FIELD OF INVENTION 
       [0001]    This invention concerns a palletising device, that is, an automatic device for stacking wrapped products, for example bottle packs, on pallets. 
       BACKGROUND 
       [0002]    A known palletising device comprises two operating platforms, one of which is superposed over the other, the upper platform being situated along a conveyor line of the products to be palletised, while the lower platform is situated along a line conveying pallets. 
         [0003]    The lower platform is associated to an elevator group which vertically moves the platform between a lowered position, in which the platform receives an empty pallet from the conveyor line, and a raised position, in which the platform positions the pallet at a short distance beneath the upper platform. 
         [0004]    The upper platform comprises support means having a variable configuration, typically a shutter, which can be shifted by activating means between a closed configuration, in which the support means provide a loading surface which restingly supports the products to be palletised, and an open configuration, in which the support means remove their support, thus allowing the products to fall downwardly under gravity. 
         [0005]    When the support means are in a closed configuration, the products to be palletised are loaded on the loading surface horizontally, such as to form a layer of grouped products, after which the support means are brought into an open configuration, so that the layer of products rests directly on the pallet which is borne by the underlying lower platform. 
         [0006]    At this point, the lower platform is lowered by an amount which is substantially the same as the height of the products collected together on the pallet, and the support means of the upper platform are brought back to a closed configuration, in order to be able to receive another layer of products. 
         [0007]    This cycle is repeated several times, until a complete stack of products is formed on the pallet. 
         [0008]    When the operations are terminated, the lower platform is brought back to the initial lowered position, so that the completely loaded pallet can be removed from the conveyor line and sent towards further operating stations, the completely loaded pallet being replaced by an empty pallet. 
         [0009]    A drawback of this device arises from the fact that during the removal of the loaded pallet, and its replacement with a fresh empty pallet, the lower platform has to remain constantly in a lowered position, which makes it impossible to commence a new stacking phase. 
         [0010]    The document DE 28 08 129 discloses a device in which an intermediate platform is provided between the upper platform and the lower surface, the intermediate platform being associated to activating means which shift it between two fixed positions, namely a raised position under the upper platform and a lowered position over the lower surface on which the pallet is located, and vice versa. The intermediate platform is not suitable for receiving progressively the layers of products resting one on the other. 
         [0011]    As a result, these operating phases can only be performed in a strictly sequential way, which means that a somewhat long overall time is necessary in order to terminate the palletising operation. 
       SUMMARY 
       [0012]    The aim of this invention is to obviate the above-mentioned drawback, by making available a palletising device which is of the type delineated above, but which operates in an overall more rapid way, thus increasing its productivity. 
         [0013]    A further aim of the invention is to achieve the above-mentioned aim within the ambit of a simple, rational and relatively economical solution. 
         [0014]    These aims are achieved by the characteristics of the invention described herein below in independent claim  1 . The dependent claims delineate preferred and/or particularly advantageous aspects of the invention. 
         [0015]    In detail, the invention provides a palletising device comprising a lower surface which restingly receives a pallet, an upper platform provided with first variably-configurable support means, and relative activating means, which move the support means cyclically between a closed configuration, in which the support means define a support for a layer of products to be palletised, and an open configuration, in which the support means remove their support, thus releasing the layer of products downwardly. 
         [0016]    In the invention, an intermediate platform is interposed between the lower surface and the upper platform, the intermediate platform being associated to activating means which shift it between a raised position and a lowered position, and vice versa. 
         [0017]    The intermediate platform comprises second variably-configurable support means, and activating means which maintain the second support means in a closed configuration while the intermediate platform is shifting between the raised position and the lowered position, in which closed configuration the second support means define a support which progressively receives the layers of products released by the upper platform, thus forming a stack, the activating means shifting the support means to an open configuration when the intermediate platform reaches the lowered position, in which open configuration the support means remove their support, thus releasing the entire stack of products towards the underlying lower surface, and resting the stack of products on the pallet. 
         [0018]    In the palletising operation, thanks to this device, an empty pallet is initially loaded on the lower support surface, while the intermediate platform is arranged in the raised position. 
