KR0141093B1 - Method of ultrasonic splicing tire tread strip edges - Google Patents

Abstract

None.

Description

Initialization and assembly method of tire tread strip edges

1 is a schematic cutaway side view of an ultrasonic welding device that may be used for ultrasonic welding of a tire tread strip by an improved method of the present invention.

2 is an enlarged cross sectional view of the welding tool of the apparatus of FIG. 1 in contact with a tire tread strip.

3 is an enlarged fracture cross-sectional view seen from the direction of arrow 3-3 in FIG. 2 showing the contact surface of the welding tool.

4 is an enlarged sectional sectional view taken along line 4-4 of FIG.

5 is an enlarged longitudinal cross-sectional view of a welding tool for ultrasonically welding a tread strip junction by an improved method of the present invention.

6 is a broken plan view of a portion of the tire tread strip in which ultrasonic welding has been performed.

* Explanation of symbols for the main parts of the drawings

4: Tire tread strip 9: Welding tool

11: strip contact surface 19, 20: inclined end

24: splice connection

The tire of the present invention relates to a method for joining the ends of rubber compound strips to be used for manufacturing. In particular, it relates to a method of joining the beveled edges of such strips to be used as tire treads of the present invention with ultrasonic energy to firmly bond between them so that the strip ends remain adherent in subsequent tire manufacturing processes.

In tire manufacture, tire parts, usually in strip form, are assembled on one or more cylindrical forming drums. Various reinforcing plies are added to the forming drum in dancing, and some strips are arranged at an angle, including a cord. The outermost tread forming strip of unreinforced rubber compound is placed on the drum around the stiffening previously added to form a final tire carcass before entering the mold for curing. The ends of the tread strip must be bonded to each other to form a green tire and remain glued until the tire carcass is placed in the curing mold. The tread strip ends are overlapped using the obliquely cut strip ends, wherein the inclined ends of the strips overlap along the inclined plane to form a continuous final joint at the top and bottom of the strip so that no protrusions occur at the joints.

These joint connections have conventionally been made by preheating the strips and / or joining the adhesive tread ends with an adhesive and applying pressure with a sewing or joining tool. The sewing process is generally performed manually by a tire forming worker. Such manual joining often results in unsatisfactory tire joints, so it is necessary to discard the tires or rejoin the joints if the joints were separated before curing. Thus, this manufacturing process reduces the manufacturing efficiency. The joint must be firmly connected to maintain the bond until the tread strip added to the drum is placed in the hardening mold. The final uncured tire, including the tread, is placed in the mold in a relatively short period of time depending on the production environment, or in other cases the molded carcass, ie the raw tire, is stored before it is cured into the final tire in the vulcanized mold. Therefore, when the tread strips are molded in the curing process after they have been molded into the tire carcass by bonding, bonding or sewing the two inclined ends of the tire tread strips of the rubber compound in a shorter time than conventionally without using an adhesive. Until then, it has been desirable to develop a way to keep the joints connected.

Conventionally, acoustic or ultrasonic energy has been used to bond various materials including cord reinforcement rubbers together. For example, US Pat. No. 4,548,771 describes a method of vulcanizing rubber by applying ultrasonic energy to the material with a predetermined amount of energy sufficient to generate heat to bond the rubber. At 8 inches, ultrasonic energy should be applied for at least 10 minutes.

U.S. Patent No. 3,874,963 describes a method for bonding superposed thermoplastic plastic sheets to each other using ultrasonic energy.

U.S. Patent No. 4,090,897 describes an ultrasonic welding device of thermoplastic material in which the free end of the fabric is butt seamed by an ultrasonic welder.

US Pat. No. 910,459 describes a method in which tire treads are produced by treatment with ultrasonic energy for some time before the tread strips are vulcanized.

Another conventional patent for ultrasonic bonding of materials is US Pat. No. 3,577,292, which describes a method of joining two thermoplastic strips together by butt welding the ends of the strips together with sonic or ultrasonic energy.

US Patent No. 3,904,457 appears to be the prior art most similar to the present invention. This patent describes a method of ultrasonic butt bonding of a reinforced tire strip in which two trimmed ply ends are in contact with each other and then ultrasonic energy is applied thereto. However, this patent method requires reinforcing cords to be contained in a relatively thin rubber strip to achieve a satisfactory butt joint. In addition, a relatively high cylinder pressure, typically around 90 psi, should be applied to the ultrasonic welding tool, because if the pressure is too low, the contact between the ultrasonic tool and the strip material will be inefficient. The patent states that in particular rubber pieces that do not contain reinforcing cords cannot be satisfactorily bonded and have no effect except for relatively thin strips of about 0.109 inch thick and reinforced with cords. Therefore, U. S. Patent No. 3,904, 457 differs from the present method of joining inclined ends of strips of relatively thick tire tread material without internal reinforcement cords.

U. S. Patent No. 2,626, 430 describes another method of using ultrasonic energy to vulcanize an uncured piece of rubber to a tire to repair the tire.

U.S. Patent No. 3,483,073 describes the use of ultrasonic energy to weld thin sheets of crosslinked polyurethane to each other.

U.S. Patent Nos. 2,487,149, 3,419,447, 3,438,428, 3,483073, and 3,725,164 also describe ultrasonic welding apparatus and methods related to the present invention, but they are not as appropriate as the patents mentioned above.

One object of the present invention is to provide a method of joining inclined ends of a tire tread strip to each other on a generally cylindrical tire forming drum, wherein both ends of the strip overlap each other to form a diagonal connection; The ends of the strips are joined to each other by an ultrasonically actuated joining tool; The tool applies a predetermined pressure to the joint at a predetermined time without vulcanizing the strip material during welding, and is sufficiently strong that the joined inclined end will not be detached until the uncured tire with the bonded tread strip is placed in the vulcanizing mold. Often a certain subsequent hold time at a given pressure is used to assist in the adhesion.

Another object of the present invention is that ultrasonic energy is applied to mating strip ends for a predetermined time, typically in the range of 2 to 12 seconds; The assembly tool is pressed against the top surface of the connection at a cylinder pressure in the range of 20 to 80 psi; Subsequent holding times are generally in the range of 0.5 to 2 seconds but may be longer, wherein the contact surface of the reception tool provides a metered method in which the contact surface is pressurized against the strip at a pressure approximately equal to the pressure acting on the tool when applying ultrasonic energy. It is. The addition and subsequent holding time of the ultrasonic energy and the cylinder pressure used for both can depend on the material, the material thickness and the design of the tool.

It is a further object of the present invention to provide an improved method used to join inclined ends of relatively thick tire tread strip material generally of 1/8 to 5/8 inches (up to 2 inches); The rubber compound of the strip makes a sufficiently firm connection without vulcanizing it, but only enough length to contact the welding tool at a distance from the outside without having to be connected through the entire diagonal length of the joint connection; No heating or adhesive or other connecting material is necessary when connecting the mating sloped ends of the strips together.

It is a further object of the present invention that the contact surface of the welding tool coincides with the contour of the strip in contact with it except for the end of the strip which is not in contact with the tool in order to reduce the possibility of the tool contacting the metal surface of the drum close to the strip end; An improved method is to provide a knurled contact surface of a tool. This does not mean to exclude other tool shapes or additional methods that can deliver ultrasonic energy to the joint.

Another object of the present invention is to eliminate the manual sewing and adhesion of the strip end to date; The width of the tool contact surface is greater than or equal to the width of the diagonal joint; Satisfactory bonding is achieved with a uniform pressure and energy supply throughout the joint; It can be carried out with existing tire forming equipment without having to be carried out on a flat surface or bonding apparatus, so that a general tire manufacturing process can be used; It is an object of the present invention to provide an improved method for satisfactorily joining the inclined ends of relatively thick tire tread material strips in less than the time required to perform such joining manually.

The above objects and advantages are achieved by the improved method of the present invention, the general feature of which is to join together a pair of paired inclined ends of a rubber compound tire tread strip having no internal cord and at least 1/8 inch in thickness. CLAIMS 1. A method comprising: overlapping approaching an inclined end of a strip of rice bran rubber compound such that an overlapping connection extends obliquely between opposing outer surfaces of the strip; Pressing the contact surface of the ultrasonic welding tool to a first pressure in the range of 20 to 80 psi against one surface of the strip at the joint connection; The rubber compound is sufficiently heated and softened so that the compound adheres across a portion of the junction connection without being vulcanized along a portion of the junction connection adjacent to the surface for a first period of time ranging from 2 to 12 seconds within the first pressure range. Applying ultrasonic energy to one surface; And 0.5 to about one strip surface at the surface of the ultrasonic welding tool such that the softening of the rubber compound is sufficiently cooled after application of the ultrasonic energy has ceased to achieve a more firm bond between the one strip surface and the inclined end of the adjacent joint connection. Maintaining the second pressure for a second period of time in the 2.0 second range.

