FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2005
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A RATCHET AND PAWL BASED DRIVE MECHANISM FOR SPRING LOADED CIRCUIT BREAKERS.
APPLICANTS:
Crompton Greaves Limited, CG House, Dr. Annie Besant Road, Worli, Mumbai -400030, Maharashtra, India; an Indian Company.
INVENTOR:
Tambe Sangram of Crompton Greaves Limited, R&D Center, Switch Gear Division, S3 Division, A-3 MIDC, Ambad, Nashik -422010, Maharashtra, India; and Teli Kunal and Roy Deosharan both of Crompton Greaves Limited, Global R&D, Electronic Design Centre (EDC), Aryabatta Building, Kanjur Marg (East), Mumbai - 400042, Maharashtra, India; all Indian Nationals
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to the field of mechanical engineering.
Particularly, this invention relates to switchgear equipment and circuit breakers.
More particularly, this invention relates to circuit breaker drive mechanism.
Specifically, this invention relates to a ratchet and pawl based drive mechanism for spring loaded circuit breakers.
BACKGROUND OF THE INVENTION:
Electrical loads, devices, circuits, assemblies, and connections may be subjected to electrical fluctuations or short-circuit due to interruptions in power supply or over load or under load. In any of these circumstances, the load or device is subjected to breakdown if the surges are not effectively prevented from acting on them. One way is to ensure seamless supply. Another way is to monitor the aberrations, and in case of faults, simply break the electrical connection.
The term 'switchgear', used in association with electric power systems, or grids, or power transmission systems and networks refers to combination of electrical disconnects, fuses, and/or circuit breakers used to isolate electrical equipment. Switchgear is used both to de-energize equipment to allow work to be done and to clear faults.
Circuit Breaker mechanisms are a type of switchgear equipment which are used in electrical equipment, as an adjunct mechanism, for preventing said electrical equipment from current / voltage aberrations such as overload, short circuit, underload, or the like. Basically, it is designed to detect a fault condition, and operates to interrupt the working of the associated electrical equipment upon detection, thereby saving its health.

Circuit breakers provide the breaking of power supply upon detection of faulty electrical conditions in the operation of associated assemblies. Thus, a circuit breaker acts as a safety device for said associated assemblies. As sensitivity of associated assemblies increase, it becomes imperative that circuit breakers be absolutely reliable in their working as a safeguard feature. Moreover, it is more essential that they act within specified time durations, in order to actuate its working upon detection of fault.
Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically-stored energy (using resilient mechanisms such as springs or compressed air) contained within the breaker is used to separate the contacts. Small circuit breakers may be manually operated; larger units have coils: trip coils to trip the mechanism; close coils to close the mechanism; and electric motors to restore energy to the springs.
It has been a constant endeavour to improve this specified time durations by attempting to reduce the time between detection and actuation. Since actuation is a mechanical process involving mechanical parts, its change of state from rest to motion is a crucial time consuming factor. This time duration to overcome inertia is a measure of goodness of the circuit breaker.
Furthermore, it is also imperative that a discharged circuit breaker be efficiently restored to its charged condition ready to be actuated upon detection of a fault. This requires aiding the mechanical storage of energy (using resilient mechanisms such as springs or compressed air) which further trigger the trip coils and / or close coils upon detection of a fault. In its charged condition, a latch mechanism is used to latch the moving parts in its energy-stored condition ready to be triggered in to action.
The term, 'overtravef relates to the excess travelling energy in the moving components which result in circuit breaker operation. Overtravel may lead to unnecessary stress in the components consisting of the latching system. Due to high impact load on circuit breaker system, reliability of components is decreased and some failures observed.

A trip coil is a type of solenoid in which the moving armature opens a circuit breaker or other protective device when the coil current exceeds a predetermined value. A closing coil is adapted to shut the circuit breaker completely.
In its working mode, if a power surge occurs in the electrical system, the breaker will trip. This means that a breaker that was in the "on" position will flip to the "off position and shut down the electrical power leading from that breaker. Essentially, a circuit breaker is a safety device. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
A close coils is a coil which closes the circuit breaker electrically using an external voltage source when a specified voltage is applied across the coil.
The operating mechanism, of a circuit breaker, consists primarily of two compression springs; 1) tripping spring; and 2) closing spring. The closing spring generates the required driving force to close the circuit breaker and charge the tripping spring. The tripping spring is directly connected to the circuit breakers link system. This means that the mechanical energy needed for the vital opening operation is always stored in the tripping spring when the circuit breaker is in closed position. In other words, a closed circuit breaker is always prepared for immediate opening.
A motor drives the spring charging gear, which automatically charges the closing spring immediately after each closing operation. The springs are kept in charged state by a latch that is released when the circuit breaker is being closed. This enables rapid reclosing of the circuit breaker after a pre-defined dead time interval.

