Plastic capillary tube mat, as well as method and apparatus for its manufacture

Abstract

Method for producing a plastic capillary tube mat (1) in which a welding zone (19) formed at the axial end of a capillary tube (3) is radially welded to a collector tube (2), wherein first the welding zone (19) and a transition area (7) of the capillary tube (3) adjacent to the welding zone (19) are heated, thereby increasing the outer diameter (D4) in the transition area (7) and then the welding zone (19) is pressed against the collector tube (2), characterized in that a predetermined outer contour is formed into the transition area (7) when they are pressed together.

Description

[0001] The invention relates to a method for producing a plastic capillary tube mat, in which a welding zone formed at the axial end of a capillary tube is welded radially to a collecting tube, wherein firstly the welding zone and a transition region of the capillary tube adjacent to the welding zone are heated, the outer diameter in the transition region is enlarged and then the welding zone is pressed against the collecting tube.

[0002] The invention further relates to a device for producing a plastic capillary tube mat, comprising at least one heating device by means of which a welding zone and a transition region at the axial end of a capillary tube and a welding zone formed on a collecting tube around a branch opening can be heated, and comprising a feeding device by means of which the welding zone can be moved towards the welding zone.

[0003] The invention also relates to a plastic capillary tube mat with at least one collecting tube having at least one branch opening and with at least one capillary tube welded to the collecting tube around the branch opening and opening into the collecting tube, wherein the outer diameter increases in a transition region at the end of the capillary tube in the direction of the collecting tube.

[0004] Such capillary tube mats and the associated methods and devices are known from the prior art. Capillary tube mats are used, for example, in air-conditioned ceilings to air-condition interior spaces, such as office spaces or entire office floors. Unlike conventional air conditioning systems, which heat or cool rooms with a conditioned air flow, capillary tube mats arranged in air-conditioned ceilings air-condition interior spaces through their thermal radiation and without the noise- and draft-generating air flow of conventional air conditioning systems.

[0005] During operation, a heating or cooling fluid flows through the capillary tube mats. The heating or cooling fluid is tempered by a heating or cooling fluid supply connected to the capillary tube mats in a circuit. A capillary tube mat typically comprises at least two manifolds connectable to the heating or cooling fluid supply, between which a plurality of parallel capillary tubes run. Commercially available capillary tube mats are made of thermally conductive, corrosion-resistant, and weldable plastic.

[0006] In the production of capillary tube mats, the capillary tubes, for example with an outer diameter of up to approximately 6 mm, are welded to the manifold tubes. The outer diameter of the manifold tubes is significantly larger than that of the capillary tubes, for example, approximately 20 mm. The manifold tubes have branch openings at the welding points, into which the capillary tubes open after welding. For welding, the welding zones of the manifold tubes around the branch openings, as well as the axial ends of the capillary tubes, are heated so that their plastic material softens. The softened areas are then pressed against each other and held until they cool.

[0007] GB 2 255 040 A describes another process in which polyolefin components are welded together. The tip of a deep-drawn tube is inserted into an opening in a holding tube and heated by a lamp inserted into the tube.

[0008] EP 0 299 182 A2 discloses a method for welding porous tube ends to a tubesheet. The tube ends protruding from the tubesheet are melted into a molten mass, with a portion of the melt being directed radially outward so that it rests on the end face of the tubesheet.

[0009] A method for welding a plastic pipe to a support plate is shown in JP 2006-046712 A. One end of the plastic pipe is pushed through a through-hole in the support plate so that it protrudes from the through-hole. The end is then ultrasonically welded to the support plate.

[0010] A known method for producing a capillary tube mat is described, for example, in DE 197 25 326 C2. In this process, the capillary tubes are heated so that the inner diameters at the ends of the capillary tubes expand. The expanded inner diameter is intended to prevent an unwanted reduction in the cross-section of the tube during welding.

