FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - DRIVESHAFT FOR MOULDED CASE CIRCUIT BREAKER
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
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 switching devices such as circuit breakers, contact systems and the like. More particularly, the invention relates to a driveshaft mechanism for use in circuit breakers.
BACKGROUND AND THE PRIOR ART
Circuit switching devices and circuit interrupters such as circuit breakers, contactors, motor starters, motor controllers and other load controllers are used to protect electrical circuitry and equipment from damage due to abnormal condition, such as an overload condition or a relatively high level short circuit or fault condition.
These switching devices typically have two positions corresponding to the status of the separable contacts. For example, these positions would include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open. In a few switching device there could be a third state which would include tripped position in which the contacts are tripped open.
These switching devices are usually installed in an enclosure so as to have all the control and distribution network laid in form of metallic sheets and or cable wires inside and all operating means from outside so as to prevent access to high voltage and thus a potential hazard.
One such switching device is a moulded case circuit breaker (MCCB) which is generally used to provide over current protection for various types of electrical equipment. MCCBs have three stable positions - ON, OFF and TRIP in which conditions of contacts as described above.

The main function of any electrical switching apparatus is to carry the rated current. Therefore the current carrying capacity of any circuit breaker is so important that if the unit fails to carry the rated current it will cause damage to itself as well as to the electrical equipment to which it is protecting.
The most severe and common, as well, issue observed by the customer in field is the thermal run away of MCCB. The detailed investigation / examination of such incidents revealed that the main reason of thermal runaway is the variation in contact mating which leads to variable contact pressure and hence variable voltage drop at joints which ultimately results into thermal run-away. When the issue of contact mating was magnified further to weed out the exact problem, it was observed that the variation in drive-shaft hole (where the contacts are hinged) drilling has played a vital role in thermal runway.
Moving contacts are hinged at these holes of drive shaft. The effect of the error in drilling the hole can be seen at the extreme point of the moving contact where it meets fixed (lower) contact to complete the electrical circuit. The alignment / positional difference between two contacts are as high as 1 mm which is 20-40% of the total over-travel of MCCB.
Apart from this the extra drilling process requires extra operational time, extra process cost and above all the Thermoset material that is used as raw material of drive shaft, which is not recyclable material. During drilling process the material equivalent to the area of the holes in the drive shaft is wasted. This material being non-recyclable gives opportunity for the new design to eliminate the above issues.
US5633483 discloses a circuit breaker is provided having a stationary contact, a movable contact and a blade which has a first end and a second end. The movable

contact is secured to the first end of the blade. The blade is rotatable about a pin between a BLOWN OPEN position and a CLOSED position, wherein the movable contact is separated from the stationary contact when the blade is in the BLOWN OPEN position and the movable contact engages the stationary contact when the blade is in the CLOSED position. The blade further has a protrusion portion extending from its second end. The circuit breaker further includes a catcher rotatably coupled to a pivot pin and having a nose portion for engagement with the blade protrusion portion. A spring is mounted about the pivot pin and engages the catcher for biasing the catcher towards the blade whereby the nose portion rests against the protrusion portion of the blade when the blade is in the CLOSED position and the nose portion overlaps the protrusion portion when the blade is in the BLOWN OPEN position thereby holding the blade in the BLOWN OPEN position.
US5874699 discloses molded case circuit breaker has a moving conductor assembly which includes a modular carrier assembly incorporating a plurality of spring biased contact cam members each of which engages contact pressure lobes on a pair of contact arm laminations to provide contact pressure. In response to the magnetic repulsion forces generated by a short circuit, the springs compress allowing the cam members to pivot and side step the contact pressure lobes so that the contact arm blows-open with little resistance. The cam members and springs are preassembled in a transverse channel in the carrier body and laterally retained in place by side plates for easier pivotal attachment of the contact arm laminations to the lobes on the side plates. The side plate lobes raise the contact arm relative to the mass of the carrier to reduce eddy current heating and provide a positive off indication for welded contacts by restricting movement of lower toggle links of the operating mechanism which are coplanar with the side plates. A modular crossbar includes molded bearings engaged by or made integral with hexagonal metal shaft sections which extend into hex openings in the carrier bodies of adjacent poles.

