Air turbine starter with bearing support structure

A air turbine starter for starting an engine, comprising:

• a stator including a housing having an inlet, an outlet, and a flow path extending between the inlet and the outlet;
• a rotor including a turbine member defining a rotating axis and having a set of blades at least partially disposed within the flow path;
• a bearing support structure disposed between the rotor and the stator comprising a first bearing support having a first radial stiffness (K1) and a second bearing support having a second radial stiffness (K2) different than the first radial stiffness (K1);
• a set of flexible connectors elongated in an axial direction and extending from the first bearing support and to the second bearing support to define a spring-finger structure, the first radial stiffness at least partially defined by the set of flexible connectors, wherein the set of flexible connectors define a load path between the first bearing support and the second bearing support;
• a first bearing carried by the first bearing support and a second bearing axially spaced from the first bearing and carried by the second bearing support, wherein the first bearing and the second bearing are in a serial arrangement with respect to the rotating axis;
• and
• a spring or spacer extending between a portion of the bearing support structure and the second bearing for preloading the set of flexible connectors.

An air turbine starter for starting an engine, comprising:

• a stator including a housing having an inlet, an outlet, and a flow path extending between the inlet and the outlet;
• a rotor including a turbine member defining a rotating axis and having a set of blades at least partially disposed within the flow path;
• a bearing support structure disposed between the rotor and the stator comprising a first bearing support having a first radial stiffness (K1) and a second bearing support having a second radial stiffness (K2) different than the first radial stiffness (K1), wherein:
• the first bearing support is spaced from the stator by a distance (d) to define a displacement gap;
• the first bearing support can move in a radial direction toward the stator;
• the bearing support structure defines a dual differential thrust rated bearing system where K1<K2 and AT1>AT2;
• a set of flexible connectors elongated in an axial direction and extending between and connecting the first bearing support to the second bearing support to define a spring-finger structure, wherein the first radial stiffness is at least partially defined by the set of flexible connectors, and the set of flexible connectors define an axial space between the first bearing support and the second bearing support;
• a first bearing carried by the first bearing support;
• a second bearing axially spaced from the first bearing, the second bearing being carried by the second bearing support, wherein at least one of the first bearing or the second bearing is axially moveable with respect rotating axis, wherein an axial movement of the first bearing partially defines a first axial/thrust load capability (AT1) for the first bearing support, wherein the first axial/thrust load capability (AT1) is different than a second axial/thrust load capability (AT2) of the second bearing support;
• and
• a squeeze film damper located in the displacement gap.

A bearing support structure comprising:

• a first bearing support having a first stiffness (K1);
• a second bearing support having a second stiffness (K2) greater than the first stiffness (K1);
• a set of flexible connectors extending between and connecting the first bearing support to the second bearing support;
• a first bearing carried by the first bearing support;
• a second bearing axially spaced from the first bearing, the second bearing being carried by the second bearing support;
• and
• a spring or spacer extending between a portion of the bearing support structure and the second bearing.