Signal device for dialysis apparatus

Claim 1

A dialysis apparatus, such as an artificial kidney, comprising: a circuit through which liquid blood is passed, said circuit including: a pump (P 1 ) coupled in said circuit for transporting blood through said circuit; a ventless float chamber (3) having an inlet at the upper portion thereof for receiving liquid blood and which is coupled in said circuit downstream of said pump, and a blood outlet in the bottom wall of said float chamber (3), said float chamber (3) always having a quantity of liquid blood therein; and means for coupling a portion of a patient's blood circulation system to said blood outlet of said float chamber (3) and to said pump (P 1 ) to close said circuit through which said blood is passed; a float (6) within said ventless float chamber (3), said float (6) having a density slightly less than the mean value of the density of the liquid blood in said float chamber (3) so that the major portion of said float (6) will normally remain submerged in the liquid blood within said float chamber (3), said float (6) having a lower surface which is arranged to at least substantially block said outlet of said float chamber to at least substantially interrupt the supply of blood from said outlet of said float chamber responsive to a lowering of said float in the blood in said float chamber caused by a predetermined increase of air pressure above the blood in said float chamber; and an alarm signal device comprising: detection means (8) coupled to said float chamber (3) for detecting a further predetermined increase in air pressure inside said float chamber (3) after a lowering of said float (6) which substantially blocks said blood outlet and which thereby substantially interrupts the blood supply to the patient's blood circulation system; and electrical means (R, 9, 12) coupled to said detection means (8) for generating an alarm signal in response to said detection of said further predetermined increase in air pressure in said float chamber (3).