FORM 2
THE PATENTS ACT, 1970 (39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION
"Panels Interlock Arrangement with an Add-on Operating Mechanism"
2.APPUCANT(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
Panels Interlock Arrangement with an Add-on Operating Mechanism
Field of the invention
The present invention is related to Low Voltage current limiting circuit breakers and the like, which are commonly used to receive, supply, protect and isolate current supply in an electrical circuit. More particularly it relates to panel interlock arrangement with add-on operating mechanism.
Background of the invention
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.
2. as a protecting device: Tripping or Isolating by breaking the contacts interrupting the fault current during abnormal conditions such as short-circuit, overload and under voltage.
Circuit breaker consists of one or more electric poles, whose number determined by the application as single pole circuit breaker, two pole circuit breaker, three pole circuit breaker, four-pole circuit breaker and so on.
They are designed for use in Switchboards, Control Panels, and Combination Starters in separate enclosures for effective single location distribution and control. Also these are housed inside an enclosure to provide safety to users operating the same.
In the most common type of installation, an operating handle is mounted on the panel door while the switching device is mounted inside the panel door. The mounting device has a shaft coming out that has to be rotated to switch the circuit breaker ON and OFF.
When panel door is closed the shaft engages with the handle mounted on the panel door and the breaker inside the panel can be operated by using the handle. When panel door is open the handle is decouple with the shaft and no engagement is left with the shaft and handle. So under standard design conditions while a door is open, due to the decoupling of the shaft and operating handle operations under this condition are not possible. This is also required from safety perspective since operating a handle under these conditions is unsafe because of live power inside the panel/enclosure.

One of the standard requirements is that in case of devices used for emergency like fire, safety alarms etc., provisioning of operations of the switching devices should be made even in conditions where the door is open. Further/ an intent to close a disconnect switch when a control panel is open must first be prevented through an interlocking provision, which can then only be bypassed through deliberate action. Main disconnect switches equipped with door mounted rotary handles have the peculiar design aspect that, with an open control panel door, there no longer is a mechanical linkage established between switch and door. Another requirement for switches requiring emergency is that the operating handle must always be permanently connected to the switch. This applies even when the control panel door is open.
As per this safety standard, the operating means should always be coupled to the switches irrespective of the door conditions.
Yet another requirement is to have a door interlock in ON condition of the switch and this interlock to also be defeat able in case of emergency requirement by means of a tool.
Once door is defeated, it should also be possible to restore back to initial conditions normally.
Yet another requirement is to have an interlock to the operations of the switch in Door open condition which should also be possible to defeat by trained user.
Present invention thus is to integrate the above mentioned requirements on a rotary operator of a switching device.
Patents 5493083 door interlocking arrangement in a similar switching device configuration. The design is however too complex and does not clearly address issues of door interlock defeat and its restoration.
Patents 6518526 and 6969813 also cites example of rotary add-on mechanism connected to a switching device but the operational safety aspects of door interlock, its defeat is not mentioned.
Objects of the invention
The main object of the invention is to have added safety feature on a conventional add-on mechanism that convert the toggle type / rocking type of switching of a breaker to a rotary type switching. This assembly is referred to herein as Direct Mounted rotary mechanism. The way of conversion of the toggle type to rotary type is through a crank lever mechanism.

Another object of the invention is to have the operating handle directly coupled with the Switching device / breaker irrespective of the door location.
Yet another object of the innovation is to have an interlock to the operating handle once the door is in open condition to prevent accidental switching (with door being in open condition).
A further object is to make said interlock defeatable by trained operators by intentional action thus providing the requisite safety and also meeting the criteria of handle directly coupled to the breaker irrespective of the door position.
Yet another objective of the invention is to have a mechanical means of sensing the position of the door which interlocks the operating mechanism in cases the door is open and releases the interlock once it senses the door close situation.
Yet another objective of the innovation is to have a door interlock while the breaker is in ON condition which would prevent the door from opening.
Yet another objective is to have a defeat which enables trained technicians with right kind of tool to defeat the said interlock for cases of emergency.
Summary of the invention
In accordance with the above objects, there is provided a panels interlock arrangement with an add-on operating mechanism, for low-voltage circuit breaker and the like placed in a panel enclosure having a panel door, the mechanism comprising:
a crank lever driven by an operating handle protruding out of a cut on the panel door, the crank lever having a crank pin;
a slider having an arm and also having a profile cut wherein the crank pin slides, an end of the slider being connected to a breaker knob of the circuit breaker;
one or more guide shafts operatively connected with and imparting straight line movement to the slider, the slider in turn driving the knob by transferring the movement thereto;
a housing having a sensor hole and a mating profile with a defeat hole;
a door position sensor hinged with the housing with a hinge pin, the sensor having a sensor end surfacing on the facia of the housing through the sensor hole and having its rear end positioned in the path of and thereby arresting movement of

the slider and thereby locking movement of the breaker knob, till the panel door is open;
a door lock component having an arm capable of engaging with the arm of the slider, having a wedge-shaped end, and loaded by a compression spring hooked thereto, the spring keeping the wedge-shaped end protruded out of the housing; and
a door interlock bracket mounted on the panel door, the bracket surpassing the wedge-shaped end when the panel door is closed and thereby locking the panel door.
Brief Description of Drawings
Figure 1 shows an add-on operating mechanism mounted on a switching device.
Figure 2 shows the panel door in open condition.
Figure 3 shows the extruded view of the direct mounted rotary operating mechanism.
Figures 4a and 4b show the mechanism in two-phases.
Figures 5a and 5b show the switching device in OFF condition.
List of Components

