FR2498278A1 - Hydraulic spring for aircraft undercarriage - has floating piston dividing cylinder with hollow rod sliding axially into cylinder and locating pressure sensor - Google Patents

Abstract

The hydraulic compensator may be used on aircraft under carriage, using a floating piston (2) to divide a cylinder into two chambers (7,8) of inversely proportional variable volume. A tubular rod (16) slides through a sealed passage (15) in one cylinder end, with one end (19) opening out into the first chamber (7), and the other (25) having a pressure-sensor. The two chambers and the rod are filled with an incompressible fluid, and the passage may be formed by a demountable pillow-block sleeve (25) with two slip surfaces (20,21). The pressure in the rod may be sensed by a manometer or by a piston (29) with two differential sections (30,31) located by a transverse bore (46).

Description

COMPENSATOR, ESPECIALLY AIR

  The present invention relates to air compensators, cIç'a-t.-pdnir, 'fo dfnpnnitifp which aanurrnt a

  spring function by means of a compressed fluid

  ble such as a gas which can, but not exclu-

  be air. These devices are also known by technicians as a spring.

fluidic or hydraulic.

  There are already such air compensators, but

  none are actually designed for aeronautical technique

  nautical, in particular when it is necessary to obtain a controlled displacement, of a landing gear relative to a median unstable equilibrium point,

especially by Tumbler effect.

  The present invention aims to achieve a com-

  thinker, especially said to air, which is reliable and

  meets all the conditions of use and

  specifications requested by aircraft manufacturers

  naves and more particularly for the landing gear

terrissage.

  The present invention also relates to a com-

  thinker, in particular with a compressible fluid such as a gas comprising a cylinder, a separating piston sliding in said cylinder to divide said cylinder into two, into a first and a second

  inversely varying volume chambers

  portable, a rod sliding in a sealed passage at one end of said cylinder, said rod comprising a longitudinal hollow cavity with an opening, said opening opening at the end of said rod plunging into said first chamber of the cylinder and comprising at its other end means for detecting the pressure in said cavity, a compressible fluid in said second chamber and an incompressible fluid in said first chamber and cavity. Other characteristics and advantages of the present invention will appear during the following description, given with reference to the appended drawing, by way of illustration but in no way limitative in which:

  - Figure 1 shows, in section, a mode of realization

  sation of a compensator according to the invention, - Figure 2 shows, in section, a part of a second embodiment of a compensator according to the invention, and, - Figure 3, in section, a part d 'a third

  embodiment of a compensator according to the invention

tion.

  FIG. 1 represents, in section, an embodiment

  tion of a compensator comprising a cylinder 1 in

  which slides, sealingly, a separate piston

  tor 2, the seal being essentially obtained by a circular joint 3 disposed in a groove 4, this piston being, in addition, guided by a shoulder

  annular 5 distant from the seal 3, and which, in association

  tion with this seal 3, allows the piston to slide

  always parallel to itself in cylinder 1.

  Of course, this shoulder 5 which slides along the internal wall 6 of the cylinder does not need

a seal.

  This separating piston motions the cylinder 1 into two chambers 7 and 8 which, when the piston moves along the wall 6, have volumes defined in the

  cylinder which vary inversely

  tional. Chamber 7 is filled with a fluid

  compressible like oil, and the chamber 8 by a compressible elastic fluid like a gas such as air. This cylinder 1 has, at its end 13, a bottom

  9 to close the chamber 8, this bottom 9 being able to

  carry an inflation valve 10 and a hollow reserve 11 defining a determined volume whose function will be explained below, and a first

  attachment means 12 such as for example a ball joint.

  The other end 14 of the cylinder 1 has a step

  wise waterproof 15 in which a hollow rod slides

  16 also comprising a cavity 17 with a single or

  groove 18 opening at the end 19 of the rod

  16 is constantly in room 7. The pas-

  waterproof seal is defined by a bearing with two sliding spans 20 and 21, the span 21 of which includes a

  seal 22 ensuring this tightness.

  This bearing is advantageously composed of a filler piece 23 like a sleeve secured by any means to the body 24 of the cylinder 1, allowing its interchangeability, but above all a dismountability

easy to compensate.

  The other end 25 of the rod Until extends before

  carefully the cavity 17 has a bottom 26 supporting

  as another attachment means 27 such as for example a second ball joint. But, in addition, this end comprises, in cooperation with the end 28 of the cavity 17, a means for measuring the pressure prevailing in this cavity and therefore in the chamber 7. To this means can be coupled an indicator allowing observers control the value of this pressure, either in absolute value or in relative value, with a display which can be

analog or digital.

