Semi-automatic scanner for ultrasonic flaw detection

A semi-automatic scanner for ultrasonic flaw detection comprises a carriage travelling on a guide rail, a guide arm extending in a direction transverse to the travel direction of the carriage and supported by the carriage so as to pivot in a plane transverse to the travel direction of the carriage, a probe holder slidably supported by the arm, and a probe mounted on said probe holder so as to pivot about two axes transverse to each other. One of the axes is generally in parallel to the travel direction of the carriage. The carriage is driven by a motor, and the probe is moved by manual or motor-driving operation in a direction transverse to the travel direction of the carriage while pressing the probe on a surface to be inspected, whereby the probe accurately follows the surface even if the surface is curved.

BACKGROUND OF THE INVENTION 
This invention relates to a semi-automatic scanner for ultrasonic flaw 
detection, and more particularly to a scanner which can satisfactorily 
perform also the inspection of a curved surface in a bent piping. 
A conventional scanner or ultrasonic flaw detector is disclosed in Japanese 
Laid-open Patent Application No. 52-108874. The detector comprises a 
carriage travelling on a guide rail mounted on a pipe, a guide rod mounted 
on the carriage and extending in the axial direction of the pipe, an 
inspection arm mounted so as to move along the guide rod and extending 
perpendicularly to the surface of the pipe, and a probe mounted on the end 
of the inspection arm so as to contact the surface to be inspected. In the 
ultrasonic flaw detector, the probe suitably follows the surface of a 
straight pipe shown in FIG. 1 of the above mentioned document, through the 
peripheral movement of the carriage as well as the guide rod, the axial 
movement of the inspection arm, and the movement of the probe 
perpendicular to the surface to be inspected of the pipe. However in a 
case where the ultrasonic flaw detector is employed to inspect the curved 
surface part of a bent pipe, the probe does not properly follow the curved 
surface. 
In pipings to be inspected in a nuclear power plant, there are more bent 
pipe portions than straight pipe portions and much time is needed for 
inspecting such a bent pipe portion. Therefore, there scanners or 
ultrasonic flaw are desired which can satisfactorily perform also the 
inspection of the curved surface portions of bent pipings. 
SUMMARY OF THE INVENTION 
An object of the invention is to provide an ultrasonic flaw detector or 
scanner, in which a probe can follow satisfactorily a curved surface such 
as a bent pipe. 
Another object of the invention is to provide an ultrasonic flaw detector 
or scanner, wherein a probe can move to cover all the surface to be 
inspected including a curved surface of a bent pipe, and which can trace 
the track of the probe even if it is operated manually. 
A further object of the invention is to provide an ultrasonic flaw detector 
or scanner which can perform an accurate inspection with manual operation. 
Still another object of the invention is to provide an ultrasonic flaw 
detector or which can detect flaws in the curved surface such as a bent 
pipe without requiring a large area for installing the detector on the 
bent pipe. 
Briefly stated, the invention resides in a semi-automatic scanner for 
ultrasonic flaw detection comprising a carriage travelling on a guide 
rail, a guide arm extending in a direction transverse to the travel 
direction of the carriage and mounted on the carriage so as to pivot or 
swing in a plant transverse to the travel direction, a probe holder 
slidably mounted on the guide arm, and probe pivotably held by the probe 
holder so that the probe follow a curved face to be inspected.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the accompanying drawings, an embodiment of a semi-automatic 
scanner for ultrasonic flaw detection according to the invention will be 
described hereinafter in detail. 
In FIG. 1, the scanner or ultrasonic flaw detector 1 comprises a carriage 
3, a guide arm 5 supported by the carriage 3 to move along with the 
carriage 3, a probe holder 7 mounted slidably on the guide arm 5, and a 
probe 9. 
The carriage 3 is fitted on a guide rail 11 so as to travel thereon. The 
guide rail 11 is mounted coaxially on a pipe 2 to be inspected, and has a 
guide groove portion 13, a rack 15, and a supporting portion 17, each 
formed thereon. The carriage 3 is provided with front rollers 21 fitted in 
the groove 13, and back rollers 23 pressing against the backside of the 
groove portion 13, which back rollers 23 each are mounted rotatably on 
brackets 37. A plurality of pairs of the rollers 21 and 23 sandwich the 
guide rail 11 so that the carriage 3 can not be dismounted from the guide 
rail 11. 
The carriage 3 will be described more in detail. In FIG. 3, the carriage 3 
has a housing 25 somewhat extending circumferentially and supporting 
thereon the guide arm 5 as previously stated, and a driving apparatus 27 
in the housing 25. The driving apparatus 27 comprises a motor 29, a safety 
device 31 connected to the motor 29 by gear means, reduction gears 33 
including a worm gearing mechanically connected to the safety device 31 by 
gear means, and a pinion 35 meshed with the rack 15 of the guide rail 11. 
