EP0072233A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Vehicle and hydraulic system with single pump therefor
Assignee: Doosan Bobcat North America Inc
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Filing: 1982-08-09
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Granted: —
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Expires: 2002-08-09
Abstract
Abstract A hydraulic system is disclosed for energizing the power steering and various work handling hydraulic load circuits of a lift truck. A single positive displacement pumpe (60) supplies the requirements of the plural load circuits and is driven by a changeable speed prime mover (62). Manually actuable selector means are operatively connected with the load circuits and speed control means are provided for the prime mover. A priority demand valve is connected between the pump (60) and the respective load circuits. When only the power steering circuit is selected, the prime mover (62) is operated in a low speed range, when the lift circuit is selected, the prime mover (62) is operated in a high speed range and when an auxiliary work handling circuit is selected, the prime mover (62) is operated in an intermediate speed range. The prime mover (62) may be either an electric motor or an internal combustion engine..
Inventors
- 👤 Willard Lyle Chichester
- 👤 George Joseph Trusock
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 22:13
CPC Classifications
B; B66; B66F; B66F9/00; B66F9/06; B66F9/075; B66F9/20; B66F9/22; B62; B62D; B62D5/00; B62D5/06; B62D5/07
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
338 words
A work vehicle of the type having at least first and second hydraulic load circuits, first and-second manually actuable selector means operatively coupled with said first and second load circuits respectively for selecting operation of circuits individually or together, said second circuit having a greater hydraulic flow requirement than said first circuit, a positive displacement hydraulic pump, a changeable speed prime mover connected with the pump and adapted to operate in a speed range between a low speed and a high speed, manually actuable speed control means operatively coupled with said prime mover for changing the speed thereof to change the flow from the pump in accordance with the requirements of the load circuits, said pump being adapted to supply the flow required by the first load circuit when the prime mover is operated at said low speed and to supply the flow required by the second load circuit when the prime mover is operated at said high speed, characterised in that: a priority demand valve (214) having an inlet port (233) connected with the pump (60), a primary outlet port (235) connected with the first load circuit, a secondary outlet port (237) r connected with the second load circuit, and normally closed valve means (244) between the inlet port and the secondary outlet port, said priority demand valve (2141 including means (242, 244) for supplying to the primary outlet port (235) all of the flow required by the first load circuit when the selector means are actuated individually or together with the pump (60) running at any speed in said speed.range, said priority demand valve (214) including means (252) for opening said valve means (244) when the inlet flow exceeds that required by the first load circuit with said first and second selector means actuated together and with said pump (60) running at any speed within said speed range, whereby the inlet flow in excess of that required by the first load circuit is supplied to the secondary outlet (237) and thence to the second load circuit.
Claim 2
Dependent Claim
338 words
A work vehicle of the type having at least first and second hydraulic load circuits, first and-second manually actuable selector means operatively coupled with said first and second load circuits respectively for selecting operation of circuits individually or together, said second circuit having a greater hydraulic flow requirement than said first circuit, a positive displacement hydraulic pump, a changeable speed prime mover connected with the pump and adapted to operate in a speed range between a low speed and a high speed, manually actuable speed control means operatively coupled with said prime mover for changing the speed thereof to change the flow from the pump in accordance with the requirements of the load circuits, said pump being adapted to supply the flow required by the first load circuit when the prime mover is operated at said low speed and to supply the flow required by the second load circuit when the prime mover is operated at said high speed, characterised in that: a priority demand valve (214) having an inlet port (233) connected with the pump (60), a primary outlet port (235) connected with the first load circuit, a secondary outlet port (237) r connected with the second load circuit, and normally closed valve means (244) between the inlet port and the secondary outlet port, said priority demand valve (2141 including means (242, 244) for supplying to the primary outlet port (235) all of the flow required by the first load circuit when the selector means are actuated individually or together with the pump (60) running at any speed in said speed.range, said priority demand valve (214) including means (252) for opening said valve means (244) when the inlet flow exceeds that required by the first load circuit with said first and second selector means actuated together and with said pump (60) running at any speed within said speed range, whereby the inlet flow in excess of that required by the first load circuit is supplied to the secondary outlet (237) and thence to the second load circuit.
Claim 3
Dependent Claim
78 words
A work vehicle according to Claim 1, characterised in that bypass means (252) is provided which is operative to permit flow from the primary outlet port (235) to the secondary outlet port (237) by way of said valve means (244) when the pressure in the second load circuit is less than that in the first load circuit whereby the inlet flow in excess of that required by the first load circuit is supplied to the second load circuit.
Claim 4
Dependent Claim
146 words
A work vehicle. according to Claim 1 or 2, characterised in that said vehicle has three hydraulic load circuits, a third manually actuable selector means operatively coupled with the third load circuit, said third load circuit having a hydraulic flow requirement intermediate that of the first and second circuits, said speed control means being operable to operate said prime mover (62) at an intermediate speed when the third selector means is actuated, said pump (60) being adapted to supply the flow required by the third load circuit when the prime mover (62) is operated at said intermediate speed, said secondary outlet port (237) of the priority demand valve (214) being connected to the third load circuit, whereby the inlet flow in excess of that required by the first load circuit is supplied to the secondary outlet port (237) and thence to second and third load circuits.
Claim 5
Dependent Claim
40 words
A work vehicle according to Claim 1,2 or 3, characterised in that said work vehicle is a lift truck (10), said first hydraulic load circuit is a power steering circuit, and said second hydraulic load circuit is a lift circuit.
