US2597226A - Fixed electrical resistance element and method of manufacturing the same - Google Patents

Description

May 20, 1952 J. N. coATEs FIXED ELECTRICAL RESISTANCE ELEMENT AND METHOD OF MANUFACTURING THE SAME 2 SHEETS-SHEET 1 Filed April 50, 1951 ,4 MORA/fx May 20, 1952 J. N. coATEs 2,597,226

FIXED ELECTRICAL RESISTANCE ELEMENT AND METHOD OF MANUFACTURING THE SAME Filed April 50) 1951 2 SHEETS-SHEET 2 JNVENTOR. c/U//zeJ /1/0f/70/7 COU/e6 TTORNEY- Patented May 20, 1952 FIXED ELECTRICAL RESISTANCE ELEMENT AND METHOD OF MANUFACTURING THE SAME James Norman Coates, Grand Rapids, Mich.

Application April 30, 1951, Serial No. 223,689

31 Claims. 1

This invention relates to fixed electrical resistance element and method of manufacturing the same.

The principal objects of this invention are:

First, to provide an electrical resistor element of the type used in radio and electronic circuits which is extremely rigid and unlikely to be damaged during installation or by flexing of its terminal leads.

Second, to provide an electrical resistance element of continuous metallic mechanical structure from end to end well adapted to sustain any mechanical loads applied to the resistor in handling, or use.

Third, to provide an electrical resistance element which may be mass produced at low unit cost with accurately controlled electrical resistance values.

Fourth, to provide a method of manufacturing xed electrical resistor elements in which a thermosetting fluid or plastic electrical resistance substance is applied to and supported by a continuous mechanical load carrying metallic structure.

Fifth, to provide a method of manufacturing electrical resistance elements in which insulated electrical conducting wires may be made to form mechanical supporting structure with spaced electrically conducting terminals for the application of electrical resistance material around the wires and between the terminals.

Sixth, to provide a method of manufacturing electrical resistance elements which permits the elements to be rapidly and automatically produced in a continuous connected string to eliminate cost in handling the elements and their parts.

Seventh, to provide a method of manufacturing electrical resistor elements which permits elements to be manufactured with a Wide variety of length of leads on the ends thereof.

Eighth, to provide an electrical resistor having lead wires which are integral extensions of the mechanical load carrying structure of the resistor.

Other objects and advantages of my invention will be apparent from the consideration of the following description and claims.

The drawings, of which there are two shee-ts, illustrate four highly practical forms of my resistor element and indicate the methods of manufacturing the same.

Fig. 1 is a side elevational View partly broken away in vertical cross section of a first form of my resistor element.

Fig. 2 is a transverse cross sectional view of the resistor shown in Fig. 1 taken along the plane of line 2-2 of Fig. 1.

Fig. 3 is a longitudinal cross sectional View through a second form of my resistor element.

Fig. 4 is a transverse cross sectional View through the element shown in Fig. 3 taken along the plane of line 4 4 of Fig. 3.

Fig. 5 is a longitudinal cross sectional view through a third form of my resistor element.

Fig. 6 is a longitudinal cross sectional view through a fourth form of my resistor element.

Fig. 7 is an elevational view of a continuous connected string of my resistor elements.

As indicated in the objects of my invention, my resistor elements are of the lower wattage or small dissipation type commonly employed in great numbers in radio and electronic circuits. Formerly resistors of this type have had an enclosed central body of electrical resistance material with separate metallic leads connected to each end thereof. The resistor material and the connected ends of the leads have then been enclosed in a body of insulating material which functions to mechanically hold the wire and the resistor together. I now disclose how Ito provide an integral load carrying body for a resistor by extending and wrapping together the inner ends of two insulated lead wires so that there is a continuous mechanical direct connection between the opposite ends of the lead wires. Any flexing or bending of the lead wires during the handling or installation of the element is resisted, and the loads created by the bending are sustained by the continuous character of the wires themselves; it is practically impossible to break oi one of the lead wires from the resistor element. After being twisted or wrapped together, portions of the insulating surfaces of the two lead wires are stripped or ground off to provide spaced electrically conducting bare areas. The twisted body of the resistor element is then coated with a layer of semi-fluid or plastic resistance material so that the resistance material contacts and extends between the bared portions of the lead wires. By controlling the spacing of the bared portions and the thickness of the resistance coating I am. able to produce a resistor element having a predeterminable electrical resistance value. The resistance coating is then allowed or caused to harden. Desirably, the resistance material is thereafter enclosed in a protective coating of thermoplastic or thermosetting material.

