Safety derail preventer

Claim 1

IN A RAILWAY STRUCTURE OF THE TYPE IN WHICH A VEHICLE TRAVELS ON FLAT TRACKS ON A ROADBED, A DERAIL PREVENTION DEVICE COMPRISING: A VEHICLE FRAME; VERTICAL WHEELS BEARING MOUNTED ON EACH SIDE OF SAID FRAME, SAID FRAME BEING ADAPTED TO TRAVEL IN A FORWARD AND REARWARD DIRECTION ON SAID WHEELS; A PAIR OF SPACED, ALLOCHIRAL, INWARDLY OPENING, CHANNEL-SHAPED RAILS SECURED ON A ROADBED BETWEEN SAID VERTICAL WHEELS AND BELOW SAID FRAME; A PAIR OF ALLOCHIRALLY ARRANGED BRAKE SHOES EXTENDING DOWNWARDLY FROM SAID FRAME, SAID RAILS BEING GENERALLY OUTWARDLY OF SAID SHOES, SAID SHOES EXTENDING INTO RESPECTIVE CHANNEL-SHAPED RAILS UNDER AN UPPER FLANGE PORTION THEREOF ABOVE THE LOWERMOST PERIPHERAL PORTIONS OF SAID VERTICAL WHEELS SO AS TO PROVIDE A BRAKING ACTION WHEN SAID FRAME IS LIFTED A PREDETERMINED AMOUNT AND TO PREVENT THE LIFTING OF SAID FRAME BEYOND SAID PREDETERMINED AMOUNT; AND HORIZONTAL SIDE WHEELS DISPOSED LATERALLY OF SAID FRAME ON OPPOSITE SIDES THEREOF IN CONTACT WITH THE OUTER SIDES OF WEB PORTIONS OF SAID RESPECTIVE CHANNELS FOR ROTATION THEREON.