According to the invention, each internal rail (
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 It is known that a rolling mill comprises, inside a stand, at least two rolls mounted to rotate around parallel axes and placed in a plane which is substantially vertical. The <<Duo>> stands, for instance, comprise only two rolls between which runs the product to be rolled. In the so-called <<Quarto>> stands, the product to be rolled runs between two working rolls of relatively small diameter and bearing directly on two back-up rolls. In the so-called <<Sexto>> stands, intermediate rolls are interposed between each working roll and the corresponding back-up roll. But one also knows other types of rolling mills, for example of the <<Sendzimir>> type which comprise a large number of rolls or the so-called <<Z-High>> rolling mills wherein each working roll is associated with lateral back-up rolls, the assembly being placed in an insert.
 The working rolls, which are in contact with the product, wear rather quickly. Besides, their diameter should be suited to the nature and to the thickness of the product to be rolled as well as, in certain cases, to the surface finish to obtain. These rolls must therefore be replaced periodically.
 The same goes for the intermediate rolls in the <<Sexto>> rolling mills, and for the inserts in the <<Z-High>> rolling mills.
 Previously, the rolls were disassembled in a cantilever position by a so-called carrying bar system, comprising a take-up member for the roll balanced by a counterweight.
 However, for several years, devices have been developed with a view to reducing the service time, the risks of damage for people or equipment and enabling automation of the sequences.
 It is known, generally, that each roll is mounted to rotate, at its ends, on centring bearings housed in two chocks whereon bear means for height adjustment of the rolls, each chock being mounted to slide along guiding faces parallel to a clamping plane running through the axes of the working rolls.
 To enable withdrawal and insertion of the rolls, the chocks are fitted, generally, with rollers which run on rails extending between both standards of the stand, parallel to the axes of the rolls.
 In certain cases, to disassemble both rolls together, the upper roll is laid on the chocks of the lower roll which run on two rails placed on either side of the clamping plane.
 However, the continuous rolling technique is used more and more extensively which implies changing the rolls while maintaining the band engaged between both working rolls. In such a case, one uses two pairs of rails for disassembling the rolls placed, respectively, at two levels for which the rolls are away from the band.
 In all cases, the rolls to be disassembled are therefore removed from the stand by displacement parallel to their axis and transferred onto an external device comprising rails placed respectively in the alignment of the rails in the stand and a carriage fitted with motor-driven extracting devices which enable the rolls to come out of the stand or, conversely, insertion of the new rolls.
 To accelerate the process, one often uses two carriages mounted to slide on rails parallel to the running direction and provided on a lateral chassis, one of the carriages comprising an empty recess for receiving the worn rolls and the other carriage carrying new rolls which can be inserted into the stand after extraction of the worn rolls. When disassembly is performed with the band engaged, each carriage comprises two pairs of rails which are placed in the alignment of two pairs of rails of the stand.
 Even if the working rolls have relatively small diameter, their weight is still sizeable and the rails intended for disassembling must therefore have dimensions sufficient to sustain them. These devices are therefore relatively cumbersome and must, however, extend on either side of the clamping plane and in the vicinity thereof since they carry the chocks of each roll to be disassembled.
 Or, generally, the internal zone of the stand, at the level of the working rolls, is already packed with all sorts of devices, such as band engagement tables, spray ramps, devices intended to protect the rolls in case of broken bands, etc. . . . .
 Even in the case of a new stand, it is difficult, in addition to these essential devices, to accommodate rails for disassembly in a confined space. Still, one may use dismountable rails which are placed in the stand only when replacing rolls, but the time necessary to the installation and to the disassembly of the rails increases the whole duration of the process, which defeats the purpose.
 On the other hand, one cannot either reduce the dimensions of the rails without making them dangerously brittle.
 This invention enables to solve these various problems thanks to a replacement device which, without dismounting the rails, enables to clear completely the space between the standards of the stand, during rolling processes.
 The invention therefore generally concerns a device for disassembly of the rolls in a rolling mill wherein the rolls are displaced by translation, parallel to their axis, from a rolling position between the standards of the stand to a disassembly position at a distance from the stand, while bearing, successively, on at least a pair of internal rails extending respectively, on either side of the clamping plane, between the corresponding stanchions of each standard and extended by at least one pair of external rails extending outside the stand, at least on one disassembly side, both chocks of the roll to be disassembled being fitted with bearing members mobile on said internal and external rails.
