WO1992008603A1

WO1992008603A1 - Method for rebelting tires

Info

Publication number: WO1992008603A1
Application number: PCT/US1991/008357
Authority: WO
Inventors: Michael J. King
Original assignee: Oliver Rubber Company
Priority date: 1990-11-20
Filing date: 1991-11-08
Publication date: 1992-05-29
Also published as: AU9075291A

Abstract

A method for rebuilding a steel-belted radial tire to restore damage belting as well as tread rubber is disclosed. The method comprises the fabrication on a mandrel (10) of a continuous, annular sub-assembly comprised of one or more layers of rubber coated steel belting material (18) plus strips of uncured rubber bonding material and capped by an outer strip of precured tread rubber (30). The sub-assembly is cured on the mandrel (10) at elevated temperature and pressure to form an integral unit. Following the preparation of a tire casing by removal of its tread rubber and damaged or worn belting a layer of uncured bonding rubber is applied to its outer tread surface. The sub-assembly is then installed on the prepared casing and the full assembly is cured in a chamber at elevated pressure and temperature.

Description

2

3 1

4

5 METHOD FOR REBELTING TIRES

⁶ SPECIFICATION 7

8 g This invention relates to a method for rebuilding Q tires and more particularly for rebelting and retreading 2 steel-belted radial tires with belts that have become worn -_? or damaged. 3 ₄ Background of the Invention 5 Radial tires have long utilized annular belts of g steel wire that are embedded in the tire casing under the 7 tread rubber to give the tire strength and durability. 8 Often, during the use of the tire, an upper steel belt 9 layer became damaged or corroded. Heretofore this o prevented the tire from being repaired or recapped and i resulted in its destruction. For larger radial tires used 2 °n trucks, the loss of expensive tires due to steel belt 3 damage presented a significant cost problem. 4 It is therefore a general object of the present 5 invention to provide a method and an apparatus for 6 rebuilding damaged or worn tires by rebelting and retreading the original tire casing. Another object of the invention is to provide a method for rebelting a tire which utilizes conventional tire making equipment and can be carried out with an efficient use of labor.

Summary of the Invention In accordance with the principles of the invention a series of method steps are performed for: (1) preparing a tire casing for rebelting by removing old tread rubber and an outer layer of steel belting material; (2) building on a mandrel a continuous belt comprised of new

1 steel belting embedded within layers of uncured rubber; (3)

2 curing the belt structure; and (4) installing the belt on

3 the prepared tire casing. After the prepared belt has been

4 installed, a precured layer of tread rubber is installed on

5 the tire over the continuous belt to form a complete tire

6 assembly and the assembly is then placed in an autoclave

7 under a preselected, elevated temperature and pressure to

8 cure the bonding layers for both the belting and the tread

9 rubber.

10

Other objects, advantages and features of the

11 invention will become apparent from the following detailed

12 description thereof, presented in conjunction with the

13 accompanying drawing.

14

15

Brief Description of the Drawing

16

Fig. 1-5 illustrates a series of method steps

17 employed for making a continuous steel belted tread rubber

18

19 sub-assembly in accordance with principles of the present

20 invention.

-. Fig. 5A is a view in section taken along the line

22 5A-5A of Fig. 5.

Fig. 6 is a view illustrating the preparation of 23 a tire casing by removal of tread rubber and old steel 24 - belting according to the method of the invention.

Fig. 7 is an exploded view in perspective showing

26 27 a belted tread rubber sub-assembly being installed on a 28 prepared tire casing. 29 Fig. 8 is a view in perspective of a completed 30 rebuilt tire that has been provided with a rebelted tread

₃₁ rubber sub-assembly according to the invention.

₃₂ Fig. 9 is an enlarged fragmentary view in section

₃₃ of the completed rebuilt tire taken along line 9-9 of

₃₄ Fig. 8.

