The field of the invention

The invention relates to an apparatus and a method for manufacturing a meander tube.

Background of the invention

Meander tubes are typically made of metal tubes such as copper, aluminum or steel tubes. Usually meander tubes are manufactured in a continuous process by means of tube bending device designed for this specific purpose. Generally, a meander tube bending device has a bending arrangement wherein the tube being used as a raw material is bent alternately in opposite directions to form a meander tube with a tube having zig-zag configuration. In such meander tube the tube comprises usually straight portions and bent portions. Thus, the length of the meander tube is defined by the radius and number of the bends and the width of the meander by the length of the straight portions between the bends. Typically, a meander tube is a part of a heat exchanger that forms channels for conducting heat exchanging medium in a heat exchanger.

In current apparatuses raw metal tube is fed through two bending rolls which the first one acts as a die and a second one as a forming tool pressing and forming the raw tube along the circumferential outer surface of first roll such that a curved tube portion is formed. The zig-zag configuration of a meander tube is achieved by rotating the incoming raw tube 180° with respect of its longitudinal axis between the each bend such that each bend next to an another occurs to opposite direction with respect to previous one. Between the each bend the raw tube is moved forwards such that a straight portion with desired length is formed between the each bent portion.

A drawback of the known apparatuses used for manufacturing meander tubes is that the size of the meander tube being manufactured is limited because when the size of the meander tube being manufactured increases the rotation of the tube with respect of its longitudinal axis between each bend becomes more complex and difficult to control without increasing risk to damage the tube. This is because the size and the weight of the already bent part of the meander tube (that has to be rotated 180° between each bend) increases as the size of the meander tube increases.

Brief description of the invention

The aim of the invention is to provide novel apparatus for manufacturing meander tubes by bending that is simpler and less space consuming as well as which has an improved bending mechanism for simplifying the bending process where the raw tube is bent in alternate directions. The aim of the invention is also to provide a new method for manufacturing meander tubes suitable for many kind of applications e.g. such as radiators or cooling elements used in heating or cooling systems.

The aim of the invention is achieved because the bending process is improved by providing a bending roll arrangement wherein two bending rolls are provided with a main shaft providing the axis with respect of which the bending occurs that is transferred from at the point of the first roll to the point of the second roll which makes it possible that bending direction can be altered without turning the raw tube with respect to its longitudinal axis in between the each bend. The aim of the invention is achieved also because in the method for manufacturing meander tubes is based on a meander tube bending device wherein the bending direction can be altered without turning the raw tube with respect to its longitudinal axis in between the each bend. To put it more precisely, the apparatus for manufacturing a meander tube according to the invention is characterized in what will be presented in the independent claim 1 and the method for manufacturing a meander tube is characterized in what will be presented in the independent claim 8. Dependent claims 2 to 7 present some advantageous embodiments apparatus according to invention and dependent claims 9 and 10 some advantageous embodiments of the method according to invention. Advantage of the apparatus according to invention that is that it is simpler and less space consuming and allows to manufacture meander tubes being substantially large in size in places having limited amount of room. Furthermore, due to utilizing such apparatus in a process of manufacturing meander tubes it is possible to arrange the meander tube production more cost effectively because the manufacturing and maintenance costs of the apparatus according to invention are lower than those of known apparatuses and because less auxiliary equipment and their maintenance (relating to hardware and software therein) is required.

Description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which

figure 1 shows side view of a bending device of the apparatus according to invention,

figure 2 shows a front view of the bending device according to figure 1 , and figure 3 shows the bending device of previous figures when viewed from above.

Detailed description of some advantageous embodiments of the invention

An apparatus for manufacturing meander tubes according to invention comprises a feeding device, a bending device, a cross-cutting device and a guiding device. The feeding device comprises a tube coiler and suitable amount of support rolls arranged to guide the raw tube uncoiled from the coiler in between the bending rolls of the bending device. There may be also some other kind of directing means such as a guiding tube directed towards the gap between bending rolls and having inner diameter slightly greater than outer diameter of the raw tube so that the raw tube can be fitted through the guiding tube and thus directed between the bending rolls of the bending device. Before the support rolls and other guiding means the feeding device may comprise couple of straightening rolls arranged in such configuration that so called coil-curvature is removed from the raw tube when feeding it through these rolls. The bending device comprises arrangement for bending the raw tube alternately in opposite directions to form a meander tube from raw tube fed to the bending device. The cross-cutting device is a device that is arranged to cut the raw tube after the last bend of the each meander tube has been finished in order to separate the finished meander tube from the incoming raw tube. The guiding device comprises a support arrangement that is configured to support and guide the already bent part of the raw tube during the bending in the bending device.

