Patent Application
20050133149
This invention relates to tire manufacturing generally and most specifically to a method and apparatus for curing a tire.
The curing or vulcanization of an uncured tire requires that the tire be maintained in a closed mold under hot temperatures and high pressures for a period of time which varies between a few minutes and several hours depending on the size of the tire. The equipment used to vulcanize a tire usually includes a press and a mold. The press may have steam or other heating elements brought into contact with the mold to impart heat into the mold to assist in the curing process.
In large volume tire manufacturing it is possible to manufacture tires very rapidly. In a matter of a minute or two an entire tire can be assembled in an automated fashion. The tire curing process, however, may take upwards of four to twenty minutes for a passenger or light truck tire, depending on the tire size, more time, of course, for the larger tires such as earthmover, farm, truck and aviation tires. Accordingly, a large number of molds or presses must be used to maintain an efficient balance between the manufacturing of the tire and the curing of the tire.
In U.S. Pat. No. 4,728,274, issued on Mar. 1, 1988, a tire curing system was proposed wherein tire curing could be provided by using mobile mold curing units, each designed to house a respective uncured tire. These mobile units were selectively and independently fed along a loop circuit having at least two parallel branches. The ends of the branches were connected to a common section extending through a station for loading and unloading the tires into and out of respective curing units. Each curing unit incorporated a mold for a green tire, a closed pneumatic circuit designed to receive at the load/unload station a given supply of curing medium under pressure, a fan device for force circulating the curing medium supply inside the pneumatic circuit, and individual elements for heating both the mold and the curing supply. These units would then be transferred along a path until the tire cure cycle had been completed. The objective of this patent was to provide a curing system involving none of the complexities of conventional tire molding while providing a high degree of production flexibility. The primary benefit of the above-referenced patent was that the number of curing presses could be minimized and that the molds themselves would be utilized in providing the heat input to cure the tire as the mobile units were being conveyed.
Another patent, U.S. Pat. No. 5,622,669, issued Apr. 22, 1997, provided an induction curing apparatus that would impart heat to a mold and then the mold would be fed into a carousel device which would rotate around a cycle for a predetermined amount of time until the tire was cured. This device required multiple molds to be supplied in order to cure the tires and to match the tire curing sequence which is typically done in tire manufacturing.
All of the prior art requires multiple molds to be used in order to maximize the efficiency. These molds, whether requiring independent presses for each mold or utilizing a carousel or trolley devices for the molds require more equipment than is necessary for the production of a tire.
The present invention provides a more efficient way of manufacturing and curing a tire. In the present invention, a single tire curing station is used whereby one mold is employed in combination preferably with a heat input source such that the tire can be cured in a very rapid fashion, off-loaded while the next tire being assembled simultaneously in such a fashion that as one tire is built another tire is being cured and that the process can be conducted in as rapid a time as possible in order to ensure that only one mold is needed and one curing station. The benefits of the present invention are that the manufacturing process can be accomplished in a timeframe of approximately four to twenty minutes and the cure station is capable of providing a fully cured passenger or light truck tire within that same timeframe. More cure time is naturally required for the larger tires. Accordingly, only one mold is needed for each tire building system.
As can be readily appreciated, the present invention provides a slower small unit production capability that is ideal for prototyping and small volume production runs of small and light tires. An objective of the present invention is to match the assembly process with the cure cycle time such that the equipment required is sufficient to produce cured tires at about the same rate the tires are being manufactured.
Historically, such manufacturing systems were avoided because the need for high speed, high volume production has always dictated that such a system be employed. It has come to the inventors' attention that such systems require large volumes of production runs, massive amounts of inventory of finished product and the associated cost of shipping and handling. It is an objective of the present invention to provide a very small yet efficient automated manufacturing and curing system such that small modular units can produce small volume runs in an efficient low-energy consuming fashion. In order to increase volumes, additional modules can be added. A primary advantage of the present system is that the entire tire manufacturing process, start to finish, from components to cured tires, is accomplished at a singular modular workstation.
