Gate valve with improved secondary body to bushing seals

A gate valve comprising;

• a body having a central gate chamber, an inlet passage extending through the body into communication with the gate chamber, an outlet passage extending through the body into communication with the gate chamber and a recess in the body surrounding the opening of each of the passages into the gate chamber,
• a floating bushing positioned in each of said recesses,
• a gate positioned within the chamber,
• means for moving the gate within the chamber between said floating bushings and between positions communicating flow between the passages and closing flow between the passages,
• inner and outer unidirectional seals positioned upstream and downstream between the surface of each of the recesses facing the gate and the opposing surface of the bushing in the recess,
• each of the seals include a U-shaped lip sealing element and a U-shaped spring positioned within the lip sealing element and urging the legs of the element apart into sealing engagement between sealing surfaces on the bushing and the body,
• the inner seal, which is positioned closest to the passage has the open end of its sealing element facing the passage and the outer seal, which is farther from the passage than the inner seal, has the open end of its sealing element facing away from the passage,
• each of the seals being positioned within a separate recess in its bushing which separate recess has an axial dimension less than the free axial dimension between the lip sealing surfaces when it is not compressed, the downstream axially seals being compressible to an axial dimension between the lip sealing surfaces which is the same as the axial dimension of their separate recesses responsive to pressure differential loading on the gate when the gate is in a closed position so that their bushings engage the body recess surface in a metal-to-metal seal when they are loaded and are recoverable from such compressed position, the seals being axially extendible to provide a tight seal and maintain sufficient sealing between the bushing and body recess sealing surfaces to prevent entry of contaminants therebetween.