US3063100A - Process for making resistors - Google Patents

Process for making resistors Download PDF

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US3063100A
US3063100A US841315A US84131559A US3063100A US 3063100 A US3063100 A US 3063100A US 841315 A US841315 A US 841315A US 84131559 A US84131559 A US 84131559A US 3063100 A US3063100 A US 3063100A
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resistor element
silicone
providing
coating
tube
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Wilbur M Kohring
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C63/00—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor
    • B29C63/18—Lining or sheathing, i.e. applying preformed layers or sheathings of plastics; Apparatus therefor using tubular layers or sheathings
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/34—Silicon-containing compounds
    • C08K3/36—Silica
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01C—RESISTORS
    • H01C1/00—Details
    • H01C1/02—Housing; Enclosing; Embedding; Filling the housing or enclosure
    • H01C1/032—Housing; Enclosing; Embedding; Filling the housing or enclosure plural layers surrounding the resistive element
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
    • Y10S264/71—Processes of shaping by shrinking

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  • FIG. 5 wlLauR M. KoHRlNG s n 191'.. r Ml had* y ATTORNEYS United States Patent Office Patented Nov. 13, 1962 3,063,100 PRUCESS FOR MAKING RESESTRS Wilbur M. Kohring, 3318 W. 159th St., Cieveland 11, @trio Filed Sept. Z1, 1958, Ser. No. 841,315 4 Ctairns. (Ci. 118-59)
  • the invention in general relates to resistors and more particularly to protective coatings for resistors and the process for making same.
  • An object of the invention is to provide a resistor with a protective tubular shield and the process for making same.
  • Another object of my invention is to provide a resistor with at least a protective coating and a tubular shield and the process for making same.
  • Another object of the invention is to provide a resistor with at least a protective coating and a tubular shield with the coating and the shield containing a silicone matcrial and the process for making same.
  • Another object of the invention is to provide a resistor with a protective shield comprising a hollow tube.
  • Another object of my invention is to provide a resistor with a protective shield comprising a hollow silicone tube.
  • FIGURE l shows a longitudinal View of a resistance -unit embodying the features of my invention, partly in section;
  • FIGURE 4 shows a section of a hollow silicone rubber tube
  • FIGURE 5 shows a method of sliding a rubber tube over a resistor element.
  • my invention comprises a non-conducting rod 20, preferably porcelain or steatite, a thin current-conducting film 21 deposited on the surface of the rod 20, end-caps 22 having terminal wires 23 electrically connected to the thin current-conducting film 21, a protective coating 25 and a tubular shield 26 enclosingr the current-conducting surface.
  • the rod may be made of any suitable material of a ceramic nature such as porcelain or steatite upon which the film 25 may adhere.
  • the lilm 25 is very thin and is exaggerated in thickness in the drawings.
  • the thin current-conducting film 21 is preferably carbon, or metal and may be a mixture of carbon and metal, and may include sulphur.
  • the next general series of steps in my process is to connect the end-caps 22 to the end portions of the thin iilm 21 by depositing an electrical substance between the current-conducting film and the end-caps Z2 and pressing the end-caps 22 over the electrical substance.
  • the resistor element may or may not be spiraled at 24 depending upon the resistance valve desired.
  • the next general series of steps consist of providing the coating 25 and the tubular shield 26 around the resistance element.
  • the protective coating 25 is deposited on the resistance film 21 and the protective tubular shield 26 is mounted around the protective coating 25.
  • the protective coating 25 comprises a silicone material preferably a silicone resin, and is referred to in the trade as a heat-resistant, water-repellent silicone electrical varnish. More specifically, the varnish is a phenyl-methyl-silicone resin. In the silicone molecular structure, the silicon alternates with an oxygen atom so that the silicon atoms are not bonded to each other. ln a phenyl-methylsilicone resin, one methyl group and one phenyl group are bonded to each silicon atom. I nd that a silicone resin made by Dow Corning Corporation, Midland, Michigan, and sold under a designation number 994 varnish is satisfactory for my invention.
