FR2524592A1 - PNEUMATIC SPRING IN BELL - Google Patents

Abstract

THE PNEUMATIC BELL SPRING FOLLOWING THE INVENTION IS CONSTITUTED BY TWO RIGID TUBULAR BODIES 2, 13 COAXIALS BETWEEN THEM, PARTIALLY ENGAGED WITH ONE THE OTHER AND CONNECTED TO ONE ANOTHER BY A SENSITIVELY CYLINDRICAL MEMBRANE 5, MADE OF '' A PRE-COMPRESSED ELASTOMERIC WAY THAT CONTAINS REINFORCING WIRES ARRANGED ACCORDING TO THE GENERATORS OF THE CYLINDRICAL SHAPE. APPLICATION ESPECIALLY IN THE AUTOMOTIVE INDUSTRY.

Description

The present invention relates to a pneumatic bell spring

  intended to contain air under pressure. The bell-shaped air springs substantially comprise a flexible envelope in which air

  under pressure is introduced to balance an ex-

  térieure. The pneumatic bell springs have a wide

  field of application They serve, for example, to

  the suspensions of motor vehicles, in cases where comfort is required during particularly large turnover and where the ratio of the weight of the vehicle to full

  load and its empty weight is very big.

  Their use extends to plant suspensions

  fixed areas which must be isolated from

  coming from outside, or to the suspensions used

  to protect from vibration the areas adjacent to a

China vibrating.

  These springs are also used to realize

  pneumatic cylinders, replacing the hydraulic cylinders

more expensive hydraulics.

  Known bellows air springs already known generally comprise a fabric membrane-rubber, thin-walled and flexible, which provides the container function for pressurized air, this air constituting

  the carrier element which provides the elastic reaction of

fate.

  The function of the membrane tissue is to support

  the voltages that have their origin in the air pressure inside the membrane and which balance the external load applied to the spring. This fabric is generally composed of two or more layers of

  wire or cable in an oblique direction with respect to

  port to the longitudinal axis of the membrane, each layer being in a cross-position relative to that of the adjacent layer; or by one or more layers of yarn

  arranged in the direction of the longitudinal axis of the

  fate. The layer of rubber that covers the fabric has

  function to make the membrane waterproof and resistant

  aunt to possible chemical or atmospheric agents.

  The membrane is substantially cylindrical in shape

or toroldale.

  In the first case, she can be surrounded

  of a metal band or a cylinder of tissue-rubber

  rubber or metal whose mission is to limit deformities

  transversal features of the spring during use.

  In the second case, the membrane generally presents

  a number of overlapping handles, between

  which are interposed reinforcing metal rings

  and limiting transverse deformations.

  The membrane is closed at the ends by bridges

  appropriate or by metal trays

  also wind for fixing the spring to the structure

  of the installation for which it is intended.

  Under the conditions of service, the wires constitute

  the tissue of the membrane are subject to stress

  quotes that are directly proportional to their

radii of curvature.

  This means that, for a given operating pressure, the greater the radius of curvature of a wire, the greater the

  big is the voltage to which the wire is subjected.

  In the membrane in which the tissue is composed

  crossed webs, the radii of curvature of the wires are always greater than the diameter of the membrane and

  are therefore relatively large.

  The stresses that the wires must bear, are in this case important and force to maintain the values of the operating pressure below the limit

maximum of 7-8 kg / cm 2.

  Another disadvantage of the membrane comprising a fabric composed of crossed and superposed layers comes from

  because, under the conditions of service, there is always

  days of relative displacements between a layer and the one adjacent to it, which are due to variations in

  the angle of intersection between the two layers.

  This gives rise to tangential tensions,

  more specifically, to shear forces in the re-

  garment threads, efforts that can produce small

  tears and small detachments in the rubber.

  This process is amplified and leads quickly to the deterioration

ration of the membrane by fatigue.

  From this point of view, it is therefore preferable to adopt

  ter a membrane whose fabric is composed of wires directed substantially in the direction of the longitudinal axis of the

  even better if they are arranged in a single

  che. However, in this case, the membrane has longitudinal segments in which the radius of curvature of the yarns of the fabric is very large and, therefore,

  the wires are subjected to heavy demands.

