FR2461852A1 - IMPROVEMENTS TO SHOCK ABSORBER AND SHOCK ABSORBER, IN PARTICULAR FOR AERODYNE LANDING TRAINS - Google Patents

Abstract

THE INVENTION CONCERNS SHOCK ABSORBERS AND SHOCK ABSORBERS-CYLINDERS. THEY INCLUDE A SHOCK ABSORBER ROD 1, CONTAINING A LOW PRESSURE ELASTIC RETURN CHAMBER 11, AND SLIDING IN A CHAMBER 3 OF A CYLINDER 4, FILLED WITH LAMINATED OIL THROUGH THE COMPRESSION LAMINATION HOLES 13 OF A PISTON D 'SHOCK ABSORBER 6 CARRYING A BRAKE VALVE 14 IN RELIEF OF CHAMBER 11. THE PRESSURE OF THE OIL OF CHAMBER 3 IS APPLIED TO A MOVABLE BOTTOM 8, ITSELF PRESSING ON AN ELEMENT WITH EFFORT THRESHOLD 17, AUTHORIZING A MOVABLE BOTTOM STROKE 8, DURING A COMPRESSED LOAD OF THE SHOCK ABSORBER, FROM A FORCE EXCEEDING A GIVEN THRESHOLD, AND INDEPENDENT OF THE DRIVE SPEED OF SHOCK ABSORBER 1 IN CYLINDER 4 APPLICATION ESPECIALLY TO THE EQUIPMENT OF SUSPENSIONS FOR HELICOPTER LANDING TRAINS.

Description

The subject of the invention is improvements to the devices and

  shock absorbers cylinders, particularly of the type of euepat the landing gear aerodsâmes, especially helicopters, and adapted to landings disaster (qualified in this technical field by the term "crash") We already know many types of suspension dampers for landing gear of aerodynes, comprising Ane damper rod mounted sliding with airtightness A 1 '

  inside a first hydraulic fluid chamber of a cy-

  Second, the rod or cylinder enclosing a low pressure elastic return chamber, such as a pressurized gas chamber, and a volume of hydraulic fluid, possibly adjacent to the low pressure chamber, and in communication with

  the first chamber of the cylinder by at least one

  in compression, presented, for example, by a piston carried by the end of the damper rod received inside the

  cylinder, the expansion of the low-pressure chamber being braked

  born by a relaxing rolling valve.

  In these devices, the low pressure chamber A acts as a spring, recalling the device in equilibrium position after damping of the displacement of the rod in the cylinder, which results from dissipation of energy by rolling the hydraulic fluid at through calibrated orifices for normal landing speeds, of the order of 3 m / s, allow

  so much to absorb the energy at impact.

  Some of these known devices also include valves with variable section rolling orifices depending on the driving speed or the direction of passage.

  fluid, as well as braking means at the end of relaxation.

  the damper, in order to make the latter effective when rolling the aerodyne on unprepared ground or tracks

  daled, or to absorb certain peaks of effort, in order to absorb

  the effects of the ground resonance phenomenon which is

  fest on the helicopters, at the limit of the lift,

  Just before take-off, and in order not to leave the

  sitive relax suddenly, with shock when it arrives

in abutment in relaxed position.

  But these ccn.nus devices turn out not to be

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  suitable for landings in disaster or the crash of the aircraft.

  dyne, with vertical speeds of the order of 10 to 12 m / s,

  for which the compression lining apertures

  are undersized, so that the damper behaves like a quasi-rigid element, transmitting to the structure of one aerodyne all efforts it receives, which causes the destruction of the aircraft, or the destruction of the shock absorber

  then driving that of the aerodyne.

  It is also known from French Patent No. 2,314,403, a damper of this type in which the rolling orifice is determined by a piston traversed, with a set clearance, by a rod carried by a rigid bottom, mounted inside. of the

  rod, and itself pierced with braking orifices ensuring the lami-

  hydraulic fluid passing from an internal chamber to the rod towards an internal chamber at the bottom rigid and separated from a

  gas chamber at high pressure by a separator piston.

