Synchronizing mechanism for shifting clutches

A synchronizing mechanism for clutches, particularly for manual gearboxes for motor vehicles, comprising:

• a rotatable shaft defining an axis;
• a guide sleeve fixed to said shaft and being provided with a first external toothing;
• a pinion rotatably seated on said shaft adjacent said guide sleeve;
• a clutch body rigidly connected to said pinion to rotate therewith and provided with a second external toothing;
• a gearshift sleeve surrounding said guide sleeve and provided with an internal toothing engaging said first external toothing;
• and
• a synchronizer ring arranged between said guide sleeve and said clutch body, said synchronizer ring engaging circumferentially said gearshift sleeve in a form-locking relationship therewith for allowing its limited rotation and further circumferentially engaging said clutch body in a frictional relationship;
• said gearshift sleeve including first coupling teeth provided internally thereon and arranged to be brought into engagement with said second external toothing upon axial displacement of said gearshift sleeve, said first coupling teeth having a first axial length and being provided at their axial ends with first wedge faces inclined at a first angle with respect to said axis;
• said second external toothing forming second coupling teeth provided at their axial ends facing said gearshift sleeve with second wedge faces inclined at said first angle with respect to said axis;
• said gearshift sleeve including first locking teeth provided internally thereon in a circumferentially offset position with respect to said first coupling teeth and having a second axial length smaller than said first axial length, said first locking teeth being provided with third wedge faces facing towards a first axial direction and being inclined at a second angle with respect to said axis, said first locking teeth being further provided with first cut-back flanks adjacent said third wedge faces, said first cut-back flanks facing towards a second axial direction and extending parallel to said first wedge faces;
• said synchronizer ring including second locking teeth provided externally thereon, said second locking teeth having fourth wedge faces facing towards said second axial direction and being inclined at said second angle with respect to said axis, said second locking teeth being further provided with second cut-back flanks adjacent said fourth wedge faces, said second cut-back flanks facing towards said first axial direction and extending parallel to said first wedge faces;
• said third wedge faces contacting said fourth wedge faces upon axial displacement of said gearshift sleeve during gearshift until attainment of synchronism with a rigid frictional connection established between said synchronizer ring and said clutch body, said third wedge faces clearing said fourth wedge faces upon further axial displacement of said gearshift sleeve to bring said first and second cut-back flanks in contact with each other and slide on each other until contact of said first and second wedge faces with said frictional connection is still established.