An apparatus and method for heating a movable web

Abstract

The present invention discloses a heating unit for heating a continuous web (18, 20), comprising: a heating roller (44) that rotates about a rotation axis (46) and has an outer surface (86) including a pattern of a heat-conducting region (88) and an insulating region (90); and at least one induction heater (98) electromagnetically coupled to the heat-conducting region (88) of the outer surface (86) of the heating roller (44).

Description

Technical Field

[0001] This invention generally relates to the packaging of articles, especially the packaging of flat articles, i.e., articles with a thickness less than other dimensions.

[0002] The development of this invention is particularly focused on its application in the packaging of articles, which are encapsulated between two opposing sheets whose edges are joined by a heat-activated adhesive, for example in the field of packaging hygiene articles such as sanitary napkins, plasters (such as plasters for covering wounds, medicated plasters, analgesic plasters, heated plasters containing or not containing medicine).

[0003] More specifically, the present invention relates to an apparatus and method for locally heating a continuous web of material moving in the longitudinal direction.

[0004] In the following description, reference will be made to this particular field, without loss of generality. Background Technology

[0005] In the medical field, there are different types of plasters. In many cases, these products are boxed without further packaging. In some cases, the plasters are individually packaged in envelope-shaped packaging before being boxed.

[0006] Individual packaging of medicated plasters is achieved by encapsulating a single plaster between two flexible sheets that overlap each other, sandwiching the plaster together and holding them together at their edges with an adhesive. Typically, heat-activated adhesives are used in this field because they ensure stable fixation of the sheets, thus protecting the item from external agents. Due to these heat-activated adhesives, once the packaging is opened, it is no longer resealable, allowing health and hygiene standards associated with medicated plasters or similar items to be met. The packaging can be formed from two sheets of paper, one of which has a heat-activated adhesive applied to its inner surface. The sheet with the heat-activated adhesive can be a layered material already provided with the adhesive.

[0007] In existing equipment, packaging plasters between two flexible sheets is accomplished by advancing a continuous array of plasters spaced apart from each other along the machine direction, and two continuous webs overlapping each other on opposite sides of the continuous plaster arrays, one of which has a layer of heat-activated adhesive, thereby forming a continuous composite belt consisting of the two continuous webs and the continuous plaster array sandwiched between them. The packaging is closed by passing the continuous composite belt through at least one pair of pressure rollers.

[0008] The bonding between the two webs is achieved by activating the adhesive with heat, which occurs when the flexible sheets are compressed together along the compression line. Packaging is then achieved by transversely cutting the continuous composite strip along the transverse weld between each pair of items.

[0009] One of the main problems with existing equipment is that the current maximum speed of packaging equipment is approximately 50-60 m / min. This speed limitation is due to the fact that as the machine speed increases, the pressure rollers cannot impart sufficient energy to the flexible sheets to allow the adhesive material to be properly transferred from one sheet to another, because the contact time between the pressure rollers and the sheets decreases proportionally. In this case, increasing the equipment speed beyond the 50-60 m / min limit would compromise the quality requirements stipulated by the plaster manufacturer.

[0010] US5613601A discloses a method and apparatus for heat-sealing a dispensing package comprising a permeable bag formed of two nonwoven webs, the permeable bag encapsulating a predetermined amount of particulate product, such as tea or coffee, which releases flavoring substances upon immersion in a liquid. The nonwoven webs have heat-activated bonding surfaces, thereby allowing for a permanent closure of the bag. One of the nonwoven webs is wound around the outer surface of a heated roller, which is locally heated by a heating resistor embedded in the heated roller.

[0011] In some applications, to increase the speed of packaging equipment, it may be necessary to heat localized areas of the heating rollers at very high temperatures (approximately 200-250°C). In these cases, the construction of the heating rollers should include a series of measures to protect various components from the effects of high temperatures.

[0012] Furthermore, due to the thermal diffusion through the metal components of the heating roller, the energy required to maintain a relatively small portion of the heating roller at the desired temperature is very large.

[0013] In existing heating rollers, heat is transferred from the heating resistor to the heating area by conduction, which is inherently slow and affected by thermal inertia and the insulation properties of the components involved.

[0014] Another drawback of the existing technology is that when the machine is started after a long period of inactivity, it takes a considerable amount of time before the heating rollers reach their operating temperature. Summary of the Invention

[0015] The purpose of this invention is to overcome the problems of the prior art.