  The problem was solved by strengthening the mem-

  ne with a circumferential metal bandage or with a

  cylinder of rubber-cloth or metal, this bandage or cy-

  lindre being fitted on its outer lateral surface.

  In this way, the stresses which are exerted on the threads of the membrane in the large segments

  radius of curvatures are counterbalanced by the wall of the

reinforcement element.

  A spring of this type is substantially constituted by two coaxial cylinders of different diameters of which

  one is hollow The two cylinders can slide axially

  the hollow cylinder, of larger diameter, receives partially or entirely the other.

  Inside the hollow cylinder is housed a mem-

  brane of the type described (i.e., rubber-fabric, with a longitudinal-threaded fabric), one end of which

  is anchored to the hollow cylinder and the other to the other cylinder.

  The outer wall of the membrane is supported on a part of its longitudinal development against the inner side wall of the hollow cylinder and against the outer wall of the other while it is bent in a U in the area between the inner side wall.

  of the hollow cylinder and the outer side wall of the

  be cylinder. In this way, during use, the only segment of the membrane which is not surrounded by a reinforcing wall, is the U-shaped segment which, being of a small radius of curvature, withstands the stresses resulting from

  the pressure of the air contained in the membrane.

  Springs of this type which are already known pre-

  However, there are the following disadvantages: the segment of the membrane which is folded in U is exposed

  light, which, as we know, determines an accelerated

  the aging process of elastomers, in

  particularly when this elastomer is subjected to

  cyclic quotations of traction, as in the case in question

  tion; in the case of two cylindrical elements between which is interposed the longitudinal wire membrane, it is not possible to obtain a variation of the effective area

  during the spring run, that is during the pas-

  wise of the maximum axial distance to the axial distance

minimum between the two cylinders.

  Effective area Ae / the area delimited by the circumference constituting the locus of

  points where the tangent to the curvature of the deformed envelope

  ble is perpendicular to the direction of the load

on the spring.

  The effective area is related to the service pressure

  of the spring and the load applied by the following relation-

  te: P p = - Ae o p = working pressure P = applied load Ae = effective area

  Consequently, for a given jurisdiction, in

  to vary the value of the effective area along the

  race, it is possible to vary the thrust of

  fate and this results in a push-stroke relationship of the spring having a curved feature.

  Similarly, by varying the load, it is pos-

  sible to maintain the spring's stiffness constant, or to vary it according to a pre-established law, by means of a

  appropriate variation of the effective area values.

  It follows from the above that the impossibility, in the known jurisdictions, of varying the values of the

  effective areas according to the spring stroke,

feels a noticeable disadvantage.

  The object of the present invention is to provide a pneumatic bell spring intended to contain air under pressure, which does not have the disadvantages

  listed above and which, in particular, makes it possible

  with pressures up to 15 kg / cm 2, and

  at the same time has excellent characteristics of

  and reliability, while using however for the

  reinforcement wires which have a resistance

  lower than that of the currently used yarns, which have excellent durability characteristics

and reliability.

  Compared to the springs already known, the res-

  A fate according to the invention also has other advantages

  which will come out in the description.

  The subject of the invention is a pneumatic spring

  bell designed to contain air under pressure and

  characterized in that it comprises: at least two

  hollow gules of substantially tubular shape, coaxial and

  able to move axially with respect to the

  at least one of these elements being open to at least

  one end and at least one having walls to pro-

  variable wire; at least one flexible membrane interposed between the one and the other of the rigid elements, which comprises a plurality of substantially inextensible wires or cables 4 q

  substantially in the direction of the longitudinal axis

  spring and embedded in a layer of rubber, and means for assembling the membrane or membranes

to rigid elements.

  The figures of the attached drawings given only in

  As a non-limitative example, we will better understand how

  The invention can be embodied in these drawings.

  FIG. 1 is a longitudinal section of a resistor

  pneumatic bell bell according to the invention; FIG. 2 shows in perspective a membrane in section in the longitudinal direction and with a portion

  coating rubber removed to highlight the

  the elements that are part of it;

  FIG. 3 shows in longitudinal section a variation

  an embodiment of a pneumatic spring bell according to the principle of the invention;

  Figure 4 shows in longitudinal section a further

  an alternative embodiment of a pneumatic spring bell according to the principle of the invention; and

  FIG. 5 is a sectional view

  of another embodiment of the principle

of the invention.

