Abstract: A spring loaded retainer includes a lug receiving portion defining a first maximum outside dimension, the lug receiving portion also defining a lug receiving slot that extends partially through the lug receiving portion, forming a first sidewall, a second sidewall, and a catch surface connecting the first sidewall to the second sidewall. A drive portion defines a second maximum outside dimension, and a first flat is disposed on the outside of the lug receiving portion proximate to the first sidewall or the second sidewall.

Abstract: A locking pin assembly for securing a wear member to a support structure may include a body portion and may include a shaft member partially disposed within and extending from the body portion and rotatable between a first position that mechanically inhibits removal of a ground engaging member from a support structure and a second position that permits removal of the ground engaging member from the support structure. A wear member for receiving a locking pin assembly may include a bore extending laterally through the bore member with a proximal opening and a distal opening, an installation ramp and a removal ramp may be disposed at the proximal opening for engaging a tang of a shaft member of the locking pin assembly.

Abstract: A tooth mounting structure for a bucket includes a tooth adapter and a tooth. The tooth adapter includes a mounting portion mounted to the bucket and a nose portion extending from the mounting portion. The tooth includes an internal space for inserting the nose portion. The nose portion includes a rectangular tip portion, a rectangular base end portion and an octagonal connecting portion. An inner surface of the tooth is formed along an outer surface of the nose portion.

Abstract: A retainer sleeve includes an at least partially annular body defining an axis of rotation, a radial direction, and a circumferential direction. The body may also have a radially inner annular surface defining a radially inner aperture, and a first anti-rotation feature extending radially inwardly from the radially inner annular surface including a sloping ledge having a locking surface, and an outer peripheral surface defining a notch that is at least partially aligned with the first anti-rotation feature or an array of a plurality of external ribs extending outwardly radially from the outer peripheral surface.

Abstract: An adaptor includes a body defining a longitudinal axis, and a transverse axis that is normal to the longitudinal axis. The body also has a leading portion defining a lock receiving recess extending transversely at least partially through the leading portion. The leading portion defines at least one linear portion in the lock receiving recess that is configured to engage the power locking device.

Abstract: A spring includes a first spring arm extending from the first side edge of the flat base, the first spring arm including a first arcuate portion extending from the flat base, a first straight portion extending from the first arcuate portion and disposed proximate to the rear face, the first straight portion defining a first obtuse angle with the rear face, and a first straight portion length.

Abstract: A wear member assembly may include a nose attachable to a bucket lip. The nose may include a rear portion having a first set of substantially planar surfaces including a first, second, and third subset of surfaces. The third subset of surfaces may be angled and positioned between the first subset of surfaces and the second subset of surfaces. The nose may also include a forward portion positioned forwardly adjacent to the rear portion, the forward portion having a second set of substantially planar surfaces including a fourth, fifth, and sixth subset of surfaces. The sixth set of surfaces may be angled and positioned between the first subset of surfaces and the second subset of surfaces. The wear member assembly may also include a wear member having a cavity comprising rear and forward bearing surfaces corresponding to the third and sixth subset of surfaces.

Abstract: An implement assembly includes an implement having a forward edge and an edge protection system. The edge protection system includes at least one edge shroud having a lower leg that includes a lower end and a lower end inner surface, an upper leg, and a wedge portion, the upper leg including an upper end portion and a connecting portion. The upper end portion has an upper end inner portion that may be angled to the lower end inner surface and/or a horizontal plane extending between the upper leg and the lower leg. The system also includes a boss assembly structured to couple the edge shroud to the implement, and including a pry boss. The angle of the upper end inner surface may be such that a clearance is formed between the upper end inner surface and the pry boss when moving the edge shroud forward in a disengaging direction relative to the implement. The clearance reduces frictional force opposing movement of the edge shroud in the disengaging direction.

Abstract: A shroud configured to be attached to a work implement comprises a ground engaging surface with a convex arcuate portion, a first concave arcuate portion on one side of the convex arcuate portion, and a second concave arcuate portion on the other side of the convex arcuate portion, or an upper outside loading surface extending from the ground engaging surface including a first concave arcuate loading portion, a first convex arcuate loading portion, and a second convex arcuate loading portion, or a slot the defines a front clearance face with a first rearward facing pad therefrom.

