A METHOD OF CONNECTING AN ARMATURE CONDUCTOR TO A COMMUTATOR SLOT

Abstract: The risers (42) of the commutator (36) have radially extending slots (44) that are defined by surfaces (46,48) that taper outwardly. The ends (31) of the armature conductors (30) are formed to a generally wedge-shaped configuration such that the side surfaces (31E-31H) are tapered inwardly. After the ends of the armature conductors have been formed to the tapered shape they are pushed into the slots of the commutator risers to such a depth that there is an interference fit between the side surfaces of the ends of the armature conductors and the tapered walls of the slot to lock the ends of the armature conductors to the commutator risers. After the ends of the formed armature conductors have been pushed into the slots, portions of the commutator risers are staked over into engagement with the top armature conductor end.

Description: This invention relates to a method of connecting the armature conductors of a dynamoelectric machine armature to the risers or bars or segments of a commutator and to an improved connection between the armature conductors and the commutator risers or bars or segments. One known method of connecting armature conductors to commutator risers or bars or segments utilizes solder to make the connections. It has been recognized by the prior art, an example being the US patent no. 2,476,795, that the use of solder has disadvantages. Thus, the solder during high current and hence high temperature operation may soften or melt to an extent that the solder is thrown out by centrifugal force when the armature and commutator are rotated at high speed, resulting in a failure of the connection. Another disadvantage of soldering is that apparatus must be provided to apply the solder between the internal surfaces of a slot in the commutator and the surfaces of the armature conductors. The above-mentioned US patent no. 2,476,795 and US patent nos. 2,572,956 and 4,402,130 all relate to armature conductor to commutator connections that do not use solder. Thus, in US patent no. 2,476,795 the armature conductors are placed in the slots of commutator risers and portions of the risers are clinched into contact with the conductors. In US patent no. 2,572,956, armature conductors are placed in commutator riser slots and some of the material of the riser is then forced against the upper conductor by a spinning tool. In US patent no. 4,402,130, the conductors are placed in a slot of a commutator riser and the conductors are then deformed by impacting the conductors by a punch. After the conductors are deformed portions of the commutator riser are moved into contact with an upper conductor. In accordance with the present invention, a method of connecting armature conductors to commutator slots, and an armature conductor to commutator riser connection is characterised by the features specified in the characterising portion of Claims 1 and 8 respectively. It is an object of this invention to provide a method of connecting armature conductors to commutator slots that requires no solder or brazing material and that minimizes the mechanical forces applied to the commutator during assembly. Thus, in practicing the method of this invention the end portions of the armature conductors are all formed from a rectangular shape to a generally wedge-shaped configuration having tapered sides by punch and die apparatus prior to being pushed into the slots of commutator risers. The commutator slots, that receive the tapered end portions of the armature conductors, have complementary tapered internal walls. After the end portions of the armature conductors have been formed to the tapered shape they are all bent or spread outwardly. A commutator is then pushed onto the shaft of the armature and as the commutator is moved toward the armature the formed end portions of the armature conductors pass through the tapered commutator slots. The formed end portions are now pushed into the complementary tapered slots of the commutator risers with an interference fit such that the end portions are wedge or taper locked to the commutator risers. Following this, the edges of a commutator slot are staked into engagement with the top end portion of a formed armature conductor. It will be apparent, from the foregoing, that mechanical forces required to deform the end portions of the armature conductors are applied to the end portions of the armature conductors before they are pushed into the commutator slots and hence are not applied to the commutator itself. Moreover, no solder or brazing compound is utilized. In regard to mechanical conductor deforming forces, it is desirable not to subject the commutator to a high deforming force particularly where the commutator is of the so-called moulded type where moulded plastic material connects an internal tubular core and an outer commutator shell. Thus, forces applied to the commutator should be kept low enough so as not to fracture the insulation or otherwise adversely effect the integrity of the commutator. Another object of this invention is to provide an improved electrical connection between the end of an armature conductor and the internal surfaces of a slot of a commutator riser wherein the end of the armature conductor has tapered outer surfaces that are in intimate contact with complementary tapered internal surfaces of the commutator slot. This invention is further described, by way of example, with reference to the accompanying drawings in which:- Figure 1 is a view with parts broken away of an armature made in accordance with this invention; Figure 2 is a view taken along lines 2--2 of Figure 1 illustrating a portion of an armature lamination and armature conductors positioned within the slots of the lamination; Figure 3 is a plan view of a winding element or hairpin armature conductor which is inserted into the slots of the core of the armature assembly shown in Figure 1; Figure 4 is an end view of a commutator which forms a component of the armature shown in Figure 1; Figure 5 is a sectional view taken along lines 5--5 of Figure 4; Figure 6 illustrates punch and die apparatus for forming armature conductors to a generally wedge-shaped cross section; Figure 7 illustrates apparatus for spreading or bending armature conductors outwardly; Figure 8 illustrates one of the risers of the commutator shown in Figure 1 and the position of formed armature conductors relative to the slot in the riser when the commutator is assembled to the shaft of the armature and moved such that the ends of the formed armature conductors pass through the slots; Figure 9 is a view illustrating the relative position of the formed armature conductors and the slot in a riser at the time that the commutator has been assembled to the shaft; Figure 10 illustrates apparatus for pushing the formed armature conductors down into a slot of a riser; Figure 11 illustrates the position of the formed armature conductors when they have been pushed completely into a slot of a riser; Figure 12 illustrates apparatus for staking over a portion of the riser into engagement with the top conductor of a pair of formed armature conductors that have been pushed into the slot of a riser; and Figure 13 illustrates portions of the riser staked into engagement with the top formed conductor of a pair of armature conductors positioned within a slot of a riser. Referring now to the drawings, Figure 1 depicts an armature 20 for a direct current motor such as a starting motor. The armature 20 has a shaft 22 which has a gear 24. The shaft 22 carries a stack of steel laminations making up a core 26. The steel laminations are forced onto a knurled portion of the shaft 22 so as to secure the steel laminations to the shaft 22. One of the steel laminations that makes up the core 26 is designated by reference numeral 26A and is illustrated in Figure 2. This steel lamination 26A, and the other steel laminations that make up the core 26, have a plurality of slots 26B, which are circumferentially spaced, for receiving armature conductors 30 which are inserted into these slots. The armature winding for armature 20 is comprised of a plurality of winding elements 28 which are U-shaped and which are known in the art as hairpin shaped winding conductors. The winding element 28 is comprised of the armature conductor 30 (of copper) that carries a length of insulating material 32 that encircles the armature conductor 30. The armature conductor 30 has a generally rectangular cross section and has slightly curved or radiused opposed end portions, as is illustrated in Figure 2. The end portions 31 of the armature conductor 30 are not covered by insulating material and they have pointed ends 33 shown in Figure 3. The pointed ends 33 facilitate the insertion of the end portions 31 into the slots 26B of the core 26. The end portions 31 of the armature conductors 30 are also connected to risers 42 of a commutator 36. The commutator 36 is of the moulded type and is illustrated in detail in Figures 4 and 5. The commutator 36 is assembled to the shaft 22 of the armature 20 such that the end portions 31 of the armature conductors 30 slide through slots in the riser portions of the commutator 36, all of which will be more fully described hereinafter. The commutator 36 comprises a tubular core 38 which is metallic and an outer shell 40 which is tubular and of copper. The outer shell 40 has ribs 