[0001] The present invention relates to an apparatus for folding a continuous strip of material
such as paper or the like, comprising a pair of mutually parallel and counter-rotating
cylinders which are provided internally with respective devices for gripping and means
for deviating the strip of material, which are totally inset within the side surface
of the associated cylinder in the respective non-operative condition.
[0002] In the art of manufacturing paper napkins and the like, machines designed to fold
and cut the said napkins from a reel of continuous-strip material of suitable width
are known.
[0003] It is also known that the step of folding the napkins is performed by means of a
pair of parallel cylinders which are arranged alongside each other and are counter-rotating
and between which the strip of paper already folded in two in the longitudinal direction
is fed by further means arranged upstream of the said cylinders.
[0004] A set of grippers, the jaws of which act so as to grip the strip of paper, is arranged
inside each cylinder, in the vicinity of its side surface, while a blade extending
over a predefined section of the width of the cylinder is provided in a diametrically
opposite position.
[0005] As it passes through the cylinders, the strip of paper is cyclically gripped alternately
by the grippers of one or other of the two cylinders; in fact, the angular synchronisation
of the two cylinders is such that, for each rotation of said cylinders, a set of grippers
and a blade of either cylinder are located in a corresponding position on opposite
sides of the strip of paper so that the blade of a cylinder, interfering with the
strip which is passing through the cylinders causes a deviation thereof in a substantially
radial direction which allows gripping thereof by the grippers of the other cylinder.
[0006] Continuing its rotation, the engaging cylinder draws with it the strip of paper through
a certain angle of rotation, thus causing the cyclical folding of the napkin alternately
on either side and forming a pleated stack which advances in a straight line along
special guides, positioning itself at the same time for subsequent central cutting
which results in the formation of two rows of folded napkins arranged alongside each
other, ready for packaging.
[0007] It is also known that, during rotation of the cylinders, the said arms and blade
which emerge from the side surface of the cylinder pass over the surface of the first
napkin of the pleated stack, damaging it and resulting in it being discarded.
[0008] In order to overcome this drawback, arms which are tangential to the two cylinders
have been introduced, said arms moving in synchronism with rotation of the said cylinders
so as to cause the movement of the pleated stack away from the surface of the cylinders
when the said blades and grippers pass opposite the surface of the last folded napkin
forming part of the outgoing pleated stack.
[0009] The introduction of said arms together with the corresponding control, synchronisation
and actuating devices results, however, in a significant increase in the component
parts and costs.
[0010] In addition to this, the said arms must assume, during the cycle, a non-operative
condition within the surface of the cylinders, resulting in the need to provide on
said cylinders circumferential seats into/from which the tangential arms are able
to enter/emerge during the various working stages.
[0011] These circumferential seats, in addition to giving rise to complicated and costly
machining of the surface of the cylinders, also limit the possibility of varying the
size of the napkin since they represent an obstacle for positioning the strip of paper
in the axial direction, said strip being unable to be arranged with its edges opposite
the recesses on the cylindrical surface since in this position it would be subject
to undesirable folding, resulting in production rejects.
[0012] The technical problem which is posed, therefore, is that of providing an apparatus
for gripping and folding strips of paper in particular for machines for forming napkins
and the like, in which it is possible to perform said operation without costly ancillary
means.
[0013] Within the scope of this problem a further requirement is that said apparatus should
be simple and inexpensive to produce and assemble and that it can be installed on
traditional machines without the need for special equipment and adaptation.
[0014] These technical problems are solved according to the present invention by an apparatus
for folding a continuous strip of material such as paper or the like, comprising a
pair of mutually parallel and counter-rotating cylinders between which said continuous
strip of material is fed and which are provided internally with respective devices
for gripping and means for deviating the strip towards the said gripping devices,
both being operated by associated actuating means from a non-operative condition into
an operative condition, wherein said means for deviating the continuous strip and
said gripping means are totally inset within the side surface of the respective cylinder
in the respective non-operative position.
