GB2581815A - Air-assisted removal of fiber offcuts and counting method - Google Patents

Abstract

A device and method suitable for collecting optical fiber offcuts generated by a cleaving device 1 which cleaves an optical fibre 6, the method includes a fan 11 (which may be mains or battery powered) and ducting to direct air flow (the fan may be a discrete component or incorporated in to an assembly), a filter 12 to block entry of fiber offcuts in to the fan, a pressure reduction chamber 13 (which may be permanently or dismountably attached to a cleaving device) in which the air flow created by the fan is directed so that there is a suction force close to the location of the offcut fibers and the suction force transports the fiber offcuts into the fiber collection means. A counting device which counts the number of times the cleaving device has been used may be included. In one embodiment the fan only operates when the cleaving device is in use. The fan may be an axial or centrifugal fan.

Description

Air assisted removal of fiber offcuts and counting method

Background

Optical fiber is used to transmit optical signals required for digital communications such as the internet. Optical fiber is typically made of silica glass and manufactured in long lengths with a glass diameter of 0.125mm. Lasers, or other light sources, inject light in to the glass fiber, the light travels a significant distance in the optical fiber and exits the fiber to arrive at optical detectors or otherwise. The end of the core of the glass fiber must be smooth to enable to transmission of the light. Because the fiber is made of glass, the fiber termination is difficult and is typically achieved by cleaving the fiber or fibers using a scratching means and a tensioning or bending means to split the glass fiber, giving a mirror-smooth end face through which the light can enter or exit. Such cleaving devices have been widely researched. The cleaved end may be perpendicular, for later use in fusion splicing to other fibers, or it may be angled or otherwise to eliminate any transmission of reflected light back down the optical fiber. Oxford Fiber Ltd. of Rugby, England manufacture such cleaving devices.

When the fiber or fibers are cleaved, short lengths of glass with a length of some millimeters are cleaved off the end of the stripped glass fiber. These short lengths of fiber represents a health hazard, with the possibility of harmful ingestion by the user. In order that the cleaving device may be used without harm by relatively unskilled operators, there is a requirement for the offcut fiber, also known as a shard, to be safely collected to prevent it accidentally harming the operator. This is particularly important in the case of cleaving ribbons of fibers which generates large numbers of offcut fibers at once.

Devices are known which safely dispose of the offcut fiber produced by the cleaving device. Typically, the cleaving device has a pair of rollers which immobilise the fiber before cleaving and where the rollers are arranged on the cleaving device on the offcut side of the cleaved fiber When the fiber is cleaved, the offcut is held in the rollers. The rollers are caused to turn after the cleaving action, so ejecting the offcut fiber in to a bin or receptacle which is attached to the cleaving device. Examples can be found in cleaving devices from Sumitomo Electric and Fujikura, both of Japan.

It is understood that rollers are an effective way of disposing of the offcut fiber. However, a sophisticated mechanical linkage may be required to operate such rollers and this adds cost and complexity to the design of the cleaving device.

A further requirement of fiber cleaving devices is that they provide a counting mechanism to record the number of cleaves which have been carried out. Because devices such as cleaving devices suffer mechanical wear, the quality of the cleaves produced may not be maintained throughout use. If clamping surfaces or cutting blades suffer wear, the operator will not know if a good cleave has been produced and there is the danger of using poor cleaves in the optical network leading to great extra costs. If the operator has a clear idea of the number of cleaves carried out by the cleaving tool, maintenance programmes may be used to mitigate the possibility of poor cleaves.

Summary of the Invention

We here reveal an invention which uses air pressure to suck the offcut fiber or fibers away from the cleaving device. The air pressure can conveniently be generated by a fan which is attached to the cleaving device. This has the advantage that the linkage between the cleaving device and the offcutdisposal mechanism is simple to design and simple to couple to the cleaving device. The air pressure should generate a suction force rather than a blowing force so that the collected offcuts are contained within a chamber, rather than a blowing force whereby the fiber offcuts may be randomly and dangerously distributed in the environment.

In one embodiment of this invention, an axial fan is positioned beyond the distal end of the optical fiber. When the optical fiber is cleaved, the fan sucks the glass offcut away from the cleaving device and deposits it for later disposal. The cleaving device may be capable of cleaving single or multiple fibers simultaneously and the cleaved fibers may have ends which are perpendicular or angled to the optic axis of the fiber or fibers. The fan is arranged to cause a reduced air pressure close to the offcut fiber. In another embodiment, a centrifugal fan, or otherwise, can be used to create the suction force. The suction power of the fan should be channelled so that the reduced air pressure is located close to the offcut fiber and this is conveniently done by employing a pre-fabricated pressure-reduction chamber between the fan and the end of the offcuts and so maximising the reduction in air pressure close to the offcut fiber. The fan reduces the air pressure in the chamber and the other end of the chamber has an opening close to the offcut fiber or fibers. This generates an air flow which causes the offcut fiber to be sucked away from the cleaving device. Preferentially, the air flow should be directed using a nozzle close to the offcuts so that the air stream lifts the fiber offcuts up away from any supporting surfaces of the cleaving device so that the fiber is easily moved; conversely an air flow which causes the fiber to be pushed on to a supporting surface will reduce the likelihood of the offcut being removed. The air stream may be directed to lift the fiber by positioning the entrance of the reduced-pressure chamber above the offcut fiber. When designing the reduced pressure chamber, volumetric air flow rate should be maximised. This is typically achieved by employing smooth internal surfaces, which may or may not be painted or coated. In addition, any transitions in the shape of the air flow which may be required to match the cylindrical flow generated by the fan to the shape of the nozzle close to the offcut fiber should be carried out gradually.

In one embodiment, a filter is introduced between the offcut fibers and the fan to stop the fiber offcuts entering the blade area of the fan. This filter may be a metal mesh or a fibrous or felted material.

In another embodiment, the pressure-reduction chamber is used to store the offcut fibers which are sucked away from the cleaving device.

In another embodiment, a separate offcut storage chamber is present to collect the fiber offcuts, with the offcut storage chamber positioned between the fan and the cleaving device.

In another embodiment, a baffle is present in the pressure-reduction chamber so that the offcut fibers are sucked in to the pressure chamber but are caused to hit the baffle which causes the offcut fibers to fall down in to the bottom of the pressure chamber so that the offcuts are stored and so prevented from entering the blades of the fan. In another embodiment, the pressure chamber may be removable.

The fan may be powered by mains or battery electricity.

The fiber offcut removal device may be permanently attached to the cleaving device or it may be dismountable. Preferentially, the cleaving device should be operable without the use of the fiber offcut-removal device so that the cleaving device may still be used where the fan is not in use-for instance in the case of a flat battery or lack of mains power.

Preferentially, the fan should be battery powered, although this may be augmented by mains power or external battery power, when available. The use of a battery-powered fan allows the cleaving device and its offcut collection system to be used independent from fixed power sources. Clearly, the use of a battery-powered device requires management of the usage of the fan. In one embodiment of this invention, a microswitch is included in the offcut removal device or in the mechanism of the cleaving device. When the cleaving device is operated, the microswitch is closed, so turning on the fan which causes the air flow to suck away the offcut. When the cleaving device has finished its operating cycle, the microswitch opens, so turning off the fan and so saving battery power. In addition to the microswitch, an on-off switch may be included in the offcut removal mechanism to prevent the fan operating when the cleaving device is stored.

In another embodiment, a microswitch is included in the cleaving device or offcut-removal mechanism and this serves to turn the fan on and off. However, the microswitch also allows the possibility of incorporating a counter which records the number of times the cleaving device and/or offcut remover are operated. Cleaving devices typically are devices which have parts which wear, such as diamond or metal blades or clamping surfaces. A counter alerts the user to the need to replace or renew these critical components and so ensures good long-term performance of the cleaving device. Without a counter, the user risks producing cleaves which are of poor quality which leads to poor optical connections and great extra costs in installing the optical network. When the cleaving device operates, the microswitch is closed and this causes the counter to increment. The counter may be mechanical, electro-mechanical or electrical. It may be powered by a battery which is either located on the cleaving device or in the offcut removal device. Preferentially, the counter and its battery may be permanently located on the cleaving device so that operation of the cleaving device is recorded even if the offcut removal device is not connected to the cleaving device. In another embodiment, the counter may be mechanically powered.

In one embodiment, a 12V dc fan is used to create the air flow required for the fiber offcut removal device. Typically, 12Vdc fans are cheaply available. 5V-1.2V dc or 15Vac may be used to drive these fans. 12Vdc is commonly available from other optical fiber installation tools. The fans should be designed to use an easily available battery power source which is not heavy and does not take up too much space. 9Vdc PP9 long-life batteries are a suitable battery. These can store in excess of 1Ahr of 9Vdc power. The 12V fans may be operated at 9V or below with reduced air flow. We have found that fans with a 12V rating of 40m3/hr may be operated at 9V with a flow sufficient to remove fiber offcuts. When the battery is exhausted, it may be easily replaced. Preferentially, the stored fiber offcuts may be removed at the same time as the battery is replaced. Typically, 500 cleaves may be carried out in a 6 months time period and this is a suitable replacement schedule of the fiber offcut removal battery.

Alternatively, the battery may be rechargeable. Preferentially, the battery should use lithium-ion technology to maximise the power storage and also ensure operation in low ambient temperatures. Conveniently, power packs, widely developed for recharging mobile electronic devices, may be used as a DC power source to drive the fan. The power packs may output 12V to drive 12V fans, or power packs with 5V output may be used to drive 5V fans, or 5V power packs may be used to drive 12V fans at reduced operating speed but still powerful enough to suck away the offcut fibers. In another embodiment, a 5V power pack may have its voltage stepped up such that the power pack drives a 12V fan. In another embodiment, a 12V rechargeable battery may be used to drive a 12V fan and the 12V battery may be charged from an easily available 5V charger which is stepped up to 12V. Power packs may conveniently be recharged overnight by using a widely available mobile phone or USB charger.

In another embodiment of this invention, the suction force is generated by a vacuum cleaner, a fan or other means of generating reduced air pressure.

We now explain the offcut removal device in greater detail by means of an illustrative drawing.

Drawings: With the help of illustrative drawings, we will now describe the invention in more detail. Figure 1 shows * a cleaving device, * an axial fan, * a pressure-reduction chamber to direct the flow of air, * a filter to prevent ingress of the offcut glass in to the blades of the fan * a portion in which the fibers are retained * a battery compartment (containing a rechargeable battery) to operate the fan, located underneath the cleaving device * a microswitch which is closed by the operation of the cleaving device and opens after the cleaving operation has finished * an on/off switch A cleaving device 1 is used to cleave the optical fiber or fibers using a Ox-SAC-08 angled fiber cleaver as manufactured by Oxford Fiber Ltd., of Rugby, UK. The cleaving device 1 is made up of a chassis 2 with a diamond blade 3 and an anvil 4 with elastomeric clamp rings 5 located on either side of the anvil. The optical fiber or fibers 6 are stripped of their coating 9 and placed in a holder 7 which is secured in the chassis of the cleaving device. The stripped optical fibers extend over a gap in which the sharp diamond blade 3 is located.

The cleaving device operates by closing the anvil 4 so that the clamp rings 5 clamp a stripped portion of the optical fiber 6 and the anvil further depresses the fiber so tensioning and bending the fiber or fibers until they touch the sharp diamond blade 3, so cleaving it. After cleaving, the anvil rises up under spring pressure, so revealing the offcut fiber lengths which are to be collected.

The cleaving device 1 is arranged to be in close proximity to the fiber collection device 8.

As the anvil descends prior to cleaving, the anvil closes a microswitch 10, this closes an electrical circuit so turning on an axial fan 11. The axial fan is arranged so that reduced air pressure is created between the fan and the cleaving device with its offcut fiber or fibers. The axial fan 11 is connected to a filter 12 and a pressure-reduction chamber 13. Nozzle 14 directs air flow over the region in which the fiber offcuts are located, causing suction. The ducting required to direct the suction air flow is manufactured in plastic, either by moulding, plastic printing or the device may be manufactured from metal or other material.

