Electricity: electrical systems and devices – Discharging or preventing accumulation of electric charge – Specific conduction means or dissipator
Reexamination Certificate
1999-11-30
2002-04-09
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Discharging or preventing accumulation of electric charge
Specific conduction means or dissipator
C361S212000
Reexamination Certificate
active
06370003
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to electrostatic charge resistant apparatuses and specifically to an electrostatic charge resistant instrument system comprising at least one instrument, a lead extending from the instrument and at least one connector associated with the lead.
2. Background of the Prior Art
Electrostatic charges tend to build up on instruments comprised of insulative materials. In certain work environments an electrostatic discharge (ESD) of charges built up on an insulative member can destroy a workpiece. In the electronics manufacturing industry, electrostatic discharges of charges built up on insulative bar code scanners have been observed to destroy sensitive electrical components such as semiconductor chips. In other work environments, particularly those containing flammable materials, electrostatic discharge of charges built on insulative instruments have been observed to cause fires.
Attempts have been made in the prior art to counter problems of electrostatic discharges from components operating in a “clean room” working environment. In one method for countering electrostatic charge build up, a spray-on conductive film is applied to numerous components of an instrument system. This approach exhibits numerous limitations. First, the conductive film tends to leave a residue on the hands of an operator working with the various components the film is applied to. Second, the conductive film tends to wear off of the components, breaking the conductive path intended to be created by the application of the film. Finally, secure electrical connections between the surfaces of various components are difficult to achieve using conductive film.
There is a need for an electrostatic charge resistant instrument system that does not utilize “spray-on” conductive film, and that provides durable resistance to electrostatic charge build up that does not diminish over time.
SUMMARY OF THE INVENTION
According to its major aspects and broadly stated the present invention is an electrostatic charge resistant instrument system comprising at least one instrument, a lead extending from the instrument, and at least one connector associated with the lead. In accordance with the invention, each component of the instrument system is made to have an electrically grounded conductive outer surface to the end that the instrument system is substantially comprehensively resistant to electrostatic charge build up.
A lead of the system can be made to have a conductive outer surface by forming about the lead a flexible conductive housing. A flexible conductive housing is readily provided by at least one small-diametered wire arranged to encircle the lead a plurality of times in a spiral, mesh or braided mesh configuration.
Conductive outer surfaces of instruments and connectors, meanwhile, may be provided by forming the instruments and connectors of the system from conductive polymeric materials containing a polymeric base material and conductive fibers and or particles embedded therein.
According to a preferred manufacturing scheme for making the invention, a connector is formed on a lead by first forming an elongated conductive flexible housing on a lead and then overmolding a conductive material directly onto the lead conductive housing during the formation of the connector. This manufacturing scheme establishes a secure mechanical connection and good electrical contact between the conductive outer surfaces of the connector and the lead.
Preferably, a conductive outer surface-to-ground electrical connection is provided for each component of the system. An instrument outer surface-to-ground electrical connection may be provided by a ground spring connecting the interior wall of an instrument with a ground conductor of an instrument printed circuit board. Lead and connector outer surface-to-ground electrical connections may be formed by routing an internal ground connector from the interior of the lead to the lead exterior, crimping the ground connector to the conductive outer surface of the lead with use of a crimping ring, and overmolding the connector housing over the ground connector and crimping ring.
These and other details, advantages, and benefits of the present invention will become apparent from the detailed description of the preferred embodiment herein below.
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Jackson Stephen W.
Wall Marjama & Bilinski LLP
Welch Allyn Data Collections, Inc.
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