US2198250A - Ignition apparatus - Google Patents

Description

April 23, 1940. R. T. HURLEY IGNITION APPARATUS Filed Sept. 24, 1936 y mw 4m Patented Apr. 23, 1940 UNITED STATES IGNITION Roy T. Hurley, Hobbs MMZSQ 7 ENT APPARA'EUS Ferry, N. W2, assignor to Bendix Aviation Corporation, douth Bend, Ind, a corporation of Delaware Application September 24, 1936, Serial No. 102,298

5 Claims.

This invention relates to ignition apparatus and more particularly to spark plugs and radio shielding means associated therewith adapted for use in the ignition systems of internal combustion engines.

Spark plugs and shielding means of the same general type or character as those comprehended by the present invention'have been heretofore proposed but insuperable difficulties have been experienced in providing a radio shielded plug which may be readily assembled and disassembled, which is capable of being quickly installed and removed from an engine and the shielding harness provided thereon, and which may be inexpensively manufactured. Furthermore, in the design and construction of similar spark plugs a great amount of time and thought has been spent by a great many skilled engineers, but without complete success, in attempting to increase the heat dissipation qualities of the plugs in order to reduce the burning of the electrodes, to obviate pre-ignition, to prevent burning of the insulation on current conducting cables connected to the terminals of the plug, and to generally increase the life and improve the operating characteristics of the plugs.

It is accordingly an object of the present invention to provide a novel radio shielded spark plug which is more reliable and efficient in operation than similar spark plugs heretofore provided and which may be readily and inexpensively manufactured.

Another object of the invention is to provide a novel radio shielding connection for usebetween a spark plug and conductor conduits of the shielding harness of an internal combustion engine. I

Still another object is to provide novel means in a radio shielded ignition circuit for electrically connecting an insulated conductor and the center electrode of a spark plug.

A further object is to provide a novel radio shielded spark plug which maybe readily and quickly connected in and disconnected from a shielded ignition circuit of an internal combustion engine.

A still further object is to provide a novel combination of a radio shielded spark plug with a shielding connecting elbow which is constituted by a small number or comparatively rugged parts which are so constructed and assembled that the possibility of failure due to vibration, jarring, etc., is minimized.

Another object of the invention is to provide a novelspark plug which is so constructed as to combine effective radio shielding with better heat and electrical conductivity characteristics than have been heretofore provided.

The above and further objectsand novel features of the invention will more fully appear from the following detailed description when thevs'ame is read in connection with 'the accompanying drawing. It is to be expressly understood, however, that the drawing is designed for the purpose of illustration only and is not intended to define the limits of the invention, reference being primarily had for this latter purpose to the a pended claims.

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

Fig. l is a side elevation, partly in section and with parts broken away, of one form of a spark plug embodying the present invention; r Fig. 2 is a similar view, partly in section andv with parts broken away, of a second embodiment;

Fig. 3 is a detail sectional view, on an enlarged scale, of the threaded connection between the spark plug and the shielding elbow showing the coupling nut in unlocked position; and,

Fig. 4 is a similar view showing said coupling nut in locked position.

In the embodiment of the invention illustrated a against a soft metallic washer it having high 3 heat conductivity and positioned on an interior shoulder of the shield to thereby provide a gastight joint between said shell and nut. Projecting upwardly from nut l4 and preferably formed integrally therewith is a barrel it having a somewhat larger bore than that provided in nut I 4,

said bore being lined with an insulating sleeve ll of mica or other suitable insulating material.

The upper edge of said barrel is peened over at ltd for the purpose of holding saidinsulation in position.

In the form shown, center electrode H3 is surrounded by an expansible tube or sleeve l8 of soft metal such as copper and said sleeve is surrounded by and insulated from nut M by a mica cigarette H9. The lower enlarged end or head 20 of electrode i3 is supported close to grounded electrode 12 and is spaced from the lower end of nut M by a stack of mica washers 2 l. Said center electrode extends upwardly into the bore ofbarrel 46, H and the upper end thereof is counter-sunk and peened outwardly or upset to engage a metallic washer 22 which constitutes a part of the center electrode and bears against a stack of mica washers 23. In assembling the paratively rugged, easily assembled parts and being adapted to be secured to a spark plug for soldered or brazed together.

2 parts last described, cigarette l9 and'sleeve II! are first inserted in the bore of nut l4 and said sleeve is expanded by means of a mandrel to thereby press cigarette is into close engagement with the inner walls of nut 14 to prevent leakage oi. gases of combustion from the engine cylinder. Electrode I3 has a drive fit in copper sleeve I 8 and the spark gap between the lower end thereof and electrode i3 is adapted to be readily adjusted by bending the prongs l2a of electrode l3.

