Method for unbinding a stack of sacks

The sacks bound into packs by straps are unbound during their travel towards a sack application device by cutting the strap or straps which bind them, making the cut in a portion of the strap or straps which has been spaced apart from the pack. The cut straps are removed from the unbound pack, which then reaches the sack application device. The arrangement comprises conveyors for conveying the bound sacks to a station for cutting and removing the strap or straps, and from this to a sack application device.

DESCRIPTION 
This invention relates to a method for supplying sacks of any type, whether 
of glued or sewn, open mouthed or valve type, to a sack application 
device, the known purpose of which is to apply said sack to the delivery 
nozzle or mouth for the powder or granular material which is to form the 
sack contents. Both sack application devices and sack filling machines 
possessing delivery nozzles or mouths are well known, especially in the 
cement industry, where such sacks are filled with cement. 
This invention also relates to the arrangement for implementing the method. 
With particular but not exclusive reference to the cement industry, it is 
well known that the handling of the empty sacks involves a human element 
which negatively affects the costs of the sack filling operation. 
The main object of the present invention is therefore to reduce the costs 
of a sack filling plant for the sector concerned, and particularly for a 
cement factory, by reducing the labour currently required, accelerating 
the handling of the empty sacks, and increasing the self-sufficiency of 
the sack filling machines. This and further objects which will be apparent 
from the detailed description given hereinafter are attained by a method 
substantially whereby the sacks bound into packs are unbound by cutting 
the binding during this travel towards the sack application device, by 
forming a region of separation between the binding and the packs and 
making the binding cut in the separation region, then removing the cut 
binding. 
The arrangement for implementing the stated method comprises means for 
feeding the bound pack of sacks to a cutting means, means for forming a 
region in which the binding is separated from the pack so as to expose 
that region in which the binding is separated from the pack to the cutting 
means, means for removing the cut binding from the pack and means for 
conveying the unbound pack to the sack application device. 
According to an advantageous and important embodiment of the device, a 
depalletizing apparatus of known type is disposed upstream of the cutting 
means.

The sacks are produced by specialist industries, i.e. by sack factories, on 
the basis of a substantially automatic cycle. The sacks are grouped, for 
example automatically, into packs. The packs are transferred to a 
conventional strapping machine which binds them. The bound pack, indicated 
by P, is shown in FIG. 1, the binding being formed from two straps 
indicated by R. The packs P are disposed in layers on a conventional 
pallet, shown in FIG. 3 where it is indicated by Z. Each layer comprises a 
predetermined pack arrangement. To place the packs P on the pallet Z a 
known palletizer can be used, such as of the type described in another 
patent in the name of the present application, for placing full sacks on a 
pallet. 
In known manner, the assembly of packs situated on the pallet Z is fastened 
to the pallet to prevent any displacement of the packs during their 
transportation. In some cases a plastic wrapping, such as of 
heat-shrinkable type, can also be provided to protect the packs from the 
weather. 
The loaded pallet is despatched by conventional means of transport such as 
trucks to the sack filling plant, for example of the cement factory. It is 
here unloaded and the means used for fastening the pack assembly to the 
pallet and the possible heat-shrinkable protective wrapping are removed. 
The pallet Z together with the assembly of packs P is loaded onto a roller 
conveyor 1 which conveys it to a depalletizing station 2 of known type, 
the purpose of which is to unload the packs P from the pallet Z one by one 
and to transfer them to another conveyor 3, such as of roller type, 
arranged parallel to the preceeding. 
In the non-limiting example considered here, the withdrawal and transfer 
station 2, i.e. the depalletizer, comprises a load-bearing structure 4 of 
bridge shape extending over the two conveyors 1, 3. The structure 4 
carries longitudinal guides 5, i.e. paralell to the conveyors, along which 
a carriage or slide 6 can move in both directions driven by conventional 
motor means, not shown. The carriage 6 comprises guides, only partly 
reproduced and indicated by 7, along which a further carriage or slide 8 
can move in both directions. This latter therefore moves in a direction 
perpendicular to the movement of the carriage 6 and conveyors 1, 3, driven 
by conventional motor means, not shown. 
The carriage 8 lowerly carries a head 9 provided with suckers 10 for 
gripping the packs P. 
The head 9 is not only able to rotate about a vertical axis X but is also 
able to move upwards and downwards. Conventional motor means, not shown, 
effect these movements of the head 9. 
By virtue of the described construction, the station 2 is able to withdraw 
one pack P at a time from the pallet Z and transfer it to the conveyor 3. 
Before it reaches a station 11 for the cutting and removal of the binding, 
the pack P which has arrived on the conveyor 3 is centered on said 
conveyor by adjustable stationary lateral guides 12. The conveyor 3 
terminates at the entry to the station 11, in which the pack P is made for 
example to advance by two endless parallel belts 13 driven by conventional 
motor means, not shown. For the purpose of supporting and moving the 
packs, the belts 13 are provided with projecting appendices 13B on which 
the pack P rests. 
During its advancement, the pack P encounters a stationary member 50, for 
example of sheet metal, the purpose of which is to insert its thinned or 
tapered front end 51 between the lower side R1 of the straps and the pack 
P (FIGS. 4 and 4A) in order to form, by means of its hollw or arcuate rear 
part 52, a separation region P1 thereat between the pack P and the side 
R1, in which a rotary blade 14 can operate to cut said side. In addition, 
the rear part 52 of the member 50 protects the pack from the blade. After 
the side R1 has been cut it produces two free ends R'1 (FIG. 5). 
On leaving the belts 13, the pack is carried on a roller conveyor 17 having 
a width less than the width of the pack P and such that the free ends R'1 
of the binding hang freely to the side of the pack, as shown in FIG. 6. 
To the side of the conveyor 17 (see FIGS. 2, 6 and 7) there is provided a 
means for removing the cut bindings R from the pack P. This means is 
indicated overall by 18 and comprises in this example a pair of belts 19 
which are very close together and are driven at speed exceeding that with 
which the pack P advances along the conveyor 17. The belts 19 are arranged 
as follows: 
(a) inclined to form an acute angle (alpha) to the direction F of 
advancement of the pack P, and 
(b) such that one of the free ends R'1 of the binding R can be gripped 
between the two belts 19 and removed from the pack. To facilitate the 
insertion of the end R'1 between the belts 17, lead-ins such as those 
indicated by 20 can be provided. To ensure that the binding is removed if 
the belts 19 fail, an identical device (indicated by 18' in FIG. 2) can be 
located on the other side of the conveyor 17, but more downstream than the 
device 18 to which the belts 19 pertain. 
The unbound pack now free of its binding then passes to a conventional sack 
application device indicated by M. The invention also covers an embodiment 
in which the part which unbinds the packs is incorporated into or forms an 
integral part of the sack application device.