JPH0538411U - Pre-wound point screw - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a pre-wound point screw that can be easily rolled. [Structure] This pre-wound point screw 11 includes a rotating means 12
A head portion 13 of arbitrary shape provided with, and a parallel thread portion 14 in which parallel threads 14a are formed on the outer periphery of the parallel shaft portion 15,
Tapered screw part 1 formed at the tip of this parallel screw part 14
6, the taper screw portion 16 is formed by rolling a screw material having a hole at the tip to form an annular cylindrical portion, and the end face is substantially closed in a manner of covering the hollow portion 16c hollowed out inside. While being plastically deformed to the tapered tapered cylinder 16a, a tapered thread 16b continuous with the parallel thread 14a is formed on the outer circumference of the tapered cylinder 16a.
Plastic deformation of the taper cylinder 16a and each thread 14a, 16
b is rolled at the same time.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a pre-wound point screw.

[0002]

[Prior Art]

 The pre-wound point screw 1 of this type has a hexagonal head 3 having a rotating means 2 at the top as shown in FIG. 4 and a parallel shaft 5 with parallel threads formed on the outer peripheral surface thereof. The parallel threaded portion 4 and the taper threaded portion 6 formed at the tip of the parallel threaded portion 4 are included. The taper screw portion 6 has a taper screw thread continuous with the parallel screw thread of the parallel screw portion 4 formed on the outer circumference of a taper shaft having a tapered diameter. In this pre-wound point screw 1, the taper screw portion 6 formed at the tip reduces the inclination with respect to the female screw hole, and improves the insertability to prevent damage and seizure of the screw, thereby improving the tightening workability. It is intended to improve.

Further, in the case of manufacturing the above-mentioned pre-wound point screw 1, first, a long coil material is cut into a predetermined length to form a fixed-length steel rod 7 as shown in FIG. Next, the head 3 is formed at one end of the steel rod 7 by the head of the press machine as shown in FIG. Using a pair of rolling dies 9 as shown in (c), the parallel thread of the parallel thread portion 4 and the plastic deformation of the taper shaft of the taper thread portion 6 and the taper thread are simultaneously rolled.

[0004]

[Problems to be solved by the device]

 However, in the above-mentioned pre-wound point screw 1, since the taper screw portion 6 is formed by rolling the steel rod 7 of the large-diameter stripped screw material 8, especially the taper screw portion 6 of the rolling die 9 is formed at that time. Excessive rolling pressure is applied to the part where the taper shaft of is plastically processed. For this reason, the thread material 8 held by the rolling dies 9 is rolled in the state of being displaced from a predetermined position of the rolling dies 9 during the rolling. As a result, it is not possible to perform accurate thread rolling without fluctuations in the axial length and thread, and the production yield is not good, such as the tip of the thread blank 8 cracking during rolling. There is a problem that the rolling die 9 is easily broken and has a short durable life and is uneconomical.

Further, in order to improve the above-mentioned drawbacks, as shown in FIG. 6 (a), the tip portion of the steel rod 7 of the screw material 8 is preliminarily made to have a reduced diameter shaft 7 a, or as shown in FIG. 6 (b). 7b is also used, and the taper screw portion 6 is also rolled. However, since each of these pre-processing must be processed separately by cutting, etc., it was not suitable for mass production because of the cost increase.

Therefore, the present invention has an object to provide a pre-wound point screw which can solve the above-mentioned problems of the conventional technique.

[0007]

[Means for Solving the Problems]

 The gist of the present invention is to provide a head having an arbitrary shape provided with a rotating means, a parallel thread portion having parallel threads on the outer periphery of the parallel shaft portion, and a taper formed at the tip of the parallel thread portion. The taper screw part is formed with a hole at the tip to form an annular tubular part, and the end face is almost closed by rolling a threaded material that covers the hollow part hollowed inside. The taper cylinder is plastically deformed, and a taper thread that is continuous with the parallel threads is formed on the outer circumference of the taper cylinder. Plastic deformation of the taper cylinder and each thread are rolled simultaneously. It is a pre-wound point screw that is adapted to do so.

