Transmission mechanism with parallel transmission systems including one way clutches, one being lockable

A transmission mechanism comprising:

• an input shaft;
• an output shaft;
• a first on-off clutch;
• a second on-off clutch;
• a first one way clutch;
• a second one way clutch;
• a first gear train having a first reduction gear ratio;
• a second gear train having a second reduction gear ratio smaller than said first reduction gear ratio;
• a third gear train having a third reduction gear ratio smaller than said second reduction gear ratio;
• a fourth gear train having a fourth gear reduction gear ratio smaller than said third reduction gear ratio;
• a first synchronizer which connects said input shaft and said output shaft via a series connection of said first on-off clutch, said first one way clutch, and said first gear train when said first synchronizer is shifted to a first side of a neutral position thereof so as to transmit rotational power from said input shaft to said output shaft in a normal rotational direction and which connects said input shaft and said output shaft via a series connection of said first on-off clutch, said first one way clutch, and said third gear train when said first synchronizer is shifted to a second side of said neutral position so as to transmit rotational power from said input shaft to said output shaft in said normal rotational direction;
• and a second synchronizer which connects said input shaft and said output shaft via a series connection of said second on-off clutch, said second one way clutch, and said second gear train when said second synchronizer is shifted to a first side of a neutral position thereof so as to transmit rotational power from said input shaft to said output shaft in said normal rotational direction and which connects said input shaft and said output shaft via a series connection of said second on-off clutch, said second one way clutch, and said fourth gear train when said second synchronizer is shifted to a second side of said neutral position of said second synchronizer so as to transmit rotational power from said input shaft to said output shaft in said normal rotational direction.