Abstract:
A tube is thermally insulated for protecting a fluid flowing therethrough from a high temperature surrounding environment of a gas turbine engine. The tube comprises a conduit, an insulating layer wrapped around the conduit, and an elongated contractible braided sleeve for preventing a separation of the insulating layer from the rigid conduit. The contractible braided sleeve is flexible along a longitudinal axis thereof and removably pulled over the insulating layer to snugly surround and maintain the insulating layer around the conduit.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a divisional application of U.S. patent application Ser. No. 11/283,838 filed on Nov. 22, 2005. 
     
    
     TECHNICAL FIELD 
       [0002]    The invention relates generally to insulated articles, such as insulated tubes for operation in high temperature environments. 
       BACKGROUND OF THE ART 
       [0003]    One example of known insulated tubes operating in a high temperature environment comprises a rigid conduit surrounded by insulation material, which is in turn surrounded by a rigid custom formed heat shield. The heat shield is generally composed of opposed sections each covering half a circumference of the conduit, the edges of which are welded together to form the complete shield. In addition to being complex to produce, these heat shields generally require special tooling and techniques to be installed as well as to be removed when the conduit needs to be inspected. 
         [0004]    It is also known to surround flexible hoses with braided sleeves, often made of metal, in order to provide structural integrity to the hose. Thus, the braided sleeve acts to strengthen the flexible hose. When the hose needs to be insulated, the braided sleeve is usually surrounded by a layer of insulating material. An additional layer is often required around the insulating material to protect it from its environment. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore an object of this invention to address the above mentioned issues. 
         [0006]    In one aspect, the present invention provides a method of insulating an article comprising: surrounding at least a portion of the article with an insulating layer; inserting the portion of the article surrounded by the insulating layer into an outer protective sleeve; and shrinking the outer protective sleeve around the insulating layer to compress and hold the insulating layer around the portion of the article. 
         [0007]    In another aspect, the present invention provides an insulated tube comprising: an inner conduit; a thermal insulation layer disposed around and in contact with the inner conduit; and a removable protective outer sleeve surrounding and compressing the thermal insulation layer around the inner conduit, the protective outer sleeve providing assistance in holding the thermal insulation layer on the inner conduit. 
         [0008]    In another aspect, the present invention provides an insulated tube comprising: a rigid conduit defining at least one bend; insulation means for at least partially insulating the conduit, the insulation means being flexible and surrounding the rigid conduit along at least a longitudinal portion thereof including the bend; and an elongated contractible sleeve for preventing a separation of the insulation means from the rigid conduit, the contractible sleeve being longitudinally flexible and removably pulled over the insulation means to snugly surround and maintain the insulation means around the longitudinal portion of the conduit. 
         [0009]    Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0010]    Reference is now made to the accompanying figures depicting aspects of the present invention, in which: 
           [0011]      FIG. 1  is a schematic side view of a gas turbine engine, illustrating an example of an environment where an insulated tube according to one particular aspect of the present invention can be used; 
           [0012]      FIG. 2  is a side view of a partially assembled insulated tube according to one particular aspect of the present invention; 
           [0013]      FIG. 3  is a cross-sectional view of a portion of the insulated tube of  FIG. 2  in an assembled state; and 
           [0014]      FIG. 4  is a perspective view of the insulated tube of  FIG. 3 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]      FIG. 1  illustrates a gas turbine engine  10  of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan  12  through which ambient air is propelled, a multistage compressor  14  for pressurizing the air, a combustor  16  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  18  for extracting energy from the combustion gases. 
         [0016]      FIGS. 2-4  illustrates an insulated tube  20  which can be used in the gas turbine engine  10  to carry oil to bearing assemblies located in a hot portions thereof, for example in proximity of the combustor  16 . However, the gas turbine engine  10  shown is merely an example of an environment for the tube  20 , the tube  20  being intended to be used in a number of other applications where a conveyed fluid needs to be insulated from a different temperature environment, whether hotter or colder than the fluid, and where heat exchange between the fluid and the environment needs to be minimized. 