The safety device 31 includes a shaft with a flange 32, and a gear 34 
pressed by a spring and brought into a frictional engagement with the 
flange 32, and it is made so that the gear 34 idles and the rotation of 
the motor 29 is not transmitted to the pinion 35 when the pinion 35 
receives a force larger than a frictional force existing between the gear 
34 and the flange 32. A rotary encoder 36 is connected to the pinion 35 
through gear means to produce signals corresponding to the travelling 
distance of the carriage 3. As previously stated, the back roller 23 is 
mounted on the bracket 37. The bracket 37 is fitted in a groove 38 made in 
the side portion of the housing 25 and separably secured thereto by screw 
means. 
The carriage 3 can run on the guide rail 11 according to the rotation of 
the motor 29 and be stopped at any position. 
As shown in FIG. 2, the guide arm 5 comprises two rods 39, 41 arranged in 
parallel to each other, a tie member 43 tying the rods 39, 41 at one end 
of the rods 39, 41, and an L-shaped connecting member 45 which connects 
the rods 39, 41 to the carriage 3. The L-shaped connecting member 45 which 
secures thereto the end portions of the rods 39, 41 by bolt and nut means 
50, is mounted rotatably on a bracket 47 secured to the side of the 
carriage housing 25 by a pin 49, whereby the guide arm 5 can pivot or 
swing around the pin 49 in a plane perpendicular to the travelling 
direction of the carriage 3. As shown in FIG. 3, the guide rods 39, 41 are 
arranged with horizontal and vertical spacings to each other when the 
carriage 3 is disposed horizontally. The guide arm 5 arranged in such that 
manner is mechanically stable and minimized in its deformation even when a 
rotating moment is applied to the guide arm 5. 
The probe holder 7 slidably mounted on the guide arm 5 through ball 
bearings (not shown) will be described more in detail referring to FIGS. 4 
and 5. The probe holder 7 comprises a holder housing 51 and a probe 
holding unit 52. The holder housing 51 has an upper arm portion 53 
slidably mounted on the guide arm 5, and a lower arm portion 55 supporting 
the probe holding unit 52. The probe holding unit 52 comprises a 
ring-shaped member 61 embracing the periphery of the probe 9, a U-shaped 
member 65 connected to the ring-shaped member 61 and a rotatable shaft 67, 
one end of which is secured to the ring-shaped member 61 and the other end 
is rotatably supported by the lower arm portion 55 of the holder housing 
51. The lower arm portion 55 has a pair of bearings 59. The rotatable 
shaft 67 of the arm holding unit 52 is inserted in the bearings 59, and it 
has a flange portion 68 at the intermediate portion which is sandwiched by 
a pair of springs 72 inserted in the lower arm portion 55 through spring 
holders 70, whereby the axial movement of the rotatable shaft 67 is 
restricted while it is rotated freely. 
The probe 9 is fitted in the ring-shaped member 61 and secured thereto by a 
screw means 69. The probe 9, supported by the probe holder 7 in such a 
manner can be moved freely on the guide arm 5 by a manual operation. The 
probe 9 can be pivoted around the pin 63 and the rotatable shaft 67 which 
are crossed at a right angle on a plane slightly spaced from a surface to 
be inspected. 
A position of the probe holder 7 on the guide arm 5 is measured by a rotary 
encoder 71. As shown in FIG. 5, the rotary encoder 71 is fastened to the 
holder housing 51 through a mounting member 73. The rotary encoder 71 has 
a rotatable shaft on which a pinion 75 is secured. The pinion 75 is meshed 
with a rack 40 formed on one 39 of the guide rods of the arm 5, whereby 
movement of the probe holder 7 is transmitted to the rotatable encoder 71. 
A push button 77 for driving the motor 29 is provided on an upper portion 
76 of a projection of the ring-shaped member 61. When the push button 77 
is pushed, the probe 9 moves circumferentially by one pitch which is, for 
example, 6 mm corresponding to about 70% of the width of a surface to be 
inspected by scanning the probe 9 once. Namely, in FIG. 3, a movement of 
the motor 29 is transmitted to the pinion 35 through the safety device 31 
and the gears 33. The movement of the pinion 35 causes the carriage 3 to 
move circumferentially on the guide rail 11 by a distance corresponding to 
the above mentioned one pitch. The movement of the carriage 3 is 
transmitted to the rotary encoder 37, and the rotary encoder 37 measures a 
circumferential position of the probe 9. An axial movement of the probe 9 
on the pipe 2 is performed by manually moving the probe holder 7 on the 
guide arm 5. The axial movement of the probe 9 is transmitted to the 
rotary encoder 71 through the rack 40 of the guide arm 5 and the pinion 75 
meshed therewith whereby the distance corresponding to the axial movement 
or shift is measured by the rotary encoder 71. 
