IL24369A - Device for braking aircraft - Google Patents

Description

flinjl |Π 3 T3i nj"l n File C l PATENTS AND DESIGNS ORDINANCE A dev±ceSPi£ f¾&$a¾ aircraft SOCIBTE GREN0B10ISE D'BTDDES BT D«APPLICATIONS HYDRATJIIQUES I (we) (SOGREAH), a French company, of 84-86 avenue Ιέοη Blum, Grenoble, France and SOCIKTE FRANCAISB AERONAUTIQUE ET MARITIME (SOFRAM), a French company, of 1, rue Billerey, Grenoble, Prance do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement :- The present invention relates to improvements in devices intended for stopping moving bodies and more particularly aircraft.

In present devices for general use in braking aircraft on the ground, mechanical brakes are employed which act on the winding drums of a cable. It is often advantageous to replace the mechanical brakes by hydraulic brakes. However, in certain particular applications, the drawbacks encountered in the use of hydraulic brakes may prohibit their utilization. In fact, in order to brake the large power at the high angular speeds existing during the braking of aircraft, the liquid employed in these hydraulic braking machines must be supplied under pressure, and this supply must be capable of being effected at low temperatures. This latter requirement is rendered necessary by the tendency of hydraulic brakes to cavitate when the speeds and power encountered exceed a certain value as a function of the temperature of the water. Γ; To this end, it has been found necessary to provide fairly large flow- ates of circulating water in such hydraulic brakes in order to evacuate the heat developed during braking. This circulation of water has been found to interfere with the correct operation of the brake, and in particular necessitates the use of auxiliary pumps and a fairly large capacity of water. The auxiliary pump can be keyed on the shaft and can thus form part of the brake. The quantity of water must however be fairly large so as to permit a number of successive stops of aircraft without an excessive rise in temperature, since a brake receiving hot water would have a tendency to even if the water were circulated under ressure. circulation of water, especially in hot countries.

By way of example and as an indication of order of magnitude, the water should not pass out of the brake at more than 70°C, which gives a fairly small difference of the order of 50°C. with a water-intake temperature of °C. As each litre of water will evacuate 50 cal./kg., there would be required about 30.000 = 600 litres to stop 50 an aircraft weighing 30 tons, with an initial speed at braking of 90 m/sec. This water must be cooled, otherwise it will become mixed with that remaining in the tank and will increase the overall temperature. Thus, if it is assumed that this tank contains 3,000 litres, the whole quantity will be heated-up by 20 to 30°C. for the first stop, which would make a greater output of the pump necessary to prevent cavitation at the second successive stop, and so on.

For certain applications, it has been found necessary to avoid these drawbacks - risk of cavitation and consequent unreliability of braking, impossibility of having available a large quantity of water or of cooling it, and difficulty of obtaining high supply pressures.

The present invention has for its object a braking arrangement for aircraft on runways, comprising the unwinding of braking bands or cables from a drum, essentially characterized in that the said drum is coupled to a rotary air-brake, proportionately dimensioned for its intended use and in direct communication with the surrounding medium.

This air-brake arrangement possesses a certain number of advantages as compared with known installations comprising rotary hydraulic brakes.

These advantages may be summarized as follows: 1 - The brake is not fluid- ight and is used at atmospheric pressure, so that it can be of the most simple construction. For example, it is possible to provide the cells of the stator in the concrete frame of the foundation walls. The absence of pressure makes it possible to employ thicknesses in the brake just as small as those essential for the construction of its parts. In consequence, economical methods of manufactur of the boiler-works type for example, can be employed. 2 - The priming of the air-brake is automatic, since it is sure to be filled by the ambient air, whereas leakage is always possible in the water circuit under pressure of a hydraulic brake, especially during long periods when the brake is not in use. 3 - Elimination of the risk of cavitation, which results in reliable operation and furthermore permits the blade to be produced with simplified outlines. 4 - The use of a large reservoir for cooling water is dispensed with.

