ENTRECIERRE ASSEMBLY FOR FUSE SWITCH
Field of the Invention This invention relates generally to electrical interrupting equipment having fuses and, more specifically, to a interlock assembly for actuating the opening of a switch after a fuse is blown and preventing the switch from being reclosed until that the fuse is replaced. BACKGROUND OF THE INVENTION Fusible switches having a fuse and a current carrying blade use externally energized devices, such as relays or solenoids, to operate the blade opening when the fuse blows due to an overload or short circuit condition. A problem may arise if external power is not available when it is needed to operate the relay or solenoid to operate the breaker opening. Therefore, there is a clear need to provide an assembly that only uses mechanical components to operate the opening of the switch. The use of interlocks to prevent the closure of the blade in a fusible switch after its fuse has flown is shown in DE 31 12295 Al. However, prior art interlocks only prevent the closing of the phase with which the fuse and the switch are associated.
There is therefore a need to use a interlock assembly to prevent the closing of all three phases in a three-phase fuse switch. Additionally, some prior art interlocking assemblies require electrical power to operate external devices, such as solenoids and relays, to prevent them from closing the switch blade after the fuse has blown. Therefore, there is a need to provide a interlock assembly that does not require external power to prevent the switch from closing. Additionally, when a single-phase fuse blows a multi-phase fuse switch and the other phases continue to conduct electrical current, there is a single-phase condition that can damage the electrical equipment that is downstream of the switch. Consequently, in order to prevent a single phase condition, there is a need for
, ~. provide a interlock assembly to trigger the opening of all phases in a multi-phase fuse switch in case any of the fuses blow. SUMMARY OF THE INVENTION It is a general object of the present invention to provide a mechanical interlock assembly for a fusible switch. It is a more specific object of the present invention to provide a interlock assembly that prevents a switch from closing when an associated fuse has flown. It is another object of the present invention to provide a interlock assembly that operates the opening of a fusible switch when the fuse detects an overload or short circuit condition. According to a preferred embodiment of the present invention, a interlock assembly is provided for use with a fusible switch having a series fuse and an operating mechanism for controlling the operation of the switch. The interlock assembly includes an indicator member disposed adjacent the fuse to indicate the status of the fuse, and an actuator member coupled to the operating mechanism for actuation to open the switch when the fuse is blown. A traversed fastener member coupled to both the indicator member and the actuator member communicates the status of the fuse to the actuator member. The crossed fastener member is arranged to be in a first position when the fuse leads and in a second position when the fuse has blown. BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of the invention will become apparent from the following detailed description and from the accompanying drawings, in which: Figure 1 is a partial perspective view of a three-phase fuse switch, including a set of interlock according to the present invention; Fig. 2 is a side view of the three-phase fuse switch shown in Fig. 1, showing a single phase of the three-phase switch with a conductive fuse and a blade in a closed position; Figure 3 is a perspective view of an interlock assembly having an indicator assembly and an actuator assembly according to the preferred embodiment of the invention.
. "* - present invention: Figure 4 is a perspective end view of the actuator assembly shown in Figure 3; Figure 5 is a top perspective view of the indicator assembly shown in Figure 3; Figure 6 is a front view; in perspective of the indicator assembly shown in Figure 3. Figure 7 is a side view of the three-phase fuse switch shown in Figure 1, showing a single phase of the three-phase switch with a blown fuse and the blade in an open position; Figure 8 is a side view of the three-phase fuse switch shown in Figure 1, showing a single phase of the three-phase switch without the fuse and having a blade in the open position Detailed Description of the Preferred Embodiments For a better understanding of the present invention, together with other and additional advantages, and their capabilities, reference is made to the following description and the appended claims , in relation to the drawings described above. As shown in Figure 1, a three-phase switch 10 (shown partially) includes a interlock assembly 12 corresponding to each of its three phases. As shown, the interlock assembly 12 includes an indicator assembly 14 to which an actuator assembly 16 is engaged by a traversing sear arrow 18. The indicator assembly 14 is secured to an interconnecting terminal 19 which is secured to one end of a connector. insulator 20, the other end of which is secured to an end wall 22. The actuator assembly 16 is mounted on the switch wall 22 and has a cover (not shown). The three actuator assemblies 16 corresponding to the three interlock assemblies are coupled together with a cross bar 24 capable of
~, rotate, so that the three phases can be activated simultaneously. Thus, all phases of the switch are opened in response to a blown fuse indication from the indicator set 14 for any of the three phases. An end lever 26 is welded to the end of the cross bar 24 and is pivotally coupled to a trigger release rod 28. By rotating the cross bar 24, the end lever 26 translates the rotational movement of the cross bar 24 into motion horizontal of the shot release rod 28.
This horizontal movement of the firing release rod 28 drives an operating mechanism 32 through a firing lever 34 (shown in Fig. 2), and will be discussed in more detail hereinafter. The operating mechanism 32 is used to simultaneously open or close the three phases of the switch. Figure 2 shows a side view of a single phase of the switch 10 and the operating mechanism 32. Each phase of the switch 10 includes the interlock assembly 12 and a current path defined by a line terminal or inlet 36, a blade 38 , the interconnection terminal 19, a fuse 44 and a load or output terminal 48. The fuse 44 is disposed with one end secured in a fuse pin 42 attached to the interconnection terminal 19. The other end of the fuse 44 is secured in a second fuse pin 46.
