FIELD OF THE INVENTION

The invention relates to a circuit breaker, and more particularly to the transmission mechanism of a circuit breaker.

BACKGROUND

Circuit breaker is an electrical switch that is generally provided in power distribution for protecting the electrical circuit from damage caused due to overload or short circuit. Circuit breaker protects the electrical circuit by detecting fault in the electrical circuit and discontinuing the electrical flow by interrupting the current. Circuit breaker can be reset either manually or automatically to resume operation so as to allow electrical flow though the electrical circuit.

Typically, a circuit breaker comprises a linkage mechanism for transmitting the energy or motion from the operating mechanism to the moving contact of the pole of the circuit breaker. The transmission of energy or motion is enabled through linkages provided in the linkage mechanism. From the functionality perspective, the linkage mechanism is also referred to as transmission mechanism.

Currently, the transmission mechanism of the circuit breaker has linkages or links with fixed leverage ratio or adjustable leverage ratio. Links with fixed leverage ratio has solid links and hence cannot be adjusted. Also, the contacts of the circuit breaker employing links with fixed leverage ratio experiences stress due to closing bounce of the solid links or that during opening operation. This increases the possibility of fatigue failure of the relevant and related components of the circuit breaker. Moreover, it becomes imperative to provide dampers to curb at least some closing bounce, if not all. Thus the manufacturing cost of the circuit breaker also increases with the addition of more and more materials, and also making the construction of the transmission mechanism and of the circuit breaker more complicated.

On the other hand, links with adjustable leverage ratio has at least one joint, but typically many joints, through which flexibility in the length of the link is achieved. Therefore, the transmission mechanism of the type having links with adjustable leverage ratio encounters transmission loss due to friction caused by the links and its joints. This requires more energy from the operating mechanism to overcome such transmission loss. Also, adjusting the length of the links involve suitably tightening the joints catering to the designed torque so as to eliminate the chances of the joints getting loose, without which the circuit breaker or of the components relating to the transmission mechanism of the circuit breaker, becomes vulnerable to permanent damage.

Hence there is a need for a circuit breaker that has adjustable leverage ratio and more reliable and eliminating the transmission loss to a greater extent.

OBJECTS OF THE INVENTION

It is an object of the invention to provide a circuit breaker that has fixed leverage ratio or adjustable leverage ratio or both.

It is another object of the invention to provide a circuit breaker that has reduced or negligible transmission loss.

It is also an object of the invention to provide a circuit breaker that has improved or increased transmission efficiency.

It is yet another object of the invention to provide a circuit breaker having transmission mechanism that is capable of withstanding dynamic loads.

It is a further object of the invention to provide a circuit breaker that is compact and simple in construction and durable and functionally more reliable.

SUMMARY OF THE INVENTION

Accordingly the present invention provides a circuit breaker comprising a transmission mechanism. The transmission mechanism is connected to an appropriate link of the operating mechanism of the circuit breaker at one end and to the movable contact of the circuit breaker at the other end. The transmission mechanism of the circuit breaker is provided for transmitting the movement provided by the operating mechanism to the movable contact. The transmission mechanism comprises at least one wire rope connected to the operating mechanism at its one end and to a lever at its other end for operating the movable contact, and the wire rope is movable over a pulley. BRIEF DESCRIPTION OF THE DRAWINGS

With reference to non exhaustive exemplary embodiments illustrated by the accompanying drawings, in which:

Fig. 1 shows a circuit breaker with solid link in accordance with the prior art;

Fig. 2 shows a circuit breaker with wire rope in accordance with the invention;

Figs. 2a and 2b show variants of the circuit breaker with wire rope in accordance with the invention in which each phase of the circuit breaker is operated independently; and

Figs. 2c and 2d show variants of the circuit breaker with wire rope in accordance with the invention in which the three phases of the circuit breaker is operated through a common shaft.

DETAILED DESCRIPTION

In Fig. 1 , a circuit breaker ( 100) in accordance with the prior art is shown. The transmission mechanism of the circuit breaker ( 100) comprises a solid link ( 1 01 ). The solid link ( 101 ) is connected at its one end to the operating mechanism ( 102) and at its other end to a lever ( 103) for operating the movable contact of the circuit breaker ( 100). Here, the solid link ( 101 ) has fixed leverage ratio and cannot be adjusted. Also, the circuit breaker ( 100) experiences stress due to closing bounce of the solid links or that during opening operation.

