METHOD OF FASTENING BAFFLES INSIDE A TUBE AND A CLOSING SYSTEM PROVIDED BY SUCH METHOD

Abstract: A method of fastening of baffles inside tubular members is provided based upon expansion of a cup-shaped plug (2) into a firm engagement with the tubular member wall by means of a special mandrel (4). A closing system for tubular members is also provided, comprising an expanded member (2) having a cross-section essentially complementary-shaped to the inner cross-section of the tubular member and exten­ ding circumferentially into the tubular member's wall.

Description: Method of fastening baffles inside a tubBR-ING and a closing system provided by such method The present invention relates to a method of fastening of baffles, serving as closing baffles or to divert medium flow, inside tubular members, and a closing system provided by such a method. The invention relates more particularly to closing baffles formed in situ inside an aluminum tube. Different heat exchangers applied in modern motor vehicles, e.g. condensers, comprising manifold tube(s) with a plurality of U-shaped tube bends constituting a circulation path for a heat exchanging fluid, are provided with closing and partition walls within the tube. These walls (baffles) are installed in order to block or divert the flow of liquid/gas through the tube. Currently, such baffles are provided by a brazing or soldering operation requiring use of heat and representing introduction of foreign materials (solder, flux) into the tube. Close temperature control is necessary, especially in the case of brazing, in order to avoid an overheating and consequently collapse of the tube. Furthermore, the introduction of foreign material (fluxes) will often promote corrosion attack on the tube. Attempts have also been made to introduce mechanical methods for fastening of baffles, which rely on application of pressure forces to the outer surface of the tube, collapsing the tube wall against a plug inserted into the tube. A leakage proof connection between the tube wall and the plug requires an uniformly applied deformation force to the whole outer surface of the tube which is difficult to achieve in practice because of limited access to the tube surface and/or shape of the tube members. It is therefore an object of the present invention to provide a method of fastening baffles inside tubular members based upon a pure mechanical deformation of the tubular member's walls, ensuring a leakage proof closure of the tubular members. Another object of the invention is to provide closing baffles for tubular members regardless the shape or location of the tubular member in heat exchanging units and even where access to the tubular member void is restricted only to one end. It is contemplated that the expression tubular member means any hollow shape suitable for the intended purpose, e.g. the tubular member may comprise a hollow shape of circular, elliptical (oval) or rectangular cross-section with single or multiple cavity (voids). The above objects of the present invention will be accomplished according to the preferred form of the invention through the provision of a method of fastening of baffles inside tubular members, comprising steps of providing an expanding member in form of a cup-shaped plug having diverging walls and a cross-section complementary-shaped to the tubular member 5 cross-section, attaching the said plug to an expansion mandrel by crimping of its diverging walls around the conical head of the mandrel in a conforming die, insertion of the mandrel with plug into the tubular member's void on a desired location preterminated by the position of a support die attached to the mandrel and expansion of the plug into a firm engagement with the tubular member wall by withdrawal of the mandrel from the plug. A closing system for tubular members is also provided, comprising an expanded member having a cross-section essentially complementary-shaped to the inner cross-section of the tubular member and extending circumferentially into the tubular member's wall causing plastic deformation of the said wall and where the expanded member is firmly interlocked in an indentation in the wall resulting from the said plastic deformation. Embodiments of the invention are shown by way of non restrictive examples in the accompanying drawings, Figs. 1-5, where Fig. 1 shows schematically a sectional view of the closing baffle inside a tubular member, Figs. 2-4 illustrate schematically individual steps in the method of in situ forming of baffles, and Fig. 5 shows schematically a sectional view of a variant of the closing system comprising an outside support ring on the tubular member. Fig. 1 shows schematically in a cross-section a tubular member (1) as a single tube, e.g. thin-walled Al-tubing, provided with a closing baffle (2) firmly interlocked in an indentation (3) running circumferentially in the tube wall. An expansion mandrel (4) carrying a support die (5) can be seen under its withdrawal from the tube after accomplished expansion of the baffle (2) and plastic deformation of the tube wall resulting in formation of the indentation (3). Referring to Figs. 2-4, illustrating schematically the individual steps in the process of pre-forming, inserting and fastening of the baffle inside the tube, the baffles is shown in Fig. 2 as a cup-shaped plug (2) with outwardly diverging walls (22) having a cross-section complementary-shaped to the inner cross-section of the actual tubular member. The crosssection can be circular, oval or as shown in Fig. 2a rectangular. Fig. 2a is a sectional view taken on line I-I of Fig. 2. An expansion mandrel (4) is provided with a head part (41) designed and dimensioned so that the plug (2) can receive this head part and by pressing into a suitable die (not shown in the picture) achieve a full encapsulation of the mandrel head by collapsed (crimped) plug wall (22) - see Fig. 3. A locating or support die (5) is attached to the mandrel (4) in order to insert the whole assembled system with the plug (2) into the tube void and positioned at the desired location within the tube. It is apparent from Fig. 4 that the suitable design of the support die allows it also to be used as a locating or positioning device for the plug by adapting its length and/or positioning with regard to the open (accessible) end of the tube. The support die is then firmly held in the place, and the expansion mandrel (4) is withdrawn from the plug causing the plug walls (22) to expand uniformly against the inner surface of the tube. The tube wall around the expanding plug (4) is subjected to a local plastic deformation resulting in formation of a circumferential indentation (3) as shown in Fig. 1. Fig. 4a is a sectional view of the tube taken on line I-I of Fig. 4 and shows an elliptical cross-section of the tube. The required forces holding the plug in position can be adjusted by proper dimensional control of the plug and/or the expansion mandrel. Furthermore, in Figure 5 it is shown an embodiment of the closing system according to the present invention where optionally an outside support ring (6) is located on the tube over the plug (2) prior to the expansion step. By proper dimensioning and choice of material in the ring, e.g. hardened aluminum, an additional increase of the fastening forces can be achieved. Fig. 5a is a sectional viw taken on line I-I of Fig. 5, showing in this case a circular (round) cross-section of the tube. The advantages offered by the above described closing system are obvious. Leakage proof contact between the baffles and tubular member wall is achieved merely by mechanical operations also no soldering/brazing or additional gluing as presently required by the known fastening methods. The baffle (plug) can be inserted and expanded into a firm engagement with the tubular member by entering the tubular member from one side only. Furthermore, the special design of the plug and its positioning in the tubular member, as a cup-shaped plug having walls diverging in direction of the medium flow or pressure in the tube, will ensure that with increased working pressure in the tube a tighter sealing between the tube wall and the baffle will be achieved.

