Electricity: circuit makers and breakers – Multiple circuit control – Multiple switch
Patent
1980-07-22
1983-08-23
Scott, J. R.
Electricity: circuit makers and breakers
Multiple circuit control
Multiple switch
200 67F, 200159B, 335206, H01H 502, H01H 1300
Patent
active
044005946
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a control keyboard of an electric or electronic device, of the type comprising a grid or an apertured plate formed with a multiplicity of holes in which are engaged keys each adapted for controlling one or several electric contacts when they are depressed.
2. Description of the Prior Art
In the present technology, the keys are generally returned to their rest position by springs. The use of springs leads to many disadvantages: loss of rigidity of the spring, fatigue phenomenon, resonance frequency, bad behaviour to vibrations and accelerations, sensitivity to corrosion, rebound phenomenon when establishing the electric contacts, etc.
It has already been proposed to remove most of said disadvantages by replacing the return springs with magnetic return means which are in part carried by the keys themselves, and in part carried or formed by the aforementioned grid or apertured plate.
This new technique, while presenting many advantages relative to the traditional art, has nevertheless a disadvantage in that the contacts, which are adapted to be acted upon by the keys when the latter are depressed, are carried by an independent plate, generally a printed circuit plate, which is placed under the grid or apertured plate. Thus, a keyboard is composed of three kinds of elements: the keys, the grid or apertured plate, and the printed circuit plate carrying the contact or switching elements associated with the keys. The mounting of such a keyboard has to be relatively accurate since the printed circuit plate carrying the contact elements has to be disposed under the grid at a predetermined distance from the latter.
A further disadvantage of the known prior art techniques is that the duration of the electrical signal corresponding to the closing of a contact obtained by depressing a key is very short relative to the total operation time of the key. However, for some technical reasons, and notably the electronic processing of said signals, it is often required that the duration of the signal thus established be at least equal to 60% of the operation time of the key.
SUMMARY OF THE INVENTION
The object of the present invention is precisely to solve all said problems, by simultaneously avoiding the disadvantages of the known prior art techniques.
Notably, the object of the invention is a monolithic-type keyboard in which the grid carrying the keys and the plate carrying the contact elements are united in one single assembly.
Another object of the invention is an improved keyboard of the aforementioned type, in which the duration of a signal obtained by depressing a key is widely superior to 60% of the total operation time of the key, and is some cases equal to this total operation time.
Therefore, the invention proposes a control keyboard for electric or electronic devices, comprising a grid or a composite plate formed with holes through which extend the stems of keys. Each key is adapted to control one or several electric contacts which are closed when the corresponding key is in one of its working and rest positions and which are open when the key is its other position, said plate or grid comprises means for returning the keys by magnetic attraction by cooperating with elements such as soft iron plates or washers rigidly connected to the lower ends of the key stems. The elements are disposed under said plate and are normally maintained in contact with the latter by magnetic attraction, thereby determining the rest positions of the keys, wherein the contacts which are controlled by the keys are at least partly carried by one of the faces of the composite plate and cooperate with closing or opening operating means associated with the keys.
According to this characteristic of the invention, a monolithic keyboard is obtained in which the grid supporting the keys and the plate supporting the contact elements are united in one single element.
According to a further characteristic of the invention, the contacts are normally closed w
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patent: 3693123 (1972-09-01), Pedersen
patent: 3736397 (1973-05-01), Pedersen
patent: 3761016 (1973-09-01), Pedersen
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patent: 3916360 (1975-10-01), Pedersen et al.
patent: 3978297 (1976-08-01), Lynn et al.
patent: 4124787 (1978-11-01), Aamoth et al.
patent: 4203013 (1980-05-01), Serras-Paulet
patent: 4211991 (1980-07-01), Lombard et al.
patent: 4354081 (1982-10-01), Serras-Paulet
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