Tyres provided with repair plaster

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Patent Board

The Netherlands © Publication number: 9302004 © A REFUND © Application number: 9302004 © Submission date: 19.11.93 © lnt.CI.⁶:

B29C 73/10 © Launched:

16.06.95 IE 95/12

Applicant (s):

Wilhelmus Maria Cornells Aarts te

Velp © Inventor (s):

Wilhelmus Maria Cornells Aarts in Velp © Authorized representative:

Mr. GL Kooy et al

Vriesendorp &amp; Gaade patent office Kuyperstraat 6 2514 BB The Hague © Tires with repair plaster © Radial pneumatic tire, which is provided with a repair plaster on the inside of the cheek at the location of damage to the cord layer of the carcass. The repair plaster is made up of at least one rubber layer, which is adhered directly to the inside of the wall of the tire, a layer of cords thereon, parallel to the cords of the carcass of the tire, a rubber layer on top of it, and a textile layer on top of it. flexible knitting construction, such as a so-called “Stabilizes Fabric”, which is finally covered with a rubber layer and can be stretched elastically in radial and circumferential directions.

NL A 9302004

The documents attached to this sheet are a print of the originally submitted description with claim (s) and any drawing (s).

Tires with repair plaster

The invention relates to tires provided with repair plaster applied thereto at the location of damaged locations on those tires. Radial pneumatic tires, such as those of tractors, earth-moving machines, etc., in particular, are subjected to large deformations at low speeds. The invention further relates to a repair patch for tires.

A repair tire 10 for pneumatic tires known from practice consists, for example, of a rubberised fabric, the warp and weft of which are made of, for example, nylon or polyester yarn, which fabric is provided on both sides with a rubber layer, whereby a flexible rubber plate is obtained, non-vulcanised rubber with a thickness of for example 2 to 4 mm.

If, for example, a tire is damaged on the side, such that the carcass cords are damaged or broken, a repair plaster is applied to the inside of the tire for the purpose of passing through the forces of the broken or damaged carcass cords. It is not uncommon for some layers of the aforementioned plaster to be applied one above the other, the lower layer applied directly to the inside of the carcass having larger dimensions than the layer applied thereon and so on. The patch package of a tire so repaired may even consist of four layers with a total thickness of 10 to 15 mm.

In order to transfer the forces from the cords to the fabric of the plaster as well as possible, the inside of the band at the location of the plaster to be applied is stripped of rubber cover as far as possible up to the cord layer. The plaster is preferably prepared to the correct dimensions and layer thickness before it is applied to the inside of the tape. In general, an adhesive is applied between the inside of the tape and the plaster. After the repair patch has been built up, the patch is vulcanized onto the tire, preferably in an oven at a temperature and time most favorable for the particular tire / patch combination. In general, this vulcanization is combined with the vulcanization of a new tread on the tire.

The prior art as described above has the disadvantage that the band is much stiffer at the location of the plaster construction than at other places of the sides. When applying multiple layers, this increase in stiffness is even greater. As a result of this discontinuity, stress concentrations will occur at the transition from the plaster area to the cheek, as a result of which new damage to the cheek of the carcass, such as cracks in the rubber, will occur faster than desired.

European patent application 0 279 901 discloses a rubber insert for repairing radial pneumatic tires, which consists of a package of rubber layers, namely a number of inner rubber layers, without cords, a rubber layer with parallel, sloping synthetic cords, and a rubber layer with radial towards converging metal cords, with a rubber block protruding outwards, which is intended to fit into a cut-out recess in the cheek of the tire to be repaired.

During the repair, an area around the damaged cheek portion is completely cut away while breaking the cords there. After placement of the insert in the rubber block fitting into the recess, the aforementioned metal cords should extend in line with the cord remnants present in the tire.

The size of the inserts should therefore be related to the size of the tire, so that for repairing a variety of tires the same number of sizes of inserts must be kept in stock.

A further disadvantage of this method of repair is that high demands are made on the accuracy when cutting away the area of ​​the cheek. Moreover, more material is hereby replaced than is actually necessary, which means a waste of material and results in more waste.

A comparable insert is known from European patent application 0 353 313. Herein the rubber layer with synthetic cords is replaced by one or more layers of rubberised fabric, the weft threads of synthetic fibers of which are at an angle with respect to the radial or not. The imperfections discussed above are also present with this insert.

The present invention has for its object to improve the foregoing by providing a tire repaired with a repair plaster, the service life of which will be considerably increased. To this end, the invention provides the features of claim 1.

In contrast to the conventional fabric construction in repair plaster, a combination of cords is used in the present invention to transmit the forces of the broken or damaged carcass cords and a flexible technical knitting structure that is at least elastic in the circumferential direction of the tire. This forces the introduced forces to be leveled and distributed, without affecting the flexibility perpendicular to the cord direction.

Preferably the flexible technical knitting construction is also elastic in the radial direction.

Preferably, a so-called sandwich construction is used, consisting of at least one inner layer of technical knit and an outer cord layer, separated from each other and both covered by a rubber layer. Sandwich constructions with two layers of technical knit, between which a cord layer, each separated by and covered with a rubber layer, are also possible. With very heavy constructions, a larger number of layers, alternating technical knitwear, rubber layer and cord layer, can be applied, the outer sides being covered with a rubber layer.

The material of the knit can be either aramid, nylon or polyester. The cords are, for example, steel cord or aramid cord for tire reinforcement.

The technical knit can be designed as described in European patent 0 425 099, the text of which is incorporated herein in its entirety by reference thereto. From this document the so-called 'Stabilized Fabric' is known, in the form of a knit, which is provided with stabilizing means such as parallel threads, which are able to break or flow under the influence of tension, without adversely affecting the knit itself . These threads ensure that the knit is initially inelastic and patterned in the direction of the threads, which is advantageous in the process step of cutting the knit and embedding it in a rubber matrix, but will then, inter alia, during the shaping the end product, such as in rubber hoses, or during deformation of the cheeks of a tire, can easily collapse to release the elastic properties of the knit.

The invention will be explained below with a description of a preferred exemplary embodiment of the patch, with reference to the accompanying drawing, in which:

8302004 Figure 1 shows a section and inside view of a radial tire in which a repair plaster according to the invention is arranged on the inside at the location of the damaged cord layer in the carcass.

Figure 2 shows a section according to II-II in Figure 3 of a plaster according to the invention comprising a cord layer and a layer of technical knit; and Figure 3 shows a plan view in partial section of the repair patch shown in Figure 2.

Figure 1 shows a cross-section of a radial tire 1 with cord layer 2 and belt 3, combined with a view from the inside thereof. The cord layer 2 was damaged at the area of ​​4 in the cheek 10 and covered during repair with a sandwich plaster 5 according to the invention. The cords included in the plaster 5 (see Figs. 2 and 3) extend in the directions B.

Figure 2 shows a cross-section of sandwich plaster 5 with steel cords 6 and technical knit 7 of aramid fiber threads. The space between the cords 6 and the knit 7 is filled with rubber layer 8a, and the outside and inside are covered with rubber layers 8b and 8c.

The layer of knit 7 is located on the side of the plaster 5, which is intended to be turned inwards in the tape, and is elastically stretchable in two perpendicular directions C and D, so that, after placement on the inner surface of the cheek area cut out as far as the cords 2, surrounding the damage 4, the knit can follow the movements in the rubber 8 and the plaster can conform to the deformations in the cheek as a result of bending forces in both radial and tangential planes, without cracking-causing stress concentrations occurring.

Figure 3 shows a top view of a sandwich plaster, wherein on the inside marked with Ά 'the inner layer with the knit and the rubber layer are partially omitted, so that the cords are visible. Note the parallel threads 9, which are characteristic of a Stabilized Fabric, as described in European patent 0 425 099. During use of the tape, these threads will quickly collapse under the forces occurring, so that the knit will also be elastic in the directions D .

The plaster can be supplied in one standard size and made to measure in the workshop. In order to simplify the placement, at least the outside of the plaster, i.e., for example rubber layer 8b, can be provided with an adhesive layer, which in turn is covered by a removable cover sheet.

Example

A repair plaster for a 26.5 R 25 earth-moving machine tire has a size of 1 = 430 and b = 340 mm (Figure 3), and contains one cord layer of aramid cord 3360 dtex x 2, with a density of 10 cords per 10 mm . The breaking strength of a cord is around 1000 N, breaking elongation around 4.7%. The highest strength of the patch is therefore approximately 10,000 N / cm perpendicular to the cord direction. The patch also contains a technical polyester knit. The total thickness of the plaster including the intermediate and covering rubber layers is approximately 3 mm.