WO1999003669A1

WO1999003669A1 - Device for separating a line of material consisting of plastic which can be deep-drawn

Info

Publication number: WO1999003669A1
Application number: PCT/EP1998/002961
Authority: WO
Inventors: Heiko Bub; Johannes Crepaz; Gerhard Wiesner
Original assignee: Tetra Laval Holdings & Finance S.A.
Priority date: 1997-07-18
Filing date: 1998-05-20
Publication date: 1999-01-28
Also published as: EP0996532A1; AU8434398A; DE19730781A1; DE19730781C2

Abstract

The invention relates to a device for separating a section (7) of a line of material (1) consisting of plastic which can be deep-drawn, said material being transported intermittently in the direction of delivery. The inventive device has a first, front contact plate (2) for heating the line of material (1) by heat contact, against which a form tool (6) can be moved, and a second contact plate (4) which is located upstream and which also heats the line of material (1) by heat contact. A third contact plate (5) can be moved in relation to the second contact plate (4) in order to squeeze and heat the lines of material (1) in between. The aim of the invention is to provide a means of efficiently separating plastic sections from a moving line of material consisting of plastic, especially propylene, said sections being difficult to cut when hot due to cobwebbing and unfavourable melting properties. To this end, a metal heating band (21) is provided in the area of the face walls (17) with which the contact plates (2, 4) rest against each other. Said heating band (21) is carried by a carrying device (20), said carrying device (20) also driving the heating band (21) in such a way that it can move, in the direction transversal to the front surface (12) of the contact plate (4) so that the heated line of material is contacted linearly and the heating band (21) extends over the width of the contact plate (4). The heating band (21) is also provided with electrical connections at both ends for resistance heating.

Description

Device for severing a material web made of thermoformable plastic

The invention relates to a device for separating a section of a material web made of thermoformed plastic, which is transported intermittently in the conveying direction, with a front contact plate against which a material tool can be heated, and against which a molding tool can be moved, and a second contact plate arranged upstream of the material web through heat contact. relative to which a third contact plate for clamping and heating the material web is movable therebetween.

For the production of plastic packaging from thermoformable plastic, it is known to transport a corresponding material web intermittently in a manufacturing machine vertically from top to bottom, the material web being held in the respective standstill phases by means of vacuum on the respective contact plate and being heated by thermal contact so that the The temperature of the material web gradually increases in the conveying direction until the web on the front, first contact plate is thermoformable. At this moment, a molding tool can be pressed vertically onto the front surface of the front, first contact plate at the edge. Compressed air on the part of the contact plate and vacuum on the part of the molding tool move the section of the material web which is heated on the first contact plate into the inner surface of the molding tool, where it cools and hardens. In this way, a packing half-shell can be deep-drawn and another packing half-shell symmetrically to it in another molding tool. Both are then glued or welded together at their open edge. Instead of a single half-shell pack, several half-shells lying next to one another can also be deep-drawn, all of which are formed from the same section of the heated material web. While in some known packaging manufacturing machines the one or more half-shells are deep-drawn from a plastic plate, which is transferred as a plate in the direction of conveyance from one contact plate to the next and heated in the process, attempts have also been made to pull the plastic material for the deep-drawing process in tape form from a supply roll . Then, however, the foremost section of the material web in the conveying direction must be separated from the web located upstream behind it.

The present invention is directed to this severing operation, which is extremely difficult when the plastic material has unfavorable cutting properties.

A plastic material suitable for the above manufacturing process for packs contains a large percentage of polypropylene. If this has a temperature of around 1 80 ° to 1 90 ° due to the heating, then it is mechanically difficult to handle because it is soft. Various types of cutting knives have already been used for severing a section of a heated plastic material web, some of which have even been designed to be movable in order to avoid thread formation, particularly in the case of polypropylene, after the cutting process. A good mechanical separation with such knives was not possible mechanically.

Form stamping tools are known which also carry out the cutting process simultaneously with the stamping process. Particularly in the field of deep drawing, devices for cutting and shaping molds at the same time have already been carried out. The punching process takes place on the cold tool, so that the material is always punched when it has cooled down considerably.

