US1198873A - Commutator-brush and method of making the same. - Google Patents

Description

R. L. SEABURY.

COMMUTATOR BRUSH AND METHOD OF MAKING THE SAME. APPLICATION HLED JULY 2]. 1914.

W1 TNESSES [NYE/v TOR Patented Sept. 19, 1916.

I is a specification.

UNIT STAS A'EN FFMYEQ RALPH LOWE SEALBURY, OFWELLSVIILLELNEW YORK.

I COMMUTATOR-BRUSH AND METHOD OF MAKING SAME.

iaaaeaa' To all whom it may concern:

Be it known that I, RALPH Lown SEA- BURY, a citizen .of the United States, residd ing at Wellsville, State of New York, have invented certain new and useful Improvements in Commutator-Br'ushes and Methods of Making the Same, of .which the following The object of my invention is the produc tion of an improved brush for use on commutators and collector rlngs of dynamo electric machines which possesses good electrical characteristics and good Wearing qualities 2O ting heavy currents and for use on low voltand a good mechanical construction.

More particularly my invention relates to brushes-that transmit heavy currents to -or from the commutator and to brushes that y are employed-at low voltages and includes not only the article but the process of making it. Heretofore brushes for transmitagemach-ines havecommonly been made of superimposed strips of thin copper or other metal or wire gauze (usually of bronze or of copper) properly rolled and flattened into a nearly solid mass oflthe desired shape. Such brushes have not been-satisfactory on account of excessive commutator and vbrush wear.

Another method commonly 'used to make I brushes of high conductivity has been to employ very finely divided copper or other metal such as would pass through a one hundred (100) mesh screen intimately mixed Y with finely divided carbon and the wholemass then being bonded together with pitch and subsequently baked or carbonized.

This method is objectionable because too high a percentage of "copper or metal is 40 necessary'in order to secure a high conductivity thus' reducing the percentage of carbon that can be used which results in a tendency of the brush to wear away itself and the commutator. Furthermore, such brushes some-' times fail to operate on low. voltage work [.owing to a thin film or coating presumably' an oxid or carbid deposited on its face or on i the commutator.

Still another method of making high con--' forms of brushes.

Specification of Letters Patent. Patented Sept. 19, 1916. Application filed July 27, 1914. Serial No. 853,503.

ductivity brushes has been to employ alternatelayers of wire gauze, the strands which would measure about .0107 in diameter and woven to about thirty (30) meshes per inch bonded :between -,stri-ps or carbon. Such separated and are open tothe further 0bjection' that the 's'trandsof wire frequently fuse andmelt away at the face of the brush 7 when transmitting heavy currentscaused by the current being carried by a comparatively few number of wires thus greatly impairing.

the conductivity 'of the brush.

Various other forms and combinations of brushes have been devised but none, so far as I amaware, has proved thoroughlyefiicient and satisfactory, for carrying very heavy machines. Y My invention aims to combine the high .currents' or for operation on low,volta'ge conductivity of metal with the lubricating qualities of carbon without encountering the difficulties and objections attending the older In making my brush I employ copper orother metal in the form of narrow ribbons and exceedingly thin (about ,QOl in thickness) or preferably finely drawn wire about 003' in diameter, which preferably has been'cut into short pieces. I

about'oneeighth-of an inch or if desired of about the same length as the thick- ,ness of the finished brush, then thoroughly mix these short metal filaments or ribbons with a certain percentage of finely ground carbon and add enough pitch or other binder to hold the mass firmly together after having been properly compressed and baked or otherwise cured. It may be remarked that the conductivity will be mainly governed by the percentage of metal filaments or ribbons present in the mix and that different commutating elfects may be secured by not only changing the cross sectionof the metal filaments or ribbons themselves, either above or below 'the dimensions given above but also by changing their lengths as used in the mix.

In the preferred form of my invention I employ a mixture containing about sixty per cent. of copper filaments, about twenty live per cent. of carbon and about fifteen per cent. of pitch. Any suitable method may be employed in forming or compressin the mix into suitable form. The method which I ordinarilyemploy consists of molding the mix in suitable molds under a pressure of about thirteen tons per square inch.

' of the particular forms that I have described of comparatively short ribbons or filaments in the mix, practically all the filaments or ribbons will arrange themselves so that their major axis will lie parallel to the sides of the brush. I attribute the formation of this arrangement to the fact that considerable air is expelled from the mix during the process of molding which rapidly escapes laterally and finally leaving between the walls of the mold and the plunger, the said air in thus escaping forces the filaments to a great extent to arrange themselves in a plane parallel to the face of the plunger. During the extrusioirprocess in a socalled jumbo such filaments or ribbons being much longer than they are wide or thick,

. would on account of the dragging effect of the die, tend to force such'elongated metallic particles to arrange themselves so that their length would lie in a plane parallel with the plane of the thickness of the brush, thus producing substantially the same effect in molding-the brush. This is a very desirable arrangement since practically each filament at the face of the brush will present against the commutator one of its ends; this construction secures a very low contact resistance between the commutator and the brush. in excellent electrical contact with the ones adjacent to it, either by actual metallic contact or through a very thin medium of carbon, brushes of this construction have an exceedingly low specific resistance, one containing sixty per cent. filaments showing as low a resistance as brushes commonly made that contain eighty per cent. metal in the usual powdered form: This not only effects a saving in metal, important particularly if silver, gold or other expensive metal is used, but also permits a much larger percentage of carbon to be used in the brush, the chief object of which is to act as a lubricant and to prevent abrasion or undue Wear- Furthermore, sinch each filament is ments and carbon such as I have previously described.

Numerous other modifications and combinations from the above description would of course be obvious to those skilled in the art.

In the accompanying drawings Figure 1, is an elevation showing the completed brush; Fig. 2, is an endview showing the ends of the metal filament in the face of the brush;'

Fig. 3, illustrates an end view of a com posite brush while Fig. 4, shows a diagrammatic side View of a composite brush.

Referring to the drawing, A designates a brush in which the metallic particles 1 are distributed throughout the body of the brush, being embedded in the material 2 formed by the carbon and pitch, as shown in Fig. l. The metallic particles 1 extend longitudinally of the brush, andin Fig. 2 only the ends of the particles lying in the end sur face of the brush are seen. In Figs. 3 and 4 a brush B is shown in which the core is composed of metal particles embedded in carbon and pitch, and around the .core is a covering 3 of carbon and pitch material.

The above described arrangements are deemed suflicient to illustrate the nature of my invention and are intended as enumera- .tions of all of its modifications.

This brush may be used in other situations where it is desired to change or switch heavy currents or where a contact for low voltage work is desired that Will minimize the voltage drop. This also may be'used as a self lubricating bearing material.

While I have hereinbefore described and illustrated the best form of my invention now known to me, it is obvious that those skilled in the art may make changes and modifications in the form of my invention without departing from its spirit.

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

1. A commutator brush comprising a block of carbon, having embedded therein a quantity of fine metallic strands, said strands being promiscuously disposed throughout the block andthe strands being substantially parallel with the major axis of the brush.

2. The herein-described process of making electric brushes, which consists in mixin'g carbon particles, a suitable binder, and metallic particles of elongated form into a plastic mass, irvith the metal particles pro- M to themselves and to the axis of the brush, and baking the brush.

July 24, 1914:.

RALPH LOWE SEABURY.

WVitnesses:

L. H. DAVIS, W. ll-RICHARDSON;

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