CA1286485C - Branch-off clip - Google Patents
Branch-off clipInfo
- Publication number
- CA1286485C CA1286485C CA000584364A CA584364A CA1286485C CA 1286485 C CA1286485 C CA 1286485C CA 000584364 A CA000584364 A CA 000584364A CA 584364 A CA584364 A CA 584364A CA 1286485 C CA1286485 C CA 1286485C
- Authority
- CA
- Canada
- Prior art keywords
- heat
- sealing material
- clip
- sleeve
- conductive member
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000003566 sealing material Substances 0.000 claims abstract description 34
- 238000010438 heat treatment Methods 0.000 claims abstract description 22
- 230000003313 weakening effect Effects 0.000 claims abstract description 5
- 239000000758 substrate Substances 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 19
- 229910052751 metal Inorganic materials 0.000 claims description 19
- 238000002844 melting Methods 0.000 claims description 14
- 230000008018 melting Effects 0.000 claims description 13
- 230000004913 activation Effects 0.000 claims description 9
- 239000000155 melt Substances 0.000 claims description 7
- 239000004831 Hot glue Substances 0.000 claims description 5
- 239000000843 powder Substances 0.000 claims description 3
- 239000000463 material Substances 0.000 description 13
- 239000000853 adhesive Substances 0.000 description 12
- 230000001070 adhesive effect Effects 0.000 description 12
- 238000011084 recovery Methods 0.000 description 9
- 238000009434 installation Methods 0.000 description 7
- 239000004020 conductor Substances 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- ODPOAESBSUKMHD-UHFFFAOYSA-L 6,7-dihydrodipyrido[1,2-b:1',2'-e]pyrazine-5,8-diium;dibromide Chemical compound [Br-].[Br-].C1=CC=[N+]2CC[N+]3=CC=CC=C3C2=C1 ODPOAESBSUKMHD-UHFFFAOYSA-L 0.000 description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 2
- 239000005630 Diquat Substances 0.000 description 2
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000003550 marker Substances 0.000 description 2
- 239000013521 mastic Substances 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 238000006722 reduction reaction Methods 0.000 description 2
- 239000000565 sealant Substances 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000010924 continuous production Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 235000019628 coolness Nutrition 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000004132 cross linking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 210000005069 ears Anatomy 0.000 description 1
- 238000005538 encapsulation Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 239000012943 hotmelt Substances 0.000 description 1
- 239000012768 molten material Substances 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000001294 propane Substances 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000012812 sealant material Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Landscapes
- Cable Accessories (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention provides a clip which comprises two outer legs and an inner leg, so arranged that the clip can be positioned over the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising: (a) a heat acti-vatable sealing material and (b) a heat-conductive member ther-mally connecting the outer legs with the sealing material, said clip being adapted on heating the heat-conductive member to reduce the rigidity of at least a portion of the inner leg by weakening the dimensional integrity of at least part of the heat-conductive member.
The present invention provides a clip which comprises two outer legs and an inner leg, so arranged that the clip can be positioned over the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising: (a) a heat acti-vatable sealing material and (b) a heat-conductive member ther-mally connecting the outer legs with the sealing material, said clip being adapted on heating the heat-conductive member to reduce the rigidity of at least a portion of the inner leg by weakening the dimensional integrity of at least part of the heat-conductive member.
Description
This invention relates to the use o~ heat-recoverable artlcles in enclosing and protecting ~oins or splices between substrates such as supply lines.
This application is a divisional application o~ copend ing application No., 441,660 filed November 22, 1983.
Heat-recoverable articles, such as heat-recoverable sleeves, are useful for forming enclosures around substrates to be insulated or protected because the article can be made large enough for easy installation, and then recovered into close con-tact with the substrate. Close tolerances in manufacture and craft-sensitivity in installation can therefore be avoided.
A heat-recoverable article is an article the dimen-sional configuration of which may be made substantially to change when subjected to heat treatment.
Usually these articles recover, on heating, towards an 20 original shape from which they have previously been deformed but the term "heat-recoverable", as used herein, also includes an artlcle which, on heating, adopts a new configuration, even if it has not been previously deformed.
In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibltiny the proper-ty of elastic or plastic memory as described, for example, in U.S. Patents 2,027,962, 3,0a~,2~2 and 3,597,372. ~S
:ls made clear ln, for example, U.S. Patent 2,027,962, the orlgi-30 nal dlmenslonal~y heat-stable form may be a translent form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in o-ther applications, a preformed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.
In the production of heat recoverable articles, the polymeric material may be cross-linked at any stage in the pro~
duction of the article that will enhance the desire~ dimensional recoverability. One manner of producing a heat-recoverable art-icle comprises shaping the polymeric material into the desiredheat-stable form, subsequently cross-linking the polymeric mate-rial, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, de~orming the article and cool-ing the article whilst in the deformed state so that the deformedstate of the article is retained. In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to assume its original heat-stable shape.
In other articles, as described, for example, in British Patent 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating weakens and thus allows the elastomeric member to recover.
Heat shrinkable sleeves find many applications, espe-cially in the connection and termination of wires, cables and pipes. However, there are other applicatlons where it is desir-able to provide a connecting, insulating, or protective heat-recoverable member for elongate ob~ects such as cables and pipeswhere the ends are not accesslble, or i~ they are accessible, where it is undeslrable to dlsconnect or otherwise to displace them. For such applications the so-called "wrap-around" sleeves have been developed. Baslcally, they are heat-recoverable sheets whlch can be wrapped around the substrate to form a generally tubular shape and whlch ln general are provided with fastening means for hold:lny them in the wrapped-up conflguratlon durlng recovery. Typlcally such fastenlng means are mechanical and com-prlse, for example, rlgld clamps, pins or channel members which co-operate with suitably shaped moulded or extruded protuberances ad~acent to the overlapplng edges of the recoverable sheet. Var-~ ~6~
ious types of fastening means are described, for example, in U.S.Pa-tent 3,379,218 and sritish Patents 1,155,470, 1,211,988 and 1, 346, 479 . In other applications, however, the sheet may be held in the wrapped-up configuration during recovery by means of an adhesive which may, in some cases, be applied on site.
~ eat recoverable sleeves have been successfully employed in many fields of application. However, when two or more substrates such as supply lines, for example cables or pipes, are joined so as to form a connection, problems may arise in obtaining an adequate seal, for example at the outlet of a heat recoverable enclosure. Amongst areas in which this problem is typically encountered there may especially be mentioned the outlets of the splice cases described and claimed in sritish Patent 1,431,167 and the duct seal devices described and claimed in British Patent 1,59~,937.
One effective solution for tubular sleeves has been to use moulded heat-shrinkable parts provided with preformed outlets for the individual supply lines. However, in general such moulded parts have to be made to suit a specific application.
Their versatility has been improved by the use of end caps which seal outlets which are not needed in a specific operation, as described and claimed in British Patent 1,59~,693 but ~hey are nonetheless expensive and thus economically infeasible ln many routine application3.
Another, less e~pensive, solution which has frequently been employed is to use mastlc tape to seal the gap between the supply lines so that, on recovery, a proper encapsula-tion is formed at the end of the heat-recoverable part. However, the use of such tape requires skill on the part of the installer and the method is not applicable to large parts. In addition, the mastic may degrade the overall performance or pro~ucts which are pro-vided with an inner lininy or coating o~ a hot-melt adhesive.
In British Patent 1,604,981 an effective branch-of~ is obtained by forming the individual outlets by means of a suitably shaped clip made from a relatively rigid material. In accordance with the invention therein described there is provided a method of forming a branch-off seal between a heat-shrinkable sleeve and at least two substrates such as supply lines, which comprises the steps of (a) positioning a clip having at least two elongate legs over the outer surface of the heat-shrinkable sleeve at the end thereof so as to form at least two terminal condui~s; (b) posi-tioning the substrates within the conduits; and (c) applying heatso as to effect shrinkage and to form the desired seal. Steps (a) and (b) may be effected in either order or simultaneously, for example in many cases the clip will be pushed into place after the sleeve has been positioned about the subs-trates.
In its slmplest form the clip used in the invention of GB 1,60~,981 is U-shaped and its two legs are slid over the outer surfaces of the pinched together heat-recoverable sleeve or wrap-around sleeve, or over the surfaces of the heat-recoverable sleeve or wrap-around sleeve and another co-operating surface.
However, in preferred embodiments the clip has three legs and the inner leg passes into the heat-recoverable sleeve whilst the outer legs pass outside it; in this way each of the two layers of the heat-recoverable material is pLnched between an inner leg and an outer leg. The inner leg may be contoured so as to reduce the possibility o~ the clip "milking off" during recovery, and advan-tageously comprises a hot-melt adhesi.ve wh:lch flows during recov-ery to seal the gap between the conduits which have been formed.
We have now designed a branch-o~E clip which possess many oE the advantages of -the three legged cllp described above, as regards positioning oE the clip, delivery of sealant material to the cable crutch reg:Lon, activatlon of such adhesive, if nec-essary, etc., but which can facilitate re-entry of an enclosure and which can reduce craft-sensitivity when used with less rugged substrates.
~6~5 Thus, the invention provides a clip which comprlses two outer legs and an inner leg, so arranged ~hat the clip can be positioned over -the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising la) a heat-acti-vatable sealing material, and ~b) a heat conductive member ther-mally connecting the outer legs wlth the sealing material; the dimensional integrlty of a-t least part of the member weakening on heating at or shortly after activation of the sealing material, thus reducing -the thermal connection, or reducing the rigidity of at least a portion of the central leg.
The heat conductive member may be a single member, ~or example a single meltable metal member connecting the outer legs and an inner adhesive leg. Alternatively it may be provided by a region, for example by a plurality of metal fibres embedded in an inner adhesive leg. Thus, re~erence is made hereinafter to a metal member or region.
Before heating, the inner leg of the clip comprises a hot-melt adhesive, a softenable sealan-t such as a mastic, or other heat-activatable sealing rnaterial, and a heat conductive member or region by means of which heat dlrected at those parts of the clip outside of the sleeve wlll be transferred within the sleeve to melt the adhesive, thereby sealing the crutch region between the cables. The embodlments of three legged clips hith-erto describe~ show the lnner leg to be generally lntegral with and substantlally similar to the outer legs. SUch an inner leg can act as a support for adhesive and can conduct heat into the crutch region to melt the adhes:Lve. Although this conduction of heat is deslrable, it rnay occasionally result in damage to the cable ~acket or other substra-te especlally where over long pos-t-heating times are employed. ~leat directed at the outside of the sleeve in this instance is conducted through the material of the clip to the inner leg which ls in contact with the cable ~ackets, and with low quality cables this can cause darnage. Also pressure L~5 of the outer sleeve causes the cables and clip to be forced together, and this may cause damage where the lnner leg is rigid.
