US3171496A

US3171496A - Hydraulic control system

Info

Publication number: US3171496A
Application number: US156744A
Authority: US
Inventors: Vaughn A Nelson
Original assignee: International Harverster Corp
Current assignee: Navistar Inc
Priority date: 1961-12-04
Filing date: 1961-12-04
Publication date: 1965-03-02
Anticipated expiration: 1982-03-02
Also published as: SE309692B; GB1025763A

Description

March 2, 1965 v. A. NELSON HYDRAULIC CONTROL SYSTEM Filed Dec. 4, 1961 R O T N E V m 0 w N 8! E W w V Rule 8 mm mm X United States Patent 3,171,496 HYDRAULHC CONTRGL SYSTEM Vaughn A. N elson, Downers Grove, Ill., assignor to International Harvester Company, Chicago, Ill., a corporation of New Jersey Filed Dec. 4, 1961, Ser. No. 156,744- 7 Claims. (Cl. 172-9) This invention relates generally to hydraulic systems. More particularly, it is directed to a hydraulic system for use with a vehicle such as a tractor in controlling the operation of implements associated therewith.

Systems of this type utilize a fluid operated motor for raising and lowering the implement between transport and working positions. Generally, operator responsive means actuates the system for directing fluid to a hydraulic ram in order to move the implement to its raised or transport position. Fluid is relieved from the hydraulic ram in order to move the implement to its lowered or working position.

Such systems also utilize the fluid operated motor for adjusting the draft control of the implement. The system is actuated by additional operator responsive means to set the implement at a desired working depth. During operation the system is additionally under the control of compressive means responsive to a positive or negative load on the implement as it encounters varying working conditions. This results in a counteracting corrective action on the implement according to conditions affecting the draft forces thereon. With the use of high pressure systems, oversensitive response to load variations results in a corrective action that may become overbalancing and cause undesirable oscillation or chattering of the implement. In addition, the buildup of fluid pressure within such a system to a value greater than that necessary for actuation of the hydraulic ram may result in excessive heating of the fluid. Under such conditions serious damage to components of the system may be encountered.

Accordingly, it is an object of this invention to provide hydraulic control means for a draft control system which will compensate for oversensing of load variations.

Another object of this invention is to provide hydraulic control means for a draft control system incorporating means for delaying the flow of fluid to an associated hydraulic ram for a predetermined period in order to prevent application of pressure in response to momentary load fluctuations.

Yet another object of this invention is to provide hydraulic control means for a draft control system including valve means operable in response to the sensing of variations in draft load for controlling the flow of fluid under high pressure, operation of the valve means initiating action of means allowing fluid pressure to build up in the system only after the valve means has remained in its operating position for a predetermined time so that undesirable chattering of the valve means does not cause fluid to flow under high pressure.

Still another object of this invention is to provide valve means incorporating a control valve for directing the flow of fluid under pressure and a bypass valve actuated by dashpot means which in turn is actuated by the control valve to delay pressure buildup for a predetermined period after operation of the control valve.

An additional object of this invention is to provide valve means incorporating a control valve for directing the flow of fluid under pressure and a bypass valve actuated by dashpot means which in turn is actuated by the control valve such that failure of the dashpot means prevents actuation of the bypass valve and buildup of pressure.

A further object of this invention is to provide hydraulic control means for a draft control system wherein exces- $121,495 Patented Mar. 2, 19 65 sive pressure buildup is prevented, thus avoiding the heating attendant thereto and damage to system components caused thereby.

A still further object of this invention is to provide valve means incorporating a control valve for directing the flow of fluid under pressure and a bypass valveactuated by dashpot means which in turn is actuated by the control valve such that the buildup of pressure is controlled within' predetermined limits in order to avoid excessive heating and damage to system components caused thereby.

