Pressure relief valve unit

Claim 1

A pressure relief valve unit for automatically relieving a container of excessive pressure of gas developing therein, comprising a housing having an internal chamber, a pipe nipple extending from one end of the housing for coupling the unit to the container, the nipple defining an inlet passage to the chamber for conducting pressurized gas from the container into the chamber, a valve seat defined about the inner end of the passage at its juncture with the chamber, a valve movable axially in the chamber relative to the seat, a spring biasing the valve to a closed condition upon the seat, the valve being movable from its seat upon development of a predetermined pressure of gas in the pipe nipple, and an escape tube depending from the underside of the housing defining a relief passage communicating the chamber with atmosphere; wherein the chamber is axially aligned with the inlet passage and is of a greater diameter, a group of circumferentially spaced ribs extend lengthwise of the wall of the chamber and depend radially for guiding the valve as it is moved relative to the seat, the ribs defining between each other radially recessed areas having direct communication with the relief passage of the escape tube, and the recessed areas having direct communication with the inlet passage upon unseating of the valve, wherein the housing has a rear closure wall provided with a sleeve extending axially forwardly into the chamber, and the valve has a circular head that is engageable with the seat and is provided with a rearwardly extending stem slidably received in the sleeve; and wherein a plug closure is frictionally engageable in the tube for closing the relief passage, the plug closure when in closed position being adapted under pressure of fluid entering the chamber to drop out of the relief passage, the plug closure having when in closed condition a position entirely within the tube, and lost motion hinge means connected with the plug closure within the tube adjacent a bottom open end of the tube which allows movement of the plug closure from a position closing the passage to a position depending externally of the bottom end of the tube.