FLEXIBLE MOLD SEGMENT WITH SIPE ELEMENT HAVING A PROJECTION FOR USE IN FORMING A TIRE

A mold segment (10) for forming a tire is provided that has a sipe element (14) with first and second ends. A first side face (20) is oppositely disposed from a second side face (22) in a width direction, and a bottom is oppositely disposed from a top in a height direction. The sipe element has a projection (30) that extends from the first side face. A mold segment base (32) made of a material that is more flexible than material making up the sipe element (14) is present. The mold segment base receives the sipe element such that the bottom of the sipe element is located inside of the mold segment base and the top of the sipe element is located outside of the mold segment base. The mold segment base defines a cavity (34), and the projection (30) is located inside of the cavity (34). The mold segment (10) is used for forming a production mold segment (68) that ultimately molds a green tire into a cured tire (12).

FIELD OF THE INVENTION

The present invention relates generally to a flexible mold segment for the formation of tires. More particularly, the present application involves a flexible mold segment that features a sipe element with a projection for insertion into a counterpart cavity of the flexible mold segment.

BACKGROUND

The production of tires includes the step of placing an uncured tire within a mold at which time heat and pressure is applied to the uncured tire in order to change its state to a cured condition. During the curing process, the uncured tire is placed inside of a metal mold that surrounds the exterior of the uncured tire. An expandable rubber bladder is positioned inside of the uncured tire, when it is within the mold, and is expanded to apply pressure to the inside surface of the uncured tire. The pressure applied by the expandable bladder forces the uncured tire against the mold to cause the uncured tire to be under pressure forces. Heat is simultaneously applied, and the combination of heat and pressure applied for a particular time effects the curing process. The cured tire is then removed from the mold and transported downstream for subsequent processing.

The expandable bladder when inflated and applying force causes the crown portion of the tire to be forced against a garniture of the mold that includes a series of features that form grooves, sipes, and tread blocks of the tire to result in the formation of the tread design of the tire. The garniture can be made of two or more multiple sections that are arranged in a circle, and these production mold segments are used to form the architecture of the tread. In order to form sipes of the tread, a series of sipe sections are present in the production mold segment. Additional sipe elements may be included to form sipes that could be V-shaped, Y-shaped, or alternatively shaped and that can extend in the longitudinal direction, lateral direction, or both in the longitudinal and lateral directions.

In order to form the production mold segment, the casting process employs a gypsum/plaster cast segment that includes the sipe elements. In order to form the gypsum cast segment, a flexible cast segment is used and into this flexible cast segment the sipe elements that are eventually transferred to the production mold segments are inserted. The flexible cast segment may be known as a flexible mold segment or as simply a mold segment. The sipe elements may be made of steel or other metal while the flexible cast segment base is made of rubber or some other more flexible material. In order to form the flexible cast segment, a master/positive segment is formed that can have preliminary sipe forming elements in it the negative of which are transferred to the flexible cast segment. In the flexible cast segment, the sipe elements may need to be forced into the flexible base of the flexible cast segment and doing so can result in difficulty in precisely aligning the sipe elements with other features of the flexible base. Due to the flexibility of the flexible base, the positioning of the sipe elements may change during the subsequent stages of the development of the production mold.

In order to maintain the positioning of the sipe elements within the flexible mold, it is known to incorporate locking features between the sipe elements that cause one of the sipe elements to be constrained with respect to another touching sipe element. This connection between the two steel sipe elements occurs at either the ends of both of the sipe elements, or in other versions occurs between the end of one and a face of the second sipe element. Although the connection of multiple sipe elements fixes their position with respect to one another to some extent, this connection does not constrain the positioning of the sipe elements to the flexible base itself and they are still able to be moved out of position therewith. As such, there remains room for variation and improvement within the art.

DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS

A mold segment10is provided that has a sipe element14that includes first and second side faces20,22with a projection30on the first side face20. The mold segment10is a flexible mold segment10that is used in forming a production mold segment68that ultimately molds a green tire into a cured tire12. The mold segment10also includes a mold segment base32that is made of a material, such as polysulfide castable mold rubber, that is more flexible than the sipe element14. The mold segment base32includes a cavity34that is within the mold segment base32and is big enough to receive the projection30. The sipe element14is pushed into the softer material of the mold segment base32in a desired position and upon doing so the projection30is received within the cavity34. This receipt enhances the stability and positioning of the sipe element14within the mold segment base32to eventually result in a more known and accurate positioning of the sipe74,82formed by the sipe element14when the tire12is cured. The cavity34is sized and shaped in such a way that it provides some holding force to the projection30upon receipt of the projection30within the cavity34.

With reference toFIG.1, a tire12is illustrated in perspective view that has a central axis72that serves as the axis of rotation of the tire12. The central axis72extends through the center of the tire12and is aligned in the axial direction76. The radial direction78of the tire12extends outward from the central axis72and is perpendicular to the central axis72. The tire12also has a circumferential direction80that extends around the circumference of the tire12and circles the central axis72. The circumferential direction80may be located at any distance from the central axis72in the radial direction78of the tire12and need not be located only at the tread84or the outer most portion of the tire12in the radial direction78.

The tire12has tread84that features various tire architecture such as tread blocks, grooves, sipes, and ribs. Other tire12architecture of the tread84shown includes V-shaped sipes74that are located in two of the three sections formed by the shoulder edges of the tread84and two grooves90that extend completely around the tire12in the circumferential direction80. A circumferential sipe82extends completely around the tire12in the circumferential direction80and is immediately adjacent the circumferential groove90and spaced slightly therefrom. This spacing may be 1, 2, 3, 4 or from 5-10 millimeters in certain embodiments in the axial direction76and can be consistent along their entire lengths or may vary at different locations along the lengths of the circumferential sipe82and circumferential groove90in the circumferential direction80. Sipes74,82are defined as grooves of the tread84that have a width at the tread surface that is 2 millimeters or less. The grooves of the tread84may thus be grooves that have widths that are greater than 2 millimeters. The widths of the sipes74,82can be measured at the surface of the tread84when the tread84is new and not worn, as in some instances the teardrop sections of the sipes74,82, if they have them, may in fact be larger than 2 millimeters. The sipes74,82and grooves90can take on any shape and extend in any direction such as angled, curved, or zig-zag. The sipes74are V-shaped in that they have two legs arranged at an angle to one another, and an apex is at the point where the two legs intersect. A pair of sidewalls extend from the crown of the tire12on either side in the axial direction76towards the center in the radial direction78. Depending upon the tire12geometry, some features of the tread84, such as lateral sipes74and grooves, may extend into the sidewalls as well.

In order to cure the tire12, the uncured tire12is placed into a mold92having production mold segments68. In order to build the projection mold segments68, a number of initial and intermediate mold segments need to be first produced. First, the initial design for the tire12could be made by a designer in a computer program, and this design could be transferred to a master mold52via a CNC machining operation. The master mold52is shown inFIG.2and includes a master mold base54that is milled from a block of material and is a positive image of the tire12to be produced. As a milled component, the master mold base54is made out of a hard, non-flexible material but is not so hard that it cannot be cut and shaped in a milling process. In order to form smaller features in the tire12, such as the sipes74,82, preliminary sipes56are set into the master mold base54. The preliminary sipes56are made of metal and can be placed by hand into cavities of the master mold base54by a user. The preliminary sipes56are placed into the areas in which sipes74,82are eventually desired to be located at in the tire12. Due to the rigidity of the master mold base54, the locations the preliminary sipes56are inserted into are fixed and at known positions without a high degree of variation.

After completion of the master mold52, the next step in the production process is the formation of a flexible mold segment10, one example of which is shown with reference toFIG.3. Here, polysulfide castable mold rubber can be poured over the master mold52and allowed to harden. It is to be understood that this material is but one material and that others are possible in forming the flexible mold segment10. Silastene may be one material that makes up the flexible mold segment10. Once sufficiently hardened, the user may peel the polysulfide castable mold rubber off of the master mold52to reveal a negative of the tire12in the flexible mold segment10. The preliminary sipes56are not transferred into the flexible mold segment10but instead remain within the master mold52, but preliminary sipes56do form complimentary voids in the flexible mold segment10at locations where sipes74,82are desired. The flexible mold segment10has a mold segment base32that is made of the polysulfide castable mold rubber and shows the negative of the tread84. Sipe elements14are provided that are made of steel or aluminum or other material harder than that of the material making up the mold segment base32. The user will then take these various sipe elements14, one of which is shown inFIG.3, and push them into the softer material of the mold segment base32. The mold segment base32will have voids into which the sipe elements14are located, but the size of the sipe elements14can be somewhat larger than these voids so that the sipe elements14are forced into the softer material of the mold segment base32and held therein as the material will push back and act to retain the sipe elements14. However, this type of placement may result in movement of the sipe elements14away from their desired location, or subsequent steps in the mold formation process may cause these sipe elements14to move or change orientation to degrade quality of the desired tire14that is eventually molded.

