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: TRIP MECHANISM FOR RESIDUAL CURRENT DEVICE
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 generally to a trip mechanism that trips in case of a
residual current sensing and this trip actuation is taken to open the circuit breaker. More particularly, the invention relates to trip mechanism that forms a standalone block which when connected to Miniature circuit breaker (MCB) performs the needed function.
BACKGROUND AND PRIOR ART OF THE INVENTION
There are various trip mechanisms that get mechanical input from Permanent Magnet Release (PMR) and trips. This trip mechanism does not have any contact system to break but it gives mechanical output to the corresponding MCB to which it is connected and breaks open the circuit. It includes a PMR which needs an external force to reset once it has got tripped. So the trip mechanism must be capable of giving required force to reset plunger of PMR. This mechanism also has to actuate a test circuit and ensure that only when the mechanism is ON the test circuit should function. Various competitors offer these in different linkage mechanisms and our invention does it in way that others are not using.
The drawbacks of the above mentioned prior art is that
In order to accomplish the required functionality different components are used which increases the number of components and complexity of mechanism.
Functionality of standalone mechanism can't be verified easily
Thus there is a need to provide a mechanism as mentioned below:
In this concept a single component is used for reset of PMR plunger and actuation of test circuit.
The same component gives mechanical output to the corresponding MCB to which it. is connected to and trips it during residual current sensing.
Since mechanism is modular type and has two side plates within which all the components are held together. Drop-in type of assembly helps in easy assembly.

OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.
A basic object of the present invention is to provide a trip mechanism that forms a standalone block which when connected to Miniature circuit breaker (MCB) performs the needed function.
These and other 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
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of. the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
According to one of the aspect of the present invention there is provided a trip mechanism for residual current device, said mechanism comprising :
a side plate means over which all components are assembled,, said side plate comprises a hole and plurality of projection means;
an actuator means comprises a latch pin means, said actuator being assembled with a main spring means that is assembled along said projection means which acts as hinge point;

a knob means hinged into a hole in said side plate, said knob means comprises a knob spring which always tend to rotate said knob to OFF position;
a MCB trip actuation component is assembled in said side plate and it rotates with respect to said projection means in the side plate;
a trip pin means is attached to said MCB trip actuation component which engages with a latch means of MCB to trip during Residual current sensing;
a PMR reset spring hinged with respect to a projection means in said side plate, said PMR reset spring comprises a PMR plunger and said projection means is hinged with a trip component dropped in the side plate such that to lock said PMR reset spring in its position and to reset said PMR plunger ,
a reset spring holder hinged with respect to said projection in side plate such that
reset spring holder is in contact with said actuator during OFF condition and at
ON there exists a gap between them which helps in tripping to happen such
that other end of reset spring holder engages with said PMR reset spring, which
resets said PMR plunger once it pops out; and such that other end of said PMR
reset spring is connected to said trip component to reset the PMR plunger , said
trip component gets input from said PMR through said PMR plunger and
trips the entire mechanism.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is related to trip mechanism for Residual current devices that are added on to MCBs. MCB protects load from short circuit and overload and in order to add residual current protection to circuit an add on module which consist of Core Balanced Current Transformer (CBCT), Permanent Magnet

Release (PMR) and trip mechanism is attached to it to form an Residual current device with overload protection (RCBO).
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
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.
Figure 1 illustrates the assembly of RCD add on module with MCBs on its left side to form an RCBO.
Figure 2 illustrates the Trip mechanism, which is assembled into RCD Add on module to form the complete product.
Figure 3 illustrates various components that go into Trip mechanism
Figure 4 illustrates Trip mechanism at OFF condition
Figure 5 illustrates Trip mechanism at ON condition
Figure 6 illustrates Trip mechanism at Trip condition
Figure 7 illustrates Trip mechanism at OFF condition
Figure 8 illustrates various components that go into test circuit part of Trip mechanism at OFF condition
Figure 9 illustrates test circuit part of Trip mechanism at ON condition.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.

Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.
By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