These thermal and mechanical effects can be overcome by the invention by causing heat transfer to the inner leg to be cut or considerably reduced at a certain point in time during installa-tion, or by causing at least a portion of the inner leg to become more flexible.
A second consideration of three legged clips also results from a feature which is generally beneficial but can in certain circumstances be disadvantageous. U.K. Patent 1,604,981 remarks that a three legged clip allows easy positioning at the end of a sleeve and makes milk-off practically imposslble espe-cially a.ter recovery. The reason for this is that the inner leg, especially when tapered towards its proximal end, becomes wedged between the recovered sleeve and the substrates. This permanence is in general to be preferred, but where the enclosure is llkely to be re-entered sometime during its life difficulty in removing the clip can be troublesome. with the present invention a seal, equally as reliable as the prior art seals, can be made which allows easy re-entry, due to transformation of, say, a three legged clip into a two legged clip whilst still benefitting from the provision of a heat-conductive member or region. If the heat conductive member or region were simply omitted the heat-activatable sealing material would not be properly activated,except perhaps at a position ad~acent the open end of the sleeve.
Three preferred techni~ues will now be discussed by means o~ which orle can achieve the desired weakenirlg oE dlmen-sional integrity of the heat conductive member or region of theinner leg. What is preferred ic: that installation is commenced with a three-legged clip, but that the clip eE~ectively becomes a two-legged clip at some stage during installation. The inner leg will not in general totally disappear; the heat conductive member may remain but in a dispersed form or it may simply move so as to conform to the shape of the cables or other substrates or it may 6~
move further away from the bridge part of the clip lnto a region oE the sleeve of larger diameter. The timing of this change should be such tha-t the heat conductive member or region is able to conduct a suf~icient amount of heat to cause melting of the adhesive (or activation of other sealing material) but is not able to damage the cables. Weakening o~ the heat conductive mem-ber or region should therefore occur shortly after sufficient adhesive in ~he crutch region has melted or has otherwise been activated. The delay between activation of adhesive and reduc-tion of the heat path or re~uction of rigidity in this embodimentis preferably from almost nothing to, say, 10 minutes depending on the means of heating employed. The adhesive is preferably activated at a temperature of from 50-120C, more pre~erably 70-100C and weakening of dimensional integrity preferably occurs within the range 70-140C, more preferably 90-120C. The differ-ence between the two temperatures is preferably from 5-35C, more preferably from 5-15C.
In a first embodiment, the heat conductive member or region comprises a low-melting point metal. Preferably the melt-ing point will be slightly above the activation temperature of the adhesive. Not only should the temperature oE meltlny be con-sidered, but also the amount of heat required should be corre-lated to the amount of heat required for recovery of the sleeve and for activation of the adhesive or other sealing material. As soon as the heat conductive member or region of the inner leg weakens, for exarnple by melting, the heat-conduc-tive path between the outer legs, or other parts of the clip which are directly heated, and the crutch reglon is broken or at leas-t subs-tantlally reduced. In general the materlal that melts wlll s:lmply flow and become dispersed in the crutch region; the cllp could, however, be designed such that the molten material Elowed in a chosen direction.
The construction of this first embodiment can be real-ized in a number of ways. Firstly, the heat conductive rnember or ~lZ~ 5 region could be a complete prong of low melting-point metal~ of much the same shape and size as the outer legs. The term prong is used for a conductive member of this general configuration because the term inner leg is used to refer to the conductive member or region together with the sealing material. ~t the appropriate stage during heat-recovery the whole of the prong would melt, leaving molten sealing material in the crutch region but preventing or reducing further flow of heat into the region.
Not only is there no further flow of heat to damage the sub-strates, but the ho-t conductive member no longer has the dimen-sional integrity to be forced against the substrates.
A second design using a low melting polnt metal as the heat conductive member or region employs a central prong which doss not melt, the low melting point metal being used as a bond to ~oin this prong to the remainder of the clip. During instal-lation, therefore, the prong becomes detached causing a break or substantial reduction in the heat path. The dimensional integrity of the inner leg, considered as a whole, is weakened but there remains the non-melting prong, which may but need not remain in the crutch region. It will be appreciated tha-t other fusible materials having a significant heat conductivity may be used in this design instead of the low melting point metal.
In a third design, a plug of low meltiny point metal is provided in the body of the clip somewhere :ln the heat path from the outer legs to a non-melting central prong. A conveni0nt place for the plug is towards the proximal end of the prong or in a bridging part ~oining together the two outer legs. If the size of this plug is signlficant compared to the thickness of the cllp at the posltlon where the plug is set, -then the heat conductivity through the cllp will be predominantly due to heat conductivity through the plug. The plug melts during installation, and is dispersed, thus cutting oEf further supply o~ hea-t to the prong.
In a second embodiment, the heat conducting member or ~ 8S
region is dispersed throughout the sealing material in the form of metal fibres or mesh. The heat conductive member thus has little or no (bulk) dimensional integrity itsel~, but has the required rigidity in conjunction with solid or unsoftened sealing material. Once the sealant has softened or melted, the fibres of metal may, for example, no longer be held sufficiently close to one another to allo~ passage of a significant amount of heat~
Also, as in the first design above where the prong melted, there is no rigldity after the desired period of time and substantially less mechanical force applied to the cables. The heat-conductive member may comprise a thermally conductive material (preferably a meta~) in the general form of a coil spring or helix extending along the length of the lnner leg and extending throughout the sealing material. On heating, the sealing material becomes less rigid and the spring or helix is able to flatten or tighten in response to any force exerted on it. Thus, the heat-conductive member does not present a rigid outer surface which could damage a substrate such as a poor quality cable.
