Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1995-04-28
1997-03-04
Cummings, Scott
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
277208, 277209, 174 65SS, 174 77R, F16J 1510, G02B 644, G02B 638
Patent
active
056071671
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to environmental sealing, especially to a sealing member, particularly for cable accessories for example housings such as cable splice closures.
Environmental sealing is frequently necessary in the cables accessories arts in order to keep out contaminants such as water and sometimes to retain pressure. When cables are spliced, for example, cable jackets must be removed in order to expose conductors for connection. Some form of closure must be created around the otherwise exposed conductors to replace the removed cable jacket. Such splice closures must have a lifetime under adverse conditions comparable to that of the cables themselves, which may be twenty years or so. Thus, the problem of environmental sealing is far from trivial.
The present invention will find uses in many fields, but it is expected to be particularly useful for sealing optical fibre splice closures and other cable or pipe accessories. Cable splice closures often must be installed under wet or muddy conditions, and it is desirable that a good seal can be achieved without the need for rigourous cleaning of the surfaces to be sealed.
An optical fibre closure where the invention is expected to find particular use is disclosed in European Patent Specification No. 0159857 (Raychem). That specification discloses an assembly capable of enclosing a butt splice between at least two optical fibre cables, which comprises: from the base plate, the base plate having at least two mutually adjacent outlets capable of receiving respective optical fibre cables; the assembly having at least one optical fibre organizer housed within the article for storing a plurality of optical fibres in a path from one of the outlets to another of the outlets, said path having a minimum radius of curvature no smaller than the minimum bend radius of said optical fibres; and means for connecting the at least one optical fibre organizer to the base plate such that when the first and second means are so connected the optical fibres are stored in at least one storage plane and characterized in that when the first means is disconnected the hollow cover is removeable from the base plate by being moved along a direction which is substantially parallel to the storage plane, substantially parallel to each outlet direction at the base plate and substantially perpendicular to the base plate.
The base plate and cover, which is preferably dome-shaped, may be held together by some mechanical clamp, optionally together with some environmental sealing means such as a gasket, O-ring, mastic seal or adhesive bond.
The use of O-rings in such a device is, of course, well known. They allow easy re-entry into the closure and easy re-sealing, they can withstand high pressures within the closure, and they do not suffer from compression set.
We have, however, become aware of certain disadvantages of the use of simple O-rings. For example, the force that they are subjected to and the consequential extent of their distortion are critical if a good seal is to be obtained. The forces required are generally high, and as a result the article to be sealed must be strong and, therefore, generally thick-walled. In the case of an optical fibre closure as disclosed above, this means that the base and at least the lower skirt of the dome cover must be ruggedly constructed. A further disadvantage is that both the O-ring and the surfaces of the base and dome to be sealed, must be carefully cleaned and must be free from scratches or moulding flash etc. Dimensional changes resulting from pressure, heat or excessive mechanical loads might prevent a good seal being achieved and performance at low temperatures is unlikely to be satisfactory due to loss of elastomeric properties of the materials from which most O-rings are made.
We have discovered that such disadvantages of O-rings can be avoided if an O-ring, or other retaining member, is used in conjunction with a suitable sealing material. This new combination produces surprising benefits not apparent from either component when used
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Burkard Herbert G.
Cummings Scott
N.V. Raychem S.A.
Zahrt II William D.
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