FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003
COMPLETE SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:
SWITCHING DEVICE WITH INTERLOCKING MECHANISM


APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED


A) TECHNICAL FIELD
[0001] The present invention generally relates to switching devices used for domestic as well as industrial purpose and particularly to a contact arrangement for low voltage switching devices and more particularly to a locking mechanism for trip alarm contacts in switching device to restrict the movement of the switching device knob in ON position.
B) BACKGROUND OF THE INVENTION
[0002] Electrical switching devices are used to protect the electrical circuitry and equipment from the damage due to an abnormal condition, such as an overload condition, a relatively high level short circuit or a fault condition. The electrical switching devices typically have two operating handle positions corresponding to the status of the separable contacts. For example, these positions include an ON position, in which the separable contacts are closed and an OFF position in which the contacts are open. Some switching devices have a third position which corresponds to a tripped condition in which the contacts are tripped open.
[0003] Switching devices are usually installed in an enclosure so that the entire control
and distribution network arranged in the form of metallic sheets and/or cable wires are
housed inside the enclosure. All the operating means are arranged outside the enclosure to
prevent an access to the high voltage sections to eliminate the generation of a potential
hazard. It is often desirable or essential that the settings of the switching devices remain
undisturbed in the switching device during a maintenance operation. Unauthorized or
inadvertent changing of the position of these breakers could result in unwanted interruptions
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to service or operations and serious damage to an electrical apparatus, or even serious harm to a person. For example, accidental actuation of a circuit breaker might result in electrocution or shock to a workman performing electrical work or repair on equipment downstream from the circuit breaker.
[0004] In switching devices such as low voltage circuit breaker, isolator and their trip alarm contacts the operating mechanism plays an important role. Since the width of the low voltage circuit breaker module is very less, the operating mechanism should be compact. Since the operating mechanism is compact the restricting of knob plays a very important role.
[0005] In currently available switching devices, the contact actuation mechanism is very slow due to the number of linkages and the components used in the assembly. Also due to large number of components, assembling of operating mechanism is quiet complex and difficult. Due to larger size of components, it is difficult to incorporate this mechanism in half module width. Hence there is a need to provide a compact contact arrangement to restrict the movement of the operating knob in switched ON position.
[0006] The need for restricting the movement of the operating knob from ON to OFF position was felt while designing the trip alarm contact for switching device. If the switching device knob is changed from ON to OFF position by an unauthorized person, it will give a wrong indication to the operator. Hence there is a need to develop a unique mechanism to overcome this error.
[0007] Therefore enough safety measures must be taken to prevent another person from
inadvertently returning the circuit breaker handle to the OFF position. One such safety
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measure is the addition of a locking assembly to the switching device to prevent the displacement of the circuit breaker operating handle. Hence there is a need to provide a compact contact arrangement with a special locking mechanism to restrict the movement of the operating knob in switched ON position.
C) OBJECTS OF THE INVENTION
[0008] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
[0009] The primary object of the present invention is to provide a locking mechanism for low voltage switching devices to restrict the movement of the switching device knob in ON position.
[0010] Another object of the present invention is to provide locking mechanism for trip alarm contact (TAC) in miniature circuit breaker to restrict the movement of the operating knob when it is switched ON and to switch OFF only when the miniature circuit breaker trips during fault condition.
[0011] Yet another object of the present invention is to provide a compact locking mechanism for low voltage switching devices which is desirable for half module width of range 9mm or 17.5mm.
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[0012] Yet another object of the present invention is to provide a compact locking mechanism with a very few linkages to reduce the switching device operating time.
[0013] These and other objects and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
D) SUMMARY OF THE INVENTION
[0014] The above mentioned shortcomings, disadvantages and problems are addressed herein and which will be understood by reading and studying the following specification.
[0015] The various embodiments of the present invention provide a switching device with
an interlocking mechanism to restrict the movement of the switching device knob in ON
position. According to one embodiment of the present invention, a switching device with
interlocking mechanism is provided with a housing. An operating knob is provided in the
housing. A connecting link is coupled to the operating knob. A rotary contact is connected to
the connecting link. A lock lever is connected to the operating knob. A trip actuating pivot is
connected to the lock lever. A pip is provided in the housing. A rotor spring is connected to
the rotary contact and to the pip. A pivot spring is connected to the trip actuating pivot and to
the pip. A triplet is connected to the operating knob and to the trip actuating pivot. The triplet
permits the movement of the operating knob from OFF position to ON position and restricts
the movement of the operating knob from ON position to OFF position. The triplet interferes
with the movement of the knob during the movement of the switch to OFF position from the
switched ON condition, unless the switch is turned OFF due to an actual fault condition.
