F O R M 2

THE PATENTS ACT, 1970
(39 of 1970)
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10; rule 13)

1. Title of the invention: AN INTRINSIC ROTARY OPERATING MECHANISM FOR CIRCUIT BREAKER

2. Applicant(s):

(a) NAME : LARSEN & TOUBRO LIMITED
(b) NATIONALITY : An Indian Company
(c) ADDRESS : L & T House, Ballard Estate, Mumbai 400 001,
State of Maharashtra, India

3. PREAMBLE TO THE DESCRIPTION

The following specification particularly describes the invention and the manner in which it is to be performed:

Field of the invention

The present invention relates to a circuit breaker. Particularly, the invention relates to an improved rotary operating mechanism for use in circuit breakers. The invention also relates to a circuit breaker comprising the rotary mechanism.

Background and the prior art

Circuit Breaker is a mechanical switching device, capable of making (i.e. switching ON), carrying and breaking (i.e. switching OFF) current under normal circuit conditions and more specifically breaking current (Tripping) during abnormal circuit conditions such as short-circuit. Quit often, the short circuit current is sensed automatically and the signal is given to the mechanism as a TRIP command which leads to opening of the contacts by means of mechanism. However, during normal ON to OFF and OFF to ON operation, input to mechanism is given through the rotation of knob by manual means. The rotation of handle leads to storing potential energy (spring charging) in the spring member. At a specified instance, the potential energy of spring is released in the form of Kinetic energy through Mechanical Linkages leading to the rotation of the contacts at high velocity. Circuit breaker mechanisms use dead-centre based Extension spring arrangements.

Conventionally, to operate a Molded Case Circuit Breaker (MCCB), pull and push type of force needs to be applied on the Breaker knob. Whereas, to be adaptable on the panel-mounting conventionally, the Circuit Breaker should be rotary operated; and instead of pull and push type of force on the knob, a torque is applied on the Breaker Handle to operate the same. So to fulfill the same requirement, an additional accessory is attached to the Circuit Breaker and instead of pull and push type force, a torque is applied on the Handle to operate the Breaker. It has been found that the use of additional accessory in the circuit breaker makes the system bulky and increases the overall cost of the circuit breaker system.

US6518526 discloses a handle-operating mechanism for a circuit breaker including a rotary operating handle for opening and closing a main-circuit contact of a circuit breaker, a rotating gear operably connected to the operating handle and having a first engaging device, and a contact opening-and-closing mechanism having a toggle gear meshing with the rotating gear. A clutch gear is connected to the operating handle to be interposed between the operating handle and the rotating gear, and has a second engaging device. An idle stroke is formed such that when the circuit breaker is turned on, the operating handle runs idly after rotation of the operating handle has been started and before the second engaging device engages the first engaging device to drive the rotating gear for actuating the toggle gear.

US 6194983B1 discloses a circuit interrupter handle mechanism disposed on the face of a molded case circuit breaker. The handle mechanism has a rotary handle, which may be rotated through approximately 90.degree. of rotation from a disposition of circuit interrupter conduction to a disposition of circuit interrupter non-conduction. The handle is not centered over the linear handle of the circuit interrupter per say, but rather is disposed in the upper left hand corner, so that a larger lever arm can be utilized. Furthermore, the larger lever has a handle opening into which the hasp of a lock may be placed to lock the circuit breaker in the open state for servicing and the like. Because of the length of the handle more hasps can be disposed therein than if the handle was disposed exactly in the center of the circuit breaker case. Lastly, the disposition of the circuit breaker rotary handle provides an indication of the conduction status of the molded case circuit breaker. If the handle is in a generally horizontal position, i.e., straight across the front of the circuit interrupter, that is an indication that the contacts of the circuit interrupter are open and that current therefore is blocked. If on the other hand the handle is 90.degree. displaced, in a rotational manner, to be parallel with the long longitudinal axis of the circuit interrupter, then an indication is given that the circuit interrupter contacts are closed and current is being conducted.

US5302925 discloses a molded case circuit breaker rotary handle operator allows the circuit breaker handle to be locked when the circuit breaker contacts are open. The handle is prevented from being locked in position when the circuit breaker contacts are welded in their closed condition.

US3697714 discloses a handle mechanism for operating a molded case circuit breaker secured to the rear wall of an enclosure is mounted separate from the enclosure cover and extends through a cover opening to be operable from outside the enclosure when the cover is closed. The mechanism is constructed so as to be readily adapted for use with enclosure covers that are hinged at either side of the enclosure.

US5219070 discloses a rotary handle operator for a circuit breaker with a linearly movable handle has a housing which is mounted over the circuit breaker handle. A slide carrying a rack engages the circuit breaker handle and is slidable within a chamber in the housing. The rack engages a pinion gear sector mounted on a rotatable shaft which extends through a cover on the housing. A rotating handle mounted on the shaft is rotated to linearly operate the circuit breaker handle or is positioned thereby when the circuit breaker trips. The handle may be locked in the off position by inserting the shackle of a lock through an aperture in a lever arm on the rotating handle to urge a pin on a spring biased locking piece within the handle lever into an aperture in the housing cover, or the shackles of several locks may engage a slot in a shroud surrounding the rotating handle to interfere with rotation of the handle out of the off position. An interlock for the door of a cabinet in which the circuit breaker may be mounted is incorporated into the rotary door operator.

US4528531 discloses a molded case circuit breaker including a highly integrated operating mechanism having an over-center toggle mechanism for opening and closing a pair of electrical contacts and a trip mechanism for responding to overload and short circuit or fault current conditions to separate the pair of electrical contacts. A generally flat, intermediate latch plate includes an upper latch surface for latching with a movable cradle of the over-center toggle mechanism and a lower latch surface for latching with a trip bar of the trip mechanism and a pair of outwardly projecting pivot arms disposed between the upper and lower latch surfaces. The over-center toggle mechanism includes a pair of upper toggle links and a pair of lower toggle links interconnected by a toggle spring pin. To increase the speed of separation of the first and second electrical contacts during a trip operation, the cradle is physically configured to engage and upwardly propel the toggle spring pin and, also, the upper toggle links have projections for physically contacting a rigid stop.

US6479774B1 discloses a circuit breaker operating mechanism that comprises of a movable handle yoke, a mechanism spring extending in tension from the handle yoke to a pin, and a lower link extending from the pin to a crank operably connected to a contact arm bearing a movable contact. The crank is positionable in open and closed positions, being in an open position when the movable contact is separated from an associated fixed contact and being in a closed position when the movable contact is mated to said associated fixed contact. The circuit breaker further comprises an interface formed on said crank and a blocking prop having a first surface that engages said interface, the first surface preventing the crank from rotating towards the closed position.

US6590172B1 discloses a circuit breaker wherein the circuit breaker comprises a contact arm movable between a closed position, an open position and a blown open position wherein the contact arm is disposed in the circuit breaker. A bumper is disposed to contact the contact arm when the contact arm is in the blown open position. In addition, a stop member is disposed to be in contact with a linkage assembly so as to create a gap between the bumper and the contact arm when the contact arm is disposed in the open position.

Many prior art documents as stated hereinabove have been studied and it has been found that the knob in a circuit breaker involves push –pull type of forces. In order for these Breakers to be operated by a Rotary Handle, an additional accessory called a Rotary Operated Mechanism is required, which needs to be mounted on top of the Knob. The inventors have studied and found that the Linear Knob-operated Breakers require higher operating force from the user, when compared to a Rotary Handle-operated Breaker. Rotary operation gives more ergonomic comfort to the user, when compared to a Knob-operated one. For the conversion of rotary to linear motion using a ROM, additional components and additional space are required. Such requirement of additional space increases the size of the circuit breaker.

The inventors have found that a unique design and a combination of a gear means and fork means if provided give rise to a rotary handle operating mechanism for circuit breakers in the same limited conventional space and the same number of components without adding any extra accessory to the conventional circuit breaker which would provide better control and lesser effort to the operator.

Objects of the invention

One object of the present invention is to overcome the drawbacks/disadvantages of the prior art.

A basic object of the present invention is to provide improved rotary mechanism for use in circuit breakers.

Another object of the present invention is to provide a circuit breaker comprising the rotary mechanism inside its housing or cassette.

Another object of the present invention is to eliminate use of rotary operating mechanism which are mounted on breaker knobs.

These and advantages of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings.

Summary of the invention

According to an aspect of the present invention there is provided an intrinsic rotary operating mechanism for use in circuit breakers, said mechanism comprising :

gear assembly; and
fork means;
wherein said gear assembly comprising
a gear pin means having a pocket adapted to receive a conventional rotary handle;
a gear means operatively engaged to said gear pin such that rotary movement of said gear means corresponds to the movement of said rotary handle;
wherein said gear means being operatively engaged with fork means such that rotation of said gear means correspondingly rotates the fork means.

According to another aspect of the present invention there is provided a circuit breaker mechanism without external rotary operating mechanism mounted on its knob, said mechanism comprising:

cassette means having mechanism module of said circuit breaker;
plate means forming base of said mechanism module;
gear assembly mounted on said plate means; and
fork means;
wherein said gear assembly comprising
a gear pin means having a pocket adapted to receive a conventional rotary handle;
a gear means operatively engaged to said gear pin such that rotary movement of said gear means corresponds to the movement of said rotary handle;
wherein said gear means being operatively engaged with fork means such that rotation of said gear means correspondingly rotates the fork means.

Brief Description of the accompanying drawings

Other features as well as the advantages of the invention will be clear from the following description.

In the appended drawings:

Fig. 1 illustrates an Isometric view of the Circuit Breaker cassette with breaker in OFF condition

Fig. 2 illustrates an Isometric view of the Circuit Breaker cassette with breaker in ON condition

Fig.3 illustrates an Isometric view of Mechanism in ON condition with breaker cassette hidden

Fig. 4 illustrates an Isometric view of Mechanism in intermediate position from ON to OFF

Fig. 5 illustrates an Isometric view of Mechanism in OFF condition.

Fig. 6 illustrates an Isometric view of Mechanism in TRIP condition.

Fig. 7 illustrates an Isometric view of the Driver and Driven members of the Mechanism.

Fig. 8 illustrates an Isometric Exploded view of Driver Gear, Gear Pin and Fork.

Brief description of the accompanying drawings

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and illustrate the best mode presently contemplated for carrying out the invention. Further functioning of the mechanism has been discussed below to describe the way the mechanism operates. However, such description should not be considered as any limitation of scope of the present unit. The structure thus conceived is susceptible of numerous modifications and variations, all the details may furthermore be replaced with elements having technical equivalence. In practice the materials and dimensions may be any according to the requirements, which will still be comprised within its true spirit.

Elements and Construction

1: Circuit Breaker Cassette: It is a Cassette on which the Circuit Breaker Mechanism module is mounted.
2: Rotor: It is the part which houses the Moving-contact assembly
3: Mechanism module: It consists of various linkages. It is a 4 bar mechanism.
3a: Side Plates: It is the base of the Mechanism module. It enables the mounting of the Driver gear.
3b: Upper Link: It decides the position of Dead Centre during ON->OFF and OFF->ON operations. One end of it is fixed during ON->OFF and OFF->ON operation, and moving- during TRIP operation.
3c: Lower Link: It is connected between the Upper Link and Rotor.
3d: Fork – It has a series of perforations (3i) on it, which receive the engaging pins (3h) from the driver gear. It is where the energy storing element- spring is connected.
3e: Driver Gear. It is a non-conventional gear, with engaging means which engages the driver gear with the fork means (3d). The engaging pins project along the axis of rotation and mesh with the perforations in the Fork.
3f: Springs – Springs are energy storing elements. Their one end is connected to the Fork, while the other end to a pin called the "Floating Pin" in the four-bar arrangement.
3g: Gear Pin – It has a pocket on its top, where the Rotary Handle is mounted. It is mounted on the Side Plates, and the Driver Gear is assembled to its bottom with the help of a split-pin.
4: Handle: It is manually rotated to achieve various positions of the circuit breaker.

Detailed description of working of the invention

The present invention relates to a Circuit Breaker which is a mechanical switching device, capable of making (i.e. switching ON), carrying and breaking (i.e. switching OFF) current under normal circuit conditions and more specifically breaking current (Tripping) during abnormal circuit conditions such as short-circuit. Quite often, the short circuit current is sensed automatically and the signal is given to the mechanism as a TRIP command which leads to opening of the contacts by means of mechanism. However, during normal ON-OFF and OFF-ON operation, input to mechanism is given through the rotation of handle(4) by manual means. The rotation of handle (4) leads to storing potential energy (spring charging) in the spring member(3f) while restricting the contact movement during the charging operation. At a specified instance the potential energy of spring is released in form of Kinetic energy through Mechanical Linkages leading rotation of the contacts at high velocity. Circuit breaker mechanisms use dead centre based Extension spring arrangements.

In the present invention, the mechanism is operated by a Rotary handle instead of a Linear knob; hence substituting the conventional linear motion (push-pull) with a rotary motion (torque).

It uses the Driver Gear (3e) and the Fork (3d). Driver Gear (3e) is mounted on the Mechanism Side-plates (3a) with the help of the Gear Pin (3g), which has provision for handle shaft insertion and the Fork (3d) is pivoted on the Mechanism pin. The pins on the Driver Gear (3e) mesh with the perforations on the Fork (3d). A Rotary Handle (4) is inserted into the Gear Pin (3g). So, to operate the Circuit Breaker, the Operator applies a torque on the Rotary Handle (4) so that the Gear Pin (3g), and subsequently the Driver Gear (3e) gets rotated- which causes the rotation of the Fork (3d). As one end of the extension springs is connected to the Fork (3d), charging of the springs take place during OFF->ON and ON->OFF operation up to dead centre.

Rotation axes of the Driver Gear (3e) and the Fork (3d) are perpendicular to each other. The Mechanism Side-plates support the Driver Gear (3e) via the Gear Pin (3g) as shown in Fig.1 and Fig. 2. The Fork (3d) is pivoted on one side plate of the Mechanism module. So instead of attaching extra accessories on top of the Circuit Breaker to convert rotary motion of Rotary Handle to a linear motion on the knob, the arrangement described above- enables the operator to perform ON to OFF, OFF to ON and TRIP to RESET operations on the Breaker effortlessly and comfortably.

Advantages:
 The Rotary operation is directly integrated into the Mechanism of the Breaker.
 No additional space is required to enable the rotary to linear conversion of motion for operating the Breaker.
 Fewer efforts are required compared to conventional pull-push type knob-operated Circuit Breakers.
 Ergonomically more comfortable to operate the circuit breaker.
 Better control on the ON-OFF, OFF-ON & TRIP-RESET operation.
 Eliminates the need for an external Rotary Operating Mechanism (ROM) to do the same job, thereby saving space and material.
 More efficient than a ROM because of direct transmission of forces from Handle to Fork.
 Gives more control over the operation to the Operator, when compared to a ROM.
 Takes up lesser space when compared to Bevel-type Gear arrangement for the same.

WE CLAIM:

1. An intrinsic rotary operating mechanism for use in circuit breakers, said mechanism comprising :

gear assembly; and
fork means;
wherein said gear assembly comprising
a gear pin means having a pocket adapted to receive a conventional rotary handle;
a gear means operatively engaged to said gear pin such that rotary movement of said gear means corresponds to the movement of said rotary handle;
wherein said gear means comprising plurality of engaging members adapted to operatively engage said gear means with said fork means such that rotation of said gear means correspondingly rotates the fork means.

2. Mechanism as claimed in claim 1 wherein said gear means is a driver gear.

3. Mechanism as claimed in claim 1 wherein said engaging members comprising plurality of pins projecting along the axis of rotation.

4. Mechanism as claimed in claims 1 to 3 wherein said fork means comprising plurality of perforation means.

5. Mechanism as claimed in claims 3 and 4 wherein said plurality of pins projecting along the axis of rotation operatively engage with said perforation means of the fork.

6. A circuit breaker mechanism without external rotary operating mechanism mounted on its knob, said mechanism comprising:

cassette means having mechanism module of said circuit breaker;
plate means forming base of said mechanism module;
gear assembly; and
fork means;
wherein said gear assembly comprising
a gear pin means having a pocket adapted to receive a conventional rotary handle;
a gear means operatively engaged to said gear pin such that rotary movement of said gear means corresponds to the movement of said rotary handle;
wherein said gear means comprising plurality of engaging members adapted to operatively engage said gear means with said fork means such that rotation of said gear means correspondingly rotates the fork means.

7. Mechanism as claimed in claim 6 further comprising spring means.

8. Mechanism as claimed in claim 6 wherein said gear means is a driver gear.

9. Mechanism as claimed in claim 6 wherein said engaging members comprising plurality of pins projecting along the axis of rotation.

10. Mechanism as claimed in claim 6 wherein said fork means comprising plurality of perforation means.

11. Mechanism as claimed in claims 9 and 10 wherein said plurality of pins projecting along the axis of rotation operatively engage with said perforation means of the fork.

12. An improved rotary mechanism for use in circuit breakers as herein substantially described and illustrated with reference to the accompanying drawings.

13. A circuit breaker mechanism without external rotary operating mechanism mounted on its knob as herein substantially described and illustrated with reference to the accompanying drawings.