FR2552514A1 - DAMPER OF THE FLUIDIC TYPE - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS SHOCK ABSORBERS. THE SHOCK ABSORBER IS CHARACTERIZED BY THE FACT THAT IT INCLUDES A FIRST PISTON 4 SLIDING IN A CYLINDRICAL HOUSING 2, A SECOND PISTON 9 SLIDING BETWEEN THE FIRST PISTON 4 AND THE BOTTOM OF THE HOUSING AND FLUIDIC COMMUNICATION MEANS 12, 15, 18, TO ALLOW A FLOW OF THE ROLLED FLUID CONTAINED IN THE CYLINDRICAL HOUSING. ADVANTAGEOUS APPLICATION FOR SHOCK ABSORBERS WITH LIMIT STOPS.

Description

"FLUID TYPE SHOCK ABSORBER"

  The present invention relates to fluid dampers, and more particularly to those which have an end stop.

  A fluidic type damper is generally of a very complex configuration, however, schematically such a dampener comprises at least one cylinder constituting a housing adapted to contain a rolling fluid, a piston sliding in this housing by laminating this fluid so as to to cause the damping of a movement. For some shock absorbers which can be subjected to very violent shocks it is necessary to provide at the end of the stroke of the piston a means to obtain an even greater and faster cushioning, these means are known by the generic name of

limit stops.

  Among the known means there is one which consists for example of a plurality of rolling ducts having increasingly smaller sections, these ducts being closed as the piston approaches the bottom of the housing. this fact, a rapidly increasing damping is obtained to prevent the piston comes in particular abut against the bottom of the housing. The device described above undoubtedly has advantages and responds perfectly to the problem posed. However, it can sometimes have a disadvantage in that it requires a plurality of conduits allowing a flow of the supply fluid of the housing, which does not It is not always easy to realize It should be noted that these supply ducts make it possible to drive the rolling fluid to cooling means, outside the damper cylinder. Moreover, for dampers which must be subjected to forces. such as on off-road vehicles, such as trucks and other armored vehicles,

  it is preferable to minimize the number of openings, ducts, etc. crossing their walls in order to make them as rigid as possible, and to avoid creating on these points of weakness that could cause them to rupture.

  The present invention aims to achieve a damper by

  fluid rolling having an end stop which has only a minimum of rolling ducts, especially in the structure of the damper, to avoid the possibility of breaking thereof, and which, moreover, makes this damper that it is a simple embodiment, and can operate with a very short response time.

  More specifically, the subject of the present invention is a damper by fluid rolling, by means of a piston moving in a cylinder, characterized in that it comprises: a first piston sliding in a closed cylindrical housing 15 to at least one end, said first piston being slidable on a first path defining a first portion of said housing, and on a second path corresponding to a second portion of said housing, said first piston defining on said second path a space between a portion of its outer surface 20 and the inner part of said housing, a conduit allowing the flow of the rolling fluid opening into said space, a second piston adapted to slide in this second portion of said housing to form a closed fluid chamber between said second piston and the closed end of said housing, first rolling communication means between the two said sides of said second piston in this case said chamber

  and said space between the two said pistons.

  Other features and advantages of the present invention appear in the following description given with reference to the drawings.

  appended by way of illustration but in no way limiting, in which FIG. 1 is a diagrammatic section, a functional embodiment of a shock absorber according to the invention, and

  FIGS. 2A, B show sectional views of an embodiment of a shock absorber according to the invention in its industrial configuration in accordance with the damper as illustrated in FIG.

  Referring more particularly to Figure 1, this is a diagrammatic sectional view of an embodiment of a damper

according to the invention.

  This damper comprises a hollow cylinder 1, defining a loa 2 in which is slidable a first piston 4 integral with a rod 3 This piston 4 can slide inside the housing 10 2 against its wall 5 under the action by example of a force that can

  This rod 3 penetrates inside the housing 2 through an opening 6 which is, depending on the case, sealed or not, if the volume between the piston 4 and the end wall 7 of the cylinder comprising this opening 6 should contain or not a rolling fluid.

