Patent ID: 8474792

Claim:
A valve device for selectively opening and closing a flow passage, the valve device comprising: a valve seat with a flat surface portion having an opening of the flow passage thereon; a valve body for selectively opening and closing the flow passage, wherein an end portion of the valve body is provided with a hollow portion recessed into the valve body relative to the end portion to define a flat bottom area recessed in the valve body, and a radial hole which makes the bottom area communicate with the external surface of the valve body; a ring shaped resin-made seat press-fit in the hollow portion and comprising a first side having a flat surface facing the valve seat, a second side having a flat surface facing the flat bottom area, a center hole connecting the first and second sides, an annular recess at said first side and surrounding said center hole, and an annular recess at said second side and surrounding said center hole, wherein the annular recesses slope continuously from the respective flat surfaces to the center hole, said resin-made seat having a thickness so that the resin-made seat partly protrudes from the hollow portion and extends outward from the end portion of the valve body, whereby the flat surface of the first side of the resin made seat may be brought into flat surface contact with the flat surface portion of the valve seat by relative movement of the valve body and the valve seat; a manually operated mechanism for operating one of the valve body and the valve seat to bring the flat surface of the first side of the resin-made seat into flat surface contact with the flat surface portion of the valve seat whereby the resin-made seat is compressed, and for further operating one of the valve body and the valve seat to compress the resin-made seat, wherein the end portion of the valve body is arranged to contact the flat surface portion of the valve seat such that the resin-made seat is not excessively compressed; a valve body housing; a first plug fixedly screwed into a receiving hole of the valve body housing and receiving therein the valve body to be axially slidable for selectively opening and closing the flow passage; an urging member for urging the valve body in a direction to open the flow passage; a second plug fixedly screwed into the receiving hole of the valve body housing; and an operating screw shaft screwed into the second plug to be manually adjustable in the axial position thereof, and contacting the valve body with point contact for moving the valve body against the resilient force of the urging member, wherein the mechanism for operating the valve body is composed of the second plug and the operating screw shaft.