Abstract:
A pump housing assembly which includes a pump casing and a liner, where the pump casing includes at least two parts which are adapted to be connected together in an assembled position with the pump casing having opposed front and rear sides and a common junction region which is disposed within one or more planes which pass through the front and rear sides of the assembled pump casing, the liner being formed in one piece and having sealing portions that are activated to provide a seal between the liner and the pump casing.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-part-application of U.S. Ser. No. 10/570,421 filed Mar. 2, 2006, to which priority is claimed. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates generally to pumps such as for example end suction centrifugal pumps that have an outer casing and an internal liner. The invention is particularly suitable for slurry pumps that have an outer casing for withstanding the pressure and pipe loadings and an internal liner that is wear resistant and which in turn is supported by the outer casing. 
         [0004]    2. Description of Related Art 
         [0005]    Centrifugal slurry pumps typically utilise a cast outer casing made in Cast Iron or Ductile Iron with an internal liner moulded from a wear resisting elastomer compound. The casing and the liners are traditionally manufactured in two parts or halves held together with bolts at the periphery of the casing. 
         [0006]    When assembled the two parts form a pump housing having a front side with an inlet therein and a rear side with a pumping chamber therein in which is disposed an impeller mounted for rotation on an impeller shaft. The impeller shaft enters the pumping chamber from the rear side and an outlet is provided at the peripheral side edge. The casing and liner halves are convex on the outside and have a concave shape on the inside. The liners normally have a metal skeleton moulded inside the elastomer which helps maintain its shape but also provides attachment points for bolts or studs to fix the liner into the casing halves. The two parts join along a plane which is generally perpendicular to the axis of rotation of the pump impeller. 
         [0007]    During assembly, the two liner halves must be squeezed together at their periphery by the casing and casing bolts to effect a pressure tight seal. The resulting joint line is a vulnerable wear area in the pump, especially as the joint line is adjacent to the impeller discharge. Any misalignment of the liner halves along this joint line will produce steps or gaps in the joint line that will lead to preferential wear. Once wear starts at a local spot, the continued disturbed flow pattern at the step or gap will lead to an accelerated wear point and in the worst case localised wear will cause the liner to be worn through, thereby exposing the pressure containing casing to wear. 
         [0008]    It is an object of the present invention to provide a pump housing assembly and including a liner which alleviates one or more of the aforementioned disadvantages. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    In accordance with the present invention, a liner is provided for positioning in a pump housing assembly that includes a pump casing having at least two parts which are adapted to be connected together in an assembled position where the pump casing includes opposed front and rear sides and the two parts of the pump casing, when in the assembled position, have a common junction region which is disposed within one or more planes that pass through the front and rear sides of the assembled pump casing. Methods of fitting the liner in the pump casing are also disclosed. 
         [0010]    In one form of the invention, with the two parts of the pump casing having the common junction region disposed in a plane which is aligned with the axis of rotation of the impeller, the liner is desirably formed in one piece from an elastomer such as for example, rubber, synthetic rubber or other materials having similar properties of flexibility and durability. The liner includes an outer generally circular portion that encircles an axis that is parallel to or coaxial with the rotational axis of the impeller. The liner also includes annular flanges on each side of outer circular portion which are adapted to be clamped between the two casing parts in the assembled position. 
         [0011]    The flanges may include sealing portions. The sealing portions may be adapted to be received within a cavity formed between the pump casing and a pump end plate assembly. The sealing portion may be generally wedge shaped, formed integrally with the liner and is responsive to pressures produced before and during operation of the pump. 
         [0012]    When in the assembled position, the liner is disposed within the pump casing and forms a pumping chamber for an impeller rotatable about a rotation axis which extends between the front and rear sides of the pump casing. 