PRIOR ART:
Circuit breakers perform the function of energizing and de-energizing the loads in normal operational condition. In conditions such as a short circuit or sustained overload they can be used to rapidly disconnect the circuit. To perform the function of rapid connection and disconnection of circuits the drive mechanisms of contacts of circuit breakers would need to store energy in some form. One of the forms in which the energy can be stored and rapidly utilized is by storing the energy in springs.
While performing any operation the stored energy of the spring would need to be used and simultaneously the spring would need to be re-energized for subsequent operations. While performing the process of re-energizing the spring it is important to ensure that the spring is not overcharged. There are different mechanisms available for performing the function of re-energizing the spring.
According to the prior art, low/medium voltage circuit breakers use single ratchet wheel placed on cam shaft to charge circuit breaker closing spring with the help of one charging pawl and one or more stopper pawls. Charging pawl placed on rocker arm which gets oscillating motion by using crank which is rotated by motor. Ratchet wheel gets angular displacement in forward direction due to charging pawl and stopper pawls prevents reverse rotation of ratchet wheel. By this way spring gets charged. After discharging of closing spring and completion of over travel one of the pawl engage with ratchet wheel tooth and prevents reverse rotation of ratchet wheel.
However, the existing practice after discharging of closing spring, there are equal chances of engagement of charging and stopper pawl with ratchet wheel during reverse rotation which results into impact load on charging pawl. Also, the required size of charging pawl for high energy mechanism of high voltage switchgears is large to sustain high impact load.

Circuit breaker systems of the prior art were riddled with problems and disadvantages, as listed below:
1. Assembly of eccentric shaft pawl was difficult;
2. Wear and tear of pawl;
3. Ratchet wheel was bulky; and
4. Higher energy loss in charging system.
According to the prior art, low/medium voltage circuit breakers use single ratchet wheel placed on cam shaft to charge circuit breaker closing spring with the help of one charging pawl and one or more stopper pawls. Charging pawl placed on rocker arm gets oscillating motion by using crank which is rotated by a motor. Ratchet wheel gets angular displacement in forward direction due to charging pawl and stopper pawls prevents reverse angular displacement of ratchet wheel. By this way, spring gets charged. After discharging of closing spring and completion of overtravel, one of the pawls engages with ratchet wheel tooth and prevents reverse rotation of ratchet wheel. After discharging of closing spring, there are equal chances of engagement of charging and stopper pawl with ratchet wheel during reverse rotation which results into impact load on charging pawl. Due to impact load on charging pawl and related components, it results into failure of charging system. The required size of charging pawl for high energy mechanism of high voltage switchgears is large to sustain high impact load. Existing single pawl charging system is not suitable for high energy mechanisms in high voltage switchgears because there are chances of impact load on charging pawl.
A high voltage circuit breaker mechanism has ratchet wheel and two charging pawl-eccentric shaft arrangement for charging closing spring. In two charging pawl-ratchet wheel system, the assembly of pawls with eccentric shaft is very critical. In that system, always required two pawls to engage and disengage from catch system which used to avoid direct contact of charging pawls with ratchet wheel teeth's during discharging of spring and reverse rotation of ratchet wheel. The same charging pawls cannot use as a stopper pawl due to high energy of mechanism in high voltage switchgear. So it needs

separate stopper ratchet wheel and pawl system to avoid reverse rotation of cam shaft/charging ratchet wheel.
OBJECTS OF THE INVENTION:
An object of the invention is to provide a high energy circuit breaker mechanisms in high voltage switchgears.
Another object of the invention is to provide a mechanism in order to avoid impact load of ratchet wheel coming on to charging pawl in closing spring charging system of (high voltage) switchgear mechanism.
Yet another object of the invention is to separate charging pawl and ratchet wheel during closing spring discharging and reverse rotation of ratchet wheel.
Still another object of the invention is to use single charging pawl and ratchet wheel high energy in closing spring and to prevent damage of charging pawl due to impact load in high voltage switchgear mechanisms.
An additional object of the invention is to prevent failure of charging pawl due to impact
load.
Yet an additional object of the invention is to reduce the size of charging pawl, because there is no need to design for impact load.
Another additional object of the invention is to provide a single charging pawl-ratchet wheel spring charging system which can be used for high energy and high voltage switchgear mechanisms.

Yet another additional object of the invention is to relegate the need of two charging pawl and eccentric shaft system, in circuit breaker mechanism, thereby eliminating criticality of assembly.
Still another additional object of the invention is to reduce cost of circuit breaker mechanism.
Another object of the invention is to combine functions of charging ratchet wheel and stopper ratchet wheel when compared with high energy mechanisms.
Yet another object of the invention is to provide a catch mechanism in order to avoid contact of charging pawl and ratchet wheel during discharging of closing spring and reverse rotation of ratchet wheel.
Still another object of the invention is to prevent damage of charging pawl due to the impact load during reverse rotation of ratchet wheel.
An additional object of the invention is to prevent overcharging, in circuit breakers, by using catch mechanism.
Yet an additional object of the invention is to achieve integration of charging ratchet and stopper wheel for high energy mechanisms in high voltage switchgears.
Still an additional object of the invention is to provide circuit breaker mechanisms for high energy, failure of charging pawl due to impact load.
Another object of the invention is to reduce the size of charging pawl for impact load.
Yet another object of the invention is to provide a mechanism in circuit breaker systems which avoid contact between charging pawl and ratchet wheel during discharging and reverse rotation of ratchet wheel.

