Derrick assembly capable of conveying pipe sections between a drill string and a rack for said pipe sections

A derrick assembly for raising or lowering a drill string made of interconnected pipe sections, comprising:

• a derrick frame having lateral sidewalls and a base together defining an elongated channel having an open outer side opposite to said base;
• a rack positioned within said channel adjacent to one lateral sidewall thereof leaving part of said channel clear for manipulating said drill string, said rack comprising at least one element extending between said base and said open outer side for housing pipe sections therebetween substantially longitudinally aligned within said channel;
• a gantry extending across said open outer side of said channel, said gantry being movable longitudinally of said channel;
• and
• a pipe gripping unit supported by said gantry for selectively holding or releasing pipe sections, said gripping unit being movable on said gantry towards or away from said base and laterally between said sidewalls;
• whereby said pipe gripping unit may be manipulated on said gantry to transfer pipe sections between said rack and said clear part of said channel for attachment to or detachment from said drill string.