CLIAMS:1. An improved thermo magnetic release assembly for use in multi pole moulded case circuit breaker, said assembly comprising: a housing;
overload shaft means mounted on said housing;
trip actuator means;
plurality of spring means;
plurality of knob means;
trip latch mechanism;
an electromagnetic system;
an auto temperature compensation arrangement;
wherein said auto temperature compensation arrangement comprising:
auto temperature compensation bimetal means hinged on said housing so as to rotate about its axis to deflect freely with respect to ambient temperature variations;
main bimetal means;
plurality of fastener means;
wherein said auto temperature compensation bimetal being substantially horizontally located with respect to said main bimetal which is arranged so as to establish a substantially vertical relation with the said housing base providing ambient temperature compensation; and wherein said auto temperature compensation bimetal during overload condition being operatively actuated by said main bimetal means being adapted to actuate said trip actuator means ;
wherein said electromagnetic system comprising:
moving magnet means;
fixed magnet means;
magnetic slider means being located in the said housing;
wherein said moving magnet means being hinged on said fixed magnet means so as to rotate about a hinge point; wherein said moving magnet means being connected to one end of one of said plurality of spring means and said magnetic slider means being connected to the other end of the said spring means;
wherein said magnetic slider means having tapered profile adapted to adjust an air gap between said moving magnet means and said fixed magnet means and simultaneously to adjust said spring force while said magnetic slider means is driven by said knob means; and wherein said auto temperature compensation bimetalduring short circuit condition being operatively actuated by said moving magnet means being adapted to actuate said trip actuator means ;
wherein said trip latch mechanism comprising:
trip plate means;
trip plate holder meansfor;
pin means;
wherein said trip plate means being hinged on said trip plate holder means by using said pin means;
wherein said holder means and said protruded portion of the overload shaft having another spring means being operatively engaged to the said holder means and the said plate means thereby producing de-latch force on trip actuator means to trip said circuit breaker when there is a fault.
2. Assembly as claimed in claim 1, wherein said auto temperature compensation bimetal is substantially U shaped.
3. Assembly as claimed in claim 1 wherein said spring means selectively comprising torsion spring, tension spring, compression spring and the like.
4. Assembly as claimed in claim 3 wherein said torsion spring is adapted for resetting the overload shaft.
5. Assembly as claimed in claim 3 wherein said torsion spring is further adapted for resetting the trip actuator means.
6. Assembly as claimed in claim 1, wherein said knob means is adapted to be rotated upto about 180 degree.
7. Assembly as claimed in any one of the preceding claims further comprising a substantially O-shaped ring.
8. Assembly as claimed in any one of the preceding claims further comprising slide-to-trip arrangement.
9. Assembly as claimed in any one of the preceding claims being optionally snap fitted.
10.Assembly as claimed in claim 1 wherein said protruded portion of the overload shaft is essentially rectangular shaped for providing a range of settings for overload protection.
11. A latch mechanism for thermo magnetic release assembly used in moulded case circuit breaker as herein substantially described and illustrated with the accompanying drawings.
,TagSPECI:TECHNICAL FIELD OF THE INVENTION
This application relates to an improvement in or relating to main patent application No. 1079/MUM/2010 filed on March 31, 2010 and is an application for patent of addition thereto and accordingly the entire disclosure of such main patent application is hereby incorporated by reference.

The present invention relates to an improved thermo magnetic release assembly for use in Moulded Case Circuit Breaker. More particularly, the invention relates to a thermo magnetic release assembly comprising a uniquely designed latch mechanism for ameliorating the de-latching force, adjusting for settings in overload and short circuit mechanism, positive latching without opening the circuit breaker, automatic temperature compensation and eliminating the slope to provide adjustability in circuit breaker.

