DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to circuit breakers,and in particular, to a stored energy operating mechanism of circuit breaker which enables which enables it to make, carry and break current under normal circuit condition and also break during abnormal conditions.

BACKGROUND

[002] Traditionally known, a circuit breaker, circuit Breaker is a mechanical switching device capable of making, carrying and breaking currents. Under normal circuit conditions it will make the circuit, carry current for a specified time and break the circuit under specified abnormal circuit conditions.

[003] Molded Case Circuit Breakers (MCCB) is employed for current interruption. More particularly MCCBs are utilized to protect instruments from damage during adverse conditions prevailing during the operation of the circuit in which molded case circuit breaker is employed. During adverse conditions like short circuit, the current rises to an alarmingly high level. This high current may cause damage to the parts in the electrical system. Hence during these conditions the circuit has to be opened to protect the system.

[004] A circuit breaker can be manually opened and closed, as well as automatically opened to protect conductors or equipments from damage caused by excessive heating due to over current in abnormal conditions such as overload or short-circuit.

[005] The mechanism of the circuit breaker plays a vital role in determining the credibility of the breaker. A good mechanism should ensure quick and manually independent opening and closing of contact system. Four operations are to be performed by the MCCB mechanism. They areON, OFF, TRIP, and/or RESET.

[006] The first two operations are initiated by operator whereas the trip signal is given by the release which senses the abnormal conditions and gives TRIP command to the mechanism, so that the latter opens the circuit.

[007] The operator has access to the mechanism through the knob which will be projected outwards from the housing of the breaker. The knob is placed over the fork of the operating mechanism. In conventional type MCCBs, breaker will feature three positions in the top cover near the knob to show ON, OFF and TRIP.

[008] When the knob indicates ON it means the breaker is in ON condition i.e., the current path is closed. Similarly the position of the knob indicates the state of the circuit breaker.

[009] According to standards, the top position of the knob (if the breaker is placed vertically) or the longest distant position of the knob away from the operator (if the breaker is mounted horizontally) should be marked as ON POSITION. The other extreme end in both cases is marked as the OFF POSITION. The knob will be near the center (based on the design of the mechanism) to indicate the TRIP POSITION.

[0010] As said above, TRIP command is given automatically to the contacts by the release if it senses an abnormal condition like overload and short circuit. If the trip signal is given, the breaker opens the circuit and the knob goes to the trip position to show the operator that a fault has occurred in the system.

[0011] If the operator wants to switch ON the breaker after the breaker is tripped, he/she cannot do it without resetting the breaker. This is to make sure that the operator shouldnotswitch ON the breaker before clearing the fault.

[0012] Resetting of the breaker is done by moving the knob (Driver link) towards the OFF position from the TRIP position. This movement loads the mechanism spring and now it is possible for the operator to ON the breaker. All these mechanisms are called semi-automatic mechanisms since for ON and OFF operation, the knob of the breaker has to be taken from their respective ON or OFF positions to a position called dead center beyond which the mechanism becomes independent of the operator and completes the respective action automatically.

[0013] There are various conventionally know techniques for providing operating mechanisms /driving mechanisms for circuit breaker, however, most of them uses high spring force for biasing latch bracket or splits the latch bracket into primary and secondary latch bracket to reduce trip force. Further, most of the existing techniques have high friction because of the typical interaction between latch bracket and latch link during RESET and TRIP operations therefore have lower tripping speed and higher reset force. Furthermore, during TRIP to RESET operating mechanisms use a single rolling pin attached to the fork link and cam action between the pin and a profile on the latch link.

SUMMARY OF THE INVENTION

[0014] 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.

[0015] An object of the present invention is to provide a latch bracket that envelopes the latch link and uses a roller pin where there is latch bracket and latch link interaction reducing the trip force and increasing the tripping speed.

[0016] Another object of the present invention is to provide at least two rolling pins (primary and secondary rolling pins) that are attached to the latch link engaging a cam profile on the fork link thus reducing reset force.

[0017] Accordingly, in one implementation, the present invention provides an improved operating mechanism of molded case circuit breaker, said mechanism module comprising: an operating knob means fixed onto a fork link means which drives a dead-centre based mechanism consisting of a plurality of upper link means, lower link means, and at least one spring mounted between a spring pin means and a floating pin means; the upper spring hinge located on the fork link means and the lower spring hinged on the floating point located on the upper link means; The said upper link means and said lower link means being pivotally connected to each other and said lower link means being operatively connected between said upper link means and said shaft assembly means; The other end of said upper link means is pivoted on a latch link means which is operatively mounted on a plurality of side plate means. Also attached to said latch link means is a pair of reset pin which engages a cam profile on the fork link means during TRIP-RESET operation. Said side plate means comprising at least one side plate profile means, wherein the said side plate profile means comprising plurality of predetermined sized slot means operatively located on said side plate means for required latch link rotation.

