Concave extension and rock trap for a thresher

Claim 1

A THRESHING MECHANISM, PARTICULARLY FOR COMBINE HARVESTERS COMPRISING, IN COMBINATION, SUPPORT MEANS; A THRESHING DRUM ON SAID SUPPORT MEANS; FEEDING MEANS ON SAID SUPPORT MEANS FORWARDLY OF SAID DRUM SAID FEEDING MEANS HAVING A DELIVERY END DIRECTED TOWARD SAID DRUM FOR FEEDING MATERIAL TO BE THRESHED THERETO, SAID DELIVERY END BEING SPACED FROM SAID DRUM BY A FIXED DISTANCE; A CONCAVE PARTLY SURROUNDING SAID DRUM AND HAVING AN ACTIVE SURFACE OF A GIVEN LENGTH FACING SAID DRUM SPACED THEREFROM BY A GIVEN MINIMUM DISTANCE CONSIDERABLY SMALLER THAN SAID FIXED DISTANCE AND COOPERATING THEREWITH, SAID CONCAVE HAVING A RECEIVING END REARWARDLY SPACED FROM SAID DELIVERY END OF SAID FEEDING MEANS AND FORMING A GAP THEREWITH; BOX-SHAPED EXTENSION MEANS FOR INCREASING SAID LENGTH OF SAID SURFACE AND BEING LOCATED BETWEEN SAID DELIVERY END OF SAID FEEDING MEANS AND SAID RECEIVING END OF SAID CONCAVE, SAID EXTENSION MEANS HAVING A TRANSVERSE WALL SURFACE BRIDGING SAID GAP BETWEEN SAID DELIVERY END OF SAID FEEDING MEANS AND SAID RECEIVING END OF SAID CONCAVE; AND MEANS AT SAID SUPPORT MEANS MOUNTING SAID EXTENSION MEANS TURNABLE ABOUT AN AXIS EXENDING SUBSTANTIALLY PARALLEL TO SAID TRANSVERSE WALL SURFACE BETWEEN AN ACTIVE POSITON IN WHICH SAID SURFACE OF SAID EXTENSION MEANS FORMS A CONTINUATION OF SAID ACTIVE SURFACE OF SAID CONCAVE FOR INCREASING THE ACTIVE LENGTH THEREOF, AND WHEREIN SAID SURFACE FORMS WITH SAID RUM A CONCVE ENTRY OF A PREDETERMINED SIZE FOR SAID FEEDING MEANS TO FEED INTO AND AN INACTIVE POSITION IN WHICH SAID EXTENSION MEANS IS TURNED SUBSTANTIALLY THROUGH 180* ABOUT SAID AXIS AND IN WHICH SAID TRANSVERSE WALL SURFACE IS DOWNWARDLY DISPLACED WITH RESPECT TO SAID RECEIVING END OF SAID CONCAVE TO INCREASE THE SIZE OF SAID CONCAVE ENTRY SO THAT STONES CARRIED BY SAID FEEDING MEANS CANNOT BECOME JAMMED AT SAID ENTRY, AND SIMULTANEOUSLY FORM PART OF A STONE CATCHING MEANS AHEAD OF SAID RECEIVING END OF SAID CONCAVE WHILE CONTINUOUSLY BRIDGING SAID GAP WITHOUT INCREASING THE ACTIVE LENGTH OF SAID CONCAVE.