F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN IMPROVED INTERLOCK ARRANGEMENT FOR DRAW-OUT MECHANISM

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:


FIELD OF THE INVENTION

The present invention relates to a molded case circuit breaker (MCCB) for electrically connecting it to switchboards. More particularly, the present invention relates to an improved interlock arrangement for draw out mechanism for Moulded Case Circuit Breakers (MCCB) and also to Air Circuit Breakers (ACB) with less manual effort without disturbing termination and to reduce the down time of an industry.

BACKGROUND OF THE INVENTION

Withdrawable unit (Draw-out module) is an arrangement which is used to connect breaker or MCCB to the main bus and rapid removal of that breaker or MCCB without unbolt or disturbing the termination.

With the help of mechanism, the MCCB is connected to main and auxiliary supplies. In draw-out module, the plug-in is used as base which is having main contacts. Two types of supplies are in the switchboard. One is main supply or power supply and auxiliary supply or control supply. The main supply is for breaker and auxiliary supply is for auxiliaries like shunt release, UV release, etc.

Three positions are in the draw-out to show the operator where the MCCB is present. They are ‘DISCONNECTION’ (both Aux. connections and power connections not connected) ‘TEST’ (Aux. connections only connected but not power supply) ‘CONNECTION’ (both Aux. connections and power connections established). In the ‘TEST’ position, the auxiliaries are able to be tested alone. The MCCB should be in tripped position so that safety operation is possible during draw-out operation.

US 4,051,335 discloses draw out apparatus including a carriage mounting a circuit breaker and supported on telescoping rails to facilitate racking movement of the circuit breaker between extreme positions of electrical engagement and disengagement with respect to switchboard primary terminals. Racking movement into the engaged position from an intermediate test position is mechanically assisted by a racking mechanism. While in the engaged position, a joint clamping mechanism is operated to perfect plural breaker-switchboard terminal joints. A trip interlock insures that the circuit breaker can only be closed while in the test position and in the engaged position with terminal joints clamped. Display apparatus indicates the various circuit breaker positions and the clamped condition of the terminal joints.

US 4,761,521 discloses a drawout and interlock assembly for manually inserting a low-voltage molded case circuit breaker into positive electrical engagement with the plug-in power terminals of a distribution switchboard panel and then withdraw the breaker into a disconnected-test position is disclosed. The drawout position of the assembly comprises a pair of guide rails and a pair of drive rails that are secured to the back of the circuit breaker housing and cooperate with a pair of support rails and a drive mechanism that are secured to the stationary power blocks of the switchboard panel to effect a sliding telescopic interfitting of parts that permits the circuit breaker to be manually racked into connected and disconnected-test positions in an efficient reliable manner with a minimum number of parts.

US 4,743,715 relates to a draw-in mechanism for an extractible molded insulated case circuit breaker, equipped with main and auxiliary circuits with fixed and movable connectors. The fixed connectors are arranged on the upper horizontal wall of the case, and the interacting movable connectors plug into the fixed connectors when the circuit breaker is immobile. The reversible mechanism movement transmission system comprises a first mechanical link with the movable connectors drive device, and a second mechanical link with the movable circuit breaker support, the assembly being arranged so that the first mechanical link is active when the second mechanical link is broken, and vice-versa. The racking mechanism comprises an operating device with a handle, and a movable mechanical support having a pair of symmetrical rails sliding in slide plates of the chassis, and a rail locking system in the drawn-in and drawn-out positions.

US 5,309,317 discloses the sliding mechanism (50) of a drawout type switchgear having a first slide arm (5) which is slidably supported by the upper and lower support rails (3A, 3B) and a second slide arm (7) which is slidably supported by the first slide arm (5). The second slide arm (7) is interlocked with the first slide arm (5) by a lock plate (12) when the first slide arm (5) is sliding from a connected position to a final drawout position of the first slide arm (5). When the first slide arm (5) reaches the final drawout position of the first slide arm (5), the interlocked second slide arm (7) is released by rotation of the lock plate (12).

WO 2001071869 discloses a draw-out arrangement for molded case circuit breakers is disclosed. A circuit breaker plug-in system generally comprises a plug-in base to which the draw-out mechanism is secured. The base includes a right plate and a left plate. A circuit breaker is movable between the right plate and the left plate and is retractably connected to the plug-in base by the action of the draw-out mechanism. The draw-out mechanism of the present invention includes a shaft connecting the right plate to the left plate which provides rigidity to the system and balances the circuit breaker during movement. When a crank is inserted into the draw out mechanism and used to rotate a lead screw connected therein, a rider positioned about the lead screw is prevented from rotating due to being sandwiched between a pair of plates. Movement is thereby translated into linear motion which is used to move the circuit breaker into or out of engagement with the plug-in base.

The drawbacks of the above mentioned prior art is that when the breaker is in the locked position, the breaker is not arrested properly in its position (in existing product like Schneider). Sluggish movements and tilting of the breaker may disturb the contact reliability, which need to be eliminated.

Further the operator should insert two hands in both the side of the breaker to remove the lock of breaker (in the case of Schneider). Due to this reason, the size of the draw-out requires more space. To remove the locking state of the breaker, the operator should open the door of the switchboard in the existing products.
In existing product (Ex. Moeller), this locking mechanism is achieved by the bracket arrangement which is cumbersome.

Thus there is a need to provide an improved interlock arrangement for draw out mechanism that will provide proper safety of switchboard operator, locking of the breaker in 3 positions (Disconnection, Test & Connection) optimized so that breaker can be arrested perfectly within draw-out so that no danger to the operator and accessibility of interlock outside the switchboard is essential and safe.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the problems/disadvantages of the prior art.

Another object of the present invention is to provide an improved interlock arrangement for draw out mechanism.

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

According to one of the aspect of the present invention there is provided an improved interlock arrangement for use in draw-out mechanism for circuit breakers, said arrangement comprising:
plurality of plate means securing said circuit breaker on its both sides;
a cover means substantially fitted on one of the side of said plate means;
plurality of rail means secured inside said plurality of plate means on its both sides adapted for interlocking of said circuit,
wherein one of the rails of said rail means comprising :
plurality of holes substantially placed on the rail , said holes defining plurality of positions and
plurality of projections substantially placed on the rail means;
a locking assembly secured inside said cover means,
said assembly being operatively engaged with said rail, said assembly comprising :
a locker means having a modular projection ;
a lock/latch remover means;
a pair of energy storing element;
wherein said locker means is substantially perpendicular to said rail ;
wherein said locker means is operatively connected with said rail being adapted to exert force on said rail means;
wherein said projection of locker means accommodates within the holes in said rail adapted to perform locking of rail means;
wherein said projection in the rail is adapted to reset said locker means.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Figure 1 illustrates front and full view of the Withdrawable arrangement with breaker & racking handle.

Figure 2 illustrates breaker assembly in rear view .

Figure 3 illustrates breaker assembly in side view.

Figure 4 illustrates front view of the Withdraw able arrangement.

Figure 5 illustrates interlock Mechanism.

Figure 6 illustrates access of the racking handle and interlock outside the switchboard.

Figure 7 illustrates cover assembly.

Figure 8 illustrates cover assembly with springs.

Figure 9 illustrates draw out mechanism with rail.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the arrangement has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous 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.

Plug-in (1) is the base of draw-out (shown in Fig 1 and 5). Plug-in (1) is having the current conducting parts (plug-in contacts (2) shown in Fig 4). Draw-out is used to establish connection between the breaker (3) and plug-in (1). The Draw out assembly consists of mechanism, locking (locking), safety trip, Position indication, Auxiliary connections and Pad locking (shown in Fig 4).

The interlock for draw-out mechanism is a push type Interlock.

