WO1995004648A1

WO1995004648A1 - Retreading device

Info

Publication number: WO1995004648A1
Application number: PCT/EP1994/002599
Authority: WO
Inventors: Paul Meyer
Original assignee: A-Z Formen- Und Maschinenbau Gmbh
Priority date: 1993-08-05
Filing date: 1994-08-05
Publication date: 1995-02-16
Also published as: JPH08506292A; AU676379B2; JP3851347B2; CN1111903A; CN1050323C; AU7611194A

Abstract

In a tire retreading device, a running strip may be laid on a carcass. A running strip supply device supplies the running strip to the carcass and an extruder extrudes a binding rubber layer. The device has two lips that delimit an extrusion nozzle. The rear lip, seen in the direction of motion of the carcass, projects over the other lip in the direction of the carcass. The lip nearer to the carcass (13) is designed as a moulding shoe (40) and is pressed at a retreading prestress.

Description

Retreading device

The invention relates to a retreading device according to the preamble of claim 1 and a method for retreading, according to the preamble of claim 12.

Tread retreading is currently carried out in two different ways:

A. Mold vulcanization, the carcass being prepared with a tread made of unvulcanized rubber with a binding rubber layer facing the carcass and then vulcanized. Here, the tire tread is pressed into the tread and the connection to the carcass is ensured by the pressure and the heat in a mold, the mold only holding one tire at the same time. The working temperature is around 150 ° C. This process is capital intensive.

B. retreading by means of pre-vulcanization, a tread already vulcanized in a flat or ring shape and provided with a profile and having a size that already fits the carcass being welded on by means of a thin layer of previously unvulcanized binding rubber. This is carried out at a much lower temperature (between 95 ° C. and 120 ° C.) and a lower pressure in an autoclave, in which a plurality of tires can usually be treated at the same time. This process is significantly less capital intensive.

Both methods require the preparation of the carcass, the removal of the worn tread and a peeling / roughening to produce a uniform surface which is curved in a plane parallel to the axis of the tire (the so-called "roughness radius" and the "roughness contour"). This results in a predetermined degree of roughness in order to enable the new tread.

Especially when retreading truck tires, each of which has significantly larger values than passenger car tires, individual local damage that is reflected in the carcass surface is repaired separately. This is done by grinding to provide a roughened and unraveled surface. The holes are then filled with heated repair material, which is also usually binding rubber. This is often done with small extruders the size of hand tools, but is labor intensive and requires a great deal of care and attention.

In the case of retreading with pre-vulcanization in particular, the binder was - historically - produced by calendering as a wide plate, the working temperatures not exceeding 80 ° C. The binding rubber was cooled and rolled up with intermediate plastic layers, later being cut into widths adapted to different tire sizes, and applied as part of the labor-intensive process of "building" a pre-vulcanized tire.

The reason for this process is that when this binding rubber is put together to create a reasonable time for vulcanization in the autoclave, this rubber ages during storage. This means that the binding rubber begins to vulcanize, so that it cannot perform its welding function later or only incompletely. At the same time, it is at risk when the extrusion "starts" if the extrusion does not take place under very closely monitored conditions - in particular if the extruded plate has to be as thin as or thinner than the calendered plate.

This requires nozzle mouthpieces the width of a carcass, that is between about 140 mm and 350 mm, but with a nozzle opening of less than 1.2 mm or 1 mm in thickness of the binding rubber, and, - depending on the swelling factor - considerably less, down to 0.4 mm. This creates a high back pressure during the extrusion and it is practically impossible to keep the extrusion temperatures in the range which is considered by the rubber manufacturers to be safe - namely that which is used in the calendering - with an excess the temperature around 6 to 15 ° is considered critical depending on the connection.

Since the guarantee of safe welding is the responsibility of the rubber manufacturer, an extrusion device for the direct application of binding rubber to the carcass in the hands of the individual retreaders has not been approved by the rubber manufacturer.