Novel simplified means are provided for readily and quickly detaching and connecting an insulated high tension conductor to center electrode i3 and for radio shielding said conductor, said means comprising only a small number of compivotal or swivel movement relative thereto. In the form-illustrated in Fig. 1, such means includes a hollow, molded insulator, one end 24 of which by a cone-shaped shoulder 26. Sleeve 24, 25

preferably made of an asbestos Bakelite compound or any other suitable insulating material and the bore in the arcuate portion is somewhat larger than the bore in the straight portion thereof, the large and small bores being joined by a tapered or conical bore.

Surrounding the smaller or lower portion 24 of insulator 24, 25 adjacent shoulder 26 is a metallic shielding sleeve 21 that is shaped to engage said shoulder and has an external flange 28 which is adapted to be held in firm engagement with and in any position relative to the upper end of barrel i6, ita by means of a coupling nut 29 that has threaded engagement with said barrel. An arcuate metallic sleeve 30 surrounds portion 25 of the insulator, the same being adapted to be placed thereon after the insulator is molded, and is secured to sleeve 2'! by any suitable means, the sleeves in the form shown having engaging flanges 3i and 32 thereof A bored coupling member 32 is permanently secured to the outer end of sleeve 30, such as by silver soldering, and insulator 24, 25 is preferably cemented in radio shielding sleeve 2?, 3G by means of some suitable cement, such as ball clay silicate of soda cement. Sleeves 2i and 30 may, of course, be detachably secured to one another, if desired.

For the purpose of electrically connecting an insulated high tension conductor 33 to center electrode 83, insulator portion 24 is centrally bored for slidably receiving a conducting bolt 34, while flexible conductor 33 extendsthrough a preferably larger bore in portion 25 of the insulator and is detachably and electrically connected to said bolt by means of a tapered nut 35. The latter is soldered or otherwise suitably secured to conductor 33 and is adapted to thread- I edly engage the inner end of bolt 34, the axis of the threaded bore of said nut being substantially a continuation of the longitudinal axis of conductor 33. In the embodiment illustrated, portions of the braided conductor 33 are led through sulator 24 and is thus'held in yielding engageshielding elbow from a magneto or othe'rsource of high tension electric current through a shielding conduit comprising a braided metallic tube 38 which encloses a coiled metallic spring 39 and is surrounded by an insulating covering such as synthetic rubber, for example. The end of tube 38 is flared outwardly and secured between ex-- temal flanges on a pair of metallic ferrules 4| and 42 and the conduit assembly is detachably connected to elbow 21, 30 by means of a nut 43 which threadedly engages coupling member 32 and is rotatable relative to said ferrules. A yieldable washer 44 is shown interposed between coupling member 32 and the end of shielding conduit 38, 40. To facilitate the insertion of insulated conductor 33 into insulator 24, 25, the opening at the outer end of coupling member 32 is conical, as is also nut 35.

In the embodiment of the invention illustrated in Figs. 2 to 4, inclusive, wherein primed reference numerals are employed to indicate parts which are similar and correspond to parts in Fig. 1 that bear the same reference numerals, insulator 24', is molded in a one-piece metallic elbow 21', with a small conducting wire 34' therein. Wire 34' is preferably quite stiif, such as piano wire, so that the same will not be displaced during the pouring of the molten Bakelite intothe mold. One end of said wire is adapted to engage or may be integral with a spring 31' and the other end, which extends into a coimtersunk bore in elbow portion 25' of the insulator, is secured such as by silver soldering to an externally threaded member 45 that is adapted to be engaged by an internally threaded nut secured in any suitable manner to the end of insulated conductor 33'. To connect and disconnect member and nut 35', either elbow El, 30', when the same is disconnected from barrel it, or conductor 33' may be rotated, depending upon which is the more convenient under the particular circumstances. Conductor 33' is preferably led from a. suitable source of high tension electric current through a suitable shielduseful life of the plug and cable insulation as well as the operating efiiciencyof the plug, to increase the electrical conductivity of the shielding, and to insure that the various elements of the assembly will not become loose during operation, novel means are provided for threadedly connecting certain of said elements. Only the connection between elbow 21', 30' and barrel 16' will be described in detail, but it will be understood that the same type of thread means may be employed-at H, at the connection 32', 43 and between nut I4 and body It). In the form shown, the threads on barrel l6 have symmetrical side faces 46 and 41 which have an included angle of approximately thirty degrees, the outer surfaces 48 of the threads, i. e., the major diameter of the threaded portion of the barrel, being cyclindrical. The surface 49 at the minor diameter of the barrel, i. e., between the bases of the threads, is tapered or inclined at a small angle to the axis of the barrel. On nut 29' similar threads are formed, except that the surface 50 of the threads thereon is tapered or inclined relative to the axis of the nut and the surface 5| at the base of the thread on the nut is cylindrical.

