CN1207227C - Apparatus for tension of fibre-optical and method for controlling tension applying to optical fibre - Google Patents

Abstract

An optical fiber tensioning device receives an optical fiber (35) by its input end from a pulling device (37) and supplies the optical fiber by its output end to a storage device (40). The tensioning device (1) comprises at least one fixed pulley (32) around which the optical fiber (35) is wound for at least a predetermined length; and at least one movable pulley (9) around which the optical fiber (35) is wound for at least a predetermined length. The means for measuring the tension applied to the fiber interacts with the motor means (24, 26, 5, 7) for moving the movable pulley (9) in order to control the axis (20, 33) of the pulley (9, 32) in the following manner The distance (Dp) between them to automatically keep the tension applied to the fiber substantially constant.

Description

Optical fiber tensioning device and method of controlling tension applied to an optical fiber

technical field

The present invention relates to an optical fiber tensioning device and a method of controlling the tension applied to an optical fiber, particularly during the winding of the optical fiber.

Background technique

Typically, optical fibers are formed from preforms of glass material in a draw tower. A draw tower usually has a pulling device ("winch"), such as a motorized pulley, that pulls the fiber down and delivers it to a storage device; the latter usually consists of a motorized drum onto which the fiber is wound.

Under many operating conditions, the speed at which the pulling device draws the fiber (drawing speed) may not coincide with the speed at which the fiber is fed to the storage device, for example due to fluctuations in the speed of the motors driving the pulling device and the storage device. The difference between these two speeds causes the tension in the fiber to vary relative to the target tension; in particular, fiber tensions greater than the target tension can damage the fiber, while fiber tensions less than the target tension can lead to inefficient depositing processes.

In order to solve this problem, it is known practice to use a tensioning device which is inserted between the pulling device and the storage device and which is able to control the tension of the optical fiber. In particular, a drawing device is known comprising at least one fixed pulley and a movable pulley capable of guiding the optical fiber. The movement of the movable pulley can change the tension of the optical fiber. Here and in the rest of the specification, the term "fixed pulley" refers to a pulley that is free to rotate about its axis and the position of the axis is fixed, while the term "moving pulley" refers to a pulley that is free to rotate about its axis and the position of the axis can be changed. pulley.

US Pat. No. 4,712,866 describes a tensioning device arranged between the pulling device of the stretching tower and the storage device including the winding drum. The tensioner consists of a fixed pair of pulleys and a movable pulley on a swing arm, also known as a "tensioner", with a weight. The tensioning arm performs conventional speed control to wind the fiber onto the reel at the tension determined by the aforementioned weight.

US Patent 5,790,292 relates to an optical fiber transmission line and describes a drawing tower in which a tensioning device with two pulleys is inserted between the drawing device and the take-up drum (Fig. 7).

US Patent No. 4,138,069 describes a winding apparatus for optical glass filaments in which a pulling device draws the filaments from molten glass and feeds them through a tensioning device to a set of winding drums. The tensioning device includes two fixed pulleys and a movable pulley installed at one end of the tensioning arm. The tensioning arm extends from a device in which a spring or other device applies a constant force to drive the movable pulley away from the fixed pulley.

Tensioners can also be used in devices other than stretch towers.

US Patent 5,076,104 describes a device for measuring the breaking load of an optical fiber having a tensioning device comprising a pair of fixed pulleys and a movable pulley. There is also a tensioning device comprising a fixed sheave and a movable sheave; the latter is located below the fixed sheave, is movable in a vertical direction and is connected to a predetermined weight. Fiber in the path is wound on fixed and movable sheaves so that constant tension is maintained.

US Patent 4,505,222 describes an optical fiber extrusion coating apparatus in which the tensioning device is placed immediately upstream of the take-up drum.

US Patent 4,127,370 describes an optical fiber extrusion coating apparatus in which first, second and third pulleys are located at the entrance of the apparatus, immediately downstream of the unwind drum. The first and second pulleys are separated from each other and from the unwind drum. The third pulley has no bracket and is supported on the optical fiber between the first and second pulleys so that due to the weight of the third pulley, the optical fiber follows a U-shaped path between the first and second pulleys. A pair of photocells are used to detect the vertical position of the third pulley and control the vertical position of the third pulley in such a way as to control the rotational speed of the unwind drum so that the tension of the fiber is kept substantially constant.

