Abstract:
A circuit breaker is disclosed that provides a warning that the current through the circuit breaker exceeds a warning threshold. The circuit breaker comprises: a switch that carries a current I; an indicator for alternatively indicating: (i) that the current I has not exceeded I W , and (ii) that the current I has exceeded I W ; and an actuator in series with the switch that: (i) causes the indicator to indicate that the current I has exceeded I W  when and only when the current I has exceeded I W , and (ii) opens the switch when and only when the current I exceeds I T ; wherein 0&lt;I W &lt;I T .

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of prior U.S. application Ser. No. 12/716,448, filed Mar. 3, 2010. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to electrical circuits in general, and, more particularly, to circuit breakers. 
     BACKGROUND OF THE INVENTION 
     The overloading of an electrical circuit is dangerous and can cause a fire. 
     One mechanism in the prior art for preventing an electrical circuit from overloading is a “fuse.” A fuse is a conductor that is placed in series with the electrical circuit that it protects. When the current through the fuse exceeds a threshold, the fuse heats up, burns, and opens the circuit. This protects the circuit and prevents a fire. A fuse is disadvantageous, however, in that it cannot be reused. 
     A second mechanism in the prior art for preventing an electrical circuit from overloading is a “circuit breaker.” A circuit breaker is an electro-mechanical apparatus that is placed in series with the electrical circuit that it protects. When the current through the circuit breaker exceeds a threshold, a switch in the circuit breaker is opened. The opening of the switch opens the circuit, stops current from flowing, and prevents a fire. The circuit breaker is advantageous because the switch can be closed and the circuit breaker can be reused. 
       FIG. 1  depicts a schematic diagram of the salient components of circuit breaker  100  in accordance with the prior art. Circuit breaker  100  comprises: terminal  101 , terminal  102 , first switch  103 , electromagnet  104 , and second switch  105 , interconnected in series. 
     First switch  103  is a single-pole, single-throw relay switch that is opened by electromagnet  104  when the current I flowing through electromagnet  104  exceeds a threshold current I T  (i.e., I&gt;I T ). When the threshold current through electromagnet  104  exceeds the threshold current, electromagnet  104  opens first switch  103 , which prevents all current from flowing through circuit breaker  100 . This protects the circuit and prevents a fire. 
     Second switch  105  is a single-pole, single-throw thermally-activated switch (e.g., a bi-metallic strip, etc.) that bends and opens when the current I flowing through electromagnet  104  exceeds the threshold current I T . When the current through second switch  105  exceeds the threshold current, second switch  104  opens, which prevents all current from flowing through circuit breaker  100 . This protects the circuit and prevents a fire. 
     First switch  103  and electromagnet  104  are designed to protect the circuit from sudden increases in current (i.e., current “spikes”), which might be caused, for example, when an electrical appliance is dropped into water. In contrast, second switch  105  is designed to protect the circuit from slowly-changing, but also dangerous increases in current, which might be caused, for example, when an electrical appliance awakes from sleep mode (i.e., an electric heater controlled by a thermostat). 
     Switch  103  and  105  can be combined into a single switch that can be acted on by an electromagnet, and can also be activated thermally. 
     One advantage of a circuit breaker over a fuse is that the circuit breaker can be re-used after it trips and is reset. One disadvantage of a circuit breaker over a fuse is that the circuit breaker is more expensive. 
     SUMMARY OF THE INVENTION 
     The present invention is a circuit breaker that avoids some of the maintenance costs and disadvantages associated with the circuit breakers in the prior art. For example, the illustrative embodiment of the present invention is a circuit breakers that:
         i. opens (i.e., “trips”) and indicates that it has tripped when the current exceeds a tripping threshold I T ; and also   ii. indicates when the current exceeds, or has exceeded, a warning threshold I W .
 
This indicator is advantageous because it provides notice of a potential problem that can be addressed before it occurs.
       

