FLUID SYSTEM

• US 3,792,643 A
• Filed: 02/17/1972
• Issued: 02/19/1974
• Est. Priority Date: 02/17/1972
• Status: Expired due to Term

• Current Assignee: Robert E. Scheafer
• Original Assignee: Robert E. Scheafer
• Inventors: Scheafer, Robert E.
• Primary Examiner(s): Geoghegan, Edgar W.
• Application Number:
  US05/227,057
• Time in Patent Office: 733 Days
• Field of Search: 60/52R,97H,425 91/411B,411R
• US Class Current: 91/519
• CPC Class Codes: F15B 11/16 with two or more servomotors
• CPC Class Codes: F15B 2211/20546 variable capacity
• CPC Class Codes: F15B 2211/20561 reversible
• CPC Class Codes: F15B 2211/27 Directional control by means of the pressure source
• CPC Class Codes: F15B 2211/30515 Load holding valves
• CPC Class Codes: F15B 2211/3057 having two valves, one for each port of a double-acting output member
• CPC Class Codes: F15B 2211/329 actuated by fluid pressure
• CPC Class Codes: F15B 2211/7055 having more than two chambers
• CPC Class Codes: F15B 2211/7135 Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
• CPC Class Codes: F15B 2211/75 Control of speed of the output member
• CPC Class Codes: F15B 2211/76 Control of force or torque of the output member
• CPC Class Codes: F15B 2211/763 Control of torque of the output member by means of a variable capacity motor, i.e. by a secondary control on the motor
• CPC Class Codes: F15B 2211/785 Compensation of the difference in flow rate in closed fluid circuits using differential actuators

Abstract

A fluid system having a variable displacement pump fluidly connected through valving means to a fluid linear actuator in such a manner that fluid pressure directed to one portion of the linear actuator causes expansion thereof at a selected rate, while fluid pressure directed to another portion of the linear actuator causes contraction thereof at the same rate. The fluid linear actuator comprises a main fluid cylinder having a piston reciprocably mounted therein, with a piston rod extending from one side of the piston and externally of the main fluid cylinder. The piston divides the main fluid cylinder into expansible pressure chambers, one of which is exposed to the rod carrying side of the piston to generate a force thereagainst when pressurized to move the piston in one direction, while the opposite side of the piston is exposed to the pressure of the fluid in the other pressure chamber which exerts a force to move the piston in an opposite direction. A secondary fluid cylinder is carried by the main fluid cylinder with the longitudinal axes of the secondary and main fluid cylinders being radially spaced and parallel to one another. The secondary cylinder has a piston reciprocably mounted therein forming one pressure chamber on the side of the piston in which a second piston rod is mounted and which piston rod extends from the secondary cylinder for connection with the piston rod of the main fluid cylinder, such that the main cylinder piston and the secondary piston reciprocate together as a unit. The effective pressure responsive area of the side of the piston in the main cylinder opposite the rod carrying side thereof is substantially equal to the sum of the effective pressure responsive area of the rod side of the piston in the main cylinder and the effective pressure responsive area of the rod side of the piston within the secondary cylinder, such that the force generated against the two pistons for moving the pistons in one direction is equal to the force exerted against the pistons for moving the same in the opposite direction. Valving means are provided for interconnecting the pressure chambers associated with both the main and secondary fluid cylinders so that the rate of expansion and contraction of the cylinders may be selectively increased as the force exerted on the pistons is decreased and vice versa to provide a fluid linear actuator having a wide speed-force range.

Claims

1. A fluid system comprising:

a first tubular member having an internal bore closed at its opposite ends;

a piston reciprocally mounted within said bore and dividing said bore into two expansible pressure chambers;

a piston rod carried on one side of said piston and extending externally of said tubular member through one of said closed ends;

first valve means for communicating fluid pressure to the pressure chamber associated with the rod side of said piston to generate a force against said piston to move same in one direction;

second valve means for communicating fluid pressure to the pressure chamber on the side of said piston opposite said rod to generate a force against said piston to move said piston in an opposite direction;

a second tubular member having an internal bore closed at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member;

a second piston reciprocally mounted within said second tubular member bore and defining an expansible pressure chamber;

a piston rod carried on one side of said second piston and extending through the pressure chamber of said second tubular member and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said pistons reciprocate together;

third valve means for communicating a pressure fluid to the pressure chamber of said second tubular member for exerting a force on the rod side of said second piston for moving said second piston in one direction;

the effective pressure responsive areas of the rod sides of said first mentioned piston opposite said rod being substantially equal to the sum of the effective pressure responsive areas of the rod sides of said first mentioned piston and said second piston;

a fluid pump having an outlet for delivering fluid under pressure at a selected rate of flow and an inlet for receiving fluid at the same selected rate of flow;

said first and second valve means being adapted to, first, communicate said pump outlet to the rod side pressure chambers of said first tubular member and said second tubular member, while commUnicating said pump inlet to the pressure chamber of said first tubular member opposite said rod for moving said first and second pistons in said one direction at a predetermined velocity and with a predetermined force;

said first and second valve means being adapted to, second, communicate said pump outlet to the pressure chamber of said first tubular member opposite said rod and to communicate said pump inlet to the rod side pressure chambers of said first tubular member and said second tubular member for moving said first and second pistons in said opposite direction at said predetermined velocity and with a said predetermined force.

