GB1574604A - Extrusion - Google Patents

Description

(54) NPROYEMENTS IN EXTRUSION (71) We, BRITISH STEEL CORPORA TION, a aJCorporation incorporated and -exist- ing under the Iron and Steel Act 1967 whose principal office is at 33 Grosvenor Place, London S.W.1, do hereby declare the in vention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to 'be particularly described in and by the following statement:-- This invention relates to the 'forming oT materials by extrusion.

In extrusion a workpiece'is subjected to pressure in a container so that the workpiece is extruded from the contain-er through an orifice defining the cross-section of the extruded product. Pressure may be applied mechanically, for example by a ram acting on the workpiece, or by subjecting the work piece to hydrostatic pressure in a liquid acting on the workpiece.

Proposals have been made to .provide a process of continuously extruding material which comprises the steps of feeding ma terial into one end of a passageway formed between first and second members with the second -member having a greater surface area for engaging the material than the first member, said passageway having a blocked end remote from said one end and having at least one die orifice associated with said 'blocked end, and moving the passageway defining surface of the second member rela tive to the passageway defining surface of the first member in a direction towards -the or each die orifice from said one end to said blocked end such that the frictional drag of the passageway defining surface of the second member draws the material substantially in its entirety through the passage way and through the or each die orifice.

'The passageway may conveniently be "formed between a wheel member having an endless 'groove therein and a shoe member covering a part of the length .of the groove, and wherein the wheel member is rotated in a direction to.draw material through the 'passageway and the or each die orifice.

Experiments have shown that the above proposal suffers from certain disadvantages.

In particular, the material being extruded tends to force itself between the first and second members as well as through the die -orifice, resúlting in so-called "flash" ma 'serial of varying thickness being extruded between the first and second -members. This flash tends to -separate the first and second members, and thereby disrupting the pro less. The problem its particularly acute when the material'to be extruded is metallic.

Itls an object of the invention to provide an improved process and apparatus for the -extrusion of material, in which the aforesaid disadvantage is ameliorated.

According -to one aspect of the present in Invention a process is provided for continu -ously extruding material which comprises the steps of feeding material into one end of a first passageway formed between first and second members with the second member having a greater surface area for engaging 'the material than the first member, said first passageway 'having an only partly 'blocked end remote from said one end such that a second passageway of smaller cross-sectional area than the first passageway extends from said first passageway be tween the first and second members, and moving the first passageway defining surface of the second member relative to the'first passageway defining surface of the first member in a direction towards the second passageway sudh that the frictional drag of the first passageway defining surface of the second member draws the material through the first and then through the second passageway.

The first member may comprise a shoe member and the second member a wheel member, and the first passageway'is then formed'between the wheel member which has an endless groove therein and the shoe member -which covers part of the length of the groove and the second passageway is formed between a die member projecting from the shoe member into the 'groove and the groove itself, and in the process the wheel member is rotated in a direction to drag material through the first passageway and then through the second passageway.

According to another aspect of the invention an extrusion apparatus is provided comprising movable and fixed members defining à first elongate passageway, a die member arranged to project into but only partially to close the first passageway so as to provide a second passageway of smaller crosssectional area than the first passageway leading from the first passageway between the die member and the movable member, means for continuously feeding material to be extruded into the first passageway at a point spaced from the die member, the amount of the surface area of the first passageway defined by the movable member being greater than the amount of surface area of the first passageway defined by the fixed member, whereby upon movement of the first passageway defining surface of the movable member relative to first passageway defining surface of the fixed member, the material fed into the first passageway is moved by frictional drag with the surface of the first passageway in the movable member towards the die member and is thereby extruded through the second passageway.

According to another aspect of the invention an extrusion apparatus is provided comprising a wheel member having an endless groove running around its periphery, a shoe member covering part of the length of the groove and forming a first passageway therewith, a die member projecting from the shoe member into the groove to partially block one end of the first passageway to provide a second passageway extending between the die member and the wheel member, said second passageway having a cross-sectional area smaller than that of the first passageway, the wheel member being rotatable relative to the shoe member, and means for feeding material to be extruded into the end of the first passageway remote from the die member so that upon rotation of the wheel member the material is carried along in the groove by frictional drag in the direction of the die member and is thereby extruded through the second passageway.

The endless groove may have a V-shaped bottom portion. The groove and die member may respectively be shaped to provide an extrudate which has a substantially square or rectangular cross-section. The groove may be of uniform shape and depth along its whole length and the die member may be constructed to continuously decrease the cross-sectional area of the material -as it moves through the second passageway.

An 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 side elevation, partly in sec tion, of an extrusion apparatus, Figure 2 is a view on line Il-Il of Figure 1, Figure 3 is a view on line Ill-Ill of Figure 1, and Figure 4 is an exploded isometric view of the apparatus of Figure 1.

