Patent Description:
In gas turbine engines, compressors and turbines typically have axially arranged sets of rotors, each comprising an array of blades mounted to rotor discs. The respective sets of rotors are located between end shafts on a tension stud that extends through all or part of the set of rotors. In operation, the rotation of the rotors causes high separation forces to develop in the rotors. To counter these separation loads, a compression load is applied to the shaft and the rotors prior to use to offset the separation loads that develop in operation. To develop the compression load in the shaft and rotors, the tension stud is stretched during assembly to develop a tension within the tension stud. The tension stud is then held in its stretched form by a load retainer that engages with the shaft. The tension stud will react against the shaft via the load retainer to apply the compression load to the shaft.

Due to the high separation loads encountered in operation, there are high compression loads applied to the shaft, which may cause deformation of one or more parts of the shaft, such as the journal. A deformed journal diameter, i.e. non-cylindrical, compromises the operation of the bearing it is paired with in operation. One solution to matching the geometry of the journal to the bearing is to machine the journal once the whole rotor assembly has been constructed. However, this is a complicated process and requires whole rotor assembly to be fitted in a machine.

<CIT> there is disclosed a protective assembly engaging in case of tensile failure comprising an elongate tubular member, and a catcher rod. The tubular member has a first end portion and an opposite second end portion, and a fuse portion is positioned between the first end portion and the second end portion. A cross-sectional area of the tubular member is reduced at the fuse portion. The catcher rod has a first end portion and an opposite second end portion, with the catcher rod being accommodated concentrically within the tubular member. The second end portion of the catcher rod is secured to the second end portion of the tubular member. The first end portion of the tubular member is provided with a first divergent conical portion, and the first end portion of the catcher rod is provided with a second divergent conical portion. In the event of breakage of the tubular member, the second divergent conical portion impinges against the first divergent conical portion to limit the axial movement of the tubular member. <CIT> relates to a mounting structure to mount an engine to the wing of an aircraft.

Therefore, there is a need to provide a safe method for providing a shaft with a journal that matches the geometry of a bearing.

According to the present disclosure there is provided an apparatus and method as set forth in the appended claims.

According to a first aspect of the invention, there is provided an assembly comprising a safety apparatus , according to claim <NUM>.

Hence there is provided a safety apparatus that enables a sub-assembly of the rotor assembly to be safely stored and transported for machining after a load has been applied to the sub-assembly. The safety apparatus is suitable for containing energy released from a sub-assembly in the event of a failure of one or more components and/or connections of the sub assembly. The provision of the safety apparatus significantly reduces the risk to nearby workers and equipment as any energy released by a failure of one or more components will be restrained by the safety apparatus. Further, the provision of safety apparatus enables the sub-assembly to be safely transported for machining.

In one example, the plurality of containment members comprises a first containment member and a second containment member having a central axis therebetween, wherein the at least two arms of the first containment member and the at least two arms of the second containment member project towards the central axis. The provision of a first containment member and a second containment member with arms projection towards each other means that an energy release will be contained by multiple arms.

In one example, the adapter is shaped such that a first end of the adapter is configured to engage with a first shaft having a first profile and a second end of the adapter is configured to engage with a second shaft having a second profile, different to the first profile. As such, the adapter may be used with shafts of different shapes and sizes.

The sub-assembly may also include a compression body engaged with the second end of the shaft, a tool head engaged with the tension stud and an actuator located between the compression body and the tool head for applying a load to the tool head and the compression body. The at least one connecting member may include a first connecting member connected to the compression body and a second connecting member connected to the adapter. The provision of a compression body, actuator and tool head provides a mechanism to apply a tension load to the tension stud and a corresponding compression load to the shaft, which is required to counter separation forces that develop in operation.

The first connecting member may be connected to the compression body via a first quick release pin and the second connecting member may be connected to the adapter via a second quick release pin. The use of quick release pins means that the safety apparatus may be quickly and securely connected to the sub-assembly.

In one example, the compression body includes a protective covering configured to cover at least part of the shaft. There may be sensitive components within the assembly that may be easily damaged or sensitive to knocks. By providing the protective covering, the compression body may fulfil the dual role of transferring load from the actuator to the shaft and also protecting some components of the assembly from damage.

The sub-assembly may also include a transport plate configured to receive the tension stud, wherein the load retainer is located between the transport plate and the shaft. The at least one connecting member may include a first connecting member connected to the transport plate and a second connecting member connected to the adapter. The provision of the transport plate provides a fixture point for a connecting member and so enables the sub-assembly and safety frame to be transported together in a state that is ready for machining.

In one example, the sub assembly includes a first machine centre configured to engage with the adapter; and a second machine centre configured to engage with the transport plate. The first and second machine centres enables the assembly to be quickly placed in the machine ready for machining.

The tool head may include a removable insert, the removable insert including a male thread for engaging with a co-operative female thread of the tool head; and a female thread for engaging with a co-operative male thread of the tension stud. The removable insert may be made of a higher grade material compared with the rest of the tool head.

