FORM 2
THE PATENT ACT 1970
&
The Patents Rules, 2003
COMPLETE SPECIFICATION (See section 10 and rule 13)
1. TITLE OF THE INVENTION:
"Device for Controlling Operation of Pneumatic Lift Axle"
2. APPLICANT:
(a) NAME: Knorr-Bremse Systems for Commercials Vehicles
India Pvt. Ltd
(b) NATIONALITY: Indian Company registered under the
provisions of the Companies Act-1956.
(c) ADDRESS: Survey Nos. 280 & 281, Village Mann,
Hinjawadi, Phase II, Taluka Mulshi, Pune -411057 M.S. INDIA,
3. PREAMBLE TO THE DESCRIPTION:
COMPLETE
The following specification particularly describes the invention and the manner in which it is to be performed.

Device for Controlling Operation of Pneumatic Lift Axle
Field of the invention
The present invention relates to a device capable of controlling pneumatic lift axle operation, accurately and automatically, more particularly, the present invention
relates to a lift axle control valve.
Background of the invention
Lift axle is mainly used in utility vehicles. The lift axle is always an additional axle attached to the vehicle. Further, the lift axle is a flexible axle which can be lifted or deployed depending on the load on the vehicle. Lift axle can be deployed when vehicle is in loaded condition to take additional load and avoid violation of legal load requirements. It can be raised up above the road when vehicle is in unloaded condition or in partial laden condition. Pneumatic air bellows also known as air bags are generally preferred for lift axle actuation.
Further, the lift axle avoids tyre wear in unloaded driving conditions as tyre looses contact with road surface when axle is lifted. The lift axle also helps in reducing vehicle rolling resistance while driving in unloaded condition which helps in saving fuel. Moreover, the lift axle system function is very critical and cannot be controlled effectively by manual means as manual control may cause various types of errors and hazards to lift axle, human life, and vehicle as a whole.
Prior Art
Figure 1 shows a block diagram of pneumatic lift axle control valve {hereinafter referred as "control valve (212)'') of the prior art. The pneumatic control valve (212) is used for the semi-automatic or fully automatic control of air suspended lift axles. The control valve (212) has a pneumatic signal inlet port (201) to which

outlet of load sensing device gets connected. Internally, the pneumatic signal inlet
port (201) gets connected to a suspension actuation valve (208) and also, to an
electrically operated valve (204). The control valve (212) also, has an air supply
inlet port (203) to which air supply from vehicle air tank gets connected.
Internally, air from air supply inlet port (203) gets connected to decision making
valve (207) and also to a lift bellow control valve (211). Valve uses this supply for
its own internal operation and also for supplying air to lift bellow on vehicle
through outlet to lift bellow (210). Internally, the control valve (212) has the
electrically operated valve (204) through which part of the control pressure passes
to flow control (205). The electrically operated valve (204) can be closed by
supplying electrical signal to manual override input (202) to stop any air flow
through it and exhaust all the residual air at its delivery. The flow control (205)
controls flow rate of air passing through it to internal volume (206). Internal
volume (206) acts as flywheel and reduces fluctuations in air pressure flowing
through it. The air from the internal volume (206) passes to decision making valve
(207). The decision making valve (207) has two reference set points which are
externally settable through setting arrangement (213). The decision making valve
(207) takes decision by comparing inlet pressure from the internal volume (206)
with set points and generates output in the form of pneumatic control signal. For
generation of pneumatic signal output, it uses supply air tapped from air supply
inlet port (203). The outlet decision signal of the decision making valve (207) is
connected to a suspension bellow control valve (208) and also connected to the lift
bellow control valve (211). Suspension bellow control valve (208) is of Normally
Closed type and the Lift bellow control valve (211) is of Normally Open type.
In operating condition, assuming that the decision making valve (207) is set at 4 Bar and 2 bar as 'axle deploy pressure' and 'axle lift pressure' respectively and sufficient operating pressure is available at the air supply inlet port (203). In unladen vehicle condition, the control signal pressure at the signal inlet port (201) is less than 4 Bar. Same pressure would be available as a signal to the decision making valve (207). As a result, the decision making valve will transmit signal to

