Keyswitch assembly with support mechanism coupled to support plate beneath ...

1 2

The keyswitch assemblies disclosed in the foregoing

KEYSWITCH ASSEMBLY WITH SUPPORT references are not intended to enable the reduction of

MECHANISM COUPLED TO SUPPORT PLATE the thickness of the keyboard. Since all of the above

BENEATH PRINTED CIRCUIT BOARD references require a base plate, none of these references

5 are able to reduce the thickness and weight of the key

BACKGROUND OF THE INVENTION board satisfactorily.

1. Field of the Invention f^V^ "^T^?*TM?, C°St f & J*"? * The present invention relates to a keyswitch assembly jf1^ h,8h md adds t0 the total cost °f the ke^

and, more particularly, to a keyswitch assembly consist- ar'

ing of a relatively small number of parts, having a sim- SUMMARY OF THE INVENTION

pie construction, capable of being manufactured at a Ti . , . A . . .. .,

, .. , , c * • . J ti c It is an object or the present mvention to provide a

relatively low manufacturing cost and suitable for use . , J ., I_.%_j * iT w

, , , f °. , keyswitch assembly which does not require a base plate,

on a thin keyboard for a portable word processor, a „r Ij-i « v * — £

. ', . v ... v consists of a relatively small number of parts, has a

portable personal computer or the like. . . .. . ,. fu . , . . .

„ T> • *»» i ^ J 15 simple construction, is capable of being manufactured at

2. Description of Related Art *, .. . . , \ . . ° ,

. . r. . ... , . a relatively low manufacturing cost and ensures satis

A known keyswitch assembly for use on such a key- f ^ tion

board has a key provided with a stem, « base plate pro, Jn o*ne £ £ of ^ t mventi a keyswitch

vaded with a key support having a hole receiving the co^ rises: a k(f ided with two flrst id_

stem of the key to guide the key for vertical movement, 2Q . projecting from the lower surface thereof; a

and a switching member such as a membrane switch, k g ^ mechanism di d under the k and

disposed under the stem. When the key is depressed the fonned b M] jomi tWQ ,evers ^

lower end of the stem of the key presses the switching having opposke en(Js ... whh pivQts in a scisSQrs.

member for switching action. like form by a pivotal joint; a printed wiring board; a

A keyswitch assembly provided with a large key, 25 switching member mounted on the printed wiring

such as a space key and a return key, is provided with a an(J a rt ,ate provided witn second guid.

mechanism for maintaining the key supported on a base m rts respectively corresponding to the first guiding

plate m a level position when the key is depressed. Such rts The iyots formed on the ends of the

^h a^n*hes are d>scl°sed in u-s- Pat- Nos- port levers are connected to the first guiding parts, and

4,580,022, 4,902,862 and 4,433,225. 30 the pivots fonned Qn the ,ower ends of the support

In a keyswitch assembly disclosed in the *022 patent, levers m connected to the second guiding parts.

a key member is supported on support levers connected when the key is depressedi the support levers turn

with pins in a scissors-like form, and switching members re]ative to each other on the pivotal joint, and the pivots

are disposed apart from the central portion of the key of the support ievers siide horizontally in the first guid

member. Pins attached to the opposite ends of the sup- 35 parts of the key md the second guiding parts of the

port levers slide horizontally along the inner surface of support plate, respectively.

the key member and the upper surface of a base plate As the key'is depressed further, the switching mem

when the key member is depressed. Stems formed in the t,er ,s compressed for switching action by the pivotal

key member and guided by a guide member slide verti- joint. When the key is released, the key and the support

cally to compress the switching members when the key 40 levers are returned to their original positions by the

member is depressed. resilience of the switching member.

A keyswitch assembly disclosed in the '862 patent is Thus, the present invention provides a keyswitch the same in basic construction as the keyswitch assem- assembly not needing any base plate, consisting of a bly disclosed in the '022 patent and is characterized in relatively small number of parts, having a simple conthat the key member can be easily connected to and 45 struction, capable of being manufactured at a relatively removed from the support levers which are coupled to iow manufacturing cost and capable of ensuring satisa base plate. factory key operation.

