Linear actuator

A linear actuator comprising:

• upper and lower frame portions vertically movable relative to one another along a central axis;
• an elongated first band wound in helical form about said central axis;
• an elongated second substantially flat band wound about said central axis, with its turns substantially transversely parallel to said central axis;
• said first band having a stored portion where said stored portion is separate from said second band, and a column portion where said column portion engages said second band;
• said second band having a stored portion where said stored portion is separate from said first band with its turns nested within one another, and a column portion with its turns forming a helix around said central axis and generally equally radially spaced therefrom, and where said column portion engages with the column portion of said first band to form a wall of a vertical column;
• said column portions of said first and second bands each having an end attached to one of said upper and lower frame portions;
• a horizontal guide member carried by the other one of said upper and lower frame portions than that to which said ends of said column portions of said first and second bands are attached, said horizontal guide member horizontally guiding turns of said second band between said stored portion and said column portion;
• a second band load-bearing member carried by one of said upper and lower frame portions, said second band load-bearing member vertically engaging said second band column portion for vertically displacing the load of said column;
• and
• a powered activation mechanism carried by one of said upper and lower frame portions that causes rotation of:
• said horizontal guide member relative to said first and second bands, to selectively extract and retract said column.