GB1437905A - Method of cleaning graphite moulds - Google Patents

Abstract

1437905 Blasting; cleaning moulds AMSTED INDUSTRIES Inc 6 March 1974 [4 June 1973] 10116/74 Headings B3D and B3F A method of removing a mould coating from the casting surface of a graphite mould (17, Fig. 1, not shown) comprises suspending a sand spray gun 58 on the axis of the mould and spaced from the mould, and then, while forcing sand through the spray gun and against the mould surface, moving the spray gun in a spiral path towards the periphery of the mould. In apparatus for carrying out the method, a succession of graphite moulds (17) are moved into position beneath the spray gun on a conveyer (16) the spray gun being mounted on a frame 10 having a hopper which feeds sand to the gun under the control of a valve 22. A sprocket 28 is mounted on blocks 26 carrying roller bearings 30, 32 engaging a stationary ring 38 mounted on the frame. A pair of spaced vertical plates 40 is mounted on the sprocket and receive between them a pair of guide wheels 88 carried by brackets 86 on a block 82 rotatably supported by bearings 80 on an outer pipe 62 of the spray gun. The spray gun is supported by a universal joint 48 on the frame and a sprocket 96 is fixed to the outer pipe 62 and connected by a chain 98 to a sprocket 94 on a gear reduction unit 90 mounted on the block 80. An output shaft 100 of the unit has a crank 102 at each end of which is a cam wheel 104, 105 arranged so that one wheel at a time engages a cam plate 106 secured to the plates 40. As the sprocket 28 is rotated, the plates 40, through the guide wheels 88, impart rotation to the block 80. As the sprocket 96 is held against rotation, the sprocket 94 rotates and the crank is moved to cause the cam wheel 105 to ride along the cam plate 106 thus swinging the spray gun 58 about the axis 56 of the universal joint, the gun thus moving in a spiral path. The effect of the cam wheel on the cam plate decreases the velocity of radial movement of the gun as it approaches the periphery of the mould so as to effect a constant blasting of the area of the mould. The sand is blasted from a compressed air source, the pressure of which is increased as the gun moves radially outward so as to compensate for the increased distance of the gun from the mould. The spray gun has a funnel 66 for receiving sand from the hopper, the sand falling through an inner pipe 60. Compressed air is supplied from an inlet 68 to the space between the inner and outer pipes, the lower ends of which receive an adaptor 71 having a tapered surface which causes the air at the outlet to create a negative pressure to modulate the velocity of the sand.