in the illustrations and in the following description , the elements constituting the structure and its principal parts have been designated in accordance with the following nomenclature : with reference to the above - mentioned illustrations , it can be seen that the elements constituting the endless chain structure in accordance with the invention are various : a static part constituted by the stationary support structures 15 , 16 which hold the shafts of the pulleys 4 and guides the cages 5 durng their travel , and like stationary elements 19 of the structure . a dynamic part constituted by the cages 5 and elements 1 and 14 secured thereto which move relative to the stationary support structure , and like members such as cabins , platforms , etc . a control system consisting of conventional means 17 and 18 for regulation of the functions for starting and stopping the movement of the cages 5 and the like . a hauling system constituted by a conventional motor - reducer ( not shown ) for regulating the power to be utilized , by the couplings of the cables 3 and 3a to the pulleys 4 , by the driving wheels or pulleys 4 , by the cables 3 and 3a , and by the support of the cage 5 by the tubular piece 1 . the components of these constituent elements may be variable , and in each case will be those most appropriate to comply with the mission assigned to them . the majority of these elements are well known in the prior art and are available on the open market , and different solutions can be organized with them . the essential characteristics on which there is based the correct and adequate functioning of the endless chain of cages which is advocated , is the slide mechanism which is illustrated in fig3 which includes a tubular hollow piece 1 , at least one of whose ends is fitted with a guide block 2 . the guide block 2 is supported and guided on either the upper or lower tracks 16 , best shown in fig5 as the cage 5 moves in the horizontal direction longitudinally through the structure . upon reaching the end of the track 16 , the ends of tubular piece 1 are each engaged in an opening in each of the two end wheels 4 and the guide block 2 rides along the semicircular track 20 to the other track 16 , to either raise or lower the cage 5 . each of the four pulleys or wheels 4 is secured to a pinion 18 , there being two at each end as shown in fig4 and 5 , which is driven or rotated by one of the two endless chains 17 mounted thereon on each side of the structure . each chain 17 is driven by conventional means including a motor - reducer which are well known in the art , where no further discussion is thought necessary . the tubular piece 1 transversely crosses over the two traction cables 3 which are parallel to one another , as shown in fig3 and pass over the two pairs of pulleys 4 or end wheels of the endless chain structure , as best shown in fig4 . the tubular piece 1 , in a conventional manner well known in the art , serves as an element for supporting a cage 5 of prismatic form and appropriate dimensions , being disposed at the upper central portions 14 of the cage 5 as shown in fig2 and 6 . the cages 5 are constituted by rigid beams and girders which define the edges of a parallelopipe , having vertical rigid plates 14 connecting the top portions of the vertical girders of each cage 5 . the plates 14 of each cage are provided with confronting openings in which the ends of the corresponding tubular piece 1 are housed so that the cage hangs from the tubular piece 1 and is free to swing relative to the tubular piece 1 . thus , when the motor drives the endless chains 17 , the chains 17 in turn rotate the associated pinions 18 and the wheels 4 connected thereto . the wheels 4 haul the traction cables 3 , 3a to move the guide blocks 2 along one of the tracks 16 to the end thereof , and then carries the ends of the tubular pieces 1 , in the openings provided therefor , to the other of the tracks 16 where the cages begin their run in an opposite direction . if each tubular piece 1 is provided with a guide block 2 at each end thereof , then two horizontally spaced apart tracks 16 will be provided at both the upper and lower positions to support the respective guide blocks 2 . the hollow tubular piece 1 is provided with two longitudinal cuts 12 and 13 perpendicular to each other , which pass its walls over diametrically perpendicular planes to define four grooves or slots 90 ° apart in the exterior of the tubular piece 1 , in which there is guided a slide 6 . the slide 6 has a section in the form of a cross , each of whose arms is guided in one of the four grooves , which permit the terminal parts of the arms of the cross , or wings of the piece , to project to the exterior . the vertical arms of the slide 6 extend through the vertically spaced apart slots 12 , and the horizontal arms of the slide 6 extend through the horizontally spaced apart slots 13 , as best shown in the cut - away view of fig3 . the terminal parts of the slide 6 have the appropriate form so that the check pieces 19 can act on them , by thrusting , coupling , etc ., to bring about the lateral movements of the slide 6 towards one or other end of the tubular piece 1 . the check pieces 19 , in a modified form as shown in fig4 are two rigid bars placed in an upper horizontal plane for the upper cage , and two rigid bars ( not shown for clarity ) placed in a lower horizontal plane for the lower cages . the bars of each pair converge together from one end of the structure where each bar is horizontally inclined towards the center , run parallel to each other along a major intermediate portion of the structure , and then diverge apart again towards the other end of the structure where each bar is horizontally inclined away from the center , so that the bars of each pair are closer together in the intermediate portion of the structure , and further apart at each end of the structure . the upper vertical arm of each slide of the modified tubular piece 1 is engaged in one of the check pieces 19 so that the check piece 19 cause the displacement of the slide and consequently the increase or reduction of the relative separation between the consecutive cages 5 due to the particular run of the cables 3 , 3a . it is noted that the modified tubular piece 1 shown in fig4 is provided with two slides , however the preferred mechanism of the present invention functions as well with only one