CA1113211A - Method of renewal of the tread on a worn pneumatic or solid rubber tyre - Google Patents
Method of renewal of the tread on a worn pneumatic or solid rubber tyreInfo
- Publication number
- CA1113211A CA1113211A CA263,036A CA263036A CA1113211A CA 1113211 A CA1113211 A CA 1113211A CA 263036 A CA263036 A CA 263036A CA 1113211 A CA1113211 A CA 1113211A
- Authority
- CA
- Canada
- Prior art keywords
- tread
- rubber
- bonding
- tyre
- internal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D30/00—Producing pneumatic or solid tyres or parts thereof
- B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
- B29D30/52—Unvulcanised treads, e.g. on used tyres; Retreading
- B29D30/54—Retreading
- B29D30/542—Retreading using envelopes or membranes provided with sealings for curing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D30/00—Producing pneumatic or solid tyres or parts thereof
- B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
- B29D30/52—Unvulcanised treads, e.g. on used tyres; Retreading
- B29D30/54—Retreading
- B29D30/56—Retreading with prevulcanised tread
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C33/00—Moulds or cores; Details thereof or accessories therefor
- B29C33/0038—Moulds or cores; Details thereof or accessories therefor with sealing means or the like
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29D—PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE
- B29D30/00—Producing pneumatic or solid tyres or parts thereof
- B29D30/06—Pneumatic tyres or parts thereof (e.g. produced by casting, moulding, compression moulding, injection moulding, centrifugal casting)
- B29D30/52—Unvulcanised treads, e.g. on used tyres; Retreading
- B29D2030/523—Ring-shaped treads
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Tyre Moulding (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
- Heating, Cooling, Or Curing Plastics Or The Like In General (AREA)
- Tires In General (AREA)
Abstract
METHOD OF RENEWAL OF THE TREAD ON A WORN PNEUMATIC OF SOLID
RUBBER TYRE
ABSTRACT OF THE DISCLOSURE
The invention is concerned with a method of renewal of the tread of a worn pneumatic or solid rubber tyre. A layer of bonding rubber is applied to the prepared body of the tyre and a prefabricated rubber tread ring is applied. Gaseous inclusions between the applied layers are avoided or led away and the resulting blank is heated in an autoclave for vulcanizing the bonding rubber. The tread rins, which on its underside exhibits a rough face of projections and recesses forming a net work of passages, produced in a press mould simultaneously with the production of the tread and kept fit for bonding, is applied to the body coated with the layer of bonding rubber and any gaseous inclusions are led away out of the layers by application of reduced pressure, where upon the lateral outlet openings from the super imposed layers are sealed off, and/or by squeezing out by means of the exertion of mechanical pressure on the tread.
RUBBER TYRE
ABSTRACT OF THE DISCLOSURE
The invention is concerned with a method of renewal of the tread of a worn pneumatic or solid rubber tyre. A layer of bonding rubber is applied to the prepared body of the tyre and a prefabricated rubber tread ring is applied. Gaseous inclusions between the applied layers are avoided or led away and the resulting blank is heated in an autoclave for vulcanizing the bonding rubber. The tread rins, which on its underside exhibits a rough face of projections and recesses forming a net work of passages, produced in a press mould simultaneously with the production of the tread and kept fit for bonding, is applied to the body coated with the layer of bonding rubber and any gaseous inclusions are led away out of the layers by application of reduced pressure, where upon the lateral outlet openings from the super imposed layers are sealed off, and/or by squeezing out by means of the exertion of mechanical pressure on the tread.
Description
21~
The invention refers to a method of retreading pneumatic or solid rubber tyre, in which a layer of bonding rubber is provided between the prepared body of the tyre and a rubber tread section; any gaseous inclusions between the applied layers being led away and the blank prepared in this way being heated in an autoclave for vulcanizing the layer of bonding rubber. In the case of heavy-cleated large tyres, the tread section may be in the form of one of separate segments and/or tread rings to be connected together, although it will usually be a single tread.
In known methods, the blank is enclosed in a rubber jacket onto which pressure is then brought into action so ~hat the gas inclusions present in the layered structure of the blank escape. Furthermore the layered structure of the blank is fixed by the jacket, especially for the~critical state which appears when, under the influence of the heat of vulcanization, the bonding rubber becomes plastic and finally shortly before vulcanization even liquid. Jackets are costly to produce, ~-they are easily damaged and are then leaky. Their life is .
limited, depending upon the materiall vulcanization temperature and kind of treatment.
Other known methods no longer indeed require rubber jackets, but they are suited only to certain types of tyre and require additional measures which increase the cost of the retreading considerably.
The practice is also fundamentally known of producing in the press mould a rough face on the underside of the tread, necessary to the fastening of the tread to the body, at the same time as the profile of the tread. For this purpose a die with the negative profile of the desired rough face is forced onto or into the raw rubber in the press mould and kept there during the vulcanizing. The die may be formed as a loose part 3Z~
such, e.g., as a layer of fabric or else directly on the inside of one of the halves of the press mould o~ ~itted there. In any case the die is released from the rough face at the end o~
the pressing process. The surface of a rough face produced in that way has, however, after longish storage pro~ed to ha~e ~ost its good bonding capacity as a result of aging and oxidatio~.
The object of the invention consists in providing a tyre-retreading method utilizing a tread section, which ca~ be stored without significant deterioration in its bonding capacity prior to being bonded to a tyre body.
It is, in accordance with the in~ention, provided that a tread or tread ring, which on its underside exhibits a rough face of projections and recesses forming a network of passages produced in the press mould and kept fit for bonding, is applied to the body coated with the layer of bonding rubber and any gaseous inclusions are led away out of the layers through side edge openings by application of reduced pressure, whereupon the openings are sealed off from the superimposed layers and/or the inclusions are squeezed out by means of the exertion of mechanical pressure on the tread.
The combination of the aforesaid measures leads to a considerable simplification and cheapening of the method men-tioned above.
An essential part is played in this by the employment of a tread with a rough face fit for bonding, already produced in the press mould.
Roughening of the tread by means of a roughening machines directly before the tread is applied is dispensed with as well as the thereby ensuing loss of rubber material as well as the considerable consumption of time for the work itself of roughening.
Furthermore no mechanical roughening can be performed .i, .;
~3Z~
anyway in the case of the employment of mixtures of rubber of high wear-resist~nce and heavy-cleated treads or tread segments, unless an additional special reinforcement under the rubber and a rubber mixture is applied which, however, on the other hand causes an undesirable increase in the quantity of material used and in the operating temperature of the tyre retreaded in this way, without any increase in the depth of the roughening.
In the case of mechanical roughening of treads only fine roughening can be achieved, so that sticking together of a possible network of passages with the danger of undesirable inclusions of gaseous and liquid components is to be feared.
This leads to rejects because of the formation of bubbles and hollows in the vulcanized layer of bonding rubber. The rough face produced in the press mould forms on the contrary a highly effective network of passages for leading away possible inclu-sions because of the appreciable separation between its pro-jections and recesses as well as because of the height of the projections and recesses being equally open to choice.
The bonding rubber can now flow very easily into the deeper parts of the rough face, whilst with the roughening applied hitherto the underside of the tread was merely slashed, so that the bonding rubber remained on the surface. In accordance with the invention a relatively deep transition layer consisting of tread material and bonding rubber is created.
This is important since the tread material and the bonding rubber exhibit different physical values. The deeper the transition layer, that is, the layer where the two different materialsof the tread and bonding rubber engage each other, the more intimate and robust is not only the bond finally attainable by the vulcanization but also already the force of adhesion with which the tread is secured by the unvulcanized layer of bonding rubber. The layer structure of the blank thus ~3211 obtai.ns adequate fixing because of the essentially intensive sticking together of the layers through the rough face pro-ducecl in the press mould. The considerably enlarged.and there-fore considerably more effective rough face thereb~ takes o~er the retaining function of the rubber jacket employed hitherto.
It is of-course ~ery important that the rough face produced in the press mould maintain its fi.tness ~or bonding, i.e., that the surface of the rough face e~en after a time in storage can always enter into an intimate bond with the bonding rubber ~r 21~1 by vulcanization. Preferably the rough face of the tread is, for this purpose after withdrawal of the d.ie when one is employed, coated shortly after removal of the tread rom the press mould with a known solution of an unYulca.nized mixture of bonding rubber dissolved in petrol or benzene or the like. In that case the solution ties the unsa.turated molecules in the surface of the rough ~ace, the structure of which is opened up by breaking the rough face out of the metallically clean: ace :
of the press mould, and thus a physicoche~ical association takes place, that is, an ion exchange between the H-bonds o the ~:
sulfhydryl groups. ~he surface o the sol~en.t coating thus remains activated and may where necessary directly before applying _ _ _ _ __ _ __ _ , .
~ .
~32~
t}~le tread t:c, t~le '~o~ly be reclc-tiva-ted by spreclding on rnore solution.
After applying -the coating of solu-tion to the rough Face of -the tread a pro-tective foil is advantageously s-tuck to -the rough iace, which is removed before -the -tread can be applied to the body. Basically in the cas,e of the employment of a fabric or the like as the die i-t is also possible to reduce the decay in the fitness for bonding if the fabric is detached from the rough face only directly before use of the t`read. ' ' .
In producing the layered structure of the blank the layer of bonding rubber is preferably applied in the plastic state.
For plasticity imparts -to the layer of bording rubber the degree of flowability necessary to flowlng into the rough face. The plastic state is achieved either by the employment of fresh bonding rubber or by heating tile bonding rubber or by appropriate additions to the bonding rubber. By the flowing of -the bonding ru~ber into the rough face an intimate connection between body~bonding rubber and tread is already brought about before vulcanization, and this is an important prerequiste for auxiliary means such as a rubber jacket or the like being able to be disper.sed with in vulcanization.
The process of flow of the bonding rubber is completed by the heat and pressure treatment in the autoclave.
The tread whenever possible is applied in ring form to the body coated with the layer of bonding rubber, preferably under prestress. For the preparation o the blank for treatment in the autoclave -there are a number of advantageous methods ~ . ` ' ~ . :: :
: . -The- ~read r~ay be rolle(i ~r~e o~ inelusi-~ns c~f -.ir onto the bod~ co~l-ted wi-tl~ bon~ling ~ubber, thd-t is, s-ta-r.ing frorn the centre clnd pro~eedinG s-t~adily tow2rds the sides so tha-t the inc]usions can flow alvng to the ` !
la-teI~aL inle-t openings and there escape. This discharge is promoted b~ a -tread applied under prestress. After-wards the ~t~t openings in -the layers can be tightly closed in order on -the one hand -to avoid fresh penetration of inclusions into -the layered structure and on the other hand by sealing of the outlet openings to achieve additional fixing of the layered structure of the blank.
In special cases, e.g., in the application of heavy-cleated tread materials, especially in the form of individual cleats or segments, i-t is advantageous -to lay a socalled building-jacket (not to he confused with the hitherto usual high grade rubber jacket) loosely round the blank and seal it at the sides to the tyre~ to put it under vacuum and roll on the loosely laid tread material. With this procedure air-inclusion-free rolling of the tread material onto the body can be enabled also in the case of a very thin underlayer of rubber. Discharge of the inclusions is effected through a network o~ passages kept free at the side of the tyre. The jacket is taken off 6~q Q~
again and the ~r~ openings from the layers are where necessary sealed off.
.
: . . . . .
,.: . . . ~ - :
.. . . . . .
-.,-.: - - .
~ `:: . ' - --
The invention refers to a method of retreading pneumatic or solid rubber tyre, in which a layer of bonding rubber is provided between the prepared body of the tyre and a rubber tread section; any gaseous inclusions between the applied layers being led away and the blank prepared in this way being heated in an autoclave for vulcanizing the layer of bonding rubber. In the case of heavy-cleated large tyres, the tread section may be in the form of one of separate segments and/or tread rings to be connected together, although it will usually be a single tread.
In known methods, the blank is enclosed in a rubber jacket onto which pressure is then brought into action so ~hat the gas inclusions present in the layered structure of the blank escape. Furthermore the layered structure of the blank is fixed by the jacket, especially for the~critical state which appears when, under the influence of the heat of vulcanization, the bonding rubber becomes plastic and finally shortly before vulcanization even liquid. Jackets are costly to produce, ~-they are easily damaged and are then leaky. Their life is .
limited, depending upon the materiall vulcanization temperature and kind of treatment.
Other known methods no longer indeed require rubber jackets, but they are suited only to certain types of tyre and require additional measures which increase the cost of the retreading considerably.
The practice is also fundamentally known of producing in the press mould a rough face on the underside of the tread, necessary to the fastening of the tread to the body, at the same time as the profile of the tread. For this purpose a die with the negative profile of the desired rough face is forced onto or into the raw rubber in the press mould and kept there during the vulcanizing. The die may be formed as a loose part 3Z~
such, e.g., as a layer of fabric or else directly on the inside of one of the halves of the press mould o~ ~itted there. In any case the die is released from the rough face at the end o~
the pressing process. The surface of a rough face produced in that way has, however, after longish storage pro~ed to ha~e ~ost its good bonding capacity as a result of aging and oxidatio~.
The object of the invention consists in providing a tyre-retreading method utilizing a tread section, which ca~ be stored without significant deterioration in its bonding capacity prior to being bonded to a tyre body.
It is, in accordance with the in~ention, provided that a tread or tread ring, which on its underside exhibits a rough face of projections and recesses forming a network of passages produced in the press mould and kept fit for bonding, is applied to the body coated with the layer of bonding rubber and any gaseous inclusions are led away out of the layers through side edge openings by application of reduced pressure, whereupon the openings are sealed off from the superimposed layers and/or the inclusions are squeezed out by means of the exertion of mechanical pressure on the tread.
The combination of the aforesaid measures leads to a considerable simplification and cheapening of the method men-tioned above.
An essential part is played in this by the employment of a tread with a rough face fit for bonding, already produced in the press mould.
Roughening of the tread by means of a roughening machines directly before the tread is applied is dispensed with as well as the thereby ensuing loss of rubber material as well as the considerable consumption of time for the work itself of roughening.
Furthermore no mechanical roughening can be performed .i, .;
~3Z~
anyway in the case of the employment of mixtures of rubber of high wear-resist~nce and heavy-cleated treads or tread segments, unless an additional special reinforcement under the rubber and a rubber mixture is applied which, however, on the other hand causes an undesirable increase in the quantity of material used and in the operating temperature of the tyre retreaded in this way, without any increase in the depth of the roughening.
In the case of mechanical roughening of treads only fine roughening can be achieved, so that sticking together of a possible network of passages with the danger of undesirable inclusions of gaseous and liquid components is to be feared.
This leads to rejects because of the formation of bubbles and hollows in the vulcanized layer of bonding rubber. The rough face produced in the press mould forms on the contrary a highly effective network of passages for leading away possible inclu-sions because of the appreciable separation between its pro-jections and recesses as well as because of the height of the projections and recesses being equally open to choice.
The bonding rubber can now flow very easily into the deeper parts of the rough face, whilst with the roughening applied hitherto the underside of the tread was merely slashed, so that the bonding rubber remained on the surface. In accordance with the invention a relatively deep transition layer consisting of tread material and bonding rubber is created.
This is important since the tread material and the bonding rubber exhibit different physical values. The deeper the transition layer, that is, the layer where the two different materialsof the tread and bonding rubber engage each other, the more intimate and robust is not only the bond finally attainable by the vulcanization but also already the force of adhesion with which the tread is secured by the unvulcanized layer of bonding rubber. The layer structure of the blank thus ~3211 obtai.ns adequate fixing because of the essentially intensive sticking together of the layers through the rough face pro-ducecl in the press mould. The considerably enlarged.and there-fore considerably more effective rough face thereb~ takes o~er the retaining function of the rubber jacket employed hitherto.
It is of-course ~ery important that the rough face produced in the press mould maintain its fi.tness ~or bonding, i.e., that the surface of the rough face e~en after a time in storage can always enter into an intimate bond with the bonding rubber ~r 21~1 by vulcanization. Preferably the rough face of the tread is, for this purpose after withdrawal of the d.ie when one is employed, coated shortly after removal of the tread rom the press mould with a known solution of an unYulca.nized mixture of bonding rubber dissolved in petrol or benzene or the like. In that case the solution ties the unsa.turated molecules in the surface of the rough ~ace, the structure of which is opened up by breaking the rough face out of the metallically clean: ace :
of the press mould, and thus a physicoche~ical association takes place, that is, an ion exchange between the H-bonds o the ~:
sulfhydryl groups. ~he surface o the sol~en.t coating thus remains activated and may where necessary directly before applying _ _ _ _ __ _ __ _ , .
~ .
~32~
t}~le tread t:c, t~le '~o~ly be reclc-tiva-ted by spreclding on rnore solution.
After applying -the coating of solu-tion to the rough Face of -the tread a pro-tective foil is advantageously s-tuck to -the rough iace, which is removed before -the -tread can be applied to the body. Basically in the cas,e of the employment of a fabric or the like as the die i-t is also possible to reduce the decay in the fitness for bonding if the fabric is detached from the rough face only directly before use of the t`read. ' ' .
In producing the layered structure of the blank the layer of bonding rubber is preferably applied in the plastic state.
For plasticity imparts -to the layer of bording rubber the degree of flowability necessary to flowlng into the rough face. The plastic state is achieved either by the employment of fresh bonding rubber or by heating tile bonding rubber or by appropriate additions to the bonding rubber. By the flowing of -the bonding ru~ber into the rough face an intimate connection between body~bonding rubber and tread is already brought about before vulcanization, and this is an important prerequiste for auxiliary means such as a rubber jacket or the like being able to be disper.sed with in vulcanization.
The process of flow of the bonding rubber is completed by the heat and pressure treatment in the autoclave.
The tread whenever possible is applied in ring form to the body coated with the layer of bonding rubber, preferably under prestress. For the preparation o the blank for treatment in the autoclave -there are a number of advantageous methods ~ . ` ' ~ . :: :
: . -The- ~read r~ay be rolle(i ~r~e o~ inelusi-~ns c~f -.ir onto the bod~ co~l-ted wi-tl~ bon~ling ~ubber, thd-t is, s-ta-r.ing frorn the centre clnd pro~eedinG s-t~adily tow2rds the sides so tha-t the inc]usions can flow alvng to the ` !
la-teI~aL inle-t openings and there escape. This discharge is promoted b~ a -tread applied under prestress. After-wards the ~t~t openings in -the layers can be tightly closed in order on -the one hand -to avoid fresh penetration of inclusions into -the layered structure and on the other hand by sealing of the outlet openings to achieve additional fixing of the layered structure of the blank.
In special cases, e.g., in the application of heavy-cleated tread materials, especially in the form of individual cleats or segments, i-t is advantageous -to lay a socalled building-jacket (not to he confused with the hitherto usual high grade rubber jacket) loosely round the blank and seal it at the sides to the tyre~ to put it under vacuum and roll on the loosely laid tread material. With this procedure air-inclusion-free rolling of the tread material onto the body can be enabled also in the case of a very thin underlayer of rubber. Discharge of the inclusions is effected through a network o~ passages kept free at the side of the tyre. The jacket is taken off 6~q Q~
again and the ~r~ openings from the layers are where necessary sealed off.
.
: . . . . .
,.: . . . ~ - :
.. . . . . .
-.,-.: - - .
~ `:: . ' - --
2~1 At the same time for leading away the inclusion~ of air and ~or holding the tread firmly onto the body the tread laid on the body may be enclosed by means of an elastic rubber or plastics pressure-band which is made with as many perforations as possible or by means of an elastic net. The cross-section of the tension-band and hence the pressure decreases from the centre to the sides, so that a pressure gradient results for automatic leading away of inclusions to the sides, which is further strengthened by the curvature of the body.
Leading gaseous occlusions out of the layers of the blank may be further facilitated if the occlusions are led via channels leading to the sides of the tread, which may be produced in the rough face of the tread as the same time as this in the press mould.
During building and vulcanizing the body should be put on a rim and under air pressure. This is particularly to be recommended in the case of those bodies which tend to shrink.
As heating medium in the autoclave, besides water hot air is also suitable, especially moist air, and steam.
If the body to be retreaded is damaged in the ply a tread may be employed which consists of a top part and a bottom part, of which the bottom part wxhibits inserts of steel mesh, plastics mesh or the like. In order to perform this method economically and reliably the bottom ~ - .
,','~
g p-ar, ~ h~ -t~E) part o~ t~!? -tr-~ad ~r~ adv~-~ntclgeously r~sp~ctiv~y pro~luced in ~he press mould as indeperldent parts alrea(ly lI.I`iin~ rough ~ce~; a-~ -the bonelin~ sides and applied -~o th~ body one ~fter the o-ther ~ith a further bonding mixture int~rposed.
Since the bottom par-t because of -the insexts cannot be stretched, in covering the body with the annular bo-ttom part the circumference of -the body must be reduced, for example, by kinking the body during the coverirlg at a number of points along the body circumference.
If the tread is applied to the prepared body already in the form of a closed ring the danger exists of the plastic layer of bonding rubber becoming non-uniform or of -the tread sticking firmly to the layer of bonding rubber before .
it has been brought into the required position.
Other known methods assume a relatively great mechanic~l ~ -effort, or frequently undesirable imbalances occur through non-uniform dis-tribution of -the tread material along the circumference of the body.
~ .
It is therefore proposed that in a stretching process there is imparted to the tread ring directly before application to the body a ; stretch running in the circumferential direction, which 1, I the tread ring maintains temporarily without stretching means, such that -the diameter of the stretched tread ring is greater than the diameter of the body.
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According to this method, the tread ring, prior to applying it to the body is stretched very hard in a simple stretching mechanism so that when the tread ring is removed from the stretch-ing mechanism a free stretch oE about 3-4% results temporarily, which allows the tread ring to be slipped over the body without further auxiliary means and the ring, preferably in the horizontal position of the body, to be arranged in exact correlation with the circumference of the body. The free stretch of, for example, 4% is rapidly and continuously reduced ro about a 1% permanent stretch. In any case, the duration of the temporary free stretch, which is available after the stretching process, is adequate for applying the tread ring to the body in a simple manner.
The e~tent of the necessary temporary stretching of the tread ring depends upon varlous factors, in particular upon the degree of free stretch desired and upon the composition of the tread rubber. In practical tests with commercial tread material, stretching of, for example, about 100% with subsequent temporary free stretch of about 4~ has been applied, but also smaller degrees of stretching have proved adequate.
Since the stretching process and likewise the state of temporary free stretch has included every part of the tread ring, there follows also the gradual reduction of the stretch to a permanent value everywhere uniformly along the circumference of the ring, so that no imbalances ~
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- , . . . ...
can oc ur.
The di.arneter of the unatre-tched tread ring m~y be given just the sarlle dimension as -the diame-ter of -the body.
In this case -the permanent remainder of the ~ree s-tretch, which amounts to only a very s~all percen-tage, cou.ld be easily equalized by rolling on -the applied tread ri~g.
/
' ;':L3:' ' .4 _ ;~ _ ~ I .
, .' '' ' ~L~13211 ~ s~rer l)ly ~i~e didr!e-~:s~r~ o~ the tr~eacl rinSr before -th~ -tchin~, procesC is sr,a1le~ than -t}l~ dil~e-rer of tl~ d~ L is, b-y clt le~s-, o~e percer!t. lihe eorl,equence of -this is tha-t a~ter the redllction of -the free stre-tch no oversize res~l~ts and th~ dia~e-~er of the tread ring and the body are i~ the end equal. The selection of a diameter of -the tread ring before -the stretching process, which is smaller by more -than 1%
leads in the end to the tread ring seating on the body under tension~ since the diameter of the tread ring after the reduction of the ~ree stretch is sm~ller than the outer diameter of the body. In this case the advantage of easy application of the tread ring to which a free stretch has temporarily been imparted, is combined with the further improvement that the tread ring is seated tightly onto the body. rurthermore in this way automatic escape of gaseous componen-ts from the gaps is achieved.
