US3568868A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Hydraulic system for a lift truck
Assignee: Doosan Bobcat North America Inc
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Filing: 1969-09-08
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Granted: 1971-03-09
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Expires: 1989-09-08
Abstract
Abstract A hydraulic system for use in a lift truck. A single pump supplies fluid to a flow priority valve which supplies fluid up to a predetermined flow to an upright tilt circuit and supplies any fluid above the predetermined flow to an upright lift circuit. The tilt circuit is connected to the lift circuit by a one-way valve so that the entire flow from the pump can be supplied to the lift circuit.
Inventors
- 👤 Willard L Chichester
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:47
CPC Classifications
F; F15; F15B; F15B13/00; F15B13/02; F15B13/022; B; B66; B66F; B66F9/00; B66F9/06; B66F9/075; B66F9/20; B66F9/22; Y; Y10; Y10T; Y10T137/00; Y10T137/2496; Y10T137/2514; Y10T137/2521; Y10T137/2524
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
259 words
For use with a vehicle having an extendible upright connected thereto for tilting movement and variable-speed motor means, the combination comprising a fluid reservoir, a pump drivingly connected to the motor means and including an inlet port connected to the said reservoir and an outlet port, a priority flow control valve having a supply port connected to the said pump outlet port, a regulated fluid flow port and a bypass port, the said priority valve being operable to direct the entire fluid flow thereto through the said regulated fluid flow port until a predetermined fluid flow is reached and to then direct any additional fluid flow through the said bypass port, first fluid motor means connected between the vehicle and upright for tilting the upright, a first open-center valve connected to the said first motor means for controlling operation of the said first motor means, the said first valve including a supply port connected to the said regulated fluid flow port and a return port, second fluid motor means connected to the upright for extending the upright, a second open-center valve connected to the said second motor means for controlling operation of the said second motor means, the said second valve including a supply port connected to the said bypass port and a return port connected to the said reservoir, and a valve connected between the said first valve return port and the said second valve supply port and operable to permit fluid flow only from the said first valve return port to the said second valve supply port.
Claim 2
Dependent Claim
259 words
For use with a vehicle having an extendible upright connected thereto for tilting movement and variable-speed motor means, the combination comprising a fluid reservoir, a pump drivingly connected to the motor means and including an inlet port connected to the said reservoir and an outlet port, a priority flow control valve having a supply port connected to the said pump outlet port, a regulated fluid flow port and a bypass port, the said priority valve being operable to direct the entire fluid flow thereto through the said regulated fluid flow port until a predetermined fluid flow is reached and to then direct any additional fluid flow through the said bypass port, first fluid motor means connected between the vehicle and upright for tilting the upright, a first open-center valve connected to the said first motor means for controlling operation of the said first motor means, the said first valve including a supply port connected to the said regulated fluid flow port and a return port, second fluid motor means connected to the upright for extending the upright, a second open-center valve connected to the said second motor means for controlling operation of the said second motor means, the said second valve including a supply port connected to the said bypass port and a return port connected to the said reservoir, and a valve connected between the said first valve return port and the said second valve supply port and operable to permit fluid flow only from the said first valve return port to the said second valve supply port.
Claim 3
Dependent Claim
24 words
The combination as set forth in claim 1 wherein the said first motor means includes at least one double-acting piston and cylinder-type fluid motor.
Claim 4
Dependent Claim
19 words
The combination as set forth in claim 1 wherein the said second motor means is a single-acting fluid motOr.
Claim 5
Dependent Claim
41 words
The combination as set forth in claim 1 and including a first relief valve connected between the said regulated fluid flow port and the said reservoir and a second relief valve connected between the said bypass port and the said reservoir.
Claim 6
Dependent Claim
294 words
For use in a vehicle having an extendible upright connected thereto for tilting movement, the combination comprising a motor control connectable to a source of electric energy and adjustable to the voltage of the source, drive motor means operatively connected to the said control, a fluid reservoir, a pump motor connectable to the source of electric energy, a pump drivingly connected to the said pump motor and including an inlet port connected to the said reservoir and an outlet port, a priority flow control valve having a supply port connected to the said pump outlet port, a regulated fluid flow port and a bypass port, the said priority valve being operable to direct the entire fluid flow thereto through the said regulated fluid flow port until a predetermined fluid flow is reached and to then direct any additional fluid flow through the said bypass port, first fluid motor means connected between the vehicle and upright for tilting the upright, a first open-center valve connected to the said first motor means for controlling the operation of the said first motor means, the said first valve including a supply port connected to the said regulated fluid flow port and a return port, second fluid motor means connected to the upright for extending the upright, a second open-center valve connected to the said second motor means for controlling operation of the said second motor means, the said second valve including a supply port connected to the said bypass port and a return port connected to the said reservoir and a valve connected between the said first valve return port and the said second valve supply port and operable to permit fluid flow only from the said first valve return port to the said second valve supply port.
Claim 7
Dependent Claim
294 words
For use in a vehicle having an extendible upright connected thereto for tilting movement, the combination comprising a motor control connectable to a source of electric energy and adjustable to the voltage of the source, drive motor means operatively connected to the said control, a fluid reservoir, a pump motor connectable to the source of electric energy, a pump drivingly connected to the said pump motor and including an inlet port connected to the said reservoir and an outlet port, a priority flow control valve having a supply port connected to the said pump outlet port, a regulated fluid flow port and a bypass port, the said priority valve being operable to direct the entire fluid flow thereto through the said regulated fluid flow port until a predetermined fluid flow is reached and to then direct any additional fluid flow through the said bypass port, first fluid motor means connected between the vehicle and upright for tilting the upright, a first open-center valve connected to the said first motor means for controlling the operation of the said first motor means, the said first valve including a supply port connected to the said regulated fluid flow port and a return port, second fluid motor means connected to the upright for extending the upright, a second open-center valve connected to the said second motor means for controlling operation of the said second motor means, the said second valve including a supply port connected to the said bypass port and a return port connected to the said reservoir and a valve connected between the said first valve return port and the said second valve supply port and operable to permit fluid flow only from the said first valve return port to the said second valve supply port.
Claim 8
Dependent Claim
23 words
The combination as set forth in claim 5 wherein the said control automatically adjusts to the voltage of the source of electric energy.
Claim 9
Dependent Claim
24 words
The combination as set forth in claim 5 wherein the said first motor means includes at least one double-acting piston and cylinder-type fluid motor.
Claim 10
Dependent Claim
41 words
The combination as set forth in claim 5 and including a first relief valve connected between the said regulated fluid flow port and the said reservoir and a second relief valve connected between the said bypass port and the said reservoir.
References Cited (Backward Citations)
US2737196A
Cited
US2859762A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-08 | 1974-09-07 | 1975-03-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-08 | 1978-09-07 | 1979-03-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-08 | 1982-09-07 | 1983-03-09 | $7700.00 | Window Closed / Lapsed |