ANNULAR SEALING MEMBER WITH ENHANCED HOOP STRENGTH

Abstract

Apparatus and method for providing a sealing member with enhanced hoop strength. In some embodiments, a valve assembly includes a piston and first means for establishing a fluid-tight seal when the piston is in a closed position and for preventing a blow out condition when the piston is transitioned to an open position. In other embodiments, a sealing member is characterized as an endless annular ring which extends about a central axis, the sealing member comprising an elongated circle cross-sectional shape while the sealing member is maintained in an uncompressed state. In other embodiments, a method comprises extruding a sealing material through an extrusion assembly to form an endless annular ring which extends about a central axis, the extrusion assembly imparting a desired amount of curvilinearity along a longitudinal length of the material to form an orthogonal seam when a leading and trailing edge of the material are adjoined.

Description

BACKGROUND

Sealing members are used in a variety of applications to establish fluidic seals, such as in a valve assembly in a pressurized fluid system. Generally, it is desirable that a sealing member retain its sealing capabilities over a wide range of operational conditions. It is further generally desirable that a sealing member remain in place when subjected to significant fluidic flow, such as when the sealing member is disposed on a piston member that is moved from a closed position to an open position.

FIGS. 1A and 1B show a prior art valve assembly 10. The valve assembly 10 includes a piston 12 that selectively regulates fluidic flow from an inlet port 14. The piston 12 is in a closed position in FIG. 1A. FIG. 1B illustrates the piston 12 as it transitions to an open position.

The piston 12 is sealed in the closed position using a conventional o-ring sealing member 16. The sealing member 16 has a circular cross-sectional shape, and is retained within an annular recess 18 of the piston 12. An outer radial surface of the sealing member 16 forms a fluidic seal against an interior annular sidewall 20 of a housing 22, and an opposing inner radial surface of the sealing member 16 forms a fluidic seal against the annular recess 18.

As the piston 12 initially moves to the open position, significant amounts of fluidic flow (arrows 24) can pass adjacent the sealing member 16. Particularly in higher pressure fluidic environments, a portion of the fluidic flow can pass between the inner radial surface of the sealing member 16 and the recess 18, exerting an outwardly directed force upon the sealing member 16. If the hoop strength of the sealing member 16 is insufficient to resist this outwardly directed force, the sealing member 16 may be deformed and/or dislocated (blown out) from the annular recess 18, as depicted in FIG. 1B.

SUMMARY

Accordingly, various embodiments of the present invention are generally directed to an apparatus and method for providing a sealing member with enhanced hoop strength (i.e., ability to retain its initial hoop shape).

In accordance with some embodiments, a valve assembly is provided in which a piston is moved from a closed position in which a pressurized fluidic flow is inhibited to an open position in which a pressurized fluidic flow is established, and the improvement is characterized as comprising first means for establishing a fluid-tight seal when the piston is in the closed position and for preventing a blow out condition when the piston is transitioned to the open position.

In accordance with other embodiments, an apparatus comprises a sealing member characterized as an endless annular ring which extends about a central axis, the sealing member comprising an elongated circle cross-sectional shape while the sealing member is maintained in an uncompressed state, said cross-sectional shape defined by parallel top and bottom flat surfaces of selected length L in a direction perpendicular to and intersecting the central axis and opposing inner and outer radiused surfaces of selected radius R and which respectively face toward and away from the central axis, wherein L is greater than R.

In accordance with yet other embodiments, a method comprises extruding a sealing material through an extrusion assembly to form an endless annular ring which extends about a central axis, the extrusion assembly imparting a desired amount of curvilinearity along a longitudinal length of the material to form an orthogonal seam when a leading edge and a trailing edge of the material are adjoined.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B generally illustrate a prior art valve assembly that utilizes a conventional o-ring with a circular cross-sectional shape to establish a fluidic seal.

FIGS. 2A and 2B show an exemplary valve assembly incorporating a sealing member constructed in accordance with various embodiments of the present invention.

FIG. 3 provides a top plan view of the sealing member of FIGS. 2A-2B.

FIG. 4 shows a cross-sectional representation of the sealing member along line 4-4 in FIG. 3 to illustrate an exemplary elongated circle cross-sectional shape of the member.

FIG. 5 shows respective exemplary length and radial dimensions of the elongated circle cross-sectional shape.

