GB2208159A

GB2208159A - Apparatus and method for treading tyres

Info

Publication number: GB2208159A
Application number: GB8814192A
Authority: GB
Inventors: Peter Jan Kent
Original assignee: R E RUBBER Co Ltd
Current assignee: R E RUBBER Co Ltd
Priority date: 1987-06-17
Filing date: 1988-06-15
Publication date: 1989-03-08
Also published as: GB8814192D0; GB8714138D0

Abstract

Apparatus is provided for re-treading a tyre 10, comprising means for applying and fixing a tread 11 to the tyre 10 progressively around the periphery of the tyre and means for simultaneously longitudinally compressing the tread along part of its length as it is applied to the tyre. This is achieved by rollers 12,19 of different radii which rotate at the same angular velocity. <IMAGE>

Description

APPARATUS AND METHOD FOR TREADING TYRES This invention relates to apparatus and a method for treading tyres, for example re-treading worn tyres.

It is common practice to extend the life of a worn vehicle tyre by permanently adhering a new tread around its periphery. Methods used include bonding unvulcanised material and forming the tread pattern simultaneously under pressure in a heated mould, now known as "mould" or "hot cure", or applying a pre-vulcanised tread either progressively or simultaneously to a prepared tread surface and thereafter completing the bond betweeen them under heat and pressure in an autoclave, often known as "pressure" or cold cure" retreading process.

In this regard, British Patent No. 1460297 discloses a general method of placing a pre-vulcanised tread band on a carcass and providing a compressive stress along the tread band, either before or after the tread band is placed on the carcass.

Furthermore, a method and apparatus for attaching a pre-vulcanised tread to the prepared surface of a tyre, in such a manner that a compressive stress is retained in the tread for the whole of the tyres life is described in each of British Patents Nos. 1471547 and 1592854. In each method described, the whole length of the pre-cured tread is shortened to contain the stress, before any contact is made between the tread and the tyre. Whilst both of these methods have given practical proof of the added quality imparted to the tyre as a result of the compressive stress, each has called for improvement.

In the method called Renprestw (Trade Mark), which employs the method of Patent No. 1471547, high accuracy is called for in matching of the size and contour of the three items involved, viz. the prepared tyre, the tread and the mould.

In the method called "Maxiprest" (Trade Mark), the subject of Patent No. 1592854, the need for dimensional accuracy has been largely eliminated, however the complexity and cost of the required apparatus together with the space required for its operation is considered unwarranted by many potential users.

It would be desirable to alleviate the problems associated with known methods, and provide apparatus for carrying out a new and improved method.

According to the present invention, apparatus is provided for treading a tyre, comprising means for applying and fixing a tread to the tyre progressively around the periphery of the tyre and means for simultaneously compressing the tread along part of its length as it is applied to the tyre.

The apparatus preferably comprises first and second gripping means, for gripping the tread and feeding it onto the tyre, the first gripping means being arranged to feed the tread at a greater rate than the second gripping means, whereby the tread is compressed therebetween.

The first and second gripping means preferably comprise first and second rollers respectively, arranged to rotate such that the tangential volocity of the first roller is greater than that of the second roller. In this case, the second roller may be arranged to press the tread against the tyre, to form the means for applying and fixing the tread to the tyre.

The first and second rollers may be linked together for simultaneous rotation at the same rotational speed, with the first roller having a greater radius than the second.

Preferably the first roller is arranged to be driven by driving means.

Means may be provided for initially compressing the tread between the first and second rollers when the tread has been fed past the first roller to be gripped by the second roller, prior to feeding the tread past the second roller.

As one alternative, means may be provided to allow initial rotation of the first roller relative to the second roller, so as to allow the initial compression of the tread and to lock the rotation of the rollers relative to each other. As another alternative, the first and second rollers may be connected by means of two sprockets and a chain, the chain having a degree of slackness, and a spring-mounted jockey wheel may be provided, acting against the chain, so that with the tread positioned between the first and second rollers, initial turning of the first roller causes tightening of the chain against the force in the spring of the jockey wheel, before the second roller turns, during which time the tread undergoes the initial compression. This method requires the addition of a friction brake applied to either the second roller or the tyre or its mounting.

