Abstract: A bottom hole assembly (BHA) and method for drilling a bore with a pneumatic percussion hammer includes an expandable packer surrounding the stem rod connected to the hammer. The packer has an inner surface confronting the outer surface of the stem rod in an axially slideable, sealed relationship. The packer is expanded and fixed in the bore to separate a region of high hydraulic pressure above the packer from a region of lower hydraulic pressure below the packer. The method includes operating the pneumatic hammer and bit, while (i) the stem rod advances with a sliding seal against an inside surface of the expanded packer; (ii) pneumatic pressurization and exhaust for the hammer are guided within the stem rod; and (iii) the exhaust from the hammer is discharged into the lower clearance region surrounding the bit at the bottom of the bore.

Abstract: A bit retention system for a hammer drill including a housing (41), a drive sub (44) connected to lower end of the housing, and a bit retainer (50) having an upper end suspendable from a shoulder of the drive sub and a lower end including a radially inwardly projecting bit retention rim (52). The upper end of a locking sleeve (70) has internal features (78) that are engageable with external features (76) at the lower end of the housing to prevent relative rotation, and a lower end sized (82) to overlap the upper end (90) of the retainer. The lower end of the locking sleeve is welded to the retainer, thus locking the threads on the drive sub from unscrewing from housing threads. The drive sub and retaining member are pinned together to stop separate rotation.

Abstract: A sleeve carried by and preferably slidable relative to the piston, for controlling air passages associated with a central air feed tube, whereby retraction pressure is applied to the piston substantially at impact. It is the impact itself of the piston against the bit, which enhances sliding of the sleeve relative to the piston, over the feed tube, and thereby switches the airflow at the moment of impact.

Abstract: The lower end portion of a pneumatic impact hammer cylinder has at least one upper fluid passage and at least one lower fluid passage. A U-shaped sleeve is mounted in a circumferential groove in the lower end portion of the piston. The sleeve includes a base, upper and lower legs extending radially outward from the base, and a cavity extending axially between the legs. The sleeve has an axial length that is less than the axial length of the piston groove such that the sleeve is slidably movable within the piston groove between an upstroke position and a downstroke position. The upper fluid passage and the lower fluid passage cooperate with the sleeve cavity, as the piston reciprocates between the impact position and the recovery position, to supply pressure fluid to the impact end of the operating chamber for a portion of each upstroke and each downstroke.

Abstract: A bit retainer for a percussion bit assembly has a bore and upper and lower lips extending into the bore. Multiple slots extend from the lower end of the retainer member to a terminal end disposed intermediate the upper and lower ends, forming multiple cantilever beam segments. The cantilever beam segments are resiliently, radially deflected by the retention shoulder of the percussion bit to mount and retain the bit.

Abstract: A bit retainer for a percussion bit assembly has a bore and upper and lower lips extending into the bore. Multiple slots extend from the lower end of the retainer member to a terminal end disposed intermediate the upper and lower ends, forming multiple cantilever beam segments. The cantilever beam segments are resiliently, radially deflected by the retention shoulder of the percussion bit to mount and retain the bit.

Abstract: A substantially tubular retainer member is provided, having a bore of substantially uniform internal diameter which can slip over the retention shoulder of the percussion bit, whether that shoulder is solid or threaded. Pins are then driven through holes in the retainer, under the retention shoulder. The pins retain the head of the bit in the event of bit breakage.

Abstract: A downhole hammer bit including at least one bit impact head mounted to a vertical guide member by a plurality of retaining ring segments. Opposed surfaces of the bit impact head and the guide member have corresponding circumferential grooves or groove sections that define a channel or channel sections, respectively, for receiving the retaining ring segments. The retaining ring segments are inserted into the respective channel/channel section via a bore that extends from an external surface of the hammer bit. A pin disposed in the bore retains the retaining ring segments in the channel/channel section. The retaining ring segments engage the upper and lower surfaces of the channel/channel sections along an extended arc, reducing the stress and possibility of mechanical failure.

Abstract: A pneumatic downhole impact drill has a backhead for mounting an inlet check valve and a mounting hub for mounting a fluid delivery tube. A split ring has an interior circumferential groove forming upper and lower shoulders and comprises two substantially identical semi-circular ring segments. The ring segments are positioned around flanges on the backhead and the mounting hub such that the upper shoulder of the split ring slidably engages the upper surface of the backhead flange and the lower shoulder slidably engages the lower surface of the mounting hub flange to mount the backhead to the mounting hub. A first gap is formed between the outside surface of the split ring and the inside surface of the casing. A second gap is formed between the inside surface of the groove and the outside surfaces of the mounting hub and backhead flanges. Taken together, the gaps allow lateral relative movement between the mounting hub and backhead flanges.

Abstract: A pneumatic downhole impact drill has a porting system for automatically supplying pneumatic pressure fluid from a fluid delivery tube received within an axial bore in the impact piston to the opposite ends of the piston operating cylinder as the piston reciprocates. A flange on the delivery tube is slidably mounted in a cavity in a mounting hub assembly. Passageways provide fluid communication between the pressure fluid inlet plenum and the operating chamber side of the cavity and between the back chamber and the inlet plenum side of the cavity. Fluid pressure forces acting on the opposite faces of the flange and on the top end surface of the delivery tube reciprocate the delivery tube between upstroke and downstroke positions. Positioning the delivery tube in the upstroke position increases the axial distance that the piston must travel before the pressure fluid supply is connected to the back end of the operating chamber on the piston upstroke.

Abstract: A downhole impact drill having a drill bit head with a drill bit sector for drilling an enlarge hole upon rotation of the drill. The bit is mounted within a chuck for movement between a retracted, working position in which the bit is coaxially mounted for drilling and an extended, non-working position in which the bit is loosely mounted within the chuck to permit the bit to swing laterally to reduce the diameter of the drill bit head envelope. In its extended, non-working position, the bit is supported on the chuck at a 3.degree. angle at which the drill bit sector is positioned inwardly to facilitate installation and withdrawal of the drill.

Abstract: A downhole drill bit having an elongated male drive shank, a separate female impact head mounted on the drive shank, the drive shank and head having cooperating external and internal, head drive splines extending helically in one angular direction to urge the drive shank and head together during impact drilling, the head drive splines having a width and spacing for inserting and then rotating the head on the shank, and elongated key inserts between the head drive splines to form therewith a head drive coupling, the head having an annulus and the drive shank having a circular arrangement of locking lugs receivable within the annulus for locking the head against axial withdrawal from the shank.