US2193886A - Spark-plug tool - Google Patents

Description

March 19, 1940. c. A. SCHULZ I 2,193,886

I SPARK-PLUG TO OL Filed Feb. 17, 1938 INVENTOR ATTORNEY i atented Mar. 19,1940 I PATENT oFFicE SPARK-PLUG TOOL Christopher A. Schulz, Guttenberg, N. L, as-

signor to The B. G. Corporation, New York,

N. Y., a corporation of New York Application February 17, 1938, Serial No. 190,953

3 Claims.

A highly successful type of spark plug widely used in aviation engines includes a center electrode that has a concave surface at its lower end, and a shell surrounding the center electrode with a complementary inner face, preferably in the form of wide prongs, uniformly spaced from the center electrode surface. The spark jumps between the center electrode and the wide-prongs, the point of discharge. shifting fitfully across the spaced complementary surfaces.

When any points on these discharge surfaces become pitted or worn away, the spark jumps between other points that remain at the correct spacing. An extremely long term of service-is required before the large surfaces between which the sparkcan jump become worn over-sufficient area to interfere with the operation of the plug. Such spark plugs give long and reliable service under severe engine conditions. When it does finally become necessary to adjust the spacing of the electrode surfaces, however, the adjustment must be made with great accuracy and it is important that the part of the shell electrode that has the complementary discharge surface spaced from the center electrode be formed to a truly complementary shape. The reforming of the shell electrode is a part of the adjustment of the spark plug.

It is an object of this invention to provide improved apparatus for forming the electrode surface of the shell and effecting correct spacing of the discharge surfaces in a spark plug of the character indicated. A more specific object of the invention is to provide a single tool with which the different operations of forming and adjusting the electrode surfaces can be efficient-- ly carried out.

plugs that have been in service for a long period. Other objects, features and advantages of the invention will appear or be pointed out as the specification proceeds.

In the accompanying drawing, forming a part hereof:

Fig. 1 is a front elevation of a tool embodying this invention and shown with the plunger against a spark plug shell for forming the elecdo- Fig. 4.

This invention is used both for manufacturing spark plugs and for reconditioning.

The embodiment of the invention shown .in the drawing has a frame Ill with countersunk screw holes I I through its base for anchoring the frame to a work bench if a permanent location for the tool is desired.

A circular bar has gear teeth out in one side to form a rack. This bar will be referred to hereinafter as the rack bar i3. There is a vertical bearing M in the frame it, and the rack bar it slides up and down in that bearing. A horizontal shaft ll turns in bearings in the frame Ill and has gear teeth out in it to form a pinion II that engages the rack II. The shaft i1 is turned by a hand-wheel l9 that is rigidly secured to one end of the shaft.

The hub of the hand-wheel l9 contacts with a boss on the side of theframe l0, and the shaft I1 is just long enough to extend through its bearing in the frame. A washer is held against the end of the shaft It by, a screw 2| that threads into the end of the shaft. The washer 20 contacts with a boss on the sideof the frame to prevent displacement of the shaft H to the right,

-- in Fig. l, and the hub of the hand-wheel i8 prevents displacement of the shaft l1 toward the left. For the use of left-handed operators, how- -ever, the screw 2i and washer 20 can be removed and the shaft I! pulled out of its bearings and inserted from the left side of the frame.

The rack bar l3 has a tapered lower end in which is a socket 23. The bottom of the rack bar is formed into a die, which is indicated generally bythe reference character 25. Thus the bottom end of the rack bar is itself a tool in the illustrated embodiment of the invention, but the die can be a separate piece and attached to the lower end of the rack bar.

0n the base of the frame It there is a carriage guldeway including a supporting surface 27 with guide surfaces 28 extending'along both the front and back edges of the surface 21.

A die 30, which is shaped for the-particular spark plug sleeve that is. to be formed, has a stem 3| that fitsinto a socket 32 in the base of the frame and in line with the rack bar i3. A hardened insert 3! in the surface 21 at the upper end of the socket 32 prevents the surface from being scratched or nicked by the die or the shoulder of the die that rests on the insert 36.

A spark-plug shell 35 fits over the die 30, and

the upper end of the die is substantially the shape desired for the discharge surface of the shell.

The actual dimensions of the die 30 are a little oversize so that the prongs 31 at the end of the shell 36 are'spaced a few thousandthstoo far apart and can be bent into exact positionas determined by a thickness gauge.

The rack bar is lowered until the die 25 is in contact with the shell. The rack bar is .then struck on the top with a hammer once or twice to bend the prongs at the end of the shell to the exact contour of the die. The die 25 at the bottom of the rack bar I3 is shaped so that it has a drawing action over the die 30 rather than a true forming action as understood in the die art. The operation is referred to herein as the forming of the shell, however, using the term in its broader sense.

The die 30 is held in position by a die lock pin 38 clamped against the stem 3| by a set-screw 39 threading through the forward wall of the base.

