Annular dual piston brake arrangement

Claim 2

An annular 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; fluid actuating means for biasing said annular 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 axially telescoping, substantially radially aligned compact relation within said service brake piston; fluid retracting means for holding said secondary brake piston in a disengaged condition, limitedly axially separated from said service brake piston; and spring engagement means for biasing said secondary brake piston directly axially against said service brake piston for subsequent peripheral brake holding engagement of said rotatable member in the absence of a predetermined pressure in said fluid retraction means.

Claim 3

The annular dual piston brake arrangement of claim 1 including seal means disposed intermediate said support structure and said rotatable member to thereby define an internal chamber therebetween, and fluid circulating means for delivering fluid in a fluid path radially outwardly through said internal chamber in order fully peripherally to cool the annular brake arrangement, said fluid also serving to aid in retracting said service brake piston.

Claim 4

The annular dual piston brake arrangement of claim 2 wherein said support structure includes a thrust surface thereon and a plurality of internal teeth on which are keyed a plurality of annular plates, and said rotatable member includes a plurality of external teeth on which are keyed a plurality of annular discs interleaved with said plates, said discs and plates being biased together and against said thrust surface upon axial movement of said service brake piston toward the brake holding position and being disposed in said fluid path.

Claim 5

The annular dual piston brake arrangement of claim 1 including retracting spring means for axially disengaging said service brake piston from said rotatable member in the absence of a predetermined pressure in said fluid actuating means.

Claim 6

The annular dual piston brake arrangement of claim 4 wherein said fluid actuating means includes a service brake actuation chamber defined between said support structure and said service brake piston, and a control system therefor permitting a predetermined volume of fluid to be exhausted from said chamber upon the selctive release of said service brake piston away from a brake holding position to thereby limit its maximum amount of travel and improve its reengagement response.

Claim 7

The annular dual piston brake arrangement of claim 4 including alignment means for establishing an axial free sliding nonrotating relation between said support structure and said secondary brake piston, and wherein said support structure has a plurality of cavities therein and said secondary brake piston has a corresponding plurality of opposing cavities therein, and said spring engagement means includes a plurality of compression springs individually seated within each of said aligned cavities.

Claim 8

The annulAr dual piston brake arrangement of claim 6 including guide pin means intermediate said secondary brake piston and said service brake piston for establishing axial free sliding and nonrotating cooperation therebetween.

Claim 9

The annular dual piston brake arrangement of claim 7 wherein said secondary brake piston includes a plurality of axial bores therethrough concentric with a limited number of said cavities, and said guide pin means includes a plurality of shouldered guide pins secured to said service brake piston and extending through said bores, and said retracting spring means includes a plurality of retracting compression springs individually mounted on said shouldered guide pins.

Claim 10

The annular dual piston brake arrangement of claim 8 wherein said service brake piston includes an axially inwardly open counterbore adapted to closely receive said secondary brake piston reciprocably therein, said secondary brake piston adaptable for relatively limited axial movement between an abutting position with said counterbore to a retracted position axially spaced away from said counterbore and serving to additionally axially compress said retracting compression springs.

Claim 11

An annular dual piston brake arrangement for use with a wheel of a vehicle, comprising; a support structure nonrotatably secured to the vehicle; a rotatable member operatively associated with such wheel; a stacked plurality of annular braking plates assembled so that alternate ones thereof are respectively connected to said rotatable member and said support structure; an annular service brake piston axially reciprocably and nonrotatably mounted within said support structure; fluid actuating means for axially biasing said annular service brake piston concentrically into peripheral engagement with said stacked plurality of annular braking plates for effecting brake holding engagement of said rotatable member and said wheel; an annular secondary brake piston axially reciprocably and nonrotatably mounted within said support structure and so constructed and arranged that said secondary brake piston and said service brake piston are nestably disposable in radially overlapping axial force transmitting contact; fluid retracting means for holding said secondary brake piston in a disengaged condition, limitedly axially separated from said service brake piston; and spring means for biasing said secondary brake piston directly axially against said service brake piston for subsequent brake holding engagement of said rotatable member in the absence of a predetermined pressure in said fluid retraction means.

Claim 12

An annular dual piston brake arrangement for use with a wheel of a vehicle, comprising; a support structure nonrotatably secured to the vehicle; a rotatable member operatively associated with such wheel; a stacked plurality of annular braking plates assembled so that alternate ones thereof are respectively connected to said rotatable member and said support structure; an annular service brake piston axially reciprocably and nonrotatably mounted within said support structure; fluid actuating means for axially biasing said annular service brake piston concentrically into peripheral engagement with said stacked plurality of annular braking plates for effecting brake holding engagement of said rotatable member and said wheel; an annular secondary brake piston axially reciprocably and nonrotatably mounted within said support structure and so constructed and arranged that said secondary brake piston and said service brake piston are nestably disposable in radially overlapping axial force transmitting contact; fluid retracting means for holding said secondary brake piston in a disengaged condition, limitedly axially separated from said service brake piston; and spring means for biasing said secondary brake piston directly axially against said service brake piston for subsequent brake holding engagement of said rotatable member in the absence of a predetermined pressure in said fluid retraction means.