     The illustrative embodiment of the present invention comprises: a switch that carries a current I; an indicator for alternatively indicating: (i) that the current I has not exceeded I W , and (ii) that the current I has exceeded I W ; and an actuator in series with the switch that: (i) causes the indicator to indicate that the current I has exceeded I W  when and only when the current I has exceeded I W , and (ii) opens the switch when and only when the current I exceeds I T ; wherein 0&lt;I W &lt;I T . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a schematic diagram of the salient components of a circuit breaker  100  in accordance with the prior art. 
         FIG. 2   a  depicts a schematic diagram of the salient components of a circuit breaker  200  in accordance with the illustrative embodiment of the present invention. 
         FIG. 2   b  depicts a schematic diagram of the salient components of circuit breaker  200  that comprises an indicator-element  211  for indicating that the current I through circuit breaker  200  has exceeded I W , in accordance with the illustrative embodiment of the present invention. 
         FIG. 2   c  depicts a schematic diagram of the salient components of circuit breaker  200  that comprises an electromagnet  204  for opening circuit breaker  200  when the current I through the electromagnet  204  exceeds I T , in accordance with the illustrative embodiment of the present invention. 
         FIG. 2   d  depicts a schematic diagram of the salient components of circuit breaker  200  that comprises a reset mechanism  213  that resets both indicators and allows the circuit breaker  200  to close. 
         FIG. 2   e  depicts a schematic diagram of the salient components of circuit breaker  200  that comprises a reset mechanism  213  that resets both indicators and allows the circuit breaker  200  to close. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2   a ,  2   b ,  2   c ,  2   d , and  2   e  depict schematic diagrams of the salient components of circuit breaker  200  in accordance with the illustrative embodiment of the present invention. Circuit breaker  200  has three mutually-exclusive states:
         (1) State #1 or the “Normal” state exists after circuit breaker  200  has been reset and the current I through the switch has not exceeded a warning-current threshold I W  since the reset. Circuit breaker  200  exhibits nearly zero impedance between its terminals while in the Normal state.   (2) State #2 or the “Warning” state exists after circuit breaker  200  has been reset and the current I through the switch has exceeded the warning-current threshold I W  since the reset. Circuit breaker  200  exhibits nearly zero impedance between its terminals while in the Warning state.   (3) State #3 or the “Tripped” state exists after circuit breaker  200  has been reset and the current I through the switch has exceeded a tripped-current threshold I T , since the reset, wherein 0&lt;I W &lt;I T . Circuit breaker  200  exhibits high impedance between its terminals while in the Tripped state.
 
 FIG. 2   a  depicts circuit breaker  200  in the Normal state;  FIG. 2   b  depicts circuit breaker  200  in the Warning state, and  FIG. 2   c  depicts circuit breaker  200  in the Tripped state.  FIGS. 2   d  and  2   e  depict circuit breaker  200  during the transition from the Tripped state to the Normal state (i.e., while it is being reset).
       

     Circuit breaker  200  comprises: terminal  201 , terminal  202 , relay switch  203 , electromagnet  204 , indicator-element  211 , catch  212 , reset  213 , adjuster  214 , axel  215 , lever  216 , spring  217 , pull rod  218 , axel  219 , axel  221 , indicator-element  222 , push rod  223 , catch  224 , lever  225 , axel  226 , spring  227 , and adjuster  228 , interconnected as shown. 
     Although the illustrative embodiment of the present invention comprises two indicators  211  and  222 , it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprises any number of indicators (e.g., one indicators, three indicators, four indicators, etc.). 
     Although the illustrative embodiment of the present invention comprises one reset  213  for both switch  203  and for indicator-element  211 , it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention that comprise a separate reset for each. 
     Relay switch  203  is a single-pole, single-throw (SPST) switch that opened by electromagnet  204  and closed by reset  213 . It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which relay switch  203  is in series with a thermally-activated switch (e.g., a bi-metallic strip, etc.), such as switch  105  in the prior art. Furthermore, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which relay switch  203  is:
         i. a single-pole, double-throw (SPDT) switch, or   ii. a single-pole, triple-throw (SPTT) switch, or   iii. a double-pole, single-throw (DPST) switch, or   iv. a double-pole, double-throw (DPST) switch, or   v. a double-pole, centre-off (DPCO) switch.       

     Electromagnet  204  is an actuator in series with relay switch  203  that:
         i. does not attract catch  212  with sufficient force to change indicator-element  211  to indicate a warning when the current I has not exceeded I W , and   i. attracts catch  212  with sufficient force to change indicator-element  211  to indicate a warning when the current I has exceeded I W , and   iii. does not attract catch  224  and leaves relay switch  203  closed when the current I through circuit breaker  200  does not exceed I T , and   iv. attracts catch  224  with sufficient force to open relay switch  203  and change indicator-element  222  to indicate an open breaker when the current I through circuit breaker  200  exceeds I T , wherein 0&lt;I W &lt;I T .       

     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which catch  212  is attracted by a different actuator (e.g., a second electromagnet, a bi-metallic switch, a temperature sensor, etc.) than electromagnet  204 . 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which catch  224  and relay switch  203  are attracted by a different actuator (e.g. a second electromagnet, a bi-metallic switch, a temperature sensor, etc) than electromagnet  204 . 
     Indicator-element  211  and indicator-element  222  together comprise an indicator that displays the state of circuit breaker  200 . 
     Indicator-element  211  is a two-state mechanical indicator that has a geometric shape of a triangular prism. Indicator-element  211  rotates on axel  219  and comprises two faces—black or “normal” face  211 - 1  and yellow or “warning” face  211 - 2 . The rotation of indicator-element  211 —and thus the face that is exposed—is governed by pull rod  218 , catch  212 , reset  213 , and electromagnet  204 . 
     Face  211 - 1  is displayed when circuit breaker  200  is in the “Normal” state, face  211 - 2  is displayed when circuit breaker  200  is in the “Warning” state. Face  211 - 1  exhibits a black circle, face  211 - 2  exhibits a yellow circle. 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the indicator-element  211  is something else and comprises, for example, and without limitation:
         i. one or more light-emitting diodes (LED), or   ii. one or more liquid crystal displays (LCD), or   iii. one or more different words, symbols, shapes, or colors, or   iv. a transmitter that transmits a signal to a terminal that is remotely located from circuit breaker  200 , or   v. any combination of i, ii, iii, and iv.       

