Abstract:
A boroscope having a flexible fiber optic bundle communicating from inside to outside a housing. The bundle has a proximal end inside the housing viewable by viewing optics and illuminable by a light source in the housing. The fiber optic bundle extends to a distal end thereof outside the housing. An external sheath is placeable over the fiber optic bundle and is attachable to a fixture on the housing. The sheath in a preferred form is a tightly coiled wire in goose neck form which is bendable but retains its bent shape for enabling aiming of the distal end of the fiber optic bundle at a remote target.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is based on and claims benefit of U.S. Provisional Patent Application No. 60/638,281, filed Dec. 21, 2004, entitled BOROSCOPE WITH SELECTABLE STIFFNESS LIGHT SHAFT, the disclosure of which is hereby incorporated by reference and to which a claim of priority is hereby made. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a boroscope and particularly to the light and image fiber optics bundle or shaft attached to the boroscope.  
         [0003]     A boroscope, often also referred to as a borescope, transmits an image from a remote target to a viewer&#39;s eye, illuminates the target and may magnify the image. There are several types of boroscopes. The invention concerns the fiber optic type of boroscope which employs a flexible channel or shaft that is packed with a bundle of up to tens of thousands of known light transmitting fibers. Each fiber transmits a “pixel” of light from the target being viewed through an eyepiece with the pixels creating a coherent image at the eyepiece. Illumination from a remote source, such as the boroscope itself, passes through light transmitting fibers in the other direction, i.e., toward the point of inspection, to illuminate the target to be viewed. The fiber bundle may extend from the boroscope from ½ meter to 1 meter, or a longer or a shorter distance in a particular application.  
         [0004]     Boroscopes have numerous applications in various industries, including without limitation automotive applications which allow inspection for problems of manufacture or subsequent servicing at otherwise hard to see interior areas of engines, transmissions, fuel injectors and other automotive parts, fuel systems including fuel injector nozzles, bodies, pumps and lines, and various engine parts including valves, manifolds, cylinders, sleeves, etc. Boroscopes are useful for looking at aerospace parts during manufacture and during servicing, which parts may be otherwise visually inaccessible. Boroscopes may be used in connection with machining metal, since their fiber bundle shape may be inserted and moved into deep bores, complex castings, bent tubes, etc. and for inspecting rifled barrels. Boroscopes may be used for inspecting interior cavities, holes, etc. The above applications for industry and manufacture are illustrative of a variety of uses. Similar devices used in surgery and medical diagnostics, are known as endoscopes.  
       BACKGROUND OF THE INVENTION  
       [0005]     The fiber bundle or shaft of a boroscope is typically a non-rigid, somewhat flexible, solid bundle of fibers, having a generally circular cross section, with a diameter dependent upon the number of fibers in the bundle and upon the protective, shape defining sheath around the fiber bundle. In a boroscope embodiment according to the present invention, the light shaft has a diameter of about 5 mm. But, this is an example only.  
         [0006]     Boroscopes are generally constructed so that the fiber bundle is relatively flexible to cater to the many uses in which the boroscope shaft must be inserted into a narrow bore or area of the machinery to be observed, and along a path having turns, bends and curves.  
         [0007]     In some applications, however, the space into which the fiber bundle shaft is inserted is not narrow, tight and confined. The distal illumination and viewing tip of the shaft is then not easily directed at the target to be viewed, because it will sag or move off the desired aiming direction. In order to deal with that, boroscopes are available which include a stiffened fiber bundle or shaft or one that is capable of being fixedly oriented as a particular application requires. This increases the weight since the stiffened light shaft is usually thicker and heavier, but it does permit the shaft to maintain its selected orientation.  
         [0008]     Such a sheath permanently disposed around the fiber bundle might be a round reinforcing wire, or the like, coiled tightly into what is sometimes referred to as a “goose neck”. Such a coiled wire sheath can be given any selected curvature along its length and the entrance and exit of light from the distal free end or tip thereof can be in a controllable direction and toward a target. Other types of stiffening sheaths may also be used.  
         [0009]     Boroscopes are relatively expensive instruments, primarily as a result of their fiber optic bundles, but also from the internal elements of the boroscope which illuminate the fiber bundle and from the optics that receive and focus the target image collected. Accordingly, it would be desirable to maximize uses for a boroscope by providing a fiber bundle shaft of small diameter which can also be precisely aimed at a target, depending upon a particular use for the boroscope at the time.  
         [0010]     Up to now, however, it has been necessary to employ separate boroscopes for these two types of uses.  
       SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to enable a boroscope to selectively either have a smaller cross-section more flexible light shaft or a more rigid fiber bundle shaft which more precisely aimable, as the user selects at the time of use.  
         [0012]     According to the invention, a conventional boroscope with standard flexible light fiber bundle illumination and target viewing fiber filaments and with a standard boroscope viewing element is provided with a detachable outer sheath which surrounds the length of the fiber bundle sheath to provide rigidity. When the sheath is removed, the fiber bundle shaft exhibits the necessary flexibility to pass through narrow curved passages.  
