Graber, Homer R. (Pretty Prairie, KS)
Mcfarland, James W. (Hutchinson, KS)

04/837605

02/16/1971

06/30/1969

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The Cessna Aircraft Company (Wichita, KS)

60/472

414/708, 137/596, 91/520, 414/700, 60/471

E02F3/43; F15B13/07; E02F3/42; F15B13/00

91/414 214/763,771,140,(Inquired) 60/52 (HE)/ 37/596

Geoghegan, Edgar W.

We claim

1. A hydraulic system for controlling the related operation of at least a first and second fluid actuated motor, comprising:

2. The hydraulic system of claim 1 further comprising check valve means located in said fluid transfer means intermediate said flow divider means and the second motor adapted to prevent reverse flow through said transfer means from the second motor to said control valve means.

3. The hydraulic system of claim 1 further comprising second control valve means communicating with the pressure fluid supply, reservoir and the second motor, said second valve means having an associated second control element shiftable to direct fluid from the pressure fluid supply to the second motor to actuate same and override actuation of the second motor by said predetermined portion of displaced fluid.

4. The hydraulic system of claim 1 wherein said flow divider means communicates with the reservoir through a discharge duct, and directs the remainder of said displaced fluid to said discharge duct and reservoir.

5. The hydraulic system of claim 4 wherein said flow divider means includes a first flow restrictor interposed in the flow path from said fluid transfer means to said discharge duct and a second flow restrictor interposed in the flow path from said fluid transfer means to the second motor, the relative sizes of said restrictions determining said portion of displaced fluid directed to the second motor.

6. The hydraulic system of claim 1 wherein said first motor has opposing variable volume fluid chambers and said first control element is movable to a float position connecting both said chambers and said fluid transfer means with the reservoir.

7. The hydraulic system of claim 6 wherein said first control element interconnects said fluid transfer means with the reservoir in all positions of said first control element other than said transfer position

8. The hydraulic system of claim 1 wherein said second motor has opposing variable volume fluid chambers and is actuatable upon introduction of said predetermined portion of displaced fluid into one of said chambers, and said fluid transfer means include a hydraulically operable piston controlling communication between the other of said chambers and the reservoir, said piston movable to an open position connecting said other chamber with the reservoir in response to a predetermined pressure in said fluid transfer means.

9. The hydraulic system of claim 8 further comprising a check valve in said fluid transfer means intermediate said flow divider means and said one chamber adapted to prevent reverse flow from said one chamber to said control valve means.

10. A control for a hydraulic power system including a fluid supply, a reservoir, first and second double acting hydraulic motors having movable barriers therein dividing each of said motors into two variable volume chambers, said control comprising:

11. The control of claim 10 further comprising a pressure relief valve adapted to relieve fluid from said transfer passage to limit pressure therein to a predetermined value.

12. The control of claim 10 wherein shifting said second control element away from said neutral position to actuate the second motor overrides actuation of the second motor by said predetermined portion of displaced fluid.

13. A control valve assembly for selectively actuating first and second fluid motors comprising:

14. The control valve assembly of claim 13 wherein said housing comprises an assembly of section valves including:

15. The control valve assembly of claim 13 further including a pressure relief valve in said housing extending between said first control passage and said discharge passage, adapted to divert fluid from said first control passage to the discharge passage in response to a predetermined pressure in said first control passage to limit pressure therein.

16. The control valve assembly of claim 15 wherein said housing comprises an assembly of section valves including:

17. In a hydraulic system including a pump, a reservoir, a first double acting motor having fist and second variable volume fluid chambers, a second double acting motor having third and fourth variable volume fluid chambers, a control valve operatively connected with the pump, reservoir and first motor, and a movable control element mounted in said control valve adapted to connect said first motor fluid chambers with the pump and reservoir to actuate the first motor; wherein the improvement comprises:

18. The hydraulic system of claim 17 further including a second flow divider communicating with the reservoir and interposed in said second fluid transfer means to direct a predetermined portion of fluid flow therein to said fourth chamber and divert the remainder of fluid flow in said second transfer means to reservoir.

19. The hydraulic system of claim 18 wherein said first transfer means includes a first check valve located intermediate the first flow divider and said third chamber biased to a closed position blocking flow therebetween and responsive to a predetermined pressure in said first transfer means to move to an open position, and wherein said second transfer means includes a second check valve located intermediate said second flow divider and said fourth chamber biased to a closed position blocking flow therebetween and responsive to a predetermined pressure in said second transfer means to move to an open position.

