FORM 2
THE PATENTS ACT, 1970 (39 Of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"CONNECTING SHAFT WITH A FLEXIBLE HEAD"
2. APPLICANT(S)
(a) NAME: Larsen and Toubro Ltd.
(b) NATIONALITY: Indian
(c)ADDRESS: L&T House, Ballard Estate, Mumbai-400 001, India
3. PREAMBLE TO THE DESCRITION
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Title
Connecting Shaft with a Flexible Head
Field of the invention
The present invention is related to Low Voltage current limiting circuit breaker and the likes, which are commonly used to receive, supply, protect and isolate current supply in an electrical circuit. More particularly the invention relates to a connecting shaft having a flexible head, which connects a rotary operating handle of a panel door with the circuit breaker contained inside the panel.
Background of the invention
An electrical circuit breaker typically serves two basic purposes:
1. as a switching device: Switching On/Off during normal operating conditions for the purpose of operation and maintenance; and
2. as a protecting device: "Tripping" or "isolating", i.e. breaking electrical contacts, and thereby interrupting fault current during abnormal conditions such as short-circuit, overload and under voltage.
A circuit breaker may have one or more electric poles, and be known as single pole circuit breaker, or two pole circuit breaker, or three pole circuit breaker, or four pole circuit breaker, and so on, depending upon the number of poles as required by respective application.
Circuit breakers are designed for use in Switchboards, Control Panels, and Combination Starters in separate enclosures for effective single location distribution and control. In order to provide safety to operator these devices are housed inside an enclosure.
Typically these devices get mounted inside a board or panel for added safety to the operator. Most often these devices are required to be operated from outside the panel with means of a rotary operating handle that is coupled to the circuit breaker (functioning as a switching device or as a protecting device).
In the most common type of installation, an operating handle is mounted on the panel door while the circuit breaker/switching device is mounted inside the panel door. The mounting arrangement typically has a shaft coming out, which has to be rotated in order to switch the circuit breaker ON and OFF.
For safety sake, only when the panel door is closed the shaft can engage itself with the operating handle mounted on the panel door, and the circuit breaker can be operated

by using the operating handle. When panel door is open the operating handle is decoupled from the shaft and no engagement is left with the shaft and handle, and thus the circuit breaker can no more be operated while the panel door is open.
For proper functioning of the operating handle the shaft has to properly get aligned and adapted to the operating handle. One common issue for loss of functionality is misalignment and sagging of the shaft due to manufacturing error and/or assembly error.
Misalignment takes place because the circuit breaker is first fixed inside the panel; then the shaft is fastened to a coupler rotating on a mechanism mounted on the circuit breaker; and thereafter the panel door cut-outs are made. In this construction, the panel door cut-outs do not get aligned with the shaft coming from the circuit breaker. Sagging is due to self-weight of the shaft, as the shaft is fixed rigidly at one of its ends and is free at the other end. It is therefore necessary to incorporate a feature within the operating handle assembly that can compensate for/nullify any variation in mounting caused due to the aforesaid manufacturing/human errors and limitations.
However, in addition to the aforesaid requirement there is yet another requirement of the operating handle assembly, which is to have a provision for defeating the panel door interlock by usage of a tool (so that in exceptional situations the circuit breaker can be accessed even when it is switched ON) and further a feature of auto-restoration to initial state of door interlock.
The above requirements, due to their different natures, pose a challenge to integrate all the different functionalities into a single operating handle assembly and yet to provide required flexibility for respective different purposes/operations as per the need of the respective situation.
Objects of the invention
Accordingly, an object of the present invention is to compensate for the misalignment of the shaft with the panel door cut-outs and finally with the rotary operating handle mounted on the panel door.
Another object of present invention is to provide frictionless functioning of the operating knob of the rotary operating handle.
Yet another object of the present invention is to ensure that the shaft is able to transmit required torque from the rotary operating handle to the circuit breaker inside the panel.
A further object of invention is to provide indication on the rotary handle of the panel door in accordance with the circuit breaker position.

Summary of the invention
In accordance with the above objects, there is provided a connecting shaft assembly for connecting a rotary operating handle of a panel door with the circuit breaker contained inside the panel, comprising:
a hollow enclosure;
a T-shaft having one of its ends extended in and rotatably connected with the hollow enclosure at one of the ends of the hollow enclosure and having its other end connected with the rotary operating handle;
a coupler shaft having one of its ends extended in and rotatably connected with the other end of the hollow enclosure such as to be able to move in a plane substantially perpendicular to plane of movement of the T-shaft, and having its other end connected with a member for operating the circuit breaker through a main shaft; and
a compression spring residing within the hollow enclosure and between the ends of the T-shaft and the coupler shaft,
wherein torque is transferred from the rotary operating handle to the member for operating the circuit breaker, despite any misalignment between door cut-outs of the panel and axes of any of the rotary operating handle, the T-shaft, the enclosure, the coupler shaft, and the member for operating the circuit breaker.
Brief Description of Drawings
Fig. 1-a shows side view of the connecting shaft assembly and Fig. 1-b shows sectional side view of the connecting shaft assembly.
Fig. 2 shows complete assembly of the shaft with breaker.
Fig. 3-a, 3-b and 3-c show various embodiments and internal connections in the shaft.
Fig. 4-a is side view of the connecting shaft arrangement and shows plane of movement of T-shaft, and 4-b is top view of the connecting shaft assembly and shows plane of movement of coupler shaft.
List of Components

