Device for stripping a cable, in particular a shielded cable with mineral insulator

Abstract

The invention relates to a device for stripping a coaxial shielded cable comprising a sheath, a layer of mineral insulator and a conductive wire, the device comprising a cutting tool (1) mounted on a rotational drive shaft (12). The device comprises means for translating the tool (1) about the rotation shaft, the tool comprising guide means for inserting the tool (1) onto the end of the cable, the tool (1) being rotatable and translatable around and along the end of the cable, the axis of which is aligned with the rotation shaft, the cutting means comprising a blade extending transversely to the path of the cable and extending between the periphery of a region of the cable, in which the conductive wires of the cable are located, and the outer sheath of the cable, the end edge of the cutting blade, cutting the sheath in the form of a shaving and scraping the layer of mineral insulator around the region in which the conductive wires are located when the cable is moved.

Description

device for stripping a cable, in particular a mineral-insulated shielded cable

[0001] The present invention relates to a device for stripping a cable, in particular a mineral-insulated shielded cable, which makes it possible to machine the outer metal sheath and remove the mineral insulation without impacting the central conductor(s).

[0002] Mineral insulated armoured cables are cables consisting of one or more central metallic conductors and one or more hollow cylindrical metallic sheaths between which is inserted a powdered refractory insulator such as mineral of the magnesia, alumina, silica or any other suitable mineral insulator, the outer sheath being metallic such as stainless steel, copper, nickel, nickel-chromium, an alloy of NiCr15Fe known under the trade name inconel 600, platinum, tantalum or any other suitable metallic material.

[0003] Such cables are fire-resistant and used in industrial environments with hazardous areas such as nuclear power plants. They are particularly used in many areas of industry where sensors, heating elements or electrical signal transmission cables are used, which must withstand environments with increasingly severe conditions (temperature, high voltage, humidity, etc.).

[0004] Such cables are used to connect devices that are spaced apart from each other, and it is therefore necessary to provide means for connecting these cables to the devices, or even the cables between them. It is therefore necessary when installing the connection means to strip the cables to expose the central metal conductor.

[0005] Cable ends are extremely critical parts of the mineral insulated cable since they must ensure the maintenance of electrical performance (electrical insulation, dielectric strength, capacity, etc.) while making the central conductor accessible for connection to the connector.

[0006] When a mineral insulated shielded cable is stripped to install a terminal device such as a connector, the outer sheath and mineral insulation are removed to expose the central metallic conductor wire and the intrinsic dielectric barrier of the cable at the connector / cable interface is greatly weakened.

[0007] To perform cable stripping, there are devices such as that described in US-A-20220239078, which comprises a rotary cutting tool rotatable about a central axis and which carries a projecting cutting blade and a diametrically opposite counter-support so that the cable engages between the two along the central axis of the cutting tool, the cutting blade being movable in order to produce a radial incision in the cable at a defined axial position. Stripping means are also provided to engage in the incision and remove the sheath and insulation from around the central conductor wire.

[0008] Such a device therefore makes a radial incision. If this is possible through a cable whose insulation is a dense material such as a polymer material like PTFE (Polytetrafluoroethylene), when the insulation is a compacted powdery mineral compound like magnesia, the radial incision leads to risks of degradation of the compaction of the insulation.

[0009] Such phenomena of decompaction and loss of insulation at the end of the cable can therefore be observed and this "decompaction" of the mineral insulation can lead to a reduction in the dielectric properties of the cable or even a variation in local impedance in the case of a transmission cable.

[0010] The main object of the present invention is therefore to propose a device for stripping shielded cables with mineral insulation without risk of degradation of the dielectric properties of the cable, in particular due to decompaction of the mineral insulation.

