Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Patent
1994-11-30
1996-03-05
Picard, Leo P.
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
335229, 335234, H01F 708
Patent
active
054971357
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a bistable electromagnet, particularly an electromagnetic valve which is actuated by an electromagnet having a yoke. A coil is connected to the yoke. The coil has an interior region. An element is located within the interior region of the coil and defines a hollow space therein. An armature is provided that is movable between two operating positions. A spring acts upon the armature. A permanent magnet is arranged in the hollow space of the element and holds the armature against a force of the spring in one of the operating positions. An electromagnet of this type usually has a cylindrical coil and is frequently called a plunger-type magnet. The yoke can contain a hollow cylinder surrounding the coil or consist of a flat material bent in a U-shape.
A known bistable electromagnet is described in European Patent Application 0 219 572. It actuates a vacuum valve and is distinguished by the fact that the entire coil core is constructed as a permanent magnet and is stationarily associated with the armature. The armature plunges into the coil by means of a positive direct-current pulse and is held in this attracted operated position by the permanent magnet in opposition to the spring force. A negative direct-current pulse weakens the holding force of the permanent magnet to such a degree that the spring force predominates and the armature goes into the released operating position.
However, the holding force of the permanent magnet is very sensitive to tolerance in the attracted operating position, that is to say the unavoidable production tolerances of the permanent magnet and the other components make an individual mechanical adjustment or adjustment of the period or amplitude of the control pulse unavoidable in series production. A further disadvantage of the known magnet consists in that the release pulse must be long enough for the armature to be no longer within the range of influence of the permanent magnet. The control power is therefore undesirably high in spite of the basically economic operation.
SUMMARY OF THE INVENTION
The invention is based on the object of developing a bistable electromagnet of the type described in such a manner that it can be produced without tolerance calibration and requires less control power.
According to the invention, this object is achieved by providing a permanent magnet that is freely movable between two end positions in the hollow space within the element. Additionally, the magnet is movable in a direction of movement of the armature. Accordingly, the permanent magnet has two end positions with respect to the stationary magnetic system, namely one which is closer to the armature and one which is more distant from the armature. In the operating position with attracted armature, the permanent magnet assumes the end position close to the armature and holds it against the spring force. During the release pulse, in contrast, it is not only the holding force of the permanent magnet which is weakened but, at the same time, it is moved away from the armature into its other end position. This eliminates its influence on the release process and distinctly reduces the sensitivity of the system to tolerance. The control pulse can end when the permanent magnet has reached its remote end position. This shortening of the time of current application results in a further reduction of the control power consumption.
To create the required hollow space in the coil core, it is preferably constructed as a pot, at the bottom of which the permanent magnet magnetically is held in the remote end position whilst the permanent magnet is held in the other end position by a stop in such a manner that its side facing the armature is approximately flush with the edge of the pot. The stop can be a magnetically non conductive transverse wall in the interior space of the coil, which extends between the permanent magnet and the armature. In a preferred application of the electromagnet as an electromagnetic valve, this transverse wall is the end wall
REFERENCES:
patent: 3755766 (1973-08-01), Read, Jr.
patent: 3775714 (1973-11-01), Heuer
patent: 4306207 (1981-12-01), Tada et al.
patent: 4383234 (1983-05-01), Yatsushiro et al.
patent: 4422060 (1983-12-01), Matsumoto et al.
patent: 4628289 (1986-12-01), Huber
patent: 4829947 (1989-05-01), Lequesne
patent: 5170144 (1992-12-01), Nielsen
Patent Abstracts of Japan, vol. 4, No. 75 (E-13) (557), May 31, 1980 & JP-A-55-43867, Mar. 27, 1980.
Geser Bernd
Wisskirchen Michael
Barrera Raymond M.
Picard Leo P.
Schrott Harald
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