Strain sensing key membrane
AssigneeApple Inc.
InventorsChia Chi Wu, Michael Vosgueritchian, Ming Gao, Nan Chen, Vyom Sharma, Wenhao Wang
Life of this patent
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Abstract
An electronic device has a keyboard with an internal membrane. The membrane has a set of strain gauges configured to respond to a key press, such as when a collapsible dome collapses into contact with the membrane. The strain gauges are connected in a half Wheatstone bridge configuration and are positioned on the membrane in order to limit effects of temperature and subtle flexure of the membrane. The strain gauges are also configured to magnify detection of a resistance differential when a keycap is pressed with sufficient force.
Claims20
A keyboard, comprising:
- a base;
- a keycap configured to translate relative to the base between a first position, a second position, and a third position;
- and
- a membrane layer positioned between the keycap and the base, the membrane layer including:
- a flexible sheet;
- a first piezoresistor positioned on the flexible sheet between the keycap and the base and having a variable first resistance;
- a second piezoresistor positioned on the flexible sheet between the keycap and the base and having a variable second resistance;
- and
- a conductor connecting the first piezoresistor to the second piezoresistor;
- wherein, in response to movement of the keycap between the first position and the second position, a voltage measured at the conductor, and influenced by a ratio of the variable first resistance and the variable second resistance, is less than a predetermined threshold value;
- and
- wherein, in response to movement of the keycap between the second position and the third position, the voltage measured at the conductor, and influenced by the ratio of the variable first resistance to the variable second resistance, is greater than the predetermined threshold value due to deformation of at least the first piezoresistor.
An electronic device, comprising:
- a bottom layer;
- a flexible membrane extending across the bottom layer;
- a piezoresistive sensor positioned on the flexible membrane;
- a collapsible dome positioned over the piezoresistive sensor and having a central portion collapsible toward the piezoresistive sensor to deflect the piezoresistive sensor;
- a controller in electronic communication with the piezoresistive sensor to measure a voltage change across the piezoresistive sensor, wherein collapse of the central portion of the collapsible dome increases the voltage change to exceed a threshold voltage.
A keyboard, comprising:
- a flexible sheet;
- a first strain gauge positioned on the flexible sheet;
- at least one additional strain gauge positioned on the flexible sheet, wherein the first strain gauge and the at least one additional strain gauge are in electrical communication with each other;
- and
- a switch structure positioned above the first strain gauge and the at least one additional strain gauge, the switch structure being movable to a position deflecting the first strain gauge and the at least one additional strain gauge.
Dependencies are inferred from the claim text.