Accordingly, although the direct application of binding rubber by means of extruders has been available on the market for a few years and a few retreaders have also used this method, there has been no widespread use of this technology.

Furthermore, for safety reasons, liability for ready-made clothing, i.e. , for gluing before vulcanization, the historical process of industry, in which the prepared carcass surface is sprayed with a rubber solution, also retained by these few retreaders.

However, such a rubber solution contains volatile constituents which are harmful to health. Spraying such a rubber solution is therefore prohibited in some areas of California and in a German state, and the more recent ones have to suspend this process. The bans are expected to increase worldwide.

From U.S. Patent 5,162,070 to the present applicant is a binder rubber extruder for direct extrusion on itself rotating tire carcass known. In this case, the binding rubber layer is basically applied in the exact dimension (1.2 mm or less), and applied to the carcass with a gentle elastic force, the radius of the nozzle mouthpiece in the horizontal plane being the largest roughness corresponds to that which occurs in practice. Outside the more or less wide band of this applied pressure, the extruded binding rubber, which cools very quickly, shrinks onto the outer areas and ensures good adhesion without air pockets.

This principle also works if, in the case of pre-vulcanized treads which have thin "wings" or side flanks, the binding rubber has to be pulled down 20 mm or 30 mm to the side of the carcass. The extrusion speeds are changed for the width adjustment, which is carried out by mechanically moved side plates, as well as for influencing the thickness of the applied binding rubber layer, the adjustment of the carcass rotation speed also serving within limits. The settings can be connected to one another and preprogrammed by a control unit.

EP-Al-0 528 683 shows a similar device with a different type of setting the extrusion width to the carcass width, namely the rotation of the extrusion head about its longitudinal axis out of the horizontal plane, in which it is suitable for the greatest width of the carcass surface che located.

In order to ensure a match of the carcass surface with the radius of the molding in all angular positions, the nozzle mouthpiece is provided with a spacer lip which lies against the housing in a position which comes to lie upstream of the extruded binding rubber due to the rotation of the carcass. The other lip, at a flat, small distance from the carcass surface, forms the outside of the binding rubber layer.

DE-Al-40 25 459 discloses the spiral winding of a thin and narrow strip of extruded binding rubber on a carcass. The spirally wound strips overlap one another, which does not reliably prevent air pockets. In this respect, this publication corresponds to the well-known method of streak wrapping for the construction of treads for vulcanization in a form as is known, for example, from DE-PS 17 29 555.

All of these known methods work with binding rubber extruders with small nozzle mouthpiece slots, i.e. with high back pressure which is generated in the nozzle mouthpiece and therefore in an extrusion temperature range which exceeds the working temperature of the historical calendering for the binding rubber film. Neither of these methods can fill holes.

FR-A-23 59 700 relates to the filling of holes and imperfections of uneven, worn tires. Here, a tread for retreading is applied by vulcanizing in a mold.

To achieve this, an extrusion spray head is provided with exchangeable nozzle mouthpieces which are adapted to the desired curvature of the tire. The nozzle mouthpiece is approximated to the carcass surface, but does not abut it and is at a fixed distance from the carcass surface on which rubber is to be applied by the extruder. The tread layer is then formed from an accumulation of rubber which is formed between the nozzle outlet and the carcass by rotating the carcass toward the downstream center of the nozzle mouthpiece with the nozzle opening between the carcass and the downstream curved nozzle surface. The radial distance between them determines the thickness of the tread strip applied to the carcass.

Devices of this type have been used in retreading from shape vulcanization, although up to now - as far as is known - they have only been used for normally prepared and roughened carcasses and have served there to a limited extent for filling holes.

