Abstract: A method and apparatus for cleaning workpieces, particularly printed circuit boards upon which electrical components have been soldered, is capable of using a potentially flammable or explosive liquid cleaning solvent. In one embodiment, there are two immersion wash stages between which is a spray wash stage. The spray wash stage is formed as a closed chamber which is sealed when the immersion wash stages by liquid seals. To reduce the danger of fire or explosion in the spray wash stage an inert gas such as Nitrogen is introduced into the closed chamber. In another embodiment the spray nozzles are immersed in liquid solvent in a combined immersion/spray wash stage. This reduces atomization of the flammable solvent further reducing the danger of fire or explosion.

Abstract: The apparatus employs a method for accurate, reproducible analytical solution evaluation eliminating the need for a reference sensor by determining the activity of selected species employing species specific sensors and species combination sensors in conjunction with Nernst-type equations. The apparatus includes sensor structures for elimination of edge effects to signals thereby yielding accurate, reproducible measurements, and a cartridge structure adapted to incorporate an array of the new sensors for employment of the new method where the cartridge is particularly adapted for miniaturization, maintaining a fixed volume of solution for analysis and providing an anaerobic testing environment. Lastly, a compact instrument embodying miniaturization especially adapted for field use and use of the cartridge is provided herein.

Abstract: Apparatus for liberating particulate material from a compressed bale and feeding the liberated material at a controlled rate to a processing station comprises a screw conveyor and means for compacting the particulate material against the conveyor screw.