Patent Publication Number: US-2003234081-A1

Title: Assembly drum for manufacturing tires

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
     [0001] This is a continuation of international application PCT/EP01/15188 filed Dec. 21, 2001, which was published in French on Jul. 11, 2002 as international publication WO 02/053355 and which claims priority of French application 00/17346 filed Dec. 29, 2000. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] 1. The Field of Invention  
       [0003] The present invention concerns an assembly drum for manufacturing tires. The invention concerns more particularly the manufacture of tires such as those used on aircraft or certain heavy vehicles, which tires comprise a carcass reinforcement having several reinforcement plies normally referred to as carcass plies and several reinforcement bead wires in each of the tire beads, one of the carcass reinforcements being wound around each bead wire forming an upturn. However, it will be clear from the following that the invention can also apply to the manufacture of tires having only one reinforcement bead wire or having no reinforcement bead wire.  
       [0004] 2. The Related Art  
       [0005] One of the difficulties in manufacturing such tires having many bead wires lies in the successive placing of carcass plies and bead wires on an assembly drum while producing the many upturns. To this end, use is generally made of assembly drums having shoulders on which the bead wire or wires are placed during assembly by a lateral approach to the shoulders, the difficulty lying in keeping the products in contact with these shoulders.  
       [0006] It should be noted that such drums can directly use bead wires or semi-finished products manufactured separately, which products may consist of the bead wire surmounted radially by a profiled section made of rubber mix. Hereinafter, the term bead wire complex will be used for a bead wire alone or a bead wire surmounted by a profiled section made of rubber mix, and possibly also including a product for coating the bead wire such as another profiled section made of rubber mix or a rubber ply comprising cables.  
       [0007] Some solutions are based on the use, in combination with the drum, of a device for holding the products to be assembled on the drum. Thus, U.S. Pat. No. 2,605,198 describes a non-expansible assembly drum with shoulders which has such a device. During assembly, a first previously stretched carcass ply is placed on the drum, its peripheral ends simply being folded down towards the inside of the drum by means of a rolling device.  
       [0008] The bead-wire complexes are fed by devices which can be moved axially with respect to the drum in order to be placed in contact with the carcass ply respectively on each shoulder and held in place by means of this same device. This holding in position of the bead-wire complexes is essential to ensure contact of the peripheral ends of the carcass ply with the shoulders. The operation is identical for feeding each bead-wire complex, which makes the step of turning over each carcass ply on the corresponding bead-wire complex particularly tricky. This is because it is then necessary to maintain the axial position of the bead-wire complex, in addition to its radial position, in order to ensure abutment on the shoulders of all of the plies and bead-wire complexes already in place, while effecting the new turning over precisely.  
       [0009] In order to simplify and make more precise the steps of turning over the carcass ply around the bead wire; other solutions use a drum on which the shoulders consist of pieces that are attached with respect to the drum and that are capable of being removed easily. This is because in this case the peripheral ends of the first carcass ply are glued onto the shoulders of the drum, which settles the problem of the axial holding of the products against the shoulders. It is then the operation of removing the tire which becomes a problem, and it is necessary, for each raw tire assembled, to remove the shoulders from the drum. It is clear that this process can only be manual.  
       SUMMARY OF THE INVENTION  
       [0010] The present invention is aimed at mitigating all the aforementioned drawbacks of the prior art.  
       [0011] According to the invention, an assembly drum for tire manufacture includes a body mounted on a central shaft and having a generally cylindrical surface for receiving the products to be assembled as well as shoulders, the shoulders being capable of moving axially and radially between a retracted position of the drum, in which the generally cylindrical reception surface has a minimum diameter and axial length, and a working position of the drum, in which the diameter and the axial length of the reception surface are very much greater than those in the retracted position, the shoulders respectively carrying means for holding the products making up the tire in contact with the shoulders.  
       [0012] This provision makes it possible to produce a drum without any additional device, in which the retraction of the drum in order to take off the assembled tire does not necessitate dismantling, the holding means also making it possible to hold the products making up the tire in contact with the shoulders during assembly. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0013] Other characteristics and advantages of the invention will emerge from the following description of an example embodiment of an assembly drum and its method of use in accordance with the invention, with reference to the accompanying drawing in which:  
     [0014]FIGS. 1A and 1B are axial half-sections of an embodiment of the drum according to the invention in the working position of the drum and in the retracted position of the drum, respectively; and  
     [0015]FIGS. 2A and 2B are radial half-sections of the drum according to the invention along the line II-II shown in FIGS. 1A and 1B, respectively.  
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
     [0016] According to FIGS. 1A and 1B, the drum  1  has a body  2  having a generally cylindrical surface  3  for receiving products to be assembled and axiable-spaced shoulders  4  and  5 . The body  2  is mounted on a central screw shaft  6  by a means of a barrel  7 .  
     [0017] The drum  1  has two different radial positions:  
     [0018] a retracted position (corresponding to the removal of a tire), shown in FIGS. 1A and 2A, in which the diameter of the reception surface  3  is at a minimum, d, and in which the shoulders  4  and  5  are axially positioned close to each other; and  
     [0019] a working position or expanded position, shown in FIGS. 1B and 2B, in which the assembly of the products making up the tire is effected, in which the reception surface  3  has a very much greater diameter D and in which the shoulders  4  and  5  are spaced much further away from each other axially.  
     [0020] This is because the shoulders  4  and  5  consist respectively of lateral elements  41  and  51  juxtaposed in the retracted position of the drum  1  and distributed regularly over the entire surface of the drum. Each element  41 ,  51  has a substantially trapezoidal shape seen in axial section, one of the bases  411 ,  511  of the trapezium partially constituting the reception surface  3 , while the other base  412 ,  512  affords the connection and articulation of the elements  41 ,  51  with respect to the barrel  7 , as will be seen in more detail below. The surfaces  414 ,  514  of the elements  41 ,  51  define the shoulders  4 ,  5 , respectively.  
     [0021] The reception surface  3  thus comprises the surfaces  411  and  511  and the surface of tiles  8  which extend circumferentially between the surfaces  411  and  511 , with their axial ends  81  and  82  partially covering the surfaces  411 ,  511 . Each tile  8  is carried by an internal support  83  fixed to it, which support  83  itself has an axially extending rod  9  passing through it. Each end  91 ,  92  of the rod  9  slides in a corresponding bore  43 ,  53  carried by each facing lateral element  41 ,  51 , so that the ends  91  and  92  of the rods  9  are always engaged in the bores  43  and  53  whatever the position of the drum  1 .  
     [0022] The number of tiles  8  corresponds to the number of lateral elements  41 ,  45 . The tiles  8  greatly overlap each other circumferentially in the retracted position of the drum  1  and circumferentially overlap each other slightly in the expanded position of the drum. It is clear that the tiles  8  are integral with the radial movements of the lateral elements  41 ,  51 .  
     [0023] Some lateral elements  41 ,  51  carry vacuum valves  15 ,  16  opening out through the surfaces  414 ,  514  in order, when they are actuated, to hold the products placed on the shoulders  4 ,  5 . It is not necessary to position such a valve in each element, it is enough to distribute them regularly, for example every three or four lateral elements. The pipes (not shown) for operating the vacuum, connected to these valves, pass inside the drum. This provision avoids the bonding or fitting of a mechanical device for holding the products in position on the drum and, in combination with the drum retraction which will be detailed later, affords easy removal of a tire once assembled on the drum.  
     [0024] Each lateral element  41 ,  51  is covered with a first sleeve  17 . A second sleeve  18  covers the entire reception surface  3 . See, FIG. 1B.  
     [0025] The lateral elements  41  forming the shoulder  4  and their articulation and the lateral elements  51  forming the shoulder  5  with their articulation are identical and symmetrical with respect to the radial plane passing through the center of the drum  1 . Therefore, only the connection and articulation of one lateral element  41  with respect to the barrel  7  will be described in detail, it being understood that this description is applicable to the other elements  41 ,  51  as well.  
     [0026] On the base  412  of each lateral element  41  there is pivotally mounted one end  101  of a rocker arm  10  on the path formed by a groove  413  in the element  412  in the form of an arc of a circle, so that the pivoting of the end  101  of the rocker arm causes an axial and radial movement of the element  41 , which thus keeps the same orientation.  
