The invention relates to a reinforced rubber product comprising a substantially axially extending flexible product body surrounding a hollow interior space, the body having at least one axial end, the rubber product further comprising at least one radially extending flange positioned at an axial end of the axially extending product body, and to a production method thereof. The product may comprise rubber/elastomeric material reinforced with fibers with integral reinforced rubber flanges such as rubber hoses, couplings, elbows and expansion joints. The product may also comprise rubber/elastomeric material reinforced with fibers with integral reinforced rubber flanges wherein the interior hollow space functions as a (closed) pressure vessel such as an air-spring or actuator. Such products typically comprise an inner rubber layer, one or more reinforcement layers, rubber layers in between the reinforcement layers and an outer rubber layer. The invention provides an improved design and production method for-such a product.

Background of invention. There are various constructions known of reinforced elastomeric products with integral flanges. An integral flange provides that (part of) the reinforcement on the product body is continued in the flange construction which flanges therefore form an integral part of the product. The integral flanges comprise layers of rubber and (rubberized) reinforcement material, and sometimes an additional insert of solid material like a metal flange ring or a bead ring is used. In most constructions the integral flanges are formed by cutting of the reinforcement layers at the end of the product leaving some extra length which is used to create the integral flange. The ends are then for example folded radially outward to form an integral flange, or folded backwards over a solid flange or bead ring to form the integral flange. The connection with the environment is created by clamping the integral flange between a (metal) backing ring flange and the connecting flange surface of the other product or apparatus it is connected to. An example of such a flange construction is provided in Patent DE4005717 which describes a coupling flange for a rubber hose which has hard elastomer insert layers and outer steel clamping plates. In other examples such integral reinforced rubber flanges are provided with bolt holes and a metal backing ring flange with bolt holes to enable a connection with a connecting flange using bolts.

An alternative design for an integral reinforced rubber flange is described in Patent application DE3441807C2. In this Patent application a hose with integral flanges is described wherein the product is reinforced with fibers by applying fibers on the hose in a cross-wise helical fashion and continuing the fibers from the hose on the flange inner side surface. In the Patent application is described and illustrated that the fibers are positioned under an angle of 20-70 angular degrees on the flange surface in relation to the radial direction. Furthermore, it is mentioned that in a preferred embodiment the fibers follow a curved path over the flange surface. It is also mentioned that an effective reinforcement in the transition area between hose and flange has been obtained by continuation of the fibers from the hose onto the flange inner side surface.

According to an aspect the product has one or more fiber reinforcement layers. To manufacture a hose with integral reinforced flanges according to the design described in Patent DE3441807C2 the reinforcement wires have to run from the cylindrical hose against the radially outward extending flange inner side surface. To be able to move the fiber radially outward at the bottom of the radially outward extending flange using a winding process the winding angle of that wire has to be approximately 90 angular degrees (circumferential) to be able to turn radially outward, to prevent fiber bridging. However, the fiber winding angle of a reinforced rubber hose will typically be between 40 and 70 angular degrees (neutral angle for a straight hose is 54.7 angular degrees). Therefore, a transition portion will exist at the end of the hose where the winding angle will (gradually) change towards approximately 90 angular degrees. The

disadvantage of this transition area is that the winding angles in this area deviate from the (optimal) winding angle in the rest of the hose. As a result the hose is not optimally reinforced in that area. The winding angle in the transition area is larger than in the rest of the hose. Assuming a neutral force equilibrium in the rest of the hose this will eventually result in axial extension of the hose in the transition area when internally pressurized. Axial extension of the hose is undesired and can lead to damage or failure of the hose.

It is an object of the invention therefore to provide a reinforced rubber product comprising a substantially axially extending flexible product body surrounding a hollow interior space, the body having at least one axial end, the rubber product further comprising at least one radially extending flange positioned at an axial end of the axially extending product body, and a production method thereof, wherein the above mentioned disadvantages are counteracted. The object is achieved according to the reinforced rubber product as defined in claim 1 and according to the production method as defined in claim 12. By using an additional reinforcement in (part of ) the transition portion which counteracts axial extension of the product body when internally pressurized, the above mentioned disadvantages of undesired axial extension of the product body which can lead to damage or failure of the product is counteracted. Furthermore, the fibers are integrally wound from the product body to the radially outward extended flanges in a continuous fashion, whereby the fibers may follow (quasi-) geodesic paths on the flange inner- and outer surfaces after which they continue again on the product body, in a repeatedly back and forth movement from flange to flange until the required amount of fibers is applied.

According to this invention the product body and radially outward extending flanges may be overwound (quasi-) geodesically in a continuous fashion. The winding procedure will preferably be executed with an automated winding process like filament winding or robotic winding. In these continuous processes the winding angle of the reinforcement fibers is controlled by the back and forth movement of a material guiding tool along the length of the mandrel that is synchronized with the revolution speed of the mandrel. The reinforcement can be yarn, cord, wire or other reinforcement materials typically used for reinforcement of elastomeric products. The reinforcement can be applied by one or multiple fibers with or without special coating (e.g. RFL) and/or be embedded in a rubber sheet or tape.

The reinforced rubber flange comprises rubber and reinforcement layers. The basic element of the reinforced rubber flange is a flange base part, around which the material layers are applied. During the winding procedure the flange base part has to provide sufficient stiffness to be overwound with reinforcement and rubber layers and can for example be made of rubber, plastic or metal or a combination of these.

The shape of the product body may vary from a straight or bended cylinder, to a conical shape (e.g. reducer) and it can contain one or multiple bellows or comprise a combination of these shapes. The interior hollow space is circumferentially surrounded by the product body. The interior hollow space may act like a canal to transport materials like liquids or gasses.

Alternatively, the hollow interior space can form a (closed) pressure vessel used for storage, actuation or vibration damping. A product body has a central portion which is overwound following (quasi-) geodesic paths, and from a certain point the winding angle will gradually change towards approximately 90 angular degrees following a quasi-geodesic path, over a distance called the transitional portion.

The transitional portion is overwound quasi-geodesically whereby the winding angle gradually changes towards a winding angle of approximately 90 angular degrees (between 85-90 angular degrees) at the intersection of the product body and flange inner side surface. From there, the fiber describes a geodesic path on the flange surface tangential to the circumferential of the product body, and (quasi-) geodesic paths over the outer radial surface of the flange.

In some situations the winding of the fibers at the intersection of radially outward extended flange and the product body, where the fiber reaches a winding angle of 90 angular degrees is continued with extra length in circumferential direction, referred to as 'dwell'.

The winding angles on the central portion of the product body of the product of invention are typically between 40 and 70 angular degrees. In general, with a straight cylindrical shape this angle is constant over the length of the product, although it can change per different

reinforcement layers. The winding angles can vary along the length of the product body, like with a bellow shape.

At the transition of the fiber from the product body to the radially extending flange inner side surface the winding angle has to be approximately 90 angular degrees. Adjacent to the flange inner side surface the product body might increase by local material built-up or be increased intensively, which creates a curved or linear slope between the product body and flange inner side surface. In another embodiment the slope is described by a profile having a point on the product body and a point on the outer radius of the flange, whereby this slope will be considered as the flange inner side surface. In such situation the winding angle at the minimum radius of the slope, which will be considered as the flange inner side surface, does not have to be

approximately 90 degrees. The fiber will continue with a (quasi-) geodesic path from the product body to the flange inner side surface.

To compensate for the higher winding angles in the transition portion compared to the central body portion, additional reinforcement providing a reinforcement substantially in the axial direction has to be arranged to prevent the product from extending in axial direction when subject to internal pressure or axial forces. To transfer the forces from this additional

reinforcement in axial direction to the flange it may be integrated with the flange. As part of the invention various options to arrange such reinforcement in axial direction are provided.

The additional reinforcement in axial direction may be formed by adding reinforcement fibers which are placed at a low winding angle (e.g. 0 degrees) on the product in (part of) the transition portion. In a preferred embodiment the additional reinforcement may be continued on the radially outward extending flange. Integration with the radially outward extending flange can for example be achieved by continuing the reinforcement wires on the flange inner- and/or outer side surface. The reinforcement may comprise a rubber sheet reinforced with unidirectional fibers which is wrapped around the product body with the fibers laying in the axial direction, whereby part of the reinforced sheet is continued on the radially outward extending flange inner-and/or outer surface. In a particularly advantageous embodiment, the part of the reinforced rubber sheet which has to be folded against the flange inner- and/or outer side surface is provided with incisions in axial direction, these incisions forming separate flaps, which makes it easier to fold the reinforcement sheet against the flange inner- and/or outer side surface. The additional layer with axial reinforcement may be placed under the main reinforcement layer, between reinforcement layers in case of multiple layers, or on top of the reinforcement layer. Placement of the additional reinforcement can be done manually or by an automated placement process.

Another option to provide reinforcement in axial direction in the transition portion is to add an axially extending tubular body in the product body and a radially outward extending flange integral with said tubular part. This can for example be an integral metal part comprising a metal tubular part and a metal flange part.

There are various options to connect the reinforced rubber flange to the surrounding environment. Two typical methods are by means of clamping between two (metal) flange plates which are connected with bolts, or by means of clamping between two (metal) flange plates whereby the bolts go through the reinforced rubber flange. In the situation whereby the bolts go through the reinforced rubber flange, the bolt holes can be made by drilling after vulcanization. When a hard (e.g. metal) insert is used, these bolt holes have to be made in the insert beforehand. Instead of making the bolt holes afterwards it is also possible to place special parts in the holes during production which enable to wind the rubber and/or reinforcement material around the holes during production. The advantage is that the reinforcement fibers are not cut in the process of drilling the holes.

As part of the invention also the rubber layer can be applied by continuously winding rubber strips on the product and on the integral flange. In a particularly advantageous embodiment, the rubber strips are wound with a back and forth movement over the radially outward extending flange following (quasi-) geodesic paths while the mandrel rotates, until the required rubber coverage of that rubber layer is obtained. Next, it will continue with winding of rubber strips on the product surface at a high winding angle to cover the product surface, with or without overlap of the strips, until the other flange is reached, which is overwound in the same fashion as the first one.

The objects of the invention will be apparent after reviewing the drawings and description thereof wherein:

FIG. la is a side view showing a product of invention, without outer rubber layer, which shows how the product body and flanges are integrally overwound with reinforcement fibers;

FIG. lb is an isometric-view of the product from FIG. la showing how the fibers from the product body continue to the inner surface of the radially outward extended flange;

FIG. lc is a front view of the product from FIG. la on which the geodesic fiber paths over the flange inner side surface and outer side surface are described;

FIG. Id is a front view of the product from FIG. la whereby the fiber path over the top surface of the radially outward extended flange is quasi-geodesic such that fiber on the outer surface of the flange describes a geodesic path tangential to an imaginary circle, which in this situation is larger than the circumferential of the product body;

FIG.2a is an isometric view of a product of invention whereby the reinforcement fibers in axial direction are provided at a transitional area;

FIG. 2b is an isometric view of a product of invention whereby the reinforcement fibers in axial direction are embedded in a rubber sheet which is wrapped around the product body, and the end of the sheet has cuts in vertical direction spaced along its length, thereby forming flaps which are folded radially outward against the flange inner side surface; FIG. 2c is a cross section of a detail of the product of invention as described in FIG. 2a showing a part o f the product body and integral reinforced rubber flanges, wherein also the rubber layers are added;

FIG. 2d is a cross section of a detail of the product of invention as described in FIG. 2a showing a part o f the product body and integral reinforced rubber flanges, wherein the rubber sheet with additional reinforcement fibers in axial direction lies under the radially outward extended flange and its flaps are folded radially outward against the outer surface of the radially outward extended flange;

FIG. 3 is a cross section of a detail of a product of invention showing a part of the product body and integral reinforced rubber flanges having an axially extending tubular part in the transition area and a radially outward extending flange base part integral with said tubular part;

FIG. 4 is a cross section of a detail of a product of invention showing a part of the product body and integral reinforced rubber flanges wherein the flange inner side surface is described by a slope between the product body and the flange outer radial surface.

The figures are only illustrations of preferred embodiments of the invention. Identical or corresponding parts in the figures are represented by the same identification numbers.

Referring to FIGS, la-d, a product of invention 1 is provided, presented here without outer cover layer and without additional reinforcement in axial direction. The purpose of FIGS. la- Id is to illustrate how the product body 2, which is indicated as the part between points A and D, and radially outward extended flanges 3 are integrally overwound with fibers forming the reinforcement layer 4. The substantially axially extending product body 2 may be cylindrical as presented in FIG. la, but may also comprise one or multiple bends (e.g. elbow hose), have a conical shape (e.g. reducer hose),have one or multiple bellows (e.g. bellowed expansion joint) or a combination of these. The reinforced rubber product comprises rubber layers and reinforcement layers. In general the product comprises an inner rubber liner and an outer rubber cover, and one or more reinforcement layers which may have rubber layers in between. In this example the reinforcement layer 4 comprises a single fiber which runs back and forth over the product's body 2 and radially outward extended flanges 3. Whereby the reinforcement fiber is wound (quasi-) geodesically using a continues winding process in which both product body and radially outward extended flanges are integrally overwound, whereby the winding angle of the reinforcement fibers is controlled by the back and forth movement of a material guiding tool along the length of the mandrel that is synchronized with the revolution speed of the mandrel. In a preferred embodiment of this invention the rubber layers are applied using a method wherein one or more of the rubber layers may be applied on the radially outward extending flange 3 by winding rubber strip with a back and forth movement from left to right over the flange 3 on (quasi-) geodesic paths while the product is rotating whereby the rubber strip is applied in a predetermined pattern until the desired surface coverage has been obtained, and/or the application of rubber strip on the radially outward extended flange 3 is continued with application of said rubber strip on the product body 2, whereby the rubber strip on the product body 2 is applied in a spiral fashion with a high winding angle such that the rubber strips are placed next to each other or with a certain overlap such that the desired surface coverage is obtained, or whereby the rubber strip is applied with a back and forth movement on (quasi-) geodesic paths over a radially outward extending part of the product body (e.g. bellow shape) in a predetermined pattern until the desired surface coverage has been obtained, or a combination of these. FIG. la shows that the fibers of the reinforcement layer 4 on the product body 2. The product body has an axial central portion 2a between points B and C which is overwound (quasi- Jgeodesically and an axial transition portion 2b, between points A and B and points C and D, where the winding angle (gradually) moves towards approximately 90 angular degrees. The product body 2 is overwound with fibers wherein the winding angle of the fibers on the product body central portion 2a is typically between 40 and 70 angular degrees, and adjacent to the radially extending flange 3 the winding angle on the product body starts to change gradually to a winding angle of approximately 90 angular degrees on the product body 2 at the intersection between the product body and the radially outward extending flange 3, over a distance which is called the transition portion 2b. FIG. lb is an isometric view of the product from FIG. la and represents how the fibers of the reinforcement layer 4 reach approximately 90 angular degrees at the intersection of the product body 2 and the flange inner side surface 6 of the radially outward extended flange 3 and continue from there on a geodesic path 7a tangential to the

circumferential of the product body 8 to the outer radius of the flange, to continue with a geodesic path 7b on the radial outer surface of the flange 9, to continue with a geodesic path 7c, tangential to the circumferential of the product body 8, on the flange outer side surface 10, to continue with a geodesic path 7b on the radial outer surface of the flange 9, and continue with a geodesic path 7a, tangential to the circumferential of the product body 8, on the flange inner side surface 6, from where it continues again on the product body 2. The circumferential of the product body 8 is defined here as the outer circumferential of the product body 2 on which the fibers are wound. FIG. lc is a front view of the flange outer side surface 10 of the radially outward extended flange 3 which shows how the fibers of the reinforcement layer 4 follow a geodesic path 7a-c whereby the fiber path of sections 7a and 7c lie tangential to product body's circumferential 8. FIG. Id is a front view of the flange outer side surface 10 whereby the fiber 4 follows a quasi-geodesic path 7d on the radial outer surface of the flange 9, which enables to continue with a geodesic path 7c, tangential to an imaginary circle 12 on the flange outer side surface 10 with a larger radius than that of the circumferential of the product body 8, to continue with a quasi-geodesic path 7d on the radial outer surface of the flange 9, and to continue with a geodesic path 7a, tangential to the circumferential of the product body 8, on the flange inner side surface 6, from where it continues again on the product body 2.

