GB2116368A

GB2116368A - Enclosed switchboard door interlock

Info

Publication number: GB2116368A
Application number: GB08305718A
Authority: GB
Inventors: Toshitaro Yamamoto; Toshiro Takagi; Yoshinobu Kihara
Original assignee: Meidensha Corp; Meidensha Electric Manufacturing Co Ltd
Current assignee: Meidensha Corp; Meidensha Electric Manufacturing Co Ltd
Priority date: 1982-03-06
Filing date: 1983-03-02
Publication date: 1983-09-21
Also published as: GB2116368B; GB8305718D0; IN160963B; SG82985G; MY8600346A

Abstract

An interlock device for an enclosed switchboard whereby the operation handle 8 can be locked automatically when the switchboard door 4 is left opened but is unlocked when the door is kept closed. The interlock device 7 is made up of only mechanical elements without use of any electrical elements such as relays or magnets, it is easy to repair, thus enhancing the safety. The device 7 comprises a pivoted disk 24, a disk latch 30 arranged so as to lock or unlock the disk 24 in relation to the closing or opening of the switchboard door 4, a door latch 32 to lock or unlock the switchboard door in relation of the angular position of the disk 24 (on or off position of a switching device). Further, a mechanically fragile portion is intentionally formed in the operation handle 8 to prevent the interlock device from being damaged and the switching device from being closed carelessly. <IMAGE>

Description

SPECIFICATION Interlock device for enclosed switchboard The present invention relates generally to an interlock device used for an enclosed switchboard and more specifically to an interlock device which can lock an operation handle so that a switching device disposed within an enclosed switchboard is not allowed to be closed when the switchboard door is left opened and unlock the operation handle so that the switching device is allowed to be closed only when the switchboard door is kept closed; in other words, which can allow the door to be opened only when the switching device is kept opened or allow the switching device to be closed only when the door is kept closed.

In an enclosed switchboard, various switches, meters, protection devices, etc. are arranged on a switchboard front panel; a circuit breaker, a disconnecting switch, bus bars, an earthing device, etc, are arranged within a switchboard casing in order to protect these electrical devices from dust and moisture and additionally to enhance safety.

In such an enclosed switchboard described above, in the case where some trouble occurs in the circuit breaker, for instance, or it is necessary to take out the circuit breaker from the switchboard for maintenance, first the switchboard panel is opened; secondly an operation handle is moved upward or downward to open a disconnecting switch for cutting off a high-voltage power supply from the circuit breaker; thirdly an inner door-like partition is moved frontward; lastly the circuit breaker is pulled out from the enclosed switchboard.In contrast with this, in the case where the circuit breaker is installed within the enclosed switchboard again, first the circuit breaker is pushed in within the switchboard; secondly the inner doorlike partition is moved backward, thirdly the operation handle is moved downward or upward to close the disconnecting switch for applying a high-voltage power supply again to the circuit breaker; lastly the switchboard panel is closed.

In the process of opening or closing the doorlike partition of the enclosed switchboard, in case the door-like partition is opened when the disconnecting switch is left closed, that is, a highvoltage power supply is left applied to the circuit breaker, this condition is very dangerous and may result in such an accident that the operator is killed by an electric shock. Therefore, there is generally provided a safety device called an interlock device within the enclosed switchboard.

This interlock device allows the door-like partition to be opened only after the disconnecting switch has been kept opened to cut off a high-voltage power supply from the electrical device, so that the operator can enter the enclosed switchboard safely. Further, the disconnecting switch can be closed for application of a high-voltage power supply to the circuit breaker only after the inner door-like partition has been closed perfectly.

Furthermore, the door-like partition is locked whenever the disconnecting switch is kept closed.

In the above-mentioned interlock device, conventionally, electrical interlock devices or electromechanical interlock devices are well known.

As the former example, it is possible to cite an interlock device as follows: In the case where a high-voltage is applied to a circuit breaker arranged within the enclosed switchboard, electric charge developed near the circuit breaker is detected by an appropriate sensor; a relay is energized in response to a signal from the electric-charge sensor to activate an electromagnet; the enclosed switchboard door is locked by the electromagnet.

