EP0956168A1

EP0956168A1 - A machine for straightening tubes and rod-shaped bodies in general

Info

Publication number: EP0956168A1
Application number: EP97952899A
Authority: EP
Inventors: Filippo Cattaneo; Roberto Brioschi
Original assignee: Demag Italimpianti SpA
Current assignee: SMS Group SpA
Priority date: 1997-01-23
Filing date: 1997-12-08
Publication date: 1999-11-17
Also published as: ITMI970130A1; WO1998032552A1; JP2001513028A; IT1288426B1

Abstract

In the machine described for straightening tubes and rod-shaped bodies in general, at least one of the working rollers (7, 8) has a hydraulic cylinder-piston unit (25) for adjusting its position relative to a straightening axis (L). Advantageously, the portion (26) constituting the piston in this unit is attached to a bridge-like portion (35) of the load-bearing structure (34, 35) of the machine and the portion constituting the cylinder (27) is guided for sliding by another portion (3) of the structure. The guide frames which were mounted on the moving parts in the prior art can thus be eliminated and these parts can therefore now be made lighter, benefiting the performance of the machine, the load-bearing structure (34, 35) of which can also be reduced in weight and size.

Description

"A machine for straightening tubes and rod-shaped bodies in general"

DESCRIPTION

The invention which is the subject of this application relates to a machine for straightening tubes and other rod- shaped bodies in general, such as rods, bars and other similar products of the iron and steel industry.

The above-mentioned straightening machines are well known and are used in the final stage of the processing of tubes or rod-shaped bodies in general to give them their final dimensional tolerances; essentially, the straightening operation performed by these machines takes place by the passage of the tube or body along an axial line of advance above and below which there are grooved working rollers usually having hyperboloid-like profiles.

The characterising feature of these machines is the particular arrangement of the axes of rotation of the rollers; in fact the rollers are arranged obliquely relative to one another in order to transmit to the tube or body being processed a combined rotational and translational movement in order to advance it along the straightening axis as well as rotating it about the same axis.

In this connection, straightening machines can be divided into two distinct classes the first of which provides for the upper and lower rollers to be arranged opposite one another whereas, in the second, they are offset; the latter class is also known to experts in the art as that in which the straightening takes place by "bending" . Moreover, within these classes, there are various possible combinations arising from the presence of driven and idle rollers.

The straightening machine according to the present invention relates without distinction to straightening machines in which the rollers are opposed, offset or in possible combinations of these two arrangements .

An important aspect which considerably affects the performance of these machines relates to the adjustment of the positions of the rollers and, in particular, of their distance from the straightening axis; currently, good results have been achieved for this purpose with the use of hydraulic devices also known by the term hydraulic "capsules"; these devices are known per se and an example is described in Italian patent application No. MI92A000289.

Essentially, these hydraulic devices can be said to consist of a hydraulic cylinder-piston unit in which there is a fixed portion constituting the cylinder, mounted rigidly on a support framework of the straightening machine and coupled hydraulically to a movable portion constituting a piston which is slidable to and fro relative to the fixed portion and on which a roller of the machine is mounted by means of a base plate.

Straightening machines having these hydraulic devices also have a suitable adjustment system which enables the positions of the rollers to be controlled in accordance with a desired working program; in this connection, it is pointed out that, to achieve an adequate level of performance, it is important nowadays for the roller position to be adjustable both in accordance with an adjustment loop which controls the force exerted by a roller on a tube or body being processed and in accordance with a loop which governs the position of the roller itself relative to the straightening axis.

Moreover, an important requirement of users of the straightening machines considered herein is a wide range of roller adjustability; in other words, given the high costs of straightening machines, it is important, for understandable reasons of economy, that they should be able to operate on a wide range of diameters of tubes or bodies to be processed.

However, the ever higher performance required of machines for straightening tubes or rod-shaped bodies also considerably increases their structural complexity and weight; in particular, because of the large travel which the portion constituting the piston has to perform to achieve the required wide adjustment of the roller, it is known to use complex diamond-shaped frames which are mounted in the region of the base plate to which the roller is fixed in order to guide the sliding of the portion constituting the piston, and which slidingly engage the guide pillars which are load-bearing elements of the machine; however, a frame of this type represents an increase in the weight of the movable portion of the hydraulic cylinder-piston unit and not infrequently causes jamming of this movable portion as a result of the inevitable coupling tolerances existing between it and the guide portions of the machine. Since this frame is also intended to transmit to the pillars along which it slides the so-called straightening torque caused by the tube or body being processed, there is a marked danger of the frame jamming during the travel of the movable portion in this prior art.

