Abstract:
A sealing arrangement is disclosed for use in a pump. The sealing arrangement can include a first pump component having a first face surface. The first face surface can have a sealing protrusion thereon. A second pump component can have a second face surface positioned in confronting relation to the first face surface. The second pump component can define a sealing cavity for holding a fluid under pressure. The sealing protrusion is positioned to engage the second face surface when the first face surface is pressed against the second face surface so that the sealing protrusion seals against the second face surface to prevent movement of the fluid from the sealing cavity past the sealing protrusion. Other embodiments are described and claimed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to co-pending Provisional U.S. Pat. App. No. 61/986,924 by Alexander et al., titled “Pump with Shaped Face Seal,” filed on May 1, 2014, which is incorporated by reference herein in its entirety and for all purposes. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The disclosure generally relates to sealing arrangements for pump assemblies, and more particularly to a shaped face seal for use in gear pumps. 
       BACKGROUND OF THE DISCLOSURE 
       [0003]    Gear pumps often include a housing or plate that holds a set of intermeshing gears. As the gears turn, fluid moves between the gear teeth and the housing and is expelled out the pump due to the intermeshing of the gears. The gears are attached to shafts that run axially from the gear faces, and these shafts run on one or more bearing surfaces. 
         [0004]    As will be appreciated, during operation it is desirable to seal the housing and plate components, including shaft sealing components, in a manner that prevents process fluid from leaking out of the pump. Often o-rings, gaskets or other sealants are disposed between the opposing sealing surfaces to prevent such leakage. In other cases sealing is achieved between a pair of opposing metal surfaces that are formed to be extremely flat and parallel and very smooth (i.e., they have a fine surface finish). 
         [0005]    When using o-rings and gaskets, issues can arise when the operating temperature of the pump exceeds the maximum temperature of the sealing component or where the o-ring material is incompatible with the fluid being pumped (e.g., where the pumped fluid is corrosive or otherwise harsh). This can cause the sealing component to degrade or disintegrate, thereby affecting its ability to seal. When using metal-to-metal face seals, the two mating faces will not produce an effective seal at high pressure or low viscosity unless the surface finish of the opposing surfaces is very fine. The opposing surfaces must also be very flat and parallel. If a rough surface finish is used, or if the surfaces are not sufficiently flat and parallel, the joint will leak. 
         [0006]    Thus, there is a need for a high temperature face sealing arrangement that eliminates the need for an o-ring, gasket or other secondary sealing component, and which can be used to effectively seal joints at high temperatures and pressures. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    A face sealing arrangement is disclosed for use with a pump. The face seal can be a metal-to-metal seal disposed on surfaces that require neither lapping nor a very fine surface finish. The disclosed face sealing arrangement is suitable for applications in a variety of applications, one non-limiting exemplary embodiment being one in which operating temperatures exceed 500 degrees Fahrenheit. 
         [0008]    A sealing arrangement for a pump is disclosed, and may include a sealing sleeve having a body portion and a flange portion, the flange portion having a first flange face and a second flange face. The first flange face may be configured to contact a face plate with an opening. The opening can receive the body portion of the sealing sleeve therein. The sealing arrangement may further include a lip seal housing with a face configured to contact the second flange face. The face of the lip seal housing may have a recess, and the recess may be able to receive a lip seal, such that pressing the face of the lip seal housing against the second flange face may cause the lip seal to form a face seal between the lip seal housing and the sealing sleeve. 
         [0009]    A sealing arrangement for a pump is disclosed, and may include a first pump component having a first face and a second pump component having a second face, one of the first face and the second face having a sealing protrusion thereon. The second face may be positioned in confronting relation to the first face. The second pump component may define a sealing cavity for holding a fluid under pressure. The sealing protrusion may be positioned to engage an opposing face when the first face and the second face are pressed together so that the sealing protrusion seals against the opposing face to prevent movement of the fluid from the sealing cavity past the sealing protrusion. 
