FR2508581A1 - PNEUMATIC OR HYDRO PNEUMATIC CYLINDER PISTON ASSEMBLY, SUCH AS A DAMPER, COMPONENT OF AN ELASTIC FORCE LEG FOR A VEHICLE OR GAS SPRING - Google Patents

Abstract

DEVICE OF THE TYPE INCLUDING A CYLINDER 1 INSIDE WHICH IS PROVIDED A CAVITY 1A CONTAINING A PRESSURIZED FLUID. THE PRESSURIZED FLUID CONSISTS OF AT LEAST ONE COMPONENT WHICH, WITHIN AN OPERATING TEMPERATURE RANGE, HAS A GASEOUS PHASE AND A LIQUID PHASE. DEPENDING ON THE VARIATION OF THE PARTIAL VOLUME OF THE PISTON ROD CONTAINED INSIDE THE CAVITY, THE VOLUME OF THE LIQUID PHASE VARIES. THEREFORE THE PRESSURE ACTING ON THE PISTON ROD REMAINS CONSTANT. APPLICATION TO THE REALIZATION OF SHOCK ABSORBERS, ELASTIC LEGS FOR VEHICLES, OR GAS SPRINGS.

Description

"Pneumatic or hydro-pneumatic cylinder-piston assembly,

  as a shock absorber component of an elastic strut

  only for a vehicle or gas spring "

  The present invention relates to a cylindrical assembly

  dre-piston. Such an assembly comprises a cylinder having an axis

  and two end walls, inside which is

  A piston rod passes through at least one of the walls and is displaceable along the axis of the cylinder of

  inside to the outside of the cavity between two posi-

  extreme conditions A system for guiding and sealing the

  piston rod is arranged near one of the ends

  of the cylinder to guide sealingly the piston rod through the wall considered A fluid at a pressure greater than the atmospheric pressure is contained in the cavity This fluid comprises a gaseous phase The pressure

  exerted by this fluid acts on the piston rod,

  to force it towards one of its ex-

  treme. Cylinder and piston assemblies of this type are well known and are described in US Pat. No. 4,270,635. For example, they can be used as

  shock absorbers or as components of an elastic strut

  in motor vehicles, or as springs in

  lockable or non-lockable gases.

  In known devices of this type, gases such as nitrogen are used, which are only in the gas phase over the entire temperature range of

  The usual operating temperature range

  tion is of the order of 700 C to + 1001 C, so as to satisfy for gas springs included in engines

  vehicles that can be used both in

  polar conditions only in tropical conditions.

  The pressure of the gases usually used, even at

  constant temperature, is dependent on the partial volume

  of the piston rod contained in the cavity, this volume

  Part me varying when the piston rod is moved

between its extreme positions.

  A first object of the invention is to provide a

  positive cylinder and piston of the type described above,

  wherein the pressure inside the cavity is

  dependent on the partial and variable volume of the piston rod contained in the cavity, so that the force resulting directly or indirectly from the renneted gas and

  acting on the piston rod remains constant.

  Another object of the invention is to provide a set of

  Cylinder and piston bleed which has a high reliability.

  According to the invention, the fluid contained in the

  cylinder cavity comprises at least one component which possesses

  a gaseous phase and a liquid phase, inside

  a certain range of operating temperatures.

  The device according to the invention is of particular interest

  especially for all applications in which the

  normal operating temperature is approximately

  The scope covers in particular the mobility

  bind and for example the chairs and armchairs at high va-

  as well as offices that are frequently equipped

  of gas springs offsetting the weight of regulating

height.

  In such a field of application, the temperature is

  always in the order of 201 C, corresponding to the temperature

  normal use in living rooms, offices or similar

  lar. Under such conditions, the pressure acting on the piston rod remains substantially constant

  regardless of the position of the relative piston rod

  This is particularly true for configurations in which the cross section of the piston rod is relatively large compared to the cross section of the cavity, and where it is for example greater than 20% of the cross-section of the piston.

the cavity.

  In such devices, when traditional gases are used, considerable variation occurs.

  even under constant temperature conditions.

aunt.

  When using tuli gas in accordance with the

  tion, a more or less important part of the fluid is condensed or liquefied, but the pressure acting on the piston rod is always the same and corresponds to the

  vapor pressure at the temperature under consideration.

