US2141141A - Ignition coil - Google Patents

Description

Dec. 20, 1938. L. P. K'oNGsTED 2,141,141

IGNITION COIL Filed Dec. 27, 1957 ATTORNEY.

Patented Dec. 20, 1938 UNITED STATES PATENT` ori-ica IGNITION con.

Application December 27, 1937, Serial No. 181,937

7 Claims.

This invention relates to ignition coils, and particularly to ignition coils, preferably non-rotatable, for magneto electric generators and battery' ignition systems in which'` the generating winding, usually primary and secondary turns arranged either one outside the other, surrounds an outwardly projecting magnetic core usually o1 laminated sheets of steel.

Ignition coils of this type contain superposed layers of turns of enameled or other insulated wires separated between layers and between the Aprimary and secondary sections by paper sheets or other insulating material, the entire coil sometimes being vacuum impregnated with wax which when molten flows into the winding of the coil, and when cooled hardens into a hard solid mass. It is known that oil of suitable grade'is a better y insulation for high-voltage vacuum-impregnatdiillculty permanently.

ed ignition coils than is wax because the wax is' more or less crystalline when solidified, and therefore does not then fill all the interstices of the paper or other insulation. But heretofore, while oil, being liquid, completely lilled the interstices of the coil at all temperatures, it gradually escaped from the winding, particularly when the coil breathed upon being repeatedly subjected to heating and cooling in normal operation, and

coils sovtreated eventually lost some of their re-l sistance to electrical breakdown. To reduce the amount' and rate of loss of the oil, the ignition coil is sometimes tightly taped and varnished by hand around the outside turns, and the end caps are machined and varnished, but this procedure is expensive without reliably It is a primary object of my invention to provide a high voltage ignition 'coil which is filled or over-saturated with or in effect bathed in oil and which retains a high degree of resistance to Another object of my invention is to provide Y an ignition coil with a casing which is substantially sealed against the entrancev of moisture and dust into the coil as wellias against the loss of oil from the co'il. .g

Another object of my invention is to. provide an ignition coil of this kind which is inexpensive to manufacture and which is reliable in operation over long periods of normal operation.

overcoming the (Cl. F-'361) These and other objects of my invention will be apparent from the ensuing description of two modifications of my ignition coil and from the separate layers are separated by a suitable in-.

sulation 5 as untreated linen or kraft paper sheets, the primary and secondary sections being suitably insulated from each other by cardboard or the like. The insulation 5 between layers projects beyond 'the end turns of the layers, but

in my coils the extent of this projection may be less than formerly onaccount of the high and permanent insulating property of the oil impregnation hereinafter described. This entire.

coil structure is subjected to a temperature of 250 E. in a suitable impregnating tank for approximately five hours, and then for several While still under this vacuum, insulating oil of well known kind, preferably mineral, under'a'tmospheric pressure and at a tempera-ture of about 250 F., vis allowed to enter the tank to a level above the top of the coil Vand to remain there until all insulations are thoroughly impregnated, and all interstlces in the coil includ.`

.ing the paper between the layers o f turns and between the primary and secondary sections, and

all spaces in andaround the laminated core, are.

assembly in a'housing which in the instance` sho/wn comprises a preformed cup-shaped member 6 of molded bakelite or bakelized paper having 'a central opening 'l vin the closed end 8 thereof. The central opening l is slightly larger `than-theexternal dimensions of the core A, and

the tubular walls of the cup-shaped member 8 have an internal diameter somewhat larger than the external diameter ofthe coll to leave a small space therebetween for ease in assembly and to permit expansion of the oil within the casing under varying temperature conditions in normal operation of the c oil. Prior to the insertion of the coil in the cup-shaped member, .a liberal. A

'amount of high melting point compound, the

properties of which are more fully described heref and I8 having openings I8 and 28 of slightly less inafter, is ilowed over one end of the coll from a heated tank. The coil I is then inserted into the housing so that the core 4 projects through the opening 1, and is pressed down firmly into the casing so that the compound, still molten or plastic, flows through all clearances between the core 4 and the sides of the opening, and also uniformly over that end of the coil, and partly into the space between the outside periphery of the coil and the housing. A layer of the same compound is then placed over the other end surface of the coil, being applied liberally around the core 4 and around the edge or rim of the cupshaped member 6. Before this compound has a chance to solidify, a preformed cover 9 with a central opening I likewise slightly larger than the core 4, and with the low tension lead II threaded through the opening I2 and the ground connection I3 accommodated in the cutout I4, is pressed down firmly so that the compound is squeezed into all spaces and interstices4 at and near that end of the coil including the clearance between the rim of the cup-shaped member 6 and the edge of the cover 8 and also around the lead II and connection I3. The compound also lls the clearances between the core and the edges of the opening I0. The cup-shaped member 8 is provided with a hollow high tension terminal l (see Fig. 2) for the secondary -wlnding of the coil and a low tension terminal connector I6 for the primary winding. The openings of these terminals are suitably sealed with solderv after the leads are pulled tightly therethrough. After the compound has hardened at all these places, the coil is sealed in a fluid-tight manner so that substantially none of the oil with which the coil has been filled is lost even upon repeatedly 'reaching operating temperatures as high as 220 F.

