Abstract: A plurality of valve structures are incorporated in a drill pipe string for drilling a well into the earth utilizing air as the drilling fluid. A first valve is located in the drill pipe string just above the drilling bit, and an additional valve or valves are located in upwardly spaced relation within the drill collar string. Each of the valves has a valve member held in a position allowing the flow of air through the valve by a fusible support, and when the support melts, the valve member will shift to a position closing the valve. The valve just above the bit is combined with a float valve to prevent the upward flow of fluid into the drill string, while the valve or valves spaced upwardly in the drill collar string are full opening valves which allow the running of instruments through the drill string to selected locations above the bit. The additional upwardly spaced valve or valves include a flap held in a position to one side of the bore through the valve body by a fusible retainer.

Abstract: A junk basket for collecting junk from a well bore and adapted for external connection to a well drilling string. The junk basket includes an elongate body having an annular interior for a releasable attachment to the exterior of a portion of the drilling string. The body includes an upwardly directed cavity for receiving junk from the well bore and one or more drain holes through the body adjacent the bottom of the cavity for draining fluid. Ribs are provided in the cavity connected to the body for engaging the exterior of the drilling string for reinforcing the body and guide means, preferably positioned on the top of the ribs, extend upwardly for preventing the top of the body from catching on downwardly facing shoulders in the well bore.

Abstract: A plurality of valve structures are incorporated in a drill pipe string for drilling a well into the earth utilizing air as the drilling fluid. A first valve is located in the drill pipe string just above the drilling bit, and an additional valve or valves are located in upwardly spaced relation within the drill collar string. Each of the valves has a valve member held in a position allowing the flow of air through the valve by a fusible support, and when the support melts, the valve member will shift to a position closing the valve. The valve just above the bit is combined with a float valve to prevent the upward flow of fluid into the drill string, while the valve or valves spaced upwardly in the drill collar string are full opening valves which allow the running of instruments through the drill string to selected locations above the bit. The additional upwardly spaced valve or valves include a flap held in a position to one side of the bore through the valve body by a fusible retainer.