US2592338A - Hydraulic system - Google Patents

Description

April 8, 1952 H. w. RocKwELl.

HYDRAULIC SYSTEM 3 Sheets-Sheet l Filed April 17, 1946 Mw wm mW uw NQ l l l l .l l.-

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5 Sheets-Sheet 2 April 8, 1952 H. w. RocKwELL HYDRAULIC SYSTEM Filed April 17, 1946 FI E E April 8, 1952 H. w. RocKWELL 2,592,338

HYDRAULIC SYSTEM Filed April 17, 1946 l 5 Sheets-Sheet 3 o o o o e n au INVEN TOR #Hel/Ey Mia 6km/nl.

Patented Apr. 8, 1952 HYDRAULIC SYSTEM Harvey W. Rockwell, Cedar Rapids, Iowaassign or to La Plant-Choate Mfg. Co., Inc., Cedar Rapids, Iowa,` incorporation .of Delaware Application April 17,

..7 Claims.

My `invention relates 'to'rneans Afor V'supplying d hydraulic fluid, suchas a liquid or oil, under'pres- "sureand under the control of an operator :for

thepurpose of actuating various instrumentalities. The invention is particularly concerned with the-system as a whole, and morevespecially With an element or unit thereof for accumulating a supply of pressure fluid.

In the operation of hydraulic systems of the type mentioned, there is often an intermittent requirement `for hydraulic actuation of sundry instrumentalities, for example, clutches or brakes; yet the pressure-supplying mechanism, such as a pump, is customarily attached .to a motor or. engine `which may run continuously, or may run at varying speeds, or ymay cease operation from time to time. The result `is that the requirement `for hydraulic actuation ldoes not necessarily coincide in .point of time with v,the availability of hydraulic energy.

Various attempts have been made to provide some mechanism for reconciling these disparate circumstances, and in certain instances, have taken the form of 'pressure accumulators, which store a supply of pressure fluid for subsequent use. The iiuid utilized has some bearing on the type of mechanism employed, butthe-problemis accentuated in the case of uids such as liquids that are normally incompressible.

It is therefore an object of my invention to provide a hydraulic system in -Which there is away of accommodating, Within the limits of the structure, a widely varying demand f or and-a widely varying'supply of pressure fluid.

Another object of the invention is to provide a Way of storing a hydraulic fluid under pressure in satisfactory quantities.

An additional object of theinvention is to providefa hydraulic system `in kwhich -the'moving parts operate relatively infrequently'to reduce Wear and possible serv-ice difculties.

vAn Vadditional object `of the invention is to provide -a hydraulicsystem in `Which the :regulating mechanism is compactly arranged and assemhledand is largely protected 4from the .adverse influenceof the elements or operating `environment of the system.

.A further 'object of the invention is to provide a generally vimproved hydraulicsystem.

Other objects, together with theforegoing, are

attained byfthepreferred form ofthe hydraulic ,system of my invention, Aas illustrated ,in the accompanying drawings, in which Fig. 1 is a schematic diagram showing the hydraulic system of my linvention Ain one .embodi- (Cl. .1GB-42.)

42 ment, portions of the structure being in :cross section on central, longitudinal planes and` other portions being illustrated diagrammatically Figs. 2, 43, '4 and 5, inclusive, are diagrammatic 5 disclosures-of the structure shown in Fig. :1 .in

'various :stages of the operating cycle.

While -the invention can be embodied in a number of variant forms, Ait has successfully been incorporated in the Vform especially disclosed l0 .herein ,.designed to operate the clutch and .brake `of 'a winch tor Windlass mechanism mounted .on 'and propelled bya tractor and designed to derive .energyior drivingmthe hydraulic pumpfrom the tractor engine. The Winch or Windlass is inter- 15 mittentl-y operated, Yand the tractor engine operates-atvarious times and at various .speeds `so that the pump is Variably operated.

