FR2503283A1 - Actuator for disc brake - has piston travel limited by combination of three stops on piston, rod and sleeve - Google Patents

Abstract

The disc brake actuator has a cylinder (1) with a piston (3) sliding in it. The piston stroke is limited to prevent its ejection from the actuator cylinder by a stop (17) on the piston and another (29) on a rod, carried by the cylinder. A third stop (22) can work with the first and is fixed to a sleeve (19) sliding on the rod (7). A flexible part is placed between the first stop and a shoulder (26) on the sleeve. One part presses on the first stop and another on the sleeve.

Description

COIWLMANDE JACK, ESPECIALLY FOR DISC BRAKES
The present invention relates to a control cylinder and more particularly a cylinder intended to exert a force against a brake disc, clutch, etc.

These control cylinders are intended for use in multi-disc aircraft brakes. These brakes are made, very succinctly, of rotors and stators arranged alternately against each other, and positioned in a wheel.

The control cylinders, distributed regularly all around the friction surfaces, are hydraulically controlled, applying a force on the rotor-stator assembly, so that they rub against each other, thus ensuring the braking of the aircraft.

These cylinders generally consist of a cylinder secured to a fixed body in which is mounted a piston whose external face, equipped with a plate, is applied against a pressure plate pressing itself against the discs.

The piston is returned to the cylinder when the hydraulic pressure ceases, using elastic means carried by a rod arranged in the axis of the cylinder.

These control cylinders have drawbacks, however, and in particular pose a maintenance problem for these types of disc brakes.

Indeed, the various pistons are not retained at the end of their travel relative to their respective cylinders and during maintenance or checking of the braking device, these pistons may accidentally eject from their housing, this causing their reassembly, and, of course, of the various parts constituting the backlash system. In addition, after it is necessary to perform a purge of the hydraulic circuits.

Another drawback is that the rotors and stators wear out depending on the number of landings and the braking intensity. This results in a reduction in their thicknesses which are compensated by the control cylinder pistons by emerging more from their respective cylinders.

However, at a certain limit, there is created an overhang of these pistons relative to their cylinders, which is undoubtedly dangerous because the cylinder can deteriorate.

Also, when the brake discs are carbon, it sometimes occurs, during very violent braking, a bursting of these discs, these pistons no longer being limited in their stroke, they eject from their cylinder since they are no longer in contact with the discs.

The ejection of these pistons causes an evacuation of the hydraulic circuit oil which can help, for example, skids or fires.

The present invention aims to overcome these various drawbacks by proposing for this a control cylinder in which is avoided the untimely and accidental exit of the pistons and which promotes maintenance during overhauls of the braking devices.

The present invention relates to a control cylinder comprising a cylinder in which is capable of sliding a piston, means for moving said piston relative to said body, characterized in that it comprises means for limiting the stroke of the piston in the cylinder in order to pocket its ejection.

More specifically, the means for limiting the stroke of the piston include a first stop disposed on the piston and a second stop disposed on a rod carried by said cylinder; the rod being positioned parallel to the cylinder.

Advantageously, a third stop, able to cooperate with the first is integral with a sleeve sliding on the rod.

The invention will be better understood with the aid of a particular example of embodiment which will be described below, with reference to the drawings annexed by way of illustration, but in no way limiting, in which - FIG. 7 represents, seen in longitudinal section, the control cylinder as it appears after the mounting of these various members, in its original position, - Figure 2 shows, still seen in longitudinal section, the control cylinder as it appears in the end position .

A disc brake comprises a plurality of control cylinders which are distributed regularly all around the rotor-stator assembly, and which all have a strictly identical structure and operation.

 I1 will therefore be described only one of these control cylinders.

With reference to FIGS. 1 and 2, the control cylinder comprises a cylinder 1, mounted in a support, not shown, and an internal bore 2 of which receives a piston 3. In the bottom 4 of the cylinder 1, a bore 5 is formed carrying the end 6 of a rod 7 positioned in the geometric axis 8 of the cylinder 1, and consequently of the piston 3. The end 6 of the rod 7 is provided with a seal 9 opposite the bore 5.

The piston 3 slides by its side wall 10 in the bore 2 of the cylinder 1 and opens by its bottom 11 out of the cylinder.

The side wall 10 envelops the rod 7, the end 12 of which, opposite the end 6, comes close to the bottom 71 of the piston 3.

The end 13 of the cylinder 1 opposite the bottom 4 is equipped with a scraper seal 14, thus preventing any introduction of external elements between the piston 3 and the cylinder 1.

The latter and the side wall 10 of the piston 3 are drilled with holes 15 and 16 respectively allowing the passage of a hydraulic fluid to control the movement of the piston 3 relative to the cylinder 1.

In the end of the side wall 10 opposite the bottom 11, is fixed, by means of a rod 18, a retaining ring 17, defining a first stop.

A sleeve 19 is disposed between the side wall 10 and the rod 7. This sleeve is capable of sliding on this rod as will be explained below.

This sleeve is guided on the rod by means of a spring-shaped friction seal 20, housed in a cavity 21 formed in the sleeve 19. This friction seal 20 is held in the cavity by means of, and between two shoulders internal annulars 22 and 23. The shoulder 22 defines one of the ends 24 of the sleeve.

In the vicinity of the second end 25 of the sleeve 19 is defined an external annular shoulder 26 on which abuts one of the ends of a return spring 27, thereby pressing the second end 25 of the sleeve 19 against the internal bottom 71 of the piston 3. The spring 27 bears by its other face against the retaining ring 17 fixed on the piston 3.