A method of assembling a tire and curing the tire has the steps of applying hot tire components onto an elevated temperature building drum core to form a hot uncured tire, placing the hot uncured tire and the elevated temperature building drum core into a preheated open mold, closing the open mold and adding additional heat energy to match a predetermined optimal cure temperature Tp and curing the tire for a predetermined time.
The additional heat energy is input by activating one or more induction heating coils. The predetermined optimal cure temperature Tp, which approximates the peak cure temperature, is greater than the elevated temperature of the building core and also greater than the temperature of the hot tire components when inserted into the mold.
The method further has the steps of assembling a second tire by applying hot tire components on a second elevated temperature building drum core as a first assembled tire is being cured, opening the mold, removing the first tire from the mold, removing the first tire from the elevated temperature building core, and inserting the second tire on the second elevated temperature building drum core into the mold, closing the mold, and curing the second tire as the first elevated temperature building core has hot tire components being applied to form a third tire. The preferred method has the additional heat energy input by activating two or more induction coils timed to a load sequence in an alternating on-off pattern.
The above method of curing a tire is best performed by utilizing an apparatus for curing a tire which has a tire curing mold, the mold having a central axis and an outer portion for imparting the tread and sidewall shape; an inner core upon which the tire is to be mounted, a frame for supporting the mold, an induction curing dome for encircling the mold, the induction curing dome having one or more heating coils, a means for removing the induction curing dome into and away from encircling alignment with the mold; and a power source for activating the heating coils.
The frame may have a mold support and one or more heating coils attached to the upper surface of the frame which can be brought into heating alignment with the lower surface of the mold.
The apparatus further may have a mold locking means for opening and closing the mold. This mold locking means is preferably attached to the means for moving the induction curing dome and this means for moving is pivotally movable to bring the induction curing dome or the mold locking means into coaxial alignment with the mold prior to encircling the mold.
The induction curing dome may have two or more coils. When using multiple coils, it is preferable that the apparatus include a power modulator for controlling the power input to each coil in an alternating pattern sequence. This ensures that the energy required to activate the coils is reduced over a broader area of power input.
Definitions
The following terms may be used throughout the descriptions presented herein and should generally be given the following meaning unless contradicted or elaborated upon by other descriptions set forth herein.
“Apex” (also “Bead Apex”) refers to an elastomeric filler located radially above the bead core and between or adjacent the plies and the turnup ply ends if the tire employs ply turnup ends.
“Axial” or “axially” refers to directions that are on or are parallel to the tire's axis of rotation.
“Bead” refers to that part of the tire comprising an annular substantially inextensible tensile member, typically comprising a cable of steel filaments encased in rubber material.
“Belt structure” or “reinforcement belts” or “belt package” refers to at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cord angles in the range from 18 to 30 degrees relative to the equatorial plane of the tire.
“Carcass” refers to the tire structure apart from the belt structure and the tread, but including the sidewall rubber, beads, plies, and, in the case of EMT or runflat tires, the sidewall reinforcements.
“Casing” refers to the carcass, belt structure, beads, and all other components of the tire excepting the tread and undertread.
“Chafer” refers to reinforcing material (rubber alone, or fabric and rubber) around the bead in the rim flange area to prevent chafing of the tire by the rim parts.
“Chipper” refers to a narrow band of fabric or steel cords located in the bead area whose function is to reinforce the bead area and stabilize the radially inwardmost part of the sidewall.
“Circumferential” refers to circular lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction, and can also refer to the direction of sets of adjacent circular curves whose radii define the axial curvature of the tread, as viewed in cross section.
“Cord” refers to one of the reinforcement strands, including fibers of metal or fabric, with which the plies and belts are reinforced.
“Crown” or “tire crown” refers to the tread, tread shoulders and the immediately adjacent portions of the sidewalls.
“EMT” refers to Extended Mobility Technology and EMT tire refers to a tire which is a “runflat”, which refers to a tire that is designed to provide at least limited operational service under conditions when the tire has little to no inflation pressure.
“Equatorial plane” refers to the plane perpendicular to the tire's axis of rotation and passing through the center of its tread, or midway between the tire's beads.
“Gauge” refers generally to a measurement, and often to a thickness dimension.
“Inner liner” refers to the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating gas or fluid within the tire. Halobutyl, which is highly impermeable to air is a common material for use as an inner liner.