The third embodiment to be described is similar to the second in that a heat-conducting material is dispersed throughout a sealing material. Here, however, the inner leg cornprises a metal powder, for example copper powder, dispersed throughout a sealing material such as a hot-melt adhesive.
The clips oE the present invention can incorporate additional feature~, ~or example, the outer legs can be provided with a sinusoidal or saw-tooth profile to reduce milk-off; the clip can be prov:Lded with a temperature indicating device to show when sufficient heat has been applied to ac-tivate seallng mate-rlal in the crutch region; the cllp can lncorporate a valve or other secondary component; the outer legs can move to~ether before, durlng or after heating to enhance grip on the recover-able sleeve; and the clip can have means such as laterally 3~ extending ears by means of which it can be removed ~rom the sleeve, or by means of which it can be properly located with respect to the substrates. O-ther features which may be applie~l to the clip of the invention are disclosed in U.K. Patent 1,604,981. The temperature indicating device, which may be a thermochromic paint or a mechanical devlce, may be used to indi-cate when the sealing material has been properly activated, whenthe inner leg has weakened, or more usually both of these changes. A suitable mechanical device is a spring set in the lnner leg in a resiliently biased state and having a marker than projects outside the sleeve when in use. when the sealing mate-lo rial softens or melts tor is otherwise activated) or when theprong melts, the spring reverts to its relaxed state causing vis-ible movement of the marker.
The invention will now be further illustrated with re~-erence to the accompanying drawings, in which:-Figures 1-5 show a three legged clip comprising two outer legs 1 interconnected by a bridge portion 2 which also bears an inner leg 3; and Figure 6 shows a branch-off clip applied to the end o~
a sleeve covering a substrate.
In Figure 1, the inner leg comprises a heat-conducting, low melting point, prong 4 coated with a heat-activatable sealant 5.
The inner leg ln Figure 2 cornprises a non-fusible prong 6 ~oined to the bri.dge portlon 2 by a bond 7 which fails on heat-ing. The inner leg would also possess a heat-activatable seallng material, but thls has been omitted for clarity. The bond 7 is conveniently a solder or o-ther low mel-ting point metal. The pre-cise location of the bond 7 is not critical providing that it lies in the heat path from the outer legs 1 or bridge 2 to a sig-ni~icant part of the prong 6. The thickness of the material con-stituting the bond 7 is preferably large enough so that when it ~ 5 'melts there is no likelihood of the prong 6 touchi.ng the bridge 2, In the embodiment of Figure 3, the prong 8 does not melt, and remains attached to the bridging portion 2. The heat path from the outer legs ~ or bridge 2 is, however, interrupted by melting of a plug 9. As before, sealing material has been omitted for clarity. The plug 9 is of significant size with respect to the part of the clip where it is situated (here the proximal end of the prong 8) and therefore heat conduction to the inne.r leg is considerably reduced when the material of the plug melts and is dispersed.
Figure 4 shows an inner leg 3 comprising a sealing material 10 having dispersed throughout its bul~ a metal powder, which is represented by stippling.
Figure 5 is similar to Figure 4, but the dispersed heat-conducting material is a metal mesh or fibre.
A branch-off clip is shown in use ln Figure 6. The clip has been positioned at the end of a sleeve 12 in order to form two -terminal conduits 13. ~ substrate 14 is shown in one of these conduits, the oth0r conduits has been left empty for a bet-ter view of the clip. The two outer legs 1 hold circumferen-t:Lally spaced portions of the sleeve together to form the con-duits, and the inner leg lS, only a stub of which remains after heating, e~tends into the sleeve to deliver sealing material to the crutch reglon 16. In the early stages o~ heating, the lnner leg 15 ls able ~o conduct heat to the crutch region from the outer legs 1 and the bridging portlon 2 over whlch a propane torch, for example, could be played. One can see from Figure 6 that iE the inner leg were to retain its original configuration it may be forced against the substrate 1~ due to shrinkage oE the sleeve 12. Where the substrates are not sufficiently heat-resis-tant this could cause damage, and in any case introduces craft s sensitivity since the workman must be careful no-t to continue heating for too long after recovery. Some post-heating is often necessary to ensure all sealiny material has been activated, but excessive post heating can cause damage. The problem is substan-tially avoided using the clip of the present invention sinceproper activation coincides with or is shortly followed by hreak-ing of the heat path to the crutch region. As mentioned above, in the preferred embodiments, there ls not only a break in the heat path, but also a failure of dimensional integrity of the whole of the inner leg.
This application is a divisional application o~ copend ing application No., 441,660 filed November 22, 1983.
Heat-recoverable articles, such as heat-recoverable sleeves, are useful for forming enclosures around substrates to be insulated or protected because the article can be made large enough for easy installation, and then recovered into close con-tact with the substrate. Close tolerances in manufacture and craft-sensitivity in installation can therefore be avoided.
A heat-recoverable article is an article the dimen-sional configuration of which may be made substantially to change when subjected to heat treatment.
Usually these articles recover, on heating, towards an 20 original shape from which they have previously been deformed but the term "heat-recoverable", as used herein, also includes an artlcle which, on heating, adopts a new configuration, even if it has not been previously deformed.
