US2575140A - Ignition device and parts thereof - Google Patents

Description

1951 w. c. SMITH 2,575,140

IGNITION DEVICE AND PARTS THEREOF Filed Dec. 29, 1948 k L 62 L94 Z Q 56 &/ A?

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Patented Nov. 13, 1951 UNITED STATES PATENT OFFICE IGNITION DEVICE AND PARTS THEREOF 'Whitfield C. Smith, Oneonta, N. .Y., assignor-to Bendix Aviation Corporation, New. York, N. Y.- acorporation ofDelawal-e Application December 29, 1948, Serial No. 67,950

.. 2tClaims. (Cl. 315-57) .This invention relates to ignition apparatus eand' more particularlyto sparkplugs and parts thereof-adapted for use-in'ignition systems of Qthe-high frequency and' low tension distribution ftype employed.for:*igniting the gaseous charges Bl the-cylinders :of internal combustion engines.

-One of-the object of the present invention is -;to provide a noveltransformer unitwhich is :adaptedtoabeaenclosed in a casing of a radio shielded spark .plugiof conventional design, and :pperati-vely-"connected with the center electrode v:Ithere'of.

-=Anothersobject-'of theinvention is to provide at novelrcombination"oferadio shielded spark plug and;- step-up voltage-transformer unit whereby g-fIthewdanger'of;ignition :failures-is materially reduc'ed.

'-5Stil1---another',objpectof .the invention .is to provide a novel transformer runit for use ina Ijspark plug or the :like which has a high degree of e'tliciemzy andaconsumes aminimum of space for iliits capacity.

A--further objectris to provide a spark plug awhich is'constructed-in a novel manner to give maximum .assurance against the presence of .'moisture and gases which tend' to cause deterioration and electrical failure.

,A still further-object is to provide novel means forinsulatlngielectricalparts,-such as the h gh -potential winding of a transformer, against-nearby conductors'whichare at ground or similar low L potential,-suchas the, shell of a spark plug.

Another object is to providenovelmeans for insuring proper positioning of an insulated trans- 'former unitin-a casing, such-as the-shielding barrel of aspark plug.

-I StiILanQtherobject isto'provide novel insulating.meanswhich-will endure the stresses pt-tremendous and sustained vibration under awidely. changing conditions of temperature and pressure.

j -The-above and. further objects and novel {eat tures-r of 9the-present invention will. more fully eappear from .the following detailed description qwhenthesameis readhinaconnection with the accompanying.drawings. It is to be expressly understood however, that the drawings are for the purpose.of. illustration only and are not in- ;tendedsas aedefin-ition vof-the limits ofthe inven- 'tion.

, 4111'; theigdrawings, wherein like reference char- .-';acters refer. to like parts throughout the several views, I Figs;- lrand 2 areaendviews of the structure r illustratednin ll'igh 3,; the, same-heing-taken from the'lef-t andrightends,respectively Fig. 3 is a longitudinal sectional view; with some parts shown in full,'of one form of shielded spark plug-transformer combination contemplated by the present invention; and

Fig. 4 is a detail view partly insection and with parts broken away ofthe transformer unit of the embodiment of Fig. 3.

ment with a threaded-opening-in anengine cylinder (not shown) A tubular insulator 12 of rigid ceramic or other suitable insulating material,

' such as aluminum oxide, may be supported in the shell by a tubular wedge 13 of relatively malleable metal, such as copper, or by some other suitable known means. A center electrode l4, l5 extends through the bore of insulator l2 into spark gap-relation with a so-called ground electrode l6 secured to shell 10 and said bore may be suitablysealed around at least a portion of thecenter electrode in any of many well known ways. Shell I0 is provided with a metallic radio shielding barrel-or-tube I1 which surrounds the projecting end of center electrode assembly I2,

l4, l5 in'spaced relation thereto andextends beyond the end thereof .to provide a space or well for receiving a novel transformer unit to be next described.

