Abstract: To supply hydraulic fluid to a hydraulic apparatus, a plurality of pumps are used. One of the pumps is used as a main pump while the remaining pump or pumps are used as sub-pumps. A flow path switching mechanism selectively disconnects the sub-pumps from a supply passage to the hydraulic apparatus. In this manner, a required minimum supply of hydraulic fluid is assured with a simple arrangement while eliminating wasteful energy loss and reducing the dissipation of the horsepower. A reliable operation is maintained without any adverse influence upon the hydraulic apparatus. In one embodiment, a pair of pumps, and a control including a pair of switching valves operating as a pressure sensor and a flow controller are assembled into a pump body. The switching valves assure a reasonable supply of hydraulic fluid to the hydraulic apparatus while minimizing the dissipation of the horsepower.

Abstract: A hydraulic fluid feeding device for a power steering device is proposed which has a plurality of pumps for feeding hydraulic fluid to the power steering device and a flow path change-over valve for switching the paths between the pumps and the power steering device, wherein the feeding rate of the hydraulic fluid to the power steering device is controlled by the action of the flow path change-over valve. The flow path change-over valve is operated according to the magnitude of the load exerted on the power steering device so that hydraulic fluid from all the pumps combined is fed to the power steering device when the load is great, and the hydraulic fluid from at least one of the pumps is fed to the power steering device when the load is small. With this device, the control of the feeding rate becomes efficient. It also becomes possible to bypass the hydraulic fluid from some of the pumps to a tank, independently of the delivery rates of the pumps, so that the power consumption may be reduced.

Abstract: A pair of pump bodies are disposed on the opposite sides of a rotor having vanes and a cam ring disposed in surrounding relationship with the rotor. These pump bodies serve the function of a sideplate and a pressure plate. The rotary shaft of the rotor is rotatably journaled in one of the pump bodies. A flow control valve is disposed in alignment with the axis of the other pump body, and a relief valve is disposed in surrounding relationship with the flow control valve. In this manner, the construction of various parts is simplified and the number of parts is reduced while simultaneously facilitating the machining operation. The overall length and the outer diameter as well as the weight of the pump can be reduced, advantageously reducing the manufacturing cost of the pump.

Abstract: A flow-control valve exhibits a flow-drooping characteristic such that the liquid supply into an oil pressure mechanism is decreased in response to an increase of the amount of liquid discharge from a pump. The pump outlet passage forms branches into a fluid supply passage communicating with an oil pressure mechanism and a recirculating passage back to an oil tank. A control valve located in the recirculating passage is opened in response to the fluid increase from the pump to recirculate a part of the fluid into the tank. An orifice not receiving large influences of the pressure variation is disposed either at the pump outlet passage or the recirculating passage and a variable orifice valve is disposed in the fluid supply passage. The variable orifice is controlled by the pressure differential existing between the upstream and downstream portions of the orifice at either location.

Abstract: A steering power control device for a power steering system which device is provided with a sensing means which detects the weight of a load carried on a vehicle and a flow control valve which regulates the flow rate of a hydraulic fluid that is supplied to the power steering in response to the detected load, thereby reducing the necessary force to operate the steering wheel when the vehicle load is large. Further, the flow control valve can be regulated also by the output of a vehicle speed sensing means. With the controlling factors of both the vehicle load and the vehicle speed, the operation of the steering wheel is made light when the vehicle speed is low and the vehicle load is large, while the operation of the steering wheel meets with a proper resistance when the vehicle is high and the vehicle load is small, thereby stabilizing the operation of the steering wheel and giving an ideal feeling to a driver in the operation of the steering wheel.

Abstract: A power steering control device which is provided with a sensing means which detects the weight of a load carried on the vehicle and a pressure control valve which regulates the pressure of the hydraulic fluid that is supplied to the power steering in response to the value of the detected load, thereby lightening the operation of the steering wheel when the load on the vehicle is large. The pressure control valve can be regulated also by the output of a vehicle speed sensing means. With the controlling factors of both the vehicle load and the vehicle speed, the operation of the steering wheel is lightened when the vehicle speed is low and the vehicle load is large, whereas the operation of the steering wheel meets with a proper resistance when the vehicle speed is high and the vehicle load is small, thereby stabilizing the operation of the steering wheel and giving an ideal feeling to the driver to operate the steering wheel.

Abstract: A low frequency medical treatment apparatus comprising an over-current preventing measure with an overcurrent detecting circuit and a switching circuit to control an output transmission path according to the detection output, a shock preventing measure having a control circuit for opening or closing an output wave transmission path in response to a switching element whose operating state is changed depending on whether or not an output controller is set at its minimum set position, and a measure of improving comfortability in use having a circuit for controlling the output wave transmission upon contact of a touching element with human body and a circuit for maintaining the output waveform unchanged.