Patent Description:
As it is known, an optical fibre is obtained by producing a primary preform (or core rod), overcladding the primary preform and drawing it to form the optical fibre. For ease of handling and shipping, the optical fibre is then wound onto a spool at high speed.

Fibre production also includes a testing phase to ensure that the fibres meet the requirements set on them by cable production. One of the tests conducted on fibres is the proof test having the purpose of ensuring that the fibre sustains the tensile stress to which is may be subjected during cable production or cable installation.

In the proof test machine, the optical fibre is first guided at high speed to an input pulling device and further to an output pulling device and then onto the shipping spool. The input and output pulling devices subject the optical fibre to a predefined value of tensile stress, as a result of which the fibre breaks if the fibre strength is insufficient.

Document <CIT> describes a method for controlling rotation of a winding spool of proof test machine for optical fibres which provides for a fiber accumulation zone adapted to accumulate a predetermined fiber length preventing that a fiber broken end resulting from the break going beyond the input point of the winding spool.

Document <CIT> discloses a proof-testing machine for optical fibre wherein the fibre end is guided in the case of break between the first and the second pulling device by means of a channel, which guides the fibre to the second pulling device.

It is noticed that the fibre to be tested is fed to the proof test machine by unwinding it from a draw spool around which the fibre is wound.

Typically, proof-test is carried out on an optical fibre formed by a core, a cladding and a buffer, i.e. on the fibre as obtained before the application of a jacket. In some cases, the buffer is coated with a dye or ink to make the fibre assuming a specific colour. Such colour allows distinguishing each fibre and its function among other fibres in an optical cable. The colour of an optical fibre buffer can be chosen among several possible colours (e.g. up to thirteen colours) and includes: white, red, black.

According to a known machine, the fibre unwinding is performed by a pulley mounted on a pay-off arm which guide the fibre along the draw spool by moving from left to right to follow the winding. According to this known machine, two optical sensors detect the fibre passing in front of them and in consequence activate a motor to move the pay-off arm from left to right and vice versa. More particularly, when the fibre is detected by one optical sensor the winding arm is moved by a predetermined amount so that the fibre essentially is re-centred between the two optical sensors. As the fibre naturally unwinds along the draw spool, the fibre angle between the fibre and the pulley increases until such time as the sensor detects the fibre and the system moves the winding arm again to re-centre the fibre between the two optical sensors. Said optical sensors are of the type based on reflected light and include an emitter and a receiver placed in the same housing.

The optical sensor has a behaviour depending on the reflective surface and, particularly, on the colour of the optical fibre buffer, which may influence the detection capability. Therefore, the sensor can include an adjustment optical module (i.e. additional optical component, such as one or more lenses) that makes it suitable for reflective light having frequency different from the one for which the sensor is configured. However, the use of the optional adjustment optical module is often not practical in optical fibre pay-off system, where it would require several adjustments in a day.

Document <CIT> describes a cable release system comprising a main frame, a spool and a driver. SUMMARY OF THE INVENTION.

The Applicant observes that the known optical fibre pay-off arms, employing optical sensors detecting the fibre passage, do not show a satisfying use flexibility and require excessive maintenance activity. Particularly, the adjustment optical module has to be re-configured or changed as an optical fibre with different colour has to be detected. Furthermore, according to another possible situation, the adjustment optical module can be damaged over time (e.g. from loose fibre after a break) and therefore its readjusting or substitution is necessary.

The Applicant has found that a pay-off arm provided with a tilting support rotatable under a corresponding action of the fibre optic to be unwound and having an activation body which can be selectively detected by two proximity sensors shows performances independent from the optical fibre colours.

According to a first aspect, the present invention relates to an optical fibre pay-off system comprising.

In an embodiment, said proximity sensors respectively include a sensor device selected from the group: inductive sensor, optical sensors, capacitive sensors, magnetic sensors.

In an embodiment, said controller is configured to alternatively receive the position signal and the further position signal and cause said pay-off arm to selectively move in the first direction and in the opposite second direction in order to reach a position in which the activation body is not detected by either first proximity sensor and second proximity sensor.

