US3353352A - Load balancing system for hydraulic jack - Google Patents

Description

21, 1967 c w. GARDNER 3,353,352

LOAD BALANCING SYSTEM FOR HYDRAULIC JACK Filed Jan. 11, 1966 2 Sheets-Sheet 2 INVENTOR. CHARLES W. GARDNER ATTORNEYS United States Patent 3,353,352 LOAD BALANCING SYSTEM FOR HYDRAULIC JACK Charles W. Gardner, Peoria, Ill., assignor to Caterpillar Tractor Co., Peoria, 111., a corporation of California Filed Jan. 11, 1966, Ser. No. 519,855 3 Claims. (Cl. 6051) ABSTRACT OF THE DISCLOSURE A fluid operated system for balancing at least a portion of the weight of a machine component wherein the system includes a fluid control circuit for supplying fluid under pressure to an internal expansible chamber located in-the rod member of a double acting hydraulic jack which jack is used to actuate said machine component and whereby during normal operation said expansible chamber is supplied with sufficient pressure fluid to balance or offset at least a portion of the weight of said machine component.

This invention relates to a load balancing or booster system for a hydraulic jack to offset or compensate for a certain portion of the load on the jack cylinder. The invention is particularly suited for use with a double acting hydraulic jack wherein the load balancing system comprises a single acting hydraulic cylinder associated with the regular double acting cylinder.

Many modern machines or vehicles, such for example as bulldozers, scrapers, wheel loaders, etc., are equipped with hydraulically actuated components or attachments. The force or energy required to manipulate the various hydraulic attachments or tools is generally derived'from a single engine, whichengine is also used to propel the vehicle. Frequently the weight of individual hydraulically actuated components runs to several tons and the power required to move such components, even in an unloaded condition, often exceeds ten percent of the rated engine output. In many cases, machines are underpowered because the engine is of insufficient power to actuate the various components while simultaneously powering the vehicle. For example, in earthmoving machines the earth engaging portion is extremely heavy and requires substantial force to manipulate it, such as in raising a bulldozer blade or loader bucket. The force required for manipulating such attachments must be produced by the engine and when this manipulation takes place at the same time the entire vehicle is maneuvered, the engine is overtaxed.

The invention is directed to a system wherein the aforementioned deficiencies are eliminated without the use of extra-large power units. Thus, the invention is directed to a system whereby otherwise wasted horsepower is converted to useful output by the use of a novel and simply constructed means for balancing the weight of hydraulically actuated components carried by the machine.

It is an object of this invention to provide a hydraulic jack for actuating components with a load balancing means for supporting at least a portion of the weight of said components.

Another object of this invention is to provide a double acting hydraulic jack with a self-contained single acting hydraulic cylinder operated by fluid from an accumulator to supply a load balancing force for components actuatet by said jack.

Yet another object of this invention is to provide a ve hicle having a double acting hydraulic jack for actuating components with an auxiliary booster chamber located it the rod member of said jack, which booster chamber is provided with hydraulic pressure from an accumulator tc offset the weight of said components and thereby relieve the vehicle power plant of extra load when power is required for maneuvering the vehicle.

The manner in which the foregoing and other objects and advantages are obtained is set forth in the following specification wherein reference is made to the accompanying drawing illustrating preferred embodiments of the invention.

FIG. 1 is a longitudinal view, partially in section, oi one embodiment of a hydraulic jack constructed in accordance with the invention;

FIG. 2 is a'longitudinal view, partially in section, of a second embodiment of a hydraulic jack constructed in accordance with the invention; and,

FIG. 3 is a schematic view illustrating a hydraulic circuit for use in conjunction with either of the embodiments shown in FIGS. 1 and 2.

Referring to FIG. 1 there is shown a double actinghydraulic jack 10 having amain cylinder 12 from which aslidable rod 14 is extended to raise or manipulate a load. Therod end of thecylinder 12 is provided with a removable -block 16 which has apacking gland 18 secured thereto as by fastening means 19. Both the block 16- and thegland 18 are provided with a central bore which slidably receives therod 14.Suitable packing 22 is provided to insure that the system is fluid-tight. Similarly, an O-ring seal 24 provides a fluid-tight connection between theblock 16 and themain cylinder 12.

