Abstract:
A safety tool is specifically adapted to aid in opening hinged rear doors of industrial containers safely, while also ensuring that the operator of the safety tool remain outside the potential zone of danger whenever the rear door has the potential to swing open. The present safety tool not only provides convenience and leverage for commonly performed door opening procedures, but also ensures that the operator&#39;s body and hands remain safely distanced from the direction of door travel and the potential discharge path of material contained within the cargo box. In addition, the present safety tool is lightweight and compact, allowing the tool to be easily stowed in or around a cargo box and/or truck to and thereby ensure that the safety tool is available whenever it may be needed to aid in opening and/or closing the cargo box door.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit under Title 35, U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No. 61/543,600 filed Oct. 5, 2011, the entire disclosure of which is hereby expressly incorporated by reference herein. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a tool used to safely open cargo doors, and in particular, to a tool adapted to safely open industrial strength hinged doors of the type commonly found in cargo trucks. 
     2. Description of the Related Art 
     Cargo trucks typically include a door at the rear opening of the cargo box to selectively prevent or allow access to the contents carried inside. In the case of industrial cargo trucks used for hauling bulk materials, such as dump trucks, the doors at the rear of the cargo box may be made from heavy duty materials, such as heavy gauge steel, to ensure that contained materials are secure within the cargo box during transport. 
       FIGS. 8 and 9  illustrate dump truck  100  in a cargo transport configuration ( FIG. 8 ) and a contents-discharging configuration ( FIG. 9 ). In industrial applications, such as in the construction and waste hauling industries, cargo box  110  mounted to dump truck  100  is made from heavy gauge steel such that cargo box  110  can be used to contain, transport and discharge large quantities of heavy bulk materials, such as gravel, building materials, earthen materials, steel and the like. As noted above, these industrial applications may provide a rear door  112  made from a similarly heavy-duty material having comparable strength to the walls and floor of cargo box  110 . 
     In use, dump truck  100  may collect cargo material M within cavity  114  of cargo box  110  at a cargo collection site, such as a raw materials manufacturer. In many cases, material M is loaded from above cargo box  110  using, e.g., a crane, front loader, elevator or other overhead loading device. During such loading from above, rear door  112  of cargo box  110  remains in the closed position shown in  FIG. 8  to ensure containment of material M within cavity  114 . 
     With material M contained in cargo box  110  and rear door  112  closed, dump truck  100  can be driven to the delivery site where material M is needed. At the delivery site, cargo box  110  can be elevated to utilize a gravity assist in discharging material M via door  112 . Alternatively, cargo box  110  can be lowered from truck  100  by sliding cargo box off of the truck frame while in the elevated configuration of  FIG. 9 , such that rollers  162  (see, e.g., FIGS.  10  and  12 - 15 ) contacting and roll along the ground as cargo box  110  slides away from truck  100 . 
     To discharge material M from cavity  114 , door  112  is opened and the front of cargo box  110  is elevated such that cargo box  110  pivots about a pivot point near the rear of cargo box  110  and underneath rear door  112 . As shown in  FIG. 9 , this reconfiguration of cargo box  110  into the discharge position causes material M to dump or fall out of cavity  114 . However, material M may also be discharged when cargo box is horizontal as shown in  FIG. 8 , or when cargo box  110  is on the ground as described above. 
     In many instances, door  112  is manually opened by an operator at the delivery site. In the case of cargo box  110  shown in  FIGS. 8 and 9 , rear door  112  pivots about a vertical axis passing through door hinges  116  ( FIG. 8 ). When cargo box is substantially filled with material M, and/or when material M shifts rearwardly during transport, a substantial amount of pressure may build up upon the inner surface of rear door  112 . This pressure is released upon the opening of rear door  112 , sometimes with significant force and suddenness. 