  As the fluid escapes outside the cavity, the pressure inside the cavity

  remains unchanged at the temperature considered as long-

  time that a sufficient amount of fluid is contained in the cavity to maintain a liquid phase inside

  Consequently, a corre-

  positive is maintained for a long time, even if there is a loss of small amounts of fluid It should also be noted that the pressure prevailing inside

  the cavity is kept below a maximum pressure of

  considered, which is tolerable in devices of this type An unusual increase in temperature

  can intervene even if the device is normally

  placed in a room at a temperature of 20 C It is ne-

  necessary that, during an unusual increase in

  temperatures, the mechanical construction of the gas spring, and more particularly the cylinder and the guiding and sealing system can withstand the higher pressure

resulting.

  Advantageously, the operating temperature range

  It can be reduced between 20 ° C and + 100 ° C and can be reduced to between 20 ° C and + 50 ° C or between 10 ° C and + 300 ° C. at least 1.5 bar within the operating temperature range, this vapor pressure possibly being at least 1.5 bar at 30 ° C, at least 2 bars OC, at least 2 bar at 20 C, at least 5 bar at 20 C, at least 10 bar at 20 C, at least 15 bar at 20 C and less than 150 bar at 600 C, less than 150 bar at 100 C, 1, less than 100 bar at 60 o C, less than 100 bar at 100 C,

  less than 50 bars at 50 C or less than 50 bars at 100 C.

  According to another aspect of the invention, the fluid phase of the liquid exists in all the positions of the piston rod between its two extreme positions, the pressure of said fluid acting on the piston rod being constant.

  at a predetermined temperature, regardless of the

sition of said piston rod.

  The gases it is most interesting to use in

  this device are those which have a condensing pressure

  (corresponding to the vapor pressure) which is sufficient

  health to create sufficient strength at the temperature of a

  piece, that is to say about 1 C These conditions are

  folded by certain hydrocarbons and halogenated hydrocarbons.

  These gases can be synthesis gases.

  It is essential that the gases used are inert-

  considering mechanical components and components

sealing of the device.

  As examples of a fluid that can be used,

  Sulfur exfluoride (SF 6) and difluorobromide

romonochloromethane (C Hci F 2).

  Anyway the invention will be well understood using

  of the following description with reference to the sclemen-

  that annexed representative by way of non-limiting example,

  an embodiment of this device, seen in longitudinal section.

  The device shown in the drawing comprises a cylinder (1) inside which a cavity (a) is formed. A piston rod (2) extends inside and outside.

  of the cavity, passing through a system of guidance and

  (6) Within the cavity 6 (1a), the piston rod is equipped with a piston (3) dividing the piston

  two working chambers (17) and (1 i 8) A valve (4) cooperates with

  with sealing elements (15) and (21) so as to separate the working chambers (17) and (18) from each other, and separating the interior of the piston rod from the working chamber (18) The piston (I) is combined with

  an operating rod (5) cooperating with a lever of ac-

  (6) passing through an opening (7) in

the piston rod (2).

  A passage (16) passes through the piston (3) in the position

  shown, the working chambers (17) and (18) are separated from each other by the valve (4) of the valve, which is held in the position shown under the effect of the internal pressure of the valve. working chamber (18) When the actuating rod (5) is moved downwards, the valve (4) is also displaced so that the passage (16) communicates the working chambers (17 and 18) When the passage (16) is closed the rod of

  piston (2) and the piston (3) are in a steady state

  relative to the cylinder (1) When the passage (16) is open, the piston rod (2) is moved upwards, as shown in the drawing, due to the internal pressure in the working chambers (17) and (18), acting on the piston rod (2) The force acting on the piston rod (2) is equal to the product of the pressure

  inside the cavity (la) through the transverse section

  dirty piston rod (2) defined by its diameter ex-

  TER AL. The cavity (la) is filled with a fluid under pressure

  having a gaseous phase (22) and a liquid phase (23).

  The volume of the liquid phase (23) is defined by the position

  of the piston rod (2) inside the cylinder (1).

  When the piston rod (2) is moved outward, a certain amount of additional steam is evaporated from the liquid phase (23) When the piston rod (2) is moved towards the inside of the cylinder some

amount of fluid is condensed.

  In the embodiment shown in the drawing, the

  lower end of the cylinder rests on a base (24) Y, itself equipped with legs (25), while the end

  free of the piston rod is equipped at its end su-

  upper plate (26) whose height is to adjust.

