Claims:1. A switch unit assembly for grounding fault electric current in an electrical switching device, comprising:
at least one drive shaft assembly (8, 9, 10, 11, 12, 13, 20, 29, 30, 31) rotatably coupled to said at least one spring assembly (17, 18, 19) to provide a toggle mechanism, wherein said draft shaft assembly actuated to enable said spring assembly to store potential energy;
plurality of movable contact assembly (1, 2, 3, 14, 15, 16) comprises at least one moving blade (1,2,3) and said movable contact assembly movably coupled to said draft shaft assembly (10); and
at least one spring loaded fixed contact assembly (22, 23, 24, 25, 26, 27, 28) coupled to a support insulator (21), wherein said fixed contact assembly comprises said fault electric current;
wherein, during toggle mechanism, said potential energy facilitates engagement of said moving blades (1, 2, 3) of said movable contact assembly with said spring loaded fixed contact assembly (22, 23, 24, 25, 26, 27, 28); and
after toggle mechanism, transmit said fault electric current from said fixed contact assembly to moving contact assembly to drive shaft assembly to ground by means of at least one connector.
2. The switch unit assembly as claimed in claim 1, wherein said drive shaft assembly, said spring assembly and said support insulator, are mounted on a base mechanical structure 4, 5, 6 and 7.
3. The switch unit assembly as claimed in claim 1, wherein said drive shaft assembly comprises multiple bearing assemblies to provide smooth operating and less resistance to said moving blades (1, 2, 3) operation and to provide locking of said drive shaft (10) for lateral movement due to vibration.

4. The switch unit assembly as claimed in claim 1, wherein said moving blades (1, 2, 3) engages with said spring loaded fixed contact assembly (22, 23, 24, 25, 26, 27, 28) by means of plurality of contact fingers (28).
5. The switch unit assembly as claimed in claim 4, wherein said contact fingers comprises at least one nano coating material to reduce probability of arcing and its effect coating.
6. The switch unit assembly as claimed in claim 1, wherein said spring assembly comprises at least one compression spring (17) adapted to store said potential energy.
7. The switch unit assembly as claimed in claim 1, wherein said connector is a copper flexible connector.
8. A method for operating a switch unit assembly as claimed in claims 1-7, said method comprising:
rotating, by applying at least one force in at least one direction, a draft shaft assembly in at least one direction corresponding to direction of force;
generating, at least one toggle mechanism in at least one spring assembly due to rotating draft shaft assembly, and enabling said spring assembly to store potential energy;
engaging, by means of said potential energy, moving blades of moving contact assembly with spring loaded fixed contact assembly, wherein said fixed contact assembly comprises fault electric current;
wherein, after said toggle mechanism, transmitting, by means of at least connector, fault electric current from said fixed contact assembly to moving contact assembly to drive shaft assembly to ground.
, Description:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to an earthing techniques used in switchgear. More particularly, the present invention relates to an efficient spring operated toggle switch assembly for efficient earthing of unwanted electrical charge in switchgear.

BACKGROUND

[002] Earthing is a connection done through a metal link between the body of any electrical appliance, or neutral point, as the case may be, to the deeper ground soil. Earthing is the process of creating an alternative low resistance path for the flow of fault/excessive currents safely into the ground in the presence of minimal resistance. One of the effective ways to do earthing is by using an earth switch. Generally, earthing is carried out by the earth switch in switch gear. The primary purpose of earthing is to reduce the risk of serious electric shock from current dripping into the insulated metal parts of an electrical device. Earthing also protect the electrical devices from large electrical disturbances like lightning strikes and power surges.

[003] The earth switch mainly consists of fixed contacts and moving contacts. In normal "ON" condition of earth switch, these two contacts are physically connected to each other due to applied mechanical pressure on the moving contacts. There is an arrangement to store the potential energy in the operating mechanism of earth switch. The potential energy can be stored in the earth switch by different ways like by compressing or expanding metal spring, by compressed air, or by hydraulic pressure. But whatever the source of potential energy, it must be released during operation. After releasing the stored potentials energy of spring, sliding contact will start moving at a very high speed.

