US2348919A - Method of making shielded spark plug connectors - Google Patents

Description

May 16,1944. T. w. MILTON METHOD OF MAKING SHIELDED SPARK PLUG CONNECTORS Filed April 6, 1942 I h/ H 5f. Z

INVENTOR 20/1145 )/2 BY f M,

ATTORNEY V Patented May 16, 1944 METHOD OF MAKING SHIELDED SPARK PLUG CONNECTORS Thomas W. Milton, Detroit, Mich., assignor to The Flex-O-Tube Company, a corporation of Delaware Application April 6, 1942, Serial No. 437,746

4 Claims.

ing such intimate contact irrespective of elongation or contraction of the spark plug and connector elements incident to a wide variation of temperature conditions encountered in practice.

A further object is to provide a spark plug connector including such a yieldable element and means for preventing the portion which makes contact with the ignition lead conductor from puncturing the latter and its insulation to such an extent that it will then puncture the connector body and cause electrical leakage or shortcircuiting.

Another object is to provide a spark plug connector with a radio shielding envelope which has no mechanical functions, in other words, the insulating body of the connector mechanically carries the load of connection to the spark plug and to the ignition lead shielding.

A further object is to provide a spark plug connector by amethod which involves first moulding the insulating body, then plating the radio shielding thereon, then securing shield connections or connection elements to the body, and then completing the electrical path between such connection elements and the shielding for such connector body.

For the purpose of illustrating the genus of the invention, a typical embodiment is depicted in the accompanying drawing, in which:

Fig. 1 is a central vertical section taken through a spark plug, a connector therefor, and a portion of an ignition conductor which leads into such connector.

Figs. 2 and 3 are transverse sections taken through the connector substantially on the line 2-2 and 3-3 of Fig. 1.

Referring to the drawing, the spark plug comprises a body shell 10, threaded externally as indicated at H for engagement with an appropriate opening in a cylinder wall. The outer end of the shell Ill is provided with an electrode piece I! and the inner end of the shell is internally threaded as indicated at l3 to receive the lower end of a retaining sleeve l4.

Disposed within the lower half of the retaining sleeve l4 and within the shell I0 is a center electrode l5 having a tip 16 formed with a shoulder l1. Disposed about the electrode 15 is a mica or like tube l8 provided with a shoulder 20 adapted to cooperate with the lower, end of retaining sleeve 14. The retaining sleeve M is internally recessed or cored out throughout the major portion of its length beginning from its upper or inner end as indicated at 2| to receive a ceramic insulating sleeve 22 which is cemented to the mica tube l8 by alayer of heat resistant cement 23. The upper end of the electrode I5 is provided with a partially spherical depression 24 and the metal at the extremity of electrode l5 adjacent such depression is swaged over a washer 26 disposed at the upper end of the mica tube I8 to fix the parts of the plug in assembled relationship. The upper end of the retaining sleeve I4 is externally threaded, as indicated at 21, to receive a spark plug nut 28.

The spark plug connector comprises a moulded plastic elbow 30 formed under conditions most favorable to moulding operations so that the elbow will have of itself the requisite mechanical strength. The elbow body 3|! is provided with bores 31 and 32 intersecting at a suitable desired angle as illustrated in Fig. l, the bore 3| being adapted to receive an ignition lead 33 and the bore 32 to receive up to a shoulder 34 a ceramic insulator and spring guide 35.

A contact spring 36, preferably of a copper beryllium alloy, as pointed in 31 and 38, the end 31 being adapted to pierce the insulation of ignition lead 33 and point 38 being adapted to make positive contact with the upper end of electrode l5 within the partially spherical depression 24. The contact spring element 36 is further provided with a number of active coils 40 disposed between the lower end of the ceramic insulator 35 and the upper end of the center electrode I5 so that with the elbow 30 in assembled relation with respect to the spark plug, these coils remain in compressed condition and force a straight portion 4| disposed within the ceramic insulator 35 upwardly so that the point 31 of this straight portion just pierces the conducting wires of ignition lead 33 without projecting through the insulating layer of lead 33 which lies above the conducting wire thereof. It is noted that the insulating element 35 abuts shoulder I4 or the elbow body 30 so that point I! cannot be driven upwardly so asto puncture the insulation of lead wire 33 which lies above the conducting wires and cannot puncture the plastic material of elbow 30 above the ignition to a thickness of from one to one and one-half thousandths in thickness... Threads 4! are provided at the ends of the ignition wire and spark plug branches of elbow 30 and fittings 44 and 45 are threaded thereon. The fittings and 48 are anchored to the plated radio shielding 42 by first cleaning the portion of the radio shielding which is to be covered by portions of the fittings 44 and 46, then wrapping the ends of the shielding with a flux solder foil, then threading the fittings onto the elbow until the solder foil is compressed between the fittings and the radio shielding, then crimping the fittings centrally at the foil, and then completing the soldering by locallzed heat.

It is noted that the lower end of the fitting 4| is internally threaded as" indicated at 4G to receive a flanged bushing 41 with an inturned flange 48 of spark plug nut II arranged on the bushing between its flange and the lower end of fitting 45. The threaded connection between the fitting 45 and the fianged bushing 41 is preferably soldered or brazed to prevent disconnection of these parts. The fittings 44, 45, electroplated shield 42, bushing 41, spark plug nut 28, retaining sleeve l4 and spark plug body l provide a complete radio shielding over the spark plug connector and spark plug, such shielding being grounded to the spark plug body ill.

As many changes may be made in the above described construction and many apparently widely difl'erent embodiments of this invention could be had without departing from the spirit and scope thereof, itis 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.

I claim:

1. The method of making a radio shielded spark plug connector body which consists in molding a plastic body having ignition wire and spark plug branches, then electroplating said body, forming threads in the plastic body free end portions of said ignition wire and spark plug branches, threading fittings on said threaded branch ends of said plastic body with solder interposed between the fittings and the plating on said body, inwardly compressing the fittings at points over the solder, and completing the soldering by local applications of heat.

2. In the manufacture of a radio. shielded spark plug connector body, the steps of molding a body of non-metallic plastic material of the desired size, shape and contour, applying an enveloping metallic coating to the exterior surfaces of said body by an electro-plating process, forming threads in said material at an end of said body, threading a metallic threaded connector member on said threaded end of said body, then metallically bonding said metallic connector member to said coating, and mechanically interlocking said connector to said body.

3. In the manufacture of a radio shielded spark plug connector body, the steps of molding a nonmetallic plastic material to the desired size, shape and contour of the desired body, subjecting said body to an electro-plating process whereby to apply an enveloping metallic coating to the exterior surfaces thereof, forming threads in said material on an end of said body, threading a connectors to said body to prevent relative rotation between them, and

metallically bonding said threaded connectors to said coating.

THOMAS W. MILTON.

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