US1521221A - Tappet - Google Patents

Description

Dec. 1,521,223

7 M. M. WILCOX Filed Nov. 19, 1923 ,MfB/B/A L M. W/LC 0x mm Patented Dec. 3d, 1924.

uranium in. wrncox, or sacrnaw, rcnreau.

TAPIEET.

Application filed November 19, 1923. Serial No. 675,741.

To all whom it may concern.

screens heretofore employed.

up slack or lost motion.

other Be it known that I, MERRILL M. WlLoox, a citizen of the United States, residing at Saginaw, in the county of Saginaw and State or Michigan, have invented certain new and useful Improvements in Tappets;

and I do hereby declare the following to be a" full, clear, and exact description. of the invention, such as will enable others skilled in the art to which it appertains to make and use the same. a -This invention relates to valve tappets for. internal combustion engines: My improvement pertains more particularly to a new and improved construction of that part of atappet commonly termed the adjusting screw. As is well known in the art this screw, or its equivalent, impinges against the end of thevalve stem or the push rod, as the case may be, when the engine is running.

Theobjects of the present invention are to provide a tappet adjusting screw with means whereby I correct certain serious defects, such as abrasion, and consequent improper valve action, that have developed during prolonged use of tappet adjusting By the term adjusting screw as used in this description I mean to include any device for flashing the valves, that is to say, devices for making any adjustment in, the valve mechanism to eliminate play or take The adjusting screw although herein shown and described as being inserted in the end of the tappet itself may, if desired, be mounted in the end of a pushrod or in a rocker arm, or in any part of the valve actuating mechanism. i To that end I have improved the construction of the impact-receiving head of the screw by inserting inthat part of the screw head which impinges against the end of the valve stem or push rod, a piece of metal possessing physical qualities that particularly adapt it to withstand long "continued striking upon the end of a valve stem Without abrading the face of the tappet screw.

Myimprovement further includes an adjusting screw construction whereby the inserted piece of metal may be easily removed from the head of the screw and replaced when desired.

With the foregoing and certain other objects in view which will appear later in the specification my invention comprises the devices described and claimed and the equivalents thereof.

In the drawings, Fig. 1 is a side view of a tappet with my improved adjusting screw in place.

Fig. 2 is a longitudinal section through the adjusting screw and its inserted impactresisting plug.

Fig. 3 is a plan view of the parts shown in Fig. 2.

Fig. 4 is a side view of a preferred form of the impact resisting plug.

Fig. 5 is a side view of a modified 101111 of my invention.

The tappet proper may be of any usual or convenient construction, as for example, a hardened head 1 secured to a tubular body 2, such as shown and described in my Patent No. 1,470,410, issued October 9, 1923.

The upper end of such a tappet is usually internally threaded to receive a screw, the head of which strikes the end of the valve stem or push rod when in action. Such an adjusting screw is usually threaded as at The screw usually has a polygonal head 5. Heretofore head 5 has commonly been made of very hard material such casehardened steel, and the cam-contacting faces of the tappet heads 1 have usually been made of similar material. For certain reasons which are set forth in my co-pcinling application Serial No. 462, l2i, hardened steel tappets have not been entirely satis factory either as to operation of the cum contacting head 1 ordurability of the screw head 5.

As claimed in the above-mentioned application I have overcome certain defects of former tappet heads by substituting chilled cast iron for the hardened steel heretofore used in the cam-contacting heads of tappets.

In practice it has long been observed that a screw head 5 made of hardened steel will in time Have its top or working face abraded by its repeated impacts against the end'ot the valve stem, necessitating repairer renewal of the adjusting screw after con tinued use. Such renewals are relatively expensive because it usually is necessary to discard the old adjusting screw and substitute a new one. Sometimes also it is difficult to secure the same fit ofthe screw threads when a new screw is inserted.

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Ill)

In my present improvement I avail myself, as I have done in the cast iron tappet head construction described in the application above referred to, of the fact that white iron or chilled cast iron will satisfactorily withstand the hammering. I have found that a plug made of this material may be removably mounted in a recess formed in the Working face of the tapped adjusting screw, and that the iron plug may be made removable and arranged so as to be easily'replaced, without the necessity of renewing the entire adjusting screw if the working face becomes worn. V

In carrying out my invention I form a recess 6 in the head 5 of the adjusting screw and in this recess I secure by a press fit or otherwise, a plug 7, preferably of chilled or otherwise hardened cast iron commonly known as white iron. The face of the plug may project slightly above the face of the screw head as shown. To minimize the weight of the adjusting screw I prefer to counterbore its threaded end, as at 8, and

' to connect this counterbore with the recess 1 6 by a smaller opening 9, through which a rod may be inserted by which to drive the plug 7 out of the recess 6 when it is desired to 'renew or replace it. v

In practice it has been found that a hardened cast iron plug 7 has the necessaryphysical properties to withstand long contin'ued impinging against the stem of an engine valvewithout any appreciable surface wear or distortion of the plug. .The

plug moreover can be easily removed and quickly replaced by a new one without dam. aging the adjusting screw.

. In the means above descr1bed I have found a commercially satisfactory solution of a difliculty that has long been recognized by designers and builders of internal combustion engines employing. puppet valves and tappets. The difficulty was caused by the inaccuracy of valve operation that occurred when the tappets became shortened by abrasion of the working faces of the adjusting screws. The resulting tappet renewals and frequent attention required have been a common source of trouble which has been removedby my present improvement.

While I have shown and described my improvement as applied to the mushroom ty e of tubular tappet, it may equally well be applied to any of the commonly used types of tappets, as for example, a roller tappet, or any other style of tappet that employs an adjustingscrew or its equivalent where it is feasible'to employ a 'removably secured plug of hardened cast iron as the impactreceiving memberr Having thus described my'invention, what I claim and desireto secured by Letters Patent is: 4

,1. An adjusting screw fora valve tappet, said screw formed with a recess in its head and a plug'of hardened material removably secured in said recess and means associated with said screw for the bodily removal of saidplug.

2. An adjusting screw for a valve tappet, said screw formed with a recess in one end and a plug of hardened material received in said recess and frictionally held therein and means associated with said screw for the bodily removal of said plug.

3. An adjusting screw for a valve tappet,

said screw formed with a recess in one end

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