GB1584292A

GB1584292A - Extrusion

Info

Publication number: GB1584292A
Application number: GB4362777A
Authority: GB
Original assignee: NII EX I AVTOMOBIL ELEKTROOBOR
Current assignee: NII EX I AVTOMOBIL ELEKTROOBOR
Priority date: 1977-10-20
Filing date: 1977-10-20
Publication date: 1981-02-11

Description

(54) IMPROVEMENTS IN OR RELATING TO EXTRUSION (71) We, NAUcHNo-IssLEDovATELsKY I EXPERIMENTALNY INSTITUT AVTOMOBIL NOGO ELEKTROOBORUDOVANIA I AVTO PRIBOROV, a Corporation organised and existing under the laws of the Union of Soviet Socialist Republics, of ulitsa, 39-41 Kirpichnaya, Moscow, U.S.S.R., do hereby declare the invention 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: The present invention relates to a method of manufacturing hollow parts by extrusion and to a device for effecting the method.

According to one aspect of the present invention there is provided a method of manufacturing hollow parts, the method comprising applying a pressure to a workpiece supported by a support portion thereof, such that material of the workpiece is extruded in the direction opposite to that of the applied pressure, and concurrently applying a force to the support portion of the workpiece in the direction of flow of extruded material whereby to overcome frictional forces acting against the flow of extruded material and to draw the material being extruded.

According to another aspect of the present invention there is provided a device for manufacturing hollow parts by the above described method, the device comprising a shaping punch, a base punch, and a container all arranged co-axially with each other and movable axially with respect to one another, a workpiece being supportable by a support portion thereof on the container between facing ends of the base punch and shaping punch, and the shaping punch being insertable into the container with an annular space therebetween, said container being biased by a spring towards the shaping punch, whereby upon relative movement of the shaping punch towards the base punch to compress a workpiece therebetween material of the workpiece is extruded into the annular space between the shaping punch and the container and the spring-loading of the container exerts a force on the support portion of the workpiece in the direction of flow of extruded material whereby to overcome the force of friction between the material of the workpiece and the container and to draw the material being extruded.

A method according to the invention and an extrusion device embodying the invention will now be particularly described by way of example in relation to the making of spark plug bodies, reference being made to the accompanying diagrammatic drawings in which: Figure 1 is a side elevation of a workpiece blank; Figure 2 is a side view, partly in section, of the workpiece after working to shape an enlarged head portion; Figure 3 is a side view partly in section of the workpiece of Figure 2 after extrusion; Figure 4 is a longitudinal section through the extrusion device.

In order to form a body of a spark plug, one end of a cylindrical blank 1 (Figure 1) is first shaped to provide a support portion in the form of an enlarged head portion 2 (Figure 2) and a lower cylindrical portion 5. The head portion 2 has an upper part 3 of external hexagonal form at its upper end for engagement with a wrench, a lower cylindrical part, and an internal blind end space 4. The diameter "d" and length "1" of the cylindrical portion 5 of the workpiece are selected so that its volume is sufficient to result, after the extrusion process to be described hereinafter, in a cylindrical portion 6 of the finished workpiece which has the required length "L" (Figure 3).

The device used in the extrusion process comprises a shaping punch 7 (Figure 4), a container 8 and a lower or base punch 9, all mounted coaxially with each other and movable axially with respect to one another.

The container 8 has a hole 10 arranged coaxially with the punches 7 and 9 for receiving the cylindrical portion 5 of the workpiece. A socket 11 is provided in the container 8 at the upper end of the hole 10 and is arranged to accommodate the lower cylindrical part of the head portion 2 of the workpiece.

The container 8 and the lower punch 9 are placed into a common cylindrical housing 12 which has a thick bottom 13 fixed to the cylindrical housing by means of an assembly nut 14. A compression coil spring 15 is installed between the bottom 13 of the housing 12 and the container 8.

The strength of said spring 15 is selected such that it sets up a reactive force exceeding the force of friction arising during the extrusion process between the container 8 and the cylindrical portion 6 of the workpiece.

The internal surface of the container 12 in the region of the shaping punch 7 is provided with a stop 16 in the form of an annular projection which limits the axial movement of the container 8 caused by the spring 15. The distance "H" between the bottom of the socket 11 in the container 8 and the upper end of the lower punch 9 in the starting position of the device (see Figure 4 right) should be at least the required length "L" of the cylindrical portion 6 in the finished workpiece.

