US2402122A

US2402122A - Resistive device

Info

Publication number: US2402122A
Application number: US501213A
Authority: US
Inventors: Frederic H Bullinger
Original assignee: Ward Leonard Electric Co
Current assignee: Ward Leonard Electric Co
Priority date: 1943-09-04
Filing date: 1943-09-04
Publication date: 1946-06-18
Anticipated expiration: 1963-06-18

Description

June 18, 1946. F. H. BULLINGER 'RESISTIVE DEVICE Filed Sept. 4, 194a I N V EN TOR. fkmffi/a A! 5014/55/1".

BY Q

Patented June 18, 1946 7 RESISTIVE DEVICE Frederic H. Bullinger, Bronxvllle, N. Y., assignor to Ward Leonard Electric Company, a corporation of New York Application September 4, 1943, Serial No. 501,213

Claims.

This invention relates to resistive devices, such as tubular resistive units wherein a resistive conductor is wound on an insulating tube and covered with an insulating coating, such as vitreous enamel. and provided with terminal connections.

In the devices of this type it is desirable to pro-' vide sheet metal terminals of copper or alloys of copper for convenience in making outside connections thereto and in some cases for supp rting the unit thereby. The terminals of copper or alloys of copper have the advantages not only of low resistance and a degree of flexibility and ease of bending but also of enabling leads or connections to be soldered thereto readily with the usual lead-tin solders.

However, if the terminal band or strip around the tube be made of copper in order to provide the sheet metal copper terminal, difficulties arise due to its comparatively high coefficient of expansion. causing crazing 01' the enamel and other dimculties as referred to in said prior Kebler patent. It is therefore desirable to use a metal or alloy for the encircling or clamping elements which will have a lower coeiilcient of expansion than copper and of a proper value in order to overcome such difficulties. For this purpose. sheet iron or sheet steel may be used, as referred to in said Kebler patent, or preferably an alloy of about 50% iron and about 50% nickel as referred to in the prior patent of Charles J. Ganci. No. 2,179,212, .granted November '7, 1939. Such bands or clamps also have the advantage of high tensile strength permitting them to be made comparatively small and to be well covered by the. insulating coating; but they have the disadvantage of not enabling the user tosolder outside connections thereto with the ordinary lead-tin solder. Therefore it is highly desirable to combine with such a band a sheet metal terminal of copper or of copper alloys which likewise secures the other advantages of a copper terminal.

On'e object of the invention is to simplify the structure disclosed in said priorKebler patent and to improve and simplify the method of making the-device. A further object is to insure. a good and permanent electrical connection between the resistive conductor and the copper terminal.

Another object is to provide a structure which is applicable to various sizes and forms of resistive with the clamping band;

thereof; and Fig. 8 is a side view of the complete 2 devices. Another object is to provide an improved form of terminal structure and method of making the same. Other objects and advantages will be understood from the follownig description and accompanying drawing which iluustrates a preferred embodiment of the invention as an illustrative example. I

Fig. 1 is a side view of a tubular resistive unit showing the assembly of the parts before the insulating coating is applied; Fig. 2 is an end view thereof; Fig. 3 is a development of the clamping element or band; Fig. 4 is a fiace view of the sheet metal terminal or tab of copper or copper alloy: Fig. 5 is an edge view thereof; Fig. 6 is a development of the copper terminal after being united Fig. '7 is an edge view device.

Referring to Fig. 1, a supporting tube l of porcelain or other insulating material is shown hav- 25 ments ing a resistive conductor 2 wound thereon. Two end terminals are shown but if desired. any number of intermediate terminals may be added to suit particular requirements. The clamping eleor bands 3 of sheet iron. or steel, or of an alloy of iron and nickel are shown having a resistive conductor connected thereto. These bands have a desirable coeilicient of expansion lower than that of the sheet metal terminals 4 of cop- 80 per or copp i!- The developmgent of one of the bands is shown in Fig. 3 and is provided near one end with a notched portion la connected by a small neck 3b with the body of the band. This band is also provided with perforations c for permitting the insulating coating to enter them and aid in firmly securing the band to the insulating support 2. This clamping element may be readily stamped out of sheet metal.

The sheet metal copper terminal strip or tab 4 portion of the strip.

is shown in Figs. 4 and 5 and is of a form which may be readily cut or stamped from sheet metal. Near one end of the strip a small interior lip or tongue 4a is punched out from an interior midproiecting in a direction toand is'shown of rectangular lb may be stamped near ward the near end form. A perforation the opposite end of the copper strip for conven-' ience in making connections to outside circuits.

Figs. 6 and '7 show the copper strip united with the clamping band and this is accomplished by slipping the end of the copper strip on to the end of the band 8 so that the lip or tongue la passes over one side of the band, the end of the so copper strip engaging the opposite face of the 3 band. The Joined parts are then firmly compressed together at their united portions forming a substantially flat strip throughout its length with the terminal or tab 4 mechanically and firmly united with the band I as shown in Fig. 7.

The combined strip is then bent substantially at right-angles along the dot and dash line shown in Fig. 6 and also near the opposite end of the strip 3 so that when the bands are slipped over the ends of the insulating tube l, the end portions come face to face, as shown in Fig. 2 with the-copper terminal 4 supported between the ends of the encircling band and extending outwardly therefrom. The meeting portions of the band are then spot welded so as to fuse the ends of the encircling band and the inner end of the terminal I together in a solid metal portion. The terminal 4 is advantageouslv made of an alloy of about 6% nickel and balance of copper because such composition melts at a lower temperature than copper and improves the electrical connection between the band and the terminal. It also permits the spot welding to be accomplished at moderate temperatures and likewise the soldering of the outside connection to the terminal I is made easier than when a terminal of pure copper is used.

In connecting theresistive conductor 2 to the projecting portions 3a of the bands, these portions are first bent so as to extend outwardly from the bands. One end of the resistive conductor is then wound around and within the notched portions Ia and around the neck and then in successive turns around the tube, the remaining end of the conductor being similarly wound around the projecting portion and neck of the other end hand. These outwardly projecting portions are then dipped in a silver solder bath for brazing and permanently connecting the conductor to the encircling bands in accordance with the disclosures of my prior Patent No. 1,932,923, granted August 31, 1933. The projections Ia are then bent inwardly close to the tube I after which the insulating coating 5, as

shown in Fig. 8, is applied, resulting in the finalproduct. It is apparent that the completed unit has a uniform and smooth external surface with no protruding portions or projections which are difficult to cover properly with the insulating coating. This coating is preferably of vitreous enamel material and is matured in a furnace at a comparatively high temperature.

In making the device the encircling bands and copper terminals are readily formed from sheet metal and are interlocked and mechanically fasicned together in a simple manner so as to be conveniently handled as a unit and mounted on the tube and then spot welded. Also, the brazed connection between the resistive conductor and the encircling bands is permanent and undisturbed by the firing in the enameling furnace and likewise the spot welding of the opposed faces of the encircling band and the intervening end of the copper terminal gives a fused connection of solid metal between the copper terminal and the band which is unaflected during the firing operation. It follows that an excellent, permanent electrical connection is formed between the copper termlnals and the conductor.

In making the unitary jterminal comprising the band and terminal tab, it is most readily accomplished by a counter-fed stamping interlocking and compressing operation according to the following process. Strips for the bands and for the terminals are first prepared of the proper width and in long lengths. These are then fed through continuously operating stamping machines in opposite directions toward each other. As the stamped and cut terminals are formed. they are passed toward each other end to end so that the tongue formed on the copper alloy terminal passes over one end of the band and the other portion of the terminal passes over the opposite side of the end of the band. In this position the engaging end portions are then compressed flrmly together giving a combined unit interlocked and mechanically united by compression of the parts. The unit then may fall into a box or basket which serves as a supply of units for use in making the resistive devices as already described. These terminal units are adapted for use in various types of electrical apparatus and may be made and sold as a unitary terminal for various uses.

