Patent GB-190825763-A (GB)
Title: Improvements in or relating to Electrolytic Devices suitable for use as or in the Construction of Switches, Circuit Makers and Breakers, and other Apparatus.
Filed: 1908-11-28
Granted: 1909-11-29
Abstract: 25,763. Thorpe, W. B., and Thorpe Meter Syndicate. Nov. 28. [Cognate Application No. 12,663, A.D. 1909, dated May 28.] Cut-outs ; switches.-Electrolytic devices such as are described in Specification No. 865, A.D. 1908, in which gases are alternately evolved and recombined, to cause a diaphragm or piston to close electric contacts periodically, are modified in detail and are employed to cause the lapse of a definite interval of time between the operation of the various contacts in motor-starting switches, switches for operating electric signs, time switches, cut-outs, and other apparatus. The diaphragm or piston that is displaced by the gases is caused to make a fluid-tight connexion with the inner surface of its containing-tube. The piston may be a body of mercury f, Fig. 3, and one or more rings or pieces e, e<1> of metal such as platinum may be fused into the wall of the tube so as to prevent gas or electrolyte from creeping past the mercury column ; to prevent oxidation, the mercury is connected to the negative main. When a flexible diaphragm is used, it is attached to the bottom of a straight tube, and may be formed with expansion chambers to operate the contacts. The gases are ignited by a spark, or by the incandescence of a platinum wire, when the diaphragm or inercnry column closes a circuit between two contacts g, h, either directly or by means of a movable contact-pin carried by a float. In the arrangement shown in Fig. 3, this causes an electro-magnet q to close the circuit of an electromagnet p, which attracts an iron armature carried by a pivoted glass stem m within the chamber a', and separates a'contact j from a fixed contact in an inductive circuit, this causing a spark. Alternatively, the spark may be produced by the electrolyte falling below the level of'one of the electrodes b<1>, which is arranged vertically, as shown in Fig. 6. A high resistance, which may be a thread of electrolyte contained in a capillary tube a<4>, is arranged between the mercury column f, and the electrodes b, b<1>. The mercury column also passes through a capillary bore a<5>. The tube d in which the mercury column rises may be sealed at the upper end to prevent temperature errors. The application to a motor-starter is shown in Fig. 2. On closing a hand switch g, the electrodes b, b<1> are connected in series with a resistance 16, across supply mains k, k<1>, and the mercury column f makes connexion between the contact g and contacts 4, u, u<1>, u<2>, u<3>, u<4>, 5 successively. At contact 4 the mercury, which normally is connected to the negative supply main k<1> through the arm 11 of a switch, is connected directly through a by-pass connexion 4<a>. At contact u, the field circuit 2 of the motor is connected across the mains, and the armature 1 is connected in series with a resistance v, which is cut out in sections as the mercury rises in the tube d. At contact 5, an electro-magnet 6 is energized and closes the switch 11, thereby connecting the motor and the electro-magnet 6 to the mains independently of the electrolytic device. Owing to the by-pass connexion 4<a>, the evolution of gases continues until the electrolyte breaks contact with the negative electrode b<1>, causing a spark which recombines the gases and allows the mercury column to return to its original position. According to the Provisional Specification No. 25,763, A.D. 1908, the mercury column may remain in the short-circuiting position while the motor is running, the gases being exploded by the selfinduced current in the field winding on switching off the motor. A tube may be similarly provided with contacts for closing the circuits of an electric sign &c. at a predetermined rate, and opening them rapidly on the explosion of the gases. Fig. 3 shows the application to an electric time switch. The electro-magnet q is energized periodically and rotates a ratchet-wheel 25 by means of a pawl 24. The wheel 25 may be arranged to make a complete rotation in twenty-four hours and may be marked with figures indicating hours. Two adjustable tappets 26, 27 are arranged to open and close respectively a switch 28, which is pivoted at 29, and is opened by a weight 36 when a catch 34 is released by the tappet 26, and is closed by the tappet 27 striking an arm 37. In order to enable the apparatus to operate correctly as a time switch when the pressure across the mains is variable, a second electrolytic cell 40, having electrodes of relatively large size, is connected in parallel with the electrodes b, b<1>. A resistance 38 is connected between the two cells as shown, and the cell 40 is shunted by a resistance 41. The rate of action of the main electrolytic device may be altered by varying the resistance 38. The cell 40 may be constructed similarly to the main electrolytic device so that the gases evolved are periodically exploded ; or the electrodes may be of catalytic platinum. A time-limit overload cut-out is shown in Fig. 6, in which an electro-magnet 50 is inserted in the circuit to be controlled, and is arranged to close switches 54, 54<a>, when a predetermined current is exceeded. The switch 54 closes the circuit of the electrodes b, b<1>, and causes the mercury f to make connexion between the contacts g, h, after a predetermined time interval. If the switch 54<a>, which is insulated from the switch 54, is still closed owing to the continuance of the overload, a tripping-coil 57 is energized opening the cut-out 59. In order to ensure the ignition of the gases evolved, whether or not the overload continues for the predetermined time, the mercury column f is arranged to rise in two tubes containing contacts h, h<1> at different heights, so that the mercury first reaches the contact h and maintains the circuit of the electrodes b, b<1>, independently of the switch 54. Alternatively, the electrolytic device may be provided with a single contact-making tube having a second contact at the lower end to close the circuit of a similar electrolytic cell which, after a slightly longer time-interval than that required for the first cell to open the cut-out, closes a circuit for exploding the gases in both cells without operating the tripping-magnet of the cut-out. The contactcontaining tube or tubes may be arranged as shown in Fig. 7, so that the contacts are made by a second mercury column 65, the motion of which .is controlled by that of the mercury column f through the air contained in the connecting-tube 64x. The mercury column 65 may be connected to the positive pole, while the mercury column f is connected to the negative pole.