Welding station and method for producing package comprising heat-sealed wrap

Abstract

The present application relates to a welding station for producing a wrap comprising a first sheet and a second sheet heat-sealed along an annular welding region, the welding station comprising a support wheel rotatable about a wheel axis and one or more welding devices housed on the support wheel, the present invention relates to a welding device comprising: a welding member that transfers heat to a first sheet of wrap until a predetermined welding temperature is reached; the supporting body comprises a radial outer wall, the radial outer wall internally limits a bracket, and the welding component is at least partially accommodated in the bracket in a swingable manner; and a rod axially movable relative to the wheel axis between a retracted position and an advanced position, the support body being integrally formed with an axial end of the rod; a support assembly comprising at least one support member adapted to provide support for the welding member; and a base assembly joined to the support wheel and supporting the head assembly and the support assembly.

Description

Field of the Invention

[0001] The present invention generally belongs to the field of packaging consumer goods ("merchandise") in wrappers made of heat-sealable sheet materials. Specifically, the present invention relates to a welding workstation and a method for producing heat-sealed wrappers suitable for preventing the product inside the wrapper from coming into contact with the atmosphere outside the wrapper.

[0002] The present invention is particularly suitable for packaging heat-sensitive, thermally unstable or generally low-melting-point products (i.e., products with a melting point below 50°C), where prolonged proximity to a heat source may cause the product itself to deteriorate and / or be damaged. Here are just a few examples of products that may fall within these definitions: chocolate-like products with a melting temperature of around 35 - 37°C; refrigerated products stored at a temperature between 2 - 6°C; products stored below 0°C, such as frozen foods, ice cream or similar products; or products that lose or change their sensory qualities when in proximity to a heat source. As other examples of low-melting-point products, mention can also be made of soap or detergent products outside the food industry, cosmetic products (such as lipsticks). Background Art

[0003] Devices for producing heat-sealed wrappers are known, which are formed by a first part that defines a cavity for accommodating the product, and a second part that is applied to the first part by heat-sealing to seal the cavity and prevent the contents therein from coming into contact with the air outside the wrapper.

[0004] The said devices are usually part of a welding workstation on a machine for packaging specific products. Each device includes a head provided with a heating element that comes into contact with the two parts of the wrapper (in the area where they overlap) to heat them and weld these two parts together, thus obtaining a sealed container.

[0005] Welding workstations generally develop linearly, with multiple welding heads carried by a horizontal conveyor belt, such that the axes of the welding heads are oriented parallel to each other. Then, a pair of wrapper parts to be welded are successively conveyed to each welding head in order to mass-produce multiple wrappers containing the corresponding products. However, a welding workstation configured in this way occupies a relatively large floor area, especially in the case of large-scale production.

[0006] To solve this problem, the welding heads can be arranged at angular intervals on a rotatable wheel, such that the axes of these welding heads are oriented along the corresponding radii of the wheel. In this way, a very compact welding head can be obtained in terms of shape and size.

[0007] An example of a welding workstation configured in this way is presented in document WO2015 / 121838A2, which describes a system for packaging coffee in capsules.

[0008] Specifically, each capsule includes a cup (containing coffee powder), the top edge of the cup is surrounded by a flange, and a sealing film is heat-sealed on the flange.

[0009] By interposing the flange and the film between a pair of support members movable perpendicular to the axis of the cup and a welding head, the two parts forming the capsule are joined together. The welding head presses the flange and the film against the support members while providing heat, thereby forming a weld seam between the peripheral edge of the film and the flange of the cup.

[0010] However, the welding device configured in this way, although suitable for joining the film to a rigid or semi-rigid support (such as the cup of a coffee capsule), is not suitable for making a sealed wrapper formed by joining two sheet materials. Because in this case, the welding surface of at least one of the two sheets is not completely flat with respect to the other sheet (such as the flange of the coffee capsule mentioned above), which may cause voids and defects at the interface between the two sheets, resulting in the loss of sealing performance.

[0011] For example, in the packaging methods described in WO2012 / 098524 and EP3160864, which involve a sealed wrapper formed by two heat-sealed sheets (which constitute a preferred embodiment that can be obtained using the welding workstation and method according to the present invention), the first wrapper sheet is preformed or stretched into a cup-shaped or U-shaped configuration, and the opening is surrounded by a radial flange. After placing the product in the first sheet thus formed, preferably a pressing operation is performed on the neck of the sheet to attach the sheet to the product. Then a second wrapper sheet (generally in the form of a disk) is superimposed on the flange, and it is heat-sealed along an annular welding area, and the two sheets are arranged between the support members and the welding head.

[0012] However, when the sheet material is preformed or stretched, in order to adhere to the surface of the product (which may be an irregular surface), it may be further deformed due to the pressing action, and naturally creases will be generated, resulting in the flange not being a perfect plane but having corrugations and wrinkles. Even after welding, it may cause channels at the junction between the two sheets, and air may creep through the channels, causing unnecessary exchange between the cavity inside the wrapper and the external environment, thereby resulting in the loss or weakening of the sealing effect. Summary of the Invention

[0013] One of the objects of the present invention is to overcome the above problems.