“Insert” refers to the crescent-shaped or wedge-shaped reinforcement typically used to reinforce the sidewalls of runflat-type tires; it also refers to the elastomeric non-crescent-shaped insert that underlies the tread; it is also called a “wedge insert.”
“Lateral” refers to a direction parallel to the axial direction.
“Meridional profile” refers to a tire profile cut along a plane that includes the tire axis.
“Ply” refers to a cord-reinforced carcass-reinforcing member (layer) of rubber-coated, radially deployed or otherwise parallel cords.
“Pneumatic tire” refers to a laminated mechanical device of generally toroidal shape (usually an open-torus) having two beads, two sidewalls and a tread. The tire is made of rubber, chemicals, fabric and steel or other materials.
“Shoulder” refers to the upper portion of sidewall just below the tread edge.
“Sidewall” refers to that portion of a tire between the tread and the bead.
“Tire axis” refers to the tire's axis of rotation when the tire is mounted to a wheel rim and is rotating.
“Tread cap” refers to the tread and the underlying material into which the tread pattern is molded.
“Turn-up end” refers to a portion of a carcass ply that turns upward (i.e., radially outward) from the beads about which the ply is wrapped.
Reference will be made in detail to preferred embodiments of the invention, examples of which are illustrated in the accompanying drawing figures. The figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these preferred embodiments, it should be understood that it is not intended to limit the spirit and scope of the invention to these particular embodiments.
Certain elements in selected ones of the drawings may be illustrated not-to-scale, for illustrative clarity. The cross-sectional views, if any, presented herein may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain background lines which would otherwise be visible in a true cross-sectional view, for illustrative clarity.
The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein:
With reference to
In a related patent application entitled “Tire Manufacturing Module and Method of Manufacturing Tires”, filed on Dec. 11, 2003, application Ser. No. ______ (Attorney Docket Number DN2003-201) which is incorporated by reference herein in its entirety, the initial building of a tire 200 is on a mobile tire building trolley 60 with a specific detachable tire building drum core 22 designed to permit the fabrication of the tire carcass 4 and tread belt structure 3 onto the toroidally expanded warmed or elevated temperature building drum core 22 so when the tire carcass 4 and tread belt structure 3 are formed it is in the toroidal shape very close to the finished tire dimensions as it is assembled. The detachable building drum cores 22 are mounted on transporter devices called mobile tire building trolleys 60. This trolley 60 accepts the building drum core 22 and will traverse along a predetermined path or line 20. The trolley 60 provides a means 62 for rotating the tire building drum core 22 at each workstation as the specific tire component is being applied. The workstations and the tire trolley 60 have the software programmed into each of the workstations and trolleys and are coordinated by supervisory software such that the proper component is provided to the tire building drum core 22 at the precise time and location desired. For purposes of this invention, the detailed views of the workstations of the building module 100 are not illustrated.
While this entire process of building the carcass 4 and tread belt structure 3 is being accomplished a simultaneous curing of the uncured tire 200 is occurring.
With particular reference to
Once the assembly is inserted into the mold 50, the mold locking means 70 is rotated 90° about a pivoting support 98 and lowered into position to engage the open segmented mold 50 and to close those segments 54 into a closed position and upon closure a top mold plate 52 is then secured onto the mold creating the self-locking mold 50 in a completely closed and contained condition. After the mold 50 is closed the mold locking means 70 is elevated and rotated back 90° and the induction curing dome system 80 mounted approximately 180° from the mold locking means 70 is then pivoted 90° into position aligned with and above the mold 50. The induction dome 80 as illustrated in
Once pressurized, the curing cycle can be initiated by activating the induction coils 81, 82, 83 around the segmented mold 50. As illustrated an induction coil 83 is adjacent the frame 94 as the mold sets upon the mold supports 90 as illustrated in
A primary feature of the coils 82, 83 of the induction heating core dome 80 and of the induction coil 81 on the outer surface of the frame 84 is that the power input to each coil 81, 82, 83 can be sequenced in an alternating fashion. This is as illustrated in
The combination of forming elastomeric components 1, 2, 5, 6, 7, 41, 48 while hot at various workstations and applying to those hot components onto the elevated temperature building drum core 22 ensures that the additional heat input is minimized. In other words, assuming that the building drum core 22 is maintained at a temperature of at least approximately 50° C., preferably 60° C. or more, throughout the building cycle and that the components are formed at approximately 60° C. at each of the workstations, the additional heat input required to bring the uncured tire, when assembled, to cure is dramatically reduced. In other words, the initial temperature of the uncured tire 200 may be between 50° C. and 70° C. and the predetermined optimal cure temperature Tp may be at approximately 160° C. Accordingly, the incremental difference between the uncured tire and the optimal cure temperature Tp is the difference. Therefore, the additional input required to bring the uncured tire to cure temperature requires only an additional amount of energy to bring the components up possibly 90 to 110° C. This can be accomplished in a rather short period of time. Once the optimal cure temperature Tp is achieved, it is common to hold the tire assembly for a predetermined period of time (t) to achieve a proper cure cycle. Once this time (t) is achieved the tire 200 will be completely vulcanized or sufficiently vulcanized such that it can be removed from the mold 50.
