Patent Description:
Fan blades for gas turbine engines are typically retained by the root in a holding disc in use, and subject to large centrifugal forces, such that the root of the fan blade is subject to high levels of wear over time. This may be mitigated by bonding a wear resistant material to the surface of the root so as to provide a sacrificial material to protect the fan blade.

<CIT> discloses tooling for fastening metal reinforcement on the leading edge of a turbine engine blade, the tooling including a blade support for receiving a blade while leaving surfaces of the leading edge of the blade disengaged; and a leading edge reinforcement support on which the blade support is designed to be mounted, and including two lateral wedges between which the metal reinforcement for the leading edge of the blade is positioned, the wedges being suitable for being capable of moving towards each other and apart from each other and each of them being provided with a suction grid for gripping the metal reinforcement.

<CIT> discloses a device for attaching a wear strip to at least one contact face of a turbo engine rotor blade, which device comprises heat-generating means for activating a product for attaching the wear strip to the blade, where the heat-generating means are designed to generate heat only on the wear strip and on the at least one contact face of the blade.

<CIT> discloses a method for repairing a laminated article having a damaged area comprising the steps of: removing the damaged area from the laminated article so as to leave a repair site; positioning a repair patch to cover the repair site; placing one or more heat blankets over the repair patch and other selected locations; placing the laminated article with the repair patch in a vacuum bag; placing the vacuum bag in an autoclave; operating the autoclave within a selected range of desired temperatures and pressures; and, curing the repair patch of the laminated article.

According to an aspect, there is provided a fixing apparatus for fixing a secondary component to a fan blade, the fixing apparatus comprising: a first clamp part comprising a first inner surface and a second clamp part comprising a second inner surface, the first inner surface and the second inner surface having a profile corresponding to a profile of a portion of the fan blade; wherein the first clamp part and/or the second clamp part comprises a recess in the respective first inner surface and/or second inner surface for receiving the secondary component, and a corresponding heater for applying heat to the secondary component located in the recess in use; wherein the first clamp part and the second clamp part are configured to cooperate with one another to clamp the portion of a blade between them in a clamping operation and to hold the secondary component against the blade when the secondary component is received within the recess.

The portion of the fan blade may comprise the root of the fan blade. The portion of the fan blade may comprise the whole fan blade. The secondary component may comprise a hard wearing material such that it serves as an anti-wear component on the fan blade. In particular, the secondary component may be disposed on the root of the fan blade to protect the root of the fan blade from damage when it is retained in a holding disc.

The fixing apparatus may comprise a cavity in the first clamp part and/or second clamp part for receiving a temperature sensor for monitoring the temperature of the secondary component in the clamping operation. The cavity may be embedded in the first clamp part and/or the second clamp part.

The fixing apparatus may comprise a temperature sensor disposed in the cavity. The temperature sensor may be a thermocouple. The temperature sensor may be a pyrometer.

In the first clamp part and/or the second clamp part which comprises the cavity, there may be a tube extending from the cavity to the respective inner surface. The tube may be configured to permit removal and replacement of the temperature sensor in the cavity.

The first inner surface and the second inner surface may have profiles corresponding to a profile of a root of the fan blade.

The recess may define an elongate strip shape. The elongate strip shape may extend along an axis. The axis may extend in a direction corresponding to a chordwise extent of the root of the fan blade.

The secondary component may be configured to be a sacrificial component comprising a sacrificial material, such as a Vespel®.

One of the first clamp part and the second clamp part may comprise a plurality of locating pins. The other of the second clamp part and the first clamp part may comprise a corresponding plurality of locating holes for receiving the locating pins when the first clamp part and the second clamp part cooperate with one another in the clamping operation.

Embodiments will now be described, by way of example only, with reference to the accompanying Figure, in which:.

<FIG> shows a cross-sectional view of a fan blade arrangement <NUM> for a gas turbine engine. The fan blade arrangement <NUM> comprises a fan blade <NUM> comprising a root <NUM> and an aerofoil portion <NUM>.

