US3056057A - Reinforcement of riveted electrical connections - Google Patents

Description

ONS

DOMIZI ETAL REINFORCEMENT OF RIVETED ELECTRICAL CONNECTI Filed June 9 1958 m hm 3% INVENTORS ARIO DOMIZI G ORGE E. CRANCH ATTORNEY I nection arises from the United States Patent Ofilice 3,056,057 Patented Sept. 25, 1962 Filed June 9, 1958, Ser.

2 Claims. (Cl. 310-249) reinforced electrical connections and methods of producing the same. More particularly, this invention relates to reinforcing a riveted shunt connection to an electrical contact brush.

Riveted brush shunt connections have long been known to the art. Such connections are usually made by drilling a hole through the brush, counterboring the hole on one side of the brush, forming an eyelet or loop on the end of the shunt, placing the eyelet in the counterbore, inserting a tubular rivet blank through the eyelet and through the drilled hole and then establishing the connection by spinning both ends of the blank to form rivet heads in situ.

A major disadvantage of this construction arises from the fact that it is difiicult to control the degree of mechanical tightness of connections at the proper level when manufacturing the riveted brushes in large quantity. If the rivet heads are not spun down tight enough, the connection may become easily loosened when the brush undergoes vibration encountered during service. When the rivet heads are spun down too tightly the relatively weak carbonaceous brush structure may crack in the area surrounding the counterbored rivet hole during the spinning operation.

A further disadvantage of the riveted type brush conpractical manufacturing necessity of maintaining a reasonably large clearance between the body of the rivet and the drilled hole in the brush when large numbers of connections are assembled. With this This invention relates to electrically useless and damage may even reach the point of actual breakage of the brush at the point where the shunt is riveted. It has been found that by keeping the rivet itself fixed in relation to the brush and allowing the brush and rivet to vibrate as a unit much of the stress on the brush at the rivet connection is relieved, and connection life is accordingly improved.

It is an object of this invention to provide a reinforced rivet connection to an electrical contact brush.

It is another object of this invention to provide a method of reinforcing a riveted brush connection which renders it relatively insensitive to normal vibration encountered during service.

In the accompanying drawings:

FIG. 1 is a perspective view of a brush embodying this invention with part of the brush cut away;

FIG. 2 is similar to FIG. 1 showing one method of introducing a reinforcing cement into a riveted brush connection;

FIG. 3 is similar to FIG. 2 showing another method of introducing the cement;

FIG. 4 is similar to FIG. 2 showing a further method of introducing the cement; and

FIG. 5 is similar to FIG. 2 showing still another method of introducing the cement.

In accord with the above objects, this invention broadly comprises the provision of a cementitious material beand the brush body of a rivet-connected the cementitious material may generally be of any type and it may be introduced between the rivet and the brush body by a variety of means,

certain materials introduced in particular ways have been found to perform very well in the practice of this invention.

Organic cements, such as self-hardening polymeric materials of the thermosetting type, mineral cements and molten metals, which solidify upon cooling to above the brush operating temperature, have been found to be entirely satisfactory materials. Any of these may be suitably provided between the brush body and the rivet by any of the means hereinbelow described with reference to the accompanying drawing.

A complete reinforced riveted connection is shown in FIG. 1

terminates the electrical shunt 14. A metal shank washer 16 is placed over the cable eyelet, and a hollow rivet blank 17 is inserted through the eyelet-shank washerbrush body assembly. A metal washer 15 is placed over the rivet blank 17 and against the brush body 10 opposite the side of said brush body 10 having said counterbore recess. The rivet heads 18 and 19 are then formed by spinning, thus securely holding the eyelet 12 in intimate contact with the brush body at the interface 20. Of course, one head of the rivet blank 17 may be spun prior to insertion of said rivet blank 17 into said hole in said brush body 10. In this case, the assembly is bound to intimate contact by spinning the remaining unspun end of spinning both heads at once, as described above. The cement 22 may be introduced into the assembly in a variety of ways.

Referring to FIG. 2, for example, the cement 22 may be introduced between the rivet body 17 and the brush body 10 through a hole 24 in the rivet 17 after the rivet heads 18 and 19 are spun. Or, as shown in FIG. 3 the cement 22 may be introduced between the rivet 17 and the brush body 10 through a hollow needle 28 inserted parallel with the electrical lead 14. Here again, the cement 22 is inserted after the rivet heads 18 and 19 are In the modification illustrated by FIG. 4, the cement 22 is introduced between the rivet '17 and the brush body 10 through a hole 30 in the brush body 10 which extends to the rivet 17. The cement 22 is inserted after the rivet heads 18 and 19 are spun in place. Another way of practicing the invention is illustrated in FIG. 5, where the cement 22 is coated on the rivet body 17 prior to insertion thereof into the brush body 10. The rivet 17 with one head 19 spun, is then inserted and the other head 18 is spun in place.

In each case, the cement is hardened in situ after the electrical connection has been secured by the rivet.

It is an important consideration in the practice of this In order to protect against this contingency, the cementitious material should preferably be added after the rivet is in place and good electrical contact has been established. Another important consideration of this invention is the choice of the materials to secure the rivet to the brush body.

range of the brush may be used successfully.

Examples of some of these materials are melaminealdehyde condensation products, epoxy and polyester resins, solidified metals added in the molten state, acrylonitrile polymers and others. Insome cases it is found advantageous to incorporate inorganic materials in the brushes of conventional'riveted construction. The data taken from, these tests showed that brushes reinforced with" a cementitious materialaccording to this invention had an average life of 11 million impacts before loosening occurred. Conventional rivet connected brushes tested underthe same conditions lasted through an average; of only940 thousand impacts before loosening occurred. Thus, it may be readily seen that the useful life of rivet connectedbrushes made according to this inventionwas about 12 times that of conventionally riveted brushes.

What is claimed is:

1. In a riveted electrical brush connection which comprises a brush body provided with a hole therethrough and an eyelet of an electrical shunt seated over and around, said hole, said brush body and said eyelet of said shunt being bound together by a rivet which extends through said hole and which-is"spun"overontosaidcom nection at both ends thereof; the improvement which comprises a cementitious material located between said brush body and said rivet and in contact with substantially the entire adjacent surfaces of said brush body and said rivet.

2. The improvement as defined in claim 1 wherein said cementitious material is chosen from'the group consisting of a self-hardening plastic, a thermo-setting resin, a phenol-formaldehyde condensation product, and a metallic material which remainsa solid at the operating temperature of said connection.

References Cited in the tile of this patent UNITED STATES PAT ENTS 847,303 Platt Mar: "12; 1907 1,585,849 Gindre May 25, 1926 1,848,142 Pierce Mar. 8, 1932 1,929,142 Hosfield Oct. 3, 1933- 1,970,022 Pietenpol et al. Aug. 14, 1934 2,199,532 Weeks May 7, 1940 2,237,474 Channell Apr. 8, 1941 2,342,732 Gudrnundson Feb. 29, 1944 2,507,780 Gilbert May 16, 1950' 2,849,631 Matz Aug. 26, 1958 FOREIGN PATENTS 451,714. GreatlBritain Aug, 11; 1936

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