GB2197070A - Pivotably mounted ultrasonic testing apparatus - Google Patents

Abstract

An ultrasonic testing apparatus comprises a shoe 3 rotatable about a tube 8 to be tested and includes at least one pivotally mounted arm 2 having at one end the shoe 3 housing an ultrasonic transducer probe and at the other end a counter-weight in the form of a chamber 1. Control means are provided to introduce liquid into, and exhaust liquid from, the chamber 1 whereby the centrifugal force generated during rotation urges the probe into or out of engagement with the tube in dependence on the mass weight of the chamber. To raise the shoe 3 from the tube 8 a control signal passes through closed contacts 10 of a microswitch 9 and a valve 5 opens an outlet port 13 to exhaust the chamber 1 and the arm 1 then pivots away from the tube 8. At the limit of travel, the arm actuates the microswitch 9 to open contacts 10 and change the state of the valve 5 so as to close the outlet 13 and open an inlet to fill the chamber again. Contacts 17 then close to open an inlet to a valve 6 which actuates a hydraulic stop cylinder 11 and a stop 4 arrests the arm 1. To lower the shoe, a control signal changes the state of valve 6 to exhaust the cylinder 11 and retract the stop 4. In another arrangement, mercury is transferred between two chambers on opposite sides of the arm pivot. The pivotal action prevents transducer damage at unfinished ends of the tube, which may be irregular. <IMAGE>

Description

SPECIFICATION Rotary ultrasonic testing apparatus This inventon relates to rotary ultrasonic testing apparatus of the kind used in testing cylindrical metal workpieces, for example for defects and dimensional accuracy by rotating an ultrasonic probe unit or a plurality of probe units in a spiral pitch about the workpiece.

It has been previously proposed to provide one or more testing units on carriers which rotate about the workpiece, more specifically steel tubes, the carriers being arranged such that when the workpiece is located within the testing apparatus, the carriers and/or probe units can be actuated by known means to bring the testing units into contact with the steel tube.

Alternatively, as patent specification GB 1376538 teaches, the probe unit can be mounted at the other end of an arm which is provided with a counter-weighting mass at one end, whereby upon rotation of the unit, the pad is urged inwards towards the axis of rotation by means of centrifugal force generated by the counter weighting mass, thus providing a means of self application of the probe unit. This invention performs satisfactorily on machined or sawn plain ended tubes. However, modern steel tubemaking methods have created occasions wherein it is necessary to test tubes with uncropped ends, when due to the asymmetric shape of such tube ends and associated splits and irregular end conditions, damage to the probe pads often occurs when they are incorporated into known self applying means.

The invention now disclosed seeks to overcome the previously stated disadvantages and prove a solution to other testing unit application probiems found, in particular, in ultrasonic rotary testing systems and current steel tube manufacturing problems.

From one aspect, the present invention provides a rotary ultrasonic testing apparatus comprising a member rotatable about an axis coincident with that of an elongate workpiece to be tested and including at least one pivotally mounted arm having at one end an ultrasonic transducer probe and at the other end a counter-weight in the form of a chamber, control means being provided to introduce liquid into, and exhaust liquid from, said chamber whereby the centrifugal force generated during rotation urges the probe into or out of engagement with the workpiece in dependence on the mass weight of the chamber.

With this invention then, the instances at which the probe is brought into and out of contact with the workpiece, e.g. a cylindrical tube, is governed by the control means, thus avoiding the drawbacks referred to above re the possibility of damage being inflicted. In addition, however, considerable production advantages may be gained if by means of suitable testing apparatus the amount of unusable tube end can be measured, thus providing for the optimum cropping of the tube into wholly tested lengths.

In order for the invention to be fully understood, the following detailed description, aided by the accompanying drawings, will show some embodiments by way of example.

Figure 1 of the drawings shows the basic test unit both in its applied state and, by way of dotted lines, in its relaxed state.

Figure 2 illustrates in schematic form the control detail applicable to a single test unit.

Figure 3 shows by way of example an alternative arrangement by which the invention may be worked.

A rotary ultrasonic test apparatus may comprise a plurality of test units, one of which is typically illustrated in Figure 1 and which consists of a hollow chamber (1) capable of retaining a liquid, e.g. water, mounted at one end of a pivotable arm (2) to the other end of which is attached, by way of a second pivot, a shoe (3) into which suitable ultrasonic transducers (not shown) can be mounted. The shoe assembly may in fact conveniently be as described and shown in GB 1376538 referred to above. The chamber has a port coupled to controllable valve means (5) furnished with an inlet port and an outlet port, see Figure 2; to allow for the escape of displaced air the chamber is further fitted with a suitable air bleed mechanism (7).

