Patent Description:
Gas turbine engines include face seal assemblies at various locations, such as at bearing compartments and/or to seal to rotating shafts. Low time, premature, wear of seal elements of face seal assemblies is problematic for gas turbine engine reliability and operability. Premature seal element wear can result in seal element fracture and lack of oil containment, thereby resulting in conditions such as cabin odor or smoke in the cabin.

<CIT> discloses a split mechanical seal incorporating a spring retainer.

<CIT> discloses a carbon seal assembly for a main shaft bearing compartment of a gas turbine engine.

<CIT> discloses a face seal arrangement of a gas turbine engine. <CIT> discloses an intelligent adjustment system and method for mechanical seals.

In a first aspect there is provided a face seal assembly that includes a seal carrier, a seal element supported by the seal carrier, a rotating seal plate interactive with the seal element to define a face seal, and a seal arrester configured to engage the seal carrier at a predetermined amount of wear of the seal element to stop wear of the seal element; characterised in that contact of the seal arrester to the seal carrier completes an electrical circuit to initiate an alarm.

Optionally, a spring element is configured to urge the seal carrier and the seal element toward the seal plate.

Optionally, the seal arrester prevents urging of the seal carrier and the seal element toward the seal plate via the spring element.

Optionally, the assembly includes a seal support, with the seal carrier and the seal element housed in the seal support.

Optionally, the seal arrester is secured to the seal support.

Optionally, the seal arrester is secured via one or more of a snap fit or installed in a groove of the seal support.

Optionally, the seal arrester includes an arrester base and an arrester arm extending from the arrester base, the arrester arm configured to engage the seal carrier. Optionally, the seal arrester is contoured to improve oil circulation at the seal arrester.

Optionally, the seal element includes a nose portion configured to engage the seal plate.

In a second aspect there is provided a gas turbine engine that includes a turbine, a rotating shaft driven by the turbine, a bearing assembly supportive of the shaft, and a face seal assembly configured to seal the bearing assembly. The face seal assembly includes a seal carrier, a seal element supported by the seal carrier, a rotating seal plate interactive with the seal element to define a face seal, and a seal arrester configured to engage the seal carrier at a predetermined amount of wear of the seal element to stop wear of the seal element; wherein contact of the seal arrester to the seal carrier completes an electrical circuit to initiate an alarm.

Certain exemplary embodiments will now be described in greater detail by way of example only and with reference to the accompanying drawings, in which like elements are numbered alike:.

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 invention is applicable to other gas turbine engines including direct drive turbofans.

The fan section <NUM> of the engine <NUM> is designed for a particular flight condition--typically cruise at about <NUM> Mach and about <NUM>,<NUM> feet (<NUM>,<NUM> meters).

Referring now to <FIG>, illustrated is an embodiment of a face seal assembly <NUM> located at a bearing assembly <NUM>. The bearing assembly <NUM> in this embodiment is located at the outer shaft <NUM>, but one skilled in the art will appreciate that the bearing assembly <NUM> and face seal assembly <NUM> may be utilized at the inner shaft <NUM> or at other rotating components of the gas turbine engine <NUM>. The face seal assembly <NUM> seals between a bearing compartment <NUM> and a buffer air cavity <NUM>.

A seal plate <NUM> is secured to and rotates with the outer shaft <NUM>. A seal element <NUM>, formed from carbon, for example, is urged toward the seal plate <NUM> to define the face seal. The seal element <NUM> is supported by a seal carrier <NUM>. In some embodiments, the seal element <NUM> and the seal carrier <NUM> are urged toward the seal plate <NUM> by a spring element <NUM>. The seal carrier <NUM>, the seal element <NUM> and the spring element <NUM> are housed in a stationary seal support <NUM>. The seal element <NUM> includes a nose portion <NUM> that during operation contacts a sealing face <NUM> of the seal plate <NUM>. As the seal plate <NUM> rotates about the engine central longitudinal axis A relative to the seal element <NUM>, the nose portion <NUM> is eroded or worn away.

Referring now to <FIG>, to prevent over wear of the seal element <NUM> and damage to the seal element <NUM> and/or the seal carrier <NUM>, an arrester <NUM> is secured to the seal support <NUM>. When the nose portion <NUM> has completely worn away or has worn past a predetermined location, the seal carrier <NUM> contacts the arrester <NUM>. This contact prevents further travel of the seal carrier <NUM> and the seal element <NUM>, and thereby prevents further wear of the seal element <NUM>. The face seal thus transitions from a contacting face seal to a close-clearance butt gap seal.

In the embodiment of <FIG>, the arrester <NUM> includes an arrester base <NUM>, with an arrester arm <NUM> extending from the arrester base <NUM> toward the seal element <NUM>. The arrester base <NUM> is affixed to the seal support <NUM>, and in particular to a support arm <NUM> of the seal support <NUM>. In some embodiments a contact surface <NUM> of the arrester arm <NUM> is configured to contact the seal element <NUM> when the seal element <NUM> is worn. Further, the contact surface <NUM> is, in some embodiments, located at a same axial location as the contact surface <NUM> of the seal plate <NUM>. In one embodiment, such as in <FIG>, the arrester arm <NUM> is curvilinear along its length to aid in circulation of oil flow in the bearing compartment <NUM>.

In another embodiment, such as shown in <FIG>, the arrester <NUM> is snapped or press fit to the seal support <NUM>. Alternatively, the arrester <NUM> may be secured to the seal support <NUM> by, for example, a threaded connection. Referring now to <FIG>, the arrester <NUM> may be a retaining ring <NUM> disposed in a retaining groove <NUM> of the seal support <NUM>, and which extends radially inwardly toward the seal element <NUM>. In another embodiment, illustrated in <FIG>, the seal carrier <NUM> includes a carrier flange <NUM> extending radially outwardly from the seal carrier <NUM>, radially inboard of the arrester <NUM>. As the seal element <NUM> wears, the carrier flange <NUM> translates axially toward the arrester arm <NUM>, which then limits travel of the seal carrier <NUM> by acting as an axial stop. This configuration increases radial engagement of the arrester <NUM> to the seal carrier <NUM> and allows the arrester arm <NUM> to be positioned axially distant from the seal plate <NUM>.

Referring again to <FIG>, the arrester <NUM> is configured to provide an alarm, for example in a cockpit or other location. In such embodiments, the seal carrier <NUM> is utilized to complete an electrical circuit, when contact between the seal carrier <NUM> and the arrester <NUM> is initiated. When the circuit is completed, an alarm indicator <NUM> such as a light or audible alarm is triggered.

Use of the arrester <NUM> stops seal element <NUM> wear at a selected level when the seal carrier <NUM> contacts the arrester <NUM>, preventing more catastrophic failure of the seal assembly. Additionally, the arrester <NUM> provides an active means for detection of seal element <NUM> wear, via the alarm indicator <NUM>.

Claim 1:
A face seal assembly (<NUM>), comprising:
a seal carrier (<NUM>);
a seal element (<NUM>) supported by the seal carrier (<NUM>);
a rotating seal plate (<NUM>) interactive with the seal element (<NUM>) to define a face seal (<NUM>); and
a seal arrester (<NUM>) configured to engage the seal carrier (<NUM>) at a predetermined amount of wear of the seal element (<NUM>) to stop wear of the seal element (<NUM>);
characterised in that contact of the seal arrester (<NUM>) to the seal carrier (<NUM>) completes an electrical circuit to initiate an alarm.