EP0569307B1 - Device for forming helical fins on the external wall of tubes - Google Patents

Abstract

The device according to the invention relates to the production, by rolling, of helical fins on tubes for a heat exchanger so as to increase their capability of heat transfer. It comprises four rollers (6, 7, 8, 9) distributed over two carriages (4, 5) which can move translationally towards each other by means of a ram enabling the four rollers to be simultaneously brought to bear against the wall of a tube (2). The four rollers, distributed around the tube, are rotationally driven at the same speed by a single motor means (50) and can be oriented about an axis (X2, X3, X4, X5) perpendicular to their forming zones. The tube (2) is driven by the rollers along a running axis (X1-X1). Application to the finning of tubes (2) made of stainless (non-oxidisable) metals or alloys. <IMAGE>

Description

The device which is the subject of the invention relates to the production of finned tubes for heat exchangers between two fluids or mixtures of liquid or gaseous fluids or also partly liquid and partly gaseous, one of which circulates inside. of the tube and the other outside.

Various devices are known which make it possible, by forming using knurling wheels, to form helical fins on the external wall of such tubes in order to increase their ability to transfer heat.

Such fins can be obtained by rolling on the outer surface of a tube, for example two knobs, arranged on either side of this tube along a helical path. Each of these knobs comprises several revolution disks mounted on the same axis. The edges of these discs gradually penetrate into the wall of the tube by pushing the metal from it in the intervals which separate them, thus forming at least one helical fin.

The knobs are given the angle of advance necessary to obtain the relative displacement of the tube with respect to the knobs, which results in the formation of helical fins.

The development of the use of tubes for heat exchangers has shown the advantages of finned tubes in the use of metals or alloys having a high resistance to corrosion by different liquid or gaseous fluids brought to relatively high temperature. Metals or alloys, such as stainless or refractory steels, titanium and its alloys, stainless or refractory alloys and in particular those with a high nickel content, have thermal conductivities which can be low and also have a relatively poor ability to cold forming.

It has been found that, in order to obtain good heat transfer characteristics, it is desirable to be able to form, on the wall of tubes made of such metals or alloys, helical fins of small height, of small thickness and of small spacing.

Thus, for example, for a height of the order of 1 mm, it is proposed to produce a helical fin whose pitch is of the order of only 1 mm or less, that is to say a number of turns per unit of tube length, or density, reaching about 10 per cm (about 25 per inch) or more. The tubes thus finned have very good performance from the point of view of heat transfer. On the other hand, their realization presents great difficulties. These difficulties increase when one seeks to produce tubes of small thickness, that is to say of a residual thickness after forming of the same order as the height of the fins or much less than this, to reduce the cost. of the metal used and further improve the heat transfer capacity. The tubes must, moreover, have great unit lengths, which can reach of the order of 20 to 30 m or more.

The difficulties encountered in the production of these tubes result in numerous faults and also numerous ruptures or deterioration of the discs of the rollers. These ruptures or deteriorations cause very significant disruptions in manufacturing and considerably increase the cost of the finned tubes manufactured. The most common of the faults are cracks which form on the edge of the fins, tearing off of fins due to the forces exerted by the discs of knurls on the side wall of these fins in formation and finally the cracks which appear on the same wall of the tube. It is noted that such defects are frequent despite the care taken in the operation of the devices used for the forming of these fins and despite low production speeds.

All these difficulties have, as a consequence, very high production costs which do not allow obtaining, in a truly economical manner, tubes for high performance heat exchangers that we would like to be able to use.

We looked for the possibility of producing a device for forming by rolling helical fins on the outer wall of metal tubes relatively difficult to transform ensuring high heat transfer performance.

We have sought, in particular, the possibility of obtaining such finned tubes, in stainless steel or refractory, in alloyed or unalloyed titanium, in stainless alloys or refractory with a high nickel content or in other metals or alloys. combining good corrosion resistance and good mechanical strength at relatively high temperature. Research has been carried out, in particular, on the possibility of producing a tube forming device for heat exchangers which makes it possible to obtain high performance finned tubes, of great length, under truly economical conditions.

We have sought more particularly to produce a device making it possible to commonly achieve, for such tubes, a helical fin whose density is of the order of 11 per cm (28 per inch) or more, with a fin height d 'About 1 mm, the thickness of the tube obtained being substantially equal to or less than about 1 mm.

Attempts have also been made to produce a device in which the holding in service of the knobs and of the disks constituting them is satisfactory.

The device which is the subject of the invention achieves all of these results.

This device is designed for forming by rolling at least one helical wing on the outer wall of a tube.