For contact of -the tread against the domed body starts, seen in cross-section, at their centre and increases progressively to the sides, so that the gaseous components can be forced out to the sides and not included. If still further pressure is needed for this~ where necessary a pressure-band or net as mentioned above may be employed in addition.
~ .
If in applying the tread ring only a small difference in diameter between the tread ring and the body is preferred it is advantageous iI the layer of bonding rubber before applieation of the tread ring is covered with a slide-foil of plastics which after pulling on of -j the tread ring is pulled out again from the applied layers.
~.. . ~ . ~ . .
.
: , . ,:. . . . . .
.. :.,, ' ~
Z~l -Pulling out again is advantageously carried out immediately after the application of the tread ring, before its free stretch further diminishes. The slide-foil is preferably hung like a tablecloth loosely over the tyre arranged horizontally, so that the edge regions of the slide-foil cover the periphery of the body at least to its centre all round. A central cut-out from the slide-foil may be used for easy centring of the slide-foil with respect to the tyre. Also for the case where the tread ring is coated with the layer of bonding rubber the slide-foil is spread over the body.
Accordingly, what is being claimed herein is a method of retreading a rubber tyre, essentially comprising the steps of:
producing a moulded and vulcanized tread section, in a press mould, having an internal surface for bonding and an outer tread surface; activating immediately after curing on the internal surface of the vulcanized tread section additional unsaturated sulfur molecules by opening up the structure of molecules on the said surface as a result of removal of the tread from the mould; coating the internal surface of the freshly vulcanized tread section having unsaturated vulcanized sulfur molecules with a solution of an unvulcanized bonding-rubber-mixture to tie the unsaturated molecules and thus to prevent oxidation and deterioration of the bonding capacity of the internal surface during storage and thereby enhance its bonding capacity during subsequent vulcanization without needing a subsequent mechanical roughening of the internal tread surface; applying the tread section to the rubber tyre with a layer of vulcaniza-ble bondlng rubber between the prepared body of the tyre and the internal surface of the tread section, and, after evacuation of gaseous inclusions occurring between the coated internal surface and the layer of bonding rubber and after evacuation of any ` gaseous inclusions between the layer of bonding rubber and the
Leading gaseous occlusions out of the layers of the blank may be further facilitated if the occlusions are led via channels leading to the sides of the tread, which may be produced in the rough face of the tread as the same time as this in the press mould.
During building and vulcanizing the body should be put on a rim and under air pressure. This is particularly to be recommended in the case of those bodies which tend to shrink.
As heating medium in the autoclave, besides water hot air is also suitable, especially moist air, and steam.
If the body to be retreaded is damaged in the ply a tread may be employed which consists of a top part and a bottom part, of which the bottom part wxhibits inserts of steel mesh, plastics mesh or the like. In order to perform this method economically and reliably the bottom ~ - .
,','~
g p-ar, ~ h~ -t~E) part o~ t~!? -tr-~ad ~r~ adv~-~ntclgeously r~sp~ctiv~y pro~luced in ~he press mould as indeperldent parts alrea(ly lI.I`iin~ rough ~ce~; a-~ -the bonelin~ sides and applied -~o th~ body one ~fter the o-ther ~ith a further bonding mixture int~rposed.
Since the bottom par-t because of -the insexts cannot be stretched, in covering the body with the annular bo-ttom part the circumference of -the body must be reduced, for example, by kinking the body during the coverirlg at a number of points along the body circumference.
If the tread is applied to the prepared body already in the form of a closed ring the danger exists of the plastic layer of bonding rubber becoming non-uniform or of -the tread sticking firmly to the layer of bonding rubber before .
it has been brought into the required position.
Other known methods assume a relatively great mechanic~l ~ -effort, or frequently undesirable imbalances occur through non-uniform dis-tribution of -the tread material along the circumference of the body.
~ .
It is therefore proposed that in a stretching process there is imparted to the tread ring directly before application to the body a ; stretch running in the circumferential direction, which 1, I the tread ring maintains temporarily without stretching means, such that -the diameter of the stretched tread ring is greater than the diameter of the body.
'' ., . .
~: ~
~, ' , . ' , ~
' ' ~ .
~;32~
According to this method, the tread ring, prior to applying it to the body is stretched very hard in a simple stretching mechanism so that when the tread ring is removed from the stretch-ing mechanism a free stretch oE about 3-4% results temporarily, which allows the tread ring to be slipped over the body without further auxiliary means and the ring, preferably in the horizontal position of the body, to be arranged in exact correlation with the circumference of the body. The free stretch of, for example, 4% is rapidly and continuously reduced ro about a 1% permanent stretch. In any case, the duration of the temporary free stretch, which is available after the stretching process, is adequate for applying the tread ring to the body in a simple manner.
The e~tent of the necessary temporary stretching of the tread ring depends upon varlous factors, in particular upon the degree of free stretch desired and upon the composition of the tread rubber. In practical tests with commercial tread material, stretching of, for example, about 100% with subsequent temporary free stretch of about 4~ has been applied, but also smaller degrees of stretching have proved adequate.
Since the stretching process and likewise the state of temporary free stretch has included every part of the tread ring, there follows also the gradual reduction of the stretch to a permanent value everywhere uniformly along the circumference of the ring, so that no imbalances ~
/
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:
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can oc ur.
The di.arneter of the unatre-tched tread ring m~y be given just the sarlle dimension as -the diame-ter of -the body.
In this case -the permanent remainder of the ~ree s-tretch, which amounts to only a very s~all percen-tage, cou.ld be easily equalized by rolling on -the applied tread ri~g.
/
' ;':L3:' ' .4 _ ;~ _ ~ I .
, .' '' ' ~L~13211 ~ s~rer l)ly ~i~e didr!e-~:s~r~ o~ the tr~eacl rinSr before -th~ -tchin~, procesC is sr,a1le~ than -t}l~ dil~e-rer of tl~ d~ L is, b-y clt le~s-, o~e percer!t. lihe eorl,equence of -this is tha-t a~ter the redllction of -the free stre-tch no oversize res~l~ts and th~ dia~e-~er of the tread ring and the body are i~ the end equal. The selection of a diameter of -the tread ring before -the stretching process, which is smaller by more -than 1%
leads in the end to the tread ring seating on the body under tension~ since the diameter of the tread ring after the reduction of the ~ree stretch is sm~ller than the outer diameter of the body. In this case the advantage of easy application of the tread ring to which a free stretch has temporarily been imparted, is combined with the further improvement that the tread ring is seated tightly onto the body. rurthermore in this way automatic escape of gaseous componen-ts from the gaps is achieved.
For contact of -the tread against the domed body starts, seen in cross-section, at their centre and increases progressively to the sides, so that the gaseous components can be forced out to the sides and not included. If still further pressure is needed for this~ where necessary a pressure-band or net as mentioned above may be employed in addition.
~ .
If in applying the tread ring only a small difference in diameter between the tread ring and the body is preferred it is advantageous iI the layer of bonding rubber before applieation of the tread ring is covered with a slide-foil of plastics which after pulling on of -j the tread ring is pulled out again from the applied layers.
~.. . ~ . ~ . .
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.. :.,, ' ~
Z~l -Pulling out again is advantageously carried out immediately after the application of the tread ring, before its free stretch further diminishes. The slide-foil is preferably hung like a tablecloth loosely over the tyre arranged horizontally, so that the edge regions of the slide-foil cover the periphery of the body at least to its centre all round. A central cut-out from the slide-foil may be used for easy centring of the slide-foil with respect to the tyre. Also for the case where the tread ring is coated with the layer of bonding rubber the slide-foil is spread over the body.