[0014] Specifically, an object of the present invention is to provide a welding head and a method for producing a package including a heat-sealed wrapper, which can obtain a sealed wrapper.

[0015] Another object is to provide a method for packaging thermosensitive or heat-labile products.

[0016] Another object of the present invention is to provide a welding head and a method for producing a package including a heat-sealed wrapper, having a high production capacity, even equal to or greater than 800 packages per minute.

[0017] To obtain such a result, when the welding device is placed on a rotatable wheel, the pressure distribution exerted by the welding head on the interface between two sheets must be as uniform as possible.

[0018] In fact, a non-uniform distribution of the welding pressure may prevent creases and wrinkles on the sheets from being fully flattened, thus affecting the sealing of the wrapper.

[0019] The higher the rotational speed of the welding head, the more severe this negative effect is, because the inertia phenomenon may hinder the welding process between the sheets.

[0020] To achieve this effect, the welding member is swingably received in a bracket formed in the support body, which is in turn carried by the rotatable wheel of the welding workstation. In this way, the welding member can compensate for any non-uniformity of the pressure exerted on the wrapper sheets.

[0021] Furthermore, according to a preferred embodiment of the present invention, the welding member includes a welding element provided with one or more protruding ridges or ribs, allowing the pressure exerted by the welding member to be concentrated on the closed area of the wrapper sheets, thus generating a local peak pressure capable of flattening the creases and wrinkles of the sheets and interrupting any channels that may be formed at the interface therebetween.

[0022] The above object and advantages, as well as other objects and advantages, can be achieved by a welding workstation and a method for producing a heat-sealed wrapper having the features defined in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The functional and structural features of some preferred embodiments of a welding workstation and a method for producing a heat-sealed wrapper according to the present invention will now be described. With reference to the accompanying drawings, in which:

[0024] Figure 1 is a schematic view of a welding workstation according to an embodiment of the present invention, in which a support wheel and a plurality of welding devices can be seen, and different operating steps are shown according to their angular positions on the wheel;

[0025] Figures 2 to 4 is a schematic cross-sectional view of a welding device according to an embodiment of the present invention, showing respectively the first step of the welding process (wherein the welding member retracts radially relative to the support wheel and the support member opens), the second step (wherein the welding member advances radially and the support member closes), and the third step (wherein the welding member further advances radially and the support member closes);

[0026] Figure 5 is a schematic perspective view of a welded member according to an embodiment of the present invention; and

[0027] Figure 6 is Figure 5 a schematic cross-sectional view of the welded member in DETAILED DESCRIPTION

[0028] Before explaining in detail the embodiments of the present invention, it should be noted that the application of the present invention is not limited to the design details and configurations of the components shown in the following description or drawings. The present invention can also have other embodiments and can be implemented or constructed in different ways in practice. It should also be understood that these phrases and terms are for descriptive purposes and should not be construed as restrictive.

[0029] The following description relates only by way of non-limiting example to the production of packages of the type described in WO2012 / 09852464 or EP3160864, or generally to the production of packages containing the above products. Furthermore, although the present invention has been developed for the production of sealed packages and is particularly suitable for the production of sealed packages, it should be understood that the hermeticity of the package is not a limiting condition, since it can be easily understood that the advantageous structural features of the present invention are equally applicable to the manufacture of general heat-sealed packages, and the term "sealed" should not be understood in an absolute sense, i.e., meaning that there is no material exchange whatsoever between the inside and outside of the package.

[0030] In addition, the sheet materials that can be used in the present invention include any packaging material that is heat-sealable per se or at least provided with a heat-sealable coating in the areas used for welding. It can be a single-layer thermoplastic packaging material, preferably a packaging material suitable for contact with food, such as polypropylene, or it can be a two-layer or more-layer joined packaging material, such as a laminate or coextrusion of an aluminum / plastic material, a paper / plastic material, optionally including an inner or outer metallized layer.

[0031] The heat-sealability characteristics can be imparted by applying a heat-sealable paint or coating to the surface used for welding or to the predetermined areas used for welding.

[0032] The sheet packaging material can further include one or more layers of plastic materials having a barrier effect, or include fillers having an oxygen and / or water vapor barrier effect, which is well known in the packaging industry.

[0033] The welding workstation according to the present invention will be described below by way of example with reference to the accompanying drawings. The welding workstation is used for producing a wrapper, which includes at least a first sheet and a second sheet. The first sheet and the second sheet jointly define a cavity for accommodating a product, and wherein the at least first sheet and the second sheet are heat-sealed along a welding area that at least partially surrounds the cavity.

[0034] The welding workstation includes a support wheel 90 that is preferably continuously rotatable about the wheel axis R-R, and one or more welding devices 1 accommodated on the support wheel 90.

[0035] The welding device 1 in turn includes a head assembly 10, which includes a welding member 11 and a support 16. The welding member is adapted to contact the first sheet of the wrapper, support the first sheet of the wrapper, and transfer heat to the first sheet of the wrapper until a predetermined welding temperature is reached. The support includes a radially outer wall 16a, which forms a bracket inside, and the welding member 11 is swingably and at least partially accommodated in the bracket.

[0036] There is also a rod 19, which can move axially between a retracted position and a forward position relative to the wheel axis R-R, wherein the support 16 is integrally formed with the axial end of the rod 19.