         [0010]    A method is disclosed for sealing a pump is disclosed. The method may include: preventing movement of a fluid from a sealing cavity past a sealing protrusion, comprising: a first pump component having a first face; and a second pump component having a second face positioned in confronting relation to the first face, the second pump component including an opening in fluid communication with the sealing cavity, wherein one of the first face and the second face has the sealing protrusion thereon, wherein the sealing protrusion is positioned to engage an opposing face when the first face and the second face are pressed together so that the sealing protrusion seals against the opposing face. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    By way of example, a specific embodiment of the disclosed device will now be described, with reference to the accompanying drawings, in which: 
           [0012]      FIG. 1  is an isometric view of a pump according to the disclosure; 
           [0013]      FIG. 2  is an exploded view of the pump of  FIG. 1 ; 
           [0014]      FIG. 3  is a cross-section of the pump of  FIG. 1  taken along line  3 - 3  of  FIG. 1 ; 
           [0015]      FIG. 4  is a detail view of a portion of the cross-section view of  FIG. 3 ; 
           [0016]      FIG. 5  is a first detail view of a portion of  FIG. 4 ; and 
           [0017]      FIG. 6  is a second detail view of a portion of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    A sealing arrangement is disclosed for use in sealing opposing face surfaces in a pump. In one embodiment the sealing arrangement includes a metal-to-metal face seal in which a small surface feature is provided on one of the opposing surfaces. The sealing feature extends all the way around the cavity that requires sealing. The surface feature may be a protrusion that causes a line contact seal to be formed between the opposing faces so that high forces applied at this line contact create an effective seal at high temperatures and pressures, and with low pumped fluid viscosities. 
         [0019]    In some embodiments the protrusion symmetrically or asymmetrically comes to a point so that one area protrudes away from the surrounding surface by a greater degree than the rest of the protrusion so that it contacts a flat mating surface of the opposing surface, thus creating the aforementioned line contact. The surface associated with the protrusion may extend radially outward sufficiently that bolt holes can be provided. Bolts may thus be used to apply force on a flange so that the protrusion is loaded against the mating seal face. The force from the bolts creates a desired high line contact force where the protrusion engages the opposing surface. The area that is in contact and under high contact force produces the desired seal. 
         [0020]    In one embodiment, the seal feature is a circumferential protrusion having a radial cross-section. It will be appreciated, however, that the protrusion can have other cross-sectional geometries, such as elliptical, triangular or other geometric or non-geometric shapes. 
         [0021]    It will also be appreciated that the disclosed seal can be used in any location where an o-ring or gasket is typically used, such as on flange faces. In one embodiment the disclosed seal is used on the flange face of a shaft sealing sleeve for a polymer extrusion pump (PEP), where the operating temperature of the PEP pump is too high for an o-ring, and where a gasket would be too small and cumbersome for the application. 
         [0022]    Referring now to  FIGS. 1-4 , an exemplary gear pump  100  is shown. The pump  100  may include a central gear plate  102 , front and rear plates  104 ,  106 , a shaft seal assembly  108  and a drive shaft  110 . An inlet port (not shown) and an outlet port  112  may be formed in the central gear plate for moving fluid through the pump  100 . The inlet and outlet ports may be coupled to inlet and outlet piping or tubing using a suitable c-ring  113 . The pump  100  may be fixed in its assembled form via a plurality of fasteners  114 ,  116 , which in the illustrated embodiment are socket head cap screws. 
         [0023]      FIG. 2  shows the pump  100  in exploded form. As can be seen, a drive shaft  110  includes a first gear  118  which intermeshes with a second gear  120  of a driven shaft  122 . First and second asymmetrical bearings  124 ,  126  are positioned on opposite sides of the first and second gears  118 ,  120  and receive the drive shaft  110  and driven shaft  122  via respective bores  128 A, B,  130 A, B, respectively. These asymmetrical bearings  124 ,  126  may be substantially the same as those disclosed in pending U.S. patent application Ser. No. 13/850,884, filed Mar. 27, 2014, and titled “Gear Pump with Asymmetrical Dual Bearing,” the entirety of which is incorporated by reference herein. It will be appreciated that the bearing style is not critical to the disclosure, and other bearing forms can be used. The first and second gears  118 ,  120  and first and second asymmetrical bearings  124 ,  126  are received within an asymmetrical opening  132  in the central gear plate  102 . 