  At impact, in this device, and in the

  similar positives with moving bottom pierced by rolling orifices,

  superimposed on the forces due to the inertia of the non-suspended parts

  such as the wheel and its equipment (particularly brakes), the forces due to rolling, which are all the more important that the vertical speed at impact is high, so that the total effort to the shock absorber is much higher than its limited elastic load and can exceed its breaking load

  or the breaking load of the undercarriage, and cause the

truction of the aerodyne.

  In addition, shock absorbers are known

  likely to bring the undercarriages into position

  re-entry, during the flight of the aerodyne, in the outbound position for landing and taxiing and in the lowered position on the ground, to facilitate the logeability of the aerodyne in a hangar, accessibility to certain parts of the aerodyne, its anchorage on its parking lot, etc. The dampers-cylinders described in the French patent applications 76/03126 and 76/33261

  include a shock absorber, which may be of the type

  mounted on the end of a cylinder rod, a first chamber acting as a cylinder for the damper, and itself secured to a cylinder piston slidably mounted in a cylinder cylinder, with which the piston defines a room controlling the lowering of the landing gear when it is powered by

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  hydraulic fluid, and controlling the lowering position,

  when it is emptied, without changing the burden of the amor-

  weaver. In addition, a lift piston, slidably mounted in a second chamber of the cylinder rod, separated from the first, and constituting a lift chamber of the undercarriage, allows to load the damper by pulling the rod of the latter to The interior of the cylinder rod, when this second chamber is fed with hydraulic fluid and that the down chamber is

  emptied, which brings the undercarriage into the retracted position. A disc

  positive mechanical locking device, for example with claws, or hydraulic, comprising a hydraulic valve with controlled opening, is, in addition, provided for locking the cylinder rod in the extended position relative to the cylinder cylinder, .after filling the chamber of descent. In the case of a hydraulic device, a pressure relief valve disposed at the bottom of the descent chamber allows an extension of

  the race by emptying the descent chamber in the event of a crash.

  This solution has the disadvantage that the race may

  damper is not used to absorb

  an extra part of the crash energy.

  The problem to be solved by the present invention is to design dampers and

  sophisticated shock absorbers, capable of absorbing a fraction

  crash energy can be three to four times

  greater than the maximum normal energy, absorbed for

  landing, this fraction of the crash energy itself being absorbed at speeds of three to four

  times higher than normal speeds, and the additional fraction

  the crash energy is absorbed by the structure of the aerodyne supporting the shock absorbers or dampers-jacks, the latter must be destroyed only after taking advantage of

  their compression stroke, regardless of the speed of

  tical of the aerodyne vis-à-vis the ground, and the stress incurred by the damper remaining close to the elastic limit load and, in any case, lower than the extreme load, breaking load of

the undercarriage or the shock absorber.

  For this purpose, the suspension damper according to the invention, of the type presented above, is characterized in that

  the hydraulic fluid pressure prevailing in the first chamber

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  bre is applied on a moving bottom, itself bearing against a stress threshold element, allowing a stroke of the moving bottom, during a compression load of the damper, from a

  effort above a given threshold, and regardless of the speed of

  depressing the damper rod into the cylinder.

  The stress threshold element can be made in very different shapes, ranging from the pressurized gas chamber, such as a capacitor. nitrogen-blown, plastic deformation devices, comprising for example cellular materials or honeycomb structures deforming by buckling, or devices with successive breaks of elements or various materials, such as perforated tubes whose holes are deformed when the tubes are stressed in buckling, tubes fitted into one another and such that the inner tube tears the outer tube when it is pressed into the latter, or such that the outer tube successively cuts necklaces or rings

  integral with the inner tube and axially distributed over the

phérie of the latter.

  The characteristic common to all these stress threshold elements is that the stroke of the movable bottom resting on them, starts only from a significant level of effort, nettemant superior to the forces experienced by the shock absorber in its operating at normal landing speeds, that this travel is complete without significant increase in this effort, so that the energy efficiency of these threshold elements is sufficient, and that these elements operate between the level

  "elastic limit" and the level "break" of adjacent structures

  these stress threshold elements allow the damper to operate as a force limiter, the load

  transmitted by the damper to the adjacent elements of the landing

  the aerodyne structure is still limited inde-

  the driving speed of the damper rod

in the cylinder.

