Abstract:
A mold device is described for use in a mold having a plurality of tread molding segments. Each tread molding segment has an end face for mating with an adjoining segment. The mold device includes a piston located on the segment and is actuated by the opening and closing of the mold. The piston is positioned within a first chamber and has a plunger end in communication with a working material and a spring. Each of the mold segments further includes a retractable blade assembly having a distal end in fluid communication with a second chamber. The first chamber is in fluid communication with the second chamber. Closing of the mold compresses the piston, forcing the working fluid to transfer from the first chamber to the second chamber, actuating the blade assembly.

Description:
CROSS REFERENCE TO OTHER APPLICATIONS 
     This application claims the benefit of and incorporates by reference U.S. Provisional Application No. 61/287,456 filed Dec. 17, 2009. 
    
    
     FIELD OF THE INVENTION 
     The invention relates in general to tire molds, and a pneumatic tire having grooves in the shoulder area oriented in the axial direction. 
     BACKGROUND OF THE INVENTION 
     Creation of internal grooves in the shoulder area of a tire that are oriented axially may have several advantages. First, the axial grooves may decrease the heat generation in the tire that is built up when the tire is rolling. Second, the grooves may evacuate the water by the tire side during operation on a vehicle, which may improve the visibility of drivers behind the vehicle. The grooves also provide tire flexibility in the shoulder area which may improve tire performance. The grooves may also be used to mount temperature sensing devices to monitor the shoulder temperature. The grooves may be also used to install retractable stud pins for enhanced winter driving. 
     DEFINITIONS 
     “Aspect Ratio” means the ratio of a tire&#39;s section height to its section width. 
     “Axial” and “axially” means the lines or directions that are parallel to the axis of rotation of the tire. 
     “Bead” or “Bead Core” means generally that part of the tire comprising an annular tensile member, the radially inner beads are associated with holding the tire to the rim being wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes or fillers, toe guards and chafers. 
     “Belt Structure” or “Reinforcing Belts” means 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 17° to 27° with respect to the equatorial plane of the tire. 
     “Bias Ply Tire” means that the reinforcing cords in the carcass ply extend diagonally across the tire from bead-to-bead at about 25-65° angle with respect to the equatorial plane of the tire, the ply cords running at opposite angles in alternate layers. 
     “Breakers” or “Tire Breakers” means the same as belt or belt structure or reinforcement belts. 
     “Carcass” means a laminate of tire ply material and other tire components cut to length suitable for splicing, or already spliced, into a cylindrical or toroidal shape. Additional components may be added to the carcass prior to its being vulcanized to create the molded tire. 
     “Circumferential” means lines or directions extending along the perimeter of the surface of the annular tread perpendicular to the axial direction; it can also refer to the direction of the sets of adjacent circular curves whose radii define the axial curvature of the tread as viewed in cross section. 
     “Cord” means one of the reinforcement strands, including fibers, which are used to reinforce the plies. 
     “Inner Liner” means the layer or layers of elastomer or other material that form the inside surface of a tubeless tire and that contain the inflating fluid within the tire. 
     “Inserts” means the reinforcement typically used to reinforce the sidewalls of runflat-type tires; it also refers to the elastomeric insert that underlies the tread. 
     “Ply” means a cord-reinforced layer of elastomer-coated, radially deployed or otherwise parallel cords. 
     “Radial” and “radially” mean directions radially toward or away from the axis of rotation of the tire. 
     “Radial Ply Structure” means the one or more carcass plies or which at least one ply has reinforcing cords oriented at an angle of between 65° and 90° with respect to the equatorial plane of the tire. 
     “Radial Ply Tire” means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire. 
     “Sidewall” means a portion of a tire between the tread and the bead. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described by way of example and with reference to the accompanying drawings in which: 
         FIG. 1  is a simplified schematic of a tire mold showing part of a mold segment, tire carcass, sidewall plate and mold device, wherein the mold is in the open position; 
         FIG. 2  is a cross-sectional view of  FIG. 1  in the direction  2 - 2 ; 
         FIG. 3  is an exploded perspective view of a second piston and sleeve; 
         FIG. 4A  is a cross-sectional view of a first chamber, T shaped member, u shaped spring and plate; 
         FIG. 4B  is a cross-sectional view of a first chamber, T shaped member, u shaped spring and plate wherein the u shaped spring is flattened; 
         FIG. 5  are cross-sectional views of the silicone skins of the first, second and third member; 
         FIG. 6  is a view of the third member in the normal and flexed position; 
         FIG. 7  is the apparatus of  FIG. 1  shown in a partially closed position; 
         FIG. 8  is the apparatus of  FIG. 1  shown in a fully closed position; 
         FIG. 9  is a cross-sectional view of  FIG. 8  in the direction  9 - 9 ; and 
         FIG. 10  illustrates the apparatus of  FIG. 1  with the blade extended and the first chamber being filled up with the working fluid; 
         FIG. 11  illustrates the apparatus of  FIG. 1  with the blade beginning to retract as the first chamber is filled up with the working fluid; 
         FIG. 12  illustrates the apparatus of  FIG. 1  with the blade fully retracted as the first chamber is filled with fluid and the wave spring is expanded; 
         FIG. 13  illustrates the apparatus of  FIG. 1  when the mold is opened. 
