GB264598A - Improved variable capacity electrical condenser - Google Patents

Abstract

264,598. Bancroft, F. E. Oct. 22, 1925. Condensers of the type in which a cam is interposed between the operating member and movable capacity part of the condenser for causing the capacity variations and dial readings to be connected by some law other than a straightline law, comprise a fixed set of vanes or plates and a movable set, the plates of each set being of substantially the same form, and a cam operated by the control knob for sliding the movable plates in relation to the fixed plates. The frame plate a, punched out of sheet metal and provided with lugs a<1>, carries the bush b by soldering, ring punching or the like, the bush serving as a bearing for the spindle c. The fixed and movable vanes e, f are shown rectangular and relative movement between them is effected by a. cam k on the spindle c, the cam being shaped according to the law required. The plates f are carried on a frame g which is slidable on guide rods h against spring action and carries a driving pin m with a leather washer or roller l engaged by the cam. The springs i may be dispensed with and the plates positively actuated in both directions by the cam, but when springs are used a balancing spring may be used to act on the spindle c. A set of interchangeable cams may be provided to vary the relationship between dial readings and capacity variations or a uniform motion cam might be employed with shaped plates or with rectangular plates of graded lengths. Further the spindle could have a number of cams and means for selecting the desired one. A fine adjusting means operated from a distance may be provided, the said means comprising a spring arm o operating the spindle c through a two-part link v<1>, v<2>, of which the part v<1> is of metal and v<2> of insulation. The washer o is slotted and the ends of the slots are turned down to engage in a cork, leather, or other friction washer p positioned by means of a metal washer q, thus constituting a friction clutch. The link is connected by a crank pin u with a fineadjustment spindle s mounted in a bushing t, a spring washer and leather washers giving the necessary friction. Similar washers may be used on the main spindle c between the washer o and bush and between the bush and look nuts w to give smooth working. The fixed plates are carried on an insulating block x which is capable of slight vertical adjustment on the reduced ends of the rods h to provide for proper positioning. One or both of the springs i may be soldered to the frames g, a to give proper connection between the moving plates and their terminal z<2>, z<1> being the terminal for the fixed plates. In a modified form, a spur wheel on the cam spindle meshes with a pinion on the fine-adjustment spindle, suitable friction being arranged for on the latter.