The assembly may include a measurement apparatus configured to measure the elongation of the tension stud. The measurement apparatus may be used to determine that the tension stud has extended by a pre-determined amount, equivalent to a pre-determined tension load being developed in the tension stud and hence, a pre-determined compression load being applied to the shaft.

According to another aspect of the invention, there is provided a method of shaping a journal of a shaft of a rotor sub-assembly using the safety apparatus as described above, the method includes applying a pre-determined compression load to the shaft, wherein the pre-determined compression load results in a deformation of the journal to produce a loaded journal with a substantially concave profile and shaping the loaded journal to produce a substantially cylindrical loaded journal, wherein when the pre-determined compression load is removed, the journal has a substantially convex profile. Applying a pre-determined compression load to the shaft effectively recreates the compression load that the shaft will be subject to in operation, which in turn recreates the deformation or barrelling of the journal. In the loaded state, the shaft is then shaped or machined back to a cylindrical shape, i.e. the effect of the barrelling is removed. When the pre-determined load is removed from the shaft, then the journal will have a substantially concave profile, but when this load is re-applied, for example when the shaft is part of the rotor assembly, then the journal will deform back to the cylindrical shape. Therefore, the effects of a misalignment between the journal and a bearing on which the journal is supported due to barrelling is removed and a bearing with a cylindrical inner profile may be used.

In one example, the step of applying the a pre-determined compression load to the shaft includes engaging an adapter with a first end of the shaft, engaging a compression body with a second end of the shaft, engaging a tool head with a tension stud extending through the shaft, providing an actuator between the compression body and the tool head, actuating the actuator to provide a load to the compression body and the tool head to cause the tension stud to extend and the pre-determined compression load to be applied to the shaft; and engaging a load retainer with the second end of the shaft to retain the load in the shaft.

The method may also include the step of connecting the safety apparatus to the compression body and/or the adapter prior to actuating the actuator. The provision of the safety apparatus means that the load can be applied to the tension stud and shaft in safety, and there is reduced risk of a nearby operator becoming injured due to a failure of one or more components as the release of energy will be contained within the safety apparatus.

The step of shaping the loaded journal may include removing the tool head, the actuator and the compression body, providing a transport plate that receives the tension stud, wherein the load retainer is located between the transport plate and the shaft, connecting the safety apparatus to the transport plate and/or the adapter, engaging a first machine centre with the adapter, engaging a second machine centre with the transport plate, positioning the first machine centre and the second machine centre between centres of a machine, removing the safety apparatus and machining the journal of the shaft.

<FIG> shows an example of a rotor assembly <NUM> of a gas turbine engine. A tension stud or tension bolt <NUM> is provided in the axial centre of the rotor assembly <NUM>, along an axis A of rotation of the rotor assembly <NUM>. In one example, the gas turbine engine is an SGT-<NUM>, SGT-<NUM> or an SGT-<NUM>.

In operation, the rotor assembly <NUM> is arranged to rotate about the axis A of rotation. All rotor parts shown in the figures may be substantially rotationally symmetric about the axis A of rotation. Stator parts are not shown in the figures and elements that interlock the rotors may not be shown in the figures.

One or more shaft elements <NUM>, <NUM>, such as an inlet shaft <NUM> and exit shaft <NUM>, and compressor discs <NUM> are provided around the tension stud <NUM> and configured to rotate about the axis A of rotation. The shaft elements <NUM>, <NUM> and the compressor discs <NUM> may be interlocked axially between axially adjacent rotating parts. For example, the inlet shaft <NUM> and the compressor discs <NUM> may comprise corresponding teeth that mesh together to interlock the inlet shaft element <NUM> and the compressor disc <NUM>. A plurality of rotor blades <NUM> are held in place by the compressor discs <NUM>. In one example, a rotor blade comprises a "t-shaped" root that is held in place between correspondingly shaped sections of the compressor discs <NUM>. In other examples, the rotor blades <NUM> may extend from the compressor discs <NUM> themselves in the form of a blisk.

As such, the tension stud <NUM>, the inlet shaft <NUM>, the compressor discs <NUM> and the rotor blades <NUM> may rotate together at the same speed about the axis A of the rotor. The tension stud <NUM> may be rotated into a threaded engagement into a threaded bore of an exit shaft <NUM> or alternatively be received in a retention nut (not shown), which engages with the exit shaft <NUM>.

The inlet shaft <NUM> includes one or more journals <NUM> that are configured to engage with one or more journal bearings (not shown) to enable the rotor assembly <NUM> to rotate about the Axis A.

In one example, the bearing may be a tilt-pad bearing. The tilt-pad bearing includes a plurality of white metal pads matched to the geometry of the journal <NUM>. In use, the pads may pivot within the bearing, which is flooded with oil. When the shaft <NUM> is rotated at to working speed, a film of oil is present between the inlet shaft <NUM> and the pads so there is no metal to metal contact between the journal <NUM> and the white metal pads of the bearing. However, the use of bearings such as tilt-pad bearings is highly reliant on the geometry being matched between the journal and the bearing. If this geometry is not aligned then there may be metal-to-metal contact, which causes friction, wear and energy loss within the rotor assemble <NUM>.

In operation, as the rotor assembly <NUM> rotates about the rotation axis A, high separation forces develop in the discs <NUM> and rotor blades <NUM>. In order to counteract these separation loads, the inlet shaft <NUM> and exit shaft <NUM> are preloaded with a compression load. As such, the discs <NUM> and rotor blades <NUM> will not separate in operation.

In order to apply the compressive loads to the inlet shaft <NUM>, the tension stud <NUM> is subject to a tension load. A load retainer <NUM> is attached to one end of the tension stud <NUM> and engages with one end of the inlet shaft <NUM>. As the load retainer <NUM> is supported by the inlet shaft <NUM>, the tension in the tension stud <NUM> causes a compression load to develop in the inlet shaft <NUM>.

<FIG> shows an example of a schematic of a part of a rotor assembly <NUM>. In the example shown in <FIG>, the tension stud <NUM> has been subjected to a tension load and is held in tension due to the presence of the load retainer <NUM>, which engages with the inlet shaft <NUM> causing a compression load to develop in the inlet shaft <NUM>.

Due to the compression load in the inlet shaft <NUM>, the inlet shaft <NUM> may deform. For example, the journal <NUM> may deform by barrelling such that part of the journal bulges outwards, as shown in <FIG>. Barrelling of the journal <NUM> is undesirable as it may compromise the function of the associated bearings employed, especially tilt pad type bearings in which the accuracy of the geometry between the bearing and the journal <NUM> is essential. As such, to minimise the effect of the deformation of the journal <NUM> when subject to a compression load, the journal <NUM> of the inlet shaft <NUM> is machine precision finished prior to final assembly within the rotor assembly <NUM>.

In order to simulate the deformation of the journal <NUM> when subject to the compressive load as part of the final rotor assembly <NUM>, the inlet shaft <NUM> is subject to a temporary compression load designed to simulate the compression load that the inlet shaft <NUM> will be subject to when part of the final rotor assembly <NUM>.

<FIG> shows an example of a first sub-assembly <NUM> comprising a tool apparatus <NUM> for applying a load an inlet shaft <NUM> and tension stud <NUM>.

The tool apparatus <NUM> includes a compression body <NUM> configured to engage with the inlet shaft <NUM> of the rotor assembly <NUM>. The compression body <NUM> has a profile at one end that corresponds with a shape of one end of the inlet shaft <NUM> to ensure a positive engagement between the compression body <NUM> and the inlet shaft <NUM>. The compression body <NUM> may be substantially cylindrical with an axial hole therethrough such that one end of the tension stud <NUM> may be received in the compression body <NUM>. The compression body <NUM> may have substantially cylindrical shaped walls which may include an aperture to enable access to the inside of the compression body <NUM>.

The tool apparatus <NUM> includes a tool head <NUM> that is configured to connect to the tension stud <NUM>. In one example, the tool head <NUM> is a nut that may engage with the tension stud <NUM>. In another example, the tool head <NUM> may be substantially cylindrical and include a first region having a first diameter and a second region having a second, smaller diameter, creating a lip to enable an actuator <NUM> to engage with the tool head <NUM> and exert a load thereon. The compression body <NUM> may be sized to receive at least part of the tool head <NUM> within the axial hole of the compression body <NUM>.

In <FIG>, the tool head <NUM> is disengaged from the tension stud <NUM>. In one example, the tool head <NUM> includes a female threaded connection which is configured to engage with a corresponding male threaded connection on the tension stud <NUM>.

Within the tool apparatus <NUM> there are critical cyclic life components that require monitoring during their repeated use, the female thread of the tool head <NUM> that engages with the tension stud <NUM> is one such component. To minimise the cost of replacing the entire tool head <NUM> once the internal female thread of the tool head <NUM> has worn to an undesirable state, the tool head <NUM> may include a removable insert <NUM> such that the tool head <NUM> is connected to the tension stud <NUM> via the removable insert <NUM>. In one example, the removable insert <NUM> includes a male thread for engaging with a co-operative female thread within the tool head <NUM> and a female thread for engaging with a co-operative male thread of the tension stud <NUM>. The removable insert <NUM> may be economically made from higher grade material compared with the remainder of the tool head <NUM>. Further, the removable insert <NUM> may be changed-out with a spare or replacement removable insert <NUM> whilst the original is away for inspection. This enables continued use of tool apparatus <NUM> whilst the original removable insert <NUM> is being inspected. Further, the removable insert <NUM> may comprise a non-shouldered outer thread, which enables its reversal. As such, the usable life of the removable insert is extended because the redundant thread is utilised.

