A METHOD OF CREATING A PROTECTED ENVIRONMENT AROUND A WORK REGION, A PROTECTIVE CHAMBER FOR CARRYING OUT THE METHOD AND A METHOD OF PACKAGING THE PROTECTIVE CHAMBER

Abstract: A method of creating a protected environment around a work region (3) comprises using an elongate protective chamber (5), e.g. in the form of a transparent sheet, which is bendable at least at the end areas. When the outer ends of the chamber are attached by means of e.g. a band (13, 14) around the work region, which may be a cable (3), and the mutual spacing between the attachment areas is somewhat smaller than the length of the protective chamber in a stretched state, the protective chamber (5) can be pushed axially with respect to the work region so that a very large work region area can be obtained by a very simple means. The invention also comprises a protective chamber (5) of the aforementioned type and a method of packaging said protective chamber. When packaging the protective chamber the chamber is compressed like a bellows and the package is arranged for protecting the compressed chamber when pushed on the cable (see fig. 6). In use the protective chamber is preferably vented with a controlled atmosphere through hoses (11, 12).

Description: A method of creating a protected environment around a work region, a protective chamber for carrying out the method and a method of packaging the protective chamber. The invention concerns a method of creating a protected environment around a work region which is e.g. to be kept free of impurities. For example the US Patent Specifica¬ tion 3 415 582 discloses a pyramidal protective chamber to be placed over a work region. The work on an object in the protected environment is performed via ports through which an operator's arm can be inserted. The prior art is vitiated by the drawback that the men¬ tioned ports have a fixed position in the wall of the protective chamber, and the extent of the work region is therefore very restricted. However, there are fields of use where it would be desirable to have a considerably larger work region, e.g. in the splicing of cables. The object of the invention is to provide a method of creating a protected environment around a work region whose longitudinal extent is considerably larger than was possible in the past. This object is achieved in that the outer ends of the chamber are attached to the object with a mutual spacing which is smaller than the spacing between said ends in the stretched state of the chamber, at least said end areas of the protective chamber being beπdable. Then, at least the part of the protective chamber in which the ports or openings for the operator's arms are provided is slidable along the work region. This is due to the use of a protective chamber in which the end areas of the chamber, which are attached around the elongate object, are arranged with a mutual spacing which is smaller than the spacing between said end areas when the protective chamber is fully stretched. The use of a foldable sheet, as stated in claim 2, pro¬ vides for a very inexpensive embodiment, so inexpensive that the protective chamber can advantageously be intended to be discarded after use. As stated in claim 3, con¬ trolled gas may be admitted to the protective chamber in a manner known per se, which is preferably provided for in the manner stated in claim 4, whereby the positive pressure in the chamber keeps the sheet stretched around the work region. When the method is carried out as stated in claim 5, both the protective chamber and its associated package can be moved in over a cable end by tearing off the mentioned tear-off areas of the package and moving the protective chamber and the package in over the cable. When the me¬ thod is carried out as stated in claim 6, the special ad¬ vantage is obtained, in addition to the advantages ex¬ plained in connection with claim 5, that the protective chamber is completely protected by the package, even if the mentioned parts are pulled in over a cable end. There¬ fore, during the very cable splicing operation it is not necessary to pay any regard to the protective cham¬ ber because this is completely enclosed in its package. The invention also concerns a protective chamber for car¬ rying out the method, said protective chamber being cha¬ racterized by consisting of sheet material which has the form of an elongate tube in the position of use, said tube being open toward at least one inlet opening trans- verse to the tube, the ends of said tube being designed to be attached around an elongate object. This protec¬ tive chamber is specially intended to be discarded after use and brings about a protected environment around an elongate work region in the performance of the method of claim 1. The sheet is preferably transparent, but may also be opaque. In the latter case, the protective cham¬ ber is provided with a window or the like so that the operator can see the work region, cf. claim 8. As mentioned before, the protective chamber can be kept in a stretched state because of a positive pressure, but alternatively, or in combination with this, the elastic stiffening means mentioned in claim 9 may be provided. The means defined in claim 10 for venting the protective chamber may e.g. be just an inlet pipe and an outlet pipe disposed closely adjacent a respective one of the spliced cable ends, so that the end areas of the protec¬ tive area surround both a cable end and one of the men- tioπed pipes . The invention will be explained more fully by the follow¬ ing description of some embodiments with reference to the drawing, in which figs. 1 and 2 show a first embodiment of the protective chamber of the invention, fig. 3 and 4 show another embodiment of the protective chamber of the invention, while fig. 5 serves to illustrate how the protective chamber may be packed in a package in which a cut has been made in the figure, while fig. 6 shows a preferred embodiment of the location of the protective chamber around the work region. The invention will be explained below in connection with the work on splicing two cable ends. The cable ends 1, 2 have already been electrically joined in the figures, so that the work relevant to the invention concerns the re-establishment of the insulation around the splice. A well-known and very effective way of re-establishing the insulation of the cable consists in winding a thin band, preferably of cross-linkable polyethylene, many times around the splice to build up the insulation, which is then vulcanized so that the band fuses with the cable insulation to a homogeneous insulation. In case of high- voltage cables, a very strong voltage field prevails through the insulation, and even very minute impurities in the insulation may result in electric field distur¬ bances which may cause breakdown in the insulation. Ac- cordingly, it is extremely important that no foreign bodies enter between the relatively large number of turns of the polyethylene band. Especially the last-men¬ tioned problems are solved neatly and cheaply by the in¬ vention, which will therefore be explained in connec- tion with a cable splicing operation. As explained before, the cable ends 1 and 2 have al¬ ready been joined electrically by a splice 3. It is shown schematically in fig. 2 how the polyethylene band 4 is wound around the splice, and it is very important in connection with this winding that no foreign bodies enter between the polyethylene layers. This is ensured by creating a protected environment known per se around the work region, which has the difficulty in relation to the prior art that the work region is long. The pro- tective chamber of the invention is shown in fig. 1 as an elongate, transparent sheet 5 having welded thereon a pair of inlet ports 6, 7 through which an operator 8 can insert the arms. Usually, this will provide only a relatively small work region, but since the entire pro- tective chamber of the invention can be moved in the longitudinal direction of the cable, the operator will have ample freedom of movement to place the polyethylene band carefully around the splice. The latter mobility is brought about in the shown embodiment by the attach¬ ment of the sheet chamber ends 9, 10 at their respec¬ tive sides of the splice with a mutual spacing which is somewhat smaller than the spacing between the said ends in the stretched position of the chamber 5. Since the chamber 5 is made of a thin sheet material, the entire chamber can be moved longitudinally, as appears by a comparison between figs. 1 and 2. In a preferred embodiment, the sheet chamber is kept stretched because of a positive air pressure which can be established by admitting air through a hose 11, the air being exhausted through another hose 12 with such a great loss of pressure that the protective chamber 5 is kept distended. The air admitted through the hose 11 may be pre-treated in manner known per se, i.e. be filtered, heated, dried, consists wholly or partly of special types of gas, etc. In a preferred embodiment, the protective chamber ends 9, 10 are attached to the cable ends 1 and 2, respective¬ ly, by means of a lacing 13, 14 surrounding both a cable end and an associated air hose. Any leakages at the lacings have no importance because of the establishment of a positive pressure in the protective chamber. In this context, it should also be noted that the interior volume of the protective chamber is essentially con- stant, independent of the longitudinal movement of the chamber, so that the chamber is in no way compressed or expanded, but rather rolls along the cable. As mentioned above, the protective chamber may be kept distended by means of a positive air pressure. Alterna¬ tively, or in combination with this, other means may be provided for keeping the chamber distended, which will be explained in connection with the embodiment shown in figs. 3 and 4. Also the latter embodiment involves the use of a transparent sheet (alternatively provided with a window), which forms the protective chamber. As ap¬ pears from the figures, the protective chamber comprises a thin elastic helix 16, preferably of plastics, so that it can easily be cut when the protective jacket is re¬ moved from the finished cable splice. In view of the ex¬ planation of figs. 1 and 2, figs. 3 and 4 should then speak for themselves. It will also be appreciated that the protective jacket does not have to be a uniform ca- sing, but that it is sufficient that just a certain part of the protective jacket ends is resilient in such a man¬ ner that the jacket ends can be attached around the work region with a mutual spacing which is smaller than the spacing between the said areas in the stretched state of the jacket . It will now be explained with reference to figs. 5 and 6 how the protective jacket of the invention can advan¬ tageously be packaged, so that protection against impuri¬ ties is ensured, even though the other part of the work, such as the mechanical splicing of the electrical con¬ ductors, takes place in a polluted environment. Fig. 5 shows a package 17, preferably of plastics, de¬ signed to enclose the protective jacket hermetically in a state of storage. Wi h a view to a better explanation of the principle the package 17 is cut, thus showing that the protective jacket 15 is folded like a bellows with an axial passage extending through it. Two of the oppo¬ site ends of the package have a weakened line 18, 19 in alignment with the axial passage, said lines surround- ing their respective tear-off areas. It will thus be ap¬ preciated that if the tear-off areas are removed, the protective jacket 15 and the associated package 17 can be pushed in over a cable end. The package is drawn incorrectly in figs. 5 and 6 to ex¬ plain the principle; fig. 6 is to illustrate a preferred method, according to which a first package side is pulled through the axial passage of the protective chamber and through the hole in the opposite package side 21, so that the protective chamber 15 is totally enclosed in a package which can now be pushed in over a cable end 22. Then the cable end 22 is joined electrically with another cable end 23, following which the insulation is to be re¬ established. The re-establishment is initiated by clean- ing the splice region, and attaching, by means of tape or the like, the necessary tools and materials for the work around the splice. Then the protective chamber and the package are pulled to a cleaned location spaced from the splice, where the package is cut open, and then the protective chamber can be pulled over the splice and at¬ tached at the ends, e.g. as shown at 13, 14 in fig. 1. When the work requiring the protected environment has been completed, the sheet chamber is cut open and is re¬ moved from the splice.

Claims: P a t e n t C l a i m s 1. A method of creating a protected environment around a work region along an elongate object, comprising using an elongate protective chamber with openings to prov-ide access to the work region, c h a r a c t e r i z e d in that the outer ends of the chamber are attached to the object with a mutual spacing which is smaller than the spacing between said ends in the stretched state of the chamber, at least said end areas of the protective cham¬ ber being bendable. 2. A method according to claim 1, c h a r a c t e r ¬ i z e d by the use of a foldable sheet for the chamber 3. A method according to claim 1, c h a r a c t e r - i« z e d by passing controlled gas into the protective chamber. 4. A method according to claims 2 and 3, c h a r a c ¬ t e r i z e d by discharging gas with a certain flow resistance so as to provide a positive pressure which keeps the sheet stretched around the work region. 5. A method of packaging a protective chamber for car¬ rying out the method of claims 1-4, c h a r a c t e r ¬ i z e d by folding the protective chamber like a bellows with openings at opposite ends and placing said chamber in a bendable package so that the openings are disposed adjacent respective tear-off areas of the package. 6. A method according to claim 5, c h a r a c t e r ¬ i z e d by placing the protective chamber with associ¬ ated package on an object by removing the tear-off areas, and pulling one package side through the protective cham¬ ber bellows and through the opening in the opposite package side, and then moving the object through said ope¬ nings. 7. A protective chamber for carrying out the method ac¬ cording to claims 1-4, c h a r a c t e r i z e d by con- sisting of sheet material which has the form of an elon¬ gate tube in the position of use, said tube being open toward at least one inlet opening transverse to the tube, the ends of said tube being designed to be attached a- round an elongate object. 8. A protective chamber according to claim 7, c h a r - a c t e r i z e d by two inlet openings disposed around the centre of the sheet tube and having their respective inlet channels extending transversely to the tube, said tube being transparent at least in an area around the in- let openings . 9. A protective chamber according to claims 7 or 8, c h a r a c t e r i z e d in that said chamber comprises elastic stiffening means. 10. A protective chamber according to claims 7-9, c h a r a c t e r i z e d by means for venting the pro¬ tective chamber with a controlled atmosphere so as to provide a positive pressure sufficient to keep the sheet chamber stretched in the position of use.

Inventors: NIELSEN OLE KJAER, NIELSEN, OLE, KJAER
Applicants: NORDISKE KABEL TRAAD, AKTIESELSKABET NORDISKE KABEL- OG TRAADFABRIKER
Application year: 1985
Main classification: B25J21
IPC codes: B08B15, H02G1