DESCRIPTION OF THE PREFERRED EMBODIMENTS One preferred embodiment, which the present applicant considers the best embodiment to which the principles of the present invention are applied, is described with reference to the accompanying drawings and is clearly described in the appended claims.

The same reference numerals are given to the same members throughout the drawings.

In figure 1 one form of a welding apparatus used to carry out each step of the method according to the invention is shown by reference numeral 1 in its entirety. The welding device 1 includes a base 2 having an upper surface 3 on which the tire tread strip 4 is supported. The tread strip is fed to the base 2 manually by a conveyor or other automatic device or by an operator. In addition, the base 2 and the upper surface 3 may be formed in a cylindrical shape or a dream type, and may be an actual tire forming drum. On the forming drum, the tread strips are combined with other tire parts assembled earlier, which are the final strips which are placed on the previously assembled strips when forming the raw tires.

The device 1 includes a sour housing 7 and a fixed post 6 which accommodate various control devices and power sources, depending on the manufacturer and type. A movable ultrasonic transducer or a converter / booster asscmbly 8 extends downwards therefrom, and a welding tool 9 is installed at the bottom of the transducer / booster. As shown in FIG. 1, the tool 9 is raised or lowered in contact with or separated from the strip 4 by a general hydraulic cylinder 12, which is installed in the housing 7 and schematically illustrated. One type of welding device 1 suitable for carrying out the present invention is an ultrasonic press as a model 43B 15 press with a 1800 W generator manufactured by Dukan Corporation, Illinois, USA. It is called. If necessary, higher or lower wattage generators may be used. The term ultrasound generally refers to a frequency whose frequency is greater than or equal to 16-20 Hz, and is equally defined herein. In addition, in this specification, the term sound waves is used instead of the term ultrasonic waves, which is also defined in the same way.

The welding tool 9 is shown in detail in the second to 4he, in which the contour of the strip contact surface 11 is preferably the same as the top surface 13 of the strip 4 as shown in FIG. 2. It has been found that the knurled surface 15 has a better transfer of ultrasonic energy to the joint than the smooth contact surface. However, the present invention is not limited to this knurled surface.

The strip 4 may consist of a composition of various rubber compounds and is used to construct the final layer of red tire tire carcass in the uncured, raw tire state, resulting in the final tread of the finished tire. The contact surface 11 of the welding tool 9 generally coincides with the cross section of the tire tread strip 4, but also does not extend over the entire width of the tread strip as shown in FIG. It is slightly spaced apart so that a pair of non-contact portions 16 are formed along the directional end. The non-contact portion 16 prevents the welding tool 9 from contacting the upper surface 3 of the base or other metal surface supporting the tire building drum or strip, thereby preventing metal-to-metal contact and the resulting problems.

As shown in FIG. 5, the strip 4 is formed with a pair of inclined ends 19 and 20 tapered at an angle in the range of 20 to 85 degrees with respect to the outer surfaces 21 and 22 thereof. The inclined ends 19 and 20 are placed so as to be continuously overlapped with each other on the tire building drum or the upper surface 3 of FIG. 1 manually or automatically as shown in FIG. 5 to form a joint connection 24. The splice 24 extends diagonally across the width of the strip as shown in FIGS. 5 and 6. After the inclined ends contact each other, the welding tool 9 is in pressure contact with the strip, in particular its upper surface 21. The width of the welding tool 9, indicated by reference numeral 25 in FIGS. 5 and 6, is greater than or equal to the width of the joint connection 24, indicated by reference sign 27, as measured in the longitudinal direction of the strip, and the contact surface 11. Is preferably aligned so as to completely cover the junction connection.

Ultrasonic energy is applied to the tread strip 4 through the welding tool 9 at a predetermined cylinder pressure for a predetermined period of time. The ultrasonic energy is heat-softened so that the rubber compound is not vulcanized so that the rubber compounds are bonded to each other on at least the upper surface of the joint connection part 24 so that the inclined ends 19 and 20 are firmly fixed to each other. This adhesion should be sufficient to maintain the connection until the raw tires to which the strips 4 are bonded are placed in the hardening mold or, if necessary, to withstand the subsequent handling of the connected strips.

According to the invention, it is preferable that the tool 9 remain pressed against the strip 4 for a predetermined period even after the application of ultrasonic energy to the strip is stopped. Subsequent holding for a period of time with respect to the joint allows the softened material to cool, set and firmly adhere to the previously assembled joint before removing the welding tool. The knurled surface 15 of the welding tool 9 imparts a knurled pattern to the outer surface 21 of the strip 4 as shown by reference numeral 28 in FIG. 6.

The inclined ends 19 and 20 do not need to be bonded along the entire diagonal length of the joint connection 24, but are satisfactorily joined even if only the inner part of the surface 21 is bonded in the diagonal direction along the connection 24. The joined or bonded strips are bent into a curved shape when assembled, and the joints adjacent to the inner surface 22 are compressed unlike the joints under tension adjacent to the outer surface 21 and do not tend to separate from one another.

Since the strip 4 is a relatively thick (functional to 2 inches) material in the range of 1/8 inch to 5/8 inch according to the invention, the invention can be used for the manufacture of pneumatic tires of almost any size. The absence of internal reinforcement cords of metal, crops, nylon, etc., in the strip 4 is a difference from US Pat. No. 3,904,457.

In summary, the most satisfactory results can be obtained by applying ultrasonic energy to the junction connection at a cylinder pressure of 20 to 80 psi when forming the oblique junction connection 24. The ultrasonic tread assembly method described above depends on the contact between the tool and the tread which transmits ultrasonic energy, the amplitude of the tool, the effective power of the tool, the contact area of the tool, the contact time, the material to be joined and the pressure dynamic of the tool. . For this reason, the low bonding pressures described above require careful attention to ensure a good relationship between these factors effective for ultrasonic bonding, and in some cases small and / or multiple tools are required in the bonding apparatus. The nominal frequency of the sound waves is approximately 0.0008 inches at 10000/1800 W for the output acoustic wave amplitude of the 20 kHz sonic transducer. The amplitude of the tool also depends on the booster's specifications and gain factors.

As a result of the experiment, it was found that the use of surface finishing by knurling on the surface 11 of the welding tool is most suitable for applying ultrasonic energy to the string material. However, this does not mean that other surface finishes which are effectively applied to the joining of other strips are not excluded from the present invention. Other experiments have confirmed that the generator output and the welding tool amplitude affect the welding time. The composition of the material to be joined also affects the time that ultrasonic energy must be applied to the joint for satisfactory connection.

The sonic bonding time, which generally ranges from 2 to 5 seconds and can be up to 12 seconds long, affects the temperature of the upper surface 21 that the welding tool surface 9 contacts. Experiments have shown that the temperature ranges from 122 ° F. in 2 seconds to 280 ° F. in 10 seconds and the bottom surface 22 of the non-contact strip is 93 ° F. in 2 seconds and 160 ° F. in 10 seconds. This temperature depends on sonic welding and holding time and pressure. Subsequent retention times were successful with recent experiments of 0.5 to 2 seconds. In order to speed up the joining process, the shorter the subsequent holding time is placed. However, in order to reduce the molecular motion of the strip material in the pressurized state, it seems desirable to have a subsequent holding time of 0.5 to 2.0 seconds after applying the ultrasonic energy rather than immediately at the end of the application of the sonic energy. If necessary, the subsequent holding time can be longer. In addition, it is believed that the subsequent holding time to which the subsequent holding pressure is applied is advantageous for the mechanical bonding action.

The amount of heat and the welding penetration depth supplied from the upper surface 21 to the lower surface 22 along the diagonal joint 24 are determined by the time and pressure at which the ultrasonic energy is applied to the upper surface of the joint. In order to effectively seal the upper surface of the inclined assembly, only a part of the diagonal length of the joint 24 needs to be joined, so that the total thickness of the strip is not important. However, the longer the connection along the diagonal bond connection 24, the higher the final bond strength between the inclined ends (19, 20). If a thin material is used, a full joint connection from the surface 21 to the surface 22 is also possible, but the tire is of such strength that subsequent handling and / or storage is possible until the tire with the strip is placed in the hardening mold. In view of the purpose of the present invention of forming a joint connection in the tread strip, such bonding of the joint connection is generally unnecessary. It is of utmost importance that the strip material remains unvulcanized as the vulcanized joint can cause problems when the raw tire carcass is placed in the mold for final vulcanization.