It is necessary in modern enginesto impress a relatively high voltage across the points of the spark plugs, and it has been found highly desirable, in order-toreduce electrical losses and operational failures, to confine the high voltage to the immediate vicinity of the spark plug. To thi 'end, it has been proposed to enclose transformers within the shieldin barrels of conventional shielded spark plugs Much difficulty has been encountered; however, *in overcoming the many hazards and difficulties which occur by reason of heat, vibrationandspace limitations. The novel transformer unit contemplated by this invention and the novel-manner in which the same is combined-with'and insulated from the spark plugv perse solves theseand other problems in a unique and satisfactory manner.

In the ,form illustrated, the step-up transformer or coil is constructed for easy-installation orreplacement as a self-contained unit in the spark plugshellor barrel l'l. Said-unit comprises an insulator l8 which is preferablyprovidedwith a shallow recess l9 atoneend and a deep reoesslllattheother. .Avcup or bent strip contact with the inner end 15 of the center electrode of the spark plug during installation. A substantial portion of the larger or outer recess 20 is preferably filled with a metallic core 23 for enhancing the efficiency and capacity of the transformer to reduce losses when a high fre quency source of electrical energy is used. Said core may be of powdered metal, such as iron, with a binder of suitable insulating material, such as Bakelite, urea resins, or the like, the same being effective to improve the coupling between the primary and secondary windings.

The secondary winding 2 f the transformer may consist of a single solid or closely wound layer of insulated wire extending approximately the full length of insulator [8. In one satisfactory embodiment, 300 turns of #44 heavy F ormvar insulated magnet wire were used.

' The beginning or low potential end of winding 24 is connected to a contact pin 25, and the high potential end is connected to cap 2| and hence to the center electrode- I5. In order to reduce electrical losses and the adverse effects of corona to a minimum, this closely or solidend of the barrel. Element 32 may be secured in barrel I! in an air-tight and moisture-proof manner by spot welding or in some other suitable manner.

Pin 25, which together with element 32 forms the male half of a plug and socket type electrical connector, extends through a central opening in said element and the annular space surround ing the pin in said opening is hermetically sealed by a glass-to-metal seal 35 or its equivalent.

The inner end of pin 25 is bent through a slot or opening 36 in the side wall of insulator l8 for suitable connection to the adjacent ends of 1y wound secondary coil is covered with a highresistance electrically-conductive coating (not shown) which may be applied to the winding by dipping and subsequent drying and baking. Such coating may comprise finely divided graphite and lamp black suspended in a resinous. base. One suitable formula for the coating material consists of a mixture of 10 grams of Acheson Colloids Corp. dispersion #154 (finely divided graphite suspended in solution with alcohol), 4

7 grams of lamp black, 50 cc. of a solvent such as I mary winding is soldered to contact pin 25 and the other end is electrically connected to a ring 28 on the lower end of sleeve 26. In one suitable embodiment the primary winding consisted of 10 turns of #21 Formvar insulated magnet wire, the same being preferably wound in the same direction as secondary winding 24.

to provide an automatic transformer hook-up whereby the voltage of the primary is added to the voltage of the secondary Ring 23, which serves several purposes, comprises a central annular portion, a plurality of projections 29 that yieldably grin the end of the insulating sleeve, and a plurality of flared resilient projections 30 which engage a shoulder 31 on the spark plug shell to rovide a ground connection and spring support for sleeve 26 to absorb lengthwise toler-i primary winding 27 and secondary winding 24.-

Novel means are provided for further insulating the above described current-carrying elements from barrel I1 and parts connected thereto, said means being adapted to withstand wide variations in temperature and the shock of sustained vibrations or the like without cracking. In the form shown, several layers of woven fiber glass, which is itself an insulator, are wound around sleeve 26 and'primary winding 2?. These layers preferably extend the full length of said sleeve but may be shorter or longer, if desired. In the completed structure as viewed in Fig. 3, the layers 3'! of woven glass fibers are embedded in or impregnated with a mass of insulating material. which will set to a rigid com= pound, but preferably remains a somewhat yieldable and resilient solid. Excellent insularing means are thus provided'which alsdserve as a mechanical binder and shock absorbing'bub fer for the unit which extends into barrel l'i.

