US2200152A - Mechanical clearance regulator - Google Patents

Description

May 7, 1940. o. M. BURKHARDT MECHANICAL CLEARANCE REGULATOR Filed April 13, 1935 I :s Sheets-Sheet 1 EMF/ ATTORNEYS I May 7, 1940.

O. M. BURKHARDT MECHANICAL CLEARANCE REGULATOR Filed April 13. 1933 Fig.5

s Sheets-Shet 2 INVENTOFZ ATTORN EVE? o. M. BURKHARDT 7 2, 0,152

MECHANICAL CLEARANCE REGULATOR Filed April 13, 1933 3 Sheets-Sheet 5 ATTORNEYS til Patented May 7, 1940 our r E srAr as ear-Em r orrics 2,200,152 MECHANICAL CLEARANCE REGULATOR Otto M. Burkhardt, Cleveland, Ohio,- assignor to Thompson Products, Inc.,. Cleveland, Ohio.

ApplicationApril-IS; 1933, Serial No.- 666338 15 Claims. (Cl. 123-90) mechanisms, for every complete cycle of the justment to insure a definite clearance between the'va-lve'and its actuating member, the conventional cam. This clearance is necessary in*co-n---- ventional mechanisms to allow'for'expansion of the linkage between this cam and the valve, otherwise thevalves would-not properly close the combustion chamber, resulting in inefficient combustion;

. Because of improperseating of'thevalveor the entirelack of seating due to lack of clearance'in the linkage .of the mechanism; the valve is'deprived ofa most essential coo-ling period which normally occurs during its contact with the Water-cooled seat in the combustion chamber. This aggravates the heating of the valve and causes further expansion and; consequently, worse seating; The valves will then start-to warp, burn, crack and break. This is often followed by serious damage to the engine.

If the clearance between the valve andits actuating-members increases, either due to normal wear of the cooperating members, or due to a difierential in expansionof these members and their supports, then the valve mechanism becomes objectionabl-y noisy and the impact forces are greatly increased, causing pounding'of valve seats, excessive Wear, surge, and breakage.

strictly speaking, a warm-up period follows every: increase in throttle opening. because: the heatvincrea'ses directlywith thepower' output.

Cooling-01f periods occur every time the throttle opening is decreased; These'difierentialsin'exgpansion and' contraction change theclearance. andwith it the-valve timing. This'is detrimental to the proper functioningof the engine;

It is further well known to automotive engineers that within thevalve mechanism there exists" considerable'surge. In general, this surge is noticeable athigher engine speeds but more particularly is it noticeable at certain speeds known'as resonance speeds. This surge interferes with the desired true kinematic relation between the valve and its actuating'member; the cam;

This surge is-thecause of the valve bouncing 01f its seat when it is expected to close andremain closed. Bouncing of the valve causes Very high uncontrolled closing velocities and consequently high impacts. The latter'are the cause. of pounding away of valve seats, excessive noise, excessive wear, and failures. Bouncing of the valve further' causes a delay in closing of the valve which results 'inlossof power;

Various devices forautomatically adjusting clearances inthe linkage system of valve mechanisms have been previously developed. The present invention overcomes many diificulties. encounteredin' the construction and operation of such devices. An arrangement operative on a principle similar in some respects to that of J the present invention is shown, described. and claimed inmy Patent Serial No. 1,943,063, February"20, 1934.

Several preferred forms of mechanism by which I accomplish the-objects above set forth are illustrated in the accompanying'drawings as appliedto an L hea'd'engine'and' also an'overhead valve type engine. 'Iheabovestated. objectsand my device for eliminating the-difficulties outlined will become more apparent'in'the following. description which relates tothese drawings, in which Fig. l is a fragmentary crosssection of an engine block of the L-head type, showing an adaptation'of my invention to a-valve mechanism;

Fig. 2 is a similar fragmentary viewshowing the position-of the parts during. a; subsequent operation;

Fig. 3-is airagmentary elevation taken'along the lines 3-3. of Fig. 1;

Fig. a'is. a simplified.forcediagram illustrating. the. forces present during certain operating- 'conditions';

Fig. 5 is a fragmentary plan view taken along the lines 5--5 of Fig. 1;

Fig. 6 is a fragmentary vertical section similar to Fig. 1, showing a modified adaptation of the regulating cam mechanism;

Fig. 7 is a fragmentary horizontal section taken on a plane indicated by the line l--'I of Fig. 6;

Fig. 8 is a vertical fragmentary section showing an adaptation of my invention to the rocker arm arrangement of an overhead valve type of engine; and

Fig. 9 is a fragmentary sectional plan taken on an offset plane indicated by the line 99 of Fig. 8.

