Abstract:
An actuated breach lock, comprises a hub for positioning on a pressurizable vessel, the hub being generally circular and having a central opening, a bearing surface disposed within the central opening, a head hingedly connected to the hub and having a shape which complements the central opening and which is received within the central opening, the hub having a plurality of teeth extending radially inward and separated by a plurality of gaps, a locking ring rotatably positioned on the head, the locking ring having a plurality of ring teeth separated by a plurality of ring gaps, each of the teeth having a circumferential length less than a circumferential length of the gaps in the hub, the bearing surface of the hub having an angle and the head having a bearing surface at the angle, the locking ring having a polygonal cross-section including two sides which engage the bearing surfaces respectively, the locking ring engaged by head and hub when the head is in a closed position, the closed position creating a line of force which is aligned from the head through the ring and to the hub, an actuator assembly disposed radially inwardly of the locking ring, the actuator assembly engaging the locking ring and causing rotation of locking between one of a first locked and unlocked position and the other of the locked and unlocked position, the locking ring in compression when the head is closed and having a line of force being substantially aligned from the hub through the head.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     None. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     None. 
     REFERENCE TO SEQUENTIAL LISTING, ETC. 
     None. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a closure for a pressure vessel and more specifically relates to an actuated breach lock closure for a pressure vessel. 
     2. Description of the Related Art 
     Prior art closures typically utilize large heavy-duty rotatable closure elements in order to open and close access to pressurized vessels for, as an example, cleaning. The rotatable elements are typically either the door or an outer ring rotating about the frame. Since these are such large rigid elements, they are typically very heavy. Thus, actuating components must generate a large force in order to properly actuate movement for these parts. This results in high cost, high energy consumption, and difficulty in providing functionality. 
     The rotatable elements must be engineered as large elements in order to carry large loadings associated with pressurized systems. The closures include a frame and a door which are typically round and have a primary axis about which the frame extends circumferentially. When the door is in the closed position, the primary axis passes through the door, which is co-axial with the frame. Locking components for the closure typically include a planar surface which is perpendicular to the primary axis of the closure. Since these locking components may carry non-aligned loadings in different areas, the load bearing elements or components are subjected to large bending forces. Thus, the rotatable elements must be designed to withstand these large bending forces. This also results in larger, heavier parts than would otherwise be necessary. 
     Some closures utilize locking rings which are deformable in order to extend into or retract from an internal annular cavity in the door frame. This allows movement of the locking ring into or out of the cavity during locking or unlocking of the closure. However, the deformability of the ring causes the ring to bind between the door and frame when the ring is beginning to engage the internal cavity therefore inhibiting unlocking and opening. Repeated locking and unlocking of the closure is therefore inhibited, especially when contaminants or corrosion develops on sliding surfaces. 
     Given the foregoing, it will be appreciated that a closure for a pressure vessel is desired which inhibits bending moment about a locking ring, which inhibits binding of the locking ring and allows rotation of lightest portion of the closure assembly for locking and unlocking. 
     SUMMARY OF THE INVENTION 
     An actuated breach lock, comprises a hub for positioning on a pressurizable vessel, the hub being generally circular and having a central opening, a bearing surface disposed within the central opening, a head hingedly connected to the hub and having a shape which complements the central opening and which is received within the central opening, the hub having a plurality of teeth extending radially inward and separated by a plurality of gaps, a locking ring rotatably positioned on the head, the locking ring having a plurality of ring teeth separated by a plurality of ring gaps, each of the teeth having a circumferential length less than a circumferential length of the gaps in the hub, the bearing surface of the hub having an angle and the head having a bearing surface at the angle, the locking ring having a polygonal cross-section including two sides which engage the bearing surfaces respectively, the locking ring engaged by head and hub when the head is in a closed position, the closed position creating a line of force which is aligned from the head through the ring and to the hub, an actuator assembly disposed radially inwardly of the locking ring, the actuator assembly engaging the locking ring and causing rotation of locking between one of a first locked and unlocked position and the other of the locked and unlocked position, the locking ring in compression when the head is closed and having a line of force being substantially aligned from the hub through the head. The actuated breach lock wherein the actuator assembly has at least one actuator causing rotation of the locking ring relative to at least one of the head and the hub. The actuated breach lock wherein the at least one actuator comprises a first actuator and a second actuator, each of the first actuator and the second actuator being selected from the group consisting of pneumatic cylinders, hydraulic cylinders, linear actuators or motorized actuators. The actuated breach lock wherein the at least one actuator is positioned near the outer surface of the head. The actuated breach lock wherein the locking ring is rotated from a first position allowing the ring teeth to pass through the gaps in the hub, to a second position wherein the ring teeth engage the plurality of teeth of the hub. The actuated breach lock wherein the line of force inhibits moment and bending along the ring. 
