Patent ID: 6948731

Claim:
A theft-proof bicycle comprising a frame structure consisting of three frame parts, a front ( 2 ) and a rear ( 3 ) slanting frame part and an intermediate transverse part ( 1 ), which are connected so as to form a triangle having a front corner ( 6 ), a bottom corner ( 7 ) and a back corner ( 8 ), where a handlebar stem ( 4 a ) between a handlebars ( 14 ) and a front wheel's supporting fork ( 4 ) is attached to the triangle's front corner ( 6 ), while a rear wheel's supporting fork structure ( 5 a , 5 b ) is attached to the frame structure ( 1 , 2 , 3 ) in the areas of the two other corners ( 7 , 8 ) of the triangle and a pedal crank is arranged at the triangle's bottom corner ( 7 ), characterised in that frame parts ( 1 , 2 ) form the triangle's front corner ( 6 ), and that one of frame parts ( 1 ) or ( 2 ) is designed with a sleeve-shaped end part, through which the handlebar stem ( 4 a ) is passed, which sleeve-shaped end part has a locking part ( 12 ), which projects forwards out of the frame part, with a transverse, through-going aperture for inserting a locking pin ( 13 ), frame part ( 1 ) in the area of front corner ( 6 ) is designed as a two-pronged fork ( 11 ), one prong of which is passed on each side of the handlebar stem ( 4 a ), the ends of the fork's prongs ( 11 a , 11 b ) being equipped with means ( 16 a , 16 b ) for releasable cooperation with the locking pin ( 13 ) in order to form a fixed connection, and the frame structure ( 1 , 2 , 3 ) in the triangle's bottom corner ( 7 ) is equipped with a pivot joint ( 15 ) in order to permit a movement of the frame part ( 1 ) with the two-pronged fork ( 11 ) forward past the handlebar stem ( 4 a ), in the supporting frame's plane, between an operating or cycling position where the locking pin ( 13 ) is inserted in the through-going aperture and a locked position where the locking pin ( 13 ) is attached to the fork's prong ( 11 a , 11 b ) in front of the handlebar stem ( 4 a ).