# US 7,464,493 B2 · Work machine

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- Number: US 7,464,493 B2
- Document ID: US7464493B2
- Status: Granted
- Kind: B2
- Application number: 11/661,972
- Filed: 2005-09-08
- Published: 2007-11-15
- Granted: 2008-12-16
- Earliest claimed: 2004-09-10
- Assignees: Hitachi Construction Machinery Co., Ltd.
- Inventors: Kouji Ishikawa; Tadatoshi Shimamura; Hidetoshi Satake; Nobuei Ariga
- Web page: https://patentgrep.com/patent/US7464493B2

## CPC

- F15B 21/005: {Filling or draining of fluid systems}
- E02F 9/2246: {Control of prime movers, e.g. depending on the hydraulic load of work tools}
- E02F 9/2285: {Pilot-operated systems}
- F15B 13/0422: {with manually-operated pilot valves, e.g. joysticks}
- F15B 2211/20523: Internal combustion engine
- F15B 2211/20546: variable capacity
- F15B 2211/329: actuated by fluid pressure
- F15B 2211/355: Pilot pressure control
- F15B 2211/7053: Double-acting output members
- F15B: SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- E02F: DREDGING; SOIL-SHIFTING (winning peat E21C49/00)

## Abstract

A work machine is provided having a starter motor for starting a prime mover, which without provision of any special hydraulic equipment, allows for draining pressure oil that still remains in a hydraulic actuator for driving a front attachment. The work machine is provided with a boom cylinder for driving a front attachment, a flow rate control valve for controlling a flow of pressure oil to be supplied to the boom cylinder, and a pilot valve for producing an output of a pilot control signal, which serves to switch the flow rate control valve, by using, as a primary pressure, pressure oil delivered from a pilot hydraulic pump driven by an engine. A fuel stop switch is provided for performing stop control on a supply of fuel, which drives the engine, and a switch is provided for maintaining drivable a starter motor, which starts the engine, responsive to the stop control of the supply of fuel to the engine by the fuel stop switch.

## Claims

### Claim 1

A work machine provided with a front attachment, a prime mover, a starter motor for starting said prime mover, a main hydraulic pump and pilot hydraulic pump drivable by said prime mover, a hydraulic actuator for being supplied with pressure oil from said main hydraulic pump to drive said front attachment, a flow rate control valve for controlling a flow of pressure oil to be supplied to said hydraulic actuator, and a control device for producing an output of a pilot control signal to switch said flow rate control valve by using, as a primary pressure, pressure oil delivered from said pilot hydraulic pump, comprising:
a fuel stop means for performing stop control on a supply of fuel which drives said prime mover, and
a holding means for maintaining said starter motor drivable without driving said prime mover responsive to said stop control on said supply of fuel to said prime mover by said fuel stop means.

### Claim 2

A work machine provided with a front attachment, a prime mover, a starter motor for starting said prime mover, a main hydraulic pump and pilot hydraulic pump drivable by said prime mover, a hydraulic actuator for being supplied with pressure oil from said main hydraulic pump to drive said front attachment, a flow rate control valve for controlling a flow of pressure oil to be supplied to said hydraulic actuator, and a control device for producing an output of a pilot control signal to switch said flow rate control valve by using, as a primary pressure, pressure oil delivered from said pilot hydraulic pump, comprising:
a fuel stop means for performing stop control on a supply of fuel which drives said prime mover, and
a holding means for maintaining said starter motor drivable responsive to said stop control on said supply of fuel to said prime mover by said fuel stop means,
wherein:
said control device comprises a pilot valve for outputting said pilot control signal,
said work machine is provided with a selector valve arranged in a line, which communicates said pilot hydraulic pump with said pilot valve each other, to prevent said output of said pilot control signal, and
said starter motor is maintained drivable while said output of said pilot control signal is prevented by said selector valve.

### Claim 3 (depends on 2)

A work machine according to claim 2, wherein said selector valve comprises a gatelock valve.

### Claim 4

A work machine provided with a front attachment, a prime mover, a starter motor for starting said prime mover, a main hydraulic pump and pilot hydraulic pump drivable by said prime mover, a hydraulic actuator for being supplied with pressure oil from said main hydraulic pump to drive said front attachment, a flow rate control valve for controlling a flow of pressure oil to be supplied to said hydraulic actuator, and a control device for producing an output of a pilot control signal to switch said flow rate control valve by using, as a primary pressure, pressure oil delivered from said pilot hydraulic pump, comprising:
a fuel stop means for performing stop control on a supply of fuel which drives said prime mover, and
a holding means for maintaining said starter motor drivable responsive to said stop control on said supply of fuel to said prime mover by said fuel stop means
wherein:
said work machine is provided with a controller for controlling said supply of fuel which drives said prime mover,
said fuel stop means comprises a fuel stop switch for turning off a power supply for said controller, and
said holding means comprises a switch for maintaining drivable said starter motor in association with said fuel stop switch.

### Claim 5 (depends on 1)

A work machine according to claim 1, wherein:
said work machine comprises a hydraulic excavator, said front attachment includes a boom, and said hydraulic actuator comprises a boom cylinder.