Hydraulic and earth engineering – Subterranean or submarine pipe or cable laying – retrieving,...
Patent
1988-03-18
1989-07-18
Taylor, Dennis L.
Hydraulic and earth engineering
Subterranean or submarine pipe or cable laying, retrieving,...
405303, 405156, F16L 5518
Patent
active
048489646
DESCRIPTION:
BRIEF SUMMARY
This invention relates to apparatus for correcting irregularities in or enlarging an underground duct.
Such apparatus is disclosed in British patent specification No. 2151325A. The known apparatus has a segmented outer shell comprising a segmented nose portion formed by a first set of shell parts, a segmented intermediate portion formed by a second set of shell parts, and a rear portion for attachment to a replacement lining pipe which is drawn through the duct behind the apparatus. Each set of shell parts is arranged symmetrically around a central longitudinal axis of the apparatus with each shell part pivotally connected at each of its ends, the front ends of the nose portion shell parts being connected to a common base element, the rear ends of the nose portion shell parts being connected to the front ends of the intermediate portion shell parts and to an internal expansion device, and the rear ends of the intermediate portion shell parts being connected to the perimeter of the rear portion. In a retracted configuration of the shell parts, the nose portion constitutes a cylindrical shell of a diameter smaller than the internal diameter of the duct to be entered, whilst the intermediate portion is approximately conical, the rear ends of its shell parts defining a larger diameter, substantially equal to the required diameter of the duct. Operation of the expansion device, typically a longitudinally mounted hydraulic ram coupled to connecting rods which act on the pivotal connection between the nose portion shell parts and the intermediate portion shell parts, causes the nose portion to expand to form a segmented approximately conical outer envelope corresponding in shape to the initial shape of the intermediate portion, while the intermediate portion is expanded to form a segmented cylinder of the said larger diameter. The expansion forces the walls of the duct outwards, and on retraction of the shell parts the apparatus can move forwards into the void it has created to carry out the same expansion and retraction cycle on a subsequent portion of the duct. The disclosure of the above mentioned Patent Specification is incorporated in the present specification by reference.
A difficulty encountered with the known apparatus is the entry of material from the wall of the duct into the interior of the shell by passage through the gaps which exist between the shell parts when they are in their expanded configuration. This happens mainly in ducts having walls formed from particles or pieces which do not adhere to each other when the device is expanded, and which then fall into the interior space of the apparatus and retraction mechanism. The present invention largely avoids this difficulty by arranging for those shell parts which lie side by side to overlap each other. In a preferred construction, this is achieved by providing each shell part with an outwardly facing, longitudinally extending border surface along one of its sides, this surface being located so as to be nearer the longitudinal axis of the apparatus than the outer surface of the shell part, thereby allowing an edge portion of the neighbouring shell part to overlap the border surface. In apparatus in accordance with the invention having segmented nose and intermediate portions, each shell part of each portion overlaps a shell part on one of its sides and is overlapped by the shell part on the other of its sides. In this way, as the nose and intermediate portions are expanded and retracted, the spaces enclosed by the shell parts can be largely sealed off from the outside so that no particles or pieces of a size sufficient to interfere with the internal mechanism can enter.
The preferred embodiment of the invention has shell parts in which each of the outwardly facing border surfaces is planar and, in a transverse cross-section at right angles to the longitudinal axis of the apparatus is at an angle to the pivot axes of the pivotal connections of its respective shell part, the angle being equal to one half of the angular spacing of the shell parts at t
REFERENCES:
patent: 4063425 (1977-12-01), Jutte et al.
patent: 4487052 (1984-12-01), Yarnell
patent: 4693404 (1987-09-01), Wayman et al.
I.P.D. Systems Limited
Taylor Dennis L.
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