Abstract:
An electrically operated equipment with a sealed enclosure containing circuitry with an exterior visual indicator to show a state of operation of the equipment. The visual indicator is illuminated by a magnetic flux sensor also exterior to the equipment, the sensor inducing an electrical current from a sensed magnetic flux passing through a permeable wall of the enclosure. The magnetic flux is provided by a magnetic field generator within the enclosure. The generator is connected to the equipment to generate the field when the circuitry is operating correctly whereby the indicator shows a correct state of operation. The invention avoids the use of sealed orifices in the enclosure for conductors to pass to exterior LEDs or LEDs sealed within the enclosure and possible resultant leakage. The invention is useful for optical network units. The invention also includes a visual indicating device of multi-layer configuration and a method of visually indicating the operational state of circuitry.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to visual indication of equipment operation.  
         BACKGROUND OF THE INVENTION  
         [0002]    Electrically operated equipment, i.e. electronic equipment or electrical power equipment, is installed both in outdoor and indoor environments. In both of these environmental situations, it has been found to be convenient and, perhaps, prudent to provide visual indications to show whether the equipment, or parts thereof, are operating correctly and effectively. If properly monitored, visual indicators will inform maintenance technicians immediately when any malfunction of equipment occurs. Visual indicators are used to identify a particular item of equipment which is malfunctioning, as distinct from those which remain functional. Such identification enables necessary repairs or equipment replacement to be effected as soon as possible and with minimal operational downtime. Hence. any customer provided with service by such equipment, e.g. telecommunication service, is indisposed for as short a time as possible by lack of this service due to malfunction.  
           [0003]    Visual indication is appropriately provided by an illumination process, e.g. with the use of a light emitting diode (LED) so as to be readily seen as required. Particularly with the use of visual indicators on outside plant equipment, problems are known to arise because of environmental conditions. Illuminated visual indicators protrude through apertures in equipment housings and these apertures, unless properly sealed, allow the surrounding environmental conditions to reach the equipment and detrimentally affect the operation. Thus, the operational parts of equipment, e.g. printed circuit boards, and electrical terminals, may be subjected to humidity conditions in the form of airborne mist or heat condensed droplets of water. Precipitation in any form, especially when wind driven, and extreme temperature changes also may cause operational problems.  
           [0004]    In known structures, with LEDs protruding through apertures in housings, the LEDs are either mounted upon printed circuit boards or are connected thereto by electric conductors. The LEDs typically are covered with clear plastic layers or windows, or with glass lens caps. Sealing always presents problems around LEDs mounted in such ways. Sealing is necessary around the covers of the LEDs to prevent moisture ingress into housings. Sealing may also be necessary to prevent electromagnetic or radio frequency transmission into and out of housings with resultant detrimental effects on the operation of equipment both within the housing and outside the housing. Where satisfactory sealing is initially effected with such structures, there is always the possibility of sealing failure during usage, particularly when subjected to outside environmental conditions.  
           [0005]    In addition, some structures may be for use underground. For such usage, sealing must be adequate to prevent water ingress when submerged in water and also to withstand extremes of water pressure when water depth increases.  
           [0006]    Attempts have been suggested to avoid sealing problems. One suggested attempt involves the incorporation of an LED into an environmentally sealed planar carrier. The LED, circuitry to the LED and the carrier being referred to as a “membrane switch”. However, while the LED and circuitry within the switch may be effectively sealed, the switch needs to be mounted upon a housing of equipment with which it is associated and is connected by an electric conductor through the housing to circuitry of the equipment. Problems may exist with sealing an aperture in the housing surrounding the conductor and with sealing the switch to the housing. Also, such sealing may be unreliable after a period of usage especially in outdoor environmental conditions.  
           [0007]    It follows that sealing failure may result in malfunction and deterioration in circuitry operation with also the possibility of allowing leaking of electromagnetic and radio frequency transmission through the housing.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention seeks to avoid or lessen leakage problems and problems caused by the surrounding environment.  
