Original Text (This is the original text for your reference.)

1434938 Electromagnetic switches LUCAS ELECTRICAL Ltd 10 July 1973 [26 July 1972] 34869/72 Heading H1N An electromagnetic switch has a plunger armature 6 and a contact biasing spring 8 acting between the armature end 9 and a contact assembly 10, 11, 12 which is urged towards an armature shoulder 17 and the armature 6 is surrounded by a, preferably magnetic, sleeve 5 biased by a spring loaded plunger 14 against the washer 12 of the contact assembly. The plunger is attached to a diaphragm 19 forming a wall of a chamber 18, which may be vented at 14a, to provide time delay of armature and contact movement, or coil energization, until the contact bridge 11 engages fixed contacts 3 when the armature alone continues its movement to stress the spring 7 and finally engage the sleeve end 13. The diaphragm may have a flap valve 21 permitting quick resetting movement and there may be clearance between the armature and sleeve which can have a block of magnetic material at its lower end (Fig. 2, not shown).