US2042884A - Tappet - Google Patents

Description

R. R. FACCHINI TAPPET Filed Jan. 31, 1936 1.8 Sum/MA,

June 2, 1936.

Paiented .inne 2, 1936 zmusi 'rerrefr 3 Clams.

My invention relates to tappets broadly, and has to do, more particularly, with the provision of a tappet structure for the silent actuation of gine or cause the uburning or "warping of the valves by reason of their failure to seat properly when the valve stems have been lengthened by heating. One of the most common of these expedients consists in the formation of the tappet head or face of a material which is relatively soft and non-resonant, for example, very hard fiber. Such a structure'sufiers from excessive wear in use and has not proven sufiicientlyv successful to be generally employed.

Another structure which has been suggested for the purpose consists of a tappet of telescoping character, the valve-Operating section of which is urged outwardly to bridge the clearance by a light spring or yieldable body of oil, but initially depresses a slight distance to a positive stop When the push rod is actuated to effect unseating of the associated valve. One such telescoping tappet employs a valve-Operating section consisting of a large ball provided with a fiat, valve-stem abutting face. Th ball socket of this tappet structure is provided with a yieldable spring and a ball seat or stop which engages the ball to unseat the valve after the tappet has been lifted a few thousandths of an inch. Such telescoping tappet structures sufier from rapid wear due to the fact that the entire strain of valve-lifting is borne by the telescoping section and itsstop. Moreover, it is dimcult, if not impossible, to accurately determine valveclearance by a "feeler gauge when such structures are employed. Consequently, even though relative silence be obtained, the effective lift of the valve may be far less than intended and necessary for efi'iciency and smooth operation of the engine.

Still another structure has been suggested, which structure consists in the provision of the tappet with a bore in which is received a fine, pin-like clearance-bridging element backed up by a light spring. In this structure, the strain of valve-lifting is borne by the rigid tappet head itself and, for a while, at least, highly satisfactory results are obtained. However, experience teaches that, as the face of the tappet head wears, a. piening over of the bore may occur, particularly when the hard, superficial surface of the tappet head has worn away under the hammering action of the valve end. The pin element then tends to stick and the spring, which backs it, is no longer able to effect its projection into clearance-bridging relation with the end of the valve stem.. Such a structure also is exceedingly difficult to adjust for clearance because of the difficulty of depressing the pin to permit insertion of the feeler gauge between the tappet head and the end of the valve stem.

With the disadvantages and problems of such prior art structures in mind, my invention has several well-defined objects. It is a primary object of my invention to provide a tappet construction for internal combustion engines and the like which will provide silent operation without the development of excessive wear of either tappet or valve stem.

It is another object of my invention to provide a silent tappet structure for internal combustion engines or the like in which there is no interference with, or difficulty in, the introduction'of a feeler gauge for the purpose of determlning and adjusting for proper tappet clearance,

It is an object of my invention, also, to provide a tappet structure for intemal combustion engines or the like in which a stick-proof clearancebridging member is interposed between the tappet proper and the end of the valve stem, which clearance-bridging member bears substantially none of the strain incident to the lifting of the valve, the strain being borne entirely upon the tappet proper.

It is an object of my invention to provide a silent tappet structure for internal combustion engines or the like in which tappet there is employed a depressible clearance-bridging element, the depression-resistance of which element is readily adjustable to provide a maximum of silence with a minimum of opposition to the closing of the valve and also' to permit re-adjustment to compensate for wear or the utiring of the spring employed for the clearance-bridging element.

It is an object of my invention to provide a silent tappet structure for internal combustion engines or the like in which the clearance-bridging element is free and encouraged to move about during operation, thus distributing such wear, as may take place, over its entire surface.

It is an object of my invention to provide a a part of an L-head engine having a closed valve chamber, will be self-lubricating and will positively direct oil upon the end of the valve stem with which it is associated.

It is an object of my invention to provide a silent tappet structure for internal combustion engines or the like which is unitary, and which does not require re-assembly each time the valves of the engine are removed for trueing or grinding.

It is an object of my invention to provide a silent tappet unit for internal combustion engines or the like which may be easily and quickly installed asa replacement for conventional tappet structures.

' Finally, it is an object of my invention to provide a silent tappet structure for internal combustion engine valves or the like which may be manufactured at extremely lowv cost and marketed in inexpensive sets by accessory houses.

Further objects and objects relating to details and economies of construction and use will more definitely appear from the detailed description to follow. In one instance, I accomplish the objects of my invention by the means set forth in the following specification. My invention is clearly defined in the appended claims. A structure constituting a preferred embodiment of my invention is illustrated in the accompanying drawing, in which:-

' Figure 1 is a transverse sectional view of a lconventional internal combustion engine taken through the camshaft and the valve and tappet operated by one of the cams thereof, said tappet specifically constituting a preferred embodiment of my invention;

Fig. 2 is a Vertical sectional view, on an enlarged scale, of the tappet element forming a part of the structure illustrated in Fig. 1; and

Fig. 3 is a top plan view of the head of the tappet element shown in Fig. 2.

Throughout the drawing, the same reference numerals refer to the same parts.

In a broad Sense, my invention is predicated upon an appreciation that the objectionable noise developed by generous clearance in the valve taplbore and extend therethrough beyond the face of the tappet head for a distance sufiicient to tangentially contact the butt end of a. properlyclearanced valve. A helical spring received within a bore in the tappet stem and subjocted to a compression of from 10 to 30 ounces effects projection of said ball to close the valve-clearance and prevent jump of the tappet base. or push rod from the cam during initiation of the lift, yet does not adversely affect the seating of the valve.

More specifically, and with reference to Fig. 1 of the accompanying drawing in which I have illustrated a preferred embodiment of my invention, there is shown a conventional cam Shaft |0 provided with a cam element ll, upon which cam rides a push rod |2, of conventional form,

suitably joumaled for reciprocation in a guiding web |3 forming a part `of the engine block. The

push rod |2 is provided with a threaded axial 5 bore M within whichis adjustably assembled a complementarily threaded stem 15 of the tappet element |6. The tappet element Hi is provided with a head l'l having a slightly crowned tappet face l'la which head is fixable in adjusted extension with respect to the push rod |2 by means of a locking nut IB threaded upon the stem 15 of the tappet and abutting the end of the push rod. Disposed in alinement with the head |1 of the tappet is a conventional valve |9, the stem |9a of which is snugly received within the guide 2| of the cylinder block. A valve spring 22, through the medium of anchoring means 23, engages the valve stem and urges the valve head |9b to its complementary seat 24. The lower end of the valve stem is, as usual in such structures, slightly spaced from the head |'l of the tappet. Thus far described, the present structure is conventional.

Referring now to Figs. 2 and 3 of the drawing, '15 it will be noted that the crowned head H of the tappet is provided with a central bore 25 of tapered form complementary to a hardened ball element 26 receivable therewithin and extending slightly therebeyond. The ball 26 and the bore 3'1 25 are of such relative size that the said extension of the ball 26 amounts to approximately 1/50 of an inch and, by means of a saddle element 21 and a saddle-supporting, helical spring 28 received within the bore 29 of the tappet stem |5, the ball 26 is yieldably maintained in contacting relation with respect to the seat formed in the head member |'l by the conical bore 25. lThe bore 29 extends completely through the lower end of the tappet stem |5 and is provided-with threads 40 which receive a screw-slotted plug 30, which supports the spring 28 and by which the spring may be readily subjected to the desired degree of compression. w

Preferably, the complementary threads of the plug 30V and the stem IS have a tight fit such that vibration will not disturb the adjustment thereof. In addition, the lower end of the stem |5 is piened inwardly at |5a to insure retention of the plug 30.

I have found that, for all practical purposes where a valve clearance of from 5/1000 to 20/ 1000 of an inch is to be maintained between the end of the valve stem and the abutting face l'la of the tappet, a compression of from 10 to 30 ounces in the spring 22 will afford substantially complete silence in the tappet. This silence, as previously indicated in this specification, is believed to obtaln by reason of the fact that the tappet |2 is caused to closely follow the cam nose during the initial lifting movement Aimparted thereto. Moreover, it should be explained, the resistance of the ball spring 28 to the valve spring 22 is so slight, in comparisonr that no appreciable opposition to the normal closing of the valve 18 is experienced. w

I am aware that my invention is susceptible of embodiment in various forms. For example. other means than the plug 30 may be employed for the adjustable support of the spring 28. Where, for the sake of simplicity and economy of manufacture, it may be desirable to dispense with compression adjustment in the spring 28, the plug 38 or its equivalent may be omitted and the spring 28 supported upon a transverse pin or other instrumentality. Likewise, my tappet structure may be fabricated of materials other than steel. Moreover, while the present invention has especial application to the tappets of internal combustion engines, it is also applicable to other machinery with similar advantage. These and other variants will definitely appear to those skilled' in the art upon familiarity with the conceptsrof my invention. I- therefore claim my invention broadly, as indicated by the appended claims.

What I claim is:

1. A tappet for intemal combustion engines and the like, comprising: an annularl tappet head provided with a substantially flat tappet face, the internal diameter of which head is less `at its tappet face than-below said face, a body ball-bearing being rotatably journaled within portion integral with said head and by which said head is supported and driven, said body portion being. provided with an axial bore of greater diameter than the intemal diameter of said annular tappet head, a hard-surfaced ballbearing rotatably journaled in said tappet head and having a diameter slightly greater than the internal diameter of said head at its tappet face, a helical spring disposed within the bore of' said body portion, and manually adjustable means for supporting one end of said helical spring and subjecting the same to any desired degree of compression, said helical spring, when compressed, having its other end bearing upon said ball-element and urging the same into centrally seated, slightly projecting relation with respect to the tappet face of said head.

3. A tappet for internal combustion engines and the' like, comprising: an annular tappet head provided with a substantially flat tappet face, the internal diameter of which head is less at its tappet face than below saidiface, a tubular body portion integral with said head and provided with an internal thread the diameter of which is greater than the internal diameter of said lannular tappet head, a hard-surfaced ball-bearing rotatably journaled in said tappet head and having a diameter slightly greater than the intemal diameter of said head at its tappet face,'

a helical spring disposed within the threaded bore of said body portion,,and a threaded plug urge the same into centrally seated, slightly pro- 35 jecting relation with respect to the tappet face of said head.

RIGO RALPH FACCHINI.

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