Welding jaw and method for thermal welding

Abstract

The invention relates to a welding jaw for thermally welding a wall (1), made of a plastic film, of a bag to a welding region (2) of a pourer (3) made of plastic, comprising a jaw body (4) which can be connected to a heating source and has a pressing surface (5) with which the wall (1) of a bag can be pressed against the welding region (2) of a pourer (3) in a surface area (1a) to be welded, wherein a pressure element (6) is arranged on the jaw body (4), in particular is fastened to the jaw body (4), which pressure element has a second pressing surface (7), lying adjacent to the first pressing surface (5), with which second pressing surface the wall (1) of a bag can be pressed in the direction of the welding region (2) of a pourer (3), or toward the central longitudinal axis (12) of a pourer channel, in a surface area (1b) which is not to be welded and is adjacent to the surface area (1a) to be welded. The invention also relates to a method for thermally welding the walls (1), made of plastic film, of a bag to a welding region (2) of a pourer (3) made of plastic.

Description

[0001] Welding jaw and method for thermal welding

[0002] The invention relates to a welding jaw for thermally welding a wall of a bag made of plastic film to a welding area of ​​a spout made of plastic, comprising a jaw body connectable to a heat source, which has a pressure surface with which the wall of a bag can be pressed against the welding area of ​​a spout in a surface area to be welded.

[0003] In particular, the pressure surface of the jaw body can be heated indirectly by the heat source due to the thermal conductivity of the jaw body, which is preferably made of metal, in particular up to a temperature above the melting temperature of the material of the wall and the welding area.

[0004] By pressing the wall against the welding area by means of the heated pressure surface, the wall and the welding area are heated, in particular to above their respective melting temperature, so that these two parts are bonded together at their mutually facing surfaces under the effect of the applied welding pressure.

[0005] The invention also relates to a method for thermally welding the walls of a bag made of plastic film to a welding area of ​​a spout made of plastic, in which two opposing welding jaws are moved from opposite directions towards the welding area, each having a jaw body connected to a heat source, each jaw body having a pressure surface with which the wall of the bag lying between the pressure surface and the welding area is pressed against the welding area of ​​the spout in a surface area to be welded.

[0006] Pouch packaging is known in the prior art, particularly so-called squeeze pouches, in which a spout is welded between two opposing wall sections of the pouch, allowing the contents of the pouch to be removed through the spout's pouring channel. The walls are preferably formed from individual film layers.

[0007] Such a spout comprises in the prior art and preferably also in the invention a pouring channel, wherein the channel wall of the pouring channel is designed as a pouring spout at the first end region and the channel wall is surrounded by a welding region at the second end region, wherein the welding region has two welding arms which extend in opposite directions perpendicular to the channel axis of the pouring channel to a respective welding arm end, in particular which extend away from the channel wall in the second end region and each welding arm has welding zones, e.g.has a plurality of rib elements which are connected to the channel wall of the second end region, are preferably spaced from one another in the direction of the channel axis and has, on a first welding side, a first welding zone extending between the channel wall and the welding arm end and, on a second welding side, a second welding zone extending between the channel wall and the welding arm end. The first and second welding zones converge in the direction of the welding arm end. In one possible embodiment, the welding zones can be at least partially rectilinear or flat. In such a case, the rectilinear regions of the first welding zone and the second welding zone enclose an acute angle between them. However, welding zones can also be curved.

[0008] Such spouts are generally known in the prior art, e.g., from publication DE 10 2017 009 693 A1 by the same applicant. The spouts are intended to be sealed between two walls, e.g., film layers of a bag, in particular a film bag, which contains, for example, a food product, in particular a free-flowing food product. Due to the converging shape of the welding zones in both welding arms, the welding area has a shape that tapers from the channel axis toward the ends of the welding arms, in particular, which is frequently referred to as boat-shaped, with the taper occurring in a plane perpendicular to the channel axis.

[0009] By means of welding jaws, via which welding energy is applied from two opposite welding sides through the respective wall of the bag to the welding zones of the welding area, a welding takes place between the welding zones and the respective wall on each of the two welding sides.

[0010] The welding sides are therefore two opposite sides of the welding area. The welding sides lie on either side of a plane that encompasses the channel axis and both welding arm ends. The channel axis is the longitudinal axis of the pouring channel, which runs through the spout.