  Preferably, however, the stress threshold element is constituted by a high-pressure elastic return chamber, the expansion of which is slowed down by a thrust rolling valve, so as to avoid rebounds in a shock absorber which is susceptible to recover in the initial conditions,

  after moving the moving floor.

  In a particular embodiment,

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  corresponding to a damper-cylinder that can fulfill the function of lift cylinder and lowering, the cylinder comprises a second hydraulic fluid chamber in which a cylinder rod, mounted sliding with sealing, defines respectively by its inner face and by its outer face; a lowering chamber and a lifting chamber, which can be supplied with hydraulic fluid to respectively supply and retract the o cylinder rod into the second chamber of the cylinder. It is possible, in a first version, to dispose one after the other in the cylinder, the first chamber, the stress threshold element and the second chamber, the first chamber being delimited between the end of the damper rod received in the cylinder and the moving bottom, and the second chamber

  being separated from the stress threshold element by a transverse partition

fixed versale of the cylinder.

  According to a preferred embodiment of this first version, a separating piston, slidably mounted with sealing inside the cylinder rod, separates the downcomer chamber.

  of an adjacent volume of hydraulic fluid retained in the second

  room and in communication with the first chamber

  towards a hollow rod, carried by the fixed transverse partition of the cylinder passing through the stress threshold element, and around which the movable bottom is slidably mounted. In this way, it ensures the separation of the hydraulic fluid ensuring the damping function from that contained in the operating circuit of the

  cylinder for controlling the retraction or the exit of the cylinder rod.

  In addition, it is possible to use the stroke of the cylinder as an over-stroke of the shock absorber, for the same length of the shock-jack,

  which is particularly advantageous.

  In a second version, suitable for

  dampers as shock absorbers-cylinders, the first chamber is delimited between the end of the damper rod

  received in the cylinder and a fixed bottom of the cylinder, provided with

  communication with an ancillary volume of hydraulic fluid.

  contained in a secondary room also receiving the element

at threshold of effort.

  This auxiliary chamber may be an annular chamber of the cylinder, surrounding the first chamber, and in which the movable bottom is constituted in the form of a piston

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  annular slidably mounted, or be contained in a cylinder outside cylinder, wherein the movable bottom is slidably mounted. But in the case of a damper-cylinder according to the second version, it is advantageous that a separating piston, sliding with sealing in the rod of the cylinder, separates the descent chamber from a volume of hydraulic fluid housed in

  the second room and in the adjoining room, opening directly

  the volume being in communication with the first chamber through a hollow rod carried by the fixed bottom, passing through the auxiliary chamber and the stress threshold element therein housed, and around which slides the

  mobile background, so that in this case also a separation

  between the damping fluid and the actuating circuit of the jack, and to be able to use the stroke of the jack as a shock stroke in a jacking device.

same total length.

  Finally, in all the embodiments, it is advantageous for a retraction piston to be slidably mounted with sealing, on the one hand inside the first chamber of the

  cylinder, on the other hand around the end of the rod of amor-

  weaver received in the cylinder, to define with the cylinder a retraction chamber capable of being supplied with hydraulic fluid to apply the retraction piston against a

  integral stop of the damper rod-and to control the retraction

  of the latter in the first chamber of the cylinder, which, if combined with the retraction of the cylinder rod

  in the second chamber of the cylinder, in the case of damper-

  cylinder makes it possible to give a minimum length to the device, cor-

  corresponding to the retracted train position.

  The invention will be better understood with the aid of the particular embodiments which will be described below, without limitation, with reference to the appended figures in which: - Figure 1 shows in axial half-sections, two dampers, of which one corresponds to the left half

  and the other half-cut right.

  FIG. 2 represents a first version of

  shock absorber-cylinder with retraction piston of the damping rod

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  which constitutes a development of the shock absorber represented

  on the left half-section of Figure 1.

  - Figures 3 and 4 show two embodiments according to a second version of damper cylinder with retraction piston of the damper rod.

  FIG. 5 represents a realization on

  damper stroke, obtained by developing the damper-

  cylinder shown in Figure 2.

  FIG. 6 represents another embodiment of

  mortiser-cylinder with over-stroke shock absorber.

