A boroscope includes a working head having first and second ends. A first optical fiber extends through the boroscope to a position between the first and second ends. A second optical fiber extends through the boroscope to the second end of the working head. A laser optical fiber extends through the boroscope. At least one lens is arranged between the first end and the second end of the working head and a mirror is gimballed to the second end of the working head. The laser optical fiber directs laser light transmitted through the laser optical fiber onto the lens and then onto the mirror. A first LED is arranged at a position between the first end and the second end of the working head and a second LED is arranged at the second end of the working head and an actuator devices adjust the position of the mirror.

The present invention relates to a boroscope and a method of laser processing a component within an assembled apparatus and in particular relates to a flexible boroscope and a method of laser processing a component within an assembled apparatus using a flexible boroscope.

Currently boroscopes are used to view internal components within an assembled gas turbine engine, or other engine, machine, apparatus etc, to determine if the components within the gas turbine engine are damaged and need repair or replacement or if they are undamaged and do not require repair or replacement. The use of boroscopes enables the components within the gas turbine engine, or other engine, machine, apparatus etc, to be viewed without having to disassemble the gas turbine engine into modules or sub modules.

There are two types of boroscopes, e.g. rigid boroscopes and flexible boroscopes. Rigid boroscopes are inserted into an assembled apparatus through an aperture in a casing to enable components within line of sight to be viewed. Flexible boroscopes are also inserted into an assembled apparatus through an aperture in the casing and the boroscope may be continuously inserted and manoeuvred so that components deeper within the apparatus, and not within line of sight, of the aperture may be viewed.

The flexible boroscopes are manoeuvred, or controlled, using cables within the boroscope which are pulled by motors in the control unit of the flexible boroscope.

It has been proposed to provide a suitable optical fibre which extends through the full length of the flexible boroscope so that a laser beam may transmitted through the optical fibre and be used to process components within the gas turbine engine, other engine, machine, apparatus etc, e.g. to laser clean a dirty component, to laser machine a damaged component or to deposit material to repair a damaged component.

However, the use of an optical fibre to transmit a laser beam within a flexible boroscope as mentioned above to carry out these processes is not suitable because the use of the cables pulled by the motors to position the flexible boroscope to carry out laser processing are slow to respond and do not give sufficient accuracy.

Accordingly the present invention seeks to provide a boroscope which reduces, preferably overcomes, the above mentioned problems.

Accordingly the present invention provides a boroscope comprising a working head, the working head having a first end and a second end, a first optical fibre extending through the boroscope to a position between the first end and the second end of the working head, a second optical fibre extending through the boroscope to the second end of the working head, a laser optical fibre extending through the boroscope, a mirror adjustably mounted on the working head, the laser optical fibre being arranged to direct laser light transmitted through the laser optical fibre onto the mirror on the working head, a first light source arranged at a position between the first end and the second end of the working head, a second light source arranged at the second end of the working head, and an actuator device to adjust the position of the mirror.

At least one lens may be arranged between the first end and the second end of the working head, the laser optical fibre being arranged to direct laser light transmitted through the laser optical fibre onto the at least one lens within the working head and then onto the mirror on the working head. The mirror may be adjustably mounted to the second end of the working head.

The baroscope may comprise a flexible hollow member having a first end and a second end, the working head being arranged at the second end of the hollow member, the first end of the working head being arranged adjacent the second end of the hollow member and the second end of the working head being arranged remote from the hollow member, the first optical fibre extending through the hollow member from the first end of the hollow member to the position between the first end and the second end of the working head, the second optical fibre extending through the hollow member and the working head from the first end of the hollow member to the second end of the working head, the laser optical fibre extending through the hollow member from the first end to the second end of the hollow member.

Preferably the first light source is arranged to direct light with a component of direction transverse to the axis of the boroscope, the end of the first optical fibre is arranged to receive light travelling with a component of direction transverse to the axis of the boroscope, the second light source is arranged to direct light with a component of direction parallel to the axis of the boroscope and the end of the second optical fibre is arranged to receive light travelling with a component of direction parallel to the axis of the boroscope.

