US3205402A

US3205402A - Spark plug with resilient connector to electrical resistor

Info

Publication number: US3205402A
Application number: US222393A
Authority: US
Inventors: Robert C Zeller
Original assignee: Zeller Corp
Current assignee: Zeller Corp
Priority date: 1962-09-10
Filing date: 1962-09-10
Publication date: 1965-09-07
Anticipated expiration: 1982-09-07

Description

R. c. ZELLER 3,205,402

SPARK PLUG WITH RESILIENT CONNECTOR 'I'O ELECTRICAL RESISTOR Sept. 7, 1965 Filed Sept. 10, 1962 wmw FIG.7.

FIG.6.

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ROBERT C. ZELLER ATTORNEYS United States Patent 3,205,402 SPARK PLUG WITH RESILIENT CONNECTOR TO ELECTRICAL RESISTOR Robert C. Zeller, Defiance, Ohio, assignor to The Zeller Corporation, Defiance, Ohio, a corporation of Ohio Filed Sept. 10, 1962, Ser. No. 222,393 14 Claims. (Cl. 315-59) The invention relates to spark plugs. More particularly the invention relates to an improved construction of shielded resistor-type electrode insulator assembly.

In the present state of the art of shielded spark plugs, it is usual to provide a metal plug which can be pressed into engagement with internal threads in the insulator. This plug forms an abutment for one end of a spring which exerts pressure on the resistor to maintain it in contact with the electrode.

My invention provides an improved closure construction to be used in place of the conventional plug. The advantages of my construction over the prior art will be more clearly apparent from the detailed descriptionand the accompanying drawings wherein:

FIGURE 1 is a longitudinal section through a spark plug.

FIGURE 2 is a longitudinal section through the insulator showing a modified form of closure.

FIGURES 3 to 8 inclusive are views similar to FIG- URE 2 showing other modifications of the invention.

FIGURE 9 is a side elevation of the spring closure prior to assembly.

FIGURE 10 is a top plan view thereof.

My invention in its broadest aspects contemplates a closure construction consisting essentially of a single part so constructed and arranged as to exert resilient pressure against the electrical resistor and also to engage the insulator in such a manner that it cannot be removed accidently or by any normal means. The single part constituting the closure is in the form of a coil spring constructed from spring wire and having a novel configuration to provide for the several functions which it is designed to accomplish.

As illustrated in the drawings, 10 is a standard spark plug ceramic insulator having the enlarged outer portion 10a for engagement with the metallic shell 11 of the spark plug. Above the enlargement the ceramic insulator is generally cylindrical as shown at 13 and below the enlargement is the tapering nose portion 14. The insulator has a central bore 15 extending through its entire length. The bore is enlarged at 16 in the upper portion forming a shoulder 17. Below this shoulder the bore is provided with internal threads 18 which are preferably of the wood screw type. Within the nose portion of the insulator is the center electrode 19, the outer end of which projects slightly beyond the nose of the insulator to form a spark gap with the ground electrode 20. The center electrode is secured to the ceramic in the conventional manner. Between the inner end of the center electrode 19 and the threaded portion of the insulator is a standard cartridge type electrical resistor 21. The resistor may be inserted into the bore after the electrode is secured in position.

The present invention relates to an improved form of closure for retaining the electrical resistor 21 under pressure in contact with electrode 19. As shown in FIGURE 1, the closure 22 is constructed from a single piece of spring wire 23. The intermediate convolutions 24 have a normal diameter which is slightly larger than the bore 18 and there are several convolutions of this size. At one end there are a series of convolutions or loops 25 of smaller diameter than the bore 15 terminating at the inner end 26. At the opposite end the wire is formed into a spiral 27 lying in a plane transverse to the longitudinal axis of the insulator. The spiral 27 has outer- 3,205,402 Patented Sept. 7, 1965 most convolutions 28 of larger diameter than the bore 15, which form in effect an enlarged integral head adapted to seat on the ceramic shoulder 17. In assembly, the closure 24 is inserted through the enlarged bore 15 with the small end toward the resistor 21. Axial pressure is applied to the

spiral convolutions

27, 28 thereby causing the intermediate convolutions 24 to contract in diameter sufiicient to move through the bore 15 until the inner end 26 is in pressure contact with the resistor. The axial pressure is continued until the spring head is seated on the ceramic shoulder whereupon the spring tension in the contracted convolutions causes them to expand and to engage the internal threads of the ceramic thereby securely interlocking the closure to the ceramic insulator.

In the modified construction of FIGURE 2, the closure is the same as in FIGURE 1 except that the head is formed by convolutions arranged in dome-shape 29.

In FIGURE 3 the head of the closure is formed by the outer convolutions 30, as in FIGURE 1, but the spiral convolutions in the transverse plane terminate without extending inwardly beyond the diameter of the convolutions 24. Instead of these inwardly continuing convolutions a seperate metallic cap 31 is provided having the inturned lip 32 for engaging beneath the outer loop 30.

In FIGURE 4 a modified cap 33 has an outer flange 34 for engaging the ceramic shoulder thereby completely eliminating the spiral spring head of FIGURE 1. The cap 33 has a shank 35 with a peripheral groove 36 for engaging the end convolution of the intermediate group 24. In FIGURE 5 a disc 37 is provided of such diameter relative to the upper spring loop that, in assembly by axial pressure, the disc 37 will temporarily push the top loop 38 over the second loop 39. When the disc reaches the second loop 39, the top loop 38 will snap back over the disc and the parts will assume the positions illustrated in FIGURE 5.

FIGURES 6 and 7 are modifications of the device shown in FIGURE 1. The small diameter loops 25 are eliminated so that the resistor 21 can extend within the intermediate convolutions 24 as illustrated. Pressure on 1 the resistor is provided by means of a depending coil spring 40. This can be formed by continuing the inner end of the spring wire forming the spiral 27 and shaping this inner end into the small diameter coil 40.

In FIGURE 8 the bore of the ceramic insulator is not internally threaded but instead is provided with a single annular groove 41. The coil spring clearance is of the same type as illustrated in FIGURE 1 and after inserting this closure into the bore by axial pressure, the spring expands into the annular groove and locks itself in position while continuing to exert axial pressure on the electrical resistor 21.

FIGURES 9 and 10 illustrate the spring closure prior to insertion in the insulator. The spring shown in FIG- URE 8 is substantially the same as the one shown assembled in FIGURE 1 except that the spring of FIGURE 9 has one additional loop 40. This loop is of the same diameter as the outermost loop 28 but is arranged immediately below the plane of the spiral 27.

What I claim as my invention is:

1. A spark plug comprising a ceramic insulator having a central bore with an internally threaded portion, an electrode within the bore of said ceramic insulator and extending outwardly from one end thereof, an electrical resistor between said electrode and said internally threaded portion, and a coil spring bearing on said resistor and having convolutions directly engaging said internally threaded portion.

2. A spark plug comprising a ceramic insulator having a central bore, an enlarged counterbore forming a shoulder therebetween, said central bore being internally threaded adjacent said shoulder, an electrode within said central bore extending outwardly from one end thereof, an electrical resistor between said electrode and said internally threaded portion, and a coil spring bearing on said resistor and having convolutions directly engaging said internally threaded portion.

3. A spark plug comprising a ceramic insulator having a central bore, an enlarged counterbore forming a shoulder therebetween, said central bore being internally threaded adjacent said shoulder, an electrode within said central bore extending outwardly from one end thereof, an electrical resistor between said electrode and said internally threaded portion, a coil spring having intermediate convolutions directly engaging said internally threaded portion and having a portion at one end thereof which is of enlarged diameter and extends within said counterbore to seat upon said shoulder.

4. A spark plug as in claim 3 in which said portion of enlarged diameter has spiral convolutions in a plane transverse to said counterbore.

5. A spark plug in accordance with claim 3 in which said enlarged portion of the spring has convolutions arranged to form a dome shaped head.

6. A spark plug comprising a ceramic insulator having a central bore, an enlarged counterbore forming a shoulder therebetween, said central bore being internally threaded adjacent said shoulder, an electrode within said central bore extending outwardly from one end thereof, an electrical resistor between said electrode and said internally threaded portion, a coil spring having intermediate convolutions directly engaging said internally threaded portion and having a portion at one end thereof which is of enlarged diameter and extends within said counterbore and having a metal cap within said counterbore With an inturned lip engaging beneath a spring convolution within said counterbore and seating upon said shoulder.

7. A spark plug in accordance with claim 3 in which said coil spring has an additional coil of smaller diameter in contact with said electrical resistor.

8. A spark plug in accordance with claim 3 in which said coil spring has convolutions of smaller diameter between said intermediate convolutions and said electrical resistor.

9. A spark plug in accordance with claim 3 in which said coil spring has convolutions of smaller diameter between said portion of enlarged diameter and said electrical resistor.

10. A shielded spark plug comprising a ceramic insulator having a central bore with an internal groove therein, an electrode within the bore of said ceramic insulator extending outwardly from one end thereof, an electrical resistor within said bore between said electrode and said internal groove, and a coil spring bearing on said resistor and having convolutions directly engaging said internal groove.

11. A shielded spark plug in accordance with claim 10 in which said internal groove is an annular groove in a plane transverse to said electrode.

12. A spark plug comprising a ceramic insulator having a central bore, an enlarged counterbore forming a shoulder therebetween, said central bore having an internal groove therein adjacent said shoulder, an electrode within said central bore extending outwardly from one end thereof, an electrical resistor between said electrode and said shoulder, a coil spring bearing on said resistor and having convolutions directly engaging said internal groove, said coil spring having a portion at one end thereof which is of an enlarged diameter and extends within said counterbore.

13. A spark plug according to claim 12 in which said portion of enlarged diameter has spiral convolutions adapted to seat on said shoulder.

14. A spark plug according to claim 12 having a metal cap within said counterbore with an inturned lip engaging beneath a convolution of said spring within said counterbore and seating upon said shoulder.

References Cited by the Examiner UNITED STATES PATENTS 1,933,304 10/33 Bell 339-252 2,118,673 5/38 Green 313134 X 2,237,362 4/41 Rieman 339- 2,336,569 12/43 Rabezzana 313134 X 2,837,679 6/58 Schwartzwalder et al. 313-118 X 2,858,361 10/58 v Candelise 313l36 X 2,954,495 9/60 Zeller 313136 GEORGE N. WESTBY, Primary Examiner.