Abstract:
Heavy equipment is attached to slings and lifted by rollers raised and lowered in a structure with four pillars. Rollers prevent torque and provide vertical vectors. Roller axle supports move along the pillars. Two gantry crane frames are joined by cross and truss beams. Hydraulic jacks and pneumatic locks are controlled and sensed movements are communicated to processors for each pillar. One master processor communicates with a remote control. Sensors check lock and hydraulic cylinder position and allow roller movements only when positions are correct and all processors agree.

Description:
BACKGROUND OF THE INVENTION 
     Lifting heavy equipment creates challenges and problems which must be solved. One of the problems, of course, is the heavy weight of the machinery. Another problem is unique sizes and shapes of heavy equipment that must be lifted. Another problem is dealing with torque that may be encountered when lifting heavy equipment. 
     Needs exist for improvements in heavy equipment lifting. 
     SUMMARY OF THE INVENTION 
     The invention provides apparatus and methods for lifting heavy equipment. 
     The apparatus has a structural frame. The structural frame has first and second open ends, first and second longitudinal sides and a top. Four spaced pillars are connected at intersections of the sides and ends. Cross beams are mounted at tops of the pillars at the first and second ends. Horizontal beams connect the cross beams at the top and connect the pillars at the sides. Truss beams connect the horizontal beams at angles on the top and the sides. The pillars are formed of two spaced parallel vertical channel beams with outward flanges. The channel beams are welded with interposed plates forming box beams with flanges. Plate assemblies are connected to two flanges on inner sides of the pillars for sliding along the inner sides of the pillars. The plate assemblies have inward facing long front plates extending parallel to aligned flanges of two channel beams. Two shorter back plates are bolted or welded to ends of each front plate to trap the aligned flanges between front and back plates. The front plates or both the front and back plates are grooved to receive the aligned channel flanges. The front plates have roller axle-supporting upward opening grooves in upper surfaces of the plate assemblies. First and lifting rollers have axles positioned in the axle-holding grooves in the upper front plates respectively at the first and second ends of the structure. 
     The rollers have cylinders with end plates at opposite ends, and the axles extend outward from the end plates. The rollers have cylinders with outer end plates and inner end plates, and the axles are welded to the inner end plates and extend through openings in the outer end plates. 
     The axles have annular grooves in ends of the axles opposite the end plates, and the annular grooves in the axles are held in the grooves in the upper front plates. 
     Slings extend over the roller and downward therefrom for connecting ends of the slings to an object to be lifted. The cylinders and piston rods are provided on axles intersecting the upper and lower plates. The front plates have extensions for mounting the pneumatic actuators. 
     The invention provides a method of lifting heavy equipment, such as mining equipment, by constructing a structural frame having first and second open ends, first and second longitudinal sides and a top. Four spaced pillars are provided at intersections of the sides and ends. Cross beams are provided at tops of the pillars at the first and second ends. Horizontal beams connect the cross beams at the top and connect the pillars at the sides. Truss beams connect the horizontal beams at angles on the top and the sides. Plate assemblies connect to the pillars for sliding along inner sides of the pillars. Roller axle-supporting upward opening grooves are provided in upper surfaces of the plate assemblies. First and lifting rollers have axles positioned in the axle-holding grooves in the upper front plates respectively at the first and second ends of the structure. 
     The rollers have cylinders with end plates at opposite ends, and the axles extend outward from the end plates. The rollers have cylinders with outer end plates and inner end plates, and the axles are welded to the inner end plates and extend through openings in the outer end plates. The axles have annular grooves in ends of the axles opposite the end plates, and the annular grooves in the axles are held in the grooves in the upper front plates. 
     Slings extend over the roller and downward therefrom for connecting ends of the slings to an object to be lifted and lifting the object with the slings. 
     In one form the apparatus of the invention has a structural frame with top, longitudinal sides and first and second open ends. The apparatus has four spaced pillars having pairs of opposite teeth parallel to the sides of the structural frame. The teeth in each pair are longitudinally spaced. The tops of the pillars have first and second cross beams at the first end and at the second end. Horizontal beams connect the cross beams at the top of the structural frame and connect the pillars at the sides of the structural frame. Truss beams connect the horizontal beams at angles on the top and the sides of the structural frame. 
