GB2537090A - Shroud tube manipulator - Google Patents

Abstract

A shroud tube manipulator raises a shroud tube in a straight line. The manipulator has a base; a main body 1202 movably mounted on the base; and a manipulator arm 1203 for holding a shroud tube. A straight line mechanism (figs 16 and 17) can connect the arm 1203 to the main body, so that the end of the arm can be raised or lowered in a substantially vertical straight line, e.g. parallel to an upright axis of rotation of the main body. The straight-line mechanism may have a hydraulic cylinder ram (1608, fig 16), linkage arm (1604, fig 16) and pins or rollers (1601, fig 16) sliding in guide channels (1602, fig 16). The manipulator may have three rotational bearings 1205, 1207, 1209, to pivot the arm 1203 into position. By raising the shroud tube 1211 vertically, horizontal and twisting forces can be minimised in connecting the shroud tube 1211 with a ladle collector nozzle on a slide gate.  A latch (2201, 2203 fig 22) on the end of the arm can connect with a moving part of a ladle slide gate (e.g. using a magnetic solenoid), to relieve lateral forces on the collector nozzle of the slide gate.

Description

SHROUD TUBE MANIPULATOR

Field of the Invention

[0001] The present invention relates to an apparatus and method for changing a tube on a ladle.

Background of the Invention

[0002] Continuous metal casting is conventionally carried out using a large ladle vessel which contains heated metal in a liquid state. The metal is poured from the ladle into a tundish, from which it is poured into one or more moulds to produce cast metal.

[0003] Referring to figure 1 herein, there is illustrated schematically a known conventional continuous casting apparatus. A furnace 1 is used to heat the metal up to a temperature at which the metal becomes liquid. The furnace has a furnace gate 2, through which molten metal 3 is poured into a ladle 4. The ladle comprises an open vessel having at its base, an outlet 5, which is closed off by a ladle gate 6. The ladle pours molten metal into a tundish 7 through a ladle shroud tube 8. Underneath the tundish are a series of moulds 9 -11, each of which receive molten metal from the tundish 7. Metal is poured into the moulds from the tundish via a set of tundish sliding gates 12 -14 respectively, each having a respective tube 15 -16 to guide the molten metal from the tundish gate into the mould.

[0004] Molten metal is heated in the furnace 1, and poured via furnace gate to enter the ladle 4. Molten metal is drained from the ladle into the tundish 7 via the ladle slide gate 6, and through the shroud tube 8. The lower end of the shroud tube 8 is immersed in liquid metal within the tundish 7. An upper end of the shroud tube 8 is retained to the slide gate 6. The shroud tube 8 shields the molten metal from the atmosphere, stopping it reacting with oxygen in the atmosphere, and thereby maintaining the chemistry of the molten metal.

[0005] Underneath the ladle the drain hole outlet 5 is fitted with the slide gate 6 which moves backwards and forwards horizontally to interrupt the flow of metal draining from the ladle into the tundish.

[0006] Typically, at the outlet of the ladle slide gate there is a relatively short cylindrical and /or conical refractory outlet tube through which molten liquid metal flows, known as a ladle collector nozzle. The ladle collector nozzle moves horizontally with the moving slide gate as the gate is opened or closed. The cylindrical tubular shroud or pipe 8 is fitted over the refractory ladle collector nozzle to guide the molten liquid into the tundish from which it can be poured into one or more moulds to make cast metal.

[0007] The shroud tube typically comprises a cylindrical hollow tube made of a refractory material, having inside diameter in the range 50 mm to 250 mm, a length of between 500 mm and 1800 mm and a wall thickness in the range 20mm to 50mm, although a wide range of diameters, lengths and wall thicknesses are possible. An upper end of the shroud tube fits over the refractory outlet tube and is held in place underneath the slide gate.

[0008] In use, an upper end of the shroud tube locates around the relatively shorter ladle collector nozzle under the slide gate, and a lower end of the shroud tube is located in the tundish. The shroud tube 8 comprises a hollow circular conical / cylindrical tube of refractory material. An upper end of the shroud tube comprises a thickened collar portion which fits over a refractory outlet tube at the base of the slide gate 6. It is important that there is a good fit between the upper end of the shroud tube and the ladle collector nozzle so as to avoid ingress of air and avoid changes to the chemistry of the molten metal.

[0009] Referring to figure 2 herein, there is illustrated schematically part of an installation for continuous casting in which a plurality of ladles are used to carry molten metal from a furnace to a plurality of movable tundishes, carried underneath the ladle on a set of tundish cars.

[0010] The installation comprises a furnace (not shown in figure 2); a ladle turret 200, capable of carrying two ladles 201, one of which is shown in figure 2, the ladle turret being rotatable allowing a full ladle to be swung round to a position in which the ladle is held above a tundish 202 carried on a tundish car 203, at which molten metal can be poured from the ladle into the tundish. A plurality of tundish cars deliver empty tundishes underneath the ladle, and molten metal is poured from the ladle into a tundish via a shroud tube. As metal fills the tundish, the lower end of the shroud tube may be immersed in liquid metal, and the shroud tube itself is at a high temperature, as liquid molten metal flows through it.

[0011] When a ladle is empty, the tundish turret rotates, so that a replacement ladle is positioned over the tundish, thereby enabling a continuous casting process.

[0012] When a new tundish is positioned underneath the ladle, a shroud tube needs to be connected to the underside of the ladle, to deliver molten metal from the slide gate under the ladle into the tundish. Fitting of the ladle shroud to the slide gate underneath the ladle is performed by a ladle shroud manipulator 204, which in this installation is carried on the tundish car. In the installation shown, each tundish car has its own ladle shroud manipulator 204.

[0013] Referring to figure 3 herein, there is illustrated schematically the continuous casting installation of figure 2 herein, with the ladle shroud manipulator shown in a burnout or park position, in which the ladle shroud is rotated away from the tundish, and away from the underside of the ladle.

[0014] As well as being connected and disconnected to the slide gate due to movement of the tundish, periodically the shroud tube needs to be replaced since it degrades or erodes with use. Changing the shroud tube is done conventionally using a known shroud tube manipulator machine.

[0015] Known shroud tube manipulator machines comprise a base and a rotatable platform onto which is mounted one end of an elongate mechanical arm. To fit a shroud tube to a ladle, with the arm swung away from the ladle to a safe location, a shroud tube is loaded onto an opposite far end of the arm. With the shroud fitted to the far end of the arm, the arm is swung around and placed under the slide gate, so that the shroud tube is located underneath the pouring outlet of the slide gate. The arm is manipulated upwardly, so that the upper end of the shroud tube fits around the downwardly projecting relatively short outlet tube. The arm needs to be moved both in a substantially horizontal arc to swing the end of the arm from the shroud loading location to a position under the ladle, and in an up and down movement to raise and lower the shroud to fit it under the ladle slide gate.

[0016] In general, the operation of known shroud tube manipulators can be fully or partially automated, with the arm being raised and lowered and the arm being swung or rotated either manually or with power assistance from electric motors, hydraulically or pneumatically or a by combination of these methods.

