Abstract:
The tracked drive device particularly protected by its frame or hood as well as by protective plates, so as to prevent any accidental insertion of a finger or any other part of the human body between the track elements. The arrangement makes access to the track, for replacement or maintenance, particularly difficult. The invention provides a pivoting construction of the driving device, whereby the driving mechanisms become easily accessible, thus facilitating track change.

Description:
The present invention concerns slender drive element devices, in particular those provided with drive tracks in the form of endless chains or belts, able to drive the said slender elements in a translation movement, the invention more particularly concerning the means facilitating access to the said endless chains or belts in order to facilitate the changing thereof. 
   BACKGROUND OF THE INVENTION 
   A particular case of a drive device as described in general terms above is a tracked drive device provided for driving cables, tubes or other elements with an essentially cylindrical cross-section in a longitudinal translation movement. 
   The U.S. Pat. No. 5,884,384 describes a method of placing, by blowing, one or more empty cables or tubes in a tube laid in the ground. The device used for this purpose comprises two endless chains, each carrying a plurality of drive pieces disposed successively on the chain, and depicted for example in U.S. Pat. No. 2,679,924, each of the said drive pieces being provided with a driving sole plate having a form adapted to the element or elements to be driven. A rectilinear length of each of the chains circulates in parallel, facing the corresponding length of the other chain, the element or elements to be driven being clamped between the driving sole plates of the drive pieces facing each other. 
   Since the driving sole plates mounted on the chains have a form and dimensions adapted to the element or elements to be driven, it is necessary to change the said sole plates or respectively to change the chain, at each change of form or dimension of the element to be placed. 
   Moreover, safety standards require that each of the two chains as well as the drive pieces and sole plates be housed in frames, casing or hoods, arranged so that it is impossible to accidentally slide therein a finger or any other part of the human body, so as to prevent any injury. 
   This latter requirement therefore makes it difficult to gain access to the chains in order to be able to remove them so as to exchange them for chains provided with drive pieces or respectively sole plates having a form and dimensions adapted to the next product to be placed. 
   SUMMARY OF THE INVENTION 
   The aim of the present invention is therefore to propose a device for driving slender elements arranged so that the removal and mounting of the drive means are facilitated thereby. 
   This aim is achieved by drive devices as described herein and equivalents thereof. 

   
     A particular embodiment of a device according to the invention is described below, a description which is to be considered with regard to the accompanying drawing comprising the figures. 
       FIG. 1  depicts a side view of a complete drive device for a slender element in the working position, 
       FIG. 2  depicts a view in perspective of the open top portion of part of the previous device; 
       FIG. 3  depicts the open bottom portion of the same device part. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The device  1  for driving a slender element  2 , here a cable, is generally associated, as can be seen in  FIG. 1 , with a first device  3  for measuring speed and placing length, as well as a device  4  for injecting a fluid responsible for introducing a flow of the fluid inside a tube  20  assisting with the placing of the cable  2  inside the tube  20 . This placing method being known, it will not be described more precisely here. 
     FIG. 1  shows that the drive device  1  is composed of a top portion  10  and a bottom portion  11 , the two portions being held together by means  12  for fixing together the two portions and adjusting the separation of the drive mechanism according to a known technique. Consequently the means  12  make it possible to disconnect the two portions  10  and  11  in order to obtain two separate portions, as can be seen in the following figures. 
   In operation, as can be seen in  FIG. 1 , the two frames, casings or hoods  100  and  110  of the top  10  and bottom  11  portions have their edges facing each other directly in contact or very close to each other, generally leaving no space or a minimum space between the said portions. For the cases where, over an interface length between the two portions, there would be too much space remaining, it can be seen in  FIG. 3  that the drive mechanism is also protected by two lateral plates  118  thus providing complete safety for the device against any accidental intrusion of a finger or any other part of the human body. 
   Since the drive mechanisms are thus deeply sunk in the frames, access to the drive chains for removing and exchanging them is difficult. 
   The drive mechanisms  101  or respectively  111  of each of the two portions  10  and  11  each comprise, as can be seen in  FIGS. 2 and 3 , a chassis  102 , or respectively  112 , carrying two toothed wheels on its ends, a first one  120  or respectively  130  visible in partial sections in  FIG. 1 , each mounted on a spindle  121  or respectively  131  directly driven by a motor  103  or respectively  113 , the second toothed wheel  104  or respectively  114  serving as a return wheel for the endless chain  105  or respectively  115 , on which there are mounted the drive pieces  1050  provided with driving sole plates  1051  as described previously, the mechanism is completed by a device for the mechanical tensioning of the endless chain, consisting, according to this embodiment of a stirrup  106  or respectively  116 , fixed firstly to the spindle of the toothed return wheels  104  or respectively  114 , and provided with a threaded rod able to be inserted in a corresponding opening in the frame  100  or respectively  110 , the tensioning being provided by the tightening of a bolt on the said threaded rod. In this embodiment of the clamping device, at least one of the housings for the spindles carrying t he toothed wheels is oblong so as to allow the said tensioning of the drive chain. 
   According to another embodiment of the mechanical tensioning device for the endless chain, this, not shown in the figures, is directly mounted on the chassis  102  and  112  and is able, by a known means with an adjustment screw and/or a knuckle joint, to slightly bring together or separate the spindles of the toothed wheels, thus putting the chain under tension. 
   Pins  107  or respectively  117  pass through holes provided on the one hand in the frames  100  and  110  serving to keep the chassis  102  or respectively  112  in place, each in its respective frame. 
   As mentioned previously, one of the portions of the drive device, here the bottom portion, advantageously comprises, on its drive mechanism  111 , two protective plates  118 , disposed on each side of the said mechanism and blocking any openings between the two frames, as can be seen in  FIG. 1 . Each of the said protective plates preferably comprises an extension  119  on its end closest to the end for insertion of the slender element  2 , so as to prevent the introduction of a finger or any other portion of the human body through this insertion opening. 
   For changing the drive chains, it suffices now to separate the measuring  3  and blowing  4  devices of the drive device  1 , and then to separate the top portion  10  from the bottom portion  11  of the said device, as a result of which, for each of the portions, by relaxing the chain and removing the pins  107  and  117 , it is possible to make each of the drive mechanisms pivot about its drive spindle, as depicted in  FIGS. 2 and 3 , thus making the chains  105  and  115  directly accessible in order to be removed in a conventional manner. The mounting of the new chains takes place exactly in the reverse order of what has just been described. 
   The facilitated access means to the drive mechanism have been described above for a mechanism for driving an endless chain provided with drive pieces each comprising a driving sole plate. It is clear that similar facilitated access means can also be provided when the drive mechanism comprises a belt, flat or shaped, which it may also be necessary to change. Likewise, these facilitated access means have been described as making the drive mechanisms pivot about drive spindles; although this arrangement is advantageous, it would be just as possible to make the mechanisms pivot about the return spindles. Moreover it is obvious that the fixing and clamping device  12  as described previously is not essential to the arrangement and that it can be designed differently from what has been described here. And finally, such facilitated means of access to a tracked drive mechanism can be used for devices for driving slender elements other than the one described above solely by way of example.