1. Plant for manufacturing pistons, comprising:
- a first loading station (11) for loading inserts (10) to be arranged in a chill (43) for casting said pistons;
- a second station (21) wherein a molten metal bath is provided in which said inserts (10) are dipped for undergoing a coating treatment;
- a third exchange station (31) wherein said inserts (10) coming from said first station (11) or from said second station (21) are temporarily put waiting for being transferred to said second station (21) or said casting chill (43) respectively;
- a fourth casting station (41) wherein said inserts (10) are placed in said casting chill (43);
- a robot (51) for transferring said inserts (10) from one of said stations to another. 2.Plant according to claim 1, wherein said robot (51) is a anthropomorhic robot having an articulate arm (55) suitable for reaching, possibly with its end (57), any of the four stations (11, 21, 31, 41) of the plant.
3. Plant according to claim 2, wherein said arm (55), possibly at its end (57), is provided with a pair of pick-up devices (59,63), a first one of said pick-up devices (59) being provided with a plurality of grippers (61) for gripping a set of said inserts (10), and a second one of said pick-up devices being provided with a single gripper (64) for gripping one or more tools to be used in the production cycle of said pistons.
4. Plant according to claim 3 wherein, in the alternative or in combination:
- the pair of pick-up devices (59, 63) is a pair of pneumatically driven devices;
- at least one of said first (59) and second pick-up devices (63) is pneumatically driven.
5. Plant according to one or more preceding claims, wherein said first loading station (11) comprises a pair of stores (13) inside of which said unfinished inserts (10) and an extraction device (15) are arranged, said extraction device (15) being arranged below the stores (13) and being provided with a pick-up head (17) that allows extracting said inserts (10) to a loading platform (19) in such way that due to the thrust of said pick-up head (17) a pair of inserts (10) is put on the loading platform (19) and can be removed from the loading station ( 11 ) by means of said robot (51).
6. Plant according to claim 5, wherein, in the alternative or in combination:
-the pair of stores (13) comprises two columns inside of which said insert (10) are arranged in a stack;
-the pair of stores (13) comprises two cylindrical and/or vertical and/or parallel columns,
inside of which said unfinished inserts (10) are arranged;
-the extraction device (15) is a pneumatic device and/or is horizontally arranged below the stores (13);
- the pick-up head (17) allows extracting said inserts (10) one by one from below said stores (13).
7.Plant according to one or more preceding claims, wherein the first loading station (11) is further provided with a chute (12) on which the inserts (10) can be put down if the picking operation of robot (51) needs to be interrupted before the inserts (10 ) are transferred to the next station. δ.Plant according to one or more preceding claims, wherein the second station (21) comprises a crucible (23) containing the molten metal in which said inserts (10) are dipped for undergoing the coating treatment.
9.Plant according to one or more preceding claims, comprising a support (71) provided with a plurality of hooks (79), one for each insert (10), to which the inserts (10) can be hung while they are immersed in the molten metal, where the support can be gripped and handled by the robot (51).
10. Plant according to claim 9, wherein the support (71) is provided with four hooks (79).
11. Plant according to claim 9 and/or 10, wherein the support (71) comprises an upper suspension rod (73) ending with a lower part provided with a crosspiece (75) to which a plurality of lower rods (77) is fixed, each of said lower rods being provided with corresponding hooks (79) arranged at different levels along said lower rods (77).
12. Plant according to claim 11, wherein in the alternative or in combination:
- two lower rods (77) are fixed to the crosspiece (75) at the lowed end of the the upper suspension rod (73); -the lower rods (77) are parallel;
-each parallel lower rod (77) is provided with a pair of the corresponding hooks (79);
- the upper rod (73) is suitable for being hung at its upper part;
-a suspension metal ring (72) is provided on the upper rod (73), said metal ring allowing to keep said support (71) suspended; - the suspension metal ring (72) is cylindrical.
13. Plant according to claim 8, wherein said second station (21) is provided with a rack bracket (81) which is provided with a series of seats (82) in order to allow suspending a plurality of said supports (71) by means of said suspension metal ring (72), said support (71) having its lower part, to which said inserts (10) are suspended, dipped in the molten
metal bath.
14. Plant according to claim 13, wherein the seats (82) of the rack bracket (81) are U- shaped.
15. Plant according to claim 13 or 14, wherein said bracket (81) is provided with at least five seats (82) for corresponding supports (71). lό.Plant according to a claim from 13 to 15, comprising a first tool (91) comprising in its turn a first handle (93) to which a first shovel (95) is fixed, said first handle (93) being suitable for allowing said tool (91) to be suspended to a seat of said rack bracket (81), said first tool being suitable for being handled by said robot (51) for collecting the oxide layer that can form on the surface on said crucible (23) creating an exit "window" of escape for one of said supports (71) that are immersed in said molten metal bath.
17. Plant according to claim 16, wherein, in the alternative or in combination:
-the first shovel (95) is fixed at its lower part to the first handle (93);
-the first handle (93) is provided with a first cylindrical metal ring (97) suitable for allowing said tool (91) to be suspended to a seat of said rack bracket (81);
-the first tool is suitable for being handled by said robot (51) so as to collect, possibly combining a translation- and a rotation movement, the oxide layer that can form on the surface on said crucible (23).
18. Plant according to claim 16 or 17, wherein said second station (21) further comprises a support (92) for a second tool (94) provided for collecting and removing from the molten metal bath oxides and films that form on the surface thereof.
19.Plant according to claim 18, wherein said second tool (94) comprises a second handle
(96) to which a second shovel (98) is fixed and wherein, in the alternative or in combination: - the second shovel (98) is fixed to the lower end of the second handle (96);
- the second shovel (98) has a substantially rectangular shape;
- the second shovel (98) has a substantially arched shape along a circumference parallel to said second handle (96);
- said second handle (96) is suitable for allowing said second tool (94) to be hung to said support (92) provided for in said second station (21);
- said second handle (96) is provided with a second metal ring (99), possibly cylindrical, that allows said second tool (94) to be hung to said support (92) provided for in said second station (21).
2O.Plant at least according to claim 9, wherein said third exchange station (31) comprises a support (33) for suspending one of said supports (71) before and after the coating treatment.
21. Plant according to claim 20, in which, in the alternative or in combination: - the support (33) comprises an upright;
- on the support (33) an U-shaped seat (35) is provided for suspending one of said supports (71) before and after the coating treatment;
- the U-shaped seat (35) is arranged on the upright (33);
- the support (33) allows one of said supports (71) to be suspended by the suspension metal ring (72) before and after the coating treatment.
22.Plant according to one or more preceding claims, wherein said fourth casting station
(41) comprises a chill (43) in which said inserts (10) that previously underwent the coating treatment can be placed simultaneously by sets of four.
23.Plant according to one or more claims from 3 to 22, wherein said first pick-up device (59) is provided with a plurality of grippers (61) for picking up and transferring a set of four or more inserts (10) at a time.
24.Plant according to claim 23, suitable for handling ring-shaped inserts (10) and wherein said first pick-up device (59) comprises a support (65) on which at least four grippers (61) are mounted. 25. Plant according to claim 24 wherein, in the alternative or in combination:
- the support (65) is made of aluminum;
- the grippers (61) are mounted aligned on said support (65);
- each gripper (61) is provided with three parallel gripping teeth (67) arranged at angles of 120° suitable for engaging with the inner circumference of said ring-like inserts (10) driven by the pneumatic drive of said gripper (61).
26.Plant according to claim 24 or 25, wherein at least a central gripper (61) is fixed relative to the support (65), while at least one gripper is movable relative to the support
(65) at least in lateral direction of the same gripper.
27. Plant according to claim 26 wherein, in the alternative or in combination: - the two central grippers (61) are fixed;
- the two external grippers (61) are movable;
- at least a movable gripper is slidable on guides, and possibly the guides are drived by pneumatic cylinders.
28.Plant according to one or more claims from 24 to 27, wherein at least four grippers (61)
are mounted on the support (65) and a pair of said four grippers (61) are driven independently from the other one.
29.Plant according to one or more claims from 3 to 28, wherein each gripper (61) is provided with three parallel telescopic pins (69) supported by springs and arranged at angles of 120°, suitable for allowing an optimal positioning of the inserts (10) in the chill (43).
