Claims:We Claim:

1. A safety shutter for a withdrawable circuit breaker (10) being mounted in a withdrawable unit (11), the safety shutter comprising of:

a insertion shutter (13) riveted on a right side plate (2.1) of the withdrawable unit (11) using a insertion shutter rivet (18), the insertion shutter (13) having a insertion shutter cam (13.1) and a insertion retention spring (19), wherein the insertion shutter (13) controls the insertion of the withdrawable circuit breaker (10) within the withdrawable unit (11);
a removal shutter (14) riveted on a left side plate (3) of the withdrawable unit (11) using a removal shutter rivet (20), the removal shutter (14) having a removal shutter cam (14.1), wherein the removal shutter cam (14.1) self actuates and holds and locks the withdrawable circuit breaker (10) after insertion within the withdrawable unit (11); and
a handle shutter (15) riveted to a ROM plate (21) using a handle shutter rivet (22), the handle shutter (15) having a handle shutter cam (15.1), wherein a cam action between the handle shutter cam (15.1) and a ROM rack (23) allows or prevents insertion of a handle (16) based on the relative condition of the withdrawable circuit breaker (10) such that it prevents insertion of the handle (16) when the withdrawable circuit breaker (10) is in ON condition; and
wherein the handle (16) is further provided with a handle cam (2.1.2), the handle cam (2.1.2) prevents the withdrawable circuit breaker (10) from being switched ON during racking between test to connected position and vice-versa, such that the handle cam profile (2.1.2) is built in the right side plate (2.1) when the withdrawable circuit breaker (10) is in ON condition restricting movement of the withdrawable circuit breaker (10), thereby reducing chances of contacting live parts and safeguarding the operating personnel and the withdrawable circuit breaker (10) from potential hazards.

2. The safety shutter for the withdrawable circuit breaker (10) as claimed in claim 1, wherein the insertion shutter (13) blocks the entry of the withdrawable circuit breaker (10) when the nut block (2.6) of a crank assembly (not numbered) is in intermediate position and allows insertion of the withdrawable circuit breaker (10) into the withdrawable unit (11) when the nut block (2.6) is retracted to its initial position by rotating the handle (16).

3. The safety shutter for the withdrawable circuit breaker (10) as claimed in claim 1, wherein the removal shutter (14) prevents collapsing of the withdrawable circuit breaker (10) from the withdrawable unit (11) when the withdrawable circuit breaker (10) is in disconnected position relative to the switchboard (not shown) and wherein sliding of the removal shutter cam (14.1) outwards releases the withdrawable circuit breaker (10) from the withdrawable unit (11).

4. The safety shutter for the withdrawable circuit breaker (10) as claimed in claim 1, wherein the removal shutter (14) is riveted to the left side plate (3) using a pop rivet.

5. The safety shutter for the withdrawable circuit breaker (10) as claimed in claim 1, wherein the handle shutter (15) is riveted on ROM plate (21) using a handle shutter rivet (22), and wherein the ROM plate (21) is fixed onto ROM (17) using screws and is further assembled and fastened onto the withdrawable circuit breaker (10) thereby making an integrated unit
, Description:SAFETY SHUTTER FOR WITHDRAWABLE CIRCUIT BREAKER

Field of the Invention

The present invention relates to protection devices for draw-out type circuit breakers. More particularly, the present invention provides a safety shutter for draw-out type circuit breakers to safe guard the system and the user while insertion and removal of the circuit breaker.

Background of the Invention

Circuit breakers are usually stationary mounted to the structural members or frame of the switchboard typically with terminal electrical connection effected via bolted joints. In such stationary installations, inspection and maintenance of the circuit breaker is difficult and quite hazardous if attempted while the switchboard is live. To overcome this difficulty, these circuit breakers are often installed in draw-out enclosures (withdrawable unit, or modules) that allow removal and interchange without dismantling the switchgear.

Withdrawable unit (Draw-out module) is an arrangement well known in the art, which is used to connect, test, and disconnect the circuit breaker or MCCB (Molded Case Circuit Breakers) to the main bus without unbolt or disturbing the termination. Draw-out apparatus are typically designed to support the electrical device for racking movement between an extended position well out of a switchboard and an engaged position within the switchboard where the load current carrying primary contacts of the device and switchboard are fully engaged. Since electrical devices, such as circuit breakers for industrial applications, are typically equipped with a variety of accessorial functions served by external auxiliary circuits, provisions must be made for making and breaking these auxiliary circuits as the device is moved between its extended and engaged positions. To this end, so-called mating secondary disconnect contacts are mounted with the device and the switchboard. These secondary disconnects are engaged while the device is in the engaged position and become disengaged at some point during movement of the device out to the disengaged position. It is common practice to provide a test position for the device intermediate it’s engaged and extended positions where the primary contacts are separated but the secondary contacts are still engaged. In this test position, the accessorial functions can be thoroughly tested in safety while the device itself is not electrically connected.

Hence, with the help of withdrawable mechanism, the MCCB is connected to the 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 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. IN a draw-out module, three positions are provided to show the operator where the MCCB is present - they are ‘DISCONNECTION’ wherein both auxiliary connections and power connections are not connected, ‘TEST’ wherein auxiliary connections are only connected but not power supply and ‘CONNECTION’ wherein both auxiliary connections and power connections are established. In the ‘TEST’ position, the auxiliaries are able to be tested alone while the circuit breaker or MCCB is not electrically connected. The MCCB should be in tripped position so that safety operation is possible during draw-out operation. However, while using such draw-out type arrangements, safety of an operator and protection to the equipments is a major concern in the industrial segments without compromise in their downtime.
US 4051335 A entitled “Switchboard draw out having trip interlock and position indicating apparatus” describes a draw out apparatus which 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. There are certain deficiencies associated with the existing patent and other prior arts. The patent does not disclose any safety mechanisms to protect the personnel from danger when the circuit breaker is between the connected position and fully drawn-out position. Further, no security means is provided to prevent insertion of circuit breaker when at intermediate position, in turn increasing the chances of touching the live contacts while racking by the personnel. Also, imprecise position of nut block affects the functionality of draw-out module at the time of insertion of MCCB. Further, the MCCB when in disconnected position may fall down from the cradle (or fixed part) due to vibration. Also, insertion of handle is possible even in breaker-ON and TRIP condition.

Accordingly, there exists a need to provide a safety mechanism for a draw-out apparatus which overcomes the drawbacks of the prior art and ensures safety of the operating personnel while performing withdrawable unit operations at different positions.

Objects of the invention

The primary object of the present invention is to ensure safety of the operating personnel while insertion and removal of the circuit breaker from the cradle or fixed part.

Another object of the present invention is to prevent insertion of circuit breaker when at intermediate position thereby reducing the chances of touching the live contacts by the operating personnel.

Yet another object of the present invention is to ensure protection of the circuit breaker from damage caused during insertion and removal of the circuit breaker from the cradle.

Still another object of the present invention is to prevent falling down of the circuit breaker from the cradle due to vibrations.

Summary of the invention

The present invention provides safety provisions for a draw-out type apparatus that permits an easy maintenance and inspection. The safety provision ensures safety of the operating personnel and the withdrawable circuit breaker while insertion and removal operation of the withdrawable circuit breaker from the withdrawable unit. According to the present invention, the safety provisions consists of three safety shutters provided for a withdrawable circuit breaker for safety of the operating personnel and the withdrawable circuit breaker. The three safety shutters includes an insertion shutter, a removal shutter and a handle shutter. The insertion shutter having a insertion shutter cam and a insertion retention spring is riveted on a right side plate of the withdrawable unit using a insertion shutter rivet, whereas the removal shutter having a removal shutter cam is riveted on a left side plate of the withdrawable unit using a removal shutter rivet, particularly a pop rivet. The handle shutter having a handle shutter cam is configured onto the withdrawable circuit breaker using a handle shutter rivet. Particularly, the handle shutter is riveted on a ROM plate using a handle shutter rivet, and wherein the ROM plate is fixed onto ROM using screws and is further assembled and fastened onto the withdrawable circuit breaker thereby making an integrated unit.

