Abstract:
An improved pump for washing machines provides resistance to roping of filamentary materials through the use of a single vane impeller. A combination of high clearance and elastomeric vane and asymmetry of the impeller serve to prevent or reduce clogging caused by filamentary materials.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       FIELD OF THE INVENTION  
         [0001]    The present invention relates to centrifugal pumps for pumping liquids containing solids and in particular to a pump suited for use with clothes washing machines wherein long fiber solids may be encountered.  
         BACKGROUND OF THE INVENTION  
         [0002]    Pumps are used in washing machines to provide water pressure to transfer water through the machine during washing and to empty the machine after use. Dirt, extracted from the clothes, passes through the pump, as does larger debris released from the clothes including items contained in the pockets of the clothes such as toothpicks, paper clips, golf tees, coins, nails, screws and including loose clothing elements such as safety pins and buttons. With high efficiency washing machines, the relative concentration of such debris and dirt increases.  
           [0003]    To some degree, passage of these large objects may be provided by increasing pump clearance. Alternatively, a filter may be placed in the water path, however, such filters must be cleaned regularly and can lead to service calls when the filter clogs by a consumer who may be unaware of the filter. A particular problem is long fiber solids such as strings, laces and threads that may entangle the pump rotor or which may “rope” within the pump stopping or greatly reducing fluid flow.  
         BRIEF SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an asymmetric, single-vane centrifugal pump, which has proven to significantly decrease roping so as to pass long fiber solids as well as compact debris.  
           [0005]    Specifically, the present invention is a pump for a clothes washing machine of a type having a chamber for containing water and clothes, a chamber having an outlet so that the pump may pump water from the chamber between the inlet and outlet. The pump includes an electric motor having a shaft and a pump housing having a housing inlet connectable to the chamber outlet. The housing provides a pump volume receiving the motor shaft along an axis. A single vane impeller fitting within the pump volume and attached to the motor shaft may drive water from the housing inlet to the housing outlet with rotation of the motor shaft.  
           [0006]    Thus it is one object of the invention to permit the pumping of long fiber solids in a washing machine with reduced risk of clogging.  
           [0007]    The vane may subtend an angle of less than 270° about an axis concentric with the motor shaft. Further, an edge of the vane closest to the motor shaft may be displaced radially from the motor shaft.  
           [0008]    Thus it is another object of the invention to provide a vane construction that is believed to break up static vortices such as may promote roping and clogging by long fiber materials.  
           [0009]    The vane may extend, in part, radially from an axis concentric with the motor shaft and a lip of the vane may taper at an end of the vane toward the motor shaft.  
           [0010]    Thus it is another object of the invention to reduce points of entanglement with long fiber materials.  
           [0011]    The vane may be constructed of an elastomeric material.  
           [0012]    Thus it is another object of the invention to provide a vane that is resistant to impacts of entrained objects and to being jammed by materials lodged between the impeller and volute of the pump.  
           [0013]    The impeller may project axially from a front surface of a backing disk extending radially from the motor shaft. The pump volume may be substantially cylindrical and the disk may extend to the cylindrical wall of the pump volume. Further, the pump housing may include a stationary vane extending radially and axially adjacent to a rear surface of the backing disk.  
           [0014]    Thus it is another object of the invention to provide a design that resists the drawing in entanglement of fibers about the motor shaft. The stationary vane prevents the rotation of water such as might pull material behind the backer plate while the backer plate blocks the material generally.  
           [0015]    The backing disk may include a counter weight balancing the backer disk and vane.  
           [0016]    Thus it is another object of the invention to provide for smooth operation of the asymmetric vane design of the present invention.  
           [0017]    The foregoing objects and advantages may not apply to all embodiments of the inventions and are not intended to define the scope of the invention, for which purpose claims are provided. In the following description, reference is made to the accompanying drawings, which form a part hereof, and in which there is shown by way of illustration, a preferred embodiment of the invention. Such embodiment also does not define the scope of the invention and reference must be made therefore to the claims for this purpose. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    [0018]FIG. 1 is a perspective phantom view of a front-loading washing machine showing location of a pump of the present invention for pumping water from a washing tub;  
         [0019]    [0019]FIG. 2 is a rotated perspective view of the pump of FIG. 1 showing the pump housing and rear positioned motor;  
         [0020]    [0020]FIG. 3 is an exploded view in partial fragment of the housing of FIG. 2 showing further an internal impeller as positioned with respect to the inlet and outlet of the pump;  
         [0021]    [0021]FIG. 4 is a side elevational view in cross-section of the assembled housing and impeller; and  
         [0022]    [0022]FIG. 5 is a front elevational view of the impeller of FIGS. 3 and 4 with the housing in phantom, showing the position of the single vane of the impeller. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring now to FIG. 1, a washing machine  10  may include a housing  12  supporting contained tub  14 , the latter opening to allow the insertion of clothes into the tub  14  and closable by a door  16  to seal the tub  14  against the loss of clothes and water during the washing process. A pump  18  may be positioned within the housing  12  to receive from a tub outlet  20  washwater, as communicated through a hose  22  to a pump inlet  24  of the pump  18 . The pump  18 , in turn, pumps the washwater out of pump outlet  26  through a hose  28  to a discharge pipe  30 .  
         [0024]    Referring now to FIG. 2, the pump  18  includes a hollow cylindrical pump housing  32  having a substantially flat front face  31  and a cup-shaped rear face  33 , concave to the interior of the housing  32 . A pump inlet  24  is axially attached to the front face  31  and is a pipe whose internal passageway communicates with the hollow interior of the pump housing  32 . Attached along a tangent of the outer rim of the pump housing  32  is pump outlet  26  also a pipe whose internal passageway communicates with the hollow interior of the pump housing  32 . Referring momentarily to FIG. 5, the pump outlet  26 , the attachment of the pump outlet to the pump housing  32  is done so that the interiors of both together approximate an involute well known in the art of pump design.  
         [0025]    Referring to FIGS. 2 and 3, a motor  34  providing an axial motor shaft  40  attaches to a cup-shaped rear face  33  of the pump housing  32  so that the motor shaft  40  may pass centrally therethrough. The housing  32  and the motor  43  are joined and supported by a mounting flange  37  used to affix the pump  18  to the interior of the housing  12  (shown in FIG. 1). The motor  34  may be a standard shaded pole motor.  
         [0026]    Referring now to FIGS. 3 and 4, the motor shaft  40 , after passing through the cup-shaped rear face  33  of the pump housing  32  is received by a mounting flange  56  centered on a rear face of a disk-shaped backer plate  44 . The backer plate  44  is an integral part of an impeller assembly  46  having a single vane  50  extending axially from the front face of the backer plate  44 . The backer plate  44  is approximately equal in diameter to that of the inner volume of the pump housing  32  and extends perpendicularly from the axis of the shaft  40  so as to isolate at its front surface, a pump volume  52  within the inner volume of the pump housing  32 . By the same measure, the backer plate  44  serves to isolate a rear volume  54  within the pump housing  32  and the cup-shaped rear face  33  providing a space for the motor shaft  40  and an attaching mounting flange  56 .  
         [0027]    Within the rear volume  54 , a stationary vane  58  attached to an inner wall of the cup-shaped rear face  33  extends axially and radially toward the shaft  40  to obstruct the circular flow of water within the rear volume  54 . This together with the close fitting of the backer plate  44  to the walls of the housing  32  reduces the tendency of filamentary materials to be drawn into the rear volume  54  to become entangled in the shaft  40 .  
         [0028]    Referring still to FIGS. 3 and 4, on the front surface of the backer plate  44  the single vane  50  extends both axially toward the pump inlet  24  and also from a periphery of the backer plate  44  toward, but not to, its center. Over most of this latter extension, the vane  50  extends axially to a uniform height above the backer plate  44 , however, at its portion closest to the center of the backer plate  44 , the vane  50  tapers downward toward the front surface of the backer plate  44  as shown best in FIG. 4.  
         [0029]    Referring now to FIG. 5, the vane  50  is curved to present a convex surface as it advances with operation of the motor as indicated by direction arrow  53 . The outlet  26  is directed tangentially to this rotation of the impeller assembly  46  to receive water accelerated by the vane  50 .  
         [0030]    The single vane  50  is positioned substantially on one-half of the front surface of the backer plate  44  so that its axial ridge  51  subtends from the center  60  of the backer plate  44 , an angle α less than 180° and the entire vane  50  is contained within a subtended angle of less than 270°. The edge of the vane  50  closest to the center  60  of the backer plate  44  is displaced from the center  60  of the backer plate  44 .  
         [0031]    While the inventors do not wish to be bound to a particular theory, it is believed that this vane configuration destabilizes a central vortex in region  62  so as to prevent prolonged retention of fibrous materials in that vortex in region  62  such as may cause roping and eventual clogging of the pump. As may be seen best in FIG. 4, the housing  32  may have a height substantially higher than the vane  50  so as to provide adequate clearance for objects to be pumped through the pump without clogging the impeller assembly  46 .  
         [0032]    The impeller assembly  46  may be constructed of a flexible elastomeric material so as to better resist impact with solid objects pumped in the wash water. The impeller assembly  46  may be statically or dynamically balanced for a particular speed by means of a counter weight of additional material  63  molded into the rear portion of the backer plate  44  of a size and location as will be understood to those of ordinary skill in the art.  
         [0033]    It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but that modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments also be included as come within the scope of the following claims.