         [0019]    The products to be palletised are loaded on the upper platform horizontally, in such a way as to form a layer of grouped-together products on the first support means, which first support means are initially in a closed configuration. 
         [0020]    At this point, the first support means are opened, so that under gravity the layer of products rests on the second support means, which are in a closed configuration on the intermediate platform. 
         [0021]    The intermediate platform is then lowered by an amount which is substantially the same as the height of the collected products, after which the first support means of the upper platform are returned into the closed configuration in order to be able to receive another layer of products, and the cycle is repeated. 
         [0022]    In practice, the intermediate platform is shifted downwardly in discrete steps. Between each step and a subsequent step, the first support means of the upper platform are initially closed in order to receive a layer of products, and subsequently opened in order to release the layer of products on the second support means of the intermediate platform. 
         [0023]    In this way, as the intermediate platform gradually descends, the second support means collect a stack of products. 
         [0024]    When the stack is complete, the intermediate platform is arranged in a lowered position, and the second support means are opened so that the stack rests on the underlying pallet. 
         [0025]    At this point, with the second support means maintained in an open configuration, the intermediate platform can be raised towards the initial position, so as to start a new stacking phase, while the previously-loaded pallet is removed from the lower support surface and replaced with an empty pallet. 
         [0026]    In this way it is effectively possible to save time and consequently to obtain greater productivity. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Further characteristics and advantages of the invention will emerge, with the aid of the appended figures of the drawings, from the following detailed description which is provided by way of a non-limiting example. 
           [0028]      FIGS. 1 to 4  show a palletising device of the invention during four successive operating phases. 
           [0029]      FIG. 5  is an enlarged detail of  FIG. 2 . 
           [0030]      FIG. 6  is a plan view of the intermediate platform of the palletising device, in which the centring means have been hidden to highlight the support shutters. 
           [0031]      FIG. 7  is a view along section VII-VII of  FIG. 6 . 
           [0032]      FIG. 8  is a plan view of the intermediate platform of the palletising device, in which the support shutters have been hidden to highlight the centring means. 
           [0033]      FIG. 9  is the view indicated by reference numeral IX in  FIG. 8 . The device described herein palletises packs  100  of bottles, although this does not exclude it from being used for palletising other wrapped products. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0034]    Proceeding from the top downwards, the palletising device  1  comprises an upper platform  2 . 
         [0035]    As shown in  FIG. 5 , the upper platform  2  comprises a pair of oppositely-positioned vertical sides  20  (only one of which is visible), between which a shutter  21  is interposed. 
         [0036]    The shutter  21  can take on a closed configuration (shown in the figure), in which it makes a horizontal loading surface available which restingly supports the bottle packs  100 , and an open configuration (not shown), in which it leaves an open passage so as to allow the bottle packs  100  to descend under gravity. 
         [0037]    More in detail, the shutter  21  comprises two groups of horizontal support rollers, indicated by reference numerals  22  and  23  respectively, the opposite ends of which are associated to the links in two identical guide and support chains  24  (only one of which is visible), which are specular and oppositely positioned, and are respectively associated to the two vertical sides  20 . 
         [0038]    Each guide and support chain  24  lies in a vertical plane and is ring-wound around a set of respective cogged pinions. 
         [0039]    All the cogged pinions are connected together kinematically, in such a way that the motion of the two guide and support chains  24  is always synchronised and at the same speed. 
         [0040]    Along their extension, the guide and support chains  24  exhibit an upper outward advancement branch and a lower return advancement branch which move in opposite directions. 
         [0041]    Both the outgoing and the return branch follow a curvilinear trajectory which exhibits a horizontal central tract, such that the horizontal tract of the outgoing branch is in the same plane as, and is adjacent to, the horizontal tract of the return branch. 
         [0042]    The support rollers  22 , which are reciprocally parallel and close to each other, are attached along the horizontal tract of the forward branch, while the support rollers  23  are attached, reciprocally parallel and close to each other, along the horizontal tract of the return branch. 
         [0043]    In this way, the two groups of support rollers  22  and  23  take on a closed configuration, in which they are coplanar and close together, and in which they therefore define a single loading surface which supports the bottle packs  100 . 
         [0044]    Starting from this closed configuration, the guide and support chains  24  can be made to travel in the direction indicated by the arrow A, in such a way that the groups of support rollers  22  and  23  move further from each other in opposite directions until they reach an open configuration in which they leave an open passage beneath the bottle packs  100 . 
         [0045]    The guide and support chains  24  can then be made to travel from the open configuration in the opposite direction, thus bringing the groups of support rollers  22  and  23  back to the initial closed configuration. 
         [0046]    The guide and support chains  24  are driven by a single motor (of known type and therefore not shown) which sets in rotation at least one of the cogged pinions on which the chains are wound. 
         [0047]    The upper platform  2  is associated to an independently-driven conveyor belt  25 , which is coplanar with and close to the loading surface which is defined by the closed shutter  21 . 
         [0048]    The conveyor belt  25  conveys the bottle packs  100  towards the upper platform  2 , for example from a wrapping machine, locating them on-board the loading surface in groups. 
         [0049]    In order for each group of bottle packs  100  to be positioned in the centre of the loading surface, the upper platform  2  is further provided with a pusher organ  26 , which moves with a kind of stepped motion in which it shifts horizontally and rises and falls in a parallel direction to the direction of advancement of the conveyor  25 . 
         [0050]    During its forward travel, the pusher organ  26  is lowered to push an entire group of bottle packs  100  slidingly on the support rollers  22  and  23  until they stop against an end stop element  27 . 
         [0051]    During its return travel, the pusher organ  26  is raised, thus enabling the bottle packs  100  coming from the conveyor belt  25  to pass beneath it. 
         [0052]    The pusher organ  26  is driven by motor means of a known type which are not shown. 
         [0053]    The palletising device  1  further comprises an intermediate platform  3 , which is coupled with at least one guide column  4  and is associated to elevator means (of known type and therefore not shown) which vertically move the intermediate platform  3  from a raised position towards a lowered position and vice versa. 
         [0054]    As shown in  FIG. 6 , the intermediate platform  3  comprises two vertical, oppositely-positioned sides  30  between which an empty space is defined which is occupied by a first shutter  31  and a second shutter  32 . 
         [0055]    The shutters  31  and  32  can take on an overall closed configuration (shown in the figure), in which they define a single horizontal loading surface which fills the empty space between the vertical sides  30  in order to support the bottle packs  100  which thus rest on them, and an open configuration (not shown), in which they leave an open passage, thus allowing the bottle packs  100  to descend under gravity. 
         [0056]    In more detail, the first shutter  31  comprises a group of support rollers  33 , which are horizontal and close together, opposite ends of which are associated to the links of two support chains  34 , which support chains  34  are identical, specular and oppositely positioned to each other and are respectively associated to the two vertical sides  30 . 
         [0057]    As shown in  FIG. 7 , the support chains  34  are open-ended, and are singly coupled to a guide rail  35  which constrains them to wind around a cogged pinion  36  and to travel in a vertical plane along a trajectory which includes a horizontal upper tract. 
         [0058]    The support chains  34  are moved by a single motor  37  which sets the two cogged pinions  36  in rotation, which are kinematically connected to a drive shaft  38  (see  FIG. 6 ), such that the motion of the two support chains  34  is always synchronised and at the same speed. 
         [0059]    The support rollers  33  are attached, parallel and close to each other, along the end portions of the support chains  34 , such as to be coplanar at the upper horizontal tract of the guide rail  35 . 
         [0060]    The second shutter  32  is structurally alike to the first shutter  31 , to which it is substantially specular. 
         [0061]    In more detail, the second shutter comprises a group of support rollers  39 , which are horizontal and parallel, opposite ends of which are associated to links of two support chains  40  which are identical, specular and oppositely positioned to each other, and respectively associated to the two vertical sides  30  of the intermediate platform  3 . 
         [0062]    Each support chain  40  is coupled to a guide rail  41  which makes the chain wind around a cogged pinion  42  and travel in a vertical plane along a trajectory comprising a horizontal upper tract. 
         [0063]    The support chains  40  are activated by a single motor  43  which sets the two cogged pinions  42  in rotation, which are kinematically connected to a drive shaft  44 , such that the motion of the two support chains  40  is always synchronised and at the same speed. 
         [0064]    The support rollers  39  are attached, parallel and close to each other, along the end portions of the support chains  40 , in such a way that the support rollers  39  are coplanar at the upper horizontal tract of the guide rails  41 . 
         [0065]    As clearly shown in  FIG. 7 , the horizontal tract of the guide rails  41  is aligned with the horizontal tract of the guide rails  35  of the first shutter  31 , so that the two groups of support rollers  33  and  39  can be shifted closer together in order to reach a closed configuration in which they define a single loading surface which supports the bottle packs  100 . 
         [0066]    Starting from this closed configuration, and by means of simultaneous travel of the support chains  34  and  40  in opposite directions, the groups of support rollers  33  and  39  can be shifted away from each other until an open configuration is achieved in which the support rollers  33  and  39  leave an open passage centrally beneath the bottle packs  100 , and subsequently, the support  33  and  39  rollers can be brought back to a closed configuration via inverse travel. 
         [0067]    The intermediate platform  3  further comprises means for centring the bottle packs  100  on the loading surface defined by the shutters  31  and  32  in a closed configuration. 
         [0068]    As shown in  FIGS. 8 and 9 , the means for centring comprise two parallel and oppositely-positioned flat pusher bars  45 , which rest on the upper horizontal edges of the vertical sides  30 , therefore at a slightly higher level with respect to the closed shutters  31  and  32 . 
         [0069]    The pusher bars  45  can move horizontally closer to and further from each other, thus enabling them to tightly grip the bottle packs  100  resting on the shutters  31  and  32 . 
         [0070]    The horizontal motion is powered by a single drive motor  46  which activates a second chain  48  by means of a first drive chain  47  (see  FIG. 9 ). 
         [0071]    The second chain  48  lies in a vertical plane externally to one of the vertical sides  30  of the intermediate platform  3 , and is ring-wound on two cogged pinions, in such a way that it exhibits two horizontal branches, an upper outward advancement branch and a lower return advancement branch, which travel in opposite directions. 
         [0072]    The pusher bars  45  are connected to the second chain  48  via a respective bracket  49 . One bracket  49  is attached to the links of the chain  48  on the outgoing advancement branch, while the other bracket  49  is attached to the links of the chain  48  on the return advancement branch. 
         [0073]    In this way, following a movement of the chain  48  in direction B, the pusher bars  45  move closer to each other, while when the chain travels  48  in the opposite direction, the pusher bars  45  move away from each other. 
         [0074]    As shown in  FIG. 1 , when the intermediate platform  3  is in a raised position, the loading surface defined by the shutters  31  and  32  is at a short distance beneath the loading surface defined by the shutter  21  of the upper platform  2 . 
         [0075]    Instead, when the intermediate platform  3  is in a lowered position (see  FIG. 3 ), the distance between the loading surface defined by the shutters  31  and  32  and the loading surface defined by the shutter  21  is greater than the maximum height of an entire stack of bottle packs  100 . 
         [0076]    The palletising device  1  further comprises a lower platform  5 , which is vertically aligned with the previously-mentioned platforms and is arranged beneath the intermediate platform  3 . 
         [0077]    The lower platform  5  comprises a motorised roller plane  50  which defines a loading surface for a pallet  101 , and is associated to an elevator group (of known type), which moves it vertically between a lowered position and a raised position. 
         [0078]    When the lower platform  5  is a lowered position, the motorised roller plane  50  is coplanar with a motorised loading roller plane  60  and a motorised unloading roller plane  70 , together with which the motorised roller plane  50  defines a conveyor line for the pallets  101 . 
         [0079]    In detail, the loading roller plane  60  advances empty pallets  101  towards the lower platform  5 , while the unloading roller plane  70  removes the pallets  101  which are already loaded with bottle packs  100  from the lower platform  5 . 
         [0080]    Naturally the roller plane  50 , like the roller units  60  and  70 , can be replaced by other types of motorised conveyors. 
         [0081]    The functioning of the palletising device  1  is as follows. The shutter  21  of the upper platform  2  is initially in a closed configuration, thus defining the loading surface which supports the bottle packs  100 . 
         [0082]    Contemporaneously, the intermediate platform  3  is in a raised position, with the shutters  31  and  32  in closed configuration in turn defining the loading surface which supports the bottle packs  100 . 
         [0083]    In the meantime, an empty pallet  101  is loaded onto the motorised roller plane  50  of the lower platform  5 , the lower platform  5  then being shifted from the lowered position into the raised position. 
         [0084]    At this moment, the conveyor belt  25  advances the bottle packs  100  towards the upper platform  2 , in such a way that the pusher organ  26  can form a layer of bottle packs  100  grouped together at the centre of the closed shutter  21  (see  FIG. 1 ). 
         [0085]    Subsequently the shutter  21  of the upper platform  2  is opened, in such a way that the layer of bottle packs  100  comes to rest under gravity on the closed shutters  31  and  32  of the intermediate platform  3 . 
         [0086]    In this phase the pusher bars  45  are also activated so that they tightly grip the just-deposited layer of bottle packs  100 , centring the layer of bottle packs and ensuring that it is more stable. 
         [0087]    With the shutters  31  and  32  closed, the intermediate platform  3  is subsequently lowered by an amount which is substantially the same as the height of the bottle pack  100 , after which it is halted for a certain period of time. 
         [0088]    During this time, the shutter  21  of the upper platform  2  is first closed again, so that the conveyor belt  25  and the pusher organ  26  can form a new layer of bottle packs  100  upon it, and is then reopened, such as to release the new layer of bottle packs  100  onto the earlier deposited layer. Subsequently the lower platform  3  is lowered again and the cycle is repeated. 
         [0089]    In other words, the shutter  21  of the upper platform  2  closes and opens cyclically, each time releasing a layer of bottle packs  100  on the closed shutters  31  and  32  of the underlying intermediate platform  3 , which moves downwardly after each release phase, until it has collected an entire stack of bottle packs  100  (see  FIG. 2 ). 
         [0090]    When the stack of bottle packs  100  is complete (see  FIG. 3 ), the intermediate platform is brought into a lowered position, while the lower platform  5  is in a raised position, in such a way that the empty pallet  101  is positioned at a short distance beneath the shutters  31  and  32 , which are still closed. 
         [0091]    At this point, the shutters  31  and  32  are opened, thus allowing the entire stack of bottle packs  100  to come to rest under gravity on the pallet  101  borne by the lower platform  5 . 
         [0092]    Note that the movement of the lower platform  5  from the lowered to the raised position is rather small, and has the sole function of arranging the pallet  101  sufficiently near to the shutters  31  and  32  for it to be able to receive the stack of bottle packs  100  in a shock-free way. 
         [0093]    After the release operation, and keeping the shutters  31  and  32  open in order to prevent interference with the stack of bottle packs  100 , the intermediate platform  3  is moved towards a raised position in order to repeat the palletising operation (see  FIG. 4 ). 
         [0094]    Meanwhile, the lower platform  5  moves to a lowered position, and when the intermediate platform  3  is completely free of the stack of bottle packs  100 , the motorised roller units  60 ,  50  and  70  are set in motion so that the pallet  101  which is loaded with bottle packs  100 , is moved away from the lower platform  5 , its place being taken by an empty pallet  101 . 
         [0095]    From the above description, it is clear that the operations of stacking the bottle packs  100  on the intermediate platform  3  and transferring the pallets  101  from and towards the lower platform  5  are carried out in an at least partially contemporaneous way, thus saving time and obtaining greater productivity. 
         [0096]    Obviously the palletising system described above can be the object of numerous technical/applicational modifications, without thereby forsaking the ambit of the invention as claimed herein below.
A palletising device including a lower surface which restingly receives a pallet, and an upper platform which is provided with a variably-configurable first support, cyclically between a closed configuration in which the first support supports a layer of products and an open configuration in which the layer of products is released downwardly; an intermediate platform between the lower surface and the upper platform, which move between a raised position and a lowered position and vice versa, comprising a variably-configurable second support which, maintain the second support in a closed configuration, thus forming a stack, and which release the stack of products towards the underlying lower surface in an open configuration.