           [0009]    Accordingly, the present invention provides electrically operated equipment comprising:— 
           [0010]    an environmentally sealed enclosure having at least one wall permeable to a magnetic flux;  
           [0011]    an electrically operated circuitry environmentally protected within the enclosure; and  
           [0012]    a magnetic field generator within the enclosure and interconnected to the electrically operated circuitry to produce a magnetic flux indicative of a state of operation of the circuitry, the flux after passage through the permeable wall to induce an electric current in a magnetic flux sensor outside the enclosure, and produce a visual indication of the state of operation of the electrically operated circuitry.  
           [0013]    As may be seen from the above invention, the enclosure is environmentally sealed and no apertures exist in the enclosure although a visual indication is made possible of the state of operation of the circuitry within the enclosure. Hence, the use of the magnetic flux generator to create a magnetic flux which passes through a permeable wall of the enclosure, avoids any possibility of leakage occurring as no apertures exist or could form during use of the equipment due to seal failure at apertures. Thus, the enclosed circuitry cannot be deleteriously affected by the surrounding environment, e.g. humidity, changes in humidity and temperature changes which could result in condensation of water droplets upon the circuitry. Also precipitation in any form outside the enclosure can have no effect upon the condition and operation of the circuitry.  
           [0014]    The use of an induction coupling through the permeable wall provides an aperture free environmentally sealed enclosure in which the environmental sealing is maintained throughout the entire use of the equipment.  
           [0015]    The equipment according to the invention may be used with any suitable magnetic flux sensor positioned outside the enclosure in a suitable location. However, in a preferred arrangement, equipment according to the invention includes a magnetic flux sensor to be influenced by the magnetic flux issuing through the permeable wall to induce an electrical current corresponding to the magnetic flux. A visual indicator is electrically connected to the sensor and is controlled by the induced current to produce visual indication of the state of operation of the circuitry.  
           [0016]    The equipment according to the invention may comprise an electronic circuitry or a power circuitry, or both.  
           [0017]    Conveniently, the magnetic field generator comprises a magnetically permeable core with an electrically conductive coil wound on to it. It is also convenient for the magnetic flux sensor and the visual indicator to be mounted upon the enclosure and for them both to be environmentally sealed.  
           [0018]    Advantageously the magnetic flux sensor and visual indicator are environmentally sealed within a multi layer structure with adjacent layers environmentally sealed together. Thus, the multi layer structure may be planar and may be conveniently attached, i.e. by adhesive, to a surface of the enclosure. The invention further includes electrically operated equipment as defined above but having both electrical power circuitry and electronic telecommunication circuitry within the enclosure. Each of these circuitries comprises its own magnetic field generator within the enclosure, and magnetic flux sensor and visual indicator outside the enclosure.  
           [0019]    In addition, the invention includes a visual indication device for indicating a state of operation of electrically operated equipment comprising:— 
           [0020]    a magnetic flux sensor capable of being influenced by a magnetic flux to induce an electrical current in the sensor corresponding to the magnetic flux;  
           [0021]    a visual indicator electrically interconnected to the magnetic flux sensor and controllable by the induced electrical current to produce a visual indication of a state of operation of the electrically operated equipment; and  
           [0022]    a common carrier, the magnetic flux sensor and the visual indicator being environmentally sealed within the common carrier and electrically interconnected within the common carrier.  
