A keyswitch for a keyboard used with a computer or similar device that has a keytop linked to the base board. A printed circuit board having a contact switch associated with each keytop is associated with the base board. Linking each keytop with the base board is a scissors type guide. A pair of resilient springs are attached to the guide. One of the springs is in continual contact with the base board and: the other spring contacts the contact switch only after the keytop has been depressed a fixed distance thereby closing the contact switch.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a keyswitch suitable for use on a keyboard which 
comprises the data-entry equipment of a word processor, personal computer 
or the like. 
2. Description of Related Art 
A known keyswitch for use on such a keyboard is disclosed in U.S. Pat. Nos. 
4,580,022 and 4,560,845. These keyswitches are provided with a rubber 
spring, which is attached to the bottom of the keytop facing downward, and 
a stem that is inserted into a key holder part built into the holder 
element for guiding and supporting up and down movement. The key switches 
also include, on the lower portion of the stem, a contact point with a 
bottom face. Also, switching components, such as a membrane switch 
constituting an electrical contact with the flexible sheet, are also 
attached to the bottom edge of the rubber spring. 
In addition, in the keyswitch described in U.S. Pat. No. 4,580,022, it was 
suggested that between the bottom face of the keytop and the holder 
element a link element be installed that has the shape of an X when viewed 
from the side, so that when one edge of the keys, such as space bars, on 
which the flat area is large compared with the contact component, is 
pushed down, the keytop will move up and down evenly and in parallel, with 
no inclination. The link element links both central portions in free 
movement. 
In keeping with the recent reductions in the thickness of keyboards, a 
large keystroke is demanded in order to secure a reliable keystroke as 
well as to facilitate keyboard operation, in spite of the flattening of 
the keyboard. 
However, in the existing keyswitches, keytop vertical movement is guided 
for the sliding contact of the keyholder component and the downwardly 
protruding stem is attached to the bottom of the keytop. Because of this, 
the vertical dimension of the guiding, sliding movement of the stem within 
the holder component must be reduced when trying to reduce keyboard 
thickness. In doing so, the problem arises that when the key is pressed 
down, a misalignment may occur between the stem and the holder. As a 
result, the key does not operate smoothly and easily. If the sliding 
contact guiding dimensions are increased to prevent this, then the problem 
arises of the keystroke being too short. Thus, it is very difficult to 
simultaneously solve the two mutually contradictory problems of obtaining 
a large keystroke and reducing keyboard thickness. 
In order to solve the above problems, the applicant has proposed a 
keyswitch, described below, in U.S. Pat. No. 5,280,147. As shown in FIG. 
5, the keytop 100 vertical movement guidance method comprises a first link 
101 and a second link 102 arranged, in profile, like an X, or scissor 
like, with both links linked to move freely at the intersection component 
103. In addition, one of the free ends 106,107 and 108,109 of the second 
link 102 and the first link 101, respectively, are fastened in horizontal, 
sliding contact with the bottom face of the keytop 100 and holder element 
104, respectively. The other of the free ends 110,111 and 112,113 of 
second link 102 and first link 101, respectively, are rotatably fastened 
to the bottom face of keytop 100 and holder element 104, respectively. 
Also, beneath the center of the intersection component 103 is a cap-form 
rubber spring 105 having a resilient shape-changing capability. When the 
top 100 is depressed, the guiding means intersection component 103 causes 
the rubber spring 105 to undergo resilient shape-changes and the switching 
component associated therewith performs a switching operation. 
However, with a keyswitch of such a design, the free end 112,113 of the 
first link 101 centers on the place on the holder element 104 that forms 
the rotational axis for the purpose of movement capability, and the 
intersection component 103 moves in an up and down motion. In addition, 
the rubber spring 105 shape is formed based on it being pressed down in a 
straight line by the intersection component 103. In other words, the upper 
face of the head of the cap shaped rubber spring is formed in a horizontal 
shape. 
