| 摘要 |
<p>1516111 Automatic control IVAC CORP 11 June 1975 [12 Aug 1974] 24944/75 Heading G3R The flow of drops of fluid for parenteral administration is automatically controlled by varying the width of pulses which regulate the flow in response to the detected drop rate, the pulses being at a high, preferably non-integral, multiple of the drop rate, and the control signals are in digital form. The desired flow is determined by selecting a pulse frequency on a generator 18. Each pulse operates a control device 15 (a clamp, a peristaltic pump or a pump driven by a stepping motor, in which case each pulse from 18 releases a burst of driving pulses). The duration of each pulse is automatically increased in steps by device 21 until a drop is detected (by photo-electric means), whereupon the duration is decreased by a fixed amount. The system stabilizes when the average pulse width per cycle, and hence the flow, is such that the drops occur at the fixed ratio to the set frequency. A circuit 23 sets an ultimate limit on pulse duration, to prevent continuous flow, and an alarm is given for any of the events shown at 14. Details of the circuits are given. Reference has been directed by the Comptroller to Specification 1361062.</p> |
