Patent GB-821558-A (GB)
Title: Improvements in or relating to spray guns for fusible materials
IPC: B05B7/20
Filed: 1956-09-20
Abstract: 821,558. Spraying fusible materials. COOK, V. A., KUNKLER, R. E., BALTIMORE, I. S., and KUNKLER, E. D., [trading as METAL-LIZING CO. OF AMERICA]. Sept. 20, 1956 [Sept. 23, 1955], No. 28829/56. Class 69 (3). A spray gun of the type incorporating a gas turbine to feed a fusible wire to a high temperature zone includes a speed regulation device for the turbine comprising an adjustable magnetic speed sensing means and a turbine speed control means responsive to the speed sensing means. As shown in Fig. 16 the gun includes a carriage 34 having a burner nozzle 120, 122 through which the wire is axially fed, and a surrounding air blast nozzle 128, 134. Air, oxygen and fuel gas are separately supplied to nipples, such as 54, on the carriage, and the flow of these gases to the respective nozzles is controlled by a suitably bored, rotatable, frusto-conical valve plug 66. The plug is held in its bore by a spring compressed between its wide end and a coaxial cap threaded to the carriage. A gun block, Figs. 4 and 9, comprising a casing 144, is supported by the carriage 34 and includes, within a recess capped by a perforated cover 168, a turbine wheel 150 which drives, via its shaft 154, a worm-gear 156 and a worm-wheel 158, a shaft 184. Compressed air is fed to the turbine nozzle from an air passage in the carriage and passages 174, 178, Fig. 9, the flow thereto being controlled in the manner described below. Air leaving the turbine passes from the perforated cover 168 via a screen 170. The shaft 184 includes a worm-gear 192, Figs. 4 and 5, located between walls 190, 194 and surrounded by a stationary sleeve 199. Oscillatably mounted on the sleeve are the trunnion ends 204, 206 of two cradles arranged on opposite sides of the sleeve and carrying bearings 212, 214, respectively, Fig. 5, which rotatably support feed-wheel drive-shafts 216, 218. Worm-wheels 220 secured to the shafts mesh with the gear 192 through slots 221 in the sleeve 199, and the feed-wheels 258, which extend above the casing 144 and engage the wire 262 are driven in opposite directions. In operation the bearings 212, 214 are maintained in a fixed position by a spindle 222, Fig. 6, which passes through lugs 228, 230 integral with the cradles, and carries compression springs 234, 236 which act on the lugs, thereby tending to turn the cradles about the shaft 184 and to compress the wire between the feed-wheels. In order to rock the cradles in the opposite directions a cam finger 242 on a cam-shaft 248 is caught between noses 244, 246 on the cradles, and by rocking the shaft the noses are moved apart; the worm-wheels 220, however, remain in contact with the gear 192. This construction enables the feed rolls to adjust themselves to different wire diameters. The magnetic speed sensing means, Fig. 9, 10 and 11, includes an electrical eddy current cup 276 secured to one end of the turbine shaft and arranged in a recess in the gun block. A permanent magnet 284 in the form of a circular block with poles 287 is arranged partly within the cup. A thin flat disc 310 of magnetic material with indentations 312 surrounds the magnet and is carried by the cover. The magnet is rotatable on a bearing carried by a pin 288 which is fixed to an axially adjustable rod 302 threadably engaged in a cover 280. Rotation of the turbine causes the magnet to be advanced or displaced through an angle dependent on the turbine speed. By advancing the magnet into the cup by a control knob 306 this displacement is increased for any given turbine speed, and vice versa. This displacement is translated into an air pressure value which is furnished to a diaphragm controlling the air supply to the turbine nozzle, and hence the turbine speed. The speed control mechanism operates in such a manner that by moving the magnet outwardly from the cup the turbine speed is raised, and by advancing it into the cup the speed is lowered. Any variation of the air pressure supply to the gun is counterbalanced by the mechanism to maintain the desired speed constant. The control mechanism diagrammatically illustrated in Fig. 20 includes a head 316, Figs. 11, 12, rigidly secured to the cover 280 and located between adjacent poles of the magnet. The head is bored for the flow of air therethrough, which is emitted from a nozzle 318 on to the flank of a pole which, in operation, is displaced towards the head. Air is fed to the head from a passage tapped from the air supply to the turbine nozzle, and via a filter 386. The passage supplying the head is also connected to one side of a flexible diaphragm 344, Figs. 11 and 20, the opposite side of which is vented to atmosphere, and the pressure of the air fed to the turbine nozzle acts on one side of a second diaphragm 342. The diaphragms are separated by a force-multiplying piston 412 having a broad section 414 influenced by the relatively weak pressure on the diaphragm 344, and a narrow section 416 influenced by the pressure on the second diaphragm. In operation, the movement of the magnet causes the pole flank to approach the nozzle 318 to set up a back pressure in the passage feeding the nozzle, and this pressure acts on the lower diaphragm. An excess of back pressure, caused by the speeding up of the turbine and the consequent additional angular displacement of the magnet, causes both diaphragms to be moved upwardly to reduce the flow of air past a bridge 422 to the turbine nozzle. A reduction in turbine speed results in a greater supply of air being allowed to flow past the bridge 422 to the turbine nozzle. The diaphragms and the piston 412 are arranged between flat plates 334, 336, 338 containing the air flow passages and secured to the base of the gun block.