Safety shut-off device for gas welding apparatus

A safety shut-off device adapted for use with a gas welding apparatus, the apparatus having a torch handle and a supply of a pressurized combustion reagent, said safety shut-off device comprising:

• (a) at least one plunger valve having a valve seat and a reciprocatable plunger member passing through said valve seat for movement along a line of travel which is parallel to the longitudinal axis of the handle, said plunger valve adapted to be positioned between the handle and the supply of pressurized combustion reagent, said plunger member having an end adapted to be adjacent the handle, and said plunger valve being actuatable between a first state, for operatively connecting the handle to the supply of pressurized combustion reagent, and a second state, for operatively disconnecting the handle from the supply of pressurized combustion reagent, said plunger valve being biased towards said second state and actuatable from said first state to said second state substantially instantaneously;
• (b) a clamp adapted to circumscribe and to be releasably secured to the handle;
• (c) an elongated trigger member having a pivotable end and a free end, said pivotable end being pivotably mounted on said clamp so that said trigger member overlays at least a portion of the handle and lies parallel to the longitudinal axis of the handle to allow said trigger member to be grasped by the user of the gas welding apparatus when the user grasps the handle, and to allow the trigger member to be moved toward said handle;
• (d) a linkage rod having a trigger end portion and a valve end portion, said linkage rod being pivotably attached at its trigger end portion to said trigger member;
• (e) a pressure plate operatively connected to the valve end portion of said linkage rod, and rotatable about an axis which is at a right angle to the longitudinal axis of the handle, said pressure plate overlying said end of said plunger member, wherein movement of said linkage rod, toward said valve, causes pivoting of said pressure plate so that the pressure plate engages the end of said plunger member, and moves said plunger member along said line of travel, said trigger member, said linkage rod and said pressure plate actuating said plunger valve from said second state to said first state only when the handle and said trigger member are grasped by the user and said trigger member pivoted about said clamp towards the handle;
• and
• (f) a lock-out member adapted to be reciprocatably interposed between said trigger member and the handle to limit the pivoting of said trigger member about said clamp and prevent inadvertent actuation of said valving means.