CLIAMS:1. A circuit breaker configured to break at least one circuit on occurrence of a short circuit current, the circuit breaker comprising:
a housing configured with at least one fixed contact;
a shaft assembly configured within the housing and comprising at least one module that incorporates at least one moving contact hinged within the at least one module to move and make or break the contact with the at least one fixed contact; the at least one module further comprising at least one compression spring operatively coupled to the at least one moving contact to exert force on the at least one moving contact and provide a contact pressure between the at least one moving contact and the at least one fixed contact; further the at least one module comprises at least one extension spring operatively coupled to the moving contact and configured to provide an additional contact pressure between the at least one moving contact and the at least one fixed contact by its extension force; wherein the at least one compression spring is configured in such a way that torque on the at least one moving contact due to the compression spring reduces as the at least one moving contact moves away from the at least one fixed contact; further wherein the at least one extension spring is configured such a way that the extension force ceases to act on the at least one moving contact as soon as the at least one moving contact breaks contact with the at least one fixed contact to eliminate the additional contact pressure and facilitate rapid opening of the contacts.
2. The circuit breaker of claim 1, wherein at least one module further comprises a block that is configured to hold the at least one moving contact, the at least one compression spring, and the at least one extension spring.
3. The circuit breaker of claim 1, wherein one end of the at least one extension spring is operatively coupled with the at least one moving contact through at least one rotating link that is in engagement with the at least one moving contact transferring the extension force of the at least one extension spring to the at least one moving contact when the at least one moving contact is in contact with at least one fixed contact.
4. The circuit breaker of claim 3, wherein the at least one rotating link loses its engagement with the at least one moving contact as soon as the at least one moving contact breaks contact with the at least one fixed contact to terminate the transfer of the extension force of the at least one extension spring to the at least one moving contact.
5. The circuit breaker of claim 3, wherein the second end of the at least one extension spring is fixed to the block by a pin.
6. The circuit breaker of claim 3, wherein the at least one rotating link incorporates a cam profile that locks with the at least one moving contact when the at least one moving contact is in contact with the at least one fixed contact to enable transfer of the extension force of the at least one extension spring to the at least one moving contact and the moving contact slips out of the cam profile under high electro dynamic repulsive forces during occurrence of short circuit current eliminating the transfer of the extension force from the at least one extension spring on the at least one moving contact.
7. The circuit breaker of claim 1, wherein the at least one compression spring is guided by at least one slider to prevent buckling of the compression spring; further the at least one slider acts to trigger a control mechanism during an abnormal condition.
8. The circuit breaker of claim 1, wherein two ends of the at least one compression spring and hinge point of the at least one moving contact are arranged so that line of action of the force of the at least one compression spring moves closer to the hinge point of the at least one moving contact as the at least one moving contact rotates to move away from the at least one fixed contact thus reducing the torque on the at least one moving contact.
9. The circuit breaker of claim 1, wherein the shaft assembly further comprises at least one coupler link rigidly connected to the shaft assembly and at least one mechanical link with one end of the at least one mechanical link connected to the at least one coupler link and other end connected to a control mechanism.
10. A circuit breaker configured to break at least one circuit during occurrence of short circuit current, the circuit breaker comprising:
a housing configured with at least one fixed contact;
a shaft assembly configured within the housing and comprising at least one module that incorporates at least one moving contact hinged within the at least one module to move and make or break the contact with the at least one fixed contact; the at least one module further comprising a shaft cap and at least one insulating cover wherein the housing, the at least one moving contact, the shaft cap and the at least one insulating cover are matched together to ensure minimal gap between them to prevent high pressure ionized gases from entering the shaft assembly.
,TagSPECI:TECHNICAL FIELD
[0001] The present disclosure relates generally to the field of low voltage power distribution systems. In particular it pertains to a single break drive shaft for current breaking in a circuit breaker.