Depending on the applications, it is a seamless or welded metal tube made of a metal or alloy adapted to the temperature conditions and to the nature of the fluid or fluids with which it is contacted. They may, for example, be carbon steels, ferritic or austenic stainless steels, refractory steels, titanium or titanium-based alloys or any other metal or alloy whose physicochemical properties are suitable for the intended conditions of use.

The device according to the invention comprises two movable carriages, arranged one opposite the other, on either side symmetrically of the axis of travel of a finned tube, each of these carriages comprising two wheels mounted each on a wheel holder head. A means of translation makes it possible to bring the two carriages symmetrically towards one another to a working position such that the four knobs come to bear against the tube to be formed, disposed along the axis of travel, with a force determined tightening. In this working position, the rollers are distributed around the tube, inclined at the same angle of advance and positioned relative to the axis of travel, relative to each other, so as to each participate in the fin of the tube. The means of translation also makes it possible to separate the two carriages from one another to release the finished tube, put the next tube in place and also, whenever necessary, carry out checks, adjustments or changes of tools.

The means of translation of the carriages allowing in particular the approximation and the tightening of the rollers is preferably constituted by at least one jack whose body is connected to one of the carriages and the piston to the other. A synchronization means ensures a simultaneous translation of the two carriages in one direction as in the other. This synchronization means comprises a tilting beam or lifting beam mounted on a fixed pivot whose axis intersects the scroll axis; rigid rods or connecting rods are each connected symmetrically in an articulated manner, to the carriage by one end and to one of the two ends of the tilting beam by the other.

A means of precise adjustment of the stroke of the clamping cylinder or cylinders is preferably used to ensure reproducible tightening, in the working position, of the knobs against the outer wall of the tube to be formed.

This adjustment means is preferably constituted by a means for closing the supply line of the cylinder with pressurized fluid. The closure means, connected directly or indirectly to the piston rod of the jack, comprises an adjustment means such as a micrometric screw making it possible to precisely adjust the length of stroke of the piston for which the closure closes l power to the cylinder and therefore causes the piston to stop. Advantageously, a means of opening a discharge pipe intervenes in the event that an incomplete closure of the supply to the jack does not immediately and completely stop the piston.

Each wheel holder head is mounted in abutment on a surface of a tool holder secured to the carriage and can rotate a few degrees around an orientation axis which intersects in the working position the forming area of the corresponding wheel on the tube.

In this working position, the four orientation axes are distributed at approximately 90 ° from each other. We thus reduce while making the effort symmetrical performed by each wheel on the tube to form the fins relative to existing conventional devices which have only three wheels distributed at 120 ° from one another around the tube.

Each wheel is mounted on a wheel holder shaft, guided in rotation on bearings integral with the wheel holder head. A motor shaft, arranged parallel to the wheel-holder shaft, is also mounted on bearings, integral with the wheel-holder head and is connected to the wheel-holder shaft by a transmission means, for example by gears. The four drive shafts are connected by articulated transmission means arranged, preferably around the axis of travel of the tube, to a common rotational drive means which ensures the rotation at strictly equal speed of the four knobs.

Preferably, the articulated transmission means consist of four shafts provided with articulated joints at their two ends, for example cardan joints and comprising a telescopic part, shafts connected, at one end, to a motor shaft of a carrying head -wheel and, at the other end to a common rotational drive means. Preferably, this common rotary drive means comprises a ring gear whose axis corresponds to the axis of travel of the tube which passes through it. A pinion, actuated directly or indirectly by a motor means, rotates this toothed crown and four identical pinions distributed around the axis of the crown, at 90 ° from each other, each driving directly or indirectly l 'corresponding drive shaft. A passage through the ring gear allows it to pass through the tube during forming.

The wheel shafts are arranged so that the orientation axis which intersects the zone of formation of the wall of the tube by the corresponding wheel also intersects the axis of travel in the clamping position, or passes in the immediate vicinity of that -this. It is thus possible, by angularly moving the wheel-holder head around the orientation axis, to give the corresponding wheel a determined angular inclination in order to give at least one helical fin a determined pitch. The range of the wheel head on the bearing surface of the tool holder end of the corresponding carriage is a plane perpendicular to the axis of orientation.

Advantageously, it is possible to interpose between the two contact surfaces of the knurling head and of the tool holder of the carriage one or more spacing plates, with parallel faces and of controlled thicknesses which make it possible to adjust the distance between the 'axis of the wheel-holder shaft and the axis of travel of the tube to be formed. This takes into account the different outside diameters of the tubes to be fined as well as the corresponding diameters of the knurls used. It is thus possible to maintain a clamping position for which the orientation axis intersects the scrolling axis and to respect a distribution of the 4 knobs at 90 ° around the tube whatever its diameter. Under these conditions, the forces exerted by each wheel on the tube during rolling forming are supported in a perfectly balanced manner on the tube.

