Abstract:
A bore-scope sealing apparatus is provided for removably sealing a bore-scope opening in a turbomachine wall with a plug. The bore-scope sealing apparatus includes a bayonet coupling via which the plug is mountable to the bore-scope opening. The bayonet coupling has a projection at the plug and a corresponding recess at the bore-scope opening. A resilient retaining device is arranged at the recess being compressed by the projection in a sealing position to retain the plug in the bore-scope opening.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the US National Stage of International Application No. PCT/EP2011/060141, filed Jun. 17, 2011 and claims the benefit thereof. The International Application claims the benefits of European application No. 10007336.0 EP filed Jul. 15, 2010. All of the applications are incorporated by reference herein in their entirety. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates in general to a bore-scope sealing apparatus and to a plug for a bore-scope sealing apparatus. In particular the invention is directed to a bore-scope sealing apparatus and a plug for turbomachines. 
       BACKGROUND OF INVENTION 
       [0003]    For a compressor like an aircraft turbine or an industrial compressor of a gas turbine engine with relatively high compression ratios of greater than 15 to 1 it may be typical for the rear static vanes to be held in a floating carrier. The carrier may be mounted in an outer pressure casing by means of radial pins to allow for compensation of thermal expansion. 
         [0004]    Bore-scope access through aligned holes in the outer casing and the inner carrier is required for inspection of blades and vanes of the compressor. In normal operation these holes are sealed to eliminate air loss and air recirculation. As large access ports in the outer casing or even removal of the outer casing has to be avoided the inner plug has to be removed and securely refitted via a small access port in the outer casing. 
         [0005]    U.S. Pat. No. 4,470,735 shows a self locking bolt where the locking device is a expanding snap ring. 
         [0006]    U.S. Pat. No. 3,139,134 discloses a locking device comprising a flexible strip at a location of the circumference of the bolt. 
         [0007]    U.S. Pat. No. 5,115,636 and U.S. Pat. No. 4,815,276 show spring loaded bore-scope plugs. 
         [0008]    U.S. Pat. No. 5,079,910 shows a spring loaded spherical sealing element used in an inspection aperture. The sealing element is pushed aside to give way for the inspection device. 
         [0009]    U.S. Pat. No. 5,152,662 discloses a pivoting flap which controls the access to the inspection port. 
         [0010]    U.S. Pat. No. 5,879,116 and U.S. Pat. No. 2,852,056 show resilient locking devices used as inserts on screws. 
         [0011]    U.S. Pat. No. 4,825,642 discloses a bore-scope plug comprising a seal locked by a screw on its arm. 
         [0012]    U.S. Pat. No. 5,897,277 shows a self locking plug with a spring loaded self locking mechanism. 
         [0013]    GB 1 579 730 shows a self-locking spring loaded fastener. 
         [0014]    The known solutions require large access ports in the outer casing and/or special headed screwed plugs or bayonet plugs on the internal carrier. 
       SUMMARY OF INVENTION 
       [0015]    It is therefore an object of the present invention to improve the sealing of a bore-scope opening. 
         [0016]    This object is solved by the features of the independent claim(s). The dependent claims offer further details and advantages of the invention. 
         [0017]    In a first aspect the invention is directed to a bore-scope sealing apparatus for removably sealing a bore-scope opening in a turbomachine wall with a plug. The turbomachine wall may be particularly a wall of a compressor. The plug is mountable to the bore-scope opening by means of a bayonet coupling, wherein the bayonet coupling comprises a projection at the plug and a corresponding recess at the bore-scope opening. A resilient retaining means is arranged at the recess and is compressed by the projection in a sealing position to retain the plug in the bore-scope opening. This sealing apparatus has a small footprint and can be removed quickly and easily. Since the bayonet coupling is arranged directly at the bore-scope opening it allows for easy handling. Hence, the apparatus can be utilized especially in or close to restricted areas. 
         [0018]    The retaining means may be a spring pin. This is a simple design with good handling allowing for easy rotation of the plug while retaining the plug in a secure manner. 
         [0019]    The retaining means may be arranged in an opening accessible from the outside and the opening may be in communication with the recess. This construction is easy to manufacture and maintenance cost and time are low since the retaining means can be removed from the outside. 
         [0020]    The projection of the plug may comprise a retaining recess for accommodation of part of the retaining means. The retaining recess allows for improved connection of the bayonet coupling as the plug latches with the retaining means. 
