WO2002045239A2

WO2002045239A2 - Slotless stator manufacturing apparatus and method

Info

Publication number: WO2002045239A2
Application number: PCT/US2001/044512
Authority: WO
Inventors: Daniel J. Shramo; Steven R. Prina
Original assignee: Centaur Motor Systems, Llc
Priority date: 2000-11-28
Filing date: 2001-11-28
Publication date: 2002-06-06
Also published as: WO2002045239A3; AU2002230503A1

Abstract

A mandrel (20) for forming field windings for a slotless stator includes a spindle (22) and a winding guide (24) substantially enclosing the spindle (22) circumferentially. The spindle (22) is rotatable relative to the winding guide (24) about a longitudinal axis (28), and the spindle has a plurality of outwardly extending guide pins (30) circumferentially arrayed in longitudinally spaced rings. The mandrel (20) also includes a winding guide (24) which surrounds the spindle (22) and guides the winding onto the pins (30) and maintains the windings on the pins until the windings can be fixed in place. The pins (30) are retractable for removing the windings from the mandrel (20) completely formed and ready to be placed in a motor.

Description

SLOTLESS STATOR MANUFACTURING APPARATUS AND METHOD

Field of the Invention

The invention described herein relates generally to electro-mechanical devices such as electrical motors, generators, and the like and, more particularly, to a method and apparatus for making a stator for a slotless, brushless electric motor.

Background of the Invention Conventional brushless motors have an outer generally cylindrical stator surrounding an inner rotor, the rotor being mounted to rotate within the stator. In most motors, the stator includes a number of spaced teeth extending radially inwardly from an inner periphery. The teeth define a corresponding number of slots. The teeth and slots extend along the entire axial length of the stator. Through various well known techniques, wires are threaded through the slots between the teeth from one end of the stator to the other, and around the teeth at the opposite ends of the stator to form the field windings. Electrical insulating material is placed in the slots to electrically isolate the windings from other parts of the stator. In this manner, the teeth precisely orient windings so that voltage applied to the windings will induce a magnetic field which has a known, predetermined orientation. The electromagnetic field is designed to react with permanent magnets or inductive windings on the rotor to turn the rotor in a desired direction.

Threading the windings through the slots can be a difficult and time consuming process, and over the years complicated machinery has been developed to accomplish this task. In addition to the manufacturing difficulties presented by the slotted stator configuration, the teeth create magnetic discontinuities and limit the number of windings which can be positioned in the critical area of the stator adjacent to the rotor, thereby adversely affecting the efficiency of the motor. In addition, the formation of the teeth and slots and the addition of insulation increases the complexity, the number of parts, and the manufacturing time and ultimately the cost of the motor. Accordingly, methods of making a slotless stator have been developed. For example, U.S. Patent No. 5,200,661 discloses a method of forming the windings by wrapping the wire around a rectangular bar. The bar is removed and the windings are collapsed under lateral shear force to form a relatively flat sheet which is rolled to form the windings into a cylindrical shape. See also U.S. Patent No. 5,294,855. This method works well, but the resulting windings are not as accurately positioned as in a slotted stator.

Other methods use a cylindrical form on which to form the windings. For example, U.S. Patent No. 5,525,850 provides a cylindrical sleeve with coil- locating tabs and axially extending pins around which the wire is wound. See also U.S. Patent No. 5,394,046. However, in this method the sleeve becomes part of the completed stator and cannot be reused, thereby increasing the cost of materials and the number of parts in the motor.

Summary of the Invention The present invention provides an improved method and apparatus for forming field windings for the stator of a brushless electric motor or other electro-mechanical device with a slotless stator. The present invention provides a stator with far fewer parts than a slotted stator, a method of forming the windings using fewer process steps than prior methods, and an apparatus for forming the field windings that does not become part of the stator and thus is reusable. More specifically, the present invention provides a mandrel or fixture including a spindle having a number of guide pins extending radially therefrom around which the windings are formed, and a winding guide which substantially surrounds the spindle and guides the winding wire onto the pins and then maintains the windings on the pins until the windings can be fixed in place. The pins are retractable so that a cylindrical set of windings can be removed from the mandrel completely formed and ready to be placed in a motor. The mandrel effectively emulates a phantom slotted rotor, forming a virtual circumferential arc slot between the pins, the body of the spindle and the winding guide, which facilitates formation of the windings but which lacks the inherent disadvantages of a toothed stator. As a result, the windings can be formed accurately and with fewer process steps on a reusable mandrel. According to one aspect of the invention, a mandrel for forming field windings for a slotless stator includes a spindle and a winding guide substantially enclosing the spindle circumferentially. The spindle is rotatable relative to the winding guide about a longitudinal axis, and the spindle has a plurality of outwardly extending guide pins circumferentially arrayed in longitudinally spaced rings.

