FLAMEPROOF SEALS FOR THE ENDS OF ELECTRIC CABLES AND KITS FOR AND METHODS OF MAKING THEM

Abstract: A flameproof cable or conduit seal includes a main gland member 11 and a tubular inner member 14. These have mat­ ing annular surfaces 24 and 25 shaped to form a tortuous path between them when assembled; this forms the whole or part of a flameproof path between the members.

Description: SEALING CABLES This invention relates to sealing of the ends of electric cables and is particularly concerned with flameproof seals thereof. According to the present invention, we provide a kit for effecting a flameproof seal to an end of an electric cable which kit includes a first annular body for direct or indirect connection to the end of the cable sheath, a second annular body for engagement with the first annular body and, surrounded by the first and/or second of the annular bodies, a tubular body which has an annular surface apt to abut an annular surface on the second annular body in such a way that'when the second annular body is engaged with the first annular body the tubular body is urged axially towards the second annular body, and is characterised in that the annular surface on the tubular body and the annular surface on the second annular body are each so shaped that they interengage to form between them a path of tortuous configuration, such path forming all or part of the required length of the flameproof path between the members. When the first and second annular bodies will be directly screwed together, the interengaging shaped surfaces will need to be shaped to permit rotation of the second annular body relative to the tubular body; preferably, the tortuous path is formed by providing on each annular surface a plurality of upstanding, spaced, concentric endless troughs, ribs on each of said annular surfaces entering troughs in the other of said annular surfaces. (By "concentric" ribs or grooves is meant ribs or grooves that enclose one another; no limitation on shape is intended). In this case the annular surfaces on the tubular body and on the second annular body preferably lie in planes normal to the axis of the body, and the ribs and grooves may fit tightly or may be slightly spaced from one another. The-ribs of each annular surface and the troughs on the other annular surface in which the ribs enter may be of any convenient cross-sectional shape and size, but, preferably,-each rib and interengagig trough is of substantially triangular cross-section. Other cross-sectionsl shapes which the ribs and interengaging troughs may take-include rectangular and sinusoidal. Preferably, all ribs on both annular surfaces are of substantially the same cross-sectional shape and size as one another. In one alternative arrangement, the tortuous path is formed by making each annular surface of a stepped configuration comprising a plurality of spaced, concentric endless steps. For ease of manufacture, preferably the circumferential surface defining each step is parallel to the axis of the body and the annular surface defining each step lies in a plane normal to the axis of the body. The kit preferably also includes a compound chamber, formed in part by the tubular body, through which the or each cable conductor will pass, and a sufficient quantity, as a preformed body or otherwise, of setting synthetic resin or other hardenable material (preferably insulating) in a pasty or viscous condition to fill the chamber. A kit for terminating a cable or conduit as described and claimed in the Complete Specification of our British Patent No. 1524684 may be modified to form a kit in accordance with the present invention. The invention also includes a method of effecting a flameproof seal to an end of an electric cable using a kit as hereinbefore described. The invention further includes a flameproof seal at an end of an electric cable formed from a kit as hereinbefore described. The invention is further illustrated by a brief description, by way of example, of two forms of flameproof seal with reference to the accompanying drawing. The drawing is a longitudinal sectional view of a termination of a three core cable made by the method of British Patent No. 1524684 using a kit as described and claimed in that Patent but modified to provide a flameproof path between the gland body 11 and the second gland member 14. The gland body 11 has a radially extending annular surface 24 from which upstand circumferentially spaced, concentric endless- ribs 26, each of triangular cross-section, defining between them endless troughs 27, each of similar shape. The- second gland member 14 has a radially extending annular surface 25 from which upstand circumferentially spaced, concentric endless ribs 28, each of triangular cross-section, defining between them troughs 29. When the gland body 11 is screwed to the gland barrel 6 to urge the second gland member 14 axially and so generate pressure in the compound 12, the ribs 26 enter and engage tightly in the troughs 29 and the ribs 28 enter and engage tightly in the troughs 27 to form a flameproof path between the second gland 14 and the second body 11.

Claims: CLAIMS 1. A kit for effecting a flameproof seal to an end of an electric cable, which kit encludes a first annular body for direct or indirect connection to the end of the cable sheath, a second annular body for engagement with the first annular body and, surrounded by the first and/or second of the annular bodies, a tubular body which has an annular surface apt to abut an annular surface on the second annular body in such a way that when the second annular body is engaged with the first annular body the tubular body is urged axially towards the second annular body, characterised in that the annular surface on the tubular body and the annular surface on the second annular body are each so shaped that they interengage to form between them a path of tortuous configuration, such path forming all or part of the required length of the flameproof path between the members. 2. A kit as claimed in Claim 1 in which the first and second annular bodies directly screw together characterised in that the interengaging shaped surfaces are shaped to permit rotation of the second annular body relative to the tubular body. 3. A kit as claimed in Claim 1 or Claim 2 characterised in that the tortuous path is formed by providing on each annular surface a plurality of upstanding, spaced, concentric endless ribs defining between them a plurality of spaced, concentric endless troughs, ribs on each of said annular surfaces entering troughs in the other of said annular surfaces. 4. A kit as Claimed in claim 3 characterised in that the ribs on each of said annular surfaces enter and fit tightly in the troughs in the other of said annular surfaces. 5. A kit as claimed in Claim 3or Claim 4 characterised in that the ribs and troughs are triangular in cross-section. 6. A kit as claimed in Claim 1 or Claim 2 characterised in that the tortuous path is formed by making each annular surface of a stepped configuration comprising a plurality of spaced, concentric endless steps. 7. A kit as claimed in any one of the preceding claims including also a compound chamber through which the or each cable conductor will pass and a sufficient quantity of hardenable material in a pasty or viscous condition to fill the chamber, characterised in that the said compound chambers formed in part by the said tubular body. 8. A method of effecting a flameproof-seal to an end of an electric cable by means of the kit claimed in apt one of the preceding claims1 the method being characterised by directly or indirectly connecting a first annular body and the end of the cable sheath, engaging a second annular body with the first annular body to surround a tubular body by the first and/or second of the annular bodies the tubular body having an annular surface that so abuts an annular surface on the second annular body ;that the tubular body is urged axially towards the second annular body and the shaped annular surfaces on the tubular body and on the second annular body interengage to form between them a path of tortuous configuration, such path forming all or part of the required length of the flameproof path between the members. 9. A flameproof seal made by the kit claimed in any one of Claims 1 - 7 or by the method claimed in Claim 8.

Inventors: HUTCHISON, JOHN BLUNDELL
Applicants: BICC PUBLIC LIMITED COMPANY
Application year: 1980
Main classification: H02G15
IPC codes: H02G15, H02G3