The foregoing along with additional objects and advantages will be apparent from the following description of a specific embodiment of the invention as shown in the accompanying drawing, in which the draft sensing means and control linkage means are shown diagrammatically and the hydraulic system, including the control valve means, is shown in section.

Referrnig now to the drawing, an associated agricultural implement is connected to a tractor by means of a pair of lower hitching links, one of which is indicated by reference numeral 1, and an upper hitching link 2. Lower links 1 are pivotally secured as at 3 to the tractor frame 4. A rockshaft 5 is connected by means of suitable linkage 6 to lower links 1. Upper link 2 is pivotally secured to the torsion spring 7 which in turn is anchored at S to the tractor frame. The torsion spring may be of the type disclosed in copending application Serial No. 76,903 filed December 19, 1960.

The position and draft control linkage 9 is shown diagrammatically. It is similar to the differential linkage disclosed in detail in copening application Serial No. 56,475 filed September 16, 1960, now Patent No. 3,123,- 152, to which attention is invited. The members 10 and 11 are pivotally secured to torsion spring 7 and rockshaft 5, respectively, and transmit forces therefrom to linkage 9. Position control lever 12 and draft control lever 13 are connected by means of members 14 and 15, respectively, to linkage 9. Extending from linkage 9 is the operating rod 16.

The control valve 17 includes housing 18 having therein the

coaxial chambers

19, 2t and 21. A passage 22 communicates chamber 19 with chamber 20. A port defining the valve seat 23 communicates chamber 29 with chamber 21. Housing 13 also includes the coaxial chambers 24 and 25, the former communicating by means of the passage 26 with chamber 19. A port defining the valve seat 27 communicates chamber 24 with chamber 25. The spaced ports 28 and 29 extend from chamber 19. The passage 313 communicates chamber with chamber 19 through port 28.

Slidably received in chamber 19 is the valve spool 31 including the

spaced lands

32, 33 and 34. The pin 35 extends from land 34 through housing 18 into chamber 20. Within chamber 21 is the check valve 36 biased by means of the spring 37 toward valve seat 23. Operating rod 16 extends through housing 18 into the chamber 19 and is engaged with land 32 of valve spool 31. It is to be understood that suitable means for biasing valve spool 31 may be provided.

The piston 38 is slidably received within chamber 24. Piston 38 has control orifice 39 extending therethrough and the pin 40 projecting therefrom. Within chamber 25 the check valve 41 is biased by means of the spring 42 toward valve seat 27.

The pump 43 is connected through the inlet line 44 with the reservoir 45. The outlet line 46 of pump 43 communicates with chamber 25 in housing 18 and through a pressure responsive relief valve with reservoir 45. The lines 47 and 4S communicate chamber 24 and port 29, respectively, in housing 18 with reservoir 45.

with the hydraulic ram 50. This hydraulic ram 50 includes the cylinder 51 and its associated piston 52 con-" nected by rneans of suitable linkage 53 to rockshaft'S.

With control valve 17 in'the neutral position shown in the drawing, fluid passes from pump 43 through line 46 into chamber 25. A partial flow of fluid is established from chamber 25 through passage 30, port 28, chamber 19 andwpassage 26 into chamber 24. Due to" the restriction to flow through control orifice 39, a biasing 4 When link 2 senses a reduction in the draft load on the implement a tension'force is transmitted therein which, after overcoming the resistance of torsion spring force is established which acts upon piston 38, thereby causing pin 40 to maintain, contact with check valve 41 and hold it away from vale seat 27. The remaining fluid entering chamber 25 is bypassed through chamber 24 and line 47 back to reservoir 45. Check valve 36 'is seated against valve seat 23,thereby trapping fluid in cylinder 51.