  With reference to FIG. 1, the shock absorber of

  pension for an aircraft landing gear comprises a damper rod 1, which can be fixed to the aerodyne structure by the fastener 2 of its upper end, and slidably mounted in a first chamber 3 of hydraulic fluid, hereinafter referred to as oil, of a cylinder 4 capable of being fixed to the wheels or to the balance wheel of the undercarriage by its

attachment 5.

  The end of the rod 1, received in the chamber 3 of the cylinder 4 carries a damper piston 6, slidably mounted on the outer face of a counter rod 7 integral with a movable bottom 8 slidably mounted with sealing to the inside the lower part 9 of the cylinder 4. The contretige 7 passes axially

  the first chamber 3 and its free end presents rai-

  The stem 1 encloses a gas chamber under pres-

  11, adjacent to a volume of oil 12 in communication with

  the interior of the chamber 3 by permanent orifices of

  compression swimming 13, drilled in the piston 6, through the passage opening of large section, relative to the orifices 13, which define the axial grooves 10, as the piston 6 is

  facing these grooves 10, and, possibly, by the dia-

  diaphragms presented by an annular check valve 14 in

  relaxation of the chamber 11, facing the orifices 13, the displacement

  the valve 14 is limited, during a compression of I '

  damper, by an internal radial abutment 15 of the rod 1, tan-

  say that an outer radial abutment 16 of this same rod 1,

  the outlet of the latter out of the chamber 3 under the thrust of the pressurized gas chamber 11. The movable bottom 8 separates the chamber 3 from a stress threshold element constituted by

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  a pressurized gas chamber 17, the pressure of which is noted

  higher than that of Room 11, and which constitutes

  the high-pressure chamber of an oleopneumatic shock absorber

  chamber, whose expansion is braked by a thrust rolling valve, constituted, in the same way as the valve 14, by an annular disk pierced with at least one diaphragm opposite a passage orifice, and whose displacements are limited by a stop. On the left half-section of FIG. 1, this expansion valve of the high pressure chamber 17 is disposed at 18, in an annular chamber 19 defined between the enlarged part 9 of the cylinder 4, the movable bottom 8 and a jacket 20

  for guiding the movable floor 8, sliding along the inside surface

  3 of the chamber-3, this annular chamber 19 being freely fed by the channel 21, pierced at the base of the jacket 20, when the movable bottom 8 is moved by compressing the high pressure chamber 17, the valve 18 being then applied against the outer radial abutment 22 of the liner 20, which, by bearing against the shoulder 23 separating the wall of the chamber 3 from the wall of the enlarged part 9 of the cylinder 4, defines the position of

  rest of the mobile bottom 8 under the pressure of the high chamber

sion 17.

  The braking of the expansion of the high-pressure chamber 17 can also be performed positively by arranging the expansion damping valve at 24 in the annular chamber 25 defined between the inner face of the chamber 3, the outer face

  end of the rod 1 received in the cylinder 4, and a

  radial outer rim 26 of the damper piston 6, pierced with at least one free passage opening 27, and sliding against the inner face of the chamber 3, the displacements of the valve 24 in the chamber 25 being limited by the stop 16 and the crown

  26, as shown in the right half-section of FIG.

  The damper, the structure of which has just been described, operates in the following way: for any landing speed, a first stroke of the rod 1 in the cylinder 4 occurs, without damping, because of the free passage of the oil from the chamber 3 to the volume 12-by the grooves 10, which allow not to superimpose the forces due to the inertia of unsprung parts, when setting

  acceleration of the latter with respect to the structure of the

  rodyne, efforts due to the rolling of the oil. The grooves 10

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  thus allow to delay the beginning of depreciation. If the landing occurs at a normal vertical speed, of the order of 3 m / s, the damping is effected by rolling through the orifices 13 of the piston 6, the oil expelled from the chamber 3, by depressing the rod 1, and coming to compress the low pressure chamber 11, the valve being lifted from its

  seat and pressed against the stop 15. The orifices 13 being cali-

  For these normal vertical speeds, the pressure in the chamber 3 does not rise sufficiently to reach the inflation pressure of the high pressure chamber 17, so that the movable bottom 8 is not displaced. By cons, for speeds

  vertically higher, of the order of 6 m / s, we obtain simul-

  at the same time a rolling through the orifices 13, and a pressure in the chamber 3 reaching the inflation pressure of the chamber 17

  which constitutes the threshold beyond which the moving bottom 8 sinks.

