CN-122029338-A - Safety mechanism for an overshot, an overshot comprising the safety mechanism, and a method of using the overshot

Abstract

An overshot (10 ') includes a release sleeve (24 ') and a safety mechanism (52) for selectively covering a portion of a latching jaw (30) of the overshot (10 '). The release sleeve (24 ') is movable along the latch between a distal position and a proximal position in which the release sleeve (24') covers the portion of the locking pawl (30) and avoids the lock (pawl), respectively. The safety mechanism (52) is configurable between a locked configuration and an unlocked configuration in which the release sleeve (24') is prevented from reaching the distal position and allowed to reach the distal position, respectively.

Inventors

• Spencer gauthier
• SALVADOR PATRICK

Assignees

• 安百拓加拿大有限公司

Dates

Publication Date

20260512

Application Date

20240924

Priority Date

20231004

Claims (20)

1. 1. An overshot, comprising: A latching jaw movable between a latching configuration and a release configuration in which the latching jaw is positioned for engagement and release, respectively, from a head assembly; a release sleeve longitudinally movable along the latch between a proximal position and a distal position, wherein In the proximal position, the release sleeve is retracted from the locking pawl, and In the distal position, the release sleeve is aligned with at least a portion of the locking pawl to engage the locking pawl to lock the locking pawl in the release configuration, and A safety mechanism mechanically coupled to the release sleeve and configurable between a locked configuration in which the release sleeve is prevented from reaching the distal position and an unlocked configuration in which the release sleeve is longitudinally movable to reach the distal position when the locking pawl is in the release configuration.
2. 2. The latch defined in claim 1 wherein the release sleeve and the safety mechanism engage one another such that with the latch supported from below, multiple cycles between applying tension to the latch and releasing the tension move the safety mechanism from the locked configuration to the unlocked configuration.
3. 3. An overshot as defined in claim 1 or 2, wherein the release sleeve and the safety mechanism are engaged with one another by a key and keyway assembly.
4. 4. The latch of claim 3 wherein the safety mechanism defines the keyway and the key extends from the release sleeve.
5. 5. The fisher as defined in claim 3 or 4, wherein the keyway defines a keyway first end and a keyway second end that are circumferentially spaced apart, the key being at the keyway first end in the locked configuration and at the keyway second end in the unlocked configuration.
6. 6. The latch of claim 5, wherein the keyway is defined at the keyway first end to receive a keyway first end section of the key in the locked configuration, at the keyway second end to receive a keyway second end section of the key in the unlocked configuration, and a keyway intermediate section extending between the keyway first end section and the keyway second end section, the keyway intermediate section being serrated circumferentially along the safety mechanism, the keyway second end section extending distally a greater extent than the keyway first end section and the keyway intermediate section.
7. 7. The latch jack as defined in claim 6 wherein The latch dog defines a latch dog mounted to a latch head and a longitudinally opposed jar terminating proximally in a rope attachment, the jar including a jar proximal element and a jar distal element mounted to one another so as to be movable in reciprocal motion relative to one another; the keyway being longitudinally fixed relative to the jar distal member; The rope attachment and the fisher head being movable relative to each other in a reciprocating motion and the release sleeve remaining longitudinally fixed relative to the fisher head, and The keyway is configured such that the reciprocation moves the key relative to the keyway toward the keyway second end section in the absence of other external influences.
8. 8. The fisher as defined in claim 7, wherein the rope attachment and the fisher head are biased away from each other in a longitudinal direction.
9. 9. The fisher as defined in claim 7, wherein the rope attachment and the fisher head are biased longitudinally away from each other by a biasing element that applies a biasing force insufficient to support at least one of a static weight and a dynamic weight of a proximal part of the fisher that is co-movable with the rope attachment.
10. 10. The fisher as defined in any one of claims 5 to 9, further comprising a biasing element that circumferentially biases the key and the keyway relative to each other such that the key is biased toward the keyway second end section.
11. 11. The fisher as defined in any one of claims 3 to 10, wherein the release sleeve defines a sleeve proximal portion and the safety mechanism defines a control sleeve configured to axially receive the sleeve proximal portion into the control sleeve, the key protruding radially outwardly from the sleeve proximal portion, and the keyway extending through the control sleeve.
12. 12. The latch defined in claim 11, wherein the release sleeve rotates axially relative to the control sleeve as the safety mechanism moves between the locked and unlocked configurations.
13. 13. The latch defined in claim 12 wherein cycling between applying the tension on the latch and releasing the tension causes a reciprocating motion of the control sleeve and the release sleeve relative to each other, the reciprocating motion causing rotation of the release sleeve between the locked configuration and the unlocked configuration.
14. 14. An latch defined in any one of claims 1 to 13, wherein the release sleeve is biased distally so as to be urged distally towards the pulling pawl when the safety mechanism is in the unlatched configuration.
15. 15. An overshot as defined in any one of claims 1 to 14, further comprising a lock for selectively locking the safety mechanism in the locked configuration.
16. 16. An overshot as defined in any one of claims 1 to 15, wherein the safety mechanism is removably attached to the overshot such that the overshot is operable in a base configuration in which the safety mechanism is absent and a sleeve actuated configuration in which the safety mechanism is present.
17. 17. An latch defined in any one of claims 1 to 16, wherein the latching dogs each define a hook for engaging the head assembly, the latching dogs extending laterally relative to the latch, the latching dogs protruding laterally to a greater extent in the latched configuration than in the released configuration.
18. 18. A safety mechanism for an overshot having a latching jaw movable between a latched configuration and a released configuration in which the latching jaw is positioned for engagement and release from a head assembly, respectively, and a release sleeve longitudinally movable along the overshot between a proximal position in which the release sleeve is retracted from the latching jaw and a distal position in which the release sleeve is aligned with at least a portion of the latching jaw to engage the latching jaw to lock the latching jaw in the released configuration, the safety mechanism comprising: A safety mechanism body defining a sleeve engagement portion for mechanically coupling to the release sleeve, the safety mechanism and the release sleeve being movable relative to one another between a locked configuration in which the release sleeve is prevented from reaching the distal position and an unlocked configuration in which the release sleeve is longitudinally movable to reach the distal position when the locking pawl is in the release configuration.
19. 19. A method of operating a latch, the latch having a latching jaw and a release sleeve for selectively retaining the latching jaw in a release configuration, the latch further comprising a safety mechanism for selectively retaining the release sleeve proximally relative to the latching jaw, the method comprising: engaging the release sleeve and the safety mechanism relative to each other such that the release sleeve is locked proximally relative to the locking pawl; moving the locking pawl to a locked configuration in which the locking pawl engages the head assembly; lowering the fisher attached to the head assembly into the borehole to a bottom end of the borehole using a wireline; Moving the locking pawl to the release configuration, and Unlocking the release sleeve from the safety mechanism and moving the release sleeve such that the release sleeve is at least partially aligned with the locking pawl to retain the locking pawl in the release configuration.
20. 20. The method as defined in claim 19, wherein unlocking the release sleeve from the safety mechanism includes performing at least one cycle of pulling the cord and releasing tension in the cord.

