Apparatus and methods for the continuous forming of material by extrusion are disclosed in GB Patents 1370894,1434201,1566152, 1590776,2028207,2103527 and 2176728. Such apparatus typically consists of a rotatable wheel constituting a moving member and defining an endless groove around the wheel for the material, with a stationary abutment projecting into the groove partially blocking the groove with a die orifice in it. A rod feed stick, moved by frictional drag between the feed stick and the groove, is forced through the die orifice. The shear action generates sufficient pressure and temperature to extrude the material through the die. This method is generally referred to as the conform method.

The conform method can be used for extruding complex sections and can also be used for cladding, especially for exotic and temperature sensitive materials.

However the use of high pressure results in wear of the wheel and, as the friction generates the heat required, there is wear of the die especially at the start of the method before the material has warmed up to the operating temperature, in addition the faster the wheel turns the more heat is generated and so cooling can be required.

We have now devised a continuous extrusion system which reduces these problems.

According to the invention there is provided apparatus for continuous forming of material by extrusion, which apparatus comprises two spaced apart rotatable coaxial members positioned face to face and inclined to each other, so that when the members rotate the material to be formed is gripped by the members, there being a guiding means and a die, the guiding means guiding the material to be extruded from the members to the die and the material being extruded through the die, there being a heating means to heat the members.

In use the members are rotated and the material to be formed is fed to the gap between the faces of the members and the members grip the material where the members are closer together and heat is conducted from the members to the material to warm it up, the material is fed towards the guiding means by the rotation of the members and, as the members rotate the grip on the material is released and the material is forced through the die.

The members can be cylinders, cones, discs etc. and the faces of the members should be substantially flat so that the material to be extruded is gripped between the faces.

There can be indentations or grooves in the faces to help grip or position the material to be formed.

The members can be mounted on a common axle or they can be mounted on separate axles. The inclination of the faces of the members to each other is not critical and will depend on the thickness of the material and its properties, the diameter of the members etc. and an angle of one to ten degrees can typically be used e. g. about three degrees. As the material is fed between the faces of the members it is gripped by the members and compressed until it reaches the point of smallest separation of the members. The inclination of the faces of the members should be such that the material is gripped for a sufficient length of the material and with sufficient force that it can be forced through the die with substantially no slippage.

Preferably external pressure is applied to the members so that they are held together with sufficient force to compress and grip the material.

The material to be formed need not be in the form of a rod as in the conform method but can be of any cross sectional shape and, for some applications a strip is preferred as, when the shape of the material is a strip there is a more even distribution of temperature on the material being extruded, and it will he easy to control the temperature changes accurately and closely. The heat required is externally supplied

and so is constantly and independently controlled.

Preferably the faces of the members form a sealed chamber with the material to be extruded'fed through an entry port in the chamber to the members as they rotate and the die being located at an exit port to the chamber so that the material is extruded through the die where it leaves the chamber.

Preferably the members are separated by a spacer preferably positioned on the axle between the faces of the members and so that, the faces of the members are held. apart at the right distance, even when pressure is applied to the members forcing them together to grip the material to be extruded.

The faces of the members are preferably sealed at their edges to form a sealed chamber so that, as the material is compressed between the faces of the members and spreads across the faces it cannot escape from between the faces of the members. The seal can comprise a bead surface on the inner edge of the faces which can rotate with the members and which seals the inner edge of the chamber and a back plate which seals the gap between the members at their outer edges to seal the outer edge of the chamber.

In the method of the present invention the material that enters the extrusion chamber will be under higher pressure and so the current limits of wall thickness in the products can be exceeded. The material is heated up as it travels towards the die, and so there is solid metal to continuously push the softer hot metal through the die. This will increase the hydrostatic pressure and will enable more complex extrudates to be formed.

The apparatus and method of the present invention can be used to produce product from feedstock comprising granules or powders of metals. Formation of products by extrusion of metal granules and powders as the source material has been proposed and it has been claimed that existing machines can do this, but in practice this has proved difficult. in the present invention the compression or compaction of the granules or powders by the faces of the members before the material is fed to the die enables the

compressed or compacted powder to behave as a feeding strip and can then be extruded through the die.

It is a feature of the invention that there is continuous deformation along the path of the faces of the members and so the grip is greater compared to the conform method and due to the grip obtained the pressure can be higher and so different shaped products can be formed. It is also easy to change the die to form a range of products.

As well as for forming metals the apparatus and method of the invention can be used to form products from polymers, ceramics, foods such as chocolate etc. and any material which can be extruded. The invention can also be used for cladding material such as metals, optic fibres etc.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings, in which: Fig. 1 is a schematic view of the members of the invention from the side Fig. 2 is a schematic view of the members from the front Fig. 3 is a side view of an embodiment of the invention Fig. 4 is a sectioned perspective view of the apparatus Fig. 5 is an perspective expanded view of the apparatus Fig. 6 is a disassembled view of the apparatus showing the component parts and Fig. 7 is a side view of an embodiment of the device in use.

Referring to the figures, in particular figures 1 and 2, the apparatus consists primarily of two mutually inclined members 1 and 2 supported for rotation about an axis X-X. Each member 1 and 2 is annular and has an aperture 1a, 2a whereby it is mounted over an axle 3. The axle consists of a shaft 3a supporting a wheel part 3b. The wheel part 3b provides a rim 3c which defines one wall of an annular chamber. The wheel part and the axle is be rotatable.

Each member 1 and 2 has a substantially annular radial surface 1 b, 2b. Each member 1 and 2 is supported so that the radial surfaces 1 b, 2b are mutually inclined and

spaced in the axial direction. The lowermost edge of the radial surfaces 1 b, 2b sealingly engages the wheel rim 3c at a sealing bead surface C so forming two opposing sides of the chamber. The wheel rim 3c need not be cylindrical but may be wholly or partially spherical. Because of the arrangement of the inclination of the members relative to the axis X-X the sides 1 b, 2b of the chamber converge progressively from a feedstock inlet region to an extrusion region adjacent an abutment 8. In the figures the inlet region is located at the top and the extrusion region towards the bottom. The members 1 and 2 together with the wheel and axle form the principle members of the rotor assembly.

A shoe 6 is statically (non-rotatably) mounted on a machine frame (not shown) and has an arcuate inner sealing surface 6a which complements the outer peripheral surfaces of the members 1 and 2 and extends sealingly around part of the circumference of the peripheries of each of the members 1 and 2.

At the top the shoe 6 provides a feedstock entry port 7. As shown in figure 2 feedstock, which is in the form of a cylindrical rod in this example, is fed into the feedstock entry region and engaged by the radial surfaces 1 b,. 2b. As the members are rotated by engagement with a drive mechanism, the feedstock is compressed and carried towards the extrusion region where it meets the abutment structure 8. The abutment structure 8 forms a part of the stator assembly together with the shoe 6 and intrudes into the chamber between the radial surfaces 1b and 2b.

Heaters are provided (not shown) in order to heat the feedstock as it progresses through the chamber. The heaters are preferably provided in the members 1 and 2 and may comprise electrical heating of resistive or induction type. The members may be heated by heaters mounted within the members 1 and 2 or within the shoe 6.

In use the members are heated to their working temperature and rotated by rotation of the axle 3. Axle 3 can be rotated by conventional hydraulic or electric motors (not shown) and feedstock material 9 is fed into the chamber through the entry port 7.

As it progresses through the chamber the radial faces of the members grip the

feedstock, compress it and heat it. When the heated feedstock within the chamber reaches the abutment 8a it is upset and extrudes through an extrusion passage formed upstream of the abutment 8a either in the abutment structure 8 or the shoe 6. In the present example the extrusion passage through which extrudate 10 passes from the chamber, is formed in the abutment structure 8 as can best be seen in figure 4.

For hot extrusion of metals a temperature above 0.5TM (Tm = half the melting temperature of the material in Kelvin) is normally required and the present invention enables this to be achieved easily. The material entering the chamber at the feedstock entry region is cold and relatively hard whereas the material at the extrusion region B is relatively soft and this facilitates extrusion through the die.

Two frame (or casing) halves 5a and 5 b which form a frame (or casing) 5 as can be most readily seen in the exploded figure 5. The frame 5 provides support for the shoe 6. Each of the frame halves 5a, 5b has an annular end plate part 4a, 4b each with a cylindrical bearing housing to accommodate axle bearings 15 which rotatably support the axle 3. Each of the frame halves 5a and 5b is formed with internal radially extending shoulders 16 which provide support for an inclination plate 18. The inclination plate 18 takes the form of a disc which is wedge shaped in cross section.

Each inclination plate 18 supports a thrust bearing 17 which provide support, one each for each member 1 and 2 as it rotates. The wedge angle of the inclination plate 18 determines the relative inclination of the members 1 and 2.

The frame 5 provides means by which an axial force is applied urging each member toward the other.

In figure 6 the abutment structure can be seen exploded showing an extrusion die part 8b.

As can be seen in figure 5, the abutment structure is held in a die holder 19 formed in the frame 5. In essence the die holder is an aperture shaped to accommodate the abutment structure 8. A further cleaning and heating opening 20 is formed in the frame 5.