Fail safe locking overshot device

A device with an overshot device comprising:

• an elongated body adapted to be connected to a hoisting line in one end and with a tubular opening receiving a spearhead in the other end, said elongated body comprising:
• first and second axially extending slots;
• first and second locking dog seats;
• two lifting dogs comprising first and second lifting lugs arranged to pivot around a common lifting dog pivot pin, said lifting lugs being configurable between a spearhead latched configuration and a spearhead unlatched configuration, each lifting lug comprising a spearhead capture member and a spearhead release member, the spearhead capture member being adapted to capture the spearhead, the two lifting dogs being axially slidable with respect to the elongated body;
• a lifting dog biasing element configured to connect the lifting lugs and urge the lifting lugs towards the spearhead latched configuration;
• two locking dogs comprising first and second locking lugs arranged to pivot around a common locking dog pivot pin, said locking lugs being configurable between a lifting dog locked configuration and a lifting dog unlocked configuration, each locking lug comprising a lifting dog locking member and a lifting dog release member, the lifting dog locking member being adapted to lock the lifting dogs in the spearhead latched configuration, the two locking dogs being axially slidable with respect to the elongated body;
• a locking dog biasing element configured to connect the locking lugs and urge the locking lugs towards the lifting lug locked configuration;
• and
• a pair of sliding bars connected to the common lifting dog pivot pin, and further connected therebetween with a lifting dog retention pin;
• wherein downward axial movement of the locking dogs is arranged to force the locking dogs into the lifting dog unlocked configuration in which the lifting dog locking members releasably interlock with the first and second locking dog seats, and wherein upward actuation of the lifting dog retention pin displaces the pair of sliding bars along the axially extending slots of the elongated body and into contact with the lifting dog locking members thereby separating the lifting dog locking members from the first and second locking dog seats and configuring the locking lugs in the lifting dog locked configuration.

A method of operating an overshot device comprising:

• providing an overshot device comprising:
• an elongated body adapted to be connected to a hoisting line in one end and with a tubular opening receiving a spearhead in the other end, said elongated body comprising:
• first and second axially extending slots;
• first and second locking dog seats;
• two lifting dogs comprising first and second lifting lugs arranged to pivot around a common lifting dog pivot pin, said lifting lugs being configurable between a spearhead latched configuration and a spearhead unlatched configuration, each lifting lug comprising a spearhead capture member and a spearhead release member, the spearhead capture member being adapted to capture the spearhead, the two lifting dogs being axially slidable with respect to the elongated body;
• a lifting dog biasing element configured to connect the lifting lugs and urge the lifting lugs towards the spearhead latched configuration;
• two locking dogs comprising first and second locking lugs arranged to pivot around a common locking dog pivot pin, said locking lugs being configurable between a lifting dog locked configuration and a lifting dog unlocked configuration, each locking lug comprising a lifting dog locking member and a lifting dog release member, the lifting dog locking member being adapted to lock the lifting dogs in the spearhead latched configuration, the two locking dogs being axially slidable with respect to the elongated body;
• a locking dog biasing element configured to connect the locking lugs and urge the locking lugs towards the lifting lug locked configuration;
• and
• a pair of sliding bars connected to the common lifting dog pivot pin, and further connected therebetween with a lifting dog retention pin;
• lowering the locking dogs to force the locking dogs into the lifting dog unlocked configuration in which the lifting dog locking members releasably interlock with the first and second locking dog seats;
• and
• raising upward the lifting dog retention pin to displace the pair of sliding bars along the axially extending slots of the elongated body and into contact with the lifting dog locking members thereby separating the lifting dog locking members from the first and second locking dog seats and configuring the locking lugs in the lifting dog locked configuration.

A pivotable lifting lug comprising:

• a spearhead release member for releasing a spearhead, the spearhead release member comprising:
• a main pivoting element connectable to a lifting lug pivoting element;
• and
• a release arm extending at an extremity of the spearhead release member;
• a spearhead capture member for capturing the spearhead, the spearhead capture member comprising:
• a spearhead capture tip;
• and
• a release arm support portion opposite the spearhead capture tip and having a shape substantially complementary to a shape of the release arm;
• a common pivoting element configured to pivotably connecting the spearhead release member to the spearhead capture member;
• and
• a lifting lug biasing element configured to urge the spearhead capture member against the release arm of the spearhead release member.