HYDRAULIC SYSTEM

• US 3,747,351 A
• Filed: 10/22/1971
• Issued: 07/24/1973
• Est. Priority Date: 10/22/1971
• Status: Expired due to Term

• Current Assignee: Parker Intangibles LLC (Parker-Hannifin Corporation)
• Original Assignee: A. P. Henry, William D. Wilkerson
• Inventors: Wilkerson, William D., Henry, A. P.
• Primary Examiner(s): Geoghegan, Edgar W.
• Application Number:
  US05/191,912
• Time in Patent Office: 641 Days
• Field of Search: 60/52R,476 91/420
• US Class Current: 60/476
• CPC Class Codes: F15B 7/006 Rotary pump input

Abstract

A hydraulic system comprising an actuator including a housing and a piston movable in the housing, a reversible, variable speed pump, and conduits for connecting the pump to both sides of the piston so that the pump can pump hydraulic fluid from one side of the piston to the other. The pump is driven by a reversible, variable speed drive with the direction of piston movement being a function of the direction in which the pump is driven. The rate of piston movement is a function of the speed at which the pump is driven. The actuator may be an unbalanced actuator, in which event the unbalance can be compensated for by the pump or by suitable piping connections.

Claims

1. A hydraulic system comprising:

an actuator including a housing and a fluid-responsive member movable in said housing, said member and said housing defining first and second chambers on opposite sides, respectively, of said member;

a reversible, variable speed pump, the output of said pump being a function of the speed at which said pump is driven;

conduit means for connecting said pump to both of said chambers whereby said pump can selectively pump hydraulic fluid from the first chamber to the second chamber and from the second chamber to the first chamber to thereby move the fluid-responsive member;

reversible, variable speed drive means for driving said pump;

means for controlling the direction in which and the speed at which said pump is driven by said drive means whereby the direction which the pump is driven controls the direction of movement of the fluid-responsive member and the speed at which the pump is driven controls the rate of movement of the fluidresponsive member;

said actuator being an unbalanced actuator whereby the change in volume of the first chamber is greater than the change in volume of the second chamber for a given displacement of the pressure-responsive member;

said conduit means including a first conduit leading from the pump to the first chamber and a second conduit leading from the pump to the second chamber;

a third conduit leading from the pump to a source of hydraulic fluid;

said pump including means for supplying make-up from the third conduit through the first conduit to the first chamber when the volume of the first chamber is being increased and means for dumping excess hydraulic fluid from the first chamber through the first conduit to said source when the volume of the first chamber is being decreased; and

said pump including a barrel pump and a valve plate, said valve plate having first, second and third ports therein communicating, respectively, with said first, second and third conduits.

2. A hydraulic system as defined in claim 1 wherein said drive means includes a reversible, variable speed electric motor, said pump including a positive displacement pump.

3. A hydraulic system comprising:

a differential actuator including a housing and a piston movable in said housing, said piston dividing said housing into first and second chambers on opposite sides of said piston, respectively, whereby movement of said piston causes the volumes of said chambers to change;

said actuator including means for causing the volume of said first chamber to undergo a greater change than the volume of said second chamber in response to a predetermined amount of piston displacement;

a reversible pump having first and second ports;

a first conduit interconnecting the first port and said first chamber;

a second conduit connecting said second port and said second chamber whereby the pump can pump hydraulic fluid through said conduits between said chambers to thereby move the piston;

drive means for driving said pump, said drive means being reversible to change the direction in which hydraulic fluid is pumped by said pump to thereby control the direction in which the piston is moved;

first valve means operatively associated with the first conduit and responsive to the first conduit being on the discharge side of the pump to open to permit hydraulic fluid to be supplied to the first chamber through the first conduit;

second valve means operatively associated with the second conduit and responsive to the second conduit being on the discharge side of the pump to open to permit hydraulic fluid to be supplied to the second chamber through the second conduit;

a first valve actuator responsive to the second conduit being on the discharge side of the pump for opening said first valve means to permit hydraulic fluid to be drawn from the first chamber by said pump;

a third conduit leading from said first conduit for dumping excess hydraulic fluid when said first chamber is being reduced in volume by said movement of the piston;

a control valve for closing said third conduit when said first conduit is on the discharge side of the pump and for opening said third conduit when said second conduit is on the discharge side of the pump;

means defining a restriction in said third conduit to provide back pressure for said pump when said control valve is open; and

Means for supplying make-up hydraulic fluid to said first chamber when the volume of said first chamber is being increased.

4. A hydraulic system as defined in claim 3 wherein said restriction is downstream of said control valve.

5. A hydraulic system as defined in claim 3 wherein said first valve actuator also opens said control valve whereby a single valve actuator operates both said first valve means and said control valve.