keep lift bellow control valve (211) open and suspension bellow control valve (208) closed. This will keep axle in lifted condition.
Now, due to vehicle loading, load sensing device will start increasing signal pressure at signal inlet port (201). When this pressure crosses 4 Bar, the decision making valve will change its pneumatic signal output to close lift bellow control valve (211) and open suspension bellow control valve (208). As a result, lift axle will get deployed to take additional load.
Again, when load on the vehicle is reduced, load sensing device will change signal pressure at signal inlet port (201). When this pressure drops down below 2 bars, the decision making valve (207) changes control signal status at its outlet to open, the lift bellow control valve (211) and close suspension bellow control valve (208).
When the vehicle is being driven, load sensing device on vehicle may experience some dynamic changes in load on the vehicle due to road surface unevenness, pot holes, speed breakers, etc. Any sudden change in pressure at signal inlet port (201) due to dynamic load change will get suppressed before reaching the decision making valve (207) due to the flow control (205) and the internal volume (206) arrangement. This arrangement makes sure that the decision making valve (207) takes decision only based on true steady state input and not due to dynamic changes in load.
In axle deployed condition, driver sometimes may need to lift the axle forcefully for some reason like tyre puncture, requirement of additional traction, etc. In this case, driver can actuate electrically operated valve (204) by operating electrical switch in vehicle. Switch will supply electrical power at manual override input (202). As a result, the electrically operated valve (204) will cut off load signal going to further circuit and pressure at its delivery drops to zero bars. Due to drop in load signal pressure below 2 bar, decision making valve takes decision to lift

the axle, and restores back when electrical supply at the manual override (202) is cut and if the pressure at signal inlet port (201) is rnore than 4 bars.
Disadvantages of the lift axel control valve available at present are as follows:
• Cost is very high.
• Less flexible for any new change adaptation in system since main operation is controlled by pneumatic means.
• Many setting are required to tune the va!ve to suit specific customer requirement which increases production cycle time.
• The setting can be disturbed very easily in the field and then resetting it back to normal is very difficult and time consuming.
• Part count per valve assembly is very high, so it becomes very difficult to manufacture and service this valve.
• Chances of failure are high due to higher part count.
• While parking the vehicle and if vehicle is empty, then axle remains lifted. This increases probability of wheel theft as it becomes very easy to remove wheel which are freely suspended without any load on it.
• The operation of the system is purely pneumatic and so it is overall performance, reliability, repeatability is highly dependent on quality of compressed air.
• Forced axle lifting operation (manual override) function doesn't function properly if signal pressure is within hysteresis window during manual override function.
Object of the present invention
Object of the present invention is to provide device for controlling operation of pneumatic lift axle, which is operated by pneumatic pressure.
Another object of the present invention is to provide device for controlling operation of pneumatic lift axle, which is flexible for any new change.

Yet another object of the present invention is to provide device for controlling operation of pneumatic lift axle, which is capable of lowering the lift axel at parking conditions.
Further object of the present invention is to provide device for controlling operation of pneumatic lift axie, which is economical in operation.
Further one object of the present invention is to provide device for controlling operation of pneumatic lift axle, which is interchangeability with prior art system.
Another object of the present invention is to ensure reliable manual override operation even if the signal pressure is within the hysteresis band.
Statement of the invention
According to the present invention there is provided a device for controlling operation of pneumatic lift axle, the device comprising:
a first inlet port (301) and a second inlet port (303) for receiving the pressurized fluid therefrom, wherein the first inlet port (301) receives the pressurized fluid depending upon load on the vehicle:
a flow control valve (302) connected to the inlet port (301), the flow control valve (302) capable of regulating the flow of pressurized fluid there through:
a reservoir (304) connected to the flow control valve (302), the reservoir (304) capable of storing pressurized fluid therein;
a pressure to electricity convenor (P to E converter (306)) connected to the reservoir (304), the P to E convertor (306) capable of sensing the pressure from the reservoir (304) and generated electrical signals upon sensing the pressure "X bars'' and "Y bar" in the reservoir (304). wherein the P to E convertor (306) has inbuilt hysteresis by design to sense the predefined pressure;

an electrically operated valve (307) connected to the P to E converter (306), the electrically operated valve (307) capable of transmitting electrical signals therefrom;
a change over valve (308) electrically connected to the electrically operated valve (307), further supplies pressurized fluid from the first inlet port (301) to a deploy bellow (309), and supplies pressurized fluid from the second inlet port (303) to a lift bellow (310),
wherein upon sensing pressure "X bars" the P to E converter (307) sends signals to the electrically operated valve (307) to operate the change over valve (308) to connect pressurized fluid from the first inlet port (30!) to the deploy bellow (309) thereby operating the deploy bellow (309) for lowering the lift axel connected thereto, wherein upon sensing pressure "Y bars" the P to E converter (307) sends signals to the electrically operated valve (307) to operate change over valve (308) to connect pressurized fluid from the second inlet port (303) to the lift bellow (310) thereby operating the lift bellow (310) for lifting the lift axel connected thereto.
Typically, wherein further comprising an electrical supply (311) to supply electricity to the P to E converter (307),
Typically, wherein further comprising a manual override electrical power supply terminal (312).
Typically, wherein "Y bars" is less than "X bars"
Brief Description of the figures
Figure 1 shows functional block diagram of a lift axel control valve of the prior art;

