Grinding apparatus for blending defects on turbine blades and associated method of use

A grinding apparatus for use with an endoscope for viewing and blending defects on a turbine engine blade is provided. In one preferred embodiment air pulses from an air supply cause a grinding head on the end of a grinding tool to reciprocate at a predetermined speed. The position of the grinding head is fixed via the operator via a trigger on the grinding tool which articulates an outer portion of a support tube of the grinding tool. In another preferred embodiment, fluid is used to reciprocate the grinding head.

FIELD OF THE INVENTION

The present invention relates to apparatus for blending defects on turbine blades such as, for example, nicks and notches. More particularly, this invention relates to a grinding apparatus for blending defects on turbine blades using an endoscope to view the defects through observation ports in an engine casing.

BACKGROUND OF THE INVENTION

Conventional gas turbine engines, such as those used in aircraft, are enclosed in an engine casing and include a plurality of turbine blades secured to a drum. Such gas turbine engines, typically mounted on the wing of an aircraft, are frequently damaged by foreign objects, such as sand particles, stones, or other objects ingested by the engine during takeoff. These foreign objects ingested by the air turbine engine often cause generally V-shaped nicks or chips on impact along the leading edge of the affected turbine blades. The process of replacing a turbine blade is very expensive, so repair in place is desirable when compared to replacement.

In order to prevent such notches or nicks from becoming more pronounced and potentially cracking the turbine blade, it is desirable to detect the nicks or notches early and, if possible, repair or blend the defects in the turbine blades. In general the term blending is used in the art for the process of smoothing a V-shaped notch or nick into a more U-shaped configuration.

The detection process involves a visual inspection of each turbine blade through a borescope or endoscope passed through observation ports or holes in the engine casing. 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. If a turbine blade having excessive damage is observed, the engine must be removed from the wing of the aircraft, and then disassembled to expose the damaged blade. Only then can the blade be accessed and repaired or replaced. This procedure is time-consuming and extremely expensive. Consequently, more practical techniques for repairing or blending notches or defects on an aircraft turbine blade have been developed.

One type of apparatus used to blend defects on turbine blades in the manner described above uses a rotary grinding head or tool located at the end of a blending tool. The tool may be passed through the observation ports in the engine casing. U.S. Pat. Nos. 5,644,394; 5,803,680 and 5,475,485 disclose such apparatus. One difficulty with tools using rotary heads is that the rotational speed required to blend the defect is so high that the surface of the turbine blade becomes very hot due to friction. Because most turbine blades are made of titanium, the integrity of the titanium may be compromised at high temperatures. The titanium metal may actually melt or deform at high enough temperatures.

An alternative to a tool which rotates a grinding head is disclosed in U.S. Pat. No. 5,102,221. This patent discloses an apparatus for repairing or blending defects on a turbine blade using a reciprocating motion, as opposed to a rotary motion. Again, this apparatus is used with an endoscope. The apparatus disclosed in this patent is difficult to use and subject to failure due to the configuration and operation of the apparatus. Therefore, there is a need for a grinding apparatus to blend defects on turbine blades which is user-friendly and utilizes a reciprocating motion, as opposed to a rotary motion.

SUMMARY OF THE INVENTION

One preferred embodiment of the present invention comprises a grinding apparatus including two principal components: an endoscope and a grinding tool operatively coupled to the endoscope. Any commercially available endoscope may be use with the present invention. One type of commercially available endoscope which has proven to work satisfactorily with the present invention is manufactured by Machidascope under model FBA-2.4-100 and may be ordered at www.machidascope.com.

In one preferred embodiment, the grinding tool is coupled to a compressed air supply via an air supply line. Air pulses provided by the air supply reciprocate a grinding head operatively coupled to the grinding tool. In another preferred embodiment, fluid is transported to the grinding tool via a supply line and functions to reciprocate the grinding head. In yet another preferred embodiment, a motorized driver is coupled to the grinding head and upon being activated mechanically reciprocates the grinding head.

The grinding tool is adapted to be used with an endoscope for blending a defect on a turbine blade inside a casing. The grinding tool comprises a base unit having a base, a handle extending downwardly from the base proximate the rear of the base, and a trigger located in front of the handle and extending downwardly from the base also. Although one configuration of base unit is illustrated, the base unit may assume numerous other configurations without departing from the spirit of this invention.