[0017] One example of a known shroud tube manipulator machine is disclosed in CN203495951U. Other known shroud tube manipulators include the fully automatic shroud tube manipulator manufactured by Mesolt GbR, and ladle shroud manipulators manufactured by CHL Systems. KR 10 2005 0006391 (Posco) discloses a device for fixing a shroud nozzle for continuous casting to a ladle collector nozzle.

[0018] Referring to figure 4 herein, there is illustrated schematically a second known shroud tube manipulator machine which is used for changing a shroud tube underneath a ladle and slide gate. The shroud tube manipulator comprises a base portion 400 which is rigidly attached to a stable platform, for example to the floor of a building adjacent a ladle, or in the installation shown in figures 2 and 3 herein, to a tundish car; a rotatable platform 401; an extended movable arm 402 mounted movably to the rotatable platform 401; a set of hydraulic rams 403 with associated hydraulics and control mechanism for raising or lowering the arm 402; and at a distal end of the arm 402, a circular collar 404 for holding a shroud tube.

[0019] In use, a shroud tube is loaded into the collar 404, by a human operator lifting the shroud tube and sliding it through the centre of the collar 404 until an upper flanged portion of the shroud tube rests upon the top of the collar.

The collar is pivoted to allow the operator to slide the shroud tube into the collar horizontally or at an incline.

[0020] To place the shroud tube underneath the ladle, an operator manipulates the arm by swinging the arm on the rotatable platform, and by raising or lowering the arm, to locate the shroud tube around the frusto-conical refractive material outlet stub underneath the slide gate. The shroud tube is held underneath the slide gate with an upward force provided by the shroud tube manipulator which provides an upthrust loading to close the upper part of the shroud tube around the shroud tube collector nozzle.

[0021] The shroud tube manipulator arm keeps the shroud in place as molten metal is outlet through the slide gate into the tundish. When the shroud tube needs to be removed, the ladle slide gate is closed, thereby shutting off the flow of molten metal out of the ladle, and the operator lowers the manipulator arm, releasing the shroud tube from the projecting frusto-conical outlet stub at the base of the slide gate. The operator then swings the arm around, by rotating the platform 401 on its base 400, so that the arm is swung to a position away from the ladle.

* ** * . * *** . * * * ** * * * * * 0* [0022] Figure 5 herein illustrates schematically a known hydraulically 5 operated slide gate valve used for opening and shutting off the flow of molten metal, for pouring molten metal from a ladle into a tundish. The slide gate valve comprises a base frame 500 containing an internal sliding gate frame 501 which can be slid horizontally with respect to the base frame 500; and an upper cover portion 502. In the upper cover portion 502 there is a recess shaped to fit a first 10 refractory plate. In the sliding gate frame 501, there is a second recess, shaped to fit a second refractory plate. The first and second refractory plates each have apertures therein, and are of an elongate shape such that as the two refractory plates are slid relative to each other, in a first position, the respective apertures lineup, thereby fully opening the slide gate, and in a second, closed position, the is apertures are not aligned, thereby fully closing the slide gate. In between the fully open and fully closed positions, the slide gate can adopt a continuously variable set of intermediate positions, in which the flow of metal controlled by throttling the slide gate, to provide the optimum rate of flow from the ladle into a tundish. Since the slide gate operates at high temperature, operation of the slide gate is automated. Sliding of the two refractory plates relative to each other is powered hydraulically, or electromechanically, with associated hydraulic or electromechanical controls.

[0023] Referring to figure 6 herein, there is illustrated schematically operation of a known slide gate valve underneath a ladle. For ease of understanding of the movement of the refractory plates relative to each other, the frame components of the slide gate shown in figure 5 herein are not shown in figure 6. An upper refractory plate 600 is located so that its aperture lines up with an outlet tube or nozzle 601 of the ladle. The outlet tube or nozzle 601 comprises a further refractory tube component. A lower refractory plate 602 is aligned such that its aperture aligns with the aperture of the first, the refractory plate 600 in a * ** * * * **** * * * first position, allowing metal to flow through the two refractory plates. At the outlet of the second, lower refractory plate 602 there is provided a ladle collector nozzle 603, being a short plant pot shaped cylindrical or frusto-conical shaped hollow tube, out of which molten metal may flow from the ladle.

[0024] The ladle collector nozzle 603 is located in the lower part of the slide gate, such that as the lower refractory plate slides relative to the upper refractory plate, the ladle collector nozzle moves with the lower refractory plate, and moves relative to the ladle. Shroud tube 604 is shown fitted over the ladle collector nozzle 603, the transferring molten metal from the outlet of the ladle, into a tundish.

[0025] Referring to figure 7, there is illustrated schematically the slide gate valve components of figure 6 herein, in a shut-off or closed position. In this position, the slide gate has slid the lower refractory plate 602 horizontally with respect to the upper refractory plate 600 such that the aperture of the upper refractory plate is now misaligned with the aperture in the lower refractory plate, and the slide gate is in a closed or shut-off position. Since the upper portion of the shroud tube 604 is fitted over the ladle collector nozzle 603, in order for the 20 shroud tube to remain vertical, the shroud tube must also move over a distance of between 0 and 400 mm, relative to the outlet of the ladle, corresponding to the horizontal movement of the slide gate.

[0026] Referring to figure 8 herein, there is illustrated schematically in cutaway view from one side a known connection between a known ladle collector nozzle 800, and a known shroud tube 801. The collector nozzle comprises a frusto-conically shaped nozzle, having a central passage through which molten metal can flow. An upper end 802 has an internally frusto-conical shaped surface. Between the frusto-conical shaped inner surface of the shroud tube and the frusto-conical shaped outer surface of the ladle collector nozzle 800, there is provided a gasket 803 to provide an airtight seal. In practice, in continuous * ** * * * * *** * * ** * * * *** * * * * is ** * * * * * * * -$-casting operations and inert gas, such as argon will be delivered to the general area around the ladle collector nozzle, to reduce the risk of metal coming into contact with the atmosphere and potentially ruining a batch of cast metal.

[0027] Referring to figure 9 herein, there is illustrated schematically a known refractory tubular frusto-conical shaped gasket as used in the known ladle collector nozzle joint / shroud tube joint shown in figure 8 herein.

[0028] Referring to figure 10 herein, there is shown in cutaway view a second known type of ladle collector nozzle 1000, together with the second known type of shroud tube 1001. In this type of nozzle, the cylindrical tubular nozzle has a flat end, which locates with a flat annular surface within a widened cup portion 1002 of the shroud tube. There is positioned between the end of the nozzle 1000 and the flat annular surface of the shroud tube, a flat annular gasket 1003, the purpose of which is to form an airtight seal between the collector nozzle and the ladle shroud.

[0029] Referring to figure 11 herein, there is shown in cutaway view a third type of ladle collector nozzle 1100 and shroud tube 1101, in which the nozzle 1100 has an outer frusto-conical shaped surface, terminating at its lower end in a flat annular nozzle surface, and the upper end of the shroud tube has a corresponding female frusto-conical surface having an annular flat shroud tube surface. The two flat annular surfaces form a butt joint, with an annular gasket 1102 place therebetween to exclude air.

