Abstract: The invention provides a self-priming centrifugal pump capable of sucking up and pumping a highly viscous liquid containing muddy substances including a large amount of bubbles, and solid foreign matters, of preventing the flow of the liquid from the side of a main pump unit into a vacuum device and from the vacuum device into the main pump unit at all stages of operation including starting, operating and stopping stages and of perfectly automatic operation, and very economical in costs of equipment and maintenance.The self-priming centrifugal pump has a main pump unit for pumping a liquid, an auxiliary pump unit for centrifugal gas-liquid separation, and an exhaust vacuum device.

Abstract: The present invention is intended to provide a self-priming centrifugal pump with an excellent self-priming and pumping performance without destroying the nearly complete morphology of the volute type centrifugal pump. The principle of self-priming action that circulates self-priming water by the characteristics of a larger volute and a smaller volute formed around the periphery of an impeller to drive out an air-water mixture produced by vortices generated by the impeller is elucidated in the description of "Double Volute Centrifugal Pump" proposed in JP-B No. 28-3039. Efforts have been concentrated on locally supporting the bottom of a tornado-like cavity formed by a whirling current of self-priming water for centrifugally separating air from self-priming water and secondary technical problems accompanying such efforts could not have been solved.

Abstract: The invention has its object to radically resolve an untapped technical issue in a non-water hammering check valve device, in which a valve disc, a valve seat and a surrounding flow passage are configured such that the valve disc is substantially seated on the valve seat at the time when input to a pump is shut off and a discharge flow in the flow passage loses inertia to stop, and to provide a reasonable non-water hammering check valve device of a simple and clear construction which suffers a small resistance loss of a valve at the time of a predetermined maximum flow rate, can readily accommodate an abrupt change in a flow state without delay in valve closing operation and provides a uniform and close seating on the valve seat at the time of valve seating to prevent water hammering.

Abstract: A check valve for preventing water hammer in which a valve element is adapted for quick initiation of a valve closing motion without delay in response to an abrupt change in fluid flow resulting from stoppage of a pump, and which is seated on a valve seat when the inertial flow of the fluid in the discharge direction stops, without generating a water hammer and impulse noise. The valve element and the valve seat are constructed so that the valve element follows the motion of the flowing fluid and is interlocked with a braking device by a linear motion transmitting mechanism.