Pipe gripping device

Details Pipe gripping device Pipe gripping device

1998-09-21

2001-03-13

Vo, Peter (Department: 3721)

Tool driving or impacting

Hammer or tool shaft reciprocated by gripping means which...

With fixed means cyclically contacted by grip structure

C173S053000, C173S149000

Reexamination Certificate

active

06199641

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a pipe gripping device for use in a pipe push/pull machine or the like.
BACKGROUND OF THE INVENTION
Pipe handling devices, commonly called snubbing or pipe push/pull machines, are used in drilling operations to push pipe into and pull pipe out of a well bore. Pipe push/pull machines include a pair of pipe gripping devices. The pipe gripping devices are mounted on an assembly that maintains the devices in vertical alignment and, while the bottom pipe gripping device is held stationary, moves the upper pipe gripping device vertically toward and away from the lower pipe gripping device. The pipe gripping devices each carry slip members that can be alternately engaged with and released from a pipe being pushed into or pulled from the well.
Pipe gripping devices are known which include a plurality of radially moveable carrier blocks on which slip members are mounted. The slip members can be shifted radially inwardly by the movement of the carrier blocks until teeth on the inner surfaces of the slips engage against the outer surface of a pipe passing through the center of the pipe gripping device. The slip members normally are centered with respect to the horizontal axis of the carrier blocks and are moveably retained in slots in the carrier blocks. Each slot has a pair of wedged surfaces that are co-operable with companion wedged surfaces on the slip member in a manner such that any vertical movement of the slip over the wedged surfaces of the carrier block will drive the slip radially inwardly or outwardly relative to the center of the pipe gripping device. The wedged surfaces are arranged in opposition such that the slip drives radially inward when pushing or pulling pipes with the pipe gripping device.
The carrier blocks are moved by use of spiral gear plates which engage teeth formed in the upper and lower surfaces of the carrier blocks.
However, previous devices have no safety systems to prevent release of pipe which is subject to substantial longitudinal force, such force being due to string weight or high well head pressure.
In addition, when the carrier blocks of previous devices are withdraw radially away from pipe gripping position, they tend to lock against the outer wall of the housing. This locking is caused by the carrier blocks loading against and, thereby, locking against the outer wall. The inertia in the movement of the carrier blocks causes the force of their impact against the housing to be greater than the force which can be exerted by the motor to move the carrier blocks radially inward. The only solution to such jamming has been to increase the size of the drive means. This solution is undesirable as it increases both the cost, as well as the size and the portability of the pipe gripping devices.
Increased use of underbalanced drilling (UBD) technology, where most wells are designed and operated to maintain less than 100 psi in the annulus at surface, has created the need for pipe handling devices able to operate in both the pipe heavy and pipe light conditions and which are able to withstand the forces placed upon them without jamming or binding. Increased use has also required that safety concerns be addressed while the industry has demanded smaller, more portable devices.
SUMMARY OF THE INVENTION
A pipe gripping device for use in a pipe push/pull machine is disclosed which can withstand the rigors of underbalanced drilling without undesirable lock ups. The pipe gripping device is of compact size and is of reasonable cost. In preferred embodiments, the pipe gripping device is selected to prevent inadvertent release of a pipe while the pipe has applied thereto a force against which the device is intended to act.
According to a broad aspect of the present invention, there is provided a gripping device for releasably engaging an elongate member, the gripping device comprising a housing including an upper wall, a lower wall, a side wall and a central opening for accepting an elongate member therethrough; a plurality of slip carrier blocks spaced circumferentially about the opening between the upper wall and the lower wall, each slip carrier block having a rear surface and a sloping front face, the sloping front faces together forming a slip bowl bore with a diameter and the slip carrier blocks each being radially moveable between a fully retracted position and an advanced position to adjust the diameter of the bore; a slip slidably mounted on each sloping front face to move over the front face; a motor to drive the movement of the slip carrier blocks; and a deceleration means for slowing the carrier blocks before the rear surfaces of the carrier blocks come into contact with the side wall of the housing.
By slowing the carrier blocks prior to their contact with the housing side wall, lock up of the carrier blocks against the housing is avoided. The deceleration means can be, for example, a switch which acts to slow the movement of the carrier blocks by slowing the motor. Alternately, the device can include a stop means which acts to stop the carrier blocks before they come into contact with the housing side wall such that a gap is formed between the carrier blocks and the housing side wall when the carrier blocks are in the fully retracted position. The stop means can be any suitable structure or system for limiting the radial outward movement of the carrier blocks. In one embodiment, the deceleration means and the stop means are combined as a switch which senses the proximity of the rear surface of at least one carrier block to the side wall and acts to stop the motor when the rear surface of the carrier block is a selected distance from the side wall.
According to a further broad aspect of the present invention, there is provided a pipe gripping device for releasably engaging a pipe, the pipe gripping device comprising a housing including a central opening for accepting a pipe therethrough, the central opening extending along an axis; a first gripping assembly and a second gripping assembly mounted within the housing, the first gripping assembly including a plurality of slip carrier blocks spaced circumferentially about the opening, each slip carrier block having a rear surface and a sloping front face, the sloping front faces together forming a slip bowl bore with a diameter and the slip carrier blocks each being radially moveable between a fully retracted position and an advanced position to adjust the diameter of the bore; a slip slidably mounted on each sloping front face to move over the front face and the second gripping assembly including a plurality of slip carrier blocks spaced circumferentially about the opening, each slip carrier block having a rear surface and a sloping front face, the sloping front faces together forming a slip bowl bore with a diameter and the slip carrier blocks each being radially moveable between a fully retracted position and an advanced position to adjust the diameter of the bore; a slip slidably mounted on each sloping front face to move over the front face; the slip bowl bore of the first gripping assembly being tapered in a direction substantially parallel with the axis of the central opening and the slip bowl bore of the second gripping assembly being tapered in a direction opposite the first gripping assembly and the slip carrier blocks of the first gripping assembly being radially moveable independent of the slip carrier blocks of the second gripping assembly, such that pipes having applied thereto a substantially axially directed upward force, relative to the opening, can be selectively gripped by the first gripping assembly and pipes having applied thereto a substantially axially directed downward force, relative to the opening, can be selectively gripped by the second gripping assembly.
According to a broad aspect of the present invention, there is provided a gripping device for releasably engaging an elongate member, the gripping device comprising a housing including a central opening for accepting an elongate member therethrough; a plurality of slip carrier blocks

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