Abstract:
A method and device for picking up stacks of blanks, whereby the stacks, arranged in at least one layer on a separating sheet having a peripheral portion projecting outwards of the layer, are removed successively by a pickup member, a free end of which is pressed onto the separating sheet in a position facing a stack for removal, and is then slid in a given pickup direction, and in contact with the separating sheet, beneath the stack for removal; a portion, crosswise to the pickup direction and facing the pickup member, of the peripheral portion of the separating sheet is clamped in position both crosswise to its plane and in the pickup direction by a gripping device before and during removal of the stacks.

Description:
[0001]    The present invention relates to a method of picking up stacks of blanks.  
           [0002]    More specifically, the present invention relates to a method of picking up stacks of blanks to transfer, one at a time, a given number of stacks stacked on a pallet to a cigarette packing machine, to which the following description refers purely by way of example.  
         BACKGROUND OF THE INVENTION  
         [0003]    In the tobacco industry, a number of stacks of blanks are arranged on a pallet in a number of superimposed layers, each of which is separated from each adjacent layer by a separating member, normally a sheet of cardboard or similar, and the stacks in each layer are picked up successively by a pickup member comprising an articulated fork, a free end of which is pressed down, facing the stack to be picked up, on the underlying separating member to deform the separating member slightly downwards. The free end of the fork, still pressing down on the separating member, is then fed towards the stack to be picked up, so as to insert the fork underneath the stack. In the course of the above operations, the fork is rotated, about an axis parallel to the plane of the separating member, between an initial-contact position in which the fork slopes downwards towards the separating member, and a pickup position in which the fork is substantially parallel to the separating member.  
           [0004]    The above pickup method is normally efficient and accurate, and only poses problems when the speed of the fork exceeds a given threshold, over and above which the fork tends to crumple and/or pierce the separating member.  
         SUMMARY OF THE INVENTION  
         [0005]    It is an object of the present invention to perfect the above method by providing a method of picking up blanks, designed to eliminate the aforementioned drawback.  
           [0006]    According to the present invention, there is provided a method of picking up stacks of blanks as claimed in claim 1 and, preferably, in any one of the claims dependent directly and/or indirectly on claim 1.  
           [0007]    The present invention also relates to a device for picking up stacks of blanks.  
           [0008]    According to the present invention, there is provided a device for picking up stacks of blanks as claimed in claim 7 and, preferably, in any one of the claims dependent directly and/or indirectly on claim 7. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which:  
         [0010]    [0010]FIG. 1 shows a schematic side view of a preferred embodiment of the pickup device according to the present invention;  
         [0011]    [0011]FIG. 2 shows a larger-scale view of a first detail in FIG. 1;  
         [0012]    [0012]FIGS. 3 and 4 show larger-scale rear and plan views respectively of a second detail in FIG. 1;  
         [0013]    [0013]FIG. 5 shows a section along line V-V in FIG. 3 of the FIG. 3 detail in two distinct operating configurations;  
         [0014]    [0014]FIG. 6 shows a section along line VI-VI in FIG. 3 of the FIG. 3 detail in two distinct operating configurations;  
         [0015]    [0015]FIG. 7 shows a section along line VII-VII in FIG. 4;  
         [0016]    [0016]FIG. 8 shows a larger-scale view of a variation of a detail in FIG. 7;  
         [0017]    FIGS.  9  to  13  show schematic views, with parts removed for clarity, of the FIG. 1 device in a succession of operating positions. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]    Number  1  in FIG. 1 indicates as a whole a pickup device for successively picking up stacks  2  of blanks off a pallet  3  resting on a substantially horizontal platform  4 , which is supported on a base frame  5  and is movable, with respect to frame  5 , in a substantially vertical direction  6 . Stacks  2  are arranged on pallet  3  in a number of superimposed layers  7 , each of which is separated from the underlying layer  7  by a separating sheet  8  normally made of cardboard or similar, and a peripheral portion  9  (FIG. 4) of which projects outwards of the periphery of layers  7 . As shown more clearly in FIGS. 1 and 4, in each layer  7 , stacks  2  are arranged in a number of parallel rows  10  in a direction  11 .  
