Patent ID: 7013996
Filing Date: 2006-03-21
Classification: E21B

Abstract:
1. A rock drill comprising a tool and means for delivering a stress pulse to the tool comprising an impact element supported to a frame of the rock drill and means for subjecting the impact element to stress to store stress energy in the impact element and correspondingly for releasing the stressed impact element suddenly from the stress, whereupon the stress energy stored in the element is discharged in the form of a stress pulse directed at the tool, the means for subjecting the impact device to stress comprising a pressure fluid space, a shoulder provided in the impact element and facing said pressure fluid space, and means for feeding hydraulic fluid to the pressure fluid space and for releasing pressure from the space, wherein the means for releasing pressure from the pressure fluid space comprise means for discharging pressurized hydraulic fluid from said pressure fluid space, the impact element being subjected to stress by feeding pressurized hydraulic fluid to said pressure fluid space and released from stress by allowing the hydraulic fluid to suddenly flow out of said pressure fluid space.