Patent GB-590605-A (GB)
Title: Combined temperature and safety control for gaseous fuel burners
IPC: G05D23/02
Filed: 1944-08-17
Abstract: 590,605. Safety cut-off valves. MAY, P. (Grayson Heat Control, Ltd.). Aug. 17, 1944, No. 15755. [Class 135] A combined thermostat and safety cut-off device for gas burners comprises a main valve opened against biassing means by thermostatic means acting on one side of the valve, and closed extinction of the pilot on burner flame whatever the position of the thermostatic means by an armature acting on the other side of the valve, the armature being held in engagement with an electromagnet and out of engagement with the valve when the pilot flame is burning and being re-set to its position in engagement with the electromagnet on extinction. of the pilot flame by manually operated means, further means being provided to hold the valve closed, independently of the armature during the re-setting operation. As shown the device has a casing 15 with a gas inlet 17 and a gas outlet 19. The inlet 17 is controlled by a plug cock 23 having a side, port 27 leading to an axial bore 25 and lateral groove 48 by which the inlet can be connected to passages 52, 54 in the casing 15. The plug 23 is operated by a dial 31 carried by the plug stem 29 and its movement is limited to 180 degrees by a flange 40 on a plate 33 co-operating with a slot 42 in the dial 31. A spring 37 presses the plug to its seat. The plug may be retained in an intermediate position in which only the passages 52, 54 leading to the pilot burner are open by a spring-loaded locating plunger carried by the dial. A screw-threaded throttling member 46 is mounted in the stem 29. The passage 54 is connected to a pipe 108 leading to a pilot burner 110 by passages 56, 80, 84, 102 and 104 the middle three of which located in an end casing 58 bolted to the main casing 15. These passages are off-set from the vertical axis of the casing 58. The passage 84 may be more or less throttled by a plug 76 screwed into the passage 80. The passages 84, 102 are separated by a chamber containing a spring closed valve 88 the stem 96 of which abuts a diaphragm 116 separating a chamber 100 from the inside of the main casing 15. The end casing 58 has a chamber 120, Fig. 4, containing a horseshoe electromagnet 122 the base 124 of which is held in an end cap 126 bolted to the casing 58 by a spring 128 abutting a retaining member 130 which guides a stem 134 carried by the armature 138. The latter is pressed away from the magnet by a spring 142 weaker than the spring 128. The limbs of the magnet carry coils 144 one end of which is connected to the retainer 130, and the other to a terminal 150 insulated from the casings 15, 58 by a sleeve 152. Fig. 6, the projecting end of which is surrounded by a a terminal sleeve 156. The terminal 150 and the terminal sleeve 156 are respectively connected to the elements 162, 160 of a thermocouple, an insulating washer 164 separating the elements. These elements are led to a position adjacent the pilot burner 110 where they are supported by a bracket 166. The combined cut-off end regulating valve has a valve member 190, Fig. 4, which seats on a ported cage-like seat member 184 screwed into a partition 182. The valve 190 is guided in the seat member 184 by a hollow stem 188 containing a plunger 196 loaded by a spring 194 and restrained by an annular plug 198. The valve 190 is regulated by a heat responsive device 206, 208 of the differential rod and tube type through a snap-action mechanism comprising opposed levers 200, a fulcrum button 202, a snap disc 204 and a thrust member 218. The latter are housed within an extension of the seat member 184 closed by a sealing disc 216. The tube 206 and the rod 208 of the thermostat are connected by a screwed plug 210 and their relative positions are adjusted by a hand lever 222 clamped to the rod 208. The lever 222 carries a pointer co-operating with a scale on the outside of the casing 15. Also mounted on the end casing 15 is a spring-pressed resetting button 170 the inner end of the stem 174 of which rigidly carries a banjo-shaped arm 256 in the lower end of which is loosely mounted a sleeve 260 surrounding an extension 236 of flanged abutment member 232 mounted on the armature stem. A sealing disc 242 is clamped on the armature stem between the member 232 and a collar 238 moving in a guide disc 240. The left-hand end of the sleeve 260 carries a washer 262 against which the arm 256 is maintained by a spring 266. A spring 268 is interposed between the valve 190 and the arm 256. A lever 246 pivoted at 248 has curved ends which move with lost motion along the stem 174 and the abutment member 232 respectively. In the position shown in Fig. 4, the armature is adjacent the limbs of the magnet and both the sleeve 260 and the extension 236 are away from the valve 190 which is therefore regulated by the thermostat 206, 208 in the normal manner. Should the pilot flame be extinguished the armature 238 is released and the extension 236 closes the valve 190 if then open, the spring 142 being stronger than the spring 194 for this purpose. To re-set the mechanism, the button 170 is pressed inwardly and the sleeve 260 is moved by the arm 256 against the valve 190, the spring 266 yielding to allow further inward movement of the arm 256 and the stem 174, whilst a collar 176 entrains the lever 246 which through the abutment member 232 moves the armature 138 into contact with the magnet 122, the valve 190 being meanwhile held closed by the sleeve 260. The same movement of the lever 246 causes a lateral extension 254, Fig. 6, thereon to open the pilot valve 88. The pilot burner 210 can now be re-lit. The magnet 122 is therefore re-energized and holds the armature 138. The button 170 is now released and this draws the sleeve 260 from the valve 190'which is once more free for thermal regulation.