Abstract:
A solar power station includes a solar panel assembly, having a substantially planar solar panel, and first, second and third towers. Each of the towers includes multiple vertically stacked floors and a main bearing structure pivotally mounting the solar panel assembly to the tower upper end. Each of the floors includes an arrangement of robots that are connected to each vertically adjacent floor. At least some of the robots including hydraulic jacks. A controller selectively actuates the hydraulic jacks, such that each of the towers is individually extendable from a bottom position to an extended position. Selectively moving one or more of the towers rotates the solar panel about one or both of the axes, whereby the solar panel is maintained at an optimal orientation for collecting solar power.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to solar power systems. More particularly, the present invention relates to solar power systems having a tracking system for accurately pointing a solar collector at the sun throughout the day. 
   Early solar power systems included solar tracking systems employing two independent drives to tilt the solar collector about two axes. The first, an elevation axis, allowed the collector to be tilted within an angular range of about ninety degrees between “looking at the horizon” and “looking straight up”. The second, an azimuth axis, is required to allow the collector to track from east to west. The required range of angular rotation depends on the earth&#39;s latitude at which the solar collector is installed. For example, in the tropics the angular rotation needs more than 360 degrees. 
   These early solar power tracking systems generally used electric drives having high ratio gear reducers to turn the collector in the direction of the sun. Error in the gear reducers or linkage between the motor and collector, such as backlash and non-linearly, detracted from the accuracy. When high accuracy was required, the gear reducers were very expensive. 
   These conventional solar power systems occasionally suffered damage from high winds. Thus, it is known to place the solar collector in a wind stow position and avoid damage when winds exceed the design specifications. “Wind stow” is an attitude of the collector that presents the smallest “sail” area to the wind. Generally, a wind sensor was used trigger a command for the elevation actuator to point the collector straight up. The electric elevation actuators and high ratio speed reducers utilized by these systems were very slow to put the collector into wind stow, sometimes taking as long as forty-five minutes. If movement to the wind stow position was initiated at a low threshold value of the wind, to account for the long lead time, the efficiency of the solar power station was adversely affected. If efficiency was optimized by increasing the threshold value of wind required to initiate movement to the wind stow position, a rapidly increasing wind would cause damage to the solar collector. 
   U.S. Pat. No. 6,123,067 proposed a solar power system that had an exoskeleton structure secured to the rear surface of the solar collection device and that is pivotally secured about a horizontal axis to the front end of an azimuth platform assembly. A hydraulic elevation actuator is pivotally mounted in the azimuth platform assembly about a horizontal axis and the front end of its piston rod is pivotally connected to the rear surface of the solar collection device, allowing the solar collection device to be pivoted approximately 90 degrees between a vertical operating position and a horizontal storage position. Primary and a secondary azimuth hydraulic actuator are used to rotate the collection device for tracking the sun. It was believed that such a tracking system would require less time to move the solar collector to the wind stow position. However, the solar collector of such a solar power system can not be scaled up significantly. 
   SUMMARY OF THE INVENTION 
   Briefly stated, the invention in a preferred form is a solar power station which comprises a solar panel assembly having a substantially planar solar panel. Multiple towers are individually extendable from a bottom position to an extended position. Each of the towers has an upper end and a main bearing structure pivotally mounting the solar panel assembly to the tower upper end. Selectively moving one or more of the towers rotates the solar panel about one or both of the axes of the solar panel, such that the solar panel is maintained at an optimal orientation for collecting solar power. 
   Preferably, the solar power station includes first, second and third towers, the first tower being longitudinally spaced from the second tower and the third tower being laterally spaced from the first and second towers. 
   The main bearing structure of the towers includes a main slide bearing box mounted to the tower upper end. A main support shaft extends longitudinally through the main slide bearing box, and is longitudinally and rotationally movable relative to the main slide bearing box. For the first and second towers, first and second support boxes are mounted on the main support shaft first and second end portions, respectively, and to the solar panel assembly. For the third tower, first and second secondary slide bearing boxes are longitudinally mounted on the main support shaft first and second end portions. First and second secondary support shafts extend laterally through the first and secondary slide bearing boxes, respectively. First and second support boxes are mounted on the first and second end portions, respectively, of each of the first and second secondary support shafts, and to the solar panel assembly. 
   The main slide bearing box includes a lower mounting assembly fixedly mounted to the tower upper end and an upper bearing assembly having a longitudinal opening for receiving the main support shaft. The upper bearing assembly is pivotally mounted to the lower mounting assembly about the lateral axis. 
   The solar power station includes a controller for actuating movement of the towers between the bottom and extended positions. The solar power station may include an earthquake senor, the controller withdrawing all of the towers to the bottom position when the detected ground vibration rises above a predetermined level. The solar power station may include a wind senor, the controller withdrawing all of the towers to the bottom position when the detected wind force rises above a predetermined level. 
   Each of the towers comprises a plurality of vertically stacked floors, including a ground floor and at least one upper floor. Each of the floors includes an arrangement of robots (R 1 , R 2 , R 3 , R 4 ) and a connecting framework of push and pull steel frames (F 1 , F 2 ). The robots of each floor are connected to each vertically adjacent floor. The robots (R 1 , R 2 , R 3 , R 4 ) and steel frames (F 1 , F 2 ) are organized in groups (HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3 , VR 4 ), the associated robots and steel frames of each group being connected together. The R 1  robots include hydraulic jacks for moving the towers between the bottom and extended positions. The hydraulic jacks of the R 1  robots of the ground floor include springs. 
   The ground floor further includes a base member, an upper plate, multiple spring devices disposed between the base member and the upper plate, and multiple poles. Each of the poles extends vertically, from a foot mounted to the base member, through an opening in the upper plate. During a strong wind or an earthquake, the upper plate moves vertically upward or downward along the pole whereby the spring devices absorb shock energy generated by lateral forces exerted on the tower by the wind or the earthquake. 
   The ground floor further includes an outer, space frame ring forming a framework mounted to the base member and having multiple of brackets disposed above the upper plate. Each of the brackets has an opening for receiving a one of the poles, whereby the space frame ring constrains horizontal deflection of the poles. 