After the completed unit illustrated in Fig."4 is installed in spark plug barrel H, the structure is thoroughly dried, and the spaces within the barrel are evacuated and filled throughan opening 38 with the insulating material 39in liquid form which will thereafter set as a solid. Preferably, a filling material is used which will set up as a solid through chemical reaction with or without the aid of heat. There are several rubber-like compounds of this type now ave-in able, such as polymerized cashew nut shell-oil mixed with formaldehyde or a styrene polyester resin. The filling may be effected under vacuum through hole 38 which may be laterplugged as shown in Fig. 3. In the interest of clarity some of the spaces within barrel l! which are filled with compound 39 are shown with the compound removed. Y

There is thus provided a novel spark plug particularly adapted for use in high frequency and low tension distribution ignition systems for internal combustion engines, the same being so constructed as to operate efficiently for long periods of time with minimum danger of failure in operation. Additionally, there'is -pro vided novel insulating means particularly adapted for use in the combination of parts disclosed, the same serving to afford mechanical re-enforcement and supportfor the parts'as well as durable insulation capable of enduring the ri orous tests of your round operation at all altitudes. The novel manner in which the parts described have been combined conserves space without a corresponding loss of efficiency or reduction in safety factor. The construction is also such that the coil unit can be removed and replaced if it fails during the useful life of the spark plug per se. y, Although only a single embodiment of the invention has been illustrated and describediin 7.6 detail, it is to'be expressly understood that the invention is not so limited. For example, various other types of spark plugs which difier specifically in construction from the one illustrated may be used. Various changes may be made in the design and arrangement of the parts illustrated, as well as in the specific materials suggested, without departing from the spirit and scope of the invention.

What is claimed is:

1. Ignition apparatus comprising a tubular metallic shell, an insulated center electrode assembly supported in said shell, a tubular metallic barrel on said shell surrounding and extend ing beyond the end of said assembly, an end closure for said barrel having a passage therethrough, a contact pin extending through said passage, 2, glass-to-metal seal in said passage around said pin, an insulated step-up voltage transformer in said barrel comprising a rigid insulator secured to said end closure and having a recess at one end for receiving said pin and a resilient terminal at the other end for electrical engagement with the conducting portion of said assembly, a core of powdered metal with a binding of insulating material in said insulator, a secondary winding on said insulator comprising a closely wound layer of insulated wire, opposite ends of said winding being electrically connected to said contact pin and said terminal, a high-resistance electrically-conductive coating covering said secondary winding, an insulating sleeve surrounding said winding and the projecting end of said assembly, a metallic ring mounted on the end of said sleeve and having resilient extensions contacting said shell, a space Wound primary winding on said sleeve around said secondary winding, opposite ends of said primary winding being connected to said pin and said ring, a plurality of layers of woven 4 glass fibers surrounding said primary winding and said sleeve, and a solid yieldable insulating material filling the remaining space in said barrel and embedding said layers of woven glass fibers.

2. In apparatus of the class described, a tubular metallic barrel having an internal shoulder, an end closure for said barrel, an electrical transformer in said barrel comprising a rigid insulator secured to said end closure, a secondary winding of insulated wire on said insulator, an insulating tube closely surrounding said winding and engaging an external shoulder on said insulator, resilient means under compression interposed between said internal shoulder and the end of said tube nearest said internal shoulder, a primary winding on said tube around said secondary winding, and an insulating mass interposed between said tube and said barrel comprising a plurality of layers of woven insulating threads embedded in rubber-like resilient insulation.

WHITFIELD C. SMITH.

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

UNITED STATES PATENTS Number Name Date 2,036,274 Holler Aug. 7, 1936 2,141,141 Kongsted Dec. 30, 1938 2,414,300 Hamilton Jan. 14, 1947 2,414,692 Harkness Jan. 21, 1947 2,434,492 Ericksberg et a1. Jan. 2, 1948 2,441,047 Wall May 4, 1948 2,461,098 Weatherly Feb. 8, 1949 2,467,531 Lamphere Apr. 19, 1949 2,482,884 Tognola Sept. 27, 1949 OTHER REFERENCES Fiber Glass Insulation for Magnet Coils, Science News Letter, page 41, July 20, 1946. (Copy in sci. libr.)

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