     Climbing assemblies are mounted on insides of each of the pillars. Each of the climbing assemblies has upper and lower plate assemblies. Each plate assembly has front plates extending along an inner side of the teeth on a pillar and has back plates behind the teeth on the pillar. Each front plate in each of the upper plate assemblies has a roller axle-supporting groove in an upper surface of the front plate. Double-acting hydraulic cylinders and piston rods are mounted between the upper and lower front plates. Each double-acting cylinder is connected to one of the upper plates, and each cylinder has a piston rod connected to one of the lower front plates. 
     Sliding lock bolts herein described as locks are connected to the plates between the front plates and the rear plates of each plate assembly for selectively and concurrently engaging or disengaging the teeth from opposite directions and alternatively locking the upper plates and the lower plates with the locks and the teeth. Upper and lower pneumatic actuators are connected to the upper and lower plate assemblies and are connected to the locks for timely inserting and withdrawing the locks into and out from the teeth. Hydraulic lines are connected to upper and lower ends of the double-acting cylinders for raising the cylinders and the upper plates when hydraulic pressure is applied to the upper ends of the double-acting cylinders while the lower plates are locked with the teeth, and for raising the lower plates when hydraulic pressure is applied to the lower ends of the hydraulic cylinders while the upper plates are locked with the locks in the teeth. A control panel is connected to valves in the pneumatic lines and to valves in the hydraulic lines for sequencing. 
     The locks are inserted and all plate assemblies are locked with the pneumatic actuators. Locks are withdrawn in the upper plate assemblies into the teeth. Hydraulic pressure is admitted to upper ends of the hydraulic cylinders to raise the upper plate assemblies. Locks are inserted in the upper plate assemblies into the teeth. Locks are withdrawn in the lower plate assemblies from the teeth. Hydraulic pressure is admitted to lower ends of the hydraulic cylinders and raising the lower plate assemblies. 
     First and lifting rollers have axles positioned in the axle-holding grooves in the upper front plates respectively at the first and second ends of the structure. The rollers have cylinders with end plates at opposite ends, and the axles extend outward from the end plates. The rollers have cylinders with outer end plates and inner end plates, and the axles are welded to the inner end plates and extend through openings in the outer end plates. 
     The axles have annular grooves in ends of the axles opposite the end plates, and the annular grooves in the axles are held in the grooves in the upper front plates. 
     Slings extend over the roller and downward therefrom for connecting ends of the slings to an object to be lifted. The cylinders and piston rods are provided on axles intersecting the upper and lower plates. The front plates have extensions for mounting the pneumatic actuators. 
     The apparatus has sensors on the pillars, pneumatic actuators and hydraulic systems for sensing positions of engaged or disengaged locks. The pneumatic actuators have double-acting cylinders with pistons and piston rods connected to the locks. The sensors on the pneumatic actuators sense position of the pistons within the pneumatic cylinders, and the sensors on the hydraulic systems sense pressure on the hydraulic lines and overforce the hydraulic cylinder and piston for over closing or over opening. The sensors on the cylinders and lower plate assemblies sense half travel of the cylinder with respect to the lower plate assemblies for admitting pressure to the pneumatic cylinders to advance the locks for engagement with the teeth. 
     These and further and other objects and features of the invention are apparent in the disclosure, which includes the above and ongoing written specification, with the claims and the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a frame structure having pillar-supported movable rollers for raising and lowering. 
         FIG. 2  is an end view of the frame structure shown in  FIG. 1 . 
         FIG. 3  is a modified side view of the frame structure shown in  FIG. 1 . 
         FIG. 4  is a top view of the frame structure shown in  FIG. 1 . 
         FIG. 5  is a perspective view of a heavy load support roller shown in  FIGS. 1-4 . 
         FIG. 6  is a side view of the load support roller shown in  FIG. 5 . 
         FIG. 7  is an end view of the load support roller shown in  FIGS. 5 and 6 . 
         FIG. 8  is a cross-section of the load support roller as shown in  FIG. 7 . 
         FIG. 9  is a perspective cross-sectional view of the load support roller. 
         FIG. 10  is a perspective cross-sectional detail of the load support roller. 
         FIG. 11  is a perspective detail of a roller end raising assembly on a pillar. 
         FIG. 12  is a front elevational detail of the assembly shown in  FIG. 11 . 
         FIG. 13  is a side detail of a pillar and the roller raising assembly shown in  FIGS. 11 and 12 . 
