FR2563882A1 - Telescopic hydraulic damper with pressure release stop - Google Patents

Abstract

The telescopic hydraulic damper with pressure release stop comprises a body and a cylinder mounted coaxially in the latter and containing a main piston and an auxiliary piston situated above. The auxiliary piston 13 with an axial orifice 14 is pushed back axially by a spring 15 towards a stop member 12 and is in contact via the outer surface of its upper part with the cylinder 2 forming at least one calibrated passage. Application to dampers having a high reaction force at the edge.

Description

TELESCOPIC HYDRAULIC SHOCK ABSORBER WITH RELAXATION STOP

  The present invention relates to the field of vehicles and in particular relates to telescopic hydraulic shock absorbers provided with expansion stops.

  The present invention more particularly finds its applica-

  tion in telescopic hydraulic shock absorbers with expansion stop

  used in suspensions of means of transport such as vehicles

  cules. At the present time, the suspension expansion stops are used more and more widely to make vehicle suspensions using telescopic hydraulic shock absorbers which makes it possible to reduce the mass and the cost of said vehicles and to decrease

  the space necessary to accommodate the suspension of the wheels of these vehicles.

  The use of hydraulic expansion stops improves the perfor-

  mances and increases the service life of hydraulic shock absorbers

  copics and the means of transport they equip and thus constitute

  a new solution in the development of hydraulic shock absorbers

  telescopic to raise the quality.

  Telescopic hydraulic shock absorbers are known

  an expansion stop comprising a body, a cylinder mounted coaxially-

  inside the body, a rod to which are attached a main piston and an auxiliary piston and which is mounted coaxially in the cylinder, a bushing serving to guide the rod and closing one end

  cylinder and a compression valve body closing the other end

mity of the cylinder.

  The auxiliary piston defining a volume of the liquid of the

  weaver, moves in the direction of reduction of this volume, which causes the liquid to flow through rolling channels, the

  passage section gradually decreases. This results in an increase

  progressive tion of the resistance to displacement of the auxiliary piston and of the rod coupled to the latter. A closed volume of liquid then forms between the auxiliary piston and the sleeve provided with a sealing ring which is mounted coaxially with the auxiliary piston and which engages in the latter (cf. British patent 949,426). This sealing ring also acts as a check valve which lets the liquid flow

  in the volume closed during the return stroke.

  The drawbacks of this telescopic hydraulic shock absorber with expansion buffer lie in the complexity and the volume of the body necessary to produce the guide sleeve of the rod, the need to produce this in two pieces, compulsory mechanical machining of the groove for seal ring, the high precision and the complicated shape required for the split seal ring, the insufficient reliability and the service life of the seal ring compared to the auxiliary piston which is caused by dry friction, the necessity

  to manufacture the auxiliary piston from high-strength materials

  tance and expensive, necessary by the high pressure of the engine liquid which

  is due to the small active surface of the internal volume of the auxiliary piston

  liary. As the closest document, according to the technical arrangement and the result obtained by the telescopic hydraulic shock absorber with buffer:

  trigger according to the invention, we can consider the hydraulic shock absorber

  two-stage telescopic liquefied with an expansion stop as described in US Patent No. 3,447,644. This shock absorber comprises a body, a cylinder mounted coaxially inside this body, a rod to which are fixed a main piston and an auxiliary piston, and which is mounted coaxially in the mentioned cylinder, a check valve mounted on the auxiliary piston, a sleeve constituting the rod guide and closing one end of the cylinder, a compression valve body closing the other end of the cylinder and a

  auxiliary cylinder placed at the end of the main cylinder. The auxiliary piston

  liaire is mounted so as to be able to engage in this auxiliary cylinder

  bonded and there is for the passage of liquid between the auxiliary cylinder

  liaire and the auxiliary piston an interval which decreases towards the end of the stroke of the piston which increases.:the resistance opposed to the displacement of the auxiliary piston penetrating into the auxiliary cylinder. In addition, the design of the shock absorber provides a check valve ensuring the flow of liquid only in the auxiliary cylinder when

  the auxiliary piston leaves said cylinder during the return stroke.

