FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. TITLE OF THE INVENTION - SINGLE SOLENOID OPERATED
MECHANISM FOR AUTOMATIC TRANSFER SWITCH ASSEMBLY
2. APPLICANT(S)
(a) NAME LARSEN & TOUBRO LIMITED
(b) NATIONALITY: An Indian Company.
(c) ADDRESS: L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed:

FIELD OF THE INVENTION
The present invention relates to single solenoid operated mechanism. Particularly, the present invention relates to a mechanically interlocked, manually independent mechanism of electrical switches. More particularly, the present invention relates to single solenoid operated mechanism for automatic transfer switch used at places where isolation of two or more switches is necessary, more specifically in transfer switches.
BACKGROUND AND THE PRIOR ART
Many times customers have a backup system for power generation, which is used when the main power source is discontinued, so that, the critical operations will continue by the help of backup power source, like generator or inverter. Thus there is need to have a device which will have two power supplies i.e. main power supply and backup power supply at input side of the switch and one output power supply for the load, further these input power supplies must have complete electrical isolation from each other, and only one power supply should get connected to a load at a time. The critical applications like Hospitals, data centers etc. can't afford manual intervention, in such cases supply deviation/failure is monitored through sensors which gives command to switch to transfer load from one supply to another.
Thus there is a need to have special switch to attain all the aforesaid requirements, such type of switch is commonly known as TRANSFER SWITCH/ Automatic transfer switch, this type of switch is able to obtain perfect isolation between two input power

supplies and only one power supply gets connected to a load at a time. Also controller gives command to solenoid to operate mechanism to operate transfer switch.
Conventionally two solenoids have been used to operate automatic transfer switch, one solenoid is to make Switch 1 ON and to make Switch 2 OFF and another solenoid to make Switch 1 OFF and to make Switch 2 ON.
The force required to operate the switch is provided by solenoid. But as force require to operate switch is high the solenoid size also becomes high, in that case if two solenoid are used in switch then overall dimensions of the switch increases. Also the cost of solenoid is high, which in turn increases the product cost.
US 5,748,432 relates to automatic transfer switch. The mechanism basically consists of a four bar chain and a disc shaped weight as an energy storing member in the form of inertia. Disc shaped weight is directly attached to the contact system. A compression spring is directly attached to the solenoid plunger through link.
When solenoid gets a pulse, it starts moving in the inward direction. Thus dead weight along with the contact system starts moving in anticlockwise direction, thus switching the contacts. After dead center compression will start releasing its energy, and spring along with the disc shaped weight will overcome dead center.
US'432 discloses a mechanism which is over center spring mechanism and does not use rack and pinion arrangement. The mechanism uses flywheel as energy storing device, which avoids

stoppage of mechanism at dead center .The contact system starts moving with the solenoid i.e. the system is manually dependant and not manually independent.
US'432 is a single solenoid operated mechanism of Automatic transfer switch. It uses dead weight and its inertia to overcome dead center and operate the switch. Because of dead weight, size of the mechanism increase, also it is a manually dependent mechanism. This particular mechanism is a four bar mechanism, so efficiency of mechanism is less.
So it was a need to design a mechanism of Automatic transfer switch, which will be, single solenoid operated, manually independent and higher efficiency mechanism. Also it should not use additional coil to make switch ON or OFF.
US 4,590,387 relates to automatic transfer switch, which comprises an operating mechanism, control mechanism and charging mechanism. The spring is directly attached to solenoid through iron core, which in turn is connected to the operating lever. As solenoid gets a pulse, it actuates lever, which is held in final position with the help of latch plate and tripping coil. The other end of operating lever is connected to connecting link which moves in 'V- shaped guide'. Connecting link is connected to control levers which are free to rotate and are used to make contacts ON or OFF. The motion of the connecting link in right or left inclined path of guide is controlled by point plate. Point plate gets actuated due to selective coil and allows link to move only in right or left inclined path. When the link is in top most position either in right or left inclined path, the switch is in ON condition i.e. either ONI

