Abstract:
A circuit breaker having an external trip indicator, having a circuit breaker housing, a trip mechanism within the housing, sensing a trip condition and being responsive thereto to mechanically break an electrical circuit, an indicator, having a selectively operable retaining mechanism and being biased outward from the circuit breaker housing, and a linkage, sensing a trip condition of the trip mechanism and selectively releasing the selectively operable retaining mechanism to allow the indicator to move outwardly from the housing. The external trip indicator is operated by sensing an overcurrent condition with the trip mechanism, breaking the electric circuit in response to the overcurrent, sensing a mechanical movement of the trip mechanism, and thereby releasing a positional restraint on the mechanical indicator; and allowing the mechanical indicator to protrude from the housing. The external trip indicator is reset by first resetting the trip mechanism and then displacing the mechanical indicator into the housing.

Description:
The present patent application claims benefit of priority from U.S. Provisional Patent Application No. 60/126,453, filed Mar. 26, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the field of circuit breakers, and more particularly to circuit breakers having an external visual indication of a trip condition. 
     BACKGROUND OF THE INVENTION 
     In the field of electrical circuit breakers, it is well known to provide an external indication of the internal state of the circuit breaker, for example ON, OFF, and TRIPPED. 
     A circuit breaker is a device, which serves to interrupt electrical current flow in an electrical circuit path upon the occurrence of an overcurrent in the circuit path. When the overcurrent occurs, the external toggle handle will normally return to the OFF position. However, a service technician of other user will have no indication whether the breaker was intentionally turned OFF or the breaker tripped. In complex breaker installations, where some breakers are normally maintained in an OFF position, this can make analysis difficult. Therefore, the art has taught the desirability of an external indication of switch state. 
     Various methods are available for indicating a Trip State of a breaker. First, the external toggle handle may be provided with a “mid-trip” state, intermediate from the ON and OFF states. This is typically accomplished by a linkage between the external toggle and trip mechanism, wherein, upon a trip condition of the breaker, the trip mechanism assumes a state, which causes the external toggle to lie in an intermediate state. See, e.g., U.S. Pat. Nos. 5,264,673, 4,528,531, 3,970,976, 3,955,162, and 3,863,042, expressly incorporated herein by reference. An electronic indicator may also be provided, for example, a light emitting diode, which is selectively illuminated by power from the load. See, e.g., U.S. Pat. No. 3,806,848, expressly incorporated herein by reference, or by means of an auxiliary switch, see, U.S. Pat. Nos. 3,742,402, 3,742,403, 3,863,042 and 3,955,162, expressly incorporated herein by reference. Some circuit breakers have an internal trip condition distinct from the OFF condition. See, e.g., U.S. Pat. No. 5,777,536. This latter solution, however, causes the problem that in the tripped condition, a small current still flows through the device. Other types of mechanical visual indicators are also possible. See, e.g., U.S. Pat. Nos. 5,847,913; 5,264,818; 5,089,796; 4,801,906; 4,446,042; 4,382,270; 4,251,789; 3,742,403; 3,742,402; 3,596,219: and 3,596,218, expressly incorporated herein by reference. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The present invention therefore provides a mechanical latch which, upon tripping of the breaker, allows an externally visible mechanical element to visibly indicate a trip condition. 
     The mechanical latch does not require substantial modifications or adaptations of the normal circuit breaker and trip mechanisms, and without modification of the form factor or substantial modification of the circuit breaker housing, and thus is compatible with a wide range of breaker designs and applications. 
     The external mechanical indication of trip state according to the present invention also is manually resettable, although it is possible to provide an additional linkage for resetting the trip indicator while the breaker is reset. 
     According to a preferred design, a spring loaded plunger is provided protruding through the front of the circuit breaker housing. The plunger itself is designed to be visible, for example having a contrasting color and sufficient physical size. The plunger has a latch portion, disposed internal to the circuit breaker housing, which is capable of selectively retaining the plunger in a non-indicating position. An arm, within the breaker housing, is provided to retain the latch portion during normal use and switching of the breaker. However, during a trip condition, the collapsing mechanism actuates the arm to release it from the latching portion. The latch portion preferably comprises a protruding portion of a cylindrical body of the plunger, while the arm is preferably pivotally mounted within the housing, one end retaining the latch portion while the other end being disposed along a path of a collapsing portion of the trip mechanism, such that during a trip condition, the arm is displaced to release tie plunger to the trip indicating position. 
