JPH0272527A - Limit switch - Google Patents

Abstract

PURPOSE:To eliminate malfunction and improve reliability of a limit switch by mounting, between a rotary shaft and a head, a seal member, which is formed with a ring shaped first seal lip and a ring shaped second seal lip each closely stuck to the periphery of a rotary shaft in one body being shifted from each other along the shaft. CONSTITUTION:A seal member 20 is formed in ring shape with a material having flexibility, and a first seal lip 23 and a second seal lip 24 shifted from each other in the direction along a shaft are formed in one body in its inner periphery. Further, the minimum inside diameters of the first seal lip 23 and the second seal lip 24 are formed smaller than the outer diameter of a rotary shaft 12 so that respective corner parts 23a and 24a of seal lips 23 and 24, when they are mounted on the rotary shaft 12, are closely stuck to the outer periphery of the rotary shaft 12 thus airtight state can be obtained. Consequently, sealing between the rotary shaft 12 and a head 11 can be securely kept, malfunction is eliminated and reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a limit switch used as an object detection switch in, for example, a conveyor line.

(Prior Art) FIG. 3 shows an example of a conventional limit switch.

In the figure, this limit switch is connected to the case body 10.
A basic switch 102 is built into the device 1, and the top of the basic switch 102 is covered with a cover 103. Further, a head 104 is attached to the upper side of the case body 101 in a state extending from the case body 101. Furthermore, a rotating shaft 105 rotatably supported by a boss portion 104a is disposed on the head 104, and this rotating shaft 105 is connected to the actuator 1 of the basic switch 102 via a return plunger 106, an actuating plunger 107, etc.
02a. The base of an operating lever 108, which has a roller 110 attached to one end via a shaft 109, is detachably attached to the tip of the rotating shaft 105 protruding from the head 104.

In addition, in this limit switch, in order to ensure sealing between the rotation @AlO3 and the boss portion 104a,
An O-ring 111 is attached to the rotating shaft 105, and
A rubber seal cap 112 is attached to prevent oil, water, etc. in the operating environment from entering the head 104 through the O-ring 111 from further entering the case body 101.

This limit switch is used by being placed on a conveyor line, for example, and when a dog on the conveyor hits the roller 110 and rotates the operating lever 108, the flat portion 105a of the rotating shaft 105 rotates. and press down the actuating plunger 107. Then, the actuator 102a of the basic switch 102 is also pressed down, causing the basic switch 102 to operate. In addition, this basic switch 10
The operation of 2 is taken out to the outside through a terminal (not shown). Furthermore, when the dog passes, the compression spring 113 in the head 104 and the return plunger 106 and the rotating shaft 10
The rotating shaft 105 is returned to its original neutral position by the flat portion 105a of the actuating plunger 107.
02a is removed and the actuating lever 108 is returned to the neutral position.

(Problem to be Solved by the Invention) In the conventional limit switch described above, the return plunger 1-106, the actuation plunger 107, etc. move forward or backward within the head 105 depending on the operating state, so the internal volume of the head 104 fluctuates. do.

Then, when the actuator 102a of the basic switch 102 is pressed down, the internal pressure of the head 104 induces a negative pressure state with respect to the external pressure. In addition, this trigger causes a breathing action that sucks in oil, water, air, etc. through the sealing portion of the O-ring 111. If this breathing action is repeated continuously, the pressure within the head 104 reaches a certain value and acts as a force to push down the actuating plunger 107, resulting in a problem of inducing malfunction. Further, if water or the like enters the head 104 at the same time as air, the pressure within the head 104 becomes a water vapor pressure, so the pressure inside the head 104 becomes a larger value. If the pressure inside the head 104 is greater than the return force of the actuator 102a, there is a problem that a return failure may occur.

In addition, since the initial starting torque of the O-ring 111 attached to the rotating shaft 105 is generally 10 to 20 times higher than normal, the O-ring 111 attached to the rotating shaft 105 is There is a problem in that the ring 111 is kinked, which further induces the above-mentioned breathing effect. Furthermore, cutting powder such as aluminum and iron powder may be removed from the O-ring 111.
The rotating shaft 105 and the O-ring 11
The rotating shaft 105 is
There were also problems such as failure to recover.

