Electricity: circuit makers and breakers – Float – Float and pressure
Patent
1982-06-22
1985-02-12
Scott, J. R.
Electricity: circuit makers and breakers
Float
Float and pressure
335207, H01H 3518
Patent
active
044993480
DESCRIPTION:
BRIEF SUMMARY
This invention relates to electrical switch devices and, more particularly, to float-controlled electrical switch devices.
DESCRIPTION OF THE PRIOR ART
A conventional reed magnet switch is shown in U.S. Pat. No. 2,823,328.
The present invention finds particular application in the control of the liquid level in the bottom of a boat, such as a sail boat or motor boat. The switch according to the invention shall in the case of application control the engagement and disengagement of a bilge pump for removing liquid which has collected in the bottom of the boat, gradually as there is a need for it, that is to say in an automatically controlled manner determined by a fixed upper and lower level of liquid in the bottom of the boat. Stated in another way the switch provides for the bilge pump to be engaged when the liquid level has risen sufficiently high in the boat and for the bilge pump to remain engaged until the liquid level in the boat has sunk again to the determined lower level in the boat. It is the permanent magnet which engages and disengages the switch, the permanent magnet being controlled towards and away from the reed contact of the switch by means of a buoyancy force in a float which follows the movements of the liquid between upper and lower liquid levels.
The invention is, however, not limited to application for bilge pumps, but can also be used for various other types of electrically driven power means which will function in connection with a controlled liquid level, for example the liquid level in a tank, in a flow passage or for similar purposes. In the following description the invention will be described having regard to its application in connection with a bilge pump in a boat.
In U.S. Pat. No. 4,165,935 there is disclosed a level switch which operates according to the reed principle but where two magnets are employed, the one for opening the reed contact and the other for closing the reed contact. In this case there is a level switch where the regulating distance is limited by the length of the reed contact. Furthermore, the level switch is particularly critical as regards the level for engagement and the level for disengagement, since the two magnets must be adapted to each other, and this adaptation must be adjusted in every single case. In addition, there is the possibility for different age weakening of the two magnets, something which in turn will be able to disturb the desired effect.
In the use of a reed contact and an associated moveable permanent magnet there can be obtained under normal working conditions a particular level for engaging the bilge pump and a corresponding particular level for disengaging the bilge pump, fixed by an upper and a lower liquid level with a distance of, for example, 5 mm between the liquid levels. By increasing or reducing the strength of the permanent magnet the distance between the liquid levels can be increased or diminished to a certain degree, but at the same time the distance between the reed contact and permanent magnet will also be increased or reduced in the engagement position (upper liquid level). This can be compensated for to a certain degree by increasing or reducing the A/turn number for the reed contact. In all cases, however, it is difficult to attain a desired significant distance between the upper and lower liquid level, that is to say the engagement and disengagement positions of the permanent magnetic field of force of the float.
FIELD OF THE INVENTION
In certain instances, for example as a consequence of the movements of the boat during heavy seas and from this ensuing rolling or pitching movements of the boat and corresponding splashing movements of the collection of liquid in the bottom of the boat, the above-mentioned distance between upper and lower liquid levels is too small so that in practice a pulsating engagement and disengagement of the bilge pump can result produced by the movements of the boat.
As a result of the relatively moderate distance between the upper and lower liquid levels in the bottom of the boat the
REFERENCES:
patent: 3149753 (1964-09-01), Forsyth
patent: 3823328 (1974-07-01), Barton et al.
patent: 4165935 (1979-08-01), Bongort et al.
patent: 4258238 (1981-03-01), Dombrowski et al.
Gismervik Jan E.
Sveinsbo Gunnar
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