DE4034092A1 - Continuous edge sealing and cutting of two synthetic films - has heated knife with step to give wide strong seal for heat-sealed packaging - Google Patents

Abstract

At least two layers of synthetic film are cut and heat sealed by a knife whose direction of movement has a normal and a parallel component relative to the film. The knife has a first, relatively broad surface to produce a wide seal and a second narrow section to produce a cut and edge seal. The knife can be rocking, rotating or reciprocating. The step between the first and second section can be 1-10mm, pref. 1-5mm. A geared drive gives a rocking motion to a heated knife and a broad seal is produced between polythene films enclosing the item to be packed to the right. A thin strip of waste is separated to the left. The broad section of the knife exerts a pressure of 1-20 mbar against a cooled bar. USE/ADVANTAGE - The invention provides a broader and stronger seal for heat sealed packaging material. (0/7)

Description

The invention relates to a device for continuous Separation welding of at least two superimposed art fabric films with a heated, the films through a Separating and separating weld seam welding knife, in addition to one towards the Welding first relative movement between the Partition welding knife and the films a second relative movement is provided between the separating welding knife and foils, the one component perpendicular to the weld.

Such a device is known from DE-PS 12 09 722. In this known device, this is weighing, rotating or butt-trained separating welding knife as electrically heated Disc formed with a very small thickness, so that the Schei the edges of the foils are melted in the manner of a cutting edge penetrates and separates from each other while through the up melting the resulting film edges on both sides of the Cut-off welding knife connected by a weld that will. The resulting weld seam is very narrow and is therefore not sufficient for the recent ge on such welds made strength requirements.  

It is therefore also known from DE-PS 36 29 497, under considerable expenditure on equipment when used obliquely fender, heated metal bands relatively wide and therefore essential Lich to produce stronger welds, but it requires derlich, the interconnected foils after the production of the wide weld seam by a special one Separating device with knives or the like to separate what requires additional equipment.

It is an object of the invention to provide a simple device ben, with the help of a single operation Separation weld seam of considerable width and thus strength can be manufactured.

The object is achieved in a generic device solved that the separating welding knife a first, the surface the relatively wide section touching a foil to the Er testify to a wide weld seam and a second, from the first stepped, penetrating the two foils, relatively narrow section for creating a separating weld having.

The following description of preferred embodiments of FIG Separation welding devices is used in connection with the enclosed the drawing of the further explanation of the invention. Show it

Figure 1 shows schematically in side view a device for continuous separation welding little least two superimposed plastic films with a weighing separation welding knife.

Fig. 2 is a front view in the direction of arrow A in Fig. 1;

Fig. 3 is an enlarged sectional view of a separating weld diameter of the apparatus of Figures 1 and 2.

Fig. 4 schematically in front view a rotating cutting welding knife;

Fig. 5 schematically in front view a stitch knife;

Fig. 6 shows schematically a cutting knife with clamping rail and

FIG. 7 is a schematic sectional view along the line 7-7 in FIG. 6.

Fig. 1 shows a on a stationary machine frame 1 by means of screws 2, 3 fixed bearing block 4 on which an electric motor is fixedly arranged with reverse gear 6 5. An output shaft 7 of the reversing gear 6 is given an oscillating movement over an angular range of, for example, between 10 ° and 60 ° by the action of this gear. At the free end of the output shaft 7 , as indicated only schematically on the drawing, a separating welding knife 8 is fastened in a manner known per se, which has a circularly curved cutting edge 9 to the axis of the output shaft 7 , which oscillates or "weighs" in the direction of arrow B ( Fig. 2) is driven. The consisting of electrically conductive Me separating welding knife 8 comprises, as shown in Fig. 2, two legs 11 , 12 which are separated by an intermediate space 13 . These legs 11 , 12 are known per se grinding members 14 , 15 and electrical feed lines 16 , 17 with an electrical power source in connection, so that the weighing cutting knife 8 can be electrically heated to a desired temperature.