Still another object of the invention is to improve reliability of charging system.
An additional object of the invention is to provide a spring charging system which can be used for low energy and low voltage switchgear mechanisms as well as for high energy and high voltage switchgear mechanisms.
Yet an additional object of the invention is to provide a ratchet and pawl based drive mechanism for spring loaded circuit breakers where wear failure is relatively reduced.
SUMMARY OF THE INVENTION:
According to this invention, there is provided a ratchet and pawl based drive mechanism for spring loaded circuit breakers, said mechanism comprises:
a. at least a ratchet charging wheel adapted to be coupled with a closing spring and
further adapted to provide momentum for charging and discharging of said
closing spring of said spring loaded circuit breaker, characterised, in that, an
operative forward / anticlockwise angular displacement of said ratchet charging
wheel for a first sector causing charging of said closing spring and a further
operative forward / anticlockwise' angular displacement of said ratchet charging
wheel for a second (remainder) sector causing discharging of said closing spring;
b. at least a charging pawl rocker arm adapted to oscillate in an operative upward
and downward manner about an operative horizontal axis, a first end of said
rocker arm being coupled to said ratchet wheel, a second end of said rocker arm
being coupled to a coupler link adapted to couple said rocker arm to at least an
angularly displaceable gear driven by a motor;
c. at least a first charging pawl adapted to engage with said rocker arm and further
adapted to engage with said ratchet charging wheel such that tip of said first
charging pawl, in a first condition, engages with said first charging pawl, tooth by
tooth, aiding charging by angularly displacing said ratchet charging wheel in an
operatively forward / anticlockwise direction and said engagement preventing

said ratchet charging wheel's operatively reverse / clockwise angular displacement, and further such that said tip, in a second condition, disengaging from any of said teeth of said ratchet charging wheel;
d. at least a holding latch adapted to hold said ratchet charging wheel in its spring
charged condition and further adapted to release said spring charged ratchet
charging wheel upon receipt of a close command to said circuit breaker;
e. at least a set of tension resetting springs adapted to be connected to one end of
said first charging pawl such that it provides anticlockwise moment about hinge
point of said first charging pawl; and
f. at least a catch mechanism adapted to break and make contact between said first
charging pawl and said ratchet wheel, characterised in that, said catch mechanism
further comprising:
i. at least a primary latch; at least a secondary latch; at least a catch; at least a first stopper pin corresponding to said at least a primary latch; at least a second stopper pin corresponding to said at least a secondary latch; and springs for pre-defined moments used to hold and release said catch.
Typically, said mechanism comprises at least a spring crank adapted to be co-axially coupled with said ratchet charging wheel by means of a spline shaft.
Typically, said mechanism comprises at least a latching crank adapted to be coupled with a spline shaft at its one end and further adapted to radially extend towards the circumference of said ratchet charging wheel.
Typically, said mechanism comprises at least a primary second pawl adapted to be a first stopper pawl actuated, appropriately, by a catch mechanism.
Typically, said mechanism comprises at least a secondary second pawl adapted to be a second stopper pawl.
Typically, said at least a catch mechanism characterised, in that:

I. said catch being is adapted to hold said first charging pawl during discharging, thereby disallowing any engagement between said first charging pawl and said ratchet wheel during discharging; II. said primary latch and said secondary latch rests against and being limited by respective stopper pins during charging and charged condition, thereby causing said catch to be restricted from moving upwards beyond a pre-defined lift;
III. said primary latch and said secondary latch is spaced apart from respective stopper pins during discharging and discharged condition, thereby causing said catch to fall down and engage with said first charging pawl;
IV. said catch further is adapted to engage said charging pawl to cause said pre-defined lift during start of charging and further adapted to engage with at least a tooth of said charging wheel after said lift of said catch in order to initiate charging; and
V. said charging pawl is further adapted to repeatedly engage with successive teeth of said ratchet wheel by moving operatively upwards and downwards, corresponding with oscillations of said rocker arm, for each successive teeth, thereby displacing each engaged tooth in a forward / anticlockwise direction, and thereby angularly displacing said ratchet wheel in order to cause charging of said closing spring.
Typically, said mechanism comprises a crankshaft adapted to couple said rocker arm's one end to said angularly displaceable gear, said crankshaft being co-axially located with said gear, thereby enabling said coupler link to cause upward and downward oscillations.
Typically, said coupler link comprises four bar linkages.
Typically, said mechanism comprises at least a spur gear train adapted to be used to reduce torque on motor which drives angular displacement of said spur gear.
Typically, said at least a charging pawl rocker arm comprises at least two arms parallel to each other and spaced apart from each other, such that said two arms of the charging pawl rocker arm being located on either side of said ratchet charging wheel.

Typically, said at least a charging pawl rocker arm comprises at least two arms parallel to each other and spaced apart from each other, such that said two arms of the charging pawl rocker arm being located on either side of said ratchet charging wheel, characterised, in that, said at least a first charging pawl being located between said two arms of said rocker arm.
Typically, said ratchet charging wheel is designed to have teeth on a first circumferential portion, said first circumferential portion being decided in such a manner that said teeth are required to be present on said first charging pawl side for engagement and consequent charging said closing spring.
Typically, said ratchet charging wheel is further designed to have no teeth on a second circumferential portion, said circumferential portion being decided in such a manner that said no teeth are required to be present on said first charging pawl side for disengagement and consequent discharging said closing spring.
Typically, diameter of said ratchet charging wheel at teethed section is smaller than diameter of said ratchet charging wheel at non-teethed section.
Typically, said holding latch is characterised, in that, upon release of said holding latch, said closing spring losing its charged energy, due to operative forward / anticlockwise angular displacement of ratchet charging wheel, and associated circuit breaker being pressed into action.
Typically, said holding latch, in its charged condition is adapted to hold on to a tooth of said ratchet wheel, which tooth lies in a starting portion of the set of teeth on a first circumferential portion.
Typically, said closing spring is held together between a fixed plate and a moving plate.

