摘要:
First and second membranes carrying contacts located on opposing faces are separated by a third or spacer membrane having holes therein so that a circuit may be completed between the contacts when a force is applied to the first membrane. The first and second membranes and the peripheries of the holes define substantially enclosed switch regions. The first, second and third membrane layers are mechanically held together, without the use of adhesives, in the regions other than the switch regions. Spacer elements are provided between the spacer membrane and one of the first and second membranes. The spacer elements form air pockets such that air may flow between the switch region and the air pockets as the first membrane is depressed and then released. The arrangement provides two advantages. First, it reduces pressure buildup, such as would occur if the membranes were sealed together, when force is applied to the first layer. Secondly, it reduces pressure variations in the switch region where a vacuum would otherwise be created as the first membrane returns to its undepressed position. The contacts thus open more quickly thereby reducing the possibility of contact bounce. The spacer elements might be either conductive or dielectric. If they are conductive they may be applied during the same screening pass that places conductors and contacts on the first or second layer. If they are non-conductive they may be applied during the same screening pass that places a dielectric on the flextail portion of a membrane.
摘要:
In a typewriter, a ribbon is contained within a cartridge which is in turn placed upon the ribbon mechanism support of the typewriter. The cartridge is maintained rigidly clamped to the support but readily releasable by means of operator actuation of a release lever. The cartridge may either be a single cartridge or may be stacked such as where two cartridges are utilized together, one containing a print ribbon, the other containing, for example, a correction ribbon. The cartridge containing the print ribbon is provided with a bottom plate or surface which is formed to define an aperture therein for the admission of a clamping member attached to the support. The clamping member is inserted into the aperture and then caused to rotate about its axis a part turn at which point the clamping member engages an inclined surface on the interior of the cartridge causing the cartridge to be wedged downward against the support. In so wedging, the hold down mechanism is capable of retaining the cartridge in a fixed position to oscillate with the support.