US3792792A

US3792792A - Hydraulic self-leveling device for a loader bucket

Info

Publication number: US3792792A
Application number: US00249604A
Authority: US
Inventors: R Bromberek; G Holloway; R Oliver; R Yeh
Original assignee: International Harverster Corp
Current assignee: Komatsu America International Co
Priority date: 1972-05-02
Filing date: 1972-05-02
Publication date: 1974-02-19
Anticipated expiration: 1991-02-19
Also published as: FR2183004A1; JPS5749689B2; GB1426357A; JPS4921902A; FR2183004B1; CA968254A

Abstract

A mechanically actuated single valve which has a sequence of opening and closing port connections controlled by a timed spool. The timing of the spool and arrangement of the hydraulic circuitry is such that high pressure fluid can be delivered to both sides of a hydraulic cylinder, with no movement thereof because of the balance of forces on the cylinder.

Description

Enited States Patent Bromberek et al.

[451 Feb. 19, 1974 HYDRAULIC SELF-LEVELING DEVICE FOR A LOADER BUCKET Inventors: Richard J. Bromberek, Lockport;

Robert J. Oliver, Westmont; Rudolph E. Yeh, Elmhurst; Gale A. Holloway, .loliet, all of 111.

International Harvester Company, Chicago, 111.

Filed: May 2, 1972 Appl. No.: 249,604

Assignee:

US. Cl. 214/763, 214/764 Int. Cl E021 3/86 Field of Search 214/762, 763, 764

References Cited UNITED STATES PATENTS Blakely 214/764 Beiley 214/764 Holsinger 214/764 Primary ExaminerGerald M. Forlenza Assistant ExaminerJohn Mannix Attorney, Agent, or FirmJohn A. Schaerli; Floyd B.

Harman [5 7] ABSTRACT A mechanically actuated single valve which has a sequence of opening and closing port connections controlled by a timed spool. The timing of the spool and arrangement of the hydraulic circuitry is such that high pressure fluid can be delivered to both sides of a hydraulic cylinder, with no movement thereof because of the balance of forces on the cylinder.

9 Claims, 3 Draiving Figures PAIENIEUFEB 1 91914 sum 2 m x mjom HYDRAULIC SELF-LEVELING DEVICE FOR A LOADER BUCKET This application is related in subject matter to application Ser. No. 249,641 filed May 2, 1972.

BACKGROUND OF THE INVENTION This invention relates to material loaders including a prime mover and a loader frame having a boom and a bucket, and more particularly, to a self-leveling device for maintaining the bucket in a constant position relative to the ground during segments of the working cycle.

As is well known in the art, assemblies of this nature comprise a self-propelled vehicle or support, the front end of which mounts a boom structure that is hydraulically actuated in a plane perpendicular to that of the vehicle. The boom of a front end loader, for example, carries a bucket which engages material as the tractor is driven forwardly, etc. As the boom is raised, the bucket containing the material must be reoriented in relationship to the ground or tilted back such that the maximum amount of material be maintained therein. As is apparent, the vehicle operator, during this series of maneuvers, is required to steer the vehicle, actuate the boom and maintain the bucket in the proper tiltback orientation as the boom is raised. Obviously, the proper and continuous performance of these functions is not feasible, and error of the operator's judgement in regard to the bucket orientation could very easily result in the rolling back or dumping of material in the bucket on himself. Accordingly, it is conventional to provide some sort of automatic self-leveling means for maintaining the bucket in the proper orientation. These have heretofore consisted mainly of mechanical linkages incorporated to some extent with the means for releasing the bucket for tilting. However, for the most part, these mechanical linkages have left much to be desired in the way of operational and cost considerations.

SUMMARY OF THE INVENTION In accordance with the invention, the self-leveling valve means is basically a two-position design with an intermediate throttling range. A sequence of opening and closing port connections are controlled by critical timing in the valve design, In its neutral position, the inlet pressure port of the valve is blocked off from the head side of the bucket cylinder. At this time, communication between the rod and the head side of the bucket cylinder is also blocked off at the valve.

When the boom is raised, the mechanical linkage connected to the bucket actuates the self-leveling valve means, causing high pressure fluid to be fed through the inlet port to the head side of the bucket cylinder means. Further actuation of the self-leveling valve opens a regenerative exit orifice for the fluid in the rod side of the cylinder, to be recirculated to the head side. This action causes the bucket cylinder to extend and level the bucket as long as the boom is raising within a given boom height range. When the boom stops, the feedback signal will dissipate, the spool will shift to a equilibrium position shutting off the exit ports in the valve. If, after the bucket has been leveled, a manual rollback is inadvertently given the bucket the selfleveling valve timing causes the forces on the rod side and head side of the bucket cylinder to be equa IIThe resulting balance of cylinder forces will not permit the cylinder to move and thus prevent accidental dumping of the bucket pay-load on the machine and/or operator during such manual actuation of the bucket control valve.

Accordingly, an object of this invention is to provide an efficient economical self-leveling device for maintaining the proper bucket/ground orientation during the material handling cycle.

It is a further object of this invention to provide a self-leveling device which cannot be overridden such that rearward spilling of the bucket contents becomes impossible.

Another object of this invention is to provide a hydraulic self-leveling device which prevents cavitation of the bucket cylinder during dumping of the bucket contents.

Yet another object of this invention is to provide a self-leveling assembly which can be adjusted such that self-leveling becomes automatic at various boom heights.

Another object of this invention is to provide a selfleveling assembly which when in the self leveling range can be manually overridden, but only into a dump positron.

Still another object of this invention is to provide a spool-type valve assembly for controlling the actuation of the bucket hydraulic cylinders automatically.

Another object of this invention is to provide a selfleveling system which provides improved self-leveling of the loader bucket regardless of bucket payload or engine RPM.

It is a further object of this invention to provide a self-leveling valve in which the valve spool returns to an equilibrium state in the self-leveling range.

Yet another object of this invention is to provide a self-leveling valve. which in a neutral self-leveled position has no significant dead band between signal input and response.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of almaterial loader of the type mentioned with parts of the mechanism indicated;

FIG. 2 is a cross section view' of the self-leveling valve; and

FIG. 3 is a diagram showing the hydraulic circuitry involved in this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to the drawings, and first to FIG. 1, the material loader 106, with which the invention is associated, includes a support vehicle means 108 and a boom means 110 upon which is mounted a bucket means 112 and a double. acting hydraulic cylinder means 20. A mechanical feedback linkage means 46 communicates movement of bucket means 112 to leveling assembly means 10.

As shown in FIG. 2, the leveling assembly means 10 herein shown is a one-spool valve assembly comprising a housing means 12 provided with a longitudinally extending bore means 14 in which the spool means 16 horizontally reciprocates. Upon actual movement of spool means 16, the manual control means 18 is cut in or cut out of the hydraulic circuitry whereby control of a head side working double acting'fluid cylinder means 20 is assumed by valve assembly means 10. As can be seen, longitudinally extending bore means 14 is intersected at axially spaced intervals by first and second port means 22 and 24 and third, fourth and fifth port means 26, 28 and 30. As will later become more apparent the above ports have been thus identified becausein some instances they function as input ports while in others they function as output ports, that is their roles are interchangable.

A power driven hydraulic pressure source, such as a pump 32 has its pressure side connected to manual control valve means 18 by line 34 and to valve means by line 36. It should be noted that valve 18 is of any conventional open-center type having a high pressure outlet means 38 and a dump line means 40 whereby fluid is selectively supplied to and exhausted from the opposite sides of hydraulic cylinder means 20. As is apparent the functions of valve 18 are reversible, at which time system A which includes line means 38 and 38a assumes the function of system B which includes dump line 40 and vice versa. This occurs simply upon moving the control spool located therein. When being actuated such a dump command is given bucket 112, high pressure fluid passes through A system, and return fluid to dump through B system. As is apparent, A and B systems perform the reversed function when a rollback command is given.

