| 摘要 |
Pivotally mounted blades within slots of a housing for an arrowhead are retracted for minimum outward extension during flight but expanded and retained in outwardly extended position upon impact with a target. The blades are retained in the retracted position by frictional engagement with the slots or by frangible or resilient members. The slot mounting of the blades permits forward pivoting relative to the arrow shaft to facilitate withdrawal from the target. The amount of outward extension of the blades upon impact is determined by a rearwardly positioned shoulder. This shoulder can be the rearward portion of the blade mounting slot or can take the form of a sleeve at the rear of the blade slots. The sleeve can further have shoulders of differing depths to allow preselection of the angle of outward extension of the blade upon impact via movement between the sleeve and the blade mounting body or housing. Minimal size with maximum blade mounting strength can be obtained by orienting the blade mounting slots within the body in an offset relation to the central axis thereof. The blades are retained by transverse set screws, retaining pins or the like for easy attachment or removal. By arranging the blade mounting body for telescopic movement within the camming sleeve, the blades can be retracted in a rearwardly oriented direction along the arrow shaft during inflight. The blades can be retained in a forwardly oriented direction by a frictional engagement means, an elastic or frangible band, slotted frangible cap or the like.
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