Patent GB-744624-A (GB)
Title: Control means for fraction collection apparatus
Inventor: GORHAM GEORGE
IPC: G01N1/18
Filed: 1953-05-04
Abstract: 744,624. Photo-electric control of tube filling. TECHNICON CHROMATOGRAPHY CORPORATION. May 4, 1953, No. 12368/53. Class 40 (3). [Also in Group XVII] In a device for filling a number of receptacles consecutively with equal quantities of liquid in which an electric motor replaces a filled container by an empty one, the motor may be controlled either after counting a predetermined number of drops into the container by means of a photo-electric cell or after a time interval. The invention is described with reference to filling one of a number of test tubes which are arranged in concentric circles T in a rack 10, the arrangement being that after each tube is filled the rack is rotated to position the next tube below the supply and when one circle is completed the feeding head is moved to the next. The amount of material in each tube is determined by counting drops entering the tube by means of photoelectric cell which, with a light source, is situated in a housing 12 pivoted on a shaft 22 and this housing also contains a device 28 which intercepts the drops and leads them to waste if the light source fails. The operation of the counting device is checked by a timer which positions device 28 if the rack containing the tube does not move regularly at set time inetrvals. Alternatively the timing device alone may be used, the rack being rotated after the time interval has elapsed. Circuits and operation, (1) Counting drops ivith overriding time control.-Passage of each drop between light source 24 and photo-cell 26 in housing 12 produces a pulse at the anode of the photo-cell which opens a normally blocked valve 64. The potential across anode resistor 88 is applied between grid and cathode of the righthand side of a double triode valve 13. The left-hand side is used as a rectifier to produce the anode potential of tube 64. The right-hand side of tube 66 normally conducts, energizing relay 32 which is shunted by condenser 80 to prevent chatter. This valve now cuts off, contacts 68, 70 sending a pulse to coil 72 which steps on a counting device when sufficient pulses have been counted whilst coil 114 is deenergized as described in U.S.A. Specification 2,329,447, when contacts 104 and 132 are in the positions shown. The circuit of rack-driving motor 18 is now completed and the motor rotates to position the next tube in the rack beneath the supply. The motor is so geared that one complete revolution of the motor produces the necessary rack movement. During its rotation motor 18 drives cams 44, 46. After a single revolution of the motor cam 44 re-establishes the circuit of clutch coil 114 to open the circuit of motor 18 which stops. Counting then commences. Cam 46 forms part of the time check apparatus and operates to deenergize a clutch coil 170 once per revolution. This coil couples a self-starting synchronous motor M to a member 164 which after a predetermined number of revolutions of motor M opens switch 134 in the main supply line L1. In consequence a solenoid 30 is de-energized allowing device 28 to run the supply liquid to waste. After a predetermined travel, motor 138 opens its own circuit by means of a switch 140. Instead of this last switch a slipping clutch device may be used. Omitting time control.-The time control may be rendered ineffective by means of a switch 150 which renders supply line L1 complete independently of switch 134 and disconnects the supply to coil 170 from cam-operated switch 50. Operation of apparatus under time control only.-If the apparatus is to operate under time control only, ganged switches 96, 78 and 128 are moved to their alternative positions thus removing the supply from contact 70 of photoelectric relay 32 removing the operating voltage from tubes 64 and 66 and connecting contact 96 direct to line L1 by-passing time-operated switch 134. In operation when the main switch is closed motor 18 commences to rotate until cam-operated switch 48 energizes clutch coil 114 de-energizing the motor which however continues to rotate over a circuit made by camoperated switch 52. Thus the motor completes one revolution and stops. When the motor stops, cam-operated switch 52 energizes timing motor M and coil 170. Timer 136 runs until switch 134 opens the circuit of clutch coil 114 which de-energizes opening contacts 130, 132 and restarting motor 18 which moves the rack one step and the cycle commences. A limit switch 100 is provided to switch off the apparatus when all test tubes have been filled. Specifications 655,896, [Group XVII], 679,992, [Group XXX], and 689,079, [Group XVII], are referred to.