Patent Description:
Centering spring bearing supports have been used on legacy engines to provide the appropriate stiffness at the bearing location to balance the engine's overall rotor dynamics and load signature. The type of center spring design has evolved, but it typically contains some elements of beams or rods that allow radial displacement that is limited and damped by an oil film.

At one location, a bearing damper pedestal and oil and air feed passages are formed into an intermediate case of the gas turbine engine, which complicates the intermediate case casting. Also, in such configurations the intermediate case requires plating or hardcoat application at the location of bearing damper piston rings. Also there are overall manufacturing improvements that can be gained by moving the damper surface, and the damper pedestal, which requires tight tolerances, wear resistant coatings and direct oil/air feeds, to a smaller and less complicated part.

<CIT> discloses a gas turbine engine having an accessory gearbox, the accessory gearbox including bearings for both an output shaft and towershaft. <CIT> discloses a power take-off system for a gas turbine engine have a drive shaft and rotor shaft both supported by a shaft support structure. <CIT> discloses a towershaft for a gas turbine engine supported by a gear pedestal.

According to a first aspect of the present invention, a bearing compartment of a gas turbine engine includes a case element, a towershaft bearing located in the case element and supportive of a towershaft, and a shaft bearing located in the case element and supportive of an engine shaft. The towershaft extends from the engine shaft and is coupled to the engine shaft via a towershaft gear.

An integral gear support and bearing damper pedestal includes a support base secured to the case element, and a gear support arm extending from the support base to the towershaft bearing. The gear support arm is supportive of the towershaft bearing. A bearing damper pedestal extends from the support base to the shaft bearing and is located radially outboard of a bearing outer race of the shaft bearing. The assembly includes a bearing centering spring including a base portion secured to the case element, a bearing interface portion secured to the bearing outer race, and a plurality of beams extending between the base portion and the bearing interface portion. The plurality of beams are located radially outboard of the bearing damper pedestal. The bearing interface portion is located radially inboard of the bearing damper pedestal.

Optionally, one or more supports extend from the case element to the bearing damper pedestal.

Optionally, the one or more supports extend between circumferentially adjacent beams of the plurality of beams.

Optionally, the base portion and the support base are secured to a same case flange of the case element.

Optionally, one or more openings are formed in the bearing centering spring and are configured for passage of fluid or air therethrough.

Optionally, the one or more openings are formed in a spring flange of the bearing centering spring, extending between the plurality of beams and the bearing interface portion.

Optionally, one or more ribs extend from the bearing damper pedestal configured to improve a rigidity of the bearing damper pedestal.

According to another aspect, there is provided a gas turbine engine according to claim <NUM>.

Optionally, the case element is an intermediate case and the shaft bearing is supportive of an outer engine shaft.

The following descriptions are by way of example only and should not be considered limiting in any way.

A detailed description of one or more embodiments of the disclosed invention is presented herein by way of exemplification and not limitation with reference to the Figures.

The geared architecture <NUM> may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about <NUM>:<NUM>. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans.

Referring now to <FIG>, the gas turbine engine <NUM> includes a towershaft <NUM> coupled to one or more of the inner shaft <NUM> and the outer shaft <NUM> via a towershaft gear <NUM>. While the disclosure herein can be applied at either of the inner shaft <NUM> or the outer shaft <NUM>, the following exemplary description will reference the outer shaft <NUM>. The towershaft <NUM> utilizes rotational energy of the outer shaft <NUM> to drive accessories of the gas turbine engine <NUM> and/or an aircraft to which the gas turbine engine <NUM> is installed. The towershaft <NUM> is supported by a towershaft bearing <NUM>. A shaft bearing <NUM> supports the outer shaft <NUM>. The towershaft <NUM> and the shaft bearing <NUM> are located in an intermediate case <NUM> of the gas turbine engine <NUM>.

A gear support <NUM> is secured to the intermediate case <NUM> at, for example, a case flange <NUM> extending from an inner case surface <NUM> of the intermediate case <NUM>. The gear support <NUM> includes a support base <NUM> located at the case flange <NUM>. A plurality of bolts <NUM> are installed through the support base <NUM> and the case flange <NUM> to secure the gear support <NUM> to the case flange <NUM>.

The gear support <NUM> includes a gear support arm <NUM> extending to a support of the towershaft bearing <NUM> and a bearing damper pedestal <NUM> extending toward the shaft bearing <NUM>. The shaft bearing <NUM> includes a bearing outer race <NUM>, a bearing inner race <NUM>, and a plurality of bearing elements <NUM> located between the bearing outer race <NUM> and the bearing inner race <NUM>. A bearing centering spring <NUM> is further secured to the case flange <NUM> via the plurality of bolts <NUM>. The bearing outer race <NUM> is supported by the centering spring <NUM>. The centering spring <NUM> extends circumferentially around the engine central longitudinal axis A.

The centering spring <NUM> is annular in shape and includes a base portion <NUM> secured at the case flange <NUM> via the plurality of bolts <NUM>, and a bearing interface portion <NUM> located at and secured to the bearing outer race <NUM>. A plurality of beams <NUM> extend from the base portion <NUM> to the bearing interface portion <NUM>, the beams <NUM> circumferentially spaced from each other. The configuration of the beams <NUM> defines a spring rate or flexibility of the centering spring <NUM> to react loads on the bearing outer race <NUM>. In some embodiments, a circumferential thickness and/or a radial thickness of the beams <NUM> varies along an axial beam length. In some embodiments, the circumferential thickness and/or the radial thickness are at their minimums at or near a midpoint of the axial beam length. The centering spring <NUM> wraps around the bearing damper pedestal <NUM> such that the bearing interface portion <NUM> is located radially inboard of the bearing damper pedestal <NUM> and the plurality of beams <NUM> are located radially outboard of the bearing damper pedestal <NUM>.

Referring to <FIG>, in some embodiments, the intermediate case <NUM> may include one or more supports <NUM>, which extend from the inner case surface <NUM> through the openings between circumferentially adjacent beams <NUM> and to the bearing damper pedestal <NUM>. The one or more supports <NUM> aid in locating and radially supporting the bearing damper pedestal <NUM>. In other embodiments, the bearing damper pedestal <NUM> may include one or more ribs <NUM> extending from a radially outboard surface <NUM> of the bearing damper pedestal <NUM> and extending along an axial length of the bearing damper pedestal <NUM>. The one or more ribs <NUM> increase radial rigidity of the bearing damper pedestal <NUM> and are utilized as needed based upon bearing loads.

Referring now to <FIG>, the centering spring <NUM> includes one or more features to allow for oil and air services to seal <NUM> to be passed through the centering spring <NUM>. The features may include one or more service openings <NUM> defined in a spring flange <NUM> located radially between the plurality of beams <NUM> and the bearing interface portion <NUM>. The service openings <NUM> allow, for example, jumper tubes <NUM> to pass to the seal <NUM> via the centering spring <NUM>. Incorporation of the service openings <NUM> into the centering spring <NUM> instead of forming cored passages in the intermediate case <NUM> reduces the cost and complexity of the intermediate case <NUM> casting.

Utilizing the gear support <NUM> and centering spring <NUM> configurations described herein reduces cost and complexity of the intermediate case <NUM>, as the number of tight tolerance cast and machined surfaces are removed from the intermediate case <NUM>. Such surfaces are moved to a smaller and less expensive part, improving manufacturability and repairability. Further, orienting the beams <NUM> radially outboard of the shaft bearing <NUM> allows for better tuning of the beams <NUM> for load and stiffness without affecting overall bearing compartment or engine length.

Claim 1:
A bearing compartment of a gas turbine engine (<NUM>), comprising:
a case element (<NUM>);
a shaft bearing (<NUM>) located in the case element and configured to support an engine shaft (<NUM>; <NUM>);
a towershaft bearing (<NUM>) located in the case element and configured to support a towershaft (<NUM>) extending from the engine shaft and coupled to the engine shaft via a towershaft gear (<NUM>);
an integral gear support (<NUM>) and bearing damper pedestal (<NUM>), including:
a support base (<NUM>) secured to the case element;
a gear support arm (<NUM>) extending from the support base to the towershaft bearing (<NUM>), the gear support arm supportive of the towershaft bearing; and
a bearing damper pedestal (<NUM>) extending from the support base to the shaft bearing (<NUM>) and located radially outboard of a bearing outer race (<NUM>) of the shaft bearing; and
characterised in that
the bearing compartment further comprises:
a bearing centering spring (<NUM>) including
a base portion (<NUM>) secured to the case element (<NUM>);
a bearing interface portion (<NUM>) secured to the bearing outer race (<NUM>); and
a plurality of beams (<NUM>) extending between the base portion and the bearing interface portion; wherein
the plurality of beams (<NUM>) are located radially outboard of the bearing damper pedestal (<NUM>); and
the bearing interface portion (<NUM>) is located radially inboard of the bearing damper pedestal (<NUM>).