  According to the most general principle of a spring

  pneumatic bell according to the invention, this spring com

  takes at least two rigid elements, generally

  hollow, coaxial with each other and which have the possibility of

  to move relative to each other along their axis, at least one of these elements being open and at least one end of at least one of these elements being

side wall with variable profile.

  These elements are positioned one after the other in the direction of the longitudinal axis of the spring

  and penetrate each other, at least partially.

  In fact, for any couple of elements con-

  two elements is open to a single ex-

  tremité or closed, while the other is always open to

  at least one end and has transverse dimensions

  sales superior to those of the first element, so

  to be able to contain it, at least in part.

  Between one element and the next, is interposed and assembled to this element by its ends a flexible membrane comprising a plurality of son (or cabled) sen-

  sibly inextensible, embedded in a layer of rubber

  rubber and arranged substantially in the direction of the axis

longitudinal of the spring.

  The membrane, which acts as a link between the two rigid elements, is folded in a U in the space between the inner part of the large element

  transverse dimensions and the outer wall of the other.

  In addition, and as will be explained later, this

  membrane is precompressed, in order to have a larger

  resistance to stresses and light.

  In FIGS. 1 and 2, the air spring in

  bell comprises a rigid element 2, hollow, sensitively shaped

  tubular element and, in particular, this element has a first segment 2 'of cylindrical shape, a second segment 2 "of curved shape and a third segment 2' '' of

cylindrical shape.

  Inside the rigid body 2, is housed partially

  a second rigid element 13, also coaxial with

  first, of substantially tubular form and which, in

  the first segment 13 'of cylindrical shape

  that a second segment 13 "of curved shape and a third

  me segment 13 "'which is again cylindrical.

  In the space between the two elements

  2 and 13, is housed a membrane 5 which comprises a series of son 6 flexible and substantially inextensible,

  disposed substantially in the direction of the longitudinal axis

  spring and embedded in a layer of rubber 8,

  generally based on neoprene.

  The membrane 5 has an approximate diameter

  equal to the maximum inside diameter of the rigid element

of 2.

  The upper end 4 of the membrane 5 is

  rolled around a ring 7 of hard rubber or metal and it is housed in a suitable housing 3 formed on the upper inner edge of the rigid body 2 A metal plate 9 fixed to the rigid element 2 by means of screws 10 closes the upper end of the rigid element and blocks

  the end 4 of the membrane 5 in the housing 3.

  The membrane 5 adheres by its outer surface to

  the inner wall of the rigid element 2 and the outer wall

  of the rigid element 13, with the exception of a segment

  in which it is U-folded in the space

taken between the two walls mentioned.

  The second end 4 'of the membrane 5 is

  rolled around a 7 'ring of hard rubber or metal.

  The ring 7 'has a diameter smaller than that

  of the membrane 5 and, consequently, the 4 'end of this

  the membrane is forced to take, by winding itself

  round of the ring 7 ', a diameter which corresponds to that of

  In this way, the threads 6 of the fabric of the mem-

  brane 5, which were initially parallel, are lightly

  converge in the longitudinal direction of the

  fate and in the direction that goes from the ring 7 to the ring 7 '.

  Correspondingly, the coating rubber of the wires 6 of the membrane 5 is compressed, in particular

  in the terminal segment near its 4 'end.

  As will be explained later, this fact

represents an advantage.

  The end 4 'of the membrane 5 wound around the ring 7' is housed in a suitable housing 1 l formed on the upper outer edge of the rigid body 13 and is blocked there by a metal flange 12 of shape

  circular fixed to the rigid body 13 by means of screws 12 '.

  This body is welded by its other end to a base

metal 14.

  In FIG. 3, a longitudinal section is shown.

  a variant embodiment of a pneumatic spring

  than bell that fits in the principle of the invention.