[0018] As compared to the conventional circuit breakers, in order to avoid the technical drawbacks as discussed in the background above, the present invention includes the latch bracket that envelopes the latch link and uses a roller pin where there is latch bracket and latch link interaction thereby reducing the trip force and increasing the tripping speed.Two rolling pins (primary and secondary rolling pins) are used as reset pins and are attached to the latch link engaging a cam profile on the fork link thus reducing reset force.

[0019] The typical construction of the latch link provides more space and facilitates use of two roller pins.However, because of the bending operation involved in the latch link or the use of single sheet of metal as latch link in the previous arts, the use of two roller pins is infeasible.

[0020] 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 above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which:

[0021] Figure 1illustratesan isometric view of the 4 pole Circuit Breaker in ON condition, in accordance with the subject matter of the present invention.

[0022] Figure 2illustratesan isometric view of mechanism in ON condition, in accordance with the subject matter of the present invention.

[0023] Figure 3 illustrates the exploded view of the mechanism, in accordance with the subject matter of the present invention.

[0024] Figure 4 illustrates a section of mechanism assembly in the ON condition, in accordance with the subject matter of the present invention.

[0025] Figure 5 illustrates a section of mechanism assembly in the OFF condition,in accordance with the subject matter of the present invention.

[0026] Figure 6 illustrates a section of mechanism assembly in the TRIP condition, in accordance with the subject matter of the present invention.

[0027] Figure 7 illustrates a section of mechanism assembly in the RESET condition, in accordance with the subject matter of the present invention.

[0028] Figure 8 illustratesinteraction of Latch Link and Latch Bracket during TRIP and RESET operations and construction of latch bracket, in accordance with the subject matter of the present invention.

[0029] Figure 9 illustratesresetting operation using Resetpin 1 and Resetpin 2, in accordance with the subject matter of the present invention.

[0030] Figure 10 illustratesthe arrangement of Latch Link and Latch Bracket in the mechanism, in accordance with the subject matter of the present invention.

[0031] Figure 11 illustratesthe distance between latching area of latch bracket and latch link and the pivot of latch bracket,in accordance with the subject matter of the present invention.

[0032] Figure 12 illustratessectional view of the mechanism when the breaker is in ON condition, in accordance with the subject matter of the present invention.

[0033] 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 PRESENT INVENTION

[0034] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary.

[0035] 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 of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.

[0036] 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.

[0037] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0038] 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.

[0039] Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments and/or in combination with or instead of the features of the other embodiments.

[0040] It should be emphasized that the term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0041] A person skilled in the art will appreciate that for understanding purpose the present invention is explained with the help of circuit breakers however the disclosed subject matter shall not be considered as the limiting factor for the scope of present invention.

[0042] In one implementation, according to the invention an improved operating mechanism for molded case circuit breaker is provided. Figure 1 shows an isometric view of the 4 pole Circuit Breaker in ON condition with the mechanism mounted on the top and bottom housing. Figure 2 shows an isometric view of mechanism in ON condition. Figure 3 shows an exploded view of the mechanism consisting of Upper Link (3e1), Lower Link (3e4), Latch Link (3b1), the Latch Link (3b1) consists of two metal plates riveted with each other using Spacer Pins, this eliminates the bending operation of one single plate into the Latch Link and ensures higher concentricity between the holes in the plates through which the Latch Link is pivoted, as against the previous construction. Fork Link (3f1); Spring Pin (3f2) is connected to the Fork Link (3f1) and Floating Pin (3e2) is connected to the Upper Link (3e1). A pair of two concentric Extension Springs (3e3) is connected to the Spring Pin (3f2) and Floating Pin (3e2). A Knob (3f3) is inserted into the Fork Link (3f1) through which user operates the mechanism. Lower Link (3e4) is connected to the Shaft Assembly (4a) which primarily consists of the Mobile Conductors (4b). During OFF-ON and ON-OFF operation Latch Link (3b1) is latched on to the Latch Bracket (3d1).

[0043] In one implementation, ON-OFF and OFF-ON operations of the mechanism are achieved by the manual rotation of knob (3f3). The rotation of knob (3f3) increases the potential energy (charging) of the extension springs (3e3) while restricting the motion of shaft assembly (4a) during charging. After a specific rotation of the knob (3f3) potential energy of springs is released in the form of kinetic energy through mechanical linkages leading to the rotation of shaft assembly (4a) at a high velocity. Circuit breaker mechanisms use dead centre based extension spring arrangements.

