In a high-biasing force, float-operated toggle link over-center valve actuating mechanism for use in a sealed pressure vessel having a bottom and a top, the bottom including a liquid inlet opening and a liquid outlet opening;
- said top having a gas inlet adapted to be connected to a compressed gas source, a gas outlet, inlet valve means controlling the gas inlet, outlet valve means controlling the gas outlet, said valve actuating mechanism alternately opening and closing said inlet and outlet valve means by first opening said gas outlet valve means and second closing said gas inlet valve means, and under reverse snap-over toggle valve actuation closing the outlet valve means and simultaneously opening said gas inlet valve means, said snap-over toggle linkage valve actuating mechanism further comprising:
- a relatively fixed main frame for support internally of said vessel, at least one compression force preload arm pivotally mounted to said fixed main frame for pivoting about a first pivot axis A, a first toggle link pivoted at a first end to said main frame about said first pivot axis A, a second toggle link operatively pivoted at a first end to said compression force preload arm at a point in said arm remote from said pivot axis A, for pivoting about a second pivot axis C parallel to said first pivot axis A, pivot means pivoting a second end of said first toggle link to a second end of said second toggle link for pivoting about a third axis B parallel to said first and second pivot axes A, C, coupling means for operatively coupling said float to said at least one compressive force preload arm at a point remote from said first axis A, and said second toggle link comprising compressible and expandable means for constantly applying a compressive force on said pivot connection between said first and second toggle link, such that upon pivoting of said at least one compressive force preload arm by rise and fall of liquid within said vessel about said first pivot axis A towards a position of longitudinal alignment with the longitudinal axis of one of said first and second toggle links, an increasing compressive force is applied to said first toggle link to maintain the first toggle link stationary in one of two oblique, over-center positions with respect to a centerline extending parallel to the longitudinal axis of said at least one compressive force preload arm, and said second toggle link pivots about said axis B and said compressible and expandable means axially compresses until said first and second links become longitudinally aligned and move across the centerline, whereupon both toggle links instantly snap over into oppositely oblique, over-center positions, and said second toggle link compressible and expandable means expands to dissipate the energy of compression, the improvement wherein:
- said compressible and expandable means comprises a plurality of stiff, short axial length large coil turn diameter compression coil spring sandwich mounted at opposite ends between two facing end plates in side-by-side symmetrical position, said plurality of compression coil springs having axial lengths less than four times the diameter of said coil spring turns, and means for maintaining said plurality of compression coil springs between said two facing plates under precompression and forming a multiple compression coil spring assembly.