US2028793A - Interference preventing cable - Google Patents

Description

Jan. 28, 1936. J. J. MASCUCH INTERFERENCE PREVENTING CABLE Original Filed July 11, 1931 INVENTOR. JZJEPH J flJCY/(W.

ATTORNEY.

Patented Jan. 28, 1936 UNITED STATES PATENT OFFICE Divided and this application February 17, 1933, Serial No. 657,167

2 Claims.

This invention relates to a shielding conduit for the ignition wires of an internal combustion engine and is a division of application Serial No. 550,076, filed July 11th, 1931.

One object of the invention is to provide a conduit system for ignition which will completely isolate, electrically, the ignition system of an internal combustion engine.

When internal combustion engines using electrical ignition systems are used in proximity to radio receiving apparatus, there is a radiation of electrical waves from the ignition system, which radiation causes interference with the reception of radio equipment.

By properly surrounding with a conductive casing, all of the parts of the ignition system through which high frequency currents pass and grounding the said conducting casing, it is possible to dissipate the energy of the electrical radiations directly to ground, thereby preventing the aforesaid interference. It is an object of this invention to provide a conductive casing or shielding for the ignition wires of internal combustion engines, whereby interference to radio communication equipment installed in proximity to the engine will be eliminated.

This invention is applicable to all types of combustion engines and particularly to engines on units such as aeroplanes, motor boats, automobiles, submarines, etc.

This invention is particularly useful in aircraft practice and will be described as used on aircraft engines but it will be understood that the invention is not restricted to such use.

Due to the extreme conditions under which an aeroplane engine operates it is necessary, in order to have an effective shield, that the ignition sys tem be protected from the possibility of failure due to outside interference. A short circuit or break in any part of the ignition system will cause most serious damage. Oil, water or gasoline will deteriorate the insulating material, at first permitting corona discharges and eventually resulting in a total breakdown of the insulation, thereby causing the necessity for the replacement of the defective conductor. Therefore, another object of the invention is to provide a shielding means for the ignition system which will prevent water, oil, gas or other detrimental foreign substances from reaching the conductors or other parts of the ignition system, and which, by en closing the entire system in a fireproof casing will minimize the risk of fire caused by short circuits, resistance flashes and sparking.

In order for a shielding system to be practical it must be constructed so that it may be easily applied to an engine and constructed so that parts thereof may be removed or replaced without the necessity of dismounting the engine and removing the entire shielding means. Therefore, another object of the invention is to provide sectional conduits so that any particular section may be easily removed and replaced.

A further object of the invention is to provide a conductive casing for the ignition wires which will intercept andground any electrical impulses from the outside which might affect the ignition system.

Where rigid shielding is used the vibration causes rapid wear and abrasion of the insulating materials of the conductors. As soon as the insulation is damaged electrical emanations are released therefrom with resultant loss of power and efiiciency. Therefore, a further object of the invention is to provide flexible conduits to the spark plugs and magnetos so that the harmful effects of vibration will be minimized. This insures longer wear and less likelihood of breakdown. Where rigid shielding is used the vibration causes the shielding to crystallize and break. By using flexible shielding this danger is eliminated.

In high tension conductors it is essential that the outer surface of the insulating material be smooth and that the conductor be kept free from kinks or sharp bends at which points charges of high potential may build up. In case the smooth or lacquered surface of the insulation becomes damaged at points or sharp bends, the accumulated charge will create a corona discharge from the rough or fuzzy points, thereby gradually deteriorating the entire insulating material and causing a complete break-down of the insulation at this point, resulting in a short circuit. By making the inside of the conduits smooth, the lacquer finish of the conductors is not damaged when they are drawn through the conduits. It is therefore a further specific object of the invention to provide a shielding means wherein the inner surface of the conduits will be smooth even Where they are bent. By making the conduits larger than the conductors an air gap will be left in the conduit around the conductors. This air gap increases the insulation and also prevents, to a certain extent, wear and abrasion of the conductors.

The invention consists of the construction, combination and arrangement of parts as herein illustrated, described and claimed.

In the accompanying drawing, forming part hereof, is illustrated a form of embodiment of the invention, in which drawing similar reference characters designate corresponding parts, and in which:

Figure 1 is an enlarged side elevation, partly broken away; and,

Figure 2 is a detail in side elevation, partly broken away, showing the method of attaching the conduit to the rest of the shielding system.

In the use of the invention with an aircraft engine the ignition wires are led from the magnetos through a manifold 25. Disposed around 36 describes a longer curve before reaching the manifold 25. The purpose of this curved section 36 is to eliminate the sharp bend otherwise necessary in the igntion wire when passing from the manifold 25 through the outlet 33. An additional advantage of the curved portion 36 is that it indicates in which direction a wire will run in the manifold 25, thus assisting in arranging the proper assemblage of the ignition wires. The

other end of the tubular member 34 is provided with a screw-threaded section 31. On the inside. adjacent the outer end, the member 34 is provided with abeveled face 38 for the purpose hereinafter described.

The ignition wires or conductors 39 are encased in insulation 40 and pass from the manifold 25 through the outlet 33 to the spark plugs. Disposed around the conductors 39 between the outlets 33 and the spark plugs are conduits 4|. The conduits 4| are secured to the outlets 33 by means of interiorly screw-threaded collar nuts 42.

