Patent Publication Number: US-RE46723-E

Title: Alignment restoration device for load transporting apparatus

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/711,269, filed Dec. 11, 2012, now U.S. Pat. No. 8,561,733, issued Oct. 22, 2013, entitled ALIGNMENT RESTORATION DEVICE FOR LOAD TRANSPORTING APPARATUS, which claims priority to U.S. Provisional Application No. 61/576,657, filed Dec. 16, 2011, entitled METHOD AND APPARATUS FOR TRANSPORTING A LOAD, the contents of which are hereby incorporated by reference. This application is related to U.S. patent application Ser. No. 13/711,193, filed Dec. 11, 2012, now U.S. Pat. No. 8,573,334, issued Nov. 5, 2013, entitled ROTATION DEVICE FOR LOAD TRANSPORTING APPARATUS, the contents of which are hereby incorporated by reference. This application is also related to U.S. patent application Ser. No. 13,711,315, filed Dec. 11, 2012, now U.S. Pat. No. 8,490,724, issued Jul. 23, 2013, entitled CENTERING DEVICE FOR LOAD TRANSPORTING APPARATUS, the contents of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     This disclosure relates generally to apparatuses for transporting a load, and more particularly to apparatuses for moving heavy loads over small distances with the ability to fine tune the resultant position of the heavy load. 
     BACKGROUND 
     Moving extremely heavy loads has generally been a complicated task because the large forces involved in lifting and transporting the heavy loads. When possible, large loads are often transported by disassembling or breaking up the load into multiple smaller loads. However, this break-down and subsequent reassembly process can be very time consuming, especially when a heavy load is only to be moved a small distance, or needs to be repositioned. 
     For heavy loads that need periodic movement or adjustment, devices commonly referred to as “walking machines” or “walkers” were developed. These machines typically move the heavy loads over small distances in incremental stages. Walking machines are particularly useful for moving large structures, such as oil rigs, which often times need to be moved in order to properly position them over pre-drilled pipes in oil fields, or moved to a new location that is undergoing oil exploration. 
     Instead of using wheels driven by rotational forces to move heavy loads, walking machines typically use hydraulic lift cylinders to lift the load above a supporting surface, and then move or rotate the load relative to the supporting surface by transporting the load via rollers or tracks in the walking machines. U.S. Pat. No. 5,921,336 to Reed and U.S. Pat. No. 6,581,525 to Smith show two methods of using walking machines to move heavy loads, such as oil rig structures. The &#39;525 patent shows elongated beams under several rollers and lift cylinders, which allows the load from the lift cylinders and rollers to be spread over a large area. However, this disclosed system in the &#39;525 patent does not allow for movement of heavy load in a direction perpendicular to the long axis of the support beams. This is, movement of the heavy load is restricted in the walking device disclosed in the &#39;525 patent to only particular directions, which can make fine tuning of the position of the heavy load difficult. 
     SUMMARY 
     Embodiments of the present invention are directed to a load transporting apparatus that automatically aligns a support foot of the apparatus with a load-bearing frame connected to the load transporting apparatus during a recovery phase of an incremental walking movement. In particular, the load transporting apparatus includes a linking device attached to a support foot of the apparatus and a biasing device connected to the linking device that is deflected during non-linear load transporting movements, where the biasing device acts to automatically return the support foot to an aligned position relative to the load-bearing frame after a non-linear movement has been completed and the support foot is raised above a ground surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are diagrams of walking apparatuses attached to various loads according to embodiments of the invention. 
         FIGS. 2A, 2B, 2C, 2D, 2E, and 2F  are detail diagrams showing an example operational progression of walking apparatuses to move a load according to embodiments of the invention. 
         FIGS. 3A and 3B  are diagrams illustrating example connection arrangements used to connect a walking apparatus to a load according to embodiments of the invention. 
         FIG. 4  is a schematic diagram illustrating movement of a load along a substantially linear path according to embodiments of the invention. 
         FIG. 5  is a schematic diagram illustrating movement of a load along a curved path according to embodiments of the invention. 
         FIG. 6  is a schematic diagram of a top view of a walking apparatus according to embodiments of the invention. 
         FIG. 7A  is a side view of an example walking apparatus in a recovery position according to embodiments of the invention. 
         FIG. 7B  is a side view of the example walking apparatus shown in  FIG. 7A  in a load-movement position according to embodiments of the invention. 
         FIGS. 8A, 8B, 8C, and 8D  are side and top views of walking apparatuses that illustrate an example operation progression of a load transporting system according to embodiments of the invention. 