[0037] The welding device 1 further includes a support assembly 20 and a base assembly 60. The support assembly includes at least one support member 21 adapted to provide support for the welding member 11. The base assembly engages with the support wheel 90 and supports the head assembly 10 and the support assembly 20.

[0038] The welding device 1 can be configured in an open configuration and a welding configuration. In the open configuration, the head assembly 10 and the support assembly 20 are spaced apart from each other, the rod 19 is axially retracted, and the at least one support member 21 is in a position adapted to allow the wrapper to be loaded onto / removed from the head assembly 10. In the welding configuration, the head assembly 10 and the support assembly 20 are engaged with each other, the rod 19 is axially advanced, and the at least one support member 21 is engaged to be supported by the welding member 11.

[0039] According to a preferred embodiment (schematically shown in Figure 5 and Figure 6 ), the head assembly 11 includes a skid 18, the cross-section of which is at least partially arched and is adapted to slidably engage with the radially outer wall 16a that defines a bracket inside.

[0040] The skid 18 preferably includes a projection 18a that axially extends from a lower section of the skid 18 in a direction opposite to the welding member 11. The head assembly 10 includes an elastically biasing device 17 that is radially interposed between the outer wall 16a and the projection 18a. Such an elastically biasing device 17 is adapted to push the projection 18a towards a coaxial state relative to the outer wall 16a.

[0041] According to one embodiment, the welding member 11 includes a welding element 12 having an exposed surface 12a that is adapted to contact a first sheet of the wrapper and transfer heat to the first sheet of the wrapper until a predetermined welding temperature is reached. The welding element has a generally closed section that defines a central region 13.

[0042] According to a preferred embodiment, the welding element 12 is at least partially made of a metallic material, preferably a bronze alloy.

[0043] Conveniently, the exposed surface 12a of the welding element 12 has at least one projection or protrusion 12b that is preferably in an annular shape and has a top ridge (round, sharp-cornered, etc.) that defines a narrow welding line or area, i.e., the surface in contact with the sheet, and this surface is capable of locally transferring a greater pressure value to the sheet than the rest of the exposed surface 12a. Even more preferably, there may be two or more concentric protrusions 12b.

[0044] According to a preferred embodiment, the welding member 11 includes a heating element 14 that is coaxially juxtaposed with the welding element 12 on a side of the welding element that is axially opposite to the exposed surface 12a. The heating element 14 includes an electrical conductor adapted to generate heat when energized and a ceramic coating that is embedded in the electrical conductor and is adapted to transfer the heat generated by the electrical conductor to the welding element 12. The ceramic coating is in direct contact with the welding element 12.

[0045] The heating element 14 is preferably made of a ceramic material having a thermal conductivity greater than 50λ (W / mK), more preferably greater than 100λ, and even more preferably greater than 140λ, for example, equal to approximately 170λ.

[0046] The ceramic material may be a technical ceramic, and even more preferably a technical ceramic selected from one of the following categories: silicate ceramics, oxide ceramics, non-oxide ceramics, and piezoelectric ceramics.

[0047] The fact that the heating element 14 is separate from the welding element 12 and includes a ceramic coating enables numerous advantages, such as those associated with the fact that since the ceramic material has thermal conductivity but is electrically insulating, heat transfer from the electrical conductor of the heating element 14 to the welding element 12 can be optimized without interposing an electrical insulating element between the two elements 12, 14, which might impede heat transfer. In this way, traditional bronze or bronze alloy welding elements 12 can be used while still expecting optimized heat transfer from the heating element to the wrapper sheet.

[0048] Furthermore, the ceramic material is fully shapeable such that the interface between the welding element 12 and the heating element 14 can be an exact plane with no voids or air between the two elements to impede heat transfer. In fact, preferably, the welding element 12 has a first plane 12c on the side axially opposite to the exposed surface 12a, and the corresponding second plane 14b of the ceramic coating of the heating element 14 abuts against this first plane.

[0049] According to one embodiment, the head assembly 10 includes an elastic element 15 that is interposed between the support 16 and the heating element 14 and is configured to axially push the heating element against the welding element 12.

[0050] Conveniently, the central region 13 includes at least one suction hole 131 that is in fluid communication with a pneumatic source. A fluid flow (preferably air) flows through the suction hole 131 by suction in order to keep the wrapper (or at least in a first case, the first sheet) attached to the exposed surface 12a.

[0051] The central region 13 may further include cooling holes 132 that are in fluid communication with a pneumatic source. A cooling fluid (such as air) flows out and through the cooling holes 132, and the cooling fluid is adapted to cool the exposed surface 12a. This feature is particularly advantageous when the product within the wrapper is of a low melting point type (such as food, confectionery products, products such as soap, washing products or cosmetic products), so that after the wrapper sheet welding is completed, heat should be removed from the welding area as much as possible to prevent the product from being damaged due to excessive temperature. The faster the production speed, the more serious the problem of excessive heat, because without forced cooling, it is difficult to discharge the heat between one welding cycle and another, and the temperature will locally increase.

[0052] According to a preferred embodiment, the welding element 12 and / or the heating element 14 has an annular shape.

