Method and device for separating groups of flat products from each other, and a folding machine comprising said device

A device for separating from each other packs or groups of flat articles including a channel for the advance of the articles and, associated with the channel, a plurality of separating fingers which are movable along a closed path is described. On each side of the advance channel at least one pair of guides, placed one above the other and having substantially equal extensions, is provided to form the closed path. Pairs of sliders are disposed along the guides, and each slider carries at least one corresponding separating finger. A phase displacement means, which temporarily moves the first slider away from the second slider of each pair to move one pack of articles away from a following pack, is disposed at the end of the forward portion.

TECHNICAL FIELD 
The present invention relates to a device and to a corresponding method for 
separating packs or groups of flat products, each containing a 
predetermined number of articles and being continuously fed to be sent, 
for example, to a packaging machine. 
Devices of this type are frequently combined with machines for forming 
paper napkins and similar products. They normally have a channel for the 
advance of the articles and, associated with said channel, a plurality of 
separating fingers which are movable along a closed path comprising a 
forward portion, which is parallel to the channel for the advance of the 
articles and in which the separating fingers advance parallel to and 
simultaneously with the articles, and a return portion. 
BACKGROUND ART 
Paper napkins are formed with forming machines comprising a pair of folding 
rollers with vertical axes forming a throat through which is fed a paper 
strip material which is normally folded along a longitudinal line. A 
system of clamps or suction holes associated with the folding rollers 
grips the strip material alternately on one side and on the other, so that 
it is folded in a zigzag configuration after the throat of the rollers. In 
this way a horizontal stack of folded strip material is formed, and this 
is pressed against a central blade which cuts the stack into two 
symmetrical parts, creating two parallel stacks of napkins. The two stacks 
have to be divided into packs or groups, each containing a predetermined 
number of napkins. Various separating devices have been designed for this 
purpose. 
In one type of folder, the separation between consecutive packs of napkins 
is carried out by disposing the napkins in a saw-tooth configuration and 
inserting separating fingers-between adjacent packs to achieve their 
separation and discharge. Examples of machines of this type are described 
in U.S. Pat. No. 3,451,521, DE-A-2,427,635 and U.S. Pat. No. 5,281,082. 
In other types of machine, the napkins leave the machine, forming a uniform 
stack. The two folding rollers of the forming machine are associated with 
two continuous conveyors disposed on both sides of the channel for the to 
advance of the stack of material leaving the folder, these conveyors 
carrying a plurality of separating fingers which are inserted between 
successive packs of napkins. Each pair of fingers is disposed in a waiting 
position behind the folding rollers or in a recessed housing in one of the 
rollers, and when the desired number of napkins has been reached the 
separating fingers are made to advance with the folded product to the 
discharge area. A device of this type is described in JP-A-55 7165 A 
separator which is similar, but which is combined with a machine which 
feeds previously cut flat sheets, is described in FR-A-2 398 007. In this 
device, the separating fingers are temporarily released from the 
continuous conveyor, represented by a chain, and remain housed in a 
recessed housing of the roller feeding the flat articles. When the desired 
number of flat articles has been reached, the fingers are engaged with the 
conveyor and begin to advance in the same direction as the stack of sheets 
leaving the machine. 
A similar system is described in U.S. Pat. No. 4,938,465. Here the 
separating fingers are engaged with or disengaged from the continuous 
conveyor by means of a complex magnetic system. In the napkin discharge 
area, the separating fingers guide a pick-up jaw which grips the 
individual packs of napkins from above and removes them. 
The systems known at the present time are complex and expensive. 
DISCLOSURE OF INVENTION 
The object of the present invention is to provide a separating device for 
the separation of packs of flat articles taken from a stack of 
continuously fed articles, which is simpler and more reliable than the 
conventional devices. 
Another object of the present invention is to provide a device which is 
more economical than the known devices. 
A further object of the present invention is to provide a machine for 
forming napkins or similar products, which has an efficient and fast 
separating device. 
The object of the present invention is also to provide a device which is 
particularly flexible, in other words one which is capable of permitting 
the forming of packs containing any number of articles, without the 
necessity of complex adaptation operations, and which has a limited number 
of moving parts and actuators. 
