Manufacturing container or tube from paper; or other manufacturi – Bending – Folding
Reexamination Certificate
1999-08-19
2001-05-08
Gerrity, Stephen F. (Department: 3721)
Manufacturing container or tube from paper; or other manufacturi
Bending
Folding
C493S425000, C493S426000, C493S427000, C493S429000, C493S430000, C493S433000
Reexamination Certificate
active
06228014
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to paper converting machines and more precisely it relates to the production of interfolded stacks of paper sheets, for example paper wipers, toilet paper, napkins and the like.
In particular, it relates to a sheet interfolding method and to a machine used to carry out such method.
BACKGROUND OF THE INVENTION
Wipers, certain types of toilet paper, paper napkins and the like are packed in stacks of a fixed height. They are made starting from sheets of absorbent material, for example “tissue” paper, non-woven fabric, etc.
The production starts from a web having a large transversal width, from which sheets are obtained that are folded, stacked and divided into small stacks of a height equal to the final product. Each of these small stacks forms a log of a length equal to said transversal width. The logs, then, are cut off into many short stacks having the final size and packed.
In some cases, the sheets obtained from the web are folded separately from one another and then stacked already folded. In other cases, the sheets are interfolded, i.e., are folded into panels by overlapping at the same time a panel of a previous sheet with a panel of a following sheet. In this way, when pulling a sheet from the stack, at the moment of the use also a panel of the following sheet is pulled out, with consequent advantages for certain types of users. Among the possible interfolding ways the L, Z or W interfolded sheets are known having 2, 3 and 4 panels respectively.
For the production of interfolded stacks machines are known that use one or two webs of paper coming from a reel that are cut into sheets and then supplied offset with respect to one another on folding counter-rotating rollers.
More precisely, cutting rollers that engage with respective blades carry out the cutting step of the webs into sheets. In case of L or W interfolding the webs are cut and then supplied in order to form a sequence of sheets coming preferably from two different directions. Therefore, the sheets coming from both directions are supplied alternately to the folding rollers so that each sheet coming from a first direction overlaps a portion of the sheet coming from the second direction, and vice versa.
The sheets coming from both directions, in order to be overlapped in the above-described way, adhere to the respective folding rollers by means of a sucking step or by means of a mechanical gripping. Therefore, the downstream portion of each sheet leaves its folding roller at the point of contact between the two rollers, then adhering to the other folding roller, to which the upstream portion of the previous sheet adhered.
The method for Z interfolding is similar to what described, with the difference that the overlap between two consecutive sheets occurs just after the cutting step and a sequence of overlapping and offset sheets come to the folding rollers from only one direction.
The interfolded stacking step is accomplished by folding arms that have an oscillating motion about a pivot and that separate in turn from the respective roller the upstream portion of each sheet joined to the overlapped downstream portion of the following sheet. The folding arms are normally arranged in two rows and operate alternatively with the paired portions of sheets, which adhere to the first or to the second folding roller.
The folding rollers have a plurality of circumferential grooves, into which the ends of said folding arms go without blocking their rotation. At the passage of two overlapped portions of two consecutive sheets, that adhere to a roller and cover an end of the folding arms, the folding arms rotate so that their ends go out the grooves and push the two overlapped portions away from the roller, thus folding them onto previously interfolded sheets stacked below.
The folding rollers have a circumference that is normally two times the length of the sheets. Therefore, a sheet adds to the stack of interfolded sheets at each fourth of turn of the folding rollers.
In
FIG. 8
an example is shown of folding rollers
57
a
and
57
b
according to the prior art having a circumference two times with respect to the length of the sheets. They comprise first sucking spots
58
that are active upstream of the point of contact P between the two rollers and second sucking spots
59
that are active downstream of the point of contact P between the two rollers. In such a point in turn the holes
58
of a roller substantially coincide with the holes
59
of the other roller. The overlap between two sheets
54
a
and
54
b
adhering to the two rollers occurs downstream of point P and folding arms
50
a
and
50
b
are provided that partially engage with grooves
55
and rotate about pivots
51
at a moment in which the separation from the rollers of partially overlapping sheets
54
a
and
54
b
can be carried out. The pivots
51
are distant from folding rollers
57
a
and
57
b.
It is however felt the need of increasing the width of the webs to interfold, thus obtaining longer stacks to cut off. This causes, however, the unavoidable deflexion of the folding rollers, that already are weakened for the presence of the grooves and of the holding means. Deflected rollers cannot work and must be, therefore, stiffened, by increasing their cross section, thus increasing the number of sheets that can be interfolded at each turn. For example, folding rollers with circumference three times the length of the sheets allow a production of one interfolded sheet each sixth of turn, and folding rollers with circumference four times with respect to the length of the sheets allow a production of one interfolded sheet at each eighth of turn.
However, for the folding arms the increase of diameter has the consequence of more fatigue and a larger length. In particular, for causing the ends of the folding arms to go completely into the grooves and to be parallel to the interfolded stack of sheets being formed, and in order to assure a correct folding step, the pivot of rotation of the folding arms must be more distant from the folding rollers, the grooves must be deeper, and the folding arms are thus too long. Therefore, the present shapes and mechanisms of the folding arms are not appropriate for an increase of diameter.
SUMMARY OF THE INVENTION
It is therefore object of the present invention to provide an interfolding method in which the movement of the folding arms is such that it allows a correct interfolding step of the sheets also in case of folding rollers of larger diameter with respect to the prior art.
It is another object of the invention to provide a interfolding machine in which the folding arms comprise a mechanical transmission that causes a portion thereof to go parallel to the stack being formed also in case of folding rollers of larger diameter.
It is a further object of the invention to provide an interfolding machine in which the folding arms are shaped so that a larger portion thereof goes completely into the folding rollers also when the latter are of larger diameter with respect to the prior art.
These and other objects are achieved by the method for the production of a stack of interfolded sheets comprising the steps of:
feeding sheets in succession on folding rollers which comprise means for selectively holding the sheets on their surface so that a sequence of offset sheets is created;
alternate holding of the sheets on the folding rollers downstream of their point of contact in order to obtain an interfolded disposition;
folding and formation of an interfolded stack by means of folding arms that go into grooves provided in the folding rollers and push away alternately the partially overlapped portions of sheets in succession that adhere to said rollers onto a stack formed below.
The peculiarity of the method is that said folding step and formation of the interfolded stack provides the use of folding arms having pivot very close to the folding rollers.
In a first embodiment the folding arms rotate about a pivot inside the grooves. Advantageously, the folding arms have
De Matteis Alessandro
Landucci Sergio
Gerrity Stephen F.
M T C - Macchine Trasformazione Carta S.R.L.
Simpson, Simpson & Snyder, L.L.P.
Tawfik Sam
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