In accordance with one or more embodiments of the invention, the guide pins are retractable into the spindle, the guide pins extend radially from the spindle, the plurality of guide pins includes twelve guide pins, the plurality of guide pins are equally circumferentially spaced, and/or the guide pins in each ring are longitudinally aligned.

In accordance with one or more further embodiments of the invention, the spindle is generally cylindrical, the spindle includes an insertion end having a relatively relieved area where the spindle has a reduced diameter longitudinally adjacent the rings of guide pins at the insertion end, the spindle includes a stop end opposite the insertion end, and a portion of the winding guide includes a relatively relieved area where the winding guide has an increased inner diameter longitudinally adjacent the rings of the guide pins at the stop end, and/or the insertion section of the winding guide and the stop section of the winding guide are separately removable from around the spindle.

In accordance with yet another embodiment or embodiments, the winding guide has a portion positioned at least adjacent each of the rings of guide pins and a portion positioned over the relieved area of the spindle, the winding guide has a base and a cap separated from the base by a plane which is parallel to the longitudinal axis of the spindle, the winding guide has an insertion section and a stop section longitudinally separate from the insertion section, the spindle and the winding guide form a substantially cylindrical gap therebetween, and/or the spindle includes an insertion end and a stop end, and the gap has a decreased inner diameter adjacent the insertion end of the spindle and the gap has an increased outer diameter adjacent the stop end of the spindle.

In accordance with another aspect of the invention, a method of making field windings for a slotless stator includes winding a wire on a mandrel having a plurality of guide pins extending outwardly from a side of a spindle such that the wire wraps around at least four of the guide pins, indexing the spindle, repeatedly winding and indexing, and removing the windings from the spindle.

According to one or more embodiments of the invention, the method also includes applying a cover over the windings, and removing the cover and the windings from the spindle as a unit.

According to another embodiment or embodiments of the invention, winding the wire includes winding the wire on a mandrel including the spindle and a winding guide substantially enclosing the spindle circumferentially, the spindle being rotatable relative to the winding guide about a longitudinal axis, and the spindle having a plurality of outwardly extending guide pins circumferentially arrayed in longitudinally spaced rings. Furthermore, indexing the spindle includes selectively indexing the spindle by rotating the spindle one hundred and eighty degrees to form another winding in the same phase and indexing the spindle by rotating the spindle through an angle formed by radii extending toward adjacent pins. Additionally or alternatively, winding, indexing and repeatedly winding and indexing includes winding and alternately indexing the spindle by rotating the spindle one hundred and eighty degrees and by rotating the spindle through an angle formed by radii extending toward adjacent pins, thereby forming at least three sets of windings.

In accordance with one or more further embodiments of the invention, applying a cover over the windings includes selectively retracting the pins into the spindle and sliding a cylindrical cover over the spindle and the windings, applying a cover over the windings includes selectively removing at least one portion of a winding guide from around the spindle before sliding the cover over the spindle, and/or further includes extending the pins and forming another set of windings.

The foregoing and other features of the invention are hereinafter fully described and particularly pointed out in the claims, the following description and annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this embodiment being indicative, however, of but one of the various ways in which the principles of the invention may be employed. Brief Description of the Drawings

Fig. 1 is an exploded assembly view of the mandrel according to the present invention.

Fig. 2 is an end view of the assembled mandrel of Fig. 1. Fig. 3 is a side view of the mandrel shown in Fig. 2, as seen along lines 3-

3.

Fig. 4 is a cross-sectional top view of the mandrel shown in Fig. 3, as seen along lines 4-4.

Fig. 5 is a plan view of the windings as they would be formed on the mandrel.

Fig. 6 is a top view of the windings shown in Fig. 10. Fig. 7 is a schematic end view of the mandrel with the windings formed thereon.

Fig. 8 is a sectional cross-sectional side view of the mandrel shown in Fig. 7, as seen along lines 8-8.

Fig. 9 is a cross-sectional side view of the mandrel shown in Fig. 4, as seen along lines 9-9.

