JPH0421227Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Field of the Invention> This invention relates to a digital switch used in a code signal extraction circuit, etc.

<Prior art and its problems> In general, in this type of switch, when setting a desired number on the display means exposed on the front part of the switch case, the operation section provided on the front part side is pressed with a finger. Since it is designed for direct operation (touch operation), it is extremely vulnerable to electrostatic discharge. In other words, the electric charge accumulated due to friction of the human body is discharged from the operation part, such as a push button, to the inside of the switch case when a finger touches the operation part during the above operation, and this is not possible with an electronic type. There is a risk that the internal integrated circuit elements etc. will be destroyed and the switch function will be lost. Of course, even if the information is mechanical, the same result will occur if the information is transmitted to the CPU of the control device through an internal mechanism or the like.

For this reason, there is a known device that prevents the electrostatic damage by providing a grounding panel near the operating section on the front side of the switch case and connecting this grounding panel to a grounding circuit (for example,
(Refer to Utility Model Application Publication No. 159123/1983).

In this device, a ground panel is pasted on the front side of the switch case, a screw hole is provided through the front wall of the switch case, and a conductive screw is screwed into this screw hole from the inside of the switch case. The tip of the screw is brought into contact with the adhesive surface of the earth panel for electrical connection, and the screw is connected to the earth circuit via a terminal fitting, a connecting fitting and a lead wire.

However, this device requires parts such as the terminal fittings and has a complicated structure, and also requires complicated assembly operations such as pasting the earth panel and attaching the terminal fittings.

<Purpose of the invention> This invention was made in order to eliminate the problems of the above-mentioned conventional devices.The purpose of this invention is to provide a digital switch that can protect circuits and elements from static electricity during operation and that is easy to assemble and has a simple structure. The purpose is

<Structure and effects of the invention> The digital switch according to this invention has a frame-shaped earth plate formed by a pair of U-shaped pieces and a pair of connecting pieces that connect the corresponding ends of both U-shaped pieces. A pair of lateral grooves into which the U-shaped pieces are fitted are provided near the operating section on the front side of the switch case, and each connecting piece is fitted between corresponding ends of the lateral grooves. A pair of vertical grooves to be fitted are provided, each piece of the ground plate is fitted into the corresponding groove, and an external lead body extending from the rear end of the switch case to the ground plate is inserted into the switch case. One end of the external lead body, which is disposed on the inner surface and connected to the ground circuit, is brought into contact with the ground plate through an opening formed in the switch case.

With this design, the earth plate prevents electric charge from the human body during touch operation from discharging into the switch case, protecting the circuits and elements.Furthermore, the earth plate can be easily attached, and the lead body Connections can be made at the same time as installation.

<Description of Embodiments> Hereinafter, embodiments of this invention will be described with reference to the drawings.

FIG. 1 and FIG. 2 each show an example of a digital switch according to this invention. In the figure, 1 is a switch case, and the case body 2
and base 3. A display window 4 is formed in the front wall 1a of the switch case 1, and a digital display, for example, a 7 segment
The numerical display on the LED display 5 is made visible. 6 is an addition side push button set at the bottom of the display window 4, 7 is a subtraction side push button set at the top of the display window 4, and 8 and 9 are mechanical switches provided corresponding to the above push buttons 6 and 7, respectively. be. Both push buttons 6 and 7 constitute an operating section 10 for rewriting a set value of a reversible preset counter, which will be described later, while looking at the numerical value displayed on the display 5.

Reference numeral 11 denotes a status indicator disposed between the mechanical switch 9 and the indicator 5, which is composed of an LED or the like. 12 is a through hole formed in the front wall 1a corresponding to the status indicator 11, and 13 is a first printed wiring board on which the indicators 5, 11 and input switches 8, 9 are mounted. A second printed wiring board 14 is electrically connected to the first printed wiring board 13 via a flexible board 15, and is equipped with an integrated circuit element 16 and other electrical components (not shown). . The integrated circuit element 16 includes a reversible preset counter that displays the output and signal status on each display 5, 11, a drive circuit for each display 5, 11,
It constitutes a pulse generation circuit for adding or subtracting a reversible preset counter, a latch circuit for holding a signal, and an input/output circuit (none of which is shown). 17 is the connecting connector, 18 is the second
A wrapping terminal 19 is fixed to the rear end of the printed wiring board 14, and a filter 19 is detachably mounted on the front wall 1a side facing the display window 4 and the through hole 12.

