GB2031352A

GB2031352A - Improvements in or Relating to Retreading Pneumatic Tires

Info

Publication number: GB2031352A
Application number: GB7840953A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-10-18
Filing date: 1978-10-18
Publication date: 1980-04-23
Also published as: GB2031352B

Abstract

In a method of retreading a pneumatic tire, the tire casing is buffed to a predetermined profile to remove the old tread. An uncured cushion or bonding layer 18 having an integral belt 19 disposed therein is wrapped circumferentially around the casing and attached thereto. A precured tread having an integral belt 15 disposed therein is wrapped circumferentially over the cushion layer and attached to the casing and cushioned layer. The tire is then cured to form a unitary structure. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Retreading Pneumatic Tyres The invention relates to pneumatic tyres and more particularly to a method of retreading to form a tyre having a cross-bias belt pattern integral therewith.

In recent years, tyres having reinforcing belts have become increasingly popular with the motoring pubiic. Such tyres characteristically have an increased life span and have generally greater traction when compared to unbelted tyres. Furthermore, the belt structure tends to increase the tyre's resistance to puncturing and increases the strength of the tyre at high speeds.

Reinforcing belts, particularly when made an integral part of the tread, also reduce tread squirm, particularly in retreaded tyres, thereby increasing the tread's wear resistance.

In retreading, it is particularly difficult to apply the belts directly to the tyre casing. The belt structure must be supported while the tyre is being retreaded. This can be difficult and complicated, particularly if a cross-bias belting system is to be applied.

According to the present invention there is provided a method of retreading a tyre by mounting a new tread on a pneumatic tyre casing, said casing having been buffed to a predetermined profile, comprising the steps of providing a precured tread having an integral belt, said belt comprising a plurality of strands disposed in a preselected orientation with respect to the tread, providing a layer having an integral belt, said belt comprising a plurality of strands disposed in a preselected orientation with respect to said layer, wrapping said layer around and securing said layer to said casing so that the strands in said layer are situated in a first orientation with respect to said casing and wrapping said tread around and securing said tread to said casing over said layer, so that the strands in said tread are situated in a second orientation different from said first orientation.

In a preferred method according to the invention a cured tread is formed having an integral belt, the individual strands of which are disposed in a preselected orientation. A cushion or bonding layer is formed also having an integral belt layer, the strands of this layer being disposed in a second orientation. The tyre casing is cleaned and buffed to a pre-selected profile. The cushion layer is then wrapped circumferentially around and secured to the casing with the belt strands oriented in a first direction. The tread is then wrapped circumferentially around the cushion layer and the casing with the belt strands therein disposed in a second direction at an angle with respect to the first direction. The tread is then secured to the tyre casing and the cushion layer.

The entire unit is then vulcanized to form a unitary structure.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a front elevational view of a tread used in the herein-described method, showing the belt structure in phantom lines; Fig. 2 is a sectional view taken along lines Il- II of Fig. 1; Fig. 3 is a front elevational view of an intermediate bonding or cushion layer used in the herein-disclosed method, showing the belt in phantom lines; Fig. 4 is a sectional view taken along lines IV IV in Fig. 3; and Fig. 5 is a perspective view, partially in section, showing the tyre illustrating the method of the present invention.

With reference to the figures, there is shown a tyre 10 made according to the herein disclosed method. Tyre 10 is a retreaded tyre made from a casing 11 in which the worn tread pattern has been buffed away to leave a rough, evenly contoured surface 12 having a predetermined profile and ready to receive new tread components. The casing may be of any type known in the art and may inciude beads and plies (not shown).

In accordance with the invention, a tread 1 3 is constructed having an elongated dimension and a narrower width dimension. The tread includes butt ends 14 disposed at an angle to the elongated direction. The butt ends are disposed non-orthogonally to the elongated dimension.

