Patent ID: 8083572

Claim:
A method of forming an engagement peripheral ridge ( 120 ; 130 ) on the edge face ( 103 ) of a lens ( 100 ) mounted to rotate about a first axis of rotation (A 2 ), the engagement peripheral ridge ( 120 ; 130 ) presenting a rear flank ( 122 ; 132 ) situated beside the rear face ( 102 ) of the lens ( 100 ) and a front flank ( 121 ) situated beside the front face ( 101 ) of the lens, the method being characterized in that it comprises: a) manually or automatically selecting either a first machining tool ( 55 ) provided with a ridging groove ( 57 ) or a second machining tool ( 70 ) presenting a first working face ( 72 ) that is a surface of revolution about a second axis of rotation (A 4 ) and that possesses a working generator line ( 73 ) that is inclined at all instants during machining relative to the first axis of rotation (A 2 ); and b) the following conditional step: if the first machining tool ( 55 ) is selected, forming the engagement peripheral ridge on the edge face of the lens with the front and rear flanks of the engagement peripheral ridge being machined on the edge face of the lens by reproducing the shape of the ridging groove ( 75 ); or if the second machining tool ( 70 ) is selected, machining the edge face ( 103 ) of the lens ( 100 ) by means of the first working face ( 72 ) of the second machining tool ( 70 ) to form the rear flank ( 122 ; 132 ) of the engagement peripheral ridge ( 120 ; 130 ), the front flank ( 121 ) of the engagement peripheral ridge ( 120 ; 130 ) being formed on a peripheral portion ( 121 ) of the front face ( 101 ) of the lens and presenting continuity of at least first order with the remainder of the front face, without any machining of said peripheral portion or with machining of said peripheral portion causing an edge ( 142 ) to appear presenting discontinuity of second order.