Patent Publication Number: US-7905528-B2

Title: Spreader frame for cargo container

Description:
FIELD OF THE INVENTION 
     The disclosure relates to spreader frames for hoisting cargo containers. 
     BACKGROUND OF THE INVENTION 
     Cargo containers (hereinafter “containers”) are used for shipping freight on commercial transport carriers such as cargo ships, railcars and trailers. “ISO” containers are a common type of container designed according to ISO (International Standards Organization) specifications which ensure that the containers are inter-operable with compatible carriers. One feature of ISO containers is a hollow lifting block in each corner of the container for securing the container to compatible equipment. The lifting block has a central cavity, and a generally rectangular opening permits access to the cavity from the exterior of the container. In order to secure the container to the compatible equipment, a bayonet or twist lock is inserted into each lifting block and a compatible fitting on the equipment. The twist lock has a spindle section on one end and a wide key section of generally rectangular profile on the end opposite the spindle section. The spindle section is captured by the fitting on the compatible equipment. The key section of the twist lock is inserted through the opening and into the central cavity of the lifting block. The twist lock is twisted or rotated ninety degrees about the spindle axis and relative to the cavity walls between an open position and an engaged position. The open position permits the rectangular key section to be inserted through and freely removed from the rectangular opening of the lifting block. When rotated to the engaged position, the rectangular key section engages the lifting block and permits vertical force to be applied to the lifting block for hoisting the container. 
     In some terminal facilities, dedicated and specially designed high-speed handling equipment is used to rapidly hoist and move high volumes of ISO containers between carriers or between a dock and carrier. High speed handling equipment designed for hoisting containers can include automated or remotely controlled twist locks for engaging the container, or automated grapple arms for grabbing the container. Such high speed handling equipment is dedicated solely for handling containers and is not useful in a terminal facility where other loads must also be moved. High speed handling equipment for containers also requires a large footprint for operation. High speed handling equipment for containers also requires a large capital investment. 
     In view of the foregoing, many terminal facilities have only a general purpose crane or hoist equipment (hereinafter “hoist equipment”) for handling ISO containers, non-ISO containers and other loads. Off-shore oil platforms are examples of terminal facilities where containers are handled with general purpose hoist equipment. As used herein, “hoist equipment” includes any overhead hoist equipment or crane providing a single point lift or having a hoist cable and terminal fitting, such as a hook, which is raised and lowered to move a load such as a container. A container or load to be hoisted is manually attached to the hook, such as by using wire rope slings. In some terminal facilities, empty containers are attached directly to the wire rope slings and raised. However, using this type of direct attachment to hoist a container is dangerous and can subject the container to stresses which damage the container or cause immediate failure of the container. These dangers and the risk of damaging the container are greatly increased when the container is loaded. Hoisting a container carrying a cargo load that has uneven distribution of weight throughout the container is more dangerous and further increases the risk of damaging the container. 
     Moving containers from a supply boat to an off-shore oil platform with general purpose hoist equipment can be particularly dangerous and presents a greater risk of damaging the container. The danger and risk are compounded by motion of the supply boat relative to the oil platform and hoist due to waves, wind and surface currents. Due to motion of the supply boat, the container on the deck of the supply boat when attached to the hoist can be jerked and subjected to additional stress in the form of sudden horizontal and vertical forces. When clear of the deck of the supply boat, the container can swing and hit projecting structure within the tight confines of the oil platform before coming to rest on the oil platform. Similar forces can be encountered when moving containers from the oil platform to the supply boat. 
     General purpose hoist equipment can be used to safely hoist a loaded container with a spreader frame attached to the hook and to the container. The spreader frame is adapted to permit the container to be hoisted without exposing the container to excessive bending stress and without applying horizontal forces to the container and twist locks. The spreader frame has a rigid frame structure which is attached to the hoist hook by a set of wire rope slings. The spreader frame includes four twist locks on the rigid frame structure at locations corresponding to the lifting blocks of the container. The twist locks are received in the lifting blocks and thus attach the container to the spreader frame. When the spreader frame is hoisted by operation of the hoist equipment to raise the hook, both vertical and horizontal force components are transmitted through the wire rope slings to the rigid frame structure. The rigid frame structure absorbs horizontal force components, such that only vertical forces are transmitted to the container by the twist locks attaching the container to the rigid frame structure of the spreader frame. The rigid frame structure supporting the twist locks and container attached thereto also reduces bending stress on the container. 
     A problem associated with hoisting ISO containers with a spreader frame is that one or more of the twist locks can be unintentionally or accidentally rotated to the open position before the spreader frame and attached container are hoisted, or while the spreader frame and attached container are suspended from the hoist. Hoisting a spreader frame with the container secured thereto by only three or fewer twist locks can be dangerous and risks damaging the container, cargo, equipment and personnel. 
     Gross weight capacity is one limiting mechanical factor of containers. Increasing gross weight causes increased bending stress on the container walls when the loaded container is hoisted from a resting position. 
     Overall length is a limiting mechanical factor for containers. Increasing overall length causes increased bending stress on the container walls when the container is hoisted from a resting position, particularly when the container is loaded. 
     Bending stress is a limiting mechanical factor for containers. Bending stress causes deflection of the container walls when the loaded container is hoisted from a resting position, particularly of the longitudinal walls extending between the ends of the container. Excessive bending stress can cause the container walls to fail by buckling. 
     For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved spreader frame for hoisting cargo containers. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The above-mentioned shortcomings, disadvantages and problems are addressed herein, which will be understood by reading and studying the following specification. 
     In one aspect, the disclosure provides an improved spreader frame. In another aspect, the disclosure provides an improved twist lock. In another aspect, the disclosure provides a safety feature for a spreader frame. 
     Apparatus of varying scope are described herein. In addition to the aspects and advantages described in this summary, further aspects and advantages will become apparent by reference to the drawings and by reading the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a spreader frame according to an embodiment. 
         FIG. 2  is a perspective view of the spreader frame of  FIG. 1 , showing the spreader frame and a cargo container attached thereto. 
         FIG. 3  is an enlarged perspective view of the spreader frame shown in  FIG. 1 . 
         FIG. 4  is a bottom plan view taken generally along line  4 - 4  in  FIG. 3 . 
         FIG. 5  is an enlarged partial perspective view of a corner of the spreader frame of  FIG. 3 , showing the twist lock, security cover, security housing, and visual indicia in the locked condition. 
         FIG. 6  is an exploded partial top perspective view of the twist lock, security housing, security cover and visual indicia shown generally in  FIG. 5 . 
         FIG. 7  is an exploded partial bottom perspective view of the twist lock, security housing, security cover and visual indicia shown in  FIG. 6 . 
         FIG. 8  is a front partial section view of the security housing and visual indicia shown generally in  FIG. 6 , with the twist lock omitted for clarity. 
         FIG. 9  is a top view, partially in section, of the security housing and visual indicia taken generally along line  9 - 9  in  FIG. 8 . 
         FIG. 10  is a bottom view of the security cover shown generally in  FIG. 6 . 
         FIG. 11  is an enlarged, isolated end view of the twist lock taken generally along line  11 - 11  in  FIG. 7 . 
         FIG. 12  is a side view of the twist lock taken generally along line  12 - 12  in  FIG. 11 . 
         FIG. 13  is a top view of the twist lock taken generally along line  13 - 13  in  FIG. 11 . 
         FIG. 14  is an exploded partial perspective view of the twist lock, security housing, security cover and visual indicia in the unlocked position. 
         FIG. 15  is an exploded partial perspective view of the twist lock, security housing security cover and visual indicia in a first alternative embodiment. 
         FIG. 16  is an exploded partial perspective view of the twist lock, security housing security cover and visual indicia in a second alternative embodiment. 
         FIG. 17  is an exploded partial perspective view of the twist lock, security housing, security cover and visual indicia in a third alternative embodiment. 
         FIG. 18  is a partial cross sectional view taken generally along line  18 - 18  in  FIG. 17  and showing the twist lock and security cover in the unlocked position. 
         FIG. 19  is a partial cross sectional view identical to  FIG. 18 , except showing the twist lock and security cover in the locked position. 
         FIG. 20  is a partial view taken from the opposite perspective of  FIG. 17 . 
         FIG. 21  is a perspective view of a spreader frame according to an embodiment. 
         FIG. 22  is a perspective view of a spreader frame according to an embodiment. 
         FIG. 23  is an enlarged partial perspective view partial perspective view of a corner of the spreader frame of  FIG. 22 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken in a limiting sense. 
       FIG. 1  is a perspective view of a spreader frame  100  according to an embodiment. Spreader frame  100  is adapted to support a container  500 . In the specific embodiment illustrated, container  500  is an ISO container. In other embodiments, container  500  can be of different design. Container  500  is a box structure formed by cooperation of four longitudinal walls  504  and spaced end walls  508 . One or both of the end walls  508  can include a door (not shown) providing access to interior space (not shown) of container  500 . Container  500  includes a hollow lifting block  510  on each corner  512  for securing the container  500  to compatible equipment. The lifting block  510  has a central cavity. The lifting block  510  also has a generally rectangular opening which permits access to the central cavity. 
     Spreader frame  100  is adapted to be attached to container  500  for hoisting the container  500 , as further described herein. In the specific embodiment shown in  FIG. 1 , spreader frame  100  is suspended above container  500  prior to being attached thereto. Container  500  initially rests upon and is supported by support surface  600 . In the specific embodiment illustrated, support surface  600  is a deck  610  of a supply ship engaged in supplying an off-shore oil platform. In other embodiments, the support surface  600  can be any suitable terminal facility floor or deck, or a carrier such as a railcar or trailer. 
