JPS623534B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Conventionally, this type of limit switch has a diaphragm type seal 15 provided between the housing 1 and the head 3, a groove 17 formed in the rotating shaft 6, and a bearing as shown in FIGS. O provided between 4
A seal ring 16 such as a ring or a V-shaped ring prevents fluid such as cutting oil from entering the housing 1, but when the rotating shaft 6 rotates during operation, the plunger 13 pushes down. As a result, the interior of the cavity 19 formed by the head 3 and the diaphragm seal 15 becomes larger. At this time, the pressure inside the chamber becomes lower than atmospheric pressure. Next, when the rotating shaft 6 returns to its original position, the size and pressure inside the cavity 19 also return to their original state, but as the rotating shaft 6 repeats its operation, the pressure inside the cavity 19 increases abnormally. Eventually, the plunger 13 loses its return action, and the plunger 13 remains in a lowered state, in other words, the pusher 14 of the switch 2 remains pressed.
Switch 2 loses its ability to open and close.

Here, the return force of the pusher 14 of the switch 2 is R, and the pressure rise in the space 19 causes the plunger 1 to
When the force pushing down 3 is F, when F<R,
The switch 2 operates normally, but when F>R, the plunger 13 continues to press the pusher 14.

The phenomenon in which the pressure inside the chamber 19 abnormally increases while the limit switch is in use has not yet been elucidated, but as shown in FIG. As a result, the volume within the empty chamber 19 increases by that amount, and its pressure decreases. During this process, for some reason, the seal ring 1
6 momentarily loses its sealing action, then outside air is sucked into the cavity 19 through the gap formed around the seal ring 16. Then, by the plunger 13, the pusher 1 is
4 is pressed and the switch 2 is activated, the shaft 6 returns to its original position, and thereby the plunger 13 and the diaphragm seal 15 also return to their original positions, and in this process, the sealing action of the seal ring 16 is completely restored. Compared to the original pressure, the pressure in the chamber 19 increases by the amount of air sucked in by the movement of the plunger 13 and the diaphragm seal 15. Here, a small cavity 2 is formed between the seal ring 16 and the cavity 19 between the shaft 6 and the bearing part 5.
Considering 2, if this small cavity and the cavity 19 are the same cavity in communication with each other, the volume inside the cavity 19 will increase when the plunger 13 and the diaphragm seal 15 are lowered. Eventually, the atmosphere flows into this interior, and the pressure changes from a negative pressure state to atmospheric pressure, but needless to say, the pressure within the chamber 19 never exceeds atmospheric pressure. However, in reality, when the plunger 13 and the diaphragm seal 15 are lowered, the pressure within the chamber 19 becomes greater than atmospheric pressure. Although the cause is not clear, it is thought to be due to the phenomenon described below. That is, the gap between the rotating shaft 6 and the bearing 4, that is, the small chamber 22, is lubricated with oil such as grease, and an oil film is formed therein.
For this reason, this small room is not substantially integrated with the vacant room 19 but is independent from it. and plunger 1
3 and diaphragm seal 15 are lowered, empty chamber 1
Since the pressure in chamber 9 decreases, the oil in small chamber 22 is reduced to empty chamber 1.
It is pulled toward the inside of 9. Due to this movement of oil, the pressure in the small chamber 22 near the seal ring 16 decreases. If the seal ring 16 loses or deteriorates its sealing performance for some reason during the rotation of the shaft 6, low pressure may occur between the seal ring 16 and the shaft 6 or between the seal ring 16 and the bearing 4. Atmospheric air is sucked into the small chamber 22. Then, the sealing performance of the seal ring 16 is restored, the shaft 6 returns to its original position, and at the same time the plunger 13 and the diaphragm seal 15 return to their original positions. , vacancy 19
As the pressure inside rises, this pressure rise inside the chamber is also transmitted to the small chamber 22, and the air sucked into this small chamber is compressed. When considering the cross section of the small chamber 22, the gap is not uniform over the entire circumference, so a part of the oil film is destroyed and the air in the small chamber 22 flows into the empty chamber 19. It is considered that the pressure inside the chamber 19 gradually increases as such a phenomenon is repeated.

