Rolling stand for rod-shaped bodies

Abstract

A rolling stand for rod-shaped bodies comprising a structure provided therein with three working rollers (3, 3') arranged at 120° from one another so as to define a passage (5) defining a horizontal rolling direction for rolling said rod-shaped bodies; wherein a working roller (3') of said three working rollers has a vertical rotation axis (X); wherein the structure of said rolling stand is provided at the top with a first surface cavity (40) open at an upper end edge (55) of the structure, placed on an inlet side of said rolling stand in a respective rolling mill compartment; wherein said first surface cavity (40) is arranged at said inlet side, opposite to a side, in which the aforesaid working roller (3') is provided, with respect to a first vertical centerline plane of the rolling stand, parallel to said horizontal rolling direction; and wherein said first surface cavity (40) is delimited, proximal to said first vertical centerline plane, by a first wall (41) adapted to abut against at least one corresponding first central abutment provided in an upper part of said rolling mill compartment.

Description

[0001] P024505WG-01_eng

[0002] ROLLING STAND FOR ROD-SHAPED BODIES

[0003] ************

[0004] Field of the invention

[0005] The present invention belongs to the technical field of production, by rolling, of rodshaped products, such as rods, bars or similar products, but also of hollow tubular products, and therefore, in particular, of pipes. In particular, the present invention relates to a rolling stand with three rollers, adapted to be inserted into a compartment of a rolling mill transversely with respect to the longitudinal axis of the rolling mill.

[0006] Background art

[0007] Various types of rolling mill are known. Among these there are, for example, the sizing mill, the stretch reducing mill, the extracting-sizing mill.

[0008] To simplify the operation of replacing the stands, by moving them along a direction transverse, preferably perpendicular, to the longitudinal axis of the rolling mill frame, rolling mills have been designed with rolling stands having three motorized rollers, each roller rotating about a rotation axis and inclined by 120° with respect to the other rollers, and a first roller of said three rollers having a vertical rotation axis actuated by a vertical axis adapter, positioned above the stand. A second roller is operatively placed above a horizontal reference plane onto which the rolling axis lies; while a third roller is operatively placed below said horizontal reference plane. The adapters of the second roller and of the third roller are operatively installed below the support surface of the rolling stands.

[0009] With this type of rolling stands, each pair of subsequent and adjacent stands comprises a stand of the "even-numbered" type and a stand of the "odd-numbered" type, in which the arrangement of the rollers of the odd-numbered stand corresponds to that of the even-numbered stand when subjected to a 180° rotation about the vertical axis passing through the rolling center.

[0010] However, this rolling stand configuration has some issues regarding, for example, the alignment among subsequent rolling stands, and therefore the correct maintenance of the rolling axis following the insertion of the stand into the respective compartment of the rolling mill; the differentiated wear of the working rollers following misalignments; the cooling system thereof; the potential interference among the rolling stands or between a rolling stand and the respective compartment during the insertion orextraction of one of them from the rolling mill; the complexity of the operation of replacing some parts subject to wear, such as runners and wheels.

[0011] Regarding the alignment among the rolling stands along the rolling axis following the transverse insertion of the stand into the respective compartment of the rolling mill, a particular issue is due to the possible rotation of the rolling stand about the vertical axis thereof during the insertion translation thereof into the compartment. This can lead to a misalignment between the stands along the rolling axis and can cause interlocking issues to the rolling product between two subsequent stands. Furthermore, this also produces a non-uniform distribution of the thermal expansions in the rolling stand. A first disadvantage relating to the cooling system is that, to cool the working rollers and consequently maintain a predetermined temperature of the rolling product, the cooling system of each rolling stand is extremely complex and arranged almost exclusively within the structure of the rolling stand. These aspects contribute to high production costs for the rolling stand and also to high maintenance times and costs due to the difficulty for operators to access different parts of the cooling system.

[0012] A second disadvantage relating to the cooling system is that the configuration thereof is such that the cooling liquid is sprayed or injected along the entire thickness of the rolling stand, often causing excessive cooling of the rolling product.

[0013] A third disadvantage relating to the cooling system is that such cooling system is provided with hydraulic junctions and connections protruding externally from the structure of the rolling stand and requires the manual intervention by operators to connect said hydraulic connections to the cooling liquid supply circuit arranged in the rolling mill frame housing the rolling stand.

[0014] A fourth disadvantage relating to the cooling system is that such a cooling system produces jets or blades of cooling liquid which interfere with one another, making the cooling less efficient.

[0015] Regarding, instead, the potential interference between the rolling stands or between a rolling stand and the respective compartment during the insertion or extraction of one of them into / from the rolling mill, the known rolling stands have several components protruding from the structure of the stand itself and this increases the risk of interference or requires the disassembly and subsequent reassembly thereof. These components include, for example, the eyebolts for moving, by means of a crane, the stand outside the rolling mill frame, and / or the hydraulic junctions and connections.Furthermore, a further disadvantage of the known rolling stands is that some parts that are subject to wear, in particular the wheels of the stand, require lengthy interventions for the replacement thereof.

[0016] From the considerations reported above, the need emerges to make an innovative rolling stand which overcomes the aforesaid drawbacks.

[0017] Summary of the invention

[0018] It is the main object of the present invention to provide a rolling stand configured so as to avoid, during the transverse insertion thereof into the respective compartment of the rolling mill, any rotation thereof about the vertical axis thereof, which can lead to a misalignment among the stands along the rolling axis, in particular by virtue of suitable means adapted to hold the stand correctly in position.

[0019] It is another object of the present invention to provide a rolling stand provided with a cooling system which is simple from a construction point of view and almost exclusively arranged outside the structure of the rolling stand, thus helping to reduce both the production costs of the rolling stand as well as the maintenance times and costs due to the ease for operators to access the various parts of the cooling system.

[0020] It is another object of the present invention to provide a rolling stand provided with a cooling system configured so as to avoid an excessive cooling of the rolling product. It is a further object of the present invention to provide a rolling stand provided with a cooling system which is more efficient with respect to known systems.

[0021] It is another object of the present invention to provide a rolling stand configured so as to avoid interference with the respective rolling mill compartment, or with the adjacent rolling stands, during the insertion thereof into or the extraction thereof from the rolling mill.