         FIG. 14  is a top view of the pillar and the roller raising assembly shown in  FIGS. 11-13 . 
         FIGS. 15 and 16  are perspective and front views of roller raising assemblies before actuating. 
         FIGS. 17 and 18  are perspective and front views of roller raising assemblies after raising a roller. 
         FIGS. 19 and 20  are flow charts of roller raising cylinder checking. 
         FIG. 21  is a representation of lock position sensing and control. 
         FIGS. 22 and 23  are representations of cylinder half travel sensors for controlling pneumatic valves. 
         FIG. 24  is a chart of checks and operation of hydraulic and pneumatic systems. 
         FIGS. 25 and 26  show connections between the lifting rollers and the loads to be lifted. 
         FIG. 27  shows the frame structure lifting a heavy object. 
     
    
    
     DETAILED DESCRIPTION 
     The frame structure  1  has two gantry crane structures  2  at its first and second ends  3  and  4 . Each gantry crane  2  has pillars  5  and a large cross beam  7  at the tops  9  of the pillars. The pillars  5  and cross box beams  7  are joined by horizontal beams  11  and truss beams  13 . The cross beams  7  have joint chairs  15  where other horizontal beams and truss beams may be joined. 
     Rollers  20  between pillars  5  are supported between roller raising assemblies  30 . 
     As shown in  FIG. 1 , the roller-raising assemblies  30  have upper plate anchor subassemblies  32  and lower plate anchor assemblies  34 . Hydraulic cylinders  60  and pistons  62  are actuated to separate plate anchor subassemblies  32  and  34  and to bring them together. 
     The pillars  5  are specially formed oppositely opening channel beams  40  spaced by welded plates  42 . Inward facing flanges  44  of the channel beams have teeth  46  milled therein. The teeth have flat upper edges  48  and outward sloped lower edge surfaces. 
     The channel beams are about ¾ inch thick and about 15 to 20 inches wide at their bases. Their flanges are about 5 to 7 inches in width. 
     The box beams  7  at the tops  9  of the pillars  5  are about 15 to 20 inches wide and about ½ inch thick. The horizontal beams  11  are square or round beams about 6 inches in diameter and ¼ inch thick. The truss beams are about 4 or 5 inches in width and about ¼ inch thick. Gussets (not shown) are welded to the horizontal beams and truss beams which are joined by bolts. The bolts are used for assembly and disassembly and for replacement with longer or shorter beams to change the length of the lifter  1 . The box beams  7  are welded to tops  9  of the pillars  5 . 
       FIG. 2  is an end view of the frame structure shown in  FIG. 1 . The end view shows pillars  5  and a large cross beam  7  welded to tops  9  of the pillars. The beam-attaching chair  15  is shown on the cross beam  7 . Edges of teeth  46  on the inner flanges  44  of the end channel beams  40  are shown. Roller  20  with axles  22  is supported on upper anchor assembly  32  of raising assembly  30 . Teeth  46  on the inner flanges  44  are engaged by locks pneumatically positioned in engagement or out of engagement with the teeth. 
       FIG. 3  is a modified side view of the frame structure shown in  FIG. 1 . The frame structure  1  and the gantry crane structures  2  at the ends  3  and  4  are shown. The lower horizontal beam  12  and truss beams  14  are used on both opposite sides  16 ,  17 . Similar rigidifying beams are used at the top  18  of the structure between the horizontal beams  11 . 
     Ends of the large rollers  20  and the raising assembly  30  with the upper and lower anchor assemblies  32 ,  34  are shown in  FIG. 2 . The pillars  5 , the large cross box beams  7  with the central beam connecting chairs  15  are also shown. 
       FIG. 4  is a top view of the frame structure shown in  FIG. 1 . The top view shows the large cross beams  7  at ends  3  and  4  and the rollers  20  below and centered on the raising assemblies  30  below the cross beams  7 . The beam-connecting chairs  15  are shown at the centers of the cross beams. The horizontal beams  11  are connected to the cross beams  7 . The truss beams  13  are connected to the chairs  15  and to the horizontal beams  11  at the sides  16  and  17 . 
       FIG. 5  is a perspective view of a heavy load support roller shown in  FIGS. 1-4 .  FIG. 6  is a side view of the load support roller shown in  FIG. 5 .  FIG. 7  is an end view of the load support roller shown in  FIGS. 5 and 6 .  FIGS. 5, 6 and 7  show perspective side and end views of roller  20  and axle  22  which extend from end plates  25  welded in the thick cylindrical rollers. The roller axles have grooves  26  near outer ends  27  of the axles  22 . The grooved portions of the axles fit in upward opening grooves in the tops of the lifting and lowering assemblies  30  shown in  FIGS. 1-4 . 
       FIG. 8  is a cross-section of the load support roller as shown in  FIG. 7 .  FIG. 9  is a perspective cross-sectional view of the load support roller.  FIG. 10  is a perspective cross-sectional detail of the load support roller. Roller  20  has short support axles  22  at opposite ends. Inner ends  21  of the support axles  22  are welded  23  in inner plates  24 , which are welded inside the rollers  20 . The axles  22  pass through central holes of outer plates  25  without being welded. The outer plates  25  are welded in ends of the roller  20 . The non-welding of the axles in the outer plates  25  prevents stress cracks which might form if the axles  22  were welded in the outer plate central holes. Grooves  26  are formed near the outer ends  27  of the axles  22 . The grooves keep the axles aligned and engaged in upward opening-receiving grooves in the roller raising and lowering assemblies  30  shown in  FIGS. 1-4 . 
       FIG. 11  is a perspective detail of a roller end raising assembly on a pillar. Pillar  5  is made from channel beams  40  that are welded to plates  50  and  52 . Before welding, teeth  46  are milled in one flange  44  of each channel beam. The teeth  46  have flat upper ledges  48  and upward and outward sloping edges  49  which lead to the ledges  48 . The channel beams  40  are spaced back-to-back and are welded in the spaced relationship to plates  50  and  52 . Plate  50  is spaced inward from toothed flanges  44  of the channel beams  40  to accommodate cylinders  60 . 
     Cylinders  60  and pistons  62  have vertical axes which are aligned with centers of inward facing upper and lower plates  33  and  35 . 
       FIGS. 11-14  are perspective front, side and top views of the pillar and the roller raising assemblies  30  shown in  FIGS. 1-4 . 
     Inward facing upper plates  33  have upward opening grooves  36  which receive grooves  26  near outer ends of axles  22  in rollers  20 . Cylinders  60  are fixed in the inward facing upper plates  33 , and pistons  62  are fixed in the inward facing lower plates  35 . Grooves  39  are formed in plates  33  and  35  to receive nuts which fasten threaded central ends of the cylinders and pistons to the plates. Backing plates  63 , as shown in  FIGS. 11-13 , are bolted to the outward facing plates  33  and  35  to hold the upper and lower anchor assemblies  32  and  34  on the toothed flanges  44  of the pillars  5 . The front plates have grooves  37  which receive the flanges  44  of the channel beams  40 . 
     Double-acting pneumatic actuators  64  advance or withdraw locks  68 . Pneumatic actuators  64  have cylinders  65  mounted on plates  66  welded to the upper and lower front plates  33  and  35 . Ends of the pneumatic cylinders  65  are bolted to the plates  66 . Inner ends of the cylinders  65  are held horizontally between the front plates and backing plates. Pistons are connected to locks  68 . Locks  68  slide in grooves between the plates. Locks  68  are extended to overlie ledges  48  of teeth  46  in channel beam flanges  44 . Locks  68  are withdrawn by the cylinders  65  and pistons before moving one of the upper or lower assemblies  32  or  34 . 
     The cylinder end and lock grooves are larger in the thicker front plates and smaller in the backing plates so that the cylinders, pistons and locks are centered on the locking teeth  46  of the channel beam flanges  44 . 
     Locks  68  are withdrawn into the grooves between front and backing plates when the pneumatic actuators  64  withdraw the locks. The locks  68  fully extend and partially extend from the grooves when the locks engage the teeth ledges  48 . When the locks are extended, more of the locks are in the grooves between the front and back plates, and a lesser part of the locks extends out from the plate. In an example, when a lock is engaged, one-third of each lock extends out of the plates, and two-thirds of the lock is retained in the plates&#39; grooves. 
       FIGS. 15 and 16  are perspective and front views of roller raising assemblies before actuating. 
       FIGS. 15 and 16  show the lifting and lowering assembly  30  close together before raising the upper assembly  32 . 
