JP2012021543A - Screw fall-out prevention structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw fall-out prevention structure serving as a protective earthing function.SOLUTION: The screw fall-out prevention structure includes a fall-out prevention member. When units A and B made of conductive metal are tightly fixed to each other to be brought into protective earthing connection with a clamp screw of which diameter is equal to or larger than a predetermined screw diameter, the fall-out prevention member prevents the clamp screw from falling out of either of the units A and B.

Description

  The present invention relates to a structure for preventing a screw from falling off that fastens at least two metal housing units in a general product such as a cabinet that has a metal housing and operates by receiving power from the outside.

In fastening between metal housing units, a protective ground connection between the housings may be required.
FIG. 5 shows a conventional example in which the screws that fasten the casings are prevented from falling off. 1 is a unit A, 2 is a unit B, 3 is a fastening screw (hereinafter simply referred to as a fastening screw), and 4 is a retainer. It is.

In FIG. 5, the screw hole 1a is formed in the unit A, and the screw portion 3a of the fastening screw 3 is screwed into the screw hole 1a.
Note that. The screw part 3a is screwed into the screw hole 1a after the unit B having the through hole 2a and the retainer 4 are passed.

Here, the inside of the retainer 4 is held by the threaded portion 3a by deformation of the material. The diameter of the outer diameter portion of the retainer 4 and the head 3b of the fastening screw are formed to be larger than the diameter of the through hole 2a formed in the unit B.
Further, a clearance 2b larger than the outer shape of the retainer 4 is formed in the vicinity of the outer periphery of the unit B where the through hole 2a is formed, and no force is applied to the retainer 4 even if the fastening screw 3 is screwed into the unit A. ing.

  According to the above configuration, even if the fastening screw 3 is loosened and removed from the screw hole 1a of the unit A, the inside of the retainer 4 is held by the screw portion 3a by the deformation of the material. The portion is caught on the outer periphery of the through hole 2a, and the fastening screw 3 can be prevented from falling off.

FIG. 6 shows another conventional example. In addition to the screw hole 1a, the unit A is formed with a relief groove 1b having a predetermined diameter and depth on the surface facing the unit B. FIG.
Further, a shaft portion 3c having a diameter that is the same as or slightly thinner than the valley of the screw portion 3a is formed between the screw portion 3a and the head portion 3b of the fastening screw.

Reference numeral 4 denotes a resin-made retainer. Leg portions 4b are formed at two opposing positions on the outer periphery of the retainer, and claws 4c are formed outwardly at the tips of the leg portions.
A hole 2a larger than the diameter of the screw portion 3a of the fastening screw is formed in the unit B, and through holes 2b through which the retainer claws 4c pass are formed in at least two places on the outer periphery of the hole 2a.

  Then, the screw portion 3a of the fastening screw is screwed into the screw hole 4a of the resin retainer 4, the retainer 4 is positioned between the head portion 3b and the screw portion 3a, and the screw portion 3a is passed through the hole 2a of the unit B so that the unit A Screw into the screw hole 1a. At that time, the claw 4c is inserted while sliding in the through hole 2b formed in the unit B in a state where the leg portion 4b of the retainer is distorted inward. The claw 4c spreads outside after passing through the through hole 2b, and the unit B and the retainer 4 are locked. The claw 4c enters the escape groove 1b of the unit A, and the units A and B are closely fixed.

  According to the above-described configuration, even if the fastening screw 3 is loosened and removed from the screw hole 1a of the unit A, the claw 4c of the retainer 4 is locked to the hole 2a of the unit B, so that the fastening screw 3 is prevented from falling off. can do.

Utility Model Registration No. 3139226 JP 2003-28129 A

  Incidentally, in the conventional example shown in FIG. 5, since the retainer 4 is located in the escape portion 2 b of the unit B, the unit A and the unit B are not in contact directly under the fastening screw 3. Therefore, it is not considered that the units A and B are sufficiently fastened by the axial force of the fastening screw 3, and the contact surface between the metal housings cannot serve as a protective grounding function.

