylinder 38, the reduced-diameter rod end 55 of which cooperates with the cylinder 38 to form the annular space 49a. leads from the piston-face end of the cylinder and a check valve 36 is interposed in this line, but for the present it is convenient to consider valve 36 as being non-existent. A conduit 34 establishes communication between the check valve 36 and the pressure supply conduit 2.- As fluid pressure increases in the conduit 2, such pressure is also applied to the face of the piston 31 to urge such piston upwardly (with respect to disposition of parts in the drawing) so as to tend to reduce the volume of the space 4611 and thus build up a higher pressure therein than that supplied by the input fluid because of the unequal areas existing on opposite sides of the piston 31. As before described, the high pressure built up in the chamber 43a will be used to re-align the master and servant pistons if and when valve 3| is opened by limit switch 23. Any fluid exhausted from annular space 49a is replenished during the return stroke of the platen, since at that time no pressure exists in conduit 2, and fluid under pressure from the auxiliary source may flow through conduit 21, past check valve 28 and to annular space 400., and such pressure acts against piston 31 and forces it downwardly against the head of cylinder 33.

Although any other suitable source of fluid under pressure may be used to operate piston 31, fluid pressure from conduit 2 is preferable, since in operating piston 37, which for a given input pressure is constructed to produce a higher pressure output than the output of the master cylinder some or all fluid is denied piston 4, and as a result piston 4 hesitates or is slowed in its movement until piston 8 is brought abreast.

During the time the platen is returning, that is, during its upward travel, against resistance, and when fluid under pressure needs to be added to spaces 5 and in order to re-align the platen, addition of fluid through conduit 30 originates in space 60 through conduit 5! which at that time is maintained at higher pressure than the pressure in space I by means of a deintensifier 59, which, in certain cases could be replaced by direct connection of conduit 51 to conduit The de-intensifler 59 and connected means are used principally to operate apparatus to be described subsequently but are also used to increase the amount of fluid originating in conduit II to be added to space 1 when required by valve 3|, so that returning motion of the platen will proceed more smoothly. In other words, because of the relatively small cross-sectional area of the annular space 9 of the servant cylinder, a small amount of fluid supplied to such space produces a comparatively large amount of movement, and likewise, if a small amount of fluid were removed from conduit H and added directly to space 1 in order to make minor correction to the angular position of the platen, while correction was being made the platen might stop entirely for an objectionable length of time dur-. ing its return motion.

The pressure de-intensifier 59 is charged during or before the platen I2 is in the advancing half of its stroke, so that at this time fluid flows A conduit 35 71. from the auxiliary; pressure conduit 2.:1, through. check valve 5.8 and through conduit tothe space 60,, so. as to drive the piston 6.:l downwardly against the rod end of cylinder 62. Fluid below the piston BI is exhausted from the cylinder 62 by means of aconduit 65,. which for the present time may be considered as, connected to drairr.

To move the piston 6| upwardly from the rod end of the cylinder 62, fluid under pressure from conduit H is utilized. For this purpose, a.- branch conduit 67 is connected to conduit vI I', a check valve 66 being interposed between the. connection of conduits 61 and65, for. the purpose of permitting fluid flow to the rod end of cylinder 62 but preventing such fluid from, returning to. the conduits 61 and; It. The check valve 66,, like check valve 36 is not required for odd job presses, and could. for these applica: tions be eliminated so that. conduit. 65 connects. directly to conduit it.

The pressure of fiuidin. annular space 63 acts; on the rod side of piston 61,. applying a. force thereto: which produces: sufiioient. motion of the piston so as: to displace fluid from space 60 in volume greater than the; volume of fluid. deliveredto space63'. In general, the ratio of. areasof: space 63- compared with: space 60 is. such as to provide a hydraulie advantage over the ratio. of. areas of space 9" compared with; space T. It will: be appreciated that any other source of; higher, pressure fluid, such as that in conduit ll). may be utilized in place: of the. pressure de-, intensifier 59..

The-foregoing description; in summary.. discloses means and methods for causing the platen to remain parallel to the bed. until some variable factor or factors cause the platento rotate either while stationary or while moving, and then. after rotative misalignment: occurs, which. isv detected by the indicating means comprising the limit switches 22,. 23:, to correct such misalignment by adding: or removing fluid as required.