BACKGROUND AND THE PRIOR ART
In low voltage distribution system, circuit breakers provide rapid and reliable protection against both overload and short-circuit currents. The overload protection module consist of bimetallic element as an actuator and short-circuit protection module consist of fixed and moving core as an actuator. Signal from both these modules will be given to the mechanism for opening the contacts, thereby interrupting the circuit during abnormal condition.
Moulded case circuit breaker calls for the compliance to IEC 60947-2 standard. According to this standard, for the thermal system, MCCB should not trip while carrying a current of 1.05 times the rated current (In) for 2 hours and should definitely trip for 1.3 times the rated current (In) within 2 hours. Most of MCCBs available in the market offer overload protection with adjustability of settings. By providing settings, it enables the customer to change the rated current of the MCCB according to his requirement.
Thermo-magnetic release (TMR) uses bimetal element (1) as an actuator to provide signal during overload condition. This bimetal is connected to the Heater (2) by means of welding, brazing, riveting or screwing. When the breaker is switched ON, current flows through the heater and due to its I2R loss, heat is generated. This heat is then thermally conducted to the bimetal. Bimetal deflects with heat with its deflection directly proportional to the rise in temperature from the ambient. This deflection of bimetal is used as a means of actuation to trip the breaker by hitting a protruded portion of the overload shaft (3). As we know the deflection varies with heat, which in turn varies with current, the difference in deflection between 1.05 In and 1.3 In is usually set as the trip gap. Trip gap is the sum of the air gap between the bimetal calibration screw (5) and the trip plate and the linear distance the trip plate moves till it trips.
Calibration screw provides adjustability to change the trip gap, if needed, only by the manufacturer.
MCCBs in the current market usually have different range of settings. The highest setting always remains at 1 In while the lowest setting is what usually determines the range. Customer buys MCCB with a long term plan. So he would most probably buy a breaker capable of carrying higher current than his current requirement. For example, if there is a current requirement of 100 A MCCB he would most probably buy a MCCB with a rated current capacity higher than 100 A, say 160 A. In this case it becomes mandatory for the MCCB manufacturers to provide a range of settings to set different rated currents. This range of settings is achieved in a TMR using trip gap compensation.
US 5608367 disclosed a molded case circuit breaker with interchangeable trip unit having bimetal assembly which registers with permanent heater transformer airgap. It is an improved circuit breaker in which the thermal trip characteristic can be easily and reliably adjusted. The improved circuit breaker, in which, the thermal trip characteristic can be adjusted by changing the gap in the magnetic core of heater transformer. In which different trip units may be interchangeably inserted and withdrawn with each providing a different gap in the magnetic circuit to provide a range of current ratings for the circuit breaker.
US 3165609 disclosed temperature compensation for ambient temperature variations in the circuit breakers. It is having a tripping mechanism that 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 arrangements.
In the prior art, the air gap was kept constant and only the spring force was adjusted which leads to earlier saturation of the electromagnet and thermo magnetic release the adjustment for different settings were made by varying the spring force. The bimetal deflection is directly proportional to the current. So it becomes obvious to have higher trip gap for higher setting (1 In) and lower trip gap for lower setting, say 0.7 In. This trip gap ensures that the mandated standard requirement (1.05 In – no trip & 1.3 In – trip) is met at every setting. The trip gap compensation for different setting is usually provided by having a ‘slope’ either on the bimetal or on the protruded portion of the overload shaft. When the user adjusts the setting outside, internally, the trip gap increases or decreases by the movement of the slope.
Since there is a slope on the protruded portion of the overload shaft, the calibration hitting point needs to be precise as desired. Any change in the hitting point due to tilting of bimetal, component tolerance, assembly tolerance would mean the screw hits the slope at an unintended point, which means undesired trip gap for that setting. Overcoming this problem calls for extensive GD&Ts and lower tolerance which increases time and cost of production. And this also is one of the major reasons for the high number of calibration iterations required to meet standards norms. Again with increase in iterations, time and money is lost. The overload shaft is usually hinged at its centre and it is intended to rotate as the calibration screw hits it. When the calibration screw hits the slope, some component of the force transmission from bimetal to overload shaft is lost, proportional to the degree of slope.
Thus, there is a need to provide an improved thermo magnetic release assembly for use in Moulded Case Circuit Breaker which would overcome the problems prevailing in the prior art. Particularly, there is a need of such Thermo-magnetic release assembly which prevents circuit breaker from overload or short circuit.
The present inventors have found that a latch mechanism designed in a unique manner when introduced in a Thermo-magnetic release assembly providing range of settings for overload protection without the need for using slope either on the bimetal or on the overload shaft. Since the usage of the slope is removed all the above stated drawbacks are either eliminated or mitigated.

OBJECTS OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another object of the present invention is to provide an improved thermo magnetic release assembly for use in Moulded Case Circuit Breaker.

Another object of the present invention is to provide a mechanism for adjustable overload settings.

Another object of the present invention is to provide a mechanism for adjustable short circuit settings.

Another object of the present invention is to provide a trip latch mechanism for thermo-magnetic release assembly.

Another object of the present invention is to provide a mechanism for eliminating the slope requirement in the protruded portion of the overload shaft, therefore providing a range of setting for overload protection.

Further object of the present invention is to provide an auto temperature compensation arrangement.

