Cross-sealing and cutting means with an elastic strip

Abstract

The invention relates to improvements of a cross-sealing and cutting means for a vertical flow-wrapper, which produces packages. The invention also relates to a set of a cross-sealing and cutting members and a method to improve the tool-life of a first cross-sealing- and cutting-member.

Description

[0001] Cross-sealing and cutting means with an elastic strip

[0002] The invention relates to improvements of a cross-sealing and cutting means for a vertical flow-wrapper, which produces packages. The invention also relates to a method to package articles.

[0003] A common method of making packages out of a film web is the use of a vertical flowwrapper. Such a packaging machine receives a continuous flat sheet, for example a film of plastic material, e.g. a thermoplastic material, which is transported continuously or intermittently and passed downwardly over a form shoulder and is then shaped into a tubular form, i.e. into a film tube, by being wrapped around a vertical form-fill tube of the packaging machine. After being wrapped around the vertical form-fill tube, the film web is longitudinally closed by means of a longitudinally extending seal which is applied to the film especially by heat sealing the lateral / longitudinal margins of the film web or by heat sealing in the vicinity of these margins thereby joining them. This is carried out by so called longitudinal-sealing means. The film tube has conventionally a rectangular, elliptical or a circular cross-sectional area. The film tube is closed by cross-sealing means, preferably in a direction perpendicular to the direction of flow, i.e. transversely. Thereby, individual packages are defined out of the continuous film tube. A product, such as a foodstuff, is introduced by dropping the product through a form-fill tube and into the film tube surrounding the form-fill-tube. During filling, the film tube is transversely open at its upper end, i.e. not cross-sealed. Thereafter and / or simultaneously, the film tube together with the product is moved downwardly and then a top cross-seal is formed above the product and thereby a hermetically closed package produced. As a last step or simultaneously to the application of the top seal, the package is separated from the film tube by cutting means by cutting the film I film tube in a cutting plane.

[0004] The cross-sealing means conventionally comprise a first and a second cross-sealing- and cutting member, which are provided on opposite sides of the film tube and which each reciprocate from a remote- to a sealing / cutting position and vice versa. The cross-sealing means heat and compress the film tube and thereby seal the film I film tube together. There is a constant desire to increase its tool-life of the cross sealing means, particularly to avoid downtime of the vertical flow-wrapper.

[0005] The purpose of the invention is therefore to provide a cross-sealing and cutting means for a flow-wrapper with an improved tool-life and an improved method to package articles. The purpose is attained by providing a cross-sealing and cutting means for a flow-wrapper comprising first- and second cross-sealing- and cutting members, which cooperate during sealing to apply a pressure and / or heat to a film to be sealed and during cutting of the sealed film tube, wherein the first cross-sealing- and cutting member comprises a sealing jaw or a sealing jaw with a sealing strip and wherein the second cross-sealing- and cutting member comprises an elastic strip preferably made from thermal rubber. Preferably the sealing strip and / or the elastic strip are designed as replaceable parts, as they may need to be replaced, e.g. when a wear limit is reached after a certain service life and / or after a certain number of bags are produced.

[0006] The disclosure regarding this embodiment of the present invention also applies to the other embodiments and vice versa. Subject matters disclosed regarding one subject matter can be included into another embodiment and vice versa.

[0007] The present invention relates to the cross-sealing and cutting means of a vertical flowwrapper. The flow-wrapper has a frame and / or a housing, which receives a continuous flat sheet, e.g. a film of plastic material, e.g. a thermoplastic material, which is transported continuously or intermittently and passed downwardly over a form shoulder and is then shaped into a tubular form, i.e. into a film tube, by being wrapped around a vertical form-fill tube of the packaging machine. After being wrapped around the vertical form-fill tube, the film web is longitudinally closed by means of a longitudinally extending seal which is applied to the film especially by heat sealing the lateral / longitudinal margins of the film web or by heat sealing in the vicinity of these margins thereby joining them. This is carried out by so called longitudinal-sealing means. The film tube has conventionally a rectangular, elliptical or a circular cross-sectional area. Conventionally, the film tube is closed by cross-sealing means, preferably in a direction perpendicular to the direction of flow, i.e. transversely. Thereby, individual packages are defined out of the continuous film tube. A product, such as a foodstuff, is introduced into the film tube by dropping the product through a form-fill tube and into the film tube surrounding the form-fill tube and onto a lower-, first cross seal. During filling the film tube is transversely open at its upper, top end, i.e. not cross-sealed. Thereafter and / or simultaneously, the film tube together with its product is moved downwardly and then a top cross-seal is formed above the product and thereby the hermetically closed package is produced. As a last step or simultaneously to the application of the top seal, the package is separated from the film tube by cutting means.

