AN APPARATUS FOR STRIPPING A POLYMERIC OUTER CLADDING

Abstract

An apparatus for stripping a polymeric outer cladding on a circular core of an elongated object including: a frame having an object inlet end and a opposite outlet end, and as seen in a direction from the cable inlet end towards the outlet end a cutting device, for stripping the cladding from the core, and a centering device for centering the elongated object, the cutting device including a table rotatable around a central rotational axis R between the object inlet end and the outlet end and provided with a one cutting tool for stripping the cladding by cutting, and the centering device including at least one centering element to engage the outer surface of the core and centering the centre line of the core and the elongated object to coincide with the central rotational axis of the cutting device.

Claims

1. An apparatus for stripping an essentially polymeric outer cladding on a central essentially circular core of an elongated object, such as a polymeric cladding, optionally including an insulation, extruded around a central conductor of a voltage cable, the central core having a centre line and an outer surface, the apparatus comprising a frame having an object inlet end and a opposite outlet end, and as seen in a direction from the cable inlet end towards the outlet end, a cutting device configured for stripping the cladding from the core and a centering device configured for centering the elongated object, the cutting device comprising a table being rotatable around a central rotational axis extending between the object inlet end and the outlet end and being provided with a central opening allowing the elongated object to pass through there and being provided with at least one cutting tool configured for stripping the cladding by cutting, and the centering device comprising at least one centering element being configured to engage the outer surface of the core by means of an engagement surface of said centering element and centering the centre line of the core and thereby the elongated object to coincide with the central rotational axis of the cutting device.

2. The apparatus according to claim 1, wherein the cutting device comprises at least one cutting tool being arranged radially moveable and adjustable relative to the table.

3. The apparatus according to claim 1, wherein the cutting device comprises at least two cutting tools arranged in essentially a common plane extending perpendicularly to the central axis of rotation of the cutting device, such as a pair of oppositely arranged cutting tools or three cutting tools arranged circumferentially equally spaced.

4. The apparatus according to claim 1, wherein the cutting device comprises a number of consecutively arranged cutting tools, such as two or three consecutively arranged cutting tools.

5. The apparatus according to claim 1, wherein the cutting device comprises at least two cutting tools arranged in essentially a common plane in each of at least two, such as three, consecutive arranged planes extending perpendicularly to the central axis of the central axis of rotation of the cutting device.

6. The apparatus according to claim 1, wherein at least one and preferably each cutting tool of the cutting device is arranged on a slide guided on a radially extending guide way.

7. The apparatus according to claim 1, wherein the at least one, alternatively each, cutting tool of the cutting device is a milling tool, such as a cylindrical cutter or an end mill.

8. The apparatus according to claim 1, wherein the centering device comprises at least one radially moveable and adjustable centering element.

9. The apparatus according to claim 1, wherein the centering device comprises a number of circumferentially mutually equally spaced and in radial direction moveable and adjustable centering elements, such as two radially oppositely arranged centering elements or three radially 120 circumferentially mutually spaced centering elements preferably being arranged in a common plane perpendicular to the central rotational axis of the machining/cutting device.

10. The apparatus according to claim 9, wherein the centering elements are arranged on respective slides arranged on respective radially extending slide ways.

11. The apparatus according to claim 8, wherein the centering device is provided with means for synchronously radially moving and adjusting the radial position of the centering elements.

12. The apparatus according to claim 11, wherein the synchronous means comprises a rotatable guide plate arranged rotatably around an axis coinciding with the central rotational axis of the cutting device and being provided with a number of mutually equally spaced spiral-shaped guide ways, such as grooves or openings, extending spirally outwardly relative to the central rotational axis and on each slide a mating member sliding cooperating with the respective guide way, such as a protruding member or pin.

13. The apparatus according to claim 8, wherein at least one, alternatively each, centering element is provided with a roller rotatable about an axis being perpendicular to the radial direction in which the centering element is radially moveable, said roller having and outer roller face forming the engagement surface of the centering element.

14. The apparatus according to claim 8, wherein the centering device is configured to move each centering element between an engagement position engaging the core of the elongated object, such as a conductor of a voltage cable and an inactive position where the engagement surface of each centering element allows the elongated object, such as a voltage cable, including the cladding thereof to pass freely through the engagement device.