The tool apparatus <NUM> includes an actuator <NUM> configured to apply a load to the tool head <NUM> and the compression body <NUM>. In the example shown in <FIG>, the actuator <NUM> is engaged with the compression body <NUM> and the tool head <NUM>. In one example, the actuator <NUM> has an axial hole therethrough for receiving at least part of the tool head <NUM>.

The tool apparatus <NUM> may include a measurement apparatus <NUM> for measuring the stretch or elongation of the tension stud <NUM>. The measurement apparatus <NUM> will be explained in more detail below.

The rotor assembly <NUM> includes a load retainer <NUM> and a connector (not shown), which will be explained in more detail below.

The tool apparatus <NUM> may also include an adapter body <NUM> configured to engage with the inlet shaft <NUM>. In one example, the adapter body <NUM> is shaped to positively engage with a first end of the inlet shaft to ensure a positive engagement between the adapter body <NUM> and the inlet shaft <NUM>.

In one example, the adapter body <NUM> is reversible such that a second side of the adapter body <NUM> is configured to engage with an inlet shaft <NUM> having a different diameter.

<FIG> shows a cross section of a schematic of a sub-assembly <NUM> of the rotor assembly <NUM> along with a part of a safety apparatus <NUM>. In the example shown in <FIG>, the tool head <NUM> is engaged with the tension stud <NUM> via the replaceable tool insert <NUM>. In one example, a temporary tension stud is connected to the tension stud <NUM> and the tool apparatus <NUM> may be connected to the tension stud <NUM> via the temporary tension stud.

In the example shown in <FIG>, the tool head <NUM> is received in the through hole in the compression body <NUM> and the removable insert <NUM> is engaged with the tension stud <NUM>. In the arrangement shown in <FIG>, the actuator <NUM> is engaged with both the tool head <NUM> and the compression body <NUM>. In the example shown in <FIG>, a safety apparatus <NUM> or safety frame is partly shown connected to the sub-assembly <NUM>. The safety apparatus <NUM> is shown in more detail in <FIG> and <FIG>.

In <FIG>, a first machine centre <NUM> is located at an end of the tension stud <NUM> to enable an engagement between the machine centre <NUM> and a machine, such as a lathe. The first machine centre <NUM> may be configured to engage with the adapter <NUM>. In one example, the first machine centre <NUM> is adjustable via one or more adjustment screws which enable an operator to achieve concentricity limits throughout the shafts manufacturing processes. In this example, a separate lose female centre is held by four adjusting screws. The female centre is compatible with standard male 'dead centres' and 'live centres' of the machine used to produce the final journal <NUM>. The pre-existing diametric features of the shaft <NUM> may used to reference the concentricity adjustments.

In operation, the actuator <NUM> is configured to expand to push against the tool head <NUM> and the compression body <NUM> and exert a load on the tool head <NUM> and the compression body <NUM>. As the compression body <NUM> is engaged with the inlet shaft <NUM> of the rotor assembly <NUM> then the load applied to the compression body <NUM> will be reacted by the inlet shaft <NUM> and the inlet shaft <NUM> will also be subject to compression.

In one example, the actuator <NUM> is a hydraulic load cell to accurately apply a pre-determined load to the tension stud <NUM>. In other examples, the actuator <NUM> may be a pneumatic load cell, a torqued threaded arrangement or an electric solenoid.

Due to the connection between the tool head <NUM> and the tension stud <NUM>, the load applied to the tool head <NUM> results in an extension of the tension stud <NUM> and a tension load to develop in the tension stud <NUM>.

The load applied to the tension stud <NUM> is pre-determined to match the 'steady state' separation loads experienced in operation of the rotor assembly <NUM>. In one example, to determine the tension load applied to the tension stud <NUM>, a change in length or extension of the tension stud <NUM> is measured by a measurement device <NUM>. The measurement device <NUM> may include a sliding plunger that projects through a bore in the tool head <NUM> and engages with an end of the tension stud <NUM> or temporary tension stud. The measurement device <NUM> may have an exposed end that projects from the tool head <NUM> and is connected to a containment bracket <NUM>. In one example, the measurement device <NUM> includes a spring to bias the plunger against the tension stud <NUM> or the temporary tension stud. The exposed end of the measurement device <NUM> may be fixed such that the elongation or extension of the tension stud <NUM> may be measured due to the corresponding reduction in length of the measurement device <NUM>.

Due to the stress-strain relationship, a pre-determined tension load can be provided to the tension stud <NUM> by stretching the tension stud <NUM> by a predetermined amount.

Once the tension stud <NUM> has been extended by a pre-determined amount, corresponding to a pre-determined tension load being developed in the tension stud <NUM>, a load retainer <NUM> is moved to engage with the inlet shaft <NUM>. The load retainer <NUM> is moved relative to the tension stud <NUM> to engage with the inlet shaft <NUM>. In one example, a connector (not shown), which may be in the form of a spinner, is connected with the load retainer <NUM> to enable an operator to move the load retainer <NUM> relative to the tension stud <NUM>, without the need for an operator to have direct access to the load retainer <NUM>. In one example, the load retainer <NUM> comprises a threaded nut configured to receive a corresponding thread on the tension stud <NUM>.

In order to access the connector, the wall of the compression body <NUM> may include an aperture to enable access to the inside of the compression body <NUM>.

Following the engagement of the load retainer <NUM> with the inlet shaft <NUM>, the actuator <NUM> may be unloaded. During unloading, the load path between the tension stud <NUM> and the inlet shaft <NUM> is changed from passing through the compression body <NUM> to passing through the load retainer <NUM>. In other words, the compression body <NUM> becomes unloaded as the actuator <NUM> is unloaded and the load retainer <NUM> becomes loaded as the actuator <NUM> is unloaded.

Following the loading of the actuator <NUM> and engagement of the load retainer <NUM> with the input shaft <NUM>, the inlet shaft <NUM> will be subject to a compression load, matching the compression that the inlet shaft <NUM> will be subject to in the rotor assembly <NUM>. As such, the journal <NUM> of the inlet shaft <NUM> will deform or barrel such that part of the journal <NUM> will bulge.

In operation, depending on the size of the rotor assembly <NUM>, the rotor assembly <NUM> may be subject to separation loads of approximately 50kN. In other examples, the separation loads may be more than 250kN, more preferably more than 500kN, more preferably more than 750kN and more preferably more than 1000kN. To compensate against this separation load, the tension stud <NUM> will be subject to a matching tension load. As such, the components of the tool apparatus <NUM> and rotor assembly <NUM> will also be subject to high loads. Whilst the components are designed to withstand the loads applied to them, in practice, there are a number of reasons why failures in the components and/or connections of the rotor assembly <NUM> that are subject to a load may occur.

A first source of potential failure is that one or more threads between connecting elements may fail. For example, the thread between the load retainer <NUM> and the tension stud <NUM> may fail, causing the load energy within the tension stud <NUM> to be released.

Alternatively, the threads between the tool head <NUM> and the corresponding thread of the tension stud <NUM> may fail during loading of the tension stud <NUM>, which causes the load from the actuator <NUM> to be unrestrained at one end.

In another example, there may be a lack of engagement between the compression body <NUM> and the inlet shaft <NUM> or the actuator <NUM> and the tool head <NUM> or the compression body <NUM>.

Further, the load applied by the actuator <NUM> may be too high, resulting in a failure of one or more component and/or connection between components.

In each of these examples, a release of energy occurs from the sub-assembly <NUM>, which may cause injury to a nearby operator or damage to nearby equipment. The energy released may be between approximately 1500J to 4000J and so the safety apparatus <NUM> is designed to withstand and contain this release of energy.

With the high loads involved, there is a large amount of stored energy within the sub-assembly <NUM> once the load retainer <NUM> is in position and engaged with the inlet shaft <NUM>. Therefore, it is essential to provide adequate safety measures to reduce the risk to nearby operators and/or equipment as a result of a release of energy from the sub-assembly <NUM>.

<FIG> shows an example of a safety apparatus or safety frame <NUM> for containing a release of energy from a shaft <NUM> of a rotor assembly <NUM> of the sub assembly <NUM>. The safety apparatus <NUM> includes a plurality of containment members <NUM>. In the example shown in <FIG>, the safety apparatus <NUM> includes two containment members <NUM>, however, in other examples, the safety apparatus <NUM> may include more than two containment members <NUM>. The containment member <NUM> includes an elongate region <NUM> or elongate element that defines a longitudinal axis B.

In the example shown in <FIG>, the elongate region <NUM> has a square or rectangular cross-section, but in other examples, the elongate region <NUM> may have a cross-section having any other suitable shape.

The containment member <NUM> includes at least two arms <NUM> projecting away from the longitudinal axis B of the elongate region <NUM>. The at least two arms <NUM> of the containment member <NUM> project away from the longitudinal axis B of the elongate region <NUM> in the same direction. In one example, the containment member <NUM> includes a first arm <NUM> and a second arm <NUM>. In this example, the first arm <NUM> may be located towards a first end of the elongate region <NUM> and the second arm <NUM> may be located towards a second end of the elongate region <NUM>.

In the example shown in <FIG> in which the safety apparatus <NUM> includes a first containment member <NUM> and a second containment member <NUM>, there is a central axis C between the containment members <NUM>. In other words, a central axis C is defined by the mid-point between the containment members <NUM>. In this example, the at least two arms <NUM> of the first containment member <NUM> and the at least two arms <NUM> of the second containment member <NUM> project towards the central axis C.

The safety apparatus <NUM> includes at least one connecting member <NUM> connected to at least two of the plurality of containment members <NUM>. In one example, the at least one connecting member <NUM> is connected to the elongate region <NUM> of a first containment member <NUM> and the elongate region <NUM> of a second containment member <NUM>.

