Field of invention

The present invention relates to a support ring mountable in contact with and around a head centre of a gyratory crusher to support an inner crushing shell (mantle) and in particular, although not exclusively, to a support ring capable of moving dynamically with the crushing shell at the head centre.

Background art

Gyratory crushers are used for crushing ore, mineral and rock material to smaller sizes. Typically, the crusher comprises a crushing head mounted upon an elongate main shaft. A first crushing shell (typically referred to as a mantle) is mounted on the crushing head and a second crushing shell (typically referred to as a concave) is mounted on a frame such that the first and second crushing shells define together a crushing chamber through which the material to be crushed is passed. A driving device positioned at a lower region of the main shaft is configured to rotate an eccentric assembly positioned about the shaft to cause the crushing head to perform a gyratory pendulum movement and crush the material introduced in the crushing chamber. Example gyratory crushers are described in WO 2008/140375 and WO 2014/053143. Typically, both the inner and outer crushing shells wear and distort due to the significant pressures and impact loading forces they transmit. In particular, it is common to use backing compounds to structurally reinforce the shells and their mounting position at the topshell and head centre respectively. Conventionally, a backing compound (typically an epoxy or polyurethane material) is cured between the shell and the corresponding frame and head centre to provide structural support during crushing particularly in tough high- pressures applications involving extremely hard materials. However, the majority of widely used backing compounds are disadvantageous for health and environmental reasons and require long curing times that extends the downtime of the crusher. Accordingly, there is a general preference to avoid their use. However, in high pressure and tough

applications the use of backing compounds is often unavoidable to in order to add structural support and this is typically difficult to predict beforehand. CN 1970154 disclosures of epoxy secured and/or reinforced crushing shell.

Additionally, due to repeated and high magnitude crushing forces imparted to the mantle, it is common for the mantle to stretch or elongate in an axial direction. Since the mantle is typically fixed to the head by an epoxy, growth is restrained axially. Accordingly, it is common for the mantle outward facing conical surface to deform which typically manifests as the mantle bulging radially outward at an axial region above the stress position. This bulging decreases the radial thickness of the crushing zone and restricts the flow of material through the crusher which in turn is undesirable for crushing reduction and capacity. Also, deformed mantles tend to crack prematurely which shorten their intended lifetime and the frequency of crusher downtime. Accordingly, there is a need for a mechanism and/or technique to support the mantle in position at the head centre that addresses these problems.

Summary of the Invention It is an objective of the present invention to provide an inner crushing shell (mantle) support ring that may be assembled and mounted in position conveniently with regard to both time and labour. In particular, it is an objective to avoid mounting delays associated with conventional epoxy based mounting techniques that typically require appreciable curing times.

It is an additional objective to provide a means of supporting a mantle at a head centre that is both time and labour efficient to remove with regard to conventional epoxy support methods where the epoxy is often very difficult to break away from the head centre.

The objectives are achieved by providing a mantle support ring mountable in contact with the head centre to sit radially between the head centre and the mantle. The present support ring may be mounted and dismounted conveniently by personnel simply lowered the ring in position around the head centre and subsequently raising the support ring from the head centre via auxiliary lifting apparatus. Accordingly, there is no requirement to crack or chisel an epoxy based support material from the head centre. The present support ring may be provided as a single piece component or may be formed as a multi-segment modular assembly as desired. Such a configuration provides a number of options for mounting and dismounting techniques and procedures. The ring may be formed from a polymer based material to be environmentally friendly. In particular, the ring may be formed from recycled materials and may be itself recycled following use. The material may be environmentally benign and in some implementations may be biodegradable and/or bio- compostable to reduce environmental impacts. According to a first aspect of the present invention there is provided a crushing shell support ring mountable in contact with and around a head of a gyratory crusher, the ring comprising: a plurality of segments connected or connectable together in a circumferential direction to form the ring having a generally frusto-conical shape profile; each segment having a length extending in a circumferential direction around a central longitudinal axis, a width extending generally in an axial direction and a thickness extending in a radial direction, the thickness defined by a radially inward facing region for positioning against the head of the gyratory crusher and a radially outward facing region for positioning against an inner crushing shell; and a plurality of articulation joints coupling the segments in the circumferential direction to enable the ring to expand and contract radially when mounted radially between the head and the inner crushing shell. The articulation joints are particularly advantageous to provide a ring that is flexible in a radial and circumferential direction. The joints allow the ring position at the head centre to adjust dynamically in use and in particular to be capable of moving axially downward with the progressive movement (axial elongation) of the mantle. That is, the present support ring, via its articulation joints and the choice of component materials, is capable of being 'squeezed ¹ between the mantle and head centre. Accordingly, the present ring positionally supports the mantle in a manner that avoids undesirable mantle deformation that may otherwise change the dimensions of the crushing zone and affect crushing capacity and reduction. Preferably, the ring comprises a polymer or polymer based material. Optionally, the material comprises any one of a polyamide, a polyalkylene or a polyalkylene glycol.

