Coil spring rail brake

A rail brake for a rail-mounted machine mounted for translation along a rail, said rail brake comprising:

• a rigid enclosure having an upper end and opposite base end rigidly mounted oppositely to said upper end, wherein said upper end is adapted for mounting to the rail-mounted machine so as to dispose said base end over and adjacent the rail,
• a top plate mounted underneath, spaced apart from and substantially parallel to, said upper end so as to define a gap between said upper end and said top plate.
• a spring carriage mounted for vertical translation within said enclosure, beneath said top plate, between an elevated position and a lowered position,
• at least one spring mounted between said spring carriage and said top plate, said at least one spring compressed when said spring carriage is in said elevated position and decompressed when said spring carriage is in said lowered position,
• at least one brake shoe mounted under said carriage so as to be oppositely disposed on said carriage relative to said at least one spring,
• at least one selectively actuable actuator mounted between, so as to bear opposite ends thereof against, said spring carriage and said base end of said enclosure respectively, said at least one actuator actuable between extended and retracted positions wherein, in said extended position, said spring carriage is in said elevated position and said at least one brake shoe is correspondingly retracted upwardly, and wherein, in said retracted position,
• said spring carriage is in said lowered position and said at least one brake shoe is correspondingly lowered so as to be urged into frictional engagement against the rail.