Typically, said spring crank is an arm which extends radially from the centre where a spline shaft is also co-axially located.
Typically, said ratchet charging wheel, spring crank, spline shaft; are all co-axially located such that they are angularly displaceable in an operative forward / anticlockwise direction during discharging (to effect circuit breaking operation), after receipt of a closing command.
Typically, said closing spring is held together between a fixed plate and a moving plate, said mechanism further comprising at least- a chain adapted to connect said moving plate to a distal portion of said spring crank.
Typically, said closing spring is held together between a fixed plate and a moving plate, said mechanism further comprising at least a chain adapted to connect said moving plate to a distal portion of said spring crank, characterised, in that, a stub adapted to hold said chain at said distal location of said spring crank.
Typically, said closing spring is held together between a fixed plate and a moving plate, said mechanism further comprising at least a chain adapted to connect said moving plate to a distal portion of said spring crank, characterised, in that, a stub adapted to hold said chain at said distal location of said spring crank and a pulley being advantageously located in order to direct said chain.
Typically, said mechanism comprises further sets of tension resetting springs being adapted to be connected to the first stopper pawl and second stopper pawl; correspondingly, separately, and advantageously.
Typically, said catch mechanism comprises at least a primary latch being an operatively horizontal element angularly displaceable about a hinge.

Typically, said catch mechanism comprises at least a secondary latch being an operatively horizontal element angularly displaceable about a hinge.
Typically, said catch mechanism comprises at least a primary latch and at least a secondary latch, characterised in that, a first end of said primary latch being adjacent said ratchet wheel and a second end of said primary latch is adapted to vertically partially overlap a first end of said secondary latch, said second end of said secondary latch being adapted to engage with an operative top end of said operative vertical element of said catch.
Typically, said secondary latch is operated by a cam profile projection which is integrated with said ratchet wheel.
Typically, said release catch is a set of elements comprising at least an operative horizontal element and at least an operative vertical element conjoined such that said operative vertical element extends operatively upwards from said operative right side of the operative horizontal element.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
The invention will now be described in relation to the accompanying drawings, in which:
Figure 1 (a) illustrates an operative mechanism of charging system of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;
Figure 1 (b) illustrates an enlarged front view of section A of Figure 1 (a) of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;
Figure 2 (a) illustrates a discharged condition of closing spring of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;

Figure 2 (b) illustrates an enlarged view of section B of Figure 1 (b) of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;
Figure 3 illustrates a lock condition of a catch mechanism of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;
Figure 4 (a) illustrates a spring charging operation of a ratchet and pawl based drive mechanism for spring loaded circuit breakers;
Figure 4 (b) illustrates a charging pawl engaged with ratchet wheel tooth of a ratchet and pawl based drive mechanism for spring loaded circuit breakers; and
Figure 5 illustrates completion of spring charging, prevention of overcharging, and catch mechanism in unlock condition for a ratchet and pawl based drive mechanism for spring loaded circuit breakers.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
According to this invention, there is provided a ratchet and pawl based drive mechanism for spring loaded circuit breakers.
In accordance with an embodiment of this invention, there is provided a charging pawl rocker arm 5 (which comprises two arms parallel to each other and spaced apart from each other) adapted to oscillate in an operative upward and downward manner about an operative horizontal axis. The two arms of the charging pawl rocker arm 5 are located on either side of a ratchet charging wheel 8. This upward and downward oscillation is caused by a coupler link 4 which couples the rocker arm's 5 one end to an angularly displaceable spur gear 2, through its crankshaft 3 which is co-axially located with the spur gear 2. A first end of the rocker arm 5 is coupled to the ratchet wheel 8, at the centre of the ratchet wheel 8. A second end of the rocker arm 5 is coupled to the coupler link 4.

Typically, four bar linkages and spur gear train may be used to reduce torque on motor 1 which drives the angular displacement of the spur gear 2.
In accordance with another embodiment of this invention, there is provided at least a first charging pawl 6.1 located between the two arms of the rocker arm 5. The first charging pawl 6.1 is adapted to engage with the ratchet charging wheel 8, such that the tip of the first charging pawl 6.1, in one condition, engages with first charging pawl 6.1, tooth by tooth, preventing its operatively reverse / clockwise angular displacement.
In accordance with yet another embodiment of this invention, there is provided a ratchet charging wheel 8 adapted to provide momentum for charging and discharging. The ratchet charging wheel 8 is designed to have teeth on a first circumferential portion, the circumferential portion being decided in such a manner that the teeth are required for charging the closing spring 14. Thus, while the ratchet charging wheel 8 traverses its angular displacement for charging, teeth need to be present on the first charging pawl 6.1 side for engagement. The ratchet charging wheel 8 is further designed to have no teeth on a second circumferential portion, the circumferential portion being decided in such a manner that the teeth are required for charging the closing spring 14. Thus, while the ratchet charging wheel 8 traverses its angular displacement for discharging, during a close condition of the circuit breaker, toothless section needs to be present on the first charging pawl 6.1 side for free motion. Typically, diameter of the ratchet charging wheel 8 at teethed section is smaller than diameter of the ratchet charging wheel 8 at non-teethed section.
In accordance with still another embodiment of this invention, there is provided a holding latch 20 adapted to hold the ratchet charging wheel 8 in its spring 14 charged condition. Upon receiving a close circuit command, the holding latch 20 is released, the closing spring 14 loses its charged energy, and circuit breaker is pressed into action due to operative forward / anticlockwise angular displacement of ratchet charging wheel 8. In its charged condition, the holding latch 20 holds on to a tooth which lies in a starting portion