[0030] The second and third types of ladle collector nozzle shown in figures 10 and eleven herein I used for relatively larger ladles, whereas the first type of ladle collector nozzle and shroud tube shown in figures 8 and nine herein are used for relatively smaller ladles.

[0031] In use, shroud tubes erode and need to be replaced after approximately 1 to 20 ladles. The relatively shorter ladle collector outlet nozzle underneath the slide gate, which is made of refractory material is changed less often, and cannot be changed during heated operation of the ladle due to the high temperatures involved.

[0032] The most important consideration in connecting the shroud tube to the ladle collector nozzle is to make sure that air is excluded from the joint, since the introduction of air into the molten metal flow changes the chemistry of the metal, and can lead to the cast metal being out of specification.

[0033] Further, because changing of the ladle collector nozzle can only be done when the ladle is drained of molten metal, and because the ladle collector nozzle is also a wearing or eroding component, to keep the continuous casting plant operating at maximum capacity, it is important to minimise the wear and stresses to which the ladle collector nozzle is exposed, in order to maximise the lifetime of the component and keep the continuous casting plant running at maximum efficiency.

[0034] Known shroud tube manipulators have arms which are raised or lowered in a circular arc relative to the upright platform portion, which means that on locating the upper end of the shroud tube over the ladle collector nozzle, the ladle collector nozzle can be exposed to forces in a horizontal direction, and/or in some cases twisting forces which act to bend the collector nozzle away from the main vertical axis. This increases the risk of the joint between the ladle collector nozzle and the shroud tube admitting air.

[0035] The ladle collector nozzle is vulnerable to cracking or fracture from horizontal or twisting forces when using conventional ladle shroud tube manipulators. This can lead to wear or damage to the downwardly projecting ladle collector nozzle or shroud tube.

[0036] Further, when the slide gate is operated, the ladle collector nozzle moves horizontally as the slide gate is moved. Since the shroud tube is fitted to the outlet stub, this means that the arm of the shroud tube manipulator must also move, in order to keep the upright shroud tube aligned with the outlet stub on the slide gate as the slide gate operates. Using conventional ladle shroud tube manipulator arms, the operator can manually push or pull the arm in a horizontal movement as the slide gate is operated, or the slide gate can drag the arm with it, since the arm is connected to the shroud tube, which is connected to the ladle collector nozzle. However, in either case this causes a strain on the ladle collector nozzle, with the risk of making an incorrect seal, and also increasing the risk of fatigue or damage to the ladle collector nozzle.

Summary of the Invention

[0037] According to one aspect of the present invention there is provided a shroud tube manipulator apparatus comprising: a main body; an arm mounted to said main body, said arm adapted for holding a shroud tube; characterised by comprising: means for raising or lowering said arm such that a distal end of said arm follows a straight line path.

[0038] In a specific embodiment disclosed herein, the main body is rotatable about a vertical axis of rotation, and a proximal end of the arm of the manipulator, is mounted in a housing on the main body, such that as the arm is raised or lowered the far end of the arm moves in an upright path in a straight line. The proximal end of the arm nearest the main body pivots about a substantially horizontal pivotal axis, and at the same time moves in a direction transverse to the main upright rotational axis of the main body. The proximal end of the arm moves in a translational motion with respect to the main vertical rotational axis of the main body. This allows a distal end of the arm to raise or lower in a straight line, preferably in a vertical straight line.

[0039] At the distal end of the arm, there is provided a pivotally mounted ring into which can be slid a shroud tube. As the distal end of the arm is raised or lowered, the pivoted mounting ring remains substantially horizontal, as long as the axis of rotation of the ring remains horizontal, thereby enabling the shroud tube to remain in a vertical orientation as the arm is raised or lowered.

[0040] Preferably the arm comprises a first arm portion and a second arm portion, wherein the first and second arm portions can be rotated with respect to each other along a main length axis of said arm.

[0041] Preferably, the arm itself comprises a first arm portion, and a second arm portion. First arm portion is mounted to the main body, and the second arm portion can be rotated relative to the first arm portion, allowing the far end of the arm to twist relative to the nearer first arm portion. This allows the annular mounting ring at the end of the arm to be tilted such that the pivotal axis of the ring can be tilted with respect to the horizontal, and can even be manoeuvred to a vertical position. A main plane of the circular opening of the ring can be moved between a horizontal and a vertical position, and at a range of inclines between those positions. This allows the arm to tilt the shroud tube as the arm is swung around on the rotational main body, to enable the shroud to pass over obstructions or obstacles as the shroud tube is moved from an area away from the ladle where a shroud tube can be loaded onto the arm, and a position underneath a ladle slide gate.

[0042] There are provided a set of mechanical linkages connecting the arm to the main body which allow distal end of the arm to move in a straight line without the need to physically move the location or position of the main body. The linkages allow an operator to raise or lower the arm substantially vertically and in line with the main central axis of a ladle collector nozzle, thereby avoiding any skew forces or horizontal forces on the ladle collector nozzle.

[0043] The invention includes a method of engaging an arm of a shroud tube manipulator apparatus to a slide gate of a ladle, using an engagement mechanism, comprising a first engagement part fitted to a sliding part of a slide gate and a second engagement portion attached to the distal end of the arm of the manipulator apparatus, in the region of the end ring or collar of the manipulator arm. As the arm is moved near the underside of the slide gate, the end of the arm is connected to the moving part of the slide gate by engaging the first and second engaging portions. Any movement of the slide gate pushes or pulls the end of the manipulator arm, thereby relieving any stress on the joint between the upper end of the shroud and the ladle collector nozzle. When the shroud is to be removed, the first and second engagement portions are disengaged, thereby allowing the manipulator arm to move freely with respect to the slide gate.

[0044] Various embodiment engagement mechanisms are provided, including mechanically connected engagement portions, or magnetically attachable engagement portions.

[0045] In the case of a mechanically connected engagement mechanism, the engagement parts may engage when the arm is moved in an upright direction relative to the slide gate, that is, when the shroud tube is abutted to the ladle collector nozzle, and to disengage automatically when the shroud tube is lowered relative to the ladle collector nozzle.

[0046] One advantage of embodiments of the invention described herein is that by providing a manipulator arm which moves in a straight line, movement of the shroud tube relative to the ladle collector nozzle is made in an orientation whereby any gaskets or seals between the upper end of the shroud tube and the lower part of the ladle collector nozzle are correctly aligned, and when the manipulator arm urges upwardly to apply force to the ladle collector nozzle, the force is applied evenly and in a direction axial to a main length direction of the ladle collector nozzle, and in a direction axially to a main direction length of the shroud tube. This may provide an improved airtight seal between a shroud tube and a collector nozzle of a ladle slide gate, thereby reducing the risk of oxygen reacting with the molten metal stream flowing from the ladle to a tundish. There is therefore less risk of a wasted batch of metal being out of specification, because the chemistry has changed due to reaction with oxygen.

