The present invention relates to continuous extrusion apparatus in which feedstock is continuously extruded using a rotary wheel. The process of continuous extrusion of metals using a rotary wheel is disclosed in UK Patent No. 1370894 and machines using this process are sold to this day under the trade mark CONFORM™. In the CONFORM™ process a wheel has at least one peripheral groove for receipt of solid or particulate feedstock and is rotated past a stationary shoe towards an extrusion die. The shoe effectively closes a length of the groove and is located to make contact with the feedstock in the groove so as to provide an extrusion chamber. The walls of the peripheral groove provide an area of contact with the feedstock that is greater than that of the shoe so that there is greater friction between the feedstock and the wheel compared to that between the feedstock and the shoe. Thus rotation of the wheel advances the material in the groove relative to the shoe. Immediately adjacent to the shoe there is an abutment that is fixed relative to the wheel and which serves to block the groove thus impeding the passage of the feedstock in the groove. Rotation of the wheel thus drives the feedstock against the abutment, creating significant pressure. The compressive loads developed are so great that the material yields and enters the plastic phase whereupon it flows out through an orifice of the extrusion die that is located adjacent to the abutment, the material thus being extruded in continuous form.

The wheel is mounted on an elongate shaft that is supported for rotation at each end by bearings that incorporate multiple seals for retaining oil and preventing ingress of dirt etc. The wheel is clamped between a pair of discs on the shaft by means of a hydraulic nut (such as, for example, a Pilgrim nut) that is screwed on to one end of the shaft and pressurised to provide the high clamping force required to prevent relative rotation of the wheel and the shaft during the extrusion process. Machines of this kind have to withstand high forces in a relatively confined space. There are significant radial loads applied to the shaft during extrusion such that it undergoes bending and the clamping discs tend to separate from the wheel below the rotational axis of the shaft but are compressed against the wheel above the rotational axis. This causes significant stress and wear on the clamping discs and the wheel. For large machines there may be up to 500kNm of torque and a radial force of over 400 tons.

Moreover, during the extrusion process high temperatures are generated by virtue of the friction and deformation of the material in the wheel, grooves, against the shoe, at the abutment and in the die. During continuous extrusion, these temperatures can be of the order of 400-500° C if no cooling is provided, particularly at high reduction ratios. Internal cooling passages in the machine carry cooling water towards the wheel, die and abutment but the high mechanical loads that the machine components have to bear means that such passages have to be small in order not to reduce the strength or mechanical integrity of components. This results in small volumetric flow rates therefore relatively low rates of heat dissipation. Moreover, the passages are prone to blockage, which prevents cooling and leads to an increased failure rate in moving components.

The extrusion process causes significant wear on the shoe, the die, the abutment and the wheel. The machine components thus have to be serviced, repaired or replaced relatively frequently (perhaps as much as 50 times a year for apparatus that is continuously operated). Moreover, the extrusion area has to be cleaned regularly.

The arrangement of such machines is such that the wheel is difficult to access for replacement, repair, cleaning or servicing etc. The hydraulic pressure of the clamping nut first has to be released so that the shaft may be withdrawn from the wheel, the clamping discs and the bearings. This process risks dirt passing seals into the bearings and contaminating lubricant. Moreover, disassembly of this kind renders the bearing seals prone to wear or damage. The wheel is then typically hammered out from between the clamping discs, risking further damage, before it is repaired or replaced.

After dismantling the machine in this manner there follows a time-intensive process of reassembly, applying the hydraulic nut clamp and then ensuring the shoe is positioned accurately relative to the wheel. Given that the wheel is clamped between the discs and further obscured by bearings and other supports, visible inspection is not easy. It is thus necessary to follow a laborious process of trial and error to ensure the relative positions of the wheel and shoe are correct, taking into account the thermal expansion of the machine components that occurs during use. More specifically, the shoe is typically positioned relative to the wheel with some sort of marker (e.g. strips of solder wire) disposed between them and the wheel is rotated for a short time period. The shoe is then moved out of the way so as to enable a visual inspection of the compressed marker and a judgement made about whether the positioning of the shoe was correct. Fine adjustment to the shoe position is then made by insertion of appropriate shims.