[0022] It is a further object of the present invention to provide a rolling stand configured so that it does not require a manual intervention by operators for connecting the hydraulic connections thereof to the cooling liquid supply circuit arranged in the rolling mill frame. It is another object of the present invention to provide a rolling stand configured so that some parts subject to wear, in particular the wheels of the stand, are easily and quickly replaced.

[0023] The present invention achieves at least one of these objects, and other objects which will be apparent in light of the present description, by means of a rolling stand for rodshaped bodies comprising a structure provided therein with three working rollersarranged at 120° from one another so as to define a passage defining a horizontal rolling direction Y for rolling said rod-shaped bodies;

[0024] wherein a working roller of said three working rollers has a vertical rotation axis X; wherein the structure of said rolling stand is provided at the top with a first surface cavity open at an upper end edge of the structure, placed on an inlet side of said rolling stand in a respective rolling mill compartment transversely to a rolling axis of said rolling mill; wherein said first surface cavity is arranged at said inlet side of the rolling stand, opposite to a side in which the aforesaid working roller with the vertical rotation axis is provided, with respect to a first vertical centerline plane of the rolling stand, parallel to said horizontal rolling direction Y;

[0025] and wherein said first surface cavity is delimited, in proximity of said first vertical centerline plane, by a first wall adapted to abut against at least one corresponding first central abutment provided in an upper part of said rolling mill compartment; preferably wherein the length of the first wall is equal to at least two thirds of the thickness T of the rolling stand, measured along said horizontal rolling direction Y. A further aspect of the invention relates to a rolling mill for rolling rod-shaped bodies, defining a rolling axis and comprising a rolling train provided with at least two rolling stands as the one described above.

[0026] Further features and advantages of the invention will become more apparent in light of the detailed description of exemplary but non-exclusive embodiments.

[0027] The dependent claims describe particular embodiments of the invention.

[0028] Brief description of the Figures

[0029] In the description of the invention, reference is made to the attached drawing tables, provided by way of explanation and not of limitation, in which:

[0030] Figure 1 shows a first perspective view of a rolling stand according to the invention; Figure 2 shows an enlargement of the upper part of the rolling stand of Figure 1 ;

[0031] Figures 2a and 2b show sectional views of part of the cooling system of the rolling stand according to the invention;

[0032] Figure 3 shows an enlargement of the lower part of the rolling stand of Figure 1 ;

[0033] Figure 4 shows a second perspective view of the rolling stand of Figure 1 ;

[0034] Figure 5 shows a side view, partially sectioned, of a rolling stand according to the invention inside a rolling mill;

[0035] Figure 6 shows an enlargement of the lower part of Figure 5;Figure 7 shows an enlargement of the upper part of Figure 5;

[0036] Figure 8 shows an example of a rolling mill comprising a plurality of rolling stands according to the invention;

[0037] Figure 9 shows a first side view, partially sectioned, of the rolling mill of Figure 8;

[0038] Figure 10 shows a second side view of the rolling mill of Figure 8;

[0039] Figures 11 and 12 show a side view of a rolling stand compartment, respectively with adapters in the extended position, i.e. , connecting with the respective rollers, and with adapters in the retracted position to allow the rolling stand to be extracted.

[0040] The same numbers and the same reference letters in the Figures identify the same elements or components.

[0041] Description of exemplary embodiments of the invention

[0042] With reference to the Figures, some examples of rolling stand according to the invention are shown.

[0043] In all the embodiments of the invention, the rolling stand comprises a structure provided therein with three working rollers 3, 3’ arranged at 120° from one another so as to define a passage 5, defining a horizontal rolling direction Y, to roll the rod-shaped body.

[0044] A working roller 3’ of said three working rollers has a vertical rotation axis X, while the other two working rollers 3 have rotation axes inclined by +30° and -30°, respectively, with respect to a horizontal reference perpendicular to the vertical axis passing through the center of said passage 5.

[0045] The rolling stand according to the invention is of the type capable of withstanding the separation force thereon, i.e., the force due to rolling, without the aid of external actuators, such as, for example, hydraulic capsules or screwdowns. Therefore, it is a rolling stand without a roller-holder cartridge.

[0046] Advantageously, the structure of the rolling stand is provided at the top with a first surface cavity 40 open at a side upper end edge 55 of the structure, preferably parallel to said horizontal rolling direction Y, arranged on an inlet side of said rolling stand, transversely to a rolling axis of a rolling mill, in a respective rolling mill compartment. In order to avoid any slight rotation of the rolling stand about the vertical axis thereof during the transverse insertion thereof into the respective rolling mill compartment, which would lead to a misalignment between the stands along the rolling axis and a non-uniform distribution of the thermal expansions, the aforesaid first surface cavity 40 (Figures 1 and 2) is arranged on said inlet side of the rolling stand, said inlet side beingopposite to the side of the stand into which the aforesaid working roller 3’ is provided with respect to a first vertical centerline plane of the rolling stand, parallel to the horizontal rolling direction Y.

[0047] Said first surface cavity 40 is delimited proximally to said first vertical centerline plane by a first wall 41 , preferably but not necessarily parallel to said horizontal direction Y, and adapted to abut against at least one first central abutment 22 (Figures 5 and 7), provided in an upper part of the rolling mill compartment, during the transverse insertion of the stand into the rolling mill compartment.

[0048] Preferably, in order to optimize the aforesaid technical effect, the length of the first wall 41, measured along the horizontal rolling direction Y, is equal to at least two thirds of the thickness T of the rolling stand measured along said horizontal rolling direction Y (Figure 2).

[0049] The first wall 41 can be flat and parallel to said first vertical centerline plane of the rolling stand. In this case, the first central abutment 22 also has a corresponding flat abutment surface.

[0050] It is not excluded that the first wall 41 can be, at least partially, not parallel to said first vertical centerline plane.

[0051] For example, said first wall 41 can be inclined with respect to said first vertical centerline plane, or can have a stepped profile or another shaped profile. In these cases, the first central abutment 22 has a corresponding side, which defines a respective abutment surface, having an inclination or profile complementary to the inclination or profile of said first wall 41 , respectively.

[0052] Preferably, the structure of the rolling stand is also provided at the bottom with a second surface cavity 40' (Figure 3), open at a lower end edge 55' of the structure, which is on the same side as said upper side end edge 55, and delimited proximally to said first vertical centerline plane, parallel to the horizontal rolling direction Y, by a second wall 4T, preferably arranged on the same plane as the first wall 41, and adapted to abut against at least one second central abutment 22' (Figures 5 and 6) provided in a lower part of said rolling mill compartment.

[0053] Also in this case, preferably the length of the second wall 4T, measured along the horizontal rolling direction Y, is equal to at least two thirds of the thickness T of the rolling stand measured along said horizontal rolling direction Y, and is preferably equal to the length of said first wall 41.Similarly to the first wall 41, the second wall 41’ can be flat and parallel to said first vertical centerline plane of the rolling stand. In this case, the second central abutment 22’ also has a corresponding flat abutment surface.

[0054] It is not excluded that the second wall 4T can be, at least partially, not parallel to said first vertical centerline plane.

[0055] For example, said second wall 4T can be inclined with respect to said first vertical centerline plane, or can have a stepped profile or another shaped profile. In these cases, the second central abutment 22’ has a corresponding side, which defines a respective abutment surface, having an inclination or profile complementary to the inclination or profile of said second wall 4T, respectively.

[0056] The first surface cavity 40 and the second surface cavity 40' can, but not necessarily, be arranged symmetrically with respect to a horizontal plane.

[0057] In a variant (Figure 2), on the first wall 41 , a first recess or seat 72 is obtained, into which a first coating element 73, for example in the shape of a parallelepiped, is solidly fixed, adapted to abut against said first central abutment 22. Preferably, said first coating element 73 protrudes into the first surface cavity 40 with a side 81 thereof, which is outermost with respect to the first recess 72 and acts as an abutment surface. Preferably, but not necessarily, this outermost side 81 is arranged parallel to said first vertical centerline plane of the rolling stand, parallel to the horizontal rolling direction Y, acting as a flat abutment surface. In this case, the first central abutment 22 also has a corresponding flat abutment surface.

[0058] It is not excluded that the outermost side 81 can be, at least partially, not parallel to said first vertical centerline plane.

[0059] For example, said outermost side 81 can be inclined with respect to said first vertical centerline plane, or it can have a stepped profile or another shaped profile. In these cases, the first central abutment 22 has a corresponding side, which defines a respective abutment surface, having an inclination or profile complementary to the inclination or profile of said outermost side 81 , respectively.

[0060] Similarly, if the second surface cavity 40' is provided at the bottom (Figure 3), on the second wall 4T a second recess or seat 72' is obtained, into which a second coating element 73', for example in the shape of a parallelepiped, is fixed, adapted to abut against said second central abutment 22'. Preferably, said second coating element 73’protrudes into the second surface cavity 40’ with a side 81’ thereof, which is outermost with respect to the second recess 72’ and acts as an abutment surface.

[0061] Preferably, but not necessarily, this outermost side 81’ is arranged parallel to said first vertical centerline plane of the rolling stand acting as a flat abutment surface. In this case, the second central abutment 22’ also has a corresponding flat abutment surface. In this variant, the aforesaid outermost sides 81 , 81’, or flat abutment surfaces, of the coating elements 73, 73’ are arranged on a same vertical plane parallel to said first vertical centerline plane.

[0062] It is not excluded that the outermost side 81’ can also be, at least partially, not parallel to said first vertical centerline plane.

[0063] For example, said outermost side 8T can be inclined with respect to said first vertical centerline plane, or can have a stepped profile or another shaped profile. In these cases, the second central abutment 22’ has a corresponding side, which defines a respective abutment surface, having an inclination or profile complementary to the inclination or profile of said outermost side 81’, respectively.

[0064] Preferably, the length of the first coating element 73, and of the possible second coating element 73', measured along the horizontal rolling direction Y, is at least equal to one third of the thickness T of the rolling stand, measured along said horizontal rolling direction Y.

[0065] The coating elements 73, 73' are preferably made of material having a higher hardness with respect to the material of the structure of the rolling stand, in order to improve the durability thereof and the accuracy of the abutment. Examples of usable materials are steels such as C40, C50, 42CrMo4, abrasion-resistant steels with a nominal hardness of 400-500 HBW, such as Hardox 400 or Hardox 500, CORC®-g compound steel, with or without surfaces hardened by means of heat treatments.

[0066] The shape of the coating elements 73, 73' can be selected so as to facilitate the maintenance or replacement thereof.

[0067] As shown in Figure 2, the first surface cavity 40 is formed along approximately half of the flat upper surface 70 of the structure, while in the other half a further surface cavity can be formed from which an upper end of the shaft of the working roller 3' with a vertical rotation axis protrudes.

[0068] Similarly, the second surface cavity 40' is formed along approximately half of aflat lower surface 80 of said structure.In a first embodiment of the rolling stand of the invention, at least at one face of the rolling stand, perpendicular to the horizontal rolling direction Y, a cooling system is preferably provided comprising:

[0069] - a hydraulic connection 47, for an inlet of a cooling liquid into the rolling stand, arranged in the upper part of the structure,

[0070] - and a set of three supplying means 49, 50, 51 for supplying the cooling liquid, coming from the hydraulic connection 47, at each working roller 3, 3’, each supplying means 49, 50, 51 being arranged on said at least one face in proximity of a respective working roller 3, 3’.

[0071] A first supplying means 49 is proximal and connected to the hydraulic connection 47, and two pipes 52, 53 are arranged externally on said at least one face and branch off from the first supplying means 49 and respectively connect said first supplying means 49 to a second supplying means 50 and to a third supplying means 51.

[0072] This cooling system is simple from a construction point of view and almost exclusively arranged outside the structure of the rolling stand, thus helping to reduce both the production costs of the rolling stand as well as the maintenance times and costs due to the ease of operators in accessing the various parts of the cooling system.

[0073] Furthermore, the cooling liquid, generally water, is supplied onto the working rollers in proximity of at least one of the faces of the rolling stand.

[0074] Preferably, the set of three supplying means 49, 50, 51 and the pipes 52, 53 protrude at least partially from a flat surface of said at least one face of the rolling stand.

[0075] In any case, both the set of three supplying means 49, 50, 51 and the pipes 52, 53 are completely and easily accessible from the outside of the rolling stand.

