GB2221929A

GB2221929A - Steel cord for reinforcing elastomers

Info

Publication number: GB2221929A
Application number: GB8918860A
Authority: GB
Inventors: Hans W Schnecko; Wilhelm Hamacher
Original assignee: SP Reifenwerke GmbH
Current assignee: SP Reifenwerke GmbH
Priority date: 1988-08-19
Filing date: 1989-08-18
Publication date: 1990-02-21
Anticipated expiration: 2009-08-18
Also published as: JPH02200881A; GB2221929B; JPH0672373B2; FR2635541A1; GB8918860D0; DE8810534U1

Abstract

The steel cord consists of a first group of non-twisted steel core filaments 1, 2 which extend parallel to one another and a second group of steel filaments 3, 4, 5 which are coiled around the first group. The first group may be formed by three steel filaments and the second group may be formed by two steel filaments. Both groups are surrounded by an outer coil 6 the length of lay of which is smaller than the length of lay of the second group. <IMAGE>

Description

T4ffi & Tr-;. ( hr; ~ THE REINFoRCEMENT OF ELASTEIC PRODUCTS The invention relates to a steel cable for the reinforcement of elastomeric products, in particular steel cord for breaker materials for use in vehicle tyres, the cable comprising a first group of non-twisted steel filaments which extend substantially parallel to one another and form the cable core and a second group of steel filaments which are helically coiled around the first group, with the second group of steel filaments being in linear contact with one another, and with each filament of the second group lying permanently opposite to a filament of the first group.

It is required of steel cables or steel cords of this kind that they not only enter into a good bond with the respective material to be in reinforced but rather they must also be so laid out that their mechanical characteristics remain as unchanged as possible in long term use, and above all so that no deterioration of these characteristics occurs due to the penetration of moisture, which leads to loss of bonding and rust formation.

The object underlying the invention is to develop a steel cable of the initially named kind in such a way that, despite the possibility of manufacturing it simply and economically, the requirement of permanent resistance to corrosion is fully satisfied, and so that1 at the same time, a substantially higher tensile stiffness can be achieved in comparison to customary constructions.

This object is satisfied in accordance with the invention substantially in that the first group consists of two or three steel filaments; and the second group consists of two or three steel filaments and in that both groups are surrounded by an outer helical coil the length of lay of which is smaller than the length of lay of the second group of steel filaments.

Through the combination of mutually parallel steel filaments of the first group with two or three helically coiled steel filaments of the second group one ensures, while simultaneously guaranteeing a good basic compressive stiffeness, that no outwardly closed off regions exist along the length of the cable which would prevent penetration of the elastomeric material.

I.e. the basic construction of the steel cable of the invention ensures that all the steel filaments are embedded with their full surface area into the elastomeric material, and thus that the effect of moisture on the steel filaments leading to loss of bonding and rust formation is precluded.

A surprising increase of the compressive stiffeness is obtained by the outer coil which is provided without in any way impairing the indicated charcteristics of the basic construction of the steel cable, so that the steel cable is particularly suited for use in breaker materials such as are preferably used in motor car tyres. The high compressive stiffness which is achieved leads to a substantial improvement of the handling and of the abrasion resistance.

Particularly advantageous developments of the invention are set forth in the subordinate claims.

Embodiments of the invention will now be explained with reference to the drawing in which are shown: Fig. 1 a schematic representation of a steel cord for use in breaker materials for vehicle tyres, Figs. 2 and 3 schematic illustrations of a further embodiment of a steel cord intended for vehicle tyres, without an outer coil, and Figs. 4 and 5 schematic illustrations of embodiments of steel cords in accordance with Figs. 2 and 3 with an outer coil.

The steel cord of Fig. 1 consists of two substantially parallel steel filaments 1, 2 which form the core of a steel cord. It is however also possible in the context of the invention to use three such steel filaments for the core. Both steel filaments 1, 2 have the same diameter and can be somewhat deformed over their length as a result of the manufacturing process, however this deformation would only represent a non-intentional insignificant side effect with regard to the function of the steel cord of the invention.

The two mutually parallel steel filaments 1, 2 are surrounded by three coiled steel filaments 3, 4, 5 which are in linear contact with one another and jointly form a band-like structure.

Each of the three steel filaments 3,4,5 lies permanently opposite a steel filament 1, 2 when considered over the length of the steel cord.

As a result of this relative position of the straight steel filaments 1, 2 and of the coil steel filaments 3, 4, 5 it is ensured that a cord structure results which is open throughout, which in turn ensures that the respective elastomer, or, in the case of manufacturing breaker plys for vehicles, the rubber of this cord structure, can penetrate fully, and thus that all steel filaments are embedded over their full area in rubber and protected against attack by moisture.

Fig. 2 shows a variant in which the mutually parallel steel filaments 1, 2, 7 of the core form a group of three. In this embodiment the band-like structure of the group of two which is coiled around the core is dispensed with and a mutual twisting of these steel filaments 8, 9 is effected whereby particularly advantageous physical characteristics can be achieved.

In the embodiment of Fig. 2 the direction of twisting of the outer group of two 8, 9 is directed in the same direction as the direction in which the filaments 8, 9 are coiled around the group of three 1, 2, 7.

The embodiment of Fig. 3 is distinguished from the variant of Fig. 2 in that the direction of twisting of the outer group of two is oppositely directed to the direction in which the steel filaments 8, 9 are coiled around the first group 1, 2, 7. The length of lay of the twisting is preferably of an amount the same as or smaller than the length of lay of the coiled steel filaments.

The full area embedding of all steel filaments into the respective elastomeric material not only prevents the occurrence of dangerous corrosion effects in long term use but also ensures that the originally present defined and specified mechanical characteristics remain unchanged in long term use.

The high compressive stiffness which can already be obtained by the use of two or three coiled steel filaments 8, 9 and 3, 4, 5 respectively is increased quite substantially in a surprising manner and almost doubled by the use of an outer coil 6 in the form of a steel filament the length of lay of which is smaller than the length of lay of the steel filaments 3, 4, 5 and 8, 9 respectively which are coiled around the core.

Fig. 4 shows the embodiment of Fig. 2 in conjunction with the advantageously acting outer coil 6 and in Fig.

5 the embodiment of Fig. 3 is likewise shown with the outer coil 6, and the different relative positions of the individual steel filaments to one another which result from the different coiling and twisting directions can also be clearly seen from these Figures.

The length of lay of the outer coil 6 lies in the range from 2.5 to 10 mm and preferably amounts to 3.5 to 5 mm. The length of lay of the steel filaments 3, 4, 5 coiled or wound around the core filaments 1, 2 is substantially larger and preferably has approximately twice of this value.

The diameter of the steel filament forming the outer coil 6 lies in the range from 0.10 to 0.25 mm and amounts preferably to 0.12 to 0.15 mm, with this diameter being generally somewhat smaller than the diameter of the steel filaments 1, 2, 3, 4 and 5 which preferably have the same diameter as each other.

Claims

Patent Claims:

1. Steel cable for the reinforcement of elastomeric products, in particular steel cord for breaker materials for use in vehicle tyres, the cable comprising a first group of non-twisted steel filaments which extend substantially parallel to one another and form the cable core and a second group of steel filaments which are helically coiled around the first group, with the second group of steel filaments being in linear contact with one another, and with each filament of the second group lying in particular permanently opposite to a filament of the first group, characterised in that the first group consists of two or three steel filaments (1, 2, 7) and the second group consists of two or three steel filaments (3, 4, 5; 8, 9); and in that both groups are in particular surrounded by an outer helical coil (6) the length of lay of which is smaller than the length of lay of the second group of steel filaments (3, 4, 5; 8, 9).

2. Steel cable in accordance with claim 1, characterised in that the diameter of the steel filaments (1, 2, 7; 3, 4, 5; 8, 9) are the same, at least within the individual groups.

3. Steel cable in accordance with claim 1 or claim 2, characterised in that the outer helical coil (6) comprises a steel wire the diameter of which is the same as or smaller than the diameter of the steel filaments (1, 2, 7; 3, 4, 5; 8, 9) of the two groups.

4. Steel cable in accordance with claim 3, characterised in that the diameter of the steel wire forming the outer coil (6) lies in the range from 0.10 to 0.25 mm, preferable in the range from 0.12 to 0.15 mm.

5. Steel cable in accordance with one of the preceding claims, characterised in that the length of lay of the outer coil (6) lies in the range from 2.5 to 10 mm and preferably in the range from 3.5 to 5 mm.

6. Steel cable in accordance with one of the preceding claims, characterised in that the length of lay of the helically twisted steel filaments (3, 4, 5) of the second group is approximately 1.5 to 2 times as large as the length of lay of the outer coil (6).

7. Steel cable in accordance with one of the preceding claims, characterised in that the mutually parallel steel fila ments (1, 2, 7) of the first group form a group of three and in that there is associated with this group of three a group of two helically twisted steel filaments (8, 9) which surrounds it and which are mutually twisted.

8. Steel cable in accordance with claim 7, characterised in that the twisting direction of the outer group of two is preferably oppositely directed to that of the steel filaments (8, 9) helically coiled around the first group.

9. Steel cable in accordance with claim 7 or claim 8, characterised in that the length of lay of the helically coiled group of two is of an amount the same as or smaller than the length of lay of the helically coiled steel filaments (8, 9).