FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Mechanism for Securing Handle Shaft to Actuating Shaft In switchboards"
2. APPLICANT:
(a) NAME: Larsen & Toubro Limited
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: Larsen & Toubro Limited
Electrical & Automation North Wing, Gate 7, Level 0, Powai Campus, Saki Vihar Road, Mumbai 400 072, INDIA
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Mechanism for Securing Handle Shaft to Actuating Shaft In switchboards
Field of invention
The present invention relates to switchboards, and more particularly, to a securing of a handle shaft to an actuating shaft in switchboards.
Background of the invention
In switchboards or switch enclosures, a switch is mounted on a base plate whereas a handle intended for its actuation is mounted on a panel door. To transmit the rotational torque required for the actuation of the switch, a handle shaft is required. The handle shaft is usually of square cross section. For convenience of the user, the handle shaft is usually made adjustable i.e. its length can be varied by inserting the handle shaft either inward into the actuating shaft or outward. Once the length of the actuating shaft is adjusted, the handle shaft is required to be firmly held to the actuating shaft so that the handle shaft does not slide out of the actuating shaft incase the user yanks at the handle or otherwise.
US Patent Application No. 2008/0247816A1 discloses a mechanism for securing a handle shaft to actuating shaft. The mechanism includes a protrusion provided in the actuating shaft. Further, the protrusion includes a threaded hole provided thereon. Furthermore, the mechanism includes a spring steel tightening piece which is held in place with the help of a tightening screw. Specifically, when the screw is tightened, the tightening piece is pressed against the handle shaft which is passing through the actuating shaft and holds the handle shaft to the actuating pipe shaft.
However, when the switch is in the mounted condition, it is difficult for the operator to adjust the length of the handle shaft. It becomes necessary for him to loosen the

hardware of the tightening piece completely. The tightening piece in such a situation detaches from the actuating pipe shaft assembly. This could result in the tightening piece getting misplaced and a great deal of inconvenience to the operator. Further, Another problem with an arrangement of the prior art is that a protrusion is required on a usually cylindrical actuating shaft. This makes the manufacturing of such a component complicated and expensive. Specifically, the secondary process is also required for creating a thread in the actuating shaft for fixing the tightening piece to the same. This further increases the complexity and cost of the process. Also, as a result of the protrusion stated above, a corresponding cut has to provided onto the switch cover for fitment. This cut impairs the aesthetics of the switch and deteriorates the degree of ingress protection.
Accordingly, there exists a need to provide a mechanism for securing handle shaft to the actuating shaft in switchboards for which overcomes disadvantages existing in the prior art.
Object of the invention
An object of the invention is to provide a mechanism for securing handle shaft to an actuating shaft of a switch mounted in switchboards in which the tightening mechanism does not detach from the assembly even if the hardware is loosened.
Another object of the present invention is to provide mechanism for securing handle shaft to the actuating shaft of a switch mounted in switchboards which does not require a protrusion in the actuating shaft thus improving the aesthetics of the switch by means of eliminating any cut in the cover or housing.

Yet another object of the invention is to provide mechanism for securing handle shaft to actuating shaft of a switch with a mechanism that is simple to manufacture and does not require a secondary process.
Yet another object of the invention is to provide a mechanism for securing handle shaft to actuating shaft of a switch that allows easy fitment of a direct handle and motorized operator.
Summary of the invention
Accordingly, the present invention provides a mechanism for securing a handle shaft to a actuating shaft in switchboards , wherein the handle shaft is capable of being inserted into the actuating shaft, the mechanism comprising: a notch configured on the actuating shaft;
a tightening piece capable of being fitted around the actuating shaft, the
tightening piece having a threaded hole for a screw to be inserted therein; and
at least one clamp disposed in the tightening piece, wherein the clamp fits into
the notch provided on the actuating shaft upon tightening the screw,
wherein upon tightening the screw, the tightening piece wedges the handle
shaft between the tightening piece and one wall of the actuating shaft thus
eliminating a need of a thread and a protrusion in the actuating shaft for securing the
handle shaft to the actuating pipe shaft.
Brief description of drawings
Figure 1 shows cross sectional view of a mechanism for securing a handle shaft to an actuating shaft in switchboards of the prior art;

Figure 2 shows a perspective view of the mechanism of figure 1 of the prior art;
Figure 3 shows an assembled view of a mechanism for securing a handle shaft to an actuating shaft in switchboards, in accordance with the present invention;
Figure 4 shows an exploded view of the mechanism of figure 3;
Figure 5 shows a sectional view of the mechanism of figure 3 and 4 before securing the handle shaft to an actuating shaft;
Figure 6 shows a sectional view of the mechanism of figure 3 and 4 after securing the handle shaft to an actuating shaft.
Figure 7 shows exploded view of a tightening piece of the mechanism of figure 3 and 4 in accordance with the present invention.
Figure 8 shows perspective view of a actuating pipe shaft of the mechanism of figure 3 and 4, in accordance with the present invention;
Figure 9 shows the fixing of direct handle to the switch, in accordance with the present invention;
Figure 10 shows a cross sectional view of the direct handle of figure 9; and
Figure 11 shows a switch assembly along with motorized operator.
Detailed description of the present invention

