Patent GB-707238-A (GB)
Title: Detecting electrically, variations in a product and operating a control in response to such detection
IPC: A24C5/34
Filed: 1951-02-22
Abstract: 707,238. Automatic control of cigarette-making and like machines; reciprocating generators. AMERICAN MACHINE & FOUNDRY CO. Feb. 22, 1951 [March 9, 1950], No. 4354/51. Classes 35 and 38 (4), [Also in Groups VI and XXXVI] In a cigarette-making or other machine for manufacturing a product in a continuous length in which the operation of the machine is controlled in accordance with the impedance of a capacitor between the plates of which the product passes, the impedance is measured at a frequency between 30 and 200 megacycles to make the measurement independent of the distribution of the particles of the product. Thus, in the cigarette machine described, the device is not affected by a change in the proportion of longitudinal to transversestrands of tobacco but does respond to changes of moisture content or of weight per cigarette length or to plugs and voids in the rod. The apparatus may control the rate at which tobacco is fed to the rod. Automatic feed regulation. The output of a rectifier 250, Fig. 16, which receives a signal in accordance with the effective permitivity of the cigarette rod passing beween electrodes E1, E2 (see Group XXXVI), modified by that of a potential divider 752 is applied to cathodefollower tube 602, Fig. 19, the output of which is adjustable and is applied, via separate A.C. and D.C. biases for each tube, to the grid of thyratron 616 and the cathode of thyratron 618. The output of 602 is zero for the correct weight of cigarette rod and for weights above or below standard is such as to fire either 616 or 618 and operate the corresponding anode relay 640, 642. This removes a ground connection from the grid of tube 644 of a multivibrator 644, 646 which has hitherto been held by this connection in a condition in which 646 is in the conducting state and 644 is not. The multivibrator thus begins to operate at a rate determined by potential dividers 652,656 by which the on and " off times are respectively determined. During the "on" period, i.e. with 644 conducting, a relay 648 is energized and connects the supply circuit to one or other of a pair of reversing contactors 666, 668 according to the condition of relays 640, 642. A gear-changing motor, Fig. 1 (not shown) of which windings 670, 672 are shown in Fig. 19, thus runs in one direction or the other to correct the rate of feed of tobacco to the cigarette rod. At the end of the on " period the contactor is released and the motor is brought to rest rapidly by connecting condenser 678. which has been charged via 674, 676, across one of its windings. If there is still an error signal at the end of the ensuing " off " period, a further operation of the motor takes place and so on. Disabling automatic feature under abnormal conditions or at will.-If the limit of control is reached, limit switches 680, 682 prevent further actuation of the control motor in the direction concerned and operate signal lamps. In normal operation the alternating component of the control signal from rectifier 250 after amplification in tube 696 and rectification in 698 provides a paralysing bias for a triode 700. If, however, the rod stops, the anode relay 702 of this tube after an interval determined by the time constant circuit 716, 718 disconnects the power supply and operates indicating lamps. Since abnormalities are to be expected immediately after the machine is re-started, it is arranged that 702 also unlocks a relay 722 to disconnect a further point in the power supply and this can only be re-operated by a push button 724 or 726 after 702 has been energized. These push buttons could be replaced by a time switch. The regulator can be shut off by the buttons 736, 738 even when the rod is travelling normally Relay 740 energized by the release of 722 stops the drive motor when the rod stops. Testing and adjusting. A switch is provided for connecting up a local potential divider 746 in place of the input signal lead to the thyratrons 616, 618 to enable the response of the device to various signal inputs to be tested and adjusted. Construction of reciprocating generator, Fig. 9.-The magnetic circuit of a permanent magnet 422 comprises the core 421 of a coil 420, a spring 418, a toothed disc 414 adjustably mounted on a gear 416 driven with the cigarette machine, and the frame 413. As the disc rotates, the end of 418 snaps past each tooth and the sudden change in the reluctance of the magnetic circuit by the introduction of an air gap produces a sharp voltage pulse in coil 420. The magnitude of the pulse depends mainly on the characteristics of the spring and is independent, within a wide range, of the speed of the disc.