Gasket Retention Systems and Methods

Abstract

A connection system for retaining and releasing a gasket, a retention mechanism for retaining the gasket with a hub, and methods for operating the same are provided. The connection system includes a hub that contains a profile configured to receive the gasket and a retention mechanism. The retention mechanism is movable between a latched position and an unlatched position and is biased toward the latched position. At least a portion of the retention mechanism is extended inwardly from the hub so as to retain the gasket with the hub when in the latched position.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. patent application Ser. No. 14/469,505, filed on Aug. 26, 2014, which claims benefit to U.S. Provisional Appl. No. 61/919,447, filed on Dec. 20, 2013, which are incorporated herein by reference.

BACKGROUND

This section is intended to provide background information to facilitate a better understanding of the various aspects of the presently described embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

The oil and gas industry is moving toward higher pressure systems in order to recover more hydrocarbons at faster rates, drill in deeper water depths, drill deeper wells and increase shut-in capacities for safer well operations. Such high pressure systems (about 15,000 psi to about 30,000 psi and above) can exert tremendous forces on gaskets used to seal connections between two parts or hubs. In larger bore systems, which may use 18-inch or larger gaskets, a gasket may have to hold back radial forces in excess of 1,000,000 lbs, for example. Existing gaskets are not designed to cope with the large radial forces and the resultant stresses produced by such high pressure systems.

When making a connection or when disconnecting parts or hubs, it is usually required that the gasket will be retained in a specifically designated hub for the maintenance of the connection and, when required, for the replacement of the gasket. If the gasket remains in the opposite hub, not as planned, then the planned maintenance process may not be achieved. Also, if the gasket is not retained positively in one of the hubs, it may fall out to the sea floor.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of a gasket retention system and method are described with reference to the following figures. The same numbers are used throughout the figures to reference like features and components. The features depicted in the figures are not necessarily shown to scale. Certain features of the embodiments may be shown exaggerated in scale or in somewhat schematic form, and some details of elements may not be shown in the interest of clarity and conciseness.

FIG. 1 depicts a schematic view of an offshore production system containing subsea connections that include a connection system for retaining and releasing a gasket, in accordance with one or more embodiments of the present disclosure;

FIG. 2 depicts a cross-sectional view of a connection system for retaining and releasing a gasket, in accordance with one or more embodiments of the present disclosure;

FIG. 3 depicts the connection system with a retention mechanism in a latched position, in accordance with one or more embodiments of the present disclosure;

FIG. 4 depicts the connection system with the retention mechanism in an unlatched position, in accordance with one or more embodiments of the present disclosure;

FIGS. 5A-5D depict different views of the connection system in absence of a gasket and one of the hubs, in accordance with one or more embodiments of the present disclosure; and

FIG. 6 depicts another embodiment of a retention mechanism, in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

In the following discussion and in the claims, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “including,” “comprising,” “having,” and variations thereof are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, any use of any form of the terms “connect,” “engage,” “couple,” “attach,” “mate,” “mount,” or any other term describing an interaction between elements is intended to mean either an indirect or a direct interaction between the elements described. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. The use of “top,” “bottom,” “above,” “below,” “upper,” “lower,” “up,” “down,” “vertical,” “horizontal,” and variations of these terms is made for convenience, but does not require any particular orientation of the components.

Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names This document does not intend to distinguish between components or features that differ in name but not function.

Referring to FIG. 1, a schematic view of a production system 100 is shown in which the disclosed gasket retention system can be used. In this example, the production system 100 is an offshore production system. The production system 100 includes one or more risers 102 extending to a platform 104 that may include mooring lines 110 to attach the platform 104 to one or more wellheads 106 or one or more other types of subsea components at or near the sea floor 108. The riser 102 provides fluid communication between the wellhead 106 or other subsea component and the platform 104. Although the platform 104 is schematically illustrated as a SPAR-type platform, other types of structures can be used for offshore systems that include, but are not limited to, one or more floating production storage and offloading (FPSO) vessels, semi-submersible platforms, tension leg platforms, and the like. Because the example shown is a production system, the riser is designed as a production riser string and the wellhead 106 is described as being a high pressure wellhead housing. However, it should be appreciated that the production system 100 and the riser 102 may also be designed and configured for drilling and completion operations and/or for fluids injection instead of production, and the subsea component may be another type of equipment in accordance with different embodiments.

