Patent GB-572392-A (GB)
Title: Improvements in and connected with dash-pot devices particularly applicable for use in electric regulators
IPC: H02P9/22
Filed: 1943-08-12
Abstract: 572,392. Automatic regulators. STONE & CO., Ltd., J., CHILTON, A. H., and NIXON, L. R. Aug. 12, 1943, Nos. 13033 and 18096. [Class 38 (iv)] [Also in Group XXXII] A dashpot for use in electric regulators, comprises a shallow pot of dish form, an annular diaphragm fixed to the open side of the pot and formed with a peripheral portion of curved channel section, a plunger device attached to the central portion of the diaphragm and a restricted air port communicating with the chamber enclosed in the pot by the diaphragm and plunger device. As shown in Fig. 6, the periphery of the diaphragm u is clamped by a ring v to the flat rim p<2> of the metal pot p to which is fixed a casing t for a needle valve t<1> which regulates the air port t<2>. The central portion of the diaphragm is clamped between discs w, w<1> to which a screw x<1> is fixed for the attachment of a plunger rod which operates the dashpot, and between the periphery of the discs and the rim p2 of the pot, the diaphragm is moulded into an arched section annulus which ensures a definite amount of movement of the discs w, w<1> without restraint. In a modification, the pot is formed without a flat rim. In another construction, Fig. 8, the diaphragm and discs are enclosed on both sides between the pot 1 and a cover 2, restricted communication between the two chambers so formed being provided by a fine bore in one or more of the rivets 6 which secure the discs to the diaphragm. To provide a frictionless packing for the plunger rod q, the cover 2 is formed with a cylindrical protuberance 2a between which and an annular projection w<2> on the disc w, a bellows packing 4 is secured. A similar bellows 5 is attached on the opposite side. In a modification, each bellows packing is connected between an annular flange on the cover 2 or pot 1 and a thimble device fixed centrally to the disc w or w<1>. To obtain an adjustable restricted communication between the two chambers, the hollow rivet or rivets 6 may be replaced by a duct 20, Fig. 10, connecting the pot chamber with a valve casing 21 on the cover 2, a disc valve 12 in the casing, controlled by an adjusting screw 16, being supported by a springy diaphragm 13 and disposed closely over a fine bore 14 leading to the cover chamber. Fig. 1 shows the dashpot p applied to an automatic voltage regulator, so as to control the movement and resist spasmodic action, the carbon pile a being de-compressed by a coiled extension spring b and placed under variable compression by an armature c when attracted by the magnet d. The arrangement is shown diagrammatically in Fig. 3. The armature c, which comprises two blades opposite gaps in the magnet, is fixed to the lower end of a Y-shaped member e, e<1>, e2, the branches e<1>, e<2> each having a formation e<4> to which one end of each of a vertical blade spring f and a horizontal blade spring g is attached, the other ends of the springs being secured to frame members h. The member e, e<1>, e<2> can thus pivot about an axis x passing through the points of intersection of the blade springs. The coiled spring b is secured between an adjusting screw j in a frame member and a slotted extension on the part e4 of the branch e<2>. One end of the carbon pile a is engaged by an adjustable screw abutment k in a frame plate l and the other end by a movable presser ring m connected with the branches e<1>, e<2> by flexible strips n. The pot p of the dashpot is supported by a frame plate o and the plunger rod q connected by a flexible strip r with a projection s on the stem e. When the magnet d is de-energized, the pull of the coiled spring b on the branch e<2> swings the member e, e<1>, e2 anti-clockwise about the axis x and the presser ring m moves to the left so that the pile a is de-compressed, the movement being limited by the stem e engaging an adjustable stop 11 on the frame plate l. When the magnet is energized, the pile a is compressed. During both operations the movement is resisted and controlled and spasmodic action avoided by the inflow or outflow of air through the restricted port in the dashpot. In another construction of regulator, the carbon pile is decompressed when the magnet is energized and is compressed by the spring.