Abstract:
An apparatus designed to alert on an abnormal condition inside of a fiber bundle ( 116 ). The apparatus includes an air pipe ( 112 ) configured inside of the fiber bundle, an air compression element adapted to apply air into the air pipe, at least one sensor ( 124, 128, 132, 136, 148 ) configured in combination with the air pipe wherein at least one sensor is coupled to at least one location on the air pipe. An alerting element ( 172, 308 ) is configured to notify on an abnormal measurements of at least one sensor.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    Reference is made to commonly-assigned copending U.S. patent application Ser. No. 12/032,716, now U.S. Publication No. 2009/0207387, filed Feb. 18, 2008, entitled A FIBER OPTIC IMAGING APPARATUS, by Eyal et al., the disclosure of which is incorporated herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates in general to a safety device for optical cables, and in particular to sensors configured to alert on excess heat in a fiber optic bundle. 
       BACKGROUND OF THE INVENTION 
       [0003]    There are a number of mechanical electrical devices that use optical fibers cables or electrical cables, collectively referred to as cables, wherein flexibility is especially important. In some applications, these cables are subjected to repetitive bending operations that may, over time, cause damage to the cables. This damage may cause electrical shorting, in the case of electrical cables, or melting of the cables due to light leakage and heat buildup, in the case of optical fiber. Both of these scenarios may cause safety issues and may result in expensive repairs. 
         [0004]    Computer-to-plate (CTP) machines present a good example of this type of problem. In a CTP machine, a bundle of optical fiber is attached to an imaging head, which is moved back and forth numerous times along a surface of a rotating drum to create an image on media attached to the drum. For the purpose of heat excess detection, along high power electric transmission cable assemblies, linear heat detectors such as from Protectowire (http://protectowire.com/) are used. Unfortunately such sensors can not be used in some cable trays due to the limited structural flexibility. 
         [0005]    It is therefore the object of the present invention to provide a heat sensors for flexible waveguides. It is also an object of the present invention to provide an alert module and an interlock module that are activated by a signal detected by the heat sensors and heat detectors. 
       SUMMARY OF THE INVENTION 
       [0006]    Briefly, according to one aspect of the present invention an apparatus for alerting on an abnormal condition in a fiber bundle including, an air pipe inside the fiber bundle, an air compression adapted to apply air into the air pipe, at least one sensor in combination with the air pipe and coupled to at least one location on the air pipe. An alerting element is configured to alarm on an abnormal measurements of at least one sensor. 
         [0007]    These and other objects, features, and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings wherein there is shown and described an illustrative embodiment of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is an illustration of an air pipe inside a fiber bundle with air pressure and air flow sensors; 
           [0009]      FIG. 2  is an illustration of a damaged air pipe inside a fiber bundle using air pressure and air flow sensors; 
           [0010]      FIG. 3  is an illustration of an air pipe inside a fiber bundle with an electric wire inserted in the air pipe with air pressure and air flow sensors; 
           [0011]      FIG. 4  is an illustration of a damaged air pipe inside a fiber bundle with an electric wire inserted in the air pipe with air pressure and air flow sensors; and 
           [0012]      FIG. 5  is an illustration of an air pipe inside a fiber bundle with microphone sensors. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    This invention presents methods and apparatus, for detecting excess heat within multi-cable configurations. For example, when high power fiber coupled lasers are deployed, laser safety measures should be introduced to avoid hazardous states. 
         [0014]    According to the present invention, longitudinal sensor elements will alert an operator of heat excess within and along a cable, such as a fiber optic bundle, electric cables pipes, and similar cable configurations. For example, a fiber optic bundle is usually made of glass fibers configured to transmit light emitted from high power lasers. An excess of heat generated within and along a bundle of fibers may be caused by a break or a cut along one or more locations of the glass fibers which form the bundle. 
         [0015]    For purposes of illustration, a typical imaging device may use high power, fiber coupled laser diodes in its optical heads. The total optical power delivered by such a device may reach, roughly 2000 watts. The usage of power levels of this magnitude may increase the need for caution so that hazardous situations do not occur. The cables should be carefully inspected to prevent light leakage or cable meltdown. 
         [0016]    In one embodiment of the invention, such a sensor is shown in  FIG. 1 . An air pipe  112  is incorporated in the fiber bundle  116 . The air pipe  112  is constructed from material with predefined melting temperature, suitable for fiber bundle  116  robust operation. An air pressure source  104  is adapted to apply air flow  108  into air pipe  112  during operation of the fiber bundle  116 . The applied air flows in the air pipe  112  and is released from the air pipe  112  at the air flow outlet  120 . The air flow outlet  120  is equipped with a small diameter air flow opening  176 . The opening diameter is optionally regulated by air flow regulator  140 . 
         [0017]    Sensor element  148  is attached to fiber bundle  116 . Sensor element may be configured from various types of sensors such as pressure and air flow sensors or a combination thereof. The sensors can be positioned at the inlet and/or at the outlet of bundle  116 , and/or along fiber bundle  116 . 
         [0018]      FIG. 1  shows sensor element  148  which is comprised of two pairs of sensors. Two sensors are attached to the inlet of air pipe  112 , an inlet pressure sensor  124  and an inlet air flow sensor  128 . In addition, another two sensors are attached to the outlet of air pipe  112 , an outlet pressure sensor  132  and an outlet air flow sensor  136 . 