40A and a plurality of recesses 40B. The outer shell 40 has a plurality of integral risers 42. The risers 42 each have a slot 44 that is defined by internal side walls or surfaces 46 and 48 and by a flat inner or bottom wall or surface 50. As will be more fully described hereinafter, the internal side walls or surfaces 46 and 48 are not parallel but taper outwardly by a small amount. Each riser 42 has side walls or surfaces 42A and 42B which are circumferentially spaced. Further, each riser 42 has a front end face 42C and a rear end face 42D. The tubular core 38 and the outer shell 40 are joined by a moulding material 52 of thermosetting plastic which is moulded between these two parts in a manner well known to those skilled in the art. The moulding material 52 fills the recesses between adjacent side walls or surfaces 42A and 42B to thereby form thin strips of insulation 52A that insulate each riser 42 from an adjacent riser, as shown in Figure 4. Moreover, this moulding material 52 fills the recesses 40B and the interior of the ribs 40A during the moulding operation. When the commutator 36, shown in Figures 4 and 5, has been assembled to the armature 20 and connected to the armature conductors 30 the ribs 40A are machined off so as to provide faces 40C that are electrically insulated from each other. The faces 40C are adapted to be engaged by the brushes of a dynamoelectric machine. It is noted that commutators, of the type described, are well known to those skilled in the art and one method of manufacturing such a moulded type of commutator is disclosed in US patent no. 3,407,491. The method of connecting the end portions 31 of the armature conductors 30 to the risers 42 of the commutator 36 will now be described. This description will include a brief description of how the armature 20, shown in Figure 1, is manufactured prior to the time that the commutator 36 is assembled to the shaft 22. In the manufacture of the armature 20 the laminations that make up the stack of laminations of the core 26 are pressed onto the shaft 22 with the slots 26B in the laminations all being aligned. A pair of insulators 54 and 56, which have slots, are pushed onto the shaft 22 with the slots in the insulators being aligned with the slots 26B in the core 26. When the core 26 and insulators 54,56 have been assembled to the shaft 22 the winding elements 28 are inserted into the slots 26B in the core. The manner in which the winding elements 28 are inserted is such that one side of a winding element will become an outer or upper conductor and the other side of another winding element will become an inner or lower conductor of a given core slot. The same is true of the end portions 31 of the winding elements 28, that is they will be located such that one of the end portions of one winding element is disposed above the other end portion of another winding element when the winding is completed. The winding is a double layer winding and after all of the winding elements 28 have been inserted into the slots 26B of the core 26 the end portions 31 of the winding elements are twisted such that portions 30A of the winding elements extend diagonally, as illustrated in Figure 1. During this twisting operation the end portions 31 are not moved to a diagonal position but rather extend axially of the shaft 22 and substantially parallel to the shaft 22. When an armature 20 has been fabricated, in a manner that has been described, that is with the end portions 31 all extending parallel to the shaft 22, the end portions 31 of the armature conductors 30 are all formed into the shape illustrated in Figure 10, where a formed upper end portion has been designated as 31A and a formed lower end portion has been designated as 31B. The formed upper end portion 31A has parallel flat planar surfaces 31C and 31D and outwardly tapered flat planar surfaces 31E and 31F. In a similar fashion, the formed lower end portion 31B, has outwardly tapered flat planar surfaces 31G and 31H and parallel flat planar surfaces 31J and 31K. The upper and lower end portions 31A and 31B are formed to the tapered configuration illustrated in Figure 10 by the punch and die apparatus illustrated in Figure 6. Thus, a pair of end portions 31 which are generally rectangular, as illustrated in Figures 2 and 6, are located within a die 60 which has a die cavity 62 that is comprised of outwardly tapered flat surfaces 62A and 62B and a lower inner flat surface 62C. The taper of the outwardly tapered flat surfaces 62A and 62B corresponds to the taper of the internal side walls or surfaces 46 and 48 of a riser 42, which will be more fully described hereinafter. With the end portions 31 positioned in the die cavity 62, as illustrated