FIELD OF THE INVENTION :-
The present invention relates to an improved constant contact side bearers (CCSBs) for a suspension of broad gauge (1676mm) Casnub 22 NLB bogie for increasing its axle load from 20.32 tons to about 23 tons, and speed potential from 80 km/h in empty condition and 75 km/h in loaded condition to about 100 km/h in empty condition and about 75 km/h under enhanced loading condition of about 23 tons. The improved suspension comprising constant contact side bearers also makes the bogie track friendly.
BACKGROUND OF THE INVENTION :-
The body of the freight car / wagon is generally supported on two trucks / bogies (spaced apart according to the length of the wagon) which permit the wagon to travel along the railway track. Each truck assembly normally consists of two side frames, one bolster, two wheel sets, primary and secondary suspensions, one centre plate, two side bearers, damping and braking arrangements. The side frames are supported over a pair of axles through roller bearings, adapter and elastomeric pads. In a wheel set, two wheels are rigidly fixed on to each axle and spaced from each other to suit the track gauge. Braking force is generally provided by the bogie / wagon mounted brake cylinders through linkages, brake beams and brake blocks.
BOXN / BOXNHS wagons of Indian railways have a similar arrangement wherein two Casnub 22 NLB bogies are placed under the car body, their spacing being determined by the spacing of car body bolsters. Centre plates and constant contact side bearers (CCSBs) are so disposed between the car body bolsters and bogie bolsters, that bulk of the empty car body weight is transferred to bogie bolster through side bearers and balance of the car body weight and pay load is transferred through centre plates.
Existing design of the Casnub 22 NLB bogie as shown in Fig.1 and Fig. 1A has two side frames and a bolster which are hollow steel castings similar in design to the side frames and bolster of a modern 3 piece truck. A rolled steel plate spring plank, riveted at the base of the spring pockets of the side frames rigidly connects the two side frames together,

making the construction a "H" frame. As shown in Fig. 1A, bolster is provided with a hemispherical bowl type centre plate in its centre and rubber spring two constant contact side bearers equispaced from the centre plate.
Existing CCSB, as shown in Fig-2, consists of a metal bonded rubber pad placed in a housing. It has a vertical stiffness of 200 Kg/mm and the CCSBs share 67% of the car body weight. Because of rubber, its pre-load characteristics change with time and temperature which affects the ride behaviour of the bogie in service. It has a service life of about 18 months and there have been lots of premature failures of this design in service.
Indian Patent Document 502/CHE/2004 discloses an improved three-piece truck system for railroad cars provides long travel side bearings for improved stability, a wide friction shoe design or equivalent to improve side frame and bolster squareness, a resilient pedestal pad for improved curving performance and enhanced wear resistance , and a suspension system tuned and optimized for rail cars to have a minimum reserve capacity of less than 1.5 to improve motion control and ride quality, increase resistance to suspension bottoming, and increase hunting threshold speed. Such a motion control truck system is able to meet recent, more stringent American Association of Railroads standards, such as M-976, for railcars having a 286,000 lb. gross rail load rating. However, CCSBs in the present invention are different from the prior art as follows.
(i) The prior art has a pre-set height of 128.59 mm (as per US railway freight car
requirements) whereas the present invention has a pre-set height of 124 mm (as per
Indian Railway freight car requirements).
(ii) CCSBs in the present invention share 90% of the empty car body weight as against
85% in case of the above cited document.
(iii) The pre-set load of CCSBs in the present invention is different from the pre-set load
of CCSBs in the above cited document.
(iv) Each CCSB in the present invention has a vertical stiffness of about 150 kg/mm
which is different from the stiffness of the CCSB in the above cited document.
(v) The shape & size of Housing, Cover and Wear liner in the present invention are
different from those in the above cited document.

