Abstract:
The present disclosure relates to an apparatus for moving a dolly longitudinally along its base. The apparatus comprises a first motorized drive that transmits a drive from a motorized unit to a first rotating axle mounted on the apparatus. A second motorized drive transmits the drive from the first rotating axle to the dolly, thereby moving the dolly longitudinally along the base. The apparatus is environmentally friendly and may be operated in a wide range of temperatures, including in sub-freezing climates.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to the field of freight transport. More specifically, the present disclosure relates to an apparatus having mechanical drives for moving a dolly. 
       BACKGROUND 
       [0002]    The transport industry relies heavily on containers, such as so-called multi-modal containers that may be conveniently be transported in ships, on trains or pulled by tractor trailers. In the particular case of the trucking industry, flatbed trailers are commonly used for carrying loads, with or without containers. 
         [0003]    Loading and unloading of trailers and containers may benefit from the use of heavy equipment but nevertheless remains a manpower-intensive operation. Billions of dollars worth of merchandize are shipped worldwide on a daily basis. Given such numbers, rapid loading and unloading of freight vehicles is an important economical requirement. 
         [0004]    Within large, fixed manufacturing plants and storage plants, apparatuses for loading and unloading of containers or flatbed trailers are oftentimes permanently installed, for example having their foundations embedded in a concrete floor. It becomes fairly easy to ensure that such a floor is smooth, level and nearly horizontal. Motion of such apparatuses is generally provided by use of hydraulic systems. Hydraulic systems are economical and powerful. Use of hydraulic systems provides loading equipment flexibility in terms of adapting to all kinds of loads. 
         [0005]    On temporary sites or on outdoor sites, loading equipment is subjected to additional constraints. These apparatus may need to be installed on uneven ground or on a modest slope. It may be required to change the location of loading equipment from time to time, according to constraints of a particular application. Hydraulic systems may not be able to withstand a wide variation of outdoor temperatures, between hot summer temperatures and sub-freezing winter climates. Additionally, the use of hydraulic systems may cause environmental concerns, as even a minor oil leak may cause stoppage of loading equipment and costly site decontamination. 
         [0006]    Therefore, there is a need for improved loading and unloading techniques enabling rapid and economical freight manipulation, in various site and weather conditions, while ensuring proper care for the environment. 
       SUMMARY 
       [0007]    According to the present disclosure, there is provided an apparatus for moving a dolly longitudinally along a base of the apparatus. A first mechanical drive transmits a drive from a motorized unit to a first rotating axle mounted on the apparatus. A second mechanical drive transmits the drive from the first rotating axle to the dolly. 
         [0008]    The foregoing and other features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Embodiments of the disclosure will be described by way of example only with reference to the accompanying drawings, in which: 
           [0010]      FIG. 1  is a perspective view of an example of apparatus supporting a dolly; 
           [0011]      FIG. 2  is a perspective view of the apparatus of  FIG. 1 , without a dolly and with supporting plates removed; 
           [0012]      FIG. 3  is a top plan view of the apparatus of  FIG. 1 , without a dolly and with supporting plates removed; 
           [0013]      FIG. 4  is a top plan view of supporting plates of the apparatus of  FIG. 1 ; 
           [0014]      FIG. 5  is a detailed view showing an attachment point of a supporting plate on the apparatus of  FIG. 1 ; 
           [0015]      FIG. 6  is a first, side elevation cutaway view of a base for the apparatus of  FIG. 1 ; 
           [0016]      FIG. 7  is a second, side elevation cutaway view of a base for the apparatus of  FIG. 1 ; 
           [0017]      FIG. 8  is a detailed view of an extremity of the cutaway view of  FIG. 7 ; 
           [0018]      FIG. 9  is a top plan view of the extremity illustrated in  FIG. 8 ; 
           [0019]      FIG. 10  is a further detailed view of the extremity illustrated in  FIG. 8 , showing a point of attachment of an electric generator; 