 According to the invention, on either side of the clamping plane, each internal rail is composed of two sections extending each on a length delineated between two ends, respectively internal and external, and mounted to slide, respectively, on both standards of the stand, parallel to the axis of the roll and the rolling mill comprises means for controlling the sliding motion of both sections of each internal rail from a rolling position for which each section extends substantially on the width of the corresponding standard to a position for disassembly of the roll for which both sections are brought towards one another, in the gap between both standards, the internal ends of said sections being separate by a free space. Moreover, each mobile bearing member of a chock is moved away from the middle plane thereof by a distance greater than the distance between said middle plane and the end of the corresponding rail section when said rail is in the rolling position and at least the chock holding the end of the roll opposite to the disassembly side is fitted, on either side of the clamping plane, with two mobile bearing members spaced from one another, on either side of the middle plane of the chock, by a distance greater than the length of the existing free space, in the position for disassembly of the roll, between the internal opposite ends of both sections of corresponding internal rails.
 According to a preferred embodiment, both chocks of the roll to be disassembled are fitted each, on either side of the clamping plane, with a pair of mobile bearing members spaced from one another by a distance greater than the length of the section of corresponding rail.
 These bearing members composed, preferably, of running rollers, are mounted each at the end of a fixed arm on the corresponding side of the chock and extend axially to the outside of the chock, in order to place the bearing member at the requested distance of the middle plane of the chock.
 On the other hand, it is advantageous that the sections of rails mounted on the same standard of the stand, on either side of the clamping plane, should be connected together and associated with a single means for controlling the simultaneous sliding motion of said sections, from the rolling position to the disassembly position and conversely.
 In case when both working rolls are dismounted simultaneously while laying the upper roll on the lower roll, the device comprises two pairs of sections of rails mounted respectively on both standards of the stand at the same disassembly level, in order to form two internal rails, on either side of the clamping plane.
 According to another more advanced embodiment, enabling disassembly with the band still engaged, the device comprises four pairs of sections of rails mounted respectively, at two disassembly levels, on both standards of the stand, in order to form, at each level, two internal rails extending respectively on either side of the clamping plane. Such a device enables therefore, while keeping the band engaged, to translate, separately or simultaneously, both working rolls while holding them apart on either side of the rolling plane. A similar arrangement enables, in a <<Z-High>> rolling mill, to disassemble and to replace, separately or simultaneously, the inserts comprising each a working roll and two lateral back-up rolls.
 Other arrangements are however possible and one could, for example in a <<Sexto>> rolling mill, use eight pairs of sections of rails mounted respectively at four levels for disassembly of the working rolls and of the intermediate rolls.
 The invention also covers the implementation method of such a disassembly device. According to the invention, once the rolls have been placed at their disassembly level, the sections of rails placed on one front disassembly side are caused to slide towards the inside of the stand, then a replacement carriage fitted with external rails is moved to said side, whereby said rails are placed in the alignment of the sections of internal rails thus fed forward. The translation of the roll to be replaced resting on the sections of internal rails is then controlled and the sections of rails mounted on the rear standard are then fed forward, towards the inside of the stand. The rear chock placed on the side opposite to the carriage rests successively on the rear sections, then on the front sections by its two spaced bearing members, while crossing the free space between said sections. By reverse operations, it is possible to insert into the stand a replacement roll, then to cause the sections of internal rails to slide towards the outside of the stand in order to replace them into rolling position each at the level of a standard, whereby the chocks of the roll can then be moved vertically for adjusting the distance between the working rolls.
 As regards the implementation of the invention, it is particularly advantageous that the rolling mill should be fitted with C-shaped hydraulic blocks comprising, on either side of the rolling plane, two protruding parts at the ends whereof are provided lateral guiding faces of the working chocks, whereby said chocks are fitted with bearing ears offset towards the rolling plane and engaging into a central scalloping of each hydraulic block, provided between the protruding parts thereof.
 Indeed, the sections of rails mounted on each standard can, in such a case, be arranged along the ends of the protruding parts of the hydraulic blocks and each rail is housed in a scalloping provided on a portion of the height of the corresponding lateral side of the chock while keeping, on said lateral side and on the end of the protruding side, guiding faces sliding over one another and having a height compatible with the level adjustment possibilities of the chock.
 Each section of rail is thus mounted to slide axially between the end of the protruding side of the hydraulic block and the bottom of the scalloping provided on the lateral side of the chock, said bottom and the corresponding face of the rail being fitted with wearing plates which slide over one another, on the one hand in the axial direction during displacements of the section of rail and, on the other hand, in the vertical direction when adjusting the level of the chock, in order to form an additional lateral back-up means of the chock.
 The invention also covers other advantageous arrangements mentioned in the claims.
