Vibrating screen with arched frame and ballast

A vibrating screen for separating screenable material, comprising:

• an arched frame having a vertical tall end, a vertical short end and two spaced apart stringer members joining upper portions of said tall end and said short end, said stringer members defining an inclined plane between said tall end and said short end;
• said tall end having a first pair of spaced apart leg members and a first ballast mounted between the leg members of said first pair;
• said short end having a second pair of leg members and a second ballast mounted between the legs members of said second pair;
• a basket having a rectangular frame, a perforated bottom surface and vertical sides for receiving a nominal load of screenable material;
• a plurality of springs mounted atop said arched frame and connected to said rectangular frame for supporting said basket above said inclined plane;
• an eccentric drive means attached to said rectangular frame and to said stringer members for retaining said basket along said inclined plane, and for imparting a reciprocal movement to said basket;
• said eccentric drive means comprising a rotatable offset shaft;
• said stringer members being flexible in an elastic region thereof a sag distance corresponding to at least an offset dimension of said offset shaft;
• and,
• power supply means mounted on said arched frame and connected to said eccentric drive means, for actuating said eccentric drive means;
• whereby during an operation thereof, an amplitude of a vibration of said basket transmitted to said arched frame is largely absorbed by said plurality of springs and by said first and second ballasts, and is at least partly absorbed by a deflection of said stringer members.