The present invention relates to a flow regulator for setting and maintaining a constant flow of blood, blood-substitute, or similar liquid and consisting of a body with a movable part mounted on it. Flow regulators of this type are employed in medical technology in particular, where it is important to set and maintain a constant flow even when the volume is very small, when the liquid is in drops for example, and must be individually set and maintained constant over a particular period--the total infusion or transfusion time.
A flow regulator of this type in the form of a compression-roller device that squeezes a flexible tube to a greater or lesser extent to vary its flow diameter is known. The device has a body through which the tube is fed. A movable, wheel-like part with axle stubs projecting from each side slides in a guide slot on the body. The guide slot is associated with a slanting plane on the body in such a way that the tubing can be squeezed to a greater or lesser extent between the movable part and the slanting plane and retained in the squeezed state. The drawback to this known flow regulator is that it does not allow the number of drops to be adjusted precisely over a long period because choking the flow with the movable roller exerts pressure on the tube and plastically preforms it more or less permanently. The elasticity and change in shape of the tube and swelling phenomena in its material will alter the preset number of drops after a while and will as is known require, often several, readjustments. Another disadvantage of the known device is that the flow cross-section of the tube narrows into more or less of a slit after a long period of administration at a low drop number, affecting the resiliency of the tube and preventing the subsequent setting of a desired higher flow. The larger volume can be administered to the patient only by replacing the tube or by other means.