The locking components are placed in plastic cover (4) which is fitted to right outer plate (5) (shown in Fig 7 and 8). This locking is used to arrest the breaker movement whenever it reaches ’DISCONNECTION’, ‘TEST’ and ‘CONNECTION’ positions.

The locking is achieved by the mechanism (rail) itself. The right side rail (6) is having holes (7) and projections (8) (shown in Fig 5) to help in locking the breaker. The locking mechanism is assembled in cover (4) with two compression springs (9, 10) shown in Fig 8. The first spring (9) is connected with the locker and the second spring means (10) is connected to a latch remover (12). But the arrows (shown in Fig 8) have shown direction of force exertion. The locker (11) always exerts force on the right rail (6). When it finds the hole (7) in the rail (6), immediately it locks the rail (6). Now the breaker (3) is locked in that particular position. Rail (6) is placed on the right side of the draw out mechanism in the present embodiment.

To remove the locking or to make the breaker (3) free from locking, the operator should press the ‘lock/latch remover’ (12) with the help of thump finger. Now the breaker (3) is free from locking /de latching or ready to move.

When the breaker moves further, it will be locked again before reaching next position. Resetting of the locker (11) is done by the projections (8) given on the right rails (6) before reaching the next position.

The present invention (shown in Fig 4), the operator can access the lock remover (12) in the front face of the draw-out. The operator is able to operate the mechanism without opening the door of switchboard. The operator is able to operate the lock remover (12) by pushing push button (13) with one finger due to the requirement of less force. The locker (11) (shown in Fig 5) is perpendicular to the rail (6). So the locking is perfect without any sluggish movements of components.

Benefits:
• Accessibility of interlock without opening of the front door of switchboard
• Optimized and effective locking
• Safety operation

WE CLAIM:

1. An improved interlock arrangement for use in draw-out mechanism for circuit breakers, said arrangement comprising:
plurality of plate means securing said circuit breaker on its both sides;
a cover means substantially fitted on one of the side of said plate means;
plurality of rail means secured inside said plurality of plate means on its both sides adapted for interlocking of said circuit,
wherein one of the rails of said rail means comprising :
plurality of holes substantially placed on the rail , said holes defining plurality of positions and
plurality of projections substantially placed on the rail means;
a locking assembly secured inside said cover means,
said assembly being operatively engaged with said rail, said assembly comprising :
a locker means having a modular projection ;
a lock/latch remover means;
a pair of energy storing element;
wherein said locker means is substantially perpendicular to said rail ;
wherein said locker means is operatively connected with said rail being adapted to exert force on said rail means;
wherein said projection of locker means accommodates within the holes in said rail adapted to perform locking of rail means;
wherein said projection in the rail is adapted to reset said locker means.

2. Arrangement as claimed in claim 1 wherein said lock remover means comprising of a push button means adapted to unlock the breaker from interlock when pressed manually.

3. Arrangement as claimed in claim 2 wherein said lock remover means is substantially placed on front face of said cover means.

4. Arrangement as claimed in claim 1 wherein said cover means is made of plastic.

5. Arrangement as claimed in claim 1 wherein said energy storing elements comprising compression spring.

6. Arrangement as claimed in claim 5 wherein said spring comprising a first spring and second spring.

7. Arrangement as claimed in claim 6 wherein said first spring is operatively connected with said locker means.

8. Arrangement as claimed in claim 6 wherein said second spring is operatively connected with said lock remover means.

9. Arrangement as claimed in any of preceding claims wherein said first spring conducts force outwards adapted to push out the locker substantially outward to perform interlocking.

10. Arrangement as claimed in any of preceding claims wherein second spring conducts force outwards adapted to push out the latch remover substantially outward to perform de-latching.

11. Arrangement as claimed in any of the preceding claims wherein the rail is located on right side of draw out mechanism.

12. Arrangement as claimed in any of the preceding claims wherein the rail is optionally located on left side of draw out mechanism.

13. An improved interlock arrangement for draw-out mechanism for circuit as herein substantially described and illustrated with reference to the accompanying drawings.