  In the known telescopic hydraulic shock absorber, achieving the expansion stop by mounting the auxiliary displacement in the main cylinder and the auxiliary piston on the rod, requires a high precision of machining of the auxiliary piston and the auxiliary cylinder, increases the number of parts, makes construction more complicated, requires the use of high resistance materials for the manufacture of the auxiliary piston which is explained by the high working pressure of the liquid which is due to the small active surface of the internal volume of the cylinder auxiliary, and ultimately decreases the reliability and duration of

  life of the telescopic hydraulic shock absorber.

  It has therefore been proposed to produce a telescopic hydraulic shock absorber with expansion stop which would increase the reliability and the service life of the shock absorber and which would make it

less complicated. -

  This problem is solved by the fact that the hydraulic telescopic damper with expansion buffer comprising a body, a mounted cylinder

  coaxially in the body, the rod of a main piston mounted coaxially

  Lement in the cylinder, a sleeve constituting the guide of the piston rod and closing one end of the cylinder, a body of compression valve closing the other end of the cylinder and a piston:

  the area mounted in the cylinder above the main piston is characteristic

  according to the invention, in that the auxiliary piston at the axial orifice, pushed axially by a spring in the direction of a stop member limiting its descent in the axial direction, is in contact with the external surface of its part upper with the cylinder by forming at least one caliber passage, in that the cylinder has a flare

  opposite an ad less part of the external surface of the auxiliary piston

  liar and in that the rod carries, between the main and auxiliary pistons

  liar, a circular element capable of closing the axial orifice of the piston

  auxiliary when the rod comes out of the cylinder.

  The design described above of the telescopic hydraulic shock absorber with rebound stop makes it possible, by taking advantage of the internal surface of the main cylinder, to simplify the shape of the auxiliary piston, to reduce the number of parts (because the auxiliary cylinder is no longer necessary), to decrease the operating pressure of the liquid and to increase the reliability and the service life of the shock absorber. Because the auxiliary piston is self-centered in the

  cylinder, it is no longer necessary to ensure a strict position-

  coaxial in the cylinder which can only be obtained by high manufacturing and assembly precision of the parts. In addition, the arrangement of the telescopic hydraulic shock absorber is simplified by the fact that the auxiliary piston provided with the spring also acts as a check valve; for this reason, we no longer need to mount

  additional parts to form the check valve.

  Thanks to the simplification of the construction and the technological improvement of the parts, it is then possible to reduce the cost of

  the hydraulic telescopic shock absorber with expansion stop.

  It is rational to use at least one projection (a ledge) on

  the inner wall of the cylinder to constitute the limit stop member

  both the lowering stroke of the auxiliary piston of the hydraulic shock absorber

  telescopic link with trigger. -

  This embodiment solves the problem of limiting

  tation of the stroke of the auxiliary piston without the need to introduce additional parts while achieving the minimum

of technological operations.

  It is also advantageous that the hydraulic shock absorber remotely

  copy trigger trigger has at least one radial hole on the:

  lateral surface of the auxiliary piston or a groove whose sec-

  transverse tion increases towards the upper part of the

your auxiliary ..

  This allows to obtain a better ratio between the resistance oppo-

  sée to the rod which leaves the cylinder and the race of this rod.

  The invention will be better understood and other aims, characteristics

  ticks and advantages of it will appear on reading the description

  tion of different embodiments made without limitation and with reference to the accompanying drawing in which: - Figure 1 shows, in longitudinal section, the telescopic hydraulic damper with expansion stop;

  - Figure 2 shows, in section on a larger scale with arra-

  chements, an embodiment of the lami-

  swimming ;: - Figure 3 shows in the same view as in Figure 2, another embodiment of the rolling channels;

  - Figure 4 also illustrates according to the same view an embodiment of

  sation of the rolling channel in the form of an annular clearance.