While almost the entire length and width of the joint should be covered with a welding tool, it is preferable that the tool does not come into contact with any metal surface near the ends of the rubber strip. This is the reason for forming the non-contact back 16 shown in FIG. Further, the subsequent holding pressure is preferably equal to the pressure exerted by the welding tool while applying ultrasonic energy so that there is no need to change the pressure. However, the concept of the present invention does not change even if the subsequent holding pressure is different from the pressure at the time of supplying the ultrasonic energy. The subsequent holding pressure may be varied within the same range as the ultrasonic energy application pressure of 20 to 80 psi in the cylinder pressure for a subsequent holding time of 0.5 to 2.0 seconds or longer if necessary. This pressure range is the pressure of the hydraulic cylinder acting on the tool, not the actual pressure exerted on the strip by the tool surface.

The improved method of the present invention joins relatively thick tire tread strips without any internal guarantee cords, so that they are firmly bonded to some extent so that the overlapping and diagonally extending joint connections are paired with each other and the tread strips are joined together. The inclined end of the strip is glued until the raw tire is placed in the hardening mold for final vulcanization.

Therefore, the improved method of the present invention is a simple, efficient, complete and inexpensive effective method, which can achieve all the above-mentioned objects, and solve all the difficulties and problems of the prior art and obtain new results in this field. .

Although certain terms are used in the above description for simplicity, clarity and understanding, they are merely illustrative and should not be unnecessarily restricted beyond the requirements of the prior art and should be interpreted broadly. In addition, since the above description and drawings are merely examples, the scope of the present invention is not limited to these detailed descriptions and drawings.

The features, advantages and principles of the present invention have been described above, the aspects in which each step of the ultrasonic bonding method of an improved tire tread strip end is performed, its features and advantages, and new and useful results are described in the appended claims. .

Claims (10)

A method of joining a pair of paired inclined ends of an unvulcanized rubber compound tire tread strip having an inner cord of at least 1/8 inch thick up speed. a) partially overlapping approaching the inclined end of the unvulcanized rubber compound strip to create a joint connection extending obliquely between opposite outer surfaces of the strip; b) forcing the contact surface of the ultrasonic welding tool to a first pressure in the range of 20 to 80 psi against one surface of the strip at the joint connection; c) during a first period of time in the range of 2 to 12 seconds in a first pressure range to sufficiently heat and soften the rubber compound such that the compound adheres along a portion of the junction joint adjacent to the surface without vulcanization of the compound across the joint junction. Applying ultrasonic energy to the surface; d) and after the application of the ultrasonic energy has ceased, the softened rubber compound is cooled sufficiently to achieve a firmer bond between the one strip surface and the inclined end of the adjacent joint connection, thereby allowing the surface of the ultrasonic generator to reach the surface of the ultrasonic generator. Maintaining a second pressure for a second period of time ranging from 0.5 to 2.0 seconds relative to the strip surface. 2. The method of claim 1 including mating the contact surface of the ultrasonic welding tool with the contour of the strip in contact therewith. The method of claim 1 including forming a knurled surface on the contact surface of the ultrasonic energy generator. The method of claim 1, wherein the longitudinally measured width of the strip of the contact surface of the ultrasonic welding tool pressed against the one surface of the strip is at least equal to the width of the joint connection measured in the longitudinal direction of the strip. Method included. 2. The method of claim 1 including the step of causing the inclination angle of mating ends of the tire tread strip to be in the range of 20 ° to 85 ° with respect to the one surface of the strip. The method of claim 1 wherein the second pressure is generally within the first pressure range. The method of claim 1 wherein the nominal frequency of the ultrasonic energy is 20 Hz. The method of claim 1, wherein applying ultrasonic energy during the first time period results in a temperature of the one surface of the tire tread strip ranging from 122 ° F. to 2 seconds to 280 ° F. for 2 seconds. The method of claim 1 wherein no adhesive is applied to the inclined ends prior to overlapping. The distance between the strips of the ultrasonic welding tool pressed against said one surface of the strips, wherein the measured length is shorter than the transverse widths of the tire tread strips so that the two spacings that do not contact the contact surfaces at the joint connection are defined. How the edges are formed.