[0015] Further details may be obtained from the following description of a non-limiting
example of embodiment of the invention provided with reference to the accompanying
drawings, in which:
- Figure 1 shows a perspective view of the apparatus according to the present invention;
- Figure 2 shows a schematic cross-section along an axial plane of the cylinders according
to Fig. 1;
- Figure 3 shows a cross-section along a plane indicated by III-III in Fig. 2 of the
cylinders with grippers during engagement with the paper strip;
- Figures 3a, 3b show a detailed cross-sectional view of the gripping and deviating
means during insertion and gripping of the strip of paper, respectively; and
- Figure 4 shows a cross-sectional view, similar to that of Fig. 3, with the cylinders
rotated through 90° and the gripping and deviating means passing without contact opposite
the folded napkins.
[0016] As illustrated in Figs. 1 and 2, the apparatus for folding napkins from a paper strip
1 comprises a pair of cylinders 10 which are mounted on shafts 11 driven in rotation
by an actuating group 12 comprising a driven shaft 12a and gear transmission and synchronisation
means 12b of the conventional type.
[0017] The bodies of the cylinders 10 are provided internally with seats 13 which extend
longitudinally and parallel to the axis of the associated cylinder 10 and are open
towards the outside so as to form a longitudinal window on the side surface 10a of
the cylinder 10.
[0018] In the example shown in the Figure, the said Seats 13 are two in number and arranged
in a diametrically opposite relative position, but it is obvious for a person skilled
in the art that the number and the angular distance of the seats 13 may be increased
or reduced as required.
[0019] Said seats 13 house inside them, respectively, means 20 for gripping the strip of
paper 1 and means 30 for deviating the latter, which co-operate with the gripping
means so as to ensure correct operation thereof.
[0020] More in detail, the said gripping means 20 consist of a plurality of arms 21 of predetermined
axial length, which are mounted on a pin 22 which can be actuated so as to rotate
in the same direction as the direction of rotation of the respective cylinder 10 by
means of a roller 23 which is integral with the pin 22 and acts against the surface
of a cam 24 mounted on the shaft 11.
[0021] The cam 24 has a suitable profile which is designed to cause opening and closing
of the gripping means 20 with which synchronisation means (known per se and not illustrated)
are also associated, said synchronisation means allowing closing of the grippers only
in given angular positions of the cylinder; it is envisaged moreover that the said
roller 23 should be kept constantly in contact with the surface of the cam 24 by means
of a spring 23a acting on an arm 23b mounted on the top end of the pin 22.
[0022] The surface 21a of each arm 21 (Fig. 3a), opposite to the gripping surface 21b, is
acted on by a spring 25 housed in an associated seat 25a inside which it is retained
by means of a grub screw 25b.
[0023] Once the arms 21 of the grippers have been opened during rotation of the cylinders
10, the said actuating and synchronisation means release the arms themselves in a
suitable angular position of the respective cylinder so that the thrusting action
exerted by each spring 25 on the corresponding arm 21 causes rotation thereof in a
direction opposite to that of the cylinder until the surface 21b comes into contact
with the corresponding surface 13b of the recess 13. In this way it is possible to
recover any play and misalignment of the arms 21 which could hinder closing of the
grippers and hence gripping of the strip 1 of paper.
[0024] Although described in relation to an example of embodiment with independent closing
segments, the gripping means could also be made as a single body of suitable length
in the axial direction.
[0025] The means 30 for deviating the strip of paper 1 for gripping thereof by the grippers
20 consist of a blade 31 extending in the axial direction over the whole length of
the respective recess 13 and integral with a respective pin 32 which can be made to
rotate by means of an associated roller 33 acting against the surface of a cam 34
mounted on the shaft 11.
[0026] Said roller 32 is kept constantly in contact with the surface of the cam by means
of a spring 33a acting on an arm 33b integral with the pin 32.