Optionally, the material comprises a reinforcement such as a particulate or fibrous material distributed within a polymer matrix. Optionally, the material comprises a glass fibre reinforcement distributed within a polyamide, a polyalkylene or a polyalkylene glycol matrix. Optionally, the material may comprise a metal having the required ductility to withstand the tensile stresses and compressive stress and to deform when in use between the head centre and mantle. Further example materials include ductile steel alloys or aluminium. The choice of material may be considered to represent a compromise between its capability to deform (so as to be compressible radially and to elongate axially) and a required stiffness to withstand the impact crushing forces. This capability of the ring to positionally adjust (in response to changes in the position and the dimensions of the mantle) whilst structurally supporting the mantle, may be considered to be achieved, by a combination of the choice of constituent material and the articulation joints that allow for radial expansion and contraction.

Each segment may comprise an upper lengthwise extending edge and a lower lengthwise extending edge, a length of the upper edge being less than a length of the lower edge. Preferably, a mount tab is provided at the upper edge and is configured to be engagable by a lifting device. Optionally, the mount tab is formed integrally with the body of the segment that may be formed from a casting or moulding manufacturing process.

Preferably, the tab comprises an eyelet attachable to a chain or cable of a lifting device. Optionally, the mount tab may be formed as a hook or one half of mechanical attachment mechanism.

Preferably, each articulation joint comprises a first part provided at a first segment of the ring and a second part provided at a second segment of the ring, the first and second parts are configured to inhibit the segments from being decoupled in a circumferential direction. Preferably, the first and second parts comprise radially extending members configured to overlap and abut one another. The fingers may be configured to overlap in a

circumferential, radial and axial directions. Preferably, the fingers comprise barbed ends such that the barbs of each respective finger of respective segments are configured to engage one another to releasably lock the segments side-by-side in a circumferential direction. Preferably, the fingers are formed integrally with the segment and due to the material of the segment, comprise a degree of flexibility. In particular, the fingers may be configured to be resiliently biased towards one another in engaging contact so as to inhibit undesirable separation of the segments in a circumferential direction. Optionally, the segments may comprise components to releasably interlock the segments axially so as to prevent a first segment moving independently of a second segment in the axial direction. Such a configuration may comprise additional overlapping or inter-engaging locking members or the same locking fingers that provide the coupling in the circumferential direction. Accordingly, such fingers may comprise members and barbs extending in the axial direction. Optionally, axial locking of the segments may be provided by

circumferentially overlapping arms and/or shoulders provided at neighbouring segments in a circumferential direction. In particular, each segment may comprise an arm or lip projecting outward from the segment at or towards one lengthwise end and a

corresponding shoulder, recess or edge section at an opposite lengthwise end such that adjacent segments via the engaging member are capable of overlapping axially (and circumferentially) to provide a part-tessellated assembly. Optionally, the widthwise extending edges may be aligned transverse to the longitudinal axis of the head centre such that the widthwise extending edges of circumferentially neighbouring segments are capable of abutting one another to axially couple the segments and prevent independent axial movement. Preferably, each segment comprises a first interengaging part at or towards a first lengthwise end and a second inter-engaging part at or towards a second opposite lengthwise end. Such first and second parts may provide coupling in both the

circumferential and axial directions.

