GB2104829A - Applying sleeves to cables - Google Patents

Applying sleeves to cables Download PDF

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Publication number
GB2104829A
GB2104829A GB08221528A GB8221528A GB2104829A GB 2104829 A GB2104829 A GB 2104829A GB 08221528 A GB08221528 A GB 08221528A GB 8221528 A GB8221528 A GB 8221528A GB 2104829 A GB2104829 A GB 2104829A
Authority
GB
United Kingdom
Prior art keywords
sleeve
moulding
sections
stem
gap
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.)
Granted
Application number
GB08221528A
Other versions
GB2104829B (en
Inventor
Edward Kitchener George
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telephone Cables Ltd
Original Assignee
Telephone Cables Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Telephone Cables Ltd filed Critical Telephone Cables Ltd
Priority to GB08221528A priority Critical patent/GB2104829B/en
Publication of GB2104829A publication Critical patent/GB2104829A/en
Application granted granted Critical
Publication of GB2104829B publication Critical patent/GB2104829B/en
Expired legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G1/00—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines
    • H02G1/14—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for joining or terminating cables
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C39/00—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor
    • B29C39/02—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles
    • B29C39/021—Shaping by casting, i.e. introducing the moulding material into a mould or between confining surfaces without significant moulding pressure; Apparatus therefor for making articles of definite length, i.e. discrete articles by casting in several steps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
    • B29C45/14467—Joining articles or parts of a single article
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C70/00—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts
    • B29C70/68—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks
    • B29C70/84—Shaping composites, i.e. plastics material comprising reinforcements, fillers or preformed parts, e.g. inserts by incorporating or moulding on preformed parts, e.g. inserts or layers, e.g. foam blocks by moulding material on preformed parts to be joined
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
    • H02G1/00—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines
    • H02G1/16—Methods or apparatus specially adapted for installing, maintaining, repairing or dismantling electric cables or lines for repairing insulation or armouring of cables
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0003—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular electrical or magnetic properties, e.g. piezoelectric
    • B29K2995/0007—Insulating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/34—Electrical apparatus, e.g. sparking plugs or parts thereof
    • B29L2031/3462—Cables

Abstract

In method of applying an insulating sleeve to a cable by surrounding the cable with a split sleeve and sealing the opposed edges of the sleeve together by an injection moulding technique utilising a shell mould fitted over the gap (13) in the sleeve, the shell mould has a series of moulding stems (19) spaced along it through which molten thermoplastics material (30) is introduced in turn, and during each injection step except the last there is inserted into the next adjacent moulding stem a member (22) which closes off the remainder of the gap (13) from the molten thermoplastics material and diverts it into the surrounding stem, (Fig. 7) the member being rotatable before the thermoplastics material has set to separate the diverted material (29) from the main body of material (30) in the gap (13) (Fig. 8) and is removable with the diverted material after solidification thereof to leave the stem clear for the subsequent introduction of further molten material through that stem. <IMAGE>

Description

SPECIFICATION Method and apparatus for applying sleeves to cables This invention relates to a method of applying insulating sleeves to cables, and to apparatus for carrying out said method.
In forming such a sleeve in situ it is usual to surround the appropriate region of the cable by a split sleeve of a flexible thermoplastics material, commonly polyethylene, and to subsequently seal the opposed edges of the split sleeve together by introducing an appropriate molten thermoplastics material into the gap formed between them by an injection moulding technique. In order to achieve this a part-cylindrical shell mould is secured over the sleeve so that it covers the gap, and molten thermoplastics material is injected into the gap through one or more hollow moulding stems projecting from the shell mould to seal the edges of the sleeve together, a demountable sleeve support of sheet metal usually being fitted around the cable under the sleeve.
It has, however, been found difficult to seal the edges of long sleeves satisfactorily by this method utilising a simple hand operated injection gun owing to the very high pressures that are required for feeding molten polyethylene along the gap for any significant distance.
According, therefore, to one aspect of the invention, in a method of applying an insulating sleeve to a cable by surrounding the cable with a split sleeve and sealing the opposed edges of the sleeve together by an injection moulding technique, the shell mould has a series of moulding stems spaced along it, molten thermoplastics material is injected into the gap between the sleeve edges through the moulding stems in sequence, and during each injection step except the last there is inserted into the next adjacent moulding stem a member which closes off the remainder of the gap from the molten thermoplastics material and diverts it into the surrounding stem, and which is shaped so that it can be rotated before the injected thermoplastics material has set, to separate the diverted material from the main body of material in the gap, and subsequently removed with the diverted material to leave the respective moulding stem clear for the subsequent introduction of molten thermoplastics material through that stem.
The process is then repeated along the sleeve, although there is, of course, no need to introduce the diverter member into the last moulding stem of the sequence. The spacing of the moulding stems can be arranged to be such that the molten thermoplastics material can be injected without difficulty into the parts of the sleeve gap between adjacent stems.
The diverter member is conveniently in the form of a channel of semi-cylindrical shape arranged to be introduced longitudinally into the moulding stems with its concave surface directed along the sleeve gap towards the stem through which the thermoplastics material is to be injected, the length and width of the member being such as to close the remainder of the gap, and the end of the member having an internal web. Then rotation of the member through 1 800 before the injected thermoplastics material has set separates the diverted material from the main body of material in the gap, and following solidification the thermoplastics material, the material which has been diverted into the stem can readily be lifted from the stem, supported by the web.The extracted plug of material can then be removed from the diverter member to allow the latter to be introduced into the next stem, and the process repeated.
The diverter member should, of course, be formed of or coated by a material to which the thermoplastics material does not readily adhere to facilitate the extraction of the plug of material from the member.
The diverter member is conveniently arranged to be secured to the moulding stems by means of bayonet type couplings which enable the member to be readily located in the appropriate operative positions, although other means of securing the member to the moulding stems could alternatively be employed. The diverter may additionally carry means giving an indication of the correct rotational positioning if desired.
In the application of an insulating sleeve to a cable, utilising a split sleeve having its opposed edges sealed together utilising an injection moulding technique, it has been found that the injected thermoplastics material tends to shrink as it solidifies. Consequently removal of a sleeve support, where employed, from the fully formed sleeve, is often difficult to achieve, the difficulty becoming significantly more pronounced as the sleeve length is increased, and this has tended to limit the length of sleeve that can be fitted.
According to another aspect of the invention the sleeve support is formed in at least three separate part-cylindrical sections, and the joint between at least two of the sections is such that, following the sealing of the sleeve edges together by the injection moulded thermoplastics material, these two sections of the sleeve support can be telescoped circumferentially, detachable means being provided for engaging the ends of the sections to hold them in their operative positions during the moulding process.
Conveniently the split sleeve is arranged to be fitted around the support with the gap diametrically opposite the joint between the two telescopic sleeve sections, and the latter are preferably quarter sections of a cylinder, the remainder of the support being a single semicylindrical section. The latter preferably carries a layer of a thermally insulating material on a region of its external surface which is arranged to lie beneath the split in the sleeve to prevent heat loss from the injected thermoplastics material to the sleeve support. The layer of thermally insulating material can be in the form of coating on the surface of the section or a separate strip attached to it. It must, of course, consist of a material which does not bond to the injected thermoplastics material and may, for example, consist of polytetrafluoroethylene (PTFE).
One method in accordance with the invention of applying a polyethylene sleeve to a multi-strand cable, such as a telephone cable, and apparatus for carrying out said method will now be described by way of example with reference to Figures 1 to 8 of the accompanying schematic drawings, in which Figures 1 and 2 represent a perspective view and an end view of a partly assembled sleeve support used to support the sleeve in carrying out the sealing of the sleeve edges by the injection moulding process, Figure 3 represents a perspective view of the fully assembled support around a cable or cable joint, Figure 4 shows a split sleeve fitted to the support, Figure 5 shows a shell mould fitted to the sleeve, Figure 6 represents a perspective view of a diverter used in the process, and Figures 7 and 8 illustrate its mode of use.
Referring first to Figures 1 and 2, in order to apply a sleeve to a cable, for example at a joint, in accordance with the invention, a demountable sleeve support 1 is first fitted around the cable, the cable being omitted from Figure 1 for the sake of simplicity.
The support comprises three interfitting partcylindrical rigid sections 3, 4, 5 of sheet metal, one section 3 being of semi-cylindrical shape, and the other two sections 4, 5 being quarter cylinders.
The sides of the section 3 have circumferentially extending crenellations 6 which interlock with complementary crenellations 7 on the adjacent edges of the sections 4, 5 when the sections are fitted together.
The opposite side of the section 4 has spotwelded to its inner surface a metal strip 8 which overlaps the adjoining edge portion of the third section 5 when the sections are assembled with their adjoining edges abutting, and curved end pieces 9, having circumferentially extending grooves 1 fit over the ends of the sections 4, 5 to hold them together.
In assembling the support, the two quarter sections 4, 5 are fitted together in their operative positions and secured by the end pieces 9. The other section 3 of the sleeve is then fitted and the whole assembly locked together by a band clip 10 at each end, as shown in Figure 3.
A split sleeve 12 of the appropriate length and circumference is then fitted around the sleeve support 1 as in Figure 4, and any excess material is removed from one edge to provide a gap 13 of predetermined width between the edges, the sleeve being disposed on the support 1 with the gap extending along the centre-line of the section 3. The central part of the section carries on its outer surface a layer 15 of PTFE which lies beneath the gap 13 when the sleeve is correctly fitted, the layer either being in the form of a separate strip attached to the section or being applied as a coating to the surface.
The ends of the gap are then closed by short split sleeve sections 1 6 of the same cross section as the sleeve 12 but with the gaps between the edges of the sections diametrically opposite the gap 13.
A part cylindrical sheet metal shell mould 18, having a plurality of hollow mould stems 19.1 to 19.5 projecting outwardly from it along its centre line, is then fitted over the sleeve 12 as in Figure 5, and is held in position by an appropriate number of band clips 21, only some of which are shown.
An electric heater (not shown) is fitted to the shell mould 18 between the first two mould stems 1 9.1, 19.2 at one end, and a spew diverter 22 is inserted into the second stem 19.2.
The spew diverter 22, as shown in Figure 6, comprises a semi-cylindrical channel portion 23 having a width which is the same as that of the gap 13 formed between the edges of the split sleeve 12. The channel portion 23, projects from a cap 24 which fits over the end of the stem 19.2 and is held in place by diametrically arranged slots 25 which engage radially projecting pins 26 on the stem 19.2 to form a bayonet-type fixing. The length of the channel portion 23 is such that its free end, which is closed by web 27, then extends into the gap 13.
The spew diverter 22 is initially fitted with the concave side of the channel portion 23 directed towards the adjacent end moulding stem 19.1 as in Figure 7, and molten polyethylene is injected into the stem 19.1 using a conventional injection gun (not shown) secured to the stem by a bayonet-type fixing.
The lower end of the spew diverter 22 closes the part of the gap 13 beyond the moulding stem 19.2 against penetration by the molten polyethylene which is thus diverted into the stem 19.2 by the diverter. The latter is then turned through 1800 to the position shown in Figure 8 which separates the diverted polyethylene 29 from the main body 30 in the gap 13. The injection gun on the first moulding stem 1 9.1 is replaced by a plunger to maintain compression, and the electric heater unit is removed and fitted to region of the mould between the second and third moulding stems 19.2 and 19.3. After a few minutes to allow the injected polyethylene to solidify and to be moulded to the sleeve edges, the spew diverter 22 is removed from the stem 19.2, utilising the handles 28, leaving the moulding stem 19.2 clear for the introduction of molten polyethylene in the next moulding step. The channel of the diverter is then cleared of the plug 29 of spew polyethylene and is then fitted to the next moulding stem 19.3 with the concave side of the channel facing in the initial direction, the injection gun is fitted to the stem 19.2 and the process repeated. The process is then continued along the sleeve until injection moulding is complete. The diverter is not fitted to the last mould stem 19.5 during injection into the stem 19.4 and on completion of injection spring plungers are fitted to both of these stems 19.4,19.5.
After the last mould region has cooled sufficiently the shell mould 18 is removed, and the end pieces 9 of the sleeve support 1 are removed to allow the sections 4, 5 to telescope circumferentially which allows them and the other section 3 to be readily removed from the fully formed sleeve.
Although only a relatively short sleeve has been illustrated, the invention is equally applicable to the fitting of longer sleeves, the lengths of the sleeve support 1 and the shell mould 18 and the number of moulding stems on the latter being selected accordingly.

Claims (14)

1. A method of applying an insulating sleeve to a a cable by surrounding the cable with a split sleeve and sealing the opposed edges of the sleeve together by an injection moulding technique utilising a shell mould, wherein the shell mould has a series of moulding stems spaced along it, molten thermoplastics material is injected into the gap between the sleeve edges through the moulding stems in sequence, and during each injection step except the last there is inserted into the next adjacent moulding stem a member which closes off the remainder of the gap from the molten thermoplastics material and diverts it into the surrounding stem, and which is shaped so that it can be rotated before the injected thermoplastics material has set, to separate the diverted material from the main body of material in the gap, and subsequently removed with the diverted material to leave the respective moulding stem clear for the subsequent introduction of molten thermoplastics material through that stem.
2. A method according to Claim 1 wherein the diverter member is in the form of a channel of semi-cylindrical shape arranged to be introduced longitudinally into the moulding stems with its concave surface directed along the sleeve gap towards the stem through which the thermoplastics material is to be injected, the length and width of the member being such as to close the remainder of the gap, and the end of the member having an internal web.
3. A diverter according to Claim 1 or 2 wherein the diverter member is securable to the moulding stems by means of bayonet type couplings.
4. A method according to Claim 1, 2 or 3 wherein the diverter carries means giving an indication of the correct rotational positioning.
5. A method of applying an insulating sleeve to a cable by surrounding the cable with a split sleeve and sealing the opposed edges of the sleeve together by an injection moulding technique utilising a shell mould wherein the sleeve support is formed in at least three separate part-cylindrical sections, and the joint between at least two of the sections is such that, following the sealing of the sleeve edges together by the injection moulded thermoplastics material, these two sections of the sleeve support can be telescoped circumferentially, detachable means being provided for engaging the ends of the sections to hold them in their operative positions during the moulding process.
6. A method according to Claim 5 wherein the split sleeve is arranged to be fitted around the support with the gap diametrically opposite the joint between the two telescopic sleeve sections, the latter are quarter sections of a cylinder, and the remainder of the support is a single semicylindrical section.
7. A method according to Claim 6 wherein the semi-cylindrical section carries a layer of a thermally insulating material on a region of its external surface which is arranged to lie beneath the split in the sleeve.
8. Apparatus for carrying out the method of Claim 1 comprising a shell mould having a series of moulding stems spaced along it, and a diverter member in the form of a channel of semicylindrical shape of a length such that in use of the apparatus it can be introduced into a moulding stem with an end projecting into the gap in the split sleeve, the diverter member being a close fit within the stems and having a web extending across it at said end.
9. Apparatus according to Claim 8 wherein the diverter member carries means giving an indication of the correct rotational positioning.
10. Apparatus for carrying out a method according to any one of Claims 1 to 7 incorporating a demountable sleeve support of sheet metal formed in at least three sections wherein the joint between at least two of the sections is such that, following the sealing of the sleeve edges together by the injection moulded thermoplastics material, these two sections of the sleeve support can be telescoped circumferentially, and detachable means for engaging the ends of the sections to hold them in their operative positions during the moulding process.
11. Apparatus according to Claim 10 in which the two telescopic sleeve sections are each a quarter section of a cylinder and the remainder of the support comprises a semi-cylindrical section.
12. A method of applying a split polyethylene sleeve to a multi-strand cable carried out substantially as shown in and as hereinbefore described with reference to Figures 1 to 8 of the accompanying drawings.
13. A sleeve support for use in carrying out the method of Claim 12 substantially as shown in and as hereinbefore described with reference to Figures 1 to 3 of the accompanying drawings.
14. A shell mould and diverter for use in carrying out the method of Claim 12 substantially as shown in and as hereinbefore described with reference to Figures 5 to 8 of the accompanying drawings.
GB08221528A 1981-08-28 1982-07-26 Applying sleeves to cables Expired GB2104829B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB08221528A GB2104829B (en) 1981-08-28 1982-07-26 Applying sleeves to cables

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8126374 1981-08-28
GB08221528A GB2104829B (en) 1981-08-28 1982-07-26 Applying sleeves to cables

Publications (2)

Publication Number Publication Date
GB2104829A true GB2104829A (en) 1983-03-16
GB2104829B GB2104829B (en) 1985-04-03

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB08221528A Expired GB2104829B (en) 1981-08-28 1982-07-26 Applying sleeves to cables

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5229058A (en) * 1987-12-01 1993-07-20 Raychem Corporation Environmental sealing
US5418001A (en) * 1987-12-01 1995-05-23 Raychem Corporation Environmental sealing

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5229058A (en) * 1987-12-01 1993-07-20 Raychem Corporation Environmental sealing
US5418001A (en) * 1987-12-01 1995-05-23 Raychem Corporation Environmental sealing
US5601668A (en) * 1987-12-01 1997-02-11 Raychem Corporation Environmental sealing

Also Published As

Publication number Publication date
GB2104829B (en) 1985-04-03

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 19940726