NZ627420B2 - Apparatus and Method of Retreading Tyres - Google Patents

Abstract

The present invention relates to an apparatus (10) and a method for retreading a tyre (16) having a worn surface (12). The worn surface (12) is made of a thermoplastic elastomer. The apparatus (10) includes a heater (34) and a 3D printer (18). The heater (34) is adapted to heat up the worn surface (12) to a desired temperature. The 3D printer (18) is adapted to lay one or more layers of the thermoplastic elastomer onto the heated worn surface (12). The or each layer of thermoplastic elastomer is capable of adhering to the heated worn surface (12) or previously laid layer without requiring an adhesive medium or agent. 12) to a desired temperature. The 3D printer (18) is adapted to lay one or more layers of the thermoplastic elastomer onto the heated worn surface (12). The or each layer of thermoplastic elastomer is capable of adhering to the heated worn surface (12) or previously laid layer without requiring an adhesive medium or agent.

Description

Apparatus and Method for Retreading Tyres Technical Field The present invention broadly relates to an apparatus and method for ding tyres. In particular, this invention relates to an apparatus and method for treading or retreading worn tyres using 3D printing technologies.

Background of the Invention Conventionally, when the treads of a tyre are worn to a certain degree, the grip ofthe tyre on the road surface, eSpecially when it is wet; is significantly diminished. The worn tyre is then required to be removed from service due to safety concerns.

Instead of abandoning the worn tyre and replacing it with a new tyre, retreading is a significantly cheaper option. For this reason, retreaded tyres are'widely used in automobiles as well as. large-scale operations such as ng, busing and cemmercial aviation. Retreading tyres is also a very environmentally friendly way of recycling used tyres.

Retreading tyres involves a remanufacturing s designed to extend the useful service life of tyres. Existing retreading process involves the physical removal ofthe tread pattern ' (known as ) and regluing ofnew treads back into the same ons. As theltreads, side walls and other components of a tyre are ly manufactured, and react to nt, as an integrated unit, the retreading process described above has a major shortcoming in that it substantially reduces the overall integrity and handling of the retreaded tyre. The retreading process described above also has another shortcoming in that if the retread portions failed and hence spun offthe tyre, the underlying surface resulting from buffing is lly close to the steel belts that are embedded in the tyre. As such, re—echsure ofthe underlying surface can potentially lead to a sudden failure of the entire tyre, particularly when the tyre is Operating at high .

It is an object of the present invention to provide an apparatus and method for retreading tyres which may overCome or ameliorate the above shortcomings or at least provide a useful alternative.

Summary of the Invention According to a first aspect ofthe present invention, there is provided an apparatus for retreading a tyre having a were surface made of a thermoplastic mer, the apparatus including: a heater adapted to heat up the worn surface to a desired ature; and a 3D printer adapted to lay one or more layers of the thermoplastic elastomer onto the heated Whm surface; wherein the or each layer moplastic elastomer is capable of adhering to the heated worn surface or a previously laid layer without requiring an adhesive medium or agent In. a preferred embodiment, the 3D printer utilises an additive cturing technology such as fused t fabrication. Other technologies suitable for carrying out 3D printing including granular type printing such as selective heat sinter’ing or ive laser sintering may be used by the-3D printer.

Preferably, the tus is adapted to reinstate atread pattern by laying the one or more layers of thermoplastic elastOmer.

Preferably, the 3D printer and tyre are in use displaceable ve to one r.

The surface may include an-extemal circumferential e and/or a l surface of the tyre.

In a preferred embodiment, the 3D printer includes One or more printheads arranged in One or more‘rows. The or each printhead is preferred to be adapted to lay the one or more layers , ofthermoplastic elastomer upon the tyre surface, as desired. Each printhead is preferred to be configured to function independently ofone another. Laying of the or each layer of thermoplastic elastomer may be achieved by way of extrusion or any other suitable methods. Preferably, each layer of thermoplafitic elastomer may be the same or different.

