The present invention relates to switch assemblies in general and particularly to elastomeric type switches.
Elastomeric switches are used in many electronic devices such as appliance control panels, automotive dashboards, consumer toys, industrial controls, and control panels for radios, such as in a keypad assembly. This type of switch enjoys several advantages over conventional rocker, toggle or key switches. They can provide a liquid tight front surface, making them quite useful in environments where a switch or switch assembly might be exposed to liquid spills, corrosive chemicals, or moisture. They offer a reduced thickness, due to the absence of mechanical parts such as springs, rockers, wiring fasteners, and large housings. This feature is extremely desirable in applications such as thin calculators and other portable consumer electronic devices that must be worn on the person or carried in a pocket. Because of the absence of such parts, they have a lower cost of materials and assembly. This factor is quite important in consumer electronics. They provide a momentary contact, as opposed to permanent contact switch. This is important in applications such as calculators where a circuit is meant to be only briefly actuated.
A typical elastomeric switch is constructed much like a conventional switch, that is a movable contact is used to momentarily complete the connection between two sides of a circuit that are normally not connected. In flat elastomeric switches, often called membrane switches, the normally nonconnected sides of the circuit are formed on the surface of a rigid or flexible printed circuit board. The printed circuit board is usually placed underneath the switch actuator assembly. The bottom printed circuit board usually contains other circuitry to interconnect the switch or switches to the remainder of the electronic device.
However, when the elastomeric switch is used in an electronic product where the controls are at fight angles to the main bottom circuit board, such as in a front panel assembly for a mobile radio, the switch printed circuit board is usually placed on a side, in parallel with and behind the switch actuator assembly. One such side orientation uses the switch board assembly--a printed circuit board, or flex circuit, with popple domes, mechanical switches, or elastomeric membrane switches assembled to it--mounted to a structure that orients it at a right angle to the main board surface.
The conventional elastomeric switch board assembly, mounted on a side or flat, often includes a movable contact which consists of a flexible plastic sheet having a conductive area that serves to complete the circuit on the printed circuit board, underneath, when it is moved into contact on top of it. The conductive area on the flexible sheet is arranged so as to be facing the circuit board and is aligned so as to be directly opposite the stationary contacts on the circuit board. When a force is applied to the exterior side of the flexible sheet, the movable contact is displaced into engagement with the stationary contact to close the switch.
With all of its subcomponents, this switch board assembly still has to be electrically connected to the main printed circuit board by some additional structure. Hence, in the conventional universal front panel assembly, the side printed circuit board is an additional component to the bottom printed circuit board. This side board is hoped to be eliminated, along with other components.
One mounting approach to eliminate the additional side printed circuit board utilizes through-hole mechanical switches that are attached to a frame which supports the switches at a right angle to the board surface. Therefore, what is needed is a reduction in necessary component parts for a perpendicularly mounted control panel while providing the advantages of thinness of the elastomeric switches.