FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Solenoid Based Mechanical Latch System for 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. O. 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.

Solenoid Based Mechanical Latch System For Switching Devices
Field of the invention
The present invention relates generally to latching mechanism for switching devices, and more particularly to a solenoid based latching mechanism for the switching devices.
Background of the invention
Existing switching devices uses an entirely specialized contactor construction for achieving a latched condition.
Specifically, US Patent No. 1980458 discloses an electrically operated switches which employs mechanical means for holding the contacts in switch closed position.
Another US Patent No. 3312808 discloses a mechanical latch for mechanically holding or locking electrical switching device in a desired contact open or closed position in response to an external force or energisation of a magnetic coil therein. The particular control circuitry used for coil energisation is matter of choice to include but not limited to, two wire control.
However, the contactor construction of the switching devices of the prior art requires prior knowledge of the user for its necessity. In case, the user is not aware about voltage sags in the power supply and purchases a normal switching device/contactor, he has to replace the entire unit.
Accordingly, there exists a need to provide a device which overcomes the drawbacks of the prior art.

Objects of the invention
An object of invention is to provide latching and de-latching ability to a switching device in the form of a separate accessory.
Another object of the present invention is to provide mechanical latch system for switching devices which a can be fitted on site with minimal labour or training.
Yet another object of the present invention is to provide a compact mechanical latch system for switching devices
Still another object of the present invention is to provide the user flexibility whenever he wishes to disable the latching feature of the contactor by simple disengagement of the accessory.
Summary of the invention
Accordingly, the present invention provides a solenoid based mechanical latch system for switching devices. The mechanical latch system comprises a housing a top cover, and a coupler mounted in the bottom portion of the housing. The system further comprises a link capable of being latched to the coupler, a first spring attached to the link, and a solenoid configured within the top portion of the housing. The solenoid includes a coil configured therein. Furthermore, the system includes a solenoid limb positioned within the solenoid, wherein the solenoid limb includes a notch configured at lower portion thereof. Also, the system includes a bar having a first end and a second end, and a second spring assembled between the solenoid limb and the bar. The first end is coupled to the notch of the solenoid limb and the second end is attached to a tail portion of the link. When the switching device is ON, the moving contact moves downward thereby pulling the coupler downward by which the link rotates clockwise and gets locked to the coupler. This prevents the coupler from moving upward

thereby latching the switching device. Further, when the switching device is to be turned OFF. a signal is given to the solenoid which causes the solenoid limb to move upward due to force of attraction generated by the energized solenoid. This compresses the second spring and moves the bar upward to rotate the link counter clockwise leaving the coupler to move upward thereby opening the moving contacts and de-latching the switching device.
Brief description of the drawings
Figure 1 shows a exploded view of an solenoid based mechanical latch system for switching devices, in accordance with the present invention;
Figure 2 shows a cross section of the solenoid based mechanical latch system of figure 1;
Figure 3 shows a latched condition of the switching device using the solenoid based mechanical latch system of figure 1; and
Figure 4 shows position of various components of the solenoid based mechanical latch system when the switching device is being de-latched.
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 an solenoid based mechanical latch system for switching device. The system provides latching and de-latching ability to the switching device as a separate accessory. The system is compact and provides

user flexibility whenever he wishes to disable the latching feature of the contactor by simple disengagement of the accessory.
Referring now to figure 1-4, there are shown various positions of the solenoid based mechanical latch system for a contactor, in accordance with the present invention. Specifically, figure 1 shows exploded view of the solenoid based mechanical latch system (100) (hereinafter "the system (100)"). The system (100) is assembled on to the switching device, for example, a contactor by the coupling means known in the art. The system (100) comprises a housing (10). a coupler (20). a link (30). a first spring (40), a solenoid (50), a solenoid limb (60), a delatch bar (70), and second spring (80).
The housing (10) comprises a top portion (12), a bottom portion (14) and a top cover (16). The bottom portion (14) includes the coupler (20) mounted thereon. The coupler (20) is attached to an arm of a moving bridge/armature of the switching device. The moving bridge/armature is known in the art and therefore not described herein for the sake of brevity of disclosure. The coupler (20) includes a stepwise profile (22) configured thereon. The stepwise profile (22) on the coupler (20) is provided to account for varied travels of the moving bridge of the switching device, which in turn, determines the travel of the coupler (20). In preferred embodiment, the coupler (20) includes three steps as shown in figure 1. However, it may be evident to those skilled in the art that the steps are not limited to the current representation, and may be varied from one to any number based on the requirement of switching device to be latched. The coupler (20) is capable of being latched by the link (30).
The link (30) is held in position by tension applied by the second spring (80) attached thereto. Specifically, the second spring (80) is attached to the link (30) which is pivoted about a pin (not shown). This helps in latching/de-latching of the link (30) with the coupler (20).

