JPH0334022Y2 - - Google Patents

Description

[Detailed description of the invention] This invention involves attaching a movable contact made of conductive rubber to the inner wall ceiling of a dome-shaped cap made of an insulating elastic material, and using the snap action of the cap to connect a fixed contact board. This relates to a push button switch that opens and closes between fixed contacts on the top with a click sensation.

A conventional push button switch using a dome-shaped cap made of elastic material has a structure as shown in Fig. 1.
is a printed circuit board, 2 is a dome-shaped cap made of insulating elastic material, 3 is a key top, 4 is a frame body,
A cap 2 is arranged on a printed circuit board 1, a key top 3 is placed on top of the cap 2, and a collar 5 of the key top 3 is force-locked by the cap 2 to a convex edge 6 of a frame 4. In order to prevent play between the flange 5 and the convex edge 6 of the frame 4, the height _H1 from the bottom of the cap 2 to the top surface of the flange 5 of the key top 3 should be
If the height H 2 from the bottom of the cap 2 to the lower surface of the convex edge ₆ of the frame 4 is kept within H ₁ ≧H ₂ , play in the key top 3 will be eliminated.

However, there are many types of keyboards with this structure,
Since it is not suitable for small quantity production, the second
A push button switch A as shown in the figure is used.

FIG. 3 is a drawing showing the mounting structure of the second push-button switch A on the frame. The push-button switch A consists of a dome-shaped cap 2 and a fixed contact board 7, and is embedded in the fixed contact board 7. The end of the fixed terminal 8 is inserted into the printed circuit board 1 and fixed. (The same parts as in Figure 1 are given the same numbers.)
In Figure 3, printed circuit board 1 and key top 3
The height H1 to the top surface of the guard 5 is the height _H1 of the push button switch A.
is related to the height _H3 , and this height _H3 includes many variable factors such as variations in the dimensions of the switch A itself, as well as the unevenness of the installation of the switch A on the printed circuit board 1, and is constant. Therefore, if the height _H2 from the printed circuit board 1 to the lower surface of the convex edge 6 of the frame 4 is constant, the key top 3 of some switches may play and generate a rattling sound, and some may Since the key top 3 is pressed more than necessary, there are various drawbacks such as the tactile feedback feel of the cap 2 being impaired.

The present invention aims to eliminate such conventional drawbacks, and the purpose of the present invention is to provide the cap with an amount of free movement, without impairing the operating characteristics of the cap, and to improve the relationship between the key top and the frame. The purpose of this invention is to provide a push button switch that eliminates the play between buttons.

Figure 4 shows the structure of the switch according to the present invention.
9 is a dome-shaped cap made of an insulating elastic material;
10 is a movable contact made of conductive rubber; 11 is a first support base provided on the lower circumference of the cap 9; 12 is a movable contact made of conductive rubber;
is a second support stand provided on the inner circumference of the first support stand 11, and is set lower in height than the first support stand 11 by a distance a. 13 is a fixed contact board 15 in which the fixed terminal 14 is buried; 15 is a fixed contact; 16 is a cylindrical projection protruding from one surface of the fixed contact board 13; 1 unit
The cap 9 is housed in a groove 17 provided between the cap 1 and the cap 9 , and the cap 9 is supported by the protrusion 16 .

Reference numeral 23 denotes a fulcrum provided on the circumference of the cap 9 corresponding to the recess 17. When the cap 9 is pressed, the protrusion 16 acts as a lever, and the fulcrum 23
The cap 9 is bent around the center. Note that the first support stand 11 is scissored to the edge 18 of the fixed contact board 13.

The push button switch of the present invention has the above-mentioned structure,
When the cap 9 is not pressed, there is a distance a between the lower surface of the second support base 12 and the upper surface 13a of the fixed contact base plate 13, as shown in FIG. When you put it on, the A part transforms,
As shown in FIG. 5, the protrusion 16 acts as a lever, and the cap 9 bends about the fulcrum 23, allowing the second support base 1 to bend.
2 moves by a distance a, the lower surface of the second support 12 comes into contact with the upper surface 13a of the fixed contact board 13, and the upper surface 9a of the cap 9 moves by a distance a from the position shown by the two-dot chain line to the position shown by the solid line. This a is the amount of free movement of the cap 9.

If a stronger pressing force is applied than in the state shown in Figure 5,
With reference to the second support stand 12, the cap 9 is located at the sixth position.
As shown in the figure, the movable contact 10 is bent and comes into contact with the fixed contacts 15, 15 with a click sensation.

FIG. 7 is a sectional view showing the state in which the push button switch of the present invention is assembled into the frame 19, where the two-dot chain line indicates the state of the cap 9 before assembly, and the solid line indicates the state of the cap 9 after assembly. is assembled in advance in a state where it is bent by an amount of free movement a, and the end of the fixed terminal 14 is inserted into the printed circuit board 20 and fixed by soldering on the back side. Therefore, the cap 9 presses the key top 21 against the edge 22 of the frame 19.

Figures 8A and 8B are graphs showing the relationship between the operating force and the amount of movement of the cap of the conventional push button switch and the push button switch of the present invention.
In Fig. 8A, in order to prevent play between the key top and the frame of the conventional push button switch, if the conventional cap is bent by a distance a in advance, play between the cap and the frame can be prevented. Initial point of pressing O
moves to B, and from the initial pressing point B to the click point A
The operating force up to S 2 decreases from the operating force S ₁ when there is no deflection a to S ₂ , which has the disadvantage that the click feel becomes unclear and at the same time the amount of movement of the key top becomes smaller. However, according to the present invention, since the cap has an amount of free movement a in advance, as shown in FIG.
The movement curve connecting B, A, and C after moving from point B to point B is approximately the same as the movement curve connecting O, A, and C in Figure 8A, and from the initial pressing point B to click point A. Since the operating force can be maintained at the conventional _S1 shown in FIG. 8A, the click feeling is clear and a predetermined amount of movement can be ensured. Furthermore, the upper surface of the cap is always pressed against the lower surface of the key top due to the amount of free movement of the cap, so play between the key top and the frame can be prevented.

As explained above, according to the present invention, a push button switch formed by placing and fixing a cap on a fixed contact board is provided with an amount of play in advance due to the second support base, and the cap can be moved within this amount of play. Since the push button switch is assembled between the key top and the printed circuit board in a pressed state, it is possible to prevent the key top from rattling without impairing the operating characteristics of the cap.

[Brief explanation of the drawing]

1 to 3 show conventional examples, FIG. 1 is a sectional view showing how a conventional push button switch is attached to a frame, FIG. 2 is a sectional view of a conventional push button switch, and FIG. The figure is a cross-sectional view showing how the push button switch shown in Fig. 2 is attached to the frame, Figs. 4 to 7 show an embodiment of the push button switch of the present invention, and Figs. Cross-sectional views showing the state in which the cap is not pressed, the state in which it is lightly pressed, and the state in which the switch is turned on by pressing it more strongly. Figure 7 is a cross-sectional view showing the state in which the push button switch of the present invention is assembled into the frame. Figure 8 stomach,
B is a graph showing the relationship between the operating force of the cap and the amount of movement of the conventional switch and the switch of the present invention, respectively. 8... Fixed terminal, 9... Cap, 10... Movable contact, 11... First support stand, 12... Second support stand, 13... Fixed contact board, 14... Fixed terminal, 15... ...Fixed contact, 16...Protrusion, 19...
Frame body, 20... printed circuit board, 21... key top, 23... fulcrum.

Claims (1)

[Scope of utility model registration request] comprising a fixed contact board provided with fixed contacts, and a dome-shaped cap made of an insulating elastic material and having movable contacts placed and fixed on the fixed contact board,
In a push button switch in which the fixed contact board and the cap are incorporated between the printed circuit board and the key top, the bottom periphery of the cap includes:
A first support stand on the outside, a second support stand on the inside that is shorter in height than the first support stand, and a thin part located between the first and second support stands, A push button switch characterized in that, when the fixed contact board and the cap are assembled between the printed circuit board and the key top, the second support base is pressed and displaced using the thin wall portion as a fulcrum.