FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
A LOCKING ARRANGEMENT FOR SWITCHING DEVICES;
LARSEN & TOUBRO LIMITED, A COMPANY INCORPORATED UNDER THE COMPANIES ACT, 1956, WHOSE ADDRESS IS L & T HOUSE, BALLARD ESTATE, MUMBAI - 400 001, MAHARASHTRA, INDIA.
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 switching devices, for example to a locking arrangement for switching devices.
DESCRIPTION OF THE BACKGROUND ART
Switching devices such as current limiting circuit breakers are well known in the related field of art. Generally, a circuit breaker is installed at an electric power distributing board among several electric power systems. The circuit breaker serves as a switch for supplying or cutting off power to a load side under no load state, and cuts off power supplied to a load side from a power side in order to protect a circuit and components of the load side when a great abnormal current due to a short-circuit or a ground fault flows on a circuit under a load state. The circuit breaker comprises of various components and contact system forms one part of the same. When a very high current flows through the system the contacts are so shaped that they repel because of current repulsion effect. Also known in the art is the different mechanism by which the contact arms of the circuit breakers are linked to the housing in which the contact arms are operatively arranged. Normally, upon flow of high current in the electric circuit the movable contacts open thereby breaking the circuit and stopping the current flow further. Most of the circuit breakers having movable contact arms that are linked via a spring and lever arrangement that helps in efficient mobility of the contact arms in case of flow of high value current.
Currently, these circuit breakers are available according to various industrial needs, the most common of which entrusts the opening of the contacts to complicated kinematic mechanisms actuated by the mechanical energy stored beforehand in special opening springs.

In certain operating conditions, particularly when the presumed short-circuit current can assume significantly high values, the use of devices that utilize in a traditional manner the energy that can be accumulated in the opening springs can be scarcely efficient and uneconomical for opening the contacts, in such cases, it is common to resort to special types of automatic circuit breaker that have technical solutions aimed at increasing their breaking capacity. The flow of current is interrupted in each pole of the circuit breaker in two separate regions that are arranged electrically in series to each other, so that each region is subjected to a lower mechanical and thermal stress A particularly critical aspect of known types of circuit breaker is the fact that the presence of electrodynamic repulsion forces, despite contributing positively to the generation of the thrust useful for contact separation, helps the moving contact structure to reach the end of its stroke at high speed and therefore with great energy; this aspect tends to cause violent impacts against the case of the circuit breaker, to the point of requiring the possible use of additional cushioning elements, and may cause bouncing of the moving contacts toward the fixed contacts and undesirable restrikes of the electric arc.
To contrast this possibility, some known solutions use additional systems for latching the moving contacts in the open position, in other known solutions, the structure of the moving contacts and of the functional elements associated therewith is instead configured appropriately so that during the separation stroke of the contacts the moving contacts are slowed.
It is quite evident after going through the aforementioned solutions that however the functional elements are so configured that upon separation movement of the contacts gets slowed but still possibility of bouncing back of the moving contacts is there which may erode the contact arms.

However, the aforementioned solutions address to the problem of locking the
contact arms upon separation, still the components of the operating mechanism
as arranged In the circuit breaker tends to be very complex, which may lead to
maintenance problems later on.
Hence there is a need of such an assembly of a circuit breaker that is relatively
simpler in construction and still efficiently solves the above-discussed problems.
SUMMARY
Accordingly it is an object of the present invention to solve atleast one of the
abovementioned problems.
Embodiments of the present invention provide a locking arrangement for
switching devices for rapidly locking upon circuit breakage condition. This rapid
locking of the switching device is provided by operatively connecting a movable
contact, a assembly of connecting pin, a connecting means and a driveshaft. In
an embodiment of the present invention a locking arrangement for switching
devices comprises a housing having a driveshaft adapted in the housing, a pair
of plates extending from the housing, and a recess provided in between the pair
of plates.
Atleast one movable contact is pivotally arranged with the plates through a first
rod. A assembly of connecting pin for each movable contact adapted to a rear
portion of the movable contact.
According to another embodiment of the present invention a compression spring
is adapted in between the driveshaft and the assembly of connecting pin and
received in the recess of the housing, wherein the movable contact, the
assembly of connecting pin, the compression spring and the driveshaft are
operatively connected in such a way that as the circuit breaks the compression