  It thus simultaneously occurs a depression of the rod 1 in the chamber 3 and a depression of the movable bottom 8 in the enlarged portion 9 of the cylinder 4. For a contact with the ground, taking place with a speed of the order from 10 to 13 m / s, during a crash, for example, the orifices 13 are of insufficient section to allow a sufficient oil flow to the volume 12. So the pressure increases rapidly in the chamber 3, and the mobile bottom 8 is moved as soon as the threshold of

  pressure of the chamber. 17. In this configuration, the

  tif works as a stress limiter, not opposing any

  important additional resistance to the depression of the movable bottom 8, whatever the speed of insertion of the rod 1 into the

  4. This damper thus has the advantage that the ef-

  strong from which the movable bottom 8 sinks is independent of the driving speed of the rod 1, and depends only on the pressure characteristics and volume of the chamber at high

pressure 17.

  To avoid rebounds, in all cases the expansion of the low-pressure chamber 11 is braked by rolling the oil passing from the volume 12 to the chamber 3 through the diaphragms of the valve 14 applied against the piston 6, and in the cases or there has been a displacement of the movable bottom 8, the expansion of the high pressure chamber 17 is braked, either by the valve 18 laminating the oil passing from the annular chamber 19 to the chamber 3, or by the valve 24 laminating oil

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  passing from the annular chamber 25 to the chamber 3, according to the

  achievements, the grooves 10 of the counter rod 7 ensuring é-ga-

  It is also a good refueling of chambers 3 and volume 12 and a good separation between gas and oil for a return to initial conditions. With reference to FIG. 2, a shock absorber

  has a damper similar to that shown on the half

  left section of Figure 1, with its damper rod 31 and its piston 36, enclosing a low pressure gas chamber 41 and a volume of oil 42 communicating with the chamber 33 of a cylinder 34 through the rolling orifices in compression 43, the piston 36 sliding around the counter-rod 37 integral with the movable bottom 47 isolating a high-pressure gas chamber 47

  in the enlarged portion 39 of the cylinder 34.

  This damping part operates in the same way as the damper according to FIG.

  relaxation of the high and low pressure chambers 47 and 41 being

  provided by valves 48 and 44, the only difference

  being that the exit of the rod 31 from the chamber 33 is limited

  not by the support of the stop against the cylinder 34, but against a retraction piston 58 slidably mounted with sealing both around the rod 31 and against the inner face of the chamber 33, with which the retraction piston 58 defines a retraction chamber 59 capable of being supplied with oil by the pipe 60 to control the retraction of the rod 31 in the

  cylinder34, by loading the damper, ie by compressing

  the low pressure chamber 41, by pressing the retraction piston

  58 against the stop 46 of the piston 36 of the rod 31.

  weaver-jack also comprises a jack rod 61 integral

  of the fastener 35, and slidably mounted with sealing to the

  2. The cylinder rod 61 defines, by its internal face, a down chamber 63, and, by its external face, a lifting chamber 64, capable of being respectively and alternately fed with oil through lines 65 and 66, connected to a hydraulic circuit of one aerodyne, by appropriate valves or distributors, which also feed the retraction chamber 59. The descent chamber 63 is separated from the high pressure gas chamber 47 by a fixed transverse partition 67 of the cylinder 34, so that the chambers 33, 47 and 63 are arranged one after the other.

1 1 2461852

  on the other in the cylinder 34. The shock absorber-suspension cylinder

  the landing gear of the aerodyne having such a structure assures, as already said, the damper function under the same conditions as the device of FIG. 1, but it also makes it possible to raise the landing gear in position " gear retracted ", when the retraction chambers 59 and lift 64 are supplied with oil and the descent chamber 63 is emptied, the device having a minimum length due to the re-entry

  of the cylinder rod 61 in the second chamber 62 and of the

  In the first chamber 33, the landing gear is lowered into the "landing gear" position when the retraction and tilting chambers 59 are emptied and the downcomer 63 is filled. having a

  maximum length, as shown in FIG.

  lower the aerodyne resting on its landing gear after the landing

  rissage, by feeding the lifting chamber 64 and by emptying the descent chamber 63, the position of the damping part under

  static load not changed.

