Bridges – Draw – Horizontally sliding
Reexamination Certificate
2001-05-25
2003-05-27
Hartmann, Gary S. (Department: 3671)
Bridges
Draw
Horizontally sliding
Reexamination Certificate
active
06568019
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
BACKGROUND OF THE INVENTION
The field of the invention is mechanical bridges and more specifically bridges including spans that are openable.
Bridges are required to facilitate convenient rail and vehicular traffic over rivers, streams, dams and the like (hereinafter collectively referred to as rivers). While bridges are necessary, unfortunately bridges can impede passage of vessels along rivers there below. In order to accommodate both rail and vehicular traffic over rivers and travel along the rivers by ships, barges, etc, bridge designers have developed several different mechanical type bridges including one or more bridge spans that can open and close.
One mechanical bridge type is generally referred to as a vertical-lift bridge. A vertical-lift bridge typically includes vertical towers at either end of a bridge span. When positioned for vehicular traffic, the span is in a low position where a top surface is aligned with top surfaces of adjacent bridge spans. To accommodate travel below the bridge span the span can be raised between the towers.
While vertical-lift bridges can accommodate both river and vehicular travel, these bridges have several shortcomings. First, vertical-lift bridges, while accommodating some river travel, still restrict travel as the lifted span remains above the area through which travel occurs. Second, the motors and other mechanical equipment required to lift the bridge span are relatively large and therefore expensive. In addition, because of the mechanics involved with vertical-lift bridges, maintenance costs for vertical lift bridges are relatively high.
Another mechanical bridge type is a swing span bridge. A typical swing span bridge includes a moveable span that pivots about a vertical axis to provide required opening clearance for navigation traffic. Swing spans are typically symmetrical with equal length cantilevers to each side of the vertical axis. Some swing span bridges, however, are configured with unsymmetrical cantilevers that are counterweighted to balance the bridge. Swing span bridges are advantageous as they provide unlimited vertical clearance for river bound traffic when the span is open.
Unfortunately swing spans also have several shortcomings. First, when a swing span is horizontally pivoted into the open position the span ends are generally considered to be navigational hazards. The span ends are directed against movement of water bound traffic and therefore are prone to vessel collision. Thus, often substantial fender systems are required to protect the span and vessels in the area. Second, swing spans typically require twice as much moveable length span as other mechanical span designs to provide the same opening width. This is because, as indicated above, most swing span bridges require equal length span segments cantilevered about the vertical pivot point. Third, the mechanical components required to manipulate the large span sections are generally relatively large and therefore relatively expensive.
Yet one other mechanical bridge type is referred to generally as a bascule type bridge. A typical bascule bridge includes a leaf that pivots about a horizontal axis to provide a required opening and clearance for river bound traffic. Counterweights are usually provided to balance the weight of the span and minimize the operating requirements on the drive machinery. The bascule span bridges provide unlimited vertical clearance when open.
Bascule bridges, like the other bridge types described above, have several shortcomings. First, the counterweight required to balance the bascule span is typically rather large. As most mechanical bridges are relatively low to the water, the counterweights are typically positioned above a span adjacent the moveable span. To support the counterweight these bridge types often require large and expensive overhead framing systems and massive foundations below the spans to handle the overturning moments that occur. Second, the mechanics required to control a bascule bridge are extremely complex and therefore expensive. Third, bascule bridges requiring massive counterweights are relatively unsafe in certain geographic areas that are subject to seismic tremors.
Thus, there is a need for a mechanical bridge that is simple, relatively inexpensive, provides unlimited vertical clearance and that does not require massive overhead or counterweight components.
BRIEF SUMMARY OF THE INVENTION
It has been recognized that a relatively simple bridge design can overcome many of the shortcomings of the prior art bridges described above. To this end, by moving a bridge span essentially within a single vertical plane from a supporting position into a storage position, system mechanics can be greatly simplified without sacrificing safety. To this end, in one embodiment, an openable span is moved laterally from a supporting position and then longitudinally along the side of an adjacent span to open a space for water bound traffic. In another embodiment an adjacent span is removed from its position adjacent an openable span and then the openable span is moved at least in part into the adjacent position to open a space for water bound traffic.
Thus, one object of the invention is to provide a simplified openable bridge design. This object is accomplished by minimizing required vertical span movement. In some embodiments there is no vertical span movement while in other embodiments vertical movement is limited in several ways. First, the vertical distance of movement is minimized. Second the size of the span that has to be moved is limited. To this end, when a first span is vertically moved and then a second span is horizontally moved into the space originally occupied by the first span, the first span is only half as large as the second span and hence a minimally sized span is vertically moved.
Another object is to provide a relatively safe mechanical bridge. To this end, because vertical span movement is limited, above deck structure is minimized. Because above deck structure is minimized bridges constructed according to the present teachings are relatively safe in various environments including those that may be subject to periodic earth quakes and other disruptive natural phenomenon.
Yet one other object is to provide a relatively inexpensive bridge system. Because most span movement is horizontal relatively small motors can be used to move spans on rollers as opposed to lifting the spans.
One other object is to provide a bridge where, when a span is open, the open space can accommodate passage of any vessel there below. To this end the present design has no components that remain above the open space after a span is moved.
Consistent with the above objects and advantages, the present invention includes a bridge assembly comprising first, second and third adjacent piers, the first and second piers defining a first space there between and the second and third piers defining a second space there between, third and fourth spaces above the first and second spaces, respectively, a first bridge span positionable so as to traverse the distance between the first and second piers within the third space, a second bridge span positionable so as to traverse the distance between the second and third piers within the fourth space, a first motivator linked to the first bridge span for moving the first span into and out of the third space and a second motivator linked to the second bridge span for moving at least a portion of the second bridge span from the fourth space to the third space so that at least a portion of the fourth space is unobstructed.
In some embodiments the invention further includes at least one intermediate pier between the second and third piers, the space between the intermediate and third piers being a fifth space, the space above the fifth space being an openable space, the openable space being the portion of the fourth space that is unobstructed when the portion of the se
Hartmann Gary S.
Quarles & Brady LLP
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