Patent Publication Number: US-4097831-A

Title: Circuit breaker accessory tripping apparatus

Description:
BACKGROUND OF THE INVENTION 
     Accessory apparatus for selectively tripping an electric circuit breaker, particularly breakers utilized in industrial applications, are of various types. Probably the most common is the so-called &#34;shunt trip&#34; accessory which is typically utilized to trip a circuit breaker from a remote location, such as a central control panel. A shunt trip typically takes the form of a solenoid whose plunger is poised to trippingly engage the circuit breaker latch upon solenoid energization. The solenoid energization circuit is wired to a remote location where a switch is closed to produce solenoid energization and consequent tripping of the circuit breaker. 
     Another common circuit breaker accessory is a so-called &#34;undervoltage release&#34; (UVR) which is utilized to trip a circuit breaker in the event the line voltage falls significantly below a nominal level for a sustained, as contrasted to a momentary duration. A UVR is typically embodied in a solenoid which is energized by nominal line voltage to magnetically hold its plunger retracted or seated against the force of a return spring. When the line voltage drops below the level necessary to enable the UVR solenoid to overcome the return spring force, the plunger is pulled out to an extended position by the spring. This movement of the plunger is communicated to the circuit breaker latch, thereby effecting tripping of the breaker. 
     In some applications, the customer may desire a circuit breaker-fuse combination, wherein fuses are connected in series with the circuit breaker to increase the effective current interrupting capacity. In a three-phase circuit, a fuse is connected in series with each of the three circuit breaker poles. In the event one fuse blows to interrupt one phase of the circuit, it is important that the other two phases also be interrupted forthwith in order to prevent the damaging consequences of so-called &#34;single phasing&#34;. To ensure against single phasing, a three-coil shunt trip solenoid can be incorporated in the circuit breaker. Each coil is connected across a different fuse, such that, when one fuse blows, current is diverted through the coil connected thereacross. The solenoid is thus actuated, causing its plunger to impact against the circuit breaker latch and trip the breaker to interrupt all three phases. 
     While the incorporation of any one of these accessory trip functions within the molded case of an industrial circuit breaker has been readily achieved, size and space limitations have made it extremely difficult to accommodate within the breaker case any two or all three of the above mentioned trip functions. Recently issued U.S. Pat. No. 3,919,674 disclosed an accessory apparatus capable of serving any one, two or all three of these accessory trip functions in a compact accessory package accommodatable within the molded case of an industrial circuit breaker. The present invention constitutes an improvement over the accessory package disclosed in this patent, particularly in terms of achieving reliable resetting of the UVR solenoid. 
     It is accordingly an object of the present invention to provide improved circuit breaker accessory apparatus universally adaptable to accommodate any one, several or all of a plurality of diverse accessory trip functions. 
     An additional object of the invention is to provide accessory apparatus of the above character where plural accessory trip functions are accommodated through a common assemblage of cooperative parts. 
     A further object is to provide accessory apparatus of the above character, wherein plural trip functions are independently resolved into the movement of a single component into tripping impact with a circuit breaker latch. 
     Another object is to provide accessory apparatus of the above character which, having precipitated a trip function, automatically resets itself in response to tripping of the circuit breaker. 
     Still another object is to provide accessory apparatus of the above character wherein accessory trip functions may be readily added or subtracted without modifying the basic operative components of the assembly. 
     Yet another object of the invention is to provide accessory apparatus of the above character which is compact in size, efficient in design, reliable in operation, and inexpensive to manufacture. 
     Other objects of the invention will become apparent from the detailed description to follow. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided accessory apparatus capable of being readily incorporated within the molded case of an electric circuit breaker and capable of serving any one, several or all of a plurality of diverse accessory trip functions. The accessory apparatus utilizes a single support for mounting the operative components in compact assembly, thus facilitating its physical incorporation within the breaker case. More specifically, the support mounts a post which, in turn, pivotally mounts a latch lever adapted, while in its reset position, to latch a trip slide in its reset position. A trip spring is connected between the slide and a reset lever pivotally mounted to the support and is held in an actuated position to charge the trip spring by the breaker operating mechanism while in its contact closure condition. A reset spring connected between the reset lever and the support is also charged while the reset lever is held in its actuated position. 
