Fire escape – ladder – or scaffold – Torso harness
Reexamination Certificate
2002-06-28
2004-07-20
Thompson, II, Hugh B. (Department: 3634)
Fire escape, ladder, or scaffold
Torso harness
C182S045000, C182S113000, C248S237000, C052S749100, C256S059000, C256SDIG006
Reexamination Certificate
active
06763910
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to products and methods for providing fall protection systems for construction workers, maintenance workers, inspectors and others who work or walk upon elevated structures. More particularly, it relates to fall protection systems which employ safety stanchions mounted to the elevated structure so as to anchor and support safety cables (commonly known as horizontal lifelines).
BACKGROUND OF THE INVENTION
It is common for workers to work and walk upon the roofs (which include large commercial skylights) of commercial buildings, which are flat and of varying slopes—some of which are quite severe. Obviously, it is important but often difficult to protect such workers and others from harm if they happen to slip and fall off the roof. It is common during the construction phases and during repair and replacement of roof structures, that the roof surface will have holes in the interior sections of the plane of the roof. Thus, falls to the interior of the building as well as off the edge of a roof are ever present dangers.
It is also important, for the purpose of controlling costs, that any fall protection system which is put in place to protect the workers be relatively inexpensive and easy to install and cause little interference with the work being carried out by the workman. Further, the fall protection system should also preferably be adaptable to virtually any roof, whether the roof is very rigid and uses more massive structural components such as those made with structural beams and joists, or the roof is relatively lightweight and designed for movement or flexion (such as a large skylight canopy), or the roof is for a lightweight metal building, which are characteristically made with lighter weight rafters and purlins. Some roof systems employ poured concrete on top of metal decking, and it would be desirable if a fall protection system were mountable to these systems as well.
Most conventional fall protection systems to which the present invention relates involve systems for supporting the worker (after a fall) with a safety cable that may be anchored and supported in various ways. Once a safety cable is anchored and supported, workers may be assured that they will be suspended in the case of a fall by attaching themselves to the safety cable, as, for example, by way of a safety lanyard attached both to the cable and to a harness worn by the worker. However, virtually all such systems involve heavy structural attachments that penetrate the roof surface to attach to structural metal below and are also rigid and unyielding. This makes such systems undesirable and extremely expensive to install if a building owner wishes to retrofit his building with system after the structure has been erected, due to the potential for damage to interior tenants, and water infiltration during construction among other inconveniences typical to a significant remodeling project.
Moreover, after a fall arrest, a typical system is taken out of service, and it is likely that the safety stanchion posts of the system will have to be removed, inasmuch as the post as well as the mounting will have been subjected to severe forces and therefore are likely to have suffered damage. Obviously, replacement of the stanchions is objectionable for the same reasons described earlier with respect to the initial installation of such systems. Replacement is also objectionable due to the additional costs and potential damage to the building as a result of the repair.
Other conventional systems (such as that described in U.S. Pat. No. 5,287,944 to Woodyard) (which is commonly employed only during construction of wood roofs) employ a large obtrusive plate that keeps the cable so low and slack so as to lay and flop against the roof surface. This is unacceptable to builders, manufacturers, and owners of finished long life roof systems made of coated sheet metals and glass. If a structure such as Woodyard's were increased in height the increased leverage would likely rip it off the roof, thus rendering it unreliable as well as larger and harder to attach and potentially causing more damage during installation. Indeed, a cable that is not adequately supported is potentially dangerous since it is likely to bang violently against the glass plates during a wind storm and potentially fracturing the glass and injuring people. If the cables are tightened, (for instance to get rid of some sag) the forces go up so significantly that the tension in the cable alone could cause damage to many roofs, even before the massive forces of a fall arrest event are applied. Therefore, it can be seen that there is a need for a system that has some height so as to keep the cable supported and off the roof; some means to support the cable at intermediate points that are not obtrusive nor expensive; does not require penetration of the roof structure; is aesthetically pleasing; allows for cable sag (or does not require cable tensioning) for reduced forces (but not so much that the cable begins to cause damage to the fragile glass, metal or other roof material); reduces forces by using sacrificial members and allows the cables to be lowered during a fall arrest to reduce leverage and force at the end points—with the feature of having the sacrificial parts easily replaceable without having to further disturb the roof system and penetrate the building which exposes the tenants and the owners to potential damage and delay. Further, the system is preferably lower cost and easier to install due to surface mounting rather than requiring significant penetration of the roof to install.
Unfortunately, in many commercial buildings such as those of the type known as system metal buildings (also known as pre-engineered metal buildings or “Butler buildings”) and large commercial skylights and canopies, workman must walk and work upon these sloped roofs where there are few or no suitable anchoring points for attaching safety cables. Many manufacturers of these structures do not have the expertise to design fall protection systems and many shy away from the liability, assuming safety systems are complex and require significant maintenance. Most commercial buildings in service today, and even those currently under construction still do not have any type of safety or fall protection roof structure installed.
A previous invention of which I am a co-inventor and which is described in U.S. Pat. No. 6,173,809 provides a safety stanchion for mounting upon a surface such as structural I or H shaped beam which are typically found in the superstructure of a bridge, a building or some other structure being built.
This safety stanchion includes a tapered tubular post having a lower end for attachment to a support base at preferably an oblique angle and an upper end for supporting a safety cable and the like. Due to its tapered shape, the post's upper end has an outside diameter which is less than that of its lower end. The post also preferably has a wall thickness of less than 0.125 inches and is frustoconically shaped. In addition, the post is preferably made out of an energy absorbing, elastic-like, high strength steel such as A595 grade steel which in cooperation with the post's wall thickness and tapered, preferably frustoconical, shape is believed to render the post capable of inelastically deforming before it fails, thereby better able to break a worker's fall without actually breaking in half. Fail or failure of the post as used herein refers to a post which has actually broken or buckled to a point where it is no longer capable of providing any significant resistant to lateral forces or other forces tending to cause bowing of the post.
In the preferred safety stanchion of this type, the tapered post is capable of flexing and permanently (or inelastically) deforming without failing, in response to sudden loads (within its design limits) that might occur when a person who is attached to the stanchion (or a cable suspended between two stanchions) via a lanyard falls from an elevated beam or simil
MC Enterprises International, Inc.
Smith, P.C. Brian D.
Thompson II Hugh B.
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