F0RM2THE PATENTS ACT, 1970(39 of 1970) &The Patents Rules, 2003COMPLETE SPECIFICATION(See section 10; rule 13)
Title of the invention - POSITION INDICATOR
2. Applicant(a) NAME : LARSEN & TOUBRO LIMITED(b) NATIONALITY : An Indian Company(c) ADDRESS : L&T House, Ballard Estate, Mumbai 400 001, State of Maharashtra, India
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in performed: which it is to be

FIELD OF INVENTION
The present invention relates to a device for indicating different positions in a switchboard or switchgear modules. More particularly, the invention relates to a device for indicating at least three different positions in a switchboard or switchgear modules without physically moving it and with door in closed condition.
BACKGROUND AND PRIOR ART
Module in the switchboards has 3 distinct positions. Service, Test and Isolation. When Power Contacts and Auxiliary contacts both are engaged it is called as Service position. When power contacts are engaged and auxiliary contacts are disengaged it is called Test condition. When both contacts are disengaged it is called Isolation condition.
Generally, for achieving these three different positions of the module, the front door of the switchboard module is to be opened and the power and auxiliary contacts, which are mounted on the rear side of the module, .are moved physically. The relative movement of the module with respect to stationary tray indicates these three different positions. This tray consists of a sticker marked as Service, Test and Isolation at particular distance..
CA104 6566 describes a draw-out mechanism capable of racking electrical devices of large size and weight in an electrical enclosure. Racking movement is powered via a racking screw and cam combination to provide enhanced mechanical advantage.
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Interlocks and latches are provided to insure authorized, safe operation.
CA1058021 describes .a position indicator for indicating the position of an electrical device relative to an electrical enclosure.
In none of the prior art is described an apparatus or a device
or an .arrangement which would indicate position of contacts
without physically moving the module and keeping the door in
closed condition.
Thus there is a need to provide for a device for indicating at least three different positions in a switchboard or switchgear modules without physically moving it and with door in closed condition.
The present inventor have found that different position indication can be achieved, more specifically at least three or more position indications can be achieved by suitable and appropriate meshing of gear with the other components of the device.
OBJECTS OF INVENTION
Accordingly, one object of the present invention is to provide a device for precisely indicating different positions in a switchboard or switchgear module.
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Another object of the present invention is to provide a
position-indicating device such that the position can be realized without opening the door of the module.
Yet another object of the present invention is to provide a position-indicating device such that the position can be realized without moving the module.
SUMMARY OF INVENTION
According to one aspect of the present invention there is provided a device for indicating different position of contacts in switchboard or switchgear modules, said device comprising:
displaying unit operatively connected to a racking mechanism which includes racking screw means, said displaying unit comprises gear means located on a shaft means and in contact with the screw means,
indicator assembly located along the shaft means comprising worm wheel means, said indicator assembly being located such that there is no interference between the gear means and the indicator means,
driver means being operatively journalled to said screw means so as to transform movement of the screw means to the shaft
characterized in that said driver means being meshed with said gear means such that the number of revolution of screw means being same as that of the gear
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thereby providing for accurate indication of the position of the
contacts.
DETAILED DESCRIPTION OF INVENTION
The power/auxiliary contacts in module are not rigidly fixed to the module frame, which is necessary for the movement of contacts without moving the door with respect to the module frame. The racking mechanism in the module racks out or racks in Power and auxiliary contacts to achieve Service, Test and Isolation positions. In this case, only power and auxiliary contacts move, the module being stationary and the door closed. The above stated situation leads to the difficulty of identifying different positions of the module from front. The present device solves this difficulty and gives indication for these distinct positions. This position indicator is able to show three distinct position of module by displaying ' S', 'T' and 'I' for Service, Test and Isolation position of contacts respectively. However, these indicator alphabets and the number of positions do not restrict the scope of the invention and are meant to be taken in true spirit.
One embodiment of the present invention comprises displaying unit mounted on the module front door and the indications can be seen from the glass window provided on the module front door. At the other end the displaying unit is mechanically connected to the racking mechanism, which includes a lead screw. The unit comprises gear means located on a shaft means and in contact with the lead screw. A driver means comprising of a pinion which is mounted and journalled on the lead screw of racking mechanism
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and is meshed with the gear means. The gear means mounted on the worm shaft comprises worm wheel. The motion of the lead screw is transferred to worm shaft with the help of pinion and gear drive. As the gear ratio of driver i.e. the pinion and driven is 1, the number of revolution of the screw and the shaft of worm is same.