Claim 6
Dependent Claim
38 words
A work vehicle according to any one of the preceding claims, characterised in that said prime mover is an electric motor (62), and said speed control means is operatively coupled with said selector means for actuation concomitantly therewith.
Claim 7
Dependent Claim
34 words
A work vehicle according to any one of Claims 1 to 4, wherein, said prime mover is an internal combustion engine, and said speed control means comprises a manually actuated throttle of said engine.
Claim 8
Dependent Claim
59 words
A work vehicle according to Claim 3, characterised in that it comprises pressure relief valve means coupled with said second and third hydraulic load circuits and being adapted to limit the pressure in said second load circuit to a first predetermined value and being adapted to limit the pressure in said third load circuit to a second predetermined value.
Claim 9
Dependent Claim
157 words
A work vehicle according to Claim 7, characterised in that said pressure relief valve means comprises: a main relief valve (224) having an inlet port (404) connected with the secondary outlet port (2371 of said priority demand valve (214) and having an outlet port (406) connected with a return line (294), a pressure sensing line (418) coupled with the second and third load circuits, first and second pilot relief valves (226, 228) each having respective inlet ports connected with said pressure sensing line and having respective outlet ports connected with said return line, said first pilot relief valve being coupled with the main relief valve and being responsive to a pressure value in excess of said first predetermined value for opening the main relief valve, said second pilot relief valve being coupled with said main relief valve and being responsive to a pressure value in excess of said second predetermined value for opening said main relief valve.
Claim 10
Dependent Claim
33 words
A work vehicle according to Claim 3, characterised in that it comprises a flow control valve (342) connected between the secondary outlet port of the priority demand valve and the third load circuit.
Claim 11
Dependent Claim
193 words
A hydraulic system having a pump and having first and second hydraulic load circuits, the second load circuit being adapted for operation at higher pressure than the first load circuit; characterised in that the system comprises a priority demand valve (214) having an inlet port (233) adapted to be connected with the pump (60), a primary outlet port (235) adapted to be connected with the first load circuit, a secondary outlet port (237) adapted to be connected with the second load circuit, and normally closed valve means (244) between the inlet port (233) and the secondary outlet port (237), . flow rate responsive means urging said valve means toward opening in response to inlet flow, pressure responsive means for urging said valve means toward opening when the pressure in the first load circuit exceeds a predetermined value, said valve means (244) being opened in responsive to the inlet flow or the pressure in the first load circuit or the combination thereof whereby the flow required by the first load circuit has priority and the inlet flow in excess of that required by the first load circuit is supplied to the second load circuit.
Claim 12
Dependent Claim
193 words
A hydraulic system having a pump and having first and second hydraulic load circuits, the second load circuit being adapted for operation at higher pressure than the first load circuit; characterised in that the system comprises a priority demand valve (214) having an inlet port (233) adapted to be connected with the pump (60), a primary outlet port (235) adapted to be connected with the first load circuit, a secondary outlet port (237) adapted to be connected with the second load circuit, and normally closed valve means (244) between the inlet port (233) and the secondary outlet port (237), . flow rate responsive means urging said valve means toward opening in response to inlet flow, pressure responsive means for urging said valve means toward opening when the pressure in the first load circuit exceeds a predetermined value, said valve means (244) being opened in responsive to the inlet flow or the pressure in the first load circuit or the combination thereof whereby the flow required by the first load circuit has priority and the inlet flow in excess of that required by the first load circuit is supplied to the second load circuit.
Claim 13
Dependent Claim
50 words
ll. A hydraulic system according to Claim 10, characterised in that the system comprises: bypass means operative to permit flow from the primary outlet port (235) to the secondary outlet port (2371 when the pressure in the second load circuit is less than the pressure in the first load circuit.
Claim 14
Dependent Claim
72 words
A hydraulic system according to Claim 10 or 11, characterised in that said flow rate responsive means comprises: a first flow restricting means (242) connected between the inlet port (233) and the primary outlet port (235), and a pressure sensing means coupled between the flow restricting means (242) and the valve means (2441 whereby the valve means is operated in response to a predetermined value of pressure differential across the restricting means.
Claim 15
Dependent Claim
62 words
A hydraulic system according to Claim 10, 11 or 12, characterised in that said pressure responsive means comprises a pressure relief valve connected with the primary outlet port and in series with a second flow restricting means whereby only a limited flow is required to produce a sufficient change of pressure across the first flow restricting means to open said valve means.
Claim 16
Dependent Claim
17 words
A hydraulic system according to Claim 11, characterised in that said bypass means is a check valve.
Claim 17
Dependent Claim
65 words
A work vehicle according to Claim 5, characterised in that said speed control means is operatively connected with said manually actuable selector means for energizing the electric motor for operation in the high speed range when the second manually actuable selector means is actuated and for energizing the electric motor in the low speed range when only the first manually actuable selector means is actuated.
Claim 18
Dependent Claim
48 words
A work vehicle according to Claim 15, characterised in that said speed control means includes regulating means for maintaining the speed of the electric motor within first predetermined limits during operation in the high speed range and within second predetermined limits during operation in the low speed range.
Claim 19
Dependent Claim
61 words
A work vehicle according to Claim 16, charzacterised in that said electric motor is a series DC motor, said energizing means is a battery, and said regulating means includes means for applying DC pulses of variable mark/space ratio.to the motor and means responsive to the motor current for adjusting the mark/space ratio to regulate the motor speed within said predetermined limits.
References Cited (Backward Citations)
US3568868A
Cited
DE2318872A1
Cited
US3964260A
Cited
GB1543509A
Cited
DE2732913A1
Cited
FR2405212A1
Cited
US4220348A
Cited
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