Patent GB-191017091-A (GB)
Title: Improvements in and relating to Wattmeters.
Inventor: WESTON EDWARD
Filed: 1910-07-18
Granted: 1911-08-18
Abstract: 17,091. Weston, E. July 18. Power meters; vibrationdampers.-The fixed and moving coils of a watt-meter are so proportioned as to produce a uniform scale of considerable range. The diameter of the moving coil has a ratio to the axial length of the field coil of about 5 to 4. The moving coil 2, Fig. 3, which is connected in series with a non - inductive resistance 9 across the mains, is of fine wire, preferably aluminium, the coil being spread out at the axial points. The coil is fixed to a spindle 29, Fig. 11, by a pair of corrugated plates 30 cemented to the coils and having ears 31 engaging the ends of a pin 32 passing through a hole in the spindle. The spindle carries at each end a sleeve 33, Fig. 8, the upper sleeve having a flattened part and a flange to carry a pointer, and being drilled to provide a socket for a pivot pin. A clamping-nut 39 screwed on the sleeve holds the pointer in position, and also retains the terminals 40, 41 of the controlling-springs 75. The lower sleeve is similar to the upper one, the flattened part serving to hold in position a bar carrying damper vanes. The lower pivot is supported in a bearing carried by a plug 44, which is retained in a pillar 45 by flanging over the ends. The upper jewel bearing 43 is carried by a screw 46 in a nut 47 supported by a bridge 49. The nut has an horizontal slot 73, Fig. 6, extending to the centre, and a screw passing across the slot may be tightened so as to lock the bearing-screw 46 in the nut when the pivot has been adjusted. The frames for carrying the field coils are formed of non-magnetic metal of high specific resistance, such as manganin, to reduce errors due to eddy-currents. The standards 11, Fig. 3, are thin and flat, and of skeleton form, and may be stamped from sheet metal; they are mounted by means of tenon-shaped parts 21 in slots in a base 12, which forms a damper box, and is fixed by insulated bolts to the casing. The tenons have pieces of softer metal fixed to their sides, the soft parts being then machined. The standards are grooved to receive flanged sectors 23, on which the coils are held by clamps 25 carried by the standards and spaced from them by sleeves. A bridge consisting of two plates 49, 50, Fig. 6, insulated from each other by a mica strip, is supported on pins projecting from the standards. The plates are insulated from the standards by washers and flanged sleeves 54, 63 of such form as to enable plates of similar shape, each having a hole at one end larger than the other, to be mounted in reverse relation and to be readily removable from the standards. Each standard carries an insulated ring 57 held in position by a screw 61 adapted to screw into the pin. The ring at one end of the bridge has a turned-up lug, that at the other end being turned down so that spring connexions between the lugs and plates 68, 69, Fig. 8, are in parallel planes. One of the plates 68 is held between the nut 47 and the upper bridge-plate 49, the other being held between a nut 72 and the lower bridge-plate 50. Spring washers 70, Fig. 10, with inwardly projecting bent tongues 71 are interposed so as to retain the plates in position while allowing them to be adjusted. The ends of the plates are bent and are connected with the coiled controlling-springs 75 by soldering, the other ends of the springs being secured to the forked members of terminals 40, 41, which have tongues 78, 79, Fig. 12, projecting one on each side of a counterweight arm 80, and connected to the ends of the moving coil. The counterweight consists of a sleeve 114 with a disk 115, the sleeve being partly split if required. For adjustment purposes, the plate 68 has a slotted extension with a wide opening, with which engages a pin 90 mounted in a block 86. The block is carried by a screw fixed in a plug in the casing of the instrument, a spring washer being placed between the block and the casing. The nuts 47, 72 are riveted to the bridge - plates. The damper box is made of non - magnetic material of high resistance such as manganin and is made as light as possible. Specifications 12,221/90, 6816/94, and 6990/98 are referred to.