     [0027] The other end  102  of each rocker arm  10  is articulated on the external peripheral edge of a ring  111  fixed to a support  11  mounted rigidly on the barrel  7 . This annular support  11  is in fact fixed to the barrel  7  by a nut and screw system which can allow its axial adjustment according to the size of the tire to be assembled.  
     [0028] The support  11  has, in addition to the annular part  111 , a cylindrical part  112  situated axially inwardly of the drum  1  with respect to the ring  111 . A slide  12  is mounted on the part  112  for axial translation, which part  112  carries a stop  113  limiting the movement of the slide  12  towards the inside of the drum  1 .  
     [0029] The slide  12  is actuated by means of a transmission finger  131  extending in the radial direction and located in a housing carried by the slide  12  (FIG. 1B). The finger  131  is mounted on a ballscrew system  13 , the casing  132  of which is carried by the central shaft  6 . The shaft  6  is motorized by two drives independently effecting the movement of the casing  132  in order to control the axial movement of the slide  12  or to rotate the whole of the drum  1  about its axis. The slide  12  is thus able to move between a position in which one of its surfaces  121  is in contact with the ring  111  (FIG. 1B) and a position in which the surface  121  is axially spaced apart from the ring  111  (FIG. 1A). It is clear that other means of actuating the slide  12  could be envisaged, such as the use of a ram.  
     [0030] The peripheral edge of the slide  12  disposed at the radially outermost end of the surface  121  with respect to the center of the drum constitutes a cam  123  for actuating each rocker arm  10 . The cam  123  cooperates with a roller  14  carried by an elbow  103  formed on each rocker arm  10 . The peripheral edge of the slide terminates radially towards the outside in a cylindrical “upper” stop surface  124  for each rocker arm  10 . The profile of the cam  10  is produced according to the required speed of lifting of the drum towards its working position.  
     [0031] The slide  12  also carries, situated axially towards the inside of the drum, a recess  125  allowing the positioning of each rocker arm  10  in contact with it in the retracted position of the drum (FIG. 1B). For this purpose, the slide  12  carries at this recess  125  a cylindrical surface  122 , radially and axially closer to the center of the drum  1  than the surface  124 , for the “bottom” abutment of each rocker arm  10 .  
     [0032] Without departing from the scope of the invention, other systems for controlling the rocker arms  10  can be envisaged such as, for example, a rack and pinion system.  
     [0033] A description will be given very succinctly hereinafter of the functioning of the drum  1  for movement from its retracted position to the working position and vice versa, concentrating on the side of the drum  1  situated to the right of its plane of symmetry P depicted in FIGS. 1A and 1B, the rest being apparent from the symmetry with respect to the plane P.  
     [0034] With the transmission finger  131  in its position furthest away axially from the center of the drum  1 , the slide  12  is in contact with the ring  111  through its surface  121  and each rocker arm  10  is in the idle position; that is to say, the end  101  is in the radially position closest to the center of the drum  1  and part of the rocker arm  10  is in abutment with the surface  122  of the slide  12  (FIG. 1B). The drum  1  is thus in the retracted position, the elements  41  being axially and radially closest to the center of the drum.  
     [0035] By actuating the drive of the shaft  6  relative to the ballscrew system, the slide  12  is driven axially by the transmission finger  131  so as to move away from the ring  111  by sliding on the part  112  of the support  11 . This movement breaks the contact between each rocker arm  10  and the stop surface  122  and affords the articulation of each rocker arm. The roller  14  of each rocker arm  10  thus follows the cam  123  until it reaches the cylindrical surface  124 , which stops its travel (FIG. 1A). The other end  101  of each rocker arm, co-operating with the groove  413 , causes in its articulation the axial and radial movement of each element  41  axially and radially towards the outside of the drum of each element  41 .  
     [0036] The elbows  103  on the rocker arms  10  rest by means of the rollers  14  on the cylindrical surface  124  to determine the working position of the drum  1  in which the lateral elements  41  are radially and axially furthest away from the center of the drum  1 .