Abstract: A recirculation device for recirculating a selected volume of preheated gas exhausted from a heating chamber in a mixture with fresh air back to the heating chamber. The device comprises a first passageway having an entrance and a pair of exits; a second passageway having a pair of inlets and an outlet; and a third passageway connecting one exit and one inlet. The other exit communicates with a preheated gas exhaust, and the other intake communicates with a source of fresh air. A back pressure damper is secured adjacent the other exit. A manual control assembly is connected to the back pressure damper so that the volume of preheated gas flowing into the preheated gas exhaust may be selectively determined. A mixing damper is secured adjacent the other intake. An automatic temperature dependent control assembly is connected to the mixing damper so that the mixture of preheated gas and fresh air entering the heating chamber is dependent upon the temperature in the heating chamber.

Abstract: The present invention provides apparatus and a process for manufacturing a bio-oxidation and nitrification module useful in treating sewage and industrial wastewater. Paired thermoplastic flat sheet and corrugated sheet are nested in a cradle and advanced beneath a bank of ultrasonic welders to produce a sonic weld along those interfacial zones of the sheets which are in contact. Welded units of flat and corrugated sheets are stacked to a height equal to the height of the module and the edges of opposite sides of the stack are softened by heated platens to form an edge-seam which bonds the welded units together to form the finished module.

Abstract: A portable, electrically energized, cordless grass trimmer device is disclosed having a rotatable hub which is adapted to alternatively mount, for substantially balanced rotation therewith, a flexible cutter strip and a line cutter and mechanical counterbalance.

Abstract: A seismic communications system including a central control and recording station and a plurality of remote data acquisition stations, the stations being approximately in line and connected to each other by one or two transmission lines. One line is all that is necessary if the central station is at one end of the line of stations; however, if the central station has some acquisition stations upstream and some downstream therefrom, two lines are required. Coded central strobe bursts put on a transmission line at the central station successively cause insertion of digital seismic data from successively more remote acquisition stations, the data being time slotted after each central station strobe burst so that reverse transmissions do not interfere with subsequent signal propagations emanating from the central station. Twin lead is preferably used for the transmission lines. Power shut down, except for a pilot receiver, is accomplished at each acquisition station between recording cycles.

Abstract: A high contact density circular connector capable of receiving, indexing, and fixedly holding a multi-element probe tip used to test the quality of tapered fastener holes. The outer surface of the probe tip has a multiplicity of conductive segments, which are covered by a thin layer of insulation at the end to be inserted into the holes being inspected. When the probe tip is inserted into a hole, capacitors are formed between the conductive segments on the probe tip and the metallic walls of the hole, which can be measured for value and correlated in a computer to disclose hole characteristics such as size, shape, and smoothness. The circular connector is the means by which probe measurements are transferred from the tip into a coaxial cable, for transmission to the electronic processor without molesting the minute capacitance measurements.