JPH0514122B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in screws and methods for manufacturing screws. The screw of the present invention is most suitable as a terminal screw for attaching an electrical terminal or the like.

[Prior Art] Conventionally, a screw for attaching an electric terminal has a head having a groove or a positive-shaped recess on one end surface, a shaft protruding from the center of the opposite surface of the head, and having a thread on the outer peripheral surface. It is made up of. With conventional terminal screws, the threads formed on the outer circumferential surface of the shaft are continuous, so there is no proper guideline for spacing when inserting electrical terminals. I often fall off.
For this reason, extra time may be required to connect the electrical terminals, such as re-screwing the screws into the nut portions.

[Problems Solved by the Present Invention] The present invention provides a screw that does not have the above-mentioned problems, and provides a method for manufacturing the screw with high productivity without increasing the number of steps compared to conventional screws. The purpose is to

[Means for Solving the Problems] The screw of the present invention includes a head and a shaft that protrudes from the center of one end of the head and has a thread on its outer circumferential surface, wherein the shaft is connected to the head. A main threaded portion having threads on the outer peripheral surface from the side toward the tip, a neck portion having an outer diameter smaller than the outer diameter of the main threaded portion, and an outer diameter and pitch that are approximately the same as the outer diameter of the main threaded portion. It is characterized by being comprised of a secondary thread portion with a high thread height.

The method for manufacturing a screw of the present invention includes a head made of a bar material, a main shaft protruding from the center of one end of the head, and a subordinate shaft part coaxial with the tip of the main shaft and having a smaller outer diameter than the main shaft. a forging step of forming an intermediate; at least a first portion of the outer peripheral surface of the main shaft portion of the obtained intermediate body near the slave shaft portion; and a first portion of the outer peripheral surface of the slave shaft portion that is constant in the axial direction from the main shaft portion side; The second part on the distal end side, separated by a distance, is rolled with the first rolling mold and the second part with a second rolling mold whose peaks and valleys are steeper than the first rolling mold. , a rolling step of forming a threaded portion having substantially the same outer diameter on the first portion and the second portion are sequentially performed.

Incidentally, both the screw of the present invention and the method of manufacturing the screw of the present invention are related to a manufacturing method and a product obtained by the manufacturing method, and the two are closely related.
Therefore, hereinafter, both will be described as the present invention.

The screw of the present invention is composed of a head and a shaft. The head is the same as the head of a conventional screw or bolt, and may be a plus/minus screw including both a minus screw having a single groove on one end surface and a plus screw having a cross groove on one end surface.
Further, the outer peripheral surface of the head may be of a hexagonal, square or other shape like a bolt, or the bolt may have a regular polygonal recess on the upper end surface.

The threaded portion that characterizes the screw of the present invention is composed of a main threaded portion, a neck portion, and a secondary threaded portion from the head toward the distal end.

The main thread part corresponds to a conventional thread part, and at least a metric thread, an inch thread, or the like is formed on the outer peripheral surface of the main thread near the neck. Note that the threaded portion may be a single-thread thread or a multi-thread thread. Further, the shape of the thread may be trapezoidal or may have various other conventionally known thread shapes.

The neck portion is a portion having an outer circumferential diameter smaller than at least the outer circumferential diameter including the top of the crest of the main thread portion. The outer peripheral surface of this neck is not threaded. Note that this neck portion does not engage with the thread of the nut into which the main thread portion is screwed. That is, it has an outer diameter smaller than the inner diameter of the screw hole of the nut. It is also necessary that the axial width of the neck be greater than the axial thickness of the nut.

The secondary thread portion is formed with a thread having approximately the same outer diameter and pitch as the main thread portion. However, the height of the thread is higher than that of the main thread.
In terms of the shape of the thread, the ridges and valleys of the slave shaft are steeper than those of the thread of the main shaft. Now, in the cross-sectional shape of the thread, if we consider the apex angle of the thread formed at the intersection of two planes including the slopes on both sides, the apex angle of the thread of the slave shaft is the same as that of the thread of the main shaft. is small compared to the apex angle of The degree of this smallness is preferably 5 to 15 degrees, more preferably 7 to 13 degrees, compared to the apex angle of the thread of the main shaft portion. Specifically, when the thread of the main shaft portion is a metric thread, the apex angle is 60 degrees. Therefore, in this case, the apex angle of the thread of the slave shaft portion is preferably about 50 degrees. In addition, in the case of an inch thread, the apex angle of the thread on the main shaft is 55 degrees. In this case,
The apex angle of the thread of the slave shaft portion is preferably about 45. still,
The width in the axial direction of the thread of the main shaft portion can be changed as appropriate depending on the purpose of use, but it is necessary to have at least a width for the thread to make one revolution. Further, depending on the use, the outer circumferential surface of the main shaft portion on the head side may not be threaded.

The nominal diameter of the screw of the present invention is determined by the thread of the main thread. That is, metric threads and inch threads can be referred to by the nominal diameter of the inch thread.