As the latter example, it is possible to cite an interlock device as follows: In the case where a high-voltage is applied to a circuit breaker arranged within the enclosed switchboard, electric charge developed near the circuit breaker is detected; a warning lamp is lit up and a relay is energized to actuate a mechanical device; the enclosed switchboard door is locked by the mechanical device.

The above-mentioned electrical or electromechanical interlock devices have some drawbacks or shortcomings. The basic problems are: (1) Another power supply is required to activate or actuate the electrical interlock device.

(2) Complicated steps are required when assembling the device using electrical elements and mechanical elements.

(3) It is relatively difficult to distinguish trouble due to mechanical elements from that due to electrical elements or vice versa.

(4) Probability of occurrence of trouble due to electrical elements is relatively high as compared with that due to mechanical elements.

For the reasons described above, it is rather preferable to construct the interlock device for an enclosed switchboard by the use of only mechanical elements.

Further, as described above, an interlock device is usually incorporated within the enclosed switchboard in order to prevent such an accident that the operation handle is erroneously operated to close the disconnecting switch when the switchboard door is open and therefore the operator is killed by an electric shock. However, in case the operation handle is operated erroneously by an excessive force in the direction to close the disconnecting switch in spite of the fact that the interlock device is functioning, there further exists such a danger thah the interlock device may be damaged and therefore the operation handle can easily be moved to a position at which the disconnecting switch is closed unintentionally when the switchboard door is left open.

For the reason described above, it is rather preferable to disable the operation handle for the interlock device for an enclosed switchboard before the interlock device is damaged due to erroneous operation such that an excessive force is carelessly applied to the operation handle.

With these problems in mind, therefore, it is the primary object of the present invention to provide an interlock device for an enclosed switchboard which is made up of only mechanical elements without use of any electrical elements such as relays, electromagnets, etc.

To achieve the above-mentioned object, the interlock device for an enclosed switchboard according to the present invention comprises an operation handle, a pivotable disk having a latch lock member, a link rod connected between the pivotable disk and a switching device, a triangular disk latch having a disk latch pawl and a disk latch slot, a disk latch actuator having an actuator rod, an actuator pin, and a spring, a partition latch having a partition latch pawl and a partition latch pin, a partition latch lever having an elongate latch lever slot, etc.

The disk latch locks or unlocks the pivotable disk in relation to the opening or closing of the door-like partition and the partition latch locks or unlocks the door-like partition in relation to the angular motion of the pivotable disk or the closing or opening of the disconnecting switch.

Since the interlock device according to the present invention is made up of only mechanical elements without use of any other electrical elements, it is easy to troubleshoot defective elements and to repair the device, while improving the life time.

The other object of the present invention is to provide an operation handle which is disabled easily into damage or bend intentionally whenever an excessive force is applied to the operation handle, before the interlock device is damaged or further the disconnecting switch is closed dangerously due to erroneous operation while the switchboard door is left opened.

To achieve the above-mentioned object, the operation handle according to the present invention comprises a handle rod including a mechanically fragile portion at an appropriate position of the handle rod. The fragile portion is a neck or a notch formed in the handle rod or a joint member sandwiched between two tubular handle rods.

The features and advantages of the interlock device for an enclosed switchboard according to the present invention will be more clearly appreciated from the following description of the preferred embodiments of the invention taken in conjunction with the accompanying drawings in which like reference numerals designate the same or similar elements or sections throughout the figures thereof and in which; Fig. 1 is a pictorial view of an exemplary enclosed switchboard for assistance in explaining the function of the interlock device according to the present invention; Fig. 2 is an enlarged diagramatical side view of the interlock device according to the present invention, in which the door-like partition is closed but the operation handle is not yet moved downward to close a disconnecting switch, both the latches being disengaged from both the latch lock members, respectively;; Fig. 3 is an enlarged diagrammatical side view of the interlock device according to the present invention for assistance in explaining the operation thereof, in which a door-like partition is closed, and an operation handle is moved downward to close a disconnecting switch, so that the door-like partition is locked by a partition latch; Fig. 4 is an enlarged diagrammatical side view of the interlock device according to the present invention for assistance in explaining the operation thereof, in which the operation handle is moved upward to open the disconnecting switch and the door-like partition is opened, so that the operation handle is locked by a disk latch; Fig. 5 is a side view of a first embodiment of the operation handle used for the interlock device according to the present invention;; Fig. 6 is a cross-sectional view taken along the line VI--VI shown in Fig. 5; Fig. 7 is a side view of a second embodiment of the operation handle used for the interlock device according to the present invention; Fig. 8 is a cross-sectional view taken along the line VIll-Vill shown in Fig. 7; and Fig. 9 is an enlarged fragmentary crosssectional view of a third embodiment of the operation handle used for the interlock device according to the present invention.

