US2603677A - Magnetic pole - Google Patents

Description

July 15, 1952 M. P. WINTHER 2,603,677

MAGNETIC POLE Filed Oct. 30, 1950 s Sheets-Sheet 1 July 15, 1952 M. P. WINTHER 2,503,677

MAGNETIC POLE Filed Oct. 30, 1950 3 Sheets-Sheet 2 FIGS.

M. P. WINTHER July 15, 1952 MAGNETIC POLE 5 Sheets-Sheet 5 Filed Oct. 30, 1950 FIG. I4.

M F r W Patented July 15, 1952 1 2,603,677 'MA N QIR LE.

\ Martin. P. Winther,

ates Mills, Ohio, assignon This invention relates generallyto magnetic poles for dyn amoelectric machines, and more particularly, but without restriction, to such poles for pole rings of toroidal magnet fields ofdynamoelectric machines operating by means of eddy currents in inductor drums.

The invention is an improvement, upon constructions such as shown in the U. S. patent of Anthony Winther and myself, No. 2,470,596, dated May 17. 1949.

Among the several objects of the invention is the preservation of the efllcient magnetic circuit disclosed in said patent but at the'same time to reduce flux density at the magnetic gap of the machine, thereby reducing the magnetomotive force required to force the magnetic field across the gap and also reducing the eccentric'pull-over between the magnetic field and rotor members of apparatusof the class described. Other objects will be in part apparent and in part pointedout hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangements of parts which will be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which, several of various possible embodimentsof the invention are illustrated,

Fig. 1 is a half longitudinal section of eddycurrent apparatus embodying the invention;

Fig. 2 is a development ofseveral pole faces-on an enlarged scale, being taken on line 2-2 of Fig. 1;

Fig. 3 is a fragmentary detailv taken on line 33fof Fig. L'showing a bottom plan view of one of the poles illustrated in Fig. 2;

Figs. 4, 5, 6 and 7 are cross sections. taken on lines 4-4, 5-5, 6-6 and 1 ofFig. 2!;

Fig. 8 is a cross section ofv an alternative form of pole;

Fig.9 is an end elevation of the, pole shown in Fig. 8, viewed from its toe-end;

Fig. 10' is a rear elevation of the pole shown in Fig. 8, viewed from its heel end;

Fig. 11 is a plan view of the face of the, pole of Fig.8; and, h

Figs. 12, 13 and 14 are enlarged cross sections taken on lines 12-12, l3-l3 and I,4l4 of Fig. 11.

Similar reference characters indicatefcorresponding parts throughout the seve'ral. views of the drawings;

Referring now more particularlyto Fig. 1. there 3 Claims. (Cl. 172--284) is shown a longitudinal section of one formof dynamoelectric apparatus to which the invention applies. At numeral l' is shown the supporting frame, in which are two coaxial sleeves 3 and 5 in which are bearings land- 9, respectively. The bearings 1 support a' rotary drive shaft il and bearings 9 support a rotary driven shaft l3. It will be understood that as is the case in all apparatus of this class, the driving and driven relationship of shafts H and i3 may be reversed, this constitutinga mere inversion. 'Itwill alsobe understood that the driven shaft may be stationary as in the case ofa dynamometer or brake.

Keyed to shaft l I is aspider 15 for supporting an annular field member shown generall at H. Keyed to the shaft I3 is a spider I 9 for supporting a magnetizable eddy-current inductor drum 2| composed of ferrous material. I

The annular field member Ilcomposed of two magnetizable field rings23-and 25, composed of ferrous material. These are welded to a magnetizable rim 21 ofthespider, alsocomposed of ferrous material. "Between the rings 23 and 25 is an annular field coil 29-which is variably excited by means'of-a suitable circuit led in through a conduit means 3-! from collector rings associated with the shaft H. The collector rings are not shown and require nofurther description, beingcommon in apparatus of thisclass.

