Electricity: magnetically operated switches – magnets – and electr – Permanent magnet-actuated switches – Plural magnets
Patent
1994-10-25
1999-01-26
Donovan, Lincoln
Electricity: magnetically operated switches, magnets, and electr
Permanent magnet-actuated switches
Plural magnets
335 78, H01H 900
Patent
active
058642722
DESCRIPTION:
BRIEF SUMMARY
The present invention is concerned with switches having at least two stable positions, especially for motor vehicles, of the kind comprising a support housing carrying a movable operating member, adapted to occupy the stable positions, together with indexing means carried partly by the operating member and partly by the housing so as to define the stable positions of the operating member.
As is known, in each stable position the switch performs a predetermined function, as is described for example in the document FR-A-2 392 479.
In that document, the indexing means make use of notches formed in the housing, together with a movable plunger which is acted on by a return spring carried by the operating member. The opposite is also possible, as is disclosed in the document FR-A-2 495 373.
Such a switch is noisy because the plunger is first caused to retract and then to extend sharply, in order to pass from one stable position to the other.
This is why there is provided, in the document FR-A-2 654 868, an arrangement having a plunger which is provided with a roller in contact with a resiliently deformable leaf which follows the shape of the notches.
Such an arrangement increases the number of components.
Whatever solution is adopted, wear takes place, and problems of reliability arise which are due in particular to fatigue effects and to dangers of breakage of the resilient elements (springs, leaves), of the switch.
In addition, these switches are sensitive to corrosion and pollution, due to the fact that the indexing means include components which are in movable contact with each other, so that particles can become detached and may, for example, make the electrical, hydraulic or other circuits dirty, as also the articulations which are included in such a switch.
This pollution may also arise from the grease which is usually applied for attenuating noise effects.
Finally, problems of control sensation occur because, in these types of switch, frictional effects occur which hinder the movement of the operating member, with a risk of jamming, and one gets a feeling of control by fits and starts. In this connection, when passing from one stable position to another, it is first necessary to compress the return spring of the plunger, which subsequently extends, these techniques arising from the flexibility of an element which has to be deformed elastically with a force that increases and then decreases in order to move from one stable position to another.
An object of the present invention is to overcome these drawbacks in a simple and inexpensive manner, and accordingly to provide novel indexing means which are less noisy and less subject to corrosion and pollution, while giving the user a more gentle sensation when actuating the operating member.
In accordance with the invention, a switch of the type described above is characterised in that the indexing means comprise a magnetic circuit having at least one permanent magnet associated with at least one counter-target and a target for closing the magnetic field and disposed in facing relationship to the counter-target at each stable position, one of the elements comprising the target and the counter-target with its permanent magnet being carried by the operating member while the other one of the said elements is carried by the housing, so as to define at least two stable positions, at least two targets and one counter-target, or the reverse, being provided for this purpose.
Thus, thanks to the invention the indexing means consists of components which do not make contact with each other, so that the noises generated by, for example, the extension of a plunger or vibrations of flexible leaves are avoided.
Wear effects are also diminished, to the benefit of the working life of the switch. This is especially so since the magnet and the target are fixed with respect to the component that carries them.
Friction effects are also avoided, as are pollution phenomena, especially due to the fact that there is no need to grease the magnetic indexing means.
Manufacture of the swi
REFERENCES:
patent: 4199741 (1980-04-01), Paulet
patent: 4317969 (1982-03-01), Riegler et al.
patent: 4481389 (1984-11-01), Johnson
Donovan Lincoln
Valeo Electronique
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