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[0016] The operating knob is connected to the connecting link and to the lock lever through a U-shaped pin. The rotor spring is provided to maintain the required contact pressure and to hold the mechanism in a stable position. The pivot spring is provided to reset the TAC pivot to its original position.
[0017] According to one embodiment of the present invention, the locking mechanism is provided for trip alarm contact (TAC) for miniature circuit breaker to restrict the movement of the operating knob once it is turned ON and it is turned OFF only when the miniature circuit breaker trips during fault condition. According to one embodiment, the switching device is provided with a triplet mechanism which acts as a mechanical interlock to restrict the movement of the switching device knob in ON position.
[0018] According to one embodiment, a locking mechanism is provided for trip alarm
contact (TAC) for miniature circuit breaker to restrict the movement of the switching device
knob in ON position. The switching device includes an operating knob connected to
connecting link and lock lever through U-pin. Other end of the lock lever is locked with trip
alarm contact (TAC) pivot which is locked with triplet. The triplet is connected between the
operating knob and the TAC pivot. The interface between the knob and the triplet rests on the
protrusion in the housing. While the other end of the connecting link is connected to rotary
contact through a pin. The movement of the connecting link is used to make and break the
electrical contacts. When the miniature circuit breaker is switched ON, if someone accidently
tries to switch OFF the TAC i.e. from ON to OFF position, a force is applied to the operating
knob which is transferred to the triplet and since in this condition there is a interference
between the operating knob and the triplet and also due to a protrusion made in housing, the
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mechanism will jam and will not allow the customer to switch OFF the mechanism. Hence the locking mechanism ensures that the TAC will only be functional when there is an actual condition of a fault or overload condition. The TAC pivot is a tripping component which moves only when there is a fault condition and also depends on the design of the miniature circuit breaker (MCB).
[0019] According to one embodiment of the present invention, when the operating knob is in OFF position the triplet will allow the mechanism to be switched from OFF to ON position. When the operating knob is switched ON, the connecting link will move and will rotate the electrical contact. In this position, the lock lever will be locked which further restricts the movement of the operating knob. In another embodiment, the pivot of the TAC is connected to the pivot of the circuit breaker. A rotor spring and a pivot spring are connected between the TAC pivot and the pin. The rotor spring helps in maintaining the required contact pressure and keeps the mechanism in a stable position. The pivot spring is used to reset the pivot to its original position.
[0020] During short circuit or overload conditions the miniature circuit breaker (MCB) pivot rotates in clockwise direction, since both the pivots are interconnected the TAC pivot also changes its position in clockwise direction and then the lock lever locks the movement of the TAC. When the miniature circuit breaker (MCB) is switched ON both the MCB pivot and TAC pivot will align and during this condition the triplet connected to the knob and TAC pivot restricts the movement of the operating knob. During fault condition, the TAC pivot moves about its axis, and frees the lock lever and hence the mechanism trips to switch OFF the circuit breaker.
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[0021] The interlocking mechanism is provided which is compact, hence can be used in half as well as full module width of range 9 to 17.5 mm. The mechanism uses very few linkages hence reduce the operating time of the switching device. The locking mechanism restricts the movement of the operating knob once it is turned ON and it is turned OFF only when the miniature circuit breaker trips during fault condition.
E) BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0023] FIG. 1 shows a sectional view of the switching device with the knob of the switch held in ON position, making contacts at four locations, according to one embodiment of the present invention.
[0024] FIG. 2 shows a sectional view of the switching device with the knob of the switch held in OFF position breaking contacts at four locations, according to one embodiment of the present invention.
[0025] FIG. 3 shows a front view of the locking mechanism for switching device in assembled condition, according to one embodiment of the present invention.
[0026] FIG. 4 shows a front view of the locking mechanism for switching device in an unassembled condition, according to one embodiment of the present invention.
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[0027] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
F) DETAILED DESCRIPTION OF THE INVENTION
[0028] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0029] The various embodiments of the present invention provide a switching device with an interlocking mechanism to restrict the movement of the switching device knob in ON position. According to one embodiment of the present invention, a switching device with interlocking mechanism is provided with a housing. An operating knob is provided in the housing. A connecting link is coupled to the operating knob. A rotary contact is connected to the connecting link. A lock lever is connected to the operating knob. A trip actuating pivot is connected to the lock lever. A pip is provided in the housing. A rotor spring is connected to the rotary contact and to the pip. A pivot spring is connected to the trip actuating pivot and to the pip. A triplet is connected to the operating knob and to the trip actuating pivot. The triplet permits the movement of the operating knob from OFF position to ON position and restricts
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the movement of the operating knob from ON position to OFF position. The triplet interferes with the movement of the knob during the movement of the switch to OFF position from the switched ON condition, unless the switch is turned OFF due to an actual fault condition.
