JPH0515372Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a plug for cold drawing of pipes, and more particularly to a plug whose plug body can be reversed and reused without the risk of breakage.

[Conventional technology]

Typical plugs used when manufacturing pipes by cold drawing include cylindrical, tapered, and spherical shapes. These are R type,
Used in combination with Ratsupa-type and intermediate-type dies. Among these, the combination of a cylindrical plug and an R-shaped die is widely adopted because the tool has a simple shape, which facilitates tool machining, and allows relatively high machining efficiency.

In this case, the cylindrical plug is generally supported on the mandrel in the following manner. A female threaded hole is drilled on the proximal end of the axis of the solid cylindrical plug body, and this female threaded hole is directly screwed into the male threaded part protruding from the tip of the mandrel, or in order to reduce the plug consumption. First, the plug body is formed into a hollow cylindrical shape with a female thread cut into its inner peripheral surface, and this plug body is supported by a mandrel via a shank. The shank has a male thread formed on the outer periphery of the small-diameter stepped portion at the tip, and the plug body is screwed onto the male thread, and the shank is also screwed into the male threaded portion protruding from the tip of the mandrel.

During the drawing process, as shown in FIG. 3, the plug 10 is positioned within the die 20, and the diameter of the raw tube 30 is reduced by the die 20, and the thickness is reduced by the die 20 and the plug 10. The pipe 40 is finished to a predetermined size by the following steps. At this time,
The raw tube 30 starts to come into contact with the plug 10 at point a in FIG.
The diameter is reduced up to point c, and plug 1 is formed at point c.
Complete contact with 0. Therefore, if the drawing process of the raw pipe 30 with the same dimensional specifications is repeated in the state shown in FIG. 3, the contact portion of the plug 10 with the raw pipe 30 between points a to c, especially between points a and b, will gradually wear out. . This a~
When the area between points b wears out, the drawn pipe 40
The inner diameter of the inner diameter becomes smaller than the predetermined size, and the wall thickness increases accordingly. Furthermore, the surface of the worn portion of the plug 10 becomes rough, and the inner surface of the tube 40 deteriorates. Therefore, the plug 10 is frequently replaced with a new one.

However, in FIG. 3, the surface on the mandrel 50 side from point a where the inner surface of the raw tube 30 starts to come into contact with the plug 10 is not worn, so if the plug 10 is frequently replaced with a new one, this part will be wasted. There was a problem that the plug consumption rate worsened over time.

In order to solve this problem, the plug body should be shortened only in the part that does not wear out, or the plug body should be made longer so that it can be used inverted with the worn side facing the mandrel. It is conceivable to use a plug with a female threaded portion, and in this case, an improvement in the plug unit consumption can be expected.

However, among the aforementioned plugs, if the length of the plug body is shortened to the length required for actual drawing, even if the plug has the same outer diameter, the machining rate (reduction) during drawing with different setups may occur. If the pulling force becomes large due to differences in area ratio), strength of the raw pipe, etc., a so-called pulling phenomenon occurs in which the plug is pulled in the drawing direction during processing and its position advances. There is a problem in that it becomes extremely difficult to set the initial position, and a large number of man-hours are required for setup setting. Furthermore, if the rate of wall thinning is different, the starting point a of contact between the inner surface of the raw pipe and the plug is also different, so plugs of different lengths are required depending on the rate of wall thinning, and it takes a lot of man-hours to store and maintain them. There is also the problem.

In addition, if the plug body is made long so that it can be used reversibly, and a through-female threaded hole is drilled in the axis of the plug, between points a to c where the raw pipe 30 contacts,
In particular, it is necessary to fill the axial center gap between points b and c where a strong radial compressive force acts to prevent breakage.
It is necessary to replace a with a longer one.

Furthermore, each plug has a female threaded hole (hole) in its axis, and this female threaded hole (hole) can be screwed into the male threaded part 50a at the tip of the mandrel or the male threaded part of the small diameter stepped part of the shank. Since the plug is designed to support the plug against the pulling force, a new problem arises in that stress concentrates on both threaded parts, causing the threaded part to tear off and break into a ring shape. It doesn't improve, and in some cases it gets even worse.

