METHOD FOR MANUFACTURING A BENT HEAT EXCHANGER
An improved bending apparatus for bending a radiused corner at a window in a brazed heat exchanger core where no tubes and fins are located. A cylindrical mandrel and sliding pressure die are designed to completely surround the manifold in the areas of the window and provide a continuous, rolling contact area or profile support around the manifold as the bending moment is applied.
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The invention relates to a method and apparatus for bending a brazed aluminum heater exchanger. Priority is claimed to provisional application 61/188,440, filed Aug. 8, 2008.
TECHNICAL FIELD OF INVENTION Background of InventionBrazed aluminum heat exchangers of the type having spaced header tanks (or manifolds), flat elongated tubes corrugated air fins or centers have been a commonplace in automotive applications, where they are of a relatively small face area and installed flat, such as air conditioning condensers. It is known to bend such automotive heat exchangers into a V or U shape, as shown in U.S. Pat. No. 4,876,778, but this is a relatively simple and straightforward bend in which the tubes and fins (core face) themselves are bent, perpendicular to the tubes, not the heavier manifolds themselves, which remain straight
That same U or V shaped bend of the core face can be applied to stationary air conditioning applications as well (residential heat pump, for example), but such applications often require a more difficult bending operation in which the tubes are left unbent, straight, and vertical, while the manifolds are bent into a rectangular perimeter. The vertical tubes drain condensation better, but the manifolds are heavier and more difficult to bend. Several different bending apparatuses and methods are known. A typical apparatus consists of a cylindrical solid mandrel that engages the tube the core face, between the manifolds, and opposed flat clamps engaging the outer core face and/or manifolds, one of which is held stationary and the other of which is swung in to bend the core around the cylindrical mandrel. The core is bent into a 90 degree, radiused corner or corners. Another issue is the behavior of the tubes and fins at the “corners” where the manifolds are bent. These can buckle and deform, presenting at least an aesthetic objection, if not a diminution in performance. Fins may also pull away from the tubes in the bend area, decreasing performance. This limits how tight or small a bend radius can be achieved.
Published Japanese application JP-2005090806 shows the basic bend configuration described above, and discloses some prior approaches to the bending problem. The most basic approach is to simply remove (leave out) the tubes and fins at the corners, and to cover the resulting open windows with a screen of some sort in the final installation. This has the obvious drawback of removing a considerable amount of heat exchange area out of the core face, besides necessitating the addition of some sort of screen at the corners to “fill in” the missing area and avoid disturbance of the forced air flow at the paths of least resistance. This is especially a problem if the bending apparatus and technique do no allow for a tight, sharp bend, because more tubes and fins have to be left out. What the art fails to disclose is a bending method and apparatus designed to bend the manifolds, even free of tubes and fins, into such a tight and well controlled radiused corner. A typical bender will clamp the core on one side of the bend area, and apply a bending force to the other, either across the core area or the manifolds or both, but no measures are taken to actively control the profile and shape of the bent sections of the manifold.
This invention will be further described with reference to the accompanying drawings in which:
In accordance with a preferred embodiment of this invention, referring to
As disclosed in
The operation of the apparatus described above to carry out the method of the invention is described by reference to
Next, as seen in
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow. Fundamentally and most simply, the basic invention entails supporting the entire profile of that portion of the manifolds located within the open area of the window during the bending process, between a rotatable cylindrical mandrel supporting the inner side of the mandrels, which has the desired radius and inner arc length of the bend to be created, and an opposed straight pressure die supporting the other side of that portion of the manifolds, and which slides along its length at a rate that maintains a continual rolling contact between it and the cylindrical mandrel as the bending force is applied, however it is applied, and until the bend is completed. It is an additional advantage to provide a pair of clamping elements in the lead of the bend area, by incorporating a straight back up clamp on the mandrel and an opposed clamp plate. It is also advantageous to support more of the manifold on the leading side of the bend and to also apply the bending force through that back up clamp, and to support more of the manifold on the trailing side of the bend with an additional length on the pressure die, more than is necessary just to support the profile of the bend. The additional manifold support provided on the leading and trailing sides of the bend cannot support the entire circumference of the manifold profile, because of the intervening tubes, but still provides an advantage. The manifold profile could be a shape other than round, meaning that the various supporting troughs would have a different matching cross sectional shape (square or elliptical), but the rolling contact lobes that provide all round support to the profile would have the same basic structure.
Claims
1. A method of manufacturing a tube-to-manifold heat exchanger comprising the steps of:
- providing a tube-to-manifold heat exchanger core having a upper manifold, a lower manifold spaced apart from and substantially parallel to said upper manifold, and a plurality of substantially parallel and vertical flat tubes running between said upper and lower manifolds, wherein said plurality of tubes are spaced so as to define at least one open window bordered by sections of unencumbered upper and lower manifold defining an intended bend area of said core,
- providing a rotatable, semi-cylindrical mandrel defining the desired radius of the bend and having a semi-cylindrical trough sized to substantially support the entire inner profile of the manifold over the desired bend,
- providing a slidable pressure die opposed to the mandrel having a straight trough sized to substantially support the entire outer profile of the manifold over the desired bend,
- applying a bending force to bend the manifold around the semi-cylindrical mandrel while concurrently rotating the mandrel and sliding the pressure die along the length of the manifold so as to maintain a rolling contact between the mandrel and pressure die to continually support substantially the entire profile of the manifold as it is being bent.
2. The method according to claim 2, further comprising the step of applying the bending force by clamping the manifolds in the lead of the bend area between a pair of clamping elements and swinging the clamping elements about the pivot of the mandrel as the mandrel rotates.
3. The method according to claim 2, further comprising the step of providing one of clamping elements to be integral to the semi cylindrical mandrel and rotating the mandrel and swinging the one clamping element concurrently.
4. The method according to claim 1, further comprising the step of providing an additional length to the sliding pressure die to support the manifold trailing the bend.
Type: Application
Filed: Aug 6, 2009
Publication Date: Aug 4, 2011
Applicant: DELPHI TECHNOLOGIES, INC. (TROY, MI)
Inventors: David E. Samuelson (Wheatfield, NY), William David Wright (Newfane, NY)
Application Number: 13/056,155
International Classification: B21D 53/02 (20060101);