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FI ELD OF THE INVENTION

The present invention relates to a drive shaft for transmitting motion from a motor or gearbox to a roll, in particular for rolling tubes.

STATE OF THE ART

A very common technique for rolling tubes without welding operated with a mandrel is nowadays carried out on a rolling mill comprising a sequence of rolling stands with two rolls or three rolls. The rotation axes of the rolls of each rolling stand are mutually coplanar and lie on a plane orthogonal to the rolling axis.

Typically in two-roll rolling stands, the rolls of one stand are arranged offset by 90 ° with respect to the previous adjacent rolling stands, whereas in three-roll rolling stands the rolls of a rolling stand are usually offset by a 60 ° angle with respect to the adjacent rolling stands in the direction of the rolling line. In three-roll rolling stands of the latter type, during rolling, the rolls of each rolling stand receive the motion generated by respective gearbox by means of drive shafts. Examples of rolling stands of this type are described in EP565772 and WO980651 5.

As a result of the offset arrangement of the rolls of each rolling stand with respect to the adjacent rolling stands, one or two of the drive shafts are arranged inclined between the ground and the roll, typically by an angle equal to 30 ° or in such an order of magnitude, while the drive shaft of the third roll is consequently arranged vertical or nearly vertical.

Generally, for the purposes of easier maintenance of the rolling stands, the rolls may be extracted from the rolling stands, for example for periodically turning the rolls or for changing the diameter of the rolls for rolling other formats. Containers or cartridges, which support three rolls held together in a set, are provided in order to facilitate and expedite the extraction and the respective re-assembly of the rolls in their place. These containers are structurally resistant and rigid, and additionally allow to extract the rolls easily for maintenance. For example, a cartridge extraction method includes sliding the container on the floor in radial direction towards a predetermined side of the rolling stand, as in the case of the rolling mill described in US6276182.

In order to be extracted from the rolling stand along the with the cartridge, the rolls of each rolling stand must necessarily be released from the drive shaft and from the radial roll position adjustment devices mounted onboard the fixed structure of the rolling mill. Furthermore, the drive shaft, which is along the path that the cartridge must follow in order to be pulled out from the rolling stand, must leave the path free so that the cartridge can be moved into the maintenance area. In the rolling mill described in WO9806515, the three drive shafts must be detached and removed from the working position in order to allow the extraction of the rolls in radial direction with respect to the rolling stand, which operation makes maintenance times longer. Fitting the gearbox and motor on slides which move the drive shaft and gearbox away from the rolling stand when the cartridge needs to be pulled out from the rolling mill is also possible.

Therefore, it is desirable to further reduce the cartridge extraction time, in particular by expediting the assembly and disassembly time of the drive shaft. Document US4945745 describes a telescopic drive shaft consisting of two parts sliding within each other, which contain a pneumatic cylinder working as gas spring capable of extending the two members of the drive shaft by preloading them against the roll in order to take the axial movements of the roll into account in such a manner to avoid possible detachments of the drive shaft from the roll. The way in which the drive shaft is assembled and disassembled is not disclosed but generally the detachment also requires moving the gearbox and the motor fitted on the slide, which is a rather laborious operation.

Document US6287208 describes a drive shaft consisting of two parts telescopically sliding within each other, which is held at its maximum working length by packs of Belleville washers arranged in the inner cavity. A traction device, external to the drive shaft, is provided, which traction device telescopically retracts one of the two parts of the drive shaft within the other exerting a very high compression force against the bias of the Belleville washers in order to unhook the drive shaft from the roll. A disadvantage of this solution is the need to provide a high number of Belleville washers in the drive shaft, which increases the overall weight of the drive shaft. Furthermore, this solution does not offer a very favorable shortening ratio of the drive shaft.

The need to have a drive shaft which offers a good shortening stroke with light weight and good handling is therefore felt.

SUMMARY OF THE INVENTION

It is the main object of the present invention to provide a rotary motion drive shaft which connects the slow shaft of a gearbox to a roll, which is light and easy to handle and which allows a long shortening stroke during the drive shaft release operation. It is a further main object of the invention to provide a drive shaft which allows a lower number of operations needed to extract the rolls from the respective rolling stand, thus simplifying and consequently expediting the respective maintenance operations. These objectives are reached by means of a rotating motion transmission device to a roll of a rolling stand according to claim 1 comprising a telescopic drive shaft having two telescopic members sliding within each other by a predefined sliding stroke, a snap-action locking mechanism for locking the two telescopic members to a predefined working length, an elastic device exerting a preloading force axially directed along the two telescopic members, in the end part of the sliding stroke, a drive shaft support incorporating a drive shaft extending and shortening device and a release mechanism, adapted to be remotely controlled, for releasing the snap-action locking mechanism.

