DESC:Position Indicator Assembly for Draw-out Circuit Breaker

Field of the invention

The present invention relates generally to electrical switching devices and more particularly, to a position indicator assembly for a draw-out circuit breaker.

Background of the invention

An electrical circuit breaker is defined as a unit designed to connect, carry, disconnect and protect equipments connected in an electrical circuit from damage caused by overload, under-voltage or short circuit. There are two popular versions of the circuit breakers namely, a fixed type and a draw-out type. In the draw-out type, the breaker is removed without dismantling terminals in order to facilitate maintenance and secure stability. Unlike the fixed breakers, the draw-out breakers are housed inside a cradle and capable of racked-in and racked-out inside the cradle.

Drawbacks of the prior art:
• The racking arrangement is available without provision of locking and acknowledgement in distinct positions of the draw-out type circuit breakers.
• The switching devices include a manual racking feature operated with the help of a racking handle and there is no provision of motorized racking.

Accordingly, there exists a need to provide a position indicator assembly that achieves position locking of a draw-out circuit breaker in a cradle with a proper indication along with an automatic racking and overcomes the above mentioned drawbacks of the prior art.

Object of the invention
An object of the present invention is to achieve position locking of a draw-out circuit breaker in a cradle with a proper visual indication along with an automatic racking without a manual intervention.

Summary of the invention

Accordingly, the present invention provides a position indicator assembly for a draw-out circuit breaker. The draw-out circuit breaker achieves a service position, a test position and an isolated position inside a cradle during a rack-in operation and a rack-out operation thereof.

The position indicator assembly comprises a housing and a cover. The housing comprises a base, a motor unit, a coupling shaft, a mounted gear member, a driven gear member, a plurality of micro-switches and a pointer enclosed therein.

The base includes a plate vertically attached at an end thereof. The plate includes a first opening, a second opening and a pair of mounting holes configured thereon. The second opening is adapted to mount a shaft therein. The motor unit is mounted on the base.

The coupling shaft at one end is coupled to the motor unit and at another is coupled to a racking screw of the draw-out circuit breaker. The coupling shaft undergoes rotation on receiving an input from the motor unit thereby facilitating motion of the circuit breaker to and fro between the rack-in operation and the rack-out operation.

The mounted gear member is rigidly mounted on the coupling shaft. The mounted gear member undergoes rotation on rotation of the coupling shaft. The mounted gear member includes a projection configured thereon.

The driven gear member is positioned on the shaft mounted in the second opening of the plate. The driven gear member includes a plurality of tooth configured on a circumference thereof and a plurality of pins mounted thereon. The plurality of tooth meshes with the projection of the mounted gear member. The plurality of micro-switches is mounted on the base and capable of being pressed by the plurality of pins during rotation of the driven gear member. The pointer is mounted on a top surface of a rod mounted on the driven gear member in such a way that a tip thereof projects out of the housing. The pointer undergoes rotation on rotation of the driven gear member to provide a visual indication of the test position, the service position and the isolated position of the draw-out circuit breaker.

The cover is mounted on the housing. The cover includes three markings corresponding to the test position, the service position and the isolated position of the draw-out circuit breaker for being indicated by the tip of the pointer.

Brief description of the drawings

Figure 1 shows different positions of a draw-out circuit breaker using a pointer of a position indicator assembly, in accordance with the present invention;

Figure 2 shows a racked-in condition of the draw-out circuit breaker, in accordance with the present invention;

Figure 3 shows a racked-out condition of the draw-out circuit breaker, in accordance with the present invention; and

Figure 4 shows a circuit diagram of the position indicator assembly, in accordance with the present invention.

Detailed description of the 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.

The present invention provides a position indicator assembly (hereinafter “the assembly”) for a draw-out circuit breaker. The assembly facilitates position locking of the draw-out circuit breaker in a cradle with a proper visual indication along with automatic rack-in and rack-out operations without a manual intervention. The assembly defines a way to achieve locking of the draw-out circuit breaker in three cradle positions namely a test condition, a service condition and an isolated condition.

The 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 figures 1-4, a position indicator assembly (100) (hereinafter “the assembly (100)”) for a draw-out circuit breaker (hereinafter “the circuit breaker”) in accordance with the present invention is shown. The circuit breaker (not shown) achieves a service position, a test position and an isolated position inside a cradle (not shown) during a rack-in operation and a rack-out operation thereof.

