FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(See section 10 and rule 13)
1. TITLE OF THE INVENTION EMERGENCY HANDLE FOR SWITCHING DEVICE (NFPA COMPLAINCE)
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
PROVISIONAL COMPLETE
The following specification describes The following specification particularly describes the
invention invention and the manner in which it is to be performed
4. DESCRIPTION (Description shall start from next page)
5. CLAIMS (not applicable for provisional specification. Claims should start with the preamble -"I/We claim" on separate page)
6. DATE AND SIGNATURE (to be given on the last page of specification)
7. ABSTRACT OF THE INVENTION (to be given along with complete specification on the
separate page)
Note:
*Repeat boxes in case of more than one entry
*To be signed by the applicant(s)or the authorized registered patent agent
*Name of the applicant should be given in full, family name in the beginning
*Complete address of the applicant should be given stating with postal index no. / code, state and
country
*Strike out the column which is/are not applicable

EMERGENCY HANDLE FOR A SWITCHING DEVICE
Field of the invention
The present invention generally relates with rotary operating mechanism/handle for electrical switching devices/MCCBs and particularly to a safety interlock mechanism for electrical switching devices. The present invention more particularly relates to safety interlock in-built in a rotary operating mechanism/ handle and a ready provision in case of emergency used for operating molded case circuit breakers.
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 operator. Most often these switching devices are operated either from outside or by opening the enclosure or panel door.
Molded case circuit breakers incorporate a mechanical switching which can be achieved by operating the knob. Conventionally the motion of knob is either 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 electrical systems and equipments. In view of operator's safety, remote operation and mechanisms extending outside the enclosure or 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 as Rotary handle mechanism.
The existing rotary operating mechanisms provide leverage to operations of switching devices, particularly 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 the ingress protection level (IP) of 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 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.
US 3324259 relates to handle mechanisms for operation of enclosure mounted circuit breakers and more particularly to more variable depth means and indexing means having front, rear and connecting section and handle extending outside the cover and having means for adjusting depth for adapting enclosures with differing depth.
US 3697714, US3970808 relates to rotary operating handles for operating a switch device secured to the rear wall of the enclosure is mounted separate from the enclosure cover and extends through a cover opening to be operable from outside.
Also few examples of lockable rotary handle operators are described in US 5219070 and US6423912, US 6596952, US 6797903 both mounted outside the enclosure and connected to the circuit interrupter mounted at the rear end through connecting sections, which provides safety interlocks and defeat able cover interlocks for the state of art circuit breakers.
NFPA 79 is the widely recognized official standard in the US for electrical and electronic an apparatus and systems for industrial machinery. The standard is analogous in its scope with the European Machinery Directive standard IEC / EN 60 204-1 [5].
The standard now more clearly reinforces, for UL listed assemblies, the requirement in NFPA 79 that states 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. Additionally it states that 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. For switches requiring emergency The North American standard stipulates that the operating handle must always be permanently connected to the switch. This applies even when the control panel door is open.
There also exists a need to provide safety interlocking with minimum components and a one which provides interlocking at various operating modes without changing the component

configuration, for an operating handle that apart from having the requirements of operation and safety interlocks as mentioned above integrates operations of a circuit breaker even if the door is open but with a deliberate and definite action by the user, thus being in line with NFPA 79 standards.
This particular design also establishes permanent connection with the breaker even when the control panel door is open however the operations are inhabited by means of interlock which can further be defeated by means of deliberate operation. The above mentioned requirements integrated to make the design adaptable for the required needs mentioned is discussed in greater details.
Object of the invention:
The object of the present invention is to provide a simple construction for rotary handle mechanism used to operate circuit interrupter enclosed within an enclosure where handle is permanently coupled to the switching device / circuit breaker irrespective of the door position.
Another objective of the invention is to have a profiled bezel mounted on the door which serves as a means for the operating handle to sense the door position and also forms means to unblock the operating interlock for door position.
Yet another objective is to operate the handle directly coupled to the breaker when panel door is in open condition by using deliberate action. To operate this handle user first has to do some deliberate action otherwise he will not be able to operate.
Further object of the present invention is to provide a positive indication of circuit interrupter.
Yet another object of the present invention is to provide an improved safety locking arrangement by which the door gets interlocked once the switching device is switched ON.
Yet another object of present invention is to provide an intelligent defeat interlock to prevent unauthorized persons from opening the enclosure when circuit interrupter is closed and a defeat able switch interlock integrated in the handle which ensures accidental closure ( switching ON ) of circuit interrupter when the enclosure cover is open and a locking means to prevent unauthorized operation.

