US Patent 9441925 Lobed nock for crossbow bolts

A lobed projectile includes a shaft having a leading end and a trailing end, a point positioned at the leading end, a number of circumferentially spaced apart vanes positioned on the shaft between the leading end and the trailing end, and a nock positioned at the trailing end. The nock includes a body portion attached to the shaft, wherein the body portion has a central axis, and the nock includes a lobe on the outer surface of the body portion which extends radially away from the central axis. The nock may be used to avoid dry fires of a crossbow by controlling an anti-dry fire mechanism and by securing a bowstring to the nock of the projectile.