[0053] A temperature sensor may also be provided, which is adapted to detect the instantaneous temperature of the welding element 12 and / or the heating element 14 and generate a signal representing the instantaneous temperature. The temperature sensor is preferably applied to or embedded in the welding element 12 or the heating element 14.

[0054] According to a preferred embodiment, the support assembly 20 includes a pair of supports 21 that are movable between a closed configuration and an open configuration. In the closed configuration, the supports 21 face the welding member 11 to create an axial gap in which the wrapper sheet to be welded can be received. In the open configuration, the welding member 11 is axially exposed to the outside of the welding device so as to be able to receive the wrapper of the food product.

[0055] According to one embodiment, the supports 21 include respective inserts made of elastic material at the interface with the welding member 11, and these inserts are adapted to deform at least partially in accordance with the profile of the exposed surface 12a of the welding member 11. In this way, the profile of the welder (including oval and flat shapes) can be "copied", thereby optimally dispersing the flattening force applied to the wrapper sheet.

[0056] Conveniently, the welding member 11 is axially movable between a retracted position and a forward position. In the retracted position, the welding member 11 is close to the center of the support wheel 90 and cannot apply pressure to the wrapper sheet to be welded. In the forward position, the welding member 11 axially approaches the at least one support member 21 in the closed configuration, such that the welding member 11 can axially apply pressure to the wrapper sheets to be welded held between the welding member 11 and the at least one support member 21.

[0057] According to a preferred embodiment (schematically shown in Figures 2 to 4 ), the welding device 1 includes a primary motion mechanism 30 for controlling the head assembly 10, and the primary motion mechanism can be configured in a thrust configuration and an open configuration. In the thrust configuration, the primary motion mechanism pushes the rod 19 to the forward position. In the open configuration, the primary motion mechanism allows the rod to move axially in the retracted configuration.

[0058] The primary motion mechanism 30 may include a primary link 300, which includes a toggle mechanism formed by two mutually hinged rods. Specifically, the first rod 310 of the toggle mechanism is hinged to a first pivot 311 at the first end and to a second pivot 312 at the opposite end. The first pivot is capable of moving integrally with the rod 19, and the second pivot is capable of moving between a first position and a second position in a direction perpendicular to the axis of the rod 19. In the first position, the second pivot 312 is not aligned with the first pivot 311 along the axis of the rod 19, and in the second position, the second pivot 312 is aligned with the first pivot 311 along the axis of the rod 19. The second rod 320 of the toggle mechanism is hinged to the second pivot 312 at the first end and is hinged to a third pivot 321 at the opposite end, and the third pivot is axially aligned with the first pivot 311. The link 300 is configured such that when the three pivots 311, 312, 321 are not aligned with each other, the rod 19 is in the retracted position, and when the three pivots 311, 312, 321 are aligned with each other, the rod 19 is in the advanced position. With the mechanism configured in this way, a relatively high thrust value of the rod 19 can be obtained without having to adopt a solution with an overly complex structure, because the small spatial travel of the pivots is sufficient to generate a relatively large thrust, which will be transmitted from the rod 19 to the welding member 11 and then from the welding member to the wrapper sheet.

[0059] The primary motion mechanism 30 preferably includes a primary control actuator 35 that engages the second pivot 312 to linearly move the second pivot in a direction perpendicular to the axis of the rod 19.

[0060] The primary motion mechanism 30 may further include a third rod 330 and an auxiliary actuator 38 (which can operate as an alternative to or in combination with the primary control actuator 35). The third rod has a hinged end 331 hinged to the base assembly 60 and a free end 332 opposite the hinged end 331. In this configuration, the third pivot 321 is preferably integrally formed with the third rod 330, and the welding device is configured such that when the auxiliary actuator 38 performs a thrust action (i.e., is adapted to push the welding member 11 toward the support 21), the third pivot 321 tends to axially displace along the rod 19 toward the support 21.

[0061] The auxiliary actuator 38 can also operate so as to retract the welding member 11 relative to the support 21 regardless of the action of the primary control actuator 35 and / or the rotational speed of the support wheel 90, thereby disengaging the welding member 11 from the wrapper. This can protect the product from damage, for example, damage caused by long-term system downtime (preventing excessive heat from being transferred to the product due to machine downtime). The auxiliary actuator 38 is preferably capable of operating to keep the welding member 11 in contact with the wrapper sheet for a predetermined time regardless of the rotational speed of the support wheel 90.

[0062] The auxiliary actuator 38 may be a pneumatic actuator including a cylinder defining a chamber in which a piston 381 is slidably received. The piston is mechanically connected to the third rod 330 via a piston rod 383 extending outside the cylinder. The piston 381 is capable of moving within the cylinder in response to the action exerted by the third pivot 321 on the third rod 330 and the reaction force generated by the pressure within the chamber.

[0063] Via the auxiliary actuator 38, an axial thrust can be obtained on the rod 19, which is an alternative or supplement to the thrust generated by the primary link 300.

[0064] The welding device 1 may further include a secondary movement mechanism 40 for controlling the support assembly 20. The secondary movement mechanism can be configured in a thrust configuration and a closed configuration. In the thrust configuration, the secondary movement mechanism pushes the support assembly 20 to open relative to the welding member 11. In the closed configuration, the at least one support member 21 is arranged facing the head assembly 10 so as to define a support surface for the wrapper sheet when the welding member 11 is in the advanced position.

