Patent GB-248485-A (GB)
Title: Improvements in variable electric condensers
IPC: H01G5/38
Filed: 1924-12-09
Abstract: 248,485. Flinn, H. V. Dec. 9, 1924. Condensers of the variable type have removable or auxiliary mechanism adapted for application as a unit to the rotatable setting or adjusting spindle or element, by which the condenser may be converted to conform to the square law or other required law by rotating said setting element as bv means of an operating knob or member at the required variable speed. Figs. 1 and 2 represent cams of a certain contour for giving a square law or other desired relation, the relative displacements being indicated by numerals 0-10 of one, corresponding with 0<1>-10<1> of the other. The cams in full lines may be used with engaging friction surfaces which may be toothed as at A<1>, B<1> to prevent slip, but preferably cams of combined geared and sliding form are used and auxiliary cams A<2>, B<2> shown in broken lines so that driving cam B can rotate cam A until the geared parts are in mesh. For cam B<2> these comprise jaws D, E between which engages a horn C extending from cam A<2>. The condenser spindle G carries a sleeve G<1> on which is rigidly mounted the cam A and loosely mounted on arm H carrying a spindle for the driving cam B and a pinion H<1> rigid with it. The latter meshes with a pinion I integral with the operating knob J which is rotated and, owing to the non-rotatable mounting of the arm H, imparts to the spindle G a velocity of rotation depending on the contour of the cams and preferably moves through 360‹ as against the 180‹ of the spindle G. If the cam H is mounted by a. friction brake on the spindle G, the original law of the condenser can be followed by means of a further complete rotation of the knob. To do this, a spring-controlled plunger may be provided to engage a hole in one of the gears or cams so that the knob can be rotated against the action of the friction brake. In Figs. 18 and 28 the cams are untoothed and connected together by a flexible driving member or members A<10>, B<10> with a spring in one member to urge the cams into contact at the end of the reverse movement. Alternatively a spring associated with one or both cams may effect the reverse movement. In a modification, the two pinions might be dispensed with by mounting the dial on cam B directly. In Fig. 3 the spindle G carries a pinion G<4> meshing with a rack G<5> which moves on a guide G<6> and carries a pin and anti-friction roller K<2> engaging a groove in a cam K formed on the dial. Rotation of the cam counterclockwise imparts to the spindle a variable speed of rotation determined by the contour of the groove. The pinion may be frictionally mounted on the spindle G so that the condenser can he operated according to its original law or alternatively the groove may be continued, as shown in dotted lines, in the form of a semi-circular continuation of the spiral. This form as well as that shown in Figs. 1 and 2 may be used for fine adjustment either by making the groove in Fig. 3 correspond closely to a circle or by superimposing a cam having such a groove on the square law cam, or by other similar vernier mechanism. In a modification of the form shown in Fig. 3, the rack may be replaced by a pinion mounted on an arm on the spindle G and carrying near its periphery a pin and roller engaging the cam groove. The sizes of the pinions are chosen according to the nature of the adjustment required. In the form shown in Fig. 7, a system of jointed levers M - - M<3> is used, the lever M being secured to the knob and the lever M<1> to the spindle, while at the junction of levers M<2>, M<3> is placed a pin working in a groove N on a cam plate. The cam plate is either fixed relatively to the panel or adapted for relative movement if a friction brake is used, and the spindle is rotated by the knob at a velocity depending on the distance x, y between the spindle axis and the groove. As before, the condenser may be operated according to its original law if a friction brake is used. Fig. 9 shows a construction in which five jointed levers P - - P<4> are used, those P - - P<3> having one point at the spindle axis O and another at a pin Q, while that P<4> extends from the pin Q to an axis O<1> mounted eccentrically of the axis 0. The solid line S shows the path of the pin Q to give a square law relation and the dotted line the actual path, the divergence being capable of modification bymounting lever P<4> eccentrically on pin Q and/or by making the axis of connection between levers P<2>, P<3> eccentric. In Fig. 11, the condenser spindle X carries a pinion X<1> having a single tooth Z engaging a groove Y<1> formed according to the square or other desired law in a curved worm Y.