Patent GB-1162151-A (GB)
Title: Improvements in or relating to Medical Respirators
Inventor: FOSTER DUDLEY GEORGE
IPC: A61M16/00
Filed: 1966-02-24
Abstract: 1,162,151. Respiratory apparatus. W. WATSON & SONS Ltd. 24 Feb., 1967 [24 Feb., 1966], No. 8124/66. Heading A5T. [Also in Division H3] A respirator .(for use in anaesthesia or respiratory insufficiency comprises an inspiration bellows and an inspiration control valve for controlling the periods, of inspiration, an expiration bellows and an expiration control valve for controlling the periods of exhalation, and control means for controlling the operation of said valves to determine the cycles of inspiration and exhalation, the control means including timing means and pressure or volume responsive means, As shown, the respirator comprises a housing within which are three bellows 20, 21, 22 connected by a platform 15 and arranged so that the bellows expand and contract in unison with an adjustable torsion spring 16 causing the contraction. The respirator also includes solenoid-operated inspiration and exhalation valves 24, 25 respectively, the valves being controlled by coils (24A, 25A) in an electronic timing circuit, Fig. 2 (not shown), the respirator including further valves 34 and valves V1-V8 which can be manipulated so that the respirator is used for manual, open circuit, or closed circuit operation. In manual operation, a source of breathing gas provided at a port 30 is arranged to inflate the manual operation bag 26 and to be available at 41 to the patient. In closed circuit operation, a driving gas (compressed air) .supplied at a port 29 is arranged to expand the bellows 21 and consequentially to induce exhalation gas into the bellows 20, the inspiration valve 24 is then opened and the three bellows contract under the spring 16 forcing gas in the bellows 22 to the patient. A gas purifier 64 is included in the circuit. In open circuit operation, breathing gas from the port 30 is arranged to inflate the bellows 21 to cause exhalation gas to be induced into the bellows 20, the valve 24 is then opened and the bellows contract exhausting the gas in the 'bellows 20 to atmosphere and passing the breathing gas in the bellows 21 to the patient. The bellows 20 has an internal projection 23 so that when this bellows is collapsed its residual volume is very small. The apparatus includes a reservoir 65. The timing circuit, Figure 2 (not shown), which controls the respiratory cycle by alternately energising the valves 24, 25 comprises an astable transistor oscillator (T 1 , T 2 ) connected to amplifiers (117, 118), power transistors (T 3 , T 4 , T 5 , T 6 ) and. the solenoid coils (24A, 25A) of the control valves 24, 25. The circuit is powered by a rechargeable battery (113) or the mains supply and .includes contacts (89A) controlled by a negative pressure switch 89 arranged so that, should the patient attempt to inspire during an expiratory period, the apparatus is retimed. By adjusting potentiometers (R 3 , R 6 ) and pressure switches 89, 90, the apparatus may be time cycled or pressure cycled, and the apparatus includes micro-switches 105, 109 actuable by a striker 'bar 100 attached to the bellows so that the apparatus may be volume cycled. The apparatus may also include a monitoring circuit (Figure 3, not shown) giving a warning of abnormal expansion or contraction of the bellows, the unit being connected to adjustable micro-switches 106, 110 also operable by the striker bar 100. A switching circuit which may provide part of the timing circuit (Figure 2) is illustrated in Figure 4 (not shown).