20. The hydraulic system of claim 19 wherein said control element connects said second transfer means with the reservoir in said first transfer position, and said discharge means include:

21. In a hydraulic valve assembly including a body having first and second axial bores intersected by a pressure inlet connected to a pump and a fluid outlet connected to a reservoir, first and second control passages intersecting the first axial bore and connected to expanding and contracting chambers of a first double acting motor, third and fourth control passages intersecting the second axial bore and connected to expanding and contracting chambers of a second double acting motor, and first and second spools mounted in said first and second axial bores respectively and shiftable away from neutral to positions directing fluid to and from said control passages to actuate said motors, wherein the improvement comprises:

BACKGROUND OF THE INVENTION

This invention relates generally to controls for fluid power systems. More particularly, this invention relates to directional fluid control valves that selectively effect automatic leveling of the bucket on a front end loader or similar device, during movement of the boom arm to which the bucket is attached.

It is conventional practice to provide a hydraulic cylinder for manipulating the bucket of a front end loader, and another cylinder for raising and lowering the boom arm. In addition to various mechanical linkages that move the bucket and keep it level while the boom is being raised, hydraulic self-leveling means have also been devised to divert fluid displaced from the boom cylinder and direct it to operate the bucket cylinder so as to keep the bucket level. A serious drawback to these hydraulic systems is the requirement of matching the sizes of the boom and bucket cylinders so that the volume displaced from the boom cylinder will extend the bucket cylinder the precise distance to hold the bucket level as the boom is raised. As a result, a more expensive, unnecessarily large bucket cylinder is included in the hydraulic system. Further, because opposite ends of a hydraulic cylinder have different displacements due to the space taken by the cylinder rod at one end, bucket leveling can be effected in only one direction of boom movement.

It is therefore apparent that a hydraulic bucket leveling system not requiring matched boom and bucket cylinders would provide a more versatile and economic hydraulic control for front end loaders.

SUMMARY OF THE INVENTION

To this end, the present invention contemplates a hydraulic control system that directs only the necessary portion of boom displaced fluid to actuate the bucket cylinder, thereby permitting greater leniency in the size and design of the boom and bucket cylinders.

Accordingly, the invention broadly contemplates a control system for selectively actuating a first hydraulic motor by a portion of the fluid displaced from a second hydraulic motor.

Another object of this invention is to provide a control valve assembly and fluid system for actuating the boom and bucket motors of a front end loader whereby the bucket is automatically leveled during both the raising and lowering of the boom.

A more specific objective of this invention is to provide a control valve assembly including separate valves for regulating the boom and the bucket and a flow divider for directing a portion of fluid returning to the boom control valve into the bucket control valve to operate the bucket cylinder.

Another objective of this invention is to provide a control valve assembly characterized by the foregoing objectives wherein manual actuation of the bucket valve overrides the automatic bucket leveling operation

For such a control valve assembly, it is another object of this invention to provide a spool-type boom control valve which has a float position connecting both ends of the boom cylinder to low pressure.

A further object of this invention is to provide a bucket leveling control system comprising a bank of spool-type sectional control valves which can be interchangeably assembled.

Other objects and advantages of the present invention are described in, or will become apparent from, the following detailed description and accompanying drawings of the preferred embodiments.

Briefly, one form of the invention comprises a spool-type control valve selectively interconnecting opposite ends of a boom cylinder motor to a source of fluid pressure and drain to maneuver the boom. A similar control valve directs fluid to and from a hydraulic cylinder motor for positioning a bucket attached to the boom. The boom valve has a transfer passage into which displaced fluid from the boom cylinder can be directed upon proper positioning of the boom valve spool. A flow divider in the transfer passage directs a portion of the boom displaced fluid to the bucket control valve and the remainder to drain, The transferred fluid flows to one end of the bucket cylinder, with pressure of the transferred fluid actuating a piston to connect the other end of the bucket cylinder with drain, whereby the bucket operates in the desired manner in correlation with boom movement.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a partial schematic of the hydraulic controls for a front end loader including longitudinal section views of the control valves, with the bucket valve in neutral and the boom valve in raise-and-level position;

FIG. 2 is a partial transverse section of a stack valve assembly including the control valves shows in FIG. 1;

FIG. 3 is an enlarged section view of the flow divider;

FIG. 4 is a section view of the boom valve of FIG. 1 in a raise position;

FIG. 5 is a view similar to FIG. 4 with the boom valve in lowering position;

FIG. 6 is a view similar to FIG. 4 with the boom valve in float position;

FIG. 7 is a partial schematic of another embodiment of the fluid control system, with the bucket valve in lift position and the boom valve in neutral position;

FIG. 8 is a partial schematic of another embodiment of the invention, with the bucket valve in neutral and the boom valve in raise-and-level position; and

FIG. 9 is a view of the boom valve of FIG. 8 in lower-and-level position.