[0008] The cross-sealing and cutting means according to the present invention comprise first- and second cross-sealing- and cutting members, which cooperate during sealing to apply a pressure and / or heat to a film to be sealed and during cutting of the sealed film tube. The first- and second cross-sealing- and cutting members are provided on opposite sides of the film tube and each reciprocate from a remote- to a sealing / cutting position and vice versa. The first and second cross-sealing- and cutting member are for example both anvils, which are during sealing pressed together.

[0009] In order to prepare for the cross-sealing and cutting, preferably the film tube is hold in place by clamping jaws, especially by a pair of upper clamping jaws that compress and hold the film tube between their clamping edges in a position just above the cross sealing area and a pair of lower clamping jaws that compress and hold the film tube in the same manner just below the cross sealing area. The clamping edges are preferably made of an elastic material.

[0010] According to the invention, the first cross-sealing- and cutting member comprises a sealing jaw or a sealing strip, which is made for example from a metal material, preferably a coated, more preferably Polytetrafluorethylen (PTFE) coated metal material. The sealing jaw or sealing strip can also be made entirely from PTFE or a plastic material, preferably with an improved thermal conductivity. Conventionally, the sealing jaw or sealing strip is directly and / or indirectly heated. Conventionally, two parallel sealing jaws or at least two sealing strips are provided, which extend transverse to the transport direction of the film.

[0011] Further according to the invention, the second cross-sealing- and cutting member comprises an elastic strip preferably made from thermal rubber. Conventionally, two parallel elastic strips are provided, which extend transverse to the transport direction of the film. During sealing each elastic strip and each sealing jaw or sealing jaw with sealing strip are pressed together.

[0012] A thermal rubber according to the invention is preferably a material with a higher elasticity than the sealing strip. The elastic strip may be made entirely from a thermal rubber material or a strip may be made partially, for example coated with a thermal rubber material. Preferably the thermal rubber material is a synthetic or natural rubber, preferably vulcanized, which preferably comprises an additive to increase its thermal conductivity. The additive can be for example particles, preferably nano-particles with a higher thermal conductivity in comparison to the rubber itself. Example for additives is for example a metal, preferably copper or aluminum powder.

[0013] Preferably, the cross section of the elastic strip is circular or oval and / or constant over the entire length of the sealing strip. Due to the combination of a sealing strip and an elastic strip, particularly an elastic strip made of thermal rubber, provided at the first- and / or second cross-sealing- and cutting members, the number of bags produced before the sealing strip and / or the elastic strip must be replaced, was improved by a factor of 3 - 4.

[0014] Preferably, the first- and / or second cross-sealing- and cutting members, particularly the elastic strip and the sealing strip are both heated. Preferably, the temperature of the elastic strip and / or the sealing strip can be steered or controlled, more preferably by a computer means, even more preferably independent from each other. The heating means of the elastic strip and / or the sealing strip can be incorporated into the respective strip or sealing jaw, like heating element(s) and thermoscouple, e. g. heating wires and / or heating films and / or heating layers, and / or the respective strip can be heated via conduction and / or convection and / or induction.

[0015] According to a preferred embodiment of the present invention, the elastic strip is preferably heated, preferably to a lower temperature than the sealing strip. More preferably, the elastic strip is heated to a temperature between 70 - 90 °C, more preferably 75 - 85 °C. The temperature of the sealing strip is preferably 130 - 180 °C, more preferably, 115 - 125° C.

