Fiberscopic device for inspection of internal sections of construction, and method for using same

An apparatus and method for using the same to inspect the interior of a construction such as a vessel, piping, machinery and the like, including jet engine combustion cans, comprises a fiberscope having a probe carrying fiberoptic systems which is inserted into the construction interior through an articulable and rotatable guide insertion tube. The guide insertion tube is articulated and/or rotated to manipulate the fiberscope probe and aim it toward a passage into an adjacent interior section. Once the fiberscope probe is extended out of the guide insertion tube and into the next interior section, it acts as a lead wire over which the guide insertion tube in pushed to extend the guide insertion tube into the next section, and so forth for the desired number of interior sections.

BACKGROUND OF THE INVENTION 
The present invention relates to a fiberscopic device for the inspection of 
the interior sections of a construction, such as a machine, vessel, piping 
and the like, and to a method for using the same, and in particular, has 
application to the inspection of the hot sections, such as the combustion 
chambers or cans, of jet engines. 
While the present invention is described hereinbelow in the context of one 
inspection procedure for a particular model of jet engine, it will be 
appreciated by those skilled in the art that this description is 
illustrative only, and that the invention disclosed herein is neither 
limited to such types of inspections nor only to inspections of jet 
engines; rather, the teachings disclosed herein have many applications. 
Further, while for ease of description the device is described as being 
useful for inspecting machine interiors, it should be understood that it 
is not so limited, and may be used to inspect many types of constructions 
or devices not admitting of easy visual inspection. 
It has long been desirable to inspect the interior sections of 
constructions, such as vessels, piping or certain types of machinery, 
including jet engines, to examine for defects such as coking, cracking, 
wear, burning, etc. To avoid the need to disassemble the engine, which 
itself suffers from several drawbacks, various other methods have been 
proposed to inspect the engine interior while the engine is assembled, or 
even still mounted on the wing of an aircraft. In one known method, the 
engine is wrapped with a radiation-sensitive film, and a radioactive 
source is inserted into the engine to expose the film from within the 
engine. While this method is usually adequate to locate gross defects in 
the engine's condition, it is not sufficiently sensitive to reveal, for 
example, cracks or burn spots which while they appear minor at the time of 
inspection, perhaps due to the insensitivity of this method, might perhaps 
warrant maintenance at that time, or even worse, lead to more serious 
defects if left untreated. Further, even when this method is able, for 
example, to locate a crack, because of its imprecision it is typically 
incapable of discerning the length of the crack. 
Accordingly, fiberscopic devices, which also have known medical 
applications, have been used to inspect the interior of jet engines, 
either or alone or as an adjunct to a radiation-sensitive film technique. 
Examples of known fiberscope devices are disclosed in U.S. Pat. Nos. 
3,583,393 and 3,788,304 assigned to Olympus Optical Co., Ltd. of Tokyo, 
Japan, which are herein incorporated by reference. Typically, a 
fiberscopic device includes an elongated tube, or probe, with light 
transmitting and fiber optical systems along its length to illuminate an 
interior section to be inspected and transmit an image back to an eyepiece 
through which the operator can view the image. 
A disadvantage of the known fiberscopic designs when used to inspect a 
machine has been the inability to control the movement of the fiberscope 
probe within the interior of the machine to enable a more thorough 
inspection, for example, into adjacent interior sections of the machine 
which are not themselves accessible from the exterior of the machine. For 
example, in the inspection of a particular aircraft jet engine, the model 
JT8D manufactured by Pratt & Whitney Aircraft, a division of United 
Technologies, the known fiberscopic devices are useful in inspecting the 
two combustion chambers, or cans, (#4 and #7) which are accessible from 
the exterior of the engine via the ignitor ports of the engine. Only with 
a great deal of operator manipulation, if at all, is it possible to extend 
the fiberscope probe through a crossover tube connecting either the #4 or 
#7 can with an adjacent can. (It will be appreciated that a JT8D engine 
comprises nine combustion cans). Thus, the condition of the two cans, 
i.e., the #4 and #7 cans, which are capable of visual inspection with the 
known fiberscopic devices has been used in conjunction with other 
inspection techniques to predict the condition of the cans which cannot be 
reached with the fiberscope probe for a visual inspection. Obviously, a 
device capable of permitting a thorough visual inspection of all of the 
combustion cans of this or any other engine, and for that matter, other 
interior sections of other constructions or machines which are not readily 
accessible from the exterior, would be highly desirable. 