US4644121 discloses a circuit breaker characterized by a movable contact carrying arm movable about a pivot and a helical torsion spring movable on the arm to and from the pivot for applying a varying force as the arm moves from closed to open positions.
US5844455 discloses a current-limiting apparatus for a circuit breaker which makes it possible to effectively protect an electric load element by quickly blocking an electric flow path when an excessive current flows due to a ground, shortage, etc. at an electric flow path and preventing a re-formation of an electric flow path after the electric flow path is blocked. The apparatus includes a guide pin passing through the second pin hole and being extended from both side surfaces of the movable contact member, a holder, a portion of which support both ends of the movable contact member rotation center pin, for rotatably supporting the movable contact member, a current-limiting latch having a curved guide surface formed on one outer circumferential surface of the same on which the guide pin slidably moves, a support groove formed on another outer circumferential surface of the same, and a pin hole for supporting the holder, a rotation center pin inserted into the pin hole of the current-limiting latch, both ends of which rotation center pin are inserted into portions of the holder, and a contact spring, both ends of which are supported by the support groove of the current-limiting latch and the support surface of the holder, for generating a variable force which prevents the movable contact member from being rotated.
US4539538 describes a molded case circuit breaker includes a movable upper electrical contact having a base portion with a slot formed therein for releasably receiving a portion of an elongated spring biased locking pin disposed in a rotatable cross bar of an operating mechanism of the circuit breaker. The locking pin is biased in the slot by a pair of tension springs secured to the cross bar, enabling the upper electrical contact to move in unison with the cross bar. Upon the occurrence of a high

level short circuit or fault current of sufficient magnitude, the pin is displaced from the slot enabling the independent rotational movement of the upper contact arm. During such movement, an elongated leaf spring is downwardly deflected and then released by the base portion. Subsequently, the upper electrical contact is prevented from contacting the lower electrical contact by the engagement of the leaf spring with the base portion. A subsequent trip operation of the operating mechanism removes the latching feature of the leaf spring.
US4626811 teaches that the gap distance separating the contacts of a low-voltage circuit breaker in the tripped position is increased by utilizing resilient stop means which is located at the bottom wall of the breaker housing rather than at the top wall (or on the handle of the breaker) in accordance with prior art practice. The movable contact arm is pivotally mounted and structured to strike the stop means as the contacts are separated and being blown open during short circuit conditions and, after the circuit breaker is tripped, the collapsed toggle assembly of the operating mechanism shifts the movable contact arm away from the stop means and allows the arm to move an additional distance away from the fixed contact and thus increase the gap distance between the opened contacts.
US4245203 discloses a circuit interrupter includes two parallel pivoting contact arms, the lower of which is connected to a stationary conductor member using a clinch-type contact. The contact arm has an axle member rigidly attached thereto which is supported by a bearing member attached to the conductor. In one embodiment, the bearing member comprises a pair of bifurcated arms which are clamped about each end of the axle member. In an alternative embodiment, the conductor member lies generally parallel to the lower contact arm and is slotted to form a pair of elongated conductor arms, each of which supports a journal bearing member. One end of the axle is extended through each journal bearing.

US 6590172 discloses a circuit breaker is provided wherein the circuit breaker comprises a contact arm movable between a closed position, an open position and a blown open position wherein the contact arm is disposed in the circuit breaker. A bumper disposed to contact the contact arm when the contact arm is in the blown open position. In addition, a stop member disposed to be in contact with a linkage assembly so as to create a gap between the bumper and the contact arm when the contact arm is disposed in the open position.
US 5266760 discloses a molded case circuit breaker having collapsible toggle linkage with rectangular cross section knee pin non-rotatably held within open rectangular slots in upper link, bifurcated movable contact fingers loosely guided for pivotal movement about fixed pin to break contact welds, helical compression springs biasing bifurcations against faces of a stationary connector, trapezoidal cross section shaft biasing shaft against a fixed corner of clamping strap and frame, increasing clamping force and increasing tool clearance, operating handle which changes pivot point moving to RESET position, reducing lateral force component of operating springs for reliable return of handle to OFF position, dual stops for movable contact fingers to spread impact forces along fingers, greater contact separation in poles not containing operating mechanism, slot motor laminations providing metal reinforcement to separate arc chamber housing which is cooperatively interlocked with base to distribute structural strength, terminal cover with arc vent extension angled downwardly, extended lug cover with second arc vent extension interlocked to terminal cover and arc chamber housing for no-fastener securement, trip unit armature pivoted in crested surface of molded pocket and connected to trip bar by wire bail for space-efficient location of parts, and accessory devices supported on and secured to trip unit housing have throw-away pin locking operator lever in correct position during installation.

