Patent Description:
Splines are ridges or grooves that form part of a component. They typically take the form of a series of uniform spaced ridges or grooves that run parallel to the axis of the component. Splines are found in a wide variety of mechanical devices including gas turbine aircraft engines. They may for example be formed within the internal surface of gas turbine engine shafts.

Splines can be male or female i.e. ridges or groves respectively. Female splines are typically formed to match or mate with male splines.

Splines can accrue debris over time. For example splines in a gas turbine engine component are typically covered by swarf or burnt oil which can cause the splines to become worn, potentially affecting performance and requiring cleaning or replacement. Excessive wearing and performance loss may even affect safe operation of the engine.

Cleaning splines can be difficult, firstly in achieving access to the splines, and secondly in cleaning them effectively. It is also difficult to capture debris that is removed from the splines.

United States patent application <CIT> relates to an apparatus for cleaning an inner surface of a slot includes a first block segment that has an outer perimeter that conforms to and fits inside the inner surface of the slot. A first cleaning pad is connected to the first block segment and extends beyond at least a portion of the outer perimeter of the first block segment.

The present invention provides a spline cleaning device and a method for cleaning splines formed within a shaft of a gas turbine engine as set out in the appended claims.

According to a first aspect there is provided a spline cleaning device for cleaning splines, according to claim <NUM>, formed within a component of a gas turbine engine, the spline cleaning device comprising a central support, a central support sleeve that surrounds and is movable with respect to the central support. A scraper having protrusions, the scraper being attachable to the central support sleeve, and configured to remove surface contaminants from the splines; and a collector sump that is attachable to the central support and configured to collect the surface contaminants that have been removed from the splines.

In some embodiments the central support is tubular with a circular cross-section. The circular cross-section allows for the central support sleeve to be indexed around the splines without having to extract the central support sleeve completely from the central support, reducing the distance that central support sleeve has to move. A circular cross section allows for easier centralisation around the support sleeve when the scraper is in contact with the splines.

In some embodiments the central support sleeve surrounds at least a substantial portion of the central support. This ensures that the location of the central support sleeve in relation to the central support is maintained.

In some embodiments the central support sleeve and the central support comprise the same material. This will reduce any preferential wear due to the reciprocating manner of the central support sleeve with the central support to be minimised.

In some embodiments the scraper has a central hub and a central hole, the central hub has an internal surface that is threaded for attaching the scraper to a corresponding threaded portion on the central support sleeve. This allows for disassembly that can support storage. It also can allow for different scrapers to be attachable to the central support sleeve, allowing for different spline configurations.

In some embodiments the central hub has viewing apertures. This enables the operator to view through the central hub to see the splines and ensure that the protrusions of the scraper are correctly engaged with the splines. It also allows for the splines to be seen to determine if further cleaning is required during operation of the device.

In some embodiments the scraper has arm portions each arm portion having an external circumferential surface upon which the protrusions are formed. Arm portions reduce the overall friction that may be experienced when using the device due to the interaction between the splines and the protrusions.

In some embodiments the arm portions are equally spaced with respect to the central hub. Equally spaced arm portions ensure that the forces are equally distributed around the central hub, this aids the centralisation of the scraper with the central support.

In some embodiments the scraper has lubrication ports and lubricant passageways, the lubrication ports being configured to receive a mobilising fluid from a source of mobilising fluid, and the lubricant passageways being configured to transport the mobilising fluid from the lubrication ports to the external circumferential surface of the scraper. The mobilising fluid may react with the debris to reduce the adherence of the debris to the spline. The fluid may partially dissolve the debris. The fluid provides a means for transporting the debris from the splines to the sump. The mobilising fluid may also reduce wear on the splines as it will act as a lubricant between the scraper and the splines.

In some embodiments the material hardness of the protrusions is less than the material harness of the splines. This may prevent wear on the splines when the two surfaces are in contact.

In some embodiments the collector sump has a threaded portion that corresponds to a threaded portion of the central support.

In some embodiments the collector sump is shaped to collect debris from the splines that has been removed by the scraper. The collector sump may be shaped to enable the position of the engine to be in either the vertical or horizontal position. This does not restrict how the engine must be positioned.

In some embodiments the collector sump has a sealing lip that seals against the component of the gas turbine engine at a position adjacent the splines. The lip ensures all debris is collected in the sump and prevents loosened debris from ingress into the engine. This may prevent an additional engine clean operation.

In some embodiments the collector sump comprises a material that has a Shore hardness of about <NUM> A. This allows for the sump to be introduced into the engine past the splines and to provide an effective seal when in its final position.

In a second aspect there is provided a method for cleaning splines formed within a shaft of a gas turbine engine, according to claim <NUM>, the method comprising the steps of: providing the spline cleaning device of the first aspect; attaching the central support and the collector sump; and inserting the attached central support and the collector sump along the central axis of the engine beyond the female splines of the IPC coupling so that it covers the oil circulation holes; and attaching the scraper to the central support sleeve; and applying the central support sleeve over the central support and moving the central support sleeve in an axial direction so that the scraper engages with the female spline; and cleaning the female splines by moving the central support sleeve in an axial direction and rotating until all female splines have been cleaned.

The term "spline" as used herein means a series of uniform spaced ridges or grooves on a component that run parallel to the axis of the component.

Throughout this specification and in the claims that follow, unless the context requires otherwise, the word "comprise" or variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other stated integer or group of integers.

The following table lists the reference numerals used in the drawings with the features to which they refer:.

The present invention provides a spline cleaning device, for example, for cleaning splines formed within a shaft of a gas turbine engine. <FIG> and <FIG> describe a gas turbine engine for which the spline cleaning device of the present invention is suitable for use, although the person skilled in the art would appreciate the spline cleaning device could be used to clean splines formed within a shaft of any gas turbine engine or indeed within a shaft of any machine or apparatus.

The resultant hot combustion products then expand through, and thereby drive, the high pressure and low pressure turbines <NUM>, <NUM> before being exhausted through the core exhaust nozzle <NUM> to provide some propulsive thrust.

The present invention concerns a spline cleaning device that is useful, for example, for cleaning splines formed in the inner surface of a gas turbine engine.

<FIG> is a cutaway view of the part of the gas turbine engine shown in <FIG> and <FIG> that identifies the location of a component that has splines that can be cleaned by using the spline cleaning device of the present invention. That component is an IPC coupling <NUM>.

<FIG> is a close-up perspective view of the IPC coupling <NUM> shown in <FIG>. It has splines <NUM> that can be cleaned by using the spline cleaning device of the present invention.

In operation the gas turbine engine <NUM> is required to provide mechanical drive to additional auxiliary components, for example fuel pump, hydraulic pumps, oil pumps. The gas turbine engine shown in <FIG> has an auxiliary gearbox <NUM> that provides mechanical drive to various units in the engine. The auxiliary gearbox is driven from an auxiliary gearbox drive shaft <NUM> that interfaces with the shaft <NUM> via the intermediate pressure compressor (IPC) coupling <NUM>. The IPC coupling <NUM> has female splines <NUM> that mate with male splines (not shown) on the shaft <NUM>. The IPC coupling <NUM> rotates with the shaft <NUM> and provides a mechanical drive to the auxiliary gearbox drive shaft <NUM> (through gears). Conversely, at engine start up the IPC coupling <NUM> is able to rotate the shaft <NUM> by driving the auxiliary gearbox through a variable frequency starter generator (VFSG). The IPC coupling <NUM> has oil ways <NUM> that allow oil to flow from the shaft to the engine.

During operation the female spline <NUM> of the IPC coupling <NUM> accrue debris such as swarf or burnt oil, this can result in excessive wear of the female splines <NUM> and the male splines as the debris acts as a grinding paste. Excessive wear may lead to the replacement of both the IPC coupling <NUM> and the shaft <NUM>.

In order to reduce wear of the IPC coupling <NUM> a method and device for cleaning debris from the female splines <NUM> is required that will enable the female splines to be cleaned without requiring the engine to be fully stripped.

<FIG> is a perspective view of a spline cleaning device of the present invention and.

