Backsplash protection for ultrasonic inspection system

A gas jet is positioned above the water nozzle of a system provided for ultrasonically detecting flaws in an article to be inspected. The water nozzle directs a substantially level water jet stream against an upright surface of the article as it is moved transversely of the nozzle. A transducer associated with the water nozzle transmits ultrasonic energy along the water jet stream toward the article, then receives echoes from flaws existing in the article. The gas jet directs toward the upright surface of the article a gas jet stream which is substantially parallel to, and vertically aligned with, the water jet stream. The gas jet stream serves to deflect the water splashing off the surface of the article after impact therewith and prevents the splashing water from descending toward and striking the water jet stream. The water nozzle and the gas jet may be positioned such that the longitudinal axes of the water jet stream and of the gas jet stream are both substantially perpendicular to the surface of the article being inspected. Preferably, the water jet stream exhibits laminar flow. Signals may be recorded which are received from the transducer representative of the attenuation of the ultrasonic energy caused by the condition of the article being inspected. In a further embodiment, opposed systems, each comprised of a water nozzle, gas jet, and associated transducer, may be positioned to direct water jet and gas jet streams against the article from opposite sides of the article, the opposed water jet and gas jet streams being substantially parallel and vertically aligned.

BACKGROUND OF THE INVENTION 
The present invention relates generally to ultrasonic testing of articles 
and, more particularly, to apparatus providing relief against backsplash 
resulting when the laminar flow water column used for transmitting the 
ultrasonic waves creates a cascading waterfall after striking the article 
being tested and impairs the quality of the water column. 
II. Description of the Prior Art 
It has long been known to perform nondestructive inspection employing 
ultrasonic waves travelling between a transducer and the article being 
inspected. Since liquids are a good media for transmitting this wave 
energy, it has been customary in the past to submerge the transducer or 
transducers and the object to be inspected, or at least part of the object 
to be inspected, in the liquid medium. This system worked as long as the 
object being inspected was not too large. However, it was completely 
impractical when the object being inspected was of substantial size such 
as, for example, large sheets or plates. 
For such large objects, it heretofore became the practice to mount the 
transducer in a suitably shaped container which had an opening shaped to 
closely match the contour of the object and, by keeping the container 
filled with liquid, to attempt to maintain a fluid seal sufficient to keep 
the container full and a liquid coupling between the transducer and the 
object. This method had the inherent disadvantage of requiring a close fit 
between the edges of the container and the surface of the object being 
inspected which made it impossible to accommodate large surface defects 
and protrusions such as weld beads, gouges, or changes in contour, without 
losing the liquid coupling. Since a break in the fluid connection between 
the transducer and the article interrupts the inspection process, this 
method proved to be unsatisfactory. 
Another method sometimes suggested for coupling the transducer to the 
article employs a housing for the transducer which has an outlet equipped 
with a nozzle. The liquid is introduced into the housing under pressure so 
that it is expelled through the nozzle toward the surface of the object as 
a high velocity, uncontained, stream or jet of liquid. The transducer is 
located in the housing so that the ultrasonic waves can travel to the 
article through this high velocity stream of liquid. In more recent 
versions of this method, a pair of aligned transducers with their 
associated nozzles are positioned on opposite sides of a large plate or 
other object to be inspected. This has generally come to be a very 
satisfactory ultrasonic inspection method. 
In order to more clearly define the evolution of ultrasonic inspection 
techniques and the existing state of the art in this regard, a number of 
specific prior art disclosures will here be mentioned. For example, U.S. 
Pat. Nos. 3,662,590 issued May 16, 1971 to Shiraiwa, No. 3,555,891 issued 
Jan. 19, 1971 to Lewis, and No. 3,255,626 issued Jun. 14, 1966 to Van Der 
Veer all broadly disclose ultrasonic inspection apparatus. U.S. Pat. No. 
3,121,325 issued Feb. 18, 1964 to Rankin et al. discloses the use of air 
jets from a manifold to keep the top surfaces of ultrasonic probes free of 
the coupling water. U.S. Pat. Nos. 3,122,661 issued Feb. 25, 1964 to Joy 
and 3,420,097 issued Jan. 7, 1969 to Battermann et al., disclose the use 
of air jets in combination with ultrasonic inspection devices to confine 
the coupling fluid to a desired area. U.S. Pat. No. 3,745,833 issued Jul. 
17, 1973 to Armstrong and French Patent No. 1,275,693 issued Nov. 2,1961 
to U.K Atomic Energy Authority both disclose the use of air jets in 
combination with ultrasonic inspection devices to deflect the coupling 
water stream. U.S. Pat. No. 2,751,783 issued Jun. 26, 1956 to Erdman and 
Japanese Disclosure No. 46-8391 dated Aug. 2,1967 to Mitsubishi Juko 
disclose, respectively, a splash box and a shield for containing the 
coupling water stream used in an ultrasonic inspection device. 
SUMMARY OF THE INVENTION 
It was with knowledge of the state of the art as noted above that the 
present invention was conceived and has now been reduced to practice. 
According to the present invention, a gas jet is positioned above the 
water nozzle of a system provided for ultrasonically detecting flaws in an 
article to be inspected. The water nozzle directs a substantially level 
water jet stream against an upright surface of the article as it is moved 
transversely of the nozzle. A transducer associated with the water nozzle 
transmits ultrasonic energy along the water jet stream toward the article, 
then receives echoes from flaws existing in the article. The gas jet 
directs toward the upright surface of the article a gas jet stream which 
is substantially parallel to, and vertically aligned with, the water jet 
stream. The gas jet stream serves to deflect the water splashing off the 
surface of the article after impact therewith and prevents the splashing 
water from descending toward and striking the water jet stream. The water 
nozzle and the gas jet may be positioned such that the longitudinal axes 
of the water jet stream and of the gas jet stream are both substantially 
perpendicular to the surface of the article being inspected. Preferably, 
the water jet stream exhibits laminar flow. Signals may be recorded which 
are received from the transducer representative of the attenuation of the 
ultrasonic energy caused by the condition of the article being inspected. 
In a further embodiment, opposed systems, each comprised of a water 
nozzle, gas jet, and associated transducer, may be positioned to direct 
water jet and gas jet streams against the article from opposite sides of 
the article, the opposed water jet and gas jet streams being substantially 
parallel and vertically aligned. 
A primary object of the invention, therefore, is to provide an improved 
system for ultrasonically detecting flaws in an article which utilizes a 
water jet stream directed against a surface of the article as the medium 
for transmission of an ultrasonic signal. Another object of the invention 
is to provide such a system which operates to deflect the water splashing 
off the article away from interfering with the water jet stream. 
A further object of the invention is to provide such a system which 
utilizes an air jet stream positioned above the water jet stream to 
deflect the water splashing off the surface of the article and prevents 
the splashing water from descending toward and striking the water jet 
stream. 
Yet another object of the invention is to provide such a system according 
to which mutually opposing water jet streams and gas jet streams are 
directed at the article from opposite sides of the article. 
Other and further features, objects, advantages, and benefits of the 
invention will become apparent from the following description taken in 
conjunction with the following drawings. It is to be understood that the 
foregoing general description and the following detailed description are 
exemplary and explanatory but are not to be restrictive of the invention. 
The accompanying drawings which are incorporated in and constitute a part 
of this invention, illustrate one of the embodiments of the invention and, 
together with the description, serve to explain the principles of the 
invention in general terms. Like numerals refer to like parts throughout 
the disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Turn now to the drawings and, initially, to FIG. 1, which illustrates a 
system 20 for ultrasonically detecting flaws in an article 22 to be 
inspected. The article 22 may be of simple or of complex shape. Detection 
apparatus 24 is suitably mounted on a frame 26 such that the article 22 
can be moved into or out of the plane of the paper, viewing FIG. 1. In 
alternative constructions, the article 22 may remain stationary and the 
detection apparatus 24 move into and out of the plane of the paper, or 
both the article and the detection apparatus may move into and out of the 
plane of the paper and relative to one another. 
In any event, the detection apparatus 24 includes a suitable nozzle 28 
which is in communication with a source of water under pressure. The 
nozzle 28 is capable of directing a substantially level water jet stream 
30 against the article 22 as it moves transversely of the nozzle. 
The detection apparatus 24 also includes a suitable transducer 32 
associated with the nozzle 28 for transmitting ultrasonic energy signals 
along the water jet stream 30 toward a surface 34 of the article 22. 
Echoes from opposite surfaces 34, 36 of the article 22 as well as from 
internal flaws within the article 22 are the returned to the transducer 32 
via the water jet stream 30. These echoes are representative of the 
attenuation of the initial ultrasonic energy signals and are transmitted 
in a known manner as schematically depicted by an electrical lead 38 to 
suitable computer apparatus 40. The computer apparatus may include a 
monitor 42 for viewing the attenuated signals, a keyboard 44 for inputting 
appropriate additional information, and an output device 46 such as a 
printer for providing a detailed printout in order to provide a lasting 
record of the attenuated signals portraying the condition of the article 
22. 
In situations wherein the article 22 is reasonably planar and has a 
relatively nominal thickness, a second detection device 50 including a 
nozzle 58 and a suitable transducer 59 may be supported on the frame 26 
and located on an opposite side of the article 22 to direct a second water 
jet stream 52 onto the surface 36. In this instance, the water jet streams 
30 and 52 are substantially aligned, or coaxial. In a preferred 
construction, the water jet streams 30, 52 are substantially perpendicular 
to the surfaces 34, 36 at which they are directed. 
Each of the detection devices 24, 50 includes an associated gas jet 54, 56, 
respectively, which is suitably connected to a source of pressurized gas, 
such as air. The gas jets 54, 56 are positioned above their associated 
nozzles 28, 58 such that they direct toward their associated surfaces 34, 
36 of the article 22 gas jet streams 30A and 52A, respectively. The gas 
jet and water jet streams are preferably parallel and generally lie in a 
common vertical plane. This relationship may be more clearly seen in FIG. 
2. 
It will be appreciated that when the water jet stream 30 strikes the 
surface 34 of the article 22 in the absence of the gas jet stream 30A, the 
water forms a splash region 60 (FIGS. 1, 2 and 3) wherein water splashes 
in all directions and that water in the region above the water jet stream 
30 often descends toward and strikes the water jet stream. This causes 
interference with the signals from the transducers 32, 59 as well as of 
the echoes returning from the article 22 and, therefore, substantially 
affects the information being processed by the computer apparatus 40. This 
has been a long known and persistent problem but has been effectively 
solved by means of the present invention. Specifically, the gas jet 
streams 30A, 52A as particularly well seen in FIG. 3 (with respect to gas 
jet stream 30A), provide an effective shield which prevents cascading 
droplets from a former splash region 62 (FIG. 3) from descending toward 
and striking the water jet stream 30. The gas jet stream 30A can be, but 
does not necessarily have to be, parallel to the water jet stream 30. The 
goal is to displace a significant portion of water from above the 
ultrasonic signals. The gas jet stream can be radially placed anywhere 
above the water jet stream where it is most effective and practical for 
that operation. It can be said in general that being parallel with the 
water jet stream and perpendicular to the test article is the most 
suitable for inspecting purposes. However, there are many arrangements, 
taking into account such variables as nozzle angle, distance from 
articles, diameter, and air pressure, that could be just as effective. 
The following parameters are typical for the operation of the invention but 
are not presented for purposes of limiting in invention in any manner: 
Average air pressure =10 psi 
Average distance from article =1 inch 
Nozzle diameter =1/8 inch 
Nozzle angle =90 degrees to article surface 34 
Turn now to FIG. 4 which illustrates a modified article 64 to be inspected. 
In this instance, the water nozzle 28 and gas jet 54 (illustrated in FIG. 
2) direct their jet streams 30 and 30A, respectively, toward a surface 66 
which is modified, for example, by means of a plurality of outwardly 
projecting blades 68, 70, 72. In FIG. 5, a computer printout 74 relates to 
the modified article 64 and depicts indica 68A, 70A, and 72A which 
represent, respectively, their associated blades 68, 70, and 72. In 
between the blades, there is substantial interference, or "noise" indicted 
by the speckled areas 76 located between the blade indicia 68A, 70A, and 
72A. A linear marking 78 adjacent each of the blade indicia 68A, 70A, and 
72A is common interference caused by the presence of the associated blade 
68, 70, and 72 and is recognizable by the skilled person who would be 
viewing the computer printout 74. 
FIG. 6 illustrates an improved computer printout 80 which results from 
operation of the gas jet 54. Unfortunately, the linear markings 78 remain. 
This condition is created when the blade 68 separates the gas jet stream 
from the water jet stream during scanning and thus backsplash cannot be 
avoided. However, this condition can be corrected if the gas jet is 
situated immediately above the water jet stream and not an inch above it, 
as was the case for this particular demonstration. 
While preferred embodiments of the invention have been disclosed in detail, 
it should be understood by those skilled in the art that various other 
modifications may be made to the illustrated embodiments without departing 
from the scope of the invention as described in the specification and 
defined in the appended claims.