Implements or apparatus for applying pushing or pulling force – Method or apparatus for placement of conductive wire – By fluid pressure differential in conduit
Reexamination Certificate
2000-04-28
2001-11-06
Wilson, Lee (Department: 3723)
Implements or apparatus for applying pushing or pulling force
Method or apparatus for placement of conductive wire
By fluid pressure differential in conduit
C254S13430R
Reexamination Certificate
active
06311953
ABSTRACT:
This invention relates to a method of installing a cable in a duct by blowing the cable into the duct using gaseous flow which is fed into one end of the duct together with the cable.
The invention is particularly, but not exclusively, applicable to installing an optical fibre cable having a plurality of optical fibres contained within a common sheath. It is also applicable to installing a single optical fibre provided with one or more protective coatings, and the term ‘cable’ as used herein is to be construed accordingly. Further, the invention may also be applicable to installing cables having one or more electrical conductors additional to or instead of optical fibres.
The blowing force exerted on the cable by the gaseous flow, which is usually high speed airflow, is proportional to the pressure gradient in the duct. The pressure gradient is not constant along the length of the duct and is usually lowest at the end of the duct into which the gaseous medium and cable are fed. The pressure gradient also depends on the distance along the duct from that end to the other end of the duct at which the gaseous flow is vented to atmosphere.
An object of the invention is to increase the length of cable which can be blown into the duct.
Briefly this object is achieved by modifying the pressure gradient within the duct during passage of the leading end of the cable through the duct. This modification is effected by selective venting of the duct at locations along its length.
The invention includes a method of installing a cable in a duct comprising blowing the cable into the duct using a gaseous flow which is fed into one end of the duct together with the cable, wherein a plurality of venting means are spaced apart along the length of the duct, and wherein the venting means are operated such that during blowing, any venting means which is upstream of the leading end of the cable is closed and when there is at least one venting means downstream of said leading end, at least the downstream venting means closest to the cable leading end is open for venting gas from the duct.
Each of said venting means may comprise a disconnectable connection between adjacent sections of said duct.
Preferably during blowing, any venting means which is downstream of the cable leading end is open.
The method may further include pulling said cable into said duct using a shuttle attached to the leading end of said cable and provided with through passageway means for said gaseous flow.
Advantageously, the flow area of the through passageway means may be varied during blowing. Preferably the through passageway means comprises at least one through passageway which has a fixed flow area and at least one through passageway which has a variable flow area.
The method may further comprise pushing said cable into said duct at said one end thereof.
In one embodiment described hereinafter all of the venting means are initially open and said venting means are successively closed by engagement with said shuttle as said shuttle travels along said duct from said one end thereof.
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Davies Martin Vincent
Lamb John Garth
Lang Ian Dewi
Sutehall Ralph
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Pirelli General plc
Wilson Lee
LandOfFree
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