FR2460745A1 - Forging machine for mfg. tube with longitudinal seam weld - where forging rolls exert uniform pressure when squeezing the tube to make the weld - Google Patents

Abstract

Metal strip or plate is bent into a tube with a longitudinal slot, the edges of which are heated to the forging temp. The tube then travels between forging rolls, which squeeze the edges of the slot together to make a weld. The machine bed supports two slides, each of which carries a servo hydraulic cylinder (SHC) (9,9') employed to move a bearing block (6,6') holding a forging roll rotating on a vertical axis. Each SHC is fitted with a sensor so the position of its piston can be fed to a control circuit; and SCH (9') is also connected to its block (6') by a sensor (11) monitoring the forging pressure, so the latter can be evenly distributed between the two rolls. The machine can be used to weld tubes with a wide range of dimensions.

Description

The invention relates to a forging block for forging the weld line of a metal tube, shaped by deformation of a strip or strip, whose lips have been brought to the forging temperature to be pushed there. against each other while the tube being formed there is driven in a space delimited, at least partially, by the running surfaces of at least
two forging rollers that can be pushed mutually sliding towards the tube, each by means of an associated double-acting jack.

 The subject of the invention is also a variant comprising, in addition, a pair of contiguous, symmetrically oblique, opposing forging rollers opposite to a fixed forging roller of axis contained perpendicularly in the plane of the axes of the two main forging rollers, the rolling surfaces. said oblique rollers acting, each, directly on one of the lips to be welded by sliding forging convergently sliding towards the tube by means of a double-acting oblique jack.

In the forza ga blocks known a worker
or a mechanical suspension must permanently act on the jacks / to ensure the thrust necessary for forging and to equalize in height the lips to be welded. It is actually a manual control operation difficult for the operator, whose intervention inevitably causes delays and pumping in the channe of regulation of which it is a part, because this work requires a sustained attention of the 'operator.

 The object of the invention is to propose a new fully automated regulator block capable of ensuring, without incident, guiding and forming the tube, to protect the mechanical members of the forging block against the widths of the strip or the raw milling strip, to maintain a constant forging pressure for each given setting, while ensuring a precise posijionnement of the weld line and ensuring a good outcrop of the lips during and after welding.

These objects are achieved, according to the invention, in a forging block of the type described at the beginning, by the fact that
the two cylinders each comprise a position sensor, at least one of them comprises a pressure and / or thrust force sensor,
the control circuit of ## EQU1 ## comprises means for controlling one of the cylinders, acting as a driven cylinder, at a position of its associated roller symmetrical with the current position of the roller associated with the other jack, which comprises the or one of the pressure sensor (s) and / or thrust force and serves as the driving cylinder,
the control circuit of the cylinders comprises means for controlling the dummy leader to a set value.

 According to a preferred embodiment, the servo control setpoint quantity of the driving cylinder is a position or pressure setpoint and / or thrust force.

 When the setpoint value is a position setpoint, it will be to move the rollers during interruption or at the start of the line, but when the setpoint magnitude is a pressure and / or thrust load setpoint, it will be obtain the normal operating conditions of forging. This is why there is provided a selection means between the position setpoint and the pressure and / or thrust force setpoint.

 It can be seen that, thanks to the means of the invention, the forging pressure is maintained irrespective of the accidental dimensional variations of the strip or strip whose lips are to be welded. At the same time, servo-positioning of the driven roller ensures the stability of the tube axis on a reference line, which is very important when there are three or five forging rollers, as will be seen later.

 In order for the forging block to be adaptable to a wide range of tube sizes, forging temperatures and strip or strip types, it is intended that at least one of the two position and pressure setpoint magnitudes and / or pushing force is adjustable in value.

In the case of the variant, recalled previously, comprising five rollers, two oblique, it is consistent with the invention that
the two oblique cylinders each comprise a position sensor and a pressure and / or thrust force sensor, and
- the control circuit of the oblique cylinders includes
selective control means of one of the two cylinders, then serving as a driven cylinder, at a sliding position of its associated roller identical to the current sliding position of the other oblique roller associated with the other oblique cylinder , then serving as a leader,
a means of reversing the selective slaving of the two oblique jacks to one another, and
- Servo control means of the selected master cylinder to a set value of the pressure and / or the thrust force.

For the leader cylinder to be selected automatically, it is consistent with the invention that
the forcing block comprises a comparator of the signals delivered respectively by the two pressure and / or thrust force sensors delivering a relative difference signal,
the relative difference signal is directed to the means for inverting the servocontrol of the two oblique jacks,
- Said reversing means controls the cylinder whose pressure sensor and / or thrust force delivers the signal of higher pressure and / or pushing force to be led by the other.

 Under these conditions, it is the roller most repelled by the lip vis-à-vis, which will receive an additional thrust tending to put the two lips flush with each other.

 For the regulation to exclude any oscillation or pumping, it is according to the invention that the inversion means is sensitive to the deviation signal only beyond an absolute threshold, which can be very low, provided, of course he is superior to the terror of measuring the gap.

 Because of their ease of adjustment and control and their positioning speed, the cylinders will preferably be hydraulic.

Other features and advantages of the invention will emerge from the description which will be given below solely by way of example, of an embodiment of said invention. For this purpose, reference is made to the appended figures, in which
FIG. 1 is a cross-sectional view, with respect to the running direction of the tube, of a forging block according to the invention, the simplification of which does not show the heating element,
FIG. 2 is a schematic view of a servo-cylinder with its accessories,
FIG. 3 is a variant of the embodiment of FIG. 2,
FIGS. 4 and 5 are diagrams illustrating the mode of action of the lateral rollers of the block of FIG. 1,
FIGS. 6 and 7 are the diagrams of the servocontrol circuits of the lateral rollers of the block of FIG. 1,
FIGS. 8 and 9 are diagrammatic diagrams of the mode of action of the oblique rollers of the block of FIG. 1,
FIGS. 11 and 12 are diagrams of servocontrol circuits for the oblique rollers of the block of FIG. 1,
FIG. 12 is the response characteristic diagram of the flip-flop circuit of FIGS.

 The forging block 1 shown in cross section in FIG. 1 is designed for the forging of the weld line 3 of a tube 2 traveling in a direction perpendicular to the plane of the figure. The block itself is mounted on a frame 4 on which are mounted two symmetrical carriages 5 each carrying a block 6, 6 'and each movable sliding on either side of a central line Z ~ through adjusting screws 7 synchronized release and nets opposite directions. Each of the blocks 6, 6 'carries a lateral forcing roller 8, 8' of vertical axis and with a concave generatrix, the gap between the two rollers 8, 8 'defining the curvature of the tube to be welded.Each block 6, 6' is mounted mobile in translation on its carriage 5 and controlled in translation by one end of a hydraulic servo-cylinder 9, 9 'whose other end is connected to a bracket 10 of the carriage. However, the end of the servo-cylinder 9 'controlling the block 6' carrying the roller @ 'is connected to this block 6' by means of a dynamometer 11.

The frame 4 further carries a support 12 for a roller 13 with a horizontal axis directed in the plane of the figure.

 The upper part of the frame 4 carries carriages 14 mounted on a support 21 with slides 15 for the approach adjustment by screws 20 of two symmetrically oblique upper rollers 16 and opposite the roller 13. Each roller 16 is carried by a support 17 sliding on its carriage 14 and controlled in translation, according to the plane of the figure, by one end of a hydraulic servo-cylinder 18, the other end is connected to a fastener 19 of the carriage. The entire support 21 with slides 15 is adjustable in height by a screw 22.

 The general structure as described up to now is quite similar to the general structure of known mechanical jacking blocks, except that the cylinders are hydraulic servo-cylinders.

 The servo-cylinders 9, 9 'and 18 will now be described with reference to FIGS. 2 and 3.