     A first shunt trip solenoid, mounted by the support, acts via its plunger on the latch lever to unlatch the trip slide, which is then propelled by the trip spring toward an actuated position. In the process, the trip slide picks up the latch lever, pivoting it into tripping impact with the circuit breaker latch to trip the breaker. As the unlatched breaker operating mechanism acticulates to open the breaker contacts, the reset lever is released, and the reset spring abruptly discharges to pivot the reset lever from its actuated position to a reset position. In the process, the reset lever picks up the trip slide, returning it to its reset position. A return spring interconnected between the latch lever and the support serves to return the latch lever to its reset position when released by the return of the trip slide to its reset position. When the breaker operating mechanism is subsequently articulated pursuant to reclosure of the breaker contacts, the reset lever is coincidentally propelled to its actuated position, thereby recharging the reset spring and the trip spring as the latch lever latchably engages the trip slide. 
     An optional second shunt trip solenoid may be mounted on the support with its plunger in end-to-end alignment with the first trip solenoid plunger which acts directly on the latch lever. The second trip solenoid plunger then acts on the lever via the first solenoid plunger to unlatch the trip slide. 
     An optional sub-assembly may be added to the support to serve an undervoltage release (UVR) accessory trip function in conjunction with or to the exclusion of one or both of the accessory trip functions served by the first and second shunt trip solenoids. This sub-assembly includes a UVR solenoid which is linked to a lever disposed to act on the latch lever in a manner to also unlatch the trip slide. During resetting of the accessory apparatus, powered exclusively by the reset spring, the trip slide, in returning to its reset position, picks up and pivots the lever such as to firmly reseat the plunger of the UVR solenoid. 
     The invention accordingly comprises the features of construction, combinations of elements, and arrangements of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     For a better understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a plan view, partially broken away, of circuit breaker accessory tripping apparatus constructed in accordance with the present invention; 
     FIG. 2 is a side elevational view of the accessory tripping apparatus of FIG. 1; 
     FIG. 3 is an exploded perspective view of the accessory tripping apparatus of FIG. 1; 
     FIG. 4 is a plan view, partially broken away, of the accessory tripping apparatus of the invention in its armed condition; 
     FIG. 5 is a side elevational view of the accessory tripping apparatus of FIG. 4; and 
     FIG. 6 is a fragmentary plan view of parts of the accessory tripping apparatus in their respective actuated positions. 
     Like reference numerals refer to corresponding parts throughout the several views of the drawings. 
    
    
     DETAILED DESCRIPTION 
     The circuit breaker accessory tripping apparatus package of the present invention, generally indicated at 10 in the drawings, is illustrated in its embodiment accommodating three diverse trip functions, namely, shunt trip, three-coil shunt trip and undervoltage release (UVR). As will become apparent from the description to follow, the accessory package of the invention may be readily embodied to accommodate any one, two or all three of these trip functions. In this embodiment as best illustrated in FIG. 3, three trip solenoids, namely a shunt trip solenoid 12, a three-coil shunt trip solenoid 14 and a UVR trip solenoid trip 16, are mounted on a common support in the form of a platform 18 having turned down feet 20 at one end and a mounting block 22 at the other end facilitating mounting of the package within a circuit breaker case (not shown). Platform 18 in turn mounts a forwardly located, elongated upright post 24 and a rearwardly located, short upright post 26. These posts extend through elongated slots 28a formed in a trip slide, generally indicated at 28, and are fitted with suitable washers serving to mount and guide the trip slide for movement between a forward actuated position and a rearward reset position. A skid 28b lanced downwardly from the body of trip slide 28 bears against the upper surface of plate 18, as best seen in FIGS. 2 and 5, to prevent tilting of the trip slide, thus to ensure smooth, non-binding sliding movement thereof. 
     A latch lever, generally indicated at 30 in FIG. 3, is provided with a hub 32 which is fitted on elongated post 24 pursuant to pivotally mounting the latch lever for movement between actuated and reset positions. A snap ring 34 maintains this pivotal mounting of the latch lever on post 24. A latch spring 35, hooked at its rearward end on post 26 and at its forward end to an upwardly turned flange 30a carried by latch lever 30, serves to bias the latch lever to its reset position (FIG. 4) where a latch shoulder 30b formed in the latch lever is disposed in latchably engaging relation with an upstanding latch pin 36 carried by trip slide 28. Under these circumstances, the slide is held in its reset position by virtue of the engagement of latch pin 36 against latch shoulder 30b. 
     Referring to FIGS. 2 and 5, a flange 18a, depending from the edge of platform 18 just beyond trip slide 28, carries a pin 38 serving to pivotally mount a reset lever 40. Flange 18a also mounts a stub shaft 42 (FIG. 1) which is received in a bore 44a formed in the body of a crank, generally indicated at 44. The crank includes an elongated crank arm 44b which is apertured adjacent its free end for receipt of a pin 46a carried at one end of a link 46. The other end of this link is provided with an elongated slot 46b through which extends a heading pin 48 carried by reset lever 40. 
     Returning to FIG. 3, trip slide 28 is formed with an upstanding flange 28c in which is formed a hole 28d to receive the hooked rearward end of a trip spring 50. The other end of this tension spring is hooked on the inner end of a pin 52 carried by reset lever 40. An upstanding bracket 53 is riveted to the depending platform flange 18a. A hole 53a formed adjacent the upper extremity of this bracket receives the hooked rearward end of a reset spring 54. The forward end of this spring is hooked through a hole 40a formed in the extremity of an upwardly extending arm 40b integral with reset lever 40. 
     The various parts described thus far are illustrated in FIGS. 1 and 2 in their respective reset positions; such positions having been achieved under the influence of reset spring 54. Specifically, the reset spring biases reset lever 40 to its clockwisemost, reset position. Pin 52, carried by the reset lever, engages the leading edge 28e of trip slide flange 28c, such that reset spring 54 also biases the trip slide to its rearward, reset position. Trip spring 50 is, under these circumstances, substantially discharged. As seen in FIG. 1, return spring 35 biases latch lever 30 to its clockwisemost reset position, with an edge 30c thereof leading to latch shoulder 30b engaging latch pin 36 to controllably position the latch shoulder in latchably engageable relation with the latch pin. 
     To arm the accessory tripping apparatus, crank 44 is rotated in the counterclockwise direction as viewed in FIGS. 2 and 5. The toggle constituted by crank arm 44b and link 46 begins to straighten, causing reset lever 40 to pivot in the counterclockwise direction which serves to charge reset spring 54. By virtue of the interconnection between trip slide 28 and reset lever 40 afforded by trip spring 50, counterclockwise pivotal movement of the reset lever causes the trip slide to move forwardly until its latch pin 36 engages latch shoulder 30b of the latch lever (FIG. 4). Continued counterclockwise pivotal movement of the reset lever by crank 44 causes the trip spring 50 to be charged since continued forward movement of the trip slide toward its actuated position is prevented by the latch lever. Crank 44 is rotated in the counterclockwise direction to the point where the toggle provided by link 46 and crank arm 44b are almost, but not quite straightened. At this point, reset lever 40 has achieved its actuated position, and the reset spring 54 and trip spring 50 are fully charged. Latch spring 35 establishes sufficient latching force which must be overcome to disengage latch shoulder 30b and latch pin 36 so as to preclude spurious unlatching. The accessory apparatus in its condition shown in FIGS. 4 and 5 is armed and ready to execute an accessory trip function. 
     Now if the latch lever 30 is pivoted in the counterclockwise direction (FIG. 4) against the bias of latch spring 35 sufficiently to swing latch shoulder 30b out of engaging relation with latch pin 36, trip spring 50 is free to discharge, and the trip slide is propelled to its actuated position. As seen in the plan views of FIGS. 1 and 4, a lateral extension 28g of the trip slide carries an upright tab 28f which protrudes through an opening 30d formed in latch lever 30. As the trip slide is propelled to its actuated position by the discharge of trip spring 50, tab 28f, as seen in FIG. 6, impacts against a rounded edge 30e of opening 30d in the latch lever, causing the latter to be pivoted counterclockwise to its actuated position. A paddle 56 affixed to the latch lever flange 30a is swung into tripping impact with a circuit breaker latch 58, thereby initiating circuit interruption. The rounded edge 30e of opening 30d in the lever against which of the trip slide tab 28f engages ensures smooth, non-binding coaction of the trip slide with the latch lever in achieving tripping impact of paddle 56 with circuit breaker latch 58. 
     As is fully described below, when the circuit breaker trips, the restraint on the clockwise pivotal movement of crank 44 is removed, and reset spring 54 is free to discharge, causing reset lever 40 to be propelled in the clockwise direction to its reset position. Pin 52 engages the leading edge 28e of flange 28c, thereby picking up the trip slide for rearward movement to its reset position under the influence of reset spring 54. Trip slide tap 28f releases latch lever 30, and latch spring 35 returns the latch lever to its reset position seen in FIGS. 1 and 2. 
     In accordance with a feature of the present invention, motivation for pivoting crank 44 pursuant to arming the accessory apparatus 10 is derived from the circuit breaker operating mechanism as it is being reset incident to reclosure of the breaker contacts. An exemplary circuit breaker operating mechanism capable of properly motivating crank 44 is disclosed in U.S. Pat. No. 4,001,742. The disclosure of this patent is specifically incorporated herein by reference. To this end, a shaft, illustrated at 60 in FIG. 1, which may be constituted by an extension of the breaker mechanism cradle pivot pin, is utilized to drive crank 44 in the counterclockwise direction coincidentally with articulation of the breaker mechanism pursuant to swinging the cradle around to its latched or reset position. The terminal end portion of shaft 60 is received in a bore 62 (FIG. 2 and 5) located in the crank body in coaxial alignment with bore 44a into which stub shaft 42 is received. The outer end of the crank body is formed with a transverse recess 64 accommodating a transverse pin 66 carried by shaft 60 when the terminal end portion of the shaft is inserted in bore 62. This recess is provided with diametrically opposed reliefs 64a (see also FIG. 1), such that clockwise rotation of the cradle pin extension shaft 60 is not coupled to the crank 44 (FIG. 2). However, counterclockwise rotation of the shaft 60 brings its transverse pin 66 into driving engagement with the diametrically opposed sides 64b of the crank recess 64, such that the crank is rotated in the counterclockwise direction in response to counterclockwise rotation of the shaft (FIG. 5). 
     In the reset condition of the accessory apparatus seen in FIGS. 1 and 2, the circuit breaker cradle is unlatched and the breaker contacts are open. As the breaker mechanism is articulated to reset the operating mechanism, i.e., relatch the cradle, the shaft 60 extension of the cradle pivot pin rotates in the counterclockwise direction. The transverse pin 66 engages the sides 64b of the crank recess 64, causing the crank 44 to be rotated in the counterclockwise direction as the cradle is swung around to its latched position. As the cradle reaches its latched or reset position, the parts of the accessory apparatus are in their positions shown in FIGS. 4 and 5 wherein the toggle constituted by link 46 and crank arm 44b are just short of being fully straightened. Latch lever 30 has latched up the trip slide 28, and both the trip spring 50 and the reset spring 54 are fully charged. With the cradle held in its latched position by the circuit breaker latch, clockwise rotation of the crank under the influence of reset spring 54 is prevented by shaft 60 and its cross pin 66. Consequently, the accessory apparatus 10 is held in its condition. 
     When latch lever 30 unlatches the trip slide to precipitate tripping of the breaker, the breaker cradle is released, and it abruptly swings to its tripped position under the influence of the breaker mechanism springs. By virtue of the reliefs 64a in crank 44, the accessory apparatus does not impede tripping movement of the breaker mechanism. Clockwise rotational restraint on crank 44 is thus removed, and reset spring 54 discharges to power the resetting of the accessory apparatus, with the parts returning to their reset positions seen in FIGS. 1 and 2. 
     To unlatch trip slide 28 pursuant to initiating an accessory trip function, shunt trip solenoid 12 is positionally mounted on platform 18 such that its plunger 12a is poised to impact against an upwardly turned tab 30f carried by an extension arm 30g of latch lever 30. It is seen that upon energization of solenoid 12, its plunger 12a engages tab 30f to pivot latch lever 30 in the counterclockwise direction seen in FIG. 4, thereby disengaging latch shoulder 30b from latch pin 36 to initiate tripping of the circuit breaker. As the breaker trips, reset spring 54 discharges to return the reset lever and trip slide to their reset positions. Latch spring 35 can then return the latch lever to its reset position with tab 30f picking up solenoid plunger 12a to return it to is retracted position. 
     If the three-coil shunt trip accessory trip function is desired, the solenoid 12 is mounted to platform 18 in place of shunt trip solenoid 12. However, if both shunt trip and three-coil shunt trip functions are desired, the three-coil shunt trip solenoid 14 is mounted behind shunt trip solenoid 12 with their plungers in axial alignment, as seen in FIG. 1. Thus, if a three-coil shunt trip function is signalled, solenoid 14 is energized and its plunger 14a impacts against the rearward end of shunt trip solenoid plunger 12a which, in turn, impacts against tab 30f of latch lever 30 to unlatch trip slide 28. 
     When the accessory apparatus package 10 is to be equipped with an undervoltage release (UVR) either in lieu of or in conjunction with one or both of the shunt trip solenoids 12 and 14, a UVR sub-assembly, generally indicated at 70 in FIG. 3, is mounted to platform 18. This sub-assembly includes a mounting bracket 72 of generally L-shaped configuration having an elevated platform segment 72a and a downturned side panel segment 72b terminating in a laterally turned foot 72c for attachment to the platform 18 by suitable means such as a screw. Platform segment 72a includes aperture 72d through which the upper reduced diameter portion of post 24 protrudes (FIG. 1) to complete the mounting of the UVR sub-assembly to the platform 18. UVR solenoid 16 is mounted to the elevated platform segment of bracket 72 so as to occupy a space generally above the space normally occupied by shunt trip solenoids 12 and 14. A vertically oriented lever 74 is pivotally mounted to the bracket side panel 72b by a pivot pin 76. The upper end of this lever is pinned to the exposed end of the UVR solenoid plunger 16a. A spring 78 has one end hooked through a hole in the upper end of lever 74, while its other end is threadedly engaged on a screw 80 extending through a hole formed in an upwardly turned flange extension 72d of bracket platform segment 72a. 
     It is thus seen that spring 78 biases lever 74 in the counterclockwise direction, as viewed in FIG. 3, to pull the UVR solenoid plunger 16a to an extended position. A lateral extending arm 74a integral with lever 74 engages the underside of bracket platform segment 72a to limit the degree of extension of plunger 16a. Screw 80 may be adjustably threaded into the end of spring 78 to establish a desired spring force acting on plunger 16a and lever 74. 
     The lower end of lever 74 terminates in a finger 74b which depends into operative relation with trip slide 28 and latch lever 30. Platform 18 is cut out at 18b so as to provide clearance for movement of finger 74b. 
     With the parts in their reset positions seen in FIGS. 1 and 2, it is noted that finger 74b of UVR lever 74 is engaged by the rearward edge 28h of lateral extension 28g of trip slide 28. This forces lever 74 to assume its clockwisemost position (FIG. 3) with the upper end of the lever forcing UVR solenoid plunger 16a to its fully seated position. This position is achieved by virtue of reset spring 54 overpowering the UVR spring 78. When the line voltage is at nominal level, the magnetic attraction of UVR solenoid 16 is sufficient to maintain its plunger seated against the bias of spring 78. 
     When the accessory apparatus 10 is armed incident to resetting of the breaker operating mechanism, trip slide 28 has moved forwardly to its latched position as seen in FIGS. 4 and 5, and the finger 74b of UVR lever 74 is left poised to engage an edge 30h of latch lever 30. If the line voltage drops below a predetermined minimum level, spring 78 becomes effective to overpower the magnetic force developed by the UVR trip solenoid 16, and plunger 16a is extended. Lever 74 is thus pivoted about its post 76 in the counterclockwise direction seen in FIG. 3. During the course of this movement of lever 74, its finger 74b engages edge 30h of latch lever 30, causing the latter to also pivot in the counterclockwise direction to unlatch trip slide 28 and precipitate tripping of the breaker. As the circuit breaker trips, the clockwise rotational restraint on crank 44 is removed, and reset spring 54 discharges to propel the parts back to their reset positions. As trip slide 28 returns to its reset position, its edge 28h engages finger 74b of UVR lever 74. This lever is thus pivoted in the clockwise direction (FIG. 3) to drive the UVR solenoid plunger 16a firmly back to its seated position. Return spring 54 is sufficiently powerful so that the reseating of the plunger 16a is done forcefully to thus ensure plunger reseating despite any counteracting frictional forces occasioned by dirt, wear, and misalignment. 
     It will be appreciated that if the line voltage has not returned to its nominal level when it is attempted to arm the accessory apparatus 10 by resetting the circuit breaker mechanism, the UVR return spring 78 will overpower the reduced magnetic force developed by the solenoid 16. Consequently, the finger 74b of UVR lever 74 will simply follow along with the trip slide as it is pulled forwardly via trip spring 50 as the reset lever 40 is pivoted counterclockwise by crank 44. The finger 74b ultimately engages the latch lever, pivoting it in the clockwise direction such that latch shoulder 30b is swung clear of latch pin 36. As a consequence, trip slide 28 continues on to its actuated position, picking up latch lever 30 and swinging paddle 56 into engagement with circuit breaker latch 58. The circuit breaker latch is thus disabled and cannot relatch the circuit breaker cradle, thereby defeating any attempt to reset the breaker mechanism. Consequently, the cradle is returned to its tripped position by the mechanism spring, and the clockwise rotational restraint on crank 44 is removed. Reset spring 54 then powers the various parts back to their reset positions, including plunger 16a back to its seated position. 
     When the line voltage returns to its nominal level, the magnetic force generated by the UVR solenoid 16 is sufficient to overpower return spring 78. Consequently, finger 74b of UVR lever 74 cannot follow the forward movement of trip slide 28 during rearming of the accessory apparatus. Consequently, the UVR lever does not engage latch lever 30, leaving latch shoulder 30b in position to engage latch pin 36. The latch lever thus acquires latching control of the trip slide, and the trip spring 50 is charged. The accessory apparatus is thus armed and ready to execute an accessory trip function when called for. 
     From the foregoing description, it is seen that the accessory apparatus of the present invention is capable of accommodating a plurality of diverse, auxiliary or accessory circuit breaker trip functions with a rather simple, compact construction of relatively few parts. As such, the various parts of the accessory apparatus can be mounted on a common support structure which can be readily accommodated within the breaker case. A signal feature of the invention is the automatic, self-resetting function performed by reset spring 54. This spring powers the movements of the various apparatus parts from their actuated to their reset positions rather than relying on the breaker mechanism springs to reset the accessory apparatus as in the above-mentioned U.S. Pat. No. 3,919,674. The return spring is of sufficient power as to readily overpower the UVR return spring 78, such that the UVR solenoid plunger 16a is forcefully returned to its seated position in snap-action fashion. Preferably, the seating of the plunger 16a within the UVR solenoid 16 serves as the ultimate stop establishing the reset position of the trip slide 28. Thus, reliable reseating of the UVR solenoid plunger 16a is always achieved with complete assurance. 
     It will also be observed that the present invention conveniently permits the adding on of additionally trip functions in the field. That is, the basic elements of the accessory apparatus can readily be augmented with one or both of the shunt trip solenoids 12 or 14, and/or the UVR sub-assembly 70 to implement the various trip functions as desired. 
     In the disclosed embodiment of the invention, latch lever 30, or more precisely paddle 56 carried by this lever, impacts the circuit breaker latch to precipitate tripping of the breaker. However, it will be appreciated that trip slide 28 or an extension thereof could just as well be responsible for providing the requisite tripping impact with the circuit breaker latch as the slide moves from its reset to its actuated position under the urgence of trip spring 50. In this modification, trip slide 28 need not engage latch lever 30 during movement to its actuated position. 
     It will thus be seen that the object set forth above, among those made apparent from the preceding description, are efficiently attained and, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpretative as illustrative and not in a limiting sense.