FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
1. Title of the invention. - NEW BRAKING MECHANISM FOR
STORED ENERGY MOTOR OPERATORS
2. Applicant
(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY: Indian
(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 braking mechanism in moulded case circuit breakers. More particularly, the invention relates to a braking mechanism adapted to stop rotation of the shaft thus bringing them to a complete stop position at a desired angular position thereby avoiding false triggering of motor operators of moulded case circuit breakers .
BACKGROUND AND PRIOR ART
According to available information, braking mechanisms are not used in motor operators for controlling the angular position of the crank. Other mechanism like push-pull slider mechanism is used to control the position of the crank. However push-pull slider mechanism is not effective for higher spring forces and higher inertia of rotating components. Energy to be absorbed increases with increasing spring forces. Braking mechanism can absorb significant amount of energy. The energy absorbed depends on the no. of buffers, area of contact and normal force between crank disc and buffers.
JP2004281175 describes a gas blowing type circuit breaker in which extinction of arc generated between a movable supply-current electrode and a counter electrode is carried out by blowing the gas, further the movable supply-current electrode is coupled with a driving device by an operating rod, and a pressure chamber with an insulation nozzle installed at the operating rod. The grooved cam has a rotating body wherein an elastic body is fitted against a stationary axis by interposition or a piston combined with a cylinder, and has a shock absorber arranged at a position where the grooved cam is
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contacted with one end of the rotating object or the piston by rotation.
US 4916422 discloses an apparatus for electrically operating a circuit breaker comprising an electrically powered pawl which is driven by an electric motor for causing a ratchet to rotate and a release mechanism for causing the electrically powered pawl to move out of driven engagement with the ratchet when the ratchet rotates to a predetermined angle. A guide bar on which a spring is mounted is secured on a main frame. A slider is slidably provided on the guide bar. The slider engages with a handle of the circuit breaker and throws the circuit breaker when it slides on the guide bar. The slider is driven into sliding motion by a cam which rotates with the ratchet gear in a unitary motion and the slider compresses the spring on the guide bar. When the slider reaches up a position where the circuit breaker is turned off, the release mechanism causes the electrically powered pawl to move out of driven engagement with the ratchet.
Angular position of the crank after discharge of the springs cannot be controlled preciously in the existing braking mechanism. This may lead to false triggering or incomplete operation of the MCCB due to travel mismatch.
Thus to overcome the above disadvantages/problems of the prior art there is a need to provide a braking mechanism for stopping rotation of the shaft at a desired angular position thereby avoiding false triggering in motor operators of moulded case circuit breakers. •
The present inventors have now surprisingly found that false triggering in motor operators can be nullified by avoiding overshooting which can be enhanced by means of a braking
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mechanism comprising braking elements being located in a manner so as to absorb dynamic force produced by the rotating crank of the motor operator.
Objects Of Invention
One of the objects of the present invention is to provide braking mechanism to avoid any possibility of false triggering of the motor by avoiding overshoot.
Another object of the invention is to enhance the life of components in the switches and electrical switches.
Yet another object of the invention is to bring down the dynamic force operating on crank.
Another object of the invention is to provide cost effective mechanism.
SUMMARY OF INVNEITON
Thus according to one aspect of the present invention there is provided a braking mechanism adapted to avoid false triggering in motor operators of moulded case circuit breakers, said mechanism comprising:
locating wall means;
rotating crank shaft provided with disc means and crank means, both in mechanical operative connection with each other having a predetermined phase angle relationship between them; plurality of braking elements operatively located on the wall means wherein said braking elements being located at fixed axes establishing angular relationships with disc means such that co-operative functioning of the disc means and the
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braking elements provides radial interference between the disc means and the braking elements
so as to generate sufficient resistive force to stop rotation of the said disc means at a desired angle.
Another aspect of the present invention is to provide a stored energy motor operator comprising :
plurality of spring means operatively connected to slider means wherein the slider is operatively linked to the braking mechanism adapted to provide braking in discharge cycle of the spring means, wherein said braking mechanism comprises
locating wall means;
rotating crank shaft provided with disc means and crank means, both in mechanical operative connection with each other having a predetermined phase angle relationship between them; plurality of braking elements operatively located on the wall means wherein said braking elements being located at fixed axes establishing angular relationships with disc means such that co-operative functioning of the disc means and the braking elements provides radial interference between the disc means and the braking elements
so as to generate sufficient resistive force to stop rotation of the said disc means at a desired angle.
DETAILED DESCRIPTION OF INVENTION
In the present invention the braking mechanism comprises one or plurality of braking . elements operatively located on locating wall means. The buffers include atleast one retarding/initial buffers, and one stopping buffer. Both type of buffers are fixed in the wall at fixed axes and at desired
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angular relationship with each other. The said buffers can be made in any suitable shape and size. Therefore, the size and shape of the buffers do not restrict the scope of the present invention.
Another embodiment of the present invention describes a rotating crank shaft bearing crank means and disc means comprising crank disc where the crank disc and the crank have a phase angle difference of 180°. The crank disc and the buffers (both retarding and stopping) are in co-operation with each other such that there is a radial interference between the buffers and crank disc at a particular angular position during the rotation of the crank disc in the discharge cycle. The crank disc is mechanically connected to crank and the said crank is located on the crank shaft of the mechanism.
