Stator Lead Wire Connection Method and Apparatus

This invention relates to the art of manufacturing stators for electric motors and more particularly to a stator coil lead wire connection method and apparatus.

When manufacturing stators having a stator core on which are mounted terminal boards with terminal-receiving receptacles having slots in which the lead wires are to be placed, it has become a common practice to position a stator at a lead connect station and, using a robot end effector, to manipulate the stator coil lead wires to insert them into the receptacle slots. The lead wires, which extend substantially axially of the stator core are bent to extend essentially radially of the stator core when they are inserted into the receptacle slots. Each lead wire is thereby bent at an essentially right angle over a sharp corner at the bottom of a receptacle slot.

The wire at the bending point is under considerable tension because the grip on the end effector against the wire must be sufficiently secure that the lead wire is invariably pulled completely down to the bottoms of the receptacle slots. The sharp bend and tension creates a weakened spot in the lead wire. These factors may be exacerbated when the terminal is inserted into the receptacle. As a result, there is an increased potential for the lead wire to break at this point, especially when the stator is exposed to substantial vibrations during use, such as in a power tool.

In order to overcome the weakness in a lead wire at the point it enters the receptacle, it has been suggested that the stator be so manufactured that the segment of each lead wire extending from the coil to its associated receptacle be made somewhat slack in order to decrease the tension on the wire where it enters the receptacle. So far as known, a satisfactory method and apparatus for providing slackened lead wires have not been developed. The task is not easy because any such method and apparatus, to be satisfactory for use in a mass production manufacturing environment, must be rugged, reliable, and so fast acting that it will not significantly increase the time needed to manufacture the stator.

The primary object of this invention is to provide a method and apparatus which would create a slack lead wire as described above. In order to provide a slack wire condition, each lead wire is gradually bent before it enters its associated receptacle slots and a short segment thereof adjacent the inner side wall of the receptacle extends substantially radially of the bore of the stator. These measures increase the length of a lead wire segment between a coil and its terminal receptacle so that the lead wire will be somewhat slack. Thus, the tension on the lead wire where it enters the receptacle is materially decreased. In addition, the abrupt, wire-weakening, right-angled bend resulting from the present practice is avoided.

In accordance with this invention, wire guide fingers are positioned adjacent one of the receptacles in the paths of the lead wires to be inserted therein. The fingers have arcuate surfaces over which the lead wires are coursed so that they are gradually curved rather than abruptly bent, and so that they approach entry into the receptacles in a radial rather than an axial direction.

Further in accordance with this invention, a tooling assembly including the fingers is provided that includes a fixed subassembly and a rotatable subassembly from which the fingers project and which is mounted on the fixed subassembly. A drive mechanism moves the tooling assembly between a first position in which the fingers are within the bore of the stator and a second position in which the fingers are retracted from the bore of the stator. Means are provided for rotating the rotatable subassembly when the fingers are within the bore of a stator as needed to circumferentially align or misalign the fingers with the receptacles. When the fingers are circumferentially aligned with the receptacles, a robot end effector sequentially inserts each of the lead wires into their respective terminal receptacles. Afterwards, the rotatable assembly is rotated to remove the fingers from between the lead wires and the receptacles, the tooling assembly retracted, and the stator removed from the lead connect station.

The rotatable assembly is preferably rotated by the end effector between detented positions but may be rotated by an air actuator.

Other objects and advantages will become apparent from the following description and the drawings.

FIG. 1 is a partly exploded, fragmentary, partly schematic, perspective view of a lead connect station of a stator winding machine which includes a presently preferred tooling assembly in accordance with this invention, a stator with which this invention may be used, and a stator supporting structure.

FIG. 2 is a fragmentary, end elevational view, with parts in cross section, of the stator and a portion of the tooling assembly of FIG. 1. FIG. 2 also illustrates by phantom lines a robot end effector used with this invention in the process of inserting a lead wire into a terminal receptacle.

