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

Electromagnet Based Mechanical Latch System for a Contactor
Field of the invention
The present invention relates generally to latching mechanism for switching devices, and more particularly to a contactor to be used in applications where it is imperative that the contactor remains closed even if its coil supply fails.
Background of the invention
Existing switchgear systems use specialized contactor construction mechanisms for achieving latched condition.
For example, US Patent No. 1980458 discloses an electrically operated switch 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 energization of a magnetic coil therein. The particular control circuitry used for coil energization is matter of choice, such as two wire control. However, the contactor construction mechanisms of the prior art require prior knowledge on part of the user for its necessity. In case the user is not aware about voltage sags in the power supply and purchases a normal contactor, he has to replace the entire unit.
Some of the prior art products use solenoid for actuation of the latching links. However, they suffer from various drawbacks.
For instance, in one of the prior art mechanisms as shown in figure 1, an off-centered link having a plunger (2), a lever (3) and a contactor bridge (4), connected to a solenoid (1) is used for actuation. However, such an arrangement may lead to loss in forces generated by the solenoid.

In another mechanism as shown in figure 2, a vertical arrangement of solenoid with a plunger (2) connected to a contactor bridge (5) through Paul (4) and Ratchet (5) and rack -pinion arrangement causes considerable increases in the depth of the product, and thus compactness is severely compromised.
Similarly, in another mechanism as shown in figure 3, a horizontal arrangement of the solenoid (1) having a plunger (2) secured to a contactor bridge (3) through Paul (4), Ratchet (5) and rack- pinion arrangement (6), again causes compromise on compactness.
Another prior art arrangement as shown in figure 4, provides latching at one distinct position only. However, in this arrangement the contactor (3) loses some travel which is introduced due to manufacturing deviations.
Accordingly, there exists a need to provide a device which overcomes the drawbacks of the prior art.
Objects of the invention
An object of the present invention is to provide a latching mechanism for switching devices with an electromagnet actuator, which addresses the aforementioned drawbacks of the prior art, and is stable and robust.
Another object of the invention is to provide latching and de-latching ability to a contactor as 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 labor 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 an electromagnet based mechanical latch system for a contactor. The contactor includes a bridge and a coil, wherein the mechanical latch system comprises a coupler coupled to the bridge of the contactor, a link capable of being latched to the coupler, a first spring attached to the link, a bar attached to a tail portion of the link, a second spring coupled to lower end of the bar, an U shaped magnet configured on the bridge, and an 1 shaped magnet configured on the bridge. The I shaped magnet comprises a first end and a second end. The first end is hinged on one side of the U shaped magnet and the second end coupled to the bar, wherein the I shaped magnet move towards the U magnet when actuated by the coil. When the coil is powered, the bridge moves down thereby pulling down the coupler and rotating the link clockwise by which the link gets latched to the coupler preventing the coupler movement in upward direction and when the bar is pressed down against the force of the second spring, the downward motion of the bar causes the link to rotate in a counter-clockwise motion, away from the coupler thereby making the coupler free to move back up to its original position as the bridge moves upward thereby de-latching the contactor manually.
Brief description of the drawings
Figure 1-4 shows solenoid based actuating mechanism for a contactor system, in accordance with the prior art.

Figure 5 shows a cross section of an electromagnet based mechanical latch system, in accordance with the present invention;
Figure 6 shows a latched condition of the contactor using electromagnet based mechanical latch system of figure 5;
Figure 7 shows a de-latched condition of the contactor using electromagnet based mechanical latch system of figure 5;
Figure 8 shows a position of various components of the condition of the electromagnet based mechanical latch system when the contactor is de-latched; and
Figure 9 shows exploded view of the electromagnet based mechanical latch system of figure 5-8.
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 electromagnet based mechanical latch system for switchgear. The system provides latching and de-latching ability to a normal power or control contactor as a separate accessory. Specifically, the system may be procured even at a later date of the contactor, when necessity of the system is identified. 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. Specifically de-latching of the contactor can be done both manually and remotely.

Referring now to figure 5-9, there are shown various positions of the electromagnet based mechanical latch system for a contactor, in accordance with the present invention. Specifically, figure 5 shows cross sectional view of the electromagnet based mechanical latch system (100) (hereinafter the system (100)) for a contactor (110) when the contactor is in OFF condition. The contactor (110) comprises a bridge (not numbered) and a coil (120). The system (100) is assembled on to the contactor (110) by the coupling means known in the art. The system (100) comprises a coupler (10), a link (20), a first spring (30), a bar (40), a second spring (50), a U shaped magnet (60) and a 1 shaped magnet (70).
The coupler (10) is coupled to the bridge of the contactor (110). The coupler (10) includes a stepwise profile (12) configured thereon. The stepwise profile (12) on the coupler (10) is provided to account for varied travels of the bridge which, in turn, determines the travel of the coupler (10). In preferred embodiment, the coupler (10) includes three steps as shown in figure 5. 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 contactor (110) which is to be latched. The link (10) is capable of being latched to the stepwise profile (12) of the coupler (10).
The link (20) is held in position by tension applied by the first spring (30). Specifically, the first spring (30) is attached to the link (20) which is pivoted about a pin (not shown). This helps in latching/de-latching of the link (20) with the coupler (10). The link (20) includes a bar (40) attached thereto.
Specifically, a lower end portion (42) of the bar (40) is attached to a tail portion (22) of the link (20). Further, the second spring (50) is coupled to the lower end portion (42) of the bar (40). The upward and downward motion of the bar (40) is controlled by the U shaped magnet (60) and the I shaped magnet (70).

