EP0555528A1

EP0555528A1 - A pipe straightening machine

Info

Publication number: EP0555528A1
Application number: EP92118388A
Authority: EP
Inventors: Giorgio Quecchia
Original assignee: Innse Innocenti Engineering SpA
Current assignee: SMS Group SpA
Priority date: 1992-02-12
Filing date: 1992-10-28
Publication date: 1993-08-18
Also published as: IT1254783B; ITMI920289A1; ITMI920289A0

Abstract

A pipe straightening machine comprises at least one lower roll (2a) and an upper roll (2b) journalled in respective supports (5), spaced to a distance D between their axes, the machine including, for at least one of the rolls (2a,2b), a hydraulic cylinder-piston unit (6) acting on respective supports (5) thereof to change said distance D between axes.

Description

This invention relates to a pipe straightening machine of a type which includes at least one lower roll and an upper roll, both journalled on respective supports and spaced one from the other to a set distance between their axes.
Well known in the pipe-making industry is the use of machines as mentioned above, for correcting production errors and attaining desired shapes and dimensional tolerances.
Pipe straightening machines apply substantially corrective deformations to pipes passed longitudinally therethrough, modifying shape imperfections like bends in their middle body or distortions originated by torsional stresses along the pipe axis.
It has to be noted that the term "straightener" will be used hereinafter as an abbreviation to indicate a pipe straightening machine of the kind outlined above.
In the prior art, a pipe straightener basically comprises a set of rolls arranged to lie in an upper plane and a set of rolls lying in a lower plane, with the rolls being disposed in juxtaposed pairs; said juxtaposed rolls have mutually skewed axes whose inclination angle in the respective planes can be adjusted using conventional means.
Additionally, the rolls are journalled on a frame structure constituting the load-bearing portion of the machine; all the rolls are provided with drives for their rotary movement which causes a pipe, to move forward along the longitudinal axis of the machine.
Such machines are equipped with conventional mechanical means for setting the position of each roll along a perpendicular direction to the longitudinal machine axis.
This setting practically enables the distance which separates the axes of the juxtaposed upper and lower rolls, to be changed and it is performed by a workman before each pipe is processed.
Machines according to this known design have, however, some drawbacks which restrict their operability.
Basically, such machines are not flexible in use: the mechanical means for adjusting the roll distance between axes does not allow further changes subsequent to its initial setting, while a pipe is being processed through the machine.
This means that in order to straighten pipes having upset ends, that is ends with a larger outside diameter than the diameter of the middle body of the pipe, the machine rolls must be provided with quick-opening devices to allow said ends to pass therethrough. In particular, after the operation of such opening devices, the rolls affected by the passage of the upset ends are moved rapidly out of their standard work setting.
With such an approach, the final sections of pipes, provided with upset ends, cannot be straightened, and such final sections oftentimes have to be straightened off the line on specially detached equipment.
It will be appreciated that such a pipe straightener, due to its rigidity in operation, tends to be slow and have inferior output when used to process pipe workpieces with upset ends.
Further, to straighten a pipe on such machines, the distances between the axes of the various rolls are set in order to achieve an ultimate deformation to be applied to the pipe; these distances are set according to previously computed theoretical values of the deformations that the pipe is to undergo in passing through the straightener.
However, the actual values of the pipe deformations during its pass through the straightener do not always coincide, for contingent reasons of various nature, with these theoretical values and hence, a previously set distance between axes of the rolls frequently will fail to secure desired ultimate tolerance values.
The mechanical means for setting the roll distance between axes do not allow the adjustment of this distance as a pipe is being processed.
The underlying technical problem of this invention is to provide a pipe straightener with such construction and performance features as to overcome the aforementioned drawbacks with which the prior art is beset.
This problem is solved by a pipe straightener as indicated being characterized in that it is provided, at the location of at least one of the rolls, with a hydraulic cylinder-piston unit acting on respective supports thereof to change said distance between the axes.
Further features and the advantages of this invention will be more clearly apparent from the following description of an embodiment thereof, given by way of illustration and not of limitation with reference to the accompanying drawings.
In the drawings:

Figure 1 is a perspective view of a pipe straightener according to the invention;
Figure 2 is a sectional view of a detail of the pipe straightener shown in Figure 1; and
Figure 3 shows in schematical form another detail of the pipe straightener in Figure 1.

