US3048704A - Coil shield - Google Patents

Description

g- 1962 s. E. ESTES 3,048,704

COIL SHIELD Filed June 9, 1960' 2 Sheets- Sheet 1 Ffa. 3. Z

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STAWLEY 5: E3755 MpL/J/m/ Aug. 7, 1962 s. E. ESTES 3,048,704

COIL SHIELD Filed June 9, 1960 2 Sheets-Sheet 2 FI Go 40 i 5 i E '.I:'

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570N457 E ESTES United States Patent 3,048,704 COIL SHIELD Stanley E. Estes, Inglewood, Calif., assignor to Hallett Manufacturing Company, Los Augeles, Califi, a corporation of California Filed June 9, 1960, Ser. No. 35,064 11 Claims. (Cl. 307-10) This invention relates to shielding of electrical systems for internal combustion engines, and more particularly to a shield for an ignition coil.

Free electrical radiations from ignition systems of internal combustion engines used in proximity to radio receiving and transmitting apparatus are picked up in such apparatus and interfere with reception and transmission. This is a serious factor in the operation of land vehicles, airplanes, and motor boats, as well as in stationary installations embodying radio equipment where these installations .are proximate internal combustion engines.

A broad object of my invention is to provide a compact electrical shielding for an ignition coil which will substantially prevent transmission of electrical interference either by radiation through space or by conducting through associated wiring.

A further object of my invention is to provide an improved shielding for an ignition coil which serves the additional function of physical protection against weather.

Still another object of my invention is to provide a new and improved shielding for an ignition coil which incorporates a simplified mounting on the shield permitting it to be installed on the coil and removed without the use of special tools.

Another object of my invention is to provide a shielding for an ignition coil of the character described which is simple in construction, and relatively inexpensive to manufacture.

With these and other objects in view, the invention consists in the construction, arrangement and combination of the various parts of the device whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in the claims, and illustrated in the accompanying drawings, in which:

FIGURE 1 is a side elevational view of an ignition coil with my housing mounted thereon;

FIGURE 2 is another side elevational view of the ignition coil and my shielding device taken in the direction of 2 in FIGURE 1;

FIGURE 3 is a top plan view of the assembly shown in FiGURES 1 and 2;

FIGURE 4 is an enlarged side elevation of an ignition coil and a cross section of the coil shield in position on the coil;

FIGURE 5 is a cross section taken on line 55 of FIGURE 4;

FIGURE 6 is a cross section taken on line 6-6 of FIGURE 4; and

FIGURE 7 is a schematic wiring diagram of the shielded coil embodying my invention in relation to the distributor and ignition switch.

My coil shield assembly comprises generally the combination of a coil 10, an ignition coil shield housing 11 of substantially high electrically conductive properties, and a filtering device 12.

The coil is a standard type of ignition coil used on internal combustion engines and comprises primary and secondary windings, not shown, encased in a metallic conductive casing 15. A non-conductive plastic cap 16 seals ofl the top of the coil and is fitted with a secondary connector boss 18, and primary terminals 21 and 22. At the top of the casing a metallic conductive annular flange 17 is formed.

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The connector portion 18 receives a secondary high tension cable 19 which is shielded with tinned copper braid 20 which affords substantial metallic conductive coverage of the cable. Primary lead and outlet cables 23 and 24 are fitted with lugs 25 to be received on the primary terminals 21 and 22, respectively. Outlet cable 24 is also shielded with tinned copper braid 20.

The coil shield housing 11 is made up of three parts, a main hollow body open at both ends, a cap 31 and a channel clamp 32 positioned around the bottom of the body 30. More specifically, as illustrated in FIG- URE 4, the body 30 is an elongated hollow, cylindrical electrically conductive tube having an upper open end 35 and a lower open end 36. At the lower end 36 the body 30 is flared outward forming a flared portion 37 and having an end extension 38. The end extension 38 forms an opening 39 which is of substantially the same diameter as the exterior dimension of the flange 17 on the coil 10. The body 30 is set on the flange 17 and will frictionally remain because of the proximity of the respective parts.

The electrically conductive channel clamp 32 is generally U shaped in section, as best illustrated in FIGURE 4, and of a size to fit around the body 30 so that one leg portion 40 of the clamp 32 bears against the exterior of the flange 37 and another leg portion 41 will bear against the bottom portion 42 of the flange 17. The clamp 32 is provided with ears 43, as best seen in FIG- URE 5 and receives a bolt 44 and nut 45. After the housing 30 has been positioned on the flange 17 of the coil 10 the channel clamp 32 is positioned as described above, and the bolt and nut tightened to retain the shielding on the coil. With the leg 41 of the clamp 32 engaging the conductive end portion of the flange 42 a metal conductive contact is created between the shield and metallic body portion 15 of the coil 10.

