FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. TITLE OF THE INVENTION - IMPROVED LOCKING SYSTEM FOR CIRCUIT BREAKERS
2. APPLICANT(S)
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to circuit breakers. More particularly, the invention relates to an improved locking system for circuit breakers.
BACKGROUND AND THE PRIOR ART
In most draw-out type switchgear, there are no provisions to indicate the intended positions of the switchgear, or the indication is in visual or audio form. This indication may not be legible at times depending on the environments that the switchgear is used in, for example in loud and dusty places. In such a condition, the switchgear position is not easily intimated to the user.
While racking the breaker into a cradle, the position of the breaker needs to be indicated for safety purposes. This is achieved using a position indicator. The position indicator may be neglected by the user, or he/she may be unaware of the positions and their related safety instructions. The safety of the operation may be jeopardized in case of an unintended motion of the switchgear within the drawing space.
In conventional switchgear, the switchgear position is locked by means of halting the motion of the racking screw depending on the motion it has traversed. Hence, the position of the switchgear is determined by the position and/or motion of the racking screw/rack. However, due to tolerances the real position of the switchgear may not match with its intended position. Hence, there is a strong possibility of false position locking. This is eliminated by deriving the real displacement of the switchgear and engagement at the rail itself. However, this would load the parts of the racking system till the latches. This unnecessary loading could lead to unwanted wear of the parts and hamper the working and accuracy of the racking system.

US 2010/0263995 disclose a position locking device is made using a screw rod, a catching plate, a positioning plate, a locking plate, and a push rod. The screw rod has key ways. The catching plate has a hole and a protrusion that can be inserted into the keyways. Positioning notches for limiting the positions are farmed on the surface of the positioning plate, and corresponding protruding platforms are disposed on the bottom surface One end of the locking plate bears against the bottom surface of the positioning plate, and the other end is locked to or unlocked from an outward protruding platform of the catching plate. One end of the push rod passes through the catching plate hole, and has an inclined surface. When the push rod is pushed, the inclined surface makes the catching plate leave the key ways.
CN1402397A discloses a locking device for a draw-out circuit breaker, which provides a device capable of locking under the three different states of off, test, and on. In the patent, this function is achieved through a cooperation of a plurality of members, that is, a fork shaft and an unlocking shaft, a locking sheet and a roller thereon, a slot and a roller slot on a square shaft, and a locking trench on a catching plate.
These inventions rely on the position of the racking mechanism rather than the actual position of the breaker. There may be a lag between the actual breaker position and the intended position of the breaker due to tolerances. This may hinder the safety of the operation and may lead to an inaccurate intimation of the breaker position.
Thus, there is a need to overcome the problems of the prior art. There is a need to facilitate a simpler indication to the user about the position of the breaker and to intimate the user about the true position of the switchgear. Therefore, the present inventors have developed an improved locking system for use in circuit breakers that would allow for precise detection of the switchgear position and rigid locking of the racking system with minimal residual load on the same.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.
Another object of the present invention is to provide an improved locking system for use in circuit breakers.
Yet another object of the present invention is to provide a rigid locking of the racking system with minimal residual load on the same.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
There is provided a locking system for circuit breakers.
According to one embodiment of the present invention, there is provided an improved locking system for circuit breakers comprising a plurality of latches engaging with corresponding slots on rails of a switch gear, said latch mounted with a spring (61) using a latch plate (62) and a latch pin (63); a plurality of wires for driving said latches; a racking system having a racking screw (9) with a nut (91) mounted thereto; a locking member (J) spring loaded against a support (5) and consisting an engagement slot (11).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the appended drawings:
Figure 1 illustrates a general view of the assembly.
Figure 2 illustrates a general view of the assembly.
Figure 3 illustrates a top view of the locking mechanism.
Figure 4 illustrates a rear view of the locking assembly.
Figure 5 illustrates a general view of the locking member.
Figure 6 illustrates a close view of the latch and rail-slot.
Figure 7 illustrates a front view of the locking mechanism.
Figure 8 illustrates a general view of the Facia.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Reference is first invited to Fig 1 where the latches mate with corresponding rail slots 71. 72, and 73 on alignment. Alignment states for the same are reached as the rails 7 are racked in.
Fig. 2 shows alignment of the latch 6 with the rail slots 71, 72, 73, the latch 6 engages and moves towards the rail 7 due to the latch spring 61.
Fig. 3 shows wire 8 turning around the wire pin 83 to reach the locking member 1.
Fig. 4 shows a locking member 1 which is spring loaded against the support 5.
Fig. 6 shows latch 6 mounted with a spring 61 using a latch plate 62 and the latch pin 63.
Fig. 7 shows locking member 1 engaging with the nut 91 as the racking operation is continued.
Fig. 8 shows locking handle 2 comes to a 'locked position' 151 as seen from the facia 4.
The invented system is thus an improved locking system for circuit breakers.
DETAILED DESCRIPTION OF THE INVENTION
Accordingly in the present invention there is provided an improved locking system for use in circuit breakers. The present invention comprises of a plurality of spring-loaded latches that engages with corresponding slots on the rails of the draw out type switchgear. Single or plural defeatable latches are used in the present invention. The latches are connected to a locking device using wires. The wires are covered with an

