GB1499875A - Fluid delivery apparatus - Google Patents

Abstract

1499875 Sensing liquid drops photoelectrically F H TOWNSEND 6 Feb 1975 [6 Feb 1974] 5379/74 Heading G1A [Also in Division G3] Apparatus for delivering discrete quantities of a liquid at a controlled rate to a patient comprises: a drip chamber 21 attached to a bottle containing a solution 20 by way of a drip-giving set 19; a drop detector 22 operable to produce a signal in response to a falling drop in the chamber; a peristaltic pump 24 driven by a stepping motor for delivering the liquid to a patient; and control logic for the stepping motor operable in response to signals from a phototransistor of the drop detector. The pump is operated intermittently and is stopped when passage of a drop is detected in a first time period and an alarm is actuated and operation of the pump is prevented if no drop is detected in the first time period. The motor control logic energizes the three inputs of AND-gate 16. One input is a constant pulse rate from oscillator 4, a second is from the control bi-stable switch 5 and the third from the alarm bi-stable 6. Pulses from the clock generator are selected manually to occur at between one and sixty pulses per minute, which pulses set a monostable 7 having a reset period of 0À9 seconds. The monostable output sets the bi-stable 5. Pulses from the photosensor drop detector each set a monostable 9 having a reset period of 0À04 seconds, from which monostable 9 the output pulse resets the control bi-stable 5 thereby stopping the stepping motor via connection 10. Lamp 11 is energized from monostable 9 to give an indication of the drip rate. If no drop falls through the drip chamber despite operation of the motor in the time set by monostable 7, or if a drip appears outside the maximum time of 0À9 seconds set by the monostable 7, the two inputs 12 to AND gate 13 are identical so a pulse passes via OR gate 14 to set the alarm bistable 6. The Q output from the alarm bi-stable is therefore zero so the motor drive gate 16 is disabled and the pump is stopped. The Q output from the alarm bi-stable 6 drives various alarm devices. Alternatively, if two drops are delivered within the period determined by the interval between two consecutive pulses from the clock generator, the arrival of a second pulse from the drop detector provides identical inputs 17 to the AND gate 18 whereby an alarm is actuated and the pump is stopped as before. In an alternative logic circuit arrangement Fig. 4 (not shown) two drops are allowed to be delivered within a first clock time period and then no drop is allowed to be delivered in the next clock time period and the arrangement is reset at the commencement of a third clock time period.