[0065] The auxiliary movement mechanism 40 may include a secondary link 400 including at least one parallelogram device 410. The parallelogram device includes a first parallelogram rod 411 and a second parallelogram rod 412 that engage with the support member 21 for guiding the rotational translation of the support member. In this configuration, the secondary movement mechanism 40 allows the thrust of the welding member 11 to be released substantially radially with respect to the support wheel 90.

[0066] Preferably, the secondary movement mechanism 40 includes a secondary control actuator 45 that engages with the secondary link 400 and is adapted to move linearly.

[0067] Conveniently, the primary control actuator 35 and the secondary control actuator 45 can control the linear movement through a cam device housed in the wheel 90. This simplifies the structure of the machine because only a single actuation is required for the two actuators.

[0068] According to a preferred embodiment, the primary control actuator 35 may house the secondary control actuator 45, and vice versa.

[0069] The welding workstation preferably includes a plurality of welding devices 1 that are equally angularly spaced and supported by the support wheel 90, wherein each rod 19 is aligned with the corresponding radius of the support wheel 90.

[0070] According to one embodiment, the base assembly 60 of the at least one welding device 1 is swingably supported by the support wheel 90 about a relevant swing axis that is parallel and non - coincident with the wheel axis R - R.

[0071] According to another aspect of the present invention, there is provided a method for producing a wrapper comprising at least a first sheet and a second sheet, the first and second sheets together defining a cavity adapted to receive a product, the method comprising the steps of:

[0072] a) providing a support wheel 90 capable of continuously rotating about a wheel axis R-R and at least one welding device 1 received on the support wheel 90, the welding device 1 comprising a welding member 11 and a support assembly 20, the welding member being translatable along the radial direction of the support wheel 90 and adapted to contact the first sheet of the wrapper and supply heat to the first sheet of the wrapper until a predetermined temperature is reached, the support assembly comprising at least one support member 21 adapted to provide support for the welding member 11;

[0073] b) when the support wheel 90 is in a first angular position, arranging the welding member 11 in a retracted position relative to the support assembly 20 and configuring the support assembly in a first open position, then feeding the first sheet of the wrapper to the welding device 1 and arranging the first sheet in contact with the welding member 11;

[0074] c) when the support wheel 90 is in a second angular position following the first angular position in the rotational direction of the support wheel 90, feeding the second sheet of the wrapper, which has been previously formed so as to define a cavity for receiving a product, so that it at least partially overlaps the first sheet along the welding zone;

[0075] d) preferably using a rotational translation movement to arrange the support member 21 of the support assembly 20 in a closed position so that it faces at least partially the second sheet and overlaps the welding zone;

[0076] e) when the support wheel 90 is in a third angular position following the second angular position in the rotational direction of the support wheel 90, advancing the welding member 11 so as to apply a predetermined pressure to the support assembly 20 and heating the welding member 11 to a predetermined temperature so as to weld the first and second sheets to each other; and

[0077] f) when the support wheel 90 is in a fourth angular position following the third angular position in the rotational direction of the support wheel 90, arranging the welding member 11 in a retracted position and returning the support assembly 20 to the open position and removing the wrapper from the welding device 1.

[0078] According to one embodiment, the above step e) is performed as follows: The welding member 11 is translated towards the support member 21 by means of the primary movement mechanism 30, thereby applying a first-stage pressure to the overlapping wrapper sheets. The primary movement mechanism 30 preferably includes a primary link 300, which includes a toggle mechanism formed by two rods hinged to each other. One rod is hinged to the welding member 11, and the other rod is hinged to a different support member (the welding member 11 can move relative to this support member). Such that when these rods are aligned with each other, the welding member 11 is translated towards the support member 21, thereby applying the first-stage pressure to the overlapping wrapper sheets. Preferably, the primary movement mechanism 30 includes a primary control actuator 35 engaged with the toggle mechanism to alternately bring its rods into an aligned configuration and a non-aligned configuration (the latter corresponding to a state where the pressure of the welding member 11 on the wrapper sheets is reduced / zeroed, and / or a state where the welding member 11 enters a retracted position relative to the support member 21).

[0079] Preferably, step e) is performed by applying an additional thrust to the welding member 11 by means of an auxiliary actuator 38 mechanically connected to the primary movement mechanism 30, in order to apply a second-stage pressure greater than the first-stage pressure to the overlapping wrapper sheets. This can be performed, for example, by mechanically connecting the auxiliary actuator 38 to the support member (which can then include a third rod) to which one of the two toggle rods of the primary movement mechanism 30 is hinged; and actuating the auxiliary actuator 38 such that when the two toggle rods are aligned with each other, the primary movement mechanism 30 transmits a thrust (possibly an additional thrust in addition to the thrust initially applied by the primary movement mechanism 30) from the auxiliary actuator 38 to the welding member 11.