Yet another object of the invention is to have flexibility of handle to bezel fitment which may arise due to manufacturing / installation variations.
Summary of the invention
An emergency handle for operating switching device comprises a switching device mounted in the distribution panel. A connecting shaft connects the switching device to the manual operating handle knob through a coupler and a cam mounted around the coupler. Operating handle provides actuation to the switching device. An intermediate frame is rigidly mounted on the rear end of the panel and has a slot on its surface. An operating handle mechanism is mounted in the slot on the intermediate frame. The operating mechanism consists of a slotted base plate mounted on the intermediate frame with a spring loaded lock lever mounted on it and a slotted escutcheon plate covering the base plate. One end of the lock lever projects out of the slot on the escutcheon plate and an operating knob is mounted in the slotted escutcheon plate. A slotted cam mounted around the coupler engages with the lock lever in OFF condition. An interlock assembly for locking the panel door in ON condition is mounted on the escutcheon plate and moves only when the cam is disengaged from the lock lever and a manual interlock defeat arrangement for opening the panel door in ON condition is provided. A bezel assembly having a fixed plate is mounted on the panel door and a spring loaded moveable bezel mounted around the fixed plate. The bezel assembly has an actuating projection for actuating the lock lever in the intermediate frame when the panel door is closed and an opening for operating the interlock assembly on the escutcheon plate.
Description of the Drawings:
Figure 1 is a perspective showing a circuit breaker mounted within a panel having an open-able cover, along with rotary operating mechanism constructed for operation in accordance with present invention.
Figure 2 shows exploded in a line end view of the rotary operating mechanism consisting of floating interlock and knob assembly.

Figure 3 shows front, top and bottom view of complete assembly showing interlocking between the bezel and knob assembly when the circuit breaker in switched ON.
Figure 4 shows front, side and bottom view of knob assembly when the knob and eventually the circuit breaker is in OFF condition, wherein the lock sub-assembly and self lock lever both are in their stand-by state creating interlock for OFF condition.
Figure 5 shows front, side and bottom view of the knob assembly when the circuit breaker is in ON condition, wherein the lock sub-assembly and self lock lever are both in action creating a interlock with bezel eventually with the panel door.
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 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 suited 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.
The various embodiments of the present invention provide simple construction for rotary handle mechanism incorporating door interlocking and other safety interlock assembly for operating switching devices. The main assembly broadly splits up in two sub assemblies. One, which is mounted on the front side of the rear end of the switching device extending through a connecting section here forth referred as Knob sub-assembly, which eventually comes out of the enclosure cover when the cover is closed and another which is mounted on the front side on the cover of the enclosure ( hence forth called as the Bezel sub assembly) which mainly functions for door

interlocking and accommodation of first sub- assembly making readily available to the user, here forth referred as cover sub assembly.
Further the Knob sub-assembly consists of a lock sub-assembly which readily slides inside the guided space and provides effective door interlocking and intelligent defeat when the switching device is closed. The knob sub-assembly, which is mounted on the front of the circuit breaker, can either be directly mounted on the circuit breaker incorporating rotary mechanism for switching operation or it can be mounted on an intermediate plate/frame extending from the rear end of circuit breaker and coupled with the rear end through an extending shaft. This sub-assembly consist of a knob lock mechanism which avoids switching ON of the circuit breaker unless until the door is closed and another sub assembly get incorporated with the first one. The knob sub assembly in a case of maintenance check or under authorized person check also allows operating the knob by actuating a tool defeat able interlock at the bottom right of the assembly. The cover of enclosure when closed brings the floating cover sub-assembly in relation with the knob sub-assembly, which carries a protruded feature at its bottom right which actuates the interlock of first sub assembly, thus enabling operation of the knob.
When the knob is operated, i.e. the circuit breaker is closed, it actuates a cam operated lock sub-assembly which interlocks the knob sub assembly with cover sub assembly thus locking the cover of the enclosure and preventing it from being opened. The knob indicates the right position of the circuit breaker and carries a padlock arrangement which is then used to manually lock the knob subassembly and eventually the circuit breaker in either closed (ON) or opened (OFF) mode. Also the various embodiment of knob sub-assembly provides for locking of the coupler shaft when the knob is switched ON. and a deliberate action is required for releasing it. Also the specific profile of the back-plate of knob sub-assembly incorporates for proper engagement of coupler shaft in case of sagging and misalignment.
Also the Knob sub-assembly being mounted on the front side of the rear end of the breaker serves for the various feature compliant with standards like NFPA and UL and also helps in reducing the cost for eradicating the use of an extra supplementary handle inside the enclosure.
The floating cover sub-assembly which is mounted on the cover of enclosure serves as a system for door interlocking and also provides a flexibility of accommodating for misalignment of knob