6. A hydraulic system as defined in claim 3 wherein said reversible drive means is a variable speed reversible drive means, thereby providing for better control of the movement of said piston.

7. A hydraulic system comprising:

a differential actuator including a housing and a piston movable in said housing, said piston dividing said housing into first and second chambers on opposite sides of said piston, respectively, whereby movement of said piston causes the volumes of said chambers to change;

said actuator including means for causing the volume of said first chamber to undergo a greater change than the volume of said second chamber in response to a predetermined amount of piston displacement;

a reversible pump having first and second ports;

a first conduit connecting the first port and said first chamber;

a second conduit connecting said second port and said second chamber whereby the pump can pump hydraulic fluid through said conduits and between said chambers to thereby move the piston, the direction of fluid flow through said conduits being a function of the direction in which said pump is driven;

reversible drive means for driving said pump to thereby control the direction in which the piston is moved;

first valve means operatively associated with the first conduit and responsive to the first conduit being on the discharge side of the pump to open to permit hydraulic fluid to be supplied through the first conduit to the first chamber;

a third conduit leading from said first conduit for dumping excess hydraulic fluid from the first chamber when said first chamber is being reduced in volume by said movement of the piston;

a control valve for opening and closing said third conduit;

a valve actuator for opening said control valve and said first valve means in response to said second conduit being on the discharge side of said pump whereby a single valve actuator opens said first valve means to allow the pump to draw fluid from the first chamber and opens the control valve to permit dumping of any excess hydraulic fluid through the third conduit; and

means for providing make-up fluid to the first chamber when the volume of the first chamber is being increased.

8. A hydraulic system as defined in claim 7 wherein said reversible drive means includes a reversible variable speed drive means whereby fine control of piston movements can be accomplished.

9. A hydraulic system comprising:

an actuator including a housing and a piston movable in said housing, said actuator being an unbalanced actuator whereby movement of said piston causes a greater change in said piston volume on one side of the piston than on the other side of the piston;

a reversible barrel-type pump, including a valve plate having first, second and third ports;

a first conduit leading from said first port to said one side of piston;

a second conduit leading from the second port to said other side of the piston whereby said pump can pump hydraulic fluid from said one side of the piston to said other side of the piston and from said other side of the piston to said one side of the piston with the direction of fluid flow being a function of the direction in which the pump is driven;

a third conduit leading from the third port to a source of hydraulic fluid;

said valve plate having first and second segments, said first port being at least partially on said first segment and said second and third ports being at least partially on said second segment;

said first and second seGments being on the intake and discharge sides, respectively, of said pump when said pump is being driven in one direction and said first and second segments being on the discharge and intake sides, respectively, of said pump when said pump is driven in the opposite direction, said third conduit drawing hydraulic fluid from said source of hydraulic fluid when said pump is being driven in said opposite direction and supplying hydraulic fluid to said source when the pump is driven in said one direction; and

said ports being sized and positioned on said segments to substantially compensate for the unbalance of said actuator whereby said pump supplies more hydraulic fluid to said one side of said piston than it draws from said other side of said piston and supplies less hydraulic fluid to said other side of said piston than it draws from said one side of said piston.

10. A hydraulic system as defined in claim 9 wherein a region of said second port is on said first segment.

11. A hydraulic system as defined in claim 9 including a casing, said pump and at least a portion of said source being within said casing.

12. A hydraulic system as defined in claim 9 including a reversible, variable speed drive means for driving said pump.

13. A hydraulic system comprising:

an actuator including a housing and a piston movable in said housing, said actuator being an unbalanced actuator whereby movement of the piston causes a greater change in volume on one side of the piston than on the other side of the piston;

a pump including first, second and third ports;

a first conduit for providing communication between said first port and said one side of said piston;

a second conduit leading from the second port to said other side of the piston;

a third conduit for providing communication between said third port and a source of hydraulic fluid;

said pump being drivable in one direction to pump hydraulic fluid from said one side of said piston through said first and second conduits to said other side of said piston and being drivable in the opposite direction to pump hydraulic fluid from said other side of the piston through said second and first conduits to said one side of said piston; and

said pump including first means for directing fluid from said first conduit to said second and third conduits when said first conduit is on the intake side of said pump and second means for directing fluid from the second and third conduits to the first conduit when said first conduit is on the discharge side of said pump to thereby at least partially compensate for the unbalance of the actuator.

14. A hydraulic system as defined in claim 13 wherein said pump includes a barrel-type pump and said first and second means include a valve plate having a plurality of ports therein sized and positioned to substantially compensate for the unbalance of the actuator.