Abstract:
An integrated boot, seal and impeller system is adapted for being driven by a pump shaft. The system includes an impeller unit having a plurality of radially extending blades, a hub portion, a recess in the hub portion and a tubular portion extending from the hub portion. The tubular portion is engaged to the shaft and has an outer diameter with at least one flat in the outer diameter. A seal head is slidingly engaged to the tubular portion. The seal head also has an inner diameter with at least one flat on the inner diameter to engage the outer diameter of the tubular portion. A flexible boot extends from the elastomeric blades. The boot has a distal portion adjacent to the seal head. Additionally, a biasing member is disposed in the recess and urges the seal head into engagement with the seal washer.

Description:
BACKGROUND OF THE INVENTION 
     This invention generally relates to pumps with impellers and in particular to an integrated elastomeric seal impeller and boot for use in a pump. 
     Water pumps with impellers are used in appliances, such as dishwashers and washing machines, to move liquid through and out of the appliance in a series of wash, rinse, and drain cycles. Typically, the pump includes a housing, a rigid cover, and an elastomeric impeller molded around a rigid impeller insert for slip fitting onto a rotatable drive shaft or motor shaft. A separate mechanical face seal assembly consisting of a seal head assembly and a seal seat for preventing liquid leakage between the fixed housing and the rotating impeller, and a two-piece thrust bearing, one half mounted in the impeller for running against the other half mounted in the rigid cover, are used. This thrust bearing resists the axial force of the mechanical face seal and also establishes the axial running clearances of the impeller with both the housing and the rigid cover. 
     The assembly of all these separate components can lead to mis-assembly and damage to critical sealing components. Some prior art pumps have used some pre-assembly of components to reduce handling and assembly time. However, these prior art pumps have not been widely adopted because of the cost of the additional pre-assembly. 
     Thus, there is a need to solve these problems and to provide a simple, more cost effective combination of a mechanical face seal boot and a pump impeller which integrates the boot with the impeller so that the biasing spring and seal seat are disposed within the pump impeller, thereby protecting these components from damage or contamination and reducing the number components, reducing cost, and reducing assembly time. 
     SUMMARY OF THE INVENTION 
     The present invention seeks to solve these problems by providing an integrated boot, seal and impeller system for use in a pump. 
     The present invention is directed to an integrated boot, seal and impeller system that is adapted for pumping fluid by a power shift. The system includes an impeller unit having a plurality of radially extending blades, a hub portion, a recess in the hub portion and a tubular portion extending from the hub portion. The tubular portion is engaged to the shaft and has an outer diameter with at least one flat in the outer diameter. A seal head is slidingly engaged to the tubular portion. The seal head also has an inner diameter with at least one flat on the inner diameter to engage the outer diameter of the tubular portion. A flexible boot extends from the elastomeric blades. The boot has a distal portion adjacent to the seal head. Additionally, a biasing member is disposed in the recess and urges the seal head into engagement with the seal washer. 
     It is an object of the present invention to provide an integrated boot, seal and impeller system for use in a water pump to protect the components from damage during the assembly process. 
     It is another object of the present invention to provide a simpler, more cost effective boot, seal and impeller construction which integrates the boot and impeller to reduce the number of components required and reduce assembly time. The present invention provides an integrated boot, seal and impeller. construction that is simpler and more cost effective, and which allows for pre-testing of the integrated boot, seal and impeller assembly for leakage prior to installation to the pump. 
     Still another object of the present invention is the elimination of the separate molding of a protective boot for the seal components thereby allowing for a simpler assembly of the seal for use in a pump. 
    
    
     These and other objects and features of the present invention will become apparent from the description and especially taken in conjunction with the accompanying drawings illustrating the invention and the preferred embodiment. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The various advantages of the present invention will become apparent to one skilled in the art upon reading the following specification and by reference to the drawings which include: 
     FIG. 1 is a cross-sectional view of the present invention as installed in the pump housing and cover; 
     FIG. 2 is a cross-sectional view of the impeller and seal ring assembled on the tubular portion; and 
     FIG. 3 is a cross-sectional view of the present invention rotated 90 degrees from FIG.  2  and showing the seal ring engaged to the tubular portion. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A water pump  100  is fitted with the integrated impeller seal and boot system  90  according to the present invention as shown in FIGS. 1 and 2. The system  90  is adapted to be used in a pump unit  5 . The pump unit  5  includes a cover  10 , a housing  80  having a generally U-shaped cross-section and an inlet  82  and outlet (not shown). The cover  10  is preferably welded to the housing  80 , however, it can be secured by any other appropriate means to the pump housing  80  to form a pump cavity  86  in which the unitized impeller, seal and boot system  90  operate. The system  90  includes an impeller  20  which has a rigid insert  30  with a tubular extension or portion  34 , a boot  40  and a seal washer  50 . The extension  34  is connected to a shaft  7  of a motor (not shown) to form a complete pump assembly. In the preferred embodiment, the motor is an electric motor but any other type of motor may be used. The motor shaft  7  is engaged to the tubular extension  34  by conventional means. The motor allows for rotational forces to be provided to the impeller  20  in order to pump a liquid for an appliance, such as a dishwasher, washing machine or the like. 