           [0020]      FIG. 11  is a detailed view of a ladder attached to the apparatus of  FIG. 1 ; 
           [0021]      FIG. 12  is an elevation cutaway view of the apparatus of  FIG. 1 ; 
           [0022]      FIG. 13  is a detailed view of an aspect of  FIG. 12 , showing a channel for a roller chain; 
           [0023]      FIG. 14  is a perspective cutaway view of the apparatus of  FIG. 1 , showing details of a motorized unit and of two mechanical drives; 
           [0024]      FIG. 15   a  is a perspective cutaway view of the apparatus of  FIG. 1 , showing details of an end of the apparatus opposite from the motorized unit of  FIG. 14 ; 
           [0025]      FIG. 15   b  shows details of an upright plate according to an embodiment; 
           [0026]      FIG. 16  is a top plan view of an actuator for transmitting motion from the apparatus of  FIG. 1  to a dolly; 
           [0027]      FIG. 17  is a detailed view of an extension of the actuator of  FIG. 16 ; 
           [0028]      FIG. 18  is a side elevation view of the actuator of  FIG. 16 ; 
           [0029]      FIG. 19  is a detailed view of a traction member of the actuator of  FIG. 16 ; 
           [0030]      FIG. 20  is a front elevation view of a dolly mounted on the apparatus of  FIG. 1 ; and 
           [0031]      FIG. 21  is a perspective, cutaway view of a power generation assembly of the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Various aspects of the present disclosure generally address one or more of the problems of rapidly and economically loading and unloading containers and trailers, in various site and weather conditions. A disclosed apparatus for moving a dolly longitudinally along its base comprises a first mechanical drive capable of transmitting a drive from a motorized unit to a first rotating axle mounted on the apparatus. A second mechanical drive then transmits the drive from the first rotating axle to the dolly, enabling the dolly to move longitudinally in relation to the base. A dolly may be pushed from the apparatus onto a trailer or in a container. Likewise, a dolly may be pulled from a trailer or from a container, and brought onto the base of the apparatus. 
         [0033]    The following terminology is used throughout the present disclosure: 
         [0034]    Load: freight, cargo or goods. 
         [0035]    Dolly: a platform for carrying heavy loads. 
         [0036]    Base: a supporting part of a structure. 
         [0037]    Roller chain: a chain for mounting on sprockets, for transmitting a force. 
         [0038]    Drive: a propulsion effort. 
         [0039]    Motorized unit: an ensemble generating a drive. 
         [0040]    Mechanical drive: mechanical system for transmitting a drive. 
         [0041]    Rotating axle: a shaft for transmitting a rotating movement to wheels, for example to sprockets. 
         [0042]    Longitudinally: related to a lengthwise dimension. 
         [0043]    Actuator: device for exerting a motion. 
         [0044]    Proximal end: a part of an apparatus near a point of origin that is, in the present disclosure, near the motorized unit. 
         [0045]    Distal end: a part of an apparatus distant from a point of origin. 
         [0046]    Extension: device appended to another one. 
         [0047]    Link: an attachment point for a chain, a cable or a rope. 
         [0048]    Load balancing system: device for transmitting force between two or more points, whereby a load is distributed in a substantially even manner. 
         [0049]    Traction plate: a plate for transmitting a drive. 
         [0050]    Operably connected: directly or indirectly connected in a functional manner. 
         [0051]    Pivot: a pin linking two elements while allowing rotation of one in function of the other. 
         [0052]    Speed reducer: a device for transmitting motion from a rotating shaft to another shaft rotating at a lower speed. 
         [0053]    Sprocket: a toothed wheel for driving a roller chain or for being driven by a roller chain. 
         [0054]    Support: component supporting another. 
         [0055]    Controller: electronic means for controlling an equipment. 
         [0056]    Remote control: device connected to a controller via wired or wireless link for controlling an equipment. 
         [0057]    Leg: a generally vertical support for a structure. 
         [0058]    Leveling: bringing to a substantially horizontal position. 
         [0059]    Power supply: equipment providing an electrical feed. 
