Patent ID: 8353498

Claim:
A manual switching valve comprising: a body having a passage through which a pressure fluid flows; a valve plug disposed displaceably inside of said body, for being seated on a valve seat formed in said body; a shaft disposed rotatably in said body, for causing displacement of said valve plug in an axial direction by rotation thereof; an operating element supported on an end of said shaft, to which a predetermined rotational force is applied; and a switching mechanism disposed between said operating element and said shaft, for changing a transmittal state of the rotational force applied to said operating element to said shaft, wherein, in both completely open and completely closed states of said valve plug, in the event that the rotational force transmitted to the shaft from the operating element is excessive, transmission of the rotational force of said operating element to said shaft is interrupted by said switching mechanism, and wherein said switching mechanism comprises: a ball disposed displaceably in a radial direction with respect to said shaft at an interior portion of said operating element; a spring, which at all times imposes a force on said ball in said radial direction toward said shaft; and a plurality of arcuate shaped tooth portions disposed on an outer circumferential surface of said shaft facing said operating element, said ball engaging with said plurality of tooth portions, a radius of curvature of said arcuate shaped tooth portions being substantially the same as a radius of said ball, wherein said ball is continuously pressed toward said tooth portions and into engagement therewith by an elastic force of said spring, wherein, during both opening and closing operations of said valve plug and upon rotation of said operating element in both opening and closing directions, said switching mechanism transmits said rotational force from said operating element to said shaft in the event that the elastic force of said spring is larger than said rotational force, and interrupts the transmission of said rotational force from said operating element to said shaft in the event that the elastic force of said spring is smaller than said rotational force, and wherein said ball is formed from a resin material, a hardness of said ball being set to be smaller than a hardness of said tooth portions, whereby said ball is subjected to frictional wearing due to contact with said tooth portions at a rate exceeding frictional wearing of said tooth portions.