Another alternative for compressing the tread between the first and the second roller may be provided by a heavy duty friction brake applied to the tyre or its mounting and the removal of the two sprockets and connecting chain. In this arrangement the tread is forced forward by the first compressing roller until resisted by contact with the tyre firmly held by the second roller until the resistance of the friction brake is overcome. Whereas the degree of compression in the first embodiment may be decided by the relative difference in tangential velocity between the two rollers, in this embodiment the degree of compression applied may be decided by the rotational resistance of the tyre by the friction brake.Provision of obvious means determining the power output of the roller driving means, preferably an ammeter, may guide the operator in adjusting the friction brake to the required loading.

In the event of need to retread a tyre without addition of compressive stress, the only difference in operation is the action of relaxing the friction brake.

The apparatus may be arranged for inclusion on an existing machine for carrying out the "pre-cure re-treading process". Such a machine can be adapted by removing the existing stitching roller, which presses the tread onto the tyre, and replacing it with the first roller described above. Existing hydraulic and other controls on the machine can be used in combination with the apparatus according to the invention. In particular, a typical re-treading machine would have hydraulic pressure means, for applying downward pressure to the stitching roller.

This existing pressure-applying means can be used for applying pressure to the first roller of the apparatus according to preferred embodiments of the invention.

Another embodiment of the present invention comprises a rotatable ring for accommodating a tread therein, the ring having a radius larger than that of the tyre, wherein in use the tyre is rotated eccentrically within the ring and loads the tread forcibly against the ring.

According to the present invention, there is also provided a method of treading a tyre, comprising the steps of preparing a tyre for receiving a tread, and applying a tread to the tyre progressively around the periphery of the tyre, while at the same time compressing the tread along part of its length, as it is applied to the tyre.

Preferably the tread is compressed by between about 1% and about 10% of its length, for example about 5% of its length.

Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a side elevation view of a tyre, tread and associated re-treading equipment in a first stage of re-treading of the tyre, where the tread is about to be applied to the tyre; Figures 2 and 3 are side elevation views of the tyre of Figure 1, with the tread in second and third stages, respectively, of being applied to the tyre; Figures 4 and 5 are side elevation views of arrangements for applying the tread to the tyre, alternative to that of Figures 1 to 3; Figures 6 and 7 are side views of rollers shown in Figures 1 to 5, in an optional arrangement; Figure 8 is a side elevation view of a second embodiment of the present invention; and Figure 9 is a side elevation view of a third embodiment of the present invention.

Referring to Figure 1, a tyre 10 is shown, which has been prepared for re-treading in a standard manner. The tyre is mounted on a jig (not shown) for free rotation about its axis. A pre-cured tread 11 is shown, which has a length about 5% greater than the circumference of the tyre. The tread 11 passes between a cylindrical compressing roller 12 and a reaction roller 13 and between upper and lower guides 14 and 15 respectively. The tread contacts the annular surface of the tyre at a point 18, where it passes between the tyre and a cylindrical stitching roller 19. The compressing roller 12 has a radius 5% greater than that of stitching roller 19. The compressing roller is driven by a motor (not shown) while the stitching roller is geared to the compressing roller to rotate at the same rotational speed as the compressing roller.

The reaction roller 13 and the tyre 10 are free-running.

The compressing roller 12 has an arcuate slot 20 in which a bolt 21 is located. The bolt 21 is connected to the drive shaft of the roller. Compressing roller 12, guide 14 and stitching roller 19 are mounted on an arm 23 which is mounted on the jig so as to swivel about the axis of compressing roller 19.

The tyre is re-treaded as follows. The tread 11 is positioned as described above and the end 24 is stitched down to the tyre. The drive roller 12 is rotated through a fraction of a turn about its drive axis and this has the effect of compressing the section of the tread between the point where it grips the compressing roller 12 and the point 18 where is contacts tyre 10. The guides 14 and 15 prevent the tread from bowing out of line, ensuring that it is compressed longitudinally. Bolt 21 is now tightened to lock compressing roller 12 to its drive shaft.

Compressing roller 12 is driven clockwise, feeding the tread onto the tyre and at the same time the tyre 10 rotates anti-clockwise. In this way the tread, under pressure from stitching roller 19, is laid onto the tyre, to which it adheres by standard means of adhesion. As the tread is fed between the drive roller 12 and the stitching roller 19, it is continually under longitudinal compression, being unable to slip against the grip surface of compressing roller 12. When the full length of the tread 11 has been laid on the tyre, the arm 23 is raised, with stitching roller 19 still holding the tread against the tyre, and the position of Figure 2 is reached.

From the position of Figure 2, the operator manually bends the unattached tread end 25 downwards, tucking it down to abut against the end 24, leaving a raised portion 26 (Figure 3). This is then pressed down to adhere to the tyre and thus make a compressed junction between the ends 24 and 25. The tyre is then rotated again while the tread is stitched down, as necessary. The retreading of the tyre is now ready to be completed by vulcanising the bonding material.

Referring now to Figure 4, an alternative arrangement of rollers 12 and 19 is shown. In this case, instead of a single reaction roller 13, there are two smaller reaction rollers 30 and 31 with a belt 32 looped around them.

Instead of two flat guides 14 and 15, there is a single, upper guide 35 which has a concave curved surface.

Compressing roller 12 has a radius of 107mm while stitching roller 19 has a radius of 102mm.

The reaction rollers 30 and 31 guide the tread 11 in an arc around the compressing roller 12, so that it is directed upwards against the surface of guide 35. Guide 35 directs the tread downwards again to pass between the stitching roller 19 and the tyre 10.

Rollers 12 and 19 are linked to rotate at the same rotational speed. Because roller 12 has a greater radius than roller 19, it has a greater tangential velocity at the tread and so maintains the tread 11 in compression between the two rollers.

Instead of two reaction rollers 30 and 31 and a belt 32, more reaction rollers (e.g. five) can be used to guide the tread around roller 12.

A third arrangement of re-treading apparatus is shown in Figure 5. The apparatus is intended especially for substituting on a known re-treading machine, having hydraulic or pneumatic pressure means, for applying downward pressure to the stitching roller. It comprises a compressing roller 12, a stitching roller 19, an arm 23, reaction rollers 40 and 41, a guide roller 42, a harness 43, a bandwheel 44 and a counterweight 45. The stitching roller of the existing re-treading machine is removed and replaced by stitching roller 19 of Figure 5. This converts the machine into a dual purpose machine which provides the option to build the tyre either with or without a compressive stress tread.This is advantageous because a proportion of tyre casings are often found to have suffered treatment in their first lives which may render it unwise to impose the extra mileage from the compressive stress.

To re-tread a tyre without compressive stress, the parts shown to the right of stitching roller 19 are lifted up clear of the tyre and balanced by the weight 45 so that the operator can enter the tread end directly to the position 18 below the centre of roller 19. That roller is then rotated to stitch the tread progressively to the tyre in known manner.

When the tyre casing is good enough to accept the compressive stress, the operator pulls down those parts lying to the right of roller 190 to a position where the end of the tread can easily be inserted through the gap between rollers 12 and 41 and can be fed through to below the centre line of roller 19. The hydraulic or pneumatic pressure means for pressing down roller 19 are then activated and thus the end of the tread is pressed down onto the tyre where the tack on the prepared surface retains it. Bandwheel 44 is then turned to pull the harness 43 upwards to enable reaction rollers 40 and 41 to press a portion of the tread firmly against a segment of roller 12. Compressing roller 12 can now be driven to feed the tread to stitching roller 19.

Rollers 12 and 19 are arranged to rotate at the same speed by means of a chain engaging equal sprockets on the rollers (not shown). Because the circumferential measurement of roller 19 is 5% greater than that of roller 12, that portion of the tread lying between the rollers is compressed by 5% as it is fed through the apparatus. The chain has a degree of slackness and a spring-loaded jockey roller presses against it, on the upper stretch of the chain between the sprockets. This imparts an initial stress to the tread between the roller contacts, before any movement of roller 19. The first few degrees of movement of roller 12 causes straightening of the chain against the jockey roller spring, before any movement of roller 19. This achieves the same object as the bolt and slot arrangement of Figure 1. In both arrangements, the power drive is applied to compressing roller 12.In this arrangement a friction brake is required to restrain movement of roller 19 during initial compressing movement.