.- Elimination of an auxiliary cooling system which, as previously indicated, is very large in the case of a hydraulic brake, since to stop an aircraft of relativel low weight (30 tons) with an initial braking speed of 90 m/sec, it is necessary for adequate cooling of the brake to provide an output of 600 litres of water which must be cooled before the next braking action.

It has been found necessary to make the air-brake of fairly large size, since the specific mass of the air is very small. However, the braking power varies as the fifth power of the diameter, so that an air-brake according two and a half times greater than that of a hydraulic brake of the same power.

It has also been found that with an air-brake it is necessary to avoid excessive heating of the air or gas employed as the braking fluid. High temperature can in fact lead to deformation and deterioration of the equipment. Furthermore, excessive temperature inevitably reduces the specific mass of the fluid and in consequence the braking capacity for operation at constant pressure. The air-brake can be appropriately cooled as follows: 1) By blowing air through the wheels by means of blowers which can be advantageously keyed on the brake shaft. This method necessitates a large quantity of air and interferes with the internal operation. 2) By supplying an intake of water or other cooling liquid to the interior of one or more cells of the stator.

The speed of the air is sufficiently high to ensure good atomization of the water supplied, and a uniform temperature. This second arrangement has been found to be particularly advantageous since the quantities of water required to effect proper cooling are relatively small for the following reasons: a) The limiting temperature is high, of the order of 90°C. b) A very small portion of the water is vaporized, but this quantity, is sufficient to carry away a considerable amount of heat. As the heat of vaporization of water is about 54-0 times greater than that of air, there would only be required, for example 3 .000 or about 60 litres of water vaporized The foregoing indications are approximate since the phenomenon of heat exchange between air and water is more complex. The water is initially heated-up before being vaporized, while on the other hand all the water is not vaporized, so that a slightly greater quantity of water than that estimated will be required in order to keep the temperature below 90°C. for example.

In any case, the quantities of water necessary will be substantially less than those required by the circulation system of a hydraulic brake.

The introduction of water into the brake can be effected by means of a pump which may advantageously be keyed on the brake-shaft or associated with this shaft by any kinematic chain such as a gear, a coupler, a speed-varying device, etc.

Tubes or nozzles may also be provided inside the cells of the stator so as to create in these tubes reduced pressures sufficient to draw-in water from a reservoir mounted slightly below the brake, so as to prevent the tubes from being drained during periods of stoppage. This arrangement is advantageous, since it eliminates parts and renders the brake automatic, priming being ensured by the actual operation of the brake.

The water which is not vaporized, that is to say the greater part,can be recovered by a light hood surrounding the brake for catching and returning this water to the tank. This recovered water will increase the temperature of the water in the tank, but this is not a disadvantage as in the case of the hydraulic brake, since it is not necessary to inject cold water, the coolin of the brake bein effected es eciall b The regulation of the power of this brake can be effected by slide valves or screens sliding between the stator and rotor, as in the case of hydraulic brakes, or alternatively, in order to avoid excessive size, these regulators may be constituted by a number of flaps, or shutters forming a variable opening.

The regulation of the power of the air-brake may alternatively be effected by aws articulated at one of their extremities, the J ws being actuated by their other extremity so as to be moved closer to or. away f om the centre of the brake.

According to the invention, this regulation of braking power can also be effected: - By variation of the axial play between stator and rotor; - By closure of the axial space between stator and rotor, carried out at the periphery of these latter; - By closure of orifices formed at the periphery of the , stator blades.

In accordance with the invention, the air-brake > preferably comprises two rotors respectively associated with taro stators, the arrangement being symmetrical with respect to a plane perpendicular to the axis of rotation ; of the whole unit.

In one form of construction, the stators are V. arranged outside the rotors which form the drum between . ■■ them, while in an alternative form, two drums are provided and these are arranged on the outside of the rotors, the latter being arranged in turn outside the stator.

In accordance with this last arrangement, the apparatus comprises a single and symmetrical central frame carr in the two stator of the ra e h shaft passing straight through the apparatus.