         [0017]    Referring particularly to  FIG. 2 , the insulated tube  20  comprises a conduit  22 , surrounded by a thermal insulation layer  24 , which is, in turn, surrounded by a protective layer  26 . 
         [0018]    The conduit  22  defines a flow path  28  for the conveyed fluid. The conduit  22  is rigid, made of a resistant material, for example metals such as stainless steel, nickel-based alloys, titanium, aluminium or copper, and is sized to resist the pressure of the fluid conveyed through the flow path  28 . The conduit  22  includes a number of spaced-apart rigid sleeves  30 , only one of which is shown in  FIG. 2 , attached around the conduit  22  for example through brazing or welding. Each rigid sleeve  30  defines a cylindrical receiving surface  32  around the conduit  22  and includes a raised border  34  around one edge thereof such as to have a “L”-shaped cross-section, the purpose of which will be explained further below. 
         [0019]    In one particular aspect and as shown in  FIG. 2 , the thermal insulation layer  24  is made of an insulating tape  36  having an adhesive back  38  to adhere the thermal insulation layer  24  around the conduit  22  and facilitate the wrapping thereof. The material of the thermal insulation layer  24  is selected according to the thermal requirements of the insulated tube  20  and can be, for example, glass fiber insulation tape, tape including ceramic material, silica-based fiber tape, or any other similar tape. In one particular aspect, the thermal insulation layer  24  surrounds at least a longitudinal portion of the conduit  22  located within the different temperature environment. As shown in  FIG. 3 , the thermal insulation layer  24  surrounds the conduit  22  and abuts the rigid sleeve  30  along an edge  42  of the sleeve  30  opposite of the border  34 . 
         [0020]    As shown in  FIG. 2 , the protective layer  26  protects at least partially the thermal insulation layer  24  against damage from the environment and acts as a retaining means to retain the thermal insulation layer  24  by compressing it against the conduit  22 . The protective layer  26  is in the form of a sleeve which is shrinkable onto the thermal insulation layer  24 . In one particular aspect, the protective layer  26  includes an elongated braided sleeve  40 . The material of the braided sleeve  40  is selected according to the environment and can include, for example, densely woven, high temperature glass fibers, a stainless steel braid, nickel-plated copper braid, silver-plated copper braid, heat-treated aluminium coated fibreglass braid, etc. The braided sleeve  40  is braided such as to be shrinkable, with its diameter increasing when the braided sleeve  40  is compressed along a longitudinal axis  41  thereof, the diameter decreasing when the braided sleeve  40  is tensioned along the same direction, such as to facilitate installation of the braided sleeve  40  around the thermal insulation layer  24 . Other types of sleeves are also possible for the protective layer  26 , including sleeves which can be shrunk around the insulation layer  24  through various processes. As shown in  FIG. 3 , the protective layer  26  surrounds the thermal insulation layer  24  and the receiving surface  32  of the rigid sleeve  30  of the conduit  22 , with an outer edge  44  of the protective layer  26  extending on the receiving surface  32  spaced-apart from the border  34 , leaving a gap  46  therebetween. 
         [0021]    As can be seen in  FIG. 3 , a clamp  48  surrounds the protective layer  26  around the receiving surface  32 , and compresses the protective layer  26  against the receiving surface  32  to retain the protective layer  26  in place around the conduit  22 . In one particular aspect, the clamp  48  covers at least part of the gap  46  such as to protect the outer edge  44  of the protective layer  26  against damage, and also to protect a user from potential injury through contact with the outer edge  44 . Thus, one conduit rigid sleeve  30  and one clamp  48  is provided to secure each free edge  44  of the protective layer  26 . Advantageously, the border  34  of the rigid sleeve  30  prevents the clamp  48  from sliding toward an adjacent end  49  of the conduit  22 . In an alternative aspect, the rigid sleeves  30  can be omitted and the clamps  48  compress the protective layer  26  directly around and against the conduit  22 . As can be seen in  FIG. 4 , additional clamps  50  can also be provided along the length of the conduit  22  to compress the protective layer  26  around and against the conduit  22 . Alternately, the clamps  48 ,  50  can be replaced by other types of adequate attachment means, such as for example a wire-tie wrap made of a material resistant to the environment of the insulated tube  20  and compressing the protective layer  26  around and against the conduit  22 . 
