Key switch

A key switch includes a base, a circuit board, a retaining board, a rubber spring, a support linkage and a key cap. A first engaging mechanism and a second engaging mechanism are formed on the base. The circuit board is positioned above the base and comprises a switch electrode. The rubber spring is positioned on the circuit board. The support linkage is engaged with the base, having a first link and a second link pivotably attached together. A pair of engaging pins of the first link engage with the base, and a pair of arcuate faces is formed on the base proximate the engaging pins. A sliding link is formed on the second link to engage with the second engaging mechanism. The key cap engages with the support linkage.

BACKGROUND OF THE INVENTION 
The present invention relates to engaging means for attaching a key switch 
to a keyboard, and especially to engaging means which facilitates assembly 
of a key switch to a base of a keyboard. 
Most common way of inputting information into a computer is through a 
keyboard. All keyboards comprise a plurality of key switches assembled to 
a base of the keyboard such as those disclosed in Taiwan Patent 
Application Nos. 83204123, 84218262, and 84214256, and U.S. Pat. Nos. 
5,462,195 and 5,512,719. Although the structure disclosed in these patents 
is partly different, they all incorporate a key switch engaging structure 
similar to the one shown in FIG. 7. 
As shown in FIG. 7, a link 91 is pivotably attached to a base 92 of a 
keyboard by means of a pivot pin 93 of the link 91 with a resilient 
engaging structure 94 formed on the base 92. The pivot pin 93 is inserted 
through an opening 95 of the engaging structure 94. The diameter of the 
opening 95 is less than that of the pivot pin 93, thus the engaging 
structure 94 are outwardly deformed when the pivot pin 93 is forcibly 
inserted through the opening 95. A significant force is required to deform 
the engaging structure 94 during insertion of the pivot pin 93. Such a 
force makes assembly laborious and may damage the elements. In addition, 
the deformation of the engaging structure 94 increases the dimension of 
the opening 95 possibly resulting in detachment of the link 91 from the 
base 92. Furthermore, the complex shape of the engaging structure 94 not 
only complicates production, but also increases manufacturing costs. In 
view of the above problems, it is desirable to provide an improved key 
switch engaging means. 
SUMMARY OF THE INVENTION 
A main object of the present invention is to provide a key switch engaging 
means which is not inclined to detach from a base of a keyboard. 
Another object of the present invention is to provide a key switch engaging 
means which can be easily manufactured and assembled to the base of the 
keyboard. 
The above objects are accomplished by providing a key switch engaging means 
comprising a base and a support linkage. First engaging means is formed on 
the base. A protrusion outwardly extends from a top portion of a first 
side of the first engaging means and a concave edge is formed below the 
protrusion. An arcuate face is formed on a second side of the first 
engaging means opposite the protrusion. The support linkage includes at 
least a link having an engaging pin for engaging with the first engaging 
means. A pair of arms are formed proximate the first engaging means. An 
arcuate side is formed on each arm to firmly abut against the second side 
of the first engaging means. 
Other objects, advantages and novel features of the invention will become 
more apparent from the following detailed description when taken in 
conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to FIGS. 1 and 2, a key switch 1 comprises a base 2, a 
circuit board assembly 3, a support linkage 4, and a key cap 5. The base 2 
includes a pair of engaging pieces 21 and an engaging arm 22 upwardly 
extending therefrom. A first side 23 outwardly extends from a top portion 
of the engaging piece 21 and the first side 23 has a protrusion 231 and a 
concave edge 232 defined below the protrusion 231. The engaging piece 21 
has a second side forming an arcuate face 25 opposite the first side 23. A 
groove 26 is defined in the base 2 below the engaging arm 22. 
The circuit board assembly 3 comprises a circuit board 31, a retaining 
board 32, and a rubber spring 33. A pair of openings 321, 322 is defined 
in the retaining board 32. A support portion 323 is formed in a center of 
the retaining board 32. The rubber spring 33 is positioned on the support 
portion 323 and comprises a conical body 331 and a circular flange 332 
upwardly extending from the body 331. If a compression force exerted on 
the rubber spring 33 exceeds a predetermined threshold, the rubber spring 
33 will deform and a movable electrode (not shown) formed on the support 
portion 323 of the retaining board 32 will contact a switch electrode 311 
formed on the circuit board 31. Accordingly, the switch electrode 311 is 
short-circuited and the switching operation is carried out. A plurality of 
slots 312, 313 are defined in the circuit board to mate with the engaging 
pieces 21 and the engaging arm 22. 
The support linkage 4 is pivotably interconnected between the key cap 5 and 
the base 2 and comprises a first link 41 and a second link 42. The first 
link 41 is substantially U-shaped and comprises a pair of first arms 43 
and a block 44 formed between ends of the first arms 43. The block 44 
forms an inner arcuate side 441. A pair of pivot pins 431 outwardly 
extends from the end of each first arm 43, and a sliding pivot pin 432 
outwardly extends from an opposite end of each first arm 43. The pivot 
pins and the sliding pivot pins 431, 432 are engaged with the engaging 
pieces 21 and the key cap 5, respectively. A pair of shaft holes 433 are 
defined in opposite inner faces of the first arms 43 and a pair of 
extensions 434 are formed on a central portion of the first arms 43 on 
opposite outer faces thereof. Each extension 434 has an arcuate edge 435. 
The second link 42 includes a pair of second arms 45, a stationary link 46 
formed between ends of the second arms 45, and a sliding link 47 formed 
between opposite ends of the second arms 45. A pair of trunnions 451 for 
engaging with the shaft holes 433 outwardly extend from opposite central 
portions of the second arm 45. With this construction, the links 41, 42 
are pivotably assembled together, and the stationary link 46 and the 
sliding link 47 are engaged with the key cap 5 and the engaging arm 22, 
respectively. 
With reference to FIG. 6, the engaging walls 51, 52 are formed on inner 
side walls of the key cap 5. The engaging wall 51 engages and pivotably 
retains the stationary link 46 of the second link 42. The sliding pivot 
pins 432 slidably engages with the engaging wall 52 in a horizontal 
direction. 
With reference to FIGS. 3, 4, and 5, in assembly, the pivot pin 431 of the 
first link 41 is received in the first side 23 of the first engaging means 
21 and the pivot pin 431 abuts against the first side 23, thus the first 
link 41 can rotate about the pivot pin 431 toward the base 2. When the 
extension 434 of the first arm 43 begins to abut against the first 
engaging means 21 approximately at an angle of 40 degrees between the 
first link 41 and the base 2, the arcuate edges 435 of the extensions 434 
slide along the second side 25 of the engaging piece 21 and the angle 
between the first link 41 and the base 2 will be less than 40 degrees, at 
last forming a pivotably engaged relationship between the first link 41 
and the base 2. When the support linkage 4 is slightly raised, the sliding 
link 47 of the second link 42 is horizontally received in the groove 26 
and firmly abuts against the engaging arm 22 (as shown in FIG. 6). 
When the support linkage 4 is assembled to the base 2, assembly thereof is 
simplified. Furthermore, since the angle between the base 2 and each link 
41, 42 is approximately 20 degrees in the normal, unpressed operating 
state as shown in FIG. 2, it is insured to prevent the detachment of the 
support linkage 4 from the base 2. 
Alternatively, an engaging rod may be formed between ends of the first arms 
43 of the first link 41 thereby replacing the block 44. The engaging 
pieces 21 may be replaced with an elongate engaging portion having a cross 
sectional shape similar to the engaging pieces 21 for pivotably engaging 
with the engaging rod. 
It is to be understood, however, that even though numerous characteristics 
and advantages of the present invention have been set forth in the 
foregoing description, together with details of the structure and function 
of the invention, the disclosure is illustrative only, and changes may be 
made in detail, especially in matters of shape, size, and arrangement of 
parts within the principles of the invention to the full extent indicated 
by the broad general meaning of the terms in which the appended claims are 
expressed.