Electricity: electrical systems and devices – Housing or mounting assemblies with diverse electrical... – For electronic systems and devices
Reexamination Certificate
1999-06-08
2001-07-31
Gandhi, Jayprakash N. (Department: 2841)
Electricity: electrical systems and devices
Housing or mounting assemblies with diverse electrical...
For electronic systems and devices
C361S752000, C361S753000, C361S799000, C439S095000, C439S101000, C439S108000, C174S051000
Reexamination Certificate
active
06269004
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to an electric module that includes a printed circuit board with electrical assemblies attached thereto and which is disposed in a metallic housing. More specifically, the present invention relates to an effective means for grounding the circuit board and electrical assemblies to the metallic housing.
BACKGROUND OF THE INVENTION
Parts of electric appliances, systems or devices which are operationally live must in principle be insulated or covered in such a way that they cannot be touched. In the event of a fault, however, conductive parts could nevertheless assume a voltage with respect to ground. Consequently, a range of protective measures are generally prescribed—depending on the field of application—in order nevertheless to eliminate risk. These include, inter alia, total insulation, protective grounding and/or neutralization. In the case of protective grounding, conductive system parts are connected via a protective conductor to a ground electrode, in the latter case to the neutral conductor of the network. Apart from such protective grounding, in many instances there is also a need for ground connections in the case of electric circuits, in order to fulfill a specific function in a defined way. For example, it is possible using such functional ground to discharge radio-frequency signal components, that is to say to eliminate RF interference.
A precondition for the proper functioning of the said measures is that such conductive appliances or system parts are connected in an electrically reliable fashion via a protective conductor to the ground electrode and/or the neutral conductor. In the case of an electric module having a pluggable printed board assembly which comprises a printed circuit board and electric subassemblies arranged thereon and is arranged in a metallic housing, one of the possibilities known for this purpose consists in connecting the ground conductor at one end to a ground conductor track of the printed circuit board in a mechanically reliable fashion. An eye is integrally formed on the end of the ground conductor to be connected to the housing, said eye possibly also being crimped on as a discrete element, and said eye is fastened to the housing part to be protected by means of a screwed connection protected against inadvertent loosening. This configuration, very reliable per se, of a ground conductor contact has the disadvantage that it is relatively expensive, in particular in the case of mass production of electric modules, and is difficult to handle. Either this screwed connection has to be performed manually, or expensive component mounting machines are required for this purpose.
A ground conductor contact which is configured as a plug-in connection is easier to handle. Since a multiplicity of solutions are known for this purpose, reference may be made in this connection to GB-B 14 63 751 merely by way of example. Although this embodiment is no less complicated in terms of production engineering, it is used nevertheless in the case of a multiplicity of applications, in particular because of the possibility of being handled without tools during maintenance work. In principle, on the housing side this plug-in connection comprises a contact element with a flat contact tongue and a cable shoe, which can be pushed over the latter and is connected in an electrically effectively conducting fashion, for example via a crimp contact, to the end of the ground conductor which is to be connected. This contact tongue is normally constructed as part of a metallic angle which, by means of a connection which has an electrically conductive configuration, is fixed to the part to be earthed of the electric module. Because of its functional reliability, this solution is used despite the expense of production in a multiplicity of applications, in particular also because it has the property of being able to be released again easily.
The foregoing comments demonstrate that a certain expense is incurred in the case of detachable ground contacts for reasons of electrical safety. In order to produce the screwed connection with the housing part to be grounded, a bore for accepting a self-tapping fastening screw is frequently forced into said housing part in order to save a dedicated nut. However, the outlay on manufacture and mounting remains high. If this outlay could be reduced even to an only noteworthy extent, this would already mean a substantial saving in costs in the case of a mass production product.
Therefore there is a need to create in the case of an electric module of the type mentioned at the beginning a further embodiment for the ground contact which can be realized in a simpler and thus more cost effective way in mass production without loss of electric safety.
SUMMARY OF THE INVENTION
The present invention satisfies the aforenoted need by providing an electric module which comprises a printed circuit board assembly comprising a printed circuit board with electrical assemblies attached thereto and which is housed in a metallic housing. The circuit board further comprises a ground conductor track electrically connected to a wire bridge. The circuit board also includes cutout that extends transversely to the wire bridge and which extends through the circuit board. The metallic housing is conductively connected to a contact tongue which extends through the circuit board and which engages the wire bridge.
In an embodiment, the circuit board comprises a component side and an underside. The wire bridge is disposed on the component side and the circuit board is disposed on the underside.
In an embodiment, the circuit board comprises two bores aligned with the ground conductor track. The wire bridge comprises two opposing ends each of which are soldered to one of the bores for making electrical contact with the ground conductor track.
In an embodiment, the contact tongue is integrally connected to the metallic housing.
In an embodiment, the contact tongue is frictionally received in the cutout.
In an embodiment, the contact tongue comprises a pair of contact element spaced apart by a predetermined spacing. The wire bridge comprises a wire having a diameter. The spacing between the contact elements is about equal to that of the diameter of the wire so that the contact elements extend through the cutout and past the wire bridge and so that the wire bridge is frictionally accommodated between the contact elements.
In an embodiment, the cutout extends transversely across the wire bridge at an angle so that despite the fact that the spacing between the contact elements is about the same as the diameter of the wire, the wire is frictionally accommodated between the contact elements.
In an embodiment, the contact elements may mar the wire.
In an embodiment, the angle is less than 90 degrees.
In an embodiment, the angle ranges from about 30 degrees to about 60 degrees.
In an embodiment, the contact elements comprise flat plugs arranged in a side-by-side fashion with narrower sides of the flat plugs facing each other. Further, the flat plugs each comprise a distal end which is tapered or slanted to form a V-shaped gap for receiving and guiding the wire bridge between the flat plugs or contact elements.
This way of achieving the object according to the present invention is based on the critical consideration that in producing a pluggable printed board assembly a specific production technology is used for fitting the printed circuit board with components and for their electric connection, whereas the production of the ground contact itself requires further mounting steps in the case of conventional realization, which differ therefrom technologically and are therefore cost intensive.
This technological discontinuity in the production process is avoided by the solution according to the invention. Part of the ground conductor is a wire bridge which is connected in a mechanically reliable fashion to the printed circuit board of the pluggable printed board assembly. In the mounting of the printed circuit board, said wire
Gandhi Jayprakash N.
Schiff & Hardin & Waite
Siemens Aktiengesellschaft
Tran Thanh Y.
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