US2600312A - Commutator for dynamoelectric machines - Google Patents

Description

June 10, 1952 Q. R:MEIER COMMUTATOR FOR DYNAMOELECTRIG MACHINES Filed July 6, 1950 l atented June 10, 1952 oomiwmr FOR DYNAMQEPEQERIC MACHINES Donald R. Meier, Erie, Pa., assignor to General I ElectricCoinpany, acorpora'tion of NewYork Ahmiem w s 1950, annew.

1 This invention relates to commutators for dynamo electric: machines and more particularly to a commutator construction wherein the commutator segments are insulated and encasedby amass of molded resinous insulating material to form a unitary structure. This invention also relatesto themethod of making such a commutator.

The problem the design of co nmutators is to hold a lurality of commutatorjbars in a circle with extreme accuracy. These commutator bars must heheld inan elastic systemto allow for movement due to thermal and centrifugal forces. This system must allow the bars to move under the stresses involved, but with a minimumof misalignment betweenhars as a result ofthemotion. In conventional commutator constructions, the bars are normallysupported at theirends only so that eachbar is ineff ct a beam supported at its ends. .This fact places a limitation on the length of conventional commuta'tors due to' the lack of supportat'the center of the bars. The barsmustnormallyjbe clamped in away which permit-stile pressure with which they areheld to be adjusted. Furthermore, the bars must-be prestressed by thesupports which must be insulated fromithe bars; yet the stress'on thesup-ports must not exceed the elastic limit of 'thefmate'ria'ls'. Usually, a pair of Viclamplringsengage V-shaped slotsat theends of, thebars, however, this method of vsur'ipo'rt produces allowing of theloars outwardly at the v( renterandthe overhanging portions of the bars beyond the clamping rings also tend to bow outwardly. 7

An objectof this invention is toprovide an improved commutator constructionl" Anotherobjec't of this invention is toprovidean improved method of making a commutator.

A further object of this invention is toprovide an improved commutator construction wherein the commutator bars are insulated and held "in' a unitary structure biy a mass of 'resinous rnolded insulating material.

Y n th rn iect o t i invent n i .1?!- vide an improved commutator. construction in high the support tor the commutator bars isdistributes, over their length.

,Further objects and vadvantages of this invention will become apparent and the invention will he betterunderstood from the following description-referring to the accompanying drawing; and the features of novelty which characterize this invention will be pointed out with particularity in the claims 'annexedto and forming a part of this specification. r Y

3 Claims. (01. via-s21) In accordance with one aspect of this invention, there is'provided a commutator construction comprising a plurality' of evenly spaced commutator bars, each of the bars having one or more transverse openings 2 formed therein. These transverse openings are arrangedin circumferential alignment and an annular ring is arranged in each opening. A mass of molded resinous'insulating material -fills the spaces between the bars and the-"portion of the' bar openings'un occupied by the annular -ring,'-'thus' forming a unitary structure. Apair of --'moun ting members are provided adapted to hesecured to a s'h'aftan'd respectively engaging the ends of the'j-molded structure; Means are provided for clamping the two'mounting members. together so that the commutator structure tightly engaged and the mounting members may be provided with openings thereinin order to admit ventilating airto the interior of the armaturecore; Furthermore, one of the mounting members may be slightly elastic to allow for axial expansion of the struc- -This type of commutator is constructed by providing a splitannular ring anda plurality of commutator 'bars, each having a transverse opening formed therein." The bars are assembledo'n the annular ring, by means of the transverse open ings, and means are provided to insulate the ring from the bars. The' 'ends of the ring are new joined; 'as 'bybrazingandthe ring with the bars bars. QThe inner-surfaces of the bars are provided with a slight taper and afterarra-ngement and spacing in the mold, a taperedplug is inserted'in; the centra'l opening formed by the bars tde'xpand the 'bars' against' the annular r'ing. Resinous molding material is "then' introduced into the inoldso as to 'fill'the spaces between the bars and the portion of the'transverse bar openings unoccupied by the annular ring." Thismaterial is then hardened in iunsuitable manner. The Plus is then removed and the-mold disassembled waving the r'esultantun'itary commutator structure. The structuremaythen be mounted on an arbor and theexterior surface fof the hars-suitahli mafliined;

