Abstract: A sliding door operator comprises a tubular housing adapted to receive first and second elongated bars in a spaced apart and parallel arrangement. Both bars include a gear-toothed rack engaged by a single motor driven gear. An end of one bar is secured to the door and an end of the other bar is secured to a wall structure. A bracket secured to the door includes registering apertures adapted to mate with a bore in the end of one of the bars so that the bar can be detachably locked to the door by a locking pin. The other bar also includes a bore adapted to mate with the aperture in a channel bracket secured to the stationary wall structure to receive a removable locking pin therethrough. In addition, the operator includes a locking mechanism for locking the bars in a fixed position with respect to each other.

Abstract: A back pressure inducer and check valve is disclosed for use with a fluid system having inlet passageway, an outlet passageway and in which fluid flows from the inlet and to the outlet passageway. The back pressure inducer comprises a valve seat secured to the system and having a fluid port fluidly between the inlet and outlet passageways. A valve member is movable between a closed and open position to variably open the fluid port while a spring urges the valve member towards its closed position. Cooperating conical surfaces on the valve member and valve seat form an annular passageway when the valve member is in its open position to produce controlled pressure drops between the inlet and outlet conduit over a wide range of fluid flow rates.

Abstract: A wallboard fastener comprising a flat base portion, an elongated tongue portion coplanar with the said base portion, a pair of flanges extending substantially normal to said base portion on opposite sides of the said tongue portion and a pair of impaling flanges mounted to said flanges so as to extend over and substantially parallel to the base portion. The improved construction of the fastener of the present invention includes an aperture in the base portion as well as in the tongue portion and separate ribs are provided for the base portion and the tongue portion so that the tongue portion is severable from the base portion without deforming the rib structures. Preferably, the fastener includes an additional rib structure disposed across the interspace between the ribs in the base portion and the ribs in the tongue portion, and which is offset from the ribs of both portions.