Component No. Name of the Component
1 Panel door
2 Panel enclosure
3 Operating handle
4 Circuit breaker/switching device
5 Add-on operating mechanism direct mounted on circuit breaker/switching device
e Knob of operating handle
7 Housing for add-on direct mounted rotary mechanism
7a Hole in add-on direct mounted rotary mechanism for ensuring door

defeat when circuit breaker is ON
8 Crank lever of add-on direct mounted rotary mechanism
9 Slider
9a Arm of slider
10 Guide shafts for imparting motion in straight line path to slider
11 Door position sensor
11a Bend on rear end of door position sensor
12 Door lock component for keeping door closed when circuit breaker is ON
12a Arm of door lock component
12b Part of door lock component mating with housing for add-on direct mounted rotary mechanism
12c Place where compression spring is hooked on to door lock
12d Wedge formed by an end of door lock component
13 Compression spring for door lock component
15 Door interlock bracket mounted on panel door
16 Hinge pin for hinging door position sensor with housing for add-on direct mounted rotary mechanism
Detailed Description
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 embodiments.
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 well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and the 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 is provided for illustration 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 indicates 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.
According to the invention, the operating handle is directly coupled with the Switching device / breaker irrespective of the door location. The door position sensor (11) is a component which serves the safety purpose of not allowing the switching device to switch on till the panel door is closed. The door position sensor (11) is hinged at a point with pin (16) such that its one end is positioned at the face of the mechanism on the rotary mechanism housing (7). The door sensor further has a bend 11(a) on its rear end. This bend comes in the path of the slider (9). Till the door is open, the door position sensor stays in the position as shown in the figure 4(a), the bend 11(a) does not allow the slider to move up. Thus, the operating handle (3) cannot be rotated as it locks the motion of the slider (9) and so the switching device cannot be switched ON thus ensuring one of the pre requisites of such mechanisms.
The panel door (1) comes and sits on the facia of the mechanism at the rotary mechanism housing (1). As the panel door comes to rest it pushes the door position sensor (11) which falls back as it is hinged at the pin (16). In doing so the bend (11a) uncovers the slider'such that there is no further obstruction in the path of the slider (9) and hence the motion can be easily transmitted from the operating handle to the slider and thus the switching device can be switched ON.
Figure 1 shows the add-on operating mechanism mounted on a switching device and housed inside a panel enclosure. The figure shows the general operating conditions of the switching device. The panel door (1) rests on the panel enclosure (2) with the operating handle (3) protruding out of the cut out for user application. The switching device is generally operated keeping the panel door (1) closed to ensure safety.

Figure 2 shows the panel door in open condition, the switching device (4) is mounted on the panel enclosure (2) and the add-on direct mounted rotary mechanism (5) is mounted on the switching device with the help of four screws.
Figure 3 shows the extruded view of the direct mounted rotary operating mechanism and shows all the components which form the part of the accessory. The mechanism basically comprises of a crank lever (8) which is driven by means of the operating handle (3). The crank liver has a pin which slides in a profile cut of the slider (9). The rotation of the crank liver thus projects a linear path which is traced by the slider which moves in a straight line path because of the guide shafts (10). The slider also clamps the knob of the switching device on its rear side and in moving through the linear path drives the knob of the switching device through the various transient states.
The add-on direct mounted rotary invention serves the purpose of converting the toggle type switching device into a rotary one. In the modern day approach, there is a need to ensure safety standards and to safeguard the safety of the operator. With regard to this the various safety agencies have handed out certain guidelines of operation. So this accessory functions in accordance to the requirement of the various safety agencies.
Figure 4 shows the mechanism in two phases, figure 4(a) shows the panel door open and the figure shows the knob interlock feature of the mechanism. The door position sensor (11) is a component which serves the safety purpose of not allowing the switching device to switch on till the panel door is closed. The ensure this the door position sensor (11) is hinged at a point with pin (16) such that its one end is positioned at the face of the mechanism on the rotary mechanism housing (7). The door sensor further has a bend 11(a) on its rear end. This bend comes in the path of the slider (9). Till the door is open, the door position sensor stays in the position as shown in the figure 4(a), the bend 11(a) does not allow the slider to move up. Thus, the operating handle (3) cannot be rotated as it locks the motion of the slider (9) and so the switching device cannot be switched ON thus ensuring one of the pre requisites of such mechanisms.
The figure 4(b) shows the mechanical sensing of the door and the consecutive unlocking of the knob. The panel door (1) comes and sits on the facia of the mechanism at the rotary mechanism housing (1). As the panel door comes to rest it pushes the door position sensor (11) which falls back as it is hinged at the pin (16). In doing so the bend (11a) uncovers the slider such that there is no further obstruction in the path of the slider (9) and hence the motion can be easily transmitted from the operating handle to the slider and thus the switching device can be switched ON.

Figures 5a and 5b show the switching device in OFF condition, the two figures are two views of the mechanism during locking of the door. One of the safety requirements suggests that the panel door should be locked when the switching device is turned ON. This is ensured by means of a door lock (12) component. The door lock component is loaded by a compression spring (13) which is hooked on to the door lock (12) through the part 12(c). Whenever the switching device needs to be switched OFF, the slider (9) moves downwards and the arm of the slider (9a) engages with the arm of the door part (12a). Thus while switching the device from ON to OFF state it pushes the door lock part back. The spring (13) gets compressed and the door lock moves in to make the door free.
When the switching device needs to be switched ON, the slider (9) moves upwards, in doing so it removes the force it was applying on the arm of the door lock (12a), as the force decreases the compressed spring (9) applies a force on the door lock and pushes it out. A part of the door lock component (12b) mates with a feature in the rotary mechanism housing to stop the door lock at designed length. The panel door (1} has a door interlock bracket (15) mounted on it. This bracket essentially locks the door. The door interlock bracket travels with the door. Due to the wedge (12d) provided the outer surface of the door the interlock bracket surpasses the door lock and in doing so locks the door as it cannot come back once surpassed. This is shown in Figures 6a and 6b.
The safety requirement demands that the door of the switching device can be opened only by a defeat. This defeat is ensured by a hole (7a) in the rotary mechanism housing, this hole allows a tool to be inserted in the mechanism and push the arm (12b) of the door lock thus pushing it back in the housing and allowing the door to be opened.
The wedge 12d allows for the auto restoration of the panel door, the wedge allows the door lock to move back in the housing as the door interlock bracket strikes it during door locking and come up again as the bracket surpasses the wedge. This feature allows the door to be closed easily in condition of unintended opening.
Another feature added in the mechanism serves the purpose that the switching device cannot be switched off without a defeat if the panel door is open. It someone opens the panel door by the defeat 7a, and tries to shut down the switching device, the door position sensor (11) ensures that the slider cannot come back and provides an obstruction in the path. So the sensor needs to be pushed manually to clear the path of the slider (9) and the device can be switched OFF.

We claim:
1. A panels interlock arrangement with an add-on operating mechanism, for low-
voltage circuit breaker and the like placed in a panel enclosure having a panel
door, the mechanism comprising:
a crank lever driven by an operating handle protruding out of a cut on the panel door, the crank lever having a crank pin;
a slider having an arm and also having a profile cut wherein the crank pin slides, an end of the slider being connected to a breaker knob of the circuit breaker;
one or more guide shafts operatively connected with and imparting straight line movement to the slider, the slider in turn driving the knob by transferring the movement thereto;
a housing having a sensor hole and a mating profile with a defeat hole;
a door position sensor hinged with the housing with a hinge pin, the sensor having a sensor end surfacing on the facia of the housing through the sensor hole and having its rear end positioned in the path of and thereby arresting movement of the slider and thereby locking movement of the breaker knob, till the panel door is open;
a door lock component having an arm capable of engaging with the arm of the slider, having a wedge-shaped end, and loaded by a compression spring hooked thereto, the spring keeping the wedge-shaped end protruded out of the housing; and
a door interlock bracket mounted on the panel door, the bracket surpassing the wedge-shaped end when the panel door is closed and thereby locking the panel door.
2. The arrangement of Claim 1 wherein when the panel door is closed it sits on the facia of the housing pushing in the sensor end and thereby de-positioning the rear end of the door positioning sensor, so as to allow movement of the slider and thereby un-lock movement of the breaker knob.
3. The arrangement of Claim 1 wherein when the breaker is switched OFF with the operating handle, the slider moves downwards and the arm of the slider engages

with the arm of the door lock component pushing door lock component inward against the compression spring, drawing the wedge-shaped end inside the housing and thereby unlocking the panel door; and when the breaker is switched ON with the operating handle the slider moves upwards removing the force it was applying on the arm of the door lock component, whereupon the compression spring pushes the door lock component out, restoring the wedge-shaped end outside the housing.
4. The arrangement of Claim 1 wherein a mating part of the door lock component mates with the mating profile of the housing so as to stop the door lock component at a designed length whilst keeping the wedge-shaped end protruded outside the housing.
5. The arrangement of Claim 1 wherein a tool can be inserted through the defeat hole and pushed further thereby pushing the door lock component inward, drawing the wedge-shaped end inside the housing and thereby unlocking the panel door.
6. The arrangement of Claim 5 wherein the breaker cannot be switched OFF unless the sensor is manually pushed in to de-position the rear end of the door positioning sensor and thereby clear path for movement of the slider.
7. The arrangement of Claim 1 wherein the add-on operating mechanism is directly mounted on the circuit breaker with one or more fastening means such as screws, nut-bolts and the like.