Abstract:
A conveyor device, in particular for an automatic packaging machine for paper rolls, having a horizontal plane of advance, at least one pair of motorized flexible transmission members extending along a closed loop and bearing a plurality of transverse bars fastened to said flexible transmission members, a plurality of thruster elements borne by said bars, and a stationary adjustment station provided with at least one adjustment assembly having a grip organ movable in transverse direction and arranged in such a way as to displace in the transverse direction along the respective bar a thruster element positioned at the grip organ.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/241,348, filed Sep. 30, 2005 now U.S. Pat. No 7,789,219, which claims benefit of European patent application serial number 04425779.8, filed Oct. 15, 2004, both of which are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a conveyor device, in particular for an automatic packaging machine, provided with an automatic system for automatically changing the size of packs of products to be conveyed. 
     2. Description of Related Art 
     The invention was developed with particular regard to the application to packaging machines for paper rolls. In this sector there is a need to provide the machine with an automatic adjustment system which allows to change the format of the packs of products to be packaged without the manual intervention of operators. 
     Automatic packaging machines for paper rolls are often provided with a conveyor device comprising a horizontal plane of advance whereon the packs of products to be packaged are made to advance. Said conveyor device comprises a chain conveyor bearing a plurality of transverse bars and a plurality of thruster elements which extend in a transverse direction relative to said bars. 
     One of the adjustments necessary to adapt the packaging machine to a new format of packs consists of varying the position of the thruster elements in the transverse direction. 
     A known solution to effect this type of adjustment automatically is described in the document EP 1 312 549. In the solution described in this document, the conveyor device comprises a plurality of chains, each of which bears a respective series of thruster elements. The adjustment of the distance in transverse direction between the thruster elements is obtained by varying the relative distance between the chains. 
     The displacement of the chains in the transverse direction entails the need substantially to modify the entire structure of the conveyor with respect to a traditional machine lacking the automatic size change device. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a device and a method for changing automatically the size of the packages of products in a conveyor device that can be applied to conventional machines lacking the automatic size change system without having to change the entire structure of the conveyor device. 
     According to the present invention, said object is achieved by a method having the characteristics set out in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention shall be described in detail with reference to the accompanying drawings, provided purely by way of non-limiting example, in which: 
         FIG. 1  is a schematic lateral view of a conveyor device according to the present invention, 
         FIG. 2  is a schematic view according to the arrow II of  FIG. 1 ; 
         FIGS. 3 ,  4  and  5  are schematic views illustrating the sequence of operation of the adjustment station indicated by the arrow III in  FIG. 1 , 
         FIG. 6  is an exploded perspective view in enlarged scale of the part indicated by the arrow VI in FIG. IV, 
         FIG. 7  is a schematic view similar to  FIG. 2  showing a second embodiment of the present invention, and 
         FIGS. 8 and 9  are partial sections respectively according to the lines VIII-VIII and IX-IX of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings, the reference number  10  designates a conveyor device comprised in an automatic packaging machine for paper rolls. The conveyor device  10  comprises a horizontal plane of advance  12  along which the packs to be packaged P (only one of which is shown in  FIG. 1 ) are made to advance in the direction indicated by the arrow. 
     With reference to  FIGS. 1 and 2 , the conveyor device  10  comprises a stationary support structure  13  which bears two parallel shafts  14 ,  16 , at least one of which is motorised. Each shaft  15 ,  16  bears two pairs of gearwheels  18 ,  20 . The first pair of gearwheels  18  co-operates with a first pair of chains  22 . The second pair of gearwheels  20  co-operates with a second pair of chains  24 . The first and the second pair of chains  22 ,  24  bear respective series of transverse bars  26 ,  28 . The transverse bars  26 ,  28  are fastened to the chains  22 ,  24  by means of attachment elements  30 . 
     The first and the second series of transverse bars  26 ,  28  bear a first and a second series of thruster elements  32 ,  34 . With reference to  FIG. 1 , the thruster elements facing each other  32 ,  34  define a series of compartments  36  able to receive the packs of products P. In the normal operation of the conveyor device  10 , the chains  22 ,  24  advance at the same speed so the dimensions of the compartments  36  remain constant. The dimension of the compartments  36  in the longitudinal direction (i.e., in a direction parallel to the direction of advance indicated by the arrow in  FIG. 1 ) can be varied by changing the phase between the chains  22 ,  24 . 