         FIG. 9A  is a top view of a walking apparatus in a perpendicular orientation according to embodiments of the invention. 
         FIG. 9B  is a side view of the walking apparatus shown in  FIG. 9A  in a load-movement position according to embodiments of the invention. 
         FIG. 9C  is a side view of the walking apparatus shown in  FIG. 9A  in a recovery position according to embodiments of the invention. 
         FIG. 10  is a top view of a walking apparatus after a load-movement phase of a walking cycle completed in a parallel direction according to embodiments of the invention. 
         FIG. 11  is a top view of a load movement system according to embodiments of the invention. 
         FIGS. 12A, 12B, 12C, 12D, and 12E  are diagrams of walking apparatuses with various alignment restoration devices according to embodiments of the invention. 
         FIG. 13  is a flow diagram illustrating method of operating a load transporting apparatus according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     As described above, walkers, or walking machines, are vehicles that are used for transporting very heavy loads, such as entire oil well drilling rigs. Such loads may be as great as several thousand tons and may be required to be sequentially positioned very precisely over spaced-apart well bores, for example. Embodiments of the present concept are directed to load transporting apparatuses, such as walking machines, for moving heavy loads over small distances with the ability to fine tune the resultant position of the heavy load. For ease of understanding, the terms, “walkers,” “walking machines,” “walking devices,” and “walking apparatuses” are used interchangeably below. Load transporting apparatuses or systems may include one or more walking machines. Additionally, a walking machine&#39;s subassembly of components that facilitate movement of the walking machine are referred herein as a “walking mechanism.” Walking machines may incorporate one or more walking mechanisms, depending on the specific configuration of a walking machine. 
     For example, with reference  FIGS. 1A and 1B , a load transporting system includes multiple walking machines that support a load being carried by the load transporting system.  FIGS. 1A and 1B  show examples of walking apparatuses attached to various loads according to embodiments of the invention. Referring to  FIG. 1A , multiple walking apparatuses  115  are positioned under or adjacent to an oil rig  100 . Typically, walking machines  115  are positioned at least near edge portions of a load  100  to balance the weight of the load over the various walking machines. However, specific situations may dictate that walking machines  115  are positioned in various other locations relative to the load  100 . 
     Referring to  FIG. 1B , multiple walking apparatuses  116  are positioned under or adjacent to a silo  101 . Although an oil rig load  100  and a silo  101  are respectively illustrated in  FIGS. 1A and 1B , walking machines may be used to move any type of relatively large load, such as bridge sections, ship sections, structures, etc. Additionally, although two walking machines are shown in  FIGS. 1A and 1B , more or fewer walking machines may be used to move loads  100 ,  101 . 
       FIGS. 2A-2F  provide an overview of an example operation of walking apparatuses to move a load according to embodiments of the invention. Referring to  FIG. 2A , walking apparatuses  215  are positioned on a base surface  205  below or adjacent to a load  200 . Referring to  FIG. 2B , the walking apparatuses  215  are attached to the load  200 , and are positioned above a base surface  205 . As described below, there are many possible connection variations that can be used to connect the walking apparatuses to a load  200 . Referring to  FIG. 2C , the walking apparatuses  215  are operated so that a foot portion of the walking apparatus contacts the base surface  205 . The walking apparatuses  215  may be operated substantially simultaneously, or may be operated in intervals depending on the conditions of the base surface  205  and the load  200  that is to be moved. 
     Referring to  FIG. 2D , the walking apparatuses  215  are operated to lift the load  200  above the base surface  205 . The walking apparatuses  215  may again be operated substantially simultaneously to lift the load  200 , or may be operated in intervals depending on the conditions associated with the desired move. 
     Referring to  FIG. 2E , the walking apparatuses  215  are operated to move the load  200  to the right. Although  FIG. 2E  shows the load  200  being moved to the right, the walking apparatuses can be operated to move the load in a variety of directions depending on the desired final location of the load. Referring to  FIG. 2F , the walking apparatuses  215  are operated to lower the load  200  to the base surface  205  and to raise the foot portions of the walking apparatuses above the base surface. That is, after the load  200  is positioned on the base surface  205 , the walking apparatuses  215  are further operated so that they are raised above the base surface. Here, the connection between the walking apparatuses  215  and the load  200  support the walking apparatuses  215  when they are raised above the base surface  205 . After the walking apparatuses  215  are raised above the base surface  205 , they are further operated to be repositioned for another movement walking step, such as by moving the foot portions of the walking apparatuses to the right so that they are in a position as shown in  FIG. 2B . That is, the base surface touching part of the walking apparatuses  215  (e.g., the support foot and related structures) is moved to the right while the walking apparatuses  215  are raised above the base surface  205 . After the walking apparatuses  215  have been repositioned, they are operated to be lowered to the base surface  205  as shown in  FIG. 2C . This completes a single walking cycle, and further walking cycles or steps can be performed by repeating the steps described above with respect to  FIGS. 2D to 2F . 
