Screw and screw fastening structure

Abstract

To provide a screw having a fall prevention mechanism.SOLUTION: A screw 1 includes: a head part 10; a shaft part 11 which is a column body connected to the head part 10 and in which a male screw 11A is formed on at least the tip side of an outer peripheral surface of the column body; and a heat-shrinkable tube 12 which covers an outer peripheral surface of the shaft part 11. The heat-shrinkable tube 12 has: a contraction part 12B which is adhered to the outer peripheral surface of the shaft part 11; and a non-contraction part 12A which is continuous with the head part 10 side of the contraction part 12B and is not adhered to the outer peripheral surface of the shaft part 11.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a screw and a screwing structure.

Background Art

[0002] It is widely practiced to fix a first member and a second member with a screw by inserting a shaft portion of the screw into an insertion hole of the first member and coupling a tip end of the shaft portion of the screw protruding from the insertion hole to a female screw of the second member.

[0003] For example, as in the invention described in Patent Document 1, a screw with a heat shrinkable tube attached to a portion disposed in an insertion hole of a first member in a screw has been proposed. The entire heat shrinkable tube is heat-shrunk.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When fixing the first member and the second member with a screw as described above, from the viewpoint of work efficiency, it may be desired to move the first member to the vicinity of the second member with the shaft portion of the screw temporarily inserted into the insertion hole of the first member.

[0006] However, when moving with the screw temporarily inserted into the insertion hole, the screw may fall out of the insertion hole. In the screw described in Patent Document 1, although the entire heat shrinkable tube is in close contact with the shaft portion by heat shrinkage, there is still a concern that the screw may fall out due to variations in the amount of heat shrinkage or variations in the diameter of the insertion hole.

[0007] The present invention has been made in view of such a background, and aims to provide a screw that can prevent dropping out from a temporarily inserted insertion hole, and a screwing structure using the same.

Means for Solving the Problems

[0008] One aspect of the present invention is a head, a columnar body connected to the head, the columnar body having a shaft portion with a male thread formed on at least the tip side of the outer peripheral surface of the columnar body, and a heat-shrinkable tube covering the outer peripheral surface of the shaft portion. The heat-shrinkable tube has a shrunk portion that is in close contact with the outer peripheral surface of the shaft portion, and a non-shrunk portion that is continuous with the head side of the shrunk portion and is not in close contact with the outer peripheral surface of the shaft portion, and is in a screw.

Effects of the Invention

[0009] According to the above aspect, the non-shrunk portion of the heat-shrinkable tube can be brought into close contact with the inner wall surface of the insertion hole of the first member. Therefore, it is possible to suppress the screw from dropping out of the insertion hole of the first member.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0011] The screw has a head, a columnar body connected to the head, a shaft portion having a male thread formed on at least the tip side of the outer peripheral surface of the columnar body, and a heat shrinkable tube covering the outer peripheral surface of the shaft portion. The heat shrinkable tube has a shrinkage portion that adheres to the outer peripheral surface of the shaft portion, and a non-shrinkage portion that is continuous with the head side of the shrinkage portion and does not adhere to the outer peripheral surface of the shaft portion.

[0012] In the above screw, the diameter of the non-shrinkage portion may be 1.06 times or more and 1.37 times or less the diameter of the shrinkage portion.

[0013] In the above screw, the length of the non-shrinkage portion may be 0.3 times or more and 0.7 times or less the length of the shrinkage portion.

[0014] In the above screw, a male thread may be formed in a region of the outer peripheral surface of the shaft portion where the shrinkage portion adheres. The adhesion of the shrinkage portion to the shaft portion can be made stronger.

[0015] In the above screw, the heat shrinkable tube may further have a second shrinkage portion that is continuous with the head side of the non-shrinkage portion and is adhered to the outer peripheral surface of the shaft portion.

[0016] Further, the screwing structure has the screw described above, a first member having an insertion hole into which the shaft portion of the screw is inserted, and a second member having a female thread that engages with the male thread. The shaft portion is inserted into the insertion hole, and the tip of the shaft portion protrudes from the insertion hole. The male thread at the tip of the shaft portion protruding from the insertion hole is engaged with the female thread of the second member. The non-shrinkage portion is elastically deformed and contacts the inner wall surface of the insertion hole, and the shrinkage portion does not contact the inner wall surface of the insertion hole.

