Method of making an insulated electromagnetic coil

For insulating a helical electromagnetic coil comprising a plurality of turns, the two turns at opposite ends of the coil having distal sections that are integrally joined, respectively, to a pair of terminal leads extending beyond the boundary of the coil to provide means for connecting the coil in an electrical circuit, an improved method comprising the steps of:

• a. wrapping a fluorinated ethylene propylene resin-coated polyimide tape around the distal section of each end turn of said coil and around each of said terminal leads, thereby covering the bare surfaces of said sections and said leads with first layers of such tape;
• b. covering said first layer on each distal section and each terminal lead with another layer of said tape;
• c. inserting between adjacent turns of said coil thin laminae of fluorinated ethylene propylene resin-impregnated glass cloth which conform to the shape of said turns;
• d. wrapping said tape around a first part of said coil to form an inner layer of such tape on the exposed surfaces of said first part, said first part excluding the distal sections of both of said end turns but including regions of said coil subtending each of said distal sections;
• e. covering a central portion of said inner layer on said first part of said coil with at least one additional layer of said tape;
• f. wrapping said tape around a second part of said coil so as to cover said second part with another inner layer of tape, said second part including a first portion of the distal section of each of said end turns and all exposed surfaces of said coil that were not covered by the first-mentioned inner layer of tape;
• g. covering said last-mentioned inner layer on said second part of said coil with at least one additional layer of said tape which is wrapped so as to overlap any previously uncovered portions of the inner layer of tape on said first part of said coil and the layers of tape covering a second portion of the distal section of each end turn of said coil;
• h. heating said coil to at least the melting point of said resin;
• i. applying pressure to the external surfaces of the various layers of tape on said coil;
• j. cooling said coil to allow said layers of tape and said laminae to bond to the respectively contiguous turns of said coil;
• and
• k. removing said pressure after said resin resolidifies.