 A servo valve 23 for the servo-cylinders is controlled by current. It delivers an oil flow on its two output ports in proportion to its control current, the flow direction being a function of the direction of this current.

The speed of displacement of the rod 24 of the jack is therefore proportional to the current of the servo valve 23 and its direction of movement depends on the polarity thereof. This assumes that the load outside the cylinder 9, 9 ', 18 is constant. In the case where this varies, the rule of proportionality between the speed of the rod 24 of the jack and the intensity of the current is changed according to known laws.

 A position sensor associated with each cylinder 9, 9 ', 18 is of the linear variable differential transformer (LVD1) type or a linear potentiometer. it delivers an electrical signal proportional to the position of the core or slider mechanically secured to the rod 24 of the jack.

 The dynamometer 11 associated with the jack 9 'is of the type with strain gauges mounted in Wheatstone bridge.

it delivers an electrical signal proportional to the measured thrust force.

 the other cylinder 9, which will be the servo-actuated cylinder of the invention, is identical to the first, except for the torque sensor that it does not have.

 the servo-cylinders 18 are similar in construction to the cylinders, 9, 9 ', with the force, but the thrust sensor is replaced, as a simple variant, by two pressure sensors 26.

 Functionally the two variants with load cell sensor II or with pressure sensor are equivalent and the choice of one or the other type is not critical according to the invention, it being understood that the electrical signals delivered by the pressure sensors are processed in such a way that the resulting information is push force information.

 Figures 4 and 5 show the relative position of the tube 2 in formation and side rollers 8 and 8 'pushing with a zero force (Figure 4) or with the reference thrust force F (Figure 5).

 FIGS. 6 and 7 both show the servocontrol circuits of the jacks 9 and 9 ', the only difference being that in FIG. 6 there is complete servocontrol in position, for example for the rest or the approach position, while in Figure 7 there is enslavement thrust force for welding the tube. On each of the two figures 6 and 7, there is shown in strong lines the servo loops then in operation.

 A relay 27 makes it possible to go from position control (FIG. 6) to force control (FIG. 7) and vice versa.

 FIG. 6 shows a servo loop 28 in which a comparator 29 measures the difference between the signals delivered respectively by a line 34 and by the loop 28 by the two position sensors 25 of the jacks 9 and 9 'and delivers a deviation signal to the servo valve 23 which acts on the cylinder 9 until the difference is zero. The two cylinders being identical, and with a symmetry adjustment at the start, it is assured that under all circumstances, within the pressure and power limits provided, the cylinder 9 will be perfectly symmetrical with the cylinder 9 ', with respect to the line z.

 By its class, the relay 27, which is in its non-energized position, closes on the servo valve 23, associated with the servo-cylinder 9 ', a servo-control loop 302 in which a comparator 31 with a target display measures the difference between the reference value and the signal, possibly shaped, delivered by the position sensor 25 of the servo-cylinder 9 'to deliver a deviation signal to the servo valve 23 which acts on the cylinder 9' in the direction tending to cancel the gap.

 In FIG. 7, the control loop 28 of the jack 9 is not modified with respect to FIG. 6.

On the other hand, the servo-control loop 30 of the driving cylinder 9 'is opened by excitation of the relay 27 which closes a servo-control loop 32 on a comparator 33 with a push-force display 1 which measures the difference between this setpoint value. and the signal, possibly shaped, delivered by the load cell sensor 11 of the servo-cylinder 9 'to deliver a deviation signal to the servo valve 23 which acts on the cylinder 9' in the direction tending to cancel the gap. Since the line 34 is permanently connected, the position signal delivered by the sensor 25 of the jack 9 'is applied to the comparator 29 which immediately causes the jack 9, that is to say of its roller 8, to be placed in exactly the same position. position and thrust that of the cylinder 9 ', that is to say its roller 8'.

 As just described with reference to FIGS. 1 to 7 for a five-roller forging block, the invention also applies to two-slot forging blocks of the type suitable for small-diameter tubes.

 The additional means of the invention concerning the forging block of FIG. 1 will now be described.