   Each upperfloor includes an upper plate, with openings for receiving the poles. The robots of each upper floor are connected to the upper plate of the respective floor and the upper plate of the floor vertically below the respective floor. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which: 
       FIG. 1  is a rear perspective view of a solar power station system in accordance with the invention, showing the system positioned for capturing sunlight at sunrise; 
       FIG. 2  is a rear perspective view of the solar power station system of  FIG. 1 , showing the system positioned for capturing sunlight at noon; 
       FIG. 3  is a rear perspective view of the solar power station system of  FIG. 1 , showing the system positioned for capturing sunlight at sundown; 
       FIG. 4  is a front perspective view of the solar power station system of  FIG. 1 , showing the system being positioned in a first direction of rotation; 
       FIG. 5  is a side perspective view of the solar power station system of  FIG. 4 ; 
       FIG. 6  is an enlarged perspective view of the support box, the support shaft, and the slide bearing box of the first or second towers of  FIG. 1 ; 
       FIG. 7  is an enlarged bottom view of the support box and the support shaft of  FIG. 6 ; 
       FIG. 8  is an enlarged perspective view of the support box and the support shaft of  FIG. 6 ; 
       FIG. 9  is a cross-section view taken along line IX-IX of  FIG. 7 ; 
       FIG. 10  is a cross-section view taken along line X-X of  FIG. 7 ; 
       FIG. 11  is an exploded view of the piston shock absorber of  FIG. 10 ; 
       FIG. 12  is an enlarged front view of the slide bearing box of  FIG. 6 ; 
       FIG. 13  is a cross-section view taken along line XIII-XIII of  FIG. 12 ; 
       FIG. 14  is an enlarged cross-section view of the turnable compression bearing of  FIG. 13 ; 
       FIG. 15  is an enlarged cross-section view taken along line XV-XV of  FIG. 13 ; 
       FIG. 16  is an enlarged perspective view of the main slide bearing box, the main support shaft, the secondary slide bearing boxes, the secondary support shafts, and the support boxes of the third tower of  FIG. 1 ; 
       FIG. 17  is an enlarged bottom view of the support box of  FIG. 16 ; 
       FIG. 18  is a cross-section view taken along line XVIII-XVIII of  FIG. 17 ; 
       FIG. 19  is a cross-section view taken along line XIX-XIX of  FIG. 17 ; 
       FIG. 20  is an enlarged front view of one of the secondary slide bearing boxes of  FIG. 16 ; 
       FIG. 21  is a side view of the secondary slide bearing boxes of  FIG. 20 ; 
       FIG. 22  is an enlarged side view of the main slide bearing box of  FIG. 16 ; 
       FIG. 23  is a front view of the main slide bearing box of  FIG. 22 ; 
       FIG. 24  is a top view of the solar power station of  FIG. 1 , with the solar panel assembly removed; 
       FIG. 25  is a top view of the solar power station of  FIG. 2 , with the solar panel assembly removed; 
       FIG. 26  is a top view of the solar power station of  FIG. 3 , with the solar panel assembly removed; 
       FIGS. 27   a ,  27   b  and  27   c  are simplified side views, partly in cross-section of the main bearing structure of the first or second tower, with the main bearing structure unexposed to an external horizontal force ( FIG. 27   a ), with the main bearing structure exposed to an external horizontal force from the right ( FIG. 27   b ), and with the main bearing structure exposed to an external horizontal force from the left ( FIG. 27   c ); 
       FIG. 28  is a simplified perspective view of the robots of a typical tower floor; 
       FIG. 29  is an enlarged view of the HR 1  and VR 1  groups of  FIG. 28 ; 
       FIG. 30  is an enlarged view of the HR 3  group of  FIG. 28 ; 
       FIG. 31  is an enlarged view of the VR 3  group of  FIG. 28 ; 
       FIG. 32  is an enlarged view of the HR 2  group of  FIG. 28 ; 
       FIG. 33  is an enlarged view of the VR 2  group of  FIG. 28 ; 
       FIGS. 34   a - 34   d  are enlarged views of one of the intersections of group HR 2  and group VR 2  of one of the upper floors of  FIG. 28 , showing the HR 2  and VR 2  groups withdrawn ( FIGS. 34   a  and  34   c ) and extended ( FIGS. 34   b  and  34   d ); 
       FIGS. 35   a  to  35   c  are enlarged views of a robot R 1 , showing the robot R 1  in the extended position ( FIG. 35   a ), showing the robot R 1  in the extended position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 35   b ), showing the robot R 1  in the retracted position ( FIG. 35   c ), and showing the robot R 1  in the retracted position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 35   d ); 
       FIGS. 36   a  to  36   c  are enlarged views of a robot R 4 , showing the robot R 4  in the extended position ( FIG. 36   a ), showing the robot R 4  in the extended position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 36   b ), showing the robot R 4  in the retracted position ( FIG. 36   c ), and showing the robot R 4  in the retracted position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 36   d ); 
       FIGS. 37   a  to  37   c  are enlarged views of a robot R 3 , showing the robot R 3  in the extended position ( FIG. 37   a ), showing the robot R 3  in the extended position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 37   b ), showing the robot R 3  in the retracted position ( FIG. 37   c ), and showing the robot R 3  in the retracted position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 37   d ); 
       FIGS. 38   a  to  38   c  are enlarged views of a robot R 5 , showing the robot R 5  in the extended position ( FIG. 38   a ), showing the robot R 5  in the extended position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 38   b ), showing the robot R 5  in the retracted position ( FIG. 38   c ), and showing the robot R 5  in the retracted position, with one of the horizontal roller frames and corresponding pair of jacks removed ( FIG. 38   d ); 
       FIG. 39  is an exploded view of a Robot R 1 /Robot R 5 ; 
       FIG. 40  is an enlarged exploded view of the lock set of the Robot R 1 /Robot R 5  of  FIG. 39 ; 
       FIG. 41  is an enlarged exploded view of the cable reel of the Robot R 1 /Robot R 5  of  FIG. 39 ; 
       FIG. 42  is an enlarged view of the cable lock of  FIG. 41 ; 
       FIG. 43  is an enlarged view of the cable fastener of  FIG. 39 ; 
       FIG. 44  is an exploded view of a Robot R 2 ; 
       FIG. 45  is an enlarged perspective view of a space frame ring of one of the towers; 
       FIG. 46  is an exploded perspective view of the space frame ring of  FIG. 45 ; 
       FIG. 47  is a sectional view of the space frame ring of  FIG. 45 ; 
       FIG. 48  is an exploded view of the first two floors of one of the towers; 
       FIG. 49  is a perspective view of one of the towers; 
       FIG. 50  is an enlarged view of the VR 4  group of  FIG. 28 ; 
       FIGS. 51   a  and  51   b  are enlarged views of one of the intersections of group HR 2  and group VR 2  of the ground floor of  FIG. 28 , showing the HR 2  and VR 2  groups withdrawn ( FIG. 51   a ) and extended ( FIG. 51   b ); 