A subsea tree 112 (e.g., a vertical tree, a horizontal tree, a combination, hybrid or flexible tree, a production tree, an injection tree, or any other type of tree or component to control fluid flow or pressure) and/or one or more other devices for controlling pressure and/or fluid flow in the production system 100 can be coupled to and in fluid communication with the riser 102 and/or the wellhead 106.

In the production system 100, any number of subsea connection systems 118, each requiring a seal, can be used to connect or couple components or hubs together. Each such connection system 118 may include one or more gaskets (not shown in FIG. 1) installed between the two connected parts or hubs. Each such gasket may be or include a multi-seal gasket on which the presently disclosed gasket retention system may be used to control gasket position in the connector, including during installation and/or production maintenance.

In one or more embodiments, the production system 100 can also include one or more flowlines 128 extending between the platform 104 and one or more riser bases 130, wellheads 106, or other types of subsea components at or near the sea floor 108. The flowlines 128 can include without limitation one or more clump weights, buoyancy modules, sensors, or any combination thereof.

The gasket retention systems and methods described herein can be used in association with any or all of a variety of connection systems. For example, as illustrated with regard to the production system 100 of FIG. 1, a variety of connection systems 118 are shown. Connection systems 118 may connect the bottom of a subsea tree 112 to a wellhead 106. Further, connection systems 118 can be or include, but are not limited to, one or more flowline connection systems, such as for connections between subsea trees 112 or other trees (XT), pipeline end terminations (PLET), pipeline end manifolds (PLEM), manifold modules (MM) 120, riser bases 130, any similar structures, or any combination thereof. As further shown, connection systems 118 may be in any position relative to the sea floor 108, such as a vertical position and/or a horizontal position. In each of the components and/or connections of the production system 100, the gasket control and maintenance requirement is similar

In one or more embodiments, the production system 100 can also include one or more flowlines 128 extending between the floating platform 104 to one or more riser bases 130, wellheads 106, or other types of subsea components at or near the sea floor 108. The flowlines 128 can include, but are not limited to, one or more clump weights, buoyancy modules, sensors, or any combination thereof.

FIG. 2 illustrates a cross-sectional view of a connection with gasket retention system (hereinafter C/GRS) 200, such as the connection systems 118 (FIG. 1), in accordance with one or more embodiments of the present disclosure. The C/GRS 200 includes a first part or hub 202 and a second part or hub 204. Each of the hubs 202, 204, can be or include, but is not limited to, a pipe, a conduit, a line, a flowline, a riser, a cap, a housing, a manifold, a valve, portions thereof, or any combination thereof. The first hub 202 and the second hub 204 are releasably connected to one another via one or more latches 206. The latch 206 can be or include, but is not limited to, a fastener, a lever, a clamp, a receiver, and/or one or more other coupling devices. A bore 210 extends through the first hub 202 and the second hub 204. The bore 210 may be used as a passageway for one or more, but not limited to, fluids, gases, tools, equipment, tubing, or any combination thereof. An axis 222 of the bore 210 can also be a common axis of the first hub 202 and/or the second hub 204.

The C/GRS 200 further includes a gasket 208 located at least partially between the first hub 202 and the second hub 204. The gasket 208 seals the joint 212 between the first hub 202 and the second hub 204 from the bore 210, thereby preventing leaks of fluid and/or pressure, for example, from the bore 210 through the joint 212. In one or more embodiments, each of the hubs 202, 204 includes a profile complementary to and/or configured to receive the gasket 208.

As shown in FIG. 2, the C/GRS 200 further includes a retention mechanism 214 at least partially contained with the first hub 202. The retention mechanism 214 can be in a latched position, as depicted in FIGS. 2 and 3, and used to maintain the gasket 208 engaged with the first hub 202. The retention mechanism 214 can also be an unlatched position, as depicted in FIG. 4 and further discussed below, and used to disengage the gasket 208 from the first hub 202.

The retention mechanism 214 includes one or more slidable members 218 located radially about the axis 222. The slidable members 218 are movable with respect to the first hub 202 between a retracted position and an extended position. As depicted in FIG. 2, the slidable member 218 is in the extended position. Each slidable member 218 may comprise body 217 that includes a ledge 216 for supporting and retaining the gasket 208 when in the extended position. As depicted in FIG. 2, the slidable member 218 is in the extended position to retain the gasket 208 with the first hub 202 after the first and second hubs 202, 204 are separated from one another, as further discussed below.

In one or more embodiments, the slidable member 218 moves radially with respect to the axis 222, which is also substantially orthogonal to the force of gravity applied to the gasket 208 when lifted away with the first hub 202. In one or more embodiments, the slidable member 218 only moves substantially orthogonally to the axis 222. The slidable member 218 further includes one, two, or more apertures 236 formed or otherwise disposed therethrough by which the slidable member 218 can be retained within the first hub 202.

The retention mechanism 214 further includes a biasing mechanism 220, which may be or include, but is not limited to, one or more springs and/or other biasing mechanisms located in a recess 219, as depicted in FIGS. 2 and 5D, behind the slidable member 218, such as between the first hub 202 and the slidable member 218. The biasing mechanism 220 biases the slidable member 218 toward the extended position and compresses when the slidable member 218 is pushed radially outward.

Still referring to FIG. 2, the retention mechanism 214 further includes one or more retention pins 224 each located in a recess 226 within the first hub 202, and can also located in a portion or a nook 227 of the recess 226. The retention pin 224 is also located through the aperture 236 in the slidable member 218 to restrict or otherwise control the movement of the slidable member 218. Each slidable member 218 can include one, two, or more retention pins 224. For example, the slidable member 218 can have two apertures 236 and two retention pins 224, so that each aperture 236 contains a retention pin 224 extending therethrough. The retention pin 224 is movable between an engaged position and a disengaged position, which correspond to the extended and retracted positions of the slidable member 218. Specifically, movement of the retention pin 224 from the disengaged position (FIGS. 2 and 3) to the engaged position (FIG. 4) moves the slidable member 218 from the extended position to the retracted position.

As illustrated in FIG. 2, the retention pin 224 includes an angled surface 232 and the slidable member 218 includes an angled surface 234 within the aperture 236. As the retention pin 224 moves, the retention pin 224 engages the slidable member 218 at the interface of the angled surfaces 232, 234 forming a tapered interface. Specifically, the angled surface 232 of the retention pin 224 contacts and applies a force on the complementary angled surface 234 of the slidable member 218, thereby translating motion of the retention pin 224 along a first direction into motion of the slidable member 218 along a second, substantially non-parallel, direction. In the illustrated embodiment, motion of the retention pin 224 in a vertical direction translates into horizontal motion of the slidable member 218.

An end 230 of the retention pin 224 protrudes into a recess 231 defined in the second hub 204 when the retention pin 224 is in the disengaged position. The end 230 moves from the recess 231 and is positioned in the recess 226 once the retention pin 224 is in the engaged position. The retention pin 224 is biased toward the disengaged position by a biasing mechanism 228, which may be or include, but is not limited to, one or more springs and/or other biasing mechanisms. The retention pin 224 may further include an extended portion or a block portion 238 that can support the biasing mechanism 228 around at least a segment of the retention pin 224 within the recess 226. For example, the biasing mechanism 228 may be located between the block portion 238 and the first hub 202 within the recess 226. When the slidable member 218 is in the extended position and the retention pin 224 is in the disengaged position, the block portion 238 will not fit through the aperture 236 of the slidable member 218 and the retention pin 224 retained within the recess 226 of the first hub 202. The retention pin 224 biased in the disengaged position allows the biasing mechanism 220 to move the slidable member 218 toward the extended position. Each biasing mechanism 220, 228 or spring can be or include, but is not limited to, one or more compression springs, wave springs, torsion springs, Belleville washers or springs, constant force springs, extension springs, spring clips, leaf springs, tensions springs, or any combination thereof.

