MXPA01001940A - Film treatment device and wrapping apparatus - Google Patents

Abstract

The invention relates to a film treatment device (1) in conjunction with a wrapping apparatus and to a wrapping apparatus provided with a film treatment device. The film treatment device comprises a cutting device (2) for the cutting of a plastic film web (F). The cutting device (2) comprises an elongated electric resistor (5) fastened by both ends with fastening elements (3, 4), against which resistor the film web can be pressed and cut via heating of the electric resistor. The cutting device (2) comprises a supporting element (6) disposed to support the electric resistor laterally substantially over the entire length of the electric resistor between the fastening elements (3, 4).

Description

DEVICE FOR TREATMENT OF FILM AND WRAPPING DEVICE The present invention concerns a film treatment device as defined in the preamble of claim 1. Furthermore, the invention concerns a wrapping apparatus as defined in the preamble of the claim 12. In the prior art, various types of wrapping apparatus are known for winding a plastic film net around an object to be packaged. One of these wrapping apparatuses comprises a film distributor positioned to surround the object to be wrapped along a ring-shaped guide while the object to be wrapped remains immobile during the wrapping operation. The movement of the film distributor can be controlled by means of a guide rail or the film distributor can be fastened to a rotating arm. The film runs from a roll in the film distributor and is wrapped around the object. There are also wrapping apparatuses in which the film distributor is fixedly installed on a column frame on a base and the object to be wrapped is surrounded on a rotating floor.

