Abstract:
A surge suppression unit contains electrical surge suppression components configured to redirect power surges. A sensor monitors the surge suppression components for a possible impending explosion or fire condition. A disconnect mechanism is configured to disconnect power from the surge suppression components when the sensor detects the explosion or fire condition.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates generally to surge suppression. 
       BACKGROUND 
       [0002]    Surge suppression units are used for protecting electrical equipment from electrical power surges. During normal non-power surge conditions, the surge suppression components provide a high resistance path between any combination of power lines, neutral lines, and/or ground lines. During a power surge event, the surge suppressor components start conducting, limiting the voltage across its terminals, which again can be connected to any combination of power lines, neutral lines, and/or ground lines. 
         [0003]    During these surge conditions, the surge suppression components that provide the voltage limiting path for the power surge, such as avalanche diodes or varistors, can become hot and can explode and/or electrically arc to other components in the surge suppression unit. These explosions and arcing can damage electrical equipment or possibly cause fires. To reduce explosions and arcing, fuses may be located in series with the diodes or varistors. The fuses are designed to blow at a particular power level and disconnect the associated diode or varistor from the power line experiencing the power surge. These fuses unfortunately have a limited power rating and do not always prevent the diodes and varistors from exploding or catching on fire during a large or extended power surge. For example, the power surge may continue to arc over the blown fuse and eventually cause a fire or explosion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    In the accompanying drawings which form a part hereof, and wherein like numbers of reference refer to similar parts throughout: 
           [0005]      FIG. 1  is a perspective view of a surge suppression unit. 
           [0006]      FIG. 2  is a perspective view of a surge suppression unit with the enclosure top removed. 
           [0007]      FIG. 3  is an isolated view of an overload disconnect system used with the surge suppression unit. 
           [0008]      FIG. 4  is a top view of a disconnect assembly. 
           [0009]      FIG. 5  is a top sectional view of the disconnect assembly in a retracted state. 
           [0010]      FIG. 6  is the same top sectional view as  FIG. 5  with the disconnect assembly in a triggered state. 
           [0011]      FIG. 7  is a side sectional view of the disconnect assembly in the retracted state. 
           [0012]      FIG. 8  is the same side sectional view as  FIG. 7  with the disconnect assembly in the triggered state. 
           [0013]      FIG. 9  is an exploded view of a latch interface used in the disconnect assembly. 
           [0014]      FIG. 10  is an alternative embodiment of the overload disconnect system. 
           [0015]      FIG. 11  is another embodiment of the overload disconnect system. 
           [0016]      FIG. 12  is yet another alternative embodiment of the overload disconnect system. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIG. 1  shows a surge suppression unit  20  that includes a bottom enclosure section  22 B that engages and is covered by a top enclosure section  22 A. A first terminal  26  extends from one end of the enclosure  22  and a second terminal  28  extends out the opposite end of enclosure  22 . A power line, neutral line, or ground line (not shown) is connected to the first terminal  26  and a power line, ground line or neutral line (not shown) is connected to the second terminal  28 . The circuitry contained within enclosure  22  starts conducting when a power surge is detected limiting the voltage across the terminals  26  and  28 . 
         [0018]    A series of vent holes  23  extend through the end of enclosure  22  and serve as a pressure release vent for some the gasses that may build up in enclosure  22  during an overload condition. The vent holes  23  will be discussed in more detail below. 
         [0019]      FIG. 2  shows the inside of the surge suppression unit  20 . A set of Metal Oxide Varistors (MOVs)  30  are aligned side-by-side on a printed circuit board  31 . The MOVs (varistors)  30  provide a high resistance path between the power, neutral, or ground line connected to terminal  26  and the power, neutral, or ground line connected to terminal  28 . When a power surge occurs on the line connected to terminal  26 , one or more of the varistors  30  start conducting, redirecting the power surge away from electrical equipment (not shown) connected to the line connected to terminal  28 . 
         [0020]    MOVs  30  are shown in the figures below for explanation purposes. However, it should be understood that the overload disconnect system described below can be used with any type of surge suppression circuitry or surge suppression components including, but not limited to, Silicon Avalanche Diodes (SAD), fuses, thyristors, and any other type of varistor. 
         [0021]    It should also be noted that the terms power line, power conductor, or power connector as used in this application can mean any neutral, ground, and/or hot conductor. 