[0047] A further advantage of embodiments shown herein is to provide a system in which the upper part of a ladle shroud tube can be better aligned with a collector nozzle of a ladle. Better alignment assists better seal, and also reduces the stresses on refractory components caused by misalignment, which can lead to greater reliability.

[0048] In the embodiment disclosed herein, a vertical lift of a shroud tube underneath a ladle collector nozzle allows a good but joint seal between the shroud tube and a collector nozzle of a ladle to a butt joint [0049] Other aspects of the invention are as recited in the claims herein

Brief Description of the Drawings

[0050] For a better understanding of the invention and to show how the same may be carried into effect, there will now be described by way of example only, specific embodiments, methods and processes according to the present invention with reference to the accompanying drawings in which: Figure 1 herein shows a known continuous casting plant apparatus comprising a furnace; a ladle; a ladle slide gate; a tundish, and one or a plurality of moulds; Figure 2 herein shows a known ladle installation, from pouring metal into a tundish carried on a tundish car, where a ladle shroud manipulator is located on the tundish car; Figure 3 herein shows the known ladle installation of figure 2, with a ladle shroud and a ladle shroud manipulator positioned in a burnout/park position; Figure 4 herein shows a known shroud tube manipulator apparatus for holding a shroud tube underneath a slide gate of a ladle, so that metal can be transferred between a ladle and a tundish; Figure 5 herein shows schematically a known hydraulically operated ladle slide gate mechanism suitable for use in a continuous casting plant; Figure 6 herein shows schematically operation of one type of known hydraulically operated ladle slide gate mechanism in an open position, where flow of molten metal occurs; Figure 7 herein illustrates schematically operation of the known slide gate mechanism of figure 4 herein, in a closed position where flow of metal is shut off; Figure 8 herein shows in cutaway view, connection between a known ladle collector nozzle and the upper end of a first type of known ladle shroud; Figure 9 herein shows a known refractory gasket used in the assembly of figure 8 herein; Figure 10 herein shows in cutaway view a connection between a second type of known ladle collector nozzle, and a second type of known ladle shroud; Figure 11 herein shows in cutaway view a connection between a third type of known ladle collector nozzle, and a third type of known ladle shroud; Figure 12 herein illustrates schematically a novel ladle shroud manipulator according to an embodiment of the present invention; Figure 13 herein illustrates schematically in plan view the shroud tube manipulator of figure 12, showing the range of operation of the end of its arm; Figure 14 herein illustrates schematically in view from one side, a main body and manipulator arm of the shroud manipulator machine, with the arm in a lowered position; Figure 15 herein illustrates schematically in view from one side the main body and manipulator arm of the shroud manipulator machine with the arm in a raised position, as would be used for engaging the upper end of a shroud tube with a projecting ladle collector nozzle underneath the ladle slide gate; Figure 16 herein illustrates schematically in view from one side connection of the manipulator arm to the main body using a straight line mechanism which, as the arm is raised or lowered, causes the distal end of the arm to follow a straight upward/downward path, rather than a curved path, in this case with the arm in a lowered position; Figure 17 herein illustrates schematically in view from one side connection between the arm and the main body, with the arm in a raised position, showing operation of the straight line mechanism in the raised position; Figure 18 herein illustrates schematically in perspective view, the base components showing the swivelling linkages on which the main body is mounted, and a further view of the straight line mechanism connecting the manipulator arm to the main body; Figure 19 herein illustrates schematically in perspective view, a distal end of the shroud tube arm, showing a pivoted tubular collar for holding a shroud tube; Figure 20 herein illustrates schematically in perspective view a stage of operation of the manipulator arm for fitting a shroud tube to a ladle collector nozzle underneath the slide gate of a ladle, with the slide gate in a closed position; Figure 21 herein illustrates schematically in perspective view, a further stage of operation of the manipulator arm, wherein the manipulator arm has urged the shroud tube over the ladle collector nozzle, fitting the shroud tube underneath the slide gate with the slide gate in a closed position, in preparation for opening of the slide gate; Figure 22 illustrates schematically a second embodiment shroud tube manipulator device, comprising the first embodiment shroud tube manipulator, fitted with an additional locking mechanism at a distal end of the manipulator arm to lock the arm to the underside of a slide gate when the manipulator arm is in a raised position; and Figure 23 illustrates schematically operation of the second embodiment shroud tube manipulator device including the locking mechanism, wherein the manipulator arm is moved in a horizontal direction as the powered slide gate moves between its open and closed positions.

Detailed Description of the Embodiments

[0051] There will now be described by way of example a specific mode contemplated by the inventors. In the following description numerous specific details are set forth in order to provide a thorough understanding. It will be apparent however, to one skilled in the art, that the present invention may be practiced without limitation to these specific details. In other instances, well known methods and structures have not been described in detail so as not to unnecessarily obscure the description.

[0052] In this specification the term "furnace " is used to mean any heated vessel used to heat metal to liquid state and includes converters such as Bessemer converters, electric arc furnaces, and any like furnaces having a heated vessel with a refractory lining.

[0053] In this specification, the term "ladle" is used to mean a holding vessel used to transport or contain molten metal.

[0054] Referring to figure 12 herein, there is illustrated schematically in perspective view a shroud manipulator apparatus according to a specific embodiment of the present invention.

[0055] The shroud manipulator 1200 comprises a base 1201 comprising a plurality of rigid mounting arms which are pivotally connected to each other; a movable main body 1202 mounted to the base 1201; and a manipulator arm 1203 having a proximal end mounted to the main body 1202; and a set of controls 1204 operable by a human operator, for raising or lowering the manipulator arm 1203 under powered operation.

[0056] The base 1201 comprises a first mounting arm 1204, a first end of which is mounted on a first rotational slew ring mounting 1205. First end of the first mounting arm 1204 is rigidly mounted to an upper part of the first slew ring mounting 1205, and the lower part of the ring mounting 1205 is rigidly mounted to a stable solid base, such as a concrete floor, a gantry, or other stable platform or location adjacent a ladle of a continuous casting plant. A second mounting arm 1206 has its first end connected to a second end of the first mounting arm 1204 via a second slew ring mounting 1207. A lower part of the second slew ring mounting 1207 is rigidly attached to an upper part of the first mounting arm 1204, and an upper part of the second slew ring mounting 1207 is rigidly connected to a lower part of the second mounting arm 1206, so that the first mounting arm can rotate 360° around the first slew ring mounting 1205, and the second mounting arm 1206 can rotate 360° about the second end of the first mounting arm 1204, allowing the second end of the second mounting 606 to be positioned anywhere within a first horizontal circle surrounding the main central axis of the first mounting ring 1205.