One reason for this is that the hole filling material is tread rubber which is designed for high mileage and road grip, and not the soft and sticky binding rubber which is normally used. A more important reason is that the pressure generated by the extruder, which presses on the excess of soft rubber, can expand freely and is not sufficient to penetrate more than just shallow holes, which, however, must be carefully shaped to allow a slight flow of rubber enable. In practice, this means that the operator has to judge which holes have to be filled in the usual way and which can be filled by the device. This gives rise to an uncertainty factor in quality control which many retreaders consider unacceptable.

In this method, the connection between the beginning and the end of the extrusion after a full rotation of the carcasses is a problem and this connection or the so-called "butt" generally require an additional step, namely the cutting off of excess rubber and thus a possible one Waste.

Another disadvantage is that the thickness of the tread varies greatly if the carcass is not exactly centered.

REPLACEMENTB In contrast, the invention has for its object to provide a retreading device according to the preamble of claim 1 and a method for retreading according to the preamble of claim 12, in which the safety in the production of retreaded tires is increased, with a considerable reduction of Labor and cost.

This object is achieved according to the invention by claims 1 and 12, respectively. Advantageous further developments result from the subclaims.

Surprisingly, with the retreading device according to the invention, holes can be completely filled, with normal manual preparation, i.e. Grinding out the damaged areas. This is favored by the suitable choice of the temperature of the binding rubber, the binding of the binding rubber to the tire being sufficiently strong at the lower temperature that a binding rubber layer is taken away from the carcass surface against the pressure of the molded shoe according to the invention. The strong pressure prevents the formation of air pockets even more reliably. At the same time, the reduced temperature allows working in the temperature range which is definitely safe for binding rubber, so that the specifications of the rubber manufacturers can be met again as in calendering.

After the imperfections and holes in the carcass are automatically filled with the warm and viscous-soft binding rubber compound by the "lubrication" according to the invention, manual filling, even by means of small repair extruders, is completely unnecessary.

In this respect, it is particularly favorable that the penetration of the binding rubber mass into the rough grain is ensured due to the pressure applied. It is only necessary that the rough grain is fresh and clean, with which the spraying

- of rubber solution for ready-made clothing becomes unnecessary and thus pollution can be avoided and usually a complete job can be saved.

After the binding rubber layer, due to the excess binding rubber present, for example in the form of a "roller" that is rolled by the rotating tire, penetrates securely into holes, it is possible to fill the manual spatula, which is always labor-intensive with regard to quality assurance and was quality critical to leave out entirely.

In principle, the invention can be used not only for retreading using pre-vulcanized tread strips, where binding rubber, which is more expensive than tread rubber, is applied in as thin a layer as possible, but also for retreading using a vulcanized mold, where the base rubber, especially for truck tires, can be cheaper than tread rubber. This can then be applied in such a way that it is thinner in the middle of the carcass and builds up its strength towards the shoulders in order to form a larger proportion of the rubber to be applied for retreading, as the basis for a tire as shown in FIG. 9 is shown. This leads to cost and quality advantages.

It is particularly favorable if an extrusion mouthpiece has two lips which adjustably cover at least the width of the carcass and are at least a multiple of the average thickness of the binding rubber layer apart. As a result, the extruder is advantageously operated with a low nozzle resistance, which allows an extrusion temperature slightly above that during calendering for the known binding rubber film.

In addition, the lip, which - defined by the rotation of the carcass - is downstream of the intended flow of binding rubber lies, protruding from the other lip by an amount which exceeds the average thickness of the binding rubber layer to be applied by a multiple, and is designed as a molded shoe or application shoe which lies against the carcass surface.

It is particularly expedient if the shaped shoe has a curvature which does not necessarily have to be completely circular, but in parts has a radius which is at least as large as the largest roughness radius of any tire to be retreaded up to the extreme case with the radius = infinite, ie a straight line, so that the carcass can be deformed in accordance with this curvature under a strong contact pressure of the extruder. If the radius is infinite, there is accordingly a flat front surface of the molded shoe.

According to a further preferred embodiment, the molded shoe has a chamfer that has a depth that changes along this curvature.

