WO1996012909A1

WO1996012909A1 - Lightweight rubber hosing

Info

Publication number: WO1996012909A1
Application number: PCT/SE1995/001239
Authority: WO
Inventors: Markku Björkqvist
Original assignee: Trelleborg Building Products Ab
Priority date: 1994-10-21
Filing date: 1995-10-20
Publication date: 1996-05-02
Also published as: SE503208C2; SE9403600D0; SE9403600L; EP0803038A1; AU3820495A

Abstract

There is provided lightweight rubber hosing which finds particular use as a suction hose in milking machines. The hosing comprises two mutually concentrical rubber layers and an intermediate reinforcement layer and can be bent or curved through 180° with a bend diameter that corresponds essentially to the inner diameter of the hose while retaining the function of the hose as a channel for flowing fluid. The reinforcement layer embraces the inner rubber layer at least substantially completely and is comprised of a thermoplastic net structure in which the meshes have an obliquely angled checkered configuration, the net structure being in one continuous piece. The two rubber layers are in close contact withthe reinforcement layer without being joined thereto, but are joined to one another through the mesh openings of the net structure. The invention also relates to a method of producing the rubber hosing.

Description

LIGHTWEIGHT RUBBER HOSING

The present invention relates to lightweight rubber hosing and then particularly, but not exclusively, to hosing adapted for use as a suction hose or pressure hose that can be used with milking machines or milking apparatus, for instance. The hosing can be bent or curved at an angle of 180° with a bend diameter that corresponds essentially to the inner diameter of the hose while still retaining an effective hose function with regard to the conveyance fluid through the hose. The hose includes two concentrical rubber layers and an intermed¬ iate reinforcement layer.

Modern milking machines require the use of lightweight rubber hosing (LWH) , and it is also desirable to use lightweight hoses in older equipment for ergonomic reasons. The use of lightweight hoses or hosing is not limited to milking machines or milking apparatus, however, since many other areas of use are found in which lightweight hoses are beneficial, among other things for ergonomic reasons. Examples of such use are found in water hoses and pneumatic hoses, both for domestic and industrial use. A lightweight hose shall be at least 30% lighter, preferably 50% lighter- than standard hoses having the same inner diameter. This requirement places specific demands on lightweight hoses. For instance, it is necessary to incorporate stiff reinforc¬ ing material in the hose. Known commercially available low- weight hoses are reinforced with a helically wound thread of thermoplastic material. It has only been possible to manufac¬ ture such hoses in relatively short lengths and the hoses therefore demand a relatively high metre price. The most essential requirement of such lightweight hoses is that they can be used without hindering the flow of fluid through the hose to any great extent, and that they can be handled without risk of sharply bending or temporarily pinching the hose. There is a commercial demand for lightweight suction hoses or pressure hoses in considerably larger lengths and at lower metre prices than those available at present, among other things because the design of more modern milking machines require the use of long suction hoses. However, the hose must still fulfil the requirements placed on the shorter hoses and the longer hose lengths must have at least equally as good properties as the short lightweight hoses that are available, at present. Despite several years of intensive development work, it has not been found possible to manufacture the old type of lightweight hose with helical reinforcements in larger lengths, either continuously or discontinuouεly.

However, it has now surprisingly been found possible to produce continuously a lightweight hose which has at least the same performance as the lightweight hoses known hitherto. The present invention thus provides lightweight hosing of infinite length which has the properties required for application in modern milking machines, and also a method for the continuous manufacture of such hoses.

The invention is characterized by the features and steps set forth in the following Claims.

The inventive rubber hosing thus includes a reinforcing layer which surrounds the inner layer of the two rubber layers in the hose wall at least generally. It will be understood that the outer sides of the reinforcement may overlap one another or may terminate short of each other. It is not essential that the reinforcement has the same width around the inner layer along the full length of the hose. The important thing is that the reinforcement extends at least substantially around the full circumference of the inner layer.

The hose reinforcement layer may consist of a thermoplastic net structure in which the meshes of the net structure form an obliquely angled checkered pattern, with the net structure in one single continuous piece. Polyamideε or polyesters are suitable thermoresinε for a net structure of this kind. It is important that the net structure has an obliquely angled checkered pattern so that desired stability against laterally and longitudinally acting shear forces can be achieved also during manufacture of the hose. A checkered pattern of this configuration results in a net structure which is more stable mechanically than a net structure whose meshes have a right- angled configuration, such as in the case of woven net structures. Stability is also enhanced because the net structure is in one single continuous piece, which means that the net structure can either be produced from a homogenous web of material, for instance by so-called expansion, wherein the web is first penetrated to form rows of slots in the cross-direction of the web, with these slots being repeated along the length of the web, and then mechanically stretched so as to widen the slots and form oblique meshes. However, it is preferred to form the net structure from elements which mutually cross one another and which are fusion-bonded at their points of intersection. These elements may consist solely of threads, or may consist of threads which extend in one direction in the net structure and bands which extend in the other direction. The reinforcing net structure will preferably have a checkered pattern with a smallest angle in the range of 20-85°, preferably about 55°. The thread diameter may be about 0.8 mm and the bands may have a size of about 0.5 x 2.0 mm, although these dimensions are not particularly critical and may vary in accordance with the reinforcement material used and the application for which the hose is intended. The two rubber layers in the hose wall are in close contact with the reinforcement layer but are not affixed thereto, and are joined together through the meshes of the net structure. Probably, this latter feature of the inventive hose can be achieved solely by continuous extrusion of the hose, which enables the earlier described rigid spirals in known lightweight hose constructions to be replaced with a plastic net structure in accordance with the invention without detracting from the specific properties required in such hoses.

According to the present invention, the inventive hosing is manufactured continuously by delivering a web of reinforce¬ ment material to a nozzle which enables two mutually concen¬ tric rubber hosing layers to be extruded continuously. As the web of reinforcement material passes through the nozzle, the web is curved or rounded to a diameter which is essentially the same as the outer diameter of the extruded inner rubber layer and is caused to embrace the inner rubber layer, whereafter the outer rubber layer is extruded onto the reinforcement layer. Upon completion of the extrusion process, the hose is vulcanized in vulcanization apparatus herefor, therewith further enhancing the adhesion of the two rubber layers one with the other. In those cases when the reinforcement overlaps, the overlapping parts can be adhered together without requiring special means, for instance by heat-treatment in the vulcanization process or optionally in a separate heating step.

Nozzles which are intended for producing hosing that includes woven reinforcements are commercially available. These nozzles can be modified to employ thermoplastic reinforce- mentε. One such nozzle is the Swiss so-called GVS-Kopf intended for hoses having inner diameters of from " up to

The invention will now be described in more detail with reference to preferred embodimentε thereof and also with reference to the accompanying drawings, in which Figures 1 and 2 are cross-sectional views of different hose construc¬ tions; Figure 3 is an enlarged crosε-sectional view of part of a hose wall; Figure 4 is a perspective view of a hose and shows part of the hose cut away; and Figure 5 illustrates a preferred net structure according to the invention. Figure l illustrates an inventive hose 10. The hose 10 is compriεed of an outer rubber layer 11, a reinforcement layer 12 and an inner rubber layer 13. The outer rubber layer 11 has a thickness of 1-2 mm, at least in the case of suction hoses, and is comprised of a rubber of the lowest possible density. Examples of suitable qualities in this regard are EPDM, SBR and NR. The reinforcement layer suitably has a thickness of 1-2 mm and is comprised of thermoplastic, suitable qualities in this regard being polyester or poly- amide, for instance polya ide 12 (PA12). In the case illus¬ trated in Figure 1, the outer parts of the reinforcement layer 12 overlap and adhere to one another. The inner rubber layer 13 is made of εo-called Food Grade-type rubber and εuitably has a thickness of 1-2 mm.

Figure 2 shows a hose 10 similar to that shown in Figure 1 but with the exception that the reinforcement layer 12 does not fully embrace the inner rubber layer 13 and therewith leaves an area in which the outer and the inner rubber layers (11, 13) are in direct contact with one another along a surface 14, these rubber layers generating strong adhesion forces in the vulcanized process. For the sake of illustra¬ tion, no mesheε have been shown in the reinforcement layer 12.