When the scanner 1 is used to inspect a welding portion 4 and a portion 
adjacent thereto as shown in FIG. 1, first, the guide rail 11 is mounted 
on the pipe 2 adjacent to a region to be inspected, that is, adjacent to 
the welding portion. Next, the scanner 1 is installed on the guide rail 
11, whereby it is ready for operation. The probe 9 is positioned at a 
proper circumferential position of the pipe 2 by travelling 
circumferentially with the carriage 3 with the push button 77 being 
operated. Under this condition, an operator moves axially the probe holder 
7 to inspect the pipe 2 while pressing the probe 9 on the surface to be 
inspected. After that, the carriage 3 is transferred by the motor 29 by 
one pitch, with the push button 77 being pushed. At the peripheral 
position, the probe 9 is moved axially as abovementioned. All the surface 
to be inspected is inspected by repeating the abovementioned operations. 
The probe 9 accurately follows even the curved surface of a bent pipe. 
When the probe 9 is moved axially while it is pressed on the curved 
surface of the bent pipe, the guide arm 5 supporting the probe holder 7 is 
pivoted or swung about the pin 47 and the probe 9 also is pivoted or 
rotated about the rotatable shaft 67 and the pin 63, according to the 
curvature of the curved surface, whereby the probe 9 faces always the 
surface to be inspected. When the probe 9 is moved in the peripheral 
direction, even if the carriage 3 is moved strictly circularly around the 
bent pipe, the probe 9 is not moved on the same track. Therefore the probe 
9 follows the curved surface to be inspected through pivotal movement of 
the guide arm 5 about the pin 47, and pivotal movements of the probe 9 
about the rotatable shaft 67 and the pin 63. 
Peripheral and axial scanning distances of the probe 9 are measured by the 
rotary encoders each rotating according to the movements of the carriage 3 
and the probe holder 7 as abovementioned. 
In case of performing the ultrasonic flaw detection of the pipe 2 or the 
like, embraced by a heat insulating material, only the heat insulating 
material on the side of the welded part 4 may be detached from the pipe 2 
in an amount corresponding to the length of the arm 5. Accordingly, the 
operation of detaching the heat insulating material for installing the 
scanner 1 can be readily executed in a short time. The danger of exposure 
of the operator lessens to that extent. The probability at which an 
obstacle exists in the movement of the probe 9 is lowered in accordance 
with the smallness of the quantity of detachment of the heat retaining 
material. 
When, in performing the flaw detection of the curved surface part, the 
position of the probe 9 in the axial direction of the pipe 2 is judged 
from only the measured value of the rotary encoder 71, an error takes 
place. This is because the arm 5 and the probe 9 pivot. In order to find 
an exact position of the probe 9, the sum between a component L.sub.1 sin 
.theta..sub.1 ascribable to the pivoting of the rotatable shaft 67 and a 
component L.sub.2 sin .theta..sub.2 ascribable to the pivoting of the arm 
5 as indicated in FIG. 7 is added to or subtracted from the measured value 
of the rotary encoder 71. 
Such method of correction for the axial position will be explained with 
reference to FIG. 6. Pulses generated from the rotary encoder 71 pass 
through a phase discriminator circuit 80 for deciding a direction, and are 
thereafter counted by a reversible counter 81. Although not shown, a 
potentiometer 85 for measuring the angle .theta..sub.1 is mounted on the 
housing 51. Further, a potentiometer 88 for measuring the angle 
.theta..sub.2 (inclination of the arm) is mounted on the carriage 3 for 
measuring the inclination. The measurement signal of the potentiometer 85 
is transmitted to a multiplier unit 87. The multiplier unit 87 receives a 
signal from a potentiometer 85 in which the length L.sub.1 between the pin 
67 and the lower face of the probe 9 is set. The operation of L.sub.1 sin 
.theta..sub.1 is executed in the multiplier unit 87. The measurement 
signal of the potentiometer 88 and a signal from a potentiometer 89 for 
setting the length L.sub.2 between the arm 5 and the pin 67 are applied to 
a multiplier unit 90 to execute the operation of L.sub.2 sin 
.theta..sub.2. The signals from the multiplier units 87 and 90 and also a 
signal obtained by converting an output of the reversible counter 81 by 
means of a converter 83 are respectively applied to an adder unit 91 and 
added therein, whereby the exact position of the probe 9 can be evaluated. 