in Figure 6, a radially movable punch 64 is moved down into the die cavity to cold form the end portions 31 from their rectangular cross section, illustrated in Figure 6, to the wedge-shaped or tapered cross section or configuration illustrated in Figure 10. The taper angle of the outwardly tapered flat surfaces 62A and 62B, which corresponds to the taper angle of the internal side walls or surfaces 46 and 48 of the riser 42, is approximately 3°. Thus, the angle between a pair of lines, which intersect the centre of the commutator 36 where one of the line bisects the slot 44 and the other line coincides with one of the internal side walls or surfaces 48, will be approximately 3°. This means that the included angle between internal side walls or surfaces 46 and 48 will be approximately 6°. In Figure 10 the upper and lower end portions 31A and 31B are shown in the position where they have been pushed into the slot 44 by a push-in blade 66 and where they just make contact with internal side walls or surfaces 46 and 48. The die cavity 62 is substantially a mirror image or counterpart of the slot 44 from a line corresponding to (lower) flat planar surface 31K of lower end portion 31B to the open end of the slot 44, as these parts are viewed in Figure 10. The flat planar surface 31C of upper end portion 31A is formed by the flat face 64A of radially movable punch 64 and the flat planar surface 31K of lower end portion 31B corresponds to lower inner flat surface 62C. The die cavity 62 extends for about the same axial length as the length of an end portion 31 and is open on both ends. The axial length of radially movable punch 64 can be about the same length as the length of die cavity 62. It is preferred that the die 60 has a plurality of circumferentially spaced die cavities 62 corresponding to the number of pairs of end portions 31 so that all of the end portions can be simultaneously inserted into the die 60. The number of radially movable punches 64 will also correspond to the number of pairs of end portions 31 so that all of the end portions are simultaneously cold formed to the configuration illustrated in Figure 10. When the end portions 31 have all been preformed, in a manner that has been described, they will extend substantially parallel to the longitudinal axis of the shaft 22. In order that the formed upper and lower end portions 31A and 31B will have sufficient clearance with the internal surfaces of the slots 44 so that they can pass through the slots 44 of risers 42, when the commutator 36 is axially assembled to the shaft 22, it is desirable that the end portions be spread or bent from the position illustrated in Figure 7 to the position illustrated in Figures 8 and 9. In order to bend the end portions 31 simultaneously outwardly away from the shaft 22 a (metallic) retaining tube 70 is slipped over the armature 20 and the armature conductors 30 to the position illustrated in Figure 7. A forming or spreading tool 72, is then moved toward the upper and lower ends 31A and 31B. The forming tool 72 has a plurality of slots 72A corresponding in number to the pairs of end portions 31. The inner surface of the slots 72A each have an inclined surface 72B. When the forming tool 72 is moved toward the upper and lower end portions 31A and 31B the inclined surfaces 72B engage the lower end portions 31B and the upper and lower end portions 31A and 31B are then bent outwardly to the position illustrated in Figure 8. An inner edge of the retaining tube 70 operates as a fulcrum during this bending or spreading operation. It is to be understood that all of the end portions 31 of the entire armature winding are simultaneously bent or spread outwardly. After the end portions 31 of the armature conductors 30 have been spread or bent outwardly the commutator 36 is assembled to the shaft 22 by pushing the commutator onto the shaft such that the tubular core 38 engages the outer surface of the shaft. As the commutator 36 is pushed onto the shaft 22 the formed and outwardly spread or bent, upper and lower end portions 31A and 31B will pass through the respective slots 44 in the risers 42. The commutator 36 is so rotatably oriented relative to the shaft 22 that the upper and lower end portions 31A and 31B are aligned with the slots 44. It can be seen, from Figure 9, that due to the fact that the upper and lower end portions 31A and 31B have been bent outwardly there is clearance between them and the internal surfaces of the slot 44. It also can be seen, from Figures 8 and 9, that a portion of lower end portion 31B is located entirely within slot 44 whereas a portion of the upper end portion 31A is located within the upper end of the slot 44. The final axially assembled