DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to a molded case circuit breaker and more particularly to an improved spring operating mechanism of molded case circuit breaker which enables it to make, carry and break current under normal circuit condition and also break during abnormal conditions.

BACKGROUND

[002] An electrical switching device may be defined as a unit designed to connect, carry and disconnect electrical supply so as to protect the equipments connected in the electrical circuit from damage caused by overload, under-voltage or short circuit etc. Circuit breakers are well-known electrical switching devices used to provide automatic circuit interruption, to a monitored circuit, when circuit fault conditions occur.

[003] An operating mechanism in circuit breaker plays an important role determining the credibility of the breaker. The operation mechanism enables the breaker to perform the following four operations which are:
1. ON
2. OFF
3. TRIP
4. RESET
Users (Operator personnel) have access to the operating mechanism through a knob which is mounted on the FORK of the mechanism and it is projected outwards from the housing of the breaker. The mechanism consists of four bar link named as latch link, upper link, lower link and drive shaft. Two pins are introduced into the operating mechanism so as to hold two ends of an extension spring. One pin is mounted on the upper link and another is on the fork. The operator personnel drive the fork by means of the knob, and hence all the links of four bar mechanism start moving.

[004] While switching the breaker from ON to OFF or OFF to ON position, the operator personnel has to apply a force on the knob so as to take it to an intermediate position called as dead center position of the spring, beyond which the operating mechanism becomes independent of the breaker and the breaker completes the respective action automatically. As the current carrying capacity increases, the spring force required for making and breaking current also increases.

[005] The prior art document, US 4528531 discloses a molded case circuit breaker includes a highly integrated operating mechanism having an over-center toggle mechanism for opening and closing a pair of electrical contacts and a trip mechanism for responding to overload and short circuit or fault current conditions to separate the pair of electrical contacts. A generally flat, intermediate latch plate includes an upper latch surface for latching with a movable cradle of the over-center toggle mechanism and a lower latch surface for latching with a trip bar of the trip mechanism and a pair of outwardly projecting pivot arms disposed between the upper and lower latch surfaces. The over-center toggle mechanism includes a pair of upper toggle links and a pair of lower toggle links interconnected by a toggle spring pin. To increase the speed of separation of the first and second electrical contacts during a trip operation, the cradle is physically configured to engage and upwardly propel the toggle spring pin and, also, the upper toggle links have projections for physically contacting a rigid stop.

[006] The prior art document, US 4864263 discloses an industrial rated molded case circuit breaker having an electronic trip circuit contained within the circuit breaker enclosure includes a reset spring in cooperation with the circuit breaker latch spring to insure manual reset of circuit breaker after an automatic trip function. The reset spring allows the circuit breaker latch assembly to be manually reset upon minimum travel of the circuit breaker operating handle due to internal circuit breaker component space restrictions. The circuit breaker latch assembly is robotically loaded to the operating mechanism which is then attached to the circuit breaker case by an automated fastening process.

[007] The prior art document, US 6479774 discloses a circuit breaker operating mechanism comprises a movable handle yoke, a mechanism spring extending in tension from the handle yoke to a pin, and a lower link extending from the pin to a crank connected to a contact arm bearing a movable contact. The crank can be positioned in open and closed conditions, being in an open position when the movable contact is separated from an associated fixed contact and being in a closed position when the movable contact is mated to the associated fixed contact. The circuit breaker further comprises an interface formed on said crank and a blocking prop having a first surface that engages said interface, the first surface preventing the crank from rotating towards the closed position.

[008] The prior art document, US 6590172 discloses a circuit breaker is provided wherein the circuit breaker comprises a contact arm movable between a closed position, an open position and a blown open position wherein the contact arm is disposed in the circuit breaker. A bumper disposed to contact the contact arm when the contact arm is in the blown open position. In addition, a stop member disposed to be in contact with a linkage assembly so as to create a gap between the bumper and the contact arm when the contact arm is disposed in the open position.

[009] In conventional spring mounting methods, a spring pin is assembled in its free length and the spring pin holding springs is lifted by means of fixture to place it on the given slot provided on a fork. Hence, the mechanism required operator personnel to lift the spring pin up to the height of the fork. Therefore, the force required to lift the spring pin increases as spring extends to the height of fork. The condition become worse in case of higher rating breakers as spring force is too high.

[0010] The drawback of conventional spring operating mechanism in a molded case circuit breaker includes fixtures to mount spring on a slot that may be provided on the fork. In case of the circuit breaker with higher current capacity, higher contact pressure may be required so as to maintain the repulsion threshold. To deliver higher contact pressure, mechanism springs needed to provide high force and this further included separate fixture to mount the spring in the operating mechanism due to high force. Also, the time required for assembly is high and the mechanism springs may go beyond its stress limit due to large deflection of spring to assemble spring pin in to the slot.

[0011] Thus, in view the hitherto drawbacks of the existing spring operating mechanism in a molded case circuit breaker, there exists a dire need to provide an improved operating mechanism that provides less spring force, thus enabling the springs to remain within its stress limit, better performance and involves lesser number of components.
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SUMMARY OF THE INVENTION

[0012] 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.

[0013] In one implementation, the present invention provides an improved spring operating mechanism in a circuit breaker. The mechanism comprises a cam profile, provided on a fork so as to provide a cam action between a spring pin and the fork, a notch at the end of the cam profile, a slot for positioning the spring pin and a knob.

[0014] In one implementation, the present invention provides an improved spring operating mechanism wherein in an event when the fork moves towards an ON position, the spring pin slides on a side plate surface of a side plate because of the cam action between fork and spring pin and at the same time expansion of springs also occurs. By pushing knob more towards ON position, the spring pin jumps from the notch because of farther sliding of spring pin on the surface of side plate and thus is positioned into the slot provided on the fork. The spring pin does not detach from the slot provided on the fork because of the notch and springs assembled on spring pin remains in tension.

[0015] In one implementation, the present invention is of automatic spring mounting and the feature given on the fork profile is the result of this concept which allows automatic assembly of the spring by cam action while moving the fork like usual on off operation and once the spring gets into the slot it will not come out. The cam is plotted by measuring the profile projected by the spring point on the fork and spring pin where the spring is mounted. In one implementation, the feature will change from product to product and it depends on the profile created by spring point while moving. So, one can give the same profile on the other product, but it will not work, as the profile projected by spring point is different from product to product. In one implementation, no separate fixture is required which will lead to save the cost to a great extent and assembly timing in assembly line. In one implementation, the material used for manufacturing is steel sheet 3mm thick for fork, and en24 rod for spring pin.

[0016] 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:

[0017] Figure 1 illustrates an isometric view of mechanism in which assembly process is in its initial condition, in accordance with an embodiment of the present subject matter.

[0018] Figure 2 illustrates a basic view of mechanism in which assembly process is in its initial condition, in accordance with an embodiment of the present subject matter.

[0019] Figure 3 illustrates an enlarge view of cam profile, in accordance with an embodiment of the present subject matter.

[0020] Figure 4 illustrates an isometric view of mechanism in which assembly process is in-between, in accordance with an embodiment of the present subject matter.

[0021] Figure 5 illustrates an isometric view of mechanism in which assembly process is in-between, in accordance with an embodiment of the present subject matter.

[0022] Figure 6 illustrates an isometric view of mechanism in which assembly process is done, in accordance with an embodiment of the present subject matter.

[0023] Figure 7 illustrates an isometric view of mechanism in which assembly process is done, in accordance with an embodiment of the present subject matter.

[0024] 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

[0025] 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.

[0026] 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.

[0027] 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.

[0028] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] Referring now to figure 1, an isometric view of an improved operating mechanism assembly before mounting of spring pin 2 into the slot 1c of the fork 1is illustrated.

[0033] Referring now to figure 2, a basic view of the improved operating mechanism in which assembly process is in its initial condition is illustrated.

[0034] Referring now to figure 3, an enlarge view of a cam profile provided in the improved operating mechanism is illustrated.

[0035] Referring now to figure 4, an isometric view of the improved operating mechanism in which assembly process is in-between is illustrated.

[0036] Referring now to figure 5,a basic view of the improved operating mechanism in which assembly process is in-between is illustrated.

[0037] Referring now to figure 6, an isometric view of the improved operating mechanism in which assembly process is done is illustrated.

[0038] Referring now to Figure 7, a basic view of the improved operating mechanism in which assembly process is done is illustrated.