or ON2. While link is at the bottom in the guide switch is in OFF condition.
US'387 discloses a mechanism which uses lever arrangement and no rack and pinion arrangement is used. It is single solenoid mechanism with tripping and selective coil. Selective coil and a point plate are used to select a particular path in the 'V- shaped guide groove.
The contact system starts moving with the solenoid i.e. the system is manually dependant, and contact system does not starts moving after dead center i.e. stored energy in spring is used to drive the contact system i.e. it is not manually independent.
US'387 is a solenoid operated mechanism of Automatic transfer switch. Even if it is a solenoid operated mechanism; when manually operated it is a manually dependent mechanism i.e. Opening and closing of switch depends on the speed with which user is operating a switch, which is hazardous to human safety. Also this mechanism use solenoid as well as selective coil to make switch ON and OFF. So use of two electromagnets, increases switch size, cost and also adds complexity in mechanism.
Thus there is a need to provide a single solenoid operated mechanism for automatic transfer switch with manually independent mechanism.

OBJECTS OF THE INVENTION
One object of the present invention is to overcome the disadvantages / drawbacks of the prior art.
A basic object of the present invention is to provide a single solenoid operated mechanism.
Another object of the present invention is to provide a single solenoid operated mechanism\ which is manually independent mechanism and also compact mechanism.
Yet another object of the present invention is to provide a single solenoid operated mechanism that does not stop at dead center position and no additional trip coil to be used for operation.
Yet another object of the present invention is to provide a single solenoid operated mechanism with higher efficiency that is provided by rack and pinion mechanism/arrangement.
SUMMARY OF THE INVENTION
There is provided a Single solenoid operated mechanism for automatic transfer switch assembly.
According to one embodiment of the present invention, there is provided a Single solenoid operated mechanism for automatic transfer switch assembly; wherein said mechanism comprising a mechanism cassette for incorporating said mechanism; a contact system comprising a plurality of terminals, a bridge and a plurality

of moving contacts; a controller means for sensing deviation in supply and giving command for switching operation; a plurality of switch means whereby main supply connected to a first switch and an emergency supply connected to a second switch; a mechanism plate for holding said assembly; a solenoid assembly comprising, a solenoid cylinder for holding a coil and a compression spring, a solenoid plunger moving linearly inside said cylinder and a compression spring having a plurality of substantially helical turns storing mechanical energy for facilitating making and breaking of said contact system; a spacer means for holding said mechanism in proper position; a rack means transmitting motion of a connecting rod to a pinion means; a slot plate having a slot whereby a connecting rod moves; a toggle pin means fitted into a slot provided in said rack means; a leaf spring fitted into a slot provided in said rack means providing force to said toggle pin means; a connecting rod having one end connected to said solenoid plunger and other end free to rotate in said slot, said connecting rod transmitting motion from said solenoid to said rack means.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawing:
Figure 1 illustrates the automatic transfer switch mechanism with
contact system.
Figure 2 illustrates exploded view of automatic transfer switch mechanism with contact system.

Figure 3a illustrates the Mechanism in different orientation as per one embodiment of the present invention.
Figure 3b illustrates the Mechanism in different orientation as per one embodiment of the present invention.
Figure 4 illustrates top view of mechanism when switch 1 is in ON position while switch 2 is in OFF position.
Figure 5 illustrates top view of mechanism with intermediate position of mechanism before dead center.
Figure 6 illustrates top view of mechanism just before the dead center.
Figure 7 illustrates top view of mechanism at dead center.
Figure 8 illustrates top view of mechanism with after dead center where transformation from switch 1 to switch 2 will start.
Figure 9 illustrates top view of mechanism with intermediate position of mechanism during transformation from switch 1 to switch 2.
Figure 10 illustrates top view of mechanism with final position of mechanism when switch 1 is in OFF position while switch 2 is in ON position
Figure 11 illustrates cross-sectional view of solenoid with solenoid in its initial position.
Figure 12 illustrates cross-sectional view of solenoid with solenoid in its intermediate position.
Figure 13 illustrates cross-sectional view of solenoid with solenoid in its final position.

