FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
As amended by the Patents (Amendment) Act, 2005
AND
The Patents Rules, 2003
As amended by the Patents (Amendment) Rules, 2006
COMPLETE SPECIFICATION
(See section 10 and rule 13)
TITLE OF THE INVENTION An improved clamping assembly.
APPLICANT(S)
Crompton Greaves Limited, CG House, Dr Annie Besant Road, Worli, Mumbai 400 030, Maharashtra, India, an Indian Company
INVENTOR(S)
Mehta Shailesh, Parab Manoj and Kulkarni Shweta; all of Crompton Greaves Limited, Drives & Automation (M7-DTS), Crompton Greaves Ltd., Ramanuja Building, Kanjur Marg (East), Mumbai 400 042, Maharashtra, India; all Indian Nationals.
PREAMBLE TO THE DESCRIPTION:
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:

FIELD OF THE INVENTION:
This invention relates to mechanical assemblies, mechanical fixtures, and mechanical engineering.
Particularly, this invention relates to auxiliary converters and all converters / inverters with disc type of devices (Diode / Thyristor / GTO).
Specifically, this invention relates to an improved clamping assembly for auxiliary converters.
BACKGROUND OF THE INVENTION:
Electric drive equipment for railway applications requires many different products. One of them is an auxiliary converter. This may be a 3-phase AC converter.
Auxiliary power converters are used on board all types of mass transit public service vehicles including high speed, light rail and main line trains, underground trains, trams and trolley buses. The auxiliary converter units (ACU) cater to the power needed by the auxiliary motors of the vehicle by switching the input voltage from overhead line or 3rd rail power supplies, which is often unstable, into constant regulated voltage.
Typically, these converters have rectifiers and inverters where the devices are clamped with certain clamping force (10KN or @ lOOOKgs in this case).
According to prior art clamping systems, fiber glass threaded rods (Ml2) were used for the insulation to be provided between the device anode and cathode points. These rods needed to be first tightened in M12 hole of the heat sink and

then force was to be applied by tightening (aluminum) M12 nuts. There were repeated instances of threads of the rods wearing away due to the force and also of rods getting broken in the field leading to device failure.
Such clamping systems were used for equipments/products such as converters / inverters with disc type of devices (Diode / Thyristor / GTO).
Hence, there is a need for a better and improved clamping system which obviates the limitations of the prior art.
OBJECTS OF THE INVENTION:
An object of the invention is to provide an improved clamping assembly.
Another object of the invention is to provide an improved clamping assembly for auxiliary converters.
Yet another object of the invention is to provide an improved clamping assembly for converters / inverters with disc type of devices (Diode / Thyristor / GTO)
Still another object of the invention is to provide an improved clamping assembly in order to remove problems relating to thread wear and tear.
An additional object of the invention is to provide an improved clamping assembly in order to remove problems relating to rod break down.
SUMMARY OF THE INVENTION:
According to this invention, there is provided an improved clamping assembly,

said assembly comprises:
a device located on an insulated cell placed on a heat sink or on a metal island attached to said heat sink; centering pins located advantageously for co-axial location of said insulating cell and said device to be clamped with respect to a pressure spring adapted to exert pressure on to a pressure plate co-axially located operatively above said device, said pressure spring being held in a device clamping yoke placed above said pressure plate and said device, characterised, in that, device clamping yoke being an Fibre-reinforced plastic yoke with laterally located through holes for allowing passage of metallic bolts, said assembly further comprising at least two metal blocks / reducer / circular inserts, with a plurality of tappings for receiving said bolts for clamping.
Typically, said assembly comprises at least two pipes adapted to be located below said yoke and co-axially located with one of said tappings of said blocks, said each of said metallic bolts pass through each of said pipes, respectively.
Typically, said metallic bolts extend through said through-holes located laterally at said yoke.
Typically, said metallic bolts include external threading at the operative bottom portion in order to engage with internal threading of said metal plate.
Preferably, said tappings are M8 tappings.
Typically, said metal blocks are located on a heat sink and adjacent said insulated cell.

Typically, said assembly comprises centering pins located advantageously (below insulated cell, between device to be clamped and insulated cell, above device to be clamped) for co-axial location of said insulating cell and said device to be clamped with respect to a pressure spring.
Typically, said pressure spring is located co-axially through said yoke.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a clamping assembly of the prior art.
The invention will now be described in relation to the accompanying drawings, in which:
Figure 2 illustrates a clamping assembly according to this invention.
DETAILED DESCRIPTION OF THE ACCOMPANYING DRAWINGS:
Figure 1 illustrates a clamping assembly of the prior art.
A device (12) to be clamped such as a diode or a thyristor or the like of equipment such as auxiliary converters is located on an insulated cell (14) placed on a heat sink (16). Centering pins (18) are located advantageously (below insulated cell, between device to be clamped and insulated cell, above device to be clamped) for co-axial location of the insulating cell and the device to be clamped with respect to a pressure spring (24). A pressure plate (22) is co-axially located operatively above the device (12). For its operation, a pressure spring (24) is located so that application of pressure from the operative top surface on to the pressure plate may be effected. The pressure load may be in the range of about 1OKN. The pressure