15. A system comprising an apparatus according to claim 1 and an extruder configured to extrude a polymeric cladding around a core of an elongated object, such as insulation around a central conductor of a high voltage cable, the apparatus being optionally arranged downstream of an outlet end of the extruder where the oblong object, such as the voltage cable leaves the extruder at a predetermined extrusion velocity and enters the apparatus at the inlet end thereof.

16. A method of producing elongated objects comprising a central core and a polymeric cladding extruded around the core, said method comprising the following steps: a) moving a first core through an extruder and extruding the polymeric cladding around the core and thereby producing a first elongated object b) stripping a start-up length of the cladding having insufficient quality and thereby providing a clean length of the first core c) separating the clean length of the first core from the produced first oblong object having cladding extruded around the core d) connecting the separated clean length of the first core to a forward end of a second core having the same outer diameter as the first core, such as by welding or soldering, whereby the clean length forms a forward portion on the second core. e) moving the second core through an extruder and extruding a polymeric cladding around the core and thereby producing a second oblong object on which a start-up length of the cladding having insufficient quality is extruded around at least a part of the clean length of the first core

Description

BRIEF DESCRIPTION OF THE FIGURES

[0066] Embodiments of the present disclosure will be described in more detail in the following with regard to the accompanying figures. The figures show one way of implementing the present disclosure and are not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

[0067] FIG. 1 shows a perspective view of an embodiment of an apparatus according to the present disclosure,

[0068] FIG. 2 shows a top view of the apparatus shown in FIG. 1,

[0069] FIG. 3 shows a vertical sectional view along the line III-III in FIG. 2,

[0070] FIG. 4 shows a longitudinal sectional view through the apparatus along the line IV-IV in FIG. 3,

[0071] FIG. 5 shows a perspective view of a milling tool arranged in a milling head of a cutting device of the apparatus according to the present disclosure,

[0072] FIG. 6 shows a vertical sectional view along the line VI-VI in FIG. 2 and shows the centering device of the apparatus,

[0073] FIG. 7 shows a perspective view of parts of the centering device of the apparatus according to the present disclosure,

[0074] FIG. 8 shows a system according to the present disclosure comprising an apparatus according to the present disclosure arranged downstream of an extruder extruding a polymeric cladding around a core, the polymeric cladding being stripped by the apparatus according to the present disclosure, an additionally illustrated method according to the present disclosure for producing elongated objects comprising a core and a polymeric cladding extruded around the core.

[0075] FIG. 9 shows diagrammatically a portion of an elongated object in the form of a high voltage cable comprising a conductor a cladding extruded around the conductor

DETAILED DESCRIPTION

[0076] The aspects of the disclosed embodiments will be described below with reference to an apparatus 1 for stripping a polymer cladding 14 of an elongated object 16 in the form of a voltage cable comprising a core 15 in the form of a conductor and a cladding extruded around the conductor (see FIG. 9). It should, however, be understood that the invention is not limited to the stripping of cables as it encompasses an apparatus for stripping of elongated objects 16, in general, comprising a core 15 and a cladding 14, such as a polymeric cladding provided around said core 15.

[0077] As shown in FIGS. 1 to 3 and 6, the apparatus 1 comprises a frame 2 being of a box-shaped lattice structure comprising a front part 3, an opposite rear part 4, a middle part 9 between the front and rear part, opposite right and left side parts 5,6, and opposite top and bottom parts 7,8. The front part forms an object inlet end 10 and the rear part 4 forms an outlet end 11 of the apparatus.

[0078] As seen in the direction from the inlet end 10 towards the outlet end 11, the apparatus 1 comprises a cutting device 12 configured for stripping, i.e. removing the cladding 14 from the core 15 of the elongated object 16, and a centering device 13 configured for centering the core 15 of the elongated object 16 and thereby also the elongated object relative to the cutting device 12.

[0079] As shown in FIGS. 1-5, the cutting device 12 comprises a table 22 being rotatable around a central rotational axis R extending between the object inlet end 10 and outlet end 11 of the frame 2. The table 22 is journaled in a bearing 23 arranged in the middle part 9 of the frame 2 and provided with a central opening 24 allowing the elongated object to pass through. In the embodiment shown, the central opening 24 is formed by or forms a continuation of the bore 25 of an inner hollow rotor 26 of a slip ring 27 comprising a stator 28 surrounding the rotor 26. The stator 28 of the slip ring 27 is connected to the frame, in the present case the front part 3 thereof, and the rotor 26 of the slip ring is connected to the inner ring of the bearing 23, the table being also connected to said inner ring. The outer ring of the bearing 23 is connected to the middle part 9 of frame 2. The table 22 is driven to rotation by means of a motor 29 and a drive 30 being shown as a belt drive.