[0011] This plane can also be called a frontal plane and corresponds to a plane that is parallel to the walls of the bag, especially the unfilled bag.

[0012] At one end region, which in the application of an upright bag forms the upper end region in its function as a pouring spout, a removable closure is typically arranged, e.g. a cap, which is preferably attached to the pouring spout with a threaded connection or can be attached and removed.

[0013] In the aforementioned application, the second end region forming the welding area is the lower end region of the spout. The invention preferably relates to the application of the method according to the invention to such aforementioned spouts and the use of such aforementioned spouts in conjunction with the welding jaws according to the invention.

[0014] When the welding jaws are applied to the welding areas of such spouts, the heated pressure surface of the welding jaw comes into contact with the wall and heats it. Furthermore, the movement of the welding jaw moves the wall toward the welding area of ​​the spout. This results in a displacement of the heated surface area of ​​the wall relative to the unheated surface areas and a stretching of the heated surface area at the transition to the unheated and non-welded surface area of ​​the wall, which can lead to leaks in the wall after welding. Such leaks can therefore primarily occur in unwelded surface areas that are directly adjacent to welded surface areas of the wall.

[0015] Against this background, it is an object of the invention to further develop a welding jaw of the type mentioned at the outset and a method for thermal welding, so that the stretching of the wall in the transition area between welded and unwelded surface areas of the wall is reduced, preferably eliminated, and thus the risk of leaks is reduced, preferably eliminated.

[0016] This object is achieved in that, in a welding jaw of the type mentioned at the outset, a pressure element is arranged on the jaw body, in particular is fastened to the jaw body, which pressure element has a second pressure surface located adjacent to the first pressure surface of the jaw body, with which the wall of a bag can be pressed in the direction of the welding area of ​​a spout in a surface area not to be welded, which is arranged adjacent to the surface area to be welded.

[0017] The term pressure surfaces refers to those surfaces of the sealing jaw with which, during the intended operation of the sealing jaw, in particular when it is moved in the direction of a welding area of ​​a spout, a force can be exerted on the wall of a bag in order to move the area of ​​the wall contacted by the respective pressure surface in the direction of the welding area of ​​the spout.

[0018] The object is achieved in a method of the type mentioned at the outset in that a pressure element is arranged on the jaw body, in particular is fastened to the jaw body, which pressure element has a second pressure surface located adjacent to the first pressure surface of the jaw body, with which the wall of the bag is pressed in the direction of the welding area of ​​the spout in a surface area which is not to be welded and which is arranged adjacent to the surface area to be welded.

[0019] Pressing the wall in the surface area not to be welded towards the welding area of ​​the spout is understood to mean that this reduces at least the distance of the wall outside the surface area to be welded from the welding area because the second pressure surface pushes the wall in this area ahead of it, in particular towards a central plane around which the spout is arranged and which comprises the central longitudinal axis that runs through the pouring channel of the spout. This does not imply that this surface area comes into a direct position opposite the welding area. Only the surface area of ​​the wall to be welded comes into a direct position opposite the welding area until it comes into contact with it.

[0020] A surface area lying outside / adjacent to the surface area of ​​the wall to be welded, which is therefore not to be welded to the welding area, is preferably located in the axial direction of the extension of the pouring channel of the spout below the welding area on the side of the welding area opposite the pouring channel and / or in a direction radial to the extension direction of the pouring channel next to the welding area, in particular radially outside next to the radially outer ends of radially outwardly tapering welding arms of the welding area.

[0021] In contrast to the prior art, the invention ensures that the welding jaw not only contacts the surface areas of the wall that are to be welded, but also contacts and pushes forward those surface areas that are not to be welded. This prevents any relative displacement between the surface areas to be welded and those not to be welded, in particular, preventing them from bending. Furthermore, stretching of the heated surface area at the transition to the surface area not to be welded is avoided, thus overcoming the aforementioned disadvantages.

[0022] The method according to the invention preferably provides that the second pressure surface is kept at a temperature lower than the temperature of the first pressure surface, in particular such that the second pressure surface does not exceed the melting temperature of the materials to be welded from the wall and the welding area, whereas the temperature of the first pressure surface is above this melting temperature.

