Pressure and thermal relief valve for fuel tank

In a cap for closing a fuel tank filling and venting tube;

• said cap being of the type having a main body with a central axial opening and means for detachably engaging said tube, and a pressure relief valve;
• said valve having a valve plug positioned outwardly of said opening, a stem attached to the valve plug, and biasing means for exerting an axial, inward force on the stem to put the stem in tension and bias the valve plug into a position in which it closes said opening;
• the improvement comprising:
• a first portion of the stem on which the biasing means exerts said inward force, a second portion of the stem attached to the valve plug, one of said first and second portions having a first abutment surface, a deflectable retainer portion of the stem carried by the other of said first and second portions and having a second abutment surface positioned to abut the first abutment surface to transmit axial forces between said first and second portions, and fusible material positioned radially between said other portion and said retainer portion substantially opposite said one portion to prevent said retainer portion from deflecting and to maintain said abutment surfaces in an abutting relationship, to in turn maintain said first and second portions in a force transmitting position relative to each other;
• said biasing means being resilient to allow the stem and the valve plug to move outwardly in response to increased pressure in the tank to relieve pressure in the tank;
• and said fusible material being meltable at elevated temperatures exceeding a predetermined level, to allow said retainer portion to deflect, said first and second portions to separate from each other, and the valve plug and said second portion to move away from the opening.

In combination:

• a cap for closing a fuel tank filling and venting tube;
• said cap having a main body with an axial opening, and means for detachably engaging said tube;
• and
• a pressure relief valve comprising:
• a valve plug positioned outwardly of said axial opening and having a vent opening for venting the tank;
• biasing means for biasing the valve plug axially inwardly into a position in which it closes said axial opening, said biasing means having an inner end located axially inwardly of the valve plug and said axial opening;
• a structure forming an interconnection between the valve plug and said inner end of the biasing means;
• said structure including a cage;
• and
• a float positioned in the cage to normally allow venting through said vent opening and to close said vent opening in response to a rising liquid level in the cage;
• said structure including fusible material positioned to maintain said interconnection between the valve plug and said inner end of the biasing means;
• said biasing means being resilient to allow said structure and the valve plug to move outwardly in response to increased pressure in the tank to relieve pressure in the tank;
• and said fusible material being located inwardly of the valve plug and being meltable at elevated temperatures exceeding a predetermined level, to release said interconnection to allow the valve plug to move away from said axial opening.