The flexible mold segment10is used to make a gypsum plaster cast segment66as shown for example inFIG.4. Gypsum plaster may be poured onto the flexible mold segment10, or the flexible mold segment could otherwise come into contact with the plaster. Once the plaster sets and hardens, the gypsum plaster cast segment66forms a positive image of the tire12that is being produced. The user can then peel the flexible mold segment10off of the gypsum plaster cast segment66to reveal the mold segment as shown inFIG.4. The sipe elements14are embedded and held within the gypsum plaster cast segment66, and peeling of the mold segment base32causes the mold segment base32to become detached from the various sipe elements14thus causing the sipe elements14to be transferred from the flexible mold segment10to the gypsum plaster cast segment66. The gypsum plaster cast segment66has various features that are imparted into the production mold segment68such as grooves, ribs, and shoulder features. To form the production mold segment68, hot liquid aluminum is poured onto the gypsum plaster cast segment66which then hardens and takes on the features of the gypsum plaster cast segment66, and the exposed pieces such as the sipe elements14are embedded into the production mold segment68. The hot liquid aluminum thus forms a production mold segment base70into which the sipe elements14are mounted. The gypsum plaster is chipped or machined away in order to remove it from the production mold segment68while leaving the sipe elements14within the production mold segment68. In this regard, the sipe elements14are transferred from the gypsum plaster cast segment66to the production mold segment base70of the production mold segment68.

TheFIG.5shows a mold92for curing a tire12. A tire12that is made of uncured rubber is placed into the mold92and cured via heat and pressure applied by the mold92. The mold92can be configured in a variety of ways. In the embodiment illustrated, the mold92includes a garniture94that has a series of production mold segments68that engage the tire12to form the tread84of the tire12. The mold92also includes a top mold section86and a bottom mold section88that engage the sidewalls of the tire12and form the sidewall portions. In other arrangements, additional top and bottom mold sections86,88can be included and thus multiple other components may be present in the mold92for forming the tire12. The green/unmolded tire12can be placed inside of the garniture94and the top and bottom mold sections86,88may be moved into engagement with the garniture94. An inflatable bladder is placed through one of the sections86,88and inside of the tire12and is inflated in order to press the tire12against the tread producing elements of the production mold segments68, which for example may be the sipe elements14that form the sipes74and82, and against the insides of the top and bottom mold sections86,88. Heating elements can be located within the various production mold segments68or they may be otherwise heated in order to transfer heat into the tire12that is within in the mold92. In this manner, the mold92is capable of applying heat and pressure to the tire12that is within the mold92. Although described as all being moveable, it may be the case that some of the production mold segments68are not movable while others are in fact movable to open and close the mold92. The production mold segments68may be movable in that they move relative to the ground onto which the mold92rests.

The bladder can be inflated with air, steam, liquid, nitrogen, or any other fluid to cause it to expand to force the tire12against the tread and sidewall forming portions of the mold92. After sufficient heat and pressure are applied to the tire12for a sufficient amount of time, the bladder can be deflated and the top and/or bottom mold sections86,88can be moved away from the garniture94to allow the cured tire12to be removed for subsequent processing.

With reference toFIG.6, the garniture94of the mold92is made of a plurality of production mold segments68that extend 360 degrees about an axis. The production mold segments68may be in engagement with one another, or a small space could be present between the production mold segments68. In some arrangements, the production mold segments68can move in the radial direction towards the central axis to further add pressure to the tire12during curing. In other instances, the production mold segments68are stationary and do not move in the radial direction. The production mold segments68can be the same size as one another or may be different sizes from one another. Although 8 production mold segments68are shown, it is to be understood that the garniture94can include any number of production mold segments68in other arrangements. For example, from 9-12 production mold segments68can be included in the garniture94in other versions of the mold92. The production mold segments68thus engage the tire12during formation and include the various sipe elements14that are used to form sipes74,82of the tire12upon molding by the mold92.