         [0060]    External power source: electrical supply external to the present apparatus. 
         [0061]    Voltage converter: equipment for converting a voltage as received from a source to another voltage usage by the present apparatus. 
         [0062]    Electric generator: electrical supply integral to the present apparatus. 
         [0063]    Selector: control means for choosing one electrical source or another. 
         [0064]    Referring now to the drawings,  FIG. 1  is a perspective view of an example of apparatus supporting a dolly. An apparatus  10  may be used for loading and unloading dollies onto or from containers, flatbed trucks, and the like. The apparatus  10  as shown comprises a base  12 , a plurality of adjustable legs  14 , a plurality of supporting plates  16  having various formats and textures, a ladder  18  and various devices  20  for providing a drive to the apparatus  10 . The devices  20 , comprising a motorized unit, a controller and a power generation assembly, are shown in details in following Figures. A dolly  22  is mounted on the base  12  of the apparatus  10 . The dolly  22  may be used for carrying heavy loads and may be pushed on or pulled from a container, a platform of a flatbed truck, and the like. Various elements of the apparatus  10  may be formed of steel, galvanized steel, aluminum, or other suitable materials and alloys, using beams and plates of sufficient gauge, with sufficient tensile and compression strength for a desired rated payload of the apparatus  10 . The various beams, plates and other components may be screwed, bolted, riveted or welded together. Various materials may be used to construct the various elements of the apparatus  10 . Those of ordinary skill in the art will be able to readily select the materials and assemble the components of the apparatus  10  for safe and reliable operation. 
         [0065]      FIG. 2  is a perspective view of the apparatus of  FIG. 1 , without a dolly and with supporting plates removed, showing details of the base  12 .  FIG. 3  is a top plan view of the apparatus of  FIG. 1 , without a dolly and with supporting plates removed. In the examples of  FIGS. 1 ,  2  and  3 , the base  12  is generally shaped as an elongated rectangular frame, having a number of longitudinal and transversal beams  24  sufficient to support the masses of the apparatus  10 , of the dolly  22  and of a load carried by the dolly  22 . The shape of the base  12  as shown is adapted to move dollies that are constructed for loading onto traditional containers. Of course, a different base could have a different shape depending on a shape of dollies intended for other applications. The shape of the base  12  as shown is therefore a non-limiting example. The base  12  rests on the adjustable legs  14  (shown in earlier Figures). Those of ordinary skill in the art will be able to construct the base  12  for supporting such masses, so the structure of the base  12  as shown is a non-limiting example. The base  12  further comprises two channels  26  running along much of the length of the base  12  for carrying roller chains (shown on later Figures). Areas  27  and  29  show connection points for rotating axles (shown on later Figures). 
         [0066]      FIG. 4  is a top plan view of supporting plates of the apparatus of  FIG. 1 . Various supporting plates  16   1 - 16   5  are mounted on the base  12  and provide a rolling surface for the dolly  22  while also providing a surface for workers desiring to climb on the apparatus  10  using the ladder  18 . Of course, the configuration of the supporting plates  16   1 - 16   5  is a non-limiting example. In an embodiment, some of the supporting plates  16   4  may have a non-slip pattern in order to provide a safe walking surface for workers on the apparatus  10 . Supporting plates  16   3  form, on both sides of the base  12 , rails  28  for guiding wheels (shown on a later Figure) of the dolly  22 . Grooves  30  are formed by gaps between the supporting plates  16   3  and  16   4 , the grooves  30  being located directly above the channels  26  of  FIG. 3 . The grooves  30  continue into supporting plates  16   2  and  16   5 , at or near both extremities of the apparatus  10 . Of course, the arrangement of the grooves and of the plates may be altered according to the needs of a particular realization. 
         [0067]      FIG. 5  is a detailed view showing an attachment point of a supporting plate on the apparatus of  FIG. 1 . A supporting plate  16  is mounted on the base  12  by attachment to a beam  24  of the base  12  using a bolt  25  or any other suitable attachment means, including for example a rivet of a welded point. 
         [0068]      FIG. 6  is a first, side elevation cutaway view of a base for the apparatus of  FIG. 1 . Specifically, a beam  34  shown on  FIG. 3  is also shown on  FIG. 6 , the beam  34  indicating where the cutaway view of  FIG. 6  relates to  FIG. 3 .  FIG. 6  shows optional diagonal braces  15  linking the adjustable legs  14  to the beam  34 . Likewise,  FIG. 7  is a second, side elevation cutaway view of a base for the apparatus of  FIG. 1 . A beam  32  is visible on both  FIGS. 3 and 7 , indicating a relationship between the views of these two Figures. As shown on the particular embodiment of  FIGS. 6 and 7 , the base  12  may comprise a top part  36  resting on a bottom part  38  on which the adjustable legs  14  are attached. 
         [0069]    It may be observed that the cutaway views of  FIGS. 6 and 7  do not show the complete extent of the length of the base  12 ; an extremity comprising the devices  20  providing the drive to the apparatus  10  are not present in those views. 
         [0070]      FIG. 8  is a detailed view of an extremity of the cutaway view of  FIG. 7 .  FIG. 9  is a top plan view of the extremity illustrated in  FIG. 8 . Braces  40 ,  41 ,  44  and  45 , and beam extensions  42  and  46 , not visible on  FIG. 7 , are added to the views of  FIGS. 8 and 9 . The braces  40 ,  41 ,  44  and  45  are for holding some of the devices  20 .  FIG. 10  is a further detailed view of the extremity illustrated in  FIG. 8 , showing a point of attachment of an electric generator. A partial cutaway view of an electric generator  48  shows a positional relationship between the electric generator  48 , a brace  48   a  integral to a casing of the electric generator  48  and a beam  47 . 
         [0071]      FIG. 11  is a detailed view of a ladder attached to the apparatus of  FIG. 1 . The ladder  18  may simply be bolted on a side of the base  12 . The ladder  18  may be omitted in some embodiments, and a precise location of the ladder  18  may be modified according to the needs of a particular installation. 
         [0072]      FIG. 12  is an elevation cutaway view of the apparatus of  FIG. 1 . The legs  14  are attached to the bottom part  38  at their top and are further supported by diagonal braces  50  connected to a horizontal beam  52  attached to both sides of the bottom part  38 . Of course, the structure of the base  12  and the manner of attaching the legs  14  thereto is illustrative and non-limiting, as those of ordinary skill in the art will be able to design a suitable base having other formats.  FIG. 12  also shows a location on the base  12  of the grooves  30  introduced in the above description of  FIG. 4 , the grooves  30  being placed above the channels  26 .  FIG. 13  is a detailed view of an aspect of  FIG. 12 , showing a channel for a roller chain. Areas  54  of  FIG. 12  are further shown on  FIG. 13 , with the understanding that two such areas  54  are mirroring each other. The channels  26  introduced in the foregoing description of  FIG. 3  comprise upper channels  26   u , placed within recesses of transversal beams  56  connecting the beams  32  and  34 , and lower channels  26   d , fixed on top of transversal beams  62  attached underneath the beams  32  and  34 . Safety guards (not shown) may be added to prevent an operator from accidentally touching the roller chains. Although not explicitly shown on  FIGS. 12 and 13 , the channels  26 , and  26   d  extend along the length of the base  12 , substantially with a same length as that of the grooves  30 . Two (2) roller chains  64 , one on each side of the base  12 , form loops running along the length of the channels  26   u  and  26   d . 
         [0073]    Returning to  FIG. 12 , the legs  14  may be individually adjustable for adjusting a height of the base. The base  12  may be leveled by extending or contracting the various legs  14 . In some embodiments, the legs  14  may be electrically adjustable. 
         [0074]      FIG. 14  is a perspective cutaway view of the apparatus of  FIG. 1 , showing details of a motorized unit and of two mechanical drives. A motorized unit may be located at a proximal end of the apparatus  10 , within the area identified as  20  on  FIG. 1 . The motorized unit comprises an electric motor  66  having a shaft coupled to a sprocket  68 . In an embodiment, the electric motor  66  may be coupled to the sprocket  68  via a speed reducer  67 . The speed reducer  67  greatly increases a driving torque transferred to the sprocket  68  by the electric motor  66 . The sprocket  68  drives a first mechanical drive which, in an embodiment, comprises a roller chain  70 . In an embodiment, the speed reducer  67  may be mounted in the apparatus  10  on beams having slots  71  for moving the speed reducer  67 , thereby adjusting a tension of the roller chain  70 . The roller chain  70  transmits a drive from the electric motor  66  to a sprocket  72  mounted on a rotating axle  74 . The rotating axle  74  is attached to the base  12  via flange bearings  76  mounted on the base  12  at areas  29 , which may be at the proximal end of the apparatus  10 . The drive of the electric motor  66  is further transmitted from the rotating axle  74  to a second mechanical drive which, in an embodiment, comprises the roller chains  64  and an actuator (described hereinbelow). Transmission of the drive to the roller chains  64  of the second mechanical drive is made via sprockets  82  and  84  mounted on the rotating axle  74 . 
         [0075]    In the specific embodiment of  FIG. 14 , the sprockets  68  and  72  and the roller chain  70  are doubled for added safety and reliability. 
         [0076]    In an alternate embodiment, the sprockets  82  and  84  and the two roller chains  64  may be replaced by a single sprocket mounted centrally on the rotating axle  74  and by a single chain  64  placed substantially at mid-width of the base  12 , a single groove  30  formed on the supporting plates  16  being centrally placed at mid-width of the base  12 , above a central channel  26 . However, for an apparatus  10  designed for 60,000-pound payloads, with an electric motor rated at 7.5 horsepower (HP) for example, use of a pair of roller chains  64  having, for example, a traction rating of 4.6 HP per chain may confer to the apparatus  10  an ample coefficient of safety. 
         [0077]      FIG. 15   a  is a perspective cutaway view of the apparatus of  FIG. 1 , showing details of an end of the apparatus opposite from the motorized unit of  FIG. 14 . The view of  FIG. 15   a  is at a distal end of the apparatus  10 . The roller chains  64  are shown at a distal end from the rotating axle  74  of  FIG. 14 . The roller chains  64  revolve around sprockets  88  and  90 , which are mounted on a rotating axle  92 . The rotating axle  92  attaches to the base  12  at areas  27  via flange bearings  94  and  96 . The flange bearings  94  and  96  are attached to the apparatus  10  via adjustment systems  97  and  99  for adjusting a tension of each roller chains  64 . 
         [0078]    The second mechanical drive also comprises sturdy upright plates  98 , attached to each of the roller chains  64  and protruding through the grooves  30 . A shape of the upright plates  98  may differ from that shown on  FIG. 15   a , as the Figure shows one of possible suitable shapes.  FIG. 15   b  shows details of an upright plate according to an embodiment. As the roller chains  64  revolve around the sprockets  82 ,  84 ,  88  and  90 , the upright plates  98  move forward or backward within the grooves  30 . The drive originating from the motorized unit is transmitted via the chains  64  and via the upright plates  98  to an actuator, as expressed hereinbelow. 
         [0079]      FIG. 16  is a top plan view of an actuator for transmitting motion from the apparatus of  FIG. 1  to a dolly. The second mechanical drive further comprises an actuator  100  located at the distal end of the apparatus  10 . The actuator  100  comprises end connectors  102  for attaching, for example using pins or bolts (not shown), to the upright plates  98  (not visible on  FIG. 16 ), two forward beams  110 , one transversal beam  112  and two rollers  114  for resting the actuator  100  on the supporting plates  16 . Safety guards (not shown) may be added in order to prevent accidental contact with the rollers  114 . 
