Abstract:
Deployable fall protection systems and components are disclosed for protecting against worker falls in cargo handling operations. Workers wearing harnesses are attached to a lifeline supported from overhead, the support being attached to ground-standing mast assemblies stabilized by the weight of a vehicle parked on a foot portion of the mast assembly.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to portable vehicle-stabilized masts and readily deployable and configurable fall protection systems, adaptable for use in cargo-handling environments. 
         [0003]    2. Description of the Related Art 
         [0004]    The loading and unloading of cargo and materials from vehicles, e.g., a flat bed truck, often requires personnel to be performing strenuous activity at a level several feet above ground level. Loading and unloading requires careful balance and stepping on or around uneven standing areas while carrying or manipulating cargo and while securing and covering the cargo. Moreover, such loading and unloading often occurs outdoors and may occur in adverse weather creating windy and/or slick conditions. Also, cargo may be unwieldy, may shift, and/or have an unstable center of gravity. Thus, for workers performing the loading and unloading tasks, there is an inherent safety risk of falling from a working-level height to the ground. 
         [0005]    The Bureau of Labor Statistics has reported that fatal work injuries involving falls number several hundred each year. The Department of Labor lists falls as one of the leading causes of traumatic occupational death, accounting for eight percent of all occupational fatalities from trauma. The Department&#39;s general guidance for worker safety provides that any time a worker is at a height of four feet or more, the worker is at risk and needs to be protected. In maritime activities, the distance is five feet and in construction, the distance is six feet. However, regardless of the fall distance, fall protection must be provided when working over dangerous equipment and machinery. In the United States, the Occupational Safety &amp; Health Administration and the labor and safety agencies of many states regulate worksite safety and require that adequate measures be taken to protect workers from falls. Thus, there is a critical need to provide fall protection for workers who are working above ground level, such as on the bed of a flat bed truck. 
         [0006]    Previous attempts to provide fall protection safety systems involve many trade-offs. For example, a fall prevention system available from Carbis, Inc. provides two fall prevention platforms between which a flatbed truck is driven and parked. At the press of a button, the platforms move together to sandwich the trailer in the middle. The system also may provide a platform on only one side. Such a system, however, has multiple disadvantages. First, the system is designed for permanent installation at a site rather than mobility for temporary use at various sites such as construction sites. Second, the height of the platform is fixed and cannot be raised or lowered for differing truck and load configurations. Third, ground-level workers and equipment (e.g., loading and unloading equipment) cannot access the platform side(s) of the truck bed. In a similar system from Safe Rack LLC, the platforms are mounted on wheels rather than being part of a permanent installation; however, platform height is not adjustable and ground-level access is equally impaired. 
         [0007]    Another fall protection system, Airtek Ireland&#39;s AirMat Safety System, may be temporarily deployed at various work sites. The system provides multiple inflatable modules in various sizes to accommodate a variety of truck and trailer length combinations. The modules are inflated by a pump-driven fan to approximately the height of the truck bed and placed alongside the truck or the truck is parked adjacent to inflated modules. If a worker falls from the truck bed to an area protected by one of the modules, the worker&#39;s fall is arrested and cushioned by the module. As with the Carbis system, ground-level workers and equipment cannot easily access the side(s) of the truck bed adjacent to the inflated modules. Moreover, a power source must continually be available to operate the fan. 
         [0008]    Systems provided by CAI Safety Systems allow a truck to park adjacent to a pair of permanently mounted “T Anchors” or mast arms. A cable or rigid rail is suspended from the T Anchors or mast arms at a height sufficiently above the truck and its cargo. A worker wearing a safety harness is tethered to the cable or rigid rail via a self-retracting lifeline. In case the worker falls, the fall is arrested by the system. Another worker must operate the self-retracting gear from its attachment point at the cable or rigid rail in order to lower the fallen worker to the ground. In an alternate arrangement interior to a building, the cable or rigid rail may be suspended from the building&#39;s overhead structure. Being permanently mounted to the ground or attached to a building structure, these systems cannot be easily deployed to temporary work sites. 