FIG. 3 is a fragmentary, end elevation view of a portion of FIG. 2, illustrating a later stage in the insertion of the lead wire into the terminal receptacle.

FIG. 4 is a fragmentary perspective view, on a scale larger than the preceding figures, of a portion of the parts of FIG. 2 and 3 after the end effector has completed the insertion of the lead wire into a terminal receptacle.

FIG. 5 is a fragmentary perspective view, on the same scale as FIG. 4, showing the lead wire fully inserted into its receptacle.

FIG. 6 is a view similar to FIG. 2 but at a later stage in the practice of the method of this invention.

FIG. 7 is a fragmentary, partly schematic elevational view illustrating a modification.

With reference to FIG. 1, this invention is directed to the manufacture of a stator, generally designated 10, comprising a laminated core 12 formed to include a central bore 14 and pole pieces 16 and 18 around which coils 20 and 22 of magnet wire are wound. Each coil 20 and 22 has a pair of lead wires, designated 24 and 26, and 28 and 30, respectively. Stator core 10 has an end face 32 on which are mounted a pair of terminal boards 34 and 36 provided, respectively, with pairs of axially-extending, terminal-receiving receptacles 40 and 42, and 44 and 46, respectively. Each of the receptacles 40, 42, 44, and 46 comprises a rectangular, open box-like configuration having radially spaced, parallel, inner and outer sidewalls 48 and 50, respectively, which have respective mutually aligned, axially-extending lead wire-receiving slots 52 and 54 (FIG. 5), each of which tapers from a larger dimension at its axially outermost end to a smaller dimension at its innermost end. The innermost ends of the slots 52 and 54 are sized to tightly engage the lead wires extending through them.

In an earlier stage of manufacture of the stator 10, the coils 20 and 22 were wound starting with the lead wires (called start wires) 24 and 28 and finishing with the lead wires (called finish wires) 26 and 30. At the same stage, the lead wires 24, 26, 28 and 30 were inserted into lead wire-retaining clamps 56, only one of which is illustrated in FIG. 1 hereof, which releasably and temporarily hold the lead wires in preparation for later insertion into the receptacles 40, 42, 44 and 46.

This invention is directed primarily to a later stage in the manufacture of the stator 10, which may be termed the "lead-connect" stage, which is carried out at a lead-connect or robot station. This is the station illustrated in FIG. 1. As shown in simplified form in FIG. 1, the stator 10 is supported on a suitable support 60, which may be part of a support track or else a support member on a turret (not shown) and held in a predetermined position with its bore 14 centered on a predetermined axis 62 by clamps 64 or the like. At this stage, a robot having a pliers-like end effector 66 grips a first one of the lead wires, for example lead wire 26, and moves in such a manner as to withdraw the lead wire from the temporary clamp 56, align the lead wire 26 with the slots 52 and 54 of its associated terminal receptacle 42, and then pull the lead wire 26 into the bottoms of the slots 52 and 54 so that the lead wire spans across the middle of the receptacle 42. During these manipulations, the end effector 66 must carry the lead wire 26 in both axial and circumferential directions to bring it into alignment with the receptacle slots 52 and 54 and then in a radial direction to lay the lead wire 26 into the same slots. Radial movement of the end effector 66 continues to the point that the lead wire 26, is laid over an external wire support block 68 (see FIGS. 2 and 3), on the outer face of the receptacle outer side wall 50. The gripping pressure applied by the end effector 66 when the lead wire is being pulled down to the bottoms of the receptacle slots 52 and 54 is adjusted to be sufficient so that the task may be accomplished despite the considerable resistance to insertion of the wire created by the narrow, axially innermost ends of the receptacle slots 52 and 54. After the lead wire 26 is fully inserted into its receptacle slots 52 and 54, a wire cutter (not shown) forming part of the end effector 66 severs the wire lead so that, as shown in FIGS. 4 and 5, only a short tail 70 extends to the outside of the stator 10. These operations are sequentially repeated to insert all of the lead wires 24, 26, 28 and 30, into their respective receptacles.

At a still later stage in the manufacture of the stator 10, as shown diagrammatically in FIG. 5, metal terminals 72 are inserted into the receptacles 40, 42, 44 and 46 in engagement with the lead wires spanning across them. During this operation, the external wire support blocks 68 and the short wire tails 70 may be severed from the receptacles.

The manufacturing procedures as thus far discussed are well known in the industry. A problem that has been encountered with stators manufactured using these procedures is that each lead wire, when inserted into its associated receptacle, is bent at an essentially right angle over the sharp corner at the bottom of the receptacle slot 52 in the receptacle inner side wall 48. The lead wire at this point is under considerable tension because the grip on the end effector 66 against the wire must be sufficiently secure that the lead wire is invariably pulled completely down to the bottoms of the receptacle slots 52 and 54. The sharp bend and tension creates a weakened spot in the lead wire. These factors may be exacerbated when the terminal 72 is inserted into the receptacle. As a result, there is an increased potential for the lead wire to break at this point, especially when the stator is exposed to substantial vibrations during use, such as in a power tool.

In order to overcome the weakness in a lead wire at the point it enters its receptacle, it has been suggested that the segment of each lead wire extending from the coil to its associated receptacle be somewhat slack. A slack lead wire can be achieved by gradually bending the lead wire before it enters its associated receptacle slots so that a short segment of the lead wire adjacent the inner side wall of the receptacle extends substantially radially of the bore of the stator instead of substantially axially as is now the case. Such a lead wire configuration is shown in FIG. 5, wherein the lead wire 26 has, as desired, a gradually rounded corner or bend 74 between its axially extending segment, designated 76, and a short radially-extending segment 78 which extends into the innermost receptacle slot 52. This causes an increase in the length of the lead wire between a coil and its terminal receptacle so that lead wire will be somewhat slack.

With reference to FIGS. 1 and 2, a tooling assembly, generally designated 80, is provided by this invention, which comprises a non-rotatable subassembly, generally designated 82, and a rotatable subassembly, generally designated 84. The non-rotatable subassembly 82 comprises a vertical support arm 86, a tooling backing plate 88 having a relieved rear face 90 which receives the top of the support arm 86, and a nosepiece, generally designated 92. The nosepiece 92 has a conical, forwardly extending arbor 94 adapted to enter into the stator bore 14 to provide support for the coils 20 and 22 during the lead-connect process. Nosepiece 92 further includes a coil-forming plate 96 which can bear against the outer extremities of the coils 20 and 22 to insure that they do not extend beyond a desired distance from the core end face 32, and a generally cylindrical hub 98 that extends from the rear face of the coil forming plate 96 to the support arm 86. For reasons which will become apparent, the hub 98, has a center axis which is coincident with the center axis 62 of the bore of the stator at the lead connect station. The rear end of the hub 98, i.e., the end most remote from the stator 10, is provided with flats that form a rearwardly-extending, generally rectangular boss 100 that projects through a mating, generally rectangular through-bore 102 in the backing plate 88 into engagement with the forward face of the support arm 86. The rear face of the hub 98 has a tapped hole 104 that receives a mounting screw 106 which holds the parts of the non-rotatable subassembly 82 together. Because of the non-circular configurations of the boss 100 and the through-bore 102, relative rotation between the nosepiece 92 and the backing plate 88 is prevented. Of course, the backing plate 88 non-rotatably receives the support arm 86. The support arm 86 itself is non-rotatably mounted for sliding movement on a suitable base (not shown), such as shown, for example, in U.S. Pat. Nos. 5,214,838 and 5,090,108, so that the entire non-rotatable subassembly 82 can move axially toward and away from the stator at the lead-connect station. An air actuator, shown schematically at 106 in FIG. 1, is provided to axially move the non-rotatable assembly 82 for purposes which will be described below.