In the '225 patent, a keyswitch assembly including an

L-shaped keytop is disclosed. The keyswitch assembly BRIEF DESCRIPTION OF THE DRAWINGS

comprises a pair of lever arms joined at intermediate 50 A preferred embodiment of the present invention will

portions thereof by a pivot to form a scissors-like link- be described in detail with reference to the accompany

age having first, second, third, and fourth ends. The first ing drawings, in which:

and second ends of the scissors-like linkage are pivotally FIG. 1 is a sectional side view of a keyswitch assem

slidable within the cantilevered portion of the keytop. bly in a preferred embodiment according to the present

However, a keyswitch portion is separately disposed 55 invention in a state where a key is depressed slightly;

from the scissors-like linkage. So, there is a problem that j FIG. 2 is an exploded sectional view of the keyswitch

the keyswitch is not perfectly operated. Furthermore, a assembly of FIG. 1;

plunger and base plate are needed, so the assembly FIG. 3 is a plan view of a first support lever; requires many parts, and the structure is complex. FIG. 4 is a plan view of a second support lever; and Recent progressive reduction in size and thickness of 60 FIG. 5 is a partial plan view of guiding parts formed word processors and personal computers requires re- on a support plate, duction in size and thickness of keyboards to be incorporated into word processors and personal computers. On the other hand, the keys of keyboards must be adequately supported to facilitate keystroke operation and 65 A keyswitch assembly in a preferred embodiment to secure a reliable keystroke. The prior art keyswitch according to the present invention will be described assemblies, therefore, utilize base plates to secure the hereinafter with reference to FIGS. 1 and 2. FIG. 1 is a key support member thereto. sectional side view of the keyswitch assembly in a state

DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS

5 6

29B, i.e., the left-hand end in FIG. 1. The pivot 21 (22) plate 25, and the pivots 21 and 22 of the second support is pressed against the first end 29A when the key 1 is not lever 8 slide horizontally to the left, as viewed in FIG. depressed. The second end 29B limits the horizontal 1, along the slots 29 of the guiding parts 27 of the supsliding movement to the left of the pivot 21 (22) of the port plate 25.

second support lever 8. 5 Consequently, the pivotal joint P pivotally joining

While the key 1 is not depressed, the pivots 15 and 16 the support levers 7 and 8 compresses the rubber spring

of the first support lever 7 are pressed against the first 31 gradually and, when the compression of the rubber

ends 28A of the slots 28, and the pivots 21 and 22 of the spring 31 exceeds a limit, the rubber spring 31 buckles,

second support lever 8 are pressed against the first ends Then, the movable electrode of the rubber spring 31

29A of the slots 29 by the resilient force of the rubber 10 connects the switching electrodes of the flexible printed

spring 31 biasing the pivotal joint P'upward to keep the wiring board 30 electrically for switching action, key 1 at its original position. Although the key 1 is depressed further after the

When the key 1 is depressed, the rubber spring 31 is switching action has been completed, the leftward slid

compressed to complete a switching action before the ing movement of the pivots 13 and 14 of the first sup

rightward sliding movement, as viewed in FIG. 5, of 15 port lever 7 along the slots 4 is limited by the end walls

the pivots 15 and 16 of the first support lever 7 and the 4A, and the rightward sliding movement of the pivots

leftward sliding movement, as viewed in FIG. 5, of the 23 and 24 of the second support lever 8 along the slots

pivots 21 and 22 of the second support lever 8 are lim- 5 is limited by the end walls 5A. At the same time, the

ited by the second ends 28B of the slots 28 and the rightward sliding movement of the pivots 15 and 16 of

second ends 29B of the slots 29, respectively. 20 the first support lever 7 along the slots 28 is limited by

The guiding lugs 35 and 36 restrain the support levers the second ends 28B of the slots 28, and the leftward

7 and 8 from free movement and prevent the shaft 12 sliding movement of the pivots 21 and 22 of the second from coming out of the hole 20. support lever 8 along the slots 29 is limited by the sec

A flexible printed wiring or circuit board 30 provided ond ends 29B of the slots 29. with printed circuits including switching electrodes, not 25 After the pivotal joint P has thus compressed the

shown, is attached to the upper surface of the support rubber spring 31 when the key 1 is depressed to bring

plate 25. The rubber spring 31 having the shape of an the movable electrode of the rubber spring 31 into

inverted cup and internally provided with a known contact with the switching electrodes of the flexible

movable electrode is placed on the flexible printed wir- wiring board 30 for switching action, the sliding move

ing board 30 at a position corresponding to the switch- 30 ment of the pivots 13 and 14, the pivots 23 and 24, the

ing electrodes, directly beneath the pivotal joint P piv- pivots 15 and 16, and the pivots 21 and 22 is limited by

otally joining the support levers 7 and 8. The upper wall the end walls 4A, the end walls 5A, the second ends 28B

of the rubber spring 31 is formed in a thickness such that and the second ends 29B, respectively, to limit the fur

the upper wall will not be deformed when pressed by ther downward movement of the key 1, so that the key

the pivotal joint P. 35 1 is restrained from free horizontal and vertical move

The flexible printed wiring board 30 is provided with ment. openings, not shown, through which the raised guiding When the key 1 is released, the resilience of the rublugs 35 and 36 protrude above the flexible printed wir- ber spring 31 pushes up the pivotal joint P pivotally ing board 30 as shown in FIGS. 1 and 2. joining the support levers 7 and 8, causing the pivots 13,

When the pivotal joint P moves downward, the piv- 40 14,15, 16, 21 and 22 to move in the reverse directions,

ots 13 and 14 slide along the slots 4 and the pivots 23 and whereby the key 1 is returned to its original position. 24 slide along the slots 5 in parallel to the surface of the As is apparent from the foregoing description, the

flexible printed wiring board 30, so that the pivotal joint keyswitch assembly in accordance with the present

P comes into contact with and compresses the rubber invention has the support plate 25 provided with the

spring 31 at the substantially central portion of the 45 guiding lugs 35 and 36 forming the guiding parts 26 and

upper wall of the rubber spring 31 to compress the 27 having the slots 28 and 29, respectively. The pivots

rubber spring 31. When compressed beyond a limit, the 13 and 14, the pivots 15 and 16, the pivots 23 and 24, and

rubber spring 31 buckles to connect the switching elec- the pivots 21 and 22 are guided for horizontal sliding

trodes electrically by the movable electrode of the rub- movement by the slots 4 of the guiding parts 2 of the

ber spring 31. 50 key 1, the slots 28 of the guiding parts 26 of the support

The operation of the keyswitch assembly thus con- plate 25, the slots 5 of the guiding parts 3 of the key i,

structed will be described hereinafter. While the key 1 is and the slots 29 of the guiding parts 27 of the support

not depressed, the pivots 15 and 16 of the first support plate 25, respectively. Accordingly, the keyswitch as

lever 7 are held in contact with the first ends 28A of the sembly of the present invention need not be provided

slots 28 and the pivots 21 and 22 of the second support 55 with any base plate, which is an essential component of

lever 8 are held in contact with the first ends 29a of the the prior art keyswitch assembly, slots 29 by the resilience of the rubber spring 31, so that Since the pivots 15 and 16 of the first support lever 7

the key 1 is maintained at its original position and is are held in contact with the first end 28A of the slots 28

horizontally immovable. and the pivots 21 and 22 of the second support lever 8

When the key is depressed, the pivots 13 and 14 of the 60 are held in contact with the first ends 29A of the slots 29

first support lever 7 slide horizontally to the left, as by the resilience of the rubber spring 31 when the key i

viewed in FIG. 1, along the slots 4 of the guiding parts is not depressed, the key 1 is restrained from horizontal

2, and the pivots 23 and 24 of the second support lever movement and kept in place.

8 slide horizontally to the right, as viewed in FIG. 1, Since the pivots 13 and 14 of the first support plate 7 along the slots 5 of the guiding parts 3. At the same 65 and the pivots 23 and 24 of the second support lever 8 time, the pivots 15 and 16 of the first support lever 7 are brought into contact with the end walls 4A of the slide horizontally to the right, as viewed in FIG. 1, slots 4 and the end walls 5A of the slots 5, respectively, along the slots 28 of the guiding parts 26 of the support and the pivots 15 and 16 of the first support lever 7 and