Contents of the invention

The inventors have found that known types of tensioning devices require the use of gravity and/or predetermined elastic action in order to control the position of the movable pulley, applying an uncontrollable predetermined force to the movable pulley. It is therefore not possible in any way to adjust the force applied to the fixed pulley in order to adjust the sensitivity of the tensioning device. Therefore, the tension control achieved with known devices is of the non-adjustable type and may not be sufficient under certain operating conditions.

The inventors have found that the above problems can be at least partially solved by using an optical fiber tensioning device having a movable pulley on which the optical fiber runs, a means for measuring the tension exerted on the optical fiber and a means for moving the movable pulley, The device is capable of controlling the position of the stop pulley based on the signal generated by the tension measuring device.

The tensioning device according to the present invention is capable of receiving, at its input end, an optical fiber from a fiber guide or a return element or from another type of device, such as a pulling device or an unwinding device, and is capable of, after automatically controlling the tension of the optical fiber, at its The output provides the fiber to a further rail or return element or to another device such as a fiber storage device (in particular a winding device).

In more detail, the tensioning device according to the present invention includes a fixed pulley supported by a bracket structure and a movable pulley supported by a slider capable of sliding along a linear guide rail supported by the bracket structure.

Fiber entering the tensioner is wound one length around a fixed pulley, and from there it is passed to a movable pulley, around which the fiber is wound another length. The distance between the axes of the fixed and movable pulleys can be varied in order to vary the length of the portion of fiber extending between the two pulleys and thus the tension applied to the fiber. In order to vary the distance between the shafts of the fixed and movable pulleys, as described above, use fiber optic tension measuring devices such as load cells connected to the fixed pulleys, and means for moving sliders that can be provided according to the tension measuring device The signal controls the distance between the pulley shafts so that the tension in the fiber is kept almost constant automatically. The moving device may include an electric motor and a system for transferring motion from the electric motor to the slider, such as a screw and nut mating pair, wherein the screw extends parallel to a linear track and can rotate under the force of the motor, wherein the nut is connected to the slider On blocks or on conveyor belts, such as zigzag conveyor belts.

Because the fiber tensioning device described above automatically controls the tension in the fiber without using gravity or other predetermined forces, it can be used to adjust the tension applied to the fiber in a desired manner.

In this way, the movement of the movable pulley has nothing to do with gravity or predetermined elastic force, but can be realized with controllable force.

A tensioning device is thus provided which itself adapts automatically to changes in operating conditions.

According to a first aspect, the present invention relates to an optical fiber tensioning device for use in the forward path of an optical fiber, the device comprising at least one movable pulley around which the optical fiber is wound for at least one length, the position of said movable pulley being variable to vary the tension applied to the optical fiber. tension on

further comprising tension measuring means capable of measuring said applied tension and generating a signal indicative of said tension, and electric means for moving said movable pulley capable of receiving said signal indicative of tension and moving the movable pulley in accordance with said signal, In order to automatically keep the tension applied to the optical fiber substantially constant.

Preferably, the tensioning device further comprises a fixed pulley around which the optical fiber is wound for at least one length, the distance between the shafts of said fixed pulley and said movable pulley being variable in order to vary the tension applied to the optical fiber, said motorized movement means The distance can be controlled so as to automatically keep the tension applied to the fiber substantially constant.

The electric moving device may include a guide rail along which the slider supporting the movable pulley can slide, and a drag device for moving the slider along the guide rail.

The pulling means may comprise a screw capable of rotational movement by the force of an electric motor and a nut connected to the slider, or an electric motor and a drive belt type connecting the motor to the slider (for example, using a A zigzag belt) transmission system.

The tensioning device may comprise an electronic control device receiving at its input a reference signal and a measurement signal and capable of generating operating signals for closed-loop control of said motorized moving device in response to said input signals.

The electronic control device is preferably a device for closed-loop control of the tension applied to the optical fiber, including:

- a subtractor to which a tension reference signal proportional to a target tension of the fiber and a measurement signal consisting of said signal representative of the fiber tension are supplied; and

- a controller, preferably a proportional-integral-derivative controller, receiving at its input the tension error signal provided at the output of said subtractor and generating at its output a signal that can be used to operate said electric moving device and a drive signal that controls the distance.

This enables a closed-loop control of the tension in the fiber, by which the tension is continuously monitored, allowing immediate adjustment of the movement device when the measured tension deviates from the reference tension. This keeps the tension in the fiber always equal to the reference tension, enabling particularly precise control.

Preferably, said tension measuring means may comprise a load sensor connected to said fixed pulley and capable of generating said signal indicative of tension at its output.

