US3643696A

US3643696A - Hydraulic control circuit

Info

Publication number: US3643696A
Application number: US68874A
Authority: US
Inventors: Norman B Christensen; Thomas A Clark; Robert J Webers
Original assignee: Rex Chainbelt Inc
Current assignee: Rex Chainbelt Inc
Priority date: 1970-09-02
Filing date: 1970-09-02
Publication date: 1972-02-22
Anticipated expiration: 1989-02-22

Abstract

A hydraulic control circuit having a control valve with a multiposition control spool having hydraulically set cutoff positions wherein the spool is hydraulically blocked against movement including a plurality of ports communicating with the control valve bore and suitable hydraulic control components for opening or closing lines connected to said ports. Further, a circuit for regenerative cylinder operation wherein the cylinder is positively blocked against movement in both directions when the control circuit is set for such condition and wherein the regenerative position of the control spool is hydraulically locked and a pressure relief valve is in circuit whereby, when the cylinder pressure exceeds a predetermined amount, the relief valve opens to release the hydraulic locking of the control spool whereby the control spool can move to a position to discontinue the regenerative flow of fluid to the cylinder.

Description

United States Patent Christensen et al.'

HYDRAULIC CONTROL CIRCUIT Norman B. Christensen; Thomas A. Clark; Robert J. Webers, all of Racine, Wis.

Assignee: Rex Chainbelt lnc.

Filed: Sept. 2, 1970 Appl. No.: 68,874

Inventors:

References Cited UNITED STATES PATENTS Schmiel et a1. ..l37/625.63 Rice ..91/436 x 3,273,468 9/1966 Allen ..9l/436x [4 1 Feb.'22,19'72 Primary Examinerl'lenry T. Klinksiek Attorney-Hofgren, Wegner, Allen, Stellman 8!. McCord [57] ABSTRACT A hydraulic control circuit having a control valve with a multiposition control spool having hydraulically set cutoff positions wherein the spool is hydraulically blocked against movement including a plurality of ports communicating with the control valve bore and suitable hydraulic control components for opening or closing lines connected to said ports. Further, a circuit for regenerative cylinder operation wherein the cylinder is positively blocked against movement in both directions when the control circuit is set for such condition and wherein the regenerative position of the control spool is hydraulically locked and a pressure relief valve is in circuit whereby, when the cylinder pressure exceeds a predetermined amount, the relief valve opens to release the hydraulic locking of the control spool whereby the control spool can move to a position to discontinue the regenerative flow of fluid to the cylinder.

12 Claims, 4 Drawing Figures HYDRAULIC CONTROL CIRCUIT BACKGROUND OF THE INVENTION This invention pertains to hydraulic control circuits having valve components providing for new and improved hydraulically controlled multiposition operation of a control spool and which is positively held in different positions and to such a circuit providing new and improved regenerative cylinder operation with the cylinder positively blocked against movement in both directions when pressure fluid is not being supplied to either extend or retract the cylinder.

Circuits for regenerative cylinder operation are known wherein the control spool has a position providing for regenerative operation of the cylinder; however, such a system is not positive in that pressure balancing in opposite ends of the control spool is utilized, rather than a blocked column of fluid as in this application, to hydraulically lock the spool in the regenerative position. Prior known units for regenerative cylinder operation have not provided for positive blocking of the cylinder against movement in either extended or retracted directions, however, the circuit disclosed herein provides positive blocking in both directions whereby inadvertent movement of the cylinder and mechanism connected to the piston rod thereof cannot occur.

SUMMARY An inventive concept embodied in the structure disclosedherein relates to a new and improved hydraulic control circuit for providing regenerative cylinder operation wherein the components can be set in a cylinder blocking position and the cylinder is blocked against both extending and retracting movements.

Another inventive concept embodied in the structure disclosed herein is the utilization of a hydraulic control circuit wherein a control spool has plural positions and wherein the control spool has at least one intermediate position where it is hydraulically locked by a blocked column of fluid to prevent movement thereof until said blocked column of fluid is free to flow to drain.

