COMPACT HYDRAULIC ACTUATOR SYSTEM

Abstract

A hydraulic actuator, comprising: a housing; a rod secured to a piston, the rod and piston being slidably received within the housing, wherein the rod along with the piston is capable of movement between a first position and a second position; a first chamber positioned on one side of the piston and within the housing; a second chamber positioned on another side of the piston and within the housing; a self contained flexible volume compensator disposed within the housing; a fluid disposed in the first chamber, the second chamber and the self contained flexible volume compensator, wherein the fluid in the self contained flexible volume compensator is pressurized to a predetermined pressure level; a bidirectional pump for moving the fluid between the first chamber, the second chamber and the self contained flexible volume compensator; a valve system disposed in the housing and for providing selective fluid communication between the first chamber, the second chamber and the self contained flexible volume compensator as the rod moves in a range of movement defined by the first position and the second position, wherein the valve system isolates the first chamber from the self contained flexible volume compensator and the second chamber when a fluid pressure in at least one of the first chamber, the second chamber and the self contained flexible volume compensator is below a predetermined level; and wherein the pressurized fluid in the self contained flexible volume compensator is transferred from the self contained flexible volume compensator to the second chamber via the pump and fluid in the first chamber is transferred to pump from the first chamber when the rod is moved toward the second position and wherein fluid in the second chamber is transferred from second chamber to the self contained flexible volume compensator and the first chamber when the rod and piston are moved towards the first position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a hydraulic actuator constructed in accordance with an exemplary embodiment of the present invention;

FIG. 2 is a cross sectional perspective view of a compact actuator constructed in accordance with an exemplary embodiment of the present invention;

FIG. 2A is an enlarged partial cross sectional view of a portion of an exemplary embodiment of the present invention;

FIG. 2B is a schematic illustration of a sensor/transducer of an alternative exemplary embodiment of the present invention;

FIG. 3 is a cross sectional schematic view of a hydraulic actuator constructed in accordance with an exemplary embodiment of the present invention;

FIG. 4 is a schematic illustration of a hydraulic actuator and control scheme in accordance with an exemplary embodiment of the present invention;

FIG. 5 is a schematic illustration of a hydraulic actuator and control scheme in accordance with another exemplary embodiment of the present invention;

FIG. 6 is a perspective view of a compact actuator constructed in accordance with an exemplary embodiment of the present invention;

FIG. 7 is a cross sectional schematic view of a hydraulic actuator constructed in accordance with another exemplary embodiment of the present invention;

FIG. 8 is a cross sectional schematic view of a hydraulic actuator constructed in accordance with yet another exemplary embodiment of the present invention; and

FIG. 9 illustrates the hydraulic actuator in a vehicle.

Claims

1. A hydraulic actuator, comprising: a housing;a rod secured to a piston, the rod and piston being slidably received within the housing, wherein the rod along with the piston is capable of movement between a first position and a second position;a first chamber positioned on one side of the piston and within the housing;a second chamber positioned on another side of the piston and within the housing;a self contained flexible volume compensator disposed within the housing;a fluid disposed in the first chamber, the second chamber and the self contained flexible volume compensator, wherein the fluid in the self contained flexible volume compensator is pressurized to a predetermined pressure level;a bidirectional pump for moving the fluid between the first chamber, the second chamber and the self contained flexible volume compensator;a valve system disposed in the housing and for providing selective fluid communication between the first chamber, the second chamber, the pump and the self contained flexible volume compensator as the rod moves in a range of movement defined by the first position and the second position, wherein the valve system isolates the first chamber from the self contained flexible volume compensator and the second chamber when a fluid pressure in at least one of the first chamber, the second chamber and the self contained flexible volume compensator is below a predetermined level; andwherein the pressurized fluid in the self contained flexible volume compensator is transferred from the self contained flexible volume compensator to the second chamber via the pump and fluid in the first chamber is transferred to the pump from the first chamber when the rod is moved toward the second position and wherein fluid in the second chamber is transferred from the second chamber to the self contained flexible volume compensator and the first chamber when the rod and piston are moved towards the first position.

2. The hydraulic actuator as in claim 1, wherein substantially no fluid passes through the piston as the rod moves between the first position and the second position.

3. The hydraulic actuator as in claim 1, wherein the first position corresponds to the rod being fully retracted within the housing and the second position corresponds to the rod being fully extracted from the housing and wherein the rod passes through an opening in the housing and the first chamber is disposed between the piston and the opening.

4. The hydraulic actuator as in claim 1, wherein the hydraulic actuator further comprises an inner cylinder, wherein the piston, the first chamber and the second chamber are disposed within the inner cylinder and the self contained flexible volume compensator is disposed between an outer surface of the inner cylinder and an inner surface of the housing, wherein the self contained flexible volume compensator is pre-pressurized to a predetermined level that is higher than one atmosphere but less than a pressure required to urge the piston and the rod between the first and second positions.

5. The hydraulic actuator as in claim 4, wherein the rod is a hollow cylinder and the hydraulic actuator further comprises a sensor positioned within the rod, wherein the sensor is configured to measure movement of the hollow cylinder, wherein the sensor outputs a signal indicative of a position of the rod within the housing and fluid in the first chamber is transferred from the first chamber when the rod is moved toward the second position by overcoming a first valve of a first subassembly and a first valve of a second subassembly, the first valve of the first subassembly providing selective fluid communication between the first chamber and the second chamber and the first valve of the second subassembly providing selective fluid communication between the second chamber and the self contained flexible volume compensator and the first chamber and wherein the pressurized fluid in the self contained flexible volume compensator is transferred from the self contained flexible volume compensator to the second chamber and fluid in the second chamber is transferred to the self contained flexible volume compensator and the first chamber from the second chamber when the rod is moved towards the first position by overcoming a second valve of the first subassembly and a second valve of the second subassembly, the second valve of the first subassembly providing selective fluid communication between the first chamber and the second chamber and the second valve of the second subassembly providing selective fluid communication between the second chamber and the self contained flexible volume compensator.

6. The hydraulic actuator as in claim 5, wherein the fluid in the self contained flexible volume compensator is pre-pressurized by a pressure means and the valve system further comprises a cross over relief module for manual operation of the hydraulic actuator.

7. The hydraulic actuator as in claim 6, wherein the pressure means is a spring applying a force to a compressible portion of the flexible volume compensator and substantially no air is in the first chamber, the second chamber, the pump, the self contained flexible volume compensator and the valve system.

8. The hydraulic actuator as in claim 4, wherein a maximum volume of the second chamber is defined when the rod and piston are at the second position and a maximum volume of the first chamber is defined when the rod and piston are at the first position, wherein the maximum volume of the second chamber is greater than the maximum volume of the first chamber.

9. The hydraulic actuator as in claim 8, wherein the first position corresponds to the rod being fully retracted within the housing and wherein the second position corresponds to the rod being fully extracted from the housing.

10. The hydraulic actuator as in claim 9, wherein the housing is linear in shape and substantially no air is in the first chamber, the second chamber, the pump and the self contained flexible volume compensator.

11. The hydraulic actuator as in claim 5, further comprising a control unit configured to receive signals from the sensor and operate the bidirectional pump, wherein the piston has an opening that allows a portion of the sensor to pass therethrough and into the rod as the rod moves between the first and second positions and wherein substantially no fluid passes through the piston as the rod moves between the first position and the second position and wherein the sensor comprises a variable resistor and a movable contact of the sensor is secured to either the rod or the piston.

12. The hydraulic actuator as in claim 8, wherein the rod is secured to either a door or a body of a vehicle and the housing is secured to either the door or the body of the vehicle.

13. The hydraulic actuator as in claim 8, wherein the pre-pressurized fluid in the self contained flexible volume compensator assists in moving the rod in the range of movement.

14. A method for actuating a rod of a hydraulic actuator, comprising: pressurizing a fluid in a self contained flexible volume compensator of the hydraulic actuator; anddisplacing a portion of the fluid of the self contained flexible volume compensator into a second chamber of the hydraulic actuator as a rod of the hydraulic actuator moves from a first position towards a second position wherein a piston coupled to the rod increases a volume of the second chamber and decreases a volume of a first chamber, wherein a portion of a fluid in the second chamber is transferred to the self contained flexible volume compensator when the rod moves from the second position to the first position, and wherein the self contained flexible volume compensator, the first chamber and the second chamber are disposed within a housing of the hydraulic actuator and a valve system disposed in the housing provides selective fluid communication between the first chamber, the second chamber and the self contained flexible volume compensator as the rod moves in a range of movement defined by the first position and the second position, wherein the valve system isolates the first chamber from the self contained flexible volume compensator and the second chamber when a fluid pressure in at least one of the first chamber, the second chamber and the self contained flexible volume compensator is below a predetermined level.

15. The method as in claim 14, wherein the hydraulic actuator further comprises a bidirectional pump disposed within the housing for displacing the fluid between the first chamber, the second chamber and the self contained flexible volume compensator, wherein the self contained flexible volume compensator is pre-pressurized to a predetermined level that is higher than one atmosphere but less than a pressure required to urge the piston between the first and second positions and wherein fluid from the first chamber does not directly flow into the self contained flexible volume compensator.

16. The method as in claim 15, wherein the hydraulic actuator further comprises an inner cylinder, wherein the piston, the first chamber and the second chamber are disposed within the inner cylinder and the self contained flexible volume compensator is disposed between an outer surface of the inner cylinder and an inner surface of the housing and the housing is cylindrical in shape.

17. The method as in claim 15, further comprising: measuring movement of the rod within the housing with a sensor disposed inside the rod, the sensor being a transducer configured to provide a plurality of signals corresponding to the movement of the rod within the housing, wherein the plurality of signals are received by a control unit configured to operate the bidirectional pump based upon the plurality of signals provided by the transducer and wherein the fluid in the self contained flexible volume compensator is pre-pressurized by a pressure means, wherein the piston has an opening that allows a portion of the sensor to pass therethrough and into the rod as the rod moves between the first and second positions and wherein substantially no fluid passes through the piston as the rod moves between the first position and the second position and wherein the sensor comprises a variable resistor and a movable contact of the sensor is secured to either the rod or the piston.

18. A hydraulic actuator, comprising: a linear housing;an inner cylinder disposed within the linear housing;a rod secured to a piston, the rod and piston being slidably received within the inner cylinder, wherein the rod along with the piston is capable of movement between a first position and a second position;a first chamber defined by the inner cylinder and the piston, the first chamber being positioned on one side of the piston;a second chamber defined by the inner cylinder and the piston, the second chamber being positioned on another side of the piston;a self contained flexible volume compensator disposed between an exterior surface of the inner cylinder and an inner surface of the housing;a fluid disposed in the first chamber, the second chamber and the self contained flexible volume compensator, wherein the fluid in the self contained flexible volume compensator is pressurized to a predetermined pressure level;a bidirectional pump for moving the fluid between the first chamber, the second chamber and the self contained flexible volume compensator;a valve system disposed in the housing and for providing selective fluid communication between the first chamber, the second chamber, the pump and the self contained flexible volume compensator as the rod moves in a range of movement defined by the first position and the second position, wherein the valve system isolates the first chamber from the self contained flexible volume compensator and the second chamber when a fluid pressure in at least one of the first chamber, the second chamber and the self contained flexible volume compensator is below a predetermined level; andwherein the pressurized fluid in the self contained flexible volume compensator is transferred from the self contained flexible volume compensator to the second chamber and fluid in the first chamber is transferred to the pump from the first chamber when the rod is moved toward the second position by overcoming a first valve of a first subassembly and a first valve of a second subassembly, the first valve of the first subassembly providing selective fluid communication between the first chamber and the pump or the second chamber and the first valve of the second subassembly providing selective fluid communication between the second chamber and the self contained flexible volume compensator and the first chamber wherein the fluid in the second chamber is transferred to the self contained flexible volume compensator and the first chamber from the second chamber when the rod is moved towards the first position by overcoming a second valve of the first subassembly and a second valve of the second subassembly, the second valve of the first subassembly providing selective fluid communication between the first chamber and the second chamber and the second valve of the second subassembly providing selective fluid communication between the second chamber and the self contained flexible volume compensator.

19. The hydraulic actuator as in claim 18, wherein the first valve of the first subassembly is a counterbalance valve and the first valve of the second subassembly is a check valve.

20. The hydraulic actuator as in claim 19, wherein the second valve of the first subassembly is a check valve and the second valve of the second subassembly is a counter balance valve and the first subassembly further comprises a first pilot check valve and the second subassembly further comprises a first pilot check valve, wherein the first pilot check valve of the first subassembly and the second subassembly are configured to provide selective fluid communication between the self contained flexible volume compensator and the check valves of the first and second subassemblies.

21. The hydraulic actuator as in claim 20, wherein the self contained flexible volume compensator is pre-pressurized to a predetermined level that is higher than one atmosphere but less than a pressure required to urge the piston and the rod between the first and second positions.