The rings 23' and 25 are provided with notches, those for ring 23 being shown at numerals'33, and those for ring 25 being shown at 35. The notches become wider and deeper along their lengths in the direction of coil 29. Each ring 23 and 25 between its notches has axially extending polar teeth of the so-calledclaw type, those for-ring 23 being indicated at numerals 31 and those for ring 25 being indicated at numerals 39. These teeth extend in opposite directions to envelope thefield coil 29; and interdigitate as indicated in Fig. 2. The bottoms of the notches 33 and 35 slope at an angle, for example, 35 to the axis of the machine. Likewise, an equal slope is given tothe bottom edges 41 of teeth 31 and bottom edges 43 of teeth39. Thusconstant spacingis left between these edges 4| and 43 and the bottoms of the notches 35 and 33, respectively.

When the coil 29 is. excited, a toroidal flux field is established, as indicatedby the dash lines F. If the teeth 39 are 'qonsideredto be of north polarity, then thistoroidal field may be traced as follows (see diagrammatic mean line F) from ring 25'through teethf39, into thedrum 2|, back tO IJGQth 31, ring 23, rim 21 andbacl; to ring 25,. As shown at G, there is an air gap between the teeth 37 and 39 extending from the rings 23 and 25. shaped and made according to the principles set forth in said Patent 2,470,596. That is, each tooth is so formed that the flux density through any tooth cross section, which cross section is substantially normal to the S-shaped parts of the mea flux path F, shall carry substantially a constant flux density. The indicated S-shaped flux paths are shown at S. It will be understood that with any two adjacent poles such as constituted by teeth31 and 39 there is interpolar flux leakage and the stated cross sections are such that after said leakage has been taken into account, thefiux density i each stated cross section is the same as the flux density for any other cross section. This makes most efiicient use of the metal constituting the toothed poles and reduces weight. This feature of itself is not new herein, but is referred to in order to show the point of departure of the present invention.

As in said Patent 2,470,596, one way of obtaining sections as specified in the paragraph above is to form the teeth as shown in Figs. 2, 3 and 4. These teeth have substantially righttriangular bottom portions 45 lying adjacent the coil 29. From the apexes of these triangles are the sloping edges H or 43, as the case may be. This results in the extending toe-ends T of the teeth flaring toward the inductor 2|. At the heel portions H, by reason of the shape of the notches 33 and 35, the teeth flare away from the inductor 2| in the regions of the ring 23 or 25, as the case may be. Further details may be obtained from said Patent 2,470,596, it being unnecessary to repeat them here.

The point of departure of the present invention is that instead of the face areas A of the teeth also carrying the same flux density as the flux density throughout tooth sections normal to the s-shaped mean flux path, the face area of each tooth right at the gap G is enlarged, so that the flux density in this face area exclusively is reduced below what it is in every other of said sections. One manner of enlarging this face area of a tooth is illustrated in the form of the invention shown in Figs. 1-7, wherein flanges 41 are superimposed along the leading and trailing edges of the teeth. Each flange, as shown in Figs. 4-7, follows the tooth contour from the region in which it flares away from the inductor 2| to where the tooth flares toward the inductor 2|. For example, in Figs. 3 and 7 the bottom of tooth 31 is show extending from the pole ring 23. The toe T of this tooth flares toward the inductor (Fig. 7) and the heel H flares away from it (Fig. 4). The flanges 41 extend along theedges' in the heel and toe and substantially exclusively enlarge thelpole face.

Figs. 21-14 show an alternative form of the invention, only one pole tooth being shown with adjacent notches of the coil being-removed. In this case the pole is numbered 49.. Its face ad- Fundamentally eachtooth is anvil jacent the gap is shown at 5|, the toe at T and the heel at H. A fragment of the pole ring is shown at 53, with the notches at 55. The notches again have sloping bottoms and they are conically shaped so that the polar tooth flares away from the inductor in the region of the heel portion H. The tooth flares toward the inductor in the region of the toe portion T (Fig. 14).

Underneaththe toe T, that'oothslopes as shown at 51 forsubstantial parallelism with'the slope of the opposite notch 55.

The pole tooth as shown in Figs. 8-14 is used analogously to the showing in Fig. 1, and an analogous toroidal flux field will be set up having an S-shap'ed mean path through each tooth as shown at S. The various sections of the pole perpendicular to the S-shape of this field will, after leakage flux between poles is accounted for, have a substantially constant flux density. Enlargement of the face area 5| is arranged in order tohave a flux density through the face 5| less than the flux densities throughout the other sections specified. The enlargement is shown at E.

From the above, it will be clear that broadly the new pole is of anvil shape, the heel of the anvil being associated with the adjacent pole ring and its toe extending toward the opposite pole ring. The bottom of the toe and adjacent flaring notch are essentially parallel. The primary qualifications for the shape of they anvil are that the toe portion shall be narrower than the heel portion, thereby providing a tapering'pole face. The parts of the pole under the toe flare toward the pole'face. The parts under the heel flare away from the pole face toward the pole ring. The'fianged or overhung edges which lead and trail .in movement relative to the inductor enlarge the face' area of the pole beyond the area of each other section of the tooth which is normall to the S-shaped mean flux path through the pole. As a result all of said other sections carry a constant flux density while the face exclusively carries a lower flux density One of the advantages is that a very efficient flux field is provided, minimizing the magnetizable material required. This is because all sections normal to the S-shaped mean flux path carry a constantfiux density after leakage flux has been taken into'account; except that the flux density through the pole face and across the flux gap into the inductor is reduced. The reduction in flux density is substantially exclusive to this pole face. The result is that a reduced amount of magnetomotive force is required to force the field across the gap G and the eccentric pull-over force normally associated with field members of this type having very small air gaps is reduced. Thus the gap can be held to smaller dimensions without introducing troubles under slight mechanical eccentricities.

It should be observed that in the form of the invention shown in Figs. 1-7, the overhang at is constituted by flat ribs which, as shownjin Figs. 4-7, also flare away from the broader portion of the pole face in the heel region and flare toward the narrower portion of the face in the toe region. That is, they have a surface twist. In the form of the invention shown in Figs. 8-14, the overhang at is not constituted by such a particular form of rib but by what in effect amounts to a simple enlargement starting just under the pole face 5|. 7

The invention is particularly useful in apparatus such as. eddy-current clutches, brakes, dynaclaimed in the U. S. patent application of Ralph L. J aeschke, Serial No. 193,417 for Magnetic Pole, filed November 1, 1950.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. For use in a dynamoelectric machine having a rotary inductor and a rotary field member composed of an annular field-producing member partially surrounded by magnetizable material including notched pole rings adjacent to the field member with magnetizable polar teeth of the claw type extending from the pole rings and interdigitating across the field member and adjacent to the inductor; a form of said polar teeth wherein each comprises a relatively wide heel portion and a relatively narrow toe portion presenting a pole face adjacent the inductor which tapers in its direction of extension from its pole ring, the adjacent notches in its pole ring comprising valleys which are substantially conical and increase in size in the direction of the annular field member toeffect a general radial flare of the heel portion away from the pole face in the heel region, the extended portion of the pole beneath its toe portion being tapered down axially but flared radially toward the narrower pole face, the arrangement being such that cross sections taken through the pole substantially normal to the resulting mean S-shaped path of flux passing therethrougli carry a substantially constant flux density, the peripheries of the pole face having overhanging narrow edges adapted to enlarge the pole face area substantially exclusively at and in the area of the pole face so as substantially exclusively to reduce the flux density passing therethrough below that of any of said cross sections.

2. Apparatus made according to claim 1, wherein said overhanging edges are constituted by rib extension portions.

3. Apparatus made according to claim 2, wherein the lateral faces of said rib portions also flare away from the broader portion of the pole face in the heel region and also flare toward the narrower portion of the pole face in the toe region.

MARTIN P. WINTHER.

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

UNITED STATES PATENTS Number Name Date 1,052,535 Volkers Feb. 11, 1913 1,502,527 Reichel July 22, 1924 2,470,596 Winther May 17, 1949 FOREIGN PATENTS Number Country Date 235,395 Germany June 9, 1911 OTHER REFERENCES Alternating Current Machinery, Thompson, pages 116-117, published by Spon and Chamberlin, London, 1904.

Images