As shown in FIG. 2, spool means 16 is in a neutral position, that is, high pressure fluid from manual control valve means 18, via system A and line 38, is passing directiy through spool valve means 10 to headside 24 of hydraulic cylinder means 20. As is evident, when spool means 16 is moved to the left from its neutral position by mechanical lever means 42 into a working position, high

pressure fluid lines

36 and 36a are opened and high pressure fluid line means 38 and'38a are closed. The sensitivity of the mechanical feed-back linkage means 46, of which lever 42 is the terminus, must be designed such that it is compatible with the loader means 106 geometry and the characteristics of valve means 10. However, it must be understood that such mechanical linkages are well known in the art and that we, in no way, intend to limit the claims and scope of the invention herein disclosed.

Mechanical input shaft means 42 passes through a plug means 44 which closes off bore means 14 against loss of high pressure fluid. Seal means 41, cutting off leaks, is provided between plug means 44 and end 48 of housing means 12. A second seal means 50 serves the same function between input shaft 42 and plug bore means 52. A shoulder means 54 on input shaft means 42 functions such that when in a neutral state, a seating means is provided to limit the rightward travel of input shaft 42. As is evident, when force is not being transmitted to input shaft means 42 to overcome spring centering means 60, spring means 60 maintains the fluid directing assemblage to the right, that is, keeps shoulder means 54 in a seated arrangement and spool 16 in a neutral position.

Spring centering mechanism 60 has a first end section means 65 positioned in a counterbore means 62 of end 64 of spool means 16. The second end means 63 thereof, is positioned in a second counterbore 66 located in plug means 68. Plug means 68 closes off second end 70 of bore means 14, and a seal is formed with second end 72 of housing 12. As is apparent, spring means 60 yieldably h-olds'spool meansl6 in a'neutral position as shown in FIG 2. ln this neutral position, high pressure fluid from manual control valve means 18 freely passes through high pressure line 38, via first port 22 and third port 26, to the head side 21 of hydraulic cylinder means 20.

A longitudinally extending channel means 74 extends directly through plug means 68 and spool means 16, groove means 76 being provided at end 56 of spool 16 allowing entrapped fluid to drain therefrom. Thus, any, fluid which might accumulate in front of plug 44 because of leakage or otherwise may be removed.

-The spool means 16 is provided with a series of land means 78, 82, 84 and 86. Separating said axial spaced land means are groove means 88, and 92. Correspondingly adjacent to said spool groove means and land means are a plurality of spool bore groove passage means 94, 96, 98, and 102. As is apparent from a consideration of FIG. 2, passage means 94, 96, 98, 100 and 102 are extensions of the correspondingly adjacent port means.

It can be seen that when the spool 16 is shifted to the left from a neutral position shown in FIG. 2, third port means 26 will be closed by land means 86 and the groove means 88 will place fifth port 30 and second port 24, via high pressure line 36, in direct fluid communication with pump 32. Thus, high pressure fluid will flow through self-leveling means 10 to fluid cylinder means 20. Slightly later or behind the opening of second port 24, grooved means 90 opens fourth port 28 such that low pressure hydraulic fluid from hydraulic cylinder means 20 passes into passage means 96 and therefrom, via groove means 88, back into the fifth port means 30.

in the operation of a loader system incorporating a self-leveling means as described, the work cycle begins with the positioning of the boom in a float position and the filling of the bucket. As the boom means 106 (as shown in FIG. I) is raised, the amount of leveling necessary to keep the bucket 112 properly aligned increases. Thus, up to a certain boom height, bucket orientation problems are minor. As is apparent, even it" the bucket is rolled back such that it dumps, the load falls in front of the vehicle and not on the operator. However, as the boom is progressively raised, dependent upon the loader system assembly, the dangers inherent with roll back increase. It should be noted that the operator may, to get a maximum bucket load initially after filling, roll the bucket back as far as possible before raising the boom.' Thus when the boom reached a certain elevation the material in the bucket would spill back on the operator. Therefore, above a certain height, it is desireable that an automatic self-leveling means performs the leveling function if the bucket is tipped into a rollback position.

Thus, when the loader system is actuated and th boom is being raised, at a certain predermined height, the mechanical linkage means 42 causes the engagement of the leveling valve means 10 to move the bucket from a rollback position into a level position. As previously stated, simultaneously with the actuation of leveling means 10, rollback, via manual means 18 is prevented due to a balance of cylinder forces 20.

At a stopped position such as at the top of the cycle,

or at any intermediate position between there and the actuation of the self-leveling valve means 10, the selfleveling valve 10 assumes a static or equilibrium position. ln this steady state position,-spool'means l6 relocates such that land means 82 just contacts lip means 98. That is, leading edge 83 just contacts lip means 85. The timing of spool means 16 is so designed that when the above relationship exists, port means 26 and 30 are open sufficiently to balance the hydraulic cylinder if a rollback command is given. It should be noted, however, that fifth port means 30 is open more than third port means 26 for reasons which will hereafter be explained.

Referring now to FIG. 3 wherein is shown a diagrammatic view of FIG. 2, the self-leveling valve being in an equilibrium or static position as described above. This position can best be described by steady state antirollback and stability equation:

where .4 and K are respectively the orifice area and flow coefficient of third port means 26. A and K are respectively the orifice area and flow coefficient of fifth port means 30.

Thus, in this static state, if the operator wishes to dump the bucket, he actuates manual control spool means 18. Upon actuation, high pressure fluid is pumped through system A and passage means 26 to head side 21 of cylinder 20. Simultaneously, fluid is dumped through B and line 40 from rod side means 25. After the initial movement of the bucket, mechanical linkage means 46 will cut self-leveling valve means 10 out of the system. As is apparent, however, if in some manner mechanical linkage means 46 failed to function, the leveling means 10 would allow high pressure fluid through fifth port means 30 sufficient to move the bucket 112 into dump position. Depending on the nature of the linkage 46 failure, the spring 65 would also be urging spool 16 into a neutral position.

As is apparent, the operator can actuate manual control means 18 such that a rollback command can be given to bucket means 112. That is, high pressure fluid can be directed through B and line means 40 into the rod side of hydraulic cylinder means 20, A through line means 38 being opened to dump. The anti-rollback feature of self-leveling valve means 10, as would overcome rolling back of the bucket in the above situation, is based on the timing arrangement of spool means 16, that is, the timing is such that the forces on both sides of hydraulic cylinder 20 remain balanced when the rollback command is given manually. As previously stated:

wherein P A and A are known values and P is the unknown for which the equation must be solved. As is apparent, P can be determined by control of the values A and A or the orifice sizes of third port means 26 and fifth port means 30 when spool 16 is in a static position. With this arrangement, when the rollback command is given, high pressure fluid is directed to rod side 25. The same pump means 32 is now directing fluid to both sides of hydraulic cylinder means 20. However, A is open to dump and A is closed. If at this initial instant, A was closed, then F F because of the difference in areas A A This would result in the rod extending to the dumping position. However, because of the timing arrangement of spool means 16, A and A in series create an intermediate pressure P necessary to balance the cylinder forces F and F The self-leveling valve 10, thus, is by itself capable of preventing rollback even if mechanical linkage 46 failed. It is known in the prior art to have the mechanical linkage timed to actuate the self-leveling means and arrest rollback, however, even some movement with an abrupt stop, might be sufficient to dump some of the load on the operator. As is apparent with leveling valve 10 even this slight movement is not possible. The invention herein disclosed incporporates both of these features such that rolling back as well as shaking loose of the load is impossible.

A further advantage flowing from the disclosed structure is lack of an appreciable dead zone at the top of the cycle. That is, the relationship of edges 83 and 85 is such that only a very small amount of movement of spool 16 is necessary to cause leveling. As will be apparent, as the boom is being raised, a second dead zone will exist from the time the mechanical linkage actuates spool 16 until spool 16 obtains a self-leveling position. This second dead zone is, however, not nearly as critical as the first since adjustments can be made for this.

It should also be noted that the oil required to move the bucket cylinder during self-leveling includes the displaced cylinder oil as well as the pump supply. Therefore, the lift time of the boom is affected very little during normal operation and the delay time to energize the leveling circuit is greatly reduced.