The grinding tool further comprises a support tube extending forwardly from the base unit and being sized to fit through an observation port in the casing. The support tube in one preferred embodiment has an opening at the forward end of the support tube, so that an articulated end of the endoscope may pass through the support tube and out the opening in the support tube.

In one preferred embodiment, an extension member is hingedly connected to the forward end of the support tube and operatively coupled to the trigger. Because the extension member is mechanically connected to the trigger, an operator may change the position of the extension member by moving the trigger, thereby flexing the hinge. The extension member has a hollow interior in which is located a piston and a spring surrounding a portion of the piston. No matter what the position of the extension member, air passes through the support tube and hinge to reciprocate the piston in the extension member.

A cylindrical grinding head is coupled to a forward end of the piston and upon activation reciprocates at a predetermined speed. Pulses of air supplied by the source of compressed air and pushed through an air supply line to the grinding tool push the piston against the bias of the spring in the extension member, causing the spring to compress. When the burst or pulse of air is exhausted, the spring forces the piston back to its original position. In this manner, the spring goes through a cycle of compression and noncompression as the piston reciprocates in response to the air pulses. Other means of reciprocating the grinding head may be used if desired.

In another preferred embodiment of the present invention, the support tube comprises a first linear portion having an opening therein so that the forward end of the endoscope can pass through the opening in the support tube and enable the operator to view the turbine blade. The support tube further comprises a second linear portion hingedly connected to the first portion and operatively coupled to the trigger so that movement of the trigger causes movement of the second portion of the support tube. A piston and spring arrangement like the one described above are located in the second movable portion of the support tube. A reciprocating grinding head is coupled to the piston.

Although the present invention preferably has a hinge incorporated into the support tube, it is within the contemplation of the present invention that the support tube lack a hinge. In such an embodiment, the support tube is preferably bent but may assume any desired configuration. In this situation, a second portion of the support tube is fixed at an angle, preferably an acute angle, relative to the first linear portion of the support tube.

In use, a defect on a turbine blade may be blended or smoothed using the grinding apparatus of the present invention. The first step in utilizing the grinding apparatus of the present invention is to couple a commercially available endoscope to the grinding tool. This is accomplished by passing a portion of the endoscope, including the lens end, through the base of the grinding tool, through the support tube of the grinding tool and out an opening in the support tube. When coupled to a light source, the endoscope enables the operator to view inside the engine casing.

Then the support tube of the grinding tool, with the endoscope passing therethrough, is passed through an observation port or hole in the engine casing. Using the endoscope, the operator locates a defect on the turbine blade by visual scanning. The operator then uses the trigger on the grinding tool to position the grinding head proximate to the defect on the turbine blade. Then a driver is activated to supply air pulses to the grinding tool via the air supply line. The air pulses pass through the support tube of the grinding tool and contact the piston, causing the piston and grinding head of the grinding tool to reciprocate at a desired speed. The frequency of the air pulses may be varied as desired by any known means to change the speed of reciprocation of the grinding head. If desired, the air pulses may be used to rotate rather than reciprocate the grinding head.

In another preferred embodiment of the present invention, fluid is used to reciprocate the grinding head. The fluid is provided via a fluid supply and passed through a supply tube to the grinding tool to reciprocate the grinding head. Any means such as a motorized pump may be used to supply fluid to the grinding tool.

In another preferred embodiment of the present invention, a wire is used to reciprocate the grinding head. The wire is operatively coupled at one end to a motorized driver such as a variable speed motor, passed through the grinding tool and coupled to a piston which is secured to the grinding head. Activation of the motorized driver reciprocates the grinding head. Any means such as a cam driven by a motor may be used to reciprocate the wire operatively coupled to the grinding tool.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings and particularly toFIG. 1, there is illustrated a grinding apparatus10including an air supply12, an air supply line13and a grinding tool14for use with an endoscope16. The endoscope16has an eyepiece17at the end of a tube19and an articulated lens end20moveable via movement of a lever18on the eyepiece17, as is known in the art. Any other sort of viewer such as a video viewer may be used in place of the eyepiece17to view or display data. Preferably, the endoscope16is used with a light source22. Although one type of endoscope is illustrated and described, the grinding apparatus10may be used with many different types of endoscopes.