Further object of the present invention is to provide slide to trip arrangement.

Yet, another object of the present invention is to provide a trip position indication.

These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

According to an aspect of the present invention there is provided an improved thermo magnetic release assembly for use in multi pole moulded case circuit breaker, said assembly comprising: a housing;
overload shaft means mounted on said housing;
trip actuator means;
plurality of spring means;
plurality of knob means;
trip latch mechanism;
an electromagnetic system;
an auto temperature compensation arrangement;
wherein said auto temperature compensation arrangement comprising:
auto temperature compensation bimetal means hinged on said housing so as to rotate about its axis to deflect freely with respect to ambient temperature variations;
main bimetal means;
plurality of fastener means;
wherein said auto temperature compensation bimetal being substantially horizontally located with respect to said main bimetal which is arranged so as to establish a substantially vertical relation with the said housing base providing ambient temperature compensation; and wherein said auto temperature compensation bimetal during overload condition being operatively actuated by said main bimetal means being adapted to actuate said trip actuator means ;
wherein said electromagnetic system comprising:
moving magnet means;
fixed magnet means;
magnetic slider means being located in the said housing;
wherein said moving magnet means being hinged on said fixed magnet means so as to rotate about a hinge point; wherein said moving magnet means being connected to one end of one of said plurality of spring means and said magnetic slider means being connected to the other end of the said spring means;
wherein said magnetic slider means having tapered profile adapted to adjust an air gap between said moving magnet means and said fixed magnet means and simultaneously to adjust said spring force while said magnetic slider means is driven by said knob means; and wherein said auto temperature compensation bimetal during short circuit condition being operatively actuated by said moving magnet means being adapted to actuate said trip actuator means ;
wherein said trip latch mechanism comprising:
trip plate means;
trip plate holder means;
pin means;
wherein said trip plate means being hinged on said trip plate holder means by using said pin means;
wherein said trip plate means is essentially rectangular shaped for providing a range of settings for overload protection;
wherein said trip plate holder means and said trip plate means having another spring means being operatively engaged to the said holder means and the said plate means thereby producing de-latch force on trip actuator means to trip said circuit breaker when there is a fault.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.
Fig 1 illustrates a rear view of entire release assembly having all components.
Fig 2 illustrates a left side cross sectional view of release latch mechanism at latched position clearly indicated inside the circle.
Fig 3 illustrates a left side cross sectional view of release latch mechanism at de-latched position clearly indicated inside the circle
Fig 4 illustrates a right side cross sectional view of torsion spring arrangement provided for reset overload shaft and trip actuator is at reset position
Fig 5 illustrates a left side cross sectional view of an assembly of electromagnet in open position and the tension spring that holds the moving core
Fig 6 illustrates a left side cross sectional view of an assembly of electromagnet in closed position which actuates the overload shaft to de-latch the release mechanism indicated inside the circle
Fig 7 illustrates a top cross sectional view of an assembly of electromagnet at maximum air gap position indicated inside the circle (i.e. at maximum SC setting)
Fig 8 illustrates a top cross sectional view of an assembly of electromagnet at minimum air gap position indicated inside the circle (i.e. at minimum SC setting)
Fig 9 illustrates a rear view of an assembly of electromagnet at minimum air gap and minimum spring force position indicated inside the circle (i.e. at minimum SC setting)
Fig 10 illustrates a rear view of an assembly of electromagnet at maximum air gap and maximum spring force position indicated inside the circle (i.e. at maximum SC setting)
Fig 11 illustrates a top cross sectional view of an assembly of electromagnet at trip position indicated inside the circle.
Fig 12 illustrates a top side cross sectional view of an assembly of bimetal at normal position indicated inside the circle.
Fig 13 illustrates a left side cross sectional view of an assembly of short circuit setting knob with O-ring in the housing with lock mechanism to arrest its motion in y axis after assembly of magnetic slider.
Fig 14 illustrates a bottom cross sectional view of lock arrangement in knob to arrest z axis motion
Figures 15 and 16 illustrate an isometric view of entire release module assembly with trip indication
Fig 17 illustrates an isometric view of entire release module assembly in general view
Fig 18 illustrates the pervious application number 1079/mum/2010 which providing variations between overload settings.
Fig 19 illustrates the side view of an embodiment of pervious application number 1079/mum/2010,
Fig 20 illustrates the hinge position of ATC bimetal (15) on the housing (1) in the present application.
Fig 21 illustrates the front view of Moulded Case Circuit Breakers