- .The means, and method aboutto be described cooperates: with the foregoing means and moth.- odsbut serves. the, additional purposezof'ant-icipating the degree of correction. of the platen which will be required: as: variables; occur and.- of? makingr correction onthis basis during; occurence; 0t variables; which,v if' left, uncorrected, would ordinarily-produce misalignment of. the platen withrespect to the bolster plate.-

The; means illustrated in the; drawing, and the means and method herein described, at the present time are. considered preferable, although it willbe appreciated that the invention: is not limited to this specific. disclosure; A. simpler means than is later described; for: examplaiollows. Experimentally, the average amount of fluid. which must be added to make up for com. pressibility, fluidleakage; elasticityof. parts and the like, is found-for increments of the stroke ot the. platen and a curve amountof addition vs. stroke is plotted. A suitable plunger pumpfor making addition and: later for; removing-this addition; maybe constructed and-operatedby. a cam. which satisfies the-conditions. of the above curve and which, inturn; is; movedrdireetly or indirectly by themotion of. the platen. In this casethe; degree of correction. is proportional. to the eflective area ofthe: pump; whereas: therate of correction is determinedi by the. slope of the cam.

- Themeans and methods; herein disclosed, .however, use the present and lorf previous-amounts ofia'dditions:and/orremovals of. fluidito. determine thedegree of; correction required and the pressure; fluctuation; of the primary supply of fluid, todetermine the rate at which correction is applied.

In the embodiment of the invention herein disclosed, apparatus to the left of the conduit 2,, that is, the apparatus within the dot-dash line 200 relates to means and method of determining and making the degree and rate of correction while-the platen is advancing and the apparatus at the right hand side of the drawing, that is the apparatus within. the dot-dash line 20lrelates to means and method of determining and making the degree and rate of correctionwhile: the platen is returning.

Referring to the drawing, fluid is added to spaces 5- and l and subsequently removed again by contraction and. subsequent expansion of the length of the annular space lll' formed bya cylinder l2; and the piston rod 14- oi. a. piston 13. The operating face of the piston 13 is normally heldagainst the head of the cylinder 12,. as willbe explained. Thepiston 13 is moved away from the: cylinder head by means of fluid supplied to an undercut H the head of the cylinder l2. Fluid reaches undercut H through. a passage 15- extending through the piston 13- andpiston rod H, and. partially through: a valve-v spool. !6 con- IlECtBdatO or integral with the piston rod. 1-4.-

The valve spool 76 has an annular groove-16w whichcommunicates with thepassage 15 The bore of. valve body TI mates: with the valve spool witha sliding, fit, and, whenthis body is caused to slide ina direction away from the piston: rod 74, the internal, annu1ar,. cored passage 18dof the; valve body passes-partially over the adjacent lip of the groove 16d and permits fluid to flowfrom a flexible conduit 18 to' groove 16a and through passage 15 to undercut H, such fluid acting on theoperating face. of the piston 13 to drive" such piston inthe same direction as that in which the valve bodyll was'moved. Movement oi the piston will continue until the groove 16ais again sealed from the passagelfla.

On return movementv of the valve body 11, if the: piston T'3'is not already" against thev head of cylinder 12, the internal cored passage 19aof: valve body H passes partially over the-adjacent lipof the groove 7 6a. and permits fluidfrompassage 15 toenter the annular coredpassage 19a.

andtopassthrough a flexible conduit 19 to drain,. thusv removing fluid fromundercut 'H' and permitting thepiston 13.- tomove: bymeans. of. pressure in space Ill, which. pressure originates inspace 7', toward the head of the-cylinder 1 2 and in the same direction as the valve: body 11 was moved. Motion of the piston 13 will continue until: the piston hits the headof the cylinder: 1.21 or. until the groove 16a hasmoved'sufliciently to-seaL cored passage 19a; This arrangement. is one form of a servo valve control; andpermits a lightforce; generally" sufilcient to; overcome sliding. friction, applied to the. valve body 11 to control theimot-ion and position" of piston 13, whichin turn controls the volume ofspace 10; It will be appreciated that my invention: is-not limited to the particular form. or arrangement ofparts as specifically shown.

Fluid for operating thepiston 13 is supplied through conduit 18, as just. described, and.- this conduit is connectedto a-iconduit 80- leading into conduit Zl A check Valve 82' is interposed in the line established. by conduits 18, 805' and this checklvalve' permits free flow of. fluid fromthe conduit.- Is to. the conduit 2. but-prevents flow ct 9,. fluid in the reverse direction. A branch conduit 8la by-passes the check-valve 82 and a low pressure relief valve 81 is interposed in this branch conduit whereby fluid may flow under slight differential pressure from the conduit 2 to the conduit 18. The relief valve 8| provides for control of minor pressure fluctuations so that the piston I3 is not shifted undesirably. The check valve, in permitting flow from conduit 18 to conduit 2 provides for rapid de-compression of the fluid in space 10. In certain instances, valves 8| and 82 may be eliminated and conduit 18 may be connected directly to conduit 2.

Since it is desirable that fluid addition from space H3 of cylinder 12 to space I of the servant cylinder should take precedence over addition of fluid from space 40a of intensifier 443 to space 1, even though valve 3! is open at that time, hydraulic advantage is provided for space 10 by making input output ratio of the cylinder 12 slightly higher than input output ratio of the intensifier 40. Thus, during advancing movement of the platen l2, when variables are encountered which would tend to produce platen rotation, the means for making simultaneous correction takes precedence over the means for making correction after rotation has occurred, and this, of course, takes precedence over means which causes further motion of the platen, until correction is made.

The valve body I! is connected to one end of a lever 90 by means of a pin 9| which both mounts the lever and permits it to rotate in the plane of the drawing. The other end of the lever is attached, by means of rod-eye and block connection 89, to a suitable small piston 81, the axis of which is substantially parallel to the axis of the valve spool 16. The piston 8! operates within a stationary cylinder 86 and is moved outwardly from this cylinder when fluid under pressure is supplied to the space 85 within the cylinder. Fluid under pressure is supplied to the cylinder by means of a conduit 83 which is connected to the conduit 80 and thus receives fluid from the conduit 2. A needle Valve 84 is interposed in the conduit 83 to control flow of fluid therethrough.

The piston 81 is normally bottomed in the cylinder 85 so that a stop collar H3 is held against the cylinder face by a light force produced by a spring 88. The opposite end of the spring 88 seats against a stationary washer, and the spring opposes motion of the piston to a certain degree. The spring 88 has suitable loading deflection characteristics so as to hold the piston 81 to accurate movement in linear proportion to the fluid pressure in space 85.

When the system is at rest, that is, when stop collar H3 is against the face of cylinder 86; when piston 13 is against the head of cylinder 12; and when the core passages 18a and 19a in servo valve body '51 are in neutral or sealed-off position, then the position of parts is such that a line which is established as the lever centerline by joining the center of pin 9| with the center of the pivot in sliding block 89 is substantially at right angles with the longitudinal axis of the valve spool iii.

A carriage 93 is slidably mounted in ways on a stationary base 94, in position to slide substantially parallel with the "at rest position of the center-line of the lever 98. The carriage has supports for trunnion pins 92 on both sides of the lever which pins are integral with blocks -slidable in machined ways in each side of the lever. By moving the carriage 93 along the base 94, the center of rotation formed by the trunnion pins 92 may be made to coincide with the rotat ing center of the servo-valve connecting pin 9! or the rotating center of the rod eye 89, or any intermediate point therebetween. The trunnion pins and blocks provide a movable fulcrum for the lever 90.

The movable fulcrum provided by the pins 92 and the lever provides a means for varying the movement of the servo-valve body 11 with respect to the movement of the piston 81, the latter moving in linear relation to the fluctuation of pressure in conduit 2. The movement of the servovalve body ll, however, controls the amount of fluid which is produced by or returned to space 10 and thus controls the amount of fluid added to or removed from space 1 of the servant cylinder, and therefore efiects a means for correcting platen rotation. Taking pressure rise from zero to a given pressure in conduit 2, less fluid will be added to space 1 of the servant cylinder if the fulcrum center of lever 99 is closer to pin 9! than if it were closer to eye 89, and vice versa.