The grinding apparatus10of the present invention is used for blending or retouching a defect, notch or nick24along the leading edge26of a turbine blade28secured to a drum30(only partially shown) in a manner known in the art. The drum30and turbine blades28attached thereto are mounting in an engine casing32having a plurality of observation ports34, as is known in the art.

As best illustrated inFIG. 1, the air supply12may include any known means to provide air pulses and push them through the air supply line13to the grinding tool14.

As best illustrated inFIG. 1, the grinding tool14comprises a base unit36including a base38, a handle40and a trigger42. The base38is preferably made of metal but may be made of any material. The base38has a top wall44, a bottom wall46, a front wall48, a rear wall50and a pair of opposed side walls52. The handle40extends downwardly from the bottom wall46of the base38proximate the rear wall50of the base38. Similarly, the trigger42extends downwardly from the bottom wall46of the base38in front of the handle40. Although one configuration of base and base unit are illustrated and described, other configurations of bases and base units may be utilized without departing from the present invention. For example, the handle and/or trigger may be located at a different location. Alternatively, the handle may be omitted and/or the trigger replaced with other apparatus.

The grinding tool14further comprises a support tube54extending forwardly from the base38. As shown inFIG. 1A, the support tube54has a circular wall56having an outer surface58and an inner surface60. The interior62of the support tube54is hollow and divided into an upper portion5and a lower portion6by a divider or guide7. As shown inFIG. 1A, the endoscope tube19passes through the lower portion6as shown inFIG. 1A. As illustrated inFIG. 2, the support tube wall56has an opening64at a forward end66of the support tube54. The articulating end20of the endoscope16protrudes through this opening64in a manner shown inFIG. 1to enable the operator to view inside the engine casing wall32. To couple or join the endoscope16with the grinding tool14of the present invention, the articulating lens end20of the endoscope16is passed through a hole68in the rear wall50of the base38, through the base38and then through the lower portion6of the support tube54before exiting the opening64in the support tube wall56.

In a first preferred embodiment, an extension member70is coupled or joined to the support tube54via hinge72. The hinge72pivots about an axis73and is coupled or joined to the support tube54and the extension member70. SeeFIG. 1.FIG. 3illustrates in detail one form of hinge72; however, any other type of suitable hinge may be used in accordance with the present invention.

In one preferred embodiment of the present invention, the extension member70is preferably a linear piece of tubing, made of metal, plastic or any other suitable material. As seen inFIG. 3, the extension member70has a circular wall74having an outer surface76and an inner surface78. However, the extension member70may assume other configurations without departing from the spirit of the present invention. If desired, the extension member70may be considered a second portion of the support tube hingedly connected to a first linear portion of the support tube. If desired, the hinge may be omitted and the second portion of the support tube fixed in position relative to the first portion of the support tube.

The extension member70is operatively coupled to the trigger42so that the operator may move the extension member70by moving the trigger42. In one preferred embodiment, at least one wire80(shown in cross section inFIG. 1A) is secured at one end82to the extension member70via welding or any other suitable method and secured at the other end (not shown) to the trigger42. SeeFIG. 3. The wire80extends the length of the support tube54on the inside thereof. Although this is one mechanical way of coupling the trigger42and extension member70so that the extension member70may be mechanically moved to its desired position, other methods of coupling the trigger and extension member may be utilized. As shown inFIG. 2, the trigger42may be moved from a first position shown in dashed lines to a second position shown in solid lines which causes the extension member70to move from an extended or first position shown in dashed lines inFIG. 2to a bent or second position shown in solid lines inFIG. 2.

As shown inFIG. 3A, the hinge72has an outer wall71inside which wire80passes. In addition, an air tube92passes through the hinge72inside the hinge outer wall71. The air tube92is a flexible piece of tubing having an outer tube wall93, preferably made of plastic, which extends from an air stop55in the support tube54to a piston86in the extension member70. SeeFIGS. 3 and 3A.

As shown inFIG. 1A, the support tube54has an air stop55at the forward end66of the support tube54which reduces the diameter through which the air flows as air passes through the hinge72. The air stop55has an opening94through which the air tube92passes and another opening96through which the wire80passes. SeeFIG. 1A. If desired, two or more wires or other structures may be used in accordance with the present invention.

As shown inFIG. 3, a piston86is located at least partially inside the extension member70and moveable therein in reaction to the pulses of air from the air supply12. The piston86has a base portion100and an finger portion102extending forwardly from the base portion100. The base portion100of the piston86has a diameter approximately equal to the inner diameter of the extension member70so that air may not get through the extension member70without moving the piston86. A spring104surrounds the finger portion102of the piston86inside the extension member70as shown inFIG. 3. The spring104extends between a stop106at the forward end108of the extension member70and the base portion100of the piston86. When a pulse of air passes through the tube92, the air exerts force or pressure on the base portion100of the piston86, moving the base portion100of the piston86forwardly against the bias or force of the spring104, thereby compressing the spring104against the stop106in the extension member70. Once the pressure from the air pulse is relaxed or extinguished, the spring104pushes the piston86back to its original position in which the base portion100of the piston86abuts a stop110in the extension member70. In this manner the spring104cycles between a compressed position and a relaxed position in response to the air pulses generated in the air supply12and passed through the air supply line13to the grinding tool14.

A grinding head112is coupled to the finger portion102of the piston86outside of the extension member70in a manner shown in detail inFIG. 3. The grinding head112is preferably cylindrical but may be other shapes or configurations. Any suitable means of securing the grinding head112to the finger portion102of the piston86may be used.

In use, the endoscope16is coupled or joined to the grinding tool14by passing the lens end20of the endoscope16through the opening68in the base38of the endoscope, through the base38of the grinding tool14, through the support tube54of the grinding tool14and out the opening64in the support tube wall56. A light source22is coupled to the endoscope16in a manner known in the art either before or after the endoscope16is coupled to the grinding tool14. The operator then passes the support tube54of the grinding tool14with a portion of the endoscope16therethrough through one of the observation ports34in the engine casing32. The operator then uses the endoscope16to locate a defect24along the leading edge26of a turbine blade28. The operator then positions the grinding head112proximate the defect24and activates the air supply to provide air pulses to the grinding tool14. The operator uses the trigger42to move the extension member70and grinding head112via the hinge72in the manner described above. The air pulses reciprocate the piston86in the extension member70of the grinding tool14. The reciprocation of the piston86causes the grinding head112to reciprocate because the piston86and grinding head112are joined together.

An alternative preferred embodiment of the present invention is illustrated inFIG. 4. For the sake of simplicity, like numerals will be used to describe like parts but with a letter “a” designation. In this preferred embodiment, fluid is used rather than air to reciprocate a grinding head112asecured to the end of an extension member or portion of a support tube70a. Any method of securing the grinding head112ato the end of the extension member70amay be used. A piston114pushes and pulls fluid from a fluid supply116through tube118to the grinding tool14a. The fluid passes through the support tube54aincluding hinge72ato a piston (not shown). The back and forth movement of the fluid in the grinding tool14areciprocates the piston (not shown) to which is connected grinding head112a. In many respects, the grinding tool14ais similar to the grinding tool14described above, except fluid rather than air is used to reciprocate the grinding head.

An alternative preferred embodiment of the present invention is illustrated inFIG. 5. For the sake of simplicity, like numerals will be used to describe like parts but with a letter “b” designation. In this preferred embodiment, a mechanical driver is used rather than air or fluid to reciprocate a grinding head112bhingedly secured to the end of an extension member70bor portion of a support tube54bwith hinge72b. Any method of securing the grinding head112bto the end of the extension member70bmay be used. A motorized driver118pulls a wire120extending through the support tube54bof the grinding tool14aaround a pulley124and secured to a piston86blocated in extension member70b. Extension member70bis hingedly connected to the support tube54bin any operable manner. A grinding head112bis secured to the piston86bin any suitable manner or fashion. A spring122located inside the extension member70bpushes the piston86bback outwardly after the tension on the wire120is partially relaxed. The back and forth movement of the piston86bdue to the motorized driver118, wire120and spring122causes the grinding head112bto reciprocate. In many respects, the grinding tool14bis similar to the grinding tool14described above, except a motorized driver in concert with a spring causes the grinding head to reciprocate.

It is to be understood that various changes and modifications may be made to the preferred embodiments discussed above without departing from the scope of the present invention, which is defined by the following claims and equivalents thereof. For example, with any of the embodiments described herein, the grinding head may be rotated rather than reciprocated.