Patent GB-665760-A (GB)
Title: Work blasting machine
IPC: B24C3/24
Filed: 1949-04-05
Abstract: 665,760. Abrasive blasting machines. PANGBORN CORPORATION. April 5, 1949 [May 20, 1948], No. 9226/49. Class 60 A blasting machine comprises a housing, a rotatable table mounted entirely within the housing, a blasting means carried by the housing and discharging across the table, the side and top walls of the housing comprising swing- able doors which can open widely enough to facilitate handling of castings being placed on or removed from the table, the doors comprising a portion of the top of the housing extending from the side thereof to a position overlying the control portions of the table. A perforated work table 10 carrying a perforated rubber liner 11 is mounted in bearings 13 for rotation about a vertical axis; the table support is carried by transverse channel or other structural members which transfer the weight of the table and loads carried thereby directly to the underlying floor. Seals 16 are provided, and the undersurface of the table has scraper blades 17 overlying a spent blastant collecting pan 18 and serving to push the collected grit or shot and detritus therefrom into an abrasive collecting hopper 19 which may have a screen plate for screening out large nails or wires before the blastant and detritus are delivered to the boot of an elevating bucket conveyer 21. The elevator conveyer extends upwardly from the rear of the machine, preferably inside the housing, to a position above the blastant supply hopper 22 and is driven by a motor 23. The material raised by the elevator 21 is delivered to a separator 25 wherein the detritus and the fines resulting from breakup of the shot or grit due to blasting impact are separated from the reusable blastant and delivered through pipe 26 to a receptacle 27. The reusable grit delivered from the separator 25 is returned to the supply hopper 22 through a screen. The elevator shaft communicates with the blasting chamber through a baffled opening, the elevator shaft being employed as the air take-off conduit from the blasting chamber, dust thrown up therein being drawn through the baffled opening and delivered from the air outlet 31 to a suction fan and dustseparating apparatus. A dust conduit leads from the separator 25 to the discharge line leading from the outlet 31. The blasting chamber 29 and the lower end of the elevator 21 are enclosed by a housing 33 having a generally semi-oval front section embracing more than a diametrical half of the table 10, the top and side walls of the housing consisting of contiguous doors openable to expose the table so that the hook of a crane may be brought directly above the centre of the table to place and remove therefrom large heavy castings. The openable sections constitute two arcuate doors 34 each embracing more than a quadrant of the table and hinged laterally to the remainder of the casing at 35. The abutting edges of the two doors 34 and the jamb edges of the doorways and of the doors abutting thereagainst are flanged at 36, 37 and one of each pair of flanged edges is provided with a rubber gasket 38. The doors are held closed by a toggle latch 39 operated by a handle 43. The table 10 has a flanged edge 45 extending to or above the height of the lower casing portion 46, the latter being marginally reinforced at 47 and provided with a hanging rubber skirt 48 for protecting it from flying blasting particles. Liners 49 are also provided for the inner walls of the blasting chamber 29 which are exposed to flying abrasive. The liners for the door sections 34 are in the form of hanging sheets of rubber and the lower edges thereof are held away from the door by baffle plates or brackets 50 which project from the door walls 34 and over the lower portions of the housing 46-48 and are provided with a sealing ring 51 engageable therewith. Baffled air inlets 52 are carried by the roof sections of the door elements 34. The table is rotated by a friction drive roll 57 carried by a depending shaft driven by motor 59 through reduction gearing 60. The roll is pressed against the table flange by a spring and the drive includes an overriding clutch enabling the table to be turned by hand after the driving power is cut off. The housing 33 is provided with a blast stream projector 61, preferably of the airless centrifugal type, supported in a housing 62 carried in the top well of the housing 33, the projector being oriented to direct its blast stream diagonally across the table. The wheel is rotated in a direction to deliver the blastant in an undershot direction so that it blasts both the top and side portions of the work, and the blast stream is directed diagonally of the blasting chamber so as to misalign it with the abutting jambs of the doors 34. The principal quantity of wild flying abrasive strikes one of the door sections in the region 65 which region is provided with a double layer of rubber lining members 49. The blast wheel 61 is driven by a motor 66; the blasting particles are fed to the wheel from the supply hopper 22 through a conduit provided with a valve 69; the bottom of the supply hopper 22 is provided with a second feed delivery valve 72 controlling the delivery of abrasive from the supply to a byepass conduit 73 discharging directly to the spent abrasive hopper 19 and thus by way of the elevator 21 to the separator 25. The valves 69, 72 are controlled by a common handle 75 ; in one setting, abrasive is fed from the supply 22 to the wheel 61; in the other setting, abrasive supply to the wheel is cut off and abrasive is fed through the byepass 73. The abrasive from the supply 22 is continuously recirculated through the separator 25 during those periods when the doors are open for inspection of the work, turning thereof to expose unblasted areas, and loading and unloading of the table; thus the separating of detritus from the abrasive continues throughout the period of blasting and also throughout the intervening non-blasting periods. By virtue of this, the size of the supply hopper 22 may be reduced, the capacity of the separator 25 minimized and a smaller dust collector used. A stop switch 76 actuated by an abutment 77 carried by one of the doors 34 cuts off the supply of abrasive to the wheel and/or stops the wheel when the doors are opened.