The terminal end ofrod 14 which is received withincylinder 12 is provided with an externalannular piston 26 which is held in place against an externalcircumferential rod shoulder 28 by means of a threadednut 30. Piston 26 is slidably received against the inner wall ofcylinder 12; an O-ring seal 32 preventing fluid passage therebetween. Alarge bore 34 extends longitudinally from the inner end ofrod 14 to a point near the outer end of said rod. The purpose ofbore 34 will become apparent from the discussion infra.

Atube 36 extends downwardly from the head end ofcylinder 12 in a manner such that it is received within thebore 34 ofrod 14 whether the rod is in an extended or retracted position. The inner end oftube 36 is provided with an enlarged ring member 38 which engages the Wall ofbore 34 in slidable and fluid-tight relation.

The outer end oftube 36 is provided with a reduceddiameter portion 40 which protrudes through an aperture in the head ofcylinder 12 and is rigidly fastened thereto by suitable means such as thenut 42. Afluid passageway 44 extends throughout the length oftube 36 and is adapted to communicate at its upper end with a hydraulic circuit which will be described With respect to FIG. 3, infra.

Normal operation of the double actingjack 10 is pr0- vided by a conventional hydraulic circuit (not shown) which selectively directs fluid under pressure through eitherport 46 orport 48 to the head androd ends of the cylinder, respectively, to thereby extend or retract theod 14. The jack is connected between the vehicle and a omponent to be adjusted by conventional means. When luid pressure is directed through thecentral passage 44 rom an external source such as an accumulator, suflicient )IGSSUIG may be introduced intobore 34 to compensate )I offset the weight of the component. With such an arangement, the fluid pressure introduced through ort 46 s utilized entirely for the manipulation of the net payload moved upon extension of the jack.

FIG. 2 illustrates a modified embodiment of a double acting jack wherein the jack is retracted rather than extended to manipulate a load. Many components of theiack 10 shown in FlG. 2 are identical with components previously described with reference tojack 10 of FIG. 1. Accordingly, prime numerals have been assigned to those components in FIG. 2 which correspond to like components in FIG. 1.

Thetube 37 of FIG. 2 has a considerably smaller outer diameter than thetube 36 of FIG. 1 and the lower end ofpassageway 44 is closed as by acap member 3%. In addition, the upper end ofrod bore 3 5 is provided with an annular plug 41 adapted for slidable sealed engagement withtube 37. Thus, a variable sized annular chamber 43 is formed having upper and lower walls defined by members 41 and 38, respectively. A plurality of radial ports 45 permit fluid communication betweentube passageway 44 and chamber 43.

When fluid pressure is directed to chamber 43, therod 14 will tend to retract intomain cylinder 12. Since retraction of jack actuates a component and its load, sufficient pressure may be introduced into chamber 43 to balance or offset the weight of the component and pressure introduced atport 48 is utilized entirely for manipulation of the net payload carried by said component. A small oneway bleed valve 47 is provided in member 38' to permit draining back to chamber 43 any fluid which might leak into the lower end ofrod bore 34.

FIG. 3 illustrates a hydraulic circuit which is adapted to supply fluid pressure to the load balancing chambers of either of the embodiments shown in FIGS. 1 and 2. However, for purposes of illustration, thehydraulic jack 10 of FIG. 1 is shown connected to the circuit of FIG. 3. In FIG. 3 aconventional accumulator 55 having apiston 56 and a supply ofcompressible fluid 57 is connected toconduit 59 viaconduit 61 and a suitablepressure control valve 63. Accumulator 55 is also connected to a fluid tank orreservoir 65 viaconduit 67, asafety valve 69 andconduit 71.

