Pipes and tubular conduits – With flow regulators and/or baffles – Restrictors
Patent
1996-08-14
2000-04-25
Hook, James
Pipes and tubular conduits
With flow regulators and/or baffles
Restrictors
138 93, 138123, F15D 102
Patent
active
060532106
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF INVENTION
The present invention relates to an expandable plug adapted to seal or to regulate pressure or flow within a tube, and also to a method of control.
Expandable plugs of this general type find application in cases where normal valving of flow is inappropriate for some reason, for example because the position of the desired seal or regulation is not fixed with respect to the tube, the desired seal is temporary, or the exterior of the tube is inaccessible.
The general approach to the design and construction of expandable plugs involves the use of an elastomeric cylinder or bladder, which is caused to increase in diameter. This may be done by a variety of mechanical means, or by application of internal pressure.
In use the plug will need to withstand diametral expansion and axial thrust, the latter being due to friction (in cases where the plug moves relative to the tube) and the differential tube fluid pressure across the plug.
Mechanically expanded plugs are suitable only for relatively small ratios of expansion and/or low axial thrusts. Larger expansion ratios may be required in cases for example where undue hydraulic obstruction of the tube cannot be tolerated when the plug is not expanded, or where the tube may vary in diameter or be caused to expand by fluid pressure behind the plug. For such applications, expansion by internal pressure is preferred.
SUMMARY OF INVENTION
The present invention relates, in its first form, to an expandable plug of the inflatable type, and aims to provide a plug construction which does not require excessive pressure for inflation, yet is capable of withstanding substantial axial thrusts.
This first aspect of the invention provides an inflatable plug comprising an inflatable bladder adapted for diametral expansion by application of internal fluid pressure, fluid inlet means communicating with the interior of the bladder for connection to a source of inflating fluid and reinforcement means including flexible reinforcing cords which provide axial reinforcement to the plug and diametral support to the bladder, said cords each spreading laterally on inflation of the bladder. The cords are preferably formed of a plurality of strands which are not twisted together, thus allowing the strands of each cord to spread out laterally as the bladder is inflated.
The cords preferably extend between the opposite axial ends of the bladder to form an envelope surrounding the outer surface of the bladder, offering little or no resistance to diametral expansion of the bladder.
A second aspect of the invention relates to a method for controlling the inflation of an expandable plug in a tube so as to control the pressure differential in the tube, or so as to allow leakage of fluid past the plug, by controlling the internal pressure in the plug according to the equation. expansion pressure)
BRIEF DESCRIPTION OF THE DRAWINGS
Further preferred embodiments of the invention shall now be described with reference to the accompanying drawings, in which:
FIG. 1 is a schematic side view, partly in cross section, of a preferred plug construction;
FIG. 2 is a perspective view of a portion of the bladder with the sheath removed to reveal the helical reinforcing cord arrangement;
FIGS. 3 and 4 schematically illustrate the spreading of the cords as the plug is inflated; and
FIGS. 5 to 7 are schematic view illustrating the control method according to the second aspect of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The plug generally consists of a pair of end cap members 10 between which a cylindrical bladder 12 extends. The upstream end cap member 10a has a fluid inlet 14 for entry of liquid or gas to inflate the bladder. In practice, the end caps may be identical and the downstream end cap blocked off or restricted to provide back pressure. At least one of the end caps is physically connected to an external support to provide reactive support against axial thrust on the plug. This support may conveniently be provided by the pipe (not shown) which provides the inflatio
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Chapman Peter Glanville
Cowling Leslie Herbert
Wallace Allan Kenneth
Hook James
Uponor B.V.
Vinidex Tubemakers Pty. Limited
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