[0057] The main body 1202 is mounted on a second end of the second mounting arm 1206 by a third slew ring mounting 1209. A lower ring of the third ring mounting 1209 is mounted on an upper part of the second end of the second arm 1206, and an upper ring of the third slew ring mounting 1209 is rigidly connected to the underside of the main body 1202, so that the main body can rotate 360° around the second end of the second arm 1206. Since the manipulator arm 1203 is mounted to the main body 1202, the distal end of the manipulator arm can move horizontally anywhere within an annular region centred about a main central axis of the first slew ring mounting 1205. The shroud tube manipulator is installed in use, such that a ladle slide gate, and a safe area away from the ladle where shroud tubes can be fitted, both reside within the horizontal annular region of operation of the distal end of the manipulator arm.

[0058] The main body 1202 comprises first and second upright side plates 1210, spaced apart from each other and rigidly joined together to form a hollow box or cage structure into which the proximal end of the manipulator arm 1203 is mounted. The proximal end of the manipulator arm is mounted to the main body by a powered mechanical straight line mechanism. A range of suitable straight line mechanisms are known in the prior art in various forms, and a common feature of such mechanisms is that they permit movement of a lever (in this case represented by the manipulator arm 1203), such that a far end of the lever moves in a straight line, rather than in a circular arc as is the case with a conventional pivoted lever.

[0059] In other versions of the shroud tube manipulator embodiment, there may be fewer arms or pivots comprising the base 1201.

[0060] Not shown specifically in figure 12, but also provided is a control cabinet comprising an electrical power source and control electronics and/ hydraulic power controls for controlling the hydraulic ram to raise or lower the manipulator arm relative to the main body; and the controls, by which the human operator may raise or lower the manipulator arm. Either electric, hydraulic, pneumatic or manually operated controls, or a combination of such controls may be used.

[0061] A shroud tube 1211 is held at the end of the arm 1203, by a collar 1212. An upper part of the shroud tube has a relatively larger diameter section 1213, which rests in the collar 1212 of the shroud tube manipulator. Further, the arm 1203 may also have a tube for delivering an inert gas (for example argon) to blow into the region around the end of the arm 1203 and the joint between the ladle nozzle and the shroud tube.

[0062] Referring to figure 13 herein, there is illustrated schematically in plan view, the shroud manipulator of figure 12 herein. The main body section 1202 is rotatable around the third ring mounting 1209. The third ring mounting 1209 can be positioned anywhere within a first circular area 1300, due to the scissor like arrangement between the first and second mounting 1204, 1206 respectively. The distal end of arm 1203 can be moved horizontally anywhere within an annular area bounded by an inner circle 1301 and an outer circle 1302. With the main body 1202 stationary, and the circular collar at the end of the arm remaining horizontal, a central axis through the collar remains stationary in plan view as the arm is raised or lowered, due to the straight line mounting mechanism between the proximal end of the arm and the main body 1202.

[0063] Referring to figure 14 herein, there is illustrated schematically, in view from one side the main body 1202 and arm 1203 with the end of the arm in a lowered position. In this position, the horizontal pivotal axis 1400 of the shroud tube holding collar is a distance x from the vertical axis of rotation 1401 of the main body 1202.

[0064] Referring to figure 15 herein, there is illustrated schematically in view from one side, the main body 1202 and arm 1203 in a raised position. In this position, the horizontal pivotal axis 1400 of the shroud tube holding collar remains a fixed horizontal distance x from the main vertical axis of rotation of the main body 1202.

[0065] At all intermediate positions between the lower most position and uppermost position of the arm, the distal end of the arm follows a straight line vertical path, parallel to the vertical rotational axis of the main body about the third ring mounting 1209. Since the arm 1203 is of invariant length, the proximal end of the mounting arm 1203 moves towards and away from the vertical rotational axis 1401 of the main body, and moves further into and out of the main body 1202.

Controls [0066] The main body 1202 may be manually maneuvered without the need for powered operation, by swinging the main body on the mounting arms 1204, 1206 and rotational bearing 1205, 1207, 1209. At the rear of the main body, there may be provided a large grab bar to assist human to manually pull the main body to the required location, and to rotate the main body on the third rotational mounting 1209 to the required positions.

[0067] In some embodiments all movements may be power assisted if required.

[0068] Operation of the raising and lowering of the arm is effected by powered operation, in the best mode being hydraulic controls to operate a double action hydraulic ram 1608 (see figure 16) which provides powered contraction or expansion for pushing or pulling a linkage arm to operate the straight line mechanism to raise or lower the arm. Suitable electromechanical and/or hydraulic and pneumatic power supplies control valves or actuators are provided in a separate cabinet adjacent to the shroud tube manipulator, with communication between the control cabinet and the hydraulic arm being via a set of umbilical cables, or in some variations, by wireless or remote control. There may be provided on the main body a manually operated lever for raising or lowering the arm.

[0069] Similarly, rotation of the distal end of the arm is powered using either hydraulic or electromechanical motors, with power supplies and controls being provided in the remote control cabinet, and a lever for operating the distal end of the arm to rotate clockwise or anticlockwise as appropriate being provided on the main body, for the operator to manipulate.

Straight Line Mechanism [0070] Various types of known straight line mechanism for mounting the distal end of the arm to the main body can be used.

[0071] Referring to figure 16 herein, there is illustrated schematically in view from one side, the main body 1202, and the proximal end of the arm 1203 with the arm in a lowered position. The straight line mechanism comprises a first pivotal mounting 1600 pivoting about a first horizontal pivotal axis, about which the proximal end of the mounting arm pivots; a pair of horizontally projecting pins or rollers 1601 mounted on the proximal end of the arm and located on a first horizontal sliding axis which can slide relative to the main body, the first horizontal sliding axis being spaced apart from the first horizontal pivotal axis, and the first pivotal horizontal axis being located between the first horizontal sliding axis and the distal end of the arm; a pair of horizontal sliding channels 1602 providing a pair of guide channels for the pins or rollers 1601 enabling the end of the arm to move horizontally away from and towards a main vertical axis of rotation of the main body; a second horizontal pivotal mounting 1603 mounted at a second end of the main body 1202 and pivoting about a second horizontal pivotal axis; a first linkage arm 1604 connecting the manipulator arm 1203 to the main body 1202 between the first pivotal mounting 1600 and the second horizontal pivotal mounting 1603, the first linkage arm 1604 having a third horizontal pivotal mounting 1605 movable about a third pivotal axis, such that the third pivotal mounting can follow a path which rotates around the second horizontal pivotal mounting 1603 as the linkage arm rotates about the second pivotal mounting 1603; a fourth horizontal pivotal mounting 1606 located on a bracket 1607 rigidly attached to the main body 1202 and movable about a fourth pivotal axis; and a hydraulic cylinder ram 1608 having a first end connected to the fourth pivotal point 1606 and a second end connected to the third pivotal mounting 1605, the hydraulic ram being a double action hydraulic ram capable of pulling and pushing, so as to draw the third pivotal axis 1605 closer to or away from the fourth pivotal axis 1606.

[0072] As shown in figure 16, with the arm in the lowered position, the third pivotal axis 1605 is approximately in the region above the first pivotal axis 1600, and the linkage arm 1604 is approximately upright.

