US 3236937 A
Description (OCR text may contain errors)
236,937 TENSION Feb. 22, 1966 J. R. HARKNESS ETAL 3,
CONNECTOR MEANS AND RECEPTACLE FOR CONNECTING HIGH LEAD TO IGNITION COIL 3 Sheets-Sheet 1 Filed April 29, 1965 6IWJM7OW Juseph .RHarknsss John ,3 I
Feb. 22, 1966 R. HARKNESS ETAL 3,236,937
CEPTACLE FOR CONNECTING HIGH TENSION LEAD TO IGNITION COIL CONNECTOR MEANS ANb RE Filed April 29, 1963 V 3 Sheets-Sheet 2 J7 mdmn p va/ J'ussph R.Hsrkn2ss wavy,
Feb. 22, 1966 J. R. HARKNESS ET AL 3,236,937
CONNECTOR MEANS AND RECEPTACLE FOR CONNECTING HIGH TENSION LEAD TO IGNITION COIL 3 Sheets-Sheet 5 Filed April 29, 1965 Jasaphfifl'arknasrs aZm 552-127.
United States Patent M CONNECTOR MEANS AND RECEPTACLE FOR CONNECTING HIGH TENSION LEAD TO IGNI- TION COIL Joseph R. Harkness, Germantown, and John D. Santi,
West Allis, Wis., assignors to Briggs & Stratton Corporation, Milwaukee, Wis., a corporation of Delaware Filed Apr. 29, 1963, Ser. No. 276,423 Claims. (Cl. 174-52) This invention relates to electrical instrumentalities such as induction coils for internal combustion engine magnetos and the like, and refers more particularly to the conection to such a coil of an external lead by which the coil is connectable with other components of an electrical circuit.
Induction coils, including both those for battery ignition systems and those for magnetos, have a secondary winding of relatively fine wire which is normally connect able with a spark plug or distributor through a high tension lead comprising a relatively heavy stranded conductor enclosed in a flexible sheath of insulating material. Obviously, it is important that there be a good electrical connection between the high tension lead and the wire of the secondary winding, but it is also important that this connection be a mechanically strong one, so that the high tension lead cannot be easily torn out of the coil. The connection of the high tension lead to the coil should also provide good insulation between the lead and the coil windings, should not be susceptible to electrical breakdown to ground, should involve a minimum of parts and labor so as to be low in cost, and should afford a weatherproof seal between the high tension lead and the body of the coil, by which moisture and dirt are kept from entering the potting in which the coil is encapsulated and by which its windings are impregnated.
However, it has heretofore been difficult to realize all of these several requirements in practice, for the reason that the high tension lead is comparatively bulky and heavy and is thus capable of imposing substantial forces upon the connection merely by its own weight, while the fine wire of the secondary winding, with which the high tension lead is connected, has very little strength.
With the foregoing in mind, it is the general object of the present invention to provide a method and means for connecting a high tension lead with one end of a wire comprising a winding of a magneto inductance coil or the like, whereby a body of insulating material, which is not necessarily homogeneous but which is nevertheless unbroken and uninterrupted, provides a potting in which the coil is encapsulated and by which its windings are impregnated, also affords a strong anchorage of the high tension lead to the body of the coil, and, further, provides a weatherproof and electrically insulating seal around the high tension lead, all without substantially increasing the bulkiness of the coil or imposing special requirements upon the shape of the coil, its core or its case.
More specifically it is an object of this invention to provide a method and means for mechanically and electrically connecting a high tension lead with a coil of the character described wherein the connection between the high tension lead and the wire of a winding of the coil comprises a substantially rigid elongated metal connector having one end portion formed as a prong that projects axially into the high tension lead to engage the conductor thereof and to be surrounded by the insulating sheath on the high tension lead, while the coil wire is electrically and mechanically connected, as by solder, to the other end portion of the connector; and wherein said connector, the adjacent end portion of the high tension lead and the coil 3,236,937 Patented Feb. 22, 1966 are embedded in a continuous though not necessarily homogeneous body of insulating material.