Thus, when nut 29' is being screwed on and off of barrel IS, the same rotates freely, the parts assuming the relative positions shown in Fig. 3. When, howeverpthe internal shoulder of said nut engages flange 28 and is further rotated, the tapered or conical thread surface 50 of the nut moves into wedging engagement with the conical surface 49 of the barrel, and as the elastic compression on these conical surfaces is increased by rotation of the nut, the thrust faces and. 52 of the barrel and nut, respectively, come into contact. erted by the faces against faces 49 increases the frictional resistance therebetween and accordingly increases the resistance of the nut to rotation. Vibration and jarring of the parts tends rather to tighten than to loosen the grip between nut 29 and barrel "5', thereby insuring that the parts will not become loose during operation. The close, firm engagement between faces 49, 50 and 46, 52 also insures better heat and electrical conductivity, the former being particularly important in the spark plug and the latter being highly important both in the plug and the shielding. A better gas seal is also provided and less accuracy is required in cutting the threads on the cooperating parts than has been heretofore necessary with other types of threads.

There is thus provided a novel shielded spark plug in combination with a radio shielding elbow and a shielded conductor, the parts of which are adapted for ready and inexpensive manufacture and are so constructed as to provide a ready and efficient means for detachably and electrically connecting an electric current-carrying, radioshielded cable to the central electrode of the plug. Novel means are also provided for securing. the plug in an engine cylinder and for securing the various parts of the plug and elbow assembly together, whereby gas leakage is reduced, the rate of heat conduction from the inner to the outer portions of the plug and heat dissipation to the atmosphere are materially increased, the resistance to flow of current to ground through the radio shielding and the plug is materially reduced, and the loosening of parts due to vibration, jarring, etc., is substantially eliminated. The novel combination provided also comprises only a small number of comparatively rugged parts which are adapted to be readily and quickly assembled and disassembled for installation, cleaning, and repair.

Although only two embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the same is not limited thereto but that various changes may be made therein, such as in the design and arrangement of parts illustrated, without departing front the spirit and scope of invention, as will now be apparent to those The compressing force ex I skilled in the art. For a definition of the limits of the invention, reference will be had primarily to the appended claims.

What is claimed is:

1. In apparatus of the class described, an insulator having a non-linear bore therethrough, a conductor extending into one end of said insulator, said conductor being threaded at the inner end thereof and having an enlarged portion adjacent the other end, a yieldable conducting member having a portion thereof interposed between said enlarged portion and the end of said insulator, an insulated conductor extending into the other end of said insulator, and means secured to said insulated conductor and adapted to threadedly engage the threaded portion of said first-named conductor.

2. In apparatus of the class described, a metallic elbow, insulating material lining said elbow, a conductor extending partially through said insulating material from one end thereof and having a threaded portion, a second conductor extending partially through said insulating material from the other end thereof, and an internally threaded member secured to said second conductor and adapted to threadedly engage said first-named conductor, the axis of the bore of said internally threaded member being substantially a continuation of the longitudinal axis of said second-named conductor.

3. In apparatus of the class described, a rigid insulating elbow having a bore therethrough, a flexible insulated conductor extending into one end of said bore, a tapered nut secured to said conductor and adapted to seat against a tapered wall portion of said bore, and a conductor extending into the other end of said bore and having a threaded portion adapted to be threadedly engaged by said nut.

4. In apparatus of the class described, a rigid insulator having a bore therethrough, the axis of a portion of said bore being arcuate, a conductor extending into said bore and having means thereon to limit the movement thereof into said bore, a flexible conductor extending into the arcuate portion of said bore, and means secured to said flexible conductor for detachably electrically connecting the adjacent ends of said conductors together.

5; In a spark plug having a center electrode and a barrel portion extending above said electrode to form a socket, the combination therewith of a metallic sleeve, means for detachably connecting said sleeve to said barrel, insulating means in said sleeve having a portion extending into said barrel, an electric current carrying conductor extending through a portion of said insulating means, means including a yieldable connection for electrically connecting said conductor and electrode, an insulated conductor extending into said insulating means, and a member secured to said insulated conductor for threadedly engaging said first-named conductors.

6. In apparatus of the class described, a rigid shielding elbow having a bore there through, electrical conductors extending into opposed ends of said elbow, one of said conductors having means thereonto limit the movement thereof into said bore, and means for detachably connecting adjacent ends of said conductors to each other within said elbow, whereby neither of said conductors may be withdrawn from said elbow.

ROY T. HURLEY.

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