[0008]

【Example】

 Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS. The pre-wound point screw 11 has a hexagonal head portion 13 of any other shape having a rotating means 12 at the top as in the case of the conventional structure as shown in FIG. 1, and a parallel thread thread on the outer peripheral surface of the parallel shaft 15. The parallel threaded portion 14 is engraved with 14a, and the taper threaded portion 16 is formed at the front end of the parallel threaded portion 14. The taper thread portion 16 has a taper thread 16b continuous with the parallel thread 14a of the parallel thread portion 14 on the outer peripheral surface of a taper cylinder 16a whose diameter is gradually reduced in a tapering state and whose end surface is substantially closed. A hollow portion 16c is formed inside the tapered cylinder 16a, which is hollowed out into a tapered conical shape so that the entire outer circumference is covered by the tapered cylinder 16a.

When manufacturing the above-mentioned pre-wound point screw 11, as shown in FIG. 2, one end of a steel rod 17 made by cutting a long coil material into a predetermined length as in the conventional case is used. The head 13 is forged by the header of the forging machine, a hole 19 is forged in the shaft center of the other end of the steel rod 17, and an annular tubular portion 20 is formed on the outer periphery of the hole 19 to form an integral body. Of the screw element 18 of FIG. For example, the depth L of the hole 19 is made substantially equal to the length of the taper screw portion 16, and the diameter d is approximately 1/2 to 2/3 of the diameter (rolling lower diameter) D of the steel rod 17. Is desirable. The screw material 18 can be formed simultaneously with the hole 19 and the annular portion 20 when the head 13 is pressed as shown in FIG.

In the press machine 21, a punch case 23 attached to a punch holder 22 is removably attached with a punch nib 24 made of cemented carbide having a desired head shape recessed to form an upper die. ing. The lower die side is housed in a die case 27 fitted into a die holder 26 on the die plate 25. The lower die is slidably accommodated in the die case 27 and is mounted on the die plate 25 via the space tube 28. The lower die is attached to the shaft center of the die 29 and the screw is attached. The steel rod 17 for making the material 18 is inserted into the fitting hole 30a from one side, and the hollow molding pin 31 is inserted into the fitting hole 30a of the die nib 30 from the other side with the small diameter protrusion 31a formed at the tip. And a protrusion sleeve 32 in which the base side of the hollow molding pin 31 is inserted into one side, and a base end portion thereof is engaged with a pushing member such as a cam member or a cylinder (not shown) so that the tip portion thereof protrudes. The protrusion pin 33 that engages with the hollow molding pin 31 that is inserted from the other end, the guide tube 34 in which the base end of the protrusion pin 33 is slidably guided, and the protrusion. It is composed of a coil spring 35 which is wound around the outer circumference of the working sleeve 32 and is mounted in a compressed state between a flange 32a formed at one end of the protruding sleeve 32 and the bottom surface of the die 29. ..

Further, a retaining pin 36 is planted in the inner peripheral portion of the die case 27, and a sliding member extending in the axial direction is formed by cutting out a part of the outer periphery of the die 29 adjacent to the retaining pin 36. The groove 37 is provided as a recess, and the die 29 is slidable within the range of the sliding groove 37. A slide pin 39 is provided which penetrates the die holder 26 and the die case 27 and whose tip is projected and retracted into a locking groove 38 formed by cutting out a part of the outer periphery of the die 29. The base of the slide pin 39 is supported by a spring member (not shown), and the inclined cam surface 39a formed at the tip is pressed into the locking groove 38. When the die 29 is pressed from above, The die 29 is held firmly, and when the die 29 is pressed from below, the slide pin 39 retracts to enable the die 29 to move.

