# US 7,743,611 B2 · Backhoe hydraulic system

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- Number: US 7,743,611 B2
- Document ID: US7743611B2
- Status: Granted
- Kind: B2
- Application number: 11/864,430
- Filed: 2007-09-28
- Published: 2008-04-03
- Granted: 2010-06-29
- Earliest claimed: 2006-09-29
- Assignees: Kubota Corporation
- Inventors: Hiroshi Horii
- Web page: https://patentgrep.com/patent/US7743611B2

## CPC

- E02F 9/2239: {using two or more pumps with cross-assistance}
- E02F 9/2292: {Systems with two or more pumps}
- E02F 9/2296: {Systems with a variable displacement pump}
- F15B 11/165: {for adjusting the pump output or bypass in response to demand}
- F15B 11/17: using two or more pumps
- F15B 2211/20576: with multiple pumps
- F15B 2211/30555: Inlet and outlet of the pressure compensating valve being connected to the directional control valve
- F15B 2211/3116: the pump port being open in the centre position, e.g. so-called open centre
- F15B 2211/329: actuated by fluid pressure
- F15B 2211/7053: Double-acting output members
- F15B 2211/7058: Rotary output members
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR

## Abstract

The present invention overcomes drawbacks whereby the supply of pressure oil to a hydraulic cylinder for operating a ground working device is temporarily cut, and operation of the ground working device is temporarily stopped when a control valve for the travel device is operated while a control valve for the ground working device is being operated. When control valves (V4, V5) for the travel devices are operated during operation of control valves (V6, V7, V8) for the ground working device, and a first flow channel switching valve (V12) is switched from an operating position (31) to a travel position (34), a second flow channel switching valve (V13) is switched from a non-feeding position (39) to a feeding position (40) before or at the same time as the first flow channel switching valve (V12).

## Claims

### Claim 1

A backhoe hydraulic system comprising:
travel pumps (P1, P2) for feeding pressure oil to control valves (V4, V5) for a travel device;
a swivel pump (P3) for feeding pressure oil to a control valve (V1) for a swivel base;
a first flow channel switching valve (V12) that is capable of switching between a work position (31) in which the pressure oil from said travel pumps is fed to control valves (V6, V7, V8) for a ground working device during non-travel, and a travel position (34) in which the pressure oil from said travel pumps is fed to control valves (V4, V5) for a left-right travel device during travel;
a second flow channel switching valve (V13) that is capable of switching between a non-feed position (39) in which the pressure oil from said swivel pump (P3) is not supplied to the control valves (V6, V7, V8) for said ground working device, and a feeding position (40) in which the pressure oil from said swivel pump (P3) is fed to the control valves (V6, V7, V8) for the ground working device;
a travel detection circuit (54) for feeding a pilot pressure to the first flow channel switching valve (V12) to switch the first flow channel switching valve (V12) to said travel position (34) when the control valves (V4, V5) for said travel device are operated; and
a flow channel switching circuit (41) that is capable of feeding a pilot pressure to the second flow channel switching valve (V13) so as to switch the second flow channel switching valve (V13) to the feeding position (40) when the control valves (V4, V5) for said travel device are operated during operation of the control valves (V6, V7, V8) for said ground working device;
wherein a flow channel switching operation valve (V17) is provided to said flow channel switching circuit (41), and the flow channel switching operation valve (V17) is configured so as to be capable of switching between a non-operating position (58) in which the pilot pressure is not fed to said second flow channel switching valve (V13), and an operating position (59) in which the pilot pressure is fed to said second flow channel switching valve (V13), and so as to be switched to the operating position (59) by the pilot pressure from said travel detection circuit (54); and
wherein said second flow channel switching valve (V13) switches from the non-feeding position (39) to the feeding position (40) at the same time as said first flow channel switching valve (V12) or before said first flow channel switching valve (V12) when the control valves (V4, V5) for said travel device are operated during operation of the control valves (V6, V7, V8) for said ground working device, and said first flow channel switching valve (V12) is switched from the work position (31) to the travel position (34).

### Claim 2 (depends on 1)

The backhoe hydraulic system according to claim 1, wherein said travel pumps have two pumps that include a first pump (P1) and a second pump (P2); and
said first flow channel switching valve (V12) is configured so as to feed the pressure oil from said first pump (P1) in said work position (31) together with the pressure oil from said second pump (P2) to the control valves (V6, V7, V8) for said ground working device, and to feed the pressure oil from said first pump (P1) in said travel position (34) and the pressure oil from said second pump (P2) independently to the control valves (V4, V5) for the left-right travel device.

### Claim 3

A backhoe hydraulic system comprising:
a travel detection circuit (54) for feeding a pilot pressure to a first flow channel switching valve (V12) to switch the first flow channel switching valve (V12) to a travel position (34) in which pressure oil is fed to the control valves (V4, V5) for a travel device when the control valves (V4, V5) for the travel device are operated; and
a flow channel switching circuit (41) that is capable of feeding a pilot pressure to a second flow channel switching valve (V13) so as to switch said second flow channel switching valve (V13) to a feeding position (40) in which pressure oil is fed to control valves (V6, V7, V8) for a ground working device when the control valves (V4, V5) for said travel device are operated during operation of the control valves (V6, V7, V8) for said ground working device;
wherein a flow channel switching operation valve (V17) is provided to said flow channel switching circuit (41), and the flow channel switching operation valve (V17) is configured so as to be capable of switching between a non-operating position (58) in which the pilot pressure is not fed to said second flow channel switching valve (V13), and an operating position (59) in which the pilot pressure is fed to said second flow channel switching valve (V13), and so as to be switched to the operating position (59) by the pilot pressure from said travel detection circuit (54).