F O R M 2

THE PATENT ACT, 1970
(39 of 1970)
&
The Patent Rules, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)

Title of the invention – SAFETY LOCKING MECHANISM
FOR SWITCHING DEVICE

2. Applicants

(a) NAME : LARSEN & TOURBO LIMITED
(b) NATIONALITY: An Indian Company
(c) Address: L&T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be
Performed :

FIELD OF THE INVENTION
The present invention relates to a safety locking mechanism for switching devices. More particularly, the invention relates to a locking mechanism for mechanically interlocked multi-pole circuit breakers such that both breakers cannot be simultaneously actuated to same electrical position i.e. in ON condition without panel cut out interference.
BACKGROUND AND PRIOR ART
The inventions detailed in the US6777628, US5782341, US6940027, talk about safety locking device wherein the actuation for the padlocking mechanism is obtained from the knob (or operating handle).
US5782341 describes a padlock assembly arranged within a circuit breaker case preventing the circuit breaker contacts from being closed and the cover from being removed. The padlock assembly is only functional when the circuit breaker contacts are in the OPEN condition.
Also in the invention pertaining to US6777628, the interlocking assembly is located at the front of the breaker, and the padlocking assembly is on the front of the breaker.
US6940027 generally describes an electrical switching apparatus and, more particularly, to a locking assembly for the operating handle of a circuit breaker operable between a first, ON position and a second, OFF position with respect to the enclosure.
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Such setups as in the prior art interfere with the panel cut-out for panel mounted breakers.
Thus there is a need to provide for a locking mechanism for mechanically interlocked multi-pole circuit breakers such that both breakers cannot be simultaneously actuated to same electrical position i.e. in ON condition without panel cut out interference.
The present inventors have found that safety locking of multi-pole circuit breakers such that both breakers cannot be simultaneously actuated to same electrical position i.e. in ON condition can be achieved by way of unique construction of linking means and profile of bracket means providing no interference in the cut out area.
OBJECTS OF THE INVENTION
Accordingly, one object of the present invention is to provide a locking/padlocking mechanism for rear type of mechanical interlock.
Another object of the present invention is to provide a locking/padlocking mechanism such that the cutout area for breaker in the panel is unobstructed.
Yet another object of the present invention is to provide a locking/padlocking mechanism such that the knob gives the true indication of the breaker status.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided a locking mechanism for a switching device comprising multi-pole circuit breakers, said mechanism comprising:
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base plate;
bar means being fixed to the base plate wherein said bar means being substantially fixed at its middle portion with the base plate in a manner to rotate in a plane having perpendicular relation to axis to which the bar is fixed to the base plate;
plurality of actuating means being operatively connected to the bar means;
said bar means comprising an extended portion being operatively fixed to a lock plate/bracket means, said plate means being located at one end of the bar means and in transverse relation to the base plate,
wherein said lock plate means comprising plural slots accommodating said extended portion of the bar means in a manner that rotation of bar means provides a curved motion of the lock plates means thereby providing the lock plate means with predetermined curvature avoiding any interference with the base plate locating the bracket/lock plate means to a position where it is padlocked such that a circuit breaker cannot be made ON when already another breaker is in ON position.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to a safety locking mechanism for a switching device comprising at least two circuit breakers, normal breaker and alternate breaker, each of which has two positions, ON and OFF, indicating the continuity or discontinuity, respectively, of the circuit. These are mounted on a base plate and fixed thereon and stationary in relation to it. These breakers are mechanically interlocked so that both of them cannot be in the ON position
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simultaneously. It can be considered, for illustrative purposes, that the normal breaker is connected to a utility power supply and the alternative breaker is connected to a backup supply. Thus there is a necessity of the mechanical interlock, which renders the two supplies mutually exclusive, preventing a short circuit.
The actuator means engage with a rigid bar means comprising of a lever, which is hinged substantially at the center, and capable of rotating in a plane perpendicular to the axis of the hinge, effectively forming a see-saw mechanism. The actuator means comprise intermediate link elements which take actuation from the drive shaft of the circuit breakers. A lock plate/bracket is attached to the extended portion of lever on one side. The slot in the bracket matches with the slot in the protrusion from base plate. A padlock is placed in these slots thereby preventing alternate breaker to be turned ON independent of position of normal breaker and at the same time allowing normal breaker to be turned OFF or getting tripped. When one of the breakers, say the normal breaker is in the ON condition, the drive shaft pushes the actuator link element downwards, thus raising the actuator of the alternate breaker upwards, by means of the linkage provided by the lever. This illustration presumes the alternate breaker being in the OFF condition (wherein the main contacts of the breaker are separated). At this point if it is tried to bring the alternate breaker to the ON condition, the drive shaft of the alternate breaker pushes the actuator down, but is hindered, via the lever, by the drive shaft and actuator of the normal breaker. Hence, the normal breaker has to be brought to the OFF condition before the alternate breaker can be made ON.
The base plate has a projection one side, protruding over the horizontal face on which the breakers are mounted. A slot is provided in this projection. Also, the lever pin has a bracket/lock plate fixed to it, with a curved projection with two slots provided in it. This bracket is assembled such that it projects from one end of the lever and is rigidly fixed in relation to it. Thus, the bracket defines a curved
