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 DRAW-OUT MECHANISM FOR CIRCUIT BREAKERS AND SWITCHBOARDS

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 NVENTION

The present invention relates generally to circuit breakers and modules of switchboards for electrically connecting it to switchboards. More particularly, the invention is concerned about an improved draw-out mechanism for circuit breakers and switchboards with less manual effort without disturbing termination and to reduce the down time.

BACKGROUND OF THE INVENTION

Any switchboard has two sources of supply namely 1) main or power supply and 2) auxiliary supply. The main supply is connected to power contacts of the circuit breaker and auxiliary supply is fed to accessories like shunt release, UV release, etc. Withdrawable mechanism is used to connect the circuit breaker (Air Circuit Breaker (ACB) & Moulded Case Circuit Breaker (MCCB)) to switchboards and to connect the modules of switchboards (ex. Full width module) to main bus in the switchboards.

US 4051335 discloses a drawout apparatus includes 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 4743715 discloses 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 5309317 discloses a sliding mechanism (50) of a drawout type switchgear has 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).

The disadvantages of existing technologies are as follows:
1. The current products are occupying more space in the switchboards and lead to increase in switchboard cost.
2. Sluggish movements and tilting of the breaker may disturb the contact reliability.
3. Smooth operation is not possible in case of lever operated designs (Schneider).
4. Number of components is more. It may reduce reliability indirectly.

Thus, there is a need to overcome the disadvantages of the conventional mechanisms of the prior art and it is also desirable to make the invention to reduce the space occupied by draw-out unit, to reduce the operating force, to reduce the number of components and to develop a common mechanism which can be used for draw-out circuit breakers and modules of switchboards. The present inventors have developed an improved draw-out mechanism for circuit breakers and switchboards with less number of components resulting into reduction of over all size of the draw-out unit into a small size and with less manual effort without disturbing termination and to reduce the down time. It is suitable for draw-out of MCCB and ACB and switchboards.

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 draw-out mechanism for circuit breakers and switchboards.

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 aspect of the present invention there is provided an improved draw-out mechanism for circuit breakers and/or switchboards, said mechanism comprising:
plurality of plate means securing said circuit breaker on its both sides such that the circuit breaker is movable on the said plate means;
plurality of rail means;
bracket arrangement engaged to said circuit breaker and is tightly fitted to said rail means so as to move said circuit breaker during draw-out operation;
shaft means being operatively engaged to said rail means;
plurality of link means adapted to provide operative linkage between said rails and said shaft means such that rotational movement of said shaft means provides corresponding linear movement of said rail means.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Other features as well as the advantages of the invention will be clear from the following
description.

In the appended drawings:
Figure 1 illustrates a front and full view of a withdrawable arrangement with breaker & racking handle.

Figure 2 illustrates a breaker assembly in rear view.

Figure 3 illustrates a breaker assembly in side view.

Figure 4 illustrates a front view of the Draw-out arrangement.

Figure 5 illustrates a mechanism with rail.

Figure 6 illustrates a rear view of the mechanism

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS

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 mechanism 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.

According to the invention there is provided an improved draw-out mechanism for circuit breakers and switchboards. In the present invention, one common mechanism is developed which is suitable for draw-out of circuit breakers as well as switchboards. Rapid removal of the breaker is possible without unbolt or disturbing the termination by using the withdrawable unit (Draw-out module) is used. In this invention, the explanation is fully focused on withdrawable mechanism for MCCBs.

The full view of the draw-out unit is shown in the figure 1. Plug-in (1) is the base of draw-out as shown in figure 6. Plug-in (1) is having the current conducting parts (7) as shown in figure 4. Draw-out is used to establish connection between the breaker (3) and plug-in (1). The Draw out assembly consists of mechanism, locking (9) (Interlock or latching), safety trip (5), Position indication (15) and Auxiliary connections as shown in figure 4.

As shown in figures 4 and 5, the draw-out is having two outer plates (8) and a mechanism. The mechanism is having two rails (13), three links (12), one nut (11), three rivets (6) and a shaft (14). The breaker (3) is moving on the outer plate (8) with the help of bracket arrangement (4) and rails (13) as shown in figures 1,2 and 3. The bracket (4) is connected to the breaker (3) with the help of mounting screws of the breaker (3). Bracket (4) is having rivets on its both sides. The breaker (3) with bracket arrangement (4) tightly fitted to rails with the help of rivets and moves on the outer plates (8) with the help of mechanism so that sluggish movement of the breaker is eliminated. The mechanism is called ‘Screw-rod mechanism’. The two rails (13) allow the breaker movement only towards and away from the plug-in base (1). Two rails (13) are connected to the shaft (14) to make synchronized movement on both sides on the breaker (3).