The present invention relates primarily to the flexible mold segment10that is a stage of the production process in making the production mold92that actually molds the tire12. The flexible mold segment10therefore is not a production mold92, and the mold segment base32is not a production mold segment base70and thus does not engage the tire12at any point. As stated, the flexible mold segment10includes a series of sipe elements14that are eventually transferred to the production mold92and thus become part of the production mold92. One example of a sipe element14is shown with reference toFIGS.7and8which are a side view and a top view respectively. The sipe element14has a first end16and an oppositely disposed second end18that are spaced from one another in a length direction42of the sipe element14. The ends14,16may be terminal ends of the sipe element14such that these portions of the sipe element14are at the extreme two ends in the length direction42. The ends14,16are shown as being parallel to one another but need not be parallel in other arrangements. The length of the sipe element14in the length direction42is the longest extent of the sipe element14. The sipe element14has a bottom26and an oppositely disposed top28in a height direction44of the sipe element14. The height direction44is parallel to the length direction42, and the height of the sipe element14can be the distance from the bottom26to the top28, and the height of the sipe element14is less distance than the length of the sipe element14in the length direction42. The bottom26is the portion of the sipe element14that is inserted into the mold segment base32and covered by it while the top28is exposed. The bottom26is shown as having a pair of triangular shaped recesses that have lips that facilitate gripping the rubber of the mold segment base32when pushed therein. A width direction24of the sipe element14is perpendicular to both the length and height directions42,44, and the sipe element14is shorter in the width direction24than it is in either the length direction42or the height direction44. The sipe element14has a first side face20and an oppositely disposed second side face22, and the side faces20,22are separated from one another in the width direction24. The side faces20,22are planar faces as shown, but need not be planar in other embodiments as they may be angled, wavy, curved or variously shaped.

The sipe element14also includes a series of projections30that extend from the first side face20in the width direction24. The projections30may extend for a longer length in the width direction24than the distances between the side faces20,22in the width direction24. The projections30are all the same as one another with respect to their shape and size and are spaced the same amount from successive projections30. The projections30extend a longer distance in the length direction42than they extend in the height direction44. Although the projections30can be located anywhere along the height of the first side face20in the height direction44, they are located as some point along the bottom half of the first side face20in the height direction44so that they are closer to the bottom26than to the top28in the height direction44. The projections30may be made of the same material as the rest of the sipe element14and can be integrally formed with the rest of the sipe element14in some embodiments but not in others. The sipe element14may be formed through casting, additive manufacturing, or vie any other process. Additive manufacturing allows the projection30to be formed on the first side face20of the sipe element14. The additive manufacturing process may have limitations regarding the amount of undercutting available in the projection30and sipe element14formation. A laser trimming process could also be employed to form the sipe element14with the projection30.

FIG.9is a perspective view of a mold segment base32of the flexible mold segment10as previously discussed that can be made out of polysulfide castable mold rubber or silastene in accordance with various exemplary embodiments. The mold segment base32has an upper surface38and an oppositely disposed lower surface40in a mold segment base height direction36. The mold segment base32is a negative image of the tire12and has features of the upper surface38that are negatives of elements of the tire12. For example, a bead60is present on the upper surface38and will be used in subsequent steps to form a groove90of the tread84. The mold segment base32includes a series of cavities34that are located within the mold segment base32so that they are spaced from both the upper surface38and the lower surface40in the mold segment base height direction36. The cavities34have a shape that is complimentary to that of the projections30and in some instances may have the exact same shape as that of the projections30. The cavities34can have a size that is the same as that of the projections30. In other embodiments, the cavities34are sized to be smaller or larger than the projections30. The cavities34are spaced from one another the same amount as the projections30so that they can receive respective projections30therein. A recess33is present and is a void in the mold segment base32. The recess33can be open at the upper surface38and may be in communication with all of the cavities34that receive the projections30of a particular sipe element14. The recess33may be present in order to aid in the formation of the cavities34within the mold segment base32. The recess33may also be present in order to aid the user in determining where the sipe element14should be inserted within the mold segment base32. It is to be understood that in other embodiments the recess33need not be present, and the cavities34can be hidden from view upon the user initially receiving the mold segment base32.