For instance, one or more polymers or cepolymcrs may be used to form one or more outer layers ofthe or each tread. These polymers or copolymers are preferred to have a range-of wear and grip characteristics suitable for forming tyre tread. A sofier but more ve material may be used to form one or more inner layers ofthe or each tread.

Preferably, the worn stirface includes one or more worn treads. The 3D r is. preferred tobe capable oflaying the One or more layers ofthermoplastic elastorner directly onto the or each wom tread without requiring the or each worn tread to be ntially remoyed or buffed away before ng; However, the or each worn tread is preferred to undergo ' surface preparation such as cleaning and reughening before printing takes place.

In a preferred embodiment, the apparatus es a mapping means adapted to measure the tepography ofthe worn surface. Preferably, the g means is in the form ofa . r which es or is electronically connected to a processor which may be ‘ programmed to process ,the‘measured topOgraphy ofthe worn tread surface and control the 131) printer accordingly. More preferably, operation of the 3D printer is automated and dictated by the ed topography taking into account and compensating for the nonuniformity ofthe worn surface so as to reinstate a tread pattern. The processor may be set to allow the 3D printer to be controlled manually by a user for retreading a specific or confined worn area ofthe surface, for example.

Theprocessor is preferred to be capable ofmomtormg the printing process and carrying out post printing examination, and ting any defects if detected.

The processor may also be mmed to construct a desired new tread pattem building on the existing worn surface.

It is preferred that the apparatus includes a sapporting structure adapted to movably hold the tyre in place during the printing process. The stipporting structure is preferred to be capable of rotating the tyre about a first axis. In use, the tyre is preferred to be rotated incrementally while the 3D r is fixed at a chosenplocation. The or each row of printheads is preferably configured to lay thermoplastic elastorner covering a strip of the ‘ circumferential surface ofthe tyre parallel to the first axis after each incremental rotation.

Preferably, the strip is substantially parallel to the first axis. As such, the entire circumferential surface is preferred to be ntially covered on tion of a full Still-degree rotatiOn ofthe tyre. Upon completion ofeach full revolution, the or each print head is preferred to be moved (upvvards) along a second aids perpendicular to the first axis by a predeterminedincrernent. The printing process is preferred to commence again once the or each printhead has moved into place. This process is preferably ed until the desired tread depth is reached and thedesired tread pattern reinstated.

In a preferred ment, the apparatus includes a mechanism adapted to apply pressure to the casing before printing takes place such that the physical and ve ties of the tyre surface are ed. This mechanism is preferred to consist ofan air flow control unit. In cembination with the pressure mechanism, the heater may be adapted to provide an adjustable temperature range to facilitate the adhesion ofthe printed material to the existing wom tread. The air flow control unit is adapted to generate ssed air for applying re on the casing and create a vacuum for removal of dust and dirt from. the tyre surface. This mechanism may also be capable of carrying out other tasks, such as curing as a subsequent or final step.

Preferably, the apparatus also includes a preparation device adapted to apply one or more chemicals to the tyre surface for cleaning purposes. The chemicals may include a solvent in the form of a spray. In a preferred embodiment, the preparation device also includes a. means adapted to prepare the tyre surface for retreading. The means is preferred tovb‘e capable ofroughening a selected area ofthe tyre surface to facilitate adhesion of a first layer ofthermoplastic elastomer to the prepared tyre surface. For example, the means may be a .

It is preferred that the preparation device, mapping means, heater, supporting structure and printheads are in communication with and under the control of the processor which is programmable to achieve full automation.

Preferably, the plastic elastomer is thermoplastic polyurethane.

According to a secoml 'ofthe present invention, there is provided an apparatus for WO 86577 retreading a tyre having a worn surface, the apparatus including a 3D printer'capable of laying one or more layers ofmaterial onto the worn surface in—situ.