In the example shown in <FIG>, the safety apparatus <NUM> includes two connecting members <NUM>. The connecting member <NUM> may have a similar shape to the containment arm <NUM>, i.e. have an elongate region <NUM> defining a longitudinal axis and at least two connecting arms <NUM> projecting away from the longitudinal axis of the elongate region <NUM>. One of the at least two connecting arms <NUM> of the connecting member <NUM> is configured to connect to one of the containment arms <NUM> and a different one of the at least two connecting arms <NUM> of the connecting member <NUM> is configured to connect to a different one of the containment arms <NUM>.

In use, the at least one connecting member <NUM> is configured to connect the safety apparatus <NUM> to the sub-assembly <NUM> at one or more connection points <NUM>. In one example, the safety apparatus <NUM> includes one or more quick release pins configured to connect the safety apparatus <NUM> to the sub-assembly <NUM> at the one or more connection points <NUM>.

The plurality of containment members <NUM> are configured to withstand an energy release from the sub-assembly <NUM> due to a failure of one or more components and/or connections of the sub-assembly <NUM>.

In one example, the material of the safety apparatus <NUM> is a nickel chromium molybdenum steel, which is preferably due to its high tensile strength and toughness. In order to retain the loads that may be applied to the safety apparatus <NUM> as a result of an energy release, the containment members <NUM> of the safety apparatus <NUM> are sized so as to withstand the loads that may be released as a result of a failure of one or more components. In one example, the containment member <NUM> has a length of approximately <NUM> to <NUM> and a cross-sectional area of approximately <NUM><NUM> to <NUM><NUM>. Further, the arms <NUM> of the containment members <NUM> will be subject to high shear loads during an energy release and have a cross sectional area of approximately <NUM><NUM> to <NUM><NUM>.

In the example shown in <FIG>, the safety apparatus <NUM> also includes one or more lifting holes <NUM> to enable the safety apparatus <NUM> to be lifted together with the sub-assembly connected to the safety apparatus <NUM>. In one example, the safety apparatus <NUM> includes one or more lifting holes <NUM> in a first direction, such as a vertical direction to enable the safety apparatus <NUM> and sub-assembly <NUM> to be lifted in the first direction. In another example, the safety apparatus <NUM> may also include one or more lifting holes <NUM> in a second direction, such as a horizontal direction to enable the safety apparatus <NUM> and sub-assembly <NUM> to be lifted in the second direction.

<FIG> shows a perspective view of the safety apparatus <NUM> attached to a sub-assembly <NUM>. <FIG> is an alternative view of <FIG> but shows the safety apparatus <NUM> in full. In the example shown in <FIG>, the safety apparatus <NUM> is connected to the sub-assembly <NUM> via the connecting arms <NUM>. In <FIG>, one connecting member <NUM> of the safety apparatus <NUM> is connected to the compression body <NUM> of the sub-assembly <NUM> and a second connecting member <NUM> is connected to the adapter <NUM>. When the safety apparatus <NUM> has been applied to the sub-assembly <NUM>, the actuator <NUM> may be safely actuated so as to apply a load to the tool head <NUM> and the compression body <NUM>, which results in a load being applied to the tension stud <NUM> and inlet shaft <NUM> as described above. Due to the presence of the safety apparatus <NUM>, there is a reduced risk of injury of a nearby operator.

The safety apparatus or safety frame <NUM> is designed to withstand the release of energy in the event of failure of any of the loaded components. It is also designed such that all lifting orientations are catered for during transportation and storage operations. In the event of a failure of one or more of the components or connections of the assembly, then the tool head <NUM> may quickly move away from the rotor assembly <NUM>. With the safety apparatus <NUM> in place, the arms <NUM> will catch the tool head <NUM> and contain the load within the safety apparatus <NUM>. As such, the safety apparatus <NUM> acts as redundancy safety mechanism, such that even in the event of a failure of one or more of the components or connections of the tool apparatus <NUM> or the rotor assembly <NUM>, then the risk of injury to a user or damage to the surrounding equipment or environment is significantly reduced because the energy released by the failure will be contained within the safety apparatus <NUM>.

It is especially essential to provide a second-tier of safety to "fool-proof" against failure scenarios such as accidental over pressure of the actuator and/or damaged or worn threads. This is achieved by the addition of the safety apparatus <NUM> to the tool apparatus <NUM>. In the event of a component failure, the safety apparatus <NUM> is capable of containing the energy released from the tension stud <NUM> and/or one of the other components of the sub-assembly subject to loading.

In the example shown in <FIG>, the compression body <NUM> includes a shroud portion configured to cover at least part of the inlet shaft <NUM>. In one example, the compression body <NUM> is configured to engage with a major diameter of the inlet shaft <NUM> and the shroud portion is configured to cover components of the sub-assembly <NUM>, such as the drive hirth teeth & spigot.