       FIGS. 52   a  to  52   f  are enlarged views of a robot R 2 , showing the robot R 2  in the extended position ( FIG. 52   a ), showing the robot R 2  in the extended position, with one of the horizontal roller frames and one upper clipper and one lower clipper of the second pair of clipper assemblies removed ( FIG. 52   b ), showing the robot R 2  in the retracted position ( FIG. 52   c ), showing the robot R 2  in the retracted position, with one of the horizontal roller frames and one upper clipper and one lower clipper of the second pair of clipper assemblies removed ( FIG. 52   d ), showing the robot R 2  in the retracted position, with the upper transverse frame removed ( FIG. 52   e ), and showing the robot R 2  in the extended position, with the upper transverse frame removed ( FIG. 52   f ); and 
       FIG. 53  is a functional block diagram of the solar power station control system. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   With reference to the drawings wherein like numerals represent like parts throughout the several figures, a solar power station in accordance with the present invention is generally designated by the numeral  10 . The solar power station  10  includes three, substantially identical, dynamic steel truss towers  12 ,  14 ,  16  supporting a solar panel assembly  18 . Supports  20   20  at the ground floor stabilize and support each of the towers  12 ,  14 ,  16 . It should be appreciated that the solar panel assembly  18  is positioned to optimize collection of sunlight and that the operating description provided below is for illustration purposes only. The operation of the towers  12 ,  14 ,  16  for orienting the solar panel assembly  18  depends on the topography, latitude and longitude of the installation site. 
   The solar power station  10  shown in  FIGS. 1-3  is installed such that the planar solar panel  19  of the solar panel assembly  18  of  FIG. 1  is positioned to receive sun light at sunrise, the solar panel assembly  18  of  FIG. 2  is positioned to receive sun light at noon, and the solar panel assembly  18  of  FIG. 3  is positioned to receive sun light at sundown. To optimize collection of the solar power, the solar panel assembly  18  is positioned perpendicular (or as close as possible) to the direction of the sunlight. To properly position the solar panel assembly  18  at dawn, the first and third towers  12 ,  16  are at a bottom position  22  and the second tower  14  is at a fully extended position  24 . As the sun rises to the noontime position, the first and third towers  12 ,  16  are extended from the bottom position  22 . The first tower  12  is extended at a greater rate than the third tower  16 , causing the solar panel assembly  18  to rotate about the longitudinal and lateral axes RA 1  and RA 2 . When the sun is at the noontime position, the first tower  12  has been extended to the fully extended position  24 , the third tower  16  has been extended to an intermediate position  26  (between the bottom position  22  and the fully extended position  24 ), and the second tower  14  has been held fixed in the fully extended position  24 . As the sun falls to sundown, the second and third towers  14 ,  16  are withdrawn from the fully extended position  24  and the intermediate position  26 , respectively. The second tower  14  is withdrawn at a greater rate than the third tower  16 , causing the solar panel assembly  18  to further rotate about axis RA 1  and RA 2 . At sundown, the second and third towers  14 ,  16  have been withdrawn to the bottom position  22  and the first tower  12  has been held fixed in the fully extended position  24 . 
     FIGS. 4 and 5  illustrate operation of the towers  12 ,  14 ,  16  to orient the solar panel assembly  18  substantially opposite to the solar panel assembly  18  shown in  FIGS. 1-3  for a site location where the light path to the solar power station  10  is opposite to that shown in  FIGS. 1-3 . In  FIGS. 4 and 5 , the second tower  14  is positioned at the fully extended position  24 , the first tower  12  is positioned at a first intermediate position  26  (proximate to the bottom position), and the third tower  16  is positioned at a second intermediate position  26 ′ (proximate to the fully extended position).  FIGS. 1-5  also illustrate the range of motion that may be required to optimize exposure of the solar panel assembly  18  of a solar power station  10  installed on a moveable object, for example a ship. 
   The main bearing structures  28 ,  28 ′ of the first and second towers  12 ,  14  are best illustrated by referring  FIGS. 6-15 . Each of the bearing structures  28 ,  28 ′ includes a slide bearing box  30 , a support shaft  32  extending through the slide bearing box  30 , and first and second support boxes  34 ,  36  mounted at either end of the support shaft  32 . The support shaft  32  is a solid steel shaft. The first and second end portions  38 ,  40  of the support shaft  32  are pinned within receptacles  42  of the first and second support boxes  34 ,  36  by steel bars  44 . A steel plate  46  is removably mounted in each support box by bolts and nuts  48  to further limit axial movement of the support shaft  32  within the receptacle  42 . A steel frame  50  is fixedly mounted to a base plate  52 , preferably by welds. 
   The second support box  36  has a shock absorber  54  disposed within an inner chamber  56  ( FIGS. 10 and 11 ). The shock absorber  54  includes a compression bracket  58  at the front of the shock absorber structure. The compression bracket  58  may include a circular, turnable, steel plate  60  sandwiched between two layers of compression bearing  62 . A recessed bolt and nut  64  mounts a plastic compression cushion  66  to the steel plate  60 . Four recessed channels  68  are equidistantly disposed around the periphery of the compression bracket  58 . A piston ring  70  welded to the end of compression bracket  58  has four recessed channels corresponding to the compression bracket channels  68 . The piston ring  70  includes an axial cylinder  72  through which the support shaft  32  passes. The piston ring  70  and compression bracket  58  are reciprocable within a cylinder block  74 . The inner surface of the cylinder block  74  has at least one, axially extending rib  76  that is received within one of the compression bracket channels  68  and piston ring channels to prevent the piston ring  70  and compression bracket  58  from rotating within the cylinder block  74 . Four shock absorbers  78  are radially spaced within the cylinder block  74 . One end of each shock absorber  78  is mounted to a strut  80 , extending from the end face of compression bracket  58 , by a pin  82  and the other end of each shock absorber  78  is mounted to a strut  84 , extending from the support box base plate  86 , by a pin  82 . Each shock absorber  78  includes a heavy duty spring  88 . 
