Patent ID: 8087701

Claim:
A hydraulic coupling device comprising: a coupling unit; a holder block to which said coupling unit is mounted in a through hole arranged in said holder block; a lock nut for securing said coupling unit to said holder block, said lock nut having a cylindrically symmetrical outer contour and having one end surface facing toward said holder block and one end surface facing away from said holder block; a hose-connection end on said coupling unit for connection to a hydraulic hose; and a nose end on said coupling unit for interconnection with a complementary coupling unit, said nose end being provided with an external thread for cooperation with said lock nut, so that said lock nut, in the mounted position, secures the coupling unit to said holder block; said lock nut having a plurality of grooves distributed around the circumference of said cylindrically symmetrical outer contour, said grooves being recessed and extending axially inward from the end surface of said lock nut facing away from said holder block, wherein the axial extension of each said groove is smaller than 70% and greater than 50% of the total axial extension of said lock nut, said lock nut further having internal threads extending from the end surface of said lock nut facing toward said holder block, wherein the axial extension of said internal threads is smaller than 60% and greater than 30% of the total axial extension of said lock nut.