Referring to FIGS. 2a-d , a product of invention 1 is provided wherein a rubber sheet with axial reinforcement 13 is applied. Furthermore, an embodiment is provided wherein a rubber sheet with axial reinforcement 13 is applied with integral flaps 14 which are continued in the radially outward extended flange construction. The main reinforcement 4, represented here as a single layer of fibers partly covering the product surface, may also comprise one or more layers, having a surface coverage up to 100% per layer, being placed on top of each other with or without rubber layers in between. FIG. 2a is an isometric view of a product of invention 1, presented here without outer rubber layer, wherein additional reinforcement in axial direction is applied on the product body 2, by wrapping a rubber sheet reinforced with fibers placed parallel to each other in substantially axial direction 13, on the product body 2 over the length of the transition area 2b. FIG. 2b is an isometric view of a product of invention 1, presented here without outer rubber layer, wherein additional reinforcement in axial direction is applied on the product body 2 and integrated with the radially outward extending flange 3 under the fiber of the reinforcement layer 4, by wrapping a rubber sheet reinforced with fibers placed parallel to each other in axial direction (0 angular degrees) 13, on the product body 2 over the length of the transition area 2b, whereby the end of the sheet has cuts in vertical direction spaced along its length, thereby forming flaps 14 which are folded radially outward against the flange inner side surface 6 of the radially outward extended flange 3. The length of the flaps may be varied such that they at least cover part of the flange inner side surface, to a situation wherein they are continued over the radial outer surface to move radially inward on the outer side surface.

FIG. 2c is a cross section of a detail of the product of invention as described in FIG. 2b showing a part of the product body 2 and integral reinforced rubber flange3. In this cross section a rubber layer 17 is added which is placed over the flange base part 5 and the additional reinforcement sheet 13 and flaps 14. Furthermore, the outer rubber layer 16 is added. The radially extending flange 3 comprises rubber and reinforcement layers and comprises a base flange part 5 which has sufficient stiffness to enable overwinding of rubber and fiber layers, and may be made of metal, rubber, plastic or the like. The base flange part 5 may be broken or deformed such that a solid backing flange ring made out of a single part can be placed on the inside of flange, around the product body 2 and against the flange inner side surface 6 . In

FIGS.2c-2d the radially extended flange comprises bolt holes, which are spaced apart following a rotational pattern on the flange surface, which pattern and dimensions may be according to international flange standards. The bolt holes may be made after application of all material layers after vulcanization of the product. In another embodiment the radially outward extending flange has bolt holes which on both sides of the flange are provided with partly outward extending inserts during the application of the reinforcement and/or rubber layers, such that the bolt holes are not covered with reinforcement and/or rubber material during this process. In this figure also the rubber liner 15, outer rubber layer 16 and rubber layer 17 between the flange base part 5 and the fiber reinforcement layer 4 are shown. FIG. 2c is a cross section showing an alternative embodiment of FIG. 2b, wherein the fiber reinforced rubber sheet 13 is applied before placing the base flange part 5, and the flaps 14 are folded radially outward against the outer surface of the flange base part 5. The length of the flaps 14 can be varied such that they at least cover part of the outer surface, to a situation wherein they are continued over the radial outer surface to move radially inward on the inner side surface 6, to be continued in axial direction on the product body 2. In another embodiment multiple sheets 13 are placed on the product body 2 and continued on the flange inner side surface 6 or flange outer side surface 10, wherein the sheets may be placed under, in between and/or on the outside of the fiber reinforcement layer(s) 4.

Referring to FIG.3 a cross section of a detail of a product of invention is provided, showing a part of the product body 2 and integral reinforced rubber flanges wherein the additional reinforcing layer includes a product body portion extending in a mainly axial direction, and at least one integrally formed flange portion directed in a mainly radial direction. The integrally formed flange portion 18 is integrally overwound with a fiber reinforcement layer 4.

Referring to FIG. 4 a cross section of a detail of a product of invention is provided, showing a part of the product body 2 and integral reinforced rubber flanges wherein the flange inner side surface 6 is described by a linear profile between a point on the product body surface and the maximum flange radius. The profile of this slope may be linear or curved, whereby the fiber on the slope follows a (quasi-)geodesic path. In this embodiment the winding angle at the intersection of the product body and the inner side flange surface 6, here represented by the slope, does not have to be approximately 90 degrees, but can be lower to be able to continue with a (quasi-) geodesic path on the flange inner side surface.