Agricultural implement

Claim 1

IN A WHEEL-SUPPORTED GROUND-WORKING AGRICULTURAL IMPLEMENT INCLUDING A TOOL SUPPORTING FRAME, A REAR WHEEL STRUCTURE COMPRISING A PAIR OF PARALLEL LINKS PIVOTALLY MOUNTED AT ONE END ON SAID SUPPORTING FRAME, A SPINDLE HOUSING CARRIED BY THE FREE END PORTION OF SAID PARALLEL LINKS, A SPINDLE ROTATABLY DISPOSED WITHIN SAID HOUSING AND INCLUDING A REARWARDLY EXTENDING LOWER PORTION MOUNTING A REAR WHEEL THEREON, MEANS FOR MOVING SAID HOUSING VERTICALLY REALTIVE TO SAID FRAME, AND MEANS FOR LOCKING SAID SPINDLE AND REAR WHEEL IN POSITION WITH RESPECT TO SAID FRAME TO PROVIDE A STRAIGHT PATH OF MOVEMENT FOR SAID REAR WHEEL, SAID LOCKING MEANS COMPRISING A CAM MEMBER CARRIED AT THE UPPER END OF SAID SPINDLE IN FIXED RELATION THERETO, SAID CAM MEMBER INCLUDING A GENERALLY UPWARDLY FACING CURVING SURFACE INCLUDING A PAIR OF SIDE WALL PORTIONS AND A LOWER CENTER PORTION, AND A CONICAL ROLLER MEMBER ROTATABLY MOUNTED ON SAID FRAME IN POSITION FOR ENGAGEMENT WITH SAID CURVING SURFACE, SAID CURVING SURFACE BEING SHAPED TO CONTACT SAID CONICAL ROLLER THROUGHOUT THE LENGTH THEREOF AND HAVING A PORTION DISPOSED GENERALLY HELICALLY ABOUT SAID CAM MEMBER, WHEREBY VERTICAL MOVEMENT OF SAID WHEEL STRUCTURE AND SAID CAM MEMBER IS EFFECTIVE TO PROVIDE FOR ENGAGEMENT OF SAID CONICAL ROLLER WITH SAID CURVING SURFACE AND SAID ROLLER IS MOVABLE ALONG SAID CURVING SURFACE TO SAID LOWER CENTER PORTION THEREOF TO THEREBY SWING THE REAR WHEEL AND LOCK IT IN POSITION WITH RESPECT TO SAID FRAME.