Methods and apparatus for making stators for electric motors and the like, and improved terminal boards therefor

Abstract: The axial end portions of the insulating members (30) which are used to line the longitudinal channels formed between circumferentially adjacent, radially inwardly projecting poles in a stator (e.g., an electric motor stator) are protected from damage by the wire being wound by providing terminal boards (20) at each axial end of the stator having portions which overhang the axial ends of the insulating members.

Description: Background of the Invention This invention relates to methods and apparatus for making stators for electric motors and similar machines such as generators. Although the invention is described herein in the context of its application to electric motor stators, it will be understood that it is equally applicable to other types of stators such as have been mentioned. Terminal boards for electric motor stators are insulating members which are typically placed on both axial ends of the main stator body for such purposes as supporting the axial ends of the windings wound on the poles of the stator and providing insulated attachment points forthe terminals at which the ends of the coil wires can be connected to wires external to the stator. Recently there has been increasing interest in winding stators without winding forms (see, for example, Wheeler U.S. patent 4,612,702 and WO-A-8 901 257. This can simplify the winding apparatus and speed the winding process, but it can also increase the strain and wear on the insulating inserts which are typically placed in the stator between circumferentially adjacent poles in order to prevent short circuits between the coils and the stator. Such strain and wearcan compromise the insulating effectiveness of the insulating member, possibly resulting in short circuits to the stator. Dislocation or distortion of the insulating member may also occur, possibly resulting in vibration or interference with free rotation of the armature in the finished motor. In view of the foregoing, it is an object of this invention to provide stator making methods and, terminal boards, which better protect the associated insulating inserts, especially during winding without winding forms, but even when winding forms are used, if desired. Another problem which may be exacerbated when winding without winding forms is the possibility that some winding turns in the axial ends of the coifs, and especially those winding turns which are intended to fill the area close to the axial end of the stator and in the radially outermost portion of the coil, may not be sufficiently tight or close together to preclude undesirable vibration of those winding turns during operation of the finished motor. It is therefore another object of this invention to provide stator making methods and terminal boards, which promote tight, regular, and complete winding and filling of the stator coils, especially during winding without winding forms, but also when winding forms are used, if desired. Summary of the Invention These objects of the invention are accomplished in accordance with the principles of the invention by providing a method of making a stator according to claim 1 and a terminal board according to claim 3. This lip or bead performs such functions as protecting the end of the insulating member, preventing the insulating member from shifting axially relative to the stator, and ensuring that the wire being wound bears on the terminal board and not on the more fragile axial end of the insulating member as the wire is drawn around the poles of the stator. This lip or bead also promotes depositing the axial ends of the coils close to the axial ends of the stator, thereby improving the tightness, regularity, density, and efficiency of the coils. The foregoing features are especially useful when winding stators without winding forms, although they may also be useful even when winding forms are employed. Brief Description of the Drawings FIG. 1 is an axial end view of an illustrative embodiment of a stator constructed in accordance with the principles of this invention prior to winding coils on the stator poles. FIG. 2 is a partial sectional view taken along the line 2-2- in FIG. 1. FIG. 3a is a view similar to FIG. 2 but showing a prior art structure. FIG. 3b is a partial perspective view of a prior art stator structure. FIG. 4 is a partial sectional view taken along the line 4-4 in FIG. 1. FIG. 5 is a partial sectional view taken along the line 5-5 in FIG. 4. FIG. 6 is an enlargement of a portion of Fig. 1. Detailed Description of the Preferred Embodiments FIG. 1 shows a terminal board 20 constructed in accordance with this invention and mounted on an axial end of a stator 10. Terminal board 20 is a complete annular ring, although it could also be made up of two or more semiannular (meaning partly annular) segments. Behind terminal board 20 in FIG. 1 is the stack