According to a third aspect of the present invention, there is provided a method of retreading a tyre having a worn surface made of thermoplastic elastomer, the method ing the steps of: ing a heater adapted to heat up the worn stirface to a desired temperature; and providing a 3D printer adapted to lay one or more layers of the thermoplastic mer onto the heated worn surface; and leaving the or each layer of thermoplastic mer to automatically adhere to the heated . worn or previously laid layer without requiring an adhesive medium or agent.

Preferably, the method includes a step of diaplacing the 3D printer and tyre relative to one another.

The method does not require a step ofsubstantially removing or buffing away any part of the wom siuface or undertread before laying the one or more layers of thermoplastic rner onto the worn surface. It should be noted that removal or buffing away ofthe worn e does not include any minor treatments on or preparation ofthe tyre surface such as roughening or sanding. 7 .Brief Description of the Drawings The‘invention may be better understood from the following non—limiting description ofthe I I present invention, in which; Figure 1 is a cross sectional view of a tyre retreading apparatus in accordance with a preferred embodiment ofthe present invention; Figure 2 is a front view of a 3D r being part of the apparatus ofFigure 1; and Figure 3 is a top end view of a tyre retreaded by the apparams ofFigure 1.

Detailed ption of the Drawings Referring to Figure 1, an apparatus 10 for retreading a used tyre 16 having a casing 14 with a surface 12 includes a 3D printer ‘18'capable of laying layers ofthermoplastic elastomer onto the casing e 12. The casing surface 12 has a plurality ofworn treads. The 3D printer ‘1 8 and tyre 16 are in use diSplaceable ve to one another. Further detail ofthis will be described below.

It should be noted that the surface 12 includes an external circumferential e 20 and/or 2 a l surface 22 of the tyre 16.

It should be appreciated that the tus 10 is intended to be used to retread the used tyre 16 having a worn surface 12 having worn treads. By way ofexample, the tyre 16 described in the present specification is a used tyre with a worn tread surface 12 (although the larly worn tread surface 12 is not readily visible in Figure 1). The3D printer 13 is capable of laying multiple layers of thermoplastic elastomer directly onto the worn tread surface 12 without requiring the pro-existing worn treads to be substantially buffed away or removal by any other means before printing.

The apparatus 10 has a supporting structure 24 with a rotor 26. A wheel 28 with a tyre 16 is mounted onto the-rotor 216 which movably holds the tyre in place. The wheel 28 (and hence tyre 16) is driven by the rotor 26 in operation to rotate about the x-axis (see Figure l).

The 3D printer 18 is contained within a g 30 which is movably supported by a column 32 which in turn is ively connected to the rotor 26. The print material which is a polymer or eopolymer is contained in a receptacle 46. In operation, the housing 30 carrying the 3D printer 18 is lowered along the z—axis (see Figure 1) to a selected level such that there exists a little gap between the housing 30 and the tyre surface 12. The tyre 16 in, use is driven by the rotor 26 to rotate about the x-axis.

As shown in Figure 1, the apparatus 10 has a mechanism which consists of a air flow control unit 36. There is also a heater 34 which is provided to apply heat to the casing 14 whereas the air flow l unit 36 is configured to apply re on the casing 14 by blowing compressed air. The heater 34 is adjustable to heat up the worn surface 12 of the tyre 16 to a desired temperature progressively. The heater 34 and air flow control unit 36' can be activated to apply Specific heat and pressure over a period oftime to the tyre e 12 such that the physical properties ofthe compounds that constitute the tyre tread are . enhanced. As a result, adhesion ofthe additional layers to be printed onto the tyre tread may be significantly improved.

The appara’nrs 10 also has a preparatiou device 38 which can apply selected chemicals to the tyre surface for cleaning purposes. The chemicals may include a liquid Spray and/or an abrasive t Although not shown in Figure 1, the ation device also has a rneans capable aring the tyre surface 12 for retreading. The means may be a sander or filer . . with abrasiVe capability which ons to toughen a selected area ofthe tyre surface 12 to facilitate on of one or more layers ’oftherm0plastic elastomer to the prepared tyre surface. Additionally, the air flow unit 36 maybe put into. a vacuum mode so as to facilitate removal of dust and dirt from the tyre e 12..

