FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF INVENTION Brake Pressure Control Of The Lift Axle With Respect To Load


APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India

INVENTORS
Amit Kumar Gupta and N.S.R Prasad N Devara
Both are Indian Nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner
in which it is to be performed.


FIELD OF INVENTION
The present invention relates to the proportioning valve system in pneumatic brake system of a commercial vehicle fitted with lift axle which includes a load sensing valve which enables the load over the rear wheels to be measured for modifying the brake pressure on the lift axle wheels with the help of the control valve of the lift axle.
BACKGROUND OF INVENTION
The brakes on commercial vehicles such as trucks, buses and the like equipped with conventional air brake systems are generally considered to be in balance, whenever a fully loaded vehicle can be brought to a safe stop without wheel skid under prescribed conditions. The conventional brake balance protects against loss of vehicle control as by skidding only under situations where the vehicle is fully loaded. It does not protect against loss of control when the vehicle is partially loaded or unloaded.. In the partially loaded and unloaded conditions, the braking force is so high that wheel skid, tire wear, axle bounce loss of control and pavement damage often results. Several attempts have been made to modify the brake pressure with load. Typical examples of such prior proposals are disclosed in U.S patents 3,109,681; 3,269,782, and 3,304,129. The effectiveness of these proposals has been limited to the vehicles without provision for lift axles.
This situation is particularly serious in case of a vehicle fitted with lift axle. These lift axle and wheel assemblies carried by the vehicle can be moved down toward load-bearing engagement with the road surface when the vehicle is heavily loaded, or can be lifted upwardly away from the road surface when there is little or no load carried by the vehicle. In general, the load on the lift axle is relatively low when compared with the rear and front axles when the load on the vehicle is just above the threshold limit for the lift axle to be down. If brakes are applied in this condition wheel lock is very certain to occur on the lift axle. In the case of lifted condition, if

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brakes are applied, brake pressure will be eventually applied on the lifted wheels also which leads to loss of some pressure. In such condition if the lifted wheels hit a bump, instead of smoothly rolling over the bump the wheels will act as a hindrance.
OBJECTS OF INVENTION
The present invention relates to the incorporation of proportioning valve system in the pneumatic brake system of a lift axle with a load sensing valve through which load on the rear axles can be measured and brake pressure on the lift axle wheel can be controlled accordingly. The advantages of such system is to avoid wheel lock in partial loaded conditions which eventually leads to better control and reduced tire wear.
The principal object of the invention is therefore to provide a proportioning valve coupled with load sensing valve and lift axle control valve to measure the load on the rear axle thereby controlling the brake pressure on the lift axle wheels in braking condition.
Another object of the invention is to provide a 3/2 pilot operated valve in the pneumatic brake line of the lift axle system to avoid unnecessary braking of the lift axle wheels when the same are in lifted condition.
STATEMENT OF INVENTION
This invention relate to a pneumatic braking system for vehicles fitted with lift axles comprising; a load sensing proportioning valve connected to an air tank for sensing load on rear axle; a lift axle control valve connected to said load sensing proportionate valve through a conduit to channel a proportionate output provided by said load sensing proportionate valve; a lift axle condition indicating means connected to a pilot control valve which is connected to a proportioning valve, such that said proportioning valve is configured to proportionate load coming from said

