Method for producing a coil

A method of producing a coil of strand-like material wound in layers on a conical surface of a substantially cone-shaped winding spool having a cone-aperture angle, with the layers being inclined with respect to the conical surface, and in which a take-up apparatus is employed that moves approximately parallel to the longitudinal axis, comprising the steps of:

• (a) beginning the winding process at a starting diameter on the portion of the winding spool having the smallest diameter;
• (b) initially winding a first layer L.sub.1a having a predetermined number of windings N.sub.1 onto the conical winding spool at an acute angle relative to the conical surface, which is greater than one-half of the cone-aperture angle, by moving the take-up apparatus in a first direction, where the number N.sub.1 is smaller than the maximum number N.sub.max of windings that can be applied to the spool at a predetermined winding pitch;
• (c) winding a second layer L.sub.1b onto the first layer L.sub.1a by reversing the movement of the take-up apparatus in a second direction opposite the first direction, with the second layer L.sub.1b having substantially the same number of windings N.sub.1 as the first layer L.sub.1a ;
• (d) winding additional pairs of layers L.sub.2a, L.sub.2b, L.sub.3a, L.sub.3b, . . . L.sub.xa, L.sub.xb, and so forth onto winding layers L.sub.1a and L.sub.1b such that the additional layers have a number of windings N.sub.2, N.sub.3 . . . N.sub.x, respectively, that increases for each pair of additional layers by a substantially constant winding factor .DELTA.N until the maximum number N.sub.max of windings are wound on the winding spool to form a double-cone shaped winding portion having an inner surface disposed parallel to the conical surface and an outer surface tapering toward the inner surface at an angle equal to the acute angle;
• and
• (e) removing the winding spool from the coil.