Flexible membrane contact key-pad with air permeable substrate - has space under each key ventilated through holes in lower contact plate and fibre layer on supporting base preventing contamination

摘要

The device uses a flexible insulating substrate carrying a conducting pattern, located face to face with a second plane insulating substrate carrying a similar pattern which together define the key contacts. The two substrates are separated by a spacing layer with holes defining each contact location. The space between the contacts is ventilated by holes in the substrate and a gas permeable layer in the supporting base. The base consists of a rigid support with a porous layer which may be composed of fibres or a rigid corrugated element or honeycomb or lattice work. The device provides a sealed keypad in which the performance does not depend on the outside air pressure.