Overshot device
A device with an overshot including a first part with an elongated body adapted to be connected to a hoisting line in one end and with a tubular opening arranged/designed to receive a spearhead in the other end. The overshot further includes a second part with a scissor like mechanism including two lifting dogs arranged to pivot around a common pivot pin. The lifting dogs are connected via a biasing unit and the elongated body includes a central, axially extending slot. The scissor like mechanism is arranged with the common pivot pin sliding in the slot between a first end position where the biasing unit is arranged to close the lifting dogs such that a spearhead received in the tubular opening is locked and a second end position where an opener including an opening pin is arranged to force the lifting dogs open against the force of the biasing unit, such that a spearhead received in the tubular opening is released.
1. An overshot device, comprising:
a first part with an elongated body adapted to be connected to a hoisting line at a first end and with a tubular opening adapted to receive a spearhead in a second end, the elongated body comprising an central, axially extending slot,
a second part with a scissor like mechanism comprising two lifting dogs and a common pivot pin about which the two lifting dogs are arranged to pivot, wherein the common pivot pin extends into the slot,
a biasing unit operatively connecting the lifting dogs to each other, and
an opener comprising an opening pin,
wherein the scissor like mechanism is arranged with the common pivot pin sliding in the slot between a first end position where the biasing unit is arranged to close the lifting dogs such that the spearhead received in the tubular opening is locked and a second end position where the opener is arranged to force the lifting dogs open against a force of the biasing unit such that a spearhead received in the tubular opening is released.
2. The device according to claim 1 , wherein the opening pin is a stationary opening pin attached to the elongated body.
3. The device according to claim 2 , wherein the stationary opening pin is positioned axially above the slot, between the slot and the hoisting line connection end.
4. The device according to claim 3 , wherein the stationary opening pin is arranged in parallel with the pivot pin.
5. The device according to claim 2 , wherein the stationary opening pin is positioned axially below the slot, between the slot and the tubular opening end.
6. The device according to claim 1 , wherein the opening pin is a sliding opening pin arranged sliding in the slot and connected to the pivot pin by a sliding bar.
7. The device according to claim 6 , wherein the sliding opening pin is arranged in parallel with the pivot pin.
8. The device according to claim 1 , wherein the body comprises a lock arranged to lock the lifting dogs inside the elongated body.
9. A method of operating an overshot device comprising a first part with an elongated body connected to a hoisting line at a first end and with a tubular opening adapted to receive a spearhead in a second end, the overshot device further comprising a second part with a scissor like mechanism comprising two lifting dogs and a common pivot pin, the overshot device further comprising a biasing unit operatively connecting the lifting dogs, the elongated body comprises an central, axially extending slot, and wherein the scissor like mechanism is arranged with the common pivot pin sliding in the slot, the method comprising:
manually operating the common pivot pin to slide in the slot from a first end position, where the biasing unit is arranged to pivot the lifting dogs to grip a spearhead received in the tubular opening to a second end position, and
forcing the lifting dogs to pivot into a non-gripping position due to the sliding movement such that the spearhead is released when the pivot pin reaches the second position.
10. The method according to claim 9 , wherein a lock locks the lifting portions of the lifting dogs within the interior of the elongated body.
11. The method according to claim 9 , further comprising:
propelling the overshot through a drill string using fluid under pressure an underground application in conjunction with an underground adapter adapted with a propulsion seal.