Abstract: A drafting board having a planar top surface with a peripheral depression. A thin, resilient, cover sheet is removably secured to the top surface by a pressure-sensitive adhesive and extends into the peripheral depression where it is retained by a peripheral retaining rim extending about the panel below the plane of the working surface. The parts are structurally related so that the cover sheet slopes gradually downwardly into the depression without lifting or bulging along the outer limits of the panel's top surface. Replacement of the cover sheet is achieved by removing the retaining rim, stripping away the old cover sheet, adhesively securing a replacement cover sheet, and securing its border within the depression by re-mounting the retaining rim.

Abstract: A filter assembly for filtering air comprises a filter housing and a filter which is removably positioned within the housing. The filter housing includes spaced-apart first and second housing portions which are connected by connecting members on opposite sides of the housing, and the filter is positioned between the two housing portions. One end of each of the connecting members is secured to the first housing portion, and the other end of each connecting member is connected to the second housing portion in a manner which permits the second housing portion to be moved along the connecting members toward and away from the first housing. When the second housing portion is moved away from the first housing portion, the filter can be removed.

Abstract: An inflatable pad combined with an air control system for producing periodic inflation and deflation of that pad. The pad is elongated and has at least two separate passages extending from one end portion of the pad to the other, such passages also having interlaced transverse portions extending in directions across the pad. Each passage has a pair of terminal openings, one at each end of the pad, for the flow of air under pressure, such flow being controlled by a valve which not only alternates in directing air to inflate one passage and then the other, but also alternates the direction of inflation so that each passage is inflated alternately from its opposite ends. In one embodiment, the valve operates to positively exhaust one passage while the other is undergoing inflation, the exhaust air being recirculated and utilized by the compressor which serves as the source of pressurized air.

Abstract: A self-aligning swivel caster for use on carts and the like, the caster being equipped with a member for locking and releasing the caster with respect to swivel movement. The locking and releasing member, which can selectively be oriented in an operative or an inoperative position, is friction and gravity actuated. The structural relationship of the caster and the member is such that automatic camming and actuation of the member occurs as the caster is swiveled from an unlocked position into a locked position or from a locked position into an unlocked position. During actuation of the locking and releasing member, the caster makes direct contact with the member until the member finally drops into the proper position to either restrict or facilitate further swivel movement of the caster.

Abstract: A fume hood is provided with seal strips to prevent or inhibit leakage of air through the sash clearance opening at the top of the hood. A front seal is mounted on the rear wall of the auxiliary air chamber and essentially engages the front surface of the sash when the sash is partially or completely raised, and a rear seal is mounted on the front wall of the working chamber and essentially engages the rear surface of the sash when the sash is raised. If desired, either or both of the seals can have a width sufficient to extend all the way across the sash clearance opening when the sash is lowered to seal the sash clearance opening.