  The telescopic hydraulic shock absorber with trigger stop, con-

  form of the invention, comprises a body 1 in which is mounted coaxial-

  a cylinder 2. In the latter, is mounted coaxially the rod 3 of a main piston 4 which carries, on the one hand, an expansion valve 5 serving to regulate the flow of liquid between the chamber located

  above the main piston 4 and the chamber located below said piston

  tone during the rise of the rod 3 and, on the other hand, a by-pass valve

  pass 6 intended to allow the liquid to flow from the chamber located below the main piston 4 to the chamber situated above this

  last, during the descent of the rod 3. At its upper part, the cylin-

  dre 2 is closed by a sleeve 7 serving as a guide for the rod 3 and

  is closed at its lower part by the body 8 of a compression valve.

  The body 8 carries a compression valve 9 which regulates the flow of the liquid from the cylinder 2 during the descent of the rod 3, and an intake valve 10 ensuring the free flow of the liquid from the

  body 1 to the chamber located below the main piston 4 of the cy-

  lindre 2, during the rise of the rod 3. The cylinder 2 has a

  local flaring 11 placed at a distance from the upper end face.

  Projections 12 (or else a single circular rim) are made at

  the lower part of the flare 11 of the cylinder 2. In the cylin-

  dre 2, above the main piston 4, is mounted an auxiliary piston

  liaire 13 mobile, in the axial direction and which can move until it comes into abutment against the projection 12. The auxiliary piston 13 has a calibrated outside diameter. An axial hole 14 is made in the

bottom of auxiliary piston 13.

  Since the auxiliary piston 13 is centered radially by the surface of the cylinder 2 and does not come into contact in the radial direction with the rod 3, it is not necessary to ensure rigorous coaxiality

  between the outer and inner cylindrical surfaces of the auxiliary piston

link 13.

  The auxiliary piston 13 is pushed down by a spring

  recall 15 exerting only a limited effort and which is centered on the

  inner meter of the auxiliary piston 13. The return spring 15 is abutted by its upper end against the sleeve 7 serving to guide

  the rod 3 and by its lower end against the bottom of the auxiliary piston

  liaire 13. On the rod 3, between the main piston 4 and the auxiliary piston

  liaire 13, is rigidly fixed a circular element 16 which can be mounted in the immediate vicinity of the main piston 4 on the surface of the

  rod 3, above the main piston 4.

  The circular element 16 is intended to close the axial orifice 14 in the bottom of the auxiliary piston 13 at the moment when the hydraulic limit stop stop of the hydraulic shock absorber begins to operate.

  telescopic hydraulics. By hydraulic rebound stop of the shock absorber

  telescopic hydraulic valve means the elements of the shock absorber which ensure, at the end of the rod 3 outlet stroke out of the cylinder 2, the increase in the resistance to displacement of the rod 3

  by rolling the damper liquid.

  The surfaces in contact with the circular element 16 and the bottom of the auxiliary piston 13 must have great precision in execution

  to ensure sealing in the area of their contact.

  The contact zone between the circular element 16 and the bottom of the auxiliary piston 13 can be sealed by means of a sealing member mounted on the rod 3. In this case, there is no longer any need for ensure good flatness and high precision of execution of the circular element 16 and of the bottom of the auxiliary piston 13 in their

contact area.

  When there is a need to provide more support

  of the hydraulic expansion stop and avoid knocking at the

  moment when the circular element 16 comes into contact with the bottom of the

  your auxiliary tone 13 you can fix an elastic circular element, for example, rubber or plastic on the upper face of the circular element 16. In addition to its direct shock absorber function, this elastic circular element simultaneously ensures sealing at the point where the circular element * 16 comes into contact with the bottom of the

auxiliary piston 13.

  On the lateral surface of the auxiliary piston 13, facing the flare 11 of the cylinder 2, there are made radial holes 17 or grooves 18 of increasing cross section in the direction of the upper part of the auxiliary piston 13, as illustrated in Figure 2. Grooves 19 of variable cross section lengthwise can be made on the inner surface of the

  cylinder 2 above the flare 11, as shown in Figure 3.

