Patent ID: 8777588

Claim:
A cylinder drum ( 1 ′) for a hydrostatic piston engine, having at least one kidney-shaped control port/cylinder bore transition ( 5 ′, 5 ″, 5 ′″) which leads into a cylinder bore ( 2 , 2 ′ a ) for receiving a piston that can be axially displaced therein, wherein the kidney-shaped control port/cylinder bore transition ( 5 ′, 5 ″, 5 ′″) is configured perpendicular to the flow direction in a stepless and edge-free manner, wherein a first and a second line of intersection ( 20 , 21 ) of the kidney-shaped control port/cylinder bore transition ( 5 ′, 5 ″, 5 ′″) with a plane containing the cylinder bore axis ( 3 ) have a first radius (R 1 ) and a second radius (R 2 ), respectively, the centers of which are formed on different sides of the lines of intersection ( 20 , 21 ), the transition of which forms an inflection point, wherein, adjacent to the radius (R 1 ) which lies closer to the end face of the cylinder drum ( 1 ′), the lines of intersection ( 20 , 21 ) extend as tangents (T 2 ) to the radius (R 1 ), which extend parallel to the cylinder bore axis ( 3 ), wherein the tangents (T 1 , T 2 ) of the lines of intersection ( 20 , 21 ) are formed by a kidney-shaped opening section, wherein the kidney shaped opening section ( 4 ′) extends along a circumferential circle ( 26 ) about a cylinder drum axis ( 8 ), and a length of the opening section ( 4 ′) in the direction of the circumferential circle ( 26 ) is dimensioned such that the radii (R 1 , R 2 ) are infinite at the ends ( 27 , 28 ) of the opening section ( 4 ′).