     To protect the operator responsible for opening rear door  112 , latch mechanism  118  is disposed along sidewall  120  of cargo box  110  such that actuation of latch mechanism  118  is performed out of the swing path (i.e., “door sweep”) of rear door  112  and away from the direction of material discharge from cavity  114 . However, the substantial weight of rear door  112 , combined with large and occasionally uneven pressures exerted upon rear door  112  by material M, can potentially cause rear door  112  to bind in the closed position even when latch mechanism  118  has been opened. When such binding occurs, the operator must improvise a way to exert additional opening force on rear door  112 . In some cases, the operator may place him or herself into the opening path of door  112  and/or the potential discharge flow path of material M in seeking to exert such additional force. In so doing, the worker may expose him or herself to injury. 
     SUMMARY 
     The present disclosure provides a safety tool specifically adapted to aid in opening hinged rear doors of industrial containers safely, while also ensuring that the operator of the safety tool remain outside the potential zone of danger whenever the rear door has the potential to swing open. The present safety tool not only provides convenience and leverage for commonly performed door opening procedures, but also ensures that the operator&#39;s body and hands remain safely distanced from the direction of door travel and the potential discharge path of material contained within the cargo box. In addition, the present safety tool is lightweight and compact, allowing the tool to be easily stowed in or around a cargo box and/or truck to and thereby ensure that the safety tool is available whenever it may be needed to aid in opening and/or closing the cargo box door. 
     In one form thereof, the present disclosure provides a method of safely manipulating a door of a cargo box through the use of a safety tool, the method including: rotatably affixing the safety tool to a lever of a latch mechanism by passing an open distal end of the safety tool over the lever, the latch mechanism operable to prevent or allow opening of the door based on a pivotal configuration of the lever; disengaging the latch mechanism from the door by pivoting the lever of the latch mechanism via the safety tool, the step of disengaging accomplished with a user of the safety tool spaced from the sweep of the door and from a direction of potential flow of material outwardly from the cargo box via the door; inserting a distal edge of a lever plate disposed at a distal end of the safety tool into a gap between the door and a sidewall of the cargo box, such that the safety tool extends away from the gap along a direction opposed to the sweep of the door; and levering the door toward an open position by applying a force to the safety tool, the step of levering accomplished with the user of the safety tool spaced from the sweep of the door and from the direction of potential flow of material outwardly from the cargo box via the door. 
     In another form thereof, the present disclosure provides a safety tool including: an elongate structure defining a tool longitudinal axis and an outer surface, the elongate structure having an open end at one of a proximal axial end and a distal axial end, the open end sized and configured to receive a lever of a latch mechanism; a handle affixed to the proximal axial end of the elongate structure, the handle defining a handle longitudinal axis substantially perpendicular to the tool longitudinal axis; and a lever plate affixed to the distal axial end of the elongate structure, the lever plate including: a proximal portion abutting and affixed to the outer surface, the proximal portion defining a plate-like structure substantially parallel to the tool longitudinal axis; and a distal portion angled with respect to the tool longitudinal axis and extending distally away from the distal axial end of the elongate structure, the elongate structure, the handle and the lever plate all affixed to one another such that the safety tool comprises a rigid monolithic structure capable of transmitting force and torque from the handle to the lever plate via the elongate structure. 