As shown in FIG. 1, the boss 100 at the rear of the hub 98 is bounded by shoulders 108 which engage the confronting front face of the backing plate 88. Accordingly, the backing plate 88 is spaced from the coil former plate 96 by the length of the circular portion of the hub 98. This spacing is sufficient to provide space for a mounting plate 110 that forms part of the rotatable assembly 84.

With reference to FIGS. 1 and 2, the mounting plate 110 has a circular through-bore 112 by which it is rotatably mounted on the circular portion of the hub 98 between the backing plate 88 and the coil forming plate 96 of the nosepiece 92. In addition to the mounting plate 110, the rotatable assembly 84 includes four circumferentially-spaced guide arms 114, one for use with each terminal receptacle, that project radially with respect to the center axis 62 of the stator bore 14 and outwardly from the side edges of the mounting plate 110. As shown in FIGS. 2 and 6, each guide arm 114 is located generally in axial alignment with one of the terminal receptacles 40, 42, 44, and 46. The guide arms have T-shaped heads 116 which act as keys that fit within mating, T-shaped key slots 118 in the mounting plate 110. The T-shaped keys and slots prevent radial movements of the guide arms 114 away from the mounting plate 110. The confronting surfaces of the nosepiece plate 92 and the backing plate 88 prevent substantial axial movements of the wire guide arms 114 relative to the mounting plate 110. This construction has the advantages of enabling assembly of the rotatable subassembly 84 without the use of fasteners or tools and the parts are relatively inexpensive to machine. Other constructions, including a one-piece rotatable subassembly are possible.

As shown best in FIGS. 3 and 4, each wire guide arm 114 has a radially-extending wire-guiding surface 120 constructed to lie adjacent the outermost opening to the associated receptacle slots 52 and 54 to ensure that the lead wires are guided into the receptacle slots. Of primary importance with respect to the present invention, each of the wire guide arms 114 has an axially extending plate portion 122 (FIG. 4) from which a wire guide finger 124 laterally projects. Each of the wire-guide fingers 124 can be located closely adjacent the inner sidewall 48 of its associated terminal receptacle, and each has an arcuate, outwardly facing surface 126.

With reference to FIG. 4, which shows one of the wire guide fingers 124 after the tooling assembly 80 has been fully advanced toward the stator core, the outermost edge of the arcuate surface 126 is located substantially coplanar with and in circumferential alignment with the bottom or axially innermost end of the inner receptacle slot 52. In operation, which will be more fully discussed below, when a finger 124 is located substantially coplanar with and in substantial circumferential alignment with the bottoms of the receptacle slots 52 and 54, and the robot operated to extend a lead wire into the receptacle slots, the lead wire is necessarily coursed over the outer, arcuate surface 126 of the finger 124 so that, instead of the right-angled bend around the sharp edge of the bottom of the slot that is experienced with present practice, the lead wire is curved around the arcuate outer surface of the finger and extends in a radial direction as it enters into the receptacle. This produces the desired lead wire configuration previously described with reference to FIG. 5. It may be noted that all of the fingers 124 are simultaneously positioned substantially coplanar with and in circumferential alignment with the bottoms of the receptacle slots 52 and 54 so that the robot can be continuously operated to sequentially insert all of the lead wires into their associated receptacles.

In order to enable retraction of the fingers 124 from between the lead wires and the adjacent inner side walls 48 of the terminal receptacles after all of the lead wires have been connected to the receptacles, the rotatable assembly 84 is rotated in a clockwise direction from its position illustrated in FIG. 2 into the position thereof illustrated in FIG. 6. This rotation causes the fingers 124 to be moved circumferentially out of alignment with the receptacle slots 52 and 54 and, correspondingly, causes the fingers 124 to be removed from between the coil lead wires and their associated receptacles. The tooling assembly 80 can now be retracted by operation of the air actuator 107 after which the stator 10 can be removed from the lead connect station and replaced by another stator.

