FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
Latching Assembly for Circuit Breaker
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: LARSEN & TOUBRO LIMITED,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification
particularly describes the invention and the manner in which it is to be performed.

Latching Assembly for Circuit Breaker Field of the invention
The present invention relates to a latching assembly for circuit breaker, and more particularly to the assembly for achieving latching by varying center of gravity of the latch.
Background of the invention
Generally, switchgear mechanisms use methods of latching for holding a moving body in place after achieving its intended motion. There are acceleration sensitive latches present in several designs, however, none of these can be used for a multiple values of acceleration
Hence, there is a need of a latch which can be used for a band of accelerations, by making slight variations in the latch.
Object of the invention
An object of the present invention is to use a latching for a band of accelerations by making slight variations in a latching member.
Summary of the invention
Accordingly, the present invention provides a latching assembly for a moving contact of a circuit breaker. The latching assembly comprises a shaft member housed rotatably in bearing members of the moving contact The latching assembly further comprises a latching member placed pivotably on an extension of the shaft member. The latching member includes an opening for .

pivoting the latching member to the shaft member, and a slot for accommodating a dummy weight, the dummy weight capable of being moved along the body of the latching member -wherein, when the shaft member moves anti-clockwise as viewed in Figure 2 and Figure 3, the shaft member gains angular acceleration, thereby increasing angular velocity thereof. Further, when the shaft member stops, the latching member experiences acceleration with respect to the shaft and lies between the shaft member and a stopper link, thereby acting as a column to restrict any displacement of the shaft member.
Brief description of drawings
Figure lshows a cross sectional view of a latching assembly showing initial condition of the latching assembly (position A), in accordance with the present invention;
Figure 2 shows a cross sectional view of the latching assembly showing locking state of the latching assembly (position B);
Figure 3 shows across sectional view of the latching member with respect to a shaft member of the latching assembly of figure 1;
Figure 4 shows a cross sectional view of a motion of a dummy weight with respect to the latching member of the latching assembly of figure 1;
Figure 5 shows a perspective view of the latching member of the latching assembly of figure 1;
Figure 6 shows forces acting in latching assembly; and

Figure 7 shows resolution of forces acting in the latching assembly.
Detailed description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
The present invention provides a latching assembly for a moving contact of a circuit breaker and a method to achieve latching by varying the center of gravity of the latching member. The latching assembly defines a way to vary the position of the center of gravity of a link to suit the acceleration of a shaft member. The invention also provides a means to constrain the motion of the shaft member by trapping the link between it and a stopper pin. The motion of the link is controlled by the acceleration of the shaft and the position of the center of gravity of the link with respect to the pivot axis of the said link.
Referring to figure 1 to 7, there are shown various views and components of the latching assembly for a moving contact of a circuit breaker. Specifically, figures 1 and 2 show various positions of the latching assembly (100]. The latching assembly (100] includes a shaft member (10] and a latching member (20).
The shaft member (10) is housed rotatably in pivot (12) in bearing members of the moving contact (not shown) of the circuit breaker. The shaft member (10) is coupled to the latching member (20).
Specifically, the latching member (20) is placed pivotably using a pivot (20a) on an extension of the shaft member (10). As shown in figure 3, the latching

member (20) includes an opening (22) for pivoting the latching member (20) to the shaft member (10). The latching member (20) further includes an elongated slot (24) configured thereon for accommodating a dummy weight (26). The dummy weight (26) is capable of being moved along the body of the latching member (20) and can be fixed within the slot (24) when needed.
During operation, the shaft member (10) moves from position A as shown in figure 1 to position B as shown in figure 2. During this motion, the shaft member (10) gains angular acceleration, and the angular velocity of the shaft member (10) increases. However, motion of the shaft member (10) is stopped at position B as shown in figure 2, thus bringing the velocity thereof to zero.
At position B, the inertia of the assembly (100) is at an apogee. As the shaft member (10) reaches position B and stops, the latching member (20) experiences acceleration with respect to the shaft member (10). Thus, the latching member (20) travels from its initial position C as shown in figure 3 to position D. In position D, the latching member (20) lies between the shaft member (10) and a stopper link (30), and acts like a column to restrict any displacement of the shaft member.
If m is the mass of the latching member (20), w is the angular velocity of the shaft member (10), R is the distance of the center of gravity of the latch member (20) from the rotational axis of the shaft member (10), and X is the angle made by the line joining the rotational axis of the shaft member (10) to the center of gravity of the latching member (20), and the line joining the pivot axis of the latching member(20) with the center of gravity of the latching member (20) as shown in Figure 4:Then, as the shaft member (10) rotates from Position A to Position B, the latching member (20) experiences centrifugal force acting at its center of gravity passing from the center of

rotation of the shaft member (10). This force would be equal to mw2R. The component of this force creating a turning moment about the pivot axis of the dynamic latch is given by mw2R sinX. The said turning moment created would thus be mw2RsinX(Rlatch) as seen in Figure 6.
The angular acceleration of the latching member (20) about its pivot axis is
say a, and the moment of inertia is 1. then I = m*Rlatch2.
The turning moment about the pivot of the dynamic latch = I. a
Then mw2RsmX(Rlatch) = m*Rlatch2* a.
Hence, a = w2RsinX/Rlatch
The angular velocity of the dynamic latch = ∫ a.dt
The angular displacement of the dynamic latch = ∫ ∫ a.dt
The time taken to cover the required angular displacement is crucial for the
latching of the shaft member (10).
The position B of the shaft member (10) is chosen such that the normal force created by the latching member (20) on the shaft member (10) causes a reverse turning moment about the rotational axis of the shaft member (10] thus locking the shaft member (10) position B as shown in figure 6
Advantages of the invention
1. The latching assembly(lOO) provides a latching systemwhich has a
canonical relation with the acceleration of the shaft which houses the latching
system rotatably.
2. The latching assembly (100)has a provision for changing the distance of
the center of gravity from a pivotable mounting position of the latching
system.

3. The latching assembly (100) of the present invention uses a dummy weight placed on the latch which can be moved along the body of the latch and fixed when needed.
4. The latching assembly (100) of the present invention uses variable center of gravity for adjusting with deviations in the acceleration of the shaft.
5. The latching assembly (100) has modularity with multiple shafts,
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

We Claim:
1. A latching assembly (100) for a moving contact of a circuit '
breaker, the latching assembly comprising:
a shaft member [10] housed rotatably in bearing members of the moving contact; and
a latching member (20) placed pivotably on an extension (10a) of the shaft member (10), the latching member having,
an opening (22) for pivoting the latching member (20)
to the extension of the shaft member (10),
a slot (24) for accommodating a dummy weight changing (26), the dummy weight (26) being capable of being moved along the body of the latching member (20)and thereby causing . change in the center of gravity of the latching member,
wherein when the shaft member (10) moves anti-clockwise, the shaft member (10) gains angular acceleration, thereby increasing angular velocity thereof and when the shaft member (10) stops, the latching member (10) experiences an acceleration with respect to the shaft member (10) and lies between the shaft member (10) and a stopper link (30), thereby acting as a column to restrict any displacement of the shaft member (10).
2, The latching assembly of claim 1, wherein the dummy weight
(26) is capable of being fixed along the body of the latching member (20)
when needed.