     The present invention specifically relates to a system for adjusting the dimension of the compartments  36  in transverse direction, i.e., orthogonally to the direction of advance of the products P along the plane of advance  12 . To each transverse bar  26  or  28  are fastened a plurality of thruster elements  32  or  34 . The adjustment in the transverse direction of the dimension of the compartments  36  is effected moving the thruster elements  32  or  34  in a transverse direction along the respective bars  26  or  28 . Said movement is effected in a stationary adjustment station  38 . 
     With reference to  FIG. 2 , the adjustment station  38  comprises at least one adjustment assembly  50  movable in transverse direction and able to engage and displace in transverse direction the thruster element  32 ,  34 , which from time to time is positioned at the adjustment assembly by effect of the motion of the chains  22 ,  24 . The transverse displacement of the or of each adjustment assembly  50  can be obtained by means of electrical actuation devices or with fluid actuators (pneumatic or hydraulic) operating under the command of a control unit which commands the advance of the chains  22 ,  24  and which selectively stops the advance of the chains when an array of thruster elements is situated at the adjustment station. As shall be described more in detail hereafter, during the adjustment operation the chains  22 ,  24  advance in steps to bring successive transverse arrays of thruster elements  32 ,  34  at the adjustment station  38 . The advance of the chains resumes after the or each adjustment assembly has completed the transverse displacement of the respective thruster element  32 ,  34  towards the new position. 
     In the embodiment illustrated by way of example in  FIG. 2 , the adjustment station  38  comprises a transverse screw  40  provided with two portions with opposite thread  42 . The screw  40  is actuated in rotation by a motor  44  associated to an encoder. The stationary support structure  13  bears a transverse guide  46  along which are movable two shoes  48  each of which bears an adjustment assembly  50  formed by two parallel grip elements  52  positioned according to a fork configuration. The two grip elements  52  of each adjustment assembly  50  are mutually distanced by a quantity that is slightly greater than the dimension in the transverse direction of a thruster element  34  in such a way as to be able to receive between them a thruster element as illustrated in  FIG. 2 . 
     With reference in particular to  FIG. 6 , each thruster element  32  or  34  has an attachment portion  54  provided with two seats able to engage two parallel bars  26  or  28 . In  FIG. 6 , the two parallel bars engaged by the thruster element  32  are designated by the references  26   a  and  26   b . The attachment portion  54  has an elongated seat  56  open on a frontal side and ending with a curved bottom wall. The seat  56  engages the outer surface of the bar  26   a  with slight play, such as not to prevent the thruster element  32  from sliding in transverse direction relative to the bar  26   a.    
     The attachment portion  54  of each thruster element  32  or  34  is also provided with an elastically deformable hook portion  58 . The hook portion  58  has an engagement seat  60  which engages the outer surface of the bar  26   b  by forcing. When the hook portion  58  of the thruster element  32  engages the bar  26   b , the thruster element  32  is fastened to both bars  26   a ,  26   b , and it is held in transverse direction by the friction produced by the force with which the hook portion  58  is pressed against the outer surface of the bar  26   b . The hook portion  58  is elastically deformable thanks to the elastic characteristics of the material constituting the thruster element (preferably constituted by plastic material, which may be reinforced with fibres). Moreover, to make the hook portion  58  elastically deformable, in the attachment portion  54  is provided a transverse through slit  62  which ends on the engagement seat  60 . 
     The hook portion  58  of each thruster element  32 ,  34  is also provided with disengagement elements  64  constituted for example by two rollers mounted rotatable around a transverse axis positioned at the free end of the hook portion  58 . The rollers  64  project laterally relative to the vertical lateral walls of the thruster element  32 ,  34 . 
     With reference again to  FIG. 6 , the grip elements  52  have at their lower end inclined invitation surfaces  66  which are destined to co-operate with the rollers  64  to deform elastically the hook portion  58  and temporarily disengage the thruster element  32  from the bars  26   a ,  26   b  in such a way that the thruster element  32  can be moved in transverse direction relative to the bars  26   a ,  26   b.    