Once the load has been applied to the tension stud <NUM> and inlet shaft <NUM>, the journal <NUM> will barrel such that at least part of the journal bulges out from the cylinder of the journal <NUM>. To remove the effect of the barrelling, the journal <NUM> can be machined at this stage such that it is returned to a cylindrical shape. As the safety apparatus <NUM> is connected to the sub-assembly <NUM>, the safety apparatus <NUM> and sub-assembly <NUM> may stored safely ready prior to machining.

<FIG> shows an example of the safety apparatus <NUM> connected to a second sub-assembly <NUM>. <FIG> is identical to <FIG>, but with the compression body <NUM>, the tool head <NUM> and the actuator <NUM> removed and replaced with a transport plate <NUM> and a second machine centre <NUM>. In other words, the second sub-assembly <NUM> is identical to the first sub-assembly <NUM>, but with the compression body <NUM>, the tool head <NUM> and the actuator <NUM> removed and replaced with a transport plate <NUM> and a second machine centre <NUM>.

In order to replace the compression body <NUM>, the tool head <NUM> and the actuator <NUM> with the transport plate <NUM> and an adjustable machine centre <NUM>, the safety apparatus <NUM> need to be temporarily disconnected from the sub-assembly <NUM>. This alteration occurs at a higher risk as the safety apparatus <NUM> will not be able to contain loads or an energy released from a failure of one or more components. As such, this operation should be done as efficiently as possible, such that the safety frame <NUM> can be reconnected as soon as possible.

As shown in <FIG>, the transport plate <NUM> is configured to engage with the inlet shaft <NUM> via the load retainer <NUM>. In one example, the transport plate <NUM> includes a bore therethough for receiving the tension stud <NUM>.

In the example shown in <FIG>, the connecting member <NUM> is configured to connect to the transport plate <NUM> of the second sub-assembly <NUM>. The second sub assembly <NUM> also includes the second machine centre <NUM>, which may be adjustable using a plurality of adjustment screws and a female centre as described above in relation to the first machine centre <NUM>. As shown in <FIG>, the end of the first machine centre <NUM> extends past the arm <NUM> of the containment member <NUM> in a first direction and the end of the second machine centre <NUM> extends past the other arm <NUM> of the containment member <NUM> in a second direction. This arrangement enables the safety frame <NUM> and second sub-assembly <NUM> to be located between machine centres.

When the safety apparatus <NUM> has been attached to the second sub-assembly <NUM>, the safety apparatus <NUM> and second sub-assembly <NUM> may be safely transported by connecting one or more lifting members to the one or more lifting holes <NUM>. The safety apparatus <NUM> is adapted for transport of the 'ready for machining' sub assembly <NUM>.

<FIG> shows an example of part of the safety apparatus <NUM> and second sub-assembly <NUM> installed in a machine <NUM> for machining the journal <NUM>. The machine <NUM> may include a headstock <NUM> and a tailstock <NUM>. In <FIG>, the first machine centre <NUM> of the second sub-assembly <NUM> is engaged with a dead centre <NUM> of the machine <NUM> and the second machine centre <NUM> of the second sub-assembly <NUM> is engaged with a live centre <NUM> of the machine. The axis C indicates the machine centre line.

With the safety apparatus <NUM> and the second sub-assembly <NUM> mounted between 'Live' <NUM> and 'Dead' centres <NUM>, safety apparatus <NUM> can be removed because any energy release will be contained by the machine <NUM>.

Following the removal of the safety apparatus <NUM>, the journal <NUM> can be machined so as the remove the bulge due to the barrelling and return the journal to a cylindrical shape. Once the journal <NUM> has been machined, the safety apparatus <NUM> can be re-fitted and the second sub-assembly <NUM> can be transported and/or stored.

To remove the tooling the Hydraulic Cell is used in a reverse procedure to that of journal compression operation described previously, which is also done whist the sub assembly <NUM> is within the safety apparatus <NUM>.

As such, the safety apparatus <NUM> performs three functions for improving safety. Firstly, the safety frame <NUM> enables the compression load to be safely applied to the inlet shaft <NUM> and the tension stud <NUM>. Secondly, once the load has been applied, the safety frame <NUM> enables the sub assembly <NUM>, <NUM> to be safely stored. Thirdly, the safety apparatus <NUM> enables the sub-assembly <NUM>, <NUM> to be transported.

In one example, a resilient material, such as rubber, is provided between the arms <NUM> of the containment member <NUM> and the components of the tool apparatus <NUM> and/or rotor assembly <NUM>. For example, resilient material may be provided between the arm <NUM> and the tool head <NUM> and also between the arm <NUM> and the adapter <NUM>.

<FIG> shows an illustration of a method of shaping a journal (<NUM>) of a shaft (<NUM>) of a rotor sub-assembly (<NUM>, <NUM>).

In step <NUM> a pre-determined compression load is applied to the shaft (<NUM>). The pre-determined compression load results in a deformation of the journal (<NUM>) to produce a loaded journal (<NUM>) with a substantially concave profile, for example, due to barrelling.