The present invention aims to eliminate such drawbacks, and one embodiment of the present invention will be described below with reference to the drawings. That is, 1 is the housing, 2 is the switch built in this housing, and 3 is the housing 1.
4 is a cylindrical bearing fitted into a bearing portion 5 of the head, which is made of, for example, a sintered metal. 6 is a rotating shaft rotatably supported by this bearing; 7 is a roller lever attached to this rotating shaft; 8 is a flat portion formed at the inner end of the rotating shaft 6;
9 is a cup-shaped return plunger that abuts against this flat portion; 10 is a hole provided in this plunger;
1 is a return spring provided between the plunger 9 and the inner wall of the head, and 12 is a cam formed on the inner end of the rotating shaft 6 on the side opposite to the flat portion 8. Reference numeral 13 denotes a plunger having one end abutted against this cam part and the other end abutted against the pusher 14 of the switch 2.
Reference numeral 5 denotes a diaphragm seal whose peripheral edge is held between the housing 1 and the head 3 and has a plunger 13 penetrated through its center, which prevents fluids such as water and oil from entering the housing 1. 16 is a seal ring fitted into the groove 17 of the rotating shaft 6. 20 includes at least the seal 16 and the head cavity 19 in the portion of the rotating shaft 6 that passes through the bearing portion 5.
It communicates with the cavity 19 through a gap provided between the two and substantially forms one space.

In the second embodiment of the invention shown in FIGS. 3, 4, and 5, four rings are provided along the axial direction of the bearing 4 between the seal ring 16 and the cavity 19. grooves 20, 20 are provided, and holes 20a, 20a communicating with the grooves are provided in proximity to the groove 17 in which the seal ring 16 is accommodated. It goes without saying that the holes 20a, 20a do not necessarily have to coincide with the grooves 20, 20. In addition, in the case shown in FIG. 6, the bearing 4 is connected to the rotating shaft 6.
A part supporting the front side, that is, the left part in FIG. 3, and a part supporting the rear part, that is, the right part in FIG.
In place of the hole 20a shown in the figure, a gap corresponding to the hole diameter is provided. Furthermore, in the one shown in FIG. 7, grooves 20, 20 are formed along the axis of the inner wall portion of the bearing portion 5 which is in sliding contact with the rotating shaft 6 between the seal ring 16 and the cavity 19. Although not shown in the figure, a gap 20 that communicates with the cavity 19 is formed by forming the portion between the rotating shaft 6, the seal ring 16, and the cavity 19 to have a narrow diameter over the entire circumference. Moreover, between the seal 16 of the rotating shaft 6 and the cavity 19,
A void 20 communicating with the cavity 19 can also be formed by forming a spiral groove along the outer periphery of the shaft.

According to the present invention, as described above, the rotating shaft 6, the bearing portion 5, or the bearing 4 is provided with the necessary number of gaps 20 that communicate with the cavity 19 of the head 3, at least between the seal 16 and the cavity 19 of the head 3. As a result, the above-mentioned conventional drawbacks could be completely eliminated. This is considered to be because the void 20 and the void 19 formed one void that was substantially in communication.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing a conventional limit switch, FIG. 2 is a side sectional view showing one embodiment of the present invention, and FIGS. 3 to 7 are sectional views showing other embodiments of the present invention. . DESCRIPTION OF SYMBOLS 1... Housing, 2... Switch, 3... Head, 4... Bearing, 5... Bearing part, 6... Rotating shaft, 7... Lever, 8... Flat part, 12... Cam part, 13 ... Plunger, 14 ... Pusher, 1
5...Diaphragm seal, 16...Seal ring, 17...Groove, 19...Vacancy, 20...Gap,
20a... hole.

Claims (1)

[Claims] 1. A housing 1 containing a switch 2, and a head 3 detachably attached to the housing.
A rotary shaft 6 is rotatably supported by the bearing portion 5 of this head via the bearing 4, and one end is connected to the cam portion 12 formed at the inner end of the rotary shaft, and the other end is pressed by the switch 2. a plunger 13 abutted against each child 14; and a plunger 13 held between the housing 1 and the head 3;
a diaphragm seal 15 that penetrates the housing 1 and prevents fluid from entering the housing 1;
a seal ring 16 provided between the bearing portion 5 and the rotating shaft 6;
and the head 3 and the diaphragm seal 15.
Between the head cavity 19 formed by
A limit switch provided with a gap 20 communicating with this cavity. 2. The limit switch according to claim 1, wherein the rotating shaft 6 is provided with the gap 20. 3. The limit switch according to claim 1, wherein the bearing 4 is provided with the gap 20. 4. The limit switch according to claim 1, wherein the bearing portion 5 is provided with the gap 20. 5. The limit switch according to claim 1, 2, 3, or 4, wherein the gap 20 is formed close to the seal ring 16.