With reference to the drawing figures, generally shown at 1 is a pipe straightener according to the invention; this machine includes a plurality of rolls 2 which are respectively grouped into a set of lower rolls 2a and a set of upper rolls 2b, advantageously opposed one to the other. The upper and lower rolls are respectively laid side-by-side along a longitudinal axis L of the machine 1, which axis would coincide with the axis of a pipe being processed.
The axes of each upper roll 2b and corresponding lower roll 2a coincide with respective skewed axes A of rotation set at a predetermined controllable distance D one to the other for each pair of juxtaposed rolls, as explained hereinafter.
The machine 1 comprises a plurality of pairs of pillars 3 extending symmetrically about the axis L from a load-bearing structure 4 provided for supporting the machine as a whole.
The upper rolls 2b are mounted on a pair of supports 5 for supporting their bearings, which are rigidly connected to a hydraulic cylinder-piston unit 6 for adjusting the distance between the axes; the unit 6 is attached to top ends 3a of a pillar pair.
The lower rolls are journalled on the load-bearing structure 4 between bottom ends 3b of the pillars 3.
Each roll 2 of the machine is connected to respective rotary drives 7 and 8 through a drive adapter 9; particularly in a preferred embodiment, the drive adapters 9 for the lower rolls 2a are connected to the drives 7, and the drive adapters 9 for the upper rolls 2b are connected to the drives 8.
The hydraulic cylinder-piston unit 6 will now be described with reference to Figure 2.
This unit comprises a stationary part 10 attached rigidly to the pillars 3 and a moving part 11.
The moving part 11 is slidable, relative by to the stationary part 10, parallel to the distance D between axes working as a piston movable inside the cylinder-piston unit 6.
The moving part 11 comprises a circular base plate 12 whence there extend three concentrical cylinder walls, respectively inner 13, intermediate 14 and outer 15 walls.
The intermediate cylinder wall 14 has a flange 16 which extends radially toward the inner wall 13 to meet a cylindrical lug 10a on the stationary part 10 of the device; the walls 13 and 14, flange 16, and plate 12 delimit a cylindrical chamber C. Provided in the lug 10a are first and second conduits 17 and 18 for feeding pressurized oil into the cylindrical chamber C at corresponding sockets 17a and 18a respectively formed in the flange 16 and the plate 12 on their cylindrical chamber C side.
Attached to the plate 12, on the remote side thereof from the three cylindrical walls, are the rests 5 for the bearings of an upper roll 2b.
The cylinder-piston unit 6 for adjusting the distance between axes also comprises a servo-control 19 having a pressurized oil pumping assembly 20 connected to said first and second conduits 17 and 18, a pressure transducer 21, a pressure relief valve 22, a valve 23, a positional transducer 24, and an adjustment block 25.
The positional transducer 24 locates inside the cylindrical lug 10a, and the pressure transducer 21 gauges the pressure of oil being pumped through the conduits 17 and 18.
Shown in Figure 3 in block diagram form is the servo-control 19, which comprises first and second loops A1 and A2 for so-called force and position setting of the cylinder-piston unit 6, respectively.
The pipe straightener of this invention also includes means 26, e.g. photocells in this embodiment, for surveying the position of a pipe within the machine, and electronic means 27 of controlling and monitoring the operations of the machine and its parts.
The operation of the invention will be now described with reference to the pipe straightener just mentioned; as a general example of its operation, the instance of a plain-ended pipe workpiece will be considered to which a constant force is applied by each roll pair.
Before a pipe is inserted through the machine for straightening, the electronic means 27 are entered a reference value of the force to be exerted on the pipe workpiece by each upper roll 2b.
The force setting loop A1 is activated by the electronic means 27 in the servo-control 19 of each upper roll 2b.
The pipe to be processed is driven along the longitudinal axis L of the machine by rotating the rolls 2 through the drives 7 and 8.
The force exerted by the rolls 2 on the pipe is adjusted in real time and maintained at the entered value by means of the servo-control 19.
In fact, wherever the pipe dimensions vary from the nominal value, changes are induced in the force between the rolls and the pipe. For example, a bend in the pipe and the corresponding rise of its middle body with respect to the axis L would generate an upward or downward displacement of the upper roll 2b, rigidly with the moving part 11 of the respective cylinder-piston unit
The upward or downward displacement of the moving part 11 results, therefore, in a change in the pressure of the oil within the cylindrical chamber C, which change will be sensed by the transducer 21. The servo-control 19 arranged to act in the force loop A1 mode will control the valve 23 via the adjustment block 25 to vary the delivery of oil through either conduit 17 or 18, depending on whether the moving part 11 is to be raised or lowered, while maintaining constant the force exerted by the upper roll 2b, rigid therewith, on the pipe.
To process pipes with aforesaid upset ends, the diameters of such ends would be entered and stored in the electronic means 27. The surveying means 26 locate the end positions along the machine and supply the information to the electronic means; the latter then control the upper rolls 2b affected by the passage of said ends to move and be promptly set by the respective cylinder-piston units to a distance between axes A equal to that stored in the electronic means.
After the upset end has moved past a roll pair, the upper roll in that pair is immediately returned to the distance between axes which corresponds to the diameter of the pipe middle body. Indead, the diameter variation from the upset end to the middle body results in an oil pressure change which, similarly to the above, is sensed by transducer 21 and communicated to the control system that will restore the machine to its original operation by means of valve 23.
Furthermore, the pipe straightener according to the present invention may be also operated in the position setting loop A2 mode; in this case, the servo-control 19 would keep the distance between the roll axes A in each pair equal to that entered on the electronic means 27 which corresponds to the nominal diameter of the pipe workpiece. In the servo-control 19 of each upper roll 2b, the position setting loop A2 is activated by said electronic means 27.
During a pipe processing operation using the position setting loop 12, the dimensional variations of the pipe tend to induce displacement of the upper roll 2b, and hence of the moving part 11 of the servo-control attached thereto; the position transducer 25 senses such displacement and reports it to the adjustment block 25, which will control the valve 23 to adjust the oil flow through either conduit 17 or 18 so as to keep the upper roll in its set position.
Even when operating in the position setting loop A2 mode, the upset ends can be processed substantially in the same way as previously described in connection with operation in the force setting loop A1 mode. In fact, it is contemplated here that the electronic means 27 should control those rolls which are not affected by the pipe being processed, to keep operating in the force setting loop A1 mode according to program. The surveying means 26 locate the positions of the upset ends through the machine and report them to the electronic means 27; those rolls which are progressively contacted by the ends while operating in the setting loop A1 mode, will position themselves at the set distance corresponding thereto in quite the same way as previously described.
After the upset end passes a roll, the electronic means will switch the operation of the respective servo-control 19 from loop A1 to the position setting loop A2.
It may be appreciated from the foregoing description that a pipe straightener according to the invention affords high flexibility of operation, since it allows processing of the pipes throughout their total length; in addition, it is indifferent whether the pipes have lenghtwise sections with uneven outside diameters or upset ends.
With the latter, in fact, it has been shown that the hydraulic cylinder-piston unit 6 with the servo-control 19 enables prompt displacement of the affected rolls upon the passage of one of said upset ends.
Further, the pressure relief valve 22 provided will ensure safe operation of the machine as a whole: in fact, where a pipe is started therethrough by mistake whose dimensions are much greater than the set dimensions according to the machine program, there would occur an abnormal rise in the servo-control oil pressure likely to result in failure of the same and a damaged machine.
In such circumstances, the relief valve will let the oil vent and stop the machine to prevent it from getting damaged.
The importance of the servo-control according to the invention should also be emphasized, since it enables the distance between the axes of the rolls to be adjusted by controlling both the roll position and its force, therefore this fact enhances the machine potential and performances.
Naturally the embodiment of this pipe straightener as described above may be improved or modified to improve its performance, e.g. by using special working programs to be stored in the electronic control means.
In particular, by having each roll controlled through a predetermined stress program or a distance setting program, in pipe straightening applications, the pipes can be deformed successively into their goal configuration. In addition, with a pipe straightener according to the invention, a program can be arranged to correct in real time any dimensional variations occurring in a pipe being processed, therefore achieving a high standard of processing accuracy.
Moreover, it is obvious that the machine according to this invention can be modified, in order to meet different requirements such as economical or throughput demands, by equipping it with hydraulic cylinder-piston units not only at the upper rolls but also at the lower ones or, alternatively, just at some of the upper and/or lower rolls, in a broad range of possible combinations.

Claims

A pipe straightening machine of a type which includes at least one lower roll (2a) and an upper roll (2b), both journalled on respective supports (5) and spaced one from the other to a set distance (D) between their axes (A), characterized in that said machine is provided, at the location of at least one of the rolls (2a,2b), with a hydraulic cylinder-piston unit (6) acting on respective supports (5) thereof to change said distance (D) between the axes (A).
A machine according to Claim 1, characterized in that said hydraulic cylinder-piston unit (6) for changing said distance (D) comprises a stationary part (10) connected rigidly to pillar pairs (3) extending from a load bearing structure (4) which supports the machine, a moving part (11) slidably reciprocable relatively to the stationary part (10) along a parallel direction to said distance (D) between the axes (A), said moving part (11) being rigid with the supports (5) of the roll (2a,2b) which is associated with the hydraulic cylinder-piston unit (6).
A pipe straightening machine according to Claim 2, characterized in that said hydraulic cylinder-piston unit (6) includes a servo-control (19) which comprises a pressurized oil pumping assembly (20), a valve (23), a pressure relief valve (22), a pressure transducer (21), a position transducer (24), and an adjustment block (25).
A machine according to Claim 3, characterized in that said moving part (11) comprises a plate (12) perpendicular to the distance D between axes having, on the one side, the supports (5) attached thereto and, on the other side, a cylindrical inner wall (13) which is guided for sliding movement by a cylindrical lug (10a) on the stationary part (10), a cylindrical intermediate wall (14) exteriorly concentrical about the inner wall (13), a cylindrical chamber defined by said walls (13,14), plate (12) and a flange (16) extending radially toward the lug (10a) from the intermediate wall (14), and at least two conduits (17,18) provided in the cylindrical lug (10a) to convey pressurized oil being supplied from said pumping assembly (20) into said cylindrical chamber.
A machine according to Claim 4, characterized in that the position transducer (24) locates inside said cylindrical lug (10a).
A machine according to Claim 5, characterized in that it comprises means (26) for surveying the position of a pipe being processed along a longitudinal axis (L) of the machine.
A machine according to Claim 6, characterized in that it comprises electronic means (27) for controlling and monitoring the machine operation to which the servo-control (19) and pipe position surveying means (26) are linked operatively.