Advantageously also the angular setting of the orientable part of the wheel holder around the orientation axis is carried out by means of shims which are introduced between a wall integral with the tool holder end of the carriage and the wall in look of a part secured to the wheel holder head.

Locking means allow, after adjusting the feed angle and after possible adjustment of the distance between the axis of the wheel-holder shaft and the scroll axis, to block the door head in rotation. -wheel relative to the tool holder end of the carriage which avoids any risk of angular displacement. The locking means used may include, for example, threaded rods which pass through the bearing surface of the wheel-holder head and are connected to the tool-holder end of the carriage.

Preferably, each of the wheel-holder heads comprises a removable part in which is housed at least one bearing on which the wheel-holder shaft is mounted at one of its ends, this removable part being fixed in such a way that, after detachment from the wheel holder head, it is possible to easily disassemble the corresponding wheel holder shaft.

Also preferably, one of the bearings of the motor shaft which drives the wheel-holder shaft is also housed in this removable part, in order to allow, if necessary, the disassembly of this shaft as well as of the holder shaft. wheel and the transmission means which connects them to each other.

Preferably, each wheel is constituted by a stack of disks of revolution. The diameter of several of these discs increases in the direction of progression of the tube in order to allow progressive formation of the fins. This forming is accompanied by an elongation of the tube with reduction of its diameter and of its thickness measured below the fins. In the case of relatively thin tubes, there is preferably arranged inside the tube a mandrel held in place by a retaining rod, of length greater than that of the tube and whose end outside the tube, at the rear of this one, is hung on a fixed point. Advantageously, the mandrel is mounted free to rotate about the axis of travel of the tube, thanks to a bearing provided between the mandrel and the retaining rod or between the retaining rod and the fixed point of attachment.

This mandrel advantageously has a substantially frustoconical shape with a generator inclined a few degrees relative to its axis, in order to support the inner wall of the tube in the section reduction zone thereof under the action of the knobs. It is advantageously adjustable in axial position in order to maintain the collapse of the tube under the action of the rollers.

Chutes can be used to facilitate guiding and moving the tube along the axis of travel. It is necessary to coat these chutes with a layer of plastic which facilitates the rotational movement of the tube, under the action of the rollers without risk of catching and deterioration of the fins. Pinch-rolls (drive rollers) placed upstream and downstream of the forming device are advantageously used for the positioning of the smooth tube on the chuck rod and for the extraction of the tube from the chuck rod at the end of the operation.

Over the length, it is possible to produce several smooth parts, the displacement of the tube then being ensured by the drive rollers and managed by proximity detectors.

Proximity detectors, such as eddy current detectors, located downstream from the start of the finning operation, as well as for the interruption thereof at predetermined intervals, are advantageously used. the forming zone at locations precisely identified along the chute with respect to the fin zone. These detectors, which are at least two in number, are connected to electronic means which allow the start-up of the finning operation and also its interruption, if necessary, in intermediate zones provided for non-finned parts which will become, for example, the curved parts of the tube. It is thus possible to produce on the tube several finned zones separated by smooth zones.

The start-up of the fin is preferably carried out by electronic means which make it possible to set the wheels in rotation at reduced speed then a gradual approach of the carriages at slow speed with the application of the wheels with progressive tightening also. The rotational speed of the knurls is then increased to their operating speed. In the case, for example, of austenitic stainless steel tubes such as 304 or 316 steel of approximately 15 to 25 mm outside diameter and 1.5 to 2.5 mm thick, before forming the clamping force of each wheel is about 30 + 10 kN. The diameter of the rollers is of the order of 25 to 50 mm and the speed of forming in regime can reach 4 to 10 m / min.

The example and the figures below describe, without limitation, an embodiment of the device according to the invention.

Figure 1 is a schematic front elevation view, in a plane perpendicular to the axis of travel of the tube, of the assembly constituted by the four knurling heads and the front end of the two carriages of the device according to the invention .

Figure 2 is a schematic view, along the cutting plane B-B of Figure 1, of a wheel head in the forming position by rolling on the wall of a tube to be fined.

Figure 3 is a schematic plan view showing the lower part of the two carriages of the device according to the invention in the separated position with their combined displacement means.

Figure 4 is a plan view of the lower part of the carriages of Figure 3 in the close position, working.

Figure 5 is a schematic view of the means for adjusting the end of travel of the carriages of Figures 3 and 4 in the working position.

Figure 6 is a schematic top view along the cutting plane A-A of Figure 1 showing the drive means and the transmission means between this drive means and the drive shafts driving the wheel-holder shafts.

