Abstract: A variable resistance device and an abdominal exercise apparatus. The device includes at least first and second resilient stages to provide a combined resistance effect. The first resilient stage has a lower coefficient of elasticity than the second resilient stage. In this way, when a user lies on the base of the apparatus and pulls on the yoke a first resistance is experienced by virtue of thin cords until a strap reaches its full length and a second resistance is experienced by virtue of thick cords.

Abstract: A rotary piston machine with a housing forming a prismatic cavity with a cavity wall. The cross section of the prismatic cavity is a cavity oval. A rotary piston is guided for rotary movement in the cavity. The rotary piston moves in consecutive intervals of motion from one blocking position to an adjacent end position. The rotary piston, during the consecutive intervals of motion rotates, in the same rotational direction, alternatingly about one of two different axes. A transmission arrangement transmits the rotary motion about two axes. When the rotary piston reaches a blocking position, there is an associated larger diameter cavity circular arc, in which the larger diameter piston circular arc was slidingly guided during the preceding interval of motion.

Abstract: A housing assembly includes first and second sides and first and second panels spaced apart from each other by an interior of the housing and traversing the first and second sides. A first porous desiccant retention plate and a second porous desiccant retention plate are spaced from each other are secured within the housing so as to define a desiccant chamber therebetween for maintaining the desiccant medium. An opening is formed within one of said panels in a location corresponding to the location of the desiccant chamber, facilitating replacement of the desiccant medium within the desiccant chamber.

Abstract: A non-metallic laboratory jack comprises two oppositely disposed reinforcing elements having I-beam cross-sectional configuration disposed in the central elevational region of the jack; a base position below the reinforcing elements and a load-bearing platform positioned above the reinforcing elements and a plurality of pairs of cross links. A rotatable threaded shaft associated with the reinforcing elements.