' In the arrangement of my invention as illustrated in Figs. 1, 2, and 3, there is shown a valve Ill having the usual stem i2on which is disposed the usual valve closing spring l4 positioned as shown between a stationary guide collar any adjustment, is slidably positioned in a guide provided in the motor casing 22. This guide is also greatly simplified because the lifter is a plain cylinder not requiring the enlarged head of conventional lifters. The lifters upper end is in contact with the lower end of the valve stem l2 as indicated at 24. The lower end of this lifter element 20 is shown as resting against the fiat side of a spherical element 26 mounted in a coacting socket 28 in the valve-actuating lever 30.

The end 32 of the lever 36 which is nearest the valve center line is bifurcated, and within it is suitably mounted a roller 34 which during the valve opening period is vigorously urged downwardly into contact with the surface of the cam 36 by pressure from the valve spring l4. When the valve is closed, the downward pressure of the valve spring I4 is reacted by the stationary valve seat 15 and its effect onroller 34 ceases.

. In the form shown, the end 38 of lever 30 is also bifurcated to carry by means of a pin 42 a regulating spiral or wedge-shaped cam member 40. For the design under consideration two nonrotating but slidable blocks 46 are further mounted on pin 42. These blocks are located to the right and left of the cylindrical end portion designated 38 of the lever 30 and they rest against coacting surfaces 41 provided on the motor casing. The cam 40, having fiat sides, also mounted on pin 42, is held in position by a slot provided in end 38 of lever 30. The cam is free to perform a-limited angular motion about the axis of pin e2. In order to continuously urge the thick part of the wedge-shaped cam 40 between suitable cooperating surfaces so as to take up excess clearance, a spring 44 is employed. This spring, in the case of Figs. 1, 2, 3, has both ends anchored to the non-rotating but slidable blocks 46. The middle portion of this spring acts on the wedge-shaped cam. as shown at 48. The spring preferably consists of a number of turns and is normally under tension urging the thick part of cam 44] between cooperating surfaces. One of these cooperating surfaces is a flexible member 50 which under normal pressure yields a very small amount,

Theoretically, the support 50 need not necessarily be of flexible metal but cam 40 may operate efficiently by engagement with an ordinary support for bearing engagement therewith. Flexibility within "he body of metal may be all that is required. However, the flexible support 50 will be found to produce better results and to act more efiiciently and is therefore deemed advisable for accomplishment of the best results. I

The outer surface of cam 40 is so shaped that a pressure'exerted on this outer surface will not pass through the center of the hole in the cam which coincides with the center line of pin 42 but will give rise to a force couple. This force couple is smaller than the sliding friction between the cooperating surfaces, that is, between the contact surfaces of cam $0 and support 5%! and between cam 46 and pin 42. This feature makes cam Myself-locking against the action of this force couple and hence against all static pressure acting on cam lt. If, however, support 50 yields,

a relative motion musttake place between the contact surfaces. The friction force between cam 49 and support 50 is opposed to sliding of the surfaces relative to each other and therefore it induces cam Ml to roll relative to support 59 anamount corresponding with the amount of deflection of support 59. It will be obvious from the design thatthe force couple above mentioned as well as the relative motion between the contact ing surfaces combine to induce cam 40 to roll toward the thin part or clockwise on pin 42. This lowers end 33- of lever 30 and with it to a smaller extent valve l0 relative tocam lobe 31. Because of this the valve opens a few thousandths of an inch less than it would open if end 38 of lever 30 were not lowered. The outer surface of cam 4i} may follow the laws of a logarithmic or an arithmetic spiral, or it may follow an involute or someother desirable curve.

To open the valve, only vertical pressure is required. When cam 36 is rotated to urge through its lobe 31 the roller 3t upward, the actuating force willbe normal to the surface of cam'lobe 3'! and will pass through the center of roller 34. The direction of this force varies, hence provi sion has been made through the proper locating of support 5% and slidable blockstt which bear against surfaces of the motor'casing, to constrain end 38 of lever 30 from all motion except that required for opening the valve and for regulating I the clearance, namely to follow the yield of support 50.

