| 摘要 |
<p>1446412 Fluid heater L M ELECTRONICS (HOLDINGS) Ltd and D F LENTON 4 Oct 1973 [5 Oct 1972] 45988/72 Heading H5H [Also in Division G3] An apparatus for heating fluids (e.g. blood transfusion liquid or anaesthetizing gases) flowing in a flexible tube, to a desired temperature, comprises a heating block 20 (Figs. 6, 10) having a channel 22 to receive the tube (e.g. nylon), electric heating elements 39, 40 formed of wire 43 wound around insulating strips 41, 42, e.g. mica, and embedded in parallel slots. The channel is U-shaped (or alternatively may be straight as in Figs. 1-5, not shown) with circular cross-section and one limb has an extended straight portion 35 whereby a single straight run of tube may be accommodated. The block is of die-cast aluminium/zinc alloy. A control circuit maintains the block at a fore-set temperature whereby fluid passing through will attain a required temperature, e.g. normal body temperature. Control circuit. Fig. 12.-Heater elements 65 (i.e. 39, 40 of Fig. 10) are connected in series with a transistor 67 and a thermal cut-out 66 across 12 Volt supply lines 60, 61. The block temperature is sensed by a thermistor 68 inserted in a hole 45 (Fig. 6) and connected in a bridge circuit including a desired temperature setting resistor 73 and resistors 71, 70, 74, 73, 75. The bridge output is a function of temperature error and is applied to an amplifier 69 and thence to an inverter 78 via a transistor 77. The inverter output controls a transistor 81 which in turn controls the transistor 67 and hence the heater current. In the event of excess temperature being sensed the cut-out 66 opens and a normally conducting transistor 90 will turn-off so that a green light-emitting diode 83 will be extinguished and a bleeper alarm 91 sounded. The alarm is energized under the control of an inverter 94 and NOR gate 96. Any fall in supply voltage is sensed by a differential amplifier 102 having one input connected to a divider 105, 106 across the supply lines 60, 61. If the potential at line 60 falls below a predetermined value a transistor 111 is rendered conducting, the potential in a line 112 will fall and as a result the green light diode 83 will cycle ON and OFF and the bleeper 91 will emit an intermittent signal. The electric supply may be derived from the mains or from a battery.</p> |