         [0009]    Japanese Patent Application JP2000-210389 discloses a dollied strut, two of which are wheeled up to a truck and affixed to the truck at several points. Once the struts are affixed to the truck, a rope is stretched between the tops of the struts and a lifeline is used to connect the rope and an on-vehicle worker. A disadvantage of this system is that the struts must be mechanically connected to the vehicle structure upon arrival of the vehicle at the work site in order for a worker to be able to safely work on the vehicle; conversely, the vehicle cannot depart upon completion of on-vehicle work until the system is mechanically disconnected from the vehicle structure. Moreover, trucks must be modified to have reciprocal attachment points for the struts. Also, due to the positioning of strut support members on and above the truck bed, free ground-level access to the truck bed and cargo is impeded. 
         [0010]    Thus, the systems mentioned above suffer from a number of deficiencies and disadvantages. The present invention can provide for easily deployable fall safety systems, easily configurable for use with differently-sized vehicles. Moreover the present invention does not require vehicles to be modified with attachment points and cargo areas remain accessible to ground-level personnel and equipment. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    According to one embodiment of the invention, a portable mast assembly for a fall protection apparatus is provided. The mast assembly has a foot configured to allow a vehicle wheel to be driven on and off the foot and parked on it, and a mast mounted on and extending up from the foot, the mast permitting the driving and parking on the foot and having a rigging attachment point at a distance away from the foot. The mast assembly is stabilized when the vehicle wheel is parked on the foot. 
         [0012]    In another embodiment, there is provided a fall protection apparatus having two portable mast assemblies and a tensionable line between their rigging attachment points. The apparatus may also include a tensioner adapted for adjusting the tension of the tensionable line. In embodiments of the invention, the mast assemblies are relocatable so that the apparatus may be used with vehicles having different wheel bases. 
         [0013]    In some embodiments, the tensioner includes a winch disposed on one of the mast assemblies. The winch may be a hand-cranked winch disposed on the mast assembly so that the hand-cranked winch is operable by a person at a ground level. The winch may include a brake configured to permit a controlled decrease in the tension of the tensionable line. In some embodiments, the tensionable line is high-strength aircraft-grade cable. In yet other embodiments, the fall protection apparatus includes a tether linkage slidably disposed on the tensionable line. In some embodiments, the apparatus includes a tether linked at a one end to the tether linkage and a worker harness linked to the other end of the tether. In some embodiments, the foot is configured to accept a lift fork for moving the mast assembly. 
         [0014]    In yet another embodiment of the invention, a vehicle stabilized portable fall protection system is provided. The system includes first and second portable mast units, each mast unit having a base and a mast mounted on and extending vertically from the base. Each mast unit is configured to allow a vehicle to be driven upon the base. The system further includes a mast-to-mast member disposed between and attached at points of the first and second mast units distal from the base. The system is configured so that a vehicle parked upon the base of each mast unit stabilizes the system to permit the mast-to-mast member to become stably load bearing. In some embodiments, the mast-to-mast member is a cable. In some embodiments, the load is an arrest of a falling mass. In some embodiments, the mass is a person wearing a personnel harness slidably tethered to the horizontal member. 
         [0015]    The above and other aspects and embodiments are described below with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments of the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. In the drawings, like reference numbers indicate identical or functionally similar elements. 
           [0017]      FIG. 1  illustrates an embodiment of the present invention in an exemplary usage scenario. 
           [0018]      FIGS. 2A and 2B  illustrate a mast in elevation and plan views, respectively, in accordance with an exemplary embodiment of the invention. 
           [0019]      FIGS. 3A and 3B  illustrate a fall protection apparatus in elevation and plan views, respectively, in accordance with an exemplary embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    With reference to  FIG. 1 , a flatbed truck  60 , carrying cargo  50  in its bed  64 , is at a work site. Worker  100  is working atop the cargo  50  and truck bed  64  at a height at which a fall to the ground could result in serious injury or death. According to one embodiment of the present invention, a safety apparatus is provided in which worker  100  is wearing safety harness  30  which is connected by lifeline  40  to cable  20 . Cable  20  is suspended between two mast assemblies  10 . Lifeline  40  is slidably attached to the cable so that the worker can easily move between the front and rear of the truck bed  64  without having to detach from the harness  30  or lifeline  40 . If worker  100  falls, the harness  30 , lifeline  40 , and cable  20  operate together to arrest the fall. Mast assemblies  10  remain stable because truck wheels  62  are parked on the feet  14  of mast assemblies  10 . The weight of the truck  60  through wheels  62  stabilizes mast assemblies  10  against movement and deflection to ensure that cable  20  remains sufficiently tensioned for proper fall arrest. 
