US1267337A - Valve-operating mechanism. - Google Patents

Description

Patented May 21,1918.

HARRY A. HUEIBOTTER, 01E DAVENPORT, IOWA,ASSIGNOR TO B. W. PHELPS, OF ROCK ISLAND, ILLINOIS.

VALVE-OPERATING MECHANISM.

Specification of Letters ratent.

Patented May 21, 1918.

To all whom it may concern:

Be it known that I, HARRY A. Hn'nno'rrnn, citizen of the United States, residing at Davenport, in the county'of Scott and State -of Iowa, have invented certain new and useful Improvements in Valve-Operating Mechanism, of which the following is a specification.

My present invention pertains to valveoperating mechanism, and contemplates the provision of a mechanism embodying a flatfaced pivoted follower or a group of said followers, arranged in such a manner that the valve opening bears a definite relation to'the piston velocity through a. predetermined portion of the piston stroke. 7

While applicable to various valves and motors, the invention is designed particularly for operating the puppet type of valves in four-cycle internal combustion engines; and its novelty, utility and practical advantages will be fully understood from the following description and claims when the same are read in connection with the accompanying drawings, hereby made a part hereof, in which:

Figure '1 is a view, partly in front elevation and partly in section, showing the application of my mechanism.

Fig. 2 is a side elevation of the same.

Fig. 3 is a perspective of one of the flatfaced pivoted followers which constitute important features of my mechanism.

Similar numerals of reference designate corresponding parts in all of the views of the drawings.

The term flat-faced follower, as hereinafter employed, is intended to be construed as meanin a follower the contact face of which is formedin such a way that the straight elements of the surface are parallel to the axis of the cam.

At 1 is a cam, fixed with respect to a. shaft 2, and designed,- in the case of a four-cycle engine, to revolve with the shaft, in the direction indicated by arrow, at one-half crank-shaft speed. 3 and 4 are followers, preferably, though not necessarily, of bellcrank type, pivoted at 5 and 6, respectively,

and adapted incidental to the action of the cam to impart to their individual valves 7 and 8 a modified motion.

In the present and preferred arrangement of the elements comprised in mynovel valve-operating mechanism, the flat-faced portion of each follower rests, when its complementary rectilinearly movable valve is closed, comparatively close to the center of movement of the cam and at an acute angle to the line of movement of the valve, and consequently in opening its valve under the action of the cam the said portion of the follower moves toward a. position at a right angle to the line of movement of its valve. The said arrangement is materially advantageous because of its compactness and also because it contributes to imparting to the valve a lift proportional to the piston speed through that portion of the stroke in which the flow of gas depends upon movement of the piston.

In the operation of the four-cycle type with the direction of cam rotation stated, 7 will be the exhaust valve, and 8 the inlet valve.

As illustrated in Fig. 1 the cam 1 is beginning to lift the exhaust valve, and in this connection it is to be understood that both valves are returned to their seats by springs (not shown) in the ordinary well known manner or any other suitable means.

In the case of the inlet follower 4 it will be noticed that the pivot 6 enables the follower to swing about it as a center but preeludes any motion of translation; the face 9 riding on the periphery of the cam 1 and being raised when the eccentric curve of the cam contacts with it, and the arm 10 being adapted to communicate the motion of the face 9 to the-valve 8, either directly as shown or through the medium of a tappet which I have deemed it unnecessary to illustrate. The face 9 is a plane surface-2'. e., a flat face, and correct valve timing is attained partly by the relative positions of cam 1 and the crank shaft (not shown) of the motor and partly by the angle made by the flat face 9 with the axis of the cylinder. The principle of the follower 3 is similar to that of the follower 4.

.It is the aim of my invention-to assure the opening or closing of each valve at such a rate as to afford an area of valve opening in direct proportion to the-speed of piston travel, with a view to maintaining a constant velocity of the inlet mixture and the exhaust gases, and thereby lessening or practically doing away with the effect of gase inertia during that period of the stroke throughout which the gas velocity depends upon the piston velocity. This will be better understood when it is stated. that for a constant angular velocity of crank-shaft travel and for a finite length of connecting rod-the piston velocity is higher adjacent to the inner end of the stroke than at an equal distance from the outer end, and reaches a maximum at a point intermediate the inner end dead center and the mid point of the stroke which makes it materially advantageous quickly to open the. inlet valve and quickly to close the exhaust valve inasmuch as it is during the inner portion of the stroke that the piston exerts the greatest effect upon the fuel mixture and the exhaust gases. Thus by correctly proportioning the length of the cam follower it is feasible to maintain the area of valve opening in constant ratio to the velocity of piston travel during that period, as is desirable, and to obtain a maximum valve opening at the time of maximum piston speed.

I attain the end stated through a sym metrical cam operating both valves and imparting to one a quick closing and to the other a quick opening. I" would have it distinctly understood, however, that it is within the essence of'my invention to'employ an individual cam for each valve. The variation'between rates of opening and closing of the valves isdue to the varying radial distance from the point of contact between cam face and flat' face follower to the/pivot" of the follower, and if angular velocity of the cam follower and hence the rate of valve opening is large'andv vice versa. 7

In comparing my improved valve motion with that of the mushroom type of cam follower operating in rectilinear guides the following relations obtain, viz: At the ular dropped from the center of the cam to the face of the follower as at 11 in Fig. 1, the valve opening and the velocity are greater than in the mushroom type, while resulting noise, and friction incident to the operation of the mushroom follower are eliminated in the nism.

It will be gathered from the foregoing operation of my mecha that incidental to the action of the cam 1 against the flat face ofeither follower, the follower will remain at rest so long as its flat face contacts with the .concentric portion of the cam periphery. When, however,

- theeccent ric curve a; b of the cam'engages the flat face of'the follower, the latter commences to rise and the point of contact moves from a toward 6. I' I The follower 3 is now moving away from the axis of rotation ofcam 1 and its angle of travel is increasing, gradually at first since the increasing length of the lever arm of the contact point relative to the point 5 counteracts the rapidity of motion of the follower due to the eccentricity of o b. With the usual clearance between the valve stem and the follower, this results in a low inertia force at this stage of the cycle. The combined forces, then, due to inertia of the mov-' 'ing parts and internal pressure in the cylinder tending to oppose the opening of the exhaust valve are comparatively low, a very desirable condition. The exhaust valve 7 continues to open until it reaches its point of maximum lift at the time the piston atv tains its maximum velocity. Up to this time the flow of exhaust gas is due largely to the-pressure inside the cylinder. Henceforth the exhaust depends upon the pumping action of the piston and throughout this period the area of valve opening bears a constant ratio to the velocity at which the piston is forcing the gas out thereby producing a constant ratio of flow through the valves, and eliminating the detrimental effects of periodic fluctuations in rate of exhaust travel.

In a similar manner the opening of the inlet valve 8 increases in proportion to the increase in volume of cylinder capacity up to the'point of greatest piston speed, then decreases slowly since after that point the rate of'flow of gas through the inlet valve depends upon its own inertia as well as upon the piston -travel. The maximum efl'ective opening of the valve, however, is the opening which it has at the time of maximum piston velocity.

For this reason one of the important advantages of my mechanism lies in the fact that it produces as great an efiective valve opening as does its nearestcompetitorthe mushroom follower type with from 8% to 20% greater total lift depending upon the valve timing thereby reducing stresses 'wear due to inertia effects throughout the and noise.

E. It gives an effective valve openingat where these entire valve mechanism from crank-shaft gear to valve springs and valve seat. The

modern tendency toward high speed internal' combustion motors renders such considerations imperative, and in reality it is these inertia forces which limit the speed of such motors. 1

To summarize br1efly, the advantages of my valve mechanism are:

A. It lends. itself readily to the opera-- tion of inlet and exhaust valves by one cam.

B. It involves a simple, symmetrical cam, easily laid out and ground. a

C. It is accessible, both for adjustments and for replacements.

D. It eliminates guides for the followers, with resulting decrease in friction, wear maximum piston speed equal to the maximum valve opening.

F. It proportions the valve opening to the rate of change in cylinder volume for both inlet and exhaust valves during that portion of the stroke throughout which the flow of gas 7 through the valve depends upon the pumping action of the piston thereby avoiding and eliminating carbureter troubles and fluctuating exhaust back pressure due to inertia of the gases.

V G. It gives low inertia forces at the points forces are particularly objectionable, i. e. at the time of opening and closing of the valve and at maximum valve lift, thus reducing stresses in the mechanism and permitting the use of alight spring- H. On account of the low inertia forces it is peculiarly adapted to the high speed motors now in demand.

I am cognizant of the fact that the operation' of two or more followers by a single cam' is not novel, and I make no claim to the same. My reason for illustrating my invention in mechanism embodying two valves driven by a common cam is that such a combination is peculiarly advantageous from theoretical, practical and commercial standpoints, and it was in such form that my inventionwas first reduced to practice. I also am aware of the fact that the interposition of pivoted, oscillating followers, whether with flat faced roller or single boss and pivot of and incapable of being 'rect motion for both.

- vacuum or the pressure created by used in the mechanical arts in many nstances. .I therefore make no claim to the same. Referring to Fig. 1 it will be appreciated that if cam. 1 rotated in a counter clockwise direction, the valves 7 and 8 would have to be inlet and exhaust valves, respectively. Furthermore the diameter of the base circle of the cam, the lift ofthe follower, and the distance from the cam to the the follower must all be correctly proportioned to obtain the proper although a slight variation between the ratioof valve lift and piston speed would not involve departure from the scope of my invention as defined in my appended claims. I

further admit that the same valve motion can be obtained by proper cam design in conjunction with a follower having a roller or a in head, but in such a case, the cam would be objectionable from the manufacturing standpoint, it beisig unsymmetrical the inlet and the exhaust valves with the cor- Having described my? invention, what I claim and desire to secure by.Letters Pat out, is:

1. In valve operating mechanism, the combination of a cam, a valve and a pivoted flat-faced follower interposed between the cam and valve; the cam, valve and follower being so constructed and relatively arranged that the diameter of the base circle of the cam, the lift of the cam and the distance from the cam to the center of movement of the follower, are proportioned .to afford a to operate both lift to the valve proportional to the piston speed during that portlon of the stroke in which the flow of gas depends upon the the piston. 2. In valve operatin mechamsm, the. combination of a cam, a p urality of valves and a corresponding number-of pivoted flatfaced followers interposed between the.cam and the valves; the cam, valves, and followers being so constructed and relatively arranged that the diameter of the base circle of thecam, the lift of the cam, and the distance from the cam to the center of movement of the follower, are proportioned to afford a lift to the valve proportional to the piston speed during that portion of, the stroke in which the flow of gas depends upon the vacuum or the pressure created by the piston.

3. In valve operating mechanism, the combination of a symmetrical cam, an inlet valve, an exhaust valve and a-pivoted flatfaced follower interposed between the cam and each valve; the cam',.valve and follower I being so constructed and relatively arranged that the diameter from the mm to the water of movemenj of In testimony whereof "I affix my signatme the followers are proportioned t0 afford "a, in presence of lbwe Witnesses. lift to the valves pmyomional b0 the piston speed during that poriion of the stroke in HARRY HUEBOTTER' 5 which the flow @f gzm depends upon the Witnesses:

vacuum 01* we pressure created by the pis- A, G. BUsH,

tun. HUGH Wmam

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