Once the tire 200 is cured the mold locking means 70 will be swung back into position and lowered over the mold 50 engaging the segments 54 and unlocking the upper mold plates 52 such that the segments 54 can move radially outwardly. Once this is accomplished, the locking means 70 releases from the mold 50, is elevated and pivots away from the open mold 50 with the top sidewall plate 52. After that, the tire pickup and transfer device 99 engages the cured tire 200 on the building drum core 22, picks the entire assembly up and extracts it from the open mold 50 and rotates to the tire building drum removal station 97 as illustrated in
While this entire process of building the carcass 4 and tread belt structure 3 is being accomplished a simultaneous curing of the uncured tire 200 is occurring.
The tire building module 100, in conjunction with the trolley 60 mechanism, is programmed to build not only the carcass 4 but also a particular tread belt structure 3. The belt layers 1 and 2 are applied to the outer peripheral surface of the carcass assembly 4 on the detachable elevated temperature building drum core 22. After the first wide belt 1 is applied and the second narrow belt 2 is applied, a gum strip 5 is applied to each edge of the first belt layer 1 at the belt workstation. If required, an optional overlay workstation 15 can be provided wherein overlays 6 having substantially 0° or very low angles in the circumferential direction are wound onto and overlaying the underlying belt structure 1, 2. Once these components 1, 2, 5 and 6 are laid onto the outer peripheral surface of the carcass 4, the tread 7 is applied over the underlying components as illustrated in
Once the tread belt assembly 3 is completely formed, the entire uncured tire 200 on the detachable building drum core 22 including the carcass 4 and tread belt reinforcing structure 3 freshly formed and preferably still hot mounted to it is removed from the trolley 60 and delivered to an open segmented mold 50 at location 140. As shown in
As shown in
With the top plate 52 of the mold 50 open, the entire building drum core 22 with the carcass 4 and tread belt assembly 3 mounted thereto can be inserted directly into the mold 50. This is made possible due to the fact that an upper portion 55 of the tread mold forming section of the mold is attached to the top plate 52. This permits the entire uncured tire 200 to be able to fit directly into the mold 50 with the carcass 4 and tread belt assembly 3 in place. Once inserted into the mold 50, the mold 50 can be closed and locked and the carcass subassembly 4 inflated by applying internal pressure to the building drum core 22 further pressing the tread 7 into the internal surfaces of the mold 50. Once this is accomplished the mold 50 can be heated and pressurized to curing mold temperatures and pressures and the mold 50 will then finish the overall vulcanization of the tire 200 encased into the mold 50. As the mold 50 finishes the heating curing cycle it is ready for mold opening and removal of the tire. At this point, the mold 50 is open, the mold segments 54 are radially expanded and the building drum core 22 with the tire mounted thereto is removed from the mold 50.
With reference to
Once this is accomplished, the tire building drum core 22 can go back to the trolley 60 for a second tire build, it will be picked up by a transfer means and placed on the trolley 60 or moved directly to a trolley mechanism 60 whereupon it will repeat the process for building a second tire. The tire building drum core 22 is explained in greater detail in a patent application entitled “Radially Expansible Tire Assembly Drum and Method for Forming Tires”, Ser. No. 10/388,773, filed Mar. 14, 2003, and the contents of which are incorporated herein by reference in their entirety.
