FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See section 10, rule 13)
"Residual Current Circuit Breaker with Overcurrent Protection (RCBO) with an improved residual current kinematic chain"
LARSEN & TOUBRO LIMITED
L & T House, Ballard Estate, P. O. Box No. 278,
MUMBAI 400 001
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 circuit breakers. More particularly, relates to residual circuit breakers with overload protection with an improved residual current kinematic chain.
Background of the Invention
A conventional residual current circuit breaker with overcurrent protection ("RCBO") includes single housing configured to provide a miniature circuit breaker (MCB) portion and a residual current (for example, a ground fault) device (RCD) portion for providing combined protection from the risk of electrocution and protection against the risk of an electrical fire and overcurrent protection of equipment and cables. A typical conventional RCBO is of a size of approximately 125 mm in height, 18 mm in width and 70 mm deep.
The conventional residual current circuit breaker with overcurrent protection includes single housing configured to enclose together the kinematic chain of neutral pole and one of the residual current devices. In a RCBO the kinematic chain of the neutral pole and one of the residual current devices interweave each other.
The housing is multi-sectional and includes an interior wall dividing the space within the housing to provide equal or unequal distribution of the space within the RCBO. Space constraints may affect the functionality of the devices provided within the housing. The RCBO's currently in use are complex and difficult to be realized since the kinematic chains of the neutral pole and the residual current device lie in the same enclosure in the same housing. The proximity of the two kinematic chains leads to a condition where braking of one of the components of one kinematic chain causes an obstacle for the other.

Therefore, separate sections for the neutral pole kinematic chain and the residual current device are desired. Also, optimized space allocation within the circuit breaker is desired.
Further, a resistance fault in the test resistance can cause the burning of the resistance itself, hence damaging completely the kinematic chain and can potentially cause the breaking of the external casing. This occurs due to the presence of the test resistance in the same housing of the kinematic chain. Moreover the residual current Kinematic chain in the conventional device is complex owing to the small amounts (20-40 gr.) of force exerted by the relay.
There is a need for proper synchronization between different operating paths which are essentially requirement in the current art.
Summary of the Invention
The following presents a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.
In accordance with one aspect of the present invention is a Residual
Current Breaker with Overload (RCBO), comprising: a casing with a first
housing and a second housing, wherein the first housing and the second housing are separated by a first separation means, wherein the first housing including electrical components of miniature circuit board (MCB), and the second housing including neutral kinematic chain and a residual current device and its kinematic

chain, and wherein the residual current device includes a containment box for the test resistance.
Brief description of the drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various implementations of the invention and, together with the description, serve to explain the advantages and principles of the invention. In the drawings:
FIG. 1 shows a perspective external view of a RCBO with improved residual current kinematic chain, in accordance with an embodiment of the invention;
FIG. 2 shows a schematic diagram of a casing of the RCBO in accordance with the invention;
FIG. 3 is a detailed schematic diagram of the right side view of the RCBO in accordance with the invention;
FIG. 4 shows a partial exploded view of the residual current device portion of the RCBO in accordance with the invention;
FIG. 5 shows a schematic diagram of the residual current device portion of the RCBO in stable closed position in accordance with the invention;
FIG. 6 shows a schematic diagram of the residual current device portion of the RCBO in stable open position of in accordance with the invention.

FIG. 7 shows a schematic diagram of the residual current device portion of the RCBO innon-stable position after earth leakage in accordance with an embodiment of the invention,
FIG. 8 shows a schematic diagram of the residual current device portion of the RCBOin final stable position after earth leakage, in accordance with the invention.
Detail description of the Invention
The following detailed description of the invention refers to the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the following description to refer to the same and like parts. Dimensions of certain parts shown in the drawings may have been modified and/or exaggerated for the purposes of clarity or illustration.
Referring now to FIG. 1, a perspective external view of a RCBO with improved residual current kinematic chain, in accordance with an embodiment of the invention is shown. The RCBO includes a first housing IB enclosing a MCB portion and components and a second housing 1A. The second housing IA which encloses both the enclosures for neutral kinematic chain IC and one for the residual current device is disclosed. The first IB and second housings IA are separated from each other by means of a main frame 4.
FIG. 2, 3 shows the two separate enclosures, one for the neutral kinematic chain labelled IC and the other enclosure for a residual current device labelled ID. This separation is made by the secondary wall 5. Furthermore enclosure ID is closed by cover 9 as shown in FIG. 3. Thus by the introduction of the separation, the two kinematic chains i.e. one for the neutral pole and the one for residual current are physically separated, hence ensuring improved electrical insulation.