It is also an object of this invention to provide a method of connecting a high tension lead to a winding of an ignition coil or the like, whereby the high tension lead is connected to the coil after the latter is potted, by endwise inserting the high tension lead into an upwardly opening well at the upper end of the coil, near one side thereof, to thereby cause a rigid conductive prong which projects upwardly in the well and which is electrically connected with the coil winding to axially enter the sheath of the high tension lead and engage its conductor; and wherein such insertion of the high tension lead into the well causes a small amount of liquid insulating material in the bottom of the well to be displaced upwardly around the high tension lead so that the displaced insulating material, when hardened, forms an anchoring bond and a weatherproof seal with the lead.
With the above and other objects in view which will appear as the description proceeds this invention resides in the novel method and means hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodi ment of the herein disclosed invention may be made as come within the scope of the claims.
The accompanying drawings illustrate two complete examples of physical embodiments of the invention according to the best modes so far devised for the practical application of the principles thereof, and in which:
FIGURE 1 is a top perspective view of an ignition coil having a high tension lead anchored thereto, embodying the principles of this invention;
FIGURE 2 is a vertical sectional view of an ignition coil assembled into a plastic shell prior to the potting operation;
FIGURE 3 is a view generally similar to FIGURE 2 but showing the coil assembly just after the potting op eration;
FIGURE 4 is a fragmentary view partly in vertical section and partly in side elevation, showing the encapsulated coil just before a high tension lead is connected thereto in accordance with this invention;
FIGURE 5 is a fragmentary vertical sectional view showing the high tension lead connected and anchored to the coil in a finished unit embodying this invention;
FIGURE 6 is a cross sectional view taken on the plane of the line 66 in FIGURE 5;
FIGURE 7 is a perspective view of a metal connector which electrically connects the high tension lead with one end of the secondary winding in a coil made according to this invention;
FIGURE 8 is a view similar to FIGURE 2 but illustrating a modified embodiment of the invention;
FIGURE 9 is a view corresponding to FIGURE 3, but illustrating the modified embodiment;
FIGURE 10 is a view corresponding to FIGURE 5 but illustrating the modified embodiment;
FIGURE 11 is a perspective view of the plastic case employed in the embodiment of the invention illustrated in FIGURES 8-11 to form the well in which the high tension lead is received; and
FIGURE 12 is a fragmentary sectional view taken on the plane of the line 1111 in FIGURE 8;
Referring now more particularly to the accompanying drawings, the numeral 5 designates generally an inductance coil, which may be either a battery ignition coil or a magneto coil, and which has a primary winding 6 and a secondary winding 7. As is conventional, one end of the secondary winding may be connected, as at 8, with an end of the primary winding, to be grounded therewith, while the other end of the secondary is connected with an end of a high tension lead 9 by which the high voltages produced in the secondary winding can be conducted to a spark plug or distributor. It will be understood that the free end of the high tension lead is provided with a terminal clip 4 or the like by which the lead can be readily connected to an electrical instrumentality to be energized from the coil.
The high tension lead consists of the usual standard conductor 10 enclosed in a fairly thick sheath 11 of flexible insulating material such as neoprene. Because the high tension lead is relatively heavy, and may be subjected to severe pulling and bending forces as well as to substantial vibration, its connection with the very light wire of the secondary winding must have great mechanical strength, and thus presents a crucial problem in the construction of induction coils.
In the coil of the present invention this connection is provided by a substantially rigid elongated metal connector 12, to one end portion 13 of which the ungrounded end portion 14 of the secondary winding is connected, as by a solder joint 15. The other end portion 16 of the connector 12 is formed as a prong which, in the finished coil, extends axially into the high tension lead, to have good contact with the stranded conductor 10 and to be surrounded by the insulating sheath 11. The high tension lead has its connected end portion securely anchored to the coil by insulating material 17 which surrounds the lead to form a weatherproof seal around it and which is bonded to, and hence continuous with a body of potting material 17 in which the coil is encapsulated and which impregnates its windings.
In the practice of the method of this invention, as more particularly described hereinafter, the connector 12 is first secured to the body of the coil by the hardening of potting material in which the connector is embedded and which impregnates the windings; and a well is formed, defined by insulating material that is bonded to the coil, which well has a diameter to receive the sheath of the high tension lead and has the prong portion 16 of the connector 12 projecting coaxially thereinto from the bottom thereof. A small amount of hardenable liquid insulating material is poured into the bottom of this well and the high tension lead is forced axially thereinto to engage the prong portion of the connector with the conductor 10 of the lead and to displace the liquid insulating material from the bottom of the well upwardly along the lead, so that such displaced material, when hardened, securely bonds the high tension lead to the body of the coil and provides the weatherproof seal around the lead.
The primary and secondary coils'6 and 7 are wound according to generally conventional practice. The primary is wound upon a tubular bobbin 18, which is of such cross section as to accommodate the core being used with the coil, being shown in this case as rectangular. The bobbin is closed at its top and open at its bottom, and has at its bottom a radially projecting disk-like flange 19 which has a diameter somewhat greater than that of the primary but less than the outside diameter of the secondary. It will be apparent that the bobbin can be formed in one piece and molded of a suitable plastic.
The secondary may be wound separately from the primary. The outside end portion 14 of the secondary is soldered to the inner end portion 13 of the rigid connector 12.
The connector 12 (see FIGURE 7) can be readily formed of any suitable conductive metal as a one-piece stamping. Its inner portion 13 comprises a flat and substantially wide leg, while its outer portion 16, as mentioned above, is relatively slender, so as to constitute a prong that is insertable axially into the high tension lead. The inner leg and outer prong portions of the connector are lengthwise parallel to one another but are disposed in laterally offset relation, being connected by a short medial portion 23 which extends substantially normal to both of them.
In the embodiment of this invention illustrated in FIGURES l6, the flat inner leg 13 of the connector, with the outside end of the secondary soldered thereto, is flatwise taped to one side of the secondary coil, near the top thereof, with the connector so disposed that its medial portion 23 extends radially inwardly and overlies the top of the secondary. Before the connection to the secondary is made, a plug 25 of Teflon, a registered trademark, or the like, having a closely fitting coaxial hole therein, is engaged over the outer prong portion 16 of the connector, which projects upwardly from the coil when the connector is taped in place. The plug 25 has a radially projecting circumferential flange 26 spaced above its lower end, and the portion 27 of the plug that is below said flange tapers slightly and has an outside diameter which is a little larger than that of the high tension lead.
The bobbin 18, with the primary thereon, is placed in an upwardly opening cup-shaped plastic shell 28 which has a very free sliding fit with the secondary coil and which has in its bottom wall a hole 28 of slightly smaller diameter than the flange 19 on the bottom of the bobbin. Preferably the flange 19 on the bobbin and the bottom wall of the shell 28 are provided with mating circumferential lips 29 that snap together when the bobbin and shell are assembled, to provide a liquid-tight seal between them. After the bobbin is thus assembled into the shell 28, the secondary, with the connector 12 taped thereto, is slipped into the shell, around the primary.
The end portions of the wire comprising the primary winding are brought out of the coil at the top of the bobbin, as at 20 and 21, and the inside end portion of the secondary winding is similarly brought out of the coil at its top to have the conventional grounded connection with the outside end portion 21 of the primary.
To expedite the potting operation a number of cupshaped shells can be molded as upwardly opening wells in a unitary tray-like member 30 having an upstanding marginal rim portion.
In preparation for the potting operation, the coil assembly is heated and then placed in a vacuum, a liquid potting material, preferably comprising an epoxy resin, is poured into the cup-shaped shell, at least to the level of the flange 26 on the plug 25, so that all of the windings and a substantial portion of the connector are submerged in the potting material. The vacuum is then released to drive the potting material into the interstices in the windings, and thereafter the potting material is cured or set in the usual manner.
After the potting operation the entire coil is encapsulated in a body 17 of insulating potting material within the shell 28, and the cured potting material bonds the coils and the connector to one another as well as impregnating the windings. The cup-shaped shell can now be cut or otherwise detached from the tray-like unit 30, and the closed upper end of the bobbin can be removed. These two operations can readily be accomplished simultaneously by a single stroke in a punch press.
When the Teflon plug 25 is removed from the prong portion of the conductive member, it leaves an upwardly opening well 31 in the layer of potting material at the top of the coil, in the center of which well the prong portion 16 of the connector projects upwardly. The plug is readily removable because Teflon will not bond to epoxy potting material, and because of the slight taper of its bottom portion. As shown in FIGURES 3 and 4, the potting material on top of the coil forms a small ridge 32 around the mouth of the well, somewhat increasing the depth of the well beyond what it would be if the potting ma terial had a perfectly flat surface all across the coil. The ridge 32 is caused by surface tension which holds the liquid epoxy potting material to the flange 26 on the Teflon plug while the potting material is driven into the interstices in the windings by the release of vacuum. After the plug is removed, a small amount of liquid insulating material (which can be an epoxy compound) is poured into the bottom of the well 31, and the end portion of the high tension lead 9 is then pushed axially down into the well, thus forcing the prong portion 16 of the connector to piercingly enter the stranded conductor 10 in the lead and make good contact therewith and at the same time displacing the liquid insulating material upwardly along the outer surface of the insulating sheath 11 of the lead. This assembly is now set or cured, as by heating it in an oven, and as a result the upwardly displaced insulating material provides a mechanically strong bond between the lead and the previously cured potting material at the top of the coil. Some of the insulating material that is displaced upwardly along the lead rises above the mouth of the well to form a smoothly rounded junction 33 (see FIGURE 5) between the lead and the potting material at the top of the coil, presenting a neat appearance at the junction of the lead with the body of the coil and, what is more important, providing a weatherproof seal around the lead at this vital point and reinforcing its anchorage to the body of the coil.
The method and structure illustrated in FIGURES 8 to 12 are especially well adapted for smaller coils, such as those used in the magneto disclosed in the copen-ding application of John Santi, Serial No. 149,140, now Patent No. 3,114,850, filed October 11, 1961, for Ignition Magneto, particularly for Single Cylinder Engines. With a smaller coil, the layer of potting material overlying the upper surface of the windings is thinner, and consequently a well like that designated by 31 in the previously described embodiment of the invention would not have sufiicient depth to afford a good anchorage for the high tension lead. With small coils, therefore, the present invention contemplates the use of a cup-shaped plastic receptacle or case 40 (see FIGURES 11 and 12) which is assembled with the connector before the latter is fastened to the coil and which defines a well 31 in which the high tension lead is insertable.
The cup-shaped receptacle 40 can be molded in one piece, from a plastic that will bond to the potting material. It cooperates with a connector 12 that can be in all respects like the one previously described, and it has a slot-like opening 41 in its bottom wall 42, near one side thereof, through which the wide, fiat lower leg 13 of the connector projects. Preferably the receptacle also has a sleeve portion 42 that projects downwardly from its bottom wall and snugly embraces the upper part of the lower leg 13 of the connector. However, a groove 43, extending axially along the inside surface of the sleeve portion 42 of the receptacle, provides a flue through which liquid potting material can flow into the receptacle from beneath the same. Inwardly opening grooves 44 extend up the side wall of the cup-shaped main portion of the receptacle, vertically in line with the ends of the slot-like opening 41 in its bottom wall, to receive the opposite edge portions of the flat lower leg of the connector as the same is inserted endwise into the receptacle from the top thereof. The medial portion 23 of the connector flatwise overlies the bottom wall of the receptacle when the connector is installed therein, and its upper prong portion 16 projects upwardly substantially coaxially in the cup-shaped main portion of the receptacle. The bottom wall of the receptacle provides an insulating spacer between the end turns of the sec ondary and the medial portion of the connector, by which short circuiting flashover is prevented.
