AIRCRAFT BRAKE AND COOLING METHODS THEREFOR

Abstract

A method of cooling an aircraft brake including a brake pack and a reservoir in the form of a removable cartridge containing a coolant. The method includes vaporizing the coolant using heat energy from the brake pack.

Claims

1. A method of cooling an aircraft brake, the brake comprising a brake pack and a reservoir comprising a replaceable cartridge containing a coolant, the method comprising vaporising the coolant using heat energy from the brake pack.

2. The method of cooling an aircraft brake according to claim 1, the method further comprising the step of melting the coolant using heat energy from the brake pack before vaporising the coolant.

3. The method of cooling an aircraft brake according to claim 2, the method further comprising the step of releasing vaporized coolant from the reservoir.

4. The method of cooling an aircraft brake according to claim 3, wherein the method further comprises releasing vaporized coolant from the reservoir in dependence on a temperature of the brake.

5. The method of cooling an aircraft brake according to claim 3, wherein the method further comprises directing the vaporized coolant released from the reservoir over a portion of the brake such that the brake is convectively cooled using the vaporized coolant released from the reservoir.

6. The method of cooling an aircraft brake according to claim 1, wherein the method further comprises replenishing the reservoir after a braking event by replacing the cartridge.

7. The method of cooling an aircraft brake according to claim 1, wherein the method further comprises replenishing the reservoir after a braking event using a quantity of coolant obtained from an aircraft system.

8. The method of cooling an aircraft brake according to claim 3, wherein the method comprises condensing the vaporized coolant released from the reservoir and using a quantity of the condensed coolant to replenish the reservoir after a braking event.

9. The method of cooling an aircraft brake according to claim 1, wherein the method further comprises moving the reservoir from a first position spaced apart from the brake pack to a second position wherein a portion of the reservoir is in contact with the brake pack to enable conductive heat transfer between the brake pack and the reservoir.

10. The method of cooling an aircraft brake according to claim 9, wherein the method further includes moving the reservoir from the first position to the second position when the brake pack reaches a threshold temperature.

11. The method of cooling at aircraft brake according to claim 1 wherein the method is carried out in response to a Rejected Take Off but not otherwise.

12. The method of cooling at aircraft brake according to claim 1, wherein the method is carried out in response to a landing.

13. An aircraft brake comprising: a brake pack and a reservoir comprising a removable cartridge containing a liquid coolant, wherein the brake is arranged such that, in use, the brake pack is cooled by vaporizing the liquid coolant using heat energy from the brake pack.

14. The aircraft brake according to claim 13, wherein when the brake is in a first configuration the reservoir is in contact with the brake pack to enable conductive heat transfer between the reservoir and the brake pack.

15. The aircraft brake according to claim 14, wherein the cartridge is mounted for movement between a first position spaced apart from the brake pack to a second position, and wherein a portion of the reservoir is in contact with the brake pack such that conductive heat transfer can occur.

16. The aircraft brake according to claim 13, wherein the reservoir is arranged to release the vaporized coolant to atmosphere during a braking event.

17. The aircraft brake according to claim 16 wherein the cartridge comprises a fusible portion arranged such that melting of the fusible portion allows the coolant to escape from the cartridge.

18. The aircraft brake according to claim 13, wherein the brake is arranged such that, in use, the reservoir receives a supply of coolant from an aircraft system.

19. The aircraft brake according to claim 13 wherein the aircraft brake is separable from one or more of the aircraft, the reservoir and/or the liquid coolant.

20. The aircraft brake according to claim 13 wherein the cartridge is separable from one or more of the aircraft brake and/or the liquid coolant.

21. An aircraft landing gear comprising a brake in accordance with claim 13.

22. The aircraft comprising a landing gear in accordance with claim 22.

23. A method to cool an aircraft brake comprising: during a landing of an aircraft, braking the aircraft by applying a brake pack to a rotating portion of a wheel of the aircraft, and cooling the brake pad during landing by vaporizing a coolant in a reservoir associated with the brake pad.

24. The method of claim 23 further comprising: freezing the coolant in the reservoir while the aircraft is in flight, and melting the coolant during the landing.

25. The method of claim 23 further comprising venting the vaporized coolant from the reservoir by at least one of melting a fusible portion of the reservoir or opening a valve on the reservoir.

Description

DESCRIPTION OF THE DRAWINGS

[0040] Embodiments of the present invention will now be described by way of example only with reference to the accompanying schematic drawings of which:

[0041] FIG. 1 shows an aircraft including a brake according to a first embodiment of the invention;

[0042] FIG. 2 shows a schematic view of the brake of the first embodiment;

[0043] FIG. 3 shows a schematic view of a brake according to a second embodiment of the invention; and

[0044] FIG. 4 shows a schematic view of a brake according to a third embodiment of the invention.