These and further objects and advantages, which will be evident to those 
skilled in the art from the reading of the following text, are obtained 
with a device of the type mentioned above, comprising at least one pair of 
guides, placed one above the other and having substantially equal 
extensions, forming the closed path, pairs of sliders being disposed along 
said guides, a first slider of each said pair being disposed in a first of 
said guides and a second slider being disposed in a second of said guides 
and each slider carrying at least one corresponding separating finger. A 
phase displacement means, which temporarily moves said first slider away 
from said second slider of each pair to move one pack of articles away 
from the following pack, is disposed at the end of the forward portion of 
the closed path of the separating fingers. During the phase in which the 
two sliders are moved away from each other, one of them is preferably kept 
stationary, to retain the articles, while the other is made to advance. 
With this disposition it is simple to move one pack of articles to be 
discharged away from the preceding pack. Since the two separating fingers 
of each pair are independent of each other, the movement of the fingers 
away from each other may be relatively large, and such as to permit the 
guidance of the pack to be discharged in its tipping movement and to 
facilitate the insertion of a temporary retaining member, for example a 
blade, between the pack being discharged and the following pack which is 
still disposed in the stack of articles advancing along the channel. 
One or two pairs of guides in which one guide is above the other may be 
provided, according to the type of articles to be handled and the shape of 
the advance channel. In the case in which the separating fingers 
penetrate, for example, into the stack of articles from below (in a 
similar way to that specified in FR-A-2 398 007), it is sufficient to 
dispose a pair of guides, placed one above the other or beside each other, 
under the advance channel, which has suitable slots in its base for the 
passage of the separating fingers. Conversely, if the separating fingers 
penetrate into the stack of articles from the sides, they will be disposed 
preferably on both sides of the stack. In this case, the device will 
comprise two pairs of guides in which one guide is above the other, 
positioned along both sides of the channel for the advance of the 
articles. 
In a possible embodiment of the device, the phase displacement means 
comprises a slotted sprocket rotating about its own axis, provided with 
two sets of first engagement means (for example, two sets of slots) 
disposed at different heights along the axial extension of said sprocket 
and angularly displaced from each other. Said first engagement means 
interact with second engagement means (appendages, for example) associated 
with said sliders. This configuration is particularly simple and reliable. 
However, different solutions, for example a pair of oscillating arms 
driven by a linear actuator or similar, are not excluded. 
Advantageously, in order to simplify the structure of the device, it is 
possible to make the sliders freely slidable in the corresponding guides 
along the forward portion of the closed path, and to have them propelled 
by the articles among which they are inserted. This provides, considerable 
advantages over the conventional machines described, for example, in the 
prior patents cited above. In particular, all the complex systems for 
propelling the fingers and for engaging and disengaging the sliders with 
and from the propelling systems are dispensed with. The device thus 
becomes much simpler and more reliable. 
In the return path, the sliders may be accumulated and pushed by the same 
phase displacement means which takes individual pairs of sliders from the 
forward path and transfers them to the return path. Conversely, a return 
actuating means associated with said return portion of said closed path 
may be provided, to return the sliders to the start of the forward portion 
of the path. The actuating means may consist of a cylinder and piston 
pushing system, a pneumatic system or, preferably, a flexible member of 
the belt or equivalent type, which engages with the sliders to propel them 
in a direction opposite to the direction of advance of the articles in the 
device. For this purpose it is possible to provide bristles interacting 
with the separating fingers associated with one of said guides, while the 
separating fingers associated with the other guide may be coupled (as a 
result of special shaping) to the fingers engaged by the bristles of the 
flexible member or other actuating means. This solution is particularly 
simple and reliable, and eliminates any type of reciprocating movement as 
well as the consumption of compressed air. 
The device may have an inserting member which takes individual pairs of 
sliders from the return portion of said closed path and inserts them into 
the forward portion, between one pack of formed articles and the following 
pack. The inserting member may cause the separating fingers to follow a 
suitable trajectory, which may also interfere with the corresponding 
folding roller of the folding machine with which the device is associated. 
In this case, the folding roller will be provided, in a known way, with a 
suitable annular groove. 
The inserting member may consist of a slotted disc rotating step by step 
about its own axis and provided with engagement elements which interact 
with corresponding engagement means associated with the sliders disposed 
in the two guides placed one above the other. 
Various systems may be provided at the discharge end of the device for the 
discharge of the packs of articles separated by the separating fingers. In 
a particularly advantageous embodiment, a tipping surface may be provided 
at the end of said channel for the advance of the articles, with a 
conveyor to remove the articles. The tipping surface comprises a stop for 
the articles, and is movable parallel to the direction of advance of the 
articles. The movement may be obtained in a passive way, by the insertion 
of an elastic member, for example a coil spring, or may be obtained by 
means of a suitable actuator controlled in a suitable way by the central 
unit of the device. 
Further advantageous characteristics and embodiments of the device 
according to the invention will be described in the following text. 
The invention also relates to a folding machine for producing paper napkins 
or similar products, and to a method for separating packs of flat 
articles, for example folded paper napkins, as specified in the attached 
claims.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION 
In the attached drawing, the numbers 1 and 3 indicate two folding rollers 
of a folding machine for the formation of a stack P of napkins. The 
folding rollers 1 and 3, which rotate about two vertical axes A and B, 
have annular grooves 1A, 3A which house curved arms 5 and 7 which detach 
the folded material from the roller and push it against the stack P of 
previously formed articles leaving the machine. A continuous strip 
material N, which may be folded along a longitudinal line, is fed into the 
throat formed between the two rollers, these rollers being associated 
systems of a known type which fold the material leaving the throat once 
around the roller 1 and once around the roller 3 to produce a stack of 
material folded in a zigzag configuration. With each fold, the 
corresponding curved arm 5, 7 detaches the material from the roller and 
pushes it towards the previously formed stack P. 
The operation of the folding machine described in summary form is known and 
therefore will not be illustrated in greater detail. 
The stack P of folded strip material is pushed against a transverse blade 9 
which cuts the stack into two parts P1 and P2, each formed by a plurality 
of napkins folded in four. After the blade 9 there is disposed a divider 
which keeps the two parts P1, P2 into which the stack has been cut 
separate from each other, permitting independent handling of these two 
parts. The stack P, P1, P2 advances in an advance channel formed by a pair 
of side pieces 11 and a base panel 12, at the end of which packs of 
napkins M1, M2 . . . Mn, each containing a predetermined number of 
articles, are discharged. 
To separate one pack of napkins M1 from the following pack M2, pairs of 
separating fingers 15, 17 are disposed at the sides of the channel for the 
advance of the stack P, P1, P2. Each separating finger 15, 17 is integral 
with a corresponding slider 19, 21 which slides in a corresponding guide 
23, 25. Two guides 23, 25, one placed above the other, and separated by a 
dividing wall 27 made of material with a low coefficient of friction, to 
facilitate the sliding of the sliders, are disposed on each side of the 
channel for the advance of the stack P, P1, P2. The guides 23, 25 form a 
closed path and in each of them is disposed an identical number of sliders 
19 and 21 respectively, in such a way that on each side of the advance 
channel each slider 19 and the corresponding finger 15 in the guide 23 is 
matched by a slider 21 and a corresponding finger 17 in the lower guide 
25. An identical number of pairs of fingers 15, 17 is disposed on each 
side of the channel. 
On each side of the channel for the advance of the stack P, P1, P2, each of 
the two guides 23, 25 has two rectilinear sections parallel to the 
direction of advance of the stack P, connected by circular end portions, 
one adjacent to the corresponding folding roller 1, 3 and the other at the 
napkin discharge area. 
As shown in FIGS. 2 to 5, the sliders 19, 21 and the corresponding fingers 
15, 17 are shaped in such a way that, when two sliders 19, 21 are 
positioned with one above the other, the upper slider 19 engages with the 
lower slider 21, in such a way that when said lower slider is propelled in 
the clockwise direction along the corresponding guide 25 it propels with 
it the upper slider 19, for purposes which will be explained subsequently. 
This is achieved by means of the stepped shape of the two facing edges of 
the separating teeth 15, 17, shown in detail in the front view in FIG. 3. 
At the curved areas of the guides 23, 25 there is a slotted disc 31 (near 
the corresponding folding roller 1, 3) and a slotted sprocket 33 (in the 
discharge area). The slotted disc 31 has a set of longitudinal slots 31A 
whose depth is approximately equal to the thicknesses the two guides 23, 
25. Each slot 31A engages with two sliders 19, 21, located one above the 
other, by means of appendages 19A, 21A provided on the rear part (in other 
words the part opposite the separating fingers 15, 17) of each slider. 
With this disposition, the step-by-step rotation in a clockwise direction 
(arrow f31) of the slotted disc 31 causes the sliders 19, 21 to be 
transferred in pairs from the corresponding outer rectilinear section of 
the guide 23, 25 to the inner rectilinear section, in other words that 
facing the stack P of articles, while the relative position of the sliders 
19, 21 one above the other is maintained. The step-by-step rotation of the 
slotted disc 31 may be produced by any suitable system, for example by a 
free-wheel mechanism driven by a linear cylinder and piston actuator, or 
by a rotary actuator. 
Conversely, the slotted sprocket 33 has two sets of slots 33A, 33B, 
angularly displaced from each other by approximately 30-40.degree. and 
disposed on two different levels along the longitudinal extension of the 
sprocket. In this way, since the appendages 19A and 21A of the sliders 19 
and 21 are disposed at different heights, the step-by-step rotation in the 
clockwise direction (arrow f33) of the slotted sprocket 33 causes the 
sliders 19, 21 to be transferred from the inner rectilinear section to the 
outer rectilinear section of the corresponding guides, and simultaneously 
causes an angular displacement of each slider 19 and of the corresponding 
finger 15 with respect to the lower slider 21 and the corresponding finger 
17. The displacement is equal to approximately 30-40.degree., in other 
words equal to the angular displacement of the slots 33A, 33B. This causes 
a significant movement of the ends of the fingers 15, 17 away from each 
other. 
In practice, the slotted sprocket 33 may be made in two discoid parts which 
are connected to each other. FIGS. 1A, 1B show separately the two discoid 
parts 33X, 33Y in the angular position with respect to each other in which 
they may be fitted. The two slots 33A are made in the discoid part 33X, 
while the two slots 33B are made in the discoid part 33Y. This 
configuration facilitates and simplifies the making of the sprocket 33. 
Slotted sprockets 33 with different displacements between the slots 33A, 
33B may also be made in this way (from identical elements). If the two 
parts 33X, 33Y are connected reversibly, the same slotted sprocket 33 may 
be adjusted according to specific production requirements, providing a 
variable and adjustable displacement between the slots 33A and 33B. 
On each side of the channel for the advance of the stack P, P1, P2 of 
articles, and parallel to the outer rectilinear section of each pair of 
guides 23, 25, there extends a continuous flexible member 35 running 
around two pulleys and provided with bristles which engage with the 
fingers 17 transferred from the slotted sprocket 33 to the outer 
rectilinear section of the corresponding guide 25 and propel them as shown 
by the arrow f35 in the opposite direction to the direction of advance of 
the stack P, P1, P2 of articles. As described above, the shape of the 
sliders 19, 21 and of the fingers 15, 17 is such that the advance of the 
finger 17 and of the slider 21 by the bristles of the continuous flexible 
member 35 causes the propulsion of the corresponding upper slider 19. The 
sliders 19, 21 are carried by the flexible member 35 until they are 
stopped by the slotted disc 31, as shown in FIG. 1. Several pairs of 
fingers 15, 17 are accumulated behind the slotted disc 31, while the 
flexible member 35 can run under them, owing to the deformation of the 
bristles with which this member is provided. With each rotation of the 
slotted disc 31, the fingers 15, 17 accumulated against it are pushed to 
maintain the contact with the disc. The number of waiting fingers 15, 17 
behind the slotted disc 31 depends on the size of the packs of articles 
M1-Mn being formed; the number of stationary pairs of fingers 15, 17 
increases with the size of each individual pack. 
The device described up to this point operates as follows. 