  The damper-jack shown in FIG. 3 has an operation identical to that of FIG. 2, of which it differs, in terms of structure, only in the fact that the

  first chamber 73 of the cylinder 74 is delimited between the end

  internal to the chamber 73 of the shock absorber rod 71 and the

  damper piston 76 on the one hand, and the rigid transverse wall

  107 of the cylinder 74 on the other hand, the latter acting as a fixed bottom of the chamber 73 that separates it from the descent chamber 103 defined by the cylinder rod 101 sliding in the second chamber 102 of the cylinder 74. The bottom fixed 107 presents

  a radial channel 111 opening into a central hole 112

  ge at the base of the counter rod 77 secured to the fixed base 107, and the central bore 112 itself communicates with the chamber 73 by two radial passages 113 formed in the counter-rod 77, so that the chamber 73 is in communication with an annex volume 114 of oil contained in an annex chamber 79, constituted in the form of an annular chamber of the cylinder 74, surrounding

  the first chamber 73, and in which the movable floor is

  arranged in the form of an annular pison 78, slidably mounted with sealing, and separating the auxiliary volume of oil 79 from the high-pressure gas chamber 87. In this particular embodiment, which reduces the overall size in length

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  compared with the embodiment of FIG. 2, the brake damper

  The pressure swing 87 of the high-pressure chamber 87 is disposed in an enlarged portion of the central bore 112 into which the radial channel 11 opens. Of course, there is found, in the damping rod 71, a low-pressure gas chamber 81, an adjacent oil volume 82 and a brake valve 84

  in expansion of the chamber 81, compression orifices

  83, a piston 98 and a retraction chamber 99, and

  caliper of the cylinder rod 101, a lifting chamber 104.

  The damper-cylinder shown in FIG. 4 also functions identically to those of FIGS. 2 and 3, and, structurally, it differs from that represented in FIG. 3 only in that the auxiliary chamber 129 is

  formed in the form of a bottle of generally cylindrical shape

  drique, external to cylinder 124, and in which the bottom

  mobile 128 is a separating piston slidably mounted with

  in the bottle, and separating the high-pressure chamber 137 from the oil auxiliary volume 164, connected to the first chamber 123 through the connecting pipe 165, the radial channel 161 in the rigid bottom 157, from the central bore 162 and radial bores 163 formed in the base of the counter rod 127 scope

  by the rigid bottom 157. This achievement provides the same advantage.

  than that of the realization of Figure 3, but it appears

  would be simpler in terms of structure

of the cylinder 124.

  FIG. 5 shows a shock absorber

  cylinder constituting a development of that of FIG. 2. A separating piston 208 is slidably mounted with sealing inside the cylinder rod 201, in which the piston 208 is retained by an end internal radial abutment 216, to separate the descent chamber 203 of an adjacent volume of oil 210 contained in the second chamber 202 of the cylinder 174, and in communication with the first oil chamber 173, through a hollow rod-217 carried by the partition transverse fixed 207 of the cylinder 174, passing through the high pressure chamber 187 disposed in the enlarged portion 179 of the cylinder 174, and whose free end opens into a blind bore 218, pierced in the counter rod 177, and connected to the chamber 173 by the radial passages 213, formed in the base of the counter-rod 177, carried by the movable bottom 178, itself slidably mounted with

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  Sealing around the hollow rod 217. In addition, the lifting chamber 204 is not defined between the outer face of the cylinder rod 201 and the inner face of the second chamber 202, but between the latter and an annular piston 209 , slidably mounted on the inside of the chamber 202, on the one hand, and on the cylinder rod 201, on the other hand, as the annular piston

  209 can enter the chamber 202 by pressing on the stop stop

  219 of the rod 201, when the lifting chamber 204 is supplied with oil through the pipe 206. From the "out of position" position, in which the damper-cylinder has a

  maximum length (as shown in Figure 5), the chambers

  retraction members 199 and lift 204 being emptied and the

  the descent chamber 203 being filled, we go into over-

  lowered by feeding the lifting chamber 204 through the pipe 206 and emptying the descent chamber 203 through the pipe 205, and one goes into "retracted train" position, while also supplying the retraction chamber 199 with the driving 200,

  so that the retraction piston 198 pulls the damping rod

  171 inside the chamber 173 by loading the damping

  on, the reverse passages from one position to another being well

  heard possible by reversing the oil movements.