     The operation of the adjustment station  38  shall now be described with reference to  FIGS. 3 ,  4  and  5 . With reference to  FIG. 3 , the adjustment assemblies  50  are positioned in transverse direction in such a way that the free space between the two grip elements  52  is exactly along the trajectory of the respective thruster elements  32 ,  34 . The chains  22 ,  24  are actuated until the thruster elements  32 ,  34  are positioned between the grip elements  52  of the adjustment assemblies  50  ( FIG. 4 ). During the advance of the thruster elements, the inclined surfaces  66  of the grip elements are on the trajectory of the rollers  64 . Therefore, when the thruster elements  32  are between the grip elements  52 , the hook portion  58  of the thruster elements  54  is elastically deformed as shown in  FIG. 4 . In this position, the thruster elements  32  are free to slide in transverse direction relative to the bars  26   a ,  26   b . In this condition, the chains  22 ,  24  are stopped and the motor that commands the movement in transverse direction of the adjustment assemblies  50  is operated. The grip elements  52  thus move in transverse direction to the respective thruster elements  32 ,  34 . The movement in transverse direction ends when the thruster elements  32 ,  34  have reached their final position. 
     At this point, the chains  22 ,  24  are operated again making the thruster elements  32 ,  34  advance relative to the adjustment assemblies  50 . As soon as the rollers  64  of the thruster elements  32 ,  34  disengage from the lower surfaces of the grip elements  52 , the hook portion  58  of each thruster element  32 ,  34  elastically returns to the gripping position, blocking the thruster element  32 ,  34  relative to the bars  26   a ,  26   b . This sequence is repeated for the next array of thruster elements, until all thruster elements are in the position corresponding to the new size of the packages. At this point, the adjustment operation is complete, and the conveyor device  10  can resume its normal operation. 
     The adjustment sequence is executed in fully automatic fashion under the control of a command unit which commands the displacement in the transverse direction of the adjustment assemblies  50  and the stepped advance of the chains  22 ,  24  according to pre-set sequences and according to the size of the package to be obtained. 
     With reference to  FIGS. 7-9 , a second embodiment of the present invention shall now be described. The components corresponding to those described above are designated by the same numerical references. 
     With reference to  FIG. 8 , the attachment portion  54  of each thruster element  32  or  34  has a frontally open seat  70 , substantially C-shaped, which engages a first transverse bar  26   a  and an elastically deformable hook portion  72  with a seat  74  which engages a second transverse bar  26   b . The seat  74  communicates with a groove  76  which renders the hook portion  72  elastically yielding. 
     With reference to  FIG. 7 , the stationary support structure  13  of the conveyor device  10  is provided at the adjustment station  38  with a transverse beam  78  whereon are mounted two adjustment assemblies  80 . Each adjustment assembly  80  comprises an electric motor  82  which actuates in rotation a respective transverse adjustment screw  84 . 
     With reference to  FIG. 9 , each adjustment assembly  80  comprises a transverse guide  86  fastened to the transverse beam  78 . The transverse guide  86  of each adjustment assembly  80  bears a sliding shoe  88  having a threaded hole in which is engaged the respective transverse adjustment screw  84 . On each shoe  88  is fastened a grip element  90  having a general “L” configuration. As shown in  FIG. 7 , each grip element  90  has a vertically projecting portion  92  which is adapted to bear against a flank of a respective thruster element  32  to displace said element in transverse direction along the bars  26   a  and  26   b.    
     In operation, the vertically projecting portion  92  of each grip element  90  bears against the flank of the attachment portion  54  of a respective thruster element  32  or  34  and drives the thruster element  32  or  34  in transverse direction. The thruster elements  32  or  34  can be driven transversely without preventively unlocking the thruster elements  32  or  34  from the bars  26   a  or  26   b . In fact, if the retaining force exerted by the hook portion  72  of each thruster element  32  or  34  is not too great, the grip element  90  is able to displace the thruster element  32  or  34  without loosening the grip of the hook portion  72  on the bar  26   b . If instead the friction force to be overcome to displace the thruster elements  32  or  34  should be too great, the grip element  90  could be configured in such a way as to slightly open the seat  74  of each thruster element  32  or  34  during the displacement in the transverse direction. This can be obtained by providing on the front surfaces of the vertically projecting portion  92  some wedge formations which engage the hook portion  72  and elastically spread said hook portion whilst they displace the thruster element  32  in transverse direction.