It should be noted that the preparation device 38, the mechanism for applying heat and . pressure, and the supporting structure 24 are all in cemmunioation With and under the control of a central processor 40 which is programmable to achieve full automation.

Referring to Figure 1, the apparatus 10 has a mapping means in the form of a scanner 42 which is capable of measuring the topography ofthe worn tyre e 12. The scanner 42 is electronically connected to a processor which may be programmed to processthe measured topography ofthe worn tread surface 12 and control the 3D printer accordingly In operation, the scanned information'is relayed to the l processor 40 where calibration calculations are made for 3D printing. Operation ofthe 3D printer 18is automated and dictated by the measured topography taking into account and compensating for the nonuniformity ofthe worn tread e 12 so as to reinstate the original tread pattern. The central processor 40 may be set to allow the 3D printer 18 to be controlled , manually by a user for ding a specific or confined worn tread surface 12.

In use, the 3D printer 18 starts with laying down new treads in a transverse line parallel to the x-axis across the tyre surface 12; Upon completion ofone line ofprinting, the tyre 16 is rotated incrementally while the 3D r 18 is fixed at the chosen location. Once the tyre 16 has d by a ermined increment, another line ofprint is then laid down by the 3D printer 18. The incremental rotational process continues for a full 360-degree- revolution until the entire tyre surface 12 is covered. Upon campletion of each full revolution, the 3D printer 18 is moved up along the column 32 which is parallel to the . z—axis by a predetermined increment, The ng process commences again once the 3D printer 18 has moved into place. This process is repeated until the desired tread depth is d and the tread pattern reinstated. The central processor 40 is capable of monitoring the printing. process and carrying out post printing examination, and ting any defects if detected.

Turning to Figure 2, the 3D r 18 has a series of printheads 48. The printheads 48 are arranged in a row and configured to lay material covering a strip ofthe circumferential surface ofthe tyre after each incremental rotation ofthe tyre about the x—axis. Laying ofthe layers of material is achieved by way of extrusion. Each ead 48, is configured to lay one or more layers of material upon the tyre surface 12, as desired. Each printhead 48, is red to function and‘move independently of one another as an individual unit. Each printhead 48, 59 can be moved and repositioned individually and independently across the - Width ofthe tyre_16 a10ng the x—axis as indicated by arrows54. Also, each printhead 48 can be moved up or down relative to the tyre surface; 12 a10ng the zz-axis indicated by arrows 52. Furthermore, any one of. the printheads 48 can be removed from the printer l8 and service without affecting the operation ofthe remaining ones. The ement of the ' printheads 48 enables rapid adaption of the printer 18 to suit different tyre designs and . teristics in regards to camber, width and tread profile.

Referring to Figure 3, the tyre 16 has tread pattern 44 which is d up into five different zones 21 to ZS, each of which beinga raised section running in a continuous and repeated fashion around the circumference ofthe tyre 16. Each zone Z1, ZZ, Z3, Z4, Z5 is separated from the adjacent one by a deep groove 56. The shape and width of each zone may differ within the overall tread design on each individual tyre. Each printhead 48 is red and arranged to be responsible for printing on a corresponding zone which is achieved through 2012/001533 its nt along the x- and zi-axes independent from the movement ofthe adjacent printheads. For example, the printhead 48 covering zone ZB would be printing over a ' relatively small section while adjacent printhead 48 covering zone 22 is printing over a larger area. It will be appreciated that the multiple printhead ement offers the advantage ofmaking the printing process quicker by eliminating the need of a single printhead having to keep stopping and starting printing as it transits from a raised tread to a groove and then to another raised tread.

