JPH0133217Y2 - - Google Patents

Description

[Detailed description of the invention] Industrial application field This invention is an extrusion stem of an apparatus for forward extrusion processing of hollow extrusion profiles, in which the extrusion stem is fitted onto a mandrel so that both move in the front and rear directions relative to each other. The present invention relates to a dummy block that is attached to the front end of a dummy block and has a mandrel insertion hole.

In this specification, "front and back" refers to the extrusion direction during extrusion processing, and "front" refers to the front in the extrusion direction, and "rear" refers to the opposite side.

Conventional technology and its problems Conventionally, as this type of dummy block, the third
The one shown in the figure was used. In this dummy block 20, when it is not used for extrusion processing, the mandrel insertion hole 21 has the same diameter from the front end to the rear end. Such a dummy block 20 has been used in a device for forward extrusion of hollow extrusion profiles as shown in FIG. This device includes a container 10, a mandrel 11 fixed at a predetermined position inside the container 10, and a mandrel 11 fixed at a predetermined position in the container 10.
An extruded stem 12 that can freely move back and forth is fitted over the
and the dice 13 placed in front of the container 10.
The dummy block 20 is attached to the front end of the extrusion stem 12.

To make a hollow extruded material using the above equipment, first,
Hollow cylindrical billet 14 heated to a predetermined temperature
is inserted into the container 10 and heated and maintained at a predetermined temperature by a heating device (not shown). Thereafter, the extrusion stem 12 is advanced to extrude the hollow extrusion material 15 forward from between the front end of the mandrel 11 and the bearing surface of the die 13. However, during such extrusion processing, the temperature at the front end of the dummy block 20 becomes higher than the temperature at the rear end.
100℃ higher. As a result, as shown by the chain line in FIG. 3 and the solid line in FIG. It has a tapered shape that gradually increases in diameter toward dummy block 2.
The gap between the inner circumferential surface of the mandrel insertion hole 21 and the outer circumferential surface of the mandrel 11 is maximum at the front and gradually becomes smaller toward the rear. Therefore, when the extrusion stem 12 is advanced, the extruded material easily enters the gap, and the extruded material that has entered this gap flows to the rear of the dummy block 20 due to the forward pressing force of the extrusion stem 12. There's a problem. In particular, when the mandrel insertion hole 21 is tapered as described above, the extruded material that has flowed into the gap applies a force to the mandrel insertion hole 21 to push it wider, so the gap widens. Therefore, there is a problem in that the flow of the extruded material to the rear of the dummy block 20 is further accelerated. Furthermore, the following problems occur due to the flow of the extruded material to the rear of the dummy block 20. That is, in order to remove the extrusion material that has flowed in and adhered to the mandrel 11, the idle time of the extrusion process becomes longer. Also, container 1
0, the center axes of the mandrel 11, die 13, etc. are misaligned, and the resulting hollow extruded material 15 suffers from uneven thickness. Furthermore, the mandrel 11 may be damaged.

The purpose of this invention is to provide a dummy block that solves the above problems all at once.

Means for Solving the Problem The dummy block according to this invention is the front end of the extrusion stem of a device for forward extrusion processing of hollow extruded materials, in which the extrusion stem is fitted over the mandrel so that both move in the front and back direction relative to each other. This is a dummy block that is attached to a dummy block and has a mandrel insertion hole, and the mandrel insertion hole has a thin tapered shape at the front end, and during extrusion processing, the mandrel insertion hole has the same diameter over the entire length due to thermal expansion, or the front end is narrow. It has a tapered shape.

Embodiments Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 1 shows a vertical sectional view of the dummy block before extrusion. The mandrel insertion hole 2 of the dummy block 1 has a thin tapered front end. The angle of inclination of the inner surface of the mandrel insertion hole 2 is preferably 5 minutes to 1 degree, and more preferably 10 minutes to 40 degrees. Further, the degree of taper is such that the mandrel insertion hole 2 has the same diameter from the front end to the rear end due to thermal expansion during extrusion processing.

When extrusion processing is performed using such a dummy block 1 in a device for forward extrusion processing of hollow extrusion mold materials (see Fig. 2), the difference in thermal expansion caused by the temperature difference between the front end and rear end of the dummy block causes The mandrel insertion hole 2 has the same diameter from the front end to the rear end, as shown by the chain line in FIG. 1 and the solid line in FIG. At this time, the gap between the inner peripheral surface of the mandrel insertion hole 2 and the outer peripheral surface of the mandrel 11 is the same as the gap between the inner peripheral surface of the mandrel insertion hole 21 at the rear end of the dummy block 20 when extrusion processing is performed using the conventional dummy block 20. It is preferable that the gap be approximately equal to or smaller than the gap between the surface and the outer peripheral surface of the mandrel 11. As described above, the diameter of the mandrel insertion hole 2 during extrusion processing becomes the same over the entire length, and the inner peripheral surface of the mandrel insertion hole 2 and the mandrel 11
If the gap between the outer circumferential surface becomes uniform from the front end to the rear end, it becomes difficult for the extruded material to enter the gap.

In the embodiment described above, the diameter of the mandrel insertion hole 2 is made equal over the entire length during extrusion processing, but instead of this, the diameter may be formed into a thin tapered shape at the front end. In order to do this, the degree of taper of the mandrel insertion hole 2 before extrusion processing may be made slightly larger than that in the above embodiment.

Effects of the invention Since the dummy block 1 according to the invention is constructed as described above, during extrusion processing, it thermally expands so that the mandrel insertion hole 2 has the same diameter over its entire length or has a narrow tapered shape at the front end. Therefore, compared to the case where extrusion is performed using a conventional dummy block in which the mandrel insertion hole has a narrow tapered shape at the rear end during extrusion, the extruded material is formed on the inner peripheral surface of the mandrel insertion hole 2 and on the outer peripheral surface of the mandrel 11. This makes it difficult for the extruded material to get between the dummy block 1 and the dummy block 1, and the occurrence of the various problems described above due to the extruded material flowing behind the dummy block 1 is drastically reduced.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of this invention; Figure 1 is a vertical sectional view of the dummy block;
The figure is a vertical cross-sectional view of a device for forward extrusion processing of hollow extruded mold materials using this dummy block, Figures 3 and 4 show conventional examples, Figure 3 is a vertical cross-sectional view of the dummy block, and Figure 4 is a FIG. 2 is a vertical cross-sectional view of the device used for forward extrusion processing of hollow extrusion profiles. 1... Dummy block, 2... Mandrel insertion hole, 11... Mandrel, 12... Extruded stem.

Claims (1)

[Scope of utility model registration request] A dummy block that is attached to the front end of the extrusion stem of a device for forward extrusion processing of a hollow extrusion material, in which the extrusion stem is fitted over the mandrel so that both can move in the front and rear directions relative to each other, and has a mandrel insertion hole, A dummy block in which the mandrel insertion hole has a thin tapered shape at the front end, and during extrusion processing, the mandrel insertion hole has the same diameter over its entire length due to thermal expansion, or the front end has a thin tapered shape.