     Spreader frame  100  is adapted to be hoisted and moved by hoist equipment  104 . As used herein, “hoisted” means raised or lowered using hoist equipment. It is to be understood that any suitable hoist equipment  104  can be used with spreader frame  100 . For example, hoist equipment  104  can include a hoist, crane, lifting equipment having a hoist or lift cable, overhead crane, overhead hoist, hoist supported on an overhead trolley, hoist supported on a rail or boom, single point lift, or any suitable equipment having a hoist cable. Hoist equipment  104  is operable for hoisting and moving the spreader frame  100  having container  500  attached thereto (see  FIG. 2 ). In the specific embodiment illustrated, hoist equipment  104  includes a hoist cable  105  having a hook  106  at a terminal end thereof. It is to be understood that hook  106  can include any suitable terminal fitting adapted for use with hoist equipment  104 . For example, hook  106  can include a clasp and pin combination, a D-ring fitting, or a terminal loop of hoist cable  105 . Hoist equipment  104  includes a hoist drum (not shown) operable for reeling and unreeling the hoist cable  105  to raise and lower hook  106  in the vertical direction. 
       FIG. 2  is a perspective view of the spreader frame  100  of  FIG. 1 .  FIG. 2  shows the spreader frame  100  attached to and supporting container  500 . Container  500  thus is hoisted above support surface  600 . Spreader frame  100  includes a rigid frame structure  142 . Rigid frame structure  142  has suitable mechanical strength to support with an adequate safety factor the container  500  when fully loaded. As used herein, “fully loaded” means that the container is loaded to maximum gross capacity. It is to be understood that the rigid frame structure  142  can be constructed in any manner suitable to provide mechanical strength adequate to support the container  500  when fully loaded. In the specific embodiment illustrated, the rigid frame structure  142  includes a pair of parallel elongated longitudinal frame members  146 . The rigid frame structure  142  includes a spaced pair of parallel end members  148  joining the pair of longitudinal frame members  146  at opposite ends thereof. Each end member  148  extends between the pair of longitudinal frame members  146  in perpendicular relation thereto. The end members  148  and longitudinal frame members  146  thus cooperate to define a generally rectangular outer perimeter having four corners  162  disposed respectively in two opposite pairs. Intermediate the pair of end members  148  and parallel thereto, the rigid frame structure  142  includes a plurality of generally equidistant, spaced, parallel cross-members  150  joining the pair of longitudinal frame members  146 . The cross-members  150  extend between the pair of longitudinal frame members  146  in perpendicular relation thereto. In the specific embodiment illustrated, the rigid frame structure  142  includes six cross-members  150 . The cross-members  150  are joined to the longitudinal frame members  146  in a suitable manner. In the specific embodiment illustrated, intermediate the ends  148  four of the cross-members  150  each abut the longitudinal frame members  146  and are joined thereto at respective welded ‘T” joints  152 . In the illustrated embodiment, two of the cross-members  150  are joined at respective corners  162  to the ends  148  of the longitudinal frame members  146  by welded joints and respective braces or gussets  164  (see  FIG. 4 ). Gussets  164  form an overlapping layer which overlaps adjacent portions of the longitudinal frame members  146  and cross-members  150 . According to the disclosure, the cross-members  150  and ends  148  of longitudinal frame members  146  are joined at corners  162  in any suitable manner. Longitudinal frame members  146  and cross-members  150  are formed of any suitable rigid material having adequate mechanical strength. In the specific embodiment illustrated, the longitudinal frame members  146  and cross-members  150  are formed of carbon steel having a rectangular cross-sectional profile. 
     The spreader frame  100  includes a plurality of security housings  166  located in alignment with the lifting blocks  510  at the uppermost four corners  512  of container  500 . In the specific embodiment illustrated, the spreader frame  100  includes four security housings  166  each located at respective corners  162  of the rigid frame structure  142  in alignment with the respective lifting blocks  510  of container  500 . It is to be understood that in other embodiments (not shown), the spreader frame  100  can include security housings  166  at other locations, such as at the T joints  152 , for being connected to differently proportioned containers. For example, it is anticipated that security housings  166  can be located to accommodate containers having nominal lengths of ten and twenty feet, as well as the forty foot container illustrated herein. In the illustrated embodiment, at each corner  162  the respective security housing  166  is intermediate and adjacent the respective cross-member  150  and end  148  of longitudinal frame member  146 . In the specific embodiment illustrated, the security housing  166  at corner  162  is intimately joined by welded joints to cross-member  150 , end  148 , and overlapping gusset  164 . 
     Each security housing  166  includes four adjoining sidewalls  170  and a bottom  174  which cooperate to form an interior compartment  178 . Cooperation of the sidewalls  170  forms a continuous, recessed upper lip  182 . The upper lip  182  has therein a plurality of spaced anchor holes  186  threaded to receive anchor bolts  190 . In the specific embodiment illustrated, the upper lip  182  has therein four anchor holes  186 . The bottom  174  has a center  194 . A circular opening  198  is located at the center  194 . The circular opening  198  forms open bore  202  having a vertical axis  204  extending in the vertical direction through the center  194  of bottom  174 . 
     The interior compartment  178  of each security housing  166  includes a first rest  206 . The first rest  206  is adapted to stop a locking member  210  of a twist lock  214  (see  FIG. 15 ) in a locked position, as further described herein. It is to be understood that the first rest  206  can be of any design suitable to stop the locking member  210  in the locked position, and other specific constructions are anticipated by the present disclosure. In the specific embodiment illustrated, the first rest  206  engages and mates with the locking member  210  in the locked position. 
