Plunger pump and liquid blow molding device

A plunger pump that is configured to draw in a liquid from an inlet flow path and deliver the liquid to an outlet flow path at a predetermined pressure, the plunger pump comprising:

• a tubular cylinder that has an internal space communicating with the inlet flow path and the outlet flow path;
• and
• a piston that is movable along an axis of the cylinder, wherein
• a head of the piston includes, on an outer peripheral surface thereof, a sealing portion that is slidable against an inner peripheral surface of the cylinder,
• the cylinder includes a body tubular portion in which the head is arranged during normal use, and a cleaning tubular portion in which the head is arranged during cleaning,
• an inner peripheral surface of the cleaning tubular portion has an inner diameter equal to an inner diameter of an inner peripheral surface of the body tubular portion,
• the cleaning tubular portion includes, on the inner peripheral surface thereof, at least one cleaning liquid circulation groove that is a through hole that passes through the cleaning tubular portion in the radial direction, and
• the at least one cleaning liquid circulation groove extends spirally around the axis.