Rotary joint

A rotary joint comprising:

• a first joint body;
• a second joint body rotatably connected to the first joint body;
• a prime seal unit which is a mechanical seal placed between opposed end portions arranged in the axial direction of the two joint bodies, the prime seal unit comprising (1) a stationary seal ring fixed concentrically to one of the opposed end portions with the axis of rotation as center, (2) a movable seal ring movable in the axial direction and held in the other of the opposed end portions concentrically with the stationary seal ring, (3) a rotation stopper mechanism provided on the outer circumferential side of the movable seal ring to keep the movable seal ring from relatively rotating while allowing the movable seal ring to move in the axial direction, and (4) a thrusting mechanism to press the movable seal ring toward the stationary seal ring, thereby providing a seal between an inner circumferential region inside the seal rings and an outer circumferential region outside of the seal rings by the sliding contact of the two relatively rotating seal rings, wherein the seal rings in the prime seal unit are made of silicon carbide with a total metal content of not higher than 200 ppm;
• and
• a continuous line of prime fluid passage made up of the inner circumferential region within the two seal rings, a first prime fluid passage section passing through the first joint body and leading into said inner circumferential region and a second prime fluid passage passing through the second joint body and leading into said inner circumferential region.

A rotary joint comprising:

• a first joint body;
• a second joint body rotatably connected to the first joint body;
• a prime seal unit which is a mechanical seal placed between opposed end portions arranged in the axial direction of the two joint bodies, the prime seal unit comprising (1) a stationary seal ring fixed concentrically to one of the opposed end portions with the axis of rotation as center, (2) a movable seal ring movable in the axial direction and held in the other of the opposed end portions concentrically with the stationary seal ring, (3) a rotation stopper mechanism provided on the outer circumferential side of the movable seal ring to keep the movable seal ring from relatively rotating while allowing the movable seal ring to move in the axial direction, and (4) a thrusting mechanism to press the movable seal ring toward the stationary seal ring, thereby providing a seal between an inner circumferential region inside the seal rings and an outer circumferential region outside of the seal rings by the sliding contact of the two relatively rotating seal rings;
• and
• a continuous line of prime fluid passage made up of the inner circumferential region within the two seal rings, a first prime fluid passage section passing through the first joint body and leading into said inner circumferential region and a second prime fluid passage passing through the second joint body and leading into said inner circumferential region, wherein the prime fluid passage is for liquid to pass through, and wherein the fluid contact area in said prime fluid passage is made of a material that will not release metal components in contact with the liquid.

A rotary joint comprising:

• a first joint body;
• a second joint body rotatably connected to the first joint body;
• a prime seal unit which is a mechanical seal placed between opposed end portions arranged in the axial direction of the two joint bodies, the prime seal unit comprising (1) a stationary seal ring fixed concentrically to one of the opposed end portions with the axis of rotation as center, (2) a movable seal ring movable in the axial direction and held in the other of the opposed end portions concentrically with the stationary seal ring, (3) a rotation stopper mechanism provided on the outer circumferential side of the movable seal ring to keep the movable seal ring from relatively rotating while allowing the movable seal ring to move in the axial direction, and (4) a thrusting mechanism to press the movable seal ring toward the stationary seal ring, thereby providing a seal between an inner circumferential region inside the seal rings and an outer circumferential region outside of the seal rings by the sliding contact of the two relatively rotating seal rings;
• a continuous line of prime fluid passage made up of the inner circumferential region within the two seal rings, a first prime fluid passage section passing through the first joint body and leading into said inner circumferential region and a second prime fluid passage passing through the second joint body and leading into said inner circumferential region;
• and
• a plurality of circumferential seal units provided side by side in the axial direction between the outer circumferential surface of the second joint body and the inner circumferential surface of the first joint body surrounding said second joint body concentrically, thereby forming a connecting region sealed with the neighboring circumferential side seal units between said outer and inner circumferential surfaces of said joint bodies, and wherein there are provided first and second auxiliary fluid passage sections in the joint bodies which do not cross said prime fluid passage sections, thereby forming a continuous line of auxiliary fluid passage made up of the two auxiliary fluid passage sections and said connecting region.