Application of the correct clamping force using the hydraulic nut is not a straightforward process. A pump is used to apply a predetermined pressure, which has the effect of drawing the shaft along its axis so as to clamp the wheel between the discs. Shims are then inserted so as to take up the slack and the pressure removed so that the shaft relaxes against the shims. Such an operation cannot be performed with great precision and is prone to error. If the clamping force is not large enough the wheel may slip relative to the shaft during the extrusion operation or it may be insufficiently supported such that it may split. If too large a clamping force is applied the shaft may be fractured or unduly strained. The process can only be performed reliably by skilled and experienced users of the machine.

Any excess metal that leaks from the groove of the wheel is scraped off and discarded. This waste material known as "flash" is very hot and must be gathered, baled and compacted for recycling.

It is one object of the present invention to obviate or mitigate the aforesaid disadvantages. It is also an object of the present invention to provide for improved or alternative continuous extrusion apparatus.

According to the present invention there is provided continuous extrusion apparatus comprising: a shaft supported for rotation in a bearing, the shaft having first and second ends; a rotary wheel fixed to the first end of the shaft so as to rotate therewith about a rotary axis, the wheel having at least one peripheral groove; a shoe extending around at least part of the wheel and co-operating with the at least one peripheral groove so as to define a passageway between the wheel and the shoe, the passageway having an inlet for receipt of material to be extruded, the wheel being rotatable relative to the shoe; an abutment member blocking the passageway so as to obstruct the passage of material; an extrusion die disposed for receipt of material from the passageway; a mounting arrangement disposed between the wheel and shaft, the arrangement comprising a mounting member having a first inner tapered surface in abutment with a second inner tapered surface defined by the shaft or a component of the mounting arrangement intermediate the shaft and the wheel; the wheel having a first outer tapered surface in abutment with a second outer tapered surface defined by the shaft or a component of the mounting arrangement that is fixed to the shaft.

The first and second inner tapered surfaces combine to ensure that an axial force applied to the mounting member, such as that provided by clamping, may be translated into a substantially radially outward directed force to support the extrusion wheel and react against oppositely directed radial forces imparted to the wheel during the extrusion process. The inner and outer tapered surfaces may also assist in ensuring accurate axial location of the wheel and facilitate separation of the wheel from the shaft when required. The outer tapered surfaces abut to afford frictional resistance to resist relative rotation of the wheel and shaft during the extrusion process.

The mounting arrangement of the wheel and the location of the wheel at the first end of the shaft means that the shaft deflects less than conventional arrangements. The mounting arrangement provides better strength and stiffness compared to existing designs. The reduced deflection ensures that the wheel runs co-axially with greater accuracy. This reduces the amount of fretting in the wheel and hence reduces maintenance and machining (or otherwise reworking) the wheel to remove the fretted surface.

The inner and outer tapered surfaces are disposed around the rotary axis and may be fully or partly annular. That is, the first and second inner tapered surfaces may each be defined on part of a surface of a frustocone. Similarly, the first and second outer tapered surfaces may each be defined on part of a surface of a frustocone. The surfaces may be defined by a discontinuous annular surface. The first and second outer tapered surfaces may extend outwards from the rotary axis and the first and second inner tapered surfaces may extend inwards towards the rotary axis, in the direction from the first to the second end of the shaft.

The first and second outer tapered surfaces may extend in the opposite direction to the first and second inner tapered surfaces. The two sets of tapered surfaces are preferably inclined such that they provide a non-locking taper between the respective components, that is the respective components can be disassembled easily by axial separation of the abutting tapered surfaces. The non-locking taper may be provided by the frustocone being inclined at an angle of 7-25° to the rotary axis and more preferably between 14 and 18°. Ideally the angle is 16°.

The first and second outer tapered surfaces may be inclined at an angle of substantially 74° to a plane that is perpendicular to the rotary axis. That is equivalent to the frustocone that the surfaces at least partly define being inclined to the rotary axis at an angle of substantially 16°. The first and second inner tapered surfaces are similarly inclined at an angle of substantially 74° to such a plane but since they extend in the opposite direction to the first and second outer tapered surfaces the angle may be expressed as substantially 106° to said plane. The mounting member is preferably in the form of a collet that is disposed substantially coaxially with the shaft and wheel. The collet preferably defines a wedge shaped cross- section and is preferably annular.

