Apparatus and method for neutralizing static electric charges in sensitive manufacturing areas

In a clean enclosure having provision for supplying virtually particle free air to sensitive manufacturing areas and the like, a filter bank comprising at least one high efficiency particulate air filter, and blower means for circulating air through said bank and into said enclosure, the improvement therein comprising means for concurrently generating both positive and negative ions in the airstream and such that the ions are able to rapidly neutralize static electricity on objects in or brought into the enclosure, said ion generating means including

• at least one cooperating pair of electrodes mounted immediately adjacent said filter bank with each cooperating pair of electrodes being spaced apart from each other a distance of between about six to twelve inches in a direction extending generally parallel to the adjacent face of said filter bank and having an intervening airspace therebetween which is free of any electrically conductive components, and each of said electrodes including a plurality of needle-like electrically conductive projections, and
• means for supplying a positive direct current voltage to one of the electrodes of each pair, and a negative direct current voltage to the other electrode of each pair, with the magnitude of the supplied voltages being sufficient to cause the electrodes to interact and cooperate in drawing ions from each other, whereby both positive and negative ions may be concurrently generated in the airstream moving into said enclosure.

In a clean room having provision for supplying virtually particle free air to sensitive manufacturing areas and the like, and including a room like enclosure, a filter bank disposed within said enclosure and including a supporting framework defining a plurality of open areas, a plurality of high efficiency particulate air filters mounted on said framework with one of the filters covering each of the open areas, and blower means for circulating air through said bank and to a manufacturing area disposed in the remainder of said enclosure, the improvement therein comprising means for concurrently generating both positive and negative ions in the airstream delivered to the manufacturing area and such that the ions are able to rapidly neutralize static electricity on objects in or brought into the manufacturing area, said ion generating means including

• a plurality of cooperating pairs of electrodes mounted to said supporting framework and immediately downstream of said filter bank, with each cooperating pair of electrodes being laterally spaced apart from each other in a direction extending generally parallel to the adjacent face of said filter bank and thus transversely to the direction of the moving airstream and having an intervening airspace therebetween which is free of any electrically conductive components, and each of said electrodes including a plurality of needle like electrically conductive projections which extend toward the cooperating electrode, and
• means for supplying a positive direct current voltage to one of the electrodes of each pair, and a negative direct current voltage to the other electrode of each pair, and with the lateral spacing of said electrodes of each pair and the voltages supplied to said electrodes being coordinated so that the electrodes of each pair interact and cooperate in drawing ions from each other, and such that both positive and negative ions may be concurrently generated in the airstream moving into the manufacturing area of said enclosure.

A method for delivering virtually particle free air to a sensitive manufacturing area and for rapidly neutralizing static electricity on objects in or brought into the area, and comprising the steps of

• moving an airstream through high efficiency particulate air filtering means to remove substantially all particulate matter therefrom,
• passing at least a substantial portion of the filtered airstream between a pair of electrodes, with the electrodes being positioned immediately downstream of the filtering means and spaced apart from each other in a direction extending transversely to the direction of the airstream and having an intervening airspace therebetween which is free of any electrically conductive components, and with each of said electrodes including a plurality of needle-like electrically conductive projections, and
• supplying a positive direct current voltage to one electrode and supplying a negative direct current voltage to the other electrode, with the magnitude of the supplied voltages being sufficient to cause the electrodes to interact and cooperate in drawing ions from each other, and so as to concurrently generate both positive and negative ions in the airstream, and
• directing the filtered airstream and entrained positive and negative ions to the manufacturing area.