[0011] To this end, the invention relates to a device for stripping a shielded cable comprising an outer sheath, a layer of mineral insulation and at least one conductive wire, the device comprising a cutting tool mounted on a rotational drive axis, characterized in that the device further comprises means for driving the cutting tool in translation along the rotational axis, said cutting tool comprising guide means for engaging said cutting tool on the end of the cable to be stripped held fixed by means for holding it in translation and in rotation, said cutting tool thus being drivable in rotation and in translation around and along the end of said cable to be stripped, the axis of the cable to be stripped being intended to be aligned with the rotational axis, the cutting means comprising a cutting blade extending transversely to the path of the end of the cable to be stripped defined by the guide means,the end edge of the cutting blade being positioned projecting in said path, and extending between the periphery of an area of ​​the cable to be stripped in which the conductive wire(s) of the cable to be stripped are located and the outer sheath of the cable to be stripped, so that the end edge of the cutting blade, when it comes into contact with the end of the cable, cuts the outer sheath in the form of a chip and scrapes the layer of mineral insulation around the area in which the conductive wire(s) are located under the effect of the rotational and translational drive of the cutting tool.,

[0012] Thus, advantageously, an operation of cutting the outer sheath and simultaneous scraping of the mineral insulation is carried out, making it possible to strip the end of the cable without the risk of decompaction of the compacted powdered mineral insulation. The stripping device according to the invention therefore makes it possible to integrate an operation of machining the sheath (cutting) and the removal of the mineral insulation (scraping) in a single step. Thus, a radial incision is no longer made at the periphery of a cable down to the conductive wire which, during removal, can cause decompaction of the mineral insulation.

[0013] Preferably the end edge of the cutting blade extends radially relative to the axis of rotation of the cutting tool, offset relative to said axis of rotation, the offset corresponding to the radius of the zone, preferably of circular section centered on the central longitudinal axis of the cable merged with the rotational drive axis, in which the conductive wire(s) are located.

[0014] The operating principle of this device is thus a high-speed rotation of the cutting tool in order to create a chip of the sheath and to evacuate by scraping, the mineral insulation as the cutting tool advances on the cable, around the area in which the conductive wire(s) are located. This advantageously obtains a very clean surface state of the cut of the sheath and maintains the compaction of the mineral insulation.

[0015] Thus, when the cable to be stripped comprises a single conductive wire positioned centrally in the cable, the end edge of the cutting blade is positioned projecting into the path of the cable to be stripped, extending from the periphery of the zone, in this case merged with the conductive wire, to the outer sheath, preferably radially relative to the axis of rotation and offset relative to said axis of rotation, the offset corresponding to the radius of the conductive wire of the cable to be stripped, so that the end edge of the blade, when it comes into contact with the end of the cable, cuts the outer sheath in the form of a chip and scrapes the layer of mineral insulation around the conductive wire under the effect of the rotational and translational drive of the cutting tool. The cutting blade extends in front of the cable end in the plane of said end, cuts the sheath and scrapes the mineral insulation at the same time, by rotation and translation.The cable is thus stripped from its end by cutting chips, and not by cutting and removing a section of sheath and mineral insulation.

[0016] When the cable to be stripped comprises at least two conductive wires, the area corresponds to a central circular section area of ​​the cable in which the conductive wires are located.

[0017] When the cable to be stripped comprises two or more conductive wires, these are housed within the mineral insulation of the cable. The end edge of the cutting blade is then positioned projecting into the path of the cable, extending between the periphery of an area surrounding the conductive wires, preferably of circular cross-section, and the outer sheath, preferably radially relative to the axis of rotation and offset from said axis of rotation, the offset corresponding to the radius of the area of ​​circular cross-section comprising the conductive wires of the cable to be stripped, so that the end edge of the blade, when it comes into contact with the end of the cable, cuts the sheath in the form of a chip and scrapes the layer of mineral insulation around the conductive wires under the effect of the rotational and translational drive of the cutting tool. The mineral insulation between the conductive wires can then be easily removed by brushing.

[0018] According to a preferred embodiment, the cutting tool comprises a support block mounted to be rotatably driven by a rotation drive axis. The support block preferably has the shape of a cylindrical block of circular section in which are formed two grooves extending orthogonally to each other and whose depth extends over a large part of the height of the cylindrical block, defining at their intersection an empty volume in the axis of rotation of the cutting tool.

[0019] The cutting means comprise means for supporting the cutting blade, said support means comprising a through hole, preferably of circular section. The support means are mounted on the support block with the through hole aligned with the axis of rotation, one end of the through hole, called the inner end, opening into the empty volume of the support block and the other end of the through hole, called the outer end, opening towards the outside of said cutting tool thus formed, constituting the engagement end of the end of the cable. The through hole of the support means of the cutting blade associated with the empty volume of the support block constitute the means for guiding the end of the cable to be stripped, the through hole having a diameter corresponding to the outer diameter of the cable to be stripped. It is thus possible to provide interchangeable cutting tools depending on the cable to be stripped and its diameter.

