Abstract: A switch mechanism 70 discriminates as to whether a lever 40 is in a detent position or not. When the lever is in the detent position, a detent device 80 is activated by a fluid pressure to produce a force for holding the lever in the detent position. The operation of the detent device is dismissed when the lever is not in the detent position. A pressure sensor 97 detects whether the operator's hand is in touch with the grip 49 of the lever, thus determining whether the operation of the detent device 80 is necessary. An actuator 30 is operated or stopped in response to manipulation of the lever. When the lever is moved to a position other than the detent position, an operation reaction force of a level corresponding to the load pressure in the actuator is applied by reaction force device 60, 60' to the lever so as to enable the operator to sense any change in the load pressure and starting operation of the actuator.

Abstract: An apparatus for controlling operating reaction of winch comprising a reaction device whose output is variable for applying the output as an operating reaction to an operating lever of a winch, load detection means for detecting a lifting load of the winch, lever operating amount detection means for detecting an operating amount of said operating lever, and a controller for indicating an output having a value corresponding to the lifting load and the lever operating amount to said reaction device on the basis of the detection amount by said load detection means and said lever operating amount detection means.

Abstract: A switch mechanism 70 discriminates whether a lever 40 is in a detent position or not. When the lever is in the detent position, a detent device 80 is activated by a fluid pressure to produce a force for holding the lever in the detent position. The operation of the detent device is dismissed when the lever is not in the detent position. A pressure sensor 97 detects whether the operator's hand is in touch with the grip 49 of the lever, thus determining whether the operation of the detent device 80 is necessary. An actuator 30 is operated or stopped in response to manipulation of the lever. When the lever is moved to a position other than the detent position, an operation reaction force of a level corresponding to the load pressure in the actuator is applied by reaction force device 60, 60' to the lever so as to enable the operator to sense any change in the load pressure and start of operation of the actuator.

Abstract: An operating force controlling device includes a pair of reactive force mechanisms (70, 70') disposed in an opposing relationship to each other in the direction of operation of an operating lever (60). A load pressure of a motor (30) is detected by a detector (91, 91'), and a controlling signal is outputted from a controller (90) in response to the load pressure. A pilot pressure is outputted from an electromagnetic proportional pressure reducing valve (80) in response to the control signal. The pilot pressure is inputted into one of the chambers of the reactive force mechanisms (70, 70') which moves a rod (72, 72') to project, to apply an operation reactive force to the lever (60). The operation reactive force is controlled such that the rate of change thereof may be high when the load pressure of the motor (30) is low but may be low when the load pressure is high.

Abstract: A hydraulic circuit suitable for use on power shovel or other construction machines, more specifically a hydraulic circuit for a cylinder in a hydraulic power transmission, of the type which is adapted to control pressurized oil flows to and from two oil chambers in the cylinder by switching the position of a directional control valve in communication with a pressurized oil source. The hydraulic circuit includes a logic valve provided between the directional control valve and a load-holding oil chamber in the cylinder. The logic circuit has first and second ports connected to the directional control valve and said load-holding oil chamber, respectively.

Abstract: A detent device for a control lever includes a cam which moves integral with a control lever by operation of the control lever. A piston is mounted such that the state wherein the end thereof comes into sliding contact with the cam, during movement of the cam, a pressure chamber is formed to communicate with a part of the piston opposite the sliding surface. A spring is provided within the pressure chamber to bias the piston toward the cam. The cam is provided with a detent portion in a part of the surface with which the piston contacts the detent portion. The sliding resistance of the end of the piston is greater at the detent position of the control lever, than at the other locations. A detector detects that the end of the piston is positioned at said detent portion. An oil-pressure supply device supplies oil pressure to the pressure chamber on the basis of a detection signal from the detector. The detector includes an electric contact constituted by a piston and a cam.

Abstract: A hydraulic circuit for a large crane furnished with a counterweight carriage detachably connectable to the swivel unit of the crane.