[0001] The object of the present invention is a stacking and/or destacking machine (hereinafter, stacking/destacking machine) .

[0002] Stacking/destacking machines are machines which are typically included in mechanical processing plants, for example, processing of metals such as aluminium. [0003] The processing operations to which aluminium is subjected can be of various nature. Typical applications for which the presence of stacking/destacking machines is particularly appreciated are extrusion and profiling of aluminium. In extrusion and profiling plants, aluminium is subjected to successive processing operations (for example, extrusion, stretching, cutting of the profiles, ageing in ageing ovens, packaging) in as many processing stations. Upon passing through some of these stations, particularly between the cutting and the ageing stations, the profiles are inserted and subsequently transported in baskets, usually along roller units or conveyor belts. Therefore, the need arises to transfer the profiles from a basket to the other one, or from a roller unit/belt to a basket, or from a basket to a roller unit/belt. [0004] The stacking machines in the strict sense of the term serve the function of withdrawing the profiles from a roller unit and positioning them within the baskets, while the destacking machines serve the function of withdrawing the profiles from the baskets and positioning them on a roller unit. Generally, the stacking machines are also adapted to destack, as well as the destacking machines are adapted to stack. For this reason, a stacking/destacking machines is generally referred to, which is capable of performing both functions. Generally, the stacking machines are arranged within extrusion plants, while the destacking machines are arranged at the front-end of packaging plants. [0005] The stacking/destacking machines can be of various types. One of the most widespread types are the so- called strip stacking/destacking machines, in which one or more layers of profiles are positioned on strips which are stacked and/or destacked by the stacking/destacking machine by means of nippers which grasp and move the strips. [0006] In order to carry out such handling of the strips, the stacking/destacking machines have a main supporting structure along which a trolley can move, according to one or more axes, which supports a handling unit which, in turn, moves a gripping unit carrying the above- mentioned nippers. The gripping unit is capable of performing lifting and lowering movements relative to the main supporting structure, for the destacking and stacking of the profiles and the strips, respectively. To this aim, the handling unit comprises one or more closed loop feedback electric motors connected to transmissions of the screw/nut screw or driving sprocket-rack type, in turn, associated to the gripping unit . [0007] However, such stacking/destacking machines are not free from drawbacks.

[0008] In fact, it is not infrequent that, in use, particularly during the lowering motion, the gripping unit meets unexpected obstacles. Given the weights involved, (a single gripping unit can weigh more than a ton) , such impacts can result not only in failures of the gripping unit, but also, given the nature of the transmissions connecting the gripping unit to the motors, damages to the handling unit or the whole main supporting structure. In fact, in the event of an impact, the forces due to the impact first discharge on the gripping unit, then are transmitted via the transmissions both to the handling unit and to the main supporting structure. [0009] Therefore, object of the^ present invention is to provide a stacking/destacking machine which is capable of at least partially overcoming the problems cited con reference to the prior art.

[0010] Particularly, the object of the present invention is to provide a stacking/destacking machine which has such a configuration as to be subjected to sufficiently reduced damages in the event of accidental impacts of the gripping unit.

[0011] Further objects of the present invention are a higher safety within the working space in which the machine is included, as well as a reliability which increases over time, therefore a limited need for extraordinary maintenance interventions.

[0012] These and other objects are achieved by a stacking/destacking machine which comprises: - a main supporting structure; a mobile trolley relative to the main supporting structure along at least one trolley direction; a gripping unit adapted to stack and/or destack profiles and/or strips in baskets; - means for the handling of the gripping unit relative to the trolley between a lifted position and a lowered position along a stacking/destacking direction, in which the handling means comprise means to guide the gripping unit along the stacking/destacking direction, and flexible connection means between trolley and gripping unit which are so shaped as to support the gripping unit without substantially exert pushing actions thereon which face said lowered position. [0013] In order to better understand the invention, and appreciate the advantages thereof, some exemplary, non- limiting embodiments thereof will be described below, with reference to the annexed Figures, in which: [0014] Fig. 1 is a perspective view of a stacking/destacking machine according to the invention in a specified use condition;

[0015] Fig. 2 is a perspective view of a gripping unit of the stacking/destacking machine in Fig. 1; [0016] Fig. 3 is a side view of a stacking/destacking machine according to a further possible embodiment of the invention;

[0017] Fig. 4 is a sectional view according to the line IV-IV of the stacking/destacking machine in Fig. 3; [0018] Fig. 5 is a further side view of the stacking/destacking machine in Fig. 3; [0019] Fig. 6 is a plan view of the ^' stacking/destacking machine in Fig. 3;

[0020] Fig. 7 is a perspective view of a nipper of the stacking/destacking machine according to a possible embodiment of the invention; [0021] Fig. 8 is an exploded, perspective view of the nipper in Fig . 7 ;

[0022] Figs. 9-11 are side views of the nipper in Fig. 7;

[0023] Fig. 12 is a side view of the gripping unit in Fig.

2 in a specified use condition; [0024] Fig. 13 is a enlarged view of a detail of the gripping unit in Fig. 12;

[0025] Fig. 14 is a side view of a stacking/destacking machine portion according to a possible embodiment of the invention; [0026] Fig. 15 is a sectional view according to the line

XV-XV of the stacking/destacking machine portion in Fig.

14;

[0027] Fig. 16 is a schematic view of a stacking/destacking machine portion according to a possible embodiment of the invention;

[0028] Fig. 17 is a schematic view of a further portion of the stacking/destacking machine according to a possible embodiment of the invention.

[0029] With reference to the Figures, a stacking/destacking machine is generally indicated with the reference number 1.

[0030] The stacking/destacking machine can be included in a complex plant, for example, an aluminium extrusion and profiling plant. In the plant, one or more stations can be present, in which the material to be processed is passed through special processing stations in sequence (for example, extrusion, stretching, cutting of the profiles, ageing in ageing furnaces, packaging) . [0031] The stacking/destacking machine 1 can be arranged between two or more of these stations, for example, between the cutting station and the ageing station. One or more layers of profiles 3, preferably supported by one or more strips 4, are sent towards and/or drawn from the stacking/destacking machine 1 by means of roller units 5, which run along development directions S, preferably rectilinear and mutually parallel in the proximity of the stacking/destacking machine 1 (it shall be noted that the profiles 3 are schematically indicated as a parallelepiped in the Figures. Instead, the strips 4 are visible, for example, in Fig. 13) . For the handling thereof along the roller units 5, the strips 4 and the profiles 3 are arranged into baskets 2 capable of moving along the same roller units 5, or they can be directly moved by the same roller units 5. The strips 4 movement is preferably automatically controlled by, for example, belt systems 6.

[0032] The main functions of the stacking/destacking machine 1 are the strips 4 and profiles 3 destacking from the baskets 2, and/or the stacking thereof into the baskets 2. Generally, when the machine function is the stacking function, it is referred to as a stacker, while when the function is the destacking function, it is referred to as a destacker. The machine according to the invention has such characteristics as to be able to perform both functions, therefore it will be conventionally referred to as a stacking/destacking machine. It shall be apparent that the stacking/destacking machine according to the invention will be able to be freely used to perform only one of the above-mentioned operations without needing specific adaptations .

[0033] With reference to Fig. 1, there are a first 5' and a second 5'' roller units. On the first roller unit 5' there is a first strip-profiles unit 4' inserted in the basket 2, while on the second roller unit 5'' there is a second strip-profiles unit 4'' directly supported by the second roller unit 5' ' . The stacking/destacking machine 1 is both able to destack the first strip-profiles unit 4' from the basket 2 arranged on the first roller unit 5' in order to successively position it on the second roller unit 5' ' , and to stack the second strip-profiles unit 4'' arranged on the second roller unit 5'' in the basket 2 supported by the first roller unit 5' . However, it shall be noted that the stacking/destacking machine 1 can be usefully included also in more complex plants, for example, comprising more than two roller units. [0034] The stacking/destacking machine 1 according to the invention comprises a main supporting structure 7, preferably of the portal type. It can be provided with, for example, four uprights 8 resting on or secured to the ground, and with as many crosspieces 9 transversally connected to the uprights 8. It shall be apparent that different configurations of the main supporting structure 7 can be provided. For example, it 'is possible to provide a different number of uprights and/or crosspieces (for example, a number of crosspieces above four) or also structures not necessarily configured as a portal . [0035] The stacking/destacking machine 1 comprises a trolley 10 which is mobile relative to the main supporting structure 7. According to a possible embodiment, the trolley 10 is mobile along only one trolley direction X relative to the main supporting structure 7 (two axes configuration) . Such trolley direction X is preferably transversal, still more preferably orthogonal, to the development direction S of the roller units 5, so that the stacking and destacking operations can occur between adjacent roller units. In accordance with a further possible embodiment (not shown in the Figures), the trolley 10 is capable of performing movements according two directions relative to the main supporting structure, particularly the direction X, transversal and preferably orthogonal to the development direction of the roller units 5, and a second direction orthogonal to the trolley direction X and parallel to the development directions S of the roller units 5

(three axes configuration) . It shall be apparent that further modes to handle the trolley 10 relative to the main supporting structure 7 are possible, relative to what has been described above.

[0036] With reference to the two axes configuration, according to a possible embodiment, the trolley 10 is provided with one or more pairs of gear wheels 11 meshing corresponding racks which are prearranged along one or more of the crosspieces 9 and which extend along the trolley direction X. The gear wheels are actuated by, for example, an electric motor controlled by special control electronics, for example, by inverter systems. In this manner, the actuation of the electric motors translates into a trolley handling along the trolley direction X.

[0037] The stacking/destacking machine 1 comprises a gripping unit 12 having the function of stacking and/or destacking the semifinished products, particularly the strips and profiles. In order to be capable of performing such stacking and/or destacking operations, the gripping unit 12 is capable of moving relative to the trolley 10 along a stacking/destacking direction I/D between a lifted and a lowered position. In the lifted position, the trolley 10 can freely move without the gripping unit interfering with the baskets. Instead, the lowered position is suitable to the strips insertion in or withdrawal from the baskets. [0038] Advantageously, the gripping unit 12 is connected to the mobile trolley 10 so as to be capable of moving integrally thereto when it moves along the main supporting structure.

[0039] The gripping unit 12 handling along the stacking/destacking direction I/D is performed via special handling means 24, which will be described below.

[0040] The gripping unit 12 is so shaped as to be capable of firmly gripping and releasing the strips and/or profiles. To this aim, it advantageously comprises a plurality of nippers 13 associated to a gripping frame 20.

[0041] The gripping frame 20 can be variously shaped (Fig. 2) . In accordance with a possible embodiment, the gripping frame 20 comprises two side beams 21 interconnected by a plurality of cross beams 22, preferably orthogonal thereto. Furthermore, supporting plates 23 are preferably provided, also arranged between the side beams 21, by means of which the connection between gripping unit 12 and mobile trolley 10 is implemented. Particularly, as it will be seen below, the handling means 24 are advantageously connected to the gripping unit via the supporting plates 23. [0042] The nippers 13 are preferably so arranged along the side beams 21 as to be able to laterally grip and release the strips.

[0043] The connection between nippers 13 and gripping frame 20 can be of a rigid type, where the term "rigid" is to be meant in the sense that the nippers are not capable of performing relative movements relative to the gripping frame 20 along the stacking/destacking direction I/D. Alternatively, according to a particularly advantageous embodiment, the connection between nippers 13 and gripping frame 20 can be of a mobile type, that is, such that relative movements between nippers 13 and gripping frame 20 along the stacking/destacking direction I/D are, on the contrary, allowed. In this manner it is possible that, during the gripping frame 20 lowering towards the lowered position, the nippers 13 stay at different levels, for example, if there is the need to grip the strips 4 at points with offset heights.

[0044] The nippers 13 preferably comprise a pair of gripping arms 14 which are mobile so that each nipper can take one open configuration and one closed configuration (Figures 7-11) . In the closed configuration, the nippers 13 are capable of holding the strips 4 for the stacking or destacking thereof, while in the open position they are capable of releasing the strips as well as positioning themselves in the correct position for the gripping thereof.

[0045] The opening and closure movements of the gripping arms 14 are controlled by a special actuation system. According to a possible embodiment, the gripping arms 14 of each nipper are actuated by a cylinder-pneumatic piston unit 15, the piston of which is associated to a first one 14' of the gripping arms 14, and the cylinder of which is associated to a second one 14'' of the gripping arms 14. The two gripping arms 14' and 14'' are respectively hinged at a first 16' and a second 16' ' pins, and are further mutually coupled via a shape- coupling, for example, via a geared coupling 17, such that a movement of the first gripping arm 14' translates into an opposite movement of the second gripping arm 14'', thereby implementing the opening (spreading apart of the gripping arms) and closure (approaching of the gripping arms) movements. The opposite movements of the gripping arms 14' and 14" can be of a substantially equal width, or one of the two arms can perform movements having a higher width than the other arm movement width.

[0046] Advantageously, the nippers 13 further comprise a tracer point 18, preferably arranged between the first 14' and the second 14'' gripping arms, capable of translating relative to the gripping arms, particularly along the stacking/destacking direction I/D. With further advantage, the tracer point 18 is connected to sensing means 19 capable of measuring the relative movements relative to portions (fixed or mobile, as it will be seen below) of the nipper. [0047] With reference to the lowering motion, that is, towards the gripping unit lowered position once the nipper has been opened, under standard use conditions the tracer point 18 contacts the strip of the gripping arms 14 to be gripped first. Following such contact, if the gripping unit performs a -further lowering, then the tracer point 18 performs a raising movement, that is, towards the gripping unit lifted position, relative to the nipper 13 arms 14. Such relative movement is detected by the sensing means 19. When the position detected by the sensing means reaches a predetermined value, the nipper results to be in the correct closure position. Also this aspect will be explained below with reference to particular embodiments of the nippers 13. [0048] The presence of the tracer- point 18, advantageous in the case of a rigid coupling between nippers 13 and gripping frame 20, results to be still more advantageous in the case of a mobile coupling thereof. In fact, in the case that the gripping points of each nipper on the strips are not all at. the same height, the gripping unit is lowered until the tracer points of each nipper have reached such a position that the nippers can correctly perform the strip gripping. As long as the gripping unit continues to lower, the nippers which are not yet in the correct position for the gripping of .the strip lower integrally to the gripping unit, while the nippers which are already in such gripping position remain fixed in an absolute position, however performing a relative movement towards the lifted position relative to the gripping frame. Therefore, the sensing means 19 associated to the tracer points 18 of each nipper 13 can be advantageously exploited in order to carry out a diagnostics for the occurred correct positioning of the gripping unit. In fact, when all the nippers have reached the correct gripping position, the respective sensing means can send a confirmation signal that the gripping position has been reached, and this implies that the gripping unit lowering has successfully occurred. If not all the nippers send this signal, this means that some abnormalities in the lowering movement of the gripping unit have occurred.

[0049] According to a particularly advantageous aspect of the invention, the gripping unit 12 handling means 24 comprise means 25 to guide the same gripping unit 12 along the stacking/destacking direction I/D. Furthermore, the handling means 24 comprise means 26 for the connection between trolley 10 and gripping unit 12 (Fig. 4) . The connection means 26 are flexible, and are so shaped as to support the gripping unit 12 without substantially exert pushing actions thereon which face the lowered position.

[0050] In other words, the flexible connection means 26 support the gripping unit 12 in a non-completely rigid manner, contrary to what happens in the prior art machines. Therefore, the flexible connection means 26 are able to oppose the gripping unit 12 weight, that is to exert forces thereon, which face the lifted position, but not to push the gripping unit 12 towards the lowered position. Consequently, the flexible connection means 26 go along with the gripping unit 12, by supporting it, in the lowering and raising movements thereof but, in the case that the gripping unit 12 meets obstacles along the path towards the lowered position, they are not capable of pushing on the gripping unit, which, thus, is not able in turn to push against the obstacle. [0051] Instead, the guide means serve the function of making so that the gripping unit 12, kept overhanging by the flexible connection means 26, follows the desired path, that is, moves along the stacking/destacking direction I/D. [0052] Therefore, it shall be apparent that in the stacking/destacking machine according to the invention, in the case of gripping unit 12 impacts against undesired obstacles, the forces associated to such impacts, particularly their components along the stacking/destacking direction I/D, are not substantially transmitted to the trolley and to the main supporting structure. Consequently the machine results to be safe and reliable, since some basic parts thereof are unlikely to incur extraordinary failures or breakings. The guide means make so that, despite the flexibility of the flexible connection means, the gripping unit correctly follows the stacking/destacking direction, but does not significantly contribute to the transmission of forces along the stacking/destacking direction. [0053] Advantageously, the handling means 24 comprise ^' an actuating unit which handles the gripping unit 12 through the flexible connection means 26. According to a possible embodiment, such actuating unit comprises an oleohydraulic actuating unit 28, in turn, preferably comprising at least one oleohydraulic cylinder-piston unit 29, in which an oleohydraulic piston slides within a chamber defined by an oleohydraulic cylinder according to an actuating direction. The oleohydraulic cylinder- piston unit 29 is preferably associated to the mobile trolley 10 so as to be able to move integrally therewith, relative to the main supporting structure 7 along the trolley direction X. For example, the oleohydraulic cylinder-piston unit 29 can be secured on a trolley 10 support plate 30, for example, at the main supporting structure (Fig. 4) topmost end. Advantageously, the oleohydraulic cylinder-piston unit 29 is so oriented that the actuating direction is transversal, preferably orthogonal, to the stacking/destacking direction I/D. Such advantageous configuration, which substantially minimizes the machine overall dimensions, is made possible by the flexibility

to the stacking/destacking direction I/D.

[0054] It shall be apparent that the actuating unit 28 can take different configurations relative to what has been described above. For example, it is possible to provide electrical drives, or linear actuators of a different nature, or non-linear drives, for example, oleohydraulic rotating actuators such as vane pumps, or the like. [0055] The flexible connection means 26 preferably comprise chains 27. Such chains 27 are advantageously directly handled by the actuating unit 28, particularly by the oleohydraulic cylinder-piston unit 29, and are also connected to the gripping unit 12, for example, at the supporting plates 23, directly or via intermediate members. The chains 27 are preferably guided according to predetermined paths via special transmission means 31. According to a possible embodiment, such transmission means 31 comprise a plurality of pulleys 32 associated to the trolley 10, and rotating relative thereto . [0056] As it shall be apparent to those skilled in the art, the flexible connection means 26 can be selected from groups alternative to the chain group. For example, the flexible connection means 26 can comprise belts, cables, or the like. According to a further possible alternative, it is possible to provide combinations of the flexible connection means listed above or non- explicitly mentioned equivalents thereof. [0057] As stated, in order to avoid undesired gripping unit 12 oscillations during the handling thereof due to the action of the handling means 24, the stacking/destacking machine 1 is provided with the guide means 25, which drive the gripping unit along the stacking/destacking direction I/D. [0058] The guide means 25 can also take a • number of configurations. According to a possible embodiment, the guide means 25 comprise one or more rigid bars 33 adapted to slide into corresponding rigid guides 34, both extending parallel to the stacking/destacking direction I/D. Preferably, the bars 33 are associated to the gripping unit 12, and the guides 34 are associated to the trolley 10, but it shall be apparent that the opposite solution can also be contemplated. It shall be noted that, although the bars 33 are rigid, they (excepted for the weight thereof) do not substantially exert on the gripping unit 12 any thrusts facing the lowered position, therefore do not compromise the given advantageous technical effects of the flexible connection means 26 in the case that there are obstacles in the lowering path, according to what has been described before. [0059] Despite the increased safety of the machine, ensured by the presence of the guide means and the flexible connection means, since the gripping unit weight is generally high (often being above a ton) , the impacts between gripping unit and optional obstacles, or even between gripping unit and strips in the event of a less than perfect control of the motion, or an incorrect positioning of the strips, can in any event lead to gripping unit damages. [0060] In order to obviate such problem, the stacking/destacking machine 1 advantageously comprises means 35 for the compensation of the gripping unit 12 weight, that is, means which are adapted to exert on the gripping unit 12 opposite compensation forces relative to the weight thereof. In other words, since, as stated, the gripping unit weight is generally high, the weight compensation means 35 make so that the resulting force (which will be called "bulk weight" herein below) exerted by the gripping unit on optional obstacles to the movement (and vice versa, in response, that is, by the obstacles on the gripping unit) is noticeably lesser than the gripping unit actual weight. In fact, the bulk weight intensity is equal to the difference between the gripping unit actual weight and the compensation forces exerted by the compensation means, opposite the actual weight .

[0061] Advantageously, the gripping unit 12 weight compensation means 35 are so shaped that the compensation forces are variable as a function of the same gripping unit 12 position between the lifted position and the lowered position. According to a particularly advantageous embodiment, the gripping unit 12 weight compensation means 35 are so configured that the compensation forces increase as the gripping unit 12 approaches the lowered position. In other words, when the gripping unit 12 is at the or in the proximity of the lifted position, the compensation forces are of a limited extent. Instead, when the gripping unit approaches the lowered position, and the risk of unexpected impacts with the strips or profiles, or with undesired obstacles, is higher, the gripping unit 12 weight compensation means 35 exert higher compensation forces, so that the _κ gripping unit bulk weight is noticeably lesser than the actual weight. It shall be apparent that this translates into a further increase of the machine safety, as well as an increase of the reliability and durability thereof, since potentially disastrous impacts translate into impacts of a small extent . [0062] The gripping unit 12 weight compensation means 35 can comprise means for the adjustment of the trend of the compensation forces acting on the gripping unit. In other words, it is possible to adjust the trend of the gripping unit bulk weight as a function of the position thereof. This characteristic allows particularly adapting the stacking/destacking machine to the particular operative conditions, for example, to different weights of the gripping units. Further details with reference to particular embodiments of the invention will be provided below.

[0063] In accordance with an embodiment, the gripping unit 12 weight compensation means 35 comprise one or more pneumatic actuating units 36 so arranged as to act between gripping unit 12 and trolley 10. Such pneumatic actuating units 36 are preferably arranged in parallel to the guide means 25, particularly at the bars 33 and guides 34, still more preferably connected to the trolley 10, so as to be moved therewith when it moves along the trolley direction X. [0064] Advantageously, the pneumatic actuating units 36 comprise one or more pneumatic cylinder-piston units 37, in which a piston 38 is slidable within a chamber defined by a cylinder 39 according to a sliding direction which is substantially parallel to the stacking/destacking direction I/D. The piston 38, given the orientation thereof, splits the cylinder chamber 39 into a lower chamber 39' and an upper chamber 39'' (see, in this regard, the schematic view in Fig. 16), where the terms "lower" and "upper" are to be meant with reference to the machine 1 in the standard use conditions thereof. Particularly, a lowering of the piston 38 translates in a decrease of the lower chamber 39' volume (and an increase of the upper chamber 39'' volume) , while a rising of the piston towards the lifted position translates in an increase of the lower chamber 39' volume (and a decrease of the upper chamber volume) . [0065] Advantageously, the pneumatic cylinder-piston units 39 are supplied by a pneumatic circuit 40 such as to supply air and/or gas at the lower chamber 39' . In this manner, the piston 38 results to be suspended on the air and/or gas volume inside the lower chamber 39' , thus implementing the compensation effect. Air and/or gas are preferably collected in a reservoir 68 connected to the pneumatic cylinder-piston units. [0066] Still more advantageously, the pneumatic circuit 40 is adapted to be kept closed, that is to be kept in such a configuration that the air and/or gas amount present therein (and in the cylinder 39 lower chamber 39' ) keeps being substantially constant. This particular embodiment implements particularly the advantageous characteristic according to which the reaction forces acting on the gripping unit increase as the gripping unit approaches to the lowered position thereof. In fact, the air and/or gas amount being constant, as the gripping unit 12 lowers, the cylinder 39 lower chamber 39' volume decreases, consequently the pressure therein increases. Due to the lower chamber positioning, on which chamber the piston 38 is suspended, such pressing action translates into forces along the stacking/destacking direction I/D facing the lifted position acting on the piston 38, which in turn acts on the gripping unit 12. [0067] As it shall be apparent to those skilled in the art, the compensation effect can be also implemented in other ways. For example, the compensation can occur through elastic means, for example, mechanical springs (not shown in the Figures), or the like.

[0068] In accordance with a possible embodiment, the gripping unit 12 weight compensation means 35 .comprise means 41 for the adjustment of the supply circuit 40 overall volume. In other words, given an air and/or gas amount present in the supply circuit 40 (and the cylinder 39 lower chamber 39' ) and the cylinder 39 lower chamber 39' volume (that is, the piston 38 position) , the adjustment means 41 are capable of changing the air and/or gas volume hold in the supply circuit and the lower chamber 39' . Therefore, the adjusting means 41 of the supply circuit 40 volume implement the means for the adjustment of the trend of the compensation forces acting on the gripping unit described above. In fact, a decrease in the air and/or gas volume involves a pressure increase, particularly in the lower chamber 39' , while a volume increase involves a decrease of such pressure. Therefore, an adjustment of the supply circuit 40 volume affects the pressure in the cylinder 39 lower chamber 39' , which, in turn, affects the intensity of the compensation forces acting on the gripping unit 12. [0069] The adjusting means 41 for the supply circuit 10 volume can be implemented according to a plurality of ways. According to a possible embodiment, the adjusting means 41 comprise a compensator-actuator 42, for example, a linear cylinder 43, in which it is possible to change the volume of a chamber 45 communicating with the same supply circuit 40 by moving a piston 44. The piston 44 can be, in turn, actuated by an external actuating means 46, for example, by an electrical actuator.

[0070] In alternative or in addition to the means 41 for the adjustment of the supply circuit overall volume, the weight compensation means 35 can provide adjusting means (not shown in the Figures) for the air/gas amount within the supply circuit. The volume being kept constant, in fact, as the air/gas amount increases, also the pressure of the latter increases, and vice versa. Such means can be, for example, so shaped as to suck and/or discharge air/gas from the external environment.

[0071] It shall be important to note that the gripping unit 12 weight compensation means 35 and the embodiment variations described heretofore can be advantageously also provided in stacking/destacking machines in which the handling means have a different configuration compared to the one which has been described. Particularly, the compensation means 35 can be provided also in the absence of the guide means 25 (and possible embodiments thereof) and/or in the absence of the flexible connection means 26 (and embodiment variations thereof) so shaped as to support the gripping unit without substantially exert pushing actions thereon facing the lowered position. [0072] Advantageously, the stacking/destacking machine 1 comprises means 47 for the compensation of the nippers 13 weight, that is, means which are adapted to exert compensation forces opposite the weight forces of the same nippers. In this manner, it is possible to minimize the nippers bulk weight in the event they meet obstacles during the gripping unit descending movement. The bulk weight notion is to be meant in the sense already explained before with reference to the gripping unit bulk weight in the whole, therefore it will not be reaffirmed herein. [0073] According to a possible embodiment, the nippers weight compensation is performed by the gripping unit 12 weight compensation means 35. In fact, it shall be apparent that such means 35, by acting on the gripping unit 12 on the whole, also act on the nippers. Such solution is advantageous, for example, in the case that the nippers are fixed relative to the gripping frame 20, but can be usefully adopted also in the case such nippers are mobile relative to it according to what has been described before. [0074] In alternative or in addition, the nippers 13 weight compensation means 47 can be so shaped as to act between the same nippers 13 and the gripping frame 20

(Figures 7-11, and Fig. 17) . In this manner the means 47 compensation action finds expression substantially only on the nippers, not on the gripping unit on the whole.

[0075] Advantageously, the nippers 13 weight compensation means 47 are so shaped that the nippers 13 weight compensation forces decrease following the gripping frame 20 relative movements relative to the nippers 13 towards the lowered position. In order to better understand this aspect, it shall be considered the following case. Under standard conditions, during the gripping unit 12 lowering movement, gripping frame 20 and nippers 13 lower in a substantially integral manner. But, if one or more of the nippers 13 contact an obstacle, the gripping unit keeps the lowering motion thereof, while such nippers, blocked by the obstacle, remain substantially steady in an absolute position, but perform a relative movement towards the raised position relative to the gripping frame. At the point when the nippers meet the obstacle, the latter is subjected to the nippers bulk weight, which bulk weight, due to the configuration of the nippers weight compensation means, increases as the gripping frame continues the motion thereof towards the lowered position, therefore when the impact has already occurred.

[0076] In accordance with a possible embodiment, the nippers 13 weight compensation means 47 comprise at least one pneumatic cylinder-piston unit 48 preferably for each nipper 13, in which a piston 49 is slidable within a chamber 69 defined by a cylinder 50 according to a sliding direction which is substantially parallel to the stacking/destacking direction I/D. The piston 49, given the orientation thereof, splits the cylinder 50 chamber 69 into a lower chamber 69' and an upper chamber 69' ' (the terms "lower" and "upper" are to be meant according to what has been already stated before ⁾ . Therefore, a piston 49 lowering translates in a decrease of the lower chamber 69' volume (and an increase of the upper chamber 69' ' volume) , while a rising of the piston 49 towards the raised position translates into an increase of the lower chamber 69' volume (and a decrease of the upper chamber 69' ' volume) . Advantageously, the pneumatic cylinder-piston units 48 of the nippers 13 are supplied _ by a pneumatic supply circuit 70 such as to supply air and/or gas at the lower chamber. In this manner, the piston 49 results to be suspended on the air and/or gas volume, which thus performs the compensation action. [0077] Still more advantageously, the pneumatic supply circuit 70 is adapted to be kept closed, that is to make so that the air and/or gas amount present therein (and in the lower cylinder 50 chamber 69' ) keeps being substantially constant. This particular embodiment implements, particularly, the advantageous characteristics according to which the reaction forces action on the nippers decrease as the gripping frame lowers relative to the nippers. In fact, advantageously, the pneumatic cylinder-piston units 48 are associated to the gripping frame 20 and the nippers 13 in such a manner that, during the gripping unit 12 movements towards the lowered position, the lower chambers 69' volumes increase in the presence of obstacles 71 which oppose the nippers movement, such as to make so that the gripping frame performs relative movements towards the lowered position relative to the nippers (such aspect is schematically illustrated in Fig. 17) . Therefore, being the air and/or gas amount constant when the supply circuit 70 is kept closed, as the gripping frame 20 lowers relative to the nippers 13, in the presence of the obstacle 71 the piston 49 rises, the cylinder 50 lower chamber 69' volume increases, and consequently the pressure inside the lower chamber 69' decreases. Given the lower chamber orientation, such pressing action translates into vertical forces facing the lifted position acting on the piston 49, which therefore implements the variable compensation of the nipper 13 weight . [0078] In accordance with a possible embodiment, the nippers 13 comprise a fixed plate 51 and a mobile plate 52 (Figures 7-11) . The fixed plate 51 is rigidly connected to the gripping frame 20, for example, by means of screws, while the mobile plate 52 is rigidly connected to a trolley 56 which is slidable relative to a track 54 arranged in a seat 55 obtained in the fixed plate 51 and secured thereto. The gripping arms 14 are connected to the mobile plate 51, as well as the cylinder-pneumatic piston unit 15 controlling them. In this manner, when the gripping arms 14 meet an obstacle during the gripping unit lowering movement, they move towards the lifted position relative to the gripping frame 20, thus dragging the mobile plate 52, which therefore slides relative to the fixed plate 51, which is in turn integral to the gripping frame 20. [0079] Advantageously, the cylinder 50 of the cylinder- piston unit 48 which carries out the nippers 13 weight compensation is connected to the fixed plate 51, while the piston 49 of the same cylinder-piston unit 48 is connected to the mobile plate 52. In this manner, the mobile plate 52 relative movement relative to the fixed plate 51 translates into a movement of the piston 49 in the cylinder 50. The connection between mobile plate 52 and piston 49 can be implemented, for example, via a cross connecting plate 57 secured to the mobile plate 52 and connected to the piston 49 so as to at least partially follow the movements thereof. Of course, as it shall be apparent to those of ordinary skill in the art, further possible connection forms between nippers weight compensation means, nippers, and gripping frame are possible in order to achieve the same technical effect. [0080] According to a possible embodiment, the tracer point 18 is mobile relative to the mobile plate 52. To this aim it can be, for example, connected to a trolley 59 slidable relative to a track 60 secured to the mobile plate 52. The connection between trolley 59 and tracer point 18 preferably takes place via an intermediate plate 61, which thereby results to be mobile relative to the mobile plate 52. Advantageously, the sensing means 19 of the tracer point 18, described above, are connected to the mobile plate 52 and the intermediate plate 61, so as to be able to detect the relative movements between tracer point 18 and mobile plate 52. Alternatively, the sensing means 19 will be able to be connected to the fixed plate 51 instead to the mobile plate 52, thereby detecting the relative movements between tracer point 18 and fixed plate 51, therefore between tracer point 18 and gripping frame 20. [0081] It shall be noted that the nippers 13 weight compensation means 47 and the embodiment variations thereof described heretofore can be advantageously provided also in stacking/destacking machines in which the handling means have different configurations compared to those described. Particularly, the compensation means 35 can be provided also in the absence of the guide means 25 (and possible embodiments thereof) , and/or in the absence of the flexible connection means 26 (and embodiment variations thereof) which are so shaped as to support the gripping unit without substantially exerting pushing actions thereon, which face the lowered position. Furthermore, as already stated, the nippers 13 weight compensation means 47 can be provided as an alternative or in addition to the gripping unit 12 weight compensation means 35. [0082] Advantageously, the stacking/destacking machine 1 is so provided that the gripping unit 12 is capable of performing comb-inserting and comb-withdrawing movements. By comb-inserting and comb-withdrawing movements is meant a movement of the gripping unit along a comb-inserting/comb-withdrawing direction P/D suitable to insert/withdraw the strips into special combs 62 arranged on the side walls of the baskets (Figures 12- 13) . Such combs 62 comprise a plurality of projecting arms 63 so arranged as to define seats 64 between consecutive arms, in which the strips can be inserted. This makes for example possible the stacking in the same basket of more strips one upon the other, therefore also of the profiles supported by the latter.

[0083] The comb-inserting and comb-withdrawing motions preferably occur in orthogonal planes to the stacking/destacking direction I/D. When the strip 4, supported by the nippers 13, is at a predetermined height, which can be obtained by acting on the handling means 24, it is inserted in the corresponding seats 64 of the combs 62. Instead, when the strip 4 has to be destacked, it is drawn from the seat 64, then unconstrained by the basket 2.

[0084] In order to make so that the gripping unit 12 performs such comb-inserting/comb-withdrawing motions, the stacking/destacking machine 1 comprises special comb-inserting/comb-withdrawing means 65 (Figures 14- 15) . Advantageously, such means 65 comprise pneumatic actuating members.

[0085] According to a possible embodiment, the comb- inserting/comb-withdrawing means 65 comprise a first 66 and a second 67 pneumatic comb-inserting cylinder-piston units preferably arranged in series. Such first 66 and second 67 comb-inserting/comb-withdrawing cylinder- piston units are so arranged as to be able to move together with the gripping unit 12 in the movements thereof between lifted position and lowered position along the stacking/destacking direction I/D, and are so oriented as to be able to transversally move the same gripping unit 12 to the stacking/destacking direction I/D along the comb-inserting/comb-withdrawing direction P/D. [0086] The arrangement in series of the first and the second cylinder-piston units has a plurality of advantages .

[0087] A first advantage is the possibility of combining the movements of the two cylinder-piston units so as to accurately reach a plurality of preset positions, corresponding to the respective stop positions as well as combinations thereof. Particularly, it is possible to accurately reach three operative positions, respectively indicated with B, C, and D in Fig. 13. Such positions can be, for example, 'reached by completely withdrawing the piston of the first, second, and both cylinder piston units, respectively. [0088] A further advantage is the possibility of carrying out a .compensation of the forces which the nippers would exert on an optional obstacle in the comb-inserting movement, which could cause an accidental and undesired opening of the gripping arms 14, therefore the strip slipping-off . Such compensation can be. achieved, for example, by supplying the first and/or second cylinder- piston units with supply circuits capable of being kept closed, according to modes similar to those described with reference, for example, to the cylinder-piston units 37 lower chamber for the gripping unit 12 weight compensation. [0089] From the description given before, those skilled in the art will be able to appreciate how the stacking/destacking machine according to the invention allows obtaining an increased safety and reliability. In fact, thanks to the presence of the flexible connection means and the guide means, it is possible to drive the gripping unit along the stacking/destacking direction substantially without the transmission of the forces, originating from optional impacts against accidental obstacles, to the trolley and the main supporting structure. Therefore, the machine is extremely adaptable to unexpected situations, and has such a configuration as not to undergo undue damages even in the presence of abnormal events. [0090] Furthermore, those skilled in the art will be able to appreciate how the provision of the gripping unit weight compensation means makes the stacking/destacking machine according to the invention safer and more reliable, since such means minimize the risk of breakings of the gripping unit in the event of accidental impacts against undesired obstacles during the movements along the stacking/destacking direction. [0091] Finally, those skilled in the art will be able to appreciate how the safety and reliability of the stacking/destacking machine according to the invention are further increased by the advantageous presence of the nippers weight compensation means.

[0092] To the embodiments described above, those skil-led in the art, to the aim of meeting contingent, specific needs, will be able to make a number of modifications, additions, or replacements of elements with functionally equivalent others, without anyhow departing from the scope of the annexed claims.

[0093] Each of the characteristics described as belonging to an embodiment can be implemented independently from the other embodiments described.