According to a further aspect of the invention, these objects are reached by means of a disassembly method of the device above from a rolling stand having the features disclosed in claim 9 and comprising the following steps:

rotating the drive shaft support slide upwards about the first axis X1 so as to move from a stand-by position thereof, angularly away from the drive shaft, to a hooked position with the drive shaft, with the carriage arranged in an axial position whereby the groove fits onto the ring, rotating the drive shaft about the longitudinal axis thereof so as to align the two hydraulic cylinders with the axis of the spring of the snap-action locking mechanism, shifting the first cylinder by means of the carriage by a short stretch directed in an opposite direction with respect to arrow F2, sufficient for opposing the force of the elastic device for releasing the snap-action locking mechanism from the fit, exerting a compression force on the spring by means of the two hydraulic cylinders, thus releasing the snap-action locking mechanism, telescopically sliding the first cylinder in the direction of arrow F2 by a predetermined length by means of the carriage, rotating the drive shaft downwards about the first rotation axis X1 .

BRI EF DESCRI PTION OF TH E FIGURES

Further features and advantages of the present invention will be apparent in the light of the detailed description of a preferred, but not exclusive, embodiment of a device for transmitting rotary motion to a roll of a rolling stand according to the invention illustrated by way of non-limitative example, with reference to the accompanying drawings, in which:

- Fig. 1 shows a frontal view of a rolling stand incorporating the device of the invention in working condition;

- Fig. 2 shows a front view of an enlarged detail of the rolling stand in Fig. 1 , in working position in which the device of the invention is in position coupled to the roll ready to be released;

- Fig. 3 shows a front view of an enlarged detail of the rolling stand in Fig. 1 in a position in which the drive shaft is in released position from the roll;

- Fig. 4 shows a side view of the device of the invention;

- Fig. 5 shows a section view taken along line D-D of the device in Fig. 4;

- Fig. 6 is a top view of an enlarged detail of the device in Fig. 4;

- Fig. 7 shows a longitudinal view of a component of the device in Fig. 6;

- Fig. 8 shows a section view taken along line A-A of the device in Fig. 4;

- Fig. 9 shows a section view taken along line B-B of the device in Fig. 4;

- Fig. 10 shows a section view taken along line C-C of the device in Fig. 4;

- Fig. 1 1 shows an axial view of an enlarged component of the device of the invention; - Fig. 12 shows a side view of the component in Fig. 1 1 , - Fig. 13 shows a section view taken along line E-E of the component in Fig. 1 1

The same reference numerals and letters in the figures refer to the same elements or components.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 , in particular, shows a partial, frontal view of a tube rolling stand, globally indicated by reference numeral 100, of the type with three rolls 1 , 2, 3. Several rolling stands are generally arranged along the rolling axis X, the number of which characterizes the rolling plant, arranged side-by-side and aligned coaxially along axis X. The figures show only one rolling stand, being known to a person skilled in the art how the stands are arranged along axis X. Rolls 1 , 2, 3 are fixed in a container or cartridge 4 which ensures the rigidity of the rolling area and makes the various assembly and disassembly operations of the rolls from the stand easier. Rolls 1 , 2, 3 and the cartridge 4 constitute an integral block indicated by reference numeral 102; in Fig. 1 , this block 102 is shown in position P2, removed laterally from the rolling stand, after having been shifted in the direction of the arrow F1 , in addition to position P1 mounted in the rolling stand 100. The movement occurs preferably by making the block 102 slide along the floor S, but other means of known type may be used to carry out this movement from or to the rolling stand 100.

The conventional representation by means of block 102 in Fig. 1 , positioned both outside and inside the rolling stand 100, provides a clearer understanding of how a cartridge containing the rolls of the rolling stand is extracted, it being understood that the rolling stand 100 during normal working operations have a single cartridge 4, provided with rolls, which is alternatively either inside or outside.

The rolls 1 , 2, 3 are made to turn about the axis thereof, during the normal working actions of the tubes, by means of the respective drive shafts 5, 6, 7 which transmit the motion generated by the motors 9, 1 1 by means of the gearboxes 8, 1 0. The gearbox and the motor of the roll 2 are not visible in the partial view of the rolling stand 100 shown in figures 1 , 2, 3.

In the rolling stand 100, according to design, the block 102 is pulled out from position P1 to position P2 from the right side of the rolling stand 1 00, with reference to the front view shown in Figures 1 , 2, 3. The coupling devices 12, 1 3, 14 on the end of each drive shaft 5, 6, 7 must be detached from the respective rolls 1 , 2, 3 in order to pull out the block 102 and arrange it on the side of the rolling stand as shown in figure 3 making it slide on the floor S in the direction of the arrow F1 . In the case of the drive shaft 5, the detachment of the coupling device 1 2 from the roll occurs with a simultaneous shortening of the drive shaft 5 in the direction of the arrow F2, followed by a rotation about axis X1 , parallel to the rolling axis X, downwards in the direction of the arrow F3. This is a sufficient rotation to clear the passage of the block 102 towards the side zone where the block 102 must be moved. Advantageously, such an angular rotation of the drive shaft 5 is equal to an angle comprised from 10 ° to 20 °, optimal for the arrangement that the rolling stand 100 has with respect to the floor S. Given the arrangement of the two rolls 2, 3 with respect to the floor S, only the detachment of the coupling devices 1 3 and 14, which is advantageously but not necessarily accompanied by a slight shortening of the drive shafts 6, 7 allows the block 102 to shift towards the right side of the rolling stand 100.

With particular reference to figures from 4 to 13, the drive shaft 5 comprises a main body 51 of cylindrical shape consisting of a first hollow cylinder 54, within which a second coaxial cylinder 55 is arranged and adapted to slide telescopically with respect to the first cylinder 54. A sliding grooved coupling 54' and 55' is provided in order to transmit motion between the cylinders 54 and 55.

The coupling device 1 2 adapted to attach the drive shaft 5 to the roll 1 is arranged on an end of the first cylinder 54. This coupling device 12 advantageously consists of a shape coupling, e.g. a profiled fitting in a seat of shape mating that of the roll 1 . In order to allow a safer hold in the engaged position, the coupling device 12 is arranged on a piston 52, which is subjected to the pressure of an elastic device 69, e.g. including springs.

A cardan joint 56 is preferably fixed to the end of the second cylinder 55, near the support base 53, but other types of joints which allow the same movements of the drive shaft may be used appropriately. A snap-action locking mechanism, shown on enlarged scale in figures 1 1 , 12, 1 3, is integrally fixed to a block device 61 on the other end of the cylinder 55, opposite to the end where the joint 56 is located, and inside the first hollow cylinder 54. The snap-action device 61 comprises a cylindrical body 64 onto which two rocker arms 62' and 62" are hinged by an end thereof by means of the hinges 65' and 65", so as to allow a rotational movement of small angular width. A spring 63 or equivalent elastic means, exert a thrust action on the rocker arms 62' and 62" towards their maximum extension position outside the cylindrical body 64. Advantageously, rolls may be provided on the ends of the spring 63, or near the same, to facilitate the sliding movement of the snap-action device 61 in the first cylinder 54.

Each rocker arm 62' and 62" has a tooth on its outer surface which is used to engage two holes in the wall of the first cylinder 54, in the axial position corresponding to the design length which must be assumed by the drive shaft 5 when it is working.

The elastic device 69 subjects the two telescopic parts 54, 55 to a predetermined load in order to avoid unintentionally release of the snap-action device 61 . Furthermore, when the extension of the two cylinders 54 and 55 is controlled and in order to allow the locking of the snap-action device 61 , the cylinder 54 is made to advance slightly beyond the working point to facilitate the insertion of the snap-action device 61 in the specific holes and then the two cylinders 54 and 55 are put into working position, by slightly retracting the cylinder 54. Similarly, for release, the drive shaft 5 is overextended by making the cylinder 54 advance, and then the release of the snap- action device 61 is controlled, as explained below.

This solution of the snap-action device 61 is particularly advantageous to lock cylinders 54 and 55, which form the drive shaft 5, in working position and may also be replaced by equivalent, even more complex solutions, for example with other mechanically, pneumatically or hydraulically actuated locking and releasing mechanisms, without because of this departing from the scope of the invention.