The blade 38 is rotatably coupled around a
, .-. blade pivot 40 at one end, and when rotated to a closed position, is electrically coupling at its other end with line terminal 36. In this way, current flows through terminal 19 when switch 10 is on the closed position and fuse 44 is driving. When the blade 38 is rotated about the pivot 40 to an open position where the end of the blade 38 is not electrically coupled to the line terminal 36, the current flowing through the current path is interrupted. The knife pivot 40 is secured to an upper portion 19a of the interconnection terminal 19 and the fuse pin 42 is secured to a lower portion 19b of the interconnection terminal. The interconnection terminal 19 is secured to the insulator 20 with a bolt 50. The second fuse pin 46 is secured to the output terminal 48 and a mounting bracket 52 with a bolt 54 and a nut 56. The mounting bracket 52 is secured to an insulator 58 with a - "" "bolt 60. As shown in figure 2, the blade 38 and the fuse 44 are placed in series with each other. When either the blade 38 is moved to the open position, or the fuse 44 blows, caused by a short-circuit or overload condition, the current flow through the switch is interrupted. The fuse 44 has a indicator pin 61, which extends outwardly when the fuse 44 flies, thereby indicating the state of the fuse 44 and initiating the movement of the blade towards the open position, as will be discussed below. Each phase of switch 10 further includes an arc chute 62, which, for example, may be similar to the arc chute described in U.S. Patent No. 4,362,915, entitled "Electrical Are Confining Device", assigned to it. assignee that the present application, and whose disclosure is incorporated herein by reference. The inlet terminal 36 and the arc chute 62 are secured to an insulator 64, which is secured to the end wall 22 with a set of bolts 66. The insulators 20, 58 and 64 are made of insulating material to insulate the end wall 22 of the current path. Any conventional trigger mechanism can be used with the present invention having means, such as trigger lever 34, to interface with the interlock assembly 12. According to a preferred embodiment form, the mechanism of operation 32 is showing including a traversed detent link 68 coupled to the blade 38 with a pivot pin 70. The link oscillates the blade 38 between the closed position and the open position. Current flows through the current path when the blade 38 is in the closed position and the fuse 44 is present and not blown. The flow of current is prohibited when the blade 38 is in the open position or the fuse 44 is
^ absent or flown. The firing lever 34 is pivotally coupled to a frame 72 through a pivot pin 74 for operating the operating mechanism 32 to move the knife 38 from the closed position to the open position. A collapsible link assembly 76 is coupled to the firing lever 34 to force the blade 38 into the closed position (as shown in Figure 2); the assembly 76 collapses to a non-forcible position when the firing lever 34 is in a firing position (as shown in Figs. 7 and 8), thereby forcing the engaged fastener link 68 to move the blade 38 to the position open The trigger release rod 28 mechanically couples the firing lever 34 to the interlock assembly 12 to move the firing lever 34 toward the firing position, thereby collapsing the collapsible link assembly 76 and moving the fastener link traversed 68 and the knife 38 to the open position. As shown in Figures 3 and 4, the actuator assembly 16 includes a lever 78, a microswitch 80 having an actuator arm 82, and a compression spring 84. A set of screws 86 secure the micro-switch 80 to a clamp 88, which is secured to the wall 22 of the three-phase switch 10. The lever 78 having the cross bar passing through and revolves around it is pivotally coupled to the cross-bolt arrow 18 with a pivot pin 90 at one extreme. A roller pin 92 extends through the cross bar and cooperates with an edge 93 of a slot 94 in a flange 96 extending from the other end of the lever 78. A sleeve 98 is positioned between the lever 78 and the clamp 88 surrounding the cross bar 24. When the fuse 44 flies, the indicator assembly 14 swings the cross-bar arrow 18 in a horizontal direction, which causes the lever 78 to rotate around the cross bar 24. By rotating the lever 78 around the cross bar 24, the edge of the slot 94 forces the cross bar 24 to rotate. The cross bar 24 couples the levers of each actuator assembly of each phase of the three-phase switch 10 to the trigger release rod 28 (FIG. 2), thereby allowing any of the phases to trigger the opening of the blade 38 (FIG. 2). Slot 94 in lever 78 serves an important function: when a fuse blows in one phase, causing the cross bar 24 and thus the pin
"~ * of roller 92 rotate, the roller pin passes through the slot 94 and does not affect the position of the lever 78 in the phases that do not have a blown fuse The micro-switch 80 may be electrically coupled to external devices or alarms, such as indicator lights, bells and horns, to indicate the condition of the fuse A pair of wires 99 is electrically coupled to the microswitch 80 to communicate the condition, either conducted, flown or missing, of the fuse 44 to the external devices As shown in Figures 3, 5 and 6, the indicator assembly 14 includes an indicator skirt 100, a missing fuse skirt 102, a torsion spring 104, a mounting bracket 106, and a pivot pin 108 The indicator skirt 100, the missing fuse skirt 102 and the mounting bracket 106 are coupled to the pivot pin 108. The pivot pin 108 passes through each side of the indicator skirt 100 and the missing fuse skirt. 102, thereby allowing them to rotate. The torsion spring 104 surrounds the pivot pin 108 and has one end engaging the mounting bracket 106 and its other end engaging the missing fuse skirt 102, thereby biasing the skirt towards the fuse 44 in a non-extended position (as shown in FIG. shown in figure 2), when the fuse is present. When the fuse is missing, the torsion spring 104 biases the skirt 102 outward to a "missing fuse" or driven position (as shown in Figure 8). The bolts 110 and the nuts 112 secure the mounting bracket 106 to the interconnecting terminal 19. The indicator skirt 100 is rotatably coupled to the crossed sear arrow 18 with a pivot pin 112., thereby coupling the indicator assembly 14 to the actuator assembly 16. The rotational movement of the indicator skirt 100 is translated into horizontal movement of the traverser arrow 18. This oscillates the actuator assembly 16 and drives the operating mechanism 32 to move the blade. 32 from the closed position to the open position. As shown in Figures 1 and 3, the compression spring 84 has one of its ends rested against the pivot pin 90 and its other end resting against the switch wall 22. The spring biases the pivot pin 90 towards the arm 82 and compresses it, thereby activating the microswitch 80 when the fuse 44 is driving. As will be described later, the micro switch 80 is deactivated when the fuse is blown or absent. Although the use of the spring 84 is shown and described above, its use is not required because the weight of the indicator skirt 100 uses gravity to polarize the traverser arrow 18 toward the position shown in Figure 3. operation of the interlock assembly 12 will now be discussed. Figure 2 shows the blade 38 in the closed position, the fuse 44 leading and the microswitch 80 in the active position. As shown in Figure 7, when the fuse 44 detects an overcurrent or short circuit condition, it will fly, causing the extending pin 61 to extend outward, forcing the indicator flap 100 to rotate clockwise. The clockwise rotation of the indicator flap 100 pulls the fastener arrow through 18 horizontally in the direction of the direction arrow 112, causing the lever 78 to rotate counterclockwise. By turning the lever 78 counterclockwise, the roller pin 92 links one end of the slot 94, thereby causing the cross bar 24 to rotate clockwise. The rotation of the cross bar 24 in the clockwise direction causes the end lever 26 to rotate in that direction. The rotation of the end lever 26 clockwise causes the trigger release rod 28 to perform a translatory movement in the direction of the direction arrow 114, which causes the trigger lever 34 to rotate counterclockwise around the pivot pin 74, towards the firing position shown in the figure. Moving the trip lever 34 to the firing position causes the link assembly 76 to collapse, thereby forcing the traverser linkage 68 to pull the blade 38 away from engagement with the entry terminal 36 and toward the open position. Because the operating mechanism 32 controls all phases of the switch 10, this action causes the operating mechanism 32 to move the blades of each phase to the open position. As the locked sear arrow 18 moves in the direction of the direction arrow 112, the pivot pin 90 is pulled away from the micro-switch actuator arm 82, thereby allowing it to move to its non-actuated position and deactivating the microswitch. 80. This action indicates to the external devices (not shown) that the fuse 44 has flown. Until the blown fuse is replaced with a good, conductive fuse, which has its extension pin 61 there lowered, the blade 38 is prevented from being moved to the closed position, because the extension pin 61 maintains the interlock assembly. 12 in the actuated position shown in Figure 7. With the extending pin 61 extended, the indicator skirt 100 remains rotated in the clockwise direction, which keeps the sear arrow through 18 in the oscillated position, thereby keeping the lever 78 in the position in the clockwise direction. With the trigger lever 78 in the position in the clockwise direction, the trigger release rod 38 is held in the position shown in Figure 7, thereby maintaining the firing lever 34 in the firing position or clockwise. With the firing lever 34 in the firing position, the link assembly 76 remains collapsed and can not move the blade 38 to the closed position. Figure 8 shows that the blade 38 is prevented from being moved to the closed position when the fuse is not present. As shown in Figures 2 and 7, the missing fuse skirt 102 is biased to bond with one side of the fuse 44 by means of the torsion spring 104. However, as shown in Figure 8, when the fuse is missing , the torsion spring 104 forces the missing fuse skirt 102 to rotate outward in a clockwise direction towards the area where the fuse would normally be located. The rotation of the missing fuse skirt 102 clockwise causes the indicator flap 100 to rotate clockwise to the actuated position, thereby keeping the fire lever 34 in the firing position e. preventing blade 38 from being closed, as previously described. An exemplary fuse that can be used as a fuse 44 is available as part No. AO55F-1DSR0-200E, from Square D Company of Palatine, Illinois, United States. The extension pin 61 is an integral part of the fuse and extends outwardly when the fuse blows due to a short circuit or overcurrent condition in the circuit it is protecting. The micro-switch 80 is available as part No.
MT-4RV-A28 from Honeywell, Minneapolis, Minnesota, United States. Although those currently considered to be the preferred embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention, as defined herein. by the appended claims.