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWING
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.
Following are the components used in the present invention:-
Mechanism cassette(l) : This is the full assembly of mechanism.
Contact System (2) : This is an assembly of terminals, bridge and moving contacts.
Switch 1 (3a) :This is the assembly of 1st switch to which main supply is connected.
Switch 2 (3b): This is the assembly of 2nd switch to which emergency supply is connected.
Mechanism Plate (4): This is used to hold the assembly.
Solenoid Cylinder (5a): This is the part of solenoid that hold coil as well as compression spring.
Solenoid Plunger (5b):This is the part of solenoid which moves linearly inside the cylinder.

Compression Spring (5c): It is an element having helical turns and is used to store mechanical energy. Force exerted by the spring is directly proportional to the compression of the spring.
Compression spring is placed inside the solenoid cylinder. It brings back solenoid plunger to its initial position.
Spacer(6): These are metallic components that holds mechanism in proper position.
Rack (7):This is a metallic component that transmits motion of connecting rod to the pinion.
Slot Plate (8): This is a metallic plate in which 'U- Shaped' slot is provided. Connecting rod moves in this slot and gives required motion to the connecting rod.
Pinion (9): This is a metallic component. Contact system is directly connected to the pinion. It transmits motion of rack to the contacts.
Leaf Spring (10): It is metal part and fits into the slot provided in the rack. It provides required force to the toggle pin, to bring it back in its initial position.
Toggle pin (11): It is a metal part that fits into the slot provided in the rack. It directs the connecting rod in proper direction and avoids stoppage of rod at dead center.
Connecting Rod(12): It is a metal part one end of which is connected to the solenoid plunger, and other end is free to rotate in the 'U-slot'. It transmits motion from solenoid to the rack.
The different states of the switch and the related parts thereof are further explained below in detail:

Automatic transfer switch is used in critical applications where slight interruption in supply is not allowed. Such application always has backup supply in support with utility supply. Automatic transfer switch is combination of Switch1 (Where supply from utility gets connected), Switch 2 (Supply from backup gets connected), mechanism ( Which mechanically and electrically interlocks two above mentioned switches, and make Switch 1 and Switch 2 ON and OFF), Controller ( Which senses any deviation in supply and give command to solenoid to operate mechanism and hence switch).
So when utility supply is available Switch 1 is in ON condition and Switch 2 is in OFF condition. But if there is any problem in utility supply then Switch 1 becomes OFF and Switch 2 becomes ON i.e. load is being supplied through backup supply.
Switch 1 in ON condition and Switch 2 in OFF condition: Fig.4 shows the mechanism position in this condition. Fig 11 shows corresponding position of solenoid. Switch 1 OFF to Switch 2 ON: Controller continuously monitors the input supply in automatic transfer switch. Whenever there power failure or variation in supply, Sensor sends a pulse to solenoid thus actuating the solenoid. As solenoid plunger starts moving inside it compresses the spring. The connecting rod which is attached to the plunger also starts moving in the 'U-slot' as shown in fig: 5. When it reaches toggle pin, it compresses the leaf spring and toggle pin moves in upward direction as shown in fig: 6 and Fig 7. The corresponding position of solenoid is shown in fig: 12.
At dead center position, the connecting rod is as shown in fig. 7. Here the connecting rod has two ways to move further. But as soon as connecting rod looses contact with toggle pin, toggle pin comes

