(1) Field of the Invention
The present invention relates to a mobile installation for loading, transporting and unloading such track parts as ties on, in and from open top railroad cars, which may be used in combination with a mobile apparatus for sequentially exchanging groups of old ties of a railroad track supporting the mobile apparatus, for example groups of one to three old ties between groups of one to three retained ties, for groups of new ties. The mobile installation comprises a train mounted for mobility along the railroad track and includes a plurality of the open top railroad cars, adjacent ones of the railroad cars being coupled together and each railroad car having two parallel side walls with top edges and two end walls, the end walls of the adjacent railroad cars defining respective gaps therebetween, a power-driven crane for loading and unloading the track parts and having an undercarriage supporting the crane for mobility in the direction of the railroad track, and a track supporting the undercarriage of the crane for mobility above the top edges of the railroad cars in this direction, the track comprising two parallel guide rails mounted on the top edges of the railroad cars and being spaced apart a distance corresponding to the gage of the crane undercarriage, the guide rails extending beyond the end walls of the railroad cars into the gaps between the adjacent cars.
(2) Description of the Prior Art
U.S. Pat. Nos. 4,175,902, dated Nov. 27, 1979, and 4,190,394, dated Feb. 26, 1980, disclose an apparatus and method for loading and unloading open top or gondola railroad cars used in the exchange of consecutive groups of ties. The apparatus comprises a train mounted for mobility along the railroad track and includes a plurality of the open top railroad cars having a considerable loading volume, adjacent ones of the railroad cars being coupled together and each railroad car having two high parallel side walls with top edges and two high end walls, the end walls of the adjacent railroad cars defining respective gaps therebetween, and a power-driven crane with booms for loading and unloading the ties and having two undercarriages supporting the crane for mobility in the direction of the railroad track. The undercarriages have pneumatic tires to enable the crane to be moved along a road or the railroad track, and the crane also has pivoted gliding feet or brackets for gripping the top edges, the relatively widely spaced top edges of the railroad cars serving as a track for moving the crane along the cars while the gliding feet grip the top edges. A cable is attached to the crane to pull the crane along the railroad cars as it is perched atop the cars. Operation of this apparatus requires great skill and a number of sometimes life-threatening manual steps. The movement of the crane between adjacent cars is particularly difficult and very time-consuming, which considerably reduces the efficiency of the operation. The crane movement along and between the cars is quite unstable, providing unsafe operating conditions and frequent interruptions. In addition, the tractor used for the crane must be specially designed to enable the crane to effectuate the required forward and rearward movements on the top edges of the gondola cars.
U.S. Pat. Nos. 4,096,954, dated June 27, 1978, and 4,099,635, dated July 11, 1978, disclose a gondola car loader and tie handler, as also described on page 68 of "Progressive Railroading", February 1978, which also uses a power-driven crane movable atop a train of gondola cars. Two beams may be pivotally mounted on the chassis of the crane at each side thereof and these pivotal beams carry two flanged wheels for guidance of the crane chassis along the top edges of the gondola cars. The spacing between the guide wheels corresponds at least to the gap between adjacent cars. Each beam is pivotal at the center thereof for rotation about a transversely extending axis and is connected to a pivoting drive so that the front beams may be swung upwardly when the crane is moved from one to the next car, the crane being advanced until the wheels of the front beams may be engaged with the top edges of the next car. The beams are then swung down while the rear beams are pivoted upwardly and then lowered again when their wheels are engaged with the top edges of the next car. The operation of this apparatus is also slow and uneconomical, the movement of the crane being unstable and, therefore, unsafe for the operating personnel. Bridging the cars is not only difficult and time-consuming but is highly accident-prone in view of the heavy weight of the crane.
The above-described mobile installations with a power-driven tie loading and unloading crane movable atop a train of gondola cars have such a low efficiency that they cannot be used economically in tie exchange operations since they would cause long sections of track to be blocked for long periods for normal train traffic.
U.S. Pat. No. 1,879,203, dated Sept. 27, 1932, discloses a train of open top railroad cars for loading, transporting and unloading bulk material. A self-propelled carriage for the bulk material runs on rails atop the cars, and a pivoted link arrangement is interposed between the rails in the gaps between adjacent cars to provide a continuous track from one end of the train to the other.