SHUTTER DEVICE FOR METAL-ENCLOSED SWITCHGEAR

Abstract: A shutter device for metal-enclosed switch gear (1) of the type having a swich box (2) provided with disconnecting parts (4A, 4B) adapted to be connected electrically by a circuit breaker when the latter is inserted into the switch box (2). The shutter device (11) has shutters (12) movable into and out of positions for covering the disconnecting parts (4A, 4B) a vertically movable rod (13) supporting the shutters (12), an operating lever (14) connected at its one end (15A) to the rod and rotatable around a fulcrum (17), and an operating roller (20) provided on the circuit breaker (8) and adapted to roll on the portion (14B) of the operating lever (14) between the fulcrum (17) and the entrance-side end (15B) of the actuating lever (14) thereby to rotate the actuating lever (14) around the fulcrum (17) to move the shutters (12) into and out of the covering positions. According to this arrangement, it is possible to manipulate the actuating lever (14) at a portion (14B) of the latter remote from the electrically charged disconnecting parts (4A, 4B) so that the works such as inspection, protective maintenance and so forth can be conducted without the fear of dangerous contact of the operator's hand with the electrically charged disconnecting parts (4A, 4B).

Description: SHUTTER DEVICE FOR METAL-ENCLOSED SWITCHGEAR BACKGROUND OF THE INVENTION The present invention relates to a shutter device for metal-enclosed switchgear and, more particularly, to an improvement in the construction of fulcrum for an actuating lever for opening and closing the shutter device. In general, metal-enclosed switchgear has a circuit breaker adapted to be detachably inserted into a switch box so as to contact the disconnecting parts provided in the box, each group of which are connected to the source side and the load side. Thereby to selectively connect and disconnected the electric connection between the source side and the load side. For inspecting the equipments/devices in the switch box or the circuit breaker, the circuit breaker is withdrawn from the switch box so that the live disconnecting parts are exposed dangerously. Therefore, in order to avoid any accidental contact, such a shutter device is provided in the switchgear to cover the disconnecting parts when the circuit breaker is withdrawn from the switch box and to uncover the same in advance to the insertion of the circuit breaker into the switch box. The shutter device has a shutter to cover and uncover the disconnecting parts and a rod supporting the shutter. The rod is attached to one end of an actuating lever supported by a fulcrum provided on the side wall of the switch box. The actuating lever is adapted to make an engagement with an operating roller provided on the circuit breaker. The arrangement is such that, as the circuit breaker is inserted into and withdrawn from the switch box, the actuating lever is rotated up and down around the fulcrum so that the shutter is also moved up and down to cover and uncover the disconnecting parts. In order to obtain a large vertical stroke of the shutter device, in general the fulcrum is located at the entrance side end on the operating lever, i.e. at an opposite end remote from the shutter to provide a large length of the rod between the fulcrum and the shutter. To the contrary, for making an inspection of the either group of dead disconnecting parts (i.e. source or load side) such as measurement of the insulation resistance after the withdrawal of the circuit breaker, the operator has to take a labour of lifting the actuating lever to uncover the disconnecting parts. This requires a considerable force because the fulcrum is located near the entrance side end of the actuating lever. In addition, there is a fear that the operators body accidentally touch the live side disconnecting parts because the actuating lever is to be held during this work by the operator at a portion thereof near the disconnecting parts. SUMMARY OF THE INVENTION Accordingly, an object of the invention is to provide a shutter device for metal-enclosed switchgear improved to ensure a safe opening and closing operation of the shutter. To this end, according to the invention, there is provided a shutter device in which the fulcrum for the actuating lever is provided at the point which permits a natural falling down of the shutter-side portion of the actuating lever due to the weight of the shutter and the rod against to that of the entrance side end of the actuating lever. In addition, the actuating lever is adapted to be slided from the top or bottom surface