FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
Single Pole Modular Changeover Switch
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.

SINGLE POLE MODULAR CHANGEOVER SWITCH
Field of the invention
The present invention relates to a modular changeover switch and more particularly, to a single pole modular changeover switch.
Background of the invention
The modular device such as modular changeover switch are generally used in distribution and building segments for isolation and transferring the load (L) from one source/ Source-I (S-I) to other source/ Source-II (S-II) with some delay. In general, the modular changeover switch is a three distinct position switch, namely: OFF, ON-I and ON-II. In OFF-state, no current will flow from source to load. Where as in ON-I and ON-II, the current flows from source to load. Consider, the supply comes to the source-I from Utility and source-II from Generator set.
In general the switch is always connected to Utility via Source-I. If there is any
major fault / variations in the supply, the load from source-I (Utility) is manually transferred (changeover) to the other source (source-II) that is the generator set. Since the load is transferred manually, it is called as manual changeover switch and under load (supply) the changeover is happening, so it is also called as on-load changeover switch. If Utility supply comes back, there is need to transfer the load from source-II to source-I. This entire process is carried out on three distinct positions namely- OFF-state, Source-I (ON-I state) and Source-II (ON-II state). These three different positions in all modular devices are achieved by means of a knob having three stable positions (OFF, ON-I and ON-II).

The termination capacity required for 63A single module (17.5mm) modular changeover switch to accommodate two different current carrying paths (box clamps of 63A) Source-I and Source-II for a common load (Source-I to Load and Source-II to Load) is as follows:

Current Rating Required Cable Cross-sectional Area Cable Outer Diameter (mm)

Rigid Cable Flexible Cable
63A 16sq.mm 5.3 6.3
Prior art methods make use of staggered ways in which the box clamps of 63 A are placed diagonally in the single module (17.5mm) modular changeover switch as shown in figure 1. Minimum space required to accommodate two box clamps diagonally in 1-module is 21.4mm which is calculated as follows:
= 2*6.3 (dim A: space for Cu conductor)
+ 2*1.5 (dim B: housing wall thickness)
+ 4*1.2 (dim C: box clamp thickness)
+ 1.5 (dim D: source separator/inter-phase thickness)
= 21.4mm
This requires an extra space. Further, protection against inter-phase and external flashover between two sources is not taken care of. Hence, accommodating two box clamps diagonally in 1-mod (17.5mm) is not feasible.
Accordingly, there is a need to provide a single pole modular changeover switch that overcomes the problems in the prior art.

Object of the present invention
An object of the present invention is to accommodate 63A box clamps in a modular changeover switch.
Another object of the present invention is to protect a single pole modular changeover switch from inter-phase flashover and external flashover between two sources.
Yet another object of the present invention is to provide an easy to assemble single pole modular changeover switch without requiring extra space and without resulting in pole width.
Summary of the invention
Accordingly, the present invention provides a single pole modular changeover
switch. The single pole modular changeover switch comprises a first housing, an
operating mechanism, a knob, a first terminal assembly, a second terminal assembly, a third terminal assembly, a second housing secured to the first housing,'a bridge assembly and a pair of din-clips.
The second housing is placed over the first housing with safety shutters positioned therebetween and the first terminal assembly is positioned above/over the second terminal assembly inside the first housing with an inter-phase barrier positioned therebetween to form the single pole modular changeover switch without resulting in an increase in pole width and without requiring extra space. Typically, the first terminal assembly and the second terminal assembly are secured to a left side of the

first housing. Typically, a first box clamp of the first terminal assembly is being positioned above a second box clamp of the second terminal assembly.
Brief description of the invention
The objectives and advantages of the present invention will become apparent from the following description read in accordance with the accompanying drawings wherein,
Figure 1 shows a single pole modular changeover switch having box clamps placed diagonally in accordance with a prior art;
Figure 2 shows an overall dimension of a single pole modular changeover, in accordance with the present invention;
Figure 3 shows the single pole modular changeover switch having first and second box clamps placed one over the above, in accordance with the present invention;
Figure 4 shows an inclined view of the single pole modular changeover switch of figure 3;
Figure 5 shows an exploded view of the single pole modular changeover switch of figure 3;
Figure 6a shows a cross-sectional view of the single pole modular changeover switch of figure 3 in OFF-position;

