Patent GB-732327-A (GB)
Title: Improvements in or relating to valve operating mechanism
IPC: F16K31/05
Filed: 1953-09-01
Abstract: 732,327. Automatic pressure control systems. KOPPERS CO., Inc. Sept. 1, 1953 [Sept. 23, 1952], No. 24193/53. Class 38 (4). In Fig. 1 a snort valve 21 controlling the cold blast main of a blast furnace may be operated through a connecting rod 24 either by a hand. wheel 36 through cables 34 or by a shunt motor 27 through reduction gearing and an electromagnetic clutch (not shown). When it is desired to close valve 21 by motor 27 a hand switch HMA, Fig. 10, is moved to a position in which contacts HMA1 are closed to energize a relay winding CR, contacts CRIC and CR2C of which prepare a circuit to motor armature A. main and auxiliary hand-operated switches are then set to their " Wind on" positions contacts complete the circuit to a relay ON, contacts ON1C and ON2C of which energize armature A in the appropriate sense to close the valve. If, however, either of the main or auxiliary hand-operated switches is set to its " Wind off" position, contacts complete the circuit to a relay OFF, contacts OFF1C and OFF2C of which energize armature A in the appropriate sense to open the valve. Contacts CVC of a relay CV energized by the back e.m.f. of armature A co-operate with contacts ON5C and OFF5C of relays ON and OFF to ensure that once motor 27 is running in one direction it cannot be reversed until its speed falls below a predetermined value. Segments 1 and 4 of a drum switch 33 driven by motor 27 co-operate with contacts SVO1 and SV04 to interrupt the circuit of the OFF and ON relays when the valve is fully closed or open respectively. Segment 5 co-operates with contacts SV05 to light lamps L when the valve is fully closed. Segment 6 co-operates with contacts SV06 to interrupt the energization of relay CR should motor 27 pass its limiting positions. Contacts OLC of relay OL switch off the motor if motor current is excessive. A resistor in series with armature A to limit starting current, is cut out by contacts ASC of relay AS when the latter is energized during starting. A braking resistor is connected across armature A when relays ON and OFF are both de-energized. When it is desired to prevent rise of the furnace pressure above a predetermined value, hand switch HMA is set to a position in which contacts HMA2 are also closed so that closure of a pressure-operated switch PRESS SW by excessive pressure, energizes a time delay relay T1 which if the pressure rise persists sufficiently long energizes a relay PR, contacts PR3C of which energize the OFF relay, causing the valve to open. The extent to which the valve opens may be predetermined by a hand switch PCT, ASS, selecting contacts SV02 or SV03 which are opened to stop motor 27 by segments 2 or 3 of drum switch 33. Contacts T2C of a relay T2 ensure a minimum period of operation of motor 27 opening the valve. Opening of switch PRESS SW on restoration of pressure below the predetermined value causes de-energization of relay PR and closure of contacts PR2C to energize relay ON and fully close the valve again. Operation of hand switch HMA to a "Hand" position opens contacts HMA1 and de-energizes relay CR so that the winding MC of the electromagnetic clutch is de-energized and an electromagnet 45 (see also Fig. 8) to allow a tooth 40 to engage a slotted wheel 39 and look the hand wheel 36 in position. Hand operation of the valve may then be effected by operating lever 41 to disengage tooth 40 and turning wheel 36. A switch 46 opens to prevent motor operation when wheel 36 is locked by lever 41.