Hammer drill

Claim 1

A FLUID-OPERATED WELL-DRILLING MECHANISM COMPRISING A TUBULAR HOUSING, AN INVERTED CUP-LIKE CYLINDER LONGITUDINALLY MOUNTED IN THE TOP OF SAID HOUSING, AN ELONGATED ANNULAR HAMMER IN SAID HOUSING AND SLIDABLY DISPOSED IN AND SEALED AGAINST THE INSIDE OF SAID CYLINDER, SAID HAMMER HAVING A LONGITUDINAL CENTRAL PASSAGE THERETHROUGH, MEANS AFFORDING OPERATING FLUID ACCESS TO THE INTERIOR OF SAID HOUSING BELOW SAID HAMMER, AN ANNULAR VALVE HAVING A LONGITUDINAL PASSAGE THERETHROUGH SLIDABLY DISPOSED IN AND SEALED AGAINST SAID PASSAGE IN SAID HAMMER, THE OUTSIDE DIAMETER OF SAID VALVE BEING LESS THAN THE INSIDE DIAMETER OF SAID CYLINDER, RESILIENT MEANS IN SAID HAMMER URGING SAID VALVE UPWARD IN SAID PASSAGE IN SAID HAMMER, A STOP ON SAID HAMMER RESTRICTING UPWARD MOVEMENT OF SAID VALVE WITH RESPECT TO SAID HAMMER, SAID STOP BEING POSITIONED SO THAT WHEN SAID VALVE IS IN ITS UPPERMOST POSITION WITH RESPECT TO SAID HAMMER THE BOTTOM END OF SAID VALVE IS PROXIMATELY ABOVE THE BOTTOM END OF SAID HAMMER, AN UPWARDLY FACING SHOULDER ON SAID VALVE, MEANS AFFORDING OPERATING FLUID ACCESS TO SAID UPWARDLY FACING SHOULDER OF SAID VALVE WHEN SAID VALVE IS IN CONTACT WITH SAID BIT STEM, AND A BIT STEM SLIDABLY DISPOSED IN AND SEALED AGAINST SAID HOUSING BELOW SAID HAMMER AND HAVING A LONGITUDINAL CENTRAL PASSAGE, THE UPPER END OF SAID BIT STEM BEING DISPOSED TO BE STRUCK BY THE LOWER END OF SAID HAMMER.