Textiles: spinning – twisting – and twining – Apparatus and processes – Untwisting
Patent
1996-06-28
1998-03-17
Stryjewski, William
Textiles: spinning, twisting, and twining
Apparatus and processes
Untwisting
57 67, 57115, 57116, 242386, A01D 7530, A01D 4502
Patent
active
057273731
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for unwrapping fibre optic cable from an overhead line. The term "overhead line" is intended to be a general reference to phase and earth conductors of overhead power lines and messenger cables strung between power lines and other such lines which pass overhead.
Fibre optic cables are now a well known and developed art and are increasingly replacing older forms of cabling in the field of communication.
Fibre optic cables can be employed to provide communication links based on power distribution networks. Conveniently, the fibre optic cable is wound directly onto the already established overhead lines, thus utilising the networks which already exist thereby linking control centres and sub-stations, etc.
It is already known to use a suitable apparatus which can move along an overhead line and simultaneously wrap the fibre optic cable around the overhead line. However, there is now a demand for an apparatus which is capable of unwrapping the fibre optic cable from overhead lines. For example, the user of a fibre optic cable communications network may wish to upgrade the system with a fibre optic cable of superior quality or damage may have occurred to existing fibre optic cable, thereby necessitating repair work to be carried out.
Unfortunately, whilst a fibre optic cable wrapping apparatus can simply apply the cable to an overhead line at constant pitch, a fibre optic cable unwrapping apparatus must provide for variations which occur in the pitch of the wrapped cable. For example, when the fibre optic cable is installed, there may be some slippage of the wrapping apparatus, particularly if there is ice present on the overhead line or if the wrapping apparatus has to move steeply uphill or downhill at the extremeties of the span of the overhead line between adjacent poles or towers. In addition, loops of fibre optic cable can form simply because the fibre optic cable was not wound onto the overhead line at the correct tension.
Clearly, it would not, therefore, be appropriate to simply reverse the action of a fibre optic cable wrapping apparatus which would not provide for any variation in pitch of the wrapped cable.
SUMMARY OF THE INVENTION
According to the present invention, there is provided an apparatus for unwrapping fibre optic cable from an overhead line comprising a carriage which sits on the overhead line and is moveable along the overhead line, a guide arm mounted for rotation about the carriage, the guide arm performing the unwrapping action of the fibre optic cable from the overhead line, a drum and drum drive means, the drum gathering the fibre optic cable which has been unwrapped from the overhead line wherein the apparatus further comprises means for varying the speed of rotation of the guide arm with respect to the forward speed of the carriage.
Preferably, the means for varying the speed of rotation of the guide arm comprise a sensor to sense the forward speed of the carriage and maintain the ratio ##EQU1##
Preferably, the guide arm and the carriage are connected by a gearing mechanism.
Preferably, the sensor is a speed encoder which provides a feedback signal to maintain the ratio R.
Preferably, the drum is provided with a slipping clutch to ensure that the tension in the fibre optic cable being unwrapped does not exceed a predetermined limit.
Preferably, the carriage is driven along the overhead line by a motor.
Preferably, an angle sensor is provided to sense the angle of the fibre optic cable at the point of leaving the overhead line and to adjust the ratio R thereby providing for variations in the pitch of the fibre optic cable being unwrapped from the overhead line.
Preferably, the angle sensor comprises a biased means which is deflected by the fibre optic cable from a first position to a second position in dependence on the angle at which the fibre optic cable leaves the overhead line.
Preferably, the drum is coaxially mounted on the carriage.
Preferably, the guide arm is coaxially mounted on the ca
REFERENCES:
patent: 3866403 (1975-02-01), Zimmermann
patent: 4584829 (1986-04-01), Heinke
patent: 4871127 (1989-10-01), Clark
patent: 5109658 (1992-05-01), Garner
patent: 5517812 (1996-05-01), Simmons
Appleford David Dale
Baker James Charles
Focas Limited
Stryjewski William
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