Fig. 10 is a cross-sectional end view of the mandrel shown in Fig. 9, as seen along lines 10-10. Figs. 11 through 13 are side views of the mandrel showing the process of inserting a housing over the completed windings.

Detailed Description An exemplary embodiment of the mandrel and method according to the invention will be described with reference to the drawings, and initially to Figs. 1 through 4. A fixture or mandrel 20 for forming windings for a slotless stator of a bipolar brushless, slotless motor according to the invention includes a spindle 22 and a shield or winding guide 24 which substantially encloses the spindle circumferentially.

The spindle 22 is rotatable relative to the winding guide 24 and has an axle 26 for rotation about a longitudinal axis 28, the longitudinal dimension being parallel to the axis of rotation for purposes of this description. The spindle has a generally cylindrical shape, although another shape could be used. The spindle also has a plurality of outwardly extending, generally radially extending, guide pins 30 although other structures may be used to create the virtual winding slot discussed below. The guide pins are circumferentially arrayed in rings which are axially spaced apart a distance equal to the length of the active stator field. Corresponding pins in each of the circumferential rings are longitudinally aligned with one another. The guide pins generally are equally spaced circumferentially, and are retractable into the spindle for removal of the completed windings. The pins can be retracted with hydraulics or mechanical linkages, for example, and may include a cam action inside the spindle, similar to the retractable ejector pins used in the ejection molding industry.

The number of pins 30 is determined by the stator field design. For example, for a four pole (two polar pair) three phase DC motor, two sets of twelve pins are used, separated longitudinally by the field length, and evenly spaced one-third of an arc length of the corresponding magnetic pole piece around the circumference of the spindle. The diameter of the spindle 22 also is determined by the motor design, and generally approximates the inside diameter of the stator.

The spindle 22 has an insertion end 32 and a stop end 34 opposite the insertion end. The spindle generally has a substantially constant width or diameter in a region extending at least between the rings of pins. However, the insertion end of the spindle has a relatively relieved area 36 where the spindle has a reduced width longitudinally adjacent the ring of guide pins 30 at the insertion end. In the illustrated embodiment, the relieved area has a smaller diameter than the body of the spindle and lies at the lower end of the illustrated spindle, below the lower ring of guide pins. As is explained further in the following paragraphs, the relieved area of the spindle cooperates with the winding guide 24 to restrict the windings at the insertion end of the spindle to a maximum outside diameter.

The winding guide 24 substantially surrounds the spindle 22 circumferentially and forms a generally cylindrical cavity within which the spindle is rotatable relative to the winding guide. The winding guide should have a portion positioned at least adjacent each of the rings of guide pins 30 and a portion positioned over the relieved area 36 of the spindle to guide the insulated conductor used to form the windings and to maintain the windings in position during the winding process. The illustrated winding guide includes a an insertion section 42 which is placed adjacent the insertion end 32 of the spindle and a stop section 44 which is placed adjacent the stop end 34 of the spindle that is longitudinally separate from the insertion section.

Each section 42,44 is formed of a base 46,48 and a cap 50,52 separated from the base by a planar opening 54 which is offset from and parallel to the longitudinal axis 28 of the spindle 22. The opening is positioned such that a wire passing therethrough is restricted to a space formed by the surface of the spindle 22, circumferentially adjacent pins 30 and the inner surface of the winding guide 24, which form a virtual circumferential arc slot. In particular, as the wire is pulled around a set of four pins, the wire should be pulled up against the pins with the opening spaced to fill the gap between adjacent pins as completely as possible. Instead of the illustrated cap 50,52 and base 46,48 in each section 42,44, the sections may be combined to form a single cap and a single base, or further divided such that the base and/or the cap are formed of multiple parts. In addition, the winding guide 24 is removable from around the spindle 22, and the insertion section 42 and the stop section 44 may be selectively removed separately. Furthermore, although the winding guide has a substantially constant inner diameter, the inner diameter of the winding guide increases in an area opposite the stop end 34 of the spindle 22 outside the guide pins 30. In other words, a portion of the winding guide has a relatively relieved area 56 where the winding guide has an increased inner diameter which will be longitudinally adjacent the rings of the guide pins 30 at the stop end 34 of the spindle 22 when the winding guide 24 is placed around the spindle. The purpose of the relatively relieved areas 36, 56 of the spindle and the winding guide, respectively, are explained below in connection with the winding process.

