Automatic car retarder control system

Claim 1

CONTROL APPARATUS FOR CLASSIFICATION YARDS HAVING A STRECTH OF RAILWAY TRACK OF PREDETERMINED LENGTH AND GRADE AND A CAR RETARDER LOCATED NEAR THE ENTRANCE END OF SAID STRETCH, COMPRISING, MEANS FOR MEASURING THE ROLLING CHARACTERISTICS OF A CAR APPROACHING SAID RETARDER, COMPUTING MEANS CONTROLLED BY SAID MEASURING MEANS FOR COMPUTING A SPEED AT WHICH THE CAR SHOULD LEAVE SAID RETARDER TO TRAVEL TO A PREDETERMINED POINT IN SAID STRETCH AND ARRIVE AT SUCH POINT AT A PARTICULAR PRESELECTED SPEED, MEANS FOR MEASURING THE ACTUAL SPEED OF A CAR PASSING THROUGH SAID RETARDER, AND MEANS JOINTLY CONTROLLED BY SAID COMPUTING MEANS AND SAID SPEED MEASURING MEANS FOR RELEASING SAID RETARDER WHEN THE SPEED OF SAID CAR SUBSTANTIALLY EQUALS SAID COMPUTED SPEED, ERROR DETERMINING MEANS OBTAINING A DIFFENENCE BETWEEN THE MEASURED ACTUAL CAR SPEED AND THE COMPUTED LEAVING SPEED, AND MEANS CONTROLLEL BY THE ERROR DETERMINING MEANS FOR MODIFYING SAID RETARDER CONTROL MEANS IN ACCORDANCE WITH THE RATE OF CHANGE OF THE SPEED OF SAID CAR WITHIN SAID RETARDER.