  • the protective coating 25 is preferably deposited on the current-conducting lm 21 by spraying the phenyl-methyl-silicone thereon, and then baking the resistor element with the phenyl-methyl-silicone deposited thereon for a duration of approximately one-half hour at about 400 F. to provide a semi-cured coating.
  • a polysiloxane resin contains dimethylsiloxane, methylsiloxane, phenylsiloxane, and diphenylsiloxane, and is prepared by the co-hydrolysis and co-condensation of a mixture containing dimethyldichloxosilane, methyltrichloxosilane, phenyltrichorosilane, and diphenyl-dichloxosilane.
  • a polysiloxane resin suitable for my invention may be obtained from Union Carbide Corporation, New York, N.Y., Silicone Division and sold under a designation number R-620.
  • the polysiloxane resin R-620 and the phenyl-methyl resin 994 may be used interchangeably.
  • the tubular shield 26 is in the form of a tube and comprises the following ingredients: initial filler, a reinforcing filler, a silicone rubber gum, benzoyl peroxide, and a Teflon filler powder.
  • the initial ller that I preferably use in my invention is a nearly pure amorphous diatomaceous silica. Principal minor ingredients include aluminum, iron, calcium and magnesium, usually combined as silicates and not readily soluble. Water and acid soluble contents are very low. The average particle size is 2-4 microns. A more precise analysis is as follows:
  • the silicone rubber gum that I use in my invention preferably comprises a polysiloxane having dimethylsiloxane, which is prepared by the hydrolysis and condensation of dimethylpoplysiloxane.
  • the silicone rubber gum has a Williams plasticity number of about 70.
  • the silicone rubber gum that is suitable for my invention may be obtanied from Union Carbide Corporation, New York, N.Y., Silicone Division, and sold under a designation number W-95.
  • the reinforcing filler is a hydrated silica of high purity and of extremely tine particle size. Typical chemical and physical properties are:
  • a benzoyl peroxide suitable for my invention may be obtained from Cadet Chemical Corporation, Buffalo, New York, under the designation of LEenzoyl Peroxide, Puried.
  • Teiion in powder form Another chemical additive that is suitable for my invention is Tellon in powder form.
  • the Teiion that I use in my invention may be obtained from E. I. du Pont de Nemours & Company, Polychemicals Dept., Wilmington, Delaware.
  • the process of making the protective tubular shield 26 may be as follows: I iirst mill in 100 grams of the silicone rubber gum, designation number W-95, with 70 grams of the initial iiller sold under the designation Super-Floss to obtain a silicone-filler mixture. Then I allow the silicone-filler mixture of silicone rubber gum and initial iiller to air set for approximately 24 hours.
  • the workable mass may be extruded into a hollow tube by any suitable method using a standard extruding machine in which the extruded tube is cured as it is passed through a heated die at about 155 C. for approximately five minutes.
  • the hollow extruded tube may be given a further cure by heating it to about 400 F for approximately live minutes.
  • the hollow tube after being cured is stretchable as rubber. Ille elongated tube is cut into short sections approximately the length of a resistor element. The unstretched internal diameter of the hollow tube is slightly less than the outside diameter of the resistor element.
  • one end of the hollow tube section is dipped into a solvent so that the dipped end of the hollow tube section may be easily stretched to a greater diameter than the resistor element.
  • the FIGURE 5 shows a convenient way of inserting the resistor element into the stretched end of the tube section. Immediately after the end of the tube has been dipped into the solvent, the dipped end readily expands, whereby the tube may be easily started over the resistor element by inserting an end-cap 22 into the expanded end of the hollow tu'be 26.
  • the tube is then pulled and stretched over the rest of the resistor until it covers the resistor as shown in FIG- URE 1.
  • the stretched or expanded end of the tube section dries, it will readily shrink and make a tight fit with the resistor element.
  • the resistor element with the protective coating 25 thereon is partially cured so that when the resistor ele- 4l ment with the hollow tube 26 thereon is allowed to dry, the tube will shrink and bond itself tightly to the protective coating 25, and thereby provide a protective shield for the resistor element.