US 7217895 discloses a contact assembly for a circuit breaker includes a fixed contact, a movable contact, and a movable contact arm. The movable contact arm includes a first end carrying the movable contact, a second end, and a pivot portion proximate the second end. A moving arm portion extends from the first end toward the pivot portion. The moving arm portion has a width, an upper edge, a lower edge, and a height defined by the distance between the upper edge and the lower edge. In response to a trip condition, the movable contact separates from the fixed contact and the movable contact arm pivots open at an angular opening velocity. The height of the moving arm portion of the movable contact arm is at least four times the width of the moving arm portion, thus minimizing the moment-of-inertia of the movable contact arm, and increasing the angular opening velocity.
US 4255732 discloses a molded case current limiting circuit interrupter includes a pair of pivoting contact arms each supporting a contact and being connected to wiring terminals such that current flows through the contact arms in opposite directions. One of the contact arms has a movable pivot point. A magnetic drive slot motor device is provided to generate electro-dynamic contact opening force upon the contact arms during short circuit conditions. A high-speed magnetic trip device releases the operating mechanism under short circuit conditions to move the arm pivot point before the contact arms reclose. A spring latch may be provided to latch the upper contact arm in a contact-separated position during short circuit conditions until such time as the overcurrent flow through the breaker operates a thermal and magnetic trip mechanism to move an operating mechanism to the tripped position. Alternatively, a cam may be provided which is connected by a link to the upper contact arm and positioned such that upon short circuit conditions the contact opening motion of the upper contact arm caused by electro-dynamic repulsion forces will cause the connecting link to rotate the cam and move the armature of the magnetic trip device to actuate the trip mechanism and release the operating mechanism to the tripped position, thereby preventing reclosing of the contact arms before the operating

mechanism is able to trip. The operating mechanism includes a bracket to allow normal contact reset yet provide a positive closed contact indication if the contacts are welded together. An anti-rebound contact arm shock absorber is provided which is made of material having a high mechanical hysteresis loop to provide maximum energy dissipation.
US 4910485 discloses a breaking device for a low voltage circuit breaker comprises in each pole a switching bar, a pair of stationary contacts connected to the connection terminals, a double-break rotary contact extending in a housing of the bar, and two arc chutes disposed on each side of the bar. Two contact pressure springs ensure elastic positioning of the rotary contact along the longitudinal direction of the pole. Pivoting of the rotary contact takes place around a fictitious axis mounted floating with respect to the fixed rotation axis of the bar.
US 6084489 relates to a circuit breaker is characterized by separable contacts operable between a closed and an open position a contact arm having a latching surface and a latch arranged to engage the latching surface when the contacts are blown-open under short-circuit conditions. The arrangement of the latch allows for a positive lock under high magnitude short circuit levels while minimizing the force required by a mechanism to unlock the arm.
US 4916421 discloses a current limiting circuit interrupter consisting of a modular unit housed in an insulating case and provided with two fixed contact arms and two movable contact arms. The movable contact arms can be actuated automatically by means of a rod coupled to an operating mechanism as well as by means of an electromagnetic actuator. The operating mechanism includes a lever and a rotating bracket arranged to hold the movable contacts in an open condition when the electromagnet within the electromagnetic actuator is de-energized.

These and other limitations of the conventional drive shafts need improvement. Such an improved drive shaft has been disclosed herein which overcomes the limitations over and above the improvements and supports the idea of green engineering by minimizing the use of non-recyclable Thermoset material.
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 driveshaft mechanism for use in circuit breakers.
These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.
SUMMARY OF THE INVENTION
According to one of the aspect of the present invention there is provided a driveshaft mechanism for use in circuit breakers, said mechanism comprising a moving contact means;
a drive shaft means adapted to perform rotational motion, said shaft means comprising a slot means ; plurality of pin means , said pin means comprising
a first pin means substantially positioned on the movable contact means,
a second pin means substantially accommodated inside said slot means
and
a third pin means substantially located at the cease of said shaft means;

a pair of energy storing elements;
wherein said energy storing element is operatively connected between said first pin means and said third pin means adapted to achieve optimum contact force in the ON condition to keep the potential drop at the contact means to the minimum;
wherein said first pin means , second pin means and third pin means are substantially in same axis/line to define a toggling position ;
wherein said moving contact means rotates substantially beyond said toggling position due to a fault and gets locked due to a predefined net force provided by said energy storing elements .
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Other features as well as the advantages of the invention will be clear from the following description.
In the appended drawings:
Figure 1 illustrates driveshaft of the prior art.
Figure 2 illustrates the 3D view of a single pole of the circuit breaker in assembled condition.
Figure 3 illustrates an exploded view of the internal arrangement without the spring.

