Apparatus and process for making a tape useful as a tire cap ply
An apparatus and process are used to make tape which can be used as cap plies, breakers and reinforcement in the carcass of tires. The tape is made by dipping a plurality of single end cords in a solvent-based cement. The cords are converged before entering the dip pan so that they are fixed in a single plane when they are dipped. The cement, which comprises solvent and an elastomeric composition, is dried so that the majority of the solvent evaporates. The elastomeric composition remains, encapsulating the cords, thereby forming the tape.
1. Field of the Invention
The present invention relates to an apparatus and a process for making tape which can be used as cap plies, breakers and reinforcement in the carcass of tires.
2. Description of the Related Art
The tire industry has long had considerable interest in belted tire constructions for reinforcing tires. An example of a tire reinforcement is described in U.S. Pat. No. 3,720,569 to Kimble. This reinforcement is formed by passing a plurality of cords in the desired spaced relationship through an extruder. The cords may be coated with a rubber latex in a multiple dip operation to form a unitary strip. Such reinforcement constructions may offer the advantage of better road stability and longer tread life in both radial and bias ply constructions. However, such constructions are subject to belt-edge separation failures because the adhesion of the reinforcement to the tire rubber is inadequate.
Cap plies that envelop radial tire belts may be used to help minimize such belt-edge separation failures. Initially, cap plies were applied as a full width strip with an overlap splice. Experience has shown that the splice could pull open during curing. In addition, there is a limitation on the extension of the belt, since the cap ply is applied over the belt. Moreover, with this configuration, the same width of material must be applied across the whole belt. As a result of these limitations, a narrower cap ply tape was developed in the 1990's. This tape is spirally wound about the belt. Such a tape is made by slitting rubberized fabric. The width of the tape depends on the number of cords per inch, which varies according to the tire manufacturer. It was found that such a tape can increase winding tension, as there is no splice. Also, such a tape can be applied in extra layers at the belt edges to improve tire performance. However, this process is dependent on several processes/steps, i.e., weaving fabric, treating fabric to achieve good adhesion to the calendered rubber, compounding rubber, skimming or calandering the rubber onto the treated fabric and slitting the rubberized fabric to specific widths. These are inherently high cost/labor intensive procedures. Because of the slitting step, there may be cut cords on the edges of the tape, which may create edge fray. Consequently, such a process produces a fair amount of scrap material. Moreover, the tape so produced can be non-uniform, due to the possible varying number of single end cords in each strip. With each step the potential for error and the additive variances requires allowance for excessive tolerances in the tire building process. Finally, the addition of rubber to ensure good adhesion of the fabric to the tire rubber adds to the overall weight of the tire.
Because of the inherent drawbacks in the slit rubberized fabric process, a process for the preparation of a cap ply tape from single end cords using a cross-head extruder has been developed. Such a process is commonly known as the “Steelastic® process”, and is illustrated in
The Steelastic® process provides improved uniformity as compared to the slit rubberized fabric process, since there no possibility of uneven slitting and hence there is exact control of the number of single end cords in the tape. Moreover, this process has reduced scrap as compared to the slit rubberized fabric process, since there are no cut cords on the edges of the tape. In addition, longer lengths per roll of tape are possible with the Steelastic® process. However, the extruder and the die heads used in this process represent a major capital investment. Moreover, the tape itself is still dependent on a rubber compounding step and the addition/application of rubber as a means to ensure good adhesion to the tire rubber compounds, hence increasing weight and cost. In addition, the Steelastic® process requires above ambient pressures and temperatures. Therefore, there exists a need in the tire industry to develop a process for making a tape or strip which can be used as cap plies, breakers and reinforcement in the carcass of tires, which is less capital intensive and less labor intensive than processes of the prior art. Moreover, there needs to be a process which produces more uniform tape and which does not produce waste. In addition, it would be desirable to produce a packaged tape or strip which is ready to apply to a tire as a cap ply or which can be used as breakers and reinforcement in the carcass of tires.
BRIEF SUMMARY OF THE INVENTIONApplicants have recognized that cement flows much better than rubber, and that the use of cement for encapsulating single end cords is superior to the rubber used in the Steelastic® process. In addition, Applicants have recognized that cement can be applied at ambient temperature and ambient pressure, as opposed to rubber in the Steelastic® process, which must be applied in a heated extruder. Thus, the present invention overcomes the problems associated with the prior art by providing a process which is does not require the use of extruder dies as in the Steelastic® process.
In addition, the process of the present invention is not as labor intensive as the slit rubberized fabric process of the prior art, as it does not involve slitting of fabric. In addition, it is not as capital intensive as the slit rubberized fabric process, as it does not require a calender roll. Moreover, the process of the present invention avoids the potential for error in that it does not have a slitting step, and hence the possibility of non-uniformity due to the possible varying number of single end cords in each strip is virtually eliminated. Also, since there is no slitting step in the process of the present invention, no edge fray is created and there are no cut cords on the edges of the tape. Thus, the process of the present invention produces less scrap than the slit rubberized fabric process. Finally, the overall weight of the tire could be reduced, since there is no need to add rubber to ensure good adhesion of the fabric to the tire rubber.
Therefore, in accordance with the present invention, there is provided an apparatus and a process for making a tape from a plurality of single end cords. The apparatus comprises a dip pan for applying a solvent-based cement comprising an elastomeric composition dissolved in a solvent to the single end cords. The apparatus also comprises means for converging the cords before they travel to the dip pan, so that the cords are converged into a single plane. In the dip pan, the cords are fixed in a single plane as the dip is applied. In addition, the apparatus comprises an oven for curing the cement so that the majority of the solvent is driven off and the cords are encapsulated in the elastomeric composition to form a tape.
Further in accordance with the present invention, there is provided a process for making a tape. The process comprises dipping a plurality of single end cords in a dip comprising a cement and an elastomeric composition; and curing the cement so that the majority of the solvent evaporates, thereby forming a tape comprising single end cords encapsulated in the elastomeric composition.
BRIEF DESCRIPTION OF THE DRAWINGS
In accordance with the present invention, there is provided an apparatus and a process for making strip, or tape which can be used as cap plies, breakers and reinforcement in the carcass of tires. The process of the present invention will be described in the context of the operation of the apparatus of the present invention with respect to
Typical synthetic yarns useful for the cords of the present invention are made from polyamides, such as 6,6 nylon, 6 nylon, or any copolymers thereof. Alternatively, the yarns may comprise polyesters, aramid fibers, rayon, glass or carbon, etc. A particularly suitable yarn for use with the present invention is T-728, which is a heat stabilized 66 nylon, commercially available from DUSA International of Wilmington, Del. To meet the strength and durability requirements for tire applications, the yarns are normally prepared from high viscosity polymers containing stabilizers and are drawn at high draw ratios to yield high tenacity yarns, as disclosed in U.S. Pat. No. 3,311,691.
The single end cord, shown generally at 10 in
The apparatus of the present invention also includes means for converging the cords before they travel to the dip pan. The means for converging the cords comprises a first comb 28 and a second comb, 30 as shown in
It should be apparent that modifications may be made to the apparatus as described without departing from the spirit of the invention. For instance, instead of using a plurality of combs to converge the cords, the means for converging the cords before they travel to the dip pan could comprise a guide roll. Such a guide roll would not have equally spaced grooves across the width of the roll. Instead, the grooves would be clustered so that as the cords travel across the guide roll, they are converged in the clustered grooves. In either case, whether combs or a guide roll are used, the converging means of the present invention is designed to converge the cords and position them into a single plane, as well as to ensure the integrity of a pre-dip, should one be applied. A converged set of cords is shown leaving the second comb at 31 in
As can be seen from
Again, variations of the specific equipment used may be made without departing from the scope of the present invention. For instance, if there is enough tension in the cords as they travel through the dip pan, the use of the press roll may not be necessary. In this case, there just must be enough tension in the cords to keep them in the valleys of the receiving roll of the dip pan. In this case, an appropriate support, such as a guide roll or a glass bar, can be used for the cords.
The dip that is used in the dip pan is a solvent-based cement. This solvent-based cement includes an elastomeric composition, which is dissolved in a solvent, such as toluene. This elastomeric composition may comprise, for example, but is not limited to, a natural rubber, or a natural rubber with styrene butadiene or styrene butadiene with polybutadiene. These constituent materials in the elastomeric composition may be mixed with reinforcing agents, activators and/or plasticizers, depending on the needs of the end user. The percentage of solvents in the cement depends on the speed at which the cords are run through the apparatus. This percentage is typically in the range of 10-30%.
The solvated, or wet tape, is then sent to a type-two guide roll 36 and to another type-two guide roll 38 as shown in
The solvated, or wet tape, is then sent to an oven 42, where it goes through one pass, to another type-two guide roll 44, and then another pass through the oven. In the oven, the cords must remain fixed in a single plane. This is done by maintaining the tension in the cords, and is necessary to maintain the integrity of the tape. The cement, including the solvent and the elastomeric composition, is dried in the oven. This drying typically occurs at about 110° C. for some period of time, which is dependent on the speed at which the cords, or the tape at this point, are being driven through the apparatus. The drying drives off, or evaporates, the majority of the solvent, such as toluene. What remains are the cords, fixed in the single plane and encapsulated in the elastomeric composition to form a tape, shown at 46 in
From the oven, the tape is sent back through guide roll 38, to a series of guide rolls, 46, 48 and 50, and to a drive unit, shown generally at 52 in
The tape, which is shown at 62 in
After the comb, the tape is sent to a guide wheel 76 as shown in
With the present invention, because the individual cords are dipped in a cement, the cords have better access to the cement than to rubber in the prior art, because rubber does not flow as well as cement. Thus more complete coverage of the cords, either individually, or in the fabric, can be achieved as compared to processes of the prior art. Consequently, with the present invention it is possible to produce a superior tape as compared to the slit fabric or Steelastic® process. While it might be possible to achieve the desired encapsulation characteristics for elastomeric compositions such as rubber at high heat and high pressures, the present invention is able to achieve these desired encapsulation characteristics at ambient temperature and ambient pressure while the cement is being applied.
The tape of the present invention is ready to use as a cap ply for a tire. When used in this application, the tape is wound directly onto the tire. The single end cord in the tape then adheres to the rubber in the tire curing process. Alternatively, as noted above, the tape may be used as a breaker and reinforcement in the carcass of tires. The tape of the present invention is generally about ¼″ to ⅜″ wide.
The invention will be described in greater detail with reference to the following examples which are intended to illustrate the invention without restricting the scope thereof.
EXAMPLE A tape may be made using the apparatus of
Then an anti-foaming agent may be added to form a solution, which should be mixed slowly. This solution may have a solids content of about 35%. This solution may then combined with the solution from the first tank. The combined solutions should be mixed together for about 30 minutes prior to use. The cords should be dipped in this combined solution for about 3 seconds. The dip should then be dried in an oven at a temperature of about 226° C., for a dwell time in the range of 100 and 200 seconds. The cords should then be sent to another oven, where the dip may be dried at a temperature of 165° C. The cords may then be dipped in a cement dip pan. The cement in the cement dip pan may be a mixture of a solvent, such as toluene, (85 kg) and a rubber-based elastomeric composition (15 kg), such as natural rubber, natural rubber and styrene butadiene, or styrene butadiene and polybutadiene. Any of these may be mixed with reinforcing agents, activators and/or plasticizers. The cement should be dried in an oven at a temperature of 110° C., so that the toluene is driven off. A tape which is about {fraction (1/2)} inch wide may thus be formed.
Claims
1. An apparatus for producing a tape suitable for use as a cap ply from a plurality of single end cords, comprising:
- a) a dip pan for applying a cement to the single end cords; and
- b) means for converging the cords before they travel to the dip pan, so that the cords converge and are fixed in a single plane as they are dipped in the dip pan.
2. The apparatus of claim 1, wherein the converging means includes:
- (i) a first comb for converging the cords before they travel to the dip pan; and
- (ii) a second comb disposed between the first comb and the dip pan for further converging the cords after they leave the first comb and before they travel to the dip pan.
3. The apparatus of claim 2, wherein the first comb has a plurality of first grooves, each first groove having a plurality of teeth with first spaces therebetween, wherein the cords travel through the first spaces to the second comb, and the second comb has a plurality of second grooves, each second groove having a plurality of teeth with second spaces therebetween, wherein the cords travel through the second spaces to the dip pan, wherein the width of each of the second grooves is less than the width of each of the first grooves, so that the cords converge as they travel from the first grooves to the second grooves.
4. The apparatus of claim 1, further including an oven for drying the cement.
5. The apparatus of claim 1, further including a dip pan roll disposed in the dip pan and having a plurality of teeth and valleys, and a press roll disposed above the dip pan roll, having a plurality of teeth and valleys, wherein the teeth of the press roll mesh with the valleys of the dip pan roll to compress the cement into the spaces between the single end cords.
6. The apparatus of claim 1, further including at least one guide roll adapted to guide the tape after the tape exits the dip pan, wherein the first guide roll has a plurality of grooves formed in the outer periphery thereof, and the second guide roll has a plurality of grooves formed in the outer periphery thereof, and wherein the grooves in the second guide roll are spaced apart by a greater distance than the grooves in the first guide roll.
7. The apparatus of claim 1, further including a winder for winding the tape after it exits the oven, wherein the winder comprises a shaft having a valley of a width sufficient for accommodating the tape after it exits the dip pan.
8. The apparatus of claim 2, further including a third comb disposed between the dip pan and the winder, the third comb having a plurality of teeth, wherein the teeth are spaced apart by a distance sufficient for accommodating the tape as it is presented to the winder.
9. A process for producing a tape suitable for use as a cap ply from a plurality of single end cords, comprising:
- a) converging the plurality of single end cords so that the cords are fixed in a single plane as they travel through the dip pan;
- b) applying a dip in the dip pan to the cords so that the cords are encapsulated in the dip; and
- c) drying the dip to form a tape.
10. The process of claim 9, further including pressing the dip into the spaces between the cords.
11. The process of claim 9, wherein the dip is a cement comprising an elastomeric composition dissolved in a solvent, and further including the step of drying the cement so that the majority of the solvent evaporates, and the elastomeric composition remains, thereby forming the tape.
12. A process for making a tape suitable for use as a cap ply, comprising:
- a) dipping a plurality of single end cords in a solvent-based cement comprising a solvent and an elastomeric composition; and
- b) drying the cement so that the majority of the solvent evaporates, and the elastomeric composition remains, encapsulating the cords, thereby forming the tape.
13. A tape made by the process of claim 12.
14. The tape of claim 13, wherein the solvent comprises 0.0009-5% by weight of the tape.
15. A tape suitable for use as a cap ply, comprising a plurality of single end cords encapsulated in an elastomeric composition, and trace amounts of a solvent.
16. The tape of claim 15, wherein the solvent comprises 0.0009-5% of the weight of the tape.
17. The tape of claim 15, wherein the solvent is toluene.
18. The tape of claim 15, wherein the elastomeric composition is selected from the group consisting of a natural rubber, a natural rubber with styrene butadiene or styrene butadiene with polybutadiene.
Type: Application
Filed: Aug 29, 2003
Publication Date: Mar 3, 2005
Inventors: Rodney Stamper (Whiteville, NC), David Stewart (Lake Waccamaw, NC)
Application Number: 10/651,356