  The bottom 8 of the housing 2 is closed to define between a second piston 9 and the bottom 8 a chamber 10 containing a rolling fluid This piston 9 can slide from an original position as shown in Figure i defined by mechanical stops 11 20 in this housing 2, to approach the bottom 8 of the housing 2.

  It is also planned in cooperation with this second piston 9 of

  fluid communication means 12 for connecting, on the one hand the chamber 10 defined between the piston 9 and the bottom 8 of the housing, and on the other hand, the portion of the housing 25 between the piston 9 and the piston 4 inside the dwelling 2.

  The piston 4 is shaped so as to delimit between a portion of its outer surface 13 facing the second piston 9 in the housing 2 and the wall 5 of the housing 2 a space 14 which is always defined so that, whatever the position of the piston 4 in this housing 2, a conduit 15 opens into this space 14, in particular through the opening 16, without it being never closed by the

first piston 4.

  In the embodiment of the damper as shown in this figure 1, the piston 4 is shaped to have a central portion 17 projecting from a portion 16 cooperating by sliding on the wall 5 of the housing, this central portion 17 having a predetermined length, and a diameter which has a value less than that of the diameter of the portion 16 in order to delimit on the periphery of this central portion 17 at least a portion of said gap 14. In this mode of The conduit 15 for the flow of a fluid is provided with rolling means which are illustrated by a constriction. As mentioned above, this conduit makes it possible to evacuate or feed the housing 2 so as to subject the rolling fluid cooling as this is well known

for this type of shock absorber.

  However, it can be conceived that for certain applications this con15 duit allowing the flow is constituted by a calibrated orifice passing directly, for example, the wall 16 of the piston to put in communication the space 14 defined above and the part of the housing between the piston 4 and the bottom 7 of the cylinder by

which penetrates the rod 3.

  In FIG. 1 is represented in phantom the end position of the pistons 4 and 9 when the piston 4 has moved inside the housing, so that the wall 13 of the central part 17 has abutted against the wall 19 of the second piston 9 and pushed the latter against the bottom 8 of the housing 2, the volume of the chamber 10 has been reduced to a minimum to be almost reduced to a zero value In this extreme position we realize that the space 14 is nevertheless constantly existing and allows the conduit 15 to always be able to open into it, the bottom 20 of the annular groove defined by the central wall of the piston 4 and the wall 5 of the housing 2, always coming to a standstill substantially before the opening

  16 of the conduit 15 so that it is never closed.

  It is clearly stated that for certain applications of making end stops for such a damper, the duct 12 made

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  in the second piston 9 constitutes a rolling duct with a pressure drop which must be much greater than that which is achieved in the duct 15 But it is also conceivable that the duct 12 which is illustrated through the piston 9 could be 5 made so that it is constituted by a constriction passage defined between the side wall of the piston 9 and the wall 5 of the housing, this embodiment being more particularly illustrated on the

figure 2.

  As mentioned above, such a damper makes it possible to achieve a limit stop to eliminate the risk of breaking unexpected shocks exceeding a certain threshold allowed with the advantages mentioned above, and operates as follows: First consider that the damper is in the configuration as shown in solid lines and that from this position the damper is subjected to a significant impact, this shock being transmitted to the rod 3 The resulting force This shock first begins to be damped by the displacement of the piston 4 which pushes the rolling fluid contained in the housing 2 upstream of the piston, so that a rolling flow occurs in the conduit 15 through This first damping is obtained by the displacement of the piston 4 on a first path which is illustrated schematically at 21 and ends at the instant when the wall 13 of the Central portion 17 of the piston 4 abuts against the wall 19 of the second piston 9. From this moment, the piston 4 begins to push the second piston 9 to tend to reduce the volume of the chamber 10.

  contained in this chamber 10 is evacuated through the rolling means 12 which have a loss of charge much higher than that of the rolling means 18 contained in the pipe 15.

  This fluid passing through the rolling means 12 is discharged through

the space 14 by the duct 15.

