US2455960A - Electrical transformer - Google Patents

Description

DCC. 14, 1948. A, C, WALL ELECTRICAL TRANSFORIER Filed Nov. 1S, 1945 /INVENTOA maar: carisma Y 2,455,960

s PATENroi-Fice U N l T E D STAT E ELECTRICAL TRANS'FDRMEB Alexander C. Wall, Ind., assignorto P. R. Mallory Co., Inc., Indianapolis, Ind., a corporation of Delaware Application November 16, 1945, Serial No. .629,174

sA claims, (c1. 11s-ssa) The present invention relates to an electrical transformer for delivering high secondary voltages and particularly to such a transformer which is adapted for use in a high frequency ignition system. l

This application is a continuation in part of my copending application, Serial No. 549,278, entitled Ignition system and apparatus thereof.

A general object of the present invention is the provision of such a device which is compact and self-contained, easily constructed, sturdy, readily replaceable, accurate and efcient in operation, moisture-proof, adapted for efficient operation under widely varying conditions of use, readily utilized in conventional structures with a minimum of alteration procedures, employable in a simple manner with associated structure to complete portions of circuits of an ignition system while effectively cooperating with said associated structure to provide complete and effective shielding thereby minimizing radiation of radio interference energy, and in which the parts are so arranged and assembled as to minimize energy losses.

A more specific object of the invention is the provision of a readily replaceable transformer construction which is adapted for a wide variety of circuit applications where ability to withstand mechanical vibrations, high voltage stresses or high temperatures is necessary or desirable.

A still more specific object of the invention is the provision of a transformer which is sufliciently small as to be readily mountable in the existing chamber of a conventional spark plug while, nevertheless, assuring freedom from flash-over, maximum coupling efficiency, minimization of corona effect and attendant energy loss, and immunity from danger of breakdown under the high temperatures of engine operation.

Other objects of theinvention will be apparent from the following description and accompanying drawings taken in connection with the appended claims.

The invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and methods of manufacture referred to above or which will be brought out and exemplified in the disclosure hereinafter set forth, including the illustrations in the drawings, the scope of the invention being indicated in the appended claims.

In the drawings:

Figure 1 is a schematic diagram of a typical ignition circuit in which the transformer of .th present invention is employable; y

Figure 2 is a sectional view, with parts broken 2 away, of the novel transformer associated with a portion of a high frequency ignition system;

Figure 3 is a detail view, with parts broken away and omitted, of the transformer shown in Figure 2 with the parts in disassembled relation;

Figure 4 is a longitudinal sectional view of a modified form of the primary winding structure shown in Figures 2 and 3;

Figure 5 is a view similar to Figure 2, but with additional parts broken away and omitted. of a modified form of the transformer structure; and

Figure 6 is an elevational View, with parts broken away and omitted and with the secondary winding structure in longitudinal section. of a modification of the structure shown in Figure 5.

While a preferred embodiment of the invention is described herein, it is contemplated that considerable variation may be made in the method of procedure and the construction of parts without departing from the spirit of the invention. In the following description and in the claims, parts will be identified by specific names for convenience but they are intended to be as generic in their application to similar parts as the art Will permit.

In accordance with the prsent invention, the secondary of the transformer is wound upon a vial or cup of glass or other dielectric material which is adapted to withstand high voltage stresses and extreme temperature conditions. The primary winding of the transformer is wound upon a removable core or plug of suitableV insulating material to provide for easy and convenient installation or removal thereof. This core may be attached to a connecting cable for supplying the prim-ary current to the transformer thus avoiding the necessity of providing separate terminal contacts for making electrical connections to the primary winding.

The secondary is preferably wound upon the glass vial or cup with the high tension end thereof adjacent the bottom of the cup. In this manner, no low resistance path is provided between the high tension end of the secondary winding and the primary winding, which is substantially at ground potential, so that flash-over and arcing difilculties at this region are eliminated. The thickness of the glass vial may be quite small to provide close coupling between the transformer windings, the minimum thickness being dependent upon the dielectric qualities of the glass and the thickness thereof which is required to effectively insulate the primary winding from the secondary winding. The secondary winding may be provided with a terminal device for connection to the secondary circuit, and such terminal device g may also be effective to rigidly support the transformer in desired position with respect to the other circuitl components.