It should be noted that the apparatus and method ofthe present invention is applicable to and ent upon a specifically manufactured tyre with a tread layer made of a thermoplastic elastomer. The thermoplastic elastomer not only possesses the physical characteristics required for use as tread on pneumatic tyres but would also allow printing f by way ofthe Fused Filament Fabricatiorr method. \The use of therm0plastic mer in both the manufacture of the original tyre and the printing process would eliminate or at least minimise any adherence issues in the'retreading process. The retreading process involves extrusion ofthe thermoplastic elastomer onto a heated base layer made of identical or at least similar material. When subjected to an appropriate amountofheat and/or re, the printed thermoplastic mer would by nature automatically bond to the worn tyre e which in the specifically manufactured tyre is also a' thermoplastic elastomer. As such, no intermediate or bonding layer is required. Also, such a retreading process would enable the tyre casing to be retreaded multiple times.

It will be appreciated that the specifically manufactured tyre referred to above only involves a modified tread layer. All ofthe other components that tute the tyre casing including the sidewalls, bead etc. may be manufactured using existing tyre technology with conventional materials.

‘ It is contemplated that plastic polyurethane (TPU) is an ideal elastomer‘for use as a printing material. TPU has the ability to be ively and consistently printed viathe lhxsed Filament Fabrication process and possesses similar physical characteristics to the als currently used for the tread oftyres. TPU also has a number of additional nmental benefits when compared to the vulcanised materials traditionally used in the manufacture of tyres.

As an Option, a specifically fabricated tyre ofthe sort described above may include two or more different layers oftread, namely an outer layer being made ofa material with similar teristics to those commonly found on existing tyres and an inner layer made of a sofier compound being d directly underneath the outer layer. The inner layer has a lower wear resistance compared with the outer layer but is more accepting of the outer layer which is laid on top of the inner layer in the ng process. Furthermore, the inner layermay have coloured lines or bars or other distinguishing features embedded. at intervals around the circumference of the tyre 16. These colour lines or bars would be exposed once the outer layer is worn away y ng an operator to'the fact that the outer layer having the higher Wear ance has been worn away. This serves as an ' indicator that the tyre is due for retreading by 3D printing which does not require any buffing, peeling or removal ofthe pre—existing worn tread comprising the inner layer in the present case. a ‘ It is contemplated that the central processor ofthe apparatus may be programmed to uct a desired new tread pattern building on an existing inner layer described above.

.In operation, the tyre16 being mounted on the wheel 28 is secured onto the rotor 26 ofthe support structure 24‘ The ation device 38 is then activated to prepare the worn surface oftreads on the tyre 16. This involves treatments including cleaning and roughening ofthe worn surface. Once the tyre surface is prepared, the mapping means 42 is brought to close proximity to the tyre 16 and activated as the tyre 16 is driven by the rotor 26 to rotate. Topographic information of the tyre 16 obtained by the mapping means 42 is relayed to and stored in the central processor 40 which will lower the 3D printer 18 along the column 32 to an appropriate level for printing to take place. During the printing , process, the eads 48, being dictated by the processor. 40,‘ all operate independently and individually to lay different number of layers ofmaterial onto different areas ofthe tyre surface 12 based on the detected topographic information. The rotor 26 and the 3D printer 18 are synchronised such that by the time the tyre 16 has been rotated a full IMO—degree, the desired tread pattern 44 ofthe tyre 16 is reinstated. The mapping means 42 is also actuated before printing commences such that the entire printing s is monitored. Also, a further scan may be performed by the mapping means 42 so as to’ ensure that correcting printing has been carried out. If no flaws or defects are detected, the 313 r is elevated to a disengaging position such that the tyre 16 can be removed from the rotor 26. It will be appreciated that the apparatus 10 ofthe present ion is controlled and operated by ' automation with a high level of efficiency; Now that a preferred embodiment of the present invention has been described in some detail,-it will be apparent to those skilled in the art that the retreading apparatus may offer at ’ A least the following advantages: ' 1) it does not alter or interfere with the original construction of the casing thereby . preserving the integrity ofthe tyre; 2) it does not require the steps of buffing and’iemoving worn treads before retreading and hence reduces the cost ofretreading;_ 3) in the event that the reprinted tread suffers fiom a failure or is stripped off due to intproper use, design failures or application faults, the original construction of the casing would still be intact and retreading by 3D printing can be performed easily and sWiftly; 4) it saves costs in that the nment of avhuge amount of tyres can be'avoided by reinstating tyres back to a serviceable condition with minimal polymeric material; ) it is ecological due to a significantly reduction ofthe number of tyres that would otherwise end up in land fill, despite the fact that some tyres are recyclable; and 6) it enables u retreading s line by line and layer by layer; 7) it improves fuel efficiencies due to reduced g resistance of the tyre tread. As g resistance is reduced relative to the ing tread depth, it is found to be economical in s to fuel consumption to print small increments oftread. depth but on a more regular basis.

