4. Description of Invention
PU CENTRE PIVOT LINER (FLAT)
Field of Invention:
This invention relates to "Polyurethane (PU) Flat Centre Pivot Liner (FCPL)" to be used in Indian Railway Freight Stock.
The PU FCPL is an innovative design/substitution of the existing steel liner used on all new wagons manufactured for Indian Railways.
Use of this Polyurethane Flat Centre Pivot Liners will drastically reduce the wear on both the top and bottom steel Centre Pivots resulting in enhanced life for them. The liner itself lasts longer than the existing steel liner, because it has a negligible wear rate.
Detailed Description of Invention:
The salient features of the invention shall be described in detail now.
Figure 1 shows the drawing of the PU Flat Centre Pivot Liner (Drawing No. ARL/CPFL-001), In this drawing the elevation, the plan and a pictorial view are shown with proper dimensions. The elevation is shown in cross section. One important point is mentioned here - the electrical or otherwise conductivity between the super structure and the bogie of the wagon is maintained through the copper conductors in the PU Flat CP Liner. There are four such conductors embedded in the PUFCPL as shown in the drawing.
The coefficient of Friction (|i) between the surface of the top and bottom parts of the Centre Pivot plays an important role in the bogie rotation of the wagon. The rubbing of the two surfaces provide rotational damping, controlling the bogie rotation.
In case of steel to steel rubbing the coefficient of friction is limited to 0.2 to 0.25. But in case of our PU CP Liner the metal to PU coefficient of friction is 0.35 giving rise to higher frictional damping force which improves the riding of the wagon.
Properties of Polymer:
The Polymer used in the manufacture of Flat Centre Pivot Liner has a high temperature
and abrasion resistance with high resilience and hydrolytic stability.
Working Environment: ^
The polymer Centre Pivot Liner (Flat) is capable of working under extreme temperature and humidity variations and is not affected by rain, dust etc.

Advantages of use of PU Flat Centre Pivot Liner;
PU Flat Centre Pivot Liner has several advantages over the conventional steel liners used at present in the Centre Pivot of wagon -
• The wear rate of the PU Centre Pivot Liner is very low therefore its service life is expected to be much longer than that of the steel liners.
• The wear of steel top and bottom surfaces will be negligible, there by enhancing the life of the top & bottom centre pivot also.
• The coefficient of friction (|4.) between PU and steel is higher than that between steel to steel, therefore higher frictional damping to the Bogie Rotation is envisaged.
• With the use of PU Centre Pivot Liner in between the Top and Bottom Centre Pivot the replacement of the Centre Pivot set will be minimized, if not, eliminated.

5. Claims;
I Claim,
Polyurethane Flat Centre Pivot Liner is an innovative design/substitution for the existing steel liner used in the flat centre pivots of all new wagons manufactured for Indian Railways.
Use of this Polyurethane Flat Centre Pivot Liner will drastically reduce the wear on both the top and bottom steel Centre Pivots resulting in enhanced! life for them. The liner itself has a longer service life than the existing steel liners because it has a negligible wear rate. The coefficient of friction (|i) between PU and steel is higher than that between steel liner and steel Centre Pivot. Therefore, this will produce higher frictional damping to the Bogie Rotation which is beneficial to the riding quality of the wagon.