US1556990A - Commutator brush - Google Patents

Description

- tains to make and use the same, reference Patented Oct. 13, 1925.

, UNITED 4s'm'rlfzs PATENTOFFICE- RALPH L. HENRY, 0F BROOKLYN, YORK, ASSIGNOR T0 vALBERT C.- HENRY, 0F

INwooD, Lone IsLAnn, NEW Yonx.

ycolumn:'heron Bausu.y

application mea october 12, 1922. Serial no. 594,938.

To all whom t may concem:

.- Be itknown that I, RALPH L. HENRY, a citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented certain new and useful -Improvements in Commutator Brushes; and I do hereby declare the f ollowing to be a full, clear, and exact description of the invention, such as will enable others skilled in the artv to which it apperf being had tothe accompanying drawings,

and .to characters of reference marked thereon, whichform a part of this specification.

v This invention relates, generally, to

brushes and contacts for electrical machines, generators motors and the like, and to a method of manufacturing the same. The

invention has for its principal object to provide a novel brush or contact 'made of a mixture o f electrically conductive materlal, such as graphite, pulverized metals, carbon,

coke, lamp-black or other suitable conduc-' tive material, combined with a, binder of electrically non-conductive or high resistance material, such as a condensation product resulting from the reaction of formaldehyde upon phenol or a phenolic body,'or other resinous gum, to provide a material similar to that commonly known as bakelite, redmanol, condensite, etc., or any other form of condensation or other product which has the property of becoming insoluble and infusible when subject to the action of heat.

Said conductive material and non-conductive or high resistance binder material are A united by pressure and heat. The pressure is applied in a, direction substantlally at right angles to the Apath of least electrical resistance it is desired to be established in the nished brush or contact body; whereby4 a finished product of desired shape is produced, which possesses a novel physical formation or internal structure adapted to establish a path of least electrical resistance throughout the 'same along predetermined lines, said lines being usually substantially parallel to the longitudinal axis of the body thus formed; while at the same time the electrical resistance of the body alongy lines perpendicular to such established path of least resistance-is considerably increased, so' that the novel physical and electrical charand especially desirable in commutatlon 1nl connection with electrical-machines, for the body thus offers comparatively low resistance to the flow of main currents through`V the same to and from lthe machine, While maintaining a comparatively high resistance to the How of the commutating, cross, short circuited or internal eddy currents, with the result that the efficiency of commutating machines is greatly increased.

In the present invention I do not lay claim broadly to a combination of the aforesaid materials generally for all purposes, but .am concerned with a certain procedure and the employment of certain proportions, whereby I am enabled to produce an electrical brush or contact having novel electrical properties, so that the same ischaracterized by the possession of a pathv of least electrical resistance along predetermined lines and directions, and comparatively high electrical resistance in directions perpendicular to said predetermined path of least resistance, y

The accompanying drawing shows a dia-v grammatic perspective of a commutator brush possessing the novel physical and electrical characteristics in accordance with the principles of this invention.

Thus I'may proceed as follows,

terial, and a suitable condensation product of the kind wabove mentioned as the non-conductive or high resistance binder. lTo nine (.9)4 parts by weight of graphite is added one ('1) part by weight of binder. The materials maybe mixed together in any suitable manner, so that the binder will-be interspersed with thev particles of graphite. After n I take graphite, for example, as the conductive ma- In thus compressing thev heating the molds, during the operation of compressing the mixture, to a degree suticient to transform the. binder into the desired final infusible and insoluble state. If the mixture is compressed while cold, the heating and transformation of the binder into the desired infusible and insoluble state may be carried out in a suitable heater or oven.

