IN A SPEED-CHANGE OPERATION MECHANISM (7), A MAIN BODY (30A) OF A LOCK MEMBER (30) IS DISPOSED TO PRODUCE A CLEARANCE BETWEEN THE MAIN BODY (30A) AND THE SURFACE OF THE HANDLE ARM (4A), WHEREAS A PIVOT OPERATION PART (30B) OF THE LOCK MEMBER (30) IS DISPOSED TO CLOSE A CLEARANCE BETWEEN THE MAIN BODY (30A) AND THE SURFACE OF THE HANDLE ARM (4A) AND SIMULTANEOUSLY TO PRODUCE A CLEARANCE BETWEEN THE PIVOT OPERATION PART (30B) AND THE SURFACE OF THE HANDLE ARM (4A). A RELATIVELY LARGE CLEARANCE IS PRODUCED BETWEEN THE MAIN BODY (30A) OF THE LOCK MEMBER (30) AND THE SURFACE OF THE HANDLE ARM (4A), WHEREAS A SMALL CLEARANCE, JUST ENOUGH TO ALLOW A PIVOT OPERATION OF THE LOCK MEMBER (30), IS PRODUCED BETWEEN THE PIVOT OPERATION PART (30B) OF THE LOCK MEMBER (30) AND THE SURFACE OF THE HANDLE ARM (4A). (FIG. 3)
