A hydraulic reciprocating piston hammer percussion drill includes an elongated piston hammer having opposed reduced diameter shank portions and disposed in a cylinder for reciprocating movement in response to pressure fluid acting continuously on one transverse face of the piston hammer and in response to valving of pressure fluid alternately to an opposed piston face of the piston hammer by a tubular sleeve valve which is disposed in sleeved relationship around the piston hammer between a piston portion of the piston hammer and an impact blow receiving bit. The tubular sleeve valve is provided with ports which communicate with high pressure and fluid exhaust ports in the piston hammer to effect reciprocation of the sleeve valve and of the piston hammer to deliver repeated impact blows to the bit. The bit may be configured to have a major portion of a transverse face disposed at an acute angle with respect to a plane normal to the bit and drill axis to allow directional drilling when the bit receives impact blows without being rotated. Retractable or fixed stabilizer or guide shoe members may be mounted on the exterior of the drill cylinder to aid in centering the drill in the drillhole or allow lateral deflection of the drill to accomplish directional drilling.
CROSS REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No. 09/239,141, filed Jan. 27, 1999, now U.S. Pat. No. 6,155,361.
A drilling attachment for use in wet and dry drilling operations includes a housing having first and second fluid conduits, and a drive shaft mounted within the housing and having fluid transmitting first and second end portions in fluid communication with a respective first and second fluid conduit. In one embodiment, at any time one end of the drive shaft is coupled to a drive unit and the other end of the drive shaft is coupled to a core drill bit. In a dry drilling operation, dust is extracted from the core of the drill bit, is passed through the drive shaft and exits the housing via one of the fluid conduits. In a wet drilling operation, fluid such as water is passed through the other of the fluid conduits, through the drive shaft and into the core of the drill bit.
A method and apparatus for enabling background caching of encrypted programming data on a storage medium for later playback in a digital video recorder (DVR) system. A set-top box (STB) equipped with a DVR searches a program guide for upcoming pay-per-view (PPV) events. When the PPV event begins, the STB tunes an appropriate transponder and begins receiving programming data packets containing audio, video, system time and conditional access data packets associated with the event, which are stored for playback on a storage medium. When the user turns the STB on and selects an option to playback a previously-recorded PPV event, the appropriate programming data is retrieved from the storage medium, and the STB recreates the original transmission timing of the data, to be displayed on a display device of the user.