<FIG> is a sectional view of the spline cleaning device in situ within the IPC coupling <NUM> of the gas turbine engine <NUM>.

The spline cleaning device <NUM> has a central support <NUM>, a central support sleeve <NUM>, a scraper <NUM> and a collector sump <NUM>.

The central support <NUM> is elongate with a first end <NUM> and a second end <NUM>. In the embodiment shown, the central support <NUM> has a circular cross section and is hollow. The first end <NUM> of the central support has a threaded portion <NUM> to enable the collector sump <NUM> to be removably attached to the central support <NUM>.

The collector sump <NUM> prevents or at least minimises the ingress of debris into the engine oil ways <NUM> of the IPC coupling <NUM>. The collector sump is flexible to enable it to be introduced passed the splines into the component and to be expandable to create a seal between the collector sump and the IPC coupling. In the embodiment shown, the collector sump <NUM> is an 'W' section. This 'W' section allows for the use of the device to be in either of the horizontal or vertical planes. The collector sump has a central hole <NUM>, the central hole has an internal thread <NUM> by which the collector sump is attachable to the threaded potion of the first end of the shaft <NUM>. The collector sump can be made from any suitable material. In the embodiment shown the collector sump is produced from polyethylene. In the embodiment shown the collector sump has a Shore hardness rating of about <NUM> A, (the Shore A hardness scale measures the harness of flexible mold rubbers that range in hardness from very soft and flexible to hard with no flexibility. Shore hardness is measured with a Shore Durometer which is commercially available standard testing equipment). The collector sump can be made by any suitable method, for example it may be moulded.

The collector sump <NUM> is configured to be attachable to the first end <NUM> of the central support <NUM>. The collector sump <NUM> can be attached to the first end of the central support <NUM> in any suitable manner. The collector sump <NUM> may be permanently attached or removable attached to the central support <NUM> as desired.

In the embodiment shown, the first end <NUM> of the central support <NUM> has a threaded portion and the collector sump <NUM> has a corresponding threaded portion <NUM> and the collector sump is removably attachable to the central support <NUM>. This in part enables the spline cleaning device to be assembled when needed and dissembled and stored when not needed.

In other embodiments, a threaded nut <NUM> may be used to attach the collector sump140 to the central support <NUM>.

The central support sleeve <NUM> has a first end <NUM> and a second end <NUM>. The central support sleeve <NUM> is a hollow section. In the embodiment shown, the first end <NUM> has a threaded portion to enable the scraper <NUM> to be attached to the central support sleeve <NUM>. The cross section of the central support sleeve <NUM> is the same as the central support <NUM>. The internal hollow section of the central support sleeve <NUM> is a clearance fit with the central support <NUM>. The clearance fit allows for the central support sleeve <NUM> to move relative to the central support <NUM> in an axial and radial direction. The central support sleeve <NUM> supports the scraper <NUM> and ensures that the scraper <NUM> is axially aligned with the central support <NUM> and the female splines <NUM>.

The scraper <NUM> has a central hub <NUM> and a central hole <NUM> that allows for the scraper to be positioned over the central support sleeve <NUM>. The scraper <NUM> is attachable to the first end <NUM> of the central support sleeve such that the scraper will move with the central support sleeve over the support shaft. The scraper <NUM> can be attached to the first end of the central support sleeve <NUM> in any suitable manner, for example the first end <NUM> of the central support sleeve <NUM> has a threaded portion (<NUM>) and the scraper <NUM> has a corresponding portion. The scraper <NUM> or at least the central hub <NUM> may have a circular cross-section. The scraper <NUM> has at least one, or ideally a plurality of protrusion <NUM> that extend form the external circumferential surface <NUM>, these protrusions <NUM> are configured to substantially correspond to the root and flanks of the female splines <NUM> of the IPC coupling <NUM>. The external circumferential surface is configured to substantially correspond to the face of the female splines <NUM>. In some embodiments, such as the one shown in <FIG>, the scraper has arm portions <NUM> that extend from the central hub <NUM> and the protrusions <NUM> that engage the splines to be cleaned are formed at distal ends of those arm potions. The scraper <NUM> has at least two arm portions <NUM>. In the embodiment shown in <FIG> the scraper has two arm portions are equally spaced around the axis of the central hub <NUM> such that the scrapper <NUM> is centralised around the axis. The equally spacing of the arm portions <NUM> allows for the acting forces to be equalised across the scraper helping the scraper to stay in contact with the female splines of the component and ensures that the spline cleaning device stays central to the cleaning axis.

