Claims:WE CLAIM:
1. An auto restored interlocking system (3) for a drawout type device , said system comprising:
a fixed unit (1) and a withdrawable unit (2), wherein
said fixed unit (1) includes
an actuating lever (4) positioned on at least one side of the fixed unit (1); an unlocking lever (6) operably coupled to balancing spring means (12) and biasing spring means (11), pivotally mounted on the actuating lever (4);
said withdrawable unit (2) inlcudes
a locking pin (7) positioned on at least one side of the withdrawable unit (2)
characterised in that the locking pin (7) operably slides along a cam (10) of the actuating lever (4) so as to get engaged in a slot formed in between the unlocking lever (6) and an edge of the actuating lever (4), to engage the fixed unit (1) with the withdrawable unit (2),
the actuating lever (4) when pushed upwards, releases the locking pin (7) from the slot to facilitate disengagement of the withdrawable unit (2) from the fixed unit (1).

2. The interlock system as claimed in claim 1, wherein the unlocking lever (6) is balanced substantially vertically by the balancing spring means (12) during disengagement of the withdrawable unit (2) from the fixed unit (1).

3. The interlock system as claimed in claim 1, wherein the biasing spring means (11) auto restores the position of the actuating lever (4) after disengagement of the withdrawable unit from the fixed unit (1).

4. The interlock system as claimed in claim 1, wherein the locking pin (7) is substantially cylindrical in shape.

5. The interlock system as claimed in claim 1, wherein the fixed unit (1) further comprises of at least one racking rail (9) to engage the withdrawable unit (2).

6. The interlock system as claimed in claim 1, wherein the withdrawable unit (2) further comprises of at least one guide pin (8).

7. The interlock system as claimed in claims 5 and 6, wherein the guide pin (8) is adapted to fit into the racking rails to engage the withdrawable unit with the fixed unit (1).

8. A drawout switchgear comprising an interlock system as claimed in any one of the preceding claims.

Dated this 31st day of March 2018

Abhishek Sen
Of S. MAJUMDAR & CO.
(Applicant’s Agent)

