JPH0220743Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention mainly relates to an improvement of a cord pull-out bush for a proximity switch.

As a proximity switch for detecting the presence or absence of an object without contact, there is a structure shown in FIG. In this type of proximity switch, the cord 2 drawn out from the switch case 1 is drawn out through a rubber bush 3 inserted into the switch case 1 for the purpose of mechanical protection as well as durability. At the same time, in addition to fixing components inside the switch case 1, such as printed circuit boards and detection coils,
The switch case 1 is filled with resin to make the inside of the case completely waterproof. Therefore, in order to obtain water resistance as described above and at the same time prevent leakage of the filled resin, it is most desirable that no gap exists between the cord 2 and the rubber bush 3.

However, if there is no gap between the cord 2 and the rubber bushing 3, that is, if the inner diameter of the rubber bushing 3 is equal to or smaller than the outer diameter of the cord 2, the friction between the two becomes very large.
The work of inserting the cord 2 into the rubber bush 3 becomes extremely difficult. Also, it is possible to strictly set the inner diameter of the rubber bushing 3 to match the outer diameter dimension of the cord 2, but since the dimensions of the cord itself vary widely, there is no point in making the dimensional accuracy of the rubber bushing 3 strict. There is no.

On the other hand, if a certain gap is set between the cord 2 and the rubber bushing 3 in consideration of workability during cord insertion as described above, there is a risk that the filled resin may leak as described above. For this reason, in the past, it was unavoidable to set a certain gap between the cord 2 and the rubber bushing 3, and to prevent resin leakage by pasting it with adhesive or the like from the inside of the case before filling the resin, as shown in Figure 2. Alternatively, at the expense of workability when inserting the cord, the inner diameter of the rubber bushing 3 is set smaller than the outer diameter of the cord in anticipation of variations in cord dimensions, and the cord is tightened with the rubber bushing 3 to prevent resin leakage. I try to do that. However, in the former case, the work process of stitching is increased by one step, and in the latter case, the workability when inserting the cord is significantly inferior, as mentioned above, and in both cases, there is still a problem in terms of workability. It also has contradictory problems.

This idea was devised in view of the above-mentioned problems, and its purpose was to form the cord insertion hole in the bushing body with a diameter larger than the outside diameter of the cord, and to make the inner circumference of one end of the cord insertion hole larger than the outside diameter of the cord. It is an object of the present invention to provide a cord drawer bushing for a switch case which simultaneously solves the conflicting problems mentioned above by forming a lip piece over the entire circumference of the bushing.

Hereinafter, an example in which an embodiment of this invention is applied to a proximity switch will be described in detail based on the drawings.

FIG. 3 shows an embodiment of the cord drawer bush in this invention, and parts common to those in FIGS. 1 and 2 will be described with the same reference numerals.
1 is a resin switch case, 4 is a printed circuit board on which predetermined circuit components are mounted, 2 is a cord, and 3 is a bush inserted into the cord outlet 1a of the switch case.

The bush 3 is made of rubber, and a flange portion 11 for positioning with respect to the switch case 1 is integrally formed at one end of the bush main body 10 constituting the bush 3. At the same time, the bush 3 with respect to the cord outlet 1a is integrally formed. In order to facilitate insertion of the bushing, the entire bushing is formed in a tapered shape so that the diameter gradually decreases from the flange portion 11 toward the other end.

The cord insertion hole 12 formed through the bush main body 10 has a diameter larger than the outer diameter of the cord 2 in order to set a constant gap l between the cord 2 and the cord 2 as shown in FIG. This gap l secures a space for installing a lip piece, which will be described later. A diaphragm-shaped lip piece 13 with a substantially triangular cross section that presses against the outer periphery of the cord 2 is provided on the inner circumferential wall of one end of the cord insertion hole 12 from the flange portion 11, and has a length that is approximately the same as the gap l. , and is formed around its entire circumference.

Therefore, according to the above configuration, the diameter of the cord insertion hole 12 is set in advance so that a constant gap l is formed between the bush 3 and the cord 2.
Since the only resistance when inserting the cord 2 into the bush 3 is the friction between the lip piece 13 and the cord 2, the lip piece 13 deforms elastically in the direction in which the cord 2 is pulled out and allows relative movement with the cord 2. do. As a result, the work of inserting code 2 can be carried out effortlessly and extremely easily.

On the other hand, when the relative movement between the bush 3 and the cord 2 is stopped, the lip 13 comes into pressure contact with the cord 2 due to its self-restoring force, exerting its original sealing effect and preventing the resin leakage as described above.

In addition, when inserting the bush 3 into the cord outlet 1a of the switch case 1,
The rubber bushing 3 is inserted from the inside of the switch case 1, but since the bushing itself is tapered as described above, the insertion work of the rubber bushing 3 can be easily performed, and the outer periphery of the bushing provided on the flange portion 11 side can be easily inserted. Insert the bushing into the case so that the wall 3a is in close contact with the cord outlet 1a.

As is clear from the above description, in the bush of the present invention, the inner diameter of the cord insertion hole is larger than the outer diameter of the cord and has a gap l, and is the above gap l
A lip piece with approximately the same length is provided, and this lip piece is configured to press against the outer circumference of the cord, so the frictional resistance when inserting the cord is only due to the lip piece, so it is extremely small. Therefore, the code insertion work can be performed extremely easily.

In particular, in the present invention, since the bush main body is made of elastic rubber, when the cord is inserted, it expands against the cord, and the pressure force of the lip piece against the cord is weak, and the bush expands outward. The frictional resistance is small compared to the case without it, and therefore the cord insertion work is easier.

In addition, in the case of the present invention, after the cord is inserted, the lip piece has a sealing effect by returning due to its self-restoring force, so leakage of the resin filled in the case can be reliably prevented, and there is no need for the conventional adhesive work. Therefore, it is possible to reduce the cost and improve the assembly work.

In particular, in the present invention, the outer circumferential wall of the bushing provided on the flange side is configured to be in close contact with the cord outlet of the case. The outer circumferential wall of the bushing is in close contact with the cord outlet and does not expand outward even when it is against the cord. Therefore, the pressure of the lip piece against the cord is strong, and the cord is pulled until the flange part contacts the case. When it is pulled, the lip piece is also pulled and adheres to the cord at the same time, and the area of contact between the lip piece and the cord increases, which further increases the sealing performance and has the effect of reliably preventing resin leakage. .

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a proximity switch, Fig. 2 shows a conventional rubber bushing installed, a cross-sectional view taken along the - line in Fig. 1, and Fig. 3 shows the cord drawer bush of this invention. FIG. 4 is an enlarged view of the main part of FIG. 3. 1... Switch case, 1a... Cord outlet, 2... Cord, 3... Rubber button, 3a...
...Button outer peripheral wall, 10...Button main body, 12
...Cord insertion hole, 13...Rip piece.

Claims (1)

[Scope of Claim for Utility Model Registration] In a rubber bush that is attached to the lead outlet of a switch case and into which a predetermined cord is inserted, the inner diameter is larger than the outer diameter of the cord, and there is a gap. a bushing main body provided with a cord insertion hole having a diameter of 1; a flange portion positioned and fixed to the switch case and integrally formed on an outer circumferential wall at one end of the bushing main body; and one end provided with the flange portion. a lip piece having a substantially triangular cross section, which is provided on the inner circumferential wall of the cord, has approximately the same length as the gap l, and presses the cord; A button for pulling out a cord of a switch case, characterized in that the button has an outer circumferential wall that is brought into close contact with an outlet.