Abstract: A tip adapter comprises a side throat surface with a variable blend defining a radius of curvature ranging from 200 mm to 270 mm, or a lower nose surface that includes a first planar portion and a second planar portion defining a lower obtuse angle therebetween, or a top throat surface with a top arcuate portion defining a radius of curvature ranging from 100 mm to 300 mm.

Abstract: A tip defining a cavity for being attached to a work implement comprises a body that defines a cavity with a cavity upper flat portion length ranging from 5 mm to 20 mm, or a cavity side transition surface configured to avoid interference with a tip adapter, or a cavity first lower planar surface that forms an oblique angle with the cavity second lower planar surface.

Abstract: A replaceable tip for a demolition tool tip may include a first sidewall having a first contact side; a second sidewall having a second contact side; and a center wall connecting the first sidewall and the second sidewall. The center wall may have a third contact side provided with a recess, the recess may have first and second abutment surfaces, and the third contact side may have a third abutment surface adjacent the recess. A channel may be defined by the first, second and third contact sides, and the channel may be configured to receive an adapter of the demolition tool.

Abstract: A connection for firmly securing an adapter for carrying a digging tooth to a lip of an excavating container. The connection has substantially aligned openings in the adapter and the lip. A pressure applying unit, such as a hydraulic actuator, is arranged inside the opening and generates a generally horizontally acting force which draws the adapter and the lip towards each other. A stress member is operatively coupled to the hydraulic actuator and resiliently deforms relative to its relaxed shape when it is subjected to the horizontally acting force. The wedge is shaped so that upon a reduction or cessation of the horizontally acting force the stress member, remains in the resiliently deformed state in which it draws the adapter and the lip towards each other and keeps them immovably secured to each other until the wedge can be withdrawn following a repressurization of the hydraulic actuator.

Abstract: A mechanical system (1) includes a support (10), a tooth (20) and a device (30) for interconnecting the two components. The device (30) includes a key (50), a nut (60) and an elastic sheath (40) provided with a wall that is adjustable by deformation in a housing (14) of the support, by screwing between the key and the nut, between an insertion configuration and a locking configuration. The device (30) also includes a support ring (70) inserted between the key and an opening (24) made in the tooth (20). In the insertion configuration of the device (30), the support ring (70) is adjusted in the opening (24), while in the locking configuration of the device (30), the support ring (70) exerts retaining forces on the tooth (20). A heavy-construction machine bucket (G) including such a system (1), and a method for implementing such a system are also described.

Abstract: An attachment system for use with an excavation implement can include a retainer which secures a wear member to a lip of the excavation implement, the retainer being fixedly attached to the lip, and a biasing device retained within the retainer. The biasing device biases the wear member toward the lip. A method of attaching a wear member to a lip of an excavation implement can include installing a biasing device in a retainer fixedly secured to the lip, and then positioning the wear member on the lip. Another attachment system can include a biasing device which is compressed between the retainer and the locking device. Another method of attaching a wear member can include positioning the wear member on the lip, then extending the locking device from the wear member, and then compressing the biasing device between the locking device and the retainer.

Abstract: Disclosed are various exemplary embodiments of a lock for a ground engaging tool. The lock may include a head portion and a C-shaped portion extending from the head portion. The C-shaped portion may define a lock slot between two circumferential ends for receiving a portion of a support member to be locked with the ground engaging tool. The C-shaped portion may further include an outer surface configured to be rotatably received in an inner surface of a retainer bushing, an inner surface configured to contact the portion of the support member, and a base extending between the outer surface and the inner surface. The base may include a helical surface with a depth increasing from a first end to a second end.

Abstract: Disclosed are various exemplary embodiments of a lock for a ground engaging tool. The lock may include a head portion and a C-shaped portion extending from the head portion. The C-shaped portion may include an inner surface extending between a first circumferential end and a second circumferential end to define a lock slot. The inner surface may include a first inner surface extending from the first circumferential end to a midpoint between the first circumferential end and the second circumferential end and a second inner surface extending from the second circumferential end to the midpoint. The first inner surface and the second inner surface may be symmetrical with respect to a first plane substantially parallel to a lock rotation axis.

Abstract: A threadless, hammerless self-aligning geometric device for ground engagement, the device may comprise a wedge mechanism having a pair of laterally spaced holes in a first and second sidewall with a semi-flexible buffer that connects a plurality of load bearings that are axially aligned within the center of the wedge mechanism, wherein a pin that is formed integrally with an indentation is disposed in a rectangular mechanism having a recess with a pair of laterally spaced holes in a first and second sidewall so when fastened by the pin, the laterally spaced holes, the wedge mechanism and the recess are in substantial axial alignment, the pin being held in place by a mechanical fit between the pin and a knob.

Abstract: The present invention is directed to a releasable locking assembly for attaching a wear member to a support structure. It may be used with excavating equipment for attaching ground-engaging teeth to adaptors, lip shrouds to bucket lips, or other analogous uses. The wear member includes at least one pin-retainer-receiving opening in one side. The opening is tapered, being narrower at its outer surface and wider at its inner surface. The support structure includes at least one pin-receiving recess which generally aligns with the opening in the wear member when the wear member and the support structure are operatively coupled. The pin retainer is a frustoconically shaped cylinder which is threaded internally. It is inserted into the opening in the wear member. The wear member is slidably mounted onto the support structure. The pin is an elongate body which is externally threaded. It is screwed into the pin retainer by the application of torque force from a standard ratchet tool.

Abstract: An attachment system for connecting a first member such as a lip plate (12) of a mechanical digging device to a second member such as a ground engaging tool (10). The first member has a lug (22) attached thereto, and the second member has a recess (50) which is located about the lug (22). A stabilizing member (98) is located within a slot (57) in the recess. A clamping member (60) is between the lug and the stabilizing member, and includes a resilient portion (90) such as a compression spring. A compressive force supplied to the resilient portion restricts the movement of the second member relative to the lug.

Abstract: A securing arrangement for a tool (7) of an agricultural tillage implement of a type having a tapered interconnection between a socket (5) on the tool and an adaptor piece (3) adapted for mounting onto a tine (1) of the tillage implement. The adaptor piece (3) has a recess (9) which can be an aperture or a pair of transverse arcuate slots (31) for receiving a retaining pin(11). The socket (5) on the tool has notches (15) on its opposed sides and a portion (13) on the retaining pin in use engages into at least one of the notches (15) to prevent disengagement of the socket (5) from the adaptor piece (3). The adaptor piece can be integral with the tine.

Abstract: A coupling arrangement for securing two separable components in an excavating operation includes a wear component, a base component and a lock. The lock has a body having a configuration adapted to be received in a hole in the base component, and a rotatable locking member. The locking member includes a flange that is movable between a locking position wherein the flange holds the lock in the assembly and a release position wherein the flange permits the lock to be removed from the assembly. In the release position, the flange sets within the axial extension of the outline of the body. In the locking position, at least part of the flange sets outside the axial extension of the outline of the body. In one construction, the rotation of the locking member to the locking position tightens the fit of the wear component on the base component.

Abstract: A locking assembly has two members which are moveable into coupling engagement with one another. The two members have lock engaging walls, and one of the members has an opening between the lock engaging walls for receiving a lock. The lock comprises a lock body and a retainer. The lock body has a channel for receiving a portion of the retainer. An end of the retainer extends underneath a retainer engaging wall, thus resisting movement of the lock out of the opening.

Abstract: A locking assembly is disclosed. The locking assembly is for coupling a first member including a receiving area, and a second member having a receiving region. The locking system includes an interference element including an interfering portion that is received within the receiving area of the first member when the locking system couples the first member and the second member together, a biasing element, a cam, wherein the cam is adapted to cause the biasing element to be in a biased position or an unbiased position, and a wedge shaped structure.

Abstract: A tooth adapter having an elastomeric clamp assembly and a method for using the same are provided. The system includes a tooth adapter having a first end operable to receive a removable tooth point and a second end having an upper blade and a lower blade, the upper and lower blades at least partially defining a cavity configured to receive a tooth horn. An upper insert is configured to be disposed at least partially within an orifice in the upper blade, and a lower insert is configured to be disposed at least partially within an orifice in the lower blade.

Abstract: The present invention is directed to a releasable locking assembly for attaching a wear member to a support structure. It may be used with excavating equipment for attaching ground-engaging teeth to adaptors, lip shrouds to bucket lips, or other analogous uses. The wear member includes at least one pin-retainer-receiving opening in one side. The opening is tapered, being narrower at its outer surface and wider at its inner surface. The support structure includes at least one pin-receiving recess which generally aligns with the opening in the wear member when the wear member and the support structure are operatively coupled. The pin retainer is a frustoconically shaped cylinder which is threaded internally. It is inserted into the opening in the wear member. The wear member is slidably mounted onto the support structure. The pin is an elongate body which is externally threaded. It is screwed into the pin retainer by the application of torque force from a standard ratchet tool.

