US1220679A - Electrical contact. - Google Patents

Description

C. PFESFFER.

ELECTRICAL CONTACT.

APPLICATION FILED NOV. 19. 1913:

m m w Patented Mar. 27,1917

ELECTRICAL CONTACT.

Application filed November 19, 1913.

To all whom it may commas.

Be it known that I, CHARLES PFEIFFER, a resident of Milwaukee, in the county of Milwaukee and State of Wisconsin, have invented certain new and useful Improvements in Electrical Contacts, of which the following is a full, clear, and exact description.

The invention relates to electrical contacts and their method of manufacture, and more particularly to that type of contact which includes a body or element of carbonaceous material, such as graphite.

Heretofore, it hasbeen the practice to electroplate the sides and one end of the carbonaceous element with an electrical conducting medium such as copper, to provide a suitable contact surface which is adapted to engage another contact or terminal. In practice the CilllJOlltHKXNlS conductors are raised to a high temperature and this causes the copper plate to become loosened, particularly when the thickness of the plate exceeds that used in the ordinary commercial plating, andv this increased thickness is desirable to withstand the mechanical stresses to which it is subjected in carrying the current desired. An example of this type of contact and the manner of its use is set forth in Letters Patent No. 1,054,902, dated March 4, 1913.

in the use of graphite as an electrical conductor, some means is necessary to make a satisfactory and durable contact with the metallic conductor or contact leading to or from the graphite conductor and the doc tro-plating of conducting medium onto the graphite was designed for this purpose.

I have found that carbonaceous material, such as graphite, which 'is used in this type of contact, may be compressed and that by pressing the graphite element and the me tallic container together, a more ei'licicnt contact results than that produced by electro-plating. By this compression operation, an intimate contact between the graphite and the metallic conductor is obtained. at considerable pressure over a relatively large area and furthermore, this intimate contact is maintained despite the expansion and contraction of the two elements when they are subjected to varying and high temperature when in use.

A further objection to the electroplating was that the processwas expensive and re- Specification of Letters Patent.

Patented Mar. 2?, 19ft.

Serial No. 801,796.

quired av long time. By employing a sepa rate container and placing the graphite body therein and compressing the two, a composite electrical. contact of high efficiency is produced and the contact may be quickly and cheaply manufactured.

ther advantages and objects of the invention will be manifest from the contact and. method of making the same, hereinafter set forth.

The invention consists in the several novel features hereinafter set forth and more particularly defined by the claims at the con clusion hereof.

In the drawings: Figure l is a View, showing the contactmember applied to a resistance device. Fig. 2 is a sectional. View showing the contact-member in position in a die before compressing it.. Fig. 3 is a sectional view showing the contact member in position in a die after it has been compressed.

The electrical contact 10 is illustrated in Fig. 1 as applied to the end of a resistance device, which comprises a resistor 1 within a containil'ig chamber 2. The. resistor 1 is made up of a series of resistance disks, which as a whole, make up the resistance element of the resistance unit. At the top of the series of resistance disks, a terminal is provided and a graphite disk 14 is placed in contact with the top resistance disk. Upon the top of this disk 14, ismounted the contact 10, which is secured to a terminal plug 16 by a screw 17 and serves as an electrical conductor between the terminal 16 and the disk 14., the contact being placed so that the bottom face of the metallic container abuts against the terminal 16.

The contact 10 comprises a body 11 of carbonaceous material, such as graphite, held within an intimatily connected container 12 made of conducting material, such copper. (The graphite body or element is provided with an aperture 13 through which the screw 1? is inserted to secure the contact 10 to the terminal 16. The aperture 13 is provided with a shoulder 15 against which the head of the screw 17 abuts.

in manufacturing the contact 10, a cylindrical cup or container 12 is formed of drawn copper or other suitable conducting metal, the walls of which are of the desired thickness, by pressing a ptece of plate of graphite conductor 11 and the depth of the cup 12 is such as to allow the graphite conductor-element to project out far enough from the upper edge of the cup, as shown at 20 to prevent any contact between the cup and the adjacent plate or conductor 14,

upon which the graphite disk is to hear.