To facilitate understanding of the present invention, a brief reference will be made of the structure of an exemplary enclosed switchboard within which the interlock device according to the present invention is installed, with reference to the attached drawing.

In Fig. 1, an enclosed switchboard 1 is made up of a casing 2, a door panel 3 and a door-like partition 4. Within the enclosed switchboard 1, there are mainly arranged a circuit breaker 5, a disconnecting switch 6 and an interlock device 7.

Further, the reference numeral 8 denotes an operation handle linked with a link rod 9 via the interlock device 7 to close or open the disconnecting switch 6;-the reference numeral 10 denotes three bus-supporting insulators; the reference numeral 11 denotes power supply bus bars connected to the disconnecting switch 6 via a branched bus; the reference numeral 12 denotes a bus supporting insulator; the reference numeral 13 denotes a load cable connected to the circuit breaker 5 via a load bus 1 3a; the reference numeral 14 denotes a cable supporting member.

In the enclosed switchboard 1, when access to the circuit breaker 5, for instance, is required for checking or maintenance, first it is necessary to open the disconnecting switch 6 by operating the operation handle 8 for cutting-off a high-voltage power supply from the circuit breaker 5. Fig. 1 shows a state where the operation handle 8 is moved upward and the link rod 9 is shifted toward the left to open the disconnecting switch 6 in such a way that a movable blade 6a is kept apart from a fixed blade 6b.

In this case, if the door-like partition 4 is first opened carelessly when the disconnecting switch 6 is closed, that is, when a high-voltage power supply is left applied to the circuit breaker 5, this condition is seriously dangerous because the operator may be killed by an electric shock. To prevent such dangerous condition, there is usually provided an interlock device 7 within the enclosed switchboard 1.This interlock device 7 serves as a safety device as follows: the door-like partition 4 can be opened only after the operation handle 8 has been moved upward to open the disconnecting switch 6; the operation handle 8 can be moved downward to close the disconnecting switch 6 only after the door-like partition 4 has been closed perfectly; the door-like partition 4 can be locked perfectly in the closed condition except the case where the operation handle 8 has been moved upward to open the disconnecting switch 6.

The interlock device 7 according to the present invention will be described hereinbelow in more detail with reference to Figs. 2, 3 and 4.

The interlock device 7 can be divided mainly into four sections: a pivotable disk section supported by a disk supporting member 20, a disk latch section supported by a disk latch supporting member 21, a partition latch section supported by a partition latch supporting member 22, and a partition latch lever 23.

The disk supporting member 20 is fixed in position within the enclosed switchboard 1, on which a pivotable disk 24 is pivotably supported through a shaft 25. To the pivotable disk 24, a handle supporting member 26 is fixed. The operation handle 8 is fixed to the handle supporting member 26 in an appropriate method (explained later in more detail with reference to Figs. 5 to 9). Therefore, when the operation handle 8 is moved up and down with the shaft 25 as its pivot, the pivotable disk 24 is rotated clockwise or counterclockwise.Further, a link rod 9 is pivotably connected to the pivotable disk 24 via a pin 24a so that when the pivotable disk 24 is pivoted clockwise (the operation handle is moved upward), the link rod 9 is shifted toward the left in the figure to open a disconnecting switch 6, for instance, and when the pivotable disk 24 is pivoted counterclockwise (the operation handle is moved downward), the link rod 9 is shifted toward the right in the figure to close the disconnecting switch 6.Additionally, the partition latch lever 23 is also pivotably connected to the pivotable disk 24 via a pin 24b, an angular distance away from the position where the link rod 27 is pivoted, so that when the pivotable disk 24 is pivoted clockwise (the operation handle is moved upward), the partition latch lever 23 is moved downward and when the pivotable disk 24 is pivoted counterclockwise (the operation handle is moved downward), the latch lever 23 is moved upward. Furthermore, a latch lock member 28 is fixed to the pivotable disk 24 an angular distance further away from the position where the latch lever 23 is pivoted.

