FORM 2
The Patents Act 1970
(39 of 1970)
&
The Patent Rules 2003 PROVISIONAL SPECIFICATION
(See Section 10 and rule 13)
TITLE OF THE INVENTION:


INDEXING MECHANISM FOR POSITIVE INDICATION OF DISTINCT
POSITIONS (ISOLATED - TEST - SERVICE) IN FULL WIDTH FEEDER
MODULES OF MOTOR CONTROL CENTER SWITCHBOARDS
APPLICANT:
LARSEN & TOUBRO LIMITED
L&T House, Ballard Estate, P.O. Box No. 278,
Mumbai, 400 001, Maharashtra . INDIA.
PREAMBLE OF THE DESCRIPTION:
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

A) TECHNICAL FIELD
[0001] The embodiments herein generally relate to the switching devices and more particularly it relates to the position indication of distinct module positions in switchboard.
B) BACKGROUND OF THE INVENTION
[0002] Switching devices such as miniature circuit breakers, residual circuit breakers and isolators etc are used in domestic and industrial applications for protection against over currents. It is generally required to control electrical power networks by switching circuit "ON", by carrying load and by switching circuit "OFF" under manual or automatic suspension. When there is an over current resulting in an electrical circuits, the contacts in the switching devices open or trips to block the current which is greater then the rating of the current device.
[0003] There are several provisions available to control the electrical contacts. In some cases it includes manual operation, where the moving contact is moved in conjunction with the fixed contact to open or close the electrical connection. In other cases, whenever the over current occurs in the power circuits, the circuit breakers trips automatically to break the contacts. The function of the circuit breakers is to maintain two stable conditions close and open.
[0004] However in certain cases the switching devices operate due to fault. During operation of switching devices like miniature circuit breaker, residual current circuit breaker, and isolator there are chances that due to high currents contact gets welded and current still flows through circuit even if knob of device showing it in "OFF" state. So in case of maintenance if someone comes in direct contact with circuit, thinking breaker is "OFF", it may result in serious shock and can be fatal. In some circumstances the moving contact remains stuck on fixed contact with an adhesive force such that the mechanism is not enough to break the joint.


[0005] In some cases where circuit breakers used are relatively smaller in size and light in weight the circuit breakers are provided with plug-in type primary disconnect contacts that do not require direct contact to effect their connection and disconnection with mating disconnect contacts of the switchboard. In these cases circuit breaker can be plugged in and unplugged from a live switchboard easily and safely,
[0006] For higher current applications, the circuit breakers used are large and quite heavy and so the movement of the circuit breaker to electrically connect and disconnect it from the switchboard is quite difficult. Due to increase of the current ratings, the contact pressures of the primary disconnect contacts becomes extremely difficult to handle. Drawout apparatus are used to support such electrical device for racking movement between an extended position well out of an enclosure compartment and an engaged position within the compartment where the load current carrying primary disconnect contacts of the device and enclosure-are fully engaged. A test position is provided for the device between its engaged and extended positions where the primary contacts are separated but the secondary contacts are still engaged. In this test position, the accessorial functions can be thoroughly tested in safety while the device is "dead". Hence it is important to provide position indication mechanism to the operator in the drawout apparatus, so that the operator can be aware of position of the device relative to the enclosure for safety purposes.
[0007] It is an object of the present invention to provide an indexing mechanism for positive indication of distinct positions (Isolated - Test - Service) in full-width feeder modules of Motor Control Center (MCC) Switchboards.
[0008] Yet another object is to provide a position indicator of the above character which is reliable and automatic in operation, and inexpensive to manufacture.
[0009] Other objects of the invention will in part be obvious and in part appear hereinafter.
C) BRIEF DESCRIPTION OF THE DRAWINGS


[0010] The other objects, features and advantages will occur to those skilled in the art from the following description of the preferred embodiment and the accompanying drawings in which:
[0011] FIG. 1 illustrates the front view of the position indication assembly according to one embodiment of the present invention.
[0012] FIG. 2 illustrates the indexing mechanism for positive indication of distinct positions (Isolated - Test - Service) in Full-width feeder modules according to one embodiment of the present invention.
[0013] Although specific features of the present invention are shown in some drawings and not in others. This is done for convenience only as each feature may be combined with any or all of the other features in accordance with the present invention.
D) DETAILED DESCRIPTION OF INVENTION
[0014] In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which the specific embodiments that may be practiced is shown by way of illustration. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments and it is to be understood that the logical, mechanical and other changes may be made without departing from the scope of the embodiments. The following detailed description is therefore not to be taken in a limiting sense.
[0015] The various embodiments of the present invention provide an indexing mechanism and assembly for positive indication of distinct positions (Isolated - Test -Service) in full-width feeder modules of Motor Control Center (MCC) Switchboards.
[0016] As shown in FIG. 2, indexing cam (1) is positively coupled with the mechanism shaft (8). As the cam is rotated clockwise through rotation of the shaft, it makes contact with roller (5). The cam engages with roller and presses the indexing fork (3) to move sideways. As the fork moves laterally, it compresses the spring (7) inside the side bracket (6) till the indexing cam gets locked in one of the indicating positions viz. Isolation-


Service- Test. The cam has four lobes such that the transition into various positions is distinctively achieved. An indicator disc (2) is directly attached with shaft to indicate the positions. The displacement of roller over cam surface is equal to the compression of indexing spring. During the initial quarter turn (clockwise) of shaft (i.e. 0° -90°), isolation - test transition is made by the indexing mechanism. In the next quarter turn of shaft (i.e. 90° - 380°), test-service transition is made. Every transition is clearly evident by the labels shown on indicator disc. Also, a clear click-sound is heard when the roller gets locked in one of the dwell positions in the cam. This audible signal in turn, confirms that the mechanism has made transition from one position to another. The mechanism indicates the true positions of service, isolation and test conditions inside the feeder. This involves a unique cam profile for roller follower movement where the cam displacement is converted into deflection of spring.
[0017] Hence the invention provides an easy-to-assemble and easily operable assembly which can be extensively used for the cases where true indication of the positions of electrical contacts such as isolated, test, service etc. can be displayed.
The detailed description and various embodiments of the invention along with the Claims shall be provided in the Complete Specification.
Dated this the,30th day of March 2009

RAKESH PRABHU
Patent Agent,
ALMT Legal,
#2, Lavelle Road, Bangalore-560 001
To,
The Controller of Patents, The Patent Office, Mumbai