Cantilever rolling mill stand with converging roll axes

Abstract: Rolling stand with rolling rings supported as a cantilever and having their axes at an angle to each other for the rolling of metallic products, the axes of the rolling rings being horizontal, vertical or tilted, the stand comprising shafts (16) to bear the rolling rings (10) with at least a first bearing (12) and a second bearing (13), at least one pair of the first and second bearings (12-13) being lodged in an eccentric support suitable to adjust the distance between centres of the rolling rings (10), the axes (15) of the rolling rings (10) coinciding with the axes (15) of the respective shafts (16), in which stand the axes (15) of the rolling rings (10) in a non-rolling condition form between them a pre-determined angle (alpha) and converge on a position outside and in front of the rolling rings (10).

Description: This invention concerns a rolling stand with rolling rings supported as a cantilever and having their axes at an angle to each other for the rolling, advantageously hot rolling, of metallic products. To be more exact, the invention concerns a rolling stand with rolling rings supported as a cantilever, the shafts bearing the rings not being parallel or not being always parallel. The invention is applicable to rolling stands with the axes of the cantilever-wise rolling rings horizontal, vertical or tilted. The known rolling stands have the axes of the shafts bearing the rolling rings substantially parallel. During rolling the shafts bend and the rings are displaced by a given angle so that their respective axes in fact diverge. To avoid such shortcomings, many contrivances are employed such as the reinforcement of the shaft at the cantilever portion holding the rolling ring, the strengthening of the shaft between the two bearings of the stand, the enlargement of the first bearing of the stand, etc. Thus efforts have been made by way of designing and dimensioning to obviate a typical, characteristic shortcoming of any beam supported at two or more points and stressed with a given weight or force. Even with the contrivances obtained in the state of the art the rolling rings undergo a widening owing to the high rolling pressures used in modern rolling plants. Although such widening is rather limited at present, yet it leads to problems regarding quality, finish and safety. GB-A-792,568 discloses a rolling stand with rolling rings supported as cantilevers, the axes of the rings lying at a suitable, selected angle to each other. This angle is fixed and serves only to enable two independent motors to be positioned. GB-A-1,240,659 teaches the adjustment of the angle between the axes of rolling rolls supported as cantilevers. This adjustment serves only to adjust the working gap between the rolls, so that a given gap corresponds to a given angle and viceversa. A rolling mill stand according to the pre-characterising part of claim is shown in DE-U-8425635. The present applicant has designed, tested and embodied this invention to obviate such shortcomings and obtain a plurality of advantages,and in a variant this invention may be applied in conjunction with the teaching of IT 1187546. A rolling stand with rolling rings supported as a cantilever and having their axes at an angle to each other according to the invention is represented and characterized in the main claim and dependent claims. The shafts supporting the rolling rings as a cantilever are fitted at an initial angle which leads their axes to converge on a position outside the rings. According to a variant this initial angle can be obtained as desired and modified in steps so as to suit, with each step of the modification, a given range of products to be rolled. For instance, the angle "alpha" will be equal to "x" and be suitable for rods having a diameter ranging from 10 to 15 mm. and will be calculated for about the requirements of the mean value, namely 12 mm., of the diameter of the product to be rolled. For a range of 15 to 18 mm. the angle "alpha" will be equal to "y", which will be greater than "x" and be characteristic of the median value of the range in question, and so on for the various ranges which can be envisaged as the extent of each single step of values. Thus, for a range of rods from 6 to 20 mm. we may have from two to seven or more steps of adjustment, each step being characterized advantageously by about the mean value. In use the variation of the angle may be graduated as required and continuous, being obtained with continuous adjustment means. The adjustment of the angle can be made functional by the rolling factor. Such adjustments made functional by the rolling factor can be obtained by providing load cells, which by means of a processing system determine in steps or continuously in real time or compensated time the optimum angle for the shafts to take up. This means that the angle may vary with variations in the properties of the material to be rolled or in the geometric characteristics of the section to be rolled. Variation of the angle may take place by acting on both shafts or on one single shaft. Moreover, the adjustment can be made by acting on the first bearing of the stand, namely the bearing nearest to the rolling rings, or on the second bearing, that is, the bearing farthest from the ring. The optimum angle between the two shafts will vary as a function of the rolling load, of the properties of the material to be rolled, of the geometric characteristics of the shafts and of the chemical and physical properties of the shafts. The angle may vary from 20 seconds up to about 2°. The angle "alpha" may have as its bisector the plane passing along the centre line of the section being rolled. According to a variant the bisector of the angle "alpha" does not pass along the centre line of the section being rolled. The invention arranges, therefore, that where the distance between centres of the rings has to be adjusted, that adjustment will be independent of the angular adjustment existing between the axes of the rings so as to compensate for the above bending problems. The attached figures, which are given as a non-restrictive example, show the following:- Fig.1 shows a prior art arrangement in an exaggerated and stylized form; Fig.2 shows the general arrangement of the roll shafts used in the invention in an exaggerated and stylized form; Fig.3 shows an example of a possible embodiment of the invention; Fig.4 gives a diagram of a system for continuous adjustment. Fig.1 shows a prior art arrangement although shown with a diagram and deformed so as to illustrate the case. In Fig.1 during an inactive, non-working phase rolling rings 10 have axes 15 substantially straight and parallel. The axes 15 of the rolling rings coincide with the axes of shafts 16 (see Fig.3) which cooperate with a first bearing 12, a second bearing 13 and advantageously with a thrust bearing 14. During the processing of a section 11 the rolling thrust tends to separate the rings 10, which take up a position 110. At the same time the shafts 16 bend and deform the axes 15 according to the position 115. As is clear, during their working step the rolling rings 110 are no longer in the best geometric condition. Fig.2 gives a deformed and amplified diagram of the idea of the solution. This figure shows that at the beginning the axes 15 of the shafts 16 supporting the rolling rings 10 are positioned at an angle "alpha" to each other. When the stand is not working and the rolling rings 10 are only rotating, they are located in the position 10. When the stand is rolling the section 11, the rolling rings 10 are displaced and take up the position 110, and their axes 15 are deformed and take up the position 115. Owing to the initial angle "alpha" the rings 10 under load take up the position 110, which is the optimum position. The angle "alpha" may be variable in steps or continuously. Variation in steps can be provided, for instance, by means of threaded shafts or wedges or jacks or other means, which act on the first bearing 12 or second bearing 13 of the stand. According to a preferred but not exclusive embodiment the adjustment is performed on the second bearing 13. Adjustment in steps can be obtained also, for instance, by means of supports with a differentiated eccentricity of lodgement, the supports serving to uphold and lodge the housing of the second bearing 13. Continuous variation can be obtained with threaded shafts, eccentric sleeves, wedges, etc. acting on the first 12 or second 13 bearing, advantageously but not exclusively on the second bearing 13. Fig.3 shows a diagrammatic example of the invention, in which there is adjustment of the distance between centres of the rings and of the angle between the axes of the rings. In this figure the shaft 16 cooperates with the first and second bearings 12-13, which are held and supported in a housing 17 that facilitates adaptation to deformations of the shaft 16. This housing is the subject of a specific right of the present applicant. In the case in question the part of the housing which cooperates with the second bearing 13 is lodged and supported on an eccentric sleeve 18 that can rotate as required owing to the action of a worm screw 19 on a threaded portion 20 forming an integral part of the eccentric sleeve 18. According to a variant the eccentric sleeve 18 can act instead on the first bearing 12 or, in another variant, two eccentric sleeves 18 could be included, one of them acting on the first bearing 12 while the other acts on the second bearing 13. As we said earlier, instead of the eccentric sleeve 18 there could be provided threaded shafts, wedges, jacks, etc. according to the design requirements. The housing 17 cooperates with a load cell 21 that monitors the rolling stress. Variations detected by the load cell 21 can be adapted advantageously to avoid hurried adjustments or adjustments depending on peaks or other random factors.