The disk latch supporting member 21 is fixed in position near the circumferential portion of the pivotable disk 24 within the enclosed switchboard 1, on which a disk latch actuator 29 is fixed and a triangular disk latch 30 is pivotably supported through a shaft 31. The disk latch actuator 29 includes a pair of actuator rod guide plates 29a standing upright from the surface of the disk latch supporting member 21, an actuator rod 29b slidably passed through the central holes formed in a pair of the actuator rod guide plates 29a, and a coil spring 29c disposed between the flange portion 29b' near the end portion of the actuator rod 29b and one of the actuator rod guide plates 29a so as to urge the actuator rod 29b toward the door-like partition 4.Further, when the door-like partition 4 is opened toward the left in Fig. 2, the actuator rod 29b is urged toward the left by the elastic force of the coil spring 29c; however, when the door-like partition 4 is closed toward the right, the actuator rod 29b is pushed toward the right against the elastic force of the coil spring 29c by the flat surface of a partition latch lock plate 4a formed integrally with the door-like partition 4. Furthermore, an actuator pin 29d is implanted perpendicular to the surface of the disk latch supporting member 21 at an appropriate position on the actuator rod 29b.

The triangular disk latch 30 is pivotably supported by the shaft 31 on the disk latch supporting member 21 at one apex thereof, having a disk latch pawl 30a formed at another apex thereof in such a way as to be engageable with the latch lock member 28, and a disk latch slot 30b formed at the other apex thereof so as to be engageable with the actuator pin 29d implanted in the actuator rod 29b.

The partition latch supporting member 22 Is fixed in position near the disk latch supporting member 21, on which a partition latch 32 is pivotably supported through a shaft 33. The partition latch 32 is formed with a partition latch pawl 32a in such a way as to engageable with the partition latch lock plate 4a of the door-like partition 4. Further, a partition latch pin 32b is fixed to the door-like partition latch 32 on the side opposite to the partition latch pawl 32a in such a way as to engageable with an elongate latch lever slot 23a formed at the end portion of the partition latch lever 23. Further, the partition latch lever 23 is positioned over the disk latch actuator 29 and the triangular disk latch 30 without contacting with these elements when moved.

Furthermore, the length of the elongate latch lever slot 23a must be sufficient to disengage the partition latch pawl 32a from the partition latch lock plate 4a of the partition 4 and to engage therewith when the pivotable disk 24 is rotated clockwise or counterclockwise, for instance, through an angle of 90 degree and therefore the partition latch lever 23 is moved to its extreme ends.

The operation of the interlock device according to the present invention will be explained hereinbelow with reference to Figs. 3 and 4. Fig. 3 shows the state where the door-like partition 4 is closed and simultaneously kept locked and the operation hapndle 8 is moved downward to close the disconnecting switch.

The partition 4 will not be opened immediately in this state shown in Fig. 3, because the partition latch pawl 32a of the partition latch 32 is engaged with the latch lock plate 4a of the partition 4. Therefore, the operator must first move the operation handle 8 upward. When the handle 8 moves upward, the pivotable disk 24 rotates clockwise, so that the link rod 9 is shifted to open the disconnecting switch (not shown) and simultaneously the partition latch lever 23 is moved downward. When the partition latch lever 23 moves downward, the upper end of the elongate latch lever slot 23a is brought into contact with the partition latch pin 32b and further moves the partition latch pin 32b downward, so that the partition latch 32 pivotes clockwise with the shaft 33 as its pivot.As a result, the partition latch pawl 32a of the partition latch 32 is disengaged from the partition latch lock plate 4a, as shown in Fig. 4. Therefore, the door-like partition 4 can be opened. When the partition 4 is once opened, since the actuator rod 29b is released and therefore urged toward the left by the elastic force of the coil spring 29c. As a result, the actuator rod pin 29d engages with the disk latch slot 30b to pivot the triangular disk latch 30 counterclockwise with the shaft 31 as its pivot and to engage the disk latch pawl 30a with the latch lock member 28, also as shown in Fig. 4.