As the nut used in the screw of the present invention, a conventional nut that matches the nominal diameter of the main thread portion can be used as is. Note that the thread on the slave shaft has a smaller apex angle than the thread on the main shaft. In other words, the mountains are thin and sharp. Therefore, when screwing a conventional nut onto the thread of the slave shaft, it may feel a little loose, but
A nut can be screwed onto the slave shaft. The nut part is screwed together, and when the nut part completely reaches the neck part as it approaches the head part, the screw thread between the nut and the thread of the slave shaft part is released, and the nut is fitted into the neck part.
That is, the nut can be moved in the axial direction without rotating the nut. Further, when the nut is screwed toward the head side, the thread on the main shaft portion and the thread on the nut are threaded together, resulting in a normal threaded engagement. It is assumed that this nut corresponds to the nut portion of a conventional electrical terminal. The main shaft part of the screw of the present invention is completely and deeply screwed into the nut part and then gradually loosened, the thread of the main shaft part and the thread of the nut part are disengaged, and the neck part of the screw engages with the nut part. Loosen the screw until it is closed. In this state, the end face of the nut and the bottom face of the screw should be set so that there is enough space to insert the electrical terminal. Therefore, the operator who turns the screw can stop the rotation of the screw thread in this state. However, the thread of the slave thread part,
Due to the threads of the nut, the screw does not fall out of the nut portion, and the screw remains held in the nut portion. Therefore, the inconvenience of the screw falling out from the nut part is eliminated.

The screw manufacturing method of the present invention is basically performed in the same steps as the conventional screw manufacturing method. That is, an intermediate body consisting of a head and a shaft is manufactured from a coiled wire through a forging process. Next, a thread is formed on the shaft portion of the obtained intermediate body using a rolling machine.

In the forging process, in the conventional screw manufacturing method, shaft portions having the same outer diameter in the axial direction are formed. In the present invention, the shaft part has a main shaft part having the same outer diameter as the shaft part of a conventional screw, and a stepped thread part having a subordinate shaft part having an outer diameter smaller than the main shaft part on the distal end side opposite to the head. It is formed. The different proportions of the outer diameters of the main shaft part and the slave shaft part depend on how the top of the thread of the slave shaft part is raised in the outer circumferential direction when forming a thread in the next rolling process. That is, in the next rolling step, if the rise of the outer circumferential diameter of the top of the thread of the slave shaft portion is small, the outer circumferential diameter of the slave shaft portion cannot be reduced. In normal cases, the outer circumferential diameter of the slave shaft portion is approximately 85 to 95% of the outer circumferential diameter of the main shaft portion.

Next, the rolling process uses a first rolling die that forms threads on the outer circumferential surface of the main shaft portion, and a second rolling die that forms threads only on the outer circumferential surface of the leading end side of the slave shaft portion.
Usually, the first rolling die and the second rolling die are integrally formed, and are configured as a rolling die having a groove between them corresponding to the width of the neck of the threaded portion to be obtained. The second rolling die has steeper slopes forming mountains and valleys than the second rolling die. Also, the second
The surface connecting the tops of the crests of the rolling molds is higher than the surface connecting the tops of the crests of the first rolling mold. The pitches of the peaks and valleys are the same in both the first rolling die and the second rolling die.

The rolling method is the same as the conventional rolling method, with 1 on both sides.
A pair of rolling dies is arranged, and while the shaft part (main shaft part and slave shaft part) of the intermediate body is held between both rolling dies, the pair of rolling dies are slid in opposite directions to form a thread on the threaded part. It is something that forms.

In the method for manufacturing the screw of the present invention, the screw of the present invention can be manufactured in two steps, a heading process and a rolling process, as in the conventional method, and there is no need to add any special process.

[Effects of the Invention] The screw of the present invention has a main thread part and a secondary thread part in its threaded part, and has a neck part between the two parts. Therefore, when the screw of the present invention is screwed into a nut, the screw and nut do not screw together at the neck portion of the screw portion of the present invention between the main thread portion and the secondary thread portion. In other words, the configuration is such that it can be seen that a certain distance has opened between the seat surface of the screw and the end surface of the nut. For this reason, when it is necessary to leave a certain distance between the end of the nut and the seat of the screw, as in the case of electrical terminal screws, this distance can be achieved very reliably. Furthermore, since the screw and nut are once unthreaded at the neck, it is possible to prevent the screw and nut from falling out or falling off completely.

In addition, in the method for manufacturing the screw of the present invention, the screw of the present invention can be manufactured using the heading and rolling processes that are basically the same as conventional ones, and the screw of the present invention having a complicated shape can be manufactured without increasing the number of manufacturing steps. can be manufactured.

