Metal deforming – By deflecting successively-presented portions of work during... – By use of deflector arranged to bend work transversely of...
Reexamination Certificate
1999-12-10
2001-05-15
Crane, Daniel C. (Department: 3725)
Metal deforming
By deflecting successively-presented portions of work during...
By use of deflector arranged to bend work transversely of...
C072S176000, C072S368000, C029S890100, C165S177000
Reexamination Certificate
active
06230533
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a folded tube for a heat exchanger such as a radiator for cooling a motor vehicle engine.
BACKGROUND OF THE INVENTION
More particularly, the invention relates to a folded tube comprising a metal strip folded on itself so as to delimit two parallel channels separated by a spacer, which, results from the joining of two borders of the strip each folded at right angles towards the inside of the tube from an outer face of the tube, forming a folded outer edge.
Folded tubes of this type are already known, and exhibit a cross-section of flattened shape and possess two flat and parallel large faces, joined together by two small curved faces. Such tubes serve to form a bank of tubes obtained by an alternate stacking of tubes arranged in parallel and of corrugated spacers, forming heat-exchange fins, which extend between the large faces of the tubes.
The ends of the tubes are accommodated with holes of appropriate shape formed by manifold plates which are capped by manifold chambers. The assembly is brazed in an appropriate furnace so as to constitute a heat exchanger.
In the majority of the known tubes of this type, the folded outer edge exhibits a circular-arc shape which results from the folding operation, so that a depression is always created at the surface of the tube at the place where the border is folded inwards. It is therefore necessary to fill in this depression, to ensure continuity of each of the large faces or the tubes in the regions close to the spacer and to ensure leaktightness of the joint between the tubes and the manifold plates of the heat exchanger. Such operation raises a practical difficulty, since it is difficult to fill in this depression conveniently with brazing alloy during the manufacture of the tube.
Tubes of this type are also known in which the folded outer edge exhibits a sharp outer corner, which eliminates the depression mentioned above. However, the shaping of a sharp-cornered outer edge poses practical implementation difficulties
Moreover, the known tubes of the abovementioned type all have the drawback of not allowing the corrugated spacers to be held properly, which generally makes it necessary to have special tooling to keep these spacers in the correct position during the brazing of the heat exchanger.
OBJECTS OF THE INVENTION
A primary object of the invention is to at least partly remedy the drawbacks of the prior art.
Another object of an embodiment of the invention is to produce, by folding, a tube which exhibits no depression at the place where the border is folded inwards and which contributes to holding the corrugated spacers which are adjacent to it.
SUMMARY OF THE INVENTION
According to one aspect, the present invention provides a folded tube for a heat exchanger, particularly of a motor vehicle, comprising a metal strip folded on itself so as to delimit two parallel channels separated by a spacer. The spacer results from the joining of two borders of the strip which are each folded at right angles towards the inside of the tube from an outer face of the tube, and a folded outer edge. Each of the folded outer edges includes a protruding swelling which extends at least on the same side as the outer face of the strip.
Each of the borders is folded at right angles, forming a protruding swelling, in such a way that the two borders can be joined together without forming a depression. Hence, during a subsequent brazing operation, the continuity of each of the large faces of the tube in the regions close to the spacer is automatically assured. This also guarantees the leaktightness of the joint between the tubes and the manifold plates of the heat exchanger.
Moreover, these protruding swellings improve the holding of the corrugated spacers by penetrating into the corrugated spacers, which avoids having recourse to special tooling in order to hold them during the brazing.
Furthermore, these protruding swellings contribute to supporting the borders against the inner face of the tube, which is opposite the outer face.
The protruding swelling may extend only on the same side as the outer face of the strip, or may extend both on the outer-face side and on the same side as the border of the strip.
The protruding swelling preferably has a dimension of 0.05 to 0.5 mm.
According to another characteristic of the invention, each of the borders is joined to an inner face of the tube, forming a fillet having a profile substantially of a quarter-circle.
According to another characteristic of the invention, the outer faces to which the borders are connected jointly form a flat large face of the tube.
According to yet another characteristic of the invention, the tube comprises two flat large faces joined together by two inward-curved small faces.
The tube according to the invention is formed from a metal material which is capable of being folded, preferably aluminum or an aluminum-based material.
According to another aspect, the invention relates to a method of shaping a tube as defined above, this method comprising the following operations:
a) providing a flat metal strip of chosen length delimited by two parallel longitudinal edges;
b) continuously deforming each of two marginal regions of the strip so as, by folding, to produce a flat border forming a variable obtuse angle with a central region of the strip which extends between the borders, such way each border is connected with the central region by a folded region of chosen profile;
c) carrying on with the deformation of the strip until each of the borders is connected to the central region by a right angle; and
d) shaping the folded region in such a way as to form an angle of 90° exhibiting a folded outer edge including a protruding swelling.
In one implementation of the method, provision is made that, in operation b), the folded region includes a rib with rounded profile which protrudes on the same side as the reflex angle, that, in operation c), the protruding rib is conserved, and that in operation d), the protruding rib is squeezed to form the protruding swelling.
According to one variant of the method, provision is made that, in operation b), the folded region includes a fold with a rounded profile, that in operation c) the fold is conserved, and that in operation d) the material of the border is made to flow in such a way as to fill in the internal space of the right angle and to obtain the protruding swelling.
According to another characteristic of the invention, each of the operations b), c) and d) is carried out by at by least one set of shaping wheels including a shaping wheel and a counter-wheel.
Advantageously, the method comprises at least one supplementary operation comprising in:
e) continuously deforming the strip in such a way as to bring the two folded borders together against one another so that they jointly constitute a spacer reaching as far as the central region of the strip in order to form a tube with two parallel channels.
Operation e) preferably comprises the deformation of the central region so as to form a flat large face joined by two inward-curved small faces to an opposed flat large face comprising two coplanar parts extending on either side of the folded borders.
According to another aspect, the invention relates to a heat exchanger comprising a multiplicity of tubes as defined above or as obtained by the method above.
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French Search Report Dated Aug. 18, 1999.
Laveran Jean-Louis
Naty Jean-Claude
Potier Michel
Crane Daniel C.
Morgan & Finnegan , LLP
Valeo Thermique Moteur
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