An assembled commutator

Abstract: An assembled commutator has a segment support portion (1) and a housing portion (6). The housing portion has housings (7) formed with axially extending "T"-shaped recesses (89) and transversely extending slots (10) for receiving armature leads (11). Insulation displacing terminals (12) are inserted in the "T"-shaped recesses (89) and formed with slots (27) which cooperate with the transversely extending housing slots (10) to grip and contact the armature leads (11). The terminals (12) are held in place by commutator segments (3). Each segment (3) has a retainer (5) with two prongs (13), which straddle a terminal (12), and convergent sides which cooperate with the sides of an inner, circumferentially extending portion (8) of a "T"-shaped recess (89) to grip the terminal (12) as the retainer (5) is pressed axially into the "T"-shaped recess (89).

Description: Field of the Invention The invention relates to an assembled commutator in which, in contrast to a moulded commutator in which the metal components are inserts in the moulded insulating base of the commutator, the base of the commutator and the metal components are formed separately and then assembled together. In particular, the invention relates to an assembled commutator provided with insulation displacing terminals for connection to the armature leads which, on engagement with the leads, slice through the insulation provided on the leads and into the surfaces of the conductive wire cores of the leads. Background Art European Patent Specification No. 0 106 444 discloses an assembled commutator, such as this, comprising an insulating cylindrical portion having an outer support surface; at least three commutator segments, each having an arcuate brush contact portion seated on the support surface; an insulating housing portion having at least three housings respectively formed with axially extending recesses and with positioning means for armature leads; and at least three slotted insulation displacing terminals respectively disposed in the recesses so as to cooperate respectively with the positioning means to make electrical contact with the armature leads. In this form of construction, the commutator segments are formed integral with the terminals and these composite components and the commutator base comprising the insulating cylindrical and housing portions are shaped so that each of the composite components can be positioned on the commutator base in a single translational movement in which the composite component is moved relative to the commutator base and in which cutting edges provided on the terminals of the composite components slice through insulation provided on the armature leads and into the conductive wire cores of these leads. Although this form of construction permits automated assembly of the commutator, the necessary simultaneous alignment of different parts of the composite components with associated parts of the commutator base involves some difficulty. Moreover, because the arcuate portions of the commutator segments are required to make good electrical contact with the brushes of an electric motor whereas the terminals are required to cut through insulation and the outer surfaces of armature lead wires, it is not always easy to provide a composite component of material having optimal properties for both of these purposes. Additionally, for a similar size rotor for a similar motor but using a different size wire for the armature winding, requires a different housing and a different set of segments in order to vary the size of the insulation displacing slots to accommodate the different size wire. Disclosure of the Invention It is the purpose of the present invention to provide an assembled commutator in which these difficulties encountered with known assembled commutators are, at least to some extent, overcome. This is achieved by providing an assembled commutator in which each commutator segment has a retainer extending axially from one end of the brush contact portion into a respective one of the recesses and physically contacting with the terminal disposed therein to provide electrical connections between the armature leads and respective commutator segments. Thus, according to the invention, there is provided an assembled commutator comprising a segment contact portion having an outer support surface; at least three commutator segments each having a brush contact portion seated on the outer support surface and a retainer extending axially from one end of the brush contact portion; a housing portion having at least three housings respectively formed with axially extending recesses respectively accommodating the retainers, and with positioning means for armature leads; and at least three, separate, slotted, insulation displacing, terminals respectively connected to the retainers, respectively disposed in the recesses and cooperating with the positioning means to electrically connect the armature leads to respective commutator segments. With this form of construction, the terminals may be inserted in the recesses in one operation and the retainers of the commutator segments may be inserted in the recesses in a subsequent operation. This not only simplifies assembly, it permits more care to be taken to ensure proper insulation displacement during insertion of the terminals into the recesses. In a preferred embodiment, the commutator segments and the terminals are of different materials. Thus, for example, the commutator segments may be made of copper for good conductivity, whereas the terminals may be made from brass, which is harder than copper, to provide good cutting edges for insulation displacement and cutting engagement with the outer surfaces of the wire cores of armature leads. The retainers, recesses