The present invention has been made in view of the above problems, and its purpose is to provide a limit switch having a structure that eliminates malfunctions and improves reliability.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a case main body portion with a built-in basic switch, and a rotary shaft that supports a rotating shaft having one end protruding outside and the other end connected to the basic switch. and a head attached to the case body, the limit switch having an annular first seal lip portion and a second seal lip portion that are in close contact with the outer circumferential surface of the rotating shaft, respectively, that are axially connected to each other. A sealing member integrally molded and shifted along the rotary shaft is interposed between the rotating shaft and the head.

(Example) Hereinafter, an example of the present invention will be described in detail using the drawings.

1 and 2 show an example of a limit switch according to the present invention.

In the figure, a basic switch 2 is screwed to a case body 1 formed in a rectangular box shape.

Further, the opening of the case body 1 is closed with a cover 4 via a gasket 3, and this cover 4 is further fixed to the case body 1 with screws 5.

The lower end of the auxiliary plunger 6 is in contact with the actuator 2a of the basic switch 2 attached to the case body 1. The auxiliary plunger 6 is slidably inserted into an actuating plunger 8 that is slidably attached to the case body 1 via a bearing 7 via a protective compression bar 1.9. J5, the double of the auxiliary plunger 6 inserted into the actuating plunger 8, the actuating plunger 8
The stopper ring 10 is fitted into the inlet of the stopper ring 10.

Further, the case body 1 is provided with a head 11 corresponding to one end portion of the actuating plunger 8. A rotary shaft 12 is mounted in the head 11 in a direction perpendicular to the actuating plunger 8 via a bearing 13 . Further, a return plunger 14 and a coil spring 15 are attached to the rotating shaft 12 in correspondence with the actuating plunger 8.

The coil spring 15 keeps the return plunger 14 and the rotation @12 at the neutral position at all times. -1】
The gates of the return plunger 14 and the actuating plunger 8 are in contact with each other, and a cam portion 14a is formed on the return plunger 14 side, and together with the rotating shaft 12, +p
When the return plunger 14 is rotated, the operating plunger 8 is in a state where a pressing blade is applied.

One end of the rotating shaft 12 protrudes from the boss portion 11a of the head 11. A roller 17 is attached to one end of the tip protruding from the head 11 with the shirt 1-16 interposed (
The base of the actuating lever 18, which is removed at 7 and ζj, is detachably attached. Further, an O-ring 19 and a seal member 20 are attached to the rotating shaft 12. and,
The O-ring 19 is tightly interposed between the inner surface of the bearing 13 and the outer circumferential surface of the rotating shaft 12, and is interposed between the inner surface of the large diameter portion 21 formed at the entrance portion of the boss portion 11a of the sealing member 201 and the outer circumferential surface of the rotating shaft 12. It is closely interposed between the

Furthermore, the sealing member 20 is formed into an annular shape using a flexible member such as rubber or Teflon. As shown in FIG. 2 as an enlarged view of the Δ section in FIG. It is in a state in which it is engaged in a circumferential lock 111121a provided on the inner circumferential surface of the large diameter portion 21 and can be positioned. On the other hand, on the inner circumferential surface side of the seal member 20, a first seal lip part 23 and a second seal lip part 24 are disposed in a state shifted in the direction along the axis.
are integrally formed. Further, the first seal lip portion 23 is inclined upward toward the center, and the second seal lip portion 24 is inclined downward toward the center. ing. Furthermore, the minimum inner diameter dimension of the first seal lip portion 23 and the minimum inner diameter dimension of the second seal lip portion 24 are the same as those of the rotating shaft 1.
The outer diameter of the rotary shaft 12 is smaller than the outer diameter of the rotary shaft 12.
When mounted on the rotary shaft 12, the corner portions 23a, 24a of each seal lip portion 23.degree. Further, the minimum inner diameter dimension of the second seal lip portion 24 is smaller than that of the first seal lip portion 23, and in the installed state, the corner portion 24a of the second seal lip portion 24 is smaller. In this case, a larger area can be obtained in close contact with the outer circumferential surface of the rotating shaft 12.