spring slides on the surface of the driveshaft thereby locking the switching
device.
The compression spring is engaged with the assembly of connecting pin and
round shape of the driveshaft.
According to another embodiment the assembly of connecting pin further
comprises of an assembly of one pin connected orthogonally to another pin by
means of threading.
Other objects, features and advantages of the invention will be apparent from the
drawings, and from the detailed description that follows below.
A BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to embodiments of the invention, examples of which may
be illustrated in the accompanying figures. These figures are intended to be
illustrative, not limiting. Although the invention is generally described in the
context of these embodiments, it should be understood that it is not intended to
limit the scope of the invention to these particular embodiments.
Figure 1 illustrates the arrangement of contact system in the driveshaft by
means of the springs and assembly of connecting pin according to the present
invention.
Figure 2 is the side view of figure 1 illustrating position of the assembled movable
contact and compression spring in close position of the switching device
according to an embodiment of the present invention.
Figure 3 illustrates the position of the assembled movable contact and
compression spring after the magnetic repulsion of the movable contact where
the movable contacts are in locked position according to an embodiment of the
present invention.

Figure 4 shows the exploded view of the movable contact, compression spring
and assembly of connecting pin arrangement according to an embodiment of the
present invention.
Figure 5 shows the exploded view of the arrangement of the switching device
according to an embodiment of the present invention.
DETAILD DESCRIPTION OF THE PRESENT INVENTION
A locking arrangement for switching devices for rapidly locking the switching
device is described herein. An assembly of connecting pin is adapted at a rear
end of a movable contact, the other end of the assembly of connecting pin is
attached to a compression spring that in turn is adapted to a driveshaft. The
driveshaft is provided in housing. As the circuit breaks, due to flowing of very
high current and magnetic repulsion between fixed and movable contacts, the
movable contact opens and a mechanical force is exerted upon the assembly of
connecting pin that transmits the force to the compression spring which slides on
round surface of the driveshaft.
Reference in the specification to "an embodiment" or "another embodiment"
means that a particular feature, structure, characteristic, or function described in
connection with the embodiment is included in at least one embodiment of the
invention.
In an embodiment of the present invention, a locking arrangement for switching
devices comprises a housing having a driveshaft adapted therein, a pair of plates
extending from the housing, and a recess provided in between the plates , atleast
one movable contact pivotally connected to the plates, an assembly of
connecting pin for each movable contact adapted to a rear portion of the movable
contact, and a compression spring adapted in between the driveshaft and the
assembly of connecting pin and received in the recess of the housing, wherein

the movable contact, the assembly of connecting pin, the compression spring and the driveshaft are operatively connected in such a way that as the circuit breaks the compression spring slides on the surface of the driveshaft thereby locking the switching device.
Figure 1 illustrates the driveshaft (2) and its arrangement in the housing of the switching device. The housing of the switching device has atleast one movable contact (1) (for the purpose of clarity two movable contacts are shown in figure 1) pivoted to the pair of plates (3,4) extending from the housing of the switching device. The movable contact (1) is preferably manufactured from copper material that can be single or multi finger movable contact (1) pivoted to the holes in the plates (3, 4). The movable contact (1) is attached to the driveshaft (2) via the assembly of connecting pin (7) and the compression spring (6) by means of molding process. A first rod (5) is used to pivot the movable contact (1) to the plates (3,4) extending from the housing.
The housing of the switching device have a recess in between the pair of plates (3,4), which retains the compression spring (6) whose one end is adapted to the assembly of connecting pin (7) and the other end is rested on round surface of the driveshaft (2). The compression spring (6) is retained in the recess provided on the housing. Further, each of the plates (3,4) of the pair of plates (3,4) extending from the housing has a set of two holes respectively. The two holes on each of the plates (3,4) are at a distance apart and coaxial with the two holes in the other plate. The movable contact (1) is always under mechanical pressure through the compression spring (6) as referred in fig. 2 and fig. 3. Figure 2 illustrates position of the movable contact (1) and the compression spring (6) in close position of the switching device. The movable contact (1) is pivoted to the plate (3, 4) by means of the first rod (5) that always remains under

mechanical pressure by means of the compression spring (6). A second rod (8) joins the pair plates (3,4) and above the first rod (5) thereby restricting the movement of the movable contact (1) beyond a certain maximum position in case of circuit breaking.
The compression spring (6) is trapped between the round shaped driveshaft (2) surface and the assembly of connecting pin (7). The assembly of connecting pin (7) is connected to a slot provided at the rear end of the movable contact (1) that applies mechanical pressure by means of the compression spring (6). The compression spring (6) slides rapidly on the round shaped driveshaft (2) surface when the magnetic repulsion occurs between movable and fixed contacts and as shown in figure 3.
As shown in Figure 3, when very high current flows through the circuit breaker due to the magnetic repulsion between the movable contact (1) and fixed contact, the contacts get separated. As per the present invention, as the movable contact (1) gets separated the compression spring (6) gets compressed exerting force on the moving contact (1). Since the compression spring (6) is rested on round shaped driveshaft (2), it changes the direction of exerting force rapidly. Thus the compression spring (6) slides rapidly on the round shaped driveshaft (2) surface due the mechanical force and crosses the dead centre i.e. changes the force direction thereby locking the movable contact (1) in the separated position as shown in fig. 3. Further, the second rod (8) joining the pair of plates (3,4) restricts the movement of the movable contact (1) beyond a certain maximum position.
According to another embodiment the assembly of connecting pin (7a, 7b) further comprises of an assembly of one pin connected orthogonally to another pin by means of threading and as illustrated in the exploded view and as shown in fig. 4.