Accordingly, what is being claimed herein is a method of retreading a rubber tyre, essentially comprising the steps of:
producing a moulded and vulcanized tread section, in a press mould, having an internal surface for bonding and an outer tread surface; activating immediately after curing on the internal surface of the vulcanized tread section additional unsaturated sulfur molecules by opening up the structure of molecules on the said surface as a result of removal of the tread from the mould; coating the internal surface of the freshly vulcanized tread section having unsaturated vulcanized sulfur molecules with a solution of an unvulcanized bonding-rubber-mixture to tie the unsaturated molecules and thus to prevent oxidation and deterioration of the bonding capacity of the internal surface during storage and thereby enhance its bonding capacity during subsequent vulcanization without needing a subsequent mechanical roughening of the internal tread surface; applying the tread section to the rubber tyre with a layer of vulcaniza-ble bondlng rubber between the prepared body of the tyre and the internal surface of the tread section, and, after evacuation of gaseous inclusions occurring between the coated internal surface and the layer of bonding rubber and after evacuation of any ` gaseous inclusions between the layer of bonding rubber and the
3;~1 tyre body, sealing off the side strips of the bonding rubber and subjecting the tyre and the tread section to heat and pressure in an autoclave to vulcanize the bonding rubber and unite the tread section to the rubber tyre.
An embodiment of the method in accordance with the invention is explained in greater detail below with the aid of the drawings. In the drawings there is shown in:
Figure l: a perspective of a tread ring with a rough face produced in the press mould;
Figure 2: a perspective of a tread segment with a rough face produced in the press mould on the underside and on the edges;
Figure 3: a cross-section through a tread with a rough face formed in the press mould, Figures 4 to 7: a number of portions cut from a rough face produced in the press mould, but with different patterns of rough face~
"
\
\
ig,~ cr:~s,~ c:t::ioll ~hrough l blank w].;.ch is cover~d hy a -tread consi.s-ting o.~ a bo-ttor, part ~ncl a -top pa~" t;
igure 9 - a c-ross-section through a buil-t-up tyre or blan~, in which for the tyre in -the lefthand half of the illustration the tapering edges oi -the tread are being put under tension and in which the righ-thand part shows a tyre covered by a bllilding-jacket;
igure 10 - a diagrammatic il].ustration of a body during pulling on of a bottom part of a tread;
Figure 11 - a diagra~matic illustration of a stretching ~:
mechanism which may be used in the first phase of the application of a tread ring to a body;
igure 12 - a.diagrammatic side elevation of the second phase in which a s-tretched tread ring is being applied to a body;
igure 13 - a sectional elevation of the body in the second phase where a slide-foil is being employed;
igure 14 - a diagrammatic side elevation of a body in the third phase in which the tread ring is resting firmly against the body~
. .
., : - :
Th~ tre~ld ring 1 ~l-lowr! in Eigure 1 ~'rlibiL-s on i-ts inside a rough ~ace 3 and on its ou~er f~ce a prori~ing 2, the two o -th~m ha~ing been formed a-t the sarn~ time by the production of -the -tread 1 in the press mould. 'I'he -tread segmen-t 4 ;llustra-ted in Figure 2 arld provided with heavy profilinz 2 also exhibits an inner rough face 3 as well as rough edge-faces 5,6, at -the poin~s where -likewise a bond is to be carried ou-t by means of bonding rubber. Depending upon the type and form of the die, rough faces 3 of any chosen structure as well as of size to be determineo and of definable separation bétween -the projections 14 and the recesses 15 lying between them are possible (comp. 4-7). Even undercut projections 15 may be produced as shown in Figure 6.
Figure 7 illustrates, for example, a structure of the rough face 3 which can be produced by mere working of irregular recesses into the top half cr cover of the press mould.
It is clear that a rough face 3 of that kind forms an excellent network of passages for leading away gaseous and liquid components out of the layered structure of a buil-t-up tyre.
.
In Figure 8 the layered structure of a built-up tyre has been illustrated, the body 8 of which is covered by means of a tread or tread ring 1 which consists of a top part la and a bottom part lb which is provided with inserts 11. The bottom part lb serves for reinforcement of the body 8 the belts of wh~ch were damaged and have been :`
- ~ -, ~ ;
,. . - :
~L~13Zl~
tOt~ll ly O~ p~rticilly grou~d off in connee~-ion ~,~ith pre?.-lring -the bo~ly ~ for retreading. The bott:om par-t: 1`D
exhil~:its on all sides rough Faces produc2d preferably irl the press mould. For the underside of -the bo-ttom par-t lb is connected hy means of a layer 10 of bonding rubber to -the upper side of the body 8, whilst a further layer 9 of bonding rubber applied all round over the bottom part lb and also advantageo~sly as illustrated carried ou-twards over the bottom part lb, bonds the top part la on the one hand -to the bottom part lb and also as far as the edg2s of the tread are concerned to the body 8. A coat of material indicated by 12 is to illustra-te how the lateral points of outlet 12a from the layered structure are closed before reduced pressure is brought in one of the ways previously mentioned into action upon the layered s-tructure of the built-up tyre for -the purpose of leading away any gaseous and~or liquid inclusions.
Figure 9 on the other hand illus-trates in the lefthand part that by laying a strip 12 of bonding rubber under the tapering edges 13 of the tread or tread ring 1 a prestress may be created at that point for -the purpose of fixing the layered structure on-to the body 8.
On the other hand the righthand part of Figure 9 illustrates how particularly in the case of heavy-cleated profiles with a thin underlayer of rubber (not shown here) the liquid and/or gaseous inclusions are advantageous].y led away under a building-jacket 13 which is put under vacuum, .
. ~ :
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. .
.
.~. . . . ' , .
~32~
hilst -the -t~s~ 1 or respec-ti~ely its -top par-t la, af-ter it has ~een laid on only loosely, is rol:led on, st.-!r~l~ing from -the middle and proceeding towar~.s .he si,des.
The bui]ding-~ac!~e-t 13 is advan-tageously sealed at -the be,~d 16 by means of a ri1n and -the inclusions led to -the sides are drawn off via a channel 15 which is for~ed in fron-t of a ring 14. Before inserting the blan]c Ln the autoclave this jacket is removed.
Figure 10 illustrates merely diagramma-tically that the circumference of the wall and hence the diameter of the body 8 must be reduced when the unstretchable bottom part l_ of the tread ring 1 is being applied to the body 8. Reducing the size of the body 8 may, for example, be carried out by means of rods indicated by 18, which are pressed mechanically, advantageously in a symmetrical arrangement, into the body 8 at its periphery and thus enable pulling on of the bottom part lb.
According to a special method of applying a tread in the form of a rin~ to a body 22 the tread ring 21 with a preformed rough face is subjected to stretching of the order of magnitude of about 100~ tdepending upon the rubber mixture, form of profile, thickness of tread rubber, desired free stretch), in which the tread ring 21 is laid over two rollers 23 as well as a roller 25 which can be displaced mechanically, electrically or~hydraulically in the direction of the arrow 24, and is stretched by appropriate displacement of the roller 25. In the case of this stre-tching of only brief duration the tread ring 21 directly after its unloading exhibi-ts a free stretch ~ .. , . ~ . .
-. . .
. ... : . .. ~
3Z~
i.n ~e circ~lim:L;~rent;2l dirQc,ion of, for ~:xample, abou-t
An embodiment of the method in accordance with the invention is explained in greater detail below with the aid of the drawings. In the drawings there is shown in:
Figure l: a perspective of a tread ring with a rough face produced in the press mould;
Figure 2: a perspective of a tread segment with a rough face produced in the press mould on the underside and on the edges;
Figure 3: a cross-section through a tread with a rough face formed in the press mould, Figures 4 to 7: a number of portions cut from a rough face produced in the press mould, but with different patterns of rough face~
"
\
\
ig,~ cr:~s,~ c:t::ioll ~hrough l blank w].;.ch is cover~d hy a -tread consi.s-ting o.~ a bo-ttor, part ~ncl a -top pa~" t;
igure 9 - a c-ross-section through a buil-t-up tyre or blan~, in which for the tyre in -the lefthand half of the illustration the tapering edges oi -the tread are being put under tension and in which the righ-thand part shows a tyre covered by a bllilding-jacket;
igure 10 - a diagrammatic il].ustration of a body during pulling on of a bottom part of a tread;
Figure 11 - a diagra~matic illustration of a stretching ~:
mechanism which may be used in the first phase of the application of a tread ring to a body;
igure 12 - a.diagrammatic side elevation of the second phase in which a s-tretched tread ring is being applied to a body;
igure 13 - a sectional elevation of the body in the second phase where a slide-foil is being employed;
igure 14 - a diagrammatic side elevation of a body in the third phase in which the tread ring is resting firmly against the body~
. .