Figures 1 to 3 show a bending device 1 of an apparatus according to invention to which a raw tube 2 being provided by uncoiling the raw tube 2 from a tube coiler of the feeding device is periodically fed such that predetermined length of the raw tube 2 is moved forwards between the bending phases to form to the meander tube to be manufactured straight portions between the curved (bend) portions. The bending device 1 shown in figures 1 to 3 comprises a main frame 3, a transfer frame 4, a first transfer assembly 5, a second transfer assembly 6, a support frame 7, a rotator 8, a first bending roll 9 and a second bending roll 10. The bending device 1 comprises further a programmable control unit for controlling all the actuators of the bending device automatically such that the incoming raw tube 2 can be bent into the configuration of a meander tube.

In order to manufacture mender tubes the bending device 1 has been arranged to form bends of 180° angle alternately in to the opposite directions. In order to take in to account of the spring-back of the material due to elastic- plastic bending the actual bending angles carried out by the bending device are slightly more than 180°. The suitable bending angle can be determined experimentally e.g. by using so called trial-and-error method, by separate laboratory tests and/or by means of theoretical calculations and/or by mathematical modeling.

The main frame 3 is in this embodiment a beam structure preferably made of e.g. aluminum or steel profile beams fixed to each other e.g. by fixing elements such as screws or bolts. The main frame 3 may comprise horizontal and vertical beams arranged in suitable configuration, for instance such as seen in figures 1 and 3. The purpose of the main frame 3 is to attach the other parts of the bending device 1 securely to the floor of the workshop as well as to support the other parts of the bending device 1 in suitable position for among others facilitating cooperation with the feeding device as well as to form suitable elevation for the bending rolls such that parts lower than these have enough space such that they can be accommodated under the feeding line of the raw tube 2 to be bend.

Transfer frame 4 is a part of the bending device 1 that has been arranged to move a linearly with respect of the main frame 3 and the support frame 7 a predetermined distance back and forth. The transfer frame 4 comprises a suitable beam or plate structure and a rotator 8 attached therein e.g. by means of bolts shown in figure 2. The transfer frame 4 is configured such that it is able to hold the rotator 8 in suitable orientation such that the shaft of the rotator forming a main shaft 12 protrudes upwardly above the transfer frame 4 and thus can be connected to the second transfer arrangement 6 holding the support frame 7. The rotator 8 is an actuator that takes care of rotating the second transfer assembly 6 and the support frame 7 by means of its main shaft 12 such that either the second bending 10 roll can be rotated along a radial path with respect to the first bending roll 9 or the first bending roll 9 can be rotated along a radial path with respect of the second bending roll 10 depending on the position to which the transfer frame 4 has been moved by means of the transfer assemblies 5 and 6. Thus, the possibility to change the point with respect of which the rotation of the main shaft 12 takes place and to which direction the raw tube 2 between the bending rolls 9 and 10 is bent is accomplished by means of adjustment of the position of the main shaft 12. Such adjustment is achieved in this embodiment by means of the first transfer assembly 5 being arranged to move the transfer frame 4 linearly with respect of the main frame 3 and the second transfer assembly 6 being arranged to move linearly the support frame 7 with respect of the transfer frame 4. Two transfer assemblies (i.e. the first transfer assembly 5 and the second transfer assembly 6) is necessary because it is important to maintain the bending rolls 9 and 10 transversally in the same position with respect to the feeding line S of the raw tube 2 regardless of the position of the main shaft 12 in order avoid bending of the raw tube 2 before feeding it between the bending rolls 9 and 10. This ensures that the straight portions of the meander tube remain always straight after passing through the bending rolls 9 and 10. The first bending roll 9 and the second bending roll 10 have been pivoted to a support frame 7 by means of roll shafts 13 and 14 freely rotatably such that they are positioned above the support frame 7 in a same plane (that is in this case a horizontal plane). The attachment of the roll shafts 13 and 14 is formed such that distance between the roll shafts 13 and 14 and thus the gap between the first bending roll 9 and the second bending roll 10 can be adjusted. This enables to have suitable setting for the bending rolls 9 and 10 to fit the raw tube 2 through the bending rolls 9 and 10 such that suitable clearance between the raw tube 2 and the outer surfaces of the rolls 9 and 10 is achieved. The support frame 7 is formed of plate structure which is attached linearly movably to the second transfer assembly 6. The shafts 13 and 14 of the bending rolls 9 and 10 are attached e.g. to a through-holes having a groove form formed to the support frame 7. The shafts 13 and 14 of the bending rolls

9 and 10 can e.g. comprise threaded portion that is fitted through the through-holes and tightened to the groove by means of two nuts placed in the opposite sides of the plate-like support frame 7. A roller bearings or other suitable type of bearings may be provided between the bending rolls 9 and

10 and their respective the roll shafts 13 and 14 to ensure smooth rotation of the bending rolls 9 and 10.