The collet may have an external surface of substantially constant diameter and an internal surface that defines said first inner tapered surface. The external surface may abut directly or indirectly against an internal surface defined by a bore in or through the wheel. The internal surface of the collet may have a portion that defines a constant diameter. This portion may be supported on a constant diameter portion of a stub shaft of the hub. The stub shaft may comprise the frustoconical portion and the constant diameter portion.

The relative movement of the abutting first and second inner tapered surfaces in the axial direction may urge the collet radially outwards. The collet is preferably radially resilient. In one embodiment the collet is penetrated by a plurality of slots that extend in a substantially axial direction from at least one end of the collet and serve to provide the radial resilience in the collet. The slots may comprise a first group of slots and a second group of slots, the first group of slots being angularly spaced relative to one another and extending in a substantially axial direction from a first end of the collet and the second group of slots being angularly spaced relative to one another and extending in a substantially axial direction from a second end of the collet, the first group of slots being angularly offset from the second group of slots. The mounting arrangement may further comprise a hub fixed to the shaft. The hub may be a discrete component or may be defined by the shaft such that it is integrally formed therewith (by for example machining the shaft). It may be releasably fixed by means of any suitable fixing means including fasteners such as bolts etc. or by any suitable coupling. Alternatively it may be fixed by a more permanent fixing method such as welding or the like.

The hub may define the second outer tapered surface. In one example the second outer tapered surface is defined by a projection on the hub. The projection may be annular or at least partly annular.

The second inner tapered surface may be defined by the hub. The second inner tapered surface may be substantially or partly annular (e.g. a discontinuous annulus). The second inner tapered surfaced may be defined by a frustoconical portion of the hub.

The second outer tapered surface and the second inner tapered surface may be defined by an annular recess a radial surface of the hub.

The mounting arrangement may further comprise a clamping ring for clamping the wheel to hub. The clamping ring and the wheel may be supported on a plurality of fixing members such as, for example, studs. The fixing members may pass through bores in the wheel. The fixing members may have a first end for fixing to shaft or hub and a second end for fixing to a clamping nut that bears against the clamping ring. The first end of the fixing members may be threaded for screw engagement in a threaded bore in the hub or shaft.

The hub, collet and wheel are preferably coaxially disposed for rotation with the shaft about the rotary axis. There may be at least one drive coupling between the hub and the wheel, such as for example, a protrusion on one of the hub and wheel for receipt in a recess in the other of the hub and wheel. In one embodiment this is a key and keyway coupling. The keyway may be defined in the wheel and the key defined by the hub, preferably on a radial face thereof. There may be more than one such key and keyway coupling.

The mounting arrangement may further comprise a clamping nut for clamping the mounting member in an axial direction. At least a portion of the mounting assembly may be disposed within the bearing. In one embodiment the bearing is supported on an external surface of the hub.

There may be provided a lubricant seal for the bearing. The seal may be disposed around the mounting assembly.

The bearing may be supported in a supporting member such as a wall. The bearing may be supported between the second end of the shaft and the wheel. The wheel may be disposed on one side of the wall and a bearing lubrication reservoir may be disposed on the other side of the wall. This provides axial separation of the lubricant from the wheel such that the wheel can be removed from the shaft (for repair, servicing or replacement etc.) without disturbing the lubrication, the bearing or the seal.

The bearing may be disposed at a distance from the rotary axis that is greater than the distance of the wheel from the rotary axis.

A second end of the shaft is preferably connected to a drive. This is preferably on the opposite side of the wall to the wheel.

A cooling chamber may be provided between the shaft and the mounting arrangement. This may be defined by a cavity defined in the shaft or the hub. The shaft may have an internal bore in fluid communication with the cooling chamber. There may be provided a fluid carrying conduit disposed in the internal bore for carrying cooling fluid. The conduit is preferably of smaller diameter than the bore so as to define an annular clearance between the external surface of the conduit and the shaft. In use the annular clearance may provide a return path for the cooling fluid. A fluid dispersing member such as, for example, a disc may be provide in the chamber for rotation with the shaft. There may be an axial clearance between the fluid dispersing member and an end surface of the chamber. The fluid carrying conduit may have an outlet end that is disposed so as to deliver fluid into the axial clearance.

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

Figure 1 is a perspective view from one end of continuous extrusion apparatus in accordance with the present invention;

Figure 2 is a second perspective view of the apparatus from the opposite end to that of figure 1 ;

Figure 3 is an end view of the apparatus of figures 1 and 2, showing a head assembly

Figure 4 is a cross-section through the head assembly of the apparatus of figures 1 to 3, taken along line A-A of figure 3;

Figure 5 is an exploded perspective view of part of the head assembly of figure

4;

Figure 6 is a sectioned view of a shoe and die assembly of the apparatus of figures 1 to 5;

Figure 7 is a sectioned view of the of the extrusion wheel of the apparatus of figures 1 to 5, the plane of the section being substantially radial and along line c-c of fig. 8;

Figure 8 is a rear end view of the wheel of figure 7;

Figure 9 is a sectioned view of a hub of the head assembly of figures 4 and 5, the sectioned being taken along a radial plane;

Figure 10 is an end view of the hub in the direction of arrow X of figure 9; and Figure 1 1 is a sectioned view of a collet of the head assembly of figures 4 and

5, the section being taken through a radial plane.

Referring now to figures 1 to 3 of the drawings, the exemplary extrusion apparatus comprises a head assembly 10 having an extrusion wheel 1 1 mounted on an exposed end of a rotary shaft assembly 12 for rotation therewith. The shaft assembly 12 is driven in rotation by a drive assembly 13 that comprises a motor 14 and a belt transmission 15 that drives a pulley 16 connected to the shaft assembly 12 via a reduction gearbox 17. The shaft assembly is supported for rotation by a bearing (hidden in figures 1 to 3) that is located in housing 18.

The wheel 1 1 has a pair of grooves 19 defined on its outer periphery for receipt of feedstock (not shown) that is delivered via a tangential feeder 20 (visible in figures 2 and 3 only). Immediately above the wheel is a coining roller 21 (visible in figures 2, 3 and 4) by which feedstock from the feeder 20 is urged into the grooves 19. Downstream of the coining roller 21 , the periphery of the wheel 1 1 is covered by a shoe 22 so as to define an extrusion passageway with the grooves 19. For the purposes of clarity the shoe 22 is not shown in figures 1 to 3, but is shown in detail in figure 6. However, an adjustable support 23 for positioning the shoe 22 relative to the wheel 1 1 is shown in figures 2 and 3. The support 23 comprises is substantially L-shaped with a horizontal platform 24, a vertical wall 25 and two adjustable wedges 26, 27. The horizontal platform 24 and vertical wall 25 are adjustable by moving the wedges 26, 27, one wedge being provided for horizontal adjustment of the wall 25 and the other being provided for vertical adjustment of the platform 24. A rotary handwheel 28, 29 is connected to a respective wedge 26, 27 by an appropriate drive transmission (e.g. a gearbox and a worm and screw drive) for effecting movement of the wedge and therefore adjustment of the shoe position.

The walls of each peripheral groove 19 in the extrusion wheel 1 1 provide an area of contact with the feedstock that is greater than that of the shoe so that there is greater friction between the feedstock and the wheel compared to that between the feedstock and the shoe. Thus rotation of the extrusion wheel 1 1 advances the material in the grooves 19 relative to the shoe. Immediately adjacent to the shoe 22 there is an abutment 30 (see figure 6) that is fixed relative to the wheel 1 1 and which serves to block the grooves 19 thus impeding the passage of the feedstock in the grooves 19. Rotation of the wheel 1 1 thus drives the feedstock against the abutment 30, creating significant pressure. The compressive loads developed are so great that the material yields and enters the plastic phase whereupon it flows out through an orifice of an extrusion die 31 (see figure 6) that is located adjacent to the abutment 30, the material thus being extruded in continuous form. In this particular embodiment where there are two peripheral grooves 19, two parallel extrusion dies 31 are provided (only one is shown in figure 6). It will be appreciated that in an alternative embodiment only one groove and die may be provided. It is also to be understood that the invention may be applicable to embodiments in which there are more than two peripheral grooves in the wheel.

At the downstream exit of the shoe 22 there is a scraper blade 35 immediately adjacent to the wheel 1 1 for removing flash from the wheel periphery. The removed flash drops on to a chute 36 from where it is delivered to a suitable receptacle or area for collection.

Referring now to figure 4, the head assembly 10 is shown separate from the other components of the apparatus. The rotary shaft assembly 12 comprises a main shaft 37 with a front half that is supported for rotation in a bearing 38 fixed in a front plate 39 of the housing 18, the front half terminating in a mounting assembly 40 by which the wheel 1 1 is fixed to the shaft 37. A rear half of the shaft extends rearwards of the housing 18 and is supported for rotation in the gearbox 17 (not shown in figure 4). The main shaft 37 is penetrated by an internal cooling system that will be described below.

At a location adjacent to the front plate 39 and bearing 38 the external surface of the main shaft 37 has a radially outward extending flange 41 to which the mounting assembly 40 is bolted by a plurality of angularly spaced bolts 41 a. The mounting assembly comprises a hub 42, which is coaxially disposed with the main shaft 37, and shown in more detail in figures 5, 9 and 10, a collet 43 disposed between the hub 42 and the wheel 1 1 , a clamping ring 44, studs 45, nuts 46, clamping nut 47 and washer 48. The hub 42, which is shown in detail in figures 9 and 10, comprises a radially extending front wall 50 from which extends, in the rearwards direction (i.e. towards the shaft), an annular collar 51 whose outer diameter is substantially equal to that of the flange 41 . The collar 51 defines a cylindrical cavity 52 and has an end face with threaded bores 53 for receipt of the bolts 41 a. The front end of the main shaft 37 is received in the cavity 52 and has an external diameter that is slightly smaller than the internal diameter of the collar 51 such that the hub 42 is supported by the shaft 37 for a short axial length. Extending in the opposite direction from the front wall 50 is a stub shaft 54 for supporting the wheel 1 1 . The stub shaft 54 has a frustoconical portion 55, nearest to the front wall 50, and terminates in a substantially cylindrical portion 56 that bears an external thread. The main shaft 37 is supported for rotation by the bearing 38, which is concentrically disposed with the hub 42 such that its inner surface is supported on the outer surface of the hub collar 51 . The bearing 38, which runs in an oil sump 49, has an annular oil seal housing 57 that extends radially inwards from the front plate 39 of the housing 12, over the front end of the bearing 38. The oil seal housing 57 supports a single lip seal 58 that prevents egression of lubricant from the bearing 38 and ingression of dirt or other contaminants into the bearing 38. The front wall 50 of the hub 42 has an annular projection 60 defined towards its outer periphery, radially outboard of the frustoconical portion 55 of the stub shaft 54. The projection 60 has an inwardly facing surface 61 that is tapered. The inwardly facing surface 61 of the annular projection 60 and the opposed section of the frustoconical portion 55 of the stub shaft 54 effectively define between them an annular recess 62 with inner and outer tapered side walls 61 , 63. In the embodiment shown, the tapered surfaces 61 , 63 are inclined relative to the rotation axis by the same amount, one being inclined at a positive angle and the other at a negative angle. It will be seen from figure 4 that the annular projection 60 that defines the outer tapered surface of the recess 62 is significantly shorter than the frustoconical portion 55 of the stub shaft 54 so that the inner tapered surface 63 continues beyond the extent of the recess 62.

The annular recess 62 is designed to receive a rear end of the extrusion wheel 1 1 , as is shown in figure 4. The front wall 50 of the hub 42 has a pair of keys 64 that project into the annular recess 62 and extend in a substantially radial direction. A corresponding pair of radial keyways 65 (see figures 7 and 8) is defined in a rear face of the extrusion wheel 1 1 for receipt of the keys 64. The key connection prevents relative rotation of the wheel 1 1 and the hub 42.

The extrusion wheel 1 1 , which is shown in detail in figures 5, 7 and 8, has a central bore 66 for receipt of the stub shaft 54 and is penetrated by a plurality of axially extending small fixing bores 67. Besides the two grooves 19, the outer periphery has a short taper 68 defined towards the rear end. This taper 68 is complementary to the outer tapered surface 61 defined by the annular projection 60 on the outside of the annular recess 62 in the hub 42 such that when the two are connected together the tapers 61 , 68 come into abutment and serve to locate the wheel 1 1 in the axial direction so that it is aligned with the coining roller 21 and the shoe 22.

The extrusion wheel 1 1 is supported on the stub shaft 54 by means of the collet 43, which is shown in detail in figures 5 and 1 1 . The collet 43 has a cylindrical outer surface 69 and an interior bore 70 the majority of which is tapered such that the wall of the collet is relatively thin at rear end and is relatively thick at a front end. The bore 70 has a short constant diameter portion at the front end. The wall of the collet is axially slotted to allow it to expand and contract under pressure. A first set of angularly spaced slots 71 extend from the rear end towards the front end but fall short of the front end by an axial distance that is similar to that of the constant diameter portion of the bore 70. Similarly, a second set of angularly spaced axial slots 72 , angularly offset from the first set 71 , extend from the rear end toward the front end but fall short thereof. When assembled into the mounting assembly 40, the collet 43 is received in the wheel bore 66 so as to provide radial support between the stub shaft 54 and the extrusion wheel 1 1 . The constant diameter outer surface 69 bears against the internal surface of the extrusion wheel 1 1 and a tapered internal surface 73 defined by the tapered portion of the bore 70 bears against the frustoconical tapered surface 63 of the stub shaft 54, the tapered surfaces 63, 73 being complementary.

The extrusion wheel 1 1 is clamped to the hub 42 by means of the annular clamping ring 44 and studs 45 that pass through the small fixing bores 67 in the extrusion wheel 1 1 . Each end of each the studs 45 is threaded, a first end being screwed into a respective threaded bore 74 in the front wall 50 of the hub 42 and the other end being screw connected to a respective nut 46 that is tightened against the clamping ring 44 to clamp the wheel 1 1 against the hub 42. A separate clamping nut 47 and washer 48 are provided for clamping the collet 42 in place, the nut 47 being screwed on to the thread defined on the cylindrical portion 56 of the stub shaft 54.

In order to assemble the extrusion wheel 1 1 to the main shaft 37, the studs 45 are first screwed into the threaded bores 74 in the hub 42. The wheel 1 1 is then offered up to the studs 45 so that they are aligned with the fixing bores 67 in the wheel 1 1 , whereupon the wheel 1 1 is slid axially towards the hub 42 so that its rear end is received in the annular recess 62. In particular the wheel 1 1 is positioned in the axial direction such that the tapered surface 68 on the outer periphery of the wheel 1 1 moves towards the complementary tapered surface 61 of the outer side wall of the annular recess 62. In addition, the keys 64 of the hub 42 are received in the keyways 65 of the wheel so as to provide a positive rotational drive. The collet 42 is then inserted into the radial clearance between the stub shaft 54 and the extrusion wheel 1 1 such that the tapered inside surface 73 bears against the tapered surface 63 of the frustoconical section 55. The collet 42 is held in place by tightening the clamping nut 47 on to the threaded end 56 of the stub shaft 54 to a predetermined torque. This holds the wheel concentric with the hub. The clamping ring 44 is then located over the studs 45 and secured in place by tightening the nuts 46 so as to secure the axial location of the extrusion wheel 1 1 . The nuts 46 are tightened to pull the wheel 1 1 on to the hub 42 so that the tapered surfaces 61 and 68 bear against one another. The clamping nut 47 is tightened against the radial face of the front end of the collet 42 and effectively pushes the collet up the frustoconical portion 55 thereby forcing the collet 42 to expand radially outwards, such radial expansion being permitted by the slots 71 , 72. This movement forces the outer surface 69 of the collet 42 against the inner surface of the wheel 1 1 thus providing radial support and ensuring the wheel is located centrally with respect to the rotational axis of the shaft assembly 12. At the same time the tapered surface 68 on the outer periphery of the wheel 1 1 bears against the complementary tapered surface 61 of the annular projection 60 with greater force. The wheel 1 1 is thus locked at its inner and outer surfaces.

As the mounting assembly 40 including the hub 42, extrusion wheel 1 1 , collet 42, clamping ring 44 and clamping nut 47, is fixed to the main shaft 37 it rotates with the main shaft 37 as it is driven in rotation by the motor 14, belt 15, pulley 16 and gearbox 17. The extrusion process generates significant radial inward directed and twisting forces. The radial force is reacted by the radial outward force applied by the collet 42 to the extrusion wheel 1 1 as a result of the application of an axial clamping force at by the clamping ring 44 and nut 47. The twisting force applied to the wheel 1 1 is reacted by means of the interference at the interface between the outer tapered surfaces 61 , 68 and the key connection 64, 65 between the wheel 1 1 and hub 42.

As will be apparent from an inspection of figure 4, the coining roller 21 is located such that its outer periphery is immediately adjacent to the outer periphery of the extrusion wheel 1 1 so that the feedstock is urged into the peripheral grooves in the wheel. The coining roller 21 is arranged for rotation with a rotary shaft 80 about an axis that is substantially parallel to the axis of rotation of the shaft assembly 12 and extrusion wheel 1 1 . Referring back to figure 4, the main shaft 37 has an internal bore 81 along its length for receipt of a lance 82 that forms part of an internal cooling system for the shaft assembly 12 and head assembly 10. At the rear end of the main shaft 37 the lance 82 is connected to a fixed manifold 83 by means of a rotational coupling 84. The manifold 83 has a first port 85 for delivering water into the lance 82 and a second port 86 for allowing water to exit the cooling system. The opposite end of the lance 82 passes through the cavity 52 in the hub 42 and terminates in a short blind bore 87 provided in the front wall 50. In the cavity 52 there is provided a water distribution member 88 comprising a sleeve 89 fixed to the lance 82 and a thin disc 90 that extends radially outwards direction from the sleeve 89. The disc 90 is axially spaced from the rear face of the front wall 50 of the hub 42 to provide a short axial clearance 91 and the sleeve 89 is penetrated by passages 92 that extend axially in parallel with the axis of rotation and then radially so that the open into the cavity 52. The water-cooling components are shown with the shaft assembly in figure 5. The lance 82 is fixed relative to the main shaft 37 so that it rotates therewith and relative to the manifold 83 by virtue of the rotational coupling 84. The lance 82 has a smaller diameter than the bore 81 so as to afford a small annular clearance with the shaft 37. In operation, cooling water enters the first port 85 in the manifold 83 and passes along the lance 82 to the hub 42 where it emerges in the short blind bore 87. As a result of rotation of the shaft 37 the water is propelled under centrifugal force along the surface of the disc 90 in the axial clearance 91 . From there it emerges to fill the cavity 52 and is forced under pressure into the radial portions of the passages 92 defined in the sleeve 89. The water passes into the axial portion of the passages 92 and then into the annular clearance around the outside of the lance 82. After travelling along the bore 81 it reaches the manifold 83 where it egresses through the second port 86.

Referring now to figure 6, an exemplary embodiment of a shoe and die assembly 100 is shown in which shoe pressure plates 101 are supported around the wheel 1 1 (the outer periphery of which is represented in dotted line. An abutment member 30 is designed to extend into each peripheral groove 19 on the wheel 1 1 and has a shape that is complementary to each groove 19 so as to block the groove but without preventing rotation of the wheel. Immediately above each abutment member 30 there is an outlet aperture 102 defined by a die entry plate 103. Material that is prevented by the abutment member 30 from continuing rotation in each groove 19 is compressed between the wheel and the shoe 22 such that it is transformed into the plastic phase, whereupon it is able to flow out of the outlet aperture 102 to an extrusion die 31 . The outlet aperture 102 of the entry plate 103 is disposed immediately adjacent to the abutment member 30 and directs the material away from the wheel 1 1 in a substantially radial direction. The die 31 is defined in a plate that is supported in a surrounding body 104 and is located at the desired position by multiple packing or spacer plates 105.

As the extrusion wheel 1 1 rotates the feedstock is forced into the peripheral grooves 19 of the wheel by the coining roller 21 and is then compressed between the pressure plates 101 of the shoe 22 and the surface of the grooves 19. The greater surface area provided by the surface of the wheel that defines the grooves 19 affords greater friction than that of the pressure plates 101 and therefore the material is dragged by the wheel 1 1 relative to the shoe 22 until it encounters the abutment 30. It will be appreciated that the extrusion process generates significant forces and heat, which the shoe body 104 and the head assembly 10 are designed to withstand.

The tapered surfaces 61 , 63, 68, 73 between the wheel 1 1 and mounting assembly 40 are designed such that the tendency of the wheel to jam on the hub 42 is reduced or eliminated. A non-locking taper of +/-16 ⁰ (relative to the axis of rotation) is ideal but other angles may be suitable. As can be seen in figure 9 the outer tapered surface 61 of the hub 42 subtends an angle of 16° to the rotary axis and the frustocone portion that defines inner tapered surface 63 subtends an angle of 64° to the rotary axis (equivalent to 16° in the opposite direction).

Similarly in figure 7 the outer tapered surface 68 defined on the outer periphery of the wheel 1 1 is represented as 16°. In figure 1 1 the tapered internal surface 73 of the collet 43 is shown having an internal angle of 32°, which is equivalent to an angle of 16° to the rotary axis. The provision of an extrusion wheel that is mounted at the end of a cantilevered shaft affords many benefits. The inner and outer tapered engagement surfaces 61 , 63, 68, 73 between the wheel 1 1 and the mounting assembly 40 ensures that the forces generated during the extrusion process can be withstood without damage to the wheel 1 1 or shaft 37.

In particular the provision of a shaft that is supported to one side of the wheel in a bearing 38 in the rigid support provided by the front plate 39 allows the wheel to be disposed at one end of the shaft where it is relative accessible for repair, service, replacement or cleaning etc. Moreover, the cantilevered arrangement ensures that the shaft is not subjected to significant bending as compared to the prior art arrangement.

The key and keyway coupling 64, 65 between the hub 42 and the wheel 1 1 provide a positive drive coupling that prevents relative rotation of the wheel 1 1 and shaft 37.

The provision of a collet 42 with a tapered engagement interface 63, 73 with the mounting assembly 40 on the shaft assembly 12 ensures that the radial forces applied to the wheel during extrusion can be reacted. The outer tapered interface 61 , 68 between the wheel 1 1 and the hub 42 of the mounting assembly 40 provides additional resistance to rotational movement of the wheel 1 1 relative to the shaft 37 and the inner and outer tapered interfaces 61 , 63, 68, 73 allow precise axial location of the wheel 1 1 relative to the shaft 37.

The location of the wheel 1 1 at one end of the shaft 37 ensures that the bearing 38 and associated seal 58 are not disturbed when accessing the wheel for replacement, repair, cleaning etc. The bearing 38 is located behind the wheel 1 1 such that it can run in oil sump 39 in the housing 18 and is therefore not prone to overheating.

The accessibility and visibility of the extrusion wheel 1 1 means that adjustment of the shoe 22 is considerably less laborious and time-consuming. The shoe location is adjusted simply by rotation of the handwheels 28, 29 to move the adjustment wedge 26. The fact that the machine is easier to set up with great precision means that there is an increased likelihood of reducing the volume of flash created during the extrusion process. The location of the wheel at the end of the shaft allows a cooling fluid to be delivered along the shaft to the wheel end. Such a cooling arrangement is not disturbed when removing or servicing the wheel.

It is to be understood that the apparatus of the present invention may be used for any extrudable material. It is particularly suitable for extrusion of copper or aluminium but may be used with any non-ferrous or even ferrous material that is capable of extrusion. It may also be used to extrude plastics materials. In one embodiment the apparatus may be used to co-extrude a coating or sleeve of one material over an extruded core of another material. The sleeve or coating may, for example, be disposed in insulating or heat-resistant plastics-based material and the core may be a material suitable for an electrical conductor.

It will also be appreciated that radial or tangential extrusion dies may be used in the shoe.

It will be appreciated that numerous modifications to the above described design may be made without departing from the scope of the invention as defined in the appended claims. For example, the hub may be defined by machining the shaft such that it is integrally formed with the shaft. Alternatively, it may be a discrete component that is fixed permanently to the shaft by means of, for example, welding.

The described and illustrated embodiments are to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the scope of the inventions as defined in the claims are desired to be protected. It should be understood that while the use of words such as "preferable", "preferably", "preferred" or "more preferred" in the description suggest that a feature so described may be desirable, it may nevertheless not be necessary and embodiments lacking such a feature may be contemplated as within the scope of the invention as defined in the appended claims. In relation to the claims, it is intended that when words such as "a," "an," "at least one," or "at least one portion" are used to preface a feature there is no intention to limit the claim to only one such feature unless specifically stated to the contrary in the claim. When the language "at least a portion" and/or "a portion" is used the item can include a portion and/or the entire item unless specifically stated to the contrary.