US1731344A - Shock-absorbing device for valves - Google Patents

Description

Oct. 15, 1929. c MCLEOD 1,731,344

SHOCK ABSORBING DEVICE FOR VALVES Filed April 19, 1927 \D 5 ZNVKNTOR,

Patented Oct. 15, 1929 CLIFFORD J. 'MQLEOD, F QUINCY, MASSACHUSETTS SHOCII-ALBSORBING DEVICE FOR VALVES Application filed April 19, 1927. Serial No. 185,039.

This invention relates to a mechanism for silencing poppet valves and for preventing wear therein. While it may be applied to reciprocating valves in general, it finds a particular use in such valves as are commonly used for admitting charges of explosive mixture into internal combustion engines and permitting the discharge of Waste gases therefrom. Valves of this type are customarily spring-actuated to their closing position, and are opened by mechanism which pushes against the end of the valve stem and against the pressure of the valve spring. When the valve-lifting or opening member is retracted 5 to allow the valve to .close, the valve moves toward its seat under the action of the valve spring and in ordinary valve construction the valve strikes its seat with a considerable blow behind which is the full force ofthe valve spring. This blow on the valve seat produces considerable noise which is objectionable and also causes unduly rapid wear between the valve and its seat. invention to provide mechanism for elimi- 'nating to a large extent the noise and wear customarily incident to the operation of poppet valves. Incidental noise in the operation of. valves also arises from the fact that in order to insure the complete closing of the valve at all times, the valve litter in ordinary construction must clear the end of the valve stem when the valve is seated in order to provide for wear between the valve and its seat and for expansion of the stem by heat. When therefore the valve lifter is moved .to open the valve, the clearance between it and the end of the valve stem causes it to strike the end of the valve stem a sharp blow which in turn causes objectionable'noise 40 in the .operation of the valve. My invention is intended to eliminate this source of noise also. In order to carry out my invention, I

rovide-a yielding connection between the valve lifter and the end of the valve stem, this 4 connecting member being of such construction as to yield easily during the first portion of motion of the valve lifter toward the valve stem, the easy yielding of the member rapidly changing to a strong resistance preferably equal to the compressive force of the It is an object of this valve spring itself. This yielding member may be carriedby the valve litter and is preferably movable so as to enga e at all times the end of the valve stem so t at there is no clearance between the valve stem and the member to be taken up when the lifter moves in a valve-lifting direction.

During the closing movement of the valve, the force of the valve spring is preferably balanced by the opposing force of the yielding member between the valve stem and the valve lifter so that as the valve lifter moves away from the valve stem in permitting the valve to close, the greater part of the pressure ofthe valve spring on the valve is opposed at 05 the instant when the valve engages its seat. Thus the spring-pressed blow of the usual valve on itsseat is avoided and the full pressure of the valve spring on the valve is built up through a brief interval of time instead of becoming effective the instantthe valve reaches its seat.

For a more complete understanding of the invention, reference is bad to the description which follows and to the drawing, of which,

Figure 1 is an elevation, partly in section, of mechanism embodying my invention.

Figure 2 is an elevation of a portion of Figure 1 showing the parts in a different position of operation.

FigureS is a perspective View of the yielding element and a portion of the valve lifter.

Figure 4 is a perspective view of'a modified form of yielding element and valve lifter.

Figure 5 is an elevation, partly in section, of a modified form of the invention.

Figure 6 is an elevation of mechanismof the type shown in Figure 1, but having slight modifications.