As a result, once the door-like partition 4 is opened, the operation handle 8 will not be moved downward to rotate the pivotable disk 24, in order words, to close the disconnecting switch. Further, in this state, although the pivotable disk 24 is not locked in the clockwise direction, the operation handle 8 will not be moved further upward, because of the presence of the end of a front plate 27.

In the case where the door-like partition 4 is required to close in this state shown in Fig. 4, the operation handle 8 will not be moved in either direction, because the pivotable disk 24 is locked.

Therefore, the operator must first close the doorlike partition 4. When the door-like partition 4 is once closed, since the actuator rod 29b is pushed toward the right against the elastic force of the coil spring 29c, the actuator rod pin 29d received within the disk latch slot 30b pivotes the triangular disk latch 30 clockwise to disengage the disk latch pawl 30a from the latch lock member 28, as shown in Fig. 3. Therefore, since the operation handle 8 or the pivotable disk 24 is released from the lock and is pivotable, the operator can move the operation handle 8 downward. When the handle 8 moves downward, the pivotable disk 24 pivotes counterclockwise, so that the link rod 27 is shifted toward the right to close the disconnecting switch 6 and simultaneously the partition latch lever 23 is moved upward.When the partition latch lever 23 moves upward, the lower end of the elongate latch lever slot 23a is brought into contact with the partition latch pin 32b and further moves the partition latch pin 32b upward, so that the partition latch 32 pivotes counterclockwise. As a result, the partition latch pawl 32a of the partition latch 32 is engaged with the partition latch lock plate 4a, as shown in Fig. 3. As a result, once the operation handle 8 is moved downward to close the disconnecting switch 6, the door-like partition 4 is locked and therefore will now be opened.

Description has been made of the case where a disconnecting switch is opened or closed in relation to the opening or closing of the door-like partition of the enclosed switchboard on the basis of the embodiment. However, without limiting to the disconnecting switch, the interlock device according to the present invention is applicable to any other switching devices arranged within the enclosed switchboard, for instance, such as an earthing switch.

Figs. 5 to 9 show the operation handle used for the interlock device according to the present invention.

The operation handle according to the present invention comprises at least one mechanically weak or fragile portion intentionally so as to be easily broken or bent. This operation handle is provided in order to prevent an danger such that the operation handle is forcibly moved carelessly in the direction to close the disconnecting switch in spite of the fact that the interlock device is functioning. In other words, this fragile portion of the handle serves as an additional safety device to previously prevent an accident due to erroneous operation.

Figs. 5 and 6 show a first embodiment of the operation handle according to the present invention. In the figure, the operation handle 8 comprises a tubular portion 8a with a mechanically weak neck portion 8b which is formed by roller compression, a handle knob 8c and a thread portion 8d. The position and the diameter (or wall thickness) of the small-diameter neck portion 8b are important in order to determine the strength of the operation handle 8.

If the neck portion 8b is formed immoderately near the thread portion 8d, the operation handle 8 may be not strong enough to pivot the pivotable disk 24 and to close or open the disconnecting switch, although the strength depends upon the diameter, wall thickness and material. On the other hand, if the neck portion 8b is formed excessively near the handle knob 8c, the operation handle 8 may not serve as a safety device. That is to say, the bending strength should be sufficient to drive the disconnecting switch but insufficient to resist against an excessive force.

Further, in order to facilitate the replacement of the damaged operation handle for a new one, the handle 8 should be attached removably to the interlock device. For this purpose, the thread portion 8d is provided for the operation handle 8.

Therefore, when replacing the operation handle, the handle 8 is readily screwed into or out of the inner thread portion formed in the handle supporting member 26 shown in Fig. 2. The neck portion 8b can be manufactured by partially drawing down a tubular material into a predetermined small diameter. In this work, a pair of rollers are brought into pressure-contact with a rotating tubular material. Fig. 6 is a crosssectional view taken along the lines VI--VI shown in Fig. 5.

Figs. 7 and 8 show a second embodiment of the operation handle according to the present invention. In the figure, the operation handle 8 comprises a rod portion 8a with a mechanically weak notch 8b' which is formed by cutting, a handle knob 8c and a flat portion 8e with a plurality of bolt holes. The position and the shape of the notch 8b' are important in order to determine the strength of the operation handle 8.