FIG. 6 illustrates an alternative construction for the sealing member which utilizes an embedded reinforcement member.

FIG. 7 shows the use of a metal washer as the embedded reinforcement member of FIG. 6.

FIG. 8 shows the use of a wire mesh screen as the embedded reinforcement member of FIG. 6.

FIG. 9 shows the wire mesh screen of FIG. 8 in conjunction with an annular reinforcing ring attached thereto.

FIG. 10 illustrates a preferred manner in which the elastomeric material of the sealing member is extruded.

FIG. 11 shows a top plan view of the extruded material after processing in accordance with FIG. 10.

FIG. 12 provides another alternative construction for the sealing member in which a reinforcement member such as shown in FIG. 7 is attached to a selected side of the sealing member.

FIG. 13 shows an alternative extrusion process that provides sealing members with other cross-sectional shapes.

FIG. 14 is a cross-sectional elevational view of an alternative sealing member configuration formed by the process of FIG. 13.

FIG. 15 is a cross-sectional elevational view of another alternative sealing member formed by the process of FIG. 13.

FIG. 16 is a side elevational, cross-sectional depiction of the extrusion mechanisms generally depicted in FIGS. 10 and 13.

FIG. 17 is an end elevational, cross-sectional depiction of the extrusion mechanism of FIG. 16.

FIG. 18 provides a flow chart for an exemplary SEALING MEMBER PROCESSING routine, generally illustrative of steps carried out in accordance with various embodiments of the present invention.

DETAILED DESCRIPTION

FIGS. 2A and 2B show relevant portions of a valve assembly 100 to generally illustrate an exemplary environment in which various embodiments of the present invention can be advantageously practiced. The valve assembly 100 is contemplated as being of the type configured to selectively alter the flow of a pressurized fluid in a pressurized fluid system, although such is not limiting.

The valve assembly 100 comprises a housing 102 with an upstream inlet port 104 and a downstream outlet port 106. A piston 108 selectively moves between a closed position (FIG. 2A) and an open position (FIG. 2B) to selectively inhibit or permit fluidic flow of the pressurized fluid from the inlet port 104 to the outlet port 106. A biasing member 110, such as a spring, biases the piston 108 in the closed position. Other biasing arrangements can readily be used, however, or omitted entirely.

An annular sealing member 112 is disposed within a corresponding annular groove 114 of the piston 108. The sealing member 112 contactingly engages an annular sidewall 116 of the housing 102 to establish a fluid-tight seal while the valve assembly 100 remains in the closed position.

When the pressure of the pressurized fluid is sufficient to overcome the biasing force supplied by biasing member 110, the piston 108 advances upwardly as shown in FIG. 2B. As the piston 108 moves to the open position, the sealing member 112 becomes disengaged from the sidewall 116 and is subjected to the fluidic flow of the pressurized fluid as the fluid initiates passage to the outlet port 106. As explained below, the sealing member 112 is advantageously configured to provide effective steady-state sealing in conditions such as depicted in FIG. 1, as well as to resist mechanical deformation and/or dislocation (blowout) while being subjected to substantial amounts of fluidic flow as in FIG. 2.

FIGS. 3 and 4 provide respective top plan and cross-sectional views of the sealing member 112 of FIGS. 2A-2B. Generally, the sealing member 112 is characterized as an endless annular ring (o-ring) which extends about a central axis 118. The sealing member 112 is preferably formed of an elastomeric material and has a cross-sectional shape characterized as an elongated circle.

As further shown in FIG. 5, the elongated circle cross-sectional shape of the sealing member 112 is generally defined by opposing, parallel top and bottom flat surfaces (linear segments) 120, 122, and opposing inner and outer radiused surfaces (semicircular end segments) 124, 126. Each of the flat surfaces 120, 122 has a respective length L in a direction perpendicular to, and which intersects, the central axis 118. Each of the radiused surfaces 124, 126 has a respective radius R.

The cross-sectional shape represented in FIG. 5 is a steady-state configuration for the sealing member 112; that is, the sealing member 112 maintains the elongated circle cross-sectional shape while in an uncompressed state (i.e., in the absence of any externally applied support or compression forces acting upon the member). For purposes of clarity, it will be noted that the cross-sections of FIGS. 4 and 5 are taken along a plane that includes the central axis 118 of the sealing member 112.

