The present invention relates to key input devices for use in portable telephones and the like, and more particularly to a seesaw key input device adapted to selectively close a plurality of key contacts.
With reference to FIG. 4, portable telephones usually have a casing 1 formed by a front case 11 and a rear case 12. Arranged on the surface of the front case 11 are a display 13, a plurality of manual keys 14 including numerical keys, and a seesaw key 15 to be manipulated in selecting a desired function. The illustrated seesaw key 15 is depressed downwardly or is inclined to forward, back, left, or right, so that one of five key contacts is adapted to selectively be closed, with the result that one desired function is selected and set.
The casing 1 has a circuit board 3 disposed in its interior as shown in FIG. 5. Arranged on the circuit board 3 are a sheet key assembly 40 to be depressed by the manual keys 14 and the seesaw key 15, a display 13, a high-frequency circuit module 32, and a vibrator 2 comprising a motor 22 and an eccentric weight 21 attached to the output shaft of the motor for notifying the user of incoming calls, etc.
The sheet key assembly 40, as already known, has a dome sheet of PET comprising a plurality of dome portions disposed over a base plate. The dome portion is elastically restorably invertable by depressing force of the manual key to bring a contact terminal formed on the inner surface of the dome portion into contact with a contact electrode formed on the surface of the base plate to close contacts.
As shown in FIG. 6, arranged below the seesaw key 15 is a seesaw key assembly 9 having a stick 90 extended. The seesaw key assembly 9 is fixed to the surface of the dome sheet 41 forming a surface portion of the sheet key assembly 40. An end portion of the stick 90 of the seesaw key assembly 9 is fixed jointly to the rear surface of the seesaw key 15. As described above, the seesaw key 15 is manipulated into being depressed to depress the stick 90 downwardly, or is inclined to forward, back, left, or right, whereby a contact out of five contacts which is incorporated in the seesaw key assembly 9 can be closed.
A key rubber 80 is provided on the surface of the dome sheet 41 constituting the sheet key assembly 40, and covers a plurality of dome portions (not shown) formed with the sheet key assembly 40. The key rubber 80 is provided with an opening 80a on a region wherein the seesaw key assembly 9 is to be installed, and the seesaw key assembly 9 is installed in the opening, whereby the seesaw key assembly 9 has its rear surface contacted with the surface of the dome sheet 41, and is surface-mounted on the dome sheet 41.
An annular waterproof member 91 is interposed between the outer peripheral surface of the seesaw key assembly 9 and the inner peripheral surface of the opening 80a of the key rubber 80. Accordingly, water ingressing from its surroundings can be prevented from reaching the surface of the dome sheet 41.
However, with the conventional portable telephone having a stick-like seesaw key assembly 9 installed, as shown in FIG. 6, the stick 90 needs to have some height since the inclination of the stick 90 causes the seesaw key assembly 9 to close the terminals, thus entailing the problem of increasing the thickness of the portable telephone. Due to the waterproof construction of interposing the waterproof member 91 between the seesaw key assembly 9 and the key rubber 80, the waterproof member is required, increasing the number of components. Further, there is likelihood that water may ingress from between the seesaw key assembly 9 and the waterproof member 91, or from between the key rubber 80 and the waterproof member 91, giving rise to another problem of insufficient waterproof.
An object of the present invention is to provide a key input device which is adapted to make the device more thinner and to make the device waterproofed completely with reduced number of components, and a portable telephone incorporating the key input device.
The key input device of the present invention comprises a seesaw switch unit 4 mounted on a base, and a key rubber 8 installed on the base covering the seesaw switch unit 4. Provided on the surface of the key rubber 8 is a seesaw key 10 to depress the seesaw switch unit 4.
The seesaw switch unit 4 comprises a base plate 5, a dome sheet 7 provided over the base plate 5 having a plurality of dome portions 71, 72, a pivotally movable member 6 provided over the dome sheet 7 to selectively depress each dome portion 71. The seesaw key 10 is installed over the pivotally movable member 6. The pivotally movable member 6 is depressed by the manipulation of the seesaw key 10 to make a dome portion elastically restorably invertable to bring a contact terminal 52 provided on the inner surface of the dome portion into contact with a contact electrode 51 provided on the surface of the base plate 5, with the result that the contacts are closed.
With the key input device of the invention, the seesaw switch unit 4 is used in place of a conventional stick-like seesaw key device 9. The seesaw switch unit 4 can be made thinner, so that the entire device is adapted to be made thinner. Further, since the seesaw switch unit 4 is adapted to close its contacts by exerting a depressing force on the pivotally movable member 6, the seesaw switch unit 4 installed directly on the surface of the base is covered with the key rubber 8 having no opening, and the depression of the seesaw key 10 provided on the surface of the key rubber 8 activates the seesaw switch unit 4. Accordingly, the key rubber has no opening as in the prior art, so that the complete waterproof construction is achieved and there is no need of the conventional waterproof member.
Stated specifically, the key rubber 8 comprises a flat plate portion 82 affixed to the rear surface of the seesaw key 10, a slanting portion 83 formed by defining the flat plate portion 82, a grounding portion 84 formed by defining the slanting portion 83. The slanting portion 83 is so inclined from the flat plate portion 82 to the grounding portion 84 as to be positioned at a lower level toward the base, and the grounding portion 84 is in close contact with the surface of the base.
Stated more specifically, when the seesaw key 10 is depressed to move the pivotally movable member 6, the flat plate portion 82 of the key rubber 8 is depressed by the rear surface of the seesaw key 10 to have the flat plate portion 82 inclined, having the slanting portion 83 of the key rubber 8 elastically deformed. The slanting portion 83 is inclined toward the grounding portion 84, so that the slanting portion 83 can be elastically deformed spontaneously, and the portion is deformed in a relatively small amount. Therefore, even if the key rubber 8 is repeatedly stressed by the repeated manipulation of the seesaw key 10, there is no likelihood of cracking, etc. on the key rubber 8.
Further stated specifically, the central portion of the rear surface of the seesaw key 10 and the central portion of the surface of the flat plate portion 82 are affixed to each other. The seesaw key 10 contacts with the flat plate portion 82 of the key rubber 8 so as to be relatively movable each other around the affixed portion.
Further stated more specifically, when the seesaw key 10 is depressed to move the pivotally movable member 6, the flat plate portion 82 of the key rubber 8 is depressed by the rear surface of the seesaw key 10 to have the flat plate portion 82 inclined and to have the slanting portion 83 elastically deformed. While the seesaw key 10 and the flat plate portion of the key rubber 8 are affixed only at each central portion thereof, the surrounding portion is not affixed and is relatively movable. This has the slanting portion 83 elastically deformed more freely.
The portable telephone of the invention comprises the key input device of the invention described in place of the conventional key input device having a stick-like seesaw key device, that is, disposed inside the casing 1 are a circuit board 3 formed with a circuit for radio communication, a sheet key assembly 40 installed on the circuit board 3, a seesaw switch unit 4 installed on the surface of the sheet key assembly 40, a key rubber 8 provided covering the surface of the sheet key assembly 40 and the seesaw switch unit 4, and arranged on the surface on the key rubber 8 are a plurality of manual keys 14 for depressing the sheet key assembly 40, and a seesaw key 10 for depressing the seesaw switch unit 4.
The seesaw switch unit 4 comprises a base plate 5, a dome sheet having a plurality of dome portions 71, 72 provided over the base plate 5, a pivotally movable member 6 provided over the dome sheet 7 to depress each dome portion 71 selectively. The seesaw key 10 is provided over the pivotally movable member 6. The pivotally movable member 6 is depressed by the manipulation of the seesaw key 10 to make one dome portion elastically restorably invertable to bring a contact terminal 52 formed on the inner surface of the dome portion into contact with a contact electrode 51 formed on the surface of the base plate 5 to close the contacts.
As described above, the key input device of the invention and the portable telephone having the device are adapted to be made thinner and waterproofed completely with the reduced number of the components.