Patent GB-729234-A (GB)
Title: Adjusting apparatus for controlling movements of a hydraulically operated structure supporting an electrode in an electric arc furnace
IPC: H05B7/109
Filed: 1952-08-29
Abstract: 729,234. Fluid-pressure servomotor-control systems; valves. PAYNE, W. H. Aug. 29, 1952, No. 21785/52. Class 135. An adjusting apparatus for controlling movements of a hydraulically-operated structure 20, Fig. 1, supporting an electrode 13 of an electric arc furnace comprises a control valve having a casing with a cylindrical bore containing a closure member movable in an angular direction by means responsive to the current flowing through and the voltage across the arc and in an axial direction by the pressure of the fluid in the hydraulic system. The electrode is carried by an arm 17 supported by a piston 21 in a cylinder 22, the pressure in which is controlled by two control valves 34, 35. Current flow in A.C. supply conductor 19 to the electrode is sensed by winding 40 and may be passed through rectifier 43 to a coil 38R. Voltage is taken by a connection 17<SP>1</SP> and may be passed through rectifier 44 to a coil 38L. Coils 38R and 38L act to turn a rotary armature 37 in opposite directions, and thus with optimum current and voltage, the armature will be held in a central position to which it is urged by springs 60, 60<SP>1</SP>, Fig. 2, acting through quadrantshaped members which limit turning movement of the armature in both directions. The inlet conduit 33 of valve 34 is fed by a pump 27 at a pressure limited by valve 32, and the outlet conduit 36 of valve 35 is connected to the pump inlet and reservoir 29. Outlet conduit 24R of valve 34 and inlet conduit 24L of valve 35 are connected to line 24 leading to cylinder 22. Valves 34, 35 each comprise a cylindrical closure member 48 rotatable in a housing 47 and having a groove 49 for controlling flow between conduits 33, 24R and 24L, 36. Armature spindle 37<SP>1</SP> has a splined connection with each member 48 which is urged by a spring 67 against housing end cap 51<SP>1</SP>. The pressure in line 24 acts through lines 68 to move the members against the springs, and changes in this pressure reflect variations in the operating load, i.e. inertia, weight and friction of the electrode and its support. When the electrode is in the correct arcing position, both valves 34, 35 are closed. If the arc length shortens, the armature 37 will turn to open valve 34, whereupon the pressure in line 24 will increase and cause lowering of member 48 to increase the effective flow area of groove 49 to overcome the inertia of the electrode. When the electrode is moving, the pressure in line 24 will drop to permit raising of member 48 and as the electrode approaches the correct arcing position, the armature will return towards its central position, thus causing the electrode to decelerate. Lowering of the electrode is similarly effected by valve 35. Bottoming of the. electrode on the melt opens switch 45, thus rendering coil 38L ineffective, whereupon coil 38R moves armature 37 to cause raising of the electrode. A lever may be fitted on the armature to permit of manual control of the electrode. In another arrangement, a single control valve connects conduits 24L and 33 and when the electrode is in correct arcing position, is sufficiently open to by-pass the fluid supplied by the pump back to the pump inlet. Reduction of the load due to wear of the electrode is compensated by axial movement of the closure member.