The automated module 10 as shown in
An advantage of the present invention over prior art invention is that that tread belt subassembly 3 and carcass 4 are inserted directly into a mold 50 while freshly formed and located on the elevated temperature tire building drum core 22 whereupon the mold 50 is closed upon the tire assembly in such a preassembled fashion that it is cured directly into the mold 50. The unique self-locking mold 50 then is opened to permit the entire carcass 4 and tread belt 3 for that particular tire size to be inserted into the mold 50 while mounted on its building drum core 22. The mold 50 is then closed and heated for a curing process which may be done by induction heating with electromagnetic fields separately or in combination with steam heat or otherwise. Once the curing cycle is completed, the mold 50 is opened and the cured tire 200 on building drum core 22 is removed. This is all accomplished while another tire 200 is being simultaneously or concurrently fabricated on the trolley 60 with a detachable building drum core 22 at the various workstations of the module 100 along the predetermined path 20.
While the embodiment of
One of the interesting differences of the present invention compared to prior art tire manufacturing is that it contemplates applying the components while hot onto the warmed or elevated temperature building drums and that while these hot components are freshly being produced, formed and applied at the carcass building and tread belt assembly workstations, they are then directly placed into a mold while hot, the mold is closed while all the components maintain their own heat from being formed and placed on the elevated temperature building drum. This has a tremendous advantage in that component materials can be provided that would otherwise bloom or cause a powdery substance called sulfur to leach out of the component prior to vulcanization. Historically, tires are made of strips and then stored. These strips set over a period of time and the material tends to bloom or have sulfur or other components leach out to the surface. This creates situations where the tires can have problems during manufacture due to the variations in freshness of the various components. The present invention ensures that the rubber materials are applied approximately as fresh as possible, preferably with no lap or butt splices. In other words they are still warm when they are placed in the mold. There has been no opportunity for contamination or deformation to occur due to subassembly storage and handling. This greatly improves the manufacturing quality of the finished product and ensures that the components will be properly place and properly mixed at the time they are applied. Furthermore, there are energy savings due to keeping materials hot instead of deliberately cooling for storage as in prior methods.
While the components are undoubtedly applied where formed creating a tremendous manufacturing advantage in terms of freshness, an additional advantage is that the component materials can be provided to each workstation in rather bulk form. The component material can be made without the use of processing aides such as anti-aging ingredients and curing accelerators needed to survive storage as no storage is needed, greatly reducing material cost. Furthermore, much of the component handling equipment commonly found in tire building can be eliminated. Therefore, inventory of intermediate components is reduced to a very low amount and in the case of the elastomer components the storage of these intermediate articles is virtually eliminated. This very compact reduced floor space tire building module greatly reduces the tonnage of raw material needed to be stored as components and eliminates such ancillary devices as storage racks and hand trucks, greatly reducing the manpower and maintenance required to support them.
This application relates to the following U.S. patent applications entitled: “A Method and Apparatus for forming an Annular Elastomeric Tire Component”, U.S. Ser. No. 10/291,279, filed on Nov. 8, 2002; “An Improved Method and Apparatus for Manufacturing Carcass Plies For a Tire”, U.S. Ser. No. 10/365,374, filed on Feb. 11, 2003; “Radially Expansible Tire Assembly Drum and Method For Forming Tires”, Ser. No. 10/388,773, filed Mar. 14, 2003; “Method and Apparatus For Tread Belt Assemblies”, Docket No. DN2003-078, filed on May 20, 2003; and “A Method For Curing Tires and a Self-Locking Tire Mold”, U.S. Ser. No. 10/417,849, filed Apr. 17, 2003; “Method for Manufacturing Tires on a Flexible Manufacturing System, U.S. Ser. No. 10/449,468, filed May 30, 2003, “Tire Manufacturing Module and Method of Manufacturing Tires”, U.S. Ser. No. ______ (Attorney Docket Number DN2003-201) filed Dec. 11, 2003.
