Abstract This device controls the amount of blood flow in an extracorporeal blood circuit of a patient requiring long term profusion to prevent the excessive blood damage as is likely to occur in the usual heart-lung machines employed during surgery if it were to be used for an extended time. The device regulates the speed of the blood pump in accordance with rate of flow of blood from the body so that the pump does not impose a back pressure on the blood supply by running too slowly and does not create suction pressure on the body by running too fast. The speed of the blood pump is controlled by a potentiometer having a slider contract driven in opposite directions by a reversible motor. A constant speed rotating cam intermittently actuates one or the other, or both, of a pair of switches on opposite sides of the cam. One switch energizes the potentiometer motor for rotation in one direction and the other switch energizes the potentiometer motor for rotation in the opposite direction. The switches are shifted relative to the cam by a platen bearing against a tubular bladder in the blood inlet to the pump. As the bladder expands, the pump is speeded up and as the bladder contracts, the pump is slowed down. In addition to normal adjustment of pump speed to comply with normal small variations in blood flow, an emergency safeguard is provided which causes the pump to stop immediately in case the blood supply is abruptly interrupted such as would occur if the blood supply tubing were suddenly closed by a kink or by an attendant stepping on it. If the blood pump were to continue to operate when the bladder is empty, the pump could draw fatal air bubbles into the blood stream.
A fluid pump control system comprising a flexible tubular bladder connected in the fluid supply line to said pump, a platen bearing on said bladder and movable in response to the expansion and contraction of the bladder with variations in the rate of inlet flow to the pump, a continuously rotating cam, a pair of switches on opposite sides of said cam movable in unison by said platen in a diametral direction relative to the axis of the cam, a reversible motor energized for rotation in opposite directions by said switches, a potentiometer having a sliding contact movable in opposite directions by said reversible motor, and a variable speed motor driving said pump under the control of said potentiometer, whereby the speed of said pump varies in accordance with said inlet flow.
Claim 2
Dependent Claim
132 words
A fluid pump control system comprising a flexible tubular bladder connected in the fluid supply line to said pump, a platen bearing on said bladder and movable in response to the expansion and contraction of the bladder with variations in the rate of inlet flow to the pump, a continuously rotating cam, a pair of switches on opposite sides of said cam movable in unison by said platen in a diametral direction relative to the axis of the cam, a reversible motor energized for rotation in opposite directions by said switches, a potentiometer having a sliding contact movable in opposite directions by said reversible motor, and a variable speed motor driving said pump under the control of said potentiometer, whereby the speed of said pump varies in accordance with said inlet flow.
Claim 3
Dependent Claim
27 words
A system as defined in claim 1 including a switch operable by said platen to stop said pump motor in response to cessation of said inlet flow.
Claim 4
Dependent Claim
19 words
A control unit as defined in claim 1, said switches and platen being mounted on a pivotal rocker plate.
Claim 5
Dependent Claim
31 words
A control unit as defined in claim 3 including an arm on said rocker plate, and a switch mounted for actuation by said arm when said bladder is substantially fully contracted.