US 2322903 A
Description (OCR text may contain errors)
June 29, 1943. H. M. wlLKoFF IGNITION HARNESS Filed Deo. 27, 1940 2 Sheets-Sheet l June 29, 1943. H. M wlLKoFF 2,322,903
IGNITION HARNESS Filed Dec. 27, 1940 2 Sheets-Sheet 2 Patented Jeune 29, 1943 UNITED STATES PATENT OFFICE IGNITION HARNESS Howard M. Wilkofl', Worcester, Mass.
Application December 27,1940, Serial No. 371,927 n (ci. 174-71) 15 Claims.
This invention pertains to ignition harness for internal combustion engines and to a method of making such harness.
An ignition harness is made up of the various ignition wires leading from the distributor of the internal combustion engine to the spark plugs. While the invention maybe of more general utility. it is vespecially designed asan improvement in the harness used in airplane engines. In some of these engines the cylinders are radially disposed andfsome have a straight-.line arrangement and the improved harness is applicable to both types of engine.
Considering the radial engine as an example, the harness usually comprises an annular tubular casing which is arranged to extend concentrically with theengine shaft and into which lead the conductors from the magneto or magnetos.
the conduit and then through the connection at the other end of the conduit before they can be connected to the spark plug terminal. If done carefully, this operation may be performed without injury to the conductor, but when repairs must be made by those who are not especially skilled or careful, the insulation may be scraped off or injured in pulling the conductor through the irregular channel provided for it, and not only may the particular conductor thus drawn in be injured but the operation may likewise injure the insulation of some of the other conductors already in place. Moreover, since airplane engines are ordinarily provided with double ignition systems, it may happen that if one of the conductors belonging to one of these systems should break down so as to emit sparks within the manifold, its failure may not be noticed during operation of the engine since the other ignitionsystem provides for this emergency, and thus before the defect is discovered the sparking may have seriously injured those art, the ignition manifold) to the spark plug of one of the respective cylinders. The conductors thus extend todiferent distances around t"e circumference of the manifold and the manifold maybe of gradually decreasing transverse area. or may be of uniform` cross section throughout its lengthaccording to the choice of the designer. l
In certain common types of harness the manifold is made of flexible' tubing and each conductor extends continuously from the magneto to its respective spark plug. In order to protect the conductors from mechanical injury and to avoid radio interference, it is necessary that each individual conductor be enclosed within metal from the time it leaves the generator until it connects with the spark plug terminal. tie ignition manifold is made of metal or is to the manifold to which is connected a conduit, usually flexible, which encloses the conductor and which extends to the spark plug to which itis secured by a special connection.r
The conductors used for this purpose, particularly for army and navy use, are very finely constructed,."being provided with insulation of the highest quality and are usually covered with a coating of lacquer. However, these finely finished conductors must be put in place in the harness by drawing them in at one end of the maniof the conductor within the manifold may be electrically connected to the ignition wire which leads from the outlet fitting through the conduit to the spark plug. In this latter form of manifold it has been proposed permanently to embed the several conductors which are arranged within it in a body of vinsulating material which is poured into the manifold casing after the as- 40' encased with metal and where each conductor leaves the manifold an outlet fitting is secured' sembled conductors have been put inv place. However, difiiculty is experienced in fllling the manifold casing with an insulating medium of appropriate type. Thelacquer used at the outer surface of the several conductors may be seriously 1 injured by any solvent which would make the insulating medium sufficiently uid to ow at normal temperatures into the manifold. Likefold, thence part way around the manifoldand wise if such a solvent be employed it is difficult to provide for its evaporation from the closed interior of the manifold within any practical period of time. On the other hand, if the insulating material be thermoplastic and be heated sufliciently to soften it, `the temperature requisite may be such that the heated insulating material will injure the individual conductors, for exrubber covering with consequent loss of insulating value. Moreover, since the insulation material which is placed in the manifold must not be brittle at arctic temperatures and must maintain its shape and insulating properties at temperatures to which it may be exposed in the tropics with the engine running, it is difficult to find such a medium which may be flowed into the manifold cavity.
It has also been proposed to encase the conductors in a Jacket of rubber and, after vulcanizing the latter, to house the rubber-lacketed cables in the outer metallic casing, but the application of heat sufficient to vulcanize the mass of rubber forming the Jacket is injurious to the insulation of the individual conductors and may so decrease the di-electrlc strength of such insulation as to result in an early breakdown and sparking under conditions of use.
A principal object of the present invention is to provide an improved ignition manifold of the kind in which the conductors are permanently fixed within the manifold casing and comprising an integral jointless jacket of oil and moisture resistant insulation of adequate thickness in which the assembled conductors are embedded. A further object of the invention is to provide an improved ignition harness comprising a manifold, and conduits leading therefrom to the several spark plugs, and wherein the individually insulated conductors within the manifold and within the respective conduits are encased in a continuous iointless insulating jacket of a highly elastic, oil, gasoline, and Water resistant material capable of withstanding extremes of temperature, vibration and shock without mechanical breakdown and which is of high dielectric strength. A further object of the invention is to provide an improved ignition harness comprising a manifold and conduits leading therefrom to the several spark plugs and wherein the conductors within the manifold and within each conduit are each encased in a metal sheathing interposed between concentric bodies of insulation, such sheathing having the two-fold function of preventing radio interference from the high tension current pass ing through such conductors, and of permitting the heat treatment f the jacket of insulating material in which the conductors are embedded without injuriously heating the insulation of the individual conductors.
A further object of the invention is to provide a method of and novel apparatus useful in the making of such ignition harness and the constituent parts thereof and in particular to provide a method whereby an individually insulated conductor or conductors may be jacketed with an insulating substance which requires heat treatment in its application but without so heating the insulation of the individual. conductor as to injure its mechanical or di-electric qualities.
A further object is to provide an improved method whereby, after wrapping an individually insulated conductor or conductors with thermoplastic insulating material to form a plurality of concentric layers, heat may be applied (or in fact, generated) in such a Way as to heat said layer or layers sufficiently to permit consolidation and integration thereof without injuriously heating the insulation of the conductor or conductors.
Other and further objects and advantages of the invention will be pointed out in the followaaaaaoa' ample by causing an over-vulcanization 'of the ing more detailed description and by reference to the accompanying drawings, wherein Fig..1 is a diagrammatic front elevationof a harness for a radial type engine, certain oi the ignition wires being broken away, only one of the spark plugs being illustrated;
, Fig. i* is a detail section to large scale, illustrative of a preferred form of fitting at the Juncirn of one of the ignition wires with the mani- Fig. 2 is a fragmentary elevation, partly in diametrica] section, illustrating one of the conductors which is comprised in the ignition manifold:
Fig. 3 is a section on the line I-l of Fig. 2;
Fig. 4 is a fragmentary elevation illustrating a plurality of the conductors arranged to form a cable-like assembly;
Fig. 5 is a section on the line B-S of Fig. 4:
Fig. 6 is a fragmentary elevation showing the assembly of Fig. 4 after having its outer surface made smooth and substantially cylindrical;
Fig. 7 is a section on the line 11 of Fig. 6;
Fig. 8 is a fragmentary elevation illustrating the step of applying a thin, flexible metallic sheathing to the structure of Fig. 6;
Fig. 9 is a section on the line 9--8 0f Fig. 8;
Fig. 10 is a fragmentary perspective view illustrating an oil and moisture resistant thermoplastic insulating tape useful in providing an insulatlng jacket for the assembly shown in Fig. 8;
Fig. 11 is a fragmentary elevation illustrating the step of applying the insulating jacket to the assembly of Fig. 8;
Fig. 12 is a section on the line I2-I2 of Fig. 11;
Fig, 13 is a vertical section diagrammatically illustrating a multi-part mold device and showing in section fragmentary portions of a press whereby pressure is applied to the mold parts;
Fig. 14 is'a plan view of the lower part of the mold of Fig. 13;
Fig. 14 is a similar plan view 0f a mold part having a mold cavity of a different formation;
Fig. 15 is a diagrammatic plan view of the mold of Fig. 13 and illustrating means for supplying heat to the wrappings of insulation;
Fig. 16 is a fragmentary elevation illustrating the composite assembly resulting from the use of the apparatus of Fig. l5;
Fig. 17 is a section on the line ll-I 'I of Fig. 16;
Fig. 18 is a fragmentary section showing the structure of Fig. 16 provided with an outer protective casing; and
Fig. 19 is a section on the line I9--i 9 of Fig. 18.