 But the invention will be understood better by the following description of a particular embodiment, given for exemplification purposes and represented on the appended drawings.
 As usual, the holding stand
 As the diameter of the working rolls
 As shown on
 For example, such a roll stand may comprise, on either side of the clamping plane P
 All these appended members and, in particular, the spray ramps B and the guard plates E must be placed close to the working rolls
 The invention enables to solve this problem thanks to a unique arrangement of the disassembly rails represented on
 In the embodiment represented on
 The invention may apply to this type of stand. However, it is particularly advantageous to use the arrangement described in the French patent n°2786415 of the same company, wherein the ears of the chocks are offset towards the rolling plane, whereas each hydraulic block is C-shaped comprising only two protruding portions for guiding the working chocks
 This preferred embodiment has therefore been represented on
 According to the arrangement described in the previous patent n°2786415, the central portion of the hydraulic block is deleted, whereas each positive cambering jack of a chock bears on the protruding side of the hydraulic block placed on the other side of the rolling plane and bound therefore, to run through said plane. To this end, as shown on
 As divulged in the Patent n°2786415, such an arrangement exhibits notably the advantage of reducing the global height of the hydraulic blocks and of the chocks, since the bearing ears of both chocks can be placed close to the rolling plane, in the central scalloping of each C-shaped hydraulic block.
 In conventional disassembly devices, the running rollers of the chocks are often mounted at the end of the bearing ears and the disassembly rails must therefore be placed between the protruding portions of the hydraulic blocks carrying the cambering jacks. The assembly is rather cumbersome and may hardly be housed between the stanchions of each standard of the stand, in the case, for instance, of modernising an existing rolling mill.
 The arrangement with C-shaped blocks described in the previous patent n°2786415 is, conversely, particularly well suited to the installation of disassembly rails. Indeed, since the bearing ears of each chock are offset on the side of the rolling plane, the whole remaining height of the chock is available to provide the lateral holding faces thereof and it is thus possible to place guiding rails on a portion of the height of the protruding side of the hydraulic block, while preserving the guiding height necessary for adjusting the level of the roll.
 Such an arrangement is represented, in particular, on
 As already stated, it is necessary to replace periodically the working rolls because they are worn and this ought therefore to be taken into account in order to determine the height adjustment possibilities of the chocks.
 As indicated previously, both working rolls
 Indeed, as shown on
 If one considers, for instance, the upper chock
 Consequently, the supporting rail
 The lower chock
 For example, on
 Consequently, as regards the upper chock
 Conversely, as regards the lower chock
 Besides, according to the invention, each supporting rail
 Thus, as shown on
 Since disassembly can take place with the band engaged, the upper roll
 Moreover, each rail section
 Thanks to this division of each rail
 Indeed, according to another characteristic of the invention, the supporting rollers
 This arrangement is represented in detail on
 It can be seen, indeed, that in such a case, each rear chock
 In this view, it should be noted that the vertical displacements of the chocks and the axial displacements of the rail sections never occur simultaneously. Consequently, each rail section
 Both faces in contact,
 Preferably, the front chock
 In their disassembly position represented as a dotted line on
 Moreover, in this disassembly position, the internal opposite ends regard
 The length l of the rail sections and the spacing d between the supporting rollers of the chock must therefore be determined, on the one hand to preserve sufficient embedding length for each section and, on the other hand, so that the spacing of the rollers is greater than the distance e between the ends of two rail sections in order to enable the disassembly of the roll while running successively on both sections, as can be seen later on with reference to the diagram of
 Obviously, all the arrangements that have just been described for the lower roll
 It is advantageous to control simultaneously the sliding motion of the whole rail sections placed on the same standard, between the retracted rolling position and the forward disassembly position.
 In this view, as shown on
 As shown on
 This central slideway
 The operation of the device is represented diagrammatically on
 In this position, the running rollers
 When the rolls
 The rail sections
 Preferably, the rail sections
 By known means mounted on the auxiliary carriage and not represented on the Figures, one then controls the axial displacement of the roll
 The rear chock
 Axial displacement of the roll
 Withdrawal of the lower roll
 In a known fashion, the auxiliary carriage may be fitted with two recesses fitted each with two pairs of external rails
 But the invention is obviously not limited to the details of the embodiment which has just been described for exemplification purposes, whereas equivalent means can be used without departing from the protection framework defined by the claims.
 In particular, it is particularly advantageous to use chocks fitted with offset ears of the type represented on FIGS.
 On the other hand, only the chocks
 The reference signs inserted after the technical characteristics mentioned in the claims, solely aim at facilitating the understanding thereof and do not limit their extent whatsoever.