GB2219691A

GB2219691A - Keyboards

Info

Publication number: GB2219691A
Application number: GB8901123A
Authority: GB
Inventors: Takashi Murakami; Yoshihiro Hattori
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1988-06-13
Filing date: 1989-01-19
Publication date: 1989-12-13
Anticipated expiration: 2009-01-19
Also published as: AU2873489A; AU618061B2; JPH01313820A; JPH0738288B2; GB2219691B; CA1316006C; GB8901123D0

Description

OPERATING KEY SWITCH UNIT BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to an operating key switch unit having a waterproof case with an electric circuit enclosed therein, and a plurality of key switch buttons for external operation exposed from the front of the case.

Description of the Prior Art A conventional operating key switch unit will now be described with reference to Figs. 1 to 4. Fig. 1 is a perspective view showing an appearance of the switch unit ; Fig. 2 is a sectional view taken on line II-II of Fig. 1 ; Fig. 3 is a partially enlarged view of Fig. 2; and Fig. 4 is a front view of a panel switch. In these figures, the reference numeral 1 denotes a waterproof case molded from a resin; numeral 2 denotes a display opening formed in the front indicated at la of the case 1; numeral 3 denotes a button hole formed in a plural number (twelve in the drawings} in the front la of the case 1 ; numeral 4 denotes a printed circuit board mounted in the case 1 using bolts 5; and numeral 6 denotes a display portion inserted in the display opening 2 between a front-side surface 4a of the printed circuit board 4 and the case front la. Numeral 7 denotes a panel switch inserted between the front-side surface 4a of the printed circuit board 4 and the case front la, and key switch buttons 8 for external operation exposed respectively from the button holes 3 are formed integrally with the panel switch 7 using an elastic material. Numeral 9 denotes an electroconductive contact of each key switch button 8 integral with the panel switch 7, the electroconductive contact 9 being provided in a recess 7a.

Numeral 10 denotes a contact printed on the front-side surface 4a of the printed circuit board 4 in an opposed relation to each electroconductive contact 9. Numeral 11 denotes an electronic part mounted on a back-side surface 4b of the printed circuit board 4.

The operation of the conventional key switch unit of the above construction will now be explained. The panel switch 7 is put on the printed circuit board 4 having the electronic part 11 and fixed to the case 1 with bolts 5.

As a result, the key switch buttons 8 of the panel switch 7 are exposed from the button holes 3 of the case so that they can be operated from the exterior.

The contacts 10 on the printed circuit board 4 and the electroconductive contacts 9 of the panel switch 7 jointly form a switch structure. Both contacts 9 and 10 are normally not in contact with each other as shown in Fig. 3, but when a key switch button 8 is depressed, the panel switch 7 is deformed through the associated recess 7a, so that both contacts are in contact with each other and as a result the contents of operation are displayed on the display portion 6.

According to the conventional operating key switch unit described above, the panel switch 7 is integrally formed using an elastic material and it is sandwiched between the front-side surface 4a of the printed circuit board 4 and the inner surface of the case front la, to thereby prevent the invasion of water from the button holes 3 to the exterior of the panel switch 7, namely the interior of the case 1, through a surrounding contact portion 7b of the panel switch 7. However, the surrounding contact portion 7b of the panel switch 7 is held by a contact pressure induced by only the urging force of the bolts 5, so when the panel switch 7 is deformed in response to depression of a key switch button 8, there occurs a change in contact pressure of the surrounding contact portion 7b, that is, a uniform contact pressure is not obtained, resulting in that water enters the interior of the case 1 through the surrounding contact portion 7b, thus causing the contacts 9,10 and the electronic part 11 to be corrode.

Further, if the mounting pitch of the bolts 5 is made smaller to increase the contact pressure of the panel switch 7, the resulting increase in the number of bolts 5 causes an increase in time required for the assembling operation, thus leading to increase of cost.

SUMMARY OF THE INVENTION The present invention has been accomplished for overcoming the above-mentioned problems and it is the object thereof to provide an operating key switch unit having a sure waterproof structure not requiring an increase in the number of panel switch fixing bolts.

The operating key switch unit according to the present invention is provided with one contactor projecting from the inner surface of the front of the case substantially in the same direction as the key switch button operating direction and disposed annularly in a surrounding relation to the key switch buttons, and the other, annular contactor formed integrally with the panel switch and in contact with the said one contactor throughout the overall circumference at all times.

Thus, in the present invention, since one contactor and the other contactor are in contact with each other at all times, there is no fear of the invasion of water to the exterior of the panel switch, namely, the interior of the case, even when the panel switch is deformed upon depression of a key switch button.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view showing an appearance of a conventional key switch unit; Fig. 2 is a sectional view taken on line II-II of Fig. 1; Fig. 3 is a partially enlarged view of Fig. 2; Fig. 4 is a front view of a panel switch ; Fig. 5 is a side view, in longitudinal section, showing an embodiment of the present invention; Fig. 6 is a partially enlarged view of Fig. 5; Fig. 7 is a front view of a panel switch; Fig. 8 is a right-hand side view of Fig. 7; Fig. 9 is a side view, in longitudinal section, showing another embodiment of the present invention; Fig. 10 is a partially enlarged view of Fig. 9; Fig. 11 is a front view of a panel switch; and Fig. 12 is a right-hand side view of Fig. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to Figs. 5 to 8. Fig. 5 is a sectional view similar to Fig. 2; Fig. 6 is a partially enlarged view of Fig. 5; Fig. 7 is a front view of a panel switch; and Fig. 8 is a right-hand side view of Fig. 7.

In these figures, portions which are the same as or equivalent to those of the foregoing conventional switch unit are indicated by the same reference numerals and will not be explained here. And in these figures the reference numeral 7A denotes a panel switch integrally formed using an elastic material; numeral 12 denotes a convex portion formed on the inner surface of a case front la, the convex portion 12 extending annularly along the marginal portion of the panel switch 7A; and numeral 13 denotes a concave groove formed annularly in the marginal portion of the panel switch 7A, in which groove is fitted the convex portion 12.

Thus, the convex portion 12 of the case front la and the concave groove 13 of the panel switch 7A are fitted together. This is advantageous in that even when the panel switch 7A is deformed upon depression of a key switch button 8, there will be no change in contact pressure between the convex portion 12 and the concave groove 13 because both are in contact with each other in the same direction as the operating direction. Therefore, there is no fear of the invasion of water to the exterior of the panel switch 7A, namely, the interior of the case 1.

Although in the above embodiment the convex portion 12 and the concave groove 13 serve as one contactor and the other contactor, respectively, they may be reversed.

Now, another embodiment of the present invention will be described with reference to Figs. 9 to 12. Fig. 9 is a sectional view similar to Fig. 5 ; Fig. 10 is a partially enlarged view of Fig. 9; Fig. 11 is a front view of a panel switch; and Fig. 12 is a right-hand side view of Fig. 11, in which figures portions which are the same as or equivalent to those in the previous embodiment are indicated by the same reference numerals and will not be explained here. In these figures, the numeral 7B denotes a panel switch integrally formed using an elastic material, and numeral 12A denotes a convex portion formed on the inner surface of the case front la, the convex portion 12A being located annularly surrounding the outer periphery of the panel switch 7B and in contact with a front-side surface 4a of the printed circuit board 4. Numeral 14 denotes a rib formed annularly on the outer periphery of the panel switch 7B and in contact with the inner peripheral surface of the convex portion 12A.

Although in this embodiment the convex portion 12A and the rib 14 serve as one and the other contactor, respectively, they may be reversed.

It will of course be understood that the present invention has been described above purely by way of example and that modifications in detail can be made within the scope of the invention.

Claims

WHAT IS CLAIMED IS: 1. In an operating key switch unit wherein an electric circuit is enclosed in a waterproof case and a plurality of key switch buttons for external operation are exposed from the front of the case, said operating key switch unit having a printed circuit board mounted in said case with bolts to partition the interior of the case into a front side and a back side, with contacts being formed on the front-side board surface which contacts are opposed to electroconductive contacts of said key switch buttons, and with electronic parts being mounted on the back-side board surface, and also having a panel switch with which are integrally formed said key switch buttons using an elastic material and which is inserted between the frontside surface of said printed circuit board and the inner surface of the front of said case, the improvement characterized by further having one contactor projecting from the inner surface of the front of said case substantially in the same direction as the operating direction of said key switch buttons and disposed annularly in a surrounding relation to the key switch buttons, and the other annular contactor formed integrally with said panel switch and in contact with said one contactor throughout the overall circumference at all times.
2. An operating key switch unit according to Claim 1, wherein said one contactor is formed convexly, while said the other contactor is formed as a concave groove engaged with said convex-shaped one contactor.
3. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a concave groove, while said the other contactor is formed with a convex portion engaged with said concave groove.
4. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a convex portion the tip end of which reaches the front-side surface of said printed circuit board, while said the other contactor is formed as a rib which is in contact with the inner peripheral surface of said one contactor.
5. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a rib, while said the other contactor is formed as a convex portion which outer peripheral surface is in contact with said rib.
6. An operating key switch unit substantially as hereinbefore described with reference to or as shown in Figures 5 to 8 or Figures 9 to 12 of the accompanying drawings.

6. An operating key switch unit substantially as hereinbefore described with reference to or as shown in Figures 5 to 8 or Figures 9 to 12 of the accompanying drawings.

Amendments to the claims have been filed as follows 1. In an operating key switch unit wherein an electric circuit is enclosed in a waterproof case and a plurality of key switch buttons for external operation are exposed from the front of the case, said operating key switch unit having a printed circuit board mounted in said case with bolts to partition the interior of the case into a front side and a back side, with contacts being formed on the front-side board surface which contacts are opposed to electroconductive contacts of said key switch buttons, and with electronic parts being mounted on the back-side board surface, and also having a panel switch with which are integrally formed said key switch buttons using an elastic material and which is inserted between the frontside surface of said printed circuit board and the inner surface of the front of said case, the improvement characterized by further having one contactor projecting from the inner surface of the front of said case substantially in the same direction as the operating direction of said key switch buttons and disposed annularly in a surrounding relation to the key switch buttons, and the other annular contactor formed integrally with said panel switch and in contact with said one contactor throughout the overall circumference at all times, wherein the two contactors bear against each other with a resilient force.

2. An operating key switch unit according to Claim 1, wherein said one contactor is formed convexly, while said the other contactor is formed as a concave groove engaged with said convex-shaped one contactor.

3. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a concave groove, while said the other contactor is formed with a convex portion engaged with said concave groove.

4. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a convex portion the tip end of which reaches the front-side surface of said printed circuit board, while said the other contactor is formed as a rib which is in contact with the inner peripheral surface of said one contactor.

5. An operating key switch unit according to Claim 1, wherein said one contactor is formed as a rib, while said the other contactor is formed as a convex portion which outer peripheral surface is in contact with said rib.