35 36 37 38 Detailed Description of Embodiment

1

The present invention comprises a method for 2 simultaneously rebelting and retreading or recapping a 3 steel-belted radial tire that has been severely worn or 4 damaged. Relatively large truck tires of the radial type 5 are particularly adaptable for such rebuilding or 6 rehabilitation because the tire casing is usually quite 7 substantial structurally and it is economically beneficial 8 to rebuild a tire rather than to destroy a worn or damaged 9 casing. In broad terms, the method according to the 10 invention involves three major steps, namely (1) the 11 fabrication of a continuous, annular sub-assembly comprised 12 of new steel belting and tread rubber; (2) the preparation 13 of the worn or damaged tire casing; and (3) the 14 installation of the sub-assembly on the prepared tire 15 casing. 16

With reference to the drawing, Figs. 1 and 2 show 17 a circular mandrel 10, preferably of aluminum, on which 18 will be built a sub-assembly 11 comprised of new steel 19 belting and pre-cured tread rubber. The mandrel has an 20 outer cylindrical surface 12 that is slightly convex and 21 with a width that is somewhat greater than the tread width 22 of a standard tire. In a first preliminary step of the 23 method (Fig. 1) , the mandrel is mounted on an expandable 24 hub 14 of a conventional tire builder apparatus. A small 25 amount of rubber cement 16 is first applied to the outer 26 surface of the mandrel to provide an initial tack for a 27 base layer of steel cord material 18 which is to be placed 28 29 on the mandrel. As shown in Fig. 1A, the steel cord material 18 comprises a flat strip of cured rubber of 30 31 constant width and thickness with bias angled steel wires ₃₂ 20 embedded therein. Generally, the thickness of the steel -₃ cord material 18 is around 0.050" and its width may vary

₃₄ depending on the width or size of the tire to be rebuilt.

₃₅ As the mandrel 10 is turned on the builder hub 14, the ,₆ steel cord material is applied around and firmly against ₃₇ the mandrel surface 14, being held in place by the cement 16. When the steel cord material is completely

1 around the mandrel, it is cut transversely, and its ends

2 are spliced to form a complete ring on the mandrel,

3 preferably on an angle in accordance with the cord material

4 as shown in Fig. 2. A spiked roller 22 is then used to

5 stitch the steel cord material 18.

6

As shown in Fig. 3, which combines several sub-

7 steps of the method, a second narrower layer 24 of steel

8 cord material forming a protector ply is applied on top of

9 the base layer 18. Thereafter, a pair of filler strips 26

10 of uncured rubber are applied along the opposite edges of

11 the protector ply layer 24. Now, a thin layer 28 of

12 uncured bonding gum having the same width as the base layer

13 18 is applied to the sub-assembly. It is cut to size and

14 its ends are held together.

15

Referring to Fig. 4, a strip of precured tread

16 rubber 30 now placed over the bonding layer 28 and wrapped

17 around the sub-assembly 11. In the conventional manner, it

18 9 is cut to size and with its ends abutting, they are spliced together, as by staples. At this point, a wieking pad 32

20

21 of suitable fabric material is placed on the tread material

22 in an area that will be located beneath the valve stem of a curing envelope.

24 At this point, as shown in Fig. 5, the subr 25 assembly 11 on the mandrel 10 is covered with a standard, 26 flexible curing envelope 34. Such an envelope, which is 27 well known in the tire recapping field, is generally made 28 of sheet rubber material and has an annular shape with a U- 29 shaped cross-section that provides side wall portions 35. 30 An outlet valve 36 provided in the envelope is connected ₃₁ through a pressure gauge 38 in a conduit 40 connected to a _₂ vacuum pump (not shown) . The sub-assembly on the mandrel -₃ completely covered by the envelope 34 is now removed from - . the tire building machine 10, and a pair of side plates 42 _₅ are bolted onto the sides of the mandrel to seal the ₃₆ envelope 34, as shown in Fig. 5A. The seal of the envelope

37 38 is tested by using a vacuum through the conduit 40 and

1 valve 36. 2

With the envelope 34 sealed on the sub-assembly 3 11 and mandrel 10, the entire assembly is placed in a 4 curing chamber. Using elevated pressure (e.g. 85 psi) and 5 temperature (e.g. °F) within the chamber, the bonding layer 6 28 is cured for a predetermined period (e.g. 2.5 - 3.0hrs) 7 to unify the sub-assembly as one integral ring comprising 8 the tread rubber 30 and inner steel belts 18 and 24. 9

