A machine manufacturing pistons, for instance for internal combustion engines

Abstract: The machine (1) can be used for the simultaneous production of a plurality of pistons by means of gravity casting. The machine includes respective supporting and actuating structures (8; 9, 10, 11; 17, 18, 19; 14, 15, 16) for the internal male plugs (A), each of the internal lateral blocks (B, C), each of the external side pieces (D, E) and the upper element F of the various casting cavities. The machine can therefore be easily reconfigured for varying the type and number of the pistons to be simultaneously produced. The machine also provides the possibility of causing its sole casting part to be selectively rocked, thus making it possible, for example, to place inserts produced in accordance with the ALFin process into the casting cavities.

Description: The present invention relates to machines for the production of pistons by means of gravity casting and, more particularly, a machine in accordance with the preamble of Claim 1 hereinbelow. In the development of the invention particular attention was paid to the needs associated with the production of pistons for internal combustion engines. However, the reference to this possible application is not in any way to be interpreted as limitative of the range of the invention. The invention, indeed, can be applied to the production of pistons of any kind whatsoever, cases in point being pistons for compressors, various heat engines, etc. Many different needs have to be taken into consideration when realizing machines of the type specified above. Even though the production volumes of the automobile industry are generally rather high, the models and the versions in which the vehicles and their propulsion units are realized are often of such numbers as to call with a certain frequency for the realization of piston lots that comprise a rather small number of pieces. This fact not only greatly reduces the advantage of using machines that, even though they have a large productive capacity, are bound up with just a single type of piston, but also makes it interesting to dispose of machines that are capable of being converted in a sufficiently rapid and convenient manner from the production of a piston of a particular type to the production of a piston of some different type. In particular, it is desirable to have at one's disposal machines that can be readily converted from the production of pistons for motor vehicle engines of small and/or average cylinder capacity to the production of pistons for industrial motor vehicles, which are usually rather larger in size. Furthermore, when making pistons for engines in which ignition is due to compression (the so-called Diesel engines), it is important to have at one's disposal machines capable of realizing a general rocking motion of the mould during the casting operation. This movement is particularly necessary when the pistons to be cast are made of aluminium or light alloy to ensure the correct anchorage of the inserts supporting the first piston ring (the so-called ALFin process). Substantially identical problems have to be faced also in the other application sectors mentioned at the beginning hereof, including, among others, the production of pistons for compressors. US-A-2 824 347 discloses a molding machine including two identical molds for molding pistons for internal combustion engines. Each of the two molding cavities is defined by elements being moved each by a different actuator between a closed or molding position and an open or extracting position. The present invention sets out to furnish a machine capable of satisfying in an excellent manner all the requirements discussed above. According to the present invention, this scope can be attained by means of a machine having the characteristics recited in the claims attached hereto. The invention will now be described, though purely by way of example and not to be considered limitative in any way, by reference to the attached drawings, where: Figure 1 shows a general view in elevation of a machine in accordance with the invention in which some parts have been removed or are represented by means of broken lines for simplicity of illustration; Figure 2 shows essentially a section view along the line II-II where - once again - some parts have been removed for simplicity and clarity of illustration; Figure 3 can essentially be considered a view along the arrow III of Figure 1; and Figure 4 illustrates the portion of Figure 1 indicated by the arrow IV at a larger scale and also in a more complete manner. The reference number 1 in these drawings is used to indicate the whole of a machine for the production by means of gravity casting of pistons, including, for example, pistons for internal combustion engines. In the most common application, the pistons concerned would be for motor vehicle engines. In particular, the solution in accordance with the invention has been developed paying special attention to its possible use for the production of aluminium (or light alloy) pistons. However, the invention should not be understood as being limited exclusively to this field of application. In very summary terms and in accordance with criteria that in themselves are very well known, the machine 1 includes essentially a robust bench or bed on which there acts a casting robot not shown on the drawings. When it is used, the said robot is intended to sustain a casting receptacle to pour the molten casting material into a plurality of casting cavities positioned in the underlying part of the machine. This part, indicated overall by the reference number 3, is shown in greater detail in Figure 4 and carries the devices intended to move the parts that define the shell or the mould acting as the casting cavity. According to a preferential characteristic of the solution in accordance with the