The two kinematic chains act of the neutral pole and residual current device act on common components in order to allow the operation of the RCBOs.
Referring now to FIG. 3, the test resistance 80 is completely closed by an enclosure comprising partly by the secondary wall 5 and partly by cover 9. This combination of the secondary wall 5 and cover 9 around the test resistance 80 forms the containment box 81. One or more walls of such a closed chamber allows for the passage of the electrical connection to and from the test resistance 80. By the usage of the containment box 81, in which the test resistance 80 is housed, thus confines the burning of the test resistance 80 to the enclosure. The breakage of the residual current kinematic chain or any disruptive effect on the casing is prevented.
Referring now to FIG. 4, the residual current device portion of the RCBO consists of the following main components; an indicator flag 10, a second arm 11, a lever 12, a drum coupled to the MCB handle 13, an actuating arm 14, and a first L lever 15 and second L lever 16. A toroidal core 17 and a relay 18 used in the RCBO are well known in the prior art and hence the operative features of the same are not described in detail The second L lever 16 is free to rotate around a fixed axis 20, which has a pin 30 of the relay 18 engaging it on one end and the first L lever 15 engaging it at the other end at a point 21. The point 21 is a toothed profile provided for stopping the counter clockwise rotation of the first L lever 15 during the operation of the RCBO.
The first L lever 15 is free to rotate around a fixed axis 22, which has its ends engaged by actuating arm 14 at a point 23 and to the second L lever 16 as described above. The actuating arm 14 does not have a fixed rotation axis; it is neither fixed to the casing or to the secondary wall 5. The actuating arm is free to rotate around its ends; one end rotatably engages with the first L lever 15 as described above, the other end rotatably engages with the arm 11 at point 24.

The arm 11 is free to rotate around its ends; one end rotatably engages with the arm 14 in 24 while the opposite end rotatably engages with the indicator flag 10 at point 25.
The indicator flag arm 10 is free to rotate around a fixed axis 26. One end of the arm is covered by the wall 10A is used for showing or hiding an indicating zone (coloured area) 10B, which is a part of the secondary wall 5, as seen in FIG. 2. The other end of the arm 10 engages with the arm 11 as stated above.
The drum 13 is free to rotate in its seat provided in the external casing and it is driven by the handle of the MCB section of the RCBO. The drum 13 is coupled with the U shaped lever 12 engaging the lever 12 at one end and the other free end is used to slide on the guiding rib 12A. The motion of this guiding rib 12A is stopped by secondary wall 5, thereby stopping the motion of the arm 10, as seen FIG. 2. The stopping rib 12B is provided for in the secondary wall 5, engages and is used to stop the motion of the arm 11 as described in the operation of the invention, as seen in FIG. 2. FIG. 2 also shows the position of the fixed axis 20, 22 and 26 on the secondary wall 5.
The residual current kinematic chain also consists of springs 40, 41 and 42. The first spring 40 is a torsional spring which acts between a support 40A of secondary wall 5 and the arm 10, hence pushing the arm 10 in a clockwise direction.
The second spring 41 is a torsional spring which acts between the fixed points of the external casing and the first lever 15. It has a fixed axis 41A which protrudes out of secondary wall 5, as seen in FIG. 2.
The third spring 42 is also a torsional spring positioned along the axis 20 and acting on the second lever 16 and on wall 5 for moving the second L lever 16 in a counter clockwise direction.

According to an embodiment of the present invention, in FIG. 5, 6, 7 and 8, the distinct phases of the RCBO operation is described.
FIG. 5 is a detailed schematic of the stable closed position of the RCBO operation. As shown the pin 30 of the relay 18 is in a retracted position. The second L lever 16 is completely rotated counter clockwise and engages the first L lever 15 at point 21, using the toothed end. The drum 13 has been rotated completely clockwise as a furtherance of the handle motion; this in turn ensures the upright motion of the lever 12, thereby facilitating the engagement and movement of the arm 14 to an upright position. The movement of arm 14 causes arm 11 to move to an upright position, till it is restricted by the stopping rib 12B. In this state the covering wall 10A hides the indicating zone (coloured area) 10B.
The RCBO is in a stable condition as arm 10 is pushed clockwise due to spring 40 and hence causing arm 14 in a clockwise direction and arm 11 is pushed counter clockwise, the latter restricted by the stopping rib 12B. This restriction ensures that the RCBO is stable.
FIG. 6 is a detailed schematic of the manually intervened, closed stable position of the RCBO operation. The drum 13 is rotated in a counter clockwise direction, through manual operation on the handle of the MCB. This counter clockwise motion of the drum 13 pushes the lever 12 to a downright position, enabling it to move freely. The rest of the components of the residual current kinematic chain retain the same position as provided in FIG. 5.
FIG. 7 is a detailed schematic of the intermediate non-stable position of the RCBO, which is reached subsequent to an earth leakage. The drum 13 is kept in complete clockwise position in other words ON position. The pin 30 of the relay 18 is extended, causing second L lever 16 to rotate in a clockwise direction, which in turn disengages first L lever 15. The counter clockwise movement of the

