The is rate is in excess of the threshold rate so as to cause the follower means (4) to move upwardly until it abuts against the underside of the cushion of particulate solid (5).

• 速率超过临界速率以引起跟随器机构(4)向上移动直到它倚靠粒状固体(5)缓冲垫的下侧邻接。