Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1997-10-06
2001-10-16
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S098000, C156S153000
Reexamination Certificate
active
06302984
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the bonding of rubber materials and more particularly to the processes for treatment, before bonding, of the surfaces of vulcanized rubber materials that constitute tires.
DISCUSSION OF BACKGROUND
The retreading of a tire consists in separating it, i.e., removal by a machining operation of what remains of the worn tread, then mounting a new tread. The retreading requires that a mechanical bond be formed between the materials of the crown of the tire and the new tread, whether or not it is prevulcanized.
Usually this mechanical bond is created by inserting a nonvulcanized cushion gum between the crown and the new tread.
Consequently, when retreading is done with a prevulcanized tread, it is necessary to obtain an excellent bond between, on the one hand, the (nonvulcanized) cushion gum and, on the other hand, the materials of the crown and the new (vulcanized) tread.
Likewise, when a tire is being repaired, an excellent bond must be obtained between the materials of the damaged areas, after their degraded parts are removed, and a nonvulcanized repair material that may or may not be accompanied by a reinforcing part or vulcanized “patch.” To obtain good bonding, it is necessary, in particular, that the surfaces of the vulcanized materials be clean, that their oxidized or degraded surface parts be removed, that they have a suitable roughness, and that contact with the nonvulcanized material be made under good conditions with, in particular, sufficient application pressure.
In the case of retreading tires, the machining intended to remove what remains of the worn tread can be performed in several ways. A first method consists in using a “buffing machine.” Such a machine uses a rotary abrasive tool including a set of metal disks having abrasive teeth on their outside circumferences. These disks are assembled perpendicular to a common axis of rotation. The buffing makes it possible to remove what remains of the worn tread and thus to bring the crown of the casing to the desired geometric shape while imparting to the rubber surface a roughness that is suitable for the subsequent bonding. An example of suitable roughness is provided by the reference plates provided for retreading and repairing tires by the Rubber Manufacturers Association. This machining by buffing which is simple and effective, is the process currently used.
However, it has several drawbacks: (1) a great deal of damaging heating of the rubber surface is caused; (2) a great deal of rubber debris is produced which needs to be vacuumed off; and (3) difficult work conditions are created because of the pollution due to the noise and the rubber crumb.
Another method consists in removing what remains of the worn tread with either hot or cold blades. However, after this machining, the rubber surfaces obtained are smooth; this necessitates a subsequent brushing operation to create the surface roughness that experiments have shown to be necessary for good bonding reliability.
A critical area of the mechanical bond between the crown of the tire and the new tread is the area located at the two lateral edges of the new tread. Depending on the geometry of the tread used (i.e. flat tread, flared tread, curved tread . . . ,), the lateral edges or flarings or “flanges” are connected to the edges of the crown or to the shoulders of the tire. This area is heavily stressed mechanically during driving, and it has been found that any bonding failure causes cracks to appear, and then to spread. These cracks can then spread along the interfaces between the cushion gum and the crown or the tread, and may also penetrate directly into the materials of the crown or the shoulders.
SUMMARY OF THE INVENTION
Accordingly one object of this invention is to provide a novel method and device for treating vulcanized rubber surfaces before bonding which makes it possible to clean the surfaces and to create a roughness that is suitable for an excellent bond without it being necessary to perform a brushing operation.
The application of this treatment method to retreading tires, repairing tires, producing prevulcanized treads as well as producing new tires, constitutes another object of the invention.
In the case of retreading, a particular object of the invention is to achieve an excellent bond in the area located between the two lateral edges of the new tread and the crown or the shoulders.
Tire “casing” is defined to mean either a used tire whose used tread remnants have been removed by a machining operation, or a vulcanized new tire that lacks only the tread.
The process for treating vulcanized rubber surfaces before bonding, according to the invention, comprises a step for creating surface roughness and for eliminating degraded surface particles by applying a high-pressure fluid jet.
This process for treating rubber surfaces before bonding has the advantage of providing clean surfaces that are free of fouling and have a fine and even roughness suitable for a bond of excellent quality.
Many operating conditions for applying a high-pressure fluid jet make it possible to create surface roughness according to the invention.
According to a preferred embodiment, use is made of a fluid jet, a section of which, perpendicular to the direction of application of said fluid jet, has an approximately elliptical shape with a ratio between the major axis of the ellipse and the minor axis of the ellipse which is greater than 6.
This “flat” fluid jet is preferably applied in such a way that the direction of the relative displacement of fluid jet in relation to said rubber surfaces is perpendicular to the major axis of said ellipse of the section of the fluid jet.
The use of such a flat fluid jet, with such an orientation in relation to the direction of the relative displacement of the treated rubber surfaces, makes it possible to treat a strip of said rubber surface at any time without this treatment affecting anything other than the surface area of said rubber surface.
Depending on the nature of the treated vulcanized rubber material, the feed pressure of the fluid is between 100 and 250 MPa. To prevent the application of a fluid jet with such pressures from causing cuts in the treated rubber surfaces, it is very important to have a high speed of relative displacement between the fluid jet and the treated surfaces; a speed of between 50 and 300 m/min is suitable.
According to another characteristic, the high-pressure fluid is sprayed on the vulcanized rubber surfaces at a distance between 8 and 20 mm.
It is a further advantage of the present invention that water can be used as the fluid applied under pressure.
The invention also has as its object a device for putting into practice the preceding process for treating vulcanized rubber surfaces before bonding. This device, using a pressurized fluid, comprises a feed pipe for said pressurized fluid, with the pipe ending in a nozzle, and includes apparatus for support and for relative displacement of vulcanized rubber surfaces in relation to the nozzle. The nozzle has an outlet orifice for the fluid which orifice is obtained by the intersection of a cone and a dihedron, with the axis of the cone being perpendicular to the straight line of intersection of the two planes of the dihedron.
According to another characteristic, an extension of the outlet orifice, along a plane perpendicular to the axis of said cone, has a elliptical shape with a ratio between the major axis of the ellipse and the minor axis of the ellipse on the order of 1.4.
Advantageously, the angle of the apex of the cone is between 25 and 35° and the angle of the dihedron is between 65 and 70°.
According to a preferred embodiment, the length of the major axis of said ellipse of said plane extension of said outlet orifice of the nozzle is between 0.30 and 0.40 mm.
The invention also has as its object a first application of the process to the retreading of tires. This tire retreading process is characterized in that, after the remaining portion of the worn tread is removed by machining with and before a new tread
Courel Jean-Marie
Schruoffeneger Denis
Solignac Serge
Copangnie Generale des Etablissements Michelin - Michelin & Cie
Knable Geoffrey L.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
LandOfFree
Process and device for treating vulcanized rubber surfaces... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process and device for treating vulcanized rubber surfaces..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process and device for treating vulcanized rubber surfaces... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2576573