The brake rotors can be locked on the shaft, in which case it is desirable to couple the two winding bands to the hooking cable by an additive load-distribution system, such as a compensation bar or a single pulley block This device is necessary in order to compensate either for differences of travel of the bands or for differences in the elasticity of the said bands.

The brake rotors may also be mounted freely rotatable on the shaft, in which case the coupling of the bands can be made directly to the extremity of the hooking cable without any special load-distribution device.

This arrangement has the following advantages: 1) Central frame of one-piece construction, carrying the stators and the bearing or bearings. 2) Drums and rotors are directly removable laterally, one after the other. It is possible in particular to change a drum, if necessary carrying. its wound cable, without difficulty in the same way as the changing of an automobile wheel. 3) Since the moving vehicle is coupled to the braking device by two bands instead of one, additional advantages are obtained: a) Each of the two bands withstands a normal load which is one-half the total load, and this enables the i extension of the upper limit to which braking devices of high power are normally restricted; b) As the normal load of one band generally corresponds to a large coefficient of safety with respect to f acture, the accidental breaking of one of the two bands can make it possible to prevent a complete In the case where the rotors are rigidly fixed i on the shaft with a coupling compensation bar, this i take-up of load is effected autom tically by the pivotal movement of the compensation bar. The construction with a single pulley block on the other hand necessitates an arresting device on the fcable, oval stops for example, so as to block its movement.

When the rotors are mounted freely rotatable on the shaft, the take-up of load will obviously only take place with half the braking force, since only one of the two brakes will remain in operation.

The objects, characteristic features and advantages of the invention villi furthermore become apparent from the description v/hich follows below of ; forms of construction chosen by way of example, reference being made to the accompanying drawings, in v/hich: Fig.l is a diagrammatic plan view of a braking installation for aircraft landing on a runway, the installation according -to the invention being provided with rotary air-brakes; Fig.2 is a view in vertical cross-section of . an air-brake according to the invention, coupled to an unwinding drum for a braking band in the type of installation shown in Fig.l; Fig.3 is a detail view to a larger scale, showing the slides for regulating the power of the brake; Fig.4. is a detail view o the blades of the air-brake, showing how the power of the brake can be regulated by varying the axial clearance between the bladesr, Fig.5 is a detail view of the blades showing Fig. is a detail view of the blades showing how the power of the brake can be regulated by controlling the closure of orifices in the stator blades; Fig.7 is a view in axial section taken along the line VII-VII of Fig.8, showing the articulated- jaws -provided for regulating the power of the brake; Fig.8 is a view in cross-section taken along the line VIII-VIII of Fig.7; Fig.9 is a partial view showing an alternative arrangement for the pivotal mounting of the Jaws; Fig.10 is a view similar to Fig.2, showing a brake wi h a central drum; Fig.11 relates to an alternative form in which the brake is provided with two lateral drums.

Fig.l shows a braking device for an aircraft landing on a runway, constituted by two braking units according to the invention, each comprising a drum 1 and l.l, from which unwinds a cable 2 in the form of a band, these drums being rigidly fixed to the rotary air-brakes 3 and 3 » During the course of landing, the aircraft becomes hooked at 5 on the band 2.

The air-brake according to the invention is constituted by a double rotor 6. The stators 7 are mounted on each side, opposite the cells of the rotors. The end-plates 8 of the rotor serve as the cheeks of the drum 9 on which the band 2 is wound. With this arrangement, the torque is transmitted directly from the band to the hub 11 the rotor shaft is carried by bearings 12 fixed on the body of the stators 7.

Sliding members 13 limit the opening for the sliding members are shown in this figure in the form of shutters 1 actuated by means of crank-arms 15, operated by a regulating ring 16. These shutters may also take the form of slides similar to those generally employed on hydraulic brakes.

