US2444317A - Mechanical self-adjusting mechanism - Google Patents

Description

June 29, 1948. H. E. VOORHIES MECHANICAL SELF-ADJUSTING MECHANISM Filed July 23, 1945 I N V EN TOR. HA R Y E Mace/was nrroewsXs Patented June 29, 1948 'MEGHA-NIGAL SEIJF HDIFUSTIN'G MECHANISM vHar-ry Voorhies, Grosse ,Eointe .Woods,.Mich.,

.assignor to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio "Application :Julytze, 1945,iseriarm coaess 9 Claims.

This invention relates to Nalve operating gmeehanism for internal combustionengines and ;m0r,e;particulariy to mechanical selfeadjusting ltapnets for opera-ting the valves of such engines.

Broadly {the invention comprehends self-adjusting mechanical tappets for use in the valve gear train of an internal combustion engine having cam -,m-ating-, parts incorporated therein relat-lvelyarotatable one to another adapted v to com- :J-BQHSate iorwchanges in the operating length of :thewal-Vie gear train/and maintain the gear train atprop zon at g ngth.

Aniobject of the invention .is the provision of a mechanical self-adjusting mechanism adapted stosautomaticallylcompensate ionoperatingleng'th toi members associated. therewith.

Another object of-the invention, is the provision flof a sent-adjustingmechanical,tappet of simple sconstruetion, and (efficientl operating charactersistics.

:Anotherwbdect of ,t-he invention is the prowieion of tan automatic adjustable mechanical fita-npet having means incorporated therein proszi ding cuickrand quiet adjustment in compensating for the operating. length of the tappet.

,furtherobjectlof the invention is the pro- .visionof a mechanical tappet having cammating .means incorporated therein providin for self- .adjustmentrdfthe tappet.

.Aafurther object of the invention is the pro- ;yision of a mechanical tappethaving cam mating relatively rotatable parts providing for compensation insoperatinglength of. the tappet.

v .Othernbjectsand.advantages o'f'ithe invention williappear fromthe following description taken yin connection with the drawings, forming a part ,ofthe specificationpand in which,

1 is a pantially fragmentary vertical sec- -.tional. view ,takendiametrically through -a tappet embodying theieatures ofthis invention showing vitlin connection with cooperating engine parts;

JEig. .2 an enlarged sectional view taken through line L2''2offZEi gQ 1;

Fig. 3 is a vertical sectional view ofgap'air-of cam matingparts of the tappet; and

'4 is a vertical sectional view of another ,pair iii-team matingg'parts of'the 'tappet.

'I'heetalmet devised by the present invention relates "to that type which includes axcylind'er and cooperating plunger interposed between a .cam and;a valveoperatedthereby;theload .carr ed my the taone bein prima ly the o transmitted vtherethrough loy the cam to open valve randvthe.rmevement of the plunger in ethev-eylinder beingresisted .nnder. such 1.loadiby Lmeanscooperatingi withthe cylinder and piling"- er. In this type of tappet construction spring means are provided which {constantly bias {the plungeroutwardly in the cylinder to increase'lthe efiective lengthoflthe tappet whereas cooperative parts interposed between the cylinder and the plunger providemeans whereby the efiective length ofethe ltappet is slightly shortenediunder normal operating conditions. "Because of theinherent structure providing for automatic selfadjustment, this type of .tappet .is efle'ctive'i'to compensate in .both directions for contraction and expansion of the valve stem and its'associated menibers occasiondhy temperature'variations, as well"asthe wear of said parts.

(In the ,pnesent invention "the means incorporated between the plunger and t cylindereiiective to.,providei for the-contraction and'the expansion of the tapnet consist .Of".tWD 'pairs of :cam mating .membiers, each of said pairs of members --being rotatable relative to one anotherstlchwhatbe cause of "their 13am mating surfaces are "moved (axially relative to one. another upon the relative rotation thereof. Theplungerwhich constitutes one of the cam mating members is "coupled-to one of the \otherp'air of cam mating members such that thesemembers may be solely axially movable relative to one another; whereas; the corresponding members associated respectively with the plunger-and the member coupledto the plunger are securely held together.

