Claims:We claim:

1. A cam based position indicating mechanism for withdrawable circuit breaker configured to rack in or out to or from a cradle, the cam based position indicating mechanism comprising:
an indicator having a cam profile configured on a right side plate of the cradle,
a spacer placed in between the indicator and the right side plate,
a screw mounted on the right side plate near the cam profile end of the indicator;
a spring connecting the indicator and the screw, and
a stopper screw fastened to the right side plate at end opposite to the cam profile end of the indicator to restrict unintended movement of the indicator;
a guide pin, and an indicator guide pin fixed to a back side plate of the withdrawable circuit breaker, wherein the guide pin and the indicator guide pin moves through a guide way of the right side plate when the withdrawable circuit breaker is racked in or out; and
a display window configured on a side cover of the cradle with status indication printed/labeled on top portion of the side cover;
wherein upon racking the withdrawable circuit breaker in the cradle, the indicator guide pin slides on the cam surface of the indicator against the force delivered by the spring, thus moving the indicator along the display window indicating status of the withdrawable circuit breaker.

2. The cam based position indicating mechanism as claimed in claim 1, wherein the indicator is riveted to the right side plate of the cradle using a rivet.

3. The cam based position indicating mechanism as claimed in claim 1, wherein the guide pin and the indicator guide pin are riveted to the back plate of the withdrawable circuit breaker using a rivet.

4. The cam based position indicating mechanism as claimed in claim 1, wherein the status indication printed on top portion of the side cover comprises Disconnected, Test and Connected.

5. The cam based position indicating mechanism as claimed in claim 1, wherein the display window comprises a see through plastic cover.

, Description:Field of the invention

The present invention relates to a withdrawable circuit breaker, and more particularly, the present invention relates to withdrawable-unit with a cam based mechanism to synchronously indicate location of the circuit breakers’ three distinct position viz. connected, test and disconnected.

Background of the invention

Withdrawable unit (Draw-out module) is an arrangement which is used to connect a circuit breaker to a main power source without unbolting or disturbing termination. This is done with the help of a mechanism wherein the operator can rack in or out the circuit breaker to or from a cradle. The cradle is a part of the draw-out module which has a jaw type spring contacts that is connected to the power source. When the circuit breaker is racked in, the plugs in the circuit breaker engages with socket (jaw contacts) in the cradle thus establishing a removable joint with the source.

Generally, there are two types of supplies in a switchboard. One is a main supply used to power the loads via the circuit breaker and other is an auxiliary supply used for auxiliaries like shunt release, UV release, and the like. Accordingly, the draw-out can be used in three different positions in order to use/test these poser sources, they are ‘DISCONNECTED’ (both Aux. connections and power connections not connected) ‘TEST’ (Aux. connections only connected but not power supply) and ‘CONNECTED’ (both Aux. connections and power connections are connected).

In order to indicate the position of the circuit breaker (disconnected, test and disconnected), a common method of indication is electrical and mechanical indication. For both these indication, the input can be taken from the circuit breaker or the draw out mechanism. The mechanical indication is indicated through an indicator, in case of electrical indication the output can be taken from a connector block and it can be used for displaying the location using a light source, or create a logic circuit.

The prior art mechanism of position indication for the circuit breaker has following disadvantages.
1. Tilting of circuit breaker causes error in indication.
2. True indication of the circuit breaker position not possible when the input is taken from the mechanism.
3. Mechanical indication given as an add-on accessory can create issues when the user assembles it.

Accordingly, there exists a need to provide a position indicating mechanism for withdrawable circuit breaker, which overcomes abovementioned drawbacks.

Objects of the invention

An object of the present invention is to provide true indication of position of circuit breaker.

Another object of the present invention is to provide position indication mechanism for the circuit breaker in which tilting of the breaker has lesser effect.

Yet another object of the present invention is to indicate “n” number of positions of a withdrawable circuit breaker.

Summary of the invention

Accordingly, the present invention provides a cam based position indicating mechanism for withdrawable circuit breaker configured to rack in or out to or from a cradle. The cam based position indicating mechanism comprises an indicator having a cam profile configured on a right side plate of the cradle, a spacer placed in between the indicator and the right side plate, a screw mounted on the right side plate near the cam profile end of the indicator, a spring connecting the indicator and the screw, and a stopper screw fastened to the right side plate at the end opposite to cam profile end of the indicator to restrict the unintended movement of the indicator.

The cam based position indicating mechanism further comprises a guide pin, and an indicator guide pin fixed to a back side plate of the withdrawable circuit breaker. The guide pin and the indicator guide pin moves through a guide way configured on right side plate of the cradle when the withdrawable circuit breaker is racked in or out.

The cam based position indicating mechanism further comprises a display window configured on a side cover of the cradle. The side cover also comprises in status indication/location label printed on top portion thereon.