Figure 7 is a schematic detail view of a wheel in section along a plane containing the axis of the wheel holder shaft.

FIG. 1 is a schematic front view of a device 1 allowing the forming on the outer wall of a tube of revolution 2 for heat exchangers of at least one helical fin 3.

This device comprises two carriages 4, 5 able to slide parallel to the plane of FIG. 1 on slides 4A, 5A shown in FIGS. 3 and 4. These two carriages are arranged opposite one another on either side another symmetrically of the axis X1-X1 of travel of the tube 2. They each comprise two knobs 6, 7 and 8, 9 fixed in rotation respectively on the shafts carrying the knurling wheel 18, 19 and 20, 21, which are driven in rotation by the drive shafts 24, 25 and 26, 27, by means of a transmission by pairs of gears such as 22 and 23 which are visible in FIG. 2. Each wheel, its wheel-holder wheel and the corresponding motor shaft are mounted on the same wheel holder head. The first two wheel-holder heads 10, 11 are mounted in abutment on the bearing surfaces 14 and 15 of the tool-holder end 4-1 of the carriage 4 and the other two 12 and 13 are in abutment on the bearing surfaces 16 and 17 of the tool-holder end 5-1 of the carriage 5. Each of these wheel-holder heads can be oriented a few degrees around an orientation axis. Each of the four orientation axes X2, X3, X4, X5 is perpendicular to the plane of the corresponding bearing surface 14, 15, 16, 17 of a wheel-holder head on one of the two tool-holder ends 4-1, 5-1. In the working position, each wheel being supported in its forming zone on the outer wall of the tube 2, driven along the axis of travel X1-X1, the four orientation axes each pass through the forming zone of the corresponding wheel and, under the optimal adjustment conditions, intersect the scroll axis. The orientation axes are distributed at 90 ° from each other around this scrolling axis X1-X1.

The carriages 4 and 5 include means of translation allowing either to bring them together, so that the knobs 6, 7, 8, 9 come into the working position against the outer wall of the tube 2, or to separate them one from the other for example every time that a finning phase has been completed or that inspection or maintenance operations should be carried out.

FIGS. 3, 4, 5 describe an embodiment of the means for translating the carriages 4, 5.

In schematic figures 3 and 4, only the lower part of each of these two carriages is shown sliding on the slides 4A and 5A, the tool holder ends 4-1, 5-1 and the wheel holder heads not being represented.

Figure 3 corresponds to the separated position, and Figure 4 to the close position, for which the knobs are in the working position. The scroll axis X1-X1 is indicated in the two figures. The translation means is the jack whose cylinder 31 is housed in the carriage 4 and whose piston 32 moves along a translation axis perpendicular to X1-X1. The end of the rod 33 of this piston 32 which passes below the tilting beam 34 is secured to the carriage 5. The tilting beam 34 is rotatably mounted in its middle around a pivot with a vertical axis X6 which intersects X1-X1. Two rigid rods 35, 36 are connected to the front ends of the carriages 4 and 5 by one of their ends 35A, 36A and by the other end 35B, 36B to the tilting beam. There is thus obtained a symmetrical displacement of the two carriages relative to the axis of travel X1-X1. The cylinder further comprises an auxiliary piston 37, of reduced section, making it possible to quickly separate the two carriages from one another at the end of a finning operation. A means of determining with precision the stopping point of the carriages in the working position makes it possible to clearly define the distance between the axis of the tube and the rollers and therefore the penetration of the latter into the tube. This means comprises a rigid lateral arm 38 connected to the piston rod 33 by one end and connected by the other end, by means of a micrometric screw 39, to a means 40 for controlling the supply of the jack 31 in high pressure fluid.

FIG. 5 schematically represents an embodiment of this control means. It can be seen that the rigid arm 38 allows the piston rod 33 to drive the micrometric screw 39 to the point where it bears against a shutter 41 which closes the high pressure fluid intake orifice coming from the pipe. 42 towards the cylinder 31 of the jack and stops its movement. If the movement does not stop, the valve seat 43 moves back and causes the opening of a fluid passage in the direction of the discharge line 44. A return spring 45 closes the valve seat 43 if the piston rod 33 moves back. This means of adjusting the stopping point of the carriages, in a safe and reproducible manner, therefore makes it possible to achieve constant and reproducible positioning of each wheel on the wall of the tube to be finned.