At the upper end 35 of the coil shield housing 11 the cap 31 having a downward extending flange is mounted on the body 30. The cap 31 is held in place on the body 30 by means of screws 51. The cap 31 is provided so that access may be had to the interior of the body 30 to secure the cables to the coil terminals.

A slotted opening is provided at the bottom end 36 of the body 30, as best seen in FIGURE 6. Opening 55 is provided with a rubber seal grommet 57. This grommet 57 is used to seal the interior of body 30 from the elements and also to insulate the primary outlet cable 24 when it passes in and out of the coil shield housing 11, best seen in FIGURE 4. In body 30 of the coil shield housing 11 above opening 55 and adjacent upper end 35 is a second slotted opening 59. This opening 59 is provided with a rubber seal grommet 60' similar to the grommet identified above and serving the same purpose. The high tension secondary outlet lead cable 19 passes out through opening 59 and grommet 60 and thus seals the interior of the body and insulates the cable from the coil shield housing 11.

I The coil shield housing 11 acts as a ground for the tlnned copper braid 20 on cables 19 and 24 in the follow1ng manner: The braid 20 is peeled back from the respective ends of cables 19 and 24, as best seen in FIGURE 4, to a position on the inside of the coil shield housing 11. The braid is then twisted or compressed, as best seen in FIGURE 2, into strands and 66 respectlvely. The strand 65 passes from inside the housing 11 at 67 around the grommet and back out between the grommet and opening 59 to the exterior of the housing 11. The end of the strand 65 is provided with a lug 68. The braided strand 66 of the primary outlet cable 24 passes around the grommet and back out between the grommet 57 and opening 55. The braided strand 66 is provided at its end with a lug 69. The lugs 68 and 69 are secured to the exterior of the cable shield housing 11 by means of screw 70 as best seen in FIGURE 2. Thus, electrical radiation which may be carried by the braid will be grounded to the shield, thence to the coil and through a coil bracket 75 to the motor, not shown.

The coil shield housing 11 is further provided with a filtering device or coaxial capacitor 12 having a metal casing 80. The housing 11 is provided with an opening 56 which conductively receives an inner end portion 81 of the casing 80 and the portion 81 will project into the housing as best seen in FIGURE 4. To retain the device 12 in the position just described a conductive O-shaped bracket 82 is provided which grips the casing 80 and when in position adjacent the housing 11 is held to the housing by means of a screw 83. The outer end portion 84 of the capacitor 12 is provided with a terminal 85 to receive one end of cable 23a which cable passes to an ignition switch 86 illustrated schematically in FIG- URE 7. The primary lead cable 23 extends from the inner end portion 81 of the device 12 to the terminal 21 of the coil 10.

With the end portion 81 within the housing 11 there is sufficient isolation from outer end portion 84 for maximum filtering action by the capacitor 12.

The cables 23 and 23a need not be shielded by tinned copper braid because any electrical radiation of cable 2311 will be grounded through the filter 12 to the housing 11 and cable 23 is within the housing 11.

To further illustrate the circuit, schematic diagram FIGURE 7 shows a distributor 88, which receives the shielded primary outlet cable 24. Shielded secondary cable 19 after leaving the boss 18 passes out of the shield 11 and is connected to a distributor cap, not shown, on distributor 88.

While the invention has been shown and described herein in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope of the invention, which is therefore not to be limited to the details disclosed herein but is to be accorded the full scope of the claims and so as to embrace any and all equivalent apparatus.

Having thus described the invention what is claimed as new and is desired to secure by Letters Patent is:

l. The combination of: an ignition coil for an internal combustion engine comprising an elongated electrically conductive casing having a flange at one end, a nonconductive end structure encompassed by said flange, primary terminals and a secondary terminal supported on said end structure, an electrically conductive cup-shaped housing having an open end and a closed end, the open end being provided with a flare seating on said flange, a conductive channel clamp contracted upon said flange and said flare to retain the conductive housing on the coil casing, and in electrically conductive relation thereto, the housing enclosing the primary and secondary coil terminals, openings through said housing for accommodation of primary and secondary cables, a primary lead cable extending through one of said openings and connected to one of the primary terminals, filter means interposed in said primary lead cable, said filter means including an electrically conductive shell conductively mounted to said housing, a conductively sheathed primary outlet cable extending through a second of said openings and connected to a second primary terminal, a conductively sheathed secondary cable extending through a third of said openings and connected to the secondary terminal, and ground connections from the sheathing of the primary outlet cable and from the secondary cable to the housing.