     The interior compartment  178  of each security housing  166  includes a second rest  226 . The second rest  226  is adapted to stop the locking member  210  of the twist lock  214  (see  FIG. 6 ) in an unlocked position, as further described herein. It is to be understood that the second rest  226  can be of any design suitable to stop the locking member  210  in the unlocked position, and other specific constructions are anticipated by the present disclosure. In the specific embodiment illustrated, the second rest  226  engages and mates with the locking member  210  in the unlocked position. The second rest  226  and first rest  206  form a ninety degree angle. 
     The spreader frame  100  includes a plurality of twist locks  214 . In the specific embodiment illustrated, the spreader frame includes four twist locks  214  each corresponding to a respective security housing  166  at each corner  162  of rigid frame structure  142 . Each twist lock  214  includes the locking member  210 . Locking member  210  is adapted to be engaged by the first rest  206  of the security housing  166  in the locked position. Alternatively, locking member  210  is adapted to be engaged by the second rest  226  of the security housing  166  in the unlocked position. Locking member  210  has a projection  213 . Projection  213  extends in the vertical direction above the upper lip  182  and has an elongated upper edge  211 . Upper edge  211  is received in a retaining recess  312  of security cover  300  when locking member  210  is received in first rest  206  or second rest  226 . The upper edge  211  of projection  213  of locking member  210  extending above the upper lip  182  thus defines a first safety feature  215  of twist lock  214 . 
     The twist lock  214  includes a spindle section  242  joined in fixed relationship to the locking member  210 . The spindle section  242  is a solid column  246  joined at an upper end  250  thereof to the locking member  210 . The spindle section  242  has a vertical spindle axis  254  which intersects locking member axis  212  of locking member  210 . The solid column  246  also defines a lower end  258  of spindle section  242  spaced from upper end  250 . 
     Twist lock  214  includes a key section  262  joined in fixed relation to spindle section  242  at lower end  258 . Key section  262  includes key upper end  266  joined to the lower end  258  of spindle section  242 . Key section  262  also has a key lower end  270  spaced from key upper end  266 . Key lower end  270  defines a lower terminal end  274  of twist lock  214 . Key upper end  266  has a generally rectangular cross sectional profile and an upper width  278 . Key lower end  270  has a generally rectangular cross sectional profile and a lower width  282 . Upper width  278  of key upper end  266  is greater than the lower width  282  of key lower end  270 . Key section  262  thus has a rectangular cross sectional profile which tapers from upper width  278  to lower width  282 . Lower terminal end  274  terminates at a flat lower surface  286 . Flat lower surface  286  is perpendicular to vertical spindle axis  254 . Key section  262  at key upper end  266  includes a generally flat key upper surface  290 . Key upper surface  290  is spaced above lower surface  286  and in general opposition thereto. 
     Spreader frame  100  includes a security cover  300 . Security cover  300  is adapted to enclose interior compartment  178  of security housing  166  having locking member  210  therein. It is to be understood that security cover  300  can be mounted to enclose interior compartment  178  in any suitable manner. In the illustrated embodiment, security cover  300  is adapted to be mounted flush on upper lip  182  of security housing  166  and thus to enclose interior compartment  178  having locking member  210  therein. In the specific configuration illustrated, security cover  300  is adapted to be secured on upper lip  182  of security housing  166  by a plurality of threaded security bolts  190  received in respective anchor holes  186  of upper lip  182 . The security cover  300  has therein bolt holes  304  for receiving the security bolts  190 . The security cover  300  has a generally planar bottom surface  308  facing the interior compartment  178 . The bottom surface  308  is flush mounted in mating relationship with the upper lip  182  and secured thereto by threading the security bolts  190  into anchor holes  186 . The bottom surface  308  has therein an elongated retaining recess  312 . Retaining recess  312  is dimensioned to receive and retain in intimate mating relationship the elongated upper edge  211  of projection  213  of locking member  210 . Retaining recess  312  retaining the upper edge  211  of projection  213  of locking member  210  thus defines a second safety feature  314  of security cover  300 . The second safety feature  314  of safety cover  300  cooperates with the first safety feature  215  of twist lock  214  to retain twist lock  214  either in the locked position with the locking member  210  engaged with first rest  206  or alternatively in the unlocked position with the locking member  210  engaged with the second rest  226 . The second safety feature  314  of safety cover  300  thus cooperates with the first safety feature  215  of twist lock  214  in the locked position and with the security housing  166  of rigid frame structure  142  to lock together spreader frame  100  and container  500 . The second safety feature  314  of safety cover  300  cooperates with the first safety feature  215  of twist lock  214  in the unlocked position and with the security housing  166  of rigid frame structure  142  to release spreader frame  100  from container  500 . It is to be understood that first and second safety features  214 , 315  and security housing  166  can be configured differently in other embodiments (not shown). For example, it is anticipated that security cover  300  can include a retaining recess or projection, and twist lock  214  can include the other of a retaining recess or projection. Also, it is anticipated that in other embodiments at least one of security housing  166 , security cover  300  and twist lock  214  can include a safety feature which retains twist lock  214  in the locked position or alternatively retains twist lock  214  in the unlocked position. In view of the foregoing, it is to be understood that according to one embodiment of the present disclosure, at least one of the rigid frame structure, twist lock, and security cover can include a safety feature which retains twist lock  214  in the locked position or alternatively retains twist lock  214  in the unlocked position. Further, it is to be understood that security housing  166  of rigid frame structure  142  cooperates with security cover  300  and security bolts  190  to prevent incidental access or ready access to twist lock  214  by personnel working without deliberate use of a tool, such as a wrench, adapted to remove security bolts  190  from threaded anchor holes  186 . Likewise, it is to be understood that security housing  166  of rigid frame structure  142  cooperates with security cover  300  and security bolts  190  to prevent enclosing twist lock  214  by incidental replacement of security cover  300  with security bolts  190  by personnel working without deliberate use of a tool, such as a wrench, adapted to tighten security bolts  190  in threaded anchor holes  186 . 