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path in its motion due to the rotation of the lever upon the hinge. The path of the bracket is adjacent to the vertical projection on the base plate and hence, the bracket is provided with a curvature to avoid any interference between the base plate and bracket in the normal course of operation.
In one of the two states of the operation of the padlocking system, the normal breaker is in the ON condition and the alternate breaker is in the OFF condition. Thus the lever end near the normal breaker is depressed, thus aligning the upper slot on the bracket with the slot on the base plate projection. These slots, being aligned, facilitate the padlocking of the lever in this position, relative to the base plate. Thus, if it is tried to bring the alternate breaker to the ON position (assuming that the normal breaker is first brought to the OFF condition), the drive shaft pushes the lever end downwards, upon which the lever tries to raise the lever end near the normal breaker upwards, which is opposed by the padlock. Hence, the alternate breaker cannot be brought to the ON position. In the second state of operation of the padlocking system the alternate breaker is in the ON condition, whereas the normal breaker is in the OFF condition. Thus, the lever end near to the normal breaker is in an elevated condition and the lower slot on the bracket is aligned with the slot on the base plate projection. When padlocked in this condition, the normal breaker cannot be brought to the ON condition.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 illustrates an isometric view of the mechanism of the present invention.
Figure 2 illustrates an isometric view of the mechanism components of the present invention. The detail is shown in figure 2A.
Figure 3 illustrates another isometric view of the mechanism of the present invention.
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Figure 4 and detail 4A illustrate that the breaker (2) cannot be made ON. Figure 5 and detail 5A illustrate that the breaker (2) cannot be made ON.
DETAILED DESCRIPTION OF THE ACCOMPANYING FIGURES
Figure 1 illustrates the assembly view of two circuit breakers, normal breaker (1) and alternate breaker (2) mounted on base plate (3), and the lock plate (4) and lock (5).
Figures 2 & 2A illustrate the rear view of the interlocking assembly wherein the actuators (7) & (8) engage with the lever (6), and the pad locking arrangement demonstrating the arrangement of lock plate (4) and lock (5).
Figure 3 illustrates the isometric view, which shows the arrangement of the base plate (3) and lock plate (4), the aligned slots that facilitate padlocking.
Figures 4 & 4A illustrate one of the stages of operation wherein the normal breaker (1) is ON and the alternate breaker (2) is OFF.
Figures 5 & 5A illustrate the second stage of operation wherein the normal breaker (1) is OFF and the alternate breaker is ON.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. The lever, lock plate/bracket and actuator as herein described do not limit the scope of the present invention and can be replaced by its technical equivalence and yet the invention can be performed. The structure thus conceived is susceptible of numerous
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modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
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WE CLAIM
1. A locking mechanism for a switching device comprising multi-pole
switching devices, said mechanism comprising:
base plate;
bar means being fixed to the base plate wherein said bar means being substantially fixed at its middle portion with the base plate in a manner to rotate in a plane having perpendicular relation to axis to which the bar is fixed to the base plate;
plurality of actuating means being operatively connected to the bar means;
said bar means comprising an extended portion being operatively fixed to a lock plate/bracket means, said plate means being located at one end of the bar means and in transverse relation to the base plate,
wherein said lock plate means comprising plural slots accommodating said extended portion of the bar means in a manner that rotation of bar means provides a curved motion of the lock plates means thereby providing the lock plate means with predetermined curvature avoiding any interference with the base plate locating the bracket/lock plate means to a position where it is padlocked such that a circuit breaker cannot be made ON when already another breaker is in ON position.
2. A locking mechanism as claimed in claim 1, wherein the bar means
comprises lever.
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3. A locking mechanism as claimed in claims 1 and 2, wherein the actuator means comprising plurality of intermediate link elements between the drive shaft of circuit breakers and the lever such that actuation from the drive shaft is transformed to the lever.
4. A locking mechanism as claimed in claim 1 to 3 wherein the base plate comprises projection vertical to the base
5. A locking mechanism as claimed in comprises slot means.
6. A locking mechanism as claimed in claim 1, wherein the lock plate means/bracket comprises slot means such that on actuation of the lever the slot locates itself in appropriate alignment with the slot means of the base plate projection where it is padlocked.
7. A locking mechanism as claimed in claims 1 to 6, wherein lever means being engaged with the intermediate link elements such that after padlocking at a desired position of one circuit breaker the position of the other switching device is not changeable by simple actuation of the switching device knob.
8. A locking mechanism as claimed in claims 1 to 7, wherein lever means comprises extended pin means.
9. A locking mechanism as herein substantially described and illustrated with reference to the accompanying figures.
Dated this the 26th day of March 2007

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ABSTRACT
TITLE : SAFETY LOCKING MECHANISM FOR SWITCHING DEVICE
The present invention relates to a locking mechanism for a switching device comprising multi-pole circuit breakers. The mechanism comprises base plate (3), bar means (6) substantially fixed at its middle portion with the base plate (3) in a manner to rotate in a plane having perpendicular relation to axis to which the bar (6) is fixed to the base plate (3). Plurality of actuating means (7&8) are operatively connected to the bar means (6). Bar means (6) comprises an extended portion operatively fixed to a lock plate/bracket means (4). Lock plate means (4) comprises plural slots accommodating the extended portion of the bar means in a manner that rotation of bar means provides a curved motion of the lock plates means.
Figure 3