Walk-behind working machine

A walk-behind working machine comprising:

• a motive power source for producing a motive power;
• right and left transmission shafts having outer peripheral surfaces having first grooves formed thereon;
• and
• a clutch for transmitting the motive power from said drive source to said right and left transmission shafts;
• said right and left transmission shafts each having one end, the ends of said right and left transmission shafts having right and left butting surfaces formed thereat, the right and left butting surfaces butting against each other, such that said right and left transmission shafts are disposed in alignment;
• said clutch including:
• a cylindrical member rotationally mounted around the ends of said right and left transmission shafts, said cylindrical member having an inner peripheral surface having second grooves formed thereon;
• and
• balls each disposed within a space defined by said first groove and said second groove;
• said cylindrical member capable of rotating to thereby rotate said right and left transmission shafts by means of said balls;
• said first grooves each having a generally V-shaped configuration and being directed in the direction of rotation of said right and left transmission shafts, said first grooves each having a leading end positioned between the right and left butting surfaces, said first grooves of the generally V-shaped configuration each having a bottom surface and a wall surface continuous with the bottom surface, the bottom surface and the wall surface contacting said ball.