         [0021]    The plug may comprise two projections, opposite to each other so that the bore-scope opening is sealed evenly along its circumference. The corresponding recess may be on bigger recess or two distinct recesses with shapes corresponding to the projections. Accordingly, the bore-scope sealing apparatus may comprise two retaining means, opposite to each other to even better retain the plug. 
         [0022]    The plug may comprise a head with a drive feature and the head may cover the retaining means at least partially in a sealing position. In this case an expensive fixture of the retaining means can be omitted as they are fixed by the plug itself. Additionally may the retaining means support extraction of the plug by spring force. The same spring force can secure the bayonet coupling by exerting pressure in a longitudinal direction of the plug to the head of the plug thereby minimizing the chance of accidental release of the plug. 
         [0023]    The plug may comprise a gasket. A gasket for improved sealing can be utilized at the outer bore-scope and/or the inner bore-scope opening. 
         [0024]    The plug may be mountable to an outer bore-scope opening in an outer turbine wall—particularly a wall in a compressor section—and the plug may comprise a shaft with a sealing end for sealing an inner bore-scope opening in an inner turbine wall like an inner carrier. For this configuration the bore-scope apparatus is beneficial as the bayonet coupling is arranged at the outer bore-scope opening which allows for easy construction and handling. 
         [0025]    The plug may be mountable to an inner bore-scope opening in an inner turbine wall. The inner turbine wall has usually a lower pressure drop than the outer turbine wall which facilitates easy construction and handling of the plug. With the small plug only a small opening is needed in the outer turbine wall to remove or refit the plug at the inner turbine wall. Also, alignment of inner and outer opening is not so critical when the plug is mounted to the inner turbine wall. 
         [0026]    The bore-scope sealing apparatus with the plug mountable to the inner bore-scope opening may have a sealing plate mountable to an outer bore-scope opening in an outer turbine wall. The sealing plate can be made massive more easily as no through hole is needed for the plug. 
         [0027]    In a second aspect the invention is directed to a plug for a bore-scope sealing apparatus according to the above description. The plug has a head and a shaft having a longitudinal direction. The shaft comprises a projection at a distance to the head in longitudinal direction. In particular, the shaft may comprise two projections arranged opposite to each other. 
         [0028]    In a further development of the shaft each projection has a retaining recess. Furthermore, the shaft may comprise a sealing end for sealing an inner bore-scope opening in an inner turbine wall. The use of the plug in the context of the bore-scope sealing apparatus has been described above with respect to bore-scope sealing apparatus. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0029]    The accompanying drawings are included to provide a further understanding of embodiments. Other embodiments and many of the intended advantages will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings do not necessarily scale to each other Like reference numbers designate corresponding similar parts. 
           [0030]      FIG. 1  illustrates a schematic cross-sectional view of a bore-scope apparatus according to the invention. 
           [0031]      FIG. 2  illustrates a schematic cross-sectional view of a bore-scope apparatus according to the invention. 
           [0032]      FIG. 3  illustrates a schematic exploded view of a plug and a bottom plate of a bore-scope apparatus according to the invention. 
           [0033]      FIG. 4  illustrates a sectional view of the bottom plate along the line IV-IV of  FIG. 3 . 
           [0034]      FIG. 5  illustrates an alternative design of the bottom plate in a sectional view. 
           [0035]      FIG. 6  illustrates a top view of a bore-scope apparatus in a sealing position according to the invention. 
           [0036]      FIG. 7  illustrates a bottom view of a bore-scope apparatus in a sealing position according to the invention. 
           [0037]      FIG. 8  illustrates a detailed view of a bayonet coupling of a bore-scope apparatus according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
       [0038]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof and in which are shown by way of illustration specific embodiments in which the invention may be practised. In this regard, directional terminology, such as “top” or “bottom” etc. is used with reference to the orientation of the Figure(s) being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims. 
         [0039]      FIG. 1  shows a bore-scope sealing apparatus  1  for sealing an outer bore-scope opening  2  in an outer turbine wall  3  and an inner bore-scope opening  4  in an inner turbine wall  5 . The walls  3  and  5  can be an outer casing and an inner carrier of an aircraft turbine, an industrial compressor or a gas or steam turbine. 
