BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present invention relates to an in-situ boroblending tool for the blending of an airfoil that is a part of a turbomachine and in particular, a gas turbine engine of an aircraft.

2. Discussion of Background Information

[0002] Conventional gas turbine engines are enclosed in an engine case and include a compressor, combustor, and a turbine. Air flows axially through the sections of the engine. Air, compressed in the compressor, is mixed with fuel which is burned in the combustor and expanded in the turbine, thereby rotating the turbine and driving the compressor.

[0003] Most compressors include a fan, a low pressure compressor, and a high pressure compressor disposed about a longitudinal axis of the engine. The low pressure compressor, the high pressure compressor and the turbine comprise alternating stages of rotating airfoils, or blades, and stationary airfoils, or vanes.

[0004] The gas turbine engines mounted on a wing of an aircraft are frequently damaged by foreign objects, such as sand particles or stones, ingested by the engine during takeoff. These foreign objects often cause nicks or chips on impact with the compressor airfoils. Most damage caused by the foreign objects is to the first few stages of the high pressure compressor blades and in particular, at the leading edge of each affected blade.

[0005] It is necessary to detect damage and then replace or repair blades when damage exceeds industry acceptable limits. The detection process involves a visual inspection of each blade through a borescope. The borescope, a fiber optic cable connected to a light source, is inserted through borescope openings within the engine case and into the engine. The small borescope openings are disposed throughout the engine case at most stages of the high pressure compressor for such borescope inspections. [0006] The currently used methods for repairing (boroblending) damaged airfoils are manual, time-consuming operations requiring highly skilled personnel on-site at the location of repair. The process (in terms of inspecting/measuring airfoil damage, and subsequently repairing to serviceable limits) is prone to human error and inconsistency. Both issues pose the risk of engine removal and teardown, compounding the risk of further delay to engine operation and damage to unrelated components during the teardown. The current methods utilize rigid tools with limited access to damaged areas of the airfoil (rotating airfoils only, with surfaces within the range of a given borescope port). Repair tools must be positioned/controlled manually from outside the engine, thereby driving the necessity for highly skilled operators.

[0007] In view of the foregoing, it would be advantageous to be able to automate the inspection and subsequent repair of airfoils in-situ with a single specialized tool, i.e., without the need for a teardown of the engine to gain access to damaged components.

SUMMARY OF THE INVENTION

[0008] The present invention provides an in-situ boroblending tool for the computer-assisted (automated) blend repair of an airfoil of a turbomachine. The tool comprises a flexible borescope line which is connected to a robotic head unit that is capable of inspecting and boroblending the airfoil. The head unit comprises (i) a stereoscopic camera suite for monitoring movement and positioning of the head unit toward and on the airfoil, (ii) at least two gripping elements which are configured to be capable of being positioned on opposite main surfaces of the airfoil, of gripping the airfoil and of moving along the airfoil, and (iii) a grinding element for executing the blend repair.

[0009] In one aspect or configuration of the tool, the borescope may further be connected to an actuation system, preferably an actuation system controlled by a computer. The actuation system is preferably configured to be located outside the part of the engine that comprises the airfoil to be repaired (blended). [0010] In another aspect or configuration of the tool, the borescope line may be connected to the robotic head unit by a rotating and/or pivoting joint to facilitate the positioning of the head unit for attachment to the target airfoil.

[0011] In another aspect or configuration of the tool of the present invention, the stereoscopic camera suite may comprise one or more (and preferably all of) a radial span distance camera or camera set for focusing perpendicular to the airfoil, a navigation edge distance camera or camera set for focusing in forward direction toward the airfoil, and a repair operation camera or camera set for focusing on a repair area of the airfoil.

[0012] In another aspect or configuration of the tool, the robotic head unit may comprise two gripping elements. However, the robotic head may also comprise more than two gripping elements, for example, four or six gripping elements (two or three sets of two gripping elements). Each of the gripping elements may comprise two or more moveable parts which preferably are connected by flexible joints. For example, some or all of the gripping elements present may comprise three, four, five, six, seven or eight moveable parts which are connected to each other b flexible joints, similar to multi-jointed legs of an insect. This allows the gripping elements to better follow the contour of the airfoil. In some configurations of the tool of the present invention the appearance of the head unit with the gripping elements may be similar to that of the head of insects with mandibles.

[0013] In another aspect or configuration of the tool, at least two gripping elements for positioning on opposite sides of the airfoil may comprise at least one roller wheel on a side thereof which is to contact the airfoil. If a gripping element comprises two or more moveable parts, at least one of these parts comprises at least one roller wheel, although it is preferred for each part of a gripping element to comprise at least one roller wheel. Preferably the axis of rotation of the at least one roller wheel is substantially perpendicular to the longitudinal extension of the gripping element or the moveable part. In this way, the head unit of the tool can be transversed along a radial span of the airfoil. [0014] In another aspect or configuration of the tool of the present invention, the grinding element may be capable of being moved to and away from a part of the airfoil that is gripped by the at least two gripping elements. The grinding element may be a grind wheel and preferably, a grind wheel having a convex shape. The grind wheel may, for example, use air turbines to spin (similar to a dental drill). For example, air could be supplied from an external source and could additionally be used as a means of powering either cooling, suction, or other locomotive parts of the design(s). At a minimum, the air power could serve to drive the grind wheel, avoiding the need for a mechanical linkage between the head and some external electric motor (or the need to embed an electric motor in the head itself, with complex gearing). Further, the distance between the grind wheel assembly from the working surface on the airfoil may be adjusted by, for example, an electric motor such as, e.g., a stepper motor driving a screw.

[0015] The present invention also provides a method of inspecting and blending a damaged airfoil of a turbomachine. The method comprises contacting the airfoil with the head unit (or a part thereof respectively) of the boroblending tool of the present invention as set forth above (including the various aspects and configurations thereof).

[0016] In one aspect of the method, the airfoil may be that of a rotor blade. In another aspect, it may be the airfoil of a guide vane.

[0017] The tool of the present invention provides a number of benefits. For example, due to the flexibility of the horoscope line which is connected to the robotic head unit the tool allows the blending of static airfoils outside the range of a borescope port. The tool also provides consistency/accuracy in orientation and measurement of the tool by gripping the airfoil to afford a reproducible orientation and basis of measurement. Further, through automation of the process a consistency/accuracy of the blend repair operation is achieved (pre-programmed profiles allow for real-time damage assessment and prognosis and can be created to tolerances based on limits in maintenance manuals). The tool of the present invention also eliminates the high skill set required for executing the repair and thus, the risk of human error. Additionally, instead of a combination of rigid blending tool(s) and flexible inspection tool(s) only a single tool is needed for the entire process. Through eliminating the cost of specialized personnel travelling on short notice to remote locations as well as the cost of potential engine dismount/teardown due to human error while performing inspection and/or blending, significant cost savings can be realized. Finally, significant time savings compared to current state manual processes result from the shorter time that is required for executing the necessary measurements and repairs (and also from the eliminated need to wait for specialized personnel to arrive at the site of the damaged turbo machinery).

[0018] It also is to be appreciated that the tool of the present invention is adaptable to conduct in- situ inspections and repairs of various components of gas turbine engines, as well as other types of machinery. The tool can also be used in non-in-situ scenarios as well where high precision is required. The tool may further be provided together with engine specific kits with adapters tailored to unique components and requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described in the detailed description which follows, in reference to the accompanying drawings by way of non-limiting examples of exemplary embodiments of the present invention. In the drawings:

FIG. 1 shows of a first embodiment of the boroblending tool of the present invention;

FIG. 2 shows the boroblending tool of FIG. 1 attached to an airfoil;

FIG. 3 shows a second embodiment of the boroblending tool of the present invention;

FIG. 4 shows of a third embodiment of the boroblending tool of the present invention;

FIG. 5 shows the boroblending tool of FIG. 4 during its operation; and

FIG. 6 is a schematic representation of the positioning of the tool of the present invention during the repair of an airfoil inside an engine. DFT ATT , FT) DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

[0020] The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.

[0021] FIG. 1 shows a first embodiment of the boroblending tool of the present invention. The tool (1) comprises a flexible borescope line (2) for moving the robotic head unit into position for the inspection and blending of a target airfoil. The borescope line (2) is connected to the robotic head unit through a rotating and pivoting joint (3) which allows the tool to position itself for the target airfoil. Attached to the joint (3) is a unit comprising the stereoscopic camera suite for monitoring the movement and positioning of the robotic head unit on the target airfoil. The stereoscopic camera suite comprises a radial span distance camera (4) for focusing perpendicular to the target airfoil, a navigation and edge distance camera (5) for focusing in forward direction toward the target airfoil, and a repair operation camera (6) for focusing on a repair area of the air foil. Attached to the unit comprising the stereoscopic camera suite is a concave grind wheel on an adjustable platform (7) which can be moved toward and away from the (edge of the) target airfoil. Arranged next to both sides of the grind wheel (7) is an elongated gripping element (8, 8’). Each of the two gripping elements (8, 8’) consists of four moveable parts (9, 9’) of different size which are connected to each other by joints to enable the gripping elements to follow the contour of the target airfoil. The gripping elements (8, 8’) can be moved toward and away from each other, as indicated by the arrows, to grip and release the airfoil as needed. Each of the parts (9, 9’) comprises a roller wheel (10, 10’) on the side of the part which is to contact the airfoil to allow the head unit to transverse along a radial span of the airfoil. The axis of rotation of the roller wheel (10, 10’) is substantially perpendicular to the longitudinal extension of the part (or the gripping element). [0022] FIG. 2 shows the tool of FIG. 1 in operation. Both gripping elements (8, 8’) are in contact with the airfoil and the tool can traverse along a radial span along the airfoil, as indicated by the arrows.

[0023] FIG. 3 shows of a second embodiment of the boroblending tool of the present invention. In this embodiment the robotic head unit comprises two sets of gripping elements (108, 108’, 108”, 108”’) arranged on both sides of the grind wheel (107), with gripping elements of each set being opposite to each other. In this embodiment, the two sets of gripping elements can be moved toward and away from each other, as indicated by the horizontal double arrow. Additionally, the platform of the grind wheel (107) is moveable in horizontal direction between the two sets of gripping elements. They gripping elements (108, 108’, 108”, 108”’) can also be pivoted toward the main axis of the head unit to make it easier for the head unit to pass through small borescope ports.

[0024] FIG. 4 shows of a third embodiment of the boroblending tool of the present invention with the gripping elements (208, 208’) in closed position (for being inserted through a borescope port). The gripping elements (208, 208’) are wedge-shaped but otherwise the third embodiment is the same as the embodiment of the tool shown in FIGs. 1 and 2. FIG. 5 shows the boroblending tool of FIG. 4 during its operation.

[0025] FIG. 6 is a schematic representation of the positioning of the tool of the present invention during the repair of an airfoil inside an engine. As can be seen, the tool is attached to one of the airfoils inside the engine and can transverse the airfoil along its radial span to inspect and blend multiple damaged areas of the airfoil.