Threaded boss for pressure vessel

Abstract

A boss includes a neck and a flange that extends radially outward from the neck. The neck includes a bore therethrough with a longitudinal axis. The flange includes an exterior surface, an interior surface, and a peripheral surface at a farthest extent from the longitudinal axis. The peripheral surface connects the interior surface and the exterior surface and includes, along any radius of the boss, a first circumferential ridge and a second circumferential ridge, wherein the first circumferential ridge is located closer to the exterior surface than the second circumferential ridge. In another aspect, a pressure vessel includes a boss and a liner. In yet another aspect, a method of assembling a pressure vessel is described, which includes inserting the boss through the aperture of the liner and connecting the boss and liner so that the peripheral surface of the boss mates with the perimeter surface of the liner.

Claims

1. A boss including: a neck including a bore therethrough, wherein the bore has a longitudinal axis; and a flange that extends radially outward from the neck, wherein the flange includes: an exterior surface; an interior surface; and a peripheral surface at a farthest extent from the longitudinal axis; wherein the peripheral surface includes a helical screw thread; wherein the peripheral surface connects the interior surface and the exterior surface; and wherein the peripheral surface includes, along any radius of the boss, a first circumferential ridge and a second circumferential ridge, wherein the first circumferential ridge is located closer to the exterior surface than the second circumferential ridge.

2. The boss of claim 1, wherein a first distance between the longitudinal axis and the first circumferential ridge is equal to a second distance between the longitudinal axis and the second circumferential ridge.

3. The boss of claim 1, wherein a first distance between the longitudinal axis and the first circumferential ridge is less than a second distance between the longitudinal axis and the second circumferential ridge.

4. The boss of claim 1, wherein the first circumferential ridge is smaller than the second circumferential ridge.

5. The boss of claim 1, wherein at least one of the first and second circumferential ridges has a substantially triangular cross-sectional shape having first and second surfaces that meet at an apex.

6. The boss of claim 5, wherein at least one of the first and second surfaces is substantially perpendicular to the longitudinal axis.

7. The boss of claim 1, wherein at least one of the first and second circumferential ridges has a convex curve shape.

8. The boss of claim 1, wherein the first and second circumferential ridges are spaced apart.

9. A pressure vessel including a boss and a liner, wherein: the boss includes: a neck including a bore therethrough, wherein the bore has a longitudinal axis; and a flange that extends radially outward from the neck, wherein the flange includes: an exterior surface; an interior surface; a peripheral surface at a farthest extent from the longitudinal axis; wherein the peripheral surface connects the interior surface and the exterior surface; and wherein the peripheral surface includes, along any radius of the boss, a first circumferential ridge and a second circumferential ridge, wherein the first circumferential ridge is located closer to the exterior surface than the second circumferential ridge; and an annular tab on an exterior surface, of the flange; and the liner includes; a perimeter surface that interfaces with the peripheral surface of the boss, wherein the perimeter surface has contours that mate with the first circumferential ridge and the second circumferential ridge; and a groove configured to accept the tab; wherein a gasket is disposed between the tab and the groove.

10. The pressure vessel of claim 9, wherein the tab and the groove are configured so that an interference fit is achieved at an interface of the tab and the groove.

11. The pressure vessel of claim 9, wherein the peripheral surface includes a helical screw.

12. A method of assembling a pressure vessel including a boss and a liner, wherein: the boss includes: a neck including a bore therethrough, wherein the bore has a longitudinal axis; and a flange that extends radially outward from the neck, wherein the flange includes: an exterior surface; an interior surface; and a peripheral surface at a farthest extent from the longitudinal axis; wherein the peripheral surface connects the interior surface and the exterior surface; and wherein the peripheral surface includes, along any radius of the boss, a first circumferential ridge and a second circumferential ridge, wherein the first circumferential ridge is located closer to the exterior surface than the second circumferential ridge; and the liner includes an aperture having a perimeter surface; the method including: inserting the boss through the aperture of the liner; and connecting the boss and liner so that the peripheral surface of the boss mates with the perimeter surface of the liner.

13. The method of claim 12, wherein connecting the boss and liner includes snap-fitting the peripheral surface of the boss with the perimeter surface of the liner.

14. The method of claim 12, wherein connecting the boss and liner includes rotating the peripheral surface of the boss against the perimeter surface of the liner to remove material from the perimeter surface of the liner.

15. The method of claim 14, further including advancing the boss along the longitudinal axis relative to the liner.

16. The method of claim 12, further including achieving an interference fit at an interface between the peripheral surface of the boss and the perimeter surface of the liner.