   With reference to  FIGS. 12-15 , the slide bearing box  30  includes an upper bearing assembly  90  and a lower mounting assembly  92 . The bearing assembly  90  includes a slide bearing  94  having a circular shape complimentary to that of the support shaft  32 . The slide bearing  94  is mounted within a box assembly  96  that is mounted to a base plate  98  by bolts and nuts. An upper bearing plate structure  100  extends downwardly from the base plate  98 . An upper structural frame  102  welded to the box assembly  96  and the base plate  98  and a lower structural frame  104  welded to the upper bearing plate structure  100  and the base plate  98  provide additional structural integrity. 
   The mounting assembly  92  includes a lower bearing plate structure  106  that extends upwardly from a base plate  108 , with a support frame  110  welded to the lower bearing plate structure  106  and the base plate  108  providing additional structural integrity. The base plate  108  is mounted to a truss platform  112  by bolts and nuts. 
   The upper and lower bearing plate structures  100 ,  106  each include multiple bearing plates  114 ,  116 , with each of the bearing plates  114 ,  116  having a bearing surround opening  118  extending therethrough. The bearing plates  116  of the lower bearing plate structure  106  are disposed between bearing plates  114  of the upper bearing plate structure  100  such that the bearing plate openings  118  are aligned. A solid, cylindrical shaft  120  passes through openings  118  in each of the bearing plates  114 ,  116  to connect the bearing assembly  90  to the mounting assembly  92  ( FIG. 14 ). A compression bearing  122  is positioned between each plate  114 ,  116  of the upper and lower bearing plate structures  100 ,  106 , with the shaft  120  extending through apertures  124  in each of the compression bearings  122 . 
   The main bearing structures  126  of the third tower  16  are best illustrated by referring  FIGS. 16-23 . The bearing structure  126  includes a main slide bearing box  128 , a main support shaft  130  extending through the main slide bearing box  128 , a secondary slide bearing box  132  mounted at each end of the main support shaft  130 , two secondary support shafts  134  extending through each of the secondary slide bearing boxes  132 , and support boxes  136  mounted at either end of the secondary support shafts  134 . The two secondary slide bearing boxes  132  are substantially identical, the four secondary support shafts  134  are substantially identical, and all of the support boxes  136  are substantially identical. All of the support shafts  130 ,  134  are solid steel shafts. 
   With reference to  FIGS. 17-19 , the first and second end portions  138 ,  140  of each secondary support shafts  134  are pinned within receptacles  142  of the support boxes  136  by steel bars  144 . A steel plate  146  is removably mounted in each support box  136  by bolts and nuts to further limit axial movement of the secondary support shafts  134  within the receptacle  142 . A steel frame  148  is fixedly mounted to a base plate  150 , preferably by welds. 
   With reference to  FIGS. 20-21 , the secondary slide bearing box  132  includes an upper bearing assembly  152  and a lower support assembly  154 . The bearing assembly  152  includes two slide bearings  156  having a circular shape complimentary to that of the secondary support shafts  134 . The slide bearings  156  are each mounted within a box assembly  158 , mounted to a base plate  160  by bolts and nuts, such that the axes  162  of the slide bearings  156  are parallel. The first and second end portions  164 ,  166  of the main support shaft  130  are each pinned within a receptacles  168  of the support assembly  154  of one of the secondary slide bearing boxes  132  by a steel bar  170 . A steel plate  172  is removably mounted in each support assembly  154  by bolts and nuts to further limit axial movement of the main support shaft  130  within the receptacle  168 . An upper structural frame  174  welded to the box assemblies  158  and the base plate  160  and a lower structural frame  176  welded to the support assembly  154  and the base plate  160  provide additional structural integrity. A 3-dimensional steel truss is mounted to the top of each bearing assembly  152  to connect the two secondary slide bearing boxes  132  ( FIG. 16 ). 
   With reference to  FIGS. 22-23 , the main slide bearing box  128  includes an upper bearing assembly  180 , a lower mounting assembly  182 , and a base assembly  184 . The bearing assembly  180  includes a slide bearing  186  having a circular shape complimentary to that of the main support shaft  130 . The slide bearing  186  is mounted within a box assembly  188  that is mounted to a base plate  190  by bolts and nuts. An upper bearing plate structure  192  extends downwardly from the base plate  190 . An upper structural frame  194  welded to the box assembly  188  and the base plate  190  and a lower structural frame  196  welded to the upper bearing plate structure  192  and the base plate  190  provide additional structural integrity. The mounting assembly  182  includes a lower bearing plate structure  198  that extends upwardly from a base plate  200 , with a support frame  202  welded to the lower bearing plate structure  198  and the base plate  200  providing additional structural integrity. The base assembly  180  of the third tower  16  also includes a rotatable compressor bracket. 
   The upper and lower bearing plate structures  192 ,  198  each include multiple bearing plates  204 ,  206 , with each of the bearing plates  204 ,  206  having a bearing surround opening  208 , extending therethrough. The bearing plates  206  of the lower bearing plate structure  198  are disposed between bearing plates  204  of the upper bearing plate structure  192  such that the bearing plate openings  208  are aligned. A solid, cylindrical shaft  212  passes through openings  208  in each of the bearing plates  204 ,  206  to connect the bearing assembly  180  to the mounting assembly  182 . A compression bearing  214  is positioned between each plate  204 ,  206  of the upper and lower bearing plate structures  192 ,  198 , with the shaft  212  extending through apertures  216  in each of the compression bearings  214 . 
   The base assembly  184  includes a rotatable compression bracket  218  mounted within a steel support frame  220 . The compression bracket  218  includes a steel plate  222  disposed between upper and lower compression bearings  224 ,  226 . The steel plate  222  is mounted to the base plate  200  of the mounting assembly  182  by recessed bolts and nuts. The support frame  220  is mounted to a truss platform  228  by bolts and nuts. 