  From this intermediate position defined by the plane shown at -6 at 22, the piston 4 moves on a second path 23 by pushing the piston 9 and causes an even greater damping of the force which is applied to the rod 3, and this to prevent the

  piston comes abut violently against the bottom 8 of the housing.

  This configuration is particularly advantageous because it allows

  for certain embodiments of shock absorbers, especially for off-road vehicles, having only one duct allowing the flow of the rolling fluid, in particular for supplying the housing 2, in this case the duct 15.

  The cylinder 1 can therefore be made with a minimum of weak points, since it comprises only one through conduit

its wall.

  The damper which has been very schematically described above makes it possible to illustrate the advantage and the object of the invention, that is to say to achieve damping or limit stop, with a single duct. allowing the fluid supply of the housing 2 being specified that this conduit could even be made in the piston 4 for

some applications.

  Of course, such a damper as described above could only operate once under these conditions. It is therefore necessary when a very large shock has been absorbed and that this has ceased, that all the elements components of this damper return to their original position and offer other possibilities

  damping in the event of successive shocks.

  FIGS. 2A, B illustrate a shock absorber in its industrial form that makes it possible to obtain a repetitiveness of the damping phenomenon. Since these two figures 2A, B represent the same device, but in two different positions, it is obvious that the same references will designate the same elements and that it will be irrelevant to refer to one or the other. other of these two figures

2 A, B.

  The damper comprises, as before, a cylinder 30 in

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  which is able to move a first piston 31 controlled by a rod 32 In the wall of this piston 31 is formed a pressure relief valve 33 and a check valve 34 constituted simply by a through hole 35 and a flexible sealing strip 5 36 to possibly come close the opening 37 of the duct 35

  opening in the part of the cylinder 38 defined between the end 39 of the piston 31 and the bottom 40 of the cylinder 30 This bottom 40 of the cylinder 30 is constituted by a tip 41 whose diameter of the inner surface 42 is greater than the diameter of the surface 43 of the central part of the cylinder 30.

  In this part of the bottom of the cylinder 30 is disposed a second sliding piston 44 of the same diameter as the inner wall 42, so that the two stops defining the extreme position of the piston 44 farthest from the bottom 40, are defined by the part the wall 45 of the cylinder constituting the narrowing due to the difference in diameter between the surfaces 42 and 43 A spring 46 is further disposed between the wall 47 of the piston 44 facing the bottom 40, and the same bottom 40; this spring tending to maintain constantly pressed the piston 44 against the stops 45 or back against these stops 45 in the center of the piston 44 is formed an opening 48 for communicating the chamber 49 defined in the bottom of the cylinder between the wall 40 and the piston 44 and the chamber of the cylinder 50 between the two pistons 31 and 44 In addition, around this orifice 48 is disposed a seal 51 25 whose diameter is smaller than the diameter of the cylindrical wall 43 of the cylinder 30, that is to say actually less than the diameter of the piston 31. According to Figure 1 it has been defined a space into which a supply conduit opens With reference to this definition the space 53 is defined in FIG. the embodiment according to FIGS. 2 between the lateral wall 52 of the piston 31, and the side wall 42 of the bottom of the cylinder 30. This space 53 appears clearly in the configuration of the damper according to FIG. which leads

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  the duct 54 whose function is identical to that of the duct 1 '

as defined in Figure 1.

  Of course, the cover 41 cooperates with the cylinder 30 so as to obtain a seal, the latter being given by a seal 58 as illustrated in the figures. The damper thus described functions in the same way in its primary functions as that described in FIG. 1, but, in addition,

has other advantages.

