Permanent magnet linear door motor

A permanent magnet linear drive motor comprising:

• a rectilinear first module formed of several aligned permanent magnets separated by gaps of fixed length and disposed so that third North and South poles alternate;
• a second module formed of at least one pair of U-shaped electromagnets whose parallel legs have a width equal to that of the gaps between the permanent magnets and are disposed on opposite sides of the first module, each pair of electromagnets being rigidly connected by a connection of a length such that when one of the electromagnets is in register with said gap between two permanent magnets, the other is opposite a third permanent magnet;
• a means (34) for sending a signal indicating a position of an electromagnet relative to a magnet;
• and,
• a control means (21) for receiving said signal and for controlling a supply of power to said electromagnets (20,22) as a function of said signal, such that said each electromagnet has:
• a first polarity between a first point when, the electromagnet has gone beyond register with a permanent magnet by a certain distance (d) and a second point when the electromagnet arrives at the same distance (d) before register with the next permanent magnet;
• no power between said second point and a third point when the electromagnet passes beyond said next permanent magnet:
• and,
• a reverse polarity at said third point.