Patent ID: 6880868

Claim:
An electromagnetic lock comprising: an electromagnet; a mobile armature; at least one return mechanism adapted to move said mobile armature towards a retracted position; said at least one return mechanism and said mobile armature being positioned to permit displacement of said mobile armature in a direction counter to a direction of force of the at least one return mechanism wherein the retracted position of said mobile armature permits opening of the lock when said electromagnet is not energized; each of said electromagnet and said mobile armature having at least one surface which, when said electromagnet is energized, forms first and second opposing surfaces; said at least one return mechanism being arranged between said mobile armature and a surface supporting said mobile armature and ensuring that said first and second opposing surfaces are spaced apart from one another when said electromagnet is not energized, whereby said mobile armature is arranged between said at least one return mechanism and said electromagnet; said first opposing surface comprising a protuberance which extends away from the first opposing surface; said second opposing surface comprising an open chamber for closely receiving said protuberance, wherein the open chamber extends into the second opposing surface; and said first and second opposing surfaces being capable of being brought into contiguous proximity with each other when said protuberance is received in said open chamber, wherein said protuberance extends from an edge of the first opposing surface and has a height less than a distance normally separating said first and second opposing surfaces when said electromagnet is not energized.