JPH0541469Y2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention relates to a keyboard switch used as an input means for various devices.

``Prior Art'' The present applicant proposed a keyboard switch as shown in FIG. 2 in ``Utility Application No. 151904/1983: Name Keyboard Switch.''

This keyboard switch has a membrane switch 12 mounted on a plate 11 made of, for example, an iron plate.
are laminated, and a positioning sheet 21 is attached to the upper surface of the membrane switch 12 via an adhesive layer 19.

The membrane switch 12 is made of a pattern sheet 1 on which conductive patterns 16 and 17 are formed on the upper and lower sides with a spacer 15 in between, as shown in FIGS. 3 and 4.
3 and 14, and a switch is formed in the hole 15A formed in the spacer 15.

The previously proposed keyboard switch is characterized by a structure in which a tactile plate 23 is placed on the membrane switch 12.

In other words, simply pressing down the membrane switch 12 does not provide a tactile notification that the conductive patterns 16 and 17 have contacted each other. For this reason, the previously proposed keyboard switch has a tact plate 23 placed on the membrane switch 12, and a coil spring 3 for operation attached to the key 30.
By pressing down with 7, the tact plate 2
3 reverses the direction of its curvature when a certain force is exceeded, and this reversal turns on the membrane sheet.
By reversing the direction of the curvature, it changes the pressing force and notifies the fingertip that the switch has been turned on, and is characterized by a structure that has a so-called tact function.

The tact plate 23 used in the previously proposed keyboard switch is formed of a band-shaped leaf spring, as shown in FIG. That is, the belt-shaped leaf spring part 23B is spanned over the rectangular frame 23A, and the belt-shaped leaf spring part 23 is curved in an upwardly convex direction.

The frame 23A supporting the leaf spring 23B is housed and positioned in the hole 22 formed in the positioning sheet 21 attached to the upper surface of the adhesive layer 19, as shown in FIG. 39 is adhered to the adhesive layer 19 and its position is fixed. Adhesive layer 19
A hole 38 is formed at a position facing the leaf spring portion 23B, and in this portion, the membrane sheet 12 directly faces the back surface of the leaf spring portion 23B.

A housing 26 is placed on the upper surface of the positioning sheet 21, as shown in FIG. The housing 26 is integrally formed with the mounting plate 25 from a resin material. A cylindrical guide part 28 is formed at a position facing the tact plate 23, and the key 3 is attached to this guide part 28.
A stem 29 protruding from 0 is attached so as to be slidable in the vertical direction.

A key top 31 is formed integrally with the stem 29 at the upper end thereof. These stems 29 and
The key top 31 constitutes a key 30 .
The key 30 has a hole 35 formed in the mounting plate 25, a leg 33 protruding from the key 30, as shown in FIG.
A claw 34 formed at the tip of this leg 33 prevents it from coming off.

36 is a return coil spring for biasing the key top 31 and stem 29 upward, and 37 is an operating coil spring.

The upper end of the operating coil spring 37 fits into the holding portion 32 formed on the back side of the key 30, and the lower end is pressed against the upper surface of the leaf spring 23B constituting the tact plate 23. For this purpose, a projection 24 is formed on the upper surface of the leaf spring 23B, and the lower end of the operating coil spring 37 is engaged with this projection 24 to prevent it from coming off from the leaf spring portion 23B.

"Problem to be solved by the invention" In the previous proposal, the operating coil spring 37 is brought into contact with the tact plate 23 to the extent that it applies a slight biasing force. In other words, even when the key 30 is at the top dead center position, the operating coil spring 37 is slightly compressed and deformed.

Therefore, due to variations in the length of the operating coil spring 37 and misalignment at the engagement point with the tact plate 23, the operating coil spring 37 is in a state where it has come off the protrusion 24 of the tact plate 23, as shown in FIG. may be retained.

As shown in FIG. 7, when the operating coil spring 37 is detached from the protrusion 24 of the tact plate 23 and a shock is applied during transportation or during actual use, the engagement between the operating coil spring 37 and the tact plate 23 may be interrupted. Accidents may occur where the alignment is incorrect.

When the lower end of the operating coil spring 37 is disengaged from the protrusion 24 of the tact plate 23, the operating coil spring 37 becomes the tact plate because the tact plate 23 has a band-like planar shape as shown in FIG. 23
It has the major drawback of becoming entangled with the sides of the body, making it impossible to return to its original state.

In addition, as shown in Fig. 7, the operating coil spring 3
7 is removed from the protrusion 24 of the tact plate 23, if a key operation is performed, the lower end of the operating coil spring 37 will slide slightly between the tact plate 23 and this sliding may generate noise. .

The purpose of this invention is to propose a key switch structure in which the operating coil spring 37 does not come out of engagement with the tact plate 23 due to impact or the like.

