Abstract: A propeller having blades designed to achieve maximum thrust at lower static velocities in both forward and reverse pitch modes is disclosed. Each blade has a generous leading edge radius leading to an upper surface having positive camber and a lower surface having positive camber adjacent the leading edge and negative camber adjacent the trailing edge. Each blade also has a high thickness-to-chord ratio and lower span-to-chord ratio or aspect ratio. This thicker blade profile and aft loading leads to a more uniform pressure distribution and laminar airflow across the blade surface resulting in a higher coefficient of lift, increased blade life and reliability, and lower noise levels.

Abstract: A chuck mechanism for a raise drill includes a rotatable drive shaft, drill pipe and a chuck for engaging the drill pipe co-axial with the drive shaft and transmitting torque from the drive shaft to the drill pipe. The drive shaft is rotatably coupled to the chuck with relative axial movement allowed. First spaced apart cooperating contact surfaces between the drive shaft and the chuck can be brought together for transmitting axial force from the drive shaft to the chuck in the downward drilling direction. Second spaced apart cooperating contact surfaces between the drive shaft and chuck can be brought together for transmitting axial force from the drive shaft to the chuck in the upward raise drilling direction. The drive shaft and chuck move axially relative to each other when contact is switched from the first to second contact surfaces or vice-versa. The second pair of contact surfaces are shaped and dimensioned for allowing relative angular movement therebetween when the drill pipe is deflected laterally.

Abstract: A propeller having blades, designed to achieve maximum thrust at lower static velocities in both forward and reverse pitch modes is disclosed. Each blade has a generous leading edge radius leading to an upper surface having positive camber and a lower surface having positive camber adjacent the leading edge and negative camber adjacent the trailing edge. Each blade also has a high thickness-to-chord ratio and lower span-to-chord ratio or aspect ratio. This thicker blade profile and aft loading leads to a more uniform pressure distribution and laminar airflow across the blade surface resulting in a higher coefficient of lift, increased blade life and reliability, and lower noise levels.