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March 15, 1938. G. E. MEGOW 2,111,220 ELECTRICAL RESISTOR Filed July 18,1956 154401144462 5mm? T M1012 / : "K G . 81442253 Patented Mar. ‘15, 1938 ' 2,111,220. UNITED‘ : STATES PATENT" OFFICE 2,111,220 ELECTRICAL RESISTOR George. E.’ Megow, South Milwaukee, as signor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin Application July 18, 1936, Serial No. 91,305 1 Claimf (01;. coll-cs) This invention relates to electrical resistor of the invention constructed according to the units and refers particularly to ?xed resistor best modes so far devised for the practical ap units used in radio circuits and especially radio plication of the principles thereof, and in which: Figures 1 to '7, inclusive, are ‘perspective views receivers. , Fixed resistors oi this type now generally of resistor units illustrating several different em consist of a molded or lumped body of resistance material with wire leads projecting from the ends thereof by which the unit is connected in the circuit. - Modern radio receivers and particularly those for use in automobiles. have their composite ele“ ments compacted into small space and the trend is to even greater compactness. Obviously, crowding the parts together in this manner en 15 tails special provision for electrical insulation as the clearances between the different parts is ordinarily inadequate. 2 ' In keeping with this growing necessity for positive electrical insulation, it is an object of this invention to provide a simple eilicient manner of insulating ?xed resistor units of the char acter described. Resistor units of this type are color coded to indicate their different values and generally the color code marking is applied directly to the body of the. unit. This marking should be visible at all times and consequently, it is another object of this invention to provide an insulation for re sistor units of the character described which is 30 transparent so as not to conceal the color code bodiments of this invention; ‘ Figure 8 is a cross section view through Figure l, on the plane of the line 8-8; and Figure 9 is a cross section view through Figure 10 ‘l, on the plane of the line 9-4. Referring now particularly to the accompany ing drawing, the numeral 5 designates the body of a lumped resistor unit which is preferably cy linclrical with an outer cylindrical wall 6 and end walls l. Projecting from the ends of the body are who leads 8 by which the unit is con nected in an electrical circuit. To indicate the resistance value of ‘the unit and possibly also its plus or minus tolerance, bands 9 of di?erent color combinations are ap plied directly to the cylindrical Wall S of the body. To attain the objects of thisinvention by pro~ viding an insulating covering which Will be trans parent so as not to conceal the color code mark ing and at the same time afford adequate elec trical insulation and a degree of protection against moisture, the body of the unit and pre1f~ erably a substantial portion of its leads 8 are encased in a shell or casing ill of transparent 30 marking. material having the desired characteristics. This A further object of this invention is to pro vide means for insulating resistor units which affords a degree of protection against moisture shell or casing it may be applied in. any of a number of different ways and in Figure 1 the shell is in the form of a tube slipped over the and which adds to the mechanical strength of the resistor unit with its end portions extending out unit and provides protection against obliteration of the color code marking. While adequate-insulation and transparency to closely engage the leads and thereby hold it are of primary importance, low cost is also an important consideration, and consequently it is another object of this invention to provide an in sulatlng enclosure for lumped resistor which is made of inexpensive material easily formed and applied. over the Wire leads and twisted as at it so as self onto the unit. . The shell or casing may be composed of any~ one of a number of different substances, prefer 40 ably some transparent organic ?lm such as “Cel lophane", “Pliofllm”, a cellulose acetate and mod i?ed' forms thereof, a. cellulose nitrate and modi ?ed forms thereof, or any other synthetic resin With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, product, and “Plio?lm” is a chlorinated rubber combination and arrangement of parts substan product. film. ' “Cellophane” as is well known is a cellulose tially as hereinafter described and more particu The casing or shell may ?t the body of the re larly de?ned by the appended claim, it being sistor snugly or loosely as shown in Figures 1 r understood that such changes in the precise em bodiment of the hereindisclosed invention may be made as come within the scope of the claim. and 8. _'I'he accompanying drawing illustrates seven 5 complete examples of the physical embodiment With certain types of material, especially . - “Cellophane”, a loose fit is preferable as this material unless specially treated will he electri cally conductive after being subjected to humid ity, if it is fitted’ closely to the unit, whereas, if a 2 2,111,220 ?tted loosely, it is free from this defect. “Plio ?lm” on the other hand will not conduct elec trically whether it is ?tted to the unit tightly or loosely. ‘ Obviously, the casing or shell may be formed in many different ways. In Figure 2, it is built up by winding a ribbon l2 of the desired trans parent material continuously and progressively over the wire leads and the body 0!’ the unit as 10 shown. If desired, only the body of the unit is cov ered with the insulating shell, and in Figures 3, 4, and 5, different ways in which this may be done are shown. 15 In Figure 3, an insulating and protecting shell is formed by winding a ribbon of the desired material onto the unit. In Figure 4, a tube l3 slightly longer than the length of the unit is closely fitted to the body. 20 Where this method is employed, it is preferable to use a substance other than “Cellophane” as it entails a tight close ?t. In Figure 5, a sleeve l4 closely ?tted to the body as in Figure 4 has its end portions crimped 25 or pressed down against the end walls ‘I of the body as at I5 to add to the protection a?orded by the covering. - The advantages of the invention are also ca pable of realization by merely slipping a tube i6 30 of suitable transparent insulating material over the unit with its end portions projecting out over the wire leads without speci?c provision for holding the same in place. In theembodiment of the invention shown in 35 Figure 7, protection against moisture is particu larly obtained. In this modi?cation, the pro tecting shell consists of two telescoped sleeves l1 and I8 pushed onto the unit from opposite ends thereof and with their adjacent open ends over lapping as at IS. The outer ends of the sleeves are reduced in diameter and have end portions 2' ,to closely hug the wire leads and thereby insure the greatest protection against the entrance of moisture. , Inasmuch as the end portions 20 frictionally engage the wire leads, no other means need be provided to hold the enclosing shell on the unit and the sleeves need not ?t the body closely. 10 However, if desired, the overlapping ends of the sleeves may be fused together or a juncture may be formed therebetween by merely bringing the inner ends of the sleeves into abutting relation and then forming a fused juncture therebetween. From the foregoing description taken in con nection with the accompanying drawing, it will be readily apparent to those skilled in this art that this invention in all of its various modi?ca tions provides a simple and e?lcient manner. of 20 electrically insulating ?xed resistor units, and that in each instance, the desired insulation is obtained without concealing the color code mark ing of the unit and without in anywise com plicating the design or construction 01' the unit as and at a minimum cost. What I claim as my invention is: An insulated electrical resistor comprising: a lumped resistor body; wire leads projecting from opposite ends thereof; and an insulating cover 30 ing for the body and its leads, said covering being composed of a thin transparent cellulose mate rial and fitting the body loosely so as to provide an air space between the body and the covering, and the ends of the covering being ?tted closely to the Wire leads. GEORGE E. MEGOW.