[0016] More specifically, one object of the present invention is to provide an apparatus and method for packaging articles encapsulated between two opposing flexible sheets bonded together by a heat-activated adhesive, the apparatus and method allowing for high production speeds without compromising packaging quality.

[0017] According to the invention, these objectives are achieved by methods and apparatus having the characteristics that form the subject matter of independent claims 1, 8, 9, and 13.

[0018] Optional features of the present invention form the subject matter of the dependent claims.

[0019] The claims are an integral part of the disclosure submitted with respect to this invention. Attached Figure Description

[0020] The invention will now be described in detail with reference to the accompanying drawings, which are given by way of non-limiting example only, in which:

[0021] - Figure 1 This is a schematic diagram of an apparatus for packaging articles according to the present invention.

[0022] - Figure 2 yes Figure 1 The side view of the heating unit indicated by arrow II in the image.

[0023] - Figure 3 yes Figure 2 A plan view of the heating unit.

[0024] - Figure 4 yes Figure 3 The perspective view of the heating roller indicated by arrow IV in the image, and

[0025] - Figure 5 yes Figure 1 The perspective view of the compression unit indicated by arrow V in the figure. Detailed Implementation

[0026] refer to Figure 1 Reference numeral 10 indicates a device for packaging a flat article A in an envelope-shaped package. The envelope-shaped package is closed around article A along the edge of the package.

[0027] Item A can be wound dressing plaster, medicated plaster, pain relief plaster, heating plaster, sanitary napkin, etc.

[0028] Items A are aligned and spaced apart in a continuous array that moves along the machine direction X on the entrance conveyor belt 12.

[0029] The device 10 includes a first supply assembly 14 and a second supply assembly 16, which supply a first continuous web 18 and a second continuous web 20 to the overlapping unit 22, respectively. The first continuous web 18 and the second continuous web 20 are unwound from corresponding spools 19 and 21.

[0030] Continuous webs 18, 20 can be made of paper or plastic material. At least one of the two continuous webs 18, 20 includes a heat-activated adhesive. One of the two continuous webs 18, 20 can be a layered material provided with the heat-activated adhesive. In other embodiments, the heat-activated adhesive can be applied online using an adhesive dispenser. The heat-activated adhesive layer can be applied to the entire surface of at least one of the continuous webs 18, 20, or the heat-activated adhesive layer may already be present thereon. The heat-activated adhesive does not have adhesive properties until it is heated to a temperature above a preset temperature (activation temperature) for a preset time. After pressure is applied, the heat-activated adhesive fixes its state, and generally, even if the heat-activated adhesive is heated to the activation temperature again, it does not change its state.

[0031] In a possible embodiment, the first continuous web 18 may be made of paper with a specific gravity of 8.3 g / m² and may have a heat-activated adhesive layer on its entire surface, while the second continuous web 20 may be made of paper with a specific gravity of 9 g / m² and may have a smooth material layer on its surface similar to silicone. The two continuous webs 18, 20 are joined such that the surface of the first continuous paper sheet 18 with the heat-activated adhesive is in contact with the smooth surface of the second continuous web 20.

[0032] The overlapping unit 22 may include a pair of connecting rollers 24, which are tangent to each other and can rotate in opposite directions about corresponding axes that are parallel to each other and perpendicular to the machine direction X. The connecting rollers 24 may idle about their respective axes of rotation.

[0033] As the two continuous webs 18 and 20 advance toward the tangential region of the two connecting rollers 24, the two continuous webs remain in contact with the outer surface of the respective connecting rollers 24.

[0034] Article A is supplied along the X direction between two continuous webs 18, 20 toward the tangent region between a pair of connecting rollers 24. The two continuous webs 18, 20 overlap each other on opposite sides relative to article A as they pass through the tangent region of the pair of connecting rollers 24.

[0035] Downstream of the overlapping unit 22, a continuous composite strip 26 is formed, comprising two continuous webs 18, 20 that overlap each other, and a continuous array of articles A that are longitudinally spaced apart from each other and sandwiched between the two continuous webs 18, 20. One of the two continuous webs 18, 20 has a heat-activated adhesive layer disposed on its surface facing the other continuous web 18, 20.

