Hydraulic and earth engineering – Earth treatment or control – Shoring – bracing – or cave-in prevention
Reexamination Certificate
2000-04-05
2004-11-23
Hartmann, Gary S. (Department: 3671)
Hydraulic and earth engineering
Earth treatment or control
Shoring, bracing, or cave-in prevention
C405S272000
Reexamination Certificate
active
06821057
ABSTRACT:
TECHNICAL FIELD
This invention relates to shoring apparatuses or devices for trenches, pits or other types of open excavations employed in construction industry.
BACKGROUND OF THE INVENTION
This invention relates to shoring devices for open excavations such as trenches and pits. The device includes vertical rail posts spaced apart from each other along the trench and arranged symmetrically on both sides of the trench. Opposite rail posts are kept vertically equidistant on either side of the trench by an articulated truss able to adjust the trench width. The rail post has on both sides a channel of stepped cross section. Each step constitutes a vertical guide to slide at least one shoring panel. The shoring panels slide between each corresponding guide of adjacent rail posts and, according to the number of the guides, form two or more shoring walls. Thus, the panels slide past each other creating stepped shoring wall from the top to the bottom of the excavation. The outermost and innermost steps of the shoring wall are called respectively “outer” and “inner walls” and so the panels. All other panels in between are called “intermediate”. The connections between rail posts and shoring panels are performed by magnetic forces engendered by magnetic flat bar incorporated in the lateral ends of the panels. For safety purposes partial locking may be used for the outer and inner panels. The intermediate panels slide completely free relative to the rail post. The articulated truss is of scissoring type composed by triangular cells only. The cross members of the truss are pinned at their midlength allowing rotation relative to each other such rotation allows adjustment of the truss width to several trench widths. The extremities of the cross members are pinned into vertical members of the truss which slide “formlockingly” along the rail post. For very deep applications, the vertical members of the truss have lateral guides for sliding additional panels at the bottom of excavation.
It is known to provide shoring devices having vertical rail posts, shoring panels and horizontal spreaders pressing the shoring walls against side wall of the trench. Such shoring devices are called as ‘Slide Rail Shoring Systems’.
Previous slide rail shoring systems as disclosed in U.S. Pat. Nos. 3,910,053 and 4,657,442 (Krings), use a rail post having individual formlocking channel connections of ‘C’ type for sliding the panels. The load developed by the active pressure of the excavation walls is spread on very limited areas of contact between post and panel whereon the stresses are highly concentrated becoming sources of high friction and temperature during the installation and removal of the system. Thus, damages is caused to both rail post and the panel, which strongly limit the application of a such system in pipeline productions, where the installation and removal of the system are effectuated continuously.
The U.S. Pat. Nos. 5,310,289 and 5,503,504 (Hess et al.), disclose a rail post having a unique channel for a maximum of two shoring walls, created by an outer and by an inner panel. Only the outer panel slides formlockingly within the post; the inner panel is completely free and slides inside the outer panel and the rail posts. The design of inner panel presents a risk of kicking in the trench when adjacent rail posts are not plumb. This is an important safety concern for the worker inside the trench. This phenomenon becomes prominent when the depth of excavation is over 20′ deep. On the other hand, shoring of excavations over 16′ deep requires the stacking and connection of two or more panels, which later must be removed at once. Removing two or more panels at once is a very difficult task and sometimes even impossible to accomplish even when heavy duty equipment is used. Yet another concern faced by this design is the difficulty of removing the inner panel when the deflection of the upper panel has begun. Also, it should be noted that a slide rail shoring system using differing types of panels a requires much bigger inventory of panels than its counterparts that use interchangeable panels.
The U.S. Pat. Nos. 3,950,952 (Krings), 5,310,289 and 5,503,504 (Hess et al) disclose very similar strut frames having a rectangular structure where the vertical members are equipped with rollers. These frames are designed to slide vertically between opposite rail posts in order to support the load coming from either side of the shoring walls. From an engineering standpoint, a frame having a rectangular cell is not a stable structure because it will deform without affecting the length of its members. Additionally, the lower horizontal strut of the frame diminishes the pipe culvert thereby requiring special solutions for the installation of pipes having big diameters or of big box culverts.
BRIEF SUMMARY OF THE INVENTION
Substantially, the intent of present invention is to provide a shoring device of the type described above that reduce the friction and the stresses in the contacts between components, while increases the safety and eases its use in great depths. Pursuing this object and others that will become explicit hereafter, one aspect of the present invention resides on the design of the rail post. The rail post has channels of stepped cross section that permit the presence of more than two shoring walls in that single channel without increasing the material expenditure and eliminate the interference between panels as well. Since the vertical guide of the rail post is of stepped cross section, it excludes the contact between rail post and back panel, while the contact area in the front panel is increased. Another new aspect of the invention is the incorporation of magnetic flat bars in the lateral ends of the panels thereby simplifying the connections between rail post and panels and reducing the risk of damage.
The first object of this invention is to present a slide rail system having partially or completely open sliding connections for the panels along the rail post. Also, it is an object of this invention to provide a rail post in which two or more panels may slide past each other, without need for stacking. This tremendously extends the shoring depth for a slide rail shoring system. Another object of this invention is to present an articulated truss able to adjust to several trench widths, while providing a big pipe culvert. The truss is able to preform a role in addition to just supporting opposing rail posts, such sliding additional panels in its vertical members. Also, it is the object of the invention to introduce accessory devices to be used in conjunction with the slide rail shoring system to increase safety and to facilitate its installation and removal. It is the final object of this invention to present a slide rail shoring system that has no practical limit to the depth of excavation.
The new features of the invention are set forth in the appended claims. Other advantages of the invention will be appreciated upon review of the following description and drawings.
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Hartmann Gary S.
Morrison & Foerster / LLP
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