Patent ID: 7707944

Claim:
Apparatus for applying ballast to a bed of a railway having a ballast deficient zone occupying a preselected span along the railway having first and second ends using a railcar that carries ballast and has a ballast door which can be opened to discharge ballast to the bed and closed to prevent ballast discharge as the railcar travels along the railway, said apparatus comprising: a plurality of radar reflective reference locations along the railway each a known predetermined distance from said ballast deficient zone; a radar transmitter on the railcar for directing a radar signal toward each reference location that is approached by the railcar; a radar receiver on the railcar for receiving a reflected radar signal reflected from each reference location; means for determining the current location of the railcar relative to each reference location based on the reflected radar signal to thereby determine the current distance of the railcar from said ballast deficient zone; means for determining the current distance of the railcar from said first and second ends of said ballast deficient zone using said current location of the railcar; means for detecting when the current distance of the railcar from said first end of said ballast deficient zone is equal to zero; means for opening said ballast door to initiate discharge of ballast from the railcar when the current distance of the railcar from said first end of said ballast deficient zone is approximately equal to zero; means for maintaining said ballast door open to continue discharging the ballast from the railcar while the railcar traverses said span from said first end to said second end; means for detecting when the current distance of the railcar from said second end of said ballast deficient zone is equal to zero; and means for closing said ballast door to terminate discharge of ballast from the railcar when the current distance of the railcar from said second end of said ballast deficient zone is approximately equal to zero.