If the amount of fluid which was added to space 1 of the servant cylinder by valve 3| during the advance portion of several previous platen strokes is used, through suitable means, to move the fulcrum of lever 90 toward eye 89, then the amount of fluid added from space 19 to space i will be increased for following strokes as the pressure rises in conduit 2, and will successively diminish the amount which must be added by valve 3| as the result of that rise in pressure if the factors which tend to produce platen rotation remain fairly constant for the set of platen strokes under consideration.

If, to the contrary, the amount of fluid removed from space 1 of the servant cylinder during the advance portion of several previous platen strokes is used, through suitable means, to move the fulcrum of lever 90 toward pin 9|, then the amount of fluid added from space 10 to space 1 will be decreased for following strokes as the pressure rises in conduit 2, and will successively diminish the amount which must be removed by valve lit as the result of that rise of pressure, if the factors which tend to produce platen rotation remain fairly constant for the set of platen strokes under consideration.

If the two functions, increasing and decreasing of fluid addition, are alternately opposed, that is, if the fulcrum of lever 98 is moved toward pin 9| while the platen is advancing and if the fulcrum of lever 90 is moved toward eye 89 while the platen is returning or at rest, and, further, if conditions which determine the need for correction by fluid from space 10 are constant for the set of platen strokes under consideration, then it follows that the fulcrum of lever will approach and oscillate with decreasing amplitude about an optimum position on the lever which would produce addition of fluid from space 18 of the exact amount of fluid necessary to compensate for variables such as fluid compressibility, pipe line expansion and the like as the pressure in conduit 2 rises.

The foregoing described means and method can be made to operate with considerable accuracy to provide (for a given position of the fulcrum of lever 99) equal increments of correction for equal increments of pressure rise of the system supply, and the foregoing should suflice for most applications. However, where it is desired to be more accurate, experiments may have to be made 1.1 ;to determine ror agiven fulcrum position what actual increment of correctionis requiredrfor each successive increment ofpressurerise in'the supply. Having determined .the relationcurve fcorrection vs. pressure,-the motion of .the eye 89 mayithen .be operated indirectly by the .motion of piston 81 through a cam mechanism satisfying .the

relations found, instead of in the direct manner illustrated.

Loss of fluid in any passage or conduit directly connected to space I of the servant cylinder will be the principal reason for causing the fulcrum of lever 90 to oscillate, if all other conditions remain substantially constant. Since the amount of fluid existing in spaces and 1 is constant, and since addition to increase'the volume of that in space I is made at the expense of a decrease in volume of space I0, "which decrease is constant fora given pressure increment and a given fulcrum position, it follows that leakage depletes the supply, :the .proper degree of correction will not result from the same amount of volume decrease in space I 9 as was .formerly sufflcient, resulting, consecutively, iin slight rotation of the platen, correction by addition through valve 3|, and finally movement of the fulcrum toward eye 89.

The next stroke after such correction for leakage occurs will result in too much of a decrease in volume of space 70 because of the new position of the fulcrum at that time which will result in platen misalignment in the opposite direction, correction by removal of fluid through valve '43, and finally movement of the fulcrum of lever 99 toward pin 9i. If leakage is slow, the "functions described will cause the fulcrum of lever 90 to again reach its original position after a few strokes.

For the average large quantity lot of work done by a press, it may be assumed that during the batch of work while dies remain in the same position, the character of the work is such that the center of work resistance to platen motion wi l occur within close limits at the same place and remain at its place throughout the stroke. The character of work, however, may be such that the center of work resistance may move radically during each stroke, but in the same manner repeatedly for successive strokes. A good example of this type of work is that of drawing, by means of a punch attached to the platen and a die attached to the bed, a large symmetrically shaped part thus establishing the center of work resistance at the center of the punch, and then, after drawing, embossing heavily one small section located considerably off-center, thus causing the center of work resistance to move rapidly toward the section being embossed. To prevent constant fulcrum oscillation of a large amplitude which would result from such conditions, the preferred method would be to provide means to temporarily block conduit 93 from conduit 2, and instead connect conduit 83 to some different source of suitable regulatory pressure at the time work resistance shifted, and thus artificially produce the desired results.