BACKGROUND
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] Switching devices like, circuit breaker typically employ at least one pair of electrical contacts to carry or interrupt electrical current in the network. Generally one of these contacts is stationary and other one moving. Depending on number of pairs of contacts configured in series, that simultaneously make or break the current the arrangement may be termed as a single break or double break
[0004] Shaft construction enables design of single break arrangement that helps in make & break of a pair of fixed and moving electrical contacts under normal and abnormal conditions. The shaft of the circuit breaker has to be robust to withstand high electro dynamic repulsive forces that develop between the fixed and moving contacts in the event of an over current situation. It also enables multiple switching operations.
[0005] The Switching device should interrupt the over current arising due to abnormal conditions in the network, as rapidly as possible to minimize damage caused by thermal and mechanical stresses to the equipment installed downstream.
[0006] Further during breaking of contacts in the event of short circuit conditions, large resultant current can lead to arcing and generation of high pressure ionized gases. The resultant formation of globules and their deposition on the moving surfaces over a period of time can lead to deterioration in performance of the circuit breaker on account of sluggish movement of the moving contact.
[0007] There is therefore need for a robust shaft construction to provide multiple switching operations at the same time ensuring desired contact pressure, frictionless rotation about its axis, high opening speed of the moving contact and gas sealing of shaft from high pressure ionized gases to ensure good health by avoiding globules entrapment between movable parts. .
[0008] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0009] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term “about.” Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.
[0010] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0011] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0012] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION
[0013] An object of the present disclosure is to provide a robust shaft assembly for a single break circuit breaker that can withstand high electro dynamic repulsive forces during short circuit condition.
[0014] Another object of the present disclosure is to provide a shaft assembly that incorporates modular construction.
[0015] Another object of the present disclosure is to provide a shaft assembly that provides multiple switching.
[0016] Another object of the present disclosure is to provide a shaft assembly that ensures desired contact pressure.
[0017] Another object of the present disclosure is to provide frictionless rotation of the shaft about its axis.
[0018] Another object of the present disclosure is to provide high opening speed of the moving contact.
[0019] Another object of the present disclosure is to provide gas sealing of shaft from high pressure ionized gases to ensure good health by avoiding globules entrapment between movable parts.
[0020] Another object of the present disclosure is to provide shaft and housings that have special geometry to avoid shaft blockage because of globules insertion during heavy fault.
[0021] Another object of the present disclosure is to provide combination of extension and compression springs to provide contact pressure between the fixed and moving contacts.
[0022] Another object of the present disclosure is to provide a configuration of the extension spring that provides zero torque during opening of electrical contacts.
[0023] Another object of the present disclosure is to provide a configuration of the compression spring that provides reduced torque during opening of electrical contacts.

SUMMARY
[0024] Aspects of present disclosure relate to a low voltage single break circuit breaker that incorporates a drive shaft assembly (also referred to as shaft assembly or simply as shaft and all the terms used interchangeably hereinafter) for current breaking. In an aspect the disclosed circuit breaker uses contact based triggering concept to break the contact in the event of occurrence of over current.
[0025] In an embodiment, the drive shaft assembly is of modular construction and comprises of at least one module configured to house a set of moving contacts of one pole, maintain adequate contact pressure between the moving contacts and a set of fixed contacts, rapidly move the set of moving contacts away from the set of fixed contacts in the event of over current and seal the moving parts from the high pressure ionized gases to avoid shaft blockage because of globules insertion during heavy fault.
[0026] In an embodiment, the at least one module can comprise a cylindrical block (also referred to as block hereinafter), at least one moving contact, at least one compression spring, at least one extension spring and a set of sealing means to seal the shaft from high pressure ionized gases generated during heavy fault.
[0027] In an embodiment, the block can be of cylindrical shape and hollow from inside. It can have a diametrical slot that can provide opening for housing the at least one moving contact. In an aspect the at least one moving contact can be hinged and held within the block by means of a pin mounted in an off-center hole in the block.
[0028] In an embodiment, the at least one compression spring can be configured between the at least one moving contact and inside surface of the hollow cylindrical block to exert pressure on the moving contact to generate contact pressure. Each of the compression springs can be guided by a slider to prevent buckling of the compression spring. In addition the slider can also act to trigger the control mechanism during an abnormal condition.