Guide roller 42 may be driven if necessary.

Whereas in the above description rollers 12 and 19 are cylindrical, further optional refinement of the apparatus according to the preferred embodiment of the invention is illustrated in Figures 6 and 7. Figure 6 shows a side view of stitching roller 19, positioned over a tyre 10 and a tread 11. The tyre and tread are shown in crosssection. It can be seen from this figure that stitching roller 19 is concave across its width, approximately conforming to the bowed shape of the cross-section of the re-treaded tyre.

In Figure 7, it can be seen that the compressing roller 12 is convex across its width, or barrel-shaped, while a reaction roller is shown beneath compressing roller 12, which may be reaction roller 13, reaction roller 30, or reaction roller 40.

When the tread 11 is fed past barrel-shaped compressing roller 12 and pressed onto the tyre by concave stitching roller 19, the combined effect of first curving the tread upwards at the edges and then curving it downwards at the edges, is to enhance the compression applied to the tread. These alternate convex and concave rollers are particularly intended for use in apparatus such as that of Figures 4 and 5, in which the tread is curved upwards towards a guide 35, before being re-directed downwards to the tyre.

Alternatively, roller 12 may be cylindrical and roller 19 concave faced.

Turning now to a second embodiment of the present invention as shown in Figure 8 of the drawings, compression of the tread 11 is effected by a first roller 50 forcing the tread 11 to contact the surface of the tyre 10 whilst rotation of the tyre 10 is resisted by means of a friction or other braking means (not shown). In this embodiment, the friction braking means is arranged to restrain either the tyre 10 or its mounting, and the degree of compression in the tread 11 may be selected by altering the friction applied, as required. As previously, the apparatus includes a stitching roller 19 and guides 14, 15.

According to a third embodiment of the present invention as shown in Figure 9, a plain ring 51, having a larger radius than that of the tyre 10 to be processed, is provided. In use, a pre-cured tread 11 is inserted inside the ring 51 and contacts a portion of the inner surface 52 of the ring 51. One end 53 of the tread 11 is positioned so that a prepared and inflated tyre 10 when rotated eccentrically loads the tread 11 forcibly against the inner surface 52 of the ring 51. When power is applied to rotate the ring 51, by means of drive roller 54 brake action is applied to the tyre 10 causing compression of the- tread 11.

It will be appreciated that for efficient working of this embodiment, both the internal and external surfaces of ring 51 need to be rough to obtain maximum friction.

Further, if extra drive is required to rotate the ring 51, idler roller 55 may be driven.

Furthermore, to assist in retaining a tread 11 in situ when first placed in the ring 51, radial holes (not shown) may be drilled into it into which pegs may be temporarily inserted and then withdrawn as the process proceeds.

It should be noted that excellent results are obtained when the compressed tread 11 contacts the tyre 10 tangentially, as occurs most favourably when using the third embodiment of the invention.

Finally, in connection with the second and third embodiments, the degree of compression can be observed at an ammeter in the driving motor circuit and can be adjusted at any time by control of the braking means.

It will, of course, be understood that the above description has been given by way of example only, and that modifications of detail can be made within the scope of the invention.

Claims

1. Apparatus for treading a tyre comprising means for applying and fixing a tread to the tyre progressively around the periphery of the tyre and means for simultaneously compressing the tread along part of its length as it is applied to the tyre.

2. Apparatus according to claim 1, comprising first and second gripping means, for gripping the tread and feeding it onto the tyre, the first gripping means being arranged to feed the tread at a greater rate than the second gripping means, whereby the tread is compressed therebetween.

3. Apparatus according to claim 2, wherein the first and second gripping means comprise first and second rollers respectively, arranged to rotate such that the tangential velocity of the first roller is greater than that of the second roller.