first L lever 15 moves arm 14, thereby moving arm 11 in a clockwise direction. The arm 10 is rotated completely clockwise due the combined effect of the clockwise movement of arm 11 and the force of spring 40. The rotation of arm 10 is restricted only by the stopping rib. The clockwise movement of the arm 10 results in the removal of 10A from the indicating zone (coloured area) 10B, this is viewed from the external casing through the window W, as seen in FIG. 1 & 4.
The RCBO is in a non-stable state as the handle of the MCB must be kept in fully clockwise position. The MCB section of the RCBO can be opened after the preceding state is reached by an action of the arm 10 to the pin 99. This engagement of arm 10 and pin 99 engages the lever of the MCB.
FIG.8 is a detailed schematic of final stable position of the RCBO, reached naturally after the state as described in FIG. 7 is reached. The spring 41 moves the first L lever 15 clockwise until the latter engages lever 16, following which the pin 30 of the relay 18 returns to a retracted position. The spring 40 cannot push first L lever 15 as the arm 10 has reached its stopping position. The indicating zone (coloured area) 10B can be viewed though the window W because of the removal of covering wall 10, this is visible till the next action on the handle of the MCB.
The state as described in FIG.5 can be reached from FIG.8 by acting on the handle of the MCB, this in turn causes drum 13 to act on lever 12 and the first L lever 15, rotating the same in a counter clockwise direction till it engages second L lever 16 at point 21.
Further action on the drum 13 causes the arm 10 to rotate causing covering wall 10A to cover the indicating zone (coloured area) 10B.
Further advantages and improvements may very well be made to the present invention without deviating from its scope. Although the invention has

been shown and described in what is conceived to be the most practical and preferred embodiment, it is recognized that departures may be made therefrom within the scope and spirit of the invention, which is not to be limited to the details disclosed herein but is to be accorded the full scope of the claims so as to embrace any and all equivalent devices and apparatus. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of the common general knowledge in this field.
In the summary of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprising" is used in the sense of "including", i.e. the features specified may be associated with further features in various embodiments of the invention.

We Claim:
1. A residual current circuit breaker with over-current protection (RCBO) for
providing combined protection from the risk of electrocution and protection
against the risk of an electrical fire and overcurrent protection of an electrical
equipment and a cable, the RCBO comprising:
a first housing 1B and a second housing 1A provided for enclosure and separated by a main frame 4;
a neutral kinematic chain 1C and a residual current device labelled ID enclosed by the enclosure formed by the first housing 1B and the second housing 1A;
a test resistance 80 enclosed by a containment box 81 disposed in the enclosure, wherein the containment box 81;
a first kinematic link disposed in the enclosure, the first kinematic link manually operated to switch on and trips in case of overload, breakage thereby preventing from overload and fire caused therefrom.
2. The residual current circuit breaker with over-current protection (RCBO)
as claimed in claim 1: wherein the first kinematic link comprises:
a handle with a drum for operating the residual current circuit breaker, in either 'ON' and 'OFF' position;
a second arm and a lever connected to the drum;
an indicator flag connected to the second arm, the indicator flag for indicating the status of the residual current circuit breaker;
an actuating arm connected to the drum;
a first lever connected to the actuating arm;
a second lever connected to the first lever; and mounted on a fixed axis;
a first spring disposed between the arm, a support and a wall of the residual current circuit breaker;
a second spring disposed between disposed the lever and the wall of the residual current circuit breaker; and

a third spring disposed on the fixed axis and acting on the second lever and the wall.
3. The residual current circuit breaker with over-current protection (RCBO) as claimed in claim 1: wherein the first spring, the second spring and the third spring are tensional spring.