Screening apparatus and method for screening mixed materials

A screening apparatus for separating mixed material into coarse materials and finer materials, said screening apparatus comprising:

• a frame having a lower section for resting on a surface, and an upper section;
• a vibrating screen unit comprising a first material separating screen sloping downward with respect to said surface from an upper edge toward a lower edge, and a second material separating screen underneath said first material separating screen and in parallel thereto, said second material separating screen having meshes smaller than meshes of said first material separating screen so that said finer materials are sieved a second time by said second material separating screen for obtaining further finer materials, said first and second material separating screens being supported by said frame between said lower and upper sections;
• shaking means for shaking said vibrating screen unit;
• a bucket for receiving the mixed materials, said bucket being located in the upper section of said frame and comprising a bottom opening located over said first material separating screen adjacent the upper edge thereof, and having a superior part provided with screen means for preventing large coarse materials from falling into said bucket, said screen means comprising a plurality of spaced bars parallel to each other and parallel to the displacement of said wall, said bars having ends inserted in slots provided in the upper section of said frame;
• means for sweeping away the large coarse materials on an upper surface of said screen means, said means for sweeping away the large coarse materials comprising a movable rack operated by a cable and pulley linkage provided for moving said rack along the upper surface of said screen means in a direction opposite to a direction of movement of said wall;
• a wall movable along the bottom of said bucket for pushing the mixed materials into said bottom opening;
• means for moving said wall at a predetermined speed, said means comprising at least two hydraulic actuators, each of said actuators operating an arm having a first end operatively attached to said frame and a second end operatively attached to said wall;
• a transversal longitudinal conveyor adjacent said lower edge of said first material separating screen for conveying said coarse materials rejected therefrom to a remote location;
• and
• at least one pair of wheels and a trailer hitch so that said screening apparatus is portable;
• whereby said first material separating screen is fed with the mixed materials as said wall pushes the mixed materials at said predetermined speed along the bottom of said bucket into said bottom opening.

A method for separating mixed material into coarse materials and finer materials, said method comprising the steps of:

• dumping mixed materials into a bucket located in an upper section of a screening apparatus;
• moving an upright wall at a predetermined speed along the bottom of said bucket for pushing the mixed materials, along the bottom of said bucket and into a bottom opening located in said bucket over a first material separating screen;
• shaking said first material separating screen;
• whereby said first material separating screen is fed with the mixed materials as said wall moves across said bucket pushing the mixed materials at the predetermined speed along the bottom of said bucket into the bottom opening.