JPS642340Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a seal structure in a limit switch.

Conventionally, in this type of limit switch, as shown in FIGS. 1 and 2, the groove 5 for accommodating the seal 6 has a simple shape in its cross section, so there may be variations in the dimensions of the seal 6 or in the machining of the groove 5. Due to variations, the influence of the tightness of the seal 6 on the operation of the switch, particularly on the movement of the operating shaft 4, is as large as an elbow. In other words, if the tightening force of the seal 6 is too large, the movement of the operating shaft 4 will become heavy, which may cause malfunctions such as delayed return, and conversely, if the tightening force of the seal 6 is too small, the sealing performance will deteriorate. It was hot.

This invention is an attempt to eliminate such conventional drawbacks, and one embodiment of this invention will be described below with reference to the drawings.

That is, in FIG. 3, a head portion 2 is attached to one end, that is, the upper end, of a housing 1 that accommodates a built-in switch (not shown), and a guide tube 3 is formed in this head portion. An operating shaft 4 consisting of, for example, an external plunger is slidably supported along its axial direction. A groove 5 is provided on the inner peripheral wall of the guide cylinder 3 on the outer periphery of the operating shaft 4, and an annular seal 6 is accommodated in the groove. A spherical protrusion 7 is formed on the surface of the seal 6 that contacts the operating shaft 4, and serves as a seal between the operating shaft 4 and the guide tube 3. Furthermore, an over-tightening absorbing recess 8 is formed in the surface of the seal 6 that contacts the bottom of the concave groove 5 to absorb over-tightening of the seal 6 with respect to the operating shaft 4.
As a result, the excessive tightening force of the seal 6 against the operating shaft 4 is released by the reduction in the volume of the recess 8 due to the deformation of the seal 6, and therefore the seal 6
The tightening force on the operating shaft 4 will be an appropriate amount.
That is, the operating shaft 4 is slidably in contact with the seal 6, and the sealing performance with respect to the guide tube 3 is ensured.

FIG. 4 shows another embodiment of this invention, which is a roller lever type limit switch. In this switch, the groove 5 is provided on the operating shaft 4, which is a rotating shaft.

Note that 9 is a cup plunger and 10 is a return spring.

FIG. 5 shows a state in which the seal 6 is accommodated in the groove 5 of the guide tube 3, and the operating shaft 4 has not yet been inserted. Therefore, the protrusion 7 of the seal 6 protrudes from the inner peripheral surface of the guide cylinder 3. In this state, when the operating shaft 4 is inserted into the guide tube 3 as shown in FIG. By tightening the shaft 4, the seal 6 is deformed so that the recess 8 is reduced between it and the groove 5 by the amount of excess tightening. This absorbs the excessive tightening force of the seal 6 against the operating shaft 4. Therefore, the volume of the recess 8 follows fluctuations during operation of the operating shaft 4, such as its eccentricity, and always maintains the frictional force of the operating shaft 4 against the seal 6 almost constant. Further, the recess 8 formed in the seal 6 may be U-shaped as shown in FIG.

As described above, this device has a seal 6 on the guide tube 3 or the operation shaft 4 between the guide tube 3 and the operation shaft 4.
In addition, an over-tightening absorption recess 8 is formed on the surface of the seal 6 facing the bottom of the recessed groove 5 to absorb over-tightening of the seal 6 against the operating shaft 4. If the tightening force of the seal 6 to the operating shaft 4 is larger than necessary, it can be absorbed by the recess 8, and the tightening force of the seal 6 to the operating shaft 4 can be maintained at an appropriate value and constant. This has the advantage of ensuring sufficient sealing performance and smooth movement of the operating shaft 4.

[Brief explanation of the drawing]

1 and 2 are side sectional views showing a conventional limit switch, FIG. 3 is a side sectional view of the limit switch according to this invention, FIG. 4 is a side sectional view showing another embodiment of this invention, and FIG. 5 is a side sectional view showing a conventional limit switch. 6 is an enlarged side sectional view of the main part, and FIG. 7 is a cross sectional view of a seal in still another embodiment. DESCRIPTION OF SYMBOLS 1... Housing, 2... Head part, 3... Guide tube, 4... Operating shaft, 5... Concave groove, 6... Seal, 7... Projection, 8... Over-tightening absorption recess, 9
...Cup plunger, 10...Return spring.

Claims (1)

[Scope of utility model registration request] A guide tube 3 is provided in the housing 1 that accommodates the built-in switch, and an operating shaft 4 for operating the built-in switch is slidably supported on the guide tube. A concave groove 5 for accommodating the seal 6 is provided in the tube 3 or the operating shaft 4, and a tightening mechanism is provided on the surface of the seal 6 facing the bottom of the concave groove 5 to absorb excessive tightening of the seal 6 against the operating shaft 4. A pass absorbing recess 8 is formed, and the operating shaft 4 is
A limit switch that maintains constant sliding.