Referring to the drawings, the numeral I designates an ignition harness of the general kind employed for engines of the radial type. This ignition harness comprises the substantially circular ignition manifold 2 which comprises an external protective casing, usually of metal, and which is provided at regularly spaced intervals with fittings 3 to each of which is connected one end of a conduit 4, through which runs an ignition wire 4B (Fig. 1*) extending to one of the spark plugs S. The outer casing of the manifold houses a plurality of individually insulated conductors 6, one` end of each conductor being secured to one of the terminals respectively of one of the magnetos 1. The several conductors 6 are of different lengths, one of such conductors terminating adjacent to each of the fittings 3. Each fitting 3 (Fig. la) is provided with means for mechanically securing to it the outer protective conduit 4 of one of the ignition wires 4, and also has provision for electrically connecting the end of the metallic core of a conductor i to the ignition wire 4 in the conduit 4.
, As illustrated in Figs. 2 and 3, each conductor 6 comprises a metallic conducting wire or core I and insulation 9 which may, for example, be of rubber, braid, lacquer or resin.
In making the manifold, in accordance with the present invention, it is preferred to cable-lay the several conductors 6 so that they twine about each other in helical turns as shown in Figs'. 4 and 5. The several conductors 6 making up the cablelike assembly thus provided are of different lengths as above suggested. For use as herein specifically illustrated merely by way of example, one end of each conductor maybe arranged near one end of the assembly, said ends being those which are connected to the magneto terminals, while the opposite ends of the several conductors are arranged each to terminate adjacent to one of the fittings 3 of the manifold when the parts are assembled. Since the number of conductors making up the cable-like assembly thus decreases from point to point along the manifold, the outer casing of the manifold may be made correspondingly to diminish in transverse .dimensions or, alternatively, it may be of uniform transverse section and the space may be filled by the use of dummy conductors which take the place in the cable of the true conductors beyond the points where the latter terminate at the several fittings.
After having thus cable-laid the conductors 6, a substantially circular transverse section is preferably then imparted to this assembly of conductors by winding insulating material, for example, a specially treated asbestos yarn or properly shaped extruded strands of plastic material into the helical grooves III extending around the cable. However, any other suitable method of providing a circular section and substantially smooth cylindrical outer surface II (Figs. 6 and 7) may be employed. Having prepared this assembly with its substantially cylindrical and smooth external surface, the next step is to encase it in a flexiblemetallic sheathing, forexample, a wrapping of thin metal ribbon I2 (Figs. 8 and 9). This Wrapping may, for example, be of Duralumin foil of approximately 0.0015 inch thick wrapped helically about the cable so as to overlap one-half its width, thus providing a complete metal sheathing I3, Fig. 9. Alternatively, the assembly might be drawn into a tubular metallic casing.
After applying this metal sheathing, the sheathed cable is Wrapped with tape Il (Fig..10)' of a thermoplastic character. Preferably this tape is made of one of the vinyl chloride or vinyl acetate resins, for instance, a polymerized vinylv chloride, such tape being, for example, 0.008 inch thick. Such a tape isa commercial product employed in the automobile industry for wrapping conductors and is of very great elasticity and toughness throughout a wide range 'of`temperatures; it is oil and gasoline resistant (a matter of high importance when it is to be used in the vicinity of an airplane engine or the like) and has high di-electric properties.
concentric layers, for example, as many as twelve layers. Preferably successive layers I are of op.- posite pitch. i
In preparation for the next step, suitable moldf ing means is provided designed ,for the simultaneous application of heat and pressure thereby to integrate the several turns and layers oi' tape, the heat being so applied (or in fact genplemental plates 30h and 3ib respectively which erate'd) that the layers of tape are heated substantially uniformly and almost instantaneously, but without injuriously heating the insulating coverings of the several conductors. The molding means may comprise a mold vconsisting of two or more separable parts II and I8 and is of insulating material, for example, wood, the several parts, when `operatively assembled, collectively dening a mold cavity I9 of variable dimensions and which is of proper shape to receive a portion at least of the wrapped cable already described. The interior of the mold cavity is lined with metal foil 20, for example, tin, the mold parts being provided with accessibly located binding posts 2| or the like with which the metallic lining 20 is electrically connected and to which electrical conductors as hereafter described may be attached. Provision is madewhereby the assembled parts of the mold may be pressed toward each other thereby to press .the wrapped cable assembly in a substantially radial direction. As illustrated in Fig.'13,Y the upper and lower mold vmembers I1 and I8 are slightly separated, as they may be when the cable assembly is first introduced into the mold cavity I9A between them. The lower mold member I8 is shown resting upon *a fixed support 22 while the vertically movable platen 23 of a power press rests upon the upper mold member I1 in readiness to apply'downward.
ressure to the latter. -That section of *the sheathed and wrapped cable which extends between one of the projecting ends o f a conductor 6 and the next, is disposedv Within the mold cavity I9 and the mold parts are then placed under compressive stress so as radially to compact the layers of wrapping material. Before applying pressure, the metal lining 20 of the mold cavity is connected into a high frequency circuit so as to constitute one condenser plate while the tape covered metal sheathing I3 of the cable is made to constitute the other condenser plate.
