Patent Publication Number: US-2007107475-A1

Title: Integrated Washing Machine Pump

Description:
CROSS-REFERENCE AND INCORPORATION BY REFERENCE  
      This application claims the benefit of U.S. provisional patent application Ser. No. 60/742,855, entitled “Integrated Washing Machine Pump” filed on Dec. 6, 2005, which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION  
      This invention relates to clothes washing machines and in particular drain or recirculating pumps for such machines.  
     BACKGROUND TO THE INVENTION  
      Clothes washing machines require a pump to drain the machine bowl of both wash and rinse water. In machines where wash water is recirculated a pump is required for this purpose also. Hitherto such pumps have taken the form of discrete components mounted outside the washing machine bowl and connected thereto by means of ducts and hoses.  
      The use of discrete component pumps in washing machines gives rise to the risk of water leakage because of the number of joints required between ducts, hoses and pumps and hose deterioration.  
     SUMMARY OF THE INVENTION  
      It is an object of the present invention to provide an integrated washing machine and pump structure which will at least reduce the abovementioned disadvantage.  
      Accordingly in one aspect the invention consists in:  
      a clothes washing machine comprising:  
      a stationary watertight outer bowl which in use may selectively contain wash or rinse liquid,  
      a perforated tub which receives the clothes load mounted within said outer bowl,  
      means for selectively agitating or spinning the clothes load within said perforated tub,  
      a rotary pump for pumping wash water or rinse water from said outer bowl, said pump having:  
      a housing integrally formed in the wall of said outer bowl,  
      a motor rotor rotatably mounted within said housing,  
      an impeller mounted within said housing and connected to said rotor,  
      said housing being open to the interior of said outer bowl to provide an inlet to said pump,  
      and a motor stator being mounted about the exterior surface of said housing in co-acting relationship with said rotor such that the housing wall lies between said rotor and said stator.  
      In a second aspect the invention consists in:  
      a clothes washing machine comprising:  
      a stationary outer bowl which in use may selectively contain wash or rinse liquid,  
      said outer bowl having an aperture in the bottom,  
      a perforated tub which receives the clothes load mounted within said outer bowl,  
      means for selectively agitating or spinning the clothes load within said perforated tub,  
      a rotary pump for pumping wash water or rinse water from said outer bowl, said pump having:  
      a housing which is sealably mounted within said aperture in said outer bowl to be integral with said outer bowl,  
      a motor rotor rotatably mounted within said housing,  
      an impeller mounted within said housing and connected to said rotor,  
      said housing being open to the interior of said outer bowl to provide an inlet to said pump,  
      and a motor stator being mounted about the exterior surface of said housing in co-acting relationship with said rotor such that the housing wall lies between said rotor and said stator.  
      In a third aspect the invention consists in:  
      a pump for a clothes washing machine having a water containing outer bowl which drains and/or recirculates liquid in said bowl, said bowl having an aperture in the bottom and said pump having a housing which includes an electric motor, comprising:  
      a housing adapted to be sealably mounted within an aperture in said outer bowl,  
      an electric motor rotor rotatably mounted within said housing,  
      an impeller mounted within said housing and connected to said rotor,  
      said housing in use being open to the interior of said outer bowl to provide an inlet to said pump,  
      and a motor stator being mounted about the exterior surface of said housing in co-acting relationship with said rotor such that the housing wall lies between said rotor and said stator.  
      Preferably said rotor includes a drive shaft and said impeller is mounted on said drive shaft.  
      Preferably a transverse partition is mounted in said housing which separates said rotor and said impeller into separate compartments and which supports a waterproof bearing in a central aperture through which said drive shaft passes and is journalled.  
      Preferably said impeller is mounted within said housing proximate to said outer bowl and said rotor is mounted in said housing distal to said outer bowl.  
      Preferably said partition has a small aperture therein to allow wash liquid to enter said rotor compartment and to vent pneumatic pressure in said compartment when hot.  