         [0080]      FIG. 17  is a detailed view of an extension of the actuator of  FIG. 16 . Bumpers  118  affixed to extension  119  may be inserted at the end of each forward beam  110  for pushing on the dolly  22 . It may be observed that when pushing the dolly  22 , in case of a sudden stop of the motorized unit, the cables, ropes or chains attached to the dolly  22  and to the links  116  effectively prevent the dolly  22  from continuing its forward motion. Likewise, when pulling the dolly  22  via the chains, cables or ropes attached to the links  116 , the bumpers  118  prevent the dolly  22  from continuing its rearward motion. Each of the forward beams  110  is traversed by a hole  120 . A plurality of holes  122  traverses the extensions  119 . A position of the extensions  119  on the forward beams  110  may be adjusted by aligning one of the holes  122  with the hole  120  and by inserting a pin or a bolt (not shown). 
         [0081]    In some embodiments, the end connectors  102  may be directly attached in a solid manner to the forward beams  110 , transferring the drive received from the upright plates  98  directly. However, in contrast with hydraulic systems in which oil pressure tends to balance any differential drive between two sides of a system, use of the roller chains  64  to transmit the drive over the length of the apparatus  10  may bring additional challenges. Despite care taken in ensuring lateral symmetry of the apparatus  10 , a path of one of the roller chains  64  may slightly differ in length from the path of the other roller chain. Any slack in one of the roller chains  64  may cause it to carry a very small share of the total drive while the other roller chain  64  carries a much larger share of the total drive. Returning to  FIG. 16 , as shown, a transversal, U-shaped first traction member  104  is attached to the end connectors  102  via pins  107 . A transversal plate is fixedly attached to the two forward beams and acts as a second traction member  106 . A sturdy pin connects the first and second traction members  104 ,  106 , substantially at their mid width.  FIG. 18  is a side elevation view of the actuator of  FIG. 16 . In the embodiment of  FIG. 18 , the second traction member  106  is made of two plates placed above and below the forward beams  110  and fixedly attached thereto. The U-shaped first traction member  104  is connected to the upright plates  98  via the end connectors  102 , receiving therefrom the drive from the motorized unit. The drive is transferred from the first traction member  104  to the second traction member  106  via a pin  108 . 
         [0082]      FIG. 19  is a detailed view of a traction member of the actuator of  FIG. 16 . The top of the Figure shows the first traction member  104  in top view while the bottom of the Figure shows the same member  104  in frontal elevation. Slots  104   a  and  104   b  allow a slidable connection of the first traction member  104  to the end connectors  102  via the pins  107  while central hole  104   c  allows connection of the first traction member  104  to the second traction member  106  via the pin  108 . In case of any slack in one of the roller chains  64  or in case of any misalignment between the actuator  100  and the dolly  22 , a slight lateral movement of the first traction member  104 , allowed by a width of the slots  104   a  and  104   b , takes up this slack and maintains a substantially even tension of both roller chains  64 , minimizing a drive difference between the two roller chains  64 . As a result, parts of the actuator  100  that are beyond the first traction member  104 , from the second traction member  106  until the bumpers  118 , are self-centered within the apparatus  10 . 
         [0083]    Continuing with the description of  FIG. 16 , links  116  are attached to actuator  100  at points beyond the second traction member  106 , for example above the two rollers  114 . A point of attachment of the links  116  may vary within the self-centered part of the actuator  100 . Cables, ropes or chains may be used to attach the links  116  to the dolly  22 , for pulling the dolly  22 . 
         [0084]    In embodiments in which a single, central rolling chain  64  is used, a single, central upright plate  98  transfers the drive centrally to the actuator  100 , without a load balancing system. 