[0016] Preferably, the cross-sealing and cutting means comprises a cutting means in the first cross- sealing- and cutting member which comprises the sealing strip(s). This preferred embodiment is particularly advantageous for the numbers of bags which can be cut without changing the cutting means. After and / or while the film tube is sealed, the cutting member is moved from a remote- to a cutting position to cut the film tube. In the cutting position, the cutting member, especially the cutting edge preferably extends into a slot provided between the two parallel elastic strips.

[0017] Preferably, the elastic strip is provided replaceable. More preferable, the elastic strip is connected to the second cross-sealing- and cutting member by a form- and / or force fit. Preferably, the second cross-sealing- and cutting member comprises a groove which accommodates the elastic strip partially and / or provides a form- and / or force-fit between the elastic strip and the second cross-sealing- and cutting member and / or supports the elastic strip during compression against deformation.

[0018] According to a preferred embodiment of the present invention, the elastic strip comprises at least one, preferably, two, three, four or more indentations, which preferably are located in the surface of the sealing strip that faces the packaging material to be sealed. Due to each indentations the seal comprises a leak at the location of the indentation, through which the package can breathe. Such breathing is advantageous for example for fruit products. Due to the indentation in the seal, a perforation of the packaging material can be omitted.

[0019] The indentation is preferably produced during molding of the elastic strip.

[0020] The indentation preferably has a rectangular cross section. The indentation preferably extends along the entire width of the elastic strip. The width of the sealing strip defines the width of the resulting seal. The indentation does not extend over the thickness of the elastic strip.

[0021] In case there are multiple indentations, they are preferably arranged symmetrical to a middle axis of the elastic strip.

[0022] The problem is also attained by vertical flow-wrapper having the inventive cross-sealing and cutting.

[0023] The disclosure regarding this embodiment of the present invention also applies to the other embodiments and vice versa. Subject matters disclosed regarding one subject matter can be included into another embodiment and vice versa.

[0024] The problem is also solved with a method to package articles which comprise and / or are covered with particulate material, in a flow-wrapper with a cross-sealing and cutting means comprising first- and second cross-sealing- and cutting members which cooperate during sealing to apply a pressure and / or heat to a film to be sealed and during cutting of the sealed film tube, wherein the first cross-sealing- and cutting member comprises a sealing strip and wherein at the second cross-sealing- and cutting member is provided an elastic strip, preferably made from thermal rubber.

[0025] The disclosure regarding this embodiment of the present invention also applies to the inventive vertical flow wrapper and vice versa. Subject matters disclosed regarding the method can be included into the inventive vertical flow wrapper and vice versa.

[0026] This embodiment of the present invention relates to a method to produce packages on a vertical fl ow-wrap per which are filled with a product, particularly a food-product, that is covered, for example breaded with a particulate material and / or that comprises particulate materials. Such food products are for example breaded escalope I Schnitzel, potatoproducts, particularly chips, cereals. This embodiment requires a hermetically sealed package. Alternatively, the product to be packaged is a fruit, a vegetable or the like. In this case, the package is not hermetically sealed but can breathe.

[0027] At these packages cross-seals are provided at the film tube by the cross sealing means and parts of the particulate material are always present at the inner circumference of the filmtube, which results in a significant wear at the cross sealing means, particularly the sealing strip.

[0028] According to the invention, the first cross-sealing- and cutting member comprises a sealing strip, which is made for example from a metal material, preferably a coated, more preferably PTFE coated metal material. The sealing strip can also be made entirely from PTFE or a plastic material, preferably with an improved thermal conductivity. Conventionally, the sealing strip is directly and / or indirectly heated. Conventionally, two parallel sealing strips are provided, which extend transverse to the transport direction of the film.

[0029] Further according to the invention, the second cross-sealing- and cutting member comprises an elastic strip for example rubber or a material with similar mechanical properties like the compression E-modulus. Conventionally, two parallel elastic strips are provided, which extend transverse to the transport direction of the film. During sealing each elastic strip and each sealing strip are pressed together.