In operation, the binding rubber is extruded into a cluster adjacent to this shaped shoe or application shoe and is hydrodynamically entrained in the chamfer between the application shoe and the rotating carcass and drawn into the gap. The accumulation thus acts in the manner of a "rolling bench" of a rolling mill or a calender, from which "rolling bench" or "roller" binding rubber is pressed with the contact pressure of the extruder into the surface roughness of the carcass surface and into holes present there. The strong contact pressure of the extruder presses the carcass surface into line with the curvature of the application shoe, which makes the need to replace extrusion mouthpieces for different roughness radii of the carcasses superfluous.

A bevel that is deep in the middle and that is almost open Reduced to zero towards the flanks produces the greatest pressure in the binding rubber flowing in the middle in order to counteract a pressure peak in the application shoe, which deforms the carcass surface against the stiffness of the steel belt there. With the correct choice of dimensions, this produces the surprising result that essentially the same thickness of the binding rubber is established over the carcass surface as is necessary for retreading by means of pre-vulcanized treads.

Conversely, a bevel that is flat in the middle and deeper towards the shoulders also produces a surprising result by increasing the thickness of the binding rubber towards the shoulders, as may be required for the "base rubber" when vulcanizing in molds .

The angle of the chamfer with respect to the carcass surface can be adapted to the requirements in a wide range. In a preferred embodiment it is, for example, 15 °, but also considerably steeper and considerably flatter angles or also roundings or roundings are possible if desired. The length of the chamfer compared to the entire height of the molded shoe - viewed in the tangential direction of the carcass - can be, for example, two thirds, although considerable variations are also possible here. The protrusion between the molded shoe and the opposite lip of the extruder can also assume, for example, ten times the average thickness of the binding rubber layer, but also values which differ considerably therefrom. The same applies to the distance between the molded shoe and the opposite lip, this distance preferably being somewhat less than the projection dimension mentioned above.

The extrusion axis preferably extends radially with respect to the carcass. According to an advantageous embodiment, movable side pieces are provided for adjusting the width of the extrusion to different widths of the carcass surfaces. These can be provided with different curvatures in three dimensions in order to produce alternative cross-sectional areas for the side edges of the binding rubber, including a slight local thickening with a sharp edge, or a run down on the flanks of the carcasses, or combinations of these effects.

The application shoe can also be provided with a separate heating element, which is preferably operated electrically, and serves to raise the temperature of the shoe to a temperature slightly above the temperature of the extruded binding rubber in order to facilitate "ironing". If the entire tire building cycle takes at least three minutes, the application of the binding rubber should take a minute or less, and this heating element can be turned on to help only during this pressing and allows the molded shoe to lower the temperature of the surrounding one Metal mass of the extrusion head returns during the rest of the cycle.

Further details, advantages and features result from the following description of several exemplary embodiments with reference to the drawing.

Show it:

1 shows a binding rubber extruder according to the invention of the CTC (cushion-to-casing) type, in which the binding rubber is applied to the carcass and which, according to the invention, can work together for the use of an existing retreading system from any manufacturer;

REPLACEMENT 2 shows an embodiment of a binding rubber extruder according to the invention, which is an integrated unit which also applies treads, again the CTC type of the extruder and a so-called swing builder according to the unpublished DE-OS 42 03 027, to which reference is made in full, is used;

3 shows a further embodiment of a retreading device with a binding rubber extruder according to FIG. 1, which is used in a known tread extruder for retreading in a vulcanizing mold;

4 shows a schematic sectional view of a detail from FIGS. 1, 2 or 3 with part of the tire carcass which is flattened out by the application shoe of the extruder according to the invention and in which a binding rubber layer is applied and holes are filled in accordance with the invention;

5 shows a view, similar to FIG. 4, of the curvature of the carcass ring surface, which is flattened by the curvature of the application shoe, FIG. 5A showing the distribution of the radial forces during this process;

6 is a front view of an extrusion nozzle according to the invention, the bevel being shaped in such a way that a binding rubber layer with a uniform thickness is produced over substantially the entire width of the annular surface of the carcass, wherein

7 indicates the effect on a section of a carcass; 8 shows a front view of the nozzle mouthpiece according to the invention, the chamfer being shaped in such a way that it creates a thickening of the binding rubber layer towards the flanks;

FIG. 9 shows the effect on a section of a carcass, a tread blank being additionally shown on the top of the binding rubber, as can occur in the embodiment of FIG. 3 when building a tire; and

10 shows an embodiment of the molded shoe which is modified from the representation according to FIG. 5.

In the embodiment according to FIG. 1, a binding rubber extruder 10 is provided according to the invention with an extrusion head 11 and an extrusion mouthpiece 12, which is described in detail in FIG. 4 and the following figures. A carcass 13 is stored in a tire building system 14 with a known construction, a center drive being provided for rotating the carcass 13. The extruder 10 is slidably guided in the direction of the carcass and away from the carcass by means of four ball bearing boxes 16, two of which are shown and which allow the extruder 10 to slide easily on rails 17. A working cylinder 18 moves the extruder relative to the tire building system 14, preferably pneumatically, which additionally enables an easily adjustable approach force for the application shoe of the nozzle mouthpiece 12 for deforming the carcass 13, as will be explained further below.

The tire building system 14 also has a roll-on device 19 for the pre-vulcanized tread, after which it is applied in a known manner to the surfaces 15 of the carcass 13 provided with binding rubber. FIG. 2 shows an integrated unit of a binding rubber extruder 10 and a tire building system, the same reference numerals indicating the same parts as in FIG. 1, as in the other figures. Instead of the device for generating a horizontal movement of the extruder 10 against the carcass 13, the tire building system here shows a pivot arm 20 which can be pivoted about a pivot point 21 by a linear screw drive 22 which is actuated by an electric motor 23.

This arrangement allows the tire carcass 13 to move in the position shown in a circular arc which is approximated to the horizontal and is pressed essentially radially against the extrusion nozzle 12 according to the invention, an approach force being generated by the drive motor 23 of the linear drive 22, which acts on the swivel arm 20 is monitored.

When moving away from the extruders 10, the swivel arm 20 can serve to allow an easy assembly of the carcass 13 from the floor, as well as to press the carcass 13 into the unit for the application of the tread strip and the rolling 24 which towards the carcass for guiding the precured tread from the roller table 25 and for applying at least the rolling force against the carcass by means of the roller 26.

This embodiment produces a particularly effective and rapid integration of all work steps for building a tire in a pre-vulcanized process, details of which can be seen from the - not previously published - DE-Al-42 03 027, to which reference is made in full.

In the two units shown, the different movements of the parts relative to one another, as well as the extrusion speed, can be coordinated by a process control unit. be dined, wherein various actions can be started and, if necessary, determined by an operator via a control panel 27, which is shown in FIG. 2, but can equally be used in FIG. 1.

This relates in particular to the coordination of the rotation of the carcass, the relative movement and the contact force between the nozzle and the carcass and the chronological sequence of starting and stopping the rotation of the carcass and the extruder screw, which is explained in detail below with reference to ¬ ter figures is described.

FIG. 3 shows an embodiment similar to FIG. 1, wherein a tire building system with a tread strip extruder is used for the mold vulcanization. The system has a tread strip extruder 30 which feeds the extruded tread blank 31 to a double-loop accumulator 32 which is controlled in a known manner by a dancer potentiometer. The accumulator loop controller 32, which operates in a known manner, stops the extruder when the loops are full and starts it again after the tread for the tire structure has been removed. However, the speed of the tread-strip extruder is preferably set such that it simply takes into account the increase and decrease in the loops without interruption in order to produce a stable tread-extrusion.

An operator standing next to a control panel 27 installs and removes the carcass and feeds the tread, which he cuts off with a knife. It forms the joint and actuates the rolling device 19 in a known manner.