Operation of the device will now be described.

When the device is in its starting position (Figure 4, right-hand side), the container 8 is pressed by means of the spring 15 against the stop 16 and the lower punch 9 rests on the bottom 13. The shaping punch 7 is withdrawn from the container 8 to a distance necessary to allow loading of the workpiece (Figure 2) into the container 8.

The workpiece is then placed into the container 8 so that its cylindrical portion 5 projects into the axial hole 10 of the container 8 while the lower part of the enlarged head 2 seals in the socket 11. This leaves a free space between the end of the cylindrical portion 5 of the workpiece and the lower punch 9.

The device is then operated by moving the shaping punch 7 downwards so that it bearss against the workpiece and moves it together with the container 8 until said workpiece comes in contact with the lower punch 9. The spring 15 is now in a compressed state and extrusion can commence.

On lowering the punch 7 still further, the material of the workpiece flows upwards into the gap between the container 8 and the shaping punch 7. This outflow of material moves the head 2 of the work piece in the direction opposite to the direction of movement of the shaping punch 7. The container 8 is continuously urged against the head 2 under the action of the spring 15 and therefore moves in the direction of the flow of the extruded material and at a speed which is equal to the speed at which the extruded material flows.

Since the force exerted by the spring 15 exceeds the force of friction between the container 8 and the cylindrical portion 5 of the workpiece, the container 8 acts on the head portion of the workpiece to draw the material in the cylindrical portion 5 in the direction in which it is being extruded. This tensile loading caused by this drawing results in stretching of the material so that speed at which the cylinder 8 moves up under the action of the spring 15 will be slightly greater than the speed at which the extruded material flows.

In this method of extrusion, considerable tensile stresses arise at the junction between the enlarged head portion 2 and the cylindrical portion 5 undergoing deformation. This radically changes the stress patterns produced so that the extrusion force can be considerably reduced. By reducing the loads placed on the punches 7 and the container 8 the service life of the device can be increased.

In addition, the described extrusion process is accompanied by slipping friction between the container 8 and the cylindrical portion 5 of the workpiece which decreases wear of the containner 8 and puts less exacting demands on the kind of lubricant necessary.

As a result both the strength and the life of the device are considerably increased.

On completion of the processs, the finished workpiece is removed from the container 8 by an upward movement of the lower punch 9. The above-described process can then be repeated.

When the hollow cylindrical parts are required without enlarged heads, the heads can be removed from the workpiece after extrusion. Thus a wide variety of hollow parts can be produced by this method.

The above described method and device could be used most effectively in cold extrusion of parts from high-strength plastic materials under the conditions of large-scale production, for example on high-speed automatic presses where frequent replacements of work tools would involve considerable loss of time and funds.

The device is very reliable and compact so that it can be easily fitted into automatic transfer presses for example cold-heading machines for large scale production of hollow parts of a complex configuration.

WHAT WE CLAIM IS: - 1. A method of manufacturing hollow parts, the method comprising applying a pressure to a workpiece supported by a support portion thereof, such that material

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. workpiece. A socket 11 is provided in the container 8 at the upper end of the hole 10 and is arranged to accommodate the lower cylindrical part of the head portion 2 of the workpiece. The container 8 and the lower punch 9 are placed into a common cylindrical housing 12 which has a thick bottom 13 fixed to the cylindrical housing by means of an assembly nut 14. A compression coil spring 15 is installed between the bottom 13 of the housing 12 and the container 8. The strength of said spring 15 is selected such that it sets up a reactive force exceeding the force of friction arising during the extrusion process between the container 8 and the cylindrical portion 6 of the workpiece. The internal surface of the container 12 in the region of the shaping punch 7 is provided with a stop 16 in the form of an annular projection which limits the axial movement of the container 8 caused by the spring 15. The distance "H" between the bottom of the socket 11 in the container 8 and the upper end of the lower punch 9 in the starting position of the device (see Figure 4 right) should be at least the required length "L" of the cylindrical portion 6 in the finished workpiece. Operation of the device will now be described. When the device is in its starting position (Figure 4, right-hand side), the container 8 is pressed by means of the spring 15 against the stop 16 and the lower punch 9 rests on the bottom 13. The shaping punch 7 is withdrawn from the container 8 to a distance necessary to allow loading of the workpiece (Figure 2) into the container 8. The workpiece is then placed into the container 8 so that its cylindrical portion 5 projects into the axial hole 10 of the container 8 while the lower part of the enlarged head 2 seals in the socket 11. This leaves a free space between the end of the cylindrical portion 5 of the workpiece and the lower punch 9. The device is then operated by moving the shaping punch 7 downwards so that it bearss against the workpiece and moves it together with the container 8 until said workpiece comes in contact with the lower punch 9. The spring 15 is now in a compressed state and extrusion can commence. On lowering the punch 7 still further, the material of the workpiece flows upwards into the gap between the container 8 and the shaping punch 7. This outflow of material moves the head 2 of the work piece in the direction opposite to the direction of movement of the shaping punch 7. The container 8 is continuously urged against the head 2 under the action of the spring 15 and therefore moves in the direction of the flow of the extruded material and at a speed which is equal to the speed at which the extruded material flows. Since the force exerted by the spring 15 exceeds the force of friction between the container 8 and the cylindrical portion 5 of the workpiece, the container 8 acts on the head portion of the workpiece to draw the material in the cylindrical portion 5 in the direction in which it is being extruded. This tensile loading caused by this drawing results in stretching of the material so that speed at which the cylinder 8 moves up under the action of the spring 15 will be slightly greater than the speed at which the extruded material flows. In this method of extrusion, considerable tensile stresses arise at the junction between the enlarged head portion 2 and the cylindrical portion 5 undergoing deformation. This radically changes the stress patterns produced so that the extrusion force can be considerably reduced. By reducing the loads placed on the punches 7 and the container 8 the service life of the device can be increased. In addition, the described extrusion process is accompanied by slipping friction between the container 8 and the cylindrical portion 5 of the workpiece which decreases wear of the containner 8 and puts less exacting demands on the kind of lubricant necessary. As a result both the strength and the life of the device are considerably increased. On completion of the processs, the finished workpiece is removed from the container 8 by an upward movement of the lower punch 9. The above-described process can then be repeated. When the hollow cylindrical parts are required without enlarged heads, the heads can be removed from the workpiece after extrusion. Thus a wide variety of hollow parts can be produced by this method. The above described method and device could be used most effectively in cold extrusion of parts from high-strength plastic materials under the conditions of large-scale production, for example on high-speed automatic presses where frequent replacements of work tools would involve considerable loss of time and funds. The device is very reliable and compact so that it can be easily fitted into automatic transfer presses for example cold-heading machines for large scale production of hollow parts of a complex configuration. WHAT WE CLAIM IS: -

1. A method of manufacturing hollow parts, the method comprising applying a pressure to a workpiece supported by a support portion thereof, such that material

of the workpiece is extruded in the direction opposite to that of the applied pressure, and concurrently applying a force to the support portion of the workpiece in the direction of flow of extruded material whereby to overcome frictional forces acting against the flow of extruded material and to draw the material being extruded.

2. A method according to claim 1 wherein the workpiece is cylindrical and is provided in advance with a support portion.

3. A method according to claim 1 or claim 2, wherein the support portion of the workpiece is removed after extrusion.

4. A method according to any one of claims 1, 2 or 3, substantially as hereinbefore described with reference to Figures 1, 2, 3 and 4 of the accompanying drawing.

5. A device for manufacturing hollow parts by a method according to any one of claims 1 to 4, the device comprising a shaping punch, a base punch, and a container all arranged co-axially with each other and movable axially with respect to one another, a workpiece being supportable by a support portion thereof on the container between facing ends of the base punch and shaping punch, and the shaping punch being insertable into the container with an annular space therebetween, said container being biased by a spring towards the shaping punch, whereby upon relative movement of the shaping punch towards the base punch to compress a workpiece therebetween material of the workpiece is extruded into the annular space between the shaping punch and the container and the spring-loading of the container exerts a force on the support portion of the workpiece in the direction of flow of extruded material whereby to overcome the force of friction between the material of the workpiece and the container and to draw the material being extruded.

6. A device according to claim 5, wherein the container and base punch are accommodated in a common housing and a stop is provided on the housing and arranged to limit the movement of the container in the direction of flow of extruded material, the distance between the stop and the said facing end of the base punch being equal to the required length of the extruded portion of the hollow part.

7. A device according to claim 6, wherein the container is spring-loaded by a compression coil spring installed between said container and the bottom of the housing.

8. A device for the manufacture of hollow parts substantially as disclosed above with reference to the accompanying drawings.