A very simple form of clearance regulating device is obtained by correctly shaping lever arm. 30 r.

and by locating the roller 34 at end 32, and the clearance regulating parts at end 38 of lever 30 in efiicient relation to cam 36. In the form shown in Figs. 1, 2, and 3, the lever 30 and the various clearance regulating parts mounted on it are so located that the forces between cam lobe 31 and roller 34 during the entire valve opening period act preponderately upward and with a bias to the so that any force acting normally upon it through cam 46 will be opposed in a manner that lever 30 can not be displaced to the left. There is another reason for inclining support 50 which will be apparent from the following The location for lever 39' and the parts mounted upon, it are chosen so that during the valve-openeingiperiod a suitable: part: ofithesva'lve spring. pres-- sure plusuthe: inertia; of-r theereciprocatingparts."

acts downwardly on endi,3.8:ot'lever-30;.. Adowm ward pressure; will produceia slight Ldefleetion of the supporta5.0:;and-consequently; blocks 463will; slide a small amount downwamil;'r.elati-ve..-to.,thev

surface. 41.. Due to;.the-.; inclinationzoi J the. support 5|]: relative to theesurface; 413; andsduee-to the, frictional; adherence'of. camAflztdthe.support..z5ll,..

:2anddue to. a. forceicouplewhic h ls the-:resultoithe. prevailing: pressurev and-,the; characteristics;

chosen for the: contour. of cam A0,". thiscamz. 405

will, according to. principles; previously. stated;-

turn; (clockwise. in.-.F.'ig. ,1) about .the; axisof pin i 42; an amount. which. is,-.in... direct relation; to the small. amount .of, deflection :of support Strand cons sequently; of 1 the; downward movement of end: 3.8

of the;lever.;30-.;. Thisdownwardmoyement isrcontrolled by, correctly proportioning; the following.

:3First, the magnitude of the downwardipressure transferred through-lever .30 from; the, point. of

application. ofthe; main force; the'pressure, of-

valvespring l4zplus the-inertia vofthe reciprocate ing parts .to .endz38 of lever 30. Second. the yield sof...the.flexible; support 50,: Third, the contour: of

cam-.140: whichrollsa definite amount againstsupport 50- toward a'smaller radius o-r..toward the thin part of; its wedge-like-shape during the slight,

downward motion.

As stated, when the; valve closes, all pressure ceases; mechanisrnthe valve opened, for example, .001" to-.005 lessthan itwouldopen were it actuated through; a conventional, mechanism. Therefore,

:lstthe. valve will also. closeloefore. roller 34 has arrived:atatheuconcentric:or. base-circle, 35: of cam 35 Asthe rollerapproaches'thebasecircle after the closing, of: thevalve, a. clearance of several,

thousandths ofzaninch will tend to1developwithinathe'valveeactuating linkage. While' this clearance tends =.to develop,r.the;.potential;energy stored in: the slightly deflected; support fiiltisr released.

Its nature is to'return to the no-load positionand bysmdoing-itiorces the end 38 of the lever. upwardly by that .amountwhich: it yielded due to the flexibility of the 'suppOrtEflQ. Whenthisis completed,v the end 3.8 tofzlever: filly-still hasto .move

upward iby thatsmall. amount whichzthe camiwa.

provided, due: to its. partialsrotation. aboutpin 5.0;, 42.. It'isimportantito note-that when theflexible sup-port 50. returns to..its unstressed. or no-loadr position, cam 4fls.doesxnot' returnto therangular position which it occupied; when the. downward. The reason for. thiSf. is; as.

movementistarted; appointed out before that during...the downward movementtthere is the frictional .-.adhesion .of the pointsin contact augmented, by. theaction .of a

force-couple causing clo-chwiserotation of the cam 40 to. its thinner or shorter radius aportion. On

(20,; the return tothe no-load position oi-the flexible support, andof the clearanceregulating parts.

