FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Interlocking Mechanism for Panel Module of Electrical Switching Device"
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,
L&T House, Ballard Estate, P. 0. Box: 278, Mumbai 400 001, India
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Interlocking Mechanism for Panel Module of Electrical Switching Device
Field of the invention
The present invention relates generally to electrical switching devices and more particularly, to an interlocking mechanism for a panel moduie of an electrical switching device.
Background of the invention
The use of switching devices, conventionally known as switchgear, is well known for making, breaking, regulating and to provide safety in a typical electrical distribution system. These devices are generally mounted inside a panel board for added safety of an operator. Most often these switching devices are operated either from outside or by opening an enclosure or a panel door.
Short circuit protection devices, usually molded case circuit breakers incorporate a mechanical switching that is achieved by operating a knob. Conventionally motion of the knob is rectilinear or rotary. Also safety assumes an utmost importance in an electrical transfer and distribution network. Any lapse of this may prove to be very fatal in terms of lives of personnel and damage to the electrical systems and equipments. In view of operator's safety, remote operation and mechanisms extending outside the enclosure or the panel door are the alternative ways to operate the switching devices. Usually to achieve this, an add-on accessory is mounted over the circuit breaker, referred to as a rotary handle mechanism.
The existing rotary operating mechanisms provide leverage to operations of

switching devices, particularly molded case circuit breakers (MCCBs) reducing the strain and the energy of switching ON/OFF of such devices. Such mechanisms in combination of a handle coupler arrangement help to enhance an ingress protection level (IP) of an overall enclosure, housing such combinations. The handle coupler arrangement is then used to operate the mechanism.
In practical usage, there are often requirements of safety interlock to prevent unintended operations which may take place either by an accident or by misuse. Also at times there could be requirements to inhibit the operations of the operator/ switching device for maintenance or for other safety reason. These are usually done by arrangements for padlock and key lock.
Various attempts have been made in the prior art to develop interlocks for switchgears. For example, US patent no. 6388868 relates to an automatically operating interlock that prevents connection of an electrical device within a cabinet unless a cabinet door is closed. The interlock is particularly useful for circuit breakers contained within arc-resistant cabinets.
Another US patent no. 6066814 relates to an interlock for switchgear with a positional interlock bar that is operated by a levering-in block in a levering-in assembly and by a finger on the dummy element.
Yet another example of the interlock includes a key-actuated slider for securing a source circuit breaker in a test position. The key necessary for accessing the levering-in mechanism for the other breaker is secured within a lock of the source breaker unless the source breaker is locked in this test position, thereby cutting off current to the other breakers.

Also few examples of interlocks related to switchgear are described in US 6038892, US 6095574, US 6244891 both mounted inside and outside the enclosure that provides safety interlocks and defeat able cover interlocks for the state of art circuit breakers. However, these locking mechanisms for switching devices do not ensure the safety of operator during device operation.
Accordingly, there is a need of an interlocking mechanism for a panel module of an electrical switching device that overcomes drawbacks of the prior art.
Objects of the invention
An object of the present invention is to provide a simply constructed mechanism including interlocks that are locked or unlocked based on the position of a module door.
Another object of the present invention is to provide the interlocking mechanism actuated by the position of the module door itself.
Yet another object of the present invention is to prevent insertion/ withdrawing of withdraw-able part when a short circuit protection device (SCPD) is in ON condition.
Still another object of present invention is to provide an intelligent defeat to prevent unauthorized persons from opening the module door when the SCPD is in ON condition.
Summary of the invention

Accordingly, the present invention provides an interlocking mechanism for a panel module of an electrical switching device. The panel module includes a module door, a rotary operating handle, a control plate, a rotary operating mechanism, a shaft, a short circuit protection device, and the interlocking mechanism. The interlocking mechanism comprises a mounting plate, a cover plate, a cam, a plurality of clinch studs, a plurality of rollers, a first slider plate, a second slider plate, a plurality of springs, a pair of defeat caps and an actuator.
The cover plate is positioned over the mounting plate. The cam is positioned behind the rotary operating handle on the shaft and sandwiched between the mounting plate and the cover plate. The plurality of clinch studs is impregnated on the mounting plate and being capable of holding a plurality of rollers thereon. The first slider plate is positioned on the mounting plate. The first slider plate is capable of locking movement of the cam thereby arresting the rotary operating handle from switching the short circuit protection device to ON position. The second slider plate is capable of sliding over the cam. The plurality of springs is configured in the first slider plate and the second slider plate. The plurality of springs is adapted to maintain initial and final positions of the first slider plate and the second slider plate. The pair of defeat caps provides access to the second slider plate. The actuator is mounted on the module door and capable of actuating with respect to the module door position.
The first slider plate locks the movement of the cam that eventually arrests the shaft and the rotary operating handle from switching the short circuit protection device to ON condition and whenever the module door is closed, the actuator positioned on the module door slides the first slider plate through a notch thus ensuring free movement of the cam and switching ON of the short circuit protection device thereby causing the second slider plate to slide in over the cam and locking the actuator thus eventually locking the module door.

