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Publication numberUS3811282 A
Publication typeGrant
Publication dateMay 21, 1974
Filing dateJan 26, 1973
Priority dateJan 26, 1973
Publication numberUS 3811282 A, US 3811282A, US-A-3811282, US3811282 A, US3811282A
InventorsL Schexnayder
Original AssigneeCaterpillar Tractor Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Hydraulic control circuit for a reversible hydraulic motor
US 3811282 A
Abstract
There is disclosed a hydraulic control system for selectively operating a remote hydraulic motor in at least two forward operating speeds and at least one reverse operating speed. The system includes first and second pumps and pilot controlled valve means to control communication of the pumps with the motor. The pilot controlled valve means are responsive to a main control valve to selectively communicate the first and second pumps to the motor and to drain, thus providing for variable speed operation of the motor. A third pump operatively communicates by way of the main control valve and a reverse check valve to provide fluid pressure for reverse operation of the motor.
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Description  (OCR text may contain errors)

United States Patent Schexnayder [111 3,811,282 I 1 May 21,1974

2,879,6l2 2,9l7,897.- 3386344 I 3.576.104

Appl. No.: 327,240

US. Cl 60/421, 60/429, 60/486 Int. Cl. Fl5b' 13/09 Field of Search 60/486, 421, 428, 429

Schultz et al. 60/421 X 60/421 60/421 X Shaffer J unck et al.

' Kokaly Primary Examiner-Edgar W. Geoghegan Attorney, Agent, or Firm-Phillips, Moore, Weissenberger Lempio & Strabala [5 7] ABSTRACT There is disclosed a hydraulic control system for selectively operating a remote hydraulic motor in at least two forward operating speeds and at least one reverse operating speed. The system includes first and second pumps and pilot controlled valve means to control communication of the pumps with the motor. The pilot controlled valve means are responsive to a main control valve to selectively communicate the first and second pumps to the motor and to drain, thus providing for variable speed operation of the motor. A third pump operatively communicates by way of the main control valve and a reverse check valveto provide fluid pressure for reverse operation of the motor.

10 Claims, 2 Drawing Figures PATENTEBHAYZI m4 $811,282

EL J

ZON

BACKGROUND OF THE INVENTION The present invention relates to a remote control sysmotor in at least two forward operating speeds and at least one reverse operating speed. More particularly, the-invention provides pilot controlled valve means which are responsive to a main control valve and are operatively associated with two sources of fluid under pressure for selectively delivering fluid under pressure from the two sources to a motor for two speed forward drive while preferably delivering excess fluid directly to drain. A reverse check valve is operative in response to the main control valve to communicate fluid from a third source of the motor for reverse drive.

Control systems of the remote control type are commonly employed, for example, to operate various hydraulic motors and implements on machinery such as earth moving equipment. The hydraulic motors for such equipment are often in a relatively remote location from pumps which provide fluid under pressure to the control system. It is particularly desirable to minimize the number and size of fluid-conduits communicating the pumps in the control system with the relatively remote motor. This is particularly important in articulated machinery where the pumps are located on one articulated section of the machine and the motor or motors are located on another articulated section with swivel joints commonly provided at the articulated intersection of the machine for each ofthe fluid conduits. I 1

Additionally, implements and hydraulic motors which may be operated by the present control system are often operated only intermittently. The control system returns output fluid from the pumps to a drain reservoir during intervals when the motor is not operated. In many prior art control systems of the type presently contemplated, this return flow of outlet fluid from the pumps is commonly delivered to a drain passage over a main control spool and provides an undesirable source of heat generation.

In many such applications it is desirable to be able to operate the motor in reverse. For example, the motor for the elevator of an elevating scraper is ordinarily operated only in a single direction. However, it has been found desirable to provide at least limited reverse drive in order to free the elevator when it becomes stalled due to large rocks and the like and to aid in unloading sticky materials.

The following patents appear to be exemplary of the known prior art and were reviewed during preparation of the subject application:

lo Schexnayder These control systems, however, are limited in their function, especially in failure to provide suitable systems to provide multiple forward speeds in conjunction with provision for reverse drive.

