Abstract: A joint device in extension drill equipment for percussive drilling is so constructed that, besides transmitting compressive pulses in the drill string in the direction towards the drill bit, it also by reflection transforms tensile pulses in the drill string into compressive pulses. Preferably, the joint device includes members that are axially movable relative to each other and provided with interacting surfaces, and an element connecting the members. Compressive pulses cause these surfaces to abut each other under pressure, while tensile pulses cause the surfaces to become separated. Also preferably, the joint device includes a structure for absorbing kinetic energy generated in the device by torsion pulses in the drill string.