US1902861A - Resistance unit - Google Patents

Description

March 28, 1933. KEBLER 1,902,861

RESISTANCE UNIT Filed July 19, 1930 Patented Mar. 28, 1933 UNITED STATES PATENT OFFICE LEONARD KEBLER, OF BRONXVILLE, NEW YORK, ASSIQNOR TO WARD LEONARD ELECTRIC COMPANY, A CORPORATION OF NEW YORK RESISTANCE UNIT Application filed July 19,

This invention relates to resistance units, and particularly to that form in which the resistive conductor is wound upon an insulating tubular support and provided with terminal connections. The invention particularly relates to the rovision of auxiliary terminal conductors which are connected to the resistive conductor and supplementary clamping means for holding the terminal '10 conductors in place upon the insulating support. The invention is an improvement upon that disclosed in the pending application of Frederic H. Bullinger, Serial Number 467,674, filed July 14, 1930, the particular object of the present invention with relation thereto being the provision of terminal connections and supporting means by which the unit may be supported, or for uses where it is desired to provide terminal connections other than flexible lead wires.

Resistanoe units of this type are usually covered with an adhesive insulating coating such as vitreous enamel, cement and the like; and one object of the present invention is to provide terminal connections of the above character and supporting means therefor, such that there will be no objectionable bump or projection on the tube which cannot readily be covered by the insulating coating. Another object is to overcome the objection in previous 'units having terminal connections of the above character where sheet metal bands of copper have been used, which 5 objection arises from the fact that the coefficient of expansion ofcopper is so much more than that of the insulating support, During the firing operation for maturing the insulating coating, the prior copper bands sometimes shift on the insulating support 4 and -cause loosening or shifting of the resistive conductor, with the possible occurrence of short-circuits therein; also, the undue ex pansiongof the sheet metal copper terminals makes it difiicult to insure the proper covering of the copper bands with the insulating coating. By means of the present invention, the use ofsheet metal copper bands is avoided and replaced by encircling jand clamping elements of sheet iron or steel, or similar metal, which not only has higher 1930. Serial No. 469,043.

tensile strength than that of copper, permitting the encircling element to be smaller and more easil covered by the insulating coat-' ing, but a so, by reason of its cocfliclent of expansion being lower than that of copper, avoiding the objectionable effects above referred to when sheet copper encircling clamping elements are used.

However, I still retain the advantage of permitting the use of copper terminals and so relate them to the resistive conductor. and clamping element as to provide for connection to theexternal circuit through direct contact with the low resistance terminal, such as copper. Another object of this i11--65 vention is to replace the prior sheet metal encircling and clamping element of copper by metal of lower cost, such as strips of sheet iron or steel, making the unit less expensive in cost of material.

Another object is to provide a construction which will be rigid where it leaves the insulating coatingand strongly support the sheet metal terminal in-that region, so that when the unit isv handled and external connections made thereto, it willnot bend where it leaves the insulating coating. '1 thereby avoid cracking oi breaking away of the insulating coating at that region. This aplies particularly to units where the proecting portions of the copper terminals aremade flexible for convenience of making connections and of cleaning the contacting surfaces.

Another object is to provide means, in cases where desired, for giving the entire terminal strength and stifi'ness and yet secure direct contact connection with the terminal strip, such as of. copper. Another object is to secure ease in assembly of the parts and also insurestrength of the assembly, by uniting the conducting terminal v with the clamping element before mounting .the parts upon the insulating support,

Other objects and advantages of this in vention will be understood from the following description and accompanying drawing.- Fig. 1 is a longitudinal section of one form of resistance unit embodying my invention; Fig. 2 is. a side elevation of the 2 same, showing the parts before the application of the insulating boating; Fig. 3 is a similar elevation of't e opposite side from that shown inv Fig. 2; Fig. 4 is a development of the conducting terminal; Fig. 5 is a development of the clamping and supporting element; Fig. 6 is a longitudinal section of another embodiment of the invention; Fig. 7 is a side elevation before the application of the insulating coating; Fig. 8 is a similar view showing the opposite side from that shown in Fig. 7; Fig. 9 is an end view of the parts before the application of the insulating coating; Fig. 10 is a development of the conducting terminal; and Fig. 11 is a development of the clamping and supporting element.

Referring to Figs. 1 to 5, the insulating tubular element 1, usually of porcelain, is shown having the. resistive conductor 2 wound thereon. The conductor 2 is electrically connected at the ends, or at any intermediate point desired, to the conducting terminal 3. This is stamped out from sheet metal, preferably of copper, in the form shown in Fig. 4. It has a ortion extending outwardly from the tu e, and an inner portion 31) which lies directly on the surface of the tube and extends in' a circumferential direction thereon. This element, in the form shown, is provided with a pair of oppositely located ears 3a, the sides of -whichare cut inwardly in the body of the conducting strip, asindicated in Fig. 4. One side of the strip is provided with a tongue 3dto which the resistive conductor is connected;

The iron or steel clamping and support- .ing element for the'terminal, shown in Fig. 5, has along narrow portion 4 which. encircles the main portion of the tube; and at one end is provided with an enlarged portion 4a. The opposite end is provided with .an enlarged portion 46 and oppositely located outwardly extending ears 40. At opposite locations, portions are cut away to form indentations 4d.

' 1 In assembly, the conducting terminal is first secured to the inside of the clamping element by bending the ears 3c ofthe terminal outwardly and inwardly so as to embrace the neck portion 4e of'the clamping element, as shown in Fig. 2. The parts are then bent substantially at right-angles along mg center lines indicated in Figs. 4 and 5. Then the parts are mounted upon the insulating support, the narrow portion 4 of .the clamping element encircling the support and bringing the part 4w thereof towards the part 46 with the conducting element extending outwardly between and beyond the end portions of the clamping element. The

ears 4c are then bent around the parts and inwardly, soas to firmly bind the end portlons of the clamping element against each resistive conductor is t en wound with a fewturns around the ton ue 3d of the conducting terminal at the le t, or otherwise secured thereto, and then passed over the narrow portion 4 of the clamping element and under a slightly upturned corner of the terminal conductor, as indicated at the left in Fig. 2, and is then wound around the supporting element and wound with a few turns around the tongue 3d of the right-hand terminal. The insulating material for forming the coating is then applied over the resistive conductorand over the parts of the conducting and clamping elements which embrace the tube, after which the unit is fired or otherwise treated to mature and;, f0rm the permanent insulating coating 5, preferably vitreous enamel. In this form of my invention, the outwardly extending portions 3a of the conducting terminals are' flexible for convenience of making connections and cleaning the surfaces, but it is evident that the portion of the conducting terminal near the tubular support and in the region of the insulating coating is prevented from having any flexibility by the enlarged end portions the parts surrounding the tubular support have no objectionable protuberances, and also are of compartively small size and capable of being conveniently and well covered and protected by the insulating coating.

In the form shown in Figs. 6 to 11, the conductlng terminal 6 is shown in development in Fig. 10 as of general rectangular form having perforations 601, 6b, 60 and 6d. It is also provided with a tongue 66 to which the resistive conductor is secured. The center llnes in Fig. 10 indicate the lines along which theterminal is bent after being assembled. The conducting element is preferably made of copper, orsimilar material.

The clamping element is shown in development in Fig. ll as having a narrowportion 7 which extends around the main arts upon the in-wH- sulat-inl support, the con ucting terminal is secure to the clamping element, such' as by punching one of the holes 60 or Gritinto -one .1 of the holes 7a or 7/ of the clamping element and forcing'part of the copper metal sl ghtly over the edge of one of the holes 76 or 7 f, orthey may be riveted or spotwelded, or secured together by ears of one part enveloping the other, as described with reference to Figs. 1 to 5, or otherwise. The parts are then bent substantially at rightangles along the center lines above referred to, except that the conducting terminal is not bent along the upper center line of Fig. 10. The parts are then mounted on the tubular support, the narrow portion 7 of the clamping element encircling the tube and the outer parts of the clamping element are brought together with the outwardly extending portion of the conducting terminal between them. The ears 7c are then bent around the parts so as to firmly clamp the outwardly extending portions together. The outer portion of the terminal is then bent on itself so as to extend inwardly towards the tube, as shown in Fig. 9, so as to form an exposed copper surface for connection in circuit as may be desired. A screw 8 is then assed through the holes 6a, 6b, 711 and 72' of the terminal structure and provided with the usual nuts for clamping the parts together and for securing the external leads thereto. The resistive conductor is then connected to the conducting terminals and wound upon the insulating support, as described with reference to Figs. 1 to 5, afterlwhich the insulating coatlng is applied as already described. The holes and 6d of the terminal coincide with the holes 7e and 7/ of the clamping element permitting the enamel, or other insulating coating to pass through them and engage the tubular support, as likewise through the hole 7g and 7714 of the clamping element, so that the insulating coating will serve to hold the clamping element in more intimate engagement with the support and be more firmly united therewith.