  The volume of oil 210, contained in the chamber 202, being constantly in communication with the oil contained in the chamber 173, the pressure prevailing in the chambers 173 and 202 will be the same, so that on landing, and if it is assumed that the shock rods 171 and cylinder 201 are of

  neighboring sections, there is almost simulta-

  the damper rod 171 is inserted into the chamber 173 and the cylinder rod 201 is pushed into the chamber 202, the oil expelled by the rod 201 and the piston 208 passing through the chamber 173, the oil of which is laminated through holes 183 and comes

  increase the volume 182 in the damper rod 171 by

  the low pressure chamber 181. This provides a cushion

  cylinder with extended damping stroke, the race of the

  cylinder rod 201 or lowering stroke of the damper-

* cylinder being used as over-damping stroke, for normal vertical landing speeds for which there is no movement of the movable bottom 178, or for the

  higher speeds for which there is both damping and

  movement and movement of the movable floor 178. This solution is

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  as it provides both a greater shock stroke in a device of the same total length as that of the apparatus of Figure 2, and a separation between the oil of the control circuit, connected to the descent chambers 203 , lift 204 and retraction 199, and the damper oil

  in the chambers 202, 173 and in the damper rod 171.

  FIG. 6 shows a shock absorber

  cylinder equivalent to that of Figure 5 for the operation and the benefits provided, but a modified structure in its central part: the counter-rod 227, which extends axially

  in the chamber 223 of the cylinder 224, and around which

  the piston 233 of the damper rod 221 is carried by the rigid bottom 257, separating the chamber 223 from the high pressure chamber 237, and is extended by a hollow rod 267, passing through the high pressure chamber 237, and opening into a volume of oil 260, housed in the second chamber 252 and in the

  part of annex room 229 opening directly onto the room

  252, and separated from the high pressure chamber 237 by the movable bottom 228 slidably mounted around the hollow rod 267. The volume of oil 260 communicates with the chamber 223 by the central channel of the rod 267, opening at the base of the the counter-rod 227 in the chamber 223 through the passage 263, so that under the same conditions as before the lowering stroke or stroke of the cylinder rod 251 is used as over-stroke damper. The oil of the circuit of maneuver and the oil of

  damper are also separated by the fact of the separate piston

  258 and annular lift pistons 259 and retraction

  248. In this embodiment, the braking of the expansion of the high pressure chamber 237 is achieved by rolling, through the diaphragms of the valve 238 carried by the movable bottom 228, facing passage holes 241 drilled in a radial ring external 270 of the movable bottom 228, the oil occupying the volume 271 and driven out of the annular chamber 272, determined by the

  flank 273 of the movable bottom 228 and its upper edge 274, flap

  kills in an enlarged portion of the annexed room 229.

  In the various embodiments of Figures 1, 2 and 5, in which the counter-rod 7, 37 or 177 is movable, because carried by the movable bottom 8, 38 or 178, it is found that the movable bottom is disposed in enlarged parts 9, 39 or 179 of the cylinder, whose sections are always greater than

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  sections of the damper rods 1, 31 or 171, so that after the initial depression of the damper rod 1, 31 or 171 on the contretige 7, 37 or 177 through the axial grooves of the latter , and if the moving bottom is moved, the stroke of the latter is less than the stroke of the damper rod along the central counter-rod, and the depression of the damper rod on the central counter-stem so increases, that

  this counter-rod is mobile or not.

  In FIG. 1, there is also completed, in phantom, an alternative embodiment which differs from that shown in solid lines only in that the counter-rod 7 'is integral with the bottom of the cylinder 4, the 8 'moving bottom which

  replaces the bottom 8 being also slidably mounted with

  around this counter-rod 7 ', and being pushed against a radial abutment 28, integral with the latter, in the rest position, under the action of the high pressure chamber 17. The device thus modified, although having a counter 7 'fixed, is of identical operation to that of the device

represented in solid lines.

