This invention relates to an assembly machine for the automatic production of structural elements for false ceilings. 
   BACKGROUND OF THE INVENTION 
   Structural elements for false ceilings are known, consisting of profile bars of inverted T-shape provided at their ends with hooks formed either directly from the central web of the T profile bar or from inserts which are formed separately for application to each profile during its production. 
   Said profile bars are connected together to form a lattice structure which by means of steel ties or cables is generally suspended at its top from the ceiling, their horizontal flanges lowerly supporting panels, staves and anything else required to form the false ceiling. 
   Such structural elements are currently formed using single-die presses, ie presses comprising a die of dimensions corresponding to the length of the profile bar to be formed, which is housed within the press and on which the various operations are carried out, possibly in a single step but more generally in several steps, and always within the actual die in which the bar is positioned. Said die is provided with a plurality of punches which are operated in sequence to effect on the bar such operations as perforating; drawing, crimping, etc. 
   These known single-die presses have however certain drawbacks, namely:
         poor flexibility in that for each size (length) of profile bar the press requires a particular die which has to be changed each time the profile bar is to be modified or following any change in dimensions or type of operation,   they require a large number of different dies depending on the type of hook, the length of the profile bars and the type of operation to be carried out,   they immobilize capital,   they occupy considerable storage space.       

   BRIEF SUMMARY OF THE INVENTION 
   
       
       
         
           An object of the invention is to eliminate these drawbacks by providing an assembly machine in which profile bars of different dimensions and different hook types can be worked. 
         
       
     
  
   This object and further ones which result from the ensuing description are attained through an assembly machine. 


   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of the invention is described in detail hereinafter with reference to the accompanying drawings, on which: 
       FIG. 1  is a plan view of the assembly machine of the invention, and 
       FIG. 2  is a cross-section there through on the line II-II of FIG.  1 . 
   


   DETAILED DESCRIPTION OF THE INVENTION 
   As can be seen from the figures, the assembly machine of the invention comprises a conveyor belt  2  provided downstream of a floating cutter  4  positioned at the exit of a forming machine  6 . 
   At the downstream end of said conveyor belt there are provided two pushers  8  which move axially perpendicular to the axis of the belt  2 . 
   Again at the downstream end of said belt there are provided two conveyor straps  10  which are inclined slightly downwards and feed a stepping device indicated overall by  12 . 
   The stepping device comprises a pair of parallel chains  14 ,  14 ′ mounted respectively on two shoulders  16 ,  16 ′, one  16 ′ of which is movable relative to the other shoulder  16  via a guide system  18  and manually operable recirculating ball sliders  20 . 
   Three pairs of dies  22 ,  24 ,  26  are mounted on the shoulders  16 ,  16 ′ and are each operated by a corresponding hydraulic cylinder  28 . 
   With the shoulder  16 ′ there is associated a bellows screen  30  able to cover the distance between the operating face of the dies and the left hand ends of the die bench following the movement of the shoulder  16 ′. 
   At the pair of dies  26 , the machine of the invention also comprises movable transverse stations  32  positionable on the central part of the profile bar to be worked, and in particular on its vertical web. 
   A reel  34  about which steel strip  35  passes is provided to the side of the intermediate pair of dies. 
   The machine of the invention operates in the following manner: after adjusting the distance between the shoulders  16 ,  16 ′ to adapt them to the length of the profile bars  38  to be worked, these profile bars, leaving the forming machine  6  already of T shape an cut by the floating cutter  4 , are made to advance along the conveyor  2  until they encounter a limit switch  42 , at which the pushers  8  transfer them onto the conveyor  10  such that they lie substantially on their side, ie with their web, vertical when installed, now lying horizontal because of the fact that the subsequent operations are performed mainly on this web. 
   The conveyor  10  transfers the profile bars stepwise to the device  12 , which with its pair of chains  14 ,  14 ′ grips each profile bar positioned transversely between the chains, raises it and advances it transversely between through a certain distance, to then lower it. The pitch of the stepping movement, ie the distance between two successive positions of each profile bar, is equal to the distance between the dies corresponding to the two working stations, and the rate of advancement of the stepping device is equal to the rate at which the pairs of dies of the two stations are operated. 
   At the pair of dies  24 , inserts formed by,a press  36  acting on the strip  35  unwound from the reel  34  are applied to the ends of the profile bar. 
   Alternatively, the inserts are joined together to form a tape from which they are separated, to be applied to the ends of the bar portions. 
   In other cases in which it is not intended to apply such inserts, the pair of dies  24  punches the ends of the profile bars to form corresponding hooks. 
   When the profile bars arrive at the pairs of dies  26 , the transverse stations  32  operate to form in the central region of the bar either holes for suspending it from the overlying ceiling, or apertures to be hooked by hooks provided on the other bars. 
   The positioning of these stations depends on the length of the bar to be worked and on the type of operation to be effected. 
   When these operations have been carried out the profile bars  38  are positioned on a conveyor belt  40  to be fed to discharge.
An assembly machine forms structural elements for false ceilings. Structural elements are cut to size and sent to two series of lateral stations. A press forms inserts which are applied to the ends of the structural elements.