A compound which is of high melting point, that is one which will not sag from gravity below a temperature of 250 F., is used to prevent socalled cold ilcw at any temperature to which the coil is subjected in normal use. Also the compound is preferably of the kind which below that temperature will not readily dissolve in, or chemically combine with, the oil with which the wound core is iilled. Preferably, a high melting coal tar rather than petroleum tar is used, and

a mineral ller or other inert material, such asl fullers earth, chalk or talcum. may be mixed as a powder in the tar -to further raise the defor use where the coil is placed in an exposed position. Where the coil is protected, as for example by enclosure in a magneto housing, I prefer the construction shown in Fig. 2 in which the coil core is encased in a housing of elastic material. Ordinary rubber isgnot suitable for this purpose since it deteriorates when in contact with oil, but synthetic rubber, such as neoprene, thiokol land the like, does not deteriorate on contact with oil and istherefore suitable for this purpose. As shown, two preformed cup-shaped members -II cross-sectional area than the cross-sectional area of the core 4 of the coil 2|-, are pressed over the assembled core and coil with the projecting end portions of the core extending through the openings I9 and 20. The untreated coil windings of this construction are substantially the same as the ones previously described except that paper orl varnished silk washers 22, having a diameter slightly larger than the secondary coil, with square holes punched in the center thereof, are placed over each end thereof prior to insertion in the cup-shaped members I1 and I8. These Washers act as protective aprons which prevent the sealing compound from sealing the ends of the paper layers between the windings. The cupshaped member II is slightly longer than the cup-shaped member I8 and the edges of the cupshaped members overlap. and are united by sealing with a neoprene or similar rubber cement which is first liquid or plastic and later vulcanized by heat to form a duid-tight lap joint extending circumferentially around the coil. The openings in the housing at the core, the high tension terminal I5, the grounding connection 24 and the low tension wire 25 are originally of slightly less size than the parts they surround so as to tightly grip them. The joints there are also sealed with neoprene cement, thus forming a completely huid-tight housing. The vulcanizing of the neoprene cement sealing all joints is accomplished by baking the entire assembly for two hours at a temperature of 260 F.

In this embodiment of Fig. 2, the coil may be first impregnated with oil before its insertion in the elastichousing as described in connection with the structure shown in Fig. 1, but preferably the casing is filled with oil after the housing structure has been vulcanized together and sealed as shown around the unimpregnated windings. In this latter case, the assembled coil structure is subjected to 'a vacuum impregnating process at 250 F. and then filled with insulating oil as previously described. The oil-enters the casing through the opening 23 in the high tension terminal. As in the nrst embodiment, this hole is afterwards sealed by soldering.

This form provides an oil-tight elastic casing which permits the necessary amount of expansion and contraction of the oil within the casing under varying temperature conditions in normal operation of the coil without loss of oil. I1' in the process of heating the oil in the casing produces a pressure therein due to expansion of vapor, the elastic casing will expand slightly instead of permitting, the oil to be forced out through some of the joints. On cooling, the casing will contract as the vapors condense, thus avoiding any tendency to draw external air and moisture into the casing.

Both constructions provide a structure in which the wires of. the superposed layers of the windings of the coil, the sheets of insulating material between the layers, and the core are filled with oil and in which t he casing is so sealed that the 2,141,141 when applied but which hardens or is hardened after being squeezed into all open spaces and cooled, and which when hardened doesnot dissolve in or chemically combine with the insulating oil in the range of normal operating temperatures of the coil extending up to 220 F. Although there are herein described but tw embodiments of the invention other embodiments within the scope of the appended claims will be obvious to those skilled in the art from a consideration of. the forms shown. For instance, it will be obvious that the coil winding with its core may be vacuum treated under heat, filled with oil as aforesaid and then completely sealed in duid-tight manner in a metal or other container by insulating material like that described in connection with the rst embodiment which has a comparatively high temperature of cold ow but whichvmelts at a suitably high temperature. Such ignition coils are particularly adapted for present battery ignition coils of well known forms which have insulating caps and no core portions projecting outside the containers, as for instance the type shown in Ehrlich et al. U. S. Patent No. 1,977,122.

Having thus described my invention, what I claim is:

1. A high-voltage ignition coil comprising win'dings of superposed layers of insulated wires; insulating sheets between said layers; a core for said coil; insulating oil lling the interstices of and the open spaces in and between said wires, sheets and core; and a fluid-tight casing comprising two preformed members of oil-resistant material surrounding said windings, each of said members forming an end Wall of the casing and each of said end walls having a central aperture therethrough through which an end of the core projects; said casing being duid-sealed interiorly at the joints between said end portions and said core with a material which below 220 F. does not flow or dissolve in or chemically combine with said insulating oil.

2. A high-voltage ignition coil comprising windings of superposed layers of insulated wires; insulating sheets between said layers; a core for said coil; insulating oil lling the interstices of and the open spaces in and between said wires, sheets and core; and a huid-tight casing comprising two preformed members of oil-resistant material surrounding said windings, each of said members forming an end wall of the vcasing and each of said end walls having a central aperture therethrough through which an end of the core projects; said casing being huid-sealed interiorly at the joints between said end portions and 'said core withl a tar product of high cold ow temperature which has an inert ller.

3. A high-voltage ignition coil comprising windings of superposed layers of insulated wires; insulating sheets between said layers; a core for said coil havingend portions projecting therefrom; insulating oil filling the interstices of and the open spaces in and between said wires, sheets and core; and a fluid-tight casing comprising two preformed members of oil-resistant material surrounding said windings, each of said members forming an apertured end wall through which said end portions of the core project; said casing being fluid-sealed interiorly at the joints between said end portions and said core with a material which below 220 F. doesv not flow or dissolve in or chemically combine with said insulating oil.

4. A high voltage ignition coil comprising windings ofsuperposed layers of insulated wires; insulating sheets between said layers; a core for said coil having end portions projecting therefrom; insulating oil lling the interstices of and the open spaces in and between said wires, sheets and core; and a non-metallic fluid-tight casing comprising two preformed members of oil-resistant material surrounding said windings each of said members forming an apertured end wall through which said end portions of the coreproject; said casing being fluid-sealed interiorly at the joints between said end portions and said core with a material which below 220 F. does not ilow or dissolve in or chemically combine with said insulating oil.

5. A high-voltage ignition coil comprising windings of superposed layers of insulated wires; insulating sheets between said layers; a core for said coil; insulating oil lling the intersticesof and the open spaces in and between said wires, sheets and core; and an elastic oil-resistant casing comprising two preformed members surrounding said windings, each of said members forming an end wall of the casing and each of said end walls having a central aperture therethrough through which an end of the core projects; said casing being fluid-sealed interiorly at the joints between said end portions and said core with a material which belowv 220 F. does not ow or dissolve in or chemically combine withsaid insulating oil.

6. A high-voltage ignition coil comprising windings of superposed layers of insulated wires; insulating sheets between said layers, a core for said coil having end portions projecting therefrom; insulating oil filling the interstices of and the open spaces in and between said wires, sheets and core; an elastic oil-resistant casing comprising two preformed members surrounding said windings, each of said members forming an apertured end wall through which said end portions project; and, extending through said casing from said winding, a sealed-off hollow high-voltage terminal which, when open, forms a passage, for insulating oil to the interior of said casing; said casing being Huid-sealed interiorly at the joints between said end portions and said core with a material which below 220 F. does not ow or dissolve in or chemically combine with said insulating oil.

7. A high-voltage ignition -coil comprising windings of superposed layers of insulated wires; insulating sheets between` said layers, a core for said coil having end portions projectingv therefrom; insulating oil filling the interstices of and the open spaces in and between said wires, sheets and core; and a fluid-tight casing comprising two preformed members of elastic material surrounding said windings each of said members forming an apertured end wall with openings of slightly smaller area than the cross-sectional area of said end portions of the core, whereby said elastic material grips tightly the projecting portions of the core when the latter are inserted into said openings; said casing being fluid-sealed interiorly at the joints between said end portions and said corev with a material which below 220 F. does not tlow or dissolve in or chemically combine with said insulating oil.

LUDVIG P. KONGSTED.

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