         [0022]    As mentioned above, the MOVs  30  limit the voltage across terminals  26  and  28 . During the power surge the varistors  30  may heat up enough to either blow up or start burning. The power surge can also create arcing between the conducting varistor  30  and other adjacent varistors  30  or create arcing between the conducting varistor  30  and the other electrical components on circuit board  31 . These fires, explosions, and arcing can destroy property located next to surge suppression device  20 . 
         [0023]    In order to reduce the possibility of property damage, an overload disconnect system is used with the surge suppression unit  20 . The overload disconnect system includes a disconnect assembly  40  that severs a conductor connected between terminal  26  and the surge suppression components  30  when one or more of the surge suppression components  30  overheat or catastrophically destruct. 
         [0024]    Referring to  FIGS. 2 and 3 , the terminal  26  is connected to the surge suppression components  30  by a power cable  38 . The power cable  38  is attached at one end to the terminal  26  as shown in more detail below. An opposite end  38 A of cable  38  is connected to a power bus  50 . The power bus  50  is connected to a first terminal of each surge suppression component  30  by individual etched connections  58  printed on a bottom side of printed circuit board  31 . A second terminal for each surge suppression component  30  is connected to a second bus  51  that is connected to terminal  28 . 
         [0025]    A cord  32  is suspended along the surge suppression components  30  between a post  56  and an actuator  44 . The cord  32  could be a made of Dacron, fiber, or any other material that would burn apart when the surge suppression components  30  reach a particular temperature that could be the prelude to an explosion or fire condition. In one example, the cord  32  is conventional fishing line. Some materials used for cord  32  may be pre-stretched to prevent a slow disconnect where the cord  32  would first slowly stretch for some period of time before then burning apart. 
         [0026]    The actuator  44  is located next to a lever  41  that can swing open in a clockwise direction  43  when viewed from the top. The lever  41  operates a trigger mechanism in disconnect assembly  40 . A spring  36  is attached at a first end to a post  52  and attached by a crimped sleeve  54  or soldered to the second end  38 A of power cable  38 . The spring  36  is attached to power cable  38  in an expanded state that exerts a constant retractive bias force on cable  38 . In one embodiment, a single post could be used instead of using two posts  56  and  52 . 
         [0027]    The cord  32  operates as a sensor for monitoring the amount of heat generated by the surge suppression components  30 . When the surge suppression components  30  overheat, the cord  32  burns apart and releases a spring  60  ( FIG. 4 ) in actuator  44 . The spring  60  pushes lever  41  open and in turn releases or triggers a spring activated cutter piston inside of disconnect assembly  40 . 
         [0028]    Any gas pressure from the overheated MOV  30  will tend to move out through the venting holes  23  in  FIG. 1  and can help move lever  41  into the open position. Even if the cord  32  does not burn apart, enough gas pressure from one or more overheated MOVs  30  may still move the lever  41  into the open position. The wall  45  further directs any gas pressure across lever  41 . 
         [0029]    The released cutter piston severs section  38 B of the power cable disconnecting terminal  26  from the surge suppression components  30 . The spring  36  further retracts back into a non-expanded (non-biased) position pulling the end  38 A further apart from the other severed portion  38 B of power cable  38 . 
         [0030]    This physical severing of the power cable  38  and further separation of the severed power cable more effectively disconnects the power surge on terminal  26  from the surge suppression components  30 . This physical severing and separation of the power cable  38  reduces arcing that could continue if a conventional fuse were used between terminal  26  and the surge suppression components  30 . As a result, the surge suppression unit  20  has less chance of exploding or starting a fire. 
         [0031]    A power surge could cause one or more of the MOVs  30  to start continuously conducting (shorting condition). If the power surge continues to pass through the conducting MOV  30  for an extended period of time, the MOV could then explode. These long drawn out over current conditions may not necessarily trigger individual fuses connected to each MOV. 
         [0032]    The disconnect system prevents the surge suppression unit  20  from exploding by melting the cord  32  and disconnecting power before the surge suppression unit  20  reaches an explosive level. Extended over voltage or over current conditions still burn apart the cord  32  and disconnect power when the MOVs  30  become hotter than normal beyond some extended period of time. The overload disconnect system in some instances may replace multiple individual fuses that are used with each MOV  30 . Thus, the surge suppression unit  20  may also be less expensive to manufacture in certain applications. 
         [0033]    A barrier wall  45  is located at the pivoting end of lever  41 . The wall  45  provides a barrier that prevents gas from passing around level  41 . When top cover  22 A is installed, the wall  45  extends up to the bottom surface of the top cover  22 A. The wall  45  directs gas from any overheating of MOVs  30  toward lever  41  further pushing the lever  41  backwards and triggering disconnect assembly  40 . This will be explained in more detail below in  FIG. 12 . 