     FIGS. 24-26  also show the subject solar power station  10  as the solar panel assembly  18  is being positioned to receive sun light at sunrise ( FIG. 24 ), the solar panel assembly  18  is being positioned to receive sun light at noon ( FIG. 25 ), and the solar panel assembly  18  is being positioned to receive sun light at sundown ( FIG. 26 ). In  FIG. 24 , the first tower  12  is being extended  230  from the bottom position, as the second and third towers are held at the bottom position. The sliding bearing  94  of the first tower  12  moves  232  within the slide bearing box  30  from the right to left (with reference to the Figures), until the first tower  12  is fully extended. The sliding bearing  94  of the second tower  14  is maintained  234  at a rest position. The main slide bearing box upper bearing assembly  180  of the third tower  16  rotates clockwise  236  about the main slide bearing box shaft  212 , the compression bracket  218  rotates clockwise  238 , and the secondary support shafts  134  move  240  within the secondary slide bearing boxes  132  to compensate for the movement of the first tower  12  relative to the second and third towers  14 , 16 . 
   In  FIG. 25 , the first tower  12  is retracted to the bottom position, as the second and third towers  14 ,  16  are held at the bottom position. The sliding bearing  94  of the first tower  12  further moves  244  within the slide bearing box  30  from left to right, until the first tower  12  is fully retracted. The sliding bearing  94  of the second tower  14  is maintained  246  at the rest position. The main slide bearing box upper bearing assembly  180  of the third tower  16  rotates counter-clockwise  248  about the main slide bearing box shaft  212 , the compression bracket  218  rotates counter-clockwise  250 , and the secondary support shafts  134  move  252  within the secondary slide bearing boxes  132  to compensate for the movement of the first tower  12  relative to the second and third towers  14 ,  16 . 
   In  FIG. 26 , the second tower  14  is extended  254  from the bottom position, as the first and third towers  12 ,  16  are held at the bottom position. The sliding bearing  94  of the second tower  14  moves  256  within the slide bearing box  30  from left to right, until the second tower  14  is fully extended. The sliding bearing  94  of the first tower  12  is maintained  258  at the rest position. The main slide bearing box upper bearing assembly  180  of the third tower  16  rotates counter-clockwise  260  about the main slide bearing box shaft  212 , the compression bracket  218  rotates counter-clockwise  262 , and the secondary support shafts  134  move  264  within the secondary slide bearing boxes  132  to compensate for the movement of the second tower  14  relative to the first and third towers  12 ,  16 . 
   It should be appreciated that in the event that an earthquake senor  266  ( FIG. 53 ) detects ground vibration above a predetermined level, or a wind sensor  267  detects a wind force above a predetermined level, the hydraulic jack control  268  will withdraw all oil so that the three towers  12 ,  14 ,  16  are withdrawn to the bottom position, as shown in  FIG. 25 . This minimizes the moment arm of the towers  12 ,  14 ,  16 , reducing the oscillation effect on the solar power station  10 . The shock absorbers  54  of the first and second towers  12 ,  14  also absorb the horizontal component of vibration produced by external force such as wind and earthquake. 
   As shown in  FIG. 27   a , the shock absorbers  54  of the second support boxes  36  of the first and second towers  12 ,  14  maintain the second support boxes  36  at a nominal contact distance  270  from the side of the associated slide bearing box  30  when the main bearing structures  28 ,  28 ′ are not exposed to an external horizontal force. 
   When the main bearing structures  28 ,  28 ′ are exposed to an external horizontal force  272  from the right (as shown in  FIG. 27   b ), the force  272  moves  274  the first and second support boxes  34 ,  36  and the support shaft  32  of both main bearing structures  28 ,  28 ′ to the left. The spring  88  of the shock absorber  54  of the second support box  36  of main bearing structure  28  of the first tower  12  is compressed and the spring  88  of the shock absorber  54  of the second support box  34  of main bearing structure  28 ′ of the second tower  14  is extended, absorbing the force  272 . At the point where force  272  and the compression force of the spring  88  of main bearing structure  28  and the tension force of the spring  88  of main bearing structure  28 ′ are at equilibrium, the second support box  36  of the first tower  12  is at a minimum contact distance  276  from the side of the associated slide bearing box  30  and the second support box  36  of the second tower  14  is at a maximum contact distance  278  from the side of the associated slide bearing box  30 . When the force  272  is removed, the compression force of the spring  88  of main bearing structure  28  and the tension force of the spring  88  of main bearing structure  28 ′ return the first and second support boxes  34 ,  36  and the support shaft  32  of both main bearing structures  28 ,  28 ′ to the positions shown in  FIG. 27   a.    
   Similarly, when main bearing structures  28 ,  28 ′ are exposed to an external horizontal force  280  from the left (as shown in  FIG. 27   c ), the force  280  moves  282  the first and second support boxes  34 ,  36  and the support shaft  32  of both main bearing structures  28 ,  28 ′ to the right. The spring  88  of the shock absorber  54  of the second support box  36  of main bearing structure  28 ′ of the second tower  14  is compressed and the spring  88  of the shock absorber  54  of the second support box  36  of main bearing structure  28  of the first tower  12  is extended, absorbing the force  280 . At the point where force  280  and the compression force of the spring  88  of main bearing structure  28 ′ and the tension force of the spring  88  of main bearing structure  28  are at equilibrium, the second support box  36  of the second tower  14  is at a minimum contact distance  284  from the side of the associated slide bearing box  30  and the second support box  36  of the first tower  12  is at a maximum contact distance  286  from the side of the associated slide bearing box  30 . When the force  280  is removed, the compression force of the spring  88  of main bearing structure  28 ′ and the tension force of the spring  88  of main bearing structure  28  return the first and second support boxes  34 ,  36  and the support shaft  32  of both main bearing structures  28 ,  28 ′ to the positions shown in  FIG. 27   a.    
   Each of the towers  12 ,  14 ,  16  includes multiple, vertically stacked floors  288  ( FIG. 28 ). Each floor  288  includes an arrangement of robots R 1 , R 2 , R 3 , R 4  and a connecting framework of push and pull steel frames F 1 , F 2 . More specifically, the robots R 1 , R 2 , R 3 , R 4  and steel frames F 1 , F 2  are organized in groups, HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3 , VR 4 , with the associated robots and steel frames of each group being connected together. The robots R 1 , R 2 , R 3 , R 4  of each intermediate floor  288  are connected to associated robots in each floor  288 ,  288 ″ above it and each floor  288 ,  288 ′ below it. Groups HR 1  and VR 1  are identical, each including three R 3  robots and four R 4  robots. The HR 2  and VR 2  groups are almost identical, each including three R 1  robots, one R 2  robot, and one R 4  robot. HR 2  also includes four double deck steel frames F 1 , while VR 2  also includes three single deck steel frames F 2  and one double deck steel frame F 1 . The HR 3  group includes three R 1  robots and two R 3  robots. The VR 3  group includes four R 1  robots and three R 3  robots. The VR 4  group includes three R 1  robots and one R 4  robot. For the ground floor  288 ′, the R 1  robots are vibration hydraulic jacks with springs, while for all of the other floors  288 , the R 1  robots are hydraulic jacks. 
   With reference to  FIGS. 45 to 49 , the ground floor  288 ′ includes an outer, space frame ring  596  which is designed to resist lateral force exerted on the towers  12 ,  14 ,  16  by strong wind or earthquakes, and thereby prevent tension, bearing and torsion forces from pulling the robot groups HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3 , VR 4  out of the space frame ring  596 . The space frame ring  596  comprises a framework including supporting members  598 , first bracing members  600 , vertical members  602 , second bracing members  604 , first gusset plates  606 , horizontal members  608 , second gusset plates  610 , and bracket  612  that are fastened together by bolts and nuts. The footing of supporting members  598  and the footing of vertical members  602  are fastened to a base member  614  which is in turn fastened to the foundation  616 , preferably by nuts and bolts. A solid rod or pole  618  extends vertically upward from a foot fixed within a bottom flange  620  mounted to the base member  614 , through a lower spring  622 , an upper flange  624  having a lower flange half  626  and an upper flange half  628 , an upper plate  630  clamped between the lower and upper flange halves ( 626 ,  628 ), an upper spring  632 , to a head fixed within an opening in the bracket  612 . The top end of the upper spring  632  engages the lower surface of the bracket  612  and the bottom end of the upper spring  632  engages the top surface of the upper flange half  628 . The top end of the lower spring  622  engages the lower surface of the lower flange half  626  and the bottom end of the lower spring  632  engages the top surface of the bottom flange  620 . In the event of a strong wind or earthquake, the upper plate  630  can move vertically upward and downward along the pole  618  such that the upper and lower springs  632   622  absorb the shock energy generated by lateral forces exerted on the tower by the wind or the earthquake. 
     FIGS. 48 and 49  illustrate the ground floor  288 ′ and a typical floor connection. The ground floor base member  614  is connected to the tie beam members  634  of the upper plate  630  by the ground floor pole  618 , which is mounted to the piling or foundation  616  and extends through the upper flange  624  mounted to the upper plate  630 . The ground floor robot groups HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3 , VR 4  are mounted to the tie beam members  636  of the ground floor base member  614  and to the tie beam members  634  of upper plate  630  of the ground floor  288 ′. The tie beam members  634  are mounted to the upper plate  630  by gusset plates and by bolts and nuts or welds. The connections for the upper floors  288  are the same as described above for the ground floor  288 ′, where the upper plate  630  of each lower floor acts as the base member of each subsequent floor. For example, the robot groups HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3 , VR 4  of the second floor are mounted to the tie beam members  634  of the upper plate  630  of the ground floor  288 ′ and to the tie beam members  634 ′ of the upper plate  630 ′ of the second floor. 
     FIG. 29  is an enlarged view of the HR 1  and VR 1  groups of  FIG. 28 . Each HR 1  and VR 1  group includes four R 4  robots  640 ,  642 ,  644 ,  646  and three R 3  robots  648 ,  650 ,  652 .  FIG. 30  is an enlarged view of the HR 3  group of  FIG. 28 . Each HR 3  group includes three R 1  robots  654 ,  656 ,  658  and two R 3  robots  660 ,  662 .  FIG. 31  is an enlarged view of the VR 3  group of  FIG. 28 . Each VR 3  group includes four R 1  robots  664 ,  666 ,  668 ,  670  and three R 3  robots  672 ,  674 ,  676 .  FIG. 32  is an enlarged view of the HR 2  group of  FIG. 28 . Each HR 2  group includes three R 1  robots  318 ,  322 ,  326 , one R 4  robot  332 , and one R 2  robot  678 .  FIG. 33  is an enlarged view of the VR 2  group of  FIG. 28 . Each VR 2  group includes three R 1  robots  334 ,  336 ,  338 , one R 4  robot  340 , and one R 2  robot  680 .  FIG. 50  is an enlarged view of the VR 4  group of  FIG. 28 . Each VR 4  group includes three R 1  robots  334 ′,  336 ′,  338 ′ and one R 4  robot  340 ′. 
   The R 1 , R 2 , R 3 , and R 4  robots all have a horizontal roller frame  290 ,  292 ,  304 ,  308  on each side of the robot. The R 1  robots also have a pair of hydraulic jacks  294  is mounted to each of the horizontal roller frames  290 . More specifically, a first end  298  of both hydraulic jacks  296  of each pair  294  is mounted to the first end  300  of the respective horizontal roller frame  290 . 
   For the HR 1  and VR 1  groups ( FIG. 29 ), the R 3  robots are disposed between the R 4  robots, with the first ends  306  of the horizontal roller frames  304  of the R 3  robots being connected to the first ends  310  of the horizontal roller frames  308  of the adjacent R 4  robots. 
   For the HR 3  group ( FIG. 30 ), the R 3  robots are disposed between the R 1  robots, with the first ends  306  of the horizontal roller frames  304  of the R 3  robots being connected to the first ends  300  of the horizontal roller frames  290  of the adjacent R 1  robots, and a pair of hydraulic jacks  294  being disposed between the R 1  robot and the R 3  robot. 
   For the VR 3  group ( FIG. 31 ), the R 3  robots are disposed between the R 1  robots, with the first ends  306  of the horizontal roller frames  304  of the R 3  robots being connected to the first ends  300  of the horizontal roller frames  290  of the adjacent R 1  robots, and a pair of hydraulic jacks  294  being disposed between the R 1  robot and the R 3  robot. 