[0023] This can generally be achieved by cooling the pressure element and / or at least heating it less than the jaw body.

[0024] For this purpose, the invention can, for example, provide that the pressure element or at least the second pressure surface is made of a material with a lower thermal conductivity compared to the material of the jaw body.

[0025] This ensures that the second pressure surface, even when heated indirectly by the heating element via the jaw body, reaches a lower temperature than the first pressure surface because a smaller heat flow reaches the second pressure surface, and this is preferably also further away from the heat source than the first pressure surface. Preferably, the pressure element, or at least its second pressure surface, is made of silicone. This material is heat-stable at typical melting temperatures of plastics and has a lower thermal conductivity than the material of the jaw body, e.g., if the latter is preferably made of metal.

[0026] Alternatively or additionally to the above-mentioned embodiment, it can be provided that the pressure element is attached to the jaw body indirectly via at least one insulation element which is made of a material with a lower thermal conductivity compared to the material of the jaw body.

[0027] An insulation element can also be used to ensure that the second pressure surface is kept at a lower temperature compared to the temperature of the first pressure surface, even if it is also heated indirectly by the heating element via the jaw body, because a smaller heat flow passes through the insulation element to the pressure element or to the second pressure surface, which is preferably also further away from the heat source than the first pressure source. When using an insulation element, the pressure element does not necessarily have to have a lower thermal conductivity than the jaw body, and can therefore also be made of metal, for example. However, in this case too, it is preferably provided that the thermal conductivity of the pressure element is lower than that of the jaw body and preferably that the pressure element is made of silicone.

[0028] In a further development of all possible embodiments, the invention can preferably provide that a gap is formed between the first and second pressure surfaces in the sealing jaw, in particular in which the wall of a bag is in no contact with the sealing jaw. In this area, heat transfer to the wall is avoided, but the wall is moved on both sides of this area by the sealing jaw and its two pressure surfaces, which avoids stresses. Preferably, the gap is formed by a spacer element arranged between the jaw body and the pressure element, which has a surface area recessed behind the first and second pressure surfaces. Such a spacer element can simultaneously also form the aforementioned insulating element. Alternatively, the gap can also be formed by at least one of the opposite edges of the first and second pressure surfaces being formed with a chamfer or a radius.

[0029] In all possible embodiments, the invention can also preferably provide for the spacer element and / or the insulation element to be formed from a heat-resistant fiber material, in particular one containing glass fibers. Heat-resistant here means, in particular, that the material can withstand the temperatures present on the jaw body without damage.

[0030] Furthermore, in all possible embodiments, it can preferably be provided that the pressure element is arranged between two holding plates, preferably wherein the holding plate located between the pressure element and the jaw body forms an aforementioned insulation element and / or an aforementioned spacer element.

[0031] For example, a pressure element, particularly one made of silicone, can be arranged between two retaining plates and secured to the jaw body on the side facing the jaw body via an insulating element. The retaining plates then preferably provide the necessary stability for the flexible pressure element.

[0032] In general, the pressure element can be attached to the jaw body directly or indirectly via one of the aforementioned elements (insulation element, spacer element, holding plate), e.g. by screwing.

[0033] In all possible embodiments, it is preferably provided that the first pressure surface is formed between two surfaces of the jaw body that are opposite one another in a thickness direction of the jaw body, and the second pressure surface is formed between two surfaces of the pressure element that are opposite one another in a thickness direction of the pressure element, wherein the two opposing surfaces of the jaw body and the two opposing surfaces of the pressure element lie in mutually parallel planes. In this case, the first pressure surface and / or the second pressure surface can preferably be flat in the thickness direction, at least over the predominant surface area.

[0034] In particular, the second pressure surface used for welding is formed by a portion of the surface which connects the two opposing surfaces in a direction perpendicular to the surfaces.

[0035] In this arrangement, the second pressure surface is opposite a surface area of ​​the wall of the bag, which is arranged next to the welding area of ​​the spout on the side of the welding area opposite the pouring channel, i.e., when the pouring channel is aligned vertically, it is located below the welding area.

[0036] The pressure element, and thus also its pressure surface, can also be attached to the jaw body in such a way that the second pressure surface faces a surface area of ​​the bag wall that lies radially adjacent to the end / tip of a welding arm mentioned above. The invention can provide pressure elements in both arrangements simultaneously on a welding jaw.