Thus, when the upper face of this type of rubber spring head portion is 
depressed in a downward slant direction by the intersection component 103, 
the degree of resilient shape change of the dome component (the dome 
component's seated position shape-change degree) of the rubber spring 
misaligns greatly relative to the near side and the far side of the 
rotation point of the first link 101 and problems arise in terms of the 
functioning of the depressed key, such as the switching operation relative 
to the switching component of the lower portion of the rubber spring. 
Because inaccuracies arise in the position of the rubber spring which 
covers the switching component due to tight tolerances, there is the 
problem of imperfections in switching operation relative to the switching 
component of the lower portion of the rubber spring. 
Also, there is the problem of the actual thickness of the rubber spring, 
which covers the switching component, becoming an obstacle to reducing the 
thickness of the keyboard. 
SUMMARY OF THE INVENTION 
The invention solves the above and other problems in the prior art. Its 
object is to provide a low-cost keyswitch that enables reliable key input 
as well as improving key input operation using a simple structure. It 
enlarges the keystroke while still allowing reduction in the size and 
thickness of the keyboard. 
In order to accomplish the object, the keyswitch of the invention comprises 
a first link and a second link, arranged to intersect in an X-shape, or 
scissor shape, and includes a guiding element linking and fastening the 
bottom face of the keytop with the supporting base of its lower component 
which guides and supports the vertical movement of the keytop, a first 
spring element attached to at least one of the first link and the second 
link to raise the depressed keytop and a second spring element attached to 
at least one of the first link and the second link, to cause the switching 
component to switching contact when the keytop is depressed. 
Also, it is preferable that the first spring element and second spring 
element be built into the first link. 
Also, it is effective if the first spring element is in constant contact 
with the supporting base component, and if the second spring element only 
makes contact with the switching component and enacts switch movement when 
the keytop is depressed a fixed distance. 
With the invention, endowed with such a structure, the guiding element is 
composed of the first link and the second link arranged to intersect in an 
X-shape, linking and fastening the keytop bottom face and the supporting 
base of its lower component for guiding and supporting vertical movement 
Of the keytop. In addition, the first spring is attached to at least one 
of the first link and the second link to raise the depressed keytop. Also, 
the second spring element is attached to at least one of the first link 
and the second link and causes the switching component to enact switch 
movement when the keytop is depressed. : 
Also, when the first spring element and the second spring element are 
attached to the first link, it is possible to create a keyswitch with a 
simple structure. 
Also, when the first spring element is in constant contact with the 
supporting base component, and when the second spring element makes 
contact with the switching component and enacts switch movement only when 
the keytop is depressed a fixed distance, the two spring elements can 
resist depression of the keytop after switching movement. 
As is clear from the foregoing explanation, because the keyswitch of the 
invention combines in one the first and second spring elements and the 
first link, the benefits arise that the second spring elements position is 
securely fixed relative to the switching component of the printed board, 
and switching movement can be reliably accomplished. In addition, the 
depression load can be easily adjusted. Also, because rubber springs with 
a certain degree of thickness have been eliminated, the keyswitch can be 
made thinner, and the number of components is reduced making the assembly 
time shorter. The benefit, of great value to industry, is the ability to 
provide a lower cost keyswitch.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
An embodiment realizing the invention will be described with reference to 
the drawings. 
The structure of the keyswitch 1 will be described with reference to FIGS. 
1A and 1B. FIG. 1A is a top face drawing in which the keytop 2 has been 
removed from the keyswitch. 1 and components of the two links have been 
removed. FIG. 1B is a side sectional drawing of the keyswitch 1. 