   For the HR 2  group ( FIG. 32 ), the three R 1  robots  318 ,  322 ,  326  are adjacent, one R 4  robot  332  is disposed at one end of the group of R 1  robots, and one R 2  robot  678  mounted to R 1  robot  318 . The first ends  302  of the extended double deck steel frame segments  291  of the horizontal roller frames  292  of the R 2  robot are connected to the first ends  300  of the horizontal roller frames  290  of R 1  robot  318 . A first end  312  of a first double deck steel frame F 1   314  is connected to the second end  316  of the horizontal roller frames  290  of the first R 1  robot  318  and the second end  320  of the first steel frame F 1   314  is connected to the first end  300  of the horizontal roller frames  290  of the second R 1  robot  322 . Similarly, the first end  312  of the second steel frame F 1   324  is connected to the second end  316  of the horizontal roller frames  290  of the second R 1  robot  322 , the second end  320  of the second steel frame F 1   324  is connected to the first end  300  of the horizontal roller frames  290  of the third R 1  robot  326 , the first end  312  of the third steel frame F 1   328  is connected to the second end  316  of the horizontal roller frames  290  of the third R 1  robot  326 , and the second end  320  of the third steel frame F 1   328  is connected to the second end  330  of the horizontal roller frames  308  of the R 4  robot  332 . 
   The VR 2  group ( FIG. 33 ) and VR 4  group ( FIG. 50 ) are very similar, each of the groups having three adjacent R 1  robots  334 ,  336 ,  338 ,  334 ′,  336 ′,  338 ′ and one R 4  robot  340 ,  340 ′ that is disposed at one end of the group of R 1  robots. A first end  342  of a first single deck steel frame F 2   344  is connected to the second end  316  of the horizontal roller frames  290  of the first R 1  robot  334 ,  334 ′ and the second end  346  of the first steel frame F 2   344  is connected to the first end  300  of the horizontal roller frames  290  of the second R 1  robot  336 ,  336 ′. Similarly, the first end  342  of the second steel frame F 2   348  is connected to the second end  316  of the horizontal roller frames  290  of the second R 1  robot  336 ,  336 ′, the second end  346  of the second steel frame F 2   348  is connected to the first end  300  of the horizontal roller frames  290  of the third R 1  robot  338 ,  338 ′, the first end  342  of the third steel frame F 2   350  is connected to the second end  316  of the horizontal roller frames  290  of the third R 1  robot  338 ,  338 ′, and the second end  346  of the third steel frame F 2   350  is connected to the second end  330  of the horizontal roller frames  308  of the R 4  robot  340 ,  340 ′. The VR 2  group ( FIG. 33 ) also has one R 2  robot  680  disposed at the second end of the group of R 1  robots, with the first ends  302  of the extended double deck steel frame segments  291  of the horizontal roller frames  292  of the R 2  robot being connected to the first ends  300  of the horizontal roller frames  290  of R 1  robot  334 . 
   As shown in  FIGS. 34   a - 34   d , the single deck steel frames F 2  of the VR 2  groups passes through the gap  351  formed by the steel members  352  of the double deck steel frames F 1  of the HR 2  groups. In  FIGS. 34   b  and  34   d , hydraulic fluid has been pumped into the hydraulic jacks  296  of the HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3  and VR 4  groups, pushing the second ends  354  of the hydraulic jacks  296  away from each other and thereby pushing the floors away from each other. This causes the towers to extend from the bottom position  22 . As the second ends  354  of the hydraulic jacks  296  are pushed away from each other, the horizontal roller frames  290 ,  308  move  356  from right to left direction, the VR 1 , VR 3  and HR 2  groups producing movement in the X direction and the HR 1 , HR 3 , VR 4  and VR 2  groups producing movement in the Y direction ( FIG. 1 ). In  FIGS. 34   a  and  34   c , hydraulic fluid has been released from the hydraulic jacks  296  of the HR 1 , HR 2 , HR 3 , VR 1 , VR 2 , VR 3  and VR 4  groups, allowing the weight of the floor to push the second ends  354  of the hydraulic jacks  296  towards each other, causing the towers to retract to the bottom position  22 . 
   With reference to  FIGS. 51   a  and  51   b , the arrangement of the VR 2  and HR 2  groups of the ground floor  288 ′ is the same as described above, except that the hydraulic jacks of robots R 1  are replaced with a vibration hydraulic jack with spring  484 . The ground floor  288 ′ has a special function. When a great wind force or earthquake occurs, the ground floor hydraulic jacks with springs  484  will absorb the energy. If the vibration force exceeds the absorption capacity of the hydraulic jacks with springs  484  at their rest supporting stage, the vibration force will push the robot groups in HR 2  and VR 2  down from top to bottom level, the horizontal roller frames  292 ,  290 ,  308  move from left to right. Finally the R 1  robot transfers the energy force through the push and pull frame F 1  and F 2  to the adjacent R 1  robots and into the R 2  robot. The HR 2  group transfers the x-direction force to the end of group, at the same time the VR 2  group transfers the y-direction force to the end of group. The floorwill be pushed down uniformly to the same level at the same time until the hydraulic jacks with springs  484  of the HR 2  and VR 2  groups absorb all the energy. When the vibration force is removed, the hydraulic jacks with springs  484  will push the HR 2  and VR 2  groups back to original position. 
     FIGS. 35-43  are external and internal views of robots R 1 , R 3 , R 4  and R 5  showing the relationship of the robot components as they move from the bottom position to the extended position. Movement of the robots R 1 , R 3 , R 4  and R 5  is controlled by the hydraulic jacks. For robots R 1 , each hydraulic jack  296  has a first end  298  connected to a shaft extending through the side of horizontal roller frame  290  and a second end  354  having a base  358 . For robots R 5 , each vibration hydraulic jack with spring  484  has a first end  486  connected to a shaft extending through the side of horizontal roller frame  488  and a second end  490  having a base  492 . 
   An upper arm  360 ,  388 ,  420 ,  452  has a first end connected to an upper clipper  362 ,  390 ,  422 ,  454  and the second end connected to a roller  364 ,  392 ,  424 ,  456  and a lower arm  366 ,  394 ,  426 ,  458  has a first end connected to a lower clipper  368 ,  396 ,  428 ,  460  and a second end connected to the roller  364 ,  392 ,  424 ,  456 . Each horizontal roller frame  290 ,  308 ,  304 ,  488  includes two frame members  369 ,  398 ,  430 ,  462  that are mounted together at each end by a pair of mounting members  371 , 400 ,  432 ,  464 . The roller  364 ,  392 ,  424 ,  456  extends through a slot  370 ,  402 ,  434 ,  466  formed between the two frame members  369 ,  398 ,  430 ,  462  and is locked therein by a washer  372 ,  404 ,  436 , 468  mounted to the roller  364 ,  392 ,  424 ,  456 . 