sub-assembly in all three spatial directions thus compensating for human errors occurring while creating door cut-outs.
Components:
1. Panel
2. Panel door
3. Cam locks
4. Circuit breaker
5. Intermediate handle mounting plate
6. Knob assembly
7. Bezel assembly
8. Bezel
9. Bezel base plate
10. Rubber tube
11. Cover plate
12. Screws
13. Padlock
14. Knob
15. Coupler
16. Escutcheon plate
17. Slotted cam
18. Lock sub-assembly
19. lock lever
20. Back plate
21. Housing spring
22. Spring loaded cam
23. Housing.
The operating mechanism majorly comprises of two assemblies:
A) Knob assembly
B) Bezel assembly

The function of knob assembly (6) is to render operations of circuit breaker from outside the enclosure and incorporate the lock sub-assembly (18), slotted cam (17) and other components between the E-plate (16) and back-plate (20). The knob (14) incorporates a padlock (13) arrangement in it and is rigidly fixed with the coupler (15) with help of screw which sandwiches in between an E-plate which forms the housing for all other components. The slotted cam (17) sits freely around the coupler (15) having planar rotational degree of freedom and constrained for any type of translational movement. The self lock lever (19) sits guided on a construction provided in the E-plate (16) which provides a dual purpose of holding and guiding the self lock lever (19) along with becoming a provision for screwing the backplate (20) with the E-plate (16). The self lock lever (19) is always kept engaged with profiled cam (17) with help of spring force. The lock sub-assembly (18) slides on parallel guide arrangement provided in the E-plate (16) and the motion is governed with help of these guides and housing springs.
The lock sub-assembly (18) consists of housing (23) which carries a spring loaded cam (22) and the housing is further spring loaded with help of housing springs fixed to E-plate (16). The coupler (11) renders to accommodate the coupler shaft. The backplate (20) carries a specific profile to deliberately accommodate the misalignment coupler shaft gets rigidly fixed with the E-plate with help of screw.
The function of bezel assembly (7) is to provide a platform for knob assembly (6) interlocking conditions and eventually provide door interlock. Also it renders for compensating misalignment is all the three spatial co-ordinates with the help of Rubber tube (10) enveloping. The Bezel Base plate (9) is rigidly fixed to the cover of enclosure by four screws, enveloping the cut out made for knob sub assembly. To the Bezel baseplate (9), bezel (8) is supported and kept hanging with the help of rubber tube (10) and gets rigidly fixed with the cover plate (11) with the help of screws (12). The Bezel (8) carries an arrangement which provide a platform for locking of knob assembly (6). When the panel door / cover of the enclosure is in opened condition, the knob (14) renders to be non-operative due to self lock lever (19) thus providing prevention to unauthorized closure of circuit breaker. As the panel door / cover is closed. The arrangement on floating cover sub-assembly gets adapted with the knob assembly (6) and self lock lever (19) is released thus providing operational mode for knob (14). As the knob is functioned to turn ON the circuit breaker, the profiled cam (17) functions the lock sub-assembly (18) and the knob assembly (6)

gets locked in the arrangement on the bezel assembly (7) eventually interlocking the cover / panel door and thus preventing opening of enclosure cover / panel door when circuit breaker is closed / ON condition. The bezel (8) carries an arrangement for tool defeat and thus the cover / panel door can be set opened.
The floating cover sub-assembly is so designed that along with achieving the functionality, it maintains the aesthetics with respect to design profiles of the knob sub assembly. Also the whole assembly provides a flexibility of using only the knob sub- assembly for the sole purpose wherever NFPA compliance is not required, thus bringing a modularity in use as per user application and requirement. Also the whole sub assembly comprises of minimal components thus making the rotary operating handle cost effective.