The conduit 4| is fabricated from three layers of material, the inner layer being formed of a single continuous strip of metal 44 spun itself to produce a flexible housing for the conductors 39 and insulation 49. The strip 44 may be made of any suitable metal but is preferably made of aluminum. The strip 44, in cross-section is substantially the shape of a'block letter 8 and is so spun as to provide oppositely disposed interlocking flanges 45f When the strip 44 is spun a packing 4B is introduced between the flanges .45. The packing 43 may be asbestos and is saturated with graphite to insure a good conducting element through the strip 44. When the inner conduit has been spun as described air spaces 43 are left between the flanges 45, thus leaving room for; flexing the conduit 4|.

With this construction the inside surface 41 of the conduit 4| is made perfectly smooth so that when the conductors 39 with the insulation 40 are drawn through the conduit 4|, the lacquer finish on the insulation 4|) will not be damaged. Even though the conduit 4| be bent or flexed the inner surface 41 will still be smooth and thus preserve the insulation 49. As pointed out heretofore if the'insulation 4D is damaged in any way a loss in efficiency in the ignition system will result. The inside of the conduit 4| is larger than the conductor 39 with its insulation 40. This leaves an air gap inside the conduit 4| which greatly increases the insulating qualities and prevents abrasion of the insulation 40.

Disposed around the inner conduit formed by the strip 44 is a jacket or casing of braided wire 48. Many types of wire may be used but it has been found highly successful to use a braiding of fine-gauge tinned copper wire. On'the outside of the conduit 4| is braided a protective casing or armor 49 composed of strips of metal or flat wire. The function of the armor 49 is to both protect the conductor 39 and act as an electrical conductor. Therefore, many types of armor may be used. However, it has'been found that for flexibility, durability, strength and lightness, an armor made of phosphor bronze ribbon is highly successful. With this construction a continuous electrical bond is made between the layers of the conduit 4 Disposed on each end of each conduit 4| is a ferrule 59. The outer end 5| of the ferrule 50 is crimped or spun against the armor 49 to hold the strips of the armor 49from movement and to insure a good electrical contact. The center portion of the ferrule 50 is formed into an outwardly extending flange 52 by means of bending the ferrule 50 upon itself. The inner end 53 of the ferrule 59 covers the ends of the armor 49, the braid 48 and the strip or inner conduit 44, and is turned inwardly in the conduit 4|. The inner end 53 is pressed against the inside 4'! of the conduit 4| so as to eliminate any raw edges and to present a smooth orifice for the conductor 39.

Disposed around the insulation 49 of the conductor 39 is a conical rubber washer 54. When a conduit 4| is connected to an outlet 33 the washer 54 strikes the beveled face 38 of the outlet 33 and the flange 52 of the ferrule 50 presses against the opposite face of the washer 54. The collar nut 42, when screwed onto the threads 31, forcesthe flange 52 against the washer 54, the conical face of which is forced against the beveled face 38 of the outlet 33 and makes a water-proof connection. When the washer 54 is thus held under pressure it holds the insulation 49 of the conductor 39 to the center of the outlet 33, thus preventing any possible friction against the inner wall of the outlet 33. At the same time the washer 54 being compressed by the nut 42 the washer 54 exerts a pressure against the nut 42 and acts as a lock-washer to hold the nut firmly in place so that the nut cannot become loosened from vibration. This same effect is produced on all outlets where a conical washer 54 is used.

The advantages of the above described construction are manifold. The sleeve 44 formed from the strip 44 forms an eflicient shield around the conductors 39. However, because of its loose construction the shielding properties are not perfect. When the braiding of fine wire 49 is added a solid electrical bond is formed. The efficiency of the sleeve 44 plus the braiding of wire 48 is equivalent to a one-piece tube of copper or other highly conductive metal, while at the same time the desired flexibility is retained. The vibration and abrasion of the braiding 48 against the other parts of the motor would quickly wear out the Wire 48. Therefore, the armor 49 is added. This not only protects the wire 48 but increases the efficiency of the shielding to a point as near perfection as is mechanically possible. While the sleeve 44 is relatively moistureproof and with the packing 46 will withstand the ordinary attacks of moisture, oil or gasoline, the addition of the wire 48 and the armor 49'renders the complete aoaeyres conduit 4i impervious to the attack of moisture or other detrimental agents. The braiding II in the armor 49, being closely .woven, prevents the entrance of moisture in suincient quantities to have any effect on the inner sleeve 44. By crimping the outside end SI of the ferrule 50 against the armor 49 and the inside end 53 of the ferrule 50 against the sleeve 44 all of the loose ends of the armor 49 and the wire 48 are securely held in position.

Having thus fully described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A flexible conduit to protect and electrically shield electric wires comprising an inner sleeve formed of a continuous strip of metal wound spirally to provide interlocking flanges, packing impregnated with an electrically conductive agent between the flanges, a plurality of braided metallic coverings on the inner sleeve and a ferrule on each end of the conduit enclosing the ends of the component parts and electrically bonding the several layers.

braided metal'on the outside of the braided wire, 10

a double walled ierrule on each end of the conduit having one wall crimped against the inside of the conduit and the other wall crimped against the outside of the conduit to enclose and hold in proper relation the ends of the component parts and 15 electrically bond the several layers and a coupling nut on each end of the conduit, said nuts being prevented from withdrawal from the conduit by a flange on each ferrule.

JOSEPH J. MASCUCH.

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