The utility model discloses a scrape trigger from clear formula, including head, interlude and afterbody. The afterbody includes afterbody casing, straining device, the driven structure of afterbody, the head includes discharge gate, head section wallboard, head section wallboard left side is equipped with button head head section housing, be equipped with head pulley in the button head head section housing and be used for bearing the weight of the circular track of carrying the tape, head pulley pretext axle is fixed, button head head section housing both sides are equipped with the bearing that is used for the fixed head axle, the head axle is provided with sealed lid and head section apron with the inside of head section wallboard respectively with outside junction. The utility model has the advantages that: adopting button head formula shape, not having the dead angle to produce, work efficiency is improved to difficult the jam, has solved head and afterbody knot material problem.