In an embodiment, said system further includes a base structure supporting the first and second proximity sensors and the tilting support. In an embodiment, said pay-off arm comprises:.

In an embodiment, the system further comprises a move assembly configured to move the movable pay-off arm in said first and second directions and having:.

In an embodiment, said base structure comprises a support plate on which the tilting support and the first and second proximity sensors are fixed and a connection plate mechanically connected to said slip. In an embodiment, said tilting support comprises: a pivot fixed to said base structure and a rotatable element mounted to said base structure by said pivot.

In an embodiment, said activation body is rod shaped and extends from a first side portion of the rotatable element towards a gap region formed between the first and second proximity sensors; said first and second contact bodies are rod shaped and extend from a second side portion of the rotatable element separated from said first side portion by the pivot.

In an embodiment, the system is configured to operate as proof test system of said optical fibre and further comprises:.

In an embodiment said test apparatus comprises: an input capstan provided by a first drive motor and an output capstan provided by a second drive motor and a plurality of intermediate pulleys; wherein: the input capstan, the plurality of intermediate pulleys and the output capstan are configured to guide the optical fibre and apply a force to the optical fibre depending from rotation velocities of said output capstan and said input capstan.

In an embodiment, said test apparatus further comprises: a load cell configured to measure a tension value associated with optical fibre in the test apparatus.

In an embodiment, said the test apparatus further comprises: a fibre break cell configured to detect a break of the optical fibre and send corresponding break detection signal to the controller; the controller being configured to initiate a stop of the movement of the optical fibre towards the take-up apparatus on the basis of said break detection signal.

In an embodiment, said take-up apparatus comprises: a movable take-up arm which is configured to be engaged with the optical fibre and move parallel to a further longitudinal axis defined by said shipping spool. In an embodiment, the system further comprises: an anti-whipping assembly having at least one accumulator pulley (<NUM>) guiding the optical fibre existing the output capstan.

According to an example, the present disclosure relates to a position detection device comprising:.

Further characteristics and advantages will be more apparent from the following description of the various embodiments given as a way of an example with reference to the enclosed drawings in which:.

<FIG> schematically shows an optical fibre pay-off apparatus <NUM> comprising a draw spool <NUM>, an optical fibre <NUM>, wound around the draw spool <NUM>, and a movable pay-off arm <NUM>. Particularly, the draw spool <NUM> defines a longitudinal axis X. The movable pay-off arm <NUM> is configured to be engaged with a pay-off portion <NUM> of the optical fibre <NUM> and is movable parallel to said longitudinal axis according to a first direction (e.g. from left to right) or an opposite second direction (e.g. from right to left).

Particularly, optical fibre pay-off apparatus <NUM> comprises a move assembly <NUM> configured to cause a movement of the movable pay-off arm <NUM> in the first direction or in the second direction. The move assembly <NUM> is connected to a controller <NUM> which is configured to control parameters characterizing the operation of the move assembly <NUM> and therefore the movement of the movable pay-off arm <NUM>.

The controller <NUM> can be a computer comprising a non-volatile memory (e.g. a read-only memory (ROM) or a hard disk), a volatile memory (e.g. a random access memory or RAM) and a processor (components not shown). The non-volatile memory is a non-transitory computer-readable carrier medium storing executable program code instructions.

As an example, the optical fibre <NUM> can be a known optical fibre such as a multimode optical fibre, a single mode optical fibre or a special-purpose optical fibre. Particularly, the optical fibre <NUM> has a core, a cladding and a buffer and, more particularly, it is not yet provided with a covering jacket (elements not shown).

According to an embodiment, the buffer is coated with a dye or ink to make the optical fibre <NUM> assuming a specific colour. As it is known, a colour allows distinguishing each fibre and its function among other fibres in an optical cable.

According to an embodiment, the buffer comprises two layers, a primary coating and a secondary coating. The secondary coating is the external layer of the buffer. In some embodiments, the secondary coating is coated with a dye or ink to make the optical fibre <NUM> assuming a specific colour. In other embodiments, the secondary coating is made of a material, such as a resin, wherein a colouring additive is included.

The colour of an optical fibre buffer can be chosen among several possible colours (e.g. up to thirteen colours) and includes, as an example: white, red, black, blue, brown, green, grey, orange, aqua, rose, violet, yellow.

