US2221707A - Dynamoelectric machine - Google Patents

Description

NOV. 12, 1940. R, M HEENTE 2,221,707

DYNAMQELECTRC MCHNE Originali Filed Nov. 55, 193@ 2 Sheets-Sheet l Nov. 12, 1940. R. M. HEIN-rz DYNAMOELECTRIC MACHINE Original Filed Nov. 5, 1958 2 Sheets-Sheet 2 AC LOAD Razn/7 M. )Ve/)772 Patented Nov.v l2, 1940 UNITED STATES PATENT OFFICE Ralph M. Heintx, Montclair, N. J., assigner to Bendix Aviation Corporation, South Bend, Ind., a corporation of Delaware Original application November 5, 1938, Serial No. 239,091. Divided and this application May 27,

1939, Serial Nol 276,197

3 Claima- (Cl. 171-321) This invention relates to a combined starting and generating unit for use with internal combustion engines and capable of functioning, first, to start an internal combustion engine by application of torque thereto, and thereafter to convert the power developed in the engine into electrical energy available for radio transmission and other purposes requiring alternating current of high, low or intermediate frequency and/or potential.

An object of the invention is the provision of a dynamoelectric machine of novel construction permitting most advantageous use thereof for multiple purposes including, for example, the initial "turning over," or cranking, of an internal combustion engine, and the subsequent generation oi' alternating current of high frequency, by conversion of mechanical energy transmitted thereto by way of said internal combustion en gine.

Among the novel features of the machine here- .in disclosed there is included that of a commutator adapted to be engaged by rotatable brushes, for transmission of current between the former and the latter at relatively low rotor speeds, the invention further including the concept of a novel method of manufacturing said commutator, and a novel mounting and mode of operation for said rotatable brushes, as a result whereof the said brushes remain in engagement with the commutator to feed low voltage direct current to the stator windings during the duration of the engine cranking operation, but move out of engagement and thereby discontinue such direct current ilow as soon as the engine crank shaft accelerates sufnciently to render further cranking unnecessary. Thereafter the stator serves solely as a supply of alternating current for outside points of distribution and consumption.

These and other objects and features of themvention will become apparent upon consideration of the following detailed description, and upon reference to the accompanying drawings illustrating the preferred embodiment of the invention. It is to be understood, however, that the drawings are illustrative only, and that the I'claims at the conclusion of the specification, rather than the drawings, measure the scope of the invention.

- In the drawings, wherein like reference char acters refer to like parts throughout the several views:

Fig. 1 is a longitudinal sectional view of a hous- "lll ing enclosing a machine embodying the invention, 'some of the enclosed parts being shown in section and some in elevation;

Fig, 2 is a diagram of the electrical connecvtions for the machine of Fig. l, and including a schematic representation of the speed responsive brush shifting means.

Fig. 3 is a view showing part of the commutator and one of the brushes disengaged therefrom (the engaged position being shown in Fis. l):

Fig. 4 is a view of the metallic annulus that eventually becomesthe commutator, as said annulus appears at an intermediate stage of manufacture;

Fig. 5 is a view of one of the insulating segments as it appears at the time of insertion into the metallic annulus of Fig. 4; and

Fig. 6 is a transverse view of a section of the completed commutator.

In the drawings reference character Il designates a source oi' direct current (battery, for example) and Il designates an alternating current receiving apparatus, such as radio transmitters, transformers, receivers, rectiilers. motors. etc., to which alternating current of high frequency may be supplied upon rotation, at relatively high speed, of an engine driven dynamoelectric machine whose rotor shaft i 2 is shown as directconnected to the crankshaft I3 of an internal combustion engine (not fully shown). Engines of a character adapted to drive high frequency alternators are commonly employed on aircraft as a power supply means for operation of electrical equipment of which the' 1units above enumerated may be taken as examples.

