Abstract:
A nonmetallic pump with a gear pump assembly having an adapter spool mounted to an electric motor. The pump assembly is designed to reduce manufacturing costs and to provide access for many service and maintenance tasks to be performed without breaking any of the pipe connections. The pump assembly also includes a splined shaft system and a lubricating fluid circulation system with spiral grooves located inside a pair of bearings disposed on opposite sides of the gear flights. The assembly also includes a replaceable precision liner that surrounds the gear flights to maintain a tight tolerance for optimal performance of the pump. Also, an O-ring disposed inside the front cover of the assembly provides for operation of the pump over a wide temperature variation with relatively loose manufacturing tolerances.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a Continuation of U.S. patent application Ser. No. 11/194,902, filed Aug. 1, 2005, which in turn claims priority of U.S. Provisional Patent Application Ser. No. 60/592,988, filed Jul. 30, 2004, the disclosures of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a gear pump. 
       BACKGROUND OF THE INVENTION 
       [0003]    Positive displacement gear pumps can be used for low rate metering pump applications. Depending on the substances to be conveyed, chemical resistance may be a required characteristic of the materials of construction for the pump. In order to handle corrosive materials, the pumps are typically constructed from corrosion resistant materials such as 316 stainless steel. There is a need for a non-metallic pump that is easier and less expensive to manufacture and that is chemically resistant. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention meets the above-described need by providing a non-metallic pump with a central housing having a suction side, a discharge side, a top flange and a bottom flange. A drive gear assembly is disposed in the central housing. The drive gear assembly comprises a drive shaft having a plurality of first gear flights extending therefrom. An idler gear assembly is disposed in the central housing in operative relation to the drive gear assembly. The idler gear assembly comprises an idler shaft having a plurality of second gear flights. A first bearing has a pair of openings defined therein. The openings are capable of receiving the drive shaft and idler shaft. A second bearing has a pair of openings defined therein. The openings are capable of receiving the drive shaft and the idler shaft. A gear insert is disposed between the first and second bearings and is sized to fit over the plurality of first and second gear flights. The gear insert has an inner wall disposed in spaced apart relation to the gear flights. A cover is attached to the top flange of the central housing and encloses the drive and idler gear assemblies. An adapter spool has a central opening for receiving a containment can. The adapter spool has a top flange and a bottom flange. The top flange is capable of mating with the bottom flange of the central housing. A drive magnet assembly is disposed in the adaptor spool. A driven magnet assembly is disposed in the containment can in operative relation to the drive magnet assembly. An electric motor is coupled to the drive magnet assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The invention is illustrated in the drawings in which like reference characters designate the same or similar parts throughout the figures of which: 
           [0006]      FIG. 1  is a perspective view of a gear pump of the present invention; 
           [0007]      FIG. 2  is a cross-sectional view taken along lines  2 - 2  of  FIG. 1 ; 
           [0008]      FIG. 3  is an exploded view of the gear pump assembly of the present invention; 
           [0009]      FIG. 4  is a side elevational view of the universal flange of the present invention; 
           [0010]      FIG. 5  is a schematic view of the pump chamber of the present invention showing the gear teeth and fluid grooves on the face of the bearing; 
           [0011]      FIG. 6  is a side elevational view of one of the bearings of the present invention; 
           [0012]      FIG. 7  is a cross-sectional view taken along lines  7 - 7  of  FIG. 6 ; 
           [0013]      FIG. 8  is a perspective view of the drive shaft; and, 
           [0014]      FIG. 9  is a partial enlarged view taken from  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0015]    Referring to  FIG. 1 , a gear pump assembly  10  includes an adaptor spool  93  mounted to an electric motor  16 . An inlet port  19  and an outlet port  22  include universal flanges  25 ,  28  with alignment features as described in greater detail herein. The assembly  10  is also provided with a front cover  31  that provides access to the internal parts. Most maintenance and service tasks can be performed by opening the front cover  31  without the need for breaking any of the pipe connections. The gear pump assembly  10  is constructed of non-metallic parts as described in greater detail below. 
