Patent Publication Number: US-2006000554-A1

Title: Cover plate for tire building drum

Description:
FIELD OF THE INVENTION  
      The present invention relates in general to tire building drums, and more specifically to tire building drums having cover plates.  
     BACKGROUND OF THE INVENTION  
      All terrain vehicle tires, aircraft tires and other tires have relatively longer sidewalls as compared to passenger tires. The longer sidewalls result in a longer chord length (i.e., the bead to bead distance) as compared to passenger tires. A longer chord length results in longer cover plates, which are mounted on the outer surface of a first stage tire building drum. Because the cover plates are longer, flexing or bending about their longitudinal axis may occur during the stitching operation. The stitching operation presses a gear-like device to the tire component layers successively mounted on the tire building drum. The function of the stitching operation is to eliminate trapped air from between the tire component layers of the green tire, and to promote adhesion of the layers. If excessive flexing of the cover plates occur, the stitching operation may not be effective in removing the trapped air between the layers. This may ultimately result in a defective tire.  
      Thus an improved cover plate and tire building drum which eliminates the problem of trapped air is desired.  
     SUMMARY OF THE INVENTION  
      The invention provides in a first aspect a tire building drum comprising a plurality of segments in a cylindrical array, a cover plate mounted over said segments, wherein said cover plate has one or more ribs aligned with the longitudinal axis of the cover plate.  
      The invention provides in another aspect a cover plate for use with a tire building drum, the cover plate comprising an upper surface and one or more longitudinal ribs connected to said upper surface.  
    
    
     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 perspective view of a first stage tire building drum;  
       FIG. 2  is a cutaway view in the direction  2 - 2  of  FIG. 1 ;  
       FIG. 2   a  is a cutaway view in the direction  2 - 2  of  FIG. 1 , shown in the radially expanded condition;  
       FIG. 3  is a perspective view of a coverplate of the present invention;  
       FIG. 4  is a top view of the coverplate of the present invention shown in  FIG. 3 ;  
       FIG. 5  is a side view of the coverplate of the present invention shown in  FIG. 3 ;  
       FIG. 6  is an end view of the coverplate shown in  FIG. 3 ;  
       FIG. 7  is a perspective view of a second embodiment of a coverplate of the present invention;  
       FIG. 8  is an exploded, perspective view of the cover plate of  FIG. 7  and respective mounting plate;  
       FIG. 9  is a top view of the coverplate of  FIG. 8 ;  
       FIG. 10  is a cutaway view in the direction  10 - 10  of  FIG. 9 ;  
       FIG. 11  is a cutaway view in the direction  11 - 11  of  FIG. 10 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Turning to the drawings and in particular  FIGS. 1-2 , there is illustrated a first stage tire building drum  10  embodying improvements especially suited for building tires having a long chord length. The tire building drum  10  comprises a generally cylindrical shape and is rotatable about a longitudinal axis  14 . The tire drum  10  has a center portion  11  for receiving successive layers of tire building components such as an inner liner, side walls, chafers, breakers, ply, and beads. The center portion  11  is also adapted to expand radially outward, in order to tighten up the tire building components over the wire beads and to turn up the ends over the beads. The center portion comprises a plurality of segments or fingers  12 , which are radially actuatable. The segments  12  are arranged in a first and second cylindrical array about a drum axis  14  on each end  1  la,b of the drum. A plurality of coverplates  30  are positioned over the segments  12 .  
      Each segment  12  has an upper mounting surface  20  for receiving a cover plate  30 . Each segment  12  is radially actuatable via an air actuated piston (not shown) for moving the cover plates  30  radially outward. Cover plates  30  are mounted upon an upper mounting surface of a guide piston  32 . The guide piston  32  functions to secure the coverplates to the drum and to allow the cover plates to move radially outward with the segments  12 .  FIG. 2A  illustrates a cross sectional view of the tire building drum  10  in the radially expanded position wherein all of the segments are in the expanded position.  FIG. 2  illustrates the tire building drum in the normal or retracted position.  
       FIGS. 3-6  illustrate more details of the cover plate of a first embodiment of the present invention. The cover plate  30  is located below flexible center sleeve  40 . The center sleeve  40  is typically comprised of an elastomer or rubber and functions to retract the segments, like a rubber band, to the collapsed position as shown in  FIG. 2 . The cover plate  30  as shown in  FIG. 3  is generally rectangular in shape with its longitudinal axis A-A aligned with the longitudinal axis  14  of the tire building drum. The cover plate further includes a curved outer surface  42  and one or more ribs  44  that are preferably aligned with the longitudinal axis A-A of the cover plate. Preferably, there are two ribs  44  located on opposite ends of the cover plate as shown in the figures. In the preferred embodiment, the ribs  44  extend down as sidewalls from the cover plate, and are oriented at about a ninety degree angle with respect to the outer surface  42 . It is desired that the ribs  44  do not extend along the entire length of the cover plate in order to avoid interference with the segments  12 .  
      In a second embodiment of the cover plate (not shown), the cover plate comprises a single rib aligned or parallel with the longitudinal axis A-A of the cover plate. Preferably, the single rib is located on the longitudinal axis. However, the rib may also be located on one end of the cover plate.  
      Ribs  44  function to increase the structural rigidity of the cover plate in order to prevent flexing of the cover plates during the stitching operation.  FIG. 2   a  illustrates a stitcher in contact with the cover plates  30  of the tire building drum.  
      A third embodiment of the cover plate  50  is shown in  FIGS. 7-11 . The cover plate has one or more sidewalls extending down from the upper surface, wherein the sidewalls form longitudinal ribs  44 . The cover plate  50  further comprises longitudinal slots  52  which together with the lots  54  of backing plate  56 , form a manifold for vacuum. When the vacuum system (not shown) is turned on, the cover plates with slots hold the tire components onto the drum via suction.  
      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.