Abstract:
A fluid conduit has a peripheral wall defining a fluid passage extending along a longitudinal access. A heating element is located in contact with the peripheral wall and extending parallel to the longitudinal access. A jacket entrained about the peripheral wall and heating element maintains the heating element in contact with the peripheral wall.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to fluid conduits such as hoses and pipes.  
         BACKGROUND OF THE INVENTION  
         [0002]    Fluid conduits are used in a wide variety of applications to convey fluids between different locations. Perhaps one of the widest uses is the provision of pipes to convey water to commercial and residential establishments but pipes are also used to convey other fluids such as fuel oils, gasoline or other chemical substances.  
           [0003]    The conduits are often installed in relatively hostile environments in which the fluids conveyed can be subject to temperatures that makes handling of the fluids difficult. Typically, in water distribution systems, there is a danger that the ambient temperature will drop below freezing and result in a blockage or bursting of the distribution pipe. In areas where this is likely to occur, the pipe may be buried beneath the frost line determined for that region, which may be over one metre below the ground level. This is of course relatively expensive and inhibits access to the pipe for routine maintenance and inspection. Moreover in some environments, it is not practical to bury the conduit due to ground conditions and essentially the pipe must remain exposed on the ground.  
           [0004]    In Canadian Patent 2,019,590, a system is described in which a self regulating electrical heating cable is installed within a pipe so that heat may be supplied to the water within the pipe to prevent freezing. This arrangement facilitates the use of insulation around the pipe to reduce energy consumption and has enjoyed wide spread commercial success.  
           [0005]    In some installations it is not practical to install a heating cable within the pipe. If the conduit is intended to carry combustibles then it is preferable to separate the heating element from the fluid itself. In other environments, the pressure of the fluid within the conduit makes the use of the internal heating cable impractical.  
           [0006]    It is well known to retrofit a heating cable to the outside of a pipe by wrapping the cables spirally about the pipe. However, this arrangement is relatively inefficient in that heat transfer depends upon the contact between the heating element and the outer surface of the pipe and this cannot be assured with a manual wrapping of the cable about the pipe. Moreover, the cable remains vulnerable to external forces that may damage the cable or present a safety risk.  
           [0007]    It is therefore an object to the present invention to provide a fluid conduit in which the above disadvantages are obviated or mitigated.  
         SUMMARY OF THE INVENTION  
         [0008]    In general terms, the present invention provides a fluid conduit having a peripheral wall defining a fluid passage extending along a longitudinal access, a heating element in contact with the peripheral wall and extending parallel to the longitudinal access and a jacket entrained about the peripheral wall and heating element to maintain the heating element in contact with the peripheral wall.  
           [0009]    Preferably, the heating element is a smaller diameter than the fluid passage and a void is created between the jacket and peripheral wall.  
           [0010]    As a further preference, an insulating sleeve is positioned over the jacket to inhibit heat transfer from the heating element. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    These and other features of the preferred embodiments of the invention will become more apparent in the following detailed description in which reference is made to the appended drawings wherein:  
         [0012]    [0012]FIG. 1 is a perspective view of a fluid conduit with portions that are removed for clarity.  
         [0013]    [0013]FIG. 2 is a view on the line  2 - 2  of FIG. 1.  
         [0014]    [0014]FIG. 3 is a view similar to FIG. 2 with an insulated sleeve installed.  
         [0015]    [0015]FIG. 4 is a schematic representation to the manner of making the conduit show in FIG. 1.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    Referring therefore to FIG. 1, a fluid conduit  10  includes a pipe  12  having a continues peripheral wall  14  to define a fluid passageway  16 . The passageway  16  is circular in cross section with a longitudinal axis indicated at A-A.  
         [0017]    The peripheral wall  14  has inner and outer surfaces  18 ,  20  respectively and is formed from a suitable material such as PVC, polyethylene, a cross linked fluoropolymer referred to as PEX, ABS or other suitable material well known in the pipe manufacturing field. Typically the wall  14  is extruded as a continuous plastic material.  
         [0018]    A heated cable  24  is located in abutment with the outer surface  20  of the peripheral wall  14  and extends parallel to the longitudinal axis of the fluid passageway  16 . The cable  14  is a self regulating heater cable having a pair of heating elements interconnected by a carbon resistive element to produce a self regulated heating effect. Such cables are available from under the trade name Raychem, Dekoron, Nelson. The cable  24  terminates in an electrical plug  26  for connection to an electrical supply.  
         [0019]    The cable  24  is held against the outer surface  20  of the wall  14  by a jacket  30 . The jacket  30  is entrained about the outer surface  20  and the cable  24  so as to define a pair of voids  32  in the vertex between the jacket  30 , cable  24  and wall  14 . The jacket  30  is formed from a polyethylene either low, medium or high density, or other suitable material compatible the materials of the cable  24  and wall  14 . The wall has a thickness of 2 mm and may range from 1 mm to 10 mm. After application, the jacket  30  is taught so as to force the cable  24  into abutment with the outer wall  20 . As indicated by the zone  34 , the pliability of the cable  24  causes a slight deformation at the abutment ensuring a substantial contact area between the cable  24  and the wall  14  over the length of the conduit  10 .  
         [0020]    To produce the conduit  10 , the pipe  12  and cable  24  are fed into an extrusion die shown schematically in FIG. 4 at reference numeral  40 . Feed stock for the jacket  30  is fed from hopper  42  into the extrusion cavity  44  to form the jacket  30 . Continued movement of the pipe  12  and cable  24  conjointly through the die allows the jacket  30  to solidify and provide the construction of the conduit  10 .  
         [0021]    The finished conduit can be coiled depending on the dimensions of the pipe  12  or delivered in discrete lengths with suitable terminating and power connection kits applied to the cable  24  at the end of each length.  
         [0022]    In operation, the conduit  12  can be installed on a surface or within shallow trenches. The jacket  30  protects the cable from external damage but does not impair the integrity of the structure of the pipe  12 . At the same time, the extended contact area ensures that the heating effect of the cable  24  is maximised and distributed to the fluid within the pipe  12 . The voids  32  provide additional area in which heat can be conducted into the surface of the pipe through air contained within the void to improve the efficiency.  
         [0023]    As shown in FIG. 3, improved thermal efficiency can be obtained by applying a thermal sleeve  50  to the exterior of the jacket  30 . The self regulating nature of the cable  24  ensures that overheating of the wall  14  does not occur and a normal operation and allows the heating to be applied on a selective basis as required in response to variations in the external temperature.  
         [0024]    Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without departing from the spirit and scope of the invention as outlined in the claims appended hereto.