[0076] In the example shown in Figures 1-2, two cooling systems are provided as described above, i.e., one cooling system for each of the two faces of the rolling stand, which are parallel to each other and perpendicular to the horizontal rolling direction Y.

[0077] Preferably, the two cooling systems are arranged symmetrically to each other with respect to a second vertical centerline plane of the rolling stand, said rolling direction Y being orthogonal to said second vertical centerline plane.

[0078] In this case, the cooling liquid, generally water, can be supplied onto the working rollers in proximity of both faces of the rolling stand. However, it is preferable to operate only one of the two cooling systems to avoid the risk of an excessive cooling of the rolling product.In a preferred, but not exclusive, variant, the hydraulic connection 47 comprises at least one pipe fitting 64 for the connection to the corresponding first supplying means 49. Said at least one pipe fitting 64 (Figure 2a) is arranged inside the structure of the rolling stand and is provided at the upper end thereof with a gasket 65, for example with a flat and circular shape, arranged tangentially to the flat upper surface 70 of the structure in a position such as to automatically adhere, in sealing manner, when the rolling stand is lifted for the locking thereof inside a respective rolling mill compartment, to a corresponding hydraulic block for the distribution of the cooling liquid, which is arranged on the upper inner surface of said respective compartment. The hydraulic link is therefore ensured by just lifting the rolling stand by means of actuators.

[0079] In particular, said at least one pipe fitting 64 is arranged inside said first surface cavity 40 of the structure (Figures 1 and 2), open at the upper end edge 55 of the structure from the transverse inlet side of said rolling stand in the respective rolling mill compartment. Therefore, the pipe fitting 64 is also easily accessible from the outside of the rolling stand. In Figure 1, the insertion direction of the rolling stand into the respective compartment is indicated by the arrow A.

[0080] This configuration of the pipe fitting 64 and of the gasket 65, on the one hand, avoids possible interference with the respective compartment of the rolling mill during the insertion or extraction of the stand, and, on the other hand, it does not require manual intervention by operators for connecting the hydraulic connection(s) to the cooling liquid supply circuit arranged in the rolling mill frame.

[0081] Preferably, but not necessarily, the first supplying means 49, the second supplying means 50 and the third supplying means 51 comprise a device provided with injection nozzles or blades 54 facing at least towards the groove of the respective working roller 3, 3’.

[0082] In a variant, these injection nozzles or blades 54 are arranged staggered with respect to one another, or they are differently orientable with respect to one another, to prevent respective jets or blades of cooling liquid from interfering with one another, thus reducing the cooling effect.

[0083] Furthermore, for example, in the case of injection nozzles, the axes of said injection nozzles can be facing completely towards the inside of said groove to further improve the cooling efficiency.In a variant shown in the sectional views of Figures 2a and 2b, the first supplying means 49 comprise, or consist of, a device or block 49' fixed, for example by means of screws or other suitable fixing means, onto a face of the rolling stand, preferably inside a recess 69 obtained on said face.

[0084] Said block 49' is provided therein with a duct 66, communicating upstream with the pipe fitting 64 while branching downstream, always inside the block 49', into at least two further ducts 67, 68, transverse to the duct 66 and opposite to each other. In the example shown, only two further ducts 67, 68 are provided, communicating downstream with the pipes 52, 53, respectively, connecting said first supplying means 49 to the second supplying means 50 and to the third supplying means 51 , respectively. Along the further ducts 67, 68, one or more injection nozzles can be provided, differently orientable from one another, facing at least towards the groove of the corresponding working roller 3.

[0085] The second supplying means 50 and the third supplying means 51, constituting two ends of the cooling system, comprise, or consist of, a device or block fixed, for example by means of screws or other suitable fixing means, onto said face of the rolling stand, preferably inside a respective recess obtained on said face.

[0086] In this case, each block is provided with at least one further duct therein, communicating upstream with the respective pipe 52, 53.

[0087] For example, a single further duct can be provided, provided with one or more injection nozzles, differently orientable from one another, facing at least towards the groove of the corresponding working roller 3, 3’.

[0088] With reference to Figure 2, the distance between the two hydraulic connections 47, measured parallel to the horizontal rolling direction Y, is such as to be crossed, during the insertion of the rolling stand into the compartment thereof of the rolling mill, by the corresponding upper central abutment 22 of said compartment, which is fixed and against which the wall 41 or, alternatively, the coating element 73 will abut. In particular, the longitudinal extension, along the horizontal rolling direction, of said coating element 73 is approximately equal to or greater than the longitudinal extension of said upper central abutment 22.

[0089] The space between the two hydraulic connections 47 is crossed by the upper central abutment 22 also during the extraction of the rolling stand from the compartment.Figures 8-10 show an example of a rolling mill comprising a plurality of rolling stands 1 , 2 arranged in sequence along the rolling axis so that the respective passages 5 are aligned to define a rolling path along said rolling axis.

[0090] In particular, the rolling stands 1, 2 are arranged, one adjacent to the next one, along said rolling axis, and the position of the working rollers 3, 3’ of an odd-numbered rolling stand 1 corresponds to the position of the working rollers 3, 3’ of the adjacent even-numbered rolling stand 2 rotated by 180° about a vertical axis V (Figure 5) passing through the center of said passage 5.

[0091] Therefore, the odd-numbered rolling stands 1 of said rolling stands 1, 2 have the working roller 3’ with a vertical rotation axis X at a first side of the rolling mill, parallel to the rolling axis, while the even-numbered rolling stands 2 of said rolling stands 1, 2 have the working roller 3’ with a vertical rotation axis X’ at a second side of the rolling mill, parallel to the rolling axis and opposite to said first side.

[0092] Advantageously, the rolling mill is provided with a frame 4, preferably a single frame, to contain the rolling stands 1, 2 along the rolling axis, said frame being designed so that the odd-numbered rolling stands 1 can be inserted in the frame 4 and extracted from said frame 4 exclusively from said first side of the rolling mill, along a direction transverse to the rolling axis, while the even-numbered rolling stands 2 can be inserted into said frame 4 and extracted from said frame 4 exclusively from said second side of the rolling mill, along a direction transverse to the rolling axis. In a preferred variant, these transverse directions coincide.

[0093] In the frame 4, odd-numbered compartments for the odd-numbered rolling stands 1 and even-numbered compartments for the even-numbered rolling stands 2 are provided. The aforesaid configuration of frame and rolling stands allows, for all the stands, to minimize the release strokes of the adapters 34, 35, 36 and to limit the downward rotation of the adapter 36 on the stand exit side to a few degrees, thus ensuring the use of adapters even without a universal joint.

[0094] Figures 11 and 12 show, for a frame compartment represented without a stand therein, the adapters 34, 35, 36 in the extended position, i.e. , connecting the respective working rollers, and the adapters 34, 35, 36 in the retracted position, allowing the extraction of the rolling stand, respectively.

[0095] The frame 4 further comprises (Figure 10) a first end wall 42 which is transverse, for example orthogonal, to the rolling axis and configured for the entry of the body orproduct to be rolled, and a second end wall 43 which is opposite, and for example parallel, to the first end wall 42 and configured for the exit of the rolled body or product. Both end walls can be arranged perpendicular to the rolling axis.

[0096] In a preferred embodiment of the rolling mill, in order to change one or more rolling stands, the following is provided (Figures 8-9):

[0097] - a first side platform 12 at said first side of the rolling mill, arranged laterally outside the frame 4 and parallel thereto, suitable for receiving at least one odd-numbered rolling stand 1 extracted from said frame 4 and for supporting at least one new odd-numbered rolling stand 1' to be inserted into said frame 4;

[0098] - and a second side platform 13 at said second side of the rolling mill, arranged laterally outside the frame 4 and parallel thereto, suitable for receiving at least one even-numbered rolling stand 2 extracted from said frame 4 and for supporting at least one new even-numbered rolling stand 2' to be inserted into said frame 4.

[0099] For extracting and inserting the rolling stands in the frame 4 of the rolling mill of the invention, the following can, for example, be provided:

[0100] - first actuators 20 at the odd-numbered compartments of the frame 4 for inserting and extracting the odd-numbered rolling stands, and

[0101] - second actuators 21 at the even-numbered compartments of the frame 4 for inserting and extracting the even-numbered rolling stands.

[0102] These actuators 20, 21 can be, for example, hydraulic or electromechanical actuators. First actuators 20 and second actuators 21 are preferably configured to hook, individually or in a group, the respective rolling stands 1 , 2 to be extracted from the frame 4 and move them towards the relative side platform 12, 13, and configured to subsequently hook, individually or in a group, the new rolling stands T, 2’ to be inserted into the frame 4 and move them from the relative side platform 12, 13 towards said frame 4.

[0103] Figure 9 shows, as an example of an actuator 20, 21 for extracting and inserting the rolling stands into the frame 4, a carriage 37 adapted to translate in a direction transverse to the rolling axis from a first position, distal with respect to the frame 4 and placed beyond the relative platform 12, 13 (considering the rolling axis as a reference), to a second position proximal with respect to the side opening of the respective compartment of the frame 4.The carriage 37, in a variant thereof, is provided with a hook configured to hook one or two protrusions 39 (Figures 2-3) provided on the vertical side of each rolling stand which is proximal to the working roller 3' thereof with a vertical rotation axis.

[0104] In a second embodiment of the rolling stand of the invention, on each face of the rolling stand, perpendicular to the horizontal rolling direction Y, three axial contact elements 56, 57, 58 are provided (Figure 1), arranged at an angular distance of 120° from one another with respect to a central point of said face substantially positioned on the rolling axis of the rolling mill once the stand has been inserted into the respective compartment, and adapted to receive, on a first face, and to transmit, on a second face, the axial thrust along the rolling axis by transferring it from one rolling stand to the next one.

[0105] Preferably, the three axial contact elements 56, 57, 58 of the first face and the three axial contact elements 56, 57, 58 of the second face are arranged symmetrically with respect to a second vertical centerline plane of the rolling stand parallel to said first face and said second face.

[0106] Even more preferably, two axial contact elements 56, 57 of said three contact elements are arranged, in an upper area of each face of the stand, symmetrically with respect to said first vertical centerline plane of the rolling stand, parallel to the rolling direction Y and perpendicular to said second vertical centerline plane, while the remaining axial contact element 58 is arranged in a lower area of each face of the stand at said first vertical centerline plane.

[0107] The axial contact element 56 is the closest to the inlet side of the rolling stand in the respective rolling mill compartment, while the axial contact element 57 is the most distal from said inlet side.

[0108] In a variant of said second embodiment, on each face of the stand, the axial contact element 56 and the axial contact element 58 have a respective contact surface, preferably flat, arranged at a distance from the second vertical centerline plane which is shorter with respect to the distance of the contact surface of the axial contact element 57 from said second vertical centerline plane, to facilitate the insertion of the rolling stand into the compartment without interference.

[0109] However, a variant is not excluded in which the contact surfaces of all the axial contact elements 56, 57, 58 are at an equal distance from said second vertical centerline plane.In all the embodiments of the invention, the set of three supplying means 49, 50, 51 and the pipes 52, 53 protrude from the flat surface of the corresponding face of the rolling stand to a lesser extent than the aforesaid three axial contact elements 56, 57, 58.

[0110] In Figures 1-4, the axial contact elements are flat and circular in shape, but other shapes other than circular are not excluded.

[0111] In the rolling mill where the rolling stands according to the invention are inserted, means are provided for the axial locking, i.e., along the rolling axis, of the rolling stands inside the frame 4.

[0112] Preferably, as shown in Figure 10, at least two thrust actuators 29 are provided in the frame 4, at the exit side of the rolled body from the rolling mill, i.e., are arranged on the second end wall 43, said thrust actuators being adapted to push the rolling stands one on the next one preferably in a direction opposite to the rolling direction (indicated by arrow B), to lock in said frame 4 along the rolling axis the rolling stands against at least two fixed abutments 33 arranged at the entry side of the body to be rolled in the rolling mill, i.e., arranged on the first end wall 42. In particular, three thrust actuators 29 can be provided, adapted to push the rolling stands one on the next one at the three axial contact elements 56, 57, 58, preferably in the direction opposite to the rolling direction, to lock the rolling stands in the frame 4 along the rolling axis against three corresponding fixed abutments 33. However, it is not excluded to provide a single fixed abutment 33.

[0113] Furthermore, in a preferred variant, elastic means 30 are provided in the frame 4, arranged between an odd-numbered compartment and an even-numbered compartment of said frame 4 and adapted to transmit the thrust produced by said thrust actuators 29 by transferring it from one rolling stand to the next one until the entire rolling train is locked against the fixed abutments 33.

[0114] In this variant, therefore, during the axial locking, the axial contact elements 56, 57, 58 of two subsequent stands do not come into direct contact with each other, but through said elastic means 30 (Figure 10).

[0115] Such elastic means 30 are designed so that, once the thrust actuators 29 are disabled, the rolling stands return to the original insertion position thereof in the frame 4, so that no friction is generated between adjacent rolling stands 1 , 2 during the step of extracting a rolling stand from the frame 4.In particular, the elastic means 30 can comprise (Figures 10-12) a system of elastic plates or sheets, for example some fixed in a cantilever manner on the upper inner surface of the frame and others fixed in a cantilever manner on the lower inner surface of the frame. As shown in Figures 11 and 12, the elastic plates or sheets 30, for example grouped in packs, are arranged transversely to the rolling axis, in particular on a vertical plane perpendicular to the vertical plane containing the rolling axis when they are in a rest configuration.

[0116] The thrust actuators 29, for example hydraulic cylinders, pack the rolling stands 1 , 2 from the exit side of the rolling mill towards the entry side. Each stand pushes the next one through the system of elastic plates or sheets which allow, once the axial locking is released, to extract a single stand without generating friction, and therefore without generating a displacement of the previous stand or next stand.

[0117] In a third embodiment of the rolling stand of the invention, at each upper corner of the structure, an eyebolt 59 is provided (Figures 1-2), or another suitable lifting or hooking ring, for moving the rolling stand by means of a crane. Advantageously, each eyebolt 59 is orientable; for example, it can rotate towards the inside of the structure, in particular towards the first surface cavity 40, from a vertical position (Figure 1) to a substantially horizontal position (Figure 2) so as to avoid interference during an insertion of the rolling stand into the respective rolling mill compartment. Once the rolling stand has been extracted from the rolling mill, it is possible to rotate the eyebolt 59 again into the vertical position thereof for moving it by means of a crane.

[0118] As anticipated above, to lock the rolling stand once inserted into the respective rolling mill compartment, said stand is lifted inside said compartment.

[0119] In particular, during the insertion of the rolling stand into the rolling mill compartment transversally, preferably perpendicularly, to the rolling axis, the first wall 41, or alternatively the first coating element 73, abuts against at least one first central abutment 22 provided on the upper inner surface of the compartment.

[0120] If provided, at the same time, also the second wall 4T, or alternatively the second coating element 73', abuts against at least one second central abutment 22' provided on the lower inner surface of the compartment.

[0121] These central abutments 22, 22' therefore define an end-of-stroke of the rolling stand during an insertion step into the rolling mill frame.The surface cavities 40, 40' allow the stand to advance, without interfering with the compartment, until abutting against the central abutments 22, 22'.

[0122] Said central abutments 22, 22’ are positioned along a vertical plane proximal to the rolling axis, preferably positioned at a distance from the rolling axis which is shorter than the distance between a vertical plane containing the rolling axis and a vertical plane containing the vertical rotation axis X of the working roller 3’.

[0123] In the example of Figures 5-7, only one central abutment 22, 22’ is visible on both the upper inner surface and the lower inner surface of the frame compartment.

[0124] It is not excluded that two or more central abutments can be provided on both the upper inner surface and the lower inner surface of the compartment.

[0125] In a fourth embodiment of the invention, the rolling stand is provided, in the upper surface 70 of the structure thereof, with at least two coating elements 48 (Figures 1-2), protruding from said upper surface 70 so as to abut against a respective upper abutment 24 arranged at an upper inner surface of the rolling mill compartment housing said rolling stand (Figure 7).

[0126] In the example shown in Figures 1-2, four coating elements 48 are provided, arranged proximal to respective upper comers of the structure of the stand.

[0127] The coating elements 48 can also be made of a material having a greater hardness with respect to the material of the structure of the rolling stand to improve the durability thereof and the accuracy of the locking. Examples of usable materials are steels such as C40, C50, 42CrMo4, abrasion-resistant steels with a nominal hardness of 400-500 HBW, such as Hardox 400 or Hardox 500, CORC®-g compound steel, with or without surfaces hardened by means of heat treatments.

[0128] The shape of the coating elements 48 can also be selected to facilitate the maintenance or replacement thereof.

[0129] To complete the side locking, i.e. , transversely to the rolling axis, of the stand inside the respective rolling mill compartment, said compartment can be also provided with (Figures 5-7):

[0130] - at least two lifting and locking actuators 23, arranged at the lower inner surface of the compartment, to lift the rolling stand after having reached said central abutment 22 or both said central abutments 22, 22’;- and at least two upper abutments 24, arranged at the upper surface of the compartment, adapted to define a lifting end-of-stroke for the rolling stand, and therefore an abutment surface for the respective coating elements 48.

[0131] The rolling stand is therefore lifted and brought in abutment, at the coating elements 48, on said at least two upper abutments 24 so that the rolling position is always repetitive and never affected by wear of the tracks or wheels or runners used for extracting and inserting the stand during the change procedure.

[0132] By way of explanation, these lifting and locking actuators 23, for example hydraulic cylinders, can be operated by a valve for each rolling stand so as to ensure better synchronization control.

[0133] Preferably, said hydraulic cylinders are provided with a stem with a wedge-shaped end 31.

[0134] The rolling stand is in turn provided in the base thereof with at least two recesses 32 (Figures 3 and 6) of a shape complementary to the wedge-shaped end 31 of a respective stem. The wedge-shaped end 31 of the stem and the corresponding recess 32 are shaped so that the reception of said wedge-shaped end 31 in the recess 32 produces, in addition to lifting, also a slight lateral translation of the rolling stand to keep it abutting against the at least one central abutment 22, 22’. For this purpose, an appropriate clearance exists between the width of the wedge-shaped end 31 and the width of the recess 32.

[0135] Preferably, with reference to Figures 2, 3 and 6, four lifting and locking actuators 23 and four upper abutments 24 can be provided in the frame of the rolling mill compartment, which are arranged in pairs at the first face and the second face of the rolling stand, respectively, and symmetrically with respect to the aforesaid second vertical centerline plane of the rolling stand parallel to said first face and said second face, and therefore perpendicular to the rolling axis.

