Patent ID: 8839885

Claim:
A drill rod comprising: a casing assembly defining a length that extends axially between a first end and an opposite second end of the drill rod, the casing assembly defining a first passage that extends axially along the drill rod from the first end of the casing assembly to the second end of the casing assembly, the casing assembly also defining a second passage that extends axially along the drill rod from the first end of the casing assembly to the second end of the casing assembly; a drive shaft rotatably mounted within the casing assembly, the drive shaft extending axially along the drill rod generally from the first end of the casing assembly to the second end of the casing assembly, the drive shaft having a center axis that is offset from axes of the first and second passages, the axes of the first and second passages also being offset from one another; the casing assembly further includes first and second end plates positioned respectively at the first and second ends of the casing assembly, the first and second end plates supporting the drive shaft, the first and second end plates also defining first openings that align with the first passage and second openings that align with the second passage; the casing assembly includes an outer shell that defines an outer boundary of the drill rod and that extends from the first end plate to the second end plate; the drill rod also including alignment pins that project outwardly from the first end plate and alignment pin receivers defined by the second end plate; the drill rod further including latches mounted between the second end plate and a backing plate adjacent the alignment pin receivers for latching alignment pins of an adjacent drill rod within the alignment pin receivers, the latches being movable between latching and non-latching positions, the latches moving in a plane that is generally transverse relative to the center axis of the drive shaft when the latches move between the latching and non-latching positions; and the drill rod including biasing structures that apply retention forces to the latches for retaining the latches in the non-latching position, the retention forces having at least components that extend along the center axis of the drive shaft, wherein the biasing structures include springs carried by the latches as the latches move between the latching and non-latching positions that cause the retention forces to be applied between the latches and the backing plate, and wherein the spring biases a plunger against the backing plate.