., : - :
Th~ tre~ld ring 1 ~l-lowr! in Eigure 1 ~'rlibiL-s on i-ts inside a rough ~ace 3 and on its ou~er f~ce a prori~ing 2, the two o -th~m ha~ing been formed a-t the sarn~ time by the production of -the -tread 1 in the press mould. 'I'he -tread segmen-t 4 ;llustra-ted in Figure 2 arld provided with heavy profilinz 2 also exhibits an inner rough face 3 as well as rough edge-faces 5,6, at -the poin~s where -likewise a bond is to be carried ou-t by means of bonding rubber. Depending upon the type and form of the die, rough faces 3 of any chosen structure as well as of size to be determineo and of definable separation bétween -the projections 14 and the recesses 15 lying between them are possible (comp. 4-7). Even undercut projections 15 may be produced as shown in Figure 6.
Figure 7 illustrates, for example, a structure of the rough face 3 which can be produced by mere working of irregular recesses into the top half cr cover of the press mould.
It is clear that a rough face 3 of that kind forms an excellent network of passages for leading away gaseous and liquid components out of the layered structure of a buil-t-up tyre.
.
In Figure 8 the layered structure of a built-up tyre has been illustrated, the body 8 of which is covered by means of a tread or tread ring 1 which consists of a top part la and a bottom part lb which is provided with inserts 11. The bottom part lb serves for reinforcement of the body 8 the belts of wh~ch were damaged and have been :`
- ~ -, ~ ;
,. . - :
~L~13Zl~
tOt~ll ly O~ p~rticilly grou~d off in connee~-ion ~,~ith pre?.-lring -the bo~ly ~ for retreading. The bott:om par-t: 1`D
exhil~:its on all sides rough Faces produc2d preferably irl the press mould. For the underside of -the bo-ttom par-t lb is connected hy means of a layer 10 of bonding rubber to -the upper side of the body 8, whilst a further layer 9 of bonding rubber applied all round over the bottom part lb and also advantageo~sly as illustrated carried ou-twards over the bottom part lb, bonds the top part la on the one hand -to the bottom part lb and also as far as the edg2s of the tread are concerned to the body 8. A coat of material indicated by 12 is to illustra-te how the lateral points of outlet 12a from the layered structure are closed before reduced pressure is brought in one of the ways previously mentioned into action upon the layered s-tructure of the built-up tyre for -the purpose of leading away any gaseous and~or liquid inclusions.
Figure 9 on the other hand illus-trates in the lefthand part that by laying a strip 12 of bonding rubber under the tapering edges 13 of the tread or tread ring 1 a prestress may be created at that point for -the purpose of fixing the layered structure on-to the body 8.
On the other hand the righthand part of Figure 9 illustrates how particularly in the case of heavy-cleated profiles with a thin underlayer of rubber (not shown here) the liquid and/or gaseous inclusions are advantageous].y led away under a building-jacket 13 which is put under vacuum, .
. ~ :
.. . .
. .
.
.~. . . . ' , .
~32~
hilst -the -t~s~ 1 or respec-ti~ely its -top par-t la, af-ter it has ~een laid on only loosely, is rol:led on, st.-!r~l~ing from -the middle and proceeding towar~.s .he si,des.
The bui]ding-~ac!~e-t 13 is advan-tageously sealed at -the be,~d 16 by means of a ri1n and -the inclusions led to -the sides are drawn off via a channel 15 which is for~ed in fron-t of a ring 14. Before inserting the blan]c Ln the autoclave this jacket is removed.
Figure 10 illustrates merely diagramma-tically that the circumference of the wall and hence the diameter of the body 8 must be reduced when the unstretchable bottom part l_ of the tread ring 1 is being applied to the body 8. Reducing the size of the body 8 may, for example, be carried out by means of rods indicated by 18, which are pressed mechanically, advantageously in a symmetrical arrangement, into the body 8 at its periphery and thus enable pulling on of the bottom part lb.
According to a special method of applying a tread in the form of a rin~ to a body 22 the tread ring 21 with a preformed rough face is subjected to stretching of the order of magnitude of about 100~ tdepending upon the rubber mixture, form of profile, thickness of tread rubber, desired free stretch), in which the tread ring 21 is laid over two rollers 23 as well as a roller 25 which can be displaced mechanically, electrically or~hydraulically in the direction of the arrow 24, and is stretched by appropriate displacement of the roller 25. In the case of this stre-tching of only brief duration the tread ring 21 directly after its unloading exhibi-ts a free stretch ~ .. , . ~ . .
-. . .
. ... : . .. ~
3Z~
i.n ~e circ~lim:L;~rent;2l dirQc,ion of, for ~:xample, abou-t
4%, wrlich after -the unloading of the tread ring 21 gradllally red~.lce~ again do~n to a residual va:Lue of abOut l~o ~ ~hich is reached in a shor-t while.
If the inside diame-ter of the tread ring 21 i.s just as large as -the diameter of the periphery of the body 22 when coated with a layer 26 of bonding rubber, or is smaller, that is, for example, by 1-2% than this body diameter, the tread ring 21 (comp. Figure 12) can easily and without effort be slipped over the body 22 coated .
with bonding rubber 26, in which case because of the temporary stretch there is a very small clearance between the body 22 and the tread ring 21... For this reason it is essential that the tread ring 21 be applied to the body 22 directly after the stretching process~ With originally equal diameters and a temporary free stretch of 12 cm the clearance amounts to abou-t 2 cm all round, so that unimpeded slipping of the -tread ring 21 over the body 22 is possible.
Because of the decrease in the stretch, in a short . while~ depending upon the choice of diameters before the stretching process, the phase illustrated in Figure 14 is reached, in which the.tread ring 21 is resting firmly against the body coated with bonding rubber 26.
The application of the tread ring 21 can be performed without special auxiliary means and the ra-tio between .: the diameters existing directly after the stretching process . -- 19 --l...... . . . . . .
- . . . , . . . ~
'' ' . ~ ~ ' ...
: ~ .. ' . : ; . ' 1~13Z~l a~f~ s the !~osribil-i~y of brillg;ng -the tre~ld ring 21 by a,~pro~ iate s~liEti ~J ~Jith respect to th~- body ?2, in o an eYlc-t]y centre~ pOSitiOIl on the body 22. L~llt c~dvant~LgeousLy, ;n order -to be able to slip the trecld ring 21 wi-thout any special precautions over -the body 22, a slide-foil 27, preferably of superfine clinging plastics fabric having a central cut-out 28 for centreing (comp.
Figure 13), is hung over the body 22 arranged horizontally.
After the application of the tread ring 21 the slide-foil 2~ is pùlled effortlessly out of the blank.
A further considerable advantage of the invention consists in the fact that the same size of tread ring may be applied for the whole field of tolerance of the bodies of one tyre size, that is, by appropriate s-tretching -the necessary equalization may be carried out.
After the third phase in accordance with Figure 14 is reached, the blank thus processed may for vulcanizing the layer 16 of bonding rubber be inserted in a pressure chamber and heated. In case of necessity another reduced pressure treatment of any kind may also be applied beforehand in order to lead away possible gaseous inclusions between the applied layers. It is also possible before -the heating in the pressure chamber to connect the tread ring 21 in the region of the lateral pOiIItS of outlet from the layer 26 of bonding rubber by mechanical or chemical action firmly and tightly to the body 22 in order to prevent possible slipping of the tread ring 21 when the layer 26 of bonding ;~`
rubber becomes liquid directly before vulcanizing.