  It can also be seen that one can obtain amor-

  weavers whose damper rods 31, 71 and 121 can be adjusted

  towed in the cylinder 34, 74 and 124 if the pis-

  retraction tone 58, 98 and 148 as well as the retraction chambers

  59, 99 and 149 of the devices of Figures 2, 3 and 4, removing the cylinder portion below the fixed walls 67, 107 and 157. Conversely, dampers-cylinders can be obtained allowing the lowering but not the retraction at the level the damper, keeping the cylinder part and removing

  the retraction pistons, in FIGS. 2 to 6.

  In their shock absorber or shock absorber versions

  jacks, with or without retraction of the damper rod, the devices according to the invention will advantageously equip the

  helicopter landing gear to limit these

  the effects of a crash and allow harmless landing

  rices with vertical speeds significantly higher than

those commonly accepted.

16 2461852

Claims (7)

R E V E N D I C A T I 0 N S   1 / Suspension damper, especially for aerodyne landing gear, comprising a damper rod, slidably mounted with sealing inside a first hydraulic fluid chamber of a cylinder, and enclosing a return chamber low-pressure elastic, adjacent to a volume of hydraulic fluid in communication with the first   cylinder chamber by at least one rolling orifice in   pressure, that has a piston carried by the end of the damper rod internal to the cylinder, the expansion of the low pressure return chamber being braked by a rolling valve   in relaxation, characterized in that the hydraulic fluid pressure   lique prevailing in the first chamber is applied on a moving bottom, itself in support against a stress threshold element,   allowing a stroke of the moving bottom, during a charge in com-   the shock absorber, from a force greater than a given threshold, and regardless of the driving speed of the   damper rod in the cylinder.   2 / Damper according to claim 1, characterized   in that the stress threshold element is constituted by a high-pressure elastic return chamber, the expansion of which   is braked by a thrust rolling valve.   3 / damper according to one of claims 1   and 2 characterized in that the cylinder comprises a second hydraulic fluid chamber in which a cylinder rod, 2.5 slidably mounted with sealing, defines respectively by its inner face and by its outer face a lowering chamber and a lifting chamber, susceptible to be supplied with hydraulic fluid to respectively ensure the exit and the retraction of the o cylinder rod in the second chamber of the cylinder.   4 / Damper according to claim 3, characterized   in that the first chamber, the stress threshold element and the second chamber are arranged one after the other in the cylinder, the first chamber being delimited between the end of the rod of damper received in the cylinder   and the movable bottom, and the second chamber being separated from the   force threshold by a transverse wall of the cylinder. 17 2461852   Shock absorber according to claim 4, characterized   characterized in that a separating piston, slidably mounted with sealing   inside the cylinder rod, separates the chamber from   an adjacent volume of hydraulic fluid retained in the second chamber and in communication with the first chamber through a hollow rod carried by the transverse partition   of the cylinder passing through the stress threshold element, and   round of which the movable bottom is slidably mounted.   6 / damper according to one of claims 1 to   3, characterized in that the first chamber is delimited between the end of the damper rod received in the cylinder and a fixed bottom of the cylinder provided with communication passages with   an annexed chamber also receiving the stress threshold element.   7 / damper according to claim 6, characterized in that the auxiliary chamber is an annular chamber of the cylinder, surrounding the first chamber, and wherein the movable bottom   is constituted in the form of an annular piston mounted health.   8 / damper according to claim 6, characterized   in that the auxiliary chamber is contained in a cylinder outside the cylinder, in which the movable bottom is slidably mounted. 9 / damper according to claim 6 as attached to claim 3, characterized in that a separating piston, slidably mounted with sealing in the rod of the cylinder, separates the descent chamber from a volume of hydraulic fluid housed in the second chamber and in the adjoining chamber, opening directly on one another, the volume being in communication with the first chamber through a hollow rod, carried by the fixed bottom, passing through the auxiliary chamber and the element at   stress threshold which is housed there, and around which smooth the moving bottom.   Shock absorber according to one of the claims   1 to 9 characterized in that a retraction piston, mounted   smoothing with sealing, on the one hand, inside the first chamber of the cylinder, on the other hand, around the end of the damper rod internal to the first chamber of the cylinder, defines with the cylinder a chamber for retraction, capable of being fed with hydraulic fluid, for applying the retraction piston against an abutment integral with the damper rod 1 8 2461852   and control the retraction of the latter in the first cylinder chamber.