Patent ID: 8419551

Claim:
A rotary shaft device comprising a rotary joint including a front joint disk arranged in a rear end face of a rotary shaft provided with reciprocating flow passages and a rear joint disk that moves forward along an axis of the rotary shaft and is pressed against the front joint disk by a pressing part at a predetermined pressure, the front joint disk and the rear joint disk being provided with a plurality of forward communication holes connected to a forward passage side of the reciprocating flow passages and a plurality of backward communication holes connected to a backward passage side of the reciprocating flow passages respectively, wherein a ring-shaped inner seal is projectingly arranged in an axial direction of the rotary shaft on at least one of a face of the front joint disk and a face of the rear joint disk opposing each other, which abuts upon the opposing end face on the axis side of the disk in the pressing state by the pressing part, a ring-shaped outer seal is projectingly arranged in the axial direction of the rotary shaft on at least one of the opposing end faces, which abuts upon the opposing end face of the other disk on the outer periphery side of the disk in the pressing state and is positioned concentrically with the inner seal, a ring-shaped inner space communicates with one of the forward communication holes and the backward communication holes and a ring-shaped outer space communicates with one of the backward communication holes and the forward communication holes, wherein the ring-shaped inner space and the ring-shaped outer space are adjacently arranged concentrically with each other between the ring-shaped inner seal and the ring-shaped outer seal, which are projectingly arranged in the axial direction of the rotary shaft and abut upon the end face of the opposing disk, and the forward communication holes and the backward communication holes at least in the front joint disk are arranged at an equal distance in the peripheral direction of the opposing face.