Abstract: A single ended turbomolecular vacuum pump operable in the free molecular flow pressure range having an improved bearing assembly between the motor rotor and the pump rotor discs is disclosed. The improved bearing assembly which is of the "plain" or "sleeve" liquid lubricated type has a relatively high ratio of journal diameter to bearing axial length. The improved bearing assembly is characterized by improved heat transmission capabilities, high tolerance for misalignment and long life.

Abstract: A unique gerotor-type pump is disclosed for pumping gases. The pump has an inner gear-type rotor mounted within and rotating off-center with respect to an outer gear-type rotor ring, about a parallel axis. Surfaces of the teeth of the inner rotor are in continuous contact with the outer rotor to define at least one pumping chamber which alternately expands and contracts as the inner and outer rotors turn. An elongated inlet port is positioned to communicate with the pumping chamber during a substantial portion of the cycle when the pumping chamber is expanding, (the intake cycle) and an outlet port is positioned to communicate with the pumping chamber only just prior to and at the end of the contraction or exhaust cycle. Oil for sealing and lubricating between moving parts of the pump is provided by employing differential pressure created by the pump's own operation to draw oil through passageways which communicate between an oil reservoir and the pumping chamber.

Abstract: A back-flow prevention valve assembly is disclosed for use with a vacuum pump or the like and employs a valve element movable between positions opening or closing a passageway through the assembly. In the event of pump failure, a control valve, which is operated by fluid from the pressure side of the pump, vents ambient air behind the valve element to assist it in moving rapidly to the closed position to prevent backflow. After resumption of pumping, a controlled withdrawal of ambient air behind the valve element delays opening of the valve until the pump has created a sufficient vacuum to minimize influx of air upstream when the valve opens.

Abstract: A teaching machine system for displaying selected frames from a multiple-frame film strip wherein instructional material is contained on a first portion of each frame and code indicia including an excursion instruction is contained on a second portion of each frame. The code indicia associated with a frame being displayed render selected answer keys operative whereby a student selects an answer, and establish an initial counting state in a counter, which is counted down as the frames of the film strip pass a projection gate in proceeding to the next frame to be viewed. When the counter reaches a predetermined minimum counting state, dependent on the particular answer key selected by the student, the film strip is stopped and the next frame is viewed. An alternate mode of operation is provided wherein fixed excursions of a predetermined number of frames occur for each answer key. A dynamic reading method is employed for reading code indicia on the film strip to reduce the number of photodetectors required.