     In yet another form thereof, the present disclosure provides a safety tool for performing operations related to the opening of a rear door of a cargo box, the safety tool including: a pin removal means for loosening or removing a safety pin from a bore formed in the rear door; a safety chain disengagement means for disengaging a safety chain from a safety chain hook; and a latch mechanism actuation means for pivoting a latch mechanism lever between engaged and disengaged configurations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a safety tool made in accordance with the present disclosure; 
         FIG. 2  is a front elevation view of the safety tool shown in  FIG. 1 ; 
         FIG. 3  is a rear elevation view of the safety tool shown in  FIG. 1 ; 
         FIG. 4  is a right side elevation view of the safety tool shown in  FIG. 1 , it being understood that the left side elevation view is a mirror image of the right side elevation view; 
         FIG. 5  is a cross-sectional, elevation view of the safety tool shown in  FIG. 1 , taken along line  5 - 5  of  FIG. 2 ; 
         FIG. 6  is a top plan view of the safety tool shown in  FIG. 1 ; 
         FIG. 7  is a bottom plan view of the safety tool shown in  FIG. 1 ; 
         FIG. 8  is a perspective view of a dump truck having an attached cargo box in accordance with the present disclosure, with the cargo box shown in a material containment/transport configuration; 
         FIG. 9  is a perspective view of the dump truck and cargo box shown in  FIG. 8 , with the cargo box shown in a material discharge configuration; 
         FIG. 10  is a partial, rear perspective view of the cargo box shown in  FIG. 8 , illustrating use of the safety tool shown in  FIG. 1  to remove a latch pin; 
         FIG. 11  is an enlarged view of a portion of  FIG. 10 , illustrating disengagement of a latch pin during the removal process; 
         FIG. 12  is a rear, perspective view of the cargo box shown in  FIG. 8 , illustrating use of the safety tool shown in  FIG. 1  for disconnection of a safety chain; 
         FIG. 13  is a side, elevation view of the cargo box shown in  FIG. 8 , illustrating use of the safety tool shown in  FIG. 1  to facilitate disengagement of a latch mechanism; 
         FIG. 14  is a rear, perspective view of a portion of the cargo box shown in  FIG. 8 , illustrating use of the safety tool shown in  FIG. 1  to pry open the rear door of the cargo box; 
         FIG. 15  is a side elevation view of a portion of the cargo box shown in  FIG. 8 , illustrating the use of the safety tool shown in  FIG. 1  to provide an opening force upon the rear door of the cargo box; 
         FIG. 16  is a rear, perspective view of the cargo box and safety tool shown in  FIG. 15 , illustrating engagement of the safety tool with a rear door structure; 
         FIG. 17  is a rear, perspective view of a pull down mechanism used to secure the cargo box shown in  FIG. 8  to the dump truck shown in  FIG. 8 , illustrating the use of the safety tool shown in  FIG. 1  to manipulate the hold down mechanism; and 
         FIG. 18  is a rear, perspective view of a portion of the cargo box shown in  FIG. 8 , illustrating use of the safety tool shown in  FIG. 1  to urge the rear door of the cargo box into a closed position. 
     
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates an exemplary embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
     DETAILED DESCRIPTION 
     Turning now to  FIG. 1 , an overall perspective view of safety tool  20  is shown. As best seen in  FIGS. 3 and 4 , proximal tube  24  and distal tube  26  cooperate to form the overall lever-like structure forming the body of safety handle  20 , and together define longitudinal axis A extending along the geometric centers of proximal and distal tubes  24 ,  26 . Handle  22  is connected to a proximal end of proximal tube  24  to form a T-shaped structure, with a longitudinal axis of handle  22  substantially perpendicular to longitudinal axis A of safety tool  20 . Lever plate  28  is disposed at a distal end of distal tube  26  and connected to a sidewall thereof, and extends distally away from the distal terminal end of distal tube  26  (as measured along longitudinal axis A) while also angling away from longitudinal axis A. In an exemplary embodiment, a proximal portion  30  of lever plate  28  is a plate-like structure that is substantially parallel to the adjacent sidewall of distal tube  26 , while distal portion  32  of lever plate  28  forms angle a with axis A, as illustrated in  FIGS. 4 and 5 . As discussed in detail below, the angled arrangement of distal portion  32  of lever plate  28  cooperates with the location and configuration of lever plate  28  to provide multiple functions in the manipulation of rear door  112  and related structures using safety tool  20 . 