[0039] In one implementation, the improved operating mechanism in a circuit breaker includes the following components:
1. Fork
1a. Cam profile on fork
1b. Notch at the end of cam profile
1c. Slot for spring pin
1d. Knob
2. Spring pin
3. Springs
4. Side plate

[0040] In one implementation, the spring pin 2 is mounted in the slot 1c of the fork 1 automatically by movement of a fork 1 towards ON side. The direction of ON side is shown by arrow in figure 1 and figure 2.

[0041] In one implementation, the profile 1a is provided on the fork 1 which provides a cam action between spring pin 2 and fork 1 as shown in figure 3. When the fork 1 moves towards ON position, spring pin 2 sliding on the side plate surface 4a on side plate 4 because of the cam action between fork 1 and spring pin 2 and at the same time expansion of springs also occurs.

[0042] In one implementation, a notch 1b at the end of the cam profile 1a on fork 1 is provided as shown in figure 4 and figure 5. By pushing a knob 1d more towards ON position, the spring pin 2 jumps from notch 1b because of farther sliding of spring pin 2 on the surface 4a of side plate 4 and is positioned into the slot 1c on the fork 1 as shown in figure 6 and figure 7. The spring pin 2 does not detach from the slot 1c on fork 1 because springs 3 assembled on spring pin 2 are remain in tension which enables the spring pin 2 to remain fixed in slot 1c.

[0043] In one implementation, the springs extends minimum and it gets lifted by cam action by the operator which is more reliable than conventional mechanism of lifting the spring by external fixture as holding the spring pin is difficult by fixture. Thus, spring pin 2 gets lifted automatically.

[0044] In one implementation, an operating mechanism for circuit breaker is disclosed. The operating mechanism comprises a fork 1, a spring pin 2, at least one spring 3, and at least one side plat 4, wherein the fork 1 is characterized in that comprising a cam profile 1a; a notch 1b at the end of the cam profile 1a; a slot 1c for spring pin 2; and a knob 1d, wherein the cam profile 1a is adapted to provide a cam action between the spring pin 2 and the fork 1.

[0045] In one implementation, when fork 1 move towards ON position, the spring pin 2 is adapted to slide on at least one side plate surface 4a on side plate 4 as a result of the cam action between the fork 1 and the spring pin 2 thereby enabling an expansion of spring 3.

[0046] In one implementation, in response to a pushing of the knob 1d towards ON position, the spring pin 2 is adapted to escape from the notch 1b as a result of farther sliding of spring pin 2 on the surface 4a of side plate 4 and rest into the slot 1c on fork 1.

[0047] In one implementation, the spring pin 2 is adapted to retain the position in the slot 1c on the fork 1 as the notch 1b and the springs 3 assembled on the spring pin 2 retains the tension.

[0048] In one implementation, the profile 1a is provided on both sides of the fork 1.

[0049] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. No separate fixture is required for the mounting of spring.
2. Assembly time reduces.
3. Springs remains in its stress limit during assembly because deflection is less in this method.
,CLAIMS:1. An operating mechanism for circuit breaker comprising: a fork 1, a spring pin 2, at least one spring 3, and at least one side plat 4, wherein the fork 1 is characterized in that comprising a cam profile 1a;a notch 1b at the end of the cam profile 1a;a slot 1c for spring pin 2; and a knob 1d, wherein the cam profile 1a is adapted to provide a cam action between the spring pin 2 and the fork 1.

2. The operating mechanism as claimed in claim 1, wherein when fork 1 move towards ON position, the spring pin 2 is adapted to slide on at least one side plate surface 4a on side plate 4 as a result of the cam action between the fork 1 and the spring pin 2 thereby enabling an expansion of spring 3.

3. The operating mechanism as claimed in claim 1 and 2, wherein in response to a pushing of the knob 1d towards ON position, the spring pin 2 is adapted to escape from the notch 1b as a result of farther sliding of spring pin 2 on the surface 4a of side plate 4 and rest into the slot 1c on fork 1.

4. The operating mechanism as claimed in any of the preceding claims, wherein the spring pin 2 is adapted to retain the position in the slot 1c on the fork 1 as the notch 1b and the springs 3 assembled on the spring pin 2 retains the tension.

5. The operating mechanism as claimed in any of the preceding claims, wherein the profile 1a is provided on both sides of the fork 1.