US1979812A - Magneto electric machine - Google Patents

Description

MAGNETO ELECTRIC MACHINE Filed Oct. 27, 1933 mg I0 INVENTOR. Cum- [/6575 Patented Nov. 6, 1934 PATENT OFFICE MAGNETO ELECTRIC MACHINE Curt F. Rois, Bcloit, Wis., assignor to Fairbanks, Morse & 00., Chicago, 111., a corporation of Illinois Application October 27, 1933, Serial No. 695,384

Claims.

This invention relates to improvements in magneto electric machines, and more particularly to improvements in rotor constructions of the type employing rotating permanent magnets,

I and methods of forming the same.

In certain prior types of magnet rotors, it is known to employ a mass of cast non-magnetic metal, such as brass, for positioning laminated pole shoes, for the rotor shaft, as well as for the purpose of intimately uniting the laminations of the pole shoes. Such structures are objectionable, in that a cast shaft is comparatively low in rigidity, and is rather expensive shafting material. In magnetos of this type, it is desirable to employ permanent magnets formed of a suitable steel having high magnetic retentivity. Such materials have not been widely used in magnetos because of the difficulty experienced in machining, and in securing the pole pieces to the rotor and the pole piece bridging members. In prior types of rotor constructions, it is usual to employ screws or other like fastening means for securing the permanent magnets to the rotor shaft and to the pole piece bridging members. Such constructions offer the objection that the screws may, and often do, become loose and ineffective, impairing the magnetic contact between the pole pieces and the bridging members, to render the rotor practically unserviceable. A general objective of the present invention is attained in the elimination of the noted diiiiculties and objections.

A further object of the present invention is attained in an improved method of forming rotors of the type employing rotating permanent magnets, which consists in suitably positioning the pole pieces, magnetic bridging member, to-

gether with the rotor shaft, in a die-casting mold, in applying pressure to the bridging member and the ends of the pole pieces, and in pouring, preferably under pressure, a mass of nonmagnetic metal into the mold, for intimately uniting in assembly with the shaft, the pole pieces and bridging member. By this method there is assured a lasting and intimate magnetic contact between the ends of the pole pieces and the bridging member.

A still further object is to provide an proved rotor construction for magnetos of the die-cast non-magnetic metal for securing the pole pieces and a magnetic bridging member, to the rotor shaft, and in providing the pole pieces with recessed portions, such as grooves, which coact with the cast metal, upon shrinkage, to

rotating field type, which includes a mass ofurge and maintain the pole pieces into intimate magnetic contact with a bridging member therefor.

Yet another object is to provide an improved rotor for magnetos of the rotating field type, in 60 which the pole pieces and the magnetic pole bridging structure are firmly assembled to the rotor shaft by means of a mass of die cast nonmagnetic metal.

An additional object is to provide an improved rotor for magnetos of the rotating field type, which is rigid and durable in construction, and is composed of but a few simple and easily assembled parts, and which results in a substantial reduction of production costs, through minimization of machining operations on the permanent magnets.

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

Fig. 1 is a longitudinal section, as viewed along line l-1 of Fig. 2; Fig. 2 is a transverse section through the rotor body, as viewed along line 22 of Fig. 1; Fig. 3 is a transverse section along line 3-3 of Fig. 1; Fig. 4 is a longitudinal section of a modified embodiment of the structure as viewed along line 4-4 of Fig.5; Fig. 5 is a transverse section along line 5-5 of Fig. 4, and Fig. 6 is an elevation in perspective of a modified form of pole-bridging member.

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 similar shafting material of substantial strength and rigidity. A plural ity 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 cobalt steel or other material possessing high magnetic retentivity, and are formed, by preference, of circular cross section to facilitate the few machining operations thereon. In the preferred examples shown, the rotor 10 ineludes four such pole pieces, although it will be understood that the number may be varied, depending upon the type and number of the poles of the magnets to be constructed. It will, of course, be understood that, in a four pole rotor, as illustrated, alternate pole pieces will be of opposite polarity.

Referring more particularly to Figs. 1, 2 and 3, a bridging member 13 of stamped iron or steel is disposed near one end of the rotor, and in con- 9 tact with the end faces of the pole pieces 12. This bridging member provides a flux path common to all the pole pieces. The bridging member is provided, by preference, with a circular aperture-l4, the inner margins of which are, by preference, 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, by preference, located as shown, and consists of stacks of soft iron laminations, each of partly sector type, which may be arranged, in a four pole machine on the free end of each pole piece.

