Stretch Hose

Description

The invention relates to an elastically stretchable stretch hose with a support spiral acting as a tension spring and with a hose wall connected with the support spiral and consisting of a synthetic material.

Elastically stretchable stretch hoses with a hose wall made of synthetic material are known in many different embodiment variants and for a multitude of applications. All these variants are characterized by getting their stretchability through an integrated support spiral or helix made of steel wire, acting as a tension spring and providing at the same time the necessary radial strength. The known stretch hoses just differ by the application of different shapes and arrangements (profiles) of the plastic band forming the hose wall.

The disadvantages of this type of hose structure are, on the one hand, the relatively high weight of the hose due to the wire spiral and the relatively high costs, because the cost price of the steel wire determines the price of the product. On the other hand, stretch hoses with steel-wire spiral usually involve relatively high stretching forces, as, for stretching the hose, the material-dependent relatively high spring resistance of the steel-wire spiral has to be overcome.

It is the aim of the present invention to provide a stretch hose which, in comparison with the currently known stretch hoses, has a reduced weight with, at the same time, minimized production costs. Furthermore, it is desirable that the stretching force required for the extension is reduced.

This task is solved according to the invention by the fact that the support spiral is made of a synthetic material.

The clearly lower density of synthetic materials as compared with steel results in a significant reduction of the weight of the stretch hose. The costs of the product are also reduced because the share of the plastic spiral in the costs is clearly lower, due to the reduced weight percentage in the total product and the usually lower cost prices of synthetic materials in comparison with steel wire. Furthermore, with this hose structure, stretch hoses with a relatively low stretching force can be manufactured because the spring resistance to be overcome is in this construction rather low.

It is particularly advantageous when in rest condition, the hose is without prestress, i.e. stressfree, and the spring tension is only built up when the hose is stretched. In order that the hose takes a blocked form in rest condition, the hose wall is manufactured with the corresponding required profiling. The band between two adjacent spiral turns, forming the hose wall, is, therefore, advantageously shaped in the form of a loop or fold, so that adjacent spiral turns lie one beside the other in rest condition.

Furthermore, it is advantageous to design the stretch hose in such a way that the spring tension building up during stretching and trying to restore the compact rest configuration of the hose, is generated both by the support spiral and by the band profile forming the hose wall. That means that the share of the “restoration-seeking” spring tension attributable to the material of the hose wall in proportion to the share attributable to the support spiral should advantageously be quite significant and should preferably amount to at least 25%, particularly preferably, to at least 50% of the total spring tension.

Through the novel design, a higher flexibility of the stretch hose can possibly be achieved also concerning the stress acting at right angles to the longitudinal direction.

For manufacturing the hose wall, all synthetic materials known from stretch hoses with steel-wire spiral can be used. These are mainly plasticized PVC and TPU, but also all other synthetic materials which are deformable under the conditions of application of the stretch hose, preferably elastic and preferably thermoplastically processable synthetic materials, such as, e.g. TPE or EPDM/PP, can be used.

For the support spiral, advantageously a thermoplastically processable synthetic material is used, whose modulus of elasticity should expediently be higher than the modulus of elasticity of the material of the hose wall, in order to achieve a sufficient radial strength, e.g. unplasticized PVC, TPU, ABS, PP, TPE.

When selecting the material for the support spiral, it should expediently be made sure that the material can well be bonded with the material selected for the hose wall.

Advantageously, the stretch ratio of the stretch hose is at least 1.5:1. That means that the stretch hose can be stretched to at least 1.5 times its basic length in compact, contracted state, without permanent deformation and without overstressing the support spiral acting as a tension spring.

Advantageously, the spring constant effective when the stretch hose is stretched has a value of 5 N/m to 25 N/m.

FIG. 1 shows a longitudinal section through a stretch hose (in detail). An exemplary embodiment of the invention is explained in detail in the following by means of the drawing.

The stretch hose 2 shown in FIG. 1 in a longitudinal section comprises a support spiral 4 (this designation has become customary, although the term “helix” or “screw” would actually be more correct) coiling in the manner of a helical line around an imaginary cylinder. It also comprises a hose wall 6, which is extruded or consists of a rolled-up plastic sheet or a plastic band whose edges are bonded or glued together, said hose wall 6 being connected (e.g. bonded) to the support spiral 4 at corresponding contact points 8 located, in the present exemplary embodiment, outside, and being supported by said support spiral 4. The stretch hose 2 can, therefore, be used as a suction and pressure hose. In a variant (not shown), the support spiral 4 can also be completely integrated in the hose wall 6 or be covered by the latter, so that it will not get into contact with the flow medium flowing in the stretch hose 2.

In the compact basic configuration shown in the FIGURE, the hose wall 6, viewed in section, has a wave-like profile or a profile provided with folds 10, so that under tensile stress, the stretch hose 2 can be stretched and thus, extended, if required, at its ends in longitudinal direction 12, in the manner of a concertina or of expansion bellows, against the building-up spring resistance of the elements support spiral 4 and hose wall 6 acting as a tension spring, maximally up to a complete extension of all freely movable profile bends or folds 10, e.g. to at least 1.5 times its basic length. When the ends are released, the stretch hose 2 will automatically contract, as a consequence of the spring resistance acting in longitudinal direction 12.

Contrary to the stretch hoses known so far, which are provided with a support spiral made of steel wire, the support spiral 4 of the stretch hose 2 is made of synthetic material, in the present exemplary embodiment, of TPU. This material has a higher modulus of elasticity than the material of the hose wall 6, in the present exemplary embodiment, also TPU, but with a lower modulus of elasticity. Therefore, this particularly preferred material selection for the support spiral 4 assures, with a relatively low weight, both a sufficient radial strength and, together with the hose wall, a suitable stretching force in longitudinal direction 12, which is, however, in general lower than that of wire spirals of the same size.

At the contact points 8, the support spiral 4 and the hose wall 6 are bonded together.

LIST OF REFERENCE NUMBERS

• 2 Stretch hose
• 4 Support spiral
• 6 Hose wall
• 8 Contact point
• 10 Fold
• 12 Longitudinal direction