     As mentioned above, walking apparatuses can be connected to loads in a variety of ways depending on the specific conditions surrounding the load.  FIGS. 3A and 3B  illustrate two such connection schemes. Although two connection schemes are illustrated in  FIGS. 3A and 3B , embodiments of the invention are not limited to such connection schemes, as many different connection variations exist and are included in the scope of this concept. 
     Referring to  FIG. 3A , a walking apparatus  315  includes a support foot  340  to interface with a base surface  305  and a lift mechanism  320  to raise and lower a load  300 . In the embodiment shown in  FIG. 3A , the lift mechanism  320  of the walking apparatus  315  is attached to a connection frame  318 , which in turn is bolted to framework  310  supporting the load  300  with bolts  312  or other connection mechanisms. In some embodiments, the connection frame  318  may be part of the walking apparatus  315  and in some instances, may be permanently welded, bolted, or otherwise connected to the lift mechanism  320  of the walking apparatus. In other embodiments, the connection frame  318  may be separate from the walking apparatus  315 , and may only be temporarily used with the walking apparatus in certain situations. In these embodiments, for example, multiple different connection frames  318  may be built or used with specific load conditions or specifications. 
       FIG. 3B  shows different embodiments where the portions of a lift mechanism  320  of a walking apparatus  315  are directly connected to a support frame  310  structured to support a load  300  with bolts  312  or other connection mechanisms. The support frame  310  may be considered part of the load  300  in some instances where it is a permanent part of the load structure. For example, in instances where the load is a silo, such as shown in  FIG. 1B , the metal frame of the silo may be considered the support frame  310  of the load  300 , while also being part of the silo, and hence part of the load. In other cases, the support framework  310  may be an ancillary structure that is only used to stabilize and support the load  300  during movement of the load. 
       FIG. 4  is a schematic diagram illustrating movement of a load along a substantially linear path according to embodiments of the invention. Referring to  FIG. 4 , a load  400  is connected to multiple walking apparatuses  415 , which are used to move the load from an initial position X 1  to a final position X 2  along a substantially linear path. Here, that path is a horizontal path moving from left to right. This type of basis linear movement can be accomplished by a variety of walking systems. 
       FIG. 5  is a schematic diagram illustrating movement of a load along a curved path according to embodiments of the invention. Referring to  FIG. 5 , a load  500  is connected to multiple walking apparatuses  515 , which are used to move the load from an initial position X 3  to a final position X 4  along a non-linear path. Here, a reference center-point  502  of the load  500  at the initial position X 3  is moved to a reference center-point  592  of the load  500  at the final position X 4 . Unlike the linear movement shown in  FIG. 4 , this curved path of travel shown in  FIG. 5  requires that the walking apparatuses be steered, which can be accomplished using embodiments of the inventive walking apparatuses described below. 
       FIG. 6  is a schematic diagram of a top view of a walking apparatus according to embodiments of the invention. Referring to  FIG. 6 , a load transporting apparatus  615  is configured to move a load (e.g., element  100   FIG. 1 ) over a base surface  605  in one or more incremental steps each including a load-movement phase and a recovery phase. The load transporting apparatus  615  includes a lift mechanism  620  structured to lift a load-bearing frame  610  supporting the load and a support foot  640  connected to the lift mechanism, the support foot structured to interface with the base surface  605 . A roller assembly  630  is also coupled to the lift mechanism  620 . A travel mechanism  660  is coupled to the roller assembly  630  and is structured to displace the roller assembly relative to the support foot  640 . The load transporting apparatus also includes one or more linking devices  670  coupled to the support foot  640 , and one or more biasing devices  680  coupled to the linking devices. The biasing devices  680  are structured to become activated during a load-movement phase when the roller assembly  630  is non-linearly displaced by the travel mechanism  660  relative to the support foot  640 , and structured to return the support foot to an aligned position relative to the load-bearing frame  610  during a recovery phase. Here, the support foot  640  may be aligned with the load-bearing frame  610  when a longitudinal centerline of the support foot is parallel with a main beam of the load-bearing frame. 
     In these embodiments, the linking devices  670  are coupled to the biasing device  680  so that when the roller assembly  630  moves the load in a direction different than the orientation of the support foot  640 , a deflection force is generated and/or stored as potential energy in the biasing device  680 . This deflection force may be stored by deforming the biasing device  680  within the elastic region of a stress-strain curve associated with a material of the biasing device. For example, in embodiments where the biasing device  680  is a torsional bar, the deflection force transmitted to the biasing device during the non-linear displacement or movement may cause the torsional bar to twist. 
     The contact between the support foot  640  and the base or ground surface  605  creates substantial frictional forces that prevent the support foot from rotating or moving during the non-linear displacement. During the recovery phase of the walking cycle, the support foot  640  is raised above the base surface  605 , which eliminates the frictional forces between the foot and the base surface. Once the support foot  640  begins to lose contact with the base surface  605 , the potential energy stored in the biasing device  680  is used to return the support foot to an aligned position relative to the load-bearing frame  610 . The alignment of the load-bearing frame  610  is dictated by the movement of the roller assembly  630  by the travel mechanism  660 . Hence, when the roller assembly  630  is non-linearly displaced (e.g., moved such as shown in  FIG. 5 ), the orientation of the load-bearing frame  610  becomes skewed from the orientation of the support foot  640 . In the above example, where the biasing device  680  is a torsional bar, the support foot  640  is returned to a positioned aligned relative to the load-bearing frame  610  when the support foot loses contact with the base surface  605  and the torsion bar is allowed to “untwist,” thereby re-orienting the support foot. In other words, the torsion bar is activated when an angular displacement occurs between the support foot  640  and the load-bearing frame  610 , where the activation of the torsion bar including a torquing force being applied to the torsion bar. 
     Although a torsion bar is discussed as the biasing device  680 , may different types of biasing devices may be used in other embodiments, such as leaf springs, coil springs, chains, hydraulic cylinders, motors, or any other type of device that can be deflected and/or store potential energy to apply a realignment force to the support foot  640 . 
       FIG. 6  is presented in a schematic style view as many possible variations in the appearance and mechanical structure of the load transporting apparatus  615  exist.  FIGS. 7A and 7B  provide a more detailed view of one embodiment of a load transporting apparatus.  FIG. 7A  is a side view of an example walking apparatus in a recovery position according to embodiments of the invention.  FIG. 7B  is a side view of the example walking apparatus shown in  FIG. 7A  in a load-movement position according to embodiments of the invention. Referring to  FIGS. 7A and 7B , a load transporting or walking apparatus  715  includes a lift mechanism  720 , a roller assembly  730 , a roller track  750 , and a support foot  740 . The lift mechanism  720  may include a hydraulic jack suspended from a horizontal beam of the load-bearing frame  710 . Additional details regarding the structure of the load transporting apparatus  715  can be found in co-pending application Ser. No. 13/711,193, entitled ROTATION DEVICE FOR LOAD TRANSPORTING APPARATUS, the contents of which are herein incorporated by reference in their entirety. 
     The roller track  750  of the walking apparatus  715  may be coupled to the support foot  740  with a connection mechanism that allows the support foot to rotate relative to the roller track. Various connection mechanisms may be used to facilitate this relative rotation, such as a rotation pin described below in  FIG. 9  and in the above mentioned application Ser. No. 13/711,193. In addition, the lift mechanism  720  may be structured to allow the roller assembly  730  to rotate about a substantially vertical axis in the center of a cylinder rod of the lift mechanism. That is, the roller assembly  730  may also be free to rotate around the cylinder rod of the lift mechanism  720 . 
     The walking apparatus  715  may also include a travel mechanism  760  that is connected to the roller track  750  and coupled to the roller assembly  730  such that when the travel mechanism is activated, the roller assembly moves relative to the roller track. In the embodiment shown in  FIGS. 7A and 7B , the travel mechanism  760  includes two travel cylinders mounted on the roller track  750  on opposite sides of the roller track. Here, the travel cylinders of the travel mechanism  760  may balance the load being moved by the roller assembly  730  over the roller track  750 . In other embodiments, one travel cylinder, or three or more travel cylinders may be used to move the roller assembly  730  relative to the roller track  750 . In other embodiments, the travel mechanism  760  may include different movement structures, such as pulleys, levers, winches, tracks, etc. 
     In the embodiments shown in  FIGS. 7A and 7B , the roller assembly  730  may include a plurality of rollers or roller chain that rotate as well as roll on the roller track  750 . That is, in some embodiments, the roller assembly  730  may include a WBOT series roller assembly from Hilman Rollers. Due to the configuration of the roller chain  730  of the roller assembly  730  and the tolerance between the roller assembly and the roller track  750  of the walking machine  715 , the rollers of the roller chain will typically be engaged with the roller track during operation and use of the walking machine. 