Preferably the first light source and/or the second light source comprise a light emitting diode.

The adjustable mounting may be arranged to change the angle of the mirror relative to the axis of the at least one lens. The adjustable mounting may comprises two perpendicular axes of rotation and the mirror is rotatable about the two axes of rotation.

The mirror may be adjustably mounted on the second end of the working head by a gimballed mounting. The actuator device may comprise a galvanometer mechanism.

The mirror may be adjustably mounted on the second end of the working head by a micro-electro-mechanical system and the actuator device comprises the micro-electro-mechanical system.

Preferably a pipe extends through the boroscope to a position between the first and second ends of the working head and a device is arranged to supply powder material through the pipe.

The first optical fibre may surround the laser optical fibre to provide a cladding for the laser optical fibre.

Preferably the working head comprises a first cylindrical portion at the first end of the working head, a second part cylindrical portion at the second end of the working head and a third portion interconnecting the first cylindrical portion and the second part cylindrical portion.

Preferably the first light source and the at least one lens are arranged in the first cylindrical portion, the second light source and the mirror are arranged on the second part cylindrical portion.

The present invention also provides a method of laser processing a component within an assembled apparatus, the apparatus comprising a casing enclosing the component, the casing having at least one aperture extending there-through, the method comprising:—a) inserting a boroscope through the aperture, the boroscope comprising a working head, the working head having a first end and a second end, a first optical fibre extending through the boroscope to a position between the first end and the second end of the working head, a second optical fibre extending through the boroscope to the second end of the working head, a laser optical fibre extending through the boroscope, a mirror adjustably mounted on the working head, the laser optical fibre being arranged to direct laser light transmitted through the laser optical fibre onto the mirror on the working head, a first Light source arranged at a position between the first end and the second end of the working head, a second light source arranged at the second end of the working head and an actuator device to adjust the position of the mirror,b) viewing the assembled apparatus within the casing using the second optical fibre,c) viewing the assembled apparatus within the casing using the second optical fibre while moving the working head of the boroscope to the component,d) transmitting a laser beam through the laser optical fibre to the mirror,e) reflecting the laser beam off the mirror onto a surface of the component to process the surface of the component, andf) viewing the surface of the component and the laser beam with the first optical fibre to monitor the processing of the surface of the component.

Step e) may comprise adjusting the position of the mirror to move the laser beam over the surface of the component.

Step e) may comprise cleaning the surface of the component.

The boroscope may comprise a pipe extending through the baroscope to a position between the first and second ends of the working head and a device is arranged to supply powder material through the pipe, and step e) comprises supplying a powder material through the pipe onto the surface of the component and melting the powder material with the laser beam.

Step e) may comprise supplying a welding material to weld the component, to repair a crack in the component, to weld the component to another component or to build up a worn portion of the component.

Step e) may comprise supplying a coating material to provide a coating on the component or to repair a coating on the component.

The assembled apparatus may comprise a gas turbine engine. The component may comprise a compressor blade, a compressor vane, a turbine blade or a turbine vane.

A turbofan gas turbine engine10, as shown inFIG. 1, comprises in flow series an intake11, a fan12, an intermediate pressure compressor13, a high pressure compressor14, a combustor15, a high pressure turbine16, an intermediate pressure turbine17, a low pressure turbine18and an exhaust19. The high pressure turbine16is arranged to drive the high pressure compressor14via a first shaft26. The intermediate pressure turbine17is arranged to drive the intermediate pressure compressor13via a second shaft28and the low pressure turbine18is arranged to drive the fan12via a third shaft30. In operation air flows into the intake11and is compressed by the fan12. A first portion of the air flows through, and is compressed by, the intermediate pressure compressor13and the high pressure compressor14and is supplied to the combustor15. Fuel is injected into the combustor15and is burnt in the air to produce hot exhaust gases which flow through, and drive, the high pressure turbine16, the intermediate pressure turbine17and the low pressure turbine18. The hot exhaust gases leaving the low pressure turbine18flow through the exhaust19to provide propulsive thrust. A second portion of the air bypasses the main engine to provide propulsive thrust.