of metal laminations 12 (see FIG. 2) which forms the main body of the stator. Terminal board 20 itself is typically made of an insulating material such as plastic. Terminal board 20 typically includes terminal receptacles (e.g., receptacles 22a-d), at least some of which hold or will receive metal terminals (e.g., terminal 50 in FIG. 2) to which the ends of the stator coil wires are attached to facilitate making electrical connections to the stator. (The terminal receptacles 22 shown in the drawings are for terminals of the type which are generally inserted when the stator is in the termination station after the coils have been wound. The depicted terminals 50, on the other hand, are of a type which are generally inserted before the terminal board is applied to the stator. These two different types of apparatus are depicted merely to make it clear that the present invention can be used in either case.) In the depicted illustrative embodiment, stator 10 has two poles 14a and 14b, although it could have more poles if desired. In front of each pole 14 terminal board 20 has a coil holder 24a, 24b which extends axially outward from the portion of the terminal board which is adjacent to the surface of the pole that is concentric with central longitudinal axis 16. At the axial end of each coil holder 24 which is remote from the main annular portion of terminal board 20 each coil holder has a coil retainer tab 26a, 26b which projects radially outward from the, associated coil holder. Before terminal board 20 is mounted on stator stack 12, an insulating member, insert, or liner 30a, 30b is pushed axially into each channel which exists between circumferentially adjacent stator poles. Each insert 30 is preferably axially somewhat longer than the stator stack (excluding terminal boards 20) so that each insert projects slightly from each axial end of the stator stack prior to attachment of terminal boards 20. After inserts 30 are in place, a terminal board 20 is mounted on each axial end of the stator stack as shown in FIGS. 1 and 2. As can be seen in FIG. 1, the main annular portion of terminal board 20 has generally the same shape and extent as the associated axial end of stator stack 12 except for a lip or bead 40 which projects over and therefore covers the axial end of the adjacent insert 30 (see also FIG. 2). The prior situation without this bead is illustrated by FIG. 3a (in which the reference numbers 20 and 24 are used merely to help the reader identify generally corresponding parts of the structure and not to mean that the FIG. 2 structure forms part of the present invention). In accordance with this invention, lip or bead 40 protects the axial ends of inserts 30 during winding of the coils on poles 14, especially when these coils are wound without winding forms. In particular, it has been found that when the stator is wound without terminal boards having lip or bead 40 (e.g., terminal boards as shown in FIG. 3a), the wire emerging, for example, from region A tends to hit the axial end portion of the adjacent insert 30 which is radially outward from region A. (Arrows 32 show the direction of motion of the needles which wind the wire in this example.) This hitting of insert 30 can have several undesirable results. For example, it can corrugate the insert (due to the wire sliding or running on the exposed surface of the insert), causing the material of the insert to displace at other locations (e.g., in region C where the insert may bulge radially inwardly so that it can vibrate against the stator stack when the finished motor is operated or so that the insert interferes with rotation of the armature). Hitting of the insert can also break through the insert, with the possible loss of insulation between the coil and the stator stack. The portion of lip or bead 40 which is radially outward from region A protects this part of the axial end of insert 30 and thereby eliminates or at least greatly reduces the foregoing possible problems. This portion of lip or bead 40, as well as other portions of the lip or bead in the vicinity of region A, also provides a smooth surface (which is typically harder than insert 30) on which the wire can more readily move or run in the circumferential direction as the end of the wire-winding needle (not shown) passes over the top (or bottom) of retainer tab 26 in order to pull the windings tightly around the poles. By facilitating the circumferential movement of coil wires during winding in this manner, lip or bead 40 may also improve the resulting coils, for example, by helping the coils to wind more tightly, regularly, and densely about the poles and by reducing the possibility that voids will form in the coil, especially close to the axial end of the stator, as the winding proceeds. On the other side of each pole 14, as the wire being wound re-enters the stator (e.g., adjacent region B), the wire must bend generally about edge B and may also need to move along edge