         [0013]     At the option of the user of the boroscope, a hollow, tubular light external sheath is installed over the flexible light shaft or fiber bundle. The tubular external sheath has an internal diameter that is minimally greater than the external diameter of the light fiber bundle. The body of the boroscope and the external sheath have cooperating attachment fixtures where the external sheath meets the boroscope body for enabling attachment of the external sheath to the boroscope body after the sheath has been installed over the light shaft or fiber bundle and also for enabling detachment of the external sheath from the body when it is desired to remove the stiffening external sheath.  
         [0014]     In one exemplary, and non-limiting embodiment, a short-length threaded shank is provided in the proximal region of the light fiber bundle at the exit of the fiber bundle from the body of the boroscope. The shank cooperates with complementary attachment fixture at the proximal end of the external sheath. A threaded connection may be provided between the sheath fixture and the body fixture to permit attachment and detachment of the external sheath to the boroscope. The external sheath is about of the length of a fiber bundle so as not to interfere with projection of light toward the target from the distal tip of the fiber bundle or with reception of an image from the target by the distal tip of the fiber bundle.  
         [0015]     As will be appreciated by those skilled in the art, other means for coupling the external sheath to the boroscope may be employed.  
         [0016]     The external sheath allows the light shaft with its own sheath to be bent along the length and shaped so that the light exiting the fiber optic bundle and the target image received there may be more precisely targeted. The external sheath is of a type which can be curved and configured as a particular application may require and which will retain that shape for the fiber bundle or light shaft. Again, by way of a non-limiting example, the external sheath may be comprised of a coiled stiff wire, optionally encased in a plastic covering, which holds successive windings of the wire in close contact, a design commonly referred to as a “goose neck”. Other stiffening arrangements of the external sheath, with memory for whatever shape they are temporarily given, may instead be used.  
         [0017]     Other objects and features of the present invention will become apparent from the following description of one preferred embodiment considered in conjunction with the accompanying drawings in which:  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a partially cross-sectioned elevational view of a boroscope with an additional light fiber bundle shaping external sheath according to the invention;  
         [0019]      FIG. 2  is a view of the boroscope without the sheath;  
         [0020]      FIG. 3  is a view of the boroscope with the fiber bundle and the separate external sheath;  
         [0021]      FIG. 4  is a view of the boroscope with the external sheath assembled on the fiber bundle;  
         [0022]      FIG. 5  is a fragmentary view of the fiber bundle at A in  FIG. 4  and in cross section.  
         [0023]      FIG. 6  is a transverse cross-section on  6 - 6  in  FIG. 5 ;  
         [0024]      FIG. 7  is an enlarged cross-section of the exit region for the fiber bundle at the boroscope;  
         [0025]      FIG. 8  is a fiber bundle end view of the boroscope. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0026]     A boroscope  10  to which the present invention is applied is shown in  FIG. 1 . Its major components include an external housing  12 , and elongated fiber-bundle shaft  30 , a light source  16  disposed in the housing  12  for illuminating a target object, and an imaging system  25  also disposed in housing  12 , including a viewer  26 .  
         [0027]     Light source  16  is preferably a light emitting diode, but may be an incandescent light source, or a source of light in any wavelength range including invisible, infrared and ultraviolet.  
         [0028]     An electric power supply  18  is supported in the housing and is connected by leads or in any other suitable or desired manner to light source  16 . In the illustrated embodiment, the supply is an electric battery, and such as two AA size batteries. These may be conventional disposable batteries. Alternatively, a conventional rechargeable battery pack may be provided, or individual rechargeable batteries may be used. A push button switch  20  may be used in conjunction with a contacts board  22  to complete a circuit from the power supply  18  to the light source  16 . Other power switch arrangements may also be provided.  
         [0029]     Imaging system  25  is designed to receive an image of the object under inspection returned by the light fibers in fiber-bundle shaft  30 . Imaging system  25  may be a conventional optical system comprised of one or more lenses, generally indicated at  27 , to focus an image of the target for viewing through an eye piece  26  which opens outwardly at the rear of the boroscope. Alternatively, an electronic imaging system of any conventional or suitable type may be provided, including an image sensor such as a charge coupled device, signal processing devices for amplification, image enhancement, etc. and light emitting diode display. Image recording capability can also be provided, if desired. Suitable means for implementation of such features will be apparent to those skilled in the art.  
         [0030]     The body of the boroscope  10  is shaped and sized to be comfortably held in one hand with the eyepiece  26  at the eye and the fiber bundle projecting outwardly of the body to be directed toward the target area.  
         [0031]     As is conventional, the light fiber bundle  30  is comprised of many, perhaps as many as several hundred or even several thousand, fine glass filaments or fibers bundled together with a thin sheath  32  around and defining the bundle. The light fibers transmit “pixels” which together define an image when viewed after being focused.  
         [0032]     The fiber bundle actually includes two sets of fibers. One set  34  provides illumination of the target object, and is arranged with its proximal end  35  optically coupled to the light source  16 . With light source  16  positioned and oriented as illustrated in  FIG. 1 , the proximal end  35  of fiber set  34  is bent toward bundle exit point  36  from the housing, but as will be obvious to those skilled in the art, other configurations may be employed as required by the placement and orientation of the light source.  
