Patent GB-347019-A (GB)
Abstract: 347,019. Fluid pressure control systems. HOPWOOD, J. M., 2716, Espey Avenue, Mount Lebanon, Pennsylvania, U.S.A. May 9, 1930, No. 14282. Convention date, May 9, 1929. [Class 51 (i).] In a fluid-pressure control system a master regulator 10 responsive to a plant condition (e.g. the pressure in a steam-header supplied by a number of boilers) controls a hydraulic or other fluid-pressure line 40 which operates a relay 42 for each boiler furnace to admit or exhaust pressure from a second pressure line 68 connected to a plurality of sub-relays 69 each controlling the operation of a remote mechanism (e.g. fuel supply 74, flue damper 79 and air supply 84) the relay and subrelays being grouped together. The master regu. lator 10 of the kind described in Specification 172,415, [Class 51 (i), Furnaces and kilns, Combustion apparatus of], directly responsive to variations in the plant load through a pipe 11 operates by means of a weighted lever 12 and link 13 a lever 14 which moves a valve 19 to supply or exhaust fluid to or from bellows 33, Fig. 6, connected through the pressure line 40 with the relays 42 associated with the different furnaces. The lever 14 is pivoted to a slide rod 34 connected to the top of the bellows 33 so that the valve 19 is returned to its central position by the movement of the bellows. Local panels 41 associated with each furnace have a relay 42 comprising upper bellows 43 connected through a three-way valve 45 with the pressure line 40, the lower end of the bellows 43 being connected with the top of lower bellows 49 by a slide rod 48 which operates a lever 63 connected by a link 64 with a valve 61 controlling the supply or exhaust of fluid to or from the lower bellows, movement of which thus returns the valve 61 to its central position. The second pressure line 68 connects the lower bellows 49 with a plurality of sub-relays 69 operating the remote individual coal and air controls 73, 78, 82 of each furnace.. The relays 42 are provided with means for adjusting the rating of each furnace independently of the others comprising springs 59, 60, Fig. 4, on the slide rod 48 adapted to act on the bellows and adjusted by a hand-wheel 58 through a screw and nut 56, 57, a bell-crank lever 54 and a sleeve 50 slidable on the rod 48 and engaging the springs. The three-way valve 45 may be turned by a handle 46 so that the bellows 43 are disconnected from the pressure line 40 and opened to the atmosphere whereupon the furnace as a whole may be manually controlled by the hand-wheel 58. Each of the sub-relays 69 is identical in construction with the relay 42 so that the individual controls may similarly be disconnected from the pressure line 68 and manually adjusted, without affecting the automatic adjustment of the other controls. To adjust the rating of the whole plant the compression of a spring 110, Fig. 6, acting on the bellows 33 of the master regulator is altered, the spring abutting against a collar 111 adjusted by a lever 112 turned by a cam 114 the shaft 115 of which is provided with a hand-wheel on the front of the master panel. The whole plant may be changed over from automatic to manual control, the link 13 being made telescopic for this purpose and having an extension 91 passing into a casing 92 and provided with a slot 96, Fig. 9, adapted to be engaged by a pin 95 on a crank 94 the shaft 93 of which passes through the master control panel and is turned by a hand-wheel 98 at the front. During automatic control the shaft 93 is retracted against a spring 97 so that the pin 95 is free of the slot 96, the shaft being held in this position by shoulders 100 on a disc 101 integral with the handle 98 engaging arcuate shoulders 99 secured to the front of the panel. To change to manual control the hand-wheel 98 is turned to disengage the shoulders 99, 100 and permit the pin 95 to engage the slot 96 whereupon the valve-operating lever 14 may be adjusted by the hand-wheel. The link 13 comprises a tube 85, Fig. 10, connected to the lever 14 and secured at its lower end to an annular member 86 carrying a lower sleeve 88 through which passes freely a rod 90 connected to the lever 12. A collar 901 on the rod 90 is acted on by springs 921, 94<1> in the tubes so that during manual control movements of the automatic-control lever 12 are taken up by the springs. Grooved surfaces 102 on the disc 101 engage corresponding fixed surfaces 103 to hold the hand-wheel 98 frictionally in adjusted position.