           [0023]    The invention also includes a method of visually indicating an operational state of an electrically operated circuitry which is environmentally sealed within an environmentally sealed enclosure comprising:— 
           [0024]    producing a magnetic flux within the enclosure, the magnetic flux indicative of the state of operation of the electrically operated circuitry;  
           [0025]    passing the magnetic flux through a permeable wall of the enclosure to the outside of the enclosure; and on the outside of the enclosure, sensing the magnetic flux, inducing the sensed flux into a corresponding electrical current and, with the electrical current, operating a visual indicator to indicate the state of operation of the electrically operated circuitry. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0026]    Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:— 
         [0027]    [0027]FIG. 1 is a cross-sectional diagrammatic representation of an electrically operated equipment according to a first embodiment;  
         [0028]    [0028]FIG. 2 is a perspective view of an electrically operated equipment according to a second embodiment;  
         [0029]    [0029]FIG. 3 is a perspective view of an environmentally sealed arrangement forming part of the equipment of the second embodiment;  
         [0030]    [0030]FIG. 4 is a sectional view of the arrangement of FIG. 3 taken along line lV-lV in FIG. 3 and showing a surrounding housing;  
         [0031]    [0031]FIG. 5 is a front view of the environmentally sealed arrangement; and  
         [0032]    [0032]FIG. 6 is an exploded isometric view of a visual indicator arrangement carried by a multi layer carrier. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENT  
       [0033]    The first embodiment, now to be described is concerned with a general electrically operated equipment to show in a general sense, the essence of the invention.  
         [0034]    In the first embodiment, as shown in FIG. 1, electrically operated equipment  10  comprises an environmentally sealed enclosure  12  which necessarily has one wall  14  which is permeable to magnetic flux. The enclosure is formed from a single non-ferrous material for convenience purposes so that, in effect, the whole enclosure is similarly permeable. The enclosure is formed throughout from aluminum, but other non-ferrous metals or other materials of sufficient strength could be used, such as suitable plastics materials, e.g. polycarbonates, polyolefins, or plastic composites, which may include carbon fibers.  
         [0035]    Within the enclosure is mounted an electrically operated electronic or power circuitry, generally shown as item  16 .  
         [0036]    It is required that an operational state of the circuitry  16  may be viewed from outside the enclosure  12  without the enclosure having apertures for either viewing visual indicators mounted in a wall of the enclosure or for the passage of wiring through the enclosure wall.  
         [0037]    To enable the outside visual indication to be provided while the enclosure remains permanently environmentally sealed, i.e. without apertures, inductive coupling is provided through the permeable wall  14 . This is effected in the following manner.  
         [0038]    As shown by FIG. 1, the circuitry  16  is provided with an AC generating source  18  (shown diagrammatically) to which a primary winding, i.e. conductive coil  20 , is electrically connected. The coil  20  forms part of a magnetic field generator  19  which includes a magnetically permeable core  22  onto which the coil  20  is wound. The core is shaped, as shown, with a central axial core arm  24  surrounded by a cylindrical wall  26  of the core, the coil  20  surrounding the axial core arm  24 . The core  22  is positioned adjacent to the permeable wall  14  to direct flux lines  26  so that they pass through the permeable wall. Hence, unwanted coupling through near field induction in the circuitry  16  is minimized or avoided. On the outside of the enclosure  12  is basically provided a magnetic flux sensor  28  and a visual indicator  30  which may be an LED. The sensor  28  comprises a secondary winding, i.e. conductive coil  32 , wound onto a magnetic permeable core  34  (or wound around an air gap not shown). The sensor  28  is positioned on the outside of the permeable wall  14  in axial alignment with the coil  20  so as to be able to sense the magnetic flux passing through the wall  14  and complete an inductive coupling. This coupling provides an electrical current in the coil  32  by mutual inductance. This current is connected to a diode-bridge rectifier  36  which rectifies the current and passes it to the visual indicator  30  so as to illuminate the indicator. In use, the magnetic flux is produced by the magnetic field generator  19  only when the circuitry  16  is operating or is operating correctly. Hence, the visual indicator  30  can only be illuminated during correct operation of the circuitry. If at any time the visual indicator  30  ceases to be illuminated, then steps should be immediately taken to correct the circuitry operation as required, possibly by complete replacement of the enclosure  12  with its contents.  