[0080] According to one embodiment, the step of arranging the welding member 11 in a retracted position downstream of the welding completion is accomplished by means of an instruction issued by the auxiliary actuator 38. For example, this is also the case when the primary motion mechanism 30 is still in the initial thrust configuration. This can be carried out, for example, by actuating the auxiliary actuator 38 such that even when the two toggles of the primary motion mechanism 30 are still aligned with each other, buckling of the support member to which one of the two rods (the rod not hinged to the welding member 11) is hinged relative to the welding member 11 is caused, thereby retracting the welding member relative to the support member 21. In addition, when the primary motion mechanism 30 is still in the initial thrust configuration, actuating the auxiliary actuator 38 to arrange the welding member 11 in the retracted position can adjust the contact time of the welding member 11 with the wrapper sheet to prevent excessive heat transfer to the product. The above step f) preferably includes the step of keeping the welding member 11 in contact with the wrapper sheet for a predetermined time, regardless of the rotational speed of the support wheel 90. For example, the welding member 11 can be arranged in the retracted position downstream of the above step e) such that even when the rotational speed of the support wheel 90 is very low or zero (which may prolong the contact time of the welding member 11 with the wrapper sheet), the welding member 11 can be separated from the wrapper sheet.

[0081] According to one embodiment, the above step b) is carried out by applying a suction effect so as to keep the first sheet attached to the welding member 11.

[0082] Preferably, downstream of the above step f), there is the step of blowing a cooling fluid (such as air) onto the welding member 11 to cool the welding member until a predetermined temperature is reached.

[0083] According to a preferred embodiment of the present invention, there is also the step of instantaneously detecting the temperature of at least a part of the welding member 11. For example, these temperature data can be used to adjust the power of the heating element 14 and / or to blow a cooling fluid (preferably air) onto the welding element 11.

[0084] According to another aspect of the present invention, a package can be obtained by means of the welding workstation and / or method according to the present invention, the package comprising a wrapper (preferably sealed), the wrapper comprising a first sheet (conveniently in the form of a disc) and a second sheet (comprising an annular flange), the sheets together defining a cavity for receiving a product (as described above), wherein the first sheet and the second sheet are superimposed along an annular contact area (at least partially coinciding with the surface of the annular flange, facing the first sheet) and heat-sealed along at least one annular welding area, which is included in the annular contact area. Within the annular contact area, such an annular welding area can be conveniently formed as an imprint (preferably in the shape of a closed circle) applied to the sheets. Preferably, there are a plurality of concentric annular welding areas.

[0085] Furthermore, according to the present invention, the rotatable wheel welding workstation can also be specifically applied as a component of a continuous packaging device, the packaging device comprising a rotatable wheel feeding workstation located upstream of the welding workstation, equipped with means for receiving and stretching the sheets to accommodate the product to be packaged. Conveniently, the feeding workstation is configured to form the sheets such that they have an annular flange around an opening. In this way, a set of sheets and a product coming out of the feeding workstation are sent to the welding workstation according to the present invention, and then an additional sheet is fed into the welding workstation, which is joined to the annular flange and heat-sealed to form a preferably sealed wrapper for receiving the product. The object thus obtained is then picked up or ejected from the welding workstation and selectively sent to a further processing or treatment workstation downstream of the welding workstation.

[0086] The various aspects and embodiments of the welding workstation and method for producing a sealed wrapper according to the present invention have been described. It should be understood that each embodiment can be combined with any other embodiment. Furthermore, the present invention is not limited to the described embodiments, but can be modified within the scope defined by the appended claims.

Claims

1. A welding workstation for producing a wrapper comprising at least a first sheet and a second sheet, the first and second sheets jointly defining a cavity for containing a product, wherein the at least first and second sheets are heat-sealed along a welding area at least partially surrounding the cavity, wherein the welding workstation comprises a support wheel (90) rotatable about a wheel axis (R-R) and one or more welding devices (1) accommodated on the support wheel (90), wherein the welding device (1) comprises: (i) a head assembly (10), the head assembly comprising: a welding member (11) adapted to contact, support and transfer heat to the first sheet of the wrapper until a predetermined welding temperature is reached; a support (16) comprising a radially outer wall (16a) which internally defines a bracket in which the welding member (11) is pivotally and at least partially accommodated; and a rod (19) axially movable between a retracted position and a forward position relative to the wheel axis (R-R), the support (16) being integrally formed with an axial end of the rod (19); (ii) a support assembly (20), the support assembly comprising at least one support member (21) adapted to provide support for the welding member (11); (iii) a base assembly (60) which is joined to the support wheel (90) and supports the head assembly (10) and the support assembly (20); wherein the welding device (1) can be configured in an open configuration and a welding configuration, in the open configuration, the head assembly (10) and the support assembly (20) are spaced apart from each other, the rod (19) is axially retracted, and the at least one support member (21) is in a position adapted to allow the wrapper to be loaded onto / removed from the head assembly (10), in the welding configuration, the head assembly (10) and the support assembly (20) are joined to each other, the rod (19) is axially advanced, and the at least one support member (21) is joined to be supported by the welding member (11).

2. The workstation according to claim 1, wherein the head assembly (11) comprises a skid (18), the cross-section of the skid being at least partially arched and adapted to slidably engage the radially outer wall (16a) which internally defines a bracket.

3. The workstation according to claim 2, wherein the skid (18) comprises a projection (18a) axially extending from a lower section of the skid (18) in a direction opposite to the welding member (11), wherein the head assembly (10) comprises an elastically biasing device (17) radially interposed between the outer wall (16a) and the projection (18a), the elastically biasing device (17) being adapted to push the projection (18a) towards a state coaxial with the outer wall (16a).

4. The workstation according to any one of the preceding claims, wherein the welding member (11) comprises a welding element (12) having an exposed surface (12a) adapted to contact a first sheet of the wrapper and transfer heat to the first sheet of the wrapper until a predetermined welding temperature is reached, and the welding element having a generally closed section defining a central region (13).

5. The workstation according to claim 4, wherein the exposed surface (12a) of the welding element (12) has at least one projection (12b) in an annular shape, the projection having a top ridge defining a welding line.

6. The workstation according to claim 4 or 5, comprising a heating element (14) coaxially juxtaposed with the welding element (12) on a side of the welding element (12) axially opposite to the exposed surface (12a), the heating element (14) comprising an electrical conductor and a ceramic coating, the electrical conductor adapted to generate heat when energized, the electrical conductor being embedded in the ceramic coating, the ceramic coating adapted to transfer the heat generated by the electrical conductor to the welding element (12), and the ceramic coating being in direct contact with the welding element (12).

7. The workstation according to claim 6, wherein on a side of the welding element (12) axially opposite to the exposed surface (12a), the welding element (12) has a first plane (12c) against which a corresponding second plane (14b) of the ceramic coating of the heating element (14) abuts.

8. The workstation according to claim 6 or 7, wherein the head assembly (10) comprises an elastic element (15) interposed between the support (16) and the heating element (14) and configured to axially push the heating element against the welding element (12).

9. The workstation according to any one of claims 4 to 8, wherein the central region (13) comprises at least one suction hole (131) through which a suction fluid flow passes to hold the wrapper attached to the exposed surface (12a), the at least one suction hole (131) being in fluid communication with a pneumatic source.

10. The workstation according to any one of claims 4 to 9, wherein the central region (13) comprises cooling holes (132) through which an outflow fluid passes to cool the exposed surface (12a), the cooling holes (132) being in fluid communication with a pneumatic source.

11. The workstation according to any one of claims 4 to 10, further comprising a temperature sensor capable of detecting an instantaneous temperature of the welding element (12) and / or the heating element (14) and generating a signal representative of the instantaneous temperature.

12. The workstation according to claim 11, wherein the temperature sensor is applied to or embedded in the welding element (12) or the heating element (14).

13. The workstation according to any one of the preceding claims, wherein the support assembly (20) includes a pair of supports (21) movable between a closed configuration and an open configuration, in which, in the closed configuration, the supports (21) face the welding member (11) so as to create an axial gap in which a wrapper sheet to be welded can be received, and in which, in the open configuration, the welding member (11) is axially exposed to the exterior of the welding device so as to receive a product wrapper.

14. The workstation according to claim 13, wherein the welding member (11) is axially movable between a retracted position and a forward position, in which, in the retracted position, the welding member (11) is close to the center of the support wheel (90) and cannot exert pressure on the wrapper sheet to be welded, and in which, in the forward position, the welding member (11) axially approaches the at least one support member (21) in the closed configuration such that the welding member (11) can axially exert pressure on the wrapper sheet to be welded held between the welding member (11) and the at least one support member (21).

15. The workstation according to any one of the preceding claims, comprising a primary motion mechanism (30) for controlling the primary movement of the head assembly (10), the primary motion mechanism being configurable in a thrust configuration and an open configuration, in which, in the thrust configuration, the primary motion mechanism pushes the rod (19) towards the forward position, and in which, in the open configuration, the primary motion mechanism allows the rod to axially move in the retracted configuration.

16. The workstation according to claim 15, wherein the primary motion mechanism (30) includes a primary link (300), the primary link including a toggle mechanism formed by two mutually hinged rods, wherein: a first rod (310) of the toggle mechanism is hinged at a first end to a first pivot (311) and at an opposite end to a second pivot (312), the first pivot being movable integrally with the rod (19), the second pivot being movable between a first position and a second position in a direction perpendicular to the axis of the rod (19), in which, in the first position, the second pivot (312) is not aligned with the first pivot (311) along the axis of the rod (19), and in which, in the second position, the second pivot (312) is aligned with the first pivot (311) along the axis of the rod (19); and a second rod (320) of the toggle mechanism is hinged at a first end to the second pivot (312) and at an opposite end to a third pivot (321), the third pivot being axially aligned with the first pivot (311); the link (300) is configured such that the rod (19) is in the retracted position when the three pivots (311, 312, 321) are not aligned with each other, and the rod (19) is in the forward position when the three pivots (311, 312, 321) are aligned with each other.

17. The workstation according to claim 16, wherein the primary motion mechanism (30) includes a primary control actuator (35) that engages at the second pivot (312) to linearly move the second pivot in a direction perpendicular to the axis of the rod (19).

18. The workstation according to claim 16 or 17, wherein: the primary motion mechanism (30) includes a third rod (330) having a hinged end (331) hinged to the base assembly (60) and a free end (332) opposite the hinged end (331); the third pivot (321) is integrally formed with the third rod (330); the primary motion mechanism (30) includes an auxiliary actuator (38); and the welding device is configured such that when the auxiliary actuator (38) performs a thrust action, the third pivot (321) tends to translate axially along the rod (19) towards the support (21).

19. The workstation according to claim 18, wherein the auxiliary actuator (38) is operable to keep the welding member (11) in contact with the wrapper sheet for a predetermined time, regardless of the rotational speed of the support wheel (90).

20. The workstation according to claim 19, wherein the auxiliary actuator (38) is a pneumatic actuator including a cylinder that defines a chamber, a piston (381) slidably received in the chamber, the piston being mechanically connected to the third rod (330) via a piston rod (383) extending outside the cylinder, and the piston (381) being movable within the cylinder in response to the action exerted by the third pivot (321) on the third rod (330) and the reaction force generated by the pressure within the chamber.

21. The workstation according to any one of the preceding claims, comprising a secondary motion mechanism (40) for controlling the support assembly (20), the secondary motion mechanism being configurable in a thrust configuration and a closed configuration, in the thrust configuration, the secondary motion mechanism pushes the support assembly (20) to open relative to the welding member (11), and in the closed configuration, the at least one support member (21) is arranged facing the head assembly (10) to define a support surface for the wrapper sheet when the welding member (11) is in the advanced position.

22. The workstation according to claim 21, wherein the secondary motion mechanism (40) includes a secondary link (400), the secondary link including at least one parallelogram device (410), the parallelogram device including a first parallelogram rod (411) and a second parallelogram rod (412) that engage with the support member (21) to guide the rotational translation of the support member.

23. The workstation according to claim 22, wherein the secondary movement mechanism (40) includes a secondary control actuator (45), the secondary control actuator being engaged to the secondary link (400) and adapted to move linearly.

24. The workstation according to any one of the preceding claims, which includes a plurality of equally angularly spaced welding devices (1) on the support wheel (90), wherein each rod (19) is aligned with a respective radius of the support wheel (90).

25. The workstation according to any one of the preceding claims, wherein the base assembly (60) of the at least one welding device (1) is swingably supported by the support wheel (90) about a related swing axis, the swing axis being parallel and non - coincident with the wheel axis (R - R).

26. A method of producing a wrapper that includes at least a first sheet and a second sheet, the first sheet and the second sheet together defining a cavity adapted to receive a product, the method comprising the following steps: a) providing a support wheel (90) capable of continuously rotating about a wheel axis (R - R) and at least one welding device (1) received on the support wheel (90), the welding device (1) including a welding member (11) and a support assembly (20), the welding member being translatable along a radial direction of the support wheel (90) and adapted to contact a first sheet of the wrapper and supply heat to the first sheet of the wrapper until a predetermined temperature is reached, the support assembly including at least one support member (21) adapted to provide support for the welding member (11); b) when the support wheel (90) is in a first angular position, arranging the welding member (11) in a retracted position relative to the support assembly (20) and configuring the support assembly in a first open position, then feeding the first sheet of the wrapper to the welding device (1) and arranging the first sheet in contact with the welding member (11); c) when the support wheel (90) is in a second angular position following the first angular position in the rotational direction of the support wheel (90), feeding a second sheet of the wrapper that has been previously formed to define a cavity for receiving the product, such that it at least partially overlaps the first sheet along a welding area; d) preferably using a rotary - translational movement to arrange the support member (21) of the support assembly (20) in a closed position, such that it at least partially faces the second sheet and overlaps the welding area; e) when the support wheel (90) is in a third angular position following the second angular position in the rotational direction of the support wheel (90), advancing the welding member (11) so as to apply a predetermined pressure to the support assembly (20) and heating the welding member (11) to a predetermined temperature in order to weld the first sheet and the second sheet to each other; and f) When the support wheel (90) is in a fourth angular position after the third angular position along the rotation direction of the support wheel (90), arrange the welding member (11) to the retracted position, return the support assembly (20) to the open position, and remove the package from the welding device (1).

27. The method according to claim 26, wherein step e) is performed by: translating the welding member (11) towards the support member (21) by means of a primary movement mechanism (30) so as to apply a first-stage pressure to the overlapping package sheets; and applying a supplementary thrust to the welding member (11) by means of an auxiliary actuator (38) mechanically connected to the primary movement mechanism (30) so as to apply a second-stage pressure greater than the first-stage pressure to the overlapping package sheets.

28. The method according to claim 27, wherein step f) comprises the following steps: Keep the welding member (11) in contact with the package sheets for a predetermined time, regardless of the rotational speed of the support wheel (90).

29. The method according to claim 27 or 28, further comprising the following steps: Arrange the welding member (11) to the retracted position downstream of the completed welding by means of an instruction applied by the auxiliary actuator (38) to the primary movement mechanism (30).

30. The method according to any one of claims 26 to 29, wherein step b) is performed by: applying a suction effect so as to keep the first sheet attached to the welding member (11).

31. The method according to any one of claims 26 to 30, wherein downstream of step f), there is a step of: blowing a cooling fluid onto the welding member (11) so as to cool the welding member until a predetermined temperature is reached.

32. The method according to any one of claims 26 to 31, comprising the steps of: Instantaneously detect the temperature of at least a part of the welding member (11).

Images