[0036] The device 10 includes a compression unit 28 configured to secure two continuous webs 18, 20 to each other by compressing a heat-activated adhesive along a sealing line extending around a single article A.

[0037] The overlapping unit 22 and the compression unit 28 are two independent modules, making the steps of overlapping and compressing the two continuous flexible sheets 18 and 20 independent. Specifically, the compression step is performed when the step of encapsulating the article A between the flexible sheets 18 and 20 is completed, so that the article is completely encapsulated between the continuous sheets 18 and 20 during the compression step.

[0038] refer to Figure 5 The compression unit 28 includes a first compression roller 30 and a second compression roller 32 that cooperate with each other, the first and second compression rollers being configured to compress a continuous composite belt 26 along a frame-shaped compression region 34 surrounding a corresponding article A. The compression region 34 is formed on the outer surface of the first compression roller 30. The compression region 34 may be defined by two consecutive longitudinal compression elements 36 and a plurality of transverse compression elements 38. The compression region 34 may be made of a soft material, such as silicone, to avoid marking on the two consecutive webs 18, 20. The second compression roller 32 may have a smooth outer surface that presses against the longitudinal compression elements 36 and transverse compression elements 38 of the first compression roller 30.

[0039] refer to Figure 1 The first pair of supply rollers 25 can be arranged between the connecting roller 22 and the compression rollers 30, 32, while the second pair of supply rollers 42 can be arranged downstream of the compression rollers 30, 32. The first pair of supply rollers 25 and the second pair of supply rollers 42 are driven at the same circumferential speed, and their purpose is to control the supply speed of the continuous composite belt 26 as it passes through the compression unit 28. The first pair of supply rollers 25 and the second pair of supply rollers 42 may have recessed central portions to avoid compressing the article A.

[0040] refer to Figure 1 The device 10 includes a first heating unit 80 and a second heating unit 82, which are configured to heat the corresponding continuous web upstream of the overlapping unit 22 when the corresponding continuous webs 18, 20 move in the corresponding longitudinal direction.

[0041] refer to Figure 2 Each heating unit 80, 82 includes a corresponding heating roller 44 that rotates about a corresponding rotation axis 46 and a corresponding heating device 84.

[0042] refer to Figure 4 Each heating unit 80, 82 has a heating roller 44 with an outer surface 86, which includes a pattern of a heat-conducting region 88 and a heat-insulating region 90.

[0043] The heat-conducting region 88 is made of a heat-conducting material, such as steel. In a possible embodiment, the heat-conducting region 88 is frame-shaped and surrounds the corresponding insulating region 90. The heat-conducting region 88 may be formed by two consecutive longitudinal heat-conducting elements 92 and a plurality of transverse elements 94 extending between the two consecutive longitudinal heat-conducting elements 92. In a possible embodiment, the heat-conducting region 88 may have the same shape as the compression region 34 of the compression unit, such that the corresponding first continuous web 18 and second continuous web 20 are heated along a localized heating region having the same shape as the compression region 34.

[0044] The insulation zone 90 can be made of insulation material (e.g. or The thermal insulation material element 96 can also be arranged laterally outward to form a continuous longitudinal thermal conductive element 92.

[0045] refer to Figure 2 and Figure 3 Each heating unit 80, 82 has a heating device 84 including at least one induction heater 98, which is electromagnetically coupled to the heat-conducting area 88 of the outer surface 86 of the heating roller 44.

[0046] An induction heater 98 is configured to heat the heat-conducting area 88 of the heating roller 44 by induction heating. Induction heating is a process of heating conductive materials such as metals through electromagnetic induction.

[0047] The induction heater 98 may include a magnetic core 100, an induction coil 102, and a power unit 104 that supplies high-frequency alternating current (AC) through the induction coil 102. A rapidly alternating magnetic field penetrates the heat-conducting region 88, thereby generating eddy currents within the conductive material. These eddy currents flow through the heat-conducting region 88 and heat it via Joule heating. The frequency of the current used for induction heating depends on the object size, material type, coupling (between the operating coil and the object to be heated), and penetration depth.

[0048] A key characteristic of the induction heating process is that heat is generated within the heat-conducting region 88 of the heating roller 44, rather than through heat conduction from an external heat source. Therefore, the heat-conducting region 88 can be heated very quickly. Furthermore, the induction heating of the heat-conducting region 88 is concentrated on the surface of the region 88 in contact with the first continuous web 18 and the second continuous web 20, with very little heat diffusion towards other parts of the heating roller. This reduces the energy required to operate the heating roller 44 and reduces the need for thermal protection elements within the heating roller 44.

[0049] refer to Figure 2 and Figure 3 In a possible embodiment, the induction heater 98 may be fixed. The magnetic core 100 may have an electromagnetic emission window 106 facing the outer surface 86 of the heating roller 44. This is particularly advantageous because it avoids the need for a rotary electrical connector for powering the movable electric heating element. Another significant advantage is that the heating roller 44 can be replaced to change the form of the packaging without replacing the heating device 84.

[0050] During operation, the first or second continuous web is wound around the outer surface 86 of the heating roller 44 and passes through the narrow gap between the outer surface 86 and the electromagnetic emission window 106.

[0051] The induction heater 98 can move relative to the heating roller 44 along direction A between a close operating position and a spaced-apart non-operating position, such that in the non-operating position, the continuous webs 18, 20 can be more easily inserted between the emission window 106 and the outer surface 86 of the heating roller 44.

[0052] refer to Figure 2 Heating units 82 and 84 may include a temperature sensor 108 configured to detect the temperature of the continuous webs 18 and 20 downstream of the induction heater 98. Power unit 104 may receive a temperature signal from the temperature sensor 108 and may be configured to adjust the intensity of the electromagnetic field generated by the induction heater 98 based on the temperature detected by the temperature sensor 108, thereby maintaining the temperature of the continuous webs 18 and 20 within a predetermined range.

[0053] refer to Figure 1 The first supply assembly 14 and the second supply assembly 16 supply corresponding first continuous webs 18 and second continuous webs 20 on the outer surfaces of the corresponding heating rollers 44. The first continuous webs 18 and second continuous webs 20 are wound on the outer surfaces of the corresponding heating rollers 44 at a winding angle that depends on the diameter of the heating rollers 44 and the supply speed of the first continuous webs 18 and second continuous webs 20.

[0054] Heating roller 44 heats the corresponding continuous webs 18 and 20 along a localized heating area, which has the same shape as the heat-conducting area 88. The continuous webs 18 and 20 can be locally heated at a temperature in the range of 200-250°C.

[0055] refer to Figure 1 The first compression roller 30 and the heating roller 44 of the compression unit 28 are controlled by an electronic control unit 78, which drives the heating roller 44 and the compression roller 30 around their respective axes at the same speed and keeps the heating and compression regions 34 of the continuous web in phase with each other, so that the continuous composite belt 26 is compressed in the compression region 34 which overlaps with the corresponding heating regions of the first continuous web 18 and the second continuous web 20.

[0056] Heating the continuous flexible webs 18 and 20 on the heating roller 44 allows the continuous composite belt 26 to have a higher speed as it passes through the compression unit 28.

[0057] The first supply assembly 14 and the second supply assembly 16 can be configured to supply the first continuous web 18 and the second continuous web 20 along their respective longitudinal directions with a certain longitudinal tension, which can be between 50 and 200 N. For continuous webs made of paper, the optimal tension is approximately 100 N. This tension is maintained along the path of the first continuous web 18 and the second continuous web 20 extending upward from the respective supply assemblies 14, 16 to the compression unit 28.

[0058] refer to Figure 1 In a possible embodiment, the first supply assembly 14 and the second supply assembly 16 may include corresponding supply rollers 58 and 60, which may be driven at a lower circumferential speed than the supply rollers 25 and 42 to maintain longitudinal tension of the first continuous web 18 and the second continuous web 20. The electronic control unit 78 may control the circumferential speed of the supply rollers 58 and 60 based on signals provided by tension measuring devices 64 and 66, which measure the longitudinal tension of the corresponding first paper sheet 18 and the second continuous paper sheet 20. Each tension measuring device 64 and 66 may include a load unit 68 formed by an idler roller on which the first continuous paper sheet 18 or the second continuous paper sheet 22 is wound. The load unit 68 sends a signal to the electronic control unit 78 indicating the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 22. If, for any reason, the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 changes relative to a preset value, the electronic control unit 78 changes the speed of the supply rollers 58 and 60 to maintain the tension of the first continuous paper sheet 18 and the second continuous paper sheet 22 at the preset value.

