FORM 2 COMPLETE AFTER PROVISIONAL
LEFT ON
20 NOV 2006
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - TRIPPING MECHANISM FOR CIRCUIT BREAKERS
2. Applicant
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : 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 INVENTION
The present invention relates to a tripping mechanism for circuit breakers. More particularly, the invention relates to a tripping mechanism adapted to ensure no change in tripping force during thermal setting change of circuit breakers.
BACKGROUND AND PRIOR ART
Generally, function of circuit breaker is to make, carry and break the current. At normal operating conditions when the circuit breaker is carrying current, the operating knob or handle of mechanism indicates ON position. At abnormal condition due to overload or under-voltage circuit breaker gets tripped because of the tripping signal from protective release or remotely tripping through the shunt release or through under-voltage release, operating handle indicates TRIP position. During the abnormal condition due to occurrence of any high voltage or current surge the operating temperature of the circuit breaker rises.
WO2005/008705 describes a trip assembly for use in an electromechanical device, such as a circuit breaker. The trip assembly is used for interrupting the flow of current upon the detection of excess current in a circuit breaker and comprises a trip bar, a stationary armature bracket, a movable armature, and a spring. The movable armature includes a first end coupled to a base portion of the armature bracket, and a trip-actuating surface being disposed proximate a trip finger of the trip bar. The spring is directly coupled at its respective ends to a spring-support portion of the armature bracket and to a spring tab of the movable armature.
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WO03/094188 describes an adjustable magnetic trip unit for a circuit breaker including a torsion spring which applies a bias force to the plunger of a trip solenoid. The torsion spring, is mounted on a" driven bevel gear and wound by an adjustment knob coupled to a driving bevel gear to adjust the current at which the solenoid is activated. An indexer having peripheral flates, which engage a seat in the circuit breaker housing, provides a plurality of discrete positions of the adjustment knob. Depressing the adjustment knob against a second spring unseats the indexer for rotation of the adjustment knob between settings. In addition, a slide with an inclined surface bearing against the plunger and coupled to the driven bevel gear, provides simultaneous adjustment of plunger gap with adjustment of the torsion spring force to increase the range of adjustment.
US6459059 describes a return spring mechanism which is arranged to operate with a circuit breaker operating mechanism during a trip condition. The circuit breaker operating mechanism is movable between a tripped position, a reset position, an off position and an on position. The return spring mechanism is attached to the exterior of the circuit breaker frame. When the circuit breaker is tripped, the return spring mechanism operates to provide an additional force to the handle yoke. The additional force applied by the return spring is predetermined to position the handle yoke intermediate to the handle yoke positions when the circuit breaker is off and on. Thus, the movement of the handle yoke to the intermediate position provides clear indication that the circuit breaker is in the tripped condition.
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None of the aforementioned prior arts are described with a mechanism for no change or for maintaining consistency in tripping force during thermal setting change of circuit breakers.
The present inventors have found that no change or consistency in tripping force during thermal setting change of circuit breakers can be achieved by a biasing element profiled/designed and operatively connected to a mechanism component desirably and suitably.
OBJECTS OF INVENTION
Thus one object of the present invention is to provide a tripping mechanism so as to achieve no change/ consistency in biasing force when the trip plate is moved during thermal setting.
Another object of the present invention is to provide proper functioning of thermal release and accessories after the calibration of the breaker.
SUMMARY OF INVENTION
Thus according to one aspect of the present invention there is provided a tripping mechanism operatively connected to an operating mechanism of any conventional type, said tripping mechanism comprising :
biasing means being profiled at middle portion in a predetermined manner;
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plate means accommodating the said biasing means partially or wholly,
wherein said plate means comprising plurality of guiding means so as to guide the said biasing means such that movement of the plate means co-operatively moves the guiding means on predetermined location of the said biasing means so as to keep forces coming from ends of biasing means remain unchanged and/or consistent during thermal setting change.
According to another aspect of the present invention there is provided a tripping mechanism operatively connected to an operating mechanism of any conventional type, said tripping mechanism comprising :
biasing means being profiled at middle portion in a predetermined manner;
plate means accommodating the said biasing means partially or wholly,
wherein said plate means comprising plurality of guiding means so as to guide the said biasing means such that movement of the plate means co-operatively moves the guiding means on predetermined location of the said biasing means
and wherein plate means rests on. latch bracket means of operating mechanism such that force coming from the biasing means generates force against latch means thereby restricting rotation of latch means when breaker is switched ON or OFF
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so as to keep forces coming from ends of biasing means remain unchanged and/or consistent during thermal setting change.
DETAILED DESCRIPTION OF INVENTION
The tripping mechanism of the present invention is operatively connected with the operating mechanism of the circuit breaker and it comprises biasing means and plate means adapted for tripping wherein the biasing means are fixed to the exterior of the operating mechanism. Operating mechanism of circuit breaker is movable between On, Off, Reset and Tripped positions. The said components of the tripping mechanism rest on the operating mechanism during On, Off and Reset positions but in case of tripping operation disengage with the operating mechanism.
The biasing means comprises a double extension spring both ends of which are fixed on the exterior of operating mechanism side plates. The middle portion of the spring is a flat profile, suitably designed in a predetermined manner and which is also guided in the guiding slot of the trip plate. The trip plate accommodates the middle portion of the spring partially or wholly. During thermal setting change, the trip plate moves with respect to the operating mechanism and tripping mechanism ensures that the force coming from the spring does not change during this movement. The suitable flat profile at the middle portion of the spring in co-operation with the movement of the guiding slot provides uniformity/consistency in the force coming from the spring independent of the plate position. This constant force is required for proper functioning of thermal release and accessories after the calibration of the breaker.
