Patent Publication Number: US-3967672-A

Title: Making foundry moulds

Description:
This invention relates to the automatic production of foundry moulds. The normal method of producing foundry moulds involves the use of flasks or boxes in which individual copes and drags are made and are then brought together in pairs. Although a considerable degree of mechanical handling of the flasks has been introduced these still involve a substantial outlay in space and have to be stored and recirculated. Proposals have been made, and indeed widely adopted, for making moulds without flasks, for example using shell-moulding techniques, and there is also our own earlier proposal forming the subject of our U.S. Pat. Spec. No. 2,871,527. In this proposal double-sided flaskless moulds are formed by a blowing technique and compacted by squeezing pressure, and then formed into lines with their mating faces vertical. Extremely high production rates are possible by this technique. However, some people feel there may be a limit to the complexity of castings that can be satisfactorily produced in moulds having a vertical parting plane. 
     The chief aim of the invention is to provide an improved method of making foundry moulds by a fully automatic process but with a horizontal parting plane. 
     According to the invention we propose to provide a pair of sliding frames, each similar to the single frame of our earlier proposal, having their planes close together and co-operating with movable pattern plates and with blowing equipment to produce single sided flaskless copes and drags back to back, one of the frames producing the copes and the other producing the drags. The copes and drags are pushed out of the respective frames onto a conveyor to form a line of mould components in the form of alternate copes and drags. 
     Preferably at this stage they are both already the right way up, that is to say, the drags have their parting faces uppermost and the copes have their parting faces at the bottom. This gives the opportunity for the easy placing of cores, either by machine or by hand, in the exposed cavities of the drags, and at the same time sprues can be cut in the copes. At an appropriate point along the conveyor each cope is lifted and held until the following drag moves into position beneath it, when it is lowered to form a mould which is moved to join a line of previously formed moulds, all the moulds being in contact to provide mutual support. Preferably the copes are very slightly smaller in horizontal dimensions than the drags, so that the contact takes place wholly between the drags, to avoid the risk of displacement of any cope in relation to its own drag. As further moulds are added to the end of the line the whole line is displaced along its length so that each mould progresses intermittently down the line and there is a fixed pouring point at which the metal is poured into the moulds, for example from an automatic teapot-type ladle. 
     There may be two conveyors, leading to two mutually independent mould lines. However, in a preferred two-conveyor arrangement the two conveyors are parallel and, after the copes have been placed on the drags, the resultant moulds from the two conveyors are pushed together to form a double line of moulds. 
     In a preferred version the sliding frames move horizontally and have their planes vertical. Thus the copes and drags, when they are ejected, have their parting planes vertical and they are then turned through 90°. 
     However it would instead be possible for the sliding frames to have their planes horizontal, which eliminates the need for turning. The rams carrying the pattern plates would then have their axes vertical. 
    
    
     The invention will now be further described by way of example with reference to the accompanying drawings, in which: 
     FIG. 1 is a simplified diagrammatic view illustrating the principle of the invention; 
     FIG. 2 is a side elevation of one form of moulding and casting installation according to the invention, designed to produce two lines of moulds; 
     FIG. 3 is a plan view of the installation of FIG. 2; 
     FIGS. 4, 5 and 6 are transverse sections through the installation of FIGS. 2 and 3, taken respectively on the lines A--A, B--B and C--C in FIG. 2; 
     FIGS. 7 and 8 are views corresponding to FIGS. 2 and 3 but showing a second embodiment, in which only a single line of moulds is produced. 
    
    
     We refer first to FIG. 1 and it is necessary also to have in mind our own earlier U.S. Pat. No. 2,871,527. In the invention which formed the subject of that earlier specification flaskless moulds in the form of blocks of sand with pattern impressions in both vertical faces were formed in one of two apertures in a slider by blowing sand into the aperture while its open faces were closed by pattern plates, which then gave the mould a balanced squeeze from both sides before being withdrawn to allow the slider to move sideways to a position where the newly formed mould could be pushed out to join a line of previously formed moulds. In the meantime another mould was being formed in the other aperture, which was now between the pattern plates. 
     The principle of the present invention is illustrated in FIG. 1. Instead of the single slider of the earlier invention we employ two sliders 1 and 2 which, in the example shown, have their planes vertical and slide horizontally. Each slider has two apertures 3 and there is a stationary bolster plate 4 between them where they overlap. Pattern plates 5 and 6 are moved by rams 7 to enter those two apertures 3 in the two sliders which are, at a given stage in the cycle, aligned. There are inflatable seals (not shown) in the bolster plate 4 to seal it to the sliders 1 and 2. Sand is blown into both apertures through slots 8 in the top of the sliders to form two moulds, back-to-back, separated by the bolster plate 4, each mould being single-sided, that is to say, having a pattern impression in only one face. 
     After withdrawal of the pattern plates 5 and 6 the two sliders 1 and 2 are then simultaneously moved horizontally in opposite directions past each other until the mould formed in the slider 1 is opposite an ejector ram 9 and the mould formed in the slider 2 is opposite an ejector ram 10. Both moulds are ejected in the direction of the arrows E, whilst at the same time two further moulds are formed in the other two apertures 3, now aligned with the pattern plates, in the two sliders. The sliders then move back again and the cycle is repeated. 
     Normally the moulds formed in the apertures in the slider 1 will be drags, that is to the lower halves of a two-part flaskless mould, and those formed in the slider 2 will be copes, i.e. the upper halves. Thus it will be seen that each ejector ram 9 and 10 is ejecting alternately a cope, then a drag. 
     We refer now to FIGS. 2 to 6 which show, in somewhat simplified form, a practical installation. The two sliders 1 and 2 again have their planes vertical and move horizontally. A blowhead 11 (or it could be two separate blowheads) to which sand is fed from a hopper (not shown) in controlled quantities through a horizontally sliding sandgate 12, has two outlet nozzles 13, through which sand is blown simultaneously into the two moulding chambers, formed by the apertures 3 in the sliders, via slots 8. As in the arrangement described in our above-mentioned earlier Patent Specification, the blowhead is then lifted slightly, by means not shown, to disengage the nozzles 13 from the slots 8, before both sliders 1 and 2 are moved in opposite directions by rams (not shown), the pattern plates 5 and 6 also having first been withdrawn. 
     Aligned with each ejector ram 9 and 10, and on the opposite side of the sliders 1 and 2 from the ram, is a tilting table 15, capable of tilting through 90° or 180° about a horizontal axis 16 and having a shorter surface 17 and two longer surfaces 18 and 19. When a cope is ejected from the slider 2, it comes to rest between the surfaces 17 and 18, the surface 17 being just long enough to meet the face of the slider 2 so that the ram 9 or 10 is able to push the cope smoothly onto the table. The table then turns clockwise (as viewed in FIG. 2) through 90° so that the cope is now face downwards, i.e. with its pattern impression on its underside. It is gripped between jaws 20 of a carrier 21 which slides on rails 22 and transfers the cope onto the start of an intermittently moving conveyor belt 23, up against the preceding mould in that line, which is a drag. 
     While the cope is being transferred, a rotary sprue cutter 24 of known kind mounted on the carrier 21 cuts a sprue in the upper face of the cope. Alternatively the pouring basin could have been formed during blowing of the cope by the incorporation, in the bolster plate 4, of a withdrawable basin-forming pattern which retracts before movement of the slider 2. 
     The table then swings back through 180° and as the slider 2 is now clear, having moved to its other end position, the longer surface 18 is able to bridge the gap left by the slider 2 so that a drag now ejected from the slider 1 by the ram 9 or 10 can move smoothly onto it and lie between the surfaces 18 and 19. Again the table turns clockwise through 90° and this brings the drag to a position in which its parting face, i.e. the face which carries the pattern impression, is uppermost. Like the cope before it, the drag is now picked up by the jaws 20 and transferred to the conveyor belt 23, which has in the meantime carried the cope forward to leave room for it. While the drag is being transferred the sprue cutter 24 is not used. 
     Each time a cope mould reaches the end of the conveyor 23 jaws 25 on a lifting plate 26 come in from opposite sides and grip it, then a ram 27 lifts the plate, and the cope with it, vertically upwards. As the cycle continues the conveyor 23 then brings the following mould, which is a drag, beneath it and the two moulds are brought into accurate mutual alignment by the fact that they both engage two mutually perpendicular vertical surfaces of an L-shaped locating body 28. The cope is now lowered onto the drag. A ram 29, acting on the body 28, then pushes the pair of moulds, now forming a mould assembly, laterally towards the centre-line of the installation. There are two lines of mould assemblies being formed simultaneously and at this stage the two lines come into contact, side by side. 
     A pusher 30, actuated by rams 31, now pushes both assemblies simultaneously onto a horizontal track 32, on which the two lines are carried along forwards, being indexed along by a distance equal to the length of one mould each time a new pair of mould assemblies is added to the end of the line. 
     At this stage weights 33 are loaded onto the tops of the mould assemblies in accordance with normal foundry practice, the weights being picked up from a storage area by a carriage 34. Metal is poured into the moulds in any known manner, either by tilting ladles or by automatic methods, such as so-called teapot ladles. When the castings have solidified sufficiently the weights are lifted off by a carriage 35 and returned to the storage area for re-use. During their advance, the mould assemblies have moved from the track 32 onto a further conveyor 36 to cool. When they reach the end of this they fall off into a rumbling barrel 37 where they are broken up and the castings are shaken out while the sand is extracted for recycling, as in the process described in our above-mentioned earlier specification. 
     It will be understood that the whole installation, apart from the metal pouring and the shake-out, operates intermittently in step with the formation of the moulds and the movements of the sliders 1 and 2. The rams are mostly hydraulic and their operation in the correct sequence is controlled by solenoid-operated valves with appropriate timers and interlocks, limit switches being used to detect completion of the various movements. Such details are well understood by those skilled in the field of automatic control and it is not felt necessary to describe them here. Certain of the features described in the specification of our other British application No. 28262/74 filed simultaneously with the present one may be used with advantage in the installation described above. 
     While the copes and drags are on the conveyor 23 the drags have their parting faces exposed, giving ample time for the insertion of even complex cores, either automatically or by hand. 
     The installation shown in FIGS. 2 to 6 has the advantage that each mould assembly on the twin track is supported by adjacent moulds on three sides. Although not shown, there could be some form of support on the fourth side of each mould as well, for example by means of spring-loaded supported bars pressing against opposite sides of the double line of moulds during pouring of the metal. This enables the moulds for a given weight of casting to be made smaller than would otherwise be necessary, and it gives a saving in sand. 
     In a modified arrangement the moulds in each of the two lines take the same two faces, e.g. the back face and the right-hand face, as the datum faces for locating the cope and drag with respect to each other and in that case, both L-shaped bodies 28 will face the same way, and the two lines of mould assemblies will have a gap between them. 
     Whereas in the process described in our above-mentioned earlier Patent Specification the moulds were bonded with sodium silicate, hardened with carbon dioxide, we now find that this is not necessary and flaskless moulds of adequate strength for the present invention can be made from straightforward green sand, bonded simply by the compaction achieved by the squeeze from the rams 5 and 6. 
     Where one requires a lower output than can be obtained with the twin-track installation shown in FIGS. 2 to 6, a simpler version could be used, shown in FIGS. 7 and 8. Reference numerals are the same, where applicable. There are still two sliders, but now each slider 1&#39; and 2&#39; has only a single aperture 3&#39; forming a mould chamber and furthermore each slider moves vertically instead of horizontally between its two end positions. It is true that each slider does still have a second aperture, but not to form a moulding chamber. The aperture 38 in slider 1&#39; is present to allow the single ejector ram 9&#39; to pass through that slider in order to push the newly formed cope out of the aperture 3&#39; in the other slider 2&#39;. Likewise the aperture 39 in the slider 2&#39; allows a drag formed in the slider 1&#39; to be ejected through the slider 2&#39;, and the aperture acts as a guide for the drag during this movement. The tilting table now only requires two walls 17&#39; and 18&#39; and moves back and forth through 90° . The remainder of the installation corresponds exactly to one half that of FIGS. 2 to 6. Instead of the simplified table shown in FIGS. 7 and 8 one could use the same table 15 as in that other version. 
     Within the scope of the invention one could employ twin sliders of FIGS. 7 and 8 but moving horizontally as in FIGS. 2 to 6. Indeed it would be possible to turn the installation of FIGS. 2 to 6 on its side, so that its sliders moved vertically, delivering alternate copes and drags to each of two vertically spaced tables. A still further possibility is for the sliders to be turned on their sides so that the axes of the apertures are vertical, with the drag pattern plate moving vertically downwards into the upper aperture and the cope pattern plate moving upwards into the lower aperture. The resulting copes and drags do not then have to be turned through 90°, but they still need to be interchanged, i.e. the cope has to be moved to a position above the drag, and there are other problems which do not arise in the vertical-faced layouts described above.