The intermediate pressure compressor13, as shown more clearly inFIG. 2, comprises a rotor36carrying a plurality of stages of compressor rotor blades38and a stator40carrying a plurality of stages of compressor stator vanes42. The compressor rotor blades38in each stage are circumferentially spaced and extend generally radially outwardly from the rotor36. The compressor stator vanes42in each stage are circumferentially spaced and extend generally radially inwardly from the stator40. The stator40also comprises a plurality of shrouds44axially interconnecting the stages of compressor stator vanes42and the shrouds44are positioned radially around a corresponding one of the stages of compressor rotor blades38. The stator40of the intermediate pressure compressor28also comprises an outer compressor casing50and the outer compressor casing50is provided with one or more apertures52to allow access for boroscopes and/or repair devices. In addition the radially outer platforms54of one or more of the compressor stator vanes42have one or more apertures56to allow access for boroscopes and/or repair devices. The shrouds44axially interconnecting the stages of compressor stator vanes42form a portion of an inner compressor casing58. The compressor stator vanes42also have radially inner platforms55.

A boroscope60, as shown inFIGS. 3 to 7, comprises a flexible hollow member62having a first end64and a second end66. A working head68is arranged at the second end66of the hollow member62and the working head68has a first end70adjacent the second end66of the hollow member62and a second end72remote from the second end66of the hollow member62. The first end70of the working head68is immediately next to and attached to the second end66of the hollow member62. A first optical fibre74extends through the hollow member62from the first end64of the hollow member62to a position between the first end70and the second end72of the working head68. A second optical fibre76extends through the hollow member62and the working head68from the first end64of the hollow member62to the second end72of the working head68. A third optical fibre78extends through the hollow member62from the first end64to the second end66of the hollow member62. The third optical fibre76is suitable for conducting a laser beam there-through. At least one lens80is arranged between the first end70and the second end72of the working head68and a mirror82is supported on the second end72of the working head68by a gimballed mounting84to the second end72of the working head68. The third optical fibre78is arranged to direct laser light L transmitted through the third optical fibre78onto the at least one lens80within the working head68and then through the at least one lens80onto the mirror82at the second end72of the working head68. A first light source86is arranged at a position between the first end70and the second end72of the working head68and a second light source88is arranged at the second end72of the working head68. Actuator devices90and92are arranged to adjust the position of the mirror82.

The first light source86is arranged to direct light with a component of direction transverse to the axis of the boroscope60and is arranged to direct light with a component of direction parallel to the axis of the boroscope60. The end75of the first optical fibre74is arranged to receive light travelling with a component of direction transverse to the axis of the boroscope60. The second light source88is arranged to direct light with a component of direction parallel to the axis of the baroscope60and the end77of the second optical fibre76is arranged to receive light travelling with a component of direction parallel to the axis of the boroscope60.

The first light source86and/or the second light source88comprise light emitting diodes, but other suitable light sources may be used, and electrical cables94and96extend through the hollow member62from the first end64of the hollow member62to the first and second light sources86and88respectively. The actuator devices90and92comprise galvanometer mechanisms to rotate the mirror82about one or the other or both of the axes of rotation X and Y of the gimballed mounting84and electrical cables98and100extend through the hollow member62from the first end62to the actuator devices90and92respectively. The gimballed mounting84is arranged to change the angle of the mirror82relative to the axis of the at least one lens80.

A pipe102extends through the hollow member62from the first end64of the hollow member62to a position between the first and second ends70and72respectively of the working head68and a device104is arranged to supply suitable material, e.g. powder material or solid material for example a wire, through the pipe102. Alternatively the pipe102may be secured to the hollow member62.

The working head68generally comprises a first cylindrical portion110at the first end70of the working head68, a second part cylindrical portion112at the second end72of the working head68and a third portion114interconnecting the first cylindrical portion110and the second part cylindrical portion112. The first light source86, the end75of the first optical fibre74and the at least one lens80are arranged in the first cylindrical portion110of the working head68. The second light source88, the end77of the second optical fibre76and the mirror82are arranged in, or on, the second part, half, cylindrical portion112. In particular the mirror82is supported on the second part cylindrical portion112by the gimballed mounting84.