Thewindlass .or Winch is not shown as l.it is a standard device. It lincorporates .a .standard 2o clutch mechanism 6, normally disengaged Vso vthat it doesnot transmit power by the action .of 4aheavy spring. The force ofthe springis indicated byan arrow 1 and is overcome by. apiston 8, hydraulically actuated when the clutch 4is 25,to be engaged.

ySomewhat similarly, the winchor .Windlass is also provided with a standardbrake .incorporatingan .actuating arm 9 connected vby a pinll `to a plunger .|2, .operating within an `enclosing 30 casing |43. The `brake is normallyheld engaged Icy-spring force indicated by an arrow i4. lThe brake is released under theinuence of a vhy idraulicmechanism 1.6 of standard construction.

The same `Aengine that drives theaclutch. mech- 35.an ism 6 Ais also .effective to rotate a .hydraulic V4,5 closed by a ,capfZB-normally eiectivevto afford some ventilation of lthe interior of the reservoir 23, so that the pressure existing therein is never vfarrfrom atmospheric.

During the operation of the engine -and only 5o when `the engine is operating, the `pump 2| .is -.e1ective to Withdraw `fluid through `theduct 22 .from thereservoir -23 and to discharge the oil underpressurethrough a conduit 21.

This conduit 21 leads to a cap 28 secured to 55 oneend of the .reservoir .23 but notimmediately 3. abutting the reservoir cylinder for the reason that this otherwise open end of the reservoir is primarily closed by an intermediate head 29. The fastening devices (not shown) that hold the cap 28 to the reservoir 23 also preferably hold the interposed head 29 in position. Oil discharging from the conduit 21 flows into a hollow interior chamber 3| in the cap, and therein passes through a suitable lter or screen 33, held in position by a flange 34 pinched between an adjacent face of the head 29 and a similar face on the cap 28.

The construction and arrangementare such that all of the oil which issues from the conduit 21 must pass through the filter 33 into the interior 36 thereof. Communicating with the filter interior 36 by a short passageway 31 is a conduit 38 constituting an extension of the conduit 21 and leading from a bored passage 39 in the head 29 to a location at the other end of the reservoir 23. Y n

This end of the reservoir is open except fo the closure thereof by an intermediate head 4| and a closure cap 42, the assembly being similar to that at the initial end of the reservoir. The conduit 38 extends into a fitting 43 threaded into the cap 42 and constituting a seat 44 for a ball check valve 46. The valve is held on its seat normally by a coil spring 41 abutting the ball 46 and likewise abutting the end of a passageway 48 formed within the cap 42. Pressure fluid from the pump flows through the lter and through the conduit 38, and past the check valve 46 into the passage 48. Joining this passage is a fluid 'conductor 49 leading from the cap 42 to a suitable location whereat is installed a control valve I.

The control valve can be of any suitable sort and, for example. there is illustrated a valve fabricated of a main valve body 52 having a major transverse bore 53 therethrough. In the bore is disposed a valve bobbin 54 having a suitable t for reasonable oil tightness yet free enough for axial translation within the bore to occupy any one of several selected valving positions. Leakage along the surface of the bobbin is precluded adjacent the margins of the body 52 by suitable ring packings 55. The bobbin 5.4 at its upper end is reduced and is pierced to receive a fastening pin 56 for securing the bobbin to an operating lever 51. This lever is provided with an actuating handle 58 and is connected by an interposed link 59 and pivot pins 6I and 62 to the body 52. In addition, the lever 51 carries a detent roller 63 adapted in one position of the lever and bobbin to ride over a detent pin 64 movably mounted in the valve body 52 and restrained by a leaf-spring 66, held on the valve body by fastenings 61.

In addition to the detent roller 63 and cooperating structure, the valve bobbin 54 is also resiliently located by a coil spring 68 nested in a cap 69 secured to the lower portion of the valve body and abutting a flanged washer 1I encompassing a reduced portion 12 of the valve bobbin. Thus, when the valve bobbin is translated, the spring is compressed or when the bobbin and its lever are free, the spring tends to restore the bobbin to a central position as shown in Fig. 1. The fluid conductor 49 joined to the valve body 52 leads into a central ring-like or annular passage 8|, which can be connected by translation of the bobbin and utilization of reduced portions 82 and 83 thereof, either to a duct 84 leading to the brake actuator I6 or to a duct 86 leading to a clutch actuator 81 including the piston 8.