Along with this type of wrapping apparatus, various film treatment devices are known, for example, from specifications WO 99/19216, US 4,993,209, Fl 91624 and EP 0493 940. Typically, a film treatment device comprises fasteners that can hold the film network at the beginning and end of the wrapping operation. In addition, the film treatment device comprises a disconnector device for cutting the film network at the end of the wrapping operation, and hot sealing element for joining the layers of superimposed films close to the closing line in a seam in a manner that the end of the network remains subject to the layer of the film below it. The seaming and disconnecting element presented in the specification WO 99/1216 comprises an infrared radiator placed in a housing with holes through which the infrared rays are directed through the film in a block containing seam and seam which absorbs the heat, which is heated in this way by cutting the film and sewing the layers of film placed against each other. The use of an infrared ray source is useful because it requires virtually no maintenance. However, the use of an infrared lamp includes the drawback of a relatively high price, requiring a higher power supply and a bulky structure. In addition, both the sewing and the cutting of the film are made using the same heat source. The time of sewing and cutting operations can not be adjusted independently of each other. If a type of wrap film plastic requires temperatures different cutting and sewing, then these can not be adjusted independently to each other in each case. In the wrapping apparatus presented in specification US 4,993,209, a device is used sewing disconnector where the film is cut and sewn by blowing hot air to it. The problem is a varying quality of sewing and an inaccurate closing line. Heating the air to a sufficient temperature and bringing it to the closing line is also difficult and problematic with respect to energy economy. The specifications Fl 91624 and EP 0 493 940 present devices for cutting a film where the film is cut by a knife cutter. The problem with a cutting blade is the dangerous nature of it. When the operator changes the roll of film and places a new film to allow the fasteners to hold it, his hand can touch the cutting blade placed near the roll. In any case, the most similar example to the previous technology is a known film treatment device of the "Octopus" wrapping machine of the applicant wherein the disconnecting device comprises a resistance wire held firmly at both ends by means of elements of clamping and freely extending without support between the clamping elements so that it is surrounded by air space on all sides. At the end of the wrapping operation, the film network is pressed against the resistance wire and an electric current passes through the wire, the wire is then heated so as to cut the film network. The problem is that a repeated fatigue induction load is transmitted from the film network to the areas near the resistance wire attachment point, eventually producing a fracture due to fatigue and rupture of the wire. In addition, the thin resistance wire (approximate diameter of 0.6 mm) is susceptible to rupture if the operator of the machine presses it carelessly when adjusting the end of the film network to the fastening element placed close to it. Another problem is that, as the film network is bent over the resistance wire, the contact area between the film and the circumference of the resistance wire is too large, which means that the entire contact area has to be burned in order to cut the network, thus producing harmful impurities in the air. If, for example, a film network with a width of 0.5 meters is bent at an angle of 120 degrees onto a 0.6 mm resistance wire, then for each cut, an area of 3.15 cm2 of plastic must be burned, producing smoke. Another problem is that the plastic crust adheres to the wire, deteriorating its functional quality. The object of the invention is to eliminate the aforementioned problems. A specific object of the invention is to invent a film treatment device in which the durability of the resistance wire has been improved so that it does not require any maintenance. Another object of the invention is to invent a film treatment device that is safer and more reliable than previous devices. A further object of the invention is to invent a film treatment device wherein the amount of plastic burned in the sectioning operation is minimized. In the claims that follow, reference is made to the characteristic functions of the film treatment device and the wrapping apparatus of the invention. According to the invention, the film treatment device comprises a support element arranged to support the lateral electrical resistance and substantially over the entire length thereof between the fastening elements. The support element constitutes a stop stop for the electrical resistance against the pressure of the film, keeping the resistance continuously and firmly immobile in position. The invention has the advantage that the distribution for supporting the electrical resistance makes it possible to achieve the same advantages as in the case of a device using an infrared radiator but more simply and at a lower cost. The susceptibility to electrical resistance damage is reduced and its useful life is considerably longer while a safer and more reliable device is achieved. Furthermore, the invention makes it possible to use an electrical resistance where the part that comes into contact with the film is as narrow as possible so that the amount of plastic burned together with the cut is minimized. In addition, plastic material will not adhere around the electrical resistance. In one embodiment of the device, the electrical resistance is a band-shaped structure and substantially has the transverse shape of a flat rectangle. The support element comprises a groove designed to receive the electrical resistance in the form of a band partially inside it. The walls of the groove support the broad sides of the band laterally from both sides while the lower part of the groove supports the narrow edge thereof. In one embodiment of the device, the slot has been adapted to receive the electrical resistance therein with a space that allows repeated thermal expansion and contraction of the electrical resistance band. In an embodiment of the device, the part of the support element that supports the electrical resistance against the pressure of the film network has a curved shape to give the electrical resistance this same shape, and the ends of the electrical resistance are fastened to the support element in a manner that at least one end is connected to the support element by means of a spring. The curvature of the electrical resistance and the tension created in it by the spring are necessary to maintain the electrical resistance in the groove. Due to the curvature, the electrical resistance is stretched in a curved shape, which means that a force component is generated in the support, such as the lower part of the groove, which presses the electrical resistance towards the lower part. of the slot and prevents it from slipping out of the slot when it is subjected to a lateral force tending to pull it out of the slot. Without the curvature, the electrical resistance could easily escape from the groove. In one embodiment of the device, the electrical resistance band comprises an outer edge that cuts the film, and an inner edge that remains at the entrance of the slot and rests at the bottom of the slot, having a curvature designed to bend to the electrical resistance band in curved form. In one embodiment of the device the support element and the electrical resistance are adapted so that in the device, while the electrical resistance bends the network of film stretched thereon, the support element also bends the film network in the points located on opposite sides of the electrical resistance at a distance from its outer edge, so that after it is cut off, the film web tends to fold free of the electrical resistance. In one embodiment of the device, the support element is made of a substantially rigid and electrically insulating heat resistant material, for example phenol formaldehyde. In one embodiment of the device, the thickness of the electrical resistance band is approximately 0.2 mm. In one embodiment of the device, the film treatment device comprises fastening elements that grip the film network. In one embodiment of the device, the film treatment device comprises sewing elements for sewing together layers of superimposed films by means of heat.

