FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
JAW ASSEMBLY CONNECTING CRADLE TERMINAL AND FIXED BREAKER TERMINAL FOR A DRAW OUT CIRCUIT BREAKER;
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 circuit breakers and more particularly to contact structure for a draw out circuit breaker.
Background of the Invention:
In electrical installations the circuit breakers are required to be fixed on a cradle. In order to provide electrical and physical connection of the electrical wirings in cradle to the terminals in the circuit breaker various means are provided in prior art.
One such means is discussed in US 6139347, which discloses an electrical fixing terminal for an electrical switchgear apparatus being disconnected by an axial withdrawal motion. In particular, an extractable circuit breaker, comprising a protruding part extending parallel to an axis of Withdrawal and, defined by its external surface on the side where its free end is located a contact surface designed to cooperate with fixing jaws of a plug-in contact whose plug-in jaws are designed to cooperate by plug-in with an electrical plug-in terminal. The contact surface follows the outline of a cylinder sector of axis perpendicular to the axis of the protruding part, of opening angle greater than 180.degree. and is designed to form a pivot for rotation of the plug-in contact around the axis of the cylinder. An application is plug-in multipole circuit breakers.
However the electrical fixing terminal as described in US 6139347 may not provide for enhanced current carrying capacity. This may result in reduction in

efficiency of the device. Also during long working of the switching device or the circuit breaker there may be heat generated which may reduce the efficiency of the switching device and the overall system.
There is therefore a requirement of such means which may provide the enhancement in the current carrying capacity of the circuit breaker.
Summary
In various embodiments of the invention a Jaw assembly allowing fixing and unfixing of a switching device to a cradle is provided. Such switching devices may be circuit breakers of various kinds.
In one embodiment herein is described a jaw assembly allowing fixing and unfixing of a switching device to a cradle, comprising; a cradle terminal having a protruding part of a hollow cylindrical shape on each of two opposite ends and a base protrusion in between said two opposite ends of the protruding parts, said protruding part and base protrusion forming the two parallel hollow cylindrical structure having an open end each; a jaw unit having a convex surface at one end, the said one end fixable into said open end of the said hollow cylindrical structure and the other end of the unit releasably fixable to a breaker terminal along outer surface of the said jaw unit.

The jaw assembly as described in the present invention makes it possible to choose the number of plug-in contacts according to the rated current and the electrodynamic withstand of the installation. The number and location of jaw unit may also be determined by the choice of the circuit breaker. Thus this configuration provides a great flexibility for a single frame.
Brief description of the Drawings:
Figure 1 shows a sectional view of jaw assembly on cradle terminal According to
an embodiment of the present invention
Figure 2 shows the cross-sectional view of the jaw assembly for one of the phase
of a multi phase circuit breaker according to an embodiment herein.
Figure 3 shows an exploded view of single jaw unit according to an embodiment
of the present invention.
Figure 4 shows side view of jaw assembly with cradle and breaker terminal
according to an embodiment of the present invention.
Figure 5 shows an isometric view of jaw assembly with cradle terminal as per an
embodiment of the present invention.
Figure 6 is sectional view of the breaker comprising jaw assembly according to
an embodiment of the present invention

Detailed Description of the Invention:
A Jaw assembly allowing fixing and unfixing of a switching device to a cradle is described. The cradle allows housing of various such switching devices with help of the jaw assembly as described. Such switching devices may be circuit breakers of various kinds.
The jaw assembly described in various embodiments of this invention provides the flexibility of the assembly in fixing of the switching device while also providing a larger surface area exposed. Among various advantages, this feature also provides consequent enhancement in heat dissipation from the surfaces through aiding natural convection currents of surrounding air.
This feature of the present invention also increases the nominal current rating of circuit breaker without resorting to increases in volume of copper of the current carrying components.
According to an embodiment of the present invention Figure 1 shows a sectional view of jaw assembly on cradle terminal. A cradle support 50 is clamped between cross pieces 51, 52, holds atleast one cradle terminal 10 and atleast one jaw unit 20. Cross pieces are supported by side frame 53, which comprises a rack-in arrangement enabling the circuit breaker housing to be inserted or extracted. Figure 2 shows the cross-sectional view of the jaw assembly for one of the phase of a multi phase circuit breaker according to an embodiment herein. As shown in figure 2, each phase of the circuit breaker comprises of cradle terminal 10, jaw assembly 20, breaker terminal 30 and a switching arrangement. Therefore, as a