A'springifor extending the plungerrelative to the cylinder isinterposed between the plunger and the member coupled thereto such that when 5 the .tappet and its constituent members are in assembled position 'in a valve gear train wherein the' valve stemengages the plunger andan engine cam engages the base of one ofthe cam members attheopposite extremity of the'tappet, .the cam matin surfacesassume a friction mat ing relationship normallyresisting contraction in the 'operating length of the 'tappet whereas at the same time should contraction or wear occur in :the valve gear train the tappet spring would function to extend the tappet and thereby take up the clearance inthe valve gear 4 train. Similarlyshould the valve stem or any of its associ ated members expand beyond their normal length-the tappet would operate to contract in length, said contraction occurring due to the valve spring load imposed upon-the plunger op- ;posingthe tappet spring and also thefrictionom curring between the respective cam mating surfaces.

Althou h the valve spring is not normally gof suiiicient force to overcome the combined tappet spring load and the friction forces set up between the cam mating surfaces, the vibration transmitted through the tappet due to its reciprocable action with and between the calm and valve stem is sufficient to momentarily relieve the surface friction set up between the cam mating surfaces and thereby permit relative rotation and axial movement between the respective cam mating members.

For the purpose of obtaining a mechanical advantage in movement between the plunger and the member coupled thereto for axial relative movement, a difierent pitch is given to the respective pairs of cam mating members so that the axial movement of the plunger is multiplied in terms of axial movement of the member coupled to the plunger. The mechanical advantage to be selected will depend upon numerous factors such as valve spring load, tappet spring load, required limits of expansion and contraction in the valve train, and. other reasons.

With reference to the drawings for more specific details of the invention, In represents generally a valve t-appet reciprocabl-e in a tappet guide sleeve l2 interposed between the end of the stem of the conventional poppet valve l4 urged downwardly by a valve spring, not shown, and a cam 16 mounted upon a conventional cam shaft 3.

' The talppet [0 comprises a pair of cam members 20 and 22- securely fastened together by a pin 23, the cam member 20 having an enlarged cam contacting head 24 adapted to be engaged by cam l6, whereas, cam member 22 is received for reciprocation in the tappet guide sleeve l2. The members 26 and 22 respectively areprovided with cam surfaces 26 and 28, said surfaces being similar in configuration but differing in pitch, the cam surface 280i member 22 having a greater pitch than the cam surface 26 on the member 20. The cam surfaces 26 and 2B are arranged concentrlc-to one another such that the peaks A and A and lowest points B and B of the cam surfaces are substantially in radial alignment.

The cam mating surfaces 26 and 28 are adapted and a cylindrical member 38 coupled to the plunger so as to be axially moveable relative thereto and reciprocablein the step bore of the tappet body.

The plunger 34 is coupled to the member 38 by a pair of pins 46 received in grooves 42 in the plunger40 and grooves 44 in the member 38. In the assembly of the plunger 34 and member 38 the cam surfaces 30 and 32 are misaligned relative to one another; that is, peaks C and C and lowest points D and D of the cam surfaces 30 and 32 are not in radial alignment with one another so that the pairs of cam surfaces "26 and 30, and 28 and 32 can never both be in complete mating relationship at any time. The cam surfaces 30 and 32 are of equal pitch and complementary configuration respectively with cam surfaces 26 and 28 of members 20 and 22.

Fig. 1 illustrates clearly the arrangement of the respective cam-surfaced members whereby upon contractive axial ,rotative movement of plunger 34 clockwise in Fig. 2 upon and relative to member 20, the cylindrical member 38 is extended axially upon and relative to member 22 by its rotation thereof, the simultaneous axial movement of member 38 and plunger 34 in opposite directi-ons resulting in compression of a spring 46 one end of which is seated on a shoulder 48 of member 38 and the other end seated on a shoulder 50 of plunger 34.

Because of the difference in pitch provided between the respective pairs of cam mating surfaces, the cylinder member'is adapted to move a greater true axial distance than the plunger, the relative axial distance being in proportion to the pitch ratio of the cam surfaces and furthermore a mechanical advantage is obtained corresponding to the ratio of movement occurring along the respective pairs of cam mating surfaces.

The cam surfaces 26, 28, 3B, and 32, as shown by the drawings, although preferably made on a true helix so as to effect maximum bearing [relationship between the respective pairs of cam mating surfaces thus providing for greater and more uniform distribution of wear, may be made of any suitable angular construction consistent with the purpose here intended.

In a normal operation of tappet Hi wherein the tappet is interposed in the valve gear train as shown by Fig. 1, the tappet assumes and maintains an extended position such that no clearance occurs between the various members going to make up the valve gear train.

Upon contraction or wear of any of the members in the valve gear train with the exception of the tappet, the tappet spring 46 operates to move the plunger 34 axially outwardly with respect to the member 38; and simultaneously, changes the mating positions of the respective pairs of cam mating surfaces.

With the taking up of the clearances in the valve gear system, the combined action of the spring and cam mating surfaces 26 and 30, and

28 and 32 cooperate to maintain the tappet in its newly extended position thereby providing for efficient and noiseless operation of the valve gear system. Should elongation occur in the valve gear system such as the expansion of the valve stem, a pressure additional to the normal valve spring pressure would be imposed on the tappet andthe tappet in turn would function to be contracted an amount equal to the expansion of the valve. stem, said contraction occurring due to additionally imposed load on the plunger and the vibration that is transmitted to the tappet in its reciprocation together with the valve gear system, tending to relieve the friction occurring between the pairs of cam mating surfaces.

It is to be observed that a relative axial movement occurring between plunger 34 and member 38 results in rotation between the respective pairs of mating members 20 and 34, and 22 and 38 wherein depending on whether the axial movement is contraction or elongation an opposite axial relative motion occurs between the pairs of cam mating members, that is, if plunger 34 elongates with respect to member 38, it elongates relative to its cam mating member 20, whereas member 38 contracts relative to its cam mating member 22.

This completes a cycle of operation of the tappet through its stages of contraction and elongation for the purpose of compensating for changes that may occur in the valve gear system with which the tappet is associated.

While this invention has been described in connection with certain specific embodiments of an internal combustion engine valve gear system, the principleinvolved is susceptible of numerous other applications that will readily occur to persons skilled in the art wherein an elongation or contraction of an operating system requires automatic means to quickly compensate for changes in operating length. The invention is, therefore, limited only as indicated by the scope of the appended claims.

What I claim is:

1. In a mechanical self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger being solely axially movable relative thereto having a cam surface at one end thereof, a sprin interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member.

2. In a mechanical self-adjusting mechanism, a plunger having a head at one end thereof and a helical cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable relative thereto having a helical cam surface at one end thereof, a spring interposed between the plunger and cylindrical member, and a pair of rigidly fixed members having helical cam surfaces for engagement respectively with the helical cam surfaces on the plunger and cylindrical member.

3. In a self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable rela tive thereto having a cam surface at one end thereof, a spring interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member, said engaging of cam surfaces being of equal pitch and complementary configuration.

4. In a self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable relative thereto having a cam surface at one end thereof, a spring interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member, the pairs of engaging cam surfaces on the integral members differing in pitch from the cam surfaces on the plunger and cylinder member.

5. In a self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable relative thereto having a cam surface at one end thereof, a spring interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member, the cam surface on the plunger being angularly offset from the cam surface on the member coupled thereto and the cam surfaces on the integral members being in concentric radial alignment.

6. In a mechanical self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable relative thereto having a cam surface at one end thereof, a spring interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member, said mechanism being adapted to increase and decrease in length upon relative rotation between the integral members and the cylindricai memher and plunger.

7. In a mechanical self-adjusting mechanism, a plunger having a head at one end thereof and a cam surface at the other end thereof, a cylindrical member coupled to the plunger axially moveable relative thereto having a cam surface at one end thereof, a spring interposed between the plunger and cylindrical member and a pair of rigidly fixed members having cam surfaces for engagement respectively with the cam surfaces on the plunger and cylindrical member, said cylindrical member and plunger axially relatively moveable to one another upon rotation thereof on the integral members.

8. An automatic compensating device comprising a member having a pair of cam surfaces at one end thereof, a second member having a pair of cam surfaces for cooperation with the cam surfaces on the first member, and means associated with the members whereby upon rotation of one member relative to the other member an elongation or shortening of the over-all length of the compensating device occurs.

9. An automatic compensating device comprising a plunger, a cylinder associated with the plunger solely axially movable relative thereto, resilient means biasing the cylinder and plunger apart, and means engaging the cylinder and plunger and angularly and axiall movable relative thereto effective to provide for the elongation or shortening of the over-all length of the compensating device upon relative movement between the means and cylinder and plunger,

HARRY E. VOORHIES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,663,345 Lievre Mar. 20, 1928 2,003,509 Jencick June 4, 1935 2,323,965 Anglada July 13, 1943 2,365,401 Fisk Dec. 19, 1944 2,372,206 Howard, Jr Mar. 27, 1945

Images