  • the solvent that I use in my invention is preferably toluol. It is also called toluene, methyl benzene, and methyl benzoyl. It is a liquid of the composition CGI-LECHE, resembling benzene but with a distinctive odor. it is obtained as a lay-product from coke ovens and from coal tar. Toluol may be produced by dehydrogenation of petroleum fractions. Another suitable solvent that may be used for dipping the end of a resistor element into is xylene.
  • a similar type of silicone tube which is chemically and physically about the same as the rubber hollow tube previously described in my invention may be obtained from the Bentley, Harris Manufacturing Company, Conshohocken, Pa., and sold under the designation Har i258 Extruded Silicone Rubber Tubing.
  • silicone rubber tubing It is possible to dilate the silicone rubber tubing by immersing it in a commercial solvent such as toluene where in approximately 11/2 minutes it will expand to roughly 11/2 times its original size. The rubber tubing will regain its normal size or conform to the objects it covers within approximately 10 to 15 minutes after it has been removed from the solution of toluene.
  • a commercial solvent such as toluene
  • a resistance code is provided and is stamped upon the tube section to show the necessary electrical specications. The resistor is now ready for final testing and shipping.
  • the process of providing a protective coating and a tubular shield on a resistor element comprising the steps of, providing a phenyl-methyl-silicone resin, spraying said silicone resin on said resistor element to provide a coating thereon, air setting said resistor element with said silicone resin coating thereon for one-half hour, then baking said resistor element with said coating thereon at approximately 400 F.
  • a silicone rubber tubing comprising the steps of, providing grams of dimethyl silicone rubber gum, providing 70 grams of amorphous diatomaceous silica filler, milling said amount of said silicone gum with said amount of silica filler to obtain a silicone-filler mixture, air setting said silicone-filler mixture for about 24 hours, providing 14.6 grams of hydrated silica and milling said amount of hydrated silica with said silicone-ller mixture, providing 5.3 grams of benzoyl peroxide powder and milling said amount of benzoyl peroxide with said silicone-liller mixture containing said hydrated silica to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter of the hollow tube slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said tol
  • the process of providing a protective shield on a resistor element comprising the steps of, providing 100 grams of dimethyl silicone rubber gum, providing 70 grams of amorphous diatomaceous silica filler, milling said amount of said silicone gum with said amount of silica iiller to obtain a silicone ller mixture, air setting said silicone-filler mixture far about 24 hours, providing 14.6 grams of hydrated silica and milling said amount of hydrated silica with said silicone-filler mixture, providing 5.3 grams of benzoyl peroxide powder and milling said amount of benzoyl peroxide with said silicone-ller mixture containing said hydrated silica to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said toluol to stretch the diameter of said
  • a silicone rubber tubing comprising the steps of providing a dimethyl silicone rubber gum, providing an amorphous diatomaceous silica filler, mixing said dimethyl silicone rubber gum with amorphous diatomaceous silica filler in a ratio of approximately 0.7 to 1.0 to obtain a silicone-ller-rnixture, air setting said silicone-filler mixture for about 24 hours, providing a hydrated silica and mixing same with said silicone-iiller mixture in a ratio of 14.6 to 170, providing a benzoyl peroxide powder and mixing same with silicone-iiller mixture containing said hydrated silica in a ratio of approximately 5.3 to 184.6 to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of

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Description

Nov. 13, 1962 w. M. KoHRiNG 3,063,100
PROCESS FOR MAKING RESISTORS Filed Sept. 21, 1959 JNVENToR. FIG. 5 wlLauR M. KoHRlNG s n 191'.. r Ml had* y ATTORNEYS United States Patent Office Patented Nov. 13, 1962 3,063,100 PRUCESS FOR MAKING RESESTRS Wilbur M. Kohring, 3318 W. 159th St., Cieveland 11, @trio Filed Sept. Z1, 1959, Ser. No. 841,315 4 Ctairns. (Ci. 118-59) The invention in general relates to resistors and more particularly to protective coatings for resistors and the process for making same.
