US3381587A - Hydraulic control system - Google Patents

Description

May 7, 1968 '0. J. PARQUET HYDRAULIC, CONTROL SY STEM Filed Sept. 10, 1965 I i l i I 34 K 38 c 74 Si 46 aeJ IZ 48 I 50% 52 INVEN R. D. J. PAROU United States Patent 3,381,587 HYDRAULIC CONTROL SYSTEM Donald J. Parquet, Dike, Iowa, assignor to Deere & Company, Moline, Ill., a corporation of Delaware Filed Sept. 10, 1965, Ser. No. 486,331 1 Claim. (Cl. 91-420) ABSTRACT OF THE DISCLOSURE A hydraulic system for controlling a two-way hydraulic cylinder and including a pair of normally closed check valves for preventing the return of fluid from either side of the cylinder, a pair of opposite coaxial pilot pistons actuatable to respectively open the check valves, and a control valve for porting pressurized fluid to either side of the cylinder and to the pilot pistons to open the check valve and dump the unpressurized side at the cylinder, or for porting pressure only to the pilot pistons to open both check valves, dumping both sides of the cylinder.

This invention relates to a hydraulic control system and more particularly to an improved hydraulic control system having hydraulically actuated check valves for interrupting the return of fluid from a pressure actuated motor.

The improved control system has particular utility on a tractor for controlling a two-way hydraulic cylinder which positions a ground-working implement or the like. It is known to provide check valves in such a system to prevent the flow of fluid from the pressurized side of the cylinder in order that the position of the loaded cylinder may be maintained. It is also known to provide hydraulically actuated pistons which unseat the check valves to permit the exhaust of either end of the cylinder.

In the operation of certain ground-working implements, such as scrapers or the like, in addition to the normal raise and lower positions of the two-way cylinder wherein alternate ends of the cylinder are pressurized, it is desirable to have another position in which both ends of the cylinder are exhausted for free floating movement of the implement. However, previous systems, utilizing hydraulically controlled check valves, have not provided for such a float position, the hydraulically actuated piston or pistons, which control the check valves, being designed to actuate only one check valve at a time, permitting the exhaust of only one end of the cylinder.

According to the present invention, there is provided a novel control valve assembly, having hydraulically actuated check valves to maintain the position of the loaded cylinder, and also having means for simultaneously opening both check valves to permit floating movement of the cylinder.

A more specific object is to provide such a control valve assembly with hydraulically actuated piston means which open alternate check valves to permit exhaust of either end of a hydraulic cylinder or will simultaneously open both check valves to provide floating movement of the cylinder, and further to provide such piston means in the form of two coaxial pistons which can be actuated in unison in either direction to alternately open the check valves, or split and actuated in opposite directions to simultaneously open both check valves.

Another object is to provide such a control valve assembly which is of simple and compact construction, easy to manufacture and maintain.

These and other objects will become apparent in the following detailed description and accompanying drawing wherein the sole figure is a combined sectional and schematic view of the hydraulic system, showing the check valve portion of the control valve assembly in section, and schematically showing the remainder of the system, the control valve assembly being shown in a neutral condition.

The hydraulic system includes a control valve assembly, indicated in its entirety by the numeral 10, and including a body 12, part of which is shown in section. The body 12 has an inlet port 14 communicating with a source of fluid pressure 16 via a conduit 18 and an exhaust port 20 communicating with a reservoir 22 via a conduit 24, fluid from the reservoir 22 being supplied to the fluid pressure source 16 through a conduit 26.

A hydraulic motor 28, in the form of a double acting hydraulic cylinder or ram, includes a cylinder 30 and a piston 32 movable within the cylinder in response to a pressure differential between the opposite ends 34 and 36 of the cylinder. One end 34 of the cylinder is connected to a first motor outlet passage 38 in the body 12 by a conduit 40, and the other end 36 of the cylinder is connected to a second motor outlet passage 42 in the body 12 by a conduit 44.

A cylindrical bore 46 extends through the body 12 and is transversely intersected by the motor outlet passages 38 and 42. Three valve passages 48, 50, and 52 communicate with the bore 46 between the motor outlet passages 38 and 42, the passages 48 and 38 and the portion of the bore 46 between said passages, forming a first passage means through the valve body 12, and the passages 52 and 42, and the portion of the bore 46 between said passages, forming a second passage means through the body 12.

A pair of cylindrical valve seats 58 and 60 are respectively mounted in the bore 46 between the passages 48 and 38 and between the passages 52 and 42, the valve seats 58 and 60 having axial orifices 62 and 64 respectively. The opposite ends of the bore 46 are closed by a pair of caps 66 and 68, and the orifices 62 and 64 are respectively closable by spherical check valves 70 and 72 biased against the respective valve seats 58 and 60 by compression springs 74 and 76, the spring 74 acting between the cap 66 and the valve 70, and the spring 76 acting between the cap 68 and the valve 72. The valves 70 and 72 are unseated against the bias of the springs 74- and 76 when they are subjected to fluid pressure from the passages 48 and 52 respectively and normally prevent the return of fluid from the passages 38 and 42. The movement of the valves 70 and 72 is limited by axial projections 78 and 80 on the respective caps 66 and 68.

A pair of pistons 82 and 84 are slidable in the bore 46 between the valves 70 and 72, the pistons having opposite faces 86 and 88 and axial shaft portions 90 and 92 substantially smaller in diameters than the orifices 62 and 64, the terminal ends 94 and 96 of the shaft portions 90 and 92 respectively extending through the orifices 62 and 64 and to engage the valves 70 and 72.

A spool type control valve 98, shown schematically in the drawing, is axially shiftable via an actuating means 99 into four alternate positions, establishing ditferent connections between the inlet 14 and the exhaust port 20 and the passages 48, 50 and 52.

In operation, when the valve 98 is in neutral position, as shown in the drawing, the inlet 14 is blocked and the passages 48, 50 and 52 are connected to the exhaust port 20 and consequently to the reservoir 22. Since there is no fluid pressure in passages 48, 50, or 52, no force is exerted on either piston 82 or 84, and the springs 74 and 76 maintain the valves 70 and 72 in a closed position, preventing the flow of fluid from either end of the cylinder 30.

When the valve 98 is moved to its raise portion, to the right in the drawing, the inlet port 14 is connected to the passage 48, the passage 50 is blocked, and the passage 52 is connected to the exhaust port 20. The pressure in the passage 48 opens the valve 70 against the bias of the 3 spring 74, supplying fluid under pressure to the lower end 34 of the cylinder 30 via the outlet passage 38 and the conduit 40. The pressure in the passage 48 also exerts a force on the piston 82, moving the pistons 82 and 84 in unison toward the valve 72, to the right in the drawing, the end 96 of the piston 84 engaging and unseating the valve 72 against the bias of the spring 76, permitting the exhaust of fluid from the upper end 36 of the cylinder 30 via the conduit 44, the passage 42, the orifice 64, the passage 52, and the valve 98.

When the valve 98 is moved to its lower position, to the left in the drawing, the inlet port 14 is connected to the passage 52, the passage 50 is blocked, and the passage 48 is connected to the exhaust port 20, reversing the previous condition. The pressure in the passage 52 moves the pistons 84 and 82 in unison, to the left in the drawing, to unseat the valve 70, permitting the exhaust of the lower end 34 of the cylinder 30, the pressure also unseating the valve 72 and pressurizing the upper end 36 of the cylinder 30.

The float position of the valve 98 is obtained by moving the valve 98 to its extreme position, to the left in the drawing, connecting the inlet port 14 to the passage 50 and connecting the passages 48 and 52 to the exhaust port 20. The pressure in the passage 50 exerts opposite forces on the opposite piston faces 86 and 88, moving the pistons 82 and 84 in opposite directions to unseat both check valves 70 and 72 and permit the return of the fluid from both ends 34- and 36 of the cylinder 30. Since both ends of the cylinder 30 are connected to exhaust, the piston 32 is free to move in either direction, providing the desired floating action.

Other features and advantages of the present invention will readily occur to those skilled in the art, as will many modifications and alterations in the preferred embodiment of the invention described herein, all of which may be achieved without departing from the spirit and the scope of the invention.

What is claimed is:

1. A hydraulic control system comprising: a source of fluid pressure including an associated reservoir; a reversible hydraulic motor having alternate inlets; a valve body having an elongated bore; first, second, third, fourth, and fifth passages in the valve body respectively communicating with the bore at axially spaced intervals in numerical order; means respectively connecting the first and the fifth passages to the alternate motor inlets; a first check valve means mounted in the bore between the first and second passages and biased toward a closed position wherein it blocks the flow of fluid from the first passage to the second passage; 9. second check valve means mounted in the bore between the fourth and fifth passages and biased toward a closed position wherein it blocks the flow of fluid from the fifth passage to the fourth passage; a first axially shiftable pilot piston normally positioned in the bore between the second and third passages; a second axially shiftable pilot piston normally positioned in the bore between the third and fourth passages, the pistons moving in unison toward and opening the second check valve means in response to pressurization of the second passage, moving in unison toward and opening the first check valve means in response to pressurization of the fourth passage, and moving in opposite directions to open both check valve means in response to pressurization of the third passage; and a control valve means shiftable into a first position wherein it connects the third passage to the reservoir only, a second position wherein it connects the second passage only to the fluid pressure source and the fourth passage to the reservoir, a third position wherein it connects the fourth passage only to the fluid pressure sourceand the second passage to the reservoir, and a fourth position wherein it connects the third passage only to the fluid pressure source and the second and fourth passages to the reservoir.

References Cited UNITED STATES PATENTS 2,572,705 10/1951 Edman 91-464 2,670,713 3/1954 Jirsa 91-20 2,691,964 10/1954 Stickney 91-426 2,830,561 4/ 1958 Lindstrom 91-420 2,959,190 11/1960 Barnes et al. 91-441 3,223,104 12/1965 Cox et al 137-62562 3,273,467 9/1966 Allen 91-4120 MARTIN P. SCHWADRON, Primary Examiner.

B. L. ADAMS, Assistant Examiner.

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