     The roller assembly  730  may be secured to the lower end of the lift mechanism  720 , with the roller assembly being captured within a U-shaped roller track  750 . The roller assembly  730  may be configured to roll along the bottom inside surface of the roller track  750  as well as along the underside of the two upper flanges of the roller track. The one or more travel cylinders  760  may be coupled between the lift mechanism  720  and the roller track  750 . Accordingly, as will be understood from the more detailed discussion below, these travel cylinders  760  permit for the translation of the roller track  750  relative to the lift mechanism  720  and vice versa. As discussed above, the roller track  750  may be secured to the elongate ground-engaging foot  740  (support foot) via a rotational pin (not shown in  FIG. 7 , but similar to element  955  of  FIG. 9 ), which enables the roller track to be rotationally positioned relative to the foot for steering of the walking machine  715 . 
     As shown in  FIGS. 7A and 7B , a linking mechanism  770  is coupled to the support foot  740  and a biasing device  780  (shown more clearly as element  880 ) in  FIG. 8A ). In some embodiments, the linking mechanism  770  may include a first linking device attached at a first end of the support foot  740 , where a second linking device connected to a second end of the support foot opposite of the first end of the first support foot (such as shown in  FIGS. 6 and 8A ). The biasing device  780  may be coupled between the first and second linking devices of the linking mechanism  770 . 
     In the embodiments shown in  FIGS. 7A and 7B , the linking mechanism  770  includes a first linking rod  772  connected to the support foot  740  with a first pivot joint  771 . In some embodiments, the first pivot joint  771  may be a spherical rod end bearing configured to allow movement in three degrees of freedom. In other embodiments, the first pivot joint  771  may be another type of joint, such as a hinge joint, that restricts movement to one or two degrees of freedom. 
     The linking mechanism  770  may also include a second linking rod  774  connected to the first linking rod  772  with a second pivot joint  773 . As with the first pivot joint  771 , the second pivot joint  773  may be a spherical rod end bearing, or any other type of joint. The second linking rod  774  may further be connected to the load-bearing frame  710 . In other embodiments, the one or more biasing devices  780  are also coupled to the load-bearing frame  710 . 
     As shown in  FIGS. 7A and 7B , the first and second pivot joints  771 ,  773  allow linking mechanism  770  to move vertically with the support foot  740  without deflecting or otherwise activating the biasing device  780 . 
     As shown in co-pending application Ser. No. 13/711,315, entitled CENTERING DEVICE FOR LOAD TRANSPORTING APPARATUS, the contents of which is herein incorporated by reference in its entirety, a walking apparatus  715  may also include one or more guide devices positioned adjacent to the roller assembly  730 , and one or more biasing devices coupled to the guide devices. Here, the biasing devices may be structured to become deflected during a load-movement phase when the movement of the roller assembly  730  deviates from a set direction of travel, and structured to return the support foot to a centered position relative to the support foot  740  during a recovery phase. 
       FIGS. 8A, 8B, 8C, and 8D  are side and top views of walking apparatuses that illustrate an example operation progression of a load transporting system according to embodiments of the invention. Here,  FIGS. 8A-8C  may show a load-movement phase of a walking cycle, while  FIG. 8D  may show a recovery phase of a walking cycle, where the walking apparatus is in a spin steering mode. 
     Referring to  FIG. 8A , a walking apparatus includes a support foot  840  positioned on a base surface  805  and connected to roller track  850 . The roller track  850  is structured to allow a roller assembly  830  to move relative to the roller track when activated by a travel mechanism  860 . A lift mechanism  820 , such as hydraulic jack, is connected between the roller assembly  830  and load-bearing frame  810 . A linking device  870  includes a first linking member  872  that is connected to the support foot, and a second linking member  874  that connects the first linking member to the load-bearing frame  810 . A biasing device  880  is also connected to the linking device  870 , and structured to become deflected or activated during a non-linear movement of the roller assembly  830  relative to the support foot  840 . As shown in  FIG. 8A , the walking apparatus  815  is in an initial position of a walking cycle in a spin steering mode. The roller tracks  850  of each walking apparatus  815  are oriented in a desired direction of travel. Here, in this first step of making a spin movement, the lift mechanisms  820  are activated to lift the load-bearing frame  810  (and load) above the base surface. 
     Referring to  FIG. 8B , a step in a walking motion of the walking machine is illustrated. Specifically, as indicated by the arrows showing rotation of the load-bearing frame  810 , the travel mechanism  860  is activated to displace the roller assembly  830  relative to the roller track  850  as shown. In this second step the walking system is moved in a circular or spin direction. Here, the travel cylinders of the travel mechanism  860  are actuated and the load-bearing frame  810  moves to a new angle. The support feet  840  are on the support surface and an angle of displacement occurs between the load-bearing frame  810  and the support feet. This non-linear movement or angular displacement causes an angular change in the biasing device  880 . In embodiments where the biasing device  880  is a torsion bar, the resulting torque on the torsion bar causes the part of the linking device  870  to be in compression and causes another part of the linking device to be in tension. 
     Referring to  FIG. 8C , the travel mechanism  860  has finished moving the roller assembly  830  and load-bearing frame  810 . Additionally, the lift mechanism  820  has been activated to lower the load and load-bearing frame  810 . Here, the load-bearing frame  810  has just contacted the ground surface. However, the support foot  840  is still positioned on the ground surface as well. Hence, the biasing devices  880  are still in a deflected, activated, or biased state. 
     Referring to  FIG. 8D , the lift mechanism  820  is continued to be operated such that the support foot  840  loses contact with the ground surface. As soon as this connection between the support foot  840  and the ground surface disappears, the biasing device  880  causes the support foot to “snap” back into alignment with the load-bearing frame  810  as shown. 
       FIGS. 9A-9C  illustrate another embodiment of a walking apparatus. Here,  FIG. 9A  is a top view of a walking apparatus in a perpendicular orientation according to embodiments of the invention.  FIG. 9B  is a side view of the walking apparatus shown in  FIG. 9A  in a load-movement position where the linking devices have been removed for clarity sake.  FIG. 9C  is a side view of the walking apparatus shown in  FIG. 9A  in a recovery position with the linking devices added back in for reference purposes. 
     Referring to  FIGS. 9A-9C , a walking apparatus  915  includes a lift mechanism  920  coupled to a load-bearing frame  910  that supports a load to be moved. The lift mechanism  920  is connected to a roller assembly  930  that is positioned on a roller track  950 . The roller assembly  930  is moved relative to the roller track  950  with one or more travel mechanisms  960 . The roller track  950  is coupled to a support foot  940  with a rotation pin  955 , such as a king pin or other connection means that allows rotation of the roller track relative to the support foot as described in the rotation device application (Ser. No. 13/711,193) cited above. A linking device  970  is coupled between the support foot  940  and the load-bearing frame  910 . A biasing device  980  is connected to the linking device  970 . As described above, the biasing device  980  becomes deflected or activated when the roller assembly  930  moves in a non-linear direction relative to the support foot  940 . For example, the roller track  950  is oriented perpendicular to the orientation of the support foot  940  in  FIG. 9A . As the roller assembly  930  moves in the direction of the orientation of the roller track  950 , the roller assembly and the load-bearing frame will also move substantially perpendicularly to the orientation of the support foot  940 . 
     Here, the movement of the roller assembly  930  in this orientation does not activate or deflect the biasing device  980  because the linking devices  970  include joints that allow for the free movement of the roller assembly. The linking devices  970  may be structured in this manner because the orientation of the support foot  940  relative to the load-bearing frame  910  does not change. 
     This can also be seen when the roller assembly is moved parallel to the orientation direction of the support foot, as shown in  FIG. 10 . Referring to  FIG. 10 , a walking apparatus  1015  has just completed a load-movement phase of a walking cycle where a roller track  1050  is oriented in the same direction as a support foot  1040 . Here, the roller assembly  1030  was moved to the right, along with the load-bearing frame  1010 , as shown. The joints of the linking device  1070 , however, allow the linking device to be angled from the linear movement without deflecting or otherwise activating the biasing device  1080 . During a recovery phase, the load-bearing frame  1010  is lowered and the support foot  1040  is raised above a base surface. The support foot  1040  can then be repositioned relative to the roller assembly  1030  by activation of the transport mechanism  960  ( FIG. 9B ). 
     Some of the embodiments discussed above rely on the load-bearing frame as a reference point to realign the support feet during non-linear movements of the load. However, in other embodiments, other linking and biasing devices can be utilized to maintain alignment of the support feet. Some of these techniques are discussed below with respect to  FIGS. 11 and 12A-12E . 