         FIGS. 14A and 14B  illustrate the time it takes a piston to travel a distance X, shown without a silicone skin ( FIG. 14A ) and with a silicone skin ( FIG. 14B ). 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the drawings, a first embodiment of a tire mold device  10  is shown. The tire mold device  10  is useful for molding lateral grooves in the side of a tire. The tire device  10  may be installed in a tire mold segment near the shoulder area of a tire. The tire mold typically comprises a plurality of tread molding segments  20 , wherein each tread molding segment has an inner face  21  which mates with a portion of a sidewall plate  22 . The tread segment further includes an inner surface  25  for molding the tire tread. The tire mold further comprises other components which have been removed for clarity, and are otherwise known to those skilled in the art. Located on the inner surface  25  of the segment is an optional plug  31 . The plug may be used to form a housing in the tire tread for a stud pin. 
       FIGS. 1 and 2  illustrate a cross-sectional view of a portion of a tread segment, and sidewall plate shown in the open or start position. A green unvulcanized carcass tread T is shown positioned within the mold. The mold blade apparatus  10  has a retractable blade  54  for forming a hole in a green tire, and is shown in the retracted position in  FIGS. 1 and 2 . The retractable blade  54  is received within a cylindrical housing  51  which is contained within an axially oriented slot  13  formed in the shoulder area of the segment. The retractable blade  54  is biased into a retracted position by a compression spring  24 . The retractable blade  54  has a bottom portion  26  which is engaged by the compression spring  24 . The bottom portion  26  of the blade  54  is also in mating engagement with a first working member  28 . Preferably the first working member  28  is encased in a silicone skin  29 . The silicone skin  29  is elastic and acts like a spring to retract the retractable blade to its starting position in a faster time than without the skin as shown in  FIG. 14 . As shown in  FIG. 6 , the working member  28  fills up with a working material from a second chamber  60 . The working material preferably has a viscosity in the range of about 800 to about 1200 MPas. One example of a material suitable for use as a working material is an RTV type silicone, which is in the form of a jelly or paste at room temperature. An RTV type silicone suitable for use as a working fluid is sold under the trade name Silgel 612 by Wacker Chemie AG. The silicone skin  29  is solid and elastic at room and elevated mold temperatures and has an elongation at break greater than or equal to 450%. The skin material may be RTV-M 536 sold by Wacker Chemie AG. 
     The mold blade apparatus  10  further includes a first piston  30  which is positioned in a radial slot  11  for engagement with the sidewall plate  22 . The engagement of the first piston  30  with the sidewall plate  22  actuates the mold blade apparatus  10  when the mold segments are in the closed position as shown in  FIG. 4 . The mold blade apparatus further includes a wave spring  12  positioned within the first piston  30 . A second piston  40  is received within the radial slot  11  and has a pin  42  received there through. The second piston  40  is received within a sleeve  44  and has an end cap  46  screwed thereon. As shown in  FIG. 3 , the pin  42  of second piston  40  slides within slots  46  of sleeve  44 . The ends of pin  42  are connected to radially oriented pins  43 . Pins  43  are positioned to engage the sidewall plate  22 . Compression of pins  43  slides the second piston  40  radially outward, expanding a first chamber  50 . The first chamber  50  is formed within the slot  11 , between the second piston  40  and a plate  54 . The first chamber  50  is preferably encased with silicone skin cap  53  to form a leak proof barrier. A compression spring  48  is positioned within the sleeve  44  and biases the second piston  40  away from the end cap  46  in a radially downwards direction. A third piston  14  is positioned between the first piston  30  and the second piston  40 . Preferably, the first piston, second piston and third piston are aligned or coaxial. 