The first transfer assembly 5 and the second transfer assembly 6 comprise elongate body portions 15 and 16 as well as a moving carriage portions 17 and 18. Both having suitable attachment means by means of which the body portions 15 and 16 can be attached to a first element and by means of which the carriage portions 17 and 18 can be attached to a second element. The carriage portions 17 and 18 are slideably attached to body portions 15 and 16 e.g. by means of guide bars 19 and 20. To the body portions 15 and 16 it have been attached actuators 21 and 22 arranged to move the carriage portions 17 and 18 with respect the body portions 15 and 16 along the guide bars 19 and 20. The actuators 21 and 22 are formed in this embodiment of an electric motor and a screw that is rotated by the electric motor. The carriage portions 17 and 18 include a threaded through-hole through which the screw is fitted such that when the screw is rotated by the electric motors the carriage portions 17 and 18 move with respect to body portions 15 and 16 along the guide bars 19 and 20. The length of the movement of the carriage portions 17 and 18 can be adjusted by controlling the rotation of the motors and/or the body portions 15 and 16 may comprise e.g. two limit switches placed at the suitable positions with respect to guide bars 19 and 20 arranged such that they stop the rotation of the electric motors when the carriage reaches either of the limit switches. Limit switches can be secured adjustably to the guide bars 19 and 20 in either sides of the carriage portions 17 and 18 such that these can be moved in order to adjust the length of the movement of the carriage portions 17 and 18.

As can be seen from figure 2 in case of the first transfer assembly 5 the body portion 15 is attached to the main frame 3 and the carriage portion 17 to the transfer frame 4 and in case of second transfer assembly 6 the body portion 16 of the second transfer assembly 6 is attached to the transfer frame 4 and the carriage portion 18 of the second transfer assembly 6 is attached to the support frame 7. Therefore, it is possible to move the transfer frame 4 with respect to main frame 3 such that support frame 7 remains stationary with respect to main frame 3 by moving the carriage portion 18 of the second transfer assembly 6 same amount in the opposite direction with respect of the carriage portion 17 of the first transfer assembly 5 i.e. by this way it is possible to move the main shaft 12 of the rotator 8 without changing the position of the support frame 7 with respect to the main frame 3.

In this apparatus there is a guiding device (not shown in the drawings) being arranged to support the already bent portion of the raw tube 2 during the second, third etc. bending of the raw tube. The guiding device may comprise a suitable support structure being made of e.g. a suitable beam or plate structure that makes it possible to support the already bent portion of the raw tube 2 coplanar with the horizontal plane formed by the first bending roll 9 and the second bending 10 of the bending device 1 during the bending process. Thus, the support structure of the guiding device is preferably also such that it moves synchronously with the bending device 1 when the bends of the meander tube are formed by means of the bending device 1 .

The apparatus further comprises a cutting device (not shown in the figures). It is e.g. an automatic tube cutter that is arranged in a suitable position (preferably after the bending rolls of the bending device). The cutting device may be placed under the feeding line S of the raw tube 2 such that when the raw tube 2 is cut the cutter is moved automatically upwards such that raw tube raw tube 2 become between the jaws of the tube cutter at a suitable point where the tube cutter cuts the raw tube once the cutter blade has reached the correct position to separate the finished meander tube from the incoming raw tube 2. Alternatively the cutting device can be some other kind of cutting device suitable for cutting the raw tube. Thus the cutting device can be alternatively such cutting device as saw type cutter or e.g. a manually usable tube cutter by means of which the operator can cut the raw tube manually after the last bend of each meander tube to be manufactured has been made.

When using the apparatus according to figures 1 to 3 the raw tube 2 is uncoiled from the coiler and guided between the bending rolls 9 and 10. The incoming raw tube 2 is moved forwards periodically such that during each feeding period predetermined amount of the raw tube pass through the gap between the bending rolls 9 and 10. In the beginning, the transfer frame 4 of the bending device 1 is moved (by moving the transfer assemblies 5 and 6) to the position wherein the main shaft is at the position of the shaft of the first bending roll 9. After the raw tube 2 has been fed suitable distance past the bending rolls 9 and 10 the first bend is accomplished by rotating the second bending roll 10 along a radial path with respect to first bending roll 9 an angle being little bit more than 180°. As result, a curved portion (i.e. an arc of a half circle) is formed such that the incoming end of the raw tube 2 is directed in the direction opposite to the feeding direction of the raw tube 2. After that, the raw tube 2 is moved forwards by feeding more raw tube 2 by the feeding device causing that the first curved portion is moved forwards. When the suitable amount of raw tube has been fed (in order to form to the meander tube to be manufactured a straight portion having a desired length) the feeding device is stopped and the main shaft 12 is moved to the position of the shaft 14 of the second bending roll 10. Thereafter, the second curved portion is formed by rotating the first bending roll 9 with respect to the second bending roll 10. Since now the first bending roll 9 rotates opposite direction with respect of the second bending roll the same amount (i.e. a little bit more than 180°) the raw tube is curved in direction which is opposite to the curvature of the previous (the first) curved portion and thus the already bent portion of the raw tube 2 is also in this bending phase directed to the direction opposite the feeding direction of the raw tube 2 but situated to the opposite side with respect to the incoming raw tube 2 as it was after the first bending (thus at this phase the already bent part contains now a tube having S-shape). Next, the raw tube 2 is fed again forwards the same amount as before the second bending. During the feeding phase and/or after stopping the feeding phase the transfer frame 4 is moved to the position wherein the main shaft 12 is again at the point of the shaft 13 of the first bending roll 9 and then the second bending roll 10 is rotated to the direction opposite the second bend the same angle as in previous bending phases (i.e. a little bit more than 180°). This results to the raw tube 2 a third curved portion having an angle of 180° in the same direction as the first curved portion. Hence, by continuing this process further to the fourth, fifth sixth etc. bending the bent tube having a zig-zag configuration wherein between each curved portion there is a straight portion will be formed. Therefore, by means of a bending device 1 described above a tube having a meander shape can be manufactured.

The size of the meander tube to be manufactured is defined by the number of the curved portions, (radius of) the curvature of the curved portions and the length of the straight portions between the curved portions such that the length of the meander is defined by the amount of the curved portions as well as the radius of curvature of the curved portion (which also defines the distance between the each straight portions from each other in lengthwise direction of the meander tube) and the width of the meander tube is defined by the length of the straight portions between the curved portions. It is, of course, possible to start bending the tube in different order i.e. by positioning the transfer frame 4 such that during the first bending it is at the point of the shaft 13 of the second bending roll 10 instead of the first bending roll 9. During the bending process the already bent portion of the raw tube 2 is in this embodiment supported by the guiding device. After the all bents of a meander tube have been formed the incoming raw tube 2 is cut by the cutting device and the finished meander tube is removed from the apparatus. The meander tubes manufactured by the above described apparatus and method are typically used e.g. as heat exchanging elements of a heat exchanger (i.e. as a conduit for circulating one of the heat exchanging mediums within the other heat exchanging medium) which heat exchanging elements typically comprise one or more corrugated heat exchanger tubes. The process for manufacturing such a heat exchangers may continue directly after formation of the meander tube such that finished meander tubes are conveyed (manually or automatically e.g. by means of some suitable conveyor) to the process stages wherein the meander tubes are assembled in to body of a heat exchanger. Alternatively, the meander tubes formed by the apparatus and method described above can be transported to an another site where the utilization of them (i.e. necessary further manufacturing phases) may be carried out.

The apparatus for manufacturing meander tube according to invention can differ in many ways from the above described embodiment. The meander tube bending device of the apparatus may have been arranged to work in plane that is not a horizontal plane as the case was with the embodiment described in figures 1 to 3. Principally, it could be possible to arrange such device work e.g. in a vertical plane. The arrangement for moving the main shaft from the point of the shaft of the first bending roll to the point of the second bending roll may be accomplished by using different kinds of transfer assemblies or mechanisms. For instance, the actuators for rotating the support frame may be hydraulic or pneumatic actuators instead of electrical motors with screws used in above described example. Hence, the invention is not limited to the embodiments described above but can vary within the scope of the appended claims.