cam Midoes not change its angular position relative to pin 42 oecause-the frictional resistance betweenthe contacting surfaces whichmight roll (Z53 cam 40 back to its original position, isnow op-' posed and overcome by that same force couple which previously helped in slightly rolling'cam lfi'. On the return motion, a rolling-of the camis further opposed-by the static frictionbetween cam and pin 42. Due to these factors; namely the force-couple 'being on downward yield" addi tive-toand on return to no-load position subtractivefrom thefriction between cam'fi'fl and'sup port' 50, andb'ecausetests-reveal -it' to beso, itis J an established fact that" on the downwa-rd motion- Because. of the; clearance regulating does not r011 v back to its original position. This partial rotation of cam 40 on pin 42 provides a. little; clearance to insure not only proper valve seating but it provides room for any expansionor other-change that'mighthave taken place within the linkage.

Now the thickend of cam Mlisconstantly urged between support 5!): and pin 42, causing endr38' of lever 30 to move further upwardly until all clearance is out of the linkage, namely, when the' valve which is nowheld firmly, to ,itsjseatby' spring M, stops lever, 38 from moving'further up-' wardly, This completes one adjustment for one. complete turnof the cam shaft which constitutes one complete engine cycle.

The arrangement shown in Figs. 1, 2, and,3:

has the advantage that the clearance regulating parts at the end 38 of lever 34! can be small in each other rather than on top of each other. Also, the sliding blocks 46-:are free to .slide considcam 40 does roll, but on the upward motion it erable distances up' or downwithout encounter ing structural limitations.

mechanisrnwill readily;compensateiforrthis;

Therefore, nottonly'does the: conventional ad-i justmentbeconrev entirely superfluous, butIdue to; the fact: that .the position of the. flexible member I 50 can be lowered or raised relative tO'ilihEfIl'lDliOl casing 22, a very Wide. range of manufacturing variations and wear changesxcanoccur. before limitations in the clearance regulating range approach inefiiciency or inefi'ectiveness.

The construction shown. inv Eigs. (Stand 7- isuso conceived that a pluralityv of l eccentrics 61- are mounted upon a. common shaft which extends parallel to the axis of thecam-shaft. This shaft is. supported at intervals bysuitable bracketszz.

Uponthe outside of each eccentric El is mounted.

one wedge-shaped cam 40 with its return-spring- 44. Alongside of camAm-with its return spring 44, there is further mounted upon the outside of eccentric Bl the end-38 m lever -30? These parts embraceandsubstantially cover the outside'of' eccentric 6i and they are adapted to'oscillate on of the spiral spring tends to turn cam 4!? so that it is. wedged snugly between the fleXibIestopBD-E and the eccentric 8i. Theotherend of thespirall fit! tends to wedgethe eccentric 6| betweenendiifia.

spring supplements this, action, in so far. as it of lever 301 and the stationary shaft $2., Asbefore, thespiral cam bears upon a flexible support.- 561 which is secured as indicated.- Thdflexible support is so formed and fastened as to permit of resilient action whenv pressure is applied thereto through the'medium of end, 33 of lever 30,

eccentric 6i and cam 40. This pressure originates and bears direct relation to forces necessary to open and close the valve.

surface 41. In the arrangement'here'under considera-tion, an analagous downward motion'ofth'e clearance regulating" parts is-- brought about This permits of very: large changes .in-the. partszof: the valve mecha- 'nismto, take. place andf the. clearance; regulatingzj The outer end:of=this-'spiral-spring'is fixed fro In the'description of'Figs. 1,12; anol'3', it was. noted that blocks 46- slide downward relative tof diameter, as the parts are mounted alongside off.

through end 38 of lever 38 being mounted upon eccentric 8| and transmitting pressure to this eccentric SI and so causing it to partially turn about fixed shaft 82. Due to the eccentric mounting of the clearance regulating parts relative to shaft 82, these parts are lowered when pressure occurs during the valve-opening period by an amount corresponding with the yield of support 58. Thus, itwill be seen that in the arrangement as shown, end 38 of lever 38 together with eccentric 6|, cam lll, return spring M, and support 58, perform during and immediately following the valve-opening period and under the influence of the prevailing pressures, the desired clearance regulation. exactly as described in detail for the arrangement shown in Figs. 1, and 3.

The mathematical principles of valve clearance regulation can best be given by referring to Fig, 4, which is a skeleton of a desirable form of clearance regulator. The support is shown reversed'in Fig. 4, with respect to its point of mounting, for the sake of convenience of illustration.