Figure 2 shows functional block diagram of a device for controlling operation of a pneumatic lift axel in accordance with the present invention;
Detail description of the invention
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art. techniques and approaches are overcome by the present invention as described below in the preferred embodiment.
The present invention describes a device for controlling operation of pneumatic lift axle. The device is a lift axel control valve capable of sensing the load condition of the vehicle and accordingly deploying or lifting the additional lift axel. Additionally, the lift axel control valve is capable of deploying the lift axle when the vehicle parked.
This present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.
Referring now to figure 2, a block diagram of a device (305) for controlling operation of a pneumatic lift axel (not shown) in accordance with the present invention is illustrated. The device (305) includes a first inlet port (301), a second inlet port (303), a flow control valve (302), a reservoir (304), a pressure to electricity converter (herein after referred the "P to E converter (306)"), an electrically operated valve (307), a change over valve (308), a lift bellow (309) and a deploy bellow (310).
The first inlet port (301) and a second inlet port (303) for receiving the pressurized fluid therefrom. The first inlet port (301) receives the pressurized fluid depending

upon load on the vehicle. The delivery of load sensing device (not shown in sketch)) is connected to the signal inlet port (301). Internally, the signal inlet port (301) is connected to an air operated change over valve (308) and also to the flow control (302). The flow control valve (302) is connected to the inlet port (301). The flow control valve (302) is capable of regulating the flow of pressurized fluid there through. The air flowing through flow control valve (302) passes further to the reservoir (304). The reservoir (304) is connected further to the P to E converter (306). The P to E converter (306) senses pressure at its inlet coming from the reservoir (304) and based on this pressure, it takes decision on axle lift or deployment the lift axel. The inlet to the P to E converter (306) is pneumatic pressure while its output is electrical signal. The P to E converter (306) has inbuilt hysteresis by design because of which it can have two distantly different actuation pressure set points. For example, the P to E converter (306) is Turn 'ON" at inlet pressure of "X bars", which is 4 bars and is turn 'OFF' at inlet pressure of "Y bars" is 2 bars, which is less then "X bars" (4 bars). For generating electrical output, the P to E converter (306) needs electrical power supply externally through an electrical supply terminal (311). The electrical output of the P to E converter (306) is given to the electrically operated valve (307). When actuated with the electrical supply, the electrically operated valve (307) connects supply to the second inlet port (303) to air operated change over valve (308). Based on status of inlet pilot signal from the electrically operated valve (307), change over valve (308) either connects the second inlet port (303) to outlet port to lift bellow (310) or connects first inlet port (301) to outlet port to the deploy bellow (309). To operate the electrically operated valve (307) manually, electrical power can be supplied directly through a manual override electrical power supply terminal (312).
In operating condition, assuming that the P to E converter (306) is set at 4 bars ("X bars") as 'axle deploy pressure' and 2 bars ("Y bars") as 'axle lift pressure'. Also, assuming that sufficient operating pressure is available at supply inlet port

(303) and electrical supply is available at the electrical power supply terminal (311).
In unladen vehicle condition, the control signal pressure at the signal inlet port (301) is less than 4 bars. Same pressure would be available as a signal to the P to E converter (306) through signal inlet port (301) and the reservoir (304). As a result the P to E converter (306) will transmit electrical signal to electrically operated valve (307) to actuate air operated change over valve (308), such that the lift bellows are inflated by connecting supply to the inlet port (303) to outlet port to lift bellow (310) and deploy bellows are depleted by blocking connection between signal inlet port (301) and outlet port to Suspension bellow (309) and exhausting air at port to suspension bellow (309) This will keep axle in lifted condition.
Now, due to vehicle loading, load sensing device will start increasing signal pressure at signal inlet port (301). When this pressure crosses mark of 4 bars, the P to E converter (306) changes signal output to electrically operated valve (307). Electrically operated valve (307) breaks connection between supply inlet port (303) and air operated change over valve (308). The air operated change over valve (308) will changeover such that signal inlet port (301) gets connected to outlel port to suspension bellow (309) and connection between outlet port to lift bellow (310) and a supply inlet port (303) breaks. Also air at port to lift bellow (310) exhausts. As a result, lift axle will get deployed to take additional load.
Again, when load on the vehicle is reduced, load sensing device will change signal pressure at signal inlet port (301). When this pressure drops down below 2 Bar, P to E converter (306) will change control signal status at its outlet to operate electrically operated valve (307) and actuate air operated change over valve (308) such that connection between outlet port to the lift bellow (309) and signal inlet port (301) breaks and supply inlet port (303) connects to outlet port to lift bellow (310).

When the vehicle is being driven, load sensing device on vehicle may sense some dynamic changes in load on the vehicle due to road surface unevenness, pot holes, speed breakers, etc. Any sudden change in pressure at signal inlet port (301) due to dynamic load change will get suppressed due to flow control (302) and the reservoir (304) arrangement. This arrangement makes sure that P to E converter
(306) takes decision only based on true steady state input and not based on
dynamic changes in load.
In axle deployed condition, driver sometimes may need to lift the axle forcefully for some reason like tyre puncture, requirement of additional traction, etc. In this case, driver can actuate electrically operate valve (307) by operating electrical switch connected to manual override electrical power supply terminal (312). As a result, electrically operated valve (307)) will supply signal to air operated change over valve (308) and air operated change over valve (308) to lift the axle.
When the vehicle is to be parked, driver will turns off ignition to switch off electrical power to all devices. So, no electrical power supply will be available at electrical power supply terminal (311). In this case, if vehicle is laden, axle will remain deployed as the air operated changeover valve (308) is already in default home status. If vehicle is in unladen condition, moment, the power is OFF, no current will pass through P to E converter (306) to electrically operated valve
(307) and electrically operated valve (307) will cut off connection between supply
inlet port (303) and the air operated change over valve (308). So air operated
change over valve (308) will go in default home status and axle will lower down.
Advantages of the present invention:
1. Since most of the parts are being manufactured in India, product cost is very low and so cost of ownership is very low
2. Product cost is low due to use of less number of parts

3. Flexible for any new change adaptation in system since main operation is controlled using eiectro pneumatic system.
4. No need of any setting or fine-tuning as operation is controlled by P to E converter which has fixed setting.
5. The setting cannot be disturbed as there is no setting arrangement.
6. Chances of failure are low due to lower part count

7. Due to special system arrangement, while parking the vehicle, if ignition is turned OFF. the lift axle gets deployed even if vehicle is empty. This decreases probability of wheel theft as it becomes very difficult to remove wheel once they touch the road surface and get reaction force from road surface
8. The Control system of system is electro-pneumatic. So its overall performance, reliability, repeatability is less dependent on quality of compressed air
9. Forced axle lifting operation (manual override) functions well even if the signal pressure is within the hysteresis window during manual override function since manual override signal processing takes place after reservoir (304).
10. No need of separate pressure switches to drive lift axle lamp for indicating lift axle status to driver. Output of inbuilt pressure switch can be connected to lift axle lamp directly. This generates system level cost savings and improves system reliability

We Claim:
1. A device for controlling operation of pneumatic lift axle, the device comprising:
a first inlet port (301) and a second Inlet port (303) for receiving the pressurized fluid therefrom, wherein the first inlet port (301) receives the pressurized fluid depending upon load on the vehicle;
a flow control valve (302) connected to the inlet port (30]), the flow control valve (302) capable of regulating the flow of pressurized fluid there through;
a reservoir (304) connected to the flow control valve (302), the reservoir (304) capable of storing pressurized fluid therein;
a pressure to electricity convertor (P to E convertor (306)) connected to the reservoir (304), the P to E convertor (306) capable of sensing the pressure from the reservoir (304) and generated electrical signals upon sensing the pressure "X bars" and "Y bar' in the reservoir (304), wherein the P to E convertor (306) has inbuilt hysteresis by design to sense the predefined pressure;
an electrically operated valve (307) connected to the P to E convertor (306), the electrically operated valve (307) capable of transmitting electrical signals therefrom;
a change over valve (308) electrically connected to the electrically operated valve (307), further supplies pressurized fluid from the first inlet port (301) to a deploy bellow (309), and supplies pressurized fluid from the first inlet port (303) to a lift bellow (310),
wherein upon sensing pressure "X bars", the P to E convertor (307) sends signals to the electrically operated valve (307) to operate the change over valve (308) to connect pressurized fluid from the first inlet port (301) to the deploy bellow (309) thereby operating the deploy bellow (309) for lowering the lift axel connected thereto, wherein upon sensing pressure "Y bars" the P to E convertor (307) sends signals to the electrically operated valve (307) to operate change over valve (308) to connect pressurized fluid from the second inlet port (303) to the lift

bellow (310) thereby operating the lift bellow (310) for lifting the lift axel connected thereto.
2. The device as claimed in claim 1, further comprising an electrical supply (311) to supply electricity to the P to E converter (307).
3. The device as claimed in claim 1, further comprising a manual override electrical power supply terminal (312).
4. The device as claimed in claim 1. wherein "Y bars" is less than "X bars".