.- ` . . . . ; -- . ~ :
,;: .. :................................. . ~, ~13Z~l I
~ sid~ ia.~l~-tD~ of ~he tread ring 21 is chose s^.lller Lhal th~ grec1te t outside diarne-ter of the dorlle~l boiy 22, ac; -11r--cldy s~cl-ted above tnere ~ol:lows automc3 L-ic escape of gaseous media from the ga~s because th~e tr-ead ring 21 makes contact wi-th the body 22 from the _entre progressively co the sides. The escape is promo-ted by the ne-twork of passages present in the pre-formed rough face.
For slipping the tread ring over, the body is advantageously laid on a centreing table having a funnel-shaped receiving or table face, so that bodies of different siæes may be covered on the same table. The -tread ring may slide down to the oblique receiving-face and then always adopts a centred position on -the body.
1, ,, , - 21 - - Claims -., , ~ ~ . , ~ - ' ' . .
:, , ,:
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If the inside diame-ter of the tread ring 21 i.s just as large as -the diameter of the periphery of the body 22 when coated with a layer 26 of bonding rubber, or is smaller, that is, for example, by 1-2% than this body diameter, the tread ring 21 (comp. Figure 12) can easily and without effort be slipped over the body 22 coated .
with bonding rubber 26, in which case because of the temporary stretch there is a very small clearance between the body 22 and the tread ring 21... For this reason it is essential that the tread ring 21 be applied to the body 22 directly after the stretching process~ With originally equal diameters and a temporary free stretch of 12 cm the clearance amounts to abou-t 2 cm all round, so that unimpeded slipping of the -tread ring 21 over the body 22 is possible.
Because of the decrease in the stretch, in a short . while~ depending upon the choice of diameters before the stretching process, the phase illustrated in Figure 14 is reached, in which the.tread ring 21 is resting firmly against the body coated with bonding rubber 26.
The application of the tread ring 21 can be performed without special auxiliary means and the ra-tio between .: the diameters existing directly after the stretching process . -- 19 --l...... . . . . . .
- . . . , . . . ~
'' ' . ~ ~ ' ...
: ~ .. ' . : ; . ' 1~13Z~l a~f~ s the !~osribil-i~y of brillg;ng -the tre~ld ring 21 by a,~pro~ iate s~liEti ~J ~Jith respect to th~- body ?2, in o an eYlc-t]y centre~ pOSitiOIl on the body 22. L~llt c~dvant~LgeousLy, ;n order -to be able to slip the trecld ring 21 wi-thout any special precautions over -the body 22, a slide-foil 27, preferably of superfine clinging plastics fabric having a central cut-out 28 for centreing (comp.
Figure 13), is hung over the body 22 arranged horizontally.
After the application of the tread ring 21 the slide-foil 2~ is pùlled effortlessly out of the blank.
A further considerable advantage of the invention consists in the fact that the same size of tread ring may be applied for the whole field of tolerance of the bodies of one tyre size, that is, by appropriate s-tretching -the necessary equalization may be carried out.
After the third phase in accordance with Figure 14 is reached, the blank thus processed may for vulcanizing the layer 16 of bonding rubber be inserted in a pressure chamber and heated. In case of necessity another reduced pressure treatment of any kind may also be applied beforehand in order to lead away possible gaseous inclusions between the applied layers. It is also possible before -the heating in the pressure chamber to connect the tread ring 21 in the region of the lateral pOiIItS of outlet from the layer 26 of bonding rubber by mechanical or chemical action firmly and tightly to the body 22 in order to prevent possible slipping of the tread ring 21 when the layer 26 of bonding ;~`
rubber becomes liquid directly before vulcanizing.
.- ` . . . . ; -- . ~ :
,;: .. :................................. . ~, ~13Z~l I
~ sid~ ia.~l~-tD~ of ~he tread ring 21 is chose s^.lller Lhal th~ grec1te t outside diarne-ter of the dorlle~l boiy 22, ac; -11r--cldy s~cl-ted above tnere ~ol:lows automc3 L-ic escape of gaseous media from the ga~s because th~e tr-ead ring 21 makes contact wi-th the body 22 from the _entre progressively co the sides. The escape is promo-ted by the ne-twork of passages present in the pre-formed rough face.
For slipping the tread ring over, the body is advantageously laid on a centreing table having a funnel-shaped receiving or table face, so that bodies of different siæes may be covered on the same table. The -tread ring may slide down to the oblique receiving-face and then always adopts a centred position on -the body.
1, ,, , - 21 - - Claims -., , ~ ~ . , ~ - ' ' . .
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Claims (10)
1. A method of retreading a rubber tyre, the method comprising the steps of:
a) producing a moulded and vulcanized tread section, in a press mould, having an internal surface for bonding and an outer tread surface;
b) activating immediately after curing on the internal surface of the vulcanized tread section additional unsaturated sulfur molecules by opening up the structure of molecules on the said surface as a result of removal of the tread from the mould;
c) coating the internal surface of the freshly vul-canized tread section having unsaturated vulcanized sulfur molecules with a solution of an unvulcanized bonding-rubber-mixture to tie the unsaturated molecules and thus to prevent oxidation and deterioration of the bonding capacity of the internal surface during storage and thereby enhance its bonding capacity during subsequent vulcanization without needing a subsequent mechanical roughening of the internal tread surface, d) applying the tread section to the rubber tyre with a layer of vulcanizable bonding rubber between the prepared body of the tyre and the internal surface of the tread section, and, e) after evacuation of gaseous inclusions occurring between the coated internal surface and the layer of bonding rubber and after evacuation of any gaseous inclusions between the layer of bonding rubber and the tyre body, sealing off the side strips of the bonding rubber and subjecting the tyre and the tread section to heat and pressure in an autoclave to vulcanize the bonding rubber and unite the tread section to the rubber tyre.
a) producing a moulded and vulcanized tread section, in a press mould, having an internal surface for bonding and an outer tread surface;
b) activating immediately after curing on the internal surface of the vulcanized tread section additional unsaturated sulfur molecules by opening up the structure of molecules on the said surface as a result of removal of the tread from the mould;
c) coating the internal surface of the freshly vul-canized tread section having unsaturated vulcanized sulfur molecules with a solution of an unvulcanized bonding-rubber-mixture to tie the unsaturated molecules and thus to prevent oxidation and deterioration of the bonding capacity of the internal surface during storage and thereby enhance its bonding capacity during subsequent vulcanization without needing a subsequent mechanical roughening of the internal tread surface, d) applying the tread section to the rubber tyre with a layer of vulcanizable bonding rubber between the prepared body of the tyre and the internal surface of the tread section, and, e) after evacuation of gaseous inclusions occurring between the coated internal surface and the layer of bonding rubber and after evacuation of any gaseous inclusions between the layer of bonding rubber and the tyre body, sealing off the side strips of the bonding rubber and subjecting the tyre and the tread section to heat and pressure in an autoclave to vulcanize the bonding rubber and unite the tread section to the rubber tyre.
2. A method according to claim 1, wherein opening up the structure of molecules in said internal surface as a result of removal of the tread from the mould is achieved by using a metal-clean moulding form or liner.
3. A method according to claim 1, wherein the internal surface is a rough surface consisting of projections and recesses for bonding and forming a network of passages to assist in evacuating gaseous inclusions between the internal surface of the tread section and a layer of bonding rubber during subsequent bonding.
4. A method according to claim 1, wherein there is applied to an area of the press mould which creates the internal surface or directly to a face of the body of vulcanizable material inserted in the press mould opposite to that area thereof a material which delays the vulcanization reaction of the internal surface of the tread.
5. A method according to claim 4, wherein the press mould is filled with the body of vulcanizable material for the production of the tread section by an injection moulding technique.
6. A method according to claim 3, wherein the internal rough surface is produced simultaneously with the tread section.
7. A method according to claim 3, wherein the producing step further comprises forming additional channels in the internal rough surface for leading gaseous inclusions directly to the sides of the tread section, the channels being produced in the internal rough surface simultaneously with the internal rough surface in the press mould.
8. A method according to claim 1, wherein the pro-ducing step comprises making the tread section of a radially outer and a radially inner part, of which the inner part is reinforced with inserts.