An object of the invention is to provide a resistor with a protective tubular shield and the process for making same.
Another object of my invention is to provide a resistor with at least a protective coating and a tubular shield and the process for making same.
Another object of the invention is to provide a resistor with at least a protective coating and a tubular shield with the coating and the shield containing a silicone matcrial and the process for making same.
Another object of the invention is to provide a resistor with a protective shield comprising a hollow tube.
Another object of my invention is to provide a resistor with a protective shield comprising a hollow silicone tube.
Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:
FIGURE l shows a longitudinal View of a resistance -unit embodying the features of my invention, partly in section;
FlGURES 2 and 3 show the steps by which my invention is constructed;
FIGURE 4 shows a section of a hollow silicone rubber tube; and
FIGURE 5 shows a method of sliding a rubber tube over a resistor element.
With reference to FIGURE l, my invention comprises a non-conducting rod 20, preferably porcelain or steatite, a thin current-conducting film 21 deposited on the surface of the rod 20, end-caps 22 having terminal wires 23 electrically connected to the thin current-conducting film 21, a protective coating 25 and a tubular shield 26 enclosingr the current-conducting surface.
The rod may be made of any suitable material of a ceramic nature such as porcelain or steatite upon which the film 25 may adhere. The lilm 25 is very thin and is exaggerated in thickness in the drawings. The thin current-conducting film 21 is preferably carbon, or metal and may be a mixture of carbon and metal, and may include sulphur.
The next general series of steps in my process is to connect the end-caps 22 to the end portions of the thin iilm 21 by depositing an electrical substance between the current-conducting film and the end-caps Z2 and pressing the end-caps 22 over the electrical substance. The resistor element may or may not be spiraled at 24 depending upon the resistance valve desired.
The next general series of steps consist of providing the coating 25 and the tubular shield 26 around the resistance element. The protective coating 25 is deposited on the resistance film 21 and the protective tubular shield 26 is mounted around the protective coating 25.
The protective coating 25 comprises a silicone material preferably a silicone resin, and is referred to in the trade as a heat-resistant, water-repellent silicone electrical varnish. More specifically, the varnish is a phenyl-methyl-silicone resin. In the silicone molecular structure, the silicon alternates with an oxygen atom so that the silicon atoms are not bonded to each other. ln a phenyl-methylsilicone resin, one methyl group and one phenyl group are bonded to each silicon atom. I nd that a silicone resin made by Dow Corning Corporation, Midland, Michigan, and sold under a designation number 994 varnish is satisfactory for my invention. The protective coating 25 is preferably deposited on the current-conducting lm 21 by spraying the phenyl-methyl-silicone thereon, and then baking the resistor element with the phenyl-methyl-silicone deposited thereon for a duration of approximately one-half hour at about 400 F. to provide a semi-cured coating. Another suitable material that may be used to provide a protective coating 2S is a polysiloxane resin and contains dimethylsiloxane, methylsiloxane, phenylsiloxane, and diphenylsiloxane, and is prepared by the co-hydrolysis and co-condensation of a mixture containing dimethyldichloxosilane, methyltrichloxosilane, phenyltrichorosilane, and diphenyl-dichloxosilane. I lind that a polysiloxane resin suitable for my invention may be obtained from Union Carbide Corporation, New York, N.Y., Silicone Division and sold under a designation number R-620. The polysiloxane resin R-620 and the phenyl-methyl resin 994 may be used interchangeably.
The tubular shield 26 is in the form of a tube and comprises the following ingredients: initial filler, a reinforcing filler, a silicone rubber gum, benzoyl peroxide, and a Teflon filler powder.
The initial ller that I preferably use in my invention is a nearly pure amorphous diatomaceous silica. Principal minor ingredients include aluminum, iron, calcium and magnesium, usually combined as silicates and not readily soluble. Water and acid soluble contents are very low. The average particle size is 2-4 microns. A more precise analysis is as follows:
I nd that an initial ller meeting the above requirements is made by Johns-Manville, Celite Division, New York, N.Y., and is sold under the trade name of Super- Floss. Hereinafter, this product will be referred to as a silica filler or as a diatomaceous silica.
