FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Mechanical Interlock Device For Interlocking Switching Devices"
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.

Mechanical Interlock Device For Interlocking Switching Devices
Field of the invention
The present invention relates generally to mechanical interlock device, and more particularly, to the mechanically interlock for interlocking two switching devices.
Background of the invention
Generally, mechanical interlocking is provided outside a switching device/contactor as an accessory. Further, the mechanical interlocking is provided as an external system to mechanically interlock the motion of two switching devices/contactors. In changeover applications, the mechanical interlocking is used so that when one switching device operates, the switching device hinders the operation of other switching device even when switching signal is provided to the other switching device externally. This can also be done using NO-NC auxiliary contacts i.e. electrical interlocking. To ensure utmost safety of the switching devices, both the mechanical and electrical type of interlocking are used together.
Specifically, an European Patent EP1157397 discloses a device for interlocking of electric apparatuses, comprising a blocking element that is operated by the associated electric apparatuses via separate, moving plungers to be pivoted similar to a cradle into alternative positions wherein the blocking element is effective for preventing an unintentional and simultaneous circuit closing motion in both apparatuses, and for securing at all times that only one of the apparatuses may be operative.
Further, US Patent No. 5216398 discloses a pair of closed contacts having moving contacts and fixed contacts provided in a mutual locking device and

excitation circuits of two electromagnetic contactors which are inversely connected to respective closed contacts to effect electrical interlocking. The moving contacts are held by respective levers interlocked with driven members to be driven by corresponding moving contact supports of the electromagnetic contactors and opened when the electromagnetic contactor closes. Thus, electrical interlocking may be simultaneously effected using a mutual locking device for mechanically preventing two electromagnetic contactors reversibly connected from simultaneously closing.
Another US Patent No. 4902859 discloses a mechanical interlock for interlocking two circuit breakers such that only one of the circuit breakers is ON at a given time. The interlock is also configured such that it permits both circuit breakers to be OFF at the same time. The interlock includes a pivoting rocker arm and a linkage assembly associated with each breaker, wherein the rocker arm and linkage assemblies cooperate to transfer motion between the tie bars of the circuit breakers.
However, the mechanical interlock of the prior art which are used as an accessory to the switching device, requires extra time and cost for assembling with the. switches.
Accordingly, there exists a need to provide a interlock system which overcomes the drawbacks of the prior art.
Objects of the invention
An object of invention is to provide mechanical interlock with an enable/disable feature which enable the customer to use single device without mechanical interlocking feature.

Another object of the present invention is to provide a inbuilt mechanical interlock for switching device.
Yet another object of the present invention is to reduce assembly time of the mechanical interlock with the switching device.
Summary of the invention
Accordingly, the present invention provides a mechanical interlock device for interlocking two switching devices. Each switching device comprises a housing having the mechanical interlock device housed therein. The housing of each switching device includes a slot configured thereon. Each mechanical interlock device includes a latching member removably coupled to an actuating arm. The latching member is capable of being moved by the actuating arm . wherein the latching member is pushed through the slot of the housing when moved by the actuating arm . The mechanical interlock device further includes a pin capable of holding the latching member for maintaining axis of rotation thereof. Furthermore, the mechanical interlock device includes a knob configured above the latching member and coupled to the latching member, wherein upon dragging the knob sideways, the latching member gets decoupled from the actuating arm and gets locked against a wall of the housing. Moreover, the mechanical interlock device includes a spring placed between the knob and the latching member. The spring maintains the latching member in de-latched position during normal condition. Upon pushing the latching member outside the slot of the housing by the movement of the actuating arm when one switching device of the two switching device is ON. the latching member locks other latching member of other switching device thereby hindering the motion thereof which in turn hinders the motion of an actuating arm of other switching device thereby locking the other switching device.
Brief description of the drawings

Figure 1 shows an exploded view of a mechanical interlock device, in accordance with the present invention;
Figure 2 shows assembled view of the mechanical interlock device of figure I:
Figure 3 shows a front view of the switching device with inbuilt mechanical interlock device of figure 2;
Figure 4 and 5 shows a front view of the switching device with inbuilt mechanical interlock device of figure 2 in disabled mode: and
Figure 6 and 7 shows coupled position of two switching devices with mechanical interlock device of figure 2.
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 mechanical interlock device for switching devices. The mechanical interlock device is provided with an enable/disable position control. The enable/disable feature of the mechanical interlock device enables the customer to use single device without mechanical interlocking feature to be added externally. The mechanical interlock device is inbuilt part of any standard switching device which saves time, money involved in training labor and the assembly time.