         [0016]    The adaptor spool  93  has a motor adaptor plate  34  with multiple patterns for use with NEMA or IEC type motor enclosures. The center housing  43  can be rotated in forty-five degree increments to provide a vertical orientation for the input and output ports  19  and  22 . The base plate  40  has multiple slotted patterns  41  that match standard motor mounting patterns for retrofitting the assembly  10  to match the footprint of existing installed pumps. 
         [0017]    Turning to  FIGS. 2 and 3 , the front cover  31  is bolted to the center housing  43  and is sealed with a first O-ring  46 . For ease of installation, the center housing  43  is provided with nut retaining plates  47  that automatically hold the nuts in place to provide for installation of the mounting bolts with a single socket or wrench. The center housing  43  and the cover  31  form a pump chamber that contains the drive gear assembly  49  and the idler gear assembly  52 . The gear assemblies  49 ,  52  may be constructed of Ethylene/Tetrafluoroethylene (“ETFE”) copolymer which is an injection molded fluoropolymer having chemical resistance properties suitable for a wide variety of applications. Alternate non-metallic materials are also suitable as will be evident to those of ordinary skill in the art. The gear assemblies  49 ,  52  have gear teeth  50 ,  51  that are integrally molded on their respective shafts  61 ,  64 . Shafts  61 ,  64  are manufactured from non-metallic and preferably ceramic materials. 
         [0018]    A pair of bearings  55 ,  58  support the drive shaft  61  and the idler shaft  64 . The bearings  55 ,  58  are disposed on opposite sides of the gears  49 ,  52  and can be mounted facing in either direction. The bearings  55 ,  58  include wear plates with fluid grooves on the surfaces facing the gear teeth  50 ,  51  as will be described in further detail herein. 
         [0019]    A gear insert or liner  67  is disposed around the teeth  50 ,  51  of the respective gear assemblies  49 ,  52 . The liner  67  is a precision manufactured part having an inner wall  68  that is disposed in spaced apart relation to the teeth on the gear assemblies  49 ,  52 . The gap between the end of the teeth of the gear assemblies  49 ,  52  and the inner wall  68  is maintained to a tight tolerance in order to provide optimal performance of the pump assembly  10 . The liner  67  provides for control of tolerances and easy replacement. The pump assembly  10  can be maintained and restored to its original performance by replacing the liner  67 . The replaceable liner  67  also prevents the gear teeth from damaging the inner wall  71  of the center housing  43  when the bearings are worn out. 
         [0020]    A second O-ring  73  is disposed inside the front cover  31  and acts as a spring and takes up any variation in tolerance resulting from variations in the length of the housing  43 , cover  31 , bearings  55 ,  58  or the liner  67 . The O-ring  73  also compensates for thermal expansion of the parts. By taking up the tolerance, the O-ring  73  reduces the cost of manufacturing the housing  43 , cover  31 , bearings  55 ,  58  and the liner  67 . Under low pressure, the O-ring  73  exerts a force against the outer bearing causing it to press against the liner. Under high pressure, the hydraulic fluid forces the bearings against the liner. An opening  66  is used in the idler shaft  64  to balance this hydraulic force equally from side to side. Other manufacturer&#39;s assemblies typically require highly toleranced metal parts to achieve tolerance control or use narrow temperature operating ranges. The present invention allows for use of non-precision non-metallic parts over a wide temperature range. 
         [0021]    The shaft  61  of the drive gear  49  engages with a driven magnet assembly  83 . The shaft  61  may be constructed from a ceramic material having chemical resistance suitable for a wide variety of applications. The shaft  61  has a spline system  85  comprising a plurality of splines  86  machined thereon such that the driven magnet assembly  83  can float on the splines  86  without any axial load being transmitted to the shaft  61 . The spline system  85  eliminates the need for keys and retaining rings for connecting the shaft to the driven magnet. The spline system  85  also spreads out the load from the driven magnet assembly  83 . The driven magnet assembly  83  is disposed inside a containment can  90  located in an adaptor spool  93 . The containment can  90  is sealed against the center housing by a third O-ring  96 . A drive magnet assembly  100  is disposed outside of the containment can  90  and is driven by the electric motor  16  ( FIG. 1 ) as will be evident to those of ordinary skill in the art. The drive magnet assembly  100  is coupled to the motor  16  by an interchangeable motor hub adaptor  103 . 
