| 摘要 |
1326371 Digital control of intravenous set IVAC CORP 10 July 1970 [14 April 1970] 33515/70 Heading G4H [Also in Division A5] In a blood or plasma drip feed apparatus a peristaltic pump driven by a stepping motor is controlled to maintain a predetermined drip rate. Drips are sensed by photo-electric sensor 11 which triggers a monostable vibrator 12 for each drop. An integrator 14 integrates these pulses negatively and also receives positive pulses at a desired drip rate from a manually set reference oscillator 16. The error signal generated by the integrator controls the output frequency of a variable frequency pulse oscillator 20 in a non-linear fashion (Fig. 4, not shown), with sensitivity increasing with increase of error signal. The variable frequency output controls, via a control voltage circuit 22, a stepping motor 23 controlling the peristaltic pump. Circuit 27 provides an alarm and shuts off the circuit in response to a number of conditions. Firstly the voltage discriminators 25 and 26 detect whether the error signal from integrator 14 is too high or too low. Secondly to detect that air is not being pumped into the patient a rotation sensor 33 coupled to the stepping motor 23 clocks a counter 34 which is reset by pulses generated by the drop sensor 11, the circuit 27 being operated upon counter 34 reaching a predetermined count. For similar reasons the integrator 29 integrates pulses from the variable pulse generator 20 but is reset by the pulses from clock sensor 11, the alarm circuit 27 being operated upon the integrator reaching a predetermined voltage set by discriminator 32. (For Figure see next page.)
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