FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
As amended by the Patents (Amendment) Act, 2005
&
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION
A ratchet wheel and circuit breaker thereof
APPLICANT (S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company.
INVENTOR (S)
Desale Rajgopal Shivdas, of Crompton Greaves Ltd, S3, Switchgear Division, A3, MIDC Ambad, Nashik-422010, Maharashtra, India; an Indian National.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

Field of the Invention:
This invention relates to the field of mechanical assemblies and mechanical engineering.
Particularly, this invention relates to mechanical assemblies and mechanical engineering with respect to switchgear equipment.
More particularly, this invention relates to a ratchet wheel with improved load bearing capability and improved shock absorbing capability, and circuit breaker incorporating such ratchet wheel.
Background of the Invention:
Circuit Breaker mechanisms are a type of switchgear equipment used with electrical equipment, as an adjunct mechanism, for preventing said electrical equipment from current / voltage aberrations such as overload, short circuit, or the like. Basically, it is designed to detect a fault condition, and operates to interrupt the working of the associated electrical equipment upon detection, thereby saving its health.
Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically-stored energy (using something such as springs or compressed air) contained within the breaker is used to separate the contacts. Small circuit breakers may be manually operated; larger units have coils to trip the mechanism, and electric motors to restore energy to the springs.

A trip coil is a type of solenoid in which the moving armature opens a circuit breaker or other protective device when the coil current exceeds a predetermined value. A closing coil is adapted to shut the circuit breaker completely.
In its working mode, if a power surge occurs in the electrical system, the breaker will trip. This means that a breaker that was in the "on" position will flip to the "off position and shut down the electrical power leading from that breaker. Essentially, a circuit breaker is a safety device. When a circuit breaker is tripped, it may prevent a fire from starting on an overloaded circuit; it can also prevent the destruction of the device that is drawing the electricity.
Conventionally, damping elements or shock absorbers are known to be used along with a moveable contact of a circuit breaker.
Figure 1 illustrates a schematic of the closing spring and its associated mechanism for charging, in a circuit breaker mechanism.
In existing circuit breaker mechanisms, a Ratchet-pawl mechanism with motor is used to charge a closing spring. Charging time of the closing spring is a critical factor. It depends on torque required to charge the spring. Closing spring is guided in a metallic drum which is fixed to mechanism frame. Motor is used to charge the closing spring via the ratchet-pawl mechanism. It includes a ratchet wheel (2) adapted to be angularly displaced through its 360 degree rotation cycle. It further includes a co-axially (7) fitted drum (3), attached to it at its base. A shaft (connecting rod) (4) is connected to the ratchet wheel, spaced-apart from the centre of the ratchet wheel, and hangs down into said drum. The drum, includes a co-axially fitted closing spring, which is compressed in its charged-up configuration.

There is provided an end plate (5), at the operative bottom of the drum and spring, connected to the operative bottom end of the shaft.
This mechanism works as a slider crank mechanism. As the ratchet wheel angularly displaces (9), the connected shaft moves up and down (6) due to a crank (8). This connecting shaft is used to transfer the forces from ratchet wheel to bottom of closing spring i.e. at the end plate. During the rotation of wheel, there is change in angle of connecting rod. This motion, brings the end plate operatively upwards, and this force results in the compression of the closing spring, thus charging it to be used, upon detection fault.
It has been observed that the goodness of a circuit breaker is a function of its charging time, the amount of torque / energy spent on charging, the ease of charging, and the charging to idle time ratio.
The ratchet wheel, therefore, imparts potential energy to closing spring. Typically, the rod is adapted to be linearly displaced by about 130 mm which is achieved by two rotations of the ratchet wheel. The ratchet wheel rotates incrementally by virtue of a teethed rim. Generally, it requires 15 seconds to complete the two rotations. Sometimes, there may be failures due to breakage of teeth due to relatively high stresses involved.
Objects of the Invention:
An object of the invention is to provide a ratchet wheel with increased load handling capability.