         [0039]    Hence the first embodiment provides a visual indication of the operation of circuitry within the environmentally sealed enclosure  12  without sealed apertures being present in the enclosure.  
         [0040]    A second embodiment will now be described and relates to a more specific electrically operated equipment.  
         [0041]    In the second embodiment, an optical network unit  40  comprises an upper housing  42  (FIG. 2) which encloses an environmentally sealed printed circuit board arrangement  44  (FIG. 3). A lower housing  46  contains a signal in/out arrangement for signal transmission and power transmission to printed circuit boards (to be described) forming part of the arrangement  44 . The signal in/out arrangement within the housing  46  is conventionally constructed, is not shown and does not form part of the present invention. However, the lower housing  46  is supplied from beneath with a power cable  48 , an optical transmission cable  50 , and two electrical transmission cables  52 . The optical transmission cable and the power cables, together with one of the electrical transmission cables, connect the optical network unit  40  with a central office (not shown) in conventional manner. The other electrical transmission cable  52  is connected to a customer&#39;s premises by means of intermediate equipment (not shown) known by various terms such as joint wiring interconnect, outside wiring interface, serving area interconnect or feeder distribution interface.  
         [0042]    The upper and lower housings  42  and  46 , together with the printed circuit board arrangement  44 , are mounted upon a planar horizontal housing mount  54 , shown more clearly in FIG. 3. A carrier  56  for the optical network unit to attach the network unit to a rigid vertical post  58  is also attached to the housing mount  54 .  
         [0043]    A door  59  at the front of the lower housing  46  may be dropped to a chaindotted position shown in FIG. 2 for access to terminal connections (not shown) of the signal in/out arrangement, and also for access to protectors (not shown). Access into the lower compartment also enables screws (not shown) to be reached, the screws to remove the upper housing  42  passing through holes  60  in the housing mount  54  (FIG. 3) to remove the upper housing  42  and also to enable screws  62  to be removed (FIGS. 4 and 5) for removal of the printed circuit board arrangement  44 .  
         [0044]    As shown particularly by FIGS. 4 and 5, the arrangement  44  comprises an environmentally sealed enclosure  64  within which a plurality of printed circuit boards or line cards are environmentally protected. The enclosure  64  comprises two enclosure halves  66 , each of which has a finned main wall  68 , the fins  70  being vertical heat exchange fins. From one side of the main wall  68  extend two long vertical side walls  72 . Two relatively short top and bottom walls  74  extend between and are joined to the side walls  72 . Free ends of the walls  72  and  74  define a rectangular opening and terminate in a continuous outwards flange  76 , surrounding the opening.  
         [0045]    The two enclosure halves  66  are secured together at the free ends of side, top and bottom walls with an environmental and EMI seal  78  disposed between free ends of the walls and between the flanges  76 . Screws (not shown) pass from flange to flange  76  to hold the enclosure halves  66  assembled with the seal  78  compressed between them. An environmentally sealed chamber  80  is thus formed between the halves  66 .  
         [0046]    The chamber  80  houses four printed circuit boards  82  and  84  to provide the required electronic function of the unit  40 . The printed circuit boards are assembled onto the two enclosure halves  66  before these are secured together. A board  82  is secured to the main wall  68  of each half  66  by heat conductive screws  86 . These pass through the printed circuit board  82  in heat conductive relationship to a ground plane (not shown) of the board and into the associated wall  68 . Each printed circuit board  82  is spaced from its associated wall  68  by heat conductive spacers  88  surrounding the screws  86 . The screws  86  are disposed in horizontally spaced vertical rows across the board  82 , one vertical row of three screws being shown for each board in FIG. 4. All of the screws  86  are aligned, each vertically with an associated fin  70 , and extend into the bases of the fins to shorten the heat exchange paths into the fins.  
         [0047]    Each printed circuit board  82  has a spaced and parallel printed circuit board  84  attached to it, each board  82  joined to its board  84  by connectors  90  between top and bottom end regions of the board.  
         [0048]    A flexible ribbon cable or flex circuit  92  connects top end regions of the printed circuit boards  82  and a power board  94  is secured to the main wall  68  in the lower regions of one of the enclosure halves  66 . Screws  96  holding the power board in place extend into bases of the fins  70 , as shown by FIG. 4.  
         [0049]    The enclosure  64 , as in the first embodiment, is formed from aluminum which is a suitable heat exchange material for conducting heat from the printed circuit boards into the fins  70 . However, other suitable heat exchange materials may be used which, for the purposes of the embodiment and the invention, must be non-ferrous. To preserve the surface of the enclosure  64  in all types of environmental conditions, it is subjected to the known irriditing process followed by a protective paint coating, such as polyurethane.  
         [0050]    The fins  70  extend from both front and rear surfaces of the enclosure  64  (see FIG. 4) into airflow passages  98  defined between the enclosure and the inner surfaces of sides  100  of the upper housing member  42 . Upper and lower air vents  102 ,  104 , (FIG. 2) in the sides  100 , enable cooling air to pass upwardly through the airflow passages  98  by convection to extract the heat from the fins during use of the equipment.  
         [0051]    As shown in FIGS. 4 and 5, two electrical cables  106  extend through the bottom wall  74  of the enclosure  64 , together with an optical cable  108  and a power cable  110 , which are sealed into position within the bottom wall to maintain the environmental seal. These cables are interconnected by connectors (not shown) within the lower housing  46  to the appropriate cables  48 ,  50  and  52 , discussed above. As shown by FIG. 4, the cables  106  are connected to the lower ends of the printed circuit boards  84 , the optical cable  108  to one of the boards  82  and the power cable  110  to the lower end region of the power board  94 .  
         [0052]    As in the first embodiment, the optical network unit is provided with at least one magnetic field generator and corresponding magnetic flux sensor and visual indicator. In fact, in this embodiment three magnetic field generators are provided. These generators  19  are of similar construction to those discussed in the first embodiment and further description is therefore not required. The three generators  19  are connected by electrical conductors  112  and connectors  114  into circuitry at a lower end region of the forwardly facing enclosure half  66  with the generators spaced in line vertically and secured to the inside surface at the lower end of the main wall  68 . One of the connectors  114  is connected into part of the circuitry which is concerned with power operation of the equipment, while a second of the connectors is connected into part of the circuitry concerned with operation of the electronic circuitry. The third connector  114  is connected in a line which bypasses the electronic and power circuitry and is directly connected to the power and transmission lines coming into the enclosure  64 .  
         [0053]    On the outside of the enclosure  64 , each of the generators  19  is provided with a corresponding magnetic flux sensor and corresponding visual indicator, as will now be described.  
         [0054]    As shown particularly in FIG. 6, there is provided a visual indication device  116  which is of laminate construction. Of its multi layers, an inner layer  118  carries three magnetic flux sensors, each of the sensors being a conductive coil  120  surrounding an air core, although this could be a permeable core. The coils  120  are disposed upon the layer  118  in positions so as to align themselves, one with each of the generators  19  when the visual indication device  116  is secured in position on an outside surface of the enclosure  64 , as will be described. Each of the coils  120  is electrically interconnected with a diode-bridge rectifier  122  which lies intermediate the coil  120  and a visual indicator in the form of a forwardly facing LED  124 .  