Cam 38 is rotated in clockwise direction. The pressure FR acting normal on. the cam surface passes through the center line of the roller as shown. Opposed to FF. is the pressure F1. which is the sum of the pressure of valve spring l4 plus the inertia of the reciprocating, parts. It is apparent that:

Fall- 1 1.

We shall first discuss application when F1. is vertical while FR is inclined. The vertical component of FR being fv acts on lever arm C which is larger then 0. Because of this, balance of the system necessitates the existence of another vertical component at end 38 of lever 38 which we call f"v. Balance of the system requires that f'v+f"v=FL FR has a horizontal component fh which is reacted by an equal and opposite force 1"h at end 38 of lever 30.

f'h and ,fh form a force couple of moment .f'nXd The system is subjected to one clockwise moment FLxc counteracted by 2 counterclockwise moments f'vC and f'hd FLc=fvC+f'hd The force fv is the vertical component of the force Fs which is the pressure exerted by end 38 of lever upon support 58. The horizontal component of Fe is not necessarily equal to f"h. The horizontal component of Fe resists 1"v only incidentally. Adequate resistance for f"v. is obtained in the guide surfaces l1. Un; der pressure Fs support 58 yields. Due to friction, the contact points (8) of the cam and support adhere together. Hence, sum of force couple FsXl plus moment of friction at (0) namely FsXJXR of cam cause rolling of cam about pin 42 toward smaller radius of cam. In the latter expression f denotes coefficient of friction. R denotes radius of that part of cam 48 which momentarily is in contact with support 50.

When force FL disappears due to closing of valve, spring support 50 continues for a moment pansion in linkage while the remainder is taken out by spring 44 through cam 48.

In Figure 4,the support 58 is located to counteract such forces as result when a e. In all cases when a. c the component f"v must'act .downward. Inasmuch as fv is derived from F3 it is evident that in all cases when a c support 50 must be so located relative to'cam that force.

Fs acts downwardly.

Effectiveness and simplicity of the device are assured by properly positioning the arm '30 in an angular relation with respect to the axi's of the: valve stem and by locating the ends 32 and 38' of the lever arm 38 so that under all operating conditions there are components of forces acting to hold the clearance regulating members in the desired position. It is also apparent that by suitably varying the angle at which the guide surfaces ill or the supporting member 58 are disposed, these components may be varied to suit the different conditions that obtain in different designs of engines. Itis not'necessary, although here shown, that the center line of the valve intersects that of the cam shaft. The principles apply equally as well when the center line of the valve does not intersect that of the cam shaft but passes either to the right or left of it.

When eccentrics are usedas in the cases illustrated in Figs. 6, 7, 8, and 9, the thick part of the eccentric may also be located to the right of the axis of the stationary shafts 62 and 83, respectively.

Figs. 8 and 9 represent an'application of the clearance regulator to an overhead valve engine now to be described in detail.

Mounted in suitable brackets is a stationary shaft 82 which through the medium of eccentrics 83 affords support for the rocker levers 84. Each rocker lever is provided with an integrally formed collar or hub 85 embracing the eccentrics 83 about which the rocker arms turn. The center of this hub is so located as to obtain the desired relation between pushrod and valve motion. Upon the circumference of each eccentric bushing is mounted a cam- 48b. The outside surface of this cam bears against a flexible support 50 which is secured to the top of the bracket. Cam 48 having flat sides 'is free only to perform a limited angular motion upon the circumference of eccentric 83. In order to continuously urge the thick part of the wedge-shaped or spiral cam.

lii between suitable cooperating surfaces so as to take out excess clearance, is aspring 88 which,

like the spring M above described, has one end lll to support fl which=will yield until its resistance" balances the turning effort.

--cam 540". v

entirely within controlthr'ough properly propor- "velop within the valve linkage.