[0030] The compression E-modulus of the elastic strip is preferably significantly lower than the compression E-modulus of the sealing strip, preferably by a factor > 10, more preferably > 1000, and even more preferably > 5000.

[0031] It has now turned out that this wear can be significantly reduced due to the combination of a sealing strip at one cross-sealing member and an elastic strip at the opposite cross-sealing member. The numbers of packages producible without changing the strip could be increased by a factor of 3 - 4 in comparison to the combination of a sealing strip at each cross-sealing member, while the quality of the seals provided by the cross-sealing means was very good.

[0032] According to a preferred embodiment, the elastic strip is made from a thermal rubber. A thermal rubber according to the invention is preferably a material with a higher elasticity than the sealing strip. The sealing strip may be made entirely from a thermal rubber material or a strip may be made partially, for example coated with a thermal rubber material. Preferably the thermal rubber material is a synthetic or natural rubber, preferably vulcanized, which comprises an additive to increase its thermal conductivity. The additive can be for example particles, preferably nano-particles with a higher thermal conductivity in comparison to the rubber itself. Example for additives is a metal, preferably copper or aluminum powder.

[0033] According to a preferred embodiment of the present invention, the elastic strip and the sealing strip are both heated, preferably by convection and / or heating wires. This preferred embodiment of the invention has the advantage that the temperature of the sealing strip can be reduced, for example from 180° C down to 120 °C. Preferably, the sealing strip is heated to a higher temperature than the elastic strip. Preferably, the temperature of the elastic strip is 30 - 40 % lower than the temperature of the sealing strip.

[0034] Preferably, during cutting, the cutting member moves from the first- cross-sealing- and cutting members towards the second cross-sealing- and cutting members; i.e. the cutting member moves into a slot between two elastic strips. This preferred embodiment of the invention has the advantage that the number of cutting cycles of the cutting member, for example a knife, can be increased by up to 100%.

[0035] Preferably, the cutting edge of the cutting member has a lower temperature than its shaft.

[0036] According to a preferred embodiment, the first- and second cross-sealing- and cutting members apply a seal which is not air-tight. Preferably air escapes through a leak in the seal. Preferably the package breathes via the leaks in the seal. At least one leak is provided in both cross-seals of a package.

[0037] The inventions are now explained referring to the figures of the attached drawings, by way of non-limiting examples. The explanations apply to all embodiments of the present invention likewise.

[0038] Figure 1 shows schematically the vertical flow-wrapper according to the invention.

[0039] Figures 2 and 3 depict an embodiment of a cross-sealing- and cutting means.

[0040] Figure 4 shows an elastic strip with indentations. In Figure 1 , the vertical flow-wrapper 1 according to the invention is schematically shown. A vertical flow wrapper is a packaging machine, which forms a plane film web into a film tube, which is transported along a form-fill tube 4. Two ends of this film tube are sealed together by a longitudinal sealing means 5. Subsequently, the packaging item is filled into the film tube and a cross-seal is applied to the film tube to close the package. Simultaneously or after applying the cross-seal, the finalized packages are cut off the film tube. The vertical flow wrapper comprises a frame / housing 12, at which a form shoulder 3, a form-fill tube 2 and longitudinal sealing means 5 and cross-sealing means 6 are provided. The vertical flowwrapper may comprise gusset- forming means to form the bottom and / or the top of each package.

