GB1564734A

GB1564734A - Pneumatic spring bellows

Info

Publication number: GB1564734A
Application number: GB4417176A
Authority: GB
Original assignee: Continental Gummi Werke AG
Current assignee: Continental AG
Priority date: 1975-10-23
Filing date: 1976-10-25
Publication date: 1980-04-10
Also published as: ATA727176A; JPS5253187A; DE2547409A1; AT347799B; FR2328892B1; FR2328892A1; IT1072861B

Description

(54) PNEUMATIC SPRING BELLOWS (71) We, CONTINENTAL GUMMI WERKE AKTIENGESELLSHAFT, of Continental Hous/Postfach 169, 3000 Hannover, Germany (Fed. Rep.): German body corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The present invention relates to pneumatic spring bellows made of rubber or rubber-like plastics material having embedded reinforcing members or plies, more especially rolling bellows for vehicle suspensions, which bellows, with at least one of its circumferential sections adjacent to its edge beads are adapted to roll off on the outer mantle of a piston member arranged on an associated vehicle part, while the diameter of said circumferential sections changes.

Conventional pneumatic spring bellows, preferably used as vehicle springs, but also for shock absorbers and cushioning means for movements, comprise short hose or tube sections with drawn-in edge beads. These beads are either clamped in rigidly or are held only frictionally similar to the mounting of a pneumatic tyre on the wheel rim, and are employed between the parts to be cushioned. These bellows are, during their inward and outward stroke relative to their installed position of equilibrium subjected to changes in shape and diameter.

This applies, regardless of their design, to folding bellows, rolling bellows and socalled semi-bellows. These changes in diameter are particularly great with rolling bellows with the rolling-off movements of the respective end sections on the piston members supporting same. The tensions originating in the internal pressure and acting in an axial as well as a circumferential direction in the walls of the bellows are absorbed by reinforcing plies while the appropriate selection of the course of the filamentary reinforcing members of the reinforcing plies at the same time assures the maintenance of the predetermined specific shape of the bellows. Instead of fabrics having a plurality of directly interwoven filaments, it is preferable to use reinforcing members which are formed from non-woven parallel filaments or wires, because in addition to manufacturing simplifications, they also bring about an improved usefulness and a substantially longer life of the bellows. According to previous opinions, based equally on theoretical considerations and practical experience, known pneumatic spring bellows always have two layers, one upon the other of filament-like reinforcing members extending at different angles relative to the longitudinal axis of the bellows, so that in projection an image of intersecting or crossed reinforcing members is produced. Thus, it is possible, by selecting the respective direction and by selecting the desired intersecting angle of the reinforcing members in both layers to influence the deflection characteristics of the bellows in the desired sense and to maintain their shape under prevailing operating circumstances.

Increased demands on the bearing capacity load of such pneumatic spring bellows can theoretically be fulfilled by increasing the internal pressure. However, such is not practically possible in view of the fixed tear-resistance of the filaments of the reinforcing members, and in view of the limited number of reinforcing members which can be accommodated in a layer per surface unit of the bellows wall. Since the selection of a high-grade material for the reinforcing member, e.g. steel wire, fibreglass or the like, does not provide the desired lattitude and in certain circumstances lead to unfavourable compromise solutions, it would appear to suggest itself to provide a plurality of overlapping layers with reinforcing members in order in this way to increase the number of available reinforcing members.

This suggestion, however, is not readily practicable for the manufacture of functionable pneumatic spring bellows, because the changes in the diameter inherent in the spring movements will necessarily lead to considerable angular displacements in the individual layers.

Inasmuch as these angular changes in the individual layers differ from each other, locally changing distortions as well as upsetting will result.

An object of the present invention is to considerably increase the number of reinforcing members to be accommodated in the bellows wall, whilst avoiding or at least substantially reducing inadmissible stresses and hence to provide the conditions for producing highly stressable high pressure pneumatic spring bellows.

According to the present invention, there is provided a pneumatic spring bellows comprising an elastomeric material and having a tubular shape with annular edge beads at the ends of said bellows, said edge beads being mounted on first and second bellows members, one member being displaceable relative to the other, said bellows including reinforcing plies embedded in the walls of said bellows and anchored in said beads, said plies comprising at least four layers of filamentary reinforcing members arranged in space parallel relationship to each other, with the reinforcing members in at least two mutually adjacent layers arranged parallel to each other and with the reinforcing members of at least two other mutually adjacent layers arranged in parallel relationship to each other and at an angle relative to the reinforcing members of said first mentioned at least two mutually adjacent layers.