of the set teeth on a first circumferential portion. The closing spring is held together between a fixed plate 17 and a moving plate 18.
In accordance with yet another embodiment of this invention, there is provided a spring crank 11 adapted to be co-axially coupled with the ratchet charging wheel 8 by means of a spline shaft 12. The spring crank 11, typically, is an arm which extends radially from the centre where the spline shaft 12 is also co-axially located. Typically, ratchet charging wheel 8, spring crank 11, spline shaft 12; are all co-axially located such that they are angularly displaceable in an operative forward / anticlockwise direction during discharging (to effect circuit breaking operation), after receipt of a closing command. The catch mechanism remains stationary during discharging. A chain 16 connects the moving plate 18 to a distal portion of the spring crank 11. Typically, a stub holds the chain 16 at the distal location of the spring crank 11. A pulley 15 is advantageously located in order to direct the chain 16.
In accordance with still another embodiment of this invention, there is provided a latching crank 13 adapted to be coupled with spline shaft 12 at its one end and further adapted to radially extend towards the circumference of the ratchet charging wheel 8.
In accordance with yet another embodiment of this invention, there is provided at least a primary second pawl 6.2 adapted to be a first stopper pawl actuated, appropriately, by the catch mechanism.
In accordance with still another embodiment of this invention, there is provided at least a secondary second pawl 6.2 adapted to be a second stopper pawl.
In accordance with yet another embodiment of this invention, there is provided a set of tension resetting springs 7 adapted to be connected to one end of the first charging pawl 6.1 such that it gives anticlockwise moment about hinge point of first charging pawl 6.1. Further sets of tension resetting springs are adapted to be connected to the first stopper pawl and second stopper pawl; correspondingly, separately, and advantageously.

In accordance with yet another embodiment of this invention, there is provided a catch mechanism adapted to avoid and make contact between first charging pawl 6.1 and ratchet wheel 8. Typically, the catch mechanism comprises at least a primary latch 10.1, at least a secondary latch 10.2, at least a catch 9, at least a first stopper pin 19.1 corresponding to the at least a primary latch 10,1, at least a second stopper pin 19,2 corresponding to the at least a secondary latch 10.2, and springs for required moments used to hold and release catch 9. The secondary latch 10.2 is operated by a cam profile projection which is integrated with ratchet wheel 8. Typically, release catch 9 is a set of elements comprising an operative horizontal element and an operative vertical element conjoined such that the operative vertical element extends operatively upwards from an operative right side of the operative horizontal element. Typically, a primary latch 10.1 in an operatively horizontal element angularly displaceable about a hinge. Typically, a secondary latch 10.2 in an operatively horizontal element angularly displaceable about a hinge. A first end of the primary latch 10.1 is adjacent the ratchet wheel 8. The second end of the primary latch 10.1 is adapted to vertically partially overlap a first end of the secondary latch 10.2. The second end of the secondary latch 10.2 is adapted to engage with the operative top end of the operative vertical element of the catch 9.
Figure 1 (a) illustrates a general arrangement of the operating mechanism of charging system of the circuit breaker of this invention. This figure represents the fully charged condition. Upon receipt of a close command, circuit breaker is pressed in to action in order to close the circuit. Motor 1 is connected to a crank shaft 3 through spur gear train 2 in order to increase torque which angularly displaces in an operative forward / anticlockwise direction. A first charging pawl 6.1 is placed in between two rocker arms 5, which gets oscillating motion about centre of ratchet wheel 8 due to a coupler link 4 and a crank shaft 3 co-axial to the spur gear 2. The coupler link 4 is a link which is coupled at its one end to the crankshaft 3 and at its other end to the rocker arm 5. Figure 1 (a) illustrates that, initially, closing spring 14 is in fully charged condition connected to spring crank 11 by chain 16 and pulley 15. One end (stationary) of closing spring 14 is rested on a fixed plate 17 and another end (moving) is coupled to a moving plate 18.

