A METHOD FOR TAKING CARE OF WORN OUT CABLES AND A PLANT FOR CARRYING OUT THE METHOD

Abstract: A plant for taking care of electric cables comprises a roller straightener (8) to straighten a cut cable piece (1), a station (9) with a pair of cutting wheels (18, 18') to bring about two axial and diametrically opposed cuts in helicoidal metal bands which form the outer sleeve of the cable, a washing station (10),and additional station (11) comprising means (26, 26') to bring about two longitudinal, diametrically opposed slits in an uncovered lead jacket, said slits dividing the lead jacket into two halves, and additional washing station (12) as well as a final treatment station comprising a cutting device (32) to cut the copper units which remain after treatment in preceding stations into smaller pieces. In this plant, the different components of the cable may be taken care of in an efficient and environmentally acceptable way.

Description: A METHOD FOR TAKING CARE OF WORN OUT CABLES AND A PLANT FOR CARRYING OUT THE METHOD Technical Field of the Invention In a first aspect, this invention relates to a method for taking care of worn out electric cables of the type that, counted from within, comprises a central core in the form of one or more units of an electrically conducting material, which are protected by at least a first insulation layer, a lead jacket, a second insulating layer as well as one or more mechanically strong metal bands, extending helicoidally on the outside of the second insulation layer. In older types of cables, the first insulation layer usually consists of oil-impregnated paper, which may insulate numerous units from each other at the same time as the units are insulated against the outer lead jacket. The second insulation layer frequently consists of a layer of asphalt, which is wound with tar-impregnated paper or jute. In this layer, creosote may also be included. In addition, the external, helicoi- dal metal bands are commonly of iron, asphalt-impregnated and jute-covered. Background of the Invention and Prior Art Worn out electric cables of the above-mentioned type are lying dug down in the ground in large quantities without being used. Such cables, which may contain copper, lead, asphalt mix, plastic and creosote, constitute an environmental problem. Furthermore, the cables contain metals representing an economic value. For these reasons, it is important that the cables are removed from the ground and are made use of in an environmentally acceptable way at the same time as the valuable metals are recovered for renewed use. In order to make use of cables in general, different methods have previously been proposed. Thus, in GB 2 241 181 and US 4 362 276, for instance, methods are described in which worn out cables are fragmented into little pieces, just as they are, for instance by grinding or cutting. However, to directly fragment the cable into little pieces entails inconveniences so far that the continued treatment with the purpose of extracting different material fractions becomes complicated without giving completely pure and separated materials. How external coverings on cables with different diameters may be cut to pieces by means of two adjustable cylinders is shown in GB 2 298 967. This method is only limited to the step of removing the external coverings of a cable. Objects and Features of the Invention The present invention aims at obviating the above-men- tioned inconveniences and shortcomings of prior art and at providing an improved method for taking care of worn out electric cables. Therefore, a primary object of the invention is to provide a cable treatment method that enables a distinct separation of different materials in the cable while guaranteeing a large purity of, and a distinct separation between, the different metal fractions that should be extracted from the cable. Another object is to create a method according to which the handling of the cable in different stations meets highly made environmental requirements in respect of, among other things, avoiding contamination and development of gas in the surroundings . According to the invention, at least the primary object is attained by the features defined in the characterizing clause of claim 1. Preferred embodiments of the treatment method according to the invention are furthermore defined in the dependent claims 2-4. In addition to the method as such, the invention also relates to a plant for carrying out the method. The features of this plant are defined in the independent claim 5. Preferred embodiments of the plant according to the invention are furthermore defined in the dependent claims 6 and 7. Further Elucidation of Prior Art A plant or machine for taking care of cables of a simpler and lighter type, e.g. of the type which, in addition to a conducting, central core, comprises one or possibly two insulation layers of polyethylene, PVC or the like, is previously known by GB 2222492. The intention with this known machine is to make use of such end pieces of newly manufactured cables that normally are thrown away as wastage. Structurally, the known machine is distinguished by including upper and lower sets of fixed knives for peeling off a first, outer insulation layer on the cable. In this first treatment station, which includes the fixed knives, a plurality of cables are machined at the same time by being fed axially past the knives by means of two pair of feeding cylinders positioned up-stream and downstream the set of knives, respectively. After the first treatment