Patent GB-754111-A (GB)
Title: Improvements in or relating to apparatus for making shell moulds and ejector devices therefor
Inventor: JENKINS GWYNVILLE
IPC: B22C23/00
Filed: 1952-08-08
Abstract: 754,111. Moulding - machines. POLYGRAM CASTING CO., Ltd: Nov. 5, 1953 [Aug. 8, 1952; Aug. 29, 1952], Nos. 20081/52 and 21782/52. Class 83 (1). Apparatus for use inmaking moulds by applying, to a heated pattern coated with a lubricant or stripping-agent, a mould mix comprising a pulverent material and a hardenable powdered synthetic - ,resin to form a shell, and curing said shell by heat, comprises a pattern-support, ejector elements movable through the pattern-support to eject a cured shell from the pattern, and means for actuating'said ejector elements. A rotatable table 1, Figs. 1, 2 and 4, carries four pairs of upstanding arms 3 which support pattern-carriers 6 in pairs of trunnions 4, 12, and is intermittently rotatable by a motor 27 driving through a belt 29, gearing 32 and a Geneva mechanism 24, 25. A bin 15, containing the moulding mixture; is supported by frame members 13 on trunnion-pins 16, 20, and the respective pattern carrier is swung into engagement with the top of the bin about the trunnions 12 and is clamped by a locking-bar 62 carrying arms 60 with' hooked ends which engage the trunnion-pins 5, the bar 62 being locked in 'the clamping position by its engagement with a spring- loaded release-arm 66. The pin 20, Fig. 6, extends into a casing 23 and is rotatable with the bin by a chain 77 controlled by pneumatic pistons 73, 74 so that the bin may be rotated through 180 degrees and back again. Operation of a plunger-knob to actuate spindle 126, causes the bin to be inverted and a bleeder valve 98 causes air-pressure to build up in a reservoir 101, which pressure, after a.predetermined time interval, usually about 5-8 seconds and determined by the setting of the valve 98, is sufficient to cause the bin to be returned to the upright position. The bin may be returned to the upright position before the predetermined time interval has elapsed by depression of a plunger. The bin also comprises a ram 151 with a resilient-pad for forcing the mould mix into contact with the pattern, the ram being attached to a piston-rod 153 by a ball-coupling and reciprocated by a piston 149. Pressure air is supplied to the cylinder 150 through the hollow trunnion-pin 16, Fig. 9, by a main control valve controlled by relay valves 167, 169 carried in a disc 17, which is integral with the pin 16 and bolted to the side of the bin. A rocker 175, 176 is supported by the stationary housing and, when the bin is upright, is in the position shown, Fig. 9, being retained therein by spring-loaded detents 178. As the bin rotates and approaches the inverted position, the operating,plunger 170 of the valve 167 engages a nose 175a of the rocker and the valve opens to cause the main operating- valve to supply pressure air to the cylinder 150 and urge the ram towards the pattern. Further rotation of the bin causes a cam surface 180 on the disc to engage the nose 175a and rock the rocker clockwise, the detents 178 engaging recesses 179a to retain the rocker in its new position. A nose 176a is thereby brought into the return path of the operating plunger 172 of the valve 169, so that when the bin rotates to return to its upright position, the valve 169 operates to cause the main controlvalve to actuate the piston 149 to withdraw the ram from the pattern. The cam 180, on its return, restores the rocker to the position shown in Fig. 9. In a modification the main control-valve is controlled by a manuallyoperated push button so that the investment of the pattern may be effected by gravity alone, or by gravity and pressure. The bin is locked in its extreme positions by a spring-loaded detent carried by a support 13 engaging a recess in a ring carried by the bin. After restoration of the bin to the upright position the associated pattern-carrier is unclamped therefrom and swung through 180 degrees about the trunnions 12 to re-engage with the trunnions 4. Rotation of the table removes the pattern-unit with the mould thereon into an oven 40 and brings the next pattern-unit, preheated from its passage through the oven 40, opposite the bin. The oven 40, heated by gas burners 55 or electrically, comprises arcuate concentric walls 41, 42, arcuate floor-plates 47, 48 having a gap 60 between them in which the arms 3 move, and at each end a closure 51, 51a having openings through which the pattern-carriers 6 may pass. Between consecutive pairs of arms 3 the table carries a plate 53 such that when a patterncarrier is opposite the bin, the plates 53 on both sides close the openings of the oven. Each pattern-carrier 6 has incorporated in it ejectormechanism, Figs. 4 and 12, comprising a sleeve 203, vertically slidable but restrained against rotary movement, in a ring 201, and a plate 207 carrying ejector-pins 208 attached to the sleeve 203, the tops of the pins being normally level with or slightly above the working surface of the pattern plate 7. A pin 210 projecting from a toothed ring 211 freely rotatable about the sleeve 203 engages a cam-groove 209 in the sleeve, and the ring teeth engage with a toothed quadrant 212 pivoted at 213 in the frame 6 and carrying an arm 214. As each carrier-unit with a cured mould thereon leaves the oven, the arm 214 engages a cam 215, Fig. 2A, to thereby rotate the ring 211, the shape of the cam-groove being such as-to cause the ejector pills to first move slightly downwards to free them from the mould and then to move upwardly to effect ejection of the mould, so that when the pattern-carrier arrives opposite the bin 15 the mould is resting on top of the ejector pins and may be removed easily. The ejector mechanism may then be reset by hand or alternatively, as the pattern unit is swung through 180 degrees to position it on top of the investment bin, the arm 214 engages a track 217 positioned on the adjacent closure plate 53 to reset the ejector mechanism. In a modification the ejector comprises pins and bar elements forming a frame normally inset in the working face of the pattern plate. Should the operator be unable to return a pattern unit from the bin to its normal position on the arms 3, an electric switch, which is held closed by a trunnion 5 depressing a spring-pressed plunger in a trunnion 4, remains open, and the opening of a switch in parallel therewith and actuated by indexing of the Geneva mechanism, will open the motor circuit and stop rotation of the table. A warning lamp may be incorporated to light up when the time. of dwell of the table has elapsed without the operator having returned the carrier to its normal position on the arms 3. In a modification there may be more than four pairs of arms 3, and there may be two stations outside the oven, at one of which the pattern may be stripped of the mould and coated with a parting agent, and at the other the pattern so prepared is invested. Means may be provided for enabling the table to be driven continuously during the preheating of the patterns. Mould materials.-The moulding-mixture may comprise sand with 4-8 per cent by weight of the mixture of powdered phenol formaldehyde or cresol resin. The mixture may also contain up to 9 per cent plumbago or up to 6 per cent of terra flake, but 3 per cent of either of said materials or a mixture of both is usually sufficient. Specifications 754,112 and 754,205 are referred to.