In the conventional example shown in FIG. 6, the unit A and the unit B are in direct contact with each other. However, since the resin retainer 4 receives the axial force of the fastening screw 3, it is assumed that creep occurs. , Unit A and Unit B are not sufficiently adhered and cannot serve as a protective grounding function.
There was a problem.

  Accordingly, an object of the present invention is to provide a mechanism for preventing a drop-out of a screw which serves as a protective grounding function by strengthening the close contact between the unit A and the unit B.

The present invention was made to solve the above problems, and in the invention of the screw drop-off prevention mechanism according to claim 1,
When the unit A and the unit B made of conductive metal are tightly fixed with a fastening screw having a size larger than a predetermined screw diameter to be connected to be a protective ground connection, the fastening screw is prevented from falling off any of the units. It is characterized by having a falling-off preventing member.

In claim 2, in the invention of the screw drop-off prevention mechanism according to claim 1,
The drop-off preventing member covers the head of the fastening screw and is formed in either the unit A or the unit B.

In Claim 3, in invention of the screw drop-off prevention mechanism of Claim 1,
The drop-off prevention member is a c-ring arranged at the head of the fastening screw.

  According to the first to third aspects of the present invention, since the head of the fastening screw is covered by the drop-off prevention member, a screw drop-off prevention mechanism that does not fall out even if the screw fastening the unit is loosened is realized. Can do.

It is a partial sectional view (b) of a top view (a) and (a) figure showing an example of an embodiment of a screw drop-off prevention mechanism of the present invention. It is the partial top view (b) of the top views (a) and (a) figure which show another Example. It is sectional drawing which shows another Example. It is sectional drawing which shows another Example. It is sectional drawing which shows a prior art example. It is sectional drawing which shows another prior art example.

FIG. 1A and FIG. 1B show the configuration of the main part of the screw drop-off prevention mechanism of the present invention. FIG. 1A is a plan view and FIG. 1B is a partial cross-sectional view of FIG.
In these drawings, a screw hole 1a is formed in the unit A, and a through hole slightly larger than the screw portion 3a of the fastening screw is formed in the unit B. The units A and B are connected to each other through a protective ground connection, and the screw portion 3a of a fastening screw of M3.5 or more is inserted into the screw hole 1 of the unit A from the unit B side through the through hole 2a. Are screwed in and the units A and B are fixed.

  Reference numeral 10 denotes a screw cover, and a flange 10b is formed at the edge of the flange 10a. The flange 10b is fixed to the unit B by screws or welding (not shown). The screw cover is formed with a fastening hole 6 slightly smaller than the outer diameter of the head 3b of the fastening screw at the bottom of the flange portion 10a. When the fastening screw is loosened, a screwdriver is inserted through the fastening hole 6 and tightened. It is possible. Further, the gap between the flange portion 10a and the head portion 3b of the fastening screw is formed such that even if the screw portion 3a of the fastening screw is removed from the screw hole 1a of the unit A, it does not fall out from the unit B.

  2A and 2B are main part configurations showing another embodiment, in which FIG. 2A is a plan view and FIG. 2B is a partial cross-sectional view of FIG. In this embodiment, the screw cover 10 does not cover the entire head 3b of the fastening screw as compared to the embodiment of FIG. 1, but covers a little more than half.

  Also in this case, the screw hole 1a is formed in the unit A, and the through hole 2a slightly larger than the screw part 3a of the fastening screw is formed in the unit B. These units A and B have a protective earth connection between the casings, and the screw portion 3a of the fastening screw of M3.5 or more enters the screw hole 1a of the unit A from the unit B side through the through hole 2a. Are screwed in and the units A and B are fixed.

  Reference numeral 10 denotes a screw cover. In this embodiment, a flange 10b is formed at the edge of the flange 10a, and the flange 10b is fixed to the unit B by screws or welding not shown. The screw cover is formed with a tightening hole 6 at the bottom of the flange portion 10a so that the tip of a screwdriver slightly smaller than the outer diameter of the head 3b of the fastening screw can be inserted. It can be tightened by inserting a screwdriver or the like through the hole 6.

