HOLE OPENER Russian patent published in 2015 - IPC E21B7/28 E21B17/10 E21B10/32 

FIELD: mining.

SUBSTANCE: hole opener contains a centralizer, a housing with a central feedthrough channel and grooves, the blades fitted with rock cutting elements and ledges designed as a teeth, fixed in housing grooves with a possibility of extension and a mechanism of blade extension into the working position, a hollow shaft with the top thread for joining with the borehole equipment, a lateral hole and a lower bushing placed in the feedthrough channel of the housing with fixing due to twisting with reference to the housing, and the blades are fitted with the roots interacting with the hollow shaft bushing during extension of blades into the working position, and the device for fixing of blades in inoperative position containing radially spring-loaded circular segments. The roots are designed as radial pistons inserted into the housing with a possibility of limited radial movement under the action of internal excessive pressure due to the ring segments which are installed inside and blades installed which are installed outside. The roots are designed with a possibility of interaction with the hollow bushing of the shaft through ring segments, and the ring segments are designed as longitudinal plates.

EFFECT: reliability and durability of the hole opener.

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