EP2934777A1

EP2934777A1 - Rest bar for double or multi-stranded production plant

Info

Publication number: EP2934777A1
Application number: EP13826960.0A
Authority: EP
Inventors: Giuseppe Bordignon; Miroslav Zerajic
Original assignee: Danieli and C Officine Meccaniche SpA
Current assignee: Danieli and C Officine Meccaniche SpA
Priority date: 2012-12-18
Filing date: 2013-12-18
Publication date: 2015-10-28
Anticipated expiration: 2033-12-18
Also published as: EP2934777B1; WO2014097177A1; ITMI20122172A1

Abstract

A rest bar (10) for a double or multi-stranded rolling plant, adapted to cooperate with a rolling stand of said rolling plant, said plant defining a rolling axis, the rest bar comprising a motor (7), a reduction unit (8), a worm screw (6), a rolling guide (11), for guiding a material to be rolled into rolling cylinders (30) of said rolling stand, said rolling guide being fixed to the worm screw (6) so that, at an angular rotation of the worm screw (6) about its axis, the rolling guide (11) translates by a linear movement which is transversal to the rolling axis.

Description

REST BAR FOR DOUBLE OR MULTI-STRANDED PRODUCTION PLANT

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Field of the invention

The field of the invention is that of the production of rolled products, e.g. strands or bars, by means of a slitting process.

Background art

Double or multi-stranded slitting plants are used to increase the production of strands and/or bars. They provide for longitudinally splitting the rolled product into two or more equal parts by passing it in channels made in specifically shaped rolling rolls, once the starting billet has passed in one or more rolling stands or units in order to achieve a substantially rectangular section, thus resulting in two or more rolled products which move parallel and, consequently, creating two or more parallel rolling lines placed side-by-side.

An important limit to the development of the technology with multiple strands/bars is the difficulty in obtaining the division of the material into exactly equal parts having the same mass within the moulder unit. According to the state of the art, there are various methods for dividing the rolled product into two or more parts: one example is described in patent US4193283.

In an attempt to improve the process of dividing the rolled product into several parts which are as equal as possible, a rest bar is used which, when manually adjusted as disclosed in patent IT1247429, adjusts the transversal position of the input guide to the moulder unit on which it is installed.

The traditional system includes moving the input guides, i.e. the rolling boxes or guides, by means of a slide moved by a worm screw. As already mentioned, the movement occurs manually and with an approximate accuracy of about 1 mm.

However, in the examples mentioned, human control is required for the parts in which the material is divided in the next cutting box, which control is in any event carried out occasionally and not very accurately. Furthermore, the state of the art includes that the adjustment of the position of the rolling box is carried out when the rolled product is not inside it, therefore the production process needs to be interrupted in order to perform the adjustment. In plants that use multi-stranded slits, strands/bars are normally produced with identical transversal sections, thus any existing mass difference between the strands is transformed into a different length thereof, which increases in the various rolling passes through the next stands. Indeed, the cylinders in the rolling units have a determined gap, which is predetermined according to the production campaign and is then maintained constant, and therefore the mass difference in the strands results into a different speed to each other, the pressing force in the respective rolling units being equal. Due to the imperfect division of the rolled product in the moulder unit, the shears downstream of the last rolling unit - one for each rolled strand - cut the strands at different lengths.

The strands are normally cut by the shears at a multiple length of the commercial length, which usually is of 6 or 12 metres, then are cooled and cut to size. As the strands or bars differ in length, a discard tail of variable dimension will remain for each bar divided into several commercial-sized pieces. In the best plants, where there is an almost continuous control by the operators on the rest bar upstream of the moulder unit, this results into a difference in length in the cooling plate (72 m) which may reach 0.3%; instead in average plants, the differences in length in the cooling plate exceed 0.5%.

Hence the discards, i.e. tails, are to be minimized when custom cutting on cooling plate by decreasing the difference in length of the strands upstream, i.e. the difference of mass flow, by improving the division of the rolled product into equal parts.