To assemble the flexible mold segment10, the user will take the sipe element14and push it into the mold segment base32, and this assembly is shown with reference toFIG.3andFIG.10which is a cross-sectional view taken along line10-10ofFIG.3. The user can insert the sipe element14into the recess33so the bottom26is pushed inside of the mold segment base32. The depth of the recess33in the mold segment base height direction36may be shorter than what is desired of the sipe element14to be inserted into the flexible mold segment10. In these instances, the sipe element14can be forced into the softer material of the mold segment base32and the bottom26pushed lower in the mold segment base height direction36than the lowest point of the recess33. The gripping forces of the mold segment base32may retain the sipe element14therein. The flexible mold segment10includes the projections30that upon insertion of the sipe element14are located within the cavities34. Some of the cavities34as shown are within the bead60of the mold segment base32. This interaction functions to further retain the sipe element14within the mold segment base32and to maintain the position of the sipe element14in the desired spot without shifting during formation process. The material of the mold segment base32may be immediately above and below the projection30in the mold segment base height direction36and if the top and bottom of the projection30is engaged by this material it may function to squeeze the projection30and hold it and the rest of the sipe element14in place. The depth of the cavity in the width direction24could be the same as the extension of the projection30in the width direction24or it may be longer. Even if the cavity34is greater in size than the projection30, placement therein will still function to hold the sipe element14in place as movement of the projection30will cause it to hit the material of the mold segment base32defining the cavity34and stop further movement.

Placement of the sipe element14into the mold segment base32may cause the recess33to open up when the projection30is within the recess33and is larger than the recess33. The flexibility of the material making up the mold segment base32allows for this deformation. Once the projection30is aligned with the cavity34the material will spring back into place to relieve this deformation of the recess33. Although shown as having the same shape as the projection30, the cavity34may have a different shape from the projection30in other embodiments. The cavity34is rectangular as shown but can be variously shaped in other embodiments. Placement of the projection30within the cavity34causes the sipe element14to be interlocked with the mold segment base32. It is to be understood that the projections30and the sipe elements14can be variously shaped in accordance with different exemplary embodiments and need not have rectangular and planar shapes in other versions of the flexible mold segment10.

FIGS.11and12show an alternate embodiment of the sipe element14in that the projections30are different from theFIGS.7and8embodiment. Here, the projections30have a longer length in the height direction44than they do in the length direction42. The extension of the projections30in the width direction24are longer than the length between the first and second side faces20,22in the width direction24. Although all of the projections30are of the same size and shape, this need not be the case in other embodiments in which different ones of the projections30have different sizes and shapes than other ones of the projections30of the sipe element14. Further, although shown as appearing on only the first side face20and not the second side face22, in other embodiments one or more of the projections30can be present on the first side20while one or more of the projections30are on the second side face22. As such, various configurations of the projections30on the sipe element14exist. The cavities34are configured in an appropriate manner in the mold segment base32based upon the establishment of the projections30on the sipe element14.

Another exemplary embodiment of the sipe element14and mold segment base32are shown inFIGS.13and14respectively. InFIG.13, the sipe element14is bent along the length direction42and thus has a first side face20that has both curved and planar portions. The projections30are again all located along the first side face20and none are on the second side face22. The projections30have a narrow portion that engages and extends from the first side face20in the width direction24. At the end of the narrow portion a semicircle shaped section is located which represents the end of the projection30and is the portion of the projection30farthest from the first side face20in the width direction24. The mold segment base32has cavities34that are shaped so as to be complimentary to the shape of the projections30and are oriented within the mold segment baes32to match the positioning of the projections30when the projections30are inserted therein. The shape narrow portion and semicircular portion function to lock the projections30into the cavities34are material will be present between the semicircular portion and the first side face20, in addition to being present both above and below in the height direction44. To insert the projections30into the cavities34sufficient force is applied to push the semicircular portions through the narrow portions of the cavities34. The recess33is present to aid in user positioning of the sipe element14, and the recess33is in communication with all of the cavities34.