`The numeral 24/J Fg. 1.5) designates the tank coil ofv a well known type of high frequency circuit, having prov'sion for tuning the circuit.
This coil forms the primary of which the coil 25 forms a secondary, and receives high frequency current from the timed circuit, for examplc, of approximately 20,000.000 cycles. This high frequency current is conducted through vthe high frequency cable 26 to the primary 21 of a resonant circuit whose seccnary 28 hasits terminais connected to a variable condenser 2 9 and alsoto auxilary condensers `30 and 3| respectively.l Each of these condensers 30 and 3l comp.ises a plate 30 and 3l respectively and comare connected to and with` the mold lining 2l and the sheathing III respectively, constitute condenser plates Vcorriplefzental to plates 30, 3|* resrecivelv. lished between. these condenser elements and ii y the material vforrrilngthe wrappings be subjected `II5v This .time lis wrapped in overlapping spirals and in v`several.
to suchhi'gh frequencyfforaperiod of 45 seconds whilcthe moldj parts'L are under pressure, the several vlayers: I5,V of the synthetic resin tape are coalevcfed vso asv to form an. integrated tubular jacket AIPF'without crevice or scam. The jacket thus provided is waterproof, oil resistant, highly elastic, `and tough and substantially unaffected `by any of the temperature conditions to vwhich the ignition manifold cf an airplane engine is ever subjected. This jacket I5l (Fig. 19) also provides very effective insulation while themetallic sheathing I3 upon which this jacket is A. hirh frequency field is estabbuilt forms effective means to prevent. radio interferences from the high tension current passing through the conductors forming the cable as well as to enable the heat treatment of the jacket as just described without heating the conductors 8.
Each of the leads I from the several fittings to the respective spark plugs may be prepared in the same way as just described except that each of these individual leads (Fig. 1) contains but a single insulated ignition wire Ia. This single insulated wire Ia is provided with a metal sheathing I3L and is wrapped with insulating thermoplastic tape which is consolidated by pressure and high frequency heat to lform the jacket I5'L as already described, and this jacket is then enclosed in a fiexiblemetallic protective casing 32', having a connection 32D at one end for engagement with one of the fittings 3 of the marilfold and having a rigid connection 32c at its opposite end (Fig. l) for union with the spark plug I.
After each section of the sheathed and wrapped cable has been subjected to heat and pressure in the mold I1, I3 as above described, a fitting I is applied at each point where the end of one of the conduits 6 projects outwardly from the jacket I5. As illustrated in Fig. l, each fitting 3 comprises a screw-threaded portion 3x for mechanical engagement with the internally screwthreaded connection 32b of the ignition wire conduit, the fitting also including a flange 3y which is placed in contact with the outer surface of the jacket I5 and is bound down to the jacket by a plurality oi wrappings of the tape II, rI'his portion of the jacket I5, to which the fitting is thus bound, is now placed in a mold IIIL having a metal lined cavity I9, I9b of suitable shape, for instance as shown in Fig. 14a, the metal lin-l ing being connected to the binding post 2l, and these wrappings of tape are consolidated so as to, form an integral mass lim permanently uniting the part 3x to the jacket I5. while at the same time adjoining sections of the jacket I5 are thoroughly integrated.
As already described, the manifold cable and the individual ignition wires are encased in any appropriate type of outer protective covering, for example, a helically wound metallic tape, such as that employed in electrical conduits; a braided metallic tube 32A (Fig, 18); or a sheet metal housing, but preferably such metallic caslngs should be so applied as to fit very snugly about the jacket and actually exert some degree of radial stress upon the enclosed material, thus to avoid any possibility of air spaces Within the -casing and providing against creeping of the fold comprising a flexible, seamless insulating jacket of oil and water-resistant material having high dielectric strength and which is tough and highly elastic, the manifold having a plurality of spaced fittings, fixedly anchored to the jacket, for the attachment of ignition wires, an ignition conduit, including an ignition wire, removably attached to each fitting, a hollow, flexible metallic sheath constituting a lining for the insulating jacket, and a plurality of individually insulated conductors housed within said metallic sheath, said conductors being of different lengths and each terminating Aat one of the respective fittings.
2. Ignition harness including a flexible manifold comprising a flexible, seamless insulating jacket of oil and water-resistant material having high dielectric strength and which is tough and highly elastic, the manifold having a plurality of spaced fittings, fixedly anchored to the jacket, for the attachment of ignition wires, a hollow, flexible metal sheath fitting snugly within the insulating jacket, and an assembly of cable-laid, individually insulated conductors housed within said metal sheath, said conductors being of dlr ferent lengths and each terminating at one of the respective fittings, a flexible protective casing tightly embracing the jacket, and an ignition conduit, including an insulated, radio-shielded ignition wire, mechanically connected to each fitting, each ignition Wire being electrically connected to one of the respective conductors within the manifold, said mechanical and electrical connections being so designed and arranged as In permit each individual ignition conduit to be detached as a unit from the manifold.
3. Ignition harness including a flexible manifold comprising a flexible, seamless insulating jacket of oil and water-resistant material having high dielectric strength and which is tough and highly elastic, the manifold having a plurality of spaced fittings, lixedly anchored to the jacket, for the attachment of ignition wires, a hollow, :flexible metallic sheath coaxial with and which is embraced by the insulating jacket, an assembly of individually insulated conductors within said hollow sheath, and means imparting a substantially smooth exterior surface to said assembly of conductors thereby to provide snug contact of the assembly with the interior of the sheath, the several conductors being of different lengths and each terminating at one of said fittings, respectively.
4. Ignition harness including a flexible manifold closed at its end and comprising a flexible, seamless jacket of oil, water and gasoline-resistant synthetic resin having high dielectric strength and which is tough and elastic, the manbe limited to these precise embodiments but is ifold having a plurality of spaced fittings flxedly anchored to the jacket for the attachment of ignition wires, an assemblyof cable-laid, individually insulated conductors within the jacket, said conductors being of different lengths and each terminating at one of the respective fittings, dummy conductors which take the place, in the assembly, of the true conductors beyond the ends of the-latter, a hollow, flexible sheath of metal foil which snugly embraces the assembly of conductors and which is snugly embraced by the insulating jacket, and insulation filling the space within the sheath which is not occupied by the conductors, and a flexible protective outer casing tightly embracing the jacket.
5. Ignition harness including a flexible manifold comprising a flexible, seamless insulating jacket of oil-resistant synthetic resin having high dielectric strength andwhich is tough and highly elastic, the manifold having a plurality of spaced fittings iixedly anchored to the jacket for the attachment of ignition wires, a hollow, flexible sheath of metal foil coaxial with and which is snugly embraced by the insulating jacket, an assembly of helically disposed individually insulated conductors within Said hollow sheath, and strand-like elements filling the helical grooves in the periphery of said assembly of conductors thereby to impart a substantially smooth cylindrical peripheral surface to said assembly, said smooth surface fitting tightly against the metal sheath, the several conductors being of different lengths and each terminating at one of said fittings, respectively. l
6. Ignition harness including a flexible manifold of normally arcuate contour, closed at one end and including a flexible, unitary, seamless resilient jacket of oil, water and gasoline-resistant insulating material, the manifold having a plurality of spaced fittings, each iixedly anchored to the jacket, for the attachment of ignition wires, an assembly of cable-laid, individually insulated conductors within the jacket, and a flexible layer of electrical conducting material interposed between the jacket and conductor assembly and operative to provide a radio shield and also to constitute a condenser plate for use in the heat treatment of the jacket by high frequency current, the conductors being of different lengths and terminating at the respective fittings.
7. Ignition harness including a flexible manifold of normally arcuate contour, closed at one end and including a flexible, unitary vseamless resilient jacket of oil, water and gasoline-resistant insulating material, the manifold having a plurality of spaced fittings, each fixedly anchored to the jacket, for the attachment of ignition wires, an assembly of cable-laid, individually lnsulated conductors within the jacket, an uninterrupted flexible layer of metal foil interposed between the jacket and theconductor assembly, said layer cf'foil constituting means to prevent radio interference and also to act as a condenser plate useful in the high frequency heating of the jacket material, the several conductors being of different lengths and each terminating at one of the respective fittings, and a flexible protective casing tightly embracing the jacket.