[004] The earth switch has to carry large rated or fault power. Heavy arcing is produced between moving contacts and fixed contact assembly comprises of components, that may include but not limited to bracket for fixed contact assembly, spacer for fixed contact, mounting bracket for contact finger and one or more contact fingers during operation of earth switch due to the large power. Opening and closing distances, as well as stroke between contact and velocity of moving contact during operation are the most important parameters to be considered during designing earth switch mechanism. Arcing time is proportional to the time required to close the moving contacts and fault current to be earthed. When it is required to earth heavy current in known prior art, it leads to limitation of desired closing acceleration of moving blade, special profile of contacting surface, coating to resist and withstand heavy arcing, material with good current carrying capacity and anti-welding properties, limited capacity to earth fault current and limited mechanical life.

[005] Reference is made to US20110078357, provides a compact medium voltage switch unit which comprises interruption and disconnection functions. The interruption unit can rotates around the pivot point (fixed point) to achieve three position. The rotation angle of interruption unit between first and second position and second and third position is between 20° and 30°.

[006] Reference is made to US3627940, provides an earthing switch, in which the movable switching contact is normally driven by a piston. The switch consists of two fixed contacts kept at a distance apart by an insulator, an axially movable hollow switching contact which is earthed. A screwed rod projecting outwards from the cylinder used to mounting of spanner to drive switching rod by handset by the user.

[007] Reference is made to US7122758, provides a switch consists of encapsulated contact, inner contact and housing. The switch is basically used for the application of Gas Insulated Switchgear. The switch used in field of high voltage application.

[008] However, the above mentioned prior art has the following drawbacks:
1. The assembly comprises more number of components. Due to large number of components assembly is very complex in nature.
2. The application US ‘357 enables the Interruption unit itself to be used for disconnecting or earthing purpose. The interruption unit is bulky in nature.
3. In the application US ‘940, the switch requires Pneumatic supply or hydraulic pressure to perform its function.
4. In the application US ‘758, the switch is used for Gas Insulated Switchgear application and is not suitable for AIS applications.

[009] Thus, there exists a dire need to address the hitherto problems of the prior art by providing a spring operated high velocity mechanical toggle switch for grounding electric current.
SUMMARY OF THE INVENTION

[0010] 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.

[0011] An object of the present invention is to provide an improved switch unit assembly with a toggle mechanism for earthing of medium voltage circuit that overcomes the above mentioned drawbacks of the prior art.

[0012] Another object of the present invention is to provide a spring operated high velocity mechanical toggle switch with specialized coating and contact finger assembly for efficient earthing of unwanted electrical charge in switchgear, therefore providing protection and safety to human life with proper grounding of unwanted charge.

[0013] Accordingly to one aspect, the present invention provides a switch unit assembly for grounding fault electric current in an electrical switching device, comprising: at least one drive shaft assembly rotatably coupled to said at least one spring assembly to provide a toggle mechanism, wherein said draft shaft assembly actuated to enable said spring assembly to store potential energy; at least one movable contact assembly comprises at least one moving blade and said movable contact assembly movably coupled to said draft shaft assembly; and at least one spring loaded fixed contact assembly coupled to a support insulator, wherein said fixed contact assembly comprises said fault electric current; wherein, during toggle mechanism, said potential energy facilitates engagement of said moving blades of said movable contact assembly with said spring loaded fixed contact assembly; and after toggle mechanism, transmit said fault electric current from said fixed contact assembly to moving contact assembly to drive shaft assembly to ground by means of at least one connector.

[0014] In another aspect of the present invention, there is provided a method for operating a switch unit assembly as mentioned above, said method comprising:
• rotating, by applying at least one force in at least one direction, a draft shaft assembly in at least one direction corresponding to direction of force;
• generating, at least one toggle mechanism in at least one spring assembly due to rotating draft shaft assembly, and enabling said spring assembly to store potential energy;
• engaging, by means of said potential energy, moving blades of moving contact assembly with spring loaded fixed contact assembly, wherein said fixed contact assembly comprises fault electric current;
wherein, after said toggle mechanism, transmitting, by means of at least connector, fault electric current from said fixed contact assembly to moving contact assembly to drive shaft assembly to ground.

