Hydraulic control circuit of boom cylinder in work machine
First Claim
1. A hydraulic control circuit of a boom cylinder for a work machine, which is provided with a boom cylinder extending and contracting to move a boom upward and downward, and a control valve that is changed to an operation position where pressurized oil is supplied to and discharged from respective oil chambers at the head side and rod side of the boom cylinder on the basis of operations of an operating member, and to a neutral position where no pressurized oil is supplied thereto and discharged therefrom, the hydraulic control circuit comprising:
- neutral holding means by which the control valve is held in the neutral position regardless of a descent operation of the operating member; and
a communication line by which the head side oil chamber and rod side oil chamber of the boom cylinder are caused to communicate with each other, the communication line is provided with opening and closing valve means that open and close the communication line, and direction valve means that is changed to an unidirectional state in which, although an oil flow from a weight holding side oil chamber, for holding the weight of the boom, to the other oil chamber of the respective oil chambers of the boom cylinder is permitted, a reverse oil flow is hindered, and a bi-directional state in which oil flows in both directions between the respective oil chambers are permitted.
3 Assignments
0 Petitions
Accused Products
Abstract
A hydraulic control circuit of a boom cylinder for a work machine, which, when controlling the supply and discharge of pressurized oil with respect to a boom cylinder, improves fuel efficiency, work efficiency in combined operations, and work efficiency and operationality in work of difficult boom operations, such as debris raking-up work and bumping work, etc. The hydraulic control circuit of a boom cylinder is provided with a first change valve for holding the boom control valve in the neutral position, a communication line for causing the head side oil chamber and the rod side oil chamber to communicate with each other, an opening and closing valve for opening and closing the communication line, and a pilot operation check valve that is changed to an unidirectional state where, although an oil flow from the head side oil chamber to the rod side oil chamber is permitted, a reverse flow is hindered, and a bi-directional state is permitted where the oil flows in both directions.
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Citations
16 Claims
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1. A hydraulic control circuit of a boom cylinder for a work machine, which is provided with a boom cylinder extending and contracting to move a boom upward and downward, and a control valve that is changed to an operation position where pressurized oil is supplied to and discharged from respective oil chambers at the head side and rod side of the boom cylinder on the basis of operations of an operating member, and to a neutral position where no pressurized oil is supplied thereto and discharged therefrom, the hydraulic control circuit comprising:
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neutral holding means by which the control valve is held in the neutral position regardless of a descent operation of the operating member; and
a communication line by which the head side oil chamber and rod side oil chamber of the boom cylinder are caused to communicate with each other, the communication line is provided with opening and closing valve means that open and close the communication line, and direction valve means that is changed to an unidirectional state in which, although an oil flow from a weight holding side oil chamber, for holding the weight of the boom, to the other oil chamber of the respective oil chambers of the boom cylinder is permitted, a reverse oil flow is hindered, and a bi-directional state in which oil flows in both directions between the respective oil chambers are permitted. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification