US2418531A - Ignition coil - Google Patents

Description

April 8, 1947. T. ToGNoLA IGNITION COIL med Dec. 21, 1939 mrow /f ,5 z |o m E O m x M m S 3 M 5 ww Rx n 7 Z Z 3 .w m y z m m\ .l M f n F www. m m. 4 a a w a \\\\f\t Y /6 4 J M F m r Q/W a L m Patented Apr. 8, 1947 UNITED STATES PATENT orrlc Tullio Tognola, Sidney, N. Y., assignor to Bendix vAviation Corporation, South Bend, Ind., a corporation of Delaware Application December 21, 1939, Serial No. 310,377

The present invention relates to ignition apparatus, and more particularly to ignition coils for transforming low voltages generated by magnetos, for example, into high voltages for providing an ignition spark in the cylinder of an internal combustion engine or the like.

One of the objects of the present invention is to provide a novel ignition coil assembly which will be eillcient and durable in operation.

Another object of the invention is to provide a novel combination of an ignition coil and radio shielding means therefor whereby the life and eillciency of the coil are materially enhanced.

A further object is to provide a radio-shielded ignition coil which has a high inductance and which has relatively small over-all dimensions for a coil having a given number of turns.

Another object is to provide an ignition coll which is so constructed and shielded that there is substantially no danger of ignition failure due to flash-overs in the coil. y

Still another object is to provide novel means for radio shielding an electrical terminal of an ignition coil or the like.

Another object is to provide an emcient and durable coil which may be readily manufactured at high speed and relatively low cost.

A still further object is to provide a novel ignition coil assembly whereby the coil is cushioned against shock or vibration and protected from the elements as Well as from the entrance of moisture.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for the purpose of illustration only and are not intended to dene the limits of the invention, reference being primarily had for this latter purpose to the appended claims.

In the drawings, wherein like reference characters refer to like parts throughout the several views,

Fig. 1 is a side elevation, partly in section and with parts broken away, of one form of radio shielded ignition coil assembly embodying the present invention.

Fig. 2 is an end elevation of said coil assembly. partly in section and with parts broken away; and, l

Fig. 3 is a detailed sectional view of a portion of said coil assembly, the section being taken substantially on line 3-3 of Fig. 1.

A single embodiment of the invention is illus- 8 Claims. (Cl. 175-361) trated, by way of example, in the accompanying drawings in the form of a shielded ignitiony coil which is now in extensive commercial use on internal combustion engines wherein low tension current distribution in the ignition system is ernployed. The coil shown is adapted to be mounted in the vicinity of the spark plug or other ignition device to which the secondary winding of the coil is connected where the available supports therefor are ordinarily subject to considerable vibration. The novel construction of the coil and radio-shielding therefor render the same efficient under the most difficult of service conditions and adapt the same for long periods of use without the necessity for overhaul or replacement.

The novel construction of the present coil makes it possible to provide a primary winding having low resistance and, hence, increase the output for any given input, and also renders it possible to provide a secondary winding having a relatively large number of turns for any given over-al1 dimensions without the danger ci the occurrence of flash-overs.

In the embodiment shown. the coil proper comprises an inner primary winding I0 and an outer secondary winding Il Wound on a laminated metallic core I2, Which projects from each end of the coil and engages a U-shaped laminated metallic core piece or bridge I3 to provide a closed magnetic path for the magnetic flux emanating from the primary winding IIJ. By winding the primary coil next to the core, less Wire, and hence less resistance, are required for a given number of turns. This, and the fact that the closed core I2, I3 enhances the inductance of the coil renders the coil particularly useful with low speed magnetos having low current output. Surrounding the coil is a cylindrical casing member I4 of insulating material, the same being initially held in circumferentially spaced relation with respect to the coil by means of insulating end plates I5. Said plates preferably nt into the ends of cylinder I4 and are provided with central openings spaced to receive rectangular core I2. Coil Il), II may be spaced from the end plates by means of suitable blocks I6. Since the casing Il, I5 is made of insulating material, the space between the same and coil I0, Il may be relatively small.

One end of primary winding I 0 is preferably connected to a terminal I l ilxed on one of the end plates I5 and thence in a manner to be hereinafter pointed out to a source of low tension electrical current. The opposite end of winding l0 iS conneted to ground by means of lead I8 which passes along core I2 through end plate I5 and engages the radio shielded casing to be later described. The inner or starting end of secondary winding isA also connected to terminal |1 and hence to ground through primary winding Ill. The other end of secondary winding |I is connected to a coil spring terminal I9 which is xed in the periphery of cylinder I4 midway between the ends thereof.

When the coil and its casing have been assembled in the above manner, the free space within casing I4, |5 is completely filled with a resilient insulating compound |9a. One compound which has been found suitable for this purpose is constituted by a cashew-nut-shell oil product of the character disclosed in Harvey Patents Nos. 1,725,797 and 1,838,077. This product in the form of a high viscosity liquid may be mixed with a small quantity of formaldehyde or other suitable drying agent and introduced into casing |4, I5, after evacuation of the latter, through suitable small openings (not shown) in plates I5. The filled coil may then`be placed in an oven and heated for several hours at a temperature of approximately 120 F. to 135 F. until the compound is dry throughout. The drying is actually brought about by chemical reaction without noticeable shrinkage but is accelerated by the application of heat. The dried compound which is solid, but of a resilient spongy nature, serves as an excellent dielectric, is not sticky, will not crack and is not adversely affected by heat. Additionally, said compound completely fills the entire free space around the coil and renders material assistance in preventing any loosening of the coil windings.

The novel combined radio-shield and protective casing comprehended by the present invention for housing the above described coil assembly is constituted primarily by a bottom section and a cover section 2|, both of which are cast of suitable light weight metal. Bottom section 2|) is shaped to receive the lower half of the abovedescribed coil assembly, that is, the lower half of casing |4, I5, U-shaped bridge piece I3 and the lower portions of the projecting ends of core I2. Core piece I3 may iit rather snugly into reduced portions 22 (Fig. 2) at the ends and bottom of section 2|), whereas cylinder I4 and end plates l5 are spaced from the inner walls f thereof as best seen in Fig. 2.

Upper section 2| is shaped in a manner similar to section 20 to receive the upper half of coil casing |4, I5 and the end portions of core I2 which extend above the upper edge of section 20. Extending upwardly from and forming an integral part of section 2| is a neck portion 23 in alignment with spring terminal I9 and having an opening in the upper end thereof. The open faces of sections 20 and 2| engage each other to form a closed casing around the coil assembly and are provided with cooperating ears 24 and 25, respectively, for receiving screws 26 or other suitable securing means whereby the same are secured together.

To provide a socket whereby a high tension lead 21 from a spark plug or other ignition device may be readily detachably connected with spring terminal I9 and means whereby a radio shield around said lead may be detachably secured to casing 20, 2|, an externally threaded nipple 28 is fixed in the opening in neck 23 by spinning the reduced inner end of the nipple outwardly beneath an internal flange on said neck as shown at 29, an external shoulder on the nipple being adapted to engage the outer end of said neck. The bore through nipple 23 is cone-shaped at the outer end thereof to form a seat 30 for a rubber grommet or washer 3| and enlarged at the inner end to provide an internal shoulder 32. Surrounding spring terminal I9 and firmly engaging cylinder I4 is an insulating ring 33 which is preferably made of a suitable resilient material which is an electrical insulator. Interposed between said ring and shoulder 32 is a rigid insulating tube or socket member 34. The various parts are preferably proportioned so that when the same are in assembled relation they form relatively tight joints separating the space within tube 34 from the space outside of said tube in casing 2D, 2|. Cable 21, having suitable contact means 35 on the inner end thereof, may accordingly be readily inserted into and removed from socket 33, 34 for electrically engaging terminal I9.

The projecting portion of cable 21 is preferably encased in a. radio-shielding tube of any wellknown construction which is, in turn, provided with a flanged ferrule 31, whereby the tube is held in electrical engagement with nipple 29 by an internally flanged nut 38. Ferrule 31 also engages grommet or washer 3| and'coacts with conical seat 30 to press the washer against the periphery of cable 21, thereby holding the latter in position and forming a water-tight joint.

A low tension incoming or supply lead 39 from a suitable source of electric energy, such as a magnet, is connected to primary winding III through a terminal bolt 40 and a lead 4| which connects with terminal I1. Bolt 40 extends through but does not contact a novel adapter 42 which is provided with a lower portion adapted to slideably fit into a non-circular opening in casing section 2| and with a slot 43 (Fig. 3) in the upper surface thereof, which slot forms upwardly extending lugs 44 for engaging the fiat sides of a hexagonal or other fiat-sided portion 45 on a novel terminal shielding member 4B. The latter is thus held against angular movement relative to the casing when in assembled relation, but may be angularly adjusted to a plurality of predetermined positions, the number of such positions depending upon the particular shape of portion 45. Terminal bolt 40 is insulated from casing 20, 2| and shield 46 by members 41 and 48, the former of which is interposed between casing member 2| and a collar on bolt 40, while the latter is interposed between an internal shoulder in shield 4B and a nut 49 on the outer end of said bolt. Cable 39 is electrically connected and secured to terminal bolt 40 by means of a nut which may, like nut 49, be applied through an internally threaded opening 5| in shield 48, which opening is in alignment with said bolt. Opening 5| is normally closed by a screw plug 52. Lead 4| may be secured to the inner end of bolt 40 by any suitable means such as a nut 53.

In assembling the above-described unit, terminal 40 is secured in place and connected to lead 4|. The coil, together with socket portions 33 and 34, are then held in assembled position within casing section 2|, while bottom section 20 is moved into place. After securing sections 20 and 2| together by means of screws 26, the entire assembly is placed in an evacuated chamber, filled with a compound 54 which may be-the same or similar to the compound with which casing I4, I5 was filled. and then baked to dry said compound. Coil I0, is thus doubly cushioned against the detrimental effects of vibration and doubly protected against the entrance of moisture or the like in any form whatsoever. In coils heretofore provided, much difiiculty has been experienced in having the windings become loose as a result of continued vibration during use and in having the coil connections broken by vibration. lIf desired, the coil per se and the shielding casingr therefor may be simultaneously iilled under vacuum with the insulating filler compound. The latter is preferably forced into the coil assembly through an opening under atmospheric pressure while the body of the assembly is in an evacuated chamber.

In order to facilitate the fastening of the coil assembly to an engine, casing section is provided With a pair of bosses 56. The latter are bored at 55 for receiving securing bolts. A rigid durable securing means is thus provided.

There is thus provided a novel ignition coil and radio-shielding therefor which is particularly adapted for use in connection with low speed magnetos having low current output and for use in low tension distribution ignition systems on internal combustion engines. A novel shielded coil which is of simple, easy construction and yet rugged and eiilcient is also provided. The entire coil assembly is moistureproof and so constructed that moisture condensation cannot take place therein. Additionally, the coil is so constructed that substantially the sole insulation therefor serves as shock absorbing means and is of such nature that it will not crack and provide easy paths for flash-overs. Novel terminal shielding means are also provided.

Although only a single embodiment of the invention has been illustrated and described in detail it is to be expressly understood that the same is not limited thereto. For example, various changes may be made in the size, shape and kinds of materials specified without departing from the spirit and scope ofthe invention as will now be apparent to those skilled in the art. For a definition of the limits of the invention reference is had primarily to the appended claims.

What is claimed is:

1. A device of the class described comprising an ignition coil including primary and secondary windings, a rigid insulating housing for said coil, an electric terminal connected to one of said windings, a metallic casing surrounding said coil and having an opening therein, and socket means comprising a rigid tube of insulating material and a resilient tube of insulating material interposed end-to-end between said casing and housing with the bores of said tubes in alignment with said opening and said terminal.

2. A device of the class described comprising an ignition coil including a metallic core, a primary winding around a. portion of said core intermediate the ends thereof and a secondary winding around said primary winding, an insulating housing for said windings, an insulating compound substantially lling the space in said housing around said coil, a metallic bridge engaging the ends of said core to form aclosed magnetic flux path, an outlet terminal on the periphery of said housing intermediate the ends thereof connected to said secondary winding, a metallic casing surrounding said coil and bridge, a socket for slidably receiving an insulated conductor comprising a rigid tube of'insulating material and a resilient ring of insulating material, said tube and ring being in alignment with each 6. other, said terminal and an opening in said'casing and interposed between said casing and said housing, and a resilient insulating compound illl-l ing the space in said casing around said coil and socket.

3. A device of the class described comprising an ignition coil including a metallic core, a. primaryl winding around a portion of said core intermediate the ends thereof and a secondary winding around said primary winding, an insulating housing for said windings, an insulating compound substantially iilling the space in s aid housing around said coil, ametallic bridge engaging the ends of said core to form a closed magnetic flux path, an outlet terminal on the periphery of said housing intermediate the ends thereof connected to said secondary winding, a metallic casing surrounding said coil and bridge, a socket for slidably receiving an insulated conductor comprising a rigid tube of insulating material and a resilient ring ofinsulating material, said tube and ring being in alignment with each other, said terminal and an opening in said casing and interposed between said casing and said housing, and a resilient insulating compound lling the space in said casing around said coil and socket.

4. A device of the class described comprising a metallic casing having upper and lower sections, means for securing said sections together, U- shaped metallic bridge means tightly fitted into a groove in said lower section, an ignition coil assembly including a metallic core, the ends of said core resting on the ends of said bridge means to form a closed magnetic path, tubular insulating means in said upper section to form a connector socket between the wall of the casing and said coil assembly, and resilient insulating means completely filling the space in said casing around said coil assembly and socket.

5. A device of the class described comprising a metallic casing having upper and lower sections, means for securing said sections together, U- shaped metallic bridge means tightly fitted into a groove in said lower section, an ignition coil assembly including a metallic core, the latter having the ends thereof engaging the ends of said bridge means to form a closed path for magnetic ilux, and tubular insulating means interposed between said coill assembly and the wall of said upper section to form a socket for a connector plug, said coil having a high tension terminal at the inner end of said socket and said tubular means beingat least partially resilient for yieldably holding said core in engagement with said bridge means.

6. A device of the class described comprising a metallic casing having upper and lower sections, said lower section having an internal groove and said upper section having a bottleneck portion, U-shaped metallic bridge means tightly fitted into said groove, an ignition coil assembly including a metallic core, the ends of said core having engagement with the ends of said bridge means for forming a closed path for magnetic flux, and axially yieldable tubular insulating means communicating with an opening in said bottleneck portion and engaging the outer wall of said coil assembly to form a socket for a connector plug, said coil assembly having a high tension terminal at the inner end of said socket.

'7. A device of the class described comprising a coil, a terminal connected to the winding of said coil, a rigid casing surrounding said coil and having van opening therein, and socket means comprising a rigid tube of insulating material and a resilient tube of insulating material, said tubes being in axial alignment and interposed between said casing and coil in alignment with said opening and said terminal.

8. A device of the class described comprising a coil, a housing for said coil, a terminal on said housing connected to said coil, a ,casing surrounding said housing and having an opening therein, and socket means comprising a rigid tube of insulating material and a. resilient tube of insulating material in axial alignment and interposed between said casing and housing, the bores of said tubes being in alignment with said opening and said terminal.

TULLIO TOGNOLA.

REFERENCES CITED The following references are of record in the file of this patent:

Number UNITED STATES PATENTS Name 1 Date Lee Nov. 30, 1926 'I'hordarson May 17, 1927 'Fisher et al Oct. 15, 1935 Money Jan, 28, 1936 Wild et al Aug. 14, 1934 Groten May 15, 1923 Toelle May 16, 1933 Allen May 23, 1939 Vaughn Mar. 9, 1920 Allen Dec. 27, 1938 Barrett May 2, 1939 Lear et al Jan. 9, 1934 Harvey Aug. 27, 1929 Harvey Dec. 22, 1931 Splitdorf July 15, 1902 Casper Nov. 3, 1914 Ruben Dec. 23, 1941

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