Patent Description:
Aircraft include a variety of shafts that transmit power from a source to another mechanism. For example, a shaft may connect a gas-breathing engine including a turbine to a generator. That is, the shaft may have a first end connected to a turbine output and a second end connected to a generator input. In some systems, the shaft may include an inner shaft that provides an interface to the turbine and the generator and an outer, torsional shaft. At certain operating speeds, the inner shaft may oscillate relative to the outer shaft. <CIT> describes a friction shaft damper for axial vibration mode. <CIT> describes an anti-resonance apparatus of a propeller shaft.

Disclosed in accordance with a non-limiting example is a shaft system having an outer shaft including an outer surface and an inner surface defining a conduit and an inner shaft extending within at least a portion of the conduit. The inner shaft includes a radially extending passage having a first end and a second end that is opposite the first end. A centrifugal force activated damper extends between the outer shaft and the inner shaft. The centrifugal force activated damper includes a first member arranged between the inner shaft and the inner surface at the first end of the radially extending passage, a second member arranged between the inner shaft and the inner surface at the second end of the radially extending passage, and a connecting member extending through the radially extending passage. The connecting member includes a first end section connected to the first member and a second end section that is received by the second member. Rotation of the shaft system causes the first member and the connecting member to shift away from the second member into the inner surface of the outer shaft.

Additionally, or alternatively, in this or other non-limiting examples, the first end section of the connecting member is fixedly connected to the first member.

Additionally, or alternatively, in this or other non-limiting examples, the first end section of the connecting member is integrally formed with the first member.

Additionally, or alternatively, in this or other non-limiting examples, the connecting member includes an outer surface portion that extends continuously from the first member to the second member.

Additionally, or alternatively, in this or other non-limiting examples, the first member includes an outer surface section that selectively engages the inner surface of the outer shaft.

Additionally, or alternatively, in this or other non-limiting examples, the contact between the outer surface section and the inner surface of the outer shaft generates a frictional force that dampens shaft oscillations.

Additionally, or alternatively, in this or other non-limiting examples, the first member includes a first mass and the second member includes a second mass that is substantially equal to the first mass.

Additionally, or alternatively, in this or other non-limiting examples, an input member is connected to the inner shaft.

Additionally, or alternatively, in this or other non-limiting examples, the outer shaft comprises a generator rotor shaft.

Additionally, or alternatively, in this or other non-limiting examples, the second member includes a central passage that is aligned with the radially extending passage, the connecting member extending into the central passage.

Also disclosed in accordance with a non-limiting example is an aircraft system including an air breathing engine including a compressor, a turbine mechanically connected to the compressor, and a combustor fluidically connected to the compressor and the turbine. A gearbox is connected to the turbine. A generator is connected to the gearbox through a shaft system. The shaft system includes an outer shaft including an outer surface and an inner surface defining a conduit and an inner shaft extending within at least a portion of the conduit. The inner shaft includes a radially extending passage having a first end and a second end that is opposite the first end. A centrifugal force activated damper extends between the outer shaft and the inner shaft. The centrifugal force activated damper includes a first member arranged between the inner shaft and the inner surface at the first end of the radially extending passage, a second member arranged between the inner shaft and the inner surface at the second end of the radially extending passage, and a connecting member extending through the radially extending passage. The connecting member includes a first end section connected to the first member and a second end section that is received by the second member. Rotation of the shaft system causes the first member and the connecting member to shift away from the second member into the inner surface of the outer shaft.

An aircraft system, shown in the form of an air-breathing engine is indicated generally at <NUM> in <FIG>. Air-breathing engine <NUM> includes a compressor <NUM> mechanically and fluidically connected to a turbine <NUM>. A shaft <NUM> mechanically connects compressor <NUM> with turbine <NUM>. A combustor <NUM> fluidically connects compressor <NUM> with turbine <NUM>. Combustor <NUM> includes a combustor inlet <NUM> connected to compressor <NUM> and a combustor outlet <NUM> connected to turbine <NUM>. Air is passed into combustor <NUM> from compressor <NUM>, combined with a fuel and combusted to form hot gases that pass into and expand through turbine <NUM> to create power.

A majority of the power generated by air-breathing engine <NUM> is used for flight operations. A portion of the power is used to drive a generator <NUM> that generates electrical power for the aircraft. Towards that end, generator <NUM> is connected to an output <NUM> of turbine <NUM> through a shaft system <NUM>. In a non-limiting example shown in <FIG>, shaft system <NUM> includes an outer shaft <NUM> that may define a rotor shaft <NUM>. Outer shaft <NUM> is supported in generator <NUM> by a first bearing <NUM> and a second bearing <NUM>. Outer shaft <NUM> includes an outer surface <NUM> and an inner surface <NUM> defining a conduit <NUM>. Outer surface <NUM> may support rotor windings (not shown).