[0020] The cutting blade is mounted on the support means to extend transversely to the through hole of the support means, with its end edge projecting tangentially into the inner end of the through hole, the end edge then extending radially or inclined relative to the circular cross-section hole but being offset from the center of the through hole, this offset corresponding to the radius of the circular cross-section area containing the conductive wire(s).

[0021] Thus, advantageously, when the translational and rotational drive means of the cutting tool bring said cutting tool onto the end of the cable to be stripped, which is held fixed in rotation and translation, the cutting edge of the blade, driven in rotation and translation, rotates around the axis of rotation while moving and, when it comes into contact with the end of the cable, it cuts the sheath in the form of a chip and scrapes the mineral insulation.

[0022] Preferably, the support means have a general U-shaped bar shape.

[0023] Preferably, in the through hole of circular section is mounted a metal sheath which comprises, coaxially mounted, means promoting the sliding in rotation of said rotary cutting tool around the cable C. These sliding means may consist of a diamond-based sheath or a ball bearing. The cable to be stripped can thus be fixedly engaged in the guide means of the cutting tool which is driven in rotation at high speed around it without risk of damaging the cable.

[0024] The device according to the invention further comprises means for holding the cable fixed in rotation and translation such as clamping jaws, means for positioning the end of the cable such as a positioning stop. This positioning stop can be retracted using an actuating lever.

[0025] The invention will now be described in more detail with reference to the drawing in which is shown:

[0026] a perspective view from above of a cutting tool according to an exemplary embodiment of a device according to the invention;

[0027] a perspective view from above of the tool associated with other elements of the device according to the invention;

[0028] a longitudinal sectional view of the cutting tool of the;

[0029] a perspective view of the cutting tool support block of the;

[0030] a perspective view from above of cutting means of the cutting tool of the;

[0031] a longitudinal sectional view of a cutting tool engaged on a cable to be stripped at the start of cutting;

[0032] a longitudinal sectional view of a cutting tool engaged on a cable to be stripped during cutting;

[0033] a longitudinal sectional view of a cutting tool engaged on a cable to be stripped at the end of the cut;

[0034] a cross-sectional view of a first example of a cable to be stripped;

[0035] a cross-sectional view of a second example of a cable to be stripped;

[0036] a cross-sectional view of a third example of a cable to be stripped and

[0037] a cross-sectional view of a fourth example of a cable to be stripped.

[0038] As can be seen in the, the stripping device comprises a rotary cutting tool 1 which consists of a support block 11 mounted to be driven in rotation by a rotation drive shaft 12 using conventional rotation drive means per se and which will not be described in more detail. This rotary cutting tool 1 is also mounted to be driven in translation using translation drive means which are conventional means which will not be described further.

[0039] In relation to this rotary cutting tool 1, the stripping device comprises clamping jaws 2 which are provided to hold the end of a cable C to be stripped, which is thus kept fixed both in rotation and in translation as can be seen.

[0040] As can be seen, the support block 11 has the shape of a cylindrical block of circular section in which two grooves 13, 14 are formed extending orthogonally to each other and whose depth extends over a large part of the height of the cylindrical block. In one 14 of the grooves 13, 14 are mounted the cutting means. The intersection of the two grooves 13, 14 forms an empty volume 15 in the support block 11.

[0041] Said cutting means comprise support means 3 which have the general shape of a U-shaped bar whose branches 32 are of a shape and dimensions complementary to the groove 14 to be housed there and thus fixed in the support block 11 (cf.).

[0042] These support means 3 have in the central part (cross section of the U) a through orifice of circular section 31 intended to extend along the axis of rotation 12 when the support means are mounted on the support block 11.

[0043] Indeed, when the support means 3 are mounted in the groove 14 of the support block 11, the hole 31 is positioned at the intersection of the two grooves 13, 14 of the support block 11 which corresponds to the axis of rotation 12 with one end opening inside the support block 11 towards the empty volume V and one end of the hole 31 opening outside the support block 11 (cf.).

[0044] As can be seen in the figure, in this hole 31 is mounted a metal sheath 32. The sheath 32 also comprises coaxially mounted means promoting the sliding in rotation of said rotary cutting tool around the cable C. These sliding means 33 consist of a diamond-based sheath.

[0045] As can be seen in la and la, cable C with its sheath G, its mineral insulation IM and its conductive wire FC is thus mounted in hole 31.

[0046] Such a cable C consists of one or more metallic thermoelectric conductors, for example nickel-chromium, nickel-aluminium, copper, iron, platinum, a metallic alloy consisting mainly of copper and nickel known under the trade name constantan, an alloy of nickel, chromium and silicon such as that known under the trade name Nicrosil.an alloy of nickel and silicon known under the trade name Nisil. It may comprise one or more hollow cylindrical metallic sheaths between which is introduced a powdered refractory insulator such as mineral of the magnesia, alumina, silica or any other suitable mineral insulator, the outer sheath being metallic such as stainless steel, copper, nickel, nickel-chromium, an alloy of NiCr15Fe known under the trade name inconel 600, platinum, tantalum or any other suitable metallic material.

[0047] The support means 3 comprise cutting means preferably comprising a blade 4 fixed to the support means 3. The blade 4 comprises a beveled end forming an end edge 42. The blade 4 is fixed to the support means 3 so as to extend transversely to the trajectory of the cable defined by the hole 31, and its end edge 42 is positioned projecting in said trajectory, to extend radially relative to the axis of rotation, but offset relative to said axis of rotation.

[0048] This offset corresponds to the radius of a zone Z in which the conductive wire(s) FC of the cable to be stripped are housed, said zone surrounding the conductive wires being of circular section, so that the end edge 42 of the cutting blade 4 extends between the periphery of the zone Z and the outer sheath G so that, when it comes into contact with the end of the cable C, the blade 4 cuts the outer sheath G of the cable in the form of a chip and scrapes the layer of mineral insulation IM around the zone Z in which the conductive wire(s) FC are located under the effect of the rotational and translational drive of the cutting tool. It is also possible to provide for the edge 42 to be non-straight and then extend inclined (non-radially) in the through hole 31.

[0049] Thus, in the case of a cable to be stripped with a conductive wire FC, the zone Z corresponds to the conductive wire FC itself of circular section and the end edge 42 of the blade 4 is positioned so as to extend radially between the conductive wire FC of the cable C and the outer sheath G when the end to be stripped of the latter is at the end of the hole 31 opening into the interior of the support block 11. The blade 4 can extend beyond the outer sheath G.

[0050] For the cable C1 which has two conductive wires FC1, the zone Z1 delimits the zone of circular section Z1 which surrounds the conductive wires FC1 at the periphery of which the end edge 42 of the blade 4 extends radially towards the outer sheath G (cf.).

[0051] Similarly for the four-conductor cable C2, the edge 42 extends radially from the circular section zone Z2 in which the FC2 conductive wires are located to the outer sheath G. The zone Z2 is centered on the axis of rotation and its periphery is as close as possible to the FC2 conductive wires.

[0052] In the, the cable C3 has an outer sheath G and an inner sheath G3. The edge 42 of the cutting blade 4 can thus remove both sheaths G and G3 in the form of shavings and without decompaction of the mineral insulation IM.

[0053] The cable C, C1, C2 or C3 is engaged in the hole 31 by the outer end of said hole 31 and emerges by the inner end in which the blade 4 extends as can be seen.

[0054] As already mentioned, the end of the cable C, C1, C2 or C3 to be stripped is housed in the clamping jaws 2 and is guided until it comes against a positioning stop 5.

[0055] This stop 5 is then retracted and the rotary cutting tool 1 is brought by the translation means thereof to the vicinity of the end of the cable to engage this end in the bore 31 until the end of the cable comes against the blade 4.

[0056] The support block 11 is driven both in translation (direction of the arrow in figures 6, 7 and 8) and in rotation in the appropriate direction so that, when the end of the beveled blade 4 comes into contact with the end of the cable C, C1, C2, C3, this makes it possible to create, with the edge 42 of said blade 4 coming into contact with the end of the cable, a cutting of the sheath G in the form of a chip and an elimination of the mineral insulation IM by scraping in the form of a chip or at least a fine powdery film or powder. Any risk of decompaction is avoided because the rotating cutting tool does not cause vibrations.

[0057] This “cut” makes it possible to obtain a clean surface condition of the cut of the G sheath as well as maintaining the compaction of the IM mineral insulation, even when there are two sheaths or several conductive wires.

