WO2001094095A1

WO2001094095A1 - Method for producing hoses for hydraulic, industrial, automotive applications and the like

Info

Publication number: WO2001094095A1
Application number: PCT/EP2000/005352
Authority: WO
Inventors: Paolo Seghi
Original assignee: Manuli Rubber Industries S.P.A.
Priority date: 2000-06-09
Filing date: 2000-06-09
Publication date: 2001-12-13
Also published as: MXPA02001470A; AU5531500A

Abstract

A method for producing hoses (10) for hydraulic, industrial, automotive applications and the like, comprising the steps of: extruding a rubber inner layer (1) without an internal supporting mandrel; applying a braided steel reinforcement (2) over the inner layer; extruding a rubber sheath (4) around the braided steel reinforcement (2) and vulcanizing the resulting rubber hose (10).

Description

METHOD FOR PRODUCING HOSES FOR HYDRAULIC, INDUSTRIAL, AUTOMOTIVE APPLICATIONS AND THE LIKE

Technical Field

The present invention relates to a method for producing hoses for 5 hydraulic, industrial, automotive applications and the like. More particularly, the invention relates to a method for producing rubber hoses having an intermediate metal braiding, particularly for hydraulic, industrial, automotive applications and the like.

Background art LO It is known that such hoses are characterized in that they have a rubber inner layer whereon there is a braided steel reinforcement over which a rubber sheath is in turn arranged.

The methods currently used to manufacture said hoses entail a plurality of steps performed sequentially, starting from the extrusion of a generally is flexible mandrel (also known as core) which is then used as a support on which the rubber inner layer is extruded. The inner layer is the component that is designed to contain the fluid, while the braided steel reinforcement is the structural element of the hose which is capable of withstanding the operating pressure, so A rubber sheath, designed to protect the hose from external agents, is then extruded over the braided steel reinforcement.

A wrapping step is then performed in order to avoid the mutual contact of the crude rubber and apply circumferential pressure to the hose during vulcanization. Alternative technologies (lead coating, plastic extrusions, •5 etcetera) can be provided. Vulcanization and unwrapping then follow.

The hose thus completed is ready to be tested after removing the flexible mandrel inserted therein.

The above described known method, while being effective from the point of view of the product that can be obtained, entails a large number of iθ production steps which accordingly require a corresponding number of machines and entail a reduced possibility of automating the process. This leads to a general negative impact on the labor and operating costs of the entire production process.

The above described process used to produce the hose further entails the

5 use of several process materials, i.e., materials which do not constitute the structure of the product and which accordingly must be disposed of at the end of their useful cycle. These materials are mandrels, generally made of elastomeric or thermoplastic materials, non-stick products applied to the outer surface of the mandrel (such products being generally based on a

,o solvent, which diffuses into the working environment), and vulcanization bandages. All these materials, besides having a cost, have also a negative impact on the environment and sometimes entail work safety problems (for example solvents).

Moreover, the use of the inner flexible mandrel entails, when such

L5 mandrel is extracted, the formation of longitudinal scoring on the inner layer, dents in the inner layer due to imperfections of the mandrel, and the presence of non-stick product residues which remain attached inside the hose after the mandrel has been removed.

Moreover, the wrapping process for performing vulcanization entails so wrinkles, denting of the rubber sheath of the hose, molding of the seams of the bandages on the sheath of the hose, torsion of the hose due to incorrect wrapping, etcetera. These are only a few examples of the quality problems suffered by the conventional production cycle. Disclosure of the Invention

!5 The aim of the present invention is therefore to provide a method for producing hoses for hydraulic, industrial, automotive applications and the like which allows a substantial reduction in the number of manufacturing steps to be carried out in order to produce the hose.

Within the scope of this aim, an object of the present invention is to so provide a method for producing hoses for hydraulic, industrial, automotive applications and the like which allows a reduction in the cycle time required to produce the hose.

Another object of the present invention is to provide a method for producing hoses for hydraulic, industrial, automotive applications and the like in which it is not necessary to use additional materials such as mandrels, non-stick products, vulcanization bandages and the like, in order to reduce environmental impact and to improve workplace safety conditions.