According to a practical embodiment of the present invention, two preferred modifications are possible as basic arrangements with the reinforcing member layers either crossing each other in pairs or staggered in a packet-like manner. In one instance, the reinforcing members of two other mutually adjacent layers, while extending parallel to each other also extend at an angle relative to the reinforcing members of two other mutually adjacent layers directly adjacent thereto. In the other case, six layers of filamentary reinforcing members are involved, the reinforcing members in three mutually adjacent layers extending parallel to each other and arranged at an angle relative to the reinforcing members of the three other mutually adjacent layers which are also parallel to each other.

The introduction of the new reinforcing member connection according to the invention leads to substantial advantages, which with regard to their influence on the dynamic behaviour of the pneumatic spring bellows could not be foreseen. The combination in accordance with the invention of the respective parallel reinforcing plies results in a more favourably overlapping of the diamondshaped filaments which form in the projection of the plies, said improved overlapping being better for the rolling off movement of the bellows wall. Since the superposed plies have different diameters increasing from the inside toward the outside and with said difference amounting to more than the thickness of filament during the inward stroke and when moving onto the supporting piston member are crimped, and in the reverse measuring ratio are rolled-off onto the outer mantle thereof, the diamond defining angles with the convtntional alternating intersection of relatively far reaching changes of an order of magnitude of several degrees. On the other hand, the stacking in pairs of the respective parallel plies with a corresponding displacement of the intersection plane, results in an insignificantly reduced difference of the diamond defining angles. The angular differences, which amount to a few hundredths of a degree, lead to correspondingly reduced distortions or upsetting of the reinforcing members and consequently a considerably longer life of the bellows is to be expected.

In addition to this, the parallel extending reinforcing members of different plies are, within the arc of rolling engagement, subjected to lesser curvature differences and thus will be subjected to a more uniform load so that the strength of the internal filament plies is utilised in an improved manner, and, as a result thereof the novel pneumatic spring bellows can be subjected to a relatively higher internal pressure.

Finally, the number of intersecting surfaces, reduced in number relative to a conventional arrangement-provided the number of plies is the same-permits the manufacture of pneumatic spring bellows having a markedly reduced wall thickness which, in turn, permits uninterrupted deflection and return deflection and rolling engagement, retains the heat produced by the squeeze action within low limits and moreover opens up extremely greater freedom in structure and adaptation of the ply sequence relative one another. Thus, for example, between adjacent plies containing reinforcing members arranged at an angle to one another, there may be provided nonreinforced rubber or plastics material intermediate plies of greater thickness than between the remaining adjacent plies which contain the reinforcing members parallel to one another, to reduce stress peaks at the crests of the filaments crossing each other and to exclude reliably mutual contact.

The invention will be further illustrated by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a rolling bellows for a pneumatic suspension, shown in longitudinal section and in the state of installation, and Figs. 2 and 3 show two modifications of a detail of the rolling bellows, said detail being shown on a larger scale and the location thereof in the bellows being indicated in Fig. I by a dot-dash circle I.

The rolling bellows 4 shown is produced in the shape of a cylindrical tubular member of rubber or rubber-like resilient plastics material having reinforcing plies embedded therein and, by means of two drawn-in edge beads 14, is secured in a hermetically-sealed manner, to associated stop surfaces of vehicle parts 5, 6 to be cushioned. The interior of the rolling bellows 4, through a connecting bore 15 in the vehicle part 5, may be subjected to gas under pressure, generally compressed air. The lower vehicle part 6 shown is formed as a supporting piston member in order to have its cylindrical outer mantle receive the rolling fold 24 which moves during the inward stroke of the rolling bellows 4. At the same time, it serves as a spare air container and for this purpose is open towards the interior of the rolling bellows via a further bore, but towards the outside is sealed by a securely inserted end plate 16.

The reinforcing plies embedded in the bellows wall are anchored in a manner (not shown) to conventional core rings in the edge beads 14 of the rolling bellows. In accordance with Fig. 2 of the drawings, the reinforcing plies comprise six layers of filamentary reinforcing members, which are located parallel to one another without contacting each other. The arrangement is such that the members denoted by "a" are arranged mutually parallel but are aligned at an angle to the mutually parallel members denoted by "b". The diagrammatic drawing, solely for reasons of clarity and easy understanding, is based on a 90" intersection system. The invention, however, is in no way limited thereto; moreover the selection of a most expedient angle difference and the overall alignment relative to the longitudinal axis of the rolling bellows is totally open to the discretion of the designer. In one embodiment of the invention the combination in pairs of the layers "a" and "b" is arranged in such a manner that between the six layers in all there are obtained only two surfaces with direct filamentary intersections. The distance between the differently aligned layer pairs "a" and "b" of reinforcing members is, by the insertion of relatively thick intermediate layers Z considerably greater than between the respective layers extending in the same direction.

In the embodiment of Fig. 3, the layers "a" and "b" are gathered in assemblies and separated from one another by a single intermediate layers Z.

WHAT WE CLAIM IS: 1. A pneumatic spring bellows comprising an elastomeric material and having a tubular shape with annular edge beads at the ends of said bellows, said edge beads being mounted on first and second bellows members, one member being displaceable relative to the other, said bellows including reinforcing plies embedded in the walls of said bellows and anchored in said beads, said plies comprising at least four layers of filamentary reinforcing members arranged in spaced parallel relationship to each other, with the reinforcing members in at least two mutually adjacent layers arranged parallel to each other and with the reinforcing members of at least two other mutually adjacent layers arranged in a parallel relationship to each other and at an angle relative to the reinforcing members of said first mentioned at least two mutually adjacent layers.

2. A pneumatic spring bellows as claimed in claim 1, in which the reinforcing members of two mutually adjacent layers, while extending parallel to each other also extend at an angle relative to the reinforcing members of two other mutually adjacent layers directly adjacent thereto.

3. A pneumatic spring bellows as claimed in claim 1, said plies comprising six layers of filamentary reinforcing members, with the reinforcing members in three mutually adjacent layers extending parallel to each other and at an angle relative to the reinforcing members of the three other mutually adjacent layers also extending parallel to each other.

4. A pneumatic spring bellows as claimed in any preceding claim, in which between the layers of reinforcing members extending in one and the same direction, there are respectively interposed layers of elastomeric material which have a thickness less than the thickness of a layer of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a rolling bellows for a pneumatic suspension, shown in longitudinal section and in the state of installation, and Figs. 2 and 3 show two modifications of a detail of the rolling bellows, said detail being shown on a larger scale and the location thereof in the bellows being indicated in Fig. I by a dot-dash circle I. The rolling bellows 4 shown is produced in the shape of a cylindrical tubular member of rubber or rubber-like resilient plastics material having reinforcing plies embedded therein and, by means of two drawn-in edge beads 14, is secured in a hermetically-sealed manner, to associated stop surfaces of vehicle parts 5, 6 to be cushioned. The interior of the rolling bellows 4, through a connecting bore 15 in the vehicle part 5, may be subjected to gas under pressure, generally compressed air. The lower vehicle part 6 shown is formed as a supporting piston member in order to have its cylindrical outer mantle receive the rolling fold 24 which moves during the inward stroke of the rolling bellows 4. At the same time, it serves as a spare air container and for this purpose is open towards the interior of the rolling bellows via a further bore, but towards the outside is sealed by a securely inserted end plate 16. The reinforcing plies embedded in the bellows wall are anchored in a manner (not shown) to conventional core rings in the edge beads 14 of the rolling bellows. In accordance with Fig. 2 of the drawings, the reinforcing plies comprise six layers of filamentary reinforcing members, which are located parallel to one another without contacting each other. The arrangement is such that the members denoted by "a" are arranged mutually parallel but are aligned at an angle to the mutually parallel members denoted by "b". The diagrammatic drawing, solely for reasons of clarity and easy understanding, is based on a 90" intersection system. The invention, however, is in no way limited thereto; moreover the selection of a most expedient angle difference and the overall alignment relative to the longitudinal axis of the rolling bellows is totally open to the discretion of the designer. In one embodiment of the invention the combination in pairs of the layers "a" and "b" is arranged in such a manner that between the six layers in all there are obtained only two surfaces with direct filamentary intersections. The distance between the differently aligned layer pairs "a" and "b" of reinforcing members is, by the insertion of relatively thick intermediate layers Z considerably greater than between the respective layers extending in the same direction. In the embodiment of Fig. 3, the layers "a" and "b" are gathered in assemblies and separated from one another by a single intermediate layers Z. WHAT WE CLAIM IS:

1. A pneumatic spring bellows comprising an elastomeric material and having a tubular shape with annular edge beads at the ends of said bellows, said edge beads being mounted on first and second bellows members, one member being displaceable relative to the other, said bellows including reinforcing plies embedded in the walls of said bellows and anchored in said beads, said plies comprising at least four layers of filamentary reinforcing members arranged in spaced parallel relationship to each other, with the reinforcing members in at least two mutually adjacent layers arranged parallel to each other and with the reinforcing members of at least two other mutually adjacent layers arranged in a parallel relationship to each other and at an angle relative to the reinforcing members of said first mentioned at least two mutually adjacent layers.

elastomeric material, interposed directly between layers of reinforcing members respectively forming an angle with each other.

5. A pneumatic spring bellows substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.