DESCRIPTION, FIG. 1

More particularly, FIG. 1 illustrates a boom arm 10 and bucket 11 as commonly mounted to the frame 12 of a mobile vehicle. Boom 10 is pivotally attached to the vehicle at pivot 13 for up-and-down movement, while bucket 11 is mounted to the boom at pivot 14 to facilitate scooping and dumping movements. Pressurization of the head end 17 of boom cylinder 15 causes extension of rod 16 and raises the boom, while pressurization of rod end 18 retracts rod 16 and lowers the boom arm. Pressurizing head end 21 of bucket cylinder 19 extends rod 20 and rotates bucket 11 clockwise about pivot 14 and boom 10, and pressurizing rod end 22 retracts rod 20 to rotate the bucket counterclockwise. The opposite ends of cylinders 15 and 19 are respectively connected to boom control valve 23 and bucket control valve 26 at control ports 24, 25 and 27, 28.

Body 29 of boom valve 23 has a longitudinal bore 30 in which a cannelured control spool 31 is movable to different positions to selectively interconnect and isolate various passages numbered 32 through 41 communicating with bore 30 at spaced positions. Passages 32 and 41 communicate with a low pressure fluid return reservoir, and port passages 34 and 40 respectively connect with cylinder chambers 18 and 17 through ports 24 and 25. Passages 36, 37 and 38 form the central bypass portion of the open center fluid delivery system, which system also includes pressure fluid delivery passage 42 and the branch passages 35 and 39 connectable with passage 42 across one-way lift check valve 43.

Port passage relief valve 54 is interposed between passages 40 and 41 to protect port passage 40 and boom cylinder chamber 17 from overpressurization by diverting fluid from passage 40 to drain passage 41 in response to excessive pressure in the port passage. Relief valve 54 is of conventional structure and operation well known to the art and will not be described in detail.

A transfer passage 33 extends in body 29 from bore 30 to parallel blind bore 44 that is intercepted by drain passage 32 and auxiliary outlet passage 46. Flow divider 45, movable within bore 44, is formed as a hollow sleeve having orifice plugs 48 and 49 securely fastened at either end to define a hollow interior communicating with transfer passage 33 through cross bores 47. The flow divider is clearly illustrated in FIG. 3. Orifice holes 50 and 51, normally of different sizes, connect the flow divider interior respectively with drain passage 32 and auxiliary outlet 46 across the flow orificing restrictions 52 and 53 formed between the chamfered ends of flow divider sleeve 45 and the cooperating portions of valve body 29. The proportional type flow divider 45 directs a certain percentage of flow from transfer passage 33 to auxiliary outlet 46, and diverts the remaining flow to drain passage 32.

Referring again to FIG. 1, bucket valve 26 is structurally similar to boom valve 23, having a fluid delivery system comprising bypass passages 36a, 37a, 38a, and pressure delivery passages 35a and 39a. Moving cannelured control spool 72 either direction within bore 71 directs pressure fluid to port passages 73 and 74 from adjacent passages 35a and 39a that connect with passage 42a across lift check valve 43a. Passages 32a and 41a, connected with a low pressure reservoir, also communicate with bore 71. Port passage relief valves 75 and 76, similar in structure and function to relief valve 54 of the boom valve, are respectively interposed between the port passages 73, 74 and drain passages 32a, 41a to protect the chambers 21 and 22 of bucket cylinder 19 from overpressurization.

An auxiliary fluid inlet bore 82 and passage 77 in bucket valve 26 directly communicate with the auxiliary outlet passage 46 of boom valve 26 when valves 23 and 26 are assembled, as shown in dotted lines in FIG. 2. Valves 23 and 26 are of the sectional type that are secured together in side-by-side relationship, along with other sectional control valves if desired, to form a conventional stack valve assembly 130. Port plates 131 and 132 fastened at either end of the bank of valves have a pressure port 133 connected with pump 134 and a drain port 135 communicating with a low pressure reservoir to provide common fluid supply and drain systems for valves 23 and 26. As seen, pressure port 133 communicates with passages 36a and 38a of the central bypass system and drain port 135 connects with passages 32, 37 and 41. Since passages 82 and 46 extend transversely through valve bodies 70 and 29, and because of their similarity in structure as shown in FIG. 2, valves 23 and 26 may be interchangeably assembled with boom valve 23 next to inlet port plate 131 and bucket valve 26 next to outlet port plate 132.

