Keyboard switch assembly

Details Keyboard switch assembly Keyboard switch assembly

B - Operations, Transporting

41

J

340/178

B41J 5/08 (2006.01) H01H 13/705 (2006.01) H03K 17/975 (2006.01)

Patent

CA 1136244

KEY SWITCH ASSEMBLY Abstract An electronic switch keyboard for typewriters of office machines includes a multiple switch at selected key posi- tions to provide two signal inputs to a utilization device. A first capacitor switch is actuated to provide a first signal upon initial key depression and a second contact switch, common to all selected key positions, is actuated to provide a second signal upon further key depression at the selected key positions. A ground plane forms a portion of the contact switch and further serves to reduce parasitic capacitance and to shield the capacitive switches from stray electrical noise occasioned by the contact switch or other electrical inputs. A dielectric material is used to accurately separate the ground plane from the capacitive switch and further serves as a force spreading device for the contact switch. When the keyboard is used in conjunction with a typewriter, the first signal may be used to effect character selection and printing and the second signal to effect repeated printing of the same character. Consistent with prior mechanical typewriter keyboards, three increasing levels of force are required to be overcome as the key is depressed: a pretravel force, a first switch actuation force, and a second switch actuation force. LE9-78-028

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