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IP.com Disclosure Number: IPCOM000228879D
Publication Date: 2013-Jul-10
Document File: 5 page(s) / 1M

Publishing Venue

The IP.com Prior Art Database


The present invention provides a technique and apparatus for inspecting permissible size of a dovetail slot in a gas turbine disk. The apparatus includes a set of gages. The set of gages have precise blue print tolerances for acceptance/failure criteria that the gages slide into dovetail groove or do not slide into dovetail groove. Further, the gages are calibrated and increased in their size to determine closest size of dovetail slot.

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The present invention relates generally to a gas turbine engine and more particularly to a technique of determining acceptability of dovetail size in a gas turbine engine.

In a gas turbine engine, components such as compressor, turbine, and turbofan have a similar construction. Each of them includes a plurality of circumferentially spaced blades connected to and extending from a disk. Typically, the blades are held in the disk by machining multiple slots around the perimeter of the disk. The blades have a similarly shaped feature at its base and into the slot. These machined slots are referred as dovetail slots.

The dovetail slot width parameter is important as respective bearing surfaces of the slot portions are crucial in maintaining the blade within the dovetail slot and incur the greatest amount of stress. Accordingly, inspecting and monitoring slot width of the dovetail slot enables wear to be recognized such that the gas turbine component is repaired or replaced.

A conventional technique and apparatus for inspecting dovetail slot of a gas turbine engine disk includes pins, a plate, a probe and an actuable member. One of the pins is fixed in a stationary position while another is oriented substantially parallel to the first pin. The actuable member functions to automatically position the two pins in a predetermined position within the dovetail slot. The probe measures a distance between the two pins when the pins are in the predetermined dovetail slot position. The plate forms a base to which the pins, the actuable member, and the probe are assembled in a predetermined manner.

Another conventional technique includes an inspection apparatus for rotor disk inspection. The apparatus includes an inspection fixture which has a base, and a guide extending from the base. Each guide is slidably engageable to one of rotor slots of the rotor disk and has a guide side shaped to slidably conform to the rotor slot side. The guide includes a bottom portion having a guide bottom surface which, in combination with a slot bottom surface, defines an elongated inspection cavity extending parallel to axis of revolution of the rotor disk. The inspection fixture is mated to the rotor disk such that each guide slides into one of the rotor slots. Inspection is performed by inserting a sensor into the inspection cavity, and sensing the rotor slot bottom using the sensor.

However, such conventional techniques use pins and calipers which do not provide prompt and accurate measurement. Also, it is difficult to work with such apparatus as it is not convenient to hold pins and calipers while taking measurement.

It would be desirable to have a simple and improved technique of determining acceptability of dovetail size in a gas turbine engine.


Figure 1 depicts the set of gages used in the apparatus.


Figure 2 depicts an assembly of gages in the apparatus.

Figure 3 depicts insertion of calibrated s...