  The flaring 11 of the inner surface of the cylinder 2 is made in order to ensure the progressive obturation of the radial orifices 17 (or of the grooves 18 and 19 of variable cross section) by the surface of the cylinder 2 or the surface of the auxiliary piston. 13 during its upward stroke in order to increase the resistance to the flow of liquid from the chamber located above the auxiliary piston 13 towards the

  chamber delimited between the auxiliary piston 13 and the main piston

  pal 4. The dimensions, the number and the height arrangement of the radial holes 17 (or the profile and the number of grooves 18 and 19) on the lateral surface of the auxiliary piston 13 or the surface of the cylinder 2 are chosen so as to ensure the correct ratio between the resistance to displacement of the rod 3 when it leaves the cylinder 2 and the

rod stroke 3.

  The contact between the surface of cylinder 2 above the flare-

  ment 11 and the lateral surface of the auxiliary piston 13 can be made

  sealed by a sealing element mounted on the auxiliary piston 13.

  In some cases, when the realization of the orifices 17 or

  grooves on the auxiliary piston 13 and the cylinder 2 is not ration-

  nelle or else is difficult to achieve, one can use, to regulate the flow of the liquid out of the chamber located above the auxiliary piston 13, the clearance or the annular passage 20 (FIG. 4) between the surface of the cylinder 2 above the flare 11 and the lateral surface of the auxiliary piston 13. The required increase in resistance to: the flow of liquid out of the chamber located above the auxiliary piston 13 is obtained thanks to the increase in the length of the annular passage 20 (FIG. 4) between the cylinder 2 and the lateral surface of the

  auxiliary piston 13 during the rise of the latter.

  The telescopic hydraulic shock absorber with trigger stops working

  tion in the manner which will now be described.

  During the operation of the telescopic hydraulic shock absorber

  when the circular element 16 (FIG. 1) does not come into contact

  tact with the auxiliary piston 13, the hydraulic expansion stop is at rest and has no effect on the operation of the shock absorber

telescopic hydraulics.

  At the end of the expansion stroke, when the circular element 16 comes into contact with the auxiliary piston 13, the isolation of the

  volume of liquid in the chamber located above the auxiliary piston.

  During the subsequent rise of the rod 3 accompanied in its movement

  by the auxiliary piston 13, the liquid flows with a lami-

  swimming from the chamber located above the auxiliary piston 13 towards the chamber located below the latter which creates resistance to the displacement of the rod 3 exiting the cylinder 2. As the auxiliary piston rises 13 a greater number of orifices 17 is closed by the surface of the cylinder 2 which increases the resistance to the flow of the liquid out of the chamber situated above the auxiliary piston. Consequently, the resistant force applied to the rod 3

  increases as a function of the piston 13 stroke.

  progressive stroke of the rod 3 which moves upwards and stops

  progressive of the latter without the hydraulic shock absorber telesco-

  spike and its attachments to the means of transport are not subject to

  significant shock constraints.

  - In the case where the laminating channels of the liquid flowing from the chamber located above the auxiliary piston 13 are produced by the grooves 18 (FIG. 2) of variable cross section lengthwise on the lateral surface of the auxiliary piston 13 or by

  grooves 19 (Figure 3) on the surface of cylinder 2 above the eva-

  ment 11, the increase in the resistance to displacement of the rod 3 exiting from the cylinder 2 is ensured by the fact that the sections for the passage of the profiles of the grooves 18 or 19 in the zone of contact between the surface

  side of auxiliary piston 13 and cylinder 2 gradually decrease-

  ment during the rise of the auxiliary piston 13.

  If the lamination of the liquid flowing from the chamber located

  above the auxiliary piston 13 is done only through the clearance

  annular 20 (Figure 4) formed between the cylinder 2, above the flare-

  11, and the auxiliary piston 13 (case where the orifices 17 or the

  19 of the cylinder 2 or the grooves 18 of the auxiliary piston 13 are eliminated), the increase in the resistance to displacement of the rod 3 leaving the cylinder 2 is obtained by the fact that the length of the annular passage 20 between the cylinder 2 and the auxiliary piston 13

  increases continuously with the rise of the auxiliary piston 13.