spring (24) is held in a device clamping yoke (26) placed above the pressure plate and the device. At the lateral sides of the device clamping yoke, slots or through holes are provided in order to allow passage of threaded rods (28). Guiding nuts (32) above the slots or through holes of the device clamping yoke are provided in order to guide the threaded rods. These guiding nuts, typically, include inner threads which engage with the outer threads of the threaded rods. The threaded rods pins the device clamping yoke to the assembly, in general. Centering washers (34) are provided about the threaded rods at their relative bottom portion. The threaded rods are screwed in to the device clamping yoke by means of the guiding nuts.
The threaded rods were fiberglass threaded Ml2 rods for providing 10 KN force and insulation. However, these were prone to threads wearing out and resulted in instances of rods breaking in the field. These guiding nuts, typically, were aluminum nuts.
According to this invention, there is provided an improved clamping assembly.
Figure 2 illustrates a clamping assembly according to this invention.
In accordance with an embodiment of this invention, there are provided at least two metal blocks (52a, 52b) with a plurality of tappings. Typically, these tappings are M8 tappings. These metal blocks are located on the heat sink (16) and adjacent the insulated cell (14). Centering pins (18) are located advantageously (below insulated cell, between device to be clamped and insulated cell, above device to be clamped) for co-axial location of the insulating cell and the device to be clamped with respect to a pressure spring (24). A pressure plate (22) is co-axially located

operatively above the device (12). For its operation, a pressure spring (24) is located so that application of pressure from the operative top surface on to the pressure plate may be effected. The metal blocks include internal threading at the tappings.
In accordance with another embodiment of this invention, there is provided a device clamping yoke adapted to be an FRP yoke (54) located above the pressure plate. The pressure spring is located through the FRP yoke, typically, through its centre.
In accordance with yet another embodiment of this invention, there are provided at least two pipes (56a, 56b) adapted to be located below the yoke and co-axially located with one of the tappings of the blocks. Two metallic bolts (58a, 58b) pass through the at least two pipes, respectively. The metallic bolts extend through the through-holes located laterally at the yoke. The metallic bolts include external threading at the operative bottom portion in order to engage with the internal threading of the metal plate.
The technical advancement of this invention lies in providing a clamping assembly with a reliable and strong clamping mechanism provisioned by the incorporation of a fibreglass yoke with fibreglass pipes with internal metallic bolts to be engaged in bottom located metal blocks for prevention of thread wear and breakage.
While this detailed description has disclosed certain specific embodiments of the present invention for illustrative purposes, various modifications will be apparent

to those skilled in the art which do not constitute departures from the spirit and scope of the invention as defined in the following claims, and it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation.

We claim
1. An improved clamping assembly, said assembly comprising:
a device located on an insulated cell placed on a heat sink or on a metal island attached to said heat sink; centering pins located advantageously for co-axial location of said insulating cell and said device to be clamped with respect to a pressure spring adapted to exert pressure on to a pressure plate co-axially located operatively above said device, said pressure spring being held in a device clamping yoke placed above said pressure plate and said device, characterised, in that, device clamping yoke being an Fibre-reinforced plastic yoke with laterally located through holes for allowing passage of metallic bolts, said assembly further comprising at least two metal blocks / reducer / circular inserts, with a plurality of tappings for receiving said bolts for clamping.
2. The improved clamping assembly as claimed in claim 1, wherein said assembly comprising at least two pipes adapted to be located below said yoke and co-axially located with one of said tappings of said blocks, said each of said metallic bolts pass through each of said pipes, respectively.
3. The improved clamping assembly as claimed in claim 1, wherein said metallic bolts extend through said through-holes located laterally at said yoke.
4. The improved clamping assembly as claimed in claim 1, wherein said metallic bolts include external threading at the operative bottom portion in order to engage with internal threading of said metal plate.

5. The improved clamping assembly as claimed in claim 1, wherein said tappings are M8 tappings.
6. The improved clamping assembly as claimed in claim 1, wherein said metal blocks are located on a heat sink and adjacent said insulated cell.
7. The improved clamping assembly as claimed in claim 1, wherein said assembly comprising centering pins located advantageously (below insulated cell, between device to be clamped and insulated cell, above device to be clamped) for co-axial location of said insulating cell and said device to be clamped with respect to a pressure spring.
8. The improved clamping assembly as claimed in claim 1, wherein said pressure spring being located co-axially through said yoke.