Again in FIG. 1, auxiliary passage 77 in bucket valve 26 communicates with port passage 73 and the head chamber 21 of bucket cylinder 19 across a one-way check valve 78 that opens, as shown, when pressure in passage 77 overcomes passage 73 pressure and the check valve spring bias. Check valve 78 has a poppet 79 spring biased to a closed position wherein it mates against a cooperating seat formed in valve body 70 to prevent fluid flow from passage 73 to passage 77. Hydraulically actuated unloading piston 81 in bore 80 is movable from the open position shown wherein passages 74 and 41a communicate across bore 80, leftwardly to a closed position blocking flow through bore 80. Piston 81 is spring biased toward its closed position and opened by pressure in auxiliary passage 77. The spring preload on piston 81 is greater than the spring preload on check valve poppet 79. The various operational modes will now be discussed in detail.

OPERATION, FIG. 1

Neutral Positions

Referring to FIG. 2 with both spools 72 and 31 in neutral, fluid entering inlet port 133 openly bypasses to drain port 135 by flowing from passages 36a, 38a through bore 71 to passages 37a, 36 and 38, across bore 30 to passage 37 and port 135. Actuating either spool 72 or 31 away from neutral blocks this bypass flow at bore 71 or 30, so that pressure builds in port 133; passages 42, 42a of FIG. 1, connected with inlet port 133, then deliver the pressure fluid across the lift checks 43, 43a to the valve work ports. Upon subsequent release of the spool, the centering spring assembly 84 or 84a returns it to neutral.

With spool 72 of bucket valve 26 in the neutral position, FIG. 1, both work ports 73, 74 are isolated from adjacent passages to hydraulically lock both cylinder chambers 21, 22 and hold the bucket in position. Similarly, boom 10 is locked in position when spool 31 is in neutral and blocking port passages 34 and 40 from adjacent passages 33, 35 and 39, 41. Spool 31 is illustrated in neutral in FIG. 7.

Bucket Lift

To rotate bucket 11 counterclockwise to effect a scooping and lifting action, spool 72 is manually moved leftwardly from neutral. (Such position of spool 72 is shown in FIG. 7) . Central bypass flow through passage 37a is blocked at bore 72, and pressure fluid delivered through passage 42a forces open the spring biased poppet 83 of lift check 43a to flow into branch passage 39a and continue through bore 71, port passage 74, port 28 and the rod chamber 22 of cylinder 19. Rod 20 retracts under hydraulic pressure, and fluid displaced from head chamber 21 returns to port 27 and passage 73 of valve 26, and flows across bore 71 to drain passage 32a.

Bucket Dump

Dumping bucket 11 by rotating it clockwise is selected by manually moving spool 72 to the right from the FIG. 1 neutral position. In a similar manner, the reduced diametral portions of spool 72 connect passages 35a and 73 to deliver pressure fluid to cylinder chamber 21 and interconnect port passage 74 with drain passage 41a at bore 71 to conduct away displaced fluid from chamber 22. Pressure in passage 73 positively holds poppet 79 in its closed position to prevent transfer of pressurized fluid from passage 73 to boom control valve 23.

Boom Raise-and-Level

The raise-and-level operation extends rod 16 to raise boom 10 and proportionally extends rod 20 of bucket cylinder 19 in order to keep bucket 11 in its same position relative to the ground as it was prior to raising boom 10. For example, bucket 11 is placed in a level position before actuating the boom; in subsequently rotating boom 10 30° counterclockwise about pivot 13, bucket 11 must, at the same time, rotate 30° clockwise about pivot 14 to remain in its original level position. To accomplish this correlated, slave operation of cylinder 19, fluid transfer means including passages 33, 46, 82 and 77 are incorporated to deliver fluid to cylinder 19 during boom raising.

The raise-and-level position of spool 31 shown in FIG. 1 blocks flow through the central bypass system and directs pressure fluid from branch passage 39 to port passage 40, port 25 and head chamber 17 of cylinder 15. Boom 10 is driven upwardly and fluid displaced to port 24 from cylinder chamber 18 passes across bore 30 into transfer passage 33 which is blocked from drain passage 32 by spool land 55. The boom cylinder displaced fluid continues through cross bores 47 to the hollow interior of flow divider 45 wherein a specified portion is directed to auxiliary outlet passage 46 and connecting auxiliary inlet passages 82 and 77. Pressure in passage 77 builds sufficiently to open check valve 78 and move unloading piston 81 rightwardly to the position shown. The regulated fluid flow into passage 77 then continues to head chamber 21 of cylinder 19 to rotate the bucket clockwise, with displaced fluid from rod chamber 22 returning through port 28, passage 74 and bore 80 into drain passage 41a.

In the fluid flow from transfer passage 33 to each of downstream passages 46 and 32, flow divider 45 places two orifices in series, the first orifice 50, 51 being fixed in size to determine the portion of flow delivered to each downstream passage, and the second orifice 52, 53 being variable in size to compensate for the difference in downstream pressures. By shifting within bore 44, flow divider 45 varies the sizes of secondary restrictions 52 and 53 so that pressure between orifices 50 and 52 at the left end balances pressure at the right end between orifices 51 and 53. With orifice 51 larger than orifice 50 for example, the majority of flow from passage 33 passes through larger orifice 51 to passage 46; flow divider 45 moves leftwardly to reduce the size of orifice 52 and build sufficient back pressure between orifices 50 and 52 to balance pressure from passage 46 exerted on the right end of the flow divider. The equal pressures at either end accordingly dictate equal pressure drops across orifices 50 and 51, so that the sizes of these orifices solely determine the rates of flow to passages 46 and 32.

Orifices 50 and 51 are appropriately sized in accordance with the volume capacities of cylinder chambers 18 and 21 to transfer the required fluid from chamber 18 through orifice 51 to chamber 21 to rotate bucket 11 and maintain the original bucket level position as the boom raises. Fluid in excess of that required by chamber 21 passes through orifice 50 to drain passage 32. Additionally, the present invention can divert more or less fluid to bucket cylinder chamber 21 by changing the sizes of orifices 50 and 51, to rotate the bucket to a load dumping or a tilted-back position respectively during boom raising. Generally, therefore, bucket 11 is automatically driven from a prescribed initial position to a predetermined end position during the raise stroke of the boom in accordance with the selection of orifice sizes in flow divider 45.

Unloading piston 81 is moved to an open position only when pressure exists in passage 77. Inadvertent drainage of fluid from cylinder chamber 22 and consequent movement of the bucket is prevented when spool 31 is not in raise-and-level position by the interconnection of passage 33 and drain passage 32 through bore 30 to relieve pressure in passage 77 and allow piston 81 to be spring biased to the closed position. Additionally, pressure operated piston 81 prevents cavitation in bucket cylinder chamber 21 during the raise-and-level operation. Whenever rod 20 tends to be pulled outwardly by a heavy load faster than the transferred fluid is flowing into chamber 21 and, accordingly, begins to establish cavitation of chamber 21, pressure in passage 77 drops and piston 81 moves toward its closed position to restrict or completely block flow from chamber 22 to drain. This metering action by piston 21 thus limits the speed of movement of rod 20 to match the rate of flow into chamber 21 and maintains positive pressure in passage 77 and chamber 21.

The automatic positioning of bucket cylinder 19 in the boom raise-and-level position can be selectively overridden by moving bucket spool 72 to a cylinder actuating position. Leftward actuation of spool 72 from neutral connects passage 73 with drain passage 32a and passage 74 with pressurized branch passage 39a. The consequent loss of pressure in passages 73 and 77 allows piston 81 to move leftwardly to isolate pressure carrying passage 74 from drain passage 41a. Bucket 11 rotates counterclockwise, and displaced fluid from chamber 21 exhausts across bore 71 to drain passage 32a. The boom is capable of continuing to raise in this override condition, with a slight pressure in passage 77 opening check valve 78 (through such pressure does not overcome the stronger spring bias on piston 81) and allowing boom displaced fluid also to exhaust to drain passage 32a. In moving bucket spool 72 rightwardly from neutral, pressure fluid delivered from passage 35a to passage 73 (acting with the transferred fluid from passage 77 if the boom continues to raise) drives bucket 11 clockwise, while passage 74 is connected with drain passage 41a across both bores 71 and 80 for exhausting fluid from cylinder chamber 22. During raise-and-level operation, therefore, bucket 11 can be selectively positioned in the normal manner by actuating spool 72 to override the bucket leveling operation.

Automatic slave positioning of cylinder 19 may also be accomplished by the present system when boom 10 is in a lowering cycle. For example, by reversing the connections of the cylinder chambers with the valve ports so that chambers 17 and 18 respectively connect with ports 24 and 25, and chamber 21 and 22 respectively connect with ports 28 and 27, the fluid displaced from head chamber 17 of boom cylinder 15 during lowering of boom 10 will now be conducted through the transfer means to rod chamber 22 of cylinder 19 to retract rod 20. In comparison to the raise-and-level operation, this lower-and-level operation requires the orifices of the flow divider to be sized to divert a smaller portion of the fluid from head chamber 17, which has greater displacement than rod chamber 18, into the rod chamber 22 of cylinder 19 which has less displacement than head chamber 21. It can be seen that a hydraulic system for effecting automatic lower-and-level has been heretofore impractical, as cylinder 19 would have to be larger than cylinder 20 so that the total volume of fluid displaced from head chamber 17 and transferred to rod chamber 22 would appropriately move the bucket to keep it level as boom 10 lowers.