         [0034]      FIGS. 4-9  explain the operation of the disconnect assembly  40  in more detail. Referring first to  FIG. 4 , the actuator  44  includes spring  60 . A stop washer  46  is positioned in-front of spring  60  and attached to cord  32 . The cord  32  pulls back on stop washer  46  pulling spring  60  back into a retracted compressed state. When cord  32  burns apart as shown in  FIG. 4 , the broken cord  32  releases stop washer  46  allowing spring  60  to extend forward. The released spring  60  pushes stop washer  46  further forward pushing the lever  41  into position  42 B. 
         [0035]    Referring now to  FIG. 5 , cable end  38 C is electrically coupled to a lug  84  formed on the bottom of terminal  26 . The middle portion  38 B of the power cable is suspended within a chamber  82  formed by walls  80 . 
         [0036]    A piston  62  includes a slot  64  that receives a rod  63  that extends down from lever  41 . A first end of piston  62  includes a cavity  67  that retains a spring  66  (see  FIGS. 6 and 7 ). An opposite end of piston  62  retains a cutter/knife  74 . In the retracted/locked position shown in  FIG. 5 , the piston  62  is pushed back against the back wall  80 C compressing the spring  66  within cavity  67 . The lever  41  is moved into position  42 A shown in  FIG. 4  causing rod  63  to insert down into slot  64  and lock the piston  62  into the retracted position shown in  FIGS. 5 and 7 . 
         [0037]    An annunciation sensor  68  is located in an opening in side wall  80 D and includes a first contact  70  that is depressed against a button  72  when piston  62  is in the retracted position shown in  FIG. 5 . 
         [0038]    Moving now to  FIG. 6 , the lever  41  is moved into position  42 B in  FIG. 4 . As described above, this happens when the cord  32  burns apart due to excessive heat coming from one or more of the surge suppression components  30 . The broken cord  32  releases spring  60  in actuator  44  allowing washer  46  to push the lever  41  into position  42 B. 
         [0039]    Moving lever  41  into position  42 B causes the lever rod  63  to move up and out of the slot  64  formed in piston  62 . This allows the spring  66  to extend out into a non-compressed/non-biased state while moving piston  62  out toward front wall  80 A. The spring  66  causes cutter  74  to slice thru and sever the suspended cable section  38 B and lodge into a notch  86  formed in front wall  80 A. 
         [0040]    As soon as the cutter  74  severs power cable  38 , the outstretched spring  36  is allowed to move back into an unbiased position pulling power cable end  38 A back and away from cable section  38 B. Any power from a power line connected to terminal  26  is then disconnected from the surge suppression components  30 . Thus, any overload conditions that could cause surge suppression unit  20  to explode or catch on fire are quashed. 
         [0041]    Physical features of the disconnect assembly  40  help prevent arcing between power cable section  38 B and other components in surge suppression unit  20 . The cutter  74  could be made from a non-metallic material, such as a ceramic. In this case, the cutter  74  forms a physical barrier between cable section  38 B and cable end  38 A. This blocks arcing that could extend between the two severed parts of power cable  38 . Of course, the cutter  74  could also me made out of a metallic material, such as steel or any other material that can sever cable section  38 B. Secondly, the spring  36  pulls the cable end  38 A further away from severed cable section  38 B making arcing less likely over the wider separation distance. Further, the severed cable section  38 B connected to the hot power line is contained within walls  80  that provide an additional barrier in front of bus  51  and the electrical components in surge suppression unit  20 . 
         [0042]    In the extended position shown in  FIG. 6 , the piston  62  moves forward and away from sensor  68 . This allows contact  70  to move outward releasing button  72 . Released button  72  activates a switch that can then be used to activate an annunciator or visual indicator that provides notification that an overload condition has been detected and the surge suppression unit  20  is now disabled. 
         [0043]      FIGS. 7 and 8  are side cut-away views that further show how the disconnect assembly  40  operates. In the retracted position shown in  FIG. 7 , the spring  66  is compressed almost entirely within cavity  67 . The lever  41  is in position  42 A such that rod  63  extends down into slot  64  of piston  62 . The power cable portion  38 B is shown suspended by side wall  80 D within chamber  82 . 
         [0044]      FIG. 8  shows the released position of the disconnect assembly  40 . The lever  41  is moved by actuator  44  in  FIG. 4  into position  42 B. While moving from position  42 A to position  42 B, a ramped interface between a bottom side of lever  41  and a top surface on wall  80 E forces the rod  63  upward out of slot  64 . This releases piston  62  allowing the spring  66  to release outward forcing cutter  74  through power cable portion  38 B and into the slot  86  in wall  80 A. 
         [0045]      FIG. 9  shows the ramped interface in more detail. The top wall  80 E has a hole  96  that receives rod  63 . Multiple lower platform areas  92  are formed around the outside of hole  96 . Each platform area  92  then transitions to a ramped area  94  that inclines upward toward a top surface of upper wall  80 E. A collar  90  surrounds the top end of rod  63  that has downwardly inclining ramps that sit into the platform areas  92  and inclined ramp areas  94  formed around hole  96 . When the lever  41  is in position  42 A, the collar  90  sits down into the platform areas  92  and  96  such that rod  63  extends down into slot  64 . When the lever  41  is moved to position  42 B, the two oppositely inclining ramps formed by collar  90  and area  94  lift the rod  63  slightly upward out of slot  64 . It should be noted that any number of ramps or alternative threaded arrangements could be used to move the lever  41  upward out of slot  64 , and the embodiment shown in  FIG. 9  is just one example. 
         [0046]    The motion of lever  41  in relation to areas  92  and  94  is analogous to the movement of a threaded screw being removed from a nut when the nut is held stationary. The twisting of the ramped collar  90  against the ramp formed by inclined area  94  moves the rod  64  upward, thereby releasing the piston  62  and cutter  74 . 
       ALTERNATIVE EMBODIMENTS 
       [0047]      FIG. 10  shows another embodiment were an infrared controller  100  includes infrared sensors  102  that detect the emission of infrared waves from the surge suppression components  30 . When the infrared waves detected by sensors  102  indicate a particular heat level, the controller  100  connects power from power bus  50  to a wire coil  104  that is wrapped around cord  32 . The coil  104  acts like a heater burning apart the cord  32  and activating the disconnect assembly  40  in a manner similar to that described above. 
         [0048]    In this arrangement, either the heat from the surge suppression units  30  can directly burn apart the cord  32  or the heat from coil  104  can burn apart the cord  32 . Thus, the infrared sensors  102  provide a second level of overload detection. 
         [0049]    In yet another embodiment, the controller  100  may include one or more pressure sensors. The pressure sensors in controller  110  detect a pressure change inside of the enclosure  22  and then activate the coil  104  to break cord  32  and trigger disconnect assembly  40 . In this embodiment, there may be no or fewer pressure release holes  23  ( FIG. 1 ) so that built up pressure inside of enclosure  22  is more accurately detected. 
         [0050]      FIG. 11  shows another embodiment where a controller  110  includes pressure, motion, and/or heat sensors  120  that detect an overload condition in surge suppression unit  20 . Instead of burning apart a cord, the controller  110  activates an electromagnet  112  that then pulls lever  41  into position  42 B triggering the disconnect assembly  40 . In this embodiment, the lever  41  may have a metal plate attached to a back side to interact with electromagnet  112 . Alternatively, an electromagnetic solenoid type switch may be used for triggering the disconnect assembly  40 . 
         [0051]    Referring  FIG. 12 , vents holes  23  extend through the end of enclosure  22 . Gas pressure  125  is created inside of enclosure  22  when electronic components in the surge suppression unit  20  overheat or rupture. Some of the gas pressure  125  will move to a lower pressure environment outside of enclosure  22  through vent holes  23 . The movement  126  of gas  125  from inside of enclosure  22  to outside of enclosure  22  can swing lever  41  from position  42 A to release position  42 B activating disconnect assembly  40 . In this embodiment, the length and/or height of lever  41  may be increased to provide a larger surface area in front of vent holes  23 . This allows more of the pressure from gas  125  to push against the larger surface area of lever  41  and provide more force for moving lever  41  into position  42 B. 
         [0052]    Any combination of the cord  32  in  FIGS. 2 and 3 ; infrared, pressure, or heat sensors  102  and heating coil  104  in  FIG. 10 ; and/or pressure, motion, or heat sensors in  FIGS. 11 and 12  can be used to detect an overload condition and disconnect power from the surge suppression unit  20 . 
         [0053]    Having described and illustrated the principles of the invention in a preferred embodiment thereof, it should be apparent that the invention can be modified in arrangement and detail without departing from such principles. We claim all modifications and variation coming within the spirit and scope of the following claims.