Accordingly, it is among the objects of the present invention to provide an 
improved fiberscopic inspection device which enables an operator to 
control and manipulate the fiberscope probe accurately while extended into 
the interior of a construction. It is another of the objects of the 
invention to enable the inspection of adjacent interior sections, 
including those to which access cannot readily be had from the exterior of 
the construction. 
SUMMARY OF THE INVENTION 
These and other objects of the present invention, which will be readily 
apparent to those skilled in the art, are accomplished by an inspection 
device including a fiberscope having a probe, of a type which is itself 
known in the art, and a hollow guide insertion tube and guide control body 
for manipulating the fiberscope probe while the latter is in the interior 
of the machine being inspected. The fiberscope includes an elongated tube 
or probe extending therefrom which in a preferred embodiment has a distal 
end portion which is articulatable at least in two direction in the same 
plane. It will be understood by those skilled in the art that the 
fiberscope probe may be of the non-articulating variety, or may articulate 
in four directions in two perpendicular planes, depending on the needs of 
the particular application. The fiberscope is connected with a light 
source, and its probe carries a fiberoptic system to illuminate an object 
to be viewed through a lens means located at the end of the probe and to 
transmit the observed image to an eyepiece to be viewed by an operator. 
The fiberscope is inserted into a fiberscope holder which in the preferred 
embodiments comprises two parts rotatable relative to each other to permit 
the rotation of the probe around its longitudinal axis. 
The fiberscope probe is guided into and through the interior sections of 
the machine to be inspected through the hollow guide insertion tube which 
extends from the guide control body. The guide control body also may 
comprise two parts rotatable relative to each other, whereby the guide 
insertion tube is rotatable around its longitudinal axis. In accordance 
with the present invention, the guide insertion tube includes at least a 
distal end portion which, in a manner similar to the fiberscope probe, is 
articulatable in at least two directions in the same plane. Again, 
depending on the needs of the application, the guide insertion tube may be 
articulatable in four direction in two planes perpendicular to each other. 
Preferably, the guide control body is mounted to the construction to be 
inspected, which advantageously frees both of the operator's hands for 
easier and more effective manipulation of the guide insertion tube and the 
fiberscope probe. For example, a commercially available plate and screw 
bolt assembly such as that used to mount a camera on a tripod is 
satisfactory. The plate can be coupled to an articulable support arm which 
in turn has a clamp at its other end for clamping the device to the 
machine to be inspected. (In the case of a jet engine, the clamp should be 
fastened to a secure part of the engine, and not to thin-walled or highly 
finished structures). 
To perform an inspection of, for example, the interiors of the combustion 
cans of a Pratt & Whitney model JT8D jet engine, the ignitor plugs are 
removed from the ignitor ports located in the #4 and #7 combustion cans of 
the engine. The guide insertion tube and probe are inserted through the 
ignitor ports, and both are moved into all nine of the combustion cans as 
described below. 
To prevent the accidental withdrawal of the guide insertion tube, for 
example, due to gravity when it is being directed upwardly, a friction 
plate or other suitable retaining means which can be affixed to the 
exterior of the machine being inspected, may be used. A bore in the 
retaining means, preferably lined with a O-ring, is aligned over the 
opening in the machine through which the guide insertion tube and probe 
are inserted. Because the bore has a diameter only slightly larger than 
the outer diameter of the guide insertion tube, it aids in preventing the 
guide insertion tube from falling out of the opening in the machine, which 
may have a substantially larger diameter, and is also useful when the 
operator wishes to insert the guide insertion tube in small increments. 
The specific inspection operation of the JT8D jet engine, which is herein 
described for illustrative purposes only, is performed as follows: After 
the friction plate is mounted to the ignitor plug boss, the guide control 
body is attached to the articulating support arm and its clamp is attached 
to a suitable engine component. The fiberscope body is then locked into 
the fiberscope holder and the fiberscope probe is inserted through a bore 
in the guide control body along the length of the guide insertion tube 
until the articulating end portion of the fiberscope probe emerges from 
the end of the guide insertion tube. A mark or other indicia may be 
applied to the fiberscope to indicate when the probe is inserted to this 
point, as for example, when the mark meets the guide control body. 
With the guide insertion tube and fiberscope probe articulation levers in 
the neutral position (i.e., so that the articulatable end portion of both 
the guide insertion tube and the probe are non-articulated), the guide 
insertion tube and fiberscope probe are inserted through the friction 
plate bore into either combustion can #4 or #7. While viewing the liner of 
the can opposite the ignitor port, the guide insertion tube is 
articulated, rotated or otherwise displaced within the can as necessary to 
locate the crossover tube leading to an adjacent combustion can. While 
keeping the crossover tube in the center of the view field, the guide 
insertion tube and probe are pushed farther into the can to move them 
closer to the crossover tube. 