For purposes of moving the carriage 93, in the embodiment herein shown, a piston IDS is connected to the carriage by a rod 95. When fluid under relatively low pressure is supplied to the space I00 formed by cylinder I91 and piston I 06, the piston is driven upwardly (with respect to disposition of parts in the drawing) so as to move the carriage 93 and fulcrum of lever 99 toward the eye 89. During such movement, the an- :nular space 199' behind the piston is decreased in volume, thus displacing fluid therein. When 'fluidunder relatively low pressure is supplied to space 99, the piston I96 is driven downwardly, moving the carriage 93 and fulcrum of lever 99 toward pin 9|, and fluidis displaced from space Fluid supplied to space '99 during normal op-- erationis that which is removed from space I of servant cylinder by valve 43 during the advance portion of the platen stroke, and such fluid flows through conduits 45 and 98. Fluid supplied to space I98 is preferably that fluid which is displaced from space 39 of intensifier 49. It has been found convenient to use this displaced fluid both because it is proportional to the amount of fluid added .to space I by valve 3| and also because it is available for such use during the return portion of platen stroke when space 99a is being recharged. "It alternates in this manner with fluid supplied through valve 43. Thus, con.- duit 19 leads from conduit 95 and connects with conduit .IsIlI leading to space I80. Space Hit-is preferably connected to drain when fluid is added to space 9.9, and conversely, when fluid is added to space I I39, space 99 is preferably connected to drain.

Connection of spaces '99 and I99 to fluid source andto drain at the proper time is preferably accomplished by means of a solenoid operated (direct or by pilot valve) spring returned, closed center cross-over, four way valve I94 of any suitable commercially available design. A check valve I95 permits free flow of fluid toward port #A of valve Ill-4 through conduit I93 but prevents outward reverse flow, the inlet side of check valve I being connected, by conduit 96 to con- 'duit 35 leading from the intensifier 49. A check valve 96, connected to port #13 of valve I94 provides free flow of fluid toward port #3 through conduit 9! but prevents flow in the reverse direction.

Space 99 is connected to the entering side of check valve '96 by means of a conduit 98 and this conduit is also connected to conduit 45 leading from check valve 44. Space Hill is connected directly to four-way valve port #C by means of conduit IOI. The drain port #D is connected directly to drain or to a fluid storage tank (not shown) by means of conduit I92.

When the platen is advancing (by reason of pressure in conduit 2) the solenoid of valve I94 is energized by means of a pressure switch I39 which is actuated by pressure in conduit 2. When the spool of valve I94 is moved by its energized solenoid, port #A is connected to port #B while port #0 is connected to the drain port #D. Fluid pressure in conduit 2, which is also present'in conduit 46, is prevented from escaping at that time to conduit 45 by check valve 96. Fluid displaced from space ID!) of cylinder I9! is thus drained through conduit Ifll, and ports #C and #D, when fluid is supplied to space 99 by valve 43 through conduits 45 and 98.

When the platen is returning (by reason of pressure in conduit II the solenoid of valve I94 is de-energized, since no pressure now exists in conduit 2 and the pressure switch I39 is springpressed to open position, thus permitting the spool of this valve to be spring returned so as to join port #A to port #6 and port #B with drain port #D. Fluid displaced from space 39 of intensifier 49, resulting from recharging of intensifier, is supplied to space I of cylinder I01 through conduit 46. check valve I05, ports .13 #A and #C, and conduit 'I9I. Fluid from .conduit 46 is prevented from passage to conduit 2 by check valve 39. As the piston I99 is driven upwardly, fluid is displaced from space 99 and passes to drain through conduit 98, check valve 96', conduit 97, ports #B and #D, and conduit of space 99 were equal to that. of space I99, and

further if space I99 were supplied with a quantity of fluid exactly duplicating that supplied through valve 3|, then a given amount of fluid from one source would produce a given amount of piston motion in onedirection, whereas an equal amount of piston motion in .the'opposit'e direction would result from the same amount of fluid from another source. Since,.however, the

amount of fluid available for use in space. I99

is larger than the actual amount passing through valve 3i by the proportion of the cross-sectional area of space 39 divided by that of space 4911, then to compensate for this, the cross-sectional area of space I99 should be larger by the same proportion than that of space 99.