The assembly (100) comprises a housing (not numbered) and a cover (90). The housing comprises a base (10), a motor unit (20), a coupling shaft (30), a mounted gear member (40), a driven gear member (50), a plurality of micro-switches for example a first micro-switch (52), a second micro-switch (54), a third micro-switch (56), a fourth micro-switch (58), a fifth micro-switch (60) and a sixth micro-switch (62) and a pointer (80) enclosed therein.

The base (10) includes a plate (8) vertically attached at an end (not numbered) thereof. The plate (8) includes a pair of mounting holes (4), a first opening (not numbered) and a second opening (not numbered). The pair of mounting holes (4) is configured on the plate (8). The assembly (100) is fastened on the cradle by fastening on the pair of mounting holes (4). The first opening is adapted to receive the coupling shaft (30). The second opening is adapted to mount a shaft (6) therein.

The motor unit (20) is mounted on the base (10) and drives the coupling shaft (30). The coupling shaft (30) passes through the first opening of the plate (8) and is coupled to the motor unit (20) at one end (not numbered). The coupling shaft (30) at another end (not numbered) is directly coupled to a racking screw (not shown) of the circuit breaker and capable of driving the circuit breaker in any one of an inward direction and an outward direction inside the cradle. In an embodiment, a motorized input drives the coupling shaft (30) whose rotation allows motion of the circuit breaker from the rack-in operation to the rack-out operation and vice versa. At three positions of the circuit breaker namely the test position, the service position and the isolated position, the assembly (100) stops further motion of the circuit breaker and allows the motion to re-start by a user interface. The three positions of the circuit breaker are indicated by the pointer (80) as shown in figure 1.

The mounted gear member (40) is rigidly mounted on the coupling shaft (30) and includes a projection (35) configured thereon. The mounted gear member (40) drives the driven gear member (50) as shown in figures 2 and 3.

The driven gear member (50) is positioned on the shaft (6). The driven gear member (50) includes a plurality of tooth (41) configured on a circumference (not numbered) thereof and a plurality of pins for example a first pin (42), a second pin (44), a third pin (46) and a fourth pin (48) mounted thereon. The plurality of tooth (41) meshes with the projection (35) of the mounted gear member (40). The plurality of pins is adapted to press the plurality of micro-switches. The pointer (80) is positioned on a top surface (not numbered) of a rod (not numbered) mounted on the driven gear member (50) in such a way that a tip (80a) thereof projects out of the housing. The pointer (80) facilitates visual indication of the three positions of the circuit breaker namely the test position, the service position and the isolated position.

The driven gear member (50) during travel from the rack-in operation and the rack-out operation presses the micro switches (58, 60 and 62). Based on a circuit of the micro-switches actuation as shown in figure 4, an operation the motor unit (20) is either stopped or continued as desired in distinct racking positions. The motor unit (20) drives the coupling shaft (30) unless the fourth micro-switch (58) is pressed by the pins (44, 46 and 48) as shown in figures 2 and 3. In extreme positions like the racked-in position and the racked-out position of the circuit breaker, the micro-switches (62 and 60) are pressed to give signal to the motor unit (20) to stop rotation of the coupling shaft (30).

In an embodiment, the first micro-switch (52) is a double pole single throw (DPST), Normally Open (NO) switch, which is the main supply control switch for the entire assembly (100). When a customer/user switches on the first micro-switch (52), NO contacts (1-3 and 2-4) thereof get closed and the circuit is powered up. Depending upon the position of the driven gear member (50), the micro-switches (58, 60 and 62) are actuated. The micro-switches (58, 60 and 62) are single pole double throw (SPDT) switches.

The cover (90) is mounted on the housing. The cover (90) includes three markings corresponding to the test position, the service position and the isolated position of the circuit breaker for being indicated by the tip (80a) of the pointer (80).

As shown in figure 3, when the circuit breaker is in the racked-out position, the fourth pin (48) of the driven gear member (50) keeps the micro-switches (58 and 60) pressed causing an opening of a normally closed (NC) contact (1-2) of the fourth micro-switch (58) thereby preventing the rack-in operation of the circuit breaker to start immediately as the supply to the motor unit (20) is stopped.

Now referring to figure 4, in order to start the rack-in operation, the third micro-switch (56) is pressed momentarily till the motor unit (20) continues to move. As the circuit breaker gets racked-in, the driven gear member (50) moves such that the third pin (46) presses the fourth micro-switch (58) causing the opening of the NC contacts (1-2) of the fourth micro-switch (58) thereby interrupting the supply to the motor unit (20) resulting in the test position. To rack-in the circuit breaker further, again the third micro-switch (56) is pressed momentarily till the circuit breaker starts to move. Pressing the third micro-switch (56) bypasses the opened NC contacts (1-2) of the fourth micro-switch (58).

Upon further rack-in, when the circuit breaker reaches the service position, the micro-switches (58 and 62) are pressed by the second pin (44) of the driven gear member (50) causing the opening of the NC contacts (1-2) of the sixth micro-switch (62) thereby interrupting the supply to the motor unit (20). At this service position, the circuit breaker moves in completely.

To rack-out the circuit breaker, the second micro-switch (54) is toggled to other position. This reverses the winding terminals of the AC synchronous motor unit (20) and also shorts terminals (1-2) of the sixth micro-switch (62). Again, the third micro-switch (54) is pressed momentarily for the circuit breaker to start moving in an opposite direction. The same cycle is repeated till the circuit breaker fully reaches the racked-out position. At this point, the fourth pin (48) actuates the fourth micro-switch (58) and the NC contacts (1-2) of the fourth micro-switch (58) get opened thereby stopping further movement of the circuit breaker. Also, at the same time, the fifth micro-switch (60) is actuated by the fourth pin (48) of the driven gear member (50) thereby stopping further movement of the circuit breaker till the direction of rotation of the motor unit (20) is reversed, that is, the second micro-switch (54) is toggled.

Again, to rack-in the circuit breaker, the second micro-switch (54) is toggled to the other position. This now reverses the motor unit (20) direction and also connects the NC terminals (1-2) of the fifth micro-switch (60) externally. Now, to rack-in the circuit breaker again, the third micro-switch (56) is pressed momentarily and the entire cycle starts again.

Advantages of the invention

1. The assembly (100) provides automatic rack-in and rack- out operations of the circuit breaker thereby enhancing reliability of the operation.
2. The assembly (100) facilitates position locking of the circuit breaker in the cradle at distinct positions followed by the acknowledgement from the user for further racking operation.
3. The assembly (100) works without addition of any new components in a rack as well as the circuit breaker and also does not need any changes to be made in a cradle arrangement.
4. The assembly (100) provides an economical option as same unit is used for different frames and sizes of a switchgear device.

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, and 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 omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

,CLAIMS:We Claim:

1. A position indicator assembly (100) for a draw-out circuit breaker, the draw-out circuit breaker being capable of achieving a service position, a test position and an isolated position inside a cradle during rack-in and rack-out operations thereof, the position indicator assembly (100) comprising:
a housing having,
a base (10) having a plate (8) vertically attached at an end thereof, the plate (8) having a first opening, a second opening and a pair of mounting holes (4) configured thereon, the second opening adapted to mount a shaft (6) therein,
a motor unit (20) mounted on the base (10),
a coupling shaft (30) at one end coupled to the motor unit (20) and at another end coupled to a racking screw of the draw-out circuit breaker, the coupling shaft (30) undergoes rotation on receiving an input from the motor unit (20) thereby facilitating motion of the circuit breaker to and fro between the rack-in operation and the rack-out operation,
a mounted gear member (40) rigidly mounted on the coupling shaft (30), the mounted gear member (40) undergoes rotation on rotation of the coupling shaft (30), the mounted gear member (40) having a projection (35) configured thereon,
a driven gear member (50) positioned on the shaft (6) mounted in the second opening of the plate (8), the driven gear member (50) having a plurality of tooth (41) configured on a circumference thereof and a plurality of pins mounted thereon, the plurality of tooth (41) being capable of meshing with the projection (35) of the mounted gear member (40),
a plurality of micro-switches mounted on the base (10), the plurality of micro-switches capable of being pressed by the plurality of pins during the rotation of the driven gear member (50), and
a pointer (80) mounted on a top surface of a rod mounted on the driven gear member (50) in such a way that a tip (80a) thereof projects out of the housing, the pointer (80) undergoes rotation on rotation of the driven gear member (50) to provide a visual indication of the test position, the service position and the isolated position of the draw-out circuit breaker; and
a cover (90) for mounting on the housing, the cover (90) having three markings corresponding to the test position, the service position and the isolated position of the draw-out circuit breaker for being indicated by the tip (80a) of the pointer (80).