[0029] In an embodiment, the compression springs can be so configured that when the moving contacts move away from the fixed contacts in the event of occurrence of over current situation, the torque generated by the compression spring is reduced even though the compression spring itself gets compressed to exert a higher force. This is achieved by arranging the two ends of the compression spring and hinge point of the moving contact so that the line of action of the force of the compression spring moves closer to the hinge point as the moving contacts rotates to move away from the fixed contact. In an aspect reduced torque on the moving contact can help in rapid opening of the contacts in the event of occurrence of over current situation.
[0030] In an embodiment, the at least one extension spring can be configured between at least one rotating link and a pin housed in the block. The extension spring and the rotating link can be configured to provide a pressure on the moving contact to generate contact pressure when the rotating links are in engagement with the moving contacts. In an aspect, the rotating link can be in engagement with the moving contact when the moving contact is in contact with the fixed contact transferring the extension force of the extension spring to the moving contact generating additional contact pressure between the moving contact and the fixed contact thus ensuring adequate contact pressure between the moving contact and the fixed contact during normal operation.
[0031] In an embodiment, the rotating link is rotationally fixed in the block by means of a pin and incorporates a cam profile that locks with the moving contacts when the moving contact is in contact with the fixed contact thus transferring the pulling force of the extension spring to the moving contact and increasing the contact pressure between the moving contact and the fixed contact at the time when the two are in contact.
[0032] In an embodiment, the moving contact can slip out of the cam profile under high electro dynamic repulsive forces during short circuit condition thus eliminating the pressure from the extension springs on the moving contact. In an aspect, the embodiment helps in rapid opening of the contacts in the event of occurrence of over current situation at the same time provides adequate pressure between the contacts under normal operations.
[0033] In an embodiment, the module can further comprise a shaft cap screwed to the block and configured to prevent ingress of high pressure ionized gases generated during separation of contacts in the event of occurrence of short circuit current. The moving contact can be configured to have a circular profile with its center coinciding with axis of rotation of the moving contact and the shaft cap can be configured to maintain a tangentially contact with the circular profile to provide the requisite sealing.
[0034] In an embodiment, the module can further comprise at least one insulating cover arranged with each of the moving contacts configured with a profile that matches the circular profile of the moving contact and assembled along with the moving contact so as to rotate about the same axis as of the moving contact such that the insulating cover along with the shaft cap provide sealing of gap between the moving contacts as also between the moving contacts and side walls of the block.
[0035] In an embodiment, the module can further comprise two cylindrical discs that can be placed on either side of the block. The block and the discs can be held together by means of a pin put through axial holes configured at the center of the block and discs.
[0036] In an embodiment, a plurality of modules can be held together by a single pin through axial holes configured at the center of the block and discs to form a shaft assembly that can do multiple switching operations for more than one pole at the same time. The shaft assembly can be housed in a geometrically compatible housing and connected to control mechanism through a coupler link.
[0037] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components

BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0039] FIG. 1 illustrates an exemplary housing assembly of a circuit breaker configured to house the disclosed shaft in accordance with embodiments of the present disclosure.
[0040] FIG. 2 illustrates an exemplary exploded view of the housing assembly in accordance with embodiments of the present disclosure.
[0041] FIG. 3 illustrates an exemplary schematic diagram of the shaft assembly in accordance with embodiments of the present disclosure.
[0042] FIG. 4A and FIG. 4B illustrate exemplary sectional views of the shaft assembly installed in the housing indicating arrangement of a moving contact, a compression spring and an extension spring in accordance with embodiments of the present disclosure.
[0043] FIG. 5A to FIG. 5D illustrate exemplary schematic diagrams of the moving contact in accordance with embodiments of the present disclosure.
[0044] FIG. 6 illustrates an exemplary schematic diagram of a block that forms a module of the shaft assembly in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION
[0045] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0046] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0047] As used in the description herein and throughout the claims that follow, the meaning of “a,” “an,” and “the” includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of “in” includes “in” and “on” unless the context clearly dictates otherwise.