A wheel 10 is rotatably mounted on a shaft 11. The wheel 10 has an endless groove 12 running around its periphery. The radially outer walls of the groove 12 are perpendicular to the axis of rotation of the wheel 10, but the bottom portion of the groove 12 is V-shaped, as seen clearly in Figures 2 and 3. The V is radiused to re duce the possibility of fracture which could result if a sharp V notch was used. The groove 12 is of uniform cross-section throughout its length.

A shoe 13 is held closely agaisst the peripheral surface of the wheel 10. A die mem ber 14 is formed on or fitted to the under side of shoe 13 and projects into the groove 12 of wheel 10. The die member 14 extends along only part of the length of shoe 13 in this example and is recessed into the under side of shoe 13. A rectangular cross-section projection 15 of shoe 13 fits into the groove 12 (see Figure 2) over the remainder of the length of shoe -13. At the end of shoe 13 distant from die member 14 the projection 15 is chamferred off as shown in Figure 1.

Thus a first passageway is formed between projection 15 of the shoe 13 and the groove 12, and a second passageway of smaller cross-sectional area than the first passageway is formed between the die member 14 and the groove 12. The cross-sectional area of the second passageway is in fact gradually reduced as the die member 14 extends gradually further into groove 12 towards one end of shoe 13.

The die member 14 is made of tungsten carbide whereas the shoe itself is made of steel. The surface of die member 14 facing the bottom of the groove 12 is V-shaped at the same angle as that of the groove, and has a re-entrant portion 16 which is developed so that together with the bottom of the groove it forms a die with an exit which is approximately square in cross-section.

Material to be extruded, e.g. steel rod 17, is fed continuously into the peripheral groove 12. The rod 17 is continuously carried forward in groove 12 beneath the shoe 13 by the frictional drag of the walls of groove 12 as the wheel- 10 is rotated by drive means which is not shown, in the direc tion indicated by arrow 18 in Figure 1. At the same time the rod 17 is forced by shoe 13 to conform to the V-shaped bottom sur face of the groove 12. As the rod 17 is forced into engagement with the die member 14, the cross-sectional area of the steel is reduced continuously to issue as an approximately square cross-section extrudate 19 (see Figure 3).

The generation of the frictional drag in groove 12 arises from the fact that the crosssectional area of the moving groove surface per unit groove length is greater than the cross-sectional area per unit length of the static face of projection 15 which also contacts the rod 17. Thus the nett frictional drag on rod 17 is towards the die member 14. Consideration of the frictional drag required for a particular extrusion is necessary in order to calculate accurately the dimensional parameters of the apparatus for a selected material to be extruded. These calculations may be made in a manner similar to those described in British Patent Specification 1,370,849.

The invention permits the use of dies which may be held under a compressive load, thereby reducing the risk of bursting the die. Furthermore, the creation of a fresh reactive metal surface, which is likely to result in galling of the die, is eliminated with the process according to the invention.

The extrudate may be assisted in its passage between the die member 14 and the groove 12 by the application of tension to the extrudate 18. This also means that there is less likelihood of the extrudate sticking in the groove 12 as it issues from the die.

WHAT WE CLAIM IS:- 1. A process for continuously extruding material which comprises the steps of feeding material into one end of a first passageway formed between first and second members with the second member having a greater surface area for engaging the material than the first member, said first passageway having an only partly blocked end remote from said one end such that a second passageway of smaller cross-sectional area than the first passageway extends from said first passageway between the first and second members, and moving the first passageway defining surface of the second member relative to the first passageway defining surface of the first member in a direction towards the second passageway such that the frictional drag of the first passageway defining surface of the second member draws the material through the first and then through the second pas sageway.

2. A process as claimed in claim 1 wherein the first member comprises a shoe member and a second member a wheel member, and wherein the first passageway is formed between the wheel member which has an endless groove therein and the shoe member which covers part of the length of the groove.

3. A process as claimed in claim 2 wherein the second passageway is formed between a die member projecting from the shoe member into the groove and the groove itself.

4. Extrusion apparatus comprising movable and fixedsmembers defining a first elongate passageway, a die member arranged to project into but only partially to close the first passageway so as to provide a second passageway leading from the first passageway between the die member and the movable member, means for continuously feeding material to be extruded into the first passageway at a point spaced from the die member, the amount of the surface area of the first passageway defined by the movable member being greater than the amount of surface area of the first passageway defined by the fixed member, whereby upon movement of the first passageway defining surface of the movable member relative to the first passageway defining surface of the fixed member, the material fed into the first passageway is moved by frictional drag with the surface of the first passageway in the movable member towards the die member and is thereby extruded through the second passageway.

