US2141307A - Commutator - Google Patents

Description

H. T. LANG ET AL COMMUTATOR Filed Sept. 10, 1937 Inventors! Henry T. Lang, Ralph E. Dunbar,

Them Abbor'nqg.

Patented ilee. this v 3M3 UNITED STATES PATENT OFFICE comwrs'ron Henry T. Lang, Cleveland, and Ralph E. Dunbar,

East Cleveland, Ohio, assignors to Electric Vacuum Cleaner Company, Inc., Cleveland, Ohio, a corporation oi. New York Application September 10, 1937. Serial No. 163,278

8 Claims. (01. 171--320) The present invention relates to commutators hydrated is used to designate the process of for dynamo-electric machines. manufacture in which the cellulose is hydrated in It been customary to insulate the copper a paper beater as distinguished from chemical segments of commutators with strips of mica arhydration by zinc chloride, sulphuric acid or other ranged between the segments. Due to its mecellulose solvents such as used in the manufac- 5 chanical strength and insulating properties. mica ture of vulcanized fiber. Chemically hydrated is a very satisfactory material. It is, however, cellulose is not as satisfactory since it is cherub much harder than the copper segments so that it cally less stable under heat, which causes arm has been necessary to undercut the mica by sawbrittlement, due to the degradation of the cellulose to lug slots between the adjacent segments 01' the by the action of the cellulose solvent which breaks I!) commutator. The slotting or undercutting redown the primary and secondary valence bonds moves the mica adjacent the brush engaging surof the cellulose. Due to the mechanical hydra faces and therefore permits the use of less abration and the subsequent compression; the ce1lusive soft carbon brushes. If the mica is not lose fibers are intimately bonded together and held undercut very abrasive brushes must be used; in a highly compressed condition producing a 1 otherwise the copper will be worn down faster tough-material having high compressive strength. than the mica and as a result the mica will pro- Other materials which comprise cellulose fibers ject beyond the copper segments causing the having the chemical stability of mechanically brushes to jump which results in excessive sparkhydrated cellulose which are bonded together and co ing which burns the comrmitator. Even with held in a highly compressed condition are satisundercutting, unless great pains are taken, some factory for segment insulation. Glaze'rolling is mica may be left in the slots and as soon as this preferable to super calendering due to the smooth mica is reached the brushes will be worn away surface which more intimately contacts the sides very rapidly. of the segments and also to the fact that higher as The object of our invention is to, provide an densities are obtained. The density of the press improved construction and arrangement in comboard is in the vicinity of 1,3 but is subject to mutators which will overcome some of the disconsiderable variation. The density of samples advantages of mica insulation, and for a conof different lots of the same grade of pressboard sideration of what I believe to be novel and my from the same manufacturer has been observed invention, attention is directed to the accompanyto vary from 1.13 to slightly above l.5. All of 30 ing description and the claims appended thereto. these lots were used for segment insulation and In the accompanying drawing, Fig. 1 is 9. diaproved satisfactory. It is obviously difficult to grammatio View of acommutator embodying my set a definite figure for the density of the pressinvention, and Fig. 2 is a fragmentary sectional board. It is felt that the density is best described view of the commutator. as of theorder of 1.3. Various grades of press- Referring to the drawing, there is drawn a board, being sold commercially, have been found typical commutator having copper segments l satisfactory for segment insulation. Among these insulated by strips of insulation material 2v are 100% rag pressboards, sold under the tradeciamped therebetwen. As shown in Fig. 2 the names of Armo, 'Duro, Spaldo, and Manning 4c ends of the segments are cut away to provide #300. These grades of pressboard are made in so notches 3 for receiving clamping members 4. One sheets and are glaze rolled. A similar material of the clamping members is integral with a sleeve made in continuous strips is available u der the d on which is threaded a nut 6 for efiecting the trade-name of Vosite. Other pressboards made clamping action. Suitable insulation 1 is arfrom mixtures of rag and wood pulp have been ranged between the segments and the clamping tried and found satisfactory. One example of 5 members and the sleeve. The sleeve may serve this type of pressboard is sold under the tradeas a, means for attaching the commutator to a name of Tufelec which comprises a mixture of shaft 8. 75% rag and 25% krait. This latter pressboard The segment insulation 2 is made of pressboard is super caiendered instead of glaze-rolled. A to or other material having the properties of pressglaze-rolled pressboard having rag and the 50 board. Pressboard is paper which obtains its remainder of wood pulp has also been tried and good mechanical properties such as denseness by found satisfactory. All of the pressboards menmechanical hydration or beating"io1lowed by tioned above have the common characteristic calendering which may be either glaze rolling" of high compressive strength due to the high as or super calendering. The term mechanically density and chemical stability under temperait tures usually encountered in commutators. This means that the commutator segments are flrmly held in position so that the segments cannot move radially outward producing high bars which result in destructive sparking. In addition, the pressboards are less abrasive than copper and under normal-black"'commutation wear substantially flush with the copper. ibis eliminates the need for undercutting. There may be some pitting or the brush enga ing suriaces or the segment insulation due to sparking. A further advantage of the pressboard insulation is that the'perticles which are worn away durimthe operation or the commutator are not abrasive and consequently the wear on the commutator segments is greatly decreased. The pressboard should be free from acid and preferably alkaline since the presence oi acid greatly decreases the resistance to heat.

What we claim as new and'desire to secure by Letters Patent 0! the United States is:

1. A commutator having meats held in spaced relation and insulated from each other by pressboard made from mechanically hydrated stock and having a density of the order of 1.8.

2. A commutator having segments held in spaced relation and insulated irom each'other by glaze-rolled pressboard having the properties of a pressboard made from mechanically imitated paper stock.

3. A commutator having segments held in by pressboard made from cellulose having the properties or mechanically hydrated cellulose.

6. A commutator having segments held in spaced relation and insulated from each other by fibrous insulation comprising cellulose fibers having the properties of mechani ally hydrated cellulose which are intimately bonded together and held in a highlyoompressed condition.

7. A commutator having segments held in spaced relation and insulated trcm each other by a super calender-ed mechanically hydrated cellulosepressboard havinga densityoi theorder of 1.3.

8. A commutator having segments held in spaced relation and insulated from each other by nbrous insulation comprising cellulose fibers having the properties or mechanically hydrated cellulose'which are intimately bonded together and held in a highly compressed condition, said insulation having a density oi the order or 1.3.

HENRY T. LANG. RALPH I. DUNBAR.

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