In operation, the latch 206 is removed from the first and second hubs 202, 204, and subsequently, the first and second hubs 202, 204 are released or otherwise separated from each other. For example, even when the first hub 202 is lifted away from the second hub 204, the gasket 208 is supported by the slidable member 218 and lifted away with the first hub 202 (FIG. 3). The gasket 208 is thus not dropped or lost during separation of the first and second hubs 202, 204. The retention pins 224 may then be placed in the engaged position to move the slidable member 218 into the retracted position. In the retracted position, the slidable member 218 is moved away from the gasket 208, allowing the gasket 208 to be released from the first hub 202 (FIG. 4).

FIG. 3 illustrates the retention mechanism 214 and the gasket 208 when the first hub 202 is separated from the second hub 204 (FIG. 2). As shown in FIG. 3, the retention mechanism 214 is in the latched position, the slidable member 218 is the extended position, the retention pin 224 is in the disengaged position, and the gasket 208 is supported by the ledge 216 of the slidable member 218 and retained with the first hub 202. In operation, depression of the retention pin 224 further into the recess 226 by applying pressure to the end 230 moves the retention pin 224 toward the engaged position, which moves the slidable member 218 into the retracted position, thereby releasing the gasket 208. The retention pin 224 can be depressed and the gasket 208 released by pushing or otherwise engaging the end 230 with a running tool docking plate (not shown). As shown in FIG. 4, the retention mechanism 214 is in the unlatched position, the slidable member 218 is the retracted position, the retention pin 224 is in the engaged position, and the gasket 208 is no longer supported by the ledge 216 of the slidable member 218 and is released from the first hub 202.

FIGS. 5A-5D depict different views of the C/GRS 200 in absence of the hub 204 and the gasket 208. FIG. 5A depicts a perspective view of the C/GRS 200. As illustrated, the hub 202 has twelve retention pins 224 radially positioned about the axis 222. FIG. 5B depicts a sectional view of the C/GRS 200 at line 5B-5B illustrated in FIG. 5A. A retention pin 224 passes through each aperture 236 formed in the slidable members 218.

FIG. 5C depicts a sectional view of the C/GRS 200 at line 5C-5C illustrated in FIG. 5B. Six slidable members 218 are located radially about the axis 222. Two apertures 236 are shown for each slidable member 218. FIG. 5D depicts a magnified view of one of the six slidable members 218 in the C/GRS 200 illustrated in FIG. 5C. The biasing mechanism 220 is located between the slidable member 218 and the first hub 202. The biasing mechanism 220 biases the slidable member 218 away from the first hub 202 toward the extended position. The biasing mechanism 220 is depicted as a wave spring, for example, but can be one or more other springs as discussed above.

While FIGS. 2-5 illustrate one or more retention pins 224 to retain the gasket 208, other devices may be used, including but not limited to, one or more prongs, one or more tines, one or more rods, one or more detent pins, one or more other type of pins, or any combination thereof. The retention pin 224 may be made from or contain one or more metals, one or more polymeric materials including natural or synthetic rubbers or elastomers, one or more ceramics, or other materials.