Example 1

  The cavity (la) is filled with sulfur hexafluoride (F 56). The operating temperature is 20 ° C.

  vapor pressure of the gas phase is 21.2 bar.

  The diameter of the piston rod is 2 cm The section of the piston rod is 3.14 cm The force acting on the piston rod is 652, 7 N This means that the

  piston rod is constrained outward by

  652.7 N, and can be pushed inward by downward application of a force of 652.7 N, when

  the passage (16) is open This force remains constant

  during the entire stroke of the piston rod (2) because there is still a liquid phase (23) inside the cavity and the pressure always corresponds to the

  SF 6 vapor pressure at the temperature of 20 C.

Example 2

  The device has the same shape and the same di-

  mensions than that previously described The cavity is replaced by

  difluoromonochloromethane plaice (CHC 1 F 2) The operating temperature is 20 C The vapor pressure at this temperature is about 9.47 bar The force acting on the piston rod is 991.35 N.

Example 3

  The fluid contained in the cylinder is butene- (1) (C 4 H 8) The operating temperature is about 400 C The vapor pressure acting on the piston rod

is of the order of 5 bars.

  It goes without saying that the invention is not limited to

  only embodiments of this device, described below.

  as examples, it embraces, on the contrary,

  all the variants of implementation and implementation.

Claims (13)

CLAIMS -   1 piston assembly of the type comprising a cylinder (1) limited by two end walls inside which is formed a cavity (10), a piston rod (2) passing through at least one of the end walls of the cylinder and movable along this axis inside and outside said cavity between two extreme positions, a set (20) sealing and guiding the piston rod adjacent to the end wall traversed ,   to guide and seal the piston rod   at the crossing of this wall, a fluid at a pressure greater than the atmospheric pressure which, contained in the cylinder cavity, comprises a gaseous phase, and whose pressure acts on the piston rod in a direction of displacement of it to one of its extreme positions, characterized in that the fluid contained in the cylinder has a component having a gas phase (22) and a liquid phase (23) to   within a certain range of operating temperatures   tioning. 2 Device according to claim 1, characterized   in that the operating temperature range becomes   between -50 C and + 1000 C. 3 Device according to claim 1, characterized   in that the operating temperature range becomes   between 200 C and +500 C. 4 Device according to claim 1, characterized   in that the operating temperature range becomes   between 100 C and + 300 C. Device according to claim 1, characterized in that the fluid has a vapor pressure of at least   1.5 bar within the operating temperature range   tioning. 6 Device according to claim 5, characterized in that the fluid has a vapor pressure of at least 1.5 bar at a temperature of 30 C. $ 7 Device according to claim 5, characterized in that the fluid has a voltage steam of at least 2 bars in O C.   8 Device according to claim 5, characterized in that the fluid has a vapor pressure of at least 2 bars at 20 C.   9 Device according to claim 5, characterized in that the fluid has a vapor pressure of at least bar A 20 C. Device according to claim 5, characterized in that the fluid has a vapor pressure of minus 10 bars at 20 C.   11 Device according to claim 5, characterized in that the fluid has a vapor pressure of at least 15 bars at 20 C.   12 Device according to claim 5, characterized in that the fluid has a vapor pressure of less than 150 bars A 600 C. 13 Device according to claim 5, characterized in that the fluid has a vapor pressure of less than from 150 bars to 100 C.   14 Device according to claim 5, characterized in that the fluid has a vapor pressure of less than 100 bar at 600 C. Device according to claim 5, characterized in that the fluid has a vapor pressure of less than from 100 bars to 100 C.   Device according to Claim 5, characterized in that the fluid has a vapor pressure of less than 50 bar at 600 C. 17 Device according to Claim 5, characterized in that the fluid has a vapor pressure of less than from 50 bars to 100 C.   Device according to claim 1, characterized   in that the fluid is tun synthesis gas.   Device according to claim 1, characterized   in that the fluid is a hydrocarbon. - in that 21 - in that F 2).   Device according to the fluid is a device according to the fluid is of claim 1, characterized halogenated hydrocarbon.   Claim 1, characterized by difluoromochloromethane (CIIC 1 22 Device according to claim 1, characterized   in that the fluid is sulfur hexafluoride (SF 6).   Device according to claim 1, characterized in that the fluid phase of the liquid exists in all   positions of the piston rod between its two ex-   tremes, the pressure of the said fluid acting on the stem of   piston being constant at a predetermined temperature 6 e,   depending on the position of said piston rod.