F0RM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - AN IMPROVED MECHANISM FOR TEMPERATURE
COMPENSATION BY THE USER IN THERMO MAGNETIC RELEASE ASSEMBLY IN MULTI-POLE MOLDED CASE CIRCUIT BREAKERS
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 an improved mechanism for temperature compensation by the user in thermo magnetic release assembly which is an integral part of the Molded Case Circuit Breaker. More particularly, the invention is concerned about temperature compensation by the user during short circuit and/or overload condition in the thermo magnetic release.
BACKGROUND OF THE INVENTION
US 3165609 discloses temperature compensated circuit breakers. It particularly relates to compensation for ambient temperature variations in circuit breakers incorporating both bimetal and electromagnetic tripping. The tripping mechanism is compensated for ambient temperature variations while at the same time preserving a constant magnetic air gap in a tripping mechanism having both magnetic and thermal tripping mechanism.
US 3,659,241 discloses a circuit breaker comprises a current responsive tripping bimetal and a pair of compensating bimetals in latching engagement with each other to compensate for movement of the current responsive tripping bimetal in response to changes in ambient temperature. The circuit breaker is a multi-pole circuit breaker with a current responsive tripping bimetal in each pole and one pair of compensating bimetals in only one of the poles.
US 5444423 discloses a latch mechanism for a circuit breaker comprises a pair of longitudinal legs, a lateral section bridging the pair of longitudinal legs, and a longitudinal section extending from the lateral section in an opposite direction relative to the pair of legs. The lateral section includes a lower bearing surface for releasably engaging a cradle of the circuit breaker. The lower bearing surface includes a coined radius for facilitating engagement and disengagement of the cradle. The longitudinal section includes a protrusion for supporting a latch spring. The latch mechanism is

manufactured in a single stamping operation, during which the protrusion is formed by cold extrusion
Latching arrangement shown in documents US 3,659,241 and US 5444423 need more de-latching force. It was not known from the prior art that the temperature compensation can also be adjusted by the user which will give the user more flexibility in selecting temperatures of circuit breaker for different applications.
Thus, there is a need to provide a mechanism for compensating temperatures by user in thermo magnetic release assembly which is an integral part of the Molded Case Circuit Breaker (MCCB).
The present inventors have found that the user can be provided with more flexibility in selecting temperatures during the operation of a molded case circuit breaker by way of an unique gear mesh arrangement which would enable the user to set the working temperature of circuit breakers such that it can be used in different environmental conditions where temperature may not be same.
OBJECTS OF THE INVENTION
An object of the present invention is to overcome the problems/disadvantages of the prior art.
Another object of the present invention is to provide an improved mechanism for temperature compensation by the user in thermo magnetic release assembly.
Another object of the present invention is to provide a mechanism to increase the short-circuit adjustment range.

Yet, another object of the present invention is to provide a mechanism to adjust overload settings.
SUMMARY OF THE INVENTION
According to one aspect of the present invention there is provided an improved
mechanism for temperature compensation by the user in thermo magnetic release
assembly used in multi-pole molded case circuit breaker during short circuit and / or
overload conditions, said assembly comprising:
a housing;
plurality of knob means;
plurality of slider means;
actuator arrangement;
shaft means;
plurality of bimetal means;
an electromagnetic system;
wherein said actuator arrangement comprising gear mesh system comprising gear I,
gear II, gear III and gear IV wherein said gear II and gear III being concentric to each
other are operatively mounted on a holder means such that angle of rotation of gear
II and gear III is equal;
wherein said gear I and gear IV being concentric to each other are operatively
mounted on another holder means in a manner such that said gear I engages with
knob means adapted for overload adjustment ;
wherein said gear I being adapted to rotate said shaft means such that gap between main slope and one of said bimetal means changes to adjust overload setting of said circuit breaker;
wherein said gear II and gear III being operatively engaged with one of said knob means such that rotation of said knob means correspondingly rotates said shaft means keeping said overload adjustment setting and displaying and varying a