Fig 22 illustrates the position of components when the user sets the adjuster (23) at the lowest setting according to the present invention.
Fig 23 illustrates the tilting in the ATC bimetal during the tripping.
Fig 24 illustrates protruded portion of the overload shaft having rectangular shape.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
The present invention shows improvement or modification over the originally filed patent application no. 1079/mum/2010 by providing a range of settings for overload protection without the need for using slope either on the bimetal or on the protruded portion of the overload shaft. The present invention provides a improved overload shaft eliminating the requirement of slope in the protruded portion of the overload shaft for overload protection.
According to the invention there is provided a thermo magnetic release assembly used in moulded case circuit breaker. The entire assembly described in the present embodiment is designed for 3 pole operation. However, this should not be considered as any limitation of the present invention as the present design construction of the assembly can also be extended for multi-pole operation. This assembly consists of heater (2) (current carrying part), set of electromagnets (core and plate), torsion spring (7) all in three sets. This assembly also consists of a pair of adjustment knobs, an electromagnet adjustment component, a bimetal adjustment component, auto temperature compensation bimetal (15) and separate trip latch mechanism which gives the output from the release. The present invention eliminates the usage of slope in protruded portion of the overload shaft or bimetal () to provide adjustability of settings to overload protection.
According to one embodiment of the invention, the trip latch mechanism consist of trip plate (10) hinged on trip plate holder (11) by a pin (18) and the compression spring (8) provided between trip plate holder (11) and (10) give de-latch force to trip main MCCB's mechanism using its stored energy. The clockwise torque produced by compression spring (8) on trip plate(10) hinged on trip plate holder (11) through pin (18) and anti clockwise torque produced by torsion spring (7) on trip actuator (9) hinge on housing (1) create a latch point (19) when two of them exactly at perpendicular to each other shown in figure 2. At latched position both the component dose not experience any torque mutually with respect to each other. While de-latching due to fault the trip actuator (9) experience minimum torque produced by trip plate (10) due to compression spring (8). In other it produces minimum opposing torque on overload and short circuit actuators. The de-latching force produced by either magnet due to short circuit or bimetal due to overload through auto temperature compensation bimetal (15) as shown in figure 3. The torsion spring (7) provided for reset the overload shaft (12) and trip actuator (9) after fault has been cleared is mounted on housing (1) through pin and its first arm reset the trip actuator (9) and the second arm reset overload shaft (12) shown in figure 4. Slide to trip arrangement provide in the trip actuator (9) can does the function of tripping and trip position indication in the release.
According to another embodiment of the invention, auto temperature compensation bimetal (15) is hinged on housing (1) as shown in figure 1 consists of two calibration screws (25). Mounting of auto temperature compensation bimetal (15) on the housing (1) can make it perfect to rotate with respect to it axis. Arrangement this bimetal here is such a way it doesn't experience any force under normal operation. The need of stress less ambient compensation bimetal is to deflect freely with respect to ambient temperature variations. Rotation of auto temperature compensation bimetal with respect to hinge point (26) is shown in figure 1. Ambient temperature variation can be solved by auto temperature compensation U shape bimetal in horizontal position. The horizontal arrangement of this component can ensure the constant offset distance between main bimetal (16) and overload shaft (12) even when the ambient temperature changes. The advantage of this compensation is no need to de-rate or upgrade the breaker due to ambient temperature variation. Auto temperature compensation bimetal (15) arrangement also provides better mechanical advantage to fault actuators due longer length shown in figure 1. Overload shaft (12) mounted in the housing (1) can act as an interface between fault actuator (i.e. magnet and bimetal).
As shown in figure 20 the auto temperature compensation bimetal (15) is hinged on the Housing (1) and is placed in such a way that it acts as the bridge between the overload shaft and the Latch (27). Adjuster (23) is used as an interface between the user and internal components. Adjuster is connected with the overload shaft. When the user selects a particular setting by turning the adjuster, the overload shaft moves in X axis. As the overload shaft moves, it hits different points of the ATC bimetal at different settings. For the highest setting (1 In) the trip plate hits at a point of the ATC bimetal say at ‘x’ distance from its hinge whereas in the lowest setting, the trip plate hits at a point say at ‘y’ distance (y < x) from the hinge. In the present invention slope is removed by using a rectangular-shaped protruded portion of the overload shaft
From the basic principles of Physics, we know that the hitting point when it goes away from the hinge point requires lesser force than the hitting point closer to the hinge, to move the same mass. But the displacement required to move a mass to the same distance, will be higher for the hitting point which is away from the hinge than to the point closer to the hinge. Based on these principles we are able to vary the force and displacement required for all the settings in the range.
According to a further embodiment of the invention, the electromagnetic system consists of a core and a movable part. Horizontally mounted electromagnet with its actuation in vertical direction provides more space for wound coil (3) on fixed core (4) for low current MCCBs. The movable part is hinged as shown in the figure 2 and figure 5 so it can be rotated about hinged point. The arrangement of the spring is such that it always opposes the electromagnetic force and holds the electromagnetic part (movable part) in its open position as shown in figure 5. The hinge point of tension spring (6) that holds moving magnet (5), its one end is fixed to magnetic slider (17) and another end at moving magnet (5) shown in figure 5. Magnetic slider (17) placed on housing (1) with tapered profile helps to adjust spring force while it was driven by knob shown in figure 9 and figure 10. Air gap (20) between moving magnet core (5) and fixed magnet core (4) can also be adjusted by the same magnetic slider (17) as shown in figure 7 and figure 8. Both air gap (20) and spring force adjusted by short circuit setting knob shown in figure 1. Actuating mechanism of moving magnet (5) on overload shaft (12) is shown in figure 6. Electromagnet is instantaneous tripping device.
Short trip is achieved by first the magnet actuate the overload shaft (12) (i.e. in figure 6) which in turn actuate the auto temperature compensation bimetal (15) (i.e. in figure 6) future it actuate trip actuator (9) (i.e. in figure 3) to de-latch the mechanism. Overload tripping is delayed here because the bimetal deflect leads to actuation only after the temperature rise across it which is usually not an instantaneous process .overload trip is achieved by first the bimetal actuate the overload shaft (12) which in turn actuate the auto temperature compensation bimetal (15) which again actuates trip actuator (9) that trips the mechanism.
The adjusting knobs namely overload setting knob (13) and short circuit setting knob (14) provided in the housing (1) for overload setting and short circuit setting respectively . Individual knobs degree of ration is restricted to less than 180 degree after the assembly of overload shaft (12) and magnetic slider. O-ring (21) provided in the knob provides enough friction to hold the knob in corresponding setting position shown in figure 13. The lock is provided in such a way that with slot (22) provided in housing (1) and the degree of rotation constrained by overload shaft (12) assembly shown in figure 10 and figure 14. The purpose of the lock is to hold the knob in the hinged position i.e. the knob can rotate with respect to y axis but will not translate in y axis until unless overload shaft (12) and magnetic slider (17) has been removed from the assembly. Snap fit is provided in the release housing assembly for reducing screws in the assembly
In figure18 one of the methods of providing variations between overload settings as disclosed in pervious application. The Thermo-magnetic release is set at its highest Overload setting. Here we can see how the trip gap (24) is adjusted using a slope in the protruded portion of the overload shaft (10), when the customer selects a particular setting using the adjuster (23)
Figure 19 shows the side view of an embodiment of this invention which depicts how the bimetal (30) is connected to the heater (2) by welding and also how the calibration screw (25) is placed on a bimetal (30)
Figure 20 shows the hinge position of ATC bimetal (15) on the housing (1), the hitting point of the overload shaft (10) on the ATC bimetal (15) and the hitting point of ATC bimetal (15) on latch (27) in the present invention
Figure 21 shows the front view of an embodiment of this invention which depicts the position of components when the user sets the adjuster (23) at the highest setting.
Figure 22 shows the front view of an embodiment of this invention which depicts the position of components when the user sets the adjuster (23) at the lowest setting. If we compare figure 21 & 22, we can clearly see the difference in the hitting point of the overload shaft on the ATC bimetal with reference to the hinge point of ATC bimetal
Figure 23 shows an embodiment of this invention when the overload shaft rotates the ATC bimetal during the process of tripping
Figure 24 shows an embodiment of this invention where the usage of slope provided for trip gap (4) compensation has been completely eliminated
ADVANCEMENT OF THE PRESENT INVENTION OVER THE PERIVOUSLY FILED APPLICATION ARE LISTED BELOW:
· It reducesthe usage of CTQ (Critical To Quality dimensions), GD&Ts and hence time and money.
· Since one of the reasons for repeated iterations to calibrate thermal system is removed, there is a possibility in the reduction of average number of calibration iterations required.
· Since there is no slope, 100% of the bimetal force is transmitted to the system without any loss component.
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 trip actuator, bimetal, knobs, trip plate, trip plate holder, pins, springs, and magnetic core as stated, do not limit the scope of the present invention. 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.