However, if the above-described deep-drawing process of a front section of a material web heated to a higher temperature of, for example, 1 80 ° or 1 90 ° C. is used, and the section is separated from the heated web while the still warm section is deep-drawn without if larger waste areas are allowed at the edges of the sections, then the conventional punches could not be used any more than the mechanical knives.

The invention is therefore based on the object of providing a device of the type mentioned at the beginning, with which hard-to-cut plastic sections can also be separated from a moving material web made of plastic, in particular polypropylene, even due to thread formation and unfavorable melting properties in the warm state. This object is achieved according to the invention in that a metal heating tape is arranged in the region of the end walls of the contact plates lying against one another on these end walls, is supported by a holding device and is driven by it in a direction movable transversely to the front surface of the contact plate in order to linearly touch the heated material web, that the heating tape extends over the width of the contact plate and is provided at both ends for resistance heating with electrical connections.

First, a few terms have to be explained. The direction of conveyance of the transported material web is also the downstream direction. It can be arranged anywhere in the room. To illustrate the device according to the invention, however, reference is made to the thermoforming machine known at the outset, in which the conveying direction runs vertically from top to bottom. The material web made of thermoformable plastic moves vertically downwards from one contact plate to the next. The material web is heated from a contact plate to an upper height, then transferred to the opposite contact plate, moved further down in the conveying direction, then transferred to the opposite contact plate. The material web is held in sections on the front surface of the respective contact plate by vacuum. The temperature of the contact plates increases in the conveying direction, so that the uppermost contact plates are at a somewhat lower temperature than the lower ones. The so-called front, first contact plate, which has the highest temperature and against which the molding tool can be moved for deep drawing, is located furthest downstream in the conveying direction. The next second contact plate is located upstream behind it, i.e. opposite to the conveying direction. These two lie against each other via end walls and can even touch each other on the end walls. In this contact area, a movable heating tape is now arranged according to the invention, which is electrically heated and extends over the entire width of the front surface of the contact plate. The heating tape is carried by a holding device and is driven with the aid of it so that it moves transversely to the front surface of the contact plate and touches the heated material web in a linear manner.

Although the separation welding is known per se in another context, in the device according to the invention a very soft, almost viscous web is cut in the hot state, at the same time or at short intervals of 1/10 to 3 seconds, preferably 0.5 to 1 Second, the deep-drawing process takes place on one side of the cut, while the web on the other side of the cut is still held on the front surface of the contact plate by the weak vacuum force. This holding force is not particularly strong, so that the cut through the movable heating tape is effective at a high temperature of the heating tape is cut from approximately 300 ° to 400 ° C. without the areas of the material web next to the cut being moved, stressed or warped. As a result, the foremost edge in the direction of transport of the still continuous web of material adheres to the front surface of the contact plate over its entire area and undamaged. In the meantime, the web is held on the other side of the cut between a narrow material strip of the molding tool and the front first contact plate, so that the material web is formed on the one hand into the separated section and on the other hand is moved into the molding tool by deep drawing.

If you look again at the well-known vertical thermoforming machine for plastic packs, the front plate in the transport direction is the so-called front, first contact plate. Upstream behind it is the second contact plate; and the latter opposite the third contact plate. The mold is located downstream of the third contact plate.

Each of the contact plates described has a front end wall and a rear end wall arranged upstream thereof. The actual heating or heating surface is the so-called front surface, which extends perpendicular to the front and rear end walls. Parallel to the front surface is the generally equally large rear surface, and the remaining two surfaces of the cuboid contact plate are the so-called side surfaces, which are separated from one another by the width of the front and rear surfaces.

A cuboid defined in this way also forms the first and the second contact plate, which therefore lie against one another on their respective end walls. In this area of contact, in the area of contact, i.e. In the region of the end walls, the metal, electrically heated heating band is arranged according to the invention and driven by the holding device in a direction transverse to the front surface. When the drive is switched on, the heating tape moves out of the space behind the front surface of the contact plate to touch the heated material web in a line. The line can be more or less long and possibly also curved, depending on the pattern of the section of the material web to be separated.