The silicone rubber gum that I use in my invention preferably comprises a polysiloxane having dimethylsiloxane, which is prepared by the hydrolysis and condensation of dimethylpoplysiloxane. The silicone rubber gum has a Williams plasticity number of about 70. The silicone rubber gum that is suitable for my invention may be obtanied from Union Carbide Corporation, New York, N.Y., Silicone Division, and sold under a designation number W-95.
The reinforcing filler is a hydrated silica of high purity and of extremely tine particle size. Typical chemical and physical properties are:
Color White Bulk density lbs/cu. ft 3 Specific gravity 1.95 Refractive index 1.445 Average particle size microns .022 Surface area sq. meters/ g 1600 pH in 5% aqueous suspension 4.5 Loss of percent 405 Ignition loss do 10 S162 ..d0 NaCl do .04 NagSO4 do .04 Oil absorption (linseed oil) gms -160 A suitable reinforcing filler for my invention may be obtained from the Columbia-Southern Chemical Cor poration, a subsidiary of Pittsburgh Plate Glass Company, Pittsburgh, Pa., and sold under the designation of "Hi-Sil X303.
A typical analysis of the benzoyl peroxide that I use in my invention is as follows:
A benzoyl peroxide suitable for my invention may be obtained from Cadet Chemical Corporation, Buffalo, New York, under the designation of LEenzoyl Peroxide, Puried.
Another chemical additive that is suitable for my invention is Tellon in powder form. The Teiion that I use in my invention may be obtained from E. I. du Pont de Nemours & Company, Polychemicals Dept., Wilmington, Delaware.
The process of making the protective tubular shield 26 may be as follows: I iirst mill in 100 grams of the silicone rubber gum, designation number W-95, with 70 grams of the initial iiller sold under the designation Super-Floss to obtain a silicone-filler mixture. Then I allow the silicone-filler mixture of silicone rubber gum and initial iiller to air set for approximately 24 hours.
Next in the series of steps, I mill in 14.6 grams of reinforcing iller with the silicone-filler mixture to obtain a composite silicone-filler mixture. Next, I mill in 5.3 grams of the benzoyl peroxide powder with the composite siliconeller mixture containing the reinforcing filler to obtain a suitable mass. Then, the suitable mass is allowed to air set for approximately 24 hours. Next in the series of steps, I mill in 2 or 3% by weight of Teflon in powder form with 189.9 grams of suitable mass to obtain a workable mass. Since the amount of Tellon that I use is very small, it may be omitted without much alteration in the workable mass.
The workable mass may be extruded into a hollow tube by any suitable method using a standard extruding machine in which the extruded tube is cured as it is passed through a heated die at about 155 C. for approximately five minutes. The hollow extruded tube may be given a further cure by heating it to about 400 F for approximately live minutes. The hollow tube after being cured is stretchable as rubber. Ille elongated tube is cut into short sections approximately the length of a resistor element. The unstretched internal diameter of the hollow tube is slightly less than the outside diameter of the resistor element. In order to facilitate the insertion of the resistor element into the hollow tube section, one end of the hollow tube section is dipped into a solvent so that the dipped end of the hollow tube section may be easily stretched to a greater diameter than the resistor element. The FIGURE 5 shows a convenient way of inserting the resistor element into the stretched end of the tube section. Immediately after the end of the tube has been dipped into the solvent, the dipped end readily expands, whereby the tube may be easily started over the resistor element by inserting an end-cap 22 into the expanded end of the hollow tu'be 26. After the end-cap 22 has been inserted into the expanded end of the hollow tube 26, the tube is then pulled and stretched over the rest of the resistor until it covers the resistor as shown in FIG- URE 1. When the stretched or expanded end of the tube section dries, it will readily shrink and make a tight fit with the resistor element.