The tread has included therein a belt 15, which may comprise strands of steel or of a synthetic or natural cord. The individual strands are disposed in the tread parallel to the butt end 14. The tread 13 further includes a tread surface 1 6 contoured and profiled to the tread pattern to contact the road, and an upper bonding surface 1 7. The tyre tread 13, including the steel belt as an integral part thereof, is cured.

With reference to Fig. 3, an uncured cushion or bonding layer 1 8 is provided including a belt 1 9 disposed therein and integral therewith. The cushion layer 18 is preferably an uncured vulcanizable gum rubber or another suitable elastomeric material and is formed having an elongated direction and two butt ends 20 at a non-orthogonal angle to the elongated direction.

The belt embedded in the layer 1 8 is comprised of a plurality of strands disposed between and parallel to butt ends 20.

In accordance with the method, a layer of cement is placed over a contoured surface 12, and cushion layer 1 8 is wrapped circumferentially around casing 11 thereover. The ends 20 of layer 1 8 are brought to abut each other, with the strands of belt 19 disposed in a preselected orientation. Layer 1 8 is then stitched to the tyre casing 11.

Subsequent to this operation, the tread 1 3 is wrapped circumferentially around casing 11 over cushion layer 18 with surface 1 7 inward and adjacent layer 18. The tread is wrapped so that the strands of belt 1 5 are disposed at a second orientation at an angle to that of the strands of belt 19. Because the tread 13 is precured, to bond ends 14 together, they are coated with a layer of cement and are both brought to abut a thin layer of uncured rubber. The tread is then stitched to the cushion layer 18 and to the casing underneath.

The entire tyre 10, including the casing 11, bonding layer 18 and tread 13 is then cured to form a unitary structure. Thus a tyre is formed having integral belt structure including belts 1 5 and 19, which form a crossed or X pattern. The reinforcement pattern serves to reduce the tread squirm, which enhances tyre wear characteristics and results in a retreaded tyre having increased safety characteristics.

The cross-bias pattern disclosed herein is merely for illustrating purposes and is not to be taken as limiting. In the disclosed embodiment, the belts 15 and 1 9 lie parallel to respective butt ends 14 and 20, so that the butt ends do not require a shortening of any particular belt proximate thereto, or so that the belt strands do not extend through the butt ends.

It will thus be seen that the objects set forth above, along with those made apparent from the preceding description, are efficiently attained, and, since certain changes may be made in carrying out the above method without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A method of retreading a tyre by mounting a new tread on a pneumatic tyre casing, said casing having been buffed to a predetermined profile, comprising the steps of: providing a precured tread having an integral belt, said belt comprising a plurality of strands disposed in a preselected orientation with respect to the tread, providing a layer having an integral belt, said belt comprising a plurality of strands disposed in a preselected orientation with respect to said layer, wrapping said layer around and securing said layer to said casing so that the strands in said layer are situated in a first orientation with respect to said casing and wrapping said tread around and securing said tread to said casing over said layer, so that the strands in said tread are situated in a second orientation different from said first orientation.

2. A method as set forth in claim 1 wherein neither said first orientation nor said second orientation extend circumferentially around the tyre casing or perpendicular thereto.

3. A method as set forth in claim 2 wherein said tread is provided with two parallel butt ends, said butt ends being parallel to the strands contained therein.

4. A method as set forth in claim 2 wherein said layer is provided with two butt ends, said butt ends being parallel to the strands contained therein.

5. A method as defined in claim 3 further comprising the steps of coating both butt ends with a layer of cement prior to wrapping said tread around said casing, and of applying a layer of uncured rubber between said butt ends after said tread has been so wrapped.

6. A method as recited in claim 1 wherein said layer-securing step includes a step of cementing the layer to the casing.

7. A method as recited in claim 1 wherein said layer-securing step includes a step of stitching said layer to said casing.

8. A method as recited in claim 1 wherein said tread-securing step includes a step of stitching said tread to said layer and said casing.

9. A method as recited in claim 1 further comprising the step of curing the retreaded tyre.

10. A method of retreading a tyre substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

1 A tyre retreaded by a method as claimed in any one of the preceding claims.