Abstract: A coupling device for equipment implements is described, which coupling device does not impair the lubricity of bearing sections when the equipment is in service, does not cause seizure during rotation of bearings, does not need frequent feeding of grease to the bearing sections from outside, and provides good noise absorbability. The coupling device has such a structure that a metal based contact material 7 capable of storing a lubricating oil and/or lubricant is interposed between an implement bushing 1 made from steel and implement pin 4 of an implement for construction equipment.

Abstract: A system for rapid and easy replacement of sacrificial machine parts, utilizing an adapter having a slot and a retainer pin fitted with at least one spring-loaded ball bearing suitable for engaging the slot when the retainer pin is inserted into the adapter.

Abstract: A tooth assembly for an excavating machine includes an adapter having first and second surfaces and first and second sides. The first surface of the adapter is generally tapered and converges toward a first end of the adapter. A tooth point is coupled with the adapter at the first end of the adapter, and the tooth point has a contact edge opposite the first end of the adapter. The tooth point also includes first and second sides, the first side having a slot adapted to receive a non-rotation ridge of a retainer pin to prevent rotation of the retainer pin with respect to the tooth point. A second end of the adapter is adapted to be removably coupled with a tooth horn. The tooth assembly further includes a central portion extending generally from the first side of the adapter to the second side, the central portion defining a central bore.

Abstract: A retainer, adapted to engage a recess in a cutting tool for securing the cutting tool to a support block, includes a retainer body having a main portion with first and second ends. The main portion defines a continuous shear zone having first and second ends. The retainer body further includes a protruding portion disposed between the ends of the continuous shear zone and spaced away from the ends of the main portion. The protruding portion extends radially from the main portion and is adapted to overlap the support block when the retainer is engaging the recess.

Abstract: A hammerless mechanical attachment system comprising a C-clamp member, a first wedge member, a second wedge member and a threaded tensioning device for attaching a tooth adapter to a base cutting edge of an implement. The C-clamp member has a generally C-shaped body with a forwardly facing abutment surface and a forwardly extending flange having a threaded aperture therein. The first wedge member has a forward side having a first wedge surface thereon, an opposite rearward side having a second abutment surface thereon positionable against the first abutment surface of the C-clamp member, and a through bolt hole disposed along a longitudinal axis parallel to the second abutment surface. The bolt hole is disposed in alignment with the threaded aperture in the flange when the second abutment surface is placed in abutment with the first abutment surface of the C-clamp.

Abstract: A spaced series of generally C-shaped wear members, representatively excavating tooth adapters, are positioned on a front edge portion of a lip structure on, for example, an excavating bucket, by placing the lip edge portion between rearwardly extending top and bottom leg portions of each wear member. Spring-loaded, low profile attachment structures are mounted within top leg recesses of the wear members prior to the installation of the wear members on the lip structure. After the wear members are in place on the lip structure, the internally disposed attachment structures are secured to the lip structure at open rear ends of the top wear member legs in a manner causing the internal attachment structures to resiliently bias their associated wear members in rearward self-tightening directions relative to the lip structure. Protective shrouds are then connected to the open rear ends of the top wear member legs to conceal and protect their internally carried attachment structures.

Abstract: A pin retention mechanism which prevents longitudinal and/or rotational movement of a mounting pin, such as used for attaching a heavy equipment tool, which provides quick and easy removal. The pin retention mechanism comprises a housing having an opening in which an end of a mounting pin is adapted to be located, and a removable member which is inserted into the housing adjacent the end of the pin. The removable member may be provided with a protruding section which is adapted to extend through a groove in the end of the pin for preventing rotation thereof. The removable member is retained in the housing by a spring catch. In each embodiment, a safety cap screw can be utilized to eliminate movement of the removable member.

