GB2461864A

GB2461864A - Ultrasonic inspection probe with spherical bearing joint

Info

Publication number: GB2461864A
Application number: GB0812759A
Authority: GB
Inventors: Simon Bates; Andrew Roy Collis
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 2008-07-14
Filing date: 2008-07-14
Publication date: 2010-01-20
Also published as: GB0812759D0

Abstract

An inspection probe has a probe body 1 that is drivable to positions around a component to be inspected. The probe also has an ultrasonic sensor 3 connected to an end of the probe body. In use, the sensor makes contact to a surface of the component. The sensor is connected to the probe body by what is termed a spherical bearing joint comprising an inner member 12 connected to the sensor and an outer member 13 connected to the body to allow rotational movement of the sensor relative to the probe body. The sensor 3 comprises a transducer 4 mounted in a housing 9 with a spring 10 to cushion the transducer. Contact with a surface is made by a delay line 5 with a delay line collar 6 also both mounted within housing 9. The arrangement preferably allows for rotational movement of the sensor through an included angle of more than 7 or 10 degrees. The probe may be used in the inspection of gas turbine fan blades after manufacture such as to determine wall thickness or the position of inaccessible surfaces.

Description

INSPECTION PROBE

The present invention relates to ultrasonic sensor inspection probes.

Manufactured components which have to conform to dimensional and/or geometrical tolerances may be subjected to post-manufacture inspection procedures. For example, gas turbine engine critical components, such as blades, vanes and discs, are commonly inspected post-manufacture.

A known technique for determining the dimensional accuracy of components involves driving a computer-controlled coordinate measuring probe over the surface of the component. The technique is described, for example, in W02007/028941. When the component has hollow portions or other features producing externally inaccessible surfaces, a variant of this technique involves using a probe body to carry an ultrasonic sensor to positions on the external surface of the component and taking ultrasonic measurements which allow wall thicknesses or the positions of inaccessible surfaces to be determined. For example, the wall thicknesses of hollow aerofoils for gas turbine engines may be inspected in this way. Two examples of such hollow aerofoils are fan blades and outlet guide vanes (OGV5) Typically, the probe body is fitted to a quill (providing z-direction movement), which in turn is mounted to a carriage assembly (providing x-and y-direction movement), and the component mounted on a measuring table, whereby the movements of both the probe and the component can be controlled via a programmable coordinate measuring machine. Sensing means, such as a strain gauge, associated with the probe detects when the ultrasonic sensor contacts a surface.

A problem can arise, however, that the ultrasonic sensor does not always align properly to the surface of the component.

Thus, in a first aspect, the present invention provides an inspection probe having: a probe body that is drivable to positions around a component to be inspected, and an ultrasonic sensor connected to an end of the probe body and which, in use, makes contact to a surface of the component; wherein the sensor is connected to the probe body by a spherical bearing joint to allow rotational movement of the sensor relative to the probe body.

Spherical bearing joints are also known as rose joints or heim joints. By using such a joint, the ultrasonic sensor can rotate freely relative to the probe body, and thus consistent and fast alignment with the contact surface of the component can be achieved. Measurement accuracy can also be increased. Further, the operator can run the probe at relatively high speeds, which reduces component inspection times.

The spherical bearing joint can allow rotational movement of the sensor relative to the probe body through an included angle of more than 7°. Indeed, preferably, the joint allows rotational movement through an included angle of more than 10°.

A second aspect of the present invention provides the use of the inspection probe according to the first aspect for ultrasonic inspection of a fan blade.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of a probe; Figure 2 is a longitudinal cross-sectional view of the probe of Figure 1; and Figure 3 shows the ultrasonic sensor of the probe of Figure 1 making contact with the surface of a component.

Figure 1 is a plan view and Figure 2 is a longitudinal cross-sectional view of a probe according to the present invention.

The probe has an elongate probe body 1 which at a proximal end has a threaded projection 2 for fitting to a probe head, such as a commercially available Renishaw PH1OTM indexable head. The distal end of the body 1 houses an ultrasonic sensor 3.

The sensor 3 comprises an ultrasonic transducer 4, a delay line 5, and a delay line collar 6. In use, exposed face 7 of the delay line makes contact with the surface of the component under inspection. A housing 9 surrounds the transducer 4 and the collar 6. A spring 10 is located between the transducer and the housing and the collar is slidably movable within the housing, whereby the spring cushions the transducer when contact is made with the component. The Renishaw PH1OTM head has a built-in strain gauge for detecting contact force overloads.

A couplant delivery line 11 provides couplant to the exposed face 7 of the delay line. However, the line can be omitted, and couplant provided by other means, for example manually by the operator.

A spherical bearing having inner 12 and outer 13 parts joins the sensor 3 to the distal end of the probe body 1.

The sensor housing 9 is interference fitted through a central hole in the inner part 12, and the outer part 13 is connected to the distal end of the probe body 1. Thus, when the inner part 12 rotates in the outer part 13, the ultrasonic sensor 3 rotates relative to the probe body.

Figure 3 shows how the sensor 3 rotates when contact is made with the surface of a component 14. The centre of rotation is indicated by the intersection of the superimposed crossed lines. The axial line of the transducer 4 and delay line 5 inclines relative to the axis of the probe body to be perpendicular to the surface of the component at the contact position of face 7, which thus fully seats on the surface. An accurate ultrasound measurement can then be obtained.

The spherical bearing has a low friction interface between its inner 12 and outer 13 parts, and so there is very little resistance to the rotational movement.

Further, the spherical bearing has no "preferred" direction of rotation, allowing the sensor to move freely in any direction. Geometrical constraints allow a maximum angle of inclination of the axial line of the transducer 4 and delay line 5 relative to the axis of the probe body of about 8°, which corresponds to a maximum included angle of about 16°. Design modifications to the distal end of the probe body, the spherical bearing and the sensor could, however, permit larger inclination angles to be achieved.

While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure.

Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

Claims

CLAIMS1. An inspection probe having: a probe body that is drivable to positions around a component to be inspected, and an ultrasonic sensor connected to an end of the probe body and which, in use, makes contact to a surface of the component; wherein the sensor is connected to the probe body by a spherical bearing joint to allow rotational movement of the sensor relative to the probe body.
2. An inspection probe according to claim 1, wherein the spherical bearing joint allows rotational movement of the sensor relative to the probe body through an included angle of more than 7°.
3. Use of the inspection probe according to claim 1 or 2 for ultrasonic inspection of a gas turbine engine aerofoil.
4. An inspection probe substantially as herein described with reference to and as shown in the accompanying drawings.