Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Reexamination Certificate
2000-10-19
2002-02-05
Nguyen, Chau N. (Department: 2831)
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
Reexamination Certificate
active
06344615
ABSTRACT:
FIELDS OF THE INVENTION
The present invention relates generally to a closure, and particularly to a closure for enclosing one or more elongate objects.
The present invention finds particular utility as a closure for protecting junctions between elongate objects such as pipes or cables. The term “cable” will be understood hereinafter to include both conductive cables and bundles of optical fibres. When it is necessary to make connections between elongate objects such as pipes or cables the junction or splice where such objects are joined end-to-end is necessarily less strong and less resistive to environmental agents liable to cause deterioration over time than the cable itself.
BACKGROUND OF THE INVENTION
In the production of, for example, cable systems such as telecommunication or power transmission systems, it is frequently necessary to make splices either to join cables end-to-end or to make a branch. The cables and the splices may be located underground, in conduits or in other environments, inside or outside buildings, but in any event are always at risk to the ingress of environmental agents such as moisture and humidity or dust. Underground installations are also subject to pressure, and in particular hydrostatic pressure, whilst above-ground installations suffer from diurnal thermal dilatations. In order to provide environmental seals for splices in cables or other elongate objects various protective measures are known. Systems utilising an enclosing casing with a gel or other suitable sealing material enclosed within it have been found to be particularly valuable. One advantage of using closures containing a gel or other such sealing material lies in the fact that they can be installed at room temperature, and by utilising compression means the gel can be maintained in contact with all the interior surfaces of a closure as well as the exterior surfaces of the cable or other elongate object the splice in which is to be protected. The force applied by the compression means must be sufficiently great to overcome any forces which may be exerted by the environmental agents, such as the hydrostatic head in underground installations. The requirement for a compressive force on a sealing material has been recognised for some years and is described in various prior art documents. In particular, U.S. Pat. No. 4,600,261 (Raychem) describes an apparatus and method for protection of electrical contacts in which the apparatus includes a gel, first means to contain the gel, second means to retain the gel within the first means, and a force means which acts on the first means so that the gel is maintained in compressive contact with the electrical contacts and substantially encapsulates the conductive portion of them.
In that document the means for applying the force comprised an external clip or spring by which two halves of a closure casing were held together and pressed into contact with one another by the spring. Although effective this system has the disadvantage that the components must be made to accommodate a particular size (or relatively narrow size range) of elongate objects over which the spring can exert an appropriate force.
In order to ensure the sealing effect cable closures incorporating relatively displaceable end walls displaceable by screw-threaded means were devised, as described in WO 95/15600 (Raychem). A spring interposed between a nut and a displaceable end wall acting effectively as a piston allowed compression to be applied to a sealing material encapsulated within the sealing closure. It was also appreciated that the displacement direction need not be parallel to the length of the elongate objects enclosed within the casing, but could be transverse this direction, and the above prior art document also describes the provision of piston-like members acting perpendicularly to the length of an enclosed cable whereby to place a gel under compression.
Although all of these arrangements act well to provide a secure seal they nevertheless offer only a secure seal over a relatively limited range of cable diameters. In order to be able to provide a secure seal over a relatively large range of diameters of elongate objects such as cables a relatively large range of movement must be available in order to change the volume of the containment closure over a wide range.
SUMMARY OF THE INVENTION
The present invention seeks to provide a closure for elongate objects which is capable of accommodating such objects over a relatively wide range of dimensions, preferably up to a 3:1 ratio of diameters, whilst nevertheless offering a secure seal against environmental agencies.
According to one aspect of the present invention a closure casing comprises two casing parts, means for holding the two casing parts together in juxtaposed relationship, and having means for sealing between an elongate article penetrating the casing and the casing itself, the casing parts having respective cavities together forming a sealant chamber for receiving sealant material and through which the elongate article passes in penetrating the closure casing, the volume of the sealant chamber being adjustable whereby to apply a compressive force to sealant material therein, the adjustment being effected by displacement of at least one element located within the said sealant chamber, the said element being displaceable within the chamber by selectively operable position—adjustment means of the casing whereby to determine the effective volume of the sealant chamber.
According to a second, more general aspect of the present invention there is provided a closure casing having means for sealing a space between an elongate article penetrating the casing and the casing itself, the casing comprising two opposite casing parts having means for holding them together in juxtaposed relationship and each having respective cavities together forming a sealant chamber for receiving sealant material and through which the elongate article passes in penetrating the closure casing, and means for applying a compressive force to the sealant material transversely of the length of the elongate article whereby to urge it into intimate contact with the said elongate article to seal thereto, in which the said means for applying a compressive force comprise selectively operable adjustment means for determining displacement of a movable member the position of which determines the effective volume of the said sealant chamber.
In one embodiment of the present invention the said displaceable element comprises a plunger guided for movement within the said sealant chamber in a direction substantially transverse the length of the said elongate article. Preferably there are two relatively displaceable plungers interconnected and guided for substantially rectilinear movement within the said sealant chamber.
The said two plungers may be interconnected by screw threaded adjustment means.
Compression on the sealant may be maintained after adjustment, despite changes in volume due to thermal and other effects if there are provided energy storage means between the adjustable position-determining means and the said at least one displacement element. Such energy storage means may comprise a spring, preferably a compression coil spring.
In a preferred embodiment of the invention the screw threaded adjustment means comprise a threaded shaft having operating means at one end thereof by which the shaft is turnable, and a cooperating threaded hole in one of the said two plungers, the spring acting between the other of the two plungers and the said operating means.
In another aspect the present invention comprises a closure comprising a closure casing having openings for the passage of elongate objects and sealing means including a sealing material enclosed within at least part of the closure casing, in which the sealing means includes a relatively displaceable wall part of the closure joined to the remaining part of the closure by a flexible hinge part, and adjustable position-determining means for determining the relative position of the said relatively d
Bos Peter
Buekers Valere
Deroost Dirk
Legrand Johan
Nolf Jean-Marie Etienne
Nguyen Chau N.
Tyco Electronics Raychem N.V.
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