Implements or apparatus for applying pushing or pulling force – Method or apparatus for placement of conductive wire – By fluid pressure differential in conduit
Patent
1991-05-07
1992-11-24
Swann, J. J.
Implements or apparatus for applying pushing or pulling force
Method or apparatus for placement of conductive wire
By fluid pressure differential in conduit
B66F 324
Patent
active
051656620
DESCRIPTION:
BRIEF SUMMARY
This invention relates to fibre blowing.
Fibre blowing is a process in which lightweight transmission lines are advanced through installation ducts by the viscous drag of a fluid, usually compressed air. This process is described in our European patent specification 108590.
A known form of fibre blowing apparatus includes a transmission line package coiled into a sealed, pressurised container, the pressure within the container providing the propellant gas, thus eliminating the need for a compressor or other separate source of propellant. Such pressurised containers may be particularly useful for repair work.
A disadvantage of such an arrangement is that, once the pressure in the container is released to commence installation of a transmission line package into a duct, the propellant cannot be shut off without a substantial risk of that portion of the package which is already in the duct being damaged by closure of a valve to block the duct. This is particularly a problem where the package contains delicate transmission lines such as optical fibres. Also, the package travelling along the duct has a significant momentum, and, if abruptly halted, the tension induced at the halting point may be harmful.
A further problem that may be experienced in the pressurised container method of fibre blowing is that the initial pressure may be very much greater than that necessary to ensure that there is sufficient propellant to ensure that all the package in the container can be installed.
The aim of the invention is to provide apparatus for selectively inhibiting the flow of fluid from a pressurised container of fibre package, and for inhibiting or retarding the advance of the fibre package.
The present invention provides apparatus for inhibiting fluid flow and fibre package motion in a fibre blowing operation, the apparatus comprising a passageway along which a fibre package and fluid flow can be passed, a first junction at which the fibre package and at least part of the fluid flow can separate along, respectively, a fibre package passageway and a fluid flow passageway, a second junction at which the fibre package passageway and the fluid flow passageway recombine, a valve disposed in the fluid flow passageway between the first and second junctions for selectively blocking the fluid flow along the fluid flow passageway, and a flexible sealing member for sealing against the fibre to inhibit fluid flow along the fibre passageway.
In a preferred embodiment, the fluid flow passageway is separated from the fibre passageway by an elastic, flexible membrane located between the first and second junctions and preceding the valve, the arrangement being such that, upon closure of the valve, pressure in the fluid flow passageway expands the membrane into the fibre package passageway.
In the context of this specification, the term "fibre package" means any line or filament capable of installation by the fibre blowing technique, and is not necessarily restricted to optical fibres.
The invention will now be described in greater detail, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a schematic diagram of a pressurised container containing a fibre package, a propellant and a fibre braking assembly, and shows the fibre package being propelled along a duct;
FIG. 1a is a close up of the braking assembly of FIG. 1;
FIG. 2 is a schematic diagram of the arrangement of FIG. 1 with the propellant and fibre package flow inhibited;
FIG. 2b is the braking assembly of FIG. 1 with the propellant and fiber package flow inhibited;
FIGS. 3a to 3c are schematic diagrams of modified forms of the braking assembly of FIG. 1, each showing the fibre package being propelled along a duct;
FIGS. 4a to 4c are schematic diagrams of the arrangements of FIGS. 3a to 3c with the propellant and fibre package flow inhibited; and
FIG. 5 shows a further modified form of the braking assembly of FIG. 1.
Referring to the drawings, FIG. 1 shows a container 1 having a central annulus 2 about which a coil of fibre package 3 is wound. The
REFERENCES:
patent: 2515953 (1950-07-01), Dufresne
patent: 3533599 (1970-10-01), Hindenburg
patent: 4206860 (1980-06-01), Lee
patent: 4702404 (1987-10-01), Einsle et al.
patent: 4850569 (1989-07-01), Griffioen et al.
patent: 4953827 (1990-09-01), Araki et al.
British Telecommunications public limited company
Swann J. J.
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