The resistor element with the protective coating 25 thereon is partially cured so that when the resistor ele- 4l ment with the hollow tube 26 thereon is allowed to dry, the tube will shrink and bond itself tightly to the protective coating 25, and thereby provide a protective shield for the resistor element.
The solvent that I use in my invention is preferably toluol. It is also called toluene, methyl benzene, and methyl benzoyl. It is a liquid of the composition CGI-LECHE, resembling benzene but with a distinctive odor. it is obtained as a lay-product from coke ovens and from coal tar. Toluol may be produced by dehydrogenation of petroleum fractions. Another suitable solvent that may be used for dipping the end of a resistor element into is xylene. A similar type of silicone tube which is chemically and physically about the same as the rubber hollow tube previously described in my invention may be obtained from the Bentley, Harris Manufacturing Company, Conshohocken, Pa., and sold under the designation Har i258 Extruded Silicone Rubber Tubing.
It is possible to dilate the silicone rubber tubing by immersing it in a commercial solvent such as toluene where in approximately 11/2 minutes it will expand to roughly 11/2 times its original size. The rubber tubing will regain its normal size or conform to the objects it covers within approximately 10 to 15 minutes after it has been removed from the solution of toluene.
A resistance code is provided and is stamped upon the tube section to show the necessary electrical specications. The resistor is now ready for final testing and shipping.
Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.
What is claimed is:
l. The process of providing a protective coating and a tubular shield on a resistor element comprising the steps of, providing a phenyl-methyl-silicone resin, spraying said silicone resin on said resistor element to provide a coating thereon, air setting said resistor element with said silicone resin coating thereon for one-half hour, then baking said resistor element with said coating thereon at approximately 400 F. for about one-half hour to provide a semicured coating, constructing a silicone rubber tubing comprising the steps of, providing grams of dimethyl silicone rubber gum, providing 70 grams of amorphous diatomaceous silica filler, milling said amount of said silicone gum with said amount of silica filler to obtain a silicone-filler mixture, air setting said silicone-filler mixture for about 24 hours, providing 14.6 grams of hydrated silica and milling said amount of hydrated silica with said silicone-ller mixture, providing 5.3 grams of benzoyl peroxide powder and milling said amount of benzoyl peroxide with said silicone-liller mixture containing said hydrated silica to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter of the hollow tube slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said toluol to stretch the diameter of said end of said tube section to t'it over said resistor element, sliding said tube Section over said resistor element and the coating thereon, allowing the tube section to dry so that said tube section will shrink and bond itself tightly to said coating and thereby provide a protective shield for said resistor element.
2. The process of providing a protective shield on a resistor element comprising the steps of, providing 100 grams of dimethyl silicone rubber gum, providing 70 grams of amorphous diatomaceous silica filler, milling said amount of said silicone gum with said amount of silica iiller to obtain a silicone ller mixture, air setting said silicone-filler mixture far about 24 hours, providing 14.6 grams of hydrated silica and milling said amount of hydrated silica with said silicone-filler mixture, providing 5.3 grams of benzoyl peroxide powder and milling said amount of benzoyl peroxide with said silicone-ller mixture containing said hydrated silica to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said toluol to stretch the diameter of said end of said tube section to t over said resistor element, sliding said tube section over said resistor element, allowing the tube section to dry so that said tube section will shrink and bond itself tightly to said coating and thereby provide a protective shield for said resistor element.
