This is a continuation of application Ser. No. 07/375,798 filed Jul. 5, 1989 now abandoned. 5
BACKGROUND OF THE INVENTION
In conventional membrane switches, when a key operating block strikes the membrane, a great deal of the collision force is transformed into noise. An addition 10 to this conventional design is implemented by IBM. The change in the conventional design is in the form of an extra layer of auxiliary flexible material (e.g., cloth, rubber, plastic, etc.) between the membrane and the supporting layer to absorb some of the force. Unfortu- 15 nately, this increases the material cost and adds an unnecessary production expense.
SUMMARY OF THE INVENTION
The present invention relates to a membrane switch, 20 and particularly to a keyboard membrane switch, comprising a membrane which has at least three layers, and a supporting layer beneath the membrane, with the addition of a plurality of holes located substantially below the said switch, for the absorption of the noise 25 and the lessening of the impact created by the collision between the operating block and the base.
A primary purpose of the invention is to absorb the noise created when a key collides with a membrane, through a series of holes in the membrane levels and/or 30 its supporting layer.
Another purpose of the invention is to decrease the additional material expenses by only requiring holes to be punched in the membrane layers and/or its supporting layer. 35
Other purposes and advantages will appear in the ensuing specification, drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated diagrammatically in the 40 following drawings where:
FIG. 1A shows an exploded cut-away view of three membrane layers of a conventional membrane switch;
FIG. IB shows a side view of the three membrane layers in FIG. 1A; 45
FIG. 2A illustrates the switch in FIG. IB with an operating block of a single key in its OFF state;
FIG. 2B illustrates the switch in FIG. 2A in its ON state;
FIG. 3A shows an embodiment of a membrane 50 switch according to the present invention wherein the auxiliary holes are located in the middle membrane layer;
FIG. 3B shows another embodiment of the membrane switch according to the present invention 55 wherein the holes are located in the lower membrane layer;
FIG. 3C shows another embodiment of the membrane switch according to the present invention wherein there are holes present in the lower end middle 60 membrane layers;
FIG. 4A shows another embodiment of the membrane switch according to the present invention wherein the holes are located in the support plate;
FIG. 4B shows another embodiment of the mem- 65 brane switch according to the present invention wherein the holes are located in the lower membrane layer and the supporting plate;
FIG. 4C shows another embodiment of the invention wherein the holes are located in the middle and lower membrane layers and in the supporting plate;
FIG. 5A shows another embodiment of the invention wherein the auxiliary projection points are added onto the bottom portion of the operating block; and
FIG. 5B shows another embodiment of the membrane switch of FIG. 5A in its ON state.
DETAILED DESCRIPTION OF THE
The present invention relates to a membrane switch in which the impact of the struck key is buffered and absorbed, utilizing a series of holes which act as shock and noise absorbers.
In the conventional membrane switch, as shown in FIG. IB, 2A and 2B, FIG. IB is a cross-sectional side view of the three membrane layers (10,11,12) and their supporting layer (13). For explanation purposes, the thicknesses in FIG. IB are exaggerated. In actuality, layers 10,11 and 12 are thin, flexible and similar to that of photography film, as shown in FIG. 1A.
FIG. 1A, however, shows only a small portion of the entire membrane layers, but it is more accurately representative of the true thickness and configurations of the three membrane layers (10, 11, 12). The top layer 10 contains a series of silver contacts (101) and silver circuit lines (102) located underneath the surface; the middle layer 11 contains a series of holes (111) corresponding to the contacts; and the bottom layer 12 also contains a set of silver contacts (121) and silver circuit lines (122) substantially corresponding to those in layer 10.
In FIG. IB the three membrane layers (10,11,12) are laminated together and placed on a supporting layer (13). Because layer 11 is sandwiched between layers 10 and 12, the silver contacts (101, 121) are separated by the hole (115) in layer 11, as shown in FIG. IB. When the operating block (21) is pressed and the silver contacts (101, 121) are touched together (as shown in FIG. 2B), they complete the closed (ON) circuit and the computer receives the signal from the depressed key. When the key is released, the silver contacts return to their original (OFF) state.
FIG. 2A roughly represents conventional technology wherein the three membrane layers (10, 11, 12) are shown in Addition to the supporting layer (13), the operating block (21), the operating block's housing (20), the operating block's spring means (210), and the operating block's triggering element (215). This shows the switch in its OFF state. When the operating block is depressed, the triggering element (215) pushes the top membrane layer (10) down, allowing its silver contacts (101) to touch its corresponding silver contacts (121) on layer 12, as shown in FIG. 2B. FIG. 2B shows the ON state of FIG. 2A.
When the operating block is depressed, and the switch is turned ON, the bottom portion (220) of the operating block simultaneously strikes the membrane (100), causing additional noise—this is the drawback of conventional membrane switch technology. The present invention reduces this noise.
FIG. 3A shows one embodiment of the invention, in which holes (115) in layer 11 absorb much of the noise present when the operating block is depressed. Because the holes act as buffer gaps, the force of the collision is absorbed.