It is apparent that the structure of Figs. 6 to 11 has the advantages already generally referred to and that instead of having fiex1-.- ble terminals as in Figs. l to 5, the whole external portions of the terminals are rigid and strongly supported. 7

Although I have described preferred embodiments of this invention, it is susceptible of various modifications without departing from the scope thereof.

I claim: 1. A resistance device comprising a support, a resistive conductor thereon, a sheet metal element embracing said support by one face thereof, asheet metal conductive terminal held in position on said support by said sheetmetal element, one face of said conductive terminal being against said supportand the other face against said sheet metalelement, said resistive conductor being directly mechanically and electrically connected to said sheet metal conductive terminal, said sheet metal element having greater tensile strength than the metal of the conductive terminal, and an insulating coating covering said resistive conductor and at least a part of said sheet metal element.

2. A resistance device comprising a support, a resistive conductor thereon, a sheet metal element embracing said support by one face thereof, a sheet metal conductive terminal held in position on said support by said sheet metal element, one face of said conductive terminal being against said support and the other face against said sheet metal element, said resistive conductor being directly mechanically and electrically connected to said sheet metal conductive terminal, said sheet metal element having a lower coeflicient of expansion than that of the metal of said conductive terminal, and an insulating coating covering said resistive conductor and at least a part of said sheet metal element.

3. A resistance device comprising a support, a resistive conductor thereon, a sheet metal element clamping said support and having outwardly extending end portions, a sheet metal conductive terminal held in position on said support by said element, and havingan outwardly extending portion between the said outwardly extending ortions of said sheet metal element, said s eet metal element having higher tensile strength and a lower coefiicient of expansion than the tween said end portions of said'sheet metal,

element, and an insulating coating covering said resistiveconductor and at least a part of said sheet metal element. 1

5. A resistance device comprising a tubular support, a resistive conductor wound thereon, a sheet metal element embracing said support and having its ends'connected together, a sheet metal conductive terminal clamped between said supportand said element, said resistive conductor being directly mechanically and electrically connected to, v said sheet metal conductive terminal, means for securing said element and terminal together, said terminal having a portionyex;

tending between and outwardly beyond the ends a said element and supported thereby, and an insulating coating covering said resistive conductor and at least a part of said 5 element. y

6. A resistance device comprising atubular support, a resistive conductor wound thereon, a sheet metal element embracing said support and having its ends connected 7 10 together, a sheet metal conductive terminal clamped between said support and said elevment, said resistive conductor being directly mechanically and electrically connected to said sheet metal conductive terminal, said terminal having a portion thereof embracing said element for securing them together, said terminal having a portion extending between and'outwardly beyond the ends of said element and supported thereby, and an insulating coating covering said resistive conductor and at least a part of said element.

7. A resistance device comprising a tubular support, a resistive conductor vwound thereon, a sheet metal element embracing said support and having enlarged outwardly extending portions, a conductive sheet metal terminal between said outwardly extending portions and extending beyond the same,

. said sheet metal element having higher tensile strength and a lower coefiicient of expansion than the metal of said conductive sheet metal terminal, said resistive conductor be- .ing directly mechanically and electrically connected to said conductive sheet metal terminal, and an insulating. coating covering said resistive conductor andv at least a part of said element.

8. A resistance device comprising a tubu- 40 lar support, a resistive conductor wound thereon, a sheet metal element embracing said support and having enlarged outwardly extending portions, a conductive sheet metal terminal betweensaid outwardly extending portions and extending beyond the same and also bent inwardly over the end of one of said end portions, said sheet metal element having higher tensile strength and a lower coeflicient of expansion than the metal of said conductive sheet metal terminal, said resistive conductor being directly echanically, and electrically connected to siiid conductive sheet metal terminal, and an insulating coating covering said resistive conductor and at least a part of said element.

LEONARD KEBLER.

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