Patent Application
20070268645
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with a general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention.
The electro-mechanical characteristics of Tungsten and other metals and or metal alloys are known:
Although a shorting stub may survive a relatively high power surge event, deformation of the shorting stub resulting form the surge event may destroy the electrical characteristics of the shorting stub for ongoing operation. The inventor has recognized that, within a common assembly size constraint, a primary limitation of shorting stub design for higher surge capacities is the electro-mechanical characteristics of the materials applied to the shorting stub.
While almost as conductive as Aluminum (high conductivity is a desirable characteristic because higher conductivity lowers the resulting “let thru” of the shorting stub), The inventor's research has revealed that Tungsten will deform far less for vastly higher surge capability (Elasticity and Tensile Strengths) and is more thermally stable thus less prone to frequency response drift. However, the significantly higher material costs of Tungsten material have previously made application of Tungsten cost prohibitive. Although the actual amount of Tungsten required in a finished shorting stub is relatively low, materials waste due to extensive machining and or stamping procedures required to form complex shorting stub geometries increased the materials costs significantly. Further, Tungsten is brittle at ambient temperatures, requiring specialized procedures during machining, stamping, bending and or folding manufacturing operations which further increase manufacturing costs.
Metal Injection Molding (MIM), also known as Powder Injection Molding (PIM), is a net-shape process for producing solid metal parts that combines the design freedom of plastic injection molding with material properties near that of wrought metals. With its inherent design flexibility, MIM is capable of producing an almost limitless array of highly complex geometries in many different metals and metal alloys. Design and economic limitations of traditional metalworking technologies, such as machining and casting, can be overcome by MIM.
In a typical MIM process, finely granulated metal material is uniformly mixed with a wax or polymer binder and injection molded. A “green” molded part is then extracted from the mold. A de-binding step extracts the majority of binder from the green part via application of low temperature and or a solvent. The de-bound 6047 green part is then sintered at high temperature wherein the de-bound part is proportionally shrunk to the final target size, concentrating the metal density and strength characteristics to close to that of a casting made from the same material by conventional means.
The inventor has recognized that modified MIM manufacturing technologies may be applied to form the complex shapes of shorting stubs and other RF components using Tungsten and or Tungsten alloys to reduce both the increased materials and machining costs previously associated with Tungsten. Thereby, the invention enables the design and manufacture of shorting stubs and other RF structures that benefit from the improved electromechanical properties of Tungsten and or Tungsten alloys.
Because of the minimal waste inherent in the MIM manufacturing process, although the superior electromechanical properties of Tungsten are realized, the increased costs associated with the application of Tungsten are minimized. Via the present invention, a surge suppressor with improved electrical characteristics including improved multiple strike survivability and significantly increased maximum strike magnitude capacity is enabled.
Exemplary highly compact Multiple Planar Inductive Loop Surge Suppressor configurations and the shorting stubs thereof are disclosed in U.S. patent application Ser. No.: 11/306,872 filed Jan. 13, 2006 titled “Multiple Planar Inductive Loop Surge Suppressor” by Howard Davis and Kendrick Van Swearingen, co-owned with the present application by Andrew Corporation of Westchester, Ill. and hereby incorporated by reference in the entirety.
As shown for example in
While the invention has been demonstrated in detail with respect to a specific embodiment of a multiple planar shorting stub, one skilled in the art will recognize that other shorting stub configurations such as single plane spiral and or helical may be similarly applied. As demonstrated in
To support multiple planar loop segments in the desired configuration during the mold retraction and or sintering step(s) of the MIM manufacturing process, one or more support(s) 22 may be included in the design that are later easily removed from the finished shorting stub.
Forming each of the support(s) 22, for example, parallel to a longitudinal axis of the inner conductor and with a frangible connection to each of the multiple planar loop segment(s) 16 enables easy removal of the supports without requiring an additional machining step. Placement of the supports along an inner diameter of the loop segment(s) 16 minimizes the overall size requirement of the MIM mold.
Alternatively, as demonstrated by
One method of manufacture according to the invention includes the steps of forming a shorting stub 10 according to a desired configuration via MIM manufacturing process(s), the shorting stub 10 formed from Tungsten and or a Tungsten alloy. Any support(s) 22 included in the configuration are removed after at least the sintering steps of the MIM manufacturing process(s) have been completed.
Adaptations to standardized MIM procedures advantageous when Tungsten and or Tungsten alloy material is being applied include selection of a compatible polymer and solvent pair for the de-binding step. Polymer rather than wax may be applied and nitric acid used as the solvent for polymer removal during de-binding. Nitric acid would react with Copper and Copper alloy material, but provides desirable de-binding results when applied to Tungsten or Tungsten alloy material.
Tungsten and or Tungsten alloys may be applied to other RF devices with similar benefit. For example, previously RF filter elements have been manufactured from specialized alloys such as INVAR™ (FeNi36) a Nickel Iron alloy, known for having an extremely low thermal expansion property (2 μin/in-° C.). Application of
Tungsten in place of INVAR™ provides an acceptable thermal expansion characteristic at a significant cost reduction.
While a MIM manufacturing process has been identified the invention is not limited thereto, a shorting stub or other RF device such as a filter element may be formed according to the invention from Tungsten and or a Tungsten alloy by other manufacturing processes.
One skilled in the art will appreciate that the present invention represents a significant improvement in power capability, overall size requirements, manufacturing and cost efficiency.
Table of Parts
Where in the foregoing description reference has been made to ratios, integers, components or modules having known equivalents then such equivalents are herein incorporated as if individually set forth.
While the present invention has been illustrated by the description of the embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative apparatus, methods, and illustrative examples shown and described. Accordingly, departures may be made from such details without departure from the spirit or scope of applicant's general inventive concept. Further, it is to be appreciated that improvements and/or modifications may be made thereto without departing from the scope or spirit of the present invention as defined by the following claims.
This application claims the benefit of US Provisional Patent Application No.: 60/747,920 filed May 22, 2006 and hereby incorporated by reference in the entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60747920 | May 2006 | US |