Next, the operation of this limit switch will be explained.

In this limit switch, when a dog or the like is not in contact with the roller 17 provided on the actuating lever 18, the rotating shaft 12 and the actuating lever 18 are placed in a neutral position by the coil spring 15. At the same time, the operating plunger 8 is also controlled by the return plunger 14 and displaced upward by the biasing force of the compression spring 9. As a result, the actuator 2a is pushed back, and the operation of the basic switch 2 is turned off.

Next, when a dog or the like hits the roller 17, the operating lever 1B
When rotational force is applied to the operating lever 8 and the rotating shaft 12
and rotate as one. Then, since the cam portion 14a of the return plunger 14 is formed at the rotation @12, the cam portion 14a moves toward the operating plunger 8 as the rotation shaft 12 rotates.
Press down.

Further, the depression of the operating plunger 8 is transmitted to the auxiliary plunger 6 via the compression spring 9, and the lower end of the auxiliary plunger 6 presses the actuator 2a to turn off the basic switch.

When the auxiliary plunger 6 is pressed down a certain amount and the actuator 2a reaches its limit of movement, the actuating lever 18
The zero rotation is absorbed by the actuating plunger 8 being pressed down while compressing the compression spring 9 therein.

Further, when the roller 17 moves further and comes off the dog, the operating lever 18 returns to the neutral position together with the rotating shaft 12 due to the restoring force of the coil spring 15. At the same time, the actuating plunger 8 is also returned by the restoring force of the internal compression spring 9, and the operation of the basic switch 2 is turned off again.

And in a limit switch configured like this,
The head 11 and the rotating shaft 12 are sealed by a seal member 20 interposed between them, and both the first seal lip part 23 and the second seal lip part 24 are connected to the rotating shaft 12.
It is tightly attached to the outer peripheral surface of the holder to provide double airtightness.

This eliminates the breathing action within the head 11 and keeps the atmospheric pressure constant.

Further, when dirt, dust, oil, water, etc. try to enter between the head 11 and the rotating shaft 12, the first seal lip portion 23 reliably prevents the dirt, dust, etc. from entering. Oil, water, etc. that cannot be blocked by the first seal lip part 23 are transferred to the second seal lip part 2.
You can block it again with 4. This makes it possible to reliably prevent dust and oil from entering. Therefore, not only dust but also oil and water do not enter into the head 11, so the seal cap 1, which is placed between the head and the case body in conventional limit switches,
12 (see Figure 3) etc. can be eliminated. Also,
It is also possible to eliminate the O-ring 19, and even if it is not eliminated, it can be placed loosely to eliminate twisting during rotation.

(Effects of the Invention) As explained above, according to the limit switch according to the present invention, a sealing member integrally having an annular first sealing lip portion and a second sealing lip portion connects the rotating shaft and the head. The seal between the parts can be reliably maintained. This makes it possible to prevent dust and oil from entering the head, and also to keep the air pressure substantially constant by eliminating the breathing action within the head. As a result, malfunctions can be eliminated and reliability can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a limit switch according to the present invention, and FIG.
The figure is an enlarged sectional view of section A in FIG. 1, and FIG. 3 is a sectional view showing an example of a conventional limit switch. 1...Case body, 2...Basic switch, 11...
・Head, 12... Rotating shaft, 20... Seal member,
23...First seal lip portion, 24...Second seal lip portion.

Claims (1)

[Claims] A limit switch comprising a case main body with a built-in basic switch, and a head attached to the case main body supporting a rotating shaft with one end protruding outside and the other end operably connected to the basic switch, An annular first seal lip portion and a second annular seal lip portion that are in close contact with the outer circumferential surface of the rotating shaft, respectively.
A limit switch characterized in that a seal member is interposed between the rotary shaft and the head, the seal member being integrally molded with the seal lip portions being shifted from each other along the axis.