Those skilled in the art Will iate that the inVention described herein is susceptible to variations and atiOns other than those specifically described. For eminple, the tyre ‘may be divided into more or less than five zones to suit tyres with different tread patterns.

Also, the tyre may be rotated more than one revolution to ensure that the desired tread depth is achieved. Furthermore, each or all of the printheads 48 may be adjusted to move upwards or downwards in unison or individually and independently within the 313 printer 18 instead ng the 3D r 18 being moved along column 32 as a whole; Besides, the apparatus may employ other forms of additive manufacturing techniques including -. granular type printing such as selective heat sinten'ng or selective laser ing vvhere the ‘ extruder mechanisrn would be replaced by a granular deposition device and curing mechanism. Additionally, other thermoplastic elastomers including styrene-butadiene-styrene may also be used as ng material in the present invention, so leng as they are able to be printed by 3D printing techniques and s the characteristics required for use as tyre treads. All such variations and modifications are to be considered ‘ within the scope and spirit of the present invention the nature ofwhich is to be determined from the foregoing description.

WO 86577

Claims (36)

Claims

1". An tus for retreading a tyre having a worn surface made of a thermoplastic elastomer, the apparatus ing: a heater adapted to heat up the worn e to a desired temperature; and a 3D printer adapted to lay one or more layers ofthe thermoplastic elastorner onto the heated worn surface; wherein the or each layer moplastic elastomer isi‘capable of adhering to the - heated worn surface or a usly laid layer without requiring an adhesive medium or agent.

2. The apparatus of claim l, Which is adapted to reinstate a tread pattern by laying the one or more layers of.therrn0plastic elastomer.

3. The apparatus of either of claim 1_ or 2,'wherein the 3D printer and tyre are in use displaceable relative to one another.

4. The apparatus 'of any one of the preceding claims, wherein the worn surface includes an external circumferential surface and/or a lateral surface ofthe tyre.

5. The apparatus of any one of the preceding claims, wherein the 3D r includes » one or more printheads arranged in one or more rows, the or each printhead being adapted to lay the or each layer ofthermoplastic elastomer upon the tyre surface.”

6. The apparatus of claims, wherein each printhead is red to function independently of one another.

7. The apparatus of any one of the preceding claims, wherein laying ofthe or each layer ofthermoplastic elastomer is achieved by way of extrusion.

8. The apparatus of any one ofthe preceding claims, wherein each layer of thermoplastic elastomer is the same or different using cue or more polymers or " ‘copolymers to form one or more outer layers ofthe or each tread. .

9. The apparatus ofclaim 8, whereina setter but more adhesive material is used to form one or more inner layers ofthe or each tread.

10. The apparatusof any one ofthe preceding claims, wherein the worn surface ‘ includes one or more wom treads.

11.The tus of any one ofthe preceding ClaimS, wherein the 3D printer is capable oflaying the or each layer ofthermoplastic elastomer directly ontothe or each outermost worn tread without requiring the, or each ost worn tread to be ntially removed or buffed away before printing.

12. The apparatus ofany one of the preceding 'claims, n the or each worn tread undergoes surface preparation before printing takes place.