     An actuated beach lock comprises a hub for closing and opening of a pressurized vessel, the hub having a central opening defined by a peripheral rim having circumferential edges, a first plurality of teeth extending radially inwardly from the rim, each of the first teeth separated by a first gap, a head pivotally connected to the hub for movement between an open position and a closed position, a polygonally shaped ring having a first surface and a second surface substantially parallel to the first surface, the first surface of the ring disposed against internal bearing surfaces of the first plurality of teeth of the hub, the second surface of the ring bearing against the head, the ring slidably rotatable about the head within the circumferential edges of the hub, the ring having a second plurality of teeth each of which fits within the first gap, the second plurality of teeth having one of the first surface and the second surface of the ring, the internal bearing surface of the hub and the external bearing surface of the head being disposed at parallel angles, and, a line of force being created when the closure is pressurized and which is substantially aligned through the head, the hub and the ring, the substantially aligned line of force inhibiting creation of bending of the ring. The actuated breach lock further comprising at least one actuator for rotating the ring relative to the head and the hub. The actuated breach lock further comprising a first actuator for rotating the ring in a first direction and a second actuator for rotating the ring in a second direction. The actuated breach lock wherein the first and second actuators are disposed on an outer surface of the head. The actuated breach lock wherein the ring is compressed between the hub and the head when the head is closed relative to the hub creating the line of force and inhibiting bending of the ring. The actuated breach lock wherein each of the second plurality of teeth on the ring are spaced apart by a second gap, the second gap having a circumferential length which is slightly greater than a circumferential length of the first plurality of teeth of the hub. The actuated breach lock wherein the second plurality teeth of the ring passes through the gaps of the hub, and the ring is rotated to lock the head in a closed position within the hub. 
     An actuated breach lock comprises a hub having a peripheral rim and a central opening, an interior bearing surface of the hub disposed at an angle to a major axis of the hub, a head, pivotally connected to the hub, the head being received by the central opening in the hub, the head further comprising an axially outward facing bearing surface disposed at an angle to the major axis, the hub having a first plurality of teeth extending radially inward from a peripheral edge, each of the first plurality of teeth spaced apart by a first gap, a ring rotatably positioned on the bearing surface of the head, the ring having a second plurality of teeth radially extending from a peripheral edge of the ring, each of the second plurality of teeth spaced apart by a second gap, the ring having at least one first position wherein at least one of the second plurality of teeth is aligned with the second gap and at least one of the second plurality of teeth is aligned with the first gap so that the ring and the head move into or out of the central opening of the hub, the ring having a first ring bearing surface and a second ring bearing surface, the first ring bearing surface engaging one of the hub interior bearing surface or the head bearing surface and the second ring bearing surface engaging the other of the hub interior bearing surface and the head bearing surface, the angle of the hub interior bearing surface, the head bearing surface and the first and second ring bearing surfaces allowing for a line of action substantially aligned through the head, the substantially aligned line of action inhibiting bending within the ring. The actuated breach lock further comprising a first actuator and a second actuator. The actuated breach lock wherein the first actuator rotates the ring in a first direction to lock the head and the second actuator rotates the ring in a second direction to unlock the head. The actuated breach lock wherein the first and second actuators being positioned on an external side of the head. The actuated breach lock wherein the ring is rotatable along an interior surface of the hub to lock or unlock the head. The actuated breach lock wherein the ring has a polygonal cross-sectional shape. 
     An actuated breach lock comprises a hub defined by a substantially circular body having a central aperture, a head pivotally connected to the hub and movable from a first position closing the central opening to a second position opening the central opening, a locking ring disposed on a surface of the head and engaging a groove in the hub when the head is in the first position, the head having a head contact surface which engages the locking ring and the hub having a hub contact surface which engages the locking ring when the head is in the first position, the locking ring having two contact surfaces, an interior contact surface and an exterior contact surface, the interior contact surface slidably contacting the head contact surface, whereas the exterior contact surface of the locking ring makes contact with the hub contact surface, wherein each of the contact surfaces of the locking ring are geometrically defined as a conical frustum, and further wherein the interior and exterior contact surfaces share a common conical angle and common axis of revolution, an interior contact surface conical radius being less than an exterior contact surface conical radius. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  depicts a perspective view of an actuated breach lock; 
         FIG. 2  depicts an exploded perspective view of the actuated breach lock of  FIG. 1 ; 
         FIG. 3  depicts a front view of an actuated breach lock in an unlocked position; 
         FIG. 4  depicts a front view of an actuated breach lock in a locked position; 
         FIG. 5  depicts a front view of a locking ring; 
         FIG. 6  depicts a first cross-sectional view of the locking ring of  FIG. 5 ; 
         FIG. 7  depicts a second cross-sectional view of the locking ring of  FIG. 5 ; 
         FIG. 8  depicts a cross-sectional view of the actuated breach lock of  FIG. 1 ; 
         FIG. 9  depicts a second cross-sectional view of the actuated breach lock of  FIG. 1 ; 
         FIG. 10  depicts a detail view of the actuator assembly in a first locked position; 
         FIG. 11  depicts a detail view of the actuator assembly in a second unlocked position; and, 
         FIG. 12  depicts a cross-sectional view of the exemplary actuated breach lock. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless limited otherwise, the terms “connected,” “coupled,” and “mounted,” and variations thereof herein are used broadly and encompass direct and indirect connections, couplings, and mountings. In addition, the terms “connected” and “coupled” and variations thereof are not restricted to physical or mechanical connections or couplings. 
     With reference now to  FIGS. 1-12 , an actuated breach lock is depicted in various views. The actuated breach lock is used to access or close pressurized vessels, in a safe, repeatable manner. 
     Referring initially to  FIGS. 1 and 2 , an assembled perspective view and an exploded perspective view of a closure  10  are depicted. The closure  10  includes a hub  12  which is connected to a pressure vessel in order to access the pressure vessel once the vessel is depressurized. Such pressure vessel may include a pipe, a pressurized tank, or any body which may be pressurized and for which access may be needed once the body or vessel is depressurized, such as for cleaning or maintenance. The hub  12  is depicted as being a circular body which has an axially extending depth and a generally hollow interior, defined by an opening, through which access to the pressurized body or vessel is gained. The hub  12  includes an outer peripheral surface  14  and an inner peripheral surface  16 . The hub  12  is connected to pressurized body at the rear edge, opposite a head  50 . At the forward edge of the hub  12 , toward the door  50  in the axial direction, the hub  12  further comprises a plurality of spaced apart hub locking teeth  20 . Each tooth  20  comprises a forward tapered surface  22  and a rear, axially inward, tooth surface  24 . Between each of the hub locking teeth  20  is a scallop  26 . Each scallop  26  has a shape which is complementary of teeth  72  disposed on a locking ring  70  allowing passage of the locking ring teeth  72  between the hub locking teeth  20 . 
     The closure  10  may be closed for operation or opened for maintenance. Extending from the hub  12  is a hinge assembly  30  which allows pivotal rotation of a head  50  from a first open position depicted in  FIG. 1  to a second closed position shown, for example, in  FIG. 3 . 
     The head  50  is a circular shaped body, which has an outer periphery that fits within the inner diameter of the hub  12  to close the opening  18  defined within the hub  12 . The head  50  comprises an axially outermost surface facing away from the hub  12  when the head  50  is closed. The head  50  further comprises an axially innermost surface facing into the hub  12  when the head  50  is closed. The hinge assembly  30  is connected at one end to the hub  12 . Distal from the hub  12 , the hinge assembly  30  is also connected to the head  50  for movement of the head  50  between the opened and closed positions. Disposed on the head  50  is an actuator assembly  80  which actuates a locking ring  70 . When the head  50  is in the closed position, the actuator assembly  80  rotates the locking ring a preselected angle so to align the locking ring teeth  70  with the scallops  26  of the hub  12  allowing the head  50  to be opened or allowing the head  50  to be fully closed. According to the instant embodiment, the preselected angle may be between about 1 and 359 degrees. According to the instant embodiment, the preselected angle is approximately 22.5 degrees although this should not be considered limiting, as various angles may be utilized. 
