JPH10188717A - Fixing structure of key top member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing structure of a key top member such that the outer periphery of a key top plate can be sandwiched between upper and lower members and easily firmly fixed under a watertight condition. SOLUTION: In a fixing structure of a key top member the outer periphery of a key top plate 40 comprising a key top 43 provided in a predetermined position on an elastic sheet 41 is sandwiched between upper and lower cases 60, 10 and fixed. A projecting wall 15 is provided on the upper surface of the lower case 10 in such a way as to surround the outer periphery of the key top plate 40. The projecting wall 15 is made to about to the lower surface of the upper case 60 and the abutting part is ultrasonically thermally fused by means of an ultrasonic vibrating horn 70, thereby fixing the upper and lower cases 60, 10 together while narrowing the interval between them, and thus firmly sandwiching the outer periphery of the key top plate 40 between the upper and lower cases 60, 10 in the cross direction in such a way as to establish a resilient contact between them.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a key top fixing structure suitable for fixing a key top member in a watertight state by sandwiching the outer periphery of the key top member between upper and lower members.

[0002]

2. Description of the Related Art Conventionally, a key top exposed on the surface of an outer case of a device has to be waterproofed so that a liquid intruding between the outer case and the key top does not further enter the inside.

[0005] Conventionally, as shown in FIG. 5, for example, a key top 83 is formed by forming a key top 83 in a single sheet 81 having no rubber through hole on a lower case 120 containing a switch substrate 90. The top plate 80 is placed, and the upper case 110 is further placed thereon. At this time, the entire outer periphery of the key top plate 80 is sandwiched between the upper and lower cases 110 and 120, and the outer periphery is fixed with screws 100 at predetermined intervals. Thus, the outer periphery of the key top plate 80 is elastically held and held.

As a result, the liquid that has entered the surface of the key top plate 80 from between the hole 111 of the upper case 110 and the key top 83 does not enter the portion of the lower case 120 where the switch board 90 is stored, and the waterproofness of the liquid is reduced. I can do it.

[0005]

However, the above-mentioned prior art has the following problems. Because of the screwing structure, the area around the part pressed by the screw 100 can be completely waterproof, but the part far from the screw 100 (the part between the screws 100) cannot be applied with a large clamping force. This part cannot be completely waterproof.

The upper and lower cases 110 and 120 are
Since the gap is fixed, the thickness of the screw cannot be reduced too much due to the height of the screw and the strength of the upper and lower cases 110 and 120.

[0007] In order to fix the upper and lower cases 110 and 120, there is a method in which a claw is provided on the upper case or the lower case in addition to screwing, and the two cases are fixed by a snap-in method. However, the pinching force is weaker than that of a screw, so that complete waterproofing cannot be further achieved, and the thickness cannot be made too thin as in the case of screwing.

The present invention has been made in view of the above points, and has as its object to provide a key top capable of sandwiching the outer periphery of a key top member between upper and lower members and fixing the key top member easily and reliably in a watertight state. An object of the present invention is to provide a member fixing structure.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention is to fix a key top member having a key top at a predetermined position of an elastic member by holding the outer periphery of the key top member between upper and lower members. In the fixing structure of the key top member, a projection is provided on at least one of the opposing surfaces of the upper and lower members so as to surround the outer periphery of the key top member, and the projection is brought into contact with the other surface. Then, the upper and lower members are fixed while narrowing the gap by heat fusion, whereby the key top member is elastically held between the upper and lower members.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an exploded perspective view showing a switch unit to which one embodiment of the present invention is applied. As shown in FIG.
The switch board 30 and the key top plate 40 are placed on the top, and the upper case 60 is placed thereon. Hereinafter, each component will be described.

The lower case 10 is made of an ABS resin or a thermoplastic synthetic resin made of a mixture of an ABS resin and a PC resin.
It is formed in a substantially square shape, and has a recess 11 having a size and shape for accommodating a switch board 30 described below in the center thereof.
And a through hole 13 is provided in one side portion thereof so as to pass through an extraction cable 35 of the switch board 30 described below.

A projection wall 15 is provided all around the recess 11 so as to surround the recess 11 in a square shape. The protruding wall 15 has a triangular cross section.

A flat key top plate mounting surface 17 is formed between the recess 11 and the projection wall 15.

Next, the switch substrate 30 is configured by providing switch contacts at 12 places of a sheet 31 formed in a square shape, and mounting a click plate 33 thereon. An extraction cable 35 for extracting a signal is extracted from one side of the switch board 30.

Next, the key top plate 40 is configured by providing 12 key tops 43 in a sheet 41 formed in a square shape. Here, the outer dimensions of the key top plate 40 are formed so as to be accommodated inside the projection wall 15.

Further, as shown in FIG. 3, the detailed structure of the key top plate 40 is such that the surface of a mold resin 45 is covered with a synthetic resin film 47 on the upper surface of a substantially flat elastomer molded sheet 41 having no holes. Key top 4
3 is attached. At a position directly below the key top 43 on the lower surface of the elastomer molded sheet 41, a pressing projection 42 is provided.

As a material of the elastomer molded sheet 41, for example, a thermoplastic transparent or translucent elastomer material, for example, a polyester elastomer material is used. As a material of the key top 43, for example, a mixed material of PC resin and PET resin is used. As a material of the synthetic resin film 47, for example, a PET resin film is used.

Returning to FIG. 1, the upper case 60 is made of an ABS resin or a thermoplastic synthetic resin made of a mixture of ABS resin and PC resin into a substantially square plate shape. A through hole 61 is provided at a position corresponding to the top 43. The outer dimensions of the upper case 60 are substantially the same as the outer dimensions of the lower case 10.

Next, a method of assembling the switch unit will be described. Here, FIG. 3 is a sectional side view of a main part showing a method of assembling the switch unit.

First, as shown in FIGS.
The switch board 30 is housed in the recess 11 of FIG. At this time, the extraction cable 35 is passed through the through hole 13.

Next, the key top plate mounting surface 1 of the lower case 10
The key top plate 40 is placed on the top 7.

Next, the upper case 60 is placed on the projection wall 15 of the lower case 10.

Next, the ultrasonic vibration horn 70 is brought into contact with the upper case 60 from above, and the portion where the projecting wall 15 of the lower case 10 is in contact with the upper case 60 is subjected to ultrasonic heat fusion.

The ultrasonic vibration horn 70 has a rectangular shape at its tip, and a horn contact portion (hatched portion) 63 shown in FIG.
Abut. That is, the portion where the ultrasonic vibration horn 70 comes into contact is the entire portion right above the projection wall 15.

When the ultrasonic vibration horn 70 is driven, the upper case 60 is ultrasonically vibrated as shown in FIG. 4 and the stress is concentrated on the contact portion a with the projection wall 15, and this contact portion a is ultrasonically heat-sealed.

By the ultrasonic heat fusion, the upper case 60 and the lower case 10 are fixed while the space therebetween is narrowed, and at this time, the elastomer molded sheet 41 constituting the key top plate 40 sandwiched therebetween is strongly elastic. It is pinched.

Since the elastic molding sheet 41 is elastically held and held over its entire circumference, it can be made completely watertight. Therefore, the liquid that has entered the key top plate 40 from between the through hole 61 of the upper case 60 and the key top 43 does not enter the switch substrate 30.

At the same time, the key top plate 40 covers the upper surface of the switch substrate 30 in a sealed state, so that the intrusion of static electricity from the upper case 60 side can be reliably prevented.

When the key top 43 is pressed, the elastic molded sheet 41 having elasticity is extended, and the pressing protrusion 42 presses the click plate 33 to be inverted, and the switch contact immediately below the switch is turned on.

Although one embodiment of the present invention has been described in detail, the present invention is not limited to this, and various modifications as described below are possible. The projection wall does not necessarily have to be formed as a single piece, but may be formed in a dotted line according to the required degree of sealing.
Also, two or more rings may be formed.

The projection wall is not necessarily provided on the lower case side, but may be provided on the upper case side. Moreover, you may provide in both cases.

The protruding wall does not necessarily have to have a triangular cross section, and may have a semicircular shape, a square shape, or another shape. In this case, the upper end side does not necessarily have to be at an acute angle, and the upper end side may be flat. In short, it is sufficient if the area is such that stress is concentrated and fused when ultrasonic vibration is applied.

The ultrasonic vibration horn need not necessarily be applied to the upper case, but may be applied to the lower case.

In the above embodiment, the upper and lower cases hold the keytop plate. However, the outer periphery of the keytop plate may be held by other upper and lower members other than the case, such as a base.

[0035]

As described in detail above, the present invention has the following excellent effects. The outer periphery of the key top member can be strongly held between the upper and lower members, and can be easily and reliably fixed in a watertight state.

The protrusions provided on at least one of the upper and lower members are fixed by narrowing the gap between the upper and lower members by heat fusion. The thickness is only the thickness of the protrusions and the upper and lower members. The thickness can be reduced as compared with the case of a retaining structure or the like, and the fixing strength can be increased.

The production is easy because the protrusions are merely heat-sealed.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a switch unit to which an embodiment of the present invention has been applied.

FIG. 2 is a perspective view illustrating a method of assembling the switch unit.

FIG. 3 is a sectional side view of a main part showing a method of assembling the switch unit.

FIG. 4 is a side sectional view of a main part showing a method of assembling the switch unit.

FIG. 5 is a schematic side sectional view showing a conventional example.

[Description of Signs] 10 Lower case (lower member) 15 Projection wall 30 Switch board 40 Key top plate 41 Sheet 43 Key top 60 Upper case (upper member) 70 Ultrasonic vibration horn

Claims (1)

[Claims] 1. A key top member fixing structure in which an outer periphery of a key top member provided with a key top at a predetermined position of an elastic member is fixed by sandwiching the key top member between the upper and lower members, wherein the upper and lower members oppose each other. On at least one of the side surfaces, a projection is provided so as to surround the outer periphery of the key top member, and the projection is brought into contact with the other surface and heat-fused to reduce the distance between the upper and lower members. A key top member fixing structure, wherein the key top member is elastically held between upper and lower members by being fixed.