| 摘要 |
1392070 Respiratory apparatus SYNTHELABO 10 Nov 1972 [10 Nov 1971 17 Oct 1972] 52056/72 Heading A5T A control unit for a respiratory apparatus having a source 14 of respirable gas connected to a mouthpiece 19 by a conduit 18 having a flow control valve 15, comprises a pressure sensor connected to the conduit and having a housing 4 closed by a membrane 1 the outer face of which is exposed to atmospheric pressure and contacts a rigid plate 2, the sensor also including a first detector of predetermined outward distortion of the membrane for controlling closure of valve 15 and a second detector of predetermined inward distortion for controlling opening of valve 15. A flexible strip 7 is coupled to membrane 1 and is clamped at one end to plate 2 and rests at its other end on an adjusting screw 9 setting the zero position. The detectors comprise strain gauges 10, 11 fixed to strip 7 and connected in a wheatstone bridge circuit for supplying signals controlling electromagnectic control valve 15. The outputs of the wheatstone bridge are applied to first and second differential amplifiers 32A 32B the outputs of the amplifiers being applied to a flip flop 34 having a single output corresponding to the output of amplifier 32B to energise winding 16 and thereby open valve 15. The output of amplifier 32A is also connected to a timing device 37 which after a predetermined delay produces an output at the output of amplifier 32B. When predetermined positive pressure exists in pipe 18 flip flop 34 operates to close valve 15 and actuate timing device 37. When the patient inhales a signal applied via amplifier 32A to flip flop 34 causes valve 15 to open. If inhalation is insufficient to produce the predetermined negative pressure in pipe 18, valve 15 opens under the control of timing device 37. The valve 15 is such that in its closed position gas source 14 is cut off from pipe 18 which is put into communication with atmosphere through an outlet 38 normally closed by valve 39, the positive pressure in pipe 18 flexing valve 39 away from the outlet. The differential amplifiers may be replaced by resistor-capacitor combinations and switching means for connecting the combinations as inputs to the flip flop so as to form therewith a multivibrator. |