For raising an associated implement, position control lever '12 is moved to one of itsraising positions. This movement is transmitted through member 14, linkage 9 and operating rod 16 to valve spool 31 whereupon valve spool 31 is moved to the left, as shown in the drawing. Land 33 clears the right side of port 28 and blocks the left side of port 28. Land 34 blocks port 29 entirely. Fluid trapped in chamber 24 above piston 38 bleeds through control orifice 39 at a predetermined rate. ing thus dissipated, check valve41 is seated on valve seat 27 whereupon-full pump flow is applied from chamber 25 through passage 30, port 28, chamber 19 and passage 22 into chamber 20. Check valve 36 is moved off of valve seat 23 and fluid flows through chamber 21 and line 49 into cylinder 51 of hydraulic ram 50. Acting upon piston 52 it creates a force which is transmitted through linkage53, rock-shaft .5 and linkage-:6 to move' The biasingforce acting upon check valve 41 be-- trol valve 17-to its neutral position once the imple- 'ment has attained the height predetermined by the setting of position control lever 12.

In order to drop the associated implement, position control lever 12 is moved to one of its lowering positions'whereupon valve spool 31 is moved to the right. Pin35 engages and moves checkvalve' 36 oil of valve seat 23 and land 34 clears port 29. Under the weight of the implement fluid flows from cylinder '51 through line 49, chamber 21, chamber 20, passage 22, chamber 19, port 29 and line 48 to reservoir 45. Linkage 9'returns main control valve 17 to its neutral position when the associated implementhas been lowered to-a position corresponding to the setting of positioncontrol lever. 12.

The position of draft control lever 13 establishes a setting from which an increase or decrease in draft load is effective for actuating the draft compensating mechanism. When the draft load on the implement becomes excessive a compressive force is transmitted through link 2 and, after overcoming 'the resistance of torsion spring 7, is further transmitted as a tension forcethrough member 10, linkage 9 and operating rod 16 to valve spool 31 whereupon valve spool 31 is moved from the neutral position to the left. It is important to note that full pump flow is applied. to cylinder '51 only after a delay determined by the time required for fluid to bleed through control'orifice '39, after which check valve sult in actuation of hydraulic'ram 50 to change the position of links 1. Ratherphydraulic ram 50 is actuated to change the draft only when a true variation in draft load is sensed by link 2.

7, is further transmitted asa compressive force through member 10, linkage 9 and operating rod 16 to valve spool 31 whereupon valve spool 31 is moved from the ';neutral' positionto the right and fluid isrelieved from cylinder 51.1, The implement dropped and control valve 17 is returned to its neutral position under the influence of linkage 9. If at this point the draft load on the implement is momentarily excessive, valve spool 31 will again be moved to the left. Over-compensation is avoided, however, because of the delay in applying full pump pressure to, hydraulic ram 50 after movement of valve spool 31to the left.v

At all times fluidpressure in the system. remains at or below the value required for actuation of hydraulic ram 50. This avoids-overheating of the fluid and resultant damage to hydraulic system components.

An additional fail-safe feature incorporated herein is provided by the arrangement-which insures that fluid will be bypassed to reservoir in the event that control orifice 35! becomes clogged. In such an event fluid trapped in chamber 24 will insure that check valve 41 ism aintained in a position away from its associatedvalve seat 27. This feature also provides insurance against overheating of the fluid in'the system.

It is to be understood that the foregoing description and the accompanying drawing have been given only by 30 way of illustration and example. Changes in the elements, rearrangement'of parts, and substitution of equivalents, all of which will be obvious to those skilled in the art; are considered to be within the scope of the present invention which is limited only by the claims which follow.

