Abstract: A retrieval head (14) coupled to a downhole tool that is used for retrieving a drill bit composed of individual drill bit segments (14). The down hole tool is adapted to travel through a drill sting and a drive sub (12) attached to the drill string. The tool also releases segments (14) which are clamped between the drive sub (12) and a bit locking sleeve (16). The retrieval head (10) includes a body (30) having a first length (32) and a contiguous second length (34). The first length (32) is of constant diameter. The second length (34) has a portion (42) of reduced diameter relative to that of the first length (32). The diameter of the first length (32) is dimensioned so that the bit segments (14) can initially collapse radially inwardly wholly onto an outer circumferential surface (38) of the length (32). The reduced diameter portion (42) is dimensioned so that when the bit segments (14) are disposed thereon, the bit segments (14) can pass through the drive sub (12) and bit locking sleeve (16).

Abstract: A down hole running tool 14 travels in a first direction through a drill pipe for installing bit segments 18 at the end of a drive sub 12 attached to the drill pipe. The tool 14 includes a first portion 82 and a second portion 84 which is retractably coupled to a leading end of the first portion 82. The first portion 82 includes a tubular extension 134 which receives a spigot 136 that extends from an upper end of the second portion 84. A pin 138 extends transversely through the tubular extension 134 and resides within opposing slots 140 formed in the spigot 136. There is a stepped reduction in the internal diameter at the lower end of the tubular extension 134 so as to form a cup-like structure 146. A spring 168 is disposed about the spigot 136 and has an upper end seated in the cup-like structure 146 and a lower end bearing against an upper face 170 of the second portion 84. The spring 168 is biased so as to push the first and second portions 82 and 84 apart in the longitudinal direction.

Abstract: A sleeve (10) comprises a cylindrical member (12) provided at one end (14) with a pair of opposing tapered peaks (16) and (18). Peak (16) is higher (longer) than peak (18). Sleeve (10) is retained within a drive sub (26) of a ground drill and is constrained to move linearly along the drive sub (26). The peaks (16) and (18) cooperate with latch dogs (20) and (22) which are evenly spaced about and extend radially from a running tool (24). When the running tool (24) travels down the drive sub (26) and enters the sleeve (10), one of the latch dogs (20, 22) will strike one of the peaks (16) and (18) causing the tool (24) to rotate toward a predetermined rotational position. Because the peaks (16) and (18) are at different heights, latch dogs (20) and (22) cannot simultaneously contact the very top of each peak (16) and (18). If latch dog (20) strikes the top of peak (16), it will then slide down one of the sides of that peak causing the tool (24) to rotate.

Abstract: A retractable drill bit system for a ground drill includes drill bit assembly, a bit assembly sleeve, and a transport member. The drill bit assembly is engagable with a drive sub attached to the bottom of the ground drill with the drill bit assembly being selectively expandable and collapsible between a transport position in which the drill bit assembly is transported through the ground drill by the sleeve and transport member and a cutting position in which the drill bit assembly locks into the drive sub and cuts the hole. The drill bit assembly in the cutting position is able to cut a hole substantially greater than the diameter of the ground drill itself. The drill bit assembly includes a circular bit attached at a lower most end of the sleeve and bit segments retained in slots formed in the sleeve. Each segment is provided with a lever that extends radially inwardly of the sleeve and engages the transport member.

Abstract: A retraction system allows disengagement of retrieval latch dogs of a down hole running tool from a bit locking sleeve. The locking sleeve is slidably retained within a drive sub and includes a pair of slots which are engaged by the retrieval latch dogs when the tool is used to retrieve bit segments from the drive sub. The retraction system includes a sleeve which is slidably mounted on a main body of the tool and spring which is biased to push the sleeve over the retrieval latch dogs. The sleeve has a pair of diametrically opposed slots through which the retrieval latch dogs can extend for contacting the inner surface of the drive sub. The retraction system also includes a length of the inner surface of the drive sub which is made of progressively reducing diameter in the direction of retraction of the tool from the drive sub. The upper end of each slot is provided with a bevel for directing the retrieval latch dogs in the inward direction.

Abstract: A spear head assembly (10) comprises a main body portion (14) with axially opposite first and second ends (16 and 18) respectively. The first end (16) is adapted for threaded connection with a down hole tool (12). The tool, which does not form part of the invention, is provided with an internal fluid flow path (13). Passage (20) is formed in the main body portion (14) and extends between first and second spaced apart openings O.sub.1 and O.sub.2 which are coincident with the first end and the second end (16 and 18) respectively of the main body portion (14). Spear point (22) is coupled to the main body portion (14) at, and extends from, the second end (18). In use, when the spear head assembly (10) is coupled to tool (12), to facilitate connection of the tool to a wireline and overshot via the spear point (22), the passage (20) is in fluid communication with the path (13). Therefore, fluid such as drilling mud can go through the path (13) in a substantially unimpeded manner.

Abstract: Locking system (196) is provided for selectively locking an external sleeve (76) to a main body (74) of a downhole tool (14). Locking system (196) comprises a pair of opposed holes (198) formed in the main body (74). The holes (198) capture respective locking balls (200). A channel (210) extends from each hole (198) longitudinally about the outer surface of the main body (74). A spring (206) held within the main body (74) acts to push the balls (200) out of holes (198). Openings (212) are also formed in the sleeve (76) and disposed so that the balls (200) can protrude therethrough and contact the inner circumferential surface (28) of a drive sub (12) by virtue of the bias of spring (206). When the internal diameter of the drive sub (12) is relatively small, the balls (200) are pushed inwardly against the spring (206) and reside, at least partially, within holes (198). This prevents the balls from moving longitudinally about channels (210) thereby locking the sleeve (76) to the main body (74).