In the form of my resistor element shown in Figs. 1 and 2 I have provided two lead wires I and 2, each of which is continuously coated with an insulating layer 3 of a familiar type of thermosetting varnish. The wires I and 2 may be of varying gauge. Desirably, the type of Wire used is similar to the copper wire used for winding small electric motors. The adjacent ends of the wires l and 2 are overlapping and twisted together in a uniform spiral twist to form a central body Il. Prior to being twisted together the wires are given a coating of a plastic or thermosetting insulating material so that after being twisted all surfaces of the twisted body 4 are doubly insulated from each other and doubly retained in place by the twisted shape of the wires and the bonding properties of the coating 5. A thermosetting synthetic varnish having high insulating properties is satisfactory for this bonding coat. The coating 5 serves to insulate the cut ends of the wires I and 2.

After the bonding and insulating coating 5 has been set by a suitable baking or curing step the resistance element is rotated about its longitudinal axis and a grinding wheel is applied to a portion of the twisted body 4 so as to grind away a portion of the bonding coating 5, the insulating coating 3 on the wires and a portion of the periphery of the wires themselves along a cylindrical surface S. This bares two adjacent spiral portions 'I and 8 on the twisted portions of the two wires l and 2. Next, a coating of electrically conducting resistance material 9 is applied by spray or brush over the twisted body 4 to enclose and cover the bared surfaces 1 and 8. The resistance material 9 is of a thermosetting or air setting, semi-liquid plastic material and is commercially available in varying grades of electrical conductivity for use as an electrical resistance substance. It will be appreciated that the resistance coating 9 extending between and contacting the surfaces 1 and 8 forms an electrical conducting path of predeterminable electrical resistance.

After the resistance coating 9 has been set, an outer insulating and protecting cover l0 of plastic material is applied over the entire body of the resistor. This coating may be provided with the familiar form of color code strips if desired, and serves, after being set, as a protective case for the resistor. The lead wires l and 2, which extend integrally from the ends of the resistor, may be bared as at Il at any time and at any selected distance from the body of the resistor to form terminal connections for the resistor. Desirably, all of the coatings employed in the resistor, including the bonding coating 5, resistance coating 9, and protective coating I0, are selected from materials that will withstand the heat generated in the wire in making a solder connection of the terminals ll to an electrical circuit.

The resistor' elements are desirably made up in a continuous mechanically connected string, as shown in Fig. 7, so that the various coating, grinding, and baking or curing steps may be carried out automatically by passing the string of the resistors in a controlled step-by-step fashion past grinding and coating wheels and brushes and through heating or baking ovens, as required. A twisting machine, the details of which are unnecessary to an understanding of the present invention, serves to receive a continuous strand of the insulated copper wire, and severs the strand into the separate lengths l and 2 which are overlapped and twisted together to form the continuous string of resistor bodies 4. As a matter of practice the trailing end of the trailing lead wires of each resistor can be left double length before being severed from the incoming stock. t then becomes the leading lead wire for the next succeeding resistor. The individual resistors can be separated at any time by cutting the wire between the resistor bodies.

The modified forms of my resistor illustrated in Figs. 3 to 6 are manufactured in the same general fashion and with the same general types of materials as that just described. Specific differences in the details of the various forms in the resistor will now be pointed out.

In Figs. 3 and 4 the two lead wires la and 2a are brought into overlapping relationship with straight parallel body portions 4a. The ends of the two wires are then given at least one complete turn or locking wrap l2 about the straight body of the other wire. The wraps l2 tightly grip the straight sections of wire and securely and mechanically connect the two lead wires which remain insulated from each other by their insulating coatings 3. The length of the central body 4a may be of course varied as desired. No bonding coating similar to the coating 5 in Figs. l and 2 is employed in this form of resistor. After being joined together the wrapped portions I2 of the two wires are bared as at 'la and 8a by rotating the wraps I2 against a grinding wheel. A coating 9 of the electrical resistance substance is then applied over the body 4a to extend across and between the bared areas and after curing a protective coating HJ is applied as in the rst form of the resistor. Quite obviously the second form of resistor provides a substantially longer electrical path between the two bared conducting areas la and Ea and will thus tend to provide a resistor of higher resistance value. The outer protective coating remains un. changed.