17. The method of claim 12, further including flexing the liner to allow passage of the boss through the aperture, wherein the aperture has a circumferential dimension smaller than a circumferential dimension of the peripheral surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosed subject matter will be further explained with reference to the attached figures, wherein like structure or system elements are referred to by like reference numerals throughout the several views. Moreover, analogous structures may have reference numerals that are indexed by one hundred.

(2) FIG. 1 is a side view of a typical conventional pressure vessel.

(3) FIG. 2 is a partial cross-sectional view of one end of the pressure vessel of FIG. 1, taken along line 2-2 of FIG. 1 and showing a typical boss, liner and shell.

(4) FIG. 3 is a partial cross sectional view of an end portion of an exemplary pressure vessel boss and liner assembly.

(5) FIG. 4 is an enlarged view of a portion of FIG. 3.

(6) FIG. 5 is an exploded view of the exemplary boss and liner components of FIG. 3.

(7) FIG. 6 is similar to FIG. 5 but shows second exemplary embodiments of a pressure vessel boss and liner.

(8) FIG. 7 is similar to FIGS. 5 and 6 but shows the boss of FIG. 6 being used with the liner of FIG. 5.

(9) FIG. 8 is a partial cross sectional view of a boss and gasket assembly.

(10) FIG. 9 is a partial cross sectional view of a portion of a liner in an intermediate formation step.

(11) FIGS. 10A-10E show different embodiments for a peripheral surface of a boss of the present disclosure.

(12) While the above-identified figures set forth one or more embodiments of the disclosed subject matter, other embodiments are also contemplated, as noted in the disclosure. In all cases, this disclosure presents the disclosed subject matter by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art which fall within the scope of the principles of this disclosure.

(13) The figures may not be drawn to scale. In particular, some features may be enlarged relative to other features for clarity. Moreover, where terms such as interior, exterior, above, below, over, under, top, bottom, side, right, left, horizontal, vertical, etc., are used, it is to be understood that they are used only for ease of understanding the description. It is contemplated that structures may be oriented otherwise.

DETAILED DESCRIPTION

(14) The orientations of the components of FIGS. 3-10E are different from those in FIG. 2, in that the exterior surface 123 of boss 116 is shown as a horizontal surface at the bottom of each of the respective drawing figures. Moreover, in the drawings of the boss 116 of the present disclosure, only half of the boss 116 is illustrated. It is to be understood that each boss 116 is a generally annular, symmetrical member, similar to boss 16 of FIG. 2. In exemplary embodiments, boss 116 is radially symmetrical about longitudinal axis 152.

(15) As shown in FIG. 3, the present disclosure describes a boss 116 for a pressure vessel. Boss 116 includes neck 122 having a port or bore 126 therethrough. Bore 126 has a longitudinal axis 152. Boss 116 has a flange 124 that extends radially outward from neck 122. Flange 124 includes an exterior side 138 facing toward exterior environment 19 and an interior side 137 facing interior environment 17. Peripheral surface 128 is located on flange 124 at a farthest extent from bore 126. Peripheral surface 128 connects exterior side 138 and interior side 137 of flange 124.

(16) FIGS. 3-10E show radial cross-sectional views of boss 116 and/or liner 120.

(17) Viewing a cross-section along any radius of boss 116, peripheral surface 128 includes circumferential ridges 158. A first circumferential ridge 158 is located closer to the exterior side 138 of flange 124 than a second circumferential ridge 158.

(18) In an exemplary embodiment shown in FIGS. 3 and 4, peripheral surface 128 includes a helical screw thread. Accordingly, in the cross-sectional view along any radius of boss 116, first circumferential ridge 158 and a second circumferential ridge 158 appear to be separate; in three dimensions, however, it is to be understood that in some embodiments, they are connected in a helical orientation about peripheral surface 128. In other embodiments, an adjacent circumferential ridges 158 are discrete structures that are separated by a valley therebetween.

(19) Boss 116 may be inserted into a pre-fabricated dome-shaped end 114 of liner 120 and annealed to secure the attachment of the boss 116 and the liner 120 in assembly 150. Such pre-fabrication may be accomplished by known means including molding and machining, for example. An additional locking feature, such as a tab 130 in the boss 116 to be inserted into a groove 136 in the liner 120, may be also included on an exterior side 138 of the flange 124 to improve sealing and to prevent movement of the boss 116 relative to the liner 120 after formation of assembly 150. Moreover, an annular groove 140 in the boss 116 can be configured to accept an annular tab 142 of liner 120 to improve sealing and to prevent movement of the boss 116 relative to the liner 120. While no shell 18 is illustrated in FIGS. 3-10E, it is to be understood that in a typical pressure vessel, such a shell would be formed over the assembly 150 of boss 116 and liner 120.