[0048] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0049] Various terms as used herein are shown below. To the extent a term used in a claim is not defined below, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0050] Embodiments of the present disclosure relate to a low voltage single break circuit breaker that incorporates a shaft assembly for current breaking. In an aspect the disclosed circuit breaker uses contact based triggering concept to break the contact in the event of occurrence of over current. The disclosed shaft assembly can be housed in a geometrically compatible housing and connected to control mechanism through a coupler link.
[0051] In an embodiment, the drive shaft assembly is of modular construction and comprises of at least one module configured to house a set of moving contacts of one pole, maintain adequate contact pressure between the moving contacts and a set of fixed contacts, rapidly move the set of moving contacts away from the set of fixed contacts in the event of over current and seal the moving parts from the high pressure ionized gases to avoid shaft blockage because of globules insertion during heavy fault.
[0052] In an embodiment, a plurality of modules can be held together by a single pin through axial holes configured at the center of the module to form a shaft assembly that can do multiple switching operations for more than one pole at the same time.
[0053] In an embodiment, the module can comprise a cylindrical block, at least one moving contact, at least one compression spring, at least one extension spring and a set of sealing means to seal the shaft from high pressure ionized gases generated during heavy fault. In an aspect plurality of moving contacts along with corresponding number of compression springs, extension springs and sealing means can be used to meet the requirement of current rating of the circuit breaker.
[0054] In an embodiment, the block can be of cylindrical shape and hollow from inside. It can have a diametrical slot that can provide opening for housing the at least one moving contact. In an aspect the at least one moving contact can be hinged and held within the block by means of a pin mounted in an off-center hole in the block.
[0055] In an embodiment, the at least one compression spring can be configured between the at least one moving contact and inside surface of the hollow cylindrical block to exert pressure on the moving contact to generate contact pressure. Each of the compression springs can be guided by a slider to prevent buckling of the compression spring. In addition the slider can also act to trigger the control mechanism during an abnormal condition.
[0056] In an embodiment, the compression springs can be so configured that when the moving contacts move away from the fixed contacts in the event of occurrence of over current situation, the torque generated by the compression spring is reduced even though the compression spring itself gets compressed to exert a higher force. This is achieved by arranging the two ends of the compression spring and hinge point of the moving contact so that the line of action of the force of the compression spring moves closer to the hinge point as the moving contacts rotates to move away from the fixed contact. In an aspect reduced torque on the moving contact can help in rapid opening of the contacts in the event of occurrence of over current situation.
[0057] In an embodiment, the at least one extension spring can be configured between at least one rotating link and a pin housed in the block. The extension spring and the rotating link can be configured to provide a pressure on the moving contact to generate contact pressure when the rotating links are in engagement with the moving contacts. In an aspect, the rotating link can be in engagement with the moving contact when the moving contact is in contact with the fixed contact transferring the extension force of the extension spring to the moving contact generating additional contact pressure between the moving contact and the fixed contact thus ensuring adequate contact pressure between the moving contact and the fixed contact during normal operation.
[0058] In an embodiment, the rotating link is rotationally fixed in the block by means of a pin and incorporates a cam profile that locks with the moving contacts when the moving contact is in contact with the fixed contact thus transferring the pulling force of the extension spring to the moving contact and increasing the contact pressure between the moving contact and the fixed contact at the time when the two are in contact.
[0059] In an embodiment, the moving contact can slip out of the cam profile under high electro dynamic repulsive forces during short circuit condition thus eliminating the pressure from the extension springs on the moving contact. In an aspect, the embodiment helps in rapid opening of the contacts in the event of occurrence of over current situation at the same time provides adequate pressure between the contacts under normal operations.
[0060] In an embodiment, the module can further comprise a shaft cap screwed to the block and configured to prevent ingress of high pressure ionized gases generated during separation of contacts in the event of occurrence of short circuit current. The moving contact can be configured to have a circular profile with its center coinciding with axis of rotation of the moving contact and the shaft cap can be configured to maintain a tangentially contact with the circular profile to provide the requisite sealing.