What is claimedis: V

-1. For use with a tractor and an implement hitched to said tractor; power means including fluid operated ram meansfor moving said implement between transport and work positions and for controlling the draft. thereof when in said workposition; means for selectively regulating the flow of fluid to and from said ram means for respectively raising and lowering said implement; manually operable means for actuating said regulating means; sensing means responsive to variations in thedraft load on 'said implement for actuating said regulating means; saidregulatingmeans including an inlet line connected to a source of fluid under pressure, a control line connected in said ram means, anexhaust line, control valve means selectively movablefrom a neutral position to first and second actuating positions communicating said inlet line with said control line and said control line with said exhaust line, respectively, unloading-valve means movable between a first position communicating said inlet line with said exhaust line and a second position blocking communicationof said'inlet line with said exhaust line, and fluid pressure responsive means communicating with said source of'fiuid under pressure through said control valve means when said control valve means is in said neutral position for biasing said unloading valve means toward itsfirst position when said control valve means is in said'neutral position and for a'p'redetermined time upon movement of said control valve means from said neutral position to said first actuating position.

2. Fluid flow regulating means comprising an inlet line adaptedto be connected to a source of fluid under pressure, a control line adapted to be connected to a fluid pressure operated device, an exhaust line, dashpot means having a relatively large inlet and a relatively small outlet communicating with'said exhaust line, control valve means movable between a neutral position communicating said inlet line with said inlet of said dashpot means, a first actuating position blocking communication of said inlet line withsaid' inlet of said dashpot meansand communicating said inlet 'line with said control line, and a second actuating position communicating said control line with said exhaust line, and unloading valve means movable between a first position communicating said inlet line with said exhaust line and a second position blocking communication of said inlet line with said exhaust line, said dashpot means having means responsive to fluid pressure in said inlet of said dashpot means for biasing said unloading valve means toward its first position.

3. For use with a tractor and an implement hitched to said tractor; power means including fluid operated ram means for moving said implement between transport and work positions and for controlling the draft thereof when in said work position; means for selectively regulating the flow of fluid to and from said ram means for respectively raising and lowering said implement; manually operable means for actuating said regulating means; sensing means responsive to variations in the draft load on said imple ment for actuating said regulating means; said regulating means including an inlet line connected to a source of fluid under pressure, a control line connected to said ram means, an exhaust line, dashpot means having a relatively large inlet and a relatively small outlet communicating with said exhaust line, control valve means movable between a neutral position communicating said inlet line with said inlet of said dashpot means and first and second actuating positions communicating said inlet line with said control line and said control line with said exhaust; line, respectively, unloading valve means movable between a first position communicating said inlet line with said exhaust line and a second position blocking communication of said inlet line with said exhaust line, and means biasing said unloading valve means toward its second position, said dashpot means having means responsive to fluid pressure in said inlet of said dashpot means for overriding said biasing means and holding said unloading valve means in its first position when said control valve means is in said neutral position, said biasing means being sufiicient to override said fluid pressure responsive means upon relief of fluid pressure through said outlet of said dashpot means when said control valve means is moved from said neutral actuating position.

4. For use with a tractor and an implement hitched to said tractor; power means including fluid operated ram means on said tractor for moving said implement between transport and work positions and for controlling the draft thereof when in said work position; means for selectively regulating the flow of fluid to and from said ram means for respectively raising and lowering said implement; manually operable means for actuating said regulating means; and sensing means responsive to variations in the draft load on said implement for actuating said regulating means; said regulating means including an inlet line connected to a source of fluid under pressure, a control line connected to said ram means, an exhaust line, dashpot means having a relatively large inlet and a relatively small outlet communicating with said exhaust line, control valve means movable between a neutral position communicating said inlet line with said inlet of said dashpot means and first and second actuating positions communicating said inlet line with said control line and said control line with said exhaust line, respectively, unloading valve means movable between a first position communicating said inlet line with said exhaust line and a second position blocking communication of said inlet line with said exhaust line, and means biasing said unloading valve means toward its second position, said dashp-ot means having piston means responsive to fluid pressure in said inlet of said dashpot means for overriding said biasing means and holding said unloading valve means in its first position when said control valve means is in said neutral position, said biasing means being sufiicient to override said fluid pressure responsive piston means upon relief of fluid pressure through said outlet of said dashpot means when said control valve means is in said first actuating position.

