Tools – Wrench – screwdriver – or driver therefor – Machine
Reexamination Certificate
1999-08-05
2001-12-11
Eley, Timothy V. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Machine
C081S057140, C081S057150, C081S057200, C081S057340
Reexamination Certificate
active
06327938
ABSTRACT:
This invention relates to a rotary for use in a tong, and a tong fitted with such a rotary.
During the construction of oil and gas wells it is necessary to connect and disconnect a large number of threaded tubulars, for example lengths of casing and drill pipe. This is generally effected by means of a tong which is a device which grips the tubular. The tubular is then rotated either by rotating the tong manually or, more usually by a hydraulic motor.
The cost of running a drilling rig is extremely high and consequently there is tremendous pressure to develop tools which can be operated more rapidly than previous tools. It is also important that such tools are reliable even under the extreme environmental conditions where drilling often takes place.
U.S. Pat. No. 4,437,363 discloses a rotary for use in a tong, comprising a casing having an opening for entry and removal of a tubular in a radial direction and having a peripheral wall, cams on an inner face of the peripheral wall, first and second jaw holders supported in the casing for guidance by the cams and for rotation between positions where they converge for gripping the tubular and positioned where they diverge for release of the tubular, and first and second jaws slidably mounted on the jaw holders.
The invention is characterised in that in a divergent position of the jaw holders the first and second jaws are slidable by contact with the tubular along arcuate paths between first positions in which the tubular is insertable into and removable from the rotary and second positions where they surround and can grip the tubular.
Advantageously, said jaw has a gripping surface which is substantially arcuate for gripping the surface of a tubular and the centre of curvature of such arcuate path lies between the centre of curvature of said gripping surface and said arcuate path. The gripping surface may be a continuous surface or defined by several spaced apart gripping elements. Jaws having arcuate gripping surfaces are disclosed for power tongs in WO 94/01249.
Preferably, the centre of curvature of said arcuate path lies between the centre of curvature of said gripping surface and said gripping surface. Advantageously, the centre of curvature of said arcuate path is substantially midway between the centre of curvature of said gripping surface and said gripping surface. Preferably, one of said jaw and said jaw holder is provided with an arcuate track which defines said arcuate path, and the other of said jaw and said jaw holder is slidably mounted in said arcuate track.
There may be provided a jaw assembly comprising two jaw units in accordance with the present invention. Preferably, said jaw units are mounted for pivotal movement about a common pivot shaft. Advantageously, said jaw assembly includes means which bias said jaw units apart.
The present invention also provides a tong fitted with a rotary in accordance with the present invention.
Traditionally, a rotary is made from three separate pieces, i.e. a top section, a bottom section and a peripheral wall. Each section has to be carefully made and machined to ensure that all three sections can be bolted together. This involves considerable skilled work and consequently a rotary is a relatively expensive item. In order to help overcome this problem, the rotary may be formed as a one piece casting.
One of the features of existing tongs is that their rotaries are difficult to furnish. Thus, routine maintenance usually involves dismantling the whole rotary, checking the parts and reassembling the whole. Whilst this is a straightforward procedure in the clean conditions of a workshop it can be problematic when carried out in a muddy field, in sand or in snow. In order to help solve this problem a rotary may be provided which comprises a top section, a bottom section, and a peripheral wall therebetween, characterised in that at least one of said top section and said bottom section is provided with an elongate slot which, when said rotary is in use, accommodates a pivot shaft on which a jaw assembly can be pivotally mounted.
Jaw holders and jaws for tongs are traditionally machined from the solid. This is a comparatively expensive procedure, and in the present invention may be made from a stack of individually cut laminations.
Conveniently, the laminations could be cut with a laser from sheet steel. The stack of laminations could then, for many purposes, be simply welded together along their sides and/or bolted together and/or glued together. Mass produced laminations are relatively inexpensive and an acceptable final product can be produced at a fraction of the cost of a product machined from the whole.
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Berry Jr. Willie
Eley Timothy V.
Moser Patterson & Sheridan LLP
Weatherford / Lamb, Inc.
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