US1255681A - Commutator. - Google Patents

Description

C. C. ZENK. COMMUTATOR.

APPLICATION FILED JULY s. 1912.

Patented Feb. 5

s E s s E UNITED STATES, PATENT oFnroE.

CHARLES C. ZENK, 0F WILKINSIBURG, PENNSYLVANIA, ASSIGNOR TO DIEHL MANUFAC- TUBING COMPANY, OF ELIZABETH, NEW JERSEY, A CORPORATION OF NEW JERSEY.

COMMUTA'IOR.

Specification of Letters Patent.

Patented Feb. 5, 1918.

Application filed July 8, 1912. Serial No. 708,244.

To all whom it may concern:

Be itknown that I, CHARLES C. ZENK, citizen of the United States of America, residing at Wilkinsburg, in the county of Allegheny and State of Pennsylvania, have invented certain new and useful Improve ments in Commutators, of which the following is a specification, reference being had therein to the accompanying drawing.

This invention relates to commutators and more particularly the invention relates to commutators in which the commutator bars are held in position by a molded insulating material of the nature of What are known as synthetic resins and having the properties of hardening, under the action of heat and pressure and' being unaffected by any subsequent rise in temperature in use. In the present invention the'commutator consists of two materials, one embedded in the other and gripped thereby: the bars and the holding body of insulating material forming a unitary, strong, rigid and permanent structure.

The commutator bars of molded commutators constructed as heretofore proposed, would become loosened, due to the softening of the installation because of rise in temperature, or due to the strain to which commutators are subjected in service. These strains are due not only to twisting stresses from rotation but also to a'centrifugal force which, with rapid rotation ma become high. Any movement or dislocation of the accurately spaced commutator segments is of coursehighlyundesirable.

An object of the present invention is to provide a' commutator formed of commutator bars held in place in a body. of molded insulation which will securely grip and hold the bars in place under all conditions of service; such material being one which will not lessen its grip on the bars with increase of temperature.

Another object of the invention is to provide an improved commutator which is especiall adapted to withstand without inury t e strains to which it may be subected by normal or abnormal conditions of operation, and to provide a commutator in which the bars are held in spaced position by a molded material to prevent them being relatively displaced.

In order to illustrate the principles of the invention, embodiments thereof are shown in the accompanying drawings, in which Figure 1 is a vertical sectional view of a complete commutator;

Fig. 2 is an end view of the same partly broken away and partly in elevation; b Fig. 3 is a perspective view of a segment Fig. 4 is an end view of the same; and

Figs. 5 and 6 are detailed sectional views illustrating a modification of my invention.

The commutator is formed of segmentshaped commutator bars 7 of copper or other suitable material, which are embedded in, and are gripped and securely held in place by, a body of molded insulation 1 this body serving not only for insulation but as a structural element. It is the holding element for the bars. .For this purpose a material which will not soften and weaken with a rise in temperature is used; a material which, although ordinarily plastic, becomes harder, stronger and more rigid with increase of temperature. Of the modern synthetic r'esinslor resinous condensation roducts having this property, the best "nown are the commercial articles known as bakelite and condensite', both of which are phenolic condensation products; that is, materials formed by chemically condensing together phenols and an aldehyde. Bakelite is quite suitable. These materials may be obtained in the form of a powder which has the property of hard ening and becoming a rigid strong body under the influence of heat and pressure. Such a body is not susceptible to heat in the sense of softening or weakening, further heating merely'serving to'further harden it. The molded body is preferablyformed of bakelite. And in a commutator formed from these materials, the segments do not become loosened under the strain of service,

even if the commutator should become conends of each, bar are preferably notched or cut away, as indicated at 9, although in some instances this notching may be dispensed with.

To form the commutator, the segmentshaped bars are circumferentially arranged, and spaced apart by mica strips, in a cylindrical mold with the wider ends of the bars outward. The bars are securely held in this position in a mold and bakelite or similar material, is forced into the mold until the interstices are completely filled. The mold is then placed in a press and the insulating material is solidified by the simultaneous application thereto of high heat and pressure.

- The simultaneous application of a high degree of heat and conslderable pressure causes the plastic bakelite to be melted or fused by a chemical or condensation reaction to form a unitary body for the commutator, this body filling the spaces between the bars and entering the grooves 8 and notches 9, and all capillaries or irregularities in the bars so as to securely grip and hold the bars in place. The mold is preferably provided with thin strips which fit between the outer edges of the bars and prevent the insulating material from completely filling the spaces between the bars. This provides shallow slots between the outer edges of the bars, as illustrated in Fig. 2. This construction permits of the segment bars being considerably worn before brushes will contact with the bakelite, and then the slots can be deepened until the bars are completely worn. It is obvious that the slots thus formed in the periphery of the commutator can be filled with mica, plaster or other soft material, but it is preferable to leave the slots open.

in making and molding the commutator the molds employed provide seats 22 at the ends of the commutator body, and one of these seats can receive the collar 23 of a metallic bushing 24, while the other seat receives a nut 25 screwed upon the bushing 24 to retain said bushing in engagement with the commutator body. A key 27- can be placed in the bushing 24 to engage in the key way formed in the body of the commutator.

The described manner of making the commutator also permits of strips of mica 26 being arranged between the commutator bars with the inner edges of the strips of mica embedded in and gripped by the molded body in the cylindrical enlargements 3 that are formed within the grooves 8 of said bars. This construction is clearly shown in Fig. 5 and the use of a mica or plaster as above referred to is shown in Fig. 6.

A mold and method especially adapted for forming commutators of this type are de scribed and claimed in a divisional application, Serial No. 718,778, filed Sept. 5, 1912.

A commutator formed as herein described has a body formed of molded insulating material which is a structural part of it and is sufiiciently hard to permit of being drilled or machined when necessary and which, due to the inherent properties of the insulating material, will securely hold the commutator bars in place without loosening under any conditions of service.

It is obvious that the specific details of construction and configuration of parts described herein may be modified in various ways without sacrificing the advantages of the invention or departing from the scope thereof as defined in the appended claims.

What I claim is:

1. A commutator comprising metal commutator bars, and a body of heat hardened resinous condensation product holding said bars in place.

2. A commutator composed of conducting bars permanently held in place by a. phenol condensation product.

- 3. A commutator comprising metal commutator bars separated by insulating strips, and a body of heat hardened resinous eondensation product holding said bars and said insulating strips in place.

4. A commutator comprising circumferentially arranged equally spaced segment bars having longitudinal rooves in the sides thereof, a body of resinous condensation product molded about said bars and embedding the inner edges thereof, said body of resinous condensation roduct having webs extending between t e bars and provided with enlargementsengaging in the grooves in said bars, and strips of mica arranged between said bars, and having their inner edges embedded in said enlargements of the resinous condensation product.

In testimony whereof I afiix my signature in the presence of two witnesses.

CHARLES C. ZENK.

Witnesses:

C. ZENK, MAX H. SROLOVITZ.

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