In the modified form of resistor shown in Fig. 5 certain elements or features of the resistor shown in Figs. l and 3 are combined in slightly different fashion. The two lead wires Ib and 2b are brought into overlapping relationship as before and the overlapped portions are twisted together in a central body 6b. In addition, the ends of the wires at each end of the twisted body are given generally circular locking wrap turn |2b. As in Fig. 3, the locking Wrap turns are then ground along cylindrical surfaces to provide bare areas 1b and 8b, and the resista-nce coating 9 is applied therebetween. The protective coating I0 is applied over the resistance ma terial as before.

The modified form of resistor shown in Fig. 6 employs the same type of insulated lead wires Ic and 2c, which are brought into overlapping relationship and twisted together in a spiral body 4c. However, instead of being spirally ground off, the inner ends of each lead Wire are axially stripped or bared of insulation, forming bare contacts 1c and 8c. The resistance coating 9 extends across and between the bare areas as before and the resistor is provided with a protective and insulating coating IU. A feature of this form of resistor is that the twisted body 4c need not be rotated to grind olf the bare areas, as the bared portions Tc and 8c may be formed by stripping a single portion of the wire stock and then severing the stock in the middle of the bared area before the ends of the wires Ic and 2c are brought into overlapping relationship and twisted.

I have thus described four highly practical forms of my electrical resistor element and the steps necessary to manufacture them. Quite obviously other modifications or combinations of the elements and features of my resistor may be devised without departing from the spirit of my invention. and I do not intend the present description of four modifications to be an expression of the limits of my invention.

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

l. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions spirally twisted together in a. central body, a bonding coating of thermosetting material on the overlapping portions of said wires and bonding the twisted body together, adjacent turns of said wires and said coatings being ground away along a cylindrical surface to form spaced spiral and parallel electrical conducting areas, a coating of electrically conducting resistance material having thermo-setting properties applied over said body and said bonding coat and extending between and across said conducting areas, and a protective insulating cover of thermo-setting material covering said resistance coating and said twisted body and extending therebeyond along the protruding ends of said wires, said coatings all being characterized by being unaffected by temperatures up to the melting point of solder.

2. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions spirally twisted together in a central body, adjacent turns of said wires being ground away along a cylindrical surface to form spaced spiral and parallel electrical conducting areas, a coating of electrically conducting resistance material having thermo-setting properties applied over said body extending between and across said conducting areas, and a protective insulating cover of thermo-setting material covering said resistance coating and said twisted body and extending therebeyond along the protruding ends of said wires, said coatings all being characterized by being unaffectedy by temperatures up to the melting point of solder.

3. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions twisted together in a central body, adjacent turns of said wires being ground away along a cylindrical surface to form spaced parallel electrical conducting areas, a coating of electrically conductive resistance material having thermo-setting properties applied over at least part of said body and extending between and across said conducting areas, and a protective insulating cover of thermo-setting material covering said resistance coating and said twisted body.

4. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions twisted together in a central body, adjacent turns of said wires being ground away along a cylindrical surface tb form spaced parallel electrical conducting areas, a coating of electrically conductive resistance material having thermo-setting properties applied over at least part of said body and extending between and across said conducting areas, and a 6 protective insulating cover covering said resistance coating.

5. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions twisted together in a central body, adjacent turns of said wires being ground away along an annular surface to form exposed spaced parallel electrical conducting areas, a coating of electrically conducted resisting material having thermo-setting properties applied over said body and extending between said conducting areas, and a protective insulating cover of thermo-setting material covering said resistance coating and said twisted body.

6. An electrical resistor element comprising, a pair of electrically conducting wires having electrically insulating coatings, said wires having overlapping end portions twisted together in a central body, adjacent turns of said wires being ground away to form exposed spaced electrical conducting areas, a coating of electrically conducted resisting material applied over said body and extending between said conducting areas, and a protective insulating cover covering said resistance coating and said twisted body.

7. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires yhaving their adjacent ends overlapped in straight parallel relation in a central body portion, the inner ends of each wire being wrapped around the other wire at an end of said body portion, the inner ends of each wire having the insulating coating thereof stripped away along a cylindrical conducting surface with the conducting surfaces of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

8. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, the inner ends of each wire being wrapped around the other wire at an end of said body portion, the inner ends of each wire having the insulating coating thereof stripped away along a cylindrical conducting surface with the conducting surfaces of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

9. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, the inner ends of each wire being wrapped around the other wire at an end of said body portion, the overlapping wires of said body portion being twisted together, theV inner ends of each wire having the insulating coating thereof stripped away along a cylindrical conducting surface with the conducting surfaces of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

lO.-An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, the inner ends of each wire being wrapped around the other wire at an end of said body portion, the overlapping wires of said body portion being twisted together, the inner ends of each wire having the insulating coating thereof stripped away along a conducting surface with the conducting surfaces of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

ll. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, the inner ends of each wire being mechanically connected to the other wire at an end of said body portion, the overlapping wires of said body portion being twisted together, each wire having the insulating coating thereof stripped away along a conducting surface with the conducting suriaces of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

12. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, the inner ends of each wire being mechanically connected to the other wire at an end of said body portion, each wire having the insulating coating thereof stripped away along a conducting surface with the conducting surface of the two wires spaced from each other, a coating of electrically conductive resistance material applied over said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating coating covering said resistance coating.

13. An electrical resistor element comprising, a pair of electrically conducting wires having an insulated coating, said wires having their adjacent ends overlapped in a central body portion, said wires being mechanically connected to each other in said body portion, each wire having the insulating coating thereof stripped away along a conducting surface with said conducting surfaces of the two wires spaced from each other, a coating of electrically conductive resistance material appliedover said body portion and contacting and extending between said conducting surfaces of said wires, and a protective insulating covei covering said resistance coating.

14. An electrical resistor comprising, a pair of elongated electrically conducting elements each having an insulating coating, said elements being partially overlapped and mechanically interlockcd to provide a central body, the inner ends of each of said elements having a portion of its insulating coating stripped away in bare contact areas with the bare area of one element spaced longitudinally from the bare area of the other element, a coating of electrically conducting resistance material applied over said body and extending across said bare areas and therebetween, and an outer protective coating of insulating materialv positioned over said resistance material,

l5. An electrical resistor comprising, a pair of elongated electrically conducting elements having an insulating coating, said elements being partially overlapped and connectively interlocked to provide a body, each of said elements having a portion of its insulating coating stripped away in bare contact areas with the bare area of one element spaced longitudinally from the bare area. of the other element, a coating of electrically conducting resistance material applied over said body and extending across said bare areas and therebetween, and an outer protective cover of insulating material positioned over said' resistance material.

16. The method of manufacturing electricalresistors which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body by twisting the overlapped portions of the wires and wrapping the inner end oi each wire about the other, baring a portion of each wire at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer insulating protective coating over said conducting coating, severing said first wire in spaced relationship from said body to form the second wire ofanother element, repeating the overlapping and mechanically interconnecting and baring and coating steps to form a continuous string of mechanically connected spaced resistor elements, and curing said coatings.

17. The method of manufacturing electrical resistors which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body by twisting the overlapped'portions of the Wires, baring a portion of each Wire at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer insulating protective coating over said conducting coating, severing said first wire in spaced relationship from said body to form the second wire of another element, repeating the overlapping and mechanically interconnecting and lbaring and coating steps to form a continuous string of mechanically connected spaced resistor elements, and curing said coatings.

18. The method of manufacturing electrical resistor elements which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnesting said wires in a body by wrapping the inner end of each wire about the other, baring a portion of each wire at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an cuter protective coating over said conducting coating, severing said first wire in spaced relationship from said body to form the second wire of another element, and repeating the overlapping and mechanically interconnecting and baring and coating steps to form a continuous string of mechanically connected spaced resistor elements, and curing said coatings.

19. The method of manufacturing electrical resistor elements which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body, baring a portion of each wire at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer protective coating over said conducting coating,

severing said first wire in spaced relationship from said body to form the second wire of another element, and repeating the overlapping and mechanically interconnecting and baring and coating steps to form a continuous string of mechanically connected spaced resistor elements, and curing said coatings.

20. The method of manufacturing an electrical resistor element which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body by twisting the overlapped portions of the wires and wrapping the inner end of each wire about the other, baring a portion of each wire at longitudinally spaced positions along said body, applying a `coating of electrically conducting material over said body and across and between said bared portions, applying an outer protective coating over said conducting coating, curing said coatings, and severing said rst wire in spaced relationship from said body to form a lead wire for said element.

21. The method of manufacturing an electrical resistor element which comprise the steps of, feeding a length of insulated wire longitudinally into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body by twisting the overlapped portions of the wires, baring a portion of each wire at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer protective coating over said conducting coating, curing said coatings, and severing said first wire in spaced relationship from said body to form a lead wire for said element.