Upon racking the withdrawable circuit breaker in a cradle, the indicator guide pin slides on the cam surface of the indicator against the force delivered by the spring. This moves the indicator along the display window indicating status of the withdrawable circuit breaker.

Brief description of the drawings

Figure 1 shows withdrawable circuit breaker at Rack-in condition i.e. in connected condition;

Figure 2 shows withdrawable circuit breaker at Rack-out condition;

Figure 3 shows the fixed part of the withdrawable circuit breaker;

Figure 4 a cam based position indicating mechanism, in accordance with the present invention;

Figure 5 shows a cam unit of the position indicating mechanism 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 embodiment.

The present invention provides a cam position indicating mechanism for withdrawable circuit breaker. The cam based position indicating mechanism provides true indication of position of circuit breaker. Further, the cam based position indicating mechanism provides position indication mechanism for circuit breaker in which tilting of the breaker has lesser effect. Also, the cam based position indicating mechanism indicates “n” number of positions of a withdrawable circuit breaker.

Referring to figure 1-5, there is shown a cam based position indicating mechanism (hereafter “the mechanism (100)”) for withdrawable circuit breaker (200) configured to rack in or out to or from a cradle (200A), in accordance with the present invention.

As shown in figure 2, 4 and 5, mechanism (100) comprises an indicator (10) fixed on a right side plate (12) of the cradle (200A). In an embodiment, the indicator (10) is riveted to the right side plate (12) using a rivet (10a). The indicator (12) is elongated member having a cam profile (10b).

The mechanism (100) further comprises a spacer (14) placed in between the indicator and the right side plate (12). The spacer (14) allows the movement of the indicator (10) along its axis and also prevents the indicator (10) from getting stuck to the right side plate (12).

The mechanism (100) furthermore comprises a screw (16) mounted on the right side plate (12) near the cam profile end (10a) of the indicator (10). The mechanism (100) moreover comprises a spring (18) connecting the indicator (10) and the screw (16). Specifically, the spring (18) exerts the force on the indicator (10) to keep the indicator (12) in the default position. The mechanism (100) also comprises a stopper screw (19) fastened to the right side plate (12) at the end opposite to cam profile end of the indicator (10). The stopper (19) restricts the unintended movement of the indicator (12).

The mechanism (100) also comprises a guide pin (20) and an indicator guide pin (22) fixed to a back side plate (24) of the withdrawable circuit breaker (200). In an embodiment, the guide pin (20) and the indicator guide pin (22) are riveted to the back plate (24) of the withdrawable circuit breaker (200) using a rivet. It is understood that though the mechanism (100) shows the guide pin (20) and the indicator guide pin (22) as parts thereof, the guide pin (22) and the indicator guide pin (24) are existing components of the withdrawable circuit breaker which provides actuation to the cam based position indication mechanism (100) of the present invention.

Specifically, the guide pin (22) and the indicator guide pin (24) moves through a guide way (not numbered) configured on the right side plate (12) of the cradle (200A) when the withdrawable circuit breaker (200) is racked in or out.

The mechanism (100) further comprises a display window (32) configured on a side cover (30) of the withdrawable circuit breaker having and status indication/locations printed or labeled on top portion thereof. In a preferred embodiment, the status indication/locations printed on top portion of the side cover (30) includes Disconnected, Test and Connected. In an embodiment, the surface of the cam profile (10a) of the indicator (10) can be modified to display the various positions in different band of the withdrawable circuit breaker.

Upon racking the withdrawable circuit breaker (200) in the cradle (200A), the indicator guide pin (20) and the guide pin (22) slides over the guide way’s in the right side plate (12). Specifically, the indicator guide pin (22) slides on the cam surface (10b) of the indicator (10) against the force delivered by the spring (18). Thus, the indicator (10) moves along the display window (32) indicating status/location such as Disconnected, Test and Connected of the withdrawable circuit breaker. Specifically, the display window comprises a see through plastic cover from which the indicator (10) can be seen pointing out printed/labeled indication of the side cover (30) showing current status of the withdrawable circuit breaker (200).

When the withdrawable circuit breaker (200) is racked out, the spring (18) bring back the indicator (10) to the default position.

Advantages of the invention
1. The mechanism (100) allows the indication at “n” number of positions of the withdrawable circuit breaker.

2. In the mechanism (100), input for indication is taken from the circuit breaker hence true position of the circuit breaker is obtained.
3. In the mechanism (100), synchronization of position of the withdrawable circuit breaker (200) is ensured by the design of the cam profile (10a) of the indicator (10).
4. In the mechanism (100), surface of the cam profile (10a) of the indicator (10) can be modified to display the various positions in different band.
5. In the mechanism (100), the indication is discrete type of indication
6. In the mechanism (100), the time band for each position of the withdrawable circuit breaker can be set by modifying the cam profile.

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.