EP2300683B1

EP2300683B1 - Gripping jaw device

Info

Publication number: EP2300683B1
Application number: EP09758575A
Authority: EP
Inventors: Olav Olsen
Original assignee: Aker MH AS
Current assignee: Mhwirth AS
Priority date: 2008-06-05
Filing date: 2009-06-04
Publication date: 2012-10-17
Anticipated expiration: 2029-06-04
Also published as: NO20082639L; NO333740B1; BRPI0913603A2; EP2300683A1; WO2009148328A1; BRPI0913603B1; CA2726916A1

Description

This invention relates to a gripping jaw. More specifically, it relates to a gripping jaw for a power tong where a plurality of gripping jaws are displaceable and provided with a gripping surface comprising relatively sharp portions, the power tong being designed to be able to grip about a pipe.
During the assembly and disassembly of pipe strings as is known from, for example, petroleum production, it is common to use so-called power tongs to connect or disconnect lengths of pipe to or from the pipe string. As a rule, a first power tong grips about the pipe string to hold it still, whilst a second, rotatable power tong grips about the length of pipe that is to be connected to or disconnected from the pipe string.
The gripping jaws of the power tongs, which are designed to be displaceable towards the pipe and to clamp around the pipe with great force, are often made having replaceable gripping elements which comprise a gripping surface with relatively sharp portions. The purpose of these sharp portions is to ensure that that power tong has good engagement with the pipe during the connecting operation.
The sharp portions are often made having optionally split ridges running parallel to the centre axis of the pipe.
CA 2 520 927 describes a device for use in power tongs in connection with the screwing together of lengths of pipe and is designed to be able to centre the pipe in the power tong. The centring is obtained with the aid of a combination of V-shaped gripping surfaces on a gripping jaw and a sideways movement of the gripping jaw.
WO 01/31165 describes a gripping jaw to be used for holding a pipe, and the gripping elements of the gripping jaw are formed of stud-like elements that are harder than the body of the gripping jaw. WO 98/34004 and US 5060542 disclose gripping arrangements for pipes, as requested in preamble of claim 1.
Occasionally, a malfunction occurs during the clamping of the clamping jaws because the pipe is clamped between two of the clamping jaws before it has been centred in the power tong.
Such a malfunction may result in damage to the pipe or the power tong and hence an interruption of the connecting operation.
The object of the invention is to remedy or reduce at least one of the disadvantages of the prior art.
The object is achieved according to the invention by the features that are disclosed in the description below and in the following claims.
There is provided a clamping jaw for a power tong where a plurality of clamping jaws are displaceable and provided with a gripping surface comprising relatively sharp portions, the power tong being designed to be able to grip about a pipe. The clamping jaw is characterised in that it is provided with a deflector.
The deflector is designed to help prevent the pipe from becoming clamped between two gripping jaws before it is substantially centred in the power tong.
The deflector can project as far as or farther out than the sharp portions in the direction of displacement of the gripping jaw. Thus, the deflector meets the pipe before the sharp portions can engage with the pipe.
The deflector may be given a smooth surface to help the pipe to slide on the deflector in the direction of the centre axis of the power tong.
The deflector may be elastic or comprise an elastic element. The deflector will thus give and allow the sharp portions to obtain good engagement with the pipe when the pipe is centred in the power tong.
Each gripping jaw may be provided with two cooperating deflectors. For example, there may be one deflector arranged on each side of the sharp portions relative to the centre axis of the power tong.
In other embodiments, the deflector may be spring or hydraulically biased in the direction of displacement of the gripping jaw, whereby the deflector is pushed back in relation to the sharp portions at a predetermined clamping force against the pipe.
The provided deflector substantially reduces the danger of a pipe becoming clamped between two gripping jaws before the pipe is centred in the power tong.
In what follows, an example is described of a preferred embodiment that is illustrated in the attached drawings, wherein

Fig. 1 is a schematic view of a power tong where a pipe is clamped between two gripping jaws before it is centred in the power tong;
Fig. 2 is a perspective view of a power tong equipped with three gripping jaws; and
Fig. 3 is a perspective view on a larger scale of a gripping jaw equipped with two deflectors

In the drawings the reference numeral 1 designates a power tong which comprises a power tong housing 2 and three gripping jaws 6 evenly distributed around the centre axis 4 of the power tong 1. The gripping jaws 6 are arranged in their respective guide 8. See Fig. 2.
In this preferred embodiment, the gripping jaws 6 are hydraulically actuated and synchronised, as all gripping jaws 6 being displaced the same distance in and out in the guides 8 relative to the centre axis 4 of the power tong 1.
Each gripping jaw 6 is provided with a replaceable gripping element 10, the gripping element 10 being constructed with relatively sharp portions 12 in the form of ridges which, when engaged, run parallel to the centre axis 4. See Fig. 3.
Each gripping jaw 6 is provided with two deflectors 14, one on each side of the sharp portions 12. The deflector 14 comprises a smooth metal band 16 which projects slightly out from the sharp portions 12, and an elastic rubber-like material 18. The elastic material 18 is arranged between the metal band 16 and the gripping jaw 6. The metal band 18 is secured to the gripping jaw 6 by screw bolt connections 20.
In Fig. 1 there is a pipe 22 in the power tong 1. The pipe 22 in Fig. 1 is clamped between two gripping jaws 6 that are not provided with deflectors 14. The centre axis 24 of the pipe 22 in this case is a substantial distance from the centre axis 4 of the power tong 1.
The pipe 22 will thus be turned eccentrically when the power tong 1 is turned, and will also very probably be pulled loose from the sharp portions 12 when a torque is to be transmitted from the power tong 1 to the pipe 22.
When the gripping jaws 6 are provided with deflectors 14, the pipe 22 will, when the deflectors 14 comes into contact with the pipe 22, slide against the metal band 16 and be centred in the power tong 1 before the sharp portions 12 engage with the pipe 22.
When the pipe 22 is centred and further force is applied to the gripping jaws 6, the elastic material 18 gives, so that the sharp portions 12 engage with the pipe 22.

Claims

A gripping jaw device (6) for a power tong (1) where a plurality of gripping jaws (6) are displaceable and provided with a gripping surface comprising relatively sharp portions (12), the power tong (1) being designed to be able to grip about a pipe (22),
characterised in that the gripping jaw (6) is provided with at least one deflector (14) arranged symmetrically with respect to a longitudinal symmetry axis (A-A) of the sharp portions, and projecting as far as or farther out than the sharp portions (12) in the direction of displacement of the gripping jaw (6) and which is designed to come into contact with the pipe (22) in order to centre it in the power tong (1) before the sharp portions (12) engage with the pipe.
A device according to claim 1, characterised in that the deflector (14) comprises an elastic material (18).
A device according to claim 1 or claim 2, characterised in that the deflector (14) is provided with a smooth surface (16) against the pipe (22).
A device according to any one of claims 1 to 3, characterised in that the gripping jaw (6) is provided with two cooperating deflectors (14).