Therefore, the piston is pressed against the bottom 4 of the cylinder 1.

 There is a groove 28 in the end 12 of the rod 7, which receives a rod 29 defining a second stop for the internal shoulder 23 of the sleeve 19. A third stop is defined by the internal shoulder 22 of the sleeve 19, the latter being able to cooperate with the part 32 of the ring 17.

The rod 7 is fixed by its end 6 against the outer face of the bottom 4 of the cylinder by a connecting means of a type well known per se and which will therefore not be described.

The outer face of the bottom 11 of the piston 3 is linked to a pressure plate 30 which can be applied against the discs 31 shown partially in the figures, when for example braking is requested.

The control cylinder according to the invention operates as follows
In Figure 1, this cylinder is shown in the rest position, that is to say that no hydraulic pressure is applied to it.

Initially, the end of the side wall 10 of the piston 3 is pressed against the bottom 4 of the cylinder 1.

The sleeve 19 is pressed against the bottom 1 * 1 of the piston under the action of the spring 27.

Thus, the pressure plate 30 linked to the piston is at a determined distance "e" of the order of a few millimeters relative to the first disc 31 of the stator-rotor assembly, and equal to the distance defined between the end 22 of the sleeve and the part 32 of the retaining ring 17, that is to say the distance defined between the first and the third stop.

When, for example, the brake has to be controlled, the pilot requests that hydraulic pressure be sent to the various control cylinders of the braking system. As a result, the pressurized hydraulic fluid passes through the various orifices 15 and 16 and will be introduced between the piston 3 and the cylinder 1 thus causing an increase in volume.

This increase in volume tends to cause the piston 3 to come out of its cylinder, which compresses the spring 27 until the part 32 abuts against the shoulder 22 if the plate 30 has not come into contact before with the disc 31. On the other hand, if the disc, for whatever reason, is not reached, the part 32 then pushes the sleeve 19 until the friction plate 30 comes into contact with the disc 31.

The sleeve is guided on the rod 7 by means of the friction seal 20; the piston being linked to the ring 17 moves in the bore 2 of the cylinder 1 and is applied by its pressure plate 30 against the various discs 31 so that the discs rub against each other.

The pressure can be maintained continuously and consequently until the aircraft stops.

When the pilot releases the control means of the braking device, the pressure no longer being applied in the jacks, the return spring 27 tends to decompress and pushes the ring 17, therefore the piston 3 towards the bottom 4 of the cylinder 1 and, therefore, the part 32 is found at a distance "e" from the shoulder 22.

As in all braking devices, the discs wear out over the course of successive braking and their thicknesses decrease. However, the distance separating the first disc 31 from the pressure plate 30 secured to the piston 3 remains the same thanks to the backlash and is equal to "e", even if the discs are very worn.

The maximum output limit of the jack is shown in FIG. 2 where the piston 3 is at the limit stop, the internal shoulder 23 of the sleeve being in abutment against the rod 29 of the rod 7.

Of course, in this case, the discs must be changed if they have not already been changed.

In any case, this ring has especially the advantage of pocketing the ejection of the piston from its cylinder during, for example, a bursting of the carbon discs sometimes occurring during severe braking.

This ring retains the piston and the sleeve
Indeed, an ejection of the piston, sleeve and spring assembly would evacuate the oil on overheated discs, which would cause risks of skidding, but more strictly a fire with the catastrophic consequences that we know.

Another advantage of this stop, in this case the rod 29, lies in the maintenance of these jacks.

Once the discs have been removed, this rod 29 provides increased security since the piston does not risk ejecting from the cylinder, since the retaining ring 17 linked to the piston 3 abuts against the shoulder 22 of the sleeve itself coming into abutment by the shoulder 23 against the rod 29.

Claims (9)

 P E V E N D I C A T I O N S  7 / control cylinder comprising - a cylinder (1), - a piston (3), capable of sliding in said cylinder, - means for moving said piston relative to said body, characterized in that it comprises means for limit the stroke of the piston in said cylinder (1) in order to prevent the ejection of said piston (3).  2 / control cylinder according to claim 1, characterized in that the means for limiting the stroke of the piston (3) in the cylinder comprise a first stop (17) disposed on the piston and a second stop (29) disposed on a rod (7) carried by said cylinder.  3 / control cylinder according to claim 2, characterized in that a third stop (22), capable of cooperating with the first stop (17) is integral with a sleeve (19) sliding on said rod (7).  4 / control cylinder according to claim 3, characterized in that it comprises an elastic means, disposed between the first stop (17) and a shoulder (26) formed on the sleeve (19), applying, on the one hand , one face against the first stop (17), and, on the other hand, against the sleeve (19).  5 / control cylinder according to one of claims 3 and 4, characterized in that the sleeve (19) comprises guide means on said rod.  6 / control cylinder according to claim 5, characterized in that the means for guiding the sleeve on the rod (7) are constituted by a friction seal (20) disposed in a cavity (21) of said sleeve and cooperating with the rod (7).  7 / Control cylinder according to one of claims 2 to 6 above, characterized in that the first stop is shaped as a retaining ring (17) integral with said piston (3).  8 / control cylinder according to one of claims 2 to 6 above, characterized in that the second stop is shaped as a rod (29) disposed in a groove (28) formed in said rod (7).  9 / control cylinder according to one of claims 3 to 6 above, characterized in that the third stop is defined by an internal annular shoulder (22) to said sleeve (19).