       FIGS. 17 and 18  are perspective and front views of roller raising assemblies after raising a roller before raising the upper assembly  32 .  FIGS. 17 and 18  show the lifting and lowering assembly  30  extended. Cylinder  60  is connected to the upper assembly  32 , and piston  62 , as shown in  FIGS. 17 and 18 , is connected to the lower assembly  34 . 
     In  FIGS. 15 and 16  all of the locks are extended into the teeth  46 . To raise the upper assembly  32 , locks in the upper assembly are withdrawn from the teeth  46  and hydraulic pressure is introduced at the upper end of the double acting cylinders  60 . The upper assembly is pushed upward, and then the locks in the upper assembly are engaged. 
     To move the lower assemblies  34  up from the position shown in  FIGS. 17 and 18 , locks in the lower assembly  34  are withdrawn from the teeth  46 , and hydraulic pressure is introduced into lower ends of the double-acting cylinders  60 . When the lower assembly  34  has been drawn upward to the upper assembly  32  by piston  62 , locks in the lower assembly are inserted into the teeth  46 . The movements are repeated to lift the assemblies  30  upward to the desired level. 
       FIGS. 19 and 20  are flow charts of roller raising cylinders and lock position sensing and checking. Each structure has four or more pillars  5 . One of the pillars is designated a master pillar. The master pillar has communications with the other pillars. 
     As shown in  FIG. 19 , the master pillar flow chart  100 , the system is idle  101 , meaning all locks are engaged, and valves of the pneumatic and hydraulic lines are closed. All sensors are checked and updated  103  for correct positions and readings. If an error is found, an error checker  105  sends error information  106  to an error information  107 . If no error is present, a message checker  109  checks for a message. If a message is present  111 , an OR gate  112  sends a slave pillar message  113 . A movement command  115  and starts a movement process  117 . If the checker  119  finds no message from a slave pillar, and a start movement  117  is in process, checker  121  checks that all sensors are in expected state. If not, the system is returned  122  to idle  101 . If all sensors are in expected state, the system stops and waits  123 . 
     Checker  125  checks that all slave pillars are ready. If not, the system  126  returns to idle  101 . If all slave pillar are ready, a drive current movement cycle  131  is started and a continue movement command  133  is sent to slaves. 
     A checker  135  checks whether the end of a movement process has occurred. 
     If the end of a movement process has occurred, an end of movement process  137  sends a stop command  139  to all slaves and returns the system to idle  101 . 
     If the end of a movement process has occurred, an end of movement cycle command  141  is sent to get the next movement cycle  143  and the system returns  136  to idle  101 . If an end of movement process has not occurred, a no end of movement cycle  141  sends a signal to get the next movement cycle  143  which is sent  146  to idle  101 . 
     A slave pillar flow chart  200  is shown in  FIG. 20 . All systems in a slave pillar start at idle  201 . 
     As shown in  FIG. 20 , the slave pillar flow chart  200 , the system starts at idle  201 , meaning all locks are engaged, and valves of the pneumatic and hydraulic lines are closed. All sensors are checked and updated  203  for correct positions and readings. If any error sensor is active, an error checker  205  sends error information  202  to an error control  207 . If no error is present, a message checker  209  checks for a message. 
     Checker  213  checks  215  for a further slave pillar. If yes, there is a slave pillar, the message is resent  217  to the slave pillar. If there is no further slave pillar or no message has been resent, a gate  221  continues a command movement  223 , starts  225  a movement command or stops  227  a command. Continuing a movement command  223  gets to the next movement cycle  229  and readies the system for the next movement by returning to idle  201 . 
     If the movement stop command  227  is made, an end movement process  231  returns  236  the system to idle  201 . 
     If a start movement command  225  starts a movement process  235 , checker  237  checks if there is a movement cycle from  235  and no message. If there is no message and no start a movement process, a signal  238  is returned to idle  201 . All sensors are checked  239  to determine they are in expected states. If not, a signal  240  is returned to idle  201 . If yes, the slave stops, sends an arrival message  241  to the master pillar control that all slaves are ready and returns  246  the pillar control to idle  201 . 
       FIG. 21  is a representation of lock position sensing and control. A controller box  301  is mounted on a flat outside of a pillar  5 . PLC controller units  303  are mounted within the box. 
