Metal working – Method of mechanical manufacture – Heat exchanger or boiler making
Reexamination Certificate
1999-09-15
2001-10-16
Rosenbaum, I Cuda (Department: 3726)
Metal working
Method of mechanical manufacture
Heat exchanger or boiler making
C029S402130
Reexamination Certificate
active
06301780
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Technology
The present invention relates to aviation oil coolers, and more specifically to the disassembly cleaning, recoring, and reassembly of an aviation oil cooler using a reassembly jig.
2. Related Art
The aircraft industry is composed of an aging fleet of aircraft many of which are no longer production. Therefore, parts for such aircraft are extremely difficult to acquire, if the parts car found at all, and in many situations, new replacement parts are non-existent. As a result, the aviation industry is now faced with repairing existing parts that have already been repaired a number of ti or scraping a part that is no longer repairable.
Oil coolers (e.g., oil hydraulic, air to oil, etc.) and other heat exchangers in the aging aviation fleet are constructed of a series of plates and fins that are stacked and vacuum braised into a solid unit called a “core”. Aviation oil coolers and “core” components are well known in the relevant art and are commercially available. In most applications, the oil cooler must be exposed to a strong flow of air in order for it to perform the heat transfer for which it was designed. This strong air flow unfortunately promotes foreign object debris (FOD) to the unit over a period of time.
In the case of aviation oil coolers and other heat exchangers, today's method of repair is no different than it was twenty years ago. The conventional method for repairing cracks and holes in an aviation oil cooler or other heat exchanger and returning it to service comprises the steps of welding, braising, soldering, epoxy and blocking off a number of tubes to repair leaks. More specifically, the core of a damaged aviation oil cooler is repaired while remaining integrated with the original oil cooler unit. This method maintains the use of the original core in the original oil cooler such that the resulting repaired oil cooler is weaker and more prone to future damage than a new oil cooler having a new replacement core.
Therefore, there is a need for a method for recoring a conventional aviation oil cooler that removes the original damaged core from an existing aviation oil cooler, replaces it with a new replacement core, and returns the aviation oil cooler to its original equipment manufacturer (OEM) specifications.
In order to return a disassembled manufactured product to its OEM specifications, the individual components of the product must be held in proper position and alignment to each other during reassembly. However, there are no available “jigs,” or structures. that function as a template for assembling a manufactured product. Therefore, there is a need for a reassembly jig for holding the components of an aviation oil cooler in their proper position during reassembly so as to maintain the OEM specifications for the reassembled aviation oil cooler.
SUMMARY OF THE INVENTION
Instead of attempting to repair the core of a damaged aviation oil cooler by trying to stop leaks in a twenty-plus year old core, the present invention repairs aviation oil coolers by replacing the entire original core with a newly constructed core, called a replacement core. In the preferred embodiment of the present invention, an original core is replaced by clean cutting the original core from an aviation oil cooler, removing the existing mounting brackets and hardware, and welding to the original aviation oil cooler a new replacement core having the same construction, dimensions, and functionality as the replaced original core and mounting hardware. All machining and welding are accomplished under guidelines outlined in the manual entitled FAA Repair Station #PC8R209J, and an additional welding certification is maintained under MIL-STD-1595A, entitled Aerospace Fusion Welding. These documents are publicly available government documents.
All exterior measurements and tolerances of the original aviation oil cooler and replacement core are maintained by using a special reassembly jig. Jigs are well known in the prior art and are used for other applications to facilitate the assembly of a mechanical unit by holding components of the mechanical unit in place and at specific tolerances during the unit's assembly. A reassembly jigs of the present invention is constructed of such dimensions and specifications such that a replacement core can be mounted in the original aviation oil cooler. The reassembly jig ensures the maintenance of close alignments and fits of the various components of the aviation oil cooler such that the finished repair of the aviation oil cooler meets the exact dimensions of the original equipment manufacturer (OEM) of the aviation oil cooler.
There are many advantages with replacing a damaged core in an aviation oil cooler with a new replacement core. For example, the cost of recoring an aviation oil cooler is much less than the cost. of a completely new aviation oil cooler. The life-span of an aviation cooler is prolonged, thereby saving repair and total replacement costs. Maintenance costs associated with an aviation oil cooler will be reduced.
REFERENCES:
patent: 1979856 (1934-11-01), Bennett
patent: 3289268 (1966-12-01), Bernardis
patent: 4769888 (1988-09-01), Desiro
patent: 5894649 (1999-04-01), Lambert et al.
Cuda Rosenbaum I
Positech International, Inc.
Steptoe & Johnson PLLC
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