JP2005074514A - Method for forming screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a screw with which the production efficiency of the screw is improved by simply forming the screw. <P>SOLUTION: This screw forming method for forming the screw from a columnar body 10, is contained of a cutting-step S10 for forming by cutting planes 11 positioned at the inner side from the cross sectional circumference of the columnar body 10 to mutually faced portions in the cross section; a pressing-step S11 for press-forming the screw grooves to these side faces by interposing the columnar body 10 with one pair of metal molds 20 from the side faces except the planes 11; and a releasing-step S12 for releasing the columnar body 10 from the metal mold 20. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a screw forming method for forming a screw from a cylindrical metal or the like.

Conventionally, when a screw made of metal is formed, a threading tool such as a die is used (for example, see Non-Patent Document 1).
FIG. 8 is an explanatory diagram for explaining a conventional screw forming method of forming a screw using a die.
A hole 901 is formed in the die 900, and a female thread groove is formed on the inner periphery of the hole 901.

When the cylindrical body 10 made of a metal molded product is processed to form a screw, the cylindrical body 10 is inserted into the hole 901 of the die 900 from its head while the die 900 is rotated. At this time, the thread groove on the inner periphery of the hole 901 of the die 900 is pressed against the side surface of the cylindrical body 10 and cuts the side surface according to the rotation.
As a result, a thread groove of a male screw is formed on the side surface of the cylindrical body 10. That is, the cylindrical body 10 is formed as a male screw.
"Die processing technique", [online], [Search August 26, 2003], Internet <URL: http://village.infoweb.ne.jp/~yamaca/jisaku2/dice.htm>

However, the screw forming method of Non-Patent Document 1 has a problem in that the screw production efficiency is poor because the troublesome work of rotating the die requires time and cost.
The present invention has been made in view of such a problem, and an object of the present invention is to provide a screw forming method in which screws are simply formed to improve screw production efficiency.

  In order to achieve the above object, a screw forming method according to the present invention is a screw forming method for forming a screw from a cylindrical workpiece, and the workpiece is formed with respect to a side portion of the workpiece. An inner surface forming step for forming inner surfaces located on the inner side of the cross-section circumference of the cross-section at opposite portions of the cross-section, and the workpiece is sandwiched between a pair of molds from the side surface excluding the inner surface, And a press step for press forming a screw groove. For example, in the inner surface forming step, a side portion of the workpiece is cut to form a flat inner surface.

As a result, since the screw groove is press-formed, it is possible to easily form a screw without taking time and effort in troublesome work such as rotating a die as in the conventional example. Can be improved. Further, after forming the inner surface located on the inner side from the cross-sectional circumference of the workpiece, the workpiece is sandwiched between a pair of molds from the side surface excluding the inner surface, and a screw groove is press formed. The burr does not protrude outward from the circumference along the arc of the cross section of the workpiece, and the adverse effect of the burr on the screw tightening can be suppressed, and a screw that can be smoothly tightened or removed can be formed.
The present invention can also be realized as a thread groove forming method or a screw formed from a cylindrical workpiece.

  INDUSTRIAL APPLICABILITY The screw forming method of the present invention produces an effect that screws can be easily formed to improve screw production efficiency.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flowchart showing a screw forming method according to an embodiment of the present invention.
The screw forming method according to the present embodiment is a method in which a screw is simply formed to improve screw production efficiency, and a cylindrical body 10 which is a workpiece is cut and a side portion of the cylindrical body 10 is cut. A cutting step S10 for forming the flat surface 11 on the surface, a pressing step S11 for forming a screw groove on the cylindrical body 10 by pressing, and an opening step S12 for releasing the cylindrical body 10 from the mold 20 used for the pressing. Is included.

