Patent GB-284395-A (GB)
Abstract: 284,395. General Electric Co., Ltd., and Eden, C. G. Oct. 20, 1926. Contact-making relays.-The movable element of a measuring instrument or relay comprises a filament having a, free end and arranged so that a small force is sufficient to deflect it from the vertical position. In the electrostatic instrument shown in Fig. 2 the movable member comprises a filament 1 in the form of a, loop having its lower ends attached to wire supports 9, 10 and carrying at the upper end or bight a small bead of sealing wax 6 adapted to move over a scale 7. Electricallv connected with the filament 1 is a springy plate 2 fixed at its lower end and adjustable towards or away from the filament at its upper end by means of a rod passing through the case of the instrument. According to the Provisional Specification, the electrodes may be U-shaped channels placed slightly above the top of the loop. The filament 1 and plate 2 are connected to a terminal 31. A plate 3 is carried! by a rod passing through an insulating bushing in the case, and may be adjusted towards or away from the filament 1. Fig. 4 shows the instrument applied to indicate when the ratio of voltage drops or potentials across elements 38, 39 varies from a predetermined value. The plates 2, 3 are connected through a reversing switch 41 to a battery 42. a variable point 43 of which is earthed at 44. The case of the instrument is earthed at 40. The filament 1 is connected to the junction of the elements 38, 39 and may be earthed by means of a switch 46. The elements 38. 31I are connected in parallel with a resistance 48 across a source of current 47, a variable point 49 of the resistance being earthed. The filament is brought to zero by adjusting the plates 2, 3 and the position of the points 43, 49. Any change in the ratio of the voltage drops across the elements 38, 39 causes a variation of the potential of the filament 1 with respect to earth and therefore causes motion in one direction or the other. The charge on the filament may be dispersed by means of the earthing switch 46. The sensitivity of the filament may be varied by altering its effective length bv means of a clamp engaging both limbs of the loop. Alternatively the device shown in Fig 3 may be employed, in which the ends of the filament loop are supported by a hoop 52 which can be rotated and secured in any position. The sensitivity is therefore varied from a maximum in the position in which the bisector of the angle of the loop is vertical. Alternatively the filament may be deflected by electrodynamic or electromagnetic forces. Fig. 5 shows a. construction in which the filament 1, carrying a current to be measures, passes at its upper end between the poles 58, 59 of a permanent magnet 56, its deflection being indicated by the shadow of its upper end cast by a beam of light from a lens 66. In another construction. Fig. 6, the filament 1 carries near its upper end a light permanent bar magnet 68, which may be arranged vertically or horizontally. On either side of the magnet 68 are horse-shoe electromagnets 69, 70, which may be in series or in parallel, or may be energized from separate sources of current. Their polarities are such that the filament 1 is caused to bend at right-angles to its plane. The filament may be arranged to touch a fixed contact and complete a relay circuit. The filament may be enclosed in a vessel which may be partially evacuated to regulate the clamping. The filament may consist of a single linear strand fixed at the lower end, but with the upper end free.