Abstract:
A cable gland assembly for an electric cable having a sheath enclosing at least one conductor core is described, the assembly comprising a body and a barrier sleeve ( 4 ) locatable in the body wherein, in use, the at least one core extends through the body and the sleeve ( 4 ) and a hardenable compound is disposed in the sleeve ( 4 ) filling the sleeve and surrounding the at least one core, wherein the sleeve ( 4 ) comprises a resilient or elastic material.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to electric cable gland assemblies. 
     2. Description of Related Art 
     A known type of cable gland assembly provides a barrier against leakage of liquid, gas or solid into the interstices of unfilled cables (i.e. cables which have voids or interstices within the cable between the cable cores and extending along its length) where the cable has had its outer sheath removed to enable the conductive elements of the cable cores to be connected to an item of electric equipment. The object of such cable glands is to avoid a flame path along the cable. Such cable gland assemblies are used in hazardous fire or explosion risk areas as are found on oil rigs for example. The invention relates particularly to cable gland assemblies of this type, wherein a hardenable compound is used to fill the space between and around the cable cores to prevent ingress of the liquid, gas or solid, the compound being contained within a sleeve or pot through which liquid, gas or solid, the compound being contained within a sleeve or pot through which the cores extend. Cable gland assemblies of this general type are known for example from GB 2 060 281A and GB 2 258 567 A. 
     Known compound sleeves or pots are made from metal, e.g. brass, or from rigid plastics material. Sleeves made of metal must be manufactured with precise tolerances. It is a burden to manufacture and check such high tolerances. Sleeves are also known which are provided with a separate seal, e.g. in annular form around the sleeve, to seal between the outer of the sleeve and the main body of the assembly. 
     An aim of the present invention is to provide at low cost a sleeve of simpler manufacture, construction and use. 
     It is also an aim of the present invention to improve the sealing of a sleeve. 
     SUMMARY OF THE INVENTION 
     According to the invention there is provided a cable gland assembly for an electric cable having a sheath enclosing at least one conductor core, the assembly comprising a body and a barrier sleeve locatable in the body wherein, in use, the at least one core extends through the body and the sleeve and a hardenable compound is disposed in the sleeve filling the sleeve and surrounding the at least one core, wherein the sleeve comprises a resilient or elastic material. 
     The resilient or elastic material preferably comprises a rubber or elastomer material. Further preferably, the sleeve substantially comprises a resilient or elastic material. More preferably, the sleeve completely comprises a resilient or elastic material. 
     The sleeve may be located with a compressed fit in the body i.e. with the resilient or elastic material, in use, located in the body under a degree of radial and/or axial deformation. An improved seal is thereby provided both between sleeve and body and sleeve and compound. 
     Advantageously, the sleeve in the invention is not required to be manufactured to the high tolerances of known sleeves. A suitable fit is easily achieved by the resilience or elasticity of the material. 
     The sleeve in the invention provides an improved seal between the outer of the sleeve and the inner of the assembly body. Since the sleeve comprises a resilient material, a seal between the outer of the sleeve and the inner of the assembly body is provided at least between a portion of the sleeve and the body, preferably between substantially the whole length of the sleeve and the body. In contrast, in the prior art, a separate annular seal is typically provided around the sleeve. Thus, the invention not only increases the degree of sealing, but it also replaces the separate two part construction of sleeve and seal with a single component. 
     The invention has also been found to be particularly advantageous in situations where the assembly may be subjected to considerable climate change, e.g. changes from high to low temperature and/or vice versa. With prior art sleeves there is always the possibility that the adhesion between the compound and sleeve may become reduced due to differing thermal expansion/contraction with potential compromise of the seal. However, in the invention, the sleeve comprising resilient or elastic material is able to deformably compensate for any loss of adhesion to provide a more consistent seal. 
     A yet further advantage is that if it is desired for any reason to remove the sleeve from the connector body, e.g. for inspection purposes, then the resilient material will allow a refitting of the sleeve in the connector body with little or no compromise in the quality of the seal either between sleeve and body or between sleeve and compound. 