The number of teeth on the worm wheel is always greater than number of turns required to be completed by racking lead screw to bring contacts from service to isolating position and vice versa. Spacer is provided in between the worm wheel and indicator wheel to avoid interference between worm and indicator wheel. Indicator wheel is attached with worm wheel with the spacer in between and it gets movement from worm wheel. Indicator wheel is printed with 'S', 'T' and 'I' for Service, Test and Isolation respectively. The portion between letters 'S1 and 'T' is printed with Red color and the portion between letters 'T' and ' I' is printed with Green color. The spacing between the printed letters is decided by the number of turns of the racking mechanism and the different combination of gear drives. However, this does not restrict the scope of the invention.
Position indicator wheel is placed in such a way that when the contacts are in Service position, indicator shows 'S' from window on the module door. The contacts are racked out using lead screw to reach Test Position from Service position. The pinion mounted on lead screw gets rotated by one revolution, which further rotates the gear mounted on worm shaft with the same number of revolution, as the gear ratio is 1. One revolution of worm shaft is transferred to worm wheel, which rotates, by one teeth and likewise, the distance between letters
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' S' and ' T' is covered by pre defined number of turns. After predefined number of rotation of lead screw, power contacts reaches test position and accordingly position indicator show 'T' which is clearly seen from the window provided on the module door.
The contacts are racked out further using lead screw to reach Isolation Position from Test position. The pinion mounted on lead screw gets rotated by one revolution, which further rotates the Gear mounted on Worm shaft with the same number of revolution, as the gear ratio is 1. One revolution of worm shaft is transferred to worm wheel, which rotates, by one tooth. The indicator assembly comprises indicator wheel having plural visual indications being spaced such that one revolution of the lead screw actuates the indicator wheel to cover space between the two adjacent indications. and likewise, the distance between letters ' T' .and ' I' is covered by pre defined number of turns. After predefined number of rotation of lead screw, power/auxiliary contacts reach Isolation position and accordingly position indicator show 'I' which is clearly seen from the window provided on the module door.
When contacts are racked in to reach Test and then to Service position from Isolation position, the backward rotation of gears will show 'T' then 'S1 respectively for Test and Service positions.
The device can be used to indicate any number of positions of
the contacts.
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BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates an isometric view of the device of the
present invention.
Figure 2A illustrates an exploded view of the device of
displaying unit of the present invention.
Figure 2B illustrates an assembly drawing of the position
indicator.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates an isometric view of the displaying unit connected to a racking mechanism. The location of position indicator (13) is as shown in the figure. As shown in figure 1 position indicating unit mechanism (13) is assembled into the module onto the module door (5) from inside in such a way that the slot on the door will facilitates the exact view of the letters passing by. Indicating device (13) comprises of a outer casing/housing which is fixed to the door (5) . A gear (6) is mounted on the shaft extended out of the casing of the indicating unit (13) . The mating gear/pinion (7) is mounted on the lead screw (9) . Thus the rotation of the lead screw (9) is imparted to the indicating unit mechanism (13) . The lead screw (9) is properly supported into various brackets (8, 14 and 15) mounted on the module frame. Thus the lead screw (9) will have only rotary motion. The nut (12) fastened to the lead screw (9) is. in turn connected to the bracket (8) , on which are mounted the power contacts/auxiliary contacts (not shown in the
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figures). This makes the nut (12) and hence power contacts/auxiliary contacts to travel along the axis of the lead screw (9) , as the later rotates. Also the rear end of bracket (8) used for supporting the lead screw (9) house some interlocks (not shown here), defeating of which is necessary for movement of the nut (12) at certain point in the travel.
Position indicator device unit (13) is placed in such a way that when the contacts are in Service position, indicator shows 'S' from window on the module door. The contacts are racked out using lead screw (9) to " reach Test Position from Service position. The pinion (7) mounted on lead screw (9) gets rotated by one revolution, which further rotates the Gear (16) (shown in figure 2A) mounted on Worm shaft (17) (shown in figure 2A) with the same number of revolution, as the gear ratio is 1. One revolution of worm shaft (17) is transferred to worm wheel (18) (shown in figure 2A) , which rotates, by one teeth and likewise, the distance between letters ‘S' and ‘T' is covered by pre defined number of turns. After predefined number of rotation of lead screw (9), power contacts reaches test position and accordingly position indicator show ‘T’ which is clearly seen from the window provided on the module door.
Figure 2A illustrates an exploded view of that position indicator showing worm shaft (17), worm wheel (18), spacer