       FIG. 11  is a top view of a load movement system according to embodiments of the invention. Referring to  FIG. 11 , multiple load transporting apparatuses  1115 ,  1116 ,  1117 ,  1118  are used to move a load supported by a load-bearing frame  1110 . Each of these load transporting apparatuses  1115 ,  1116 ,  1117 ,  1118  include a roller track  1150 , a roller assembly  1130  that moves relative to the roller track, and a support foot  1140 . Here, load transporting apparatuses that are in orientation-rows are connected with one or more biasing devices  1182 ,  1184 . In particular, the support foot  1140  of a first load transporting apparatus  1115  is connected to the support foot of a second load transporting apparatus  1116  with two biasing devices  1182 A and  1182 B. These biasing devices  1182 A,  1182 B ensure that the first and second load transporting apparatuses  1115 ,  1116  are maintained in alignment with one another and the load-bearing frame  1110 . 
     Here, the linking devices include a first linking device  1182 A coupled between a first side of a first end of the first support foot  1140  and a first side of a first end of the second support foot  1140 , and a second linking device  1182 B coupled between a second side of the first end of the first support foot and a second side of the first end of the second support foot. The placement of the first and second linking devices  1182 A,  1182 B may ensure that the support feet  1140  are aligned together during a non-linear movement. 
     Similarly, the support foot  1140  of a third load transporting apparatus  1117  is connected to the support foot of a fourth load transporting apparatus  1118  with two biasing devices  1184 A and  1184 B. These biasing devices  1184 A,  1184 B ensure that the third and fourth load transporting apparatuses  1117 ,  1118  are maintained in alignment with one another and the load-bearing frame  1110 . 
     Although  FIG. 11  illustrates one example embodiment of biasing device connections that can maintain alignment of a support foot relative to a load-bearing frame, many different configuration variations exist.  FIGS. 12A, 12B, 12C, 12D , and  12 E are diagrams of walking apparatuses with various alignment restoration devices that illustrate some of these variations according to embodiments of the invention. 
     Referring to  FIG. 12A , a linking device  1271  is connected between a first support foot  1240  of a first load transporting apparatus  1215  and a second support foot  1241  of a second load transporting apparatus  1216 . The linking device  1271  may be attached to the first support foot  1240  with a first joint  1291 , and may be attached to the second support foot  1241  with a second joint  1292 . In some embodiments, the first and second joints  1291 ,  1292  may be ball joints that allow rotational movement. The linking device  1271  may be rigid rod, or may include a section of chain. 
     Referring to  FIG. 12B , a linking device  1272  is connected between a first support foot  1240  of a first load transporting apparatus  1215  and a second support foot  1241  of a second load transporting apparatus  1216 . The linking device  1272  may be rigidly attached to the first support foot  1240 , but may be attached to the second support foot  1241  with a first biasing device  1281  and a second biasing device  1282 . The first and second biasing devices  1281 ,  1282  may be placed on opposite sides of the linking device  1272  to provide a balanced system to return the support feet  1240 ,  1241  to uniform alignment after a non-linear movement. 
     Referring to  FIG. 12C , a first biasing device  1283  and a second biasing device  1284  are connected between a first support foot  1240  of a first load transporting apparatus  1215  and a second support foot  1241  of a second load transporting apparatus  1216 . This embodiment may be similar to the shown in  FIG. 11 , except that the first and second biasing devices  1283 ,  1284  are specified as spring devices. 
     Referring to  FIG. 12D , the support foot  1240  of a load transporting apparatus  1215  is connected to a load-bearing frame  1210  via a first linking cylinder  1273  and a second linking cylinder  1274 . The first and second linking cylinders  1273 ,  1274  may be hydraulic cylinders that are activated during a recovery phase of a walking cycle to return the support foot  1240  to alignment with the load-bearing frame  1210 . Alternatively, the first and second linking cylinders  1273 ,  1274  may be spring cylinders that automatically return the support foot  1240  to alignment with the load-bearing frame  1210  during a recovery phase of a walking cycle without additional operator input. 
     Referring to  FIG. 12E , a support foot  1240  of a load transporting apparatus  1215  is connected at each corner to a biasing device  1285 ,  1286 ,  1287 ,  1288 . These biasing devices  1285 ,  1286 ,  1287 ,  1288  may ensure that the support foot  1240  is maintained in alignment with a load-bearing frame during the recovery phase of a walking cycle by releasing potential energy stored during compression and/or elongation during non-linear movements. 
       FIG. 13  is a flow diagram illustrating method of operating a load transporting apparatus according to embodiments of the invention. In particular, the flow diagram of  FIG. 13  illustrates a method of aligning a support foot of a load transporting device relative to a load-bearing frame during a load-transporting movement. The load transporting device includes a roller assembly coupled to a lift mechanism, a travel mechanism structured to displace the roller assembly relative to the support foot, one or more linking devices coupled to the support foot, and one or more biasing devices coupled to the linking devices. 