The bobbin 18 of the coil assembly shown in FIGURES 8 to 10 is esesntially the same as that in the previously described embodiment of the invention, and the primary and secondary coils 6 and 7 are wound and assembled onto the bobbin in the maner described above. The connector 12 must of course be inserted into the receptacle 40 before the ungrounded end 14 of the secondary winding is soldered to the flat lower leg 13 of the connector, but thereafter the connector is taped to the side of the coil in much the same manner as previously described, with the bottom wall of the receptacle overlying the upper end of the secondary winding so that the cup-shaped upper portion of the receptacle projects upwardly from the top of the coil.
In this receptacle, again, liquid potting material is poured into a cup-shaped shell member 28 which contains the primary and secondary coils, the latter having the connector 12 and well-forming receptacle 40 held in place thereon as just described. The potting material which enters the flue 43, and through it the bottom of the cup-shaped upper portion of the receptacle 40, helps to bond and anchor the receptacle and the connector 12 to the body of the coil when the potting material is cured.
After the potting material is cured, the cup-shaped shell is detached from the tray-like unit of which it is a part, and the closed top of the bobbin is removed, all as described above. A small amount of a liquid insulating material is then poured into the well 31 formed by the receptacle 49, and the end portion of a high tension lead is axially forced down into it, displacing the liquid material upwardly along the lead. After curing, the connection thus formed is similar in all respects to that produced by the first described version of the method of this invention, since the plastic material of the receptacle 40 is bonded to the insulating material that is inside it and outside of it.
From the foregoing description taken together with the accompanying drawings, it will be apparent that this invention provides a method and means for encapsulating an ignition coil and connecting a high tension lead to its secondary in such a manner as to insure a weatherproof seal around the high tension lead, a good electrical connection of the lead to one end of the secondary, and a strong anchorage of the lead to the body of the coil, all in a manner which eliminates chances for a breakdown to ground; and it will be further apparent that the invention allows such a connection to be obtained very inexpensively, with a minimum of material and labor.
What is claimed as our invention is:
1. In an electrical instrumentality of the type comprising a wire wound into a coil and a lead having a conductor in an insulating sheath for connecting the coil with another instrumentality, means anchoring the inner end portion of the lead in endwise relationship to one end surface of the coil and providing a weatherproof electrical and mechanical connection between said end portion of the lead and an end portion of the wire comprising the coil, said means comprising:
(A) an elongated substantially rigid metal connector having (1) a leg that overlies a side surface of the coil and to which said end portion of the wire is connected,
(2) a prong projecting axially outwardly from said end surface of the coil from a point radially inward of said side surface of the coil, said prong being in lengthwise contact with the conductor of the lead at the inner end portion thereof and being surrounded by the inner end portion of the insulating sheath of the lead, and
(3) a medial portion which extends laterally between said leg and prong, connects them in offset relation, and overlies said end of the coil in supported relation thereto; and
(B) substantially hard insulating material, all portions of which are bonded to one another,
(1) surrounding and encapsulating the coil and said leg of the connector to mechanically connect them to one another, and
(2) surrounding and bonded to the inner end portion of the sheath of the lead to provide a seal between the lead and the encapsulation of the coil and to anchor the lead to the coil and hence to the connector.
2. As an article of manufacture, a subassenrbly for a potted inductive device comprising:
(A) a coil of wire having a terminal end portion accessible at an external side surface of the coil;
(B) an elongated substantially rigid conductive connector having (1) a substantially flat lower leg element to which said end portion of the wire is connected,
(2) an upper substantially slender prong element,
(3) a medial element integral with and connecting said leg and prong elements and extending transversely to them to dispose them in laterally oflset relationship;
(C) a receptacle of insulating material surrounding all of the connector except the lower end portion of its lower leg element, said receptacle comprising (1) an upper cup-shaped portion in which the prong element of the connector projects upwardly and which has its side wall spaced from said prong elements, said cup-shaped portion having a substantially flat bottom wall portion which the medial element of the connector supportedly overlies, and
(2) a sleeve portion which projects downwardly from the bottom of the cup-shaped portion at one side thereof and in which the upper portion of the lower leg element of the connector is snugly received; and
(D) means securing the receptacle, with the connector therein, to the coil, with said sleeve portion of the receptacle and the lower leg element of the connector overlying and contiguous to said side surface of the coil, with said flat bottom wall portion of the receptacle flatwise engaged with one end of the coil, and with the cup-shaped upper portion of the receptacle projecting axially from said end of the coil.