We claim,
1) An emergency handle for operating switching device comprising,
a switching device, the switching device mounted on the rear end of the distribution panel,
a connecting shaft, one end of the shaft connected to the said switching device and operates the switching device based on external actuation,
an intermediate frame, the frame being rigidly mounted on the rear end of the panel, the frame having a slot on its surface,
an operating handle mechanism, the operating handle mechanism mounted in the said slot on the intermediate frame, the operating mechanism having a slotted base plate with a spring loaded lock lever mounted on the slotted base plate and a slotted escutcheon plate covering the base plate wherein one end of the said lock lever projects out of the slot on the escutcheon plate, an operating knob mounted in the slotted escutcheon plate with a coupler connecting the operating knob to the said connecting shaft and a slotted cam mounted around the coupler wherein, another end of the lock lever engages with the slotted cam in OFF condition,
an interlock assembly for locking the panel door in ON condition, the interlock mounted on the said escutcheon plate and moves only when the cam is disengaged from the lock lever and a manual interlock defeat arrangement for opening the panel door in ON condition and
bezel assembly, the bezel assembly having a fixed plate mounted on the panel door and a spring loaded moveable bezel mounted around the fixed plate, the bezel assembly having an actuating projection for actuating the said lock lever in the intermediate frame when the panel door is closed and an opening for operating the said interlock assembly on the escutcheon plate.

2) An emergency handle for operating switching device of the claim 1 wherein, when the panel door is closed, the actuating projection on the bezel actuates the lock lever thereby releasing the slotted profile cam and allowing movement of the knob.
3) An emergency handle for operating switching device of the claim 1 wherein, closing of panel door allows operation of knob which transmits the torque through the coupler and the connecting shaft to the switching mechanism of the breaker.
4) An emergency handle for operating switching device of the claim 1 wherein, when the panel door is opened, the lock lever engages with the slotted cam thereby restricting the motion of the knob.
5) An emergency handle for operating switching device of the claim 1 wherein, the interlock assembly consists of a spring loaded lever with a guide for engaging the interlock with the bezel assembly.
6) An emergency handle for operating switching device of the claim 1 wherein, when the knob is switched ON, the slotted cam actuates the interlock assembly which locks the panel door.
7) An emergency handle for operating switching device of the claim 1 wherein, the manual interlock defeat arrangement consists of a provision of pin access in the bezel to defeat the interlock only when door is to be opened in ON condition and avoiding accidental operation of the switching device.
8) An emergency handle for operating switching device of the claim 1 wherein, the spring loaded movable bezel mounted around the fixed plate provides for flexible accommodation of operating mechanism on panel door along all three axis.

9) An electrical distribution panel comprising;
a switching device, the switching device mounted on the rear side of the distribution panel,
a connecting shaft, one end of the shaft connected to the said switching device and operates the switching device based on external actuation.
an intermediate frame, the frame being rigidly mounted on the rear end of the panel, the frame having a slot on its surface,
an operating mechanism, the operating mechanism mounted in the said slot on the intermediate frame, the operating mechanism having a slotted base plate with a spring loaded lock lever mounted on the slotted base plate and a slotted escutcheon plate covering the base plate wherein one end of the said lock lever projects out of the slot on the escutcheon plate, an operating knob mounted in the slotted escutcheon plate with a coupler connecting the operating knob to the said connecting shaft and a slotted cam mounted around the coupler wherein, another end of the lock lever engages with the slotted cam in OFF condition,
an interlock assembly for locking the panel door in ON condition, the interlock mounted on the said escutcheon plate and moves only when the cam is disengaged from the lock lever and a manual interlock defeat arrangement for opening the panel door in ON condition and
bezel assembly, the bezel assembly having a fixed plate mounted on the panel door and a spring loaded moveable bezel mounted around the fixed plate, the bezel assembly having an actuating projection for actuating the said lock lever in the intermediate frame when the panel door is closed and an opening for operating the said interlock assembly on the escutcheon plate.