Fluid drainage container

A fluid drainage device (10;

• 10A;
• 10B) for use in a closed wound drainage system, the device comprising:
• a body (12), with a cylindrical bore (26) which defines at least part of a fluid-receiving volume (60),
• an inlet (16) to the fluid-receiving volume (60),
• a piston (28), in sealing contact with the bore (26), which partly bounds the fluid-receiving volume (60), the piston (28) being movable between a first position and a second position against a friction force between the bore and the piston,
• a piston rod (32) which extends from the piston (28),
• an energy storage device (34) which exerts a piston moving force on the piston,
• a user-actuated handle mechanism (14) which is movable relative to the body in a first direction, to allow the piston (28) to move from the first position at which maximum energy is stored in the energy storage device (34) to the second position at which the energy stored in the energy storage device (34) is reduced,
• wherein as the piston (28) moves automatically from the first position to the second position, the size of the fluid receiving volume (60) is increased establishing a vacuum level in the fluid receiving volume (60) whereby fluid is caused to flow through the inlet (16), into the fluid-receiving volume (60), and
• wherein the friction force reduces from a maximum value with the piston at the first position to a minimum value with the piston at the second position thereby to minimise a change in the vacuum level as the piston moves from the first position to the second position so that fluid flow into the fluid receiving volume takes place at a substantially constant rate as the piston moves from the first position into the second position.