An object of the invention is to provide a new and improved hydraulic control circuit providing for regenerative cylinder operation and embodying the concepts set forth above which provides for reliable, safe operation of a cylinder with blocking of movement of the cylinder against movement in either direction when the system is inactive and, further, which provides for regenerative flow of fluid from the rod end of the cylinder to the other end of the cylinder until such time as a predetermined cylinder pressure is exceeded and the regenerative feature is discontinued.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view of a regenerative manifold embodying the hydraulic control circuit utilizing USASI Symbols and with the control valve shown in vertical section and with the parts positioned in neutral position for blocking of movement of the cylinder in both directions;

FIG. 2 is a view, similar to FIG. 1, showing the components of the hydraulic control circuit positioned for extension of the piston rod of the cylinder in the regenerative cycle of operation;

FIG. 3 is a view similar to FIG. 2 except for showing the change in position of certain parts to have the piston rod extending and acting on a load and under full system pressure; and

FIG. 4 is a view similar to FIG. 1 and showing the components of the hydraulic control circuit positioned for retracting the piston rod of the cylinder.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG. I, the hydraulic control circuit, which can be constructed as a manifold device, has a series of major components including the main control valve having a bore 11 which movably receives a control spool 12. The control valve 10 has a pair of

cylinder lines

15 and 16 extending from

valve ports

17 and 18, respectively, and connectable to a cylinder 20 having a piston 21 with a piston rod 22. The line 15 connects to the rod end of the cylinder, while the line 16 connects to the opposite end of the cylinder.

Reference is made herein to a number of lines" which can be in the form of either internal body passages or external piping, both variations being well known in the art.

Other major components are a four-way directional control valve, indicated generally at 25, having

solenoids

26 and 27 providing for shiftthereof from either side of a spring-centered position. A pilot-controlled, four-way valve, indicated generally at 30, is responsive to hydraulic pilot action at either ends thereof under the control of the position of the directional control valve 25 and is the primary control of connection of the main fluid power lines for the cylinder to either pressure or tank.

A three-position pilot valve, indicated generally at 31, has a connection to a line 32 connecting to a port 33 at one end of the bore 11 of the control valve 10. This three-position pilot valve is spring-centered and hydraulically piloted at both ends to control the connection of the port 33 either to drain or to pressure from either of two lines to be described subsequently. Two additional primary components are a settable pressure relief valve, indicated generally at 35, and a pressure-responsive valve, indicated generally at 36.

The pressure fluid is supplied to the circuit through a pressure line 40. The circuit has a tank line 41 and a drain line 42. For operation of the cylinder 20 in either extending or retracting movement, fluid under pressure ultimately reaches one or the other of a pair of

main lines

45 and 46 which are connectable to the control valve and communicate with the bore thereof through the

ports

47 and 48, respectively. In the cylinder-blocked position of FIG. I, it will be noted that there is no fluid communication between the

main line ports

47 and 48 and the

cylinder line ports

17 and 18. This blocking is accomplished by a pair of intermediate lands 50 and 5] on the control spool. Additionally, the control spool has the

control lands

52 and 53 at the ends thereof which are responsive to fluid pressure conditions at opposite ends of the valve bore to determine which of several positions the control spool will be The control spool 12 is in its right-hand limit position in FIG. 1 with said position being maintained by a compression spring 55 in an end of the valve bore acting between a wall of the control valve casing and extending into a recess in the control land 52 of the control spool. There is no fluid pressure being exerted against either end of the control land at this time. The control land 53 of the control spool through port 33 and the three-position valve 31 is exposed to drain through a line 56. The control land 52 of the control spool is in fluid communication with first and second fluid ports 60 and 61 in the control valve body. These ports are spaced lengthwise along the length of the valve bore with the port 61 being at the end of the bore and the first port 60 being intermediate thereof and the opposite end of the bore. The port 60, through a line 62, is at all times connected to the drain line 63 which is an extension of the drain line 56. The second fluid port 61 can be connected to pressure through passage means, to be described; however, in the positioning of the parts in FIG. I the passage means is not connected to pressure through the directional control valve 25. The other connections to the port 61 are for the purpose of selectively connecting this port to the drain line 42 and, therefore, there is no pressure acting on the control land 52 with the positioning of the parts shown in FIG. I.