3. The process of providing a protective coating and a tubular shield on the surface of a resistor element comprising the steps of, providing a phenyl-methyl-silicone resin, spraying said silicone resin on said resistor element to provide a coating thereon for one-half hour then baking said resistor element with said coating thereon at approximately 400 F. for about one-half hour to provide a semicured coating, constructing a silicone rubber tubing comprising the steps of providing a dimethyl silicone rubber gum, providing an amorphous diatomaceous silica filler, mixing said dimethyl silicone rubber gum with amorphous diatomaceous silica filler in a ratio of approximately 0.7 to 1.0 to obtain a silicone-ller-rnixture, air setting said silicone-filler mixture for about 24 hours, providing a hydrated silica and mixing same with said silicone-iiller mixture in a ratio of 14.6 to 170, providing a benzoyl peroxide powder and mixing same with silicone-iiller mixture containing said hydrated silica in a ratio of approximately 5.3 to 184.6 to obtain a suitable mass, allowing said suitable mass to set for about 24 hours, extruding said suitable mass into a hollow tube having an internal diameter slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said toluol to stretch the diameter of said end of said tube section to fit over said resistor element, sliding said tube section over said resistor element and the coating thereon, allowing the tube section to dry so that said tube section will shrink and bond itself tightly to said coating and thereby provide a protective shield for said resistor element.
4. The process of providing a protective shield on a resistor element comprising the steps of providing a dimethyl silicone rubber gum, providing a amorphous silica ller and milling same with said dimethyl silicone rubber gum to obtain a silicone-filler mixture, providing a hydrated silica and milling same with said silicone-filler mixture, provding a benzoyl peroxide powder and milling same with said silicone-ller mixture containing said hydrated silica to obtain a suitable mass, and surrounding said resistoielement with said suitable mass to provide a protective shield for said resistor element, extruding said workable mass into a hollow tube having an internal diameter of the hollow tube slightly less than the outside diameter of the resistor element, cutting said hollow tube into sections approximately the length of said resistor element, providing a toluol, dipping one end of a section of said tube into said toluol to stretch the diameter of said end of said tube section to iit over said resistor element, sliding said tube section over said resistor element and the coating thereon, allowing the tube section to dry so that said tube section will shrink around said coating and thereby provide a protective shield for said resistor element.
References Cited in the le of this patent UNITED STATES PATENTS 2,460,795 Warrick Feb. 1, 1949 2,634,352 Boykin Apr. 7, 1953 2,660,653 Berkelhamer Nov. 24, 1953 2,742,551 Kohring Apr. 17, 1956 2,744,988 Tierrnan May 8, 1956 FOREIGN PATENTS 584,549 Great Britain Jan. 17, 1947

Claims (1)

1. THE PROCESS OF PROVIDING A PROTECTIVE COATING AND A TUBULAR SHIELD ON A RESISTOR ELEMENT COMPRISING THE STEPS OF, PROVIDING A PHENYL-METHYL-SILICONE RESIN, SPRAYING SAID SILICONE RESIN ON SAID RESISTOR ELEMENT TO PROVIDE A COATING THEREON, AIR SETTING SAID RESISTOR ELEMENT WITH SAID SILICONE RESIN COATING THEREON FOR ONE-HALF HOUR, THEN BAKING SAID RESISTOR ELEMENT WITH SAID COATING THEREON AT APPROXIMATELY 400*F. FOR ABOUT ONE-HALF HOUR PROVIDE A SEMICURED COATING, CONSTRUCTING A SILICON RUBBER TUBING COMPRISING THE STEPS OF, PROVIDING 100 GRAMS OF DIMETHYL SILICONE RUBBER GUM, PROVIDING 70 GRASMS OF AMORPHOUS DIATOMACCEOUS SILICA FILLER, MILLING SAID AMOUNT OF SAID SILICONE GUM WITH SAID AMOUNT OF SILICA FILLER TO OBTAIN A SILICONE-FILLER MIXTURE, AIR SETTING SAID SILICONE-FILLER MIXTURE FOR ABOUT 24 HOURS, PROVIDING 14.6 GRAMS OF HYDRATED SILICA AND MILLING SAID AMOUNT OF HYDRATED SILICA WITH SAID SILICON-FILLER MIXTURE, PROVIDING 5.3 GRAMS OF BENZOYLTED PEROXIDE POWDER AND MILLING SAID AMOUNT OF BENZOYL PEROXIDE WITH SAID SILICONE-FILLER MIXTURE CONTAINING SAID HYDRATED SILICA TO OBTAIN A SUITABLE MASS, ALLOWING SAID SUITABLE MASS TO SET FOR ABOUT 24 HOURS, EXTRUDING SAID SUITABLE MASS INTO A HALLOW TUBE HAVING AN INTERNAL DIAMETER OF THE HALLOW TUBE SLIGHTLY LESS THAN THE OUTSIDE DIAMETER OF THE RESISTOR ELEMENT, CUTTING SAID HALLOW TUBE INTO SECTIONS APPROXIMATELY THE LENGTH OF SAID RESISTOR ELEMENT, PROVIDING A TOLUOL, DIPPING ONE END OF A SECTION OF SAID TUBE INTO SAID TOLUOL TO STRETCH THE DIAMETER OF SAID END OF SAID TUBE SECTION TO FIT OVER SAID RESISTOR ELEMENT, SLIDING SAID TUBE SECTION OVER SAID RESISTOR ELEMENT AND THE COATING THEREON,, ALLOWING THE TUBE SECTION TO DRY SO THAT SAID TUBE SECTION WILL SHRINK AND BOND ITSELF TIGHTLY TO SAID COATING AND THEREBY PROVIDE PROTECTIVE SHIELD FOR SAID RESISTOR ELEMENT.
