| 摘要 |
<p>An electromagnetic device comprises an outer annular member and an inner member, the two members each having a helical rib on their presented surfaces. Two presented side faces of the ribs define working surfaces and on one of the working surfaces is defined a groove which extends the length of the rib and the groove accommodates an electrical winding which when energized creates a pair of magnetic poles on the one working surface. The magnetic circuit of the poles includes the other working surface and the two surfaces move towards each other to reduce the magnetic reluctance thereby causing relative movement of the members.</p> |
