FORM2
THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)
Title of the invention - IMMUNIZATION AGAINST VIBRATION OF
UNDER VOLTAGE RELEASE FOR MCCBs
2. Applicant
(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 speci fication particularly describes the invention and the manner in which it is-to be
performed:

FIELD OF INVENTION
The present invention relates to immunization of vibration of an under voltage release mechanism for moulded case circuit breakers (MCCBs). The invention particularly, relates to a latch adapted for avoiding malfunctioning due to influence of vibration forces in the under-voltage (U/V) release mechanism for moulded case circuit breakers (MCCBs) by elimination of torque generation on the latch.
BACKGROUND AND PRIOR ART
In an MCCB which is a switching as well as protection device for an electrical system various combinations of accessories are required. One such accessory is the under-voltage release (U/V) . The function of a U/V release is to allow the MCCB to carry current when the voltage is above a particular threshold and disconnect the supply when the voltage reduces below the threshold. Thus U/V should not trip the MCCB if the input supply is above threshold and should trip the MCCB if the input supply is below threshold.
For this the U/V consists of a voltage sensor and an actuating device combination as shown in the figure 1. The voltage sensor consists of a solenoid device which is optimized in size by using it in conjunction with a latching type of actuating device. When the solenoid senses voltage above threshold limit it allows the holding latch to hold the . actuating arm in reset position thereby
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preventing it from tripping the MCCB. If the input voltage of the solenoid drops below threshold limit the solenoid pushes the holding latch which rotates and frees the actuating arm. This arm in-turn travels and trips the MCCB.
To optimize the solenoid coil it is required that the holding latch should operate at very low forces. But to increase the reliability of operation it is also required that the holding latch not be affected by vibration forces. These two requirements are contradictory in nature. The holding latch is kept biased towards the plunger of the solenoid. This causes the holding latch to closely follow the plunger such that it latches or releases the actuating arm based on the position of the plunger. This biasing force on the holding latch is critical since it has to be much less than the plunger force so as to allow the'plunger to push the holding latch and at the same time it has to be large enough to maintain the holding latch in contact with the plunger continuously.
For reliable operation under above conditions it is required that external forces should not be able to act on the holding latch giving it a torque. Taking into account the conditions on the design of the solenoid and therefore on the biasing spring if the assembly of the MCCB with the U/V release is subjected to vibration it generates an undue torque causing the holding latch to rotate irrespective of the plunger position and release the actuating arm which in turn rotates and trips the MCCB. Such tripping is a nuisance in the general operation and is hence unwarranted.
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Conventional wisdom suggested that the problem be tackled by vibration Mounts. But this adds to the cost of production and assembly. It increases the number of components reducing the statistical reliability. It also increases assembly complications and production time.
The prior art design of the Under-voltage release is shown in Fig 1. The voltage sensor is a solenoid (15) which in absence of sufficient input voltage rotates the Latch (12) about the Pivot pin (11) . The Actuator (14) is thus either latched or released by the Latch (12) based on the input to the solenoid (15) . This Actuator (14), when released by Latch (12) , impacts on the suitable component of the MCCB to trip the MCCB in under voltage condition.
In the prior art design if the entire assembly is subjected to vibration then the force balancing about the Pivot pin 11 becomes critical. In normal circumstances, the Biasing spring (13) keeps the Latch (12) biased towards the Solenoid (15) and hence the Latch (12) can hold the Actuator (14) against tripping the MCCB. But under vibration there is a torque on Latch (12) about Pivot pin (11).
As seen in Fig 2A the forces of vibration and gravity acting on Center of Gravity (22) causes a torque about the pivot point (21) which counters the action of the Biasing spring (13). If this torque exceeds the biasing.torque, the Latch (12) rotates about the Pivot pin (11) irrespective of the input to solenoid (15) and thus results in nuisance tripping of the MCCB.
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GB743138 discloses a device for operating U/V release in which a cam type device does the release function. The cam is not pivoted as the C.G. of the latch and forces of vibration can cause the cam to vibrate within a sector of tolerance.
Thus there is a need to provide for a latch adapted for avoiding malfunctioning due to influence of vibration forces in the under-voltage (U/V) release mechanism for moulded case circuit breakers (MCCBs) by elimination of torque generation on the latch.
The present inventors have found that by way unique construction of the latch, superimposition of the latch C.G. with pivot point/hinge point can be achieved which could eliminate torque generation in the latch thus avoiding malfunctioning of the latch.
OBJECTS OF INVENTION
Accordingly, one object of the present invention is to overcome all the disadvantages of the prior art.
Another object of the present invention is to provide a latch to avoid the possibility of malfunctioning of the U/V release under the influence of any vibration forces by eliminating the possibility of torque generation on the holding latch (hereinafter referred to as "latch").
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Another object of the present invention is to eliminate the nuisance tripping during the "switch on" operation of the MCCB.
Yet another object of the present invention is to provide a device for operating under voltage release comprising a latch such that there is no torque on the latch.
SUMMARY OF INVENTION
Accordingly, one aspect of the present invention is to provide a latch adapted for avoiding malfunctioning due to influence of vibration forces in the under-volt age (CJ/V) release mechanism for moulded case circuit breakers (MCCBs) by elimination of torque generation on the latch, said latch comprising :
rectangular portion having plural projections protruding out laterally,
wherein the projection protruding out laterally in conjunction with the rectangular portion define functional requirements and a curvature adapted to pivot the latch at its central axis
characterized by projection traveling laterally to a predetermined length whereby it is almost vertically projected upward to define a biasing profile means such that the center of gravity of the latch superimposes with the central axis of the pivot.
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According to another aspect of the present invention there is provided a device for operating under voltage release comprising
trip actuator;
latch;
voltage sensor;
wherein the trip actuator is operatively connected to one end of latch and is pivoted at a pre-determined point on the assembly as shown; and
wherein the latch comprises rectangular portion having plural projections protruding out laterally,
wherein the projection protruding out laterally in conjunction with the rectangular portion define functional requirements and a curvature adapted to pivot the latch at its central axis . ,
characterized by projection traveling laterally to a predetermined length whereby it is almost vertically projected upward to define a biasing profile means such that the center of gravity of the latch superimposes with the central axis of the pivot.
DETAILED DESCRIPTION OF PRESENT INVENTION
In the present invention device for operating under voltage release comprises trip actuator, latch and voltage sensor.
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In one embodiment of the invention the latch comprises rectangular portion having plural projections protruding out laterally. The lateral projection in conjunction with the rectangular portion define a curvature ,adapted to pivot the latch at its central axis. The projection travels laterally to a predetermined length whereby it is almost vertically projected upward to define a biasing groove profile such that the center of gravity of the latch superimposes with the central axis of the pivot.
The trip actuator is operatively connected to one end of latch and is pivoted at a pre-determined point.
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
i Figure 1 illustrates an isometric view of under voltage
release device of the prior art.
Figure 2A illustrates a plan view of the latch of the prior art.
Figure 2B illustrates a plan view of the latch of the present invention.
Figure 3 illustrates a schematic isometric view of the device with the latch of the present invention.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
As shown in Fig 2B is the Latch (32) with the Center of Gravity (24) and Pivot Point (23) are coincident and hence
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the forces acting through the Center of gravity (24) also pass through the Pivot Point (23) through which the Pivot pin (31) is passed. Since the pivot pin applies a reaction to the forces due to gravity (Fg) and vibration (Fv) the resultant leads to zero and as the moment arm length between pivot point and center of gravity is zero the toque due to above forces is zero. Latch {32) comprises a rectangular portion (36) having plural projections (37J protruding out laterally. Lateral projection (37) in conjunction with the rectangular portion (36) defines a curvature (38) adapted to pivot the latch at its central axis by means of the pivot pin (31). Biasing groove profile (39) is located at one end of the lateral projection (37) . Rectangular portion (36) further comprises a notch means which includes an appropriate/suitable angular projection (40).
In Fig. 3, the Latch (32) pivoted about Pivot pin (31) rotates only when the input to solenoid (35) is reduced below preset threshold. Hence the Latch (32) releases the actuator (34) only in case of under voltage condition at input of solenoid (35) . The resultant force of the vibration & gravitational forces act on the C.G. which is located closed to the pivot & get balanced by the reaction due to pivot pin. Under forces of Vibration the Latch (32) remains immobile and hence does 'not release the actuator (34) which in turn can not trip the MCCB merely due to vibration.
The invention has been described in a preferred form only and many variations may be made in the invention which will
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still be comprised within its spirit. The invention is not limited to the details cited above. 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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CLAIM
1. A latch adapted for avoiding malfunctioning due to
influence of vibration forces in the under-voltage
(U/V) release mechanism for moulded case circuit
breakers (MCCBs) by elimination of torque generation
on the latch, said latch comprising :
rectangular portion having plural projections protruding out laterally,
wherein the projection protruding out laterally in conjunction with the rectangular portion define functional requirements and a curvature adapted to pivot the latch at its central axis
characterized by projection traveling laterally to a predetermined length whereby it is almost vertically projected upward to define a biasing profile means
such that the center of gravity of the latch superimposes with the central axis of the pivot.
2. Latch as claimed in claim 1, wherein the rectangular projection further comprises a notch means.
3. Latch as claimed in claim 2, wherein the notch means comprises an appropriate projection.
4. Latch as claimed in claim 1, wherein the biasing profile means comprises a groove.
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5. A device for operating under voltage release
comprising :
trip actuator;
latch;
voltage sensor;
wherein the trip actuator is operatively connected to one end of latch and is pivoted at a pre-determined point on the assembly as shown; and
wherein the latch comprises rectangular portion having plural projections protruding out laterally,
wherein the projection protruding out laterally in conjunction with the rectangular portion define functional requirements and a curvature adapted to pivot the latch at its central axis
characterized by projection traveling laterally to a predetermined length whereby it is almost vertically projected upward to define a biasing profile means such that the center of gravity of the latch superimposes with the central axis of the pivot.
6. Device as claimed in claim 4 further comprises a biasing spring adapted to be co-operatively engaged with the groove.
7. A latch and device adapted for avoiding malfunctioning due to influence of vibration forces in the under-
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voltage (U/V) release mechanism for moulded case circuit breakers as herein substantially described and illustrated with reference to the accompanying figures.
Dated this the 29th day of March 2007.
ihishek Sen
Of S. Majumdar & Co. Applicant's Agent
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ABSTRACT
TITLE : IMMUNIZATION AGAINST VIBRATION OF UNDER VOLTAGE RELEASE FOR MCCBs
The present invention relates to a latch adapted for avoiding malfunctioning due to influence of vibration forces in the under-voltage (U/V). release mechanism for moulded case circuit breakers. The latch comprises rectangular portion (36) having plural projections (37) protruding out laterally, which in conjunction with the rectangular portion (36) define functional requirements and a curvature (38) to pivot the latch (32) at its central axis. The rectangular portion (36) travels laterally to a predetermined length whereby it is almost vertically projected upward, to define a biasing profile means (39) such that the center of ' gravity of the latch (32) superimposes with the central axis of the pivot (31).
Figure 2B