Patent Publication Number: US-2013236297-A1

Title: Pump

Description:
This present invention relates to a pump, in particular a canned motor pump, to deliver liquids in water carrying domestic appliances or such like which comprises a stator, a rotor and a drive shaft non-rotatably coupled to an impeller disposed in a pump compartment which is rotatably arranged inside a motor casing via bearing means wherein seal means are fitted on a first face end of the casing to seal said casing against the pump compartment. 
     Prior known from DE 38 23 461 A1 is a pump for water carrying domestic appliances which comprises a motor casing with integrated stator and rotor on the one hand and an impeller arranged outside said casing on the other hand. The impeller shaft is firmly connected to a motor drive shaft which latter is via friction bearings arranged inside the motor casing. A packing type special shaft seal fitted to an end shield of the motor casing is provided on a first face end of the motor casing to seal the motor casing off against a pump compartment that is housing the impeller. 
     DE 93 02 945 U1 is disclosing a pump having an electric motor and an impeller fixed to a drive shaft thereof wherein a rotor of the electric motor is disposed inside a can (motor casing). The drive shaft is in sliding arrangement via bearing bushes in the area of a first and second face end of the can. A sealing collar is fitted to the first face end end of the motor casing to seal off said latter against a pump compartment housing the impeller. The bearing bushes need to be retained in a separate bearing support. A drawback affecting this prior art pump resides in that the extent of assembly work is relatively large within the area of the first face end of the motor casing that is facing the pump compartment. 
     It is an object of this present invention, therefore, to improve a pump comprising a drive shaft disposed inside a motor casing and an impeller non-rotatably connected to said drive shaft in such a way that the extent of assembly work needed to arrange the drive shaft and to seal off the motor casing against the pump compartment is simply being reduced. 
     To achieve this object the invention is in conjunction with the generic clause of Patent claim  1  characterized in that the bearing and seal means disposed on the first face end of the motor casing are integrated into a seal-bearing combination which comprises an axial bushing section for sliding arrangement on the drive shaft, a radial closing section to cover up the motor casing and at least one flexible seal element formed to said axial bushing section and/or said radial closing section. 
     The invention provides for a one-part seal-bearing combination which serves both to support the drive shaft and to seal off the motor casing against a pump compartment. The one-part seal-bearing combination hence provides in combination a number of sealing and bearing functions other than the multi- component solution that has been adopted in the art so far. This affords the advantage that the extent of assembly work and/or assembly time can be reduced. 
     According to a preferred embodiment of the invention is the seal-bearing combination provided with a radial closing section to the radial outer marginal edge of which a motor casing seal element is formed. This helps to ensure dependable sealing action between motor casing and pump compartment. The motor casing seal element adjoins the closing section in radial direction and is preferably annular and of relatively small radial thickness. This affords the advantage that it takes a relatively small quantity of material to provide a seal. 
     Another preferred embodiment of this present invention provides for the seal-bearing combination to have an axial bushing section to the axial end of which a shaft seal element is formed. Said shaft seal element is substantially an axial extension of the bushing section and permits to achieve compact sealing of the motor casing in the area of the drive shaft. 
     According to the invention the closing section and/or the bushing section is intended to serve as a carrier for seal means which are disposed close to and distant from the centerline to achieve relative compactness. The seal near the centerline (shaft seal element) and the seal means distant therefrom (motor casing seal element) are not direct connected, but just linked to each other via a disk of the closing section to form a one-piece unit. 
     A modification of this present invention provides for the motor casing seal to be spray bonded to the bushing section and/or the closing section of the seal-bearing combination. This permits seal means to be fitted to a bearing in precise positions by easy methods. 
     Other advantages of this invention are as disclosed in the further subclaims. 
    
    
     
       One exemplary embodiment of the invention will now be described in closer detail with reference to the accompanying drawings. 
       In these drawings: 
         FIG. 1  is an axial section through a canned motor pump comprising an electric motor and 
         FIG. 2  is a larger-scale axial section of a seal-bearing combination disposed in the area of the first face end of the motor casing that is facing the pump compartment. 
     
    
    
     A pump according to an exemplary embodiment of this present invention as shown in the Figures is a canned motor pump  1  which can be preferably used in water carrying domestic appliances such as a dishwasher or such like. 
     The motor casing of said pump  1  is a can  2  within which a rotor  3  of a synchronous motor and a drive shaft non-rotatably connected to said rotor  3  are arranged. A not-shown stator of the synchronous motor may be disposed outside said can  2 . 
     The drive shaft  4  is non-rotatably connected to a pump impeller  6  that is arranged in a pump compartment  5 . Alternatively it is possible also to have the drive shaft  4  coupled to the pump impeller  6  in a free-wheel or rotational backlash mode. 
     A seal-bearing combination  8  having a bearing and sealing function is arranged in the area of a first face end  7  of the can  2  that is facing the pump compartment  5 . As will be seen more clearly from  FIG. 2 , the one-part seal-bearing combination  8  has an axial bushing section section  9  for sliding arrangement of the drive shaft  4 . This bushing section  9  is made of the same material as another bushing section  10  that is integral with the can  2  and by means of which the drive shaft  4  is slidingly arranged on said can  2  in the area of a second face end  11  thereof. 
     The seal-bearing combination  8  moreover has a radial closing section  12  to cover up an opening of the can  2 . This closing section  12  is integral with the bushing section  9  which it adjoins in a radially outward direction. Closing section  12  and bushing section  9  are made of an identical plastic material. The can  2  also preferably consists of that same material as said sections  9  and  12 . 
     Bushing section  9  and the further bushing section  10  provide a bearing means for the drive shaft  4  to be rotatably arranged in the motor casing (can  2 ). Said closing section  12  extending in radial direction of the seal-bearing combination  8  has a disk  13  from which a first lock ring  14  protrudes on a side facing the motor casing  2 . Said first lock ring  14  serves to keep the seal-bearing combination  8  to the motor casing and/or can  2  and is coaxial with the drive shaft  4  and/or with an axis A of the can  2 . The outer surface of the first lock ring  14  is in full contact with an offset  15  of can  2 . 
     A second lock ring  16  protrudes from the side of the disk  13  facing the impeller  6  from which a shoulder ring  17  of the impeller  6  extends to form a labyrinth seal. This prevents undesirable ingress of threads and such like to the drive shaft  4 . Said second lock ring  16  is coaxial with the can  2  and/or the impeller  6 . 
     The seal-bearing combination  8  is also provided with a flexible seal element  18  arranged distant from the centerline as well as a flexible seal element  19  close to it. 
     The seal element  18  distant from the centerline is a motor casing seal element formed to a radial outer marginal edge  20  of the closing section  12 . The circular motor casing seal  18  is angular and comprises a first leg  21  that extends from a periphery  22  of said radial outer marginal edge  20  of the closing section  12 . This substantially provides sealing action in radial direction. 
     The motor casing seal  18  is moreover provided with a second leg  23  that extends from a radial surface  24  of the radial outer marginal edge  20  of the closing section  12 , i.e. preferably on the side of the disk  13  that is facing the impeller  6 . This provides sealing action in axial direction. 
     The sealing element  19  close to the centerline is a shaft seal formed to an axial end of the bushing section  10  preferably on a side of said bushing section  9  that is facing the impeller  6 . It serves to align the can  2  relative to the pump compartment  5  in the area of the drive shaft  4 . 
     Motor casing seal  18  and shaft seal  19  are joined to the closing section  12  and/or the bushing section  9  of the seal-bearing combination  8  by spray bonding. These seal means consist of identical elastic material, in particular an elastomer. 
     Motor casing seal  18  and shaft seal  19  are separated from each other and substantially extend within a radial plane E along which the disk  13  of the closing section  12  is disposed. 
     Both the motor casing seal  18  and the shaft seal  19  are of annular shape. 
     Closing section  12  and bushing section  9  are made of a rigid plastic material which is suitable for the drive shaft  4  to be arranged in. 
     It goes without saying that the seal-bearing combination  8  is adapted for use in other types of pumps also. 
     The seal-bearing combination  8  is substantially for a bearing and a sealing function, but may also perform a closing and/or joining function which in this present exemplary embodiment is achieved by forming the lock rings  14  and  16 .