As can be seen from Fig. 1, on the machine frame 1 two parallel to the cutting edge 9 of the separating welding knife 8, cooling strips 18 , 19 fixedly arranged, which form such a distance between them that the cutting edge 9 of the separating knife 8 from top to bottom can penetrate between them. The strips 18 , 19 form a base for two plastic films 21 , 22 , for example made of polyethylene, which are to be joined together by a separating weld. The two foils 21 , 22 usually wrap a packaging material on the right side of the separating welding knife 8 in FIG. 1. On the left of the separating welding knife 8 , te is separated from the films 21, a relatively narrow waste strip from the films 21 , 22 .

The foils 21 , 22 are advanced perpendicular to the plane of the drawing in FIG. 1 and in the direction of arrow C in FIG. 2 relative to the separating welding knife 8 . During the welding process, the oscillating separating welding knife 8 performs a second movement relative to the plastic foils 21 , 22 , which has a component that is oriented perpendicular to the weld seam formed.

In the embodiment shown, two foils 21 , 22 are welded together. It is possible to connect more than two foils with the aid of the described device by means of a separating weld.

The strips 18 , 19 serving to support the foils 21 , 22 can also be replaced by other documents, for example by transports leading in the direction of arrow C, which carry the foils 21 , 22 and act on the lower foil 22 . Transport belts oriented in parallel can also act on the upper film 21 . Such means of transport are known per se.

The cross-sectional profile of the cutting knife 8 is best seen in FIG. 3. Accordingly, the separating welding knife 8 comprises a first, the surface of the upper film 21 touching, relatively wide section 23 for producing a wide weld on the films 21 , 22 , the width of which corresponds approximately to the width of the section 23 of the separating knife 8 . Furthermore, the separating welding knife 8 has a second, from the first section 23 stepped, the two foils 21 , 22 penetrating and separating, relatively narrow section 25 , on which the cutting edge 9 is formed by appropriate bevels.

The wide section 23 of the separating welding knife 8 lies on the foils 21 , 22 with a pressure of, for example, 1 to 20 mbar.

As shown in Fig. 3, on the left side of the separating welding knife 8 from the foils 21 , 22 the already mentioned te waste strip is formed, which on its lateral edge on the flank of the separating welding knife 8 in a conventional manner with a narrow, the springs 21 , 22 connecting separating weld seam is provided. Such a separating weld seam is produced in the known separating welding knives, which only consist of the narrow section 25 which is provided with the cutting edge 9 and which penetrates the foils 21 , 22 , also on the right side of the separating welding knife. In the device described here, however, the two foils 21 , 22 in the region of the wide section 23 of the separating welding knife 8 are additionally connected to one another by the wide weld seam 24 , the strength of which is substantially greater than that of a conventional, narrow separating seam.

The wide weld 24 is, as can be seen from Fig. 3, with its edge on the side flank of the section 25 stepped from the section 23 , so that hereby on this edge by melting and re-solidification of the plastic forming the films 21 , 22 a clean Randver conclusion of the wide weld seam 24 arises.

In Fig. 4 a modified device for continuous separation welding is schematically shown at least two plastic films lying on top of each other, which differs from the embodiment according to FIGS. 1 and 2 only by the fact that instead of an oscillating or driven driven separation welding knife, a continuously rotating one and just if electrically heated circular knife 28 is provided. The circular knife 28 rotates in the direction of arrow D and is oscillated up and down by a corresponding additional drive in the direction of arrow E. The profile of the circular knife 28 corresponds to the profile of the "weighing knife" 8 shown in FIG. 3. For the rest, the operation is the Vorrich processing shown in FIG. 4, the same as that from Fig. 1 to 3.

FIG. 5 shows a further modified embodiment of a separating welding apparatus. This device differs from the devices described in that the separating welding knife is designed as an abutting, ie in the direction of arrow F continuously up and down stitch knife 38 , which is electrically heated by current supply lines 39 , 40 indicated schematically in FIG. 5. Moreover, the device according to Fig has. 5, the same effect as diejeni gene according to Fig. 1 to 3 and 4 respectively.

