Modulating arrangement for servo-motor actuated disc brake

Claim 1

A friction brake comprising: means defining a generally enclosed space containing engaging friction braking surfaces, a fluid operated servo-motor for urging the friction braking surfaces together, said servo-motor defining in part said generally enclosed space, and a retarding means for counterbalancing the urging force of the servo-motor to thus retard the engagement of the braking sufaces as a pressurized fluid is being supplied to the servo-motor, said retarding means comprising means for introducing oil under pressure directly into said generally enclosed space such that said oil under pressure also passes between the friction braking surfaces, the pressure of the oil in said generally enclosed space being sufficiently great to at least partially retard the urging force of the servo-motor tending to bring about engagement of the braking surfaces, said retarding means being operable to introduce said pressurized oil in response to the delivery of said pressurized fluid to the servo-motor to engage the friction braking surfaces and concurrent with the introduction of said fluid to the servo-motor, said retarding means further including limiting means for limiting the time during which the said oil is introduced to said generally enclosed space to only an initial part of the time during which brake engagement is being brought about, and for thereafter permitting reduction of the pressure in the said generally enclosed space to permit the servo-motor to complete the bringing about of brake engagement, said limiting means including a cylinder, a movable member within the cylinder, one side of the movable member being in a fluid communication with the pressurized fluid entering the servo-motor, and the other side of the movable member containing said oil and being selectively in fluid communication along a fluid path with the said generally enclosed space, whereby as the movable member moves from an original position under the force of the pressurized fluid being delivered to the servo-motor, the movable member urges said oil from the cylinder along said path to the said space and including a maximum pressure valve in said fluid path between the said other side of the movable member and the said generally enclosed space, said maximum pressure valve being openable to permit oil to flow therethrough only after the pressure thereagainst exceeds a predeterminable level, and including a further means separate from the movable member for modifying the opening of said maximum pressure valve independently of the movable member.