to fig1 a support bracket 12 which includes a pair of parallel horizontal flanges 13 and 14 extends from and is integral with cylinder 9 flanges 13 and 14 respectively support sets of three freely rotatable pulleys 15 and 16 cables 17 18 and 19 are passed over respective pulleys of each of sets 15 and 16 and are anchored at first ends to the base of column 1 the cables extend through the interior of the support member 6 with cable 19 passing over a pulley 21 at the end of support member 6 disposed within column 4 pulley 21 rotating about a horizontal axis the second end of cable 19 is affixed to the upper end of column 4 the structure of the columns 1 2 3 and 4 which permits this arrangement and particularly the location of pulley 21 may best be seen from fig5 the cable 18 is passed over a pulley 22 which freely rotates about a vertical shaft within member 6 and continues about a pulley 23 which is mounted for free rotation about a vertical shaft within support member 5 cable 18 thereafter passes around a freely rotatable pulley 24 at the end of support member 5 disposed within column 3 and the second end of cable 18 is affixed to the top of column 3 similarly the cable 17 is passed around a pulley 25 coaxial with pulley 22 then around a pulley 26 coaxial with pulley 23 along the interior of support member 5 about a pulley 27 located at the end of member 5 disposed within column 2 and the second end of cable.