Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-06-03
2001-05-15
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S816000, C361S818000, C361S827000, C379S433020, C405S198000
Reexamination Certificate
active
06233155
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to high-volume production of products having a printed circuit board encapsulated by mechanical shells.
2. Brief Description of the Related Art
Prior products which are formed of a housing which encloses electronic components have typically encapsulated the printed circuit board (PCB) with two plastic parts produced by separate tools. The trimming of the tools is approached in two ways. The two tools are produced in pairs, that is, one supplier or toolmaker is responsible for trimming the two different tools against each other. This approach can offer a good solution to the problem of forming housing to close mechanical and cosmetic tolerances, as it usually guarantees that the parts fit nicely together. Consequently, very tight tolerance requirements can be met. This first solution implies, however, that a significant amount of risk is concentrated with one supplier or toolmaker; if something goes awry with the sole supplier's manufacturing facility or die tools, the entire production of the product stops.
Alternatively, the risk of a significant production stoppage can be spread out among a number of suppliers. In this alternative risk spreading scheme, several different suppliers for the tools produce the housings for the product, i.e., no single one of the suppliers produces a pair of tools. If something goes wrong with any one of the multiple suppliers, the consequences are relatively minor compared with the first solution, outlined above. However, the tolerances between the parts produced by different suppliers must be, by necessity, significantly rougher to assure that the parts will actually fit together. Consequently, the product will more likely have larger gaps between its parts and larger cosmetic mismatches (e.g., structure and color differences between its parts). This can lead, in turn, to malfunctioning of electromechanical connections within the product, and also can result in a final product which is less attractive.
U.S. Pat. No. 4,939,792 describes a moldable/foldable radio housing onto which four solderable printed circuit patterns are vacuum deposited on the interior and exterior of a base and cover, which are joined by a hinge. U.S. Pat. No. 4,703,160 describes a casing structure of a portable electronic appliance, in which four panels are joined by hinges and are releasably attached when folded together. U.S. Pat. Nos. 5,432,676 and 5,541,813 describe a portable telephone having a case with a wiring member in a molded plastic hinge, in which the hinge is opened and closed during regular use, and the hinge is formed of a material different from that used to form the rest of the case. U.S. Pat. No. 3,580,650 describes a cabinet for holding, e.g., a complete radio, in which four sections are joined together by hinges that can be opened and closed during regular use. EP 547 994 A1 describes a stamped sheet of metal which is folded upon itself and joined with tabs to form a housing. None of these prior devices resolve the problems outlined above.
SUMMARY OF THE INVENTION
The present invention provides a solution to the problems associated with outsourcing and the spreading of risks among a number of different suppliers of housings for electronic components, and the tolerances of the parts produced.
In its simplest form, the basic problem is to encapsulate and secure a PCB in and by injection-molded mechanical shells in an assembly procedure requiring as few and as simple operations as possible, and with a minimum number of mechanical shells required to form the completed product. The greater number of mechanical shells that is needed to form the product, the greater the number of injection-molding tools that must be trimmed against each other so that these parts fit together. Trimming of tools against each other can be crucial in high-volume production, where the production of each plastic part might require a large number of tools, e.g., up to twenty similar tools.
Choosing between the two different solutions outlined above presents a major dilemma to any company facing the basic problem of mass-producing a housing which encloses a PCB, since neither of these two solutions are optimized with respect to both risk spreading and tolerances.
In accordance with the present invention, a solution to the problem, as well as to the dilemma, described above is to injection mold the two plastic parts of a housing, e.g., the back and front covers, as one single, unitary, monolithic, unitary piece. In accordance with an exemplary embodiment of the present invention, the back and front covers can be connected by a “living hinge” which is formed of the same material and at the same time as the covers are formed.
Thus, an exemplary embodiment of an assembly process in accordance with the present invention includes the steps of inserting the PCB and other components of the product into the back and front covers. Encapsulation of the PCB and other product components is achieved when either the back or the front cover is rotated 180° relative to the other cover about a hinge, thereby enveloping the PCB and components. The joined covers can be secured by means of screws, snap fits, ultrasonic welding, or other relatively permanent processes. Because the hinge could then extend out of the closed housing, which may be aesthetically and commercially unacceptable, a cosmetic cover can be joined to the exterior of the housing to mask, cover, or otherwise hide the hinge.
The present invention can thus essentially eliminate the necessity of trimming tools against one another, as was needed with prior devices and processes. And, different from prior solutions, the present invention facilitates the combination of risk spreading and the optimization of tolerances.
Still other objects, features, and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of embodiments constructed in accordance therewith, taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3580650 (1971-05-01), Morris
patent: 4703160 (1987-10-01), Narishima et al.
patent: 4809875 (1989-03-01), Takano
patent: 4939792 (1990-07-01), Urbish et al.
patent: 5224023 (1993-06-01), Smith et al.
patent: 5406027 (1995-04-01), Matsumoto et al.
patent: 5432676 (1995-07-01), Satoh et al.
patent: 5475752 (1995-12-01), Mischenko
patent: 5541813 (1996-07-01), Satoh et al.
patent: 0 547 994 (1993-06-01), None
patent: 1 404 143 (1965-05-01), None
Larsson Mats
Larsson Paul
Möster Erik
Olsson Mats
Portela Rafael
Burns Doane Swecker & Mathis L.L.P.
Dinh Tuan
Gandhi Jayprakash N.
Telefonaktiebolaget LM Ericsson (publ)
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