Figures 4 and 5 illustrate the working of the contact system with different positions.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
In the following detailed description, reference is made to the accompanying drawings that form a part thereof, 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.
Contact system is shown in Fig 2. It consists of a rotating member of the MCCB mechanism, driveshaft 1 to which the moving contact 2 is pivoted at pin 4. Spring 5 (2 no's) are connected at one end to Pin 3 and the other end to pin 6. Rotational movement of driveshaft will allow moving contacts to come in contact with the fixed contacts and thereby complete the electrical circuit.
Fig 2 shows the 3D view of a single pole of the circuit breaker in assembled condition. Fig 3 shows an exploded view of the internal arrangement i.e. excluding the springs. For multiple poles multiple such assemblies will be used side by side using a common connecting driveshaft across all the poles.
The working of the contact system is shown in Fig 4 & 5 with different positions. When the fault occurs, there is an upward force on the moving contact 2 thereby which it will rotate about the pivot pin 4 & will move in upward direction. Therefore

out of the points across which the spring is connected, point at pin 3 will be moving whereas point at pin 6 is stationary.
Fig 4 shows the toggling or the locking position. Toggling position is that instant at which the points or pins 3, 4 & 6 come in the same line. If due to fault the moving contact rotates beyond the position shown in the fig 4, it will get locked to the position shown in fig 5 due to a net force provided by the spring in that direction. Thus, the spring which is stretched to its maximum deflection reaches an equilibrium state by reducing its length and releasing energy in the process to move the moving contact. If the repulsion force on the moving contact is not enough to move the positions beyond the toggling position, the arrangement will fall back to the positions shown in fig 2 i.e. in their ON condition.
From the working of driveshaft in MCCB explained above, it can be concluded that the most critical point for accurate functioning of driveshaft is its pivot point i.e. hinging point of pin 4. It is also very important to achieve optimum contact force in the ON condition to keep the potential drop at the contact buttons to the minimum.
The present invention takes care of the above points which are described in following paragraphs by avoiding drilling operation itself
In driveshaft with drilling operation it has been observed that it is difficult to maintain centre of all pivot points on same axis. Because of this MCCB behaves differently in pole to pole & variation in all the important parameters like contact force, over travel & repulsion force is observed.
Advantages:
Following are the features and benefits of the invention

• Driveshaft without drilling operation to provide the hole for hinge of moving contact.
• Reduce number of operations for manufacturing i.e. from two operations, molding followed by drilling to single operation of molding.
• By avoiding drilling operation the holes in all the poles will be maintained coaxial. As all the holes will be formed will be through the mold, so the co-axial holes can be ensured.
• Plain core cavity tool construction will be enough to manufacture this type of driveshaft.
• Total cycle time of manufacturing will get reduce significantly.
• There will be reduction in total assembly time of driveshaft with moving contact.
• Contact force, over travel & repulsion force for all poles will remain same.

WE CLAIM
1. A driveshaft mechanism for use in circuit breakers, said mechanism comprising
a moving contact means;
a drive shaft means adapted to perform rotational motion, said shaft means comprising a slot means ; plurality of pin means , said pin means comprising
a first pin means substantially positioned on the movable contact means,
a second pin means substantially accommodated inside said slot means
and
a third pin means substantially located at the cease of said shaft means; a pair of energy storing elements;
wherein said energy storing element is operatively connected between said first pin means and said third pin means adapted to achieve optimum contact force in the ON condition to keep the potential drop at the contact means to the minimum;
wherein said first pin means , second pin means and third pin means are substantially in same axis/line to define a toggling position ;
wherein said moving contact means rotates substantially beyond said toggling position due to a fault and gets locked due to a predefined net force provided by said energy storing elements .

2. Mechanism as claimed in claim 1 wherein said drive shaft means is operatively pivoted to the moving contact means by said second pin means.
3. Mechanism as claimed in claim 1 wherein said energy storing element is spring means.
4. Mechanism as claimed in claim 1, wherein said second pin means being rotatable.
5. Mechanism as claimed in claim 1, wherein said third pin means being stationary.
6. Mechanism as claimed in claim 1 wherein said driveshaft is constructed by cut bearing construction.
7. An improved driveshaft mechanism for use in circuit breakers as herein substantially described and illustrated with the accompanying drawings.