In the following, the invention will be described in detail with the help of some examples of its embodiments which refer to the accompanying drawings that are included herein. Figure 1 presents an axonometric diagram of an embodiment of the wrapping apparatus of the invention having a film treatment device according to the invention, seen obliquely in plan, Figure 2 presents an axonometric view of the treatment device of film of the wrapping apparatus in Figure 1, Figure 3 presents the film treatment device of Figure 2 on a side edge, Figure 4 presents the film treatment device of Figure 3 as seen from the IV direction -IV, Figure 5 presents the detail A of Figure 4, Figure 5 presents a diagrammatic section from VI-VI through the device in Figure 3, Figure 7 presents a side view of the support element of the disconnector the invention with an electrical resistance band in the groove, Figure 8 presents the support element and the resistance band of Figure 7 as seen from the direction VIII-VIII, Figure 9 presents an enlarged section IX-IX of Figure 7 with a plastic film bent over the support element and the outer edge of the electrical resistance band so that the film can be cut, the Figures 10-23 illustrate the operation of the film treatment device in different stages during the wrapping process. Figure 1 shows a wrapping apparatus designed to roll a wrapping film (wrapping film) around a fixed product P to be packaged. The wrapping apparatus comprises a structure 18 installed on a fixed base. A movable frame 19 can be moved vertically in relation to the structure 18. A circular ring guide 20 is placed in a horizontal plane and is supported by the movable frame 19 so that it can move vertically in relation to the structure. The wrapping apparatus comprises a film distributor 16, which is arranged to move at a constant speed, driven by a drive motor (not shown) provided in the film distributor 16, along a circular path as it is guided. by the ring guide 20 around the product P that is being packed. During the wrapping operation, the ring guide 20, supported by the moving frame 19 moves vertically to allow the film to wrap up like a spiral wrap around the product. Installed so that it can move on the mobile frame 19 is a portal beam 29 with a film treatment device 1 mounted thereon. By moving the portal beam 29 horizontally relative to the mobile frame 19, the film processing device 1 can be moved towards and away from the product P being packaged. It should be noted that the film treatment device 1 described herein can be employed in any wrapping machine, for example one where the film distributor is connected to a rotating crank that circulates the film distributor around a fixed product that will be wrapped, or in a wrapping machine where the film distributor is connected to a fixed column and the product is rotated to roll the film around it. Figures 2-6 present more detailed views of the film treatment device 1 and its components. As the device, in other aspects except for the distribution of the invention to support the electrical resistance 5, is of a type known per se (general construction known for example from specification US 4,993,209), its structure will not be described in detail in the present only when necessary to understand the invention and the operation of the device. As shown in Figures 2-6 the film treatment device 1 comprises fasteners 12, 13 to grab the movie network. It also comprises sewing elements 12, 14 for sewing together layers of superimposed films by means of the application of heat. In addition, the film treatment device comprises a disconnecting device 2 for cutting the film network along a line close to the seam. The film treatment device comprises a frame 12, which can be rotated by means of a first energy source 21 between a vertical and a horizontal position around a rotating shaft 22. The device also comprises a holding bar 13, which can be rotate about the rotating shaft 22 by a second power source 23. As can be seen in Figure 6 the fastening elements comprise a recess 30 between the circumference of the round retaining bar 13 and a flat surface 24 of the frame 12 positioned against the retention bar, the recess adapted to hold in its space clamp a network of film placed on it (see also Figures 12 and 23). The film treatment device 1 further comprises a back bar 14, which can be rotated by a third energy source 25 around the rotating shaft 22 between a vertical and a horizontal position. The frame 12 comprises a second stop surface 26, which is placed against a third stop surface 27 on the back bar 14, forming the sewing elements, which are heated by means of a seam resistor 28 embedded within the frame 12 near the stopping surface 26. The film distributor 1 further comprises a disconnecting device 2 for cutting the plastic film net F. The disconnecting device 2 is installed on the frame 12 between the sewing element and the aforementioned fastening element. .

The disconnecting device 2 is presented in great detail in Figures 7-9. The disconnecting device 2 comprises a prolonged support element 6, which can be fastened to the frame 12. The support element 6 is made of a dielectric material of a substantially rigid and heat resistant nature, such as phenol formaldehyde (PF), which It is also called "Bakelite". The support element 6 has a longitudinal groove 7, in which an electrical resistance in the form of a band 5 of a transverse shape resembling a flat rectangle is installed with a space so as to allow thermal expansion and contraction of the band in the groove . The lower part 11 of the groove 7 supports the inner edge 10 of the electrical resistance band 5 while the opposite walls support the two wide sides of the band. The outer edge 9 of the electrical resistance band 5 extends in some way upwards from the surface of the support element 6. One end of the electrical resistance band 5 is fixedly connected to the support element 6. One end of the electrical resistance band 5 is fixedly connected to the support element 6 with a holding element 3. The other end of the electrical resistance band 5 is connected to the support element 6 with a second holding element 4, which comprises a movable train 31 moving along a guide 32 formed in the support element, the movable train is loaded by a spring 8 in the longitudinal direction to keep the band 5 stretched in the slot 7. As can be seen in Figure 7, the lower part 11 of the groove 7 has a slightly curved shape with a large radius R of curvature to bend the electrical resistance band 5 into a corresponding curved shape. This again helps keep the band 5 in the slot 7. Figure 9 illustrates how the resistor 5 bends the film network F by tensioning it over it when the net is held in the space of the seam element on one side and the clamping element on the other side of the resistor as illustrated in Figure 23. The support member 6 causes the film network to be bent into elements A and B, which are close to the electrical resistance 5 on opposite sides of the same but still at a distance from it so that, after the film web has been cut by instantaneous heating of the electrical resistance, the ends of the film web F tend to fold free of the electrical resistance 5 as indicate the dashed lines of Figure 9. The resistance band 5 that is used may have a very thin construction as it is very well supported in the groove 7 of the support element 6. In a form of an The electrical resistance band consists of a resistance band available under the brand name KANTHAL DSD, which has a width of 6 mm, a thickness of 0.2 mm and a specific resistance of 2,466 O / m. In the example of the embodiment, the resistor band has a resistance of 1.3 O and receives power with a voltage of 24 V. The electric power is 500 W. Figures 10-23 are diagrammatic illustrations of the operation of the device. processing of film 1 in different stages during the wrapping of a fixed package P. The film distributor 16 is simply represented by means of a roll of film 17 that delivers the film. Figure 10 (side view) and 11 (plan view) illustrate the initial phase of the wrapping process of a pack P, where the film F is held in the space of the frame 12 and the retaining bar 13, as it can also be seen in the enlarged detail of Figure 12, while the frame 12, the retaining bar 13 and the back bar 14 are in a vertical position. Figures 13 and 14 illustrate a situation at the beginning of the wrapping process wherein the assembly consisting of the frame 12, the holding bar 13 and the back bar 14 have been rotated about the rotating shaft 22 to the horizontal position with the film F still held in the space of the frame 12 and the holding bar 13, so that the film can be roll around the P package without these parts hindering it. In Figure 15 and 16, the assembly of the frame 12, holding bar 13 and back bar 14 is still in the same position as Figure 11 and 12 and the film roll 17 has taken a full turn and part of the a second round around the package P. The end of the film that remains under a film layer can now be released from the space of the frame 12 and the retaining bar 13. Figures 17 and 18 illustrate a situation in a final phase of the wrapping operation. The back bar 14 has been rotated about the rotating shaft 22 to the vertical position while the frame 12 and the holding bar 13 are still in the horizontal position, and the back bar 14 is between the film and the pack P while the The film is wound on the back bar 14. FIGS. 19 and 20 illustrate a situation where the film roll has made yet another round around the pack P after the situation in FIGS. 17 and 18. The holding bar 13 has rotated about the rotating shaft 22 in the vertical position and the film has been wound onto the holding bar 13. The wrapping operation is stopped here. Figures 21-23 illustrate the final situation, when the frame has rotated about the rotary shaft 22 to the vertical position against the retaining bar 13 and the back bar 14 has in order to cut and sew the film. The electrical resistance band 5 is heated by passing an electric current through it, whereby it burns the film F, cutting it in that way. At the same time, the electrical stitching resistor 28 inside the frame 12 is heated by passing an electric current through it, heating it in this way so that the film layers that now lie on each other are welded together between the retaining surface 26 of the frame and the retaining surface 27 of the back bar 14 so that the final end of the film is secured to the film layer below it. After that, the frame 12 and the holding bar 13 rotate to the horizontal position and the film treatment device 1 moves upwards, thereby stretching the backing bar 14 from under the last layers of film in the package. After this, the package wrapped P can be pulled out and a new one is placed for wrapping, starting again from a situation illustrated in Figures 10-12. The invention is not limited to the examples of the embodiments described above; but many variations are possible within the scope of the invention defined in the claims.

