Railroad track gripping apparatus

Claim 1

APPARATUS FOR TRAVELLING ALONG A RAILROAD TRACK WHILE SIMULTANEOUSLY LIFTING A SPAN OF SAID TRACKS, THE RAILS OF WHICH ARE JOINED TOGETHER BY ANGLE BARS, COMPRISING: (A) A VEHICLE COMPRISING A PAIR OF CARTS SPACED APART ALONG THE TRACK AND A BOOM INTERCONNECTING SAID CARTS, (B) A LIFTING FRAME VERTICALLY MOVABLY MOUNTED ON SAID BOOM INTERMEDIATE SAID CARTS, (C) AT LEAST FOUR GROUPS OF RAIL-LIFTING ROLLERS, (D) EACH GROUP COMPRISING A PLURALITY OF ROLLERS WITH AT LEAST ONE ROLLER OF THE GROUP POSITIONED ON EACH SIDE OF A RAIL OF SAID TRACK, (E) EACH ROLLER INCLUDING A FLANGE PORTION FOR SUPPORTINGLY ENGAGING THE UNDERSIDE OF A RAIL HEAD, (F) EACH GROUP INCLUDING MEANS FOR MOVING THE ROLLERS THEREOF BETWEEN A CLOSED, RAIL-EMBRACING CONDITION AND AN OPEN, RAIL-RELEASING CONDITION, (G) SAID MOVING MEANS FOR EACH GROUP BEING OPERABLE INDEPENDENTLY OF THE MOVING MEANS FOR EACH OTHER SAID GROUP, (H) AND MEANS MOUNTING ALL SAID ROLLER GROUPS ON SAID FRAME WITH A PAIR OF SAID ROLLER GROUPS ENGAGING EACH RAIL OF THE TRACK WITH SAID PAIR OF GROUPS SPACED FROM EACH OTHER IN THE LONGITUDINAL DIRECTION OF THE VEHICLE WITH A CLEAR SPACE BETWEEN THE TWO NEAREST ROLLERS OF ADJACENT GROUPS ON EACH SIDE OF THE VEHICLE GREATER THAN THE LONGEST ANGLE BAR IN USE ON SAID TRACK, THE ROLLERS OF A FIRST GROUP OF EACH SAID PAIR OF GROUPS BEING MOVABLE BY SAID MOVING MEANS TO OPEN CONDITION TO AVOID AN ANGLE BAR WHILE THE SECOND GROUP OF SUCH PAIR REMAINS IN CLOSED CONDITION, SO THAT THE SIDE OF THE TRACK ON WHICH SUCH PAIR IS SITUATED REMAINS SUPPORTED FROM SAID LIFTING FRAME BY SAID SECOND ROLLER GROUP, THE FIRST ROLLER GROUP BEING RECLOSEABLE BEYOND THE ANGLE BAR TO MAINTAIN SUCH SUPPORT FROM SAID LIFING FRAME BEFORE OPENING THE SECOND ROLLER GROUP TO AVOID THE ANGLE BAR.