Electrical switch construction

A switch construction comprises a housing which has a base wall and an upstanding side wall with first and second contact terminals arranged in spaced locations in the housing and with one of them bent over on its top so as to form a contact making portion. A spring member has an upper part with one end engaged in a V-shaped bearing on the one contact terminal and has a lower part with a contact arm which is engageable with the contact portion of the other terminal. The upper and lower parts of the spring member are interconnected by a curved bearing portion which is engaged and supported in the housing sidewall. In addition the spring member has an intermediate part of the upper portion which is substantially straight and which is engageable by an extension of an actuation member which is engaged on the housing and confined for movement upwardly and downwardly within predetermined limits. The spring member biases the actuating member to an uppermost end position and it is movable downwardly against the spring member to cause a pivotal motion of the spring member upper part about the bulging portion at one end of the intermediate part and a bulging portion at an opposite end of the intermediate part. The lower part of the spring which includes the contact member is first moved in an upward direction by the downward movement of the actuating member and is thereafter moved into engagement with the contact portion of the second contact terminal.

BACKGROUND OF THE INVENTION 
1. FIELD OF THE INVENTION 
This invention relates in general to the construction of switches and in 
particular to a new and useful electrical switch which includes a spring 
member which is supported in a housing between a housing wall and a first 
contact terminal and which is deflectable by an actuating member engaged 
on the housing so as to bring a contact arm portion into engagement with a 
second contact terminal. 
2. Description of the Prior Art 
Switches of a general type which include a spring member which is 
deflectable by an actuating member are known. However, in various 
applications particularly in the data processing field there is a 
necessity for having a switch with a distinctly perceptible switching 
instant at the actuation. This is not achieved with the known designs of 
the prior art. 
SUMMARY OF THE INVENTION 
In accordance with the present invention there is provided a switch which 
is constructed so that the switching instant during a switching operation 
is clearly perceptible by the sense of touch. 
In accordance with the invention the switch includes a spring contact 
member which has an upper part with one end engaged on a first terminal 
member seated in a housing and which includes a lower contact portion 
which is connected to the upper portion by a curved bearing portion which 
is seated in a wall of the housing. The upper portion of the spring member 
is engaged at an intermediate straight part by an extension of an 
actuation member which is movable upwardly and downwardly on the housing 
within confined limits. The arrangement of the spring member and the 
actuating member is such that the actuating force which is applied may be 
increased to a predetermined maximum and then after having risen to the 
maximum value will decrease. The result is that the switching instant at 
which the contact portion of the spring contact member moves into 
engagement with the contact portion of a second terminal is easily 
discernible on the actuation member. The actuation member may for example 
comprise a small key and thus the operator becomes aware of the fact that 
the switching has taken place or is just taking place. Advantageously, the 
switch is monostable, that is upon disappearing of the actuation force the 
spring and the contact arm return to their initial positions during which 
travel they reset the actuating member in those cases where no separate 
resetting mechanism or other reset means is provided. The characteristic 
for the back travel of the switch of the invention corresponds 
substantially to that of the forward travel for the actuation of the 
switching mechanism. A relatively long back travel of the key prior to the 
breaking off of the contact is also advantageous. In such a manner a 
relatively smooth separation of the contacting element is obtained. On the 
other hand for closing the movable contact applies abruptly against the 
fixed contact due to the variation of the actuation force during the 
switching. Scientific tests have shown that with a switch which has a 
tangible switching instant, the expended energy is smaller than with a 
switch without such a provision. This is probably due to the circumstance 
that with a conventional device the operator produces a greater effort 
because he is never quite sure whether the contact is in fact closed. To 
insure the closure in switches of the prior art the actuating member is 
pushed down to the extreme final position. With the inventive switch on 
the other hand the actuating member can be released shortly after reaching 
the switching instant and there is no need for making sure that the key 
abuts the housing for example. In considering that there are professions 
today which require an actuation of keys for hours, the extraordinary 
importance of a tangible switching instant of such a switch, particularly 
a key switch, becomes very clear. An increasing key force is termed a 
tactile swelling signal. 
In a development of the invention one of the bearings of the bow type 
spring is connected in an electrically conducting manner to a terminal 
element of the switch. Consequently, the current can flow from the 
terminal through the bow type spring and the contact arms to the 
cooperating contact. 
According to a further feature of the invention the switch includes a 
spring member with an upper part having an intermediate substantially 
straight portion located between a bulging portion at each end one of 
which is curved upwardly against the actuation direction and the other of 
which is curved downwardly in the direction of actuation. The actuation 
member advantageously applies against the intermediate portion and it is 
designed with a sufficient width so that it will not get clamped in one of 
the bulging portions or between the two bulging portions. Advantageously 
the switch also includes a lower portion which is connected to the upper 
portion by a curved bearing portion and which carries a contact arm which 
extends approximately parallel or at a small angle to the upper portion. 
The contact arm of course may be either straight or arcuate or angular. In 
the mounted state the spring member is biased against the actuation member 
and urges it into one end position that is an upper position. The spring 
member is advantageously made in one piece and includes the upper and 
lower portions interconnected by a curved bearing portion and with an 
upper portion having an intermediate substantially straight portion with a 
bulging part adjacent each end. The cross-section of the spring member is 
similar to a leaf spring in construction and of course the member must be 
of electrically conducting material. 
In accordance with a feature of the invention the free end of the spring is 
advantageously supported in a V-shaped bearing notch which is formed in a 
first lug member which is engaged through the bottom of the housing and is 
positioned in an upright position along one side thereof. This feature 
makes the construction very inexpensive to manufacture and requires only a 
very few parts. The other end of the spring at the location of the curved 
bearing portion is engaged in a recess of the housing so that the spring 
may pivot in such location. 
The lower portion of the spring member advantageously is befurcated so that 
there are two contact arm portions and each one carries a bead preferably 
a golden contact element. When the spring member is made in a single piece 
the entire switch assembly can comprise only five component parts 
including the first and second terminals, the housing, the spring member 
and the actuating member. Both the housing and the actuating member or 
keys are advantageously made of a plastic material. 
Accordingly it is an object of the invention to provide an improved switch 
construction which comprises a housing having first and second spaced 
contact terminals therein and with a spring member having first and second 
parts which are interconnectable by a curved bearing portion which is 
positioned in a recess in a wall of the housing and which includes an 
upper part having an intermediate part which is engaged with an actuating 
member which is movable upwardly and downwardly on the housing, the spring 
member being constructed with a bulge on each side of the intermediate 
straight portion so that it may move downwardly under the force of the 
actuation member by a predetermined amount before the contact portion is 
switched into contact with the second contact member and wherein the 
movement of the contact into engagement is discernible through the 
actuator. 
A further object of the invention is to provide a switch which is simple in 
design, ruggen in construction and economical to manufacture. 
For an understanding of the principles of the invention reference is made 
to the following description of a typical embodiment thereof as 
illustrated in the accompanying drawings.