Claims (12)

1. CLAIMS 1. Film treatment device together with a wrapping apparatus, the device comprises a disconnector device for cutting a plastic film network F, the disconnector device comprises an elongated electrical resistance that is held at both ends by fasteners , the film web can be pressed against the resistance and cut by means of heating the electrical resistance, characterized in that the disconnect device comprises a support element positioned to support the electrical resistance laterally and substantially over the entire length of the electrical resistance in the fasteners. Device as defined in claim 1, characterized in that the electrical resistance is a band-like structure and has substantially the transverse shape of a flat rectangle; and that the support element comprises a groove designed to receive within it the electrical resistance in the form of a band. The device as defined in claim 2, characterized in that the slot is adapted to receive the electrical resistance therewith with a space that allows thermal expansion and contraction of the electrical resistance band. 4. The device as defined in any of claims 1-3, characterized in that the part of the support element that supports the electrical resistance against the pressure of the film network F has a curved shape to give it this curved shape to the electrical resistance; and that the ends of the electrical resistance are attached to the support element so that at least one end is connected to the support element by means of a spring. The device as defined in any of claims 2-4, characterized in that the electrical resistance band comprises an outer edge that cuts the film, and an inner edge that remains within the groove and rests on the part bottom of the groove, which has a curvature designed to bend the electrical resistance band to a curved shape. The device as defined in any of claims 1-5, characterized in that the support element and the electrical resistance are adapted so that, while the electrical resistance bends the film network F stretched thereon, the support element also bends the film network F at the points (AB), which are located on opposite sides of the electrical resistance at a distance from it, so that after they are cut, the film network tends to fold free of electrical resistance. The device as defined in any of claims 1-6, characterized in that the support member is made of electrically insulating material, substantially rigid and heat resistant. 8. The device as defined in claim 7, characterized in that the support element is made of phenol formaldehyde. The device as defined in any of claims 2-8, characterized in that the thickness of the electrical resistance band is approximately 0.2 mm. 10. The device as defined in any of claims 1-9, characterized in that the film treatment device comprises fastening elements for holding the film network. 11. The device as defined in any of claims 1-10, characterized in that the film treatment device comprises sewing elements for sewing together layers of superimposed films by means of heat. 12. The wrapping apparatus for wrapping a plastic film net F around an article P to be packaged, the wrapping apparatus comprises a film distributor for wrapping a plastic film net of a roll around the article to be packaged, and a film treatment device comprising fastening elements for gripping the film network and a disconnecting device for cutting the film network, the disconnecting device comprises an elongate electrical resistance which is held at both ends by fastening elements. 15. The wrapping apparatus as defined in any of claims 12-14, characterized in that the part of the support element supporting the electrical resistance against the pressure of the film network has a curved shape to give this form to the electrical resistance; and that the ends of the electrical resistance are fastened to the support element so that at least one end is connected to the support element by means of a spring. 16. The wrapping apparatus as defined in any of claims 13-15, characterized in that the electrical resistance band comprises an outer edge that cuts the film, and an inner edge that remains within the groove and rests on the lower part of the groove, which has a curvature designed to bend the electrical resistance band into a curved shape. 17. The wrapping apparatus as defined in any of claims 12-16, characterized in that the support element and the electrical resistance are adjusted so that while the electrical resistance bends to the film network F stretched over the same, the support element also bends the film network F at the points AB which are located on the opposite sides of the electrical resistance at a distance from it, so that, after being cut, the film network tends to fold free of electrical resistance. 18. The wrapping apparatus as defined in any of claims 12-17, characterized in that the support member is made of an electrically insulating material, substantially rigid and heat resistant. 19. The wrapping apparatus as defined in claim 18, characterized in that the support element is made of phenol formaldehyde. 20. The wrapping apparatus as defined in any of claims 12-19, characterized in that the thickness of the electrical resistance band is approximately 0.2 mm. 21. The wrapping apparatus as defined in any of claims 12-20, characterized in that the wrapping apparatus comprises a structure installed on a fixed base; a mobile frame that can move vertically in relation to the structure; a circular ring guide placed in a horizontal plane and supported by the mobile frame; the film distributor has been placed to move along the ring guide around the article P that is packed; and the film treatment device is installed on the movable frame so that it moves towards and away from the article P being packaged.