The retention mechanism 214 may have a variety of different configurations which keep the gasket 208 retained within the first hub 202 when the retention mechanism 214 is in the unlatched position. FIG. 6 illustrates another embodiment of a retention mechanism 614 positioned between first and second hubs 602, 604. The retention mechanism 614 includes a slidable member 618 and a retention pin 624. The slidable member 618 provides a ledge 616 for supporting and engaging a gasket 608. The slidable member 618 further includes one, two, or more apertures 636 formed or otherwise disposed therethrough by which the slidable member 618 can be retained within the first hub 602. Each slidable member 618 can include one, two, or more retention pins 624. For example, the slidable member 618 can have two apertures 636 and two retention pins 624, so that each aperture 636 contains a retention pin 624 extending therethrough. The retention pin 624 is movable between an engaged position and a disengaged position, which correspond to the extended and retracted positions of the slidable member 618. Specifically, movement of the retention pin 624 from the disengaged position (FIG. 6) to the engaged position (not shown) moves the slidable member 618 from the extended position to the retracted position.

As illustrated in FIG. 6, the retention pin 624 includes angled surfaces 632, 634 and the slidable member 618 includes angled surface 610, 612 within the aperture 636. As the retention pin 624 moves upward as situated in FIG. 6, the retention pin 624 engages the slidable member 618 at the interface of the surfaces 610, 632. Specifically, the angled surface 632 of the retention pin 624 contacts and applies a force on the complementary angled surface 610 of the slidable member 618, thereby translating motion of the retention pin 624 along a first direction into motion of the slidable member 618 along a second, substantially non-parallel, direction. Once the retention pin 624 is in the engaged position and the slidable member 618 is in the extended position (not shown), as the retention pin 624 moves downward to engage the slidable member 618 at the interface of the surfaces 612, 634. Specifically, the angled surface 634 of the retention pin 624 contacts and applies a force on the complementary angled surface 612 of the slidable member 618, thereby translating motion of the retention pin 624 along a third direction (opposite of the first direction) into motion of the slidable member 618 along a fourth direction (opposite of the second direction) that is substantially non-parallel. In the illustrated embodiment, motion of the retention pin 624 in a vertical direction translates into horizontal motion of the slidable member 618.

In operation, vertical movement of the retention pin 624 moves the slidable member 618 horizontally, thereby placing the slidable member 618 into the extended or retracted position depending on the position of the retention pin 624. An end 630 of the retention pin 624 protrudes into a recess 631 defined in the second hub 604 when the retention pin 624 is in the disengaged position. The end 630 moves from the recess 631 and is positioned in a recess 626 formed in the first hub 602 once the retention pin 624 is in the engaged position.

A biasing mechanism 620, which may be or include, but is not limited to, one or more springs and/or other biasing mechanisms, is used to bias the slidable member 618 in the extended position. Also, a biasing mechanism 628, which may be or include, but is not limited to, one or more springs and/or other biasing mechanisms, is used to bias the retention pin 624 in the disengaged position. The retention pin 624 may further include an extended portion or a block portion 638 and a support member or a plate 640 that can support the biasing mechanism 628 around at least a segment of the retention pin 624 within the recess 626. For example, the biasing mechanism 628 may be located between the first hub 602 within the recess 626 and the plate 640.

In one or more embodiments, each biasing mechanism 620, 628 can independently be omitted from the retention mechanism 614. For example, the retention mechanism 614 can include biasing mechanism 620 and exclude biasing mechanism 628. In other examples, the retention mechanism 614 can include biasing mechanism 628 and exclude biasing mechanism 620. Alternatively, the retention mechanism 614 can include both biasing mechanisms 620, 628 or can exclude both biasing mechanisms 620, 628. The retention mechanisms 214, 614 are illustrated as being located in the first hub 202, 602. However, in other embodiments, the retention mechanisms 214, 614 can be located in the second hub 204, 604 and thereby retain the gaskets 208, 608 with the second hub 204, 604.

In one or more embodiments, a method for retaining and releasing a gasket by operating a connection system, such as the C/GRS 200, and/or a retention mechanism, such as the retention mechanism 214, 614. The method includes biasing a slidable member into an extended position, where the slidable member is extended radially inward from the hub, and retaining a gasket at least partially between the slidable member and the hub. The method includes forcing the slidable member into a retracted position, where the slidable member retracts into the hub, and releasing the gasket from the hub. The method also includes biasing a retention pin into a disengaged position, thereby allowing the slidable member to be biased into the extended position, forcing the retention pin into an engaged position, thereby forcing the slidable member into the retracted position, and/or biasing the slidable member at an angle, such as substantially orthogonally, with respect to an axis of the hub.