The fan blade arrangement <NUM> further comprises a pair of secondary components <NUM> disposed on either side of the root <NUM>. The secondary components <NUM> are fixed to the root <NUM> and protrude from the root <NUM>. The secondary components <NUM> are configured to provide an interference fit for the root <NUM> within a holding disc in use.

The secondary components <NUM> are shaped in elongate strips to provide protruding strips on the surface of the root <NUM>. The secondary components <NUM> are elongate along an axis, and the axis of the secondary components may extend along a chordwise axis of the fan blade arrangement <NUM> (i.e. into the page with reference to <FIG>). In other examples, the secondary component may be positioned in any suitable location on the fan blade, and the axis may extend in any suitable direction on the fan blade.

The secondary components <NUM> serve as a sacrificial component on the fan blade arrangement <NUM>, to protect the fan blade <NUM> from damage when held in a holding disc during use. In this example, the material of the secondary component <NUM> is a Vespel®. In other examples, the material of the secondary component <NUM> may be any fibre reinforced plastic (FRP). The secondary component material may be a hard-wearing material. The material of the secondary component may have a lower hardness than the material of the fan blade so that the secondary component preferentially wears in use to protect the fan blade.

The fan blade <NUM> comprises a FRP, in this example carbon fibre reinforced plastic (CFRP). In other examples, the fan blade <NUM> may comprise any suitable material.

<FIG> shows a close up side view of a second example fan blade arrangement <NUM>. The second example fan blade arrangement <NUM> is similar to the first example fan blade arrangement <NUM>, and differs only in that there are two pairs of secondary components <NUM> disposed on either side of the fan blade <NUM>. <FIG> shows only one side of the fan blade <NUM>, such that only two secondary components <NUM> are visible.

One pair of secondary components <NUM> are in the same position on the root <NUM> as the secondary components <NUM> in the first example fan blade arrangement <NUM>, described with reference to <FIG> (i.e. the axis extends in a chordwise direction along the root <NUM>).

The second pair of secondary components <NUM> are disposed on either side of the aerofoil portion <NUM> of the fan blade <NUM>. The axes of these secondary components <NUM> extends in a direction having a chordwise direction component, and a spanwise direction component and are also configured to protect the fan blade from wear from the holding disc in use.

<FIG> shows a cross-sectional view of a fixing apparatus <NUM> around a portion of a fan blade <NUM>. The fixing apparatus <NUM> is configured to perform a clamping operation to fix a secondary component <NUM> to the fan blade <NUM>. In this example, the fixing apparatus is configured to form a fan blade arrangement <NUM> as described with reference to <FIG>. In this example, the portion of the fan blade <NUM> is the root <NUM>. In other examples, the portion of the fan blade may be any part of the fan blade, or the whole fan blade.

The fan blade <NUM> in this example is cured before the secondary component <NUM> is applied to the fan blade <NUM> in the clamping operation.

The fixing apparatus <NUM> comprises a first clamp part <NUM> and a second clamp part <NUM>. The first clamp part <NUM> comprises a first inner surface <NUM> which has a profile corresponding to a profile of the portion of the fan blade, in this example, the root <NUM>.

The second clamp part <NUM> comprises a second inner surface <NUM> which has a profile corresponding to a profile of an opposing part of the root <NUM> to the first clamp part <NUM>. The first clamp part <NUM> and the second clamp part <NUM> are configured to cooperate with one another to clamp the root <NUM> between them. In this example, the first clamp part <NUM> and the second clamp part <NUM> are made from CFRP. In other examples, the first clamp part and the second clamp part may comprise any suitable material.

In this example, the first clamp part <NUM> comprises a first recess <NUM> in the first inner surface <NUM> for receiving the secondary component <NUM>. The second clamp part <NUM> comprises a second recess <NUM> in the second inner surface <NUM> for receiving another secondary component <NUM>. The first recess <NUM> and the second recess <NUM> are shaped to receive the secondary components <NUM>, such that in this example, the first recess <NUM> and the second recess <NUM> are of an elongate strip shape extending along an axis. The axis of the recess extends in a direction corresponding to a chordwise axis of the fan blade <NUM> (or the root <NUM>). In the clamping operation, secondary components <NUM> are received in respective the first and second recesses <NUM>, <NUM>.

