Hydraulic apparatus

Claim 1

FOR USE IN A HYDRAULIC UNIT OF THE TYPE REFERRED TO, SUCH AS INCLUDES A CAM SURFACE AND A DRIVE MEMBER ROTATABLE IN A PLANE GENERALLY PARALLEL TO AND CLOSE TO SUCH SURFACE, AND FORMED WITH EQUIANGULARLY SPACED AND AXIALLY DIRECTED BORES, A SLIPPER RECIPROCABLE IN AND BEARING WITHIN EACH BORE, AND BEARING AT ITS END SURFACE UPON SAID CAM SURFACE, A ROTATIVE CYLINDER BARREL, A PISTON IN EACH CYLINDER OF THE BARREL AND OPERATIVELY CONNECTED TO THE CORRESPONDING SLIPPER FOR CONJOINT ROTATION, AND RECIPROCABLE TO RECEIVE AND DISCHARGE FLUID, AND THEREBY TO PRODUCE THRUST FROM THE PISTON TO URGE THE SLIPPER ONTO THE CAM''S BEARING SURFACE, THE IMPROVEMENT IN THE BEARING BETWEEN THE SLIPPER AND ITS BORE INCLUDING MEANS DEFINING AN ANNULAR WORKING SPACE BETWEEN EACH SLIPPER AND ITS BORE IN THE DRIVE MEMBER, A PASSAGE TO DELIVER PRESSURE FLUID WITHIN SUCH WORKING SPACE, THE WORKING SPACE BEING SO ARRANGED THAT THE DELIVERED PRESSURE FLUID OPPOSES THE PISTON''S THRUST, THE WORKING SPACE BEING SO PROPORTIONED, IN RELATION TO THE PRESSURE DEVELOPED THEREIN, THAT ITS OPPOSING FORCE CANNOT EXCEED THE PISTON''S THRUST URGING THE SLIPPER AGAINST THE CAM SURFACE, BUT RESISTS AT LEAST AN APPRECIABLE PORTION THEREOF