Claims: Claims 1. A method of fastening of baffles inside a tubular member, comprising steps of providing an expanding member in form of a cup-shaped plug (2) having diverging walls (22), and a cross-section essen tially complementary-shaped to the tubing' fi cross-section, attaching the said plug to a mandrel (4) by crimping of the diverging walls around a head part (41) of the mandrel (4), in serting of the assembled mandrel (4) with plug (2) into the tubular member void and expansion of the plug into a firm engagement with the tubular member on a desired location, predeterminated by the position or length of a support die (5) attached to the mandrel, by withdrawal of the mandrel from the plug. 2. Method according to claim 1, where the tubular member is an aluminum tube and an outside support ring (6) is located on the tube over the inserted plug (2) prior to the expansion step. 3. A closing system for tubular member (1) comprising an expanded member (2), having a cross-section essentially complementary-shaped to the inner cross-section of the tubular member and extending circumferentially into the tubular member's wall causing plastic deformation of the said wall, where the expanded member (2) is firmly inter locked in an indentation (3) in the tubular member wall resulting from the said plastic deformation. 4. The closing system according to claim 1, where the expanded member (2) is a cup-shaped plug having outer walls (22) diverging in direction of the prevailing flow and/or pressure in the tubing. 5. The closing system according to claim 4, where the tubular member (1) is an aluminum tube provided with an outside support ring (6) surrounding the indenta tion area (3) of the tube.

Inventors: CLAUSEN, EDVIN LIST
Applicants: NORSK HYDRO A/S
Application year: 1986
Main classification: F16L55
IPC codes: B21D39, F16L55, F28F9, F28F1, B21D41, F28F11