The function of the binding rubber extruder is automated as described below. Automation can also be extended to tread attachment, cutting, butting and rolling, but the easiest way is

SPARE BLADE (RULE 26) - solve

Se the tread handling shown here, which is sufficient to illustrate the invention. As far as the binding rubber extruder is concerned in this and the other examples, it operates fully automatically to the extent that in any case it does not distract from the construction work to be carried out essentially by one man.

4, 5 and 6 show the downstream lip of the extrusion spray head 12 according to the invention in contact with the cash register 13, the extrusion spray head having the shape of an application shoe 40.

This application shoe 40 is at a vertical distance from the lower lip 41, between which the depth of the nozzle or the spray head is formed, and also projects from the lower lip to the carcass by a different distance, which distances in in any case be a multiple of the average thickness of the layer 15 of the binding rubber to be applied.

These features mean that the extruder can operate against a low nozzle resistance with an extrusion temperature which is closer to that in the usual calendering than with known extruders, and that an accumulation of rubber is formed adjacent to the application shoe 40.

A chamfer or bevel of the application shoe causes rubber to be pulled under the contact surface of the contact surface by the rotation of the tire. In addition, the chamfer has the effect that the rubber accumulation acts like a rolling bench or roller of a rolling mill or a calender, from which the binding rubber layer is formed with a thickness which is determined by the size of the rolling bench and the size of the approach pressure of the extruder and the resistance to deformation the checkout surface is determined.

The size of the binding rubber roller, on the other hand, determines which The size of the holes can be filled reliably, based on the contact pressure of the extruder, in order to ensure penetration into the depth, and a larger binding rubber roller can fill a group of holes which occur together without interrupting the thin layer of binding rubber in between.

An electrical heating element 43 can be provided for heating the application shoe to a temperature above that of the rubber compound. The heating element 43 can be switched on so that it is only switched on during the binding rubber application time, which is, for example, a quarter of the total tire building cycle, it being possible for the shoe to reach the temperature of the reverse almost immediately ¬ metal mass returns during the rest of the build cycle. 4 shows holes filled in the carcass surface at 48 and holes still open at 49.

FIG. 5 gives an idea of the deformation of the carcass, in which FIG. 5A shows a pattern of the pressure change across the carcass width as a result of the changing resistance when the steel belt of the carcass is deformed.

5 and 6 also show side pieces 45 which are slidably adjustable by a suitable device, which is not shown, in order to be able to machine different widths of the surface of the carcasses.

FIG. 5 shows two types of side pieces of this type, which differ by different forward-looking projections: the projection 46, which can also be seen in FIG. 6, is designed in such a way that it has the width of the binding rubber exactly up to the width of the carcass ring surface limited. The protrusion 47 allows the accumulation of rubber so that it extends a certain length down the flank of the carcass in order to produce a covering with binding rubber there as well.

ERSÄΓZBLÄTT (RULE 26) FIG. 6 shows the application shoe or molded shoe 40, the chamfer 42 being lower in the middle and flatter towards the flanks, as is shown diagrammatically in FIG. 6A.

FIG. 7 shows a section of a carcass 13 which is produced with a thin and substantially uniform binding rubber layer through the shoe which is chamfered with the side pieces 46 as in FIG. 6.

FIG. 8 shows an application shoe 50 with a chamfer 51 which is flatter in the middle and becomes deeper towards the flanks, as shown diagrammatically in FIG. 8A.

FIG. 9 shows the binding rubber layer 52 which results from this and which becomes thicker towards the flanks. Also using a side piece 47, the binding rubber extends a certain distance down the flanks of the carcass. The corresponding tread blank 53 can be seen as it would result after a complete tire construction according to the embodiment in FIG. 3.