Abstract: An earthworking implement adapted to normally engage the ground in a primary direction of travel has a replaceable ground engaging tool retained onto a tool mounting portion of the implement by an elongated retainer. The tool mounting portion has an exterior surface with a first retainer pocket providing a first abutment surface facing in a direction substantially away from the primary direction of travel. The ground engaging tool, in turn, has an interior surface with a second retainer pocket positionable in alignment with the first retainer pocket and provides a second abutment surface disposed in a generally spaced, diametrically opposing relationship to the first abutment surface. An elongated retainer is positionable within the retainer pockets and has a pair of opposite solid end portions oriented to abut the first and second abutment surfaces such that the end portions restrict the tool from coming off the mounting portion in the direction of the primary direction of travel.

Abstract: A system for rapid and easy replacement of sacrificial machine parts, utilizing an adapter having a slot and a retainer pin fitted with at least one spring-loaded ball bearing suitable for engaging the slot when the retainer pin is inserted into the adapter.

Abstract: A mechanical retention system is disclosed for detachably retaining a ground engaging tool onto an earthworking implement. The retention system uses an elongated steel retainer, which has a convolute spring portion between opposite the end portions of the retainer to allow the retainer to be compressible in one direction in order to be mounted through a retainer opening in the tool into a retainer pocket in the mounting portion of the implement.

Abstract: A bucket tool comprising an edge 7 secured to the lower part of a bucket in a lateral direction, tooth-mounting fittings 8 secured to the edge 7 with an interval between the fittings in the lateral direction, excavation teeth 9 attachably/detachably mounted in the tooth-mounting fittings 8 and protruding forward beyond the edge 7, a ground-leveling plate 10 having a lateral width equal to the lateral width of the lower part of the bucket, and coupling fittings 11 secured to the upper surface of the ground-leveling plate 10 at an interval nearly equal to the interval between the tooth-mounting fittings 8 and capable of being detachably attached to the ends of the excavation teeth 9. Upon attaching or detaching the coupling fittings 11 secured to the upper surface of the ground-leveling plate 10 to, or from, the ends of the excavation teeth 9, the ground-leveling plate 10 can be easily attached to, or detached from, excavation teeth of a bucket for excavation.

Abstract: An extensible lock for securing a wear member to a support structure of an excavator. The lock includes a base and a body which are extensible and retractable to hold and release the wear member, respectively. The body includes an inclined bearing face which engages a complimentary bearing face on the wear member to pull the wear member onto the support structure and prevent its inadvertent release.

Abstract: A lock system removably connects an earthengaging tooth point to an adapter. The lock system is particularly suited to tooth points for large excavating buckets, such as dragline buckets. The forward-extending nose of the adapter fits within the rear-facing socket of the tooth point. Ears extend back from the tooth point on both sides of the adapter and define apertures adapted to receive pins. A hole in the adapter is also adapted to receive the pins. The pins extend through the apertures and into the hole, thus fixedly connecting the tooth point to the adapter. To remove the tooth point, both pins can be driven into the adapter hole and housed there concurrently. The tooth point can then be removed and the pins later driven out of the hole.

Abstract: A hydraulic fastening device, for securement of two components, for example, securement of teeth to a bucket on earthmoving or mining equipment. Each component has an orifice therein adapted to be substantially aligned. A body member is inserted in the aligned orifices. A control device is then operated to move at least one protrusion to protrude from the body and to fasten the components. This is achieved by hydraulic operation and connection of a fluid conduit between the control device, e.g. a grease nipple, and the protrusions.

Abstract: Retaining pin assemblies for use in releasably securing an excavating tooth or point to a mounting adaptor. Each pin assembly includes one or more holders insertable lengthwise in registering apertures in the adaptor and tooth and movable thereafter widthwise to cause interengagement. The holder and the apertures are provided with complementary portions. A locking member is inserted after engagement of the pin to fix the adaptor and tooth together.

Abstract: Apparatus is provided for protecting a base edge of a ground engaging implement of a work machine from wear. The apparatus includes a base edge cover and retaining apparatus of a construction adapted for time saving removal and installation. A mounting base is carried on the upper face of the base edge and has opposite sides and a outwardly opening cavity. The cavity has a concave frontal face thereon and a retainer opening through the one side in registry with the concave frontal face. A hook portion is provided on the base edge cover, which is adapted to be received within the cavity of the mounting base and positionable at a operative position where the convex face on the hook portion is disposed in a spaced opposing relation to the concave face in the cavity to define an arcuate groove therebetween.