by means of rollers provided on the circuit breaker. According to this arrangement, normally the actuating lever usually takes a lowered state to make the shutter cover the;disconnecting parts, due to the weight of the shutter and the shutter rod, but the moments acting on both arms, i.e. the portions of the operating arm at both sides of the fulcrum are substantially balanced by each other. Therefore, by applying a minimum force to the entrance side end of the actuating lever, the operator can easily move the shutter to cover and uncover the disconnecting parts. In addition1 since the entrance side end of the actuating lever at which the latter is manipulated is sufficiently far from the disconnecting parts, there is no fear that the operator accidentally touch the live disconnecting parts. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional side elevational view of a metal enclosed switchgear incorporating a shutter device embodying the present invention; Fig. 2 is a sectional side elevational view of a shutter device; Fig. 3 is a side elevational view of an actuating lever; Figs. 4 and 5 are side elevational views of different examples of the actuating lever; Fig. 6A is a sectional plan view of a stopper mechanism; and Figs. 6B and 6C are side elevational views of the actuating lever. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention will be explained hereinunder with reference to the accompanying drawings. Fig. 1 shows a metal-enclosed switchgear 1 to which the present invention is applied. The metalenclosed switchgear 1 has a switch box 2 which is provided at its one side with an entrance adapted to be opened and closed by means of a door 2A. A partition wall 3 is mounted in the switch box 2. An upper disconnecting parts 4A secured to the partition wall 3 is connected to source-side conductors 5 having three phases, while a lower disconnecting parts 4B also secured to the partition wall 3 is connected to load-side conductors 6 having three phases. The source-side conductors 5 are connected to source BUS 7 while the load-side conductors 6 are connected to a load which is not shown. These disconnecting parts 4A, 4B are adapted to be contacted at their other sides by disconnecting contacts 9 of a circuit breaker 8. The circuit breaker 8 is provided with wheels 10 by means of which it is easily moved into the switch box to connect the contacts 9 with the disconnecting parts 4A and 4B. As the circuit breaker 8 is drawn out from the breaker compartment, the contacts 9 are electrically separated from the disconnecting parts 4A and 4B to expose the disconnecting parts 4A and 4B either or both of which are charged electrically to high voltage. In order to avoid accidental contact with the disconnecting parts, therefore, a shutter device 11 is provided to cover and uncover the disconnecting parts in accordance with withdrawal and insertion of the circuit breaker into the switch box. The detail of the shutter device 11 will be explained hereinunder with specific reference to Fig. 2. The shutter device 11 has shutters 12 adapted for covering the disconnecting parts 4A, 4B and secured to a rod 13 at a constant interval. The rod 13 is fixed by means of a fixing means 16 to one end 15A of an operating rod 14 adjacent to the rod 13. The actuating lever 14 extends along the side wall of the switch box. The side wall is designated at reference numeral 22 in Fig. 6. The actuating lever 14 is rotatably supported by a fulcrum 17 fixed to the wall of the switch box. Therefore, as the entrance-side end 15B of the actuating lever 14 is pressed, the actuating lever 14 is moved up and down around the fulcrum 17, so that the shutters 12 uncover and cover the disconnecting parts 4A, 4B. The position of the fulcrum 17 will be explained with specific reference to Fig. 3. The length of the first portion of the operating lever 14, between the rod-side end 15A and the fulcrum 17, is represented by held while the length of the second portion of the same between the fulcrum 17 and the entrance-side end 15B is represented by Q2. Representing the total weight of the shutter 12 and the rod 13 by W and the force applied to the entrance-side end 15B by F, the position of the fulcrum is selected to meet the following condition: A < B *.