Another object of the present invention is to provide a method for producing hoses for hydraulic, industrial, automotive applications and the like in which the resulting hose is substantially free from the defects that can be noted when using known methods, in order to improve the quality level of the product.

Another object of the present invention is to provide a method for producing hoses for hydraulic, industrial, automotive applications and the like which is highly reliable, relatively easy to manufacture and at competitive costs.

This aim, these and other objects which will become better apparent hereinafter are achieved by a method for producing hoses for hydraulic, industrial, automotive applications and the like, characterized in that it comprises the steps of: extruding a rubber inner layer without an internal supporting mandrel; applying a braided steel reinforcement over said inner layer; extruding a rubber sheath around said braided steel reinforcement and vulcanizing the resulting rubber hose. Brief description of the drawing

Further characteristics and advantages of the invention will become better apparent from the description of a preferred embodiment of the method according to the invention, together with the enclosed drawing figure which illustrates a hose manufactured with the method according to the invention. Ways of carrying out the invention

The method according to the invention entails a first step for extruding a rubber inner layer 1 of a hose 10 without using a generally flexible inner mandrel (as occurs in conventional methods) and without using the corresponding release agents, i.e., non-stick products which allow to subsequently remove the mandrel from the hose.

The rubber inner layer 1 is therefore produced without using the mandrel. In order to avoid excessive deformations of the inner layer (possibly to the point of collapse) when the inner layer is arranged on a reel (as normally done in conventional methods), the inner layer 1 is arranged on a collecting surface, and a fluid (gas or liquid) can be injected into it in order to increase its collapse resistance.

After the inner layer has been provided, a braided steel reinforcement 2 (with one or two braids) is applied, having the following particular characteristics:

~ low tension of the strands that form the braid, produced by means of an appropriate tension reduction device which accordingly allows the inner layer to withstand the braiding pressure;

— the presence of continuous (i.e., on-line) industrial refrigeration of the inner layer prior to the application of the braided steel reinforcement; the cooling of the inner layer entails a hardening of the rubber of the inner layer and therefore provides greater resistance of the inner layer when the steel braiding is applied thereon;

~ optional pressurization of the inner layer by means of a fluid (gas or liquid) can be applied in order to increase the squeezing resistance of the hose.

During this step, one or more textile threads or metallic strands 3 are deposited longitudinally along the hose 10 and give the inner layer 1 a longitudinal rigidity which, together with cooling and braid tension reduction, prevents the longitudinal deformation of the inner layer 1, allowing to comply with the braiding parameters (pitch, angle, lay diameter).

After the braiding step, a step for extruding a rubber covering 4 and for vulcanizing the resulting hose is performed. 5 The vulcanization step can be performed separately from the step for extruding the rubber covering but so as to be integrated in the industrial timing and handling or directly on-line with respect to the extrusion step.

The type of vulcanization provided is preferably the open-steam technology; alternative technologies (microwaves, hot air, molten salts, et o cetera) can optionally be used as a replacement or as an addition.

Finally, a step for checking, testing, coiling and packaging the resulting hose is performed.

It is evident that the number of manufacturing steps is reduced to approximately 50% with respect to conventional methods and therefore 5 there is a corresponding reduction in cycle time for producing the hose.

The reduction in the number of steps further allows to reduce the number of machines and therefore allows greater possibilities to automate the process.

The lack of additional materials, such as mandrels, non-stick products :o and bandages for vulcanization, allows to achieve advantages in ecological and environmental terms besides reducing the costs of the method.

The resulting product, i.e., the hose 10 with steel reinforcements, is free from recurring defects caused by use of the inner mandrel.

The hose obtained by means of the method according to the invention in

S5 fact does not have the longitudinal scoring on the inner layer 1 that are normally produced during mandrel extraction, the dents in the inner layer caused by imperfections of the mandrel, residues of non-stick products caused by the presence of the mandrel, etcetera.

The wrapping step, which is not present in the method according to the 50 invention, therefore also no longer causes the above described defects, such as wrinkles, dents on the rubber sheath, molding of the seams of the bandages onto the sheath of the hose, torsion of the hose due to poor wrapping, etcetera.