         [0024]    The shaft seal assembly  108  may include a plurality of sealing elements configured to prevent fluid leakage around the drive shaft  110 . In the illustrated embodiment, the shaft seal assembly  108  comprises a lip seal housing  134 , a lip seal  136  and a sealing sleeve  138 , which may be fixed together in the stacked relation shown in  FIG. 3 . The lip seal  136  may be held in a recess formed in the lip seal housing  134  and may form a radial seal around the drive shaft  110 , and may form a face seal between the sealing sleeve  138  and the lip seal housing  134 . 
         [0025]    A cylindrical body portion  144  of the sealing sleeve  138  may be received in an opening  146  of the front plate  104 . The sealing sleeve  138 , lip seal  136  and lip seal housing  134  may all have corresponding central bores which receive a portion of the drive shaft  110  therethrough. The central bore  152  of the sealing sleeve  138  may include a helical groove  154  for sealing against the surface of the drive shaft  110 . The helical groove  154  allows the sealing sleeve  138  to act as a screw-type pump during operation. As fluid attempts to leave the gear pump (around the outer diameter of the drive shaft  110 ), the shaft&#39;s rotary motion forces the fluid into the groove  154 . This creates a pressure greater than the pressure forcing the fluid out of the pump, and forces the fluid back toward the central gear plate  102 . Thus arranged, the pumped fluid is prevented from leaking past the drive shaft  110  during operation. 
         [0026]    The pump  100  may also include alignment, or “piloting” features on the sealing elements, thus improving concentricity between the axes of the sealing elements and the axis of the shaft, which are otherwise independent features. As shown, the sealing sleeve  138  includes a flange portion  158  having a forward facing circumferential alignment recess  160  disposed adjacent to the perimeter of the flange portion. As will be appreciated this alignment recess  160  can be used to align one or more secondary seals. In the illustrated embodiment, the alignment recess  160  receives a rearward protruding circumferential lip portion  162  of the lip seal housing  134 . By fitting the circumferential lip portion  162  into the alignment recess  160 , a desired high degree of concentricity between the axis of the drive shaft  110  and the lip seal axis can be achieved. As shown, the lip seal housing  134  includes its own alignment recess  164  disposed on a forward facing portion of the housing. This alignment recess  164  can be used to align additional sealing elements (not shown), as desired. 
         [0027]    During assembly, the sealing sleeve  138  may be bolted to the front plate  104 . There may be a loose clearance fit between the outer surface of the cylindrical body portion  144  of the sealing sleeve and the front plate  104 . Since the sealing sleeve is not tightly located on the front plate  104 , this loose fit reduces the chances of pump binding during assembly, when the fasteners  114  are tightened. 
         [0028]    As can be seen in  FIGS. 4-6 , the sealing protrusion  170  is disposed on a first face surface  172  of the flange portion  158  of the sealing sleeve  138 . In the illustrated embodiment the sealing protrusion  170  is positioned directly adjacent to the cylindrical body portion  144  of the sealing sleeve  138 . Although not visible in this view, it will be appreciated that the sealing protrusion  170  runs in a continuous circular manner about the circumference of the cylindrical body portion  144  so as to form a sealing “ring” arrangement. 
         [0029]    The first face surface  172  is positioned in confronting relation to an opposing second face surface  174  of the front plate  104  so that the sealing protrusion  170  is disposed directly adjacent to the opening  146  in the front plate  104 . Thus arranged, tightening the fasteners  114  causes the lip seal housing  134  to press the sealing sleeve  138  against the front plate  104 , forcing the sealing protrusion  170  against the second face surface  174  of the front plate. The sealing protrusion  170  thereby forms a line contact seal with the second face surface  174  of the front plate  104 . This effectively seals off the opening  146  in the front plate  104  and prevents fluid from the interior of the pump  100  from passing out of the opening. 
         [0030]      FIG. 6  shows sealing sleeve  138  including the first face surface  172  and the sealing protrusion  170  extending therefrom. The front plate  104  and its associated second face surface  174  are shown in dashed lines. In this embodiment the sealing protrusion  170  has having a circular cross-section of radius “r.” In one non-limiting exemplary embodiment this radius can be from about 0.140 inches to about 0.150 inches. In addition, the sealing protrusion  170  has a protrusion height “PH” as measured from the first face surface  172  to a contact portion  176  of the sealing protrusion. In one non-limiting exemplary embodiment this protrusion height can be from about 0.004 inches to about 0.006 inches. The sealing protrusion  170  may also have a protrusion length “L” ( FIG. 5 ) which can have dimensions that will be described in greater detail below. 