4. Apparatus according to claim 3, wherein the second roller is arranged to press the tread against the tyre, to form the means for applying and fixing the tread to the tyre.

5. Apparatus according to either of claims 3 and 4 wherein the first roller is arranged to be driven by driving means.

6. Apparatus according to any one of claims 3 to 5 wherein means are provided for initially compressing the tread between the first and second rollers when the tread has been fed past the first roller to be gripped by the second roller, prior to feeding the tread past the second roller.

7. Apparatus according to claim 6, wherein means are provided to allow initial rotation of the first roller relative to the second roller, so as to allow initial compression of the tread.

8. Apparatus according to any one of claims 3 to 7, wherein the first and second rollers are linked together for simultaneous rotation at the same rotational speed and wherein the first roller has a greater radius than the second.

9. Apparatus according to claim 7, wherein the first and second rollers are connected by means of sprockets and a chain, the chain having a degree of slackness, and a spring-mounted jockey wheel is provided, acting against the chain, so that with the tread positioned between the first and second rollers, initial turning of the first roller causes tightening of the chain against the force in the spring of the jockey wheel, before the second roller turns, during which time the tread undergoes the initial compression.

10. Apparatus according to any one of claims 1 to 7 which includes a braking means for resisting rotation of the tyre.

11. Apparatus according to claim 10 wherein the braking means is a friction brake.

12. Apparatus according to any of claims 3 to 11, wherein the first roller is convex and presses the tread against a concave opposing roller, while the second roller is concave, pressing the tread against the tyre.

13. Apparatus according to any one of the preceding claims, wherein the means for compressing the tread is selectively disengageable to allow retreading of the tyre without compression.

14. Apparatus according to claim 1 which comprises a rotatable ring for accommodating a tread therein, the ring having a radius larger than that of the tyre, wherein in use the tyre is rotated eccentrically within the ring and loads the tread forcibly against the ring.

15. Apparatus according to claim 14 which comprises drive means for rotating the ring.

16. Apparatus according to claim 14 or claim 15 which comprises braking means for resisting rotation of the tyre.

17. Apparatus according to claim 16 wherein the braking means is a friction brake.

18. Apparatus according to any one of claims 14 to 17 wherein the ring has rough internal and external surfaces.

19. Apparatus according to any one of claims 14 to 18 wherein the ring has radial holes.

20. Apparatus according to any preceding claim which comprises means for measuring the degree of compression of the tread.

21. Apparatus substantially as hereinbefore described and as shown in Figure 1, 4 or 5 and/or Figures 6 and 7.

22. Apparatus substantially as hereinbefore described with reference to or as shown in Figure 8 and/or Figures 6 and 7 of the accompanying drawings.

23. Apparatus substantially as hereinbefore described with reference to or as shown in Figure 9 of the accompanying drawings.

24. A method of treading a tyre, comprising the steps of preparing a tyre for receiving a tread, and applying a tread to the tyre progressively around the periphery of the tyre, while at the same time compressing the tread along its length, as it is applied to the tyre.

25. A method according to claim 24 wherein the tread is compressed by being fed through first and second gripping means, its rate of feed through the first gripping means being greater than through the second gripping means.

26. A method according to claim 25, wherein the first and second gripping means comprise rollers having different tangential velocities.

27. A method according to claim 26 wherein rotation of the second gripping roller is resisted by applying a friction brake.

28. A method according to claim 24 wherein a tread is mounted inside a rotatable ring and the tyre is rotated eccentrically within the ring to load the tread forcibly against the ring.

29. A method according to claim 28 wherein the ring is driven by drive means

30. A method according to claim 29 wherein braking means resists rotation of the tyre.

31. A method of retreading a tyre substantially as hereinbefore described with reference to Figures 1 to 3r or Figure 4 or 5 and/or Figures 6 and 7 of the accompanying drawings.

32. A method of retreading a tyre substantially as hereinbefore described with reference to or as shown in Figure 8 and/or Figures 6 and 7 of the accompanying drawings.

33. A method of retreading a tyre substantially as hereinbefore described with reference to or as shown in Figure 9 of the accompanying drawings.