invention, the part 3 (which has the characteristics that are to be described in greater detail hereinbelow) constitutes an assembly that, taken as a whole, is capable of performing a general rocking motion with respect to the base 4 of the machine 1, which is intended to rest on a solid foundation floor F. The base 4 of the machine is realized in the form of a robust steelwork frame provided with a pair of arched rails 5 that can be seen from above in Figure 3 and are represented by means of broken lines in Figure 1. The rails 5 are normally two in number, one each respectively on the front and the rear side of the machine base 4, and are therefore capable of sustaining the rocking structure defining the part 3 in a position generically between them. The rocking structure in question is also provided with respective revolving bodies, which may be, for example, rollers or wheels 6 capable of engaging with and moving longitudinally along the guides or rails 5. The reference number 7 represents a motor element (typically a linear actuator such as a fluid-operated jack) that acts between the machine base 4 and the rocking structure defining the part 3 of the machine and selectively produces the to and fro motion of the said structure along the rails 5. The said motion is realized around a horizontal axis X3 that in actual practice is identified by the centres of curvature of the arched trajectories of the guides or rails 5 and located (with respect to the machine base 4) in a position that substantially corresponds to the one in which the casting receptacle carried by the casting robot pours the casting material into the cavities to form the pistons. The rocking motion has been indicated schematically by means of the arrow B in Figure 1, where the part 3 of the machine has been shown both in full line and in broken line. The two positions thus illustrated preferably correspond to the two extreme positions reached by the part in question in the course of its rocking motion controlled by the motor organ 7. It will therefore be appreciated that the said rocking motion is not normally symmetrical with respect to the vertical direction, but rather has an unsymmetrical pattern with respect to the said vertical direction: the full-line representation of the rocking structure shown in the figure corresponds in fact to a position of the said structure that is generically symmetrical with respect to the ideal transverse median plane and the vertical of the machine 1. As already mentioned, the aforesaid rocking motion is intended to be used, for example, when the pistons to be produced by gravity casting are of the type employed in engines where ignition is obtained due to compression, a type of piston produced with the help of inserts that are normally placed by means of the ALFin process. The reference number 2 indicates the whole of a device that can be used both for picking up the pistons (or, more correctly, the rough-cast pistons that still have attached to them the casting burrs caused by the feeding heads) from the casting cavities and (possibly) also for positioning the glass-fibre filters that are usually inserted into the feeding heads that permit the molten metal to reach the casting cavities. In this connection it will readily be appreciated that in the solution in accordance with the invention the part of the machine that is subjected to the rocking motion is de facto limited to just the part 3 that carries the moulds, that is to say, the casting cavities. This solution has undoubted advantages as compared with the traditional solutions in which practically the whole of the machine is made to rock with respect to its supporting base. The most obvious advantages are in terms of the volume and weight of the machine and, consequently, also in terms of the power and energy absorbed by the motor organs that control the said rocking motion. As far as the realization of individual pistons is concerned, the machine in accordance with the invention employs the current solution that defines the casting cavity of each individual piston by employing a series of elements comprising the following: for the part of the cavity that corresponds to the internal part of the piston, a lower male plug A (which is really made up of three blocks, of which the principal one A1 is motorized and the two secondary ones A2 and A3 are dragged along by the said principal block) and two lateral blocks B and C (see Figure 4); for the definition of the lateral surface of the piston skirt, two side pieces D and E, and for the definition of the upper part of the piston (which is normally also the position where the so-called feeding head is located), a block or upper element F. The block F, which is specifically illustrated only in Figure 1, is carried by the device 8, which moves in a coordinated manner to ensure that the block will be accurately positioned at the upper end of the casting cavity. The solution in accordance with the invention also includes as an important characteristic the fact of associating the lower male plugs A, the lateral blocks B and C, the side pieces D and E and the blocks F of at least two and therefore several pistons that are to be cast simultaneously (four pistons, for example) and making provision for the use of common supporting and actuating structures for the homologous male plugs/blocks/side pieces of several pistons. This solution proves to be advantageous both as regards the possibility of realizing simultaneously a plurality of pistons (four, for example, as illustrated on the drawings) within the ambit of a single machine, and also on account of the possibility of rapidly modifying the machine - which in practice implies its re-fitting - to change to a different type of casting operation. For example, by simply modifying the number and the arrangement of the aforesaid elements that define the mould cavity, the machine structure illustrated by the drawings can be readily converted for the simultaneous production of two pistons for an internal combustion engine of greater cylinder capacity, that is to say, two larger pistons. And this can be done while the other parts of the machine remain to all intents and purposes unchanged. In particular, the lower male plugs A (each of which in actual fact consists of the three blocks A1, A2 and A3) are mounted (by screwing, for example, in accordance with the general configuration of a vise) on a common supporting structure 9 that can move on vertical guides 10 under the action of a series of actuators such as the fluid-operated jacks 11a and 11b. With a view to limiting the vertical encumbrance of the machine, the jack 11a that acts on the structure 9 is preferably carried by a mobile assembly 110 that is moved with respect to the machine base 4 by the jacks 11b. These actuators (activated by the general control unit, a so-called PLC for example, that supervises - in a known manner - the proper functioning of the machine) are selectively controlled in such a way as to move the structure 9 with the male plugs A projecting upwards and into the position needed for actually carrying out the casting operation. On completion of the casting and after the newly formed pistons have been allowed to cool sufficiently, the actuators 11a, 11b can therefore be commanded to move in the opposite direction and thus to lower the structure 9 and the male plugs A carried by it in such a manner as to permit the extraction of the castings from the mould cavities. The fact that all the male plugs A are mounted on the same structure 9, which in its turn presents a substantially symmetrical structure, this both as regards the arrangement of the guides 10 and as regards the intervention position of the actuators 11a and 11b (which is usually either barycentric or substantially barycentric) makes it possible to achieve casting conditions that are to all intents and purposes identical for all the simultaneously cast pistons. In particular, one may advantageously provide for the structure 9 to be associated with respective elastic means - such as spring means 12 - situated in the zones in which the male plugs A are mounted, the said elastic means having the function of elastically forcing the male plugs A into the desired penetration position within the mould cavity while the structure 9 is maintained by the actuators in its uppermost raised position. This forcing action is applied both to the principal blocks A1 and - of course - also to the auxiliary blocks A2 and A3, since these, in their turn, are dragged along by and elastically linked with their respective blocks A1. As is better brought out by Figures 3 and 4, a substantially analogous solution is adopted also for the mould elements D and E employed to define the sides of the piston skirt. In particular, one may note in Figures 3 and 4 that the side pieces D and E (usually ordered into groups of counterposed elements, where each group is made up of the side pieces of two pistons) are capable of being mounted - by means of screws 13, for example, or some similar fixing elements - on two mobile devices or slides 14 that can perform counterposed to and fro motions with respect to the casting cavity. This movement is realized under the action of actuator elements 15 that could be, for example, fluid-operated jacks. In particular, the movement of the slides 14 is realized on guides 16 mounted on the upper part of a plate (see also Figure 1) that constitutes the upper part of the rocking structure of the machine 1. The described arrangement for supporting and moving the side pieces D and E has the advantage of being intrinsically self-centering (note the substantially barycentric position of the stem of the respective actuator element 15 with respect to its particular slide 14) and making possible (by intervening on the fixing elements 13, for example) the ready and rapid substitution of the side pieces D and E intended to realize a certain type of piston (for example, four simultaneous pistons for motor car engines) with different side pieces, of a larger size for example, that can be used for the simultaneous casting, for example, of two pistons for the engine of an industrial vehicle. As can be more readily appreciated by examining the elevation shown in Figure 4, an on the whole similar solution is also adopted for sustaining and moving the blocks B and C (often denominated «block 4» and «block 5»). In particular, the blocks B and C are each mounted on a slide 17 that can move in a respective guide member 18 under the action of a respective fluid actuator 19. This makes it possible for the blocks B and C to be pushed against the male plug A in such a manner as to define the part of the mould corresponding to the interior and lower part as the result of a general movement of convergence towards the male plug A brought into its uppermost position. At the end of the casting operation, and after having obtained the consolidation of the casting material, each male plug A (consisting of the three blocks A1, A2 and A3), as well as the elements B, C, D, E and F, can be displaced with respect to the position reached to define the casting cavity by causing them to move under the action of respective actuator elements such as the actuators 11a, 11b, 15, 19 and 8 that can be seen in the figures. In particular, when the newly formed piston is to be extracted from the mould, the side pieces D and E are moved away from each other in such a manner as to cause them to become detached from the surfaces of the piston skirts. The male plugs A, on the other hand, are withdrawn downwards by causing the supporting structure 9 to move vertically along the guides 10, thus making it possible for the blocks B and C to move towards each other (while the respective male plug A is withdrawn downwards) and becoming detached from the undercut parts normally defined on the inside of the piston, especially in the position of the thickenings for the passage of the gudgeon pins. The pistons detached from the various blocks can thus be picked up and removed from the machine, for example, by means of the device 2. According to a particularly advantageous solution, at least one of the slides 17 carrying one of the blocks B or C (in the example illustrated by Figure 4 this solution has been adopted for the slide carrying the block B) is configured in such a manner as to be able to move not only in a horizontal direction to come either closer to or further removed from the slide that carries the block C (and therefore in a radial direction with respect to the casting cavity), but also to execute a movement in a direction that is orthogonal with respect to the said radial direction, thus making it possible for the slide 17 and the block B carried on it to move downwards with respect to the common plane in which the casting cavities are located, thereby becoming detached from the piston interior. This result can be obtained, for example, by mounting the respective guide member 18 on a pair of tubular sleeves 20 that, in their turn, are mounted so as to be able to slide in the same guides 10 along which the supporting structure 9 of the male plug A performs its movements. The guide member 18 is made to move vertically along the guides 10 by means of yet another actuator element such as the fluid-operated jack 21. Lastly, the device 8 that moves the upper block F is designed in such a manner as to act simultaneously on a plurality of such blocks F. Referring to the illustrated solution, for example, the device 8 simultaneously moves the blocks F of all the four casting cavities shown on the drawings. In all cases where this may be necessary, the action of pouring the casting material into the mould defined by the blocks in question can be accompanied by a general rocking motion of the realized mould structure under the action of the jack 7, this in accordance with the criteria described in the introductive part of the present detailed description of the invention. Naturally, the realization details and the implementation forms can be widely varied with respect to what has here been described and illustrated (especially as regards possible applications for the production of pistons other than pistons for internal combustion engines) without in any way altering the principle of the present invention or going beyond its scope as defined by the claims that follow.

Claims: A machine for producing simultaneously a plurality of pistons by means of gravity casting in a plurality of casting cavities, the machine including, as the elements defining the casting cavity of a respective piston: an internal male plug (A), two internal lateral blocks (B, C), two external side pieces (D, E), and an upper element (F) wherein: homologous elements (A-F) that define casting cavities of at least two respective pistons are mounted on common supporting structures (9, 17, 14), each common supporting structure (9, 17, 14) is movable along guides (10, 18, 16) under the action of respective actuators (11, 19, 15), and said guides (10, 18, 16) and said actuators (11, 19, 15) are arranged symmetrically with respect to each common supporting structure (9, 17, 14). A machine according to claim 1 , including: a base (4), a casting part (3) carrying said male plugs (A), said lateral blocks (B, C), said side pieces (D, E) and said upper elements (F), as well as their respective supporting and actuating structures, motor means (7) to impress upon the said casting part (3) a general rocking motion with respect to the said base (4), guide means (5) interposed between said casting part (3) and said base (4), for guiding the said rocking motion, the said guide means (5) extending in accordance with an arched trajectory the centre (X3)of which defines a pouring position that remains substantially fixed with respect to the said base (4). A machine according to claim 2, further including a device (8) for placing casting filters in the casting cavities, said filter-placing device (8) being likewise mounted on the base (4). A machine according to claim 1, wherein the actuator (11a) acting on the supporting structure (9) for the internal male plugs (A) of the casting cavities of the said plurality of pistons is mounted on a mobile assembly (110) movable by a further actuator (11b). A machine according to claim 1, wherein said actuators (11, 19, 15) are arranged so as to act on said respective supporting structures (9, 17, 14) in substantially barycentric positions. A machine according to claim 1, wherein the supporting structure (9) for the male plugs (A) of the casting cavities of the said plurality of pistons includes elastic means (12) to force the said male plugs (A) elastically towards their respective casting cavities. A machine according to claim 1, wherein the respective supporting structure of the said two internal lateral blocks (B, C) of the casting cavities of the said plurality of pistons includes a respective further upper mobile assembly (17) that supports the said lateral block (B, C), said upper mobile assembly (17) being movable under the action of a further actuator (19). A machine according to claim 7, wherein the respective supporting structure (17) of at least one (B) of the said two internal lateral blocks (B, C) of the casting cavities of the said plurality of pistons is movable along at least two substantially orthogonal directions in coming closer to or moving away from the casting cavities of the said plurality of pistons.

Inventors: BOSCOLO FABRIZIO, BOSCOLO, FABRIZIO
Applicants: FATA ALUMINIUM S P A, FATA ALUMINIUM S.P.A.
Application year: 1999
Main classification: B22D15
IPC codes: B22D15