Patent ID: 8376040

Claim:
A cutting device for emergency cutting of a line at an upper portion of a well when said line is moving downward into the well, the cutting device being arranged for incorporation of the line: wherein the cutting device comprises: a tapering guide arranged for stationary positioning relative to said upper portion of the well, said tapering guide including a narrow end portion and a wide end portion for feed-through of the line, the narrow end portion being placed, when in its position of use, at a lower position than that of the wide end portion; at least one sliding block arranged axially movable within the tapering guide, thereby allowing the at least one sliding block, when in its position of use, to move downward, by virtue of gravity, from the wide end portion to the narrow end portion of the tapering guide; and at least one cutting knife connected to the at least one sliding block and directed inwards toward the center of the tapering guide, thereby allowing the at least one cutting knife to move downward along with the at least one sliding block until engaging and cutting off said downwardly moving line, the downward movement of the line contributing to pull the at least one knife toward the center of the tapering guide so as to facilitate the cutting of the line; wherein the cutting device also comprises at least one releasable holding mechanism for standby holding of the at least one sliding block at the wide end portion of the guide, and for releasing the at least one sliding block in connection with emergency cutting of the line moving in a downward direction through the stationary tapering guide; wherein the at least one sliding block includes a magnet-affectable material, and wherein the releasable holding mechanism is comprised of an electromagnet for releasable standby holding of the at least one magnet-affectable sliding block.