station in the machine, a second station is furthermore present including two co-operating cylinders or shafts which, on the periphery thereof, have a plurality of cutting wheels or discs 53 by means of which a second insulation layer on each cable may be peeled off while uncovering the electric conducting core of the cable. The machine described in GB 2222492 has no capacity of fulfilling the task to make use of thick, terrestrial cable of the initially mentioned type. Thus, entirely different requirements are placed on a plant that should be able to machine such, thick cable. Among other things, it is required that the dug-up cable pieces in question are machined one by one in order to be exerted to the forces that are necessary to step- wise remove and structure the different component parts of the cable. An important feature in this respect is that the metal tape or tapes extending helicoidally and surrounding the thick cable externally, are cut by means of rotatable cutting wheels, the forces of which on the cable counterbalance each other, because otherwise no efficient cutting up of the relatively thick metal tapes would be achieved. According to the invention, such balancing is achieved by the fact that the two co- operating cutting wheels are brought to rotate in one and the same direction of rotation; meaning that the peripheral portions of the wheels will move in tangentially opposite directions. The result hence will be that the axial force which, for instance, the upper cutting wheel applies to the metal tape is counteracted by an opposite axial force from the opposite cutting wheel. Brief Description of the Appended Drawings In the drawings Fig 1 is a partial perspective view showing different components included in the type of cable which is to be taken care of, and Fig 2 is a schedule illustrating different stations included in the preferred plant, which are used to carry out the method according to the invention. Detailed Description of a Preferred Embodiment of the Invention In fig 1 an electric cable 1 of an older type, known per se is shown. This cable includes a core in its entirety designated 2 which comprises one or more units or ropes 3 of an electrically conducting material, preferably copper. In the example, four such units are shown, each one of which being made of bundles of thin copper wire. Each unit 3 is protected by a first insulation layer 4, which may consist of oil-impreg- nated paper. In the insulation, an impregnated paper or a weaving may also be included surrounding the core in its entirety. On the outside of the core 2, there is a lead jacket 5, more precisely in the form of a weldless, soliddrawn tube of lead which constitutes a flexible, although semi-rigid material. On the outside of the lead jacket 5, a second insulation layer 6 is arranged which per se may include different materials. The insulation layer 6 may, for instance, consist of a layer of asphalt, which is wound with tar-impregnated paper or jute. Also other materials, such as creosote, rubber or plastic, may be included in the insulation layer 6. On the outside of the layer 6, there are two bands 7 of metal, commonly iron, which extend helicoidally along the envelope surface of the cable. These metal bands may in practice be asphalt-impregnated and covered with jute. The bands 7 render the cable mechanical strength but allows deflection of the cable by being helicoidally wound. Older cables of the above-mentioned type dug down in the ground are most common. At times, they may also be immersed in watercourses . Reference is now made to fig 2, which schematically illustrates a plant according to the invention. In this figure, a number of main treatment stations designated 8, 9, 10, 11, 12 and 13 are shown. These stations are located along a treatment line marked with a dash dotted line 14 along which individual cable pieces 1 are conveyed, one after the other. Before the dug-up cable is taken inside for treatment in the plant, the same is cut off while forming individual cable pieces with a suitable length, e.g. within the range of 1-5 . This cutting may advantageously be carried out already in connection with the digging up of the cable, although it is also feasible to take care of the cutting in an initial step adjacent to the plant. Up-stream the first main treatment station 8, a particular washing station 15 may advantageously be arranged to wash away possibly occurring external dirt, such as soil, from the cable pieces. The station 15 includes a proper washing chamber 16 with nozzles for spraying of water under high pressure towards the individual cable piece. Removed dirt may be collected in a container 17, and the washing water is suitably recirculated and/or filtered before discharge. Initially, external washing of the cable pieces may also be carried out in a treatment step separated from the plant. The first main treatment station 8 consists of a straightener which includes a set of rolls 8 ' co-operating in pair, of which certain ones are positioned at 90° relative to others in order to bring about a dressing or straightening effect from all sides. In this straightener, possibly curved cable pieces are straightened out. The second station 9 comprises two rotatable, cutting wheels 18, 18', e.g. of ceramics or cemented carbide. The wheels are arranged in a vertical plane with one of the wheels above the other one, a gap being formed between the wheels, the height of which gap is at least somewhat less than the inner diameter of the screw band 7 of the cable. In practice, the wheels 18, 18' are vertically adjustable to enable machining of cables with different diameters. In operation, the two wheels are rotated in one and the same direction of rotation, as shown by the arrows in fig 2. This means that the peripheral portions of the wheels which are turned against each other will move in tangentially opposite directions, whereby the cutting forces which are applied to the helicoidal bands 7 on the top side and the underside of the cable, respectively, will counterbalance each other. Upstream and downstream of the pair of cutting wheels 18, 18', there is a pair of feed rollers 19, 19' for axially feeding the cable piece through the pinch between the wheels. Downstream the feed rollers 19', two guiding knives 20 are furthermore arranged. When an individual cable piece 1 passes between the wheels 18, 18' by means of the feed rollers 19, 19', the two wheels will cut two diametrically opposed, axial cuts 21 in the helicoidal metal bands 7. Of these two cuts, it is the upper one that is visible in fig 1. By a suitable height adjustment of the two wheels 18, 18' in relation to each other, the depth of the cuts 21 may be adjusted so that the wheels not only cut through the metal bands 7 completely, but also cut into the insulation layer 6, without, because of this, coming in contact with the lead jacket 5. Then, when the cable piece passes the knives 20 - which are adjusted so that they engage under the bands 7 - semicircular pieces of the bands on both sides of the cable will be torn apart and loosened. These band pieces may be collected in a container 22, e.g. a barrel. Chips or particles from the cutting operation may be collected in another container 23. Gases which possibly develop during the cutting operation may be sucked up and filtered in a filter 24 in a hous- ing 25 placed above the wheels 18, 18'. The third station 10 consists - like station 15 - of a washing station with a washing chamber 16 and a collection container 17. In the washing chamber 16, there means are arranged for washing the remaining cable piece with hot water under high pressure in order to, in this way, remove the second insulation layer 6 (which may consist of creosote-impregnated paper) . The fourth station 11 includes means to bring about two longitudinal, diametrically opposed slits in the lead jacket 5 now uncovered, which slits divide the jacket into two halves. In the preferred embodiment of the plant according to the invention, these means consist of two rotatable cutting pulleys 26, 26', which advantageously are driven and toothed, the teeth advantageously consisting of cemented carbide. The cutting pulleys are rotatable in opposite directions of rota- tion. More precisely, the upper pulley 26 is rotatable in the anti-clockwise direction viewed in the drawing, while the lower cutting pulley 26' is rotatable in the clockwise direction. This means that the pulleys bring about an axially feeding effect at the same time as the teeth of the pulleys may cut through the lead jacket 5. Two guiding knives 27 are arranged downstream the cutting pulleys, by means of which the lead jacket may be torn apart on both sides of the upper and lower slits which are achieved by the cutting pulleys. The two full- length halves of the lead jacket 5 which are obtained in station 11 may pass through a subjacent washing chamber 28 in which chips and particles may be washed away and separated to a collection container 29. The cleaned lead jacket halves may then pass a cutting device 30 by means of which the halves are cut into smaller pieces, which are collected in a barrel 31 or the like. It should be pointed out that the first insulation layer 4 in the cable is of a fat nature, involving that the layer does not have any adhesion against the inside of the lead jacket 5. During the washing in the chamber 28, occurring grease from the lead jacket halves is, of course, also removed. Also the fifth station 12 consists of a washing station with a washing chamber 16 and a collection container 17. Washing is carried out by means of hot water under high pres- sure, more precisely with the purpose of removing the core of the cable piece from the first insulation layer 4. When the treated cable piece has passed the washing station 12, only the copper conduits or the copper units 3, which are pure, remain. The units are fed further on to the sixth station 13, which constitutes a final treatment station. In this station, a cutting device 32 is included by means of which the units may be cut into short pieces to finally fall down into a barrel 33 or the like. In all washing stations, the used washing water should be cleaned and as far as possible re-used through recirculation in the individual station. A substantial advantage of the stepwise method according to the invention is that all components included in the cable are taken care of individually without being mixed together during the treatment course. Thus, the valuable metal materials (copper, lead, and iron, respectively) are taken care of in the form of small, simple manageable pieces which may be collected in an absolutely pure state in suitable containers, such as barrels, for further delivery to consumers. Other components, which have the character of waste products, are taken care of in turn in an environmentally good state by being separated from the lead jacket and the cable core, respectively, in spaced-apart stations and in phases before the lead jacket and the units, respectively, are fragmented into smaller pieces.

Claims: Claims 1. Method for taking care of cables of the type that, counted from within, comprises a central core (2) in the form of one or more units (3) of an electrically conducting material, which are protected by at least a first insulation layer (4), a lead jacket (5), a second insulating layer (6) as well as one or more mechanically strong metal bands (7) which extend helicoi- dally on the outside of the second insulation layer, c h a r- a c t e r i z e d of the consecutive steps: a) to cut the cable into pieces having a limited length and, if required, dress the individual cable piece (1) to make the same straight, b) to feed the straight cable piece (1) axially between two rotatable, cutting wheels (18, 18') which bring about two axial and diametrically opposed cuts (21) in said metal bands (7) while splitting these in approximately semicircular pieces, said two cutting wheels (18, 18'), after adjustment of the desired cutting depth, being brought to rotate in one and the same direction of rotation in order to counterbalance the cutting forces acting on the opposite sides of the cable piece (1) , c) ι to feed the cable piece further on through a station (10) in which the same is released from said second insulation layer (6), d) to feed the cable piece further on through a station (11) in which the lead jacket (5), uncovered in the preceding station, is divided into two halves by means of longitudinal, diametrically opposed slits, e) to feed the remaining cable piece further on through a station (12) in which the same is released from the first insulation layer (4) , and f) to feed the uncovered metallic unit or units (3) to a final treatment station (13) in which the units are fragmented into smaller pieces. 2. Method according to claim 1, c h a r a c t e r i z e d in that the cable piece (1), before splitting of the metal bands (7) and before possible dressing adjustment, is submitted to a washing operation with the purpose of washing away possibly occurring external dirt from the cable piece. 3. Method according to claim 1 or 2, c h a r a c t e r i z e d in that the two divided halves of the lead jacket (5) are cut into minor pieces in a operation in direct proximity to the division of the lead jacket. 4. Method according to any one of the preceding claims, c h a r a c t e r i z e d in that the removal of said first and second insulation layers (4, 6) is carried out by washing by means of hot water under high pressure. 5. Plant for taking care of cables of the type that, counted from within, comprises a central core (2) in the form of one or more units (3) of an electrically conducting material, which are protected by at least a first insulation layer (4), a lead jacket (5), a second insulating layer (6) as well as one or more mechanically strong metal bands (7) which extend helicoi- dally on the outside of the second insulation layer, c h a r- a c t e r i z e d in that the same comprises the following treatment stations arranged consecutively: a) a first station (8) in phe shape of a roller straight- ener to, if required, straighten a cut cable piece (1) having a limited length, b) a second station (9) with a pair of rotatable, cutting wheels (18, 18') as well as a feeding device (19, 19') to feed the straight cable piece between said wheels with the purpose of bringing about two axial and diametrically opposed cuts (21) in the helicoidal metal bands (7) of the cable pieces so as to split these in approximately semicircular pieces, said two cutting wheels (18, 18') , being adjustable at various centre distance from each other with the purpose of enabling variation of the cutting depth of the cutting wheels, and the wheels being arranged to rotate in one and the same direction of rotation in order to counterbalance the cutting forces acting on the opposite sides of the cable piece (1) , c) a third station (10) in the form of a washing station with means to wash the cable piece with hot water under high pressure with the purpose of removing the second insulation layer (6), d) a fourth station (11) which comprises means (26, 26') to bring about two longitudinal, diametrically opposed slits in the uncovered lead jacket (5) which divide the lead jacket into two halves, e) a fifth station (12) in the form of a washing station with means to wash the cable piece with hot water under high pressure with the purpose of removing the first insulation layer (4), and f) a sixth station (13) that comprises a cutting device (32) to cut the metallic unit or units (3) which remain after treatment in the preceding stations into smaller pieces . 6. Plant according to claim 5, c h a r a c t e r i z e d in that a washing station (15) is arranged up-stream the first station (8) to initially clean the individual cable piece (1) before treatment in subsequent stations. 7. Plant according to claim 5 or 6, c h a r a c t e r i z e d in that the division means of the fourth station (11) consists of a pair of rotatable teeth-equipped pulleys (26, 26') which are rotatable in opposite directions of rotation to together feed the cable piece forward axially in connection with the pulleys cutting two splitting slits in the lead jacket (5) .

Inventors: HOERNELL BERNT, HOFFBRANDT ULLA, HOERNELL, BERNT, HOFFBRANDT, ULLA
Applicants: HOERNELL BERNT, HOFFBRANDT ULLA, HOERNELL, BERNT, HOFFBRANDT, ULLA
Application year: 2000
Main classification: H01B15
IPC codes: H01B15