Abstract: A pressure sensor (17) is provided for detecting the discharge pressure of a hydraulic pump (11). An abnormality detection section (23) of a controller (21) detects a dry operation of the hydraulic pump (11) when the discharge pressure detected by the pressure sensor (17) becomes equal to or lower than a judgment reference pressure determined in advance according to the driving rotation speed of the hydraulic pump (11).

Abstract: A pressure sensor (17) is provided for detecting the discharge pressure of a hydraulic pump (11). An abnormality detection section (23) of a controller (21) detects a dry operation of the hydraulic pump (11) when the discharge pressure detected by the pressure sensor (17) becomes equal to or lower than a judgment reference pressure determined in advance according to the driving rotation speed of the hydraulic pump (11).

Abstract: In a hydraulic unit (A) including a hydraulic pump configured to be driven by a motor (2) and a hydraulic cylinder (3) for actuating a chuck, a fixed displacement hydraulic pump is combined with an adjustable speed motor (2) for driving the pump. In order to concurrently provide rapid movement of the cylinder (3) and reduction in the surge pressure, upon the cylinder (3) actuating the chuck, after a teaching movement is imparted to the cylinder (3) to determine an operating stroke of the cylinder (3) based on the number of rotations of the motor (2), the motor (2) is rotated at a high rotational speed for movement until a preset deceleration start point short of the end of movement of the cylinder (3) within the determined operating stroke and then rotated at a low rotational speed for deceleration from the deceleration start point to the end of movement of the cylinder (3), thereby allowing the chuck to chuck a work with a soft touch.

Abstract: A pump driving apparatus has a characteristic changing section which receives a set pressure, a set flowing amount, a set horse power, and a DC voltage of the converter section as input, outputs modified values of pressure, flowing amount, and horse power, and supplies the modified values to the horse power command generation section. Therefore, the motor can be driven to suit the change in power voltage so that the motor capacity can be utilized sufficiently.

Abstract: A first pump of small capacity and a second pump of large capacity are connected directly with each other and are driven by a variable-speed motor. The rotational speed of the variable-speed motor is controlled by a control device. In a first mode, a first discharge line of the first pump and a second discharge line of the second pump are disconnected with each other, making the first pump unloaded. With the first pump in the unloaded state, a constant-horsepower operation is performed, where the discharge fluid is brought into a high pressure by relatively small torque. In a second mode, the first discharge line and the second discharge line are connected with each other by a switching valve. With the first and second discharge lines in the connected state, a constant-horsepower operation is performed, where a high flow rate of discharge fluid is discharged at relatively low rotational speed.

Abstract: In a hydraulic unit (A) including a hydraulic pump configured to be driven by a motor (2) and a hydraulic cylinder (3) for actuating a chuck, a fixed displacement hydraulic pump is combined with an adjustable speed motor (2) for driving the pump. In order to concurrently provide rapid movement of the cylinder (3) and reduction in the surge pressure, upon the cylinder (3) actuating the chuck, after a teaching movement is imparted to the cylinder (3) to determine an operating stroke of the cylinder (3) based on the number of rotations of the motor (2), the motor (2) is rotated at a high rotational speed for movement until a preset deceleration start point short of the end of movement of the cylinder (3) within the determined operating stroke and then rotated at a low rotational speed for deceleration from the deceleration start point to the end of movement of the cylinder (3), thereby allowing the chuck to chuck a work with a soft touch.

Abstract: An apparatus for warm up control of an autonomous inverter-driven hydraulic unit has a warm up control section and a switch section. The warm up control section performs a predetermined process using a current speed and current pressure as input information and outputs a first switch command. The switch section is controlled by the first switch command so as to control on/off of power supplied to a fan motor. The apparatus causes an oil temperature to quickly rise to a level where a hydraulic unit driven by a hydraulic pump can work in an optimum condition.

Abstract: An apparatus for warm up control of an autonomous inverter-driven hydraulic unit has a warm up control section and a switch section. The warm up control section performs a predetermined process using a current speed and current pressure as input information and outputs a first switch command. The switch section is controlled by the first switch command so as to control on/off of power supplied to a fan motor. The apparatus causes an oil temperature to quickly rise to a level where a hydraulic unit driven by a hydraulic pump can work in an optimum condition.

Abstract: A pump driving apparatus has a characteristic changing section which receives a set pressure, a set flowing amount, a set horse power, and a DC voltage of the converter section as input, outputs modified values of pressure, flowing amount, and horse power, and supplies the modified values to the horse power command generation section. Therefore, the motor can be driven to suit the change in power voltage so that the motor capacity can be utilized sufficiently.

Abstract: A first pump of small capacity and a second pump of large capacity are connected directly with each other and are driven by a variable-speed motor. The rotational speed of the variable-speed motor is controlled by a control device. In a first mode, a first discharge line of the first pump and a second discharge line of the second pump are disconnected with each other, making the first pump unloaded. With the first pump in the unloaded, state, a constant-horsepower operation is performed, where the discharge fluid is brought into a high pressure by relatively small torque. In a second mode, the first discharge line and the second discharge line are connected with each other by a switching valve. With the first and second discharge lines in the connected, state, a constant-horsepower operation is performed, where a high flow rate of discharge fluid is discharged at relatively low rotational speed.

Abstract: An exhaust device whose inner surface is coated with a heat-insulating layer and a refractory layer. Each layer is formed by conducting at least one cycle of the steps of: (a) coating the inner surface with an inorganic binder solution, (b) immediately adhering a coating powder to the binder solution layer so that the powder is fully and uniformly impregnated with the binder solution, and (c) drying and solidifying it by heat treatment. The coating layer does not suffer from cracking, peeling and breakage.

Abstract: Hydraulic heat-resisting material of an improved thermal property which has high strength and high volume stability under high temperature is disclosed. The material substantially consists of 5 to 70 parts by weight of a mixture, the mixture consisting of 49.95 to 87.3% by weight of hydraulic cement, 49.95 to 9.7% by weight of amorphous silica and 0.1 to 3% by weight of a dispersing agent, and 95 to 30 parts by weight of a heat-resisting aggregate. Premold product made of the above material is also disclosed.