The gimballed mounting84comprises two perpendicular axes of rotation X and Y. The mirror82is circular and the gimballed mounting84comprises a C-shaped, or U-shaped, member81. The mirror82is rotatably mounted about one of its diameters, the axis of rotation axis X, between the ends of the limbs83A and83B of the C-shaped member81. The trough85of the C-shaped member81is rotatably mounted to the second part cylindrical portion112at the second end72of the working head68about the axis of rotation Y.

The working head68has a diameter of approximately 9 mm and the working head is made from a suitable metal or alloy, for example aluminium, aluminium alloy, titanium, titanium alloy, steel, nickel or nickel alloy. The lens80has a specific focal length, but the focal length may be altered depending on how much space is available within the gas turbine engine10and the focal length is expected to be between and including 20 and 100 mm to account for the mirror82. The mirror82is mounted by the gimballed mounting84so that two dimensional profiles of the laser beam L may be directed onto the surface of the component. The working envelope, the shape and area, of the laser beam L on the component depends upon the distance between the mirror82and the component. The greater the distance between the mirror82and the component, the greater is the area of the envelope. The angle at which the laser beam L strikes the component determines the shape of the envelope.

In operation the boroscope60is inserted through an aperture52in the outer compressor casing50and through an aperture56in the inner compressor casing58. The baroscope60is then manipulated so that the working head68is in proximity to a component, e.g. a rotor blade38, a stator vane42or other component, which has been damaged. The working head68of the boroscope60, as mentioned above, is provided with two light sources86and88and with respective associated optical fibres74and76. The second optical fibre76and the second light source88enable an operator to view in a forward direction, parallel to the axis or longitudinal direction, of the hollow member62of the boroscope60so that the operator is able to position the working head68of the boroscope60at the required location within the gas turbine engine10and with respect to the component which has been damaged. Thus, the operator uses the second optical fibre76to view the assembled gas turbine engine10within the outer compressor casing50and the inner compressor casing58of the gas turbine engine10using the second optical fibre76while moving the working head68of the boroscope60to the component. The first optical fibre74and the first light source86enable the operator to view in a sideways direction, transverse to the axis or longitudinal direction, of the hollow member62of the boroscope60so that the operator is able to monitor the operation and working of the laser. The gimballed mounting84of the mirror82is used to direct the laser beam from the third optical fibre78and lens80onto the surface of the component. The galvanometer mechanisms90and92enable the mirror82to be operated sufficiently quickly to provide laser processing of the surface of the component. The galvanometer mechanisms90and92are operated to move the mirror82about one or both of the axes of rotation X and Y to move the point, or area, of contact of the laser beam over the surface of the component to process as much or as little of the surface of the component as is required without having to move the working head68. Rotation of the mirror82about the axis of rotation X moves the point, area, of contact of the laser beam generally longitudinally with respect to the boroscope60whereas rotation of the C-shaped member about the axis of rotation Y moves the point, area, of contact of the laser beam generally transversely with respect to the boroscope60. Thus the gimballed mounting84provides an adjustable mounting which is arranged to change the angle of the mirror82relative to the axis of the at least one lens80. The adjustable mounting, the gimballed mounting,84comprises two perpendicular axes of rotation X and Y and the mirror82is rotatable about the two axes of rotation X and Y.