The folding rollers 1 and 3 rotate continuously, forming the stack P, which 
is then cut by the blade 9 into the two parts P1, P2. In this phase, a 
pair of separating fingers 15, 17 is waiting next to each roller 1 and 3, 
and remains stationary outside the folding area. When a predetermined 
number of folds has been reached, producing a predetermined number of 
napkins by means of the cut made by the blade 9, on each side of the 
machine the corresponding slotted disc 31 rotates by one step, bringing 
the pair of sliders 19, 21, and therefore the corresponding fingers 
located one above the other 15, 17, from the withdrawn position outside 
the folding rollers towards the folding area, in a position more advanced 
than the point at which the following fold of the strip material N is 
made. This movement is made possible by the presence of annular grooves in 
the folding rollers 1 and 3. The sliders 19 and 21 are fully released from 
the slotted disc 31 and become free to slide in the guides 23 and 25 
respectively along the section of the path facing the advance channel. 
When the feed of the strip material N, and consequently the folding of the 
material with the accumulation of the folded material in the stack P, is 
continued, the two pairs of fingers 15, 17 on the two sides of the advance 
channel, propelled by the corresponding slotted discs 31 into the active 
folding area, remain engaged between one fold and the next, and start to 
advance along the guides 23, 25 pushed by said stack P, P1, P2 of articles 
advancing as a result of the action of the arms 7. No positive means of 
advancing the separating fingers along the active section of their path is 
required. 
When the two pairs of sliders located one above the other 19, 21 on the two 
sides of the channel for the advance of the stack P, P1, P2 reach the end 
of the rectilinear section of the guides 23, 25, a rotation of the toothed 
sprockets 33 by one step causes the angular movement of the upper 
separating fingers 15 (with the corresponding sliders 19) away from the 
lower separating fingers 17 (with the corresponding sliders 21). This 
operation is represented in FIGS. 7 and 8. This moves the more advanced 
pack of napkins M1 away from the following pack M2, to facilitate the 
discharge of the pack M1 by the discharge means which will be described in 
the following text. Each lower slider 19 is retained in its angular 
position shown in FIG. 8 by the striking of the appendage 19A against the 
circumferential edge of the sprocket 33, until the slot 33B engages the 
corresponding appendage 19A, rotating the slider 19 and the corresponding 
finger 17 in the clockwise direction. 
This successive rotation (FIG. 9) of each of the two toothed sprockets 33 
causes the lower separating fingers 17 to be disengaged from the stack of 
articles, which is retained temporarily by a blade 81, described in 
greater detail in the following text. By successive rotations by one step 
of the slotted sprockets 33, the sliders 19, 21 are brought above the 
corresponding continuous flexible members 35 so that they are returned 
towards the slotted discs 31 and start a new cycle. 
The means of discharge of the individual packs M1, M2 . . . Mn of articles 
are illustrated in detail in FIGS. 10 to 12. 
The wall 12 forming the base of the channel for the advance of the stack P, 
P1, P2 ends in a comb-shaped portion 12A which interacts with a movable 
surface 41 formed by a plurality of strips 41A carried by a bracket 43 
hinged at 45 to a block 47. Each strip 41A has a slot 41B in which a bar 
49 orthogonal to the surface 41 is engaged in an adjustable position. The 
bars 49 are aligned with each other to form a vertical surface to stop and 
contain the stack of articles. 
The surface 41 formed by the strips 41A can be tipped about the axis 45 by 
means of a cylinder and piston actuator 51 carried by a plate 53 which is 
integral with the block 47. The block 47 with the plate 53, the actuator 
51 and the surface 41 also move in the direction of the double arrow f47. 
The movement is permitted by the fact that the strips 41A forming the 
surface 41 penetrate into the voids formed in the comb portion 12A of the 
surface 12 for the sliding of the stack P of articles. This movement is 
controlled by a "brushless" electric motor or similar 61, which transmits 
the motion through a toothed belt 63 and a pair of pulleys 65, 67 to a 
threaded rod 69 engaged with a ball screw nut 71 carried by the block 47. 
The disposition is symmetrical on the two sides of the channel for the 
advance of the stack of articles. The motor 61 may advantageously be 
controlled by a PLC which controls its movement as a function of the 
thickness of the strip material N and of the rate at which this material 
is fed and folded, for the purposes which will be made clear in the 
following text. 