Fig 1 depicts the assembly of RCD add on module with MCBs on its left side to form an RCBO.
In order to ensure that the attached RCD Add on module is functioning for residual current sensing and tripping the circuit the MCBs must be allowed to be made ON only when RCD Add on module is switched ON. The test circuit should function only when RCD Add on module is ON. When the PMR plunger pops out due to residual current sensing it trips the entire mechanism and external force is to be applied on PMR plunger in order to push it back to its initial position. The trip mechanism has to ensure all these requirements are taken care of and our mechanism has the components as explained below. The fig 2 depicts the Trip mechanism which is assembled into RCD Add on module to form the complete product.
The trip mechanism consists of a side plate (1) over which all components is assembled. An actuator (2) which is assembled with a main spring (3) is assembled over the side plate (1) in the projection (4) which acts as hinge point. This main spring (3) always tend to rotate the actuator (2) in counter clock wise direction. The actuator (2) has a latch pin (5) attached to it. The Upper latch (6) is hinged with respect to the latch pin (5). The lower latch (7) is hinged with respect to projection (4) in side plate (1) and it rests on the actuator (2).The lower latch is connected to latch spring (8) which rotates the latch always in clockwise direction. Both the lower and upper latch engages during OFF and ON operation. The knob (9) is hinged with respect to the hole present in the side plate (1) and it consist of knob spring (10) which always tend to rotate knob to OFF position. Both the Knob (9) and the upper latch are connected together with a u-pin (11). A MCB trip actuation component (12) is assembled in the side plate and it rotates with respect to projection (4) in the side plate. A trip pin (13) is attached to the MCB trip actuation component (12) which engages with the latch of MCB to trip during Residual current sensing.
Trip mechanism consist of a PMR reset spring (14) which is hinged with respect to projection (15) in side plate. In order to lock the spring in its position and to

reset PMR plunger (20) a reset spring holder (16) is hinged with respect to projection (17) in side plate (l).This reset spring holder (16) is in contact with actuator (2) during OFF condition and at ON there exists a gap between them which helps in tripping to happen. The other end of reset spring holder engages with PMR reset spring (14) which resets PMR plunger (20) once it pops out. A trip component (18) dropped in the side plate (1) which is hinged with respect to projection (15). The other end of the PMR reset spring (14) is connected to trip component (18) to reset the PMR plunger (20). The trip component gets input from PMR (19) through the PMR plunger (20) and trips the entire mechanism. Finally the PMR (19) is assembled on the side plate (1) through snap fits.
Once all the components are dropped into side plate (1) the other side plate (21) is assembled over it which holds all the components in its corresponding position. Both the side plates are rigidly connected together through snap fits located at three different locations.
The other side of the side plate (1) consist of a test burton (22) assembled over it and a test button spring (23) is hinged with respect to projection (24) on side plate (1). A resistor (25) is connected to the phase terminal at one end and at the otheT end it consists of a copper flat (26). This resistor (25) with copper flat (26) is assembled on the side plate (l).The one end of test button spring (23) will come in contact with copper flat (26) when the test button is pushed down by the user. The other end of test button spring (23) gets actuation from a projection (27) in actuator (2). The other end of test button spring (23) will come to contact with another copper flat (28) only when the mechanism is switched ON. The other end of copper flat is connected to neutral terminal.
Fig 8 depicts various components that go into test circuit part of Trip mechanism at OFF condition
Fig 9 depicts test circuit part of Trip mechanism at ON condition
Working

Fig 4 represents the trip mechanism in OFF condition. When the knob (9) of the trip mechanism is given a rotational input the 4 bar linkage system pushes the actuator (2) in clockwise direction. This is against the main spring force which pushes the actuator in counter clockwise direction. During this operation the upper latch (6) which is hinged to latch pin (5) found on actuator also rotates along with actuator. Since lower latch (7) is engaged to upper latch, lower latch also starts to rotate and takes up a position as showed in Fig 7 which is ON condition of trip mechanism. When there is a residual current sensed by the CBCT it gives an electrical output to the PMR (19) which in turn converts it into mechanical output through linear movement of PMR plunger (20). This plunger will push the trip component (18) and creates a torque in it. The trip component hits the lower latch and gives a force leading to counter clockwise rotation of lower latch leading to opening of latches. Due to the main spring energy the actuator comes back to its initial condition as in OFF state. When the actuator returns back it performs 3 main functions.
1. Actuator has a latch pin (5) attached to it. When actuator rotates this latch pin also rotates and moves the MCB trip actuation component (12) which helps in tripping the attached MCB.
2. During ON condition (Fig 5) the PMR reset spring (14) takes up zero degree deflection position giving no force to trip component (18) as well as reset spring holder (16) component. So now the PMR plunger can trip the entire mechanism. Once the mechanism is tripped the actuator rotates and engages with the reset spring holder. Due to this the reset spring holder rotates on clockwise direction which deflects the PMR reset spring. Due to this deflection the trip component gets force which will reset the PMR plunger.
3. The actuator has a projection (24)'which engages with one of the arm of test button spring (23) and gives actuation to it. When trip mechanism is at ON condition the projection takes the lower arm of test

button spring to override on the copper flat (28) assembled on the side plate. When the actuator rotates back to its initial position this contact override is broken leading to open in test circuit. So in this case of OFF condition the test circuit will not complete even if user presses the test button and makes the top contact (26) of test circuit.
• In order to achieve tripping of attached MCB due to residual current sensing the trip mechanism should give a rotary output to latch of MCB with having same pivot axis position and degree of rotation.
• MCB should not be made to switch ON until RCD Add on module that consists of Trip mechanism is switched ON.
• The trip mechanism should be capable enough to trip a 4pole MCB when a residual current is sensed.
• The test circuit of RCD Add on module should not function when trip mechanism is at OFF condition.
• The mechanism should be a bi-state type and should be capable enough to rest the PMR plunger one it has tripped the entire mechanism. The trip mechanism should be ready to operate for next cycle once the knob has completely fallen back to OFF condition.
Advantages:
Use of a single component (actuator) to achieve required functionality. Thus reducing introduction of extra number of components to achieve entire functionality. Subassembly and drop in kind of mechanism leading to ease of assembly.
Features:

• Use of single component (actuator) to achieve required functionality leading to reduction in dependencies of various components for entire functionality
• Test circuit has 2 contact openings
• The same trip component which trips the mechanism acts as reset for PMR plunger

WE CLAIM:
1. A Trip mechanism for residual current device, said mechanism comprising
a side plate means over which all components are assembled, said side plate comprises a hole and plurality of projection means;
an actuator means comprises a latch pin means, said actuator being assembled with a main spring means that is assembled along said projection means which acts as hinge point;
a knob means hinged into a hole in said side plate, said knob means comprises a knob spring which always tend to rotate said knob to OFF position;
a MCB trip actuation component is assembled in said side plate and it rotates with respect to said projection means in the side plate;
a trip pin means is attached to said MCB trip actuation component which engages with a latch means of MCB to trip during Residual current sensing;
a PMR reset spring hinged with respect to a projection means in said side plate, said PMR reset spring comprises a PMR plunger and said projection means is hinged with a trip component dropped in the side plate such that to lock said PMR reset spring in its position and to reset said PMR plunger
a reset spring holder hinged with respect to said projection in side plate such that reset spring holder is in contact with said actuator during OFF condition and at ON there exists a gap between them which helps in tripping to happen such that other end of reset spring holder engages with said PMR reset spring, which resets said PMR plunger once it pops out;

and such that other end of said PMR reset spring is connected to said trip component to reset the PMR plunger , said trip component gets input from said PMR through said PMR plunger and trips the entire mechanism.
2. Mechanism as claimed in claim 1 wherein said main spring (3) always tend to rotate the actuator (2) in counter clock wise direction.
3. Mechanism as claimed in claim 1 wherein said Upper latch (6) is hinged with respect to the latch pin (5).
4. Mechanism as claimed in claim 1 wherein said lower latch (7) is hinged with respect to the projection (4) in side plate (1) and said lower latch rests on the actuator (2).
5. Mechanism as claimed in claim 1 wherein said lower latch (7) is connected to a latch spring (8) which rotates the latch always in clockwise direction.
6. Mechanism as claimed in claim 4 and 5 wherein said lower and upper latch engages during OFF and ON operation.
7. Mechanism as claimed in claim 1 wherein said both the Knob (9) and the
upper latch are connected together with a u-pin (11).
8. Mechanism as claimed in claim 1 wherein said other side of the side plate (1) comprises of a test button (22) assembled over it and a test button spring (23) is hinged with respect to projection (24) on side plate (1).
9. Mechanism as claimed in claim 1 wherein side plate (1) the other side plate (21) is assembled over all the components of said mechanism and

holds all the components in its corresponding position, such said side plates are rigidly connected together through snap fits located at three different locations.
10. Mechanism as claimed in claim 1 further comprises a resistor (25) which is connected to the phase terminal at one end and at the other end it consists of a copper flat (26); such that said resistor (25) with copper flat (26) is assembled on the side plate (1).
11. Mechanism as claimed in claim 1 wherein said one end of test button spring (23) comes in contact with said copper flat (26) when the test button is pushed down by the user and said other end of test button spring (23) gets actuation from a projection (27) in actuator (2).
12. Mechanism as claimed in claim 1 wherein said other end of test button spring (23) will come to contact with another copper flat (28) only when the mechanism is switched ON and other end of copper flat is connected to neutral terminal.
13. Mechanism as claimed in claim 1 wherein said knob (9) of the trip mechanism is given a rotational input and pushes the actuator (2) in clockwise direction, such that it against the main spring force which pushes the actuator in counter clockwise direction.
14. Mechanism as claimed in any of the preceding claims wherein said upper latch (6) which is hinged to latch pin (5) found on actuator also rotates along with actuator.

15. Mechanism as claimed in claim 1 further comprises a CBCT such that a residual current sensed by the Core Balanced Current Transformer (CBCT) it gives an electrical output to the PMR (19) which in turn converts it into mechanical output through linear movement of PMR plunger (20).
16. Mechanism as claimed in any of the preceding claims wherein said plunger push the trip component (18) and creates a torque in it and said trip component hits the lower latch and gives a force leading to counter clockwise rotation of lower latch leading to opening of latches.
17. Mechanism as claimed in any of the preceding claims wherein said actuator comes back to its initial condition as in OFF state for said main spring energy.
18. A Trip mechanism for residual current device as herein substantially described and illustrated with the accompanying drawings.