Abstract:
An improved diesel engine water pump includes three main features that aid in extending the maintenance free life of the pump. The impeller shaft is carried by tapered roller shaft support bearings of which the impeller bearing has a floating outer race that is urged axially by a preload spring to provide a prescribed axial preload that maintains concentricity of the shaft with the axis and prolongs bearing life. An improved oil seal combines an oil slinger, a stationary deflector and a lip oil seal with a return passage to the engine to more effectively limit oil leakage from the pump. An improved water seal includes pressurized water jets fed from the pump volute that flush wear particles from the water seal surface and increase water seal life. Further details of these features are also disclosed.

Description:
TECHNICAL FIELD 
     This invention relates to water pumps of the centrifugal impeller type intended primarily for use in diesel engine cooling systems, especially for railroad locomotives, but also useful for other purposes. 
     BACKGROUND OF THE INVENTION 
     It is known in the art relating to diesel engine cooling systems to provide an engine with one or more centrifugal water pumps, each having a centrifugal flow or mixed flow impeller carried on a shaft and driven by a drive gear or other drive means. The shaft is supported on spaced bearings carried in a housing and lubricated by oil flow from the associated engine oil system. Both ball and roller bearings have been used in the past to carry rotary support loads and axial thrust forces acting on the shaft. 
     Oil passing through the impeller end bearing is returned to the engine oil sump through a drain line or passage in the water pump housing. A lip-type oil seal is conventionally utilized to prevent oil from passing along the shaft into the water impeller portion of the pump. Similarly, a conventional cartridge-type carbon water seal running against an annular seal surface has been used to prevent the escape of pressurized water from the impeller end of the pump into the oil lubricated portions. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved water pump construction including multiple features which combine to provide increased operating life for the supporting and wearing components of the pump. 
     The bearings utilized for support and thrust loads are preferably tapered roller-type bearings including a drive bearing at the drive gear end for accepting drive forces and major thrust loads developed in the impeller. An impeller tapered roller bearing is mounted in the housing toward the impeller end and includes an inner race spaced a fixed distance from the inner race of the drive bearing, the outer race of which is fixed in the pump housing. 
     The outer race of the impeller bearing is mounted to be axially slidable in the housing. A spring element, such as a wave spring, is mounted in the housing and biases the outer race in a direction to provide a controlled preload on the roller bearings. The spring maintains the bearings in a controlled preload condition which is sufficient to absorb minor reverse thrust loads which may occur in the pump. The preload increases bearing life by maintaining shaft concentricity and avoiding runout, or eccentric rotation of the shaft, which could increase bearing loads and generate wear problems. 
     A further feature is the additional of an oil slinger mounted on the inner race of the impeller bearing and adapted to centrifugally direct oil passing thorough the adjacent bearing into an annular collector groove. The groove carries the oil to the internal oil drain passage of the pump. Any oil escaping past the oil slinger contacts a deflector which also directs oil toward the oil drain passage. The deflector forms part of an oil seal including a conventional lip seal for preventing any remaining oil reaching the seal from passing through to the water side of the pump. 
     Still an additional feature of the improved water pump is a water seal which includes a stationary seal member mounted in the housing and having an annular seal surface formed on a radial wall. A rotatable seal member of conventional construction rotates with the impeller and engages the radial seal surface to prevent water from behind the impeller from escaping into the oil lubricated portion of the pump. 
     Seal life is improved by the addition of a seal flush arrangement which receives high pressure water from the pump volute at the outlet of the impeller and directs it through angled orifices or nozzles in a cylindrical wall of the stationary seal member. The nozzles spray pressure water against the outer portion of the seal surface to flush away particles of debris from seal wear. This reduces the collection of wear particles remaining on the seal surface and embedding in the seal. Removal of the wear particles thus increases the wear life of the seal. 
     These and other features and advantages of the invention will be more fully understood from the following description of certain specific embodiments of the invention taken together with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The single FIGURE of the drawing is a cross-sectional view along the longitudinal axis of the pump and illustrating the various improved features of a water pump according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings in detail, numeral  10  generally indicates a water pump of the centrifugal type adapted for use in diesel engine cooling systems or other suitable applications. Pump  10  includes a housing  12  containing a shaft  14  rotatable on an axis  16  extending through the housing. The shaft mounts a drive member in the form of a gear  18  that is carried adjacent a drive end  20  of the housing  12 . 
     A centrifugal impeller  22  is mounted on an opposite end of the shaft adjacent an impeller end  24  of the housing. The impeller is contained within a volute  26  that is carried on the impeller end of the housing. The volute includes an axial inlet opening  28  and a radial outlet  30  to direct water or other coolant into vanes  32  of the impeller. These draw the water axially into the impeller and expel it radially into the associated volute for discharge to an external cooling system. 
     The pump shaft  14  is supported in the housing  12  by a pair of axially-spaced tapered roller bearings including a drive bearing  34  and an impeller bearing  36 . The drive bearing  34  is designed to accept major rotational loads applied to the gear  18  as well as primary thrust loads resulting primarily from the axial flow of the water drawn in by the water pump and expelled radially. Bearing  34  includes an outer race  38  fixed within the housing  12  and an inner race  40  mounted on the shaft  14 . The impeller bearing  36  carries primarily centrifugal loads and reverse thrust loads from the impeller, which are limited in force. 
     Bearing  36  also has an outer race  42  carried in the housing and an inner race  44  mounted on the shaft  14 . The inner races  40 ,  44  of the bearings are fixed to the shaft along with the drive gear  18  by a nut  46  threaded on the shaft. The nut clamps the gear against the inner race  38  of the drive bearing  34  which in turn engages a spacer tube  48  that forces the inner race  44  of the impeller bearing against a shoulder  50  on the shaft. This fixes the spacing of the bearings and clamps them solidly in position on the shaft. 
     In accordance with the invention, the outer race  42  of the impeller bearing  36  is made axially slidable in the housing. A biasing element in the form of a wave spring  52  is mounted in the housing around the shaft and engages the housing and the drive end of the outer race  42  of the impeller. The spring biases race  42  axially toward the impeller and exerts a predetermined preload force against the outer race  42 . This preloads both of the shaft bearings with a pre-selected axial thrust force. 
     The preload force is adequate to offset any reverse thrust forces which may be applied against the impeller bearing while the major thrust forces are taken up by the drive bearing  34  as previously described. The preload wave spring  52  thus provides a minimum thrust loading on the bearings which is adequate to avoid the development of any looseness or clearance in the bearing set and thus maintains the shaft in concentric rotation around the axis  16  within the housing  12 . The development of any centrifugal forces on the bearings due to eccentric rotation of the shaft is thereby prevented so that bearing life is extended. 
     Bearings  34 ,  36  are lubricated within the housing by oil delivered through a feed passage  54 . The passage receives lubricating oil from a lubricated portion of an associated engine on which the pump is mounted and directs the oil into an annular chamber or enclosure  56  from which it may lubricate both bearings. The impeller bearing  34  may also be lubricated by oil splash from the adjacent engine system which can also enter the enclosure  56  to lubricate the impeller bearing  36 . Excess oil in the enclosure can escape either by passing through the drive bearing  34  into the adjacent engine enclosure, not shown, or by passing through the impeller bearing  36  into an annular collector groove  58 . The groove  58  connects with a drain line or passage  60  that carries oil from the collector groove back to the associated engine oil system for return to the engine sump. 
     An oil control  61  is provided in order to prevent oil from escaping from the bearing enclosure  56  into the water side of the pump housing. The control may include a conventional lip seal  62  mounted in the housing for engagement of the seal lip with a seal surface of the shaft. To improve the operation of the seal, the invention includes a radial deflector  64  extending from the body of the lip seal and adapted to intercept oil splashed from the bearings and direct the oil downward into the oil collector groove  58  for draining to the engine system. 
     In addition, the pump oil control  61  includes a radial oil slinger  66  mounted on the impeller end of the impeller bearing inner race  44 . The oil slinger  66  is positioned to centrifugally throw oil passing the bearing  36  and engaging the slinger into the collector groove  58 , from which it is directed through passage  60  to the engine lubrication system. 
     The combination of the three elements provided by the oil control  61  provides a three fold arrangement for control of oil flow from the impeller bearing to the collector and out through the drain passage  60 . The conventional lip seal forms a back up to limit the passage of any oil passing the first two elements, that is the oil slinger  66  and the deflector  64 , from escaping into the water side of the pump. 
     In accordance with the invention, pump  10  includes an additional feature comprising an improved water seal assembly  68 . Assembly  68  includes a stationary water seal member  70  which is mounted behind the impeller in the impeller end of the housing. Member  70  includes a cylindrical wall  72  closed at one end by a radial wall  74  having a radial seal surface  76  surrounding the shaft and facing toward the impeller end of the housing. 
     Within the stationary member  70 , a rotatable water seal member  78  is mounted on the shaft  14 . Member  78  includes a shaft seal  80  adjacent to a rotatable seal ring  82  that rotates with the impeller. The seal ring  82  has an end engaging the seal surface  76  for preventing water flow from the water side of the pump into the oil lubricated areas at the drive end of the housing. A conventional coil spring  84  extends between the impeller  22  and the shaft seal  80  and biases the seal ring  82  against the seal surface  76  to maintain a positive seal against leakage. 
     In accordance with the invention, pressurized water from the volute  26  is delivered, such as through passages  86  and  88  in the volute and housing respectively, to an annular groove or plenum  90 . The plenum  90  connects with angled orifices or nozzles  92  extending thorough the cylindrical wall  72  of the stationary water seal member  70 . The nozzles  92  are aimed in the direction of the radial seal surface  76 . 
     In operation of the pump, rotation of the seal ring  82  against the water seal surface  76  causes wear particles of the ring to be dislodged from time to time and collect adjacent the ring  82  on the seal surface. The particles are dislodged and carried away from the seal surface by high pressure water spray which is directed from the volute supply source to the annular groove or plenum  90  and through the nozzles  92  against the seal surface surrounding the ring  82 . The seal surface  76  is thereby maintained clear of wear particles which would otherwise collect around the surface and impair the wear life of the seal ring. Accordingly, the life of the seal ring is extended and longer maintenance-free operation of the water seal is provided. 
     In similar fashion, the oil control  61  of the pump, including the oil slinger  66 , deflector  64  and lip seal  62 , provide superior oil control which avoids the escape of lubricating oil into the water side of the pump. This extends the life of the lip oil seal to prevent leakage. 
     Finally, the wave spring  52 , providing a predetermined thrust preload on the shaft support and thrust bearings  34 ,  36 , maintains the shaft in fully concentric operation on its axis and thereby improves bearing life. As a result, a water pump having an extended operating life with reduced need for repair is provided by the present invention. 
     While the invention has been described by reference to certain preferred embodiments, it should be understood that numerous changes could be made within the spirit and scope of the inventive concepts described. Accordingly, it is intended that the invention not be limited to the disclosed embodiments, but that it have the full scope permitted by the language of the following claims.