Preferably, the electric moving device includes a guide rail and a drag device, the slider supporting the movable pulley can move along the rail, and the drag device is used to move the slider along the guide rail; the electric control The device constitutes a system for closed-loop control of the position of said slider along said guide rail.

Preferably, for operation, the tensioning device is connected to means for storing optical fibers, said means for storing optical fibers is capable of receiving optical fibers from the tensioning device, and said means for closed loop controlling said slider along said guide rail The location system includes:

- another subtractor, to which a position reference signal related to the reference position of said slider along said guideway and a measurement signal proportional to the actual position of said slider along said guideway are supplied; and

- another controller, preferably a proportional-integral-derivative controller, receives at its input the position error signal provided at the output of said further subtractor and generates at its output a signal which can be used to operate said Another drive signal for the storage device.

Said storage device preferably comprises at least one motorized drum on which the optical fiber from said tensioning device is wound, which motorized drum rotates about its axis of rotation under the action of an electric motor, and said another A drive signal can be used to control the electric motor.

The electronic control device preferably includes an integrator which receives at its input a signal related to the velocity of the slider along the track and generates at its output a signal related to the velocity of the slider along the track. The measurement signal is proportional to the actual position of the track.

In this way, it is ensured that the movable pulley always remains near a reference position, from which it can always be moved in the usual way in order to compensate for tension variations; The movable pulley cannot be moved in one of the directions of motion.

According to another aspect, the present invention relates to a method of controlling the tension applied to an optical fiber along its advancing path, the method comprising the step of forming a portion of said path having a length that can be varied to vary the applied tension. tension to said optical fiber, and the steps of measuring the tension applied to said optical fiber and controlling said length in an automatic manner with a motor based on said measured tension so as to maintain the tension in the optical fiber substantially constant.

Preferably, the method comprises the step of closed-loop controlling the tension applied to said optical fiber based on at least one reference signal proportional to a target tension of the optical fiber and a measurement signal generated during the step of measuring tension and Proportional to the actual tension on the fiber.

The step of said closed-loop tension control preferably comprises the following steps:

- comparing said tension reference signal with said measurement signal to generate a tension error signal; and

- processing said tension error signal to produce at an output a drive signal which can be used to vary said length by means of a motor and to keep the tension in the fiber substantially constant.

The method preferably comprises the step of closed-loop controlling the position of the movable element based on at least one position reference signal proportional to the target position of the movable element and a measurement signal proportional to the movable element. A change in the position of the movable element causes a change in the length in proportion to the instantaneous position of the movable element.

The method preferably further includes the step of depositing an optical fiber at a terminal end of the advancing path; the step of closed-loop controlling the position of the movable element includes the following steps:

- comparing said position reference signal with said position measurement signal to generate a position error signal; and

- processing said position error signal to generate a drive signal at the output, which drive signal can be used to vary the speed at which the fiber is deposited.

According to another aspect, the present invention relates to an optical fiber processing system, such as a draw tower, an extrusion line, or an apparatus for measuring the breaking strength of an optical fiber, having an optical fiber tensioning device capable of The input end of the optical fiber source receives the optical fiber such as the optical fiber pulling device, and can provide the optical fiber to the device for storing the optical fiber at its output end, such as a motorized reel, the tensioning device includes at least one movable pulley, and the optical fiber surrounds the moving pulley is wound over at least one length, the position of the moving pulley can be varied to vary the tension applied to the optical fiber, the tensioning device also includes a tensioning device capable of measuring the applied tension and generating a signal indicative of the tension measuring means, and a means for electrically moving said movable pulley capable of receiving said signal indicative of tension and capable of moving said movable pulley in response to said signal indicative of tension so as to automatically maintain a substantially constant tension in the optical fiber.

Preferably, the system includes an electronic control device capable of providing a closed-loop control system for tension applied to the optical fiber, and includes:

- a subtractor to which a tension reference signal proportional to a target tension of the fiber and a measurement signal consisting of said signal representative of the fiber tension are supplied; and

- a controller, preferably a proportional-integral-derivative controller, receiving at its input the tension error signal provided at the output of said subtractor and generating at its output a signal that can be used to operate said electric moving device drive signal.

Preferably, the electric moving device includes a guide rail and a drag device, the slider supporting the movable pulley can move along the guide rail, and the drag device is used to move the slider along the guide rail; An electronic control unit provides a closed loop control system of the position of the slider along the rail.

Preferably, for operation, the tensioning device is connected to the fiber storage device and said system for closed loop controlling the position of said slider along said guide rail comprises:

- a further subtractor to which a position reference signal related to a reference position of said slider along said track and a measurement signal proportional to the actual position of said slider along said track are supplied; and

- another controller, preferably a proportional-integral-derivative controller, receives at its input the position error signal provided at the output of said further subtractor and generates at its output a signal which can be used to operate said Another drive signal for the storage device.

Description of drawings

The invention will now be described with particular reference to the accompanying drawings, which represent, without limitation, preferred embodiments of the invention, in which:

Figure 1 shows a plan view of an optical fiber tensioner made in accordance with the present invention; and

Figure 2 shows a block diagram of an electronic unit for controlling the device of Figure 1 made according to the invention.

Detailed ways

In Fig. 1, numeral 1 denotes an optical fiber tensioning device as a whole.

The tensioning device 1 comprises a support plate 3 (for example made of metal), supported by a frame (not shown) which enables the support plate 3 to be positioned in a fixed manner, for example in a horizontal or vertical position.

The tensioning device 1 also comprises at least one linear guide 5, formed in this particular case by two cylindrical rods 12a, 12b, which are supported by the support plate 3, and a slide 7 which can It moves back and forth along the linear guide rail 5 and supports the first pulley 9, which will be called a movable pulley hereinafter. The direction of movement of the slider 7 is indicated by D in FIG. 1 .

The cylindrical rods 12a, 12b are arranged parallel to each other, and their respective end positions are supported by a pair of brackets 15a, 15b fixed to the support plate 3. The slider 7 may be rectangular in plan view, and may have sliding elements 7a, 7b respectively cooperating with the rods 12a, 12b; for example, the sliding fit between the slider 7 and the rods 12a, 12b may utilize a sliding bearing 18 or a ball bearing ring formation.

The movable pulley 9 is preferably supported by a pin 20 , and the pin 9 protrudes from the slider 7 and is perpendicular to the slider 7 . At this time, the rotation axis of the movable pulley 9 is perpendicular to the moving direction D of the slider 7 .

The slider 7 can be moved by the force of an electric motor 24, preferably the output shaft of which is connected to a screw 26 located between the rods 12a, 12b and extending parallel to them. The motor 24 may be mounted in a protruding manner on a support 28 fixed to the support plate 3 , and the ends of the screw 26 are preferably supported by corresponding brackets 30 a , 30 b also fixed on the support plate 3 . Preferably, the screw rod 26 is connected to a ball nut (circulating ballnut not shown) fixed on the side of the slider 7 opposite to the side where the movable pulley 9 is located.

Alternatively, the transmission from the motor 24 to the movable pulley 9 can be realized by a belt drive, for example a zigzag belt (not shown).

The tensioning device 1 also comprises a second pulley 32, hereafter referred to as a fixed pulley, supported by pins 33 which preferably extend perpendicularly to the support plate 3, for example on the part of the support plate 3 opposite to where the motor 24 is located superior.

The fixed pulley 32 preferably has the same diameter as the movable pulley 9, and the rotation axes of the pulleys 9 and 32 are preferably parallel to each other.

The angular displacement of the motor 24 produces a linear movement of the slider 7 along the guide rail 5 , thereby changing the distance Dp between the rotational axis of the movable pulley 9 and the fixed pulley 32 .

Specifically, the distance Dp can be continuously varied between a minimum value (DpMin) and a maximum value (DpMax), for which the slider 7 is located in a first extreme position (not shown), where it rests against On the brackets 15 a , 15 b remote from the motor 24 , the slider 7 is in a second extreme position (not shown) for said maximum value, in which it rests on the brackets 15 a , 15 b close to the motor 24 .

The tensioning device 1 can also comprise a transparent protective cover (housing - not shown) which can be connected to the support plate 3 and which can accommodate all the components supported by the support plate.

The tensioning device 1 may be mounted on the path of advancement of the optical fiber 35, for example in a fiber draw tower (not shown), and is capable of receiving the fiber from a fiber source 37 (schematically shown). In the non-limiting example considered here, the fiber source 37 is the pulling device ("capstan") of a fiber draw tower (not shown). Alternatively, the fiber source 37 may be any element or device that returns or guides a fiber or a fiber unwind drum.