[0030] The operating knob is connected to the connecting link and to the lock lever through a U-shaped pin. The rotor spring is provided to maintain the required contact pressure and to hold the mechanism in a stable position. The pivot spring is provided to reset the TAC pivot to its original position.
[0031 ] According to one embodiment of the present invention, the locking mechanism is provided for trip alarm contact (TAC) for miniature circuit breaker to restrict the movement of the operating knob once it is turned ON and it is turned OFF only when the miniature circuit breaker trips during fault condition. According to one embodiment, the switching device is provided with a triplet mechanism which acts as a mechanical interlock to restrict the movement of the switching device knob in ON position.
[0032] According to one embodiment, a locking mechanism is provided for trip alarm contact (TAC) in miniature circuit breaker to restrict the movement of the switching device knob in ON position. The switching device includes an operating knob connected to connecting link and lock lever through U-pin. Other end of the lock lever is locked with trip alarm contact (TAC) pivot which is locked with triplet. A triplet is connected between the operating knob and the TAC pivot. The interface between the knob and the triplet rests on the protrusion in the housing. While the other end of the connecting link is connected to rotary contact through a pin. The movement of the connecting link is used to make and break the electrical contacts. When the miniature circuit breaker is switched ON, if an unauthorized
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person accidently tries to switch OFF the TAC i.e. from ON to OFF position, a force is applied to the knob which is transferred to the triplet and since in this condition there is a interference between the knob and the triplet and also due to a protrusion made in housing, the mechanism will jam and will not allow the customer to switch OFF the mechanism. The locking mechanism ensures that the TAC will only be functional when there is an actual condition of fault or overload condition. The TAC pivot is a tripping component which moves only when there is a fault condition and also depends on the design of the miniature circuit breaker (MCB).
[0033] According to one embodiment of the present invention, when the operating knob is in OFF position the triplet will allow the mechanism to be switched from OFF to ON position. When the operating knob is switched ON, the connecting link will move and will rotate the electrical contact. In this position, the lock lever will be locked which further restricts the movement of the operating knob. In another embodiment, the pivot of the TAC is connected to the pivot of the circuit breaker. A rotor spring and a pivot spring are connected between the TAC pivot and the pin. The rotor spring is provided to maintain the required contact pressure and to keep the mechanism in a stable position. The pivot spring is provided to reset the pivot to its original position.
[0034] During short circuit or overload conditions the miniature circuit breaker (MCB) pivot rotates in clockwise direction, since both the pivots are interconnected the TAC pivot also changes its position in clockwise direction and then the lock lever locks the movement of the TAC. When the miniature circuit breaker (MCB) is switched ON both the MCB pivot and TAC pivot will align and during this condition the triplets is connected to the knob and as well as connected to TAC pivot to restrict the movement of the operating knob. During fault
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condition, the TAC pivot moves about its axis, and frees the lock lever and hence the mechanism trips to switch OFF the circuit breaker.
[0035] The interlocking mechanism is provided which is compact, hence can be used in half as well as full module width of range 9 to 17.5 mm. The mechanism uses very few linkages hence reduce the operating time of the switching device. The locking mechanism restricts the movement of the operating knob once it is turned ON and it is turned OFF only when the miniature circuit breaker trips during fault condition.
[0036] FIG. 1 and 2 shows a sectional view of a switching device with the knob of the switch held in ON and OFF positions to make and break the electrical contacts at four locations, according to one embodiment of the present invention. The switching device includes an operating knob 2 connected to connecting link 4 and lock lever 5 through U-pin 6. Other end of the lock lever 5 is locked with trip alarm contact (TAC) pivot 7 which is locked with triplet 8. A triplet 8 is connected between the operating knob 2 and the TAC pivot 7. The interface between the operating knob 2 and the triplet 8 rests on the protrusion 11 in the housing. While the other end of the connecting link 4 is connected to rotary contact 1 through a pin 3. When the switching device knob is moved to ON position (Refer FIG. 1), the connecting link 4 connected to the operating knob 2 moves. The movement of connecting link 4 is transferred to rotary contact 1 with the help of the pin 3. The movement of the rotary contact 1 helps in making the electrical contact at four locations. In another embodiment, the pivot of the TAC is connected to the pivot of the circuit breaker. A rotor spring 9 and a pivot spring 10 are connected between the TAC pivot 7 and the pivot pin 3. The rotor spring 9 is connected between rotary contact 1 and a pip in housing 12. The pivot spring 10 is connected between pivot 7 and a pip in housing 12. The rotor spring 9 is provided top maintain a
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required contact pressure to keep the mechanism in a stable position. The pivot spring 10 is provided to reset the pivot 7 to its original position.
[0037] With respect to FIG. 1, when the miniature circuit breaker is switched ON, if an unauthorized person accidently tries to switch OFF the TAC i.e. from ON to OFF position, a force is applied to the operating knob 2 which is transferred to the triplet 8. In this condition since there is interference between the knob 2 and the triplet 8 and also due to a protrusion 11 made in housing 12, the mechanism will jam and will not allow the operator to switch OFF the circuit breaker. As a result, the locking mechanism in the present invention ensures that the TAC will only be functional when there is an actual condition of a fault. The TAC pivot 7 is a tripping component which moves only when there is a fault condition and also depends on the design of the miniature circuit breaker (MCB).
[0038] In an embodiment of the present invention, the miniature circuit breaker pivot and
the TAC pivot 7 are interconnected with each other. During an overload or fault condition the
miniature circuit breaker pivot rotates in clockwise direction. Since both pivots are
interconnected, the TAC pivot 7 also changes it position in clockwise direction and then the
lock lever 5 locks the movement of the TAC. When the miniature circuit breaker (MCB) is
switched ON both the MCB pivot and TAC pivot will align and during this condition the
triplet 8 is connected to the knob 2 and as well as connected to pivot 7, initially since the
knob is in OFF position the triplet 8 will allow the mechanism to be switched from OFF to
ON position. With respect to FIG. 2, the operating knob of the switch is held in OFF position
to break the electrical contacts at four locations. Initially, when the operating knob is in OFF
position the triplet 8 will allow the mechanism to be easily switched from OFF to ON
position.
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[0039] FIG. 3 and 4 shows an assembled and an exploded view of the individual locking mechanism, according to one embodiment of the present invention. The operating knob 2 is connected to connecting link 4 and lock lever 5 through U-pin 6. The other end of the lever 5 is locked with TAC pivot 7. The TAC pivot 7 is locked with triplet 8. The triplet 8 is locked with the trip alarm contact (TAC) pivot 7 towards one end and connected to operating knob 2 to the other end. The rotor spring 9 is connected to rotary contact 1 and a pip in housing and the pivot spring 10 is connected to TAC pivot 7 and a pip in the housing. The TAC pivot 7 is a tripping component which moves only when there is a fault or over overload condition. When the TAC pivot 7 moves about its axis it frees the lock lever 5 and hence the mechanism trips. While the other end of the connecting link 4 is connected to rotary contact 1 through a pin 3.
G) ADVANTAGES OF THE INVENTION
[0040] The embodiments of the present invention provide a locking mechanism for low voltage switching device. It restricts the movement of the switching device knob in ON position. The locking mechanism is compact, hence can be used in half as well as full module width of range 9 to 17.5 mm. The mechanism uses very few linkages hence reduce the operating time of the switching device. The locking mechanism restricts the movement of the operating knob once it is turned ON and it is turned OFF only when the miniature circuit breaker trips during fault or overload condition.
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[0041] Although the invention is described with various specific embodiments, it will be obvious for a person skilled in the art to practice the invention with modifications. However, all such modifications are deemed to be within the scope of the claims.
[0042] It is also to be understood that the following claims are intended to cover all of the generic and specific features of the present invention described herein and all the statements of the scope of the invention which as a matter of language might be said to fall there between.

Place: Bangalore RAKESH PRABHU
Date: 31July2009 Patent Agent
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CLAIMS
What is claimed is:
1. A switching device with interlocking mechanism comprising:
A housing;
an operating knob;
a connecting link coupled to the operating knob;
a rotary contact connected to the connecting link;
a lock lever connected to the operating knob;
a trip actuating pivot connected to the lock lever;
a pip provided in the housing;
a rotor spring connected to the rotary contact and to the pip;
a pivot spring connected to the trip actuating pivot and to the pip;
a triplet connected to the operating knob and to the trip actuating pivot;
wherein the triplet permits the movement of the operating knob from OFF position to
ON position and restricts the movement of the operating knob from ON position to
OFF position.
2. The device according to claim 1, wherein the triplet interferes the movement of the knob during the movement of the switch to OFF position from the switched ON condition, unless the switch is turned OFF due to an actual fault condition.
3. The device according to claim 1, wherein the operating knob is connected to the connecting link and to the lock lever through a pin.
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4. The device according to claim 3, wherein the pin is a U-shaped pin.
5. The device according to claim 1, wherein the rotor spring is provided to maintain the required contact pressure and to hold the mechanism in a stable position.
6. The device according to claim 1, wherein the pivot spring is provided to reset the TAC pivot to its original position.

RAKESH PRABHU Patent Agent,
ALMT Legal,
#2, Lavelle Road, Bangalore-560 001
To,
The Controller of Patents, The Patent Office, Mumbai
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