[0061] In an embodiment, the module can further comprise at least one insulating cover arranged with each of the moving contacts configured with a profile that matches the circular profile of the moving contact and assembled along with the moving contact so as to rotate about the same axis as of the moving contact such that the insulating cover along with the shaft cap provide sealing of gap between the moving contacts as also between the moving contacts and side walls of the block.
[0062] In an embodiment, the module can further comprise two cylindrical discs that can be placed on either side of the block. The block and the discs can be held together by means of a pin put through axial holes configured at the center of the block and discs.
[0063] FIG. 1 illustrates an exemplary housing assembly 100 of a circuit breaker configured to house the disclosed shaft in accordance with embodiments of the present disclosure. The housing can comprise of two parts namely an upper housing 102 and a lower housing 104 with the disclosed shaft assembly (not shown here) held within the two.
[0064] FIG. 2 illustrates an exemplary exploded view 200 of the housing assembly 100 in accordance with embodiments of the present disclosure. As shown the housing assembly 100 can comprise of the upper housing 102, the lower housing 104 and a shaft assembly 202 configured within the two. The disclosed shaft assembly can comprise plurality of moving contacts 204 configured to come in contact with corresponding fixed contacts 214 that can be configured on the lower housing and make multiple circuits. Alternatively the fixed and the moving contacts can get separated and break the circuits. The shaft assembly can have axial protrusions 206 on either end which can be fitted with circular sleeves to work as bearings and help in smooth rotation of the shaft within the housing 100. The upper housing 102 and the lower housing 104 can incorporate corresponding circular cavities 210 and 212 at their two ends to accommodate the sleeves 208.
[0065] FIG. 3 illustrates an exemplary schematic diagram of the shaft assembly 202 in accordance with embodiments of the present disclosure. In an embodiment, the drive shaft assembly 202 can be of modular construction and comprises of at least one module such as 302 configured to house a set of moving contacts 204 of one pole. In an aspect number of moving contacts in each module 302 can depend on the current rating of the circuit breaker. The module 302 can be configured to maintain adequate contact pressure between the moving contacts 204 and the fixed contacts 214, rapidly move moving contacts 204 away from fixed contacts 214 in the event of over current and seal the moving parts from the high pressure ionized gases to avoid shaft blockage because of globules insertion during heavy fault. In an aspect the fixed contacts 214 can correspond in number to the number of at least one module 303 such that there is one fixed contact for each moving contact.
[0066] In an embodiment, a plurality of modules 302 can be held together by a single pin 304 through an axial hole 306 configured at the center of the module 302 to form a shaft assembly 202 that can do multiple switching operations for more than one pole at the same time.
[0067] In an embodiment, the module 302 can comprise a cylindrical block, at least one moving contact 204, at least one compression spring, at least one extension spring and a set of sealing means to seal the shaft from high pressure ionized gases generated during heavy fault. The detailed configuration of these is provided in succeeding paragraphs.
[0068] In an embodiment, the exemplary block 602 illustrated in FIG. 6 can be of hollow cylindrical construction incorporating a diametrical slot from one cylindrical surface through the cylindrical axis to the other cylindrical surface thus forming a front opening 308 (FIG. 3) and a rear opening 604 (FIG. 6). The slotted cylindrical block 602 can have at least two circular surfaces 310 and 312 (FIG. 3) and two plane surface 314 and 316 (C) at the sides.
[0069] Referring to FIG. 6 the block 602 can be is attached with two cylindrical discs 606 and 608 that can be placed on either side of the block 602. The block 602 and the discs 606 and 608 can be held together by means of a pin 304 of FIG. 3 put through axial holes such as 306 (FIG. 3 and FIG. 6) configured at the center of the block 602 and discs 606 and 608. In an aspect combination the block 602 and the discs 606 and 608 can form a single module 302 after assembly with other items.