The said buffers absorb the excess energy of the rotating components of the braking mechanism comprising crank and the crank disc. The buffers being made up of elastomeric material and its location in the mechanism in co-operation with the crank disc provides frictional resistance between crank disc and the buffers. The frictional resistance is directly proportional to the normal force between the crank disc and the buffers. This force depends on the amount of compression of the elastomer buffers during braking. The initial buffers as described above retards the crank disc by absorbing most of the energy and subsequently the crank disc is stopped by the stopping buffer placed at desired angular position stopping the crank disc completely.
Another embodiment of the present invention describes a stored energy motor operator, wherein the braking mechanism of
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the present invention mechanism is co-operatively linked with energy storing main springs, spring charging arrangement and latching arrangement. The operator comprises slider being operatively connected to the crank of the braking mechanism located on the crank shaft. During discharge cycle of the main springs followed by change in configuration of the springs, the crank rotates through a predetermined discharge angle. The crank is co-operatively connected to the crank disc, placed on the crank and held by the crank shaft in a manner that the rotation of the crank causes the crank disc to rotate along the crank disc path. The profiles of the crank disc and crank provides co-operative latching at a desired position after the charging cycle is completed. Linear position of the slider depends on the angular position of crank. Once the crank is delatched, main springs release their energy through the slider and cause the said crank and crank disc to accelerate.
r
To take into account the variations in the operating force requirements of different MCCBs, the closing springs are designed with higher operating forces than what is generally required.
This results in excess energy in the system after the MCCB has closed. The excess energy can result in wearing of the mechanism and reduce its life.
In mechanism of present invention, angular position of the rotating components of the braking mechanism can be controlled and overshoot of the said components is avoided.
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BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates the different components of the operating mechanism.
Figure 2 illustrates the plan view of the braking mechanism of the present invention.
Figure 3 illustrates an exploded view of the braking mechanism of the present invention.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
In figure 1 different components of the operating mechanism are illustrated. Main storing springs (1) are operatively connected with slider (2) and crank (3). Crank disc (4) is mechanically connected to crank (3) . Elastomeric buffers (5) located in the wall (6) of the braking mechanism provides radial interference to the crank disc (4).
In figure 2 the plan view of the braking mechanism of the present invention is illustrated. From figure 2 it is realizable that the crank disc (4) is its initial position with the main storing springs (1) in charged condition. During the discharge cycle the crank disc (4) (also shown in the exploded view in figure 3) rotates and is stopped at a desired angular position by the buffers (5) (also shown in the exploded view in figure 3).
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
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to the details cited above. The shape, size and quantity of the buffers as described and illustrated in the above description and the drawings do not restrict the scope of the invention. The angular spacing provided between the crank and the crank disc does 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.
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WE CLAIM
1. A braking mechanism adapted to avoid false triggering in
motor operators of moulded case circuit breakers, said
mechanism comprising:
locating wall means;
rotating crank shaft provided with disc means and crank
means, both in mechanical operative connection with each
other having a predetermined phase angle relationship
between them;
plurality of braking elements operatively located on the
wall means wherein said braking elements being located at
fixed axes establishing angular relationships with disc
means such that co-operative functioning of the disc
means and the braking elements provides radial
interference between the disc means and the braking
elements
so as to generate sufficient resistive force to stop
rotation of the said disc means at a desired angle.
2. A braking mechanism as claimed in claim 1, wherein the braking elements comprises atleast one retarding buffer and a stopping buffer.
3. A braking mechanism as claimed in claims 1 and 2, wherein said buffers are made of elastomeric material.
4. A braking mechanism as claimed in claim 1, wherein the disc means comprises crank disc having 180° phase angle difference with the crank.
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5. A stored energy motor operator comprising :
plurality of spring means operatively connected to slider means wherein the slider is operatively linked to the braking mechanism adapted to provide braking in discharge cycle of the spring means, wherein said braking mechanism comprises
locating wall means;
rotating crank shaft provided with disc means and crank
means, both in mechanical operative connection with each
other having a predetermined phase angle relationship
between them;
plurality of braking elements operatively located on the
wall means wherein said braking elements being located at
fixed axes establishing angular relationships with disc
means such that co-operative functioning of the disc
means and the braking elements provides radial
interference between the disc means and the braking
elements
so as to generate sufficient resistive force to stop
rotation of the said disc means at a desired angle.
A stored energy motor operator as claimed in 5, wherein the braking mechanism wherein the braking mechanism comprises atleast one elastomeric retarding buffer and a stopping buffer so as to provide sufficient compression during braking without any distortion of the buffers.
A stored energy motor operator as claimed in claims 5 and 6, wherein the retarding buffer is adapted to absorb most of the energy' released during discharging cycle of the spring means.
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8. A stored energy motor operator as claimed in claims 5 and 6, wherein the stopping buffer being placed establishing angular relation with the retardin buffer and the crank disc so as to provide sufficient resistance to stop the crank disc from rotation thereby avoiding overshooting.
9. A braking mechanism substantially as herein described and illustrated with reference to the accompanying figures.

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ABSTRACT
TITLE : NEW BRAKING MECHANISM FOR STORED ENERGY MOTOR OPERATORS
The present invention relates to a braking mechanism adapted to avoid false triggering in motor operators of moulded case circuit breakers. The mechanism comprises locating wall means (6), rotating crank shaft provided with disc means (4) and crank means (3), plurality of braking elements (5) operatively located establishing angular relationships with disc means (4) on the wall means (6) such that co-operative functioning of the disc means (4) and the braking elements (5) provides radial interference between the disc means (4) and the braking elements (5) so as to generate sufficient resistive force to stop rotation of the said disc means (4) at a desired angle.
Figure 1
13 JUL 2006