[0136] Consequently, the following can be provided in the structure of the rolling stand:

[0137] - four coating elements 48 protruding from the upper surface 70 of the structure of the rolling stand and arranged, proximal to respective upper corners of said structure, in pairs at the first face and the second face, respectively, of the rolling stand, and symmetrically with respect to said second vertical centerline plane;- and four recesses 32 arranged in the base of said structure substantially at the respective four coating elements 48 and preferably having a shape complementary to the wedge-shaped end 31 of the respective stem.

[0138] In a fifth embodiment of the invention, the rolling stand is provided, at the lower comers of the structure, with four wheels 60 (Figure 3). Each wheel 60 is mounted inside a respective cartridge 61 removably fixed in a respective recess 90 obtained in a lower edge of the structure.

[0139] The wheels 60 are mounted on the cartridges 61 for an easy replacement in case of wear and are all equal to facilitate the production and assembly thereof.

[0140] The four wheels 60 are also arranged in pairs at the first face and the second face, respectively, of the rolling stand, and symmetrically with respect to the second vertical centerline plane of the rolling stand, parallel to said first face and said second face, and therefore perpendicular to the rolling axis.

[0141] Preferably, each cartridge 61 has an inverted-T shape and is removably fixed to the structure by means of fixing means 62, for example screws, connecting the two arms of the T to a lower edge of the structure.

[0142] In a variant of said fifth embodiment, each cartridge 61 is provided at the bottom with one of the recesses 32, preferably having a wedge shape to accommodate the corresponding wedge-shaped end 31, complementary in shape, of a respective stem of a lifting and locking actuator 23. Such recess 32, as shown in Figure 3, can be arranged adjacent to the compartment housing the respective wheel 60.

[0143] In a further variant of said fifth embodiment, at the lower edge of each face of the rolling stand, perpendicular to the horizontal rolling direction Y, at least one containment runner 63 is provided, for example a single containment runner 63 for each face (Figure 3), fixed to the structure.

[0144] The containment runners 63 of the two faces of the rolling stand are arranged parallel to each other and perpendicular to said rolling direction.

[0145] Each containment runner 63 extends longitudinally, has the shape of a substantially flat plate, and is positioned between two wheels 60 of the corresponding face of the stand to keep the wheels 60 correctly aligned along a corresponding sliding track 71 (Figure 6).Preferably, the spacing distance between the containment runners 63 of the two faces is greater or shorter than the spacing distance between the wheels 60 of a first face and the wheels 60 of a second face of the stand.

[0146] The shape of the containment runners 63 can also be selected to facilitate the maintenance or replacement thereof.

[0147] The containment runners 63 can also be made of a material having a greater hardness with respect to the material of the structure of the rolling stand in order to contain the wheels 60 and ensure a correct resting on the tracks, and also to improve the durability thereof. Examples of usable materials are steels such as C40, C50, 42CrMo4, abrasion-resistant steels with a nominal hardness of 400-500 HBW, such as Hardox 400 or Hardox 500, CORC®-g compound steel, with or without surfaces hardened by means of heat treatments.

[0148] The optional features described above in each of the embodiments of the rolling stand of the invention can be combined with each other, totally or partially, in a further embodiment.

Claims

CLAIMS1. A rolling stand for rod-shaped bodies comprising a structure provided therein with three working rollers (3, 3’) arranged at 120° from one another so as to define a passage (5) defining a horizontal rolling direction (Y) for rolling said rod-shaped bodies; wherein a working roller (3’) of said three working rollers has a vertical rotation axis (X); characterized in that the structure of said rolling stand is provided at the top with a first surface cavity (40) open at an upper end edge (55) of the structure, placed on an inlet side of said rolling stand in a respective rolling mill compartment transversely to a rolling axis of said rolling mill;in that said first surface cavity (40) is arranged at said inlet side of the rolling stand opposite to a side, in which the aforesaid working roller (3') is provided, with respect to a first vertical centerline plane of the rolling stand, parallel to said horizontal rolling direction (Y);and in that said first surface cavity (40) is delimited, in proximity of said first vertical centerline plane, by a first wall (41 ) adapted to abut against at least one corresponding first central abutment (22) provided in an upper part of said rolling mill compartment; preferably wherein the length of the first wall (41 ) is equal to at least 2 / 3 of the thickness (T) of the rolling stand, measured along said horizontal rolling direction (Y).

2. A rolling stand according to claim 1 , wherein said structure is provided at the bottom with a second surface cavity (40'), open at a lower end edge (55') of the structure, which is on the same side as said upper end edge (55), and delimited in proximity of said first vertical centerline plane by a second wall (41'), preferably arranged on a same plane of said first wall (41 ), adapted to abut against at least one corresponding second central abutment (22') provided in a lower part of said rolling mill compartment; preferably wherein the length of the second wall (41') is equal to at least 2 / 3 of the thickness (T) of the rolling stand, measured along said horizontal rolling direction (Y), and it is preferably equal to the length of said first wall (41).

3. A rolling stand according to claim 1 or 2, wherein, on said first wall (41 ), a first recess (72) is obtained, in which a first coating element (73) is integrally fixed, preferably protruding into said first surface cavity (40), adapted to abut against said first central abutment (22);preferably wherein, on said second wall (41'), a second recess (72’) is obtained, in which a second coating element (73') is integrally fixed, preferably protruding into said second surface cavity (40'), adapted to abut against said second central abutment (22').

4. A rolling stand according to claim 3, wherein the length of the first coating element (73), and preferably of the second coating element (73'), is equal to at least 1 / 3 of the thickness (T) of the rolling stand, measured along said horizontal rolling direction (Y).

5. A rolling stand according to claim 3, wherein said first coating element (73) protrudes into the first surface cavity (40) with one outermost side thereof, with respect to the first recess (72), which acts as an abutment surface, and which is preferably arranged parallel to said first vertical centerline plane of the rolling stand;preferably wherein said second coating element (73’) protrudes into the second surface cavity (40’) with one outermost side thereof, with respect to the second recess (72’), which acts as an abutment surface, and which is preferably arranged parallel to said first vertical centerline plane;preferably, wherein said outermost sides, or abutment surfaces, of said first coating element (73) and second coating element (73') are arranged on a same vertical plane parallel to said first vertical centerline plane.

6. A rolling stand according to any one of claims 3 to 5, wherein the material of said first coating element (73), and preferably of said second coating element (73'), has a greater hardness with respect to the material of the structure of the rolling stand.

7. A rolling stand according to claim 1 or 2, wherein said first surface cavity (40) is obtained along approximately half of a flat upper surface (70) of said structure, while in the other half a further surface cavity is obtained, from which an upper end of the shaft of the working roller 3' with the vertical rotation axis protrudes;preferably wherein said second surface cavity (40') is obtained along approximately half of a flat lower surface (80) of said structure.

8. A rolling stand according to any one of the preceding claims, wherein at least at one face of said rolling stand, perpendicular to the horizontal rolling direction (Y), a cooling system is provided;preferably wherein said cooling system comprises- a hydraulic connection (47), for an inlet of a cooling liquid into the rolling stand, arranged in the upper part of the structure,- a set of three supplying means (49, 50, 51) for supplying the cooling liquid, coming from said hydraulic connection (47), at each working roller (3, 3’), each supplying means (49, 50, 51 ) being arranged on said at least one face in proximity of a respective working roller (3, 3’);wherein a first supplying means (49) is proximal and connected to said hydraulic connection (47), and two pipes (52, 53) are provided, arranged on said at least one face, which branch off from said first supplying means (49) and respectively connect said first supplying means (49) to a second supplying means (50) and to a third supplying means (51).

9. A rolling stand according to claim 8, wherein said hydraulic connection (47) comprises at least one pipe fitting (64) for the connection to the first supplying means (49), said at least one pipe fitting (64) being arranged inside the structure and provided at the upper end thereof with a gasket (65), arranged tangentially to a flat upper surface (70) of the structure in a position such as to sealingly adhere, when the rolling stand is lifted inside the respective rolling mill compartment, to a corresponding cooling liquid supplying pipe arranged on the upper inner surface of said respective compartment.

10. A rolling stand according to claim 9, wherein said at least one pipe fitting (64) is arranged inside said first surface cavity (40).

11. A rolling stand according to any one of claims 8 to 10, wherein first supplying means (49), second supplying means (50) and third supplying means (51) comprise injection nozzles or blades (54) facing at least towards a groove of the respective working roller (3, 3’), and preferably arranged staggered with respect to one another, or differently orientable with respect to one another, to prevent the respective jets or blades of cooling liquid from interfering with one another;preferably wherein, in the case of injection nozzles, the axes of said injection nozzles face towards the inside of said groove.

12. A rolling stand according to any one of the preceding claims, wherein on each face of the rolling stand, perpendicular to the horizontal rolling direction (Y), three axial contact elements (56, 57, 58) are provided, arranged at an angular distance of 120° from each other and adapted to receive, on a first face, and to transmit, on a second face, an axial thrust along the rolling axis of the rolling mill, transferring said axial thrust from one rolling stand to the next;preferably wherein the three axial contact elements (56, 57, 58) of the first face and the three axial contact elements (56, 57, 58) of the second face are arranged symmetrically with respect to a second vertical centerline plane of the rolling stand parallel to said first face and said second face.

13. A rolling stand according to claim 12, wherein two axial contact elements (56, 57) of said three contact elements are arranged, in an upper area of each face, symmetrically with respect to said first vertical centerline plane of the rolling stand, perpendicular to said second vertical centerline plane, while the remaining axial contact element (58) is arranged in a lower area of each face at said first vertical centerline plane.

14. A rolling stand according to claim 12 or 13, wherein, on each face, the axial contact element (56), more proximal to the inlet side of said rolling stand into the respective rolling mill compartment, and the axial contact element (58), arranged in a lower area of the face at said first vertical centerline plane, have a respective contact surface arranged at a distance from the second vertical centerline plane which is shorter with respect to the distance of the contact surface of the remaining axial contact element (57) from said second vertical centerline plane, said remaining axial contact element (57) being the most distal from said inlet side of the rolling stand.

15. A rolling stand according to any one of the preceding claims, wherein, at each upper corner of the structure, a lifting ring (59) is provided for moving the rolling stand by means of a crane; and wherein each lifting ring (59) is foldable towards the inside of the structure so as to avoid interference during an insertion of the rolling stand into the respective rolling mill compartment.

16. A rolling stand according to any one of the preceding claims, provided, in an upper surface (70) of the structure thereof, with at least two coating elements (48), protruding from said upper surface so as to abut against a respective upper abutment (24) arranged at an upper inner surface of the rolling mill compartment housing said rolling stand and defining a lifting end-of-stroke of the rolling stand;preferably wherein four coating elements (48) are provided, arranged proximal to respective upper comers of the structure.

17. A rolling stand according to any one of the preceding claims, provided, at the lower corners of the structure, with four wheels (60), wherein each wheel (60) is mountedinside a respective cartridge (61) removably fixed into a respective lower recess (90) of the structure;preferably wherein each cartridge (61 ) has an inverted-T shape and is removably fixed to the structure by means of fixing means (62) connecting the two arms of the T to a lower edge of the structure.

18. A rolling stand according to claim 17, wherein, at a lower edge of each face of the rolling stand, perpendicular to the horizontal rolling direction (Y), at least one containment runner (63) is provided, fixed to the structure, each containment runner (63) being positioned between two wheels (60) of the corresponding face to keep the wheels (60) aligned along a corresponding track;preferably wherein the spacing distance between the containment runners (63) of the two faces is greater or shorter than the spacing distance between the wheels (60) of a first face and the wheels (60) of a second face.

19. A rolling stand according to claim 17 or 18, wherein each cartridge (61) is provided at the bottom with a recess (32) having a wedge shape to accommodate a corresponding wedge end (31), of a shape complementary to the recess (32), of a respective stem of a lifting and locking actuator (23) of the rolling stand, arranged at a lower inner surface of the rolling mill compartment;preferably wherein said recess (32) can be arranged adjacent to a compartment housing the respective wheel (60).

20. A rolling mill for rolling rod-shaped bodies, defining a horizontal rolling axis and comprising a rolling train having at least two rolling stands (1 , 2) according to any one of the preceding claims.

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