Figure 3 is an enlarged view of part of the hose 10 shown in Figures l and 2. The section has been laid transversely through the meshes in the reinforcement layer 12, and hence only the longitudinally extending threads in the reinforce- ment layer 12 are shown. There is no adhesion between the threads of the reinforcement layer 12 and respective contact surfaces 15 of the rubber layers 11, 13, although these surfaces are in very close mechanical contact. In this illustration adhesion of the connecting surface 14 between the two rubber layers 11, 13 is seen only between the threads in the reinforcement layer 12. Figure 4 illustrates a preferred hose 10. The illustrated hose has been cut away to show the three layers of the hoεe, i.e. the outer rubber layer 11, the reinforcement layer 12 and meεhes 16 in a checkered pattern, and the inner rubber layer 13. Figure 5 εhowε a reinforcement layer 12 in a generally natural εize and in the form of a web in itε vertical direction. The left and the right defining edges 17 thus form the outer edges of the web, whereas the upper and lower defining lines 18 are εimply contemplated cutε acroεε the web. The reinforcement layer 12 is compriεed of vertic¬ ally extending round-εection threadε 19, aε illustrated in an enlarged cross-sectional view A, and obliquely extending bands 20. An example of the cross-sectional shape of the bands is shown in the separate enlarged view B. The threadε 19 and the bands 20 are joined together at their respective intersection points 21, for instance by fusion-bonding. The threads 19 and the bands 20 form an angle 21 other than 90°, this angle preferably lying within the range of 20-85°, more preferably about 55°. The distance between the vertical threadε 19 is suitably about 8-9 mm, while the distance between the bands is about 5-6 mm.

Claims

1. Lightweight rubber hosing particularly suitable for use aε suction hosing in milking machines, wherein the hosing comprises two mutually concentrical rubber layers and an intermediate reinforcement layer and iε capable of being bent to an angle of 180° with a bend diameter that correεpondε essentially to the inner diameter of the hoεe, while retain¬ ing the function of the hose aε a channel for flowing fluid, characterized in that the reinforcement layer embraces the inner rubber layer at least substantially around itε circum¬ ference; in that the reinforcement layer has the form of a thermoplaεtic net structure with the meεhes of the net structure forming an obliquely angled checkered pattern, said net structure being in one continuous single piece; and in that the two rubber layers are in close contact with the reinforcement layer without being joined thereto and are joined to one another through the mesh openings of the net structure.

2. Rubber hosing according to Claim 1, characterized in that the reinforcement layer is comprised of polya ide, polyester^' or some other thermoplastic material having corresponding properties.

3. Rubber hosing according to Claim 1 and Claim 2, charact¬ erized in that the reinforcement net structure is formed by fusion-bonding mutually crossing elements at their points of intersection.

4. Rubber hosing according to Claim 1 and Claim 2, charact¬ erized in that the reinforcement net structure is formed from a homogenous web of material by εo-called expansion.

5. Rubber hosing according to Claims 1-4, characterized in that the reinforcement net structure has a checkered pattern with a smallest angle in the range of 20-85°, preferably about 55 .

6. Rubber hosing according to Claim 3, characterized in that the net-forraing elements are solely in the form of threadε or in the form of threadε and bands which extend in mutually different directions.

7. Rubber hosing according to Claim 6, characterized in that the thread diameter iε about 0.8 mm and the band εize about 0.5 x 2.0 mm.

8. A method of producing rubber hoεing according to Claims 1-7, characterized by passing a web of reinforcement material to a nozzle for the continuous extrusion of two mutually concentrical rubber hosing layers; bending the web of rein¬ forcement material as it paεεeε through the nozzle into a ^■ round-εection having a diameter which iε eεεentially equal to the outer diameter of the extruded inner rubber layer and causing the web of reinforcement material to embrace the inner rubber layer; extruding the outer rubber layer onto the reinforcement layer; and vulcanizing the thus extruded and reinforced hosing so aε to obtain adhesion between the outer and the inner rubber layers.

9. The use of the rubber hosing according to Claimε 1-7 aε a vacuum hose in milking machines.

10. The uεe of the rubber hoεing in Claims 1-7 as a water hose or pneumatic hoεe for industrial or hobby use.