Reference throughout this specification to “one embodiment,” “an embodiment,” “an embodiment,” “embodiments,” “some embodiments,” “certain embodiments,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present disclosure. Thus, these phrases or similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ,” it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).

Although the present disclosure has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.

Claims

1. A connection system for retaining and releasing a gasket, comprising:

a hub comprising a profile configured to receive the gasket and a retention mechanism, wherein the retention mechanism is movable between a latched position and an unlatched position and is biased toward the latched position; and

wherein, when in the latched position, at least a portion of the retention mechanism is extended inwardly from the hub so as to retain the gasket with the hub.

2. The system of claim 1, wherein the retention mechanism further comprises a biasing mechanism configured to bias the retention mechanism toward the latched position.

3. The system of claim 2, wherein the biasing mechanism comprises a spring selected from the group consisting of a compression spring, a wave spring, a Belleville spring, and a combination thereof.

4. The system of claim 1, wherein the retention mechanism comprises a slidable member movable between an extended position and a retracted position.

5. The system of claim 4, wherein the slidable member is movable substantially orthogonally with respect to the axis of the hub.

6. The system of claim 4, wherein the retention mechanism comprises a plurality of slidable members located radially about the hub.

7. The system of claim 4, wherein the retention mechanism further comprises a retention pin movable between an engaged position and a disengaged position; wherein the retention pin is biased toward the disengaged position; and wherein the slidable member is biased toward the extended position.

8. The system of claim 7, wherein:

the hub further comprises a recess;

the retention pin protrudes from the recess when in the disengaged position; and

movement of the retention pin into the recess moves the retention pin toward the engaged position.

9. A retention mechanism for retaining a gasket with a hub, the retention mechanism comprising:

a slidable member movable between an extended position and a retracted position;

a retention pin movable between an engaged position and a disengaged position, wherein the retention pin is biased toward the disengaged position;

wherein movement of the retention pin into the disengaged position moves the slidable member into the extended position; and

wherein movement of the retention pin into the engaged position moves the slidable member into the retracted position.

10. The retention mechanism of claim 9, wherein movement of the retention pin into the disengaged position moves the retention mechanism into a latched position.

11. The retention mechanism of claim 9, wherein movement of the retention pin into the engaged position moves the retention mechanism into an unlatched position.

12. The retention mechanism of claim 9, wherein the slidable member comprises an aperture formed therein and the retention pin is positioned through the aperture.

13. The retention mechanism of claim 9, further comprising a biasing mechanism configured to bias the retention pin toward the disengaged position or the slidable member toward the extended position.

14. The retention mechanism of claim 13, wherein the biasing mechanism comprises a spring mechanically coupled to the retention pin or the slidable member.

15. The retention mechanism of claim 9, wherein the slidable member is movable substantially orthogonally with respect to an axis of the hub.

16. The retention mechanism of claim 9, wherein a direction of motion of the slidable member is substantially orthogonal to a direction of motion of the retention pin.

17. A method for retaining and releasing a gasket, comprising:

biasing a slidable member into an extended position, wherein the slidable member is extended radially inward from a hub;

retaining the gasket at least partially between the slidable member and the hub;

forcing the slidable member into a retracted position, wherein the slidable member retracts into the hub; and

releasing the gasket from the hub.

18. The method of claim 17, further comprising biasing a retention pin into a disengaged position, thereby biasing the slidable member into the extended position.

19. The method of claim 17, further comprising forcing the retention pin into an engaged position, thereby forcing the slidable member into the retracted position.

20. The method of claim 17, further comprising biasing the slidable member substantially orthogonally with respect to an axis of the hub.