Patent GB-775541-A (GB)
Title: Improvements relating to electromagnetic carbon-pile regulators
Inventor: NIXON LESLIE REGINALD
IPC: H02P9/22
Filed: 1952-12-31
Abstract: 775,541. Carbon pile regulators. STONE & CO. (DEPTFORD), Ltd., J. Dec. 18, 1953 [Dec. 31, 1952], No. 33068/52. Class 37. An electromagnetic carbon pile regulator having the pile and magnet system sealed in an inert atmosphere, wherein, for limiting heat conduction between pile and magnet system the wall of an enclosure closely surrounding the pile is connected to one end of a casing enclosing the magnet system by a tubular extension of the wall through which a pile compressing chamber operates. Carbon pile housing (Fig. 1).-Carbon discs 5 are housed in a ceramic tube 6 on which is shrunk metal tube 7 with a finned cylinder 12 diecast around it. The pile is compressed between the end seal 15 of tube 6 and contact 30 which is moved by the clapper of the pile compressing mechanism through operating rod 24. Tube 7 communicates with the interior of the casing 1 of the pile compressing mechanism which is filled with heat-conducting inert gas, e.g. He, through a thin-walled tube 8 of austenitic steel soldered into its end and into cover 2 of the casing at 9. The finned structure is fixed to lugs 20 of the compressing mechanism supporting frame 21 by composite rods 17 of adjustable length sealed through the casing at 19 and the expansion coefficient of which is chosen to compensate pile expansion. These rods may comprise studs 171, 17<SP>2</SP> having threads of different pitch engaging internal threads in sleeve 17<SP>3</SP> which is rotated to adjust the length. Pile compressing mechanism.- The composite clapper structure (41, 35, 34, &c.) which carries armature 42, is mounted on frame 21 by crossed leaf springs 45, 46 so as to pivot about axis 47, and moves operating rod 24 via a jewel 28 recessed in an arm 32 pivoted to the clapper structure at 33. In the minimum resistance position it is held against adjustable stop 65 by control spring 49, which acts on it through double bimetal strip element 60, 61. In this position auxiliary spring 35 compresses the pile via the pivoted arm thus ensuring that the pressure on the pile is substantially constant and unaffected by pile shrinkage. When the horseshoe electromagnet 55 is energized, armature 47 is attracted to rotate the clapper. After the last motion between stop 66 on the clapper and arm 32 has been taken up the latter is positively withdrawn and operating rod 24 is forced to follow its motion by the pile reaction assisted by spring 36, which acts through movable contact carrying ferrule 29 and also serves as electrical connection to the pile. The bimetal strip 60 acts to reduce the tension of spring 49 and 61 to decrease its leverage about the axis of rotation with rising temperature to compensate for reduced current in the windings 56. A heating element in recess 41 may be used to maintain the strip at the temperature of the windings. Alternatively or in addition a negative temperature coefficient resistor may be wound with or adjacent to and in series with the windings 56. The motion of the clapper which is balanced by masses 77 on outriggers 76 is damped by connection through crossed leaf springs 73, 74 to a bar 73 which moves the pot of annular diaphragm dashpot 67 via arms 72. Specifications 725,793, [Group XXXV], 775,542, 775,543 and 775,544 are referred to.