Brief description of the drawings
Figure 1 shows a top view of a panel module for an electrical switching device, in accordance with the present invention;
Figure 2 shows a front view of the panel module of figure 1;
Figure 3 shows a top perspective view of an internal configuration of the panel module of figure 1;
Figure 4 is an exploded view showing a short circuit protection device (SCPD) and a rotary operating handle of the panel module of figure 1;
Figure 5 shows a front view of an interlocking mechanism, in accordance with the present invention;
Figure 6 is a side perspective view showing components of the interlocking mechanism of figure 5;
Figure 7 shows a back view of the interlocking mechanism of figure 5;
Figure 8 shows position of plates of the interlocking mechanism of figure 5 when the SCPD is in OFF position and a panel door is open;
Figure 9 shows position of the components of the interlocking mechanism of figure 5 when the SCPD is in OFF position and the panel door is closed;
Figure 10 shows position of the components of the interlocking mechanism of

figure 5 when the SCPD is in ON condition and the plates lock the panel door via an actuator; and
Figure 11 is a front view of the interlocking mechanism showing provision for tool defeat for unlocking the module door.
Detailed description of the invention
The foregoing objects of the present 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.
The present invention provides an interlocking mechanism for a panel module of an electrical switching device. The interlocking mechanism provides interlocking at various operating modes of a short circuit protection device without changing the component configuration. The interlocking mechanism is designed to accommodate any type of a rotary operating handle thus forming an exclusive system and serves for various requirements compliant with standards like ARAMCO and NFPA.
The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers in bracket indicate corresponding parts in the various figures.
Referring to figures 1-4, a panel module (200) for an electrical switching device (not numbered) is shown. The panel module (200) includes a module door (10), a rotary operating handle (20) (hereinafter "the handle (20)"), a control plate (30), a rotary operating mechanism (40), a shaft (not shown), a short circuit protection device (50) (hereinafter "the SCPD (50)") and an interlocking mechanism (100).

The handle (20) and the shaft (50) are directly connected to the SCPD (50) through the rotary operating mechanism (40). The handle (20) is mounted on the module door (10) and used for making the SCPD (50) in any one of ON and OFF position.
Referring to figures 5-11, the interlocking mechanism (100) comprises a mounting plate (52), a first slider plate (54), a second slider plate (56), a cover plate (58), a cam (60), an actuator (62), a plurality of rollers (not shown), a plurality of clinch studs (64), a pair of defeat caps (66) and a plurality of springs (68).
The mounting plate (52) houses all components of the interlocking mechanism (100) along with the handle (20). The cover plate (58) is positioned over the mounting plate (52). The plurality of clinch studs (64) is impregnated on the mounting plate (20) and capable of holding the plurality of rollers thereon. The first slider plate (54) and the second slider plate (56) are located over the mounting plate (52) in the plurality of rollers. The plurality of rollers provides sliding motion to the plates (54, 56). The plurality of springs (68) is configured in the first slider plate (54) and the second slider plate (56) and adapted to maintain initial and final positions of the plates (54, 56). The spring loaded plates (54, 56) ensure self restoration from any state.
The cam (60) is positioned behind the handle (20) on the shaft. The cam (60) is sandwiched between the mounting plate (52) and the cover plate (58). The actuator (62) is mounted/fixed on the module door (10) and actuates the interlocking mechanism (100) with respect to the module door (10) position.
The function of the first slider plate (54) is to lock the movement of the cam (60) as shown in figure 8 that eventually arrests the shaft and the handle (20) from switching the SCPD (50) to ON condition. Whenever the module door (10) is

