shaped notch 350 formed therein in other preferred embodiments the v shaped notch may have different geometric shapes 0117 fig2 a 25c show clip 132 preferably made of a flexible material such as metal the clip 132 is fastened over the outer surface of tube 122 fig2 a for holding an end of cord 134 securely fastened to the tube 122 0118 fig2 a and 26b show tube 122 having an outer surface 346 with elongated grooves 348 formed therein in certain preferred embodiments the tube has one elongated groove in other preferred embodiments the tube has two three or more elongated grooves 0119 fig2 a and 27b show pulley 266 having teeth 284 and a square shaped opening 267 formed at one end thereof as noted above the square shaped opening 267 is adapted to receive the square shaped outer surface of the drive shaft so that the pulley 266 and drive shaft rotate simultaneously with one another referring to fig2 b the opposite end of pulley 266 includes an annular opening 269 adapted to engage the outer surface of stub shaft 226 fig1 a 0120 fig2 a 28c show retainer 270 including inwardly projecting teeth 272 the retainer 270 has a curved surface 290 in certain preferred embodiments the retainer 270 includes a substantially convex surface 291 opposite the curved surface 290 0121 fig2 shows the power assembly 144 of fig1 a coupled with tube 122 by drive shaft 138 the tube 122 has an opening at a right end thereof and a drive plug 136 inserted in the opening the tube is supported by a first cradle 116 and a second cradle 118 the cradles include bearing surfaces.