The presently preferred method for rotating the rotatable subassembly 84 is to provide the mounting plate 110 with an upwardly extending lug 128 which can be engaged by the robot end effector 66. Two sets of detent assemblies are provided to frictionally hold the rotatable assembly in one position shown in FIG. 2 or in another position shown in FIG. 6. With reference to FIGS. 1, 2, and 6, one detent assembly comprises a vertically-spaced pair of ball plunger assemblies 130 threadedly received in the nosepiece 92 and a pair of confronting detent recesses 132 in the front face of the mounting plate 110. When the rotatable assembly 84 is in the position shown in FIG. 2, the balls of the ball plungers 130 are frictionally lodged in the recesses 132. When the rotatable assembly is in the position thereof shown in FIG. 6, the ball plungers 130 are out of alignment with the recesses 132.

The second detent assembly includes a pair of horizontally spaced ball plungers 134 and associated detent recesses 136. These are misaligned when the mounting plate 110 is in the FIG. 2 position and aligned when the mounting plate 110 is in the FIG. 6 position. Accordingly, the second detent assembly frictionally holds the mounting plate 110 in the FIG. 6 position in which the fingers 114 are circumferentially out of alignment with the receptacle slots 52 and 54. Mutually cooperating stops comprising surfaces forming the ends of a stop slot 140 in the mounting plate 110 and a roll pin 142 lodged in the backing plate 88 may be provided to prevent accidental over travel of the mounting plate 110.

An alternative apparatus for rotating the mounting plate is illustrated in FIG. 7. Here a mounting plate, designated 110A, has a depending lug driven by an air actuator 144 which can be mounted on the support arm (not shown in FIG. 7). The operation of this embodiment will be apparent from the description of the operation of the preferred embodiment of FIG. 1. It will be realized that the use of the air actuator 144 in FIG. 7 may obviate the use of the detents and stops described above.

In operation of the preferred embodiment of FIG. 1, after the tooling assembly is retracted from the stator 10, another stator is positioned in the lead connect station. During this time, the rotatable assembly 84 remains in its clockwise rotated position illustrated in FIG. 6 under the influence of the horizontally spaced detent plungers 134 and recesses 136. The tooling assembly 80 is then advanced toward the new stator in the lead connect station until the wire guide fingers 114 are substantially coplanar with the bottoms of the receptacle slots. At this time, the robot end effector is manipulated to rotate the rotatable assembly 84 in a counterclockwise direction to return it to the position illustrated in FIG. 2 wherein the fingers are simultaneously brought into circumferential alignment with the bottoms of the receptacle slots. The robot end effector 66 is then manipulated to sequentially insert each of the lead wires into the receptacle slots. In each case, after a lead wire is gripped by the end effector 66, the end effector 66 is moved to remove the lead wire from its temporary clamp, and also moved axially, circumferentially, and radially as needed to course the lead wire over the wire guide finger and into its associated receptacle. The lead wire is then trimmed by operation of the cutter associated with the end effector 66. The foregoing operations of the end effector 66 are conventional and are deemed apparent from an inspection of FIGS. 2, 3 and 4. When these operations are completed for the first lead wire, the robot moves onto the next lead wire to be inserted into its terminal receptacle. During this time, the rotatable assembly remains in its counterclockwise rotated position shown in FIG. 2 under the influence of the vertically aligned detent plungers 130 and recesses 132. After all four lead wires are thus connected to their respective terminal receptacles, the end effector 66 is moved to engage the left side of the lug (as viewed in FIGS. 2 and 6) and push it to the right so that the wire guide fingers 124 are moved out of circumferential alignment with the receptacle slots 52 and 54 as described above. At this time, the end effector 66 is moved to an out-of-the-way location and the tooling assembly 80 again retracted. As is apparent, these operations can be repeated indefinitely.

It will be noted that the entire tooling assembly 80 has a width which is sufficiently small that it can fit within the ambit of the stator 10 between the terminal boards 34 and 36 and so as not to interfere with the operation of the robot end effector 66.

Although the presently preferred embodiments of this invention have been described, it will be understood that within the purview of this invention various changes may be made within the scope of the appended claims.