Component No. Name of the Component
1 T- shaft

la
Teeth of T-shaft
2 Coupler shaft
3 Compression spring
3a Rivet joint
4 Enclosure
5 Main shaft
6 Circuit breaker
7 Operating handle/rotary handle
8 Panel door
9 Panel
Detailed Description
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of weli-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for iilustration purpose only and not for the. purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.
By the term "substantially" it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for

example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of .skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
Accordingly, the present invention provides a connecting shaft assembly for connecting a rotary operating handle of'a panel door with the circuit breaker contained inside the panel.
On the field, during assembly or when the circuit breaker is getting mounted, axis of the operating handle does not go in line with axis of the mechanism on the breaker. Owing to this, the panel door cannot be closed properly, and/or large amount of friction is encountered during this process. The present invention deals with tackling the problem without affecting the basic function of the circuit breaker or the operating handle.
According to present invention, a connecting shaft assembly is used along with a universal coupler arrangement. The assembly transfers the torque from the rotary operating handle on the panel door to the circuit breaker inside the panel.
The connecting shaft assembly comprises the following components:
1) T-shaft
2) Coupler shaft
3) Compression spring
4) Enclosure
In the present invention, the connecting shaft assembly comprises two sub-shafts i.e. a T-shaft and a coupler shaft that are connected together through a compression spring which gives the whole assembly the required flexibility. The connection of the compression spring with both the sub-shafts is enclosed inside an enclosure.
In comparison with fixed shaft, the coupler shaft in accordance with the present invention provides flexibility in terms of tackling misalignment due to assembly/ human errors. Moreover it also facilitates frictionless operation of the rotary knob mounted on the panel door as the compression spring in the assembly allows the coupler shaft to reorient itself according to the position of the rotary knob assembly mounted on the panel door. This ensures suitable entry of the T-shaft across the panel door through a coupler of a door-mounted assembly, and also assists in giving correct indication on the rotary handle of the panel door in accordance with the circuit breaker position.

The T-shaft has a peculiar shape at a front end so that it gets coupled with the rotary operating handle on the panel door. The T-shaft has two teeth la coming out of its cylindrical body which go inside the coupler of the knob of the rotary operating handle for proper torque transmission. The T-shaft 1 is riveted at one end of enclosure 4.
Since the T-shaft is riveted 3a at one end of the enclosure, it is free to move it in a plane perpendicular to the axis of the rivet. Similar is the case with the coupler shaft at the other end of the enclosure, with the plane of motion being upright, i.e. perpendicular to the axis of its rivet, and perpendicular to the plane of motion of the T-shaft. The enclosure is provided with flat surfaces where both the sub-shafts are riveted with it in order to ensure appropriately transfer of torque from the rotary operating handle to the circuit breaker inside the panel.
Referring to Figures 4-a and 4-b, connection between the coupler shaft and the enclosure compensates for misalignment in y-y direction, and connection between the T-shaft and the enclosure compensates for misalignment in x-x direction. Thus, with the two connections and the compression spring the entire continuum of any misalignment due to assembly errors and sagging can be overcome.
The assembly of the T-shaft end, the enclosure, the spring, and the coupler shaft end is collectively referred to as flexible head.

We Claim:
1. A connecting shaft assembly for connecting a rotary operating handle of a panel
door with the circuit breaker contained inside the panel, comprising:
a hollow enclosure;
a T-shaft having one of its ends extended in and rotatably connected with the hollow enclosure at one of the ends of the hollow enclosure and having its other end connected with the rotary operating handle;
a coupler shaft having one of its ends extended in and rotatably connected with the other end of the hollow enclosure such as to be able to move in a plane substantially perpendicular to plane of movement of the T-shaft, and having its other end connected with a member for operating the circuit breaker through a main shaft; and
a compression spring residing within the hollow enclosure and between the ends of the T-shaft and the coupler shaft,
wherein torque is transferred from the rotary operating handle to the member for operating the circuit breaker, despite any misalignment between door cut-outs of the panel and axes of any of the rotary operating handle, the T-shaft, the enclosure, the coupler shaft, and the member for operating the circuit breaker.
2. The connecting shaft assembly of Claim 1 wherein the compression spring allows the coupler shaft to reorient itself according to the position of the rotary operating handle assembly mounted on the panel door, thereby facilitating frictionless operation of the knob of the rotary operating handle, which in turn ensures suitable entry of the T-shaft across the panel door through a coupler of a door-mounted assembly, and also assists in giving correct indication on the rotary handle of the panel door in accordance with the circuit breaker position.
3. The connecting shaft assembly of Claim 1 wherein the T-shaft and the coupler shaft are riveted to the enclosure.
4. The connecting shaft assembly of Claim 1 wherein the enclosure has flat surfaces at its ends where the T-shaft and the coupler shaft are connected with it.

5. The connecting shaft assembly of Claim 1 wherein the T-shaft is rigidly coupled with the rotary operating handle through one or more teeth extending out from the body of the T-shaft.
6. The connecting shaft assembly of Claim 1 wherein the main shaft is a hollow square shaft.