Methods of producing slotless and toothless wound stator

Abstract

Slotless and toothless wound stators are produced for electrical machines, in particular brushless DC motors, by providing temporary teeth at opposite ends of an iron cylinder with smooth inner wall end-to-end, placing an electrical winding without supporting form against the inner wall and between and around the teeth, pressing the winding against the smooth inner wall by an expandable retaining cylinder, and removing the temporary teeth. A temporary fixture can provide the temporary teeth by radially inwardly extendable and radially outwardly retractable fingers, the fingers being removed by outward retraction through cam means. Alternately, plastic end members with teeth may be glued to opposite ends of the smooth-walled iron cylinder to provide temporary teeth, the teeth being machined off after positioning the winding. One or more longitudinally cut plastic cylinders may be overlapped at the cut edges, inserted inside of the positioned winding, and expanded and glued at the cut edges to reform an uninterrupted cylindrical retainer. The winding may be positioned on the temporary teeth by hand, conventional winding machines or conventional winding and insertion machines. The completed stators lack teeth and slots from end to end of the iron cylinder, have the winding placed against the smooth inner wall of the iron cylinder, and have the reformed plastic cylinder pressing and retaining the winding against the smooth inner wall.