     Spreader frame  100  includes visual security indicia  330 . It is to be understood that any suitable visual security indicia  330  can be provided. In the specific embodiment illustrated, visual security  330  is adapted to provide personnel a visual indication that each twist lock  214  is securely retained or locked in the unlocked position or alternatively in the locked position. Visual security indicia  330  includes an unlocked position label  334  stamped on one of the sidewalls  170  of security housing  166  corresponding to the unlocked position of locking member  210  and twist lock  214 . Visual security indicia  330  includes a locked position label  338  stamped on an alternate one of the sidewalls  170  of security housing  166  corresponding to the locked position of locking member  210  and twist lock  214 . Visual security indicia  330  include an indicator arrow  342  stamped on security cover  300  in general alignment with the longitudinal axis of retaining recess  312 . When security cover  300  is oriented in the first position corresponding to the unlocked position of twist lock  214  and the position of locking member  210  against the first rest  206 , and the upper edge  211  of the projection  213  locking member  210  is received in retaining recess  312 , the indicator arrow  342  aligned with retaining recess  312  points to the unlocked position label  334 . Alternatively, when security cover  300  is oriented in the second position  320  corresponding to the locked position of twist lock  214  and to the locked position of locking member  210  against second rest  226 , and the upper edge  211  of the locking member  210  is received in retaining recess  312  aligned with the locked position of locking member  210 , the indicator arrow  342  aligned with retaining recess  312  points to the locked position label  338 . Observation of the indicator arrow  342  in relation to the open indicator label  334  and locked indicator label  338  thus provides personnel a visual indication that each twist lock  214  is securely locked in the open position or alternatively in the locked position. 
     The container  500  is attached to the spreader bar  100  by aligning the security housings  166  at corners  162  of spreader frame  100  with the lifting blocks  510  at the corners  512  of container  500 . At each corner of the spreader frame  100 , the security bolts  190  and security cover  300  are initially removed from the upper lip  182  of the sidewalls  170  of the security housing  166  to provide access to the interior compartment  178 . A twist lock  214  is rotated to the open position, and the key section  262  is inserted in the vertical direction through the open bore  202  in the bottom  174  of security housing  166 , through the aligned rectangular opening  516  and received in the central cavity  514  of the respective lifting block  510 . The twist lock  214  is rotated ninety degrees to the locked position, and the locking member  210  is received against the second rest  226  in the locked position. The security cover  300  is rotated to the second orientation corresponding to the locked position of the locking member  210 , such that the retaining recess  312  is aligned with the upper edge  211  of locking member  210 . The security cover  166  is lowered such that the upper edge  211  is received in the retaining recess  312  and permits the security cover  300  to be flush mounted on the upper lip  182  of security housing  166  by returning and tightening the security bolts  190  in the anchor holes  186 . With the security cover  300  flush mounted on the upper lip  182 , the indicator arrow  342  points to the locked position label  338  and thus provides visual indication to personnel that twist lock  214  is secured in the locked position. In the locked position of the twist lock  214 , the key section  262  is rotated inside the central cavity  514  to a respective locked position engaging the lifting block  510  in a known manner to permit vertical force to be applied to the lifting block  510  and thus to container  500 . Spreader frame  100  is attached to the hook  106  of hoist equipment  104  by a set of wire rope slings  107 . Each wire rope sling  107  has an end attached to the hook  106  and an opposite end attached to a respective eye  165  on the rigid frame structure  142 . The hoist  104  is operated to lift the hook  106  and thus raise the spreader frame  100  having container  500  attached thereto. The lifting blocks  510  of container  500  are supported by the key section  262  of the respective twist locks  214 . The locking member  210  is retained against the second rest  226  by cooperation of the security cover  300  and upper lip  182  joined by the security bolts  190  threaded into the anchor holes  186 . The security cover  300  must be rotated to the second orientation in order to align and permit the retaining recess  312  to receive the upper edge  211  of locking member  210 . With the security cover  300  secured by the security bolts  190  threaded into the anchor holes  186 , the indicator arrow  342  points to the locked position label  338  and thus provides personnel visual indication that the container  500  is locked to the spreader frame  100  by the twist lock  214 . 
