US3777535A

US3777535A - Spark plug pin gapping tool

Info

Publication number: US3777535A
Application number: US00238132A
Authority: US
Inventors: W Paxton
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1972-03-27
Filing date: 1972-03-27
Publication date: 1973-12-11
Anticipated expiration: 1990-12-11

Abstract

A spark plug gapping tool is disclosed for adjusting the spark gap width of a pin type plug. A plate is threaded to position the spark plug shell with the end of the shell extending beyond the surface of the plate. A pusher pin member is provided to move against the firing end of the ground electrode pin to widen the spark gap, or the working end of an adjusting screw can be used to narrow the gap.

Description

United States Patent 1 Paxton Dec. 11, 1973 SPARK PLUG PIN GAPPING TOOL 1,990,430 2/1935 Fitzgerald 33/168 R 2,193,886 3/1940 Schutz [75] [mamm- Pam, 2,432,703 9/1949 Call 12/125 [73] Assignee: General Motors Corporation,

Detroit, Mich. Primary Examiner-Richard J. Herbst Assistant Examiner-Gene P. Crosby [22] Flled 1972 Attorney-Sidney Carter et al. [2]] Appl. No.: 238,132

, [57] ABSTRACT [52] US. Cl. 72/293, 29/203 R, 72/454, A spark plug gapping tool is disclosed for adjusting the 72/457 spark gap width of a pin type plug. A plate is threaded [51] Int. Cl B2111 26/02 t p siti n th spar plug sh ll with th end of th [58] Field of Search 72/293, 454, 457, shell extending beyond the surface of the plate. A 72/125; 29/203 R, 25.12 pusher pin member is provided to move against the firing end of the ground electrode pin to widen the [56] References Cited spark gap, or the working end of an adjusting screw UNITED STATES PATENTS can be used to narrow the gap. 1,985,410 12/1934 Isaacs 72/293 I 4 Claims, 3 Drawing Figures SPARK PLUG PIN GAPPING TOOL It haslong been recognized that the spark plug firing gap requires periodic adjustment in orderto maintain maximum efficiency of an ignition system in an internal combustion engine. This results from the fact that the firing end of the plug operates under severe conditions of thermal stress-and in an environment conducive to the erosion and corrosion of the electrode elements.

Typical of the gapping tools available in the prior art are devices disclosed by the patents to C. A. Schulz, U.S. Pat. No. 2,193,886datedMar. 19, 1940 and entitled Spark Plug Tool, M. D. Fitzgerald, U.S. Pat. No. 1,990,430 dated Feb. 5, 1935 and entitled Gauging Tool for Spark Plugs, and the patent to E. A. Call, U.S. Pat. No. 2,482,703 dated Sept. 20, 1949 and entitled Aviation Spark Plug Adjusting Tool. Each of these patents discloses mechanisms for adjusting the gapsof the standard type plug having the gap forming portions of the electrodes extending beyond the end of the spark plug shell.

The pin type or retracted gap spark plug is not suited for use with such tools since the electrode elements are recessed within the spark plug shell. A gapping tool currently available for use with such retracted gap plugs comprises a plate-like member having a heartshaped opening therein forming a V-shaped saddle on which the firing end of the plugis positioned with the ground electrode pin hole facing an adjusting screw threaded into the plate. Turning the adjusting screw into the opening and into contact with the ground electrode pin forces the pin closer to the center electrode. In order to widen the retracted gap a pin is provided on the outer surface of the block adapted to fit within the gap between the ground and center electrodes. A second adjusting screw is provided with a V-block positioned on the end thereof adapted to seat the threaded end of the plug in order to push the plug with respect to the pin on the outer surface of the block and thus move the ground electrode pin away from the center electrode. It is readily apparent that the force applied by the pair of adjusting screws can deform the threads on the spark plug shell with resultant damage to the threaded openings in the engine block.

It is therefore an object of my invention to provide a gapping tool for use with retracted gap type plugs whereby the gapping forces applied by the tool cannot damage the threaded portion of the spark plug shell. It is another object of my invention to provide a spark plug gapping tool for use with spark plugs of different shell diameters.