Boom Raise

Boom 10 can be selectively raised without automatically leveling the bucket by positioning spool 31 slightly rightwardly from the FIG. 1 raise-and-level position to a position as shown in FIG. 4. In this position spool land 55, being narrower than passage 33, affords intercommunication between port passage 34, transfer passage 33 and drain passage 32. Pressure fluid is still delivered from branch passage 39 to port passage 40 to raise the boom; however, displaced fluid from the boom cylinder flows directly from port 24 and passage 34 through passage 33 and bore 30 to drain passage 32, rather than being transferred to the bucket control valve. The bucket will remain hydraulically locked in position while the boom is so raised since no pressure fluid is transferred to passage 77 of bucket valve 26 (FIG. 1) to open poppet 79 and piston 81.

Boom Lower

As shown in FIG. 5, spool 31 is moved to the right of neutral to lower the boom arm. Central passage 37 is again blocked from passages 36 and 38 so that pressure fluid from the valve inlet opens lift check 43 to deliver fluid through branch passage 35 to passage 34 and the rod end of the boom cylinder. Displaced fluid from the opposite cylinder end returns to port 25 of valve 23 and continues through bore 30 to drain passage 41. Passage 33 remains in communication with drain passage 32 and is blocked from passage 34 by land 55 to relieve pressure from the transfer passage means.

Boom Float

A float position of spool 31 is incorporated in control valve 23, as illustrated in FIG. 6, wherein both port passages 34 and 40 are connected with drain passages 32, 41 through bore 30. Reduced diametral portions 57 and 58 reestablish the central bypass flow of the open center fluid delivery system through interconnection of passages 36, 37 and 38, which accordingly relieves pressure from passage 42 to close check valve 43. Again, passage 33 is drained through bore 30 to relieve pressure from the transfer passage means and render inoperative the automatic actuation of the bucket.

With both ports 24 and 25 and the opposite ends of the boom cylinder so drained, the boom rod can freely move within the boom cylinder, and the boom is capable of floating over irregular terrain. Maintenance of a low back pressure within drain passages 32 and 41 to which the cylinder chambers are connected in float position, positively prevents formation of cavitation conditions within the boom cylinder chambers during float operation.

In addition to providing a preferred float operation, location of transfer passage 33 intermediate port passage 34 and drain passage 32 circumvents hydraulic lock of the transfer passage means. As described, transfer passage 33 communicates with drain passage 32 in all positions of spool 31 with the exception of the raise-and-level position wherein it connects with port passage 34. Never being hydraulically isolated, the transfer passage means, therefore, are not subject to collection of pressure fluid leakage, and the consequent inadvertent opening of piston 81 and undesired bucket movement is avoided.

FIG. 7 EMBODIMENT

As shown by like numerals for like parts, FIG. 7 is similar in construction and operation to the FIG. 1 control system and additionally includes port passage relief valve 59 in boom valve 60, and a flow divider valve section 100 sandwiched between the boom and bucket control valve sections. Bucket control valve section 26 is shown with its spool 72 positioned in a rod retracting position, and spool 31 of the boom valve is in neutral.

Port passage relief valve 59 is interposed between port passage 63 and drain passage 32 of valve body 61 to divert fluid to drain passage 32 and prevent excessive pressure buildup in passage 63. Valve 59 is similar in construction and operation to conventional port passage relief valves 54, 75 and 76. In raise-and-level operation the relief valve 59 protects both interconnected passages 33 and 63, and is preset to a higher pressure setting than is port relief valve 75 of control valve 26 to which transfer passage 33 is interconnected in the raise-and-level operation. This higher relief pressure setting on valve 59 takes into account the pressure drops in the fluid transferring from passage 33 to passage 73 so that pressure in passage 73 can build to the level allowed by relief valve 75. Also, when rod 20 reaches the end of its stroke while spool 31 is in raise-and-level position, relief valve 59 protects passages 33 and 63; relief valve 75 cannot reliably communicate with and protect these passages in such instance because check valve 78 may be locked in a closed position.

