Abstract:
The present invention relates to an apparatus for providing the upper and lower portions of two-part tire molds with an expansible opening to provide clearance for the insertion of green tires, in particular large green tires of the sort used on industrial or off-road vehicles. The tire mold according to the present invention provides a segmented tire mold wherein a plurality of circumferentially arranged segments that contribute to the shaping of the circumferential tread portion of a tire being molded are able to move in such a way as to include a radial and axial component of motion that provides a larger diameter for each of the two mold portions during the green tire loading operation. Thus the internal circumferential region of the top portion and of the bottom portion is able to expand in diametrical dimension when the two part tire mold is open.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates in general to tire molds, and more particularly to tire molds for large heavy duty tires. 
       BACKGROUND OF THE INVENTION 
       [0002]    The manufacturing of pneumatic tires for motor vehicles of nearly all sizes entails the steps of creating the carcass and attaching thereto the tread and sidewalls, which are made of uncured rubber. The combination of carcass, tread and sidewalls, prior to curing of the rubber, is called a ‘green tire.’ The final step in the manufacture of a tire is the insertion of the green tire into a tire mold, wherein the tire is heated to a sufficiently high temperature to vulcanize the tire. The tire is then removed from the mold and the manufacturing process is complete. 
         [0003]    Whereas the manufacturing of tires for automobiles, even large automobiles such as sport utility vehicles, is a straightforward process involving relatively light-weight green tires, the manufacture of large tires for industrial or large off-road type vehicles of the sort used in earth moving and construction work entails the handling of very large green tires weighing hundreds of pounds. The loading of such massive tires, in the green-tire stage of production, into the standard two-part tire molds having an upper portion and a lower portion can result in damage to the green tires during the loading process, because the diametrical and circumferential dimensions of the mold are so close to each green tire being loaded into the mold as to result in interference. Thus it is desired to have an improved tire mold which allows for ease of loading and unloading of the green tire into and out of the tire mold. 
     
    
     
       BRIEF DESCRIPTIONS OF THE FIGURES 
         [0004]    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 FIGURES, wherein: 
           [0005]      FIG. 1  is a cross-sectional side view of a tire mold of the present invention shown in the closed position; 
           [0006]      FIG. 2  is a cross-sectional side view of the tire mold of  FIG. 1  shown in the open position; 
           [0007]      FIGS. 3-6  are cross-sectional side views of the tire mold of  FIG. 1 , showing the sequence of a tire being loaded into the tire mold; and 
           [0008]      FIG. 7  is a cross-sectional side view of the tire mold of  FIG. 1  shown in the closed position. 
           [0009]      FIG. 8  is a rear view of a mold segment; 
           [0010]      FIG. 9  is a side view of a lower actuating ring; 
           [0011]      FIG. 10A  is an end view of an annular lifting ring; and 
           [0012]      FIG. 10B  is a side view of the annular lifting ring. 
           [0013]      FIG. 11A  is a side view of a bottom portion of a tread segment shown with an optional guide fin. 
           [0014]      FIG. 11B  is a front view of a bottom portion of a segment and an optional guide fin. 
       
    
    
     DEFINITIONS 
       [0015]    “Axial” refers to the direction that is parallel to the primary axis of a tire or a tire mold. 
         [0016]    “Major Axis” refers to the major cylindrical axis of a circular cylinder. 
         [0017]    “Radial” refers to the direction that is normal to the primary axis of a tire or to a tire mold. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]      FIG. 1  illustrates a cross-sectional side view of an improved tire mold  10  of the present invention shown in the closed position, while  FIG. 2  illustrates the mold in the open position. The mold as shown has an upper portion  11  which includes a sidewall annular ring  18  having a central opening  14 . The sidewall annular ring  18  may be further divided into two or more sidewall components  18   a ,  18   b  as shown, for ease of manufacturing. The sidewall components  18   a ,  18   b  each include an inner surface  17   a ,  17   b  for molding the sidewall of a tire. The upper mold portion  11  further includes an optional annular shoulder ring  20 . The optional shoulder ring  20  is located between the sidewall components  18   a ,  18   b  and an annular actuating ring  24 . The shoulder ring has an inner molding surface  21  for molding the shoulder/tread area of the tire. The annular actuating ring  24  comprises an inner frustroconical surface  25  aligned for engagement with an outer frustroconical surface  31  of the tread segments, and functions to align the tread segments during closing of the mold. 
         [0019]    Mounted on the exterior surface of the annular actuating ring are two or more alignment cylinders  26  positioned for receiving an alignment pin  27  mounted on the outer circumference of the lower mold portion. The alignment pins  27  together with the alignment cylinders ensure proper alignment of the upper portion of the mold with the lower portion of the mold. 
         [0020]    Referring again to  FIG. 1 , a lower portion  12  of the mold  10  includes a lower sidewall ring  34  having a central opening  33 . The lower sidewall ring may be further subdivided into two or more components  34   a ,  34   b . An optional shoulder ring  36  is positioned radially outward of the sidewall ring. The optional shoulder ring has a tread forming surface  35  for forming the shoulder section of the tire and an axially inward surface  37  in engagement with an annular lifting ring  38 . 
         [0021]    The annular lifting ring  38  is positioned between a bottom mold ring  52  and the lower sidewall ring components  34   a ,  34   b . The annular lifting ring  38  is fixedly connected to the sidewall ring  34  and the optional shoulder ring  36 . As shown in  FIGS. 10A and 10B , the annular lifting ring has a tabular end  2  that is received within a slot  3  of the bottom mold ring  52 , wherein the tabular end of the annular lifting ring is in slidable engagement with the slot  3  of the bottom mold ring  52 . The annular lifting ring further comprises an axially outer surface  39  for engagement with the tread segments. The axially outer surface  39  may further include an optional wear plate. 
         [0022]    The lower portion of the mold further comprises a plurality of tread segments  32 , which are arranged circumferentially about the green tire to be molded. Each tread segment  32  has a tread molding surface  33  having for example, lands and grooves for molding the tread of a green tire. The tread segments join together to form an annular ring to encircle and mold a tread of a green tire. Preferably, each tread segment is formed of a one piece unit and is not split into two or more pieces. Thus each tread segment has a tread molding surface  33  which extends substantially unbroken across the outer tread surface of the green tire, from one shoulder to the opposite shoulder. As shown in  FIG. 8 , each tread segment further has an upper frustroconical surface  31  opposite the tread molding surface that is aligned for engagement with the conical surface  25  of the annular actuating ring  24 . Each tread segment  32  further comprises a lower frustroconical surface  28  that is aligned for engagement with a frustroconical surface  53  of the bottom mold ring  52 . The tread segment lower conical surface  28  further includes a groove  44  for receiving a guide member  45  therein. As shown in  FIG. 9 , the guide member  45  is positioned on the inner frustroconical surface  53  of the bottom mold ring  52  and is slidable within the tread segment groove  44 . At other circumferential locations, one or more guide pins  43  are positioned on the inner frustroconical surface  53  of the bottom mold ring  52 . Each guide pin  43  is received in a groove  72  located on the lower frustroconical surface  53  of the bottom mold ring  52  as shown in  FIG. 8 . The guide pins  43  act as a stop to prevent the segments from moving too far axially outward. The guide pins  43  may also have a tight tolerance with respect to tread segment groove  72  to ensure precise movement or translation of the segments during opening and closing of the molds. Each tread segment further has an axially inner surface  47  that is slidable along the outer surface  39  of the bottom lifting ring  38 . As shown in  FIGS. 11A and 11B , the tread segment axially inner surface  47  may further comprise optional guide fins  80  that are slidably received in slots  82  of the lower lifting ring  38 . 
         [0023]    Each segment is actuatable in both a radial and an axial direction. During the opening of the mold, each segment is actuated axially and radially by a lifting plate  50 . The lower mold components including the lower sidewall ring  34   a ,  34   b  and the annular lifting ring  38  are positioned upon the lifting plate  50 . As the lifting plate lifts the lifting ring  38  and the sidewall components  34 , the annular lifting ring  38  slides in an axial direction within the outer mold ring  52  and lifts the segments. As the segments are lifted, the segment radially inner surface  47  slides radially outward along the surface  39  of the lifting ring. As the lifting plate  50  lifts the tread segments, the segment lower frustroconical surface  28  slides into engagement with the cammed or frustroconical surface  53  of the bottom mold ring  52 . 
         [0024]    As the segments are lifted, the guide members of the mold bottom half slide within the groove  44  of the segment outer surface to ensure the segments slide axially and radially outwards. The optional guide fins  80  may be utilized to guide the segments as they are slid axially, and may further assist the movement of the tread segments during closing of the mold. 
         [0025]      FIGS. 3-7  illustrate the loading of a green tire into the mold. As shown in  FIG. 2 , the upper portion  11  of the mold is removed. The lifting plate  50  is raised to its maximum vertical elevation relative to the lower actuating ring  52  as shown in  FIG. 3 . Also at maximum vertical elevation are those parts of the lower mold portion  12  that are lifted by the lower actuating ring  52 , namely the sidewall ring  34 , the shoulder ring  36 , the annular lifting ring  38  and the segments  32 . At the maximum vertical elevation of the lifting plate, the segments are positioned in an open position wherein they are disposed at their maximal radial displacement from one another. This position provides clearance for the insertion of a green tire. 
         [0026]    Once the green tire had been loaded into the lower mold portion  12  as shown in  FIG. 4 , the lifting plate lowers the lower mold portion  12  to a point where the segments  32  almost make contact with the green tire as shown in  FIGS. 4-6 . Next the upper mold portion  11  is lowered until the camming surface of the upper mold ring contacts the upper segment outer wall  31  ( FIG. 6 ). Then the upper and lower mold portions are lowered by the lifting plate, as the upper mold ring guides the segment into position ( FIG. 7 ). When the mold  30  is fully closed and the top segments  42  and the bottom segments  43  are in their radially inward most locations (with respect to centerline CL), the upper dowels engage and lock with the lower dowels. 
         [0027]    The mold opening can now be described in more detail. The upper part  11  of the mold  10  is hoisted or otherwise lifted vertically off of the tire (not shown) and the lower portion  12  of the mold. Upon lifting of the upper portion as shown in  FIG. 2 , the tread segments  32  slide along the mold lower half to a lower and diametrically larger position within the conical section upper actuating ring  44 , causing said segments to move radially apart from one another with respect to the main axis CL of the upper portion  32  of the tire mold  30 . 
         [0028]    Upon removal of the upper portion of the tire mold  30 , actuation of the lifting place  50  and the parts lifted by the lifting plate causes the tire to rise upward and the movable segments to move apart from one another and from the tire, thereby providing clearance for easy removal of the tire. 
         [0029]    Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, certain equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more features of the other embodiments as may be desired and advantageous for any given or particular application.