JP2631195B2 - Screw forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for forming a thread for connecting a valve, a thread for a pipe joint, a thread for connecting a pipe end, and the like.

[0002]

2. Description of the Related Art In general, a thread portion of a valve or a pipe joint is finished by cutting a base material formed by casting or the like with an NC machine tool or the like, and thereafter, finishing the finished mold. Is formed by performing a threading process on a threaded portion using a threading tip.

[0003] For example, as shown in FIG.
When forming the mold joint B, as shown in a partially enlarged sectional view of FIG. 7, a screw portion 11 of a prototype including a cylindrical portion 11a and a tapered portion 11b formed by prototype finishing (hereinafter referred to as a thread portion prototype). Threading is performed by using a threading tip, and a thread portion prototype 1 is formed along the outer line 12a of the screw 12.
By cutting off the one-dot chain line portion, the screw 12 is formed.

When the thread is cut by the conventional threading method as described above, the burrs 13 frequently occur near the tapered portion 11b of the threaded portion mold 11 or near the boundary between the cylindrical portion 11a and the tapered portion 11b. When observing the state of occurrence of the burrs 12, as shown in FIG. 7, the burrs 13 occur frequently near the intersection P between the outer shape line 12a of the screw 12 formed in a sectional view and the tapered portion 11b. It is practically almost impossible to eliminate burrs.

[0005] Therefore, in processing a threaded portion of a valve, a joint, or the like, a burr 13 is removed by forming a screw and then retreating a threading tip after the screw is formed, or performing a buffing process or the like after forming the screw. In order to remove the burrs 13 by applying the method. However, in the actual production of valves and fittings, 1/1000 to the number of products
With a probability of 1/2000, the burrs 13 that have an adverse effect as described later remain, and it is difficult to completely remove the burrs by the above-described deburring method.

If the burrs 13 remain on the threaded portions 12 of the valves and the joints, the worker may be injured when the sealing tape is wound in piping work, or the threaded portions may be damaged.
When the screw is tightened, seizure occurs in the screw portion, and it becomes difficult to disassemble the screw connection portion later, or the screw portion 12 is damaged when the screw connection portion is dissociated and leaks at the time of reconnection. .

[0007]

SUMMARY OF THE INVENTION According to the present invention, the above-mentioned problems in the conventional method of forming a screw for a valve or a joint, that is, the occurrence of burrs cannot be avoided. However, it is difficult to eliminate burrs completely even when deburring is performed.
The purpose of the present invention is to solve the problem of occurrence at a probability of about / 2000. Instead of removing the burrs generated after the formation of the screw, the burrs themselves do not occur when the screw is formed by the threading tip. Thus, a method for forming a screw is provided.

[0008]

According to a first aspect of the present invention, there is provided a screw member prototype 6 having a cylindrical portion 6a and a tapered portion 6b formed in a base material 5, and the tapered portion 6b is formed in a sectional view. After forming a groove 8 for cutting off the vicinity of the intersection P between the external line 7a of the screw 7 to be formed and the tapered part 6b in a ring shape, the screw 7 is formed on the screw part prototype 6 by a screw forming tip. This is a basic configuration of the present invention.

The invention according to claim 5 of the present invention is directed to a tapered portion 6 of the screw portion prototype 6 according to the invention of claim 1.
b, and a cylindrical portion 6a adjacent to the groove 8
The basic configuration of the present invention is to form a groove 8 for cutting off the vicinity of the apex Q of the thread of the screw 7 to be formed in a ring shape.

[0010]

[Function] A thread 7 is added to the thread prototype 6 by a threading tip.
Is formed, a large amount of burrs remain near the intersection P between the outer shape line 7a of the screw 7 to be formed and the tapered portion 6b in a sectional view. In the present invention, since the groove 8 is formed to preliminarily cut off the area where the burr of the thread part prototype 6 is likely to remain, there is no burr generated when the screw is formed by the threading tip. Become.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process diagram of a thread forming method according to the present invention, wherein 1 is a base material forming step, 2 is a prototype forming step, 3 is a grooving step, and 4 is a thread cutting step.

In a base material forming step 1, a metal raw material is formed by forging, casting, or the like into a shape substantially similar to the outer shape of a product. The base material (for example, a valve box or a joint member) 5 formed in the base material forming step 1 is subsequently machined in a prototype forming step 2, and in the joint member or the like, a through hole is formed or a screw is formed. Is cut into a cylindrical shape having a predetermined outer shape and length, and a prototype 6 of the screw portion is formed.

[0013] After the thread portion prototype 6 is formed in the prototype forming step, a groove is formed in a predetermined position of the thread portion prototype 6 in a grooving step 3. FIG. 2 is a partially enlarged cross-sectional view of the thread part prototype 6 of the joint or the valve body.
Denotes a cylindrical portion, 6b denotes a tapered portion, 7 denotes a screw cut and formed by a threading tip, and 7a denotes an outline of the screw.

In the grooving step 3, a plurality of triangular grooves 8 as viewed in cross section are fixed on the tapered surface 6b of the threaded portion mold 6 by a grooving tip, as shown by a dashed line in FIG. It is formed in a ring shape at intervals. That is, in a cross-sectional view, the intersection P between the external line 7a of the screw 7 and the tapered portion 6b
Are cut off in a ring shape as grooves 8a, 8b, 8c having the tapered portion 6b of a certain length as the hypotenuse.

In this embodiment, the tapered portion 6b
Although the three grooves 8a, 8b, and 8c are formed in a ring shape in FIG. 3, the grooves 8 may be formed only at the uppermost position where the adverse effect of the remaining burrs is greatest.

Further, in this embodiment, the groove 8 is a triangular groove having a fixed length of the tapered surface portion 6b as a hypotenuse in a sectional view. However, as shown in FIG. It is also possible to form a rectangular groove 8 having a side of a taper part 6b of a fixed length including an intersection P between the part 6b and the outline 7a of the screw.

Further, in the present embodiment, the groove 8 is formed in the tapered portion 6b.
Only in the groove 8 of the tapered portion 6b.
Alternatively, a groove 8 may be provided in the cylindrical portion 6a close to the tapered portion 6b to cut off the vicinity including the thread apex Q of the screw 7. In addition, the width of the groove 8 is preferably about 1/5 to 1/3 of the screw pitch, and the depth of the groove 8 is preferably about 1/8 to 1/4 of the thread height. If the width and the depth of the groove 8 are larger than the above values, the smoothness of the screwing of the threaded portion is reduced.

When the formation of the groove 8 in the grooving step 3 is completed, in a thread cutting step 4, a screw 7 having a predetermined pitch and thread is formed using a threading tip.

4 and 5 show a partially enlarged cross section of the screw 7 formed according to the present invention. FIG. 4 shows the screw 7 formed by the manufacturing method of FIG. 2 and FIG. 5 shows the screw 7 formed by the manufacturing method of FIG. It shows. As is clear from FIGS. 4 and 5, the screw 7 according to the present invention is slightly different from the conventional screw 7 in the shape of the first three threads and the shape of the screw 7 in the prior art. In the grooving step 3, the vicinity of the intersection point P between the external line 7a of the screw 7 and the tapered portion 6b where burrs tend to remain when the tip is threaded is cut off in advance. Will never occur.

In the embodiments shown in FIGS. 1 to 5, a so-called straight external thread is formed, but it is a matter of course that the external thread may be a tapered thread. In each of the above embodiments, the outer thread is formed. However, it is needless to say that the inner thread may be formed. If the formed screw is the inner thread, the tapered portion 6b may be formed at the outer end. The tapered portion gradually increases in diameter toward the portion.

[0021]

According to the present invention, a groove cutting step is provided before the thread cutting step, and the intersection point P of the thread outline and the tapered part of the thread part prototype where burrs are likely to occur during threading with the tip is provided.
Is cut off from the pre-screws prototype. As a result, no burrs remain on the threaded part in the threading process using the tip, eliminating the need for complicated and accurate deburring as before, and tightening due to the remaining burrs. There is no occurrence of seizure of the screw at the time. In addition, in the present invention, a groove forming step is required in the process of forming a screw, but a complicated and highly accurate deburring step is not required as in the past, so that the screw forming cost does not increase. The present invention has excellent practical utility as described above.

[Brief description of the drawings]

FIG. 1 is a process diagram of forming a screw according to the present invention.

FIG. 2 is a partially enlarged cross-sectional view showing a state of formation of a groove in a grooving step of the present invention.

FIG. 3 is a partially enlarged cross-sectional view showing another groove formation state in a grooving step.

FIG. 4 is a partially enlarged sectional view showing an example of a screw formed according to the present invention.

FIG. 5 is a partially enlarged sectional view showing another example of a screw formed according to the present invention.

FIG. 6 shows an example of a conventional T-type threaded joint.

FIG. 7 is a partially enlarged cross-sectional view showing a state of formation of a thread portion of a conventional T-type threaded joint.

[Explanation of symbols]

1 is a base material forming step, 2 is a prototype forming step, 3 is a grooving step, 4 is a thread cutting step, 5 is a base material, 6 is a thread part prototype, 6
a is a cylindrical portion, 6b is a tapered portion, 7 is an external thread, 7a is an external line of the screw, 8 is a groove, P is an intersection between the external line of the screw 7 and the tapered portion, and Q is a screw of a screw formed in the cylindrical portion. Mountain peak.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-86821 (JP, A) JP-A-55-110984 (JP, A) JP-A-2-100821 (JP, A) JP-A 63-86 312107 (JP, A) Japanese Utility Model 1-78716 (JP, U) Japanese Utility Model 7-18015 (JP, U)

Claims (5)

(57) [Claims] 1. A thread part prototype (6) having a cylindrical part (6a) and a tapered part (6b) is formed on a base material (5), and is formed in the tapered part (6b) in a sectional view. After forming a groove (8) for cutting off the vicinity of the intersection P between the external line (7a) of the screw (7) and the tapered portion (6b) in a ring shape, the screw (7) is screwed into the screw part prototype (6) using a screw cutting tip. 7) A method of forming a screw, characterized by forming 2. The screw forming method according to claim 1, wherein the groove has a triangular shape having a tapered portion having a fixed length including the intersection point P as a hypotenuse in cross section. 3. The screw forming method according to claim 1, wherein the groove (8) is formed in a quadrangular shape having one side of a taper portion (6b) having a fixed length including the intersection point P in a cross-sectional view. 4. The screw according to claim 1, wherein the groove (8) is provided only at a portion including the intersection point P located at the uppermost position of the tapered portion (6b). Method 5. A thread part prototype (6) having a cylindrical part (6a) and a tapered part (6b) is formed on a base material (5), and is formed in the tapered part (6b) in a sectional view. A groove (8) for cutting off the vicinity of the intersection P between the external line (7a) of the screw (7) and the tapered portion (6b) is formed in a ring shape, and the cylindrical portion (6a) close to the tapered portion (6b). To
A groove (8) for cutting off the vicinity of the apex Q of the thread of the screw (7) to be formed in a sectional view is formed in a ring shape.
Screw (7) to screw part prototype (6) by screw forming tip
Forming a screw, characterized by forming