The unexpected success in the operation of the device according to the invention is a good and complete separation of the downstream section of the material web from the material web behind it at a point which is at such a high temperature that the plastic is relatively softened and just because of it Vacuum on the front surface of the respective contact plate holds. In other words, the inventive device according to a hot film cut exactly on the heat source from the material web, a separation process that was previously not possible without the heating tape and its arrangement and movement according to the invention.

It is advantageous according to the invention if the holding device is arranged in a recess which opens towards the end wall of the contact plate and also has a passage to the front surface of the contact plate which extends across the width of the contact plate, behind which the heating tape stands back in the idle state and through which it passes Cutting off the section of the material web with the help of a drive. According to the invention, in the front first or in the second contact plate arranged behind it, a recess is provided in the region of the end wall, which opens towards this end wall. If the heating tape extends across the width of the contact plate, the holding device will generally also extend across the width of the contact plate; consequently, the recess is just as wide. The recess opens not only to the front wall, but also to the front surface of the contact plate, which gives the heating tape the opportunity to enable a flush front surface of the contact plate or even the contact plates in the idle state, whereas the heating tape is also driven by the passage mentioned in the figure Front surface of the contact plate can move out towards the material web. This movement results in the aforementioned line-like contact of the heated material web and thus the separating cut. The passageway may be in the form of a straight or curved slit, a wider opening, or some other form of passageway. The drive moves the heating tape over the holding device at a favorable time in relation to the deep-drawing process. It is even largely independent of this, provided that the molding tool only presses the lower section of the material web against the first contact plate next to the passage.

It is useful if the holding device has the shape of a bar extending across the width of the contact plate and has a front and a rear support bar attached to the latter, each of which is provided with an extension engaging in the passage of the contact plate, between which one in cross section The L-shaped gap remains, in which the heating tape with an L-shaped cross section is loosely inserted. By dividing the holding device into two support strips, you can easily and quickly replace the L-shaped heating tape when it has been used up. So that the front surface of the contact plate, in the end wall of which the recess for receiving the holding device is located, is as smooth as possible for the material web to be heated without larger openings or slits, the passage described above is as narrow as possible, if possible only move a flat heating tape towards or out of the front surface. The heating tape alone would not have the necessary rigidity, which is why the extensions mentioned are provided on the support strips, between which the gap for receiving the heating tape is located.

According to the invention, the support strip of the holding device can also be surrounded by a hard anodizing layer and preferably a Teflon layer can be applied over the hard anodizing layer. The best strength properties for the support strips are metals, but they conduct both heat and electrical current. It is preferred to make the support strips from aluminum, and then one can hard-anodize their surfaces to thereby turn off the electrical heat conduction. In this way, you can insert the heating tape directly between the hard anodized support bars without a short circuit can be generated on the support bars. Both support strips are preferably additionally provided on the outside over the hard anodizing layer for electrical insulation with a non-stick layer, for example coated with Teflon. This ensures that the material web of the heated plastic does not stick to the front narrow sides of the support strips or their extensions. This measure also serves good separation welding, according to which the heating tape can be pulled back into the recess behind the passage of the front face of the contact plate without thread formation and without annoying adhesions.

In an advantageous further embodiment of the invention, the heating tape together with the holding device can be moved by the drive in the recess of the contact plate. This allows a fine, thin band of metal to be guided precisely and pushed forward with a certain pressure when moving out of the elongated passage. In addition, it is sufficient to use only the L-shaped band as L in this simple embodiment. When it is used up, it can be replaced with a new one at little cost.

The L-shaped heating tape is also not firmly clamped between the support bars of the holding device, but is only loosely in the L-shaped gap formed between the two support bars. This L-shaped gap forms a kind of mounting bed in which the L-shaped heating tape is loosely inserted. The L-shape of the heating tape has one long and one short leg. The long leg preferably lies in the extensions of the support strips which engage in the passage of the contact plate, and the short leg lies transversely thereto, that is to say in a plane parallel to the front surface and parallel to the material web to be heated and cut. The heating tape expands due to its temperature increase by about 2 -3 mm and shortens after switching off the electrical heating energy this contribution. The L-shaped gap between the support strips allows the heating tape to move freely in the gap by inserting it. Due to the angle, it is held between the support strips so that it does not fall out or slip out.