     A two-piece thrust bearing consisting of a graphite phenolic thrust button  13  mounted in a cavity  12  in the cover  10  and a ceramic thrust disk  14  mounted in a partial opening or cavity  23  in the face  22  of the impeller  20  establishes the axial running clearance  98  of the face  22  of the impeller  20  with both the housing  80  and the cover  10  and it also determines the axial running height of the mechanical face seal assembly  59 . 
     The elastomeric blade impeller  20  is molded onto or, alternatively, attached by conventional means to a rigid impeller insert  30 . The rigid insert  30  may be made of metal such as steel or aluminum or the like or preferably from a glass filled reinforced thermoplastic such as nylon  6 — 6  with 30% glass filled fiber. Alternatively, the rigid insert  30  may be made from a glass filled thermoset plastic polymer such as phenolic. The rigid insert  30  has a tubular extension  34  which extends axially from the inner portion of face  22  of the rigid insert  30  to the projecting end  31 . The outer diameter  37  of the tubular extension  34  has a pair of flats  38 , as shown in FIG.  3 . 
     Returning to FIGS. 1 and 2, the graphite phenolic thrust button  13  is inserted into a partial cavity  12  in the cover  10  and a ceramic thrust disk  14  mounted in a partial opening  23  in the face  22  of the impeller insert  30 . As stated earlier, the thrust button  13  sets the axial clearance  98  of the face  22  relative to the cover  10 . 
     The rigid impeller insert  30  has a radially extending portion  25  which is formed radially from the outer portion of the face  22 . An axially extending section  26  and a second radially extending section  19  extend from the radially extending portion  25 . A second axial projection  21  extends axially from the inner portion of the face  22  and radially between the radially extending portion  25  and the outer diameter  37  of the tubular extension  34 . 
     The blades  92  of the impeller  20  are preferably made of elastomeric material which permits the blades  92  to be bonded and molded onto the rigid impeller insert  30 . The elastomeric material is also molded and bonded around radially extending portion  19 , radially extending portion  25  and the axially extending section  26 . The elastomeric material is a polymer which is preferably nitrile or, alternatively, it may be hydrogenated nitrile or any other suitable thermoset or thermoplastic elastomeric material. A conventional bonding agent is used to bond the elastomeric material to the insert  30  and to radially extending portions  25 ,  19  and axially extending section  26 . When the elastomeric material is molded to the rigid impeller insert  30  and while the elastomer is still in a plastic state, the elastomer flows from the face  22  of the insert  30  through the holes  29  in portion  19  and around radially extending portion  19  and axially extending portion  26 , to form the blades  92  and the boot  40 . After the vulcanization process, an elastomeric portion  41  forms and extends axially and radially to form an elastomeric boot  40 . The boot  40  extends axially from the elastomeric portion  41  of the inner diameter of the axially extending section  26  and radially along the outside surface of the radially extending section  25  and the radially extending portion  19  of the impeller insert  30 . The boot  40  is integrally formed with the blades  92  and the elastomeric portion  41 . The axially extending distal end  42  is formed from the boot  40  and is adjacent to but spaced away from the outer diameter  37  of the tubular extension  34 . The distal end  42  is cantilevered from the axially extending section  26  and the radially extending portion  19  so as to form an open ended receiving cavity  46 . 
     The distal end  42  cooperates with a step  57  in an annular seal ring or washer  50  with the corresponding stepped portion  48  in the rubber boot  40 . The seal washer  50  is preferably made of ceramic material but, alternatively, it can be made of carbon, metal, or plastic, or any other suitable material. In forming the seal washer  50 , it may be cast, sintered, fired, or molded, as is conventional. 
     The seal washer  50  is disposed around the tubular extension  34  and is positioned axially adjacent to the seal seat  60 . The seal seat  60  has an outer diameter  62  with a pair of flats, preferably in opposing orientation. The outer diameter  62  of seal seat  60  is surrounded by a thin elastomeric annular layer  68 . The elastomeric layer  68  and the seal seat  60  are disposed in a partial bore in the shoulder  87  in the housing  80 . The partial bore has a pair of flats (not shown) which correspond to the pair of flats (not shown) in the seal seat  60 . The seal seat  60  and the annular layer  68  are pressed or inserted into the partial bore in the housing  80 . The press fit forms a compressive force on the elastomeric layer  68  which in turn puts a slight compressive force on the outer diameter  62  of the seal seat  60  to capture the seal seat  60  in the partial bore. The pair of flats in the seal seat  60  cooperatively engage the pair of flats in the housing  80  to prevent rotational movement of the seal seat  60  relative to the housing  80 . The seal seat  60  abuts against the shoulder  87 . 