FIGS.15and16illustrate another exemplary embodiment of the flexible mold segment10in which the projections30include an additional locking feature to render them even further attached to the flexible mold segment base32.FIG.15shows the sipe element14detached from the mold segment base32but about to be inserted into the mold segment base32, whileFIG.16is a top, cross-sectional view of the mold segment10with the sipe element14in fact inserted into the mold segment base32so that the projections30are disposed within the cavities34. The projection30extends from the first side face20in the width direction24and is shaped so as to define a lip46on one end in the longitudinal direction. An empty space48is in turn defined from the lip46to the first side face20in the width direction24. In a complimentary configuration, the cavity34has a lip receiving portion50that is shaped and sized to receive the lip46. The lip receiving portion50in turn is formed by a notch shaped protrusion of the material making up the mold segment base32. The cavity34is also shaped and sized to receive the remaining portions of the projection30, and when the projection30is inserted into the cavity34the lip46is disposed within the lip receiving portion50. The material making up the mold segment base32may flex in order to allow the lip46to be inserted, and in some instances the sipe element14can slide in the length direction42so the lips46can be inserted into the lip receiving portions50without the need to deform or significantly deform the material making up the mold segment base32. When inserted, the lip46has material of the mold segment base32between it and the first side face20which functions to further lock the projection30within the cavity34and in turn further hold the sipe element14in position within the mold segment base32.

FIGS.17and18show another exemplary embodiment of the flexible mold segment10in which the sipe element14is disposed proximate to a bead60of the mold segment base32. The bead60is provided in order to form a groove90of the tread84, and this groove90may be a circumferential groove that extend completely 360 degrees about the tire12in the circumferential direction80, or a groove that is not a circumferential groove and/or a groove that does not completely extend 369 degrees about the tire12. The sipe element14is placed into the mold segment base32in a position to be parallel to the bead60. In this regard, the bead60has a bead side wall64that extends in the length direction42over at least a portion of its length. The sipe element14engages the bead side wall64, and in some embodiments the cavity34may extend into the side wall64and the projection30could in turn go into the side wall64via this cavity34. In other arrangements, the cavity34is located lower than the side wall64in the mold segment base height direction36and the projection30is likewise lower than the side wall in this direction36. The front side face20engages the side wall64and is also free from contact with the side wall64along some of its length and height. The sipe element14could be bent in the width direction24at its top area to effect this separation, or the material making up the mold segment base32and the side wall64may extend away from the sipe element14at this location to cause space to be present. The sipe element14may be spaced from the bead60at its top a distance of 0.5 millimeters, 1.0 millimeters, 1.5 millimeters, or from 0.01 to 2 millimeters in accordance with different exemplary embodiments to form a sipe82that is parallel and adjacent to the groove90.

The flexible mold segment10arrangement set up inFIGS.17and18is used to result in a production mold92capable of forming the tread84shown inFIG.19. It is to be understood thatFIG.19only shows a portion of the tread84, and includes a circumferential groove90formed by the bead60ofFIGS.17and18. The circumferential sipe82is located adjacent the circumferential groove90and is formed by the sipe element14. The inclusion of the projection30and cavity34arrangement allows for the sipe element14to be stabilized within the mold segment base32so that the circumferential sipe82can in fact be located precisely adjacent the circumferential groove90and parallel thereto. The sipe82has a width that can be two millimeters or less. The circumferential sipe82can be parallel to the circumferential groove90along the entire circumferential length of the circumferential groove90or may be parallel only along a portion of the circumferential length of the circumferential groove90.

A portion of a master mold52in accordance with one exemplary embodiment is shown inFIG.20. The master mold52again includes preliminary sipes56put into a master mold base54as previously discussed. However, the preliminary sipes56have preliminary sipe projections58that extend from their face. The preliminary sipe projections58are used to form the cavities34of the mold segment base32. In this regard, the material making up the flexible mold segment10, such as polysulfide castable mold rubber or silastene, is poured over the preliminary sipes56and the master mold base54. The presence of the preliminary sipe projections58create the cavities34in the mold segment base32when the hardened mold segment base32is peeled off of the master mold52. It is to be understood that this method is but one way of making the cavities34, and others are possible in accordance with other exemplary embodiments. The recesses33need not be present in other arrangements as well. The sipe element14is made of a harder material than the material making up the mold segment base32. The master mold52can be formed via a number of different methods, and in some instances the preliminary sipes56are separate pieces that are inserted into the master mold base54. In other instances, the preliminary sipes56and the master mold base54are formed by stereolithography such that the master mold base54, preliminary sipe56with the preliminary sipe projections58are all formed as a single part without being assembled together.