(vi) Self lubricating Liner sleeve fitted with cover is the unique feature in the present invention which is absent in the above cited document.
On Indian Railways, Casnub 22 NLB Bogie is predominantly used under open wagons type BOXN / BOXNHS which have an operating speed of 80 Km/hr in empty condition and 75km/hr in loaded condition. These wagons are used for carrying bulk commodities like Coal, Iron ore, Lime stone, Gypsum, Steel, Food Grain, Fertilizer, and Cement etc. These wagons with axle load of 20.32 tons have a carrying capacity of 58.81 tons. During the year 2005-06, Indian Railways decided to increase the carrying capacity of these wagons by 10 tons, thereby increasing the axle load to approx 23 tons. Research Design and Standard Organization (RDSO), Lucknow, was asked to take up this upgradation as a project. RDSO accordingly upgraded the suspension of Casnub 22 NLB bogies and conducted oscillation trials in April 2006. However, lateral forces encountered during the trials almost reached the Prud- Homme limit at 70 Km/h. The wagon could, therefore, be cleared in loaded condition only upto 60 km/h.
Subsequently RDSO approached the indigenous bogie and component manufacturers to come up with a solution consisting of complete suspension covering primary and secondary suspensions and constant contact side bearers (CCSB).
The present inventors have found that by selecting a coil spring having an appropriate stiffness value, constant contact side bearers (CCSBs) for an improved suspension of Casnub 22 NLB bogie of Indian Railways for increasing its axle load from 20.32 tons to about 23 tons, increasing its speed potential from 80Km/h in empty condition and 75 Km/h in loaded condition to about 100 km/h in empty condition and about 75 km/h under enhanced loading condition can be achieved.
OBJECT OF THE INVENTION :-
An object of the present invention is to provide improved constant contact side bearers (CCSBs) that help increase the axle load of Casnub 22 NLB bogie to about 23 tons.

Another object of the present invention is to provide constant contact side bearers (CCSBs) that share 90% of the empty car body weight and the balance car body weight and the pay load are borne by the centre plates.
A further object of the present invention is to provide a construction of constant contact side bearers (CCSBs) that would resist the bogie yaw and lateral movements.
A further object of the present invention is to provide constant contact side bearers (CCSBs) that would prevent the springs from bottoming in service and also would not permit any lateral loading of the springs.
Yet another object of the present invention is to provide constant contact side bearers (CCSBs) that would retrofit in the existing Casnub 22 NLB bogie.
These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention.
SUMMARY OF THE INVENTION :-
Thus the present invention relates to improved constant contact side bearers (CCSBs) for a suspension of broad gauge (1676mm) Casnub 22 NLB bogie for increasing its axle load from 20.32 tons to about 23 tons comprising two rubber spring constant contact side bearers equispaced from and on either side of the centre plate on the bogie bolster and a metal bonded rubber pad placed in a housing the improvement wherein comprising triple nested concentric steel coil spring constant contact side bearers (CCSBs) arrangements having a vertical stiffness of about 150 kg/mm

According to preferred embodiment the constant contact side bearers (CCSB's) comprises of outer, inter, and inner coil springs placed in a housing, a cover fitted with non metallic liner sleeve by using countersunk (CSK) head screws on the inside and a wear liner on top, cover rests on the nest of the coil springs and moves up and down during service and the housing also serving as a vertical stop provides for a long travel up to 16 mm from set up height and prevents the coil springs from going solid in service.
According to further embodiment of the invention the wear liner undergoes rubbing against the corresponding wear liner fitted on the car body bolster and provides necessary friction damping against bogie rotation. The metallic wear liners can be replaced by a non-metallic wear liners (polymeric materials such as polyurethane and other polymer compounds and the like) if the non-metallic wear liners reduce the maintenance further.
The constant contact side bearers (CCSBs) of the present invention share 90% of the empty car body weight and the balance car body weight and the pay load being borne by the centre plates. The suspension using these CCSBs increases the speed of Casnub 22 NLB bogie to about 100 km/h in empty condition and about 75 km/h under enhanced loading conditions. The suspension is capable of being retrofitted in the existing Casnub 22 NLB bogie.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
The invention will be better understood and objects other than those set forth above will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:
Fig 1 illustrates the existing Casnub 22 NLB Bogie.
Fig. 1A illustrates the side view of the existing bogie indicating the location of constant contact side bearers (CCSBs) and Centre Plate.

