US1928856A - Valve actuating mechanism - Google Patents

Description

Oct. 3, 1933. HAIN VALVE ACTUATING MECHANISM Filed Dec. 8, 1928 I Q A.

Patented Oct. 3, 1933 ENT OFFICE VALVE ACTUATING MECHANISM Leon Hain, Brooklyn, N. Y. Application December 8, 1928. Serial No. 324,649 3'Claims. (Cl. 123-410) This invention relates to valve actuating means, and is more particularly concerned with new and improved'means for lessening noise in the valve tappet.

An object of the invention is to lessen the noise accompanying the operation of a valve tappet.

It is an object also to provide a valve actuating mechanism in which there is provision for automatic compensation for variations in length of the valve stem but in which the engagement of the actuating member with the part to be moved is eased to such an extent as to prevent undesirable noise.

Another object is to provide a valve stem havingcooperating .cam members with a clearance between the ends of 'theircontact surfaces.

Still another object is to provide a new manner of seating the lower cam member on the valve stem. v I

Yet another object is to provide a novel form of locking means for the cooperating cam members, to enable the determination of the amount of lost motion between the tappet and the valve stem mechanism. 1 c,

Other objects will appear hereinafter.

In the drawing, which illustrates one embodiment of my invention.

Fig. 1 is a vertical section through a portion of the cylinder head of an internal combustion engine, employing my invention;

Fig. 2 is an elevation showing the two cam members, the lower of which is hereinafter termed the cam, and the upper member; the cam-follower; v

Fig. 3 is a fragmentary vertical section, on an" enlarged scale, illustrating the cam and cam-fol- 7 lower in assembled relation on the valve stem;

Fig. 4 is a drop perspective illustrating the elements of the cam mechanism, while Fig. 5 is a perspective view illustrating a device for holding the cam and cam-follower'together against the tension of the springs; and

Fig. 6 is a view in elevation showing the cammember, cam follower and valve stem in position for opening the valve.

At 1 is shown a conventional form of cylinder head employing an overhead valve, and provided with the usual water-jacketing 2, combustion chamber 3, and port 4. Therev are also illustrated a water outlet 5, a spark plug 6, a push rod 7, a rocker arm 8, and a valve 9 having a valve stem 10, surrounded by a bushing 11 and extending upwardly through the cylinder head to a point adjacent the rocker arm 8. As shown, the rocker arm 8 terminates in a tappet 12.

It is known that a certain clearance or lost motion is generally provided in some part of the actuating mechanism of an internal combustion engine valve because of the variation in the length of the valve stem incident to temperature variation or to other conditions. When such clearance is provided that an actuating part such as the tappet comes into engagement with a part to be moved, such as the valve stem, with a free blow due to movement of the actuating part prior to the direct engagement, an undesirable sound is created. This is commonly referred to as tappet noise.

By this invention I provide a clearance between the actuating part and the part which it engages to effect movement of the valve and I interpose between the two partsa mechanism which prevents a free blow and causes the parts to engage in such a way that the undesirable noise is materially lessened.

Restricted between a shouldered member 13 fixed to the stem 10 and a flange on the bushing 11 is a spring 14 forming, together with the spring 15, a spring assemblage of the conventional type for returning the valve stem upwardly when the tappet pressure is released. As shown, the valve stem 10 has a tapered portion 16 connecting the main body of the valve stem with an extremity l'l'of reduced section. Seated on the tapered portion 16, and having a central bore 19 of a size to fit the taper, is a cam 18 having cam surfaces 20 inclined to the axis of the valve stem andprovided with an outwardly extending flange 21 which has a plurality of apertures 22, the purpose of which is described hereinafter. By this manner of seating the cam 18, it is possible merely to drop it over the extension 17 and let it fall into its properseating position. A slight twist will then secure it firmly in place. Any knocking due to improper seating is thus avoided. As shown, the cam surfaces 20 are preferably made in two semi-circular identical sections and in order to increase the eifective bearing surface, these cam surfaces are bevelled radially from their outer to their inner edges as well as being inclined circumferentially. The cam member is adaptedto receive, along the cam surfaces 20, conjugate surfaces 24 of a two section cam-follower 23, likewise provided with a flange 25 hav ing a plurality of apertures 26. The cam-follower 23 has a central bore 27 providing for the snug reception of the reduced-section portion 17 of the valve stem 10.

When the tappet 12 is rocked by the rockerarm 8 to engage the headed portion 28 of the cam follower 23, it causes the bearing surfaces 24 of the cam-follower to engage the cam surfaces 20 of the cam member 18, the surfaces 24being bevelled and otherwise shaped to conform to the cam surfaces 20. The member 23 is thus guided down the surfaces 20,- rotating the while, against the tension of the spring 28 which is adjustably mounted between the cam member 18 and the cam follower 23. The spring 28 terminates at each end in a longitudinally extending portion 29, adapted to engage one of the openings 22 and 26 of the members 18 and 23. The spring tends to turn the cam follower and to cause itto ride up on the cam surfaces 20. By varying the angular spacing between the ends of the spring, its force may be varied and in this manner the resistance of the spring to the downward travel of the cam-follower can be varied-at will. This adjustment of the spring tension is effected by inserting one projection 29 into an opening of one of the members 18 or 23, and holding that member stationary while the other end 29 of the spring 28 is inserted in a desired one of the apertures in the other of the two members. The spring thus gives the cam follower a permanent bias into engagement with the tappet.

When pressure is applied by the tappet, camfollower 23 begins its rotating, downward travel and continues to a point just short of contact between the adjacent vertical walls 30 and 31 of themembers 18 and 23 respectively, the length of the recess 27 being so designd that the closed end of the member 23 will seat on the extremity of the portion 17 of the valve stem 10 before the faces or walls 30 and 31 contact with each other.

In this manner the chatter or noise which would be occasioned by the clashing contact of the faces 30 and 31 is avoided, the noise caused by members 17 and 23 being inappreciable because of the nature of the engagement of these members. As the member 23 approaches engagement with the top of the stem 17, it is slowed down by the torsional resistance of the spring 28 and by reason of the friction between the engaging cam faces 20, 24 which cause a part of the force of the tappet to be transmitted to the valve via the cam 18 rather than directly to the valve stem. In a sense, the follower 23 is eased into engagement with the valve and no free or hammer-like blow is given as in the usual construction.

At this time the tappet motion is transferred vertically downward by the direct engagement of the follower and thestem. The valve 9 is thereby unseated the desired amount, and is reseated upon withdrawal of the tappet by the springs 14 and 15. It will be noted that a channel .32 is shown; as extending between the exterior and the head of the recess 27, to provide for the admission of a suitable lubricant. The recess 27 provides the clearance for expansion of the valve stem.

To permit uniform wear of the contact surfaces 20 and 24 of the members 18 and 23, they are preferably recessed as at 33, so that the inclination of the faces will not be changed materially as wear occurs.

In order to prevent too great a movement of the tappet, and to provide the correct clearance to allow for expansion, means have been devised to readily ascertain the play between the head 28 and the tappet 12. These means, as shown in Fig. 5, comprise in the present instance,cooperating yoke members'34 and 35, the member 34 having arms 36 and 37 and the member having arms 38 and 39. Each yoke member terminates in a pair of reai'wardly extending arms 40 and 41, having adjacent their extremities orifices 42 for the reception of a bolt or other suitable means 43, about which they are pivotally mounted. Across each pair of arms 40 and 41 is a stirrup 44 having a central threaded aperture for the reeep tion of a suitable wing-headed adjusting screw 45.

In this manner the yokemembers, after the arms 38 and 39 have been placed between member 13 and cam member 18 and the arms 36 and 3'7 about the skirt 25, can be tightened down against the action of the spring 28 to secure the members 18 and 23in firm engagement. At this time accurate measurement of the play between the tappet and head can readily be made, a measurement impossible of determination were the spring 28 permitted to urge the cam-follower 23 up into constant engagement with the tappet. It is to be understood that the adjusting means for the yoke members 34 and 35 may take any desirable form without departing from the essential features of the invention.

It will be further noted from the drawing, that the arms 36 and 37 of the yoke member 34 each terminate in an eye 46, formed in any suitable manner, as by folding over the metal of the arms themselves; These eyes are adapted to receive a lockbar 4'7 by means of which the locking members can be secured in position to clamp the members 18 and 23 together. The eyes 46 and bar 4''! maybe placed on whichever yoke member is preferred, or on both. Its function is to prevent the locking means from sliding off the cam members and being thrown by the spring 18.

It is of course understood that the invention is susceptible to numerous modifications and adaptations, and it is intended that it be limited only by the scope of the appended claims.

I claim.

1. In a .valve mechanism employing a tappet, a valve stem, a cam member seated on said stem, a cam-follower freely mounted over said stem and adapted to move along the stem in engagement with said cam member and said tappet to transmit partial force from the said tappet to said cam member and thereby to the stem, and a spring normallymaintaining a clearance'between said follower and the endof said stem and holding the follower against the tappet, the spring and the friction between the cam and follower serving toretard the follower and to ease it into dl rect engagement with said stem uponmovement of the tappet.

'2. In a valve mechanism employing a tappet, avalve stem, a cam member secured to said stem, a cam-follower mounted over said stem and having a closed head above said stem and a spring pressing it against the tappet, the cam and. the follower having inclined contacting faces and substantially vertical faces terminating their contact faces, the follower being adapted to move downward along the cam member under actuation by the tappet until the headed portion of the follower seats on the stemjust short of contact between adjacent vertical faces of the'cam and the. follower.

3. In a valve mechanism having a valve stemand a tappet, a cam member seated on said stem, a cam-follower mounted on said stem and adapted to transmit partial force from said tappet to said cam and thereby to said stem, said cam and said follower each having a flange in which there are a plurality of apertures, and a spring coiled about said cam and said follower, and terminating in fingers adapted to engage desired ones of said apertures.

LEON HAIN.

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