System for moving mast of drilling machine

A mast assembly for a drilling machine, the mast assembly comprising:

• a mast;
• and
• a system for moving the mast, the system including:
• a hydraulic actuator defining a rod end and a head end, wherein
• the rod end of the hydraulic actuator is coupled to the mast to move the mast about a pivot axis;
• a fluid line in fluid communication with the head end of the hydraulic actuator;
• and
• a counterbalance valve disposed in the fluid line, wherein the counterbalance valve is disposed in fluid communication with the head end of the hydraulic actuator, wherein the counterbalance valve includes an atmospheric vent passage, and wherein, during a lowering operation of the mast, a back pressure in the hydraulic actuator is alleviated, via the atmospheric vent passage.

A drilling machine comprising:

• a frame;
• a mast coupled to the frame that is movable relative to the frame;
• and
• a system for moving the mast relative to the frame, the system including:
• a hydraulic actuator defining a rod end and a head end, wherein the rod end of the hydraulic actuator is coupled to the mast to move the mast about a pivot axis;
• a fluid line in fluid communication with the head end of the hydraulic actuator;
• and
• a counterbalance valve disposed in the fluid line, wherein the counterbalance valve is disposed in fluid communication with the head end of the hydraulic actuator, wherein the counterbalance valve includes an atmospheric vent passage, and wherein, during a lowering operation of the mast, a back pressure in the hydraulic actuator is alleviated, via the atmospheric vent passage.