displacement of one of said slider means between main slope and said bimetal means to change the working temperatures of said circuit breaker;
said electromagnetic system comprising plural sets of spring means comprising two spring in a set wherein one spring means in a set having spring force less than the other spring means of the set and arranged adjacent to each other such that spring means with less spring force acts for lower short-circuit fault and wherein during higher short circuit fault both spring means in a set worked in combination so that the effective spring force becomes sum of two spring forces.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig 1 illustrates overall view of thermo-magnetic release with casing
Fig 2 illustrates temperature compensation mechanism
Fig 3 illustrates integrated view of gear system and trip shaft/main shaft.
Fig 3A illustrates integrated view of shaft2 and main bimetals.
Fig 4 illustrates gear system for temperature compensation
Fig 5 illustrates improved electromagnetic system representing spring 2 is in deactivation stage
Fig 6 illustrates improved electromagnetic system representing spring 1 and 2 are in activation stage
Fig ? illustrates side view of thermo-magnetic release

DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS
According to the invention there is provided atemperature compensation mechanism in thermo magnetic release assembly which is an integral part of a multi-poleMolded Case Circuit Breaker.
The entire assembly is designed for multi-pole operation. This assembly consists of heater (3) (current carrying part), set of electromagnets (core (11) and moving magnet (10)), two torsion springs (12a & 12b) all in three sets. This assembly also consists of a pair of adjustment knobs (4a,4b & 4c), a short circuit adjustment slider (5a) and an overload adjustment slider (5b) which along with the main shaft provides the trip signal for the main mechanism. Adjustment knobs, a short circuit adjustment slider and an overload adjustment slider are shown in figure 2.
According to one embodiment of the invention, the temperature compensation is achieved by special gear meshing arrangement which is shown in figure 4 consisting of an actuator arrangement having four gears. Gear I (7a) and gear IV (7d) is concentric and similarly gears II (7b) and gear III (7c) are concentric. Gear II (7b) and gear III (7c) are mounted on a single holder such that angle of rotation of gear two and three are always equal. Gear I (7a) is combined with overload adjustment knob (4b) and is used for overload adjustment. Gear II and gear III are used for temperature compensation adjustment. Combination of gear ll (7b) and gear III (7c) forms temperature compensation gear. This temperature compensation gear is interconnected with the gear I (7a) and gear IV (7d) which are attached to the overload adjustment knob (4b). Gear IV (7d) is used for synchronous rotation of overload knob (4b) and overload rating display during temperature compensation adjustment i.e. the overload ratings are marked on gear IV (7d).
When gear I (7a) is rotated main shaft two (6b) rotates changing the gap between main slope (9) and the bimetal (8) as shown in figure 3A. Varying the gap between bimetal (8) and main slope (9) adjusts the overload setting of the breaker. In this

invention the gear mechanism used for temperature compensation is such when the temperature compensation knob (4c) is rotated the main shaft two (6b) rotates keeping the overload adjustment and the display in synchronous and varying the displacement between the main slope and bimetals which inturn changes the working temperature of the MCCB. Depending on the rotation of the temperature compensation gear the relative gap between the main slope (9) and the bimetal (8) varies keeping the MCCB working independent of the environment temperature. Integrated view of gear system and trip shaft/main shaft is as shown in figure 3. Indications of temperature compensation and overload settings are provided on the top cover (2) to easy of user interface as shown in figure 1.
In this invention electromagnetic system consists of two springs (12a & 12b) for each pole as shown in figure 5. The arrangement of torsion springs are such that only the spring with less force acts at lower rating and the second spring comes into picture at the higher rating as shown in figure 6. At higher ratings the two springs are working and the effective spring force becomes the sum of two spring forces. This methodology(i.e. the method of using combination of spring to get required force at different stages) solves the requirement of low spring for lower short-circuit fault and high spring force required for at the higher short-circuit fault considering the hold force requirement.
The arrangement of electromagnet is such that when a short-circuit fault occurs the electromagnet gets attracted and in this process the main shaft one (6a) rotates rotating the inter connected shaft two (6b) which inturn resets the main mechanism. The entire release assembly with housing (1) is represented in figure 1 and side view of thermo magnetic release assembly is represented in figure 7.
The invention has been described in a preferred form only and many variations may be made in the invention which will still be comprised within its spirit. The invention is not limited to the details cited above. . The bimetal, knobs, trip plate, gear system, pins, springs, shaft and magnetic core as stated do not limit the scope of the present