By then pushing the fiberscope holder and fiberscope toward the guide 
control body, which preferably are connected, for example, by an 
articulating arm, the fiberscope probe is further extended outwardly of 
the end of the guide insertion tube and through the crossover tube into 
the adjacent can. A second mark or other indicia may be applied to the 
probe to indicate when a predetermined length of the probe has been 
extended, e.g., when the second mark meets the guide control body. 
The guide insertion tube articulating control lever should then be returned 
to the neutral position and the guide insertion tube pushed farther into 
the engine so that it follows along the fiberscope probe, which acts as a 
lead wire into the adjacent can. Preferably, while the guide insertion 
tube is being pushed farther into the engine, the probe is being gradually 
withdrawn (by moving the fiberscope holder away from the guide control 
body), until the first mark again meets the guide control body, thus 
indicating that only the articulating end of the fiberscope probe 
protrudes from the end of the guide insertion tube. 
Once the fiberscope probe is inserted into the last combustion can 
accessible along the particular route chosen for insertion into the 
engine, the probe and guide insertion tubes are articulated, rotated and 
otherwise displaced, with respect to each other and the can, as necessary 
to inspect thoroughly the interior of that can. Each of the cans is then 
inspected as the scope is withdrawn. The foregoing steps are then repeated 
to snake the fiberscope probe through the remaining cans accessible from 
the particular ignitor port through which the device has been inserted and 
all of those cans are inspected as the device is withdrawn. The device is 
then inserted through the other ignitor port and the procedure is 
repeated, thereby enabling the inspection of every combustion can of the 
engine.

DESCRIPTION OF EXEMPLARY EMBODIMENT 
With reference to FIGS. 1 and 2, there is illustrated an inspection device 
constructed in accordance with the principles of the present invention. 
The device includes a fiberscope 8 of a type which is itself known in the 
art. One such fiberscope particularly suited to the present invention, 
although others are contemplated, is the model IF6D3-20 Flexible 
Fiberscope manufactured by Olympus Optical Co., Ltd., of Tokyo, Japan. The 
fiberscope 8 is connected with a light source (not shown) and includes an 
elongated tube or probe 12 extending therefrom, and an eyepiece housing 14 
through which an operator may view images observed by the fiberscope 8. In 
accordance with the exemplary embodiment, the fiberscope probe 12 includes 
a distal end portion 16 which is articulatable in a known manner in at 
least two direction in the same plane. Examples of such articulating 
fiberscopes are disclosed in the aforementioned incorporated patents. 
Typically, wires or cables extend from the fiberscope body 8 along the 
length of the probe 12 to a fixed location near the end of the probe, and 
are manipulated by a knob or lever 18 on the fiberscope body 8. The 
fiberscope could also be articulatable in four directions in two planes, 
depending upon the desired application. It will be understood also that 
the fiberscope need not be one including articulating means, and that a 
non-articulating fiberscope may be used in conjunction with the guide 
control body of the present invention to great advantages). The probe 12 
carries a fiberoptic system to illuminate an object to be viewed through a 
lens means located at the distal end 16 of the probe and to transmit the 
observed images to the eyepiece 14 to be for viewed by an operator, again 
in a manner known to those skilled in the art. 
The fiberscope 8 is held in a fiberscope holder 10. In the exemplary 
embodiment the holder 10 comprises two cylindrical parts 10a and 10b, part 
10a being mounted for rotation within part 10b. The fiberscope body 8 is 
held securely in the fiberscope holder part 10a by a set screw 11, and the 
two cylinders are locked in a desired position relative to each other by a 
locking screw 13. When it is desired or necessary to rotate the probe 12 
during the insertion or inspection procedures, described more fully below, 
the locking screw 13 is released and the fiberscope body 8 and the holder 
part 10a are rotated in the holder part 10b into a desired position, then 
relocked in place by tightening the locking screw 13. Thus, an operator is 
able to rotate the probe 12 around its longitudinal axis. 