         [0019]    Controller  144  controls air pressure source  104 , through control/status line  164 . Controller  144  also sends a test validation signal  156  from time to time, to inspect sensor elements  148  as well as the state of air pipe opening  176 . The data from sensor element  148  is collected by controller  144  via sensor data collection line  160 , and is compared to the expected values that should have been read during a normal operation. The validation procedure will usually involve stopping the operation of the air pressure source  104  for a predefined time interval. This will be followed by reading data from sensor elements  148 , and comparing the read data to normal operation. As for an example, when air pipe opening  176  is fully clear without any clog, the air trapped in air pipe  112  will evacuate from air pipe  112  during the validation procedure much quicker than in the case the air pipe opening  176  is partially clogged. By that controller  144  may alert the user on a possible problem with air pipe opening  176 . Similarly by stopping air pressure source  104  and restarting it after a predefined time interval, the readings from sensor elements  148  are compared to the expected readings in normal operation elements, thus producing an alert when an abnormal condition within sensor elements  148  is detected. 
         [0020]    Optionally a controlled air valve  180  can be added at the air pipe  112  inlet. In the case of blockage along air pipe  112 , it can be used in combination with inlet pressure sensor  124  to check and estimate blockage position along air pipe  112 . This can be achieved by the following the steps:
       a) Open air valve  180  to release trapped air from air pipe  112 .   b) Close air valve  180  and apply air into air pipe  112 .   c) Measure the time it takes to achieve maximal air pressure is achieved in air pipe  112 .   d) Estimate blockage position along air pipe  112 , by air pipe  112  diameter and the time it took to achieve maximal air pressure, deducing from that the length of the blocked segment of air pipe  112 .       
 
         [0025]    In operation, air pressure source  104  applies air flow  108  into air pipe  112 , the applied air flow  108  will exit from air flow outlet  120 . Air pressure and air flow are measured constantly by sensors  124 ,  128 ,  132 , and  136  at air flow inlet and air flow outlet locations. Similar measurement results showing similar air pressure levels measured by inlet pressure sensor  124  and by outlet pressure sensor  132 , will indicate on normal operation of the fiber bundle  116 . Similarly, equal flow intensity levels measured by inlet air flow sensors  128  and outlet air flow sensor  136  will indicate on normal operation as well. 
         [0026]    In the case of a hazardous event, such as excess of heat or fire, air pipe  112  can be damaged or destroyed as is indicated by the heat damaged area  152 . In this case the air pressure inside the air pipe  112  may break the melting pipe causing air flow leakage  168 , as is depicted in  FIG. 2 . 
         [0027]    The hazardous situation described above will be detected by sensor element  148 . In the event of a damage in air pipe  112  due to melting by fire, air flow  108  can be trapped between pipe inlet and heat damaged area  152 , resulting in inlet pressure sensor  124  high pressure readings, whereas outlet pressure sensor  132  will show no pressure. In this case both air flow sensors ( 128 ,  136 ) will not read any air flow. 
         [0028]    Alternatively, a hole can be created in heat damaged area  152  causing air flow  108  to exit from heat damaged area  152  and leak out  168  from the damaged air pipe  112 . In this case the readings of air pressure sensor  124  will show significantly higher results than outlet pressure sensor  132 . Similarly inlet air flow sensor  128  will show high values whereas outlet air flow sensor  136  will show almost no air flow. In this case inlet air pressure sensor  124  will read high pressure, and the outlet pressure sensor  132  will show low or no pressure. 
         [0029]    The combination or variety of sensor elements  148  can differ between sensor configurations. For example a single air pressure sensor can be used at the outlet end of air pipe  112 , and produce sufficient information on air pipe  112  status. 
         [0030]    These readings will indicate an abnormal situation that should cause invoking an interlock to stop system operation, and produce an alert via alert line  172  to the user. Such an alert should be generated at any stage where pressure sensors ( 124 ,  132 ) read different values or the flow sensors ( 128 ,  136 ) read different values. 
         [0031]      FIG. 3  shows a shrinking air pipe sleeve  312 . The shrinking air pipe sleeve  312  will shrink at predetermined temperatures. The sleeve is usually constructed from flexible material, and as such may bend during operation. Such a bend will cause a blockage in air pipe  112 , and create false abnormal alarms.  FIG. 3  shows an electric wire  304  inserted into air pipe  112 . The electric wire  304  due to its rugged features will prevent from shrinking air pipe sleeve  312  to bend. In addition the electric wire will be connected to an interlock  308 . In the case of a fire causing a damage in heat damaged area  152  (as is shown in  FIG. 4 ), the electric wire will automatically set interlock  308 , to stop laser imaging. 
         [0032]      FIG. 5  shows microphone sensors  504 ,  508  can be used instead of air flow sensors and air pressure sensors. Microphone sensors can be placed in proximity to inlet and/or outlet of air pipe  112 . The audio levels generated by the air flow are measured and translated into flow intensity terms, thus indicating the air flow levels. Similarly, measuring pressure oscillations generated by air flow turbulences can be used for air pressure measurement. 
         [0033]    The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention. 
       PARTS LIST 
       [0000]    
       
           104  air pressure source 
           108  air flow 
           112  air pipe 
           116  fiber bundle 
           120  air flow outlet 
           124  inlet pressure sensor 
           128  inlet air flow sensor 
           132  outlet pressure sensor 
           136  outlet air flow sensor 
           140  air flow regulator 
           144  controller 
           148  sensor element 
           152  heat damaged area 
           156  test validation signal 
           160  sensor data collection 
           164  control/status line between controller and air pressure source 
           168  air flow leakage 
           172  alert line 
           176  air pipe opening 
           180  air valve at the air pipe inlet 
           304  electric wire 
           308  interlock 
           312  shrinking air pipe sleeve 
           504  microphone sensor at inlet 
           508  microphone sensor at outlet