[0015] 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

[0016] 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 structure with spring, blade and drive shaft assembly.
[0018] Figure 2 illustrates a base mechanical structure for mounting the components of the switch unit, in accordance with an embodiment of the present invention.
[0019] Figure 3 illustrates moving blade and bearing assembly mounted on the drive shaft assembly.
[0020] Figure 4 illustrates the spring assembly with a toggle mechanism, in accordance with an embodiment of the present invention.
[0021] Figure 5 illustrates schematic arrangement of complete earth switch with finger assembly in close condition.
[0022] Figure 6 illustrates schematic arrangement of complete earth switch with finger assembly in close condition.
[0023] Figure 7 illustrates schematic arrangement of finger type fixed contact assembly mounted on insulator.
[0024] Figure 8 illustrates schematic arrangement of complete earth switch with pin assembly in close condition.
[0025] Figure 9 illustrates schematic arrangement of pin type fixed contact assembly mounted on insulator.
[0026] Figure 10 illustrates schematic arrangement of spring assembly & drive shaft assembly mounted on base structure.

[0027] 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

[0028] 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.

[0029] 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.

[0030] 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.

[0031] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] It is also to be understood that the term “module” is used in the specification to indicate an apparatus, unit, component and the like. The term “means” when used in the specification is taken to specify the mode by which desired result is achieved. It is to be understood that the term “coupled” is used to define mechanical or electro-mechanical connecting members to hold the components of switch unit assembly in the electrical switching system.

[0036] The present invention can be implemented with an electrical switching system that may include but not limited to, circuit breakers or thermo-magnetic breaker, molded case circuit breaker (MCCB), residual circuit breaker (RCB), earth leakage circuit breaker (ELCB) and the like.

[0037] Reference is made to figures 1-10 which illustrates the following components of the switch unit assembly:
• 1, 2, 3- moving contact assembly
• 4, 5, 6, 7- All the four sides of the base mechanical structure
• 8, 9 – Right hand side drive shaft end plate and pin
• 10 – Drive shaft
• 11, 12 – Support plate for drive shaft and bearing
• 13- Left hand side drive shaft end plate
• 14, 15, 16 – Moving blade support bracket
• 17, 18, 19- Main spring with toggle linkages
• 20 – Lock nut for drive shaft end plate
• 21 - Support insulator
• 22, 23, 24 – Bracket for fixed contact assembly
• 25 – Spacer for fixed contact
• 26 – Mounting bracket for contact finger
• 27 – Pin for spring mounting
• 28 – Contact fingers
• 29 – Cam for drive shaft
• 30 – Pin for connecting cam and rose bearing

[0038] In the present invention, a switch unit assembly is provided for grounding electric current in an electrical switching device. The switch unit assembly comprising: at least one drive shaft assembly (8, 9, 10, 11, 12, 13, 20, 29, 30, 31) which is operably coupled to plurality of movable blades of moving contact assembly (1, 2, 3, 14, 15, 16) and there are multiple bearing assemblies (11, 12) in the drive shaft assembly to provide locking of said drive shaft 10 for lateral movement due to vibration. There are one or more spring assembly (17, 18, 19) coupled with said bearing assembly (11, 12) to provide a toggle mechanism (as shown in figure 4) to store the potential energy of said switch unit assembly. A support insulator 21 coupled to at least one fixed contact assembly (25, 26, 27, 28) and loaded with at least one spring 17, wherein said support insulator 21 adapted to maintain sufficient clearance for high voltage zone from grounded area in said electrical switching device, thereby safeguarding said electrical switching device.

[0039] In one implementation, the switch unit assembly comprises a basic sheet metal structure (4, 5, 6, 7), drive shaft assembly (8, 9, 10, 11, 12, 13, 20, 29, 30, 31) with moving blades (1, 2, 3, 14, 15, 16), spring assembly (17, 18, 19) with toggle mechanism (17, 18, 19, 20, 6, 8, 9, 12) and support insulator 21 with spring loaded fixed contacts (22, 23, 24, 25, 26, 27, 28). Each of the said components of the switch unit assembly is coupled/connected by means of one or more mechanical linkages that may include but not limited to pins, fastener, contact fingers and the like.