         [0013]    In another aspect of the invention, methods of fitting the liner in a pump casing are disclosed. Also disclosed are methods for activating the seal between the liner and casing when the liner is installed within the casing. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0014]    In the drawings, which currently illustrate the best mode for carrying out the invention: 
           [0015]      FIG. 1  is an exploded view of a pump according to the present invention; 
           [0016]      FIG. 2  is an exploded view of a pump housing assembly according to the present invention; 
           [0017]      FIG. 3  is a schematic illustration of the two sections of the pump casing of the assembly shown in  FIGS. 1 and 2 ; 
           [0018]      FIG. 4  is a schematic illustration of the pump casing shown in  FIGS. 1 and 2  when assembled together; 
           [0019]      FIG. 5  is a perspective view of the liner shown in  FIGS. 1 and 2 ; 
           [0020]      FIG. 6  is a side elevation view of the liner shown in  FIG. 5 ; 
           [0021]      FIG. 7  is a view in cross section of the liner, the left side of the drawing figure showing a cross section through the flange and the right side of the drawing figure showing a cross section taken through the stiffening ribs; and 
           [0022]      FIG. 8  is an enlarged view in cross section of out outer portion of the assembled pump illustrating the pump casing and liner arrangement. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring to  FIG. 1  of the drawings there is shown an exploded view of a pump generally indicated at  10  which includes a pump casing  12  having two parts  13  and  14  which can be assembled together, an elastomeric liner  20 , a drive shaft assembly  22 , an impeller  24 , back and front side liners  25  and  26  (the front side liner is often referred to as the “throat bush”) and an end plate  28 . 
         [0024]    In an assembled position, the impeller  24  is disposed within a pump chamber  29  and operatively connected to drive shaft assembly  22  for rotation and about rotation axis X-X. Slurry is drawn into the pump chamber  29  via inlet  27  and discharged through outlet  23  as is conventional. 
         [0025]    The pump casing  12 , as best seen in  FIGS. 3 and 4 , includes two parts  13  and  14  which can be fitted together. Flanges  15  on the pump casing parts  13 ,  14  have apertures  16  therein for receiving mounting bolts to hold the two parts  13 ,  14  together. In the assembled position, the pump casing  12  includes a front side  17  having an inlet  21  therein and a rear side  18  to which parts of the shaft assembly are operatively connected. The two parts  13  and  14  are fitted together in a plane which contains the axis of rotation X-X. Thus, the plane extends through the front and rear sides  17  and  18  of the casing when the pump is assembled. 
         [0026]    The liner  20  is a one piece structure formed from a suitable elastomeric material. As best seen in  FIGS. 5 to 7 , the liner  20  includes an outer generally circular portion  30  that encircles an axis  40  that is parallel to or coaxial with the rotation axis X-X of the impeller  24  of the pump. Annular flanges  31  and  32  extend axially outwardly from the outer portion  30  of the liner  20  at an angle to the axis  40  of the liner  20 , and are adapted or configured to be clamped within the pump casing parts  13  and  14 . 
         [0027]    The annular flanges  31  and  32  have seal portions  33  and  34  which extend from the flanges  31 ,  32  in a generally radial direction toward the axis  40  of the liner  20 . Each seal portion  33 ,  34  may also include a flexible lip  35 ,  36  which, as shown, extends from the sealing portion  33 ,  34  at an orientation generally parallel to the flange  31 ,  32  with which it is associated. An annular cavity  46  is thus formed between the flange  32 , seal portion  34  and flexible lip  36 , as best seen in  FIG. 8 . Notably, a similar annular cavity is formed between the flange  31 , seal portion  33  and flexible lip  35  on the other side of the liner  20 , but is not shown in the illustrations. 
         [0028]    The flanges  31  and  32  and associated seal portions  33  and  34  may have strengthening ribs  38  on the surface thereof as shown in  FIG. 5 . The section shown in  FIG. 7  shows the configuration of the flange and seal portions  31  and  33  on the left side of the illustration, whereas the section on the right side is taken through one of the ribs  38 . Strengthening ribs  38  may be optional and may not be required for some applications or pumps. 
         [0029]    Referring to  FIG. 8  the seal assembly is shown in an installed position. The seal portion  34  and flexible lip  36  are disposed within a cavity  42  formed between the casing  14  and the end plate assembly  19 . The seal portion  34  fits within the cavity  42 . The diameter of the flexible lip  36  is less than the outer diameter of side liner  26  so that the flexible lip is compressed during assembly of the side liner  26  into the liner  20 ; that is a seal is effected and flexible lip  36  ensures that the pump holds the static pressure when first filled. The cavity assists controlling the shape and pressure applied to the seal portion  34 . During operation the annular cavity  46  is pressurized, the pressure acting on the seal to increase its sealing capacity. 
         [0030]    The pump assembly is formed, as best illustrated in  FIG. 1 , by providing the two parts  13 ,  14  of the pump casing, the drive shaft assembly  22 , end plate  28 , back side liner  25  and front side liner  26 , impeller  24  and the elastomer liner  20 . The impeller  24  is positioned on the drive shaft assembly  22 , the liner  20  is positioned within the two parts  13 , 14  of the pump casing and the front side liner  26  is positioned against the liner  20 , as shown in  FIG. 8 . In the fitting of the liner  20  to the parts of the pump casing, the flanges  31 ,  32  and seal portions  33 ,  34  are positioned respectively within the cavity  42  formed between the back side liner  25  and front side liner  26  respectively. 
         [0031]    The flanges  31 ,  32  and seal portions  33 ,  34  are then clamped into place with the attachment of the two parts  13 ,  14  of the assembled pump casing  12  to the drive shaft assembly  22  and attachment of the end plate  28  to the connected pump parts  13 ,  14 , respectively. Pressure applied within the pump provides pressurization to the annular cavity  46  of the liner  20  and provides the seal as described herein. 
         [0032]    Because the elastomer liner is produced in one-piece, it avoids the vertical joint line of conventional pumps and the weakness that it introduces due to wear at the joint line. Further the elastomer liner may not require an internal metal skeleton and consequently, the liner can be manufactured to a more uniform thickness or known high wear regions can be made thicker without affecting the liners manufacturability or compromising its wear life. 
         [0033]    Further, without internal reinforcement, the elastomer liner will more easily conform to the internal shape of the pump casing due to the internal pump pressure generated while the pump is running. Any looseness or gaps between the metal casing and the liner are thereby minimized leading to a more robust liner as looseness and gaps will potentially lead to vibration and hysteresis heating of the elastomer and therefore reduced life. 
         [0034]    As described earlier, to enable the liner to be held by the outer metal casing, a thickened region is provided around the liner horizontal centreline and an extension is provided on either side of the liner to allow clamping by the outer metal casing. The extension on either side of the rubber liner further includes an integral seal which is activated initially by the clamping provided by the outer casing and then by the internal pressure of the pumped fluid. With this arrangement, no internal metal skeleton or reinforcing may be required which also more easily facilitates the liner sealing when the liner is moulded in different elastomer compounds. 
         [0035]    The liner being one piece without a vertical split line simplifies the casing design as well as obviating the need for casing bolts. The liner projection and seal on either side of the liner is made of a large enough diameter to allow the impeller to be installed through the side of the liner and as well to suit the side liners. 
         [0036]    The outer casing is thereby required to be in two pieces to enable the fitment of the one-piece liner. It will be appreciated that the split line for the casing could be selected from a number of different positions. The requirements for casing bolts therefore reduce to a small number of bolts on the pump centerline. The casing bolts have the dual function of holding the casing halves together as well as squeezing the raised elastomer land to hold the liner in the casing. 
         [0037]    The sides of the outer metal casing also assist in compressing and holding the elastomer projections and seals on both sides of the elastomer liner and prevent it from both being pushed out under pressure or being sucked in under vacuum. The metal casing can be produced either as two separate pieces or cast as one and then later split in the manufacturing cycle. 
         [0038]    The use of a one-piece liner and two piece casing assists to lower maintenance costs. In most cases, the pump discharge pipework can be left attached to the pump. By removing the pump&#39;s suction pipework, front liner and impeller, it is possible to gain access to the pump internals for inspection. 
         [0039]    The casing design may or may not have ribs for high-pressure applications. The casing bolts are designed to take the full design pressure without passing their elastic limit. 
         [0040]    Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. 
         [0041]    Finally, it is to be understood that the inventive concept in any of its aspects can be incorporated in many different constructions so that the generality of the preceding description is not to be superseded by the particularity of the attached drawings. Various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.