LOST FOAM CASTING SYSTEM

Abstract: A lost foam casting system utilizes an interconnected train of open frame gondolas (19) supported on a set of elevated parallel horizontal rails (11) forming a closed loop which passes through a loading and compaction station (12), a metal pouring station (13) and mould unloading station (14). Drive means (21) are provided to move the train intermittently so that the gondolas (19), which removably carry mould holding flasks (22), are accurately sequentially positioned in each of said stations.

Description: The present invention relates to a lost foam casting system with mould loading and unloading stations, a metal pouring station, and movable flask supporting gondolas. The lost foam or evaporative foam casting process involves the placement of a foam model or pattern, usually expanded polystyrene or "styrofoam", in a container or flask, then surrounding it with dry unbonded sand which is compacted to form a mould. Molten metal is then poured into the mould thereby vaporising the foam and filling the resulting void. The metal solidifies to form a casting of this same shape which is then removed from the flask. A handling system for foundry sand moulds is disclosed in US-A-4 299 269 and although not lost foam casting it forms the precharacterising portion of claim 1. A lost foam casting process is disclosed for example in EP-A-0 166 228. According to the present invention, there is provided a lost foam casting system comprising a closed loop track having a loading station, a metal pouring station and a mould unloading station; a plurality of flask carrying gondolas supported for movement along the track; drive means for effecting intermittent movement of the gondolas between indexed positions along said track; and a plurality of mould forming flasks adapted for registry in said gondolas and detachably supported thereon; characterised in that the loading station includes a compaction station; in that each gondola includes means for registering a flask thereon for alignment in said compaction station; and in that the system further comprises means connecting each of said gondolas pivotally to each adjacent gondola. Such a system can be simple in structure and operation and require minimal maintenance. The system of the invention can provide gentle movement of the moulds between dwell points where foundry operations are conducted, thereby reducing wear and tear on the system components and maintaining the integrity of the moulds. Furthermore the system is flexible and adaptable to various parameters such that the basic system may be used in a number of foundry operations. In order that the present invention will be more fully understood, the following description is given, merely by way of example, reference being made to the accompanying drawings in which:- FIG.1 is a perspective view of one embodiment of a system according to the present invention, showing various stations at which operations are performed; FIG.2 is a plan view of a system similar to FIG.1; FIG.3 is a sectional view taken along line 3-3 of FIG.2; FIG.4 is a sectional view taken along line 4-4 of FIG.2; FIG.5 is a perspective view of the gondola of the system of Figures 1 and 2 showing one example of flask alignment construction; and FIG.6 is a side elevation of one of the drivers illustrating locations of various control sensors. The present invention is primarily concerned in the structures utilized to automate the lost foam process; thus it will be understood that certain components depicted and discussed herein are conventional foundry components which may be replaced by equivalent structures for performing the same operation. Referring to FIGS. 1 and 2, it will be seen that the system utilizes a closed curvilinear set of rails 11 to connect a plurality of stations whereat the lost foam processing operations are carried out. The stations may include a compaction station 12 which may also serve as a foam insertion station depending on the compaction unit selected, a pouring station 13 where one or more automated or manually controlled pouring units pour molten metal into the mould; and a dump station 14 where the mould is emptied. Additional stations, such as a robotic casting removal station 16 may also be provided dependent upon the wishes of the foundry and the specific handling requirements of the casting being done. The track 11 is a pair of rails 11a and 11b which are configured as may be convenient depending upon the space available and the cooling requirements of the metals used. In the embodiments shown herein, the track 11 is oval shaped including a linear section 17 which may be added to or subtracted from and fixed sections 18 which have a predetermined radius of curvature. Preferably, the track 11 is elevated to provide easy access to the components for maintenance and to simplify and economize construction of the system. The rails 11a and 11b support a plurality of carriages or gondolas 19 which are interconnected to form a continuous train about the track 11. The gondolas 19 are moved by a driver mechanism 21 (Fig. 2) which provides for indexed movement and positions the gondolas 19 for appropriate dwell times at each operation station. Each gondola 19 carries a flask 22 which is essentially a hollow structural member wherein a foam model is received and wherein sand is compacted to form a casting mould. The specific configuration of the flask 22 will be dependent on the type of equipment utilized in the various operating stations. For example, the equipment available for use in the compaction station 12 is available from a variety of suppliers and each type engages the flask 22 in a different manner. Therefore, a specific flask configuration will be discussed herein as an example of a flask 22 having features which allow it to be used in the present system. With reference to FIG. 4, it will be seen that the flask 22 is a hollow upright container having a body portion 23, a base 24, and alignment means 26 which in this embodiment utilize three support posts 27 depending from the base 24, the posts having hollow lower ends 28, to receive mating supports 30 projecting upwardly from a compaction station 12 shown in FIG. 3. The flask 22 also includes a flange 29 at the top thereof which is sturdy enough to allow the flask and its contents to be lifted thereby. The gondola 19 is adapted to receive the flask 22 cooperatively with the alignment means 26 such that the flask 22 is properly positioned relative to the compaction station 12 and the dump station 14 to permit proper operation thereof. In the embodiment shown, the gondola 19 is essentially an open frame 31 supporting an alignment plate 32 having opposed cut away portions 33 as shown in FIG. 5. The cutout portions have beveled edges 34 and are spaced apart such that the alignment plate 32 will fit between two of the support posts only if the flask 22 is properly aligned on the gondola 19. The base 24 rests on the frame 31 and the posts 27 extend through the frame for engagement in the compaction station 12. The open frame gondola 19 is amenable to use with other compaction equipment in that it allows the flask 22 to be lifted from the frame 31 for manipulation by the compaction equipment. In this manner, neither the gondola 19 nor the track 11 is stressed by the forces required for compaction. The gondola 19 is supported by an inner and outer swivel caster 36 and 37 respectively. The inner caster 36 is located beneath the inner rear corner of the gondola 19, with respect to the direction of travel, and is attached to an inwardly and rearwardly extending clevis-like member 38 formed on the gondola. The clevis member 38 is formed to cooperate with an inwardly and forwardly extending tongue 39 which is formed on the inner forward corner of the gondola 19 such that the clevis member 38 of each gondola 19 receives therein the tongue of the following gondola. An interlocking pin 40 pivotally connects the members 38 and 39 to secure each gondola 19 to the adjacent gondola. It will be noted that with this arrangement each gondola 19 is supported on the inner rail 11a on both the caster 36 affixed to its own clevis member 38 and the caster 36 affixed to the leading gondola. The outer casters 37 of each gondola 19 supports the individual gondola on the outer rail 11b and is positioned at the mid-point of the frame 31. The inner caster 36 is provided with a set of guide rollers 41 which keep the casters centered on the inner rail 11a. The clevis members 38 of the gondolas 19 serve as more than mere connections between the gondolas. They are also the point at which force is applied by the driver 21 to move the train of gondolas 19 about the track 11. The driver 21 is shown in FIG. 6 as a hydraulically driven carriage 42 which moves parallel to the linear track section as shown in FIG. 2. It will be appreciated that other embodiments such as a geneva movement may be employed. In the illustrated embodiment, the carriage includes a latch member 43 which is pivotally mounted and biased for movement about a horizontal axis parallel to the track 11 and has the rear portion 44 thereof beveled. As the latch 43 is retracted, the beveled rear portion engages the clevis member 38 of the next gondola 39 and acts like a cam surface to pivot the latch 43 outwardly as the carriage 42 returns to its initial position. A shock absorbing stop 45 is provided forwardly of the driver to ensure that the train stops at the proper position by engaging the gondola 19 at the end of one increment of travel. This stop is pivotally mounted to be moved out of the way of the gondola's clevis member 38 during the first part of each driver stroke. A rebound latch 46 is mounted rearwardly of the driver 21 to prevent the train of gondolas from backlashing when it encounters stop 45. The rebound latch has the same construction as the latch 43 but is not movable on a carriage. A plurality of limit switches 47 are mounted on the driver 21 and the stop 45 to generate signals indicative of the carriage position and the stop position, as well as the speed of the carriage 42. With reference to FIGS. 1 and 2, as with the compaction station 12 and driver 21, a variety of physical embodiments of the pouring station 13 may be provided, including either manual or automated pouring equipment. Likewise, the flask 22 may be modified to cooperate with vapour removal apparatus located at this point to prevent the escape of noxious vapours generated during the pouring process. In as much as the system is a closed loop, the flasks must be emptied of the sand mould and casting at some point during the cycle, and this is done in the dump station 14. A dump assembly 49 shown in FIG. 4 includes a main frame 51, a lift frame 52, a dump chute 53, a hydraulic cylinder 54 for raising the lift frame 52 which carry a clamping mechanism 56 which engages the flange 29 of the flask 22. The clamping mechanism includes a pair of jaws 57 shaped to engage the flange 29 and impart an upward force component thereto such that the top of the flange 29 and flask 22 is urged in sealing engagement with the bottom of the dump chute 53. A plurality of limit switches 58 are located to sense the position of the clamping mechanism 56 and the lift frame 52. In some instances, it may be preferable to remove the casting from the flask 22 prior to the dump station 14. In such instances a robotic removal station 16 (FIG. 2) is employed intermediate the pouring station 13 and the dump station. This removal station essentially is a movable gripper arm 59 which can retrieve the casting from the flask 22 while the flask is in the gondola 19. The arm 59 may be capable of moving pivotally or linearly depending on the space available to position the casting on an auxiliary conveyor 60 for further processing. The limit switches 47 and 58 as well as similar sensors at the compaction station 12, pouring station 13, and removal station 16 all provide signals to a controller 61 which may be a programmable microprocessor. The signals indicate the position or status of the various components to the controller 61 which is programmed to actuate the driver 21, the compaction station 12, the pouring apparatus, the lift cylinder 54 and clamping mechanism 56, and the retrieval arm 59 in a specified sequence and at predetermined intervals. For example, it may be desirable to operate the system such that a train of 30 flasks completes a circuit in one hour, thereby delivering thirty castings to the auxiliary conveyor. The controller would be programmed to initiate the sequence at each station once during each two minute interval. Through the use of a programmable controller 61 and a controllable driver 21,it is possible to operate at such speeds with smooth and gentle inertial transitions as the train is moved. While the present invention is simple in its individual components, the combination of elements provide a remarkably versatile conveyor system. With reference to FIG. 3, it may be seen that the entire conveyor system is designed to be supported above the floor such that easy access to the equipment is facilitated and installation is simplified. It may be further appreciated that the separate flask and gondola arrangement permits the flask to be removed from the gondola for specific operations and replaced in proper alignment for subsequent operation at various stations, and thus allows the system to be tailored to the specific needs and resources of the foundry wherein it is installed.

Claims: A lost foam casting system comprising a closed loop track (11) having a loading station (12), a metal pouring station (13) and a mould unloading station (14); a plurality of flask carrying gondolas (19) supported for movement along the track (11); drive means (21) for effecting intermittent movement of the gondolas (19) between indexed positions along said track (11); and a plurality of mould forming flasks (22) adapted for registry in said gondolas and detachably supported thereon; characterised in that the loading station includes a compaction station; in that each gondola (19) includes means (26) for registering a flask (22) thereon for alignment in said compaction station (12); and in that the system further comprises means (38-40) connecting each of said gondolas (19) pivotally to each adjacent gondola. A system according to claim 1, wherein said track (11) comprises a pair of horizontally spaced generally parallel rails (11a,11b) and wherein each gondola (19) is supported on one of said rails on an inner and outer cater (36,37) respectively with the inner caster (36) of each gondola additionally supporting an adjacent gondola. A system according to claim 1 or 2, wherein said flasks (22) include means (27) affixed thereto for engagement with said compaction station such that said flasks may be lifted from said gondola during compression of the mould in said flask. A system according to any preceding claim, wherein each gondola (19) comprises: (a) a longitudinal frame (31); (b) a plurality of horizontally disposed support members (32) affixed to said frame and spaced apart to support said flask (22) and permit engagement of said engagement means (27) with said compaction station (12); (c) guide means (33) for registering said flask on said support members; and (d) track engaging means (41) for supporting said gondola on said track (11). A system according to any preceding claim wherein said flasks (22) each include an upper peripheral member (29) extending outwardly therefrom and adapted for engagement with said mould unloading station (14) for removal from said gondola. A system according to any preceding claim, wherein the centerline of said track (11) coincides with the centerline of said loading and compaction station (12), said pouring station (13), and said mould unloading station (14) and wherein each gondola (19) has a laterally extending clevis (38) at one interior corner and coupling tongue (39) at a second interior corner with said gondolas (19) being coupled one to another via said tongue and clevis. A system according to any preceding claim, wherein a plurality of sensors (47, 58) are positioned about said track (11) for detecting the position of said gondolas (19) and the status of said unloading station (14) and said driver means (21) and outputting a signal responsive thereto and a programmable controller (61) is provided to receive signals from said plurality of sensors and provided with data to control said system components in accordance with said signals and a set of predetermined control parameters A system according to any preceding claim and further comprising means (16) for removing a casting from said flask (22) intermediate said pouring station (13) and said mould unloading station (14). A system according to any preceding claim, wherein said plurality of gondolas (19) supported on said track (11) are so connected to each other as to form a continuous closed loop train of gondolas extending completely around said track. A system according to any preceding claim, wherein said gondolas include means for registering said flasks on said gondolas for proper alignment with each of said operating stations.

Inventors: MCMELLON, BRUCE A
Applicants: VULCAN ENGINEERING CO.
Application year: 1988
Main classification: B22C9
IPC codes: B22D47, B22C9, B22D33