Also shown are the compression spring (6) and the assembly of connecting pin (7a, 7b) assembly. The connecting pin assembly (7a, & 7b) is co-axial with the compression spring (6).
Fig. 5 shows the exploded view of the switching device as illustrated in fig.1. The compression spring (6) is placed into the recess provided in the housing of the switching device and rear end of the same is adapted to the round surface of the driveshaft (2). The driveshaft (2) is adapted inside the housing. Front end of the compression spring (6) is attached to the assembly of connecting pin (7), the assembly of connecting pin (7) being adapted to the slot provided on the movable contact (1) in such a way that the compression spring (6) is trapped in between the assembly of connecting pin (7) and the round surface of the driveshaft (2). Further, a pair of holes is also provided in each of the plates (3,4) extending from the housing as shown in figure 5. the first rod (5) pivots the movable contact (1) to the plates (3,4) and the second rod (8) restricts the opening of the movable contact (1) beyond a predetermined position (as referred in figure2).
One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of other switching devices particularly for locking in case of circuit break condition. It is understood by a person skilled in the art, the foregoing preferred embodiments of the present invention are illustrative of the present invention rather than limiting of the present invention. It is intended that various modifications and similar arrangements be included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.

WE CLAIM
1. A locking arrangement for switching devices, comprising;
a housing having a driveshaft adapted therein, a pair of plates extending
from the housing, and a recess provided in between the plates;
atleast one movable contact pivotally connected to the plates;
an assembly of connecting pin for each movable contact adapted to a rear
portion of the movable contact; and
a compression spring adapted in between the driveshaft and the assembly
of connecting pin and received in the recess of the housing, wherein the
movable contact, the assembly of connecting pin, the compression spring
and the driveshaft are operatively connected in such a way that as the
circuit breaks the compression spring slides on the surface of the
driveshaft thereby locking the switching device.
2. The locking arrangement as claimed in claim 1, further comprises of one pin connected orthogonally to another pin by means of threading in the assembly of connecting pin.
3. The locking arrangement as claimed in claim 1, wherein more than one movable contact may be pivoted to the plates of the housing.
4. The locking arrangement as claimed in claim 1, wherein the compression spring is engaged with the assembly of connecting pin and round shape of the driveshaft.
5. The locking arrangement as claimed in claim 1, wherein a slot is provided at the rear end of the movable contact to which the assembly of connecting pin is adapted.

6. The locking arrangement as claimed in claim 1, wherein one end of the compression spring engages with the assembly of connecting pin and the other end engages with the round shape of the driveshaft.
7. The locking arrangement as claimed in claim 1, wherein the compression spring is retained in the recess.
8. The locking arrangement as claimed in claim 1, wherein the assembly of connecting pin is coaxially adapted to the compression spring.
9. The locking arrangement as claimed in claim 1, wherein each plate of the pair of plates has a set of two holes respectively, the set of two holes on each plate are coaxial to each other.
10. The locking arrangement as claimed in claim 1, wherein a first rod pivots the movable contact with the pair of plates.
11. The locking arrangement as claimed in claim 1, wherein a second rod joins the pair of plates and above the first rod thereby restricting the movement of the movable contact beyond a certain maximum position in case of circuit breaking.
12. The locking arrangement as claimed in claim 1 as described in previous description and drawings.

ABSTRACT
A locking arrangement for switching devices comprises a housing having a driveshaft adapted therein, a pair of plates extending from the housing, and a recess provided in between the plates, atleast one movable contact pivotally connected to the plates, a assembly of connecting pin for each movable contact adapted to a rear portion of the movable contact, and a compression spring adapted in between the driveshaft and the assembly of connecting pin and received in the recess of the housing, wherein the movable contact, the assembly of connecting pin, the compression spring and the driveshaft are operatively connected in such a way that as the circuit breaks the compression spring slides on the surface of the driveshaft thereby locking the switching device.
Reference figure 5.