US1988570A - Magneto rotor construction - Google Patents

Description

Jan. 22, 19 c. F. REIS 1,988,570

MAGNETO ROTOR COWSTRUCTION Filed Oct. 27, 1933 KJ/ g INVENTOR. [7 CURTF RE/j Z4 [7 BY j ATTORNEY,

Patented Jan. 22, 1935 UNITED STATES mormro PATENT OFFICE Curt F. Rois, Beloit, we, assignor to Fairbanks. Morse & 00., Chicago, 111., a corporation of Illinois "Application ctober,?7, 1933, Serial No.

' comma. (bl. 111-452) This invention relates to improvements in magneto rotor constructions -andrnoge p'artictypes of rotor constructions embodying perl manent magnets, have utilized screws or other similar fastening expedients for securing the permanent magnets and associated parts to the rotor shaft. Besides involving expensive drilling and tapping operations in an extremely hard metal, screws and like holding elements often become loose and ineffective. Accordingly, an object of thepresent invention is to provide an improved rotor for magnetos of the type noted, which includes a rotor shaft formed of steel or other-similar material, a cast body for positioning the magnet bars or pole pieces in assembly" to the shaft, together with such assembly ex-- pedients as to minimize the number of necessary machining operations on the magnets.

A further object of the invention is attained in a simplification of structure whereby a magneto rotor embodying-a rotating field, may consist only of three major items,'viz., a shaft, a cast body, and the magnet bars.

Yet another object of the invention is attained in an improved construction of magneto rotor such as to eliminate any precision assembly op-' erations and to obviate the necessity for highly skilled assembly labor.

Another object of the inventionis attained in an improved rotor structure for magnetos which, by reason of the construction and arrangement of its parts, eliminates the necessity for machining or grinding the end faces of the magnet bars, 45 this object being attained by employing an initially plastic cementitious material so pocketed within the body of the rotor as-to fill any voids or spaces otherwise existing between the ends of the bars, and the metal surfaces internally of 50 the body.

A still further object of the inventionis attained in a construction according to whi h a plate usually provided. is eliminated at one end or the rotor, it being customary in structures of 55 the present order to provide say a magnetic permanent plate at one end of the structure in engagement with the ends of the bars, and a non-magnetic plate at the opposite end of the structure. Since even most of the so-called non-magnetic materials of substantial strength contain a certain 5 amount of iron, the elimination of the so-called non-magnetic plate, minimizes demagnetization effects. I V

Further advantages resulting from a realization of this object, are found in improved facilities for magnetizing the bars, which, due to the absence of a plate at one end, are presented in assembly, each with a free or exposed end.

A further general object of the'invention may be considered as attained in the production of a magneto rotor of rotating field type which consists of a minimum number of parts, is extremely sturdy and durable in construction, and in use exhibits a superior retentivity as compared to prevailing rotors for revolving field type magnetos.

Further objects and avantages of the invention will appear from the following detailed description of a presently preferred embodiment of the invention, as. coordinated-with the accompanying drawin in which:

Fig. 1 is a longitudinal section, and Fig. 2 a transverse section, through the rotor assembly, the section of Fig. 1 lying along the planes indicated by line 1-1 of Fig.v 2, and the section of Fig. 2 being taken along line 2--2 of Fig. 1; Fig. 3 is a transverse section along line 3-3 of Fig. 1; Fig. 4 is a section along line 4-4 of Fig. 1; Fig. 5 is a section corresponding generally to that of Fig. 1, except as showing an alternate arrangement for securing and magnetically bridging the magnet bars in assembly, and Fig. 6 is a transverse section through the rotor, Figs. 5 and 6 being sectional views of the'same structure, each as viewed alo g the indicated plane of the other figure. J

Proceeding now to a description of the drawing, it will be understood that the present invention is confined to the construction and arrangement of parts of a rotor or similar magnetic structure of an electrical machine, being herein described by way of example, with reference to an assembly of rotatable permanent magnets. The secondary elements of the machine, forming of themselves no part of the invention, may be suita ly arranged according to existing known practices, or in any other manner appropriately t'o'an operative organization. In Fig. 1 there is indicated at 10 a rotor shaft, formed, bypreference, of steel or other material of substantial strength and rigidity. A plurality of pole pieces or permanent magnets 11, preferably of bar form, are by preference arranged in spaced relation and substantially parallel to each other, and to the shaft. The pole pieces or magnet bars are, by preference, formed of cobalt steel or other highly coercive magnetic material, and are formed. by

preference, of circular cross section to facilitate the few necessary machining operations. In the preferred examples shown, the rotor includu four 'such pole pieces, although it will be understood that the number may be varied, depending p n the type and number of poles of the magneto with which the rotor is to be utilized.

At 12 is indicated a body formed of cast metal, preferably aluminum, zinc, or alloys of either or both of said materials, the body 12 being by preference pressure cast or die cast upon the shaft 10 and so rigidly connected thereto. In an order to provide an interlocking or interengaging keyed connection between the shaft 10 and the body 12, I prefer to form the shaft, over a portion of its length, of squared or other angulate section as indicated at -13 (Fig. 3). The faces 5 of this portion of polygonal section are provided .further with flared integral keying elements 14 so shaped that upon casting the body of metal 12 to the shaft, there results what may for convenience be termed a mortise connection between 0 themetal body and the shaft. The engagement of the cast metal with the ends of the portions 1314 prevents any movement of the magnet- .holding body endwise of the shaft, and the mortis'ed relation between the body and shaft result- 5 ing from lugs 14, definitely prevents any angular movement of the body with respect to the shaft, and thus prevents any possibility of disturbance of the timed relation of parts of the magneto.

According to the arrangement of Figs. 1 and 2, the body is provided, at the time of casting, with a transversely disposed magnetic plate 15 (Fig. 2), this plate being preferably of iron, steel or other magnetic material and extending transversely of the axes of the magnet bars. The

arrangement of the plate 15 with respect to the bars appears from the dotted line circles of Fig. 2. According to the arrangement of Fig. 1, the

areas defined by the circles of Fig. 2-extend to the bottom of sockets l6 cored in the cast body, the sockets serving, as appears from the drawing, to receive and preferably frictionally to engage the magnet bars over a portion of their length. Before the assembly operations of inserting the bars 11 in the sockets 16, according to the structure of Fig. 1, the areas intervening the ends of the bars and the plate 15 are supplied with a Y suitable amount of a magnetic metal cement. A number of cements will suitably serve this purpose, among the commercially available substances for this purpose is a product offered to the-trade under the name of Smooth-on". This product serves adhesively to engage, in assembly, the end faces of the bar magnets 11, and the opposite surfaces of the plate 15, and thus firmly (35 to unite the bars and plate in assembly. The

I materials are admixed with water in an amount 7 to render them plastic, and applied over the areas shown by Fig. 2 and so as to be disposed between the ends of the bar magnets and the plate 15. The body of magnetic metal cement is indicated at 17 in Fig. 1, between one of the bars and the plate.

My preference, by reason of economy in metal. is to form the cast body 12 of anaxial length substantially less than the length of the bars 11. According to this arrangement the bars are embraced by the body only over say half of their length, the remaining length of the bars being free and projecting from the inner face of the body to receive pole shoes indicated generally at 18. According to preference the pole shoes are constructed of an assembly or stack of laminations 19 each of which consists, in preferred form, of a pair of spaced eye portions 20 bridged by a laterally offset connecting piece 21, each of the eye portions 20 being provided with a peripheral cut 22. By further preference the bridge of connecting piece 2l'i's offset from the eye portions 20,

in a direction toward the periphery of the rotor, it'being understood that the laminations serve to bridge, according to the present example, magnet bars 11 of opposite polarity. By recessing the laminations between the bars 11 and locating the connecting piece 21 peripherally of the rotor, the flux lines tend to be concentrated near the air gap with advantages which will appear to those skilled in the present art.

As an expedient for assembling the laminations 19 in stacked relation over the free ends of the bars 11, it is my preference to provide each of the bars with two spaced circumferential grooves, one thereof somewhat 'close to the free end of the bar and the other inwardly of such end a distance corresponding to the thickness or axial length of the completed shoe. Serving to seat in the circumferential grooves of each bar, are a pair of snap rings 23 (Fig. 1), each being formed of resilient material and cutthrough at one point so that the rings may be sprung over the bar as applied endwise thereof. Upon being brought over the seat therefor, .each ring will snugly engage such seat and form an abutment, by virtue of which the stacked laminations are kept in pressed engagement and in assembly on the bars. The arrangement of snap rings and grooves as described, is or may be substantially the same as shown by Patent No. 1,843,222, granted to T. J. Harley, February 2, 1932, and assigned to the present applicant.

The use of the snap rings 23 may be obviated by employing in lieu thereof end abutments 24 (Fig. 5) which maybe in form the same as the laminations 19 of Fig. 4. If desired, however, the abutment members 24 may be formed as indicated by Fig. 5, of slightly heavier gauge than that of the laminations 19. In assembly, the members 24 may, if desired, be formed of somewhat resilient material or of a different stock than that constituting the laminations, whereby the eye portions thereof, slotted as shown in Fig. 4,.

are caused to spring. into seating engagement with the circumferentialgrooves of the bars. Where the shoes consist of only a few laminations, it has been found entirely satisfactory to employ the two laminations at the ends of the stack, in lieu of the separate members 24, and to serve the purpose of the snap rings 23 of the construction of. Fig. 1. It will be obvious'that the rings 23 and members 24 may be omitted at the inner ends of the pole shoes, thus avoid ing an operation incutting or grinding one groove on each magnet bar. This may be accomplished by extending the block or body of cast metal sufficiently to abut the inner end faces of the pole shoes.

Proceeding now to a description of the modification Figs. and 6, it will appear that, according to Fig. 5, the use of the plate 15 is avoided, and that thebar-bridging function of the plate 15 and cement 17 of Fig. 1, is provided for entirelyby suitably disposed bodies of cement 25. Each of these bodies of magnetic cement serves to bridge a pair of the pole pieces of opposite polarity, and the magnetic areas or elements thus provided by the cement are undercut or recessed as at 26 so as to clear the shaft as best appears in Fig. 6. The cement employed in the constructions of Figs. 5 and ,6 may be the same as above described in connection with Fig. 1.

- openings 16 of socket form, to receive the ends of the magnet bars. According to Fig. 1 the bottoms of the sockets are provided with suitable amounts of cement 17. The magnet bars 11 are then provided with their innermost snap rings 23 or one of the members 24 upon which the laminations are stacked, compressed, and retained in compressed and assembled relation upon the addition of the outermost snap ring 23 or element 24. Following the assembly of the laminations to form the shoes, and the magnet bars, the bars are inserted in the sockets therefor in the cast body and firmly pressed into engagement with the cementing elements and areas 17, following which, and after setting of the cement. the rotor is completed and ready for installation in the frame of the magneto.

The construction of Figs.5 and 6 and the order of assembly events identified therewith is or may be the same as that outlined with respect to Fig.

, 1, except for theelimination of the plate at the time of casting, suitable cored openings being provided for the elongate transversely disposed cementing elements 25, within the cast metal body 2'7.

While I have shown, as alternate expedients for assembling the laminated shoes, the snap rings 23 of Fig. 1 and the bridging members 24 of Fig. 5, it will be understood that either of these expedients'may be employed with either of the described structures as well as in a variety of other magnet assemblies for kindred uses.

It will appear as a distinct production advantage, that by reducing the mass and dimensions of the body of cast metal, according to the practices presently outlined, I have materially reduced the volume and weight of non-magnetic materials, and hence pro tanto reduced the cost of the finished rotor. It will also appear as a distinct advantage in production, that either before the bar and shoe assembly is united to the cast body, or in case the shoes are applied to the bars after inserting the bars in the body. there always remains a free end, of substantial length, of each of the bars, thus facilitating magnetization of the bars. A further distinct advantageappears in the utilization of a material which serves the dual function of a metal cementingsubstance, and also that of a magnetic bridge between bars of opnosite polarity?" By the use of a cement which, in plastic form, serves fully and completely to fill any voids or irregularities resulting from a non-planar surface at'the ends of the bars, there is obviated the necessity of machining such end faces. The elimination of this operation, due to the hardness of the bars, materially reduces assembly costs. While numerous other advantages result, it will appear from the foregoing that each of the several objects set forth is fully attained by the described structures.

While the invention has been described by making specific reference to ertain presently preferred embodiments-the description" is to be understood in an vexplanatory, rather than in a limiting sense, since numerous changes may be made in the parts, their combinations and arrangements, without departing from the spirit and full intendment of the invention as defined by the claims hereunto appended.

I claim:

1. A magneto rotor including a shaft, a polepiece holder formed of a body of non-magnetic material secured to said shaft, a plurality of pole pieces, of bar form, arranged in spaced parallel relation to each other and the shaft, the body being of an axial length substantially less than that of the polepieces and provided with sockets to receive the ends thereof so that the pole pieces project endwise of the body, the inner ends of certain of the sockets being provided with a magnetic metal cement, serving to position the pole pieces within the body, pole shoes carried by the free ends of the pole pieces, and means externally embracing the pole pieces at each side of theshoes for positioning the shoes along the pole pieces.

2. A magneto rotor including a shaft, a magnet holder formed of a body of non-magnetic material cast onto said shaft, a plurality of bar magnets arranged in spaced parallel relation to each other and the shaft, the body being of an axial length substantially less than that of the magnets and provided with sockets of a size to receive and snugly embrace the ends of the magnet bars, with the bars projecting endwise of the body, the inner ends of certain of the sockets being provided with a magnetic metal cementj' serving to position the bars with respect to the body, a plate coacting with said magnetic-cement to constitute a magnetic bridge between certain of the bars, laminated pole shoes carried by the free ends of the magnet bars, and resilient means externally embracing the bars at each side of the pole shoes, for positioning the assembly with respect to the bars, the bars being externally recessed to receive and seat said resilient elements.

3. In a magnet assembly, a plurality of magnets, a group of laminations stacked on said magnets and bridging a, plurality thereof, and a member at one side of the group of said laminations for maintaining them in stacked assembled relation on the magnets, said member having eye portions externally embracing the magnets, the magnets being .circumferentially grooved to seat the eye portions, and a bridge interconnecting the eye portions of said member.

4. In a magnet assembly, a plurality of spaced bar magnets, a group of laminations, constitutthe end laminations of the group each having eye portions grippingly engaging the grooved portions of the magnets and maintaining the shoe in assembled relation thereto.

5. In a magneto rotor, a shaft, a magnet holder formed of a body of non-magnetic material secured to said shaft, a plurality of bar magnets arranged in spaced parallel relation to each other and the shaft, the body being provided with sockets to receive one end of each of the magnet bars, means within the sockets for positioning the bars therein, laminated pole shoes carried by the magnet bars, externally of the body, the laminations constituting said shoes, each consisting of a plurality of eye portions, each eye portion adapted to receive one of the magnets therethrough, and a bridge portion connecting the eye portions, the bridge portion being offset from the eyes, in a direction toward the periphery of the rotor, and'means for positioning the pole shoes along the magnet bars.

6. In a rotor-for revolving field magnetos, a cast body structure formed of non-magnetic metal and provided with sockets of a trend parallel to the axis of the rotor, magnet bars carried by the holder and disposed each within one of said sockets but projecting from the holder to a substantial extent endwise of the rotor, shoes carried by the projecting portions of said magnet bars, and a cementitious material in each of said sockets, said material containing finely divided particles of a magnetic metal, and'means coacting with the material in said sockets, to form a magnetic bridge between certain of the magnet bars.

7. In a rotor for a revolving field magneto, a shaft, a magnet holder. formed of a body of nonmagnetic metal cast upon said shaft, a plu- "lality of bar magnets arranged in spaced relation parallel to said shaft, the body being provided with sockets to receive one end of each of the magnet bars, means for positioning the bars ments detachably carried circumferentially of r the bars for assembling the shoes thereto.

8. In a magneto rotor, a shaft, a magnet holder formed of a boob; of non-magnetic metal cast upon said shaft, a plurality of bar magnets arranged in spaced parallel relation to said shaft, said body being provided with socketed bores a size frictionally to receive corresponding ends of the bar magnets, the magnet bars projecting endwise beyond the said body, magnet bridging elements within the body of cast metal, and extending transversely of the body so as to interconnect the bars of opposite polarity, said bridging elements including a magnetic material adapted to cement said bars within the body, Dole shoes carried by the free ends of the magnet bars, and annular elements resiliently embracing and seated upon the bars at opposite ends of the pole shoes, for positioning the shoes along the bars.

9. In a rotor for a revolving field magneto, a shaft of ferrous metal, a magnet holder consisting of a body of non-magnetic metal cast upon said shaft, the shaft having a portion of angulate section, for lockingly interengaging the body of cast metal, a plurality of bar magnets arranged in spaced parallel relation to said shaft, the said body being provided with socketed bores of a size frictionally to receive corresponding endsof the bar magnets, the bores being of a length substantially less than that of the magnets whereby the bars project substantially beyond one end of the body, magnet-bridging elements within the body of cast metal, and extending transversely of the body so as to interconnect certain of the bars, said bridging elements including a plate of magnetic metal cast within the body, and a cementitious substance adapted to secure the bars in assembled relation to the body within the sockets, pole shoes of laminated construction, carried by the free ends of the magneto bars, and snap rings seated upon the bars at opposite ends of the pole shoes for positioning the shoes in stacked compacted relation with respect to each other and along the bars.

' CURT F. REIS.

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