     As shown in  FIGS. 4A and 4B , the plate  54  has a center T shaped member  56  which is seated in a T shaped passageway by U shaped spring  58 . The T shaped member  56  has an interior passageway  55  for passage of a working fluid from the first chamber  50  to a second chamber  60 .  FIG. 4A  illustrates when the U shaped spring holds the T shaped member against the T shaped passageway so that flow is prevented in the T shaped passageway by engagement of the member  45  with the sidewalls  47 . Flow is only permitted through center passageway  55 . When the U shaped spring force is overcome as shown in  FIG. 4B , flow may occur through the T shaped passageway and into the interior passageway  55 , from the first chamber  50  to the second chamber  60 . Thus the T shaped member  56  acts as a flow restrictor that is designed to allow only a small amount of flow when the fluid flows in a first direction. When the flow reverses direction, a much larger flow rate q may pass through the restrictor due to the restrictor being unseated from the channel edges that block off the outer flow paths. The larger flow rate allows rapid charging of the first chamber and a return to the initial position for restarting of the mold sequence. 
     Positioned with the second chamber  60  is a second member  70  and a third member  72 . The second and third member  70 ,  72  are preferably formed from a working material that has a viscosity in the range of about 800 to about 1200 MPas. One example of a material suitable for use as a working material is an RTV type silicone, which is in the form of a jelly or paste at room temperature. An RTV type silicone suitable for use as a working fluid is sold under the trade name Silgel 612 by Wacker Chemie AG. Preferably the second member  70  is contained within a silicone U shaped skin  71 , as shown in  FIG. 5 . Preferably the third member  72  is also contained within a silicone skin  73 , as shown in  FIG. 5 . The silicone skins  53 ,  71 ,  73  are solid and elastic and have an elongation at break greater than or equal to 450%. The silicone skin material may be RTV-M 536 sold by Wacker Chemie AG. 
       FIGS. 1 and 2  illustrate the molding device  10  in the start position wherein the blade  54  is retracted, and the first piston  30  is positioned for engagement with the sidewall plate  22 .  FIG. 7  illustrates the tread segment in a partially closed position. The first piston  30  engages sidewall plate  22 . The two pins  43  on each side of the first piston  40  are in contact with the sidewall plate. The pins  43  push up the second piston  40 , overcoming the force of the compression spring  48  to enlarge the first chamber  50 . The first piston  30  and third piston  14  force the working material into the second chamber  60  and then into the skin  29  to move the retractable pin  52 . As shown in  FIG. 7 , the retractable pin  52  is out of the tread segment at its maximum position, but the mold is not yet closed. A gap between the tread segment and the sidewall plate still exists. 
       FIG. 8  illustrates the mold in a closed position. The waved springs  12  are compressed (the waved springs must be still compressed to ensure the variation of the silicone expansion) The spring force of the waved springs  12  must be greater than the compression spring force  24  to maintain the retractable pin  52  at its maximum position. The force of the waved springs acts on the working material, moving from chamber  60  to chamber  50  by the smaller orifice  55  of the T shaped member  56 . The dimension of this orifice and the compression forces of the springs will be adjusted to respect the curing time. 
       FIG. 10  illustrates the mold still in the closed position and the blade still in its extended position. The volume of the working material in the first chamber  50  is increasing, which decreases the force exerted on the waved springs. When the wave spring force is the same as the compression spring  24  force+elastic force of the skin  29 , the retractable pin  52  is beginning its backwards movement.  FIG. 14A  illustrates the time T 2  needed for a piston to travel a distance X, shown without a silicone skin.  FIG. 14B  illustrates the time it takes a piston (with a silicone skin) to travel a distance X. The piston with a silicone skin travels the distance faster because of the spring effect. 
       FIG. 11  illustrates the blade  54  retracting from the tire tread. The force of the compression spring  24  forces the working material from the first member  29  into the chamber  50 .  FIG. 12  illustrates that the pin  52  is fully retracted, which is timed with the end of the tire curing cycle. Chamber  50  is filled with the working material. 
       FIG. 13  illustrates the end of the tire curing cycle and the mold is opened to remove the cured tire. The two pins  43  on each side of the second piston  40  no longer exert a force on the second piston  40 . The compression spring  48  acts on the chamber  50 , forcing the working material out of the chamber and into the second chamber  60 . The U shaped spring  58  is compressed as shown in  FIG. 4B , and the working fluid passes through passage  55  and through the T shaped passageway. The chamber  50  is emptied as the working fluid is returned to chamber  60 , filling members  70 ,  72 . 
     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.