Patent GB-937628-A (GB)
Title: Shot blasting and the like machines
Inventor: GRAY DOUGLAS WILLIAM
IPC: B24C3/26
Filed: 1961-08-18
Abstract: 937,628. Blasting. BAKER PERKINS HOLDINGS Ltd. Aug. 20, 1962 [Aug. 18, 1961], No. 29849/61. Class 60. [Also in Group XXX] A shot blasting or like machine includes a conveyer for conveying workpieces through a cleaning or treatment region whereat means are provided for projecting shot or other granular material on to the workpieces, the conveyer having upper perforated conveying surface means for conveying the workpieces and lower conveying surface means for collecting the shot or other granular material and thence conveying it to means for returning it to the projecting means. A shot blasting machine consists of a vibratory conveyer 1 arranged to convey castings to be cleaned through a treatment region comprising a blast cabinet 2 having blasting equipment 3 associated with it. The conveyer 1 consists of troughs 4, 5 mounted one above the other on leaf springs 6 and arranged to be vibrated continuously by a motor and connecting rod system 7 or similar vibratory drive means. The upper trough 4 is provided with a perforated conveying surface to which are attached a number of wear plates over impingement areas where the conveying surface would otherwise be subjected to an intense blast of shot from the shot blasting equipment. A step 8 is provided in the upper conveying surface so that as small castings are conveyed along the surface they fall off the step and in so doing present other surfaces of the casting to the blast of shot. In the case of larger castings it may be necessary to employ two machines in series, suitable mechanical means, such as a hoist, being provided between the machines for turning the castings over. The lower trough 5 is provided with an irnperforate base defining a lower conveying surface and is used for collecting shot and sand removed from the castings passing through the upper trough conveying surface and conveying them to the end of the trough. The troughs of the vibratory conveyer are arranged to pass through the blast cabinet 2 which extends for approximately two-thirds of the length of the conveyer. At the inlet and outlet of the cabinet are provided screens 9 consisting of a series of curtains of narrow rubber strips, together with a nylon thread curtain, serving to prevent escape of shot from the cabinet while permitting the passage of castings into and from it. Inclined deflector plates 10 are located in the cabinet above the upper trough and extending for the full length of the cabinet to collect shot bouncing around inside the cabinet and directing it through the upper trough into the lower trough. Nylon sheets 11 clamped together and to the moving upper trough 4 are arranged to abut against the outside surfaces of the fixed deflector plates 10 to provide a seal which will present the escape of dust from the cabinet. When very hot castings are to be cleaned the nylon sheets are replaced by brass ones. Positioned in the upper part of the blast cabinet are turbines 12, 13 for projecting shot down on to the castings carried in the upper trough. The upper part of the cabinet is also provided with a dust extractor outlet 14. A sump 15 is provided at the end of the lower trough to which the shot and sand is conveyed, and a vertical bucket conveyer 16 conveys shot and sand from the sump and delivers them through a sieve 31 in a hopper 17 to a shot cleaning device 18 located above and feeding the turbines. Additional cleaning means for the shot may be provided in the sump, e.g. incorporating a worm conveyer discharging into a rotary separator where larger scrap and flash are removed. The shot cleaning device 18 includes an inlet 19 through which shot and sand are fed by gravity from the hopper 17, the shot and sand then passing through perforated cones 20, 21 into a weir 22 on a solid distributing cone 23. Shot cascades over the weir 22 and passes through a sieve 24 and discharges through an outlet 25 into reserve hoppers 32. The suction side of the dust extractor fan of the cabinet 2 is connected by ducting to the transverse outlet 26 of the shot cleaning device so as to cause a flow of air to pass through a gap 27 and a central orifice 28 in a cylindrical member 29. Dust of lower specific gravity than the shot is drawn into the central orifice 28 and discharged to a receptacle, whereas heavier particles fall through the cylindrical member 29 and are discharged at the outlet. Specification 806,441 is referred to.