Optionally, the segments are separate segments that may be coupled and decoupled from one another. Optionally, the segments may be coupled to one another so as to be formed integrally during the moulding or casting process. Optionally, the segments may be connected with one another via webbing, ribs, tendrils or the like. Preferably, such ribs are configured to be flexible relative to the segments so as to allow the segments to move relative to one another and to compress and expend radially as a unitary body. Optionally, such ribs may extend in a circumferential direction from the lengthwise ends of each segment and may be provided at different regions along the length of the widthwise extending edges so as to span the junction between segments. Such an arrangement may be advantageous to provide a unitary body for convenient mounting and dismounting at the head centre. Preferably, the segments are configured to provide respective gaps between the widthwise extending edges (lengthwise ends) to enable the ring to expand and contract radially.

Preferably, at least a part of a main body of each segment comprises a generally corrugated profile that defines ribs at the radially inward and outward facing regions. Optionally, each of the ribs extend in a lengthwise direction along the segments. The ribbed structure of the segments is advantageous to enhance the flexibility of the ring and its capacity to compress and expand radially between the mantle and head centre in use. That is, the corrugated cross sectional profile (in an axial plane) enables the segments to dynamically compress and to elongate axially with the mantle. A further advantage of the ribs is to correctly seat the ring in position between the head centre and the mantle and in particular to accommodate surface roughness and imperfections at the mantle and head centre as such surfaces are typically not machined. Preferably, the ribs extend over a majority of each segment and may extend over a surface area at both the radially inward and outward facing surfaces in a range 50 to 100% of the total surface area.

Preferably the ring is mounted at the head centre exclusively via the non-bonded mating contact between the outward facing region (surface) of the head centre and the inward facing region (surface) of the support ring. That is, the support ring, as a free standing component or assembly, is configured to rest or sit on the head centre under gravity and is not otherwise mechanically or chemically attached the head centre. According to a further specific implementation of the present invention there is provided a gyratory crusher head assembly comprising: a head capable of an oscillating gyroscopic motion within the crusher; an inner crushing shell mounted at the head; and a crushing shell support ring as claimed herein mounted radially between the head and the inner crushing shell.

Preferably, the inner crushing shell comprises at least one shoulder projecting radially inward towards the head and configured to abut a part of the support ring. More preferably, the shoulder extends continuously or discontinuously in a circumferential direction around a central longitudinal axis of the crusher.

According to a further aspect of the present invention there is provided a gyratory crusher inner crushing shell comprising: a main body mountable at a head of a gyratory crusher, the main body extending around a central longitudinal axis; the main body having a mount surface being radially inward facing relative to the axis for positioning opposed to at least a part of the head and a crushing surface being radially outward facing relative to the axis to contact material to be crushed, at least one wall defined by and extending radially between the mount surface and the crushing surface, the wall having an upper axial end and a lower axial end; an annular foot region positioned axially at or towards the lower axial end and projecting radially inward from the wall, the foot region having a radially inward facing raised contact surface for positioning opposed to a radially outward facing surface of the head, the contact surface extending continuously around the axis; an annular neck region positioned axially at or towards the upper axial end and configured to support a mounting position of the crushing shell at the head; at least one shoulder projecting radially inward from the wall at an axial position between the foot region and the neck region, the shoulder having a generally axially downward facing abutment surface being configured to abut an axial upper end of a segment of a support ring.

Optionally, the at least one shoulder comprises a single annular shoulder projecting radially inward from the wall. Optionally, the shoulder comprises a plurality of shoulder sections distributed in a circumferential direction around the axis. Optionally, a angular separation between the shoulder sections is substantially uniform around the axis.

Optionally, the angular separation between the shoulder sections is non-uniform around the axis. Optionally, an angular length of each shoulder section is substantially uniform for all shoulder sections. Optionally, the shoulder sections may comprise different angular lengths in a circumferential direction. Preferably, the shoulder projects radially inward from the wall by a distance being less than a distance by which the annular foot region projects radially inward from the wall. Such an arrangement is advantageous to avoid the shoulder contacting the head centre. Preferably, the annular neck region comprises at least a section that projects radially inward from the walls. Preferably, the shoulder section projects radially inward by a distance being less than a distance by which the neck region projects radially inward from the wall.

Preferably, the shoulder is positioned at an axial mid-length region of the crushing shell. Optionally, the shoulder is separated axially from the upper and lower ends by a substantially equal separation distance.

Preferably, the downward facing abutment surface is aligned perpendicular to the longitudinal axis of the crushing shell. Optionally, the abutment surface may be aligned transverse to the longitudinal axis. Preferably, a radial length of the downward facing abutment surface is less than a minimum radial thickness of the wall. Optionally, a radial thickness of the downward facing abutment surface is in a range 1 to 30%, 1 to 20%, 1 to 15%, 1 to 10%, 2 to 10%, 3 to 10%, 4 to 10% or 5 to 10% of a minimum radial thickness of the wall. Such a configuration is advantageous to avoid the shoulder contacting the head centre and to provide sufficient abutment contact against an upper edge or region of the support ring. Preferably, the shoulder section is positioned within a lower axial half of the crushing shell. Such an arrangement is configured to positionally support a support ring within the lower axial half of the crushing shell.

Preferably, the shoulder is recessed (to sit radially outside) relative to an imaginary cone defined in part by the foot contact surface that is aligned transverse to the longitudinal axis. Optionally, the imaginary cone defined partially by the foot contact surface comprises a conical surface being declined relative to the central axis by angle in a range 25 to 35° and more preferably 30°. Such an arrangement avoids contact between the inward projecting abutment shoulder and the generally conical radially outward facing surface of the head centre where the mantle rests on the head centre via the foot contact surface.

According to a further aspect of the present invention there is provided a gyratory crusher inner crushing shell assembly comprising: i) an inner crushing shell having a main body mountable at a head of a gyratory crusher, the main body extending around a central longitudinal axis, the main body having a mount surface being radially inward facing relative to the axis for positioning opposed to at least a part of the head and a crushing surface being radially outward facing relative to the axis to contact material to be crushed, at least one wall defined by and extending radially between the mount surface and the crushing surface, the wall having an upper axial end and a lower axial end; and ii) a support ring mounted at the mount surface of the crushing shell to contact the head and support the mounting of the crushing shell at the head.

Optionally the ring is a single piece ring extending continuously around the central axis and in contact with the crushing shell. Optionally, the ring comprises a generally uniform shape and configuration in a direction around the axis. Preferably, the ring is pre-formed and may be a free standing unitary body. Preferably the ring does not comprise and is devoid of an epoxy material. Optionally, the ring is bonded to the crushing shell via an adhesive such as an epoxy based material. Preferably the ring is formed from a polymer material such as any one of a polyamide, a polyalkylene or a polyalkylene glycol as described herein. According to a further aspect of the present invention there is provided a gyratory crusher inner crushing shell assembly comprising: i) an inner crushing shell having a main body mountable at a head of a gyratory crusher, the main body extending around a central longitudinal axis, the main body having a mount surface being radially inward facing relative to the axis for positioning opposed to at least a part of the head and a crushing surface being radially outward facing relative to the axis to contact material to be crushed, at least one wall defined by and extending radially between the mount surface and the crushing surface, the wall having an upper axial end and a lower axial end; and ii) support segments mounted at the mount surface of the crushing shell to contact the head and support the mounting of the crushing shell at the head.

Optionally the support segments are pre-formed. Preferably the support segments do not comprise and are devoid of an epoxy material. Optionally, the support segments are bonded to the crushing shell via an adhesive such as an epoxy based material. Preferably the support segments are formed from a polymer material such as any one of a polyamide, a polyalkylene or a polyalkylene glycol as described herein. Preferably, the support segments are arranged at the mount surface of the crushing shell in non-touching contact with one another and extend in a circumferential direction around the axis substantially at a common axial position. According to a further aspect of the present invention there is provided a gyratory crusher head assembly comprising: i) a head having a main body mountable and capable of gyroscopic precession within a gyratory crusher, the main body having a generally conical mount surface being radially outward facing relative to a central longitudinal axis for positioning opposed to at least a part of a mount surface of an inner crushing shell, the shell having an opposite crushing surface being radially outward facing to contact material to be crushed; and ii) support segments or a support ring mounted at the mount surface of the head to contact and support the mounting of the crushing shell at the head. Optionally, the support segments are arranged at the mount surface of the head in touching or non-touching contact with one another and extend in a circumferential direction around the axis and mounted substantially at a common axial position.

