Interlock system for a fuel dispensing nozzle

A nozzle for dispensing fuel into a fillpipe of a motor vehicle fuel tank and comprising:

• a. a discharge spout for insertion into a fillpipe of a motor vehicle fuel tank;
• b. a shut-off valve for shutting off fuel being dispensed by the nozzle;
• c. actuating means for closing said shut-off valve in response to fuel backed up into a fillpipe and including a vent line having an open end at the discharge end of the discharge spout, said vent line being supplied with a vacuum such that when gasoline covers the open end of the vent line, the pressure in the vent line drops and the pressure drop may be sensed to actuate said shut-off valve;
• and
• d. interlock means for preventing the dispensing of fuel through the nozzle until the discharge spout of the nozzle is properly inserted in a fillpipe and including a valve means located at the outlet of the vent line at the end of the discharge spout, said valve means having an open position wherein the vent line is open to the atmosphere and a closed position wherein the end of the vent line is sealed closed, and means, responsive to the nozzle being inserted in the fillpipe a predetermined distance and the lower side of the discharge spout being urged against the inside of a fillpipe inlet, for actuating the valve means so that the valve is placed into its open position, thereby permitting the dispensing of fuel.