(20) The described concepts lead to reduced stress concentrations in the boss 116, thereby increasing the potential lifetime of the boss 116. Moreover, the boss 116 can be secured to the liner 120 after the liner 120 is molded. In an exemplary embodiment, structures such as ridges, which can be connected in the form of threads, on peripheral surface 128 are positioned at a far extent of the flange 124, distant from port 126. In an exemplary embodiment, an opening 144 in the liner 120 (labeled in FIG. 9) is smaller than the outer diameter of flange 124 at peripheral surface 128. Thus, the liner 120 is typically flexed to allow passage of the larger boss flange 124, which can be connected to the liner 120 from the interior 17 of the liner 120 (as shown in FIGS. 5-7, for example). This leads to a secure connection, wherein boss 116 and liner 120 are connected not only by cooperating mechanical structures at peripheral surface 128 of boss 116 and opening 144 of liner 120, but also by a liner portion 135 that overlies part of the boss flange 124. It is contemplated that a snap-lock configuration can also be used instead of a threaded engagement.

(21) FIG. 4 is an enlarged view of the joint between boss 116 and liner 120 at interface 162. In the illustrated embodiment, an interference fit is provided between tab 130 of boss 116 and groove 136 of liner 120 on the exterior surface of flange 124. In the illustrated embodiment, liner 120 is formed so that an uncompressed surface of groove 136 would extend to the dotted line 146 in the absence of boss 116. Once boss 116 and liner 120 are assembled together, that portion of groove 136 of liner 120 is compressed by tab 130 of boss 116. This interference fit thereby provides a robust seal between boss 116 and liner 120 at the interface of tab 130 of boss 116 and groove 136 of liner 120.

(22) FIG. 8 illustrates another mechanism that can be used in addition or alternatively. In FIG. 8, a sealing element 148 is shown on a surface of flange 124 on exterior side 138 that will be adjacent portion 135 of liner 120. Such a sealing element 148 may be formed as an annular gasket in one embodiment. In another embodiment, sealing element 148 can be provided on flange 124 and/or portion 135 as a coating or layer of caulking material, for example.

(23) An assembly 150 of boss 116 and liner 120, as shown in FIG. 3, can be formed by the methods described above with reference to FIG. 2, wherein a molten liner material is allowed to flow around portions of boss 116, thereby molding to flange 124. In another method of manufacture, liner 120 may be pre-fabricated separately from boss 116. Such pre-fabrication may be accomplished by known means including molding and machining, for example. FIGS. 5-7 illustrate several embodiments of cooperating bosses 116, 116 and liners 120, 120 for forming assembly 150. In an exemplary method, boss 116 is inserted into opening 144 of liner 120 so that boss 116 is attached to liner 120 from an interior 17 of liner 120. In some embodiments, insertion of boss 116 through opening 144 includes flexing of liner 120, especially in a case where opening 144 has a circumferential dimension smaller than a circumferential dimension of flange 124 (e.g., at peripheral surface 128, measured orthogonally from axis 152). As used in this description, the terms circumferential, circumference and the like refer to perimeter references for shapes that may or may not be circles, including polygons, oval, ellipses, and other substantially closed shapes.

(24) In one embodiment, the surfaces of boss 116 and liner 120 at interface 162 are formed with cooperating structural features to allow the boss 116 and liner 120 to be snap-fit together (i.e., wherein cooperating elements flex and return to their respective unflexed configurations to allow mutual passage of complementary structures). In another assembly method, boss 116 including threaded peripheral surface 128 can be used as a tap to create a corresponding cooperating feature in opening 144 of liner 120 as boss 116 is inserted into opening 144. In such a method of assembly, the boss 116 would be rotated about its longitudinal axis 152 (through a center of port 126) as it is inserted into liner 120 in direction 154. The combination of the turning and axial advancement motions causes the threaded peripheral surface 128 to carve out and remove portions of the liner material at perimeter surface 160 of opening 144 of liner 120 to form an interlocked interface 162.

(25) FIG. 5 shows a boss 116 having a threaded peripheral surface 128 that is oriented substantially parallel to longitudinal axis 152. Moreover, perimeter surface 160 of opening 144 of liner 120 is also substantially parallel to longitudinal axis 152. In FIG. 6, components are shown wherein boss 116 has a threaded peripheral surface 128 that is inclined relative to longitudinal axis 152. Liner 120 has an opening 144 having perimeter surface 160 with a complementary inclined orientation. In FIG. 7, the boss 116 of FIG. 6 having an inclined threaded peripheral surface 128 is shown with a liner 120 having an opening 144 with a perimeter surface 160 that is substantially parallel to longitudinal axis 152. Accordingly, in the assembly of boss 116 and liner 120 of FIG. 7, an interference fit is provided at a portion of interface 162 between peripheral surface 128 and perimeter surface 160, for a robust seal there between.