[0027] The profile of the cam 34 is such as to cause rotation of the blade 31 from a non-operative
position, which is totally inset within the side surface 10a of the cylinder 10 (Figs.
3b, 4), into an operative position radially projecting from the said side surface
of the cylinder (Fig. 3a), where it engages with the strip of paper, deviating it
radially towards the gripper 21 which is thus able to close, keeping it attached to
the cylinder 10. As it continues its rotation, the engaging cylinder draws with it
the strip of paper 1 through a certain angle of rotation, thus causing cyclical folding
thereof alternately on one side or the other and forming a pleated stack 50 which
advances in a straight line along special guides 50 for subsequent cutting by corresponding
means, not shown.
[0028] Once the strip 1 has been deviated towards the grippers 20, rotation of the cylinder
10 and hence the roller 33 on the cam 34 causes retraction of the blade 31 inside
the seat 13 until it is completely concealed below the level of the side surface of
the cylinder itself, so that (Fig. 4), when the blade 31 and the grippers 20 pass
opposite the surface of the pleated stack 50, there is no relative contact between
napkin and mechanical means integral with the cylinders and only the smooth surface
10a of the cylinders touches the surface of the folded strip, thereby avoiding damage
to the latter.
[0029] It is therefore obvious how the apparatus according to the invention allows the folding
of strips of continuous material, such as for example paper for making napkins, without
the need for complicated ancillary devices designed to avoid contact between the already
folded strip of material and the folding means.
1. Apparatus for folding a continuous strip (1) of material such as paper or the like,
comprising a pair of mutually parallel and counter-rotating cylinders (10) between
which said continuous strip (1) of material is fed and which are provided internally
with respective devices (20) for gripping and means (30) for deviating the strip (1)
towards the said gripping devices, both being operated by associated actuating means
(21,22,23,24) from a non-operative position into an operative position, characterized
in that said means (30) for deviating the continuous strip (1) and said gripping means
(20) are totally inset within the side surface (10a) of the respective cylinder (10)
in the respective non-operative position.
2. Apparatus according to Claim 1, characterized in that said cylinders are mounted on
associated shafts (11) which are driven in rotation by suitable actuating means (12).
3. Apparatus according to Claim 1, characterized in that said gripping means are arranged
inside an associated seat (13) formed on the cylinder (10).
4. Apparatus according to Claim 1, characterized in that said gripping means are mounted
on a pin (22) which can be made to rotate alternately in both directions by actuating
means (23,24) and recall means (25) so as to cause opening and closing against the
wall of the said seat (13).
5. Apparatus according to Claim 1, characterized in that said gripping means (20) consist
of a plurality of arms (21) of suitable length in the axial direction.
6. Apparatus according to Claim 1, characterized in that said gripping means consist
of a continuous arm of suitable length in the axial direction.
7. Apparatus according to Claim 1, characterized in that said means for actuating the
pin (22) carrying the gripping means (20) consist of a roller (23) acting on an associated
cam (24).
8. Apparatus according to Claim 7, characterized in that said cam (24) is mounted on
the shaft (11) of the respective cylinder (10).
9. Apparatus according to Claim 4, characterized in that said means for recalling the
gripping means (20) consist of resilient elements (25).
10. Apparatus according to Claim 1, characterized in that said means (30) for deviating
the strip (1) of continuous material consist of a blade (31).
11. Apparatus according to Claim 1, characterized in that said deviating means are arranged
inside an associated seat (13) formed on the cylinder (10).
12. Apparatus according to Claim 1, characterized in that said deviating means (30) are
mounted on a pin (32) which can be made to rotate alternately in both directions by
actuating means (33,34).
13. Apparatus according to Claim 1, characterized in that said means for actuating the
pin (32) carrying the deviating means (30) consist of a roller (33) acting on an associated
cam (34).
14. Apparatus according to Claim 13, characterized in that said cam (34) is mounted on
the shaft (11) of the respective cylinder (10).