Specifically, the insertion shutter ensures a nut block of a crank assembly is in disconnected position, before inserting the withdrawable circuit breaker into the withdrawable unit; the removal shutter prevents collapsing of the withdrawable circuit breaker from the withdrawable unit when in disconnected position by holding and locking the withdrawable circuit breaker after insertion within the withdrawable unit; and the handle shutter prevents insertion of a handle when the withdrawable circuit breaker is in ON (connected) condition. The cam between the handle shutter and the ROM rack decides the handle insertion and blocking, based upon the withdrawable circuit breaker condition. The withdrawable circuit breaker cannot be switched ON when racking between test to connected position and vice-versa using Cam profile is built in the right side plate of the withdrawable unit.

Brief description of the drawings

Figure 1 shows a withdrawable circuit breaker in rack-in or connected position;

Figure 2 shows a withdrawable circuit breaker in rack-out or disconnected position;

Figure 3 shows a perspective side view of a Breaker unit;

Figure 4 shows a perspective view of a screw rod assembly on right side plate with Insertion shutter assembled;

Figure 5 shows a front view of an insertion shutter, in accordance with the present invention;

Figure 6 shows a perspective view of a removal shutter, in accordance with the present invention;

Figure 7 shows a top view of a handle shutter, in accordance with the present invention;

Figure 8 is a side view of an insertion shutter, blocking insertion of the breaker unit in the withdrawable unit, in accordance with the present invention;

Figure 9 is a perspective view showing the insertion and movement of the breaker unit to disconnected position within the withdrawable unit, in accordance with the present invention;

Figure 10 shows a perspective view of the removal shutter assembled onto the left side plate of the withdrawable unit, in accordance with the present invention;

Figure 11 shows a perspective view of the removal shutter holding the rear plate of the breaker unit at disconnected position within the withdrawable unit, in accordance with the present invention;

Figure 12 shows a perspective view of ROM with handle shutter assembled, in accordance with the present invention;

Figure 13 shows a sectional view of the ROM with handle shutter assembled, in accordance with the present invention;

Figure 14 shows a perspective view of a handle shutter preventing insertion of the handle when the withdrawable circuit breaker is in ON condition;

Figure 15 shows a perspective view of the inserted handle, wherein a handle cam prevents the withdrawable circuit breaker to switch ON.

Detailed description of the present invention

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

Accordingly, the present invention provides safety shutters for a withdrawable circuit breaker. The safety shutters ensures safety of the operating personnel and the withdrawable circuit breaker, and consists of three safety shutters- an insertion shutter and a removal shutter built within the withdrawable unit, and a handle shutter secured onto the withdrawable circuit breaker. The term ‘withdrawable unit’ may be alternatively referred to a ‘draw-out type apparatus’ or a ‘draw-out module’ throughout the description.

This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring to figure 1 and 2, shown is the perspective view of the withdrawable circuit breaker (10) in two different positions- rack-in or connected state and rack-out or disconnected state with respect to the switchboard (not shown). The withdrawable circuit breaker (10) is alternatively referred as “the breaker unit (10)” throughout the specification. In an embodiment, the withdrawable unit (11) is adapted to support the withdrawable circuit breaker (10) for racking movement between extended and engaged positions with respect to the switchboard (not shown). In fully engaged state, alternatively referred as the ‘connected state or position’, primary and secondary contacts of the withdrawable circuit breaker (10) mate with the complementary primary and secondary contacts of the switchboard (not shown) incident to racking movement of the breaker unit (10) within the withdrawable unit (11) to its innermost, engaged position thereby making the electrical joints requisite to electrically connecting the withdrawable circuit breaker (10) into the switchboard (not shown). In extended position, alternatively referred to as the ‘disconnected state or position’, the withdrawable circuit breaker (10) is electrically disconnected to the switchboard (not shown).

Referring to figure 3, the breaker unit (10) comprises of a back plate assembly consisting of a split back plate left (5), a split back plate right (4) and a rear plate (not numbered). The split back plate left (5) and split back plate right (4) each further includes atleast one position pin (7) and atleast one guide pin (9). In a preferred embodiment, the breaker unit (10) includes three position pins (7) and four guide pins (9). Further, atleast one hook (6) is provided on the rear plate (not numbered) of the withdrawable circuit breaker (10). In a preferred embodiment, the withdrawable circuit breaker (10) is provided with two hooks (6). Particularly, the breaker unit (10) is a molded case circuit breaker (MCCB). However, it is evident to those skilled in the art that any other type of withdrawable circuit breaker (10) can be used.