invention. For example, mechanical system such as gear system can be replaced by other mechanical systems such pneumatic arrangements, hydraulic arrangements and the like for the movement of the slider means. Non-mechanical system such as electro-magnetic solenoid can also be used for the movement of the slider. 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.
housing--1
cover -—2
heater —3
shor circuit setting knob —4a
overload setting knob 4b
temperature compensation setting knob —4c a short circuit adjustment slider —5a
an overload adjustment slider (trip plate) 5b
shaft 2 —6b shaft 1 —6a gear system -7 gear I-7a gear II-7b gear III—7c gear IV—7d main bimetal —8 main slope —9 moving magnet 10 fixed magnet 11 (core) spring 1 (low spring) 12a spring 2 (high load spring) 12b

WE CLAIM
1. An improved mechanism for temperature compensation by the user in thermo magnetic release assembly used in multi-pole molded case circuit breaker during short circuit and / or overload conditions, said assembly comprising: a housing;
plurality of knob means; plurality of slider means; actuator arrangement; shaft means;
plurality of bimetal means; an electromagnetic system;
wherein said actuator arrangement comprising gear mesh system comprising gear I, gear II, gear III and gear IV wherein said gear II and gear III being concentric to each other are operatively mounted on a holder means such that angle of rotation of gear II and gear III is equal;
wherein said gear I and gear IV being concentric to each other are operatively mounted on another holder means in a manner such that said gear I engages with knob means adapted for overload adjustment ;
wherein said gear I being adapted to rotate said shaft means such that gap between main slope and one of said bimetal means changes to adjust overload setting of said circuit breaker;
wherein said gear II and gear III being operatively engaged with one of said knob means such that rotation of said knob means correspondingly rotates said shaft means keeping said overload adjustment setting and displaying and varying a displacement of one of said slider means between main slope and said bimetal means to change the working temperatures of said circuit breaker;
said electromagnetic system comprising plural sets of spring means comprising two spring in a set wherein one spring means in a set having

spring force less than the other spring means of the set and arranged adjacent to each other such that spring means with less spring force acts for lower short-circuit fault and wherein during higher short circuit fault both spring means in a set worked in combination so that the effective spring force becomes sum of two spring forces.
2. Assembly as claimed in claim 1, wherein said spring means being selected from torsion springs, compression springs, tension springs and the like.
3. Assembly as claimed in claim 1 further comprising a cover adapted to indicate said overload setting and temperature compensation.
4. Assembly as claimed in claim 1, wherein said plurality of bimetals being arranged parallel to each other.
5. Assembly as claimed in claim 1, wherein said knob means comprising short circuit setting knob.
6. Assembly as claimed in claim 1, wherein said knob means further comprising over load setting knob.
7. Assembly as claimed in claim 1, wherein said knob means further comprising temperature compensation setting knob.
8. Assembly as claimed in any of the preceding claims further comprising overload display means.
9. Assembly as claimed in claim 8 wherein said overload display means is adapted to be rotated synchronously with said overload setting knob.
10. Assembly as claimed in claim 1 wherein said actuator arrangement optionally comprising pneumatic arrangements and/or hydraulic arrangements and/or electro-magnetic solenoid arrangements and the like.
11. An improved mechanism for temperature compensation by the user in thermo magnetic release assembly used in multi-pole molded case circuit breaker

during short circuit and / or overload conditions as herein substantially described and illustrated with the accompanying drawings.