     In an exemplary embodiment, handle  22  is welded to the proximal end of proximal tube  24 . The distal end of proximal tube  24  is received within and extends into the proximal end of distal tube  26  by a distance D ( FIG. 5 ). Distance D is sufficient to ensure full transfer of torque and force from proximal tube  24  to distal tube  26  during use, as discussed in detail below. Proximal tube  24  is welded to the proximal end of distal tube  26  at this location, thereby affixing proximal and distal tubes  24 ,  26  to one another. Lever plate  28  abuts an outer surface of distal tube  26  near the distal end thereof, as shown in  FIGS. 2-4 . In an exemplary embodiment, lever plate  28  is welded to distal tube  26  to affix lever plate  28  to distal tube  26  is this abutting position. 
     Welding is an exemplary and effective method of joining handle  22 , proximal and distal tubes  24 ,  26  and lever plate  28 , such that safety tool  20  becomes a single rigid monolithic structure with no parts detachable from the structure. However, it is appreciated that other methods of joining the various parts of safety tool  20  may be employed within the scope of the present disclosure, such as fasteners, press or interference fits, and the like. In addition, it is contemplated that safety tool  20  could be created as a single, monolithic part without any pre-assembly or welding, such by casting, molding or 3D printing methods, for example. 
     In an exemplary embodiment, the overall length L ( FIG. 5 ) of safety tool  20 , measured along axis A, is about 3 feet, or more particularly 35.75 inches. In this exemplary embodiment, proximal tube  24  is a hollow rectangular steel tube having outside dimensions of 1 inch by 2 inches and a wall thickness of 0.063 inches. Handle  22  may be formed from a piece of round solid bar stock having a diameter of ⅞ inch or 1 inch, such that the cylindrical outer surface of handle  22  is substantially tangent to the wide (i.e., 2 inch) face of proximal tube  24  after assembly and welding. In this exemplary embodiment, handle  22  is approximately 8 inches long, thereby providing sufficient length to grip handle  22  with two hands during use of safety tool  20 . 
     Distal tube  26  may also be formed from a length of rectangular tube stock. In the above-described exemplary embodiment, distal tube has outer dimensions of 1.5 inches by 2.5 inches and a wall thickness of 0.063 inches. This larger cross-sectional size of distal tube  26  facilitates a firmly grasp by the user during use, while the relatively smaller size of proximal tube  24  reduces the overall weight and size of safety tool  20  in the area of tool  20  that is less likely to be grasped during use. In this exemplary embodiment, the axial length of distal tube  26  is approximately 10 inches to provide for a firm grasp thereof by the user at multiple different positions along axis A. 
     Continuing with specifications of the above exemplary embodiment, lever plate  28  is formed from a plate 3 inches wide (i.e., along a direction perpendicular to axis A) and about 4.25 inches long, and includes a bend formed about 2.5 inches from the distal edge of lever plate  28  to form angle a ( FIGS. 4 and 5 ). Lever plate  28  is centered on an outer surface of distal tube  26  along the wide dimension thereof (i.e., along one of the 2.5 inch faces). In the exemplary embodiment disclosed herein, lever plate  28  has a thickness of about 5/16 inch to provide substantial strength, as well as to facilitate use of safety tool  20  as a wedge to open a gap between door  112  and cargo box  110  (as described in detail below). 
     Continuing further with specifications of the above exemplary embodiment, distance D of overlap between the distal portion of proximal tube  24  and the proximal portion of distal tube  26  ( FIG. 5 ) is equal to about 2 inches, which is large enough to ensure full transfer of force and torque exerted upon handle  22  to distal tube  26  via proximal tube  24 , and small enough to avoid any unnecessary additional weight of safety tool  20 . Because the outer periphery of proximal tube  24  is smaller than the inner periphery of distal tube  26 , small gaps are formed between adjacent surfaces thereof when proximal tube is inserted into distal tube  26 . In order to fill these gaps, shims  34 ,  36  may be placed in abutting contact with the outer surfaces of proximal tube  24  and the inner surfaces of distal tube  26  (as shown in  FIGS. 5 and 7 ). Shims  34 ,  36  further prevent any relative movement between tubes  24 ,  26  and enhance the potential for full transfer of torque and force between handle  22 , tubes  24 ,  26  and lever plate  28 . 