  For this purpose, it is considered first that the damper is in the configuration as illustrated in FIG. 2A. These conditions being specified, when the damper is subjected to a large shock, for example transmitted to the rod 32, the piston 31 sinks in the cylinder 30 towards the bottom 40 and pushes the rolling fluid contained in the chamber 50 to obtain a flow in the conduit 54 This fluid is subjected to a first rolling which provides a first damping The piston 31 thus undergoes a first displacement on a first path (as previously mentioned) to come in a median position abutting against the second piston 44. The extreme surface of the piston 31 then comes into contact with the piston 31. apply against the seal 51 and thus delimits as illustrated in Figure 2 B an auxiliary chamber 55 having a constant volume regardless of the positions of the two pistons Again, even when these are held in this position, the volume of oil contained in the auxiliary chamber 55 is equivalent to a closed volume and can not flow from this auxiliary chamber. From this intermediate position and if the force continues to be applied on the rod 32, the piston 31 drives in its same movement the piston 44 and therefore tends to reduce the volume 30 of the chamber 49 The fluid contained in this chamber 49 is thus evacuated and rolled into the throat 60 defined between the side wall of the piston 44 and the wall 42 of the bottom cover of the cylinder 30 producing a much greater damping than that given in the conduit 54. This fluid laminated between the two side walls allows it to flow from the chamber 49 to the space 53 and then to flow in the conduit 54 in the same way as explained in the device according to Figure 1 However, in order to limit r 5 the efforts made by means of this additional damping in order to avoid the rupture of the damper, the pressure prevailing inside the chamber 49 is limited by the overpressure valve 33 disposed in the piston 31, thanks to at the communication 48 which makes it possible to connect the chambers 49 and 55. When the force has been completely damped, and the spring 46 has been compressed, the

  two pistons can thus return to their equilibrium position, the piston 31 under a force due for example to the weight of the suspension of the vehicle associated with this damper, and the piston 41 under the action of the spring 46 which relaxes, until the lateral edges of this piston come into contact with the stops 45.

  However, as the two pistons have disengaged the auxiliary chamber 55 has been opened and can be fed again by the fluid arriving through the conduit 54 which re-energizes the chamber 50 with a relatively large flow rate. in the chamber 50 can also flow to the chamber 49 through the orifice 48 which has a large diameter This flow then allows to refill the chamber 49 to refill it with fluid and allow the piston 44 to come to repositioning very quickly against these stops 45 and be ready to ensure its end stop func25 tion in the event of a new shock In these conditions the two pistons have resumed very quickly their original position and can therefore replay their role of depreciation in case

  another, very violent, subsequent shock.

  Thus, a damper having the above-mentioned functions and advantages finds a particularly advantageous application on heavy vehicles or vehicles, such as off-road vehicles, or armored vehicles, and makes them a safe ride and a long service life

  whatever lands they move on.

Claims (4)

  1) Damper by fluid rolling by means of a piston moving in a cylinder characterized in that it comprises a first piston (4,31) sliding in a cylindrical housing (2, 30) closed at least one end (8, 40), said first piston 5 (4,31) being able to slide on a first path (21) defining a first portion of said housing, and on a second path (22) corresponding to a second portion of said housing, this said first piston defining on said second path a space (14, 53) between a portion of its outer surface the inner portion of said housing, a conduit (15, 54) allowing a flow of rolling fluid opening into said space (14 , 53), a second piston (9.44) slidable in this second portion of said housing to form a fluid chamber (10, 49) closed between said second piston and the closed end of said housing, and first means (12, 60) communication in rolling between the two sides of said second piston, in this case said chamber (10, 49) and the part of said space (14, 53) situated between the two so-called pistons.   2) damper according to claim 1, characterized in that it comprises stop means (11, 45) for defining a reference limit position of said second piston (9, 44) in said cylindrical housing (2, 30),   and means for applying an elastic force (46) between said second piston (44) and said closed end (40) of said housing.   3) Damper according to claim 1 or 2, characterized in that it comprises: communication means (48) having a loss of pressure much lower than said first means (12, 60) for communicating the two sides both sides of said second piston (44),   means (51) for forming a closed continuous seal line around said second communication means when said first   piston (31) is in contact with said second piston (44).   4) Damper according to claim 3, characterized in that said first piston comprises means of pressure relief valve (33).   ) Damper according to one of the preceding claims, characterized in that said closed cylindrical housing (30) has at least one end, comprises at least a first and a second portion (43, 42), said second portion (42) located on the side of the closed end, has a section greater than that of said first portion, said second piston sliding in said second portion, and said conduit (54) having its end opening into this second portion.