[0070] In an embodiment, the block 602 can incorporate off-center axially parallel holes such as 318, 320 and 322 as also slots / groves such as 610 and 612 for assembly of different constituent items through corresponding pins such as pins 324, 326 and 328. For example the hole 318 can be used to hold a set of moving contacts 204 by means of the pin 326. In an aspect the block 602 and other parts of the shaft can be made of an insulating material such as but not limited to a thermosetting resin.
[0071] In an embodiment, the shaft assembly 202 can further comprise at least one coupler link 330 connected with shaft assembly 202 at the center of the shaft assembly 202 by the pin 304 through a hole 332 in the coupler link 330. There can be another hole 334 in the coupler link 330 to rigidly hold it along with the shaft assembly 202 by means of the pin 324 through the hole 322. A third hole 338 on the coupler link 330 can be used to connect mechanical link 336 to a control mechanism. In an aspect the coupler link 330 and the mechanical link 336 can be of sheet metal.
[0072] FIG. 4A and FIG. 4B illustrate exemplary sectional views 400 and 450 respectively of the shaft assembly 202 installed in the housing 100 indicating arrangement of a moving contact, a compression spring and an extension spring in accordance with embodiments of the present disclosure. The module 302 can comprise a set of movable contact 204 (elaborated in FIG. 5) held by pin 326 along with insulating covers 406 with rotational freedom, a shaft cap 404, at least one compression spring 408 held between the moving contact and a slot 610 in the block 602. There can be at least one slider 410 configured with the compression spring 408 to guide and prevent the compression spring 408 from buckling. The slider 410 can also act to trigger the control mechanism during an abnormal condition. The module 302 can further comprise at least one extension spring 412 configured between at least one rotating link 414 and a pin 416 housed in the block. The rotating link 414 can be held in the block 602 by a pin 328 and can have freedom to rotate.
[0073] In an embodiment, corresponding surfaces of the block 602, the shaft cap 404 and the housing (102 and 104) are matched together to ensure minimal gap between them for preventing high pressure ionized gases from leaving contact system (the fixed contact 402 and moving contact 204 and moving towards the shaft assembly 202. The shaft cap 404 can be screwed to the block 602. The moving contact 204 can be configured to have a circular profile with its center coinciding with its axis of rotation and the shaft cap 404 can be configured to maintain a tangentially contact with the circular profile to provide the requisite sealing.
[0074] In an embodiment, the insulating cover 406 can be arranged with each of the moving contacts configured with a profile that matches the circular profile of the moving contact 204 and assembled along with the moving contact 204 so as to rotate about the same axis as of the moving contact 204 such that the insulating cover 406 along with the shaft cap 404 provide sealing of gap between the moving contacts as also between the moving contacts 204 and side walls of the block 602.
[0075] In an embodiment, the at least one compression spring 408 configured between the moving contact and inside surface of the hollow cylindrical block can exert pressure on the moving contact 204 to generate contact pressure. Each of the compression springs 408 can be guided by a slider 410 to prevent buckling of the compression spring. In addition the slider can also act to trigger the control mechanism during an abnormal condition.
[0076] In an embodiment, the compression springs 408 can be so configured that when the moving contacts 204 move away from the fixed contacts 402 in the event of occurrence of over current situation, the torque generated by the compression spring 408 is reduced even though the compression spring 408 itself gets compressed to exert a higher force. This is achieved by arranging the two ends of the compression spring 408 and hinge point of the moving contact so that the line of action of the force of the compression spring 408 moves closer to the hinge point as the moving contacts 204 rotates to move away from the fixed contact 402 as can be apparent from comparison of views 400 and 450. In an aspect reduced torque on the moving contact 204 can help in rapid opening of the contacts in the event of occurrence of over current situation.
[0077] In an embodiment, the extension spring 412 configured between the rotating link 414 and the pin 416 can provide a pressure on the moving contact to enhance the contact pressure when the rotating links 414 are in engagement with the moving contacts 204. In an aspect, the rotating link can be in engagement with the moving contact when the moving contact 204 is in contact with the fixed contact transferring the extension force of the extension spring to the moving contact generating additional contact pressure between the moving contact and the fixed contact thus ensuring adequate contact pressure between the moving contact 204 and the fixed contact 402 during normal operation.
