Purely by way of example, the present invention relates to a method of sealing two portions of a bag for containing an infusion substance, in particular, tea.

The teachings of the present invention may, obviously, be applied to advantage to seal portions of any type of bag or box, of paper or cardboard.

BACKGROUND ART In the packaging industry, it is common practice to manufacture bags of porous material containing leaves for infusion, e. g. tea; and each bag has a thread, normally of cotton, to which a label is attached identifying the product in the bag.

In practice, there are two basic methods of manufacturing such bags, a first of which comprises folding a sheet of porous paper, and folding and stapling the edges. This'method has the advantage of employing

sheets of porous paper substantially comprising cellulose, which releases no harmful substances when steeped in boiling water, but has the drawback of the staples possibly working loose and, in the worst case scenario, being swallowed by the consumer in the infusion itself. Moreover, bags produced using this method come apart fairly easily, thus resulting in spillage of part of the product which is rendered unusable in contact with the environment, A second method of manufacturing bags for infusion employs porous sheets impregnated with thermoplastic material, which, on contact with heat-sealing heads on opposite sides of the portions for sealing, melts to seal the superimposed portions as required. Bags of this sort are advantageously made of porous paper impregnated with substances such as polyethylene or polypropylene.

Though undoubtedly advantageous as compared with bags produced using the first method, bags produced using this method have the major drawback of releasing substances into the infusion.

DISCLOSURE OF INVENTION It is an object of the present invention to provide a method of sealing at least two portions of two flat bodies, designed to eliminate the aforementioned drawbacks.

More specifically, the method according to the present invention provides for obtaining bags for infusion made of porous paper substantially comprising

cellulose and having no thermoplastic substances, and which ensures perfect sealing of the product inside.

The main object, therefore, of the present invention is a method of sealing at least two portions of two flat bodies, as claimed. in Claim 1.

A further object of the present invention is a head for use in a system for producing bags for infusion in accordance with the invention.

Yet a further object of the present invention is a teabag produced in accordance with the method which is the main object of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described with reference to the accompanying drawings, which show a non- limiting embodiment of a system illustrating the method which is the main object of the present invention, and in which: Figure 1 shows a first sealing head for longitudinally sealing a strip of paper containing an infusion product, in particular tea, to form a substantially tubular body; Figure 2 shows the operation by which the tubular body is cut and folded to form a bag containing the infusion product; Figure 3 shows a second sealing head for sealing the bag formed in the Figure 2 step.

BEST MODE FOR CARRYING OUT THE INVENTION Figure 1, as stated, shows a first sealing head 10

forming part of a system for producing bags containing infusion substances; which system is not described in detail herein, by not being essential to a clear understanding of the present invention.

A strip 11 of porous paper material is fed by feed and unwinding means (not shown) in the direction of arrow F1 towards sealing head 10; and dispensing means (not shown) intermittently deposit quantities ql, q2, q3, q4 of infusion product with a predetermined spacing.

Folding means (not shown) fold strip 11 in the direction of arrows F2 to form a substantially tubular body 12, which continues traveling towards head 10.

A yarn 13 of heat-seal material, e. g. polyethylene or polypropylene, is unwound off a reel 14 by known means not shown, and, by means of a guide member 15, is. run parallel to body 12 in its feed direction, i. e. the direction of arrow F1. A similar elongated element, e. g. in the form of. a ribbon, may be used in place of yarn 13.

The elongated element may be made of polyethylene, polypropylene, material of vegetable origin, or a mixture of these.

Yarn 13 is inserted in known manner between the free portions of strip 11 when folding strip 11 in the direction of arrows F2 to form body 12.

Together, the longitudinal portions of strip 11 and yarn 13 form a bead 16 for sealing by head 10.

Head 10 comprises a sealing device 17; and a countermember 18 located on the opposite side of bead 16

to device 17. In other words, as it is fed in the direction of arrow F1, bead 16 passes between device 17 and countermember 18.

By known means not shown, countermember 18 is moved towards device 17 in the direction of arrow F3, perpendicular to the feed direction of body 12.

Device 17 may be either a heat-producing or ultrasonic wave-producing device.

Both heat and ultrasonic waves, whichever is used, at least partly melt yarn 13, which, as stated, forms part of bead 16; and the molten thermoplastic material penetrates the pores of the sheet of paper material defining strip 11, so as to seal one portion perfectly to the other.

Figure 2 shows how body 12 is cut to retain quantities ql, q2 (or q3, q4) of the infusion product inside the cut portion 19.

As shown in Figure 2, the cut portion 19 is folded in the direction of arrows F4 to form a bag 20 containing quantities ql, q2 of the infusion product, and having four portions 11,12,13,14, which are sealed as shown in Figure 3.

More specifically, as shown in Figure 3, the bottom f of bag 20 is folded, by means not shown, to form two pockets 20a, 20b containing quantities ql, q2 of infusion product respectively.

As bag 20 is fed in the direction of arrow F1, systems identical'with those in Figure 1 insert yarn 13

of heat-seal material inside portions 11,12,13,14 to form a bead 21 for sealing by a sealing head 30.

Sealing head 30 comprises a heat-producing or ultrasonic wave-producing device 31; and a countermember 32, which is moved, by means not shown, in the direction of arrow F2, i. e. perpendicular to the feed direction of bag 20.

It should be stressed that, by virtue of the porosity of the material of which strip 11 is made, the molten material resulting from melting yarn 13 ensures portions 11,12,13,14 are sealed, even if yarn 13 is not inserted between portions 11,12 on one side and 13, 14 on the other. That is, portions 11,12,13,14 are sealed even if yarn 13 is simply rested on portion 11 or 14, or is inserted between portions 11 and 12 or 13 and 14.

The advantages of the device according to the present invention are as follows: -use of strips of paper substantially comprising cellulose, to preserve the original flavour of the infusion product; and -perfect sealing of the bag, while at the same time eliminating the use of staples, which could work loose and be accidentally swallowed by the consumer in the infusion.