2. A fluid system comprising:

a first tubular member having an internal bore closed at its opposite ends;

a piston reciprocally mounted within said bore and dividing said bore into two expansible pressure chambers;

a piston rod carried on one side of said piston and extending externally of said tubular member through one of said closed ends;

first valve means for communicating fluid pressure to the pressure chamber associated with the rod side of said piston to generate a force against said piston to move same in one direction;

second valve means for communicating fluid pressure to the pressure chamber on the side of said piston opposite said rod to generate a force against said piston to move said piston in an opposite direction;

a second tubular member having an internal bore closed at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member;

a second piston reciprocally mounted within said second tubular member bore and defining an expansible pressure chamber;

a piston rod carried on one side of said second piston and extending through the pressure chamber of said second tubular member and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said pistons reciprocate together;

third valve means for communicating a pressure fluid to the pressure chamber of said second tubular member for exerting a force on the rod side of said second piston for moving said second piston in one direction;

the effective pressure responsive areas of the rod sides of said first mentioned piston opposite said rod being substantially equal to the sum of the effective pressure responsive areas of the rod sides of said first mentioned piston and said second piston;

the rod side pressure chamber of said first tubular member being in constant fluid communication with said second tubular member pressure chamber;

a first conduit means connecting said second valve means to the pressure chamber of said first tubular member opposite said rod;

second conduit means connecting the rod side pressure chamber of said first tubular member and the pressure chamber of said second tubular member to said first valve means;

said first and second valve means being adapted to selectively direct fluid under pressure to one of said conduit means while exhausting fluid pressure from the other of said conduit means;

check valve means disposed in each of said conduit means for normally preventing flow from said pressure chambers to said first and second valve means, said check valve means being responsive to open and permit fluid to flow from said pressure chambers through their associated conduits when said first and second valve means are actuated to direct fluid pressure to the other of said conduits.

3. The fluid system defined in claim 1 wherein said first and second valve means are further adapted to communicate said pump outlet to the rod side pressure chambers of said first tubular member and said second tubular member while the pressure chamber opposite said rod of said first tubular member is communicated to said pump inlet to exert a second force on said piston of a lesser value than said first predetermined value aNd to move said pistons in said one direction at a second velocity greater than said predetermined velocity but with the same volume of fluid from said pump;

and said first and second valve means being adapted to connect the outlet of said fluid pump to said pressure chamber of said first tubular member opposite said rod, while communicating the inlet of said pump to the rod side pressure chambers of said first tubular member and said second tubular member to move said piston in said other direction at the said second velocity and with said second force.

4. The fluid system defined in claim 1 wherein said first and second valve means are further adapted to communicate said pump outlet to both fluid pressure chambers of said first tubular member and communicate said inlet of said pump to said second tubular member pressure chamber to move said piston in said one direction at a second velocity greater than said predetermined velocity and a second force less than said predetermined force, and said first and second valve means being adapted to communicate the outlet of said pump to said second tubular member pressure chamber while communicating the inlet of said pump to both pressure chambers of said first tubular member to move said pistons in said other direction at said second speed and second force.

5. A fluid system comprising:

a first tubular member having an internal bore closed at its opposite ends;

a piston reciprocally mounted within said bore and dividing said bore into two expansible pressure chambers;

a piston rod carried on one side of said piston and extending externally of said tubular member through one of said closed ends;

first valve means for communicating fluid pressure to the pressure chamber associated with the rod side of said piston to generate a force against said piston to move same in one direction;

second valve means for communicating fluid pressure to the pressure chamber on the side of said piston opposite said rod to generate a force against said piston to move said piston in an opposite direction;

a second tubular member having an internal bore closed at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member;

a second piston reciprocally mounted within said second tubular member bore and defining an expansible pressure chamber;

a piston rod carried on one side of said second piston and extending through the pressure chamber of said second tubular member and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said pistons reciprocate together;

third valve means for communicating a pressure fluid to the pressure chamber of said second tubular member for exerting a force on the rod side of said second piston for moving said second piston in one direction;

the effective pressure responsive areas of the rod sides of said first mentioned piston opposite said rod being substantially equal to the sum of the effective pressure responsive areas of the rod sides of said first mentioned piston and said second piston;

a plurality of said second tubular members, each having a second piston connected to said first piston, the effective pressure responsive area of the side of said rod being substantially equal to the sum of the effective pressure responsive area of the rod side of said first piston and the effective pressure responsive areas of the sides of said second pistons associated with said second tubular members.

6. The system defined in claim 2 wherein said check valves are pilot operated valves and are operable to open in response to a control pressure communicated to said first and second valve means.

7. A linear actuator comprising:

a first tubular member having an internal bore enclosed at its opposite ends;

a piston reciprocally mounted within said bore and dividing said bore into two expansible pressure chambers;

a piston rod carried on one side of said piston and extending through one of said pressure chambers and externally of said tubular member to one of said closed ends;

said one pressure chamber being adapted to be communicated to a source of fluid pressure to generate a force against the rod side of said piston to move same in one direction;

the pressure chamber opposite said rod being adapted to be communicated to said source of fluid pressure to generate a force against the other side of said piston to move same in an opposite direction;

a second tubular member having an internal bore at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member;

a second piston reciprocably mounted within said second tubular member bore and defining an expansible pressure chamber therein;

a piston rod carried on one side of said second piston and extending through said last mentioned pressure chamber and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said first and second pistons reciprocate together;

said second tubular member pressure chamber being adapted to be communicated to a source of pressure fluid to exert a force on the side of said second piston carrying said piston rod to move said second piston in said one direction; and

the effective pressure responsive area of the side of said first piston opposite said rod being substantially equal to the sum of the effective pressure responsive areas of the rod side of said first piston and the side of said second piston associated with said second tubular member pressure chamber, said linear actuator further comprising a plurality of said second tubular members, each having a second piston connected to said first piston, the effective pressure responsive area of the side of said first piston opposite said rod being substantially equal to the sum of the effective pressure responsive areas of the rod side of said first piston and of the rod sides of said second pistons.

8. A linear actuator comprising:

a first tubular member having an internal bore closed at its opposite ends;

a piston reciprocally mounted within said bore and dividing said bore into two expansible chambers;

a piston rod carried on one side of said piston and extending externally of said tubular member through one of said closed ends;

a second tubular member having an internal bore closed at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member, a second piston reciprocally mounted within said second tubular member bore and defining an expansible pressure chamber;

a piston rod carried on one side of said second piston and extending through said second tubular member pressure chamber and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said pistons reciprocate together;

means for variably supplying fluid pressure to said chambers to thereby vary the force generated by said linear actuator said means comprising a first and second variable displacement motoring means connected with said chambers and control means coupling said first and second variable displacement means such that the displacement of one of said motoring means is increased as the other of said motoring means is decreased.

9. A fluid system comprising:

a first tubular member having an internal bore enclosed at its opposite ends;

a source of fluid pressure;

a piston reciprocally mounted within said bore and dividing said bore into two expansible pressure chambers;

a piston rod carried on one side of said piston and extending through one of said pressure chambers and externally of said tUbular member to one of said closed ends;

said pressure chamber on the rod side of said piston being adapted to be communicated to said source of fluid pressure to generate a force against said piston to move same in one direction;

the pressure chamber on the side of said piston opposite said rod being adapted to be communicated to said source of fluid pressure to generate a force against said piston to move same in an opposite direction;

a second tubular member having an internal bore at one end, said second tubular member having a longitudinal axis radially spaced from and parallel to the longitudinal axis of said first tubular member;

a second piston reciprocably mounted within said second tubular member bore and defining a second expansible pressure chamber therein;

a piston rod carried on one side of said second piston and extending through said second pressure chamber and externally of said second tubular member through said closed end;

means for connecting the extended external ends of said piston rods such that said first and second pistons reciprocate together;

first and second variable displacement motoring means, said first motoring means having an inlet connected to the pressure chamber on the rod side of said first piston and an outlet connected to said second pressure chamber, said second motoring means having an inlet connected to pressure chamber opposite said rod and an outlet connected to said second pressure chamber, displacement control means coupling said first and second motoring means such that the displacement of one of said motoring means is increased as the displacement of the other is decreased;

said second tubular member pressure chamber being adapted to be selectively communicated to said source of pressure fluid through said first and second motoring means to exert a force on the rod side of said second piston to move said second piston in said one direction; and

the effective pressure responsive area of the side of said first piston opposite said rod being substantially equal to the sum of the effective pressure responsive area of the rod side of said first piston and the effective pressure responsive area of said side of said second piston associated with said second tubular member pressure chamber.

10. The fluid system defined in claim 9 wherein said first and second motoring means comprise:

a housing having a longitudinally disposed bore;

a pair of axially spaced cylinder barrels rotatably mounted about a common axis in said housing bore, each of said cylinder barrels having a plurality of arcuately spaced, parallel bores opening to the opposite faces of each of said cylinder barrels;

first valving means at one end of said housing bore communicating one face of one of said cylinder barrels with high and low pressure passages defining said first motoring means inlet and outlet;

second valving means at the other end of said housing bore communicating one face of the other of said cylinder barrels with high and low pressure passages defining said second motoring means inlet and outlet;

first piston means reciprocably mounted in said plurality of bores in said one cylinder barrel and having outer ends extending therefrom for engagement with a thrust surface, the amount of inclination of which controls the amount of displacement of said one cylinder barrel and thus the amount of displacement of said first motoring means;

a second piston means reciprocably mounted in said plurality of bores in said other cylinder barrel and having outer ends extending therefrom for engagement with a second thrust surface, the amount of inclination of which controls the displacement of said other cylinder barrel and thus the displacement of said second motoring means, said first and second thrust surfaces being formed on the opposite side of a common swash plate adapted to be pivoted in one direction to increase the displacement of one of said motoring means while simultaneously and in syNchronism decreasing the displacement of the other motoring means.