As shown in Figs. 9 and 10, for example, the spindle 22 and the winding guide 24 cooperate to form a substantially cylindrical cavity or gap 60 therebetween. The gap has a thickness which is slightly larger than the radial height of the pins 30 above the surface of the spindle. As a result, when the gap between adjacent pins is filled by the windings, the windings are retained therebetween and cannot pass between the end of a pin and the inner surface of the winding guide. The illustrated embodiment provides sufficient space for two layers of wires in each winding.

In the areas longitudinally outside the pins 30, in the vicinity of the relatively relieved areas 36, 56 in the spindle 22 and the winding guide 24, respectively, the end turns of the windings partially overlap and tend to build up a larger diameter. However, an area 36 at the insertion end 32 of the spindle is relieved to allow the windings to build up without exceeding a maximum diameter established by the inner surface of the winding guide and substantially equal to the inside diameter of a backiron, housing or other cylinder into which the winding will be placed. Similarly, at the stop end 34 of the spindle, the relieved area 56 of the winding guide allows the windings to build up a larger diameter which will act as a stop to prevent the cylinder into which the windings are placed from being pushed past the end windings at the stop end. As a result, a housing, back iron or other cylindrical form can be applied over the completed windings on the mandrel 20 against a positive stop formed by the end turns of the windings at the stop end of the spindle.

The illustrated mandrel described herein is used to form an exemplary winding pattern for a brushless three phase motor having a slotless stator. Three phase motors typically have a stator with three coils. To operate the motor, current is passed through one or more of the coils, and switched (referred to as "commuted" or the act of "commutation") at desired times to effect changing magnetic fields, thereby causing the magnetic rotor to rotate with respect to the stator coils. Different current paths through the coils are created by selectively turning on and off the power to the coils in a sequence. In a bipolar mode, for each path in the sequence, only two of the three coils conduct while the third coil is unenergized. Further, the sequences are defined so that when the unenergized coil is switched into the current path, current flows through the newly added coil in the same direction which it flowed through the coil which is now removed from the path. In this manner, six sequences are defined for each electrical cycle of a three phase motor. The number of coil segments corresponds to the number of pole pairs of the motor. Two coil segments are used to form each phase of the winding in the illustrated embodiment. However, additional segments and/or phases may be used in a known manner. Each segment is electrically connected in series and each phase will be connected to a control circuit in the assembled motor.

However, the windings form a complete cylinder which extends three hundred and sixty degrees (360°) to completely surround the rotor in the assembled motor.

In summary, for a three phase motor, three bipolar windings arranged as a cylinder form a slotless stator which is designed to be parallel to pairs of magnetic poles on a rotor. A minimum of three bipolar windings to two magnetic pole pairs may be used, although any multiple of three-to-two pairs for a three phase motor winding or multiples of three phases, connected for a multi-phase motor system connected in a wye or a delta configuration. Two bipolar windings to two magnetic pole pairs may be used for a two pole system connected to provide a two phase motor or multiples of two phases. This winding scheme offers excellent motor performance and ease of manufacturing.

A typical winding scheme is shown in Figs. 5 and 6 for a three phase, two pole pair stator design. Figs. 5 and 6 illustrate the winding pattern formed on the mandrel, as if the mandrel were longitudinally split and unrolled to lay flat so that the pins extend perpendicular to a substantially planer surface. Two bipolar windings are wound in series with a continuous wire or with multiple continuous wires for bifilar windings or tri-filar windings. The two windings are one magnetic pole arc length apart, and N turns of wire are wound in a flat coil in a single or multiple layers, two layers in the illustrated embodiment. Rather than the flat substantially two dimensional configuration shown in Figs. 5 and 6, by forming the windings on the cylindrical spindle, the end turns of the windings actually follow an arcuate path such that the completed windings together form a cylindrical set of windings which act as a slotless stator. As is clearly evident, the end turns of the windings of different phases overlap one another, thereby necessitating the relieved portion 36 of the spindle 22 at the insertion end 32 (see Fig. 1 ) in order to maintain a maximum diameter of the windings in that region. The windings are formed using the mandrel described above in the following manner. The method of forming the windings will be described with reference to Figs. 9-13. In effect, the mandrel emulates a phantom slotted rotor, forming a virtual circumferential arc slot which facilitates formation of the windings but which lacks the inherent disadvantages of a toothed stator, as will be apparent from the following description. Prior to initiating the first winding, an insulator (not shown) may be applied to the spindle 22, on what will become the inner surface of a , cylinder formed by the windings. The pins 30 shown in Fig. 6 have been individually identified as pins 30a-30l to facilitate the following description. The spindle is rotated to position the opening 54 in the wire winding guide 24 such that a wire winding machine (not shown) will guide the wire into two layers which fill the space between adjacent pins 30I and 30k and adjacent pins 30h and 30i in the rings of pins, with pins 30i and 30k defining the inside of the winding.