Fig.2 illustrates the existing design of the metal bonded rubber type constant contact side bearers (CCSBs).
Fig 3 illustrates the sectional view of the constant contact side bearers (CCSBs) in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION :-
The ride behaviour and the critical speed of the freight car depends on a number of factors Viz empty / loaded condition, track gauge, design and condition of the rails, structure and the condition of the track, design and the condition of the wheels, primary suspension, secondary suspension, constant contact side bearers (CCSBs), design of the centre plate and various clearances in the system etc., and these parameters differ from one railway system to other railway system. Therefore, a bogie suspension has to suit the given set of parameters of a particular railway system.
In view of the above, in response to the request from RDSO, Lucknow, an Indian Railway specific design of the suspension including primary suspension, secondary suspension, constant contact side bearers (CCSBs) and flat centre pivot has been invented. NUCARS (software) simulations of the same by RDSO, using Indian Railways main line worn out track data file have indicated that Casnub 22 NLB bogie with the new improved suspension for 23 t axle load is
i) Capable of operating at about 100 km/h in empty condition and about 75 km/h in loaded condition.
ii) Lateral forces encountered upto 110 Km/h on a tangent track and upto 85 km/h on a 2 deg track remain considerably below the Prud-Homme limit.
Track irregularities and contour conditions can induce various kinds of oscillations in the freight car and trucks which if not controlled can create unstable operating conditions. Such a phenomenon gets more pronounced on curves. Necessary control over such oscillations is provided by damping the relative movements of bolster and side frames by

way of friction between friction wedges provided in the bolster pockets and the vertical columns of the side frames. In case of Casnub 22 NLB bogie friction force exerted by the wedges depends on the vertical load shared by the snubber springs over which they are supported. Thus the damping so provided is a load variable damping, and the same is so very necessary for freight cars with high payloads.
Conicity provided on the wheel tread results in sinusoidal movement of the wheel set on the rail track. Lateral amplitude of such movement, if left unattended, would grow with speed of the train and would reach a stage when wheel flange starts hitting the rail. Such a state of motion is referred to as 'hunting of the wheel set' and the speed at which it is reached is called the 'critical speed'. In case of bogies, stiffness of the primary suspension provides restraint / damping to the lateral motion of the wheel set and, therefore, critical speed is higher than that of a free wheel set. At speeds higher than the critical speed, hunting oscillations tend to become violent and the flange impacts against the rail can be very severe increasing the possibility of derailment.
After the clearances available at axle box and bolster level in a bogie are used up, the hunting oscillations of the wheel sets induce similar oscillations in the bogie frame and then in the car body. Car body being the heaviest mass, once it starts hunting, the oscillations tend to get sustained unless damped. Such damping is provided by the friction between the top and bottom centre plates and that between constant contact side bearers (CCSBs) on the bogie bolster and the corresponding wear liners of the side bearer on the car body bolster. Constant contact side bearers (CCSBs) also provide a restraint to the car body roll which again has a bearing on the lateral ride behaviour of the car, thus improving the critical speed.
The constant contact side bearers (CCSBs) of the present invention as shown in Fig 3, equispaced from and on either side of the centre plate on the bogie bolster, are disposed between bogie bolster and car bogy bolster in such a way that they share 90% of the empty car body weight and the balance car body weight and the pay load are borne by the centre plates. A constant contact side bearer (CCSB) designed under this invention

