Title of Invention

UNIT FOR SEALING FILTER BAGS FOR PRODUCTS FOR INFUSION.

Abstract

AS unit for sealing filter bags for products for infusion comprises at least a shaped revolving roller (3) with circumferial and redial track (3, 4) that act as guides to make longitudinal and transversal contact seals on a web (5) of filler paper folded onto itself and moveing order the roller (2) using sealing sonotrode means (6) arrenged in sealing position under the roller (2) and close to the inmoving web (5) of filter paper with is sucession of substentially flaslened filter bages formed on it the sealing sonotrode means (6) being operated upon by fluid driven menas (7) desinged to control through approprate means (8) the variable constitute by the contact force and/or the diseses between the sizilling means (6) and the roller (2)

Full Text

UNIT FOR SEALING FILTER BAGS FOR PRODUCTS FOR INFUSION Technical field The present invention relates in general to unit for sealing filter bags for products for infusion and in particular to an ultrasound unit for sealing lengths of filter paper. We refer in particular to the sealing process performed in machines for making filter bags or sachets containing a product for infusion such as tea, camomile and the like. Background Art Prior art machines for making filter bags from a web of filter paper comprise a plurality of stations, including a station for feeding a web of filter paper, a folding station and a first station for longitudinally sealing the folded web to form a continuous tubular wrapping of filter paper and preferably for transversally sealing the continuous tubular wrapping to form a succession of filter bags of substantially flattened shape. The longitudinal and transversal sealing station comprises a specially shaped upper roller with tracks for longitudinally and transversally sealing the continuous tubular wrapping of filter paper. The seals may be made by heat sealing means or, in the solutions of the latest generation, by sonotrodes, positioned in contact with the product to be sealed. In practice, the sonotrode is the transducer element that converts the power supply into vibrations that are discharged onto the product to be sealed. Current sealing units based on sonotrodes usually comprise a pair of sonotrodes placed side by side to enable both seals to be made. The sonotrodes are positioned so that they face the roller and are mounted on a rigid structure so as to keep the gap between each sonotrode and the filter paper as constant as possible. Indeed, the applicant has found that the relative position between the emitting surface of the sonotrode and the product supporting surface constitutes a fundamental variable for good sealing quality. Current sealing units based on sonotrodes, however, involve highly rigid systems of supports with a multiplicity of sensors and devices for controlling the force applied to the sonotrodes which make it extremely difficult to keep this relative position firm and constant. Indeed, the system is unsuitable for very thin materials such as filter paper since the rigidity of the supports and the high number of external control variables for maintaining the distance between the sonotrode and the product create vibrations resulting in distances that are larger than acceptable for a good quality" seal and slowing down sealing operations themselves on account of control and feedback between the sonotrodes and the control systems. In this context, references are made to DE 19536881, US 6592711, JP 2004123150 which do not disclose that the sealing sonotrode means are arranged in sealing position under the roller. By contrast, DE 19536881 and US 6592711 disclose that the sealing sonotrode means are arranged in sealing position over the roller, whilst JP 2004123150 discloses that the sealing sonotrode means are arranged in sealing position on the side of the roller. The feature of positioning the sonotrode means under the roller , as suggested by the present invention, solves the objective technical problem of providing a more stable working of the machine, since, the weight of the sonotrode means aims to maintain the sonotrodes away from the roller (downwards), so avoiding accidental and undesired shocks between the sonotrode means and the roller (for example, due to vibration of the sonotrode). None of the aforesaid prior art documents (DE 19536881, US 6592711, JP 2004123150) are suitable for solving said objective technical problem, since, DE 19536881 and US 6592711 teach away from the solution of the problem (the weight of the sonotrode means tends to push them and shock against the roller. In US 6592711, even if it provides damping means for reducing vibrations, shocks can occur, since, the weight of the sonotrodes tend to push them towards the roller and JP 2004123150 does not have a useful action of weight of the sonotrode means to prevent said shocks (the sonotrodes move horizontally). It would be also kindly appreciated that such considerations are not linked to a necessary heavy weight of the sonotrode, since, even a low-weight sonotrode can reach the same advantages. In fact, irrespective of the exact value of the sonotrode"s weight, the latter tends anyway to push the sonotrode away from the roller in the case that the sonotrode is mounted under the roller, and therefore, a very useful effect is achieved and any hammer-effect on the roller, due to vibrations of the sonotrode, is avoided. Both DE 19536881 and US 6592711 refer to the welding of thermoplastic material whilst the present invention, as discussed hereinafter, refers to the welding of a continuous web of filter paper. It is known that sheets or webs of thermoplastic material (for example, those for plastic folders as commonly used) have a thickness that is greater than the thickness of the filter paper commonly used for making filter bags of sachets. Consequently, different technical problems arise when processing the two types of material. Such different problems involve important implicit technical differences between corresponding unit for sealing, which involve, for example, differences in the distance between the sonotrode and the product or differences in the rigidity of the unit or, even more, differences in the length of the stroke movement of the sonotrode towards and away from the roller. In particular, the technical problem underlying the instant invention is that the rigidity of the supports and the high number of external control variables for maintaining the distance between the sonotrode and the product create vibrations resulting in distances that are larger than acceptable for a good quality seal and slowing down sealing operations themselves on account of control and feedback between the sonotrodes and the control system. Such a technical problem can be considered as avoiding disengagement between the filter paper which is very thin and the sonotrode. DE 19536881 does not face such a technical problem, since, it does not disclose means for reducing vibration of the sonotrode. US 6592711 faces the technical problem of making the sonotrode correctly follow, with constant pressure, the surface of the web to be welded. Furthermore, US 6592711, does not disclose the processing of a filter paper, which is thinner than a thermoplastic web. The present invention therefore has an object to overcome the above mentioned drawback through a unit that enables the sealer sonotrode to apply a substantially constant contact force on the product to be sealed, while at the same time allowing high operating speeds and reducing costs. Disclosure of the invention According to the invention, this object is achieved by a unit for sealing filter bags for products for infusion, the unit comprising at least : a shaped revolving roller with circumferential and radial tracks that act as guides to make longitudinal and transversal contact seals on a web of filter paper folded onto itself and moving under the roller, characterized by using : sealing sonotrode means arranged in sealing position under the roller and close to the moving web in such a way as to form a tubular web of filter paper with a succession of substantially flattened filter bags formed on it; said sealing sonotrode means being caused to be operated upon by fluid-driven means designed to control, through appropriate means, the variable constituted by the contact force and / or the distance between the sealing means and the roller. Description of the drawinqs The technical characteristics of the invention, with reference to the above aims, are clearly described in the claims below and its advantage are apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate a preferred embodiment of the invention provided merely by way of example without restricting the scope of the inventive concept, and in which: - Figure 1 is a front view, with some parts cut away and others in cross section, of an ultrasound unit for sealing lengths of filter paper according to the invention; - Figure 2 is a side view, with some parts cut away and other parts in cross-section, of the unit of Figure 1; - Figure 3 is a schematic top plan view, with some parts cut away and other parts in cross-section, of the unit of Figure l. Detailed description of the preferred embodiments of the invention With reference to the accompanying drawings, in particular Figure 1, the unit according to the invention is used to seal filter bags for products for infusion. More specifically, the unit, which is denoted in its entirety by the numeral l, may be used to make longitudinal and transversal seals on a web of filter paper 5 (drawn with a dashed line) unwound from a roll of filter paper and folded onto itself at a suitable station (neither of these being illustrated in the accompanying drawings). The unit 1 essentially comprises: - a shaped revolving roller 2 with circumferential and radial tracks 3 and 4 that act as guides to make a longitudinal and transversal contact seal on a web 5 of filter paper folded onto itself and moving under the roller 2 (see arrow A), using - sealing sonotrode means 6 arranged in sealing position under the roller 2 and close to the moving web 5 in such a way as to form a tubular web of filter paper with, a succession of substantially flattened filter bags formed on it. Still with reference to Figure 1, the sealing sonotrode means 6 are operated upon by fluid-driven means 7 designed to control, through appropriate means 8, the variable constituted by the contact force and/or the distance between the sealing means 6 and the roller 2. More specifically, the fluid-driven means 7 may consist of at least one pneumatic cylinder 7c linked at one end to a fixed lower frame 9 (forming part of the machine) and at the other end to the upper portion of the sealing sonotrode means 6. As