Patent Application
20190184656
The invention relates generally to rubber processing, and more particularly to a method and apparatus for making a strip of rubber.
The invention describes a method and apparatus necessary to make a strip of rubber material useful for tire building. Typical prior art methods of making a rubberized strip generally utilize expensive equipment such as gear pumps and extruders. Extruders are typically very high pressure and require large amounts of horsepower in order to form a small strip. Extruders are expensive, and if not used properly, may overheat or overwork the rubber. Thus, an apparatus and method of efficiently producing a rubber strip is desired.
According to one aspect of the invention, an apparatus for forming a strip of rubber is described. The apparatus comprises a support frame; a first and second roller mounted on the support frame, wherein the first and second rollers are spaced apart from each other; and an application roller located adjacent a head, and a channel formed between the head and the outer surface of the application roller and the inner surface of the head; wherein said channel has an inlet and an outlet, wherein the inlet is located near the second roller, and the outlet is located adjacent a die.
A method of forming a rubber strip comprising the steps of providing a support frame with a first and second roller mounted thereon, wherein the first and second rollers are spaced apart from each other; threading a rubber stock about the first and second roller, and then through a channel formed between a head and a rotating application roller, and then through an outlet die.
“Aspect ratio” of the tire means the ratio of its section height (SH) to its section width (SW) multiplied by 100 percent for expression as a percentage.
“Asymmetric tread” means a tread that has a tread pattern not symmetrical about the center plane or equatorial plane EP of the tire.
“Axial” and “axially” means lines or directions that are parallel to the axis of rotation of the tire.
“Chafer” is a narrow strip of material placed around the outside of a tire bead to protect the cord plies from wearing and cutting against the rim and distribute the flexing above the rim.
“Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction.
“Equatorial Centerplane (CP)” means the plane perpendicular to the tire's axis of rotation and passing through the center of the tread.
“Footprint” means the contact patch or area of contact created by the tire tread with a flat surface as the tire rotates or rolls.
“Inboard side” means the side of the tire nearest the vehicle when the tire is mounted on a wheel and the wheel is mounted on the vehicle.
“Lateral” means an axial direction.
“Lateral edges” means a line tangent to the axially outermost tread contact patch or footprint as measured under normal load and tire inflation, the lines being parallel to the equatorial centerplane.
“Net contact area” means the total area of ground contacting tread elements between the lateral edges around the entire circumference of the tread divided by the gross area of the entire tread between the lateral edges.
“Radial” and “radially” means directions radially toward or away from the axis of rotation of the tire.
The invention will be described by way of example and with reference to the accompanying drawings in which:
Referring to
As shown in
Each preheat roller has internal heaters (not shown). Preferably, each preheat roller is heated to a different temperature than the other preheat rollers. Preferably, the preheat rollers are progressively heated to a higher temperature so that the first preheat roller 130 is the coolest roller, while the second preheat roller 140 is heated to a higher temperature than the first preheat roller 130. The third preheat roller 150 is heated to a higher temperature than the second preheat roller 140, and the fourth preheat roller 160 is heated to a higher temperature than the third preheat roller 150. Likewise, the fifth preheat roller 170 is heated to a higher temperature than the fourth preheat roller 160. In summary, the preheat rollers are preferably maintained at progressively higher temperatures, increasing in temperature in the incremental range of about 5-20 degrees per roller with decreasing height of the mounting frame, so that the first or highest roller 130 is the coolest and the lowest roller is the hottest.
It is also preferred that the preheat rollers progressively increase in rotational speed from the highest vertical roller 130 to the lowest vertical roller 170, so that the lowest vertical roller 170 is the fastest.
The rubber strip path is wound around the preheat rollers as shown in
As the application roller 230 rotates, it pulls rubber between the roller 230 and the milltruder head 220. As the rubber moves toward a die 250, the rubber is compressed and mixed both circumferentially and axially in the channel 240 between the milltruder head 220 and application forming roller 230. The axial mixing/movement is also increased due to the conical shape of the application roller. Since the outer diameter of the roller has a higher surface speed than the smaller diameter of the cone, rubber will tend to migrate to the surfaces with higher surface velocities, ie towards the band 236, generating additional mixing and pressure at the die opening. If more work or heat is required to process the rubber, the die 250 can be moved out to allow rubber to form a band around the application roller similar to a mill. This will allow multiple “passes” of rubber between milltruder head and roller, thus increasing work input.
The strip forming apparatus 100 may apply a strip of rubber onto a drum 300 or onto a carcass under construction. The application pressure may be adjusted by adjusting the angle α that the apparatus forms with the vertical direction.
An alternate embodiment of a milltruder head 400 is shown in
The advantages of the system are: Significant reductions in capital costs of a system vs extrusion. Significantly lower horsepower required (lower energy costs). Since the size of the system is small, multiple strips can be applied to the building drum simultaneously. This reduces capital cost and increases output because fewer drums and less conveying of building drums is required. Since the entire assembly is hanging vertically, stitching application pressures can be more easily achieved vs present extrusion technology. This leads to reduced trapped air and a higher quality product. Being able to control this stitching pressure also allows for reinforcement to be applied directly to the building drum without pre-calendering, further reducing complexity and costs.
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