skilled person in the art would realize various jaw units and cradle terminals may be arranged based on the number of phases of the circuit breaker. Cradle terminal remains fixed and constrained between cradle supports 50 on a base 16 and a protrusion 14 on each side of the jaw assembly as shown in figure 2. Each jaw unit 20 is fixed on the cradle terminal and when the circuit breaker is extracted from cradle frame, jaw unit remains on cradle terminal 10. The protrusion 14 restricts the forward movement of the cradle terminal. The cradle terminal as described in the present invention allows better flexibility in fixing of the switching device, while at same time providing a rugged arrangement of the jaw unit on the cradle terminal. The cradle terminal 10 comprises of two protruded parts 11a and a base protrusion 11b. The protruded parts 11a and the base protrusion together form two hollow cylindrical structure with open ends when seen along the cross-section. The hollow cylindrical structures have axes 15a and 15b respectively, which are parallel to each other. Each jaw unit may be fixed in the hollow cylindrical structures formed by the base protrusion and the protruded parts. The open ends of the hollow cylinders allow the jaw assembly to fit into the base protrusion and the protruded parts. The opposing forces from each of the jaw units ( ) are cancelled at the base protrusion.
Each jaw unit engages with the cradle terminal at the protruded surface and base protrusion. In particular a circular surface 22 of the jaw unit engages with the inner wall of the protruded parts and the base protrusion.

An E shaped breaker terminal may be engaged with the jaw units. The breaker terminal 30 comprises of entry surface 32 that eases jaw insertion into breaker terminal and two parallel U shaped contact surfaces 31 where contact surface 23 of jaw mates and provides connection with the main power circuit. This breaker terminal may be connected to basic switching unit 40.
According to an embodiment herein the figure 3 shows an exploded view of single jaw unit. The jaw unit comprises of two twin jaw fingers stack placed opposite to each other. Further according to an embodiment herein the side view of jaw assembly with cradle and breaker terminal is shown in figure 4. Each jaw unit 20 comprises of two twin jaw fingers stack 21 which provides connection between cradle terminal and breaker terminal to enable current flow after the breaker terminal is engaged with the jaw units. A side support 27 on each side of the jaw unit which restraints the vertical movement of jaw while being guided in slot 17 on cradle terminal 10 is provided. A guiding pin 24 which enables the swiveling motion of jaw fingers stack about the axis of the guiding pin when the jaw unit is not connected to cradle terminal 10 that eases jaw's entry into cradle terminal.
A spring 25 provides the required contact pressure, and spring support 26 that supports spring that compresses against this support. Any type of spring may be used in the embodiments of the invention such as for example leaf spring, compression spring etc.

Figure 5 shows an isometric view of jaw assembly with cradle terminal as per an embodiment of the present invention. The present invention allows the jaw units to be arranged vertically as well as horizontally. During arrangement of the jaw units in vertical position with respect to each other the arrangement allows for easy flow of heat through convection. This reduces the temperature of the arrangement and therefore improves the overall current carrying capacity of the switching device.
Figure 6 is sectional view of the breaker comprising jaw assembly according to an embodiment of the present invention. With vertical arrangement, convection and surface area can be increased at the same time. Vertical arrangement naturally aids heat dissipation because of upward flow of surrounding air through the jaw assembly. If certain vents can be provided in the cradle support that holds the jaw and cradle terminal so that air circulation through current carrying part increases, it will further release the generated heat to the surrounding. Also the jaw assembly as described in the present invention makes it possible to choose the number of plug-in contacts according to the rated current and the electrodynamic withstand of the installation. The number and location of jaw unit may also be determined by the choice of the circuit breaker. Thus this configuration provides a great flexibility for a single frame.

WE CLAIM:
1. A jaw assembly allowing fixing and unfixing of a switching device to a
cradle, comprising:
a cradle terminal having a protruding part of a hollow cylindrical shape on each of two opposite ends and a base protrusion in between said two opposite ends of the protruding parts, said protruding part and base protrusion forming the two parallel hollow cylindrical structure having an open end each;
a jaw unit having a convex surface at one end, the said one end fixable into said open end of the said hollow cylindrical structure and the other end of the unit releasably fixable to a breaker terminal along outer surface of the said jaw unit.
2. The jaw assembly as described in claim 1, wherein the said cradle
terminal is screwlessly fixable in the cradle.
3. The jaw assembly as described in claim 1, wherein two of said jaw units
placed horizontally allows fixing of an E-shaped breaker terminal into said
two jaw units, such that each jaw unit fixes along each of the U shaped
surface of the said E shaped circuit breaker terminal.
4. The jaw assembly as described in claim 1, wherein the jaw unit comprises two twin jaw fingers stack placed opposite to each other moving in unison with respect to anair gap between the said twin jaw fingers stacks.
5. The jaw assembly as described in claim 4, further comprising a guiding pin which enables the swiveling motion of each of said twin jaw unit parts.

6. The jaw assembly as described in claim 4, comprising a spring between two twin jaw unit parts providing required contact pressure of the jaw unit to the cradle terminal.
7. The jaw assembly as described in claim 4, wherein the air gap between said twin jaw finger stacks allowing unrestricted flow of air currents.

ABSTRACT
A Jaw assembly allowing fixing and unfixing of a switching device to a cradle is described. The cradle allows housing of various such switching devices with help of the jaw assembly as described. In its various embodiments jaw assembly allowing enhanced current carrying capacity. In one embodiments