Floating seal for fluid control devices

A fluid flow control faucet comprising:

• a faucet body having a first passageway communicating between a fluid inlet and a fluid outlet with said first passageway including a sealing seat area disposed therein intermediate said inlet and outlet, said body further including an open ended second passageway communicating with said first passageway on the other side thereof from said sealing seat area;
• a stem assembly disposed in said second passageway for controlling liquid flow through said faucet body between said inlet and outlet, said stem assembly including an elongated stem member having inner and outer ends with valving means at the inner end thereof for selective engagement with said sealing seat area and means disposed at the outer end thereof for selectively reciprocating said stem member within said second passageway for moving said valving means between a first position engaging said sealing seat area for blocking fluid flow between said inlet and outlet and a second position spaced from said sealing seat area for allowing liquid flow between said inlet and outlet;
• a bonnet covering the open end of said second passageway and closely surrounding that portion of said elongated stem member extending therethrough;
• primary stem seal means for preventing fluid flow past said stem member in said second passageway and outward of said faucet at said bonnet;
• and,
• secondary stem seal means spaced from said primary seal means toward said bonnet, said secondary stem seal means being axially movable relative to and independently of said stem member between a normal non-sealing condition with said stem member and a sealing condition with said stem member only upon failure of said primary seal means and then being so movable into said sealing condition solely in response to the pressure of fluid by-passing said primary seal means.