SUMMARY AND OBJECTS OF THE INVENTION Accordingly, it is the primary object of the present invention to provide a hydraulic control system for minimizing the problems discussed above.

It is another object of the invention to provide a hydraulic control system for selectively communicating one or more hydraulic pumps with a motor for multiple speed drive and for reverse of the motor.

It is a further object to provide for substantially direct communication of any excess pump outlet fluid toa suitable drain passage.

In accordance with the primary aspect of the present invention, there is provided a remote control system which employs restrictive valve means which are re sponsive to a main control valve for respectively communicating a plurality of fluid pumps with the motor and with a suitable drain passage.

BRIEF DESCRIPTION OF THE DRAWING I Additional objects and advantages of the present in vention will become apparent from the following description having reference to the accompanying drawing wherein:

FIG. 1 is a schematic representation, with parts shown in section, of a control system in accordance DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawing, operating communication ofa pair of hydraulic pumps 10 and l2 with a reversible rotary output hydraulic motor 14 is selectively controlled by a pilot valve assembly indicated at 16. The pumps 10 and 12 provide first and second sources of pressurized fluid and are selectively communicated with the motor 14 to provide for variable forward speed of the motor. A third pump or'source of pressurized fluid 18 is communicated with motor, to provide reverse drive of the motor. Operation of the pilot valve assembly 16 for selectively communicating the pumps with the motor is in turn regulated by a main control valve assembly, generally indicated at 20. I

The pilot valve assembly 16 includes pilot controlled 7 valves 22 and 24 which are respectively operatively connected to control the flow from pumps 10 and 12 in a manner more fully described below. The pilot valves 22 and 24 provide restricted fluid flow into first and second pilot control passages 26 and 28 which are operative to control the respective valves. The pilot control passages are in selective communication with a drain passage 30 across the main control valve 20 so that the valves 22 and 24 are made responsive to selective positioning of the main control valve 20.

To briefly set forth operation of the components summarized above, outlet fluid from the. first pump 10 is in communication by way of conduit means 32 and a fluid passage 34 formed in a housing 36 of the pilot valve assembly 16 with a forward inlet passage 33 of motor 14. The housing 36 also includes a drain passage 38 which is in communication with a common drain reservoir 40 by means of a conduit 42.

The pilot controlled valve 22 permits unrestricted fluid flow from the fluid passage 34 into drain passage 38 when the pilot control passage 26 is in open communication with sump 40 as shown. The valve means 22 is responsive to the main control valve 20 for either communicating the fluid passage 34 with the drain passage 38 or for blocking communication between those two passages so that fluid under pressure in the passage 34 is caused to operate the motor 14. A spring biased poppet 43 is operatively associated with piston 44 to limit working pressure in passage 34 to a predetermined safe level.

The valve 22 includes a spring loaded piston 44 reciprocably mounted within a bore 46. The piston 44 forms a restrictive orifice 48 which communicates the fluid passage 34 with the first pilot flow passage 26. Differential pressure caused by flow of fluid from the passage 34 through the orifice 48 produces a resultant upwardforce' upon the piston 44 so that the piston is shifted to the position shown in thedrawing. With the piston 44 in its open position, a plurality of ports 50, defined by the piston 44, communicates fluid from the passage 34 into the drain passage 38. This condition occurs when a control valve spool 52 is in its neutral position and a slot .54 formed thereon is disposed to communicate fluid from the first pilot control passage 26-to drain. V

The pilotcontrolledselector valve 24 provides unrestricted fluid flow from the second pump l2 through a" conduit 56 into the drain passage 38 when the pilot control passage 28 is open to sump 28 as shown. The valve 24 is responsive to the control valve for either communicating the second'pump outlet fluid to the drain'passage 38 or alternatively to the fluid passage 34 where it is combined with fluid from the pump 10 to operate the motor 14 at a higher speed.