The four motor shafts 24, 25, 26, 27 which drive the four wheel-holder shafts 18, 19, 20, 21 are mounted parallel to these and are driven at strictly equal speeds using the means shown schematically in FIG. 6 This figure is a top view along the section plane AA of Figure 1. In that Figure 6, only are shown, schematically, the two lower drive shafts 24 and 27 behind the plane of Figure 1, as well as the transmission means which connect them to the single motor means which is also shown diagrammatically. This motor means comprises a direct current motor 50, of high power, with adjustable speed over a wide interval and with high starting torque, connected by a transmission means 51, provided with a toothed pinion 52 to a toothed crown 53, axis X1-X1 of which only the lower half is visible. This ring is mounted on bearing surfaces 53A of an inner tubular support 54 connected to a fixed frame, not shown. A guide tube, not shown, ensures the passage of the tube to be fined inside the tube 54 along X1-X1. On this crown 53, driven by the pinion 52, mesh four pinions of which only two 55, 56 are visible, which each drive a transmission shaft connected to a motor shaft 24, 25, 26, 27. In FIG. 6, only the two lower pinions 55, 56 are visible which drive the lower drive shafts 57, 58, themselves connected to the lower drive shafts 24, 27. The four drive pinions, such as 55, 56, are distributed uniformly around the ring gear 53, at 90 ° from each other, so that the transmission shafts are also distributed uniformly around the axis X1-X1 of movement on which the ring gear 53 is centered.

The four drive shafts such as 57, 58 are telescopic and fitted at their two ends with universal joints. They thus make it possible to drive the four drive shafts and therefore the knurls at the same speed smoothly, even during the translational movements of the carriages 4 and 5.

The four knobs 6, 7, 8, 9 with which the device 1 is equipped are of identical structure. They preferably include each a set of revolution disks whose diameters and profile of the forming edges are designed to allow progressive formation of the fins, with successive penetration into the wall of the tube of the forming edges of these rollers, in the grooves already started by the discs of the preceding roll or rollers, following a helical path on the wall of this tube. To obtain such a result, use is made of knurls comprising discs of revolution of increasing diameter and of variable profile.

FIG. 7 represents, diagrammatically, a wheel such as for example the wheel 7 of FIGS. 1 and 2, in section, along a plane containing the axis of its wheel-holder shaft 19. This wheel comprises, from its end of small diameter, oriented in the upstream direction of the fin tube 5 forming discs 61, 62, 63, 64, 65 of revolution, which ensure the gradual growth of at least one helical fin thanks to successive passages of discs of increasing diameters in the same grooves. The last two discs 66, 67, of the same diameter as the disc 65, make it possible to equalize the profile of at least one helical fin. The helical course of the rollers on the wall of the tube is achieved thanks to the angle of advance obtained by angular displacement of the roll-holder heads around their axis of orientation. Each of the four knurls must have a different axial setting along the knurling shaft so that the forming edges of the discs penetrate into the grooves formed by the previous discs. This axial offset depends on the angle of advance, and the number of helical fins, that is to say of the propeller threads. This axial offset is obtained by giving the annular rings such as 68, 69, arranged on each side of the rollers such as 7, the desired width.

As shown in Figure 2, each wheel holder shaft such as 19, has a shoulder 19A located in the immediate vicinity of its drive pinion such as 22. We therefore give the ring 68, located on the upstream side of the tube and which abuts against the shoulder 19A, a width which takes account of the axial offset which it is necessary to give to this wheel relative to that which is immediately upstream or downstream. The tightening of the wheel discs against the shoulder 19A is ensured by the nut 70 which bears against the ring 69.

Each wheel-holder head such as 11 comes to bear by a flat surface, perpendicular to its axis of orientation X3, against a corresponding surface 15 of the tool-holder end 4-1 of the carriage 4.

At least one angular setting means can be slid into at least one of the two intervals e1, e2 (see FIG. 1) existing between a cylindrical rod of revolution 72 secured to the wheel-holder head 11, with an axis perpendicular to the surface of bearing surface 15 and a housing 73 formed in the end of the tool holder 4-1 in which the end of the rod 72 engages.

The introduction of shims in one and / or the other space e1, e2 makes it possible to vary the angular setting of the wheel-holder head 11 around the axis X3 by a few degrees. This angular inclination relative to the plane of Figure 1 does not exceed about 4 ° in the case of a single helical thread and about 8 ° in the case of a double helical thread.

The rotation of the wheel-holder head 11 around the axis X3 takes place around a part of revolution 74 (see FIG. 2) engaged without play in facing housings 75, 76 produced on either side of the bearing plane 15 and held by a threaded rod 77. Parts forming tie rods, such as 78, engaged by one end in an inverted T-shaped groove 79 of the knurling head 11 and by the other in a housing 79A formed in the tool-holder end 4-1, are capable of tightening the wheel-holder head 11 on the seat 15 by means, for example, of a wedge wedge 80, transverse, pulled by a threaded piece 81.

The possibility of easy separation of each wheel head from the corresponding tool end makes it easy to adjust the distance between the 2 wheel heads of each tool holder and to ensure 90 ° contact between the wheels on the tube depending on the diameter thereof. For this, a metal strip of constant thickness and sufficient surface is introduced into the bearing zone such as 15, this strip, not shown, having holes for the passage of the axial piece 74, tie rods such as 78 and the piece for angular setting 72. The angular setting at 90 ° of the knurling wheels around the tube to be fined is thus adjusted, taking into account the diameter of these knurling wheels as well as the diameter, thickness and reduction rate of this tube.

In some cases, it is necessary to support the wall of the tube subjected to the action of the rollers by means of a mandrel 82, housed inside the tube 2 in the forming zone, as shown in FIG. 2. This the mandrel is approximately frustoconical in shape and the slope of its generatrix depends on the conditions of forming of the tube to be finned. This mandrel is secured with a retaining rod 83 whose end upstream, located beyond the upstream end of the tube 2, is mounted to rotate freely, not shown, in the attachment zone at a fixed point. It is also possible to directly mount the free-rotating mandrel 82 on the retaining rod 83. The position of the mandrel is advantageously adjustable axially.

As shown in FIG. 2, each wheel-holder shaft such as 19 is mounted inside the corresponding wheel-holder head such as 11 on bearings such as 84, 85 and is wedged at its two ends by bearings of stop, such as 86, 87, to avoid axial displacements.

The corresponding drive shaft such as 25 is mounted on bearings such as 88, 89, arranged on either side of its pinion 23 which meshes with the pinion 22 of the wheel-holder shaft 19.

Each wheel-holder head such as 11 (see FIG. 2) is provided with a means of rapid disassembly of the wheels, such as 7, which makes it possible to check the wear of the forming discs as well as the wear of the shaft bearings such as 19, 25 and gear transmissions such as 22, 23. For this, the bearings such as 84 of the wheel shaft 19 and such as 88 of the motor shaft 25, are mounted inside d 'A removable part 90 which is secured to the rest of the structure of the wheel-holder head 11 by a fastening means for rapid assembly and disassembly.

This removable part 90 can be removed, after separation of the two carriages 4, 5 from the scroll axis X1-X1, by unscrewing two bolts 91, 92. These bolts ensure the locking of the removable part 90 against a range 93 of the wheel head.

The end of the removable part has a projecting abutment edge 94, forming a dihedral, the edge of which engages in a re-entrant edge 95 forming a dihedral of the same angle. The bolt rods 91, 92 inclined at approximately 45 ° relative to the plane of the bearing surface 93 pass through it and are connected to a hooking means 96 located on the other side of the bearing surface 93. The horizontal component of the the tensile force of the bolts 91, 92 thus ensures effective locking of the removable part 90 against the bearing surface 93 and the re-entrant edge 95.

After extraction of the removable part 90, it is possible to remove the shaft 19 which carries the wheel 7. It is thus possible to control the discs, to change them if necessary and also to modify, if necessary, the axial setting. It is also possible to completely disassemble the motor shaft 25 and therefore the gear transmission between the two.

The tube is scrolled during finning along the axis X1-X1 along a chute not shown. This metal chute is coated with plastic material to facilitate sliding and avoid any snagging which risks damaging the tube and its fins.

For the start-up of the finning operation and the interruption thereof, there are, at determined intervals relative to the forming zone, along the axis of travel near the chute, detectors not shown, used to signal the passage of the front end of the tube. These detectors are, for example, of the eddy current type.

They are connected to electronic means ensuring either the start-up or the interruption of the finning operation.

Each finned zone on a tube uses 2 electrical boxes which are connected to a bus: a box with a detector for switching on the fin, a box with 2 detectors: a controller for switching to the low rotational speed of the knobs , the other controlling the start-up of the return piston and the stop of the knurled rotation.

It should be noted that without the slowing down of the knobs at the end of the finning of a finned zone, it is impossible to ensure precise finned lengths, given the relatively rapid advance speed of the tube.

The bus is made up of 3 wires which start from the automaton of the forming device and which run along the guide troughs of the tube which can, for example, be 40 m. The device can thus include 40 bus connection sockets, along the guide troughs, which makes it possible to produce 20 different finned zones along the length of the tube. These 3 bus wires thus avoid 60 wires which would have been necessary if all the detectors had to be wired to the device independently.

In addition, this bus manages the consistency of the sequential information: for example, if in the middle of a finning operation, information "start of finning" arrives at the PLC because 2 boxes with detectors have been reversed, the bus can handle this kind of error.

