Electricity: circuit makers and breakers – Special application – Liquid or moisture responsive
Patent
1984-02-13
1985-12-17
Marcus, Stephen
Electricity: circuit makers and breakers
Special application
Liquid or moisture responsive
200 67E, 200244, H01H 2144
Patent
active
045594228
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to electrical switches, and more particularly, it concerns microswitches.
The invention may be useful as a limit switch in automated control and protection signalling systems in electric drives of machines and mechanisms.
2. Description of the Prior Art
The precision of operation of automatic lines and also control systems for technological processes is much dependent upon the sensitivity of the microswitches employed, which must provide for the precision of transmitted information. It is very difficult in practice to correct the errors made by microswitches.
To actuate movable contacts in microswitches metal plates are preferably used which respond to temperature or pressure and which are subject only to insignificant bending under tension or compression. Therefore, one of the main characteristics of microswitches is sensitivity which is defined by the distance of travel of an actuating member, i.e. by its differential stroke (the shorter the path required for shifting a movable contact in a microswitch the higher its sensitivity).
Known in the art is a microswitch (see, for example, U.S. Pat. No. 2,729,714, Int. Cl.sup.2 HOIH 13/28) comprising an insulating base 1' (see FIGS. 1,2) fixed contacts 2', 3' secured on this base 1', a movable contact 4' adapted to selectively contact the fixed contacts 2' and 3', and means for shifting the movable contact 4' by the use of an actuating member. The means for shifting the movable contact includes an actuating lever 5' and an intermediate lever 6' connected with one another, a flat spring, and a contact lever 8'. The actuating and the contact lever 5' and 8' are connected by their ends in a single point on the insulating base 1'. The movable contact 4' is mounted on the opposite free end of the contact lever 8' whose middle portion is connected with an end of the flat spring 7'. The other end of the flat spring 7' is connected with an end of the intermediate lever 6' and when in its extreme positions it bears up against a limit stop 9' formed on the insulating base 1'. The other end of the intermediate lever 6' is connected with the end of the actuating lever 5' which is opposite to the end connected to the insulating base 1'.
In the initial position of the microswitch, the preliminarily compressed spring 7' exerts a force P upon the contact lever 8', which is connected with it (see FIG. 1).
The contact pressure is equal to: and the spring 7'.
The actuating lever 5' moves under the action of an external force F, and the intermediate lever 6' changes its position with respect to the spring 7'.
As the actuating lever 5' moves to the position of operation (when point A takes position A.sub.1), the spring 7' compresses, the force P increase till the value P.sub.1, and the contact pressure P.sub.k somewhat increases to P.sub.k1 =P.sub.1 Sin .beta. (FIG. 2).
As the point A crosses the line of the unstable position of the spring 7', line I--I, shifting the contacts 4' takes place at the inherent speed of motion.
With further motion of the actuating lever 5', point A reaches the final position A.sub.2 (FIG. 1).
When the external force F is removed from the actuating lever 5', all the levers of the means for shifting the movable contacts 4' tend to return to their initial position.
When the point A of the actuating lever 5' crosses the line II--II, the line of the unstable switched position of the spring 7', i.e. when the point A reaches the position of A.sub.3, the reversal shift of the movable contacts 4' takes place.
As can be seen from the description, the contact pressure in the microswitch does not decrease below the nominal value and even slightly increases with the motion of the actuating lever 5' to the position of actuation.
To provide for shifting the contacts 4' in such microswitch, the surfaces defining the motion of the intermediate lever in the limit stop 9' must be located beyond the area defined by the lines of the position of the contact lever 8' in the initial and in the shifte
REFERENCES:
patent: 2601152 (1952-06-01), Kmieck
patent: 2821588 (1958-01-01), Fisher
patent: 2929891 (1960-03-01), Tyler
patent: 2975249 (1961-03-01), Friend
Chaly Fedor P.
Emelyanenko Vadim V.
Filatov Nikolai I.
Kosovtsev Vladimir A.
Litvinov Vladimir I.
Kidorf Renee S.
Marcus Stephen
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