WO2006010961A1 - Formations de joints et d'emballages - Google Patents

Formations de joints et d'emballages Download PDF

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Publication number
WO2006010961A1
WO2006010961A1 PCT/GB2005/050119 GB2005050119W WO2006010961A1 WO 2006010961 A1 WO2006010961 A1 WO 2006010961A1 GB 2005050119 W GB2005050119 W GB 2005050119W WO 2006010961 A1 WO2006010961 A1 WO 2006010961A1
Authority
WO
WIPO (PCT)
Prior art keywords
welding
electrodes
knife edge
seam
flange
Prior art date
Application number
PCT/GB2005/050119
Other languages
English (en)
Inventor
Michael Alan John Feast
Original Assignee
Stanelco Rf Technologies Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Stanelco Rf Technologies Limited filed Critical Stanelco Rf Technologies Limited
Publication of WO2006010961A1 publication Critical patent/WO2006010961A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/74—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area
    • B29C65/743—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area using the same tool for both joining and severing, said tool being monobloc or formed by several parts mounted together and forming a monobloc
    • B29C65/7441—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area using the same tool for both joining and severing, said tool being monobloc or formed by several parts mounted together and forming a monobloc for making welds and cuts of other than simple rectilinear form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/04—Dielectric heating, e.g. high-frequency welding, i.e. radio frequency welding of plastic materials having dielectric properties, e.g. PVC
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/74—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area
    • B29C65/743—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by welding and severing, or by joining and severing, the severing being performed in the area to be joined, next to the area to be joined, in the joint area or next to the joint area using the same tool for both joining and severing, said tool being monobloc or formed by several parts mounted together and forming a monobloc
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/01—General aspects dealing with the joint area or with the area to be joined
    • B29C66/05—Particular design of joint configurations
    • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/11—Joint cross-sections comprising a single joint-segment, i.e. one of the parts to be joined comprising a single joint-segment in the joint cross-section
    • B29C66/112—Single lapped joints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/01—General aspects dealing with the joint area or with the area to be joined
    • B29C66/05—Particular design of joint configurations
    • B29C66/10—Particular design of joint configurations particular design of the joint cross-sections
    • B29C66/13—Single flanged joints; Fin-type joints; Single hem joints; Edge joints; Interpenetrating fingered joints; Other specific particular designs of joint cross-sections not provided for in groups B29C66/11 - B29C66/12
    • B29C66/131—Single flanged joints, i.e. one of the parts to be joined being rigid and flanged in the joint area
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/53—Joining single elements to tubular articles, hollow articles or bars
    • B29C66/534—Joining single elements to open ends of tubular or hollow articles or to the ends of bars
    • B29C66/5346—Joining single elements to open ends of tubular or hollow articles or to the ends of bars said single elements being substantially flat
    • B29C66/53461—Joining single elements to open ends of tubular or hollow articles or to the ends of bars said single elements being substantially flat joining substantially flat covers and/or substantially flat bottoms to open ends of container bodies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/814—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps
    • B29C66/8141—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined
    • B29C66/81431—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined comprising a single cavity, e.g. a groove
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/818—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the cooling constructional aspects, or by the thermal or electrical insulating or conducting constructional aspects of the welding jaws or of the clamps ; comprising means for compensating for the thermal expansion of the welding jaws or of the clamps
    • B29C66/8187—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the cooling constructional aspects, or by the thermal or electrical insulating or conducting constructional aspects of the welding jaws or of the clamps ; comprising means for compensating for the thermal expansion of the welding jaws or of the clamps characterised by the electrical insulating constructional aspects
    • B29C66/81871—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the cooling constructional aspects, or by the thermal or electrical insulating or conducting constructional aspects of the welding jaws or of the clamps ; comprising means for compensating for the thermal expansion of the welding jaws or of the clamps characterised by the electrical insulating constructional aspects of the welding jaws
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/84—Specific machine types or machines suitable for specific applications
    • B29C66/849—Packaging machines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/71—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the composition of the plastics material of the parts to be joined
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/70—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material
    • B29C66/73—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset
    • B29C66/731—General aspects of processes or apparatus for joining preformed parts characterised by the composition, physical properties or the structure of the material of the parts to be joined; Joining with non-plastics material characterised by the intensive physical properties of the material of the parts to be joined, by the optical properties of the material of the parts to be joined, by the extensive physical properties of the parts to be joined, by the state of the material of the parts to be joined or by the material of the parts to be joined being a thermoplastic or a thermoset characterised by the intensive physical properties of the material of the parts to be joined
    • B29C66/7314—Electrical and dielectric properties
    • B29C66/73143—Dielectric properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/812—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B29C66/8122—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps characterised by the composition of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/812—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B29C66/8124—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps characterised by the structure of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps
    • B29C66/81241—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the composition, by the structure, by the intensive physical properties or by the optical properties of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps characterised by the structure of the material constituting the pressing elements, e.g. constituting the welding jaws or clamps being porous or sintered
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/81—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps
    • B29C66/814—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps
    • B29C66/8141—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined
    • B29C66/81411—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined characterised by its cross-section, e.g. transversal or longitudinal, being non-flat
    • B29C66/81421—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined characterised by its cross-section, e.g. transversal or longitudinal, being non-flat being convex or concave
    • B29C66/81423—General aspects of the pressing elements, i.e. the elements applying pressure on the parts to be joined in the area to be joined, e.g. the welding jaws or clamps characterised by the design of the pressing elements, e.g. of the welding jaws or clamps characterised by the surface geometry of the part of the pressing elements, e.g. welding jaws or clamps, coming into contact with the parts to be joined characterised by its cross-section, e.g. transversal or longitudinal, being non-flat being convex or concave being concave
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/80—General aspects of machine operations or constructions and parts thereof
    • B29C66/83—General aspects of machine operations or constructions and parts thereof characterised by the movement of the joining or pressing tools
    • B29C66/832—Reciprocating joining or pressing tools
    • B29C66/8322—Joining or pressing tools reciprocating along one axis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux

Definitions

  • This invention relates to a process and an apparatus for making seams and enclosures such as sachets by welding a film of a polymeric material, and also to the resulting seams and enclosures.
  • GB 908 344 (Lavaud) describes a process in which such enclosures are made by first deforming each film into a recess in a cylindrical mould, filling the deformed film with the required contents, and then welding around each recess using a electrode concentric with the mould. Lavaud suggests it might be possible to combine welding with cutting out, suggesting that the ends of the electrodes may be knife- edged.
  • EP 0 026 330 (Johnson & Son) describes a way of bonding together two half shells of rigid thermoplastic material by dielectric welding, using opposed electrodes bevelled to provide a cutting edge, but the dielectric field is turned off when the electrodes get close together so that the cutting can then follow.
  • the films are preferably both flexible, and the resulting enclosures may be referred to as sachets, and may contain a wide range of different liquids such as foodstuffs, detergents, personal care products, agrochemicals or pharmaceuticals.
  • the films may be of any thermoplastic material whose dielectric loss factor is suitable, including edible polymers such as hydroxypropylmethyl cellulose, or starch, and other water-soluble polymers such as polyvinyl alcohol.
  • a process for welding together polymer films of substantially equal thickness by dielectric welding between opposed electrodes to form a seam or flange of a sachet wherein one electrode is connected to a solid- state source of radio frequency signals, wherein at least one of the electrodes is coated with a hard insulating layer at least 50 ⁇ m thick, and wherein the electrodes are shaped so as to define a welding zone of substantially uniform thickness extending along the said seam or flange, and a knife edge extending along the welding zone, wherein the knife edge projects a distance in the range 30% to 150% of the thickness of a single film.
  • the knife edge may project from one or other of the electrodes, and may extend along one edge of the welding zone, or along within the welding zone.
  • the knife edge may project at least as far as the thickness of a single film.
  • the radio-frequency electrical signals are provided to the electrodes.
  • the frequency may be between 1 MHz and 200 MHz, usually between 10 MHz and 100 MHz, but stringent limits are imposed on any emitted radio waves. In practice therefore the choice of frequency may be more limited.
  • the supply frequency may be 27.12 MHz, or 40.68 MHz.
  • one electrode is connected to the generator through a matching network, preferably an active matching network, and the other electrode may be earthed.
  • the effect of the electrical insulation on one or both of the electrodes is to ensure that the electrodes are still electrically insulated from each other even when the knife edge cuts through the films.
  • the matching network incorporates an inductor and at least one variable capacitor controlled by a servo motor; it monitors the radio frequency current and voltage, and adjusts the value of the or each variable capacitor so that the impedance presented to the generator remains at a constant value such as 50 ⁇ .
  • the matching network and the generator ensure that, even if there is a localised fault in the electrical insulation, this does not lead to a breakdown (with consequential damage to the films) .
  • the invention provides an apparatus for welding together polymer films of substantially equal thickness by dielectric welding to form a seam or flange of a sachet, wherein the apparatus comprises two opposed welding electrodes for forming the seam or flange, and a solid-state source of radio- frequency signals connected to one electrode, wherein at least one of the electrodes is coated with a hard insulating layer at least 50 ⁇ m thick, and wherein the electrodes are shaped so as to define a welding zone of substantially uniform thickness extending along the said seam or flange, and a knife edge extending along the welding zone, wherein the knife edge projects a distance in the range 30% to 150% of the thickness of a single film.
  • the insulating layer must not only be a good electrical insulator but also be sufficiently hard to withstand the cutting process.
  • at least one of the electrodes is of aluminium, and the insulating layer comprises a layer of aluminium oxide formed by hard anodising, this oxide layer being somewhat porous and being impregnated with a polymer insulator such as polytetrafluoroethylene (PTFE) .
  • PTFE polytetrafluoroethylene
  • the knife edge may extend along either edge of the welding zone, or indeed may extend between two parts of the welding zone. Where the knife edge extends along the edge of the welding zone remote from an enclosure formed by the films, then the resulting enclosure will have a welded flange, whereas where the knife edge extends along the edge of the welding zone adjacent to an enclosure formed by the films, the resulting enclosure will be flangeless; in the latter case the welding process must be such as to generate a bead along the inside of the seam.
  • Figure 1 shows a sectional view of apparatus for forming sachets, the elements within the moulding apparatus being shown separated from each other for clarity;
  • Figure 2 shows the welding region of the apparatus of figure 1 to a larger scale
  • Figure 3 shows a circuit diagram of the matching network in the apparatus of figure 1.
