Pipe end fittings

Details Pipe end fittings Pipe end fittings

1996-03-11

1997-09-30

Nicholson, Eric K.

Pipe joints or couplings

Nonmetal to metal

Internal member

2853825, 29507, F16L 3320

Patent

active

056719531

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to pipe end fittings. It particularly relates to towing heads and pressure test sets for connection to pipes (or other at least partly tubular objects).
Towing heads may be useful in pipe laying and in directional drilling. For example, a hole for a pipe may be produced, e.g. under a road, by means of a drill string. This is then connected to a reamer and pipe and drawn back. High pressure mud is pumped down the drill string and through the reamer during the drill and reaming operations. The reamer enlarges the hole to accommodate the pipe. However in the process the pipe is subject to considerable stresses. It risks being damaged or detached. Even if neither of these happens, mud may be forced into its interior, necessitating cleaning before use, especially if it is for use as a water supply pipe.


BACKGROUND ART

A known type of pipe towing head employs a threaded shaft with a towing eye at one end. The shaft passes through an expandable element, and engages a tapered expansion mandrel. In use, a pipe is passed onto the head so as to surround the expandable element. Rotation of the shaft draws the mandrel further into the expandable element, causing it to expand radially and grip the bore of the pipe. The pipe-engaging surface of the expandable element has annular ribs of sawtooth section for gripping the pipe. Thus a strong connection can be attained quite easily. This is generally sufficient for normal pipe laying processes. But when very high forces are involved, e.g. in directional drilling processes, it may not suffice. The mandrel can be drawn up further to apply greater force to the pipe, but this increases the risk of splitting the pipe. Further problems are caused by the fact that the internal diameters of nominally identical pipes can vary quite considerably. Furthermore pipes of different wall thickness are used for different purposes, so that pipes of the same outside diameter may have very different internal diameters. Such problems are also relevant to other end fittings, e.g. to pressure test sets which must be couplable to pipes and the like with reliable sealing.


DISCLOSURE OF THE INVENTION

According to the invention there is provided an end fitting for a tubular element having: elongate element extends and a rear portion defining a skirt; and at least partly radially within the skirt; and elongate element, so that, in use, the mandrel can be drawn forwardly to urge expansion of the expandable element by relative rotation of the elongate element.
Generally, the diameter of the expandable element in a non-expanded state will be less than the internal diameter of the skirt (at least at a rear portion) and at least in part less than the internal diameter of a pipe to be engaged. Thus a pipe can be engaged over at least part of the expandable element whose subsequent expansion causes the pipe to be engaged between the element and the skirt.
Preferably the skirt has sealing means on its radially inner surface for sealing to a pipe. Since the external diameters of pipes are normally accurately controlled in manufacture, this leads to reliable sealing. A single end fitting is suitable for use with a range of pipes with different internal diameters.
Generally the expandable element has radial projections such as circumferentially extending ribs (e.g. complete or partial annular ribs) that engage the pipe as it expands. Since the rearward ribs tend to be forced more strongly against a pipe than the forward ones, a rearward rib may be shaped and/or dimensioned so as to be less inclined to cut into a pipe.
The end fitting may be a towing head, in which case the elongate element may be a threaded bolt, typically having an engagement formation such as an eye at its front end. A towing head's body normally has a tapered front portion. There may be separate front and skirt portions. They may be connected by a screw-threaded connection. Of course the handedness of the thread should be such that the parts do not tend to become unscrewed in use.
Component

REFERENCES:
patent: 1753005 (1930-04-01), Grady
patent: 2071478 (1937-02-01), Wilk
patent: 2146756 (1939-02-01), Miller
patent: 2228018 (1941-01-01), Scholtes
patent: 2735473 (1956-02-01), Diget
patent: 2766804 (1956-10-01), Kaiser
patent: 2947409 (1960-08-01), Dodge
patent: 3490793 (1970-01-01), Wagner
patent: 3575447 (1971-04-01), Merkle

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