Another adverse aspect resulting from the improved performance of known straightening machines consists of the excessive weight and bulk due to the mechanical parts present in the load-bearing structure of the machine; in fact, if the travel of the movable portion of the hydraulic cylinder-piston unit is increased, the fixed portion which constitutes the cylinder and is mounted inside the aforementioned structure has to have dimensions suitable for withstanding the forces which result from the working and which, in addition to the straightening torque mentioned, also include the thrust directed radially relative to the straightening axis due to the force which is produced by a tube or body to be straightened and which moves a roller away from its working position. In this connection, it should also be borne in mind that room also has to be found in the region of the base plate for the means necessary for adjusting the angle of inclination of the axis of rotation of each roller to the straightening axis; since these means cannot be eliminated, other solutions have to be found for lightening the moving mechanical parts .

The object of the present invention is therefore to provide a machine for straightening tubes and rod-shaped bodies which has structural and functional characteristics such as to overcome the disadvantages referred to in the prior art; this object is achieved by a straightening machine the characteristics of which are set out in the claims appended to this description.

For a better understanding of the invention in general with its characteristics and the advantages resulting thereform, a description relating to an embodiment thereof is given by way of non-limiting example below, on the basis of the appended drawings, in which: Figure 1 is a simplified perspective view of a machine for straightening tubes, according to the invention,

Figures 2 and 3 are a side view and a plan view of the machine of Figure 1, respectively, and

Figures 4 and 5 are partially-sectioned views of a detail of the previous drawings in respective operating conditions.

In the drawings, a straightening machine according to the invention is generally indicated 1; the machine extends longitudinally along a straightening axis L along which the tubes or bodies to be processed are advanced in the direction indicated by the arrow in Figure 3.

It is appropriate, however, to point out that, in these machines, the straightening axis does not remain fixed; for example, its level may vary according to the working diameter or it may differ between one roller position and the next in the machine; this latter aspect is more marked in machines operating by "bending", which will be referred to further below.

The structure of the machine comprises a base 2 which, in this embodiment, is disposed below ground level, above which there is a framework 3 supported by a series of pillars 4.

In the machine 1 there are three pairs of opposed rollers 5 and 6, 7 and 8, 9 and 10, having oblique axes oriented in known manner; all of the rollers 5 to 10 are driven in conventional manner by means of two electric motors 11 and 12 and two reduction units 13 and 14 which transmit the drive to respective sets of three drive extensions 15 and 16.

The machine 1 also has known means for changing the rollers which, in this embodiment, consist of a carriage 18 provided with a platform on which a roller removed from the machine is loaded and which can move parallel to the axis L along suitable guides 19; the roller-replacement means also comprise a pusher/extractor 20 for loading rollers on the carriage 18 and unloading them therefrom.

In the machine 1 there are also means for adjusting the angular position of the axis of rotation of each roller 5-10, the means being constituted by mechanisms which are preferably operated hydraulically and are visible in the drawings, adjacent the rollers and interposed between the base 2 and the framework 3 ; these adjustment means will be considered in greater detail below.

The upper rollers 5, 7, 9 and the lower roller 8 have respective hydraulic cylinder-piston units 25; only one of these, associated with the roller 7, will be described below with reference to Figure 4 and its structure may therefore be referred to for the others .

The cylinder-piston unit of Figure 4 comprises a fixed portion 26 attached to a bridge-like structure or, in short, a bridge and constituting the piston of the unit 25, coupled hydraulically to a movable portion 27 constituting the cylinder of the aforementioned unit.

The movable portion has, on its outer surface and on opposite sides, two tenon-like appendages 28 which engage in corresponding mortice-like counter- guides 29 extending parallel to the pillars 4 in the base 2 for the roller 8 and in the framework 3 for the rollers 5, 7 and 9.

The fixed portion 26 also contains ducts 30 and 31 for supplying the oil for the hydraulic operation of the cylinder-piston unit 25; in this connection, it is pointed out that the movable portion is slidable to and fro under the effect of the oil supplied by means of the ducts 30 and 31 like a double-acting piston which slides along an axis indicated R extending radially relative to the straightening axis L.

As stated above, the fixed portion 26 of the hydraulic cylinder-piston unit is attached to a bridge 35 which is mounted rigidly on the framework 3 or base 2 of the machine by means of the pillars 4, and the movable portion 27 bears a lower base plate 36 on which the roller 7 of the machine is mounted rotatably; the angular position of the axis of rotation of this roller can be adjusted by known mechanical means, not shown in Figures 4 and 5 for clarity. The means can be seen in Figures 1, 2, 3, however, and consist, essentially, of an arm 40, preferably operated hydraulically as stated, and connected to the edge of the base plate 36 which is rotatable about the sliding axis R of the movable portion 27; a forward or rearward movement of the arm 40 along a tangent to the base plate 36 brings about a rotation of the plate in one direction or the other and an angular adjustment of the roller mounted thereon. The hydraulic drive acting on each arm 40 is conventional and has not been shown in the drawings; in a preferred embodiment of the invention, however, it is controlled both with regard to the force which it applies to the base plate and with regard to the rotation undergone thereby; this functional aspect will be explained further below.

With regard to the bridge 35, it should be pointed out that, in the machine according to the present invention, it is structurally independent of the framework 3 and of the base 2; that is, it does not transmit any force to them since it is fitted on the ends of the pillars 4 which project beyond the framework 3 (see Figures 4 and 5) or the base 2 as the case may be; the bridge 35 is clamped onto the pillars 4 and the fixed portion 26 constituting the piston is clamped onto the bridge 35, by means of nuts 42, 43; this allows the bridge 35 and the piston 26 to be removed very quickly and easily in order to carry out maintenance operations .

The straightening machine described above also has a control system comprising electronic means for adjusting the rollers under load both with regard to their distance from the straightening axis (position loop) and with regard to the force exerted thereby on a tube or other body being processed (force loop) .

With regard to the operation of the apparatus described, reference is made to the following.

As a tube or other body being processed is gradually advanced along the axis L, it simultaneously rotates about this axis as a result of the action due to the oblique arrangement of the axes of rotation of the rollers, in known manner; the control system of the machine, as stated, allows the rollers to move away from or towards the straightening axis L along the radial axis R; this adjustment takes place particularly effectively by virtue of the performance which the hydraulic cylinder-piston unit 25 according to the invention achieves .

The fact that the roller is fixed to the portion constituting the cylinder of the unit 25 permits the use of the guide and counter-guide system 28 and 29, favouring the to and fro movement of the movable portion 27; in contrast to Italian application MI92A000289 already mentioned, the portion constituting the piston is now no longer the movable portion on which the roller to be adjusted is mounted; any frame or other equivalent system necessary for guiding the portion constituting the piston according to the teaching of the prior art is thus eliminated.

In fact it can be understood that, if the movable portion were to constitute the piston, it would not be possible to fit along it a tenon- mortice guide system according to the teaching based on the foregoing example since the guides would interfere with the relative sliding of the hydraulically-coupled portions.

Moreover, another important effect is also achieved by the invention; in the straightening machine in question, its structural portions which are intended to compensate for the forces produced by a tube or other body being processed and moving the rollers apart, that is, forces acting radially relative to the straightening axis and moving the rollers away from the nominal working position, can in fact be separated from those which are intended to withstand the so-called "straightening torque" . The latter results from the reaction which is caused by the tube or body being processed and which acts on the roller causing it to rotate about the axis R referred to above.

With regard to this aspect, it is appropriate to point out that, in addition to its intrinsic guiding action, the guide and counter-guide system 28 and 29 associated with the movable portion of the hydraulic cylinder-piston unit also has a restraining effect on the movable portion 27, opposing any rotation thereof relative to the above- mentioned radial axis R; as stated at the beginning, in the prior art, and particularly in straightening machines having cylinder-piston units of the type described in the Italian application already mentioned, the straightening torque is transmitted by the roller mounted on the movable portion constituting the piston to a pair of vertical guide pillars, by means of the above- mentioned frame which is fitted on the movable portion in the region of its base plate.

Another significant advantage achieved by the present invention relates to an important functional aspect of straightening machines, that is, that of roller maintenance; in fact, as a result of the rotational-translational movement of a tube or body being processed, the contact between it and the working surfaces of the rollers inevitably causes considerable slippage and friction; the rollers of the machines in question therefore wear quite rapidly and thus require very frequent re- turning and subsequent replacement.

With the straightening machine according to the present invention, on the other hand, it is possible to perform a calibration of the rollers which limits the above-mentioned damage.

As a result of friction, with time, the actual dimensions of the rollers in fact become smaller than the nominal dimensions because of loss of material from their working surfaces; this means that the force exerted thereby on a tube or body being processed no longer corresponds to the nominal force for which the program for adjusting their position has been set in the control system; this situation results in a progressive decline in processing quality as the wear of the rollers gradually increases.

The above-mentioned calibration prevents this situation.