The improved method of forming the rotor consists in suitably positioning the pole pieces 12, the bridging member or members, together with the rotorshaft 11, in the space relation of their assembly, in a die-casting mold. The mold, prior to casting, may be provided with cores corresponding in size and shape with, and so as to result in, channels 17, and suitable pins or studs 31 are displaceably provided in the mold opposite the ends of and aligned with each pole piece 12, and at one end of the rotor adjacent the magnetic bridging member 13; the studs corresponding in size and shape with, and so as to result in channels 18. The clamping studs are preferably tapered slightly at the ends, so as to facilitate their draft. Suitable means (not shown) -areprovided in connection with the diecasting mold, for applying pressure inwardly of the mold, upon the clamping studs. betweenthe magnetic bridging member 13 and the opposite ends of the pole pieces 12, so as to maintain the ends of the pole pieces in contact with the bridging member, prior to and during ,the die casting process. A mass of non-magnetic metal 19, such as a suitable aluminum or zinc alloy is then poured into the mold for intimately uniting to the shaft, the pole pieces and bridging member. After pouring and freezing of the metal, the resulting rigid, unitary structure is removed from the mold. Following this, the

laminated pole shoes 16, which are each provided with one or more apertures 20, are assembled on the free ends of the pole pieces, the pole pieces thus extending through the laminations stacked thereover. The laminations are, by preference, secured in place on the pole pieces, following their compression, by means of split rings 21 or the equivalent, which are disposed in grooves 22 provided peripherally near the free end 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.

In Figs. 4 and 5 there is shown a modified form of rotor construction. In this modification, the parts common to both constructions bearing similar reference numerals, a pole-piececonnecting member 23 shown as a block of soft iron or steel, is disposed near corresponding ends of the pole pieces and is, by preference, also secured as by a key 24, to the shaft 11. This pole piece connector is provided, by preference, with a tapered portion 25 which is arranged to make contact with a correspondingly sloped, plane surface 26 resulting by undercutting pole pieces 12. In Fig. 6 the connecting members are provided with semi-circular seats 27 for receiving the ends of the pole pieces, and thus to make a good lateral contact with the poles, which in this case are not undercut as in Fig. 4. It will be readily understood that the method of assembling the' various parts is substantially the same as described in connection with the structure of Fig. 1. It will be noted that when a clamping pressure is applied to the pole pieces and bridging member of either construction, these parts are urged into intimate magnetic contact. Each pole. piece is, by preference, provided with a grooved portion 29 which coacts' With the mass of metal 19, during shrinkage upon freezing of the metal, to urge and maintain the pole'piece into intimate Contact with the magnetic end plate, after the clai. ,pi,ng pressure on the mold studs is released.

In the structure of Figs. 4 and 5, the diametral shrinkage of the metal/upon freezing, serves to set the magnets 12 into close magnetic contact with the bridging blocks 23, it being understood that the clamping studs engage, during casting, these blocks, at one end of the rotor, and engage the free ends of the magnets or pole pieces, at the opposite end of the'rotor. The shrinkageclamping effects arefsubstantially the same in case the structure and molding practice is effected by utilizing the bridging block of Fig. 6. It will be understood that the groove 29 of Fig. 1 may likewise be employed in the structures of Figs. 4, 5 and 6.

In either construction the rotor shaft is, by preference, provided with a raised or roughened portion 30 to insure good interlocking securement between the mass of cast metal, and the shaft. This portion, due to an improved bond, prevents relative movement between the cast metaLarrd the shaft, either angularly or longitudinally ofthe'shaf t.

It will, of course, beunderstood that the present detailed description of parts and the accompanying drawing relates to only a preferred executional embodiment of the invention and that substantial changes may be made in the described construction and arrangement of parts and in the described method of forming the same without departing from the spirit and full intended scope of the invention.

-I claim as my invention:

1. The herein described method of assembly, by casting, a rotor for a magneto of the rotating field type, which consists in grooving a plurality of magnets, in disposing said magnets in endwise abutting relation with a bridging member in a mold, in subjecting said magnets and bridging member to a positive pressure, endwise of said magnets, and in pouring a body of cast metal about the grooved portions of the magnets and 'said bridging member, whereby, upon shrinkag f the casting metal, the freezing 'shrinka of said metal maintains said "mpr'essive engagement in assemwhereby to, secure, during casting, an effective magnetic engagement of the bridging member and bar magnets.

3. A rotor for a magneto of the rotating field type, including a plurality of parallel bar magnets, a member magnetically bridging said magnets, and a body of cast non-magnetic metal embracing said magnets and member, said magnets having grooved portions coacting with the a body of cast metal to maintain said magnets and member in compressive engagement, whereby to effect a positive magnetic engagement between the magnets and bridging member.

4. In a rotor for a magneto of the rotating field type, in combination with a shaft, a plurality of pole pieces having peripheral grooves therein, a bridging plate abuttingly and compressively engaging the end faces of the pole pieces, and a body of non-magnetic metal cast about a portion of said shaft, embracing 'said plate and portions of the pole pieces, and extending into the grooves of the pole pieces to maintain said pole pieces and bridging plate in compressive engagement.

5. A magneto rotor for a machine of the rotating field type, including, in combination with pole shoes, pole pieces of circular section, and a shaft, a pole piece bridging block disposed inwardly of the corresponding ends of the pole pieces, and having pole-piece-receiving seats each conforming to the adjacent surfaces of the pole pieces, and a body of die 'cast nonmagnetic metal, substantially embracing the corresponding ends of the pole pieces, shaft and said bridging block, said pole shoes being carried by the respective pole pieces, exteriorly of said body of cast metal.

CURT F. REIS.

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