The optical fiber 35 extends from the traction device 37 to the fixed pulley 32 to form a first straight portion 35a, is surrounded by the fixed pulley 32 (for example, goes around 180°), extends between the fixed pulley 32 and the movable pulley 9 to form a second straight portion 35b, and is formed by Wrapping around the movable pulley 9 (for example, by 180°), and finally extending between the movable pulley 9 and the other device 40, thus forming the third straight portion 35c. In the non-limiting example considered here, the device 40 (shown schematically) is a storage device comprising a motorized reel 42 on which the optical fiber 35 can be wound. The motorized reel 42 can rotate around the rotation shaft 43 under the action of the motor 45 . Alternatively, device 40 may be any element or device for returning or guiding an optical fiber.

Preferably, the straight portions 35a, 35b, 35c are parallel to each other, but not necessarily.

Between the device 37 and the tensioning device 1 and between the tensioning device 1 and the device 40 there are preferably return pulleys, not shown in FIG. 1 for the sake of simplicity.

The electronic control unit 50 is capable of controlling the electric motor 24 and the electric motor 45 via respective power drive circuits ("drivers") 24p, 45p.

Preferably, the tensioning device 1 comprises a tension measuring device 56 , such as a load cell, preferably connected to the pin 33 of the fixed pulley 32 . The tension measuring device 56 is capable of generating a signal Tmis proportional to the tension experienced by the optical fiber 35 and is connected to the electronic control unit 50 to provide the signal Tmis to the electronic control unit 50 .

With particular reference to Figure 2, the electronic control unit 50 is shown in detail. The electronic control unit 50 comprises a subtractor 60 to which a signal T ₀ proportional to the target tension of the fiber and a signal Tmis proportional to the tension actually experienced by the fiber 35 are supplied. Subtractor 60 generates at its output an error signal ε=ΔT=T ₀ −Tmis (tension error) and supplies this error signal to controller 62, in particular a PID controller (proportional-integral-derivative) controller, The proportional-integral-derivative controller generates a signal ω (voltage signal, matched to the drive circuit 24p operated by voltage) at its output.

A PID controller is a controller that, upon receiving an input signal S _i, produces an output signal S _o , usually given by:

${\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; p</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; l</span>}}{{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{<span\; class="notranslate">\; \&Integral;</span>}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; dt</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; T</span>}}_{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}{\mathrm{<span\; class="notranslate">\; S</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; dt</span>}}<span\; class="notranslate">\; )</span>$

Therefore the PID controller can be represented by three constants K _p , K _i =K _p /T _i and K _d =K _p ·T _d .

The signal ω is used to operate the motor 24 after it has been converted and transformed into a power signal by a drive circuit 24p (of known type). The rotational speed of the motor 24 is therefore dependent on the signal ω. The signal ω is also supplied to a conversion unit 64 which generates at its output an output signal V which is related to the linear velocity of the movement of the slide 7 along the guide rail 5 .

In practice, if V _max is the maximum speed of the motor 24 (expressed in revolutions per second), ω _max is the (voltage) value of the signal ω related to the maximum speed V _max , p is the pitch of the screw 26, ω(t) is the general value of the signal ω at the instant t (provided by the output of the controller 62), at its output the conversion unit 64 produces a signal V whose value V(t) at the instant t is given by:

$\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; v</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}{{\mathrm{<span\; class="notranslate">\; \&omega;</span>}}_{\mathrm{<span\; class="notranslate">\; max</span>}}}<span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; \&omega;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; t</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span>\mathrm{<span\; class="notranslate">\; p</span>}$

In practice, the conversion unit 64 completes the conversion function between the rotation angle of the screw 26 and the linear velocity of the slider 7 .

The signal V is supplied to a further conversion unit 66 which, by integrating the signal V, generates at its output a signal P _mis (voltage) related to the instantaneous position of the slider 7 along the guide rail 5 .

The position signal P _mis is supplied to a subtractor 70 , to which is also supplied the signal P ₀ corresponding to the target position of the slide 7 along the guide rail 5 . Preferably, the target position of the slider is an intermediate position between the first and second extreme positions.

Subtractor 70 produces an error signal ε=ΔP=P ₀ −P _mis at its output terminal, and provides this error signal to controller 72 (actually PID (proportional-integral-derivative) controller), which controls The converter generates at its output a signal ωb, which is used to operate the motor 45 after conversion and conversion of this signal into a power signal by a drive circuit 45p (of known type). The signal ωb is related to the rotational speed of the spool 42 .

In operation, when the velocity imparted to the input fiber 35 by the storage means is greater than the velocity supplied to the fiber from the output end of the pulling means 37, the tension Tmis in the fiber increases and deviates from the target value _T0 .

Therefore, the absolute value of the tension error ΔT (a negative value in this case) increases, and the controller 62 rotates the motor 24 through the drive circuit 24p to move the slider 7 to the first limit position, so that the tension between the two pulleys The distance Dp between them and the length of the fiber portion 35b between them are reduced; such a reduction in the length of the portion 35b relatively increases the tension in the fiber, so that the tension in the fiber remains substantially unchanged.

Therefore, when the velocity imparted to the input fiber 35 by the storage device 40 is less than the velocity supplied to the fiber from the output end of the pulling device 37, the tension Tmis in the fiber decreases and deviates from the target value _T0 . Therefore, the tension error ΔT (a positive value at this time) increases, and the controller 62 rotates the motor 24 through the drive circuit 24p so as to move the slider 7 to the second extreme position, so the distance Dp between the two pulleys and part The length of 35b increases; such an increase in the length of portion 35b relatively reduces the tension in the fiber such that the tension in the fiber remains substantially constant.

This provides an electrical closed-loop tension control, thereby returning the tension in the fiber to the target value T ₀ .

Furthermore, the unit 66 determines the instantaneous position P _mis of the slider 7 along the guide rail 5 by integrating the signal V (related to the linear velocity of the slider 7 ). The instantaneous position is compared with the target position P ₀ , and the position error ΔP is processed by the conversion unit 72 to generate a rotational speed variable of the motor 45 . Specifically, when the slider 7 is closer to the first extreme position than the reference position (the slider 7 moves to the left in FIG. 1 ), the control system causes the rotation speed of the motor 45 to decrease so as to reduce the tension in the optical fiber 35. Small, and in order to compensate for the tension deviation, the tension control loop moves the slider 7 to the second extreme position (in other words, to the right in FIG. 1 ) (through the motor 24 and the screw 26), thereby compensating for the change in position.

Furthermore, when the slider 7 is closer to the second extreme position than the reference position (the slider 7 moves to the right in FIG. 1 ), the control system causes the rotation speed of the motor 45 to increase so that the tension in the optical fiber 35 increases, In order to compensate for the tension deviation, the tension control loop moves the slide block 7 to the first limit position (in other words, to the left in FIG. 1 ) (by the motor 24 and the screw rod 26), thereby compensating for the position change.

This provides an electrical closed-loop position control to return the slider to the target value P ₀ .

If desired, the position controller can be omitted; in this case, the control unit does not include the elements indicated by reference numerals 64, 66, 70, 72 and 45p.

The above description clearly shows that the advantage of the present invention is that the movement of the movable pulley 9 depends only on the action of the motor 24, and is completely independent of gravity or other predetermined forces (such as known elastic types) exerted on the movable pulley 9. In this way, a force whose value can be automatically controlled according to the operating signal applied to the motor 24 is applied to the optical fiber 35 . The tensioning device 1 itself automatically adapts to any changes in operating requirements (such as a change in drawing speed or a change in the position of the slider 7) and restores the value of tension applied to the fiber to the target value.

In addition, it is also ensured that the movable pulley 9 is always kept close to the reference position (specifically the middle position of the guide rail 5), so that it can always move from this position in an effective route (to the right or to the left) in order to compensate for tension changes . In other words, the slider 7 is prevented from being located close to the first or second limit position, where the slider cannot move in one of the two directions.

The tensioning device 1 can be used in different types of equipment, for example in draw towers, in extrusion lines or in testing equipment (also called "screening equipment") for measuring the breaking stress of optical fibers.

A draw tower typically includes a furnace for melting a preform of glass material, a pulling element (or "capstan," such as one of the single or double pulley types) for downwardly drawing the optical fiber resulting from the molten preform, A coating device for applying a protective surface coating (usually formed of acrylate) to the optical fiber, located between the furnace and the pulling element, and a fiber optic spool for receiving the optical fiber from the pulling element. As mentioned above, the tensioning device 1 can advantageously be positioned between the traction element and the winding drum.

Extruded lines are lines processed such that a plurality of optical fibers are advanced along the line along with a linear support element and along which a polymeric material is extruded onto the support element in such a way as to join the fibers and hold them In a fixed position around the support element, thereby forming the fiber core of the optical fiber. Extrusion lines typically include an unwind drum for the support element, a plurality of fiber unwind drums, an extruder capable of receiving the optical fiber and the support element at its inlet, for receiving from the extruder the Cooling chamber for optical fiber core, and terminal winding drum. A tensioning device 1 may eg be arranged downstream of each fiber unwinding drum in the extrusion line.

Screening equipment is often used to test whether an optical fiber can withstand a predetermined tension so that it is not affected by significant structural defects. Screening equipment typically includes an unwinding drum for the optical fiber, a take-up drum for the optical fiber and a plurality of guide and/or return elements capable of forming a fiber path between the unwinding and winding drums, Also, a predetermined tension can be imparted to the optical fiber during passage of the optical fiber. In the screening equipment, the tensioning device 1 can be arranged at any point of the above-mentioned path.

Finally, it is obvious that modifications and variants can be made to the tensioning device without departing from the scope of protection of the present invention.

In particular, the system for moving the slider 7 (screw 26 and nut connected to the slider 7) may differ from the system described, for example may include a Zigzag belt (not shown).

Finally, the position Pmis of the slider 7 along the guide rail 5 can be determined not by the indirect method shown in FIG. Photocells, or optical strips (in other words linear photosensitive elements, such as linear CCDs—not shown), are arranged along the guide rail 5 .

Claims (20)

1, a kind of apparatus for tension of fibre-optical is used for the progress path of optical fiber (35), comprises at least one travelling block (9), and optical fiber (35) twines a length at least around this travelling block (9); The position of described travelling block (9) can change so that change the tension force that is applied on the optical fiber (35),

It is characterized in that: it comprises that one can measure the tension force that is applied and produce the tension measuring device (56) of signal of an expression tension force (Tmis), and the electronic running gear (24 that is used for moving described travelling block (9), 26,5,7,50), this device can receive the signal of described expression tension force (Tmis) and move travelling block according to the signal of described expression tension force (Tmis), so that keep the tension force that is applied on the optical fiber (35) constant basically automatically.

2, according to the device of claim 1, it is characterized in that: it also comprises a fixed pulley (32), and optical fiber (35) twines at least one length around this fixed pulley (32); Distance (Dp) between the axle (33,20) of described fixed pulley (32) and described travelling block can change so that change the tension force that is applied on the optical fiber; Described electronic running gear (24,26,5,7) can be controlled described distance (Dp) so that the tension force that keeps automatically being applied on the optical fiber is constant basically.

3, according to the device of claim 1 or 2, it is characterized in that: described electronic running gear (24,26,5,7) comprise a guide rail (5) and an actuator (26,24), the slide block (7) that supports described travelling block (9) can move along described guide rail (5), described actuator (26,24) is used for moving described slide block (7) along described guide rail (5).

4, according to the device of claim 3, it is characterized in that: described actuator is included in the screw rod (26) that the effect of the power of an electric motor (24) can rotate down and is connected to a nut on the described slide block (7).

5, according to the device of claim 3, it is characterized in that: described actuator comprises an electric motor (24) and a belt-type motion transmission system.

6, according to the device of claim 2, it is characterized in that: comprise an electric control gear (50), at its input terminus reception reference signal (T ₀, P ₀) and measurement signal (Tmis, P _Mis), and can respond the operation signal that described input signal produces the closed-loop control that is used for described electronic running gear (24,26,5,7) (24p, 45p).

7, according to the device of claim 6, it is characterized in that: described electric control gear (50) forms one and is used for closed-loop control and is applied to tensile system on the optical fiber (35), and it comprises:

-one subtractor (60) is with the proportional tension force reference signal of the goal tension of optical fiber (T ₀) and the measurement signal (Tmis) that constitutes by described expression tensile signal offer this subtractor (60); With

-one controller (62) receives the tension error signal epsilon that provides from the output terminal of described subtractor (60), ε=Δ T=T at its input terminus ₀-Tmis, and produce one at its output terminal and can be used in operation described electronic running gear (24,26,5,7) and control the actuate signal (ω) of described distance (Dp).

8, according to the device of claim 7, it is characterized in that: described controller (62) comprises a proportional-integral derivative controller.

9, according to the device of claim 7, it is characterized in that: described tension measuring device (56) comprises a load transducer (56), and this load transducer is connected to described fixed pulley (32) and goes up the signal that also can produce the described expression tension force of expression (Tmis) at its output terminal.

10, according to the device of claim 6 or 7, it is characterized in that: described electronic running gear (24,26,5,7) comprise a guide rail (5) and an actuator (26,24), the slide block (7) that supports described travelling block (9) can move along described guide rail, described actuator (26,24) is used for moving described slide block (7) along described guide rail (5); Described electric control gear (50) is configured for the system of the described slide block of closed-loop control (7) along the position of described guide rail (5).

