Pumps with Improved Drive Shaft/Casing Seals

Abstract

A pump includes a drive shaft linked to a motor. The drive shaft passes through a seal assembly before passing into the pump chamber. The seal includes an outer seal housing that accommodates a lip seal. A portion of the drive shaft that passes through the seal assembly is coated with PTFE to prolong the working life of the seal assembly.

What is claimed is: 
     
         1 . A pump comprising:
 a casing accommodating a seal assembly and a drive shaft;   the drive shaft passing through the casing and through the seal assembly;   the seal assembly includes a resilient annular seal member that sealingly engages the drive shaft; and   at least a portion of the drive shaft that passes through the seal assembly being coated with PTFE.   
     
     
         2 . The pump of  claim 1  wherein the PTFE coating has a thickness ranging from about 0.45 to about 0.75 mils. 
     
     
         3 . The pump of  claim 1  wherein the seal assembly further includes an annular seal casing that surrounds the resilient annular seal member that engages the PTFE coating on the drive shaft. 
     
     
         4 . The pump of  claim 3  wherein the resilient annular seal member is a lip seal. 
     
     
         5 . The pump of  claim 1  wherein the resilient annular seal member is fabricated from a material selected from the group consisting of:
 a copolymer of hexafluoropropylene (HFP) and vinylidene fluoride; a terpolymer of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP); perfluoromethylvinylether (PMVE); a nitrile rubber, a polyethylene propylene, a fluoro rubber, a silicone rubber, a urethane rubber, a natural rubber, ethylenetetrafluoroethylene (ETFE), a polyamide and a perfluoroelastomer. 
 
     
     
         6 . The pump of  claim 1  wherein the seal assembly comprises an annular seal casing that surrounds the resilient annular seal member that engages the PTFE coating on the drive shaft, the resilient annular seal member being fabricated from at least one fluoroelastomer. 
     
     
         7 . The pump of  claim 1  wherein the resilient annular seal member is a lip seal. 
     
     
         8 . The pump of  claim 7  wherein the lip seal includes two lip members. 
     
     
         9 . The pump of  claim 7  wherein the lip seal includes three lip members. 
     
     
         10 . A drive shaft for a pump, comprising:
 a shaft body having an inboard end, an outboard end and an outer surface;   at least a portion of the outer surface of a shaft body being coated with PTFE.   
     
     
         11 . The drive shaft of  claim 10  wherein the portion of the drive shaft that is coated with PTFE extends from the inboard end of the drive shaft partially towards the outboard end of the drive shaft. 
     
     
         12 . The drive shaft of  claim 10  wherein the PTFE coating has a thickness ranging from about 0.45 to about 0.75 mils. 
     
     
         13 . A method for pumping trans-fat free cooking oils, the method comprising:
 providing a pump including a casing that accommodates a seal assembly and a drive shaft, the drive shaft passing through the casing and through the seal assembly before being coupled to a rotor, the rotor being enmeshed with an idler, the seal assembly including a resilient annular seal member, and at least a portion of the drive shaft that passes through the seal assembly being coated with PTFE;   engaging the portion of the drive shaft that is coated with PTFE with the resilient annular seal member; and   rotating the drive shaft and PTFE as the PTFE engages the resilient annular seal member.   
     
     
         14 . The method of  claim 13  wherein the PTFE coating has a thickness ranging from about 0.45 to about 0.75 mils. 
     
     
         15 . The method of  claim 13  wherein the resilient annular seal member is fabricated from a material selected from the group consisting of:
 a copolymer of hexafluoropropylene (HFP) and vinylidene fluoride; a terpolymer of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP); perfluoromethylvinylether (PMVE); a nitrile rubber, a polyethylene propylene, a fluoro rubber, a silicone rubber, a urethane rubber, a natural rubber, ethylenetetrafluoroethylene (ETFE), a polyamide and a perfluoroelastomer. 
 
     
     
         16 . The method of  claim 13  wherein the seal assembly comprises an annular seal casing the surrounds the resilient annular seal member. 
     
     
         17 . The method of  claim 13  wherein the resilient annular seal member is fabricated from at least one fluoroelastomer. 
     
     
         18 . The method of  claim 13  wherein the resilient annular seal member is a lip seal. 
     
     
         19 . The method of  claim 18  wherein the lip seal includes two lip members. 
     
     
         20 . The method of  claim 18  wherein the lip seal includes three lip members.