Fifth wheel coupling

A fifth wheel coupling for connecting a semitrailer to a towing vehicle, comprising:

• two swivel-articulated closing jaws having semicircular clearances for grasping a king pin on the semitrailer;
• means for swiveling the jaws between open and closed positions, comprising:
• a hydraulic cylinder comprising an actuating piston displaceably seated in the hydraulic cylinder and having a piston head defining with the cylinder a piston head space, an actuating piston rod defining with the cylinder a piston rod space, and a channel connecting the piston head space and piston rod space, the piston movable between an outward position in which the jaws are opened and an inward position in which the jaws are closed;
• means for biasing the actuating piston in the inward position;
• a spool valve seated in one end of a central bore in the actuating piston rod and movable between a first position in which the channel is closed and a second position in which the channel is open;
• a tappet seated in the other end of the central bore in the actuating piston rod and protruding into the semicircular clearances so as to be engagable with the king pin, the tappet being movable between a first position in which the tappet actuates the spool valve to its second position channel tappet allows the spool valve to move to its first position closed;
• and
• means for biasing the tappet in the outward position.