Whilesupport-Sfl yields in direction of arrow X, the'eccentric through cam 40 pushes in direction of arrowY. 'Due'to the frictional adhesion %between the contact surfaces of cam 40 and 'support '50 the cam 40 will'tend to' follow supportill indirection of arrow 'X, which causes a "turning of cam Won-eccentric 83. This turning is further helped by-a force couple which is due to the pressure of the moment onthe contour of This motion, as previously stated, is

tioning the cooperating parts. I Y -Identically as in the previously described ar- 'rangements, when'the valve closes, the cause of all pressure ceases. Due to the yield of support 50 the eccentric 83 has slightly turned about shaft-82, raising-the center of the hub of'the rocker'arm t4 which causes! the valve to close a little sooner than it would close were it actuated through a conventional roller approaches the base circle, a clearance of several thousandths of an inch'will tend to de- As soon as pressure diminishes, the potential energy stored up in support 50 is released. Support Ell will through medium of cam lil cause'eccentric 83 to turn counterclockwise and sourge the hub portion of the rocker arm downward. This eliminates only part of the lost motion brought about :duringthe opening of the valve; because during the return to the no-load position of support 50 cam 40 will not turn on eccentric 83 because through the'friction between the contacting surfacesof cam lll and support 50, the potential energy of this support would now tend to cause came!) to rotate clockwise, which'it can not readily do because this would involve entering the thick part of the wedgashaped cam between the cooperating surfaces; but moreover themoment of a force couple due to the design or cam 40 counteracts clockwise motion of cam 4% and eccentric-.83. It is only after the effect or the potential energy from support50 has been exscope of the appended claims, I therefore do notwish to be limited to-theparticular designs illustrated.

"In the 'earlypart of this application it'was stated that the invention will eliminate surge from'thelinkage "of the valve mechanism. How this is accomplished will appearfrom the follow It iszwell-known that the entire valve-opening 'period' which lasts aboutone-third of a cam shaft revolution or about:120- cam shaft angular v motion, usually less than .39" only are available problems the linkage has to be; made light. High 1 pressures and light :linkage .cause appreciable mechanism. As the elastic yield within the linkage. The product of the pressure multiplied by this yield represents the energy which is stored up in the Valvelinkage. 'Ata car speed of 60 to 70 miles per hour, this storing of energy in the valve linkage occurs in less than .003 secondf This time interval hap: pens to coincide vnth the frequency of conventional valve springs. Coincidents of this nature are recognized as prolificsources of resonance or surge in mechanisms.

More specifically, what happens within the valve linkage is that when the geometry of" the cam contour requires a valve velocity of say50 inches per second, the valve moves at a' less'er velocity, perhaps'edinches per second, more ortlfi less. At thebeginning of the valve opening period, the valve always lags behind'the ca'ms angular velocity bya-n amount corresponding "to the energy stored up within the valve mechanism 7 due to elastic deformation. 'Hen'ce resonance or surge is' bound to occur within the valve mechanism. The surge frequency of the valve linkage set up by this elastic deformation, remains constant but the angular velocity of the cam is-subject to wide variations," due tovaria'ticns: in en gine speed and periods in the mechanism is driving the cam. shaft.

These facts briefly account for noticeable surge which in the valve linkage. Ifthere is clearancein the valve linkage, the pressure above referred tousually occurs as a shock to the linkage which in turn is known to aggravate this surge. Now inasmuch as the invention eliminates all excess clearance, it is obvious that shocks are reduced and consequently one cause ofsurge'aggravation is eliminated.

"It' is: wellknown that surge 'or'vibr'ations in structural parts canbelessened by the use'of friction devices which tend 'to dampenthem out. One of the advantageous characteristics of my invention is that it is'made'up of a number of parts: which in the performance of their functions move relatively to one another-and so introduce a small amount of friction into the linkage members. This small amount. of friction helps further to minimize surgein the entire linkage.

Therefore, With the'invention'I attain not only "clearance regulation but surge dampening as well ii In an internal combustion engine, the combination with a valve and a cam shaft, of valveoperating linkage including a lever interposed between said valve and cam shaft and adapted to transmit'motio-n therebetween, oscillatable cam means associated with one end'of said lever, a

spring normallyforcingthe cam' in one direction,

means permitting movement of the axis of said cammeans, and a substantially stationary abut ment contacting said cam means, so that. saidca'm means affords a movable fulcrurn'for one end of said leverand acts to move said fulcrum toregulate clearancesand absorb impacts between said valve and camshaft.