[0037] It is particularly preferred if the first pressure surface and / or the second pressure surface is concave, in particular in a direction perpendicular to the thickness direction or viewed in cross section parallel to one of the opposing surfaces.

[0038] In such a case, the first pressure surface preferably encompasses the welding area in certain areas, in particular on one side of the central longitudinal axis of the pouring channel, preferably over at least 170 degrees around the central longitudinal axis. The welding area is thus enclosed on both sides by two opposing welding jaws after the welding jaws have moved toward each other.

[0039] In this embodiment, it can preferably be provided that the first pressure surface and / or the second pressure surface is designed to be concave in that the respective pressure surface comprises two partial surfaces, in particular two planar partial surfaces, which enclose an angle greater than 90 degrees, preferably greater than 100 degrees, between them, preferably which merge into one another, in particular continuously, preferably rounded, in a transition region.

[0040] Flat partial surfaces are preferably located in planes parallel to the central longitudinal axis of the pouring channel.

[0041] In a matching combination of spout and welding jaws, the angles at which the welding arms taper at the welding area and the angles enclosed between the partial surfaces of the first pressure surface are matched to each other, allowing full contact between the partial surfaces and the welding zones on the welding arms of the welding area. Preferably, the angle enclosed between the partial surfaces corresponds to 180 degrees minus the angle of the welding arms' taper.

[0042] The invention can preferably provide that the second pressure surface is moved in some areas in a leading and / or lagging manner relative to the first pressure surface. In particular, in the case of a pressure surface extending symmetrically from the inside to the outside, outer surface regions of the second pressure surface are moved in a leading manner relative to outer surface regions of the first pressure surface, and inner surface regions of the second pressure surface are moved in a lagging manner relative to inner surface regions of the first pressure surface. In particular for this purpose, but also for other reasons, the invention can preferably provide that the angle enclosed between the partial surfaces of the second pressure surface is smaller than the angle enclosed between the partial surfaces of the first pressure surface.

[0043] It is further preferred, in particular in order to achieve the said lagging / leading, if the first pressure surface and the second pressure surface each form a concave recess, in particular when viewed in cross section parallel to the opposing surfaces, wherein each recess has a recess base which is surrounded by two opposing recess edges, wherein the recess bases of both pressure surfaces and / or the recess edges of both pressure surfaces are not arranged in alignment with one another or are arranged offset from one another, in particular when viewed in the intended direction of movement of the welding jaw during welding.

[0044] The recess base preferably encompasses the area or is preferably the area where the partial surfaces merge into one another. The recess edges are preferably the areas up to which the pressure surface or its two partial surfaces rise upwards from the recess base.

[0045] It is preferably provided that the recess edges of the second pressure surface protrude beyond the recess edges of the first pressure surface, in particular protrude in the direction of the welding area and / or the recess bottom of the second pressure surface protrudes behind the recess bottom of the first pressure surface, in particular with respect to a direction of movement of the welding jaw towards the welding area.

[0046] It is further preferred if the recess edges of the second pressure surface, particularly viewed in the direction of the spacing of the recess edges, form a longer plateau than the recess edges of the first pressure surface, in particular if the second pressure surface continues outwards beyond the first pressure surface. Outwards here means from the recess base beyond the recess edge. The respective pressure surface preferably extends from the recess base across the partial surfaces to the highest point of the recess edges, in particular until the recess edges slope down again towards the outside. The recess edges of the second pressure surface therefore preferably slope down later towards the outside than the recess edges of the first pressure surface.

[0047] It is further preferred if the concave first and / or concave second pressure surface is formed symmetrically around a central plane, in particular which lies parallel to the thickness direction.

[0048] The figures illustrate the invention in comparison with the prior art. Figures 1 and 2 illustrate the prior art, while Figures 3 to 6 illustrate embodiments of the invention.