[Embodiment] FIG. 1 shows a side view of a screw according to an embodiment of the present invention. This screw is made by Shinchiyu and is composed of a head 1, a main shaft 2, a neck 3, and a slave thread 4. The head 1 has a height of 2.3 mm, an outer diameter of 6.0 mm, and a recess 11 for use as a Phillips/minus screw at its upper end. The height of the main shaft part 2 is 2.5 cm, close to the head.
Upper shaft 2 without threads with an outer diameter of 3.04 mm
1 and a main screw portion 22 having a height of 4.0 mm and an outer diameter of 3.36 to 3.47 mm at the top. The apex angle of the thread of the main thread portion 22 is 60 degrees, and the pitch of the thread is 0.6 mm.
The neck portion 3 has a height of 2.5 mm and an outer diameter of 2.80 mm. The neck portion 3 is not threaded. Slave shaft part 4
is 1.5 mm in height, and the outer diameter of the top of the thread is
It is 3.36-3.47mm. The apex angle of the thread of the secondary thread part 4 is 50 degrees, and the pitch of the thread is 0.6 mm.

The screw in this example has a secondary thread part 4 and a main thread part 2.
In both parts of 2, conventional nuts can be screwed together. Moreover, the threaded connection with the nut part is released in the neck part 3, so that it can be moved in the axial direction.

Next, a method for manufacturing a screw according to an embodiment will be explained. First, the intermediate shown in FIG. 2 was manufactured using a cold heading machine from a wire rod (coil) made of thin wire in the same manner as in the past.
The head 10 of this intermediate body is the same as the head of the embodiment. Also, the main shaft part 20 has an outer diameter of 3.04 mm and a height of 6.5 mm.
mm, and the slave shaft portion 30 has an outer diameter of 2.80 mm and a height of 4 mm. Next, the outer circumferential surface of the portion near the tip of the main shaft portion 20 and the outer circumferential surface of the portion near the tip of the slave shaft portion 30 are formed by a rolling die, a plan view of a portion of which is shown in FIG. A thread was formed on the surface. This rolling die is the first
Rolled portion 5, second rolled portion 6 and its first rolled portion 5
and a groove 7 with a width of 2.5 mm formed between the second rolled portion 6
have. The pitch of the first rolled part 5 and the second rolled part 6 is 0.6 mm, the peak angle of the peak of the first rolled part 5 is 60 degrees, and the peak angle of the peak of the second rolled part 6 is 50 degrees. . The bottom portions of the valleys of the rolling mold are at approximately the same position in both the first rolled portion 5 and the second rolled portion 6, and the height of the peaks is such that the second rolled portion 6 is higher than the first rolled portion 5. ing. The manufacturing method is the same as the conventional manufacturing method, and only the rolling die is different from the conventional rolling die. That is, by arranging two rolling molds shown in FIGS. 3 and 4 so that their mold surfaces correspond to each other, sandwiching the shaft portion of the intermediate body between the warps, and shifting both rolling molds in opposite directions, Threads are formed on the outer peripheral surface of the threaded portion.

[Brief explanation of the drawing]

Fig. 1 is an elevational view of a screw that is a typical embodiment of the present invention, Fig. 2 is an elevational view of an intermediate used in manufacturing the screw of Fig. 1, and Figs. 3 and 4 are The rolling mold used in the method of manufacturing the screw shown in FIG. 1 is shown, FIG. 3 is a plan view of the main part thereof, and FIG. 4 is a sectional view of the main part thereof. 1...Head, 2...Main shaft, 3...Neck, 4...
...Following screw part.

Claims (1)

[Scope of Claims] 1. A screw consisting of a head and a shaft protruding from the center of one end of the head and having a thread on its outer circumferential surface, wherein the shaft extends outward from the head side toward the tip. A main threaded portion with threads on its surface, a neck portion with an outer diameter smaller than the outer diameter of the main threaded portion, and a secondary thread having a high thread height with an outer diameter and pitch that are approximately the same as the outer diameter of the main threaded portion. A screw comprising a threaded portion. 2. The apex angle of the thread formed by the plane including the slopes on both sides of the thread of the secondary thread part is 5 to 5 to
The screw according to claim 1, which is 15 degrees smaller. 3. A forging process in which an intermediate body is formed from a bar material, consisting of a head, a main shaft protruding from the center of one end of the head, and a subordinate shaft that is coaxial with the tip of the main shaft and has a smaller outer diameter than the main shaft. , at least a first portion of the outer circumferential surface of the main shaft portion of the obtained intermediate body that is close to the slave shaft portion, and a first portion of the outer circumferential surface of the slave shaft portion that is on the tip side that is a certain distance away from the main shaft portion side in the axial direction. The first part is rolled with a first rolling mold, the second part is rolled with a second rolling mold whose peaks and valleys are steeper than the first rolling mold, and the first part is rolled with a second rolling mold. A method for manufacturing a screw, comprising sequentially performing a rolling step of forming thread portions having substantially equal outer diameters on the second portion. 4. The method for manufacturing a screw according to claim 3, wherein the first rolling die and the second rolling die are integrally configured with a constant interval between them.