Patent Publication Number: US-5295786-A

Title: Liner ring for a pump

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a liner ring for a pump, and more particularly to a pump liner ring which is provided between a pump casing and an impeller to check counterflow therebetween. 
     Conventionally, in a centrifugal pump, in order to prevent the liquid discharged out of the impeller from being leaked toward the suction side of the pump casing, there are provided a wearing ring (or impeller ring) on the side of the impeller, and a liner ring (or a casing ring) on the side of the casing in confrontation with the wearing ring. The wearing ring and the liner ring are provided in such a manner that the clearance between the rings is kept small. 
     Since the wear condition of the liner ring or the wearing ring cannot be easily observed from the outside, wear resisting material must be used for the liner ring or the wearing ring. When a non-corrosive liquid is used in the pump, bronze, cast iron or surface hardened steel or the like is employed as the wear resisting material. On the contrary, when a corrosive liquid is used in the pump, 18Cr-8Ni stainless steel is often employed, but such stainless steel is not effective against wear. Therefore, in this case, the clearance between the rotating member and the stationary member must be larger than the average clearance commonly used. 
     In addition to the above-mentioned metal for a liner ring, the use of carbon material or Teflon (trademark) material having excellent wear resistance is desirable. 
     However, carbon material or Teflon material is difficult to handle when it is used in a high temperature environment or the like. That is, since material, such as carbon or Teflon, which is suitable for an annular member has a different thermal expansion coefficient than that of metal used for a pump casing, such material cannot be installed on the pump casing by mean of a force fit which is generally used for liner rings made of metal. Therefore, a housing made of rubber is often used in conjunction with the annular sealing member made of carbon or Teflon, or the usage temperature range of the liner ring is often limited to a certain range. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a pump liner ring comprising carbon material or Teflon material which is difficult to handle when it is used in high temperature liquids, and which can be easily used in the same manner as the liner ring made of metal. 
     In order to achieve the above object, in accordance with one aspect of the present invention, there is provided a liner ring for a pump, comprising: a housing provided on a casing body; an annular sealing member provided in the housing in such a manner that a predetermined gap is provided in a radial direction between the sealing member and an impeller; and an elastic member provided between the sealing member and the housing. 
     According to another aspect of the present invention the liner ring further comprises a means for preventing the sealing member from rotating relative to the housing. 
     According to still another aspect of the present invention, the sealing member comprises material having a thermal expansion coefficient larger than that of the housing. A predetermined gap is formed between the housing and the sealing member. The gap corresponds to variations in dimensions of the housing and the sealing member due to a difference in the thermal expansion coefficients of the housing and the sealing member, and a predetermined pre-load is applied to the elastic member so as to enable the elastic member to perform a sealing function at the lowest usage temperature. 
     According to still another aspect of the present invention, the sealing member comprises a material having a thermal expansion coefficient smaller than that of the housing, the sealing member is tightly fitted with the housing, and a predetermined pre-load is applied to the elastic member so as to enable the elastic member to perform a sealing function at the highest usage temperature. 
     According to still another aspect of the invention, the housing is made of sheet metal and is pressed into shape, the housing is in the form of a cylindrical receptacle-like body comprising a cylindrical side wall, a bottom wall (or housing end wall) and a corner portion between the cylindrical side wall and the bottom wall. The cylindrical side wall is formed at the side of the impeller with a flange, and the elastic member is located at the corner portion. 
     According to still another aspect of the present invention, the flange of the housing is formed with an engaging member which is bent radially inwardly after inserting the sliding member into the housing so that the engaging member prevents the sealing member from moving in an axial direction and/or rotating in a circumferential direction. 
     According to still another aspect of the present invention, the housing is formed at the bottom wall thereof with a first engaging member, the sealing member is formed with a second engaging member, and the first engaging member is engageable with the second engaging member so as to prevent the sealing member from rotating relative to the housing. 
     In accordance with the present invention, the sliding member is housed in the housing made of sheet metal in such a manner that a predetermined gap is provided between the sealing member and the housing. The gap corresponds to the variation in dimensions due to the difference in thermal expansion coefficients of the sealing member and the housing. The gap is sealed by the elastic member provided between the sealing member and the housing. 
     Further, the sealing member is prevented from moving in an axial direction by the engaging member which is formed on the flange of the housing and bent radially inwardly. If an engaging member is provided on the sealing member, the sealing member may be prevented from rotating relative to the housing. 
     Furthermore, the sealing member is prevented from rotating relative to the housing by engagement of the first engaging member provided on the housing and the second member 
     The above and other object, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings in which preferred embodiments of the present invention are shown by way of illustrative example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a cross-sectional view showing a liner ring incorporated in a pump casing according to an embodiment of the present invention; 
     FIG. 2 is a cross-sectional view showing the liner ring according to the embodiment of FIG. 1; 
     FIGS. 3(a) and 3(b) show a sliding member of the liner ring according to the embodiment of FIG. 1, FIG. 3(a) showing a cross-sectional view taken along line III--III of FIG. 3(b) and FIG. 3(b) showing a cross-sectional view of the sliding member; 
     FIGS. 4(a) and 4(b) show a housing according to the present invention, FIG. 4(a) being a front view showing the housing and FIG. 4(b) being a cross-sectional view taken along a line IV-IV of FIG. 4(a); and 
     FIG. 5 is a cross-sectional view similar to FIG. 1, but showing an annular sealing member formed of ceramics. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A liner ring according to an embodiment of the present invention will be described below with reference to FIGS. 1 through 4. 
