Self-braking caster

Claim 1

A SELF-BRAKING CASTER FOR A VEHICLE, COMPRISING A TOP PORTION AND SUBSTANTIALLY PARALLEL SIDE PORTIONS PROJECTING DOWNWARDLY THEREFROM, A BRAKE SURFACE ASSOCIATED WITH THE UNDERSIDE OF THE TOP PORTION, A CASTER WHEEL AND AXLE ASSEMBLY DISPOSED BETWEEN THE SIDE PORTIONS GENERALLY BELOW THE BRAKE SURFACE, SAID SIDE PORTIONS HAVING ALIGNED SLOTS THEREIN EXTENDING ALONG A PLANE INTERSECTING THE BRAKE SURFACE, EACH OF SAID SLOTS TERMINATING AT ITS OPPOSITE ENDS, RESPECTIVELY, A DISTANCE FROM THE BRAKE SURFACE GREATER THAN, AND LESS THAN, THE RADIUS OF THE WHEEL, THE AXLE BEING RECEIVED IN THE SLOTS AND MOVABLE THEREIN, AND A SINGLE ELEMENT SPRING HAVING A U-SHAPED UPPER PORTION, THE BASE OF SAID U-SHAPED PORTION ENGAGING THE UNDERSIDE OF SAID TOP PORTION AND THE ARMS OF SAID USHAPED PORTION EXTENDING DOWNWARDLY THEREFROM, ALIGNED AXLE ENGAGING SURFACES ON THE FREE ENDS OF THE ARMS SPACED FROM AND OPPOSING THE BASE PORTION, EACH OF SAID ARMS BEING BOWED SO THAT THE LINEAR LENGTH ALONG THE ARMS IS GREATER THAN THE STRAIGHT LINE DISTANCE BETWEEN THE BASE PORTION AND THE AXLE ENGAGING SURFACE, SAID SPRING BEING DISPOSED IN THE CASTER WITH THE BASE PORTION DIRECTLY ENGAGING THE TOP PORTION, THE ARMS EXTENDING BETWEEN THE SIDE PORTIONS ON OPPOSITE SIDES OF THE WHEEL AND THE AXLE ENGAGING SURFACES DIRECTLY ENGAGING THE AXLE, THE FREE LENGTH OF THE SPRING ARMS BETWEEN THE AXLE ENGAGING SURFACES AND BASE PORTION BEING GREATER THAN THE DISTANCE BETWEEN THE LOWER ENDS OF THE SLOTS AND THE SPRING IS OPERABLE BOTH TO SUPPORT THE CASTER RESILIENTLY AND TO DEFLECT UPON OVERLOAD OF THE VEHICLE TO BRAKE THE CASTER AUTOMATICALLY.