"Means for Solving the Problem" In this invention, when the key is at the top dead center position, the lower end of the operating coil spring is positioned slightly above the protruding apex of the protrusion 24 of the tact plate 23, The lower end portion is a tightly wound end turn portion that does not undergo compression deformation, and the length a of the end turn portion in the axial direction is equal to the sum of the reversal stroke length b of the tact plate 23 and the protrusion length c of the protrusion 24. It is said to be larger than b+c.

With this configuration, even if the lower end of the operating coil spring comes out of engagement with the tact plate during a pressing operation, the lower end of the operating coil spring will separate from the tact plate when the key returns to the top dead center position. Therefore, the operating coil spring does not become entangled with the tact plate. Therefore, it is possible to provide a keyboard switch with a highly reliable tact function.

``Example'' Figure 1 shows an example of this invention. In FIG. 1, parts common to those of the conventional keyboard switch explained in FIGS. 2 to 7 are given the same reference numerals, and duplicate explanations thereof will be omitted. The length is selected to be such that the lower end of the operating coil spring 37 is slightly separated from the tact plate 23 when the key 30 is at the top dead center position.

The distance M between the lower end of the operating coil spring 37 and the tact plate 23 is selected so that M is slightly larger than the height C of the protrusion 24 formed on the upper surface of the tact plate 23.

Furthermore, a tightly wound end-turn portion 37A that does not undergo compression deformation is formed on the lower end side of the operating coil spring 37. When the dimension of the end turn portion 37A is a, the reversal deformation stroke of the tact plate 23 is b, and the height of the protrusion 24 is c, the relationship is selected to be a>b+c.

With this configuration, the lower end of the operating coil spring 37 is released in a free state when the key 30 is at the top dead center position. Therefore, the operating coil spring 37 is supported by the holding part 32 so that its axis is aligned with the axis of the holding part 32.

When the key 30 is pressed down, the operating coil spring 3
The lower end of the end turn portion 37A of No. 7 comes into contact with the upper surface of the tact plate 23, and the operating coil spring 37 is gradually compressed and deformed. The compression deformation of the operating coil spring 37 progresses, and the biasing force of the operating coil spring 37 is applied to the tact plate 2.
When the reversal threshold of 3 is reached, the tact plate 23 reverses its curve direction and deforms into a downwardly convex state.
This deformation pushes the membrane switch 12 and turns it on.

"Effect of the invention" According to this invention, the length a of the end turn portion 37A in the axial direction is greater than the sum b+c of the reversal stroke length b of the tact plate 23 and the protrusion length c of the protrusion 24.
Membrane switch 1 is activated by pressing key 30.
2, even if the lower end of the operating coil spring 37 disengages from the tact plate 23 due to some kind of impact, the pressing force on the key 30 is released and the key 30 is turned on.
When it returns to the top dead center position, the lower end of the operating coil spring 37 separates from the tact plate 23 and returns to a free state. As a result, the axis of the operating coil spring 37 returns to its normal position, allowing the next pressing operation to be performed normally. Furthermore, even if the outer periphery of the operating coil spring 37 comes into contact with the side of the tact plate 23 when the operating coil spring 37 is disengaged from the tact plate 23,
Since the end turn portion 37A is formed at the lower end of the operating coil spring 37, the operating coil spring 37 is connected to the tact plate 23.
It won't get tangled.

Further, since the operating coil spring 37 is not entangled with the tact plate 23, the lower end of the operating coil spring 37 does not slide against the tact plate 23 during the pressing operation. As a result, it is possible to provide a quiet keyboard switch that does not generate frictional noises when pressed.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of this invention, FIGS. 2 and 3 are sectional views for explaining the conventional technique, and FIG. 4 is an exploded perspective view for explaining the conventional technique. FIG. 5 is a plan view for explaining the conventional technique, and FIGS. 6 and 7 are cross-sectional views for explaining the conventional technique. 11...Plate, 12...Membrane switch, 23...Tact plate, 30...Key, 37...
Coil spring for operation.

Claims (1)

[Scope of Claim for Utility Model Registration] A tact plate having a curve such that the upper side is convex is arranged on the upper surface of the membrane switch, and a coil spring for operation protruding from the key is pressed against this tact plate, so that the key can be pressed. Therefore, the operating coil spring is compressed and deformed, and the bending direction of the tact plate is reversed by the biasing force of the compressed and deformed operating coil spring, and the membrane switch is turned on by the reversing force. In the keyboard switch with a tact function, a protrusion is formed in the center of the tact plate to protrude upward facing the axis of the operating coil spring, and a fixing part is integrally formed around the periphery of the tact plate. is fixed to the upper periphery of the membrane switch by an adhesive layer, and a return coil spring is provided for returning the pressed key to its original position. The lower end of the coil spring is located slightly above the protruding apex of the protrusion of the tact plate, and the lower end of the operating coil spring is a tightly wound end portion that does not undergo compression deformation. The length a in the axial direction is greater than the sum b+c of the reversal stroke length b of the tact plate and the protrusion length c of the protrusion. A keyboard switch characterized by: