GB740869A - Improvement in method and apparatus for blowing sand moulds and cores - Google Patents

Abstract

740,869. Moulding- machines. FEDERAL FOUNDRY SUPPLY CO. Nov. 19, 1953 [Aug. 3, 1953], No. 32111/53. Class 83 (1). In a method of sand mould and core blowing, the receptacle is prefilled with sand at a relatively low blowing pressure and the sand is subsequently rammed at a higher blowing pressure. The higher blowing pressure may be applied continuously or intermittently. The apparatus comprises a base 10, and a cross-head 11 on columns 12, 13. A sand-transfer chamber 14 is pivotally supported on the column 12 and comprises an inner perforated partition 30, a blow-plate closure 38 with vents 34 and a sand agitator 35 driven through gearing 36, 37. The blow-plate is connected to a vent-plate 40 having blow-hole bushes 45 which may be replaced by plugs 46 which block the opening through the blow-plate but vent the box to the atmosphere. Pressure-fluid enters the chamber by an inlet 33 through a valve 49, and exhausts through a filter 27 and exhaust opening 28 controlled by a piston 29. In operation, and with a selector switch in one position, the box is clamped against the chamber 14 by opening valve 25, a pressure-controlled switch 69 closing when a predetermined clamping pressure is reached. Actuation of a start button then energizes solenoids 80, 81 actuating valves 55, 61 respectively to admit pressure fluid from a restricted supply conduit through an adjustable throttle-valve 59 and inlet 33 to cause sand to fill the box under a reduced pressure and also to close the exhaust 28. When the box is filled, build up of pressure in the chamber 14 actuates a pressure-switch 67 to de-energize the solenoids 80, 81 and energize solenoid 87, actuating valve 55 which opens valve 49, and hence the chamber 14, to full fluid-pressure. When the pressure in the box 21 reaches a predetermined value, a pressure switch 71 actuated thereby de-energizes the solenoid 87, closing valve 49 and opening exhaust 28, interrupting the ramming until the pressure falls. Thus the sand is rammed intermittently until the operating circuit is opened. With the selector switch in an alternative position, ramming at high pressure, once started, is continuous. Closing of another switch in the circuit causes the sand to be blown at high pressure, continuously and intermittently, without prefilling. In a modification, a timer mechanism controls the period of prefilling.