Abstract: Bucket tip retention means for retaining an excavator bucket tip to an adapter on an excavator bucket including a retention pin extending through co-axial bores in the bucket tip and the adapter, the retention pin having a groove defined in a front face, a positioning shoulder extending from the rear face of the pin, and a resilient locking clip element retained in the locking clip groove by a clip retaining pin, the locking clip element having a first locking portion and a second locking portion extending from the locking clip groove for engaging the bore in the adapter and urging the positioning shoulder to engage the bore in the adapter.

Abstract: A wear resistant excavating apparatus provides reduced wear, resilient compensation for such wear, reduced time required for installation, maintenance, and repair, and reduced hazards of operation. In a preferred embodiment, a wear resistant excavating apparatus has a lip which penetrates the earth, a structure which overlaps the lip, a fastener which biases the overlapping structure to contact the lip, and a compression member which resiliently maintains the overlapping structure in contact with the lip.

Abstract: An excavating tooth for attachment to the digging edge of excavating equipment includes a wear member provided with bearing faces in a socket which extend substantially parallel to the longitudinal axis of the tooth. The bearing faces are formed to widen significantly as they extend rearward to provide broad bearing surfaces at the rear ends of the wear member. The bearing faces are placed between the converging walls and the side walls of the socket at obtuse angles thereto to avoid areas of stress concentration. The bearing faces are further formed in a plurality of tiers to provide enhanced resistance to vertically applied loads at the front end of the member. The wear members are further secured to the adapter by locks which ease installation and removal of the wear members.

Abstract: A cutting tool retention system for retaining a cutting tool having a tool recess. The cutting tool retention system comprises a support block having a block bore and a block recess intersecting the block bore and a clip movably situated in the block recess, the clip having a spring structure which engages the support block and urges the clip into an engaging relationship with the tool recess of the cutting tool situated within the block bore, the spring structure allowing the clip to be disengaged from an engaging relationship with the tool recess of the cutting tool situated within the block bore by applying force directly to the clip so as to overcome the urging of the spring structure.

Abstract: A spool and wedge assembly for securing replaceable cutting teeth or cutting elements to the nose portions of earth moving buckets. The spool and wedge assembly comprises first and second parallel longitudinally extended spool elements, which are transversely displaced apart to engage the aligned side walls of the securing element receiving apertures, and, first and second wedge shaped elements. The wedge and spool elements are interconnected by a longitudinally disposed screw threaded bolt mechanism which is tightened to draw the first and second wedge elements together while forcing the first and second spool elements apart, such that the cutting teeth are locked in position.

Abstract: An excavation tooth point longitudinally extending along an axis and having a pocket area extending inwardly through a rear end thereof is telescoped onto a nose portion of an adapter structure by inserting the nose portion into the tooth point pocket area. The inserted nose portion has a tapered side opening therein that is positioned between a corresponding pair of similarly tapered tooth side wall openings. To removably couple the tooth point to the adapter nose an elongated, wedge shaped connector member is inserted, small end first, through the generally aligned tooth and adapter openings. A bolt is then passed through a central opening in a flat spring member and tightened into a threaded axial opening in the small connector member end.

Abstract: A locking pin (100) for use captively retaining a tooth (14) on an adapter portion (12) of an excavating tooth and adapter assembly has a primary wedge member (110) with an integral spring (120) extending upward from the member's distal end (116). A first positive slop means (130) extends from the wedge member (110) while an opposing second positive stop means (122) extends from the integral spring (12). After insertion, the locking pin (100) prevents separation of tooth (14) from adapter portion (12) while the first and second positive stop means (130, 122) prevent accidental loss of the locking pin (100) from the assembly. To remove the locking pin, a force sufficient to separate the first positive stop means (130) from the pin (100) is exerted to drive the pin (100) from the assembly. In another embodiment, the integral spring extends from a lateral surface of the locking pin (700, 800).

Abstract: The invention provides a liner sleeve (8) adapted, in use, to be interposed between the external periphery of a round shank (3) of a point attack, mineral cutter pick (1), and the internal periphery of a circular, shank-receiving bore (5) of a pick box (6), the sleeve (8) being constituted by a plurality of individual rings (14A, 14B, 14C) stacked end-to-end in abutting relationship about a common longitudinal axis (15), the rings (14A, 14B, 14C) together having an axial length (17) approximating to the axial length (12) of the bore (5).