According to an example, the movable pay-off arm <NUM> comprises a slip <NUM> and at least a first pulley <NUM> mechanically connected to the slip <NUM>. In accordance with such example, the first pulley <NUM> is rotatable around an axis parallel to the longitudinal axis X. Particularly, the movable pay-off arm <NUM> is also provided with a second pulley <NUM> mechanically connected to the slip <NUM> and rotatable around an axis perpendicular to the longitudinal axis X.

In accordance with an example, the move assembly <NUM> comprises a motor <NUM> connected to a linear actuator, such as an example, a ball screw, comprising a screw <NUM> (or another guide) on which the slip <NUM> can translate.

Moreover, the optical fibre pay-off apparatus <NUM> comprises a position detection device <NUM>, only schematically represented in <FIG>. <FIG> shows an embodiment of said position detection device <NUM> comprising a base structure <NUM> to be mechanically connected to the pay-off arm <NUM> and particularly to the slip <NUM>.

As an example, the base structure <NUM> includes a support plate <NUM> fixed to a transversal (e.g. perpendicular) connection plate <NUM> to be mechanically coupled to the slip <NUM> of the movable pay-off arm <NUM>. A first proximity sensor <NUM> and a second proximity sensor <NUM> are mounted on said support plate <NUM> so as to be separated by a gap region <NUM>.

The first proximity sensor <NUM> and the second proximity sensor <NUM> may include a respective inductive sensor which, as known, operates by electromagnetic induction to detect an object. The first proximity sensor <NUM> and the second proximity sensor <NUM> are connected to respective cables <NUM> for carrying signals generated by the proximity sensors. Alternatively to the inductive sensors, other type of proximity sensors can be employed, such as: optical sensors, capacitive sensors, magnetic sensors. (To be checked.

Moreover, the position detection device <NUM> is provided with a tilting support <NUM> rotatably mounted on said support plate <NUM> to which an activation body <NUM>, a first contact element <NUM> and a second element <NUM> are fixed. The tilting support <NUM> comprises a rotatable element <NUM> rotatable fixed to the support plate <NUM> by a pivot <NUM>. At a first portion end of the rotatable element <NUM> the activation body <NUM> is fixed, which can be, as an example, a rod or a bar that extends up to the gap region <NUM> formed between the first proximity sensor <NUM> and the second proximity sensor <NUM>. The activation body <NUM> is made by a material (as an example, stainless steel) that can be detected by the first proximity sensor <NUM> and the second proximity sensor <NUM> when the activation body <NUM> is in a corresponding detection range.

The first contact element <NUM> and the second element <NUM> are fixed to a second portion end of the rotatable element <NUM>. Particularly, the first portion end and the second portion end of the rotatable element <NUM> are on opposite sides with respect to the pivot <NUM>. Particularly, the first contact element <NUM> and the second element <NUM> are under the form of corresponding bars extending parallel each other, and in a direction opposite to the extending direction of the activation body <NUM>.

The first contact element <NUM> and the second element <NUM> define an intermediate space <NUM> wherein the pay-off portion <NUM> of the optical fibre <NUM> can move during a pay-off procedure. As visible from <FIG> and <FIG> and <FIG> (showing part of the pay-off arm <NUM>), the first pulley <NUM>, the gap region <NUM> and the intermediate space <NUM> have respective centre lines included into a plane perpendicular to the longitudinal axis X, when the tilting support <NUM> is not subject to a contact action by the pay-off portion <NUM> of the optical fibre <NUM>.

<FIG> also show a further motor <NUM> optionally provided to rotate the first pulley <NUM> for facilitating the unwinding of the optical fibre <NUM> from the draw spool <NUM>.

An example of operation of the pay-off system <NUM> is described hereinbelow. According to said example, the controller <NUM> is configured to cause, via the motor <NUM>, a movement of the pulley <NUM> of the pay-off arm <NUM> along the screw <NUM> only when the activation body <NUM> is detected by the first proximity sensor <NUM> or the second proximity sensor <NUM>.

<FIG> shows the situation in which the activation body <NUM> is substantially aligned with the centre line of the of the gap region <NUM> and is not detected by either first proximity sensor <NUM> and second proximity sensor <NUM>. In accordance with the described example, in this situation the controller <NUM> does not activate the motor <NUM> and the first pulley <NUM> of the pay-off arm <NUM> in not moved along the screw <NUM>.

As shown in <FIG>, while the unwinding occurs the pay-off portion <NUM> of the optical fibre <NUM> comes into contact with the second element <NUM> because of an inherent winding angle assumed by the pay-off portion <NUM> or a change in the winding direction around the draw spool <NUM>. The change of winding occurs, as an example, when the optical fibre <NUM> reaches the end side (e.g. the left side) of the draw spool <NUM>. Due to the physical contact of the pay-off portion <NUM> on the second element <NUM>, the tilting support <NUM> rotates counter-clockwise and therefore the activation body <NUM> enters the detection region of the first proximity sensor <NUM>. The first proximity sensor <NUM> detects presence of the activation body <NUM> and generates a corresponding first detection signal that is received by the controller <NUM>, via the cable <NUM>.

On the basis of the first detection signal, the controller <NUM> generates a command signal which is provided to the motor <NUM> so as to cause a motion of the pay-off arm <NUM> of a preestablished amount in order to re-establish the condition shown in <FIG> in which the activation body <NUM> is substantially aligned with the centre line of the of the gap region <NUM>.

In greater detail, the slip <NUM>, supporting the first pulley <NUM> and the second pulley <NUM>, starts moving from left to right so following the optical fibre <NUM> due to the action of the motor <NUM> on the screw <NUM>. The pay-off portion <NUM> of the optical fibre <NUM> assume again the position shown in <FIG>. <FIG> refers to the situation in which, as an example, starting from the configuration of <FIG> or <FIG>, the pay-off portion <NUM> of the optical fibre <NUM> comes into contact with the first element <NUM> because of the inherent winding angle or another change in the winding direction around the draw spool <NUM>. As an example, the optical fibre <NUM> reaches the right side of the draw spool <NUM>. Due to the physical contact of the pay-off portion <NUM> on the first element <NUM>, the tilting support <NUM> rotates clockwise and therefore the activation body <NUM> enters the detection region of the second proximity sensor <NUM>. The second proximity sensor <NUM> detects the presence of the activation body <NUM> and generates a corresponding second detection signal that is received by the controller <NUM>.

The controller <NUM> generates another command signal which is provided to the motor <NUM> so as to cause a motion of the pay-off arm <NUM> of the preestablished amount in a direction opposite to the previous described one. Therefore, the slip <NUM>, supporting the first pulley <NUM> and the second pulley <NUM>, starts moving from right to left so following the optical fibre <NUM>. The pay-off portion <NUM> of the optical fibre <NUM> assume again the position shown in <FIG> and the motor <NUM> is deactivated. It is noticed that the above described pay-off apparatus <NUM> employing the position detection device <NUM> allows unwinding the optical fibre <NUM> from the draw spool <NUM> without any human intervention and without damaging the coating of the optical fibre.

According to a preferred embodiment, the optical pay-off apparatus <NUM> can be employed, not exclusively, in a proof test system <NUM>, as the one schematically represented in <FIG>.

<FIG> shows an example of the proof test system <NUM> comprising the optical fibre pay-off system <NUM> (analogous or identical to that above described), a dancer assembly <NUM>, a test apparatus <NUM> and a take-up apparatus <NUM>. Particularly, the proof test system <NUM> lies on a horizontal base <NUM> and is configured to operate under the control of the controller <NUM>.

The dancer assembly <NUM> comprises at least one fixed pulley <NUM> and at least one position adjustable pulley <NUM> that guide the optical fibre <NUM>, unwound from the draw spool <NUM>, towards the proof test apparatus <NUM>. As an example, two position adjustable pulleys <NUM> are employed. Moreover, the dancer assembly <NUM> is configured to set a suitable tension between the draw spool <NUM> and an input capstan <NUM> of the test apparatus <NUM> by a fixed weight. The positions of the adjustable pulleys <NUM> are adjusted by the controller <NUM> to correctly synchronize the speed of the motor <NUM> and/or the further motor <NUM> (if adopted) with that of the input capstan <NUM>.

As an example, the test apparatus <NUM> is provided with at least one input pulley <NUM>, the already mentioned input capstan <NUM>, a plurality of upper pulleys <NUM>, a plurality of lower pulleys <NUM> and an output capstan <NUM>. Particularly, the input capstan <NUM> and the output capstan <NUM> are positioned at a same high from the horizontal base <NUM>, greater than the high at which the dancer assembly <NUM> is positioned. The upper pulleys <NUM> are arranged, according to an example, at the same high of the input capstan <NUM>, while the lower pulleys <NUM> are placed at lower level, such as the one of the longitudinal axis X of the draw spool <NUM>.

The input capstan <NUM> is configured to draw the optical fibre <NUM> into the test apparatus <NUM> and is provided with a respective drive motor (not shown) which operates according to a line speed set point provided by the controller <NUM>. Particularly, a numerical counter (not shown), used to count the length of the portion of the optical fibre <NUM> which is submitted to the test, is arranged between the input capstan <NUM> and the corresponding drive motor.

The test apparatus <NUM> provides a path for the optical fibre <NUM> comprising: the input capstan <NUM> followed by a sequence including lower pulleys <NUM> interleaved by upper pulleys <NUM> and followed by the output capstan <NUM>.

A load cell <NUM> is, as an example, fixed to one of the upper pulleys <NUM> or the lower pulleys <NUM> to measure a tension value of the optical fibre <NUM> in the test apparatus <NUM>. Particularly, the measured tension value can be provided to the controller <NUM>.

Furthermore, the test apparatus <NUM> comprises a fibre break cell <NUM> configured to detect an online break of the optical fibre <NUM> and, in this case, send a corresponding signal to the controller <NUM> which can initiate a quick stop of the optical fibre shipping towards the take-up apparatus <NUM>. As an example, such quick stop can be performed in no more than <NUM>, considering a speed of <NUM>/min of the optical fibre shipping. The stop of optical fibre shipping is obtained by interrupting/braking the rotation of the draw spool <NUM>, the input capstan <NUM>, the output capstan <NUM>. It is also observed that above stop/braking procedure shows the advantage of avoiding the undesired whipping effect that can occur when the optical fibre breaks.

The output capstan <NUM> is provided with a respective drive motor (not shown) that operates under the control of the controller <NUM> which takes into consideration tension values measured by the load cell <NUM>. Typically, the output capstan <NUM> turns faster than the input capstan <NUM>. Particularly, another numerical counter (not shown) is arranged between the output capstan <NUM> and the corresponding drive motor to measure the length of optical fibre <NUM> that is spooling.

Furthermore, the test apparatus <NUM> may comprise an anti-whipping assembly <NUM> and a take-up dancer <NUM> arranged between the anti-whipping assembly <NUM> and the take-up apparatus <NUM>.

The anti-whipping assembly <NUM> comprises at least one accumulator pulley <NUM> guiding the optical fibre <NUM> existing the output capstan <NUM>. The anti-whipping assembly <NUM> is designed to avoid a whipping effect at the take-up apparatus <NUM> that could occur when the optical fibre <NUM> breaks in the test apparatus <NUM>. The accumulator pulleys <NUM> cause the fibre end to rotate whilst giving time for stopping the operating of the take-up apparatus <NUM>.

The take-up dancer <NUM>, including at least one dancer pulley <NUM>, is configured to set the tension of the optical fibre <NUM> in the take-up apparatus <NUM>. The angular positions of the dancer pulleys <NUM> are used by the controller <NUM> to synchronise the speed of a motor of the take-up apparatus <NUM> and the speed of the output capstan <NUM>.

The take-up apparatus <NUM> comprises a shipping spool <NUM> around which the optical fibre <NUM> is to be wound and defining a further longitudinal axis Y. The shipping spool <NUM> can be rotated around said further longitudinal axis Y by a respective drive motor controlled by the controller <NUM>. Moreover, the take-up apparatus <NUM> is provided with a movable take-up arm <NUM> which is configured to be engaged with the optical fibre <NUM> and is movable parallel to further longitudinal axis Y in opposite directions.