     FIG. 1 shows a liner ring of the present invention which is incorporated in a pump casing. A liner ring 10 is provided between a pump casing body 42 and an impeller 41 which is rotatably supported by a shaft 43 as shown in FIG. 1. The liner ring 10 comprises an annular sealing member 1 made of carbon material or Teflon material, a housing 2 made of metal for housing the sliding member 1 and an O ring 3 made of rubber as shown in FIG. 2. As shown in FIGS. 3(a) and 3(b), the sealing member 1 is formed with an inner cylindrical surface 11 which confronts an end portion of the impeller 41 located at the suction side thereof so as to form a predetermined gap therebetween (see FIG. 1). The inner cylindrical surface 11 is slightly inclined so as to make the gap between the sealing member 1 and the impeller 41 decrease from the inlet side toward the outlet side of the impeller 41 as shown in FIG. 1. Further, the sealing member 1 is formed with an outermost cylindrical surface 12, an intermediate cylindrical surface 13, and an end surface 14 which extends vertically and connects the outermost cylindrical surface 12 with the intermediate cylindrical surface 13 as shown in FIGS. 3(a) and 3(b). The intermediate cylindrical surface 13 and the end surface 14 define a space for accommodating the O ring 3. The sealing member 1 has an opposite end, which is located on a side of the sliding member 1 opposite the impeller 41, and a plurality of projections 16 (six in this embodiment) are formed at regular intervals on the opposite end. 
     On the other hand, as shown in FIGS. 4(a) and 4(b), the housing 2 housing the sealing member 1 is provided with a cylindrical side wall 21, a bottom wall (or housing end wall) 22 and a corner portion 23 which connects the cylindrical side wall 21 and the bottom wall 22. The housing 2 is made of sheet metal pressed into shape and is provided with a flange 24 which extends radially from the cylindrical side wall 21 at the side of the impeller 42. The flange 24 serves as a stopper for stopping an axial movement of the housing 2 relative to the pump casing body 42 (see FIG. 1). Further, the flange 24 is formed with pawls 25 constituting an engaging portion which are formed by means of two adjacent slits extending radially outwardly. That is, after inserting the O ring 3 and the sealing member 1 into the housing 2, the pawls 25 are bent radially inwardly, thereby fixing them to the housing 2. 
     Further, the housing 2 is provided at the bottom wall 22 with a plurality of notches 26, at regular intervals, which are engageable with the projections 16 (FIG. 3) of the sliding member 1. 
     As shown in FIG. 2, the sealing member 1 is housed in the housing 2 in such a manner that a gap δ is provided between the outermost cylindrical surface 12 and the cylindrical side wall 21 of the housing 2 in order to absorb (or accommodate) variation in the dimensions caused by differences in the thermal expansion coefficients of the two materials and the temperature of the liquid. Further, the O ring 3 is disposed in the annular space defined by the intermediate cylindrical surface 13, the end surface 14 and the corner portion 23 of the housing 2, whereby the gap δ is sealed by the O ring 3. 
     With the above structure, the sealing member confronts the impeller 41 with a certain gap therebetween. The sealing member 1 is inserted into the housing 2 so as to form the gap δ corresponding to the variation in dimension due to the difference in thermal expansion coefficients of the respective members and the temperature of the liquid. The gap δ is sealed by the O ring 3 as mentioned above. 
     Further, the sealing member 1 is fixed to the housing 2 by the pawls 25 provided on the flanges 24. The pawls 25 are bent radially inwardly after inserting the sliding member 1 and the O ring 3 into the housing 2, thereby stopping the axial movement of the sliding member 1. Further, in order to prevent the sealing member 1 from rotating relative to the housing 2, engaging means may be provided at the inner surfaces of the pawls 25 and at the end surface of the sealing member 1, respectively. 
     On the other hand, the sealing member 1 is prevented from rotating relative to the housing 2 by engagement of the notches 26 formed on the bottom wall 22 with the projections 16 formed on the end surface of the sealing member 1. 
     In the embodiment mentioned above, the sealing member 1 is made of a material having a thermal expansion coefficient larger than that of the housing. However, if the sealing member 1 is made of a material such as ceramics (see FIG. 5) having a thermal expansion coefficient smaller than that of the housing, it is not necessary to provide the gap δ between the inner surface of the cylindrical side wall 21 of the housing 2 and the outermost cylindrical surface 21 of the sealing member 1. Alternatively, the size or dimension of the O ring 3 provided between the housing 2 and the sliding member 1 can be selected so as to impart a pre-load, corresponding to the difference in the thermal expansion coefficients of the housing 2 and the sealing member 1, to the O ring 3 in a radial direction. Accordingly, the pre-load applied to the O ring 3 remains at the maximum usage temperature of the pump. 
     As is apparent from the foregoing description, the liner ring according to the present invention offers the following advantages: 
     The housing can use the same metal as the pump casing or can use a similar metal having almost the same thermal expansion coefficient as that of the pump casing. Therefore, the housing can be attached to the pump casing by force fit. Further, since the housing is not made of an elastic material such as rubber, handling such as replacement of the housing is easy. 
     Further, since an elastic member is provided between the housing and the sealing member, even if the sealing member is positioned eccentrically relative to the impeller, the pump can be operated without hindrance. 
     Furthermore, since there are provided the necessary gap between the housing and the sealing member, and means for preventing the sealing member from rotating relative to the housing, the liner ring is not rotated together with the impeller, and is prevented from falling off, even at high temperatures. 
     Further, according to the present invention, the housing is made of sheet metal and pressed into shape, and the flange at the opening side of the housing is provided with pawls which can be bent radially inwardly. The housing is provided with notches or projections at the bottom wall thereof. Thus, it is easy to prevent movement of the sealing member in an axial direction and to prevent the sealing member from rotating relative to the housing. 
     Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.