In the cutting step S <b> 10, the flat surface 11 is formed on the side portion of the cylindrical body 10 by cutting only two side portions of the cylindrical body 10. Such two planes 11 are located on the inner side of the cross-sectional circumference of the cylindrical body 10, are elongated along the axial direction of the cylindrical body 10, and are substantially opposed to each other in a cross section substantially perpendicular to the axial direction of the cylindrical body 10. It is formed in the site.
In the press step S <b> 11, the cylindrical body 10 is sandwiched and pressed by a pair of molds 20 from the side surface excluding the flat surface 11.

The mold 20 is formed with a groove portion 21 having a semicircular cross section and having an internal thread formed on the inner surface. When pressing the cylindrical body 10 with the mold 20, the cylindrical body 10 is fitted into the respective groove portions 21 of the pair of molds 20, and the surfaces on which the groove portions 21 of the pair of molds 20 are formed are brought into contact with each other. The
In the release step S12, the respective molds 20 are moved in the direction opposite to the direction when pressed in the press step S11, the respective molds 20 are separated from each other, and the cylindrical body 10 is opened.

Thereby, the thread groove of a male screw is formed by press work in the side part except the plane 11 of the cylindrical body 10, As a result, the cylindrical body 10 is formed as a screw.
Here, in this Embodiment, the bad influence by a burr | flash can be suppressed by including cut step S10. That is, when the thread groove is formed by pressing without providing the flat surface 11 to the cylindrical body 10, the cylindrical body 10 may not function as a screw due to burrs generated by the pressing.

FIG. 2 is an explanatory diagram for explaining a state in which a screw groove is formed by press working without providing a plane with respect to the cylindrical body 10.
As shown in FIG. 2, when a cylindrical body 10 having no flat surface is sandwiched between and pressed by a pair of molds 20, screw grooves are formed on the side portions of the cylindrical body 10, while On the side portion of the cylindrical body 10 corresponding to the abutting surface, the constituent members of the cylindrical body 10 pushed by the formation of the screw grooves become burrs 12 and are generated in a streak shape.

FIG. 3 is a cross-sectional view showing a state in which burrs 12 are generated during press working.
As shown in FIG. 3, even if the mold 20 is abutted during press working, there is a gap between the mold 20 and the mold 20, and the constituent members of the cylindrical body 10 enter the gap, and the above-described burrs are formed. 12 is formed.
If there is such a burr 12 in the cylindrical body 10 formed as a screw, even if the cylindrical body 10 is to be tightened into a screw hole in which a thread groove of a female screw is formed, the burr 12 may be obstructed and tightened. It is not possible.

However, in the present embodiment, by providing the flat surface 11 on the cylindrical body 10 in the cut step S10, it is possible to prevent the adverse effects due to burrs as described above.
FIG. 4 is an explanatory diagram for explaining the state of occurrence of burrs in the press step S11 in the present embodiment.
As shown in FIG. 4A, in the pressing step S <b> 11, the cylindrical body 10 is sandwiched between a pair of molds 20 from the side surface of the cylindrical body 10 except the plane 11 and pressed.

When pressed in this way, as shown in FIG. 4 (b), the structural member of the cylindrical body pushed by the formation of the screw groove by the press extends along the inner surface of the groove portion 21 of the mold 20 from the peripheral portion of the flat surface 11. The protruding part becomes the burr 13. Such a burr 13 is inside the circumference along the arc of the cross section of the cylindrical body 10.
FIG. 5 is a perspective view showing the external appearance of the screw (cylindrical body 10) formed as described above.

As described above, the burr 13 is generated in the present embodiment. However, since the burr 13 is located on the inner circumference along the arc of the screw cross section, even if the screw is inserted into the screw hole and tightened, the burr 13 is There is no contact with the thread groove of the screw hole. That is, the burr 13 does not adversely affect the screw tightening.
Therefore, the screw formed by the screw forming method in the present embodiment can be tightened or removed smoothly.