         [0021]      FIGS. 2A and 2B  illustrate an exemplary embodiment of mast assembly  10  in elevation and plan views, respectively. Mast assembly  10  has a post or other substantially vertical member  16  attached to and extending upward from foot  14 . Angular members  12  may connect foot  14  and vertical member  16  for additional stability of the mast assembly  10 . Foot  14  may include receiving areas  15  which are placed and spaced so that a hand truck or fork lift may securely engage mast assembly  10  so that mast assembly  10  may be moved from work site to work site or within a work site. Foot  14  may also include drive-on and drive-off ramps  17 , which can allow a truck wheel or other weight to be rolled up onto the deck  19  of foot  14 . Sufficient weight (i.e., the weight of a parked vehicle) on deck  19  provides for stability of mast assembly  10  against lateral forces which would otherwise deflect or displace mast assembly  10 . 
         [0022]    In one embodiment, ramps  17  and deck  19  may be constructed of ½-inch reinforced steel. Mast assembly  10  may be further constructed of ASTM A36 compliant bars and/or tubular components. Components of mast assembly  10  may be welded or bolted together. 
         [0023]      FIGS. 3A and 3B  illustrate an exemplary embodiment of a fall protection system in elevation and plan views, respectively. Two mast assemblies  10   a  and  10   b  are deployed to a work site and are spaced apart in an area in which a fall safety device is required (e.g., a truck loading and unloading area). The mast assemblies  10   a  and  10   b  may be oriented and spaced apart from one another so that a truck may drive onto their feet  14   a  and  14   b  such that a forward wheel is parked on foot  14   a  of mast assembly  10   a  and a rearward wheel is parked on foot  14   b  of mast assembly  10   b . A mast-to-mast or horizontal member  20  is attached between mast assemblies  10   a  and  10   b  at attachment points  28   a  and  28   b , respectively. In one embodiment, horizontal member  20  is a cable attached via coupling  22 , block  24 , and winch  18 . Coupling  22  may include an eye bolt and utility swivel hook. The cable may be tensioned between two vehicle stabilized mast assemblies  10   a  and  10   b  by operating winch  18  to establish a pre-determined tension. When the fall protection system is deployed for simultaneous use by two workers, the pre-determined tension may be 500 pounds. The cable may be ⅜-inch diameter galvanized aircraft cable having a nominal strength of 14.4 KIPS. 
         [0024]    The fall protection system may further include one or more lifelines  40 , slidably attached to horizontal member  20 . In embodiments using a cable, the slidable attachment may be effected with a caribiner  26 . Lifeline  40  may be a retractable lifeline which, when attached to a worker harness  30  (see  FIG. 1 ), is played out to a length appropriate to mobility requirements of the worker in view of the height at which the worker is working. 
         [0025]    In embodiments having winch  18 , the winch may include a braking feature by which the cable may be controllably detensioned. This feature allows a worker whose fall has been arrested by the fall protection system to be safely lowered to ground level by an individual operating winch  18  from ground level. An advantage of this feature is that worker can be promptly and safely lowered to the ground personnel at ground level, thus avoiding any delay in which suspension trauma, i.e., orthostatic intolerance, can set in. Suspension trauma can result in unconsciousness in minutes and subsequent fatality. In one embodiment, the winch may be a Thern winch with brake (e.g., model M492B), having a load rating of 10,000 pounds. 
         [0026]    In one operational scenario, mast assemblies  10  are aligned and positioned a distance apart so that a flatbed truck  60  may drive wheels  62  onto feet  14  such that a forward wheel  62  is parked on a forward mast assembly  10  and a rearward wheel  62  is parked on a rear mast assembly  10 . One or two carabiners  26  are clipped onto cable  20  and a corresponding number of retractable lifeline spools  40  are connected to the carabiners  26 . The cable  20  is then winched to an approximate 500 pound preload. Workers ascend to the truck bed level  64  using portable stairs (not shown) and attach their body harnesses  30  to lifelines  40 . In the event of a fall, personnel working at ground level can promptly detension cable  20  using braking winch  18  to lower the fallen worker  100  to ground level. 
         [0027]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments.