Meterless hydraulic system having restricted primary makeup
First Claim
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1. A hydraulic system, comprising:
- a primary pump;
a hydraulic actuator;
first and second passages fluidly connecting the primary pump to the hydraulic actuator in a closed-loop manner;
a charge circuit, the charge circuit including a displacement control valve configured to affect displacement control of the primary pump, wherein the charge circuit includes a charge pump and an accumulator configured to pressurize charge fluid in the charge circuit;
a makeup valve movable to selectively allow charge fluid from the charge circuit to enter the first or second passages; and
at least one restricted pilot passage configured to direct pilot fluid to the makeup valve to move the makeup valve and allow the charge fluid into the first and second passages.
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Abstract
A hydraulic system is disclosed. The hydraulic system may have a primary pump, a hydraulic actuator, and first and second passages fluidly connecting the primary pump to the hydraulic actuator in a closed-loop manner. The hydraulic system may also have a charge circuit, a makeup valve movable to selectively allow charge fluid from the charge circuit to enter the first or second passages, and at least one restricted pilot passage configured to direct pilot fluid to the makeup valve to move the makeup valve and allow the charge fluid into the first and second passages.
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Citations
18 Claims
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1. A hydraulic system, comprising:
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a primary pump; a hydraulic actuator; first and second passages fluidly connecting the primary pump to the hydraulic actuator in a closed-loop manner; a charge circuit, the charge circuit including a displacement control valve configured to affect displacement control of the primary pump, wherein the charge circuit includes a charge pump and an accumulator configured to pressurize charge fluid in the charge circuit; a makeup valve movable to selectively allow charge fluid from the charge circuit to enter the first or second passages; and at least one restricted pilot passage configured to direct pilot fluid to the makeup valve to move the makeup valve and allow the charge fluid into the first and second passages. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A hydraulic system, comprising:
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a primary pump; a hydraulic actuator; first and second passages fluidly connecting the primary pump to the hydraulic actuator in a closed-loop manner; a charge circuit, the charge circuit including a displacement control valve configured to affect displacement control of the primary pump, wherein the charge circuit includes a charge pump and an accumulator configured to pressurize charge fluid in the charge circuit; a primary makeup valve movable to selectively allow charge fluid from the charge circuit to enter the first or second passages; a first restricted pilot passage configured to direct pilot fluid from the first passage to a first end of the makeup valve to move the makeup valve and allow the charge fluid into the second passage; a second restricted pilot passage configured to direct pilot fluid from the second passage to a second end of the makeup valve to move the makeup valve and allow the charge fluid into the first passage; a first secondary makeup valve configured to allow charge fluid into the first passage based on a pressure differential between fluid in the first passage and the charge fluid; and a second secondary makeup valve configured to allow charge fluid into the second passage based on a pressure differential between fluid in the second passage and the charge fluid. - View Dependent Claims (12, 13)
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14. A method of operating a hydraulic system, comprising:
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pressurizing fluid with a pump; directing pressurized fluid from the pump through a hydraulic actuator to move the hydraulic actuator, and returning fluid from the hydraulic actuator back to the pump in a closed-loop manner; pressurizing charge fluid in a charge circuit using a charge pump and an accumulator; directing at least one restricted flow of pilot fluid to move a makeup valve and selectively allow charge fluid to join with pressurized fluid from the pump or with the fluid returning to the pump, the charge fluid further being selectively directed by a displacement control valve to a stroke adjusting mechanism associated with the pump. - View Dependent Claims (15, 16, 17, 18)
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Specification