GB891446A - Automatic blasting control - Google Patents

Abstract

891,446. Sand blasting. ZIEBER, H. C., BROWN, R. E., and ZIEBER, E. I. July 18, 1960, No. 24954/60. Class 60. Apparatus for sandblasting tombstones, tiles, tablets of stone, steel, copper, bronze or other material to produce a satin or frosted surface, grooved lettering, border line and similar surface, with or without the use of a stencil, comprises a curtain structure covering an access opening in an enclosure and movable relative thereto in one direction, a blasting nozzle movable with the curtain structure and also movable relative thereto in a direction at right angles to the direction of movement of the curtain structure, and means for reversibly effecting the two movements, reversing being effected by electrical switches actuated by stops. An enclosure 10 receives the work 11 which, if heavy, is mounted on a truck. A stencil 16, e.g. of rubber, is adhesively secured to the face of the work. Comminuted abrasive material, e.g. sand, and pressure fluid, e.g. air at 200 lb. p.s.i., are supplied from a mixer through a flexible conduit 22 to a jet 14 having a nozzle 20. The enclosure 10 has an access opening 25 and is maintained at a slightly sub-atmospheric pressure by a suction fan or blower 26 discharging into a sand separator. A frame having channel-shaped members 28, 29, 30 is attached to the enclosure 10 by brackets 32 so as to surround the access opening 25. The frame carries a curtain structure including an upper flexible curtain 40, a lower flexible curtain 41 and an intermediate panel construction 42. The upper curtain 40 is connected to a roller 44 which maintains the curtain under upward tension by means of weights 46 attached to cables 47 connected to pulleys 48 secured to the roller 44. A reversible motor 50 drives, through gear reducer 52 and belt and pulley transmission 53, a shaft 54 which is connected by cables 56 to the panel 42 so as to raise and lower the latter and therefore the curtain structure. The panel 42 comprises upper angle member 38 and lower channel member 60 connected by side members 61. The cables 56 are secured to the member 58, and the member 60 is secured to the upper edge of the flexible curtain 41 which is of heavy flexible material so that it can hang, slide and pleat at 62 near the lower end of the enclosure 10. A sealing surface at the edge of the curtain structure co-operates with the edge of the access opening 25 to prevent any substantial outward escape of air and abrasive material. The blast jet 14 passes through a slit 63 in a rubber sheet 64, the jet carrying a plate 66 which bears tightly on the sheet 64. The jet is held by a carriage 68 having wheels 70 riding in the lower channel member 60 and in an upper channel member 72. A metal plate 74 has a clamping construction 76 to receive the lower edges of window panes 78 held at their upper edges by the clamping construction 80. A rod 88 secured to the carriage 68 is connected through a bracket 86 to the rod 84 of a piston in a cylinder 82 carried by the plate 74. The opposite ends of the cylinder 82 are connected to a valve 90 having an air pressure line 102 with a hand valve 103, and an exhaust pipe 104. The valve 90 includes two solenoids selectively energized under the control of a two-way switch 94 fixed to the channel member 60 and actuated by dogs 96, 97 adjustably secured to the rod 88. The electrical energization of the valve 90 is controlled by on-off switch 106 which may also control the motor 50; alternatively the latter has its own on-off switch. Reversing of the motor 50 is effected by a reversing switch 108 fixed on the frame member 29 and actuated by dogs 110, 111 adjustably secured on one side member 61 of the panel 42. The horizontal motion of the carriage 68 is faster than the vertical motion of the curtain structure. In a modification, Figs. 3 and 5, a rigid plate 73 forming part of the intermediate panel of the curtain structure has a horizontal slot 120. A flexible belt 122 and its upper and lower edges riding in channels 60a, 65a. A plate 68a is secured to the belt 122 by rivets 124 and a flanged disc 126 adjustably secured to the jet 14 is secured to the belt 122 and plate 68a by rivets 128. The ends of the belt 122 are wound on rollers 130, 132 carried on bearings supported on the panel. A motor 134 also carried on the panel drives a gear box 140 which drives the roller 130 and also drives, through shaft 142 and bevel gear 143, a shaft 144 connected to the perimeter of the roller 132 by a spiral spring biased to maintain the belt in tension. The motor 134 is reversed by a switch 150 mounted on the plate 68a and actuated by a pivoted arm 152 provided at its lower end with a fork straddling a rod 160 having its ends welded to the channel 60a, the rod carrying adjustable stops 170, 172 for activating the switch.