Theaccumulator 55 is initially charged in a conventional manner by alternately directing fluid from a hydraulic jack circuit (not shown) toports 46 and 48. Thus, extension ofrod 14 will initially draw fluid fromreservoir 65, through acheck valve 73,conduit 59 and into rod bore chamber 34 (see FIG. 1), while reverse movement ofrod 14 will direct such fluid back throughline 59 and acheck valve 75 into theaccumulator 55. Successive cycles ofjack 10 will eventually charge theaccumulator 55 to a predetermined pressure which will open thepressure control valve 63 and further strokes ofrod 14 will have no effect oncheck valves 73 and 75 due to the pressure which has built up inlines 59 and 67. It should be apparent that successive strokes of therod 14 of the jack embodiment shown in FIG. 2 would serve to initially charge theaccumulator 55 in like fashion.

When the pressure in theaccumulator 55 is in the operative range, thepressure control valve 63 will remain open to permit flow of fluid throughline 59 in both directions. In this manner as the load balancing chamber in rod bore 34 (see FIG. 1) expands, fluid flows from theaccumulator 55 to the said chamber and as the chamber contracts, the fluid flow is in a direction back to the accumulator. Should leakage in the system result in a reduction of pressure in theaccumulator 55 below a predetermined minimum,control valve 63 will close and as therod 14 is extended and retracted, the circuit will be re- 4 charged by flow of oil through thecheck valves 73 and 75, as previously described.

Thesafety valve 69 is provided with aspool 77 which is normally urged to open the valve under the action of spring St). However, when the engine of the vehicle is running, lubricating oil pressure therefrom enters throughconduit 82 to forcespool 77 against an internalcircumferential shoulder 81 as shown and thus prevent fluid communication betweenaccumulator 55 and thereservoir 65. When the engine is shutdown or the engine oil pressure is lost for some other reason, thevalve spool 77 is spring biased to a position establishing communication betweenaccumulator 55 andreservoir 65. Such an arrangement allows the hydraulic jack components to be brought to rest in a lowered or inoperative position during extended shutdown periods as a safety precaution.

Although a specific embodiment ofsafety valve 69 is illustrated, it should be recognized that any suitable alternate form could be used. For example, thevalve 69 could be responsive to any signal which indicates when the vehicle engine is operative. In addition to engine oil pressure the valve could be controlled by transmission control pressure or by pressure from the main implement control system pump which is operative any time the engine is running. On an electric drive vehicle the valve could be solenoid controlled in response to opening or closing of the main power switch.

I claim:

1. In an engine driven vehicle having a machine component actuated by a hydraulic jack, apparatus for balancing at least a portion of the weight of said machine component, said apparatus comprising in combination, a hydraulic jack having the usual cylinder, piston and rod, said rod having a bore opening at its inner end, a tube having a first end fixedly secured to and extending through the head end of said cylinder, said tube having a second end portion extending into said rod bore, a stationary wall member fixedly secured to the tube and slidably fitting the rod bore to define one end of an internal expansible chamber within said rod bore, hydraulic fluid means for extending and retracting said jack, and a hydraulic circuit for directing fluid from a pressure fluid reservoir through said tube and into said expansible chamber, said hydraulic circu t comprising an accumulator chargeable to a pred termined pressure by extending and retracting said jack, a pressure control valve located in said hydraulic circuit between said accumulator and said expansible chamber for prventing fluid flow between said expansible chamber and said accumulator when the pressure in the hydraulic circuit drops below said predetermined pressure, check valve means located in said hydraulic circuit between said expansible chamber and said reservoir to communicate pressure fluid from said reservoir to said expansible chamber when the pressure in the hydraulic circuit drops below saidpredetermined pressure, whereby during normal operation said expansible chamber is supplied with pressure fluid which is suflicient to balance or offset at least a port1on of the weight of said machine component, and a safety valve situated between said pressure fluid reservoir and said accumulator, means responsive to operation of said engine to normally close said safety valve and prevent fluid flow from said accumulator to said reservoir, said safety valve further having means operable to open said safety value to allow fluid to flow from said accumulator to said reservoir when said engine is shut down.

2. Apparatus as set forth in claim 1 wherein said expansible chamber is located in said rod so that admission of pressure fluid to said chamber tends to extend said rod from said cylinder.

