Heat exchange – Side-by-side tubular structures or tube sections – With manifold type header or header plate
Reexamination Certificate
2002-05-23
2004-09-07
Bennet, Henry (Department: 3743)
Heat exchange
Side-by-side tubular structures or tube sections
With manifold type header or header plate
C165S176000, C165S153000, C165S149000
Reexamination Certificate
active
06786275
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to headers for heat exchangers, and more particularly, to a manifold and header assembly and method of manufacture of the same resulting in improved strength while reducing cost and packaging.
BACKGROUND OF THE INVENTION
Heat exchangers for vehicles and stationary combustible engine power plants are known to have a header and a tank connected by tubes interspaced by fins, with sideplates providing rigidity. In this type of heat exchanger the fins provide a large surface area for heat transfer and support for the tubes.
Such heat exchangers may be used as radiators or plate oil coolers. They may also be used in a number of other applications including charged air coolers.
The typical, modern, automotive and truck brazed heat exchangers consist of a fin and tube assembly called the core. The tubes are attached to headers on opposing ends of the core. The whole assembly is baked in an oven to bond together the fins, tubes, and header. The remaining tank portions are attached to the headers to form manifolds by any of a number of retaining features, such as welding or a mechanical crimping process, depending on the header design, the environment and the material composition of the tank portion.
Conventionally, the header is stamped from sheet stock and resembles a rectangular tray with edges folded upward approximately 90° from the bottom surface. The bottom surface contains many punched oval and/or rectangular slots to accommodate the core tubes. The header slots are recessed formed upwards, pierced and/or a collar is formed upwards to guide the tube into the header slots. The shape formed around the tube slots is sometimes called ferrules or collars.
Headers meant to accommodate plastic molded tanks have a trough formed into the perimeter of the rectangular area to accept the foot of the plastic tank and a gasket. Also, retaining features are formed into the edges to facilitate the crimping operation for the tank retention at the tank foot.
The current manifold requires substantially increased packaging space along the direction from grill to engine. Cast Aluminum tanks require increased material thickness, due to the material's ability to withstand higher pressures and the molding process, which leads to added weight and cost. The durability of the tube-to-header joint is limited and usually needs to be reinforced.
Additional operations after brazing are required to weld the cast tank and/or to retain the plastic tank with gasket to the header.
Design limitations of cast tanks limit bracket features and other hardware attachment options due to molding process and cost impact. The header gauge is increased to overcome the unsupported bending moments between the vertical wall of the header and the horizontal portion where the tubes are inserted in the slots.
The need therefore exists to reinforce the core tube entry junction to the header where the prime mode of failure are thermal, primarily failing in the tube radius at the header braze junction near the end tube on the inlet side.
Additionally, the need exists for a manifold design resulting in substantial weight savings, reduced vehicle package size, and reduced manufacturing costs.
SUMMARY OF THE INVENTION
This invention provides a manifold having improved strength produced from flat sheet stock with reduced wall thickness requirements.
One purpose of this invention is to provide a stronger manifold in the sheet metal header area near the ends of the core tubes. In accordance with this invention, the manifold has reduced material weight and manufacturing costs, while retaining the functional performance with current materials and manufacturing brazing process capabilities.
The advantage of the manifold design described below is improved thermal performance, substantial weight savings, reduced vehicle package size, and reduced cost to manufacture.
The header of this invention provides manufacturing options not available in traditional designs. Formed tube slots provide more surface contact area with the tubes for added braze strength. Return bends in the header material serve to reinforce the tube-to-header joint and to strengthen the header itself. The cross section of the design has a narrower footprint resulting in space savings for the final product. The design can be adapted to accommodate multiple manifold options including a one-shot braze concept or a plastic tank, both of which yield weight savings.
The reverse bending of the header flange exploits the inherent strength of the core by forming a bond to the core. The bond, consisting of double manifold material, creates a truss-like formation with the core because the clad material and subsequent brazed joint on the interior of the double wall further enhances strength and durability. The combination of the ribs and gussets formed into the manifold and the aforementioned bond creates a structural union unobtainable by the manifold alone.
The header flange material is approximately doubled and juxtaposed along the tubes by reverse bending the material back and approximately against itself forming a substantial portion of the sides of the manifold, which is then closed with a cap. The sidewalls and cap areas may be contoured to specific vehicle packaging constraints.
The new header incorporates trusses, ribs and gussets and doubled walls to improve the structural integrity of the heat exchanger manifolds. The turbulator is bonded to the inside of the core tube during the brazing operation forming trusses to make the area around the tube more rigid and allow the thermal and pressure loads to be more evenly distributed across many tubes. The tube slot, which is formed in the header, bonds to outer surface of the core tube as well as to the inside of the header wall forming ribs and gussets. The core tube bonds to the reverse header flange forming another gusset. General fatigue is reduced due to the improved structural integrity and reduced mass in the manifold.
The combinations of the structural shapes when brazed together form compound gussets and trusses, thus permitting the use of thinner header material gauges for better brazing results, reduced cost and less weight. The header and cap may be ribbed and/or have tie bars incorporated into key locations in order to increase the manifold's ability to withstand the internal pressure with thinner gauge materials.
Another versatile aspect is multiple manifold designs and material options including a one-shot braze design in addition to the cast aluminum and plastic tank designs already in use. The one-shot braze tank consists of a formed cap joined to the header prior to the braze process hence bonded to the header during braze.
The doubled wall is applicable to multiple manifolds such as cast metal tanks or those made from flat sheet stock.
The single wall is applicable to multiple manifolds such as those using plastic tanks where the inner wall at the tank foot is restricted from rotating during retaining or pressure cycling because of the increased rigidity of the tube and slot ferrule wall.
In the all sheet metal stock manifolds, additional operations required after brazing with certain manifold options such as mechanical retention of the tab over the tank foot or welding the tank to the header are eliminated.
The cost of the sheet metal manifold assembly is reduced compared with the cast tank manifold.
The overall manifold tank thickness is reduced in the completed heat exchanger assembly by folding the header back into a doubled wall allowing reduced vehicle packaging in the grill-to-engine direction.
The overall assembly has a reduced weight using the all sheet metal stock manifold but retains the strength required to withstand the pressure.
The double wall being juxtaposed to the tube areas near and along the core face form a stronger tube-to-header joint.
The increased header strength allows the header area of the manifold to provide improved structural integrity to withstand the internal pressures and during thermal stress loading.
The all-sheet-meta
Dey Lavoyce
Fitzgerald Jonathan
Powers Michael
Bennet Henry
Duong Tho
Liniak Berenato & White
Valeo Engine Cooling
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