11, according to the device of claim 10, it is characterized in that: be connected to the device (40) that is used to deposit optical fiber in order to operate it, the described device that is used to deposit optical fiber can receive optical fiber from tightening device, is that also the described described slide block of closed-loop control (7) that is used for comprising along the system of the position of described guide rail (5):

-another subtractor (70), with described slide block (7) along the relevant position reference (P in the reference position of described guide rail (5) ₀) and offer this subtractor (70) with described slide block (7) along the proportional measurement signal of physical location (Pmis) of described guide rail (5); With

-another controller (72) receives the position error signal ε that the output terminal by described another subtractor (70) provides, ε=Δ P=P at its input terminus ₀-Pmis, and produce another actuate signal (ω b) that can be used in the described storing unit of operation (40) at its output terminal.

12, according to the device of claim 11, it is characterized in that: described another controller (72) comprises a proportional-integral derivative controller.

13, according to the device of claim 11, it is characterized in that: described storing unit (40) comprises at least one electric reel (42), optical fiber (35) from described tightening device (1) is wrapped on this electric reel (42), this electric reel (42) can rotate around its turning axle (43) under the effect of electric motor (45), and described another actuate signal (ω b) can be used to control described electric motor (45).

14, according to the device of claim 11, it is characterized in that: described electric control gear (50) comprises an integrator (66), this integrator (66) receives and the signal (V) of described slide block (7) along the velocity correlation of described guide rail (5) motion at its input terminus, and its output terminal produce with described slide block (7) along the proportional described measurement signal of the physical location of described guide rail (5) (Pmis).

15, a kind of control is applied to tensile method on the optical fiber along optical fiber (35) progress path, this method comprises the step of the part with certain-length (Dp) (35b) that forms described path, described length can change so that change the tension force that is applied on the described optical fiber

It is characterized in that: also comprise and measure the tensile step be applied on the described optical fiber and utilize an electric motor to control the step of described length (Dp), so that keep the tension force that is applied on the optical fiber constant basically with automated manner according to described measured tension force.

16, according to the method for claim 15, it is characterized in that: also comprise according at least one reference signal (T ₀) and measurement signal (Tmis) closed-loop control be applied to the tensile step of described optical fiber, described at least one reference signal (T ₀) proportional with the goal tension of optical fiber, described measurement signal (Tmis) produces in measuring the tensile step and is proportional with the actual tension force that bears of optical fiber.

17, according to the method for claim 16, it is characterized in that: described closed-loop control tensile step comprises the steps:

-more described tension force reference signal and described measurement signal (Tmis) produce a tension error signal epsilon, ε=Δ T=T ₀-Tmis; With

-handle described tension error signal, produce an actuate signal (ω) at output terminal, this actuate signal can be used in by an electric motor and changes described length (Dp) and keep the tension force in the optical fiber constant basically.

18, according to the method for claim 15, it is characterized in that: also comprise according at least one position reference (P ₀) and the step of the position of measurement signal (Pmis) closed-loop control one moving element (7), described at least one position reference (P ₀) proportional with the target location of described moving element, described measurement signal (Pmis) is proportional with the instantaneous position of described moving element, and the change in location of described moving element (7) causes that described length (Dp) changes.

19, according to the method for claim 18, it is characterized in that depositing optical fiber in the terminal of described progress path, be that also the step of the position of the described moving element of described closed-loop control comprises the steps:

-more described position reference (P ₀) and described position measurement signal (Pmis), produce a position error signal ε, ε=Δ P=P ₀-Pmis; With

-handle described position error signal, produce an actuate signal (ω b) at output terminal, this actuate signal can be used in and changes the speed of depositing optical fiber.

20, a kind of optical fibre management system, comprise that a fiber optic source (37), can receive the optical fiber storage device (40) of optical fiber at its input terminus from tightening device (1) from the apparatus for tension of fibre-optical (1) and of this fiber optic source (37) reception optical fiber (35), described tightening device (1) comprises at least one travelling block (9), and described optical fiber (35) twines at least one length around described travelling block (9); The position of described travelling block (9) can change so that change the tension force that is applied to described optical fiber; Described system is characterised in that described tightening device (1) comprises that one can measure the tension force that is applied and produce the tension measuring device (56) of signal of the described tension force of expression (Tmis), with an electronic running gear (7,24,26), this device can receive described expression tensile signal and can move travelling block (9) according to described expression tensile signal, so that keep the tension force in the optical fiber constant basically automatically.

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