Chain 16 is connected to moving plate 18. Ratchet wheel 8, spring crank 11, and latching crank 13 are placed on spline shaft 12 through internal spline. The total torque in the operative forward / anticlockwise direction about spline shaft 12 due to closing spring 14 is balanced by reaction torque of holding latch 20 through latching crank 13.
Figure 1 (b) illustrates an enlarged front view of catch mechanism of the circuit breaker of this invention. Initially, when closing spring 14 is in charged condition, at that position, power supply of motor 1 is disconnected by limit switch (which is not shown). The catch mechanism contains at least a catch 9, at least a primary latch 10.1, at least a secondary latch 10.2, and at least two stopper bar pins 19.1 and 19.2. The first charging pawl 6.1 is rested on tip of catch 9 (typically, in a notch pre-designed to that effect such that the first charging pawl 6.1 rests in the notch of the catch 9) so that it does not engage with any of the teeth of the ratchet charging wheel 8. Tension springs 7 are connected to one end of pawls 6.1 and 6.2 such that it gives anticlockwise moment about hinge point of pawls 6.1 and 6.2. Torsion / compression / tension springs can be provided such that catch 9, primary latch 10.1, and secondary latch 10.2 get momentum in anticlockwise, clockwise, and anticlockwise directions; respectively as shown by arrows about respective hinge points. [In Figure 1(b), the arrows show direction of spring torques]. Stopper bar pins 19.1 and 19.2 are placed on one side of primary latch 10.1 and secondary latch 10.2. Due to projected cam profile 8.1 on ratchet wheel 8, secondary latch 10.2 is in inclined position. Secondary latch 10.2 pushes down the left arm primary latch 10.1 and holds it in that position. Due to anticlockwise torque of spring on catch 9 about hinge, it is in such a position that its tip is in front of charging pawl 6.1 as shown in Figure 1 (b). Each of the at least catch 9, at least a primary latch 10.1, at least a secondary latch 10.2 - are imparted a pre-determined and pre-directed torsion force by corresponding spring mechanisms which impart pre-defined momentums. Catch 9 comprises inbuilt anticlockwise torsion due to spring. Primary latch 10.1 comprises inbuilt clockwise torsion due to spring. Secondary latch 10.2 comprises inbuilt anticlockwise torsion due to spring.

For discharging, holding latch 20 is released by actuator, closing spring 14 gets discharged and spring crank 11 along with ratchet wheel 8 angularly displaces in operative forward / anticlockwise direction. Figure 2 (a) illustrates closing spring 14 in discharged condition after crossing the bottom dead center going into overtravel. During discharging process, even when ratchet wheel 8 teeth comes in front of first charging pawl 6.1, there is no physical contact between first charging pawl 6.1 and ratchet wheel 8 which is shown in Figure 2 (b). This is because catch 9 holds the first charging pawl 6.1. During discharge operation (i.e. after angular displacement of charging ratchet 8 in operative forward / anticlockwise direction), after crossing the bottom dead center, closing spring 14 again gets compressed as shown in Figure 2 (a). After completion of overtravel, ratchet wheel 8 tries to come to bottom position due to closing spring 14 torque and angularly displaces in operative reverse / clockwise direction. Since there is no contact between first charging pawl 6.1 and ratchet wheel 8, impact load due to reverse rotation is checked by one of the engaged stopper pawl 6.2. The provisioning of the catch mechanism and catch 9, per se, prevent loading on to the charging pawl 6.1, during overtravel. Hence, this avoids damage of first charging pawl 6.1 which could have occurred due to impact load. Figures 2 (a) and 2 (b) show the stopper pawl 6.2 engaged with ratchet wheel 8 tooth and closing spring in discharge condition. Projected cam profile 8.1 is provided only on some portion of ratchet wheel 8. Due to spring torque on secondary latch 10.2 about operative forward / anticlockwise direction (shown by arrow) it rests on stopper bar pin 19.2, because there is no lift by cam profile 8.1. In the same way, the primary latch 10.2 rests on stopper bar pin 19,1 due to torque in clockwise direction (shown by arrow).
To start the charging of closing spring 14, power supply is provided to motor 1 through a limit switch. The limit switch is operated by cam plate (not shown) which is placed on spline shaft 12. When motor 1 starts, crankshaft 3 angularly displaces in the operative forward / anticlockwise direction through spur gear train 2.
When crankshaft 3 angularly displaces, for the first time after limit switch is engaged, the first cycle of angular displacement can be divided into two parts; a first part and a second

part. During the first part, the operative upper tip of the first charging pawl 6.1 reaches its maximum top position. The first charging pawl 6.1 lifts the catch 9 which is shown in Figure 3 (due to the fact that the tip of the first charging pawl 6.1 rests on a notch of the catch 9. Initially, the catch's 9 vertical portion end tip rests below the operative right face of primary latch 10.1. The first charging pawl 6.1 keeps on moving operatively upwards and at maximum top position of the first charging pawl 6.1, catch's 9 vertical portion end tip begins to move operatively laterally rightwards and eventually rests on operative right face of primary latch 10.1. So, it prevents the falling down (anticlockwise angular displacement) of catch 9. There is spring torque about catch 9 hinge which is shown by arrow. The line of action of force due to catch 9 on face of primary latch 10.1 is predetermined (due to designing), in that, it gives torque to primary latch 10.1 about its hinge in clockwise direction. So, primary latch 10.1 rests on stopper bar pin 19.1 and in horizontal position, which holds the catch 9 shown Figure 3. During the second part, the operative upper tip of the first charging pawl 6.1 reaches its maximum bottom position. In this, the first charging pawl 6.1 disengaged from the catch 9 and engages with a tooth of the ratchet wheel, which tooth is below the catch's 9 position.
For the next complete cycle of angular displacement of crank shaft 3, and for each successive cycles of angular displacement of crank shaft 3, until the charging cycle is completed, the first charging pawl 6.1 gets engaged with successive teeth of ratchet wheel 8, shown in Figure 4 (a). The operative upper engaging tip of the first charging pawl 6.1 moves between the operative top position and the operative bottom position, as discussed in its first cycle of angular displacement. However, after the first cycle of angular displacement, the first charging pawl 6.1 engages with successive teeth in corresponding cycles of crankshaft 3 angular displacement. Since the first charging pawl 6.1 engages with teeth, it drives each tooth along with it to its maximum top position, thereby driving the ratchet wheel 8 in the operative forward / anticlockwise direction. Initially, charging pawl 6.1 starts to push ratchet wheel 8 in the operative forward / anticlockwise direction to charge the closing spring 14 (refer Figure 4 (b)), upon engagement of each teeth. Also during charging operation (upward motion), first charging pawl 6.1 lifts the catch 9 by some amount and during return motion of first