In accordance with the present invention, the fiberscope probe 12 is guided 
into and through the interior sections of the machine to be inspected by a 
hollow guide insertion tube 20 which extends from a guide tube body 22. In 
accordance with the present invention, the guide insertion tube 20 
includes at least a distal and portion 24 which is articulatable, via a 
lever 26 on the guide control body 22, in at least two direction in the 
same plane. The articulating means of the guide control body 22 and 
insertion tube 20 are similar to the known articulating means of the 
fiberscope probe 12. If desired or necessary, the guide insertion tube 20 
may be articulatable in four direction in two perpendicular planes. 
The guide control body 22, comprises two parts 22a and 22b which are 
coupled to each other in a suitable manner so as to permit rotation of the 
parts 22a and 22b relative to each other. For example, the guide control 
body part 22a may comprise a cylindrical portion extending into a 
cylindrical bore in the guide control body part 22b, the latter having 
screws or pins riding in a circumferential groove provided on the outer 
surface of the cylindrical portion of the guide control body part 22a. A 
locking screw 23 on the guide control body part 22b functions as the 
locking screw 13 on the fiberscope holder part 10b to fix the two guide 
control body parts 22a and 22b in a desired position. Thus, just like the 
fiberscope probe 12, the guide insertion tube 20 also is rotatable about 
its longitudinal axis by rotation of the guide control body part 22a from 
which it extends. 
Preferably, the inspection device is mounted to the machine to be 
inspected. For example, a commercially available arrangement such as a 
plate and screw bolt assembly 28 used to mount a camera on a tripod (an 
example of which is manufactured by Manfrotto, S.A. of Italy and 
distributed in the U.S. by Bogen Photo Corp. of New Jersey), is 
satisfactory. The guide control body part 22b is provided with a 
1/4".times.20 thread screw hole, standard for such camera mounts, to 
permit it to be fastened to the support plate. Preferably, the mounting 
means further includes an articulating arm 30, (an example of which is 
"The Magic Arm", which also is manufactured by Manfrotto, S.A.), which 
includes a clamp 32 at one end and a lever 34 which serves to lock all 
three joints 36(a), (b) and (c) when the arm is moved to the desired 
position. (When inspecting, for example, an aircraft jet engine, the clamp 
32 should be fastened to a secure part of the engine, and not to 
thin-walled or highly finished structures). The use of the articulating 
support arm 30 or other suitable mounting assembly advantageously frees 
both of the operator's hands for easier and more effective manipulation of 
the guide insertion tube 20 and probe 12, as will be described more fully 
below. 
Referring to FIGS. 3(a) and 3(b), to perform an inspection of the 
combustion cans 40 of a Pratt & Whitney model JT8D jet engine, the 
description of which herein is only for purposes of illustration, the 
ignitor plugs (not illustrated) are removed from the ignitor ports 38 
located in the #4 and #7 combustion cans of the engine. To prevent the 
accidental withdrawal of the guide insertion tube, for example, due to 
gravity when it is being directed upwardly, a friction plate 42 (FIG. 5) 
can be affixed to the exterior of the engine. The plate 42 has a bore 44 
therein aligned over the ignitor port, which is lined with an O-ring, and 
has a diameter slightly larger than the outer diameter of the guide 
insertion tube 20. The plate 42 is mounted to the ignitor plug boss by 
inserting expanding push pins, which are located in holes in the plate 
that are complementary to holes in the ignitor port boss 38. While the 
friction plate 42 illustrated herein has particular application to the 
ignitor ports of the JT8D engine, it will be appreciated that other plates 
suitably configured may be used in other applications to achieve the 
desired result of retaining the guide insertion tube 20 within the machine 
being inspected. 
After the friction plate 20 is mounted to the ignitor plug boss, the guide 
control body 22 is attached to the articulatable support arm 30 and the 
clamp 32 of the support arm 30 is attached to a suitable engine component, 
the fiberscope probe 12 is inserted through a bore in the guide tube body 
22 and along the guide insertion tube 20 until the articulating end 
portion 16 of the fiberscope probe 12 emerges from the end of the guide 
insertion tube 20. It will be appreciated that the probe 12 is movable 
longitudinally within the guide insertion tube 20. A mark 48(a) or other 
indicia may be applied to the fiberscope probe 12 to indicate when the 
probe 12 is inserted to this point, as, for example, when the mark 48(a) 
meets the guide control body 22 as illustrated in FIG. 1. 
With the articulation levers 26 and 18, respectively, of the guide 
insertion tube 22 and fiberscope probe 12 in the neutral position (i.e., 
so that both articulatable end portions 24 and 16, respectively, of the 
guide insertion tube 20 and probe 12 are non-articulated), the guide 
insertion tube 20 and fiberscope probe 12 are inserted through the 
friction plate bore 44 covering the ignitor port 38 and into one of either 
combustion can #4 or #7. While viewing the liner of the can opposite the 
ignitor port 38, the guide insertion tube 20 is articulated, rotated and 
otherwise displaced within the can as necessary to locate the crossover 
tube 46 leading to an adjacent combustion can, as illustrated in FIG. 
4(a). While keeping the crossover tube 46 in the center of the view field, 
the guide insertion tube 20 and probe 12 are inserted farther into the can 
40 to move closer to the crossover tube 46, as illustrated in FIG. 4(b). 
The fiberscope holder part 10b and the guide control body part 22b are 
preferably connected, for example by an articulating arm 50, to permit 
relative movement between the guide control body 22 on the one hand, and 
the fiberscope holder 10 and fiberscope 8 on the other hand. By pushing 
the fiberscope holder 10 toward the guide tube body 22, the fiberscope 
probe 12 is pushed through the guide insertion tube 20 and extended 
outwardly of the end of the guide insertion tube 20 and through the 
crossover tube 46 into the adjacent can 40, as illustrated in FIG. 4(c). A 
second mark 48(b) or other indicia may be applied to the probe 12 to 
indicate when a predetermined length of the probe 12 beyond its 
articulatable end portion 16 e.g., sufficient to reach into about the 
middle of the can, has been extended from the guide insertion tube 20, as, 
for example, when the mark 48(b) meets the guide control body 22. 
The articulating control lever 26 of the guide insertion tube 20 should 
then be returned to the neutral position and the guide insertion tube 20 
pushed farther into the engine so that it follows along the fiberscope 
probe 12, which acts as a lead wire, and into the adjacent can 40, as 
illustrated in FIG. 4(d). Preferably, while the guide insertion tube 20 is 
being pushed farther into the engine (as in step 4(d)), the probe 12 is 
gradually being withdrawn, by pulling the fiberscope holder 10 away from 
the guide control body 22, until the first mark 48(a) again meets the 
guide control body 22 (thus indicating that only the articulating end 
portion 16 of the fiberscope probe 12 is protruding from the end of the 
guide insertion tube 20). 
The foregoing steps are thus repeated to snake the fiberscope probe 12 
through the adjacent cans 40 accessible through the particular ignitor 
port first entered, along routes such as those illustrated schematically 
in FIGS. 3(a) or 3(b). For example, with reference to FIG. 3(a), if the 
guide insertion tube 20 and fiberscope probe 12 are first inserted into 
the right ignitor port 38 (as seen in the drawing), the procedure is 
followed to guide the probe 12 into can #4 and along one of the routes to 
can #6 or #1. Performing the insertion step first allows the operator to 
take advantage of the relative alignment of the crossover tubes 46. Also, 
by first inserting the guide insertion tube and probe fully, before 
beginning to inspect, and then performing the inspection from the remote 
cans back toward the ignitor port, the operator can give his full 
attention to the inspection. Thus, the farthest can, e.g., #1, is 
inspected, the probe is withdrawn to can #2, which is then inspected, etc. 
to can #4; the probe is then reinserted through can #5 and into can #6, 
which is then inspected, the probe is then withdrawn to can #5 for 
inspection, and then out of can #4. The guide insertion tube 20 and probe 
12 are then inserted through the other ignitor port (the left port 38 as 
seen in the drawing) and the procedure followed as before, thereby 
enabling the inspection of combustion cans #9, #8 and finally #7. Thus, it 
can be seen that with the present invention, an operator is able to 
inspect every combustion can of the engine. 
While the present invention has been described with reference to an 
exemplary embodiment thereof, and with reference to one particular 
inspection procedure of a particular engine, it will be appreciated by 
those skilled in the art that variations and modifications may be made 
thereto without departing from the spirit of the inventive concepts 
disclosed herein. For example, even without modifications to the structure 
of the device, it will be appreciated that the increased ability to 
control the movement of a fiberscope within a construction or machine 
achieved by the guide control body and guide insertion tube of the present 
invention can increase the effectiveness of many other types of inspection 
of many other types of construction such as storage or manufacturing 
vessels, piping, etc., and not necessarily only to situations requiring 
the maneuvering of the probe into interior adjacent sections. Further, 
increasing or decreasing the lengths of the guide insertion tube and 
probe, or using articulating means capable of moving one or both of the 
probe and guide insertion tube in four directions also would lend the 
device to many different applications. All such variations and 
modifications are intended to fall within the scope of the appended claims 
.