GENERAL DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in particular the invention embodied therein 
comprises a switch which is a single pole key button switch and which 
includes a housing 1 having a base 1a through which first terminal member 
19 and a second terminal member 24 are engaged. In the embodiment 
illustrated the housing 1 is shown as positioned in a recess 2 of a plate 
member 3 which may be part of a calculator for example. An actuation 
member or key button 4 is engageable over the housing 1 and it is confined 
or trapped for movement upwardly and downwardly in respect to the housing 
between defined limits. The actuation member 4 is movable downwardly in 
the direction of arrow 5 in the actuation direction and is movable in a 
return direction in the direction of the arrow 7 shown in FIG. 2. 
In accordance with the invention a spring member generally designated 6 has 
a first or lower portion 6a in the form of a contact arm 8 which is 
engageable with a contact portion 23 of the second terminal contact member 
or lug 24. 
In the normal position of the spring member 6 shown in FIG. 1 it acts upon 
a central extension or projection 17 of the actuating member 4 and urges 
the actuating member upwardly to the uppermost end position. In this 
position the spring member 6 is in a biased state. 
Advantageously the spring member 6 is manufactured in a single piece and 
includes a contact arm 8 which as shown in FIG. 3 may be bifurcated and 
have two leg portions 12, 12 each with a contact bead or button 10. FIG. 4 
shows the unbiased condition of the spring member 6 in which the contact 
arm 8 extends at an angle to the upper portion 6b. the upper portion 6b 
includes an intermediate straight part 16 with an upwardly bulging portion 
13 on one end and a downwardly bulging portion 15 on the opposite end. The 
downwardly bulging portion 15 which extends in the actuation direction 5 
is connected at its outer end to an upwardly bulging portion 14 which in 
turn is connected to a terminating portion or end which is engaged in a 
V-shaped bearing 18 of the first contact terminal 19. Both the bulging 
portion 13 and the bulging portion 14 are curved upwardly or in a 
direction opposite to the actuation direction indicated by the arrow 5. 
Bulging portion 15 blends directly into the bulging portion 14. 
As shown in FIG. 1 the stud-shaped extension 17 of the key 4 projects into 
the interior of the housing 1 and permanently applies against the 
connecting intermediate portion 16. More exactly expressed the spring 6 is 
inserted into the housing 1 in a biased state and urges the key 4 through 
the intermediate portion 16 into the upper end position thereof. 
The upper bulging portions 13 and 14 serve to accommodate the horizontal 
spreading of the spring member caused by the biasing while the lower 
bulging portion 15 provides a pivotal radius during the actuation movement 
of the spring. The force resulting from the bias at the actuating key is 
very small. 
FIG. 5 indicates various phases of switch operation namely phase 0, 1, 2, 3 
and 4. These same phases are indicated on the curve shown in FIG. 6 in 
which the values of the actuating force for the various stages of path 
movement of the actuating member 4 are indicated. Upon actuation the 
spring 6 while pivoting in both bearings moves toward the interior of the 
switch housing and deforms downwardly. In the initial phase the contact 
arm 8 moves first against the direction of actuation 5 and only 
subsequently in the same direction. This results in a characteristic shown 
in FIG. 6 where the switching phases from 0 to 4 are indicated on an 
upward curve 21 which is the actuation curve. The same phase occur in a 
lower return curve 22 which shows the relation during the resetting of the 
component parts. At the bottom of the curve the on and off positions are 
indicated symbolically. It will be noted therefrom for example during the 
switch off operation that the contact remain in contact relatively long 
for a relatively long period of time so that the key can travel through 
approximately one half it its path before the contacts are separated from 
each other. During the closing of the contacts the inventive switch 
behaves similarly. Thereby a smooth opening as well as a smooth closing of 
the contacts is obtained. 
The invention thus provides a switch which can be made up of only five 
separate components namely the housing 1, the spring member 6, the first 
contact terminal 19, the second contact terminal 24 and the actuating 
member or key 4. 
While a specific embodiment of the invention has been shown and described 
in detail to illustrate the application of the principles of the 
invention, it will be understood that the invention may be embodied 
otherwise without departing from such principles.