Patent GB-545886-A (GB)
Title: Improvements in and relating to devices for testing the continuity of conductive paths
IPC: G01R31/02
Filed: 1941-03-10
Abstract: 545,886. Transformers. GRUENBERG, C., and DAVIS, H. March 10, 1941, No. 3238. [Class 38 (ii)] [Also in Group XXXVI] In apparatus for testing the continuity of conductive paths, the components, including a source of current and a signalling device, are enclosed in a sheathing of rubber, artificial rubber or similar synthetic material which also covers the connecting conductors and serves for mechanically uniting the various parts. Two test electrodes 1, 2, Fig. 1, a dry battery 3, a lamp or other indicator 4, and a conductor 5 connecting these parts in series are enclosed in a sheathing 6 which covers the root portions of the testing electrodes 1, 2. As shown in Fig. 2, the end of the sheathing 6 is enlarged to form a recess and is provided with a flange 9 fitting into a corresponding groove in the root of the testing electrode 1. A stiff tube 28 of presspahn is inserted into the recess, accommodating a tubular lamp 4. The conductor 5 ends in a contact piece 7, against which bears a spring 8 which presses the lamp. 4 against the root of the electrode 1. Window openings 29 are provided in the tube 28 and in the sheathing 6, that in the sheathing being closed by transparent synthetic material moulded into the sheathing so as to be airtight. Replaceable electrodes of various shapes, such as pointed, hooked, or formed like a cable socket, may be used by providing disconnectible flange couplings. The recess may alternatively be provided with a screw or bayonet socket for ordinary lamps. The dry battery is accommodated in a similar recess but without a window. For testing high-resistance paths a stepup transformer is employed with a telephone receiver in the secondary circuit. The transformer may be enclosed in the sheathing or, as shown in Fig. 5, the primary winding 10 is enclosed in the sheathing 6 of the testing circuit while the secondary winding 11 and the conductor 13 connected to the telephone receiver are covered by another common sheathing 14, so that the secondary forms a ring which can be slipped over the enlargement of the sheathing 6 embedding the primary 10. A buzzer may be included in the primary circuit, the test electrodes being connected either in the primary or the secondary circuit. A microphone may be included in the circuit and may be used for signal transmission if the test electrodes are connected together. In the construction shown in Fig. 9, the primary and secondary windings 10, 11 of a step-up transformer are embedded in the sheathing 6 covering the conductor 5 and other parts of the primary circuit, the ends of the secondary winding being connected to sockets 15. These may be engaged by a plug having pins connected to a telephone receiver, the testing electrodes being connected in the primary circuit, or, as shown, by an adaptor 20 having pins 23, sockets 27, and testing electrodes 21, enclosed in a sheathing 26. A flange portion 24 is formed in the sheathing of the adapter and fits a corresponding groove in the socket portion 16. A plug having pins connected to a telephone receiver is plugged into the sockets 27 and has a flange similar to the flange 24 which engages a corresponding groove in the socket portion of the adapter. The transformer may be provided with an iron core.