Figure 6b shows another cross-sectional view of the single pole modular changeover switch in OFF-condition and contact position at corresponding condition;
Figure 6c shows a cross-sectional view of the single pole modular changeover switch in ON-I-condition and contact position at corresponding condition;
Figure 6d shows a cross-sectional view of the single pole modular changeover switch in ON-II-condition and contact position at corresponding condition;
Figure 7 shows a construction of the box clamp of the single pole modular changeover switch of figure 3;
Figure 8 shows housings of the single pole modular changeover switch of figure 3;
Figures 9a -9d show a safety shutter fitted in the housing of figure 8;
Figure 10 shows a bridge assembly of the single pole modular changeover switch, in accordance with the present invention;
Figure 11 shows an inclined view of a stopper of the bridge assembly of figure 10; and
Figures 12-14 respectively show a terminal-1 assembly, a terminal-2 assembly and a terminal-3 assembly of the single pole modular changeover switch of figure 3.

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 embodiment.
The present invention provides a single pole modular changeover switch. The single pole modular changeover switch of the present invention is easy to assemble and accommodates two box clamps placed one above the other with minimum space utilization. The single pole modular changeover switch protects from inter-phase flashover and external flashover between two sources.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures.
Referring now to figures 2-14, there is shown a single pole modular changeover switch (100) (herein after 'the switch (100)'), in accordance with the present invention. Specifically, the switch (100) is a single pole 63A modular changeover switch having dimensions of width=17.5mm (1-Mod) and height= 100.6mm. However, it is understood that the other modular devices like miniature circuit breaker (MCB), isolator, earth leakage miniature circuit breaker (EL-MCB) and automatic changeover with current limiter (ACCL) with varying dimensions may be used in other alternative embodiments.
The switch (100) comprises a first housing (10), an operating mechanism (not numbered), a knob (20), a first terminal assembly (30), a second terminal assembly (40), a third terminal assembly (50), a second housing (60), a bridge assembly (70)

and a pair of din-clips (80). The above mentioned components are assembled using any suitable means known in the art. The first and the second housings (10, 60) (alternatively referred to as left and right housings) have common construction as shown in figure 8. The first terminal assembly (30) is secured inside the first housing (10).
The first terminal assembly (30) (figure 12) includes a first terminal/ source-I (S-I) incoming terminal (22), a first button (24), a first box clamp (26) and a first termination screw (28). The first terminal assembly (30) includes the second terminal assembly (40) (figure 13) mounted thereon. The second terminal assembly (40) includes a second terminal/ source-II (S-II) incoming terminal (32), a second button (34), a second box clamp (36) and a second termination screw (38). The first terminal assembly (30) (figure 13) is placed above the second terminal assembly (40) in such a way that the first box clamp (26) is placed above the second box clamp (36). In an embodiment, the first box clamp (26) and the second box clamp (36) have a width=9mm, thickness= 1.2mm and maximum termination capacity of 6.3mm as shown in figure 7.
The second housing (60) is placed over the first housing (10) in such a way that safety shutters (35) are positioned therebetween (as shown in figures 9a-9d) to act as external barriers for the two incoming terminals (22, 32) thereby preventing against external flashover and also provides IP20/ finger proof protection during termination. The construction of the housing (10, 60) is such that the S-II incoming terminal (32) always terminates first followed by the S-I incoming terminal (22). The safety shutter (35). Specifically, the safety shutters (35) are easily flappable for terminating the second termination screw (38) of the second terminal assembly (40). The first terminal assembly (30) and the second terminal assembly (40) include inbuilt inter-phase barriers-positioned between S-I and S-II incoming terminals (22,

32) as shown in figure 3. The inter-phase barriers separate entire current path at the S-I and S-II incoming terminals (22,32) thereby protecting against from inter-phase flashover.
The third terminal assembly (50) is secured inside the first housing (10) opposite to the first terminal assembly (30). The third terminal assembly (50) (figure 14) includes a third terminal (42), a pair of third buttons (44), a third box clamp (46) and a third termination screw (48). The third terminal (42) is used as a common outgoing terminal (L) for the S-I and S-II incoming terminals (22, 32). In an embodiment, the first, the second and the third termination screws (28,38, and 48) are M5 termination screws. The first, second and third terminal assemblies (30, 40, 50) have a termination capacity of 16 sq.mm c/s area. Thus 16sq.mm cross-sectional area flexible Cu cable is capable of easy accommodation in the switch (100).
The housings (10,60) have cam profiles means the housings (10,60) are symmetric about X as well as Y axis, facilitating face to face assembly with each other to form a pole of the switch (100). The housings (10,60) are secured to each other. The pair of din-clips (30) is secured to bottom of the housings (10, 60). The second housing (60) is secured to the first housing (10) by the bridge assembly (70). The bridge assembly (70) includes a bridge (61), a bridge pin (62), a stopper (63), a contact spring (64), a mechanism spring (65) and a pair of moving contact units (67) having a moving contact (66)). In an embodiment, the pair of moving contact units (67) is used for the S-I and S-II incoming terminals (22, 32) to provide contact pressure at contact joints. The contact spring (64) is used to maintain contact pressure at joints. The stopper (63) and the mechanism spring (65) are. adapted to operate in ON-I, OFF and TRIP positions of the switch (100). The stopper (63) is under loading