[0011] The method described in DE 197 25 326 C2 has the disadvantage that mechanical stress, for example, during installation of the capillary tube mats, can cause damage to the pipe connection between the collecting pipe and the capillary tube. Such damage can lead to leaks and increased installation effort. In view of these disadvantages, the present invention is based on the object of improving the mechanical load-bearing capacity of capillary tube mats.

[0012] The problem is solved for the above-mentioned method in that a predetermined outer contour is formed into the transition area when pressed together.

[0013] For the above-mentioned device for producing a capillary tube mat, the object is achieved by a die with at least one shaping surface, through which a predetermined outer contour can be formed into the transition region.

[0014] In the case of the capillary tube mat mentioned, the task is solved in such a way that a predetermined outer contour is formed into the transition area.

[0015] The solution according to the invention has the advantage that the pipe connection between the capillary tube and the collecting pipe is stronger than the prior art and can better withstand mechanical stress, for example, due to bending during installation of the capillary tube mat. The predetermined outer contour avoids shapes such as steps or ledges that can cause a notch effect. Consequently, a shape of the connection between the capillary tube and the collecting pipe that avoids the notch effect is ensured. By shaping the transition area to the predetermined outer contour, the connection is strengthened in the transition area, which is subject to particularly mechanical stress, because the polymer chains of the plastic align during molding.

[0016] The solution according to the invention can be further developed through various independent, individually advantageous embodiments. These embodiments and the advantages associated with each embodiment are briefly discussed below.

[0017] For example, in the aforementioned process, in which a welding zone formed on the manifold around a branch opening is heated prior to welding, heat can be dissipated via a heat sink located in the branch opening during the heating of the welding zone. This has the advantage that the branch opening is heated only slightly and its diameter remains essentially unchanged.

[0018] The method according to the invention can be carried out particularly quickly and easily if, by forming the outer contour into the transition area, the welding zone is pressed against the manifold, particularly in a feed direction. Furthermore, during welding, a die can press the welding zone against the manifold and simultaneously form the predetermined outer contour into the transition area.

[0019] To support the forming of the outer contour by the die, a mat section of the capillary tube adjacent to the transition area can be pulled away from the manifold in the opposite direction to the feed direction. This pulls the transition area toward the forming surface of the die in a supporting manner.

[0020] To create an easy-to-manufacture and mechanically robust weld, the end of the capillary tube can be formed into a substantially conical outer contour. Of course, other contours, such as curved ones, can also be formed.

[0021] In an advantageous embodiment of the aforementioned device, the die can have a contact surface through which the welding zone can be pressed against the weld zone. Thus, when the die forms the outer contour into the transition area, it can simultaneously support the welding process. The contact surface can be adjacent to the forming surface or be formed by it.

[0022] Furthermore, the heating device can have at least one unheated heat sink arranged in the branch opening, through which heat can be dissipated. This has the advantage that the heat sink cools the manifold in the region of the branch opening and thus prevents a change in the cross-section of the branch opening due to thermal expansion.

[0023] To achieve good heat exchange between the manifold and the heat sink, the heat sink can be pin-shaped, essentially complementary to the branch opening. This also prevents the diameter of the branch opening from being reduced by the inserted pin, which has a specified diameter. A reduced diameter leads to lower flow rates and can result in reduced performance during heating or cooling of the capillary tube mat.

[0024] The heat sink can be made of a plastic, especially Teflon. Teflon is a particularly suitable material because it conducts heat well and is stable up to about 350°C.

[0025] In an advantageous further development of the above-mentioned capillary tube mat, a substantially conical outer contour can be formed in the transition region, whereby the connection between the collecting tube and the capillary tube is structurally simple and yet robust.

[0026] In the capillary tube mat mentioned above, the diameter of the branch opening can be larger than that of the capillary tube outside the transition area. This overcomes the limitations of the method described in DE 197 25 326 C2, in which the diameter of the branch opening had to be smaller than or equal to that of the capillary tube.

[0027] The invention is explained below by way of example with reference to the accompanying drawings. The various features can be combined independently of one another, as already explained above for the individual advantageous embodiments.

[0028] They show: Fig. 1 a schematic representation of an exemplary embodiment of a capillary tube mat according to the invention; Fig. 2 a schematic sectional view of a connection between a collecting tube and a capillary tube of the capillary tube mat from Fig. 1; Fig. 3 a schematic representation of a device according to the invention for producing a capillary tube mat with the pipe connection according to Fig. 2; Fig. 4 the device from Fig. 3 in a second mounting position.

[0029] First, the general structure of a capillary tube mat 1 according to the invention is described with reference to the Fig. 1 described.

[0030] The capillary tube mat 1 comprises two collecting tubes 2, which are connected by a plurality of parallel capillary tubes 3. The collecting tubes 2 each have a connecting adapter 4 at one axial end, with which they can be connected to a heating and cooling fluid circuit. During operation of the capillary tube mat 1, a heating or cooling fluid flows into one of the two collecting tubes 2. From the collecting tube 2, the heating or cooling fluid flows through the capillary tubes 3 towards the other collecting tube 2. From the second collecting tube 2, the heating or cooling fluid flows back into the heating or cooling fluid circuit. The capillary tube mat 1 is installed, for example, in an air-conditioned ceiling of an interior space. When the heating or cooling fluid flows through the capillary tubes 3, the air-conditioned ceiling and thus the interior space is tempered accordingly.

[0031] Both the collecting tubes 2 and the capillary tubes 3 are made of a thermally conductive, corrosion-resistant, and weldable plastic. Each capillary tube 3 is welded fluid-tight at its axial ends to the two collecting tubes 2. Such a pipe connection 5 between a collecting tube 2 and a capillary tube 3 is described below by way of example with reference to Fig. 2 described.

[0032] As in Fig. As shown in Figure 2, the wall of the collecting tube 2 has a branch opening 6 in the region of the capillary tube 3. The branch opening 6 extends essentially radially and has a substantially constant diameter D1. The branch opening 6 connects the interior of the collecting tube 2 with the interior of the capillary tube 3.

[0033] The capillary tube 3 extends from the collecting tube 2 essentially radially outwards and has in this direction a welding zone 19, a transition region 7 and an undeformed mat region 20.

[0034] At the Fig. 2, the inner diameter D2 in the mat region 20 of the capillary tube 3 is smaller than the diameter D1 of the branch opening 6. The outer diameter D3 of the mat region 20 is significantly smaller than an outer diameter D6 of the collecting tube 2. In the transition region 7 at the end of the capillary tube 3, the outer diameter of the capillary tube 3 increases continuously from the outer diameter D3 to an outer diameter D4. In the transition region 7, the capillary tube 3 has a substantially conical outer and inner contour. The inner diameter D5 in the welding zone 19 at the end of the transition region 7 is larger than the diameter D1 of the branch opening 6. The capillary tube 3 is integrally welded to the collecting tube 2 in the welding zone 19 at an annular connecting surface 8. The annular connecting surface 8 is formed on the end face between the diameters D4 and D5.

[0035] The conical transition area 7 ensures a particularly stable connection between the capillary tube 3 and the collecting tube 2, as the contour is smooth and notched. The outer contour runs from the welding zone 19, across the transition area 7, to the mat area 20 with smooth transitions. This avoids edges that cause notch effects, so that the connection according to the invention has a high mechanical strength. The connection can withstand mechanical influences, such as relative bending of the capillary tube 3 to the collecting tube 2. Furthermore, the conical contour enlarges the connecting surface 8 compared to an annular surface between the diameters D2 and D3.

[0036] The following describes the production of the Fig. 2 shown pipe connection 5 of a capillary tube mat 1 with reference to the Fig. 3 and Fig. 4 described.

[0037] The pipe connection 5 can be manufactured, for example, using a manufacturing device 17. The manufacturing device 17 comprises a heating device 14, a feeding device 25, and a die 15.

[0038] To produce the pipe connection 5, the still undeformed capillary tube 3 to be connected is first heated on its end face 10 and on the outer circumference over a length L by a first heating element 11 of the heating device 14. Since the heating element 11 does not protrude into the interior of the capillary tube 3 and heats the interior less intensely, the plastic material of the capillary tube 3 melts faster on the outer circumference than on the inner circumference. It has been shown that the molten material flows from the inside to the outside, thus increasing the inner and outer diameters in the heated transition area 7. At the same time, the capillary tube wall thickens in the transition area 7, increasing towards the end of the capillary tube 3. The longer the heating element 11 heats the capillary tube, the more its tube wall thickens in the heated area.

[0039] At the same time, the collecting pipe 2 is heated in an annular welding zone 21 around the branch opening 6 by a second heating element 12 of the heating device 14. The second heating element 12 is in contact with the welding zone 21 located on the outer circumference of the collecting pipe 2. While the collecting pipe 2 is being heated, a pin-shaped heat sink 13, which has essentially the same diameter D1 as the branch opening 6, is inserted into the branch opening 6. The heat sink, designed as a pin 13, is made of a plastic, preferably Teflon. Teflon has good thermal conductivity and is stable up to approximately 350°C. As the collecting pipe 2 heats up, the heat sink 13 cools the inner circumferential surface of the branch opening 6, thus preventing a change in the diameter D1 due to thermal expansion.

[0040] The heating device 14 according to the invention comprises in the exemplary embodiment in the Fig. 3 and Fig. 4 the first heating element 11, the second heating element 12 and the heat sink 13.

[0041] After heating the capillary tube 3 and the collecting tube 2, the heating device 14 is removed. The collecting tube 2 and the capillary tube 3 are then brought together by the feed device 25. The feed device 25 has a first holding means 18 for the collecting tube 2 and a second holding means 19' for the capillary tube 3. The holding means 18, 19' can be moved relative to one another in order to move the welding zone 19 of the capillary tube 3 relative to the welding zone 21 of the collecting tube 2.

[0042] When the capillary tube 3 touches the collecting tube 2, the feeding device 25 stops. Then the die 15 surrounding the capillary tube 3 moves in a feeding direction Z towards the collecting tube 2, as shown in Fig. 4. As a result, a contact surface 24 of the die 15 presses the welding zone 18 of the capillary tube 3 with the connecting surface 8 against the collecting tube 2, so that the capillary tube 3 is welded to the collecting tube 2. At the same time, the pressure of the die 15 with a force in the feed direction Z from the shaping surface 16 forms the above-described conical outer contour in the transition region 7. To assist the forming in the transition region 7, the capillary tube 3 in the mat region 20 can additionally be pulled away from the collecting tube 2 by the holding means 19' against the feed direction Z, while the die 15 presses the end of the capillary tube 3 against the collecting tube 2. In this way, the still warm, deformable transition region 7 of the capillary tube 3 takes on the shape of the shaping surface 16 of the die 15 even better.

[0043] Alternatively, the capillary tube 3 can first be moved by the feed device 25 into the vicinity of the collecting tube 2 for welding. The die 15 is then moved toward the collecting tube 2 so that it presses the connecting surface 8 of the capillary tube 3 against the collecting tube 2 and welds it. The movement of the die 15 simultaneously forms the conical outer contour of the transition region 7.

[0044] The die has a die opening 22 with a diameter D7, which is slightly larger than the diameter D3 of the capillary tube. On the side facing the collecting tube 2, the die opening 22 has a chamfer 23, which forms the shaping surface 16. In the embodiment in the Fig. 3 and Fig.4, the chamfer 23 runs at an angle of approximately 45°. The transitions to the chamfer 23 are preferably rounded to avoid edges at the pipe connection 5. Alternatively, the shaping surface 16 can also have other shapes, such as an arc.