Buch aircraft installations ordinarily include a battery such as that shown at Il, charged sufflc/iently to energize the rotor and stator windings it and i1, respectively, for use as a starting motor in the initial cranking and acceleration of y the engine crank-shaft il to self-sustaining speed; Attainment of this normal running speed produces a centrifugal force of sufficient mag-V nitude to raise rotor brushes Il, Il, II, and 2l out of contact with commutator 23, whereupon `the passage of current therebetween is interrupted. Thereafter stator windings I1 serve 'solely as a source of alternating current, to be fed to the A. C. load il by way of multi-phase conductors 2l, 2l, and 2l.

of said brushes being in turn connected with collector ring 3l of positive polarity while the other two connect with collector ring Il of negative polarity. Brushes 3l. mounted in brush assemblies secured to the housing 4I by suitable means (of which that shown at 42 in Fig. 1 is an example) engage collector ring 34; while brushes I1, correspondingly mounted, engage collector ring 8l. Conductors and Il complete the connections from battery Il to the stationary brush sets, while a conductor 20 connects each of the rotating brushes Il to 2| with its corresponding collector ring.

As hereinabove indicated, the stationary commutator assembly is made in a novel manner. including (as a step in the process) the union of two annular metallic members 23 and 21, of which the former eventually becomes the segmented commutator, per se, while the latter is the supporting core that is eventually secured to the housing by suitable means 29. A molding compound 3l) is the uniting element for parts 23 and 21. the latter being provided. if desired, with compound receiving holes 41 to insure more complete union therebetween.

A preceding step in the process is to cut slots I (Fig. 4) extending part-way through the metallic annulus 23, and spaced around the inner periphery thereof, in accordance with a predetermined formula. to provide pockets for receipt of segments l (Fig. 5) of mica or equivalent insulating material. The annulus 23 (after union with core 21 in the manner above described) is machined down to finish shape (Fig. 6), in which process all metal located beyond (and, if desired, additional material within) the radially outermost part of the mica Segments 50 (see line Il, Fig, 4) is removed. thus exposing the mica edges to view, at the outer side, and likewise resulting in the creation of a corresponding number of spaced conducting segments to constitute the commutator. As shown each segment thereof has a nnal shape as indicated at I2 in Fig. 6, and each of said segments has now become electrically separate from every other metallic part.

By this process of fashioning the commutator segments in situ, and from a single piece of metal, there are eliminated all problems of accurate tltting and positioning of segments individually;

each segment is automatically caused to appear in its proper relative position, since all remain unshiftable from start to finish of the process.

In order to offset any tangling tendency, as between the conductors I! and the rotating brush assemblies, I provide radially extending ribs forming pockets 40 in the housing l I, along which pockets the conductors I are run, and to which they may be secured, thus preventing their dropping inwardly into contact with the brush assemblies il to 2l.4

This application is a division of my co,

pending application Serial No. 239,091 filed November 5, 1938.

What I claim is:

l. The method of making a commutator of the molded type, in which the successive conducting segments are fashioned out of a single metallic annulus, which method includes the steps of cutting slots at spaced angular intervals along the inner side of the metallic annulus, inserting sheets of insulation in said slots, uniting said sheet-containing annulus to a metallic cylindrical core by placing a molding compound therebetween and causing said compound to unite therewith, and thereafter removing all that part of the metallic annulus which is disposed beyond the reach of said insulating sheets.

2. A dynamoelectric machine having commutator segments having smooth outer surfaces for engagement with the commutator brushes and also having inner surfaces of corrugated contour, and a supporting core integral with said segments, said supporting core having an inner part of metallic material and an outer part of nonmetallic material, the surface of said outer part being united with the inner corrugated surface of each commutator segment.

3. The method of making a commutator of the type in which the successive conducting segments are fashioned from a single metallic annulus, which method includes the steps of cutting slots at spaced angular intervals along the inner side of the metallic annulus, inserting insulation material in said slots, uniting said insulation-containing annulus to a cylindrical core, and thereafter removing all that part of the metallic annulus which is disposed beyond the reach oi' said insulation material.

RALPH M. HEINTZ.

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