     Catch  212  comprises ferromagnetic material that is attracted to electromagnet  204  on one side and is connected to indicator-element  211  on the other via pull rod  218 . Catch  212  engages the tooth of the ratchet in reset  213  depending on how far it is pulled by electromagnet  204 .  FIG. 2   a  depicts the relationship of catch  212  and reset  213  in the Normal state,  FIG. 2   b  depicts the relationship of catch  212  and reset  213  in the Warning state. 
     Indicator-element  222  is a two-state mechanical indicator that has a geometric shape of a triangular prism. Indicator-element  222  rotates on axel  221  and comprises two faces—black or “normal” face  222 - 1  and red or “tripped” face  222 - 2 . The rotation of indicator-element  222 —and thus the face that is exposed—is governed by push rod  223 , catch  224 , reset  213 , electromagnet  204 , and relay switch  203 . 
     Face  222 - 1  is displayed when circuit breaker  200  is in the “Normal” state, face  222 - 2  is displayed when circuit breaker  200  is in the “Tripped” state. Face  211 - 1  exhibits a black circle, face  222 - 2  exhibits a red circle. 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the indicator-element  222  is something else and comprises, for example, and without limitation:
         i. one or more light-emitting diodes (LED), or   ii. one or more liquid crystal displays (LCD), or   iii. one or more different words, symbols, shapes, or colors, or   iv. a transmitter that transmits a signal to a terminal that is remotely located from circuit breaker  200 , or   v. any combination of i, ii, iii, and iv.       

     It will be clear to those skilled in the art, after reading this disclosure, how to combine the functions of indicators  211  and  222  into a single indicator element that can display which one of the 3 states—normal, warning, and tripped—circuit breaker  200  is in. 
     Catch  224  comprises ferromagnetic material that is attracted to electromagnet  204  on one side and is connected to indicator-element  222  via push rod  223 . Catch  224  engages the tooth of the ratchet in reset  213  depending on how far it is pulled by electromagnet  204 .  FIGS. 2   a  and  2   b  depicts the relationship of catch  224  and reset  213  in the Normal state,  FIG. 2   c  depicts the relationship of catch  224  and reset  213  in the Tripped state. Catch  224  is linked to relay switch  203  so that if switch  203  is tripped through a mechanism other than through the magnetic action of electromagnet  204 , such as a bimetal strip or other thermo-sensor, the catch  224  will be moved to catch the ratchet on reset  213 . Catch  224  rotates indicator-element  222  through the action of push rod  223 . Catch  224  and the ratchet on reset  223  prevents the circuit breaker relay switch  203  from re-closing until circuit breaker  200  is reset. 
     Reset  213  is a rod with a pair of ratchets that engage catches  212  and  224 . The rod is pressed against the catches  212  and  224  with one or more light springs. In accordance with the illustrative embodiment, reset  213  comprises two teeth, and, therefore, the combination of catch  212 , catch  224 , and reset  213  can assume any one of four possible states. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which reset  213  comprises any number of ratchet teeth (e.g., three teeth, four teeth, five teeth, etc.) which would enable circuit breaker  200  to assume more states. This would be advantageous to enable circuit breaker to detect and display more warning states (e.g., a “low” warning state and a “high” warning state, etc.) It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the reset mechanism that employ independent resets for the early warning indicator, and for the trip indicator. 
     Adjuster  214  is a threaded bolt which, with spring  217 , moderates the tension on catch  212  through the action of lever  216  which opposes the force of electromagnet  204  on catch  212 . By adjusting  214 , the tension on catch  212  can be changed, changing the effective value of I W . In accordance with the illustrative embodiment, the force exerted by the adjuster  214  on lever  216  can be set by rotating the warning threshold current adjuster  214  clockwise or counter-clockwise to increase I W  or decrease I W , respectively. 
     Adjuster  228  is a threaded bolt which, with spring  227 , moderates the tension on catch  224  through the action of lever  225  which opposes the force of electromagnet  204  on catch  224 . By adjusting  228 , the tension on catch  224  can be changed, changing the effective value of I T . In accordance with the illustrative embodiment, the force exerted by the adjuster  228  on lever  225  can be set by rotating the warning threshold current adjuster  228  clockwise or counter-clockwise to increase I T  or decrease I T , respectively. 
     It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which to either adjuster  214  or adjuster  228  or both are manufactured with electrical components. 
     It is to be understood that the disclosure teaches just one example of the illustrative embodiment and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.