2. in an internal. combustion engine, the 'combination with a valve and' acam shaft, of valveoperating linkage includinga lever interposedbetween'said valve and cam shaft and adapted to transmit motion therebetween, oscillatable cam means associated with one end or said lever, a spring normally forcing the cam in one direce tion, and means permitting movement of the axis of said cam means so that said cam means affords a moveable fulcrum for one end of said lever and acts to absorb impacts and to regulate clearance between said valve and cam shaft.

3. In a valve mechanism for an internal combustion engine, the combination of a valve, a cam shaft, a lever interposedbetween said valve and cam shaft, one end of said lever contacting said cam shaft and the other end of said lever having associated therewith an oscillatable wedge-acting cam member, and means permitting movement of the axis of said cam member, said lever being disposed angularly with respect to the movement of said valve and said cam having means normally forcing the same in one direction whereby a preponderant force is at all times exerted in one direction to maintain said lever in an operating position and said cam afiords a moveable fulcrum to regulate clearness in. the valve mechanism and to insure constrained movement of said lever effecting opening and closing of the valve.

4. In a valve mechanism for an internal com bustion engine, the combination with a valve and a cam shaft, of valve-operating linkage including a lever angularly interposed between the said cam shaft and valve, a fixed auxiliary shaft, an eccentric oscillatably disposed on said shaft, said lever embracing said eccentric, a wedging cam oscillatably disposed on said eccentric, means normally urging said cam in one direction, and a reaction element contacting said cam, whereby the force moments about the center of said aux" iliary shaft would be unbalanced if substantial clearances should exist in the valve mechanism and whereby said cam and eccentric are automatically actuated by such tendency so as to regulate said clearances.

5. In an internal combustion engine, the com bination with a valve and a cam shaft, of a lever interposed between and linking said valve and cam shaft and adapted-to transmit motion therebetween, said lever being actuated at its one end by said cam shaft and said valve being actuated from a point on said lever intermediate its ends, and automatically adjustable cam means associated with the other end of said lever and adapted under pressure through said lever to alter the relative inclination thereof to change the linkage distances between said valve and cam shaft, and adapted when pressure ceases to again change the distances to insure minimum clearance.

6. In an internal combustion engine, the combination witha valve and a cam shaft, of an inclined lever interposed between and linking said valve and. cam shaft and adapted to transmit motion therebetween, said lever being actuated at its one end by said cam shaft and said valve being actuated from another point on said lever, and automatically adjustable cam means associated with the other end of said lever and adapted underpressure through said lever to alter the relative inclination thereof to change the linkage distances between said valve and cam shaft, and adapted when pressure ceases to again change the distances to insureminimum clearance.

7. In an internal combustion engine, the combination of valve-operating linkage including a lever arranged between the cam shaft and valve stem and adapted to transmit motion therebetween, a wedge-acting cam oscillatably mounted upon the one end of said lever means permitting movement of the axis of said cam, spring means arrangedbetween said cam and lever so as to normally force said'cam towards its larger radius, and a resilient abutment for bearing engagement by said cam, said parts being so constructed" and arranged that said cam will be turned about its axis towards its smaller radius during the valveopening period and being adapted thereby to store energy during said period, and said cam turning automatically towards its larger radius during the post valve-operating period so as to therebyregulate the clearance in the mechanism and 'to release such stored energy during saidpost valveoperating period but only to the extent required.

8. In an internal combustion engine, the combination of valve-operating linkage including. a

lever arranged between the cam shaft and valve stem and adapted to transmit motion therebetween, a wedge-acting cam oscillatably mounted upon the one end of said lever, spring means arranged between said cam and lever so as to normally force said; cam towards its larger radius, an abutment for bearing engagement by said cam, a slidable mounting for the end of said lever upon which the cam is mounted and being so arranged as to permit movement of said lever end substantially transversely thereof and to wards and from said abutment, whereby said cam will turn about its axis towards its smaller radius during the valve-opening period and being adapted thereby to store energy during said period and said cam turning automatically towards its larger radius during the post valve-operating period so as to thereby regulate the clearance in the mechanism.

9. In an internal combustion engine, the com-, f

bination of valve-operating linkage including a lever arranged between the cam shaft and valve stem and adapted to transmit motion therebetween, 2. wedge-acting cam oscillatably mounted a slidable mounting for the end of said lever upon which said cam is mounted, said mounting com prising a block having slidable engagement with a stationary abutment, a resilient abutment for said cam, said resilient abutment extending angularly with respect to said stationary abutment so as to afford a wedging engagement, the lever .end upon which said cam is mounted sliding movement substantially transversely thereof and towards and from said resilient abutment, said parts being so constructed and arranged that said cam will be turned about its axis towards its smaller radius during the valve-opening period and being adapted thereby to store energy during said period, and said cam turning automatically towards its larger radius during the post valvee operating period so as to thereby regulate the clearance in the mechanism.