In this example, the recesses <NUM>, <NUM> are <NUM> deep to accommodate the secondary components <NUM>. The first and second recess <NUM>, <NUM> have the same net shape as the secondary components <NUM> such that the secondary components <NUM> can be snugly received within the first and second recess <NUM>, <NUM>.

In some examples, only the first clamp part may comprise a recess or only the second clamp part may comprise a recess. In other examples, there may be more than one recess in either of the first clamp part or the second clamp part, each for receiving an additional secondary component.

The first clamp part <NUM> and the second clamp part <NUM> are configured to hold the secondary components <NUM> received in the first and second recesses <NUM>, <NUM> against the root <NUM> during the clamping operation. A controlled pressure is applied to the first clamp part <NUM> and the second clamp part <NUM>. In this example, the controlled pressure is applied via pneumatics. The secondary components <NUM> are provided with a film adhesive on a surface of the secondary component <NUM> which contacts the root <NUM>. The film adhesive bonds the secondary component <NUM> to the root <NUM> on heating. In this example, the film adhesive is epoxy. In other examples, the film adhesive may be any suitable material.

The first clamp part <NUM> further comprises a first heater <NUM> corresponding to the first recess <NUM>. The second clamp part <NUM> comprises a second heater <NUM> corresponding to the second recess <NUM>.

The first heater <NUM> and second heater <NUM> are configured to apply heat to the secondary component <NUM> when received in respective first recesses <NUM> and second recess <NUM> to cure the film adhesive, and bond the secondary component <NUM> to the root <NUM>. In this example, the first heater <NUM> and the second heater <NUM> are configured to apply heat to heat the secondary component to at least <NUM> degree Celsius. The first heater and the second heater may be configured to stop heating when the secondary component is at a maximum temperature of approximately <NUM> degrees Celsius, in order to avoid damaging the fan blade, a metal work bond line between metal components and the fan blade or the secondary component. In examples where there are more recesses for receiving additional secondary components, there may be a corresponding heater for each recess. In some examples, there may be one or more heaters in each clamp part, each of which is configured to heat a plurality of secondary components in a corresponding plurality of recesses.

The first heater <NUM> is disposed within the first clamp part <NUM> and the second heater <NUM> is disposed within the second clamp part <NUM>. In other words, the heaters <NUM>, <NUM> are embedded in the respective first clamp part <NUM> and second clamp part <NUM>. In other examples, they may be disposed on an outer surface of the first clamp part and second clamp part.

In some examples, there may be heatsinks disposed around the heaters to ensure that the fan blade is not damaged by over-heating. Using a material for the adhesive that only needs to be heated to <NUM> degrees Celsius, for example, to activate, ensures that heatsinks are not necessary.

In this example, the fixing apparatus <NUM> further comprises a first cavity <NUM> in the first clamp part <NUM>, and a second cavity <NUM> in the second clamp part <NUM>. The first cavity <NUM> and the second cavity <NUM> are for receiving a temperature sensor <NUM> for monitoring the temperature of the secondary component <NUM> in the respective first recess <NUM> and second recess <NUM>, during the clamping operation. The temperature is monitored to ensure that it is sufficiently high to cure the adhesive, but not so high as to damage the secondary component <NUM>, the root <NUM> or the adhesive between them.

There may be a controller to control the first heater <NUM> and the second heater <NUM>. The controller may receive signals from the temperature sensors <NUM>, and may be programmed to ensure that the temperature is maintained within a lower bound and an upper bound, such as with a negative feedback loop in response to the signals received from the temperature sensor <NUM>.

In this example, the first cavity <NUM> is embedded in the first clamp part <NUM> close to the first recess <NUM>, and the second cavity <NUM> is embedded in the second clamp part <NUM> close to the second recess <NUM>. In some examples, the cavity may be in the form of a recessed cavity in the first inner surface of the first clamp portion or the second clamp portion, as opposed to being embedded.

<FIG> shows a temperature sensor <NUM> disposed in the first cavity <NUM> and in the second cavity <NUM>. In other examples, there may be a temperature sensor embedded in the first clamp part and/or the second clamp part, such that there is no cavity. In further examples, there may be no temperature sensor or associated cavity.

In some examples, there may be additional auxiliary temperature sensors disposed further away from the recesses. If an auxiliary temperature sensor, which is disposed further away from the first recess or second recess, registers an abnormally high temperature during a clamping operation, this may indicate that there is an unexpected heatsink, such that the clamping operation may be aborted and reset. The registering of a heatsink may be due to misalignment of the first clamp part <NUM> and the second clamp part <NUM>, or misalignment of the root <NUM> within the first clamp part <NUM> and second clamp part <NUM>.

In this example, the temperature sensor is a thermocouple. In other examples, the temperature sensor may be a pyrometer. Using a pyrometer means that the temperature sensor does not have to be embedded in the first clamp portion or the second clamp portion. In an example where the temperature sensor is a pyrometer, the first clamp portion and/or the second clamp portion comprise through holes to allow light to shine through them for operation of the pyrometer.

The first clamp part <NUM> comprises a first tube <NUM> extending from the first cavity <NUM> to the first inner surface <NUM>. The second clamp part <NUM> comprises a second tube <NUM> extending from the second cavity <NUM> to the second inner surface <NUM>. The first tube <NUM> and the second tube <NUM> are configured to permit removal and replacement of the temperature sensor in the respective first cavity <NUM> and second cavity <NUM>.

The second clamp part <NUM> comprises a plurality of protruding locating pins <NUM>, which are configured to be received in corresponding locating pin seats (i.e. locating holes, such as blind holes) in the first clamp part <NUM> so that the first clamp part <NUM> and the second clamp part <NUM> can be clamped together reliably during the clamping operation. In some examples, there may be a plurality of pins in the first clamp part which are configured to be received in corresponding pin seats in the second clamp part. In other examples, there may be a plurality of pins in both the first clamp part and the second clamp parts, and a plurality of corresponding pin seats in the first clamp part and the second clamp part which are each configured to receive a pin.

Use of the fixing apparatus <NUM> in a clamping operation to fix a secondary component <NUM> to a fan blade <NUM> ensures that heat and pressure can be applied in a controlled and reliable manner to the secondary component <NUM>. This results in a more even bondline thickness and fewer voids than in previously considered methods.

Further, consumables to hold the secondary component to the fan blade, such as a vacuum bag and tape, are not required. Therefore, the fixing apparatus <NUM> requires fewer consumables to form a fan blade arrangement <NUM>, and provides a more reliable means of positioning and adhering secondary components <NUM> to a fan blade <NUM>.

Although it has been described that the first clamp part and the second clamp part have inner surfaces with profiles corresponding to a profile of the root, the profile of the inner surfaces may not correspond directly with the profile of the portion of the blade, but may have any suitable profile to securely clamp the portion of the blade between them.

Claim 1:
A fixing apparatus (<NUM>) for fixing a secondary component (<NUM>, <NUM>) to a fan blade (<NUM>), the fixing apparatus (<NUM>) comprising:
a first clamp part (<NUM>) comprising a first inner surface (<NUM>) and a second clamp part (<NUM>) comprising a second inner surface (<NUM>), the first inner surface (<NUM>) and the second inner surface (<NUM>) having a profile corresponding to a profile of a portion of the fan blade (<NUM>); and
a heater for applying heat to the secondary component;
characterised in that the first clamp part (<NUM>) and/or the second clamp part (<NUM>) comprises a recess in the respective first inner surface (<NUM>) and/or second inner surface (<NUM>) for receiving the secondary component (<NUM>, <NUM>), wherein the heater is for applying heat to the secondary component located in the recess in use;
wherein the first clamp part and the second clamp part are configured to cooperate with one another to clamp the portion of a blade between them in a clamping operation and to hold the secondary component against the blade when the secondary component is received within the recess.