         [0019]    With reference to FIG. 1, pickup device  1  comprises a pickup assembly  12  facing a portion  9   a , crosswise to direction  11 , of peripheral portion  9  of each separating sheet  8 . Pickup assembly  12  comprises an articulated fork  13  which projects, in direction  11  and by a length similar to the length of a stack  2  in direction  11 , from one end of a connecting rod  14 , which is movable in a plane parallel to direction  11 , and the opposite ends of which are hinged to two cranks  15  and  16  in turn hinged to a carriage  17  powered to run, under the control of a logic unit not shown, along an overhead rail  18  parallel to direction  11 . Carriage  17  houses a known drive unit (not shown) which, under the control of said logic unit (not shown), operates cranks  15  and  16  independently to move articulated fork  13  and possibly also adjust its tilt with respect to a horizontal plane.  
         [0020]    Pickup device  1  also comprises a stabilizing device  19  for keeping each separating sheet  8  taut and substantially undeformed when, as explained in detail later on, separating sheet  8  is engaged by fork  13  of pickup assembly  12 .  
         [0021]    With reference to FIG. 1, stabilizing device  19  comprises a rocker arm  20  positioned substantially vertically between pickup assembly  12  and platform  4 , and pivoting on a horizontal pin  21 , which is perpendicular to direction  11  and supported in a fixed position on frame  5 . Rocker arm  20  comprises a bottom arm  22  and a top arm  23 , and is fitted, between arms  22  and  23 , with a bracket  24  projecting towards platform  4  from rocker arm  20  and connected at the free end to the end of a spring  25  extending downwards and stretched between bracket  24  and a point on frame  5 , so as to normally push top arm  23  towards platform  4 , and in particular towards a pallet  3  resting on platform  4 . The bottom end of bottom arm  22  is positioned laterally contacting the free end of an output rod  26  of a linear actuator  27 , which is supported by frame  5  in a horizontal position parallel to direction  11  and on the opposite side of bottom arm  22  to platform  4 .  
         [0022]    As shown more clearly in FIG. 5 a , top arm  23  is closed at the top end by a plug  28 , through which a pin  29 , having an axis  30  of rotation coaxial with top arm  23 , is fitted in rotary and axially fixed manner and connects top arm  23  in axially fixed manner to a head  31  rotating idly about axis  30 . Head  31  supports at the top end (FIG. 1) supporting and clamping means  32  defined by a gripping device  32 , which comprises a movable top jaw  33 , and a feeler  34  defining a substantially fixed bottom jaw of gripping device  32 .  
         [0023]    As shown more clearly in FIGS. 3, 4 and  7 , feeler  34  comprises a supporting member defined by an L-shaped apron  35  fitted to the top of head  31  to oscillate, with respect to head  31 , about a substantially horizontal axis  36  crosswise to both axis  30  and direction  11 . More specifically, apron  35  comprises a plate  37  substantially perpendicular to axis  30 , at least as wide as pallet  3 , and for supporting portion  9   a  of peripheral portion  9  of a separating sheet  8 . On the underside surface facing the top of head  31 , plate  37  is fitted with an arm  38 , which is perpendicular to plate  37 , is traversed by axis  36 , and penetrates inside head  31  so that a bottom-end portion contacts a substantially horizontal spring  39  crosswise to axis  30  and tensioned between arm  38  and a lateral wall  40  of head  31 . Spring  39  controls the movement of platform  4  in direction  6  and pushes arm  38  towards platform  4  and against both a stop sensor  41 , which detects the movements of arm  38  in opposition to spring  39 , and a stop  42  on top of head  31 . Apron  35  also comprises a number of teeth  43  extending downwards from plate  37  and equally spaced along an edge of plate  37  facing platform  4 .  
         [0024]    In the FIG. 8 embodiment, each tooth  43  has contact rollers  44  mounted for rotation about respective axes parallel to axis  36 .  
         [0025]    Top jaw  33  of gripping device  32  comprises an actuating device  45 , in turn comprising a shaft  46  parallel to axis  36  and mounted for rotation through head  31 ; a number of cranks  47  (only one shown) fitted to shaft  46 ; and a number of rocker arms  48  (only one shown) pivoting about axis  36 . Each rocker arm  48  comprises an arm  49  facing platform  4 ; and an arm  50  hinged to a respective connecting rod  51 , the small end of which is connected in rotary manner to the free end of a respective crank  47 . Members  46 - 51  define a transmission  52  controlled by a piston  53 , which is parallel to top arm  23  of rocker arm  20 , is supported by rocker arm  20 , and has an output rod  54  connected by a connecting rod  55  to the end of a further crank  56  fitted to shaft  46 .  
         [0026]    Top jaw  33  also comprises a number of fork members  57 , each of which is connected to arm  49  of a respective rocker arm  48 , is substantially U-shaped, and in turn comprises two arms  58  facing platform  4 , extending over plate  37 , and separated by a distance greater than the width of fork  13 .  
         [0027]    In actual use, once pallet  3  is placed on platform  4  maintained in the lowered position shown in FIG. 1, platform  4  is raised in direction  6  to position the second layer  7  from the top—indicated  7   a —facing feeler device  34  (FIG. 9). More specifically, platform  4  is raised until the separating sheet  8 —indicated  8   a —interposed between layer  7   a  and the top layer  7 —indicated  7   b —is positioned just slightly higher than plate  37 , the teeth  43  of which are kept detached from the lateral surface of the facing layer  7   a  by output rod  26  of linear actuator  27  acting on bottom arm  22  of rocker arm  20  in opposition to spring  25 .  
         [0028]    Rod  26  is then withdrawn (FIG. 10) so that teeth  43  of feeler device  34  contact the facing lateral surface of layer  7   a . In this connection, it should be pointed out that any lack of parallelism between the lateral surface of layer  7   a  and the surface of teeth  43  is compensated for by head  31  rotating about axis  30 .  
         [0029]    All the above operations are performed with gripping device  32  in the open position.  
         [0030]    Platform  4  is then lowered (FIG. 11) so that plate  37  contacts the underside surface of portion  9   a  of peripheral portion  9  of the separating sheet  8  interposed between layers  7   a  and  7   b  and marked  8   a . Which contact rotates the whole of apron  35  slightly about axis  36  and in opposition to spring  39 , so that plate  37  contacts stop  42  and activates sensor  41 , which stops platform  4  in the operating position shown in FIG. 11, in which portion  9   a  of peripheral portion  9  of separating sheet  8   a  facing fork  13  rests on a portion of plate  37  adjacent to teeth  43  and facing platform  4 . At this point (FIG. 12), top jaw  33  of gripping device  32  is moved towards plate  37  into the closed position to grip peripheral portion  9  of separating sheet  8   a  and keep it taut and firmly in position when fork  13  is lowered to successively remove stacks  2  in layer  7   b.    
         [0031]    More specifically, and as shown by the dash line in FIG. 12, fork  13  contacts portion  9   a  of peripheral portion  9  of separating sheet  8   a  on plate  37 —which strengthens and so prevents tearing of separating sheet  8   a —and then slides smoothly, with no creasing, over separating sheet  8   a  towards the selected stack  2  in layer  7   b , by virtue of sheet  8   a  being kept taut by gripping device  32 .  
         [0032]    To pick up a stack  2  positioned facing a fork member  57 , separator sheet  8  is still engaged correctly by fork  13 , by arms  58  of fork member  57  being spaced sufficiently far apart to permit insertion of fork  13 .  
         [0033]    Once all the stacks  2  in layer  7   b  have been removed, gripping device  32  is opened (FIG. 13) and withdrawn from layer  7   a ; separating sheet  8   a  is removed in known manner by a pickup device not shown; and all the above operations are repeated for one layer  7  at a time until all of stacks  2  are removed.  
         [0034]    In a variation not shown but easily deducible from the drawings and the above description, top jaw  33  of supporting and clamping means  32  is dispensed with, and bottom jaw  34  is replaced by a supporting member  34  for supporting peripheral portion  9   a . The top surface of supporting member  34  has a number of suction holes for supporting and retaining peripheral portion  9   a  from underneath, and the suction holes are connected to appropriate known suction means.