[0049] Figure 1 schematically shows, in the initial stage, the thermal welding of a bag wall 1 to the welding area 2 of a spout 3, which here has a pouring channel closed by a cap in the upper area, which extends around the central longitudinal axis 12, with the pouring channel merging into a welding area 2 below / beneath the cap. Figure 1B shows that the welding area 2 can be described as boat-shaped, which is a common term in this technical field. The welding area is known and also formed in the invention by two welding arms, which extend radially outward in opposite directions from the central longitudinal axis 12 and taper outward from the central longitudinal axis, in particular in a plane perpendicular to the central longitudinal axis 12.The radially outward-facing surfaces of the welding arms form the welding surfaces of the welding area 2, with which the wall is welded. Figures 1A and 1B show, from different viewing directions, an initial position of the jaw body 4 of a welding jaw, which can be heated by a heating element 14, wherein only one of two jaw bodies 4 is shown, which are opposite one another around the central longitudinal axis and preferably move simultaneously in the direction of the arrow shown toward the central longitudinal axis or toward the welding area 2, thereby pressing the wall 1 of the bag toward the welding area 2.

[0050] In this process, a surface area 1a of the wall to be welded comes into contact with the contact surface 5 of the jaw body 4 and heats up. The arrangement of the welding jaws / jaw bodies 4 and the wall 1 is mirror-symmetrical relative to the spout 3 in the prior art, as well as in the invention, to a plane in which the central longitudinal axis 12 and the tips of the welding arms lie.

[0051] It can be seen here in Figures 1A and 1B that a surface area 1b of the wall which is not to be welded and which is arranged adjacent to, in particular directly adjacent to, the surface area 1a to be welded is neither contacted by the pressure surface 5 of the jaw body 4 nor by any other element which guides this surface area.

[0052] Figures 2A and 2B show the associated problem, namely that there is a strong relative movement between the two surface areas 1a and 1b, because only the area to be welded is pressed in the direction of the welding area 2 or the central longitudinal axis 12, but not the adjacent, non-welded areas 1b, which therefore lag behind the movement. The heated surface area 1a to be welded is therefore stretched in the transition to the non-welded surface area 1b and thereby weakened, which can lead to leaks in the areas circled in Figures 2A and 2B in the bag produced accordingly. The invention counteracts this problem shown in Figures 1 and 2 in that a pressure element 6 is arranged on the jaw body 4, in particular is fastened to the jaw body 4, e.g.by screwing, which has a second pressure surface 7 located adjacent to the first pressure surface 5 of the jaw body 4, with which the wall 1 of a bag in the surface area 1 b not to be welded, which is arranged adjacent to the surface area 1a to be welded, can also be pressed in the direction of the welding area 2 of the spout 3 or towards the central longitudinal axis 12 of the pouring channel.

[0053] Figures 3A and 3B show the initial position of the jaw body 4 in the invention in comparison to the initial position of the prior art according to Figures 1A and 1B, wherein Figures 4A and 4B show the end position of the jaw body 4 of the invention in comparison to the end position of the prior art according to Figures 2A and 2B.

[0054] It can be seen here that the second pressure surface 7, which is provided by the pressure element 6 and acts on a surface area 1b not to be welded, which is arranged adjacent to, in particular directly adjacent to, the area 1a to be welded, ensures that there is no or not such a strong relative movement between the surface areas 1a and 1b. This reduces or even completely prevents the stretching and weakening of the heated surface area 1a at the transition to the surface area 1b.

[0055] This is advantageously supported by the fact that the second pressure surface 7 of the pressure element 6 is kept at a lower temperature than the first pressure surface 5 of the jaw body 4, in particular a temperature below the melting temperature of the material of the welding area 2 and wall 1.

[0056] This can be achieved by ensuring that the pressure element 6 has a lower thermal conductivity compared to the material of the jaw body 4, or by indirectly attaching the pressure element to the jaw body 4 via an insulating element 8, wherein the insulating element 8 has a lower thermal conductivity compared to the material of the jaw body 4. The material of the pressure element 6 is preferably silicone. A metal or other plastic can also be selected.

[0057] Due to the lower thermal conductivity of the pressure element 6 and / or the insulation element 8 compared to the material of the jaw body 4, the heat flow from the heat source 14 to the second pressure surface 7 is significantly lower than the heat flow from the heat source 14 to the first pressure surface. Cooling by the ambient air is sufficient to keep the temperature of the second pressure source 7 below the temperature of the first pressure surface. Alternatively, the pressure element 6 can also be actively cooled in all possible designs.

[0058] Figures 3 and 4 illustrate that multiple pressure elements 6 can be used, the second pressure surfaces 7 of which border the first pressure surface 5 in different / multiple directions. For example, Figures 3A and 4A show pressure elements 6 that are located next to / below the jaw body 4 in the axial direction of the central longitudinal axis 12, while Figures 3B and 4B show pressure elements 6 that are located at least substantially radially next to the jaw body 4, or radially outside of the pointed ends of the welding arms. Both types of pressure elements 6 can be used simultaneously.

[0059] Figures 3 and 4 further show a distance 9 between the pressure element 6 and the jaw body 4, which can be formed by the insulation element 8 or a spacer element 10 located between the pressure element and the jaw body. The distance 9 can also be formed solely or additionally by forming the edges of the opposing edges of the pressure element 6 and the jaw body 4 with a bevel or a radius. In the distance region 9, the wall 1 is free of contact with both pressure surfaces, which results in even less heating in this region. In the embodiments of Figures 3 and 4, it can also be provided that the pressure element arranged at the tip of the welding arms in Figures 3B and 4B is omitted and only one pressure element 6 is provided, which is shown in Figures 3A and 4A, in particular which contacts a surface area 1b not to be welded in the axial direction of the axis 12 below the welding area 2.

[0060] Figures 5 and 6 show different views of a concrete preferred embodiment of a welding jaw according to the invention without showing the heat source on the jaw body 4. In general, the heat source 14 can be attached to a surface of the jaw body 4 which is not occupied by a pressure element 6.

[0061] Figures 5 and 6 show that the pressure element 6 is designed as a flat element / plate, wherein its large surfaces spaced apart in the thickness direction lie parallel to the opposing surfaces 4a and 4b of the jaw body 4, which are spaced apart in the thickness direction and between which the first pressure surface 5 is formed across the thickness.

[0062] The first and second pressure surfaces 5, 7 each form, at least in a sectional plane parallel to the surfaces 4a, 4b, a concave recess with a recess base 5c or 7c and recess edges 5d or 7d. Each concave recess rises from the recess base 5c or 7c outwardly toward the recess edge 5d or 7d. Between the recess base 5c or 7c and the recess edge 5d or 7d lie partial surfaces 5a, 5b or 7a, 7b of the first and second pressure surfaces 5, 7.

[0063] Figures 6A and 6B in particular illustrate that the respective concave recesses are preferably mirror-symmetrical to a plane that passes through the recess base and is perpendicular to the surfaces 4a, 4b. The concave recess of the first pressure surface is preferably precisely adapted to the outer shape of the welding area 2 of the spout, so that the wall 1 in the area to be welded can be pressed against the welding area. Essentially, the concave recess of the first pressure surface 5 can correspond to a negative shape of one of the two opposing welding surfaces of the welding area 2.

[0064] The concave recess of the second pressure surface 7 can be identical to the concave recess of the first pressure surface 5 in section of a plane parallel to the surfaces 4a and 4b, but is preferably different therefrom.

[0065] Figures 6A and 6B clearly show that the angle a1 enclosed between the partial surfaces 5a and 5b of the first pressure surface 5 is greater than the angle a2 enclosed between the partial surfaces 7a and 7b of the second pressure surface 7.

[0066] Furthermore, it is provided here that the recess base 7c of the second pressure surface 7 is set back behind the recess base 5c of the first pressure surface 5, in particular with respect to a direction of movement of the welding jaw toward the welding area 2, which is symbolized here by the arrow 15. As a result, the recess base 7c lags behind the formation base 5c in the direction of movement 15 during the welding process.

[0067] Additionally, it is provided that the recess edges 7d of the second pressure surface 7 protrude beyond the recess edges 5d of the first pressure surface 5, in particular protrude in the direction of the welding area 2. As a result, the recess edges 7d advance the recess edges 5d in the direction of movement 15 during the welding process.