When pressure fluid from the line 49 passes through the valve and through the duct 84 to the actuator I6, it is effective to overcome the urgency of the spring I4 and to release the normally applied brake by operation of the linkage 9. When pressure fluid from the duct 49 is led through the conduit 86, it enters the clutch actuator 81 and is effective therein to translate the piston 8, with the assistance of a light spring 88, to overcome the urgency of the clutch spring and to engage the normally disengaged clutch.

When the lever 58 is otherwise manipulated, the ducts 84 and 86, or either of them, are cut off from communication with the pressure duct 49 and rather are placed in communication with either one of a pair of drain ducts 9| and 92, merging into a drain conduit 93 extending to the head 29 and communicating by means of a passage 94 therein with the interior of the reservoir 23. In this valve position, fluid which has left the reservoir has been advanced by the pump 2|, has passed through the conduit 21, the filter 33, the conduit 38, the check valve 46, and the conduit 49, and has passed through the valve 5I and into either of the actuators I6 or 81, or both of them, is finally restored through the valve 5I and the return conduit 93 to the reservoir 23.

Under some circumstances, the hydraulic circuit as so far described might alone almost be sufficient to produce reasonable results, but because of the disparity between the operating characteristics and times of the pump 2|, and of the clutch 6 and of the brake 9, I provide in accordance with the invention, special mechanism for improving the operation. This special mechanism is preferably incorporated with the reservoir structure for ease in servicing, for protection from the elements, and for providing certain other advantages.

Consequently, the head 4I is preferably formed with a circular, cylindrical extension 96 in order to define an accumulator chamber 91 substantially co-axial with and located within the reservoir 23. Operating within the cylinder 96 is a piston 98 having a close running t with the cylinder and sealed against major leakage by a ring packing 99. With this arrangement, the piston 98 is reciprocable within the cylinder and with the cylinder defines a variable, enclosed volume forming an accumulator chamber in communication through the passageway 48 with the pressure conduit 38.

l The piston is connected to a follower cup I0| by an interposed aligning pin |02, for the purpose of taking care of any minor misalignment between the piston and the cup |0I. This cup has an elongated skirt carrying at its extremity a guide washer |03 abutting a shoulder on the cup and likewise in the position shown in Fig. 1, abutting a stop |04 in the nature of a spring or snap ring slipped into the interior of the reservoir 23. The washer |03 is in contact with an elongated coil spring |06 located within the reservoir and in effect extending for substantially the length thereof. The spring |06 itself does not continue for the entire length of the reservoir, but rather is in abutment with an interposed washer |01 suitably provided with apertures |08 for the passage therethrough of reservoir oil. The w'asher |01, in turn, is in contact with another coil spring |09 in effect a continuation of the spring |06 and ".in-Lahutmentwith :a 'washer :lzl :heldin f.the.-iend 'of thexreservoir .23 by;arsnap:r.ing l2.

"lfIhestructurezso fardescribedis eective when Lpressureisiexertedon the piston-98 to translate thetpiston :Within 'the icylinder 9.6 and through thefmediumiof the cup |0| to;compresstthespring |06 and the spring |09 andthus to'maintainxthe `desiredpressure on the oil `within the; accumulaltoricl'iamber .91. .Since the aggregate. spring 06 and .|09 is -quite long, it .changesits effective pressure very'little with change in AlengthA so that sub- 'stantially aconstantgpressure 'is maintained Von .thezoil `within the accumulator.

.With this structure, the valve 5| can .be closed during operation of .the lpum .p'2| :andstill the pump will `be veffective to. open ,the check valve ...'46 and vto Atranslate the piston .98 Atoward .the

left. inFig. ..11 .to .store` an. accumulation of ,pres- `sure oil. Upon operation "of the Avalve-5|, the

:stored pressure oil will ow'to operate the actuarespect to the capacities ofthe actuators land i 81 -s suchthat a number of actuations can occur .even if the pump 2| is not operating.

