# US 10,370,824 B2 · Work machine

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- Number: US 10,370,824 B2
- Document ID: US10370824B2
- Status: Granted
- Kind: B2
- Application number: 15/122,540
- Filed: 2015-03-13
- Published: 2017-03-16
- Granted: 2019-08-06
- Earliest claimed: 2014-05-30
- Assignees: Hitachi Construction Machinery Co., Ltd.
- Applicants: Hitachi Construction Machinery Co., Ltd.
- Inventors: Kenji Hiraku; Hiromasa Takahashi
- Web page: https://patentgrep.com/patent/US10370824B2

## CPC

- E02F 9/22: Hydraulic or pneumatic drives {(for dipper or bucket arm position control E02F3/43, for blade position control for graders E02F3/844; for turntables E02F9/121; for fork-lift trucks B66F9/22)}
- E02F 9/2228: {including an electronic controller}
- E02F 9/2264: {Arrangements or adaptations of elements for hydraulic drives}
- E02F 9/2289: {Closed circuit}
- E02F 9/2292: {Systems with two or more pumps}
- E02F 9/2296: {Systems with a variable displacement pump}
- E02F 3/32: working downwardly and towards the machine, e.g. with backhoes
- F15B 7/006: {Rotary pump input}
- F15B 11/17: using two or more pumps
- F15B 21/14: Energy-recuperation means
- F15B 2211/20546: variable capacity
- F15B 2211/20569: capable of working as pump and motor
- F15B 2211/20576: with multiple pumps
- F15B 2211/27: Directional control by means of the pressure source
- F15B 2211/30595: with additional valves between the groups of valves for multiple output members
- F15B 2211/613: Feeding circuits
- F15B 2211/7135: Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
- F15B 2211/7142: the output members being arranged in multiple groups
- F15B 2211/785: Compensation of the difference in flow rate in closed fluid circuits using differential actuators
- 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

To provide a work machine which, in a configuration provided with a closed-circuit pump and an open-circuit pump, is capable of stabilizing respective pump operations of the closed-circuit pump and the open-circuit pump and of improving the mountability of the closed-circuit pump and the open-circuit pump. The present invention is provided with a closed circuit in which a closed-circuit pump and a boom cylinder are connected annularly, and an open circuit which has an open-circuit pump for making hydraulic fluid flow in from a reservoir and flow out and a connection passage capable of introducing hydraulic fluid into the closed circuit, wherein the closed-circuit pump is installed above the open-circuit pump.

## Claims

### Claim 1

A work machine comprising:
an undercarriage provided with a travel device;
an upperstructure pivotally attached to the undercarriage;
a closed circuit provided with at least one closed-circuit hydraulic pump having two outlet/inlet ports each enabling the outlet and inlet of hydraulic fluid in both directions and a single-rod cylinder having a piston, a cap-end chamber into which the hydraulic fluid is introduced when the piston extends, and a rod-end chamber into which the hydraulic fluid is introduced when the piston retracts, the two outlet/inlet ports of the closed-circuit hydraulic pump being annularly connected with the cap-end chamber and the rod-end chamber;
an open circuit provided with an open-circuit hydraulic pump having an inlet port into which hydraulic fluid flows from a reservoir, and an outlet port from which hydraulic fluid flows out;
a connection circuit which introduces the hydraulic fluid flowing out from the open-circuit hydraulic pump into the closed circuit;
an engine; and
a power transmission device that includes four rotational shafts and transmits a rotational power of the engine to the closed-circuit hydraulic pump and the open-circuit hydraulic pump; wherein
the reservoir is mounted on a frame supporting the upperstructure;
the engine is mounted on the frame adjacent to the reservoir;
the closed-circuit hydraulic pump is connected to the two upper rotational shafts among the four rotational shafts; and
the open-circuit hydraulic pump is connected to the two lower rotational shafts among the four rotational shafts.

### Claim 2 (depends on 1)

The work machine according to claim 1, comprising:
a plurality of the open-circuit hydraulic pumps;
a first connection pipe connected to the reservoir; and
a plurality of second connection pipes connected to the first connection pipe at respective one ends and connected to inlet ports of the plurality of open-circuit hydraulic pumps at the respective other ends.

### Claim 3 (depends on 1)

The work machine according to claim 1, comprising:
a plurality of the open-circuit hydraulic pumps; and
a plurality of connection pipes connected to the reservoir at respective one ends and connected to the inlet ports of the plurality of open-circuit hydraulic pumps at the respective other ends.