In step <NUM>, the loaded journal (<NUM>) is shaped to produce a substantially cylindrical loaded journal (<NUM>) such that when the pre-determined compression load is removed, the journal (<NUM>) has a substantially convex profile.

<FIG> shows an illustration of a method of applying a pre-determined compression load to a shaft <NUM> of a rotor assembly <NUM>. In one example, the load is applied to an inlet shaft <NUM>.

In step <NUM>, the adapter <NUM> is engaged with a first end of a shaft <NUM> of the rotor assembly <NUM>. In one example, the shaft comprises an inlet shaft <NUM>.

In step <NUM>, a compression body <NUM> is engaged with a second end of the shaft <NUM>. The compression body <NUM> may be sized to ensure a positive engagement between the compression body <NUM> and the inlet shaft <NUM>.

In step <NUM>, a tool head <NUM> is engaged with a tension stud <NUM> extending through the shaft <NUM>. The tool head <NUM> may extend through a central bore through the inlet shaft <NUM>.

In step <NUM>, an actuator is provided between the compression body <NUM> and the tool head <NUM>. In one example, the tool head <NUM> includes a removable insert <NUM> comprising a hollow cylinder in which both the outside face and the inside face of the hollow cylinder are threaded. The thread on the outer face of the removable insert <NUM> may connect with a corresponding thread of a cavity within the tool head <NUM> for receiving the removable insert <NUM>. The thread on the internal face of the removable insert <NUM> may connect with a corresponding thread on the tension stud <NUM>.

In step <NUM>, the safety apparatus <NUM> as described above is connected to the compression body <NUM> and/or the adapter <NUM>. The safety apparatus <NUM> may include one or more connecting arms <NUM> that are connected to the compression body <NUM> and/or the adapter <NUM>.

In step <NUM>, the actuator <NUM> is actuated to provide a load to the compression body <NUM> and the tool head <NUM> to cause the tension stud <NUM> to extend.

In step <NUM>, a load retainer <NUM> is engaged with the second end of the shaft <NUM> to retain the load in the compression body <NUM>.

In a further step, the method may include measuring the elongation of the tension stud <NUM> via measurement apparatus <NUM>. The method may further include determining that the tension stud <NUM> has elongated by a predetermined amount and rotating the load retainer <NUM> which is co-operatively threaded to the tension stud <NUM>. The load retainer <NUM> is moved so that it engages with the shaft <NUM> of the rotor assembly <NUM>.

Following the application of the load to the inlet shaft <NUM> and the tension stud <NUM> and the load retainer <NUM> has been moved to engage with the inlet shaft <NUM>, the method may further include removing the tool head <NUM>, the actuator <NUM> and the compression body <NUM> and providing a transport plate <NUM> that receives the tension stud <NUM>. In this example, the load retainer <NUM> is located between the transport plate <NUM> and the inlet shaft <NUM>.

The method may further include the steps of connecting the safety apparatus <NUM> to the transport plate <NUM> and/or the adapter <NUM>.

The method may further include the steps of engaging a first machine centre <NUM> with the adapter <NUM> and engaging a second machine centre <NUM> with the transport plate <NUM>.

The method may further include positioning the first machine centre <NUM> and the second machine centre <NUM> between centres of a machine <NUM>, removing the safety apparatus <NUM> and machining the journal <NUM> of the shaft <NUM>.

Claim 1:
An assembly comprising:
a safety apparatus (<NUM>);
and a sub-assembly (<NUM>, <NUM>)
the safety apparatus (<NUM>) for containing an energy release from a rotor sub-assembly (<NUM>, <NUM>) having a tension stud (<NUM>), the safety apparatus (<NUM>) comprising:
a plurality of containment members (<NUM>), wherein each containment member (<NUM>) comprises:
an elongate region (<NUM>) defining a longitudinal axis (B); and
characterised by
at least two arms (<NUM>) projecting away from the longitudinal axis (B) of the elongate region (<NUM>); and
at least one connecting member (<NUM>) connected to at least two of the plurality of containment members (<NUM>), wherein in use the at least one connecting member (<NUM>) is configured to connect the safety apparatus (<NUM>) to the sub-assembly (<NUM>, <NUM>) and the plurality of containment members (<NUM>) are configured to withstand an energy release from the sub-assembly (<NUM>, <NUM>) in the event of a failure of one or more components and/or connections of the sub-assembly (<NUM>, <NUM>),
and characterized by the sub-assembly (<NUM>, <NUM>) comprising:
a shaft (<NUM>) of a rotor assembly (<NUM>), the shaft (<NUM>) comprising a journal (<NUM>);
a tension stud (<NUM>) extending through the shaft (<NUM>);
an adapter (<NUM>) engaged with a first end of the shaft (<NUM>); and
a load retainer (<NUM>) configured to engage with a second end of the shaft (<NUM>) and receive the tension stud (<NUM>), wherein, in use, the load retainer (<NUM>) is configured to move relative to the tension stud (<NUM>) and transfer a load from the tension stud (<NUM>) to the shaft (<NUM>).