In the next general step of the present method, 10 as shown in Fig. 6, a used tire casing 44 to be rebelted is 11 prepared for receiving the sub-assembly 11. Using a 12 conventional buffing tool 46, the used tread rubber 48 is 13 removed. Also, below the tread rubber, a worn or damaged 14 steel belt 50 is removed using a knife or slitter tool 52 15 which is held in a jig and moved under the damaged belt as 16 the tire is rotated on a builder machine. 17

After the tire casing has been fully buffed and 18 prepared, its outer surface is relatively even and smooth. 19 20 To this outer surface a layer 54 of bonding gum is applied ₂₁ and preferably stitched in place.

Now,^'"- as shown in Fig. 7, the precured sub-

22 23 assembly 11 with its inner integral belt portion 18, is 24 moved axially onto the tire casing 44 and over the bonding 25 layer 54 thereon. With the sub-assembly properly aligned on the tire casing, the entire assembly is covered by 26 27 another suitable curing envelope (not shown) . With the 28 curing envelope in place, a suitable sealing apparatus, 29 such as described in U.S. Patent No. 4,624,732 is installed 30 so that the envelope is held tightly around the full tire

-. and the attached sub-assembly 11. Now, the full tire

32 assembly with the sealed envelope is placed in a curing

₃₃ chamber (not shown) where it is subjected to elevated _A temperature and pressure to cure the bonding layer 54 and ₅ thereby secure the sub-assembly to the tire casing. _g As described, the present method provides for the ₇ rebuilding and rehabilitation of a valuable but worn or 8 damaged tire carcass that might otherwise have become useless except for salvage value.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will make themselves known without departing from the spirit and scope of the invention. The disclosure and the description herein are purely illustrative and are not intended to be in any sense limiting.

WHAT IS CLAIMED IS:

Claims

1. A method for rebuilding a radial tire carcass having one or more steel belts which have been damaged, comprising the steps of:

- preparing a damaged tire carcass by buffing it to remove old tread rubber and removing at least one layer of damaged steel mesh belting to provide a relatively smooth uniform surface on the tread area of the carcass;

- preparing an endless, annular sub-assembly on a circular mandrel, comprised of at least one inner belt consisting of flexible wire cord material embedded within a rubber layer and an outer layer of tread rubber secured to said inner belt;

- removing said annular sub-assembly from said mandrel;

- placing a layer of uncured bonding rubber on said tread area of said tire carcass;

- placing said sub-assembly over said bonding layer on said tire carcass;

- installing a curing envelope around said sub- assembly on said tire carcass; and

- piacing said tire carcass and said sub-assembly within a curing chamber at a preselected temperature and pressure for-a time sufficient to cure said bonding layer and thereby secure said sub-assembly to said tire carcass.

2. The method of claim 1 wherein the step of preparing said sub-assembly comprises the steps of:

- applying a section of flexible wire mesh and rubber belting material to an outer cylindrical surface of said mandrel and securing its ends together to form said inner belt thereon;

- applying a layer of uncured bonding rubber over said inner layer;

- applying a section of precured tread rubber over said bonding rubber and securing its ends together; - placing a flexible curing envelope over said sub-assembly on said mandrel and sealing it along the sides of the mandrel;

- placing said sub-assembly on said mandrel within a chamber at elevated temperature and pressure for a time sufficient to vulcanize said bonding rubber and thereby secure said tread rubber to said inner belt.

3 The method of claim 2 wherein the step of applying a section of wire mesh belting material comprises the steps of installing a first belting layer on said mandrel, a second narrower layer on said first layer, and a pair of filler layers of rubber material on opposite sides of said second layer.

4. The method of claim 2 wherein said sub- assembly is retained within said chamber at a pressure of at least 85 psi and a temperature of 250° for at least 2.5 - 3.0 hours.

5. T e method of claim 2 including the step of applying a thin layer of adhesive to the surface of said mandrel before said belting material is applied thereto.