     The spring  70  is a helical coil compression spring but, optionally, the spring  70  may be an elastomeric member that is compressed or a cantilevered biasing member. The spring  70  is disposed around the tubular extension  34  and one end abuts against the partial bore  24  in the impeller  20  and the other end abuts against the seal washer  50  to bias it into engagement with the seal seat  60 . The elastomeric boot  40  is made of the same polymer as the elastomeric blades  92   
     As shown in FIG. 3, the seal washer  50  is rotationally driven by flats  52  on its inside diameter  54  which engage corresponding flats  38  on the outer diameter  37  of the tubular extension  34 . Thus, the seal washer  50  is positively driven rotationally by the mechanical engagement of the flats  52  on the inner diameter  54  of the seal washer  50  with the corresponding flats  38  on the extension  34  of the impeller insert  30 . Those skilled in the art will recognize that the number of flats  52  on the seal washer  50  and the corresponding flats  38  of the tubular extension  34  are shown to be two but may optionally vary between one and eight. As a result, the present invention does not rely on the elastomeric friction and bias forces between the seal washer  50  and the boot  40  to engage the stepped diameter portion  48  with the stepped portion  57  and to rotationally drive the seal washer  50  but does so in a secondary capacity until substantial wear occurs between the flats  38 ,  52  permitting movement between them. Preferably, there is a slight gap between the flats  52  and the flats  38 . 
     Returning to FIG. 1, the pump front cover  10  and pump housing  80  are preferably made of thermoplastic material such as polypropylene, nylon, or polyvinyl chloride or the like so that the cover  10  can be hot plate or ultrasonically welded to the pump housing  80  as is conventional. The seal seat  60  is press-fit into the partial bore and against the shoulder  87  of the pump housing  80  and is prevented from rotation in the partial bore by the cooperating flats (not shown). When the pump unit  5  is assembled, the tubular extension  34  of insert  30  is passed through the inner diameter  54  and the flats  52  of the seal washer  50  and the inner diameter  61  of seal seat  60 . Because the axial distance between the seal washer  50  and the seal seat  60  is less than the uncompressed axial height of the spring  70 , the spring  70  is compressed axially causing the seal washer  50  to bear axially against the seal seat  60 . The seal washer  50  axially deflects the coil spring  70  and the distal end  42  of the boot  40  until the end of the tubular extension  34  of insert  30  passes through housing bore  88  and extends out of the housing  80 . The insert  30  is temporarily held in this axially extending position by grasping the tubular extension  34  protruding out of the housing  80 . The pump cover  10  is then welded to the housing as described earlier. After welding, the cover  10  to the housing  80 , the tubular extension  34  on the rigid insert  30  is released allowing face seal assembly  59  which includes the spring  70  and the boot  40 , to decompress somewhat axially until the ceramic thrust disk  14  mounted in the partial cavity  23  in the face  22  of the insert  30  is prevented from further axial movement by the graphite phenolic thrust button  13  mounted in the cavity  12  of the cover  10 . The thrust button  13  sets a gap  98  between the face  22  and the cover  10  to set the running clearance between the impeller face  22  and the cover  10 . 
     In operation, the motor causes the shaft  7  to rotate the elastomeric bladed impeller  20  to pump fluid in and out of the pump  100 . As the impeller  20  rotates, it causes the seal washer  50  to rotate by virtue of the positive drive of the flats  38  on the tubular extension  34  engaging the complimentary flats  52  on the inner diameter of the seat washer  50 . The axial compression of the spring  70  biases the seal washer  50  into contact with the seal seat  60 . The seal washer  50  is frictionally engaged by the distal end  42  of the boot  40  which grips around the first outer diameter  56  of the seal washer  50  and the second outer diameter  58  acts as a secondary rotation drive between the boot  40  and the washer  50 . In this condition, the elastomeric lip  44  forms a static seal  49  around the first outer diameter  56  and second outer diameter  58  of the seal washer  50  to prevent any leakage past the seal washer  50  and out of the housing  80 . The seal washer  50  is also forced to move axially towards the seal seat  60  by the axial compression on the boot  40 . The boot  40  also forms an axial compressive force against the stepped portion  48  by the fluid pressure in the cavity  86 . The compressed elastomeric material in the stepped portion  48  also forms a static seal  49  against the corresponding stop  57  which prevents any fluid being pumped by the impeller  20  from leaking past the seal washer  50 , around the tubular extension  34  and out of the housing  80 . A rigid annular case  75  with an optional radially extending lip may be disposed around the first outer diameter of the boot  48  to put a clamp load around the distal end  42  to engage the seal washer  50 . 
     While the invention has been described in connection with a preferred embodiment, it will be understood that it is not intended to limit the invention to that embodiment only. On the contrary, it is intended to cover all alternative modifications and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims.