Screen surfacing with exchangeable screen elements

Claim 1

A screening unit which comprises: a load-bearing generally horizontally substructure formed with upwardly open U-shaped profiles having first and second metal rails with top edges bent inwards to define a gap between them; a pair of screen elements supported on said substructure and having outer peripheries; a profiled lower elongated one-piece plastic screen-element retainer directly affixed to said substructure, extending longitudinally along a respective one of said upwardly open U-shaped profiles, having a pair of upwardly directed and longitudinally extending opposite upper edges, formed on its underside with a pair of downwardly open channels each receiving the top edge of a respective one of said rails, and provided between said channels with a downwardly projecting member engaged in said gap, said upwardly directed upper edges being provided with formations upwardly engaging said peripheries of said screen elements; a profiled upper elongated one-piece plastic screen-element retainer detachably affixed directly to said lower retainer and having above the upper edges of said lower retainer downwardly directed opposite longitudinally extending edges; and means including formations on said edges of said upper retainer engaging downwardly with said peripheries for clamping said pair of screen elements each between a respective edge of said lower retainer and the respective edge of said upper retainer, one of said retainers being formed with at least one recess opening toward the other retainer, said other retainer being formed with at least one projection engaging releasably into said recess and molded integrally with said other retainer, said projection being a feather-shaped bar provided with substantially parallel lateral faces having a sawtooth profile engaging in complementary sawtooth profiles on flanks of said recess.