Electricity: circuit makers and breakers – Electric switch details – Actuators
Patent
1980-07-22
1982-10-12
Little, Willis
Electricity: circuit makers and breakers
Electric switch details
Actuators
200 67F, 200159B, H01H 1300
Patent
active
043540813
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates in general to electric or electronic switching devices, forming a push-button or a keyboard with depressable keys, with magnetic means for returning the push-button or the keys to their rest position.
BACKGROUND OF THE INVENTION
One knows already such push-buttons and such keyboards with depressable keys and magnetic return means, which have the advantage, relative to the known prior devices, of not using a return spring, and therefore of not presenting the disadvantages associated therewith (loss of rigidity, fatigue phenomenon, resonance phenomenon, sensitivity to corrosion, return force increasing in proportion to the path covered by the key or push-button when being depressed, sensitivity to vibrations and accelerations, etc.).
Said push-buttons and keyboards with keys and magnetic return means have nevertheless the disadvantage that the duration of the signal produced by depressing the push-button or key is far shorter than the total operation time of the push-button or key. In some applications, it is necessary that the signal has a duration representing at least 60% of the total operation time of the push-button or key.
SUMMARY OF THE INVENTION
For solving this problem, the invention provides an electric or electronic switching device, forming a push-button or a keyboard with depressable keys, comprising an upper plate formed with a hole through which extends the body of a button or key, a lower plate placed under the upper plate at a predetermined distance therefrom and carrying at least one contact or switching element intended for being brought by the key or button to a state of conduction or non-conduction according to whether the key or button is in a working position or in a rest position, the lower portion of the body of the key comprising means for returning the key or button to its rest position, said means cooperating thereto by magnetic attraction with the aforementioned upper plate, and the stroke of the key or button being such that the magnetic attraction force exerted by said return means on the key or button exceeds always the weight of the key or button, wherein the aforementioned key or button is associated with at least one free piston provided for operating or controlling, when the key or button is displaced from its rest position to its working position, the aforementioned contact or switching element carried in the lower plate in order to have its conduction state changed, said free piston having a stroke far shorter than the stroke of the key or push-button so that the duration of the electric signal resulting from the change of conduction state of the aforementioned element, when the key or button is operated, is superior to a predetermined fraction of the total operation time of the key or button, the free piston being axially movable relative to the key or button and being constantly subjected to a magnetic attraction force exerted by magnetic attraction means which are rigidly attached to the key or button.
Because the free piston has a stroke far shorter than the stroke of the associated key or push-button, it is caused to actuate very quickly the contact or switching element in order to change its conduction state as soon as the key or button leaves its rest position. The action of the free piston on the contact element lasts until the key or button is on the point of resuming its rest position. Thus, the duration of the electric signal produced by the change of conduction state of the contact element actuated by the key or push-button can be very slightly less than the total operation time of the key or button, and in any case always in excess of 60% of the total operation time of the key or button.
According to a further characteristic of the invention, the said magnetic means for returning the key or button to its rest position form also the magnetic attraction means of the free piston.
Said characteristic feature of the invention allows greatly simplifying the construction of a push-button or keyboard according to t
REFERENCES:
patent: 2847528 (1958-08-01), Combs
patent: 3366766 (1968-01-01), Umpleby
patent: 3443043 (1969-05-01), Schmid-Zeller
patent: 3586888 (1971-06-01), Dorfman
patent: 3829632 (1974-08-01), Klehm, Jr.
patent: 3942145 (1976-03-01), Sobczak
patent: 4054944 (1977-10-01), Lau
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