Patent ID: 8869882

Claim:
A ball injector, comprising: an injector spool having a top end, a bottom end and an axial passage that extends from the top end to the bottom end; and at least two independently operated ball injector assemblies respectively connected to respective radial ports through a sidewall of the injector spool, each ball injector assembly supporting a ball cartridge that accommodates a plurality of frac balls and comprises a ball launcher with a ball chamber that extends completely through the ball launcher, the ball launcher further comprising a travel limiter on an inner end thereof, the travel limiter contacting a sidewall of the axial passage after the ball launcher has been moved to a ball launch position; the ball launcher being reciprocated by a ball launcher drive from a ball load position in which a ball is loaded from the ball cartridge into the ball chamber, to the ball launch position in which the ball is released from the ball chamber after the ball launcher has been moved far enough into the axial passage by the ball launcher drive that the frac ball moves down through a bottom of the ball chamber, wherein the ball launcher drive comprises a motor that rotates a threaded drive rod which extends into an axial bore in a rear end of the ball launcher, the axial bore extending from a rear end of the ball launcher through a rear side of the ball chamber.