Referring now to the drawing, Fig. 1 is a side elevational View, partly in section, il1ustrating the improved commutator construction of this 'i nvention; Fig. 2 isacross-sectional view taken alongthe line 2 -2 of Fig. 1; Figs; 3,4; 5 a nd 6 illustrate the method'of making the improved commutator construction or this inventidny'ana more transverse openings 3 formed therein. Each 1 bar is also provided with a slight taper 4 on its inner surface, for reasons which will be hereinafter described. The openings 3 are arranged in circumferential alignment and an annular ring 5 is arranged therein, the ring 5 being suitably insulated from the bars I by insulation 6. A mass of molded resinous insulating material fills these spaces between the bars I, as at I, and the portion of the bar openings 3 unoccupied by the bars 5, as at 8. This provides the insulation between the bars and joins the bars I and rings 5 to form a complete unitary structure.

In order to mount the molded commutator structure thus far described on a shaft, a pair of mounting members 9 and IE! are provided adapted to be secured to the shaft II in any suitable manner. These mounting members 9 and I engage the ends of the bars I and are insulated therefrom by suitable cones I2 and I3. The mounting members 9 and I0 are clamped together by bolts I4 (only one of which is shown) in order to tightly grip the molded commutator structure and may be provided with a plurality of suitable openings I5 therein in order to admit ventilating air to the interior of the armature core (not shown). The web section I6 of the mounting member I9 may be formed so as to have some elasticity in order to permit axial expansion of the commutator structure.

In the construction of the commutator of Figs. I

1 and 2, a plurality of bars I is provided, each having one or more transverse openings 3 formed therein. A split annular ring 5 is provided and the bars I are assembled on the ring 5 by means of the transverse openin s 3. For this assembly operation, the ends of the ring 5 are separated, as shown at I! in Fig. 5. The annular ring 5 may be pre-insulated as at 6 by suitable continuous insulation surrounding the entire ring except the ends II. may be provided on the inner circumferential surface of the ring 5 only, as shown at I8 in Fig. 7. In this case, the insulation I8 could be applied to the inner surface of the ring 5 by a suitable adhesive. After the bars I have been assembled on the ring 5, the ends I! are joined and connected together in any suitable manner, as by brazing as shown at I9 in Fig. 6. The ends I! are then insulated as at 20. The ring and bar assembly is then inserted in a suitable mold 2I having a cavity portion 22 and a cap portion 23 secured to the cavity portion 22 in any suitable manner, as by bolts 24. The cavity portion 22 and the cap portion 23 may be provided with suitable spacing veins 25 and 25 respectively for spacing the commutator bars I, or the bar may be spaced in any other suitable manner. A tapered plug 21 is then inserted in the central opening formed by the commutator bars I and, mating with the tapered surface 4 on the inner surfaces of the bars I, expands the bars I outwardly against the rings 5. Mold seals 28, formed of suitable material such as rubber, are seated in grooves in the mold portions 2| and 23 and press against the plug 21.

Alternatively, insulation After the mold 2I has been assembled with the ring and bar assembly therein and the plug 21 inserted in the central opening, a suitable resinous molding material is introduced into the mold filling the spaces between the bars I and the portion of the openings 3 unoccupied by the bars 5. The molding material is then hardened in any suitable manner, the plug 21 is removed, and the resultant unitary structure is then removed from the mold 2|.

The resinous molding material used in the construction of this commutator may be a suit able casting resin which will harden under the influence of heat or through an oxidation medium. Such resinous casting materials may include copolymers of styrene and other copolymerizable materials for example styrene and an unsaturated alkyd resin, styrene and a cross linking agent for example divinyl benzene, or styrene and dialkyl phthalate, etc. It will be also readily understood that the improved commutator construction of this invention could be injection molded for example with such plastic materials as chloro-trifluoroethylene or tetrafluoroethylene, etc. The structure could also be pressure molded with a suitable phenolic resin or a silicone resin, etc. The resinous molding materials pointed out above are, of course, only examples of many resins well known in the art and it will be readily understood that any suitable resinous molding material or process may be utilized. It will also be readily understood that the ring 5 may be circular in cross section, for instance in the form of steel wire, or may have any other suitable cross-sectional shape.