3. Apparatus as set forth in claim 1 wherein said expansible chamber is located in said rod so that admission of pressure fluid to said chamber tends to retract said rod into said cylinder.

(References on following page) References Cited UNITED STATES PATENTS Simpson 92-108 Onions 92-108 Buchet 60-51 Jelinek 60-51 Green 92-108 X Kling 91-411 X MARTIN P. SCHWADRON, Primary Examiner.

I. C. COHEN, Assistant Examiner.

Claims (1)

1. IN AN ENGINE DRIVEN VEHICLE HAVING A MACHINE COMPONENT ACTUATED BY A HYDRAULIC JACK, APPARATUS FOR BALANCING AT LEAST A PORTION OF THE WEIGHT OF SAID MACHINE COMPONENT, SAID APPARATUS COMPROSING IN COMBINATION, A HYDRAULIC JACK HAVING THE USUAL CYLINDER, PISTON AND ROD, SAID ROD HAVING A BORE OPENING AT ITS INNER END, A TUBE HAVING A FIRST END FIXEDLY SECURED TO AND EXTENDING THROUGH THE HEAD END OF SAID CYLINDER, SAID TUBE HAVING A SECOND END PORTION EXTENDING INTO SAID ROD BORE, A STATIONARY WALL MEMBER FIXEDLY SECURED TO THE TUBE ANS SLIDABLY FITTING THE ROD BORE TO DEFINE ONE END OF AN INTERNAL EXPANSIBLE CHAMBER WITHIN SAID ROD BORE, HYDRAULIC FLUID MEANS FOR EXTENDING AND RETRACTING SAID JACK, AND A HYDRAULIC CIRCUIT FOR DIRECTING FLUID FROM A PRESSURE FLUID RESERVOIR THROUGH SAID TUBE AND INTO SAID EXPANSIBLE CHAMBER, SAID HYDRAULIC CIRCUIT COMPRISING AN ACCUMULATOR CHARGEABLE TO A PREDETERMINED PRESSURE BY EXTENDING AND RETRACTING SAID JACK, A PRESSURE CONTROL VALVE LOCATED IN SAID HYDRAULIC CIRCUIT BETWEEN SAID ACCUMULATOR AND SAID EXPANDIBLE CHAMBER FOR PREVENTING FLUID FLOW BETWEEN SAID EXPANDIBLE CHAMBER AND SAID ACCUMULATOR WHEN THE PRESSURE IN THE HYDRAULIC CIRCUIT DROPS BELOW SAID PREDETERMINED PRESSURE, CHECK VALVE MEANS LOCATED IN SAID HYDRAULIC CIRCUIT BETWEEN SAID EXPANSIBLE CHAMBER AND SAID RESERVIOR TO COMMUNICATE PRESSURE FLUID FROM SAID RESERVIOR TO SAID EXPANSIBLE CHAMBER WHEN THE PRESSURE IN THE HYDRAULIC CIRCUIT DROPS BELOW SAID PREDETERMINED PRESSURE, WHEREBY DURING NORMAL OPERATION SAID EXPANSIBLE CHAMBER IS SUPPLIED WITH PRESSURE FLUID WHICH IS SUFFICIENT TO BALANCE OR OFFSET AT LEAST A PORTION OF THE WEIGHT OF SAID MACHINE COMPONENT, AND A SAFETY VALVE SITUATED BETWEEN SAID PRESSURE FLUID RESERVOIR AND SAID ACCUMULATOR, MEANS RESPONSIVE TO OPERATION OF SAID ENGINE TO NORMALLY CLOSE SAID SAFETY VALVE AND PREVENT FLUIDFLOW FROM SAID ACCUMULATOR TO SAID RESERVOIR, SAID SAFETY VALUE FURTHER HAVING MEANS OPERABLE TO OPEN SAID SAFETY VALUE TO ALLOW FLUID TO FLOW FROM SAID ACCUMULATOR TO SAID RESERVOIR WHEN SAID ENGINE IS SHUT DOWN.

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