On the front wall 1a of the switch case 1, there is a third
As shown in the figure, horizontal grooves 20, 20 are formed near the display 5 side of each push button 6, 7, and each horizontal groove 20, 20 has a pair of corners of a frame-shaped earth plate 21. The letter-shaped pieces 21a, 21a are fitted. A pair of connecting pieces 21b, 21 connecting the tips of the U-shaped pieces 21a, 21a.
b denotes a vertical groove 2 formed on the outer surface of the switch case 1, that is, on each outer surface of the case body 2 and the cover 3.
2 and 22 (see FIG. 4), and the connecting piece 21b on the case body 2 side is removably locked to filter locking protrusions 23 and 23 provided near the vertical groove 22. There is. 19a is an engagement groove provided in the filter 19 and engaged with the projection 23.

A conductive tape 24 as an external lead body for the earth plate is attached to the inner surface of the case body 2, and one end 24a extends to the rear side of the case body 2 and passes through the rear wall to the second printed wiring board. 14
The other end 24 is connected to the ground potential wiring section of
b extends to the front side, projects into an opening 25 (FIG. 5) formed in one of the longitudinal grooves 22, and comes into contact with one of the connecting pieces 21b of the earth plate 21.

In the above configuration, for example, the data written by the CPU is displayed numerically on the display 5, but if the operator sees the numerical value on the display 5 and finds that it differs from the set value, he or she presses push button 6 or push button 7. It can be corrected by manipulation.

When the push button 6 or 7 is operated, the charge accumulated in the operator's body tries to discharge into the switch case 1, but since the earth plate 21 is installed near the push button 6 or 7, the charge is discharged to the ground plate 21, and the conductive tape 2
4, it will flow to the earth, for example.
Therefore, there is a risk that the display 5 and the integrated circuit element 16 will be destroyed by static electricity.
a, 21b are fitted into the respective grooves 20, 22 of the front wall 1a of the corresponding switch case 1, making assembly easy.
4b is in contact with the ground plate 21 through the opening 25 formed in the switch case 1, so that the ground plate 21 and the conductive tape 24
The electrical connection with the earth plate 21 can be made simultaneously with the fitting of the earth plate 21.

The shape of the ground plate 21 is not limited to the above, and can be changed depending on the switch case 1 and the mounting structure.Also, instead of the conductive tape 24, a conductor may be inserted into the inner surface of the switch case 1. It is also possible to construct the lead body using a material or the like.

Although the above embodiment has been explained using an electronic type as an example, even if it is a mechanical type in which a slider is attached to a rotary number disc that operates by clicking, the above configuration can be used to easily control the control equipment side. This prevents the negative effects of static electricity on the CPU, etc.

[Brief explanation of drawings]

Figures 1 and 2 are a side sectional view and a bottom sectional view showing an example of the digital switch according to this invention, respectively, Figure 3 is a perspective view of the digital switch showing the mounting structure of the earth plate, and Figure 4 shows the filter. Front view of the digital switch with it removed.
FIG. 5 is a sectional view showing the connection structure between the earth plate and the lead body. 1... Switch case, 1a... Front part, 10
...Operation unit, 21...Earth plate, 24...
External lead body, 24b... end of external lead body 24, 25... opening.

Claims (1)

[Scope of utility model registration request] A frame-shaped earth plate is constructed by a pair of U-shaped pieces and a pair of connecting pieces that connect the corresponding tips of both U-shaped pieces, and is placed near the operating section on the front side of the switch case. A pair of lateral grooves into which the U-shaped pieces are fitted are provided, and a pair of vertical grooves into which the connecting pieces are fitted are provided between corresponding ends of the lateral grooves. Each piece of the plate is fitted into the corresponding groove, and an external lead body extending from the rear end of the switch case to the ground plate is arranged on the inner surface of the switch case, and connected to the ground circuit. One end of the above external lead body,
A digital switch, characterized in that the switch case is brought into contact with the ground plate through an opening formed in the switch case.