Patent ID: 6935373
Filing Date: 2005-08-30
Classification: F16K,H01F,H01H,Y10T

Abstract:
1. An electromagnetically operable device comprising: (a) a magnetic circuit having permanent N and S poles defining an air gap; (b) an armature assembly which extends into the air gap and at least a portion of which is magnetisable and is movable between two end positions adjacent the two permanent poles through an intermediate position towards which it is resiliently biased; (and) (c) an electromagnet which when energised by an electric current polarises the magnetisable portion of the armature assembly so that the part thereof in the air gap becomes a S or N pole and will thereby be attracted towards, one of the permanent poles, and (d) two springs each of which extends between the armature and one of the two permanent poles, which in the absence of other forces would position the armature in its said intermediate position; wherein the residual permanent flux linking the magnetic part of the armature assembly and the relevant adjacent permanent pole after a current of a given magnitude and direction has flowed in the electromagnet and displaced the armature, is sufficient to generate a force of attraction which is greater than the resilient spring force acting to return the armature to its intermediate position so as to retain the armature in its displaced position, but which is less than the sum of the resilient spring force and the force of attraction created by the magnetic flux linking the magnetic part of the armature assembly and the other permanent pole, when a similar current, but flowing in the opposite direction, flows in the electromagnet, so as to impart a bistable characteristic to the device.