  As can be seen in FIG. 3, the rigid element 19 of the spring 18 differs from the rigid element

  13 of spring 1 by the fact that it is open to one

  ture, so that its inner cavity 20 is in communica-

  direct contact with the space delimited by the membrane 5 and the metal plate 9 In this case, the inner end of the membrane 5 is assembled to the element 19 by

  through the ring 27 and screws 28.

  In the cavity 20 of the element 19 is positioned another deformable membrane 21 of fabric-rubber or elastic material The membrane 21 (shown in position

  stretched on the figure) is of a substantially hemispheric

  that and its circumferential end is wrapped around

  ring 21 'made of hard rubber or metal and is

  created at the base 22 of the rigid element 19 by means of a metal plate 24 clamped on the base 22 by screws 23. Between the plate 24 and the base 22 is interposed

  a seal 25 of a known type.

  On the metal tray, an opening is planned

  re 26 for the passage of a liquid under pressure of this

  way, it is possible to introduce into the

  under pressure in the space delimited by the membrane

No. 21 and the plate 24.

  The introduced liquid determines the inflation of the membrane 21, which reduces the volume available for the compressed air contained in the spring and, consequently, makes it possible to vary the compression ratio between the volumes of the compressed air contained in the which are measured, respectively, in the state of maximum elongation

  and in the state of minimum elongation of the spring.

  The possibility of varying the relationship between

  pressure Vmax Vmin (o Vmax means the volume of the compressed air under the conditions of maximum elongation of the spring and

  Vmin the volume of compressed air measured in the conditions

  - Minimum elongation of the spring), allows to act on the degree of stiffness of the spring In this way, there is still another way to vary the behavior

  the appropriate way, depending on the type of use

  tion and variations in the load applied to it.

  In FIG. 4, a longitudinal section is shown in FIG.

  another embodiment of a pneumatic spring

  which falls within the field of the principle of the invention

tion.

  As can be seen in FIG. 4, the tire spring

  30 comprises three rigid elements 32 ', 31 and 32, all hollow and able to move relative to each other.

the other along their axis.

  Elements 31 and 32 are open to one end

  The element 32 has a cylindrical shape and receives partially

  element 31, which has a shape similar to that

  the element 2 of the spring 1 The element 31 receives at its

  element 32 ', in the same way as it has been described

spring position 1.

  The upper end of the rigid element 31 is

  partially closed by a circular ring 38

  the remainder of element 31, which delimits a circular opening whose function is to allow the assembly of

  the ring 33 This is fixed to the rigid body by gou-

  jons prisoners with nut 34 and it blocks the su

  membrane 35 (which is substantially identical to the membrane 5 of the spring 1), which is wound around a ring 35 'of hard rubber or metal, at the level of the

  inner upper edge of the rigid member 31.

  The upper end of the rigid element 31 is closed by a metal disk 36 fixed to the element 31,

by bolts 37.

  Between the disk 36 and the element 31 is interposed

  a seal 38 of known type.

  At the outer edge of the outer edge of the

  31, is fixed, also by means of the studs

  prisoners with nut 34 who secure ring 33, a

  metal plate 39 which blocks the inner end of a

membrane 40 of the type described.

  The other end of the membrane 40 is fixed in one of the ways shown at the upper inner edge

  rigid member 32 and is U-folded into the

  pace between the outer wall of the element 31 and

  the inner wall of the element 32.

  The rigid element 32 has a sensitive shape

  cylindrical and is closed at its upper end.

  re by a plate 41 which is fixed there by means of studs

  prisoners with nut 42 and which blocks the upper end

of the membrane 40.

  Finally, Figure 5 still shows a varian

  embodiment of the principle of the invention.

  As can be seen in FIG. 5, the air spring 50 comprises a rigid element 51 identical to the rigid element 13 of the spring 1 and a second element

  rigid 52, of a shape substantially identical to that of the

  the rigid element 2 of the spring 1, with this difference that the rigid element 52 is formed of two parts 52 'and 52 "that are separated from one another The two elements 51 and 52

  are coaxial and partially engaged in each other.