When the chamber is empty of liquid, it and its associated components are of a weight less than the weight of the transducer unit, the effect of which, when incorporated into the rotary scanning apparatus, causes the arm (2) to pivot outwardly under the influence of the centrifugal force generated by rotation. To reverse this effect, a predetermined amount of liquid is allowed to enter the chamber, via the inlet port in valve (5), which is then closed; the balance effect on the arm is thus changed by the increase in the mass weight of the chamber such that the centrifugal force now acts to cause the arm to pivot inwardly, forcing the transducer unit shoe (3) into and holding it in contact with the workpiece (8).

In the preferred method of operation to raise the transducer unit shoe from the workpiece, a control signal is applied, via conventional slip rings (not shown) through the closed contacts (10) of microswitch (9). The valve (5) operates such as to open the outlet port and allow the water from the chamber to be exhausted to atmosphere through outlet (13), thus causing the mass weight of the chamber to be reduced and the arm (2) to pivot lifting the shoe (3) away from the workpiece in the manner hereinbefore described. At its limit of travel the arm actuates the microswitch opening contacts (10) thus changing the state of valve (5) such as to close its outlet port and open its inlet port allowing water to flow into the chamber again.At this time, contacts (17) close applying the control signal to valve (6) causing its inlet port to open filling the hydraulic stop cylinder (11), the actuating rod of which extends causing stop (4) to abut the arm and prevent same from pivoting in spite of the increasing mass weight of chamber.

To lower the shoe, a control signal is applied to change the state of valve (6) to close its inlet port and open its outlet port allowing the hydraulic cylinder (11) to exhaust to the atmosphere via its flow control valve (12).

This retracts the stop (4) and allows the transducer unit shoe to move inwardly under the influence of the centrifugal force since the chamber is filled-see above-and into contact with the workpiece. As the arm (2) moves inwardly, the microswitch assumes its former state closing contacts (10) and opening contacts (17) i.e. the operational cycle is completed.

In a further embodiment typically illustrated in Figure 3, a secondary chamber is attached to the arm, both chambers being interconnected. The chambers are fully sealed and each contain an amount of liquid metal, preferably mercury. In operation with the shoe (3) in its lowered state, the mercury is contained in the upper chamber (1), the increased mass weight of chamber causing the arm to be operated in a manner hereinbefore described.

When it is required to raise the transducer unit shoe a control signal is applied to a linear motor (14) which pumps the mercury from chamber (1) to chamber (16), the enclosed air being allowed to bleed into the emptying chamber via interconnecting tube (15).

To lower the transducer unit, the actuating signal is removed from the linear motor and the mercury in chamber (16) transfers to chamber (1) under the action of the centrifugal force caused by rotation of the test system unit.

The transfer of the mercury from chamber to chamber could also be achieved, for example, by means of a Torricellian vacuum.

Claims (10)

1. A rotary ultrasonic testing apparatus comprising a member rotatable about an axis coincident with that of an elongate workpiece to be tested and including at least one pivotally mounted arm having at one end an ultrasonic transducer probe and at the other end a counterweight in the form of a chamber, control means brink provided to introduce liquid into, and exhaust liquid from, said chamber whereby the centrifugal force generated during rotation urges the probe into or out of engagement with the workpiece in dependence on the mass weight of the chamber.

2. Apparatus according to Claim 1, to which the control means includes first and second valves and a changeover switch having first and second states, the application of a signal to said first valve, with the switch in said first state, exhausting liquid from the chamber for the probe to engage the workpiece, whereupon the switch changes to said second state to re-introduce the liquid and actuate the second valve to arrest the said arm, the application of a further signal to the second valve, with the switch in this state, releasing the arm enabling the probe to engage the workpiece whereupon the switch reverts to its first state.

3. Apparatus according to Claim 2, in which the second valve is operative upon a cylinder/piston unit for selectively arresting and releasing the said arm.

4. Apparatus according to Claim 2 or Claim 3, in which the changeover switch is a microswitch actuated by the said arm.

5. Apparatus according to any one of Claims 1 to 4, in which the liquid is water.

6. Apparatus according to Claim 1, comprising a further chamber, closer to the workpiece than said first mentioned chamber, the control means governing a single source for said liquid coupled between these chambers whereby as liquid is introduced into one chamber it is exhausted from the other.

7. Apparatus according to Claim 6, in which the liquid is mercury, the chambers, the said source and the parts therebetween being sealed.

8. Apparatus according to any one of Claims 1 to 7, in which the probe incorporates a shoe assembly as disclosed in Patent Specification No.1376538.

9. A rotary ultrasonic testing apparatus substantially as herein described with reference to Figures 1 and 2 in the drawings.

10. A rotary ultrasonic testing apparatus substantially as herein described with reference to Figure 3 in the drawings.