Through the gap there are small spaces, empty spaces between the rear support bar and the front support bar. If plastic is now pushed past the heating tape to the two extensions of the support strips in the welding cutting operation and moves slowly due to the high temperature, this flowable plastic could penetrate into the gap between the heating tape and support strip extensions. However, the above-mentioned Teflon layer or another plastic layer envelops the respective support strips and has such a resistant or repellent surface that the plastic material does not stick to it. The plastic can not clog the gap in any way, because it falls out due to this non-sticking effect of the Teflon surface.

The drive for the holding device and thus for the heating tape can be designed according to the invention in a particularly simple and effective manner in that the drive has a pressure medium and a compressible counterpressure medium, which are located in a first space behind or a second space in front of the holding device in the recess in the contact plate are arranged. The holding device consisting of the two support strips lies loosely in the recess. The two support strips are firmly connected to one another by means of a series of screws which are arranged approximately parallel behind the front surface of the contact plate, the L-shaped gap still remaining in the front in the region of the extensions. This unit of the holding device is arranged movably in the described recess near the end wall of the contact plate. There is even space in front of and behind the holding device for the pressure and counter-pressure media. The pressure medium is located in the space facing the rear surface of the contact surface, i.e. behind the holding device, which is called the first space, and on the opposite side near the front surface there is the so-called second space in the recess, i.e. in front of the holding device, and the counter pressure medium is located in this. If the pressure medium is actuated, it exerts a pressure, which is supported on the rear wall of the recess and moves the holding device forward, against the force of the counter pressure medium. This is compressible and acts like a compression spring. When the pressurization of the pressure medium has been completed and the separation process has ended, that is if one wants to retract the holding device again, the pressure force of the counterpressure medium can push the holding device back into the original position, the pressure medium being compressed. This is a very simple drive, which nevertheless moves the heating tape precisely and with precisely timed control.

It is also advantageous according to the invention if the pressure medium is a glass fiber reinforced silicone hose which is closed at one end and provided with a pneumatic nipple at the other end. If a hose from a pressure source, for example compressed air, is connected to the nipple, then pressure and thus the sliding movement of the holding device toward the front toward the front surface of the contact plate can be achieved with the simple means described. Conversely, you can also apply a vacuum to the silicone hose and thus quickly move the holding device backwards from the welding position.

This is particularly favored by the fact that, according to the invention, the counterpressure medium can also be an empty, elastic hose. Through this completely empty plastic hose, a spring effect of the counter pressure medium is achieved. With this spring action of the hose, which can also be an elastic silicone hose, the counter pressure can be absorbed and the counter pressure for pushing the holding device back in the recess can be achieved when the silicone hose connected to the pneumatic device is subjected to a vacuum. The counter-pressure medium thus acts only as a spring which, in the event of a vacuum, relaxes in the silicone hose acting as a pressure medium and thereby pulls the heating tape out of its shape from the front welding plate protruding position.

The heating tape is preferably heated by an electrical pulse. The duration of the heating is about 1 second and the temperature after the electrical pulse is about 250 ° C. At the moment when the heating tape has reached this high temperature, it is shot out of the passage by the application of the pressure medium to the front and creates the desired cut in the plastic film in front of it, i.e. the material web.

This works particularly well if, according to the invention, an elastically soft insert, preferably a Teflon tape, is held by the molding tool on the side opposite the passage of the contact plate at the height of the heating tape that can be moved out. This soft insert, which acts as a cutting counter bar, could also be held by the third contact plate arranged upstream in front of it. However, it is cheaper to hold the molding tool, because this requires the not be continuously heated on the opposite side. The insert, preferably the Teflon tape, again has non-adhesive properties for the plastic of the material web. If, at the moment the pressure medium is applied, the heating tape carries out the separation welding, it strikes against this use as a cutting counter strip, so that the film or the material web is completely cut through. After that, and especially when the heating tape is pulled back, the thread formation is prevented by the non-adhesive effect of the insert. In contrast to previous mechanical cutting devices, when using the heating tape according to the invention, no more threads are drawn from the area next to the separating cut. This is by no means a matter of course if the material web is made of polypropylene, which has to be heated to 180 ° - 190 ° (only a narrow temperature range!) So that it becomes soft, but easily becomes too thin when this temperature is exceeded.

