GB771825A - Improvements in or relating to electric coils - Google Patents

Abstract

771,825. Electric coils. PHILIPS ELECTRICAL INDUSTRIES, Ltd. Dec. 21, 1955 [Dec. 24, 1954], No. 36654/55. Class 35. In a rectangular electric coil wound with its turns in planes at right-angles to the axis, each coil having a cranked portion passing from one plane to the next, this cranked portion is prevented from progressing from a flat part of the coil to a corner by causing it to reverse its progression after a certain number of turns. As shown in Fig. 1, the winding is commenced with turns 1, 2, 3, &c. having cranked portions 11, 21, &c. At the end of the layer, turn 6 rises up into the next layer so that subsequent turns, e.g. 7, lie between turns of the first layer, except for the cranked parts which naturally ride over the thickness of the wire producing a hump in the coil. As shown, the cranked part tends to be progressively displaced along a line A<SP>1</SP>, B<SP>1</SP> and then B<SP>1</SP>, C<SP>1</SP> and would eventually reach the corner of the coil and upset the winding. To avoid this the progression is reversed after a few layers have been wound, by spacing the turns as shown in Fig. 6. This may be achieved by reducing the wire diameter, e.g. by increasing the tension or by compression between rollers to flatten the wire slightly. Alternatively the winding mandrel may be stepped so that at a certain diameter the winding length is increased by about 10 per cent of the wire diameter. Alternatively a sector of the winding space may be enlarged, so that as the cranked part progresses into this sector its direction is reversed. A further alternative is to suddenly increase the pressure of a leather pad bearing on the coil as it is being wound. If desired, the progression may be reversed several times.