This invention relates to fall protection systems, and in particular, to a truss-style trolley beam for fall a protection system.
The fall protection equipment industry in both the United States and abroad manufactures and installs several types of overhead fall protection systems. Fall protection systems are typically, though not exclusively, used to prevent workers from accidental falls from the tops of railroad cars, tanker trucks and similar rolling or stationary vehicles (used primarily during loading/unloading), and other stationary structures such as at the tops of tall silos and buildings and other structures that, while being traversed, provide fall hazards and may require supplemental protection for workers who traverse them.
Virtually all fall protection systems typically include a safety harness (which is worn by the user of the system) which is secured to a lanyard (often a spring loaded retractable webbed belt feeder) to restrain the worker from falling. The lanyard is also commonly referred to as a "lifeline". The lifeline portion of the lanyard is usually manufactured of nylon woven belt webbing or stainless steel cable. The safety harness is normally manufactured of nylon webbing material and is designed to distribute the loading stresses of a fall arrest toward the seat and thighs of a worker, thus preventing serious injury in the event of a fall.
Most applications for these systems also allow the worker to move with ease about the structure or vehicle being traversed, and the majority of these systems therefore include some sort of trolley, or traversing mechanism, which allows the worker to tether himself to the system and move about while maintaining constant protection in the event of a fall.
The most common fall protection system currently in use today is the "safety cable" system. In this system, a stainless steel cable (or a similar cable made of a synthetic material) is securely strung between two or more anchor points. A trolley mechanism is mounted on that cable to secure the lanyard and therefore support the worker in the event of a fall.
A second type of fall protection system, in limited commercial use today, is the trolley beam (or I-Beam) style system. The typical I-beam style fall protection system includes an I-beam supported above the structure to be traversed, a trolley which rides on the I-beam, and a safety harness which is worn by the worker. The trolley in the I-beam system is typically a four-wheeled device that is designed to ride on the lower leg or flange of the I-beam, and includes an attachment point (typically a carabiner) to secure the lifeline to the trolley.
Due to static loads and the loads placed on the I-beam when a worker falls, the I-beam is prone to flexing, sagging, drooping, warping or otherwise distorting. To overcome this, supporting members have to be installed every 6'-7' feet along the length of the I-beam to prevent the I-beam from flexing or otherwise distorting. Further, because of the flexing, the I-beam systems typically have a maximum weight allowance. These factors severely limit where I-beam style systems can currently be installed. Practical applications are limited to those in which the I-beam rail can be directly and securely attached to an existing structure. The only previously known and recognized means of mounting the I-beam was to hang the I-beam over the planned area by attaching it with bolts or welds directly onto existing steel roof beams, perlins, or other similar pre-existing structures already in place at the point of installation. Because of these limitations to the I-beam style fall protection system, the safety cable fall protection system has dominated the industry.