5. Extrusion apparatus comprising a wheel member having an endless groove running around its periphery, a shoe member covering part of the length of the groove and forming a first passageway therewith, a die member projecting from the shoe member into the groove to partially block one end of the first passageway to provide a second passageway extending between the die member and the wheel member, said second passageway having a cross-sectional area smaller than that of the first passageway, the wheel member being rotatable relative to the shoe member, and means for feeding material to be extruded into the end of the first passageway remote from the die member so that upon rotation of the wheel member the material is carried along in the groove by frictional drag in the direction of the die member and is thereby extruded through the second pas sageway.

6. Extrusion apparatus as claimed in claim 5 wherein the endless groove has a V-shaped bottom portion.

7. Extrusion apparatus as claimed in claim 5 wherein the groove and die mem ber are respectively shaped to provide an extrudate which has a substantially square or rectangular cross-section.

8. Extrusion apparatus as claimed in claim 5 wherein the groove is of uniform shape and depth along its whole length and the die member is constructed continuously

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. forced into engagement with the die member 14, the cross-sectional area of the steel is reduced continuously to issue as an approximately square cross-section extrudate 19 (see Figure 3). The generation of the frictional drag in groove 12 arises from the fact that the crosssectional area of the moving groove surface per unit groove length is greater than the cross-sectional area per unit length of the static face of projection 15 which also contacts the rod 17. Thus the nett frictional drag on rod 17 is towards the die member 14. Consideration of the frictional drag required for a particular extrusion is necessary in order to calculate accurately the dimensional parameters of the apparatus for a selected material to be extruded. These calculations may be made in a manner similar to those described in British Patent Specification 1,370,849. The invention permits the use of dies which may be held under a compressive load, thereby reducing the risk of bursting the die. Furthermore, the creation of a fresh reactive metal surface, which is likely to result in galling of the die, is eliminated with the process according to the invention. The extrudate may be assisted in its passage between the die member 14 and the groove 12 by the application of tension to the extrudate 18. This also means that there is less likelihood of the extrudate sticking in the groove 12 as it issues from the die. WHAT WE CLAIM IS:-

1. A process for continuously extruding material which comprises the steps of feeding material into one end of a first passageway formed between first and second members with the second member having a greater surface area for engaging the material than the first member, said first passageway having an only partly blocked end remote from said one end such that a second passageway of smaller cross-sectional area than the first passageway extends from said first passageway between the first and second members, and moving the first passageway defining surface of the second member relative to the first passageway defining surface of the first member in a direction towards the second passageway such that the frictional drag of the first passageway defining surface of the second member draws the material through the first and then through the second pas sageway.

2. A process as claimed in claim 1 wherein the first member comprises a shoe member and a second member a wheel member, and wherein the first passageway is formed between the wheel member which has an endless groove therein and the shoe member which covers part of the length of the groove.

3. A process as claimed in claim 2 wherein the second passageway is formed between a die member projecting from the shoe member into the groove and the groove itself.

4. Extrusion apparatus comprising movable and fixedsmembers defining a first elongate passageway, a die member arranged to project into but only partially to close the first passageway so as to provide a second passageway leading from the first passageway between the die member and the movable member, means for continuously feeding material to be extruded into the first passageway at a point spaced from the die member, the amount of the surface area of the first passageway defined by the movable member being greater than the amount of surface area of the first passageway defined by the fixed member, whereby upon movement of the first passageway defining surface of the movable member relative to the first passageway defining surface of the fixed member, the material fed into the first passageway is moved by frictional drag with the surface of the first passageway in the movable member towards the die member and is thereby extruded through the second passageway.

5. Extrusion apparatus comprising a wheel member having an endless groove running around its periphery, a shoe member covering part of the length of the groove and forming a first passageway therewith, a die member projecting from the shoe member into the groove to partially block one end of the first passageway to provide a second passageway extending between the die member and the wheel member, said second passageway having a cross-sectional area smaller than that of the first passageway, the wheel member being rotatable relative to the shoe member, and means for feeding material to be extruded into the end of the first passageway remote from the die member so that upon rotation of the wheel member the material is carried along in the groove by frictional drag in the direction of the die member and is thereby extruded through the second pas sageway.

6. Extrusion apparatus as claimed in claim 5 wherein the endless groove has a V-shaped bottom portion.

7. Extrusion apparatus as claimed in claim 5 wherein the groove and die mem ber are respectively shaped to provide an extrudate which has a substantially square or rectangular cross-section.

8. Extrusion apparatus as claimed in claim 5 wherein the groove is of uniform shape and depth along its whole length and the die member is constructed continuously

to decrease the' cross-sectional area of the material as it moves through the second passageway.

9. A process forwcontinuously extruding material substantially as herein -described with reference to Figures 1 to 4 of the accompanying drawings.

10. Extrusion apparatus substantially as herein -described with reference to Figures 1 to 4 of the accompanying drawings.