     The sleeve of the invention is able to withstand cracking or melting over a wide range of temperatures. Preferably the sleeve of the invention is able to withstand temperatures from −60° C. to +100° C. 
     Preferably the sleeve material is not readily combustible. 
     The bore of the sleeve preferably has a frusto-conical shaped entry portion. 
     In many other respects the cable gland assembly of the invention may be constructed using known design features of cable glands. 
     Typically, the part of the assembly body in which the sleeve is located in use is an entry adapter, i.e. that part which connects to the equipment. 
     Preferably, the assembly comprises a camping spigot which, in use, is disposed at the frusto-conical end of the sleeve. Also, preferably, in use the spigot is urged against the sleeve by the engagement of a compression sleeve with the adaptor. 
     Further preferably the assembly comprises a clamping ring in use located annularly around a, typically complimentary shaped, surface of the spigot thereby to clamp an armour or earth element of the cable between the clamping ring and spigot. 
     The assembly also preferably further comprises a cap nut and outer cable seal to engage the exterior of the outer cable sheath by engagement of the cap nut with the compression sleeve. 
     The invention will now be described by way of the following examples and the accompanying drawings in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is an end view of an embodiment of a cable gland assembly according to the invention; 
     FIG. 1B is a side cross-sectional view along line A—A of the embodiment in FIG. 1A; 
     FIG. 1C is an exploded view of the embodiment in FIGS. 1A and 1B with the components shown disassembled; 
     FIG. 2A is a perspective view of an embodiment of barrier sleeve according to the invention; 
     FIG. 2B is an end view of the sleeve embodiment in FIG. 2A; 
     FIG. 2C is a side cross-sectional view along line A—A of the embodiment in FIG. 2B; 
     FIG. 2D is a side view of the embodiment in FIG. 2A; 
     FIG. 2E is an opposite end view of the embodiment in FIG. 2A; 
     FIG. 3A is an end view of a further embodiment of a cable gland assembly according to the invention; 
     FIG. 3B is a side cross-sectional view along line A—A of the embodiment in FIG. 3A; 
     FIG. 4A is an end view of a still further embodiment of cable gland assembly according to the invention; and 
     FIG. 4B is a side cross-sectional view along line A—A of the embodiment in FIG.  4 A. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1A shows an end view and FIG. 1B a side cross-sectional view on line A—A of an embodiment of a cable gland assembly  1  according to the invention. The assembly comprises an entry adapter  2 , barrier sleeve  4 , clamping spigot  6 , clamping ring  8 , compression sleeve  10 , cable outer seal  12 , seal urging member  14  and cap nut  16 . In use the parts of the assembly are assembled axially as shown in FIG. 1B around the electric cable (not shown). The series of disassembled components are shown in FIG.  1 C. 
     The entry adapter  2  has a threaded surface  2   a  for engagement with a threaded bore of an item of electric equipment (not shown). 
     The barrier sleeve  4  is made of a resilient or elastic material as described above. It is shown in more detail in FIGS. 2A to  2 E. The bore of the sleeve  4  has a frusto-conical portion  4   a  near its opening. The sleeve  4  is of generally cylindrical form and has a widening portion  4   b  towards its frusto-conical end. The sleeve  4  also has a small shoulder  4   e  at its entry end. The sleeve  4  is designed for a sealing fit within the bore of the adapter  2 . Typically, the sleeve  4  will be at least slightly compressed in the adaptor bore. In use the sleeve  4  is located within the bore of the adapter  2  with the annular end surface  4   c  of the sleeve abutting the shoulder  2   c  in the bore of the adapter  2 . The clamping spigot  6  in use is located against the sleeve  4 . On the entry side of the spigot  6  is an annular surface  6   a  adjacent to a shoulder  6   b . The annular surface  6   a  locates within the bore of the sleeve  4  such that the shoulder  6   b  abuts the annular end surface  4   d  of the sleeve  4 . 
     The clamping ring  8  has a tapering bore  8   a  which in use is located around the clamping spigot  6  to enable an armor or earth element of the cable (not shown) to be clamped between the surface  8   b  of the ring  8  and the annular surface  6   c  of the spigot  6 . 
     The compression sleeve  10  is located around the spigot  6  and ring  8 . The compression sleeve  10  has a threaded portion  10   b  which in use engages with the threaded portion  2   b  of the adapter  2 . The compression sleeve  10  has a shoulder  10   a  which abuts the end of the ring  8 . 
     The cap nut  16  has a threaded portion  16   a  which in use engages with a threaded portion  10   c  of the compression sleeve  10 . Located within the cap nut  16  are the cable outer seal  12  and seal urging member  14 . 
     In use there will also be a hardenable compound (not shown) disposed within the bore of the sleeve  4  and spigot  6  and filling the space around and between the cable conductor cores which pass therethrough (not shown). 
     The assembly and use of the cable gland will now be described. 
     A portion of the outer sheath of the electric cable (not shown) is removed to expose the inner conductor cores, inner sheath and e.g. armour. The cap nut  16 , seal urging member  14  and cable seal  12  assembled with compression sleeve  10  (but not compressed) are passed over the outer sheath of the cable. 
     Then the clamping ring  8  is passed over the armour and the clamping spigot  6  with its tapered surface  6   c  is located under the armour. The compression sleeve  10  may be located and tightened onto the entry adapter  2  to firmly clamp the armour between the ring  8  and spigot  6 . The compression sleeve  10  is then removed from the adaptor  2  so that the conductor cores may be spread apart for compound packing. 
     The conductor cores are spread apart and the hardenable compound is applied to the crutch between the cores. The cores are then brought back towards each other and the area around the cores and the space between the cores and the spigot  6  are filled with the compound. Details of the compound, including its preparation and application, are well known to the skilled person. 
     The barrier sleeve  4  is then passed over the cores and the compound before it starts to harden and the end of the sleeve  4  is located on the spigot  6 , the end face  4   d  of the sleeve  4  abutting against the shoulder  6   b  of the spigot  6 . Any excess compound is trimmed away. The conductor cores, sleeve  4  and spigot  6  are then located in the entry adapter  2  and the compression sleeve  10  is located on the entry adapter  2  and tightened. This compresses the compound and also forms a flame proof seal between the entry adapter and the sleeve  4 . The sleeve  4  by radial and/or axial deformation has a sealing fit in the bore of the adaptor  2 , particularly in the region of the widened portion  4   b  of the sleeve  4 . An improved seal between the sleeve  4  and the adaptor  2  is thereby achieved. Moreover, the need for a separate seal between the sleeve and adaptor is avoided. The cap nut  16  is tightened on the compression sleeve  10  such that the seal urging member  14  urges the cable outer seal  12  into engagement with the outer sheath of the cable to form a seal therebetween. 
     The foregoing embodiment is just one construction of cable gland assembly that the resilient or elastic barrier sleeve of the invention may be used in. It will be appreciated by the skilled person that the invention may be employed in many other constructions of cable glands assemblies. Another construction of cable gland assembly is shown in FIGS. 3A and 3B. Similar components in the embodiment in FIGS. 3A and 3B to the components in FIGS. 1A and 1B are given similar reference numerals ( 2 ′,  4 ′ etc.). 
     Another construction of cable gland assembly is shown in FIGS. 4A and 4B. Similar components in the embodiment in FIGS. 4A and 4B to the components in FIGS. 1A and 1B are given similar reference numerals ( 2 ″,  4 ″ etc.). The cable gland assembly in FIGS. 4A and 4B is for a non-armoured cable. It can be seen that the spigot  6 ″ and compression sleeve  10 ″ are of different construction than in the cable gland assembly in FIGS. 1A and 1B. Moreover, the cable gland assembly in FIGS. 4A and 4B comprises a different form of cable outer seal  22 , seal urging means  24  and cap nut  26 .