[0073] As shown in figure 17 herein, with the arm in the raised position, the hydraulic ram 1608 is extended, pushing the third pivotal axis 1605 away from the fourth pivotal axis 1606, and causing the lower end of the linkage arm 1604 to raise the arm at the first pivot point 1600, whilst the rear end of the arm, the horizontal position of which is restricted by the horizontal sliding guides remains at the same level.

[0074] As the arm moves from a lowered position to a raised position, the pins/rollers 1601 move backwards in the guide slots 1602 as the arm passes through the horizontal position. The proximal end of the arm follows a horizontal straight line path in the guide slots 1602, whereas the distal end of the arm follows a vertical straight line path.

[0075] Referring to figure 18 herein, there is illustrated schematically in perspective view, the main body 1202 including the straight line mechanism, with associated ram 1608 and hydraulic pipes for operating the ram. In order to manipulate the main body to swing the main body and arm on the sets of slew ring mountings [0076] In use, the shroud tube manipulator is located in an area adjacent a continuous casting ladle or other metal casting apparatus, so that the arm can reach underneath a slide gate, and also can be swung to a location away from the slide gate, where it is safe for a human operator to load a shroud tube onto the end of the arm, and/or to a location where the shroud tube can be cleaned, for example under an oxygen shower.

[0077] The main body is mounted at a height such that in a lowered position, the distal end of the arm can be placed on the floor or a few tens of centimetres above the floor, where a shroud can be loaded into the far end of the arm, and also such that when the arm is swung underneath the ladle, the distal end of the arm can be located under the ladle slide gate, both of these locations being within the range of movement of the distal end of the arm.

[0078] The shroud tube manipulator can be operated by either one or more human operators. An operator standing adjacent the main body can manually swing the main body on the scissor like arrangement comprising the plurality of base arms, such that the distal, far end of the arm is positioned in an area away from the hot ladle, where an operator, can lift a shroud tube a few tens of centimetres off the ground and insert a lower end of the shroud tube through the collar ring mounting at the end of the arm. The operator raises the arm, such that, with the shroud tube upright, the mounting ring / collar slides up the shroud tube until it reaches the larger diameter shroud tube collar portion at the upper end of the shroud tube. The operator may use a crane or other mechanical handling equipment, to assist in loading the shroud tube into the collar mounting at the end of the arm.

[0079] The operator swings the main body around, either manually or with power assistance, if necessary operating the powered arm-twisting feature to tilt the shroud towards a horizontal position, in order that the shroud can be maneuvered around any intervening obstacles until the far end of the arm is underneath the slide gate of the ladle. The arm is rotated or manipulated such that the shroud is substantially vertical. With the main body holding the arm in position under the slide gate, and without moving the overall location of the main body during raising or lowering, the operator can raise the arm using the hydraulic and/electromechanical controls so that the upper end of the shroud tube slides over the ladle collector nozzle in a straight line movement along the main axis of the ladle collector nozzle.

[0080] The slide gate is opened, allowing metal to flow through the shroud.

In some types of slide gate this involves the shroud tube being displaced as the ladle collector nozzle is attached to the sliding refractory plate. Since the end of the manipulator arm hold the shroud tube, this also involves moving the arm so that the distal end moves across horizontally, This horizontal movement is accommodated by the scissor like base moving the main body.

[0081] When the shroud tube has been used for predetermined time, or when the operator judges that the shroud tube needs to be replaced, the slide gate is closed, shutting off the flow of metal through the shroud tube. Since the ladle collector nozzle moves with the lower part of the slide gate, the distal end of the manipulator arm is pulled or pushed a short distance of perhaps a few tens of centimeters, with the closing slide gate. Once the slide gate is closed, the operator then lowers the arm disengaging the upper end of the shroud tube from the ladle collector nozzle. The shroud tube can then be moved away from the ladle by swinging the arm towards the loading/unloading location, or cleaning station.

[0082] At the loading/unloading location, the manipulator arm can be rotated/twisted about its own length axis, thereby tipping the still hot used shroud tube out of the mounting ring. The arm can be twisted so as to tip the used shroud tube out of the collar at the end of the arm, or an operative may knock the 2 0 hot shroud tube with a hammer to release it.

[0083] The distal end of the arm is lowered to a position near the floor of the loading/unloading area where a human operator can manually load, or load with automated assistance, a new shroud tube into the end of the manipulator arm, for a repeat of the operation [0084] Referring to figure 19 herein, there is illustrated schematically in perspective view the distal end of the manipulator arm. The end of the arm comprises a ring or collar 1900 for holding a shroud tube. The collar 1900 is pivotally mounted within a frame 1901 at the end of the arm, so that the annular circular cylindrical collar can swing about a single axis. As the arm is raised or lowered, with the shroud fitted into the collar 1900, the shroud maintains a substantially vertical attitude, due to gravity. As shown in figure 12 herein, at its upper end, the shroud has an external projecting upper part 1213 of relatively greater diameter, which prevents the shroud tube from sliding through the collar 1900 at the end of the arm. As the distal end of the arm is rotatable, relative to its own main length axis, the collar 1900 can be tilted, so that when the shroud tube is fitted into the collar, the shroud tube can be placed in a horizontal attitude.

[0085] In the embodiment shown, there is provided a collar or ring having a single horizontal axis of pivot. However in other embodiments, the collar or ring may be provided with a gimbal mounting, so there are two transverse axes of pivot.

[0086] Referring to figure 20 herein, there is illustrated schematically the distal end of the manipulator arm, fitted with a shroud tube 2000 and about to locate the shroud tube over a ladle collector nozzle projecting downwardly from a slide gate 2001 underneath a ladle. The shroud tube 2000 hangs substantially vertically underneath the ladle collector nozzle 2002. From this position, the manipulator arm can be raised in a straight line vertically so that the shroud tube is fitted over the ladle collector nozzle 2002, and is held there in place with an upward force exerted by the shroud tube manipulator arm, thereby urging the upper end of the shroud tube to the end of the ladle collector nozzle, to ensure a tight fit.

[0087] Referring to figure 21 herein, there is illustrated schematically the shroud tube 2000 held in place around the ladle collector nozzle underneath the slide gate. Movement of the manipulator arm between the positions shown in figures 20 and 21 is by a straight line vertical movement of the end of the manipulator arm as described hereinbefore.

Latching Mechanism [0088] Referring to figure 22 herein, there is illustrated schematically in partial cutaway view a second embodiment shroud tube manipulator, comprising a modification to the distal end of the manipulator arm, with a corresponding modification to the underneath of the slide gate, to enable the manipulator arm to be locked to the underside of the slide gate, so that sliding operation of the slide gate automatically urges the manipulator arm horizontally, as the slide gate moves, thereby relieving stress on the ladle collector nozzle.

[0089] The manipulator is substantially as described herein with respect to figures 12 to 21 herein before, with the exception of the modification now described. At the distal end of the manipulator arm 2200, there is provided an upwardly projecting engagement means 2201, in this case in the form of a peg or stud. On the underside of the slide gate 2202, there is provided a corresponding recess or channel 2203 into which the peg or stud 2201 locates when the manipulator arm is in the raised position, when the shroud tube 2204 is raised such that it engages the ladle collector nozzle 2205. Keeping the manipulator arm in the raised position urges the upper end of the shroud tube 2204 into engagement with the projecting ladle collector nozzle 2205. At the same time, the upwardly projecting peg or stud 2201 engages with the recessed component 2203 such that any horizontal movement of the lower part of the slide gate will push the peg / stud 2201 horizontally, thereby pushing and/or pulling the manipulator arm horizontally.

[0090] Since the manipulator arm is mounted on a movable main body as herein before described, any horizontal movement of the manipulator arm will be accommodated by movement of the main body. At the same time, because the strain of moving the manipulator arm is borne by the projection 2203 on the underside of the slide gate, the horizontal shear force which would otherwise occur between the shroud tube 2204 and the ladle collector nozzle 2205 is relieved.

[0091] Referring to figure 23 herein, there is illustrated schematically the slide gate arrangement of figure 22, with the slide gate in an open position for pouring molten metal through the shroud. The lower part 2206 of the slide gate has moved horizontally relative to the upper part 2207 which is fixed to the underside of the ladle, causing the distal end of the arm to be pushed backwards towards the manipulator main body.

[0092] When the lower part of the slide gate 2206 is powered to the closed position as shown in figure 22, the distal end of the arm 2200 is pulled horizontally in the opposite direction, pulling the main body with it, under power of the powered slide gate 2206. Since the arm is pulled by the locking mechanism comprising the upwardly projecting peg /stud 2201 and the engagement member 2203, horizontal forces are routed through the locking means, rather than through the upper end of the shroud 2204 and the ladle collector nozzle 2205.

[0093] Variations on the upper and lower engagement member 2201, 2203 respectively are possible. Instead of a stud and recess arrangement, there may be provided a powered opening/closing claw arrangement which engages around a projecting loop on the underside of the slide gate. However in all cases, the purpose of the locking mechanism is to lock the distal end of the arm to the lower sliding plate of the slide gate so that powered operation of the slide gate acts on the locking means to move the arm backwards and forwards without placing any additional stresses on the ladle collector nozzle 2205.

[0094] In a further embodiment, the latching mechanism shown in figures 22 and 23 herein, may use magnetic plates, and/or a metal plate and solenoid arrangement. In this case, a magnetic solenoid on the end of the manipulator arm may attach magnetically to a magnetic metal plate on the movable underside part of the slide gate, so that the moving slide gate pushes and/pulls the end of the manipulator arm when the solenoid engages and is magnetically attracted to the plate of magnetic material.

[0095] When the shroud tube is moved underneath the ladle collector nozzle, so that the butt joint between the shroud tube and the ladle collector nozzle is engaged, the engagement mechanism can be activated so as to effectively lock the end of the manipulator arm to the sliding portion of the slide gate. When the shroud tube is to be removed from the ladle collector nozzle, the first and second engagement portions are disengaged, so that the manipulator arm can move independently of any movement of the slide gate.

Claims (17)