The keyswitch 1 comprises a keytop 2, a guiding element 3 which can be 
attached to and detached from the keytop 2, and a supporting base 
component 50 that supports the guiding element 3. The keytop 2 is made of 
a synthetic resin, Such as ABS resin, and has a numeral, alphabetic 
character, or symbol placed on it through engraving or printing or the 
like. On the bottom face of the keytop 2 are built in circular-shaped 
pivot fastener components 15,15 to fasten and make possible only 
rotational movement of pivot axis components 13A,13B of a base component 
22 (FIG. 3c) in a second link 5 (described below), and elongate groove 
shaped sliding fastener components 16,16 which receive pin components 
11A,11B of the upper free ends of a first link 4 (described below) for 
brief horizontal sliding in front and back directions relative to the 
keytop 2. 
Guiding element 3 is formed of the first link 4 and the second link 5 
linked form an X when viewed from the side. 
The first link 4 and the second link 5 are made of a synthetic resin, such 
as glass fiber reinforced synthetic resin, and are described in detail 
hereafter with reference to FIGS. 3A-3D. FIG. 3A is a plan view of the 
first link 4, FIG. 3B is a side view of the first link 4, FIG. 3C is a 
plan view of the second link 5, and FIG. 3D is a side view of the second 
link 5. 
The first link 4 is made so that the base component 18, the upper free end 
components 19A,19B and the lower free end Components 20A,20B form an H 
shape when viewed in plan. Supporting shafts 25A,25B are attached to the 
side face of the base component 18. Also, pin components 12A,12B are 
attached to the outside side faces of the lower free end components 
20A,20B and the pin components 11A,11B extend from the outside sides of 
the upper free end components 19A,19B. 
The second link 5 is structured so that the base component 22 and the free 
end components 24A,24B substantially form block U when viewed in plan. 
Supporting holes 21A,21B pass horizontally through the free end components 
24A,24B. Into the supporting holes 21A,21B are inserted the supporting 
shafts 25A,25B of the first link 4. As a result, the first link 4 and the 
second link 5 are linked to provide rotational centering on the supporting 
shafts 25A,25B. To the outside sides of the free end components 24A,24B of 
the second link 5 are attached pins 14A,14B. Built into the base component 
22 are rotational shafts 13A,13B. The depth of the supporting holes 
21A,21B is dependent on the length of the support shaft 25A,25B which must 
be long enough to ensure a dependable linkage. 
The first link 4 and the second link 5 are made of synthetic resin, such as 
glass fiber reinforced resin, as noted above. It is preferable that each 
link is made of a different material. If the materials are of different 
materials, little friction is produced between supporting holes 21A,21B, 
and the supporting shafts 25A,25B or at the contact faces of the first 
link 4 and the second link 5. However, if the area of contact points is 
small, then there is little problem if they are of the same material. 
According to the embodiment, the structure is such that the distance 
between the center line of the first link 4 support shafts 25A 25B and the 
center line of top and bottom pin components 11A,11B and 12A,12B and the 
distance between the center line of the support holes 21A,21B of the 
second link 5 and the center line of the rotation shaft components 13A,13B 
and pin components 14A,14B are equal. When constructed in this way, as 
explained below, the guiding element 3 changes position, centered on the 
bottom side free edge component pins 12A,12B of the first link 4, so that 
keytop 2 can raise and lower maintaining a parallel position with regards 
to the upper face of the holder element 8 of the supporting base component 
50. 
The support base component 50 is composed of the holder element 8 which 
supports the guiding element 3, a flexible printed board 9 stretched 
across the bottom face of the holder element 8 so that switching component 
29 (see FIG. 1A) is facing toward an opening 26 in the holder element 8, 
and strengthening board 10 beneath the printed board 9. The holder element 
8 is made from a synthetic resin such as a glass reinforced synthetic 
resin, and the opening 26 is formed or created therein. 
As shown in FIGS. 1A-3, a first spring element 6 is formed integral with 
the base component 18 of the first link 4. The first spring element 6 is a 
belt shaped flat spring and is further shaped for resilient shape changing 
by being bent twice, i.e., containing two generally oppositely directed 
bends to lengthen the flat spring. As a result, the properties of the 
first spring element 6 are improved and the lifetime of the first spring 
element 6 is increased. When the first spring element 6 is short, the load 
is concentrated on a single point and the first spring element 6 is easily 
broken. Also, the flat spring bends need not be limited to two. Thus, the 
distance between the ends of the first spring element 6, when it is 
folded, is shorter than the distance between the ends if first spring 
element 6 is stretched out in a straight line. Also, the tip 6A of the 
first spring element 6 is constructed so that it is in constant contact 
with the printed board 9. When the keytop 2 is depressed, the tip 6A 
slides while in contact with printed board 9. 
At this point, to reduce friction resistance between the tip 6A of the 
first spring element 6 and the printed board 9, the structure is such that 
the tip 6A and the printed board 9 are in line or point contact. In the 
embodiment, the tip component 6a has the shape of a cylinder. When the 
user releases pressure after depressing the keytop 2, the keytop 2 is 
restored to the initial position (stroke 0 mm position) by the resilient 
restoring force of the first spring element 36 and the second spring 
element 7. 
The second spring element 7, built integrally into the first link 4, makes 
possible the depression of the switching component 29, that is built into 
the printed board 9 by passing through the opening 26. Also, on the right 
and left sides of the opening 26 of the holder element 8 (left 
corresponding to the location of rotation fastener 27 and right 
corresponding to the location of the elongate groove Sliding fastener 28 
as viewed in FIGS. 1A,1B) are injection molded the rotation fastener 27 
and the elongate groove sliding fastener 28 so that each of the upper and 
lower components of the fasteners 27,28 will release. Also, with regard to 
the two rotation fasteners 27, the bottom edge pin components 12A,12B of 
the first link 4 are inserted so they can rotate therein and, with regard 
to the two sliding fasteners 28, free edge pin components 14A,14B of the 
second link 5 are inserted so they can slide therein. 
The shape dimensions of the pins 11A,11B, the pins 14A,14B, and the sliding 
fasteners 16 (in the keytop 2), 28 (in the supporting base component 50) 
are set so that the first link 4 and the second link 5 become immobile 
relative to the FIG. 1A vertical direction, and also so that lateral 
sliding of pins 11A,11B and 14A,14B is uninhibited. Specifically, 
according to the embodiment, the base of each pin 11A,11B and 14A,14B is 
structured so that it will contact the inside face of the corresponding 
sliding fastener 16,28 and slide. Thus, the support shafts 25A,25B are 
prevented from slipping out of support holes 21A,21B. 
Also, as Shown in FIGS. 1A and 1B, the second spring element 7 is integral 
with the base component 18 of the first link 4, so that it can be 
installed over the upper component of the switching component 29 
(electrical contact point component) in the printed board 9. This second 
spring element 7 is made in a belt-shaped flat spring shape so that there 
will be overtravel (sliding) after the switching component 29 is 
electrically "on". Also, the tip 7A of the second spring element 7 is 
formed in a shape (for example, according to the present embodiment an 
arc, shape) that can reliably accomplish the switching movement of the 
switching component 29. 
FIG. 4 shows the depression characteristics of keyswitch 1 by means of the 
first spring element 6 and the second spring element 7. The depression 
force for pretravel 17 space is determined by the spring characteristics 
of the first spring element 6 and the depression force for the overtravel 
23 space is determined by the combination of the spring characteristics of 
the first spring element 6 and the second spring element 7. The depression 
force can be adjusted by changing the shapes and material specifications 
of the spring elements 6,7. Point X (FIG. 4) shows an electrical "on" 
point. When the stroke is at a position greater than point X, the 
keyswitch 1 is constantly electrically "on". Point Y shows an electrical 
"off" point. When the stroke is in a position less than point Y, the 
keyswitch 1 is constantly electrically "off". The points X, Y can also be 
adjusted by changing the shape of the spring elements 6,7. Because the 
depression force will necessarily change after the electrical "on" point 
at point X, due to the combination of spring characteristics of the first 
spring element 6 and the second spring element 7, the user can tell by 
touch when the keyswitch 1 is electrically "on". 