The foregoing objects of the 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.
Accordingly, the present invention provides a mechanism for securing a handle shaft to an actuating shaft in switchboards, in accordance with the present invention The tightening piece of this invention does not detach from the assembly even if the hardware is loosened. Also, this arrangement does not require a protrusion in the actuating shaft thus improving the aesthetics of the switch by means of eliminating any cut in the cover or housing.
Referring now to 3 to 11, there are shown various view and components of the mechanism for securing a handle shaft to an actuating shaft in switchboards, in accordance with the present invention (hereinafter the mechanism (100)). Specifically, the handle shaft (40) is capable of being inserted into the actuating shaft (10).
The mechanism (100) includes a notch (12) configured on the actuating shaft (10), a tightening piece (20) capable of being fitted around the actuating shaft (10), at least one clamp (30) disposed in the tightening piece (20). Specifically, the tightening piece (20) is capable of being fitted around the actuating shaft (10). Further, the tightening piece (20) includes a threaded hole (22) for a screw (24) to be inserted therein.
Figure 5 shows a sectional view of the mechanism (100) before securing the handle shaft (40) to the actuating shaft (10). In this position the clamp (30) (as shown in figure 7) lies outside the cavity of the actuating shaft (10). This allows the handle shaft (40) to be inserted into the actuating shaft (10) without any difficulty i.e. there is no restriction to its free movement in and out of the actuating shaft (10).

When the screw (24) is tightened, the clamp (30) on the tightening piece (20) begins to move towards the actuating shaft (10). Further, when the screw (24) is completely tightened, a position is reached which is similar to the one indicated by Figure 6 which shows a sectional view of the mechanism (100) after securing the handle shaft (40) to an actuating shaft (10). Specifically, the clamp (30) touches the handle shaft (40) and the mating surfaces between them are substantially parallel. In this position, the handle shaft (40) is clamped against the actuating shaft (40). The handle shaft (40) in this position cannot be slid inward or outward with a normal operating force.
As shown in figure 3 and 4, there is no protrusion required on the actuating shaft (10) for the accommodation of the tightening piece (20). As a result, there is no need to introduce a cut of similar proportions on to the housing or the switch cover as in the case of prior art.
Further, the mechanism (100) includes bulges (26), for example two bulges, provided on the tightening piece (20) for fixing the tightening piece (20) on to the actuating shaft (10). Furthermore, the actuating shaft (10) comprises grooves (14) thereon which corresponds to the bulges (26) of the tightening piece (20) as shown in figure 7 and 8.
Specifically, the tightening piece (20) is initially fixed to the actuating shaft (10) by press fitting the bulges (26) into the grooves (14). The grooves (14) does not permit the axial movement of the tightening piece (20) but allow its lateral movement. In this way, even though the tightening screw (24) may be completely removed by the operator, the tightening piece (20) remains fixed to the actuating shaft (10).
Referring now to figure 9 which shows fixing of a direct handle (50) on to the switch assembly (60). The absence of a protrusion on the actuating shaft (10) enables easy

accommodation of the direct handle. The direct handle (50) construction is shown in Figure 10. The direct handle (50) includes a cylindrical cut (50a) provided in the handle body. This cut accommodates the actuating shaft (10) while the integral shaft (50b) drives actuating shaft'(10).
Further, figure 11 shows switch assembly along with motorized operator which follows the same principle as the fixing of a direct handle and the same advantages may be achieved with the invention .
Advantages of the invention
1. The tightening piece (20) of the mechanism (100) does not detach from the
assembly even if the other hardware is loosened.
2. The mechanism (100) do not require thread on the actuating shaft, which decreases the secondary operations on the component and decreases cost.
3. The mechanism (100) does not require a protrusion in the actuating shaft thus improving the aesthetics of the switch by means of eliminating any cut in the switch cover or housing.
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, to thereby enable others skilled in the art to best utilize the present invention and various embodiments

with various modifications as are sutied to the particular use contemplated. It is
understood that various omission and substitutions of equivalents are contemplated as
circumstance may suggest or render expedient but such are intended to cover the
application or implementation without departing from the spirit or scope of the
present invention.

We claim
1. A mechanism for securing a handle shaft to a actuating shaft in switchboards , wherein the handle shaft is capable of being inserted into the actuating shaft, the mechanism comprising:
a notch configured on the actuating shaft;
a tightening piece capable of being fitted around the actuating shaft, the tightening piece having a threaded hole for a screw to be inserted therein; and
at least one clamp disposed in the tightening piece, wherein the clamp fits into the notch provided on the actuating shaft upon tightening the screw,
wherein upon tightening the screw, the tightening piece wedges the handle shaft between the tightening piece and one wall of the actuating shaft thus eliminating a need of a thread and a protrusion in the actuating shaft for securing the handle shaft to the actuating pipe shaft.
2. The mechanism as claimed in claim 1, wherein the tightening piece comprises bulges thereon for fixing the tightening piece on to the actuating shaft.
3. The mechanism as claimed in claim 1, wherein the actuating shaft comprises grooves thereon which corresponds to the bulges of the tightening piece.