         [0055]    Both the bridge rectifier and the LED are mounted on the inner layer  118  so that electrical interconnection also takes place on this layer. Forwardly of the inner layer  118  is disposed a spacer layer  126  having apertures  128  to accommodate the forward projection of the coils  120  and the LEDs  124  from the layer  118 . The spacer layer  126  is attached to the inner layer  118  by adhesive. Forwardly of the spacer layer  126  is an environmental seal layer  130  and a front layer  132 . The front layer is attached to the spacer layer  126  by the seal layer  130 . Both the spacer and front layers are transparent in regions  133  directly in front of the LEDs  124 . Behind the inner layer  118  is disposed a further spacer layer  135  and a support layer  134 , the layers  118 ,  134  and  135  being adhesively secured together. The visual indication device structure is environmentally sealed to prevent environmental conditions from affecting the performance of any of the operational features carried upon the inner layer  118 . Further, the layers of the structure are permeable to magnetic flux and are conveniently formed from suitable plastics materials, such as polyurethanes and polypropylene with non-ferrous materials being absent. The visual indication device  116  is adhesively attached below fins  70  to the outside surface of the main wall  68  of the front enclosure half, (FIGS. 4 and 5), with the coils  120  suitably aligned with their corresponding magnetic field generators  19 . This surface of the enclosure half is planar for attachment purposes.  
         [0056]    In use, with the optical network unit operating correctly, then each of the LEDs is illuminated. The visual indication device  116  lies directly behind the front lower vent  104 , which is provided by an upwardly hinged door  136  in the upper housing  42 . In FIG. 2, the door  136  is shown in an upward position. Thus, inspection of the LEDs may be performed as required. The door is provided with a tamper-proof lock (not shown) to prevent unauthorised personnel from obtaining entry.  
         [0057]    As will be seen from FIG. 5, a graphic overlay is provided upon the front layer of the visual indication device. This shows that the upper and central LEDs are the visual indicators for the power and electronic circuitries respectively, and in which the electronic circuitry is represented by the term “STATUS”. The lower LED is shown as “LINK” which is concerned with the operation of the incoming optical transmission lines.  
         [0058]    In use, with the optical network unit operating correctly, an AC source provides current to each generator  19  to create a magnetic field, the flux lines of which pass through the lower part of the front main wall  68 . The flux lines are sensed individually by the coils  120  to induce electrical currents. The currents, after being rectified by the rectifiers  122 , illuminate the LEDs  124 .  
         [0059]    If the “LINK” LED is not illuminated at any time during use, then this indicates that there is a failure in cable connectivity between the optical network unit  40  and the central office over the optical transmission lines. This may indicate a problem with the optical transmission cable external to the optical network unit  40 , or a problem internal to the optical network unit, i.e. with the electronics. If the power LED is not illuminated, this indicates the optical network unit is not receiving power or is not receiving sufficient power to operate. This may indicate a problem external to the optical network unit in the external power node or OSP power feed pairs, or an internal failure in the optical network unit, i.e. in the power board  94 . If the “STATUS” LED is not illuminated, this indicates the optical network unit is not in an operational state. The problem may reside either with software configuration parameters or with failed electronics, within the arrangement  44 .  
         [0060]    If any of the three LEDs is not illuminated, diagnostic actions are required by maintenance personnel. If it is then ascertained the problem lies within the arrangement  44 , this requires removal and replacement with an operational arrangement  44 . Removal and replacement of the arrangement  44  to correct any of the above three non-operational situations, firstly requires the upper housing  42  to be removed from the housing mount  54  with the door  59  open and disconnections are made to all the cables into the arrangement  44 . The arrangement  44  is then removed by first removing the screws  62  and a replacement and operational arrangement  44  is added to the optical network unit.  
         [0061]    As may be seen, therefore, a visual indication may be provided of any activity within the environmentally sealed arrangement  44 , while avoiding apertures in the enclosure for visually positioning LEDs or for conductors extending to exterior LEDs, such apertures being difficult to seal on a permanent basis.  
         [0062]    In a modification of the second embodiment, the circuitry may be arranged such that instead of the LEDs failing to be illuminated when a circuitry problem occurs a dual LED is installed for each LED. The message sent from the internal circuitry is such as to alter the color of any dual LED, e.g. from green (indicating correct operation) to red to show that there is indeed a circuitry problem.