JP2011241944A - Screw fall preventing structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw fall preventing structure capable of surely preventing a fall of a screw without raising the manufacturing cost of a product.SOLUTION: A screw 10 is inserted into a through hole 12 from an inlet 12a of the through hole 12 before connecting a first component 11 to a second component 14. When the screw 10 is inserted into the through hole 12, a male screw part 10d pushes a fall preventing piece 13. The pushed fall preventing piece 13 is elastically deformed in the inserting direction of the male screw part 10d. When the male screw part 10d passed through the fall preventing piece 13, the fall preventing piece 13 abuts on a surface of a shaft part 10b of the screw 10 while elastically deforming, directing in the inserting direction of the male screw part 10d. With this structure, even if the screw 10 moves in a direction opposite to the inserting direction (an upper direction in the figure), the fall preventing piece 13 is engaged with a thread of the male screw part 10d to prevent the screw 10 from being fallen from the through hole 12.

Description

  The present invention relates to a screw drop-off prevention structure for preventing a screw connecting parts before assembly from dropping from the part.

  Conventionally, before assembling a product, a method is used in which a screw is inserted into a through hole of a component constituting the product, and the product is assembled by fastening the screw of each through hole when the product is assembled. As a result, it is only necessary to fasten the screws when assembling the product, so that the assembly efficiency of the product can be increased. However, if you simply insert the screw before fastening into the through-hole, the screw will fall off due to vibration during parts transportation, for example. Measures were taken to prevent the dropout or to prevent the screw from falling off by suppressing the screw in the transport packaging. However, this easily removes the screw, so use a tapping screw to fix it to the through hole, or use a screw with a thread formed at the tip of the shaft, and the washer Measures such as inserting a washer through the shaft so as to be located between the mountains were taken. However, in the method using a tapping screw, the trouble of fixing the tapping screw is generated, so that the number of work steps is increased and the cost of the product is increased. Moreover, in the method using a washer, the number of parts increases, leading to an increase in product cost.

  In order to eliminate such inconvenience, in Patent Document 1, the relationship between the screw shaft diameter K, the thread diameter M, and the through hole diameter N is K <N <M, and the screw thread has a through hole. It has been proposed to insert a screw to pass through. According to this, it is possible to prevent the screw from dropping after the thread has passed through the through hole due to the above-described diameter relationship.

Japanese Patent Laid-Open No. 8-045464

  However, Patent Document 1 describes that when a thread passes, the through hole undergoes plastic deformation, but the diameter of the through hole after plastic deformation may be substantially the same as the thread. If the diameter of the through hole and the diameter of the screw thread are substantially the same, the screw thread may pass through the through hole and the screw may fall off.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw drop-off prevention structure that reliably prevents screw drop-off without increasing the manufacturing cost of the product.

  In achieving the above object, the present invention has a male screw part having a diameter larger than the shaft diameter at the tip of the shaft part, and a head having a diameter larger than the male screw part at the rear end of the shaft part, A screw used to connect the first part and the second part is held so as not to drop off at the first part before the connection to the second part, and the first part is made of resin. In the drop-off prevention structure, a through hole provided in the first component, having a diameter larger than the male screw portion and smaller than an outer diameter of the head, and receiving the screw from the distal end via an entrance, It is integrally molded with resin together with one part, protrudes up to the insertion path of the male screw part toward the center of the through hole, and is pressed by the male screw part when the screw is inserted into the through hole, and the tip is elastic Deformed and engaged with the male screw part, and the screw coming out of the through hole Is obtained by a drop-off prevention pieces stopped.

  The through hole is formed by communicating a first through part and a second through part having a larger inner diameter than the first through part in order from the inlet side, and the drop-off prevention piece is formed in the first through part. It is preferable to provide in the vicinity of the communicating part of the first penetrating part and the second penetrating part on the inner peripheral wall of the part.

  According to the present invention, it is possible to prevent the through-hole from being deformed without providing another part, and it is possible to reliably prevent the screw from falling off without increasing the manufacturing cost of the product.

It is a perspective view which shows the structure of the dropping structure of the screw | thread of this invention. (A) Structure of screw and through hole (B) It is explanatory drawing which shows the structure of a fall-off prevention piece. (A) State where drop-off preventing piece is engaged with male screw part (B) It is an explanatory view showing a state where a screw is inserted into a through hole.

  As shown in FIG. 1, in the screw fall-off preventing structure of the present invention, the screw 10 is inserted into the through hole 12 from the inlet 12 a of the through hole 12 formed in the first component 11. The first component 11 is connected to a second component 14 (see FIG. 3) described later. The screw 10 is formed of, for example, a coarse screw (metric coarse screw, unified coarse screw, etc.), and includes a head portion 10a and a cylindrical shaft portion 10b. The head 10a is provided at the rear end of the shaft portion 10b. A driver (not shown) is inserted into the groove 10c of the head 10a, and when the driver is rotated, the entire screw 10 is rotated. A male screw portion 10d is formed at the tip of the shaft portion 10b. The male screw portion 10d has a thread diameter larger than that of the shaft portion 10b. The outer diameter of the head portion 10a is larger than that of the male screw portion 10d.