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pilot control valve and to deliver said proportioned load to lift axle brake chambers only when said lift axle is in the down condition.
BRIEF DESCRIPTION OF DRAWINGS
Fig-1 shows the flow diagram of the present invention using a 3/2 pilot operated valve and proportioning valve in the pneumatic brake line of the lift axle.
Fig-2 shows the flowchart of the system working with 3/2 pilot operated valve and a proportioning valve.
Fig-3 shows the brake circuit of a commercial vehicle with lift axle system
Fig-4 shows the lift axle pneumatic circuit
DETAILED DESCRIPTION OF INVENTION
In the present invention a 3/2 pilot operated valve and a proportioning valve is connected in series in the pneumatic brake line of lift axle. As shown in the Fig-1, conduit 1 draws air at a certain pressure directly from the air tank. A load sensing proportioning valve 2 is connected to the conduit 1 which senses the load on the rear axle. The load sensing proportioning valve 2 will then proportionate the pressure accordingly. Conduit 3 connects the proportionate output from the load sensing proportioning valve 2 and the lift axle control valve 7. Conduit 6 connects lift axle control valve 7 directly to the air tank. Conduit 5 connects the lift axle control valve 7 and lift bellows 17 (fig 4) of the lift axle. Conduit 4 connects the lift axle control valve 7 and main bellows 16 (fig 4) of the lift axle. If the pressure in the conduit is above certain value then lift axle control valve 7 allows the pressure from the conduit 3 to the main bellows. Otherwise lift axle control valve 7 blocks pressure form conduit 3 and allows pressure from conduit 6 to lift bellows. Now pressure from the conduit 4 can serve as a pilot signal to know whether lift axle is in lifted condition or in down condition. The air from the conduit 4 is connected to a 3/2 pilot control valve 10. Conduit 9 connects the air from the relay chamber of the lift axle braking system to the 3/2 pilot control valve 10. Once the pressure is available in the conduit
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4, 3/2 pilot control valve 10 allows pressure from the conduit 9 to the conduit 11. Conduit 11 connects the 3/2 pilot control valve 10 and proportioning valve 12. The proportioning valve 12 proportionates the pressure in the conduit 11 and delivers to conduit 13. Conduit 13 connects the proportionate valve 12 and the brake chambers 14, 15.
Figure 2 discloses the flow of the system working with proportionate valve and 3/2 pilot valve. The load of the rear axle is measured (2) by a load sensing proportionate valve to proportionate the pressure accordingly. The lift axle control valve determines if said load is above the prescribed limit. If load is above the prescribed limit, the lift axle is maintained in the down condition and the lift axle control valve allows pressure from conduit (3) to main bellows. Otherwise lift axle control valve 7 blocks pressure from conduit 3 and allows pressure from conduit 6 to lift bellows and maintained in the lifted condition. The air from the conduit 4 is connected to a 3/2 pilot control valve 10. Also brake pressure is received from brake valve through conduit 9. If lift axle is down, the proportioning valve proportions the brake pressure to apply to the brake chambers in the lift axle. If the lift axle is in the lifted position, the brake pressure is blocked to avoid unnecessary braking of the lift axle wheels when they are in lifted condition.
Fig-3 illustrates a brake circuit of a vehicle fitted with lift-axle arrangement. Fig-4 discloses the pneumatic circuit of a lift-axle system. The present invention is a system which works in between the two above mentioned system. Input is taken from the lift-axle pneumatic system through the conduit 8 which is shown in the
Fig-4 and is given to the conduit 9 which is shown in fig-3. Thus, the system consists of a 3/2 pilot valve and a proportioning valve in series, will act in between the brake circuit and lift-axle pneumatic circuit, and therefore gives the brake pressure control on the lift-axle.

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The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.

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WE CLAIM
1. A pneumatic braking system for vehicles fitted with lift axles comprising:
a load sensing proportioning valve connected to an air tank for sensing load on rear axle;
a lift axle control valve connected to said load sensing proportionate valve through a conduit to channel a proportionate output provided by said load sensing proportionate valve;
a lift axle condition indicating means connected to a pilot control valve which is connected to a proportioning valve, such that said proportioning valve is configured to proportionate load coming from said pilot control valve and to deliver said proportioned load to lift axle brake chambers only when said lift axle is in the down condition.
2. The system as claimed in claim 1, wherein said lift axle control valve is directly connected to an air tank, lift bellows and main bellows of the lift axle through separate conduit means.
3. The system as claimed in claim 1, wherein said lift axle condition is indicated by pressure from conduit connecting said lift axle control valve to said main bellows of said lift axle.
4. The system as claimed in claim 1, wherein brake pressure from brake valve of said braking system is provided to be channelled to said pilot control valve .
5. The system as claimed in claim 1, wherein said pilot control valve is a 3/2 pilot control valve.
6. The system as claimed in claim 1, wherein said proportioning valve is provided to block said load when lift axle is in the lifted condition.
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7. A pneumatic braking system for vehicles fitted with lift axles as hereinabove described with reference to the accompanying drawings.