The laser beam may be used alone to clean the surface of a component. The laser beam may be used in conjunction with a supply of suitable material through the pipe102. The pipe102may be arranged to supply welding material, metal or alloy, into the laser beam to weld a component, to repair a crack in the component, or to weld two components together etc. The pipe102may be arranged to supply welding material, metal or alloy, into the laser beam to provide a weld deposit on the component to build up a worn portion of the component. The welding material in these two examples may be in the form of a solid material, e.g. welding wire. The pipe102may supply coating material, metal or alloy or ceramic, to provide or repair a coating on the component. The coating material may be a MCrAlY powder where M is Ni, Co, Fe or a mixture of one or more of Ni, Co and Fe. The coating material may be NiAl powder or a mixture of Ni and Al powders to form a beta nickel aluminide coating or PtNiAl powder or a mixture of Pt, Ni and Al powders to form a beta platinum modified nickel aluminide coating. The laser beam is used to provide direct laser deposition process to provide or repair the coating. The coating material may be a mixture of zirconia and yttria powders or a mixture of zirconia and one or more other stabilising oxide powders to form a thermal barrier coating. The pipe102may be used to supply a metal coating, e.g. MCrAlY, NiAl or PtNiAl as discussed above, to provide a bond coating and then supply a ceramic coating, e.g. zirconia and yttria as discussed above, a thermal barrier coating.

The laser beam is reflected off the mirror onto the surface of the component during the processing of the surface of the component. In the case of cleaning of the surface of the component the laser beam is defocused using the lens or lenses so that the laser beam is spread over a large area. In the case of repairing the component the laser beam is focused using the lens or lenses so that the laser beam is concentrated on a smaller area than for cleaning to heat and/or melt the surface of the component and melt the welding material supplied into the laser beam so that the welding material fills the crack in the surface of the component or builds up on a worn portion of the surface of the component. If the component has a coating the surface of the coating forms the surface of the component and the laser beam is reflected onto the surface of the coating on the component. The laser beam may thus be used to clean or repair the coating in a similar manner to that described above for a component without a coating except that a coating material is supplied into the laser beam rather than a welding material, e.g. to fill a crack in the coating or build up a worn portion of the surface of the coating. If the component does not have a coating, the component may be provided with a coating by reflecting the laser beam onto the surface of the coating and supplying coating material into the laser beam to build up the coating on the surface of the component.

A boroscope160with an alternative working head168is shown inFIG. 8. The baroscope160and working head168are substantially the same as that shown inFIGS. 3 to 7and like parts are denoted by like numerals. The boroscope160differs in that the mirror82is not mounted on the working head168by a gimballed mounting84, but instead the mirror82is mounted on a micro-electro-mechanical systems (MEMS)184chip. The micro-electro-mechanical systems (MEMS)184chip is able to rotate, or tilt, about two perpendicular axes like the gimballed mounting84in order to rotate the mirror82about one or the other or both of the axes of rotation X and Y of the MEMS chip184and electrical cables198extend through the hollow member62from the first end62to the MEMS chip184. The mirror82is nominally arranged at 45° to the axis of the at least one lens80and the MEMS chip184is arranged to change the angle of the mirror82relative to the axis of the at least one lens80. The mirror82is provided with a reflective coating which has greater reflective properties to the frequency of laser beam transmitted through the third optical fibre78to reduce the possibility of overheating of the mirror82and hence the MEMS chip184. Thus the MEMS mounting184provides an adjustable mounting which is arranged to change the angle of the mirror82relative to the axis of the at least one lens80. The adjustable mounting, the MEMS mounting,184comprises two perpendicular axes of rotation X and Y and the mirror82is rotatable about the two axes of rotation X and Y. The MEMS chip184also enables the mirror82to be operated sufficiently quickly to provide laser processing of the surface of the component.

In operation of the boroscope162the laser beam transmitted through the third optical fibre78is interrupted periodically, after preset time intervals, to allow the mirror82and hence the MEMS chip184to cool down. For example in operation the laser beam is transmitted through the third optical fibre for a time period of 10 seconds and then interrupted for a time period of several seconds, e.g. 1 to 3 seconds, and then the laser beam is transmitted though the third optical fibre for a time period of 10 seconds etc. Other suitable times may be used for transmission and interruption of the laser beam.

The boroscope of the present invention allows the translation of a laser focal point around a component within the gas turbine engine, or other engine, machine or apparatus, without having to move the working head of the boroscope. The working head of the baroscope enables accurate control of a laser beam for laser processing of a component within the gas turbine engine, or other engine, machine or apparatus, without having to move the working head of the boroscope.

In an alternative boroscope, not shown, the first optical fibre74surrounds the laser optical fibre78and provides a cladding for the laser optical fibre78.