US2322173A - Valve actuating mechanism - Google Patents

Description

June 15, 1943. L. R. SPENCER VALVE ACTUATING MECHANISM Filed Dec 24, 19 11 INVENTOR.

HIS ATTORNEYS Patented June 15, 1943 VALVE ACTUATING MECHANISM Louis R. Spencer, West Hartford, Conn., assignor to Spencer Aircraft Motors, Inc., West Hartford, Cnn., a corporation of Connecticut Application December 24, 1941, Serial No. 424,343

6 Claims.

This invention relates to improvements in valve actuating mechanism wherein a cam actuated rocker arm engages a valve stem for effecting reciprocatory motion of said stem and particularly to that type of mechanism wherein the rcoker arm is capable of a limited rotary motion around its longitudinal axis to insure proper engagement between the surfaces of the rocker arm assembly which contact the valve stem and actuator cam, especially the latter. An actuating mechanism of this specific type is illustrated in my United States Letters Patent No. 2,226,985, granted December 31, 1940.

The primary object of the invention is to provide a pivotal support for the rocker arm which will insure proper positioning of the rocker with respect to its actuator cam and the valve stem under normal operating conditions.

In the structure disclosed in said Patent No. 2,226,985, the rocker arm is pivotally supported in a member which is free to revolve and which is also capable of a limited axial movement, and a further object is to effect the axial movement of the supporting member with a variable pressure which will permit said member to revolve rather freely for a limited period of time before the said member is forced to its limit of axial movement with the pressure that is applied under normal operating conditions.

A still further object is to utilize fluid pressure means for effecting the axial movement of rocker arm supporting member.

Still another object is to effect the axial movement of the rocker arm supporting member by fluid pressure means responsive to the lubricating system of the engine, of which the valve mechanism is a part, whereby the full force cleveloped by that system will not be exerted on the supporting member until it and the rocker arm have had opportunity to properly adjust themselves with respect to the valve stem and the actuator cam. 7

With these and other objects in view, the invention consists in certain details of construction and combinations and arrangements of parts, all as Will be hereinafter more fully described and the novel features thereof particularly pointed out in the appended claims.

In the accompanying drawing,

Figure 1 is a horizontal sectional view through the rocker arm and its supporting structure, the head of the valve stem being shown in plan;

Fig. 2 is a vertical section taken longitudinally of the rocker arm; and

Fig. 3 is an elevaticnal view of the free end of the rocker arm.

In the present illustration, there is shown a portion of the stem [0 of one of the valves con trolling the intake and exhaust passages of an internal combustion engine cylinder. The stem, as usual, has springs ll associated therewith to maintain its valve closed, and the valve is unseated by being depressed by a rocker arm l2 which, under the influence of its actuating cam l3, compresses spring II and opens the valve. The rocker arm has a disk I4 rockably held in a recess therein, adapted to engage the end face of the valve stem, and said arm also has a roller :5 journaled therein with which the cam l3 on cam shaft l3a engages. The rocker arm is sup ported on a hollow pivot pin l6 and lubricant is fed under pressure to the interior of said pin through a passage I! by the lubricating system of the motor. Pin I6 has radial ports therein through which the lubricant has access to a passage IS in the rocker arm and from this passage 58 the lubricant is diverted by ducts [9 in disk 14 to the contacting surfaces of the disk and valve stem and to a tube 20 which discharges into a recess 2| in which the roller is located to lubricate the periphery of said roller. Rocking motion of disk [4 is limited by a set screw 22.

It has been found that, in the event the periphery of the roller 15 does not engage flatly against the surface of the actuator cam, particularly during the upward movement of the arm, the metal at the contact point will be overstressed and start breaking away. For instance, as illus- 'trated in dotted lines in Fig. 3, if the periphery of the roller I5 is tilted with respect to the cam surface, contact is made only at a point which tends to localize stresses. For this reason, the pivot pin I6 is supported in a member 23 which is capable of at least a limited rotary motion which will permit the rocker arm to revolve about its longitudinal axis, so that the roller l5 can accommodate itself to the peripheral surface of its actuator cam. Preferably, member 23 is of circular sleeve-like formation, closed at one end by an end wall 24 for purposes which will presently appear. Any suitable means may be provided for limiting the rotary motion of member 23.

