Rest for drilling rig

摘要

The rest comprises a housing accommodating a device for centering a drill rod connected with a rotating mechanism actuated by a hydraulic drive. The characteristic feature of the rest is that the drill rod centering device has at least three link gears with bearing rollers. The rollers are uniformly circumferentially spaced within the housing and each is mounted on a vertical spindle for radial displacement by the drive by means of the rotating mechanism and the link gears. The rollers have their external side surfaces permanently urged against the drill rod to define the centering diameter. The centering device is also provided with hydraulic valves underlying the rollers. The rollers are spring-urged along their axes and are mounted for axial displacement so that, upon a certain friction value developing between the rod and the rollers, the rollers travel jointly with the rod in the direction of drill to engage the hydraulic valves, so that the hydraulic valves are operated to set the centering diameter in correspondence with the rod diameter.