Snap-action switch

A snap-action actuator, which comprises:

• a fixed support having a ferromagnetic insert;
• a plunger reciprocably mounted in the support for movement from a first position toward a second position, the plunger having a ferromagnetic armature;
• a magnet movably mounted in the support between the insert and the armature so that, absent a force applied to the plunger, the magnet attracts both the insert and the armature to form a sandwich, which sets the first plunger position;
• and
• means for applying a gradually increasing force to one end of the plunger until the magnetic attractive force forming the sandwich is exceeded, to suddenly drive the plunger to the second position, with a snap action after the magnetic release point.

A force-operated, snap-action switch for mounting in a keyboard comprising:

• a. a ferromagnetic toroid
• b. means for fixedly mounting the toroid to the keyboard;
• c. a nonmagnetic elongated plunger slideably held by, and extending past both ends of, the toroid;
• d. a toroidal permanent magnet loosely, slideably mounted on the plunger on one side of the toroid, one surface of the magnet normally abutting the toroid;
• e. a toroidal armature mounted on the plunger, the other surface of the magnet normally abutting the armature;
• f. means for rendering the attractive force of the magnet for the toroid greater than the attractive force thereof for the armature;
• g. a first, stationary electrical contact, spaced from one end of the plunger and aligned with the plunger's major axis at the side thereof adjacent the armature;
• h. a second electrical contact movable along the major axis of the plunger and located between the normally spaced from the first contact and the one plunger end;
• i. a spring member for maintaining the second contact in the normal position;
• j. a hollow cylinder open at only one end having its open end loosely slideably fitted about the other end of the plunger and normally spaced from the toroid;
• k. a coil spring positioned between the closed cylinder end and the other plunger end which maintains the open cylinder end in the normal position;
• and
• l. means responsive to a force applied to the cylinder for moving the open cylinder end toward the toroid to compress the coil spring until the compressive force thereon on the plunger overcomes the attractive force of the magnet to impact the plunger on the second contact with a force sufficient to deform the spring member until the contacts engage the spring member and the attractive force of the magnet for the armature returning the armature to its normal position and the coil spring returning the cylinder to its normal position upon removal of the force.

A keyboard-mounted snap-action electrical switch for completing an electrical circuit comprising:

• a. a first stationary electrical contact;
• b. a second electrical contact normally spaced from and movable into engagement with, the first contact to complete the circuit;
• c. first spring means for biasing the second contact toward its normal position with a first force inversely proportional to the distance between the contacts;
• and
• d. means for moving the second contact into engagement with the first contact, which means includes:
• i. a ferromagnetic toroid;
• ii. means for fixedly mounting the toroid to the keyboard;
• iii. a non-magnetic plunger extending slideably through, and beyond both sides of the toroid, a first end of the plunger abutting the second contact, application of a second force to the other end of the plunger tending to move the contacts into engagement;
• iv. a toroidal, ferromagnetic armature mounted on the plunger for movement therewith;
• v. a toroidal, permanent magnet slideably mounted on the plunger between the toroid and the armature, opposed surfaces thereof being normally respectively adjacent the toroid and the armature;
• vi. means for rendering the attractive force of the magnet for the toroid greater than the attractive force thereof for the armature, so that movement of the first plunger end toward and away from the first contact moves the armature toward and away from the toroid and the magnet, the attractive force of the magnet for the armature and the first force being vectorially additive, the summation of such vectorial addition being normally greater than the second force and the attractive force of the magnet for the armature being inversely proportional to the distance between the armature and the magnet;
• and
• vii. means responsive to a finger-applied force for momentarily increasing the second force to a magnitude greater than the summation to slide the plunger and to move the armature and the second contact toward the first contact until engagement thereof occurs.