[0017] In the above screwing structure, the diameter of the insertion hole may be 0.94 times or more and 0.97 times or less the diameter of the non-shrinkage portion.

[0018] In the above screw fastening structure, the first member may be a blower, and the second member may be an electric device.

[0019] (Embodiment 1) An embodiment of the screw and the screw fastening structure according to the present disclosure will be described with reference to the drawings. FIG. 1 is a view showing a screw 1 in Embodiment 1. Further, FIG. 2 is a cross section perpendicular to the axis of the screw 1 in Embodiment 1, and shows an end face of a cut portion at II-II in FIG. 1. Further, FIG. 3 is a cross section perpendicular to the axis of the screw 1 in Embodiment 1, and shows an end face of a cut portion at III-III in FIG. 1.

[0020] As shown in FIG. 1, the screw 1 in Embodiment 1 has a head 10, a shaft portion 11, and a heat shrinkable tube 12. The screw 1 of this Embodiment 1 is used to fix the first member 2 to the second member 3. The specific usage state of the screw 1 will be described later. In this specification, the end side opposite to the head 10 in the axial direction of the screw 1 will be described as the tip side, and the opposite side (head 10 side) will be described as the base end side.

[0021] The shaft portion 11 is a columnar member connected to the head 10. The outer peripheral surface of the shaft portion 11 has a male screw 11A. The male screw 11A has a structure in which a helical thread is formed. A head 10 having a larger diameter than the shaft portion 11 is connected to one end of the shaft portion 11. The male screw 11A is provided on the entire outer peripheral surface of the shaft portion 11. Note that the male screw 11A only needs to be provided at least at the tip of the shaft portion 11 (one end opposite to the head 10 side), and does not need to be provided over the entire surface.

[0022] The heat shrinkable tube 12 is tubular and is provided so as to cover the entire outer peripheral surface at the central portion of the shaft portion 11. Further, the heat shrinkable tube 12 is made of an elastic material that shrinks by heat, and is made of vinyl chloride, silicone resin, polyethylene resin, fluororesin, or the like.

[0023] Further, the heat-shrinkable tube 12 has a non-shrinking portion 12A that has not shrunk due to heat and a shrinking portion 12B that has shrunk due to heat. The non-shrinking portion 12A is provided in a region on the head 10 side of the shaft portion 11. Further, the shrinking portion 12B is provided continuously with the non-shrinking portion 12A in a region on the tip side of the shaft portion 11. Thus, since the tip side of the shaft portion 11 in the heat-shrinkable tube 12 is the shrinking portion 12B, the shaft portion 11 can be easily inserted into the insertion hole 4.

[0024] As shown in FIG. 3, the non-shrinking portion 12A does not contact the outer peripheral surface of the shaft portion 11, and an air layer exists between the non-shrinking portion 12A and the outer peripheral surface of the shaft portion 11. On the other hand, as shown in FIG. 2, the shrinking portion 12B is in close contact with the outer peripheral surface of the shaft portion 11 due to shrinkage by heat. Therefore, the non-shrinking portion 12A functions as a cantilever spring having one end fixed to the shrinking portion 12B and the other end being a free end, and is elastically deformable.

[0025] Further, since the shrinking portion 12B is in close contact with the region where the male thread 11A is formed, the shaft portion 11 and the shrinking portion 12B can be more firmly adhered to each other by the anchor effect.

[0026] The outer diameter of the non-shrinking portion 12A increases from the shrinking portion 12B side toward the head 10 side, and the outer diameter is maximum at the end on the head 10 side of the non-shrinking portion 12A. This maximum outer diameter is simply referred to as the outer diameter D3 of the non-shrinking portion 12A below. In a state where no force is applied to the non-shrinking portion 12A, the outer diameter D3 of the non-shrinking portion 12A is preferably 1.2 to 1.6 times the diameter D1 on the tip side of the shaft portion 11. By setting it within this range, the function of the non-shrinking portion 12A as a cantilever spring can be sufficiently exhibited.