The winding machine will wind a number of turns of wire about the pins as required by the design of the stator to form a bi-polar stator winding for one half of the first phase. When the winding is complete, the spindle is indexed or rotated one hundred and eighty degrees (180°), wrapping the wire circumferentially around the spindle, and the winding procedure is repeated for the spaces between pins 30b and 30c and 30e and 30f. As the spindle is indexed the winding guide also functions to retain the wire on the spindle while the other windings are formed.

When the second winding of the first phase is completed, the wire is terminated and may be held in a clip (not shown) mounted to an upper portion of the spindle, for example. The spindle is indexed by one pin to begin winding the next phase. In other words, the spindle is rotated through an angle formed by radii extending toward adjacent pins. The illustrated embodiment has twelve equally spaced pins in each ring, with radii from adjacent pins forming an angle of thirty degrees (30°). Thus the winding forming the first half of the second phase will fill the spaces between pins 30d and 30e and 30a and 30b, for example, if the spindle is rotated clockwise. This procedure of winding and selectively indexing the spindle is repeated until the desired number of windings are formed for the desired number of phases called for in the motor design. The illustrated embodiment includes three phases 70, 71 , 72, with two windings 70a, 70b, 71a, 71b, 72a, 72b, respectively, (the windings are generally identified by reference number 74), forming each phase. Once the windings are completed, the guide pins can be retracted into the spindle and the windings can be removed from the mandrel. As discussed above, the relieved areas 36, 56 of the spindle 22 and the winding guide 24, respectively, are such that the winding end turns will be within the inside diameter of the winding guide at the insertion end 32 of the spindle, and the end turns at the stop end 34 will have an inner diameter approximately equal to the outside diameter of the spindle, but will have a larger outside diameter than the windings 74 between the rings of pins 30 thereby forming a stop.

According to one method of removing the windings 74 from the mandrel 20, the guide pins 30 at the insertion end 32 of the spindle 22 are retracted and the insertion section 42 of the winding guide 24 is removed. At this point, the windings can be secured together in a well known manner by a coating of varnish, by the drying of a previous coating, by the stiffness of the conductor itself, or by some other means. An insulator can be placed over the completed windings, and the flux return path assembly, back iron, or other cylindrical housing 76 is tightly applied over windings 74 at the insertion end of the spindle to hold the windings in place on the spindle. Then the pins 30 at the stop end 34 of the spindle are retracted and the stop section 44 of the winding guide 24 is removed and the cylindrical housing 76 is slid to its final position up against the stop formed by the end windings at the stop end of the spindle. The windings and the cover can then be removed as a unit. Before or after removing the windings, the wires can be terminated into the designated electrical configuration, and/or the end turns at the insertion end of the spindle can be expanded to secure the windings in the cylindrical housing and/or to maintain the shape of the windings. After this assembly is removed from the spindle, it can be further processed as required. In summary, a first set of windings is formed on the spindle, the spindle is indexed one hundred and eighty degrees (180°), and the same wire is used to form the second set of windings for the first phase of windings. The wire is terminated, and the spindle is indexed one pin and the first set of windings for the second phase is formed. Again the spindle is rotated one hundred and eighty degrees (180°) to form the second set of windings for the second phase. This procedure is repeated to form the windings for the third phase. The guide pins are retracted and the sections of the winding guide are sequentially retracted as the housing is forced over the insertion end of the spindle. The end turns at the insertion end of the spindle are deformed radially outwardly to retain the windings in the housing, and the windings and housing are removed from the spindle as a unit. The guide pins can then be extended and the winding guide replaced to form another set of windings. The mandrel may be used with a two-axis wire winding machine with the mandrel being rotated about an axis perpendicular to the axis of the spindle and the wire essentially emanating from a constant point, or the mandrel may be used with a fly winder with the mandrel essentially held stationary and the wire being guided and moved around to pass the wire between the cap and base of the winding guide and around the guide pins to form the windings. As a further alternative, the spindle may be held stationary and the winding guide may be rotated about the spindle, although this configuration may or may not be practical with existing winding machines.

