Shaft seal assembly
A primary technical goal of this shaft seal device is to decrease the pressure of a sealant at a communication passage between a fluid chamber and a first seal portion, to further reduce the pressure by a floating ring, to make the first seal portion pressure-proof for sealing a high pressure process fluid, and to reduce the cost of the shaft seal device by simplifying its structure. The device comprises a fluid chamber being located between the first seal portion and the second seal portion, an intake passage being communicated to a communication passage between the fluid chamber and the first seal portion for allowing a sealant S to flow in, a floating ring being disposed within the fluid chamber and defining a pressure reduction gap between its own inner surface and the rotary shaft, and an outlet passage being communicated to the pressure reduction gap for circulating the pressure reduced sealant.
1. A shaft seal assembly for providing a seal between a housing and a rotary shaft, said shaft seal assembly comprising:
a) a first seal portion located at a first end of said rotary shaft and disposed between said housing and said rotary shaft in a radial direction relative to a longitudinal axis of said rotary shaft;
b) a second seal portion located at a second end of said rotary shaft opposite to said first seal portion and disposed between said housing and said rotary shaft in said radial direction relative to said longitudinal axis of said rotary shaft process fluid side relative to said first seal portion;
c) a fluid chamber defined between said first seal portion and said second seal portion in an axial direction relative to said longitudinal axis of said rotary shaft;
d) an intake passage in communication with a communication passage, said intake and communication passages being defined and located between a first end of said fluid chamber and said first seal portion relative to said longitudinal axis of said rotary shaft;
e) a floating ring that is axially movable with respect to both the rotary shaft and the housing and includes a pressure reduction inner surface that defines a pressure reduction gap between an inner diameter surface of said floating ring and said rotary shaft, wherein said fluid chamber is defined between an outer diameter surface of said floating ring and an inner diameter surface of said housing;
f) an outlet passage communicating with said pressure reduction gap;
g) a sleeve formed directly on the rotary shaft, wherein said first and second seal portions are located directly on an outer circumferential surface of the sleeve and are between an inner circumferential surface of the housing and the outer circumferential surface of the sleeve; and
h) a biasing member disposed between an inner radial wall portion of said floating ring and an inner radial wall portion of said housing,
wherein said biasing member urges said floating ring to contact said inner radial wall portion of said housing.
2. The shaft seal assembly according to claim 1 wherein said intake passage is in further communication with said fluid chamber via a gap defined between said housing and said rotary shaft.
3. The shaft seal assembly according to claim 1 wherein said intake passage communicates with a first seal installation chamber located between said first seal portion and said fluid chamber.
4. The shaft seal assembly according to claim 1 wherein said first seal portion is arranged for a mechanical seal and a rotary seal ring of said mechanical seal is retained by a sleeve disposed between said housing and said rotary shaft.
5. The shaft seal assembly according to claim 1 wherein a bearing is disposed in the opposite side of said floating ring with respect to said second seal portion and said bearing supports said rotary shaft in a rotary movable manner and a supply passage communicates with a second seal installation chamber wherein said second seal portion is disposed.
6. The shaft seal assembly according to claim 1 , wherein the pressure reduction inner surface of the floating ring has a tapered surface that gradually decreases the pressure reduction gap in a direction approaching the outlet passage.
7. The shaft seal assembly according to claim 1 , wherein the pressure reduction inner surface of the floating ring has a labyrinth seal.
8. The shaft seal assembly according to claim 1 , wherein the pressure reduction inner surface of the floating ring has a plurality of sets of labyrinth seals disposed along the pressure reduction gap with predetermined intervals therebetween.
9. The shaft seal assembly according to claim 1 , further comprising a third seal disposed between at least two of said fluid chamber, said housing and said floating ring.