Patent GB-626683-A (GB)
Title: Improvements in and relating to electric integrators
IPC: G01N30/86
Filed: 1946-12-30
Abstract: 626,683. Controllers associated with clutches or gears. BARNES, J. W. Dec. 30, 1946, No. 38027. [Class 38(iii)] [Also in Group XXXVIII] Relates to apparatus for integrating a variable with respect to time in which a voltage proportional to the variable is applied to an electric motor M which operates an integrator (counter) C. According to the invention, to ensure proportionality between the motor speed and the voltage input across terminals 11, 12, for large variations of input voltage, means are provided for varying the ratio of the variable to the voltage applied to the motor when the input increases or decreases to limit values, and simultaneously varying correspondingly the gear ratio between the motor shaft and the counter shaft in a corrective sense. As shown, Fig. 1, the whole voltage input is applied to the motor M, which drives the counter C through a gear-box G, the ratio of which is set to 1 to 1. Upon rise of input voltage to a predetermined value, a voltage responsive device 20 operates through a spring- biassed rod 19 to throw the two-way switch 15, thereby reducing the voltage applied to the motor by means of the potentiometer 13, 14..At the same time the gear-change lever 18 is actuated by rod 19 to increase the gear ratio between the motor and counter shafts in the same ratio as the motor-applied voltage is reduced. The switch arms 15, 18 may, alternatively, be actuated by a speed responsive device 22, and instead of only one reversible changeover as shown, there may be a series of stepped changes. Fig. 2 shows an accelerometer wherein a rod 64 is resiliently mounted at 65, 66 on a rigid base 67. Acceleration of the apparatus to the right or left moves the coil 57 in an air gap to upset the balance of an A.C. bridge connected to a phase-sensitive rectifier 61, the output of which at lines 51, 52 is a unidirectional voltage which varies in magnitude and sense according to the magnitude and direction of the acceleration. The rectifier output voltage is integrated as above described by a motor M, and is also fed back negatively to the pot-magnet coil 70 on the rod 64 to oppose movement of the rod. When the acceleration reaches an upper limit a secondary and relatively insensitive accelerometer in the form of a roller 76 is displaced along a grooved member 77 sufficiently for a spring-biassed contact 80 to make with contacts. 81, 82 in succession whereby series-connected relays 85, 86 are energized and respectively (a) cut a resistance 75 out of the feed-back circuit of coil 70 to decrease the sensitivity of the primary accelerometer, and (b) change the gear ratio in the gear box 6 to compensate for the loss in sensitivity. Hunting is prevented, as relays remain energized until the acceleration has fallen sufficiently for contacts 80, 81 to open, contact 82 being ineffective. The switching may, as in the Fig. 1 embodiment, be effected in stages, and two accelerometers responsive to accelerations in two cardinal horizontal directions may be provided and controlled by the same secondary accelerometer. The attenuator 75 may be replaced by a further amplifier, the gain of which is changed at the limit values.