, Description:FIELD OF INVENTION
The present invention pertains to the field of protection devices in general, and, more particularly, to a universal auto restored interlocking mechanism in switchgears.
BACKGROUND
Withdrawable unit (Draw-out module) is an arrangement which is used to connect, test, disconnect the breaker or MCCB to the main bus without unbolt or disturbing the termination. With the help of this mechanism, the MCCB is connected to main and auxiliary supplies. In draw-out module, the plug-in is used as base which is having main contacts. Two types of supplies are in the switchboard. One is the main supply or power supply and auxiliary supply or control supply. The main supply is for breaker and auxiliary supply is for auxiliaries like shunt release, UV release, etc. Three positions are in the draw-out to show the operator where the MCCB is present. They are ‘DISCONNECTION’ (both Auxiliary connections and power connections not connected), ‘TEST’ (Auxiliary connections only connected but not power supply), ‘CONNECTION’ (both Auxiliary connections and power connections established). In the ‘TEST’ position, the auxiliaries are able to be tested alone. The MCCB should be in tripped position so that safety operation is possible during draw-out operation.
Safety of an operator and protection to the equipment is a major concern in the industrial segments without compromise in their downtime. The withdrawable unit consists of plug-in main contacts, withdrawable mechanism, distinct position lock, position indication and safety shutter/ prevention of unconditional operation.
For the safety shutter, there are three safety provision in withdrawable unit i.e., at the time of insertion, removal of the breaker from unit and the last one is to ensure the safety of handle insertion. Insertion shutter ensures the position of nut block to be in disconnected position at the time of breaker insertion into cradle. The removal shutter or disengage lock prevents the falling of breaker from cradle, when breaker is in disconnected position. The handle shutter prevents the insertion of handle when the breaker is in ON condition.
Reference has been made to US 6031192A, relating to arrangement for controlling the movement of a drawout circuit-breaker, mounted in a switchgear, which can be moved in an operating position, test position and disconnect position relative to a drawout frame using an actuating shaft pivoted in the drawout frame and operated by a detachable actuating crank. A controllable closure member enables or prevents the actuating crank from coming into contact with the actuating shaft, and the drawout circuit-breaker can be removed from the drawout frame after a door is opened. Such arrangement is used in low-voltage circuit-breaker equipment. It further discloses to expand the safety precautions for drawout circuit-breakers to include protection of the equipment, keeping the existing construction largely unchanged or implementing additional safety measures with as little additional technical equipment as possible. The invention achieves this goal by allowing the closure member to be controlled by a locking arrangement that is located in the drawout frame and interacts with the drawout circuit-breaker and by a closing cylinder located in the switchgear door in a way that prevents the drawout circuit-breaker from moving in a preferred position, especially in the disconnect position, while allowing the drawout circuit-breaker to be removed from the drawout frame.
Reference has been further made to US4051335A, pertaining to a drawout apparatus includes a carriage mounting a circuit breaker and supported on telescoping rails to facilitate racking movement of the circuit breaker between extreme positions of electrical engagement and disengagement with respect to switchboard primary terminals. Racking movement into the engaged position from an intermediate test position is mechanically assisted by a racking mechanism. While in the engaged position, a joint clamping mechanism is operated to perfect plural breaker-switchboard terminal joints. A trip interlock insures that the circuit breaker can only be closed while in the test position and in the engaged position with terminal joints clamped. Display apparatus indicates the various circuit breaker positions and the clamped condition of the terminal joints.
Yet another reference has been made to US2921998A, disclosing a novel interlock system for controlling and coordinating the operation of the circuit breaker contacts and the racking mechanism. A further feature of the instant invention is to extend the number of positions of the circuit breaker from the normal three positions which are operating, test and disconnected, and add a fourth position which is a withdrawn position where the circuit breaker is carried to a fully withdrawn position with the cubicle door open whereby a simple vertical lift will remove the circuit breaker from the cubicle.
In the general art, the breaker in disconnected position may fall down from cradle due to vibration, requires simultaneous actuation of lever to unlock while disengaging the moving unit from fixed unit, bi-stable position is not there to understand the position lock and they are not reliable in cases of lock as they do not have two positions such as locked and unlocked.
Thus there is a need for an auto restored automatic locking system for withdrawable devices, including drawout switchgears, thereby enhancing the ease of operation and safety of the personnel.
SUMMARY OF THE INVENTION
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.
An object of the present invention is to provide an auto restored interlocking mechanism in switchgears, thereby providing safety to the user and to avoid any inadvertent practices.