[0045] As described above, the diameter of the tube wall of the capillary tube 3 increases upon heating. This thickening allows the conically shaped transition region 7 to have the same wall thickness as the capillary tube 3 in the undeformed mat region 20. This prevents weakening of the capillary tube 3 in the transition region 7. By forming the conical outer contour in the transition region 7, the polymer chains of the plastic material are aligned, so that the connection between the tubes 2, 3 is particularly stable. The conical transition region 7 bridges diameter differences between the branch opening 6 and the inner diameter D2 of the capillary tube 3, so that it is uncritical if the diameter D1 of the branch opening 6 is larger than the diameter D2 of the mat region 20.

Claims

[1] Method for producing a plastic capillary tube mat (1), in which a welding zone (19) formed at the axial end of a capillary tube (3) is welded radially to a collecting tube (2), wherein firstly the welding zone (19) and a transition region (7) of the capillary tube (3) adjacent to the welding zone (19) are heated, the outer diameter (D4) in the transition region (7) is increased and then the welding zone (19) is pressed against the collecting tube (2), characterized by that when pressed together, a predetermined outer contour is formed into the transition area (7). [2] Method according to claim 1, wherein prior to welding, a welding zone (21) formed on the manifold (2) around a branch opening (6) is heated, characterized by that when the welding zone (21) is heated, heat is dissipated via a heat sink (13) arranged in the branch opening (6). [3] Method according to claim 1 or 2, characterized bythat by forming the outer contour into the transition area (7) the welding zone (19) is pressed against the collecting pipe (2). [4] Method according to one of the above claims, characterized by that during welding a die (15) presses the welding zone (19) against the collecting pipe (2) and at the same time forms the specified outer contour in the transition area (7). [5] Method according to claim 4, characterized by that during welding and during forming of the outer contour, the die (15) is pressed against the collecting pipe (2) in a feed direction (Z). [6] Method according to one of the above claims, characterized by that when forming the outer contour, a mat area (20) of the capillary tube (3) adjacent to the transition area (7) is pulled away from the collecting tube in the opposite direction to a feed direction (Z). [7] Method according to one of the above claims, characterized bythat a conical outer contour is formed in the transition area (7). [8] Device (17) for producing a plastic capillary tube mat (1), with at least one heating device (14) by means of which a welding zone (19) and a transition region (7) at the axial end of a capillary tube (3) and a welding zone (21) formed on a collecting tube (2) around a branch opening (6) can be heated, and with a feed device (18) by means of which the welding zone (19) can be moved towards the welding zone (21), characterized by a die (15) with at least one shaping surface (16) through which a predetermined outer contour can be formed into the transition region (7). [9] Device according to claim 8, characterized by that the die (15) has a contact surface (24) by means of which the welding zone (19) can be pressed against the welding zone (21). [10] Device according to claim 8 or 9, characterized bythat the heating device (14) has at least one heat sink (13) which can be arranged in the branch opening (6) and via which heat can be dissipated. [11] Device according to claim 10, characterized by that the heat sink (13) is pin-shaped, complementary to the branch opening. [12] Device according to claim 10 or 11, characterized by that the heat sink (13) is made of a plastic. [13] Plastic capillary tube mat (1) with at least one collecting tube (2) having at least one branch opening (6) and with at least one capillary tube (3) welded to the collecting tube around the branch opening (6) and opening into the collecting tube (2), wherein the outer diameter (D4) increases in a transition region (7) at the end of the capillary tube (3) in the direction of the collecting tube (2), characterized by that a predetermined outer contour is formed in the transition region (7). [14] Capillary tube mat (1) according to claim 13, characterized by that a conical outer contour is formed in the transition area (7). [15] Capillary tube mat (1) according to claim 13 or 14, characterized by that the diameter (D1) of the branch opening (6) is larger than the diameter (D2) of the capillary tube (3) outside the transition area (7).

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