Variable ratio brake pedal lever assembly

#The invention relates to a variable ratio brake pedal lever system and mor particularly to one utilizing a cam arrangement on the pedal lever and a cam follower arrangement on the master cylinder push rod to shift the effective point at which force is transferred from the brake pedal lever during brake actuating movement of that lever so as to increase the effective brake pedal ratio during brake actuating movement from a release position to a full brake apply position. In one modification the brake pedal lever is a unitary member. In another modification it is a jointed member having yieldable means resisting jointed movement until a predetermined amount of brake pedal force is applied. When the predetermined force is reached and exceeded, the jointed movement of the pedal lever occurring due to yielding action of the yieldable means causes the pedal ratio to increase at a faster rate than when the pedal lever is a unitary member.

#In the Drawings:

#FIG. 1 illustrates a portion of a vehicle with parts broken away and in section and showing in elevation a brake pedal lever assembly embodying the invention. The assembly is in the brake release position.

#FIG. 2 illustrates the brake release position and the full brake apply position of the mechanism of FIG. 1, parts being broken away and in section and the full brake apply position being in phantom lines.

#The vehicle 6 is illustrated as having a brake actuating system installed so as to be readily operable by the vehicle operator. The system includes a master cylinder 8 which is actuated by a push rod 10. One end 12 of the push rod is pivotally mounted to a portion of the master cylinder in a manner well-known in the art so as to permit push rod pivotal movement of the type illustrated in FIG. 2 as the pedal lever system is actuated. The brake pedal lever 14 is pivotally mounted on pivot 16, which is provided on a fixed brace 18 forming a part of the vehicle body. The master cylinder 8 is illustrated as being mounted on the fire wall 20 of the vehicle body. A cam follower 22 is mounted on the other end of push rod 10. The follower is illustrated as being of the roller type in order to minimize friction losses and provide an adequate force transmitting arrangement. Guide checks may be provided on each side of such a roller. A first cam surface 24 is formed on one edge of the brake pedal lever 14 and so arranged that it is engaged in camming relation by the cam follower 22. Cam surface 24 extends generally along the lever edge from a first point 26 to a second point 28. The first point 26 is spaced from the pivot 16 of lever 14 toward the food-engageable end of the brake pedal lever, and the second point is spaced in the same direction but further from the pivot 16 than the first point. A cam follower surface 30 is provided on the push rod 10 adjacent the end on which the cam follower 22 is mounted. Cam follower surface 30 extends axially along the lower side of the push rod from the cam follower 22 toward the push rod end 12. A cam 32 is formed on the brake pedal lever 14 and extends generally toward the master cylinder 8 from the brake pedal lever second point 28 so as to engage the cam follower surface 30 and provide a fulcrum point 34 for the push rod 10. A cam follower stop 36 is formed on the brake pedal lever at the first point 26 of cam follower 24. In the embodiment illustrated, the stop 36 is essentially an extension of the first cam surface 24, covering an arcuate portion of substantially the same radius as that of the roller type cam follower. A sufficient arc is utilized so that the cam follower 22 will engage the stop 36 and remain against it without tending to roll out of the depression formed by the stop and the cam surface 24 in the brake pedal lever edge.

#When the system is in the brake release position shown in FIG. 1 and shown in solid lines in FIG. 2, the cam follower 22 engages the first cam surface 24 immediately adjacent the second point 28. Cam 32 engages the cam follower surface 30, tending to support the push rod 10 at the cam follower end. For this purpose cam follower surface 30 is on the bottom of the push rod with cam 32 extending slightly upwardly. Also, cam surface 24 extends at a slight angle relative to the center line of lever 14 passing through the axis of pivot 16. The plane in which cam surface 24 is positioned, if extended, would pass between pivot 16 and the master cylinder 8.

#Movement of the brake pedal lever 14 by the vehicle operator is accomplished in the usual manner. The operator's foot is pressed against the brake pedal 38 on the end of the lever 14 opposite pivot 16 so as to move lever 14 arcuately about pivot 16 in a clockwise direction as seen in the drawings. This lever movement causes the push rod 10 to move axially to pressurize brake fluid in the master cylinder 8. It also causes cam 32 to move in an upward arc as it moves axially along the cam follower surface 30, forcing the push rod to move pivotally about push rod end 12 in the plane of the brake pedal lever movement. The arrangement is such that this causes movement of cam follower 22 along the first cam surface 24 toward the first point 26. This decreases the distance between the point of engagement of cam follower 22 with cam surface 24 and pivot 16, thereby increasing the effective pedal lever ratio as brake actuating movement increases. If the brake pedal lever is moved to its full extent in the brake actuating direction, the cam follower 22 will engage cam follower stop 36 to prevent further camming movement.