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BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates a side elevation view of tripping mechanism of the present invention in ON position.
Figure 2 illustrates a side . elevation view of tripping mechanism of the present invention in TRIP position.
Figures 3a and 3b illustrate the two extreme positions of the trip plate of the tripping mechanism of the present invention during thermal setting change.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
Circuit breaker with said tripping mechanism (10) is shown in fig. 1 to 3. Circuit breaker comprises of fixed contact (1) which is rigidly mounted in housing (2), moving contact (3) pivoted in operating shaft (4) which is operated by operating mechanism (6) and thermal and magnetic releases, to avoid the overload and fault currents.. Tripping mechanism (10) is arranged with the operating mechanism (6) of the circuit breaker. Operating mechanism (6) of circuit breaker is movable between On, Off, Reset and Tripped positions. Tripping mechanism (10) rests on the latch bracket (13) of operating mechanism (6) during On, Off and Reset positions but in case of tripping it disengages with the operating mechanism (6). Tripping mechanism (10) consists of double extension spring (7) and the trip plate (8). The double extension spring (7) is fixed on the exterior of operating mechanism side plates (9).
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The middle portion of the biasing spring is a flat portion (11), which is guided in the guiding slot (12) of the trip plate (8). Tripping mechanism (10) ensures that whenever there is a thermal or magnetic overloading or tripping command is given through accessories, it trips the breaker and breaker contacts (1) and (3) open.
For proper tripping function of the breaker, it is required that the force coming from the spring (7) should not change when the trip plate (8) moves during thermal setting change of the breaker. To ensure this, the guiding slots (12) are provided in the trip plate (8), which move over the flat portion (11) of spring (7) during the movement of the trip plate (8) . Hence forces coming from both ends of the double extension spring (7) remain unchanged, thus ensures that the force required to trip the breaker remains unchanged during thermal setting change.
Fig.l shows the ON position of circuit breaker. This condition of circuit breaker is achieved when mechanical energy from operating mechanism (6) is transferred to operating shaft (4). Moving contact (3) being coherent to operating shaft (4) rotates with the operating shaft (4) and touches the fixed contact (1). In this condition the trip plate (8) rests on the latch bracket (13) of the operating mechanism (6). Force coming from the biasing spring (7) generates the force against the latch bracket (13) and hence restricts the rotation of latch bracket (13), which holds the latch (14) when breaker is switched ON, or OFF.
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Fig.2 shows the TRIPPED condition of the circuit breaker. This condition of circuit breaker is> achieved when the tripping command is given to the breaker. In this case the trip plate (13) rotates with respect to the operating mechanism (6) and force coming from the biasing spring (7) to the latch (14) diminishes, hence the latch bracket (13) rotates and releases the latch (14), to bring the breaker to tripped condition.
Fig. 3 shows the two extreme positions of the trip plate (8) during thermal setting change. These two conditions of circuit breaker are achieved when during thermal setting change the trip plate (8) moves with respect to operating mechanism (6). In this condition, the guiding slot (12) provided in the trip plate (8) is sliding over the flat portion (11) of the biasing spring (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 components as herein used can be replaced by its technical equivalence and yet the invention can be performed. 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.
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WE CLAIM
1. A tripping mechanism operatively connected to an
operating mechanism of any conventional type, said
tripping mechanism comprising :
biasing means being profiled at middle portion in a predetermined manner;
plate means accommodating the said biasing means partially or wholly,
wherein said plate means comprising plurality of guiding means so as to guide said biasing means such that movement of the plate means co-operatively moves the guiding means on predetermined location of said biasing means
so as to keep forces coming from ends of biasing means remain unchanged and/or consistent during thermal setting change.
2. Mechanism as claimed in claim 1, wherein the biasing means comprises double extension spring.
3. Mechanism as claimed in claims 1 and 2, wherein the double extension spring is flat profiled suitably at the middle portion.
4. Mechanism as claimed in claim 1, wherein the plate means comprises trip plate.
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5. Mechanism as claimed in claim 1, wherein the guiding means comprises suitable slots being profiled in a manner to accommodate the middle portion of the double extension spring.
6. A tripping mechanism operatively connected to an operating mechanism of any conventional type, said tripping mechanism comprising :
biasing means being profiled at middle portion in a predetermined manner;
plate means accommodating said biasing means partially or wholly,
wherein said plate means comprising plurality of guiding means so as to guide said biasing means such that movement of the plate means co-operatively moves the guiding means on predetermined location of said biasing means
and wherein plate means rests on latch bracket means of operating mechanism such that force coming from the biasing means generates force against latch means thereby restricting rotation of latch means when breaker is switched ON or OFF
so as to keep forces coming from ends of biasing means remain unchanged and/or consistent during thermal setting change.


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7. A tripping mechanism as herein substantially described and illustrated with reference to the accompanying figures.
Dated this 20th day of November 2006,

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20 NOV 2006

ABSTRACT
TITLE : TRIPPING MECHANISM FOR CIRCUIT BREAKERS
The present invention relates to a tripping mechanism. The tripping is operatively connected to an operating mechanism of any conventional type. The tripping mechanism (10) comprises biasing means (7) being profiled at middle portion in a predetermined manner, plate means (8) accommodating biasing means (7) partially or wholly. Plate means (8) rests on latch bracket means (13) of operating mechanism (6) such that force coming from the biasing means (7) generates force against latch means (14) thereby restricting rotation of latch means (14) when breaker is switched ON or OFF. The plate means (8) comprises plurality of guiding means (12) so as to guide the biasing means (7) such that movement of the plate means (8) co-operatively moves the guiding means (12) on predetermined location of the biasing means (7) so as to keep forces coming from ends of biasing means remain unchanged and/or consistent during thermal setting change.
Figure 1
'2 0 NOV 2006