3O.Plant according to one or more claims from 25 to 29, wherein said first station (11) further comprises a basin (14) containing a bath of liquid graphite in which it is possible to dip the gripping teeth (67) of grippers (61) at each cycle in order to facilitate the separation of inserts (10) from the gripper (61) itself.
31. Method for manufacturing pistons comprising the following steps:
- in a first loading station (11) loading a set of inserts (10) to be placed in a casting chill
(43) for forming said pistons by casting;
-transferring said inserts (10) in a third exchange station (31); - transferring said inserts (10) from said third exchange station (31) to a second station (21) in which a molten metal bath is provided in which said insert (10) can be dipped; -transferring said inserts (10) from said second station (21) to said third exchange station (31) in which said inserts (10) coming from said second station (21) are temporarily placed, waiting for being transferred to said casting chill (43); -transferring said inserts from said third station (31) to a fourth casting station (41) in which said inserts are placed in said casting chill (43); said operations of transferring said inserts (10) from one of said stations to the other being carried out by a robot (51). 32. Method according to claim 31, wherein said inserts (10) loaded in said loading station (11) are put two by two by said robot (51) on a support (71) suitable for taking at least four of said inserts (10).
33. Method according to claim 32, wherein said support (71) is placed at said third exchange station (31).
34.Method according to claim 33, comprising the step of picking up the support (71) that is at the third station (31) with said robot (51) and transferring the support to said second station (21) for coating said inserts (10).
35.Method according to one or more claims from 31 to 34 wherein, by means of a plant according to one or more claims from 16 to 30, before said inserts (10) are transferred from said second station (21) to said third station (31) a step is provided wherein said robot (51) picks a tool (91) up provided with said first shovel (95) and cleans the surface
of the molten metal bath from oxides and films, freeing therefore the exit zone from said bath for said inserts (10).
36.Method according to or more claims from 32 to 35, comprising the step of picking four inserts (10) up two by two from said support (71) that is in the third exchange station (31) and to place said inserts in said casting chill (43) in the fourth casting station (41).
37. Method according to claim 36, comprising the step of picking four inserts (10) up two by two from said support (71) that is in the third exchange station (31) and immediately to place said inserts in said casting chill (43) in the fourth casting station (41). 38.Method according to one or more claims from 31 to 37, wherein said inserts (10) have a ring-like shape.
39. Method according to one or more claims from 31 to 38, wherein said robot (51) comprises a first pick-up device (59) on which a plurality of grippers (61) is mounted, each gripper being provided with a plurality of gripping teeth (67) suitable for engaging with the inner circumference of said ring-like inserts (10), said method comprising the step of dipping said gripping teeth (67) in a basin(14) containing liquid graphite before picking the ring-shaped inserts (10) up from the loading station (11) for facilitating the separation of said inserts (10) from said teeth (67).
40. Method according to claim 39 wherein, in the alternative or in combination: - said robot (51) comprises a first pick-up device (59) on which at least four pneumatic grippers (61) are mounted;
-each gripper is provided with three gripping teeth (67), possibly arranged parallel and/or at angles of 120°.
41.Method according to one or more claims from 31 to 40, wherein in case of anomaly on the casting station (41) the robot (51), if already picked the rings (10) up, carries out an "abort" operation unloading said rings in an unload chute (12) provided in the first station (11).
42.Method according to one or more claims from 31 to 41, further comprising the step of picking a tool (94) up by means of said robot (51) and of collecting with said tool oxides and films from the molten metal bath, evacuating them in a collection container (100). 43. Method according to one or more claims from 31 to 42, wherein said molten metal bath is an aluminum bath or a bath of alluminium alloys.
44. Method according to one or more claims from 31 to 43, wherein said inserts (10) are cast iron rings. 45.Method according to claim 44, wherein said rings are aluminated rings of "Alfm" kind,
that is pre- worked centrifuged cast iron rings.
46.Method according to claims 43 and 44, or 43 and 45, wherein the residence time of the rings in the aluminum bath is approximately 120-240 seconds.
47.Method according to one or more claims from 31 to 46, wherein the time for placing inserts (10) in the chill, covering the chill included, is less than 25 seconds.
48. Method for manufacturing pistons for Diesel cycle internal combustion engines, comprising the steps according to one of the claims from 31 to 47.