(26) As shown in FIGS. 3 and 4, when boss 116 and liner 120 are attached in assembly 150 to form at least a portion of a pressure vessel, perimeter surface 160 of liner 120 interfaces with peripheral surface 128 of boss 116 at interface 162. Perimeter surface 160 has contours that mate with the contours (e.g., circumferential ridges 158) of peripheral surface 128. Perimeter surface 160 may be manufactured with such contours. In another embodiment, the contours are imparted to perimeter surface 160 as boss 116 and liner 120 are assembled together.

(27) FIG. 9 shows liner 120 in an intermediate formation step, wherein a molded portion of liner 120 includes stand-offs 156, formed by liner material in cavities of the mold. Such cavities are provided so that excess liner material can be received therein. This helps to ensure a high fidelity of surface molding at opening 144, as the use of excess liner material in molding liner 120 helps to eliminate bubbles, voids, and other molding irregularities. After the molding and curing of liner 120, stand-offs 156 can be removed by means including cutting or breaking from the desired form of the completed liner 120.

(28) FIGS. 10A-10E show different embodiments of a ridged peripheral surface 128a-128e for a boss 116a-116e of the present disclosure. While several variations are explicitly illustrated, it is contemplated that other configurations can also be devised.

(29) FIG. 10A shows a boss 116a with a threaded peripheral surface 128a having variable pitch diameter threads. For example, first circumferential ridge 158a is smaller than second circumferential ridge 158a. A thread of this form makes it easier to install the boss 116a into an unthreaded plastic liner 120, as shown in FIG. 5. In such a case, threaded peripheral surface 128a carves out complementary grooves in liner 120 when boss 116a is twisted into opening 144 of liner 120. A lead-in thread 158a is smaller, allowing for easy insertion of boss 116a into the liner opening 144, thereby acting as a pilot for a larger thread 158a. In this embodiment, a reduced pitch is also provided, as first circumferential ridge 158a and second circumferential ridge 158a are spaced apart, as viewed as a radial cross section. With this reduced or lower pitched thread, few revolutions are needed to seat the boss 116a into the opening 144 of liner 120. A resulting benefit is a reduction in assembly time required to form assembly 150.

(30) FIG. 10B shows a boss 116b with a threaded peripheral surface 128b that is inclined, as discussed with reference to FIGS. 6 and 7. With such an inclination of peripheral surface 128b, first circumferential ridge 158b is closer to longitudinal axis 152 (shown in FIG. 7) than second circumferential ridge 158b. As shown with reference to FIG. 7, this type of thread configuration increases the sealing potential at interface 162 because of an interference between the surface 128b and perimeter surface 160 of liner 120.

(31) FIG. 10C shows a boss 116c with a threaded peripheral surface 128c having few, spaced-apart threads or ridges 158. Thus, first circumferential ridge 158c and second circumferential ridge 158c are spaced apart, as viewed as a radial cross section. With this reduced or lower pitched thread, fewer revolutions are needed to seat the boss 116e into the opening 144 of liner 120. A resulting benefit is a reduction in assembly time required to form assembly 150.

(32) FIG. 10D shows a boss 116d having a threaded peripheral surface 128d with buttress threads. With a surface of each of the circumferential ridges 158d oriented substantially normal to longitudinal axis 152, there is more shear area contact at interface 162 than with a standard configuration of threaded peripheral surface 128 shown in FIG. 4. Accordingly, once assembled into opening 144 of liner 120, this configuration of threads 158d resists separation from liner 120 in the direction opposite the insertion direction 154. This design increases the axial load capability in one direction. Thus, the connection between the boss 116d and the liner 120 remains robust during the filament winding process for forming a shell 18 and during the service life of the pressure vessel 10.

(33) In the embodiments of FIGS. 10A-10D, each of the circumferential ridges 158a-158d has a substantially triangular cross-sectional shape having first and second surfaces that meet at an apex. However, other ridge configurations are also possible.

(34) For example, FIG. 10E shows a boss 116e having a threaded peripheral surface 128e with knuckle threads, in which circumferential ridges 158e have convexly curved, rather than sharply angled, edges. This can reduce stress in the interface 162 between the threaded surface 128e and in opening 144 in liner 120, which can prevent the plastic material of the liner 120 from forming defects.

(35) Although the subject of this disclosure has been described with reference to several embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the disclosure. In addition, any feature or description disclosed with respect to one embodiment is applicable to and may be incorporated in another embodiment, and vice-versa.