         [0031]    Force applied to the sealing sleeve  138  by the fasteners  114  (disposed in fastener holes  178 ) is illustrated as arrow “F.” The region requiring sealing (i.e., the interior of the pump cavity) is illustrated as region “SR.” 
         [0032]    Referring to  FIG. 5 , the following rules can apply for sizing the disclosed sealing arrangement: 
         [0033]    (1) The size of the sealing cavity (e.g., the diameter of the opening  146  in the front plate  104 ), as a diameter, can be defined as “C.” The inner radial edge  171  of the sealing protrusion  170 , as a diameter, can be defined as “E.” “E” should be at least 0.005-inches greater than “C.” 
         [0034]    (2) The length of the sealing protrusion  170  (i.e., the distance between the inner radial edge  171  and the outer radial edge  173  can be defined as “L.” The maximum outer diameter of the flange portion  158  of the sealing sleeve  138  is defined as “M” (see  FIG. 4 .) “L” should be 5-10% of the size of “C,” but no larger than 3% of “M.” 
         [0035]    (3) The distance that the seal feature protrudes from the first face surface  172  can be defined as “PH.” “PH” should be 7-10% of “L,” but not greater than 0.015-inches. 
         [0036]    (4) A tangent angle line “TAL” exists that intersects the inner radial edge  171  of the sealing protrusion  170 , and is also tangent to the sealing protrusion profile. The angle of this line relative to the first face surface  172  can be defined as “A.” “A” should be no greater than 85% of the cutting angle of the tool used to produce the sealing protrusion  170  profile. This limitation prevents the tool from damaging the part when the profile is being generated. 
         [0037]    (5) The surface finish of the sealing protrusion  170  should be better than or equal to 32 Ra. The surface finish of the second face surface  174  can be 16 Ra or better. 
         [0038]    As previously noted, the sealing protrusion  170  can take any of a variety of cross-sectional shapes in addition to the disclosed circular cross-section. For example, the sealing protrusion  170  may have a triangular shape, an elliptical shape, or the like. 
         [0039]    In addition, although the sealing protrusion  170  is described as being a continuous circular protrusion disposed about the cylindrical body portion  144  of the sealing sleeve  138  (i.e., a circular ring), it will be appreciated that the sealing protrusion need not form a “circular” seal ring. Other geometric and non-geometric shapes could be employed. The sealing protrusion may be milled, cast, turned or permanently molded on the first face surface  172 . In addition, more than one sealing protrusion could be used, as desired. 
         [0040]    Further, although the sealing protrusion  170  is described as being formed on the first face surface  172  of the sealing sleeve  138 , it could instead be formed on the second face surface  174  of the front plate  104 . In such a case the first face surface  172  would be flat, and the sealing protrusion  170  would bear against it upon application of force via the fasteners  114 . In addition, one or more sealing protrusions could be formed on other surfaces of the pump  100  in which flat surfaces are placed in confronting relation. For example, the disclosed sealing arrangement could be used between any of the plates in the pump, eliminating the need for using other metal-to-metal seals or o-rings. In addition, the disclosed sealing arrangement could be very used on port flanges in lieu of the c-rings  113  (see  FIG. 2 ) 
         [0041]    Based on the foregoing information, it will be readily understood by those persons skilled in the art that the invention is susceptible of broad utility and application. Many embodiments and adaptations of the invention other than those specifically described herein, as well as many variations, modifications, and equivalent arrangements, will be apparent from or reasonably suggested by the present invention and the foregoing descriptions thereof, without departing from the substance or scope of the present invention. Accordingly, while the invention has been described herein in detail in relation to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for the purpose of providing a full and enabling disclosure of the invention. The foregoing disclosure is not intended to be construed to limit the invention or otherwise exclude any such other embodiments, adaptations, variations, modifications or equivalent arrangements; the invention being limited only by the claims appended hereto and the equivalents thereof. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for the purpose of limitation.