position of the commutator 36 is illustrated in Figures 8 and 9. It can be seen from Figure 8 that the formed upper and lower end portions 31A and 31B extend through a slot 44 and the pointed ends 33 are located to the left of front end faces 42C. When the commutator 36 has been pushed onto the shaft 22 to its final assembled position, and with portions of the upper and lower end portions 31A and 31B located within the slots 44, the upper and lower end portions 31A and 31B are pushed into a slot 44. This is accomplished by the push-in blade 66 which is radially movable and illustrated in Figure 10. The front to back length of this push-in blade 66 is about the same as the axial length of a slot 44. As the push-in blade 66 is moved radially inwardly it will engage the flat planar surface 31C of upper end portion 31A and push the upper and lower end portions 31A and 31B from the Figure 9 position to the Figure 10 position. The Figure 10 position of upper and lower end portions 31A and 31B is a position in which the tapered flat planar surfaces 31F and 31G and 31E and 31H just make contact respectively with the internal side walls or surfaces 46 and 48 of the slot 44. As the push-in blade 66 continues to move inwardly it will force the upper and lower end portions 31A and 31B from the Figure 10 position to the Figure 11 position in which the flat planar surface 31K of lower end portion 31B has bottomed out on the flat inner surface 50 of the slot 44. As the upper and lower end portions 31A and 31B are moved from the Figure 10 position to the Figure 11 position the rubbing or scrubbing contact between the tapered surfaces of the end portions and the internal side walls or surfaces 46,48 of the slot 44 provide a scrubbing action which cleans any oxidation or other material from these surfaces. This provides bright, shiny, clean surfaces. When the end portions 31 are moved from the Figure 10 position to the Figure 11 position they have an interference fit with the internal side walls or surfaces 46,48 of the slot 44. As a result, when the end portions 31 have been moved to the Figure 11 position there is an interference fit between the tapered flat planar surfaces 31E, 31F, 31G, 31H of the upper and lower end portions 31A, 31B and the internal side walls or surfaces 46,48 of the slot 44 which locks the end portions 31 in position in the risers 42. The apparatus for pushing upper and lower end portions 31A and 31B into the respective slots 44 preferably includes a plurality of push-in blades 66 equal in number to the number of pairs of formed upper and lower end portions so that all of the upper and lower end portions are simultaneously pushed into all of the slots of the commutator 36. When the end portions 31 have all been pushed into the slots 44, portions of the risers 42 adjacent the slots are staked into engagement with the flat planar surface 31C of upper end portion 31A. This is accomplished by apparatus, which is illustrated in Figure 12, that includes a staking tool 74 which is radially movable and which has a curved end 76. When the staking tool 74 is moved toward a riser 42 it strips or peels portions 42E and 42F from the riser 42 and moves these portions into engagement with the flat planar surface 31C of upper end portion 31A, as illustrated in Figure 13. The axial length of staking tool 74 can be such that it does not stake over the entire axial length of a riser 42 between front and rear end faces 42C and 42D. Thus, one edge of the staking tool 74 can be spaced inwardly slightly from the front end face 42C during the staking operation so that a radial wall, that includes front end face 42C of about 0.2 mm thick, is not staked over. The staking tool 74 may also be of such a length that a radial wall of a thickness less than 0.2 mm, that includes rear end face 42D, is not staked over. In general, the staking tool 74 stakes over substantially the entire length of a riser 42. The reason for not staking over the entire length of a riser 42 is that the force required for the staking operation is reduced. If desired, the entire length of the riser 42 may be staked over. In the final formed condition of Figure 13, virtually all exposed sides of the upper and lower end portions 31A and 31B are tightly engaged by the material of the riser 42 so that there is intimate electrical contact between the flat planar surfaces 31D to 31K of the formed upper and lower end portions 31A and 31B and the internal side walls or surfaces 46,48 of slot 44 and between flat planar surface 31C and the internal surfaces of staked over portions 42E and 42F. It is preferred that a plurality of staking tools 74 be provided that are equal in number to the number of slots 44 of the commutator 36. The staking tools 74 are suitably supported for radial movement by apparatus, which has not been illustrated, and the staking tools are all moved simultaneously inwardly to thereby simultaneously stake all of the risers 42. When all of the end portions 31 have been connected to the commutator 36, in a manner that has been described, the commutator is machined off to remove the ribs 40A to provide a smooth outside surface for the commutator. In addition the portions of upper and lower end portions 31A and 31B, that extend beyond the front end faces 42C of the riser 42, are machined off. The armature 20 preferably includes three turn banding 80,82 for retaining the armature conductors 30 in the slots 26B against the effects of centrifugal force. This three turn banding 80,82 comprises, for example, three turns of glass roving which is impregnated with a suitable material such as an epoxy resin. The three turn banding 80 is disposed closely adjacent the rear end faces 42D of the risers 42 and engages the armature conductors 30 at this point. The other three turn banding 82 is located adjacent the insulator 56 and also engages the outer periphery of the armature conductors 30. At the expense of some reiteration, the following sets forth the sequence of process steps that are utilized to connect the armature conductors 30 to the slots 44. 1. The end portions 31 of the armature conductors 30 are formed into a wedge-shaped or tapered configuration by the punch and die apparatus 60-64 illustrated in Figure 6. 2. The formed upper and lower end portions 31A,31B of the armature conductors 30 are preferably spread or bent outwardly. 3. A commutator 36 is assembled to the shaft 22 and as it is pushed onto the shaft to its final assembled position, the outwardly bent and formed upper and lower end portions 31A, 31B pass through the slots 44 in the risers 42. 4. The formed upper and lower end portions 31A, 31B are pushed into the slots 44. 5. The top edges of the slots 44 are staked into engagement with the upper end portion 31A. 6. The portions of the armature conductors 30 that extend beyond the front end faces 42C of the risers are machined off as well as the ribs 40A of the risers. By way of example, and not by way of limitation, the following are dimensions (millimeters) of the formed upper and lower end portions 31A, 31B and the risers 42 and slots 44 that can be used in practising this invention where the sides of the formed upper and lower end portions and internal side walls or surfaces 46 and 48 have a 3° taper. In addition to the foregoing, the dimension between the internal side walls or surfaces 46 and 48 and respective side walls or surfaces 42A and 42B of a riser 42 is about 1.77 mm when measured at the outer circumference of the risers. When the upper and lower end portions 31A and 31B are in their bent out or spread out positions, shown in Figures 8 and 9, there will be a clearance of about 0.075 mm between the tapered flat planar surfaces 31E-31H of the end portions 31 and internal side walls or surfaces 46 and 48 of a slot 44. This clearance is sufficient to allow the formed upper and lower end portions to pass through the slots 44 when the commutator 36 is pushed onto the shaft 22. As previously mentioned, Figure 10 illustrates the position of the formed upper and lower end portions 31A, 31B where they have been pushed into a slot 44 to such a depth that the tapered flat planar surfaces 31E to 31H of the end portions 31 just come into contact with the complementary internal side walls or surfaces 46 and 48. When the end portions 31 are pushed all the way into a slot 44, as illustrated in Figure 11, there is an interference fit between the flat planar surfaces 31E to 31H of the end portions 31 and internal side walls or surfaces 46 and 48 of about 0.14 mm at each side of the end portion 31. At the expense of some reiteration, it is noted that when the formed upper and lower end portions 31A and 31B are moved from the Figure 9 position to the Figure 11 position a scrubbing action will begin to occur between the flat planar surfaces 31E-31H of the end portions 31 and internal side wall or surfaces 46 and 48 as soon as these surfaces become engaged, as illustrated in Figure 10. As the armature conductors 30 are moved from the Figure 10 position to the bottomed-out Figure 11 position the tapered flat planar surfaces 31E-31H of the end portion 31 are scrubbed against the internal side walls or surfaces 46 and 48. The radial length of movement of the armature conductors 30, from the Figure 10 to the Figure 11 position, can be about 2.55 mm when using the previously described dimensions and the scrubbing action takes place during the entire length of this movement. This scrubbing action of the engaged surfaces causes the surfaces to be wiped clean with the result that there is a good intimate copper-to-copper electrical connection between the flat planar surfaces 31E-31H of the end portions 31 and the internal side walls or surfaces 46-48 that define the slot 44. This scrubbing action will wipe off any oxidation and the contacting surfaces become bright and shiny due to the scrubbing action. When the armature conductors 30 have been moved to the Figure 11 position, the tapered flat planar surfaces 31E-31H of the end portion 31 are fixed or locked to the internal side walls or surfaces 46 and 48. This is due to the interference fit between the parts. Putting it another way, the end portions 31 are wedged into the slots 44 so that parts are locked together in what may be termed a taper-lock connection. The interference fit begins at the Figure 10 position of the end portions 31 and the amount of interference progressively increases as the end portions are moved from the Figure 10 position to the Figure 11 position. After the risers 42 have been staked, as illustrated in Figure 13, and the ends of the armature conductors 30 and the front end faces 42C have been machined off, the line joining the flat planar surfaces 31E-31H of the end portions 31 and the internal side walls or surfaces 46,48 of the slots 44 is virtually imperceptible to the naked eye. Further, the flat planar surfaces 31D and 31J are tightly engaged so that a line representing these engaged surfaces is virtually imperceptible. Thus, after final machining, the front end faces 42C of the risers 42 appear as solid planar substantially unbroken copper surfaces. In the description of this invention, it has been pointed out that the formed upper and lower end portions 31A, 31B are pushed entirely into the slots 44, as illustrated in Figure 11, such that flat planar surface 31K bottoms-out against flat inner surface 50. It is not necessary, in practicing this invention, that the flat planar surface 31K be pushed against flat inner surface 50. Thus, the armature conductors 30 may be pushed into a slot 44 to such a depth that there would be some clearance between flat planar surface 31K and flat inner surface 50 as long as the dimensions of the parts and the taper of the engaged surfaces 31E-31H, 46, 48 are such that a scrubbing action will occur and such that there is ultimately an interference fit between the parts. If the depth of the slot 44 is made long enough and if the armature conductors 30 are pushed into the slot to such a depth that the flat planar surface 31K has some clearance with flat inner surface 50 it is believed that some cold welding will be experienced between the engaged surfaces 31E-31H, 46, 48. In the description of this invention a commutator 36 of the so-called moulded type has been described. The connecting method of this invention is applicable to commutators 36 that are not of the moulded type, for example a type of commutator that uses copper segments and V-rings with separate strips of insulation between the segments. In the description of this invention it was pointed out that the internal side walls or surfaces 46,48 and the flat planar surfaces 31E-31H of the armature conductors 30 have a taper of 3°. The amount of taper may vary within limits and may be, for example 2°. The included angle, where a 2° taper is used, would of course be 4°. The taper angle is limited by the width of a riser 42 and should not be so large as to lose the scrubbing action or the ability of the armature conductors 30 to be fixed or locked to the riser when it is pushed into the slot 44. When all of the armature conductors 30 have been connected to the commutator 36 the armature 20 can be rolled in a liquid varnish which subsequently dries or cures to thereby impregnate the armature with varnish. Following this, the commutator 36 can be subjected to a final machining operation. It is pointed out that the connecting method of this invention does not utilize hot staking of a type wherein current carrying electrodes engage a commutator bar and cause current to flow through a portion of the riser 42 and armature conductor 30 to heat these parts to a temperature that softens the parts to a condition where they can be deformed or staked by one of the current carrying electrodes. By not using hot staking or any other form of applied heat this invention has the advantage of not subjecting the commutator 36 to high temperature. Further, by not using hot staking this invention eliminates the need for current carrying electrodes and the power supply for these electrodes and other apparatus that is required when hot staking is employed.

Claims: A method of connecting an end portion (31) of an armature conductor (30) of an armature (20) to a riser (42) of a commutator (36), the method being characterised by the steps of forming the end portion (31) of the armature conductor (30) into a generally wedged-shaped configuration such that opposed side faces (31E-31H) of the formed end portion are tapered; positioning the riser (42) which has a slot (44) that is defined by opposed internal surfaces (46,48) that are tapered and complementary to the opposed side faces of the formed end portion such that the open end of the slot is aligned with the formed end portion; forcing the formed end portion into the slot to such a depth that there is an interference fit between the opposed side faces of the formed end portion and the internal surfaces of the slot whereby the formed end portion is taper locked to the internal surfaces of the slot; and then staking portions (42E,42F) of the riser located adjacent the outer end of the slot into engagement with the formed end portion. A method as claimed in Claim 1, characterised in that the forcing step comprises pushing the formed end portion (31) into the slot (44), the taper of the opposed side faces (31E-31H) of the formed end portion and the taper of the internal surfaces (46,48) of the slot being such that as the formed end portion is pushed into the slot the internal surfaces of the slot and the opposed side faces of the formed end portion just become engaged at a first pushed-in position of the formed end portion, the formed end portion being pushed radially inwardly from the first position to a second position, the engaged opposed side faces and internal surfaces having an interference fit as the formed end portion is pushed in from the first position to the second position, the opposed side faces of the formed end portion scrubbing against the internal surfaces of the slot when the formed end portion is pushed from the first position to the second position, the formed end portion being locked to the internal surfaces of the slot when the formed end portion has been pushed to the second position. A method as claimed in Claim 1 or Claim 2 for connecting the end portions (31) of upper and lower armature conductors (30) to the riser (42) characterised in that the forcing step forces the formed end portions into the slot (44) to such a depth that a lower surface (31K) of the formed end portion of the lower armature conductor engages a bottom surface (50) of the slot. A method as claimed in any one of the preceding Claims, characterised in that formed end portion or portions (31) is or are at least partially disposed within the slot (44) during the positioning step. A method as claimed in Claim 3 or Claim 4 characterised in that one of the formed end portions (31B) is disposed entirely within the slot (44) and the other formed end portion (31A) is disposed at least partially within the slot during the positioning step. A method as claimed in any one of Claims 3 to 5, characterised in that the formed end portions (31) are simultaneously pushed into the slot (44) during the forcing step. A method as claimed in any one of the preceding Claims in which the armature (20) includes a shaft (22) and a core (26), the method being characterised by the step of bending the end portion or portions (31) of the armature conductor (30) away from the shaft by an amount that will provide clearance between the opposed side faces (31E-31H) of the end portion or portions and the internal surfaces (46,48) of the slot during the positioning step. A connection for at least one armature conductor (30) to the riser (42) of a commutator (36) for an armature (20) of a dynamoelectric machine in which the riser has a radially extending slot (44), and the at least one armature conductor has an end portion (31) thereof located within the slot, the riser having an integral portion (42E,42F) engaging a surface (31C) of the end portion of the armature conductor adjacent the outer periphery of the riser, characterised in that the slot (44) has opposed surfaces (46,48) which taper outwardly, and the end portion (31) has opposed tapered surfaces (31E-31H) that tightly engage the internal surfaces of the slot, the engaged tapered surfaces of the end portion of the armature conductor and the internal surfaces of the slot having an interference fit. A connection as claimed in Claim 8 comprising an upper and a lower armature conductor (30) located within the slot (44), characterised in that the end portion (31A) of the upper armature conductor having a lower flat surface (31D) and the end portion (31B) of the lower armature conductor having an upper flat surface (31J), the flat surfaces being parallel to each other and tightly engaged throughout their width. A connection as claimed in Claim 9, characterised in that the slot (44) defines a bottom flat surface (50) the end portion (31B) of the lower armature conductor (30) having a lower flat surface (31K), the lower flat surface tightly engaging the bottom flat surface of the slot.

Inventors: LEECH, HOWARD EUGENE, PAHLS, TERRY JOHN
Applicants: GENERAL MOTORS CORPORATION
Application year: 1986
Main classification: H01R39
IPC codes: H02K13, H01R39