From the locked position of FIG. 1, the circuit can be shifted to cause extension of the cylinder rod or retraction thereof. For purposes of description, it will be assumed that the desired operation is to cause extension of the rod which, with little load on the rod, will cause regenerative operation and the positioning of the parts as shown in FIG. 2. To place the circuit in the condition shown in FIG. 2, the solenoid 27 of the directional control valve 25 is energized to shift this valve to the position shown in FIG. 2 wherein a line 65 connected to the pressure line 40 directs pressure fluid through the directional control valve 25 to a control line 66 having a branch line 67 connected to the pilot 68 of the pilot-controlled four-way valve 30. Line 66 also extends to passage means having a first branch 69 and a second branch 70. The actuation of the pilot section 68 of the valve 30 shifts this valve to the position shown in FIG. 2 wherein pressure fluid from line 40 passes through this valve and connects to the main powerline 46 with the other powerline 45 being connected to the tank line 41 through the pilot-controlled fourway valve 30. Thus, shifting of the pilot-controlled four-way valve 30 conditions the

lines

45 and 46 to have one connected to pressure and the other connected to tank whereby connections can be made to the cylinder dependent upon the position of the control spool 12 of the control valve 10.

The positioning of the control spool 12 is accomplished by a pressure differential acting on both ends of the control spool through the passage means having the first branch 69 and the second branch 70. The second branch passage 70 extends to the three-position pilot valve 31, with pilot pressure acting through a line 71 to shift the valve 31 to the position shown in FIG. 2 and connect a passage continuation 72 of the second branch passage 70 to the line 32 leading to the port 33 of the control valve whereby system pressure is exerted against the control land 53 to act against the urging of the spring 55. The first branch passage 69 has an orifice 74 which causes a pressure drop downstream thereof as fluid flows to the port 61 and which can flow into the valve bore and out through the port 60 to the drain line 42 through the line 63. This flow condition occurs initially upon actuation of the solenoid 27, as clearly shown by the initial position of the control spool at such time in FIG. 1. This condition terminates when the control spool, moved by a pressure differential, reaches the position shown in FIG. 2 where the control land 52 has moved to the position to block the first port 60. This movement has occurred because of the orifice 74 causing a pressure drop whereby the pressure, differential is sufficient to overcome the force of the spring 55 and have the greater pressure acting on the control land 53 shift the control spool toward the left as viewed in FIG. 2.

Shifting the control spool to the position of FIG. 2 positions the

intermediate spool lands

50 and 51 whereby the main line 46 connected to the pressure line 40 communicates with the cylinder line 16 through the

ports

18 and 48. The

control valve ports

17 and 47 are still blocked from communication by coaction of the intermediate spool land 50 with a raised land of the valve bore. This results in supplying pressure fluid to the cylinder to extend the rod, with flow from the cylinder through the cylinder line entering the bore of the valve through the port 17. This flow does not go to tank through main line 45 but is used in the regenerative cycle to add to the fluid delivered through line 16 to the cylinder. This regenerative effect is obtained by an internal passage 80 in the control spool 12 having

passages

81 and 82 communicating with the bore whereby fluid delivered from the rod end can enter passage 81, pas through the passage 80 and out the passage 82 for delivery to the port 18 and to the cylinder line 16.