[0059] Of course, without prejudice to the principles of the invention, the details of the construction and embodiments may be varied extensively with respect to what is described and shown, without departing from the scope of the invention as defined by the appended claims.

Claims

1. An apparatus for packaging articles (A), comprising: - first and second feeding assemblies (14, 16) configured for feeding first and second continuous webs (18, 20) in respective longitudinal directions, - an entry conveyor (12) configured for feeding a string of articles (A) between the first and second continuous webs (18, 20), - a compression unit (28) configured for compressing the first and second continuous webs (18, 20) around the articles (A), - at least one heating unit (80, 82) configured for heating at least one of the first and second continuous webs (18, 20), the at least one heating unit comprising a heating roller (44) rotating around an axis of rotation (46) and having an outer surface (86) comprising a pattern of thermally conductive regions (88) and thermally insulating regions (90), and - heating means (84) for heating the thermally conductive regions (88), wherein the heating means (84) comprise at least one induction heater (98) electromagnetically coupled with the thermally conductive regions (88) of the outer surface (86) of the heating roller (44), wherein the induction heater (98) is located outside the heating roller (44), characterized in that it comprises: - an overlapping unit (22) configured for overlapping the first and second continuous webs (18, 20) with each other on opposite sides of the string of articles (A) upstream of the compression unit (28), and the at least one heating unit configured for heating at least one of the first and second continuous webs (18, 20) is located upstream of the overlapping unit (22).

2. The apparatus of claim 1, wherein, The induction heater (98) is stationary.

3. The apparatus of claim 1, wherein, The induction heater (98) has an electromagnetic emission window (106) facing the outer surface (86) of the heating roller (44).

4. The apparatus of claim 3, wherein, The induction heater (98) is movable with respect to the heating roller (44) between a close operating position and a spaced apart non-operating position, so that in the non-operating position a continuous web (18, 20) can be inserted between the electromagnetic emission window (106) and the outer surface (86) of the heating roller (44).

5. The apparatus of claim 1, wherein, The heating roller (44) comprises a plurality of frame-shaped thermally conductive regions (88) surrounding corresponding thermally insulating regions (90).

6. The apparatus of claim 1, wherein, The thermally conductive regions (88) are formed by two consecutive longitudinal thermally conductive elements (92) and a plurality of transversal heating elements (94) extending between the two consecutive longitudinal thermally conductive elements (92).

7. The apparatus of any one of claims 1-6, comprising: a temperature sensor (108) configured for detecting a temperature of the continuous web (18, 20) downstream of the induction heater (98); and a power unit (104) configured for adjusting an intensity of the electromagnetic field generated by the induction heater (98) as a function of the temperature detected by the temperature sensor (108).

8. A method for packaging articles (A), comprising: - feeding first and second continuous webs (18, 20) in respective longitudinal directions by means of first and second feeding assemblies (14, 16), at least one of the first and second continuous webs having a heat-activated adhesive on one surface, - feeding a string of articles (A) between the first and second continuous webs (18, 20) by means of an inlet conveyor (12), - heating at least one of the first and second continuous webs (18, 20) by passing it over an outer surface (86) of a heating roller (44), the outer surface (86) comprising a pattern of thermally conductive regions (88) and thermally insulating regions (90), wherein the thermally conductive regions (88) are heated by an induction heater (98) located outside the heating roller (44) and electromagnetically coupled to the thermally conductive regions (88), - overlapping the first and second continuous webs (18, 20) on opposite sides of the string of articles (A) by means of an overlapping unit (22) after the heating step, - compressing the first and second continuous webs (18, 20) around the articles (A) and fixing them to each other by the heat-activated adhesive by means of a compression unit (28) after the overlapping step.

9. The method of claim 8, wherein, The at least one continuous web (18, 20) is locally heated along a frame-shaped heating region.

10. The method of claim 9, wherein, The first and second continuous webs (18, 20) are compressed along a frame-shaped compression region (34) that surrounds the respective articles (A) and overlaps the respective heating region. The at least one continuous web (18, 20) is locally heated along a frame-shaped heating region. The first and second continuous webs (18, 20) are compressed along a frame-shaped compression region (34) that surrounds the respective articles (A) and overlaps the respective heating region.

Images