5. In the invention according to claim 4, said outlet of said dashpot means being an orifice extending through said piston means.

6. The invention according to claim 4, further comprising fluid pressure responsive check valve means in said control line movable between a first position communicating said control line with said ram means and a second position blocking communication of said control line with said ram means, and means associated with said control valve means for holding said check valve means in its first position when said control valve means is in said second actuating position.

7. Fluid flow regulating means comprising an inlet line adapted to be connected to a source of fluid under pressure, at least one control line adapted to be connected to a fluid pressure operated device, an exhaust line, dash pot means having a relatively large inlet and a relatively small outlet communicating with said exhaust line, control valve means movable between a neutral position communicating said inlet line with said inlet of said dashpot means and a plurality of actuating positions selectively communicating said inlet line with said control and exhaust lines, unloading valve means movable between a first position communicating said inlet line with said exhaust line and a second position blocking communi cation of said inlet line with said exhaust line, and means biasing said unloading valve means toward its second position, said dashpot means having means responsive to fiuid pressure for overriding said biasing means and holding said unloading valve means in its first position when said control valve means is in said neutral position, said biasing means being sutficient to override said fluid pressure responsive means upon relief of fluid pressure through said outlet of said dashpot means when said control valve means is in at least one of said actuating positions.

References tilted by the Examiner UNITED STATES PATENTS ABRAHAM G. STONE, Primary Examiner.

T. GRAHAM CRAVER, Examiner.

Claims

1. FOR USE WITH A TRACTOR AND AN IMPLEMENT HITCHED TO SAID TRACTOR; POWER MEANS INCLUDING FLUID OPERATED RAM MEANS FOR MOVING AND IMPLEMENT BETWEEN TRANSPORT AND WORK POSITIONS AND FOR CONTROLLING THE DRAFT THEREOF WHEN IN SAID WORK POSITION; MEANS FOR SELECTIVELY REGULATING THE FLOW OF FLUID TO AND FROM SAID RAM MEANS FOR RESPECTIVELY RAISING AND LOWERING SAID IMPELEMENT; MANUALLY OPERABLE MEANS FOR ACTUATING SAID REGULATING MEANS; SENSING MEANS RESPONSIVE TO VARIATIONS IN THE DRAFT LOAD ON SAID IMPLEMENT FOR ACTUATING SAID REGULATING MEANS; SAID REGULATING MEANS INCLUDING AN INLET LINE CONNECTED TO A SOURCE OF FLUID UNDER PRESSURE, A CONTROL LINE CONNECTED TO SAID RAM MEANS, AN EXHAUST LINE, CONTROL VALVE MEANS SELECTIVELY MOVABLE FROM A NEUTRAL POSITION TO FIRST AND SECOND ACTUATING POSITIONS COMMUNICATING SAID INLET LINE WITH SAID CONTROL LINE AND SAID CONTROL LINE WITH SAID EXHAUST LINE, RESPECTIVELY, UNLOADING VALVE MEANS MOVABLE BETWEEN A FIRST POSITION COMMUNICATING SAID INLET LINE WITH SAID EXHAUST LINE AND A SECOND POSITION BLOCKING COMMUNICATION OF SAID INLET LINE WITH SAID EXHAUST LINE, AND FLUID PRESSURE RESPONSIVE MEANS COMMUNICATING WITH SAID SOURCE OF FLUID UNDER PRESSURE THROUGH SAID CONTROL VALVE MEANS WHEN SAID CONTROL VALVE MEANS IS IN SAID NEUTRAL POSITION FOR BIASING SAID UNLOADING VALVE MEANS TOWARD ITS FIRST POSITION WHEN SAID CONTROL VALVE MEANS IS IN SAID NEUTRAL POSITION AND FOR A PREDETERMINED TIME UPON MOVEMENT OF SAID CONTROL VALVE MEANS FROM SAID NEUTRAL POSITION TO SAID FIRST ACTUATING POSITION.