[0041] A web of a film 13, 4, especially a weldable plastic film 13, 4, is supplied from a reel 14, which supplies the plane film 13 continuously or intermittently to a form shoulder 3, which shapes the film web 13 into a rather tubular form around a form-fill tube 2. In the context of the present invention, a “tubular form” of the packages or of the film means any cross- sectional form including a circular form or another form, and especially a rectangular or generally a polygonal form. Longitudinal sealing means 5, which are provided downstream from the form shoulder, seal the edges to the film tube together. After sealing, the bottom of the package can be formed by a special bottom forming means, for example gusset-forming means (not shown). Finally, cross seals, extending preferably perpendicularly to the direction of flow of the film 11 , are applied, especially by means of cross-sealing means 6. These cross sealing means 6 apply to the package not only an upper / second cross-seal closing the top of the package, but these cross-sealing means 6 advantageously also provide, preferably simultaneously a lower / first cross-seal defining the bottom of the subsequent, upstream package. The packages produced are separated from one another by a cutting member 9, which is preferably incorporated into the cross-sealing means 6. Between the application of the bottom- and top-cross-seal of each package, the package is filled with the product, preferably an edible product.

[0042] Figures 2 and 3 show an embodiment of a cross-sealing and cutting means 6. This crosssealing and cutting means 6 comprises a first and second cross-sealing- and cutting member 6.1., 6.2 provided on two opposite sides of the film tube 4 to be sealed. The first cross- sealing- and cutting member 6.1 has at least one here two sealing strip(s) 8 at its end which faces the film 13. The sealing strip 8 is for example made from a metal material which is partially coated with an anti-stick material for example PTFE. Each sealing strip is heated. The opposite second cross-sealing- and cutting member 6.2 comprises at its end which faces the film at least one here two elastic strips 7, which are preferably made from a rubber or rubber-like material, more preferably a thermal rubber. Preferably, the elastic strip 7 is heated, more preferably to a lower temperature than the sealing strip, e. g. by heating means 15. The heat transfer to the elastic strip is preferably by conduction. During sealing, the sealing strip and the rubber strip are pressed together. Since there are two sealing strips 8 at the first cross-sealing- and cutting member 6.1 and two elastic strips 7 at the second cross- sealing- and cutting member 6.2, two seals are provided at the film simultaneously. Each elastic strip 7 is preferably provided partially in a groove 10, which provides a form- and / or force-fit connection between the cross sealing member and the elastic strip. The elastic strip extends partially out of the groove. The elastic strip is preferably made from a thermal rubber, to improve its heat-transfer-conduction coefficient.

[0043] The first cross-sealing- and cutting member 6.1 has a cutting member 9, for example a knife, that is provided in a slot between the two parallel sealing strips 8. During cutting, the cutting member 9, especially its cutting edge 9.1 moves in a cutting direction 17 between the two elastic strips 7, preferably into a slot 16.

[0044] In order to prepare for the cross-sealing and cutting, the film tube is hold in place by clamping jaws 18, especially by a pair of upper clamping jaws that compress and hold the film tube between their clamping edges 18.1 in a position just above the cross sealing area and a pair of lower clamping jaws that compress and hold the film tube in the same manner just below the cross sealing area, both by moving in the clamping direction 19. The clamping edges 18.1 are preferably made of an elastic material, e. g. like a Silicon based material. After the cross sealing and cutting has taken place, the first and second cross-sealing and cutting members, including the cutting member 9, and the clamping members are driven back into their outer position, in order to free the space for the next packaging. At that moment, when the lower clamping jaws lose contact to the packaging, the packaging will fall, preferably onto an exit conveyor.

[0045] Figure 4 shows a preferred embodiment of the present invention in three different views. In the present case, the elastic strip 7 has at least one, here four indentations 20. Due the indentations 20 in the elastic strip, no seal of the packaging material takes place, so that the package is not air-tight. Gas can be ventilated in and out of the package. Such gas exchange is particularly advantageous for packaging goods such as fruit or vegetables. A perforation of the package and / or the usage of perforated packaging material can be omitted. In the present case, the indentations are provided symmetrically to a middle axis 21 of the elastic strip. The indentations are provided on the surface of the flexible strip 7 that faces the packaging material. Each indentation preferably has a rectangular cross section. The indentation preferably extends along the entire width of the elastic strip. The width of the sealing strip defines the width of the resulting seal. The indentation does not extend over the thickness of the elastic strip. At each end, fastening means 22, here a hock, may be provided. The fastening means 22 preferably form a form- and / or force-fit with a corresponding means at the packaging machine to fix the flexible strip 7 at the packaging machine. An optional orientation means 23, here an indentation, opposite from the side that comes into contact with the film, may be provided. The orientation means 23 assures the correct orientation of the flexible strip at the packaging machine.

[0046] The dimensions shown in Figure 4 are preferred dimensions for the indentations.

[0047] List of Reference Signs:

[0048] 1 vertical flow-wrapper

[0049] 2 form-fill tube

[0050] 3 form shoulder

[0051] 4 film tube

[0052] 5 longitudinal-sealing means

[0053] 6 cross-sealing and cutting means

[0054] 6.1 first cross-sealing and cutting member

[0055] 6.2 second cross-sealing and cutting member

[0056] 7 elastic strip

[0057] 8 sealing strip

[0058] 9 cutting member, knife

[0059] 9.1 cutting edge

[0060] 10 groove

[0061] 11 transport direction

[0062] 12 frame, housing

[0063] 13 web, plastic film

[0064] 14 film reel, reel

[0065] 15 heating means

[0066] 16 slot

[0067] 17 cutting direction

[0068] 18 clamping jaw

[0069] 18.1 clamping edge

[0070] 19 clamping direction

[0071] 20 indentation

[0072] 21 middle axis

[0073] 22 fastening means

[0074] 23 orientation means

Claims

Claims:

1. Cross-sealing and cutting means (6) for a vertical flow-wrapper (1) comprising firstand second cross-sealing- and cutting members (6.1 , 6.2) which cooperate during sealing to apply a pressure and / or heat to a film to be sealed and during cutting of the sealed film tube, wherein the first cross-sealing- and cutting member (6.1) comprises a sealing strip (8) characterized in, that the second cross-sealing- and cutting member (6.2) comprises an elastic strip (7) made from thermal rubber.

2. Cross-sealing and cutting means (6) according to claim 1, characterized in, that the first- and second cross-sealing- and cutting members (6.1 , 6.2), particularly the elastic strip (7) and the sealing strip (8) are both heated.

3. Cross-sealing and cutting means (6) according to claim 2, characterized in, that elastic strip (7) is heated to a lower temperature than the sealing strip (8).

4. Cross-sealing and cutting means (6) according to one of the preceding claims, characterized in, that a cutting member (9) is provided in the first cross-sealing- and cutting member (6.1) which comprises the sealing strip.

5. Cross-sealing and cutting means (6) according to one of the preceding claims, characterized in, that the elastic strip comprises at least one, preferably, two, three, four or more indentations.

6. Vertical flow-wrapper (1) having the cross-sealing and cutting means (6) according to one of the preceding claims.

7. Method to package articles which comprise and / or are covered with particulate material, in a flow-wrapper (1) with a cross-sealing and cutting means (6) comprising first- and second cross-sealing- and cutting members (6.1 , 6.2) which cooperate during sealing to apply a pressure and / or heat to a film to be sealed and during cutting of the sealed film tube, wherein the first cross-sealing- and cutting member (6.1) comprises a sealing strip (8), characterized in, that the second cross-sealing- and cutting member (6.2) is provided with an elastic strip (7), preferably made from thermal rubber.

8. Method according to claim 7, characterized in, that elastic strip (7) is made from a thermal rubber.

9. Method according to claims 7 or 8, characterized in, that the elastic strip (7) and the sealing strip (8) are both heated.

10. Method according to claims 7 - 9, characterized in, that sealing strip (8) is heated to a higher temperature than the elastic strip.

11. Method according to one of claims 7 - 10, characterized in, that during cutting, the cutting member (9) moves from the first- cross-sealing- and cutting members (6.1) towards the second cross-sealing- and cutting member (6.2).

12. Method according to one of claims 7 - 11 , characterized in, that the first- and second cross-sealing- and cutting members (6.1 , 6.2) apply a seal which is not air-tight.

13. Method according to claim 12, characterized in, that air escapes through a leak in the seal.

14. Method according to one of claims 7 - 11 , characterized in a breathable package is produced.

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