helical blades 20 are provided that are disposed in slots 22 formed in the periphery of the plates 18 the housing b includes a pair of side walls 24 and first and second end walls 26 and 28 the housing b is illustrated in fig1 and fig2 as being of split construction and defined by first and second engaging sections b 1 and b 2 that are either bonded together at their abutting edges or removably secured to one another by fastening means of a conventional design not shown the housing a served to support a prime mover d within the interior of and adjacent of the first closed end 10 the prime mover d in fig1 and 2 is illustrated as an electric motor that is supplied power through a pair of insulated conductors 32 that have a prong plug of conventional design mounted on the free end thereof the plug 34 is adapted to be removably inserted in a domestic outlet not shown the prime mover d is illustrated as including a projecting driving shaft 36 that has a driving gear 38 secured thereto a driven gear 40 is mounted on the shaft 16 and is disposed adjacent of the first end wall 26 of the housing and in alignment with the driving gear 38 first and second idling gears 42 and 44 are provided that have first and second shafts 42a and 44a extending transversely through the centers thereof the first and second shaft 42a and 44a have end portions thereof mounted in interior recesses 26a formed in.