3. In an electrical instrumentality of the type comprising a wire wound into a coil and a lead for connecting the coil with another instrumentality and which comprises a conductor and an insulating sheath, means providing a weatherproof electrical and mechanical connection between the inner end portion of the lead and an end portion of the Wire comprising the coil, said means comprising:
(A) a body of insulating material encapsulating the coil and having a portion with an exposed upper face overlying one end of the coil;
(B) an elongated upright substantially tubular receptacle of insulating material in which the inner end portion of the lead is substantially coaxially and snugly received and which has its lower portion embedded in said body of insulating material beneath the exposed upper face thereof and has an upper end portion projecting axially above said face;
(C) an elongated conductive connector (1) having an upper portion which comprises a prong that is axially disposed in the tubular receptacle in contact along a substantial portion of its length with the conductor of the lead and which projects above the level of the said exposed upper face of the body of insulating material, and
(2) having a lower end portion which projects beneath the receptacle and is connected to said end portion of the wire and which is embedded in said body of insulating material; and
(D) solid insulating material in the receptacle bonding the inner end portion of the lead thereto to thus anchar the lead to the receptacle and provide a weatherproof seal around the inner end portion of the lead.
4-. The structure of claim 3, wherein the body of insulating material which encapsulates the coil is substantially cylindrical and its exposed upper face is substantially flat; and wherein the receptacle is located near but inwardly of the substantially cylindrical side wall of the body and partly overlies the upper end of the coil.
5. As an article of manufacture, a subassembly for an inductive device comprising:
(A) a coil of wire having ends and side surfaces and having a terminal end portion accessible at an external side surface of the coil;
(B) an elongated substantially rigid conductive connector having (1) a substantially fiat lower leg element to which said terminal end portion of the Wire is connected,
(2) an upper substantially slender prong element,
(3) a medial element integral with and connecting said leg and prong elements and extending transversely to them to dispose them in laterally oflset relationship;
(C) means securing the connector to the coil with said leg element of the connector flatwise engaging an outer side surface of the coil, the medial element of the connector overlying an end surface of the coil in supported relation thereto and the prong element projecting axially from said end surface of the coil;
(D) a plug-like well defining member made of a material that does not adhere to hardenable liquid insulating material, said member having an axially extending bore in which the prong element is received, and having (1) a body portion which tapers toward said end surface of the coil and terminates in a bottom surface which opposes said end surface of the coil, and
(2) means defining a radially projecting circumferential flange on the plug-like member spaced above its bottom surface; and
(E) a substantially cup-shaped open-topped shell-like mold member which closely embraces the sides of the coil, the leg element of the connector and the opposite end surface of the coil, leaving the first designated end surface of the coil exposed at the top of the mold member, said mold member having an upstanding marginal rim portion which extends above said flange on the plug-like member so that hardenable liquid insulating material can be poured into the mold member to the level of said flange.
References Cited by the Examiner UNITED STATES PATENTS 1,333,004 3/1920 Vaughn. 1,372,065 3/1921 Conklin 339 X 1,729,492 9/1929 Sauer 336107 X 1,854,401 4/1932 Fitzsimmons 336-107 X 2,285,136 6/ 1942 Abendroth. 2,695,856 11/1954 Firth. 2,720,617 10/1955 Sardella 264-272 X 2,914,600 11/1959 Smith 17452 2,944,297 '7/1960 Maynard 17452 X 2,994,844 8/1961 Niederman 17452 X 3,041,562 6/1962 Gammel 336-96 3,140,140 7/1964 Kohler et al. 339218 FOREIGN PATENTS 477,994 10/1951 Canada.
JOHN F. BURNS, Primary Examiner.
JOHN P. WILDMAN, LARAMIE E. ASKIN, Examiners.