GB2240520A

GB2240520A - Repairing tyres

Info

Publication number: GB2240520A
Application number: GB9002379A
Authority: GB
Inventors: Stanley Charles Elderfield
Original assignee: ABRASION RESISTANT LININGS Ltd
Current assignee: ABRASION RESISTANT LININGS Ltd
Priority date: 1990-02-02
Filing date: 1990-02-02
Publication date: 1991-08-07
Anticipated expiration: 2010-02-02
Also published as: GB2240520B; GB9002379D0; KR910014498A

Abstract

A method of curing a tyre repair in which heater pads 51, 54 are applied to the portion of the tyre to be repaired and pressure is applied to hold the pads in position, the improvement being that an inner inflatable bag 53 is used to hold the inner 51 in place, which bag has a relatively flexible zone to be positioned near the repair area. This enables wide cross-section tyres, of which the inner surface may be sharply contoured, to be repaired. The inflatable bag 53 may be of rubber encased in a nylon cover or covers which in the region of the relatively flexible zone are made of elasticated material. <IMAGE>

Description

IMPROVEMENTS RELATING TO THE REPAIR OF TYRES The present invention relates to a method and apparatus for curing a tyre repair. The invention is particularly applicable to the repair of large tyres for trucks, tractors, graders, earth movers and the like with radial ply carcasses, but may be applied to tyres of other sizes and to tyres with cross ply carcasses. Although the invention is particularly applicable to the repair of tyres which have become damaged in use, it may also be applied to the rectification of faults occurring in the manufacture of the tyres.

Our earlier U.K Patent Specification 1 483 894 discloses a method of repairing a tyre which includes the steps of applying an inner heater pad to the inner surface of the portion of the tyre to be repaired, applying an outer heater pad to the external surface of the portion of the tyre to be repaired, and applying pressure to hold the inner and outer heater pads firmly in place.

The present invention is concerned with solving the problem which arises in this known method where the inner surface has a more sharply contoured shape.

Modern tyres with wide cross-sections and low profiles are examples where this problem arises.

Accordingly, an inner inflatable bag is provided with a relatively flexible zone located adjacent the inner surface of the tyre portion to be repaired and the zone is so flexible as to accommodate the inner contour of the tyre. In saying that the zone is relatively flexible, this is relative to the remainder of the inner inflatable bag.

The spacer bag is usually made from rubber encased in a nylon cover or covers and in the region of the flexible zone the nylon covers are made of an elasticated material allowing that area to have full flexibility while the remainder of the bag is restrained by the nylon cover.

The flexible zone should be positioned so that it allows the pressure to be exerted evenly on the critical side wall area of the tyre and this is particularly important when repairing radial and low profile tyres.

An embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Figure 1 is a perspective view of a tyre and the repair apparatus; and Figure 2 is a section on the plane II-II in Figure 1.

A tyre 1 whose tread has received damage has the necessary repair plug 50 placed in the damaged area and the plug is covered on the inside with a flexible electric heater pad 51. A spacer air bag 53 is then positioned within the U formed by the tyre to hold the heater pad 51 in place. The spacer bag 53 has a rectangular zone of greater flexibility than the remaining part of the spacer air bag 53 and of a shape so as to cover the region shown by the arrows 56. Thus half of the tyre is adequately covered.

The spacer bag is of sufficient size and shape to provide adequate support within the tyre. A heater pad 54 is then placed on the outside of the tyre in the region of the plug 50; this pad is then covered by an inflatable bag 8 and a harness 9 is passed around the outside of the bag 8 and through the opening in the middle of the tyre.

The harness 9 consists of several straps 7 (three are shown but there are usually about six) of nylon webbing, and a buckle 11 is provided for each of the straps 7. The straps lie generally side by side and each buckle has a lever 10 and ratchet 12 so that it can be individually tightened after the end has been passed through the buckle.

The apparatus includes a control panel 20. Two air lines 21, 22 lead from pressure regulators 24, 25 respectively which are mounted on the panel. The regulators 24, 25 are supplied with compressed air through a common non-return valve and two on/off valves 27, 28, one for each regulator. The pressure in the lines 21, 22 is indicated by gauges 30, 31 respectively. The air line 21 leads to the spacer air bag 53,'and the air line 22 leads to the air bag 8.

The panel has two electrical sockets 33 to receive plugs 34 connected by leads 35 one to the outer heater pad 54 and one to the inner heater pad 51. A temperature-sensing thermocouple is fitted in a pocket on the back of each pad, and the lead 35, plug 34 and socket 33 associated with each pad from electrically independent connections, on the one hand between the thermocouple and a thermostat associated with that pad and mounted on the control panel 20, and on the other hand between the heating element of the pad and the thermostat. The thermostats associated with the two pads 51, 54 are controlled by a single knob 37, but act independently to control the current passing through the associated heater pad to maintain the temperature at the pad at the value set by the knob 37. The time for which the temperature is maintained can be controlled by a timer 36.

When the tyre has been prepared in the manner described above, the plugs 34 are inserted in the sockets 33. The valve 27 is turned on to admit air to the air line 21 to raise the pressure in the spacer air bag 53 to the level pre-set by the regulator 24 which may, for example, be between thirty and sixty pounds per square inch. Forty pounds per square inch might be used in a typical case. The valve 28 is then turned on to admit air to the air line 22 to inflate the bag 8 to the pressure set by the regulator 25, which should be lower than that set by the regulator 24. Thus the heater pads 51, 54 are firmly pressed against the inner and outer surfaces of the tyre in the region to be repaired. The timer 36 is then turned to the time for which heating is required. The heater pads then heat up to the temperature set by the knob 37 and remain heated for the time required to cure the plug 50 and are then switched off automatically. The air from the bag 8 can then be exhausted by turning off the valve 28; and the harness 9 and the outer heating pad 54 are then removed. The tyre is allowed to cool to below 1800F, about one hour or so, and the valve 27 is turned off to deflate the spacer air bag 53. The spacer air bag 53 and the inner heating pad 51 are then removed from the tyre. The repair is then trimmed.

Claims

1. A method of curing a tyre repair including the steps of applying an inner heater pad to the inner surface of the portion of the tyre to be repaired, applying an outer heater pad to the external surface of the portion of the tyre to be repaired and applying pressure to hold the pads firmly in place, characterised in that the inner heater pad is maintained in position by an inner inflatable bag which has a relatively flexible zone located adjacent the inner surface of the portion of the tyre to be repaired and the zone is so flexible as to accommodate the inner contour of the tyre.

2. A method according to Claim 1 in which the bag is made of rubber having a nylon reinforcing cover which is elasticated in the region of said flexible zone.

3. A method of curing a tyre repair according to Claim 1 and substantially as herein described.

4. Apparatus for curing a tyre repair comprising an inner heater pad to be applied to the inner surface of the tyre in the area of the repair, an outer heater pad to be applied to the outer surface of the tyre in the area of the repair and means for applying pressure to hold the pads firmly in place, said means including an inner inflatable bag for maintaining the inner inflatable bag in position which has a relatively flexible region to be located adjacent the inner surface of the tyre in the region to be repaired and the zone being so flexible as to accommodate the inner contour of the tyre.

5. Apparatus according to Claim 4 in which the inner inflatable bag is of rubber having a nylon reinforcing cover which is elasticated in the region of said flexible zone.

6. Apparatus substantially as herein described with reference to the accompanying diagrammatic drawings.