     The present exemplary embodiment, when made from carbon steel components, weighs about 7 lbs. and is therefore easily carried and manipulated by a user. Alternatively, aluminum components may be used to bring the overall weight of safety tool  20  to less than 5 lbs. However, it is contemplated that other sizes, materials and structures maybe used within the scope of the present disclosure as required or desired for a particular application. For example, where additional weight can be tolerated and additional strength is desired, the size and/or thickness of handle  22 , tubes  24 ,  26  and/or lever plate  28  may be increased. Where size is desired to be minimized while preserving substantial strength, proximal and distal tubes  24 ,  26  may be formed from a single, monolithic solid bar or from a single thick walled tube, for example. 
     As illustrated in  FIGS. 1-5 , lever plate  28  includes notch  38 , which in an exemplary embodiment forms a half circle centered along the distal edge of distal portion  32  of lever plate  28  and having a radius of about ⅞ inch. In addition, this distal edge includes a tapered portion  40  extending across the width of lever plate  28 , interrupted by intersecting notch  38 . As described in detail below, notch  38  and taper  40  facilitate the use of safety tool  20  in various tasks relating to manipulation of door  112  during the opening procedure thereof. 
     Various functionalities and methods of use for safety tool  20  will now be described with reference to  FIGS. 10-18 . Turning to  FIGS. 8 and 10 , rear door  112  of cargo box  110  is shown in the fully closed, locked and secured configuration. In this configuration, one or more safety pins  122  ( FIG. 10 ) are received in corresponding bores formed in door  112  and in safety pin brackets  124  affixed to the frame of cargo box  110 , thereby preventing pivoting of rear door  112  into the open position. As described below, removal of pins  122  removes this barrier to opening movement. 
     In addition, an auxiliary safety chain  126  is affixed to rear door  112  and received within safety chain hook  128 , thereby also affixing safety chain  126  to sidewall  120  of cargo box  110  (i.e., the sidewall to which hook  128  is affixed). Safety chain  126  therefore prevents opening of door  112  when connected to hook  128  in the illustrated connected position of  FIG. 10 , while allowing such opening when safety chain  126  is disconnected from hook  128 . 
     Still further, main latching mechanism  118  is illustrated in a locked configuration in  FIG. 10 . In this locked configuration, latch boss  132  (affixed to rear door  112 ) is received within latch hooks  130  of latch mechanism  118 , thereby preventing any pivoting motion of rear door  112  about door hinges  116 . As described below, latch mechanism is configurable into a disengaged position which allows door  112  to pivot open. 
     With the above mentioned mechanisms in place and secured, rear door  112  is triple secured against opening. With door  112  redundantly secured in the closed position, dump truck  100  having cargo box  110  ( FIG. 8 ) can be loaded with material M and can transport material M as needed while ensuring containment of material M within cavity  114  of cargo box  110 . 
     When dump truck  100  arrives at its destination and a determination is made to discharge material M from cavity  114  of cargo box  110 , each of the above described safety/closure mechanisms must be disengaged to allow rear door  112  to pivot about door hinges  116  into the open configuration as shown in  FIG. 9 . 
     Normally, a first step toward opening rear door  112  is to remove safety pins  122 . However, pressure on rear door  112  from material M and/or eventual material deformation or degradation in the bores which receive pins  122  may result in a high level of friction between pins  122  and door  112  and/or pin blocks  124 . As illustrated in  FIGS. 10 and 11 , safety tool  20  may be utilized to provide the requisite leverage to free pin  122  from pin block  124 . Starting with lever plate  28  facing down (i.e., such that proximal and distal tubes  24 ,  26  are positioned above lever plate  28  as shown in  FIG. 10 ), lever plate  28  is inserted between the L-shaped protrusion  134  of pin  122  and the adjacent horizontal surface of the door reinforcement rib. As noted above, lever plate  28  may include taper  40  ( FIG. 1 ), which presents a less blunt and relatively sharp leading edge to facilitate initial insertion of lever plate  28  when the L-shaped portion of pin  122  is close to or abutting the adjacent surface of door  112 . 