illustrated in Figures 2 and 3/ the sealing sonotrode means 6 are two separate sonotrode units 6a and 6b mounted side by side in such a way as to perform two separate sealing operations, resulting in a longitudinal seal (made by the unit 6a) " and a transversal seal (made by the unit 6b), acting in conjunction with respective plates 6c, 6d that come into contact with the passing product and with the aforementioned tracks 3 and 4. The first sonotrode 6a is in constant contact with the web 5 against a circumferential track 3 on the roller 2, whilst the second sonotrode 6b is spaced from the web 5 and makes a transversal each time one of the radial tracks 4 passes. The sonotrode units 6a and 6b are supported by a plate 10 that is linked to a shaft 11 protruding from the fixed frame 9. The fluid-driven means 7 preferably comprise two cylinders 7c and 7d linked at the top to the plate 10 in such a way that the first cylinder 7c permits adjustment of the contact force on the first sonotrode 6a that makes the longitudinal seal on the web 5, and the second cylinder 7d permits adjustment of the gap between the working end of the other sonotrode 6b and the respective transversal sealing track 4 facing the sonotrode 6b. The aforementioned means 8 for controlling the cylinders 7c and 7d may consist of a respective pressure switch 8a designed to vary the contact force and/or the distance of the sonotrode units 6a, 6b. It will be understood that the invention can be modified and adapted in several ways without thereby departing from the scope of the inventive concept. Moreover, all the details of the invention may be substituted by technically equivalent elements. WE CLATM : 1. Unit for sealing filter bags for products for infusion, the unit (1) comprising at least: a shaped revolving roller (2) with circumferential and radial tracks (3, 4) that act as guides to make longitudinal and transversal contact seals on a web (5) of filter paper folded onto itself and moving under the roller (2), characterized by using : sealing sonotrode means (6) arranged in sealing position under the roller (2) and close to the moving web (5) in such a way as to form a tubular web of filter paper with a succession of substantially flattened filter bags formed on it; said sealing sonotrode means (6) being caused to be operated upon by fluid-driven means (7) designed to control, through appropriate means (8), the variable constituted by the contact force and / or the distance between the sealing means (6) and the roller (2). 2. The unit as claimed in claim 1, wherein the fluid-driven means (7) consist of at least one pneumatic cylinder (7c). 3. The unit as claimed in claim 1, wherein the fluid-driven means (7) consist of at least one pneumatic cylinder (7c) linked at one end to a fixed lower frame (9) and at the other end to the upper portion of the sealing sonotrode means (6). 4. The unit as claimed in claim 3, wherein the sealing sonotrode means (6) are two sonotrode units (6a, 6b) mounted side by side on a plate (10) linked to a shaft (11) protruding from a fixed frame (9), and the fluid-driven means (7) comprise respective pneumatic cylinders (7c, 7d) linked at the top to the plate (10) in such a way that the first cylinder (7c) permits adjustment of the contact force of the first sonotrode (6a) that makes the longitudinal seal on the web (5), and the second cylinder (7d) permits adjustment of the gap between the working end of the other sonotrode (6b) and the respective transversal sealing track (4) facing the sonotrode (6b). 5. The unit as claimed in claim 1, wherein the means (8) for controlling the fluid-driven means (7) consist of a pressure switch (8a). A unit for sealing filter bags for products for infusion comprises at least : a shaped revolving roller (2) with circumferential and radial tracks (3, 4) that act as guides to make longitudinal and transversal contact seals on a web (5) of filter paper folded onto itself and moving under the roller (2), using sealing sonotrode means (6) arranged in sealing position under the roller (2) and close to the moving web (5) in such a way as to form a tubular web of filter paper with a succession of substantially flattened filter bags formed on it; the sealing sonotrode means (6) being operated upon by fluid-driven means (7) designed to control, through appropriate means (8), the variable constituted by the contact force and / or the distance between the sealing means (6) and the roller (2).

Documents:

01675-kolnp-2005-abstract.pdf

01675-kolnp-2005-claims.pdf

01675-kolnp-2005-description complete.pdf

01675-kolnp-2005-drawings.pdf

01675-kolnp-2005-form 1.pdf

01675-kolnp-2005-form 3.pdf

01675-kolnp-2005-form 5.pdf

01675-kolnp-2005-international publication.pdf

1675-kolnp-2005-granted-abstract.pdf

1675-kolnp-2005-granted-assignment.pdf

1675-kolnp-2005-granted-claims.pdf

1675-kolnp-2005-granted-correspondence.pdf

1675-kolnp-2005-granted-description (complete).pdf

1675-kolnp-2005-granted-drawings.pdf

1675-kolnp-2005-granted-examination report.pdf

1675-kolnp-2005-granted-form 1.pdf

1675-kolnp-2005-granted-form 18.pdf

1675-kolnp-2005-granted-form 3.pdf

1675-kolnp-2005-granted-form 5.pdf

1675-kolnp-2005-granted-gpa.pdf

1675-kolnp-2005-granted-letter patent.pdf

1675-kolnp-2005-granted-reply to examination report.pdf

1675-kolnp-2005-granted-specification.pdf

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