As the anvil 4 rises, so revealing the offcut fibers, the air flow sucks the offcut fibers in to the pressure-reduction chamber 13. The pressure chamber may or may not contain a baffle 14 (not visible in Fig.1) to block the passage of the fibers, so allowing them to fall to the bottom of the chamber, a region of reduced air flow in which the offcut fibers may collect. In addition, the offcut fibers are blocked from entry in to the blades of the fan by a filter 12 which may be a metal mesh or fabric material. As the anvil rises further, after the fiber offcuts have been collected, the microswitch 10 is opened, so breaking the electrical circuit and so stopping the fan. An on-off switch 15 is also present to permanently disable the fan to prevent accidental operation of the fan during storage and so discharge of the battery.

The cleaving device and the offcut removal mechanism are mounted on a lid 20 and a base box 21. The battery 22 (not visible in Fig.1) is contained within the base box 21. The charge state of the battery 22 may be seen through holes 23a, 23b in the base box. 21 The battery may be charged by inserting a charging lead through a hole (not shown) in the base box. The output power of the battery may be connected via leads (not visible in Fig.1) to the fan, causing it to operate.

A voltage step-up circuit 24 (not visible in Fig.1) is also located within the base box 21 to ensure that the battery delivers an appropriate voltage.

A totalising counter 30 may or may not be mounted on the lid 21. The microswitch may be electrically connected with a resistance-capacitance circuit 34 (not visible in Fig.1) to de-bounce the microswitch i.e. to ensure that the microswitch only delivers a single pulse to the counter. The counter 30 is connected to the battery 22, optionally using a Zener diode 31 (not visible in Fig.1) to ensure the correct operating voltage to the counter.

In the case where the cleaving device is used separately to the fiber offcut removal system, it is desirable that a counter 30 is present to track the number of times the cleaving device is used. Optionally, a stand-alone battery 32 (not visible in Fig.1) is included in the cleaving device to generate sufficient voltage to operate the counter; typically a 3.7V battery using Lithium ion technology is sufficient to power the counter for several years. In addition, a microswitch 10 (with its de-bounce circuitry 34) is incorporated in the body of the cleaving device and operation of the anvil 4 closes and opens the microswitch to measure the number of times the cleaving device is used. In the case where a microswitch is present in the cleaving device, this microswitch can be used to trigger operation of the fan-powered offcut-removal system.

We use a fan of axial design which is manufactured by Sanyo Denki: San Ace 9GAX Series Axial Fan (40 x 40 x 28mm, 54m3/h, 15.6W, 12 V dc). We use a Belkin, CA, USA power pack with a storage capacity of SAhr at 5V, with its voltage stepped up to 12V. The fan is connected so that its low pressure side is proximal to the cleaving device and it blows air out in a direction distal to the cleaving device. The stripped optical fiber is placed in the cleaving device so that the distal end of the fiber protrudes in to the nozzle of the offcut collection device. The fan draws approximately 10W of power from the battery for an operating time of about 3 seconds. Therefore, we expect at least 500 operations of the fan from a full battery charge. The battery can be recharged overnight.

We thermally strip acrylate-coated ribbon fiber, revealing 30mm of stripped optical fiber. The fiber ribbon is inserted in to a ribbon version of the Ox-RAC-08 angled cleaver, as made by Oxford Fiber Ltd., Rugby, England. We ensure that the end of the stripped fibers protrudes in to the nozzle 14 of the fiber offcut. The stripped fibers are arranged in the cleaving device so that a cleave is obtained with a cleave length (distance between the end of the coating and the cleave position) of 16mm or less, implying that all fiber offcuts have a length of 14mm or more. When the fibers are cleaved, the air flow originating from the fan is sufficient to collect all of the fiber offcuts.

It is understood that the above description of the device is illustrative only and in no way limits the operation of this invention.