These and other objects of my invention are accomplished by providing a plate having threaded means for threadedly positioning the spark plug shell with its end extending beyond the surface of said plate, a shaft positioned in said plate, the longitudinal axis of said shaft being parallel to the axis of said threaded means, an adjusting screw threadedly positioned in said shaft, the axis of said adjusting screw being perpendicular to the axis of said threaded means, link means rotatably positioned on said shaft adjacent said adjusting screw the plane of rotation being perpendicular to the axis of said threaded means, a pusher pin positioned on one end of said link means and extending toward said threaded means and being adapted to be positioned in the spark plug gap, said link means being adapted to be contacted by the working end of said adjusting screw to move the pusher pin against the firing end of the ground electrode pin to widen the spark gap, said working end being adapted to contact the outer end of the ground electrode pin topush the electrode closer to the ground electrode to narrow the gap.

The device of my invention is readily understood from the following description taken in conjunction with the drawing in which:

FIG. 1 is a plan view of a preferred embodiment of the gapping tool showing the firing end of a spark plug threaded into the tool forgap narrowing;

FIG. 2 isa side view taken on line 2-2 of FIG. I with the spark plug removed and with the shell receiving bores not shown for the sake of clarity; and

FIG. 3 is an isometric view of the gapping tool showing the spark plug firing end positioned for gap widening.

The gapping tool of I my invention, as shownin the drawing, comprises a plate 1 provided with threaded means 2 for receiving and retaining in fixed position the threaded end 20 of the spark plug shell. lnthe preferred embodiment, as shown in the drawing, the retaining means consists of a threaded bore sized to receive the threaded firing end of the spark plug. Also as shown, two or more threaded bores may be used in order to accommodate the various sizes of spark plugs.

A shaft 3 is positioned within the plate 1 with its longitudinal axis parallel to the axis of the threaded bores 2. Snap rings 4 are provided on each end of the shaft 3 in order to retain the shaft within the plate 1. The shaft 3 is rotatable and slidable with respect to the plate in order to enable easy positioning of the gap adjusting mechanism of the tool regardless of where the spark plug firing end 20 is positioned in the plate. A threaded adjusting screw 5 is positioned in the shaft for threaded adjustment with respect thereto, the axis of the adjusting screw being perpendicular to the axis of the threaded bores 2. As is clearly shown in FIG. 1, the working end 6 of the adjusting screw is formed so as to fit within the bore 21 formed in the threaded wall 20 of the spark plug shell and to abut the outer end 22 of the ground electrode pin press fitted within the bore.

As is clearly shown in FIGS. 1 and 3, the tool of my invention is provided with link means 7 for enabling gap widening adjustment of the pin ground electrode. More particularly, a link 8 is rotatably mounted at one end on shaft 3, a pusher arm 9 being rotatably mounted at one of its ends on the other end of the link. As shown in the drawing, link 8 and arm 9 are joined by means of the rivet or pin 10. The link 8 and the pusher arm 9 are free to rotate about their mounting points in planes parallel to each other. A pusher pin II is positioned on the free end of the pusher arm 9 and extends axially toward the plate and its threaded bores 2, the pusher pin being adapted to be positioned in the spark plug gap.

As is readily seen in FIGS. 2 and 3, the pusher pin 11 is axially adjustable in the pusher arm 9 in order that the extending length of the pusher pin may be adjusted so as to fit between the two electrodes in the gap. As shown, pin 11 is threaded in arm 9, it being obvious that other means, i.e., set screw positioning, may be used. As is also clear in FIGS. 2v and 3, the end of the pusher pin 11 which fits in the spark gap has a centerbore to enable the end to fit over the center electrode with one portion of the annular side wall in the gap between the electrodes. The portion of the annular side wall opposite that portion positioned in the gap is removed to form an aperture 12 to permit the pusher pin 11 to be moved over the end of the center electrode 23 and apply the necessary force against the firing end 24 of the ground electrode to thus widen the gap.

In operation, as shown in FIG. 1, the firing end of the spark plug is threaded into the appropriate threaded bore 2 to locate the ground electrode shell bore 21 in axial alignment with the adjusting screw 5. Since the shaft 3 is both free to rotate and slide with respect to the threaded bore, this alignment is readily accomplished. The spark plug gap is narrowed by moving the working end 6 of the adjusting screw into abutment with the outer end 22 of the ground electrode pin and forcing the pin closer to the center electrode 23. Widening of the gap is simply accomplished by aligning the pusher pin over the end of the spark plug shell so that movement of the link means 7 toward the plate 1 positions the pusher pin 11 in the spark plug gap. As is readily apparent, the freedom of the link 8 and the pusher arm 9 to rotate with respect to each other and with respect to the plate 1, as well as the axial freedom of movement of the shaft 3 permit the ready alignment of the pusher pin 11 with the spark gap. On threading the adjusting screw into the shaft 3, the working end 6 is placed in abutment with the pusher arm 9 and further forward movement pushes the ground electrode pin away from the center electrode. As can be seen in FIG. 3, a notch 14 may be provided on the side of the pusher arm to prevent slippage of the working end 6 on the surface of the arm.

Modifications of my invention will be readily apparent to those skilled in the art and it is intended that such modifications be within the scope of my invention. For example, it would be obvious that in lieu of using a plurality of threaded bores, a plurality of threaded bushings of different bore diameter may be removably positioned in the plate to enable use of the tool with different size plugs. Accordingly, the scope of my invention is as defined in the claims which follow.

What is claimed is:

l. A spark plug gapping tool for adjusting the spark gap width of a retracted gap type plug characterized by a ground electrode pin press-fitted in the threaded portion of the spark plug shell adjacent the end thereof and extending into spaced relationship with the center electrode to define a spark gap, said tool comprising a plate having threaded means for threadedly positioning the spark plug shell with its end extending beyond the surface of said plate, a shaft positioned in said plate, the longitudinal axis of said shaft being parallel to the axis of said threaded means,'an adjusting screw threadedly positioned in said shaft, the axis of said adjusting screw being perpendicular to the axis of said threaded means, link means rotatably positioned on said shaft adjacent said adjusting screw, the plane of rotation being perpendicular to the axis of said threaded means, a pusher pin positioned on the free end of a pusher arm attached to said link means and extending toward said threaded means and being adapted to be positioned in the spark plug gap, said pusher arm being adapted to be contacted by the working end of said adjusting screw to enable force to be applied upon advancement of said screw to move the pusher pin against the firing end of the ground electrode pin to widen the spark gap, said working end being adapted to contact the outer end of the ground electrode pin to push the electrode closer to the center electrode to narrow the gap.

2. A gapping tool in accordance with claim I wherein said link means comprises a link mounted at one end on said shaft, said pusher arm rotatably secured at one end to the other end of said link with the planes of rotation of said link and said pusher arm being parallel, said pusher pin being positioned in said pusher arm.

3. A gapping tool in accordance with claim 2 wherein said shaft is rotatable and slidable with respect to said plate, said threaded means being at least two spacedapart threaded bores adapted to receive spark plug shells of different diameters.

4. A gapping tool in accordance with claim 3 wherein said pusher pin is axially adjustable in said pusher arm to enable positioning in the spark gap regardless of the retracted positioning of the spark gap within the shell, and wherein a notch is provided in the side of said pusher arm adjacent said pusher pin to retain the working end of said adjusting screw on said pusher arm during gap adjustment.

Claims

1. A spark plug gapping tool for adjusting the spark gap width of a retracted gap type plug characterized by a ground electrode pin press-fitted in the threaded portion of the spark plug shell adjacent the end thereof and extending into spaced relationship with the center electrode to define a spark gap, said tool comprising a plate having threaded means for threadedly positioning the spark plug shell with its end extending beyond the surface of said plate, a shaft positioned in said plate, the longitudinal axis of said shaft being parallel to the axis of said threaded means, an adjusting screw threadedly positioned in said shaft, the axis of said adjusting screw being perpendicular to the axis of said threaded means, link means rotatably positioned on said shaft adjacent said adjusting screw, the plane of rotation being perpendicular to the axis of said threaded means, a pusher pin positioned on the free end of a pusher arm attached to said link means and extending toward said threaded means and being adapted to be positioned in the spark plug gap, said pusher arm being adapted to be contacted by the working end of said adjusting screw to enable force to be applied upon advancement of said screw to move the pusher pin against the firing end of the ground electrode pin to widen the spark gap, said working end being adapted to contact the outer end of the ground electrode pin to push the electrode closer to the center electrode to narrow the gap.

2. A gapping tool in accordance with claim 1 wherein said link means comprises a link mounted at one end on said shaft, said pusher arm rotatably secured at one end to the other end of said link with the planes of rotation of said link and said pusher arm being parallel, said pusher pin being positioned in said pusher arm.

3. A gapping tool in accordance with claim 2 wherein said shaft is rotAtable and slidable with respect to said plate, said threaded means being at least two spaced-apart threaded bores adapted to receive spark plug shells of different diameters.