[0080] Additionally, the cutting device 12 comprises a number of cutting tools 31 arranged on the table 22. In the embodiment shown, the cutting tools are milling tools in the form of end mills. As most clearly shown in FIGS. 3 and 4, the apparatus comprises six milling tools, i.e. end mills 31.1 to 31.6 arranged so that the shafts thereof extend essentially radially to the rotational axis R of the table 22 and with a mutual spacing as seen in the direction from the front end towards the outlet end of the frame 2. As seen in said direction from the front end towards the outlet end of the frame 2, the table 22 comprises a first and a second mutually spaced rough milling tools 31.1, 31.2 for carrying out a rough machining of the cladding 14, thereafter a spacing and a first and second mutually spaced medium milling tools 31.3, 31.4 for carrying out a medium machining of the cladding, and finally a spacing and a first and a second mutually spaced fine milling tools 31.5, 31.6 for carrying out a fine machining of the cladding up to the outer surface 18 of the core 15. The spacing between the consecutive milling tools 31 is advantageously selected corresponding to the diameter d of the milling tools, i.e. end mills. In the embodiment shown, the tools are arranged essentially in pairs of tools comprising two diametrically oppositely arranged tools. A first pair comprises the first rough milling tool 31.1 and first fine milling tool 31.5, the second pair comprises the second rough milling tool 31.2 and the second fine milling tool 31.6, whereas the third pair comprises the first and second medium milling tools 31.3, 31.4.

[0081] Alternative to the above arrangement of the milling tools, the milling tools 31 can be arranged in pairs comprising two oppositely arranged tools arranged essentially in line in a common plane extending perpendicular to the central rotational axis R of the table 22, and the table is provided with tree axially spaced and consecutively arranged pairs of milling tools, each pair comprising two oppositely arranged milling tools 31. In the above alternative arrangement, the table comprises a pair of oppositely arranged rough milling tools, a first spacing, a pair of oppositely arranged medium milling tools, a second spacing, and a pair of oppositely arranged fine milling tools as seen in the direction from the front end towards the outlet end of the frame.

[0082] The shaft of each milling tool extends essentially radially to the rotational axis of the table 22 and, as seen in the direction from the front end towards the outlet end of the frame 2, a first pair of oppositely arranged milling tools carries out a rough machining of the cladding, a second pair of oppositely arranged milling tools carries out a medium machining of the cladding and a third pair of oppositely arranged milling tools carries out a fine machining of the cladding up to the core.

[0083] As most clearly shown in FIG. 5, each milling tool 31 is arranged in a tool holder of a milling unit 32 being provided with a motor 33 configured to rotate a spindle and thereby the milling tool 31 held by the tool holder at the outer free end of the spindle. Each milling unit 32 is arranged on a slide 34 guided on a radially extending guide way 35 whereby the milling unit 32 together with the slide 34 is radially moveable and adjustable by means of a respective linear actuator 36.

[0084] The milling units provided with the rough milling tool 31.1 and 31.2, respectively, are denoted 32.1 and 31.2, respectively, the milling units provided with the medium milling tool 31.3 and 31.4, respectively, are denoted 32.3 and 31.4, respectively, and the milling units provided with the fine milling tool 31.5 and 31.6, respectively, is denoted 32.5 and 31.6, respectively.

[0085] In the embodiment shown, the centering device 13 comprises three radially movable and adjustable centering elements 37 configured to engage the outer surface 18 of the core 15 of the elongated object 16 by means of an engagement surface 38 of each element 37 in order to centre the core 15 and thereby the elongated object 16 to coincide with the central rotational axis R of the cutting device 12. The centering elements 37 are arranged in a common plane extending perpendicularly to the central rotational axis R of the cutting device 12 and are mutually equally circumferentially spaced, i.e. 120 mutually spaced. Each centering element 37 is arranged on a slide 39 arranged on a radially extending slide way 40. The slide ways are rigidly connected to the rear part 4 of the frame 2. Additionally, the centering device 13 is provided with synchronous means for synchronously radially moving and adjusting the radial position of the centering elements 37 on the slides 39. In the embodiment disclosed, the synchronous means comprises a rotatable guide plate 41. By means of a bearing having an outer bearing ring being rigidly connected to the rear part 4 of the frame 2, the guide plate is rotatable relative to the frame 2 around an axis coinciding with the central rotational axis R of the cutting device 12. The guide plate 41 is provided with three mutually equally spaced, i.e. 120 circumferentially mutually spaced spiral-shaped guide ways 42 extending spirally outwards relative to the central rotational axis R of the cutting device 12. Each centering element slide 39 is provided with an engagement member 43 slidingly engaging a respective guide way and movable along said guide way. In the embodiment shown, the guide ways 42 are grooves in the guide plate 41, the guide plate being arranged between the rear part 4 of the frame 2 and the radially extending slide ways 40, and the engagement members 42 of the respective centering element slides 39 are a pin extending into a respective groove.

