Lock for relatively pivoted structures

Claim 1

A LOCK FOR A SPRUNG CASTER COMPRISING: (A) A FIRST HORIZONTALLY SERRATED LOCK SEGMENT FIXED TO A WHEEL-CARRYING CASTER PORTION; (B) A FRAME MEMBER PIVOTALLY CONNECTED TO AND IN COMMON WITH THE WHEEL-CARRYING CASTER PORTION AND A LOWER EXTREMITY OF A CASTER PORTION ADAPTED FOR SUPPORTING STRUCTURE, THE CASTER PORTION ADAPTED FOR MUTUALLY SPRING LOADED SUCH THAT OPPOSITE ENDS THEREOF TEND TO SEPARATE; (C) A STEP UPON SAID FRAME AT A POSITION SUBSTANTIALLY OPPOSITE SAID CONNECTION TO THE CASTER PORTIONS; (D) AN ARM MEMBER PIVOTALLY CONNECTED TO THE STRUCTURE SUPPORTING CASTER PORTION AT A POSITION SUBSTANTIALLY OPPOSITE SAID FRAME CONNECTION, SAID ARM INCLUDING A SECOND HORIZONTALLY SERRATED LOCK SEGMENT ADAPTED FOR LOCKING ENGAGEMENT WITH SAID FIRST SEGMENT; (E) AN OVER-CENTER LOCK MEMBER HVING A FIRST END PIVOTALLY CONNECTED TO SAID FRAME ADJACENT SAID STEP AND A SECOND END CONNECTED TO SAID ARM MEMBER; AND (F) STOP MEANS ATTACHED TO SAID ARM MEMBER AND ADAPTED TO BE CONTACTED BY SAID OVER-CENTER LOCK MEMBER TO PREVENT EXCESSIVE MOVEMENT OF SAID OVERCENTER LOCK MEMBER.