Abstract:
A mattress packaging machine with an automatic roll replacement device for automatically replacing a roll for feeding a sheet for wrapping the mattress, having: a horizontal frame upon which the mattress slides; a sheet guiding mechanism so the sheet is arranged over and under the mattress; a sheet joiner and cutter after the mattress is wrapped; a sliding carriage with feed roll supporting assemblies for unwinding and takeup of a respective sheet and with a transferable take-up roll with which an end of the sheet is connected.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a device for automatically changing the roll for feeding the sheet in which mattresses and the like are wrapped in packaging machines. 
     Mattress packaging machines are known which comprise a horizontal surface for conveying the mattress to be wrapped and in which a sheet for packaging the mattress, drawn from a roll, is guided at right angles thereto. As the mattress advances, the sheet is folded and laid over and under it so as to form a bag which is then closed to the rear and laterally by heat-sealing. 
     When the roll is empty, it is replaced with another full one. However, the time required for this replacement is currently excessively long and leads to downtimes which have a negative effect on the production cycle. Moreover, it is often necessary to replace the feeding of one sheet with the feeding of another sheet having different characteristics in terms of quality, color and the like or bearing indications on a different type of packaged mattress. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide a device which allows to automate the replacement of the empty roll with a new one, so as to increase the efficiency of mattress packaging machines or to replace the packaging sheet with another one having different characteristics in relation to the prerogatives and intended uses of the mattress. 
     This aim is achieved with a device whose characteristics are defined in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the present invention will become better apparent from the following detailed description of an embodiment thereof, illustrated only by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a side elevation view of a mattress packaging machine, equipped with the device according to the invention; 
     FIGS. 2,  3  and  4  are views of a detail of the device in three different operating conditions; 
     FIG. 5 is an enlarged-scale view of the detail of FIGS. 2 to  4 ; 
     FIG. 6 is a sectional view, taken along the line VI—VI of FIG. 5; 
     FIGS. 7,  8  and  9  are views of the machine in three successive steps of packaging. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to FIG. 1, the reference numeral  1  generally designates a machine for packaging mattresses, which comprises a frame composed of four posts  2  arranged at the corners of an imaginary rectangle and interconnected by cross-members and longitudinal members. In particular, the posts are connected at the top by longitudinal members which form two rails  3  for the sliding of a carriage  4  which is motorized so that it can move in both directions A and B. 
     The frame comprises a supporting surface  5  for a mattress M which is co-planar to a conveyor  6  for removal. A gap  7  remains between the outlet of the surface  5  and the conveyor  6 , and the packaging sheet F is guided downward in the direction C at right angles to the surface  5  and to the conveyor  6 . The mattress M, by means of a pusher  8  or the like, is pushed in the direction A against the sheet F which, by means of a guiding roller  9 , is laid over and under the mattress M. When the mattress M, after moving beyond the gap  7 , reaches the conveyor  6 , the upper and lower flaps of the sheet F that lie upstream of the mattress are joined by a heat-sealing and cutting device  10  (FIG. 2) which is composed of two heat-sealing bars  11  and  12  which produce two heat-sealing lines which are parallel and spaced so as to allow a blade  13 , arranged between them, to cut away the sheet. 
     In this manner, the heat-sealing line that lies downstream of the cut closes the sheet F, forming a ring which surrounds the mattress, while the heat-sealing line that lies upstream of the cut allows the sheet F to remain attached to the takeup roller arranged below the surface  5  in order to allow it to take up a portion whose length is sufficient to prevent the heat-sealing line from remaining in the portion of sheet used to package the following mattress. 
     After the mattress M, with the sheet F wrapped in a ring around it, has advanced onto the conveyor  6 , two lateral heat-sealing units  14 , actuated in the direction D, close it laterally so as to form a hermetic bag. 
     According to the invention, various roll supporting assemblies, fitted on the carriage  4 , are provided for the automatic replacement of the roll from which the sheet is drawn both due to imminent depletion or due to the need to change the type of sheet used to package the mattresses. In the illustrated example, there are four assemblies  15 ,  16 ,  17  and  18 , but there may be any number of such assemblies. 