The U shaped magnet (60) and the I shaped magnet (60) are configured on the bridge. The I shaped magnet (70) comprises a first end (72) and a second end (74). The first end (72) is hinged on one side of the U shaped magnet (60) and the second end (74) is coupled to the bar (40) by means of a pin. When the U shaped magnet (60) and the I shaped magnet (70) are energized by the coil (120), the I shaped magnet (70) move towards the U shaped magnet (60).
During operation, when the coil (120) is powered, the bridge moves down thereby pulling down the coupler (10) and rotating the link (20) in clockwise direction by which the link (20) gets latched to the stepwise profile (12) of the coupler (10) preventing the coupler (10) movement in upward direction and thereby latching the contactor (110) as shown in figure 6.
The de-latching of the contactor (110) is done either manually or automatically by using a remote control. To de-latch the contactor (110) manually, the bar (40) is pressed down, against the second spring (50) as shown in figure 5. The downward motion of the bar (40) pushes the tail (22) of the link (20). This causes the link (20) to rotate in a counter-clockwise motion, away from the coupler (10), and compressing the first spring (30). The coupler (10) is now free to move back up to its original position immediately as the contactor (HO)'s bridge moves upward.
Alternately, to switch off the contactor (110) remotely, a signal is given to the coil (120) via terminals (not shown) provided for powering thereto. The powered coil (120) actuates the I shaped magnet (70) to move towards the U shaped magnet (60).
Accordingly, when the I shaped magnet (70) is pulled towards the U shaped magnet (60) due to the flux developed when the coil (120) is given supply, the bar (40) is pulled down against the second spring (50) and the bar (40) moves

the tail (22) of the link (20) downward causing the link (20) to rotate and move away from the coupler (10)) to which the link (20) was previously locked leaving the coupler (10) free to move upwards thereby de-latching the contactor (110). This also results in the first spring (30) getting compressed. Specifically, figure 7 shows the various components in the de-latched condition of the contactor (110).
Further, when the manual pressure on the bar (40) is removed, the bar (40) moves to its original position due to the opposing force from the second spring (50). Alternately, if the power supply to the coil (120) is removed, the attractive force between the 1 shaped magnet (70) and the U shaped magnet (60) ceases to exist, and due to the opposing force of the second spring (50), the bar (40) and the I shaped magnet (70) move upwards back to their original positions as shown in figure 8.
The system (100) provides latching and de-latching ability to a normal power or control contactor (110) as it is a separate accessory.
Advantages of the invention
1. The system (100) can be any contactor, even on site, by simply fitting the system (100) to the contactor.
2. The system (100) offers both manual and remote de-latching of the contactor.
3. The system (100) is compact which can be used on the contactors of three
different frames here or any no. based on number of steps defined.
4. In the system (100), the force required to de-latch the contactor is minimized.
5. The overall travel of the electromagnetic actuator is minimized due to electromagnet based actuator
6. The system (100) latching and de-latching ability to the contactor 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. An electromagnet based mechanical latch system for a contactor, the
contactor having a bridge and a coil, the mechanical latch system comprising:
a coupler coupled to the bridge of the contactor;
a link capable of being latched to the coupler;
a first spring attached to the link;
a bar attached to a tail portion of the link;
a second spring coupled to lower end of the bar;
a U shaped magnet configured on the bridge; and
an I shaped magnet configured on the bridge, the I shaped magnet having a first end and a second end, the first end hinged on one side of the U shaped magnet and the second end coupled to the bar, wherein the I shaped magnet moves towards the U shaped magnet when actuated by the coil,
wherein when the coil is powered, the bridge moves down thereby pulling down the coupler and rotating the link clockwise by which the link gets latched to the coupler preventing the coupler movement in upward direction and when the bar is pressed down against the force of the second spring, the downward motion of the bar causes the link to rotate in a counter-clockwise motion, away from the coupler thereby making the coupler free to move back up to its original position as the bridge moves upward thereby de-latching the contactor.
2. The electromagnet based mechanical latch system as claimed in claim 1, wherein the coupler is provided with a stepwise profile capable of being latched to the link.
3. The electromagnet based mechanical latch system as claimed in claim 1, wherein the link is pivoted on a pin.