| 摘要 |
An electromagnetic device comprises a pair of a plurality of pairs of helical coils the turns of the coils being alternatively arranged. Each of the coils is formed from a length of tubular magnetizable material and within each coil is an electrical conductor. The conductors in the turns of adjacent coils carry electrical current in opposite directions and the walls of the coils which are adjacent each other are of reduced section so that when the conductors carry electrical current, magnetic flux leakage occurs and the turns of the coils separate thereby producing an extension of the coils which is transmitted to a pair of members.
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