Abstract: A hydroponic irrigation system reduces the time spent actively circulating a nutrient solution through one or more growing beds to provide an ebb-and-flow irrigation cycle. Nutrient solution is pumped from a nutrient tank to each growing bed via a liquid transport unit, having a liquid tube connected to a pump located in the nutrient tank at one end, with the other end anchored in the growing medium in the growing bed. A controller coordinates the operation of the pumps, selectively operating each pump to supply nutrient solution until the growing bed is saturated to a specified depth, after which the pump returns the nutrient to the tank, either passively via gravity or by actively pumping, to drain the nutrient solution from the growing bed back into the nutrient tank. The pumps can be activated sequentially, with the sequence initiated at selected time intervals to suit the plants being grown.

Abstract: A hydroponic irrigation system reduces the time spent actively circulating a nutrient solution through one or more growing beds to provide an ebb-and-flow irrigation cycle. Nutrient solution is pumped from a nutrient tank to each growing bed via a liquid transport unit, having a liquid tube connected to a pump located in the nutrient tank at one end, with the other end anchored in the growing medium in the growing bed. A controller coordinates the operation of the pumps, selectively operating each pump to supply nutrient solution until the growing bed is saturated to a specified depth, after which the pump returns the nutrient to the tank, either passively via gravity or by actively pumping, to drain the nutrient solution from the growing bed back into the nutrient tank. The pumps can be activated sequentially, with the sequence initiated at selected time intervals to suit the plants being grown.

Abstract: A variable pitch propeller has a two part hub assembly, each part of the hub has generally semi-cylindrical half sockets formed therein for receiving the cylindrical blade root shanks of individual fan blades. The sockets have enlarged portions, defining semi-annular shoulders, which receive an enlarged portion of the blade root shank so as to prevent axial movement of the fan blade. The half sockets of at least one part of the hub further have recessed portions for receiving locking insert members having a curved upper surface and a longitudinal keyway formed therein. A radially projecting key extends longitudinally along at least an a portion of the blade root shank and fits into the keyway formed in the locking insert member when the fan blade is placed into the half socket containing the locking insert member. The two parts of the hub assembly are coupled to clamp the fan blades within the aligned half sockets.