to its original position, due to leaf spring attached to it. Thus blocks the upward path of connecting rod, and forces it to move in downward direction. At this particular position, the edge of the toggle pin exactly matches with inclined edge of the slot as shown in fig: 7, thus it guides connecting in lower limb of the slot and avoids stoppage of mechanism at dead center.
Now after dead center, compression spring starts giving out its energy and connecting rod moves in downward direction as shown in fig: 8. Now when connecting rod touches the lower rack, rod pushes rack in forward direction, thus making pinion to move in anticlockwise direction and upper rack in backward direction. The corresponding positions are shown in fig: 9. As pinion moves in anticlockwise direction, moving contacts which are positively connected to pinion, also moves. Moving contacts of Switch 1 disconnects from terminal of Switch, and moving contacts of Switch2 gets connected to terminal of Switch2.
Thus after completion of the stroke, switch 1 becomes OFF and switch 2 becomes ON, As contact system starts moving only after dead center, the energy required to operate the contact system is provided by spring. Thus even if switch is being operated manually, human energy is gets used only to compress the spring; actual making and breaking of contact system i.e. operation of switch is done by energy from compression spring, so its speed of operation do not depend upon human applied force making the system manually independent.
Switch 1 ON to Switch 2 OFF: When normal supply is restored sensor will again send pulse to solenoid. Solenoid will get actuated; moving in backward direction, thus connecting rod will now move in lower limb of the 'U-slot' in backward direction. After dead

center, toggle pin which is fixed in lower rack will block the downward path of the rod, forcing it to move in upper limb. Now when rod touched upper rack, upper rack starts moving in forward direction. This will make pinion to move in clockwise direction and lower rack in backward direction. Now as pinion move in clockwise direction, moving contacts which are positively connected to pinion starts moving. Moving contacts of Switch2 disconnects from terminal of Switch2, and moving contacts of Switch 1 gets connected to terminal of Switch1. Thus after completion of the stroke, Switch 2 becomes OFF and Switch 1 becomes ON. So load is then supplied from utility supply.
FEATURES:
■ Single solenoid operated mechanism
■ Manually independent mechanism.
■ Compact mechanism
■ Mechanism should not stop at dead center position
■ No additional trip coil to be used for operation
■ Higher efficiency which is provided by rack and pinion mechanism.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the claims.
It is also to be understood that the following claims are intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between.

WE CLAIM
1. A single solenoid operated mechanism for automatic transfer switch assembly; wherein said mechanism comprising:
a mechanism cassette (1) for incorporating said mechanism;
a contact system (2) comprising a plurality of terminals, a
bridge and a plurality of moving contacts;
a controller means for sensing deviation in supply and giving
command for switching operation;
a plurality of switch means whereby main supply connected
to a first switch (3a) and an emergency supply connected to a
second switch (3b);
a mechanism plate (4) for holding said assembly;
a solenoid assembly comprising a solenoid cylinder (5a) for
holding a coil and a compression spring, a solenoid plunger
moving linearly inside said cylinder and a compression
spring (5c) having a plurality of substantially helical turns
storing mechanical energy for facilitating making and
breaking of said contact system;
a spacer means (6) for holding said mechanism in proper
position;
a rack means (7) transmitting motion of a connecting rod to
a pinion means;
a slot plate (8) having a slot whereby a connecting rod moves;
a toggle pin means (11) fitted into a slot provided in said rack
means;
a leaf spring (10) fitted into a slot provided in said rack
means providing force to said toggle pin means;
a connecting rod (12) having one end connected to said
solenoid plunger and other end free to rotate in said slot,

said connecting rod transmitting motion from said solenoid to said rack means.
2. Mechanism as claimed in claim 1 wherein said slot plate is substantially U shaped.
3. Mechanism as claimed in claim 1 wherein said controller means sending actuation signal to said solenoid assembly.
4. Mechanism as claimed in claim 1 wherein said pinion means (9) directly connected to said contact system for transmitting motion of said rack means to said contact system.
5. Single solenoid operated mechanism for automatic transfer switch assembly as herein described and illustrated with reference to accompanying drawings.