     Extending from the hub  12  is the hinge assembly  30 . This assembly  30  comprises at least one arm  32  which is connected to a pivot member  36 . The pivot member  36  is pivotally connected to the arm  32  by a hinge pin  34 . According to the exemplary embodiment, upper and lower arms  32  are utilized and each connects to a first and second end of the pivot member  36 . The head  50  is spaced from the hub  12 , in  FIG. 2 , and has a substantially circular shape. The outer surface of the door or head  50 , spaced farthest from the hub  12 , is substantially flat for mounting of various components, including the actuator assembly  80  described further herein. However, such flat surface is not required and should not be considered limiting. The head  50  comprises a lip  52  adjacent a tapered surface  54 . The locking ring  70  is disposed on the tapered surface  54  and seated around the lip  52 . 
     The locking ring  70  is circular in shape, having a hollow center area, and is slidably positioned against the head  50  and about the lip  52  along the tapered surface  54 . About the peripheral edge of the locking ring  70  are teeth  72 . Each of the teeth  72  has a forward bearing surface or interior surface  76  opposite the head  50  and an adjacent surface  78  near the head  50 . Between the teeth  72  are locking ring scallops  74 . These scallops  74  receive the teeth  20  along the inner peripheral edge of the hub  12 . In the closed position, the surface  76  engages the rear tooth surface  24 , inhibiting opening of the head  50 . 
     Also positioned about the inner peripheral edge of the locking ring  70  are lug slots  79  which receive lugs  89 . These lugs  89  are rotated by the actuator assembly  80  to rotate the ring  70  such that the teeth  72  may be aligned with scallops  26  or alternatively so that the teeth  72  are disposed behind teeth  20 . In the former configuration, the head  50  is locked in a closed position relative to the hub  12 . 
     Mounted along the outer surface of the head  50  is the actuation assembly  80  which comprises at least one actuator  82 . According to the exemplary disclosure, a first actuator  82  and a second actuator  84  are utilized to rotate the locking ring  70  through a preselected angle to either lock or unlock the head  50  in a closed position relative to the hub  12 . Each actuator  82 ,  84  comprises a cylinder portion  86  and a piston portion  88  which is extendable or retractable within the cylinder  86 . Each of the pistons  88  are connected to a lug  89 . The lugs  89  are positioned within the locking ring gaps  79  and the pistons  88  are pivotally connected to the lugs  89  by a fastener. The cylinders  86  are also pivotally connected to the head  50 . 
     Also mounted on the head  50  is a safety lock  90 . The lock  90  comprises a cylinder  92  and an extendable piston  94 . The extendable piston  94  extends into a safety notch  77  located on the inner periphery of the locking ring  70 . This piston  94  is extended into the notch  77  when the locking ring  70  is angularly positioned with the teeth  72  locked or aligned with teeth  20  of the hub. Thus, the locking ring  70  is inhibited from rotating relative to the teeth  20  of the hub  12  so that the head  50  cannot be accidentally opened while the pressure vessel is pressurized. 
     A plate  40  hides or conceals portions of the components disposed on the outer surface of the head  50 . This head plate  40  is connected at one end to the hinge assembly  30  allowing opening and closing of the head by grasping of a handle  44 . The plates  40  serve as a means of opening the head  50 . The plates  40  also provide safety from the pressurized actuators  82 ,  84  and lock on the head  50 . 
     On an axially inward surface of the head  50  for seating against the hub  12  is a seal  60  which is fluid energized by the pressurization on the axially inward side of the head  50 , when the head is in the closed position and the assembly is in use. The seal  60  inhibits fluid transfer from within the closure to the outer side of the head  50  during operation by being seated within a circumferential groove along the inner side of the head  50 . By this structure, a seal is imparted between the head  50  and hub  12 . The seal  60  may have an upper portion with radially inward facing groove and is fluid energized with pressure acting on this groove forcing the seal  60  against the head  50 . The seal  60  may include a rectangular portion for seating into a circumferential groove about an inner surface of a door. Rapidly inward facing groove provides the fluid energized seal  60  wherein pressure acting on a groove forces the seal  60  against the head  50  and hub  12   
     Referring now to  FIG. 3 , a front view of the closure  10  is depicted. The Figure depicts the teeth  20  of the hub  12  aligned with the scallops  74  of the locking ring  70 . Similarly, the teeth  72  of the locking ring  70  are aligned with the scallops  26  of the hub  12  with the locking ring  70 . In this position, the head  50  is moved from its open position shown in  FIG. 1  to a closed position but unlocked. In the unlocked position, the actuators  82 ,  84  are disposed in one of an extended or retracted position. According to the embodiment depicted in  FIG. 3 , when the locking ring  70  is disposed in an unlocked position, the actuators  82 ,  84  are retracted. 