The need to contain the length difference of the bars as much as possible in plants where the cut is instead carried out at commercial length (for example 6 or 12 m) directly in-line, immediately out of the rolling mill, is even greater. If we assume that the same percentage difference in length in the cooling plate of the standard process is also kept for bar lengths cut in-line at 12 m, products which are not compatible with the market requirements will be obtained, since this difference is to be added to the machine cutting error. Therefore, the differences in length of the strands or bars cut directly in-line at commercial measurement are to be minimized to prevent them from being off size.

US 5,174,142 discloses a rest bar solution which allows certain drawbacks to be partly overcome. However, the mechanics for moving the rolling box in this solution is under dripping, that is subjected to external agents, such as water, limestone, iron oxide, etc., which reach the most delicate members of the mechanics, thus compromising the adjustment accuracy because scale and dirt are created, which hinder an accurate and linear movement of the rolling box.

A further adjustment inaccuracy of the rolling box position is also due to the use of linear dovetail sliding guides. By using these guides, the application of an appropriate, accurate blocking system becomes necessary.

Summary of the invention

It is the primary object of the present invention to provide a rest bar with features allowing the length difference of the strands or bars to be minimized with high accuracy, while then reducing discards and increasing the performance of the production process.

It is another object of the invention to provide a rest bar which allows its position to be adjusted even during the rolling operation.

It is another object of the invention to provide a rest bar which carries out an in-line micrometric adjustment, thus ensuring absolute accuracy.

A further object of this invention consists in providing a rest bar which eliminates or at least minimizes the presence of operators required for the adjustment activities in a bar production plant with double or multi-stranded slits.

These and other objects are achieved by means of a rest bar for a rolling plant which divides a rolled product into two or multiple strands, the rest bar being adapted to cooperate with a rolling stand of said rolling plant, said plant defining a rolling axis, the rest bar comprising, according to claim 1 :

- a worm screw, defining a longitudinal axis,

- a rolling guide, for guiding a material to be rolled into rolling cylinders of said rolling stand, the rolling guide being fixed to the worm screw so that, at an angular rotation of the worm screw around its longitudinal axis, the rolling guide translates by a linear movement which is transversal to the rolling axis,

wherein there are provided a motor and a reduction unit, both integrated within the rest bar, the motor being configured to be controlled by a remote control or automatically controlled by a PLC, whereby an adjustment of said angular rotation of the worm screw and, thus, of said linear transversal movement of the rolling guide can occur during the rolling operation,

wherein said rolling guide is supported by a carriage which can slide along linear guides when it is moved by the worm screw,

characterized in that protection covers are provided in order to prevent the entry of dust or water in said linear guides of the carriage.

Advantageously in the rest bar solution of the invention, the movement mechanics of the rolling box is all enclosed and protected inside the same rest bar: thus external agents, such as water, limestone, iron oxide etc., cannot reach the most delicate members of the mechanics.

In the following description, the term strand also includes the bar-like rolled product in brief. A double stranded slit process is also used as an example, but it is understood that the invention also refers indifferently to the division into three, four, five or more strands.

In light of the difference detected between the two strands, the required counter- measures are implemented: according to the differences in mass flow detected downstream of the rolling line, the rest bar is moved so as to perfectly centre the material in the moulder unit channels. The adjustment of the position of the rest bar may take place remotely, i.e. at a distance, or automatically: the operator can activate the motor, which is integrated within the rest bar and which controls the same rest bar, by means of the controls from the station, or a feedback system can be used which automatically activates the motor according to the data received from the line downstream. When required, the bar may also be adjusted manually.

Advantageously, the adjustment of the rest bar can also be carried out during the rolling operation and, therefore, in combination with the micrometric adjustment, can ensure an optimal positioning for the proper separation of the material, due to a continuous control and repositioning.

The dependent claims refer to preferred embodiments of the invention.

Brief description of the drawings

Further features and advantages of the invention will become more apparent from the detailed description of a preferred, but not exclusive, embodiment of a rest bar which is in accordance with the invention for a double stranded production plant, shown by way of non-limiting example with the aid of the accompanying drawings, in which:

Figure 1 diagrammatically depicts a sequence of rolling units for a double stranded production plant of the state of the art, in which the rest bar of the invention is included;

Figure 2 depicts a front view of the rest bar of the invention;

Figure 3 depicts a sectional view along plane A-A of the rest bar in Figure 2;

Figure 3a depicts an enlargement of a part of the view in Figure 3;

Figure 4 diagrammatically depicts the cross section of the rolling material before splitting.