13. The apparatusofany one ofthe preceding , which, includes a mapping means adapted to measure the topography ofthe worn surface.

14. The apparatus of claim 13, wherein the mapping means is in the form of a scanner which includes or is electronically connected to a processor programmed to process the measured topography ofthe worn tread surface and control the 3D printer accordingly.

15. The apparatus of either claim 13 or 14, wherein operation of the 3D printer is automated and dictated by the measured aphy taking into account and compensating for the formity of the worn e so as to reinstate a tread pattern.

16. The apparatus of claim 14, wherein the processor is set to allowthe 3D printer to be centrolled manually by a user for retreading a specific or confined worn area ofthe surface.

17. The apparatus of either claim 14 or 16, wherein the processor is capable'of one or more ofthe following: monitoring the printing process, carrying out post printing examination, ting any s if detected, and being programmed to construct a desired new tread pattern building on the existing warn e.

18. The apparatus of any one ofthe preceding claims, which includes a supporting structure adapted tornovably hold the tyre in place during the printing process.

19. The apparatus of claim 18, wherein the supporting structure is capable of rotating thetyre incrementally about a first axis.

20 The apparatus ofclaim 19, wherein the or each row ofprintheads'rs configured to lay thermoplastic elastorner covering a strip of a circumferential surface of the tyre parallel to the first axis after each incremental rotation.

21 The apparatus of claim 20; wherein the. strip is substantially parallel to the first axis.

22. The apparatus of either claim 20 or 21, wherein upon completion of each full revolution ng the entire circumferential surface ofthe tyre, the or each print head is moved along a second axis perpendicular to the first axis by a predetermined increment.

23. The apparatus of claim-22, wherein the printing process is to commence again once the or each printhead has moved into place and is repeatedvuntil the desired tread depth is reached and the desired tread pattern reinstated.

24. The tus of any one of the preceding , which es a mechanism adapted to apply pressure to the casing before printing takes place such that the physical and adhesive properties of the tyre surface are enhanced.

25. The apparatus of claim 24, wherein the mechanism consists of an air flow control unit adapted to generate ssed air for applying pressure on the casing and create a vacuum for removal of dust and dirt from the tyre stirface.

26. The apparatus of either claim 24 or 25, wherein the mechanism is capable of curing.

27. The apparatus of any one of the preceding claims, n the heater is adapted to provide an able temperature range to facilitate the adhesion of the printed layer to the existing worn tread. \

28. The apparatus ofany one of the preceding , which includes a ation device adapted to apply one or more chemicals to the tyre surface for cleaning purposes.

29‘ The apparatus ofclaim 28, wherein the preparation device includes a means capable ofroughening a selected area ofthe tyre surface to facilitate adhesiorr ofa first layer ofthermOplastic elastcmer to the prepared tyre surface.

30. The apparatus ofclaim 28, wherein the preparation device, mapping means, heater, supporting structure and printheads are in ication with and under the l ofthe processor which is programmable to achieve automation.

31 . The apparatus of any one of the preceding claims, wherein the thermoplastic elastomer is thermOplastic polyurethane.

32. The apparatus ofany one ofthe preceding claims, wherein'the 3D printer utilises an additive manufacturing technology including one ofthe followings: fused filament fabrication, selective heat ing and selective laser sintering.

33. A method of retreading a tyre having a worn surface made of plastic elastomer, the method including the steps of: providing a heater d to heat up the worn surface to a desired temperature; providing a 3D printer adapted to lay one or more layers of the thermoplastic elastomer onto the heated worn surface; and leaving the or each layer of thermoplastic elastomer to tically adhere to the heated worn surface or a previously laid layer without requiring an adhesive medium or agent.

34. The method of claim 33, which includes a further step of displacing the 3D printer and tyre relative to one another.

35. An apparatus for retreading a tyre substantially as herein described with reference to any one of the accompanying drawings.

36. A method of retreading a tyre ntially as herein described with reference to any one of the accompanying drawings. WO 86577 WO 86577