Referring to the drawings in detail, 1 represents a yielding member or shoe normally supported in a recess in one arm of a rigid rocker bar 2. The rocker bar is mounted for rocking motion on a suitableshaft 11and may be actuated as by a push rod 8 which is suitably connected therewith. The opposite arm of the rocker bar is adapted to lift a valve 10 from its seat 9 by engaging the end of the valve stem 3 and pushing against the compression of a valve spring 6, one end of which bears against a suitable collar 12. According to the invention, the shoe 1 is interposed between the rocker bar 2 and the valve stem 3, this shoe having a longitudinally ex tending face 5 which is preferably convex or outwardly curved and which engages an opposing face 17 on the rocker bar 2. The face 17 is preferably concave for the greater part of its length, the curvature of the face 17 being variable but always less than the curvature of the shoe face 5, so that the shoe has a rolling or rocking engagement against the face 17 of the rocker bar. In order to maintain the shoe 1 in its proper position, the recess in the rocker arm which receives the shoe may be provided with end walls 21 adapted to engage the end surfaces of the shoe and to prevent longitudinal sliding motion thereof relative to the rocker bar.- The shoe itself may be provided with side rails 19 adapted to engage the side faces of the rocker bar and thus to prevent lateral movement of the shoe relative to the rocker bar. The shoe is so arranged that the end of the valve stem 3 engages the shoe directly at' point 24 adjacent to one end thereof. Pressure of the valve stem 3 against the end portion 24 of the shoe tends to cause the shoe to roll or rock on the surface 17 toward its end 24. In order to oppose this rocking motion of the shoe, a suitable spring such 'as the leaf spring 4 shown on the drawing may be provided to bear against the opposite end portion 25 and thus to tend to roll orrock the shoe on the surface 17 toward the end 25.

The pressure of the spring 4 and that of the valve stem 3 against opposing ends of the shoe thus causes the shoe to-act as a variable lever, the fulcrum being at the movable point of contact 22. Since a rocking motion of theshoe 1 produced by the valve stem '3 moves the fulcrum point 22 over in the direction of the end portion 24, the mechanical advantage against the valve stem and in favor of the s ring 4 rapidly increases since the lever arm etween the fulcrum point 22 and the point of contact between the valve stem and the shoe decreases while the lever arm be tween the point 22 and the spring pressed end 25 increases. Thus the spring 4 may be relatively weak compared wit-h the valve spring 6 but when the valve stem rocks the shoe so as to move the point 22 over near theend port-ion 21, the weaker spring 4 may balance the action of the valve'stem 3. As shown in Figure 1, the curvature of the face 17 of the rocker bar 2 is in general concave, but the end portion of the face adjacent to the spring 4 is shown with slightly reversed curvature. This enables the end 24 of the shoe to swing downwardly for a considerable distance if necessary to keep in 'contact with the end of the stem 3 at all times.

The curvature of the face 17 adjacent to the short portion of reverse curvature is prefon the valve 10 will be almost ture of the face 17 decreases 'asit extends away from the spring 4. The curvature of the convex face 5, however, may conveniently be made uniform, but is preferably greater than the maximum curvature of the face 17. As a result of this configuration of the opposing faces 5 and 17, during a rocking or rolling movement of the shoe 1 under pressure from the valve stem 3, the contact fulcrum point 22, as shown in Figure 1, moves rapidly toward the right during the early part of the rocking movement of the shoe 1. On account of the change in curvature of the face 17, the movement of the point 22 toward the right decreases in proportion to the movement of the end portion 24 of the shoe 1 toward the rocker bar 2 as the point of contact moves toward the left? Thus, when the rocker bar is actuated to open the valve, the reactive thrust of the valve stem 3 against the shoe 1 is resisted at first by a relatively weak pressure which' however rapidly mounts to a value preferably equal to the force of the spring 6 on the valve stem, so that by means of the leverage of the shoe 1, the springs 4 and 6 are balanced. A lip 23 may be provided at the outer end ofthe shoe 1 to engage a face 26 adjacent to the end of the rocker bar 2, but as ordinarily adjusted, the face 23 will not cont-act with the face 26, until the valve lifterhas moved far enough to lift the valve clear of its seat. The additional compression of the valve spring 6 incident to the full opening of the valve will, as. the device is usually adjusted, bring the also provide a convenient point for gaging to facilitate adjustment of the mechanism. The faces are preferably made so as to be parallel when the valve is closed and the lifting mechanism is in the position shown in Figure 2. When in this position the clearance between the gaging faces 23, 26 may be adjusted by manipulation of the checkfaces'23, 26 together. These facesmeasured by inserting a gage strip of desired thickness between the faces. When the rocker bar is moved to permit the valve to seat, the spring 6 is balanced by the spring 4 so that at the instant when the valve 10 reaches its seat 9, the force of the spring 6 entirely op posed by the reactive force of the shoe 1 on the valve stem 3. The instant after the valve is seated, further motion of the rocker bar 2 away from the valve stem will cause the shoe 1 to rock on the face 17, such rocking bemgaccompanied by a rapid decrease of pressure by the shoe against the valve stem 3, so that when the rocker bar reaches its furtherest position in a direction away from the valve, the shoe 1 will still be in contact with the end of the valve stem but will press against it with little force. This momentary opposition of the shoe 1 to the ress'ure of the spring 6 on the valve during the instant following the seating of the valve prevents the hammering of the valve against its seat under the full force of the spring 6 and thus both reduces wear on the valve and its seat and also eliminates a large percentage of the noise. The noise of the parts may also be further reduced by the interposition of a strip 27 of soft metal such as brass or copper, between the opposing faces and 17. This strip is shown as attached to the face 5, but it may if desired be attached to the face 17 or may be held loosely between the two faces. It is an important feature of my invention that the shoe 1 acts directly against the stem 3 without the interposition of other mechanism parts, the movement of which involves friction. Since the action of the shoe 1 and the spring 4 in relieving the valve of its usual blow against the seat 9 when the valve is closing depends on the force of the spring 4 opposing and balancing the spring 6, this opposing forcev would be decreased by any moving parts interposed between the spring 4 and the valve stem since the friction of the moving parts would reduce the efi'ectiveness of such opposition. I also regard the arrangement by which the shoe 1 is held against longitudinal transverse motion relative to the rocker bar 2 as important. The reliable and uniform operation of the device depends to a considerable extent on the prevention of alteration of the faces 5 and 17 through wear. Since the arm of the rocker bar 2 moves in an arc while the valve stem 3 moves in a straight line, there is necessarily a certain amount of sliding movement between the rocker arm and the end of the stem. This relative movement takes place between the outer face of the shoe 1 and the end face of the valve stem which engages it. Thus all the wear incident to such sliding movement is taken on the outer faceof the shoe, while the inner face 5 which rolls against the face 17 of the rocker bar 2 is held against relative sliding movement and therefore against appreciable wear thereon.

A modified form of the invention is illustrated in Figures 4 and 5, this form showing the invention adapted to a valve lifter which the other end' portion works in line with the valve stem rather than through a rocker bar. In the modified form, a push rod 37 is secured to a lifting member 39 which is provided with a face 32 on which ashoe 29 is held in rolling or rocking engagement. The valve stem 28 engages the shoe 29 at 'a point on the end portion 31, a spring 33 being arranged to press against 34. The spring 33 is held in place as by a suitable bolt 35 which is mounted in the lifter 39. The rocking motion of the shoe 29 under the influence of the valve stem 28 may be lifted by an end face 30 whichmay engage the face of the lifter 39. As shown in Figure 5, the face of the lifter may be plain, thecontacting face of the shoe beingconvexly curved with a curvature at the spring-pressed end 34 which increases toward the valve-pressed end 31.

Having thus described certain embodiments of this invention, it should be evident to those skilled in the art that various changes and modifications might be made therein without departing from its spirit or scope as defined by the appended claims.

I claim:

1. Valve-silencing mechanism comprising a rocker bar having an arm, a valve stem movable by rocking motion of said arm, and yielding means carried by said arm and engaging said stem, said yielding means including a member having direct rocking contact with said arm, said stem bein arranged to bear on the outer end portion 0 said member, and a spring bearing on the inner end portion of said member.

2. Valve-silencing mechanism comprising a rocker bar having an arm, a valve stem movable by rocking motion of said arm, and yielding means carried by said arm and engaging said stem, said yielding means including a member mounted for rocking motion on said arm, said stem being arranged to bear on one end portion of said member, and a spring fixed to said arm on the same side thereof with said member and directly en aging the opposite end portion of said mem er, the'arrangement being such that when the member rocks with respect to the arm, the length of the lever arm between the rocking fulcrum of the mem her and the point of contact of the spring on the member varies. I

3. In combination with a valve having a stem, valve-silencing mechanism comprising a rocker bar having an arm with a recess therein, a shoe carried in said recess, said shoe and arm having contacting faces for rocking engagement, and a spring one end portion of said shoe and tending to rock said shoe in one direction within said recess, said valve stem engaging the opposite end portion of said shoe and opposing the action of said spring on said shoe.

.4. Valve-silencing mechanism comprisin a valve stem, a member actuable to move sai stem, and a yielding member carried-by said stem-moving member in direct contact with said stem, said members having mutually engaging curved faces with different curvatures means thereon normally preventing relative endwise and lateral movement.

5. Valve-silencing mechanism comprising a valve stem, 9. member actuable to move said stem, and a yielding member carried by said stem-moving member in direct contact with said stem, one of said members having a recess bearing against.

for relative rocking movement and fitted to receive the other said member and with means to limit longitudinal transverse position.

7. Valve-silencing mechanism comprising a valve stem, a metal member actuable to move said stem, a metal yielding element carried by said member in rolling engagement therewith and in direct engagement with said stem, and a liner of softer metal between the opposing faces of said member and element.

8. Valve-silencing mechanism comprising a valve stem, a member actuable to move said stem, a yielding element between said member and stem having a convex face in rolling engagement with said member and one end portion in direct engagement with said stem, and a spring carried by said member and engaging the other end portion of said element, said member having a vconcave face engaged by said element, said concave face having a varying curvature less than that of said convex face and decreasing toward the end of the face remote from said spring.

9. Valve silencing mechanism comprising a valve stem, a member actuable to move said stem, a yielding element between said member and stem having a convex face in rolling engagement with said member and one end portion in direct engagement with said stem, and a spring carried by said member and engaging the other end portion of said element, said member having a concave face engaged by said element, said-concave face having a varying curvature less than that of said convex face and decreasing toward one end of the face.

10. Valve silencing mechanism comprising a valve stem, a member actuable to move said stem, a yielding element between said member and stem having a convexface in rolling engagement with said member and one end portion in direct engagement with said stem, and a spring carried by said member and engaging the other end portion of said element, said member having a concave face engaged by said element, said concave face having a varying curvature less than that of said convex face and decreasing toward both ends of the face.

11. Valve silencing mechanism comprising a valve stem, a member actuable to move said stem, a yielding element between said member and said stem, said member and element having confronting faces of different curvatures for mutual rolling engagement whereby when said element is rocked on said member, the point of contact moves longitudinally along said element, the curvature of. one of said faces being varied adjacent an end thereof to diminish the motion of the contact point caused by rocking said element when the point approaches said end, and a-spring carried by said member, said element having one end portion in direct engagement with said stem, and its opposite end portion in engagement with said sprin 12. Valve silencing mechanism comprising a rocker bar extending from a rocking axis, driving and driven reciprocable members operatively associated with said bar, and yielding means carried by of said members, said yielding means including an element having direct rocking contact with said bar, said engaged member being arranged to bear on one end portion of said element, and a spring having direct engagement with the opposite end portion of said element, said spring and forward element being located on the same side of said arm.

13. Valve silencing mechanism comprising a rocker bar having a pair of arms extending in opposite directions from the rocking axis, driving and driven reciprocable members as sociated respectively with said two arms, and yielding means carried by one of said arms and engaging its associated reciprocable member, said yielding means including a shoe mounted for rocking motion with respect to sald carrying arm, said associated member being arranged to bear on outer end portion of said shoe, and a spring fixed to said carrying arm and bearing on the of said shoe, the arrangement being such that when the shoe rocks with respect to the carrying arm, the length of the lever arm between the rocking fulcrums of the shoe and point of contact of the spring on the shoe varies.

CLIFFORD J. MoLEOD.

said bar engaging one inner end portion

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