   When the robots are extended, the upper clipper  362 ,  390 , 422 ,  454  is pushed upward and lower clipper  368 ,  396 ,  428 ,  460  is pushed downward, and the upper arm  360 ,  388 ,  420 ,  452  and lower arm  366 ,  394 ,  426 ,  458  urge roller  364 ,  392 ,  424 ,  456  away from the first end  300 ,  310 ,  306 ,  494  of the horizontal roller frame  290 ,  308 ,  304 ,  488  toward the second end  316 ,  330 ,  307 ,  496  of the horizontal roller frame  290 ,  308 ,  304 ,  488 . An upper cable clevis  374 ,  406 ,  438 ,  470  is fixed on the shaft between the upper base  376 ,  408 ,  440 ,  472  and the upper clipper  362 ,  390 ,  422 ,  454  and a lower cable clevis  378 ,  410 ,  442 ,  474  is fixed on the shaft between the lower base  380 ,  412 ,  444 ,  476  and the lower clipper  368 ,  396 ,  428 ,  460 . A first end of secondary cable  382 ,  414 ,  446 ,  478  is fastened to the main cable  384 ,  416 ,  448 ,  480  by a clip  385  ( FIG. 43 ) and the second end is fastened to the retractable cable reel  386 ,  418 ,  450 ,  482 . 
   When the robots retract, the upper clipper  362 ,  390 ,  422 ,  454  is pushed downward, the lower clipper  368 ,  396 ,  428 ,  460  is pushed upward, and the secondary cable  382 ,  414 ,  446 ,  478  is rolled onto the retractable cable roller  386 ,  418 ,  450 ,  482 , pulling the secondary cables  382 ,  414 ,  446 ,  478  and the main cables  384 ,  416 ,  448 ,  480 . 
     FIG. 40  shows a locking device  548  for locking the upper clipper  362  to the lower clipper  368 . The locking device  548  includes a shaft  550  that is reciprocally moved by a hydraulic jack  552 . The end of the hydraulic jack  552  is mounted to the shaft  550  by a pin  554  that passes through a pair of angles  556  and a slot in the jack shaft  558 . The angles  556  are mounted to the shaft  550 . The jack body  560  is mounted to the lower clipper  368  by a pin  562  that passes through plates  564 , mounted to another pair of angles  566 , and the jack body  560 . The angles  566  are mounted to the guide  568 . Three guides  568 ,  570 ,  572  are mounted to the lower clipper  368  and one guide  574  is mounted to the upper clipper  362  for guiding and receiving the shaft  550 . The shaft  550  extends through the first and second guides  568 ,  570  in both the unlocked and locked positions. When Robot R 1  and R 4  are in the bottom position, the fourth guide  574  mounted to the upper clipper  362  aligns with the first, second and third guides  568 ,  570 ,  572  mounted to the lower clipper  368 . At this time, the hydraulic jack  552  may be actuated to extend the jack shaft  558  and the shaft  550  through the fourth guide  574  and into the third guide  572 , thereby locking the upper clipper  362  to the lower clipper  368 . To extend Robot R 1  and R 4 , the hydraulic jack  552  must again be actuated to withdraw the jack shaft  558  and the shaft  550  from the third and fourth guides  572 ,  574 . 
   As shown in  FIG. 41 , the cable reel  386 ,  418 ,  450 ,  482 , includes a pair of coil springs  576 ,  578 . Each coil spring  576 ,  578  has a first end fixed to a wall of an internal cylinder  580  of recess wheel  582  by bolt and nut that pass through the recess wheel  582  and then fix to the shaft  584 , the second end is fixed to the external cylinder  586  by bolt and nut. The internal and external cylinders  580 ,  586  are mounted to a center nut  588 . The center nut  588  has a recess  590  having an opening  592  through which passes the secondary cable  382 ,  414 ,  446 ,  478 . A lock  594  holds the secondary cable  382 ,  414 ,  446 ,  478 . 
     FIGS. 44 and 52  are external and internal views of robot R 2  showing the relationship of the robot components as they move from the bottom position to the extended position. Movement of the robots R 2  is controlled by the hydraulic jacks of the robots R 1 . 
   Robot R 2  comprises a first pair of clipper assemblies  497 , each of the clipper assemblies  497  including an upper arm  498  having a first end connected to an upper clipper  500  and a second end connected to a roller  502 , and a lower arm  504  having a first end connected to a lower clipper  506  and a second end connected to the roller  502 . The roller extends through a slot formed in each horizontal roller frame  292 . The second end  301  of the extended double deck frame F 1   291  is connected to the roller  502 . The first ends of the upper and lower clippers  500 ,  506  each have a base  508 ,  510  and the second ends of the upper and lower clippers  500 ,  506  are each connected to a shaft  512 ,  514  by a slot plate  516 . Slot plate  516  is mounted to the second end  518  of horizontal roller frame  292  by fixed plate  520  and bracket frame  522  by bolts and nuts. The shafts  512 ,  514  are locked to the slot plate  516  by round disk lockers. The upper clipper  500  is fixed to an upper transverse frame  524  and the lower clipper  504  is fixed to a lower transverse frame  526 . 
   Robot R 2  also comprises a second pair of clipper assemblies  528 , each of the clipper assemblies  528  including upper and lower clippers  530 ,  532 . The first ends of the upper and lower clippers  530 ,  532  each have a base  534 ,  536  and the second ends of the upper and lower clippers  530 ,  532  are each connected to a shaft  538 ,  540  by a pair of slot plates  542 . Slot plates  542  are mounted to the first end  302  of horizontal roller frame  292  by fixed plate  544  and by bolts and nuts. The shafts  538 ,  540  are locked to the slot plate  542  by round disk lockers. The upper clipper  530  is fixed to an upper transverse frame  524 ′ and the lower clipper  532  is fixed to a lower transverse frame  526 ′. 
   When the robots are extended, the upper clippers  500 ,  530  are pulled upward and lower clippers  506 ,  532  are pulled downward, and the upper arm  498  and lower arm  504  urge roller  502  away from the first end  302  of the horizontal roller frame  292  toward the second end of the horizontal roller frame  292  ( FIG. 52 ). When the extended double deck frame F 1   291  engages the panel  546  connected to the horizontal roller  502 , the robot R 2  has reached its maximum extension and the floor is locked at the maximum height, preventing over extension of the robots. 
   While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.