charging pawl 6.1, catch 9 rests on right face of primary latch 10.1. This sequence of operation repeats until spring crank 11 crosses the top dead center (means fully charged condition of closing spring 14). Chain 16, which is connected to spring crank 11 and moving plate 18, passes from pulley 15.
When spring crank 11 along with ratchet wheel 8 crosses the top dead center, again cam profile 8.1 comes in front of secondary latch 10.2 and angularly displaces it in clockwise direction against anticlockwise spring torque shown by arrow. Right arm of secondary latch 10.2 comes into contact with left arm of primary latch 10.1. Due to this, primary latch 10.1 angularly displaces in anticlockwise direction about its hinge and releases the catch 9, which results into fall down of catch 9 (anticlockwise rotation about hinge) in front of charging pawl 6.1 shown in Figure 5. At that position, first charging pawl 6.1 is on uncut portion (having no teeth) of ratchet wheel 8 and engaged with catch 9, so even motor 1 is running and first charging pawl 6.1 has oscillatory up-down motion then also there is no contact between first charging pawl 6.1 and ratchet wheel 8 tooth. This prevents overcharging of closing spring.
The technical advancement of this invention lies in provisioning a catch mechanism adapted to engages with a first charging pawl such that it suitably engages with the ratchet charging wheel while charging and suitably disengages with the ratchet charging wheel while discharging. This mechanism is designed to prevent failure of charging pawl due to impact load. This mechanism reduces the size of charging pawl, as there is no need to add factor or design for impact load. This mechanism improves reliability of charging system. This mechanism can be used for high energy and high voltage switchgear mechanisms. There is no need of two charging pawls and eccentric shaft system. This mechanism removes the assembly criticality.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing

descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

WE CLAIM :
1. A ratchet and pawl based drive mechanism for spring loaded circuit breakers, said mechanism comprising:
a. at least a ratchet charging wheel adapted to be coupled with a closing spring and
further adapted to provide momentum for charging and discharging of said
closing spring of said spring loaded circuit breaker, characterised, in that, an
operative forward / anticlockwise angular displacement of said ratchet charging
wheel for a first sector causing charging of said closing spring and a further
operative forward / anticlockwise angular displacement of said ratchet charging
wheel for a second (remainder) sector causing discharging of said closing spring;
b. at least a charging pawl rocker arm adapted to oscillate in an operative upward
and downward manner about an operative horizontal axis, a first end of said
rocker arm being coupled to said ratchet wheel, a second end of said rocker arm
being coupled to a coupler link adapted to couple said rocker arm to at least an
angularly displaceable gear driven by a motor;
c. at least a first charging pawl adapted to engage with said rocker arm and further
adapted to engage with said ratchet charging wheel such that tip of said first
charging pawl, in a first condition, engages with said first charging pawl, tooth by
tooth, aiding charging by angularly displacing said ratchet charging wheel in an
operatively forward / anticlockwise direction and said engagement preventing
said ratchet charging wheel's operatively reverse / clockwise angular
displacement, and further such that said tip, in a second condition, disengaging
from any of said teeth of said ratchet charging wheel;
d. at least a holding latch adapted to hold said ratchet charging wheel in its spring
charged condition and further adapted to release said spring charged ratchet
charging wheel upon receipt of a close command to said circuit breaker;
e. at least a set of tension resetting springs adapted to be connected to one end of
said first charging pawl such that it provides anticlockwise moment about hinge
point of said first charging pawl; and

f. at least a catch mechanism adapted to break and make contact between said first
charging pawl and said ratchet wheel, characterised in that, said catch mechanism
further comprising:
i. at least a primary latch; at least a secondary latch; at least a catch; at least a
first stopper pin corresponding to said at least a primary latch; at least a
second stopper pin corresponding to said at least a secondary latch; and
springs for pre-defined moments used to hold and release said catch.
2. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising at least a spring crank adapted to be co-axially coupled with said ratchet charging wheel by means of a spline shaft.
3. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising at least a latching crank adapted to be coupled with a spline shaft at its one end and further adapted to radially extend towards the circumference of said ratchet charging wheel.
4. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising at least a primary second pawl adapted to be a first stopper pawl actuated, appropriately, by a catch mechanism.
5. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising at least a secondary second pawl adapted to be a second stopper pawl.
6. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said at least a catch mechanism characterised, in that:
I. said catch being adapted to hold said first charging pawl during discharging, thereby disallowing any engagement between said first charging pawl and said ratchet wheel during discharging;