         [0040]    The bore-scope sealing apparatus  1  has a plug  6  with a head  7  at an outer end of a shaft  8  and with an inner end  9  or sealing end for sealing the inner bore-scope opening  4  in the shown sealing position. 
         [0041]    A cover plate  10  is mounted to the outer turbine wall  3  and seals the outer bore-scope opening  2  apart from a through hole  11  for the plug  6  which is sealed by the plug  7  in the sealed position. 
         [0042]      FIG. 2  shows an arrangement of the bore-scope sealing apparatus  1  in which the plug  6  is sealing the inner bore-scope hole  4  in the inner turbine wall  5 . The cover plate  10  with the through hole  11  is mounted to the inner turbine wall  5  accordingly. The plug  6  can have the same dimensions as compared to  FIG. 1 . The length of the plug  6  may be reduced. 
         [0043]    The diameter of the outer bore-scope opening  2  in the outer turbine wall  3  is slightly bigger than the diameter of the head  7  of the plug  6 . Slightly bigger means that the outer bore-scope opening  2  is spacious enough for easy removal and mounting of the plug  6 . Usually the head  7  has the largest diameter of all parts of the plug  6 . In case another part than the head  7  has the largest diameter the diameter of the outer bore-scope opening  2  is adapted to this part. 
         [0044]    The outer bore-scope opening  2  can be sealed with a sealing plate  10   a.  As the sealing plate  10   a  needs no through hole it is a massive plate at least in the area of the outer bore-scope opening  2 . In a section right to the bore-scope opening  2  the sealing plate  10   a  can have an opening to fix it to the outer turbine wall  3 . 
         [0045]      FIG. 3  shows an exploded view of the bore-scope sealing apparatus  1  and  FIG. 4  shows a sectional view through the cover plate  10  along the line IV-IV in  FIG. 3 . The head  7  of the plug  6  has a drive feature  12  of the screwdriver type slot for example for fastening and releasing the plug  6 . The bore-scope sealing apparatus  1  further has a bayonet coupling  13  for mounting the plug  6  to the outer bore-scope opening or to the cover plate  10 . 
         [0046]    The bayonet coupling  13  has two projections  14  at the shaft  8  of the plug  6 . The two projections  14  are arranged opposite to each other. The projections  14  have a distance to the head  7  in longitudinal direction of the plug  6  which allows the projections  14  to fit in a corresponding recess  18  at the bottom side of the cover plate  10 . The recess  18  has a circular shape and enlarges the through hole  11  so that the plug can be rotated about the longitudinal axis of the shaft  8  when the projections  14  are located in the recess  18 . The recess  18  allows for accommodating the projections  14  of the plug  6  in any rotational position. Except for the recess  18  the through hole  11  has the shape of the circular shaft  8  with the two projections  14  so that the plug  6  can just pass through the through hole  11  in a single rotational orientation. 
         [0047]    The bore-scope sealing apparatus  1  has a resilient retaining means in form of a spring pin  15  to retain the plug  6  in the outer opening  2  in a sealing position. The spring pin  15  has the shape of a cylinder and can be solid or hollow. The spring pin  15  can be resilient in its longitudinal and/or its radial direction. In the case of resilience in longitudinal direction the spring pin  15  presses against the head  7  of the plug  6  to retain it in the sealed position. In the case of resilience in radial direction the spring pin  15  presses against the projection  14  of the plug  6  to retain it in the sealed position. A combination of both retaining mechanisms is possible. 
         [0048]    Two spring pins  15  are arranged opposite to each other around the through hole  11 . The spring pins  15  are arranged in an opening  16  each. The openings  16  are located so close to the through hole  11  that they partly project into the space formed by the recess  18  (compare  FIG. 4 ), i.e. into the enlarged area of the through hole  11  that allows for accommodating the projections  14  of the plug  6 . When the plug  6  is rotated the spring pins  15  will be compressed by the projections  14 . This is described later on in conjunction with  FIGS. 6 to 8 . 
