Abstract: When an engine is started in a state where a support member of a multi-coupler is attached to a mating support member, the pressure of hydraulic oil increases in a detection target pipeline part. A pressure detection unit detects the pressure of the hydraulic oil in the detection target pipeline part. A connection state determining unit determines whether a tank-side pipeline part and a motor-side pipeline part are connected to each other, based on the pressure. When the connection state determining unit determines that the tank-side pipeline part and the motor-side pipeline part are not connected to each other in a state where the engine is started, a pressure increase suppression unit carries out an operation for suppressing an increase in the pressure of a hydraulic motor.

Abstract: Provided is a work machine capable of effectively discharging air from a hydraulic circuit of a winch unit capable of applying braking to a winch drum by receiving a working oil. The work machine includes: a winch unit having a winch drum, a winch motor, a cylinder portion and a clutch portion; a hydraulic sources; a braking operating unit; a brake valve; a connecting portion; and a throttle portion. The throttle portion includes an opening having an opening diameter that is set so as to hold a pressure in a positive oil chamber for generating a brake force applied to the winch drum and to discharge a working oil from the positive oil chamber.

Abstract: A changing device easily and safely changes the posture of the backstop of a crane between a support posture and a storage posture. The backstop posture changing device is provided with a first support member, a second support member, a push-up mechanism, and a connection member. The first support member and the second support member are rotationally connected to a backstop and a lower boom respectively. When a cylinder rod of the push-up mechanism is extended with respect to a cylinder body, a push-up member pushes up the first support member and the posture of the backstop is changed from a storage posture on the lower boom to a support posture in which it is possible to support a boom while the crane is in a working posture.

Abstract: A steering apparatus provided in a wheeled working machine according to the present invention includes mechanical steering means for steering front wheels in accordance with the operation of operating means by connecting the operating means to a link member for changing the direction of the front wheels so as to transmit a steering force, full-hydraulic steering means, having steering cylinders for respectively changing directions of the front and rear wheels, for steering at least one of the front and rear wheels by introducing hydraulic oil to predetermined steering cylinders in accordance with the operation of the operating means and a selected mode, and switching means for switching the means so as to selectively actuate one of the mechanical steering means and the full-hydraulic steering means.

Abstract: A steering apparatus provided in a wheeled working machine according to the present invention includes mechanical steering means for steering front wheels in accordance with the operation of operating means by connecting the operating means to a link member for changing the direction of the front wheels so as to transmit a steering force, full-hydraulic steering means, having steering cylinders for respectively changing directions of the front and rear wheels, for steering at least one of the front and rear wheels by introducing hydraulic oil to predetermined steering cylinders in accordance with the operation of the operating means and a selected mode, and switching means for switching the means so as to selectively actuate one of the mechanical steering means and the full-hydraulic steering means.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: A winding-down side pilot port of a control valve is of a 2-port construction comprising a normal winding-down side port having a large pressure receiving area and a free fall side port having a small pressure receiving area, wherein in the free fall operation carried out by setting a motor to a small capacity, a pilot pressure of a winding-down side remote control valve is supplied to the free fall side port through a mode switching valve. Thereby, a stroke of the control valve can be suppressed so that a speed of a motor does not exceed an allowable speed.

Abstract: According to the present invention, when a winch drum is in the wind-down rotation, operating a control valve is operated to the wind-down side in a state in which capacity of a hydraulic motor is set to small capacity by a free fall valve to thereby rotate the hydraulic motor to the wind-down side at high speeds, and at the same time, motor holding pressure is controlled according to an operating amount of the free fall valve by a holding pressure control valve to thereby regulate rotational speed of the hydraulic motor and stop the latter.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.