| CPC E21B 7/002 (2013.01) [E21B 3/02 (2013.01); E21B 7/046 (2013.01); E21B 17/00 (2013.01); F16D 3/06 (2013.01)] | 18 Claims |

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1. An apparatus for connecting to a dual-member drill string, comprising:
an inner assembly including a drive shaft and a hollow sleeve, the hollow sleeve being configured for axial movement relative to the drive shaft;
an outer assembly disposed about the inner assembly, wherein the outer assembly includes a structure extending into the interior space of the outer assembly, the structure configured to engage with the hollow sleeve upon its axial movement and transfer axial force from the inner assembly to the outer assembly; and
a spring disposed between the drive shaft and the hollow sleeve, the spring biasing the hollow sleeve to a position away from the drive shaft.
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