[0086] The guide plate 41 is rotatable by means of a motor 44 and a drive 45 shown as a belt drive. When rotating the guide plate 41 in a first direction, the engagement of the pins of the slides in the respective grooves of the guide plate 41 entails a radial movement of the slides 39 on the respective slide ways 40 in an radially inwards direction to bring the engagement surface 38 of the respective centering elements 37 into engagement with the outer surface 18 of the core 15, i.e. into an engagement position, and thereby centre the elongated object 16 on the central rotational axis R of the cutting device. Correspondently, a rotation of the guide plate 41 in a second direction opposite to the first direction entails that the slides 39 and thereby the centering elements 37 are moved radially outwards on the respective slide ways 40 to bring the engagement surfaces 38 out of engagement with the outer surface 18 of the core 15 of the elongated object 16. The centering element slides 39 and thereby the centering elements 37 can be moved into an outer inactive position in which the elongated element 16 can feely pass through the centering device 13. As seen in FIG. 7, each centering element 37 is provided with a roller 45 arranged rotatably about an axis being perpendicular to the radial direction in which the centering element 37 is radially moveable. The roller 45 has an outer roller face 46 forming the engagement surface 38 of the centering element 37 and being convex, in the shown embodiment, as seen in a radial sectional view of the roller 45.

[0087] When stripping a given elongated object 16, the cutting tools 31 can be preset or adjusted to a preselected cutting depth in the cladding corresponding to the outer diameter D of the core 15 of the elongated object whereby the cladding is removed up to a diameter corresponding to the preselected cutting depth. Additionally, the centering device 12 can be configured to continuously monitor the diameter D of the core 12 and the cutting device can be configured to adjust or control the cutting depth of the cutting tools 31 into the cladding, i.e. the radial position of the cutting tools, in dependency of the diameter of the core monitored by the centering device 13, e.g. by means of a control means or control system. Further, the diameter D of the core 12 can be monitored by means on sensors connected to the centering elements 37 of the centering device 13 or by means of sensors separated from the centering device, i.e. be parts of a separate diameter monitoring device configured to continuously monitoring the diameter of the core and communicating the monitored diameter to the cutting device 12, whereby the cutting device continuously removes the cladding 14 up to the outer surface of the core 15.

[0088] Reference is now made to FIG. 8 diagrammatically disclosing an apparatus according to the invention used in connection with an extruder configured to extrude a polymeric cladding 14 around a core 15 of an elongated object 16 and a system comprising an apparatus according to the invention and an extruder configured to extrude a polymeric cladding around a core of an elongated object, such as an insulator comprising a layer 61 of XLPE and two layers of a polymeric semiconductor 60,62 around the conductor of a high voltage cable, the apparatus being arranged downstream of the extruder where the cable leaves the extruder. Additionally, FIG. 8 illustrates a method according to the invention for producing elongated objects 16 comprising a central core 15 and a polymeric cladding 14 extruded around the central core, the method being illustrated by means of the production of a high voltage cable comprising a core 15 in the form of a central conductor and a polymeric cladding 14 comprising an insulation layer of XLPE extruded around the central conductor.

[0089] The shown system comprises a conductor pay-off reel 50 with a coil 51 of the conductor 15. From the pay-off reel 50, the conductor is moved through a conductor accumulator 59, around a wheel 52, also named a capstan, and into a preheater 53 preheating the conductor 15 before it enters a triple head extrusion machine 49 extruding a polymeric cladding 14 around the conductor 15. The triple head extrusion machine 49 comprises a triple extension head 54, a first extruder 55 extruding through the head 54 a first semiconductor layer 60 around the conductor, a second extruder 56 extruding through the head 54 an insulation layer 61 around the first semiconductor layer 60 and a third extruder 57 extruding through the head 54 a second semiconductor layer 62 around the insulation layer 61. From the triple head extrusion machine 49, the conductor provided with the insulation layer and the semiconductor layers is moved into a processing and conditioning device 58 in which the XLPE layer is vulcanized and cooled to form the high voltage cable 16. From the processing and conditioning device 58, the cable 15 is moved into the stripping apparatus 1 according to the invention to remove from the conductor the initial length or start-up length of the cladding 14 that is of insufficient quality. The conductor 15 freed from the cladding 14 leaves the apparatus 1 via a draw device 63, such as a caterpillar or draw rollers, and passes around a conductor return wheel 64.

