Abstract: The present invention relates to a fluid-operated percussion drill tool comprising an outer wear sleeve comprising a substantially cylindrical wall and having inner and outer surfaces. The tool also comprises a percussion bit having a head portion and a bit retaining portion and located at a forward end of the outer wear sleeve. The tool further comprises a sliding piston mounted for reciprocating movement within the outer wear sleeve to strike the percussion bit. The tool also includes a drive ring having a substantially cylindrical wall and comprising connection means adapted for connecting the drive ring to a drive means of the fluid-operated percussion drill tool. At least one flushing channel provides a fluid path to the cutting face of the bit for a flushing medium.

Abstract: The present invention relates to a flapper valve for a percussion drill tool. The valve comprises a first side engageable with a planar surface of an element of the percussion drill tool to alternately close first and second fluid flow paths of the percussion drill tool. The planar surface comprises first and second apertures in fluid communication with the first and second fluid flow paths, respectively. The first side of the flapper valve comprises a first planar portion and a second planar portion and a first curved tip portion intermediate the first and second planar portions. The flapper valve is pivotable about the first curved tip portion between a first position, in which the first planar portion of the flapper valve is in sealing contact with the planar surface to close the first aperture, and a second position, in which the second planar portion of the flapper valve is in sealing contact with the planar surface to close the second aperture.

Abstract: The present invention relates to a fluid-operated percussion drill tool comprising an outer wear sleeve comprising a substantially cylindrical wall and having inner and outer surfaces. The tool also comprises a percussion bit having a head portion and a bit retaining portion and located at a forward end of the outer wear sleeve. The tool further comprises a sliding piston mounted for reciprocating movement within the outer wear sleeve to strike the percussion bit. The tool also includes a drive ring having a substantially cylindrical wall and comprising connection means adapted for connecting the drive ring to a drive means of the fluid-operated percussion drill tool. At least one flushing channel provides a fluid path to the cutting face of the bit for a flushing medium.

Abstract: A learning system comprising a database for storing predetermined articles having embedded linguistic hypertext links, vocabulary, grammatical rules, and grammatical data; a software engine configured to display a selected article from the predetermined articles and generate selectable teaching tools such that the selection of a teaching tool from the selectable teaching tools results in the selected article displaying embedded linguistic hypertext links associated with the selected teaching tool; and wherein the selection of one or more of the embedded linguistic hypertext links in the article provides a contextual explanation that teaches a student the conventions of standard written English.