     Referring to  FIG. 13 , a flow begins at process  1305  where the lift mechanism is activated to lower the support foot to a ground surface and raising a load supported by the load-bearing frame. In process  1310 , the travel mechanism is activated to displace the roller assembly connected to the lift mechanism relative to the support foot and ground surface, thereby moving a position of the load. Depending on the movement of the travel mechanism relative to the support foot, the position of the support foot may be aligned with the load-bearing frame or may not be aligned with the load-bearing frame. As discussed above, when the load is moved in a direction perpendicular to the orientation of the support foot, or moved parallel to the orientation of the support foot, the support foot typically remains aligned with the load-bearing-frame. If the load is moved in a different direction relative to the support foot, such as when the load is being steered in a non-linear path, the support foot can become misaligned with the load-bearing frame. In process  1315 , it is observed whether the resulting position of the support foot is aligned with the load-bearing frame. 
     When the support foot remains aligned with the load-bearing frame, the flow proceeds to process  1320  where the lift mechanism is activated to lower the load and raise the support foot. However, when the support foot is not aligned with load-bearing frame, the biasing device is deflected via the linking device as the load is displaced as shown in step  1325 . That is, the biasing devices are deflected when movement of the roller assembly results in an angular displacement between a centerline of the support foot and an orientation of the load-bearing frame. In process  1330 , the lift mechanism is activated to lower the load and raise the support foot from the ground surface. As the support foot loses contact with the ground surface, the deflected biasing device acts on the support foot to align the support foot with the load-bearing frame, as shown in step  1335 . That is, the centerline of the support foot is automatically aligned relative to the orientation of the load-bearing frame. After step  1335  or process  1320 , the flow may include optional process  1340  where the lift mechanism is repositioned with respect to the support foot. If further walking steps are needed to move the load to a final position, the flow may return to process  1305  to initiate another walking cycle. 
     As described above, some embodiments of this invention are directed to a load transporting apparatus configured to move a load over a ground surface in one or more incremental steps each including a load-movement phase and a recovery phase. To move the load, the load transporting apparatus is coupled to a load-bearing frame configured to support the load. The load transporting apparatus includes a first support foot structured to interface with the ground surface, the first support foot having a length, width, and longitudinal centerline bisecting the width of the first support foot. The load transporting apparatus also includes a second support foot structured to interface with the ground surface, the second support foot also having a length, width, and longitudinal centerline bisecting the width of the second support foot. 
     First and second roller tracks are respectively coupled to the first support foot and second support foot via a first king pin connector and a second king pin connector. Additionally, first and second roller assemblies are respectively positioned on the first and second roller tracks. Each roller assembly includes a roller frame and one or more rollers set in the roller frame. First and second lift mechanisms are respectively coupled to the first and second roller assemblies. Each of the first and second lift mechanisms includes a lift cylinder connected to the load-bearing frame, and a cylinder rod, where each of the first and second lift mechanisms are structured to lift the load-bearing frame at the start of the load-movement phase. 
     The load transporting apparatus also includes first and second travel mechanisms respectively coupled to the first and second roller assemblies. Each of the travel mechanisms are structured to move the respective roller assembly relative to the respective support foot during the load-movement phase. A first linking device coupled to the first support foot, and a second linking device coupled to the second foot. A first biasing device is connected to the first linking device, where the first biasing device is structured to become activated during a load-movement phase when the first roller assembly is non-linearly displaced by the first travel mechanism relative to the first support foot, and structured to return the first support foot to an aligned position relative to the load-bearing frame during a recovery phase. A second biasing device is connected to the second linking device, where the second biasing device is structured to become activated during a load-movement phase when the second roller assembly is non-linearly displaced by the second travel mechanism relative to the second support foot, and structured to return the second support foot to an aligned position relative to the load-bearing frame during a recovery phase. 
     In some embodiments, the first linking device is coupled between the first support foot and the second support foot. In these embodiments, the second linking device is also coupled between the first support foot and the second support foot, as shown in  FIG. 11 , for example. In other embodiments, the first and second biasing devices are respectively coupled to the load-bearing frame, such as in  FIG. 7A , for example. 
     Some embodiments of the invention have been described above, and in addition, some specific details are shown for purposes of illustrating the inventive principles. However, numerous other arrangements may be devised in accordance with the inventive principles of this patent disclosure. Further, well known processes have not been described in detail in order not to obscure the invention. Thus, while the invention is described in conjunction with the specific embodiments illustrated in the drawings, it is not limited to these embodiments or drawings. Rather, the invention is intended to cover alternatives, modifications, and equivalents that come within the scope and spirit of the inventive principles set out herein.