In fact, if a reference tube or rod-shaped body having a diameter and straightness conforming to predetermined dimensional tolerances is positioned periodically between the rollers, it is possible to calibrate the straightening machine by first of all bringing the rollers into contact with the reference tube or body with a force predetermined on the basis of the operation of the loop control system for adjusting the aforesaid force; at the same time, the actual positions of the rollers relative to the reference tube are detected by suitable measurement devices normally integrated in the control system and of known type.

The calibration thus carried out therefore compensates for the above-mentioned effects of wear.

Once the calibration in the vertical plane is completed, a similar operation can be performed with regard to the angular positions of the rollers by action on the angular adjustment means of the machine; this operation is possible only in a straightening machine in which the vertical adjustment of the rollers is hydraulic so that it is possible to operate in predetermined and in any case limited vertical load conditions.

By performing the angular adjustment of the rollers by means of the arms 40 when the reference tube or rod-shaped body is in the machine, it is possible to achieve this adjustment without risk of displacement of the rollers from the position which they adopt after the aforementioned calibration; in fact, if the force applied to the rollers as a result of the rotation of the corresponding base plate 36 during the angular adjustment is kept under control, this force being monitored by the control system by means of the force adjustment loop, it is possible to stop the angular adjustment when a predetermined force such as not to jeopardize the positioning of the rollers has been reached. In this connection, it should be pointed out that, with the use of the hydraulically-operated adjustment means, the force applied thereby during the angular adjustment stage can also be controlled in the same manner as described for the rollers so as to achieve the above-mentioned maximum precision and control of the angular adjustment.

Finally, variants of the machine according to the invention with respect to the embodiment described should not be excluded; by way of indication, it should simply be noted that the objects achieved by the invention apply equally to the aforementioned straightening machines with opposed rollers and with offset rollers and, with regard to the movable portion 27 constituting the cylinder of the unit 25, solutions other than the tenon-mortice guide system mentioned above should not be omitted.

These and other possible variants in any case fall within the scope of the following claims.

Claims

1. A machine for straightening tubes or rod- shaped bodies in general, which comprises at least one pair of rollers (5 and 6; 7 and 8; 9 and 10) situated on opposite sides of a straightening axis (L) along which the machine is arranged, a hydraulic cylinder-piston unit (25) for adjusting at least one of the rollers (5, 7, 8, 9), the unit including a fixed portion (26) rigidly connected to a load- bearing structure (2, 3, 4, and 35) of the machine and a movable portion (27) slidable to and fro along an axis (R) which is substantially radial relative to the straightening axis (L) , one of the rollers being mounted on the movable portion (27) , characterized in that the fixed portion (26) and the movable portion (27) constitute the piston and the cylinder of the hydraulic unit (25) , respectively, and in that the machine also comprises means (28, 29) extending along the said sliding axis (R) for guiding the movement of the movable portion (27) .

2. A straightening machine according to Claim 1, in which the guide means (28, 29) can prevent the movable portion (27) from rotating about its sliding axis (R) thus compensating for the force due to the straightening torque during the processing of a tube or rod-shaped body.

3. A straightening machine according to Claim 1 or Claim 2, in which the load-bearing structure comprises a base (2) and a framework (3) disposed above the base, the at least one pair of rollers (5 and 6; 7 and 8; 9 and 10) being housed between the base (2) and the framework (3), and in which the guide means (28, 29) comprise a pair of guides (29) disposed on opposite sides of the cylinder- like movable portion (27) and extending in the region of the base (2) or of the framework (3) of the machine.

4. A straightening machine according to Claim

3, comprising a bridge structure (35) which is fixed transversely relative to the straightening axis (L) of the machine on upright elements (4) supporting the framework (3) above the base (2), the fixed portion (26) constituting the piston of the hydraulic unit (25) being rigidly connected to the bridge structure which is also independent of the base (2) and of the framework (3) so as to withstand predominantly forces directed along the sliding axis

(R) of the movable portion (27) .

5. A straightening machine according to Claim

4, in which the bridge structure (35) is removably attached to the upright elements (4) .

6. A machine according to Claim 4 or Claim 5, in which the fixed portion (26) constituting the piston of the hydraulic unit (25) is removably attached to the bridge structure (35) .

7. A machine according to any one of the preceding claims, which has means (40) for adjusting the angular position of the axis of rotation of the at least one roller (5, 7, 8, 9), which has a hydraulic cylinder-piston unit (25) for its adjustment.

8. A machine according to Claim 7 , in which the said angular-position adjustment means are hydraulic .