Abstract: An improved chair frame and method of fabrication is disclosed in which an extremely rigid uniframe chair construction can be assembled from a variety of components fabricated out of sheets of plywood. The chair frame includes a base frame assembly having a one-piece D-shaped base plate upon which one or more side plates may be stacked and secured to achieve the desired base frame assembly thickness. The chair frame also includes a back frame assembly having a pair of back posts and a pair of front posts secured to the base frame assembly. A top rail interconnects the rear posts and a pair of arm rails interconnect the front posts and the rear posts. The various components of the chair frame are interconnected with mechanical joints to further enhance the strength and structural rigidity of the chair frame.

Abstract: A cryogenic device comprises a vessel to be maintained at a cryogenic temperature. The vessel is mounted on a storage tank in a pressure Eight relationship. Cryogenic fluid under pressure is forced into the vessel through a transfer tube. The temperature in the vessel is controlled by flow of cryogenic fluid through the vessel. A throttle valve in a line leading from the cryogenic vessel regulates the cryogenic fluid flow in relation to a sensed temperature in the vessel.

Abstract: A single stage, twin piston cryogenic refrigerator for cooling supercondung devices. The refrigerator uses helium as the heat transfer medium and is constructed with two nested, concentric pistons, an inner piston and an outer piston, mounted in a cylinder and driven 90.degree. out of phase by a common crankshaft. The inner piston extends through and below the outer piston and is received in a stationary insert mounted in the cylinder. The outer piston has a first piston face which forms a compression space with the stationary insert while the inner piston has a second piston face which forms an expansion space with the cylinder and the insert. The inner piston is formed with upper and lower piston halves joined by a flexible joint positioned in the compression space. Cylindrical regenerator gaps are present at the interface of the inner piston with the stationary insert and at the interface of the stationary insert with the cylinder.

Abstract: A simply constructed low input power cyclic cryogenic refrigerator suitable or cooling superconducting quantum interfering devices (SQUID) and similar instruments is provided. A Stirling machine having a multistage displacer and a piston as its only essential moving parts, with helium gas as the working fluid, achieves and maintains a temperature of substantially 8.5.degree. K. The working cylinder and displacer are separated by a tube and are fitted together precisely at steady-state operation rather than at room temperature. The displacer preferably is made of nylon and its cylinder of an epoxy-glass composite to provide the nearly optimum clearance required to maintain the 8.5.degree. K. temperature for continuous periods on the order of several weeks.