The respective values of L and R can vary depending on the requirements of a given application, with the length L being greater than the radius R (L>R). Preferably, the length L is several times greater than the radius R, such as L>5*R. It is noted that the flat surfaces 120, 122 lie along respective planes normal to the central axis 118, and the radiused surfaces 124, 126 compressingly engage corresponding sidewalls to effect fluidic sealing at corresponding innermost diameter (ID) and outermost diameter (OD) extents of the sealing member 112. Exemplary radial values R for different industry standard classes of circular cross-sectional shaped o-rings are set forth in Table 1:

TABLE 1
CLASS RADIUS R (inches)
2-0   0.0350
2-1   0.0515
2-2   0.0695
2-3   0.1050
2-4   0.1375

The sealing member 112 can be adapted to have inner and outer radii that correspond to any of the above classes, and used in an associated application provided that the corresponding retention aperture (e.g., 114 in FIGS. 2A-2B) is extended (deepened) by a sufficient distance to accommodate the length dimension L of the sealing member 112. It will be noted that a two-piece configuration is preferably set forth for the piston 108 in FIGS. 2A-2B to facilitate installation of the sealing member 112.

For reference, the sealing member 112 of FIGS. 2-4 is contemplated as comprising an equivalent class 2-3 member, with R being nominally 0.1050 inches, in (10.0060 in). The corresponding length value L of the sealing member 112 is nominally 0.5400 in (10.0060 in). The OD of the sealing member 112 is nominally 3.2700 in (±0.0200 in), and the ID is nominally 1.9800 in (10.0160 in). The same L and R values can be used with different respective ID and OD values, and vice versa, as desired.

The elongated circle cross-sectional shape has been found by the present inventor to provide unexpected operational improvements over conventional configurations, such as the circular o-ring of FIGS. 1A-1B. The elongated circle cross-sectional shape significantly enhances hoop strength of the sealing member 112, and the length dimension L reduces the amount of pressure that is able to get behind the sealing member 112 within the recess when the sealing member 112 is initially exposed to the high pressure fluid.

Accordingly, the sealing member 112 maintains a fluid-tight fluidic seal in captured sealing environments (e.g., FIG. 2A), provides low-frictional sliding contact, and is highly resistant to damage and/or dislocation in high pressure environments (e.g., FIG. 2B).

A suitable material from which the sealing member 112 can be advantageously formed is a fluoroelastomer such as commercially available under the registered trademark Viton® by E. I. Du Pont De Nemours & Company, Wilmington, Del., USA. Other suitable materials can include any number of natural or synthetic rubbers, urethanes, plastics, etc. A suitable durometer (hardness) may be on the order of 70-80, depending on the requirements of a given application, although both harder and softer materials can be used as desired. The seal member material can further be filled with a suitable filler such as glass fibers, carbon filaments, nanotubes, etc.

FIG. 6 shows an alternative sealing member 132 which retains the aforedescribed elongated circle cross-sectional shape, but additionally incorporates an internally embedded reinforcement member 134. The reinforcement member 134 generally serves to further strengthen the sealing member 132 against damage and removal during operation, as well as to enable the sealing member 132 to further retain its initial elongated circular shape prior to, and after, application of compressive forces thereto.

The reinforcement member 134 of FIG. 6 can take any number of forms. For example, as shown in FIG. 7, a rigid washer (annular disk) 136 can be used to reinforce the sealing member 132. The washer 136 is formed of a suitably rigid material such as metal, plastic, nylon, etc.

Alternatively, the reinforcement member can comprise a wire mesh screen, such as generally depicted at 138 in FIG. 8. The screen 138 is formed of individual wires (filaments) arrayed in a substantially planar, cross-hatched pattern. While linear filaments are shown in FIG. 8, other shapes can be used including curvilinear filaments, as well as “out of plane” filaments that cooperate to form a 3-dimensional lattice structure. As shown in FIG. 9, the wire mesh screen 138 of FIG. 8 can further be augmented with one or more reinforcing rings 140 of a suitably rigid material, such as nylon.

The sealing members 112, 132 can be formed in a number of ways. U.S. Pat. No. 6,315,299, assigned to the assignee of the present application, generally discloses a compression molded process whereby a reinforcement ring is placed into an annular molding cavity. Sealing material is injected into the cavity, such as a suitable elastomer, and the combination is cured to form a reinforced sealing member.