The same numbers in the various figures correspond to the same elements or components.

Detailed description of preferred embodiments of the invention

With reference to figures 2 and 3, a rest bar 10 is depicted according to the present invention.

With reference to figure 1 , a sequence of rolling units, known per se, is shown and comprises the rest bar 10, by way of non-limiting example, placed after the rolling stand 4 and immediately upstream of the moulder unit or stand 15.

The device for guiding the material, called rolling box or guide 11 , which is installed on the rest bar 10, and the moulder unit 15 form together the step of dividing the bar or strand to be rolled into two parts, or the first part of said step of dividing. The slitting process starts at the rolling stand 14 where the profile of the bar is generally shaped with a cross section also known as star square or with another geometry which allows the material to be prepared for the subsequent division. Figure 4 diagrammatically shows the relationship of channels A and B of the moulder unit 15 and of the profile 20 of the bar coming from the rolling stand 14 in two different alignment positions, with the position of the profile (in the right part of figure 5) offset by a distance ds.

In the following rolling step, the "double round" 40 is first shaped and then perfected and permanently cut in the next step, where a cutting box 50 is provided, known per se, to which the step of separating the rolled material into two separate strands 51 , 52 corresponds. A sufficient number of oval and round section rolling units are arranged downstream of the cutting box 50 to take the strands to the final section, it being normal for the last rolling unit 60 to have a round section. A cutting shear 70 is arranged downstream of the last rolling unit 60.

The guiding devices for guiding the material into the rolling cylinders 30 of the moulder unit 15 thus determine the balance between the sections of the two output profiles from the moulder unit 15. The material guiding device, called rolling box 1 1 , comprises the input guide 12 and vertical and horizontal rollers 9, which rotate tangent to the surfaces of the material to facilitate the sliding movement thereof. When entering the rolling box 11 , the rolled bar or strand-like product is accurately positioned inside the next rolling channel, formed between two cylinders 30 of the moulder unit 15 placed side-by-side. The distance between the plane containing the axes of rollers 9 and the plane containing the axes of rolling cylinders 30 is in a range from 90 to 20 mm, preferably 1 19 mm.

A reduction unit 8 and motor 7, preferably of the brushless type, provide the rotational motion to the worm screw 6 arranged between thrust bearings 5 which support it on the support structure 2. Motor 7 is controlled by an inverter to allow the adjustment of the revolutions.

Unlike known rest bars, motor 7 is advantageously integrated within the same rest bar 10 and moves therewith, and is configured to be controlled by a remote control or automatically controlled by a PLC (programmable logic controller).

The reduction unit 8 has a high reduction ratio, advantageously comprised from 1 :50 to 1 :150, preferably from 1 :90 to 1 :130, even more preferably from 1 :115 to 1 :120, for example 1 :1 9: this allows a very accurate adjustment of the rotation of the worm screw 6 which transforms into a linear translation of micrometric dimension, in the order of 0.01 mm, of the carriage 31 of the rest bar 10. Such a ratio also provides a self-braking system which allows the position to be kept at the end of the in-line adjustment. The worm screw 6 preferably, but not necessarily, has a pitch comprised from 3 to 20 mm, preferably from 4 to 12 mm, preferably equal to 5 mm.

The combination of the worm screw 6 and of the reduction unit 8, with the suitable sizes, allows the movement of the rolling box 1 1 even during the rolling of the strands.

The carriage 31 of rest bar 10 slides along two linear guides 3 when it is moved by the worm screw 6. The processing accuracy of the components of the screw/nut screw and carriage/guides couplings allows not to have any clearances.

To keep the adjustment accuracy efficient over time, the whole rest bar 0 of the invention is provided with protection covers in order to prevent the entry of external agents, such as dust (for example limestone, iron oxide) or water on the linear sliding guides 3 and/or on the worm screw 6.

In particular, both the linear guides 3 and the worm screw 6 are protected by a fixed cover 32 which extends along the whole longitudinal extension or length of the worm screw 6 and of the linear guides 3, thus protecting them against external agents such as water, limestone, iron oxide, etc.

As better shown in the variant in figure 3a, the fixed cover 32 encloses the worm screw 6 and the linear guides 3 therein. In particular, the linear guides 3 are integrally fixed inside said fixed cover 32 or are an integral part of the same cover 32.

Carriage 31 is shaped so as to completely surround a portion of the fixed cover 32 along the longitudinal axis Y defined by the worm screw 6. In particular, carriage 31 runs along said fixed cover 32.

In an advantageous variant, carriage 31 has an upper part 33 having an inner surface 34 substantially conjugated with the outer surface 35 of the fixed cover 32, and has a lower part 36 internally provided with protrusions 37 sliding on the respective linear guides 3. Therefore, carriage 31 slides on the linear guides 3, which are in fixed position, as are the worm screw 6 and the cover 32. Said lower part 36 of carriage 31 is also provided with a connection element 38 which allows the motion transmission from the worm screw 6 to the carriage 31. Such a connection element 38, which surrounds part of the worm screw 6 along the axis Y and is arranged between the protrusions 37, moves along the axis Y inside a cavity of the fixed cover 32.

Inside the fixed cover 32, there can also be provided, for example, bellows-like covers 4 made of plastic material, which further protect the linear guides 3 and the worm screw 6. Thereby, the linear guides 3 and the worm screw 6 are kept in an advantageously aseptic ambient to extend the useful life thereof.

The linear guides 3 are preferably of the ball recirculating type, therefore do not require any blocking system, being able to keep the position with extreme accuracy.

The linear guides 3 can be subjected to an anti-corrosion treatment.

An air-oil lubrication circuit is provided to lubricate the worm screw 6. Alternatively, centralized grease lubrication in a single spot is provided to facilitate maintenance. The geometry of the support on which the rolling box 11 is fixed allows a lateral sliding thereof and prevents it from oscillating or tilting with respect to the support structure 2. In order to support the worm screw 6 and the reduction unit 8 both radial ball bearings and axial ball bearings are used in an appropriate combination for properly positioning worm screw 6.

The position of the rest bar can be adjusted remotely, i.e. at a distance, for example the operator may activate motor 7 from the control station. The adjustment can also be made automatically, for example in feedback according to the signals coming from the line downstream. Furthermore, since the adjustment is micrometric, the possibility of adjusting the position of the rest bar remotely/automatically allows a continuous control and repositioning of the rest bar to ensure an optimal accuracy and hence a perfect separation of the mass into two equal parts.

The control of the rest bar 10 also includes a two-mode operation: the "quick movement" mode allows the rolling box 11 to be quickly moved in order to change the rolling channel; the "slow movement" mode allows small micrometric modifications to be made to the position of the rolling box 11 and therefore to the relative speeds of the two strands.

However, the rest bar can also be manually activated by rotating a protruding pin on the operator side, when needed.

Motor 7 is advantageously equipped with an electromagnetic brake to prevent involuntary movements of the rolling box 11 in the inactive steps, while the brake is released during the movement time of the rolling box 11 to allow the rotation of the worm screw 6. Motor 7 is also equipped with a resolver which controls the rotation thereof and hence the amount of the lateral movements of the rolling box 11. When the worm screw 6 is rotated, exceeding the torque values set on the PLC causes the system to stop. The movement speed of the rolling box 1 can be parameterized and adjusted according to the movement accuracy required. The automation of the rest bar 10 can interface with the automation of the rolling mill for a better control of the whole system.

It is apparent from the above description that the main advantages of the rest bar of the invention consist in:

- being able to be automatically adjusted when rolling, unlike rest bars of the state prior art on which the operator can carry out a manual adjustment only when the plant is stopped;

- preventing the manual operations of blocking/releasing the carriage with mechanical means at the end of the adjustment (which in any event is to be done when the plant is stopped in plants with rest bars of known type);

- being able to carry out the adjustment in-line by means of a remote control, e.g. from a station, or automatically by means of a PLC (e.g. in accordance with a feedback signal from a point further downstream of the plant);

- being able to carry out a micrometric adjustment which allows an accurate division of the mass between the two rolling lines.

Being able to carry out the adjustment also when rolling allows the mass distribution effects to be observed in real time by moving the rolling box 11 by means of the rest bar, and hence allows the adjustment to be continued until the optimal distribution of the material is achieved.

Claims

1. A rest bar for a rolling plant which divides a rolled product into two or more strands, the rest bar being adapted to cooperate with a rolling stand of said rolling plant, said plant defining a rolling axis (X), the rest bar comprising

- a worm screw (6), defining a longitudinal axis (Y),

- a rolling guide (11 ), for guiding a material to be rolled into rolling cylinders (30) of said rolling stand, the rolling guide being fixed to the worm screw (6) so that, at an angular rotation of the worm screw (6) around its longitudinal axis (Y), the rolling guide ( ) translates by a linear movement which is transversal to the rolling axis, wherein there are provided a motor (7) and a reduction unit (8), both integrated within the rest bar, the motor being configured to be controlled by a remote control or automatically controlled by a PLC, whereby an adjustment of said angular rotation of the worm screw (6) and, thus, of said linear transversal movement of the rolling guide ( 1) can occur during the rolling operation,

wherein said rolling guide (11) is supported by a carriage (31 ) which can slide along linear guides (3) when it is moved by the worm screw (6),

characterized in that protection covers are provided in order to prevent the entry of dust or water in said linear guides (3) of the carriage (3 ).

2. A rest bar according to claim 1 , wherein said protection covers are a fixed cover (32) which extends along the entire length of the worm screw (6) and of the linear guides (3), thus enclosing both the worm screw (6) and the linear guides (3) therein.

3. A rest bar according to claim 2, wherein the linear guides (3) are integrally fixed inside said fixed cover (32) or are an integral part of the fixed cover (32) and are arranged in the inner part thereof.

4. A rest bar according to claim 3, wherein the carriage (31 ) is shaped so as to surround a portion of the fixed cover (32) along the longitudinal axis (Y).

5. A rest bar according to claim 4, wherein the carriage (31 ) has an upper part (33) having an inner surface (34) which is substantially conjugated with the outer surface (35) of the fixed cover (32), and has a lower part (36) internally provided with protrusions (37) sliding on the respective linear guides (3).

6. A rest bar according to any one of the preceding claims, wherein said linear guides (3) are of the recirculating ball type.

7. A rest bar according to any one of the preceding claims, wherein the reduction unit (8) has a reduction ratio from 1 :90 to 1 :130, so as to obtain a micrometric adjustment of the angular rotation of the worm screw (6), said worm screw (6) preferably having a pitch from 3 to 20 mm.

8. A rest bar according to any one of the preceding claims, wherein the rolling guide (11 ) comprises an input guide (12) to the rest bar, and vertical and horizontal rollers (9) which rotate tangent to the surfaces of the material to be rolled.

9. A rest bar according to any one of the preceding claims, wherein the worm screw (6) is arranged between thrust bearings (5) which support it on a support structure (2).

10. A rest bar according to any one of the preceding claims, wherein the worm screw (6) is protected with a bellows-like cover (4).

11. A rest bar according to any one of the preceding claims, wherein an air-oil or air-grease lubrication circuit is provided to lubricate the worm screw (6) and the linear guides (3) of the carriage (31 ) of the rolling guide ( 1 ).

12. A rest bar according to any one of the preceding claims, wherein the motor (7) is a brushless motor controlled by an inverter, and is preferably equipped with a resolver and an electromagnetic brake.

13. A method for controlling a rest bar according to any one of the preceding claims, wherein an in-line adjustment of the angular rotation of the worm screw (6) and, thus, of the linear transversal movement of the rolling guide ( ) is carried out during the rolling operation, by means of a remote control or of an automatic control by PLC acting on the motor (7).

14. A method according to claim 13, wherein said remote control is carried out from a station, or wherein said automatic control by means of a PLC is carried out according to a feedback signal from a position further downstream of the rolling plant.

5. A rolling plant for dividing a rolled product into two or more strands fed on respective rolling lines, the plant comprising a rest bar, according to any one of the claims from 1 to 12, which cooperates with a slitting station provided with at least one rolling stand.