Patent GB-920490-A (GB)
Title: Apparatus for introducing a fluent substance into a gas stream
IPC: B24C7/00
Filed: 1961-11-15
Abstract: 920,490. Blasting. SYLVANIA ELECTRIC PRODUCTS Inc. Nov. 15, 1961 [Nov. 17,1960], No. 40925/61. Class 60. Apparatus for introducing a fluent substance into a gas stream flowing under pressure in a conduit comprises a tank for holding a body of the substance, a feed connection between the tank interior and the conduit and means for periodically producing a sufficient pressure difference between the conduit and the space in the tank above the body of the substance to blow a charge of the substance through the feed connection into the conduit each time the said pressure difference is produced. Apparatus for abrasive cutting comprises a source 10 of compressed air connected by an on-off valve 11 to a conduit 12 connected by a flexible conduit 14 to a nozzle 15 having a wear-resistant head 16 formed with an opening 17. A tank 19 containing abrasive material, such as aluminium oxide powder, has a removable cap 25 for replenishing the abrasive material and is connected to the conduit 12 by a feeder conduit 22 having an extension 23 projecting into the tank. The upper end of the extension 23 is closed and the extension side wall has a constricted feed opening 24. A pneumatically-operated valving mechanism comprises a cylinder 40 and a valve 42 in the base of the cylinder actuated by a plunger 41 movable in the cylinder 40. Air from the conduit 12 passes to the cylinder 40 through a conduit 43 fastened to the cylinder 40 by a fitting 44. The valve 42 comprises a rubberlike insert 45, the lower end 45a of which forms a seat, and a head 48 on a stem 47 having a scallop-shaped flange 49. The bore 50 of the insert 45 has a diameter larger than that of the stem 47, the bore 51 of the fitting 44 has a diameter larger than that of the valve head 48 and the bore of the cylinder 40 has a diameter larger than that of the plunger 41. The latter has a stem 54 projecting through the cylinder cap 56 which has a breather opening 58. A spring clip 60 mounted on the cap 56 presses against the stem 54 to retain the plunger 41 in raised position. When the main valve 11 is opened, pressure builds up in the conduit 12 closing the valve 42 and air enters the tank 19 pressurizing the space above the abrasive material. The spring clip 60 is then moved out of locking engagement with the stem 54 and the plunger 41 falls by gravity to the bottom of the cylinder 40 where it strikes the flange 49 and opens the valve 42. Air escapes through the opening 58 so reducing the pressure in the conduit 12, whereby abrasive particles are blown through the constriction 24 and feeder conduit 22 into the conduit 12 and are carried to the nozzle. The uprush of air through the valve insert 45 forces the plunger 41 upward in the cylinder 40 out of contact with the flange 49 so that the valve 42 closes. The cycle repeats automatically. By the use of an appropriate length of air line between the abrasive feed point and the nozzle opening 17, the intermittently injected charges of abrasive material become mixed in the line so that the discharge from the nozzle is substantially continuous. The charge may be varied by changing the effective length of the cylinder 40, by varying the weight of the plunger 41 or by varying the size of the opening 58. When the valve 11 is closed, a cam 35 on its handle opens a valve 27 which releases the pressure in the tank 19 to atmosphere.