Traversing hoists – Traveling bridge
Reexamination Certificate
2000-10-05
2001-05-15
Brahan, Thomas J. (Department: 3652)
Traversing hoists
Traveling bridge
C212S344000, C105S215200
Reexamination Certificate
active
06230911
ABSTRACT:
BACKGROUND OF THE INVENTION
Gantry cranes are conventionally used in railyards or other types of shipping yards for loading and unloading large containers or other loads to and from railcars, trailers, etc. Such a crane typically has a steel frame including four vertical columns located at corners of the crane. The columns are joined by upper horizontal beams. These beams support a movably suspended lifting mechanism, known as a grappler or spreader, configured to engage, lift and lower a container or load.
The crane runway surface of a shipping yard may be asphalt, concrete, gravel, dirt, or another suitable surface, collectively referred to herein as a “road surface.” So that a conventional gantry crane can be driven around on the road surface of a shipping yard, the crane is equipped with four corner-mounted sets of one or more wheels, referred to herein as “roadwheels” (such cranes are generally described herein as “road traveling” cranes). More specifically, each of the roadwheels is mounted in a yoke or truck at the bottom of a respective one of the columns. Typically, at least two of the roadwheels are steerable, and at least two of the roadwheels are motor-driven. The operator can thereby maneuver the crane around the shipping yard as desired for lifting, lowering, and moving containers.
Conventionally, each of the roadwheels has a rigid steel center having a circumferential rim with a rubber off-highway tire mounted concentrically thereon. The rubber tires are compressible under a load. More specifically, the rubber tires deflect against the road surface under the weight of the crane. The amount of deflection increases due to weight of a container lifted by the lifting apparatus. Additionally, the lifting apparatus may be traversed along the horizontal upper beams of the gantry crane, shifting the weight distribution non-uniformly among the respective roadwheels depending on the particular position of the grappler or spreader. Additionally, tire deflection may result in increased tire wear against the road surface.
It is desirable to minimize tire deflection in order to reduce tire wear. It is also desirable to improve steering control of gantry cranes which lift heavy loads.
SUMMARY OF THE INVENTION
In shipping yards, standard railroad tracks are commonly present to accommodate the movement of freight trains, railcars and/or other rail-supported equipment. These tracks are often located immediately adjacent a location where containers must be loaded or unloaded from railcars, trucks, pallets, etc. The loading and unloading of containers in such environments is typically performed by a gantry crane.
Accordingly, a specific object of the invention is to provide a railwheel for a road-traveling gantry crane to utilize a rail of a standard railroad track for auxiliary load support.
Another specific object of the invention is to provide a railwheel for a road-traveling gantry crane to utilize a rail of a standard railroad track to provide crane-steering guidance.
The present invention achieves these objects by providing a gantry crane that may be selectively driven only on wheels having rubber tires and, the crane is additionally equipped with steel railwheels on one or both sides of the crane so the crane can be operated in a rail-supported mode.
The present invention also achieves these and other objects by providing a system including a plurality of railwheels which are respectively mounted relative to the roadwheels of a gantry crane. The system of the invention includes an apparatus and method for transferring crane loads through the railwheel to the rail. In a particular embodiment, the railwheel is mounted on a common axle to the rigid wheel center of the roadwheel. The rigid wheel center may have a flange to accommodate mounting of the railwheel thereto by bolts. Railwheels are provided on one or both sides of the crane.
The railwheel is sized relative to the tire so that a clearance exists between the rail wheel flange and the road surface when the tire is at maximum deflection under the maximum load. This allows the crane to travel freely about in the loading yard supported only by its rubber tires on the crane runways and to lift loads in a conventional manner.
For placing the railwheels to ride along the rail, according to one embodiment of the invention, a ramp is positioned adjacent the rail. The crane is driven so that the rubber tires adjacent the railwheels travel down the sloping ramp until the railwheels contact the rail. In this embodiment, it is possible that the roadwheels may become suspended over the ground, with all of the wheel loading being transmitted from the associated railwheel to the rail. More specifically, as the crane continues moving, the railwheel rides along the rail, while the ramp may continue to slope downwardly, away from the tire of the associated roadwheel. Thereby, one side of the crane is supported by the railwheels on the rail, and the other side of the crane is supported by the rubber tires on the road. Also, in an embodiment wherein railwheels are equipped on both sides of a crane, a second rail and ramp arrangement may be provided at the other side of the crane to position both sides of the crane supported on the rails.
According to an embodiment of the invention, the railwheel is normally raised over the ground a distance greater than the height of a rail during unloaded or light loading conditions. In such a state, the railwheel does not contact the rail, and, therefore, all of the axle load is borne by the roadwheel and is transmitted to the ground via the tire. The difference in circumference between the railwheel and the tire provides vertical clearance of the railwheel over the ground sufficient that the crane may be maneuvered to position the railwheel vertically over the rail. However, the difference in circumference is also such that when the tire deflects against the road a predetermined amount due to increased loading, the railwheel moves downwardly to contact against the rail. At this point, additional loading is transmitted to the rail through the railwheel, and further deflection of the tire of the associated roadwheel is prevented. Such an embodiment advantageously limits the amount of tire deflection beyond a predetermined amount.
An advantage of the present invention is that it provides a crane that can operate fully on rubber tires on both sides of the crane, or supported on a rail on one side, or supported on a rail on both sides.
The crane utilize one of the rails of a railroad track, independently of the gauge of the track. This advantageously permits the crane to be used in an environment with a railroad track without a need to adapt the crane for a particular track gauge.
A further advantage of the present invention is that it provides a dual-flange railwheel which guides movement of the gantry crane along the rail, eliminating steering effort by the operator.
Additional features and advantages of the present invention are described in, and will be apparent from, the disclosure herein, including the drawings, description, and claims.
REFERENCES:
patent: 1853572 (1932-04-01), Nugent
patent: 2120098 (1938-06-01), Hug
patent: 2135307 (1938-11-01), Keator
patent: 2150348 (1939-03-01), Strauss
patent: 3247974 (1966-04-01), Dechantsreiter
patent: 4708066 (1987-11-01), Heckman
patent: 6158602 (2000-12-01), Zakula et al.
patent: 314212 (1919-09-01), None
patent: 331913 (1930-07-01), None
patent: 364635 (1939-03-01), None
Van Gorp Eric Brian
Zakula, Sr. Daniel Brian
Brahan Thomas J.
Leydig , Voit & Mayer, Ltd.
Mi-Jack Products Inc.
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