A further aspect of the timing of spool means 16 involves the identical feathering or metering notch means 81, 81a, and 81b which are designed to handle the flow requirements during the leveling operation without the spool moving out of their range. Without such feathering means upon opening of the corresponding land means, a pressure peak would result causing the bucket to jump or chatter, etc. The notch means 81, which is identical to the others, comprises a generally V like indentation on the surface of the land extending horizontally from the face means 118 of groove means 88. The timing arrangement of the notch means 81, 81a and 81b is such that the working side of hydraulic cylinder means 20 is pressurized before the exit port side opens. That is, as shown in FIG. 2, port means 30 opens prior to port means 26, thereby avoiding cavitation. The feathering is timed such that antirollback is achieved due to two orifices in series creating an intermediate pressure to the head side of the cylinder. Thus, the cylinder forces balance if a rollback command is given during the leveling cycle and the command is nulified. Additionally the dead zone between the equilibrium or static position and the working position is minimized response thereby being immediate.

It is also important to note that during the selfleveling operation, oil under pressure is trapped in both sides of the bucket cylinder at all times and cavitation is prevented. That is, when the spool 16 is shifted to the left from its neutral position, third port 26 will be closed, and hydraulic fluid under pressure will enter second port 24. In this position of the spool 16, the groove means 88 places the passage 98 and chamber 94 in fluid communication with each other, whereby fluid under pressure from the rod side chamber 25 flows through the passage 28 to the chamber 94 and, hence, to the head side 21 of the cylinder means 20. As evident, the weight of the bucket 112 itself and that of the load therein, act in a direction to extend the cylinder 20. Such movement would tend to be faster than the pump capacity, in which case there would be cavitation of the system. In this way, additional fluid conducted to the chamber 94 to preclude cavitation as aforesaid.

What is claimed is:

1. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprismg:

a fluid pump means pumping high pressure hydraulic fluid;

a manual fluid direction control means;

a movable mechanical feedback linkage connected to the bucket, and to said valve assembly means;

a valve means including:

a housing means having a longitudinally extending bore means intersected at axially spaced intervals therealong by first, second, third, fourth and fifth port means, said first port means being connected to said manual fluid direction control means and said second port means being connected directly to said fluid pump means, said third and fifth port means being connected to said double acting fluid cylinder means on the head side thereof and said fourth port means being connected to said double acting fluid cylinder means on the rod side: thereof;

a valve spool means axially movable in said bore means from a neutral position blocking fluid from all port means except said first means and said third means, to a working position wherein first and third port means are closed and second, fourth and fifth port means are open, and an equilibrium position wherein only said fourth port means is closed;

a link means connected to said valve spool means for transferring force from said mechanical linkage means to shift said spool means whereby said manual fluid direction means is cut out and said bucket is automatically maintained level to ground.

2. The valve assembly of claim 1 wherein said spool means has a timed feathering means whereby said third and fifth port means in series create an intermediate pressure to the head side of said cylinder means such that cylinder forces are balanced. 4

3. The valve assembly of claim 2 wherein said spool means has a plurality of axially spaced apart circumferentially extending groove means whereby communicating said first and third port means, and said second, fourth and fifth port means.

4. The valve assembly of claim 3 wherein said spool means has a plurality of axially spaced apart circumferentially extending land means attenuatively covering and opening said corresponding adjacent port means. A

5. The valve assembly of claim 4 wherein said plurality of axially spaced apart circumferentially extending land means include a first, second and third land means, said first means covering said first and third port means, said second covering said fourth port means and said third covering said second and fifth port means.

6. The valve assembly of claim 5 wherein:

said bore means has a plurality of spaced apart circumferentially extending groove means positioned adjacent said inlet port means; and said land means have feathered edge means.

7. The valve assembly of claim 6 wherein said longitudinally extending bore means has first and second end means each being provided with first and second stop means respectively, said first stop means carrying by said mechanical link means and said second stop means has a channel means therein.

8. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising:

a valvemeans including:

a spool means moving between a neutral, working, and equilibrium position, wherein said spool means has feathering means whereby forces on said cylinder in an equilibrium or self leveling position are described by the formula: KXA JKK 14, A P /P, wherein: A and K are respectively the orifice area and flow coefficient of the fifth port means, A and K are respectively the orifice area and flow coefficient of the third port means, P is the pressure on the head side of the cylinder means and P is the pressure on the rod side.

a non-leveling fluid conduit means communicating said manual control means and first end of said double acting fluid cylinder means when said spool means is in a neutral position;

a leveling fluid conduit means including an inlet fluid means communicating said fluid pump means and a first end of said double acting fluid cylinder means, and whereby when said bucket has been leveled said leveling fluid conduit means prevents rollback thereof;

an anti-cavitation fluid conduit means connecting said inlet fluid means and the discharge outlet of said double acting fluid cylinder means when said spool means is in a working position.

9. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising:

a housing means having a longitudinally extending bore means intersected at axially spaced intervals therealong by first, second, third, fourth and fifth port means;

a spool means carried in said bore moving between a neutral, working, and equilibrium position, wherein said equilibrium position is described by the equation:

P is the pressure on the rod side.

Claims

1. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising: a fluid pump means pumping high pressure hydraulic fluid; a manual fluid direction control means; a movable mechanical feedback linkage connected to the bucket, and to said valve assembly means; a valve means including: a housing means having a longitudinally extending bore means intersected at axially spaced intervals therealong by first, second, third, fourth and fifth port means, said first port means being connected to said manual fluid direction control means and said second port means being connected directly to said fluid pump means, said third and fifth port means being connected to said double acting fluid cylinder means on the head side thereof and said fourth port means being connected to said double acting fluid cylinder means on the rod side thereof; a valve spool means axially movable in said bore means from a neutral position blocking fluid from all port means except said first means and said third means, to a working position wherein first and third port means are closed and second, fourth and fifth port means are open, and an equilibrium position wherein only said fourth port means is closed; a link means connected to said valve spool means for transferring force from said mechanical linkage means to shift said spool means whereby said manual fluid direction means is cut out and said bucket is automatically maintained level to ground.

2. The valve assembly of claim 1 wherein said spool means has a timed feathering means whereby said third and fifth port means in series create an intermediate pressure to the head side of said cylinder means such that cylinder forces are balanced.

4. The valve assembly of claim 3 wherein said spool means has a plurality of axially spaced apart circumferentially extending land means attenuatively covering and Opening said corresponding adjacent port means.

6. The valve assembly of claim 5 wherein: said bore means has a plurality of spaced apart circumferentially extending groove means positioned adjacent said inlet port means; and said land means have feathered edge means.

8. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising: a valve means including: a spool means moving between a neutral, working, and equilibrium position, wherein said spool means has feathering means whereby forces on said cylinder in an equilibrium or self leveling position are described by the formula: K22A022/(K12A012 + A022) P2/P1 wherein: A02 and K2 are respectively the orifice area and flow coefficient of the fifth port means, A01 and K1 are respectively the orifice area and flow coefficient of the third port means, P2 is the pressure on the head side of the cylinder means and P1 is the pressure on the rod side. a non-leveling fluid conduit means communicating said manual control means and first end of said double acting fluid cylinder means when said spool means is in a neutral position; a leveling fluid conduit means including an inlet fluid means communicating said fluid pump means and a first end of said double acting fluid cylinder means, and whereby when said bucket has been leveled said leveling fluid conduit means prevents rollback thereof; an anti-cavitation fluid conduit means connecting said inlet fluid means and the discharge outlet of said double acting fluid cylinder means when said spool means is in a working position.

9. A valve assembly which automatically cuts out manual control and governs controlling actuation of the double acting fluid cylinder means of a work bucket to achieve leveling thereof upon boom raising comprising: a housing means having a longitudinally extending bore means intersected at axially spaced intervals therealong by first, second, third, fourth and fifth port means; a spool means carried in said bore moving between a neutral, working, and equilibrium position, wherein said equilibrium position is described by the equation: P2 P1((K22A022)/(K12A012 + K22A022)) where A01 and K1 are the orifice area and flow coefficients of said third port means, A02 are the orifice area and flow coefficients of said fifth port means; and P2 is the pressure on the head side of the cylinder means and P1 is the pressure on the rod side.