Referring to figure 1-7, there are various views of the mechanical interlock device for interlocking two switching devices. Specifically, figure I shows exploded view of the mechanical interlock device (100), and figure 2 shows an assembled view of the mechanical interlock device (100). Each switching device (not shown and numbered) comprises a housing (200) having the mechanical interlock device (100) housed therein. The housing (200) of each switching device includes a slot (112) configured thereon. Each mechanical interlock device (100) includes a latching member (10). a pin (20), a knob (30). and a spring (40).
The latching member (10) is removably coupled to a actuating arm(!5). The actuating arm(15) is the actuating arm of the switching device known in the art. The latching member (10) is capable of being moved by a actuating arm (15). In an embodiment, the latching member (10) is driven by a moving bridge of the contactor when used in contactor of the switching devices. The latching member (10) is pushed through the slot (112) of the housing (200) when moved by the actuating arm(15) on switching ON the switching device (hereinafter referred to as 'the first switching device'). The latching member (10) is held in position by the pin (20).
The pin (20) holds the latching member (10) for maintaining axis of rotation thereof. The latching member (10) is configured below the knob (30).
Specifically, the knob (30) is configured above the latching member (10). Further, the knob (30) is coupled to the latching member (10) by coupling means known in the art. Upon dragging the knob (30) sideways manually, the latching member (10) gets decoupled with the actuating arm(15) and gets locked against a wall (114) of the housing (200). The knob (30) includes the spring (40) placed therebetween and the latching member (10). The spring (40) maintain the latching member (10) in de-latched position during normal condition. Figure 3

shows the front view of the first switching device with inbuilt mechanical interlock device (100) assembled therein.
To disable the mechanical interlock device (100). the knob (30) is moved on left side in a bracket (116) of the housing (200) as shown in figure 4, Due to moving of the knob (30), the latching member (10) gets coupled with the actuating arm(15) and is held back inside the housing (200) by the housing wall (114) as described earlier and shown in figure 4 and 5.
Figure 6 and 7 shows coupled position of the two switching devices with each switching device having the mechanical interlock devices (100) configured therein. Specifically, the two switching devices are placed or mounted side by side. When the first switching device of the two switching devices is ON, the latching member (10) is pushed outside the slot (112) of the housing (200) by the actuating arm (15). Thereafter, the latching member (10) locks other latching member, for example, the latching member (210) of other mechanical interlock device (300) of other switching device thereby hindering the motion thereof which in turn hinders the motion of a moving contact, for example, the actuating arm (220) of the other mechanical interlock device (300) of other switching device thereby locking the other switching device.
Specifically, when the first switching device of the two switching devices is operated, the latching member (10) of the mechanical interlock device (100) of the first switching device hinders the motion of latching member (210) of other mechanical interlock device (300) of other switching device there by restricting the motion of the actuating arm (220) of other switching device (not shown). Accordingly, the other switching device cannot be operated, i.e. locked.
Further, when the first switching device is turned off. the actuating arm (15) is moved back and the latching member (10) of the first mechanical interlock device (100) restores its original position with the help of the spring (40). The

other switching device gets unlocked for operation. The same operation sequence is applicable when other switching device is operated and locks the first switching device for operation. This ensures only one switch is operated at any point of time.
Advantages of the invention
1. The switching device (100) includes a knob to enable/disable mechanical interlocking feature, which was previously done by externally adding or removing the add on device.
2. The mechanical interlock device (100) is inbuilt in the switching device which saves time required for assembling the interlocking device with the switching device.
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. 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 omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient. but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

We Claim
1. A mechanical interlock device for mechanically interlocking two
switching devices, each switching device comprising a housing having the
mechanical interlock device housed therein, the housing of each switching
device having a slot configured thereon, each mechanical interlock device
comprising:
a latching member removably coupled to an actuating arm. the latching member capable of being moved by actuating arm. wherein the latching member is pushed through the slot of the housing when moved by the actuating arm;
a pin capable of holding the latching member for maintaining axis of rotation thereof;
a knob configured above the latching member and coupled to the latching member, wherein upon dragging the knob sideways, the latching member gets decoupled with the actuating arm and gets locked against a wall of the housing; and
a spring placed between the knob and the latching member, wherein the spring maintain the latching member in de-latched position during normal condition,
wherein upon pushing the latching member outside the slot of the housing by the actuating armwhen one switching device of the two switching device is ON, the latching member locks other latching member of other switching device thereby hindering the motion thereof which in turn hinders the motion of a actuating arm of other switching device thereby locking the other switching device.
2. The mechanical interlock device as claimed in claim 1. wherein the
knob includes at least two leg members for enclosing the latching member.