The cooling of the air-brakes is effected by the water-intake tubes 17 in one or more cells of the stator. The orientation and the positions of the holes 18 in these tubes 17 are determined in such manner as to take advantage of the lowest areas of reduced pressure. The water is thus naturally sucked-in from a storage tank 19. This reserve of water can be completed periodically from a tank-lorry or from an available natural source by. a motor-pump set 20 which ensures a constant level of water in the tank 19. A hood 21 enclosing the brake permits the water to be recovered and led back to the tank 19.

The. regulation of the power of the brake in the particular case of an air-brake such as that described, can be effected by varying the axial clearance between the rotor and the stator, as shown in Fig. , in which-the clearance 22 between the stators 7 and the rotors 6 is varied by axially displacing one or both the stators in the direction of the arrows f, by means of jacks.

This regulation of power can also be effected by means of the arrangement, shown in Fig.5, by closing the axial clearance at the periphery 23 between the stators 7 and the rotors 6 by means of a ring 2. which is moved in the direction of the arrows f^.

In an alternative form of construction, this regulation of power can also be effected by means of the arrangement shown in Fig.6, by closing to a greater stator blading 7 by means of a sleeve 25 which is axially displaced in the direction of the arrows f^. These orifices could also be closed by means of a sleeve movable in rotation and provided with orifices corresponding to the orifices 26 of the stator blading.

As previously indicated, the sliding members or screens 13 may take the form of jaws articulated at one of their extremities and actuated at their other extremities in order to vary their positions with respect to the centre of the brake. A construction of this kind is shown in Figs.7 and 8, to which reference will now be made.

In Fig.7, there can be seen an air-brake constituted by a stator 31 with its cells 2, and a rotor 33 with its cells 34 mounted on a shaft 35.

The power-regulating screens are shown at 36 and 36V between the stator cells 32 and the rotor cells 34·.

These screens 36 and 3 » are shown in a more complete manner in Fig.8, in which the rotor 33 has been removed.

In this figure, there can be seen the stator 31 with its cells 32 and the two screens 36 and 6' in the form of Jaws pivoted about a shaft 37 rigidly fixed to the stator.

The movements of closure and opening of the Jaws are controlled by a double-acting hydraulic Jack 38, shown in broken lines, mounted behind the stator, the extremity. 39 of the Jack body and its rod 4-0 being pivoted respectively on pins 4.1 and 42, rigidly fixed on the Jaws 36 and 36.».. triangulation system coupling them to each other.

The periphery of the stator is shown by the broken line 43, the jaws 36 and 36' being shown in the fully-open position, their inside line 44 coinciding with the inner peripheral line 45 of the cells of the stator and of the rotor, shown in Fig.7.

The shaded portions 6.and J^L represent a closure zone in which the jaws are in the partially-closed position, corresponding to a reduction of the power of the brake of about 60$.

The position of zero braking power will be obtained by the most complete closure of the jaws, to which an appropriate shape will be given. In the case where the brake generally operates between its, full power and of that value, the closure corresponds to the shaded zones 46 -a¾¾d¾¾:¾, and the inner line 44 will be given a form corresponding to that of the periphery 4$ of the stator and the rotor, as shown in Fig.S, so that the said closure zones 46-and= 7 remain substantially symmetrical with respect to the axis 35 of the brake over their entire travel,, which is relatively small.

Fig.9 shows an alternative form of the pivotal system of the jaws 36 and 36' , each jaw being articulated on a separate shaft 49 and 49!., fixed to the stator 31 like the shaft 37 of the previous example.

Reference will now be made to Fig.10 in which the arrangement is similar to that which has been described above with reference to Fig.2, and comprises a central drum mounted between the two rotors of the brake. The apparatus is symmetrical with respect to a plane perpendicular to the axis of rotation of the whole unit.

In the example of construction of Fig.10, there can be seen at 51A and 51B the two frames directly carrying the stators 52A and 5B of the aerodynamic brakes, and the bearings 53A and 53B supporting the shaft 54·· Tne drum 55 on which is wound or stored the tension band 57 is held by direct connection between the rotors 56A and 6B of the brakes.

In the example shown in Fig.11, the apparatus is symmetrical with respect to a plane perpendicular to the axis of rotation of the whole unit, as in Fig.10, but two winding drums are provided and are arranged laterally on the two rotors of the brake.

There is seen at 8 the central frame of the apparatus, carrying two lateral bearings 59A and 59B, and also carrying the stators 60A and 60B of the two brakes. On the shaft 61 are mounted the rotors 62A and 62B, on which the end-plates ^A and 6½B of the drums 63A and 63B are directly fixed.

For that purpose, the end-plates 64A and 64B are provided with orifices in which are engaged corresponding studs of the rotors 62A and 62B, the drum being held gripped on the rotors by the end-plates 66 which are fixed on the shaft 61 by means of screws 67.

The shaft 61 serves solely as a support for the rotor-drum assemblies, and ensures between them a coupling which only transmits a torque representing the difference between the forces due to the two bands.

It will of course be understood that the invention is not limited to the forms of construction described and shown, but includes all its alternative

Claims (14)

HAVING NOW particularly described and ascertained the nature of our said invention and in what manner the sa¾ . is to be performed, we declare that what we claim is

1. A device for braking aircraft on runways, comprising a drum receiving a cable which unwinds at a variable radius when a force is applied to said cable by an aircraft which lands on the runway, characterized in that a rotary air-brake is coupled to said drum and is adapted to retard the rotation of said drum caused by the cable which unwinds, said air-brake comprising an associated stator and a rotor in communication direct with the surrounding air and adapted to be cooled by the surrounding air. ,

2. A braking device in accordance with Claim 1, characterized in that auxiliar cooling means for the said air-brake comprise a source of atomizable cooling liquid arranged on the outside of the air-brake, a conduit leading the cooling liquid from said source to the interior of the stator, while liquid-atomization orifices are arranged at the discharge extremity of the said conduit.

3. A braking device in accordance with Claim 1, characterized in that means for regulating the power of the said air-brake are provided and are adapted to control the flow of air between the stator and the rotor. .

4. A braking device in accordance with Claim 3, characterized in that the said power-regulating means are movably mounted on the stator so as to control the flow of air which passes through the space comprised between the stator and the rotor.

5. A braking device in accordance with Claim characterized in that the said power- egulating means comprise pivoted shutters disposed in the space comprised between the stator and the rotor.

6. A braking device in accordance wit Claim 4., characterized in that the said power-regulating means comprise a pair of articulated jaws arranged in the space comprised between the stator and the rotor.

7. A braking device in accordance with Claim 3, characterized in that the said power- egulating means comprise an axially-movable mounting of the stator in order to vary the axial space between the stator and the rotor.

8. S. A braking device in accordance with Claim J>, characterized in that the power-regulating means comprise an axially movable ring adapted to control the axial space between the rotor and the stator, at the periphery of these latter.

9. A braking device in accordance with Claim 3, characterized in that the said power-regulating means vary the section of passage of orifices formed at the periphery of the stator blading and putting the interior of the said stator into communication with the atmosphere.

10. A braking device i accordance with Claim 3, characterized in that the shaft of the rotor passes through the drum, and end-plate of the rotor forming one cheek of the drum, the cable being connected to the rotor shaft, so that the torque is transmitted directly from the said cable to the rotor shaft.

11. A braking device in accordance with Claim 3, characterized in that the air-brake comprises two rotors associated respectively with two stators, with an arrangement which is symmetrical with respect to a plane perpendicular to the axis of rotation of the whole unit.

12. A braking device in accordance with Claim 3, characterized in that the stators are arranged on the between the said rotors.

13. A braking device in accordance with Claim 1, characterized in that two drums are provided and are arranged on the outside of the rotors, the said rotors being themselves arranged on the outside of the stators.

14. Braking devices for bringing aircraft to a stop on runways, substantially as hereinbefore described and as illustrated in the accompanying drawings. Dated this 24th day of September, 1965 For the Applicants DR. REI HOLD CGHN & CO.