DETAILED DESCRIPTION

[0045] FIG. 1 shows an aircraft 2 having main landing gear 4, the main landing gear 4 including a landing gear bogie 5 and wheels 6. Each wheel 6 is associated with a brake 8 (not shown separately in FIG. 1). As shown schematically in FIG. 2, each brake 8 includes a brake pack 10 having several disk-like carbon stators 10a connected to the landing gear bogie 5 and several disk-like rotors 10b connected to the wheel 6, and a hydraulic system 12 arranged to move the stators 10a into contact with the rotors 10b in order to apply the brake 8. Also included in brake 8 is a cartridge 14 which is in contact with the inner rim of each stator 10a. Prior to use the cartridge 14 contains a quantity of distilled water 16. The cartridge 14 also includes a bung 18.

[0046] In use, when the brakes are applied heat is generated within the brake pack 10 due to friction between the rotors 10a and stators 10b. A portion of this heat energy is transferred to the cartridge 14 and from there to the water 16 by the process of conduction. The water 16 is initially in a liquid state, but once the temperature of the water has reached boiling point, further heat energy acts to change the state of the water from liquid to gas. The energy absorbed by this process cannot contribute to a rise in the temperature of the brake pack. Accordingly, in embodiments according to the present invention vaporisation of a coolant is used to limit the temperature rise (i.e. cool) a brake pack during a braking event thereby allowing the size (and therefore mass) of the brake pack to be reduced in comparison with prior art brakes.

[0047] If the brakes are applied during an RTO event the water will be in a liquid state. However, if the brakes are applied during landing the distilled water may be in a solid (frozen) state due to prolonged in-flight exposure to the low temperatures found at high altitude. In this case heat energy will be absorbed both in changing the state of the water from frozen to liquid and from liquid to vapour.

[0048] In some embodiments in accordance with FIG. 2 the amount of heat generated during normal braking operations is sufficient to melt the bung 18. In other embodiments, temperatures sufficient to melt bung 18 are only reached during extreme cases such as RTO. In either case, once the bung 18 is melted vaporised coolant can escape from the cartridge 14, through the brake pack 10 and out of the brake 8 to atmosphere. This flow of vaporised coolant may itself act to further cool the brake pack convectively. Moreover, as the latent heat of vaporisation decreases as pressure increases allowing vapour to escape and thereby maintaining a substantially constant pressure in the cartridge 14 may increase the amount of energy absorbed by a given quantity of water 16. Accordingly, in embodiments according to the present example, the material properties (e.g. melting point) of the bung 18 may be used to control the cooling process. Using a fusible bung 18 to release the coolant at a given temperature also renders systems in accordance with the present embodiment passive which is advantageous in safety-critical systems. Once a cartridge 14 has been used (i.e. after the coolant 16 has been allowed to escape) it is replaced with a new cartridge 14 containing a full quantity of coolant. Where the melting point of the bung 18 is low enough that vaporised coolant is released during normal operations, the coolant cartridge 14 will need to be replaced after every flight. Where the melting point of the bung 18 is high enough that only the RTO case results in the release of vaporised coolant, the coolant cartridge 14 will only need to be replaced occasionally.

[0049] FIG. 3 shows a schematic view of an aircraft brake in accordance with a second example embodiment (like reference numerals have been used to indicate like parts). Only those aspects of the second embodiment which differ from the first embodiment will be discussed here. In the second embodiment the cartridge 114 is connected to an actuator 115. In use, prior to a braking event, the cartridge 114 is spaced apart from the inner rim of the stators 10a and the brake pack is at ambient temperature. When the brakes are applied the temperature within the brake 102 begins to rise. Once the brake pack reaches a predetermined temperature, for example the lower limit of the temperature range in which the brake is designed to operate, the actuator 115 moves the cartridge 114 into contact within the inner rim of the stators 10a. Accordingly, in embodiments according to the present example, the actuator may be used to control the point at which the coolant is exposed to the full heat of the brake pack and thereby maintain the brake in the optimal performance envelope.

[0050] FIG. 4 shows a schematic view of an aircraft brake in accordance with a third example embodiment (like references numerals have been used to indicate like parts). Only those aspects of the third embodiment which differ from the first embodiment will be discussed here. In the third embodiment a refillable reservoir 214 has replaced cartridge 14. The refillable reservoir is in fluid communication with the waste water system 220 of the aircraft 202. The reservoir 214 includes a pressure-release valve 218. Prior to take-off fluid is drawn from the waste water system 220 of the aircraft 200 into the reservoir 214. During a braking event, heat is transferred to the reservoir 214 and acts to change the state of the water 216 as discussed for the first embodiment, above. When a given pressure is reached inside the reservoir 214, pressure-release valve 218 opens and allows the vaporised coolant to escape. During flight or when the aircraft is on the ground the reservoir 214 can be replenished from the waste water system 220 so that the cooling system can be used again on landing.

[0051] Whilst the present invention has been described and illustrated with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that the invention lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0052] In the above embodiments the cartridge or reservoir is in contact with the inner rim of the stators of the brake pack. It will be appreciated that the cartridge or reservoir may be in contact with other elements of the brake pack.

[0053] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments.