Abstract:
A seal assembly including a rotatable seal head subassembly also includes a fan that rotates with the seal head assembly, with the fan drawing air through a pump housing for purposes of cooling.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority from U.S. Provisional Application No. 60/381,968, filed May 20, 2002. 

   BACKGROUND OF THE INVENTION 
   This invention relates in general to seals for rotating shafts. In particular, this invention relates to a shaft seal having a fan cooled seal seat. 
   An automatic dishwasher includes a pump for discharging wash water from an interior of the appliance. The pump includes a motor having a rotatable shaft that is connected to a pump impeller. A mechanical face seal is used to provide a seal about the rotatable shaft at the point where it extends from a pump housing. The pump housing, face seal, and motor are subject to heat due to friction. Extended exposure to heat can cause failures of the housing, face seal, and/or motor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a sectional view of a mechanical face seal assembly having a compressor and an impeller according to this invention, wherein the seal assembly is illustrated mounted on a shaft of a dishwasher pump. 
       FIG. 2  is a sectional view taken along line  2 — 2  of  FIG. 1 . 
       FIG. 3  is a perspective view of the assembled compressor and impeller of  FIG. 1  removed from the remainder of the seal assembly for clarity of illustration. 
       FIG. 4  is an end view of the compressor illustrated in FIGS.  1 — 3  removed from the remainder of the seal assembly. 
       FIG. 5  is a sectional view taken along line  5 — 5  of  FIG. 4 . 
       FIG. 6  is a sectional view taken along line  6 — 6  of  FIG. 5 . 
       FIG. 7  is an enlarged view of a portion of the compressor found in circle  7  of  FIG. 5 . 
       FIG. 8  is a perspective view of the compressor of  FIGS. 4–6 . 
       FIG. 9  is a bottom end view of the impeller of  FIGS. 1–3  removed from the remainder of the seal assembly. 
       FIG. 10  is a sectional view taken along line  10 — 10  of  FIG. 9 . 
       FIG. 11  is a sectional view taken along line  11 — 11  of  FIG. 9  that has been rotated. 
       FIG. 12  is a top end view of the impeller of  FIGS. 9–11 . 
       FIG. 13  is a perspective view of the impeller of  FIGS. 9–12 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   A mechanical face seal assembly is indicated generally at  10  in  FIG. 1 . The seal assembly  10  is shown mounted on a rotatable shaft  12  of a pump motor  14 . A terminating end of the shaft  12  is secured to a pump impeller  16 , which is mounted inside a pump housing  18 . One application of the seal assembly  10 , shaft  12 , pump motor  14 , pump impeller  16 , and pump housing  18  is a dishwasher. 
   The seal assembly  10  includes a seal head subassembly  20  that is mounted on and rotates with the shaft  12 . The seal head subassembly  20  includes a case  22  and a spring seat  24  that are received within a cavity of a boot  26 . An annular insert  28  is provided at a terminating end of the boot  26 . One end of a spring  30  is placed against the spring seat  24 . An opposite end of the spring  30  is placed against a washer  32  that fits in an annular groove of a seal washer  34 . 
   The seal washer  34  engages a stationary seal seat  40 . The spring  30  provides a force to maintain the engagement of the seal washer  34  with the seal seat  40 . The seal seat  40  is placed against a grommet  42  that is placed against the pump housing  18 . 
   The seal assembly  10  also includes a fan subassembly  50 , illustrated separately in  FIG. 3 . As the fan subassembly  50  rotates with the shaft  12  and seal head subassembly  20 , air is drawn from outside the pump housing  18 , flows past the seal washer  34  and the seal seat  40 , and is expelled through an outlet in the pump housing  18 . Arrows in  FIG. 1  indicate the flow of air. This circulating air provides a cooling effect to the seal seat  40 , seal washer  34 , and the pump housing  18 . This cooling effect can extend the effective life of the seal assembly  10  and the associated pump. 
   The fan subassembly  50  includes a compressor  60 , illustrated separately in  FIGS. 4–8 , and an impeller  70 , illustrated separately in  FIGS. 9–13 . The compressor  60  includes a longitudinal tube portion  61  having a first end  62  that fits into the spring seat  24 . An outer profile  63  (see  FIG. 7 ) is formed on an outer wall of the first end  62  that is complementary to an annular groove formed in the spring seat  24 . A second end  64  of the compressor  60  includes a plurality of vanes  65 . Preferably, the vanes  65  are formed as spiral segments that can capture air and force it toward the first end  62 . Intake openings  66  are provided at an originating point of each vane  65  into which air is drawn. The tube portion  61  is slip fitted onto the shaft  12  so that the compressor  60  rotates with the shaft  12 . 
   The impeller  70  includes a collar portion  71  having a first end  72  and a second end  73 . A rim  74  can be formed at the second end  73 . Along an inner circumferential wall  75  of the collar portion  71 , a plurality of axial vanes  76  is provided. In the embodiment of  FIGS. 9–13 , four vanes  76  are divided into two pairs. Each pair of vanes  76  includes a bridge  77  that is provided at the intake side of each vane  76 . As seen best in  FIG. 9 , arcuate openings  78  are provided between each bridge  77 . The bridges  77 , openings  78 , and vanes  76  enhance the flow of air along the tube portion  61  of the compressor  60 . Along an outer circumferential wall  79  of the collar portion  71 , a plurality of axial vanes  80  are provide that enhance the exit of air from inside the pump housing  18 . Exit channels or air outlets  81  are formed between the vanes  80 . 
   As illustrated in  FIG. 1 , the rim  74  of the impeller  70  is placed at an exterior point of the pump housing  18 . The intake openings  66  of the compressor  60  are provided beyond the rim  74  away from the pump housing  18 . In this manner, the intake openings  66  and air outlets  81  permit air from outside the pump housing  18  to cool an interior portion of the pump housing  18 . 
   In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.