[0027] Further, the outer diameter D3 of the non-shrinking portion 12A is preferably 1.06 times or more and 1.37 times or less the outer diameter D4 of the shrinking portion 12B. By setting it within this range, the function of the non-shrinking portion 12A as a cantilever spring can be sufficiently exhibited.

[0028] Also, the length L1 of the non-shrinking portion 12A (the axial length of the shaft portion 11) is preferably 0.3 to 0.7 times the length L2 of the shrinking portion 12B (the axial length of the shaft portion 11). By setting L1 and L2 in this way, the function of the non-shrinking portion 12A as a cantilever spring can be fully exerted.

[0029] Also, the length L2 of the shrinking portion 12B is preferably 2 to 4 times the diameter D1 of the shaft portion 11. The shrinking portion 12B can be sufficiently adhered to and fixed to the shaft portion 11.

[0030] Also, the overall length L3 (=L1 + L2) of the heat-shrinkable tube 12 is preferably 0.3 to 0.6 times the length L4 of the shaft portion 11. It is possible to sufficiently enhance the effect of preventing the screw 1 from falling off by the heat-shrinkable tube 12 while not impairing the original function of the screw 1.

[0031] Also, the length from the tip of the shrinking portion 12B to the tip of the shaft portion 11 only needs to be set so that the shrinking portion 12B does not protrude from the insertion hole 4 when the screw 1 is inserted into the insertion hole 4 of the first member.

[0032] The length from the base end of the non-shrinking portion 12A to the tip of the head 10 only needs to be set so that the non-shrinking portion 12A does not interfere with the head 10. That is, when the non-shrinking portion 12A is elastically deformed until it contacts the outer peripheral surface of the shaft portion 11, the non-shrinking portion 12A does not need to contact the head 10. For example, the length from the non-shrinking portion 12A to the head 10 may be a length of L1 or more.

[0033] Next, the usage state of the screw 1 in Embodiment 1 will be described with reference to FIGS. 4 and 5.

[0034] The screw 1 in Embodiment 1 is used to fix the first member 2 to the second member 3. FIG. 4 is a diagram showing the configuration of a screwed structure in which the first member 2 and the second member 3 are fixed by the screw 1, and is a cross-sectional view in a plane including the central axis of the screw 1. As shown in FIG. 4, the first member 2 is provided with an insertion hole 4 for passing the shaft portion 11 of the screw 1. A plurality of insertion holes 4 may be provided in the first member 2, and the screw 1 may be inserted into each of them.

[0035] The diameter D2 of the insertion hole 4 is larger than the diameter D1 of the shaft portion 11 and is set so as not to contact the shrinkage portion 12B of the heat shrinkable tube 12.

[0036] Also, the diameter D2 of the insertion hole 4 is smaller than the outer diameter D3 of the non-shrinking portion 12A. Therefore, when the shaft portion 11 of the screw 1 is inserted into the insertion hole 4, the non-shrinking portion 12A elastically deforms and adheres to the inner wall surface of the insertion hole 4. Also, since the heat shrinkable tube 12 itself is an elastic material, the adhesion to the inner wall surface of the insertion hole 4 is high. Therefore, even when the screw 1 is moved by carrying it in a state where the shaft portion 11 of the screw 1 is inserted into the insertion hole 4 of the first member 2, it is possible to prevent the screw 1 from falling out of the insertion hole 4.

[0037] The diameter D2 of the insertion hole 4 is preferably, for example, 0.94 times or more and 0.97 times or less the outer diameter D3 of the non-shrinking portion 12A. By setting it within this range, it is possible to make the non-shrinking portion 12A adhere sufficiently to the insertion hole 4.

[0038] For example, as shown in FIG. 5, even if the head portion 10 of the screw 1 is in a posture such that it is vertically downward in a state where the shaft portion 11 of the screw 1 is inserted into the insertion hole 4, since the non-shrinking portion 12A is in close contact with the inner wall surface of the insertion hole 4, it is possible to prevent the screw 1 from falling off.

[0039] Note that the non-shrinking portion 12A does not need to be in close contact with the entire circumference of the inner wall surface of the insertion hole 4, but in order to sufficiently enhance the effect of preventing falling off, it is preferably in close contact with 60% or more of the entire circumference. Of course, it is most preferable that it is not in close contact with the entire circumference.

