Wood screw forming die

Abstract

To enable a wood screw to be driven into wood without cracking at a head part and without a flange part getting in the way.SOLUTION: A wood screw has a head part 3 and a shaft part 4 protruding from the lower surface of the head part, where a cross recess 6 is formed in a head top 3A, and a flange part 7 connecting a lower edge d of the head part and the shaft part 4 is formed. The flange part is formed into a curved concave surface that gradually deepens from the lower edge d of the head part and the shaft part toward the middle, and an outer peripheral surface 3B of the head part is formed as a straight circle from the lower edge d to an upper edge u. A wood screw forming die has a shaft insertion hole A and a flange forming seat part B. The flange forming seat part has a curved convex surface formed, whose midsection is raised, an outer peripheral wall part C of the head part is formed in a protruded manner, which has an inner peripheral surface Ca that regulates radial outward flow of the head part from the enlarged end part of the flange forming seat part toward the outside of an inlet, and the inner surface is formed as a straight circle so that the outer peripheral surface 3B of the head part is formed as a straight circle from the lower edge d to the upper edge u.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention provides Tree This relates to the same molding die. [Background technology]

[0002] As a screw for fastening wood, a cross-recessed wood screw, also known as a coarse thread screw or a screw, is specified in JIS B1112 and is also disclosed in Patent Document 1.

[0003] The wood screw structure in Patent Document 1 is described as "a wood screw structure having a head and a shaft, wherein a shaft extending downward is integrally formed with the head, the shaft having a body portion and a screw portion, the screw portion having a threaded portion and a cut portion, the cross-sectional outer diameter of the body portion being larger than the cross-sectional bottom diameters of the threaded portion and the cut portion, a tip portion being provided at the front end of the threaded portion, a screw thread being arranged helically from the tip portion to the head around the bottom diameter of the threaded portion, the threaded portion being connected to the cut portion, a cutting unit being provided on the bottom diameter surface of the cut portion, the body portion being provided between the cut portion and the head, and the outer diameter of the cutting unit of the cut portion being smaller than the outer diameter of the body." The wood screw has a cross recess on the top of the head, and the jaw that connects the lower edge of the head to the shank is conical. The outer periphery of the head is not a straight circle from the lower edge to the upper edge, but has a tapered surface or other shape where the outer diameter changes.

[0004] To manufacture the wood screws, for example, as shown in Figure 4, a wood screw forming die 22 is used, which has a shaft insertion hole 22a that is positioned concentrically with the cross recessed part 23 and into which a rod material is inserted, and a conical jaw forming seat 22b that widens outward at the entrance of this shaft insertion hole 22a.

[0005] A cut piece of rod material is inserted into the shaft insertion hole 22a, and the cross-hole forming body 23 is pressed to cause the rod material to flow radially outward and axially, while the rod material is pressed against the conical jaw forming seat 22b on the entrance side of the shaft insertion hole 22a to form a jaw portion, and the head 21 and cross-hole are formed while the rod material is caused to flow radially outward outside the conical jaw forming seat 22b.

[0006] In this case, since there is nothing to restrict the outer periphery of the material flowing into the head portion 21, the outer periphery becomes barrel-shaped with a bulge in the middle. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-17979 Summary of the Invention [Problem to be solved by the invention]

[0008] The wood screws of the above-mentioned prior art have a conical jaw formed on the underside of the head, which increases the strength of the screw, but the conical jaw can get in the way when driving it into wood. Also, during manufacturing, a large amount of material flows toward the conical jaw forming seat, so the flow of material reaching the outer periphery of the head is reduced, making it difficult for excessive expansion to occur toward the outer periphery of the head and preventing cracks from occurring on the outer periphery. However, if the jaw forming seat is shaped in a way that makes it difficult for material to flow, it becomes difficult to prevent cracks from occurring due to excessive expansion of the outer periphery of the head.

[0009] The present invention is intended to solve the problems of the prior art. Tree The object of the present invention is to provide a screw forming die.

[0010] The present invention To provide a wood screw forming die that can suppress the occurrence of cracks in the head by forming the jaw part into a curved concave surface that deepens upward and the outer peripheral surface of the head into a straight circle, and that can form wood screws that can be driven into wood without the jaw part getting in the way. [Means for solving the problem]

[0011] The present invention A specific means for solving the problems in the wood screw forming die is a wood screw forming die having a shaft insertion hole A, which is positioned concentrically with the cross recessed portion 8 and into which the rod material S is inserted, and a jaw forming seat portion B, which is flared outward at the entrance of the shaft insertion hole A, The jaw forming seat B has a curved convex surface with a high middle part, A head outer peripheral wall portion C having an inner peripheral surface Ca that restricts the radially outward flow of the head 3 is formed protruding from the enlarged side end of the jaw forming seat portion B toward the outside of the inlet, and the inner peripheral surface Ca of this head outer peripheral wall portion C is formed in a straight circle so that the outer peripheral surface 3B of the head 3 forms a straight circle from the lower edge d to the upper edge u. [Effects of the Invention]

[0012] The present invention The wood screw forming die can suppress the occurrence of cracks in the head, and can form wood screws that can be driven into wood without the jaws getting in the way. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view showing an embodiment of a wood screw according to the present invention. FIG. [Figure 2] 1 is a cross-sectional view showing the main parts of a wood screw and a wood screw forming die according to the present invention. [Figure 3] 1 is a cross-sectional explanatory view showing a method for manufacturing a wood screw according to the present invention using a wood screw forming die. [Figure 4] FIG. 10 is an explanatory cross-sectional view showing the manufacturing method of a conventional wood screw. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0015] In FIG. 1, a wood screw 1 is shown that can be classified as a JIS B1112 cross recessed countersunk wood screw.

[0016] The wood screw 1 has, as its main components, a head 3 and a shank 4 protruding from the underside of the head 3, with a cross-shaped hole 6 formed in the head top 3A, a jaw 7 connecting the lower edge d of the head 3 and the shank 4, and a spiral-shaped thread portion 5 formed in the lower half or along the entire length of the shank 4.

[0017] The outer diameter of the head 3 is approximately twice the diameter of the shaft 4, and its underside is flattened and connected to the shaft 4 by a jaw 7, which avoids stress concentration and increases strength.

[0018] The jaw portion 7 is conical in the prior art, but in the present invention, it is formed into a curved concave surface that gradually deepens from the lower edge d of the head 3 to the middle of the shank 4. When viewed from the shank 4, it has a trumpet shape that widens upward.

[0019] Because the jaw portion 7 has a curved concave surface, when the wood screw 1 is driven into wood, the amount of wood that is crushed is less than with the conical jaw portion of the prior art, and the screw can be driven in smoothly.

[0020] The outer peripheral surface 3B of the head 3 is formed as a straight circle from the lower edge d to the upper edge u, and the head top 3A is flat except for the cross recess 6. The head top 3A can also be formed as a spherical surface with a higher center to make a countersunk wood screw or a slotted wood screw.

[0021] The wood screw 1 can be made of stainless steel or aluminum alloy, and a particularly strong titanium alloy, such as beta titanium (β-type titanium alloy), can also be used.

[0022] 2 and 3 show a wood screw forming die 2 and a forming process for manufacturing the wood screw 1 (cold header processing, forging, rolling).

[0023] The wood screw forming die 2 is formed as a two-part die (or one piece) and has a cross recessed part 8 that can move back and forth.

[0024] The wood screw forming die 2 has a shaft insertion hole A, which is positioned concentrically with the cross-recessed hole forming body 8 and into which cut rod material S is inserted, and a jaw forming seat portion B, which flares outward at the entrance of this shaft insertion hole A (Figure 3(a)).

[0025] The jaw forming seat B has a curved convex surface with a higher middle part, and when viewed from the shaft insertion hole A, it has a trumpet shape that widens upward, and when the bar material S is pressed from the upper end (the left side in Figures 3(b) and 3(c)), it forms a curved concave jaw portion 7.

[0026] In Figure 2, the conical jaw forming seat 22b of the prior art is shown by a two-dot chain line, and it can be seen that the curved convex surface of the jaw forming seat B has a higher middle part than the conical jaw forming seat 22b.

[0027] When the bar material S is pressed from the upper end, a curved concave jaw portion 7 is formed, but less material flows downward (to the right in Figure 3(c)) than in the case of the conical jaw forming seat 22b, and the material that does not flow downstream flows radially outward (up and down in Figure 3(c)) to form the head portion 3.

[0028] At the top of the wood screw forming die 2, a head outer peripheral wall portion C having an inner peripheral surface Ca is formed to protrude outward from the enlarged end of the jaw forming seat portion B toward the outside of the entrance. The inner peripheral surface Ca of this head outer peripheral wall portion C is formed in a straight circle so that the outer peripheral surface 3B of the head 3 forms a straight circle from the lower edge d to the upper edge u.

[0029] When the bar material S is pressed from the upper end, the inner peripheral surface Ca of the head outer peripheral wall portion C hits the jaw forming seat portion B, preventing the downward flow of the material and forcing it to flow radially outward to form the head 3. However, rather than allowing this outward flow of the head 3 freely, the inner peripheral surface Ca of the head outer peripheral wall portion C restricts the radially outward flow and sets the maximum outer diameter of the head 3 (Figure 3(c)).

[0030] As a result, there are no excessive flowing areas on the outer periphery of the head 3, as occurs with free flow, and the flow up to the inner periphery Ca forms the outer periphery 3B of the head 3 into a straight circle from the lower edge d to the upper edge u.

[0031] The cross-hole formed body 8 is formed with a cross-hole forming portion 11 that presses the rod material S from the upper end to carve a cross hole 6 in the head 3A, and a head pressing portion 12 on the base side of this cross-hole forming portion 11 that abuts against and presses the head 3A of the rod material S.

[0032] The outer surface 12a of this head top pressing portion 12 is formed as a straight circle that fits into the inner surface Ca of the head outer wall portion C, and when the head 3 is formed within the inner surface Ca of the head outer wall portion C, the material is pressed from above to bring the outer surface 3B of the head 3 into tight contact with the inner surface Ca from the lower edge d to the upper edge u, and also form the head top 3A.

[0033] After the head 3 and jaw 7 are formed on the top of the rod material S using the wood screw forming mold 2, the rod material S, which has become an intermediate wood screw product, is removed from the wood screw forming mold 2 (Figure 3(d)) and, in the next step, a spiral-shaped thread portion 5 is formed on the lower half or entire length of the shank 4 by rolling or the like.

[0034] Since the head top pressing portion 12 is formed flat, the head top 3A of the head 3 is flat and the wood screw 1 becomes a countersunk wood screw, but if the head top pressing portion 12 is formed into a hemispherical concave surface, the head top 3A of the head 3 will have a mountain shape and can be made into a round countersunk wood screw.

[0035] In the embodiment of the wood screw 1 described above, it has a head 3 and a shank 4 protruding from the underside of the head 3, a cross recess 6 is formed in the head top 3A, and a jaw 7 is formed connecting the lower edge d of the head 3 and the shank 4. The jaw portion 7 is formed into a curved concave surface that gradually becomes deeper from the lower edge d of the head 3 and the shank 4 to the middle, and the outer peripheral surface 3B of the head 3 is formed into a straight circle from the lower edge d to the upper edge u.

[0036] With this configuration, the wood screw 1 can be driven into wood without cracking at the head 3 and without the jaw 7 getting in the way.

[0037] In the embodiment of the wood screw 1, the head 3 and the shank 4 are made of stainless steel, aluminum alloy, or titanium alloy.

[0038] This construction allows it to be manufactured from stainless steel or aluminum alloys, and even titanium alloys, which are particularly strong.

[0039] In the embodiment of the wood screw forming die 2 described above, the wood screw forming die has a shaft insertion hole A, which is positioned concentrically with the cross recessed part 8 and into which the rod material S is inserted, and a jaw forming seat B, which widens outward at the entrance of the shaft insertion hole A, and the jaw forming seat B has a curved convex surface with a higher middle part, and a head outer peripheral wall C, which protrudes from the enlarged end of the jaw forming seat B toward the entrance, has an inner peripheral surface Ca that restricts the radial outward flow of the head 3, and the inner peripheral surface Ca of the head outer peripheral wall C is formed in a straight circle so that the outer peripheral surface 3B of the head 3 forms a straight circle from the lower edge d to the upper edge u.

[0040] This configuration not only prevents cracks from occurring in the head 3, but also allows the formation of a wood screw that can be driven into wood without the jaw 7 getting in the way.

[0041] In addition, in the embodiment of the wood screw forming die 2, the cross-recessed portion forming body 8 is formed with a cross-recessed portion forming portion 11 and a head top pressing portion 12 on the base side of this cross-recessed portion 11 that abuts against and presses the head top 3A of the bar material S, and the outer surface 12a of this head top pressing portion 12 is formed into a straight circle that fits into the inner surface Ca of the head outer peripheral wall portion C.

[0042] This configuration can sufficiently suppress free radial outward expansion of the head portion 3 without any constraint.

[0043] The present invention is not limited to the above-described embodiment, and the shapes, configurations, and combinations of the components can be changed.

[0044] For example, the depth of the curved concave shape of the jaw portion 7 and the height of the middle portion of the curved protruding surface of the conical jaw forming seat portion 22 can be selected appropriately depending on the size and material of the wood screw 1. [Explanation of symbols]

[0045] 1 Wood screw 2 Wood screw forming die 3 Head 3A Head top 3B Outer peripheral surface 4 Shaft part 5 Thread part 6 Cross recess 7 Jaw part 8 Cross recess forming body 11 Cross recess forming part 12 Head top pressing part 12a Outer peripheral surface 22a Shaft insertion hole 22b Conical jaw forming seat part 22b Conical jaw part 23 Cross recess forming body A Shaft insertion hole B Jaw forming seat part C Head outer peripheral wall part Ca Inner peripheral surface S Bar stock d Lower edge u Upper edge

Claims

1. A wood screw having a head (3) and a shank (4) protruding from the underside of the head (3), a cross recess (6) formed in the top of the head (3A), and a jaw (7) connecting the lower edge (d) of the head (3) and the shank (4), The jaw portion (7) is formed into a curved concave surface that gradually deepens from the lower edge (d) of the head portion (3) and the stem portion (4) to the middle, The wood screw is characterized in that the outer peripheral surface (3B) of the head (3) is formed in a straight circle from the lower edge (d) to the upper edge (u).

2. 2. The wood screw according to claim 1, wherein the head (3) and the shank (4) are made of stainless steel, aluminum alloy, or titanium alloy.

3. A wood screw forming die having a shaft insertion hole (A) positioned concentrically with a cross recessed part (8) and into which a rod material (S) is inserted, and a jaw forming seat portion (B) that widens outward at the entrance of the shaft insertion hole (A), The jaw forming seat (B) has a curved convex surface with a high middle part, A head outer peripheral wall portion (C) having an inner peripheral surface (Ca) that restricts the radially outward flow of the head (3) from the enlarged side end of the jaw forming seat portion (B) toward the outside of the inlet, and the inner peripheral surface (Ca) of this head outer peripheral wall portion (C) is formed in a straight circle so that the outer peripheral surface (3B) of the head (3) forms a straight circle from the lower edge (d) to the upper edge (u).

4. The wood screw forming die according to claim 3, characterized in that the cross-recessed formed body (8) is formed with a cross-recessed formed portion (11) and a head pressing portion (12) on the base side of the cross-recessed formed portion (11) that abuts against and presses the head top (3A) of the bar material (S), and the outer peripheral surface (12a) of the head pressing portion (12) is formed into a straight circle that fits into the inner peripheral surface (Ca) of the head outer peripheral wall portion (C).

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