     In addition, the shaft of safety pin  122  may be received within notch  38  formed in lever plate  28  ( FIG. 1 ) to facilitate full engagement of lever plate  28  with the surrounding structures. With lever plate  28  fully engaged with safety pin  122 , force F P  ( FIG. 10 ) is applied to handle  22  and/or one of proximal and distal tubes  24 ,  26  in order to pivot safety tool  20  upwardly about the point of engagement between safety pin  122  and lever plate  28 . As such pivoting occurs, the leading, distal edge of lever plate  28  advances upwardly, i.e., along the direction of removal of pin  112 , carrying pin  112  upwardly and out of the locked position. Because the hinge point of the lever action applied by such pivoting is at or near the bend between proximal and distal portions  30 ,  32  of lever plate  28  ( FIG. 1 ), a substantial mechanical advantage is made available to free safety pin  122  from pin block  124  with a relatively small force F P . With pins (s)  112  so removed, pin(s) no longer present an impediment to movement of rear door  112  with respect to the adjacent structures of cargo box  110  presented by safety pin  122 . 
     At this point in the door-opening procedure, latch mechanism  118  and safety chain  126  are the two remaining structures preventing rear door  112  from swinging open. Accordingly, disengagement of either latch mechanism  118  or safety chain  126  will eliminate redundancy of such safety mechanisms, leaving only one remaining before rear door  112  is free to open. An emphasis on safety of the operator dictates that from this point forward, the operator should remain next to sidewall  120  of cargo box  110 , and therefore away from the opening sweep of rear door  112  and the potential flow of material M discharging from cavity  114  once rear door  112  is opened. 
     The next step in the opening procedure is normally removal of safety chain  126 , which leaves only the primary latch mechanism  118  left for disengagement prior to freeing rear door  112  to pivot about door hinges  116 . To remove safety chain  126 , safety tool  20  can be employed to dislodge safety chain  26  from safety chain hook  128  as shown in  FIG. 12 . Standing in the vicinity of sidewall  120  of cargo box  110 , the operator can grasp safety tool  20  by handle  22  and distal tube  26 , which facilitates a firm grasp and reliable control of safety tool  20 . However, the user may grasp any convenient part of safety tool  20  as needed for this step. Notch  38 , formed in lever plate  28  as discussed above, can then be engaged with a link of safety chain  126  in the vicinity of hook  128  such that the engaged safety chain link is at least partially captured by lever plate  28 . Still standing near sidewall  120  and with hands spaced away from safety chain  126  and hook  128 , the user may then apply force F C  in a generally upward and rearward direction to dislodge safety chain  126  from hook  128 . In an exemplary method, force F C  is applied substantially along longitudinal axis A ( FIGS. 3 and 4 ) of safety tool  20 , which in turn provides optimal force transfer of force F C  via tubes  24 ,  26 . In this procedure, the operator&#39;s hands are kept well free and distanced from rear door  112 . If door  112  were to open suddenly upon disconnection of safety chain  126  from hook  128  (e.g., by a defective or improperly latched latch mechanism  118 ), neither the operator&#39;s body nor hands would be susceptible to impact by rear door  112  or by any material M flowing out of cargo box  110 . 
     With safety chains  126  and safety pins  122  now disengaged, latch mechanism  118  is the only remaining mechanism preventing rear door  112  from opening. When pressure on rear door  112  is present, such as where material M contained in cavity  114  is piled up on the inside face of door  112  ( FIG. 8 ), a large amount of friction may be present between latch hooks  130  and latch bosses  132  ( FIG. 13 ). In the illustrated embodiment of  FIG. 13 , lever  134  is provided as part of latch mechanism  118  to aid in the disengagement of latch hooks  130  from latch bosses  132 . More particularly, lever  134  can be grasped by the operator and pivoted around pivot points  136  to simultaneously disengage latch hooks  130  (which are joined by linkage  138 ) of latch mechanism  118  from latch bosses  132 . However, to provide mechanical advantage for such disengagement, the open distal end of distal tube  26  may be coupled with lever  134  as shown in  FIG. 13 . More particularly, lever  134  is passed into the internal cavity of distal tube  26  to rotationally couple safety tool  20  to lever  134  (and, ultimately, to latch hooks  130 ). Force F L  may then be applied upon proximal tube  24  and/or handle  22  of safety tool  20 , effectively increasing the length of lever  134  and providing additional mechanical advantage for disengagement of latch mechanism  118 . 
     At this point in the process of opening door  112 , the structures and mechanisms of cargo box  110  designed to maintain rear door in a closed position are all disengaged such that rear door  112  is free to pivot about door hinges  116 . In some cases, however, friction between rear door  112  and surrounding structures of cargo box  110  may still prevent rear door  112  from pivoting to the open position of  FIG. 9 , even if material M has built up pressure behind rear door  112 . Until rear door  112  is opened and any such pressure of material M is relieved, the operator cannot safely move away from sidewall  120  and toward the rear of dump truck  100 . 
     In order to urge rear door  112  open in such a situation, without leaving the safe position near sidewall  120 , safety tool  20  may be used as shown in  FIG. 14 . First, the distal edge of lever plate  28  is inserted into gap  140  formed between door  112  and sidewall  120 . Taper  40  formed at the distal edge of lever plate  28  ( FIG. 1 ) facilitates such insertion into gap  140  even if gap  140  is relatively small. Lever plate  28  should be inserted into gap  140  such that lever plate  28  faces forward toward the front of dump truck  100  and proximal and distal tubes  24 ,  26  face rearwardly toward the back of rear door  112 . As noted above, angle a is formed by distal portion  32  of lever plate  28  with respect to axis A ( FIGS. 4 and 5 ), which in turn causes proximal and distal tubes  24 ,  26  to be angled toward the front of dump truck  100  in the vicinity of sidewall  120 . This angled arrangement of safety tool  20 , facilitated by angle a, allows the operator to maintain his or her position near sidewall  120  and spaced away from the opening sweep of rear door  112  and any flow of material M from cargo box  110  upon opening of door  112 . With safety tool  20  inserted into gap  140  as shown in  FIG. 14 , the operator can push upon handle  22  and/or proximal and distal tubes  24 ,  26  to lever open gap  140  via lever plate  28 . In order to maximize leverage, the operator will naturally gravitate toward using handle  22  and the proximal end of proximal tube  24 , which in turn also spaces the operator as far from rear door  112  as possible. 
     The lever action shown in  FIG. 14  may be sufficient to open rear door  112 . However, if gap  140  has been opened as much as possible by safety tool  20  and rear door  112  remains stuck in a closed position,  FIG. 15  illustrates how safety tool  20  can be used to apply additional force tending to open rear door  112  while keeping the operator in a safe zone near sidewall  120 . The open end of distal tube  26  can be placed over lateral flange  142  formed at the end of latch boss  132 , as best shown by  FIG. 16 . Lever plate  28  is positioned away from rear door  112 , as illustrated, to prevent lever plate  28  from interfering with shaft  144  of latch boss  132 . In this position, the operator can apply force F B  to handle  22  along longitudinal axis A ( FIGS. 3 and 4 ) either continuously or in a “hammering” motion. Force F B  is efficiently transmitted to latch boss  132  via proximal and distal tubes  24 ,  26 , while the partially-nested engagement between flange  142  and the open end of distal tube  26  prevents safety tool  20  from slipping off of or away from latch boss  132  during the operation. Force F B  can be used to finally free rear door  112  from its closed position, all while the operator and his or her hands remain in the safe zone near sidewall  120  and safely spaced from rear door  112 . 
     With rear door  112  now open, cargo box  110  can be elevated into the configuration of  FIG. 9  and material M can be safely discharged from cavity  114  of cargo box  110  in accordance with standard procedures. 