The valve 24 also includes a spring loaded piston 58 reciprocably arranged within a bore 60 and forming a restrictive orifice 62 which communicates fluid from the second pump outlet conduit 56 into the second pilot flow passage 28. When the second pilot flow passage is in communication with drain across the control valve 20, the piston .58 is similarly shifted upwardly to the position shown in the drawing by a differential pressure caused by the orifice 62. With the piston 58 in itsupwardly shifted position, it communicates a substantial portion of fluid flow from the conduit 56 into the drain passage through a plurality of ports 64 formed in the piston 58.

In many applications, such as the operation of an elevator for a scraper, the motor 14 is locatedin a relatively remote location from the pumps 10,12 and the pilot valveassembly 16 of the drawing. It is particularly noted that the remote 'motor 14 is in communication with the pumps l0, l2 and pilot valve assembly 16 by the common conduit 33 and-with the common drain reservoir 40 by another conduit indicated at 68. I

The main control valve includes the selector spool 52 reciprocally mounted in a bore 70 such that the annular groove 54 controls venting of the valve 22 by way of line 26. The valve 24 is vented by way of a line 28 and an annulus 72 disposed in circumscribing relation to the valve bore and the spool 52. An annulus 74 is provided as a supply annulus for pressure fluid to drive the motor 14 in reverse. The return line 68 from motor 14 communicates directly with return passages 38 in the valve 16 which, in turn, communicates-with the reservoir 40' by way of a line 42.

Annulus 74 of theselector valve communicates by way of a line 76, with an annulus .78 disposed adjacent the lower end of valve 16. A bore provides a flow path between the annulus 78 and the return passage 38 and is coaxially -aligned with that portion of the return passage.

A reverse drive check valve 82 is reciprocably disposed within passage 80 and is biased by a spring 84 to a position normally substantially blocking communication between the annulus 78 and the passage 38. A plurality of radial passages 86 adjacent the lower end of the check valve 82 communicates the annulus 78 with a chamber 88 within the check valve. The check valve further includes a plurality of radial orifices 90 which are normally blocked with the check valve in the position shown and an orifice 92 which continually comm unicates between chamber 88 and the return passage 38.

Fluid pressure for reverse operation of the elevator motor 14 is supplied by the implement pump 18 which normally supplied fluid under pressure for operation of other scraper components such as bowl lift and ejector which are under the control of a pair of spools 94 and 96, respectively, which are also'reciprocably disposed in thelvalve body 98. Body 98 also includes a relief FIG. 2 shows an alternate embodiment of the reverse check valve wherein a'check valve 102 is disposed inline between the line 76 and the line 68 communicating with the reverse drive input portof motor 14. The check valve is biased by a spring 104 toward the position illustrated providing communication between line 68 and return passage 38 in the body 36. An orifice 106 is provided in the end face of the check .valve to com municate flow from the line 76 to the line 68. The orifree is sized to provide sufficient pressure drop at minisage 38 during reverse drive operation.

OPERATION Neutral Condition When the spool 52 is in the neutral condition illustrated, the output of pump 18 flows from passage across the open center section 108 to a discharge passage 110 from where it is returned to reservoir 40 by way of return lines 30 and 42. Theline 26 is vented by way of groove 54 to reservoir 40 such that the fluid flow through orifice 48 of the relief dump piston 44 generates a pressure differential thereacross to urge the piston to the position shown. This communicates the output of pump 10 to the reservoir by way of passage 32, radial passages 50in the valve piston 44, return passage 38, and return line 42. At this time the line 28 is also vented to reservoir by way of annulus 72, return passage 110, and return lines 30 and 42. The resultant flow through orifice 62 of valve piston 58 generates a pressure differential thereacross to shift piston 58 upward to the position shown. In this position, the output of pump 12 is communicated by way of line 56, a plurality of radial ports 64 in the valve piston, returnpas- 3 sage 38 and return line 42 to the reservoir 40. Under these conditions the pumps are all vented to the reservoir so as to prevent the generation of sufficient pressure for driving motor 14.

First Forward When the spool 52 is moved downward to the F-1 position, communication of the line 26 to the reservoir is blocked so as to permit equalization of pressure on the opposite side of the piston 44 such that its biasing spring controls and urges it to a closed position wherein the radial ports 50 are blocked. Under these conditions, the output of the pump is directed through the lines 34 and 33 tothe forward drive port of motor 14 to drive the elevator in a forward direction. Eitpended oil from motor 14 is returned to the reservoir by way of line 68, passage 38, and return line 42. In order to minimize travel, the check valve 82 projects outwardly into the flow path of return oil in the line 68. The resulting flow interference creates a zone of static pressure, 6-8 psi higher than prevailing return line pressure, immediately around the projecting end of the check valve. This static pressure leaks along the operating clearance between the check valve 82 and the bore 80 to the radial ports 90 and thence to chamber 88. This tends to generate a pressure differential across the check valve which could result in unwanted closing of the check valve. In order to avoid this problem, orifice 92 communicates the chamber 88 directly to the passage 38 at the end face of the check valve. This equalizes the pressure in the chamber 88 with the prevailing pressure in the return line to prevent closing of the check valve under forward drive conditions.

Second Forward When the spool 52 is moved to the F-2 position, both of the pilot lines 26 and 28 are blocked'thereby to maintain the drive conditioning of valve piston 44 and also allow equalization of pressure on opposite sides of valve piston 58 through the orifice 62. Under these conditions, the biasing spring-for piston 58 controls and the piston is moved downward to block communication of the output of pump 12 to the return line 38 and to communicate that output through radial passages 65 to the passage 34 for supply to the forward drive inlet port of the motor 14 by way of line 33. This conditioning combines the output of pump 12 with that of pump 10 to provide a second forward speed drive of the elevator.

Reverse Drive When spool 52 is moved upward to the R position, the open center bypass section l08is blocked and the passage 100 is communicated with annulus 74. This is effective to direct the output of pump 18 through the line 76 to annulus 78 associated with the reverse check valve 82. This oil is communicated through radial ports 86, chamber 88, and orifice 92 to generate a pressure differentialovercomingthe bias of spring 84 and move the check valve upward in seating relation to block communication between line 68 and return passage 38. Under these conditions. the flow in the chamber 88 is communicated through radial orifices 90 to the-line 68 for supply of driving pressure to the reverse drive inlet port of motor 14. The restrictive nature of radial ports 90 is effective to maintain a pressure differential thereacross under minimum flow conditions (low engine speed). This insures that the check valve 82 will remain in the upward closed position at all times fluid pressure is directed through the line 76.

With spool 52 in the R position, pilot line 26 is vented to allow valve piston 44 to open thus communicating passage 38 to the reservoir as previously described. This permits the fluid exiting from motor 14 by way of line 33 to be returned to the reservoir along with the output of pump 10. Pilot line 28 is still vented by way of slots 55 so as to maintain the illustrated position of tion and flow is directly through the ends of the. check valve. The reorientation of the check valve 102 compared to FIG. 1 eliminates the static pressure zone described above.

What is claimed is:

l. A hydraulic control system for remotely controlling a hydraulic motor for at least two forward operating speeds and at least a single reverse speed, comprising in combination;

a reversible hydraulic motor having forward and reverse inlet passages;

a first source of pressurized fluid communicating with the forward inlet passage of said motor;

a return passage communicating with a sump;

means including a pilot operated valve for selectively communicating said first source of fluid with said return passage;

a second source of pressurized fluid;

conduit means for communicating said second source of fluid with said forward-inlet passage. of said motor and with said return passage;

a pilot operatedselector valve selectively operable to control said conduit means to selectively direct fluid from said second source alternately to said motor or to said return passage;

a third source of pressurized fluid; and,

means for selectively communicating said third' source of fluid to said reverse inlet passage of said motor or to said sump.

2. The hydraulic control system of claim 1 wherein said-means for selectively directing said third source comprises a reverse check valve operative to normally communicate said reverse inlet passage with said return passage and responsive to fluid from said third source to block said communication of said reverse inlet passage with said return passage and to communicate said third source with said reverse inlet passage.

3. The hydraulic control system of claim 2 comprising a main control valve, and said main control valve is operative to control said pilot operated valve and said pilot operated selector valve and to selectively communicate fluid from said third source to said reverse inlet passage of said motor. 6

4. The hydraulic control system of claim 3 comprising a single pilot control passage for controlling said pilot operated valve, and a single pilot control passage for controlling said pilot selector valve, and said main control valve is operative in a neutral position to communicate said pilot control passages to said sump to thereby render said pilot operated valve and said selector valve effective to direct pressurized fluid from said first and said second sources to said sump.

'valve to direct fluid from said first and said second sources to said motor for at least a second forward speed while'simultaneously therewith directing fluid from said third source to said sump, and operative in a third position to direct fluid from said third source to said motor for reverse operation thereof while controlling said pilot operated valves to direct fluid vfrom said first and saidsecond sources to sump. I

6. The hydraulic control system of claim {wherein said reverse check valve comprises:

a cylinder bore; a first port at one end of said bore communicating said third source therewith; I a second port at the other end of said bore communicating said reverse inlet passage therewith;

a third port disposed at said other end communicat- 4 ing said bore with said return passage; and, a substantially cylindrical valve member reciprocally disposed in'said bore and operative to control communication betweensaid ports. 1 7. The hydrauliccontrol system of claim 6 wherein said valve member includes a restrictive orifice communic'ating between said first port and said third port to maintain said valve member in a proper control position under low volume flow from said third source.

8. The hydraulic control-system of claim 6 wherein said first port and said third port are c oaaially disposed with respect to said bore;

said valve member defines substantially a sleeve configuration; and,

communication of said first port with said second port'is through said valve member.

9. A hydraulic control system for remotely controlling a hydraulic motor for at least two forward operating speeds and at least a single reverse speed, comprising in combination: I

a reversible hydraulic motor having forward and reverse inlet passages;

means providing a source of pressurized fluid communicating with the forward inlet passageof said motor to drive said motor in a forward direction;

a return passage communicating with a sump;

pilot operated valve me'ans for selectively communicating said source of fluid with said return passage;

means providing a separate source of pressurized fluid for driving said motor in a reverse direction;

means for selectively communicating said third source of fluid to said reverse inlet passage of said motor or to said sump, said means comprising a reverse check valve operative to normally communicate said reverse inlet passage with said return passage, and responsive to fluid from said separate.

a substantially cylindrical valve member reciprocally I disposed in said bore and operative to control com 'munication between said ports.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2879612 *May 2, 1956Mar 31, 1959Gar Wood Ind IncHydraulic drive for ditcher conveyor
US2917897 *Feb 4, 1955Dec 22, 1959Walter M ShafferHydraulic drive mechanism
US3386344 *Sep 30, 1966Jun 4, 1968Caterpillar Tractor CoSelf-loading scraper hydraulic circuit with diverter
US3576104 *Sep 29, 1969Apr 27, 1971Caterpillar Tractor CoControl system for hydraulic motors
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4089171 *May 24, 1976May 16, 1978Webster Electric Company, Inc.Four position valve assembly
US5842848 *Jan 3, 1997Dec 1, 1998Knowles; Frederick W.Compact high-volume gear pump
Classifications
U.S. Classification60/421, 60/486, 60/429
International ClassificationF15B11/17
Cooperative ClassificationF15B2211/40515, F15B2211/67, F15B11/17, F15B2211/428, F15B2211/6355, F15B2211/3116, F15B2211/30505, F15B2211/20576, F15B2211/7058, F15B2211/45
European ClassificationF15B11/17
Legal Events
DateCodeEventDescription
Jun 12, 1986ASAssignment
Owner name: CATERPILLAR INC., 100 N.E. ADAMS STREET, PEORIA, I
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905
Effective date: 19860515
Owner name: CATERPILLAR INC., A CORP. OF DE.,ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:CATERPILLAR TRACTOR CO., A CORP. OF CALIF.;REEL/FRAME:004669/0905