US1978692A

US1978692A - Magneto

Info

Publication number: US1978692A
Application number: US695383A
Authority: US
Inventors: Curt F Reis
Original assignee: Fairbanks Morse and Co
Current assignee: Fairbanks Morse and Co
Priority date: 1933-10-27
Filing date: 1933-10-27
Publication date: 1934-10-30
Anticipated expiration: 1951-10-30

Description

c. F. REIS MAGNETO Filed Oct. 27, 1953 INVENTOR. Cum l-T RE/s ATTORNEY.

Patented Oct. 30, 1934 PATENT OFFlCE MAGNETO Curt F. Rois, Beloit, Wis., Morse & 00., Chicago,

Illinois assignor to Fairbanks, 111., a corporation of Application October 27, 1933, Serial No. 695,383

4 Claims.

This invention relates to improvements in magnetos, and more particularly to improvements in rotor constructions of magnetos of the rotating field type.

In certain older prevailing types of magnet rotors, it is usual to employ a mass of cast nonmagnetic metal for positioning the pole pieces, as Well as for the purpose of intimately uniting the pore shoe laminations to the rotor shaft.

It has been found that such structures are objectionable, in that excessive magnetic leakage, between adjacent pole pieces, occurs through the mass of cast metal in which the pole pieces are embedded. It has also been found that with A such structures there is a decided tendency for the magnetic lines to encircle the pole pieces through the mass of cast metal. Such conditions are objectionable since they result in a reduction in the effective magnetic flux of the rotor.

It is, therefore, an object of the present invention to provide an improved rotor for magnetos of the rotating field type, in which permanent magnets or pole pieces are arranged, in spaced relation and substantially parallel to each other, in a mass of cast metal having slotted portions between adjacent pole pieces of opposite polarity, for the purpose of interrupting the usual lines or paths of magnetic leakage through the mass of cast metal.

A further object is to provide an improved rotor construction for magnetos of the rotating field type, in which permanent magnets or pole pieces are arranged in spaced relation and substantially parallel to each other within a mass of cast metal having slotted or channeled portions extending from the periphery of the rotor to the pole pieces, and substantially throughout the length of the portion of the pole pieces embedded in the cast metal. By this provision the tendency of the magnetic lines to encircle the pole piece through the cast metal, is minimized.

Further objects and advantages Will appear from the following detailed description of parts, and from the accompanying drawing, in which:

Fig. l is a longitudinal section of a preferred form of rotor for magnetos of the rotating field type, the section being taken along line l-l of Fig. 2; Fig. 2 is a section taken along line 2-2 in Fig. l, and. Fig. 3 is a section taken along line 3-43 in Fig. 1.

Referring to the drawing, the numeral 10 designates generally, a preferred form of rotor for magnetos of the rotating field type, and which includes a rotor shaft 11 formed, by

preference, of mild steel or other suitable shafting material of substantial strength and rigidity. A plurality of pole pieces or permanent magnets 12 are, by preference, arranged in spaced relation and substantially parallel to each other, and to the shaft. These pole pieces are, by preference, formed of a suitable steel possessing high magnetic retentivity, and are formed, by preference, of circular section. In the preferred example shown, the rotor includes four such pole pieces, although it will be understood that the number may be varied, depending upon the type and number of poles of the magneto to be constructed.

A bridging member 13 of soft iron or steel, is disposed near one end of the rotor and in contact with the corresponding end portions of the pole pieces 12. This bridging member provides a flux path common to all the pole pieces. The bridging member 13 is provided with a circular aperture 14, the inner margins of which are separated from the shaft 11 by an annular space 15. It will, of course, be understood that the bridging member may, if desired, be secured to the shaft in any suitable manner. Pole shoes 16 are provided and consist of stacks of soft iron laminations, each of partly sector type, which are arranged on the free ends of each pole piece.

In assembling the rotor, the pole pieces 12, bridging member 13, together with the rotor shaft 11, are suitably positioned in a die casting mold. The mold, prior to casting, is provided with cores corresponding in size and shape with, and so 'as to result in, slots or

channels

19 and 20. A mass of non-magnetic metal 21, such as a suitable aluminum and/or zinc alloy is then poured into the mold for intimately uniting to the shaft, the pole pieces and bridging member. After the die-casting process, the resulting rigid, integral structure is removed from the mold, and the cores corresponding to the slots 19 and 29 removed from the mold. Then the laminated pole shoes, which are each provided, by preference, with apertures 28, are assembled on the pole pieces, the pole pieces extending through these apertures. The laminations are, by preference, secured in place on the free ends of the pole pieces by means of split rings 22 which are disposed in grooves 23 provided in the outer surface of each of the pole pieces. These rings serve securely to fasten the laminated pole shoes in place. The rotor is now completely assembled and ready for use in a magneto.