Further in accordance with my invention, I provide means Afor regulating the iiow of oil to .the accumulator when the accumulator is sub- 1;., `stantially full and arrange matters so that not .every Yactuation or depletion will Vserve to recharge the accumulator. If each slight variation in accumulator capacity served to cause the aocumulator to recharge, the mechanism Would be working an excessive amount and wear andfailure would vbel accelerated. y

In accordance with the invention, therefore, I preferably provide a relief valve in the pressure .conduit between the pump 2| and the accumulator 96. This valve is preferably mounted in connection with the head 29 and incorporates a central tube ||6 substantially coaxial with the reservoir 23 and serving as a support for a composite valve stem ||1, likewise coaxially located within the reservoir and having an open end ||8 extending into the lter chamber 36 so that oil owing `into 'the filter has a by-pass passageway ||9 through the hollow interior of the valve stem I |1. From vthe interior of the valve stem, the fluid ows through a number of apertures 2| into the in terior of the tube I6. The ow of fluid from the tube ItY is normally prevented by a poppet valve |22 incorporated. with the valve stem H1 and normally'held von a seat |23'by a surrounding yIn'accordance with my invention, the valve |22 isnormally closed, but is opened'in response to certain positional effects of the accumulator. For that reason, the valve ||1 is provided with an extended stem |28 disposed within the reservoir axially thereof and in the path of the washer |01. j

'Whenthe accumulator is substantially empty, the washer |01 is spaced v'from the end ofthe stem |28 and is ineffective thereon. While vthe :accumulator is filling, however, the washer |01 istranslated towardtheleft in Fig.. l andeventually:ajouts the stem lztfiand'zunseats thempDet Ivalve :|22, :This .valve itis an 'unbalanced zlvalve, Jbengisub'jected on: its enlarged z-or headfside `to-'- V.wardlthezscreen orltertchamber 36 to the` pres- `rsureof the fluid from ,the pumppalthough itzis -exposed on its .otheror'stemside merely to the .atmospheric pressurein lthe reservoir. Furthermore, thecoil spring |f24tends to hold the poppet valvezonitsseat so that in closed position there 'is considerably more seating pressure 4on .the

:poppet'valve than when itzisin its openposition, for nthat position, while the spring |24 is .effective, .the hydraulic pressure on opposite sides :of

:the lvalve is substantially -equalized `and atmospheric pressure .from the .reservoir also.pervades .zmostof the .rest of the structure,levengasiarias thecheck valve.46.

Thus, f as the;accumulatorstarts to :enlargeland move toward the left in Fig. -1, the .two springs |06 and 09.are compressed at substantially their combined rate until the washer |01approximately abuts the stem |28. This movement ofthe washer is in proportion to but is somewhatless ythanthe axial movement of the accumulator piston. -'but as soonas the washer contacts the abutmentits .progress is arrested due not only tothe .eiect of the spring |24 but due to the hydraulic seating pressure on the unbalanced relief valve. The washer |01 is held in position during further expanding movement or lost-motion of the accumulator until,at a critical point, the pressure from the washer |01 is sufficient to overcome'the resistance of the unbalanced valve and the valve opens. Immediately the valve is substantially balancedand the spring |06, which hasbeen excessively compressed with respect `to lthe "spring |09, then tends ,to expand. quickly so that equilibriumbetween the springs |06-an'd |09 occurs. This. results in an abrupt leftwardtranslationo'f the washer |01 and also ofthevalve |22, which therefore not only abruptly opens but opens a large amount. As soon, however, nas therelief valve opens, thepressure within the pressure lines over to the check valve .46fal1s'to atmospheric, thus relieving the pump'2l of further Pressure load or unloadingmthe pump.

The controller valve 5I can be actuated'a number of times if desired andy when actuated'sufiiv ciently causes the accumulator to contractor shrink accompanied by expansion of the two springs |06 and |09. As these springs expand, they drive out fluid under pressure from the accumulator until such time as the washer |01 is partially restored to itsinitial'position andthe spring |24 is eiective to reseat the Doppet' valve |22. The ire-seating of the poppet valve does not occur at the same accumulator piston position as the uri-seating of the valve occurs. "I'hat is, the poppet valve is unseated near the extreme expansion of the acci1mulator,whe1eas thepoppet valve re-seats at approximately one half the contracted volume of the accumulator. As so'on .as the relief valve |22 is again seated, thepump .2| is effective to build up pressure within 'the ccnduits 21 and 38 and again to unseat the check valve 44 when the pressure is suiicient and thereupon to repeat the cycle previously described. With this mechanism, therefore, the accumulator. is always maintained in operating condition and is effective to control the unloading of the pump, although not every operation ofthe valve l`5l produces a corresponding restorationof .the

accumulator. Since the relief valve unseats "and seats at different accumulatorvolumes,hunting or excessive operation is prevented.