Flow divider section 100 is interposed between valves 26 and 60 in the valve bank assembly and has transverse through passages 32b, 37b, 41b and 42b properly interconnecting with the boom and bucket valve passages denoted by corresponding numerals. Flow divider 45 in axial bore 102 is located in the transfer passage means in the same manner as in FIG. 1, since: transverse through passage 104 communicates with bore 62 and transfer passage 33 of boom valve 60; the left passage 103 connects with drain passage 32b; and the right passage 105 connects with through passage 106 that leads to auxiliary inlet bore 82 of valve 26. Accordingly, the operation of flow divider 45 and the FIG. 7 system is the same as described with respect to FIG. 1.

DESCRIPTION, FIG. 8

The hydraulic control system of FIG. 8 is capable of selectively automatically positioning the bucket when the boom is both raised and lowered, by diverting a portion of displaced fluid from boom cylinder 15 to bucket cylinder 19. The control system comprises a boom control valve 64, flow divider valve section 107 and bucket valve 85 generally similar in construction to the valve sections of previous embodiments as illustrated by using the same numerals to identify like features.

Control spool 66 of boom valve 64 is movable from neutral to four cylinder actuating positions and has no float position, though such may be incorporated if desired. Body 65 has a second fluid transfer passage 67 intermediate port passage 40 and drain passage 41. A transverse through bore 68 similar to bore 62 communicates with passage 67 and functions to deliver displaced fluid from cylinder chamber 17 to control valve 85 when spool 66 is in lower-and-level position.

Flow divider section 107 between valve sections 64 and 85 in the assembled bank of valve sections functions to deliver a specified portion of fluid from valve 64 to valve 85 as well as provide a free flow return passage to drain for fluid displaced from cylinder 20. In addition to flow divider 45 in bore 102, body 108 includes bore 109 which receives a second, identical flow divider 45a that operates in like manner as flow divider 45 to regulate flow to bucket cylinder chamber 22 during lower-and-level operation. Three passages 111, 112 and 113 intercept bore 109 at spaced locations: passage 111 connects with drain passage 41b; passage 113 communicates with transverse through bore 114 that connects to auxiliary inlet bore 91 of bucket valve 85; and passage 112 extends transversely through body 108 to communicate with bore 68 of valve 64. Also included within body 108 are a flow divider bypass passage 115 extending between bore 114 and passage 112, and a similar bypass passage 117 between bore 106 and passage 104. Check valves schematically illustrated at 116 and 118 are located in passages 115 and 117 to assure that fluid flows from passages 112, 104 to passages 114, 106 respectively via the flow divider orifices 51 and 51a.

Bucket control valve 85 has an elongated plunger piston 87 and spring loaded check valve 88 in place of the unloading piston 81 of the previously described embodiment of the bucket valve. Check valve 88, like check valve 78 in structure and function, has a poppet 89 normally spring biased to a closed position blocking flow between port passage 74 and passage 90 in body 86. Pressure in either of passages 77 to 90 operates directly and through piston 87 to open both check valves 78 and 88. For instance, as shown in FIG. 8, high pressure in passage 77 acts directly on poppet 79 to move it leftwardly to the open position, and forces piston 87 rightwardly to engage and move poppet 89 rightwardly to the open position. With low pressure in both of passages 77 and 90, the spring bias on poppets 79 and 89 move them inwardly to closed positions as piston 87 is not long enough to simultaneously contact both poppets 79, 89.

OPERATION, FIG. 8

The operation of FIG. 8 in the neutral, bucket lift, bucket dump, boom raise and boom lower modes is as described with respect to FIG. 1 and need not again be set forth in detail. Note that land 69 of spool 66, similar to land 55, is not as wide as passage 67 so that selection of the boom lower operation positions land 69 midway in passage 67 to permit interconnection of the three adjacent passages 40, 67 and 41, and thereby direct displaced fluid entering port 25 and passage 40 to drain passage 41. In boom raise and boom lower, check valves 78 and 88 remain closed as passages 77 and 90 of the bucket valve are drained through boom valve passages 62 and 67 which are respectively communicating with drain passages 32 and 41.

Boom Raise-and-Level

Boom spool 66 is illustrated in raise-and-lvel position in FIG. 8. The transfer of a portion of displaced fluid from cylinder chamber 18 to cylinder chamber 21 to effect the raise-and-level operation is the same as described with respect to the previous embodiments, check valve 118 in flow divider section 107 being held closed by pressure in passage 104 to direct the transferring fluid through flow divider 45 to bore 106. However, fluid displaced from bucket cylinder 19 returns through the boom valve to discharge to drain: Pressure in passage 77, having opened check valve 88 by forcing piston 87 rightwardly, allows fluid displaced from chamber 22 to return through passages 74, 90 and 91 to bore 114 of the flow divider section. This return flow bypasses flow divider 45a by opening check valve 116 and continues to conduit 115, passages 112, bore 68, passage 67 and through the bore 30 to drain passage 41 in the boom control valve.

Boom Lower-and-Level

By moving spool 66 to the right until land 69 interrupts flow between passages 67 and 41 as shown in FIG. 9, the lower-and-level operation is selected. Transfer passage 33 is connected with drain passage 32 through the spool bore, and pressure fluid from branch passage 35 is directed to passage 63, port 24 and the boom cylinder rod chamber to retract the boom cylinder. Fluid displaced from the boom cylinder returns to port 25, passage 40 and continues through passage 67 and bore 68 out of valve 64 and into flow divider section 108 (FIG. 8) at passage 112. This transfer fluid flow closes ball check valve 116 and passes to the interior of flow divider 45a to there be divided, with a specified portion directed through orifice 51a to passages 113 and 114 and the remainder diverted through orifice 50a to drain. The transferred fluid in passage 114 continues to passage 90 of bucket valve 85 to open poppet 89 and urge piston 87 leftwardly to engage and open poppet 79. Fluid in passage 90 continues past poppet 89 to port passage 74 and cylinder chamber 22 and retracts bucket cylinder rod 20 in correlation with the boom cylinder rod retraction to keep the bucket level during boom lowering. Exhausted fluid from bucket cylinder chamber 21 returns past open check valve 78 to passage 77, bore 82 and bore 106 of the flow divider section. The return flow bypasses flow divider 45 by opening check valve 118 and continues to passage 104 into valve 64 (FIG. 9) at passage 33 and through the spool bore 30 to drain passage 32.

Selective overriding of the automatic leveling actuation of the bucket cylinder is accomplished upon movement of bucket spool 72 away from neutral. This function is the same in lower-and-level as it is in raise-and-level. Referring to FIG. 8 and the raise-and-level operation, to override and retract rod 20, spool 72 is moved leftwardly from neutral to interconnect passage 39a with port passage 74 and connect drain passage 32a with port passage 73. Pressure fluid introduced into passage 74 passes through opening 92 to the rear of poppet 89 into spring carrying chamber 93 to assist the spring bias of check valve 88 in moving poppet 89 to its closed position. Pressure in passage 74 and chamber 93 exerts sufficiently greater force on poppet 89 than pressure in passage 77 exerts on piston 87, and poppet 89 cannot open. The pressure fluid in passage 74 passes onto cylinder chamber 22 to retract rod 20 and thereby override the raise-and-level operation. Fluid displaced from chamber 21 drains through passage 73, bore 71 to passage 32a. Assuming the boom continues raising at this time, the fluid in passage 77 displaced from cylinder 15 opens check valve 78 to flow to drain passage 32a.

Moving spool 72 rightwardly to extend rod 20 during raise-and-level simply complement the flow of pressure fluid to chamber 21 and draining of fluid from chamber 22.

Overriding during lower-and-level is accomplished in the same manner, and poppet 79, accordingly, has an opening 94 communicating chamber 95 with passage 73 to assure closure of check valve 78 upon introduction of pressure fluid into passage 73 from passage 35a.

Automatic bucket leveling while lowering and raising the boom can be effected without including a flow divider in each path of transferring fluid flow from passages 33 and 67 to the bucket valve. Leveling while raising the boom can instead be accomplished by the prior art method of matching the cylinder sizes so that all fluid displaced from boom cylinder chamber 18 during raising is used by bucket cylinder chamber 21 in extending rod 20, and during boom lowering is effected by the improved method of the present invention. Flow divider 45 is now and it along with bore 102, passages 103, 105 and check valve 118 can be eliminated from flow divider section 107 to leave continuous fluid communication between passage 33 of valve 64 and bore 82 of valve 85 through the flow divider section. The operation in raise-and-level and in lower-and-level is the same as before except all fluid displaced from f the boom cylinder is transferred to the bucket cylinder in raise-and-level, while still only a specific portion of fluid, as controlled by flow divider 45a, is transferred from boom to bucket during lower-and-level. The adaptability of the correlated bucket movement described before is now, of course, available only while the boom is being lowered.

Modifications to the construction and uses of the invention as specifically set forth in the foregoing description will be apparent to those skilled in the art. For instance, the several valve sections depicted in each of the embodiments may be incorporated into a unitary control valve, or a different pressure fluid delivery system may be used to supply fluid to the bucket and boom control valves, or various forms of flow dividers may be used in place of that shown, or a pair of cylinder actuators may be substituted for either of the single cylinders 15 or 19. Accordingly, the specific embodiments of the invention herein described are to be considered exemplary in nature and not limiting to the scope and spirit of the invention as set forth in the appended claims.