When the operator inserts the racking handle (2) into the hole as shown in figure 4 provided in the front face of the draw-out, the racking handle (2) connects with the screw-rod (10) of the mechanism. When the operator rotates the racking handle (2) in clockwise direction, the screw-rod (10) rotates, the nut (11) (as shown in figure 5) moves, rivet (6) moves, link (12) rotates and the rail (13) moves. Thus the mechanism pulls the breaker (3) into plug-in (1).

The force is applied at the one side by the operator hands. Then the force is transmitted to other end by the mechanism (shaft (14) and links (12)) without any high level of stress. This is the key feature in this invention. The angle of the link (12) rotation is kept between +40° to -40° with reference to vertical side of the plug-in base (1) to reduce the applied force. Total distance is kept 40 mm. Due to this mechanism; over-all size of the draw-out unit is reduced to the extent of 10mm in width as well as depth of the draw-out when compared to Schneider & Moeller.

Position Indication (15):

Three distinct positions generally provided in the draw-out unit as shown in figure 4 to indicate the operator about the actual position of the breaker. They are ‘DISCONNECTION’ (both Aux. connections and power connections not connected), ‘TEST’ (Aux. connections only connected but not power supply) and ‘CONNECTION’ (both Aux. connections and power connections established). In the ‘TEST’ position, the auxiliaries are able to be tested. A safety trip feature (5) is also available in a draw-out unit to ensure that the breaker trips positively during rack-in and rack-out operation so that safety of operator and breaker is taken care.

The position of the breaker is clearly shown in front face of the draw-out. In this new invention, an arrow moves whenever the breaker moves so that the operator can know still how much distance to travel between positions. But in the existing product (Moeller), after reaching the ‘DISCONNECTION’ or ‘TEST’ or ‘CONNECTION’ positions, then only the arrow will come to those appropriate positions. Before that, the arrow is between those positions only and not moving even if the breaker is moving.

Visible area is converted to curve surface to reduce the components. The Latching, position indication (15) and mechanism are very close to each other to reduce the size and number of components.

ADVANTAGES OF THE INVENTION
1. Reduced space (in terms of width, height and depth) and reduction in applied force.
2. Suitable for draw-out circuit breakers and modules of switchboards.
3. The mechanism is scalable which is suitable for different frames of circuit breakers.
4. Reduction of number of components.

CONSTRUCTIONAL FEATURES

Plug in base 1
Racking handle 2
Breaker 3
Bracket 4
Safety trip assembly 5
Rail rivets 6
Plug in contacts 7
Outer plates 8
Lock/latch remover 9
Screw rod 10
Nut 11
Links 12
Rails 13
Shaft 14
Position indication 15

WE CLAIM:

1. An improved draw-out mechanism for circuit breakers and/or switchboards, said mechanism comprising:
plurality of plate means securing said circuit breaker on its both sides such that the circuit breaker is movable on the said plate means;
plurality of rail means;
bracket arrangement engaged to said circuit breaker and is tightly fitted to said rail means so as to move said circuit breaker during draw-out operation;
shaft means being operatively engaged to said rail means;
plurality of link means adapted to provide operative linkage between said rails and said shaft means such that rotational movement of said shaft means provides corresponding linear movement of said rail means.

2. Mechanism as claimed in claim 1, wherein said link means comprising slot means.

3. Mechanism as claimed in claims 1 and 2 wherein said link means having angle of rotation between about +40° and -40°.

4. Mechanism as claimed in claims 1 to 3 wherein said rail means comprising rivet means adapted to engage said rail means with said slot means of the link means.

5. Mechanism as claimed in claim 1 comprising a screw rod arrangement.

6. Mechanism as claimed in claim 5 wherein said arrangement comprising link means providing operative linkage between said screw rod arrangement and said shaft means.

7. Mechanism as claimed in claim 5 wherein said arrangement comprising rivet means.

8. Mechanism as claimed in claim 5 wherein said arrangement further comprising a holder means.

9. Mechanism as claimed in claim 1 further comprising a position indicator means.

10. An improved draw-out mechanism for circuit breakers and/or switchboards as herein substantially described and illustrated with the accompanying drawings