Patent Application
20090133999
1. Field of the Invention
The present invention relates to a key switch arrangement of a keyboard serving as an input device for use in information processing equipment, measuring apparatuses, medical instruments, etc., specifically excellent in waterproofing property.
2. Description of the Background Art
In general, a keyboard for use in a portable personal computer or the like is arranged to secure operability such that a key-top descends, when depressed at any portion thereof, without being inclined. For this aim, a conventional key switch arrangement has link mechanism provided under the key-top. Such a switch arrangement having the link mechanism provided under the key-top is disclosed, for example, by Japanese patent laid-open publication No. 2001-229764.
Reference will be first be made to
The back plate 17 has an embossed portion 17a formed to protrude upward, which enters a through-hole 16b formed in the membrane sheet 16. In the lower part of the holder 15 there is formed a welding pin 15a, which is arranged to enter a hole 17b formed in the embossed portion 17a of the back plate 17. The back plate 17 is welded to the holder by intervention of the membrane sheet 16 in a state of the welding pin 15a having entered the hole 17b.
In the key switch arrangement described above, even when an edge part of the key-top 11 is depressed, the key-top 11 descends while keeping itself horizontal thanks to the link mechanism consisted of the first and second link members 12, 13. For example, when an edge of the key-top 11 shown in
Moreover, in preparation for the case where an operator spills liquid over the keyboard by accident during operation of the key switches, a prior art keyboard device has been improved to be equipped with waterproofing property. Such a keyboard is disclosed, for example, by another Japanese patent laid-open publication No. 2002-216575. The keyboard device disclosed by the publication has a membrane sheet, on which there is provided a waterproof sheet having waterproof walls around it, so that a circuit board and others in the lower part of the keyboard are not influenced, even when liquid is spilled over the keyboard by accident.
However, in recent years, a progress in keyboards has been accelerated in respect of thinning and downsizing, which makes it difficult to secure a sufficient gluing width in a single membrane sheet. For this reason, in a prior art key switch arrangement, when spilled liquid has been left for a long period of time, the liquid enters the key switch structure through a glued portion of the membrane sheet. More specifically, as shown in
On the other hand, in the key switch arrangement provided with a waterproof sheet, when a resin film or other material is molded on the waterproof sheet to then form waterproof walls around it, the waterproof sheet tends to be thicker. In the keyboard with accelerated thinning and downsizing, as a rubber dome presses the waterproof sheet in the upper part of a contact at the time when a key is depressed, it tends to take time from the start depression of a key-top till the closing of the contact. In order to avoid that, the keyboard disclosed by above '764 Japanese publication has a recess formed on the waterproof sheet above the contact. However, when water stays in the recess for a long period of time, water possibly immerses into the membrane sheet, depending on the condition of the gluing width of the membrane.
It is an object of the present invention to provide a key switch arrangement capable of preventing liquid from entering a membrane sheet as well as from staying therein.
In accordance with the present invention, a key switch arrangement including a key-top depressable to close an electric contact provided on a membrane sheet comprises a waterproof sheet arranged above the membrane sheet, a first fixing member arranged above the waterproof sheet and having a first projection protruding toward the waterproof sheet, and a second fixing member arranged below the membrane sheet and having a second projection protruding toward the membrane sheet, each of the waterproof sheet and the second projection having a hole formed to accept the first projection, the membrane sheet having a hole to accept the second projection, thereby adhering the waterproof sheet closely to the second projection.
Further, in accordance with another invention, a key switch arrangement including a key-top depressable to close an electric contact provided in the membrane sheet comprises a first fixing member arranged above the membrane sheet and having a first projection protruding toward the membrane sheet, and a second fixing member arranged below the membrane sheet and having a second projection protruding toward the membrane sheet, the membrane sheet having an upper sheet, each of the upper sheet and the second protrusion having a hole to accept the first projection, the membrane sheet having a spacer sheet and a lower sheet, each of the spacer sheet and the lower sheet having a hole formed to accept the second projection, thereby adhering the upper sheet closely to the second projection.
In accordance with the present invention, since the upper part of a membrane sheet is covered with the waterproof sheet and the hole for fixing the waterproof sheet is closely adhered with the first fixing member and the first projection of the first fixing member, liquid does not enter the membrane sheet. Further, since the first fixing member has the drain groove formed therein, liquid is discharged outside the first fixing member, and therefore, liquid does not stay in the upper part of the membrane for a long period of time.
According to one aspect of the present invention, since close adhesion is made with the first fixing member and the second projection of the second fixing member by interposing the upper sheet of the membrane between them, liquid does not enter the membrane sheet. Further, since the first fixing member has the drain groove formed therein, liquid is discharged outside the first fixing member, and therefore, liquid does not stay in the upper part of the membrane for a long period of time.