 Figure 8 shows a tube in formation, the lips of which are spaced apart from each other with an exaggerated gap in the figure for better visualization. FIG. 9 represents the same tube forming in the forging block of FIG. 1.

 FIGS. 10 and 11 both show the servocontrol circuits of the cylinders 16, the only difference being that in FIG. 10 there is complete servocontrol in position, for example for the rest or the approach position, while In FIG. 11 there is enslavement in the thrust force of the lips flush with each other for welding the tube simultaneously tightened by the rollers 8 and 8 'exerting the horizontal thrust force setpoint. On each of the two figures 10 and 11 there is shown in strong lines the servo loops then in operation.

 A relay 36 controlling contacts 37 makes it possible to go from position control (FIG. 10) to force control (FIG. 11) and vice versa.

 Referring first to Figure 11, where the cylinders 18 have been distinguished respectively by the designations 18a and 18b and so on for accessories associated with them. Relay 36 is in the excited position closing contacts 37a1 and 37b1 and actuating in the position shown the rocker contacts 37a and 37b, the role of which will be explained below. Around the cylinders 18 and their accessories are mounted servo circuits identical in all respects. The pressures measured on the pressure sensors 26 are converted by encoders respectively 26'a and 26'b delivering push force signals comparable to the same setpoint value introduced at two suitable inputs of two comparators 38a, 38b.The same push-force signals are fed to the input of a comparator 39 which subtracts them from one another and sends the resulting signal in + direction and value E to a logic flip-flop circuit 40 whose function will be exposed more far. According to the latch state of the logic circuit 40, one or the other of two relays 41a or 41b is excited through the contact, respectively 37a1 or 37b <, these two contacts being both closed by relay 36 as it was said. In the figure it has been assumed that the relay 41b is energized, the relay 41a not being so. When the relay 41a is not energized a contact 41a1 closes a control loop 42a comprising the servo-cylinder 18a-23a, a position sensor 25a and a comparator 46a of the position signal to the position signal of the position sensor 25b of the other servo-cylinder 18b-23b, the signal of which is supplied to the comparator 46a by a line 45b and the contact 37a in the excited position of the relay 36. The difference signal of the comparator 46a is sent to the servo-cylinder through a signal amplifier 44a.

In this way the jack 18a will be driven by the jack 18b as long as the latch of the logic circuit 40 will not excite the relay 41a.

 Moreover, the excitation of the relay 41b opens the circuit 42b symmetrical circuit 42a by tilting of the contact 41b1 which then closes a control circuit 43b including the servo-cylinder 23b-18b, its encoder 26'b of thrust force signal and a comparator 38b of this signal to a thrust force reference value. In the configuration of FIG. 11, it can be seen that the jack 18a is driven in a position that is slaved to the position of the jack 18b, itself slaved into a thrust force by a set value *.

 We shall now return to the role of the discriminator 39 and the logic circuit 40. As has been said, the logic circuit 40 receives information from the discriminator 39 on the direction and the value of the difference of the output signals of the encoders 26 ' a and 26'b of thrust force signals. The logic circuit 40 gives an excitation signal s or F to only one of the two polarized relays 41a or 41b. According to the invention the direction of the excitation signal is that which excites that of the two relays which is associated with the least loaded cylinder, namely the signal exciting relay 41b in Figure 11. To avoid failovers for values signal less than the measurement errors and to avoid beats, the flip-flop circuit 40 is a hysteresis circuit responding only in response to a given absolute value of the discriminator 39, as summarily indicated by the response curve shown in Figure 12.

 If the signal having the value s in FIG. 11 takes the value s, it is easy to understand that the jack 18a becomes the leader of the jack 18b, which is then driven until the signal returns to the value s and so on.

 In FIG. 10, the relay 36 is no longer energized, which opens the contacts 37a1 and 37b1, whence the fallout of the two relays 41a and 41b, which puts into service simultaneously the two control loops in position 42a. and 42b.

