Electricity: conductors and insulators – Conduits – cables or conductors – Combined
Patent
1992-01-21
1994-01-11
Nimmo, Morris H.
Electricity: conductors and insulators
Conduits, cables or conductors
Combined
174 72R, 174 77R, 174DIG8, H02G 1508
Patent
active
052783553
DESCRIPTION:
BRIEF SUMMARY
This invention relates to environmental sealing, particularly by means of a heat-shrinkable sleeve of substrates, such as telecommunications or other cables, particularly at cable splices or other regions where cables run close to one another, especially spaced apart by a fixed amount.
Heat-shrinkable articles are now widely used in many areas where environmental sealing, for example, insulation, bonding or encapsulation, is required. Usually these articles dimensionally-recover on heating to a shape from which they have previously been deformed, but the term "heat-shrinkable" as used herein also includes an article which, on heating, adopts a new configuration, even if it has not previously been deformed.
In their most common form, such articles comprise heat-shrinkable sleeves made from polymeric material exhibiting the property of elastic or plastic memory as desired, for example, in U.S. Pat. Nos. 2,027,962, 3,086,242 and 3,957,372.
Heat-shrinkable sleeves find many applications, especially in the connection and termination of wires, cables and pipes. However, there are applications where it is desirable to provide a sealing member for elongate substrates such as cables or pipes or other supply lines whose ends are not accessible. For such applications so-called "wrap-around" sleeves have been developed. Basically, they are heat-shrinkable sheets which can be wrapped around a substrate to form a generally tubular shape and which, in general, are provided with fastening means for holding them in the wrapped-around configuration during heat-shrinkage. Examples of such sleeves are disclosed in GB1155470.
Heat-shrinkable sleeves have been successfully employed in many fields, but problems may arise when two or more substrates have to be sealed at one position. This problem, which is known as "branch-off", may occur, for example, at the outlet of a heat-shrinkable part. Amongst fields in which this problem is typically encountered there may especially be mentioned the outlets of the splice cases described and claimed in GB1431167 (Raychem), the disclosure of which is incorporated herein by reference.
One effective solution for tubular sleeves has been to use moulded heat-shrinkable parts provided with preformed outlets for the individual substrates. However, in general, such parts have to be made to suit a particular application, and many different such parts will therefore be required to cover all the applications likely to be encountered.
A solution of major commercial importance to this problem is disclosed and claimed in U.S. Pat. No. 4,648,924 (Raychem), the disclosure of which is incorporated herein by reference. In that patent, a method of forming a branch-off seal between a heat-shrinkable sleeve and at least two substrates, comprises the steps of: clip having at least two elongate legs over the outer surface of the heat-shrinkable sleeve at an open end thereof, wherein at least two of said legs are positioned externally of the sleeve and the substrates are within the terminal conduits; and sleeve, applying heat so as to effect shrinkage of the sleeve and to form the desired seal.
U.S. Pat. No. 4,400,579 (Raychem) discloses and claims an assembly comprising a heat-shrinkable sleeve capable of being positioned around at least first and second elongate substrates, and a clip formed as a trident, the outer legs of which are capable of being positioned over the outer surface of the sleeve at the end thereof with the central leg of the trident (which may taper towards its proximal end and may be coated with an adhesive) inside the sleeve so as to form, and maintain during subsequent heat shrinkage of the sleeve, at least two terminal conduits respectively capable of receiving the first and second substrates.
Whilst the clips disclosed in these patents are outstandingly successful for most uses, some difficulties may be noticed under unfavourable conditions, for example, where the distance between the substrates is significant and cannot be altered. For example, in some countries it is common to enclose a
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Read Michael
Vanhentenrijk Robert
Burkard Herbert G.
Nimmo Morris H.
Raychem Limited
Zavell A. Stephen
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