The cycles of operation are illustrated in Figs. 2 to 5 inclusive. As shown in Fig. 2, for example, the pump 2| is operating to draw uid from the reservoir 23 and is passing it through the conduit 38 inasmuch as the by-pass poppet |22 is closed. It happens that the valve bobbin 54 is mits intermediate cr neutral position, so that the line 49 is blocked and hence, the pressure fluid cracks the check valve 46 and causes a displacement of the accumulator piston 98 as the accumulator fills. It will be particularly observed that the washer |01 has come into abutment with the end of the stem |28 of the valve |22 and that the spring |09 is only somewhat; compressed, Whereas the spring |06 is compressed almost as much as it may be. At this time, the actu-ator |6 for the brakes, which are applied, and the actuator 81 for the clutch, which is disengaged, are both con- "nected through the valve 5| to the drain line 93 so that they are at atmospheric pressure through communication with the reservoir 23.

In a succeeding stage,` asillustrated in Fig. 3,

the charging of the accumulator has continued to such an extent that the compression of the spring |06 has translated the Washer |01 even farther, so'that the poppet valve |22 has suddenly opened, thereby relieving the pressure from the pump 2| and permitting the pump to by-pass through the tube I6 into the interior of the reservoir 23. Since the line 38 is likewise connected to the same passageway, its pressure has dropped to atmospheric and the check valve 46 has been closed due to the higher pressure in the accumuing against substantially an atmospheric pressure. The relief valve |22 remains open because the accumulator 98, although no longer in its largest volumetric or fully translated position, has not yet shrunk suiiiciently so that the spring |09 is effective in connection with the spring |24 to close the poppet valve |22. The valve bobbin 54 has been displaced from its intermediate or neutral position, so that pressure iiuid from the line 49 has been able to pass through the valve and into the actuator I6 for the brake thus releasing it.

In a comparable fashion, as shown in Fig. 5, the accumulator has been further displaced due to the operation of the brake instrumentality, perhaps a number of times, depending upon the relative volume of the brake actuator and of the accumulator, so that suiiicient fluid has been discharged from the accumulator to permit the check or relief valve |22 again to seat, thus blocking the passageway through the tube I6. When this occurs, the pump 2| continuing its rotation and again pumping against the pressure existing within the line 36, quickly builds this up to the pressure within the accumulator chamber 91 so that the check valve 46 again opens and the accumulator begins to refill, thus repeating the former cycle. This figure also shows that the .valve bobbin 54 has been translated in the opposite direction from its neutral or intermediate position andis now located so that pressure from the line 49 passes through the valve 5| and is still effective upon the brake actuator I8, thus holding the brake in released position, and is also now effective upon the actuator 81 for the clutch, thus engaging the clutch. The drain line 93, in this position of the valve, is not connected to either of the actuating devices but remains simply at atmospheric pressure.

In accordance with my invention, therefore, there is provided a structure effective to secure operation a number of times of an actuated instrumentality at the desired pump or fluid pressure value despite variations in operation of the pump itself, even though the pump may for the time being be inoperative. The accumulator is effective to achieve its maximum volume automatically and to unload or relieve the pump of pressure when the accumulator is full, so that the power requirements of the pump are substantially reduced. Furthermore, the accumulator and pressure-relieving instrumentalities are associated with the reservoir in such a way that they are mechanically protected and so that any leakage is immediately drained into the reservoir'itself. The arrangement of the relief is such that the system does not hunt or continually turn itself on and off with slight variations in accumulator volume, but there is a substantial change in accumulator volume required before the pump unloading mechanism is effective. I provide in accordance with my invention a hydraulic system which achieves the objects mentioned hereinabove and which constitutes a substantial improvement over the prior art.