[0090] From the wheel 64, the conductor freed from cladding 14 can be moved to and winded up on a conductor take-up reel 65. The conductor 15 freed from cladding 14 can, at a later point in time, be connected to the front end of a coil of conductor and thereby form the initial or start-up length of said conductor during a extrusion process where a cladding is extruded around the conductor. Thereby, the length of the conductor, from which the cladding from a previous extrusion process has been removed, forms the start-up length on which cladding of insufficient quality is formed during the extrusion process. The above procedure can be repeated a number of times, such as 4-10 times, using the same length of the conductor freed from cladding each time.

[0091] The removal of cladding of insufficient quality from the conductor is stopped when the cladding is of the desired quality and the conductor-length freed from the cladding is severed from the conductor provided with cladding of the desired quality adjacent the outlet end of the apparatus 1. After the conductor length freed from cladding 14 has been removed from the cable, the cable with cladding of the desired quality is moved via return wheels 66 and 67 to and winded up on a cable take-up reel 68. As described above, the same length of conductor freed from cladding can be reused several times and serve as the start length of a conductor on which the extruded cladding is of insufficient quality and is removed by the apparatus according to the present disclosure and the corresponding conductor start length reused.

LIST OF REFERENCE NUMERALS

[0092] 1. apparatus [0093] 2. frame [0094] 3. front part [0095] 4. rear part [0096] 5. right side part [0097] 6. left side part [0098] 7. top part [0099] 8. bottom part [0100] 9. middle part [0101] 10. object inlet end [0102] 11. outlet end [0103] 12. cutting device [0104] 13. centering device [0105] 14. cladding [0106] 15. core/conductor [0107] 16. elongated object [0108] 17. centre line [0109] 18. outer surface [0110] 19. [0111] 20. [0112] 21. [0113] R rotational axis [0114] 22. table [0115] 23. bearing [0116] 24. central opening of table [0117] 25. bore of inner hollow rotor [0118] 26. inner hollow rotor [0119] 27. slip ring [0120] 28. outer stator [0121] 29. motor [0122] 30. drive [0123] 31. cutting tool/milling tool [0124] 31.1 first rough milling tool [0125] 31.2 second rough milling tool [0126] 31.3 first medium milling tool [0127] 31.4 second medium milling tool [0128] 31.5 first fine milling tool [0129] 31.6 second fine milling tool [0130] 32. milling unit [0131] 32.1 milling unit with first rough milling tool [0132] 32.2 milling unit with second rough milling tool [0133] 32.3 milling unit with first medium milling tool [0134] 32.4 milling unit with second medium milling tool [0135] 32.5 milling unit with first fine milling tool [0136] 32.6 milling unit with second fine milling tool [0137] 33. motor of milling unit [0138] 34. milling unit slide [0139] 35. milling unit slide way [0140] 36. linear actuator [0141] 37. centering elements [0142] 38. engagement surface [0143] 39. centering element slide [0144] 40. radially extending centering element slide way [0145] 41. guide plate [0146] 42. spiral shaped guide ways [0147] 43. engagement member [0148] 44. motor drive [0149] 45. roller [0150] 46. roller face [0151] 47. [0152] 48. [0153] 49. triple head extrusion machine [0154] 50. pay-off reel [0155] 51. conductor coil [0156] 52. wheel [0157] 53. preheater [0158] 54. extruder [0159] 55. first extruder [0160] 56. second extruder [0161] 57. third extruder [0162] 58. processing and conditioning device [0163] 59. conductor accumulator [0164] 60. first semiconductor layer [0165] 61. insulation layer [0166] 62. second semiconductor layer [0167] 63. draw device/caterpillar [0168] 64. conductor return wheel [0169] 65. conductor take-up reel [0170] 66. cable return wheel [0171] 67. cable return wheel [0172] 68. cable take-up reel [0173] D. diameter of core/conductor [0174] d. diameter of end mill [0175] c. centre line of core/conductor