         [0033]     A second set of fibers  38  transmits the image of the target object to optical system  25 . With the orientation of bundle exit point  36  and the configuration of the internal parts of boroscope  10  as illustrated, image fiber-set  38  extends straight to the focusing optics  25 . Again, other configurations may be employed, as necessary or desired.  
         [0034]     The two fiber sets  34 ,  38  are bundled together in the bundle  30  in a conventional manner. The combined light fiber bundle  30  extends from inside the housing  12  and projects through the exit point  36  to outside the housing. The bundle  30  and a surrounding protective sheath  32  are firmly held at exit point  36  in a support fixture  42  which is secured in the housing wall in any conventional or desired manner.  
         [0035]     One exemplary, but non-limiting construction for fixture  42  includes a shaped portion  44  on its interior end which engages with the interior  46  of the housing. A locking piece  47 , e.g., a lock nut positioned around the exterior of the fixture  42  just outward of the housing wall is tightened over a projecting part  48  of the fixture  42  and with the part  44  of the fixture  42  engaged on the inside of the housing wall, the nut cooperates to securely hold the fixture  42  and therefore the light fiber bundle  30  securely at the housing wall.  
         [0036]     Projecting outwardly from light fiber bundle securement fixture  42  is a sleeve portion  50  best illustrated in  FIGS. 1 and 7 . This may be integral with fixture  42 , or attached in any suitable manner. Sleeve  50  is externally threaded at  51  (see  FIG. 7 ) to receive an attaching fixture  56  for an external shape retention and aiming sheath  54  as described below. Light fiber bundle  30  extends from inside the housing  12  through sleeve  50  and then out to a distal tip  52  defining the end of the fiber optic bundle. The distance to tip  52  is dictated by the application, and may, for example, be in the range of from one half meter to one meter, but longer or shorter lengths are obviously possible.  
         [0037]     Light from the light source  16  within the boroscope passing through fiber set  34  exits through the tip  52  to illuminate the target. Similarly, an image of the illuminated target enters fiber set  38  through tip  52  and passes to optical system  25 .  
         [0038]     The light fiber bundle  30  is constructed to be sufficiently flexible and bendable to pass through a narrow and curving path to the target object, as shown in  FIG. 2 . In that condition, however, it is not sufficiently rigid to hold a shape, or to be accurately aimable in a relatively open passage to permit precise illumination and viewing of desired portions of the target object.  
         [0039]     To overcome this problem, which still permitting use of the boroscope for applications requiring a flexible, small-diameter fiber-bundle shaft  30 , a separate external shape retaining and aiming sheath  54  as seen in  FIG. 3  is placed over the protective sheath  32  of the flexible light fiber bundle  30  as seen in  FIG. 4 , and is detachably retained thereon, as described below. Sheath  54  may be comprised of a tightly wound, steel wire coil  55 , covered with a thin protective plastic layer  57 . The coils preferably so tightly wound and held together that the external sheath can be bent in any desired manner along its length and will retain whatever shape it is given. Such a construction is often referred to by the term “goose neck”. As will be understood by those skilled in the art, however, any other construction for sheath  54  which functions similarly may be employed, if desired.  
         [0040]     With the construction according to the invention, when boroscope  10  is used to inspect a target in a relatively open passage, sheath  54  holds a set shape. Thus, if the light emitting and target viewing tip  52  of bundle  30  is placed at or aimed at the target, the tip can be precisely oriented and positioned.  
         [0041]     As seen in  FIGS. 1 and 7 , in this preferred exemplary embodiment, the wire  55  of the external sheath  54  is wound to define a hollow tubular shape with an internal diameter only slightly greater than the external diameter of the sheath  32  on the light fiber bundle  30  so that the external sheath  54  may be slid onto the inner sheath  32 , which is thereby received in the sheath  54 .  
         [0042]     To detachably secure external sheath  54  to the boroscope body  12 , the proximal end  56  of the external sheath  54  is provided with a fixture  58  for engaging with the cooperating sleeve  50 . Fixture  58  is rotatably captured or permanently secured on external sheath  54  in any other suitable manner, and is internally threaded at  57  to engage with external threads  51  on sleeve  50 . As shown in  FIG. 4 , the length of the external sheath  54  is selected so that when it is secured to sleeve  50 , its open distal end  62  does not interfere with illumination of the target or the viewing of the target.  
         [0043]     The construction described enables a user to employ the same boroscope instrument to view a target which requires the boroscope light fiber bundle to pass through a narrow closely confined curved path which may preclude use of a stiffened external covering sheath or selectively enables a user to apply the covering sheath so that the light emitting and image receiving tip of the boroscope is aimed at the target without the light fiber bundle being difficult to aim or bending or drooping off the target.  
         [0044]     Although the present invention has been described in relation to a particular embodiment thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is intended, therefore, that the present invention not be limited by the specific disclosure herein, but that it be given the full scope permitted by the appended claims.