[0078] In an embodiment, the rotating link 414 can incorporate a cam profile such as 420 and 422 that locks with the moving contact 204 when the moving contact 204 is in contact with the fixed contact thus transferring the pulling force of the extension spring 412 to the moving contact 204 increasing the contact pressure between the moving contact 204 and the fixed contact 402 at the time when the two are in contact.
[0079] In an embodiment, the moving contact 204 can slip out of the cam profile 420 under high electro dynamic repulsive forces during short circuit condition thus eliminating the pressure from the extension spring 412 on the moving contact 204. In an aspect, the embodiment helps in rapid opening of the contacts in the event of occurrence of over current situation at the same time provides adequate pressure between the contacts under normal operations.
[0080] FIG. 5A to FIG. 5D illustrate exemplary schematic diagrams 500, 525, 550 and 575 indicating constructional details of the moving contact sub assembly in accordance with embodiments of the present disclosure. Moving contact sub-assembly can comprise at least one moving contact 204 (FIG. 5A) and at least one insulating cover 406 (FIG. 5B) configured over it. The moving contact 204 can incorporate circular profile 508 and 510 whose center coincides with axis of rotation of the moving contact 204 so that when the moving contact 204 moves to break contact with the fixed contact 402, these circular profiles 508 and 510 can remain in contact with the shaft cap 404 to provide sealing and prevent ionized gases to enter the shaft 202. The moving contact can further comprise a hole 506 that can be used for its mounting within the block 602 by a pin 326 and can form the axis of rotation of the moving contact 204. The insulating cover 406 can comprise two side walls 512 and 514 that can be parallel to each other and have a profile generally matching the profile of the moving contact 204 to provide an effective sealing. There can be a third wall 516 linking the other two walls 512 and 514. The insulating cover 406 can accommodate a moving contact 204 within it as shown in FIG. 5C and can be mounted within the block 602 along with the moving contact 204.
[0081] As illustrated in FIG. 5D, the moving contact 204 can be connected with a flexible conducting material 502 and then to a flexible conductor fixing block 504 for connecting the moving contact to the terminal contact 418 ( FIG. 4A). Plurality of moving contacts 204 can be stacked together for assembly in the block 602 to form a module 302. In the exemplary module 302 the number of moving contacts is five and can be varied depending on various factors such as current rating of the pole to which the module 302 caters.
[0082] While the foregoing describes various embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope
thereof. The scope of the invention is determined by the claims that follow. The invention is not limited to the described embodiments, versions or examples, which are included to enable a person having ordinary skill in the art to make and use the invention when combined with information and knowledge available to the person having ordinary skill in the art.

ADVANTAGES OF THE INVENTION
[0083] The present disclosure provides a robust shaft assembly for a single break circuit breaker that can withstand high electro dynamic repulsive forces during short circuit condition.
[0084] The present disclosure provides a shaft assembly that incorporates modular construction.
[0085] The present disclosure provides a shaft assembly that provides multiple switching.
[0086] The present disclosure provides a shaft assembly that ensures desired contact pressure.
[0087] The present disclosure provides frictionless rotation of the shaft about its axis.
[0088] The present disclosure provides high opening speed of the moving contact.
[0089] The present disclosure provides gas sealing of shaft from high pressure ionized gases to ensure good health by avoiding globules entrapment between movable parts.
[0090] The present disclosure provides shaft and housings that have special geometry to avoid shaft blockage because of globules insertion during heavy fault.
[0091] The present disclosure provides combination of extension and compression springs to provide contact pressure between the fixed and moving contacts.
[0092] The present disclosure provides a configuration of the extension spring that provides zero torque during opening of electrical contacts.
[0093] The present disclosure provides a configuration of the compression spring that provides reduced torque during opening of electrical contacts.