| 摘要 |
1,174,491. Anaesthetic apparatus. P. E. MOYAT and H. P. VONDERSCHMITT. 2 May, 1967 [5 May, 1966], No. 20187/67. Heading A5T. [Also in Divisions Gl and G3] A device for measuring the concentration of an anaesthetic gas in the gas flow to be applied to a patient in clinical routine comprises a casing having a passage 28 through which the gas flow passes, tapes 68, 70, 72 being supported under tension in the passage 28 and being of such material that the length of the tapes varies in a reversible manner with the concentration of anaesthetic gas contacting the tapes, the variation in length of the tapes being sensed by a string 78 passing round a spindle 80 carrying a pointer 20, the string 78 being fixed to the free end of a single blade spring 82 secured in a block 84, and the spring 82 carrying a plate 110 (Figure 3) which partially interrupts a light beam B incident on a photoresistor 118 connected in a bridge circuit having a recorder R which records the variations in the position of the free end of the spring 82 and thus the concentration of the anaesthetic gas. The voltage developed across a resistor in series with the recorder R may be used to control a servomotor actuating a valve in the supply line for the anaesthetic gas, so that the device may be used to maintain the concentration of this gas constant. The tapes are preferably of silicone rubber and may be used in the detection of 1-bromo-1-chloro-2, 2, 2-trifluoroethane, 1, 1, 1-trifluoro-2-chloro-2-bromoethane, 1-bromo-1-chloro-2, 2-difluoropropane, and 2, 2-dichloro-1, 1-difluoroethyl methyl ether. The tapes are mounted between two frames 42, 58, the frame 42 being supported by a flat spring 38 having a hooked end attached to one end of a string 48 of nylon the other end of which is secured to the wall of the passage 48. The string 48 increases in length with water vapour concentration so that this mounting of the frame 42 compensates for changes in water vapour concentration affecting the length of the tapes 68, 70, 72. The frame 58 is carried by a bimetallic spring 54 which compensates for the effect of temperature changes on the tapes. A frame 60 is mounted to tension the tapes at their midpoints, through the action of the string 78 and spring 82. The light beam 8 emanates from a casing 112 (Figure 3) containing a lamp and collimating lens, and is deflected by a mirror 116 passed the edge of the plate 110 on to the photoresistor 118. |