     Referring now to  FIG. 4 , a front view of a closure  10  is depicted. The locking ring  70  is rotated a preselected angle from the position shown in  FIG. 3  to its new position in  FIG. 4 . In the depicted position, the locking ring teeth  72  are positioned behind and engaging the hub teeth  20 . Additionally, the scallops  26  are circumferentially aligned with the locking ring scallops  74 . The positioning of the locking ring  70  in  FIG. 4  locks the head  50  closed relative to the hub  12 . In order to open the head  50 , the locking ring  70  must be rotated to its unlocked position. 
     In order to achieve the positioning of locking ring  70  in a position depicted in  FIG. 4 , the first and second actuators  82 ,  84  are moved from their position determined in  FIG. 3 . Specifically, the pistons  88  are extended causing rotation of the ring  70  from the position in  FIG. 3  to the position depicted in  FIG. 4 . This causes the head  50  to be locked in the closed position relative to the hub  12 . In the locked position shown in  FIG. 4 , the head  50  cannot be hingeably opened by pulling the handle  44  and pivoting about the hinge assembly  30 . Thus, the vessel and closure  10  may be pressurized for operation. It should also be understood that the actuators  82 ,  84  may be arranged to cause rotation of the locking ring  70  in opposite directions, as opposed to working together in the depicted embodiment. For example, a first actuator rotate the ring in a first direction to lock the head and a second actuator rotating said ring in a second direction to unlock the head. This of course would occur where one actuator extends while the second actuator retracts and vice-versa, as opposed to both extending and retracting at the same time. 
     Referring to  FIG. 5 , the locking ring is shown in a front view. As previously described, the locking ring  70  is generally circular in shape having a periphery including a plurality of teeth  72  which are separated by scallops  74 . Each of the teeth  72  has a front surface  76  which is tapered and of an angle which is substantially parallel to the rear tooth surface  24  of each tooth  20  along hub  12 . More specifically, the surface  76  is defined by a frusto-conical geometry and is substantially equivalent to the frusto-conical geometry of the rear tooth surface  24  insuring uniform contact between the mating surfaces  76  and  24 . This allows the locking ring  70  to rotatably slide behind the teeth  20  of the hub  12  and accordingly move between locked and unlocked positions. Disposed at diametrically opposite positions along the locking ring  70  and radially inward of the teeth  72  are lug slots  79 . These slots  79  receive the lugs  89  which are pivotally connected to the first and second actuators  82 ,  84 . Also positioned along the inner peripheral edge of the locking ring  70  is a safety notch  77  which receives a piston arm  94  of the safety lock  90 . When the piston  94  of lock  90  is seated in the notch  77 , the ring  70  cannot rotate. When disengaged, the actuators  82 ,  84  can rotate the ring  70 . 
     Referring now to  FIG. 6 , a side section view of the locking ring  70  is depicted which passes through scallops  74 . According to the sectioned ends of the locking ring  70 , the shape of the locking ring  70  may be described as a polygon. A rear bearing surface  75  of the locking ring  70  is tapered and slidably mates with the tapered head contact surface surface  54  of the head  50 . Thus, the rear bearing surface  75  has an angle which is parallel to the head surface  54  which allows for sliding and bearing thereon. Specifically, the surface  75  is defined by a frusto-conical geometry and is substantially equivalent to the frusto-conical geometry of the head surface  54  ensuring uniform contact between the mating surfaces  75  and  54 . Also shown are the radially outward portions of adjacent teeth  72  which engage the teeth  20  to lock the head  12  in the closed position. 