In their most common form, such articles comprise a heat-shrinkable sleeve made from a polymeric material exhibltiny the proper-ty of elastic or plastic memory as described, for example, in U.S. Patents 2,027,962, 3,0a~,2~2 and 3,597,372. ~S
:ls made clear ln, for example, U.S. Patent 2,027,962, the orlgi-30 nal dlmenslonal~y heat-stable form may be a translent form in a continuous process in which, for example, an extruded tube is expanded, whilst hot, to a dimensionally heat-unstable form but, in o-ther applications, a preformed dimensionally heat stable article is deformed to a dimensionally heat unstable form in a separate stage.
In the production of heat recoverable articles, the polymeric material may be cross-linked at any stage in the pro~
duction of the article that will enhance the desire~ dimensional recoverability. One manner of producing a heat-recoverable art-icle comprises shaping the polymeric material into the desiredheat-stable form, subsequently cross-linking the polymeric mate-rial, heating the article to a temperature above the crystalline melting point or, for amorphous materials the softening point, as the case may be, of the polymer, de~orming the article and cool-ing the article whilst in the deformed state so that the deformedstate of the article is retained. In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to assume its original heat-stable shape.
In other articles, as described, for example, in British Patent 1,440,524, an elastomeric member such as an outer tubular member is held in a stretched state by a second member, such as an inner tubular member, which, upon heating weakens and thus allows the elastomeric member to recover.
Heat shrinkable sleeves find many applications, espe-cially in the connection and termination of wires, cables and pipes. However, there are other applicatlons where it is desir-able to provide a connecting, insulating, or protective heat-recoverable member for elongate ob~ects such as cables and pipeswhere the ends are not accesslble, or i~ they are accessible, where it is undeslrable to dlsconnect or otherwise to displace them. For such applications the so-called "wrap-around" sleeves have been developed. Baslcally, they are heat-recoverable sheets whlch can be wrapped around the substrate to form a generally tubular shape and whlch ln general are provided with fastening means for hold:lny them in the wrapped-up conflguratlon durlng recovery. Typlcally such fastenlng means are mechanical and com-prlse, for example, rlgld clamps, pins or channel members which co-operate with suitably shaped moulded or extruded protuberances ad~acent to the overlapplng edges of the recoverable sheet. Var-~ ~6~
ious types of fastening means are described, for example, in U.S.Pa-tent 3,379,218 and sritish Patents 1,155,470, 1,211,988 and 1, 346, 479 . In other applications, however, the sheet may be held in the wrapped-up configuration during recovery by means of an adhesive which may, in some cases, be applied on site.
~ eat recoverable sleeves have been successfully employed in many fields of application. However, when two or more substrates such as supply lines, for example cables or pipes, are joined so as to form a connection, problems may arise in obtaining an adequate seal, for example at the outlet of a heat recoverable enclosure. Amongst areas in which this problem is typically encountered there may especially be mentioned the outlets of the splice cases described and claimed in sritish Patent 1,431,167 and the duct seal devices described and claimed in British Patent 1,59~,937.
One effective solution for tubular sleeves has been to use moulded heat-shrinkable parts provided with preformed outlets for the individual supply lines. However, in general such moulded parts have to be made to suit a specific application.
Their versatility has been improved by the use of end caps which seal outlets which are not needed in a specific operation, as described and claimed in British Patent 1,59~,693 but ~hey are nonetheless expensive and thus economically infeasible ln many routine application3.
Another, less e~pensive, solution which has frequently been employed is to use mastlc tape to seal the gap between the supply lines so that, on recovery, a proper encapsula-tion is formed at the end of the heat-recoverable part. However, the use of such tape requires skill on the part of the installer and the method is not applicable to large parts. In addition, the mastic may degrade the overall performance or pro~ucts which are pro-vided with an inner lininy or coating o~ a hot-melt adhesive.
In British Patent 1,604,981 an effective branch-of~ is obtained by forming the individual outlets by means of a suitably shaped clip made from a relatively rigid material. In accordance with the invention therein described there is provided a method of forming a branch-off seal between a heat-shrinkable sleeve and at least two substrates such as supply lines, which comprises the steps of (a) positioning a clip having at least two elongate legs over the outer surface of the heat-shrinkable sleeve at the end thereof so as to form at least two terminal condui~s; (b) posi-tioning the substrates within the conduits; and (c) applying heatso as to effect shrinkage and to form the desired seal. Steps (a) and (b) may be effected in either order or simultaneously, for example in many cases the clip will be pushed into place after the sleeve has been positioned about the subs-trates.
In its slmplest form the clip used in the invention of GB 1,60~,981 is U-shaped and its two legs are slid over the outer surfaces of the pinched together heat-recoverable sleeve or wrap-around sleeve, or over the surfaces of the heat-recoverable sleeve or wrap-around sleeve and another co-operating surface.
However, in preferred embodiments the clip has three legs and the inner leg passes into the heat-recoverable sleeve whilst the outer legs pass outside it; in this way each of the two layers of the heat-recoverable material is pLnched between an inner leg and an outer leg. The inner leg may be contoured so as to reduce the possibility o~ the clip "milking off" during recovery, and advan-tageously comprises a hot-melt adhesi.ve wh:lch flows during recov-ery to seal the gap between the conduits which have been formed.
We have now designed a branch-o~E clip which possess many oE the advantages of -the three legged cllp described above, as regards positioning oE the clip, delivery of sealant material to the cable crutch reg:Lon, activatlon of such adhesive, if nec-essary, etc., but which can facilitate re-entry of an enclosure and which can reduce craft-sensitivity when used with less rugged substrates.