     The spreader frame  100  is released from container  500  by using a tool to remove security bolts  190  from anchor holes  186 , removing security cover  300  from upper lip  182 , rotating twist lock  214  to the unlocked position with locking member  210  engaging second rest  226 , turning security cover ninety degrees to the first orientation with the indicator arrow  342  indicating the unlocked position label  334 , returning security cover  300  to upper lip  182  such that upper edge  211  of projection  213  is retained in retaining recess  312 , and using a tool to tighten security bolts  190  in anchor holes  186 . 
       FIG. 15  is an exploded partial perspective view of the twist lock, security housing security cover and visual indicia in a first alternative embodiment. Spreader frame  700  shown in  FIG. 15  is identical to previously described spreader frame  100  except as specified herein. Spreader frame  700  includes a rigid frame structure (not shown) having a plurality of security housings  702  each located at the respective corners thereof. Security housing  702  includes and is formed by cooperation of housing first section  704  and housing second section  708  joined in fixed relation thereto. Housing first section  704  and housing second section  708  each include a respective portion of bifurcated bottom  712  having opening  716  therein. The bifurcated bottom  712  and opening  716  permit spindle section  720  of twist lock  724  to be installed in opening  716  before housing first section  704  and housing second section  708  are permanently joined in fixed relation. With spindle section  720  installed in the opening  716  of bottom  712 , housing first section  704  and housing second section  708  are permanently joined in intimate fixed relation and thus permanently capture the twist lock  724 . Housing first section  704  and housing second section  708  can be permanently joined in any suitable manner and, in the illustrated embodiment, are welded. Housing first section  704  and housing second section  708  when permanently joined cooperate to form the security housing  702 . Housing first section  704  and housing second section  708  are joined to the longitudinal members (not shown in  FIG. 15 ) and cross members (not shown in  FIG. 15 ) in integral fixed relation thereto in a manner which ensures structural integrity of the rigid frame structure. 
       FIG. 16  is an exploded partial perspective view of the twist lock, security housing, security cover and visual indicia in a second alternative embodiment. Spreader frame  800  shown in  FIG. 16  is identical to previously described spreader frame  700  except as specified herein. Spreader frame  800  includes a rigid frame structure (not shown) having a plurality of security housings  802  each located at the respective corners thereof. Security housing  802  includes and is formed by cooperation of housing first section  804  and housing second section  808  joined in fixed relation thereto. Housing first section  804  includes wall sections defining three adjacent corners of the housing  802 , as further specified. Housing first section  804  includes first inner wall  812 . Housing first section  804  includes second inner wall  816  which intersects first inner wall  812  at inner corner  820 . It is to be understood, in the illustrated embodiment, that inner corner  820  is proximate the innermost intersection of the respective longitudinal member (not shown in  FIG. 16 ) and cross member (not shown in  FIG. 16 ) at the respective corner formed thereby, as generally illustrated in  FIG. 5 . Housing first section  804  includes a first outer wall portion  824 . First outer wall portion  824  intersects first inner wall  812  at respective first intermediate corner  828 . Housing first section  804  also includes a second outer wall portion  832 . Second outer wall portion  832  intersects second inner wall  816  at respective second intermediate corner  836 . Housing second section  808  includes third outer wall portion  840 . Housing second section  808  also includes fourth outer wall portion  844 . Fourth outer wall portion  844  intersects third outer wall portion  840  at respective outer corner  848 . Outer corner  848  thus is spaced from inner corner  820  in general opposition thereto. Housing first section  804  and housing second section  808  are permanently joined in a suitable manner. In the illustrated embodiment, housing first section  804  and housing second section  808  are joined together by welding along two intersecting weld seams (not shown) at abutting edges of bottom  852  and along two intersecting weld seams (not shown) at respective abutting edges of first outer wall portion  824  with third outer wall portion  840  and second outer wall portion  832  with fourth outer wall portion  844 . Housing first section  804  and housing second corner section  808  when permanently joined thus cooperate to form the security housing  802 . In the illustrated embodiment, security housing  802  is joined to the respective longitudinal member (not shown) and cross member (not shown) by weld seams at respective intersecting surfaces. 
       FIG. 17  is an exploded partial perspective view of the twist lock, security housing, security cover and visual indicia in a third alternative embodiment.  FIG. 18  is a partial cross sectional view taken generally along line  18 - 18  in  FIG. 17  and showing the twist lock and security cover in the unlocked position.  FIG. 19  is a partial cross sectional view identical to  FIG. 17 , except showing the twist lock and security cover in the locked position. Spreader frame  900  shown in  FIG. 17 ,  FIG. 18 ,  FIG. 19  and  FIG. 20  is identical to previously described spreader frame  100  except as otherwise set forth herein. Spreader frame  900  includes a rigid frame structure (not shown) having a plurality of security housings  902  each located at the respective corners thereof. Each security housing  902  includes a set of adjoining walls  906  which cooperate to define a cylindrical compartment  908 , as further described. Cooperation of adjoining walls  904  defines a continuous inner wall  910 . Inner wall  910  has a primary radius  912  relative to a vertical axis  914 . Compartment  908  thus defined by inner wall  910  also has a primary radius  912  relative to vertical axis  914 . Inner wall  910  has therein a recessed groove  916  ( FIG. 20 ). Recessed groove  916  has a rear wall  917  spaced slightly in the outward radial direction from inner wall  910 . Recessed groove  916  thus defines a race  918 . Race  918  includes a major portion  922 . Major portion  922  extends from a terminus in the horizontal direction to a vertical transition  930 . Race  918  also includes a minor section  934  extending in the vertical direction from vertical transition  930  and upwardly to an external opening or mouth  938 . Horizontal major portion  922  and vertical transition  930  thus are lower than vertical minor portion  934  and mouth  938 . Race  918  has a substantially uniform width along the length thereof. 
     Security housing  902  also includes a flat bottom wall  942 . Bottom wall  942  cooperates with inner wall  910  to define a lower end of cylindrical compartment  908 . Bottom wall  942  has defined therein central opening  946 . It is to be understood that, in the specific arrangement shown in  FIG. 17 , central opening  946  is sized to permit key section  950  of twist lock  954  to be inserted there through when twist lock  954  is rotated about the vertical axis  914  to the unlocked position (shown in  FIG. 17  and  FIG. 18 ). Twist lock  954  thus can be inserted into and completely removed from central opening  946  and security housing  902  when rotated to the unlocked position. When rotated to the locked position (see  FIG. 19 ), twist lock  954  engages the lifting block (not shown) of a cargo container as previously described. In other arrangements (not shown), central opening  946  is sized to permanently capture twist lock  954  and thus prevents removal of twist lock  954  from security housing  902 . 
     Twist lock  954  includes spindle section  958  intermediate key section  950  and locking member  962 . Locking member  962  is adapted to be received in race  918  of recessed groove  916 . Locking member  962  is movable from the unlocked position at mouth  938  and downward through vertical minor section  934  to vertical transition  930 . Locking member  962  thus remains in the unlocked position throughout vertical minor section  934  and vertical transition  930 . Locking member  962  when rotated from the unlocked position to the locked position moves ninety degrees from the vertical transition  930  through the major section  922  to the terminus  926 . With twist lock  954  in the locked position, key section  950  engages the lifting block (not shown) for hoisting the cargo container as previously described. Locking member  962  thus is adapted to interact with the recessed groove  916  of security housing  902  to lock or retain twist lock  954  alternatively in either the locked position or the unlocked position. 
     Locking member  962  can be of any specific construction suitable to be received in race  918  of recessed groove  916  for movement between the unlocked and locked positions. In the specific arrangement shown in  FIG. 17 ,  FIG. 18  and  FIG. 19 , locking member  962  includes a continuous cylindrical wall  966  having thereon a horizontal projection  970 . Horizontal projection  970  extends outwardly from cylindrical wall  966  and is sized to be received in race  918  of recessed groove  916 . Cylindrical wall  966  is supported relative to spindle section  958  by radial connecting member  974 . Locking member  962  includes handle  978  spaced in the vertical direction from connecting member  974 . Handle  978  extends between opposite points on cylindrical wall  966  and thus permits manual handling of twist lock  954  by personnel. In the specific arrangement illustrated, handle  978  is received by security cover  982 . Security cover  982  is adapted to receive and engage handle  978  when twist lock  954  is in the locked position (see  FIG. 19 ). Security cover  982  thus is adapted to maintain twist lock  954  in the locked position. Alternatively, security cover  982  receives and engages handle  978  when twist lock  954  is in the unlocked position (see  FIG. 18 ). Security cover  982  thus is adapted to maintain twist lock  954  in the unlocked position. 
       FIG. 21  is a perspective view of a spreader frame  400  according to an embodiment. Spreader frame  400  is identical to previously described spreader frame  100  except as otherwise described herein. Spreader frame  400  is adapted to support a container  500  as previously described. Spreader frame  400  includes a rigid frame structure  402 . Rigid frame structure  402  has suitable mechanical strength to support with an adequate safety factor the container  500  when fully loaded. It is to be understood that the rigid frame structure  402  can be constructed in any manner suitable to provide mechanical strength adequate to support the container  500  when fully loaded. In the specific embodiment illustrated in  FIG. 21 , the rigid frame structure  402  includes a pair of parallel elongated longitudinal frame members  404 . The rigid frame structure  402  includes a spaced pair of end members  406  joining the pair of longitudinal frame members  404  at opposite ends thereof. Each end member  406  extends between the pair of longitudinal frame members  404  in perpendicular relation thereto. The end members  406  and longitudinal frame members  404  thus cooperate to define a generally rectangular outer perimeter having four corners  408  disposed respectively in two opposite pairs. The rigid frame structure  402  includes a pair of intersecting, elongated x-brace members  410 . Each x-brace member  410  extends between a respective opposite pair of corners  408 . Respective ends of each x-brace member  410  are joined at respective corners  408  in a suitable manner. Intermediate corners  408  the pair of x-brace members  410  intersect in an x-intersection  412  at center  414  of the rectangular outer perimeter of rigid frame structure  402 . It is to be understood that the x-brace members  410  and x-intersection  412  can be constructed and joined in any suitable manner. It is anticipated that in some specific embodiments, x-brace members  410  will not be of identical construction. The rigid frame structure  402  also includes four security housings  416  each disposed at a respective corner  408 . The security housings  416  cooperate with respective twist locks  418  to support the container  500  as previously described. Rigid frame structure  402  has fewer intersecting members than previously described rigid frame structure  100  and thus can be manufactured with fewer welds or other suitable joining operations. 