industrial sheath. The locking device comes into operation when the slots in the rails align with the latches. It also provides a defeatable mechanism to unlock the racking system.
This invention relates to improving the position locking system for draw-out breakers. The invention is the use of wire driven latches to lock and unlock the movement of the switchgear within the drawing space. This technology is used in the switchgear industry and allied areas. The present invention is provided with a means to defeat the engagement of the latch with the rail. This is achieved by the displacement of the wire manually by the user. The present invention is provided with a means to actuate the locking at the racking screw using the position of the rails as a signal.
The present invention takes care of the problem of inaccurate intimation of breaker position by sensing the position of the switchgear within the draw-out device and actuating the position locking of the racking system using this signal. This arrangement allows for precise detection of the switchgear position and rigid locking of the racking system with minimal residual load on the same.
CONSTRUCTIONAL ELEMENTS:
1. Locking member
11. Engagement slot
15. Locking Handle
151. Handle lock position
152. Handle open position
2. Locking spring
4. Facia
41. Facia slot

5. Support
51. Slot in support
6. Latch
61. Latch spring
62. Latch plate
63. Latch pin
7. Rail
71. Rail slot1 .
72. Rail slot 2
73. Rail slot 3
8. Wire
81. Wire eye 82.Wire sheath 83.Wire pin 9.Racking screw 91.Nut
According to a preferred embodiment of the invention, there is provided an improved locking system for use in circuit breakers. The racking system consists of a racking screw 9 with a nut mounted on it. The rotation of the racking screw 9 moves the rails 7 in a straight line. The rails 7 of the draw-out device move to and fro. These rails are farmed with rail slots 71, 72, 73, the latch 6 has a corresponding male geometry so that the two mate when aligned as shown in figure 1.
The latch 6 is mounted with a spring 61 using a latch plate 62 and the latch pin 63 as shown in figure 6. The eye of the wire 81 is connected to the latch 6 as shown in figure 1 and figure 6. The facia 4 side eye 81 of the wire 8 is connected to the locking member 1 as shown in figure 3 and figure no.4. The locking member 1 is spring loaded against the support 5 as shown in figure 4. The locking member 1 consists of

an engagement slot 1 i as shown in figure 5. The wire 8 turns around the wire pin 83 to reach the locking member 1 as shown in figure.3.
The latches mate with the corresponding rail slots 71, 72, and 73 on alignment. Alignment states for the same are reached as the rails 7 are racked in as shown in figure 1.
On alignment of the latch 6 with the rail slots 71, 72, 73, the latch 6 engages and moves towards the rail 7 due to the latch spring 61 as shown in figure 1 and figure 2. This displaces the wire 8. This also displaces the locking member 1. The locking spring 2 is defeated and the engagement slot 11 engulfs the outer geometry of the nut 91 as shown in figure 6 and figure 7. The locking member 1 engages with the nut 91 as the racking operation is continued as shown in figure 7.
The nut 91 on the racking screw 9 is rigidly fastened to the racking screw 9. Hence, locking the nut 91 locks the motion, and thus the position of the racking screw 9. Meanwhile the locking handle 2 comes to a 'locked position' 151 as seen from the facia 4 as shown in figure 8.
The locking handle 15 juts out of the facia 4, and can be operated by the user from the outside as shown in figure no.1 and figure 2.
On displacing the locking handle 15 to an open position 152, the latches 6 are disengaged from the rail slots 71, 72, 73 as shown in figure 6 and figure 8. The racking system is unlocked and the racking operation can be performed.
The user is required to continue racking in the switchgear. On attaining a locked condition 151, the user is required to press the locking handle 15 toward the open position 152 and continue with the racking action as shown in figure no.8. The

locking handle 15 can be left idle and the racking operation can be continued. The same process applies to the to and fro motion of the switchgear.
ADVANTAGES:
1. Physical indication of the position of switchgear.
2. Locking of the position of the switchgear at multiple locations.
3. Locking actuated by the position of the rails.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM:
1. An improved locking system for circuit breakers comprising:
a plurality of latches engaging with corresponding slots on rails of a switch gear, said latch mounted with a spring (61) using a latch plate (62) and a latch pin (63);
a plurality of wires for driving said latches;
a racking system having a racking screw (9) with a nut (91) mounted thereto;
a locking member (1) spring loaded against a support (5) and consisting an engagement slot (11).
2. System as claimed in claim 1 wherein said plurality of wires covered with an industrial sheath.
3. System as claimedin claim 1 wherein said latches lock and unlock movement of switchgear within a drawing space.
4. System as claimed in claim 1 wherein displacement of said wire defeat engagement of said latch with said rail.
5. System as claimed in claim 1 further comprising a wire (8) turning around a wire pin (83) and further joining to said locking member (1).

6. System as claimed in claim 1 further comprising a locking handle (15) for disengaging said latches from said slots.
7. System as claimed in claim 6 wherein said locking handle is manually operated to disengage said latches.
8. An improved locking system for circuit breakers as herein described and illustrated with respect to accompanying drawings.