In addition, because the first spring element 6 is formed in a folded 
state, there is already a certain amount of depression load on the first 
spring element 6 (about 40 grams as shown in FIG. 4). Therefore, the 
depression force to take the keyswitch 1 to the electrical "on" point X is 
that much reduced when reaching point X. 
Next, the movement of the keyswitch 1 according to the embodiment will be 
explained with reference to FIGS. 1-4. When the user presses down on the 
keytop 2 of the keyswitch 1, the guiding element 3 rotates around pin 
components 12A,12B on first link 4 bottom free ends 20A, 20B, and changes 
position centering in resistance to the restoring force of the first 
spring element 6. At this time, the tip component 6A of first spring 
element 6 slides while in constant contact with printed board 9 and keytop 
2 descends while remaining in a parallel position with regards to the top 
face of holder element 8. 
Then, as shown in FIG. 4, when the stroke passes through the pretravel 
space 17 (0 mm-2.5 mm) and arrives at point X, the tip component 7A of 
second spring element 7 makes contact with switching component 29 to 
produce the switching movement. In addition, when the keytop 2 is further 
depressed by the user, the guiding element 3 further rotates around the 
pin components 12A,12B on the bottom free edge of the first link 4, and 
changes position centering against the resistance of the restoring force 
of the first spring element 6 and the second spring element 7, with the 
stroke within the overtravel space 23 (2.5 mm-4.0 mm), and the keytop 2 
descends while remaining in a parallel position with regards to the top 
face of holder element 8. 
Then, when the keytop 2 reaches the lowest position (stroke at 4.0 mm), 
even if the user presses down further, the keytop 2 will not descend 
further. The keyswitch 1 is then as shown in FIG. 2B. 
Last, when the user releases from depression the keytop 2, the keytop 2 is 
restored first to the point Y due to the resilient restoring force of the 
first spring element 6 and the second spring element 7. Then, the keytop 2 
is restored to the initial position (stroke position 0 mm) due to the 
resilient restoring force of the first spring element 6. 
As detailed above, because the keyswitch in the invention is molded with 
the first link element 4, the first spring element 6 and the second spring 
element 7 as one piece, benefits occur such as that the second spring 
element's 7 position with regards to the printed board's switching 
component is reliably set, switching movement can be reliably 
accomplished, and the depression load can be easily adjusted. Also, 
because rubber springs with a certain degree of thickness are eliminated, 
the keyswitch can be made thinner. As the number of components is reduced, 
the assembly time is reduced and a lower cost keyswitch can be provided. 
The invention is not limited to the embodiment detailed above, and many 
modifications can be made to it without departing from the limits of the 
main intent thereof. 
For example, according to the embodiment, each of the first and second 
spring elements 6,7 is attached to the first link 4, but it is acceptable 
that the design may be such that multiple springs of each kind are so 
attached. In this case, it is acceptable to have either multiple switching 
components for one keyswitch or only one switching component. If multiple 
switching components are attached, by changing the height of each spring 
element's tip component, each switching component's switching movement may 
be accomplished based on the amount of keytop depression so that one key 
may be set with many functions. 
Also, the keyswitch 1 may be constructed so that the first and second 
spring elements 6,7 are attached to the second link 5. 
Also, the supporting base 50 of the embodiment uses a three layer 
construction comprising a holder element 8, a printed board 9, and a 
strengthening board 10, but it is acceptable to make a holder element in a 
one layer board with a certain degree of hardness, and at the same time 
construct one printed-circuit layer. Also, other multiple layer 
constructions besides three are acceptable. 
In addition, when making each spring element 6,7 in first link 4's base 
component 18, it is acceptable to make the link base material and the 
spring element material using different varieties of resin material, make 
a two color item, and/or to make the link component's resin material and 
the spring element's metal material in insert or outsert form.