In order to solve these problems, plugs having a through hole without a female thread in the shaft center have been proposed, one of which is the one disclosed in Japanese Utility Model Application Publication No. 131715/1983. be. The details of the internal structure of the plug disclosed in this publication are not shown, but since the plug body is made of ceramics with low resistance, it is assumed that the internal structure is as shown in Figure 4. Ru. That is, the stepped portion 70 of the shank 60 is formed into a threadless tapered shape, and the unthreaded through hole 10a of the plug body 10 is formed into a tapered hole that closely fits into the tapered tapered portion of the stepped portion 70, so that the outer periphery of the tip portion of the shank 60 is formed. It is assumed that this structure is such that the plug body 10, which is made of ceramics and has a small transverse rupture strength, is prevented from breaking.

[The problem that the idea attempts to solve]

However, since the conventional plug body shown in Fig. 4 has a single tapered hole with a diameter that decreases (enlarges) from one end to the other end, the through hole drilled in the axis may become partially worn. It cannot be used by reversing the front end and rear end sides. In addition, as seen in Japanese Patent Application Laid-Open No. 60-166118, a large-diameter pipe in which the mouth shape at the tip of the raw pipe is an inner flange type, and the pull head is inserted into the raw pipe and is locked to the inner flange. During the drawing process, since the tightening nut is located on the tip side of the plug, the plug tip surface and the pull head tip surface come into contact. the result,
At the initial stage of drawing, it is not possible to set the plug in the proper position within the die, and as a result, the length of blank drawing becomes long, where the thinning process is not performed and the product is not produced. Therefore, although breakage of the plug can be prevented, it is not only impossible to improve the plug unit consumption, but also there is a problem that the product yield is poor when drawing large diameter pipes.

The present invention was developed in view of the above circumstances, and its purpose is to make it necessary to adjust the initial setting position even when the plug position shifts due to a difference in the pulling force, and to invert the plug. To provide a plug for cold drawing of pipes which can be used and which can prevent breakage of the plug, and which does not deteriorate the product yield even when drawing large diameter pipes. be.

[Means to solve the problem]

The plug of the present invention includes a plug holder in which a threadless tapered end is formed at the tip, and a tapered taper in the plug holder whose diameter increases from the axial center as a boundary and toward the end face. An unthreaded taper hole with the same slope is formed which tightly fits into the outer part, and
A plug body formed to have an outer diameter equal to the longitudinal direction of the shaft, and a tightening member that is screwed onto the plug holder and has a threadless taper formed on the outer periphery that closely fits into the threadless taper hole of the plug body axis. It is characterized by consisting of.

[Effect]

The unthreaded taper hole at one end, which is drilled at the axis of the plug body, is tightly fitted into the unthreaded tapered taper of the plug holder, and the unthreaded taper hole at the other end, which has the same slope, fits the plug holder. The threadless taper of the tightening member screwed onto the tool fits tightly inside. In other words, since the taper hole at the axis of the plug body is the same as the threadless taper formed in the plug holder and the tightening member, it can be used in reverse.

In addition, the inner surface of the plug body is supported in intimate contact with the outer surfaces of both the plug holder and the fastening member over virtually its entire surface, and since there are no threads on the contact surface and no local stress concentration areas, the plug body will not break even if a strong force is applied in the diameter direction during drawing. As a result, even a plug body made of ceramics, which has a low flexural strength, can be used without any problems.

Furthermore, since there is nothing protruding from the tip of the plug body, the length of the empty drawing part can be made as short as possible even when used for drawing large-diameter pipes. This does not cause a deterioration in yield.

Furthermore, since the length of the plug body is such that it can be used in reverse, it is possible to cope with the so-called pull-in phenomenon at the initial stage of the drawing process without any problem.

〔Example〕

The present invention will be described in detail below with reference to its embodiments.