An object of the present invention is to provide an auto restored interlocking mechanism in switchgears, locking or interlocking two different units automatically when engaged.
Yet another object of the invention is to provide an auto restored interlocking mechanism in switchgears where manual intervention is required to unlock to disengage both the units.
In accordance with an aspect of the present disclosure, is to provide a auto restored interlocking system for a drawout type device , said system comprising:
a fixed unit and a withdrawable unit , wherein
said fixed unit includes
an actuating lever positioned on at least one side of the fixed unit ; an unlocking lever operably coupled to balancing spring means and biasing spring means, pivotally mounted on the actuating lever;
said withdrawable unit inlcudes
a locking pin positioned on at least one side of the withdrawable unit
characterised in that the locking pin operably slides along a cam of the actuating lever so as to get engaged in a slot formed in between the unlocking lever and an edge of the actuating lever, to engage the fixed unit with the withdrawable unit,
the actuating lever when pushed upwards, releases the locking pin from the slot to facilitate disengagement of the withdrawable unit from the fixed unit.
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 the embodiments of the present disclosure will be more apparent in the following description taken in conjunction with the accompanying drawings, in which:
Figure 1 illustrates a withdrawable unit (draw-out circuit breaker in cradle) constructed in accordance to the invention.
Figure 2 illustrates a perspective view of a cradle or fixed unit o in accordance to the invention.
Figure 3 illustrates perspective view of a Draw-out circuit breaker or moving unit in accordance to the invention.
Figure 4 illustrates perspective view of a moving unit interlocked with fixed unit in accordance to the invention.
Figure 5 illustrates a bi-stable interlock mechanism in accordance to the invention.
Figure 6 illustrates a locking lever in accordance to the invention.
Figure 7 illustrates a bi-stable interlock mechanism - to Unlock in accordance to the invention.
Figure 8 illustrates an unlocking mechanism in accordance to the invention.
Figure 9 illustrates an unlocking lever in accordance to the invention.
Figure 10 illustrates a locking pin or cylindrical member in accordance to the invention.
Figure 11 illustrates units in unlocked position where the lever is restored to its position in accordance to the invention.
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
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.
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 present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.
All terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments belong. Further, the meaning of terms or words used in the specification and the claims should not be limited to the literal or commonly employed sense, but should be construed in accordance with the spirit of the disclosure to most properly describe the present disclosure.
The terminology used herein is for the purpose of describing particular various embodiments only and is not intended to be limiting of various embodiments. As used herein, the singular forms "a," "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising" used herein specify the presence of stated features, integers, steps, operations, members, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, components, and/or groups thereof. Also, Expressions such as "at least one of," when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The present disclosure will now be described more fully with reference to the accompanying drawings, in which various embodiments of the present disclosure are shown. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the various embodiments set forth herein, rather, these various embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the present disclosure. Furthermore, a detailed description of other parts will not be provided not to make the present disclosure unclear. Like reference numerals in the drawings refer to like elements throughout.
The subject invention lies in providing a universal auto restored interlock system for a drawout device.
According to one implementation of the present invention auto restored interlocking system (3) for a drawout type device comprises a fixed unit (1) and a withdrawable unit (2). The fixed unit (1) includes actuating lever (4) which is positioned on at least one side of the fixed unit, an unlocking lever (6) operably coupled to balancing spring means (12) and biasing spring means (11). The unlocking lever (6) is pivoted on the actuating lever (4). The withdrawable unit (2) includes a locking pin (7) positioned on at least one side of the withdrawable unit (2). The locking pin (7) slides along a cam (10) of the actuating lever (4) so as to get engaged in a slot formed in between the unlocking lever (6) and an edge of the actuating lever (4), to engage the fixed unit (1) with the withdrawable unit (2). The actuating lever (4) when pushed upwards, releases the locking pin (7) from the slot to facilitate disengagement of the withdrawable unit (2) from the fixed unit (1).
In an embodiment of the invention, an interlock mechanism (3) is pivoted on to the cradle or fixed unit (1) and the locking pin (7) is fixed on same side of moving unit of draw-out circuit breaker (2). The moving unit (2) with help of element guide (8) is inserted in to the cradle (1) through means of rail (9) as shown in figure 2. The locking pin (7) slides on the cam of locking lever (10), once reaching the position the locking lever (4) latches the locking pin (7) of moving unit (2). Thus the moving unit and fixed are interlocked.
Another embodiment of the invention describes unlocking or disengagement of the moving kit from fixed unit, by pushing up the actuating lever (4) to release the locking pin (7), the balancing lever (6) of unlocking mechanism (5) holds the locking lever (4) in unlocked position until the disengagement of the moving unit (2) from fixed unit (1). After disengagement the position of the locking lever (4) is restored by its biasing spring (11).
Another embodiment of the invention describes the unlocking mechanism (5), where the balancing lever (6) is balanced in the required position with help of the balancing spring (12) at static condition (no external force condition). The pivoted balancing lever (6) rotates with respect to its axis in clockwise or anticlockwise direction when an external force is applied.
In an exemplary embodiment of the invention, draw-out unit of a circuit breaker has three different positions namely disconnected, test and connected, which plugs-in the breaker and draws out from the cradle unit together called withdrawable unit. The cradle consists of plug-in unit, which has female conducting parts in a solid housing called plug-in base. The crank assembly is hinged to the right side plate also inserting a racker in a nut slot in the right side plate assembly which is fastened firmly to the plug-in base. The left side plate is also fastened to the plug-in base. The back plate assembly is fixed to the breaker. The left and right side plates have built-in cuts or slots to provide rails (9) for the breaker to slide in to the draw out unit.
Rack in the breaker unit by means of rotating a handle, which in turns rotate a screw rod, using racker and crank assembly the breaker moves from disconnected position to test position. A push button is pressed and released to actuate the rack in or rack out of the breaker unit from the one position to the other position. The releasing pin of the rotary subsystem rotating clockwise and the balancing blocker is retained back to its position by a balancing spring through a push button lever to release the lock. The working phenomena is same as above for locking at TEST position and the connected position and vice versa.
The disengage latch or safety interlock consists of an actuating cum locking lever (4), unlocking mechanism (5) and a biasing spring (11) for auto restoration. The unlocking mechanism follows a balancing principle, it consists of unlocking or balancing lever (6) pivoted to the locking or actuating lever, and the unlocking lever is balanced vertically by an elastic member called balancing spring (12).
When the moving unit (2) or draw-out breaker is inserted in to the cradle (1), the cylindrical member or locking pin (7), which is part of moving unit (2), rotates or actuates the locking lever (4) anticlockwise by means of cam of locking lever (10). The cylindrical member (7) of the moving unit (2) gets locked or latched once it reaches the desired position, thereby interlocking the fixed unit and the moving unit.
Referring to figure 4, the position of actuating lever or locking lever is always downwards and this position indicates locked condition. The locking lever (4) is moved upwards to unlock the cylindrical member (7) of the moving unit (2). The balancing lever (6) of unlocking mechanism holds the unlocking lever in unlocked position as shown in fig. 7 until the cylindrical member escapes from the locking lever. Thus the moving unit gets unlocked and is free to disengage from the cradle or fixed unit as shown in figure 11. Immediately after disengagement the locking lever restores its position as shown in figure 11.
The unlocking mechanism as shown in figure 8 and a biasing elastic member (11) help in restoring the mechanism. This auto restoration is needed for locking automatically without any manual intervention on mechanism by a user. The moving unit is locked automatically when inserted in to cradle (1).
The actuating lever further comprises of a locking lever pivot (13) and a locking lever guide (14) to facilitate the functioning of the actuating lever (4) during engagement and disengagement of the withdrawable unit (2) from the fixed unit (1).
In all the embodiments of the invention herein above, the fixed unit and the moving unit has been interchangeably used with terms cradle and withdrawable unit respectively.
Some of the non-limiting advantages of the present invention are:
a) Even if push button disengages the position lock for breaker removal in disconnected position, the user has to intently press the removal shutter for breaker removal from rail.
b) The safety mechanism is universal an it is not restrained only for Moulded Case Circuit Breakers (MCCB) and Air Circuit Breakers (ACB).
c) Hassle free operation – no simultaneous action is required.
d) Auto restoration-lever actuated to unlock position to disengage (position will be in unlocked condition unless breaker or moving unit is removed) after disengagement the goes back to locking condition. So that the breaker gets locked once breaker or moving unit is engaged in to fixed unit.
e) Failsafe security or safety is ensured.
f) Since it is bi stable mechanism, for remote indication the electrical signals can be taken from the mechanism.
Although an auto restored interlock system for a drawout devices like switchgear has been described in language specific to structural features, it is to be understood that the embodiments disclosed in the above section are not necessarily limited to the specific methods or devices described herein. Rather, the specific features are disclosed as examples of implementations of an auto restored interlock system for a drawout devices like switchgears.