slide 6 provided in each tubular piece 1 , as shown in fig3 which will be discussed below . furthermore , with only one slide 6 , only one upper check piece bar 19 and one lower check piece 19 is required , the bars having a similar configuration as mentioned above where the bars horizontally incline towards and away from opposite longitudinal sides of the structure at the ends thereof , respectively . referring to fig3 the traction cables 3 proceeding from the mechanism of the anterior slide of the preferred tubular piece 1 . at these ends the tubular piece the tubular piece 1 . at these ends the tubular piece has two diametric cross - pieces 7 and 8 , rotatory or with a rotation of some sheaves 9 provided on them . the sheaves 9 , according to the case , can be fixed or not , and receive the cables 3a which link the slide mechanism with the tubular piece of the cage which follows it . one of the ends of these cables 3a is connected in the anchorage 10 of the slide 6 , and passing over the upper sheave 9 of the diametric cross - piece 7 becomes directly joined to the tubular piece of the following cage . the end of the other cable 3a is connected in the anchorage 11 on the same side of the slide 6 , and passing over the lower sheave 9 of the diametric cross - piece 7 , retrocedes through the interior of the tubular piece 1 and passes over the sheave 9 of the diametric cross - piece 8 , and moves towards the tubular piece of the following cage in a direction parallel to that of the other cable , and with joint forward and backward movements by means of which there is permanently maintained the parallelism between the different slide mechanisms of the system . thus , as shown above and indicated in fig3 the lateral movement of the slide 6 by the check piece 19 toward the end of the tubular piece 1 having the cross - piece 7 , lets out the cables 3a to increase the distance between this cage 5 and the cage which follows it . accordingly , the opposite lateral movement of the slide 6 by the check piece 19 toward the opposing end of the tubular piece 1 having the cross - piece 8 , draws in the cables 3a to decrease the distances between this cage 5 and the cage which follows it . if desired , the tubular piece 1 can be modified to include two slides as shown in fig4 where one cable 3a would be connected to one of the slides , and the other cable 3a would be connected to the other slide , where the movement of the slides toward and away from each other on each half of the tubular piece would decrease or increase the distances between the cages . however , the single slide 6 in each tubular member 1 is preferred , where the single slide 6 has a lateral movement across the tubular piece 1 so that movement towards one end lets out the cables 3a and movement towards the opposite end draws in the cables 3a . therefore , no further discussion of the modified two slides - tubular piece is thought necessary . in the diagram of fig1 there is illustrated the functioning of the system , and in it there can be seen the cages 5a which remain very close together in the centre of the structure . in the case when the system travels in a clockwise direction , the cage 5b has begun its advance movement on drawing near to the left end of the structure , to be able to ascent without interference . passing through the intermediate position illustrated with the cage 5c , the cage becomes situated in the upper row and in the position 5d to draw near to the cages that are closer to one another as cage 5a . simultaneously with the advance of the cage 5b , there is produced the advance of cage 5e of the upper row , which begins the descent . passing through the position 5f of the right end of the structure , the cage becomes situated in the lower row and begins , in position 5g to approach the cages that are close to one another as cage 5e . all these variations are effected jointly and simultaneously , compensating each other with the result that the length of the hauling cable constituted by the sections 3 , 3a , 3b , etc ., brought into service by the different slide mechanisms , is always the same . the functioning of the system , as set forth above , produces stresses or forces causing displacements of the cables 3 and 3a in the interior of the tubular pieces 1 as shown by way of arrows in fig1 . obviously , the double arrows signify equal stresses in opposite directions , and no displacement , while the single headed arrows signify unidirectional stresses in the direction shown and therefore displacement . additionally , the rotational arrows indicate a change or turning in the direction of the stresses about the tubular piece 1 of the cages adjacent to the pulleys 4 . these stresses take place in a horizontal plane , even though the scheme of the forces has been superimposed on the elevational view in a vertical plane to better identify the points at which the forces take place along the run of the tubular piece 1 . the structure , as best shown in fig4 is formed by pairs of vertical beams 15 , which vary in number according to the length of the structure . the upper ends of the beams 15 are connected to the two upper tracks or girders 16 disposed in the same horizontal plane , with the lower two tracks or girders 16 being connected to lower portions of the beams 15 in a lower horizontal plane . the tracks 16 have a u - shape with their wings confronting each other to serve as guides for the guide blocks to ride along , as mentioned above . the installation is designed in such a manner that there exists at least one point where there can be carried out the loading and unloading of the string of cages 5 , each one of which can be situated in a position facing the said position , or two positions if it pertains to the upper level and the lower level . thus , as shown above the cables 3 , 3a , etc . provide a continuous and closed arrangement extending from a slide member of one cage to the tubular piece of the next cage , and so on , etc ., for defining an endless chain structure of the present invention . the circumstances of size , form and material of each of the elements that constitute the whole can be varied ; there may be varied in the complex all that which does not imply an alteration of the essence of the purpose expounded in the preceding description , which should be taken in its widest sense and not as a limitation of possibilities of embodiment .