Brief description of drawings

A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

Figure 1 is a perspective view of the gyratory crusher mantle support ring mountable in contact with and around a head centre of a gyratory crusher according to a specific implementation of the present invention; Figure 2 is a perspective view of the support ring of figure 1 mounted in position around the head centre of a gyratory crusher;

Figure 3 is a further perspective view of the support ring of figure 2 illustrating the head centre and mantle in partial cross section;

Figure 4 is a magnified view of the cross sectional perspective view of figure 3;

Figure 5 is a perspective view of one of the articulation joints forming part of the support ring of figures 1 to 4 from a radially outward facing surface of the ring;

Figure 6 is a further magnified view of the articulation joint of figure 5 from a different angle;

Figure 7 is a further perspective view of the articulation joint of figures 5 and 6 from the radially inward facing surface of the ring; Figure 8 is a perspective view of one of the segments of the ring of figures 1 to 7 from an external region outside of the ring;

Figure 9 is a perspective view of one of the segments of the ring of figures 1 to 7 from an internal region inside of the ring;

Figure 10 is a further perspective view of one of the ring segments of figures 8 and 9 comprising lengthwise extending ribs to provide each segment with a corrugated profile according to a specific implementation;

Figure 11 is a cross section through A-A of a segment of figure 1;

Figure 12 is a cross sectional perspective view of a mantle according to one aspect of the present invention comprising an abutment shoulder projecting radially inward at the wall of the mantle;

Figure 13 is a further underside perspective view of the interior of the mantle of figure 12;

Figure 14 is an underside perspective view of a mantle according to a further

implementation having an abutment shoulder that is discontinuous in a circumferential direction around the mantle;

Detailed description of preferred embodiment of the invention Referring to figures 1 to 4, a mantle support ring 10 comprises a plurality of segments 11 arranged to extend in a circumferential direction around a central longitudinal axis 12 such that when arranged side -by- side the segments 11 form an annular collar capable of mounting onto a head centre of a gyratory crusher. Each segment 11 is formed from a polymer based material such as a polyamide and comprises a hardness and a stiffness configured to withstand compressive and tensile stress when in use. Each segment 11 comprises a general trapezoidal shape profile such that when arranged side-by-side around axis 12, ring 10 comprises a frusto-conical shape profile. In particular, each segment 11 comprises an axially upper edge 14 that is shorter than an axially lower edge 15. Such edges 14, 15 may define respective planar end faces or may be rounded or curved in the axial direction. Each segment 11 further comprises respective lengthwise end edges 13 by which the segments 11 are interconnected circumferentially. Accordingly, upper and lower edges 14 and 15 extend lengthwise perpendicular to axis 12 and end edges 13 represent widthwise extending edges aligned in the axial plane. When the frusto-conical ring is assembled around axis 12, widthwise extending edges 13 extend transverse to axis 12 so as to be declined according to the angle of the cone. Each segment 11 comprises a radially outward facing surface 24 and an opposite radially inward surface 25 with each surface 24, 25 defined by the perimeter edges 13, 14, 15. Each surface 24 and 25 is aligned transverse to axis 12 at the corresponding declined angle of the cone which mirrors that of the conical head centre.

According to the specific implementation, ring 10 is formed from eight separate segments 11 that are releasably coupled together around axis 12 via a set of articulation joints indicated generally by reference 18. Each joint 18 is formed, in part, by the lengthwise ends of each segment 11 (at the region of widthwise extending edges 13). Joints 18 enable each segment 11 to move radially relative to axis 12 such that ring 10 is configured to expand and contract relative to axis 12 with each joint 18 expanding or contracting in a circumferential direction.

According to further specific implementations, segments 11 may be interconnected so as to be formed integrally via webbing, ribs or other circumferentially extending members so as to provide a unified fully integral single body. In such implementations, such webbing, ribs or members would be flexible to provide the articulation joints 18 as described herein.