Ignition harness including a flexible 'manifold closed at one end, said manifold comprising a flexible seamless insulating jacket of oil and gasoline-resistant synthetic resin having high dielectric strength and which is toughand elastic throughout a wide range lof temperature variations, the jacket being provided at intervals along its length with fittings flxedly anchored thereto and designed for the attachment of ignition in the assembly, of thetrue conductors beyond the terminals of the latter, and insulation snugly filling the space within the sheath which is' not occupied by the conductors and dummies.'
9. An ignition harness of the kind including a flexible manifold comprising an assembly of individually insulated conductors housed in an elongate, flexible jacket of insulating material, the jacket having ilxedly anchored thereto a plurality of spaced fittings for the attachment of ignition wires; and the several conductors being of difierent lengths and each terminating at one of the respective fittings, a thin flexible layer of metal interposed between the conductor assembly and the inner wall of the jacket, the jacket being of l unitary, seamless construction and sufficiently flexible to permit it to be bent to arcuate contour.
10. An ignition harness of the kind including a flexible manifold comprising an assembly of individually insulated conductors housed in an elongate, flexible jacket of insulating material, the
jacket having iixedly anchored thereto a, plurality of spaced fittings for the attachment of ignition wires, and the several conductors being oi' different lengths and each terminating at one of the respective fittings, a thin flexible layer of metal foil interposed between the outer surface of the conductor assembly and the inner surface of the jacket, the jacket being a unitary, seamless mass of synthetic resin which is resistant to oil and gasoline.
11. An ignition harness comprising a manifold which is sufliciently flexible to permit it to be manually bent and straightened at will, said `manifold having a plurality of flttingsspaced along it and designed for the attachment of ignition wires, the manifold comprising a flexible,
seamless unitary jacket of oil-resistant insulate ing material, and an assembly of individually rinsulated conductors within the jacket, the several conductors being of different lengths and terminating at the respective fittings, and a flexible tube of thin metal embracing the conductor assembly and fitting snugly within the jacket.
l2. Ignition harness including a flexible mani braced by a jacket of oil and water-resistant insulating material, eachv lead having a connector at'each end operative removably to unite the lead to one of the manifold fittings and to a spark plug respectively, the metal sheathing of each ignition lead extending into said connectors.
13. Ignition harness including a flexible mani-` fold comprising a flexible, seamless insulating jacket of oil and water resistant material, a hollow, flexible metal sheathing fitting snugly within said jacket, insulated conductors within said vfsheathing, a plurality of ignition leads each including a flexible, seamless insulating jacket of oil and water-resistant material, a hollow, flexible metal sheathing fitting snugly Within said jacket, and an insulated conductor within said sheath, each ignition lead having a connector at one end by means of which it may be removably secured to the manifold, and each of said connectors including means operative electrically to connect its respective conductor to one of the manifold conductors.
14. An ignition harness for use with internal combustion engines of the radial type, said harness comprisingan annular manifold designed to be arranged coaxially with the engine shaft and having a plurality oi' flexible spark plug leads, the manifold having a plurality oi! unitary fittings spaced circumferentlally thereof and corresponding in number to the number of spark plug leads, said fittings being designed to receive the ends of the several spark plug leads, characterized in that each of the spark plug leads includes a flexible, seamless, insulating jacket o! an oiland waterresistant synthetic resin, a hollow flexible metal sheath ntting snugly within said jacket, and a single insulated conductor within said sheath, each spark plug lead having a connector at one end by means of which it may -be removably connected both mechanically and electrically to one of the fittings of the manifold and each of the said spark plug leads having a connector at its opposite end for uniting it to a spark plug.
15. A normally substantially annular, flexible ignition manifold comprising a plurality of conductors encased within a unitary resilient, seamless jacket of oil-, gasolineand moisture-resistant synthetic resin, the Jacket having a plurality of circumlerentially spaced openings in its outer terminal of an ignition wire lead, and a thin,
flexible, tubular sheathing o! metal between the conductor and the jacket, said tubular sheathing constituting means to prevent radio interference and to act as a condenser plate during high Irequency heating of the Jacket-forming material.
HOWARD M. WILKOFF.