The objects and features of the present invention will become more apparent from consideration of the following detailed description taken in conjunction with the accompanying drawings in which:
A preferred embodiment of a key switch arrangement in accordance with the present invention will be described reference to the accompanying drawings.
In
On the upper surface of the key-top 111, there is printed a letter, character or symbol 111c. On the rear surface of the key-top 111, there are provided rotary supports 111d rotatably supporting one end of the first link member 112 and slide supports 111e supporting one end of the second link member 113 rotatably and movably in a horizontal direction, which is in parallel with the plane formed by back plate 117. The first link member 112 comprises a pair of legs 112a, 112b, which have one end provided with a first coupling rod 112c inserted into and supported by the rotary supports 111d of the key-top 111 in a fashion connecting between the legs 112a, 112b, and have the other end correspondingly provided with a second coupling rod 112d in a fashion connecting between the legs 112a, 112b. Further, on the respective external surfaces of the legs 112a, 112b, there are provided shafts 112e, 112f lying on a line connecting between the first coupling rod 112c and the second coupling rod 112d and placed in a location at an equal distance from the respective coupling rods 112c, 112d.
The second link member 113 comprises a pair of legs 113a, 113b, which have one end provided with first supporting projections 113c, 113d protruding outward and supported by the slide support 111e of the key-top 111 rotatably and movably in parallel in a horizontal direction, and have the other end provided with second supporting projections 113e, 113f protruding outward and placed in a location at a distance equal to that between the coupling rods 112c, 112d of the first link member 112. Further, there are provided shaft holes 113g, 113h lying on a line connecting between the first supporting projections 113c, 113d and the second supporting projections 113e, 113f and placed in a location at an equal distance from the respective supporting projections 113c, 113d; 113e, 113f. Moreover, the legs 113a, 113b are connected with a connection 113i to each other at the tip side far from the first supporting projections 113c, 113d.
The rubber dome 114 is made of an elastic material, such as rubber, formed generally in a cup shape which has its internal surface protruding downward at the central part to form a contact depression part 114a. The holder 115 is formed into a frame-like shape dedicated for a single key. The holder 115 has its one end, in the vicinity of which there is provided a slide guide 115b for supporting the second coupling rod 112d of the first link member 112 rotatably and movably in parallel in the horizontal direction, while it has its other end, in the vicinity of which there are provided rotary guides 115c, 115d for supporting the second projections 113e, 113f of the second link member 113 in a freely rotatable fashion.
In the central part of the holder 115 there are arranged arcuate guide walls 115e in opposition to each other for fixing the circumference of the rubber dome 114, and in the underside of the holder 115 there are welding pins 115a having a predetermined length and formed in a plurality of places in a fashion surrounding a through-hole 116f of the membrane sheet 116. Also, in the underside of the lower part of the holder 115 there are drain grooves 115f formed in a plurality of places. The drain groove 115f is arranged to be able to discharge liquid staying in the frame of the holder 115 outside the holder 115.
The membrane sheet 116 is, as shown in
Arranged to cover allover the membrane sheet 116 is the waterproof sheet 118, the rear side of which is applied allover the surface thereof with an adhesive, except for a non-gluing portion 118a located in a position opposite to the contact of the membrane sheet 116. With this adhesive the waterproof sheet 118 is adhered to the membrane sheet 116. The waterproof sheet 118 is arranged to cover allover the membrane sheet 116. The waterproof sheet 118 is glued on the membrane sheet 116 in size substantially equal to the membrane sheet 116, when the gluing width on the outer circumference of the membrane sheet 116 can be secured sufficiently. In such a case, the lower part of the circumference of the membrane sheet 116 and the upper part of the circumference of the back plate 117 are glued to each other with a double-faced tape.
Formed around the non-gluing portion 18a there are welding holes 118b in positions opposite to welding pins 115a of the holder 115. The welding pins 115a are inserted into the welding holes 118b, so that the waterproof sheet 118 is welded in a state of being interposed between the holder 115 and embossed parts 117b of the back plate 117, which will be described later. The welding holes 118b are totally blocked up to be thermally welded and sealed with the holder 115.
The back plate 117 is placed in the lower part to mount thereon the components described above. In the back plate 117, there are formed the embossed parts 117b in a plurality of places corresponding to the through-holes 116g of the membrane sheet 116. The embossed parts 117b have holes 117a provided penetratingly for passing the welding pins 115a of the holder through them. The height of the embossed part 117b is approximately equal to the thickness of the membrane 116. Accordingly, in an assembled state, the top of the embossed part 117b closely adheres to the waterproof sheet 118, as shown in
Subsequently, assembling process will be described. In
From the top thereof, the welding pins 115a are inserted into the holes 117a of the embossed parts 117b through the welding holes 118b of the waterproof sheet 118 and thermally welded. The tip, i.e. the lower end, of the welding pin 115a is deformed into a flat shape by heating so as to closely adhere and fix the holder 115 and the back plate 117 to each other via interposition of the waterproof sheet 118 and the membrane sheet 116. Thereby, the membrane sheet 16 is perfectly sealed on the underside of the waterproof sheet 118, and thus, liquid will not enter the membrane sheet 116, should it be spilled over the upper part of the waterproof sheet 118.
