Patent Number: 046817301
Section: description

DETAILED DESCRIPTION The device shown schematically in FIG. 1 is intended to be placed on a structure 8 provided in a pool in the vicinity of an assembly 10 to be checked. FIG. 1 shows the silhouette of the top part of such an assembly 10, comprising an end piece 12 on which braces 14 are fixed. A single element 16, closed by a cap 18, has been shown. The plate 8 compises jaws 20 for clamping the end piece 12 and a mechanism for rotating the assembly in the open jaws, around its vertical axis. Another method may consist of a simple suspension from a lifting equipment having a turning hook associated with the same jaws 20. The detection device, properly speaking, comprises a framework 22 made from several welded parts, having sleeves for centering on studs 26 of the support 8 and a handling gantry 38. The parts of the device for moving the transducer respectively in the directions X, Y and Z will now be described. The first two parts may be of any conventional construction used for providing crossed movements. In the embodiment illustrated, the X movement part comprises a motor 30 whose output shaft drives a screw 31 threadedly connected by recirculating balls to a ring 32 fastened to a support plate 33. This plate is provided with shoes sliding on guide slides 34 in the direction X, which, as will be seen, is transversal to the direction for introducing the transducer into the assembly. The part for movement in direction Y, comprises a motor 36, of the step by step type, like motor 30, and whose output shaft drives a screw 40. A ball socket 42 mounted on screw 40 drives a table 44 which slides over slides (not shown). For manually removing the transducer in case of an operating defect in motor 36, a manual control is provided. It comprises a control square 46 driving screw 40 through a bevel gear 47. Limit switches 48 will generally be provided for actuation by socket 42 when this latter arrives at the end of its working course. The X movement assembly also generally comprises limit switches. Finally, the motors of the two parts are associated with movement measurement coders (not shown). The part 50 for moving in direction Z, (i.e., along the axis of assembly 10) is shown only by its contour in FIG. 1. As shown in FIGS. 2 and 3, this part comprises a frame 52 supported by table 44 through a resilient device 54 capable of sliding in the direction in which the transducer is introduced into the assembly and absorbing the shocks caused by engagement of the transducer, so as to avoid damage to the equipment or the elements to be checked. A limit switch 56 detects the sliding and stops motor 36 in case of an engagement causing sliding. Frame 52 of part 50 is formed by a welded structure comprising a slide carried by table 44, brackets 53 and a flange 64. On flange 64 is fixed, for example by means of screws, a second structure 66 made from crossed plates welded together, forming the bottom of a sealed case 58 which contains a step by step drive motor 60 and electric connections 62 for supplying control pulses to motor 60. The pressurization fluid arrives in this case through a fluid tight connection 68 (FIG. 2). Frame 52 (FIG. 3) comprises transverse plates 70 for guiding a mobile equipment in direction Z. This equipment comprises two columns 72 connected together by a connecting piece 74 and sliding in ball bearings carried by plates 70. Plate 74 is supended from the end piece 76 of a threaded rod 78 secured against rotation and engaged in a tapped tube 80 keyed to the output shaft 82 of motor 60. A bearing 84 carried by the upper plate 70 provides guiding of the rotary tube 80. The connection piece 74 has a finger 86 (FIG. 3) for tripping a contactor 88 carried by a frame 52 when the mobile assembly arrives at the top end of its travel. A part, which, will be called hereafter "sword" because of its shape, will be called hereafter "sword", comprises a vertical plate 92 fixed to columns 72 by collars 90 and a metal rod 94 of rectangular section locked on plate 92 so as to be directed in direction Y. In the plate is formed a groove for guiding a cable 96, extended by a sheath 98 fixed to rod 94. The groove is covered by a plate preventing the cable from escaping. The end of cable 96 is fixed by a screw 100 to the connecting piece 74 and is held in position over only a fraction of its length by a guide 102. Thus, the cable 96 remains free over a length d. The end part of rod 94 (FIG. 4) carries a transducer 104 through a double articulation allowing the transducer to move freely vertically with respect to the rod and guaranteeing clean engagement of the transducer against each cap of elements 18. The double articulation is provided by fork 106 mounted for rotation on a shaft 108 carried by the rod and on which the transducer rotates around a shaft 110 parallel to the first one. The cable 96 is fixed, for example by welding, to a projection 112 on the fork 106 offset with respect to shaft 108. The operation of the device is as follows. The assembly to be checked is positioned in the mechanism, or suspended from its handling tool, allowing it to be rotated around its vertical axis between the jaws 20 for positioning piece 10 with respect to the detection device shown schematically in FIG. 1. With the device in position, and the "sword" withdrawn in direction Y, the dimensional characteristics of the assembly are stored in a control system of the device, then the checking sequence begins. Motor 30 is actuated to bring the "sword" opposite to a diagonal network of elements to be checked. Motor 30 can be started and stopped automatically by a Program Logic Controller (PLC), whose input signal is provided by a coder associated with motor 30. With the position along Z of the "sword" such that transducer 104 and rod 94 may be reliably engaged in the free space between the end piece 12 and the elements, motor 36 is in its turn actuated to bring the transducer above a first element 16 to be checked. The parts are then arranged as shown in FIG. 4. Motor 60 is then actuated in its turn to lower the "sword". If this latter stops because the bottom of rod 94 abuts against an obstacle such as an element placed in front of the one to be checked, the connecting piece 74 continues to descend slightly. Cable 96 then slides in its sheath 98 and allows the transducer 104 to rock until it comes into contact with the cap 18 of the elements 16 to be checked. Once piece 74 is in its turn immobilized, the end piece 76 is freed therefrom and can continue to descend until the motor 60 stops, controlled by the PLC. The ultrasonic exploration is then carried out using a method which may be the one described in document EP-A-0 115 231 already mentioned. The "sword" is then raised, by motor 60, up to a level such that it may freely pass through the space between the elements and the end piece 12. The transducer is advanced one step in the direction Y and the sequence is repeated. Because of the presence of the braces, access to all the elements cannot be obtained through a single diagonal direction of the assembly 10. Consequently, the "sword" will be removed once a fraction of the elements have been checked. The assembly will be rotated by at least once 90.degree. and another fraction of the elements will be checked. It can be seen that, because of the rocking mounting of the transducer 104, the active face of the transducer will always be applied flat against the end face of cap 18. Moreover, because the transducer may continue its downward movement if the rod should come into abutment, it is possible to test one element masked by another such as element 16a, in FIG. 4.