DESC:TECHNICAL FIELD

[001] The present subject matter described herein, in general, relates to electrical switching devices specifically to a circuit breaker and more particularly to a spring loaded finger assembly for withdrawal type switching device.

BACKGROUND

[002] An electrical switching device may be defined as a unit designed to connect, carry and disconnect electrical supply so as to protectequipment’s connected in the electrical circuit from damage caused by overload, under-voltage or short circuit etc. Air circuit breaker is a switching device designed to make, carry and break the circuit. The main contact system of the air circuit breaker consists of a moving terminal and a fixed terminal. Energy is stored in a suitable mechanism which is utilized to join the moving terminal with the fixed terminal and thereby close the circuit. Under normal operating conditions the circuit will remain closed. Circuit breaker also has a tripping mechanism to open the circuit. Opening of the circuit can be done intentionally by the operator or can happen automatically during an abnormal electrical condition like overload, under voltage or short circuit.

[003] Switching devices can be segregated into two main categories based on the functionality to shift the device. They are fixed type switching devices and draw out type switching devices. Fixed type devices will be mounted on a suitable framework to facilitate the working of the device, it will remain connected to the framework throughout the operational life. A draw out type device will be loaded on a cradle made of suitable material and sufficient mechanical arrangements will be provided in the cradle to facilitate the movement of the breaker inside the cradle. Cradle will be fixed to a suitable framework for enabling the functionality of the switching device. There are 3 main positions for the switching device inside a cradle, they are connected, test and disconnected positions. Racking-in is the operation of moving the device from disconnect position to test position and eventually to connected position. Racking-out is the operation of moving the device from connected to test and eventually to disconnected position. In disconnected and test positions terminals of the device and the cradle will be electrically isolated. The invention discussed here is used to connect the terminals of the device to terminals of the cradle during connected position using fingers of conductor loaded with spring force to provide adequate contact pressure at the joints. Providing a conductive path with less resistance to the flow electric current between cradle and device terminals is critical in a withdraw type switching device as the mechanical joints formed by these conductors will play a crucial role in the heat generation of the device and heat flow in the system during normal operation and stability of the device during an abnormal electrical condition like short circuit.

[004] The prior-art document US 4486636 discloses a break contact arrangement for pullout-type switchgear. A break contact arrangement is disclosed in which contact segments are spaced by the arms of the spacer. The contact forces are supplied by one piece springs which have spring arms for each contact segment. However, the prior-art document discloses use of multiple components and requires secondary processes for manufacturing the assembly.

SUMMARY OF THE INVENTION

[005] 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.

[006] The mainobject of the present invention is to provide an apparatus incorporating a set of conductors which are loaded by a spring, for the purpose of providing a conductive path between terminals of a draw-out type switching device and terminals of the enclosure of the switching device.

[007] Another object of the present invention is to provide and ensure a low resistance conductive path between switching device terminals and cradle terminals while facilitating the racking-in and racking-out operations of a switching device.

[008] Another object of the present invention is to eliminate the variation in contact pressure due to change in spring compression due to variations in assembly dimension.

[009] Yet another object of the present invention is to eliminate the phenomenon of heat production in jaw assembly and eventual overheating of jaw assembly.

[0010] Yet another object of the present invention is to provide a design of components used to provide and ensure appropriate contact pressure between switching device and cradle.

[0011] Yet another object of the present invention is to provide a design of components that facilitates assembly of fingers, springs and comb without using any hardware.

[0012] Yet another object of the present invention is to provide a single component holds the springs and ensures proper contact pressure on the fingers during the connected position and hence reduces resistance at the joints.

[0013] Still another object of the present invention is to provide at least one component that reduces temperature rise as open type construction of jaw assembly enables high convection rate.

[0014] In one implementation, the present invention provides jaw comb (1), jaw finger (3), jaw assembly spring (2). Jaw assembly is fixed in the cradle assembly (8)using terminal supports (6). Jaw assembly connects air circuit breaker terminal (4) to cradle terminal (7).

[0015] Accordingly, in one implementation, a component to be used between at least one switching device and at least on cradle assembly comprises at least one contact finger (3) having at least one projection at one side and at least one slot at the opposite side, wherein the contact finger (3) is adapted to trap in at least one jaw assembly (1) and communicate with at least one contact spring (2) using the projections.

[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 illustratesthe jaw assembly with jaw comb (1), jaw fingers (3) and contact springs (2), in accordance with the subject matter of the present invention.

[0018] Figure 2 illustrates the jaw comb with protrusion to act as guiding for contact springs and extension to prevent sway motion of the jaw fingers (3), in accordance with the subject matter of the present invention.