The application of ressure, in the manner above described, t at is, in a direction at right angles to a plane of the mass parallel to which it is desired to'establish the path of least electrical resistance therethrough, tendsto flatten out the Hake-like conductlve particles of graphite in planes or lines transverse or at right angles to the direction of theY applied pressure, and even particles of granu ar conductive material would have a tendency' to thus Hatten or crush down under the pressure exerted thereupon. As a consequence of this tenflency, the ends of adjoining particles would also tend, in many instances, to break the iilm of the binder at such ends and thereupon make contact one with another, while the films of binder at the top and bottom sides would tend to remain intact'. In any event, since by the flattening process, the conductive particles have greater length and width than thickness, there would be, in the physical structure of the iinished brush or contact, a larger number of insulating or high resistance lms interposed between the conductive particles in the direction of applied pressure, than would be interposed therebetween in a direction at right angles to the applied pressure. It follows therefore that the nished brush or contact body is iven a novel internal physical structure which so modifies itsI -electrical characteristics as a conductor, that it possesses in ,predetermined lines or directions a hi h current carrying capacity of comparative y low resistance, while in lines or directions perpendicular thereto a comparatively high resistance4 is offered or interposed to the flow of cross electric currents. A brush or contact device is thus provided which possesses decidedly novel and advantageous electrical properties, especially when. used for commutation urposes. The peculiar and novel internal p ysical structure, which characterizes the brush or contact body, may not necessarily be in regular or symmetrical stratas, lines or layers, butk it is, I believe, as above stated, a formation of comparatively free or uninterrupted conductive lines alternated more or less with lines of high resistance or insulating effect, running, generally, in a given desired direction through the body of the brush or contact; and, furthermore, it may be stated, as a rough description of such internal physical structure, that the conductive material and the nonconductive or high resistance Ybinder material tends toward a stratified relative' disposition. y

In the example above given, I have stated the proportions of conductive material relative to binder material to be nine to one, that isl 90 per cent conductive material to l0 per cent of non-conductive or high resistance binder material. I do not wish to be understood, however, as thereby coniining myself 'to the use of such specific relative proportions, since more or less variation either way as to the proportion of the binder material maybe made', according to the tensile strength and carrying capacity it is desired that the finished brush or contact shall possess. I have also found that. 85 per cent of conductive material to 15 per cent of binder material forms a very satisfactory brush for generator use, since it is of adequate physical strength and durability, while at the same time is electrically of comparatively high current carryin capacity. VAs a practical limiting range I prefer to use not more than 25 per cent of 90 the binder material, for beyond such proportion of non-conductive or high resistance binder, the electrical resistance becomes so high that the current carrying capacity is re uced beyond practical limits.

While it is preferable that the condensation product providing the binder element of the brush be solidified or hardened without carbonizing the same, whereby its in- -herent non-conductive or high resistance electrical characteristics are unchanged, it may, neverthele, be desirable in someV instances and for certain specific uses to submit the brush to a heat suiiciently great to carbonize or partially carbonize the binder, to thus produce a brush possessing a maximum current carrying capacity. In either case, however, the binder material formed from the described condensation products is comparativel non-abrasive although adapted to reasonably resist wear, so that a brush containing the same is both strong and durable or long-lived.

I claim 1. An electrical brush or contact, comprisl ing a mixture of a, preponderance of electrically conductive material with a binder consisting of a relatively high resistance material capable of becoming insoluble and infusible when subjected to heat, said mixture being consolidated in such manner that the elements of the mixture are relatively disposed to form an internal physical struca path of least electrical ture providgn resistance in es substantially parallel to 125 one plane of the mass.

2. An electrical brush or contact, comprising a mixture of electricall conductive material with between `one an twenty-five per cent of a non-conductivemr high resistance binder consisting of a condensation productA ing an electricallylconductive material mixedy with not to exceed approximately twentyfive per cent of a non-conductive or high resistancelbinder consisting of an infusible condensation product, said vmixture being molded by pressure applied in one direction and solidified by heat, whereby the elements thereof vare relatively disposed throughout the mass to form aninternal physical structure having a path of least resistance. substantially parallel to one plane of the mass.

4. An electrical brush or contact comprising graphite mixed with not to exceed approximately twenty-tive per cent of an infusible and insoluble phenolic condensation.

product, said mixture being consolidated in such manner that the graphite and condensation product are relatively disposed throughout the mass to form a substantially stratified internal physical structure providing a path of leastI electrical resistance substantially parallel to one plane of the mass.

5. The process of manufacturing electrical brushes or contacts. which conslsts in intlmately mixing a dry comminuted conductive 'material with a relatively high resistance binder consisting of a condensation Aproduct capable of becoming insoluble and infusible, compressing the mixture by pressure applied in the direction of one ax1s of the mass, and solidiying the binder by heat.

6. The process of manufacturing electrical brushes or contacts which consists in mixing a dry comminuted conductive material with not to exceed approximately twenty-five per cent of a binder consisting of a condensation product capable of becoming insoluble and infusible, compressing the mixture by pressure applied in the direction of one axis of the mass, solidifying the binder by heat.

In testimony that I claim the invention set forth above I have hereunto set my hand this 28th day of Auist, 1922. i

- ALPH L. HENRY.

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