Referring to figures 2 and 3, ring 10 is conveniently mountable and demountable at head centre 20 (mounted at main shaft 19) by mating contact between ring inward facing surface 25 and a radially outward facing head centre mount surface 21. Ring 10 comprises a height in the axial direction being in the range 1/4 to 1/2 of an axial height of head centre 20. In particular, ring 10 is dimensioned so as to comprise a radius to seat ring 10 generally in the lower half of head centre 20 whilst leaving an exposed annular lower skirt 43 being a lowermost region of head centre 20. Ring 10 may be lowered and raised as a unitary body relative to head centre via a set of mounting tabs 16 provided at each respective segment 11, with each tab 16 comprising an eyelet 17 engagable by a chain or cable of an auxiliary lifting device. With ring 10 mounted in position at head centre 20, a mantle 22 is mounted in opposed relationship to head centre 20 so as to radially sandwich ring 10 in position (between head centre 20 and mantle 22). That is, with ring 10 mounted in position, a small gap 26 is provided and maintained between head centre 20 and mantle 22 at a region axially above ring 10. The frusto-conical shape profile of ring 10 provides uniform mating contact between the ring radially outward facing surface 24 and an inward facing surface 23 of mantle 22. As will be appreciated, mantle comprises a radially outward facing surface 36 that defines a part of the crushing zone in combination with an outer crushing shell (concave) not shown. According to the specific implementation, a radial thickness of each segment 11 is appreciably less than a radial thickness of mantle 22. In particular, a thickness of each segment 11 may be in a range 1 to 50%, 2 to 30% or 2 to 10% of a radial thickness of mantle 22.

Referring to figures 5 to 7, each segment 11 is connected at its lengthwise ends (in a circumferential direction) to two neighbouring segments 11 via two corresponding articulation joints 18. Each joint 18 according to the specific implementation is divided axially into an upper part 18a and a lower part 18b. Each part 18a, 18b comprises the same inter-engaging formations to releasably couple the segments 11 to form the frusto-conical ring 10. In particular, each part 18a, 18b comprises respective fingers 27 having barbed ends 28. The fingers 27 and barbs 28 are formed integrally with segment 11 and are positioned in a circumferential direction in-board of lengthwise end edges 13. That is, each segment 11 comprises a first lengthwise end edge 13a and an opposite lengthwise end edge 13b, with each end region having a respective upper and lower joint part 18a, 18b. Figures 27 are formed by a relatively thinner wall section of each segment 11 such that fingers 27 comprise a degree of flex in a radial direction. However, fingers 27 also comprise sufficient stiffness to achieve and maintain the interconnection between segments 11 in the circumferential direction. Each finger 27 is terminated at its end by a radially extending bard 28. Each joint 18 comprises an upper and lower opposed pair of fingers 27 and barbs 28 in opposed and overlapping position. That is, the fingers 27 of a first segment 11 extend radially over the corresponding fingers 27 of a second segment 11 such that the fingers 27 of the first and second segments 11 overlap in a circumferential direction with the fingers of the first segment 11 being respectively radially external relative to the fingers 27 of the second segment 11. The respective barbs 28 of the first and second segments overlap radially such that the first and second segments are inhibited from being circumferentially separated by abutment contact between the opposed bards 28.

The capability of ring 10 to compress and expand radially is provided by respective gap regions 29, 31 as illustrated in figures 5 to7. That is, with the barbs 28 of the neighbouring first and second segments 11a, 1 lb slightly spaced apart circumferentially by a small gap 31, a corresponding gap 29 is provided between the respective lengthwise end edges 13a, 13b and a corresponding shoulder 44 from which the fingers 27 extend circumferentially. Accordingly, joint parts 18a, 18b of the first segment 1 la are capable of sliding or passing over the corresponding and underlying parts 18a, 18b of the second segment 1 lb by a circumferential distance (or width) of the gap regions 29, 31. As illustrated, each joint part 18a, 18b is separated in the axial direction by a mid-section 30 that effectively is a continuation of the main body of each segment 11.

Referring to figures 8 and 9, segments 11 are maintained in axial position relative to one another via an upper region of each joint 18. In particular, finger 27 at joint upper part 18a is terminated at its uppermost end by a radially and circumferentially extending lip or shoulder 45 that is a continuation of the lengthwise extending upper edge 14. Accordingly, with the first and second segments 11a, 1 lb mounted in side-by-side relationship as shown in figures 5 to 7, shoulder 45 is dimensioned to sit axially immediately above an uppermost lengthwise end edge 46 of finger 27 of the second segment 1 lb. Accordingly, the segments 11a, 1 lb are coupled axially and prevented from independent axial movement relative to one another via axial abutment contact between shoulder 45 and end edge 46.

Referring to figure 10, the main body of each segment 11 may be considered to comprise ribs 32a, 32b provided respectively at the regions of the radially outward facing surface 24 and inward facing surface 25. Each rib 32a, 32b extends in a lengthwise direction of each segment 11 (corresponding to the circumferential direction around axis 12). The ribs 32a, 32b are separated axially and, in part, defined by, respective lengthwise extending grooves 33a, 33b. Grooves 33a, 33b extend only a partial radial distance into the wall of segment 11 and in particular extend less than half of the radial thickness. The axial position of the radially outward and radially inward facing ribs 32a, 32b are 'staggered ^' ' by a distance of each respective groove 33a, 33b. That is, each inward facing groove 33b is positioned immediately behind (and at the same axial position as) each radially outward facing rib 32a whilst an outward facing groove 33a is positioned at the same axial position as an inward facing rib 32b. Accordingly, a cross sectional profile of each segment 11 in an axial plane comprises a generally corrugated shape profile as illustrated in figure 11.

Referring to figures 12 and 13, ring 10, as an assembly is maintained in axial position between mantle 22 and head centre 20 by an annular shoulder or lip 38 that projects radially inward at the radially inward facing side of mantle 22. According to the specific implementation, shoulder 38 extends continuously around axis 12 at mantle inward facing surface 23. Shoulder 38 is formed as a relatively short projection extending radially from the mantle wall 39 so as to present a generally downward facing annular abutment face 40. Face 40 is configured to abut against each upper lengthwise extending segment edge 14. Accordingly, as mantle 22 is pressed axially downward in use, ring 11 is coupled to mantle 22 and is, in turn, forced axially downward with mantle 22 by engaging contacts between face 40 and edge 14. Shoulder 38 does not project radially inward to an extent that would otherwise bridge the gap 26 between the opposed mantle surface 23 and head centre surface 21. As such, a radial length of shoulder 38 is in a range 1 to 10% of a radial thickness of mantle wall 39. Shoulder 38 is positioned approximately at a mid-axial height location at mantle 22. That is, shoulder 38 is positioned approximately equidistant in the axial direction from a mantle lower annular edge 35 and an upper annular edge 34. Accordingly, shoulder 38 is positioned axially lower than mounting bores 37 that are configured to receive locking pins (not shown) that rotationally couple mantle 22 to head centre 20.

Mantle 22 may be considered to comprise an annular foot 50 extending axially upward from lower annular edge 35. Foot 50 comprises a radially inward facing contact surface 52 configured to abut head centre mount surface 21 at an axially lower region so as to positionally support mantle 22 at head centre 20. Additionally, mantle 22 comprises a neck region 51 positioned at upper annular edge 34. Neck 51 is similarly configured to positionally mount mantle 22 at head centre 20. According to the implementations described herein, shoulder 38 is positioned at a mid-axial region between foot 50 and neck 51. Importantly, shoulder 38 is recessed relative to an imaginary cone defined partially by foot contact surface 52 that is aligned transverse to axis 12. According to the specific implementation, the imaginary cone comprises a conical surface that is declined relative to axis 12 by angle in a range 25 to 35° and more preferably 30°. Such an arrangement avoids contact between shoulder 38 and head centre surface 21. Accordingly, a region 53 defined axially between shoulder 38 and an upper end of foot contact surface 52 is recessed radially relative to shoulder 38 and contact surface 52 so as to at least partially house support ring 10 radially intermediate mantle 22 and head centre 20. Accordingly, a radial thickness of shoulder 38 is less than a radial thickness of each support ring segment 11 mounted at region 53.

A further embodiment of mantle 22 is illustrated in figure 14. According to the further embodiment, shoulder 38 is discontinuous in the circumferential direction around axis 12 and is formed as shoulder sections 41 that are interrupted circumferentially by pockets or recesses 42. The segmented shoulder 38 also comprises the generally downward facing abutment face 40 as described referring to figures 12 and 13. However, face 40 is similarly discontinuous around axis 12 to provide discrete regions of contact against the upper edge 14 of at least some of the segments 11 (or all segments 11). The features of the shoulder 38 relating to its position and radial size (for example relative to foot 50 and neck 51) as described with reference to figures 12 and 13 apply equally to the further embodiment of figure 14.