Accordingly, the withdrawable unit (11) consists of a plug-in base (1), a right side plate (2.1) and a left side plate (3) fastened and secured to the plug-in base (1) therein. In an embodiment, the right side plate (2.1) and the left side plate (3) have build-in cuts or slots to provide rails (not shown) for the withdrawable circuit breaker (10) to slide in and out of the withdrawable unit (11). Particularly, the right side plate (2.1) and the left side plate (3) is provided with guideways (2.1.1, 3.1) respectively, for allowing sliding or racking movement of the breaker unit (10) within the withdrawable unit (11) thereby moving the breaker unit (10) between a connected position, test position and a disconnected position with respect to the switchboard (not shown).

As shown in figure 4, a screw rod assembly (not numbered) is provided and is hinged to the right side plate (2.1) of the withdrawable unit (11). The screw rod assembly (not numbered) includes a detachable handle (16), a screw rod (2.2), a screw lock (2.3), a nut block (2.6), a rotary sub-system (2.4), a blocker sub-system (2.5), and a push button (not numbered). Particularly, in operation, the withdrawable circuit breaker (10) is moved from disconnected position, to test position and connected position relative to the switchboard (not shown) by means of the screw rod assembly (not numbered), operated by the detachable handle (16). More particularly, rotating the handle (16), rotates the screw rod (2.2) thereby allowing movement of the withdrawable circuit breaker (10) from disconnected (OFF) position to test position wherein the screw lock (2.3) prevents further movement of the withdrawable circuit breaker (10) relative to the withdrawable unit (11) on reaching the desired position. Further, pressing and releasing the push button (not numbered) actuates the releasing pin (not numbered) of the rotary sub-system (2.4) rotating clockwise, and the balancing blocker (not shown) of the blocker sub-system (2.5) is retained back to its position by a balancing spring (not numbered) through a push button lever (not shown) to release the screw lock (2.3) thereby bringing the withdrawable circuit breaker (10) back to its initial position.

Referring to figure 5, 6 and 7, in accordance with the present invention, the withdrawable unit (11) and the breaker unit (10) is provided with safety provisions including safety shutters to ensure safety of the operating personnel and the breaker unit(10) while connecting and disconnecting the breaker unit (10) onto the switchboard (not shown). Particularly, the safety provision consists of three safety shutters and includes an insertion shutter (13), a removal shutter (14) and a handle shutter (15). More particularly, the right side plate (2.1) of the withdrawable unit (11) is provided with the insertion shutter (13), and the left side plate (3) of the withdrawable unit (11) is provided with the removal shutter (14). The handle shutter (15) is provided and is securely fastened onto the breaker unit (10). Specifically, the insertion shutter (13) has a cam surface (13.1), the removal shutter (14) has a cam surface (14.1) and the handle shutter has a cam surface (15).

Now, referring to figure 8, shown is the side view of the insertion shutter (13) blocking the insertion of the breaker unit (10) into the withdrawable unit (11). The insertion shutter (13) is provided and is riveted to the right side plate (2.1) using an insertion shutter rivet (18). Further, an insertion retention spring (19) is attached between the right side plate (2.1) and the insertion shutter (13) to retain its position. The insertion shutter (13) ensures that the nut block (2.6) is in disconnected position at the time of insertion of the withdrawable circuit breaker (10) into the withdrawable unit (11), since the in-precise position of the nut block (2.6) affects the functionality of the withdrawable unit (11). In an embodiment, the insertion shutter (13) has a cam surface (13.1). As shown in figure 8, when the nut block (2.6) is in intermediate position, action of the cam surface (13.1) between the nut block (2.6) and the insertion shutter (13) blocks and prevents the entry of the breaker unit (10) into the withdrawable unit (11). The handle (16) is rotated to bring the nut block (2.6) to its initial position, so that the cam surface (13.1) actuates the insertion shutter (13) to move away from the insertion slot (not shown) thereby making a way for insertion of the breaker unit (10) within the withdrawable unit (11) and further allowing it to reach the disconnected position relative to the switchboard (not shown), as shown in figure 9. During this time, the insertion retention spring (19) is also charged to regain energy, wherein the energy is utilized for movement of the insertion shutter (13) again towards the insertion slot (not shown) when the nut block (2.6) moves from its initial position.

