Radial piston pump

A radial piston pump (1) comprising:

• a pump body (2) in which pistons (4) and cylinders (5) are arranged in a radial array about a cam (14);
• wherein upon a radially inward movement of the piston (4), the piston (4) draws a fluid through at least one pressure port (7) and into the corresponding cylinder (5), and upon a radially outward movement of the piston (4), the piston (4) conveys the fluid through a check valve (9) and a pressure port (7) in an outer end wall (6) of the cylinder (5) and into a plenum (10);
• each piston (4) includes a connection bore (32) located in the base of the piston (4) and connecting between the corresponding cylinder (S) and the cam (14), and
• each connection bore (32) includes an associated pressure relief valve (18), and wherein when a pressure in the cylinder (5) exceeds an opening pressure of the pressure relief valve (18) the fluid flows through the pressure relief valve (18) and to the cam (14) to reduce a pressure peak in the cylinder (5) and to provide a fluid buffer between the base of the piston (4) and the cam (14);
• and
• radial acceleration forces resulting from radial movement of a piston (4) due to rotation of the cam (14) act upon the closure element (22) of the corresponding pressure relief valve (18) to open the pressure relief valve (18) after movement of the piston (4) due to rotation of the cam (14) passes a radially lower dead point of piston (4) movement and to close the closure element (22) of the pressure relief valve (18) after movement of the piston (4) due to rotation of the cam (14) passes a radially upper dead point of piston (4) movement.