Patent GB-1248881-A (GB)
Title: Method and apparatus for maintaining a laminated article under compression
Inventor: SIMS MARION WILSON
IPC: H02K15/02
Filed: 1970-02-03
Abstract: 1,248,881. Making stators. GENERAL ELECTRIC CO. 3 Feb., 1970 [27 Feb., 1969], No. 5185/70. Heading B3A. A method of maintaining an article having magnetic elements under compression during a part of manufacture thereof comprises: positioning a first electromagnetic device 44 and the article, e.g. a stator core 10, adjacent to one another, and magnetically compressing preselected regions of the magnetic elements together by energizing the first device 44. The stator core is loaded into the device 44, when opened, by aligning core slots 40 with lugs 60, 62, and when the core is inserted, it is rotated so that the slots and lugs are out of alignment. The device is closed by energizing a coil 58, to make the lugs apply clamping pressure to the core laminations. A powder deflector 64 is then affixed to either side of the device 44, by aligning pins 66 with apertures 68 in the deflectors, and it is moved on a dolly 92 from Station A to Station B between slewing rings 74, 76. Fusible insulating powder is sprayed through nozzles 78-84 on the faces of the outer laminations. During each work cycle, the nozzles are rotated approximately 195 degrees to ensure even deposition of the powder. The powder may also contain magnetic particles, which are drawn together with the melted resin to the edges of the stator teeth, to form a layer of increased thickness thereat. The magnetic lines of force of the polepieces 48, 50 tend to compress the laminations thereby eliminating flaring of the tooth tips, Fig. 3 (not shown). A mask assembly 38 may be positioned in the stator bore 22 while at the station A. The mask engages the inside of the bore 22 to prevent coating material building up at the entrances to the stator slots and in the bore. In an alternative embodiment an electromagnetic device (115) is used to clamp the core laminations and inductively heat the core 10 prior to spraying powder thereon, Fig. 5 (not shown). The core is heated by an A.C. power source to the melting temperature of the powder, which is then applied and when it has melted, a D.C. power source is used to apply a unidirectional magnetic field. After the coating has built up to the required thickness along the slot edges, A.C. power is again applied and maintained until the resin is cured. In a further embodiment, a coil (138) is wound around a leg (135), which abuts another leg (120) around which is wound a coil (134), (136). The coil portion (136) lies within the stator bore and the portion (134) and coil (138) abut the stator end faces. The coil (58) is not used in the inductive heating step in this embodiment, Fig. 6 (not shown). A switch (142) is provided, which connects the coils (138), (134) and (136) in series across an A.C. source or alternatively similarly connects the coils (138), (134), (58) across a D.C. source, Fig. 7 (not shown). A modification to the first embodiment comprises inserting an electromagnetic device (144) in the bore 22 the device consisting of a coil (146) on a core (148), Fig. 9 (not shown). The coil (146) is connected to the same D.C. source as the coil 58 and its effect is to move the centre of the magnetic force to the centre of the laminations, thereby more uniformly distributing the resultant clamping force, Fig. 10 (not shown).