Patent GB-178789-A (GB)
Title: Improvements in or relating to instruments having filar control
IPC: G01R1/12
Filed: 1920-11-16
Abstract: 178,789. Field, M. B. Nov. 16, 1920. Suspensions. - In a measuring - -instrument in which the moving system is controlled by a filar combination, the load or axial force on the filaments is produced by one or more weights independent of the weight of the moving system, which may be suspended or supported on a pivot. The filar combination may be arranged above or below the moving system, the filaments may be crossed or may have the lower portion of V-formation, and the load may be anchored so as to permit axial movement thereof while preventing rotary movement. The filar combination may be arranged in positions other than vertical and means may be provided to compensate for the stretching of the filaments. In one construction as shown in Fig. 2 the filaments 55 are attached to a load 57 anchored by hinged links 58-60 and 67-69 to spring members 61-63 carried by supports 64, 65 and to bell-crank levers 70-72 supported by brackets 73, 74 respectively on a base plate 66. The arrangement is such that vertical motion of the load 57 alone is permitted and tension in the links is adjusted by weights 75-77 on the bell-crank levers. In another from the indepen. dent load may be Y-shaped controlled by three hinged links. Fig. 4 shows the control applied to an electrostatic voltmeter the moving vanes 91 being supported by a torsion ligament 93 and the filament 97 having a load 98 anchored by links 99. In a modification the load may be attached to an horizontally disposed member the other end of which is carried by a vertical cord attached to the frame at a point level with the point of suspension of the moving system. Examples of the filar combination for an electrostatic voltmeter which is arranged above the moving system is described; as shown in Fig. 19 the moving vanes are suspended by a torsionless filament 152 and a cross-bar 158 on the spindle 151 is attached to the ends of a crossed filar control suspended from a counterbalanced member 159. In the form shown in Fig. 8 the filar combination is arranged above the moving system on an overbalanced drum the axial tension in the filaments being less than the weight of the moving system so that a residuum of weight is carried by the pivot of the moving system. In this arrangement if silk filaments are employed stretching of the filaments is automatically compensated for by the drum. Various forms of control with the lower portion of V-formation are described, one of which is shown in Fig. 9, the load being represented by weights w. The application to the torsion head of a watt-meter is shown in Figs. 15 and 16, readings being obtained by the null method. A rotatable disc 120 is carried by a bracket 121 and supports a bracket 123 on which is pivoted a frame 124 and cross-bar 125. The cross-bar carries jewel cups with which engage struts 128 the other ends of which are supported in similar jewel cups attached to a cross-bar on the end of the filar control. In a further modification suitable for the comparison and measurement of forces two separate sections of equal length may be employed with the filament turned through 90‹ and attached to cross-members 45, 46 of a light frame 44, Fig. 1, and controlled by weights W, W1. Specification 175,723 is referred to.