Implements or apparatus for applying pushing or pulling force – Method or apparatus for placement of conductive wire – By fluid pressure differential in conduit
Patent
1995-05-17
1998-06-09
Watson, Robert C.
Implements or apparatus for applying pushing or pulling force
Method or apparatus for placement of conductive wire
By fluid pressure differential in conduit
B66F 300
Patent
active
057623210
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of inserting one or more cables into tubing that is intended to encase the cable or cables, with the aid of a liquid.
According to the invention, the specific gravity of the cable shall correspond, or essentially correspond, to the specific gravity of the liquid used to the greatest possible extent.
This enables the liquid and the liquid flow through the tube or tubing to function as a means of supporting the cable and the various cable sections in the tube or of reducing the weight of said cable and cable sections, and as a means of entraining the cable and cable sections through the tubing.
Each cable section to be laid within the tube is intended to pass through a nozzle before it passes through one end of the tube and into the tube.
A method of this kind finds particular application when a non-metallic optic fibre cable is to be lain in or drawn through a tube with the aid of water.
The invention also relates to a special piston unit and a nozzle that can be used when practicing the method.
The piston unit and/or the nozzle may also be used when laying cables in tubes in other ways, for instance when using compressed air instead of a liquid medium or water.
BACKGROUND ART
It is known to lay an optical fibre cable in a ground-buried tube, normally a plastic tube, with the aid of flowing water.
In this regard, it has been necessary to allow large volumes of water to pass through the tube at high rates of flow, and therewith create conditions under which the cable can be inserted carefully into the tube, wherein the water flow exerts on the cable within at least an upstream end-part of the tube a pressure which is sufficiently great for the cable to be able to pass through an adapted, short section of the tube.
It is known that optical fibre cables are sensitive to compression and tensile forces, and that there is a risk of damage to one or more of the fibre filaments or threads even when a moderate force is exerted.
DISCLOSURE OF THE PRESENT INVENTION
TECHNICAL PROBLEMS
When laying cables in a tube in accordance with the aforegoing, or when laying cables in tubing or piping with the aid of a liquid, it will be seen when considering the present state of the art that a technical problem resides in the ability to adapt the pressure and/or tensile (pulling) forces that act on the cable within the tube and to readily adapt the pushing force exerted on the cable from outside the tube, so as to greatly reduce the risk of damage to the cable or completely eliminate such risk.
Another technical problem is one of realizing that cables can be laid in tubes with a smaller volume of water than required with earlier known methods and with a filled tube and through long sections of tubing.
A further technical problem with cable drawing or laying operations of the aforesaid kind is one of creating conditions for adaptation between the tensile force acting on the forward end of the cable (the downstream end) and the pushing or pressing force acting along the cable as a result of the liquid-flow, among other things.
A technical problem is also found in realizing the significance of using a specially constructed nozzle which can provide the aforesaid adaptation in a simple manner.
When considering the present state of the art as described above, it will be seen that a technical problem resides in providing a method by means of which one or more cables can be inserted into a tube surrounding said cable or cables with the aid or a liquid and also with the aid of a piston unit which requires a smaller volume of water than the earlier methods and which provides a greater degree of flexibility than said methods.
It will also be seen that a technical problem resides in realizing the significance of inserting mutually sequential cable sections into a tube and of laying the cable in said tube is facilitated when the cable is relatively clean when inserted into the tube, and that this requirement requires a novel approach with regard to the configuration and constr
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F.o slashed.rst.o slashed. Jean
Petersen J.o slashed.rgen
MEAB Mobile Equipment AB
Watson Robert C.
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