The casing of the transformer is constructed' so as to completely enclose the windings which may be advantageously illled with or impregnated by an insulating compound to eliminate gases or air from the interior of the transformer and thus reduce or overcome corona discharge. The insuf lating compound used should be heat ystable if the transformer is to be subjected to high temperatures to prevent emission of gases during operation of the transformez'. From the foregoing dis cussion, it will be appreciated that the trans-s former structure is characterized by small size, ease of shielding, and high stability when subjected to jarring or vibrations.

As pointed out in my copending application Serial No. 549,278, filed August 12, 1944, .for Ignition system and apparatus thereof," the transformer of the present invention is adapted for use in an ignition system for internal combustion engines which periodically generates pulses of electrical energy, distributes these pulses toward the spark plugs of the various cylinders, then converts the energy of the pulse to a high frequency current and finally steps up the voltage of said high frequency current for supply to the spark plug gaps thus overcoming ring dliiiculties caused by fouling of spark plug electrodes with carbon and oil. Such apparatus may be incorporated in an ignition harness similar in many respects to those with which radial airplane engines are now equipped. Each engine cylinder, the wall of one of which is indicated at il) in `Figure l, may be equipped for dual ignition and accordingly may have mounted in side walls thereof a pair of transformer spark plug units, one of which is diagrammatically indicated at l l, to each oi which is connected a supply cable l2, in turn connected to an ignition manifold indicated at lil. The ignition manifold may be similar to that now used in ignition harnesses for other types of ignition systems and, as such, may be an encasing and shielding structure in which are located a plurality of supply conductors each of which is anchored to coupling means mounted on the manifold for connecting that conductor to the spark. plug supply cable l2. The coupling means includes a converter unit which is diagrammatically inditage, may comprise a source i or means for generating pulses of electrical energy such, for example, as a standard magneto which may com-- prise a primary coil i6, a secondary coil I'I and breaker mechanism I'a including an operating cam I9. One side of the secondary coil I'I of the magneto I5 may, as shown, be connected by a conductor to the rotary element 2I of a distributor unit 22, which rotary element is adapted successively to cooperate with a plurality of fixed distributor terminals 23--23. Each of a plurality of conductors 24 is connected to one of the distributor terminals 23 to form one side of a supply circuit to one of the transformer spark plug unit II. The other side of the supply circuit is provided by a. grounding connection 26 for the'secondary coil I'I, such as through the case of the magneto I5 tothe engine frame, and the manlfold I3 is also grounded, preferably to the engine Iframe. The converter unit I4 comprises a metalllc casing 26 connected to the manifold I3- at 21 and grounded thereby, the casing 26 in turn bein connected at to one end of a shielding sheath 29 provided for the cable li. The other end of the shielding sheath 2Q is connected at Sil to the shell or metallic casing iii of the transformer spari: plug unit il which is grounded to the cylinder wall i@ and, in a lsnown manner, carries one or more spark plug electrodes .iii-32.

The supply conductor is connected at 33, as hy a socket coupling, to a conductorlli within the converter unit id. A condenser bridges the conductor idd and the metallic casing 2G. rihe conductor lili is also connected to one electrode of spark gap means Sii, the other electrode of which is connected to a circuit connector Sl, which may also be a socket coupling. A cable conductor 38 is connected between the socket coupling 3i and one end of the primary winding 39 of the novel transformer, the other end of the primary being connected by a cable conductor dll to the grounded side of the circuit, such as to the shielding sheath 29, preferably at or near the connection 28. A

Corona effect tends to occur in gaseous media adjacent elements carrying current at high voltages and particularly. at high altitudes where rarefaction becomes appreciable, resulting in se,

rious power losses attended by decreased eiiiciency. I

In accordance with the present invention, this problem is efficiently overcome by excluding air or gases from the interior of the transformer if desired, may be llled with particles of refracdoo tory material such as ground glass, asbestos, mica, or the like. lf the mechanical structure assures hermetic sealing or the parts within the encasing shell, heat-stable uids known in the industry as Dow-Corning compound, Sigo-Resin, and 200 Fluid are satisfactory for impregnating the interior of the spark plug unit.

The spari: plug ll, ligures 2 and 5, is partially of conventional construction and prior to adaptation to the disclosed ignition system, may comprise a metallic casing or shell 3l lined with a sleeve il of suitable insulating material, such as a heat-stable ceramic or porcelain, which cooperates with an element lil of similar material supporting the central electrode d, the latter being exposed at the bottom of an interior chamber 80 of the spark plug. In the conventional construction, the chamber 80 is provided for reception of a circuit connector unit which, in accordance with the present invention, is replaced by a transformer. The metallic casing or shell 3Iv is threaded Ias at 8l for insertion into a passage formed in the wall I0 of an engine cylinder and the connecting cable I2 may be detachably secured to a threaded portion 82 of the casing.

The transformer secondary winding (I is preferably wound about the exterior of a substantially cylindrical elongated cup or vial 83 of suitable insulating material, preferably glass, having the minimum wall thickness necessary for effective lnsulationof the transformer windings. In this manner, close coupling is afforded between the transformer windings while still obtaining ade# quete insulation. For efficient operation. the distance between the primary and secondary windings should be quite small compared to the distance between the secondary Winding and the metallic casing II of the spark plug. Theyial l! ausbau ployed provided thin layers thereof are capable of withstanding thehigh temperatures and voltages to which they are subjected in operation of the system, in which voltage stresses of the order of 2,000 to 3,000 volts per mil are common and localized stresses may at times be as high as about 10,000 volts per mil. l

The secondary winding 4| is arranged upon the glass cup 83 with the low tension end 42 located adjacent the rim of the cup and the high tension end 43 located adjacent the bottom of the cup. Preferably, the low tension end is anchored directly to the rim of the cup by a body or smear 84 of metallic material, such as a silver compound, which may be adhered to the glass by firing and which is preferably tinned with solder to anchor the wire. The high tension end 43 is preferably anchored to the bottombf the cup 83 by another smear 85 of similar metallic material.

In accordance with one embodiment of the invention, a terminal 43 is provided for the high tension end by soldering a piece 88 of metallic foil to the smear 88. lThe foil, before soldering, may be a disc having a diameter approximately twice as great as that of the vial. After the foill is soldered, the disc is coned or drawn out to a peak as shown in Figure 3 so as to readily nt into the chamber 80 together with the secondary winding. When the secondary assembly is forced into chamber 80, the foil cone 36 is wadded against the electrode'terminal 18 and adapts itself to the contour of the adjacent structure to assure good electrical connection and effective mechanical support. AIt is to be understood that other means may, if desired, be employed to afford a terminal for the secondary winding. For example, a small helical spring may be compressed between the smear 85 and the electrode terminal 19 to provide effective electrical connection and a resilient mechanical support.

When the transformer secondary assembly is mounted in the chamber 80, a low tension terminal or pigtail at 42 may be held in contact with the edge 81 of casing 3| by the connecting cable I2. Alternatively, the transformer secondary assembly may be permanently mounted within the cham-ber 80 by a soldered connection between the low tension terminal at 42 and the edge 81, or by a body of solder bridging the spark plug casing and the smear 84, or by any other suitable anchoring means that may readily occur to one skilled in the art.

The primary winding 39 is adapted to be received in the glass cup .83 in closely coupled relation to the secondary winding 4|. This primary winding may comprise an elongated substantially cylindrical sleeve or core 88, Figures 2 and 3,

which has an axial bore for receiving an end of the conductor 33, together with a base portion 89, a fiange 90 providing a shoulder 9|, and a helical groove 92 in .which the wire of the primary winding 39 is received and seated. Any insulating materials may be used for the core which will withstand-the high temperatures encountered at the spark plugs without gassing, such, for exand soldered to conductor 38 at the time the washer 93 is soldered thereto for anchorage. The other end 85 of the primary 39 may extend through a passage in the base portion 89 to serve as a terminal for connection to the conductor 40.

As previously pointed out, the transformer structure is thoroughly impregnated, after assembly, with a suitable insulating compound to avoid corona effect and attendant energy loss. A body of such impregnating `compound is indicatedat 96. The transformer windings may be held within the chamber in the spark plug casing 3| by an internally threaded sleeve nut 81 which engages the threaded portion 82. The nut 91 may have a flange 98 which is seated on a flange 99 formed on a sleeve |00, an internal shoulder in the sleeve |00 bearing against the core shoulder 9|. The outer edge of the sleeve |00 is thus held in contact with the edge 81 of the spark plug casing 3| to clamp, if desired, the secondary terminal at 42 therebetween and to afford a good electrical connection between the casing and the sleeve as at 30.

From the foregoing description, it will be appreciated that a small, compact transformer unit is obtained which affords close coupling between the transformer windings without breakdown or flash-over difficulties. Although the structural features of this transformer are well adapted to g the rather rigid requirements of mounting of the transformer in the relatively small space or chamber present in a spark plug of conventional design, it is to be distinctly understood that. thetransformer per se is adapted for various other uses where an eilicient transformer is desired which is capable of withstanding high temperatures and severe mechanical vibrations. This mounting effects an efilcient shielding of the transformer and eliminates long leads between the transformer secondary and the adjacent electrodes whereby energy losses are avoided. The transformer assembly of a typical embodiment of the invention is in overall dimensions about one inch long and about three-eighths of an inch in diameter and has a turn-ratio of the order of 15 to 20:1 with the secondary winding having about 400 turns of very fine wire. In conventional transformers Where voltage stresses on the insulation separating the primary winding from the secondary winding run as high as 2,000 to 3,000 volts per mil, and may in the case of localized stresses run possibly as high as 10,000 volts per mil, there is a serious possibility of flash-over between the primary winding, which is substantially at ground potential, and the high tension end of the secondary Winding if mere sleeve separating insulation is used. The use of the closed-bottom glass cup 83 in' this invention avoids the necessity of providing a long flash-over path, as by extending a separating tube or sleeve far beyond the high tension end of the secondary winding. The relatively thin-walled glass cup or vial element of the novel transformer effectively eliminates flash-over while assuring a structure of minimum dimensions that is capable of eiliciently standing up under such high voltage stresses and the relatively high heat of operation without an undue separation of the two windings, thereby assuring maximum operational efficiency.

In Figure 4 is shown an alternative construction which may be employed for the primary winding 39. This so-called air-core structure may comprise a cupped metallic member |0| having a peripheral flange |02. A plug |03 of suitable insulating material is molded into the cup |0| 7 Y Y and extends through a passage in the hottom thereoi, with an' axially extending conductor or metallic rod iti fixed therein. The primari winding 99 is disposed about the rod it with one end seated against the cup i9@ and the other end preferably twisted about and soldered to the rod itt at lilo.. in mounting this structure, the rod. tilt and the flange Q92 may he connected in' any suitable manner, to the conductors 99 and il respectively.

ri Figure is shown a modified iorm oi trans former constroctiohand inonritin7 thereof. 'ioe @loss coo 'with the secondaw winding il mounted thereon is secured within the charnloer 99 hy metaiiic ring iidsoldcred to the casing within sind harige di. The low tension end oi the secondary di is also soldered to the ring ii. The core 8d is formed oi suitable insulating rial which is initially of, such' resiliency as to new mit the wire of the primary to he ernhedded therein when wound. This primary construction preferably ci a diameter to permit sito@ soolret= ing theretoa into the glass cup 83 during essentiel?. The escape of excess impregnating compound may loe provided ior during; assembly oi parte in any suitable man-ner, such hy longitudinally extending ways, to avoid difficulties which may arise as a result oi piston action. ilteriiativeiia piston action may he avoided by tapering liotii glass con 93 and the core as suggested in Figure il.

The operation of the device oi7 the present in ventlon will he more readily understood oy refers ence to theL circuit diagram shown in Figure i. The magneto successively delivers noises oi our rent having a seals voltage oi about 1,990 to i509 volts through the distributor to the various son ply circuits itl-2d, each of which includes, as a part oi the converter unit lil, the condenser which is thus charged. 'The condenser 95, spark gap 39 and transiormer primary winding 89 are connected in series to provide a irish frequento oscillatory circuit which is excited oy the puise impressed on condenser 99. The peak voltase oi" the high frequency oscillations is steloied up to in excess oi 30,900 volts by the transformer with the result that high frequency sparks are created at the gaps between the spark plug electrodes 3Q .and 32, which efficiently ilre charges o1? iuel even though the spart', plug electrode be fouled with cai-oon or oil.

t will oe thus seen that the objects set forth above, among/others, are emciently attained and since certain changes may 'loe made in the above construction and different embodiments ci the invention could` be madewithout departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood thatthe following claims are intended to cover all oi the generic and v cured by Letters Patent is:

. 1. An electrical transformer comprising. in combination, a primary winding, a substantially cylindrical fiat-loottomed glass cup for receiving said winding, a secondary winding wound about the exterior oi said con, a disc oi metallic foil substantially greater in diameter than said con, and a hotly ci solder anchoring the high tension end of said secondary winding and said. foil dice to the substantially dat Tcottom oi said cup, said ioil disc ticino oreliminariiy conoci to seme as c. contour-adaptable terminal for the high teosioh end oi said secondary windinge l En an electrical transformer the combination comprising a substantially dathottomed @dass con, a seconda@ Winding wound about the er terior of said cup with one end mociiored adiacenti the lio oi said con, a disc oi' metallic toil. schoten@ tlallr greater in diameter said con, o holly oi solder anchoring the high tension end said seconden? winding and seid foil disc to the substantially dat bottom oi said coo. said ioil di c hein@J preliminarily coined to serve as a contour adaptable terminal ior the high tension. edd oi said secondary winding'.

'in an electrical transformer the comhiriotioo comorisina a substantially datbottomed drlcal glass cup, a secondary winding Wound shoot the exterior ci said cup, said winding hating e low tension end thereof anchored to said com adjacent the lio thereof lofi a bcolyoi solder fior connection. toa secondary circuit and the high tension end thereof anchored by another lood? oi solder to the substantially dat bottom oi said coll, and a disc o2? metallic foil substantially greater in diameter than said cup anchored to the bottom ci the latter hy the last-mentioned body of solder with the edges oi said foil disc heine drawn olitwardly substantially to a peak to preliminarily cone said foil disc which serves as a contour adaptable terminal ior ,the high tension end of said winding.

ALEXANDER WALL" REFERENEES @HEER The following references are oi'record in the die oi this potent:

UNITED STATES PATENTS Number Name Date 1,455,199 Groton, Jr. May 15, 1929 1,852,605 Carlton et al. Apr. 5, 1932 1,898,931 Bahrmann Feb., 21, 1939 1,940,840 Bellaschi Dec. 26, 1939 1,956,334 Parker Apr. 24, 1934 1,977,122 Ehrlich Oct. 16, 1934 2,014,650 Heintz Sept. 1'?, 1935 2,153,090 Libbe Apr. 4, 1939 2,180,704 Dietrich et al Nov. 21, 1939 2,279,635 Morley Apr. 14, 1942 2,375,309 McCoy May 8,' 1945 2,403,629 Berkey et al. July 9, 1946 2,414,692 Harkness et al. Jan. 21, 1947 FOREIGN PATENTS Number 1 Country Date 343,468 Great Britain Feb. 18, 1931

Images