While generally operable, a problem associated with the '299 patent process is the inability to consistently maintain the reinforcement ring within a centrally disposed orientation of the sealing material. Often, the injected material deflects the ring and pushes it to one side of the annular cavity, resulting in nonuniform thicknesses of elastomeric material coverage, or even exposure of the ring through the cured sealing member.

Accordingly, various embodiments presented herein preferably form the sealing member using an extrusion process, such as set forth by FIG. 10. An extrusion mechanism 142 extrudes uncured seal material 144 so that the extruded material remains in a soft, malleable state. A guide 146 at the exit portion of the mechanism 142 preferably induces a desired amount of curvilinearity to the extruded material 144 along a longitudinal length thereof as it exits the mechanism 142 to provide a substantially circular shape.

As depicted in FIG. 11, this advantageously forms an orthogonal mating seam 148 between the leading edge and the trailing edge of the extruded material 144; that is, the leading and trailing edges nominally align at the seam (unction) 148, ensuring substantially uniform thickness and eliminating voids or other discontinuities in the sealing material. It is contemplated that the seam 148 will remain visible in the sealing member at the conclusion of the subsequent curing process without affecting the operation thereof, and will enhance the hoop strength at the seam by facilitating improved joining of the respective edges.

When an internal reinforcement member as shown in FIGS. 6-9 is to be incorporated into the sealing member, the extruded material 144 is preferably hollow; that is, as shown in FIG. 10, a central channel, or interior aperture 150 will extend through the extruded material 144 as it exits the extrusion mechanism 142. A slit can be subsequently formed in the extruded material 144 at the ID thereof to facilitate placement of the reinforcement member 134 therein.

Alternatively, as shown in FIG. 10 an extruded slit 152 can be formed directly in the extruded material 144 during the extrusion process, facilitating subsequent insertion of the reinforcement member 134. In either case, the extruded material 144 is thereafter cured in a suitable curing operation to form the final sealing member.

FIG. 12 shows another alternative embodiment for a sealing member, numerically denoted therein at 162. The sealing member 162 includes an elastomeric material with an elongated circle cross-sectional shape as before. An externally disposed reinforcement member 164 is affixed to a selected side of the elastomeric material, in this case the bottom flat surface 122. The reinforcement member 164 in FIG. 12 is generally disk shaped, similar to the washer configuration previously set forth in FIG. 7. However, such is not limiting in that any number of alternative configurations for the externally disposed reinforcement member 164 can be used including, but not limited to, the screen-based configurations of FIGS. 8-9.

While various embodiments presented above provided a sealing member with enhanced hoop strength in conjunction with the provision of an elongated circle cross-sectional shape, other embodiments disclosed herein are provided with alternative cross-sectional shapes. FIG. 13 illustrates an alternative extrusion process generally similar to that previously set forth in FIG. 10.

The process of FIG. 13 preferably uses an extrusion mechanism 166 and guide 168 to provide curvilinearly extending, uncured extruded material 170 that mates at an orthogonal seam 148, as before (FIG. 11). However, the extruded material 170 in FIG. 13 is provided with a substantially circular cross-sectional shape, unlike the elongated circle shape formed in FIG. 10.

An interior aperture 172 is formed in the material 170 to accommodate the insertion of a suitable reinforcement member 174, such as an annular nylon ring as shown in FIG. 14. The formation of the interior aperture 172 during the extrusion process substantially ensures that the reinforcement member 174 will be maintained within the extruded material 170 with a uniform thickness of the material 170 surrounding the member 174.

As desired, a slit can be cut at the ID of the material 170 to facilitate insertion of the member 174, or an extruded slit 176 can be formed during the extrusion process (FIG. 13). It is contemplated that the existence of the slit will remain observable upon curing of the sealing member.

Because the extrusion process precisely locates the centrally disposed aperture 172, any number of cross-sectional shapes can be employed in the extruded material 170, such as an exemplary rounded rectangle cross-sectional shape as shown in FIG. 15.

FIGS. 16-17 further illustrate preferred aspects of the various extrusion processes disclosed herein. For clarity, FIGS. 16-17 are illustrated with respect to the extrusion process of FIG. 10, although it will be understood that these figures can readily be adapted to the process of FIG. 13.

In FIG. 16, a housing 178 defines an interior sidewall 180 with a shape nominally conforming to the desired cross-sectional shape of the extruded material (144 in FIG. 10). A cantilevered, centrally disposed barrier portion 182 is supported by a support arm 184 to form the interior aperture 150 in the extruded material. As desired, the interior sidewall 180 can include a curvilinearly shaped exit portion 186 to initiate the desired curvilinearity along the longitudinal length of the extruded material 144, with or without the further use of the external guide 146.

FIG. 17 generally provides an end view of the arrangement of FIG. 16. A diverting flange 188 extends from the barrier portion 182 in a direction substantially orthogonal to the support arm 184 (FIG. 16). The flange 188 further interrupts the flow of the extruded material 144 to form the aforementioned slit 152 (FIG. 10).

FIG. 12 provides a flow chart for a SEALING MEMBER PROCESSING routine 200, generally illustrative of preferred steps carried out in accordance with the foregoing discussion.

At step 202, a suitable sealing material is initially extruded from a suitable extrusion process such as depicted in FIGS. 10, 13 and 16-17. The extruded material (such as 144) is preferably in an uncured state such as an uncured elastomeric material. The extrusion process further preferably imparts a desired level of curvilinearity to the extruded material 144 as it exits the extrusion process, thereby ensuring an orthogonal mating seam (148, FIG. 11).

When an interiorly placed reinforcement member is desired, the extruded material is supplied with an extruded central aperture, such as 150 in FIG. 10 or 172 in FIG. 13. In such case a slit is additionally formed at step 204 in the extruded material. This can be carried out by a separate slitting operation, or by extruding the slit into the extruded material 144 (FIG. 17). The interiorly placed reinforcement member is then inserted at step 206 into the central aperture.

Alternatively, when an exteriorly placed reinforcement member is desired, the reinforcement member is attached directly to an appropriate outer surface of the member at step 206. It will be noted that urethane exhibits adhesive properties when cured, so that the use of urethane as the extruded material may not necessarily require the use of a separate bonding agent (adhesive, etc.) to adhere the reinforcement member to the extruded material.

The material is next cured in a suitable curing operation at step 208. This preferably involves placing the material into a molding cavity and subjecting the material to selected pressure and/or temperature levels for a suitable dwell time associated with the material to effect the curing process. Other arrangements, such as curing ovens, can readily be used, however.

As shown by step 210, the cured sealing member is thereafter removed from the molding operation and used in an appropriate application to effect a fluidic seal, such as in a valve member as depicted in FIGS. 2A-2B. The process then ends at step 212.

For purposes of the appended claims, the recited first means will be understood to correspond to the aforedescribed sealing members that achieve enhanced hoop strength, namely the elongated circle cross-sectional shaped sealing member 112 of FIGS. 2A-2B, 3-5; the elongated circle cross-sectional shaped sealing member 132 with an associated internally disposed reinforcement member 134-140 of FIGS. 6-9; the elongated circle cross-sectional shaped sealing member 162 with externally disposed reinforcement member 164 of FIG. 12; and the extruded sealing members with respective circular and rounded rectangle cross-sectional shapes and interiorly placed reinforcement members of FIGS. 14-15. Prior art conventional o-rings as discussed in FIGS. 1A-1B, and prior art reinforced o-rings with molded in place reinforcement rings as disclosed by the aforementioned '299 patent process, are not included within the scope of the recited first means and are explicitly excluded from the definition of an equivalent.

Moreover, for purposes of the appended claims the term “elongated circle” will be understood to correspond to a shape such as set forth in FIG. 5 in which a circle is linearly extended in a single direction (i.e., opposing 180 degree semicircular segments separated by linear line segments), and will thus exclude continuously curvilinear shapes such as ellipses and ovals, as well as segmented shapes such as a rounded rectangle.

It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. In a valve assembly in which a piston is moved from a closed position in which a pressurized fluidic flow is inhibited to an open position in which a pressurized fluidic flow is established, the improvement characterized as comprising first means for establishing a fluid-tight seal when the piston is in the closed position and for preventing a blow out condition when the piston is transitioned to the open position.

2. The improvement of claim 1, wherein the first means comprises an annular sealing member characterized as an o-ring with an elongated circle cross-sectional shape while the sealing member is in an uncompressed state, the cross-sectional shape taken along a plane that includes a central axis of the sealing member and defined by opposing inner and outer semicircular end surface segments of a selected radius R, and opposing top and bottom linear surface segments therebetween of a selected length L greater than R.