The separating welding knife 8 , 28 and 38 can be made with their Abschnit th 23 , 25 in one piece. Alternatively, it is also possible to manufacture the two sections 23 , 25 of the cutting blades 8 , 28 , 38 , which are stepped apart from one another, from two separate, interconnected parts. The height of the step between the first section 23 and the second section 25 can be between 1 and 10 mm; it preferably has a value between 1 and 5 mm.

In the further embodiment shown in FIGS. 6 and 7, the oscillating or weighing driven cutting welding knife 8 according to FIGS . 1 to 3 is shown schematically. The plastic foils 21 , 22 to be connected are fed in the direction of arrow C. As can be seen from FIG. 7, the foils 21 , 22 are in turn supported by stationary strips 18 , 19 , however, on both sides of the separating welding knife 8 moving conveyor belts 41 , 42 engage the foil 21 above.

As shown, a tensioning rail 43 is arranged between the relatively narrow section 25 of the separating welding knife 8 and the strip 18 to be separated from the foil strip Le receiving, which in the forward direction (arrow C) of the foils 21 , 22 before the separating welding knife 8 starts up behind this knife he stretches and the upper edge 44 of the ledge 18 , 19 forming the Unterla ge so obliquely from bottom to top that the distance of this edge from the surfaces of the strips 18 , 19 in the forward direction C from one below the strip surface to one above the position of the groin surface increases. This causes the waste strip-forming film parts on the left in Fig. 7 side of the separating weld diameter 8 inevitably raised and tensioned, so that in this way the separating action of the blade weld diameter 9 of the separating support 8 by the strip of scrap, due to its inevitable increase by the tension rail 43 of the wide weld seam 44 formed on the opposite side of the separating welding knife 8 is pulled away.

Claims (10)

1.Device for the continuous separation welding of at least two plastic foils lying one on top of the other with a heated separating welding knife which connects and separates the foils by means of a weld seam, in addition to a in the direction of the weld seam, the first relative movement between the separating welding knife and the foils runs a second relative movement between the separator Welding knife and foils is provided, which has a component directed perpendicular to the weld seam, characterized in that the separating welding knife ( 8 , 28 , 38 ) has a first, relatively wide section ( 23 ) for producing, which contacts the surface of the one foil ( 21 ) a wide weld seam ( 24 ) and a second, from the first stepped, th, penetrating the two foils, relatively narrow section ( 25 ) for producing a separating weld seam has. 2. Device according to claim 1, characterized in that the separating welding knife ( 8 ) is designed as an oscillating weighing knife. 3. Apparatus according to claim 1, characterized in that the separating welding knife is designed as a rotating circular knife ( 28 ). 4. The device according to claim 1, characterized in that the separating welding knife is formed as a butting knife ( 38 ). 5. The device according to claim 1, characterized in that a clamping rail ( 43 ) is arranged between the relatively narrow section ( 25 ) of the separating welding knife ( 8 , 28 , 38 ) and a sheet (strip 18 ) receiving the film parts to be separated, which in the forward direction (C) of the foils ( 21 , 22 ) in front of the separating welding knife starting behind the separating welding knife and whose edge ( 44 ) runs obliquely with respect to the base such that the distance of the edge from the base in the forward direction of one below the base increases to a position above the base. 6. The device according to claim 1, characterized in that the two sections ( 23 , 25 ) of the cutting welding knife ( 8 , 28 , 38 ) are made in one piece. 7. The device according to claim 1, characterized in that the two sections ( 23 , 25 ) of the cutting welding knife ( 8 , 28 , 38 ) form two separate, interconnected parts. 8. The device according to claim 1, characterized in that the second, wider section ( 23 ) of the Trennschweißmes sers ( 8 , 28 , 38 ) is sharpened to a cutting edge ( 9 ). 9. The device according to claim 1, characterized in that the height of the step between the first and second sections ( 23 , 25 ) of the cutting welding knife ( 8 , 28 , 38 ) between 1 and 10 mm, preferably between 1 and 5 mm . 10. The device according to claim 1, characterized in that the first, relatively wide portion ( 23 ) of the separation welding knife ( 8 , 28 , 38 ) touches the surface of the film ( 21 ) with egg nem pressure between 1 and 20 mbar.