         [0085]      FIG. 20  is a front elevation view of a dolly mounted on the apparatus of  FIG. 1 . The dolly  22  comprises at least one transversal beam, such as beam  130 , on which the bumpers  118  of the apparatus  10  may push. The dolly  22  also comprises pairs of guiding wheels  132  rolling on the supporting plates  16  and guided by the rails  28 . Though the rails  28  are shown on an interior side of the guiding wheels  132 , rails may also be placed on an exterior side of the guiding wheels  132 . Safety guards (not shown) may be added in order to prevent accidental contact with the guiding wheels  132 . The above mentioned cables, ropes or chains, for attachment to the links  116  of the actuator  100 , may be attached at various places of the dolly  22 , near a distal extremity thereof in order to allow pulling of the dolly  22 . 
         [0086]      FIG. 21  is a perspective, cutaway view of a power generation assembly of the apparatus of  FIG. 1 . A power generation assembly  140  may be located at a proximal end of the apparatus  10 , near the motorized unit. It comprises the electric generator  48 , which may be a diesel power generator, and a fuel tank  144 , which may hold diesel fuel for the electric generator  48 . Because the fuel tank  144  and the electric generator  48  are proximally located, no elongated fuel conduit is present and risks of spillage are minimized. 
         [0087]    A controller  86  controls the electric motor  66 . In some embodiments, the controller  86  may control other functions of the apparatus  10 . Of course, other embodiments may comprise a plurality of dedicated controllers for separately controlling the electric motor  66  and other functions of the apparatus  10 . Electrical power may thus be provided to the electric motor  66  from a power supply comprising the electric generator  48 . Alternatively, the power supply may comprise an external power source (not shown). Because the apparatus  10  may be transported between various sites where distinct industrial voltages are available, the apparatus  10  may comprise a transformer acting  89  as a voltage converter of the external power source. The controller  86  may further comprise a selector for making a selection between the electric generator  48  and an external power source. 
         [0088]    In operation, the controller  86  controls a movement of the dolly  22 . Commands entered by an operator on the controller  86  are transferred to the motorized unit for pushing the dolly  22  in a rolling motion from the apparatus  10  onto a container or a flatbed trailer, or for pulling the dolly  22  from the container or flatbed trailer onto the apparatus  10 . The controller  86  may further control a variable speed of the motorized unit, controlling its acceleration and deceleration. When the controller  86  senses that current is applied to the motor  66  while the motor  66  is not rotating, it interprets this event as an indication that the dolly  22  has reached a maximum forward point on the container or trailer, a maximum rearward point on the apparatus  10 , or a potentially dangerous blockage position. The controller  86  then cuts off the electrical power applied to the electric motor  66 . Because the controller  86  interprets a discrepancy between a voltage applied to the motor  66  and a lack of rotation of the motor  66  as a need to stop a movement of the motorized unit, the apparatus  10  does not require the use of mechanical limit switches for operation. 
         [0089]    A remote control (not shown), connected via wire or wirelessly to the controller  86 , may be used by an operator for entering various commands for controlling operation of the apparatus  10 . Instead of or in addition to the remote control, one or more manual commands may be positioned at various locations on the base  12  for actuating an emergency brake (not specifically shown) operably connected to the electric motor  66 . 
         [0090]    Those of ordinary skill in the art will realize that the description of the apparatus are illustrative only and are not intended to be in any way limiting. Other embodiments will readily suggest themselves to such persons with ordinary skill in the art having the benefit of the present disclosure. Furthermore, the disclosed apparatus may be customized to offer valuable solutions to existing needs and problems of loading and unloading heavy freight. 
         [0091]    In the interest of clarity, not all of the routine features of the implementations of the apparatus are shown and described. It will, of course, be appreciated that in the development of any such actual implementation of the apparatus, numerous implementation-specific decisions may need to be made in order to achieve the developer&#39;s specific goals, such as compliance with application-related and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it will be appreciated that a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the field of heavy machinery having the benefit of the present disclosure. 
         [0092]    The controller  86  described herein may comprise software, firmware, hardware, or any combination(s) of software, firmware, or hardware suitable for the purposes described herein. 
         [0093]    Although the present disclosure has been described hereinabove by way of non-restrictive, illustrative embodiments thereof, these embodiments may be modified at will within the scope of the appended claims without departing from the spirit and nature of the present disclosure.