condition in OFF, ON-I and ON-II positions of the switch (100) that are indicated by the knob (20). The knob (20) includes a knob sleeve (12).
When the switch (100) is in OFF position (shown in figure 6), the changeover is terminated with the two incoming sources (22/S-I and 32/S-II) from the first and the second terminal assemblies (30, 40) and outgoing load terminal (42/L) of the third terminal assembly (50). In OFF position as shown in figure 9a, the moving contact unit (67) of the S-I and S-II incoming terminals (22, 32) are isolated by an equal distance (3+3=6mm) on each side. In ON-1 position of the switch (100) (as shown in figure 9b) the current flows through the S-I incoming terminal (22) to load terminal (42/L) of the third terminal assembly (50). The S-II incoming terminal (32) is isolated by 8mm distance (4+4 =8mm, 1mm is over travel) at contacts. In ON-II-condition of the switch (100) (as shown in figure 9c), the current flows through the S-II incoming terminal (32) to the load terminal (42/L) of the third terminal assembly (50). The S-I incoming terminal (22) is isolated by 8mm distance (4+4 =8mm, 1mm is over travel) at contacts.
Advantages of the present invention:
1. With unique construction of the housings (10, 60), the two box clamps (26, 36) are arranged one over the above in the switch (100) forming single pole 1-mod (17.5mm) changeover switch (100). This arrangement of the two box clamps (26, 36) does not result in increment in pole width and also no extra space is needed, hence, accommodating two box clamps (26, 36) one over the above in 1-mod (17.5mm.) is possible.
2. Prevents inter-phase flashover and external flashover and also provides IP20 protection (Ingress protection - Finger proof).

3. The unique construction of the housings (10, 60) means the two housings (10,60) are assembled face to face to form a modular pole thereby reducing the number of components such as side core in tool and hence tooling investment.
4. With unique construction of the housings (10, 60), few components are commonized, hence reducing tool cost and complexity and increasing the
production. The construction of the housings (10, 60) is such that, fixed terminal is commonized.
5. With unique construction of the housings (10, 60), no need of poka-yoke and all components are assembled easily.
6. The tri-stable position mechanism is used to get three distinct positions namely: OFF, ON-I and ON-II, which is achieved by providing a peculiar profile in the housings (10,60) and the stopper (63).
7. Very compact mechanism that occupies only 2% volume in the switch (100).
8. Cam profile on the housing (10, 60) is symmetric about X as well as Y axis, facilitating face to face assembly of the housings (10, 60) to form a pole of the switch (100).
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed

herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.

We Claim:
1. A single pole modular changeover switch (100) comprising a first housing (10), an operating mechanism, a knob (20), a first terminal assembly (30), a second terminal assembly (40), a third terminal assembly (50), a second housing (60) secured to the first housing (10), a bridge assembly (70) and a pair of din-clips (80), characterized in that the second housing (60) being placed over the first housing (10) with safety shutters (35) positioned therebetween and the first terminal assembly (30) being positioned above/over the second terminal assembly (40) inside the first housing (10) with an inter-phase barrier positioned therebetween to form the single pole modular changeover switch (100) without resulting in an increase in pole width and without requiring extra space.
2. The single pole modular changeover switch (100) as claimed in claim 1 is characterized in that the first terminal assembly (30) and the second terminal assembly (40) being secured to a left side of the first housing (10).
3. The single pole modular changeover switch (100) as claimed in claiml is characterized in that a first box clamp (26) of the first terminal assembly (30) being positioned above a second box clamp (36) of the second terminal assembly (40).