The blade 81, driven by a mechanism illustrated separately in detail in 
FIGS. 12 and 13, is disposed above the surface 41. The blade 81 is fixed 
to a shaft 83 which extends parallel to the direction of advance of the 
stack P, P1, P2 of articles, in such a way that it oscillates integrally 
with the shaft about the axis of the shaft. The shaft 83 is fixed by an 
arm 85 to a cylinder and piston system 87 which causes it to oscillate 
about its axis to cause the oscillation of the blade 81 between an upper 
position in which it is withdrawn from the stack P, P1, P2 (shown in solid 
lines in FIG. 12) and a lower position (shown in broken lines in FIG. 12) 
in which the stack of articles rests on the blade. 
The support 81A of the blade (FIG. 13) is also fixed to the rod 88 of a 
further cylinder and piston actuator 89 which moves the blade 81 in a 
direction parallel to the direction of advance of the stack P. 
The disposition described here is symmetrical, a pair of blades 81 being 
provided side by side, one for each portion P1, P2 of the stack of 
articles issuing from the machine. 
The operations of discharging the packs of articles take place in the 
following way. 
The bars 49 are initially brought into their position closest to the 
folding rollers 1 and 3, and the leading articles in the stack P, P1, P2 
rest on the bars 49 and are pushed against them. As the strip material N 
is folded and the napkins are formed by the rollers 1, 3 and by the blade 
9, the bars move under the control of the motor 61 to provide space for 
new articles issuing from the machine. 
A sensor (not shown) sends a signal when a pair of fingers 15, 17 reaches 
the position shown in FIG. 1. This signal represents the permission for 
the start of the discharge cycle for the pack M1 of napkins, which takes 
place as follows: the fingers 15, 17 on each side of the advance channel 
are moved apart into the position shown in FIG. 8; the blade 81 is lowered 
and penetrates into the void created by the movement apart of the fingers 
15, 17; the surface 41 is rotated through 90.degree. by means of the 
cylinder and piston actuator 51 to tip the pack M1 onto a conveyor 91 
consisting of a plurality of parallel belts between which the strips 41A 
and the corresponding bars 49 pass. In this phase, the finger 15 
accompanies the tipping movement of the pack of napkins through a first 
part of said tipping movement, retaining the pack from the rear. The 
following pack M2 is retained frontally by the corresponding finger 17 and 
by the blade 81. When the pack M1 has been deposited on the conveyor 91 
and removed from the discharge area by the conveyor, the surface 41 is 
raised again by means of the cylinder and piston actuator 51, while the 
brushless motor 61 causes the system 41, 43, 47, 49 to move back to a 
position in which the bars 49 come into contact with the front surface of 
the pack M2. This position is determined by the PLC controlling the 
brushless motor 61 according to the values of the thickness of the strip 
material N and the rate of production, since in the meantime the blade 81 
has advanced under the pushing action of the stack of articles to permit 
the continuous operation of the folder without a substantial increase in 
the compression of the articles. Before the surface 41 and the bars 49 
return to their position of support for the advancing stack, the fingers 
17 are made to withdraw by the sprockets 33 (FIG. 9), so that the pack M2 
is retained in the last phase by the blade 81 only, which is free to 
advance under the pushing action of the stack P, extending the rod of the 
cylinder and piston system 89. When the bars 49 are again in contact with 
the first napkin of the advancing stack, the blade 81 is withdrawn upwards 
by means of the actuator 87 and then returned to the initial position by 
means of the actuator 89. 
As may be seen in the attached figures, the actuators and the devices which 
permit the discharge of the packs of articles are double and symmetrical, 
since the discharge of the packs M1 from the two portions P1 and P2 into 
which the stack P has been cut may not take place simultaneously. 
It is to be understood that the drawing shows only an example provided 
solely as a practical demonstration of the invention, and that this 
invention may be varied in its forms and dispositions without departure 
from the scope of the guiding concept of the invention. Any presence of 
reference numbers in the attached claims has the purpose of facilitating 
the reading of the claims with reference to the description and to the 
drawing, and does not limit the scope of protection represented by the 
claims.