Pressure Reversing Valve Assembly For a Down-the-Hole Percussive Drilling Apparatus

A pressure reversing valve assembly for a down-the-hole drilling apparatus comprising:

• a housing;
• a distributor within the housing, the distributor including;
• an exhaust stem,
• a central bore extending axially through the distributor, and
• a plurality of apertures extending radially through the exhaust stem;
• and
• a valve sealingly engaged with the exhaust stem and movable between an open position, wherein a high pressure port is in communication with a drive chamber, and a closed position, wherein the high pressure port is sealed off from the drive chamber, the valve including;
• a first valve pressure surface,
• a second valve pressure surface,
• a third valve pressure surface, and
• a valve passageway extending through the valve and in communication with a first volume of the down-the-hole drilling apparatus,
• wherein the first volume is formed by surfaces of the distributor and at least one of the first, second and third valve pressure surfaces.

A pressure reversing valve assembly comprising:

• a distributor that includes;
• an upper body portion, and
• a lower body portion having a side wall, and
• an exhaust stem extending distally from the lower body portion;
• and
• a valve that includes:
• a base having a proximal surface, a distal surface and a thru hole for receiving the exhaust stem,
• a side wall extending from the base, the side wall having an inner side surface and an outer side surface, and
• a valve passageway extending through the valve and in communication with an area formed by the distributor and the proximal surface of the base.