and terminals may be so shaped that on axial insertion of the retainers into respective recesses, the retainers are pressed transversely into engagement with respective terminals. According to one form of construction, the terminals comprise laminate elements respectively disposed in angularly-spaced radial planes, the retainers comprise forked members with prongs which straddle respective terminals, and each retainer tapers so that, on axial insertion of the retainers into respective recesses, the prongs of each retainer are pressed together to clamp the terminal which they straddle. Alternatively, or in addition, the part of each recess which receives the retainer may also be tapered to provide the clamping effect. However, constructions such as this can be difficult to mould and so it is preferred to provide the "clamping" tapers solely on the retainers. In this case, each prong is preferably formed with a barb which engages the recess in which the retainer is disposed and each prong tapers from the barb. To facilitate manufacture, each terminal is preferably formed from a single piece of stamped and folded sheet material, because it is easier to stamp the thinner sheet metal, even though the shear cut is twice as long. This is of particular importance when cutting slots for engagement with small diameter wires because the thickness of the sheet metal preferably should be less than the width of the slots being stamped in the sheet metal. Although the segment support portion and the housing portion may comprise integral parts of a commutator base, difficulty is encountered in moulding this relatively bulky and complicated component and so it is preferred that the segment support portion and the housing portion are formed as separate elements which are subsequently interconnected. With this form of construction, it is therefore possible to fit the housing portion of the commutator to the armature of an electric motor and to make electrical connections between the armature leads and the terminals before fitting the segment support portion, thus allowing more room for the insertion of the terminals into the recesses in the housing portion and thereby simplifying this operation. Another advantage of this construction of the invention is that the segments and the segment support portion can be made standard for a commutator having a particular number of segments with the housing portion (if need be) and the terminals being changed to accommodate armature windings of different size wire. At the same time, the terminals can be standardized for the same size armature winding wire regardless of the actual number of poles of the armature. It should be noted that the terminals may be fitted to the housings before or after the armature has been wound depending on the orientation of the terminals. However, post wind fitting is preferred as this gives greater reliability and mechanical protection to the connection between the terminal and the armature lead. An embodiment of the invention is hereinafter described, by way of example only, with reference to the accompanying drawings. While the invention is described in relation to a cylindrical commutator, it should be realized that the invention is equally applicable to face plate or planar commutators. Brief Description of the Drawings Figures 1 and 2 are an axial end elevation and a sectional side elevation of a housing portion of an assembled cylindrical commutator according to the invention; Figures 3 and 4 are schematic isometric views of a cylindrical segment support portion of an assembled commutator in relation to a housing portion, as shown in Figures 1 and 2, at two different stages in the assembly of the commutator with the housing portion shown incomplete for clarity; Figure 5 is a schematic isometric view similar to Figure 4 but showing a terminal fitted and a commutator segment positioned for assembly with the cylindrical and housing portions; Figure 6 is a blank, stamped from a sheet of brass, for use in forming a terminal as shown in Figure 5; Figures 7 and 8 are side and end elevations of a terminal formed from the blank shown in Figure 6; and Figures 9 and 10 are schematic isometric views of a commutator segment and a terminal before and after assembly of the commutator segment with the terminal with the cylindrical and housing portions removed for clarify. Detailed Description of Preferred Embodiment As shown in Figures 1 and 2, a circular housing portion 6 comprises a hub 14 supporting an annular ring 15 with twelve radial projections 16 which, together with the annular ring 15, form twelve housings 7 which each enclose an "T"-shaped recess 89 having an inner, circumferentially extending portion 8 and an outer radially extending portion 9. The radial projection 16 of each housing 7 is formed with two transversely extending slots 10, separated by a divider 17, which serve as positioning means for positioning armature leads 11 (only two of which are shown in Figure 1) relative to the housing 7. In assembling an electric motor, a housing portion 6 (only partly shown in Figures 3 to 5) is mounted on the shaft of the motor, adjacent the armature, and secured in place by glue or some other fastening means. A cylindrical segment support portion 1 is then connected to the housing portion 6 by means of an axially extending connector 18 which is received by the annular ring 15, as shown in Figures 3 and 4. The housing portion 6 is also formed with three equiangularly-spaced projections 19 extending both radially and axially into complementary recesses 20 formed in the cylindrical portion 1 to key the cylindrical portion 1 and housing portion 6 together. Each commutator segment 3 is stamped from copper sheet, typically 0.8mm thick, and, as shown in Figures 5, 9 