     Each assembly comprises two rollers  19  and  20  which are rotatably supported on the carriage  4  and are motorized, by means of a chain drive, by a gearmotor  21  so as to turn the rolls B 1 , B 2 , B 3 , B 4  in the direction E. 
     The sheet F that exits from the roll is diverted by a guiding roller  22  into a channel  23  formed by two vertical walls  24  and  25  which lie between the longitudinal beams  26  of the carriage  4 . 
     The outgoing sheet end is fixed to a takeup roll  27  whose axis is parallel to the axis of the roll from which it is unwound; the roll  27 , in the inactive position of the assembly, is accommodated in a compartment  28  (FIG. 3) which is formed at the lower end of the channel  23 . 
     The roll  27  is supported on a shaft  29  (see FIG. 6) whose mutually opposite ends form two pivots  30 . The roll  27  can rotate about the shaft  29  only in one direction due to the presence of a freewheel mechanism  31 , and is supported in the compartment  28  by two respective forks  32  which engage pivots  30  and are actuated horizontally by respective actuators  33 . The actuators  33 , by means of brackets  33   a , are rigidly coupled to the longitudinal beams  26  of the carriage  4 . The forks  32 , when retracted by the actuators  33 , disengage from the pivots  30 , allowing the roll  27  to descend. 
     In the position in which the pivots  30  are engaged in the forks  32 , the roll  27  is prevented from rotating by a toothed sector  34  (see FIG. 2) which is rigidly coupled to one of the forks and is adapted to mesh with a gear  35  which rotates rigidly with the roll  27 . 
     At the gap  7  that separates the surface  5  from the conveyor  6  there is a transfer unit  36  (FIGS. 2 and 5) which lowers the roll  27 , with the end of the sheet attached thereto, below the surface  5 , so as to arrange the sheet F at right angles in front of the mattress M to be packaged. 
     The transfer unit  36  is composed of two mutually opposite C-shaped vertical guides  37  whose upper ends are fixed under the rails  3  and which extend below the surface  5 . The guides  37  lie on a vertical plane which lies upstream of the heat-sealing device  10  and is adjacent thereto. 
     The guides  37  have two longitudinal slots  38  for sliding, through which the pivots  30  protrude outward. 
     In order to guide the roll  27  along the guides  37 , there are bearings  39  which are mounted on the shaft  29  and can slide in the channels formed by said guides. 
     Upstream of each guide  37  there is a further guide which is composed of a pair of parallel and vertical bars  40 . 
     Two respective sliders  41  can slide on the bars  40 , and respective actuators  42  are fixed thereon. 
     The actuators  42  actuate respective forks  43  which, in the raised position of the sliders  41 , are adapted to engage the pivots  30 , disengaging from the forks  32 . 
     A sector  44  is rigidly coupled to a fork  43 , as provided for one of the forks  32 , and is adapted to mesh with the gear  35  of the roll  27  so as to lock its rotation. 
     The toothed sector  44  is provided with an arm  45  which, in the lowered position of the sliders  41 , i.e., at a level that lies below the supporting surface of mattress M, is capable of activating a sensor  46  for actuating a motor  47  which actuates a pinion  48  with which the gear  35  meshes in the lowered position. 
     The sliders  41  are actuated between the raised position for the alignment of the forks  43  with the forks  32  and the lowered position for the meshing of the gear  48  with the gear  35  by means of an actuation assembly which is not shown but can be easily envisioned. For example, the assembly can be constituted by a vertically arranged chain which has a point which is rigidly coupled to a slider  41  and is motorized by a gearmotor. 
     The operation of the apparatus is as follows. 
     Assume one wishes to package a mattress M, which lies on the surface  5 , with a sheet F taken from the roll B 3  (see FIG.  1 ). 
     For this purpose, the carriage  4  is arranged on the rails  3  so that the assembly  17  arranges the compartment  28  of the channel  23 , in which the roll  27  is accommodated, so that it lies above the guides  38 , rests within the forks  32  and is rotationally locked upon engagement of the toothed sector  34  in the gear  35 . The sliders  41  that support the actuators  42  are raised to the top of the bars  40  with the forks  43  aligned horizontally to the pivots  30  of the shaft  29  but are disengaged therefrom. 
     At this point, by activating the actuators  33  and  42 , the forks  32  are retracted from the pivots  30 , while the forks  43  are made to advance so as to transfer the support of the pivots  30  from the forks  32  to the forks  43  (see FIG.  2  and FIG.  5 ). The sector  44  prevents the rotation of the roll  27  and keeps the gear  35  in the angular orientation provided in order to ensure meshing with the pinion  48 . 
     Once this step has been completed, the gearmotor  21  is activated and, by actuating the rollers  19  and  20 , produces the rotation of the roll B 3  in the direction E for the unrolling of the sheet F. At the same time, the descent of the sliders  41  is actuated so that the roll  27 , no longer retained by the forks  32 , can descend along the guides  38  (see FIG. 7) until it reaches the lower position, below the surface  5  (see FIG.  8 ), at which the gear  35  meshes with the pinion  48  and the sensor  46 , activated by the arm  45 , activates the motor  47  (see FIG.  5 ). 
     The actuation of the motor  47 , by means of the gear  48 ,  35 , turns the shaft  29  and, by means of the freewheel mechanisms  39 , the roll  27 . The actuation of the motor  42  is timed so that only a given portion of the sheet F is wound onto the roll  27 . Such winding allows, at the end of each packaging step, and specifically after the sheet has been closed in a ring and cut, to take up the end portion of the sheet that has the unsightly heat-sealing line, as will become apparent hereinafter, and tension the sheet F so that it is perpendicular to the surface  5 . 
     By then making the mattress M advance along the surface  5  while keeping the motor  47  locked, the sheet F is applied over and under the mattress M (see FIG. 9) and then closed in a ring-shaped configuration by the heat-sealing and cutting device  10 . Conveniently, the feeding of the sheet F and its arrangement around the mattress M are facilitated by actuating the gearmotor  21  in the direction for the unwinding of the roll B 3  so as to prevent the mattress from applying excessive traction to the sheet. 
     By opening the heat-sealing and cutting device  10 , the packaged mattress can advance further along the conveyor  6 , while by way of the heat-seal provided upstream of the cut, the sheet F maintains its vertical continuity, so that by actuating the motor  47  it is possible, as mentioned, to take up a small portion thereof which corresponds to the waste and comprises the heat-sealing line S. 
     The apparatus is thus restored to its initial position, ready to work on a new mattress. 
     If the roll B 3  is about to end or if one wishes to replace it with another one, for example with the roll B 1 , for other reasons, one proceeds by lifting the sliders  41  and by turning in the opposite direction the gearmotor  21  so as to take up the portion of sheet F that runs from below the surface  5  up to the compartment  28 . 
     After the roll  27  has entered the compartment  28 , the actuators  42  and  33  are activated so as to disengage the forks  43  from the pivots  30  and at the same time transfer the pivots  30  into the forks  32 . The roll  27  thus remains suspended from the carriage  4 . After lowering the sliders  41  to such a level as to not hinder the movement of the carriage  4 , the carriage is moved until the compartment  28  of the assembly  15  for supporting the roll B 1  lies in alignment with the guides  37 . The subsequent steps of operation comprise the lifting of the sliders  41  until the forks  43  reach the level of the pivots  30 , so that by actuating the actuators  42  it is possible to transfer the support of the roll  27  to the forks  43 . Once the transfer of the roll  27  onto the forks  43  has been completed, the sliders  41  are lowered and the operating steps are repeated as described above. 
     It should be noted that the freewheel mechanisms  39  allow, on the one hand, the rotation of the roll  27  on the shaft  29  in the direction for taking up the waste and, on the other hand, allow to rotationally lock the roller  27  so as to allow the unwinding of the sheet F from the roll. 
     Attention is also drawn to the locking action applied by the toothed sectors  34  and  44  which, by preventing the gear  35  from turning during the lifting and lowering of the sliders  41 , maintains the angular orientation of the gear  35  and ensures its meshing with the pinion  48  upon any roll change. 
     The described device is susceptible of numerous modifications and variations, all of which are within the scope of the same inventive concept. In particular, the movement of the sliders  41  can be provided by means of a hydraulic cylinder or by means of a system which has, instead of one of the bars  40 , a threaded rod actuated by a gearmotor. 
     The disclosures in Italian Patent Application No. BO99A000560 from which this application claims priority are incorporated herein by reference.