Patent GB-475629-A (GB)
Title: Apparatus for measuring and supervising the heart-action
IPC: A61B5/024
Filed: 1937-04-12
Abstract: 475,629. Current and voltage measurements. STRAUSS, S., and WEISGLASS, L. April 12, 1937, No. 10427. Convention date, April 15, 1936. [Class 37] [Also in Groups VI, XXXVIII, and XL] Apparatus for measuring the frequency and intensity of the human pulse and also for measuring the blood-pressure, comprises two compression cuffs, one 70 of which receives a measured air-pressure and is applied to the body in such a manner as to intercept the blood flow towards an artery, around which the other cuff 71 is applied so as to serve, through the medium of a pressure-responsive piezo-electric crystal 1, to indicate the frequency and intensity of the pulse. The cuffs are individually supplied with pressure-air, or exhausted to atmosphere, under control of two three-way valves 77, 76, a hand-pump 78 or compressed-air accumulator being provided. The pressure in the upper cuff 70 as the pulse vanishes, corresponds to the blood-pressure and is indicated pneumatically by a pointer 75. Pressure in the lower cuff 71 acts through a flexible diaphragm 82 on the piezo-electric crystal 1, which is thereby caused to generate current-impulses forming the input to a pentodevalve 6 followed by a power pentode amplifier 10. The output circuit of the latter includes a glow-lamp 15, which lights at each pulsebeat, a milliammeter 14, and a relay 17, which last-named actuates means for directly indicating at 25 the frequency of the pulse-beats, whilst the amplitude of the output of the valve 10 is directly measured at 44 to indicate the intensity of the pulse. A buzzer-alarm 49 is sounded if the pulse-beats cease. The frequency-indicator is the same as that described in Specification 446,031, [Group XIX], and comprises a large condenser 19, permanently arranged across two electrodes of a glowdischarge voltage-divider 31, energized from the mains through a transformer 35, full-wave rectifier 36 and smoothing means 32, 34. Part of the charge thus imparted to the condenser 19 is taken from it by a smaller condenser 18, which, at every pulse-beat, is alternately first shunted across the condenser 19 and then short-circuited, under control of contacts operated by the armature 17a of the output relay 17. The charge remaining in the large condenser 19 is thus a measure of the frequency and is measured by a voltmeter-valve 23, the grid of which receives the condenser charge through a resistance 21 shunted by a condenser 22, and further contacts closed by the relay 17. The output circuit of the valve 23 includes a milliammeter 25, calibrated to read the pulse-frequency directly. A similar voltmeter-valve 43, measuring the amplitude and so the pulse-intensity, is connected to the screened-grid of the amplifier-valve 10 through a diode 39 or a metal rectifier. A variable resistance 12 allows the initial reading to be set at a desired valve. Grid-bias is applied to the detector-valve 6 by a battery 4, and to the amplifier 10 and voltmeter-valve 23, by the voltage-divider 31, through resistances 8 and 20 respectively. The audible alarm, which sounds when the pulse stops beating, comprises a valve 28, having a condenser 27 and high resistance 26 shunted between its grid and cathode. At every pulse-beat, the condenser 27 is given a charge from the voltage-divider 31 through further contacts closed by the relay armature 17a. If the pulse-beats cease, the relay 17 no longer operates and, after lapse of a certain timeconstant, the condenser 27 discharges through the resistance 26. The blocking bias is thereby removed from the valve 28, so that a relay 29, in its plate circuit, is energized to close the circuit to the buzzer 49. The latter then sounds the alarm, and also, if desired, operates an electro-magnetic valve to reduce the pressure in the cuff 70. The buzzer can be taken out of circuit by a switch, which at the same time lights a warning lamp 47 to indicate that the buzzer is no longer operative. An additional pilot lamp 46 lights constantly to indicate the operating condition of the apparatus. The mains current is smoothed by a member 45 containing iron fillings in an atmosphere of hydrogen.