As described above, in the present embodiment, by forming the screw groove by press working, it is possible to easily form a screw without taking time and effort for troublesome work such as rotating a die as in the conventional example. As a result, the production efficiency of screws can be improved.
Moreover, in this Embodiment, after forming the plane 11 located inside from the cross-sectional periphery of the cylinder 10 in the side surface of the cylinder 10, a pair of metal mold | dies 20 so that the plane 11 may be located in a butt | matching surface. Since the screw groove is formed by press working, the burr 13 by the press work does not jump out from the circumference along the circular arc of the cross section of the cylindrical body 10, and the adverse effect on the screw tightening by the burr is suppressed. be able to.

(Modification 1)
Next, a first modification of the present embodiment will be described.
In the above embodiment, the flat surface 11 is provided in the cylindrical body 10 in the cut step S10. However, in the screw forming method according to this modification, a concave groove is provided in the cylindrical body 10 instead of the flat surface.
FIG. 6A is a perspective view showing the external appearance of the cylindrical body 10 provided with a concave groove.
In the cut step S10 according to this modification, four concave grooves 14 along the axial direction are cut and formed on the cylindrical body 10 so that the concave grooves 14 are arranged at equal intervals in the cross section of the cylindrical body 10. . The inner surface of the concave groove 14 is formed in an arc shape.

FIG. 6B is an explanatory diagram for explaining a state in which a screw groove is formed by pressing in the cylindrical body 10 provided with the concave groove 14.
In the press step S <b> 11, the cylindrical body 10 provided with the concave grooves 14 as described above is sandwiched between the pair of molds 20 so that the two concave grooves 14 are positioned on the abutting surfaces of the pair of molds 20. Press.

  Also in such a modification, a screw can be easily formed by forming a screw groove by press working as in the above-described embodiment, and as a result, the production efficiency of the screw can be improved. . In addition, after forming the concave groove 14 whose surface is located on the inner side from the cross-sectional circumference of the cylindrical body 10 on the side of the cylindrical body 10, the pair of molds 20 is arranged so that the concave groove 14 is positioned on the abutting surface. Since the screw grooves are formed by press working together, the burrs produced by the press work do not jump out of the circumference along the arc of the cross section of the cylindrical body 10, and the adverse effect on the screw tightening by the burrs can be suppressed. it can.

  Furthermore, in this modification, by forming the four concave grooves 14, the burrs generated by increasing the escape space of the constituent members of the cylindrical body 10 at the time of press working can be dispersed, and the adverse effects due to the burrs can be further suppressed.

(Modification 2)
Next, a second modification example of the present embodiment will be described.
In the above embodiment, the flat surface 11 is provided on the cylindrical body 10 in the cutting step S10. However, in the screw forming method according to the present modification, the hollow cylindrical body is provided with a recess.
FIG. 7A is a perspective view showing an appearance of a cylindrical body provided with a recess.
In the cut step S10 according to the present modification, two hollow recesses 15 along the axial direction of the hollow cylindrical body 10a made of a metal plate are formed in a surface arc shape toward the center of the cross section of the cylindrical body 10a. It is formed to be concave.

FIG.7 (b) is sectional drawing which shows AB cross section of Fig.7 (a) in the cylindrical body 10a.
As shown in FIG. 7 (b), the columnar body 10a is integrally formed hollow from a metal plate.
Here, when the concave portion 15 as described above is provided in the cylindrical body 10a, for example, the cylindrical body 10a is sandwiched between a pair of pressing members, and the side wall of the cylindrical body 10a is recessed inward.

FIG.7 (c) is explanatory drawing for demonstrating a mode when a thread groove is formed by press work with respect to the cylindrical body 10a in which the recessed part 15 was provided.
In the press step S11, the cylindrical body 10a provided with the recess 15 as described above is sandwiched and pressed between the pair of molds 20 so that the two recesses 15 are positioned on the abutting surfaces of the pair of molds 20. .