  As shown in FIG. 2 (A), the through hole 12 is formed by communicating the first through part 12b and the second through part 12c having a larger inner diameter than the first through part 12b in order from the inlet 12a side. Each has a cylindrical shape. The inner diameters K and L of the first through portion 12b and the second through portion 12c are larger than the diameter M of the male screw portion 10d of the screw 10 and smaller than the outer diameter N of the head portion 10a. A drop-off prevention piece 13 is provided in the vicinity of the communication portion between the first through portion 12b and the second through portion 12c on the inner peripheral wall of the first through portion 12b. The drop-off prevention piece 13 is formed by integral molding with, for example, plastic together with the first component 11. The inner diameter L of the second through portion 12c only needs to be larger than the diameter M of the male screw portion 10d, and may be larger than the outer diameter N of the head portion 10a.

  As shown in FIG. 2B, the drop-off prevention piece 13 protrudes toward the center of the through hole 12. The protruding direction of the drop-off prevention piece 13 is orthogonal to the axial direction of the central axis 12 e of the through hole 12. The drop-off prevention pieces 13 are formed at four positions at intervals of 90 degrees. Since the drop-off prevention piece 13 is made of plastic, the tip end side thereof is elastically deformed in the axial direction of the central axis 12 e of the through hole 12. The distance P between the tips of the drop-off prevention pieces 13 facing each other is smaller than the diameter R of the shaft portion 10 b of the screw 10. Since the diameter R of the shaft portion 10b is smaller than the diameter M of the male screw portion 10d, the drop-off prevention piece 13 protrudes up to the insertion path of the male screw portion 10d.

  Next, the operation of the above configuration will be described.

  As shown in FIG. 3A, the screw 10 is inserted into the through hole 12 from the inlet 12 a of the through hole 12 before connecting the first part 11 to the second part 14. When the screw 10 is inserted into the through hole 12, the male screw portion 10 d presses the drop-off prevention piece 13. The pressed-off prevention piece 13 is elastically deformed in the insertion direction of the male screw portion 10d. When the male screw portion 10d passes the drop-off prevention piece 13, the drop-off prevention piece 13 contacts the surface of the shaft portion 10b of the screw 10 while being elastically deformed in the insertion direction of the male screw portion 10d. As a result, even if the screw 10 moves in the direction opposite to the insertion direction (upward in the figure), the drop-off prevention piece 13 engages with the thread of the male screw portion 10d, and the screw 10 falls off from the through hole 12. Can be prevented.

  As shown in FIG. 3B, when the screw 10 is inserted into the through hole 12, the male screw portion 10 d is in a state where the tip protrudes from the outlet of the through hole 12. In this state, if the screw 10 is rotated and the male screw portion 10d is fastened to the female screw 14a of the second component 14, the first component 11 and the second component 14 can be connected.

  In the above embodiment, the drop-off prevention pieces are provided at four locations, but the number of drop-off prevention pieces may be appropriately set. Further, the shape of the drop-off preventing piece is not limited to a rectangle, and may be appropriately formed, for example, by forming a triangular shape on a disk. Further, the drop-off preventing piece may be provided in the vicinity of the inlet or outlet of the through hole without being provided in the communicating portion of the through hole. Further, the through hole may be formed with a constant diameter from the inlet to the outlet without being constituted by the first through part and the second through part.

  In each of the above-described embodiments, the protruding direction of the drop-off preventing piece 13 is orthogonal to the axial direction of the central axis 12e of the through-hole 12, but the tip may be in a state of facing the insertion direction of the male screw 10d in advance.

DESCRIPTION OF SYMBOLS 10 Screw 10a Head part 10b Shaft 10d Male thread part 11 1st part 12 Through-hole 12a Inlet 12b 1st penetration part 12c 2nd penetration part 12d Step surface 13 Drop-off prevention piece 14 2nd part

Claims (2)

The first part and the second part are connected to each other with a male screw part having a diameter larger than the shaft diameter at the tip of the shaft part and a head having a diameter larger than that of the male screw part at the rear end of the shaft part. In the structure for preventing the screw from falling off, the screw used in the first part before being connected to the second part is prevented from falling off, and the first part is made of resin.
A through hole provided in the first part, having a larger diameter than the male screw portion and a smaller diameter than the outer diameter of the head, and receiving the screw from the distal end side through an entrance;
It is integrally molded with resin together with the first component, protrudes toward the insertion path of the male screw portion toward the center of the through hole, and is pressed by the male screw portion when the screw is inserted into the through hole. A drop-off prevention structure comprising: a drop-off prevention piece which is elastically deformed and engages with the male screw portion to prevent the screw from coming out of the through hole. The through hole is formed by sequentially communicating the first through part and the second through part having a larger inner diameter than the first through part from the inlet side,
The screw drop-off prevention structure according to claim 1, wherein the drop-off prevention piece is provided in the vicinity of a communication portion between the first through-hole and the second through-hole on the inner peripheral wall of the first through-hole.

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