[0040] The length L4 of the shaft portion 11 of the screw 1 and the length of the insertion hole 4 are set such that the tip of the shaft portion 11 of the screw 1 protrudes from the insertion hole 4. The protruding tip is coupled to the internal thread 5 of the second member 3. In this way, a screwed structure in which the first member 2 and the second member 3 are screwed and fixed by the screw 1 is constituted.

[0041] As a method for preventing the screw from falling off, after inserting the shaft portion 11 of the screw 1 into the insertion hole 4 of the first member 2, it is conceivable to fit an O-ring or the like on the tip of the shaft portion 11 protruding from the insertion hole 4.

[0042] However, in such a method, a gap is generated between the first member 2 and the second member 3 due to the O-ring. Such a gap may impair the functions of the first member 2 and the second member 3. For example, when the first member 2 is a blower, the exhaust and intake functions of the blower are reduced due to the gap between the first member 2 and the second member 3. In order to eliminate such a gap, it is also conceivable to previously provide a recess for fitting the O-ring in the first member 2 or the second member 3, but a space for providing the recess is required, and a processing cost for the recess processing is incurred.

[0043] On the other hand, if the screw 1 in the first embodiment is used, the screw 1 can be prevented from falling off without providing an O-ring or the like at the tip of the shaft portion 11 of the screw 1, so that the first member 2 and the second member 3 can be fixed in a state of being in close contact without a gap.

[0044] The diameter D2 of the insertion hole 4 is preferably 1.03 to 1.3 times the outer diameter D3 of the non-shrinking portion 12A. By setting it within such a range, the area where the non-shrinking portion 12A is in close contact with the inner wall surface of the insertion hole 4 can be made sufficiently wide, and the adhesion can be improved.

[0045] As described above, according to the screw 1 in the first embodiment, when the screw 1 is inserted into the insertion hole 4 of the first member 2, the non-shrinking portion 12A can be brought into close contact with the inner wall surface of the insertion hole 4. Therefore, the screw 1 can be prevented from falling out of the insertion hole 4 of the first member 2.

[0046] (Embodiment 2) FIG. 6 is a diagram showing the configuration of the screw in Embodiment 2. The screw in Embodiment 2 is obtained by further adding a second shrinkage portion 12C to the heat shrinkable tube 12 of the screw in Embodiment 1, and the rest is the same as in Embodiment 1. The second shrinkage portion 12C is provided continuously to the non-shrinkage portion 12A on the head 10 side of the non-shrinkage portion 12A. The non-shrinkage portion 12A functions as a spring with both ends fixed by being curved and is elastically deformable. Similar to the screw 1 in Embodiment 1, the screw in Embodiment 2 can elastically deform the non-shrinkage portion 12A when inserted into the insertion hole 4 of the first member 2 and bring it into contact with the inner wall surface of the insertion hole 4. Therefore, it is possible to prevent the screw from falling out of the insertion hole 4. Also, similar to Embodiment 1, since the tip side of the shaft portion 11 in the heat shrinkable tube 12 is the shrinkage portion 12B, the shaft portion 11 can be easily inserted into the insertion hole 4. Further, since the head 10 side of the heat shrinkable tube 12 is the second shrinkage portion 12C, it is possible to easily remove the shaft portion 11 from the insertion hole 4. That is, according to Embodiment 2, it is possible to prevent the screw 1 from falling out of the insertion hole 4 while making it easy to insert and remove the screw 1.

[0047] The length L3 of the second shrinkage portion 12C may be set to the same length as the length L2 of the shrinkage portion 12B. Also, the length L1 of the non-shrinkage portion 12A in Embodiment 2 may be made longer than the length L1 of the non-shrinkage portion 12A in Embodiment 1, for example, 1.5 to 2 times the length L2 of the shrinkage portion 12B.

[0048] Also, it is preferable that a male screw 11A is provided on the outer peripheral surface of the shaft portion 11 with which the second shrinkage portion 12C is in close contact. The adhesion of the second shrinkage portion 12C can be improved by the anchor effect.

[0049] (Modification of the Embodiment) In Embodiments 1 and 2, there is nothing between the head 10 of the screw 1 and the first member 2, and the head 10 and the first member 2 are in contact, but a third member such as a washer or an O-ring may be interposed.

