Method for closing a filter bag for infusible products and for connecting a tagged thread thereto

A single dose filter bag for infusible product is closed by folding a flap made in the upper part of the filter bag, attaching a connecting thread to the filter bag and to a pickup tag by first and second terminal portions respectively of the connecting thread, forming a short vertical or horizontal stitch using first and second auxiliary threads respectively.

TECHNICAL FIELD 
The present invention relates to a filter bag for infusible products, 
particularly for single-dose packages of tea, extracted beverages and the 
like. 
BACKGROUND ART 
It is known that for the preparation of hot infusions, there are commonly 
used single-dose portions of ground product, closed in a filter bag, that 
is soaked at the time of consumption of the infusion in a suitable 
container with boiling water. 
These filter bags may have different structures, according to the solutions 
found in order to improve the ground product expansion after it has been 
dipped in water, so as to allow its best dissolution. 
The most common structures are obtained from a sheet of filter paper, 
suitably folded after the ground product has been put thereonto, and then 
closed so as to prevent the ground product from going out. 
Most common filter bags feature one or more sections or lobes for 
containing the ground product, with or without the side bellow-like folds. 
This filter bag is closed either by thermowelding, if it is made of 
thermoweldable filter paper, or by gluing different outer edges of the 
filter bag, or using a metallic clip blocking the said edges. 
One end of a cotton thread is fixed to the filter bag, while the other end 
of the thread bears a tag forming the pick-up element for handling the 
filter bag when introduced in or withdrawn from boiling water. 
The thread is usually fixed to the filter bag by gluing or using a metallic 
clip, or by application of a label made of thermoweldable material that 
connects the thread with the upper edge of the filter bag. 
Also the other end of the thread can be fixed to the tag by gluing or using 
a metallic clip. 
For filter bags produced with thermoweldable filter paper, artificially 
obtained or, anyway, treated materials are used. These materials, when in 
contact with boiling water, could release substances which can change the 
infusion organoleptic features. 
The metallic clip is preferably used for closing filter bags (and fixing 
the tagged thread) made of natural fibres, that cannot be thermally 
welded. 
Also in this embodiment, the metallic clip, when in contact with boiling 
water and subsequently with the extracted beverage, could contaminate the 
infusion. 
The object of the present invention is to provide a single-dose filter bag 
for infusible products, and a new method for closing the same and fixing a 
pick-up tagged thread thereto, without using materials harmful to health. 
Accordingly, elements that sometimes could appear not quite safe, like 
metallic clips, are not used, since they can contaminate the infusion. 
DISCLOSURE OF THE INVENTION 
The above mentioned object is obtained, in accordance with the contents of 
claims, by means of a method for closing a filter bag for infusible 
products, and for connecting a tagged thread to the said filter bag, the 
said filter bag including at least a lobe and at least a flap folded to 
prevent the filter bag from opening and the infusible product from going 
out, a pick-up tag and a connecting thread, the said method being 
characterised in that in that it includes fixing means for locking the 
said flap in a pre-determined position and simultaneously fixing a free 
first terminal portion of the said thread to the said filter bag, the said 
terminal portion being defined at an end of the said thread other than the 
end where a second terminal portion is defined, and destined to be fixed 
to the said pick-up tag.

BEST MODES OF CARRYING OUT THE INVENTION 
With reference to FIGS. 1 to 4, a filter bag 1 has e.g. two lobes, 
respectively first 1a and second 1b, suitably folded so as to face each 
other and form an upper edge 2 (FIG. 2). 
Each lobe of the filter bag 1, that is not shown in the initial step when 
unfolded, is firstly filled with one dose of ground product for infusion 
7, and then the filter bag is closed longitudinally by a multiple mutual 
folding and pressing of the outer edges 1c. 
It will be understood that the double lobe configuration of the filter bag 
1 is not limitative, but helps the description of some preferred 
embodiments of the present invention; therefore, it is clear that what 
described in the following, is applicable to different structures of the 
filter bag 1, e.g. the one with a single lobe. 
In order to prevent the ground product 7 from going out of the filter bag 
1, a flap 30 is defined by a fold 3 (FIG. 4) e.g. formed by simple 
foldings, respectively first 4, second 6 and third 8, made one after the 
other at the upper edge 2. 
Fixing means 100, that carry out the proposed method, fasten the flap 30 in 
a predetermined position, close the filter bag, and, at the same time, fix 
a free first terminal portion 11 of the thread 10 thereto. 
The filter bag 1 includes also a pick-up tag 13, fixed thereto by means of 
a thread 10, usually made of cotton. 
The tag 13 facilitates insertion of the filter bag 1 into the boiling water 
and its subsequent withdrawal during infusion preparation. 
This pick-up tag 13 is fixed to a second terminal portion 12 of the thread 
10 opposite to the first terminal portion 11. 
In a first embodiment of the present invention, shown in FIGS. 5a and 5b, 
the fixing means 100 are formed by a first auxiliary thread 31, usually 
made of cotton or other similar natural fibre. 
The thread 31 fastens the flap 30 and, at the same time, connects the 
thread 10 to the filter bag 1 by a vertical stitch, e.g. chain stitch 130. 
The chain stitch 130 sews also two adjacent sections 11a, 11b of the free 
first terminal portion 11, arranged vertically on opposite sides of the 
flap 30. 
The two sections 11a, 11b rest on two opposite sides of the flap 30, 
passing over the horizontal flap line 8b (FIG. 5a), and then are sewn by 
the stitch 130 using the auxiliary thread 31. 
In a second embodiment, shown in FIGS. 6a and 6b, the said fixing means 100 
are formed by a second auxiliary thread 41, made of cotton or another 
natural fibre. 
In this embodiment, a straight, e.g. horizontal, short stitch 40, performed 
along the flap 30, closes the flap 30 and fastens the free first terminal 
portion 11, sewing the adjacent sections 11a, 11b thereof, arranged 
vertically on the opposite sides of the flap. 
As in the precedent embodiment, the two adjacent sections 11a, 11b are 
placed on the opposite sides of the flap 30 (FIG. 6a), and then are sewn, 
by known and not illustrated sewing means, by the straight stitch 40 using 
the second auxiliary thread 41 (FIG. 6b). 
In a third embodiment the fixing means 100 are constituted by the same 
first terminal portion 11, the terminal part 11c of which is used to 
perform, by known sewing means, like e.g. shown in FIGS. 11a to 11m, the 
said vertical stitch 130 along the flap 30, as described in the following. 
The second terminal portion 12 of the thread 10 can be fastened to the 
pick-up tag 13 by sewing, preferably by a vertical stitch 70 as described 
in the first embodiment of the present method. 
In this case, a third auxiliary thread 71 is used (FIG. 7), designed to 
sew, with the vertical stitch 70, two adjacent sections 12a, 12b of the 
second terminal portion 12 of the thread 10, arranged vertically on the 
opposite sides of the tag 13 and turning around the upper edge thereof. 
The possible working steps to perform the vertical stitches are shown in 
figures from 11a to 11m. 
In connection with the figures, the reference number 200 indicates the 
material (that is the flap 30 and the adjacent head of the filter bag 1, 
or tag 13), on which the stitch is made. 
On one side of the material 200, there is a needle 201, provided with a 
thread 202, made to oscillate between two extreme working positions X1, 
X2, while on the other side there are positioned two rotating hooks, or 
looper 203, 204, that oscillate in a suitable time relation with respect 
to the relative axes 203a, 204a parallel one to the other. 
In particular, the working positions X1, X2 are symmetrical with respect to 
a vertical plane, and the axes 203a, 204a are, with reference to the FIGS. 
11a to 11m, respectively on the right and on the left of this plane, 
therefore, the respective loopers 203, 204 will be indicated respectively 
as right looper and left looper, and the said working positions X1, X2 are 
indicated, with reference to the said plane, as right and left positions. 
In the FIG. 11a, the needle 201, in the right position X1, is outside the 
material. The needle 201 translates in the direction F, in synchrony with 
clockwise rotation K of the two loopers (with reference to the figures), 
passes through the material, thus making therein a hole 205 (FIG. 11b). 
When the needle goes up, a loop C1 is formed in the part of the thread 
connected with the needle and it is hooked by the left looper 204 (FIG. 
11c) rotating in the said direction K. 
When the needle has turned up, it is brought to the left position X2 (FIG. 
11d). The subsequent descent of the needle is in time relation with the 
oscillation of the two loopers in counterclockwise direction W (FIG. 11e). 
The needle 202 is introduced in the loop C1, hooked by the left looper 204, 
before the latter (said looper 204) has been released from the same loop 
(FIG. 11e). 
The loop C1, already released from the left looper, becomes gradually 
smaller, because, during the needle descent, the part of the loop, 
connected with the section of the thread adjacent to the needle, is 
pulled, thus making the same section slide from the hole 205 to the new 
hole 206 made in the material 200 by the needle placed in the left 
position X2: all this is illustrated in FIGS. 11f, 11g and 11h, in which 
the loop is deliberately loose in order to point it out. 
Raising of the needle situated in the left position X2, makes a new loop 
(or second loop) C2 that is hooked by the right looper 203 (FIG. 11g), 
rotating in the counterclockwise direction W. 
In the FIG. 11h the needle 201 is shown in the raised position and again in 
the right position X1; this figure points out that the loop C1 tightens 
the thread portions that go out from the hole 206 and extends so as to 
form the second loop C2, hooked by the right looper 203. 
The working cycle described in FIGS. 11a to 11h, is usually repeated for a 
predetermined number of times, obviously using again the holes 205, 206. 
It has been found that two or three cycles are sufficient for the stitch 
to be made in best way. 
At the end of the predetermined number of cycles, with the second loop C2 
hooked by the right looper 203, a needle cutting device is activated, 
constituted by a circular arm, which fork-like head 208 intercepts a 
branch P1 of the loop C2 in order to cut it in cooperation with a cutting 
blade 209 situated on the back of the right looper. 
The remaining part P2 of the second loop C2 is withdrawn from the hole 206 
and, subsequently, it is made translate in direction Y (FIG. 11m). 
The so obtained stitch, has a shape that satisfies all its provided 
functions, in particular closes the filter bag and fixes the tag 13 to the 
thread 10. 
The stitch is defined by a portion of thread that passes through the hole 
205, beginning from a surface of the material 200, forms a loop in 
correspondence with the other surface, passes again through the hole 205, 
then crosses the adjacent surface of the material, passes through the hole 
206 and the loop, the whole is tightened so as to be firmly connected with 
the material 200. 
The conformation described above can be repeated, using the same holes, in 
order to improve the connection of the stitch to the material 200. 
The present invention allows to obtain filter bags for infusible products 
exclusively of natural fibres, therefore, not harmful to health of 
infusion consumers. 
At this point, it is particularly advantageous, to avoid filter paper made 
of thermoweldable materials for manufacturing filter bags. 
Anyway, this possibility is not limitative, since according to the present 
invention, the filter bags can be made also of these thermoweldable 
materials or others, not described.