Multiple stage feed leg assembly

Claim 1

IN COMBINATION WITH A PNEUMATICALLY OPERATED DRILLING UNIT, A FEED LEG ASSEMBLY PIVOTALLY CONNECTED TO SAID DRILLING UNIT AND HAVING MULTIPLE STAGES MOVABLE SIMULTANEOUSLY EITHER TOWARD THEIR RETRACTED OR THEIR EXTENDED POSITIONS, SAID FEED LEG ASSEMBLY HAVING A COMBINED BRACKET AND END CAP AT ITS UPPER END PROVIDED WITH A SPINDLE SUPPORTED AT ONE END ON SAID BRACKET AND EXTENDING TRANSVERSELY OF THE EXTERIOR OF SAID END CAP, SAID SPINDLE BEING JOURNALED TO THE MIDPORTION OF SAID DRILLING UNIT AND HAVING A FIRST AND A SECOND AIR PASSAGE THEREIN IN COMMUNICATION RESPECTIVELY WITH AIR-VENTING AND PRESSURIZED AIR SUPPLY MEANS IN SAID DRILLING UNIT, THE OPPOSITE ENDS OF SAID FIRST AND SECOND PASSAGES EXTENDING ALONG SAID BRACKET AND THROUGH THE INTERIOR BOTTOM PORTION OF SAID END CAP, THE MAIN BODY PORTION OF SAID FEED LEG ASSEMBLY COMPRISING A PLURALITY OF ELONGATED CONCENTRIC TUBES AND THE TWO LOWER ONES OF WHICH ARE PROVIDED AT THEIR UPPER ENDS WITH PISTONS HAVING A CLOSE SLIDING FIT AXIALLY OF SAID TUBES, THE UPPER END OF THE LARGER ONE OF SAID TUBES BEING RIGIDLY SECURED TO SAID END CAP, SAID PISTONS EACH HAVING AN AXIAL AIR PASSAGE THERETHROUGH, A FIRST OPEN-ENDED TUBE SECURED AXIALLY TO THE INTERIOR BOTTOM OF SAID END CAP AND HAVING A FLUIDTIGHT SLIDING CONNECTION THROUGH THE UPPER ONE OF SAID PISTONS AND CONNECTED AT ITS UPPER END DIRECTLY TO SAID FIRST AIR PASSAGE, A SECOND OPEN-ENDED TUBE CLOSELY SURROUNDING SAID FIRST OPEN-ENDED TUBE AND HAVING ITS UPPER END MOUNTED IN AND SEALED TO THE UNDERSIDE OF SAID UPPER PISTON AND ALSO HAVING A SLIDING FIT IN AN AXIAL OPENING THROUGH THE PISTON IMMEDIATELY BELOW SAID UPPER PISTON, SAID UPPER PISTON HAVING A SECOND AIR PASSAGE THERETHROUGH SPACED TO ONE SIDE OF FIRST OPEN-ENDED TUBE, SAID SECOND AIR PASSAGE THROUGH SAID END CAP OPENING INTO THE SPACE ABOVE ALL OF SAID PISTONS IN ALL OPERATING POSITIONS OF SAID FEED LEG THEREBY TO SUPPLY AIR TO OR BLEED AIR FROM THE INTERIOR SPACE OF SAID FEED LEG ABOVE EACH OF SAID PISTONS SIMULTANEOUSLY TO EXTEND AND RETRACT EACH STAGE THEREOF BY PROPORTIONAL AMOUNTS AND RADIAL PASSAGE MEANS THROUGH THE LOWER PORTIONS OF EACH OF SAID PISTONS HAVING THEIR INNER ENDS IN COMMUNICATION WITH THE LOWER ENDS OF SAID FIRST AND SECOND TUBES AND THEIR OUTER ENDS IN COMMUNICATION RESPECTIVELY WITH THE ANNULAR SPACES BETWEEN SAID MAIN TUBES BELOW THE LOWER ENDS OF SAID PISTONS IN ALL OPERATING POSITIONS OF SAID FEED LEG THEREBY TO MAINTAIN SUBSTANTIALLY THE SAME PRESSURE CONDITIONS IN EACH OF SAID ANNULAR SPACES.