B. Once again, the presence of lip or bead 40 overhanging and thereby protecting the axial end of insert 30 prevents the wire from damaging the insert, with possible loss of insulation between the coil and the stator stack. Lip or bead 40 in region B also ensures that the wire contacts a smooth, hard surface which facilitates motion of the wire along edge B. As in the case of the portion of the lip or bead 40 in the vicinity of region A, this may help produce better windings by increasing the tightness, regularity, density, and completeness of the coils. Another advantage of lip or bead 40 on the terminal boards at both ends of the stator stack is that these lips or beads help to hold inserts 30 in their proper axial positions in the stator and reduce the risk that an insert may be dislocated by handling of the stator or before enough windings have been applied to permanently retain the inserts. Small, localized clips 34 (FIG. 3b) have been used in the past to help hold insert 30 in place both axially and radially. But structures like continuous lip or bead 40, with all the additional advantages described above, were unknown prior this invention. Note that (as shown in FIG. 2) in order to prevent coil holders 24 from becoming too thick as a result of the need to provide the adjacent portion of lip or bead 40, that portion of terminal board 20 is thicker in the radial direction than either the portion which is immediately adjacent the stator stack or the portion which forms coil holder 24. The transition from coil holder 24 to this thicker portion is preferably inclined as shown at 42 in FIGS. 2 and 5. This incline promotes running of wire being wound toward the adjacent stator pole, which tends to improve the coils in the ways that have been mentioned above. Also note that the bead surface 44 on the other side of the channel depicted in FIG. 2 is preferably inclined relative to both the longitudinal axis of the stator and the axial end face of the stator so that surfaces 42 and 44 are svnclinal in the direction into the stator.

Claims: The method of making a stator comprising the steps of providing an annular stator body having a plurality of radially inwardly projecting poles (14a,14b), wherein adjacent poles define a longtudinal channel therebetween; lining the surface of such channel with an insulating member (30a); winding a coil of wire around each pole, the method being characterized in that it further comprises the step of mounting on each axial end of said stator body a terminal board (20) having an edge with a bead portion (40) which overhangs an adjacent axial end of said insulating member (30a) and ensures that the wire being wound bears on the terminal board and not on the axial end of the insulating member on the wire in drawn in a circumferential direction around the poles of the stator. The method of claim 1 wherein said terminal board (20) has a major plane which is perpendicular to said longitudinal channels when said terminal board is mounted on said stator body and wherein the longest dimension of said overhanging portion (40) is parallel to said major plane. A terminal board incorporated in a stator, the stator comprising a hollow annular stator body (12) having a plurality of radially inwardly projecting poles (14a,14b) and an insulating member (30a) disposed in longitudinal channels defined by adjacent poles, wire coils being disposed around said poles in the longitudinal channels said terminal board being at an axial end of the stator body and being characterized in that it is provided with a bead (40), which extends from the remainder of the terminal board (20), transverse to the longitudinal axis of the stator body by an amount sufficient to cover an axial end of the insulating member (30a), the wire wound around the poles bearing on the terminal board and not on the axial end of the insulating member. The terminal board defined in claim 3 wherein the insulating member (30a) projects axially beyond the axial end of the stator body (12), and wherein said bead (40) is axially spaced from the surface of the terminal board (20) which contacts the axial end of the stator body (12) by an amount greater than the axial projection of the insulating member (30a) beyond the axial end of the stator body (12). The terminal board defined in claim 3 wherein said terminal board (20) has a major plane which is perpendicular to said longitudinal channels when said terminal board (20) is mounted on said stator body (12) and wherein the longest dimension of said bead (40) is parallel to said major plane. The terminal board defined in claim 3 wherein said bead (40) is provided with an axially outward surface (42) which is inclined relative to both the axial end of the stator body (12) and the longitudinal axis of the body (12).

Inventors: SANTANDREA LUCIANO, SANTANDREA, LUCIANO
Applicants: AXIS SPA, AXIS S.P.A.
Application year: 1990
Main classification: H02K15
IPC codes: H02K3, H02K15