~6~5 Thus, the invention provides a clip which comprlses two outer legs and an inner leg, so arranged ~hat the clip can be positioned over -the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising la) a heat-acti-vatable sealing material, and ~b) a heat conductive member ther-mally connecting the outer legs wlth the sealing material; the dimensional integrlty of a-t least part of the member weakening on heating at or shortly after activation of the sealing material, thus reducing -the thermal connection, or reducing the rigidity of at least a portion of the central leg.
The heat conductive member may be a single member, ~or example a single meltable metal member connecting the outer legs and an inner adhesive leg. Alternatively it may be provided by a region, for example by a plurality of metal fibres embedded in an inner adhesive leg. Thus, re~erence is made hereinafter to a metal member or region.
Before heating, the inner leg of the clip comprises a hot-melt adhesive, a softenable sealan-t such as a mastic, or other heat-activatable sealing rnaterial, and a heat conductive member or region by means of which heat dlrected at those parts of the clip outside of the sleeve wlll be transferred within the sleeve to melt the adhesive, thereby sealing the crutch region between the cables. The embodlments of three legged clips hith-erto describe~ show the lnner leg to be generally lntegral with and substantlally similar to the outer legs. SUch an inner leg can act as a support for adhesive and can conduct heat into the crutch region to melt the adhes:Lve. Although this conduction of heat is deslrable, it rnay occasionally result in damage to the cable ~acket or other substra-te especlally where over long pos-t-heating times are employed. ~leat directed at the outside of the sleeve in this instance is conducted through the material of the clip to the inner leg which ls in contact with the cable ~ackets, and with low quality cables this can cause darnage. Also pressure L~5 of the outer sleeve causes the cables and clip to be forced together, and this may cause damage where the lnner leg is rigid.
These thermal and mechanical effects can be overcome by the invention by causing heat transfer to the inner leg to be cut or considerably reduced at a certain point in time during installa-tion, or by causing at least a portion of the inner leg to become more flexible.
A second consideration of three legged clips also results from a feature which is generally beneficial but can in certain circumstances be disadvantageous. U.K. Patent 1,604,981 remarks that a three legged clip allows easy positioning at the end of a sleeve and makes milk-off practically imposslble espe-cially a.ter recovery. The reason for this is that the inner leg, especially when tapered towards its proximal end, becomes wedged between the recovered sleeve and the substrates. This permanence is in general to be preferred, but where the enclosure is llkely to be re-entered sometime during its life difficulty in removing the clip can be troublesome. with the present invention a seal, equally as reliable as the prior art seals, can be made which allows easy re-entry, due to transformation of, say, a three legged clip into a two legged clip whilst still benefitting from the provision of a heat-conductive member or region. If the heat conductive member or region were simply omitted the heat-activatable sealing material would not be properly activated,except perhaps at a position ad~acent the open end of the sleeve.
Three preferred techni~ues will now be discussed by means o~ which orle can achieve the desired weakenirlg oE dlmen-sional integrity of the heat conductive member or region of theinner leg. What is preferred ic: that installation is commenced with a three-legged clip, but that the clip eE~ectively becomes a two-legged clip at some stage during installation. The inner leg will not in general totally disappear; the heat conductive member may remain but in a dispersed form or it may simply move so as to conform to the shape of the cables or other substrates or it may 6~
move further away from the bridge part of the clip lnto a region oE the sleeve of larger diameter. The timing of this change should be such tha-t the heat conductive member or region is able to conduct a suf~icient amount of heat to cause melting of the adhesive (or activation of other sealing material) but is not able to damage the cables. Weakening o~ the heat conductive mem-ber or region should therefore occur shortly after sufficient adhesive in ~he crutch region has melted or has otherwise been activated. The delay between activation of adhesive and reduc-tion of the heat path or re~uction of rigidity in this embodimentis preferably from almost nothing to, say, 10 minutes depending on the means of heating employed. The adhesive is preferably activated at a temperature of from 50-120C, more pre~erably 70-100C and weakening of dimensional integrity preferably occurs within the range 70-140C, more preferably 90-120C. The differ-ence between the two temperatures is preferably from 5-35C, more preferably from 5-15C.
In a first embodiment, the heat conductive member or region comprises a low-melting point metal. Preferably the melt-ing point will be slightly above the activation temperature of the adhesive. Not only should the temperature oE meltlny be con-sidered, but also the amount of heat required should be corre-lated to the amount of heat required for recovery of the sleeve and for activation of the adhesive or other sealing material. As soon as the heat conductive member or region of the inner leg weakens, for exarnple by melting, the heat-conduc-tive path between the outer legs, or other parts of the clip which are directly heated, and the crutch reglon is broken or at leas-t subs-tantlally reduced. In general the materlal that melts wlll s:lmply flow and become dispersed in the crutch region; the cllp could, however, be designed such that the molten material Elowed in a chosen direction.
The construction of this first embodiment can be real-ized in a number of ways. Firstly, the heat conductive rnember or ~lZ~ 5 region could be a complete prong of low melting-point metal~ of much the same shape and size as the outer legs. The term prong is used for a conductive member of this general configuration because the term inner leg is used to refer to the conductive member or region together with the sealing material. ~t the appropriate stage during heat-recovery the whole of the prong would melt, leaving molten sealing material in the crutch region but preventing or reducing further flow of heat into the region.
Not only is there no further flow of heat to damage the sub-strates, but the ho-t conductive member no longer has the dimen-sional integrity to be forced against the substrates.