  The means for measuring the pressure illustrated in FIG. 1 comprises a differential piston 29 arranged

  in a transverse bore 46 to the cavity, that is

  that is to say comprising two sections of different diameters

  rents 30 and 31, the diameter section 31 being above

smaller than that of diameter 30.

  Therefore, the pressure in the cavity 17 is exerted on the crown 32 delimited by the change in section of the diameters 30 and 31, so as to maintain this differential piston against the bottom 33 against the pressure exerted by a spring. 44 having a determined stiffness which must be less than that of the pressure exerted on the crown 32, as long as the pressure in the cavity 17 is greater than the value given by the pressure of the compressible gas contained in the chamber 8 and which is transmitted by the separating piston 2 and the incompressible fluid

  contained in this chamber 7 and the cavity 17.

  An opening 34 is made in the wall 35 of the rod 16 in the axis of movement 36 of the differential piston 29, it being noted that this movement is limited by a stop 37. The differential piston supports a lug 38 which, when this piston is in

  a normal position pressed, does not emerge from the ori-

  fice 34, but which, on the other hand, emerges when the pressure on the crown 32 is no longer strong enough to counteract the pushing force of the spring 44; the piston then coming, by its crown 32, to be pressed against the stop 37. Therefore, when the lug 38 emerges from the orifice, it indicates that the pressure of the

  elastic gas is no longer strong enough and that the res-

spell no longer has its initial stiffness.

  Of course, the compensator also includes a valve for filling the incompressible fluid which

  may be the bottom 33 which is removable, the filling

  ge taking place, in this case, before being placed

the piston 29.

  The structure of the "air" compensator which has just been described above is advantageous, in particular because it allows filling of the two fluids making

  the use of a reliable and secure compensator.

  Indeed, to fill the compensa-

  tor, it is first necessary to place it in the vertical position, the ball 12 being in the low position. Therefore, the chambers 8 and 7 containing no fluid, the separator piston 2 comes into contact with the bottom 13 of the cylinder 1 and the rod 17 also comes

  in turn place against this separator piston 2.

  At first, it is introduced, in the

  chamber 8, a certain amount of a lubricating fluid

  ficitor which will fill the cavity II, the excess of which is eliminated by the filling valve 12 since, as said above, the compensator is in the vertical position.

  So knowing the volume value of this cavi-

  tee 11 the quantity of lubricating fluid, in particular

  for the joint 3, will be perfectly known.

  To perform the actual filling of the

  thinker, first of all chamber 7 is filled with incompressible fluid like oil until

  it comes to touch, up to the level of the

  positive pressure detector essentially the orifice of the plug 33, it being understood that the separator piston 2 and the rod 16 are still in

the position defined above.

  The plug 33 is then replaced before closing

  placed the differential piston in its position

  as shown in Figure 1.

  Once this operation is completed, the chamber 8 is gongled with elastic gas at

by means of the inflation valve 10.

  The pressure of this gas is gradually increased so as to push the separator piston 2 until the clip 47 comes to abut against the sleeve-shaped bearing 23.

  As the diameter of the i6 rod is less than the diameter

  inside of cylinder 1, the oil volume re-

  pushed by the separator piston is greater than the volume of displacement of the rod i6. Therefore, the

  separator piston moves in relativity from the former

  end of the rod 16 plunging into the chamber 7, that is to say that the rod rises faster than the

separator piston.

  Since the volumes of the cavities and of the cylinder are perfectly known, the position of the separating piston 2 inside the cylinder is easily

  determined and therefore the volume occupied by the gas

  pressible and elastic introduced into chamber 8 of the cylinder.

  The qualities, and in particular the response of such a compensation

  are determined with precision.

  The operation of such a compensator is then obvious for example if two opposite forces are applied respectively to the ball joints 12 and 27, the rod 16 will enter the cylinder and push back

  the separator piston without coming into contact with it

  ci due in particular to the filling process as described above. Indeed, the rod cannot come into contact with the piston

  separator only when the chamber 8 is almost tota-

  emptied of its compressible fluid.

  This point is important because it constitutes a safety, that is to say a mechanical stop at the end of travel for the rod, but having used the maximum of possibilities of elasticity or spring function of

this compensator.

  Of course, the compensator includes a means which makes it possible to monitor the value of the pressure of the

  compressible fluid in chamber 8, as mentioned-

  born previously, which determines whether the compensator

is still usable.