Description

Safety mechanism for an overshot, an overshot comprising the safety mechanism, and a method of using the overshot Technical Field The present invention relates to core drilling and, more particularly, to a safety mechanism for an overshot, an overshot including the safety mechanism, and a method of using the overshot. Background A common method used in the mining and mineral exploration industries to study mineral geology is to extract core samples by corded diamond coring drilling. The method uses a diamond impregnated drill bit (diamond IMPREGNATED DRILL bit) to cut a core sample collected inside an inner tube. At regular intervals, the inner tube is retrieved from the bottom of the borehole and brought to the surface for emptying and collection. An apparatus called an overshot for collecting an inner pipe and a core section contained in the inner pipe from the bottom of a borehole is connected to a head assembly screwed onto the inner pipe. The drill holes may be wet holes or dry holes. Wet holes are more common and can be considered to always have a ground water level near the beginning of the orifice or hole, while dry holes have a very low or non-existent ground water level in the borehole. This is important because the groundwater level determines how the inner tube is installed in the borehole after the emptying for collecting the next core section. In wet holes, the inner tube is typically simply plunged into the borehole, and the water serves as a buffer to limit its maximum velocity during descent within the borehole. This cannot be performed in dry holes because the inner tube descends too fast and causes damage to the equipment. Thus, in a dry bore, a fisher and attached wireline cable are used to lower the inner tube to the full depth of the borehole, and the fisher is released at the bottom of the bore. There are two types of fishers on the market, spearhead fishers and spearhead-receiving fishers. Two types of fishers use pivotable levers (referred to as latching dogs) to selectively engage and disengage a head assembly that is threaded onto an inner tube. The locking pawl has two positions, an engaged position and a disengaged position. Many fishers automatically switch between these positions depending on whether they carry a load, a passive safety feature. When the latch jack is connected to the unsupported inner tube, the latching dogs move to an engaged position where the head assembly is engaged. When the locking dogs are in the engaged position they cannot be released. Once the inner tube is supported (e.g., on the ground or at the bottom of the borehole), the locking dogs move to a disengaged position, allowing the latch to release. Outside the borehole, the fisher is disengaged manually. Inside the borehole, a release mechanism is required. When the locking dogs are in the disengaged position, the release sleeve can slide over the locking dogs, holding them in that position, which allows disconnection from the head assembly/inner tube. When the locking dogs are in the engaged position, the release sleeves cannot slide past them and therefore the latch cannot release when carrying a load. A problem that plagues this solution occurs when the inner tube hits or is caught by an obstacle during travel, which partly or completely removes the load required to hold the locking pawl in the engaged position, creating the possibility that the locking pawl may move to the disengaged position. This can occur very quickly and allows the release sleeve to slide over the locking dogs, releasing the latch. In this context, there is a need in the art to provide a safety mechanism for the latch to reduce or eliminate the risk that the release sleeve may inadvertently move to cover the latch dogs and retain the latch dogs in their released position. It is therefore an object of the present invention to provide a safety mechanism. Disclosure of Invention In a broad aspect, there is provided an latch comprising a latching jaw movable between a latched configuration and a released configuration in which the latching jaw is positioned for engagement with and release from a head assembly, respectively, a release sleeve longitudinally movable along the latch between a proximal position in which the release sleeve is retracted from the latching jaw and a distal position in which the release sleeve is aligned with at least a portion of the latching jaw so as to engage the latching jaw to lock the latching jaw in the released configuration, and a safety mechanism mechanically coupled to the release sleeve and configurable between a locked configuration in which the release sleeve is prevented from reaching the distal position and an unlocked configuration in which the release sleeve is longitudinally movable to reach the distal position when the latching jaw is in the release configuration. It is also possible to provide a latch wherein the release sleeve and the safety mechanism engage each other such that wit