[0068] Furthermore, the recess edges 7d of the second pressure surface 7, particularly viewed in the direction of spacing of the recess edges 7d, form a longer plateau 7e than the recess edges 5d of the first pressure surface 5, in particular with the second pressure surface 7 extending outward beyond the first pressure surface 5. The construction of Figures 5 and 6 shows that the pressure element 6 can preferably be held between two holding plates 11, in particular those comprising thermally resistant fibers, e.g., glass fibers. This is advantageous if the pressure element is made of an otherwise insufficiently stable material, such as silicone. These holding plates 11 themselves also provide thermal insulation from the jaw body 4.The holding plates 11 can preferably also have a concave recess, preferably replicating the contour of the concave recess of the first pressure surface 5, i.e., in particular, in the plane parallel to the surfaces 4a, 4b, they can be identical to the contour of the concave recess of the first pressure surface, but more preferably, they can be set back parallel to it, in particular with respect to the direction of movement 15 toward the central longitudinal axis 12. The recess base of the holding plate 11 can be aligned with the recess base 7c of the pressure element 6, in particular at least at the lowest point. The unit comprising the pressure element 6 and the two surrounding holding plates 11 is attached to the jaw body 4 indirectly via the insulation element 8. This leads to a sufficient temperature reduction at the second pressure surface 7.

[0069] Preferably, in general, when carrying out the method, the temperature of the first pressure surface is greater than 190 degrees Celsius, and that of the second pressure surface is less than 190 degrees, preferably less than 170 degrees, in particular less than 150 degrees Celsius. Preferably, the temperature of the first pressure surface is at least substantially uniform across the surface, and the temperature of the second pressure surface 7 decreases in a direction away from the first pressure surface 5.

Claims

Patent claims 1 . Welding jaw for thermally welding a bag wall (1) made of plastic film to a welding area (2) of a spout (3) made of plastic, comprising a jaw body (4) which can be connected to a heat source and which has a pressure surface (5) with which the wall (1) of a bag can be pressed against the welding area (2) of a spout (3) in a surface area (1a) to be welded, characterized in that a pressure element (6) is arranged on the jaw body (4), in particular is fastened to the jaw body (4), which pressure element has a second pressure surface (7) located adjacent to the first pressure surface (5) of the jaw body (4), with which the wall (1) of a bag can be pressed in a surface area (1b) not to be welded, which is arranged adjacent to the surface area (1a) to be welded, in the direction of the welding area (2) of a spout (3) or towards the central longitudinal axis (12) of a pouring channel.

2. Welding jaw according to claim 1, characterized in that the pressure element (6) or at least the second pressure surface (7) is made of a material with a lower thermal conductivity compared to the material of the jaw body (4).

3. Welding jaw according to one of the preceding claims, characterized in that the pressure element (6) is attached to the jaw body (4) indirectly via at least one insulation element (8) which is made of a material with a lower thermal conductivity compared to the material of the jaw body (4).

4. Welding jaw according to one of the preceding claims, characterized in that a distance (9) is formed between the first pressure surface (5) and the second pressure surface (7), in particular in which the wall (1) of a bag is free of contact with the welding jaw.

5. Welding jaw according to claim 4, characterized in that the distance (9) is formed by a spacer element (10) arranged between the jaw body (4) and the pressure element (6), which has a surface area receding behind the first pressure surface (5) and second pressure surface (7), in particular which also forms an insulation element (8) according to claim 3, or in that at least one of the opposite edges of the first pressure surface (5) and second pressure surface (7) is formed with a chamfer or a radius.

6. Welding jaw according to one of the preceding claims 3 to 5, characterized in that the spacer element (10) and / or the insulating element (8) is formed by a material containing heat-resistant fibers, in particular glass fibers.

7. Welding jaw according to one of the preceding claims, characterized in that the pressure element (6) is arranged between two holding plates (11), preferably wherein the holding plate (11) lying between the pressure element (6) and the jaw body (4) forms an insulation element (8) according to claim 3 and / or a spacer element (10) according to claim 5.

8. Welding jaw according to one of the preceding claims, characterized in that the first pressure surface (5) is formed between two surfaces of the jaw body (4) opposite one another in a thickness direction of the jaw body (4) and the second pressure surface (7) is formed between two surfaces of the pressure element (6) opposite one another in a thickness direction of the pressure element (6), wherein the two opposite surfaces of the jaw body (4) and the two opposite surfaces of the pressure element (6) lie in mutually parallel planes.

9. Welding jaw according to one of the preceding claims, characterized in that the first pressure surface (5) and / or the second pressure surface (7) is flat in the thickness direction at least in the predominant surface area.