II. said primary latch and said secondary latch resting against and being limited by respective stopper pins during charging and charged condition, thereby causing said catch to be restricted from moving upwards beyond a pre-defined lift;
III. said primary latch and said secondary latch spaced apart from respective stopper pins during discharging and discharged condition, thereby causing said catch to fall down and engage with said first charging pawl;
IV. said catch further being adapted to engage said charging pawl to cause said predefined lift during start of charging and further adapted to engage with at least a tooth of said charging wheel after said lift of said catch in order to initiate charging; and
V. said charging pawl further adapted to repeatedly engage with successive teeth of said ratchet wheel by moving operatively upwards and downwards, corresponding with oscillations of said rocker arm, for each successive teeth, thereby displacing each engaged tooth in a forward / anticlockwise direction, and thereby angularly displacing said ratchet wheel in order to cause charging of said closing spring.
7. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising a crankshaft adapted to couple said rocker arm's one end to said angularly displaceable gear, said crankshaft being co-axially located with said gear, thereby enabling said coupler link to cause upward and downward oscillations.
8. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said coupler link comprising four bar linkages.
9. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising at least a spur gear train adapted to be used to reduce torque on motor which drives angular displacement of said spur gear.

10. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said at least a charging pawl rocker arm comprising at least two arms parallel to each other and spaced apart from each other, such that said two arms of the charging pawl rocker arm being located on either side of said ratchet charging wheel.
11. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said at least a charging pawl rocker arm comprising at least two arms parallel to each other and spaced apart from each other, such that said two arms of the charging pawl rocker arm being located on either side of said ratchet charging wheel, characterised, in that, said at least a first charging pawl being located between said two arms of said rocker arm.
12. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said ratchet charging wheel being designed to have teeth on a first circumferential portion, said first circumferential portion being decided in such a manner that said teeth are required to be present on said first charging pawl side for engagement and consequent charging said closing spring.
13. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1 wherein, said ratchet charging wheel being further designed to have no teeth on a second circumferential portion, said circumferential portion being decided in such a manner that said no teeth are required to be present on said first charging pawl side for disengagement and consequent discharging said closing spring.
14. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein diameter of said ratchet charging wheel at teethed section is smaller than diameter of said ratchet charging wheel at non-teethed section.

15. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said holding latch characterised, in that, upon release of said holding latch, said closing spring losing its charged energy, due to operative forward / anticlockwise angular displacement of ratchet charging wheel, and associated circuit breaker being pressed into action.
16. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, characterised, in that, said holding latch, in its charged condition being adapted to hold on to a tooth of said ratchet wheel, which tooth lies in a starting portion of the set of teeth on a first circumferential portion.
17. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, characterised, in that, said closing spring being held together between a fixed plate and a moving plate.
18. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein, said spring crank being an arm which extends radially from the centre where a spline shaft is also co-axially located.
19. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein, said ratchet charging wheel, spring crank, spline shaft; are all co-axially located such that they are angularly displaceable in an operative forward / anticlockwise direction during discharging (to effect circuit breaking operation), after receipt of a closing command.
20. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, characterised, in that, said closing spring being held together between a fixed plate and a moving plate, said mechanism further comprising at least a chain adapted to connect said moving plate to a distal portion of said spring crank.

21. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, characterised, in that, said closing spring being held together between a fixed plate and a moving plate, said mechanism further comprising at least a chain adapted to connect said moving plate to a distal portion of said spring crank, characterised, in that, a stub adapted to hold said chain at said distal location of said spring crank.
22. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, characterised, in that, said closing spring being held together between a fixed plate and a moving plate, said mechanism further comprising at least a chain adapted to connect said moving plate to a distal portion of said spring crank, characterised, in that, a stub adapted to hold said chain at sais distal location of said spring crank and a pulley being advantageously located in order to direct said chain.
23. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said mechanism comprising further sets of tension resetting springs being adapted to be connected to the first stopper pawl and second stopper pawl; correspondingly, separately, and advantageously.
24. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said catch mechanism comprising at least a primary latch being an operatively horizontal element angularly displaceable about a hinge.
25. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said catch mechanism comprising at least a secondary latch being an operatively horizontal element angularly displaceable about a hinge.
26. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as claimed in claim 1, wherein said catch mechanism comprising at least a primary latch and at least a secondary latch, characterised in that, a first end of said primary latch being adjacent said ratchet wheel and a second end of said primary latch being

adapted to vertically partially overlap a first end of said secondary latch, said second end of said secondary latch being adapted to engage with an operative top end of said operative vertical element of said catch.
27. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as
- claimed in claim 1, wherein said secondary latch being operated by a cam profile
projection which is integrated with said ratchet wheel.
28. The ratchet and pawl based drive mechanism for spring loaded circuit breakers as
claimed in claim 1, wherein said release catch being a set of elements comprising at
least an operative horizontal element and at least an operative vertical element
conjoined such that said operative vertical element extends operatively upwards from
said operative right side of the operative horizontal element.