In a non-limiting example, an inner shaft <NUM> is arranged within conduit <NUM> and selectively coupled to outer shaft <NUM>. In a non-limiting example, inner shaft <NUM> may be coupled to outer shaft <NUM> through a splined interface. Of course, other types of interfaces, both mechanical and otherwise are contemplated. Inner shaft <NUM> includes a first end <NUM> and a second end <NUM>. Second end <NUM> is opposite first end <NUM>. First end <NUM> includes an input member <NUM> that provides an interface with turbine output <NUM>. In a non-limiting example, turbine output <NUM> may take the form of a gearbox <NUM> (<FIG>). Inner shaft <NUM> includes an outer surface section <NUM> and an inner surface section <NUM> that forms a hollow interior <NUM>.

Referring to <FIG> and with continued reference to <FIG>, inner shaft <NUM> includes a radially extending passage <NUM> arranged proximate to first end <NUM>. Radially extending passage <NUM> includes a first passage portion <NUM> extending through outer surface section <NUM> into hollow interior <NUM> and a second passage portion <NUM> that is directly opposite first passage portion <NUM>. Second passage portion <NUM> extends through outer surface section <NUM> into hollow interior <NUM>.

In a non-limiting example, shaft system <NUM> includes a centrifugal force (CF) actuated damper <NUM> that reduces torsional differences between outer shaft <NUM> and inner shaft <NUM>. CF actuated damper <NUM> includes a first member <NUM>, a second member <NUM>, and a connecting member <NUM>. First member <NUM> is arranged between inner shaft <NUM> and inner surface <NUM> of outer shaft <NUM> at first passage portion <NUM> and second member <NUM> is arranged between inner shaft <NUM> and inner surface <NUM> of outer shaft <NUM> at second passage portion <NUM>. Connecting member <NUM> extends through radially extending passage <NUM> and includes a first end section <NUM> coupled to first member <NUM> and a second end section <NUM> arranged at second member <NUM>. Connecting member <NUM> includes an outer surface <NUM> that extends between first end section <NUM> and second end section <NUM>. Outer surface <NUM> is continuous in a non-limiting example. First member <NUM> possesses a first mass and second member <NUM> possesses a second mass that acts as a counter-balance to reduce an out-of-balance condition that could lead to unwanted vibrations.

In a non-limiting example, first end section <NUM> is fixedly attached to first member <NUM>. In another non-limiting example, first end section <NUM> is integrally formed with first member <NUM>. Second end section <NUM> may float relative to second member <NUM> in accordance with a non-limiting example. In a non-limiting example, second end section <NUM> is slidingly received by a passage <NUM> formed on second member <NUM>. That is, when shaft system <NUM> is exposed to rotational forces, first member <NUM> and connecting member <NUM> may move radially outward to frictionally couple inner shaft <NUM> and outer shaft <NUM> so as to dampen oscillations of the outer shaft relative to the inner shaft that may promote undue wear of shaft system components.

In a non-limiting example, first member <NUM> includes an outer surface section <NUM> that selectively engages inner surface <NUM> of outer shaft <NUM>. In a non-limiting example, as shaft system <NUM> rotates first member <NUM> shifts radially outwardly causing outer surface section <NUM> to engage with inner surface <NUM> of outer shaft <NUM>. As centrifugal force increases on first member <NUM>, outer surface <NUM> of first member <NUM> is forced into inner surface <NUM> of outer shaft <NUM>. Relative motion between outer surface section <NUM> and inner surface <NUM> of outer shaft <NUM> creates a frictional reaction force that resists or dampens oscillations that may be generated.

Claim 1:
A shaft system comprising:
an outer shaft (<NUM>) including an outer surface and an inner surface defining a conduit;
an inner shaft (<NUM>) extending within at least a portion of the conduit, the inner shaft (<NUM>) including a radially extending passage having a first end and a second end that is opposite the first end; and
a centrifugal force activated damper (<NUM>) extending between the outer shaft (<NUM>) and the inner shaft (<NUM>), the centrifugal force activated damper (<NUM>) including:
a first member (<NUM>) arranged between the inner shaft (<NUM>) and the inner surface at the first end of the radially extending passage;
a second member (<NUM>) arranged between the inner shaft (<NUM>) and the inner surface at the second end of the radially extending passage; and characterised by
a connecting member (<NUM>) extending through the radially extending passage, the connecting member (<NUM>) including a first end section connected to the first member (<NUM>) and a second end section that is received by the second member (<NUM>), wherein rotation of the shaft system causes the first member (<NUM>) and the connecting member (<NUM>) shift away from the second member (<NUM>) into the inner surface of the outer shaft (<NUM>).