closed, the actuator (62) positioned on the module door (10) slides the first slider plate (54) through a notch (not shown) thus ensuring free movement of the cam (60) and switching ON of the SCPD (50) as shown in figure 9.
As soon as the handle (20) is operated and the SCPD (50) is turned ON, the second slider plate (56) slides in over the cam (60) and locks the actuator (62) thus eventually locking the module door (10) as shown in Fig. 10.
As shown in figure 11, the mounting plate (52) has provision enclosed by the pair of defeat caps (66) that gives access to the second slider plate (56). Thus using a specific tool the second slider plate (56) slides back thus unlocking the actuator (62) and eventually unlocking the module door (10) and rendering to open the module door (10) even though the SCPD (50) is in ON condition.
Referring to again to figures 1-11, in operation, the plates (54, 56) slide to achieve positive interlocking governed by the cam (60) position and the actuator (62) on the module door (10). The handle (10) is directly connected to the SCPD (50) and the spring operated plates (54, 56) are intact in the initial position wherein the first slider plate (54) actively serves positively interlocking the cam (60) and eventually the handle (20) from being operated, until the module door (10) is closed and the second slider plate (56) rests against the cam (60). As the module door (10) is closed, the actuator (62) actuates the first slider plate (54) and allows the free operation of the handle (10) for switching ON and switching OFF of the SCPD (50). As the module door (10) is closed and the SCPD (50) is turned ON, the second slider plate (56) resting on the cam (60) gets actuated and achieves a positive interlocking between the actuator (62) and the module door (10) thus enabling the module door (10) locking in the SCPD (50) ON condition.

Advantages of the present invention:
1. The interlocking mechanism (100) is designed to accommodate any type of the handle (20) thus forming an exclusive system and serves for various requirements compliant with standards like ARAMCO and NFPA.
2. The interlocking mechanism (100) comprises of fewer components, greater reliability and easier manufacturability than previous interlocks.
3. The interlocking mechanism (100) is actuated by the position of the module door (10) instead of the position of the handle (20).
4. The interlocking mechanism (100) provides interlocking at various operating modes of the SCPD (50) without changing the component configuration.
The foregoing objects of the invention are accomplished and the problems and shortcomings associated with prior art techniques and approaches are overcome by the present invention described in the present embodiment. Detailed descriptions of the preferred embodiment are provided herein; however, it is to be understood that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or matter. The embodiments of the invention as described above and the methods disclosed herein will suggest further modification and alterations to those skilled in the art. Such further modifications and alterations may be made without departing from the spirit and scope of the invention.

We Claim:
1. An interlocking mechanism (100) for a panel module (200) of an
electrical switching device, the panel module (200) having a module door (10), a
rotary operating handle (20), a control plate (30), a rotary operating mechanism (40), a shaft and a short circuit protection device (50), the interlocking mechanism (100) comprising:
a mounting plate (52);
a cover plate (58) positioned over the mounting plate (52);
a cam (62) positioned behind the rotary operating handle (20) on the shaft and sandwiched between the mounting plate (52) and the cover plate (58);
a plurality of clinch studs (64) impregnated on the mounting plate (52) and being capable of holding a plurality of rollers thereon;
a first slider plate (54) positioned on the mounting plate (52), the first slider plate (54) being capable of locking movement of the cam (60) thereby arresting the rotary operating handle (20) from switching the short circuit protection device (50) to ON position;
a second slider plate (56) capable of sliding over the cam (60);
a plurality of springs (68) configured in the first slider plate (54) and the second slider plate (56) and adapted to maintain initial and final positions of the first slider plate (54) and the second slider plate (56);
a pair of defeat caps (66) providing access to the second slider plate (66); and
an actuator (62) mounted on the module door (10) and being capable of actuating with respect to the module door (10) position,
wherein, the first slider plate (54) locks the movement of the cam (60) that eventually arrests the shaft and the rotary operating handle (20) from switching the short circuit protection device (50) to ON condition and whenever the

module door (10) is closed, the actuator (62) positioned on the module door (10) slides the first slider plate (54) through a notch thus ensuring free movement of the cam (60) and switching ON of the short circuit protection device (50) thereby causing the second slider plate (56) to slide in over the cam (60) and locking the actuator (62) thus eventually locking the module door (10).