     If desired, a mechanism may be provided to automatically reset the external indicator when the circuit breaker is reset. For example, a cam or other linkage may be provided which retracts the external indicator when the handle is moved to the OFF position. 
     It is therefore an object of the invention to provide an external indicator for a trip state of a breaker which is compatible with existing circuit breaker packaging and form factors. 
     It is a further object according to the present invention to provide an automatic external indication of circuit breaker trip status. 
     These and other objects will be apparent from an understanding of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and further objects and advantages of the invention will be more apparent upon reference to the following specification, claims and appended drawings wherein: 
     FIG. 1 is a side view of an embodiment of a circuit breaker mechanism having a trip state indicator according to the present invention with a housing half removed, in a normal ON state and no external trip indication; 
     FIG. 2 is a side view of an embodiment of a circuit breaker mechanism having a trip state indicator according to the present invention with a housing half removed, in a contact OFF state, handle restrained in the ON position state, and external trip indication; 
     FIG. 3 is a side view of an embodiment of a circuit breaker mechanism having a trip state indicator according to the present invention with a housing half removed, in a contact OFF state, handle restrained in a mid-trip position, and external trip indication; 
     FIG. 4 is a side view of an embodiment of a circuit breaker mechanism having a trip state indicator according to the present invention with a housing half removed, in an OFF state and external trip indication; 
     FIG. 5 is a side view of an embodiment of a circuit breaker mechanism having a trip state indicator according to the present invention with a housing half removed, in a contact OFF state handle in the OFF position state, and no external trip indication; and 
     FIGS. 6A and 6B are detail views of a known breaker toggle mechanism. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments will no be described by way of example, in which like reference numerals indicate like elements. 
     EXAMPLE 
     Components of a conventional type single pole circuit magnetic-hydraulic breaker are well known in the art. See, U.S. Pat. No. 5,293,016, expressly incorporated herein by reference. A single pole circuit breaker  10  includes an electrically insulating casing  20  which houses, among other things, stationary mounted terminals. In use, these terminals are electrically connected to the ends of the electrical circuit that is to be protected against overcurrents. As its major internal components, a circuit breaker includes a fixed electrical contact, a movable electrical contact, and an operating mechanism. 
     The trip mechanism includes a contact bar, carrying a movable contact of the circuit breaker, which is spring loaded by a multi-coil torsion spring to provide a force repelling the fixed contact. In the closed position, a hinged linkage between the manual control toggle is held in an extended position and provides a force significantly greater than the countering spring force, to apply a contact pressure between the moveable contact and the fixed contact. The hinged linkage includes a trigger element which, when displaced against a small spring and frictional force, causes the hinged linkage to rapidly collapse, allowing the torsion spring to open the contacts by quickly displacing the moveable contact away from the fixed contact. The trigger element is linked to the trip element. 
     As is known, the casing  20  also houses a stationary electrical contact  50  and an electrical contact  60  mounted on a contact bar  70 . Significantly, the contact bar  70  is pivotally connected via a pivot pin  80  to a stationary mounted frame  100 . A helical spring (not shown), which encircles the pivot pin  80 , pivotally biases the contact bar  70  toward the frame  100  in the counterclockwise direction. A contact bar stop surface limits the pivotal motion of the contact bar  70  relative to the frame  100  in the non-contacting position (contact bar  70  rotated about pin  80  in the counterclockwise direction to separate contacts  50  and  60 , shown in FIGS.  2 - 5 ). By virtue of the pivotal motion of the contact bar  70 , the contact  60  is readily moved into and out of electrical contact with the stationary contact  50 . In the contacting position, shown in FIG. 1, the stationary contact  50  limits the motion of the contact  60 , thus limiting the angular rotation of the contact bar  70  about pin  80 . Thus, in the contacting position, the contact bar  70  is forced by the pressure of the toggle linkage composed of cam link  190  and link housing  200  in the aligned relative orientation, shown in FIG. 1, against a force exerted by the helical spring, to provide firm contact between the contacts  50 ,  60 . 
     The circuit breaker trip mechanism may be triggered in a number of known ways. Preferably, the trip mechanism is a so-called magnetic or magnetic hydraulic breaker. The trip mechanism sits in the left side of the breaker, on the portion  110  of the frame, receiving the entire current passing through the breaker. An electrical coil, which encircles a magnetic core topped by a pole piece, is positioned adjacent the frame  100 . An electrical braid connects the end of the coil to the contact bar  70 , proximate to the pivot pin  80 . Thus, when the contact bar  70  is pivoted in the clockwise direction, against the biasing force exerted by the spring  85 , to bring the contact  60  into electrical contact with the contact  50 , a continuous electrical path extends between the terminals of the circuit breaker. 
     The circuit breaker  10  also includes a handle  160 , which is pivotally connected to the frame  100  via a pin  170 . Handle  160  includes a pair of ears with apertures for receiving a pin  180 , which connects handle  160  to a cam link  190 . In addition, a toggle mechanism is provided, which connects the handle  160  to the contact bar  70 . The handle  160  is provided with a helical spring, which applies a counterclockwise force on the handle  160  about pin  170  with respect to frame  100 . A significant feature of the cam link  190 , shown in expanded view in FIG. 6B, is the presence of a step, formed by the intersection of non-parallel surfaces  194  and  198 , in the outer profile of the cam link  190 . Cam link  190  is pivotally connected by a rivet or pin  210  to a housing link  200 , which in turn is pivotally connected to the contact bar  70  by a rivet  220 . 
     The toggle mechanism further includes a sear assembly, including a sear pin  230  which extends through an aperture in the link housing  200  generally corresponding to a location of an outer edge  195  of the cam link  190 . This sear pin  230  includes a circularly curved surface  232  (see FIG. 6B) which is intersected by a substantially planar surface  233 . The sear assembly also includes a leg  235  (see FIG.  6 A), connected to the sear pin  230 , and a sear striker bar  240 , which is connected to the leg  235  and projects into the plane of the paper, as viewed in FIG. 6A. A helical spring  250 , which encircles the sear pin  230 , pivotally biases the leg  235  of the sear assembly clockwise, into contact with the leg  205  of the link housing  200 , and biasing the planar surface  233  of the sear pin  230  into substantial contact with the bottom surface  198  of the step in the cam link  190 . A force exerted against the sear striker bar  240  is transmitted to the leg  235 , and acts as a torque on the sear pin  230  to angularly displace the substantiailly planar surface  233  of the sear pin  230  from coplanarity the surface  198  of the cam link  190 , thus raising the leading edge  234  of the substantially planar surface  233  of the sear pin  230  above the top edge of the surface  194 . This rotation results in elimination of a holding force for the contact bar  70  in the contacting position, generated by the helical spring  85  acting on the contact arm  70 , through the rivet  220  and link housing  200  and sear pin  230  leading edge  234 , against the surface  194  of the cam link  190 , acting on the pin  180 , the ears of handle  160 , held in place by pin  170  with respect to the casing  20  and frame  100 . 
     The initial clockwise rotation of the cam link  190  is limited by a hook  199  in the outer profile of the cam link  190 , at a distance from the step, which partially encircles, and is capable of frictionally engaging, the sear pin  230 . In addition, the distance from the step to the hook  199  is slightly larger than the cross-sectional dimension, e.g., the diameter, of the sear pin  230 . This dimensional difference determines the amount of clockwise rotation the cam link  190  undergoes before this rotation is stopped by frictional engagement between the hook  199  and the sear pin  230 . As a consequence, the sear pin  230  engages the step in the cam link  190 , i.e., a portion of the surface  194  of the cam link  190  overlaps and contacts a leading portion of the curved surface  232  of the sear pin  230 . Thus, it is by virtue of this engagement that the toggle mechanism is locked and thus capable of opposing and counteracting the pivotal biasing force exerted by the spring  85  on the contact bar  70 , thereby maintaining the electrical connection between the contacts  50  and  60 , as shown in FIG.  1 . 
     By manually pivoting the handle  160  in the counterclockwise direction, the toggle mechanism, while remaining locked, is translate and rotated out of alignment with the pivotal biasing force exerted by the spring  85  on the contact bar  70 . This biasing force then pivots the contact bar  70  in the counterclockwise direction, toward the frame  100 , resulting in the electrical connection between the contacts  50  and  60  being broken, thus assuming a noncontacting position. This represents a transition from the state indicate in FIG. 1 to the state indicated in FIG.  5 . When in the full counterclockwise position, the handle  160  applies a slight tension or no force on the cam link  190 , resulting in a full extension of the cam link  190  with respect to the link housing  200 , as shown in FIGS. 4 and 5. In this position, the leading edge of the surface  232  of the sear pin  230  engages the surface  194 , and thus the toggle mechanism is in its locked position. Therefore, manually pivoting the handle  160  from the left to right, i.e., in the clockwise direction, then serves to reverse the process to close the contacts  50 ,  60 , since a force against the action of spring  85  is transmitted by clockwise rotation of the handle to the contact bar  70 . This represents a transition from the state indicated in FIG. 5 to the state indicated in FIG.  1 . 
     An armature (not shown in the figures), pivotally connected to the frame  100  about pivot  300 , includes a leg which is positioned adjacent the sear striker bar  240 . In the event of an overcurrent in the circuit to be protected, this overcurrent will necessarily also flow through the coil of the breaker, producing a magnetic force which induces the armature to pivot toward the pole piece. As a consequence, the armature leg will strike the sear striker bar  240 , pivoting the sear pin  230  out of engagement with the step (intersection of surfaces  194 ,  198 ) in the cam link  190 , thereby allowing the force of spring  85  to collapse the toggle mechanism, resulting in the state represented in FIGS. 2 and 3. In the absence of the opposing force exerted by the toggle mechanism, the biasing force exerted by the spring  85  on the contact bar  70  will pivot the contact bar  70  in the counterclockwise direction, toward tile frame  100 , resulting in tile electrical connection between the contacts  50  and  60  being broken. 
     As a safety precaution, the operating mechanism is configured to retain a manually engageable operating handle  160  in its ON (see FIG. 1) or an intermediate, tripped position (see FIG.  3 ), if the electrical contacts  50 ,  60  are welded together. Thus, the handle  160  will not assume the OFF position if the contacts are held together. In addition, if the manually engageable operating handle  160  is physically restricted or obstructed in its ON position, the operating mechanism is configured to enable the electrical contacts  50 ,  60  to separate upon a trip, e.g., due to an overload condition or upon a short circuit or fault current condition. See, U.S. Pat. No. 4,528,531, expressly incorporated herein by reference. 
     According to the present invention, a lever arm  310 , pivotally mounted by pin  320  to the housing  20  proximate to the trip mechanism, biased in a clockwise direction by a spring (not shown in the figures), is provided having a surface disposed in the path of the link housing  200  as it moves generally diagonally upward toward the right during a trip condition, e.g, a transition from the state indicated by FIG. 1 to the states indicated by the FIGS. 2 or  3 . When this occurs, the lever arm  310  pivots about pin  320 , and against the bias force of the spring, and disengages the lip of the plunger  340 , held by catch  330 . The plunger  340  is normally near flush with an upper surface of the housing  20 , as shown in the states indicated in FIGS. 1 and 5, and is thus visually unobtrusive or obscured. The plunger  340  is normally held in the depressed state by the catch  330  of lever arm  310  at a lip portion  350 , against the externally urging force of spring  360 , situated to propel the plunger  340  outward from the housing  20  if unrestrained. However, if the lever arm  310  is rotated clockwise about pin  320 , the catch  330  of lever arm  310  disengages the lip portion  350 , and the plunger  340  is free to protrude from the housing  20 , providing a visual indication of a trip state. The plunger  340  may then be manually reset by depression thereof into the housing  20 , after the circuit breaker mechanism is reset into the state indicated by FIGS. 1,  4  or  5 . 
     As seen in FIGS. 2 and 3, when the toggle linkage collapses, as due to an overcurrent, the seer pin  240  is rotated about axis  230 , and the cam link  190  folds into the link housing  200 . In this condition, the link housing depresses the lever arm  310 , releasing the catch  330  from the lip portion  350  of the plunger  340 . The plunger  340  will only remain inside the housing  20  when manually depressed if the toggle linkage is reset into the states indicated in FIGS. 1,  4  or  5 . 
     In summary, FIG. 1, shows the lever arm  310  restraining the lip portion  350  of the plunger  340 , and the contacts  50 ,  60  and external handle  160  are in the ON state. FIG. 2, on the other hand, shows a trip state wherein the external handle  160  is restrained in the ON position. The link housing  200  of the collapsible toggle linkage presses against the lever arm  310 , thereby releasing the plunger  340  preventing a manual reset thereof, until the circuit breaker  10  is reset. 
     FIG. 3 shows the breaker in a mid-trip state. In this case, the external handle  160  further displaces the lever arm  310  beyond the state represented in FIG.  2 . 
     FIG. 4 shows the external toggle in the OFF state, with the collapsible toggle linkage reset. The lever arm  310  is in the normally biased position. FIG. 5 shows the circuit breaker  10  in the same state as in FIG. 4, but the plunger  340  has been manually reset and is held in place by the lever arm  310 . 
     The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein. 
     The term “comprising”, as used herein, shall be interpreted as including, but not limited to inclusion of other elements not inconsistent with the structures and/or functions of the other elements recited.