 At the same time, the tilting of the contacts 37a and 37b connects the inputs of the two comparators 46a and 46b on a line 48 bringing therein an adjustable value signal of the position setpoint to which the two jacks are thus simultaneously servocontrolled.

 The situation of FIG. 10 is that in which the two jacks can be controlled while the situation of FIG. 11 is the working situation leading to a greater force of the rollers 16 on the most protruding lip, by reversing the side of this greater effort when the lip defect is reversed. When there is no decelerable lip defect, the two jacks are exactly the same height and exert the same thrust force.

Claims (11)

REVENDICAvIONS  1) Forging block for the forging of the weld line of a metal tube, shaped by deformation of a strip or strip, whose lips have been brought to the forging temperature to be pushed against each other while the tube being formed is driven in a space delimited, at least partially, by the rolling surfaces of at least two forging rollers  which can be urged together towards the tube, each by means of an associated double-acting jack, characterized in that  the two cylinders (9, 9 ') each comprise a position sensor (25), at least one (9') of which comprises a pressure and / or thrust force sensor,  - The control circuit of the cylinders (9, 9 ': comprises servo means (28) of one of the cylinders (9), serving as a driven cylinder, at a position of its associated roller (8) symmetrical with the current position of the associated roller (8 ') to the other cylinder (9'), which comprises the one or one of the pressure and / or thrust force sensor (s) and serves as a driving cylinder (1  - The control circuit of the cylinders comprises control means of the control cylinder (9 ') to a set value.  2) Forging unit according to claim 1, characterized in that the servo control setpoint magnitude of the driving cylinder is a position or pressure setpoint and / or thrust force.  3) Forging block according to claim 2, characterized in that it comprises a selection means (27) between the position setpoint and the pressure setpoint and / or thrust force.  4) Forging block according to claim 2, characterized in that at least one of the two variables of position and pressure and / or thrust force is adjustable in value.  5) The drill block according to claim 1, further comprising a pair of contiguous, symmetrically oblique, opposing forging rollers opposite to a stationary forging roller of axis contained perpendicularly in the plane of the axes of the two main forging rollers, the surfaces of rolling said oblique rollers each acting directly on one of the lips to be welded by sliding forging convergently sliding towards the tube by means of a double-acting oblique jack, characterized in that  the two oblique jacks (18) each comprise a position sensor (25) and a pressure sensor (26) and / or thrust force, and  the control circuit of the oblique jacks (18) comprises  - Selective control means (42a, 4> b) of one of the two cylinders (18) then acting as a driven cylinder, at a sliding position of its associated roller (16) identical to the current sliding position of the other associated oblique roller (16) to the other oblique cylinder (18), then serving as a leader cylinder? an inversion means (40) for selectively isolating the two oblique jacks (18) from one another, and  - Control means (38a, 38b) of the control cylinder (18) selected to a set value of the pressure and / or the thrust force.  6) Forging block according to claim 5, characterized in that:  it comprises a comparator (39) of the signals respectively delivered by the two pressure and / or thrust force sensors or their associated coders (26'a, 26'b) delivering a relative difference signal,  the relative deviation signal is directed on the means for reversing the servocontrol (40) to each other of the two oblique jacks (18),  said inverting means (40) slaves the jack (18) whose pressure and / or thrust force sensor or its associated encoder (26'a, 26'b) delivers the signal of greater pressure and / or push force to be led by the other.  7) Forging block according to claim 6, characterized in that the reversing means (40) is sensitive to the difference signal only beyond an absolute threshold (  8) Block-forging machine according to claim 6, characterized in that it comprises a controllable means (36) for simultaneous control of the two oblique cylinders (18) at a given identical position of sliding of their associated rollers (Figure 11).  9) block-forager according to claim 5, characterized in that the set value of the pressure and / or the thrust force is adjustable.  10) Forging block according to claim 8, characterized in that the given position of sliding is adjustable.  11) Forging block according to any one of claims 1 to 10, characterized in that the cylinders (9, 9 ', 18) are hydraulic.