Accordingly, the fact of eliminating the inner mandrel and the wrapping 5 of the hose for vulcanization entails an advantage in terms of quality of the final product.

A rubber hose produced with a manufacturing method of the described type generally has a number of characteristics which allow to distinguish it from the similar product manufactured with the conventional production o process:

~ the presence of optional textile threads or steel strands 3 for longitudinal tensioning in the reinforcement (generally between the inner layer 1 and the steel reinforcement 2);

— an internal surface of the inner layer 1 which has no evident 5 longitudinal scoring which can be ascribed to the mechanical action of removing the mandrel;

— the possible reduced adhesion between the inner layer 1 and the reinforcement 2, which without appropriate developments of the materials (mixes) can be close to the minimum limit provided by most of the reference so standards (2.5 kg/cm);

— a rubber inner layer 1 which has a medium-high hardness (generally > 85 Shore A);

— a beating of the braided reinforcement 2 which is generally high and higher than 85% (at least the first braiding);

'5 ~ a smooth sheath (lack of wrapping);

— longitudinal resting marks on the sheath due to the lack of external protection during vulcanization.

The presence of all or of some of the described characteristics indicates the use of a production process according to the present invention. 10 In practice it has been found that the method according to the invention allows to substantially reduce the number of production steps required to produce hoses.

The method thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept. Thus, for example, the step for extruding the rubber sheath 4 that overlaps the steel braiding 2, associated with the vulcanization step, as mentioned, can be performed separately from the vulcanization step; specifically, the step for extruding the rubber sheath 4 can be performed before the vulcanization step, as normally known in the art. All the details may furthermore be replaced with other technically equivalent elements.

In practice, the materials used, so long as they are compatible with the specific use, as well as the dimensions, may be any according to requirements and to the state of the art.

Claims

1. A method for producing hoses for hydraulic, industrial, automotive applications and the like, characterized in that it comprises the steps of:

- extruding a rubber inner layer without an internal supporting mandrel; 5 ~ applying a braided steel reinforcement over said inner layer;

— extruding a rubber sheath around said braided steel reinforcement and vulcanizing the resulting rubber hose.

2. The method according to claim 1, characterized in that said step of applying said braided steel reinforcement over said inner layer is performed 0 after reducing the tension of steel strands that compose said braided reinforcement.

3. The method according to claim 1, characterized in that said step of . applying said braided steel reinforcement over said inner layer provides for continuous cooling of said inner layer before said braided steel L5 reinforcement is applied.

4. The method according to claim 1, characterized in that said step of extruding said rubber sheath over said braided steel reinforcement is performed in the same machine in which the subsequent vulcanization of said hose is performed. so 5. The method according to claim 1, characterized in that said step of vulcanizing said rubber hose is performed by means of open steam.

6. The method according to claim 1, characterized in that said step that consists in vulcanizing said rubber hose is performed according to one or more technologies chosen among hot air, microwaves and molten salts.

!5 7. The method according to claim 1, characterized in that said step of applying said braided steel reinforcement over said inner layer comprises a simultaneous step of depositing at least one textile thread or steel strand for longitudinal tension which is arranged on said inner layer.

8. The method according to claim 1, characterized in that it comprises a so final step for checking, coiling and packaging said hose.

9. The method according to claim 1, characterized in that said vulcanization step is performed separately from said step of extruding the rubber sheath over said braided steel reinforcement.

10. The method according to claim 1, characterized in that it comprises a step of using a pressurized fluid to increase squeezing resistance in at least one of the steps of inner layer extrusion, braiding, sheath extrusion and vulcanization.

12. A hose for hydraulic and industrial applications and the like, characterized in that it comprises a rubber inner layer over which a braided steel reinforcement is applied, at least one textile thread or steel strand being arranged between said inner layer and said braided steel reinforcement in order to provide longitudinal tension, a rubber sheathing element being extruded over said braided steel reinforcement and being then vulcanized.

13. The hose according to claim 12, characterized in that said braided* steel reinforcement is applied with reduced tension over said inner layer.