The start-up of the fin of a tube such as an austenitic stainless steel tube of the type 316 L of about 16 mm of external diameter is carried out in the following way: installation of the smooth tube of a length about 25 m on the chute from downstream. A pinch-roll (drive roller) not shown allows it to be engaged on the mandrel 82 and its retaining rod already secured with its attachment point. After installation, the motor is started to drive the four knobs at a reduced speed of around 300 rpm. The cylinder 31 is then started at reduced speed to bring the two carriages 4 and 5 closer to their working position. The rollers are then progressively tightened on the wall of the tube 2 supported by the mandrel and the tube is rotated by the rollers in the opposite direction to the rollers, with a determined advance. As soon as the position of the wheels corresponding to the working distance is reached, the speed of rotation of the wheels is accelerated to the speed of about 1400 rpm. Under these conditions, depending on the type of wheel used and depending on the angle of advance and the axial setting chosen, it is possible to reach a running speed of the order of 4 m / min for a fin comprising a single helical fin and approximately 8 m / min for a double thread fin. By suitably choosing the reduction rates, the profiles and the tightening forces of the knurls, of the order of 20 to 40 KN per knurl, we obtain a finned tube of approximately 14 mm outside diameter, at the foot of the fins, 1 mm fin height, 0.9 mm tube thickness at the bottom of the fins and with a density of about 30 turns per inch of axial length in single thread. At the end of knurling after having reduced the speed of rotation of the knurls to precisely control the finned length, the operation can be stopped almost instantaneously, without transition, by actuating the return piston 37 of the jack at high speed.

Claims (20)