  Further, the gap between the flange portion 10a and the head portion 3b of the fastening screw is formed such that even if the screw portion 3a of the fastening screw is removed from the screw hole 1a of the unit A, it does not come off from the unit B.

FIG. 3 shows still another embodiment, and in this example, a sectional view when the thickness of the unit B is thicker than the entire length of the fastening screw 3 is shown.
Also in this case, the screw hole 1a is formed in the unit A, and the through hole 2a slightly larger than the screw part 3a of the fastening screw is formed in the unit B. Further, the unit B has a screw accommodation hole 2c formed coaxially with the through hole 2a. The diameter of this hole is at least larger than the outer diameter of the head 3b of the fastening screw, and the depth is formed so that sufficient strength can be obtained when the screw portion of the fastening screw is screwed into the screw 1a of the unit A. .

  Reference numeral 8 denotes a retainer (c-ring) disposed in a c-ring housing groove 8a formed near the entrance of the screw housing hole 2c. The c-ring is attached after the fastening screw 3 is accommodated in the screw accommodation hole 2b and the screw portion 3a is protruded from the through hole 2a. These units A and B have a protective earth connection between the casings, and a screw portion of a fastening screw of M3.5 or more is inserted into the screw hole 1 of the unit A from the unit B through the through hole 2a. 3a is screwed in and the units A and B are fixed.

  Further, the gap between the stopper 8 and the head 3b of the fastening screw is formed such that even if the screw portion 3a of the fastening screw is removed from the screw hole 1a of the unit A, it does not fall out of the unit B.

FIG. 4 is a sectional view showing still another embodiment.
This embodiment is structurally similar to that shown in FIG. That is, here, the pressure collar 7 is fixed to the unit B by press-fitting or welding. Reference numeral 8 denotes a retainer (c-ring) formed near the entrance of the screw storage hole 2b, which is attached after the fastening screw 3 is stored in the screw storage hole 2b and the screw portion 3a protrudes from the through hole 2a.

  These units A and B have a protective earth connection between the casings, and a screw portion of a fastening screw of M3.5 or more is inserted into the screw hole 1 of the unit A from the unit B through the through hole 2a. 3a is screwed in and the units A and B are fixed.

  Further, the gap between the stopper 8 and the head 3b of the fastening screw is formed such that even if the screw portion 3a of the fastening screw is removed from the screw hole 1a of the unit A, it does not fall out of the unit B.

The above description merely shows a specific preferred embodiment for the purpose of explanation and illustration of the present invention. For example, the shapes of the unit A, the unit B, and the fastening screw can be appropriately changed without being limited to the illustrated example, and may be any state as long as the protective ground connection between the cases is applied. In the embodiment, the fastening screw is provided on the unit B side, but may be provided on the unit A side.
Therefore, the present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

1 Unit A
1a, 4a Screw hole 1b Escape groove 2 Unit B
2a Through-hole 2b Escape 2c Screw accommodation hole 3 Fastening screw 3a Screw part 3b Head 3c Shaft part 4 Retainer 4b Leg part 4c Claw 6 Fastening hole 8 Retaining (c-ring)
8a c-ring storage groove
10 Screw cover
10a
10b 鍔

Claims (3)

  When the unit A and the unit B made of conductive metal are closely fixed with a fastening screw having a diameter larger than a predetermined screw diameter so as to be a protective ground connection, the falling-off for preventing the fastening screw from falling off any one of the units. A screw fall-off prevention mechanism comprising a prevention member.   The screw drop-off prevention mechanism according to claim 1, wherein the drop-off prevention member covers the head of the fastening screw and is formed on either the unit A or the unit B.   2. The screw drop-off prevention mechanism according to claim 1, wherein the drop-off prevention member is a c-ring arranged at a head of the fastening screw.

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