Further, the solenoid (50) is configured within the top portion (12) of the housing (10). The solenoid (50) includes a coil (not shown) and a side plate configured therein. The solenoid limb (60) is positioned within the solenoid (50) The solenoid limb (60) includes a notch (62) configured at lower portion thereof. The delatch bar (70) is coupled to the solenoid limb (60), and the first spring (40) is assembled between the solenoid limb (60) and the bar (70).
Specifically, the delatch bar (70) comprises a first end (72) and a second end (74). The first end (72) is coupled to the notch (62) of the solenoid limb (60) and the second end (74) guides the tail portion (32) of the link (30).
During operation, when the switching device is ON, the moving bridge/armature moves in downward direction. Downward motion of the moving bridge/armature causes the coupler (20) to pull downward. This causes the link (30) to rotate in clockwise direction thereby locking the link (30) to the coupler (20) and preventing the coupler (20) from moving upward when the control supply to the switching device fails or is removed. Thus, the switching device is latched.
Further, when the switching device is to be turned OFF, a signal is given to the solenoid coil to energize the solenoid(50). In an embodiment, the signal to the solenoid (50) is given by remote control means. After receiving the signal, the solenoid limb (50) moves upward due to force of attraction generated by the energized solenoid (50), compressing the first spring (40) and moving the delatch bar (70) in upward direction. This causes rotation of the link (30) in counter clockwise direction leaving the coupler (20) to move upward thereby opening the link (30) and de-latching the device.
Advantages of the invention

1. The system (100) can be fitted on any electromagnetic switching device, even on site, by simply fitting the system (100) thereon.
2. The system (100) offers both manual and remote de-latching of the switching device.
3. The system (100) is compact.
4. In the system (100), the force required to de-latch the switching device is minimized.
5. The system (100) has latching and de-latching ability for the switching device as it is a separate accessory.
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 solenoid based mechanical latch system for switching devices, the mechanical latch system comprising:
a housing comprising a top portion, a bottom portion and a top cover;
a coupler mounted in the bottom portion of the housing, the coupler attached to an arm of a moving bridge/armature;
a link capable of being latched to the coupler;
a first spring attached to the link;
a solenoid configured within the top portion of the housing, the solenoid having a coil configured therein;
a solenoid limb positioned within the solenoid, the solenoid limb having a notch configured at lower portion thereof;
a delatch bar having a first end and a second end, the first end coupled to the notch of the solenoid limb and the second end guiding the tail portion of the link; and
a second spring assembled between the solenoid limb and the delatch bar,
wherein when the switching device is ON, the moving bridge/armature moves downward thereby pulling the coupler downward by which the link rotates clockwise and gets locked to the coupler, preventing the coupler from moving upward thereby latching the switching device, and when the switching device is OFF, a signal is given to the solenoid which causes the solenoid limb to move upward due to force of attraction generated by the energized solenoid, compressing the second spring and moving the delatch bar upward to rotate the link counter clockwise leaving the coupler to move upward thereby opening the moving contacts and de-latching the switching device.

2. The solenoid based mechanical latch system as claimed in claim \, wherein the coupler is provided with a stepwise profile for latching the link thereto.
3. The solenoid based mechanical latch system as claimed in claim 1, wherein the link is pivoted on a pin.