1. Claims A shroud tube manipulator apparatus comprising: a base; a main body movably mounted on said base; an arm mounted to said main body, said arm adapted for holding a shroud tube; characterised by comprising: means for raising or lowering said arm such that a distal end of said arm follows a straight line path.
2. 2. The shroud tube manipulator apparatus as claimed in claim 1, wherein said means for raising or lowering said arm comprises a set of mechanical linkages linking a proximal end of said arm to said main body to form a mechanical straight-line mechanism.
3. 3. The shroud tube manipulator apparatus as claimed in claim 1, adapted such that said distal end of said arm follows a substantially vertical straight line as said arm is raised or lowered.
4. 4. The shroud tube manipulator apparatus as claimed in claim 1 or 2, wherein a distal end of said arm follows a path which is parallel to an upright axis of rotation of said main body.
5. 5. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said arm is connected to said main body by a mounting mechanism which permits a proximal end of said arm to move in a direction transverse to a main upright axis of said main body, so that as said arm is raised or lowered, a distal end of said arm follows a substantially vertical path of movement.
6. 6. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said means for raising or lowering said arm comprises a straight line mechanism connecting a proximal end of said arm to said main body, which causes a distal end of said arm to move up or down in a straight line.
7. 7. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said means for raising or lowering said arm com prises: a first linkage arm having a first end pivotally connected to said manipulator arm, and a second end pivotally connected to a ram; said first linkage arm having a third pivotal connection, connecting said 2 o linkage arm to said main body; and a guide means for guiding an end of said arm in a substantially horizontal direction relative to said main body.
8. 8. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said base comprises: a first rotational mounting having a lower part adapted to be rigidly mounted on a rigid mounting; a first mounting arm rotationally mounted on an upper part of said first rotational mounting; a second rotational mounting having a lower part adapted to be rigidly mounted to a second end of said first mounting arm; a second mounting arm having a first end rigidly mounted to an upper part of said second rotational mounting so that said second mounting arm can rotate relative to said second end of said first mounting arm; and a third rotational mounting rigidly mounted to a second end of said second mounting arm.
9. 9. An engagement mechanism for engaging an arm of a shroud tube manipulator apparatus to a slide gate said mechanism, said mechanism characterised by comprising: a first engagement portion for fitting to a sliding part of a slide gate; a second engagement portion adapted for attaching to an arm of a shroud tube manipulator apparatus; wherein said first and second engagement portions are adapted to engage with each other when urged together in a first direction; and when said first and second engagement portions are engaged with each other, movement of said first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and said first and second engagement portions are adapted to disengage with each other when urged in a third direction, opposite to said first direction.
10. 10. The engagement mechanism as claimed in claim 9, wherein said first and second engagement portions are adapted to automatically engage with each other when urged together in a first direction; and when said first and second engagement portions are engaged with each other, movement of said first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and said first and second engagement portions are adapted to automatically disengage with each other when urged in a third direction, opposite to said first direction.
11. 11. The engagement mechanism as claimed in claim 9 or 10, wherein said first and second engagement portions engage which it with each other when they are moved towards each other in a vertical direction and disengage with each other when they are moved away from each other in said vertical direction.
12. 12. The engagement mechanism as claimed in any one of claims 9 to 11, wherein: said first engagement portion comprises a recess for accepting said second engagement portion; and said second engagement portion comprises a protrusion projecting upwardly from said manipulator arm.
13. 13. The engagement mechanism claimed in any one of claims 9 to 11, wherein said first engagement portion comprises a controllable magnet; and said second engagement portion comprises a magnetic material; wherein in use, activation of said magnet causes said magnet to engage said magnetic material, thereby engaging said first and second engagement portions; and de-activation of said magnet causes said magnet to disengage said magnetic material, thereby disengaging for said first and second engagement portions.
14. 14. The engagement mechanism as claimed in any one of claims 9 to 12, wherein one of said first and/or second engagement portion comprises a magnetic solenoid; and the other one of the first and/or second engagement portions comprises a magnetic material.
15. 15. The engagement mechanism as claimed in any one of claims 9 to 14, comprising means for automatically latching a distal end of said arm to a movable gate of a slide gate valve, such that as said slide gate valve travels horizontally, said distal end of said arm is moved by said slide gate valve.
16. 16. A method of engaging an arm of a shroud tube manipulator apparatus to a slide gate of a ladle, using an engagement mechanism, said 30 engagement mechanism characterised by comprising: a first engagement portion for fitting to a sliding pad of a slide gate; a second engagement portion adapted for attaching to an arm of a shroud tube manipulator apparatus; said method comprising: engaging said first and second engagement portions with each other; operating said slide gate such that movement of said slide gate causes said first engagement portion to automatically urge second engagement portion, thereby automatically urging said manipulator arm.first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and said first and second engagement portions are adapted to disengage with each other when urged in a third direction, opposite to said first direction.
17. 17. The method as claimed in claim 16, further comprising disengaging said first and second engagement portions from each other when disengaging said shroud tube from a ladle collector nozzle.Amendments to the Claims have been filed as follows Claims A shroud tube manipulator apparatus comprising: a base; a main body movably mounted on said base; a lever arm pivotally mounted to said main body, said arm adapted for holding a shroud tube; characterised by comprising: a straight line mechanism for raising or lowering said lever arm such that a distal end of said arm follows a straight line path; wherein said lever arm pivots about a substantially horizontal pivotal axis located at O said proximal end of said arm, such that said arm moves in a translational movement with respect to said main body; thereby allowing said distal end of the arm to raise or lower in a straight line.2. The shroud tube manipulator apparatus as claimed in claim 1, wherein said straight line mechanism for raising or lowering said arm comprises a set of mechanical linkages linking a proximal end of said arm to said main body to form a mechanical straight-line mechanism.3. The shroud tube manipulator apparatus as claimed in claim 1, adapted such that said distal end of said arm follows a substantially vertical straight line as said arm is raised or lowered.4. The shroud tube manipulator apparatus as claimed in claim 1 or 2, wherein a distal end of said arm follows a path which is parallel to an upright axis of rotation of said main body.5. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said arm is connected to said main body by a mounting mechanism which permits a proximal end of said arm to move in a direction transverse to a main upright axis of said main body, so that as said arm is raised or lowered, a distal end of said arm follows a substantially vertical path of movement.6. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said straight line mechanism connects a proximal ICS end of said arm to said main body, which causes a distal end of said arm to move up or down in a straight line.7. The shroud tube manipulator apparatus as claimed in any one of cr) the preceding claims, wherein said straight line mechanism for raising or loweringCDsaid arm comprises: a first linkage arm having a first end pivotally connected to said arm, and a second end pivotally connected to a ram; said first linkage arm having a third pivotal connection, connecting said linkage arm to said main body; and a guide means for guiding an end of said arm in a substantially horizontal direction relative to said main body.8. The shroud tube manipulator apparatus as claimed in any one of the preceding claims, wherein said base comprises: a first rotational mounting having a lower part adapted to be rigidly mounted on a rigid mounting; a first mounting arm rotationally mounted on an upper part of said first rotational mounting; a second rotational mounting having a lower part adapted to be rigidly mounted to a second end of said first mounting arm; a second mounting arm having a first end rigidly mounted to an upper part of said second rotational mounting so that said second mounting arm can rotate relative to said second end of said first mounting arm; and a third rotational mounting rigidly mounted to a second end of said second mounting arm.cr) 9. The shroud tube manipulator as claimed in any one of theCDpreceding claims comprising an engagement mechanism for engaging said arm of said shroud tube manipulator apparatus to a slide gate, said engagement mechanism characterised by comprising: a first engagement portion for fitting to a sliding part of a slide gate; a second engagement portion adapted for attaching to an arm of a shroud tube manipulator apparatus; wherein said first and second engagement portions comprise engagement means adapted to engage with each other when urged together in a first direction; and when said first and second engagement portions are engaged with each other, movement of said first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and said first and second engagement portions are adapted to disengage with each other when urged in a third direction, opposite to said first direction.10. The shroud tube manipulator as claimed in claim 9, wherein said first and second engagement portions are adapted to automatically engage with each other when urged together in a first direction; and L.0 when said first and second engagement portions are engaged with each other, movement of said first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and O said first and second engagement portions are adapted to automatically disengage with each other when urged in a third direction, opposite to said first direction.11. The shroud tube manipulator as claimed in claim 9 or 10, wherein said first and second engagement portions engage with each other when they are moved towards each other in a vertical direction and disengage with each other when they are moved away from each other in said vertical direction.12. The shroud tube manipulator as claimed in any one of claims 9 to 11, wherein: said first engagement portion comprises a recess for accepting said second engagement portion; and said second engagement portion comprises a protrusion projecting upwardly from said manipulator arm.13. The shroud tube manipulator as claimed in any one of claims 9 to 11, wherein 1 o said first engagement portion comprises a controllable magnet; and said second engagement portion comprises a magnetic material; ICS wherein in use, activation of said magnet causes said magnet to engage said magnetic material, thereby engaging said first and second engagement portions; and cr) de-activation of said magnet causes said magnet to disengage saidCDmagnetic material, thereby disengaging for said first and second engagement 20 portions.14. The shroud tube manipulator as claimed in any one of claims 9 to 12, wherein one of said first and/or second engagement portion comprises a magnetic solenoid; and the other one of the first and/or second engagement portions comprises a magnetic material.15. The shroud tube manipulator as claimed in any one of claims 9 to 14, comprising means for automatically latching a distal end of said arm to a movable gate of a slide gate valve, such that as said slide gate valve travels horizontally, said distal end of said arm is moved by said slide gate valve.16. A method of engaging an arm of a shroud tube manipulator apparatus to a slide gate of a ladle, using an engagement mechanism, said shroud tube manipulator comprising: a base; a main body movably mounted on said base; a lever arm pivotally mounted to said main body, said arm adapted for holding a shroud tube; a straight line mechanism for raising or lowering said lever arm, such that said distal end of said arm follows a straight line path, wherein cr) said lever arm pivots about a substantially horizontal pivotal axis located atCDsaid proximal end of said arm, such that said arm moves in a translational movement with respect to said main body; thereby allowing said distal end of said arm to raise or lower in a straight line; said engagement mechanism comprising: a first engagement portion for fitting to a sliding part of a slide gate; and a second engagement portion adapted for attaching to an arm of a shroud 3 0 tube manipulator apparatus; said method comprising: engaging said first and second engagement portions with each other; operating said slide gate such that movement of said slide gate causes said first engagement portion to automatically urge said second engagement portion, thereby automatically urging said lever arm; whereby moving said first engagement portion in a second direction transverse to said first direction, automatically urges said second engagement portion in said second transverse direction; and said first and second engagement portions are adapted to disengage with each other when urged in a third direction, opposite to said first direction. I'-17. The method as claimed in claim 16, further comprising disengaging said first and second engagement portions from each other when disengaging cr) said shroud tube from a ladle collector nozzle.CD