Next, a case where the screw blank 18 is formed by using the above-described forging machine 21 will be described. First, the push-out means 33 engaged with the base end pushes up the push-out pin 33 to insert the hollow molding pin 31 into the fitting hole 30a of the die nib 30 by a predetermined depth, thereby forming a necessary mold space. The lower end side of the steel rod 17 for forming the screw material 18 is inserted. At this time, the die 29 to which the die nib 30 is attached is biased by the elastic force of the coil spring 35 and is slid upward while retracting the slide pin 39, and the die 29 is pulled out. It is supported at the top dead center with the lower edge of the sliding groove 37 being locked. Then, when the upper die is lowered, the die 29 is pressed by the contact of the punch case 23 having the punch nib 24 mounted thereon, and the die 29 is lowered against the repulsive force of the coil spring 35 and slid into the locking groove 38. When the cam surface 39a of the pin 39 is projected and pressed into contact, the lower surface of the die 29 contacts the upper surface of the space tube 28, and the die 29 is supported at the bottom dead center. As a result, the steel rod 17 for the screw material 18 surrounded by the die space while receiving the pressing force of the hollow forming pin 31 from the lower side of the punch nib 24 from the upper side has the head 13 on the upper side and the lower side of the steel bar 17 on the lower side. An annular tubular portion 20 having a hole 19 at the same time is pressed and formed into a screw material 18. After that, when the upper die is lifted, the die 29 is also returned to the top dead center by the elastic force of the coil spring 35. At this time, the protrusion pin 33 is further pushed out and the hollow molding pin 31 is pushed up. The screw material 18 is discharged from the mold space.

When the thread blank 18 is rolled using a pair of rolling dies as in the conventional case, the parallel thread portion 14 and the taper thread portion 16 are simultaneously rolled. In this case, the annular tubular portion 20 of the thread material 18 is not plastically deformed into the tapered tapered tubular portion 16a in sequence, but the outer peripheral surface of the annular tubular portion 20 is continuous with the parallel thread 14a of the parallel threaded portion 14 to form the taper thread 16b is rolled. In particular, the annular tube portion 20 having the hole 19 formed therein is easily plastically deformed into the tapered taper tube 16a without requiring an excessive rolling pressure, and the hole 19 is wrapped by the taper tube 16a. Since it is deformed into the substantially conical hollow portion 16c, the rolled taper thread 16b is formed into a continuous thread without breaks.

[0014]

[Effect of the device]

 As is apparent from the above-described embodiment, the pre-wound point screw of the present invention has the following effects. (1) Since a taper screw portion is formed by rolling a screw material having a hole at the tip and forming an annular tubular portion, even a highly rigid material can be easily formed by a small rolling pressure. .. (2) Since there is little difference in the rolling pressure between the parallel thread part and the taper thread part, there is no positional deviation of the screw material with respect to the rolling die during rolling, and it is possible to form a thread with no variations. It also prevents accidents such as cracking of the tip of the screw material. (3) The load on the rolling die is small and the durable life is improved. (4) The material can be saved and the weight of the screw can be reduced.

[Brief description of drawings]

FIG. 1 is a front view of a pre-wound point screw according to an embodiment of the present invention.

FIG. 2 is a front view of a screw material for making the pre-wound point screw of FIG.

FIG. 3 is a vertical cross-sectional view of a forging machine for forging the screw material of FIG.

FIG. 4 is a front view of a pre-wound point screw according to a conventional example.

5 is an explanatory view of a method of manufacturing the pre-wound point screw of FIG.

FIG. 6 is an explanatory view of a modified example of the method of manufacturing the pre-wound point screw of FIG.

[Explanation of symbols]

11 Pre-wound Point Screw 12 Rotating Means 13 Head 14 Parallel Thread 14a Parallel Thread 15 Parallel Shaft 16 Tapered Thread 16a Tapered Tube 16b Tapered Thread 16c Cavity 17 Steel Rod 18 Screw Material 19 Hole 20 Annular Tube 21 Forging machine D Diameter of steel bar (rolling diameter) L Hole depth d Hole diameter

Claims (1)

[Scope of utility model registration request] 1. A head having an arbitrary shape provided with a rotating means, a parallel thread part having parallel threads formed on the outer periphery of the parallel shaft part, and a taper thread part formed at the tip of the parallel thread part. The taper screw portion is formed in a tapered shape in which the end face is almost closed in a manner of covering the hollow portion hollowed out by rolling the screw material in which a hole is formed at the tip to form an annular tubular portion. The taper cylinder is plastically deformed, and a taper thread continuous with the parallel thread is formed on the outer circumference of the taper cylinder so that the plastic deformation of the taper cylinder and each thread are simultaneously rolled. Pre-wound point screw that is characterized by