Abstract: A flue damper is rotated 360.degree. in a predetermined direction in 90.degree. increments to be selectively opened and closed in 90.degree. increments. The incremental rotation is accomplished by a motor driven timing mechanism with power to the motor being controlled by the timing mechanism and a single pole double throw relay.

Abstract: Method of and apparatus for handling a microsample comprising a probe for aspirating a sample and a cleaning mechanism having a passageway within which the probe is movable. The passageway has a cleaning chamber having opposite ends, one end being open to the atmosphere and proximate the sample. The cleaning mechanism further includes a fluid directing means and two vacuum applying means, the vacuum applying means being disposed at opposite ends of the chamber and the fluid directing means being disposed between them. During a cleaning mode the fluid directing means directs a wash fluid against the probe and the vacuum applying means removes the wash fluid, prevents exiting of the wash fluid and drys the probe, the later two by permitting gas from the atmosphere to flow into the cleaning chamber.

Abstract: An improvement is presented for a timing mechanism wherein the closing of a particular circuit results in a high electrical current surge. The rapidity of the circuit closure (made necessary by the current surge) results in contact bounce. A fast drop of a cam follower is provided by a cam having a substantially flat outer periphery and a face which has a steep drop with a gentle curvature. Upon dropping the cam follower, electrical contact arms are engaged which include a coil spring damper to dissipate kinetic energy encountered during contact closure, thereby preventing the contacts from bouncing.