Pressure Balanced Shaft Seal Assembly

Abstract

A pressure balanced shaft seal assembly that allows a seal to dynamically respond to angular or radial misalignment of a shaft is disclosed. The pressure balanced shaft seal assembly includes a fixed stator, a floating stator, and a labyrinth seal. In one embodiment, the floating stator and labyrinth seal are mounted within an annular groove formed in the fixed stator such that the floating stator and labyrinth seal may move a predetermined amount in the radial direction with respect to the fixed stator. A spherical interface between the labyrinth seal and floating stator may allow the labyrinth seal to pivot with respect to the floating stator during angular misalignment of a shaft around which the pressure balanced shaft seal assembly is mounted. A pressure balancing annular channel formed in the floating stator allows pressurized seal fluid to balance the axial pressure exerted on the floating stator by the process fluid.

1 . A shaft sealing member comprising:
 a. a floating stator, wherein said floating stator is positioned in an annular groove such that said floating stator is capable of a predetermined amount of radial movement within said annular groove, wherein the radial-interior surface of said floating stator is substantially concave in shape, and wherein said floating stator has an annular recess to form a pressure balancing annular channel therein; and   b. a labyrinth seal, wherein said labyrinth seal has a radial-exterior surface with a substantially convex shape that corresponds to the radial-interior surface of said floating stator so as to create a semi-spherical interface therebetween, and wherein said labyrinth seal has a radial-interior surface with a plurality of labyrinth pattern annular grooves.   
   
   
       2 . The shaft seal member according to  claim 1  wherein said annular groove is further defined as being formed in a fixed stator. 
   
   
       3 . The shaft seal member according to  claim 1  wherein said annular groove is further defined as being formed in a motor housing. 
   
   
       4 . The shaft sealing member according to  claim 2  wherein said floating stator is axially located through first and second radial interfaces between said floating stator and said annular groove of said fixed stator. 
   
   
       5 . The shaft sealing member according to  claim 4  further comprising first and second O-ring channels fashioned in said fixed stator at said first and second radial interfaces, respectively, wherein one O-ring is positioned in each said first and second O-ring channel. 
   
   
       6 . The shaft sealing member according to  claim 1  wherein a plurality of radially oriented anti-rotation grooves are fashioned in said labyrinth seal, and wherein a plurality of corresponding anti-rotation pins are positioned within said anti-rotation grooves and within a portion of said floating stator adjacent said anti-rotation grooves in said labyrinth seal. 
   
   
       7 . The shaft sealing member according to  claim 1  further comprising a plurality of O-ring channels fashioned in the radial-interior surface of said floating stator, wherein one O-ring is positioned in each said O-ring channel. 
   
   
       8 . The shaft sealing member according to  claim 1  further comprising a first fluid return pathway fashioned in said labyrinth seal and a second fluid return pathway fashioned in said floating stator wherein said first and second fluid return pathways are in fluid communication with one another. 
   
   
       9 . A shaft seal assembly comprising:
 a. a stator, wherein the radial-interior surface of said stator is substantially concave in shape, and wherein said stator has an annular recess to form a pressure balancing annular channel therein; and   b. a labyrinth seal, wherein said labyrinth seal has a radial-exterior surface with a substantially convex shape that corresponds to the radial-interior surface of said stator so as to create a semi-spherical interface therebetween, wherein said labyrinth seal has a radial-interior surface with a plurality of labyrinth pattern annular grooves adjacent a rotatable shaft.   
   
   
       10 . The shaft seal assembly according to  claim 9  further comprising an alignment skate positioned in each said annular groove of said plurality of labyrinth pattern annular grooves. 
   
   
       11 . The shaft seal assembly according to  claim 10  wherein said alignment skates are further defined as having the required dimension to contact said rotatable shaft. 
   
   
       12 . The shaft seal assembly according to  claim 11  wherein said shaft seal assembly is further defined as including a pressurized seal fluid introduced into said shaft seal assembly through a seal fluid inlet formed in said stator. 
   
   
       13 . The shaft seal assembly according to  claim 12  wherein said shaft seal assembly is further defined so that the clearance between said plurality of labyrinth pattern annular grooves in said labyrinth seal and said rotatable shaft is such that a predetermined amount of said pressurized seal fluid may pass between said plurality of labyrinth pattern annular grooves and said rotatable shaft. 
   
   
       14 . A shaft seal assembly comprising:
 a. a shaft protruding from a vessel or housing;   b. a first sealing means adjacent said shaft with a defined clearance between said shaft and said first sealing means, said shaft moveable axially in relation to said first sealing means; and   c. a second sealing means, said first sealing means partially encompassed within second sealing means and in cooperative communication with said second sealing means through a semi-spherical interface such that said first and second sealing means cooperate to respond to yaw and pitch misalignment of said shaft with respect to said shaft seal assembly while maintaining said defined clearance between said shaft and said first sealing means, wherein said second sealing means includes a pressure balancing annular channel formed therein.   
   
   
       15 . The shaft seal assembly as set forth in  claim 14  wherein said shaft seal assembly is further defined as including a sealing fluid introduced into said second sealing means to pressurize said shaft seal assembly.