The member 23 is preferably carried in a circular opening in the wall of the engine block and, as it is free to revolve in said opening, it is necessarily free to slide axially therein. Consequently, the rotation of the cam shaft in a clockwise direction, or away from said member 23,

causes the wiping action of the cam on the roller to exert an endwise pull on the rocker. For this reason, the wall of the opening in the engine block is formed with a stop, such as a shoulder 25 against which the member 23 engages. It has been proposed to provide means for normally holding member 23 firmly against its stop 25. For instance, Patent No. 2,226,985 proposes the use of a spring between the end wall 24 of member 23 and the exterior closure 26 for opening the engine block. However, it has been found that such arrangements are not entirely satisfactory, particularly because the endwise pressure exerted against member 23 is either such as to bind said member and prevent it from adjusting itself circumferentially, or too little, so that the member is not held properly against the shoulder forming the seat or stop for limiting axial movement of the member. Also, where a spring is used, the member 23 is permitted to hammer in its supporting opening if the spring breaks. To overcome these difficulties, the present invention provides fluid pressure means for forcing member 23 against its seat or stop 25. Preferably, a variable pressure is utilized. That is, the axial pressure initially imposed on the member is comparatively low, so that there is no tendency for the member to bind against its seat. Thus, the member might be said to be free to float in the sense that it can rotate freely in its opening and permit the surfaces of roller l5 and actuator cam to adjust themselves to each other. The pressure gradually builds up or increases and the member is then firmly positioned against the stop 25. This gradual increase in the fluid pressure can be produced in several ways, but, for simplicity, it is preferred that passage I! be connected to the force lubricating feed of the motor, of which the cylinder forms a part. By-passes 21 in member 23, communicating with passage I1 and the space 28 between closure 26 and end wall 24 of said member, supply lubricant to said space under the pressure developed in the lubricating system. When the motor is first started, this pressure, as stated, will be so slight as to not materially interfere with the member 23 adjusting itself circumferentially, and, as the speed of the motor increases, the pressure of the lubricant in chamber 28 will gradually increase andpress the member 23 firmly against its seat or stop.

What I claim is:

1. In a valve actuating mechanism. a cylindrical rotatable member, a rocker arm pivoted in said member having a valve stem engaging surface, said member being rotatable about an axis disposed longitudinally of the rocker arm, a seat for said cylindrical member, and fluid pressure means for forcing said member in a direction lengthwise of the rocker arm against its seat.

2. In a valve actuating mechanism, a valve stem rocker arm, a member in which said arm is pivoted, said member being rotatably supported and movable axially of its support, a stop for limiting axial movement of said member in one direction, and fluid pressure means for forcing said member against said stop.

3. In a valve actuating mechanism, a valve stem rocker arm, a member in which said arm is pivoted, said member being rotatably supported to rock about an axis disposed longitudinally of the rocker arm, and movable axially of its support, a stop for limiting axial movement of said member in one direction, and means for moving said member axially lengthwise of the rocker arm toward said stop with an increasing pressure until a maximum pressure is exerted on said member.

4. In a valve actuating mechanism, a valve stem rocker arm having an oil duct therein, a member in which said arm is pivoted, said member having an oil passage therein communicating with the duct in the rocker arm and said member being rotatable and movable axially, a stop for limiting axial movement of said member in one direction, and means for by-passing oil from the passage in said member against a surface of said member to force the same axially against said stop.

5. In a valve actuating mechanism, a valve stem rocker arm, a piston member in which said arm is pivoted, a supporting structure having a cylindrical cavity therein, said piston member being rotatable and slidable axially in said cylindrical cavity, an abutment on the wall of said cavity for limiting axial movement of the piston member, and means for supplying fluid under pressure to said cavity to force the piston member toward said abutment.

6. In an internal combustion engine having a force-feed lubricating system, a valve stem actuating mechanism comprising, in combination, a rocker arm, a piston member in which the arm is pivoted, a cylinder in which said piston member is movable axially and rotatable about an axis disposed longitudinally of the rocker arm, means for limiting axial movement of the piston in one direction, and means for supplying lubricant from said lubricating system to said cylinder for moving said piston axially lengthwise of the rocker arm toward said limiting means.

LOUIS R. SPENCER.

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