Patent GB-425507-A (GB)
Abstract: 425,507. Controlling combustion in furnaces. BAILEY METER CO., 1050, Ivanhoe Road, Cleveland, Ohio, U.S.A.- (Assignees of Johnson, C. ; 2128, Reyburn Road, Cleveland, Ohio, U.S.A.) Feb. 23, 1934, No. 5974. Convention date, Feb. 24, 1933. [Class 51 (i)] A pilot valve for a servomotor is composed of two elements co-operating to form a conduit through which the actuating-fluid flows continuously, one of the elements being constructed of varying cross-section so as to cause the pressure of the fluid stream to vary correspondingly from point to point in its travel, so that relative longitudinal adjustment of the elements produces a variation in the pressure of the fluid at the point where communication is made with the actuating-member of the servomotor. Fig. 5 shows the two elements constituted by (1) a rod 61 formed with spherical enlargements 77 at points adjacent the connections 63, 64 to opposite sides of the servomotor piston, and (2) sleeves 78 .. 81 arranged around the rod to provide the conduit for the actuating-fluid, which may be air, water, oil, &c., and is admitted at A. The sleeves 78 and 79 are held abutting one against the other by a spring 82, which also holds the sleeves 80 and 81 in abutment. Narrow annular grooves 87, Fig. 7, are formed between each pair of sleeves, so as to form ports leading by passages 84, 85, 86, to the passages 63 and 64. The enlargements 77 fit with very slight clearance in the sleeves, so that there is a constant leakage of fluid from A past each enlargement to exits at the ends of the sleeves, and the pressure of the fluid gradually decreases in passing the enlargements in proportion as the cross section of the enlargements increases. Hence as the rod 61 is moved longitudinally, the pressure of fluid at the ports 87 varies so as. to produce a corresponding actuation of the servomotor piston. Screw caps 83 bearing on the ends of the sleeve provide adjustment of the position of the ports 87. Where there is only a single passage leading from the pilot valve to the piston, only one enlargement 77 and port 87 is provided. Also the enlargements may be in the form of double or single truncated cones. In either case, the enlargements tend to centre themselves in the sleeves, due to the action of the fluid flowing past them, and friction is thereby considerably reduced. Fig. 1 shows a controlling-apparatus for a steamgenerator furnace provided with several pilot valves of the kind described above. Fuel supplied at 3 to the furnace 2 is controlled by a valve 7 with a servomotor control 8 ; combustion air supplied at 4 is regulated by a damper 10 with servomotor 12 ; and the outflow of the products of combustion at 5 is varied by a damper 11 connected to a servomotor 13. Steam from the generator 1 passes away by a pipe 6, the rate of flow being indicated by a flow meter 17 with a pointer 19 moving over an index 20. Rate of flow of gaseous products through the furnace, and consequently of the air supply thereto, is indicated by a meter 25 and scale 27. An indication of the pressure in the furnace is also given on a scale 31 by a meter 28, and of the steam pressure in the pipe 6 by means of a connection 21 to a Bourdon gauge 22 and scale 24. This gauge 22 is further connected to a lever 36 and pilot valve 37 similar to that described above, but with only one enlargement controlling a connection 39 to a valve 32, Fig. 1 and 3, which normally connects the pipe 39 by a recess 43 to a pipe 41 actuating the servomotor 8 and fuel control 7. The pipe 39 is also connected to another Bourdon gauge 24 which has a balancing action on the lever 36. The valve 32 is provided to allow of hand adjustment of the fuel control 7, by rotation of the valve so as to put the recess 43 out of action and bring into use another recess 49, which extends around the circumference of the valve not occupied by the recess 43 and connects the pipe 41 to another pipe 44 leading from a pilot valve 45. The rod 46 of this valve, with its double-conical enlargements, is simultaneously moved longitudinally by means of a screw device 47, 48, thereby adjusting the fluid pressure supplied from the inlet A to the pipe 33 and thus through the pipe 41 to the servomotor 8. The pipe 41 is further connected to a Bourdon gauge 50 acting, together with a balancing-gauge 57 upon a lever 53 connected to the pilot valve 52 of the servomotor 13. The steam pressure in the pipe 21 is thus used to control the supply of fuel at 7 and the damper 11. The servomotor 12 of the air damper 10 is controlled by a pilot valve 75 connected to the meter 28. The desired ratio between the rate of flow of the steam in the pipe 6 and the rate of flow of gases through the furnace is automatically maintained by connecting the indicators of the meters 17 and 25 to opposite ends of a lever 69, which is connected by a link 70 to a lever 71 having contacts at opposite sides of its fulcrum, which cause rotation in one direction or the other of an electromotor 73 connected to the lever 55.