10. In a valve mechanism for an internal combustion engine, the combination with a valve and a cam shaft, of a motion-transmitting lever interposed between said cam shaft'and valve, a fixed auxiliary shaft, an eccentric oscillatably mounted upon said auxiliary shaft, the one end portion of said lever embracing said eccentric, a wedge-acting cam oscillatably disposed on said eccentric, spring means arranged between said eccentric'and can]. so as to normally urge thetwo in opposite angular directions, and a substantially stationary abutment for said cam, said parts being so constructed and arranged that said cam will be turned about its axis towards its smaller radius by movement of said eccentric by said lever during the valve-opening period, and

. valve and cam shaft and adapted to transmit [actuated from a point between the ends of said motion therebetween, one end portion of said lever having operative engagement with said cam shaft for actuation of said lever, said valve being lever, a wedge-acting cam oscillatably mounted upon the other end of said lever, spring means arranged between said cam and lever for normally forcing the cam towards its larger radius, means permitting movement of the axis of said cam and an abutment for said cam, saidparts being so constructed and arranged that said cam will be turned towards its smaller radius during the valve-opening period and will turn automatically towards its larger radius during the post valveoperating period so as to regulate the clearance in the mechanism. 7

12. In an internal combustion engine, the com bination with a valve and a cam shaft, of an inclined lever interposed between and linking said valve and cam shaft and adapted to transmit motion therebetween, one end portion of said lever having operative engagement with said cam shaft for actuation of said lever, said valve being actuated from a point between the ends of said lever, a wedge-acting cam oscillatably mounted upon the other end of said lever, spring means arranged between said cam and. lever for normally forcing the cam towards its large. radius, means affording vslidable movement of the end of the lever upon which the cam is mounted and in a direction substantially transverselyof said lever, said cam having an abutment extending angularly to the direction of such slidable movement so as to afford a wedging engagement, said parts being so constructed and arranged that said cam will be turned towards its smaller radius during the valve-opening period and will turn automatically towards its larger radius during the post valve-operating period so as to regulate the clearance in the mechanism.

13. In an internal combustion engine, the combination with a valve and a cam shaft, of an inclined lever interposed between and linking said valve and cam shaft and adapted to transmit motion therebetween, one end' portion of said lever having operative engagement with said cam shaft for actuation of said lever, said valve being actuated from a point between the ends of said lever, an eccentric oscillatably mounted upon a fixed shaft, the other end of said lever being oscillatably disposed about said eccentric, a wedgeacting cam oscillatably mounted upon said eccentric, spring means for normally forcing said cam towards its larger radius, and a substantially'stationary abutment for said cam, said parts being so constructed and arranged that said cam will be turned towards its smaller radius during the valve-opening period and will turn automatically towards its larger radius during the post valveoperating period so as to regulate the clearance in the mechanism.

14. In an internal combustion engine, the combination with a valve and a cam shaft, of an inclined lever interposed between and linking said valve and cam shaft and adapted to transmit motion therebetween, one end portion of said lever having operative engagement with said cam shaft for actuation of said lever, said valve being actuated from a point between the ends of said lever,

an eccentric oscillatably mounted upon a fixed shaft. the other end of said lever being oscillatably disposed about said eccentric, and cam means having oscillatable connection with said eccentric for controlling the oscillatable movement of said eccentric so as to thereby regulate the clearance in the mechanism. i

15. In an internal combustion engine, the combination with a valve and a cam shaft, of valveoperating linkage including a lever interposed between said valve and cam shaft and adapted to transmit motion therebetween, oscillatable cam means associated with one end of said lever, a spring normally forcing the cam in one direction, means permitting movement of the axis of said cam means, and an abutment contacting said cam means, so that said cam means affords a movable fulcrum for one end of said lever and acts to move said fulcrum to regulate clearances and absorb impacts between said valve and cam shaft.

OTI'O M. BURKHARDT.

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