9. A method according to claim 8, further comprising making the inner part and the outer part of the tread section as independent parts both having internal rough surfaces, and the applying step comprises applying the inner and outer parts to the tyre one after the other with a further layer of bonding rubber interposed therebetween.
10. A method according to claim 9, wherein the later of binding rubber is brought in the plastic state into contact with the internal rough surface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000371312A CA1118972A (en) | 1975-10-10 | 1981-02-19 | Method of renewal of the tread on a worn pneumatic or solid rubber tire |
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP2545463.1 | 1975-10-10 | ||
| DE2545463A DE2545463C2 (en) | 1975-10-10 | 1975-10-10 | METHOD FOR REPLACING THE TREAD OF A DEALED AIR OR SOLID TIRE |
| DEP2617760.6 | 1976-04-23 | ||
| DE2617760A DE2617760C2 (en) | 1976-04-23 | 1976-04-23 | METHOD FOR REPLACING THE TREAD OF A DEALED AIR OR SOLID TIRE |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1113211A true CA1113211A (en) | 1981-12-01 |
Family
ID=25769498
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA263,036A Expired CA1113211A (en) | 1975-10-10 | 1976-10-08 | Method of renewal of the tread on a worn pneumatic or solid rubber tyre |
Country Status (20)
| Country | Link |
|---|---|
| JP (1) | JPS5278284A (en) |
| AR (2) | AR213182A1 (en) |
| AU (1) | AU508728B2 (en) |
| BR (1) | BR7606805A (en) |
| CA (1) | CA1113211A (en) |
| CH (1) | CH623508A5 (en) |
| DK (1) | DK156382C (en) |
| EG (1) | EG12502A (en) |
| FI (1) | FI66311C (en) |
| FR (1) | FR2327079B1 (en) |
| HU (1) | HU175749B (en) |
| IE (1) | IE43980B1 (en) |
| IL (1) | IL50635A (en) |
| LU (1) | LU75962A1 (en) |
| NL (1) | NL181418C (en) |
| NO (1) | NO152594C (en) |
| PL (1) | PL111002B1 (en) |
| PT (1) | PT65692B (en) |
| SE (2) | SE428778B (en) |
| YU (1) | YU248176A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2439667A1 (en) * | 1978-10-23 | 1980-05-23 | Hedlund John | Tyre retreading method - in which a belt reinforced tread is secured to a buffed carcass by an intermediate belt-like layer |
| FR2496004A1 (en) * | 1980-12-16 | 1982-06-18 | Michelin & Cie | PROCESS FOR BONDING TWO RUBBER BODIES, PARTICULARLY FOR RETREADING OR REPAIRING A TIRE |
| EP0715948A1 (en) * | 1994-12-06 | 1996-06-12 | Kurt Edler | Process for retreading a worn tyre |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2292286A (en) * | 1941-10-08 | 1942-08-04 | Hawkinson Paul E Co | Method of treading tire casings |
| GB746375A (en) * | 1953-04-09 | 1956-03-14 | Channel Islands Tyre Company L | Improvements in and relating to the retreading of tyres |
| BE551071A (en) * | 1955-07-26 | |||
| DK92978C (en) * | 1955-08-04 | 1962-03-12 | Wilhelm Schelkmann | Procedure for circumferential renewal of the tread on worn car tires. |
| GB812155A (en) * | 1955-11-01 | 1959-04-22 | Dunlop Rubber Co | Apparatus for making pneumatic tyres |
| AT296799B (en) * | 1969-07-17 | 1972-02-25 | Bruno Edler | Method for retreading a vehicle tire and device for carrying out the method |
| CH498711A (en) * | 1970-04-03 | 1970-11-15 | Firestone Prod | Treads for application to vehicle tires |
| GB1399864A (en) * | 1971-07-21 | 1975-07-02 | Dunlop Ltd | Manufacutre of pneumatic tyres |
| DE2244391B2 (en) * | 1972-09-09 | 1978-03-02 | Vakuum Vulk Holdings Ltd., Nassau | Process and vulcanization molds for retreading vehicle tires |
| GB1486782A (en) * | 1973-10-05 | 1977-09-21 | Uniroyal | Raw pneumatic tyre carcass and method of fabricating same |
| ZA746058B (en) * | 1974-09-24 | 1976-04-28 | Republic Rubber Ind Ltd | Improvements in or relating to the retreading of tyress |
-
1976
- 1976-10-05 FI FI762832A patent/FI66311C/en not_active IP Right Cessation
- 1976-10-06 SE SE7611061A patent/SE428778B/en not_active IP Right Cessation
- 1976-10-07 IL IL50635A patent/IL50635A/en unknown
- 1976-10-08 PT PT65692A patent/PT65692B/en unknown
- 1976-10-08 CH CH1278176A patent/CH623508A5/en not_active IP Right Cessation
- 1976-10-08 NO NO763430A patent/NO152594C/en unknown
- 1976-10-08 HU HU76HO1930A patent/HU175749B/en unknown
- 1976-10-08 IE IE2224/76A patent/IE43980B1/en not_active IP Right Cessation
- 1976-10-08 AU AU18482/76A patent/AU508728B2/en not_active Expired
- 1976-10-08 CA CA263,036A patent/CA1113211A/en not_active Expired
- 1976-10-08 LU LU75962A patent/LU75962A1/xx unknown
- 1976-10-08 DK DK453176A patent/DK156382C/en active
- 1976-10-08 FR FR7630269A patent/FR2327079B1/en not_active Expired
- 1976-10-09 JP JP51121781A patent/JPS5278284A/en active Granted
- 1976-10-10 EG EG621/76A patent/EG12502A/en active
- 1976-10-11 AR AR265048A patent/AR213182A1/en active
- 1976-10-11 YU YU02481/76A patent/YU248176A/en unknown
- 1976-10-11 NL NLAANVRAGE7611239,A patent/NL181418C/en not_active IP Right Cessation
- 1976-10-11 PL PL1976192949A patent/PL111002B1/en unknown
- 1976-10-11 BR BR7606805A patent/BR7606805A/en unknown
-
1977
- 1977-07-29 AR AR268626A patent/AR223809A1/en active
-
1981
- 1981-05-14 SE SE8103028A patent/SE444913B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| AU508728B2 (en) | 1980-04-03 |
| FI66311C (en) | 1984-10-10 |
| NO152594B (en) | 1985-07-15 |
| IL50635A (en) | 1981-03-31 |
| LU75962A1 (en) | 1977-05-09 |
| FR2327079A1 (en) | 1977-05-06 |
| DK156382C (en) | 1990-01-08 |
| PT65692B (en) | 1978-04-14 |
| SE8103028L (en) | 1981-05-14 |
| AR213182A1 (en) | 1978-12-29 |
| AR223809A1 (en) | 1981-09-30 |
| IE43980B1 (en) | 1981-07-15 |
| SE428778B (en) | 1983-07-25 |
| FR2327079B1 (en) | 1982-06-11 |
| FI66311B (en) | 1984-06-29 |
| JPS6139185B2 (en) | 1986-09-02 |
| IE43980L (en) | 1977-04-10 |
| EG12502A (en) | 1979-09-30 |
| FI762832A (en) | 1977-04-11 |
| BR7606805A (en) | 1977-08-30 |
| AU1848276A (en) | 1978-04-13 |
| DK156382B (en) | 1989-08-14 |
| NL7611239A (en) | 1977-04-13 |
| CH623508A5 (en) | 1981-06-15 |
| HU175749B (en) | 1980-10-28 |
| NO152594C (en) | 1985-10-23 |
| SE7611061L (en) | 1977-04-11 |
| IL50635A0 (en) | 1976-12-31 |
| PT65692A (en) | 1976-11-01 |
| NO763430L (en) | 1977-04-13 |
| JPS5278284A (en) | 1977-07-01 |
| DK453176A (en) | 1977-04-11 |
| PL111002B1 (en) | 1980-08-30 |
| SE444913B (en) | 1986-05-20 |
| YU248176A (en) | 1982-05-31 |
| NL181418C (en) | 1987-08-17 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |