upper sub rod 11 an upper end of the wire 51 is connected to the key 22 in the through hole 21 of the lower rib collector 30 the wire 51 can be lead into the upper sub rod 11 through the pulley 52 one end of the wire 51 is connected to the key 22 the key 22 may be pushed by the elastomer 23 in the lower rib collector through hole 21 another end thereof is connected to the tenon 54 in the lower sub rod 14 referring to fig4 other than connecting with a plurality of ribs 60 the lower rib collector 30 has a buckle unit 33 the buckle unit 33 includes an inserting bar 36 which vertically passes through the straight through hole 301 in the lower rib collector 30 an elastomer 37 in the straight through hole for elastically moving the inserting bar 36 a positioning pin 38 transversally installed in the lower rib collector transversal hole 302 and operated by an elastomer 39 and a button 34 transversally installed in the lower rib collector transversal hole 303 and operated by an elastomer 35 the inserting bar 38 passes through the positioning pin 38 vertically and the button 34 passes through the lower end of the inserting bar 36 the rear end of the positioning pin 38 is pushed by the elastomer 39 so that the front end thereof is embedded into the positioning hole 111 of the upper sub rod 11 thereby the lower rib collector 30 is fixed to the upper end of the upper main rod 10 moreover the rear end of the button 34 is pushed by the elastomer 35 to protrude out of.