  Inside the rigid element 51 is housed a membrane 53 shorter than the membrane 5 of the spring 1 The lower end 53 'of the membrane 53 is anchored to the rigid element 51 (in the direction described for the membrane 5 of the spring 1) while the upper end is anchored to the inner wall of the rigid element 52 at the level o the element 52 can be divided into two

parts 52 'and 52 ".

  For this purpose, the portion 52 'comprises a ring 56 and the portion 52 "comprises a ring 56', which are tightened one on the other by bolts 57 and between which

  is enclosed the upper end 53 "of the membrane 53.

  A metal tray 54 closes the upper end

  the rigid element 52 and is attached thereto to the

means of screws 55.

  The pneumatic bell spring according to the invention

  tion achieves the intended goals.

  Indeed, this spring makes it possible to vary in the desired manner the effective areas of the spring, or by a suitable profiling of the walls of at least one of the bodies

  stiffness of the spring, either by means of a variation of the

  port of compression obtained by introducing a quantity

  appropriate liquidity in the space delimited by a

  membrane contained in one of the rigid bodies of the spring.

  The variation of the effective areas determines the variation of the

  degree of stiffness of the spring, that is to say of its

  behaviors in service conditions.

  As a result, it is possible, by acting on

  variations in effective areas and the relationship between

  pressure, to obtain an optimal behavior of the spring, within the limits of its mechanical resistance, whatever

  the load conditions and the type of

  tions. The use of one or more precompressed membrane (s) (the number of membranes depending on the

  number of rigid elements which form part of the

  finishes greater resistance of rubber to

  especially in the area in which the membra-

  is the most exposed, that is to say the area

  calf from the edge of the open end of the rigid element

  in which the membrane is housed In fact, in this area

  in the state of maximum exposure to light (fully extended spring), the membrane has the maximum compression of the rubber and, therefore, the maximum resistance to deterioration under the known effects of

the light.

  Since, in addition, the precompounding membrane

  is more resistant to stress, it presents

  longer life and greater reliability.

  Another advantage of the air spring according to the

  principle of the invention consists in the possibility of using

  a membrane with a tissue or longitudinal threads

  dinals smaller than those of the fabric or

  used in known springs having dimensions of

and a similar race.

  Indeed, in a pneumatic spring according to the

  principle of the invention, it is possible to anchor an ex-

  end of the diaphragm in an intermediate position

  be the extremities of the rigid element in which the

  brane is housed This allows to obtain the same results

  using a membrane that does not almost completely cover

  the inner wall of the rigid element

  holds and using for the effect of retaining air under pressure a part of the wall of this rigid element It is obvious that modifications may be

  made to the embodiments just described.

  in particular by substitution of technical means

  equivalent, without departing from the scope of the invention.

tion.

Claims (5)

R E V E N D I C A T IO N S   1 bell-shaped air spring intended to con-   of air under pressure, characterized in that   takes at least two hollow rigid elements (2, 13; 18, 19; 32, 31, 32 '; 52, 51) of substantially tubular shape, coaxial and capable of sliding axially with respect to   port to the other, at least one of which is open to one   mity and at least one has walls of variable profile; at least one flexible membrane (5; 35; 53) interposed between the one and the other of the rigid elements and which comprises   a plurality of wires or cords (6) substantially inextensi-   substantially in the direction of the long axis.   of the spring and embedded in a layer of rubber   Chouc; and assembly means that fix the membrane   or membranes with rigid elements.   2 pneumatic bell spring according to the claim   1, characterized in that the membrane is precom- winning.   3 pneumatic bell spring according to the   2, characterized in that the rigid elements   (18, 19) are two in number and have their cavity in direct communication.   4 pneumatic bell spring according to the claim   3, characterized in that, in the cavity of one (19) of the rigid elements (18, 19), is housed a deformable membrane (21) in which it is possible to introduce a liquid under pressure.   Pneumatic spring bell according to one   any of claims 1 to 4, characterized in that   that one end of each membrane (53) is anchored circumferentially   substantially to the wall of the rigid element (52) in which it is contained, in a position between   both ends of this rigid element.   6 pneumatic bell spring according to the   5, characterized in that the position in which   each membrane (53) is anchored is approximately equidistant from both ends of the rigid member (52)   in which this membrane is contained.