Keyboard multiple switch assembly
First Claim
1. A keyboard switch assembly comprising:
- a plurality of manually movable keys;
a capacitive switch assembly including a circuit board having individual circuit elements associated with individual keys, plural members each responsive to movement of an associated keybutton for moving relative to the associated individual circuit elements, capacitive sensing means for sensing a change in relative position between individual ones of said plural members and said associated individual circuit elements;
a contact switch located below said circuit board and including a grounded planar member forming a first switch member and a ground plane electrical shield for said capacitive switch assembly, a second switch member having an electrical potential applied thereto, sensing means for sensing contact between the first and second switch members; and
means extending through said circuit board and responsive to further movement of an associated keybutton for causing contact between said first and second switch members.
2 Assignments
0 Petitions
Accused Products
Abstract
An electronic switch keyboard for typewriters or office machines includes a multiple switch at selected key positions 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.
28 Citations
8 Claims
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1. A keyboard switch assembly comprising:
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a plurality of manually movable keys; a capacitive switch assembly including a circuit board having individual circuit elements associated with individual keys, plural members each responsive to movement of an associated keybutton for moving relative to the associated individual circuit elements, capacitive sensing means for sensing a change in relative position between individual ones of said plural members and said associated individual circuit elements; a contact switch located below said circuit board and including a grounded planar member forming a first switch member and a ground plane electrical shield for said capacitive switch assembly, a second switch member having an electrical potential applied thereto, sensing means for sensing contact between the first and second switch members; and means extending through said circuit board and responsive to further movement of an associated keybutton for causing contact between said first and second switch members. - View Dependent Claims (2, 3, 4, 5)
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6. A keyboard switch assembly comprising:
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a first capacitive switch circuit actuated upon motion of a key; a second switch circuit sequentially actuated thereafter upon further motion of said key; said switch assembly including a common element serving as a ground plane electrical shield for the first capacitive switch circuit and as a switch element for the second switch circuit whereby electrical noise introduced by closure of the second switch circuit and extraneous electrical signals are shielded from the first capacitive switch circuit by the common element, said common element further acting to reduce parasitic capacitance in said first capacitive switch circuit. - View Dependent Claims (7, 8)
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Specification