1. A device permitting the shaping by rolling of at least one helical fin (3) on the outer wall of a tube (2), characterized in that it comprises two carriages (4, 5) which are disposed symmetrically on either side of the axis of translation (Xl-Xl) of the tube (2) to be shaped and which are approaching each other in order to come into a working position or of moving apart from each other, each of these carriages comprising two forming rolls (6, 7, 8, 9), each being mounted on a forming roll carrier shaft (18, 19, 20, 21) and each being driven by a drive shaft (24, 25, 26, 27) which is parallel to the corresponding forming roll carrier shaft and connected thereto by a rotary transmission means (22, 23), the four forming roll carrier shafts (18, 19, 20, 21) being distributed about the axis of translation (XI-XI) of the tube (2) to be shaped in such a way that when the two carriages (4, 5) are brought together the four forming rolls come to bear simultaneously against the wall of the tube (2) to be shaped, the four drive shafts being connected to a common drive means comprising one single motor means (50) which drives the four drive shafts at the same speed, each of the four assemblies formed by one forming roll carrier shaft and the corresponding drive shaft being capable of moving about an axis (X2, X3, X4, X5) which intersects the shaping zone of the tube (2) by the corresponding forming roll (6, 7, 8, 9), the four axes being distributed at 90° relative to one another when the two carriages (4, 5) are brought together.
2. A device according to Claim 1, characterised in that the means for translation of the two carriages (4, 5) making it possible for these carriages to be brought towards or moved away from the axis of translation (X1-X1) of the tube (2) to be provided with fins is at least one jack, the cylinder (31) of which is integral with one of the carriages (4), the rod (33) of the piston (32) being connected to the other carriage (5).
3. A device according to Claim 1 or Claim 2, characterised in that a means for synchronising the translation of the two carriages (4, 5) is a swinging beam (34) mounted to a fixed pivot, the vertical axis (X6) of which intersects the axis of translation (X1-X1) of the tube, the ends (35B, 36B) of the beam each being connected by means of a rigid rod (35, 36) to the end (35A, 36A) of a carriage (4, 5).
4. A device according to Claim 2 or Claim 3, characterised in that it comprises a means for accurate adjustment of the end of the travel of at least one piston (32) of a jack, this means comprising a closure means (41) for the pipe (42) for supplying the cylinder (31) of the jack with high pressure fluid, connected directly or indirectly to the rod (33) of the piston (32) of the jack and comprising a control means (39) permitting accurate adjustment of the length of the travel of the rod (33) of the piston (32), for which the closure means has to interrupt supply to the jack.
5. A device according to one of Claims 1 to 4, characterised in that each forming roll carrier shaft (18, 19, 20, 21) is perpendicular to the corresponding axis of orientation (X2, X3, X4, X5) which it intersects.
6. A device according to one of Claims 1 to 5, characterised in that each forming roll carrier shaft (18, 19, 20, 21) and the corresponding drive shaft (24, 25, 26, 27) are mounted on a forming roll carrier head (10, 11, 12, 13) which bears against the tool carrier end (4-1, 5-1) of a carriage (4, 5) by virtue of a bearing plane (14, 15, 16, 17) which is perpendicular to the corresponding axis of orientation (X2, X3, X4, X5), a means for angular setting (72, 73) making it possible for each forming roll carrier head to rotate a few degrees about its axis of orientation.
7. A device according to Claim 6, characterised in that a setting means for the forming roll carrier head (10, 11, 12, 13) can be introduced into the bearing zone (14, 15, 16, 17) in order to displace the forming roll carrier head along its axis of orientation in order to adjust the angular position of the forming roll about the tube to 90°.
8. A device according to one of Claims 1 to 7, characterised in that each of the drive shafts (24, 25, 26, 27) is connected to one single motor means (50) by way of transmission means which comprise at least one telescopic shaft (57, 58) which is pivotally connected to the drive shaft.
9. A device according to Claim 8, characterised in that the transmission means between the single motor means (50) and the telescopic shafts (57, 58) comprise a toothed rim wheel (53) through which the axis of translation (X1-X1) of the tube (2) to be provided with the fins passes, this toothed rim wheel being driven by a toothed pinion (52) which is connected to the motor means (50) and the toothed rim wheel driving four toothed pinions (55, 56) which are disposed at 90° relative to each other about the axis of translation (X1-X1), each driving a telescopic shaft (57, 58) which is connected to a drive shaft (24, 25, 26, 27).
10. A device according to one of Claims 6 to 9, characterised in that each forming roll carrier head (10, 11, 12, 13) comprises a detachable piece (90) inside which is accommodated at least one bearing of the forming roll carrier shaft, this detachable piece, when dismantled, permitting removal and, if necessary, replacement, of the appropriate forming roll (6, 7, 8, 9).
11. A device according to one of Claims 1 to 10, characterised in that each forming roll (6, 7, 8, 9) is constituted of a plurality of discs of revolution (61, 62, 63, 64, 65) having the same axis as the forming roll carrier shaft (18, 19, 20, 21), the side of each forming roll oriented towards the upstream part of the tube (2) which is to be provided with fins comprising at least one disc (61, 62, 63) which is less in diameter than the following disc, the forming roll being held to its forming roll carrier shaft by at least one axial setting means which allows the axial position of the forming roll to be adjusted on the corresponding forming roll carrier shaft relative to that of the other forming rolls.
12. A device according to one of Claims 1 to 11, characterised in that the wall of the tube (2), during the operation of providing it with the fins, is held in the shaping zone by an internal mandrel (82) of approximate frustoconical shape and connected to the retaining rod (83), the upstream end of this latter itself being attached to a fixed point situated beyond the upstream end of the tube (2).
13. A device according to Claim 12, characterised in that the mandrel (82) is mounted freely to rotate about the axis of translation (X1-X1).
14. A device according to one of Claims 1 to 13, characterised in that the tube (2) is supported, along the axis of translation (X1-X1), by channels which are covered, at least below the zone with fins, with a layer of plastic material.
15. A device according to one of Claims 1 to 14, characterised in that at least one pinch-roll (drive roller) allows the tube (2) to be placed on the axis of translation (X1-X1), prior to the operation during which the tube (2) is provided with fins.
16. A device according to one of Claims 1 to 15, characterised in that at least two proximity detection means are disposed along the axis of translation (X1-X1), below the shaping zone at pre-determined spacings from it.
17. A device according to Claim 16, characterised in that each proximity detection means or group of proximity detection means is connected to electronic means which either set in motion, or interrupt, the operation of forming fins.
18. A device according to Claim 16, characterised in that the detection means or group of detection means is connected to the electronic means by way of a bus bar which permits a very large number of connections to be made and which thus allows a large number of finned zones to be formed on the tubes.
19. A device according to Claim 17 or Claim 18, characterised in that starting of the fin-providing operation, which is controlled by the electronic means, comprises, after placement of a smooth tube (2), the setting in motion of the forming rolls which are disposed at a spacing away from the axis of translation (X1-X1) at reduced speed, and then the setting in motion at reduced speed of the jack in order to gradually bring the forming rolls (6, 7, 8, 9) closer to the wall of the tube (2) until each forming roll gradually tightens against the wall of the tube (2), then stopping the forward travel of the jack by a means of closure and finally gradually increasing the speed of rotation of the forming rolls until a normal operating speed is reached.
20. A device according to one of Claims 17 to 19, characterised in that the stopping of the fin-providing operation, which is set off by a group of proximity detection means, is carried out by the reduction of the speed of rotation of the forming rolls, then by the setting into rotation of the return piston (37) with rapidity, so as to distance the carriages (4,5) from the axis (Xl-Xl), the rotation of the forming rolls being then interrupted.

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