Patent GB-479022-A (GB)
Title: Improvements in method and apparatus for testing eggs
IPC: G01N33/08
Filed: 1936-04-25
Abstract: 479,022. Determining physical qualities; anthropometrical appliances; switch contacts. RIVENBURGH, F. L. April 25, 1936, No. 11791. Convention date, April 25, 1935. [Class 37] [Also in Groups VI and XXXVII] A method of and apparatus for testing eggs for life activity consists in momentarily applying an exciting electromotive force to the egg and determining the current response of the egg subsequent thereto and consequent thereon. A fertile egg gives rise to a current flow of a particular direction dependent upon the direction of the exciting voltage and increasing with the incubation of the egg, while an infertile egg gives rise to a negligible current flow. The egg E is preferably brought to incubation temperature before test and is then arranged with a minor axis vertical between electrodes 10, 11, pads soaked in salt solution being inserted between the egg and the electrodes. A switch, which comprises arms 68, 69 of different lengths and relatively adjustable, adapted to engage mercury cups 64, 63 is provided, and at the commencement of a test, switch 21 is closed and the arms 68, 69 engage their respective mercury cups whereby a voltage from the battery 12 is applied to the primary winding 25 of a coil, the secondary winding 22 of which is in the circuit of the electrodes 10, 11, while the measuring instrument is short-circuited. Upon raising the arms 68, 69, the battery circuit is first broken at contacts 68, 64, resulting in a flow of current in the winding 22 whereby a momentary e.m.f. is applied to the egg. After a predetermined time the short-circuit of the measuring instrument is interrupted at the contacts 69, 63 and a current thereupon flows through the instrument, the magnitude and direction of which are dependent upon the fertility and the degree of incubation of the egg under test. The measuring instrument may be a galvanometer G or a voltmeter 49, and in the latter case the current flowing is amplified by valves 37, 39. In order to compensate for accidental voltages in the circuit, a compensating battery 34 is provided and the direction of this compensating voltage may be altered as desired by a reversing switch 27. A second reversing switch 15 enables the direction of the applied voltage to be changed. In a modification, the voltage to be applied to the egg is obtained from a condenser charged through a rectifier. A spring contact maker, released by a handoperated latch, first connects the voltage to the egg-engaging terminals, then breaks this circuit and after a predetermined interval connects the terminals to the grid of an amplifier valve. A rectifying valve in the grid circuit prevents the passage of any but a positive response current, the effect of which is to modify the grid bias of the first valve and a voltmeter arranged in the plate circuit of a second amplifying valve indicates the magnitude of the response current through the egg. The initial grid bias of the first valve can be adjusted to compensate for stray currents in the circuit. The Specification as open to inspection under Sect. 91 comprises also the application of a series of impulses to the egg from an induction coil and determining the current response a pre-determined time after the impulses have ceased. This subject-matter does not appear in the Specification as accepted.