A second design using a low melting polnt metal as the heat conductive member or region employs a central prong which doss not melt, the low melting point metal being used as a bond to ~oin this prong to the remainder of the clip. During instal-lation, therefore, the prong becomes detached causing a break or substantial reduction in the heat path. The dimensional integrity of the inner leg, considered as a whole, is weakened but there remains the non-melting prong, which may but need not remain in the crutch region. It will be appreciated tha-t other fusible materials having a significant heat conductivity may be used in this design instead of the low melting point metal.
In a third design, a plug of low meltiny point metal is provided in the body of the clip somewhere :ln the heat path from the outer legs to a non-melting central prong. A conveni0nt place for the plug is towards the proximal end of the prong or in a bridging part ~oining together the two outer legs. If the size of this plug is signlficant compared to the thickness of the cllp at the posltlon where the plug is set, -then the heat conductivity through the cllp will be predominantly due to heat conductivity through the plug. The plug melts during installation, and is dispersed, thus cutting oEf further supply o~ hea-t to the prong.
In a second embodiment, the heat conducting member or ~ 8S
region is dispersed throughout the sealing material in the form of metal fibres or mesh. The heat conductive member thus has little or no (bulk) dimensional integrity itsel~, but has the required rigidity in conjunction with solid or unsoftened sealing material. Once the sealant has softened or melted, the fibres of metal may, for example, no longer be held sufficiently close to one another to allo~ passage of a significant amount of heat~
Also, as in the first design above where the prong melted, there is no rigldity after the desired period of time and substantially less mechanical force applied to the cables. The heat-conductive member may comprise a thermally conductive material (preferably a meta~) in the general form of a coil spring or helix extending along the length of the lnner leg and extending throughout the sealing material. On heating, the sealing material becomes less rigid and the spring or helix is able to flatten or tighten in response to any force exerted on it. Thus, the heat-conductive member does not present a rigid outer surface which could damage a substrate such as a poor quality cable.
The third embodiment to be described is similar to the second in that a heat-conducting material is dispersed throughout a sealing material. Here, however, the inner leg cornprises a metal powder, for example copper powder, dispersed throughout a sealing material such as a hot-melt adhesive.
The clips oE the present invention can incorporate additional feature~, ~or example, the outer legs can be provided with a sinusoidal or saw-tooth profile to reduce milk-off; the clip can be prov:Lded with a temperature indicating device to show when sufficient heat has been applied to ac-tivate seallng mate-rlal in the crutch region; the cllp can lncorporate a valve or other secondary component; the outer legs can move to~ether before, durlng or after heating to enhance grip on the recover-able sleeve; and the clip can have means such as laterally 3~ extending ears by means of which it can be removed ~rom the sleeve, or by means of which it can be properly located with respect to the substrates. O-ther features which may be applie~l to the clip of the invention are disclosed in U.K. Patent 1,604,981. The temperature indicating device, which may be a thermochromic paint or a mechanical devlce, may be used to indi-cate when the sealing material has been properly activated, whenthe inner leg has weakened, or more usually both of these changes. A suitable mechanical device is a spring set in the lnner leg in a resiliently biased state and having a marker than projects outside the sleeve when in use. when the sealing mate-lo rial softens or melts tor is otherwise activated) or when theprong melts, the spring reverts to its relaxed state causing vis-ible movement of the marker.
The invention will now be further illustrated with re~-erence to the accompanying drawings, in which:-Figures 1-5 show a three legged clip comprising two outer legs 1 interconnected by a bridge portion 2 which also bears an inner leg 3; and Figure 6 shows a branch-off clip applied to the end o~
a sleeve covering a substrate.
In Figure 1, the inner leg comprises a heat-conducting, low melting point, prong 4 coated with a heat-activatable sealant 5.
The inner leg ln Figure 2 cornprises a non-fusible prong 6 ~oined to the bri.dge portlon 2 by a bond 7 which fails on heat-ing. The inner leg would also possess a heat-activatable seallng material, but thls has been omitted for clarity. The bond 7 is conveniently a solder or o-ther low mel-ting point metal. The pre-cise location of the bond 7 is not critical providing that it lies in the heat path from the outer legs 1 or bridge 2 to a sig-ni~icant part of the prong 6. The thickness of the material con-stituting the bond 7 is preferably large enough so that when it ~ 5 'melts there is no likelihood of the prong 6 touchi.ng the bridge 2, In the embodiment of Figure 3, the prong 8 does not melt, and remains attached to the bridging portion 2. The heat path from the outer legs ~ or bridge 2 is, however, interrupted by melting of a plug 9. As before, sealing material has been omitted for clarity. The plug 9 is of significant size with respect to the part of the clip where it is situated (here the proximal end of the prong 8) and therefore heat conduction to the inne.r leg is considerably reduced when the material of the plug melts and is dispersed.
Figure 4 shows an inner leg 3 comprising a sealing material 10 having dispersed throughout its bul~ a metal powder, which is represented by stippling.
Figure 5 is similar to Figure 4, but the dispersed heat-conducting material is a metal mesh or fibre.