3. The improvement of claim 2, wherein the sealing member further comprises an elastomeric material and an annular reinforcement member affixed to the elastomeric material.

4. The improvement of claim 3, wherein the annular reinforcement member is disposed within an annular interior aperture of the elastomeric material.

5. The improvement of claim 3, wherein the annular reinforcement member is affixed to an outermost top or bottom surface of the elastomeric material.

6. The improvement of claim 1, wherein the first means comprises a sealing member formed of extruded material with an induced curvilinear longitudinal shape to form an orthogonal seam when a leading edge and a trailing edge of the extruded material are adjoined.

7. The improvement of claim 6, wherein the extruded material further comprises a central aperture that is extruded in the extruded material.

8. The improvement of claim 7, wherein the extruded material further comprises a slit that is extruded in the extruded material at an innermost diameter of the sealing member, the slit and central aperture accommodating placement of an interiorly placed reinforcement member into the extruded material.

9. The improvement of claim 1, wherein the first means comprises an extruded sealing member with an interiorly placed annular reinforcement member inserted through a slit at an innermost diameter of the sealing member.

10. An apparatus comprising a sealing member characterized as an endless annular ring which extends about a central axis, the sealing member comprising an elongated circle cross-sectional shape while the sealing member is maintained in an uncompressed state, said cross-sectional shape defined by parallel top and bottom flat surfaces of selected length L in a direction perpendicular to and intersecting the central axis and opposing inner and outer radiused surfaces of selected radius R and which respectively face toward and away from the central axis, wherein L is greater than R.

11. The apparatus of claim 10, wherein the sealing member is formed of an elastomeric material.

12. The apparatus of claim 11, wherein the sealing member further comprises a rigid annular reinforcement member affixed to the elastomeric material.

13. The apparatus of claim 12, wherein the reinforcement member is embedded within the elastomeric material so that the elastomeric material wholly surrounds the reinforcement member.

14. The apparatus of claim 12, wherein the reinforcement member is affixed to a selected one of the top or bottom fiat surfaces of three sealing member.

15. The apparatus of claim 10, wherein the sealing member further comprises an annular reinforcement member characterized as a rigid washer.

16. The apparatus of claim 10, wherein the sealing member further comprises an annular reinforcement member characterized as a wire mesh screen.

17. The apparatus of claim I 0, wherein the annular reinforcement member further comprises at least one rigid annular ring affixed to the wire mesh screen.

18. The apparatus of claim 10, wherein L is greater than 5*R.

19. The apparatus of claim 10, further comprising a valve member comprising an annular groove in which the sealing member is disposed so that the outer radiused surface of the sealing member contactingly engages an interior annular sidewall to effect a first fluidic seal and the inner radiused surface of the sealing member contactingly engages the annular groove to effect a second fluidic seal, wherein said elongated circle cross-sectional shape of the sealing member facilitates retention of the sealing member within the groove.

20. A method comprising a step of extruding a sealing material through an extrusion assembly to form an endless annular ring which extends about a central axis, the extrusion assembly imparting a desired amount of curvilinearity along a longitudinal length of the material to form an orthogonal seam when a leading edge and a trailing edge of the material are adjoined.

21. The method of claim 21, further comprising a step of curing the material to form a cured sealing member configured to establish a fluidic seal.

22. The method of claim 20, wherein the extruding step further comprises extruding a central aperture in the material along the longitudinal length thereof.

23. The method of claim 22, further comprising a step of inserting an annular reinforcement member into the central aperture through a slit formed through the material.

24. The method of claim 22, wherein the extruding step further comprises extruding a slit along the longitudinal length of the material in communication with the central aperture.

25. The method of claim 24, further comprising inserting an annular reinforcement member into the central aperture through the extruded slit.

26. The method of claim 20, wherein the extruded material is provided with an elongated circle cross-sectional shape while the material is in an uncompressed state, the cross-sectional shape taken along a plane that includes the central axis and defined by opposing inner and outer semicircular end surface segments of a selected radius R, and opposing top and bottom linear surface segments therebetween of a selected length L greater than R.

27. The method of claim 26, wherein L is greater than 5*R.