US 996253 A
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Description (OCR text may contain errors)
F. A. JOHNSON.
DX'NAMO ELECTRIC MACHINE. APPLICATION IILBD JAH.9',1911.
996.253, Patented June 27,1911.
UNITED STATES FREDERIC .AYRES JOHNSON, OF COLORADO SPRINGS, COLORADO.
Specification of Letters Patent. Patented ine 2'7, 1911,
Application filed January 9, 1911. Serial No. 601,667.
T 0 all whom it may concern:
Be it known that I, FREDERIC Arnns JOHNSON, a citizen of the United States, and resident of Colorado Springs, El Paso county, and State of Colorado, have invented certain new and useful Improve-j ments in Dynamo-Electric Machines, of'
which the following is i specification.
My invention relates to dynamo electric machines, and more particularly to machines of that type in which means are provided for varying the reluctance of the magnetic field circuit so as to produce corresponding variations in the flux.
In my pending application, filed July 16, i
1910 Serial Number 572,362, I have shown and described several arrangements for thus varying the flux, the generic object being to 3 provide means for varying the main field, 1
while preserving a connnutating field of the proper strength and location to insure sparkless commutation without the necessity for nifting the brushes.
The present invention has the same broad objects in view, and is in the nature of an improvement on the arrangement shown in the above mentioned application.
Specifically, this invention seeks to provide more effective means for preventing the distortion and shifting of the commutating field when theinain field is varied, and for concentrating the flux at the point of commutation when the main field is 'Uzlhened.
lVith the above objects in view, the iiivcntion consists in the construction and arrangen'ient of parts hereinafter described. and claimed, and illustrated in thc accompanying drawing, in which Figure l is a diagrammatic sectional clevation showing my invention as embodied in a bipolar machine, and ljig. 2 is a similar view, showing the parts in shifted position.
Referring to the drawings in detail. relerence character 1 designates a field tramc which, for the purpose of illustration, is shown as an annular ring. Projecting inwardly from this ring in the usual manner are a plurality of poles, two of such poles being shown by way of example. El designates the field coils surrounding the poles, 4 the armature, and 5 the brushes resting upon the commutator.
Between cach ot' the poles aml the armature are the movable. elements. members or shoes (3, which are capable of being shil'tcd around the axisof the armature as a center.
1. The shoes 6 may be shifted by means of any suitable or desired mechanism. As illustrated in the drawings, these shoes may be secured to end plates, one of which is provided with an are shaped rack 8 adapted to mesh with a worm 9, carried by a shaft 10, the outer end of which is provided with. a. hand wheel 11. i
l Referring particularly to Fig. 1 it. will be seen that theinner face of each pole is made up of cylindrical surfaces having two diti'erent centers of curvature. The portions A, B, and A, B, of the poles are cut on the are of a circle of which the axis, C, of the armature is the center, while the remaining portion of each pole face such as indicated as extending from B to l) is cut on the arc of a circle of which C is the center. The t corresponding portion B, I) of the other i pole face is cut on the arc-o't' a circle having its center symmetrically located at a point diametrically opposite from C, the radial i lines of which have been omitted for the l sake of clcarness. It. will thus be seen that each pole face is cut partly concentric and partly eccentric with the armature. It will also be noted that the shittable members 6, as clearly shown in Fig. l have their outer peripheries corresponding in contour with the pole faces. and their inner surface concentric with the armature. 'll cretore each men'ibcr (3 is made up of a cylindrical seg ment, comprised between concentric arcs, and a wedge shaped segment comprised be tween eccentric arcs.
produce the maximum main licld flux through the arn'iaturc, that: is, this figureshows the parts arranged tor the lowest speed of the armature, it' the machine is a variable speed motor. Fig. 2 shows the members (3 shifted to the extreme high speed position, in which the main flux through the armature is a minimum. This \vealwning of the field results from the production of an air gap 7 betweei'i the eccentric portions of the polclace and shoe, thereby greatly increasing the reluctam-c. it. will be observed however, that, in this position and in all intermediate positions, the concentric portions of the shoe and pole tacc remain in intimate contact, thus atl'or'ding a ready path for the llux at one side ol" the pole face. This results in concentrating the llux at the connnutating point adjacent the brushcs 5,
In Fig. l the parts are in a position to as clearly shown in Fig. 2, thereby producing substantially sparkless commutation at all speeds of the motor. It will be further observed that,.since the movement of the shoes 6 takes place in a direction concentric with the are A, B, concentric with the armature, any movement whatever will cause a separation of the shoe and pole face along the eccentric arc B, D, and that this separation increases rapidly as the shoe is move Thus comparatively small movements of the shoes produce relatively large variations in the reluctance and consequent flux values. It will beparticularly noted, however, that in all positions of the shoes an unbroken path for the flux is afi'orded at the point of commutation.
It will thus be seen that by the above described employment of pole faces partly eccentric and partly concentric with the armature, I have provided a very effective means of weakening the main field while preserv ing the intensity of the commutating field, and it is thought that the advantages of my improved construction will be readily appreciated by those skilled in the art.
What I claim is:
1. In a dynamo electric machine, the combination with an armature, of a field structure having a pole, part of the face of said pole being concentric with said armature, and part being eccentric therewith, and a. shiftable member arranged between said pole f, cc and armature.
2. In a dynamo electric machine, the combination with an armature, of a field structure having a pole, the face of said pole being made up of a plurality of cylindrical surfaces each having a different center of curvature, and a shittable member arranged between said pole face and armature.
3. In a dynamo electric machine, the combination with an armature, of a field structure having a pole, the face of said pole being made up of a plurality of cylindrical surfaces each having a different center of curvature, and a shiftable member arranged between said pole face and armature, the outer periphery of said member conforming with the contour of said pole face.
4. In a dynamo electric machine, the combination with an armature, of a field structure having a pole, the face of said pole being made up of a plurality of cylindrical surfaces each having a different center of curvature, and .a shiftable member arranged between said pole face and armature, the outer periphery of said member conforming with the contour of said pole face, and the inner face of said member being concentric with said armature.
5 In a dynamo electric machine, the com bination with an armature, of a field structure having a. pole, the faceof said ole be ing made up of a plurality of cylindrical surfaces each having a difierent center of curvature, one of such centers co-inciding with the axis of the armature, and a shiftable member arranged between said pole face and armature.
6. In a dynamo electric machine, the combination with an armature, of a field structure having a pole, the face of said pole be ing cut partly concentric and partly eccentric with said armature, and a shoe shiftable around the axis of the armature as a center, and having concentric and eccentric portions corresponding-with those of the pole piece, the arrangement being such that, when in one position, said shoe is in contact with the entire face of the pole, while, when in other positions, said parts are in contact at their concentric portions only, an air gap being formed between their eccentric portions.
In testimony whereof I aflix my signatu e in presence of two witnesses.
FREDERIC AYRES JOHNSON. Witnesses i C. REYER, F. N. France.