According to an example, the movable take-up arm <NUM> comprises a further slip <NUM> and a first shipping pulley <NUM> mechanically connected to the further slip <NUM>. In accordance with such example, the first shipping pulley <NUM> is rotatable around an axis perpendicular to the further longitudinal axis Y. Particularly, the movable take-up arm <NUM> is also provided with a second shipping pulley <NUM> mechanically connected to the further slip <NUM> and rotatable around an axis parallel to the further longitudinal axis Y.

The take-up apparatus <NUM> includes a take-up move assembly <NUM> which comprises a take-up motor <NUM> connected to a further linear actuator, such as an example, a ball screw, comprising a further screw <NUM> (or another guide) on which the further slip <NUM> can translate.

Preferably, the take-up apparatus <NUM> is provided by at least one anti-static nozzle <NUM> configured to reduce the amount of electrical static charge generated by the moving optical fibre <NUM> and/or the rotation of the shipping spool <NUM>. As it is known, an anti-static nozzle produces a stream of ionized compressed air to neutralize static on surfaces and effectively blow-off particles.

The proof test system <NUM> can be used to test the mechanical strength of an optical fibre <NUM>. The proof test system <NUM> allows removing fibre portions that show a low quality and transfer the optical fibre unwound from the draw spool <NUM> onto more than one shipping spool <NUM>, in accordance with specific need. As an example, the shipping spool <NUM> is adapted for fibre length comprised between <NUM> and <NUM> while the draw spool <NUM> is in general adapted for a fibre length between <NUM> and <NUM>.

The proof test system <NUM> is configured for applying a specified tensile load to continuous lengths of the optical fibre <NUM>, according to a proof test cycle. The tensile load is applied for a short time as possible, yet sufficiently long to ensure the glass of the fibre experiences the proof stress.

The test can be performed according the standard IEC <NUM>-<NUM>-<NUM> which fixes a proof test level with <NUM> % elongation for <NUM> second. To reach that conditions a force applied to the optical fibre is of <NUM> Gpa (<NUM> Kpsi). The force is applied to the optical fibre by means of turning the output capstan <NUM> faster than the input capstan <NUM>. The force applied is controlled and adjusted by means of the load cell <NUM>.

It is noticed that the pay-off apparatus <NUM> provided with the position detection <NUM> allows efficiently performing the proof test cycle by the proof test system <NUM>, avoiding any damage of the optical fibre cladding and reaching a high level of automation of the proof test cycle.

Claim 1:
An optical fibre pay-off system (<NUM>, <NUM>) comprising.
a draw spool (<NUM>) around which an optical fibre (<NUM>) is wound and defining a longitudinal axis (X);
a pay-off arm (<NUM>) movable parallel to said longitudinal axis (X) and engaged with a pay-off portion (<NUM>) of the optical fibre (<NUM>);
a controller (<NUM>) configured to receive first and second position signals and cause said pay-off arm (<NUM>) selectively moving in a first direction and in an opposite second direction;
the system (<NUM>, <NUM>) being characterized by further comprising:
a first (<NUM>) and second proximity sensors (<NUM>) mounted on said pay-off arm (<NUM>);
a tilting support (<NUM>) rotatably mounted on said pay-off arm (<NUM>);
an activation body (<NUM>) fixed to said tilting support (<NUM>) and extending between said first (<NUM>) and second proximity (<NUM>) sensors to be selectively detected by said sensors according to positions assumed by the tilting support (<NUM>);
a first (<NUM>) and a second contact elements (<NUM>) fixed to said tilting support (<NUM>) and defining an intermediate space (<NUM>) in which the pay-off portion (<NUM>) can move;
wherein the tilting support (<NUM>) is rotatable under a corresponding action of the pay-off portion (<NUM>) on said first (<NUM>) and second (<NUM>) contact elements and configured to selectively assume:
a first detection position in which the activation body (<NUM>) is detected by the second proximity sensor (<NUM>) which generates a position signal, and
a second detection position in which the activation body (<NUM>) is detected by the first proximity sensor (<NUM>) which generates a further position signal.