GB724731A - Method of and apparatus for making a sand core or mold in which sand is blown into amold core box - Google Patents

Abstract

724,731. Moulding machines. FEDERAL FOUNDRY SUPPLY CO. May 5, 1953 [May 8, 1952], No. 12479/53. Class 83 (1). Sand is blown into a core or mould box by applying the blowing pressure in pulses until the box is filled. The apparatus comprises a sand-transfer chamber 14 mounted on arms 15, 16 rotatable about a column 12 into and out of position under a sand hopper 18, a cylinder 22 containing a piston 23 supporting a clamping table 24 which supports a mould or core box 25. The chamber has an inner perforated partition 30 and an agitator 35 motor driven through gearing 36, 37 and communicates through its filling opening 26 and filter 27 with a normally open valve 29, and with a pressure fluid inlet 33 controlled by a normally closed valve 44 when in the operative position. The spring-loaded inlet and exhaust valves are controlled by an electromagnetically operated valve 51, and a similar valve 50 controls a reduced fluid-pressure supply to the lift piston 23 through a small-bore conduit 56. The electrical circuit of the valve 51 contains a mercury switch 73, pressure actuated by fluid pressure through vents 42 in the vent plate 40 carried by the blow plate 38, Fig. 8. This switch is adjusted to "break" when the pressure in the chamber reaches a predetermined maximum, thereby opening the exhaust valve and closing the inlet valve, and to "make" when the pressure falls to a predetermined minimum, thereby supplying pressure fluid once more to the chamber. Alternatively a check-valve in the fluid pressure circuit to the exhaust valve 29 may prevent the valve from opening until the end of the blowing cycle, so that the pressure in the chamber is not reduced to atmospheric pressure each time the switch 73 opens. The reduced pressure through the restricted conduit 56 to the lift piston results in a safe rate. of travel of the clamping table, and the clamping of the box and the chamber against the cross-head 11 is achieved without shock. After the clamping position has been reached, pressure builds up in the cylinder 22, and operates a spring-loaded valve 100 to initiate connection of the main pressure-fluid supply to the cylinder. A switch 110 operated by a differential pressure-valve 112 may be connected in series with the solenoid of valve 51 so that said valve does not function until the box has been clamped in position, and a switch 121 may control the motor driving the sand agitator. The complete blowing cycle is controlled by a mercury switch 76 on a differential pressureoperated device 75. Opposing ends of the device are connected to points adjacent the air inlet 33 and the discharge end of the transfer chamber, the pressure differential maintaining the switch 76 open until, when the box is filled with sand, the resultant equalization of pressure within the chamber causes the switch 76 to close and the blowing cycle to be stopped thereby.