A branch-off clip is shown in use ln Figure 6. The clip has been positioned at the end of a sleeve 12 in order to form two -terminal conduits 13. ~ substrate 14 is shown in one of these conduits, the oth0r conduits has been left empty for a bet-ter view of the clip. The two outer legs 1 hold circumferen-t:Lally spaced portions of the sleeve together to form the con-duits, and the inner leg lS, only a stub of which remains after heating, e~tends into the sleeve to deliver sealing material to the crutch reglon 16. In the early stages o~ heating, the lnner leg 15 ls able ~o conduct heat to the crutch region from the outer legs 1 and the bridging portlon 2 over whlch a propane torch, for example, could be played. One can see from Figure 6 that iE the inner leg were to retain its original configuration it may be forced against the substrate 1~ due to shrinkage oE the sleeve 12. Where the substrates are not sufficiently heat-resis-tant this could cause damage, and in any case introduces craft s sensitivity since the workman must be careful no-t to continue heating for too long after recovery. Some post-heating is often necessary to ensure all sealiny material has been activated, but excessive post heating can cause damage. The problem is substan-tially avoided using the clip of the present invention sinceproper activation coincides with or is shortly followed by hreak-ing of the heat path to the crutch region. As mentioned above, in the preferred embodiments, there ls not only a break in the heat path, but also a failure of dimensional integrity of the whole of the inner leg.
Claims
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A clip which comprises two outer legs and an inner leg, so arranged that the clip can be positioned over the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising: (a) a heat activatable sealing material and (b) a heat-conductive member thermally connecting the outer legs with the sealing material, said clip being adapted on heating the heat-conductive member to reduce the rigidity of at least a por-tion of the inner leg by weakening the dimensional integrity of at least part of the heat-conductive member.
2. A clip according to claim 1, in which the heat-con-ductive member comprises a metal prong which substantially en-tirely melts at or shortly after activation of the sealing mate-rial.
3. A clip according to claim 1, in which the heat-con-ductive member comprises a non-fusible prong and a bond which constitutes the thermal connection to the remainder of the clip, the bond melting at or shortly after activation of the sealing material.
4. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises a metal powder dispersed throughout the sealing material.
5. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises metal fibres dispersed throughout the sealing material.
6. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises a mesh of metal fibres dispersed throughout the sealing material.
7. A clip according to claim 1, 2 or 3, in which the sealing material is a hot-melt adhesive.
8. A clip according to claim 1, 2 or 3, in which the sealing material is activated at a temperature of from 50-120°C.
9. A clip according to claim 1, 2 or 3, in which the said dimensional integrity fails at a temperature of from 70-140°C.
10. A dip according to claim 1, 2 or 3, in which the difference between the temperature of failure of dimensional integrity and of activation of the sealing material is from 5-35°C.
11. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 1.
12. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 2.
13. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 3.
14. An assembly according to claim 11, 12 or 13, in which the sleeve is heat shrinkable.
15. An assembly according to claim 11, 12 or 13, in which the sleeve has sealing material on an inner surface thereof.
16. An assembly according to claim 11, 12 or 13, in which the sleeve has a hot-melt adhesive on the inner surface thereof.
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A clip which comprises two outer legs and an inner leg, so arranged that the clip can be positioned over the outer surface of a recoverable sleeve at an end thereof with the outer legs outside the sleeve and the inner leg inside the sleeve; the inner leg comprising: (a) a heat activatable sealing material and (b) a heat-conductive member thermally connecting the outer legs with the sealing material, said clip being adapted on heating the heat-conductive member to reduce the rigidity of at least a por-tion of the inner leg by weakening the dimensional integrity of at least part of the heat-conductive member.
2. A clip according to claim 1, in which the heat-con-ductive member comprises a metal prong which substantially en-tirely melts at or shortly after activation of the sealing mate-rial.
3. A clip according to claim 1, in which the heat-con-ductive member comprises a non-fusible prong and a bond which constitutes the thermal connection to the remainder of the clip, the bond melting at or shortly after activation of the sealing material.
4. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises a metal powder dispersed throughout the sealing material.
5. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises metal fibres dispersed throughout the sealing material.
6. A clip according to claim 1, in which the sealing material has dimensional integrity before heating, and the heat-conductive member comprises a mesh of metal fibres dispersed throughout the sealing material.
7. A clip according to claim 1, 2 or 3, in which the sealing material is a hot-melt adhesive.
8. A clip according to claim 1, 2 or 3, in which the sealing material is activated at a temperature of from 50-120°C.
9. A clip according to claim 1, 2 or 3, in which the said dimensional integrity fails at a temperature of from 70-140°C.
10. A dip according to claim 1, 2 or 3, in which the difference between the temperature of failure of dimensional integrity and of activation of the sealing material is from 5-35°C.
11. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 1.
12. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 2.
13. An assembly for enclosing a branched substrate, which comprises a recoverable sleeve and a clip according to claim 3.
14. An assembly according to claim 11, 12 or 13, in which the sleeve is heat shrinkable.
15. An assembly according to claim 11, 12 or 13, in which the sleeve has sealing material on an inner surface thereof.
16. An assembly according to claim 11, 12 or 13, in which the sleeve has a hot-melt adhesive on the inner surface thereof.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8234001 | 1982-11-29 | ||
GB8234001 | 1982-11-29 | ||
CA000441660A CA1261595A (en) | 1982-11-29 | 1983-11-22 | Branch-off clip |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000441660A Division CA1261595A (en) | 1982-11-29 | 1983-11-22 | Branch-off clip |
Publications (1)
Publication Number | Publication Date |
---|---|
CA1286485C true CA1286485C (en) | 1991-07-23 |
Family
ID=25670218
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA000584364A Expired - Lifetime CA1286485C (en) | 1982-11-29 | 1988-11-28 | Branch-off clip |
Country Status (1)
Country | Link |
---|---|
CA (1) | CA1286485C (en) |
-
1988
- 1988-11-28 CA CA000584364A patent/CA1286485C/en not_active Expired - Lifetime
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