Key for the keyboards of electric-input office machines

Claim 2

A key for keyboards of electric-input devices, including a head and a shank for operating at least one movable electric contact to close a circuit by bearing on a fixed electric contact, wherein the improvement comprises: an insulating plate carrying said movable electric contact, a spring normally holding said plate so that it bears against said shank in at least two different bearing points, said bearing points being situated on opposite sides of the point of attachment of said spring to said plate, hook means carried by said plate, fixed means engageable by said hook means during the depression stroke of the key, said hook means during engagement with said fixed means first causing said plate to turn about one of said two bearing points and then causing said plate to disengage said hook means from said fixed means, whereby said spring suddenly moves said plate and said movable contact to touch said fixed contact temporarily through inertia, said spring then returning said plate to contact both said bearing points, and stop means to stop said shank in such a position as to cause said movable contact to be separated from said fixed contact when said key is held depressed, as a result of which a single electric signal in the form of a pulse is generated.

Claim 3

A key according to claim 1 further comprising: a stop surface in said stop means for defining the stroke of a key, a tooth secured to said shank to cooperate with said stop surface, a cam surface, and a flexible extension of said shank carrying said tooth and cooperating with said cam surface to remove said tooth upon depressing the key for a stroke greater than said defined stroke so as to hold said movable contact in contact with said fixed contact as long as the key is kept depressed for said greater stroke in order to supply a continuous electric signal.

Claim 4

A key according to claim 1, wherein said hook means comprise: a hook element, anD a cam extension integral with said plate and carrying said hook element; and wherein said fixed means comprise: a shoulder engageable by said hook element, and a fixed support normally contacted by said cam extension under the urging of said spring to cam said cam extension upon engagement of said hook element during said depression so as to disengage said hook element from said shoulder.

Claim 5

A key according to claim 1, wherein said movable contact is constituted by a pair of leaves fixed with one end substantially in correspondence with said point of attachment and directed towards said extension, said fixed contact being constituted by the ends of a pair of conductors of a printed circuit.

Claim 6

A key according to claim 1, wherein said shank is slidable in a prismatic guide, said bearing points being disposed on that end of the shank which is remote from the head of the key.

Claim 7

A key according to claim 5, wherein said fixed support comprises a surface parallel to said prismatic guide, and said extension includes a rounded surface cooperating with said support, said shoulder being perpendicular to said prismatic guide.

Claim 8

A key according to claim 6, wherein said shank and said prismatic guide are made of plastic, said prismatic guide comprising a portion of L-shaped section and a portion constituted by two parallel walls.

Claim 9

A key according to claim 6, comprising: two opposite prismatic notches on said shank, a head of the key also made of plastic material and mounted removably thereon, two semi-cylindrical projections provided internally on said head to engage said notches, and a recess arranged in said shank between said notches to enable said notches to be brought nearer to each other for removing or mounting the head.

Claim 10

A keyboard for an electric-input device comprising a set of different keys, each said key including a shank for operating at least one movable electric contact to close a circuit by bearing on a corresponding fixed electric contact, said fixed contact being carried by a fixed flat body, wherein the improvement comprises: a set of insulating plates associated with said keys and each one carrying the corresponding said movable electric contact, a set of springs associated with said plates and each said spring normally holding the associated said plate so that said plate bears against said shank of the associated key in at least two different points, said points being situated on opposite sides of the point of attachment of said spring to said plate, hook means connected to each one of said plates, fixed means engaged by said hook means during the depression stroke of the associated key, said hook means during engagement with said fixed means first causing the associated plate to turn about one of said two points, and then causing the associated plate to disengage said hook means from said fixed means, whereby said spring suddenly moves said plate and said movable contact to touch said fixed contact temporarily through inertia, said spring then returning said plate to contact both said different points, stop means for stopping said shank in such a position as to cause the associated movable contact to separated from the fixed contact when the key is held depressed, as a result of which a single electric signal in the form of a pulse is generated, a guide block for each one of said shanks secured to said flat body, each one of said guide blocks having an internal opening for receiving said shank, and a holed plate parallel to said flat body for engaging said guide blocks with said shank protruding outwardly therethrough.

Claim 11

A keyboard for an electric-input device comprising a set of different keys, each said key including a shank for operating at least one movable electric contact to close a circuit by bearing on a corresponding fixed electric contact, said fixed contact being carried by a fixed flat body, wherein the improvement comprises: a set of insulating plates associated with said keys and each one carrying the corresponding said movable electric contact, a set of springs associated with said plates and each said spring normally holding the associated said plate so that said plate bears against said shank of the associated key in at least two different points, said points being situated on opposite sides of the point of attachment of said spring to said plate, hook means connected to each one of said plates, fixed means engaged by said hook means during the depression stroke of the associated key, said hook means during engagement with said fixed means first causing the associated plate to turn about one of said two points, and then causing the associated plate to disengage said hook means from said fixed means, whereby said spring suddenly moves said plate and said movable contact to touch said fixed contact temporarily through inertia, said spring then returning said plate to contact both said different points, stop means for stopping said shank in such a position as to cause the associated movable contact to separated from the fixed contact when the key is held depressed, as a result of which a single electric signal in the form of a pulse is generated, a guide block for each one of said shanks secured to said flat body, each one of said guide blocks having an internal opening for receiving said shank, and a holed plate parallel to said flat body for engaging said guide blocks with said shank protruding outwardly therethrough.

Claim 12

A keyboard according to claim 9 further comprising: a stop surface comprised in said stop means for defining the stroke of each one of said keys, a tooth secured to each one of said shanks to cooperate with said stop surface, a stationary cam surface, a flexible extension of each one of said shanks carrying said tooth and cooperating with The associated cam surface to be bent thus removing said tooth upon depressing the associated key for a stroke greater than said defined stroke so as to hold the associated movable contact in contact with the associated fixed contact as long as the associated key is kept depressed for said greater stroke in order to supply a continuous electric signal, and a rigid extension associated with some of said keys to prevent bending of said flexible extension.