2. The combination as defined in claim 1 wherein said openings through said housing are fitted with cable accommodating insulating grommets.

3. The combination as defined in claim 1 wherein said filtermeans is a coaxial capacitor.

4. The combination as defined in claim 2 wherein the conductive sheathing of the primary outlet cable and of the secondary cable are stripped, from the respective cables at their respective terminal ends and grounded to said housing.

5. The combination of: an ignition coil for an internal combustion engine comprising an elongated conductive casing having a flange at one end, a nonconductive end structure encompassed by said flange, primary terminals and a secondary terminal supported on said end structure, a conductive tubular housing having open ends, a cap mounted on one end, and the other open end being provided with a flare seating on said flange, a conductive channel clamp contracted upon said flange and said flare to retain the conductive housing on the coil casing and in conductive relation thereto, the housing enclosing the primary and secondary coil terminals, openings through said housing for accommodation of primary and secondary cables, a primary lead cable extending through one of said openings and connected to one of the primary terminals, filter means interposed in said primary lead cable, said filter means including a conductive shell conductively mounted to said housing, a conductively sheathed primary outlet cable extending through a second of said openings and connected to a second primary terminal, a conductively sheathed secondary cable extending through a third of said openings and connected to the secondary terminal, and ground connections from the sheathing of the primary outlet cable and the secondary cable to the housing.

6. Electrical shielding means for use with an ignition coil of an internal combustion engine which coil comprises an elongated conductive casing having a flange at one end, a nonconductive end structure encompassed by said flange, primary terminals and a secondary terminal supported on said end structure, said electrical shielding means comprising a conductive cup-shaped housing having an open end and a closed end, the open end being provided with a flare adapted to seat on said flange, a conductive channel clamp adapted to contract upon said flare and said flange to retain the conductive housing on the coil casing, and in conductive relation thereto, the housing being adapted to enclose the primary and secondary coil terminals, openings through said housing for accommodation of primary and secondary cables, a primary lead cable extending through one of said openings and connectable to one of the primary terminals, filter means interposed in said primary lead cable, said filter means including a conductive shell conductively mounted to said housing, a conductively sheathed primary outlet cable extending through a second of said openings and connectable to a second primary terminal, a conductively sheathed secondary cable extending through a third of said openings and connectable to the secondary terminal, and ground connections from the sheathing of the primary outlet cable and the secondary cable to the housing.

7. Electrical shielding means for use with an ignition coil of an internal combustion engine which coil comprises an elongated conductive casing having a flange at one end, a nonconductive end structure encompassed by said flange, primary terminals and a secondary terminal supported on said end structure, said electrical shielding means comprising a conductive tubular housing having open ends, a cap mounted on one end, and the other open end being provided with a flare adapted to seat on said flange, a conductive channel clamp contracted upon said flare and adapted to contract said flange to retain the conductive housing on the coil casing, and in conductive relation thereto, the housing adapted to enclose the primary and secondary coil terminals, openings through said housing for accommodation of primary and secondary cables, a primary lead cable extending through one of said openings and connectable to one of the primary terminals, filter means interposed in said primary lead cable, said filter means including a conductive shell conductively mounted to said housing, a conductively sheathed primary outlet cable extending through a second of said openings and connectable to a second primary ing through a third of said openings and connectable to the secondary terminal, and ground connections from the sheathing of the primary outlet cable and the secondary cable to the housing.

8. Electrical shielding means as defined in claim 7 wherein said filter means is a coaxial capacitor.

9. Electrical shielding means as defined in claim 7 wherein the conductive sheathing of the primary outlet cable and the secondary cable are stripped from the respective cables at their respective terminal ends and grounded to said housing.

10. The combination as defined in claim 1 wherein the filter means includes a portion of said conductive shell conductively mounted in said first opening of said housing.

11. Electrical shielding means as defined in claim 7 wherein the filter means includes a portion of said conductive shell conductively mounted in said first opening of said housing.

References Cited in the file of this patent UNITED STATES PATENTS

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