[0044] In one implementation, figure 4 shows the sectional view of the Mechanism in ON condition. When Knob (3f3) is rotated by the user, Extension Springs (3e3) connected to the Spring Pin (3f2) and Floating Pin (3e2) get deflected to a maximum extension i.e. dead centre position and after the dead centre position the stored energy in the springs is converted into kinetic energy which is used to rotate the Shaft Assembly (4a) and hence the Mobile Conductors (4b) from ON to OFF condition through Upper Link (3e1) and Lower Link (3e4).

[0045] In one implementation, figure 5 shows the sectional view of the Mechanism in OFF condition. When Knob (3f3) is rotated by the user, Extension Springs (3e3) connected to the Spring Pin (3f2) and Floating Pin (3e2) get deflected to a maximum extension i.e., dead centre position and after the dead centre position the stored energy in the springs is converted into kinetic energy which is used to rotate the Shaft Assembly (4a) and hence the Mobile Conductors (4b) from OFF to ON condition through Upper Link (3e1) and Lower Link (3e4). Mobile Conductors (4b) and Fixed Conductors (4c) touch each other and the breaker is said to be in ON condition.

[0046] In one implementation, figure 6 shows the sectional view of the Mechanism in TRIP condition. When actuation signal is given to the Trip-D Shaft (3c) it rotates and the Latch Bracket (3d1) is unlatched which in turn causes the unlatching of Latch Link (3b1). The Latch Link (3b1) is now free to rotate. Throughout its rotation, the Latch Link (3b1) maintains contact with the Roller Pin (3d2) assembled with the Latch Bracket (3d1). The Roller pin (3d2) is constrained in such a way that it is free to revolve around itself, this reduces the friction between the Latch Link (8a) and the Roller pin (8b) shown in figure 8, thus increasing the speed of rotation of the Latch Link (3b1). In the ON condition the springs have specific deflection therefore have stored potential energy which enables the Latch Link (3b1) to rotate so that the springs are in a state minimum deflection. Upper Link (3e1) is connected to Latch Link (3b1) and Lower Link (3e4); Lower Link (3e4) is further connected to the Shaft Assembly (4a), therefore the rotation of Latch Link (3b1) results in the rotation of Shaft Assembly (4a). Mobile Conductors (4b) and Fixed Conductors (4c) are separated and the breaker is said to be in TRIP condition.

[0047] In one implementation, figure 7 shows the Mechanism in TRIP position. During the RESET operation user rotates the knob (3f3) from the TRIP position. At TRIP position Fork Link (3f1) rests on Primary Reset Pin (3b3) which is inserted in the latch link (3b1). So when force is applied on the knob (3f3), latch link (3b1) rotates causing the upper link (3e1) & lower link (3e4) to move from TRIP to RESET position. A Secondary Reset pin (3b4) with a Roller, inserted in the latch link (3b1) serves two purposes (1) It increases the scope for optimization of the cam profile on the Fork Link (3f1) as the Secondary Reset pin (3b4) engages with the latter portion of the cam profile on the Fork Link for greater leverage on the Latch Link (3b1) thus reducing reset force and (2) It reduces the rotation of the Fork Link (3f1) required to rotate the Latch Link (3b1) to the reset position, shown in figure 9. Also rolling coefficient of friction between fork link (3f1) and the pair of reset pins further reduces the reset force. The slots provided in the side plates (3a1 and 3a2) prevent further rotation of Latch Link (3e1).

[0048] In one implementation, Figure 8 shows the construction of Latch Bracket (3d1). The Latch Bracket (3d1) is constructed in a U-shape and the latching of Latch Link and Latch Bracket is ensured by a Latching Roller Pin (3b2) in Latch Link (3b1) and the bottom surface of the first wall of Latch Bracket (8e). The width of Latch Bracket (3d1) shown in figure 10, is greater than that of Latch Link and the Latch Bracket pivot (3d3) is divided into two parts each riveted on the Side Plates (3a1 and 3a2), in order to control the distance (11c) between the latching area (11a) shown in Figure 11, of Latch Bracket (3d1) and Latch Link (3b1) and the Latch Bracket pivot (3d3). The force required for rotating the Trip-D Shaft in order to TRIP the mechanism and hence the circuit breaker is very low in spite of the high reaction force due to the stored energy in the springs on the Latch Bracket (3d1) when it is latched with the Latch Link (3b1), in ON condition. This is achieved by reducing the distance (11c) between the latching area (11a) of Latch Bracket (3d1) and Latch Link (3b1) and the Latch Bracket pivot (3d3).

[0049] In one implementation, an improved operating mechanism of molded case circuit breaker is disclosed. The mechanism modulemay include at least one operating knob fixed onto at least one fork link which drives at least one dead-centre based mechanism consisting of at least one upper link, at least one lower link, and at least one spring mounted between at least one spring pin and at least one floating pin; wherein the fork link comprises at least one upper spring hinge and at least one lower spring hinged on the floating pin located on the upper link; the upper link and the lower link is pivotally connected to each other and the lower link is operatively connected between at least one end of the upper link and at least one shaft assembly; at least one other end of the upper link is pivoted on at least one latch link means which is operatively mounted on at least one side plate; the latch link comprises at least a pair of reset pin adapted to engage with at least one cam profile on the fork link during a TRIP-RESET operation; and the side plate comprises at least one side plate profile means, wherein the side plate profile includes at least one predetermined sized slot operatively located on said side plate enabling rotation of the latch link.

[0050] In one implementation, the present invention comprises a latch bracket means adapted to lock and/or unlock said latch link means.

[0051] In one implementation, the present invention comprises a bend portion of latch bracket means being operatively located on one side of said latch bracket means.

[0052] In one implementation, the present invention comprisesa latch bracket means enveloping the latch link means to reduce the distance between the latching area of latch bracket means and latch link means and the pivot of latch bracket means for reducing trip force.

[0053] In one implementation, the present invention comprisesof latch bracket means with a roller pin to reduce the friction during RESET and TRIP operation hence increasing tripping speed and reducing reset force.

[0054] In one implementation, the present invention comprisesa Trip-D Shaft means adapted to lock and/or unlock said latch bracket means.

[0055] In one implementation, the present invention comprisesa knob means operatively connected to said fork link means.

[0056] In one implementation, the present invention comprises a cam profile of fork link means operatively located on end portions of side limbs of said fork link means, engages a rolling pair of reset pin means operatively connected to the latch link means during TRIP-RESET operation.

[0057] In one implementation, said cam profile of fork link means operatively located on end portions of side limbs of said fork link means, engages a rolling pair of reset pin means for reducing reset force by design of the cam profile on end portions of side limbs of said fork link means for greater leverage on Latch Link means during RESET operation.

[0058] Apart from the advantages and benefits mentioned above, other advantages and benefits are mentioned below:
· The present inventionincreases the tripping speed.
· The present inventionreduces the reset force required.
· The present inventionreduces the trip force required.
· The present inventionuses less number of components.
· The present invention provides better ergonomic considerations.

[0059] It may be understood by the person skilled in that art that, the coupling, joining, fitting of the two components mentioned the present invention may be achieved by any of the existing coupling techniques that may include but not limited to nut and bolt arrangement, gluing, pasting, welding, and the like.
,CLAIMS:1. An operating mechanism of circuit breaker, said operating mechanism comprising:
at least one operating knob fixed onto at least one fork link which drives at least one dead-centre based mechanism consisting of at least one upper link, at least one lower link, and at least one spring mounted between at least one spring pin and at least one floating pin; wherein
the fork link comprises at least one upper spring hinge and at least one lower spring hinged on the floating pin located on the upper link;
the upper link and the lower link is pivotally connected to each other and the lower link is operatively connected between at least one end of the upper link and at least one shaft assembly;
at least one other end of the upper link is pivoted on at least one latch link means which is operatively mounted on at least one side plate;
the latch link comprises at least a pair of reset pin adapted to engage with at least one cam profile on the fork link during a TRIP-RESET operation; and
the side plate comprises at least one side plate profile means, wherein the side plate profile includes at least one predetermined sized slot operatively located on said side plate enabling rotation of the latch link.

2. The operating mechanism as claimed in claim 1, wherein the pair of reset pin is preferably a pair of rolling pins i.e., a primary rolling pin and a secondary rolling pin.

3. The operating mechanism as claimed in claim 1, comprises at least one latch bracket adapted to lock and/or unlock the latch link.

4. The operating mechanism as claimed in claim 1, wherein the latch bracket comprises at least a bend profile.

5. The operating mechanism as claimed in claim 1, comprises a Trip-D shaft adapted to lock and/or unlock said latch bracket.

6. The operating mechanism as claimed in claim 1, the fork link comprises at least one limb wherein the cam profile of fork link is operatively located on end portions of the limb and adapted to engage with the pair of reset pin operatively connected to the latch link during TRIP-RESET operation.