Importance

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Abstract

A chain-powered pipe tong device for spinning up and torquing drill pipe and casing when making up or disconnecting a string of tubular elements in the drilling and casing of oil wells, the tong device including a chain sprocket drivingly connected through a clutch subassembly to a gear train which drives an open centered main gear. The main gear is rotatably supported in a gear housing having an open center aligned with the open center of the main gear. The main gear and gear housing each have aligned radially opening pipe receiving slots at one side thereof. Pipe engaging dog subassemblies are mounted in the gear housing for radial reciprocation relative to the main gear and the gear housing. Each dog subassembly includes a cam rod which has one edge bearing against a V-shaped cam surface defined by the main gear. The cam rod functions for interlocking the main gear and gear housing against relative rotation in one direction at one time period during operation of the device, and also functions, in following the V-shaped cam surface, to extend pipe engaging dogs in the dog subassembly into clamping engagement with a pipe extending through the opening at the center of the main gear and the gear housing. A shifting and clutch subassembly is provided and is connected to a braking shaft which is positioned for lockingly engaging the gear train to prevent radial retraction of the pipe engaging dogs when the clutch subassembly is in a neutral position.

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First Claim