[0058] The rotational and translational drive is carried out until the desired stripping length has been obtained.

[0059] All the elements constituting the device according to the invention are mounted on a frame. Each cutting tool comprises guide means adapted to a cable to be stripped and to strip cables of different diameters, the cutting tool is changed.

Claims

Device for stripping a shielded cable comprising an outer sheath (G), a mineral insulating layer (IM) and at least one conductive wire (FC, FC1, FC2), the device comprising a cutting tool (1) mounted on a rotational drive axis (12), characterized in that the device further comprises means for driving the cutting tool (1) in translation along the rotational axis, said cutting tool (1) comprising guide means for engaging said cutting tool (1) on the end of the cable to be stripped (C) held fixed by means for holding in translation and rotation, said cutting tool (1) thus being drivable in rotation and in translation around and along the end of said cable to be stripped (C), the axis of the cable to be stripped being intended to be aligned with the rotational axis, the cutting means comprising a cutting blade (4) extending transversely to the path of the end of the cable to be stripped (C) defined by the means of guidance,the end edge (42) of the cutting blade (4) being positioned projecting in said trajectory, and extending between the periphery of a zone (Z, Z1, Z2) of the cable to be stripped in which the conductive wire(s) of the cable to be stripped are located, and the outer sheath (G) of the cable, so that the end edge (42) of the cutting blade (4), when it comes into contact with the end of the cable, cuts the outer sheath (G) in the form of a chip and scrapes the layer of mineral insulation (IM) around the zone (Z, Z1, Z2) in which the conductive wire(s) (FC, FC1, FC2) are located under the effect of the rotational and translational drive of the cutting tool (4)., Device according to claim 1, characterized in that, when the cable to be stripped comprises a single conductive wire (FC), the zone (Z) is merged with the conductive wire (FC). Device according to claim 1, characterized in that, when the cable to be stripped (C) comprises at least two conductive wires (FC1, FC2), the zone (Z1, Z2) corresponds to a zone of central circular section of the cable in which the conductive wires (FC1, FC2) are located. Device according to one of claims 1 to 3, characterized in that the end edge (42) of the cutting blade (4) is positioned projecting in said trajectory, to extend radially relative to the axis of rotation, offset relative to said axis of rotation, the offset corresponding to the radius of the zone (Z, Z1, Z2) of circular section in which the conductive wire(s) (FC, FC1, FC2) of the cable to be stripped are housed. Device according to one of claims 1 to 4, characterized in that the cutting tool (1) comprises a support block (11) mounted to be rotatably driven by a rotation drive axis (12), said support block having the shape of a cylindrical block of circular section in which are formed two grooves (13, 14) extending orthogonal to each other and whose depth extends over a large part of the height of the cylindrical block, defining at their intersection an empty volume (V) extending in the axis of rotation of the cutting tool (1). Device according to claim 5, characterized in that the cutting means comprise support means (3) for the cutting blade (4), said support means (3) comprising a through hole (31) of circular section, the support means (3) being mounted on the support block (11) with the through hole (31) aligned with the axis of rotation, one end of the through hole (31), called the inner end, opening into the empty volume (V) of the support block (11) and the other end of the through hole (31), called the outer end, opening towards the outside of said cutting tool (1) thus formed, constituting the engagement end of the end of the cable (C). Device according to one of claims 5 and 6, characterized in that the means for guiding the cutting tool (1) are constituted by the through hole (31) of the support means (3) of the cutting blade, associated with the empty volume (V) of the support block (11). Device according to one of claims 5 to 7, characterized in that the support means (3) have a general shape of a U-shaped bar whose branches (32) can be housed in one of the grooves (13, 14) of the support block (11). Device according to one of claims 1 to 8, characterized in that, in the through hole (31) of circular section is mounted a metal sheath (33) which comprises, mounted coaxially, means promoting the sliding in rotation of said rotary cutting tool around the cable C, such as a diamond-based sheath (34), a ball bearing. Device according to one of claims 1 to 9, characterized in that it comprises means for holding the cable (C) fixed in rotation and in translation such as clamping jaws (2) aligned with the cutting tool (1). Device according to one of claims 1 to 10, characterized in that it comprises means for positioning the end of the cable (C) such as a positioning stop (5). Device according to claim 11, characterized in that the positioning stop (5) is retractable using an actuating lever.

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