After the forming of the shell 36 in the manner described above, the shell 36 is screwed onto the rest of the plug 4|, as shown in Fig. 4, and the assembled spark plug is inserted through a bushing 43 and threaded into a face plate 44 of a carriage 45 until the shoulder 41 of the plug comes against the end of the bushing 43.

The carriage 45 rests on the supporting surface 21 and has a width substantially equal to the distance between the guide surfaces 28, best shown in Fig. 2. When the carriage has been moved into position to locate the electrode end of the plug in the proper relation to the path of movement of the rack bar l3,-a set-screw 50, threaded into the front of the frame I 0, is tightened against the carriage 45 to lock it in position.

The carriage 45 includes a body portion 52, a part of which extends upward at a substantial acute angle to the vertical as shown in Fig. 4. The face plate 44 has a sleeve 53 extending from its back face. This sleeve 53 fits into the upstanding part of the carriage body 52, and is held in the carriage body by a set-screw 54, that extends into a circumferential groove 55 in the sleeve 53 9.nd leaves the sleeve and the face plate 44 free to rotate.

The bushing 43 surrounds the tops of the outside threads of the shell 36 and limits the extent to which the spark plug can be screwed into the face plate 44 by providing an abutment against which the shoulder of the spark plug strikes. The bushing 43 has a circumferential groove registering with a groove on the inside surface of the sleeve 53, and a spring 59 confined in these grooves holds the bushing against displacement from the sleeve. The spring 59 yields, however,-to permit the bushing to be forced from the sleeve when a longer bushing is to be inserted for a different model of spark plug.

An electrode adjusting foot 6| has an enlarged upper end that fits snugly into the socket 23 in the bottom of the rack bar 13. The adjusting foot 6| is held fast in the socket by a set-screw 62 (Figs. 1 and 2), and the rack and pinion mechanism is operated to bring the adjusting foot down against the uppermost prong 3'! of the spark-plug shell 35. A thickness gauge 64 is inserted between the center electrode of the spark plug and the uppermost prong 31 of the shell; the hand-wheel is then operated, and the prong is pressed against the thickness gauge with sufllcient force to reduce the clearance between the electrode surfaces to the dimension of the thickness Y gauge.

The face plate 44 is turned to bring each of the four prongs on the end of the shell 36 successively into position under the adjusting foot 6|. Fig. 3 illustrates the manner in which an operator holds the thickness gauge 64 in' one hand and turns the hand-wheel IS with the other hand. The hand-wheel is of such a size in proportion to the size of the pinion and other parts that no injury to the plug will be caused with any reasonable force that is applied to the hand-wheel.

The preferred embodiment of the invention has been illustrated and described, but modifications can be made and some features of the invention may be used without others.

, I claim:

1. A tool for spark plugs that have a center electrode with a curved surface, and a sleeve portion having one or more other electrodes each with a complementary surface that is uniformly spaced from the center electrode surface over a substan' tial area when the spark plug is assembled, said tool comprising a frame with means for engaging and holding said sleeve portion of a spark plug in a fixed position, a rack bar movable in a bearing in a portion of said frame toward and from an electrode of a sleeve portion so held, and a die which is located at the end of the rack bar and which is so curved that it forms the electrode of the sleeve portion on the engaging and holding means to said complementary surface when said die on'the rack bar is pressed against the electrode with a deforming pressure.

2. A spark-plug tool for making the surface of an electrode on a spark-plug shell correspond to the curve of a complementary center electrode of the spark plug, said tool including a frame having a base on which is a supporting surface, an upper frame portion with a bearing, a rack bar slidable in the bearing toward and from the supporting surface on the base, a handle and pinion for causing the rack to move up and down, a socket in said supporting surface, die means comprising a member with a stem at the lower end that fits into the socket, an upper portion shaped to receive a spark-plug shell and a top surface that forms a die with a surface of substantially the desired shape of the surface of the electrode on the spark-plug shell, 9. second die that cooperates with the die means on which the electrode shell is supported, said second die being formed at and integral with the lower end of the rack bar and being of a curved shape to cooperate with the die on the shell-supporting die means to form the shell electrode surface to the desired shape.

3. A tool for spark plugs of the type which have a shell with electrode prongs that converge inward from the end of the shell and toward the axis of the spark plug, said tool including a first die having a portion that engages and holds the spark-plug shell in a definite position and having another portion with a tapering surface of substantially the desired shape of one side of the converging electrode prongs, a second die having a tapering surface complementary to the tapering surface of the first die and constructed and arranged to compress the electrode prongs against the die that receives the spark-plug shell, supporting means associated with the die that receives the spark-plug shell for holding that die and said shell in a definite position in the path of said second die, and means connected in definite relation to the die supporting means for forcing one of the dies against the other to com- 3 press the electrode prongs between said dies.

CHRISTOPHER A. SCHULZ.

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