[0019] Figure 3 illustrates the contact finger, in accordance with the subject matter of the present invention.

[0020] Figure 4 illustrates withdraw type air circuit breaker (8) is placed inside a cradle assembly (9)and movement of breaker is facilitated in the cradle from disconnected position to connected position, in accordance with the subject matter of the present invention.

[0021] Figure 5 illustrates withdraw type air circuit breaker (8) is placed inside a cradle assembly (9), in accordance with the subject matter of the present invention.

[0022] 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

[0023] 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.

[0024] 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.

[0025] 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.

[0026] It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] In one implementation, the present invention provides a jaw comb (1), jaw finger (3), jaw assembly spring (2). Jaw assembly is fixed in the cradle assembly (8)using terminal supports (6). Jaw assembly connects air circuit breaker terminal (4) to cradle terminal (7).

[0031] A withdraw type air circuit breaker (8) is placed inside a cradle assembly (9) and movement of breaker is facilitated in the cradle from disconnected position to connected position and vice versa. At connected position top terminal (4) and the bottom terminal (5) of the switching device will be connected to the terminal of the cradle (7) using the jaw contact assembly. Jaw contact assembly consist of jaw comb (1) which is the back bone of the jaw assembly providing support for the jaw fingers (3) and contact springs (2). In the cradle assembly (9) cradle terminals (7) are fixed with the use of terminal supports (6). In disconnected and test positions breaker terminal (4) will be isolated from jaw assembly. The breaker terminal (4) will push the finger assembly (3) apart as the breaker is racked-in, there by compressing the contact spring (2) and producing contact pressure.

[0032] At connected position breaker terminal (4) will get trapped inside the jaw finger assembly (3) and an electrical contact is established between breaker terminal (4) and jaw finger (3).Cradle terminal can be connected to conductors and bus bar system so as to connect the breaker to an electrical system. The greatest advantage of this system is the possibility to rack-out the breaker during maintenance and carry out the necessary works without disturbing the framework to which cradle is connected. It also has an added advantage of providing isolation of breaker from electrical system during maintenance thereby ensuring operator safety.

[0033] The properties of the electrical contact established between breaker terminal (4) and jaw finger (3) greatly affect the performance of the circuit breaker. The resistance of the joint affects the heat production in the jaw assembly. During operational life of the switching device heat will be generated due to the inherent losses and this will lead to variations in jaw comb dimension there by reducing the contact pressure and resulting in over heating in jaw assembly. More over assembly dimension tolerances in multi component jaw comb design will lead to further variations in applied spring force and result in overheating of jaw. Present invention uses a single component as the jaw comb thus eliminating the possibility of variation in assembly dimension and providing consistent contact pressure.

[0034] Referring now to figure 1, shows the jaw assembly with jaw comb (1), jaw fingers (3) and contact springs (2).

[0035] Referring now to figure 2,shows the jaw comb with protrusion to act as guiding for contact springs and extension to prevent sway motion of the jaw fingers (3)

[0036] Referring now to figure 3,shows the contact finger. Small projections in the lower side of the jaw finger trap it in the jaw comb (1).

[0037] Figure 4 illustrates withdraw type air circuit breaker (8) is placed inside a cradle assembly (9)and movement of breaker is facilitated in the cradle from disconnected position to connected position, in accordance with the subject matter of the present invention.

[0038] Figure 5 illustrates withdraw type air circuit breaker (8) is placed inside a cradle assembly (9), in accordance with the subject matter of the present invention.

[0039] Some of the important features of the present invention, considered to be noteworthy are mentioned below:
1. The present invention provides Single component design for jaw comb
2. The present invention provides Ease of assembly
3. The present invention provides consistent performance
4. The present invention Ensures consistent contact pressure
5. Assembly provided in the present invention eliminates the problem of loss of spring force due to change in assembly dimension.
6. The present invention Eliminates overheating of jaw comb.
7. The present invention open type construction of the jaw assembly enables high convection rate for the heat in the device.
,CLAIMS:1. A component to be used between at least one switching device and at least on cradle assembly comprising:
at least one contact finger (3) having at least one projection at one side and at least one slot at the opposite side, wherein the contact finger (3) is adapted to trap in at least one jaw assembly (1) and communicate with at least one contact spring (2) using the projections.

2. The component as claimed in claim 1, wherein a movement of the contact finger (3) is restricted in 2 axes of motion by the jaw assembly (1).

3. The component as claimed in claim 1, wherein the jaw assembly (1) is fixed in the cradle assembly (8) using a terminal support (6).

4. The component as claimed in claim 1, wherein the jaw assembly (1) connects the switching device (4) to a cradle terminal (7) of the cradle assembly (8).