Dual piston brake arrangement and cooling circuit therefor

A dual piston brake arrangement for selective holding engagement of a rotatable member of a drive train, comprising;

• a support structure;
• an annular service brake piston axially reciprocably and nonrotatably mounted within said support structure including a plurality of fluid flow directing passages therethrough;
• fluid actuating means for biasing said service brake piston concentrically toward a brake holding position with respect to such rotatable member;
• an annular secondary brake piston axially reciprocably and nonrotatably mounted within said support structure in substantially radially aligned relation within said service brake piston for axially telescopic selective movement from an abutting to a separated condition therefrom;
• spring engagement means acting upon said support structure for biasing said secondary brake piston directly axially against said service brake piston;
• fluid retracting means for holding said secondary brake piston in a disengaged condition in overcoming relation with respect to said spring engagement means;
• seal means intermediate said support structure, said service brake piston and said secondary brake piston serving to define a spring chamber therebetween;
• and
• a fluid circulating apparatus for delivering a fluid radially outwardly toward said rotatable member for cooling thereof and subsequently along an egress path including flow of said fluid through said plurality of fluid flow directing passages in said service brake piston and through said spring chamber.