     When discharge of material M is complete and the operator desires to reconfigure rear door  112  into the closed position of  FIG. 8 , safety tool  20  may be used to aid in this process, as shown in  FIG. 18 . In some instances, especially over time, rear door  112  may lower or “sag” upon opening. Such sagging may result from the weight of door  112  deforming hinges  116 , for example, or deforming the metal surrounding hinges  116 . When such sagging occurs, latch boss  132  may not align properly with latch boss receiver  146  formed on sidewall  120  of cargo box  110  when the operator attempts to pivot door  112  shut. In effect, the door must be slightly lifted up during the closing operation, such that latch boss  132  and receiver  146  align and allow door  112  to be fully closed. 
     Safety tool  20  can be used for this purpose by positioning the distal edge of lever plate  28  upon an adjacent truck frame structure  148 , as shown in  FIG. 18 . Proximal and/or distal tubes  24 ,  26  are then brought into contact with the lower edge of door  112 , establishing the distal edge of lever plate  28  as a pivot point. Force F D  is then applied to handle  22  and/or proximal tube  24  to apply both an upward lifting force and a forward closing force to door  112 , helping to simultaneously align latch boss  132  with receiver  146  and pivot door  112  into the closed position. In many circumstances, the distance between lever plate  28  and the point of contact between tubes  24  or  26  with the lower edge of door  112  is less than the distance from such point of contact to handle  22 , thereby providing a mechanical advantage in the closing of door  112 . In an exemplary embodiment, the step-like junction between proximal and distal tubes  24 ,  26  can be engaged with the corresponding lower/rear edge of door  112 , to further facilitate the lever action provided by safety tool  20 . 
     Once door  112  is placed into the closed position, latch mechanism  118  may be re-engaged by lowering lever  134  in the opposite motion shown and described above with respect to  FIG. 13 . If necessary, safety tool  20  may be used to re-engage latch mechanism  118  by reversing the procedure of  FIG. 13 . Safety chain  126  may then be re-engaged with hook  128  in typical fashion, and pins may be reinserted through door  112  and pins blocks  124  to effect the final securement of door  112 . Safety tool may be used as a blunt instrument to “hammer” or otherwise strike safety chain  126  and/or safety pins  122  as necessary. 
     Turning to  FIG. 17 , safety tool  20  has an additional use as a lever for manipulation of ratchet mechanism  150 . Ratchet mechanism  150  may be used to secure frame member  152 , located on the underside of cargo box  110 , to frame member  154  which is part of dump truck  100 . When so secured, cargo box  110  is prevented from lifting or pivoting away from its secured transport position shown in  FIG. 8 . 
     Ratchet mechanism  150  is affixed to truck frame member  154  as shown in  FIG. 17 , with ratchet strap  156  and hook  158  extending from ratchet mechanism  150 . Hook  158  is sized to be secured to cargo box frame member  152 , as shown. Ratchet mechanism  150  includes ratchet shaft  160 , which rotates freely in one direction to tension strap  156 , thereby pulling hook  158  firmly against cargo box frame member  152  and drawing frame member  152  firmly toward truck frame member  154 . Shaft  160  is prevented from rotating in the other direction by ratchet mechanism  150  unless catch  164  is released. 
     Ratchet shaft  160  can drive mechanism  150  in the free-spinning direction, and includes a transverse bore formed therethrough for receipt of a lever to provide driving torque. To facilitate the use of safety tool  20  as this lever, handle  22  can be sized to fit within the transverse bore of ratchet shaft  160  as illustrated in  FIG. 17 . With handle  22  so received, force F R  can be applied to one of tubes  22 ,  26  or to handle  22 , thereby providing torque to ratchet shaft  160 . The overall length of handle safety tool  20  offers a substantial mechanical advantage in tightening or otherwise manipulating ratchet mechanism  150 . 
     While this disclosure has been described as having exemplary designs, the present disclosure can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.