         [0022]    In use, and as seen in  FIG. 2 , the conduit  22  is first surrounded by the thermal insulation layer  24 . This can be done by wrapping the insulating tape  36  by hand around the conduit  22  with an overlap  52  selected according to the thermal requirements of the insulated tube  20 , until the tape  36  abuts the edge  42  of the rigid sleeve  30  of the conduit  22 . The thermal insulation layer  24  is then surrounded by the protective layer  26 . This is done by inserting the conduit  22  wrapped in the thermal insulation layer  24  into the sleeve of the protective layer  26 , then shrinking the protective layer  26  to compress the insulation layer  24  therewith. One example of this is compressing the braided sleeve  40  along its longitudinal axis  41  to increase its diameter, inserting the conduit  22  wrapped in the thermal insulation layer  24  into the braided sleeve  40 , and tensioning the braided sleeve  40  along its longitudinal axis  41  to reduce its diameter until the braided sleeve  40  snugly surrounds and compresses the thermal insulation layer  24  and the receiving surfaces  32  of the spaced apart conduit rigid sleeves  30 . If required, the protective layer  26  is then attached to the conduit  22  such as to prevent separation of the thermal insulation layer  24  from the conduit  22 . This can be done by looping one of the clamps  48  around each free edge  44  of the braided sleeve  40  and tightening it to compress the braided sleeve  40  against and around the receiving surface  32  of the respective rigid sleeve  30 , thus maintaining the sleeve  40  in a longitudinally tensioned state such that the sleeve  40  continues to compress the insulation layer  24 . Optionally, the additional clamps  50  are installed between consecutive rigid sleeves  30  to compress the braided sleeve  40  around and against the conduit  22  wrapped in the thermal insulation layer  24 . 
         [0023]    Thus, the insulated tube  20  allows for a fluid to be conveyed while minimizing heat exchanges between the fluid and the environment of the insulated tube  20 , whether the environment is hot or cold. The installation of the thermal insulation layer  24  and protective layer  26  around the conduit  22  can be done quickly and by hand, using off-the-shelf material, without the need for special tooling or joining techniques (e.g. seam welding). Since no welding is necessary in installing the layers  24 ,  26 , risk of damage to the conduit  22  during assembly of the insulated tube  20  is greatly reduced. The materials and process used in the assembly of the insulated tube  20  also contribute to reducing fabrication costs. Moreover, the layers  24 ,  26  can be easily removed for inspection of the conduit  22 , and the conduit  22  can be easily re-insulated without the need for special tools or techniques. 
         [0024]    The flexibility and versatility of the layers  24 ,  26  allows rigid conduits  22  even with complex shapes to be easily insulated. Although the thermal insulation layer  24  and protective layers  26  have been described as surrounding a rigid conduit  22  to produce an insulated tube  20 , it is to be understood that other type of conduits can be similarly insulated, as well as a variety of other types of articles, such as for example wire harnesses, cables, various solid articles, etc. 
         [0025]    As the protective layer  26  surrounds and retains the thermal insulation layer  24 , the thermal insulation layer  24  is prevented from being separated from the conduit  22 , even if the environment of the insulated tube  20  damages the thermal insulation layer  24 , for example by breaking down the fibers of its insulation or decomposing its adhesive. Since the conduit  22  is rigid, the protective layer  26  does not play a structural role, as opposed to when braided sleeves are used around flexible hoses to maintain structural integrity, which results in possibility of using a cheaper braided sleeve (e.g. thinner, less resistant, etc.). 
         [0026]    The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without department from the scope of the invention disclosed. Modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.