Another object of the invention is to provide a ratchet wheel with increased shock absorbing capability.
Yet another object of the invention is to provide a ratchet wheel with reduction in cost of material.
Still another object of the invention is to provide a circuit breaker with increased closing spring energy.
An additional object of the invention is to provide a circuit breaker with increases impact capacity.
Summary of the Invention:
According to this invention, there is provided a ratchet wheel with improved load bearing capability and improved shock absorbing capability, said ratchet wheel comprises:
a) a wheel element with pre-defined slots equi-angularly defined about wheel centre and within the circumference of said wheel element;
b) a substantially circular bracket adapted to be fitted co-axially with respect to an operative back plane of said wheel element, said bracket including integral raised machined projections with a pre-defined degree of curvature defined by its lateral sides, said raised machined projections being adapted to be fitted into a portion of said slot such that one of its lateral sides abuts one edge of said slot; and

c) a bumper element adapted to be fit in remainder of said slot such that it fills the remainder of the slot completely, thereby providing a tight fit of said bumper element and said stopper element within said slot.
According to this invention, there is also provided a circuit breaker incorporating a
ratchet wheel with improved load bearing capability and improved shock
absorbing capability, said ratchet wheel comprises: i. a wheel element with pre-defined slots equi-angularly defined about wheel
centre and within the circumference of said wheel element; ii. a substantially circular bracket adapted to be fitted co-axially with respect to an operative back plane of said wheel element, said bracket including integral raised machined projections with a pre-defined degree of curvature defined by its lateral sides, said raised machined projections being adapted to be fitted into a portion of said slot such that one of its lateral sides abuts one edge of said slot; and
iii. a bumper element adapted to be fit in remainder of said slot such that it fills the remainder of the slot completely, thereby providing a tight fit of said bumper element and said stopper element within said slot.
Typically, said wheel element is a teethed wheel element.
Typically, said raised machined projection is a stopper element.
Typically, said ratchet wheel includes pins to fit said bumper element.

Typically, the degree of curvature as defined by lateral arms of said bumper element is 45 degrees.
Typically, said bumper element is a rubber shock absorbing element.
Typically, said stopper element is a metallic element.
Brief Description of the Accompanying Drawings:
Figure 1 illustrates a schematic of the closing spring and its associated mechanism for charging, in a circuit breaker mechanism;
Figure 2a illustrates a front view of a ratchet wheel of the prior art used in circuit breaker mechanisms;
Figure 2b illustrates a side view of a ratchet wheel of the prior art used in circuit breaker mechanisms; and
The invention will now be described in relation to the accompanying drawings, in which:
Figure 3 illustrates an auxiliary view of a ratchet wheel used in circuit breaker mechanisms.
Figure 4 illustrates an auxiliary exploded view of a ratchet wheel used in circuit breaker mechanisms.

Detailed Description of the Accompanying Drawings:
Figure 2a illustrates a front view of a ratchet wheel of the prior art used in circuit breaker mechanisms. Figure 2b illustrates a side view of a ratchet wheel of the prior art used in circuit breaker mechanisms.
The ratchet wheel is used to charge a closing spring in a circuit breaker mechanism. The details of its working are explained with respect to Figure 1 of the accompanying drawings, above. Further with respect to Figures 2a and 2b of the accompanying drawing, the ratchet wheel construction may be elaborated further. The ratchet wheel (11) receives a bracket (12) which is co-axial and engages itself from one planar side of the ratchet wheel body. The ratchet wheel is slotted in an equi-angular manner with respect to the tentre of the wheel. The slots incorporate a stopper element (14) and an adjacent bumper element (15). Each stopper element
(14) is connected to the bracket by means of a pin (15) which passes through a slot in both the bracket (12) and the stopper dement (14). The stopper element (14) is preferably made of steel, while the bumper element (15) is preferably made of rubber. The degree of curvature defined by the lateral edges of the bumper element
(15) is 30 degrees in the ratchet wheel of the prior art. It can be seen that 4 pairs of stopper elements (14) adjacent to bumper elements (15) are provided in the ratchet wheel (11). Reference numeral 13 refers to another bracket of the ratchet wheel.
In its operative configuration, load is exerted on the bracket (12) through pins (16) from stopper element (14). The bumper element (15) acts as a shock absorber and is subject to wear and tear. The stopper element increases the time period of

rotation, thereby resulting in energy accumulation and consequent slow action of the ratchet wheel, thereby also reducing stress.
The ratchet wheel is a teethed wheel assembly. The media which acts as a shock absorbing whilst transferring load from ratchet wheel to the shaft is rubber. Load is exerted on to a bracket of the ratchet wheel through a pin.
The number of parts of the ratchet wheel of the prior art was as follows:
Ratchet wheel - 1
Bracket - 2
Stopper element - 4
Bumper element - 4
Pins - 4
This results in 15 different parts.
According to this invention, there is provided a ratchet wheel with improved load bearing capability and improved shock absorbing capability, and circuit breaker incorporating such ratchet wheel.
Figure 3 illustrates an auxiliary view of a ratchet wheel used in circuit breaker mechanisms, according to this invention. Figure 4 illustrates an auxiliary exploded view of a ratchet wheel used in circuit breaker mechanisms.
In accordance with an embodiment of this invention, there is provided a ratchet wheel (20) with pre-defined slots (21) equi-angularly defined about wheel centre and within the circumference of the wheel. The wheel is a teethed wheel.

In accordance with another embodiment of this invention, there is provided a substantially circular bracket (22) adapted to be fitted co-axially with respect to an operative back plane of the ratchet wheel (20), said bracket (22) including integral raised machined projections (24) with a pre-defined degree of curvature defined by its lateral sides. The raised machined projections (24) are adapted to be fitted into a portion of the slot (21) such that one of its lateral sides abuts one edge of the slot. The raised machined projection is the stopper element (24). The remainder of the slot is fitted with a bumper element (26) such that it fills the remainder of the slot completely, thereby providing a tight fit of the bumper element (26) and stopper element (24) within the slot. Pins (28) are provided to fit the bumper element.
The degree of curvature as defined by the lateral arms of the bumper element is 45 degrees, thereby providing more area for shock absorption and to handle more load effectively. Mathematically, shock absorbing capacity is increased by 150%. Hence, capacity of shock absorption is improved by 150%.
The number of parts of the ratchet wheel of the invention is as follows:
Ratchet wheel - 1
Bracket - 2
Bumper element - 4
Pins - 4
This results in 11 different parts, thereby resulting in saving of 4 additional parts,
and costs, thereof.

While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim,
1. A ratchet wheel with improved load bearing capability and improved shock absorbing capability, said ratchet wheel comprising:
a) a wheel element with pre-defined slots equi-angularly defined about wheel centre and within the circumference of said wheel element;
b) a substantially circular bracket adapted to be fitted co-axially with respect to an operative back plane of said wheel element, said bracket including integral raised machined projections with a pre-defined degree of curvature defined by its lateral sides, said raised machined projections being adapted to be fitted into a portion of said slot such that one of its lateral sides abuts one edge of said slot; and
c) a bumper element adapted to be fit in remainder of said slot such that it fills the remainder of the slot completely, thereby providing a tight fit of said bumper element and said stopper element within said slot.

2. A ratchet wheel as claimed in claim 1 wherein, said wheel element is a teethed wheel element.
3. A ratchet wheel as claimed in claim 1 wherein, said raised machined projection is a stopper element.
4. A ratchet wheel as claimed in claim 1 wherein, said ratchet wheel includes pins to fit said bumper element.

5. A ratchet wheel as claimed in claim 1 wherein, the degree of curvature as defined by lateral arms of said bumper element is 45 degrees.
6. A ratchet wheel as claimed in claim 1 wherein, said bumper element is a rubber shock absorbing element.
7. A ratchet wheel as claimed in claim 1 wherein, said stopper element is a metallic element.
8. A circuit breaker incorporating a ratchet wheel with improved load bearing capability and improved shock absorbing capability, said ratchet wheel comprising:
i. a wheel element with pre-defined slots equi-angularly defined about wheel
centre and within the circumference of said wheel element; ii. a substantially circular bracket adapted to be fitted co-axially with respect to an operative back plane of said wheel element, said bracket including integral raised machined projections with a pre-defined degree of curvature defined by its lateral sides, said raised machined projections being adapted to be fitted into a portion of said slot such that one of its lateral sides abuts one edge of said slot; and iii. a bumper element adapted to be fit in remainder of said slot such that it fills the remainder of the slot completely, thereby providing a tight fit of said bumper element and said stopper element within said slot.
9. A circuit breaker as claimed in claim S wherein, said wheel element is a teethed
wheel element.

10.A circuit breaker as claimed in claim 8wherein, said raised machined projection is a stopper element.
11.A circuit breaker as claimed in claim 8 wherein, said ratchet wheel includes pins to fit said bumper element.
12.A circuit breaker as claimed in claim 8 wherein, the degree of curvature as defined by lateral arms of said bumper element is 45 degrees,
13.A circuit breaker as claimed in claim 8 wherein, said bumper element is a rubber shock absorbing element.
14.A circuit breaker as claimed in claim 8 wherein, said stopper element is a metallic element.