Key switch with snap-action contact and resilient actuator

A key switch, comprising:

• a housing;
• a fixed switch contact on the housing;
• elongated snap-action spring means having a first end secured to the housing, and a cantilevered portion extending away from the first end to a free second end defining a movable switch contact which can be displaced between first and second bi-stable positions in which the contacts are open and closed respectively in response to an actuating force applied to the snap-action spring means;
• elongated actuator spring means having a first end secured to the housing, a cantilevered portion extending away from the first end to a free second end, and an intermediate portion which acts against the snap-action spring to apply said actuating force;
• an elongated keystem slidably mounted on the housing and having a portion extending laterally from the central axis of said keystem in contact with the free end of said actuator spring means to deflect the actuator spring means in response to keystem movement and thereby to deflect and actuate the snap-action spring means;
• and
• said actuator spring means and said snap-action spring means being constructed such that deflection of said actuator spring means by said keystem will cause the free end of the actuator spring means to be deflected through a larger displacement than a displacement of the snap-action spring means which is necessary to drive the snap-action spring from the first position to the second position, thereby providing a mechanical advantage enabling keystem actuating force to be lower than the actuating force of the snap-action spring means.

A keyboard assembly, comprising;

• a housing;
• a printed circuit board underlying said housing;
• a plurality of key switches supported on the housing;
• each key switch having a conductive snap-action spring carrying a movable contact normally spaced apart from a fixed contact on the printed circuit board, an actuator spring having a free end which is movable to deflect a portion of the actuator spring against the snap-action spring, and a keystem movably mounted on the housing and having a portion positioned to bear on the free end of the actuator spring to apply an actuating force through the actuator spring to the snap-action spring to close the contacts, the direction of actuating force being generally parallel to the direction of keystem motion;
• at least some of the key switches being arranged in rows, the key switches in a given row having snap-action springs which are integrally connected together by a first narrow conductive strip, and said key switches in said given row having actuator springs which are integrally connected together by a second narrow conductive strip parallel to and overlying said first strip;
• and
• said first and second conductive strips being clamped between said housing and said board.

A key switch comprising:

• a housing including a base and a cover;
• a fixed switch contact on said base;
• a bi-stable snap-action conductive spring secured to the housing, said snap-action spring being movable between first and second bi-stable positions and having a portion defining a movable switch contact positioned above and normally out of engagement with the fixed contact in said first position;
• an actuator spring secured at one end to the housing and having a free end and a second portion, said second portion being closer to said one end than is said free end, said second portion being disposed above said snap-action spring, said free end being movable downwardly to urge said second portion against the snap-action spring;
• a keystem slidably mounted on the housing above said springs and having a portion positioned to bear on the free end of said actuator spring, downward depression of said keystem causing an actuating force to be applied through said second portion of the actuator spring to the snap-action spring to bring said movable switch contact into engagement with said fixed switch contact, the direction of the actuating force being generally parallel to the direction of keystem motion;
• said snap-action spring returning by its inherent resilience to said first position when the downward pressure on said keystem is released;
• said snap-action spring being a generally rectangular sheet of spring metal having a pair of parallel sides and two generally parallel ends;
• said sheet being bowed between said sides to provide an upraised intermediate section engageable by said second portion of said actuator spring;
• said intermediate section embodying said movable switch contact;
• and
• said ends having grooves formed therein stressing said sheet into said bowed configuration.

A key switch, comprising:

• a housing;
• a fixed switch contact on the housing;
• snap-action spring means having a first end secured to the housing, and an upraised portion extending away from the first end to a movable portion defining a movable switch contact which can be displaced between first and second bi-stable positions in which the contacts are open and closed respectively in response to an actuating force applied to the snap-action spring means;
• elongated actuator spring means having a first end secured to the housing, a cantilevered portion extending away from said first end to a free second end, and a second portion which is closer to said first end than is said free end and acts against the snap-action spring to apply said actuating force;
• an elongated keystem slidably mounted on the housing and having a portion extending laterally from the central axis of said keystem positioned to contact the free end of said actuator spring means to deflect the actuator spring means in response to keystem movement and thereby to deflect and actuate the snap-action spring means;
• and
• said actuator spring means and said snap-action spring means being constructed such that deflection of said actuator spring means by said keystem will cause the free end of the actuator spring means to be deflected through a larger displacement than a displacement of the snap-action spring means which is necessary to drive the snap-action spring from the first position to the second position, thereby providing a mechanical advantage enabling keystem actuating force to be lower than the actuating force of the snap-action spring means.

A keyboard assembly comprising:

• a printed circuit board having at least one row of conductive layers thereon;
• a housing mounted on said board and embodying at least one row of key switch cavities open to said board, each said cavity being positioned over a corresponding one of said conductive layers;
• a snap-action spring in each said cavity embodying a movable contact normally spaced above said corresponding conductive layer;
• a first conductive strip between said housing and said board interconnecting at least some of said snap-action springs;
• an actuator spring in each said cavity above said snap-action spring, said actuator spring having a free end movable to urge a portion of the actuator spring against the snap-action spring;
• a second conductive strip between said housing and said board interconnecting at least some of said actuator springs;
• and
• a plurality of keystems mounted on said housing each for one of said cavities, each said keystem having a portion positioned to bear on the free end of the actuator spring in its respective cavity to apply an actuating force through the actuator spring to the snap-action spring to cause said movable contact to engage said corresponding conductive layer, the direction of actuating force being generally parallel to the direction of keystem motion.