I claim:

1. A hydraulic system comprising a reservoir, a conduit, a pump withdrawing from said reservoir and discharging into said conduit, a bypass extending from said conduit to said reservoir, a valve when closed blocking said by-pass, an actuator' for said valve extending into said reservoir, a spring in said reservoir, means for flexing said spring, and abutment means associated with an intermediate part of said spring and movable in accordance with the flexure of said part, said abutment means being positioned adjacent said actuator for moving said actuator in a direction to open said valve upon sufficient flexing of said spring.

2. A hydraulic system comprising a reservoir, a conduit, a pump withdrawing from said reservoir and discharging into said conduit, a bypass extending from said conduit to said reservoir, a valve biased to closed position for blocking said by-pass, an actuator extending into said reservoir for opening said valve upon movement in one direction, a spring in said reservoir, means for flexing said spring, and abutment means associated with an intermediate part of said spring and movable in accordance with the flexure of said part in a direction to open said valve, said abutment means being positioned adjacent said actuator for moving said actuator to open said valve upon sufficient flexing of said spring.

3. A hydraulic system comprising a reservoir, a conduit, a pump withdrawing from said reser- -voir and discharging into said conduit, a bypass extending from said conduit to said reservoir, a valve biased to closed position for blocking said by-pass, said valve also being positioned and arranged to resist opening thereof in accordance with the pressure differential in said conduit and said reservoir, an actuator extending into said reservoir for opening said valve upon movement in one direction, a spring in said reservoir, means wlfor flexing said spring. and abutment means associated with an intermediate part of said spring and movable in accordance with the flexure of said part in a direction to open said valve, said abutment means being positioned adjacent said actuator for moving said actuator to open said valve upon suicient flexing of said Spring.

4. A hydraulic system comprising a reservoir, an accumulator having a moving member associated with said reservoir, a pump, a conduit for supplying said accumulator with iiuid under pressure from said pump, a by-pass extending from said conduit to said reservoir, a valve in said by-pass biased to closed position, a spring in said reservoir arranged to be flexed by movement of said moving member, and abutment means associated with an intermediate part of said spring and movable in accordance with the flexure of said part, said abutment means being positioned adjacent said actuator' for moving said actuator in a direction to open said valve upon su'icient flexing of said spring.

5. A hydraulic system comprising a reservoir, an accumulator having a moving member associated with said reservoir, a pump, a conduit for supplying said accumulator with fluid under pressure from Said pump, a by-pass extending from said conduit to Said reservoir, a valve in said by-pass biased to closed position for blocking said by-pass, said valve also being positioned and arranged to resist opening thereof in accordance with the pressure differential in said conduit and said reservoir, a spring in said reservoir arranged to be flexed by movement of said moving member, and abutment means associated with an intermediate part of said spring and movable in accordance with the iiexure of said part, said abutment means being positioned adjacent said actuator for moving said actuator in a direction to open said valve upon suicient flexing of said spring.

6. A hydraulic system comprising a reservoir, an accumulator having a moving member associated with said reservoir, a pump, a conduit for supplying said accumulator with iiuid under pressure from said pump, a by-pass extending from said conduit to said reservior, an unbalanced relief valve in said by-pass, a spring for resisting movement of said member, and abutment means associated with an intermediate part of said spring and movable in accordance with the iiexure of said part, said abutment means being positioned adjacent said actuator for moving said actuator in a direction to open said valve upon sufficient movement of said member.

7. A hydraulic system comprising a reservoir, an accumulator having a moving member associated with said reservoir, a pump, a conduit for supplying said accumulator with nuid under pressure from said pump, a by-pass extending from said conduit to said reservoir, an unbalanced relief valve in said by-pass normally maintained in closed position responsive to the pressure in said conduit, a spring in said reservoir arranged to be flexed by movement of said member, abutment means associated with an intermediate portion of said spring and movable therewith in accordance with the movement of said moving member, said abutment means being effective in one position of movement of said moving member for opening said relief valve, and means eiective in another position of movement of said moving member for closing said relief valve.

HARVEY W. ROCKWELL.

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

UNITED STATES PATENTS Pardee Apr. 7, 1942

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