The cup 12 and the cylindrical graphite conductor-element contained therein are then pressed into a cylindrical die 21 oi such dimensions that the metallic cup is pressed firml y around the graphite with sufficient force to reduce the diameter of both the metallic cup and the graphite conductor contained therein.

' The result of this construction and mannor of making it, is a metallic conductor surface which intimately contacts with the graphite conductor element; the metal aird the graphite being constantly under a yielding pressure regardless of the relative changes of dimensions of the metallic cup and the graphite conductor due to the different co-ellicientsof expansion of the materials when heated, or changes of dimension from other causes. The metallic element of the contact can be made of any. desired thickness, thereby afl'ording any amount of mechanical strength and conductivity neccssary. r

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus described the invention, what I claim as new and desire to secure by Letters Patent, is:

1. The method of making composite electrical contact members, consisting. in connecting an elastic graphite element with a metallic conductor clement under suiiicicnt resilient pressure of one element upon the other to compensate tor differences in expansion and contraction due to the extreme cl'iang'es in temperature to which such con tact members are subjected and to maintain intimate pressure contact oia substantially cons'an'l. degree between the elements not withstanding such temperature changes.

2. The method of making composite electrical contact members, which consists in subjecting a. body of elastic carbonaceous material to clamping pressure of a metallic container sutiicient to reduce the volume of the portion of the carbonaceous material which the container engages and develop suiiicient elastic reactionary pressure to maintain'the carbonaceous element and the container in intimate pressure contact under the varying temperature conditions to which such contact members are subjected.

3. That improvement in making a composite electrical contact member which consists in uniting an elastic carbonaceous element with a metallic container by subjecting the container to sufiicient pressure to distort the container and density the carbonaceousmaterial therein suiiiciently to produce an elastic reaction against the container under all service conditions of temperature variations.

4-. An electrical contact composed of an elastic carbonaceous material and a conducting device adapted 'to maintain said material in a state of distortion under all service conditions of varying temperature, and notwith- I action.

6. An electrical contact composed of compressed carbonaceous material. and electrical conducting means adapted to maintain said material in a state of compression sufficient to reduce its volume under all conditions of working temperature notwithstanding differences in the normal rate of thermal expansion and contraction of the carbonaceous material and the conducting means.

7. An electrical contact composed of compressed elastic graphite and means for maintaining said graphite in a state of compres sion under all service conditions of varying temperature. e

S. In an electrical contact, the combination of an elastic carbonaceous body and a metallic container, having walls against which the carbonaceous body resiliently cX- pands, said body being suiiiciently elastic to maintain an eflective pressure upon the container under varying temperature conditions.

S). That improvement in making an electrical contact-member, which consists in placing a body of an elastic carbonaceous material in a metallic container and subjecting the container and material to pressure so as to produce an intimate contact between the container and the carbonaceous material, the pressure being suflicient to densify the body of carbonaceous material, and develop a. permanent reactionary pressure of said material upon the container.

10. That improvement in making an electrical contact member, avhich consists in placing an elastic carbonaceous body or element in a separately formed metallic eontainer of conducting material and subjecting the container to pressure to contract it around the carbonaceous element.

11. an electrical contact comprising an elastic carbonaceous body which is com- ;ed and maintained in estate of coma surrounding member under temperature conditions.

An electrical contact comprising an elastic carbonaceous body, which is c0md maintained in a state of com- )n by a surrounding metallic member, diameter of which is relatively increased diminished by changes '11 temperature. 13. in an electrical contact, the combination of an elastic cylindrical carbonaceous be "y and a metallic cup, having a portion thereof compressed In saic l by the pressure of the, Walls of the tion of a said carbonaceous cup and its volume materially re-' 14. In an electrical contact, the combinagraphite body and a metallic container, said graphite body having a portion thereof inclosed by the container and held therein by expansive pressure oft-he inclosed f portion against the Walls of the container, said inclosed portion having a co-eflicient of expansion, greater than that of the container.

15. In an electrical contact, the combination of a cylindrical graphite body and a metallic cup, said graphite body being compressed Within said cup and maintained therein by expansive pressure against the Walls of the cup:

CHAS-H PFEIFFER. 'Witnesses:

F. FREMONT BURNHAM, FRANK A.

WASSON.

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