-*----- (1) where A represents the product of the length Q1 and the weight W, while B represents the product of the length Q2 and the force F. In other words, the fulcrum is located at the point which permits the natural falling down of the actuating lever 14 by the weights of the shutter and the rod against to that of the entrance-side rod. This position of fulcrum is usually located at a point 14C near the mid point of the actuating lever. The circuit breaker 8 is provided with an operating roller 20 adapted to engage the upper surface of the actuating lever 14 to rotate the actuating lever 14 up and down around the fulcrum 17 in accordance with the insertion and withdrawal of the circuit breaker 8 into and out of the switch box. In other words, the operating roller rolls on the upper surface of the second portion 14B. By locating the fulcrum 17 at a point 14C substantially coinciding with the mid point of the actuating lever, the aforementioned product A takes a value greater than the product B when the circuit breaker 8 has been withdrawn from the breaker compartment. Namely, the moment on the first portion 14A of the actuating lever is greater than that on the second portion by an amount corresponding to the total weight of the shutter 12 and the rod 13. Therefore, a balance of moment is obtained when the actuating lever takes the position illustrated by chain line in which the first portion 14A is lowered while the second portion 14B is raised around the fulcrum 17. In this state, the disconnecting parts are covered by the shutter 12. As the operator applies a force F to the entrance-side end 15B in the direction of the arrow Y, the product B comes to take a value greater than the product A. In consequence, the second portion 14B is rotated downward while the first portion 14A is rotated upward around the fulcrum 17, so that the actuating lever takes a position shown by solid line in Fig. 2. In consequence, the shutters 12 are moved upward to uncover the disconnecting parts. As has been described, the balance of moment is maintained in such a state that the first portion of the operating lever is lowered as compared with the second portion of the same by a height corresponding to the weight of the shutter and the rod. Therefore, as a force is applied to the second portion, the shutters are moved easily to uncover the disconnecting parts. It is thus possible to operate the shutter with minimum manual force exerted by the operator to cover and uncover the disconnecting parts, as desired. In addition, since the entrance-side end 15B of the actuating lever touched by the operator is sufficiently far from the disconnecting parts 4, the fear of accidental contact of the human body with the electrically charged disconnecting parts 4A, 4B is completely avoided. Needless to say, the fulcrum 17 may be provided on the portion of the lever 14 between the rod-side end 15A and the entrance-side end 15B. Fig. 4 shows another embodiment in which an auxiliary roller 20A is mounted on the portion of the circuit breaker 8 corresponding to the second portion of the actuating lever 14 besides the aforementioned operating roller 20 mounted on the portion of the circuit breaker 8 corresponding to the first portion 14A. By so doing, it is possible to completely avoid the undesirable lowering of the shutters 12 in the operating state in which the contacts 9 of the circuit breaker 8 are held in contact with the disconnecting parts 4A, 4B. Namely, as the operating roller 20 is rolled to the first portion of the actuating lever beyond the fulcrum 17, the roller 20 acts to depress the first portion of the actuating lever 14 downwardly as indicated by an arrow Y1 to cause a tendency to move the second portion of the same upwardly as indicated by an arrow Y2 This tendency, however, is perfectly suppressed by the auxiliary roller which acts to depress the second portion 14B. In this embodiment, the second portion 14B of the actuating leer 14 is provided with an upward protrusion 24 which projects above the level of the first portion 14A when the actuating lever 14 takes the position shown by chain line in Fig. 2. As the entrance-side end 15B of the protruded second protion is depressed, the shutter 12 is raised without delay so that it is possible to increase the speed of uncovering action of the shutter. Fig. 5 shows still another embodiment in which the shutter device 11 is constructed to include a downward protrusion 24A, and a tension spring 13A which pulls the rod 13 and the shutters 12 upwardly when the circuit breaker 8 is not contained in metal-enclosed switchgear 1. The tension spring 13A is stretched between the supporting tabs 13B and 13C provided on the rod 13. The shutter device 11 of this embodiment operates in a manner explained hereinunder. Namely, as the circuit breaker 8 is moved toward the disconnecting parts 4A, 4B, the operating roller 20 rolls in contact with the lower side of the protrusion 24A, so that the actuating lever 14 is raised to the position shown by chain line from the position shown by solid line around the fulcrum 17. In consequence, the rod 13 is lowered while loading the tension spring 13A. In this state, the shutters 12 uncover the disconnecting parts 4 to expose the latter. Then, as the circuit breaker 8 is drawn out from the metal-enclosed switchgear 1, the tension spring 13A releases the energy to take the position shown by the solid line so that the shutters 13 covers the disconnecting parts 4A, 4B. As the operator lifts the entrance-side end 15B, it is possible to further lower the shutter 12 to achieve the same result as the foregoing embodiments. Figs. 6A, 6B and 6C show a further embodiment of the invention having a stopper mechanism adapted to prevent an unintentional operation of the shutter due to any accidental touch on the actuating lever by the operator when the circuit breaker 8 has been drawn out from the switch box 2. Namely, a case 23 is provided on the side wall 22 of the switch box opposing to the actuating lever 14. The case 23 accommodates a pressing plate 25 loaded by a spring 24 and a stopper 26 provided on the pressing plate 25. The stopper 26 continuously urges the actuating lever 14. As will be seen from Fig. 6B, the actuating lever 14 is provided with a through hole for receiving the stopper 26. Then, as the actuating lever 14 is moved to the position shown in Fig. 6C, the stopper 26 is inserted into the through hole 27 to prevent the rotation of the actuating lever 14. For withdrawing the stopper 26 from the through hole 27, one end 25A of the pressing plate 25 movable in an elongated hole (not shown) in the case 23 is moved away from the actuating lever 14 to move the stopper 26 out of the through hole 27 In this embodiment, thanks to the provision of the stopper which prevents the rotation of the actuating lever 14, it is possible to avoid unintensional operation of the shutter due to accidental touch on the actuating lever by the operator. When the circuit breaker 8 has been drawn out from the switch box 2. In consequence, the danger of accidental touch of the human body with the electircally charged disconnecting parts is completely eliminated. As has been described, according to the invention, the actuating lever can be rotated with minimum force because the fulcrum thereof is located substantially at the mid point. In addition, since the entrance-side end of the actuating lever at which the actuating lever is manipulated by the operator is located remote from the contact sections, the danger of accidental touch of the operator's body with the electrically charged disconnecting parts is avoided to ensure the safety in the work such as protective maintenance and inspection.

Claims: Patent Claims: 1. In a shutter device for a metal-enclosed switchgear (1) having a switch box (2) provided with an entrance through which a drawout type electrical apparatus (8) comes in and out of the switch box (2) and disconnecting parts (4A, 4B) for connection and disconnection with said electrical apparatus (8) in said switch box (2), said shutter device (11) including shutters (12) for opening and closing said disconnecting parts (4A, 4B), a vertically movable rod (13) for supporting said shutters (12), an actuating lever (14) connected to one end of said rod (13) for swinging movement around a fulcrum (17) provided on the side wall of said switch box (2) to move said rod (13) up and down, and an operating part (20) provided on said drawout type electrical apparatus (8) for swinging said actuating lever (14) around its fulcrum (17) by pushing and drawing said electrical apparatus (8) within said switch box (2), characterized in that said fulcrum (17) is disposed between the ends of said actuating lever (14) on the side of said rod (13) and on the side of said entrance. 2. A shutter device for enclosed switchboards as claimed in claim 1, characterized in that said fulcrum (17) is disposed between the rod side end and the entrance side end (15B) of said actuating lever (14) nearer to the latter than a point where said actuating lever (14) naturally descends by the action of the weights of said shutters (12) and said rod (13). 3. A shutter device as claimed in claims 1 and 2, characterized in that said operating part (20) is disposed on the side wall of said drawout type electrical apparatus (8) at a location where it can slide on the upper surface of said actuating lever (14) between said fulcrum (17) and the entrance side end (15B) of said actuating lever (14). 