and 10, has an arcuate portion 4 seated on the outer support surface 2 of the cylindrical portion 1, a retainer 5 at one end of the arcuate portion 4, and a hook having a radially inwardly extending portion 21 and an axially extending portion 22 at the other end. These hook portions 21,22 are received within twelve circumferentially-spaced spaced radially-extending notches 23 formed in the outer end 24 of the cylindrical portion 1 and within axially extending recesses 25 which communicate with the radially inner ends of the notches 23. After the cylindrical portion 1 has been fitted to the housing portion 6, as shown in Figures 3 and 4, terminals 12 are inserted in the outer, radially-extending portions 9 of the recesses 89 and extend across the inner, circumferentially-extending portions 8. Commutator segments 3 are then positioned on the outer support surface 2 of the cylindrical portion 1 and moved axially into their assembled positions as schematically illustrated in Figures 9 and 10. As shown in Figure 6, each terminal blank 26 is stamped from a thin sheet of brass, typically 0.5mm thick, and folded as shown in Figures 7 and 8 to form a two-layer terminal 12 having two slots 27, separated by a divider 28, and a barb 29 at its radially outer end for retaining engagement with the radially outer end of the recess 89 in which the terminal 12 is inserted. Each slot 27, typically 0.85mm wide, for accommodating a 1mm diameter armature lead 11, has a convergent mouth 30 and two sharp edges 31. During winding of the armature, armature leads 11 are placed across the face of the housings 7 and held in position by the transversely extending slots 10. The slots 10 and divider 17, of each housing 7, support at least one armature lead 11 while the terminal 12 is being inserted. During this operation, the sharp edges 31 slice through insulation on each lead 11 and into the outer layer of the wire core of the lead 11. The slots 27 and divider 28 in the terminal 12 then cooperate with the slots 10 and divider 17 to grip each of the leads 11 supported by the slots 10 and divider 17. As shown in Figures 9 and 10, each retainer 5 is a forked member having two prongs 13 which straddle a terminal 12 inserted in a recess 89 and are received in the inner, circumferentially-extending portion 8 of the recess 89. As shown, the outer edges of the prongs 13 are formed with barbs 14 and converge to provide a tapered retainer 5. Thus, when the prongs 13 are inserted into the inner recess portion 8, on opposite sides of the terminal 12, the tapering end of the retainer 5 cooperates with the substantially parallel side walls of the inner recess portion 8 to press the prongs 13 towards each other, to clamp the radially inner end of the terminal 12. At the same time, the barbs 14 bite into these side walls and so resist axial removal of the commutator segment 3. The terminal 12 is therefore securely held in place by the barb 29, at its radially outer end, and by the barbs 14 on the prongs 13, at the other end. A similar barb, not shown, can also be provided on the free end of each axially extending hook portion 22, for locking engagement with the internal surface of an axially extending recess 25.

Claims: An assembled commutator comprising: a segment support portion (1) having an outer support surface (2); at least three commutator segments (3), each having a brush contact portion (4) seated on the support surface (2); a housing portion (6) having at least three housings (7) respectively formed with axially extending recesses (89) and with positioning means (10) for armature leads (11); and at least three separate slotted insulation displacing terminals (12) respectively disposed in the recesses (89) and cooperating with respective positioning means (10) to make electrical contact with the armature leads, characterized in that: each commutator segment (3) has a retainer (5) extending axially from one end of the brush contact portion (4) into a respective one of the recess (89) and physically contacting with the terminal disposed therein (12) to provide electrical connections between the armature leads (11) and respective commutator segments (3). A commutator, according to Claim 1, in which the commutator segments (3) and the terminals (12) are of different materials. A commutator, according to Claim 1 or Claim 2, characterized in that the retainers (5), recesses (89) and terminals (12) are so shaped that on axial insertion of the retainers (5) into respective recesses (89), the retainers (5) are pressed transversely into engagement with respective terminals (12). A commutator, according to Claim 3, characterized in that: the terminals (12) comprise laminate elements respectively disposed in angularly-spaced radial planes; the retainers (5) comprise forked members with prongs (13) which straddle respective terminals (12); and each retainer (5) tapers so that, on axial insertion of the retainers (5) into respective recesses (89), the prongs (13) of each retainer (5) are pressed together to clamp the terminal (12) which they straddle. A commutator, according to Claim 4, characterized in that each prong (13) is formed with a barb (14) which engages the recess (89) in which the retainer (5) is disposed and each prong tapers from the barb (14). A commutator, according to any preceding claim, wherein each terminal (12) is formed from a single piece of stamped and folded sheet metal. A commutator, according to any preceding claim, characterized in that the segment support portion (1) and the housing portion (6) are separate interconnected elements.

Inventors: HO SEUNG PUN, STROBL GEORG, HO, SEUNG PUN, STROBL, GEORG
Applicants: JOHNSON ELECTRIC SA, JOHNSON ELECTRIC S.A.
Application year: 1993
Main classification: H01R39
IPC codes: H01R43, H02K13, H01R39