  • films of starch containing a plasticiser and of thickness 50 ⁇ m, and which are soluble in hot water are used to produce sachets of soup concentrate on which can be mixed with hot water to form soup.
  • the sachets are formed by a flat bed process, in which a first sheet 10 of the film is laid on a flat tray or mould 12 in which are forty-eight recesses 14. The recesses 14 are evacuated to pull the film 10 into them. Appropriate quantities of soup concentrate 16 are then dispensed into each recess in the film 10. A cover film 18 is then laid across the mould 12.
  • the mould 12 is of aluminium, and its upper surface is hard anodised to provide a coating 15 of alumina of thickness 100 ⁇ m, which is impregnated with PTFE to ensure that it is a good electrical insulator.
  • the mould 12 may then be moved to a second location, at which an upper tray 20 with a matching set of recesses 21 is placed on top of the mould 12, and pressure is applied between them.
  • the upper tray 20 may also be of aluminium, but is preferably of a harder metal such as brass.
  • the mould 12 is connected to earth, while the upper tray 20 is connected via a conductor 24 and a matching network 36 to a solid-state radio-frequency generator 26.
  • the matching network 36 (shown in greater detail in figure 3) incorporates variable capacitors and servomotors operated such that the impedance presented to the generator 26 remains at a constant value such as 50 ⁇ , despite changes in the load.
  • the regions of the films 10 and 18 around each recess 14 are hence subjected to dielectric heating and pressure, and the polymeric starch material melts at the interface between the two films 10 and 18. As explained below, the sachets are also cut out during this step. After welding has been performed, the upper tray 20 is removed, and the resulting forty-eight sachets are removed from the mould 12, as is the remaining web of bonded portions of the films 10 and 18.
  • Such a sachet can simply be dropped into a cup of boiling hot water, and stirred to form soup.
  • the films 10 and 18 are of thickness selected to provide rapid dissolution, although with sufficient strength to be handled. Even where the films are bonded together, they still undergo rapid dissolution.
  • This process can also be used to form sachets from films of other materials such as polyvinyl alcohol, and containing other fillings such as a detergent composition. Only the polymer is heated during the welding process, as the heating effect of the radio- frequency is concentrated in the flange regions around each recess, where welding is required. This has the advantage that the polymer does not get as hot as with conventional heated-press welding, and the molecular structure of the polyvinyl alcohol membrane is not changed. Consequently the solubility of the polyvinyl alcohol is not changed by the welding process.
  • the upper tray 20 defines a projecting knife edge 30 around each recess 21, at a distance of 2 mm from the edge of the recess 21 (so that each sachet has a 2 mm-wide projecting flange) .
  • Each knife edge 30 projects 50 ⁇ m below the lower surface of the tray 20.
  • the knife edge 30 may instead be immediately adjacent to the edge of the recess 21, so that the resulting sachet is flangeless, but securely sealed by virtue of the bead 32 around the seam.
  • the mould 12 and the upper tray 20 must be substantially rigid, and that their facing surfaces must be accurately parallel, so that all the sachets across the entire width and breadth of the mould 12 are cut out.
  • FIG. 3 shows the matching network 36 in more detail.
  • the signal from the generator 26 passes through a monitoring circuit 40 (shown diagrammatically) , an inductor 42, and a variable capacitor 43, and so to the conductor 24 leading to the upper tray 20.
  • a variable capacitor 41 connects the junction between the monitoring circuit 40 and the inductor 42 to earth.
  • the monitoring circuit 40 monitors the radio frequency current and voltage, and adjusts the values of the variable capacitors 41 and 43 using servo ⁇ motors 44 and 45 so that the impedance presented to the generator 26 remains at a constant value such as 50 ⁇ .
  • a welding apparatus may incorporate a different active matching network to that described above.
  • the knife edge 30 may be of a different size and shape to that described and shown, and in particular its height depends on the thickness of the films that are to be welded, and on their physical characteristics. Compression of the films 10 and 18 between the dies 12 and 20 is essential to the welding process, and this compression does not increase once the knife edge 30 comes into contact with the other electrode 12. Hence for comparatively incompressible films the knife edge 30 may project further than the thickness of a single film, while for readily compressible films the knife edge may project less than the thickness of a single film. As a rule, the knife edge will have to project a distance in the range 30% to 150% of the thickness of a single film, in accordance with its compressibility.
  • Such a knife blade 30 may be formed while machining the lower surface of the upper tray 20. Alternatively in some situations it may be more convenient to use a length of brass printer's rule, with a sharp edge, to form the blade 30, with a flat-edged length of printer's rule to form an adjacent seam.
  • the blade can be held at the desired position projecting above the level of the seam by using shims of an appropriate thickness, for example of copper foil.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)