It will now be readily apparent that this improved commutator construction and method produces a superior commutator design wherein the initial stresses are considerably lower than in a conventional commutator construction. Furthermore, in this construction the bar loading is more uniform along its entire length and is divided over any appropriate number of rings, whereas in conventional commutators, as indicated above, the load is taken at each end of the bar. In this construction, the bar deflections will be more uniform along the length of the bar. Axial expansion can take place in this improved commutator with practically no restriction since the supporting shell need only be strong enough to center the commutator when running and to take torsional vibration. In conventional commutators, however, the bound-up pressure may double with an increase in temperature of C. because of the greater coefficient of expansion of copper bars as compared with the steel supports. A cost saving is effected in this construction since the copper stresses are low and hence silver bearing copper bars are not required. A large moment of inertia is not required in the mounting members 9 and I0 and therefore they may be of small section effecting a considerable saving in length. During the assembly, as described above, the bars I are squeezed outwardly against the insulation 6 under ring 5 by the tapered plug 21. The squeezing pressure may be several times the normal centrifugal force so that the bars will be firmly seated without spinning the commutator. Furthermore, this squeezing action tests the rings 5 for mechanical strength so that there need be no subsequent fear of bursting during operation. An additional purpose of this squeezing action is to expand the rings 5 and therefore the space between adjacent segments during the molding period. When this is done, arch pressure will be created between the commutator segments when the tapered plug is removed. This arch pressure, in effect, preloads the rings 5 and thereafter, the expansion of the rings due to centrifugal force will be less than if arch pressure had not been introduced since when the rings expand there is a decrease in arch pressure tending to subtract from the increment of centrifugal load applied. This construction also provides more available space for ventilating air under the commutator since the depth of the bars may be decreased, which also effects a further saving in material cost.

While I have illustrated and described a Particular embodiment of this invention, further modifications and embodiments will occur to those skilled in the art. I desire it to be understood, therefore, that this invention is not limited to the particular embodiments shown and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A commutator comprising a plurality of circumferentially arranged evenly spaced segments, each of said segments having a transverse passageway formed therein, said passageways of said segments being in circumferential alignment, an annular ring arranged in said passageways and engaging the inner walls thereof for supporting said segments, means for insulating said ring from said segments, a mass of molded resinous insulating material filling the spaces between said segments and the portions of said segment passageways unoccupied by said ring for binding said segments and said ring into a unitary structure, and mounting means engaging the inner surfaces of said segments and adapted to be mounted on a shaft.

2. A commutator comprising a plurality of circumferentially arranged evenly spaced segments, each of said segments having a transverse passageway formed therein, said passageways of said segments being in circumferential alignment, an annular ring arranged in said passageways and engaging the inner walls thereof for supporting said segments, means for insulating said ring from said segments, a mass of molded resinous insulating material filling the spaces between said segments and filling the portion of said segment passageways unoccupied by said ring for binding said segments and said ring into a unitary structure, a pair of mounting members adapted to be secured to a shaft and respectively engaging the inner surfaces and the ends of said segments, and means for clamping said mounting members whereby said segments are tightly gripped.

3. A commutator comprising a plurality of circumferentially arranged evenly spaced segments, each of said segments having a transverse passageway formed therein, said passageways of said segments being in circumferential alignment, an annular ring arranged in said passageways and engaging the inner walls thereof for supporting said segments, means for insulating said ring from said segments, a mass of molded resinous insulated material filling the spaces between said segments and the portion of said segment passageways unoccupied by said ring for binding said segment and said ring into a unitary structure, and a pair of mounting members respectively engaging the inner surfaces and the ends of said segments, said mounting members having annular web portions respectively adapted to be secured to a shaft, one of said web portions being more elastic than the other to allow for axial expansion of said structure.

DONALD R. MEIER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 523,140 Dennison July 17, 1894 745,336 Emmet Dec. 1, 1903 996,895 Sutton July 4, 1911 1,017,945 Allen Feb. 20, 1912 1,430,866 Varley Oct. 3, 1922 1,506,756 Kempton Sept. 2, 1924 1,736,988 Tupper Nov. 26, 1929 2,477,455 Hinchliir July 26, 1949 FOREIGN PATENTS Number Country Date 468,616 Great Britain July 8, 1937 477,251 Great Britain Dec. 24, 1937

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