FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"A 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. 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 Latch System for Switching Devices
Field of the invention
The present invention relates generally to mechanical latch for switching devices, and more particularly to a solenoid based latching mechanism for the switching devices.
Background of the invention
Existing applications in industry need continuous operation. Shutdown in such industries due to voltage fluctuation even for few minutes causes heavy damage and losses to the company. Also, voltage fluctuation may cause malfunction of the switching devices like contactor. Therefore, in such industries, a mechanical latch is used along with switching device. The mechanical latch maintains the switching device in ON state even when the control supply is switched OFF. In some other applications, the control supply is cut off, but still the switching device remains in ON condition due to the mechanical latching thereby reducing energy consumption. Accordingly, the mechanical latch for such switching devices needs to be compact and error free.
Specifically, 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 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.

The mechanical latches of the prior art are designed for particular travel of the moving arm. Thus, for the different ratings of the switching device having different travel needs different mechanical latches. This makes the mechanical latch specific for the specific switching device.
Accordingly, there exists a need to provide a latch system which overcomes the drawbacks of the prior art.
Objects of the invention
An object of invention is to provide a mechanical latch system that can be used for variety of travels and thus can be used with n number of ratings of the switches.
Another object of the present invention is to provide universal mechanical latch along with one pair of auxiliary contacts.
Yet another object of the present invention is to provide a compact mechanical latch system for switching devices
Summary of the invention
Accordingly, the present invention provides a mechanical latch system for switching devices. The mechanical latch system includes a coupler configured in a lower portion of a housing. The coupler is attached to a moving arm and includes a stepwise profile configured on both sides thereof. Further, the mechanical latch system includes a solenoid configured in an upper portion of the housing, a solenoid arm positioned within the solenoid, and a first spring positioned between the solenoid arm and the solenoid. Furthermore, the mechanical latch system includes an actuating arm having a first end and a second end. The actuating arm is coupled to the solenoid arm. Moreover, the

mechanical latch system includes at least two latching units. Each latching unit is attached to the actuating arm. Specifically, each latching unit is capable of being latched to the stepwise profile on the coupler. A pin provides axis of rotation of the at least two latching units. The mechanical latch system also includes a second spring capable of holding the at least two latching units in position, a pair of auxiliary contacts assembled in the coupler, at least two stoppers provided externally for arresting the reversal motion of the at least two de-latching units and a bar coupled to the two latching units. Wherein upon operating the switching device, the coupler moves down depending upon the travel of the moving arm and pushes the at least two latching unit aside latching therewith. The reversal motion of the latching units is prevented by the stoppers which in turn blocks the motion of the moving arm and keeps the switching device in ON condition. Further, when the solenoid is energized, the solenoid pulls the actuating arm thereby pulling the two latching units apart. This makes the coupler free to move upwards turning off the switching device.
Brief description of the drawings
Figure 1 shows an exploded view of a mechanical latch system for switching devices, in accordance with the present invention;
Figure 2 shows assembled view of the mechanical latch system of figure 1:
Figure 3a & 3b shows a cross-sectional view of the mechanical latch system of figure 2 in latched condition with two different positions in accordance with the present invention;
Figure 4 shows a cross-sectional view of the mechanical latch system of figure 2 in de-latched condition; and

Figure 5 shows the mechanical latch system of figure 2 for de-latching manually.
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 a mechanical latch system for switching device that can be used for variety of travels and thus can be used with n number of ratings of the switches. The system provides universal mechanical latch along with one pair of auxiliary contacts. Further, the system provides a compact mechanical latch system.
Referring now to figure 1-5, there are shown various positions/views of a mechanical latch system for switching devices. Specifically, figure 1 shows exploded view of the mechanical latch system (100) (hereinafter "the system (100)':). The system (100) is configured in a housing (not shown) of the switching device. The system (100) includes a coupler (10), a solenoid (15), a solenoid arm (20), a first spring (25), an actuating arm (30). at least two latching units (35), a pin (40), a second spring (45), a pair of auxiliary contacts (50), at least two stoppers (55), and a bar (60).
The coupler (10) is configured in a lower portion of the housing. The coupler (10) is attached to a moving arm (not shown) of the switching device. In an embodiment, the coupler (10) connected to a bridge of the contactor. Specifically, the coupler (10) includes a stepwise profile (12a, 12b) configured on both sides thereof. Further, the coupler (10) includes a pair of auxiliary contacts (50) assembled thereto.

Further, the solenoid (15) is configured in an upper portion of the housing. The solenoid (15) includes the solenoid arm (20) positioned therewithin. The first spring (25) is positioned between the solenoid arm (20) and the solenoid (15). The solenoid arm (20) includes the actuating arm (30) coupled thereto.
Specifically, the actuating arm (30) includes a first end (32) and a second end (34). The first end (32) and the second end (34) attaches to the at least two latching units. In preferred embodiemnt. the at least two latching units (35) includes a first latching unit (35a) and the second latching unit (35b). The first latching unit (35a) is attached to first end (32) of the actuating arm and the second latching unit (35b) is attached to the second end (34) of the actuating arm. Specifically, the first latching unit (35a) and the second latching unit (35b) are capable of being latched to the stepwise profile (12a, 12b) of the coupler (10) respectively. The pin (40) is provided for fixing axis of rotation of the first latching unit (35a) and the second latching unit (35b). The second spring (40) is capable of holding the first latching unit (35a) and the second latching unit (35b) in position. The bar (60) is coupled to the first latching unit (35a) and the second latching unit for de-latching the first latching unit (35a) and the second latching unit from the stepwise profile (12a, 12b) ofthe coupler (10).
Furthermore, at least two stoppers are provided for arresting the reversal motion of the first latching unit (35a) and the second latching unit (35b). Specifically, the first stopper (55a) arrest the reverse motion of first latching unit (35a) and the second stopper (55b) arrest the reverse motion of the second latching unit . (35b).
Referring now to figure 2, assembled view of the system (100) is shown, where the first latching unit (35a) and the second latching unit (35b) are held in de-latched or default condition by the second spring (45). The position of the

coupler (10) indicates that the switching device to which the system (100) is connected is in OFF state. The pair of auxiliary contacts (50) are assembled in the coupler (10) and it can be either 2 NO or 2 NC or 1 NO and 1 NC, supplied based on the requirement.
When the switching device with the system (100) is operated, the coupler (10) moves down depending upon the travel of the moving arm of the switching device. During the travel of the moving arm. the coupler (10) pushes the first latching unit (35a) and the second latching unit (35b) aside and gets latched as shown in Figure 3. The coupler (10) cannot move upward due to latching of the first latching unit (35a) and the second latching unit (35b) with the stepwise profile (12a, 12b) respectively. The reversal motion of the first latching unit (35a) and the second latching unit (35b) is prevented by external stoppers (55a, 55b). This in turn blocks the motion of the moving arm of the switching device and keeps it in ON condition.
Figure 3a & 3b shows the cross-sectional view of the system (100) in latched condition with two different positions. The system (100) is suited for switching devices with different travels. The two latching positions in the coupler (10) are to accommodate two different variants of the switching device being latched, where this can be extended to any number as per the designers requirement.
Referring to figure 4, there is shown turning off of the switching device having the system (100) configured thereon. To turn OFF the switching device, the solenoid (15) is energized. As the solenoid (15) operates, the solenoid (15) pulls the actuating arm (30) along therewith to pull the first latching unit (35a) and the second latching unit (35b) apart and makes the coupler (10) free to move upwards. The coupler (10) returns to its default state thereby turning off the switching device.

Further, as shown in figure 5, switching device with system (100) can be de-latched manually, using the bar (60). When the bar (60) is pressed, the bar (60) separates the first latching unit (35a) and the second latching unit (35b) thereby making the coupler free to return to OFF condition.
Advantages of the invention
1. The system (100) provides flexibility to use with different travels of the moving arm i.e. same device for several product sizes.
2. The system (100) has compact design with a pair of auxiliary contacts inbuilt therein.
3. The system (100) makes efficient use of solenoid energy, due to synchronization of direction of increase in spring energy with that of solenoid energy along the travel, due to which the size of solenoid is reduced.
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 latch system for switching devices configured in a housing thereof, the mechanical latch system comprising:
a coupler configured in a lower portion of the housing, the coupler attached to a moving arm, the coupler having a stepwise profile configured on both sides thereof;
a solenoid configured in an upper portion of the housing;
a solenoid arm positioned within the solenoid,
a first spring positioned between the solenoid arm and the solenoid;
an actuating arm having a first end and a second end, the actuating arm coupled to the solenoid arm;
at least two latching units, each latching unit attached to the actuating arm, each latching unit capable of being latched to the stepwise profile on the coupler;
a pin capable of fixing axis of rotation of the at least two latching units;
a second spring capable of holding the at least two latching units in position;
a pair of auxiliary contacts assembled in the coupler;
at least two stoppers provided externally for arresting the reversal motion of the at least two de-latching units; and
a bar coupled to the latching unit,
wherein upon operating the switching device, the coupler moves down depending upon the travel of the moving arm, thereby pushing the at least two latching unit aside and latching therewith, whereby the reversal motion of the latching units is prevented by the stoppers which in turn blocks the motion of the moving arm and keeps the switching device in ON condition, and when the solenoid is energized, the solenoid pulls the actuating arm thereby pulling the

two latching units apart and makes the coupler free to move upwards turning off the switching device.
2. The mechanical latch system as claimed in claim 1, wherein the solenoid arm includes a notch configured at lower portion thereof for the actuating arm to get coupled.
3. The mechanical latch system as claimed in claim 1. wherein when the bar is pressed, the bar separates the at least two latching units to makes the coupler free to return to OFF condition.
4. The mechanical latch system as claimed in claim 1, wherein the first end of the actuating arm attaches to the one latching unit of the two latching units and the second end of the actuating arm couples to the other latching unit of the two latching units.