As shown in FIG. 1, the plug of the present invention includes a plug holder 1, a plug body 2 held at the tip thereof, and a plug body 2 held at the tip of the plug holder 1.
The mandrel 4 is supported by a support shaft 5 and a shank 6.

The plug holder 1 has an annular shape and is fitted onto a small diameter stepped portion 5a formed at the tip of the support shaft 5. The tip portion of the small diameter stepped portion 5a protrudes from the plug holder 1 and forms a male threaded portion 5b. The outer circumferential surface of the tip end of the plug holder 1 is a threadless taper 1a whose outer diameter gradually decreases toward the tip.

The plug body 2 is also annular and has a tapered hole in the axial center. The taper holes are symmetrical taper holes 2a, 2a whose diameter increases toward both end faces with the center in the axial direction as a boundary. Tapered hole 2
Both a and 2a have a depth, a diameter, and an inclination to closely fit into the tapered taper 1a of the plug holder 1, and are not threaded. The axial length of the plug body 2 is set to be sufficiently long compared to the length required for drawing so that the plug body 2 can be used in reverse. The outer circumferential surface of the plug body 2 is a straight circumferential surface having substantially the same diameter in the axial direction.

The tightening member 3 is also annular and has a female threaded portion 3a on its inner circumferential surface that is screwed into the male threaded portion 5b of the support shaft. The outer circumferential surface of the tightening member 3 has a taper 3b whose outer diameter gradually decreases toward the proximal end. The taper 3b is similar to the tapered taper 1a of the plug holder 1, and the taper holes 2a, 2a of the plug body 2.
has a depth, diameter, and slope that can fit interchangeably and closely into both, and is not threaded. The axial length of the tightening member 3 is approximately equal to the depth of one tapered hole 2a. Therefore, when the tightening member 3 is tightly fitted into the tapered hole 2a on the distal end side, the distal end surface of the tightening member 3 is substantially flush with the distal end surface of the plug body 2. A tool locking hole 3c for locking a tightening tool is provided in the front end surface of the tightening member 3.

The support shaft 5 has a male threaded portion 5c at its base end. The shank 6 is cylindrical and has an outer diameter equal to the outer diameter of the mandrel 4. A male threaded portion 6a is provided on one end of the inner circumferential surface of the shank 6, and is threaded into a male threaded portion 4a formed in a small diameter stepped portion at the tip of the mandrel 4, and a male threaded portion 5c of the support shaft 5 is provided on the other end. A female threaded portion 6b is provided to be screwed into. Support shaft 5
With the male threaded portion 5c of the shank 6 screwed into the female threaded portion 6b of the shank 6, the small diameter stepped portion 5a of the support shaft 5 protrudes toward the distal end side of the shank 6.

The plug having such a configuration is attached to the mandrel 4 in the following manner.

Attach a shank 6 to the male threaded part 4a at the tip of the mandrel 4.
The shank 6 is attached to the tip of the mandrel 4 by externally fitting the threaded portion 6a of the shank 6, and the male threaded portion 5c of the support shaft 5 is screwed and externally fitted to the female thread 6b of the shank 6 to support it on the tip side of the shank 6. Supports the shaft 5. Then, the plug holder 1 is inserted into the small-diameter stepped portion 5a of the support shaft 5 protruding toward the distal end side of the shank 6, and held concentrically.

Next, after fitting one taper hole 2a of the plug body 2 into the tapered taper 1a of the plug holder 1, a tightening tool is inserted into the tool locking hole 3c of the tightening member 3, and the tightening tool is protruded toward the tip side of the plug body 2. The female threaded portion 3a of the tightening member 3 is screwed into the male threaded portion 5b of the support shaft 5.

By this screwing, the taper 3 of the tightening member 3 is inserted into the taper hole 2a on the distal end side of the plug body 2, and by further screwing, the taper hole 2a on the proximal side of the plug body 2 is inserted into the taper hole 2a on the proximal side of the plug holder 1.
The tapered hole 2a on the tip side is completely and tightly fitted into the taper 3a of the tightening member 3. As a result, the plug body 2 is held concentrically on the outer surfaces of the tapered holder 1 and the tightening member 3. Neither the tightening member 3 nor the support shaft 5 protrudes from the distal end side of the held plug body 2.