4. A shutter device for enclosed switchboards as claimed in claims 1 or 2, characterized in that said actuating lever (14) is formed at a first area between said fulcrum and the entrance side. end tlSB) thereof with a portion (14A) which protrudes above a portion at a second area between said fulcrum (17) and the rod side end (15A) of said actuating lever (14). 5. In a shutter device for a metal-enclosed switch gear (1) having a switch box (2) provided with an entrance through which a drawout type electrical apparatus (8) comes in and out of the switch box (2) and disconnecting parts (4A, 4B) for connection and disconnection with said electrical apparatus (8) in said switch box (2), said shutter device (11) including shutters (12) for opening and closing said disconnecting parts (4A, 4B), a vertically movable rod (13) for supporting said shutters (12), an actuating lever (14) connected to one end of said rod (13) for swinging movement around a fulcrum (17) provided on the side wall of said switch box (2) to move said rod (13) up and down, and an operating part (20) provided on said drawout type electrical apparatus (8) for swinging said actuating lever (14) around a fulcrum (17) by pushing and drawing said electrical apparatus (8) within said switch box (2), characterized in that, when said drawout type electrical apparatus (8) is operably in contact with said disconnecting parts (4A, 4B), said shutter device (11) comprises a fulcrum (17) provided between the ends of said actuating lever (14) on the side of said rod and on the side of said entrance, an operating part (20) and an auxiliary operating part (20A) provided on the side wall of said drawout type electrical apparatus (8) and adapted to contact the rod side end (14A) and the entrance side end (14B) of said actuating lever (14), respectively, with said fulcrum (17) between said parts. 6. In a shutter device for a metal-enclosed switch gear (1) having a switch box (2) provided with an entrance through which a drawout type electrical apparatus (8) comes in and out of the switch box (2) and disconnecting parts (4A, 4B) for connection and disconnection with said electrical apparatus (8) in said switch box (2), said shutter device (11) including shutters (12) for opening and closing said disconnecting parts (4A, 4B), a verti- cally movable rod (13) for supporting said shutters (12), an actuating lever (14) connected to one end of said rod (13) for swinging movement around a fulcrum (17) provided on the side wall of said switch box (2) to move said rod (13) up and down, and an operating part (20) provided on said drawout type electrical apparatus (8) for swinging said actuating lever (14) around a fulcrum (17) by pushing and -drawing said electrical apparatus (8) within said switch box (2), characterized in that said shutter device (11) comprises a fulcrum (17) provided between the ends of said actuating lever (14) on the side of said rod (13) and on the side of said entrance, a protruding portion (14B) provided at a first area between the fulcrum (17) and the entrance side end (15B) of said actuating lever (14) and extending downwardly beyond a second area between the fulcrum and the rod side end (1.3)3) of said actuating lever (14), an operating part (20) adapted to slide along the lower surface of said protrudincj portion (14B), and a tension spring (13A) mounted on said rod (13) for storing energy when said operating part (20) slides on the protruding portion (14B) to lower said rod (13) through the medium of said fulcrum (17). 7. A shutter device for metal-enclosed switch gear as claimed in clams 1 through 6, characterized in that said operating part (20) comprises an operating roller. 8. A shutter device for metal-enclosed switch gear as claimed in claim 5, characterized in that said auxiliary operating part (20A) comprises an auxiliary roller. 9. A shutter device for metal-enclosed switch gear as claimed in claims 1 through 8, characterized by a stopper mechanism including a resilient member (24) mounted on the side wall (22) of said switch box (2) and a stopper (26) biased by said resilient member (24) to protrude into a through hole (27) formed in said actuating lever (14). 10. A shutter device for metal-enclosed switch gear as claimed in claims 1, 5 and 6, characterized in that said fulcrum (17) is disposed between the rod side end (14A) and the entrance side end (14B) of said actuating lever (14) nearer to the latter than a point where said 'actu- ating lever (14) naturally descends by the action of the weights of said shutters and said rod.

Inventors: IDA, MITSUYOSHI, MATSUZAKI, ATSUHIDE
Applicants: HITACHI, LTD.
Application year: 1982
Main classification: H02B11
IPC codes: H02B11