  Due to the fact that the auxiliary piston 13 (FIG. 1) is self-centered in the cylinder 2, its seizure or its jamming is avoided during its

mounted in cylinder 2.

  The limitation of the rise stroke (go or rebound) of the auxiliary piston 13 occurs when it comes into abutment by its upper face against the lower end of the sleeve 7 serving as a guide for the rod 3. In this case, the spring 15 is not compressed with contiguous turns and, therefore, is not loaded by the axial force

extra shock.

  During the downward stroke (return or shock) of the rod 3,

  the circular element 16 moves away from the auxiliary piston 13 which is

  The reason for this is that the pressure of the liquid in the chamber located above the auxiliary piston 13 drops almost instantaneously during the descent of the latter while the pressure of the liquid is always maintained in the chamber located below the auxiliary piston 13. It As a result, throughout the duration of the return stroke, the auxiliary piston 13 remains raised above the circular element 16. Thanks to the weak reaction of the spring 15, the liquid from the chamber located above is easily passed through. below the auxiliary piston 13 towards the chamber located above the auxiliary piston 13. The value of the reaction force of the spring 15, the area of the passage section of the axial orifice 14 and the surface of the auxiliary piston 13 subjected at the pressure prevailing in the chamber located below the auxiliary piston 13

  when the orifice 14 is closed by the circular element 16, are chosen

  sies so as to prevent it from occurring in the chamber located above the auxiliary piston 13, an excessive drop in the pressure of the liquid which influences the operation of the telescopic hydraulic damper. The return stroke of the auxiliary piston 13 is limited by the: projections 12 provided on the cylinder 2. The limitation of the return stroke of the auxiliary piston 13 can be ensured by other known methods, for example using the spring 15 by fixing its upper end to the sleeve 7 and its lower end to the piston

auxiliary 13.

  Because the auxiliary piston 13 fitted with the return spring

  pel 15 with low reaction force ensures the function of a valve

  being able to pass the liquid into the chamber located above the auxiliary piston

  not necessary to use an inlet valve

additional.

  Thus the telescopic hydraulic shock absorber according to the invention is characterized by a better serviceability, a longer service life, a simple design and a manufacturing technology.

  easy. It also requires less manpower for its manufacture.

  tion and its cost is reduced accordingly.

  Of course, the present invention is not limited to the embodiments described and shown and it is capable of numerous variants accessible to those skilled in the art without that any

  departs from the spirit of the invention.

Claims (3)

  1.- Telescopic hydraulic shock absorber with expansion stop comprising a body, a cylinder mounted coaxially in the body, the rod of a main piston mounted coaxially in the cylinder, a sleeve serving as a guide for the piston rod and sealing one end   of the cylinder, a compression valve body closing the other end   of the cylinder and an auxiliary piston, placed in the cylinder   above the main piston, characterized in that the auxiliary piston (13) with axial orifice (14), pushed axially by a spring (15) in   direction of a stop member (12) is in contact with the outer surface   upper part with the cylinder (2) forming at least one calibrated passage, in that the cylinder (2) has a flare (11)   facing at least part of the external surface of the auxiliary piston   liaire (13) and in that the rod (3) carries, between the main piston (4) and the auxiliary piston (13), a circular element (16) capable of closing the axial orifice (14) of the auxiliary piston ( 13) when the rod (3) comes out of the cylinder (2).   2.- Hydraulic telescopic shock absorber with expansion stop according to   claim 1, characterized in that the stop member is constituted   killed at least one projection (12) provided on the inner surface of the cylinder   dre (2) and able to limit the lowering stroke of the auxiliary piston (13). 3.- Hydraulic-telescopic shock absorber with expansion stop according to   one of claims 1 and 2, characterized in that the lateral surface   rale of the auxiliary piston (13) has at least one radial orifice (17) or a groove (18) whose cross section increases in direction   of the upper part of the auxiliary piston (13).