In reaching the position of FIG. 2, the control spool has travelled until it reached a hydraulically set cutoff position where flow from the left-hand end of the valve bore was blocked by blocking the port 60. The control spool shifts from the position of FIG. 2 to the position of FIG. 3 to discontinue the regenerative cycle only in response to the pressure of the fluid acting to extend the cylinder. The operation is obtained by control obtained from the pressure relief valve 35 which is connected by a line 83 to the second port 61 of the control valve. A line 84 connects the outlet of the pressure relief valve to the drain line 42. Under load, the pressure in line 46 builds up, which pressure buildup is transmitted to the control line 66 connecting to the

branch passages

69 and 70 through the pilot-controlled four-way valve 30 which cross-connects lines 46 and 66 through the line 65. This buildup in pressure in

branch passages

69 and 70 does not result in any shift of the control spool 12 until the pressure exceeds the setting of the relief valve 35. When the pressure is exceeded, the valve shifts and flow to drain from port 61 through lines 83 and 84 releases the blocked fluid from the end of the bore whereby the greater pressure acting on the control land 53 shifts the control spool to the position shown in FIG. 3. This shifted position of the pressure relief valve 35 is shown in FIG. 3.

As a result of the shift of the control spool 12 to its left-hand limit position, shown in FIG. 3, the intermediate land 50 of the valve has moved to a position to no longer block communication between the

ports

47 and 17 whereby the cylinder line 15 can communicate with the main line 45 which, through the pilot-controlled, four-way valve 30, connects to the tank line 41. Thus full system pressure is available to extend the cylinder rod acting under load. The position of the control spool 12, as shown in FIG. 3, at the left-hand end of the bore is the directional control position of the control spool in the sense that the control spool 12 in this position permits direct flow through to the

cylinder lines

15 and 16 and the direction of pressure application to the cylinder is solely dependent upon which of the

lines

45 and 46 are connected either to tank or pressure. This is illustrated by the same position of the control spool 12 shown in FIG. 4, which Figure illustrates the positioning of the circuit components when the cylinder is retracting and which will be described more fully subsequently.

At the end of the desired extension of the cylinder, the solenoid 27 is deenergized with the result that the directional control valve 25 centers, which connects control line 66 to tank whereby

branch passages

69 and 70 are connected to drain. This permits centering of the three-position valve 31 which places the port 33 in communication with drain and also connects the opposite end of the valve bore with drain to have the spring 55 return the control spool 12 to the position of FIG. I blocking the cylinder.

The retraction of the cylinder is accomplished by positiorr ing of the circuit components, as shown in FIG. 4, resulting from energization of the solenoid 26 of the directional control valve. This shifts the latter valve to the position shown in FIG. 4 whereby a pressure signal through a signal line acts on the pilot section 101 of the valve 30 to shift the valve to the position shown whereby pressure from line 40 communicates with main line 45 and main line 46 is connected to the tank line 41. The control spool 12 is initially in the position shown in FIG. 1 which blocks communication between the

main lines

45 and 46 and the

cylinder lines

15 and 16. The main line 45 is now the pressure line and it connects to control

lines

105 and 106, branching off therefrom, with the control line 106 having a pilot line 107 to the three-position pilot valve 31 to shift the valve to the position shown in FIG. 4 which places the valve port 33 in communication with the branch control passage 106 to exert pressure on the control land 53 and urge the control spool toward the left. The movement of the control spool to the left is permitted, to the regenerative control position, by outflow through the port 60, but the spool must travel to the left limit position and, therefore, there must also be flow out through the port 61. This is accomplished by opening of the pressure-responsive valve 36 which is shiftable against the urging of a spring by a pilot line 110, branching from the control branch passage 105, to shift the pressure-responsive valve 36 to the open position shown in FIG. 4. This connects the port 61 of the control valve 10 to the drain line 42 through a line 111 connected to the outlet side of the pressure-responsive valve. As a result, the control spool 12 can shift to the left limit position, which then places the

main lines

45 and 46 in communication with the

cylinder lines

15 and 16. Upon deenergization of the solenoid 26, the same action occurs as upon deenergization of the solenoid 27, with release of all pressure on the control spool 12, whereby the spring 55 can return it to the cylinder-blocking position shown in FIG. 1.

In order to prevent any inadvertent operation and shift of the three-position pilot valve 31, the branch control line 105 extends to the drain line 42 and has a restricted flow communication therewith through an orifice 115 whereby'there cannot be any buildup in pressure in the

control passages

105 and 106 which might cause shift of the valve 31 from the neutral position thereof when the cylinder is blocked, as shown in FIG. 1. Similarly in the blocked condition of PEG. 1, the line 66, which communicates with the

branch passages

69 and 70, is connected through the directional control valve to the drain line 42 so that there cannot be any inadvertent buildup of pressure acting on the three-position valve 31 tending to shift it to the position of FIG. 2.

From the foregoing, it will be seen that a hydraulic control circuit providing for regenerative cylinder operation has been provided wherein the cylinder, when the circuit is in neutral position, is positively blocked against movement in either direction and further wherein the control spool disclosed herein is positively-hydraulically locked in position and by a system which provides for plural positioning of a control valve spool by selective control of outflow from ports associated therewith.

We claim:

1. A hydraulic control circuit including a control valve having a bore with a movable control spool therein, a pair of control lands adjacent opposite ends of said spool, a first control fluid port to said bore for communicating fluid with said one control land to urge said control spool in one direction, yieldable means urging said control spool in the opposite direction, a plurality of fluid ports to said bore spaced apart lengthwise thereof for coaction with the other of said control lands, a separate control line to each of said last-mentioned ports, and means in at least one of said control lines to alternatively open or block the respective control line whereby the position of said control spool under the urging of fluid in said first control port is controlled by the open or closed condition of said control lines.

2. A hydraulic control circuit including a control valve having a bore, a movable control spool having a plurality of hydraulically set control positions at different locations along the length of said bore, a plurality of control lands on said spool with one control land adjacent each end thereof, a first control port to said bore for selectively directing fluid under pressure against one of said control lands, second and third control ports to said bore adjacent an end thereof remote from said first control port and spaced apart lengthwise along said bore, a pair of control lines connected one to each of said second and third control ports, a shutoff valve in the control line connected to said second port which is nearest said end of the bore whereby said control spool can move a full stroke when said shutoff valve is open and can move a lesser stroke to an intermediate locked position determined by the location of the third port and which when blocked by said other control land terminates fluid outflow from the bore.

'3. A hydraulic control circuit as defined in claim 2 wherein said second port is connected to said fluid under pressure through an additional line having an orifice therein to provide a pressure drop, and spring means in said bore urging said control spool toward said first port.

4. A hydraulic circuit for regenerative cylinder operation including a pair of cylinder lines connectable to a cylinder, a control valve connected to said lines and having a control spool, a pair of input fluid lines to said control valve individually connectable to pressure or tank, said control spool having three positions wherein one end limit position places said cylinder lines in fluid communication with said input fluid lines for operating a cylinder in a selected direction, another limit position of the control spool blocks communication between said lines for locking a cylinder, and an intermediate locking means includes a control fluid line having a pressureresponsrve valve whereby a predetermined pressure in the control fluid line will open said pressure-responsive valve to release the hydraulic lock on the control spool.

7. A circuit as defined in claim 4 including hydraulic locking means to hold said control spool in the intermediate position, said means comprising a passage with branches communicable with opposite ends of the control spool and an orifice in a first of said branches to obtain a relatively reduced pressure therebeyond, a bore for said control spool, an outlet from said bore near one end thereof and communicable with said first branch line whereby pressure applied through said branches causes movement of the control spool toward one end because of the pressure differential, said movement stopping and the control spool being hydraulically locked when said bore outlet is closed by the control spool.

8. A circuit as defined in claim 7 wherein a'drain line connects with said first branch passage, a pressure relief valve in said drain line openable at a predetermined pressure to drain said first branch passage downstream of said orifice and permit movement of said control spool to said one end limit position.

9. A circuit as defined in claim 8 wherein said control spool has internal passage means to provide said cross-connection between the cylinder lines.

10. A circuit as defined in claim 8 including a second pres' sure-responsive valve openable by pressure to drain said first branch passage and said one end of the bore and permit full movement of the control spool to said one end limit position whereby said control spool can move to said one end limit position either at the termination of regenerative operation or when a cylinder is to operate in retracting movement.

11. A hydraulic circuit for regenerative cylinder operation comprising a pair of cylinder lines connectable to the cylinder, a control valve connected to said lines and having a bore with a control spool, a pair of fluid lines to said control valve individually connectable to pressure or tank, a three-position pilot valve having an outlet connected to one end of said bore whereby in one position the pilot valve connects the bore to drain and in the other two position connects said bore to pressure fluid to move said control spool, a pair of ports adjacent the opposite end of the bore with a first port spaced lengthwise of the bore from the second of the ports, said second port being connected by passage means to said three-position pilot valve and to a fluid pressure line with an orifice in said passage upstream of said second port whereby a pressure differential applied to said control spool causes movement thereof toward said second port, said first port being connected to drain to permit fiow from the second port to the first port, said movement of the control spool being stopped and hydraulically locked when the control spool blocks said first port, and two alternate systems for bleeding fluid from said second port to permit movement of the control spool to an end limit position.

12. A circuit as defined in claim 11 wherein one of said two alternate systems includes a drain line connected to said second port with a pressure relief valve openable in response to a predetermined pressure applied to the cylinder, and the other system includes a pressure-responsive valve connected to said second port and responsive to pressure applied to one end of said three-position pilot valve.

Claims

3. A hydraulic control circuit as defined in claim 2 wherein said second port is connected to said fluid under pressure through an additional line having an orifice therein to provide a pressure drop, and spring means in said bore urging said control spool toward said first port.

4. A hydraulic circuit for regenerative cylinder operation including a pair of cylinder lines connectable to a cylinder, a control valve connected to said lines and having a control spool, a pair of input fluid lines to said control valve individually connectable to pressure or tank, said control spool having three positions wherein one end limit position places said cylinder lines in fluid communication with said input fluid lines for operating a cylinder in a selected direction, another limit position of the control spool blocks communication between said lines for locking a cylinder, and an intermediate control spool position which provides regenerative operation for a cylinder by cross-connecting said cylinder lines.

5. A circuit as defined in claim 4 including means hydraulically locking said control spool in the intermediate position.

6. A circuit as defined in claim 5 wherein the hydraulic locking means includes a control fluid line having a pressure-responsive valve whereby a predetermined pressure in the control fluid line will open said pressure-responsive valve to release the hydraulic lock on the control spool.

8. A circuit as defined in claim 7 wherein a drain line connects with said first branch passage, a pressure relief valve in said drain line openable at a predetermined pressure to drain said first branch passage downstream of said orifice and permit movement of said control spool to said one end limit position.

10. A circuit as defined in claim 8 including a second pressure-responsive valve openable by pressure to drain said first branch passage and said one end of the bore and permit full movement of the control spool to said one end limit position whereby said control spool can move to said one end limit position either at the termination of regenerative operation or when a cylinder is to operate in retracting movement.

11. A hydraulic circuit for regenerative cylinder operation comprising a pair of cylinder lines connectable to the cylinder, a control valve connected to said lines and having a bore with a control spool, a pair of fluid lines to said control valve individually connectable to pressure or tank, a three-position pilot valve having an outlet connected to one end of said bore whereby in one position the pilot valve connects the bore to drain and in the other two position connects said bore to pressure fluid to move said control spool, a pair of ports adjacent the opposite end of the bore with a first port spaced lengthwise of the bore from the second of the ports, said second port being connected by passage means to said three-position pilot valve and to a fluid pressure line with an orifice in said passage upstream of said second port whereby a pressure differential applied to said control spool causes movement thereof toward said second port, said first port being connected to drain to permit flow from the second port to the first port, said movement of the control spool being stopped and hydraulically locked when the control spool blocks said first port, and two alternate systems for bleeding fluid from said second port to permit movement of the control spool to an end limit position.