It will be readily seen that the slots or channels 19, which are, by preference, disposed intermediate the pole pieces oi opposite polarity, extend radially from the periphery of the rotor toward the shaft ll, being separated from the shaft by a narrow strip 24 of the cast metal. These slots or channels are, by preference, extended longitudinally of the shaft from an end portion 25 of the cast mass 21, to the connecting plate 13; the plate being separated from the slot by means of a narrow Web 26 of the cast metal. lhese strips and Webs of metal may be made only of such dimensions as to insure adequate strength for holding the parts securely to the,

shaft, and preserving the rigidity of the body of cast metal. It has been found that magnetic leakage occurs through the die cast mass of metal from the pole pieces, the paths and lines of leakage resulting in greatest losses,.,being indicated in dotted lines in 2. The above described. channeled portions are particularly so located as to interrupt these leakage paths.

In the example of preferred construction, the

channeled or slotted portions 20 are, by preference, disposed radially oi each pole piece and or" the shaft, and are extended from the periph cry of the rotor to the outer surface of the pole pieces. These slots by preference, of a trend longitudinally of the shaft, and extend from the end portion 25 of the cast mass 21 to the bridging member 13. It has been found that the magnetic lines tend to encircle the pole pieces resulting leakage losses, and the purpose of the above slotted portions is to interrupt these magnetic lines. By the above provisions, the magnetic leakage through the mass of cast metal is minimized, such leakage otherwise and normally tending to reduce the magnetic power of the rotor. it will, of course, beunderstood that, although according to the above process, the

slots

19 and 28 are cored into the casting, these slots may be cut or milled 'into the cast mass after the moldin process. The rotor shaft 11 is, by preference, provided with a raised or roughened portion 2'7 to insure good interlocking or interengaging coherence between the mass of cast metal 21 and the shaft. ThlS portion, due to an improved bond, prevents relative movement between the cast metal and the shaft, either angularly or longitudinally of the shaft.

It will, of course, be understood that the present detailed description and the accompanying drawing, relate only to a single preferred executional embodiment of the invention, and that substantial changes may be made in the described arrangement and construction of parts without departing from the spirit and full in tended scope of the invention.

I claim as my invention:

1. In a rotor for a rotating field type of magneto, a pair of pole pieces of opposite polarity, disposed longitudinally of the rotor, a bridging member connecting end portions of said pole pieces, a body of metal serving to receive and position said pole pieces and bridging member,

said body of metal having recesses of a radial trend, and of a depth at least sufficient to intersect a plane including pole pieces of opposite polarity, said slots extending from said bridging member to the opposite end of said body.

2. In a rotor for magnetos of the rotating field type, a plurality of magnetized pole pieces extending parallel to the axis of rotation of the rotor, a shaft, a body of metal die-cast about said shaftand substantially embracing said pole pieces and positioning them in assembled relapieces and maintaining the same in assembled relation, slots of radial trend formed in said body and extending substantially over the length of said body, certain of said slots being disposed between the pole pieces of opposite polarity so as to interrupt normal paths of flux leakage therebetween, others of said slots being located along and adiacent'to the several pole pieces, whereby to interrupt normal circular leakage flux lines aboutthe several pole pieces.

4. In a rotor for a rotating field type of magneto, a plurality of permanent magnets, constituting pole pieces, said magnets being disposed. longitudinally of the rotor and parallel to its axis of rotation, a bridging member connecting certain of said pole pieces, a shaft of ferrous metal, a body of an aluminum alloy die cast about said shaft, and embracing and maintaining in assembled relation said pole pieces and bridging member,,;the body embracing only a portion of the length of each pole piece to provide free ends, pole shoes secured upon the free ends of certain of said pole pieces, said body being radially slotted, substantially over the greater portion of its depth and length, between pole pieces of opposite polarity, and being further provided with channels, extending inwardly of the periphery of the rotor and adjacent and along the several pole pieces, whereby to interrupt normal circular lines of magnetic leakage flux about the several pole pieces.

' CURT F. REES.

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