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3205467A (en) * 1962-07-27 1965-09-07 Ward Leonard Electric Co Plastic encapsulated resistor
US3214719A (en) * 1964-03-20 1965-10-26 Westinghouse Electric Corp Thermistor device
US3345597A (en) * 1963-08-27 1967-10-03 Kanthal Ab Electric heating resistors
DE3334533A1 (en) * 1983-09-23 1985-04-04 Transformatoren Union Ag, 7000 Stuttgart Surge arrester
US4551293A (en) * 1984-03-05 1985-11-05 Jamak, Inc. Method of forming spark plug boots
DE3607225A1 (en) * 1986-03-05 1987-09-10 Siemens Ag Electrical chip-type component and method for producing it

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB584549A (en) * 1944-08-02 1947-01-17 British Insulated Cables Ltd Improvements in the construction of electric condensers and resistors
US2460795A (en) * 1944-10-03 1949-02-01 Corning Glass Works Method for making rubbery polymeric organo-siloxane compositions
US2634352A (en) * 1952-06-23 1953-04-07 Boykin Fruth Inc Electrical resistor
US2660653A (en) * 1950-04-05 1953-11-24 David T Siegel Resistor and method of manufacture
US2742551A (en) * 1951-07-27 1956-04-17 Wilbur M Kohring Precision resistances
US2744988A (en) * 1952-02-07 1956-05-08 Sprague Electric Co Molded resistors

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB584549A (en) * 1944-08-02 1947-01-17 British Insulated Cables Ltd Improvements in the construction of electric condensers and resistors
US2460795A (en) * 1944-10-03 1949-02-01 Corning Glass Works Method for making rubbery polymeric organo-siloxane compositions
US2660653A (en) * 1950-04-05 1953-11-24 David T Siegel Resistor and method of manufacture
US2742551A (en) * 1951-07-27 1956-04-17 Wilbur M Kohring Precision resistances
US2744988A (en) * 1952-02-07 1956-05-08 Sprague Electric Co Molded resistors
US2634352A (en) * 1952-06-23 1953-04-07 Boykin Fruth Inc Electrical resistor

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3205467A (en) * 1962-07-27 1965-09-07 Ward Leonard Electric Co Plastic encapsulated resistor
US3345597A (en) * 1963-08-27 1967-10-03 Kanthal Ab Electric heating resistors
US3214719A (en) * 1964-03-20 1965-10-26 Westinghouse Electric Corp Thermistor device
DE3334533A1 (en) * 1983-09-23 1985-04-04 Transformatoren Union Ag, 7000 Stuttgart Surge arrester
US4551293A (en) * 1984-03-05 1985-11-05 Jamak, Inc. Method of forming spark plug boots
DE3607225A1 (en) * 1986-03-05 1987-09-10 Siemens Ag Electrical chip-type component and method for producing it

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