The scraper <NUM> may have lubricant passageways <NUM> that extend from the central hub to the external circumferential surface <NUM>. The scraper <NUM> has lubrication ports <NUM> that extend into the lubricant passageways <NUM>. The lubricant passageways <NUM> are formed to receive fluid, such as a mobilising fluid e.g. acetone, and to transport the fluid to the circumferential surface. This mobilising fluid is used to aid the release of debris from the surface of the female spline <NUM> by partially dissolving the debris.

The scraper <NUM> may include viewing apertures <NUM>, these viewing apertures enable the female splines <NUM> to be seen when the scraper is in operation. In the embodiment shown the viewing apertures are formed in the central hub <NUM> of the scraper.

The proposed use of the spline cleaning device of the present invention and a method of using the spline cleaning device to clean splines of a gas turbine engine will now be described with reference to the embodiment shown in <FIG> and <FIG>.

The central support <NUM> and the collector sump <NUM> are assembled and fastened with the threaded nut <NUM>. Alternatively, the central support <NUM> and the collector sump <NUM> may be permanently attached. By allowing the components to be assembled allows for easy storage of the individual components. Having a permanently fixed assembly reduces time needed to assembly the components.

The assembled central support <NUM> and collector sump <NUM> are inserted along the central axis of the gas turbine engine through the rear of the engine.

The collector sump <NUM> engages the engine beyond the spline <NUM> of the IPC coupling <NUM> and covering the oil circulation holes.

The scraper <NUM> is attached to the central support sleeve <NUM>.

The central support sleeve <NUM> is positioned over the central support <NUM>, so that the central support sleeve is free to slide and rotate around the support shaft.

The central support sleeve <NUM> is moved down the central support <NUM> until the protrusion <NUM> of the scraper engage with the female spline <NUM> of the IPC coupling. The central support sleeve <NUM> is moved with a reciprocating movement forward and aft in the axial direction through the IPC coupling <NUM> to remove surface debris from the female splines <NUM>. The central support sleeve <NUM> is moved to disengage with the female splines before being rotated and re-engaged with the female spline. The reciprocating and rotational movement of the central support sleeve is repeating until all female splines have been cleaned. Optionally, flexible solvent pipes are inserted into the ports <NUM> of the scraper <NUM> solvent may be introduced into the flexible solvent pipes to the lubricant passageways <NUM>, to provide mobilising fluid to the surface of the internal splines <NUM>.

The central support sleeve <NUM> and scraper are removed along the axis of the engine. Additionally, the female splines may be further swabbed to ensure that the female spines <NUM> are cleaned of all oil debris. These additional steps are not covered by the appended claims. Further the collector sump may be swabbed to remove oil debris prior to removal of the collector sump may be swabbed to be removed from the collector.

Attaching a swabbing head onto a secondary central support sleeve to form a swabbing head assembly.

Inserting the swabbing head assembly around central support <NUM> and passing it down the centre line.

Using the swab pads to clean the front and rear of the spline teeth and along the length, sides and crowns on the teeth.

Removing the swabbing head assembly and replacing the swabs and reinserting to continue cleaning, repeating until all debris is removed.

Claim 1:
A spline cleaning device (<NUM>) for cleaning splines (<NUM>) formed within a component of a gas turbine engine (<NUM>), the spline cleaning device comprising:
a central support (<NUM>);
a central support sleeve (<NUM>) that surrounds and is movable with respect to the central support;
a scraper (<NUM>) having protrusions (<NUM>), the scraper being attachable to the central support sleeve, and configured to remove surface contaminants from splines; and
a collector sump (<NUM>) that is attachable to the central support and configured to collect the surface contaminants that have been removed from the splines.