In a preferred operation of the retreading device according to the invention, the rotation of the carcass is started a predetermined small time period before the activation of the extruder, so that the thickness of the binding rubber builds up from a thin film which just covers the roughness on the carcass surface until the Extruder has reached its preset speed. When the checkout has made substantially a full rotation, the extruder speed is reduced to zero over essentially the same distance as that used to build up the full strength of the binding rubber layer. Over this distance, the binding rubber roller is reduced to zero, which creates a smooth "shock". In this way, there is no waste and the next tire can be used with a freshly formed binding rubber roller. Since - as mentioned - the size of the binding rubber roller or rolling bench and the contact pressure of the extruder determine which hole size can be filled, it can be stated as a surprising result that the hole filling by the device according to the invention is more reliable than if an operator it carries out, which should always exercise special care and attention for this task. This effect can be supported by binding rubber material, which is especially designed for this purpose and also for the purpose of adhering without spraying on the rubber solution, although good results have already been achieved when using normal binding rubber materials currently available.

Regarding the extrusion temperature, there is a direct comparison with the above-mentioned US Pat. No. 5,162,070: in order to achieve a rubber binding time of one minute for a truck tire size 12-R-22.5, an extruder speed of 100 U / min against the nozzle resistance of a slot of 0.4 mm in width, which resulted in a binding rubber layer of 1 mm in thickness at an extrusion temperature of about 90 ° C.

With an extrusion die according to the invention with a slot width of 2.8 mm, the extruder only had to be operated at 40 rpm and gave an extrudate temperature of 80 ° C.

The embodiment of the molded shoe 40 shown in FIG. 10 shows a molded shoe with a straight temple edge. The radius of curvature of the molded shoe 40 is thus infinite in this embodiment. When the binding rubber layer is applied, the molded shoe presses the carcass in such a way that a flat contact is made over the entire width of the carcass, although the carcass is slightly curved in the transverse direction. In this respect, the pressure distribution corresponds to that distributed in FIG. 5 A, although the central region is emphasized more strongly. It is particularly favorable that the roughened carcass surface for the rubber roller that forms acts like a kind of solid feed pump which, despite the high contact pressure on the molded shoe 40, takes a rubber layer with it. All repair holes are filled, the filling being carried out more reliably than in the case of manual repair using a hand extruder. Due to the considerable pressure applied, all fine grooves, furrows and other unevenness in the carcass are evenly filled, which also serves to improve the anchoring of the binding rubber layer in the carcass, and also the ventilation which would otherwise occur during autoclaving must take place, prepared.

The thickness of the binding rubber layer can be adapted to the desired extent to the desired extent, it being readily possible to adapt the uniformity of the binding rubber layer over the width of the tire through the different possible shapes of the molded shoe.

It is also particularly favorable that a shock does not occur practically when the binding rubber layer is applied. By initiating the rotation of the carcass at the same time as the extrusion begins, the binding rubber roller builds up slowly, so that the binding rubber layer also only slowly increases to the preset thickness. When the extruder is switched off in good time before the target thickness is reached, a kind of overlap is achieved between the beginning and end of the binding rubber layer after the binding rubber roller then degrades uniformly with the end of the rotation. The shock is then completely lubricated by appropriate running and omitting the carcass.

Another particular advantage lies in the fact that the additional spraying of the carcass with rubber solution becomes superfluous due to the strong pressure applied if the coating is within a few hours after the roughening of the carcass. checkout is done. This is preferred for several reasons.

It is also readily possible to cover so-called wings with so-called wings, by applying a binding rubber plate of about 100 mm width by hand in a manner known per se. This is also possible for treads with a convex undersurface, so-called contour treads, which run out in very short wings, a further possibility for such treads being to design side parts 46, 47 accordingly, so that to a depth of 30 mm down the flanks lubrication takes place reliably.