  Indeed, if the pressure of the gas contained in the chamber

  bre 8 decreased by too large a quantity

  te, the pressure exerted on the crown 32 would drop below a certain value threshold allowing the spring 34 to push the piston, and in particular to make the indicator 38 appear in the eyes of

  all observers who can then act accordingly

  and carry out the usual interventions.

  In FIG. 1, an embodiment has been described.

  tion of a differential piston whose sealing of the two sections of different value is obtained by seals such as, for example, "0-rings". However, such seals can, in certain cases, present drawbacks, and in particular leak

for very high pressures.

  FIG. 2 represents another embodiment of a means allowing the value of the pressure prevailing inside the chamber 8 to be detected.

  taking the compressible fluid which can be used

  dried for high pressures, but also on

corrosive fluids.

  This means consists of a differential piston

  to two sections of different value, respectively-

  ment 50 and 51, joined together by a connecting means such as in particular a rod

  rigid 52, the section 50 being less than the sec-

tion 51.

  In this case, the seals at the periphery of sections 50 and 51 are obtained respectively by two bellows membranes 53 and 54, welded for example to sections 50, 51, and to the wall of the

rod 16.

  As above, in the case of the embodiment

  tion according to Figure 1, the differential piston is subjected to the action of spring 55. Possibly, to limit the crushing of the spring 55, a mechanical stop 56 can be provided. It is further specified that the development of

  membranes is important enough that when

  as the pressure inside the cavity 17 drops to an unacceptable value, the section 50 can emerge from an orifice 57 formed in the wall 35 of the rod 16 to indicate as before

  describes, this weakness of pressure.

  Figures 1 and 2 show two embodiments.

  sation of the means making it possible to measure all or nothing the value of the pressure inside the compensator. However, despite their sensitivity, they can have a drawback, in particular due to the indication of the value of the pressure

under this form.

  Indeed, it may be advantageous, in some cases, to know the true value of the pressure at

any moment.

  For this, the means for measuring the pressure at the

  in particular the cavity 17 can be constituted

  killed by a pressure gauge 60 plugged directly into the

  cavity 17 at the end of the most distant rod 16

from cylinder 1.

  The pressure gauge comprises a means of displaying the true value of the pressure prevailing inside the compensator, this signaling means which can be constituted as illustrated in FIG. 3, by a dial 61 appearing gradually, more and more, in a window 62 as and when

  the pressure in the cavity 17, and therefore in the cham-

bre 8 decreases.

R E V E N D ICAT 0 TION S

  1 / Compensator, in particular & compressed fluid

  ble like a gas comprising a cylinder (1), a

  your separator (2) sliding in said cylinder (1) to divide said cylinder in two, or a first and a second chamber (7,8) with volume varying from

  inversely proportional, a sliding rod

  health (16) in a sealed passage (15) at one end

  tee (14) of said cylinder (1), said rod (16) includes

  nant a hollow cavity (17) longitudinal to one or

  verture, said opening (19) opening & out-

  mite of said rod plunging into said first chamber (7) of the cylinder and comprising at its other end (25) means for detecting the pressure in said cavity, a compressible fluid in said second chamber (8) and an incompressible fluid

  in said first chamber (7) and cavity (11).

  2 / compensator according to claim 1, ca-

  characterized by the fact that the sealed passage (15) is defined by a removable bearing comprising two sliding surfaces (20, 21).

  3 / Compensator according to claim 2, ca-

  characterized by the fact that said bearing consists of a sleeve (23) disposed in said cylinder (1) and means for fixing said sleeve (23) in said cylinder.

  4 / Compensator according to one of claims

  1 to 3, characterized in that the means for detecting the pressure in said hollow cavity (17)

  include a piston (29) with two different sections

  tials (30231) arranged in a bore (46) sensi-

  completely transversely to said cavity (17) having two sections complementary to those of the piston (29) of the sealing means, respectively between the two sections of said piston and those corresponding

of said bore.

  5 / compensator according to claim 4, characterized by the fact that said sealing means

  consist of sliding gaskets

health.

  6 / Compensator according to claim 4, ca-

  characterized by the fact that the sealing means are constituted by bellows membranes (53, 54), linked respectively to the sections of the piston (29)

  and to the sections of said transverse passage (15).

  7 / compensator according to one of claims

  4 to 6, characterized in that said piston sup-

  carries a lug (38) capable of emerging from said bore for

  a determined position of said piston (29).

  8 / compensator according to one of claims

  above, characterized in that it comprises means for measuring the pressure of said cavity (17)

  9 / compensator according to claim 8,

  characterized by the fact that said means for measuring the pressure consist of a pressure gauge (60)

connected to said cavity (17).