[0050] The screws in Embodiments 1 and 2 are suitable for fixing the blower (the first member 2) to the electrical device (the second member 3).

[0051] Fig. 7(a) is an exploded view showing the structure of fixing the first member 2, which is a blower, to the second member 3, which is an electrical device, by the screw 1 in Embodiment 1, and Fig. 7(b) is a view showing the state where the screw 1 in Embodiment 1 is inserted into the first member 2. As shown in Fig. 7, the blower has a rectangular parallelepiped housing that encloses the blades, and has insertion holes 4 at the four corners of the housing. Further, the electrical device has four female screws 5 corresponding to the insertion holes 4. The blower is fixed to the electrical device by inserting the shaft portion 11 of the screw 1 into the four insertion holes 4 and coupling the tip of the shaft portion 11 with the female screw 5 of the electrical device. As shown in Fig. 7(b), even if the blower is carried with the screw 1 inserted into the insertion hole 4 of the blower, the screw does not fall out from the insertion hole 4, so that the blower can be smoothly attached to the electrical device.

[0052] In addition, in Fig. 7, a finger guard 20 is inserted between the head portion 10 of the screw 1 and the first member 2, and the finger guard 20 is fixed to the first member 2 by the screw 1 in Embodiment 1. The finger guard 20 prevents a finger or the like from touching the blades of the blower and causing an injury, and also prevents foreign matter from entering the blower.

[0053] After inserting the screw into the insertion hole 4 of the blower housing, in order to prevent the screw from falling off, it is also possible to prevent the screw from falling out of the insertion hole of the blower by fitting an O-ring on the tip of the screw. However, in that case, a gap will be formed between the blower and the electrical device. If there is such a gap, the exhaust and intake functions of the blower will deteriorate, and the electrical device cannot be efficiently cooled. However, by using the screw 1 in Embodiments 1 and 2, it is possible to prevent the screw from falling out of the insertion hole of the blower without creating a gap between the blower and the electrical device.

Explanation of reference numerals

[0054] 1: Screw 2: First member 3: Second member 4: Insertion hole 5: Female thread 10: Head 11: Shaft portion 11A: Male thread 12: Heat shrinkable tube 12A: Non-shrinking portion 12B: Shrinking portion 12C: Second shrinking portion

Claims

1. A head, a columnar body connected to the head, the columnar body having a shaft portion with a male thread formed on at least the tip side of the outer peripheral surface of the shaft portion, and a heat-shrinkable tube covering the outer peripheral surface of the shaft portion. The heat-shrinkable tube has a shrinkage portion in close contact with the outer peripheral surface of the shaft portion, and a non-shrinkage portion that is continuous with the head side of the shrinkage portion and is not in close contact with the outer peripheral surface of the shaft portion.

2. The screw according to claim 1, wherein the diameter of the non-shrinkage portion is 1.06 times or more and 1.37 times or less the diameter of the shrinkage portion.

3. The screw according to claim 1, wherein the length of the non-shrinkage portion is 0.3 times or more and 0.7 times or less the length of the shrinkage portion.

4. The screw according to claim 1, wherein the male thread is formed in a region of the outer peripheral surface of the shaft portion where the shrinkage portion is in close contact.

5. The screw according to claim 1, wherein the heat-shrinkable tube further has a second shrinkage portion that is continuous with the head side of the non-shrinkage portion and is in close contact with the outer peripheral surface of the shaft portion.

6. A screw according to any one of claims 1 to 5, a first member having an insertion hole into which the shaft portion of the screw is inserted, and a second member having a female thread that engages with the male thread. The shaft portion is inserted into the insertion hole, and the tip of the shaft portion protrudes from the insertion hole. The male thread at the tip of the shaft portion protruding from the insertion hole is engaged with the female thread of the second member. The non-shrinkage portion is elastically deformed to contact the inner wall surface of the insertion hole, and the shrinkage portion is not in contact with the inner wall surface of the insertion hole.

7. The screw fastening structure according to claim 6, wherein the diameter of the insertion hole is 0.94 times or more and 0.97 times or less the diameter of the non-shrinkage portion.

8. The screw fastening structure according to claim 6, wherein the first member is a blower and the second member is an electrical device.

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