Abstract:
An assembly line, wherein at least one operating branch of fixed length accommodates a number of platforms aligned with one another and with a given travelling direction; each platform being designed to receive a respective vehicle body, feed it in the travelling direction, and subject it to a succession of n assembly operations along the operating branch; each platform being designed for connection to at least one longitudinal extension to assume a total length, which depends on the length of the body carried, and ranges between a minimum length equal to the length of the platform with no extension, and a maximum length; and the length of the operating branch being equal to n times the maximum length.

Description:
[0001]    The present invention relates to a motor vehicle assembly line. 
       BACKGROUND OF THE INVENTION 
       [0002]    Currently used motor vehicle assembly lines comprise a succession of moving platforms, each for transporting a vehicle body along an assembly path, and of a length depending on the length of the body. 
         [0003]    Assembly lines of this sort are designed to transport a specific type of body, and have to be completely restructured to switch from one body type to another. 
       SUMMARY OF THE INVENTION 
       [0004]    It is an object of the present invention to provide a versatile assembly line, i.e. adaptable cheaply and easily to different types of vehicle bodies. 
         [0005]    According to the present invention, there is provided a motor vehicle assembly line as claimed in the accompanying Claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    A number of non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which: 
           [0007]      FIG. 1  shows a schematic layout of a preferred embodiment of the assembly line according to the present invention; 
           [0008]      FIG. 2  shows a larger-scale view in perspective of a detail in  FIG. 1 ; 
           [0009]      FIG. 3  shows the same view as in  FIG. 2 , of a variation of the  FIG. 2  detail; 
           [0010]      FIG. 4  shows a side view of the  FIG. 3  detail; 
           [0011]      FIG. 5  shows the same view as in  FIG. 2 , of a further variation of the  FIG. 2  detail. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Number  1  in  FIG. 1  indicates as a whole a motor vehicle assembly line. 
         [0013]    Line  1  is an endless line comprising two U-shaped portions  2  and  3 , which are located at different levels, portion  2  lower than portion  3 , and overlap as described below (for the sake of clarity, portion  3  is shown coplanar with and alongside portion  2  in  FIG. 1 ). 
         [0014]    Portion  2  comprises an input branch  4 , an output branch  5 , and a transfer branch  6  connecting the output of input branch  4  to the input of output branch  5 . Input branch  4  and output branch  5  are the same length L, and each comprise a conveyor  7  for a number of platforms  8  contacting end to end and each of which supports a motor vehicle body  9  and is of a length S depending on the length of relative body  9 . 
         [0015]    As shown in  FIG. 2 , each conveyor  7  is housed inside a pit  10  formed in a floor  11 , and comprises two rails  12  parallel to a travelling direction  13  and supported in a fixed position on supporting blocks  14 . 
         [0016]    As shown in  FIG. 3 , each platform  8  comprises a frame  15  supported on rails  12  with the interposition of a number of trolleys, and in turn comprising two outer longitudinal members  16  and a number of intermediate longitudinal members  17  connected by two end cross members  18  and a number of intermediate cross members  19 . Each end of each longitudinal member  17  projects from the relative end cross member  18 , and is fitted with a plate  20  for the purpose described below. 
         [0017]    Each platform  8  also comprises a normally wooden floor  21 , which covers the rectangular grid defined by frame  15 , and defines a walk-on surface coplanar with floor  11  ( FIG. 2 ). Finally, each platform  8  also comprises a known electromechanical lift table  22 , which is fitted to the centre of frame  15 , through an opening in floor  21 , supports a respective body  9 , and is connected in known manner to an electric power supply mains (not shown) by sliding contacts or induction (not shown) on frame  15 . 
         [0018]    Input branch  4  and output branch  5  are each equipped in known manner (not shown) with a device for moving platforms  8 , contacting end to end, forward, and which comprises, in known manner not shown, a friction push device located at the input of relative input branch  4 , output branch  5 , and cooperating frictionally with the outer lateral surfaces of longitudinal members  16 ; and a friction brake device located at the output of relative input branch  4 , output branch  5 , and which frictionally engages the outer lateral surfaces of longitudinal members  16 , and cooperates in known manner with the friction push device to move platforms  8 , contacting end to end, in travelling direction  13  at a given constant speed V. 
         [0019]    As shown in  FIG. 1 , a receiving branch  23  and a pickup branch  24  are connected in-line to the input and output respectively of each of input and output branches  4  and  5 . 
         [0020]    More specifically, receiving branch  23  of input branch  4  receives platforms  8  at zero linear speed from an elevator  25 , accelerates them to a speed V 1 , and then decelerates them to a speed V 2  (V 1 &gt;V 2 ) approximating but no less than the travelling speed V of platforms  8  along input branch  4 . And pickup branch  24  of input branch  4  receives platforms  8  at the travelling speed V of platforms  8  along input branch  4 , accelerates them to speed V 1 , and then decelerates them to zero linear speed for loading onto an input turntable  26  of transfer branch  6 . 
         [0021]    Receiving branch  23  of output branch  5  receives platforms  8  at zero linear speed from an output turntable  27  of transfer branch  6 , accelerates them to speed V 1 , and then decelerates them to a speed V 2  (V 1 &gt;V 2 ) approximating but no less than the travelling speed V of platforms  8  along output branch.  5 . And pickup branch  24  of output branch  5  receives platforms  8  at speed V, accelerates them to speed V 1 , and then decelerates then to zero linear speed at an elevator  28 . 
         [0022]    Elevator  28  connects the output of portion  2  to the input of portion  3 , and elevator  25  connects the output of portion  3  to the input of portion  2 . 
         [0023]    From elevator  28 , portion  3  comprises an input branch  29  and an output branch  30  connected by a transfer branch  31 . Input branch  29  extends through an unloading station for unloading the assembled bodies  9  off respective platforms  8 , and between elevator  28  and an input turntable  33  of transfer branch  31 ; and output branch  30  extends through a loading station  34  for loading the unassembled bodies  9  onto respective platforms  8 , and between an output turntable  35  of transfer branch  31  and elevator  25 . 
         [0024]    With reference to  FIGS. 3 and 4 , the length P of each platform  8  is adjustable to the length of body  9  by fitting platform  8  with one or two end extensions  36 , each comprising a frame  37  covered with a floor (not shown) similar to and coplanar with floor  21 . Frame  37  is the same width as frame  15 , and comprises two cross members  38 , the corresponding ends of which are connected by two outer longitudinal members  39  spaced the same distance apart as longitudinal members  16 ; and the intermediate portions of cross members  38  are connected by a number of intermediate longitudinal members  40 , of length E, which are fitted on each end with a plate  41  similar to plates  20 , and are spaced the same distance apart between longitudinal members  39  as longitudinal members  17  between longitudinal members  16 . 
         [0025]    Each platform  8  of length: 
         [0000]      S=Smin=P 
         [0000]    is extended to form a composite platform  8  of a total length S: 
         [0000]        S=S int= P+E or S=S max= P+ 2 E    
         [0000]    by positioning frame  37  of (or of each) extension  36  coplanar with frame  15 , with longitudinal members  39  aligned with respective longitudinal members  16 , with longitudinal members  40  aligned with respective longitudinal members  17 , and with plates  41  (the ones facing frame  15 ) positioned contacting respective plates  20 ; and by connecting each two contacting plates  41  and  20 , using screws and/or through bolts and/or any other removable fast-fit connecting devices, to fit extension  36 , or each extension  36 , to and projecting from frame  15  of platform  8  to form a respective composite platform  8 . 
         [0026]    In the example shown, platforms  8  along both input and output branches  4  and  5  are arranged contacting end to end and have all the same length S, and the length L of each of input and output branches  4  and  5  is calculated as follows: 
         [0000]        L=n·S max;  L=m·S min;  L=r·S int 
         [0000]    where: 
         [0000]        m=L/S min&gt; n r=L/S int&gt; n&lt;m    
         [0000]    and where, hereinafter and in the Claims:
       n is intended to represent the number of assembly operations to be performed along each of input and output branches  4  and  5 , and   the term ‘assembly operation’ is intended to mean all the operations performed on the body as respective platform  8  moves forward by a distance equal to the length of platform  8 .       
 