         [0049]    In an open position of the bore-scope opening  2 , i.e. with removed plug  6 , the openings  16  are accessible from the outside. In the sealing position the spring pins  15  are held inside the openings  16  by the head  7  of the plug  6 . The head  7  may have a special collar to cover the spring pins  15  or part of them. At the bottom side, the spring pins may  15  be held in place by the outer turbine wall  3  or inner turbine wall  5 , respectively, or by some kind of washer located between the cover plate  10  and the outer turbine wall  3  or inner turbine wall  5 , respectively. According to an alternative design of the cover plate  10 , which is shown in  FIG. 5 , the recess  18  is located at an axial distance from the bottom side of the cover plate  10 . Towards the bottom side of the cover plate  10 , a section of the through hole  11  that is circular with a reduced diameter as compared to the diameter of the recess  18  follows on the recess  18 . The reduced diameter is just large enough to let the circular shaft  8  of the plug  6  pass this section. 
         [0050]    The cover plate  10  has a mounting opening  17  for a screw or a bolt to fix the cover plate  10  to the outer turbine wall  3 . Other fastening mechanisms either removable or not can be employed. The cover plate  10  can also be part of the outer turbine wall  3 . 
         [0051]      FIG. 6  shows the bore-scope sealing apparatus  1  in the sealing position in which the plug  6  is mounted and secured to the bore-scope opening or the cover plate  10 . The plug is inserted to the outer bore-scope opening  2  while part of the shaft  8  extends beyond the cover plate  10  to seal an inner bore-scope opening  4 . The length of the shaft  8  depends on the distance between inner and outer turbine wall and may be greater than depicted. Also, special designs of the inner end  9  of the shaft  8  are possible. They depend on the design of the inner bore-scope opening  4 . 
         [0052]    Compared to  FIG. 3  the plug  6  is rotated by approximately ninety degrees as can be seen by the drive feature  12 . The rotation enables the bayonet coupling  13  to be locked into the sealing position. The spring pins  15  are retained in their respective openings  16  by the head  7  of the plug  6 . 
         [0053]      FIG. 7  shows the bottom or inner side of the bore-scope sealing apparatus  1  in the sealing position. The details of the bayonet coupling  13  are now explained which is locked in the sealing position. 
         [0054]    The through hole  11  has a recess  18  which is a circular extension of the shaped through hole  11 . The recess  18  has a diameter which allows for rotation of the plug  6  with its projections  14  inside the recess  18 . An upper surface  19  or shoulder of the recess  18  secures the plug  6  against removal by its contact with the projections  14 . 
         [0055]    The openings  16  are in communication with the recess  18 . They overlap each other so that the spring pins  15  arranged in the openings  16  project partially into the recess  18 . The diameter of the recess  18 , the position and size of the openings  16 , the size and form of the spring pins  15  and the size and form of the projections  14  are designed such that the projections  14  press against the resilient spring pins  15  in the sealing position. The spring pins  15  secure the plug  6  against accidental rotation and subsequent removal. 
         [0056]      FIG. 8  shows a bottom view of the plug  6  with the head  7  depicted in the background and the shaft  8  in the foreground. Here, the projections  14  each have a retaining recess  20  for accommodation of part of the spring pin  15 . The retaining recesses  20  hold the plug  6  even better in the sealing position. The design of the bore-scope sealing apparatus  1  can be such that the spring pins  15  are not compressed by the projections  14  in the sealing position. In this case the spring pins  15  are only compressed while moving in the sealing position. Alternatively the design can be such that the spring pins  15  are compressed in the sealing position, either only to a small amount or to a greater amount. Both designs guarantee proper fixing of the bore-scope sealing apparatus  1  in the sealing position. 
         [0057]    Gaskets can be utilized at both bore-scope openings. They are not depicted for the sake of clarity. 
         [0058]    The bore-scope sealing apparatus  1  is brought to the sealing position by inserting the plug  6  into the outer bore-scope opening  2  and if existent the inner bore-scope opening  4  or by inserting the plug directly into the inner bore-scope opening  4 . Once the head  7  of the plug  6  abuts against an upper surface of the cover plate  10  or of the turbine wall  3  the plug is being rotated by approximately ninety degrees. During the rotation the projections  14  are sliding inside the recess  18  thereby abutting against the upper surface  19  which tightens the plug  6 . Upon further rotation the projections  14  engage with the spring pins  15 . The spring pins  15  are being compressed thereby holding the plug  6  securely in the sealing position. 
         [0059]    To release the plug  6  from the sealing position the plug  6  is turned ninety degrees so that the projections  14  leave the recess  18  and fit into the through hole  11  for extraction of the plug  6 . The spring pins  15  can be dimensioned such that they have a length longer than the length of the openings  16 . Then, they can support the extraction of the plug  6  by spring force.