Abstract: A pressure regulating valve is disclosed as including a valve seat having a flat working surface and a central inlet bore extending perpendicularly from the flat working surface through the seat. A valve disc having a flat circular working surface, the diameter of which is at least three times as large as the diameter of the inlet bore, is positioned against the seat in a coaxial relationship with the inlet bore to provide a large annular area of contact with the flat seat surface. The disc is biased toward the seat by an assembly including a spring within a spring housing, a piston, reciprocally engaged in the innermost end of the spring housing, and a ball bearing received in opposed recesses in the seat and disc. When subjected to high pressure bypass flow through the valve seat inlet bore, the disc is forced from the seat and attains a stable, parallel orientation relative to the seat under the influence of the bypass flow.

Abstract: A foldable two-piece boom is provided with an outer boom wing pivoted about an upright axis and being slidable relative to an inner boom arm which is pivoted to a frame member for both horizontal and vertical motion. A spring and cables in a mounting mechanism are arranged to permit the outer wing to pivot either forwardly or rearwardly when contacted by an abutment and thereafter gently returned to a neutral position parallel to the longitudinal axis of the inner boom arm at a controlled rate which minimizes impact forces. The spring and cables are also arranged to permit pivotal movement of the boom in a vertical plane while maintaining the inner and outer sections in vertical planar alignment. In response to the horizontal swinging of the boom through 90.degree. from its extended to its folded transport position, the spring and cables cause the outer wing to fold in the opposite direction of the arm to firmly clamp against the inner arm.