JPH04303529A - Limit switch - Google Patents

Abstract

PURPOSE:To provide a safety function capable of forced separation when a movable piece is fused to an NC contact. CONSTITUTION:In a limit switch in which turning-on or -off is performed between a movable piece 5 and NC and NO contacts 7 and 8 by depressing the movable piece 5, provided in a main body case 1, via a push button 4 with a plunger 3 supported vertically movably with an upper case 2, an operating piece 6, its one end is axis-supported, is provided above the movable piece 5, the lower end of the push button 4 is abutted on the upper surface of the operating piece 6, and also the tip of the operating piece 6 is engaged with the tip side upper surface of the movable piece 5. When the movable piece 5 is fused to the NC contact 7, the movable piece tip can be forcedly separated from the NC contact 7 with the operating piece 6 tip by pushing down the operating piece 6 with the plunger 3 via the push button 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limit switch having a safety function of forcibly separating welded contacts.

0002

[Prior Art] A conventional horizontal limit switch as shown in Fig. 4.
The following are known.

The above limit switch has an upper case b attached to the upper surface of the main body case a, and a plunger d urged upward by a return spring c to the upper case b.
is supported to be movable up and down, and a roller e is rotatably attached to the upper end of the plunger d.

Further, the lower end of the plunger d is in contact with the upper end of the push button f, and the lower end of the push button f is in contact with the upper surface of a movable piece g provided in the main body case a, and the roller When the plunger d is pushed down via e, the movable piece g is also pushed down via the push button f.

One end of the movable piece g is supported by a receiver h, and the other end is inserted between a normally closed (NC) contact i and a normally open (NO) contact j that are vertically spaced apart. It is configured such that it is normally in contact with the NC contact i, and when pressed down by the push button f, it is in contact with the NO contact side. Note that k in the figure is a movable spring that urges the movable piece g upward.

[0006]

[Problem to be Solved by the Invention] In the limit switch as described above, if the movable piece g is welded to the NC contact i during use, the movable piece g will be elastically deformed even if the plunger d is pushed down, and the movable piece g There was a problem with the NC contact i not opening, making it unusable.

The present invention was made in order to improve the above-mentioned conventional problems, and it is an object of the present invention to provide a limit switch having a safety function that allows the movable piece to be forcibly opened even if it is welded to the NC contact. This is the purpose.

[0008]

[Means for Solving the Problems] In order to achieve the above object, the present invention presses a movable piece provided in the main body case via a push button by a plunger supported vertically movably in the upper case. Accordingly, in a limit switch that turns on and off between a movable piece and an NC contact and an NO contact, an operating piece whose one end is pivoted is provided above the movable piece, and the lower end of the push button is mounted on the upper surface of this operating piece. are brought into contact with each other, and the tip of the operating piece is engaged with the upper surface of the tip end side of the movable piece.

[0009]

[Operation] If the movable piece is welded to the NC contact with the above configuration, the tip of the movable piece can be pushed down by the tip of the operating piece by pushing down the plunger and pressing the operating piece downward via the push button. , force the movable destination to N
It can be opened from the C contact.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings shown in FIGS. 1 to 3. Figure 1 shows a vertical cross-sectional view of a horizontal limit switch. In this figure, 1 is a main body case, 2 is an upper case, 3 is a plunger, 4 is a push button,
5 is a movable destination, 6 is an operating piece, 7 is an NC contact, 8 is an NO contact, and 9 is a movable spring.

A receiver 11 is fixed in the main body case 1, and the base end of the movable piece 5 is rotatably supported on one end side of the receiver 11, and the upper side of this support is rotatably supported. Both ends of a pin 6a protruding from one end of the operating piece 6 are rotatably supported.

The operating piece 6 is made of a rigid plate and is formed into a substantially U-shape as shown in FIG. 3, with an open end extending toward the distal end of the movable piece 5. The open end of the operating piece 6 is bent upward in a substantially inverted L shape,
The tip of this bent portion 6b is brought into contact with the top surface on the tip side of the movable piece 5 from above.

Further, a contact 5a that projects vertically is fixed to the tip of the movable piece 5.
The movable piece 5 is inserted between the contact 7 and the NO contact 8.
Due to the elasticity of the movable spring 9, which is formed by cutting and bending, the movable spring 9 is pressed against the NC contact 7 side.

On the other hand, a plunger 3 urged upward by a return spring 15 is supported in an upper case 2 attached to the upper surface of the main body case 1 so as to be movable up and down.

A roller 16 is rotatably attached to the upper end of the plunger 3 by a pin 17, and the lower end of the plunger 3 is in contact with the upper end of a push button 4 supported by the upper case 2 so as to be movable up and down. ing.

[0016] The pushbutton 4 is equipped with a dustproof rubber cap 1.
8, the lower end side protrudes into the main body 1, and both ends of a pressing portion 4a attached to the lower end portion are brought into contact with the upper surface of the movable piece 5 from above, as shown in FIG.

Next, the operation of the limit switch configured as described above will be explained. When no force is applied to the roller 16 attached to the tip of the plunger 3, the plunger 3 is raised as shown in FIG. 1 by the action of the return spring 15. located in
At this time, the tip of the movable piece 5 is raised by the action of the movable spring 9, and the contact 5a is connected to the NC contact 7.

When the plunger 3 is pushed down from this state via the roller 16, the operating piece 6 is pushed down by the pressing portion 4a of the push button 4, and the movable piece 5 is further pushed down by the tip of the operating piece 6.

As a result, the contact point 5a at the tip of the movable piece 5 is
The C contact 7 is opened and the NO contact 8 is connected.

Furthermore, when the pressure of the roller 16 is released, the plunger 3 returns to its original position by the action of the return spring 15, so the movable piece 5 also returns to its original position by the action of the movable spring 9, and the contact 5a becomes an NC contact. Connected to 7.

The above is a normal operation, but if for some reason the contact 5a of the movable piece 5 becomes welded to the NC contact 7 during use, the plunger 3 is strongly pushed down via the roller 16.

As a result, the operating piece 6 is also strongly pressed down via the pressing portion 4a of the push button 4. Since the operation piece 6 is formed of a rigid plate material, the tip portion strongly presses down the tip side of the movable piece 5 without being elastically deformed at this time.

[0023] As a result, the welded contact 5a of the movable piece 5
can be forcibly opened from NC contact 7.
be able to use it again.

[0024]

[Effects of the Invention] As detailed above, this invention has a safety function that forcibly separates the movable piece from the NC contact even if it is welded to the NC contact, so welding does not occur during use. However, the limit switch does not become unusable, and the reliability of the limit switch can be improved.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a limit switch according to an embodiment of the present invention.

FIG. 2 is a detailed side view of circle A in FIG. 1;

FIG. 3 is a plan view of the same.

FIG. 4 is an explanatory diagram of a conventional limit switch.

[Explanation of symbols]

1 Main body case 2 Upper case 3 Plunger 4 Push button 5 Movable piece 6 Operation piece 7 NC contact 8 NO contact

Claims (1)

[Claims] [Claim 1] A movable piece provided inside the main body case,
In a limit switch that turns on and off between a movable piece and an NC contact and an NO contact by pressing through a push button with a plunger supported on an upper case so as to be movable up and down, one end is pivotally supported on the upper side of the movable piece. The limit switch is provided with an operating piece, the lower end of the push button is brought into contact with the upper surface of the operating piece, and the tip of the operating piece is engaged with the upper surface on the tip side of the movable piece.