Wave transmission lines and networks – Long line elements and components – Waveguide elements and components
Reexamination Certificate
2001-06-20
2003-10-07
Le, Don (Department: 2819)
Wave transmission lines and networks
Long line elements and components
Waveguide elements and components
C333S239000
Reexamination Certificate
active
06630876
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to manufacturing a hollow electronic component such as a waveguide or antenna or optical component, wherein the inner surface of the hollow object needs to have a precisely smooth thin film coating such as gold or copper, and wherein the object must also have a low weight, and be structurally sound.
BACKGROUND OF THE INVENTION.
Prior art “outside in” techniques for manufacturing a hollow electronic component such as a microwave waveguide filter comprise the steps of forming the device from the outside in. See U.S. Pat. No. 5,398,010. Typically a fiberglass composite like shell is hand laid on a disposable or reusable mandrel. This fiberglass like shell is called a composite material in the trade. It may be composed of carbon fiber reinforced plastics, graphite fibers, reinforced plastics, carbon-carbon composites, dielectric fibers, other fiber polymer-matrix composites, and metal/metal matrix composites. The mandrel has the desired final shape of the hollow component to be made. Once the fiberglass composite like shell is made the mandrel is removed by any one of several methods including physical retraction.
At this point in the process a delicate and rigid fiberglass composite like structural shell is formed having a rough surface in the inside and outside surfaces. The typical surface smoothness might be 64 rms.
Next a series of chemical plating processes are done to coat the interior of the hollow device with an electronically functional precise coating(s). Such coatings include gold, silver, copper and nickel. Examples of these processes are taught in U.S. Pat. No. 3,982,215 and 5,398,010, wherein both of these references are incorporated herein by reference. Both of these patents teach an “outside in” process to create a composite material waveguide having a copper inside coating.
The main problem is quality control to coat an interior rough surface of a composite material pipe with close tolerance metal coatings. This problem leads to high costs for the resultant devices, wherein the ultimate usefulness for these devices is often found in a space application. For space use one pound in a satellite can cost up to $30,000 in lift off and operational costs.
Extremely good electrical or optical performance has been achieved by the old technique using a disposable mandrel and then electroforming complex components or assemblies as a single piece or assembly around the outside of the mandrel. The materials used for this have typically been copper and/or silver. Structural reinforcement has been provided by the additional thickness of copper and/or nickel. The resultant hollow devices are heavy and have limited thermal stability properties.
Improved thermal stability and/or lower mass have been realized by the electroless and/or electro plating of pre-formed composite components as shown in the '010 and '215 patents. However, this technique has demonstrated problems with plating thickness uniformity, plating adhesion, plating surface roughness, and plating adhesion degradation with exposure to moisture, which all lead to poor or unacceptable electrical performance.
The techniques of the '010 and '215 patents have generally been limited to producing straight pipe segments, unless a two part mold is formed for a complex shape like a right angle, and then the two parts are bonded together and then electroplated inside.
At least five problems arise from the “outside in” manufacturing techniques. First the roughness of composite materials creates a best surface smoothness of 32 rms. This is the result of coating copper over a rough surface of fiberglass composite (generally called a composite material).
Second the fiberglass composite shell does not have the extraordinary dimensional accuracy of ±0.0002 inch that a machined metal mandrel can achieve.
Third when coating the inside of an irregular shaped fiberglass composite shell, linear flow of the electrolyte is inhibited. This is especially true for shapes with cavities and blind ends. Without linear flow a linear coating depth cannot be achieved. Therefore, the rough surface defects of the fiberglass composite shell are made worse by uneven coating of the copper (or chosen metal) on them.
Fourth a multi-piece mold to create a single piece irregular shaped product adds unnecessary cost to the final product.
Fifth there exists a ratio of cross sectional area of a pipe to the necessary smoothness of the inside of the pipe to be useful as a microwave waveguide. The smaller the cross sectional area, the smoother the surface smoothness must be, with a required rms of 32 or lower. A fiberglass composite shell cannot be coated to obtain this necessary smoothness.
The present invention is based on the technique of applying from the “inside out” materials over a precision mandrel via a known electroplating process. Then the fiberglass composite shell is applied over the newly formed metal layer while the mandrel is still in place. Finally the mandrel is etched away leaving a fiberglass composite shell with a super smooth inner coating. The resultant waveguide device is low mass, has improved thermal stability, improved thermal performance without the typical adhesion and/or surface roughness issues associated with plating composites from the “outside in.”
The term waveguide component also further includes what is known in the industry as co-axial waveguides, square co-axial waveguides, and TEM line components. The present invention can create extremely lightweight versions of the latter devices, wherein the prior art method for creating the latter devices is limited to a heavier version using known methods such as machining, casting, and die brazing.
SUMMARY OF THE INVENTION
The main aspect of the present invention is to provide a method to make from the “inside out” a lightweight hollow structure, using a sacrificial or reusable mandrel.
Another aspect of the present invention is to provide a method to create spacecraft waveguides and the like, wherein each component has a hollow core with a precision coating thereon, and/or a curved precision reflective surface.
Another aspect of the present invention is to provide a method to manufacture various components simultaneously.
Another aspect of the present invention is to provide a method to protect certain pieces of the hollow component, for example an epoxy seam between two sub-components, by means of coating the seam with a non-reactive metal before bathing the component in a chemical to erode the mandrel away.
Another aspect of the present invention is to provide a means to protect the composite structure from the chemical etching process used to erode the mandrel away, the protective step being to coat the composite material with a non-reactive material.
Another aspect of the present invention is to provide a high strength and a high stiffness end product formed by the inside out process.
Another aspect of the present invention is to provide a ultra-low loss (of transmitted signal) waveguide component formed by the inside out process.
Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.
A mandrel can be fabricated out of stainless steel, aluminum, zinc, plastic, or any metal alloy. The mandrel can be fabricated by conventional milling, turning, stamping, shearing, casting, or injection molding. Selective areas on the mandrel maybe masked where no plating is desired. The mandrel is prepared to accept plating depending on the composition of the mandrel material. Any material that can be metalized can be used as a mandrel in this invention.
Typically, aluminum alloy 6061 is used as the mandrel due to the alloy's machining and processing characteristics. Conventional techniques are used in the preparation of the aluminum alloy for plating. The mandrel is first cleaned in a non-etch alkaline c
Lee-Yow Lee Mancheong Edouard
Noyes Michael J.
Applied Aerospace Structures Corp.
Le Don
Martin Rick
Patent Law Offices of Rick Martin P.C.
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