When the plug supported by the mandrel 4 is used for cold drawing of a pipe, the outer circumferential surface of the plug body 2 is set to be sufficiently long compared to the length required for the drawing process. Even if a so-called pulling phenomenon occurs in which the plug is pulled in the drawing direction, the predetermined drawing process is performed. Therefore, setting the initial position of the plug becomes easy.

Wear due to the use of the plug occurs on the tip side of the outer peripheral surface of the plug body 2, and not on the proximal side, so if the tip side is worn to the extent that the product dimensions become a problem, the worn side of the plug body 2 should be replaced. The plug body 2 can be reinstalled by turning it over to the mandrel side. That is, even if the plug body 2 is reversed, since the taper holes 2a, 2a on both sides are formed symmetrically, the plug body 2 can be placed on the outer surface side of the plug holder 1 and the tightening member 3 in the same way as before reversing. can be retained. This inverted use can double the service life of the plug body 2.

While the plug is in use, the pull-out force acting on the plug body 2 is received by the taper 3a of the tightening member 3, and the plug body 2 is reliably supported even when the pull-out force is strong. That is, since there is no thread in the part that receives the pulling force, and there is no stress concentration part, the problem that occurs when the threaded part is torn off does not occur. Therefore,
The plug body 2 made of ceramic can also be used without any problems.

When drawing large diameter pipes, there are cases where the opening at the tip of the raw pipe is an inner flange type, and the puller head is inserted into the raw pipe and locked to the inner flange (Japanese Patent Laid-Open No. 60-166118 Even in that case, there is nothing protruding from the tip end of the plug body 2, so even if the plug body 2 is set in the correct position in the die at the beginning of drawing, the plug body 2 will not touch the puller head. do not interfere with Therefore, the empty drawing length is suppressed as much as possible, and the product yield is improved.

The material of the plug body 2 is preferably carbide or ceramic from the viewpoint of wear resistance. Even if these materials with low resistance are used, there is almost no risk of breakage. However, this does not exclude the use of other materials such as carbon steel tool steel, alloy steel tool steel, etc.

The plug of the present invention is not limited to the above-mentioned embodiment, but for example, as shown in FIG. You can do it like this.

[Effect of idea]

The plug of the present invention allows the plug body to be used inverted, and there is no risk of breakage even if ceramic or the like with low resistance is used as the material, making it possible to greatly reduce tool consumption. In addition, since it can be used in reverse, the plug body has sufficient length and can handle the so-called pull-in phenomenon without any problems, making it easier to set the initial position of the plug and reducing the number of setup steps. can. Furthermore, since the length of the empty drawing part when drawing a large diameter pipe can be shortened as much as possible, the product yield can also be improved.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view showing the structure and installation state of an example of a plug embodying the present invention, Fig. 2 is a cross-sectional view showing another embodiment of the present invention, and Figs. 3 and 4 are views of a conventional plug. It is a sectional view showing a structure and an attached state. In the figure, 1...Plug holder, 1a...Taper, 2...Plug body, 2a...Tapered hole, 3...
...Tightening member, 3b...Taper, 4...Mandrel, 5...Support shaft, 6...Shank.

Claims (1)

[Scope of utility model registration request] A plug holder has a threadless taper formed at its tip, and the diameter increases toward the end face from the center in the longitudinal direction of the shaft, and the plug holder is tightly fitted into the tapered taper of the plug holder. An unthreaded taper hole with the same slope is formed, and a plug body is formed to have an equal outer diameter in the axial direction, and the plug holder is screwed into the unthreaded taper hole on the outer periphery of the plug body axis. A plug for cold drawing a pipe, characterized by comprising a tightening member formed with a threadless taper that fits tightly therein.