US758157A - Means for preventing arcing between commutator-brushes. - Google Patents

Description

PATBNTED APR. 26, 1904.

E. THOMSON. MEANS FOR PREVENTING ARGING BETWEEN GOMMUTATOR BRUSHES.

APPLICATION FILED MAY 29. 1903.

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N0. 758,157. PATENTED APR. 26,1904. E. THOMSON.

MEANS FOR PREVENTING ARCING BETWEEN OOMMUTATOR BRUSHES.

- APPLIIOATION FILED MAY 29. 1903.

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UNITED STATE Patented April 26, 1904.

PATENT OFFICE- ELIHU THOMSON, or sWAMrsooT'r, MASSACHUSETTS, ASSIGNOR TO GEN;

ERAL ELECTRIC COMPANY, A 'coaPoRATIo oF NEW Yorue MEANS FOR PREVENTING ARCING BETWEEN COMMUTATOR-BR USHES.

SPECIFICATION forming part of Letters Patent No. 758,157, dated April 26, 1904. Application filed May 29, 1903. Serial No. 159,229. (No model.)

ent potentials in the space through which the arcing would otherwise take place. Preferably the material out of which the barrier or shield is made is some non-combustible heatresisting non-disintegrating insulating sub stance. Fused silicious matter, such as silicious sand or silica or silica cemented by clay in the form of fire-resisting bricks, form suitable materials out of which the barrier may be made. In place of these materials I may use compounds of asbestos with cemented materials. I prefer, however, to employ fused silica, which is non-porous and stands excessive changes of temperature without cracking or disintegration.

For a better understanding of my invention reference may be had to the accompanying drawings, in which I illustrate several embodiments of my invention.

Of the drawings, Figure 1 is an end elevation, with parts broken away, showing one form of my invention. Fig. 2 is a partialsectional elevation of the same form. Figs. 3, 4, and 5 each show different arrangements of the barriers or shields; and Fig. 6 is a sectional elevation of a bipolar motorhaving its brushes and barriers arranged as in Fig. 3.

In all of the figures of the drawings an armature-shaft A of a dynamo-electric machine is shown upon which is mounted an armature B and cylindrical commutator C. The field of the machines comprises two or more poles D. The armature and poles are not shown in all the figures of the drawings. Two brushes E E bear against the commutator.

railway-motor.

In Figs; 1 and 2. of the drawings'I have 5 conventionallyshown a four-pole .tWo-brush The brushes-E E are placed in position to engage the commutator on its upper side and are separated from each other by an arc of ninety degrees, the armature beand between the brushes E E. In the construction which I have illustrated in the drawings the block-F is provided with an integral extension G, by which the block may besecured to a lug or projection H, which extends 5 from or is carried by the motor casing or frame in any suitable manner. This block F may be of a length somewhat less than the distance between the brushes E E and may be separated from the commutator only far 7 enough to provide suitable clearance, and under some circumstances it may rest in contact with the commutator.

When the blocks Fare in place, no'arcing or flashing over can occur under ordinary circumstances. The block itself being quite massive and being formed out of non-conducting material and the space, if any, which exists between the inner curved surface of the block and the outer edges of the commutatorsegments being small, any are which may be formed or start to formis cooled and smothcred and cannot maintain itself.

In Fig. 3 I have shown the brushes E bearing against the surface of the commutator C' 5 at diametrically opposite points. The barriers or shields F in this case are shown as extending through an angle of nearly one hundred and eighty degrees.

In Fig. 4 the brushes E are at diametrically 9 opposite points of the commutator C, as in Fig. 3. Instead of employing a single shield or barrier, however, a plurality of-barriers or shields are employed. The barriers or shields F above the line of commutation are held in clasp-like holders I, while the blocks F below the line of commutation are formed with grooves in their sides and are held inposition by wires J, which extend parallel to the axis of the shaft and engage with the walls of said groove.

The use of a plurality of barriers or shields, as shown in Fig. 4, is desirable in substations, as with such a plurality of barriers it is easier to make adjustments which become necessary from time to time to compensate for the wear of the commutator and of the barriers or shields if they be in contact with the commutator. IVhen the barriers or shields are in contact with the commutator, it will of course be understood that suitable lubrication may be made in order to avoid undue friction between the parts.

In Fig. 5 I have illustrated a motor intended to rotate only in the direction indicated by the arrow. The brushes are diametrically opposed with respect to the commutator. The barriers or shields F in this case, however, extend throughout only a comparatively small portion of the entire are between the brushes and are placed each immediately in advance of the brushes of the commutator, having reference to the direction of rotation of the machine.

WVhen the machine is intended to rotate in one direction only, it should be so designed that the magnetic field tends to drive the are or arcs which may be formed between brushes in the direction indicated by the arrow in Fig. 6 away from the inner ends of the commutator-segments and the armature and under the barrier F WVhile my invention is generally applicable in the operation of dynamo-electric machines, it is particularlyuseful in connection with railway-motors, which by reason of the very sudden changes in the load put upon them and by reason of the sudden opening and closing of circuit produced by failure of the trolley or contact shoe to continuously engage the supply-conductor are especially liable to areing troubles.

What I claim as new, and. desire to secure by Letters Patent of the United States, is-

I. In combination, a commutator, brushes in operative relation therewith, and a barrier or barriers of non-conducting material in the space between the brushes.

2. In combination, a commutator, brushes therefor, and means for preventing sparking between the brushes comprising a shield or barrier of fused silica located between said brushes.

3. In combination, a commutator havingits operative surface cylindrical, brushes engaging said cylindrical surface, and an arc-shaped shield or barrier of non-conducting material located between adjacent brushes of different material.

4. In a dynamo-electric machine, a lieldproducing member, an armature, a commutator, brushes therefor, and a shield or barrier interposed between adjacentln'ushes of differ ent polarities, said field and said armature be ing so arranged that the field tends to force an are between the brushes away from the armature and under the barrier.

5. In combination, a rotating commutator, brushes therefor, and means for preventing sparking between the brushes comprising a shield or barrier of a fused silica placed slightly in advance of each brush having reference to the direction of rotation of the commutator.

In witness whereof I have hereunto set my hand this 27th day of May, 1903.

ELIHU THOMSON.

WVitnesses:

DUcALn McK. MoKILLor, Jenn A. MoMANUs.

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