       FIG. 22  is a perspective view of a spreader frame  450  according to an embodiment. Spreader frame  450  is identical to previously described spreader frame  100  except as otherwise described herein. Spreader frame  450  includes a pair of parallel, elongated longitudinal frame members  452  intersected by a pair of end members  454  extending perpendicular thereto. A plurality of cross members  455  are disposed intermediate end members  454  as previously described. Longitudinal frame members  452  and end members  454  are adjoined at respective corners  456 . Spreader frame  450  includes a plurality of spaced longitudinal alignment members  458  each mounted on a respective end member  454  for finding and aligning with a respective end wall (not shown) of a container (not shown). Spreader frame  450  includes a plurality of spaced side alignment members  460  each mounted on a respective longitudinal frame member  452  for finding and aligning with a respective side wall (not shown) of the container. In the specific embodiment illustrated in  FIG. 22 , spreader frame  450  includes four of the longitudinal alignment members  458  and four side alignment members  460 . In the specific embodiment illustrated and as shown in  FIG. 23 , one of the longitudinal alignment members  458  and a respective one of the side alignment members  460  are disposed in a respective alignment pairing  462  adjacent a respective corner  456 . The longitudinal alignment member  458  and side alignment member  460  of each alignment pairing  462  cooperate with the respective end wall and side wall of the container and thus find and align respective corner  456  with a respective lifting block (not shown) of the container. The spreader frame  450  thus includes four alignment pairings  462  which each cooperate with the container to align a respective twist lock  464  with the respective opening (not shown) of the respective lifting block of the container. The alignment pairings  462  thus cooperate with the container to align each twist lock  464  with the opening of each respective lifting block of the container. The alignment pairings  462  thus improve and speed alignment of the twist locks  464  with the lifting blocks for being attached to and supporting the container to be hoisted. 
     As can best be appreciated in  FIG. 23 , each alignment pairing  462  is mounted outboard of the respective supporting member in order to transfer horizontal forces from the spreader frame  450  to the container. More particularly, in each alignment pairing  462  the respective longitudinal alignment member  458  is mounted on the outer side or outboard of the respective end member  454 . The longitudinal alignment member  458  has an inner surface or stop  466  which stops against the end wall of the container when either the spreader frame  450  or the container is subject to horizontal force in the respective longitudinal direction. Also, in each alignment pairing  462  the respective lateral alignment member  460  is mounted on the outer side or outboard of the respective longitudinal frame member  452 . The lateral alignment member  460  has an inner surface or stop  468  which stops against the side wall of the container when either the spreader frame  450  or the container is subject to horizontal force in the respective lateral direction. The alignment pairings  462  being mounted outboard of the respective supporting members  452 , 454  thus prevent the twist locks  464  from being subjected to excessive horizontal forces when the container or spreader frame  450  experiences a collision. 
     Embodiments provide a spreader frame for hoisting a container which prevents the twist locks from being unintentionally or accidentally rotated to the open position before the container is hoisted or while the container is suspended from the hoist. Embodiments provide a spreader frame for hoisting a container wherein only vertical forces are applied to the container and twist locks when the container is suspended from the spreader frame. Embodiments provide a spreader frame which is connected to hoist equipment and to a container to permit the container to be safely hoisted from a supply boat to an off-shore oil platform even though slack is introduced into the hoist cable or wire rope slings. Embodiments provide a spreader frame which includes a safety feature that requires personnel acting deliberately with a tool to gain access to the twist locks to unlock or lock the spreader frame and container. 
     CONCLUSION 
     A spreader frame for hoisting a container is described. Although specific embodiments are illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations. For example, although described in terms of a spreader frame, one of ordinary skill in the art will appreciate that implementations can be made for other apparatus that provide the required function. One of skill in the art will recognize that embodiments having different dimensions and lengths can be constructed for use with containers of any desired size. For example, specific embodiments can be constructed for use with commonly used containers which are forty feet in length, or longer if desired, or shorter, such as six feet in length, if desired. 
     In particular, one of skill in the art will readily appreciate that the names of the apparatus are not intended to limit embodiments. Furthermore, additional apparatus can be added to the components, functions can be rearranged among the components, and new components to correspond to future enhancements and physical devices used in embodiments can be introduced without departing from the scope of embodiments. One of skill in the art will readily recognize that embodiments are applicable to future spreader frames and containers, different materials, different hoist equipment, and new container designs. The terminology used in this application is meant to include all environments and alternate technologies which provide the same functionality as described herein.