Air turbine starter having a force balanced, pressure energized, weighted check valve

A check valve assembly for placement between and for selectively providing fluid communication between a first environment, at least a portion of which is at a first pressure (P1), and a second environment, at least a portion of which is at a second pressure (P2), wherein the difference between the first and second pressures generate a pressure force (Fp), the check valve assembly comprising:

• a backing plate having an inlet port, an outlet port, and a flow passage extending therebetween;
• a cage coupled to the backing plate, at least one portion of the cage extends across the flow passage;
• a protrusion extending from a surface of the at least one portion of the cage configured to selectively contact the valve element;
• a valve seat adjacent to the cage and having an opening therethrough, the valve seat opening in fluid communication with the valve body flow passage;
• and
• a valve element disposed between the valve seat and the valve body and having a density that is greater than the density of the fluid to be communicated between the first environment and the second environment, the valve element capable of being acted upon by a gravitational force (Fw), a viscous force of the fluid to be communicated between the first environment and the second environment (Fv), a buoyancy force of the valve element (Fb), and the pressure force on the valve element (Fp), the valve element further configured to translate axially to a closed position when P2<P1 and Fw<Fv+Fb+Fp.

An air turbine starter, comprising:

• a starter housing adapted to couple to a gearbox assembly, the starter housing including an opening configured to provide fluid communication between the gearbox assembly and the starter housing, wherein at least a portion of the gearbox assembly is at a pressure of P1 and at least a portion of the starter housing is at a pressure of P2, thereby generating a pressure force (Fp) therebetween;
• and
• a check valve assembly disposed within the opening, the check valve assembly comprising:
• a valve body having an inlet port, an outlet port, and a flow passage therebetween;
• a valve seat adjacent the valve body and having an opening therethrough, the valve seat opening in fluid communication with the valve body flow passage;
• and
• a valve element disposed between the valve seat and the valve body and having a density that is greater than the density of the fluid to be communicated between the gearbox assembly and the starter housing, the valve element capable of being acted upon by a gravitational force (Fw), a viscous force of the fluid to be communicated between the gearbox assembly and the starter housing (Fv), a buoyancy force of the valve element (Fb), and the pressure force on the valve element (Fp), the valve element further configured to translate axially to a closed position when P2<P1 and Fw<Fv+Fb+Fp.