Abstract: A power operated surfboard which has a raised rear hollow portion at the rear in which is disposed an impeller housing having an impeller therein and a water discharge passage extending rearwardly from the housing. An internal combustion engine is supported above the impeller housing and has a short vertical axis connected to the impeller which rotates about a vertical axis. Surrounding the impeller housing is an exhaust gas housing which communicates with the exhaust gas passage of the engine and with a discharge chamber beneath the floor of the surfboard. The exhaust gas housing is gas tight and provides a gas cushion which retards the entrance of water through the discharge chamber into the exhaust passage of the engine, when the surfboard is not being operated. This is aided by a flexible valve disposed at the discharge outlet of the discharge chamber to retard the entrance of water into the discharge chamber.

Abstract: An air purifier which includes an air intake with electrically charged plates for ionizing particles of smoke, dust, and impurities entrained in the air, a fan or other air-moving device to move the polluted air through the intake and over the ionizing plates and to discharge the air against a collector which is spaced from the charged plates and is electrically grounded and upon which the ionized pollutants will deposit, and an air outlet through which the purified air can be discharged, leaving the pollutants behind on the collector element.

Abstract: An axial flow pump structure utilizing an impeller of improved design, constituting essentially a propeller blade delivering forces to the fluid either gaseous or liquid being pumped in both axial and centrifugal modes. The blade is an evolute wherein the evolute is defined as the path on a sphere traced out by a point starting at longitude 0.degree. latitude (90 minus .alpha.).degree. and having at any time the position longitude .phi..degree. latitude (90 minus X).degree., where .phi. and X are given as functions of .theta. by Cos X = Cos .alpha. Cos (.theta. Sin .alpha.);Cox (.theta. - .phi.) = tan .alpha. cot X and;.theta. increases from zero to (90 cosec .alpha.).degree. as the evolute descends to the equator of the sphere.