     Referring now to  FIG. 7 , a second section view of the locking ring  70  is depicted along section line  7 , shown in  FIG. 5 . The section line passes through two opposed ring teeth  72 . The front surface  76  of tooth  72  is parallel to the rear bearing surface  75 . In this configuration, the two load bearing surfaces of the locking ring  70  are parallel. That is, the front surface  76  of tooth  72  is a load bearing surface and the rear bearing surface  75  is also a load bearing surface. As described further, the parallel load bearing surfaces  75 ,  76 , in part, result in substantial alignment of loads on the locking ring  70 , inhibiting movement and bending of ring  70 . 
     Referring now to  FIG. 8 , an alternative section view of the closure  10  is depicted in locked position along section line  8 ,  FIG. 5 . The section line  8  passes through scallops  26  of hub  12 . The locking ring  70  is shown abutting the head  50 . Additionally, the tooth  72  of the locking ring  70  is shown engaging the tooth  20  of the hub  12 . Specifically, the rear surface  24  of tooth  20  is shown engaging the front surface  76  of tooth  72 . The hub  12  further comprises a recess  13  along the inner surface of the hub  12  which allows for positioning of the locking ring tooth  72  therein. 
     Referring now to  FIG. 9 , section view of the closure  10  is depicted with the section line passing through teeth  72  and  20 . The locking ring  70  is in compression when the pressure vessel is pressurized. The locking ring  70  is loaded along parallel surfaces  75  and  76 . The loading occurs as two equivalent forces equal and opposite acting along the same line of action. In the instant embodiment, the line of action is represented by line F. As a result, due to the equal and opposite forces acting along the single line of action, no moment is generated in the locking ring  70 . This allows for a lighter weight part to be designed and utilized for the locking ring structure. 
     Referring now to  FIGS. 10 and 11 , detailed perspective views of the actuator assembly  80  are depicted in two positions. First, referring to  FIG. 10 , for example actuator  82 , is shown in an extended position. The actuator  82  is shown in a first orientation extending to the lug  89 . According to the instant embodiment, the first orientation is generally horizontal. In comparison with  FIG. 11 , the actuator  82  is retracted and the locking ring  70  is rotated some preselected angle from the first position shown in  FIG. 10 . Due to the rotation of the locking ring  70 , the lug  89  is translated from the first position shown in  FIG. 10  to a second position shown in  FIG. 11 . In order to remain connected to the stationary head  50  and the moving lug  89 , the actuator  82  pivots at a pivot point  83  relative to the head  50  to a second orientation from the first orientation shown in  FIG. 10 . A large arrow A indicates the location of direction of the actuator  82  caused by the rotation of the locking ring  70 . Stops  87  inhibit over-rotation of locking ring  70  by actuators  82 ,  84 . 
     Referring now to  FIG. 12 , a cross-sectional view of an exemplary closure having the hub  12 , the head  50  and the locking ring  70 . At the right side of the figure is a centerline C L  about which the locking ring  70  rotates. As previously described the head  50  includes a head contact surface  54  which slidably receives the locking ring  70 . The head contact surface  54  is parallel to a tooth front or exterior surface  75  of the locking ring  70 . Relative to the centerline C L  the exterior surface  75  and the head contact surface  54  are disposed at an angle α. The exterior surface  75  slides along the head contact surface  54 . On the opposite side of the locking ring  70  is a tooth rear or interior surface  76  which is partially positioned in the recess or groove  13  engages the inner tooth surface or hub contact surface  24  to inhibit opening of the head  50 . Relative to the centerline C L  about which the locking ring  70  rotates, the interior surface  76  is also disposed at angle α to the centerline. Thus, the exterior and interior surface  75 , 76  are parallel to one another. 
     The interior surface of locking ring  76  defines a first conical frustum C F1  which extends toward the centerline C L . The exterior surface  75  of the locking ring  70  also defines a second conical frustum C F2  which extends toward the centerline C L . The first conical frustum C F1  has a first conical radius defined from the centerline C L . The second conical frustum C F2  is also defined from the centerline C L . The conical frustums are also indicated in part, for ease of viewing, by broken line projections extending from the conical surfaces toward the centerline C L . According to the exemplary embodiment, the first conical radius R 1  is greater than the second conical radius R 2 . Since the surfaces  75 ,  76  are parallel, forces between the head  50  and the hub  12  are substantially aligned which inhibits bending of the locking ring. It also results in the locking ring  70  being in compression. 
     The foregoing description of several embodiments of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise steps and/or forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention and all equivalents be defined by the claims appended hereto.