Abstract

Des films polymères (10, 18) sont soudés par soudage haute fréquence entre des électrodes opposées (12, 20) pour former un joint ou rebord d'un sachet, et sont découpés simultanément. Une électrode (20) est connectée à une source à semi-conducteurs (26) de signaux radiofréquence par un réseau correspondant actif (36), au moins une des électrodes est revêtue d'une couche isolante dure (15) d'au moins 15 νm d'épaisseur, et les électrodes sont conformées de manière à définir une arête coupante (30) s'étendant selon la zone de soudage, en saillie entre 30 % et 150 % de l'épaisseur du film. Cela permet la formation et la découpe d'emballages tels que des sachets de détergent en une seule opération.
PCT/GB2005/050119 2004-07-30 2005-07-27 Formations de joints et d'emballages WO2006010961A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0417043A GB0417043D0 (en) 2004-07-30 2004-07-30 Forming enclosures
GB0417043.7 2004-07-30

Publications (1)

Publication Number Publication Date
WO2006010961A1 true WO2006010961A1 (fr) 2006-02-02

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PCT/GB2005/050119 WO2006010961A1 (fr) 2004-07-30 2005-07-27 Formations de joints et d'emballages

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GB (1) GB0417043D0 (fr)
WO (1) WO2006010961A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2450366A (en) * 2007-06-22 2008-12-24 Stanelco Rf Technologies Ltd Dielectric bonding
WO2011040860A1 (fr) * 2009-09-30 2011-04-07 Mölnlycke Health Care Ab Procédé de fixation de languettes de saisie d'une couche de support de pansement film

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2638963A (en) * 1949-03-31 1953-05-19 Us Army Apparatus for dielectric fabrication
US2686556A (en) * 1950-05-31 1954-08-17 Gerber Eugene Machine for sealing thermoplastic materials
US2896055A (en) * 1953-04-21 1959-07-21 Kohler Fred Arc suppressor for dielectric heating equipment
US4978055A (en) * 1989-04-27 1990-12-18 Rembrandt Photo Services Reinforced pocket structure for thermo-adhesive materials
EP0546502A2 (fr) * 1991-12-09 1993-06-16 W.R. Grace & Co.-Conn. Procédé et appareil à haute fréquence pour le sondage de films en matière thermoplastique

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2638963A (en) * 1949-03-31 1953-05-19 Us Army Apparatus for dielectric fabrication
US2686556A (en) * 1950-05-31 1954-08-17 Gerber Eugene Machine for sealing thermoplastic materials
US2896055A (en) * 1953-04-21 1959-07-21 Kohler Fred Arc suppressor for dielectric heating equipment
US4978055A (en) * 1989-04-27 1990-12-18 Rembrandt Photo Services Reinforced pocket structure for thermo-adhesive materials
EP0546502A2 (fr) * 1991-12-09 1993-06-16 W.R. Grace & Co.-Conn. Procédé et appareil à haute fréquence pour le sondage de films en matière thermoplastique

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2450366A (en) * 2007-06-22 2008-12-24 Stanelco Rf Technologies Ltd Dielectric bonding
WO2011040860A1 (fr) * 2009-09-30 2011-04-07 Mölnlycke Health Care Ab Procédé de fixation de languettes de saisie d'une couche de support de pansement film
US9486366B2 (en) 2009-09-30 2016-11-08 Mölnlycke Health Care Ab Method of attaching grip tabs to the carrier layer of a film dressing

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