Accordingly, the present invention provides a mandrel which facilitates the more accurate formation of windings for a slotless stator in a brushless motor by forming the windings on a cylindrical spindle. In addition, the mandrel according to the present invention facilitates the assembly of the windings in a stator by forming the windings in such a manner as to have a minimum diameter at one end and a maximum diameter at the other so that the windings may be inserted into a cylindrical body of the stator prior to removal of the windings from the mandrel. As a result the overall manufacturing process for the stator is greatly improved.

Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, equivalent alterations and modifications will occur to others skilled in the art upon reading and understanding this specification and the annexed drawings.

Claims

What is claimed is:

1. A mandrel for forming field windings for a slotless stator, comprising: a spindle and a winding guide enclosing the spindle circumferentially, the spindle being rotatable relative to the winding guide about a longitudinal axis, and the spindle having a plurality of outwardly extending guide pins circumferentially arrayed in longitudinally spaced rings.

2. A mandrel as set forth in claim 1 , wherein the guide pins are retractable into the spindle.

3. A mandrel as set forth in claim 1, wherein the guide pins extend radially from the spindle.

4. A mandrel as set forth in claim 1 , wherein the spindle is generally cylindrical.

5. A mandrel as set forth in claim 1 , wherein the spindle includes an insertion end having a relatively relieved area where the spindle has a reduced width longitudinally adjacent the rings of guide pins at the insertion end.

6. A mandrel as set forth in claim 5, wherein the spindle includes a stop end opposite the insertion end, and a portion of the winding guide includes a relatively relieved area where the winding guide has an increased inner diameter longitudinally adjacent the rings of the guide pins at the stop end.

7. A mandrel as set forth in claim 5, wherein the winding guide has a portion positioned at least adjacent each of the rings of guide pins and a portion positioned over the relieved area of the spindle.

8. A mandrel as set forth in claim 1 , wherein the winding guide has a base and a cap separated from the base by a plane which is parallel to the longitudinal axis of the spindle.

9. A mandrel as set forth in claim 1 , wherein the winding guide has an insertion section and a stop section longitudinally separate from the insertion section.

10. A mandrel as set forth in claim 9, wherein the insertion section of the winding guide and the stop section of the winding guide are separately removable from around the spindle.

11. A mandrel as set forth in claim 1 , wherein the plurality of guide pins are equally circumferentially spaced.

12. A mandrel as set forth in claim 1 , wherein the guide pins in each ring are longitudinally aligned.

13. A mandrel as set forth in claim 1 , wherein the spindle and the winding guide form a substantially cylindrical gap therebetween.

14. A mandrel as set forth in claim 13, wherein the spindle includes an insertion end and a stop end, and the gap has a decreased inner diameter adjacent the insertion end of the spindle and the gap has an increased outer diameter adjacent the stop end of the spindle.

15. A method of making field windings for a slotless stator, comprising: winding a wire on a mandrel having a plurality of guide pins extending outwardly from a side of a spindle such that the wire wraps around at least four of the guide pins, indexing the spindle, repeatedly winding and indexing, and removing the windings from the spindle.

16. A method as set forth in claim 15, further comprising applying a cover over the windings, and removing the cover and the windings from the spindle as a unit.

17. A method as set forth in claim 15, wherein winding the wire includes winding the wire on a mandrel including the spindle and a winding guide substantially enclosing the spindle circumferentially, the spindle being rotatable relative to the winding guide about a longitudinal axis, and the spindle having a plurality of outwardly extending guide pins circumferentially arrayed in longitudinally spaced rings.

18. A method as set forth in claim 15, wherein indexing the spindle includes selectively indexing the spindle by rotating the spindle one hundred and eighty degrees to form another winding in the same phase and indexing the spindle by rotating the spindle through an angle formed by radii extending toward adjacent pins.

19. A method as set forth in claim 18, wherein winding, indexing and repeatedly winding and indexing includes winding and alternately indexing the spindle by rotating the spindle one hundred and eighty degrees and by rotating the spindle through an angle formed by radii extending toward adjacent pins, thereby forming at least three sets of windings.

20. A method as set forth in claim 16, wherein applying a cover over the windings includes selectively retracting the pins into the spindle and sliding a cylindrical cover over the spindle and the windings.

21. A method as set forth in claim 20, wherein applying a cover over the windings includes selectively removing at least one portion of a winding guide from around the spindle before sliding the cover over the spindle.

22. A method as set forth in claim 20, further comprising extending the pins and forming another set of windings. * * *