The drive shaft support comprises a carriage 59 and the slide 50. On the carriage 59 there are two hydraulic cylinders 66' and 66" which can exert a pressure on the ends of the spring 63 to overcome the force of such a spring 63 and make the two rocker arms 62' and 62" retract enough to disengage the two respective teeth of the holes obtained in the wall of the first hollow cylinder 54. In such a manner, the snap-action locking device 61 is freed allowing the telescopic sliding of the second cylinder 55 in the first cylinder 54 in the direction of a shortening of the drive shaft 5. On the opposite end, the engagement of the snap-action device 61 in the final position thereof, following the elongation operation of the drive shaft 5, occurs as a result of the pressure exerted by the spring 63 which spreads the two rockers arms 62' and 62", making the respective tooth engage the two holes provided in the wall of the first cylinder 54.

The carriage 59 has a groove 68 which is adapted to accommodate a circular ring 67 integral with the outer surface of the first hollow cylinder 54 and which constitutes a seat for engaging the carriage 59.

The slide 50 is hinged on the support base 53 so as to have the rotation axis X1 preferably, but not necessarily coinciding with the rotation axis of the cardan joint 56. A hydraulic or electric actuator 57 is arranged between the base structure 53 and the slide 50, in position such as to control the rotation of the slide 50 about axis X1 .

The slide 50 has a hollow inner zone shaped so as to accommodate part of the first cylinder 54 and the second cylinder 55. The slide 50 has on the inside a carriage 59 which preferably has wheels sliding along two guides 58', 58" so as to allow the sliding relatively to the slide 50 and parallel thereto under the bias of a hydraulic or electric actuator 60.

Normally, the slide 50 turns about the axis X1 between two angular positions with respect to the drive shaft 5 during the various fitting and releasing operations of the drive shaft 5. A first position in which the slide 50 is arranged aligned and hooked to the drive shaft 5 is shown in figures 2, 3, 4 and a second position in which the slide 50 is angularly detached with respect to the drive shaft 5 is shown in figure 1 . When the slide 50 is in the aligned, hooked position with respect to the drive shaft 5 it follows the drive shaft 5 in its angular rotation movements about axis X1 . In the second detached position of the drive shaft 5, the slide 50 allows the drive shaft 5 to rotate and feed the roll 1 . The release operation of the drive shaft 5 from the roll 1 is carried out as follows. The slide 50, which is initially angularly detached from the drive shaft 5 is made to turn about the axis X1 so as to be arranged in its gripping position parallel to the drive shaft 5 by means of an actuator 57. The carriage 59 is provided in a position along the slide 50 so as to arrange the two hydraulic cylinder pistons 66' and 66" at the axis of the spring 63, by means of a controlled rotation of the main motor of the rolling stand 100 and so as to fit the groove 68 on the ring 67 making them integral with the carriage 59, the slide 50 and the hollow cylinder 54. A short translation movement of the cylinder 54 in direction opposite to the arrow F2, sufficient to contrast the force of the elastic device 69 which holds the snap-action device 61 in stable position by engaging the rocker arms 62', 62" in the respective seats, facilitated the exiting of the rocker arms from the holes in the cylinder 54. Essentially at the same time, the two pistons 66', 66" are actuated so as to exert a pressure on the spring 63, which shortens it and makes the rockers retract towards the inside of the cylinder 54. In this manner, the block 61 is no longer fitted inside the cylinder 54 and is free to slide telescopically inside it. The carriage 59 is translated along the axis of the drive shaft by means of the action of the actuator 60 so as to feed the hollow cylinder 54 in direction of the arrow F2, being the ring 67 integral with the carriage 59, for a segment of predetermined stretch needed for the drive shaft 5 to assume the position sufficient to clear the space in front of the block 102 as shown in figure 3 with a rotational movement in the sense of the arrow F3.

The block 102 is then extracted from the rolling stand 100 in side direction.

The assembly operation of the block 102 in the rolling stand 100 is carried out by reversing the sequence described for the disassembly operation.

Although, the description refers to a drive shaft for transmission motion to a roll of a rolling stand for tube rolling, the device of the invention may be applied also to rolling stands for other types of metallic products, e.g. rods or sections etc.