When liquid is spilled over the waterproof sheet 118 and gets inside the frame of the holder 115, depressing the key-top 111 causes the liquid to be discharged outside the frame of the holder 115 through the drain groove 115f. Accordingly, liquid does not stay on the upper part of the contact 116e of the membrane sheet 116 for a long period of time.
Subsequently, switch operation will be described. Still with reference to
As has been described above, according to the illustrative embodiment, since the waterproof sheet 118 is arranged on the membrane sheet 116 to seal all portions of the embossed parts 117b of the back plate 117 brought into contact with the membrane sheet 116, liquid, such as water or the like, does not get into the membrane sheet 116, even when the liquid is spilled over the keyboard. Further, when liquid is spilled over the waterproof sheet 118 and enters inside the frame of the holder 115, the entered liquid is discharged out of the frame of the holder 115 through the drain groove 115f, and thus, the liquid does not stay on the contact of the membrane sheet 116 for a long period of time.
Next, an alternative embodiment in accordance with the invention will be described.
Among those components, the key-top 211, the first link member 212, the second link member 213, the rubber dome 214 and the holder 215 may be similar to those of the illustrative embodiment shown in and described with reference to
The membrane sheet 216 is constituted of, as shown in
Formed in the upper sheet 216a of the membrane sheet 216 there are welding holes 216h which are sized such that only the welding pins 215a of the holder 215 can pass through them. Also, formed in the lower sheet 216b and the spacer sheet 216c, as shown in
The back plate 217 is arranged in the lower part so as to mount thereon the respective components described above. In the back plate 217 there are formed embossed parts 217b in a plurality of places corresponding to the through-holes 216, and the embossed part 217b is penetratingly provided with a hole 217a for passing the welding pin 215a of the holder 215 therethrough. The height of the embossed part 217b is approximately equal to the thickness of the lower sheet 216b of the membrane sheet 216 being lapped over the spacer sheet 216c thereof, i.e. approximately equal to the height of the through-hole 216g. Accordingly, in an assembled state, as shown in
Subsequently, assembling process will be described. In
The tip, i.e. lower end, of the welding pin 215a is deformed into a flat shape by heating so as to closely adhere and fix the holder 215 and the back plate 217 to each other via interposition of the upper sheet 216a of the membrane sheet 216. Thereby, the membrane sheet 216 is perfectly sealed on the underside of the upper sheet 216a. At this instance, the upper sheet 216a is more firmly fixed to the embossed part 217b by applying the periphery of the rear side of the welding hole 216h of the upper sheet 216a with an adhesive.
Should liquid be spilled over the upper part of the membrane sheet 216, it will not enter deeper than the upper sheet 216a. Further, should liquid be spilled over the membrane sheet 216 and get inside the frame of the holder 215, depressing the key-top 211 causes the liquid to be discharged outside the frame of the holder 215 through the drain groove 215f. Accordingly, the liquid does not stay on the upper part of the contact of the membrane sheet 216 for a long period of time.
As has been described above, in accordance with the alternative embodiment, since the through-hole 216g into which the embossed part 217b of the back plate 217 is inserted is sealed with the upper sheet 216a of the membrane sheet 216 and also the welding hole 216h of the upper sheet 216a and the welding hole 217a of the back plate 217 are sealed with the holder 215, liquid, such as water, does not enter inside the membrane sheet 216, even when the liquid is spilled over the keyboard. Further, when liquid is spilled over the membrane sheet 216 and enters inside the frame of the holder 215, the entered liquid is discharged out of the frame of the holder 215 through the drain groove 215f, and thus, the liquid does not stay on the upper part of the contact of the membrane sheet 216 for a long period of time.
The invention is not confined to those embodiments described above, but it may be deformed in various ways. For example, the membrane sheet 116, 216 and a back plate 117, 217 may be constituted of the same material, for example polycarbonate and the like. To constitute the membrane sheet and the back plate from the same material as described above eliminates an occurrence of deflection and the like in the membrane sheet, because the back plate thermally expands correspondingly when the membrane sheet thermally expands. Moreover, an equivalent effect can be obtained, if materials, each having an equivalent thermal expansion coefficient, are used instead of using the same material. Particularly in the alternative embodiment described above, as the upper sheet 216a of the membrane sheet 216 is adhered to the embossed part 217b of the back plate 217, the effect is of particular note.
The entire disclosure of Japanese patent application No. 2007-306742 filed on Nov. 28, 2007, including the specification, claims, accompanying drawings and abstract of the disclosure is incorporated herein by reference in its entirety.
While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-306742 | Nov 2007 | JP | national |