The notch portion 8b' can be manufactured by cutting the rod portion with a lathe. In this embodiment, the operation handle 8 is fixed to the handle supporting member 26 by the use of a plurality of bolts. Fig. 8 is a cross-sectional view taken along the line VIll-Vill shown in Fig 7.

Fig. 9 shows a third embodiment of the operation handle according to the present invention. In this embodiment, the tubular portion 8a is first divided into two sections and then the divided two tubular portions 8a are joined to each other with a joint member 8f made of wood, synthetic resin or light metal so as to form a mechanically fragile portion.

In any embodiments described above, the shape of the cross-section of the handle is not important, but the bending strength must be strong enough to pivot the pivotable disk, that is, to close or open the disconnecting switch and weak enough to be broken or bent easily when an excessive bending moment is applied to the operation handle.

As described above, in the interlock device for an enclosed switchboard according to the present invention, the door-like partition can be opened only when the disconnecting switch is opened and locked automatically whenever the disconnecting switch is closed and further the disconnecting switch can be closed only after the door-like partition has been closed perfectly; in other words, the operation handle is locked automatically when the door-like partition is left open and is unlocked when the door is kept closed.

Further, since the interlock device according to the present invention is made up of only mechanical parts or elements without use of any electrical elements, there existing no trouble with electrical elements, it is easy to troubleshoot defective elements and easy to repair, thus enhancing the safety and the life time.

Furthermore, since the operation handle according to the present invention is formed with a mechanically weak or fragile portion, even when an excessive bending moment is applied to the handle erronously or carelessly, it is possible to prevent the interlock device from being damaged or to prevent such a danger that the operation handle is forcibly moved carelessly in the direction to close the disconnecting switch, thus enhancing the safety doubly.

It will be understood by those skilled in the art that the foregoing description is in terms of preferred embodiments of the present invention wherein various changes and modifications may be made without departing from the spirit and scope of the invention, as set forth in the appended claims.

Claims

1. An interlock device for an enclosed switchboard for allowing a switching device to be closed or opened in relation to the closing or opening of a door-like partition provided for the enclosed switchboard, which comprises: (a) an operation handle; (b) a pivotable disk having a latch lock member, said operation handle being removably fixed thereto for pivoting said pivotable disk to positions to close or open the switching device; (c) a link rod, one end of which is pivotably connected in position to said pivotable disk and the other end of which is pivotably connected to the switching device in such a way that the switching device can be closed when said pivotable disk is pivoted in one direction and opened when said pivotable disk is rotated in the other direction; (d) a disk latch having a disk latch pawl and a disk latch slot;; (e) a disk latch actuator having an actuator rod, an actuator pin, and a spring, said actuator rod being urged toward the door-like partition by the elastic force of said spring, said actuator pin being received within said disk latch slot of said disk latch in such a way that said disk latch pawl of said disk latch is engaged with said latch lock member of said pivotable disk when said door-like partition is opened but disengaged from said latch lock member when said door-like partition is closed; (f) a partition latch having a partition latch pawl and a partition latch pin;; (g) a partition latch lever having an elongate latch lever slot at one end thereof, the other end thereof being pivotably connected in position to said pivotable disk, said partition latch pin being received within said elongate latch lever slot in such a way that said partition latch pawl of said partition latch is engaged with a partition latch lock plate provided for the partition when said pivotable disk is pivoted in the direction to close the switching device but disengaged from said partition latch lock plate when said pivotable disk is pivoted in the direction to open the switching device;; whereby the door-like partition can be opened only after said pivotable disk has been pivoted in the direction to open the switching device and locked in the closed condition except the case described above and further said pivotable disk can be pivoted in the direction to close the switching device only after the door-like partition has been closed perfectly.

2. An interlock device for an enclosed switchboard as set forth in claim 1, wherein said operation handle comprises a handle rod formed with a mechanically fragile portion at an appropriate position thereof.

3. An interlock device for an enclosed switchboard as set forth in claim 2, wherein said fragile portion is a joint member for connecting two separate tubular handle rods on either side thereof.

4. An interlock device for an enclosed switchboard as set forth in claim 3, wherein said joint member is made of a synthetic resin.

5. An interlock device for an enclosed switchboard as set forth in claim 3, wherein said joint member is made of a wood.

6. An interlock device for an enclosed switchboard as set forth in claim 3, wherein said joint member is made of a light metal.

7. An interlock device as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.