Abstract:
An air circuit breaker bell alarm accessory interacts with the circuit breaker contact position indicator to provide local and remote indication of the occurrence of a circuit interruption. A drive pin extending from the bottom of the accessory interacts with a slot on the contact position indicator lever to prevent release of the circuit breaker closing spring until the bell alarm accessory is manually reset.

Description:
BACKGROUND OF THE INVENTION 
     Air circuit breakers as described within U.S. Pat. No. 3,095,489 entitled &#34;Manual Charging Means for Stored Energy Closing Mechanisms of Electric Circuit Breakers&#34; and U.S. Pat. No. 3,084,238 entitled &#34;Ratchet Mechanism for Charging a Closing Spring in an Electric Circuit Breaker&#34; include operating mechanisms that are mainly exposed to the environment. Since the air circuit breakers are rated to carry several thousand amperes of current continuously, the exposure to convection cooling air assists in keeping the operating components within reasonable temperature limits. 
     U.S. patent application Ser. No. 08/878,598 entitled &#34;Contact Position Indicator for an Industrial-Rated Circuit Breaker&#34;, filed concurrently herewith, describes the use of a target device to indicate the condition of the circuit breaker contacts as well as an interlock arrangement for preventing false indication thereof. 
     Various accessory devices are used with such air circuit breakers to provide auxiliary function along with overcurrent protection. One such accessory is the bell alarm accessory that provides local and remote indication as to the occurrence of circuit interruption. U.S. Pat. No. 5,502,286 entitled &#34;Bell Alarm and Lock-Out for High Ampere-Rated Circuit Breakers&#34; describes a bell alarm accessory used with so-called &#34;insulated case&#34; circuit breakers wherein the circuit breaker interrupting components are completely enclosed within an insulating plastic enclosure. This patent describes one such bell alarm accessory that interacts with the circuit breaker operating mechanism to activate the bell alarm upon circuit interruption and to prevent the closing of the circuit breaker contacts until the accessory is manually reset. 
     It would be beneficial to provide a similar bell alarm with air circuit breakers to indicate the occurrence of a circuit interruption and to prevent the closing of the circuit breaker contacts until the accessory is manually reset. 
     One purpose of the instant invention is to provide a bell alarm accessory that provides local as well as remote indication of such circuit interruption as well as preventing circuit breaker contact closure until and unless the accessory has become manually reset. 
     SUMMARY OF THE INVENTION 
     An air circuit breaker bell alarm accessory interacts with the contact position indicator to provide local and remote indication of the occurrence of a circuit interruption. The signal flag in the form of a pin arranged at the top part of the accessory projects through an opening in the circuit breaker cover to provide visual indication as to the separation of the circuit breaker contacts. A drive pin extending from the bottom of the bell alarm accessory interacts with a slot on the contact position indicator lever to prevent release of the circuit breaker closing spring until the bell alarm accessory is manually reset. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is top perspective view of an air circuit breaker containing the bell alarm-interlock accessory in accordance with the invention; 
     FIG. 2 is a top perspective view of the circuit breaker of FIG. 1 with the circuit breaker cover removed to detail the bell alarm accessory in isometric relation with the trip indication mechanism; 
     FIG. 3 is an exploded top perspective view of the bell alarm accessory in isometric projection with the components contained within the trip indication mechanism of FIG. 2; 
     FIG. 4 is a bottom plan view of the trip indication mechanism of FIG. 2; and 
     FIG. 5 is a side view of the trip indication mechanism of FIG. 2. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The air circuit breaker 10 of FIG. 1 is similar to that described within the aforementioned U.S. Pat. No. 3,095,489 and includes a metal frame 11 which supports the trip unit programmer 12A and the operating mechanism enclosure 13. The trip unit programmer is similar to that described in U.S. Pat. No. 4,672,501 entitled &#34;Circuit Breaker and Protective Relay Unit&#34;. The top cover 12 includes a trip button 19 for releasing the circuit breaker operating mechanism contained within the enclosure 13 for separating the circuit breaker contacts 16, 17 to their open condition and a closing button 21 for moving the contacts to their closed position. Visual indication of the contact condition is provided by means of the pop-up target aperture 37 in the manner to be described below. The circuit breaker contact arms 15 within each pole of a three pole circuit arrangement, are interconnected by means of the operating mechanism crossbar 14 to insure that all contacts within the separate poles both open and close in unison. The ratchet mechanism 22 improves over the earlier mechanism described in the aforementioned U.S. Pat. No. 4,167,988 by allowing the operating mechanism closing spring described therein to be charged remotely by means of a motor operator as well as by means of the circuit breaker operating handle 18 that interacts with the ratchet mechanism 22 by means of a pair of plate connectors, one of which is indicated at 18A. 
     The circuit breaker 10 of FIG. 2, depicted with the circuit breaker cover 12 removed from the circuit breaker operating mechanism enclosure 13, illustrates the contact arm connector assembly 9 arranged on one side of the enclosure 13 and the ratchet assembly 22 on an opposite side thereof. The contact arm connector assembly 9 interacts with indicator drive lever 28 by means of the extended rod 8 to provide accurate indication of the condition of the circuit breaker contacts 16, 17 of FIG. 1 in the manner described in aforementioned U.S. Ser. No. 08/878,598. The bell alarm interlock assembly 20, hereinafter &#34;interlock assembly&#34;, interacts with the indicator drive lever 28 by capture of the bell alarm drive pin 26, extending from the interlock slide 38, within the slot 27 formed in the drive lever 28, as illustrated. The interlock assembly support plate 23 carries the T-shaped actuation arm 30 that interacts with the blocking prop 29 by means of the offset tab 30C. The bell alarm module 32, described in the aforementioned U.S. Pat. No. 5,502,286, is positioned on the support plate such that the pop-up target 33, on the top of the module, extends within the aperture 37 formed in the circuit breaker cover 12 and the lock-out plunger 34, on the bottom of the module, extends within the aperture 36 in the support plate 23. 
     The interlock assembly 20 is shown now in FIG. 3 prior to attaching the support plate 23 and T-shaped actuation arm 30 to the operating mechanism enclosure 13 of FIG. 2 by means of stand-off connectors 24, 25, bushing 45 and nuts 24A, 25A. The interlock slide 38 that carries the drive pin 26 is attached to the bent tab 23A, extending downward from the support plate 23, by means of the screws 41, 42, spacers 39, 40 and threaded openings 43, 44. The T-shaped actuation arm 30 is positioned on the support plate 23 by first passing the off-set end 30A of the T-shaped actuation arm within the slot 46 and arranging the off-set end under the aperture 36 to interact with the lock-out plunger 34 extending from the bottom of the bell alarm module 32 opposite the pop-up target 33 when the bell alarm module is fastened to the support plate 23 by means of the screw 35, slot 32A and threaded opening 23B. The T-shaped actuation arm return spring 47 connects with the aperture 47A on the T-shaped actuation arm 30 at one end and with the aperture 47B on the support plate 23 at the opposite end thereof. The end 30B of the T-shaped actuation arm 30 is inserted within the slot 38A at the end of the interlock slide 38 and the off-set tab 30C of the T-shaped actuation arm is positioned within the elongated slot 23C formed in the edge of the support plate 23 to interact with the tab 29A on the end of the blocking prop 29 in the manner best seen by now referring to the interlock assembly 20 as depicted in FIGS. 4 and 5 wherein the standoff connectors 24, 25 on the support plate 23 are included as points of reference relative to the circuit breaker operating mechanism enclosure 13. 
     With the circuit breaker contacts 16, 17 of FIG. 1 in the OPEN condition, the interlock assembly components are indicated in solid lines and with the circuit breaker contacts in the CLOSED condition, the same components are indicated in phantom. As the contacts move from the OPEN to CLOSED positions as so indicated, the drive pin 26, carried by the interlock slide 38 drives the indicator drive lever 28 in the same direction by engagement within the drive lever slot 27 thereby moving the end 30B of the T-shaped actuation arm 30 in the same direction by capture of the end thereof in the slot 38A within the interlock slide 38 and rotating the T-shaped actuation arm in the counterclockwise direction against the bias of the extended return spring 47. The off-set tab 30C of the T-shaped actuation arm 30 is rotated into abutment with the tab 29A on the end of the blocking prop 29. With the blocking prop in this position, as explained in U.S. Pat. No. 5,889,250, entitled &#34;Circuit Breaker Closing Springs Button Interlock Mechanism&#34;, filed concurrently herewith, the closing pin 48 is captured within the slot 50 in the blocking prop 29 under the bias provided by the spiral spring 49 to thereby prevent release of the charged circuit breaker closing spring (not shown). At the same time, the off-set end 30A of the T-shaped actuation arm 30 becomes positioned under the lock-out plunger 34 extending from the bottom of the bell alarm module 32 through the aperture 36 within the support plate 23. The bell alarm module 32 is still operational for providing indication of a fault occurrence by release of the pop-up target 33 at the top of the bell alarm module through the aperture 37 formed in the circuit breaker cover 12 shown in FIG. 2, while at the same time releasing the lock-out plunger 34 at the bottom of the bell alarm module as indicated in phantom into the path of the off-set end 30A of the T-shaped actuation arm 30. This now prevents the extended return spring 47 from rotating the T-shaped actuation arm 30 back to the position indicated in solid lines and release the closing pin 48 from the slot 50. It is therefore seen that the bell alarm module 32 is effectively preventing the circuit breaker closing springs from closing the circuit breaker contacts 16, 17 of FIG. 1. To allow the release of the closing pin 48 from the slot 50 on the blocking prop 29, the lock-out plunger 34 on the bottom of the bell alarm module 32 must move away from the off-set end 30A of the T-shaped actuation arm 30. This is accomplished by depressing the pop-up target 33 of the bell alarm module of FIG. 3, in the manner described in the aforementioned U.S. Pat. No. 5,502,286, which releases the lock-out plunger allowing the lock-out plunger to recede within the bottom of the bell alarm module. This allows the T-shaped actuation arm 30 to rotate to the solid position shown in FIG. 5 under the bias of the return spring 47 and release the closing pin 48 and allow the closing spring to respond in the manner described in the aforementioned U.S. Pat. No. 5,889,250, to close the circuit breaker contacts.