It becomes necessary to have a circuit breaker that provides adjustable leverage ratio and experiences reduced or negligible transmission loss and stress.

Accordingly, the circuit breaker of the invention is further explained herein after with reference to non exhaustive exemplary embodiments illustrated by Figs. 2 through 2d.

In Fig. 2, a circuit breaker (200) is shown in which the transmission mechanism of the circuit breaker (200) has a wire rope (201 ) movable or sliding over a pulley (204). The wire rope (201 ) is connected at its one end to an operating mechanism (202) and at its other end to a lever (203) for operating the movable contact of the circuit breaker (200). The pulley (204) is adjustable in respect of its position and provides required tension for the wire rope (201 ) which is a requisite for proper movement and functioning of the transmission mechanism. The operating mechanism (202) provides energy and of the motion required to be transmitted to the movable contact through the transmission mechanism. The energy can be produced by a suitable source that may be automatic such as motor, or manual.

The operating mechanism (202) through its corresponding movement pulls the wire rope (201 ). The wire rope (201 ) moves or slides over the rotatable pulley (204), and in turn moves the lever (203) against the force of the compression spring (205) that is provided along with a guide to hold the compression spring (205) in its position, and being disposed accordingly within the circuit breaker (200).

During the closing operation, the compression spring gets charged due to compression caused due to the movement of the lever (203). The closing operation entails the movable contact to engage with the fixed contact of the circuit breaker (200) to close the electrical circuit. The movement of the operating mechanism (202) is arrested by a latch provided for the said purpose.

During the opening operation, the latch is released allowing movement of the operating mechanism and of the transmission mechanism. The compression spring (205) moves the lever (203) away from it and against the force of the damper (206), which is a compression spring, utilizing the charge accumulated during the closing operation. The damper (206) is provided to counter or eliminate the bounce exhibited during the closing and / or opening operation. It is to be noted through this, that the invention renders the circuit breaker (200) to a critically damped system as compared to the under damped system of the prior art. This eliminates the negative feedback and reduces the time required to reach equilibrium position.

This embodiment corresponds to a circuit breaker in which each phase operates independently.

Figs. 2a and 2b shows other non limited variants of the circuit breaker (200) in which each phase of the circuit breaker (200) operates independently. The primary constructional difference of Figs. 2a and 2b as compared with Fig. 2 is that in Figs. 2a and 2b the damper (206) is a tension spring that been coupled to the operating mechanism (202). With respect to Fig. 2b, the movement of the lever during opening operation is caused by the pull of the tension spring (205) provided for the purpose served by the compression spring (205) of Fig. 2 or 2a. Similarly, Figs. 2c and 2d purports to embodiments that correspond to a circuit breaker (200) in which the three phases are connected by a common shaft (207). Constructionally, Figs. 2c and 2d correspond to Figs. 2a and 2b respectively.

However, functionally the circuit breaker (200) of Figs. 2a through 2d is similar to the circuit breaker (200) of Fig. 2.

The adjustable leverage ratio is achievable by suitably adjusting the position of the pulley and / or by suitably adjusting the lever or link connecting the wire rope with the movable contact. It is to be noted that various other combination of compression spring and tension spring for the purpose of causing movement to the lever during opening operation and as damper is possible, and each of such other variants that not been specifically mentioned here in the description can be well understood by a person skilled in the art.

Thus, the invention provides a circuit breaker that has fixed leverage ratio or adjustable leverage ratio or both, and has reduced or negligible transmission loss without much of joints and friction thereof. The circuit breaker of the invention has improved or increased transmission efficiency, and has transmission mechanism that is capable of withstanding dynamic loads. Besides this, circuit breaker of the invention is compact and simple in construction and durable and functionally more reliable.

Only certain features of the invention have been specifically illustrated and described herein, and many modifications and changes will occur to those skilled in the art. The invention is not restricted by the preferred embodiment described herein in the description. It is to be noted that the invention is explained by way of exemplary embodiment and is neither exhaustive nor limiting. Certain aspects of the invention that not been elaborated herein in the description are well understood by one skilled in the art. Also, the terms relating to singular form used herein in the description also include its plurality and vice versa, wherever applicable. Any relevant modification or variation, which is not described specifically in the specification are in fact to be construed of being well within the scope of the invention. The appended claims are intended to cover all such modifications and changes which fall within the spirit of the invention.

Thus, it will be appreciated by those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the invention is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein.