Abstract:
A removable control unit of a motor control center has an auxiliary operator handle linked to a molded case circuit breaker handle for control of the circuit breaker externally of the motor control center cabinet. An interlock slide bar is driven by the auxiliary handle to an extended position to block removal of the unit with the circuit breaker in the ON condition, and follows the handle by gravitational force to a withdrawn position upon movement of the handle to an OFF condition of the circuit breaker, the slide bar abutting a fixed stop prior to the handle reaching the OFF condition to separate the handle from the slide bar in the OFF condition. A spring carried on the interlock slide bar is engaged by the handle to effect driving engagement, compression of the spring occurring only as the handle is nearly in the ON condition.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to auxiliary operator mechanisms utilized on removable control units of a motor control center of the type disclosed in U.S. Pat. No. 4,760,220 issued July 26, 1988 to Ronald J. Fritsch and Francis A. Lubinski, and assigned to the assignee of this application, which patent is hereby incorporated herein by reference. More particularly, this invention relates to an improved drive connection between a handle assembly and a unit interlock slide bar of the auxiliary operator mechanism. 
     Motor control centers comprise a cabinet having a plurality of vertically arranged compartments which open to a front face of the cabinet. Removable control units are individually contained within respective compartments to be slidably withdrawn through the front opening. Each removable control unit comprises a frame to which motor control apparatus such as contactors, overload relays, fuse blocks, disconnect switches, molded case circuit breakers or motor circuit protectors or combinations of the foregoing are mounted. An operator mechanism is also mounted to the removable control unit for operating the circuit interrupting apparatus of the control unit such as the disconnect switch, molded case circuit breaker or the motor circuit protector. The molded case circuit breaker and the motor circuit protector each have self contained handles and operator mechanisms. Therefore, the operator mechanism of the motor control unit functions as an auxiliary operator for these devices. 
     The auxiliary operator also functions to operate a unit interlock member which extends to a position of interference with stationary framework of the cabinet in an ON condition of the circuit interrupting apparatus to prevent withdrawal of the removable control unit while the apparatus is electrically live. In an OFF position of the circuit interrupting apparatus and of the auxiliary operator, the unit interlock member assumes a withdrawn position out of interference with the cabinet framework. 
     The self contained operator handle of molded case circuit breakers or motor circuit protectors assumes one of four positions, i.e. ON, OFF, TRIP and RESET. Through linkage that interconnects the auxiliary operator handle with the circuit interrupting apparatus operator handle, the handle of the auxiliary operator also assumes one of four positions corresponding to the aforementioned ON, OFF, TRIP and RESET positions of the circuit interrupting apparatus handle. In prior art auxiliary operator assemblies, e.g. that of the above referenced patent, the interlock member is a slide bar which is spring biased to an extended position and is driven to a withdrawn position by the auxiliary operator handle when moving to the OFF position, compressing the spring that provides the aforementioned bias to the slide bar. While it is desirable to have the interlock slide bar biased to its extended position unless specifically withdrawn by operating the apparatus to an OFF condition, it has been found that the spring can introduce certain problems with regard to position of either handle. For example, when the auxiliary operator handle is moved to the OFF position and therefore moves the circuit interrupting apparatus handle to the OFF position, the auxiliary operator handle drives the interlock slide bar to a withdrawn position which compresses the interlock slide bar bias spring. Due to tolerances in the auxiliary operator, circuit interrupting apparatus handle/operator and in the interconnecting linkage, the bias provided by the spring of the interlock slide bar may move the auxiliary operator handle upward from a true OFF position sufficiently to permit the interlock slide to bar extend to an interference position, blocking withdrawal of the removable control unit from the motor control center cabinet, necessitating the workman to hold the handle down while attempting to withdraw the control unit. Moreover, when resetting the circuit interrupting apparatus, the handle is moved beyond the OFF position to a RESET position. In so doing, the auxiliary operator handle compresses the interlock slide bar spring further, potentially to a solid condition under adverse tolerance conditions. If compressed solid, the interlock slide bar spring can prevent the auxiliary operator handle from moving fully to the RESET position and therefore prevent resetting of the circuit interrupting apparatus. Although prior art operator mechanisms have adjustment features built in, the effective adjustment range is often quite small and adjustment becomes difficult. 
     SUMMARY OF THE INVENTION 
     This invention provides an auxiliary operator for circuit interrupting apparatus of a motor control center wherein the operator handle is free of the unit interlock member in the OFF position of the handle and the circuit interrupting apparatus whereby the auxiliary operator handle is not influenced by a biasing means for the unit interlock member. The auxiliary operator handle drivingly engages a spring or an equivalent resilient portion of the unit interlock member during movement from OFF to ON positions, compressing the spring or other resilient member in a late portion of the movement as the handle nears the ON position whereby the spring or resilient member of the unit interlock provides minimum adverse bias to the operator mechanism. The unit interlock abuts a fixed stop to determine its withdrawn position as the operator handle moves to the OFF position, thereby moving free of the unit interlock member in the OFF position and in continued movement to a RESET position. 
     The invention and its advantages will become more readily apparent when reading the following description and claims in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross sectional view of the auxiliary operator of this invention and of fragmentary portions of a motor control center cabinet and a removable control unit, showing the auxiliary operator and the circuit interrupting apparatus in an ON position; 
     FIG. 2 is a view similar to FIG. 1 but showing the auxiliary operator handle and circuit interrupter apparatus in an OFF position and showing a unit interlock member against a fixed stop defining a withdrawn position thereof; 
     FIG. 3 is a rear view of the auxiliary operator assembly taken along the line 3--3 in FIG. 1; and 
     FIG. 4 is a perspective view of the unit interlock member, a fragmentary portion of the handle member and a fragmentary portion of a support plate of the auxiliary operator providing a fixed stop for the unit interlock member. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A motor control center comprises a cabinet having a plurality of compartments open to the front of the cabinet, which compartments are closed by respective doors such as 4 and 6 shown in the drawings which are hinged to the cabinet, usually along a side edge of the respective doors. Each compartment has a removable control unit 8 slidably mounted therein through the open front when the respective door is open. A removable control unit comprises a rear panel 10 and pair of side panels 12 (only one of which is shown. Circuit interrupting apparatus such as a molded case circuit breaker 14 or a nearly identical motor circuit protector is mounted to the rear panel 10 by suitable means (not shown). A plug-on connector module 16 for the removable control unit 8 is attached to rear panel 10. While not specifically shown herein, connector module 16 has a plurality of plug-in connectors which engage with bus bars within the motor control center cabinet to provide electrical power to the removable control unit 8 when the same is fully inserted within the respective compartment. Preformed insulated connector straps 18 (only one shown) are bolted to respective terminals of connector module 16 and the circuit interrupting apparatus 14 to supply power to the circuit interrupting apparatus. 
     The auxiliary operator 20 of this invention comprises a molded housing 22 which has a pair of upwardly projecting tabs 22a at its upper end (FIG. 3). Each of the tabs 22a are provided with a central hole through which screws (not shown) or other suitable fastening means may be inserted to be cooperably received within aligned holes in an inverted U-shaped channel 24 secured between the side walls 12 of the removable control unit near its upper forward end. Auxiliary operator 20 also comprises a lower support plate 26 which is attached to the rear of molded housing 22 by suitable means (not shown). Support plate 26 has a tab 26a projecting from the upper end thereof which is aligned with one tab 22a of housing 22 and is disposed between that tab 22a and channel 24. A second tab 26b extends rearwardly along an edge of the operator mechanism 20 (FIG. 3). A brace 28 is attached to the rear panel 10 by a pair of screws 30. Although only fragmentally shown in FIGS. 1 and 2, brace 28 extends forwardly to overlap the tab 26b. A hole is provided in the end of brace 28 which aligns with the hole in tab 26b and the two members are firmly secured together by a rivet or other suitable fastener which extends through the aligned openings. Thus the operator 20 is mounted to the removable control unit 8 at the forward edge thereof. The doors, e.g. 6, are provided with openings, e.g. 6a, which surround a forwardly extending bezel of the housing 22 when the respective doors are closed to afford exterior accessibility of the auxiliary operator. 
     An operator handle 32 is supported for sliding movement on support plate 26, the handle comprising a drive leg 32a which projects rearwardly through a slot 26c in support plate 26. A forwardly extending leg 32b of handle 32 projects through an elongated slot 22b in housing 22 and has an operator knob 33 attached to the outermost end thereof. Auxiliary operator 20 is oriented such that linear sliding movement of handle 32 occurs in a vertical direction for reasons that will be discussed hereinafter. 
     A drive lever 34 is pivotally mounted on brace 24 at the base thereof by a shouldered rivet 36. The forward extending end of drive lever 34 is disposed against an outer surface of drive leg 32a of handle 32. Drive leg 32a has a slot 32c elongated in a direction perpendicular to the direction of linear sliding movement of the handle 32. A rivet 38 extends through a hole of drive lever 34 and through the slot 32c to form a hinged connection between drive lever 34 and drive leg 32a. Thus, as handle 32 is slid linearly reciprocably along support plate 26, the drive lever 34 is pivoted about rivet 36 by the hinge connection provided by rivet 38, the later translating forward and rearward within the elongated slot 32c as the drive lever 34 moves over center of the rear pivot at rivet 36. 
     A bracket 40 is mounted to rear panel 10 of the removable control unit 8 by screws 42. While not shown in the drawings, a similar bracket may be mounted at the opposite side of the circuit breaker 14. A U-shaped yoke 44 is pivotally mounted between the support brackets 40 by rivets 46. The bight portion of yoke 44 has an opening therein which surrounds an operating handle 14a of circuit breaker 14. A link member 48 is pivotally connected to drive lever 34 by a shouldered screw 50 and to yoke 48 by a shouldered screw 52. Thus, pivotal movement of drive lever 34 in response to linear sliding movement of handle 32 is transferred to yoke 44 for movement to and fro about rivet 46 through the driving connection of link 48, thereby operating the circuit breaker 14 between ON and OFF positions in a substantially concentric manner with the pivot of handle 14a. 
     A unit interlock which functions to prevent insertion or withdrawal of the removable control unit while the circuit interrupting apparatus 14 is in an ON condition is incorporated in the auxiliary operator 20. The unit interlock preferably comprises a slide bar 54 which extends through a slot 26d in a rearward extension 26e of support plate 26 as seen best in FIG. 4. The lower end of slide bar 54 extends through a slot 56a in a drive bracket 56 which is attached to drive leg 32a of handle 32 by screws 58. It will be appreciated that drive bracket 56 guides the lower end of slide bar 54 for sliding movement while itself sliding as handle 32 is moved. An offset arm 54a extends from the slide bar 54 near its central section to overlie and rest upon an offset finger 26f of support plate 26 as best seen in FIG. 4. Finger 26f serves as an anchor for a helical tension spring 60 which biases a door interlock lever 62 counterclockwise about a pivot 64 as seen in FIG. 3. The lowermost or withdrawn position of slide bar 54 with respect to the support plate 26 and housing 22 of the auxiliary operator 20 is determined by the abutment of the distal end of arm 54a against the surface of finger 26f. A helical compression spring 66 is disposed over the lower end of slide bar 54. The upper end of spring 66 is trapped against a shoulder 54b on slide bar 54 (FIG. 4) by sliding the uppermost loop of the spring over a pair of ears 54c formed on the slide bar. 
     As seen best in FIGS. 2 and 4, when the handle 32 is moved to the OFF position of the circuit breaker 14, the drive bracket 56 moves away from the lower end of the spring 66 to fully disengage the handle 32 from a driving or biasing condition with respect to the unit interlock slide bar 54 or its spring 66. As the handle 32 is moved upward from the OFF position to the ON position, the upper surface of drive bracket 56 picks up the lower loop of spring 66 and drives slide bar 54 upwardly to an extended position wherein the upper end of slide bar 54 extends behind a flange 68a of a structural member 68 of the motor control center cabinet to block removal of the control unit 8 from the cabinet through the forward opening when door 6 is open. The travel of handle 32 is such that the handle is nearly in the 0N position and the interlock slide bar 54 is in its extended position before drive bracket 56 begins to compress spring 66 to provide a bias to the interlock slide bar 54. In this way, the interlock member does have a bias to its extended position and the spring 66 affords a tolerance-compensating lost motion connection between the handle and the slide bar without providing adverse spring forces to the handle 32 and the linkage that joins handle 32 to the circuit breaker handle 14a. When the circuit breaker handle 14a is moved to the OFF position as shown in FIG. 2, the interconnecting linkage causes the handle 32 to assume a corresponding position which may be marked by suitable indicia on the front surface of the housing 22. Drive bracket 56 moves away from the lower end of spring 66 as the slide bar 54 stops against finger 26f , and therefore spring 66 provides no bias to handle 32 that would cause it to move from the OFF position. 
     The auxiliary operator 20 is oriented such that the sliding movement of the handle 32 and the unit interlock 54 are in a vertical direction. Therefore, the handle 32 has a gravitational bias downward to assume, through the interconnecting linkage, the position of the circuit breaker handle 14a, and interlock slide bar 54 is gravitationally biased to the withdrawn position wherein the distal end of arm 54a rests upon the upper surface of finger 26f. In the event that interlock slide bar 54 is pinched or wedged against a flange 68a or is otherwise hung up and does not return to the fixed STOP position by gravitational force, a screw 70 is threaded through a hole in the lower end of slide bar 54 to create an enlarged boss which will not pass through the slot 56a in drive bracket 56. If, when the handle 32 is moved from the ON position to the OFF position, the interlock slide bar 54 does not follow by gravity, the slide bar is directly driven by continued downward manual movement of handle 32 and the resulting movement of drive bracket 56 bearing upon screw 70. It will further be appreciated that the reset action of handle 32 for circuit breaker 14 requires handle movement further downward beyond the OFF position. In the arrangement provided by this invention, the handle 32 only moves further away from engagement with spring 66 when going toward the RESET position. Therefore, spring 66 does not interfere with movement of the auxiliary operator handle to the RESET position and resetting of the circuit breaker 14. 
     The foregoing describes a preferred embodiment of an auxiliary operator for circuit interrupting apparatus of a motor control center or the like. Although the auxiliary operator of this invention has been shown and described in a single preferred embodiment, it is to be understood that it is susceptible of various modifications without departing from the scope of the appended claims.