Although a, preferred form of the invention has been described and preferred methods of making, it will be understood that the same is subject to various modifications and adapted for use in various forms and types of devices according to particular conditions and requirements without departing from the scope of the invention.

I claim:

1. A resistive device comprising an insulating support, a resistive conductor thereon, a terminal unit to which said conductor is electrically con nected, said unit comprising a sheet metal strip embracing said support and having end portions facing each other, and a sheet metal strip mainly of copper having an end portion located between said facing end portions, one of said strips having an interior tongue extending from the body thereof and extending over the end and engaging a face of one of the end portions opposite from the face thereof engaged by said last named strip.

2. A resistive device comprising an insulating support, a resistive conductor thereon, a terminal unit to which said conductor is electrically connected, said unit comprising a sheet metal strip embracing said support and having end portions facing each other, and a sheet metal terminal mainly of copper having an end portion located between said facing end portions, said terminal having an interior tongue extending from the body thereof engaging a face of one 01' said end portions opposite from the face thereof engaged by said terminal.

3. A resistive device comprising an insulating support, a resistive conductor thereon, a terminal unit to which said conductor is electrically connected, said unit comprising a sheet metal strip embracing said support and having end portions facing each other, and a sheet metal terminal mainly of copper having an end portion located between said facing end portions, said terminal having an interior tongue extending from the body thereof and extending over the end and enging a face of one of said end portions opposite flrom the face thereof engaged by said termina 4. A resistive device comprising an insulating support, a resistive conductor thereon, a terminal unit to which said conductor is electrically connected, said unit comprising a sheet metal strip embracing said support and having end portions facing each other, and a sheet metal terminal mainly of copper and nickel having an end portion located between said facing end portions, said terminal having an interior tongue extending from the body thereof ensuing a face of one of said end portions opposite from the facethereof engaged by said terminal, said meeting end portions being spot welded to form a solid joint.

5. The method of making a resistive device comprising forming strips of sheet metal, one of said strips being of material having high tensile strength and the other of said strips being mainly of copper, forming an interior protruding tongue on one of said strips, joining said strips end to end with the faces of their end portions in con tact and said tongue embracing the face of the other strip opposite from the contacting face portions, compressing the engaged portions to form a mechanically joinedunit, embracing an insulating support by said unit and bringing one end of said unit to face said compressed portions, welding said last named end to said compressed portions, mounting a, resistive conductor on said support, and electrically connecting said conductor to said unit.

6. A terminal unit comprising two strips of different material joined end to end with the faces of their end portions in contact, and one of said strips havingan interior tongue portion projecting therefrom and embracing the face of the other strip opposite from the contacting face portions, said joined portions being compressed to form a mechanical connection between the ends of said strips.

7. A terminal unit comprising two stripsof dif ferent material joined end to end with the faces of their end portions in contact, and one of said strips having an interior tongue portion projecting therefrom and extending over the end of the other strip and embracing the face of the other mainly of copperand nickel joined end to end 1 with the faces of their end portions in contact, and one of said strips having an interior portion embracing the face of the other strip opposite from the contacting face portions, said joined portions being compressed to form a mechanical connection between the ends of said strips.

9. The method of making a terminal unit com prising forming two strips of different material, joining said strips end to end with the faces of their end portions in contact, and with an interior tongueportion projecting from one of said strips embracing the face of the other strip opposite from the contacting face portions, and compressing said joined portions to form a mechanical connection between said strips.

10. The method of making a terminal unit comprising forming two strips of different material with one-of said strips having an interior tongue portion projecting therefrom, feeding said strips end to end toward each other to bring the faces of their end portions in contact and with said tongue extending over the end and embracing the face of the other strip opposite from the contacting face portions, and compressing the engaged portions to form a mechanical connection between said strips.

. FREDERIC H. BUILINGER.