         [0029]    When using platforms  8  of length Smin or Sint, there will therefore be, at the end of each of input and output branches  4  and  5 , a certain number of platforms  8  (m-n or r-n) not used to perform any assembly operations on respective bodies  9 . 
         [0030]    In actual use, after fitting line  1  with platforms  8  of the right length to support bodies  9  for assembly, all the branches of line  1  are set in motion. In particular, input and output branches  4  and  5  are set in motion at a given constant speed compatible with the work to be carried out. 
         [0031]    Platforms  8  are loaded with respective bodies  9  at loading station  34 ; after which, each platform  8  loaded with respective body  9  is fed to elevator  25 , which lowers it to the level of the input of receiving branch  23 , which feeds it onto input branch  4 . 
         [0032]    Platforms  8 , contacting end to end, travel along input branch  4 , are transferred by transfer branch  6  to the input of output branch  5 , and, contacting end to end, travel up to pickup branch  24  and elevator  28 , which raises them successively to the level of input branch  29 . 
         [0033]    At this point, platforms  8  are fed to unloading station  32 , where the finished bodies  9  are unloaded off respective platforms  8 ; and platforms  8  are fed back along transfer branch  31  to loading station  34  to receive further bodies  9  for assembly. 
         [0034]    As will be clear from the above description :
       line  1  provides for assembling bodies  9  of different lengths; and   the working space occupied along each of input and output branches  4  and  5  varies in proportion to the length of bodies  9  being assembled, thus minimizing operator movement.       
 
         [0037]    Obviously, in a variation not shown, input and output branches  4  and  5  may be arranged in-line by eliminating transfer branch  6 , pickup branch  24  of input branch  4  and receiving branch  23  of output branch  5 , and by modifying portion  3  of line  1  accordingly. In which case, a return line must obviously be provided to return the empty platforms  8  from unloading station  32  to loading station  34 . 
         [0038]    In a variation not shown, extensions  36  are mounted on platforms  8 , and are connected to and extractable from frames  15  telescopically.