         [0022]    The gear pump assembly  10  may be provided with flush and drain ports  110  and  113 , respectively. 
         [0023]    In  FIG. 4 , universal connection flange  25  is provided to allow the pump to mate to ANSI (American National Standards Institute) and two different DIN (Deutsches Institut fur Normung E.V.) size flanges. This is achieved by incorporating three different patterns for bolt holes  197 . To properly align the holes  197  on the universal flange  25  concentrically, a visual indicator is necessary. The visual indicator is provided by utilizing the outside diameter  200  of the raised face sealing surface  203  for one size and a stepped outside diameter with two different diameters  206 ,  209  for the other two sizes. The raised face sealing surface insert  203  is Polytetrafluoroethylene (Teflon) in the embodiment described, but can be any compliant material. The insert  203  is replaceable in case of damage so the main housing is not sacrificed. The insert  203  can also be reversed to present a fresh side for sealing. 
         [0024]    Turning to  FIGS. 5-7 , the pump uses a lubrication system where there are an odd number of teeth  50 ,  51  on the gear assemblies  49  and  52  which alternately cover and uncover fluid circulation grooves  300 ,  301 ,  302 , and  304  to recirculate fluid from the discharge side  303  of the pump to the intake  306  of the pump. At the bottom of  FIG. 5 , the groove  300  on the left hand side of the figure is uncovered providing an open flow path. The groove  304  on the top right hand side of the figure is also open. When the teeth rotate, the grooves  300 ,  301 ,  302 , and  304  alternate between the open and closed position as described below. 
         [0025]    As best shown in  FIGS. 6 and 7 , the fluid grooves  300  and  302  start on the face of the bearing  55  and follow a spiral pathway  306 ,  308  (grooves  301  and  304  have identical spiral pathways that are not shown due to the direction of the orientation of the cross-section) to the opposite side of the bearing where the pathway  306  ends on the same side of the bearing. Accordingly, each bearing  55  has a fluid groove that begins at the front and a fluid groove that begins at the rear. Because the orientation of the teeth alternately exposes the grooves  300 ,  301 ,  302 ,  304  to the pumped fluid stream, there is never a time when two grooves are exposed on the same gear. Due to the meshing of the gear pair, as one groove is exposed on the discharge side of a gear, an alternate groove is exposed on the suction side of the second gear. As shown in  FIG. 6 , the fluid pathway indicated by arrows  307  is as follows: fluid enters the uncovered groove  304  on the discharge side and goes through the spiral pathway to the bottom of the bearing where it then crosses over to the other side. The fluid enters the spiral pathway  306  leading to the uncovered groove  300  on the face at the suction side. Because of the arrangement of the teeth on the gears, the pathway alternates from pathway  307  to a second pathway indicated by arrows  310  in  FIG. 6 . 
         [0026]    Turning to  FIG. 8 , drive shaft  61  with teeth  50  is shown in greater detail. The spline system  85  on drive shaft  61  is manufactured such that the ends of the splines  86  form a smooth transition with the body of the shaft  61 . A first feathered section  350  provides a transition from the body of the shaft  61  to the spline  86 . At a position located distal to the first feathered section  350 , a second feathered section  353  is provided. The smooth transition between the spline system  85  and the shaft  61  eliminates any sharp transitions that could create stress points on the shaft  61 . 
         [0027]    In  FIG. 9 , the locating feature of the containment can  90  is shown in greater detail. The containment can  90  fits into a recessed portion  400  in the adapter spool  93  such that the containment can  90  is disposed above the top of the adapter spool. The top of the containment can  90  mates with a recessed portion  403  in the center housing  43 . Accordingly, the parts locate themselves during assembly such that once the containment can  90  is seated properly, the center housing  43  slides into the correct position and there is a positive indication of proper alignment due to the engagement with the top of the containment can  90 . 
         [0028]    While the invention has been described in connection with certain embodiments, it is not intended to limit the scope of the invention to the particular forms set forth, but, on the contrary, it is intended to cover such alternatives, modifications, and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.