Pump with shaped face seal

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.

Claims

1. A sealing arrangement for a pump, comprising a sealing sleeve having a first face; and a front plate having a second face positioned in confronting relation to the first face, the front plate defining a sealing cavity for holding a fluid under pressure, wherein one of the first face and the second face has a sealing protrusion thereon, wherein the sealing protrusion is positioned to engage an opposing face of one of the first face and the second 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.

2. The sealing arrangement of claim 1, wherein the sealing protrusion has a geometric cross-sectional shape.

3. The sealing arrangement of claim 1, wherein the sealing protrusion has a non-geometric cross-sectional shape.

4. The sealing arrangement of claim 1, wherein the sealing protrusion is disposed about a cylindrical body portion of the sealing sleeve.

5. The sealing arrangement of claim 4, wherein the sealing protrusion engages a second face surface of the front plate around a circumference of the sealing cavity.

6. The sealing arrangement of claim 1, wherein the sealing protrusion has a circular cross-section of radius r.

7. The sealing arrangement of claim 6, wherein the radius r is in a range from 0.140 inches to 0.150 inches.

8. The sealing arrangement of claim 1, wherein the sealing protrusion has a protrusion height PH as measured from a first face surface to a contact portion of the sealing protrusion.

9. The sealing arrangement of claim 8, wherein the protrusion height is in a range from 0.004 inches to 0.006 inches.

10. The sealing arrangement of claim 1, wherein the sealing protrusion has a protrusion length L as measured from an inner radial edge of the sealing protrusion and an outer radial edge of the sealing protrusion, wherein L is 5-10% of the size of the diameter of the sealing cavity.

11. The sealing arrangement of claim 10, wherein the protrusion length L is no larger than 3% of an outer diameter of a flange portion of the sealing sleeve.

12. The sealing arrangement of claim 11, wherein the sealing protrusion has a protrusion height PH as measured from a first face surface to a contact portion of the sealing protrusion, the protrusion height PH being 7-10% of the protrusion length L, and not greater than 0.015 inches.

13. The sealing arrangement of claim 1, wherein a surface finish of the sealing protrusion is 32 Ra or better, and a surface finish of the opposing face of one of the first face and the second face is 16 Ra or better.

14. A method for sealing a pump, comprising the steps of: preventing movement of a fluid from a sealing cavity past a sealing protrusion, comprising: a sealing sleeve having a first face; and a front plate having a second face positioned in confronting relation to the first face, the front plate including an opening in fluid communication with the sealing cavity, wherein one of the first face and the second face has the sealing protrusion disposed thereon, wherein the sealing protrusion is positioned to engage an opposing face of one of the first face and the second face when the first face and the second face are pressed together so that the sealing protrusion seals against the opposing face.

15. The method of claim 14, wherein the sealing protrusion forms a line contact seal when the first face and the second face are pressed together.

16. The method of claim 14, wherein the sealing protrusion surrounds the opening in the second pump component.

17. The method of claim 14, further comprising the step of contacting the sealing sleeve with a lip seal housing by aligning one or more corresponding alignment features.

18. The method of claim 14, further comprising the step of pressing the first face and the second face together with one or more bolts.

19. The method of claim 14, further comprising the step of pressurizing the sealing cavity with a fluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) By way of example, a specific embodiment of the disclosed device will now be described, with reference to the accompanying drawings, in which:

(2) FIG. 1 is an isometric view of a pump according to the disclosure;

(3) FIG. 2 is an exploded view of the pump of FIG. 1;

(4) FIG. 3 is a cross-section of the pump of FIG. 1 taken along line 3-3 of FIG. 1;

(5) FIG. 4 is a detail view of a portion of the cross-section view of FIG. 3;

(6) FIG. 5 is a first detail view of a portion of FIG. 4; and

(7) FIG. 6 is a second detail view of a portion of FIG. 4.

DETAILED DESCRIPTION

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) 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 128A, B, 130A, 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.

(14) 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.

(15) 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'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.

(16) 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.

(17) 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.

(18) 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.

(19) 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.

(20) 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.

(21) 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.

(22) Referring to FIG. 5, the following rules can apply for sizing the disclosed sealing arrangement:

(23) (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.

(24) (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.

(25) (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.

(26) (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.

(27) (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.

(28) 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.

(29) 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.

(30) 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)

(31) 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.