      Preferably a filter is mounted in said aperture to prevent foreign objects from entering said rotor compartment  
      Preferably said distal portion of said housing has a cylindrical wall and said cylindrical wall lies between said stator and said rotor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Preferred embodiments of the invention will now be described with reference to the accompanying drawings in which:  
       FIG. 1  diagrammatically shows a first embodiment of a drain/recirculating pump integrated with a washing machine bowl,  
       FIG. 2  shows a second embodiment of a drain/recirculating pump integrated with a washing machine bowl  
       FIG. 3  shows an enlarged view of detail A in  FIG. 2 ,  
       FIG. 4  shows an exploded pictorial view of a drain/recirculating pump to be integrated with a washing machine bowl  
       FIG. 5  shows a cross-section through the pump of  FIG. 4 .  
    
    
     DETAIILED DESCRIPTION  
      The essence of the present invention is the integration of a drain/recirculation pump (preferably a centrifugal pump) with a washing machine bowl, thereby reducing the number of water connections outside the watertight bowl. One embodiment of the invention is illustrated diagrammatically in  FIG. 1 .  
      A washing machine outer bowl  1  has a floor  2  into which is moulded a cylindrical recess  3  which forms part of the drain/recirculation pump housing. In particular a cylindrical recess  3  forms the lower portion of the pump housing and houses a rotor  4  of an electric motor (generally indicated as  5 ). The motor stator  6  is mounted exteriorally of the washing machine bowl  2  about the cylindrical wall  14  of recess  3  so as to be co-axial and co-planar with rotor  4 . The wall of the pump housing, which forms part of the outer bowl lies in the motor air gap. Motor  5  is preferably a brushless dc motor with the windings of stator  6  commutated electronically.  
      Rotor  4  carries a drive shaft  7  which is connected to a pump impeller  8  which in turn is contained within the upper portion  9  of the pump housing. The pump housing  9  has an inlet  10  in the form of an opening to the interior of outer bowl  1  through which wash and rinse water may flow to be pressurised by impeller  8 .  
      The pump outlet duct  11  extends from pump housing  9  within the outer bowl and terminates at a connector  12  to which a flexible hose  13  may be connected to convey drain water external to the bowl. A recirculating outlet (not shown) feeds a pipe contained within the bowl, configured so as to discharge onto the clothes load.  
      Exemplifying an advantage of the invention, in this embodiment it can be seen that there is only one potential leak path and that is at connection  12 . Since that is located inside the bowl then if the joint leaks the leakage remains within the watertight bowl  1 . Some advantage could be achieved by putting the pump inside the outer bowl and the entire drive motor outside it. However, by also putting the rotor of the pump motor within the outer bowl the need for an aperture in the outer bowl and a dynamic shaft seal, with associated potential for leakage, is avoided.  
      A more easily fabricated embodiment will now be described with reference to FIGS.  2  to  5 . Here the pump  19  is a separate part which is integrated with base  21  of a washing machine outer bowl  20  (see  FIGS. 2 and 3 ). The bowl is plastics moulded and is of the type disclosed in U.S. Pat. No. 4,813,248. Within base  21  at a suitable drain point near a side wall of the bowl there is moulded a drain sump and in the floor of the sump a flanged aperture  22  is provided. In the preferred form this is elliptical. Pump  19  is mounted in this aperture  22  and when mounted completely closes it off.  
      Referring in particular to  FIGS. 4 and 5 , the pump housing comprises a proximate portion  26  which houses a pump impeller  27  and a distal portion  28  which houses a rotor  29  of an electric motor  64  powering the pump. In the particular arrangement shown the housing connects to the bowl base with its axis substantially vertical. With this orientation the distal portion  28  of the housing is lower than the proximate portion which contains the impeller. The lower portion  28  of the pump housing is cylindrical and closed off at the bottom with an integrally moulded floor section  30 . The flange  48  of the pump housing  25  fits about the flange of the bowl aperture  22 . A static sealing ring  50  which fits around the periphery of housing cap  42  seals the pump housing within the bowl aperture. The housing is fastened to the outer bowl by screws passing through lugs  47  provided about flange  48  of the upper portion  26  of the housing.  
      The pump is of the centrifugal type with impeller  27  configured so as to be capable of pumping when driven in either a clockwise or an anti-clockwise direction. The electric drive motor  64  is of the brushless permanent magnet DC type. The permanent magnet rotor  29  is rotatably mounted within the lower portion  28  of the pump housing. Rotor  29 , which in the preferred embodiment may run wet (see below), rotates on a drive shaft  31  which connects to impeller  27 . A partition member  33  (see in particular  FIG. 5 ) separates the upper and lower portions of the pump housing into an upper compartment  65  (containing the impeller) and a lower compartment  66  (containing the rotor) and provides a support for an upper bearing  34  within which drive shaft  31  is journalled. Partition  33  together with dynamic shaft seal prevents materials entrained in the machine wash or rinse water from entering the lower compartment  66  of the pump housing to thereby cause wear or jamming of the rotor. However a small aperture  60  is provided in partition member  33  to allow controlled water flow into the lower compartment of the pump housing. The presence of water assists in cooling and lubricating the rotor and bearings  61  and  34 . Aperture  60  is preferably provided with a filter (not shown) to exclude particulate matter or other foreign bodies from entering the motor rotor compartment  66 . Aperture  60  also vents pneumatic pressure in the rotor compartment when hot.  
      Rotor drive shaft  31  is also journalled in a lower bearing  61  which is supported in a cavity  62  in the floor  30  of the pump housing. The motor stator  35  is mounted on the exterior of the pump housing co-axially with the rotor and in the same principal plane as the rotor about the lower portion  28  of the pump housing. The cylindrical walls of the lower portion of the pump housing reside within the “air gap” between the rotor and stator. The stator may typically be of the salient pole type preferably having six poles  36 . The stator, being external to the pump housing, is in a dry environment notwithstanding the rotor part of the motor is contained within the pump housing and therefore in essence within the washing machine bowl. The stator is protected by a plastics cover  37  which has a removable base  38  held in place by screws  63 .  
      The stator  35  comprises substantially annular laminations of magnetic steel which are over moulded with a plastics case which also covers the integrally formed poles to provide plastic bobbins around which the windings  36  are wound. The pole tips are arcuate and lie on a circle of a diameter equal to the outer diameter of the cylindrical wall of the lower portion of the pump housing. The stator is clamped in place by base  38 .  
      The brushless DC motor preferably has a controller which uses the back EMF induced in an unused stator winding to provide the necessary rotor position sensing. Controllers of the type suitable for the present motor are disclosed in U.S. Pat. No. 6,034,493 and WO 2005/062460.  
      Instead of back EMF sensing of the rotor position other known techniques can be used such as Hall effect sensing.  
      In operation water pressurised by the centrifugal forces induced by rotation of impeller  27  leaves the upper portion of the pump housing through either outlet  40  to which is connected a drain hose or through outlet  39  into a recirculation duct (not shown) which guides the water back onto the top of the clothes load. Whether the water is drained or recirculated is determined by the direction in which impeller  27  is rotated. Mounted in association with impeller  27  is a bi-state flapper valve  41  which depending on the direction in which water leaves impeller  27  revolves between one of two states. In one state valve  41  seals off outlet  39  and water is directed to drain outlet  40  and in the other state water is directed to the recirculation outlet  39 .  
      It is necessary to direct water from drain sump  23  in an efficient manner into the pump housing while at the same time ensuring that foreign objects are prevented from entering the pump, and also minimising the potential for blockage by clothes lint. These objectives are met by the use of a top cap  42  in association with a complementary pump hood  43  which define the water inlet path to the pump. Water from the drain sump enters under the hood and over the top of the scalloped peripheral wall  44  of top cap  42  (which forms a first weir) and into the cap inlet aperture  45  defined by cylindrical wall  46  which forms a second weir.  
      A drain/recirculating pump integrated with a washing machine outer bowl in the manner disclosed ensures a water handling system with reduced leak paths external to the bowl.