Patent ID: 8550111

Claim:
An overfill prevention device comprising a first tubular member, a cylindrical piston slidably fitted within the first tubular member, a spring arranged within the first tubular member, a first and second O-rings fitted in the first and second neck portions of the piston, a second tubular member having a cylindrical recess open at a top, a plug arranged within the second tubular member, a float rod having a cam plate at an upper end, the cam plate being pivotally mounted to the second tubular member by a pin, a float connected with a lower end of the float rod, a valve body having a lower end engaged with the first tubular member, the improvement comprising that a pinion is pivotally connected to said second tubular member by said pin so that the cam plate and the pinion are rotatable in unison with each other, a toothed rack meshed with said pinion and slidably fitted in and circumferentially enclosed by a protruded block of said second tubular member, said toothed rack having a plurality of teeth each having two convex sides so that said convex sides will be in contact with teeth of said pinion at a point thereby reducing friction between said toothed rack and said pinion and therefore reducing force required for converting rotation of said pinion into linear motion of said toothed rack, so that even though floating force produced by said float in a liquefied gas is small, said float is still able to rotate said pinion to drive said toothed rack, a control rod having an upper end and a lower end, said lower end of said control rod being directly connected with a head portion of said toothed rack to transmit motion of said toothed rack to said control rod, wherein the direct connection between the said lower end of said control rod and said head portion of toothed rack is such that a clearance is present therebetween to allow limited relative movement in a direction non-parallel to the transmission of the motion for making the transmission of the motion easier and without being stuck, said upper end of said control rod extending upwardly into said valve body, said lower end being secured to said toothed rack, a first magnet mounted at said upper end of said control rod, and a gauge mounted on said valve body and provided with a second permanent magnet and a needle operatively connected with said second magnet, whereby when said float is moved, said pinion will be rotated thereby moving said toothed rack and said control rod in unison with said float, so that said first magnet mounted at said upper end of said control rod will be moved up or down in said valve body thereby forcing said second magnet to move and therefore moving said needle to indicate amount of gas remaining in a gas tank.