[0040] In one implementation, there is a base mechanical structure assembly (as shown in Figure 2), said base structure assembly comprising: a basic sheet metal structure 4, 5, 6, 7 on which different components are to be mounted. There is a drive shaft assembly with moving blades (shown in Figure 3) to be mounted on the structure assembly; a spring assembly with toggle mechanism mounted on base mechanical structure (as Shown in Figure 4); an Insulating support insulator 21 with fixed contact assembly 22, 23, 24, 25 mounted on base mechanical structure 4, 5, 6, 7 for each phase. The insulating support insulator 21 is to maintain sufficient clearance for high voltage zone from grounded area in switchboard, thereby safeguarding switchboard. The drive shaft 10 with bearing assembly 8, 9, 11, 12 for smooth operating and less resistance to moving contact operation. This also provides locking of shaft for lateral movement due to vibration.

[0041] In one implementation, earth switch assembly can be mounted on panel or base structure (4, 5, 6, 7) of a switchboard. Operating arrangement of earth switch assembly by human interface may include but not limited to mechanical linkages, pneumatic arrangement or hydraulic arrangement or combination thereof. Said arrangement may be operatively connected to the drive shaft 10 with the means of pins for connecting cam 30 and cam for drive shaft 29. By applying force on cam for drive shaft 29, drive shaft assembly (8, 9, 10, 11, 12, 13, 20, 29, 30, 31) will start rotating in clockwise or anticlockwise directions based on the direction where the force is applied. Said drive shaft assembly is connected to the spring operated toggle mechanism (17, 18, 19, 20, 6, 8, 9, 12). During rotation of drive shaft 10, end plate 8 of the draft shaft assembly starts rotating and allows compression spring 17 to compress and store energy. At toggle line spring 17 will store maximum energy and same energy is used for closing moving contact 1, 2, 3 with spring loaded fixed contacts (22, 23, 24, 25, 26, 27, 28). After toggle line, moving contacts will travel at a high rotary speed and will get engaged with fixed contact which contains fault current. So, fault current will travel from fixed contact assembly to moving blade & drive shaft assembly to ground with using proper copper flexible connector means.

[0042] In one implementation, the moving blades and the fixed contact assembly is coupled to each other by means of one or more contact finger assembly (28) (as shown in figure 7). It is used for proper engagement with moving blade and allowing fault current to flow from system to ground. It helps in making rigid joint with moving blade and hence complete the circuit to earth.

[0043] In one implementation, the contact finger assembly comprises a specialized nano coating to reduce probability of arcing and its effect coating. Special nano coating comprises of different coating that may include but not limited to silver coating, Tungsten Carbide Carbon coating, aluminum Chromium Nitride coating, Titanium aluminum Nitride coating or any combination thereof.

[0044] In one implementation, contact finger assembly has a profile (28) which helps to withstand arcing produced during fault making. Contact finger 28 profile shown in figure 7, helps in reducing amplitude of arc by changing its concentration on specific area. Said profile will help in arc to travel over smooth profile and eliminate possibility of concentrated high temperature and melting of base material.

[0045] Some of the noteworthy features of the present invention, considered to be noteworthy are mentioned below:

• In the present invention there is an optimized Toggle mechanism switch for earthing of medium voltage circuit.
• The simple toggle mechanism switch is compact in nature, highly suitable for switchgear earthing applications.
• The present invention requires less operating force during manual operation of switch.
• There is a specialized Nano coating on contact finger to reduce probability of arcing and its effect.

[0046] Some of the advantages of the present invention, are as follows:

• The spring unit assembly of the present invention has lesser number of components.
• Compression springs are used to store the energy.
• Simple mechanism (Toggle switch) used to operate switch with does not required wide opening area.
• Very easy manual operation to operating the switch.
• Mechanical structure of the spring unit assembly withstand forces during mechanical and electrical testing.
• Contact finger assembly has profile and design which helps to withstand arcing produced during fault making.

[0047] Although a mechanical toggle switch unit assembly for grounding electric current and a method thereof have been described in language specific to structural features and/or methods, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific features or methods or devices described. Rather, the specific features are disclosed as examples of implementations of the mechanical toggle switch unit assembly for grounding electric current and a method thereof.