10. Welding jaw according to one of the preceding claims, characterized in that the first pressure surface (5) and / or the second pressure surface (7) is / are concave, in particular in a direction perpendicular to the thickness direction or viewed in cross-section parallel to one of the opposing surfaces, preferably wherein the welding region (2) can be encompassed in regions by the first pressure surface (5), in particular on one side of the central longitudinal axis (12) of the pouring channel, preferably over at least 170 degrees around the central longitudinal axis (12).

11. Welding jaw according to claim 10, characterized in that the first pressure surface (5) and / or the second pressure surface (7) is concave in that the respective pressure surface (5, 7) comprises two partial surfaces (5a, 5b, 7a, 7b), in particular two respectively flat partial surfaces (5a, 5b, 7a, 7b), which enclose an angle (a) greater than 90 degrees, preferably greater than 100 degrees, preferably which merge into one another, in particular continuously, in a transition region, preferably rounded.

12. Welding jaw according to claim 10 or 11, characterized in that the angle (θ2) enclosed between the partial surfaces (7a, 7b) of the second pressure surface (7) is smaller than the angle (αi) enclosed between the partial surfaces (5a, 5b) of the first pressure surface (5).

13. Welding jaw according to one of the preceding claims 10 to 12, characterized in that the concave first and / or concave second pressure surface (5, 7) is formed symmetrically around a central plane (13), in particular which lies parallel to the thickness direction.

14. Welding jaw according to one of the preceding claims 10 to 13, characterized in that the first pressure surface (5) and the second pressure surface (7) each form a concave recess, in particular viewed in cross-section parallel to the opposing surfaces, wherein each recess has a recess base (5c, 7c) which is surrounded by two opposing recess edges (5d, 7d), wherein the recess bases (5c, 7c) of both pressure surfaces (5, 7) and / or the recess edges (5d, 7d) of both pressure surfaces (5, 7) are not aligned are arranged relative to one another or are arranged offset relative to one another, in particular when viewed in the intended direction of movement of the welding jaw during welding.

15. Welding jaw according to claim 14, characterized in that the recess edges (7d) of the second pressure surface (7) protrude beyond the recess edges (5d) of the first pressure surface (5), in particular protrude in the direction of the welding area (2) and / or the recess base (7c) of the second pressure surface (7) protrudes behind the recess base (5c) of the first pressure surface (5), in particular with respect to a direction of movement of the welding jaw towards the welding area (2).

16. Welding jaw according to claim 14 or 15, characterized in that the recess edges (7d) of the second pressure surface (7), in particular viewed in the direction of the spacing of the recess edges (7d), form a longer extended plateau (7e) than the recess edges (5d) of the first pressure surface (5), in particular the second pressure surface (7) continues outwards beyond the first pressure surface (5).

17. A method for thermally welding the walls (1) of a bag made of plastic film to a welding area (2) of a spout (3) made of plastic, in which two opposing welding jaws are moved from opposite directions towards the welding area (2), each having a jaw body (4) connected to a heat source (14), each jaw body (4) having a pressure surface (5) with which the wall (1) of the bag lying between the pressure surface (5) and the welding area (2) is pressed against the welding area (2) of the spout (3) in a surface area (1a) to be welded, characterized in that a pressure element (6) is arranged on the jaw body (4), in particular is fastened to the jaw body (4), which pressure element has a second pressure surface (7) lying adjacent to the first pressure surface (5) of the jaw body (4),with which the wall (1) of the bag in a surface area (1 b) not to be welded, which is arranged adjacent to the surface area (1a) to be welded, in the direction of, welding area (2) of the spout (3) or to the central longitudinal axis (12) of the pouring channel.

18. Method according to claim 17, characterized in that the second pressure surface (7) is kept at a temperature lower than the temperature of the first pressure surface (5).

19. Method according to claim 17 or 18, characterized in that the second pressure surface (7) is moved in some areas in a leading and / or lagging manner relative to the first pressure surface (5), in particular in the case of a pressure surface (5, 7) extending symmetrically from the inside to the outside, outer surface regions of the second pressure surface (7) are moved in a leading manner relative to outer surface regions of the first pressure surface (5) and inner surface regions of the second pressure surface (7) are moved in a lagging manner relative to inner surface regions of the first pressure surface (5).

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