Referring to figure 10, the removal shutter (14) is further provided within the withdrawable unit (11) to prevent falling of the breaker unit(10) from the withdrawable unit (11) when the breaker unit (10) is in disconnected position relative to the switchboard (not shown). The removal shutter (14) is riveted to the left side plate (3) of the withdrawable unit (11) using removal shutter rivet (20), specifically a pop rivet. The removal shutter (14) holds the withdrawable circuit breaker (10) by holding the rear plate (not numbered) of the withdrawable circuit breaker (10) when at disconnected position, and thereby prevents falling of the withdrawable circuit breaker (10) from the withdrawable unit (11) as can be seen from figure 11. In an embodiment, the removal shutter (14) has a cam surface (14.1), that self actuates during insertion of the withdrawable circuit breaker (10) into the withdrawable unit (11) thereby making the removal shutter (14) to move outwards in turn locking the withdrawable circuit breaker (10) using the cam surface (14.1) at the disconnected position within the withdrawable unit (11). Particularly, sliding the removal shutter (14) outwards, releases the withdrawable circuit breaker (10) from the withdrawable unit (11). The removal shutter (14) adds an additional level of safety to safeguard the operative person and the withdrawable circuit breaker (10) against damage caused due to human error.

The handle shutter (15) is further provided, and is fixed to the breaker unit (10) for preventing insertion of the handle (16) when the breaker unit (10) is in ON condition. As shown in figure 12 and 13, the handle shutter (15) is riveted to ROM plate (21) using handle shutter rivet (22), which is further fixed to ROM (17) using screws, and is in turn assembled and fastened to the withdrawable circuit breaker (10) thereby making an integrated unit altogether. In an embodiment, the handle shutter (15) has a cam surface (15.1) wherein the cam surface (15.1) and ROM rack (23) is built in ROM (17), and allows or prevents insertion of the handle (16) based on the relative position of the breaker unit (10). When the breaker unit (10) is in OFF condition, positions of the handle shutter cam (15.1) and the ROM rack (23), allows insertion of the handle (16), as shown in figure 13. Further, when the breaker unit (10) is in ON condition, the handle shutter (15) prevents insertion of the handle (16), as can be seen from figure 14. Once the handle (16) is inserted, the movement of the breaker unit (10) from OFF to ON state by rotating the handle (16) is further based on position of the handle cam (2.1.2).

As shown in figure 15, movement of the breaker unit (10) from OFF to ON state is blocked or prevented depending on the position of the handle cam (2.1.2). Thus, the handle shutter (15) and the handle cam (2.1.2) prevents the handle (16) insertion and rotation when the breaker unit (10) is in ON condition, thereby reducing the chances of contacting live parts and creating hazards to the operative personnel and the withdrawable circuit breaker (10).

Advantages of the invention

1. The present invention ensures safety of the operating personnel and the withdrawable circuit breaker (10).
2. The insertion shutter (13) ensures that insertion of the withdrawable circuit breaker (10) is allowed only when the nut block (2.6) is in disconnected position, since imprecise position of the nut block (2.6) at the time of insertion of the withdrawable circuit breaker (10) affects functionality of the withdrawable unit (11).
3. The removal shutter (14) prevents falling down of the withdrawable circuit breaker (10) from the withdrawable unit (11) due to vibrations and requires the operating personnel to intently press the removal shutter (14) outwards for removing the withdrawable circuit breaker (10) from the withdrawable unit (11).
4. The handle shutter (15) ensures that insertion of the handle (16) is possible only when the breaker unit (10) is in OFF condition.
5. The present invention is suitable for Molded Case Circuit Breakers (MCCB) and also to Air Circuit Breakers (ACB).
6. The safety shutters including the insertion shutter (13), the removal shutter (14) and the handle shutter (15) are easily accessible even in unexpected conditions.
7. Chances to touch the live contacts are reduced thereby reducing the potential hazards to the operating personnel.
8. The present invention does not require any additional rails to ease the insertion or removal of the breaker unit (10) from the withdrawable unit (11).
9. Breaker unit (10) cannot be operated when racking between test position to connected position and vice-versa.
10. Right side plate (2.1) handle cam (2.1.2) act as an interlock by seizing the handle shutter (15) which prevents unnecessary breaker unit (10) operation.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.