comprises a nest of three concentric steel coil springs as outer (13) inter (14) and inner (15) placed in a housing (12) and a cover (16) placed above them. The cover is provided with a non-metallic liner sleeve (17) on its inside and can move up and down during running of the train and it is so disposed vis a vis housing that coil springs are subjected to practically no lateral / longitudinal flexing during bogie rotation and lateral movements in service. A vertical stop provides for a long travel of 16 mm from set up height and prevents the coil springs from going solid in service. This provides effective control over car body roll. A wear liner (18) has been provided over the cover. Sliding friction between the same and corresponding wear liner on the car body bolster provides the necessary constraint against bogie rotation and the tendency to hunt. The wear liners provided with constant contact side bearers (CCSBs) can be made out of non-metallic materials (polymeric materials such as polyurethane and other polymer compounds and the like) if the same can increase the life of the wear liners is increased and the maintenance requirements of the bogie are reduced further.
This invention makes the Casnub bogie (with the increased 23 t axle load) a track friendly bogie suitable for operation about 100 km/h in empty condition and about 75 km/h under enhanced loading condition.
Constant contact side bearers (CCSBs) under this invention have been so designed that the same can be easily retrofitted in the existing axle load Casnub Bogie.
Although the foregoing description of the present invention has been shown and described with reference to particular embodiments and applications thereof, it has been presented for purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the particular embodiments and applications disclosed. It will be apparent to those having ordinary skill in the art that a number of changes, modifications, variations, or alterations to the invention as described herein may be made, none of which depart from the spirit or scope of the present invention. The particular embodiments and applications were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable

one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such changes, modifications, variations, and alterations should therefore be seen as being within the scope of the present invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.

WE CLAIM:-
1. An improved constant contact side bearer (CCSB) for the suspension of broad gauge (1676mm) Casnub 22 NLB bogie for increasing its axle load from 20.32 tons to about 23 tons comprising two rubber spring constant contact side bearers equispaced from and on either side of the centre plate on the bogie bolster and a metal bonded rubber pad placed in a housing the improvement wherein comprising triple nested concentric steel coil spring constant contact side bearers (CCSBs) each having a vertical stiffness of about 150 kg/mm.
2. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as claimed in claim 1 wherein the constant contact side bearer arrangement comprising:

a) housing;
b) a cover having a non metallic liner sleeve detachably fixed on to the inside surface of said cover by means of countersunk head screws;
c) wear liner located on the top outer surface of said cover;
d) triple nested concentric steel coil springs placed in the said housing in an outer .inter, and inner configuration in a manner to provide support to the said cover such that when acted upon by a load during service, said cover performs up and down vertical movement.
3. The improved constant contact side bearers (CCSBs) for the suspension of broad
gauge Casnub 22 NLB bogie as claimed in claims 1 and 2 wherein the said housing
being adapted to be additionally serve as a vertical stop providing long travel up to
16 mm from set up height thereby preventing the coil springs from going solid in
service.

4. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as claimed in claim 2 wherein the wear liners are made up of metals such as steel and the like..
5. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as claimed in claim 2 wherein the wear liners are optionally made up of non metals such as polyurethane and other polymer compounds and the like.
6. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as claimed in claims 1 to 5 adapted to increase the speed of Casnub 22 NLB bogie to about 100 km/h in empty condition and about 75 km/h under enhanced loading conditions.
7. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as claimed in claims 1 to 5 is retrofitted in the existing Casnub 22 NLB bogie.
8. The improved constant contact side bearers (CCSBs) for the suspension of broad gauge Casnub 22 NLB bogie as herein substantially described and illustrated with the accompanying drawings.

A constant contact side bearer for the 23 ton axle load Casnub 22 NLB bogie comprising of a nest of three concentric steel coil springs as outer (13), inter (14) and inner (15) springs; a housing (12) to accommodate the nested springs and to serve as a vertical stop; a cover (16), fitted with non metallic liner sleeve (17) with the help of CSK head screws (19) on the inside of the said cover and a wear liner (18) on its top, rests on the nest of the coil springs and moves up and down during service. The housing also serving as a vertical stop provides for a long travel up to 16 mm from set up height and prevents the coil springs from going solid in service. These CCSBs alongwith improved secondary suspension and improved elastomeric pad make the Casnub 22 NLB bogie track friendly at its increased axle load of 23 tonne and increased operating speed of 100 kmph in empty condition and 75 kmph in loaded condition.