The maximum capacity of space 99 preferably should be several times that of fluid which is anticipated to be the maximum to. be supplied to space 99 during any one stroke of the platen, and conversely, the same holds true with respect to space I99. This is largely to prevent large amplitude oscillation of the fulcrum with a resulting wide variation in the amount of correction fluid added from one stroke to the next by means of space III of servo-controlled intensifier I2.

When for anyreason, such as changing the type of work done by the platen, it. is desired that nocorrection on the next stroke (or reduced correction) be made, the solenoid of normally closed two-way valve I99 may be energized only when no pressure exists in conduit 2, and thus supply space 99 with fluid from the auxiliary pressure source through passage 21, flow-control needle valve II9, two-way valve I99 (check valve Ill preventing accidental reverse flow) and passages H2 and 98. Fluid supplied at this time isprevented from escaping to space 39, by means of check valve I95, and also from accidentally supplying space I of servant cylinder by'means of check valve 44. Supplying fluid. under pressure in this manner to space 99, while exhausting fluid from space I99 through valve I94, causes carriage 93 and fulcrum 92 to move toward pin 9I, thus decreasing the next stroke of piston I3 and, as a result, decreasing the amount of fluid added to space I through passage I9 during the next pressure rise in conduit 2.. I

If it is desired to eliminate all correction by space I9 during the next" platen advance stroke,

then solenoid of valve I99 is de-energized by means of a limit switch (not shown) which is tripped by a dog attached to carriage 93 when the center of fulcrum 92 approximately coincides with the center of the pin 9|. cidence of centers occurs, provision should be made to allow additional carriage movement in the same direction of an order suflicient to handle the normal anticipated discharge from valve 43 to space 99 during the next stroke. Positioning When this coin- '14 fulcrum 9?; of lever 99 coincident; with the center of pin. 91; does not permanently decommission the function of. space; 1.9, but instead allows the. necessary degree of correction. to. be. developed in. the regular manner.

All that has. been. described so far is. apparatus which would; be necessary to obtain the desired degree of accuracy to.- an application to, for example, a presshaving the anticipated use of producing large quantities of the. average. class of work, using dies which customarily remain fixed inone. position in the die. space. and which process of performing workpresents: forces resisting the returning motion of the platen ('die stripping forces for exan'lplel' which are. fairly small in comparisonv to the forces resisting the advancing motion of: the platen. By this is. meant that a large fluctuation of pressure does. not occur in space. 5; of the master cylinder during the time the platen returns, andv therefore, no major correction' will be. needed during return and thus there existsv no real need 'to make correction on the basis of anticipation, since correction of valves 3I and. 43c: would sufflce. The embodiment may be. altered, if correction by anticipation were. desirable only during the advance portion of the stroke, to the extent that. apparatus tothe rightzof conduit 9?, that is. that apparatus enclosed in dotted lines 291, and conduit. H19, would not be required, and conduit 65 would connect directly to. conduit II, making check valve 66 non-essential, and valve 430, 42c, and 40 together with conduit 950 would be. non-ex:-

istent.

If conditions were such, however, that a large pressure fluctuation, which could be anticipated as repetitive from one stroke to the next, occurs in space 5 during the return portion of the platen stroke, then apparatus shown within the. dotted lines 29I would be required. Such apparatus is similar to apparatus within the dotted lines 299, and similar reference numerals with suffix 0 added, designate similar parts. The main material difference is that all functions of the apparatus within dotted lines 29I bear the same relation to the existence of pressure in the con duit II as all functions of the apparatus within dotted lines 299 relate to pressure in the conduit 2. Construction of parts is substantially similar, with the exception of reversal of piston and rod relations. To supply the apparatus within dotted lines 2-91 an additional valve 930 for removing fluid is necessary and is the counterpart of valve 43. By some suitable means, such as by a separate set for contacts operated by pressure switch I39, valve 43 solenoid is only energized by limit switch 2 2 when pressure exists in conduit 2, whereas valve 430 is energized only when no pressure exists in conduit 2.

From the foregoing, it will be apparent to those skilled in the art that I have accomplished at least "the principal object of my invention, and it also will be apparent to those skilled in the art that the embodiment herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiment is illustrative only, and that my invention is not limited thereto.

respect to a relatively fixed Work surface, a plurality of hydraulically actuated means connected at spaced points to said platen means for moving the same, a supply line for supplying liquid under pressure to at least one of said hydraulically actuated means, said hydraulic actuated means being connected in a hydraulic circuit so that movement of one causes movement of another, pressure intensifier means operated by pressure in said liquid supply line to produce a pressure higher than that in said supply line, and means for selectively introducing said higher pressure liquid into said hydraulic circuit.

2. In a system for maintaining movable platen means in substantially true angular relative with respect to a relatively fixed working surface, a master hydraulically actuated device and at least one servant hydraulically operated device, said devices being connected to said platen means at spaced points for moving the same, and the exhaust of said master device being hydraulically connected to the inlet of the servant device so that movement of one causes movement of the other, a supply line for supplying liquid under pressure to the inlet of said master device, pressure intensifier means operated by pressure in said liquid supply line to produce a pressure higher than that in said supply line, conduit means connecting said intensifier outlet to the both exhaust of said master device and inlet of said servant device, and control means controlling flow of higher pressure liquid through said conduit means, whereby when said control means is actuated certain fluid from said supply line is denied the inlet to said master device to operate said intensifier means and said higher pressure is delivered to both the exhaust of said master device and the inlet of said servant device.

3. In a system for maintaining movable platen means in substantially true angular relation with respect to a relatively fixed working surface, a plurality of hydraulically actuated means connected at spaced points to said platen means for moving the same, said hydraulically operated means being connected in hydraulic circuit so that movement of one causes movement of another, pressure intensifier means operable to increase pressure in said hydraulic circuit to correct undesirable rotation of said platen means during the down-stroke of said platen means, and pressure die-intensifier means to reduce pressure in said hydraulic circuit to correct undesirable rotation of said platen means during return-stroke of said platen means.

4. In a system for maintaining predetermined alignment of relatively movable elements, a plurality of fluid actuated means adapted to effect relative movement of said elements, and means controlled by fluid displacement and operable prior to misalignment of said elements and constructed and arranged to anticipate the amount of correction required and accordingly alte operation of said fluid actuated means in anticipation of such correction.

5. In a system for maintaining predetermined alignment of movable platen means with respect to a fixed work surface, a plurality of fluid actuated means connected to said platen means at spaced points for moving the same, said fluid actuated means being connected in fluid circuit, and anticipating means controlled by fluid displacement and operable prior to misalignment of said platen means and constructed and arranged to anticipate the amount of correction '16 required and accordingly alter operation of said fluid actuated means, said anticipating means having a portion operable during advancing motion of said platen means and a portion operable during return motion of said platen means.

6. In a system for maintaining predetermined alignment of relatively movable elements, a plurality of fluid actuated means adapted to efiect relative movement of said elements, means for ascertaining alignment of said elements, and pressure intensifier and de-intensifler means selectively controlled by said ascertaining means to efiect desired relative movement of said fluid actuated means.

7. In a system for simultaneously moving two or more hydraulically actuated means in predetermined relation, correction means operable when said hydraulically actuated means are out of predetermined relation to aifect operation thereof to restore said hydraulically actuated means to predetermined relation, and anticipation means responsive to prior corrections resulting from operation of said. correction means and operable in accordance therewith to affect operation of the system before said hydraulically actuated means move out of predetermined relation.

8. In a system for simultaneously moving two or more hydraulically actuated means in predetermined relation, a hydraulic circuit connecting said hydraulically actuated means in series relation so that movement of one causes movement of the other, correction means operable when said hydraulically actuated means are out of predetermined relation to continuously modify the volume of fluid in said hydraulic connecting circuit during the time said hydraulically actuated means are out of predetermined relation, and anticipation means responsive to prior corrections resulting from operation of said correction means and operable in accordance therewith to modify the volume of fluid in said hydraulic connecting circuit before said hydraulically actuated means move out of predetermined relation.

9. In a system for simultaneously moving two or more hydraulically actuated means in predetermined relation, a hydraulic circuit connecting said hydraulically actuated means in relation so that movement of one causes movement of the other, detection means affected by movement of said hydraulically actuated means from predetermined relation, and means under control of said detection means and operable to restore the predetermined relation of said hydraulically actuated means by applying a single correction to the volume of said hydraulic connecting circuit, the

amount of said correction being determined by the duration thereof.

ROBERT C. WILSON.

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

UNITED STATES PATENTS

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