  Since the side wall of the recess 15 in the cylindrical body 10a is formed in an arc shape, the side wall of the screw (cylindrical body 10a) formed in this way has elasticity. That is, since the screw has elasticity in a direction substantially perpendicular to the arrangement direction of the pair of recesses 15 in the cross section (the direction of the double-headed arrow in FIG. 7C), when tightening the screw into the screw hole, The side surface can press the inner peripheral surface of the screw hole to increase the tightening strength.

Also in this modification, as in the above-described embodiment, by forming the screw groove by press working, the screw can be easily formed, and as a result, the production efficiency of the screw can be improved. . Further, after forming the concave portion 15 whose surface is located on the inner side from the cross-sectional circumference of the cylindrical body 10a on the side portion of the cylindrical body 10a, the pair of molds 20 are brought together so that the concave portion 15 is positioned on the abutting surface. Since the thread groove is formed by press working, the burr produced by the press work does not jump out of the circumference along the arc of the cross section of the cylindrical body 10a, and the adverse effect on the screw tightening by the burr can be suppressed.
In addition, in this Embodiment and the modification, although the cylindrical bodies 10 and 10a were made into the metal, it cannot be overemphasized that it may be a resin molded product.

  INDUSTRIAL APPLICABILITY The screw forming method according to the present invention has an effect that a screw can be easily formed to improve screw production efficiency, and is useful in the field of the machine industry.

It is a flowchart which shows the screw formation method in embodiment of this invention. It is explanatory drawing for demonstrating a mode when a screw groove is formed by press work, without providing a plane with respect to a cylindrical body same as the above. It is sectional drawing which shows the state which the burr | flash has generate | occur | produced at the time of press work same as the above. It is explanatory drawing for demonstrating the generation | occurrence | production state of the burr | flash of a press step same as the above. It is a perspective view which shows the external appearance of the screw formed by the method same as the above. It is a perspective view which shows the external appearance of the cylindrical body provided with the ditch | groove which concerns on the modification same as the above. It is a perspective view which shows the external appearance of the cylindrical body provided with the recessed part which concerns on the other modification same as the above. It is explanatory drawing for demonstrating the conventional screw formation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Cylindrical body 11 Plane 20 Mold 21 Groove S10 Cut step S11 Press step S12 Release step

Claims (8)

A screw forming method for forming a screw from a cylindrical workpiece,
An inner surface forming step for forming inner surfaces located on the inner side of the cross-sectional circumference of the workpiece with respect to the side portion of the workpiece, at portions facing each other in the cross-section,
A screw forming method comprising: a pressing step of sandwiching the workpiece from a side surface excluding the inner surface with a pair of molds and press-forming a screw groove on the side surface. In the inner surface forming step,
The screw forming method according to claim 1, wherein a side portion of the workpiece is cut to form a flat inner surface. In the inner surface forming step,
The screw forming method according to claim 1, wherein a side portion of the workpiece is cut to form an inner surface in an arc shape. The workpiece is formed hollow from a metal plate,
In the inner surface forming step,
The screw forming method according to claim 1, wherein a side portion of the workpiece is pressed to form an inner surface in an arc shape. A thread groove forming method for forming a thread groove on a cylindrical workpiece,
An inner surface forming step for forming inner surfaces located on the inner side of the cross-sectional circumference of the workpiece with respect to the side portion of the workpiece, at portions facing each other in the cross-section,
A method for forming a screw groove, comprising: a step of pressing the workpiece from a side surface excluding the inner surface with a pair of molds, and press-forming a screw groove on the side surface. In the inner surface forming step,
The thread groove forming method according to claim 5, wherein a side portion of the workpiece is cut to form a flat inner surface. A screw formed from a cylindrical workpiece,
An inner surface located on the inner side of the cross-sectional circumference of the workpiece is formed at a portion facing each other in the cross-section with respect to a side portion of the workpiece, and the workpiece is formed from a side surface excluding the inner surface. A screw characterized in that it is formed by sandwiching between a pair of molds and press forming a screw groove on the side surface. The screw according to claim 7, wherein the inner surface is planar.

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