After going through a converter 84, an output from the adder unit 91 is 
displayed on a coordinate value display unit 82 together with the 
circumferential position measured by the rotary encoder 36. It is also 
possible that, without making the correction as stated above, the signal 
of the reversible counter 81 is transmitted directly to the coordinate 
value display unit 82 through the change-over of a switch. 
Another embodiment of the scanner according to the invention will be 
described hereinafter in detail, referring to FIG. 8. This embodiment 
differs from the abovementioned embodiment mainly in a construction of a 
probe holder 7A, the probe holder 7A is suitable for axially transferring 
the probe 9 one pitch by one pitch by manual operation. 
In FIG. 8 showing a sectional view of the probe holder 7A taken along the 
same direction as in FIG. 1, a holder housing 51A moving slidably on the 
guide rods 39, 41 of the guide arm 5 holds the probe 9 in the same manner 
as in FIG. 4. A shaft 95 with knob is rotatably mounted on both the holder 
housing 51A and a bearing supporter 96 fixed to the holder housing 51 
through bearings 97, and it is provided with a pinion 98, the rotation of 
which is transmitted to the rotary encoder 71 through gears to measure a 
scanning distance of the probe holder 7A on the guide arm 5. A shifter 94 
is provided on the end portion of the shaft 95 with the knob. The shifter 
94 comprises a disc 99 fixed to the end of the shaft 95 and a ball holder 
100. The disc 99 has a plurality of ball receiving grooves 101 formed 
therein, two adjacent grooves determine an axial scanning pitch of the 
probe 9, for example 6 mm. The ball holder 100, which is cylindrical, is 
rotatably fitted on the knob shaft 95. The ball holder 100 is provided 
with one hole which is spaced from the axis thereof and extends axially. 
In this hole, a ball 106 is inserted loosely, and pressed on the disk 99 
by a spring 102. The ball holder 100, furthermore, has another hole 110, 
formed perpendicularly to the axis of the ball holder 100, and receiving a 
pin 103 which is inserted in a pin holder 104 secured to the probe holder 
51A. The pin 103 has a knob 105 fixed to one end thereof, and it is 
pressed by a spring 107 so as to fit in the hole 110 of the ball holder 
100. 
Under this condition, when the knob shaft 95 is rotated by manual 
operation, the ball 106 goes out from the groove 101, and enter the 
adjacent next groove 101, whereby the probe holder 7A is shifted by one 
pitch, and the distance shifted is measured by the rotary encoder 71. The 
probe 9 or the probe holder 7A can be shifted precisely one pitch by one 
pitch by repeating such operation. 
When it is intended to release the probe holder 7A from the shifter 94, the 
knob 105 is pulled leftwards on FIG. 8 to take off the pin 103 from the 
hole 110 by about the length of a pin 111, and then rotated by a certain 
angle, whereby the pin 111 comes out of a groove 112 formed in the knob 
105 so that the pin 103 is kept from the hole 110, and the probe holder 7A 
can be freely shifted. 
The probe holder 7A with the shifter 94, for example in the case of 
inspection of a pipe, of which a portion to be inspected is shorter in its 
axial length and longer in its circumference, is shifted by one pitch by 
the manual operation as abovementioned as for axial transfer of the 
scanner 1, while circumferential shifting of the scanner 1 is performed by 
driving the motor 29, with the probe 9 being manually pressed on the 
portion to be inspected. By repeating the axial shift and the 
circumferential transfer, all the portion to be inspected is inspected 
effectively. 
As mentioned previously, the circumferential scanning of the probe 9 is 
carried out by the carriage 3. The operation is performed while pressing 
the probe 9 on the surface to be inspected and an effective inspection can 
be carried out if the scanning speed changes in proportion to the force 
applied to the probe 9 toward the scanning direction. In order to carry 
out this, a direct current motor 29A for the motor 29 may be used, and 
there are provided a potentiometer 117 changing electric currents fed to 
the motor 29A, and an amplifier 116 for amplifying the electric currents, 
as shown in FIG. 9. The potentiometer 117, as shown in FIG. 4, is mounted 
on the holder housing 51, and actuated by a lever 118 mounted on a shaft 
67. In this construction, the shaft 67 compresses the spring 72 and the 
lever 118 actuates the potentiometer 117 whereby the motor 29A is driven. 
As the probe 9 is further pushed, the resistance of the potentiometer 117 
changes to increase electric current to the motor 29A whereby the scanning 
speed increases. Thus, the scanning speed of the carriage 3 is freely 
changed by a manual operation, and effective inspection can be achieved. 
Further another embodiment of a scanner according to the invention will be 
described hereinafter in detail, referring to FIGS. 10 to 13. 
In FIG. 10, a carriage 132 or a circumferentially driving apparatus is 
provided with a plurality of guide rollers 145, 146 and a gear 150. The 
guide rollers 145 sandwich an annular guide rail 131 up and down, and the 
guide rollers 146 sandwich the guide rail 131 from opposite sides, so that 
the carriage 132 can travel on and along the guide rail 131. The gear 150 
is meshed with rack 147 formed on the guide rail 131. The gear 150 is 
driven by a motor 152 through a worm 153 and gears 148, 149. Rotation of 
the gear 150 allow the carriage to move circumferentially on the guide 
rail 131. Rotation of the motor 152 is transmitted to a rotary encoder for 
measuring a circumferentially travelling amount of the carriage 132 
through the gear 148, 149 and a gear 154. 
A probe holder 134 having a driving apparatus which has a shifter as 
previously described in FIG. 8 is mounted slidably on a guide arm. The 
arm, as best shown in FIG. 11, comprises an upper rod 155 and two lower 
rods 136 each extending in a transverse direction of the travel direction 
of the carriage 132, and a pair of tying members 154 for tying ends of the 
rods 155, 136. The upper rod 155 is supported by the carriage 132 with a 
pin 140 fired to the carriage so that the arm can swing or pivot in a 
plane transverse the travel direction of the carriage 132. The probe 
holder 134 is slidably mounted on the lower rods 136, and has a rotary 
encoder 135, to which axial movement of the probe holder 134 is 
transmitted through a pinion 156 meshed with a rack formed on the rod 136, 
gears 157, 158. On the probe holder 13A, a rotatable shaft 139 is 
rotatably mounted, extending in the travel direction of the carriage 132. 
A probe 124 is fitted in a probe mounting member 138 which is rotatably 
connected to the rotatable shaft 139 by a pin 159 so that the probe can be 
pivoted about two axes as shown by arrows in FIGS. 10 and 11. A knob 137 
of the shifter is for shifting the probe 124 intermittently with an 
interval of one pitch. The pitch is taken in such a way that two adjacent 
tracks of the probe 124 are overlapped partially. 
In FIGS. 12 and 13, the annular rail 131 is mounted on a piping 130 to be 
inspected through three (3) poles 160 with spacing adjustable devices 163. 
The poles each have a roller 161, whereby the guide rail 131 can be 
transferred circumferentially. 
In case where ultrasonic flaw detection of the piping 130 is effected, the 
probe 124 is gripped by an operator's hand, and shifted manually between 
the tying member 154 and the opposite tying member 154. The probe 124 is 
held so as to be easily inclined axially and circumferentially so that the 
probe 124 accurately follows and contacts even a curved and complicated 
surface of an object to be inspected, and can emit a proper ultrasonic 
beam on the surface to be inspected. In a circumferential scanning for 
flaw detection, the carriage 132 is transferred circumferentially on the 
rail 131 by the motor 152. Axial and circumferential positions are 
automatically measured by the rotary encoders 135 and 133, and signals 
corresponding to the positions are sent to a display and a control 
apparatus, wherein the position of the probe can be automatically 
displayed. Of course, the results of the ultrasonic flaw detection 
scanning are recorded. In the case of circumferential ultrasonic flaw 
detection scanning, as shown in FIG. 12, the travelling range is limited 
by the poles 150, but the rail 131 is constructed so as to move 
circumferentially, whereby the ultrasonic flaw detection scanning can be 
performed over the surface. As regard positioning of the probe 124 after 
the movement of the annular rail 131, a precise position can be detected 
by setting the probe 124 on the marked points to reset the position 
display device after marking several points on this surface of the object 
to be inspected, and setting the probe 124 on the marked points. 
Thus, the scanner for piping according to this embodiment is constructed in 
such a way that the probe 124 can be inclined axially and 
circumferentially to contact with the surface, therefore inspection can be 
performed on welding portions in straight pipes, elbows, valves, pumps, 
and welding portions formed by various combinations of them, and its 
application range is increased. Furthermore, in accordance with the 
invention skilled inspectors are exposed less to radioactivity in the case 
of inspection of radioactive piping, and a great reduction of time 
necessary for analyzing inspecting results can be obtained. 
Further, in the case of the inspection of a pipe provided with heat 
retaining or insulating material, since the annular guide rail is arranged 
on a surface to be inspected, the amount of the heat insulating material 
to be removed is reduced greatly, compared with for example the prior art 
discussed.