Claims

Expectations

1. Retreading device for tires, in which a tread can be loaded onto a carcass, with a tread feed device for feeding the tread to the carcass and with an extruder for the extrusion of a binding rubber layer, which has two lips delimiting an extrusion nozzle, of which the in the direction of movement of the carcass, the rear lip protrudes toward the carcass with respect to the other lip, characterized in that the lip closer to the carcass (13) is designed as a molded shoe (40) and is pressed against the carcass (13) to deform it.

2. Retreading device according to claim 1, characterized in that the shaped shoe (40) has a bevel or chamfer (42) which extends at an angle of 2 ° to 50 °, preferably between 10 ° and 30 °, to the carcass surface .

3. Retreading device according to one of the preceding claims, characterized in that the molded shoe (40) relative to the other lip (41) of the extruder (10) by three to fifteen times, in particular approximately ten times the thickness of the binding rubber layer (15) protrudes.

4. retreading device according to one of the preceding claims, characterized in that there is a clear width between the Form¬ shoe (40) and the lip (41), the thickness of the binding rubber layer (15) by the two-

REPLACEMENT BUTT (RULE 26) up to twelve times, in particular about eight times.

5. retreading device according to one of the preceding claims, characterized in that the shaped shoe (40) has a radius of curvature which is equal to or greater than the largest radius of the carcass surface or is substantially straight over its entire width.

6. Retreading device according to one of the preceding claims, characterized in that the extruder (10) only heats the binding rubber to a temperature which is in the range of the calendering temperature of, for example, somewhat less than 80 ° C or corresponds to it, or is somewhat higher , an alarm sensor for a limit value of about 90 ° C being provided at an extruder temperature of about 85 ° C.

7. Retreading device according to one of the preceding claims, characterized in that the nozzle mouthpiece of the extruder (40, 41) over the width of the carcass (13) has a changing chamfer (42), in particular the molded shoe (40) positive in the nozzle mouthpiece or is negatively curved so that the chamfer (42) is greatest in the center of the tire or on the tire flanks.

8. retreading device according to one of the preceding claims, characterized in that the binding rubber has such an adhesion to the carcass (13) and such a viscosity that it against the contact pressure of the molded shoe (40) in a gap produced by the binding rubber layer (15) between the carcass (13) and molded shoe (40).

9. retreading device according to one of the preceding claims, characterized in that the supply of Binding rubber is electronically controlled by the extruder (10), a binding rubber roller forming on the opposite side of the molded shoe (40) being used as an indicator, which is always kept so large by supplying new binding rubber that any depressions and injuries to the Carcass surface can always be filled completely.

10. Retreading device according to one of the preceding claims, characterized in that in the region of the nozzle mouthpiece of the extruder (10) the molded shoe (40) can also be heated with a heater (43) acting briefly during the application of the rubber layer (15) .

11. Retreading device according to one of the preceding claims, characterized in that in particular heated side flank shaped pieces (46, 47) laterally on the in particular unheated molded shoe (40), the distance between the shaped pieces being adapted to different carcass widths a Einteilvor¬ direction (45) is adjustable and the side flank fittings according to the design of the molded shoe (40) guide a binding rubber roller.

12. A method for retreading a tire, in which an extruder (10) binds rubber to a carcass

(13) is applied, characterized in that a molded shoe (40) of a nozzle mouthpiece of the extruder (10) is pressed against the carcass so strongly that the radius of curvature of the carcass (13) is adapted to the molded shoe (40) and any Depressions in the carcass (13) can be filled out via a free excess of binding rubber.

13. Method for retreading, characterized by the characterizing features of one of claims 1 to 11.

REPLACEMENT BUTT (REG & 26)

14. A method for retreading according to claim 12 or 13, characterized in that first the rotation of the carcass (13) is initiated just before the activation of the extruder (10) and then the binding rubber layer (15) of a thin layer, which the roughness of the Carcass surface just covers, is built up, and that the extrusion speed is reduced after a full revolution of the carcass (13), so that the binding rubber excess is reduced to zero when the binding rubber layer (15) is finished.

REPLACEMENT TT (RULE 26)