Claims: Rolling mill stand with cantilever rolling rolls (10) having their axes (15) substantially stationary, the distance between centres of the rolling rolls (10) being substantially constant, the axes (15) of the rolling rolls (10) being horizontal, vertical or inclined, the rolling mill stand comprising roll-bearing shafts (16), each shaft (16) having at least a first bearing (12) adjacent to the rolling roll (10) and a second bearing (13) distant from the rolling roll (10) the two bearings (12-13) being lodged in respective eccentric supports,, the rolling rolls (10) being coaxial with their respective shafts (16), the axes (15) of the rolling rolls (10) forming between them an angle α and converging at a position outside and in front of the rolling rolls (10) themselves, independent eccentric means (18-19-20) being included which adjust the angle α by acting on one single eccentric support (17), the rolling mill stand being characterized in that the respective eccentric supports are (17) connected torsionally by a sleeve, the supports (17) having a substantially spherical outer surface, the front support (17) being associated with a load cell (21), to monitor the rolling stress and means (21-25) to adjust the value of angle α in dependence thereof. Rolling mill stand as claimed in Claim 1, in which the bisector of the pre-determined angle α passes substantially along the centre line of the section (11) being rolled. Rolling mill stand as claimed in Claim 1, in which the bisector of the pre-determined angle α runs outside the centre line of the section (11) being rolled and is displaced in relation to that centre line. Rolling mill stand as claimed in any claim hereinbefore, in which the predetermined angle α is comprised between 20 seconds and 2°. Rolling mill stand as claimed in any claim hereinbefore, in which the adjustment of the pre-determined angle α takes place at the first bearing (12) of the stand. Rolling mill stand as claimed in any claim hereinbefore, in which the adjustment of the predetermined angle α takes place at the second bearing (12) of the stand.

Inventors: NONINI GEREMIA, NONINI, GEREMIA
Applicants: DANIELI OFF MECC, DANIELI & C. OFFICINE MECCANICHE S.P.A.
Application year: 1989
Main classification: B21B13
IPC codes: B21B31, B21B13