     Sensors  311  and  313  are mounted on double-acting pneumatic cylinders  310  that move the locks  68 . Magnetic sensors  311  and  313  are read switches which sense the internal position of a piston  312  with a magnetic ring. Sensor  311  senses when lock  68  is fully extended into engagement with a tooth ledge  48 . Sensor  313  senses when the lock is fully withdrawn from engagement with teeth  46 . 
     There are four locks, four cylinders and eight sensors on each pillar  5 . 
       FIGS. 22 and 23  are representations of cylinder half travel sensors for controlling pneumatic valves.  FIGS. 22 and 23  show switches  340  with sensor arms  342  having rollers  344  for contacting indicators  346  attached to the hydraulic roller raising and lowering cylinders. As shown in  FIG. 22 , the roller  344  is in contact with the cylinder-attached indicator. The activation of the sensor arm  342  signals that the hydraulic cylinder is in a position that an associated valve should be opened and that air should be admitted to the outer ends of the pneumatic cylinder to push the lock  68  inward. The lock  68  may be over a ledge  48  of the teeth or in contact with the slope  49  leading to a ledge. 
     When the hydraulic cylinders are halfway in their upward or downward travel, the indicators  346  cause the sensor arms  342  to be deactivated to permit the supply of pressurized air to outer ends of cylinders  310  ( FIG. 21 ) to push the locks inward. 
     Each pillar  5  has its own control box with a processor, one solenoid-operated three-position hydraulic fluid valve, two two-position pressurized air valves that also are solenoid operated, and electrical sensor connections. Each pillar  5  has one double-acting lifting and lowering hydraulic cylinder and four pneumatic cylinders on one two-part raising and lowering assembly. Each pillar  5  has sixteen sensors. Eight sensors sense positions of the pistons in the four pneumatic cylinders and therefore the positions of the locks  68  attached to their piston rods. 
     One sensor senses the middle position of the hydraulic cylinder and piston extension. One sensor senses sufficiency of hydraulic pressure at the valves. One sensor senses sufficiency of pneumatic pressure at the valves. One sensor senses height of the lower raising and lowering assembly. One sensor senses height of the upper raising and lowering assembly. 
     Upper and lower limit switch sensors are connected to the raising and lowering assembly to limit movement of the hydraulic piston with relation to the cylinder. 
     One complete hydraulic system with a motor, pump, tank and relief is connected to each pillar. Two hydraulic lines, a high pressure line and a return line to the tank, are connected to the three-way hydraulic fluid valve in the pillar control box. 
     A single high pressure air system with a compressor, a pressurized tank and a pressure controller is provided for the entire structure. One pressurized air line leads from the pressurized air tank to each pillar control box. The pillar control box has a pressure regulator and oil mister which provides pressurized air to two two-way solenoid-operated valves. Two lines lead from a first two-way valve to the upper lifting assembly. Two lines lead from the second valve to the lower lifting assembly. Near the pneumatic cylinders each of the two lines is split. One line is split and connected to outer ends of the pneumatic cylinders. The other of the two lines is split for connections to inner ends of the pneumatic cylinders. The two-position valves either supply or exhaust pressurized air to or from opposite ends of the pneumatic cylinders. 
     Locking support wheels may be attached to the bottoms of the pillars to relocate the lifting structure. 
       FIG. 24  is a chart showing stages or states of the cycles of the hydraulic and pneumatic valves in five states for upward movement “U” to raise the rollers and loads and six states “D” for downward movement to lower the rollers and loads. 
       FIGS. 25 and 26  schematically show connections between the lifting rollers and the loads to be lifted. 
     Slings  80  are placed around rollers  20  that are mounted in the frame structure  1  between pillars  5 , as shown in  FIG. 1 . The slings are attached to lifting points  92  on load  90 , as shown in  FIG. 2 . Alternatively, the slings  80  are attached to the plates  94  below the load  90  or pass under the loads, as shown in  FIG. 26 . 
     The slings  80  may be steel ropes or cables, braided straps, chains or high tensile composite material. Examples of the heavy loads that may be lifted are large mining machines and sections thereof. 
       FIG. 27  shows the frame structure  1  lifting a heavy object  95 . In this case the heavy object  95  is a hopper. The slings  80  can be seen attaching the heavy object  95  to the rollers  20 . 
     While the invention has been described with reference to specific embodiments, modifications and variations of the invention may be constructed without departing from the scope of the invention, which is defined in the following claims.