22. The method of manufacturing an electrical resistor element which comprise the steps of,

feeding a length of insulating wire into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body by wrapping the inner end of each Wire about the other, baring a portion of each wire with the bared portions located at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer protective coating over said conducting coating, and curing said coatings.

23. The method of manufacturing an electrical resistor element which comprise the steps of, i feeding a length of insulating wire into axially overlapping relation with another length of similar wire, mechanically interconnecting said wires in a body, baring a portion of each -wire with the bared portions located at longitudinally spaced positions along said body, applying a coating of electrically conducting material over said body and across and between said bared portions, applying an outer protective coating over said conducting coating, and curing said coatings.

24. The method of manufacturing an electrical resistor element which comprises the steps of, bringing the ends of a pair of insulated electrically conducting wires into longitudinal overlapping relation, mechanically connecting the lapped ends in a body by twisting said wires and wrapping the end of each wire about the other, baring portions of each wire in said body by grinding away the insulated coats thereof at spaced positions along said wrapped portions, applying a coating of electrically conducting resistance material over said body and said bare portions, curing said resistance coating, applying a protective insulating coating over said resistance coating and the adjacent ends of said wires, curing said insulating coating, and baring the outer ends of said wires to form attaching terminals for said resistor.

25. The method of manufacturing an electrical resistor element which comprises the steps of, bringing the ends of a pair of insulated electrically conducting wires into longitudinal overlapping relation, mechanically connecting the lapped ends in a body .by twisting said wires, baring portions of each wires in said body by grinding away the insulated coats thereof at spaced positions along said twisted portions, applying a coating of electrically conducting resistance material over said body and said bare portions, curing said resistance coating, applying a protective insulating coating over said resistance coating and the adjacent ends of said wires, curing said insulating coating, and baring the outer ends of said wires to form attaching terminals for said resistor.

26. The method of manufacturing an electrical resistor element which comprises the steps of, bringing the ends of a pair of insulated electrically conducting wires into longitudinal overlapping relation, mechanically connecting the lapped ends in a body by wrapping the end of each wire about the other, baring portions of each wire in said body by grinding away the insulated coats thereof at spaced positions along said wrapper portions, applying a coating of electrically conducting resistance material over said body and said bare portions, curing said resistance coating, applying a protective insulating coating over said resistance coating, and curing said insulating coating.

27. The method of manufacturing an electrical resistor element which comprises the steps of, bringing the ends of a pair of insulated electrically conducting wires into longitudinal overlapping relation, mechanically connecting the llapped ends in a body, baring portions of each .wire in said body by grinding away the insulated coats thereof at spaced positions, applying a coating of electrically conducting resistance material over said body and said bare portions, curing said resistance coating, applying a protective insulating coating over said resistance coating, and curing said insulating coating.

28. The method of manufacturing an electrical resistor element which comprises the steps of, bringing the ends of a pair of insulated electrically conducting wires into longitudinal overlapping relation, mechanically connecting the lapped ends in a body, baring portions of each wire in said body by grinding away the insulated coats thereof at spaced positions, applying a coating of electrically conducting resistance material over said body and said bare portions, and curing said resistance coating.

29. The method of manufacturing an electrical resistor element Vwhich comprises fthe -steps of, bringing two lengths of insulated electrically conducting .wire into longitudinal Ioverlapping relation, mechanically -connecting the lapped lengths in a body by twistingsaid lengths, baring spaced portions of each .length fin -said .body by removing the insulation thereof, applying a .coating of electricallyconducting resistance material over said body Yandsaid bareportionsrfand curing said resistance coating.

30. The method of `manuiacturinganelectrical resistor element which comprises Athe steps of,

vbringing two lengths of insulated electricallyuconducting Wire .into longitudinal overlapping lrelation, mechanically connecting the lapped 'lengths in a body, baring spaced portions oi each Vlength by removing `the insulation thereof, vapplying a coating of electrically conducting :resistance material over said body and .said bareeportionsfand curing said resistance coating.

.31; An electricalresistor comprising, apair of Vlelectrically conducting elements having an `insulating coating, said elements 4being partially overlapped vand connectively interlocked to provide a body, each of said elements having a por- -tion of its insulating coating stripped away in bare contact areas with the-bare area of one ele- -ment spaced from the bare area of the other element, a coating of electrically conductingresaid body as terminals.

JAMES NORMAN yCOATES.

No references cited.

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