The insert, which acts as a cutting counter strip, in particular the tefion tape, is best held by means of a resilient plate which is screwed onto the end wall of the molding tool and presses the teflon tape resiliently into the holder recess. It is known that screwing or gluing the Teflon tape is not possible. In particular, this is not possible because the Teflon tape has little mass. Due to the thin wall of the mold in the area of the resilient plate, the attachment of screws or other clamping devices is excluded.

In a further advantageous embodiment of the invention, the front flat end wall of the third contact plate is set at an angle (σ) of 40 ° -70 °, preferably 45 °, to the flat front surface of the second contact plate. In other words, this causes a pointed edge of the third contact plate to slide close to the Teflon tape. The front surface of the third contact plate facing the material web is thereby given a maximum size, with the result that the material web can be optimally heated. In addition, the oblique withdrawal of this flat end wall of the third contact plate increases the space for the wall of the molding tool, so that the molding tool is given a larger mass behind the Teflon tape. In this massive area of the molding tool, coolant bores and also vacuum or compressed air bores, which are required for the deep-drawing process, can be accommodated.

It goes without saying that the band-shaped insert or the Teflon band also extends over the width of the contact plate, that is to say approximately as long as the heating band. The same applies to the resilient plate, which - like the other parts - has a width of about 700 mm runs.

By using the device according to the invention, a good, flawless cut is possible in a heated material web made of plastic, which is even still on the heated contact plate. This makes it possible to cut immediately during molding, especially with polypropylene as the material of the web to be cut. Upstream of the cut, the material web is held on the contact plate only by vacuum. The cut can be made with the help of the heating tape carefully, even so delicately that the film does not stand out from the second contact plate in addition to the cut in the edge area. The edge region of the material web arranged above the cut or upstream of the cut is not displaced and remains in the preferably flat contact with the flat contact plate. This allows sections of plastic plates to be produced, which can be deep-drawn into package halves and have a very narrow edge on the outside, with the advantageous result that almost no material has to be sacrificed as waste.

Further advantages, features and possible uses of the present invention result from the following description of a preferred exemplary embodiment in

Connection with the attached drawings. It shows:

FIG. 1 broken off and enlarged the cutting area near the edges of abutting end walls of contact plates and the molding tool,

FIG. 2 shows more detailed representations of the parts of the molding tool and the contact plates arranged near the welding area,

Figure 3 on a smaller scale the outer contours of three contact plates and the mold and

Figure 4 is a plan view of the rear of the mold and the third contact plate arranged above, when looking from right to left in Figure 3.

In the deep-drawing machine for plastic packs of a material web 1 shown, the contact plates lie vertically one above the other in such a way that a second contact plate 4 is arranged above the front, first contact plate 2, upstream and counter to the conveying direction 3, relative to which a third contact plate 5 is arranged movably , which is located on the other side of the material web and can clamp and heat the material web 1. Under the third contact plate 5 and opposite the front, first contact plate 2 there is a shaping tool 6 for deep-drawing packaging half-shells from the front, separated section 7 of the material web 1. In Figure 4, one looks at the rear surface 8 and the front, lower end wall 9 of the third contact plate 5 positioned at an angle a thereto. and on the rear surface 10 of the molding tool 6. Opposite runs parallel to the rear surface 8 of the third contact plate 5, the front surface 1 1 and parallel to this on the other side of the material web 1, the front surface 1 2 of the second contact plate 4, the rear surface 1 3 of which is flush with the Rear surface 14 of the front first contact plate 2 is located.

In the area generally designated 1 5, where (except for the recess 1 6) the front, i.e. lower end wall 17 of the second contact plate 4 and the rear, i.e. Touch the upper end wall 18 of the first contact plate 2, where, in other words, the first two and second contact plates 4 also touch, the already mentioned recess 16 is machined in a cuboid shape at the lower end of the second contact plate 4. It extends essentially over the entire width B of the contact plate 4 and opens towards the front and down towards the front end wall 17. The recess 16 also has a passage 19, which creates the connection between the recess 16 and the space in front of the front surface 12 of the contact plate 4 and connects these spaces in a slot-like manner. The lower end of the second contact plate 4 is thus U-shaped in cross section, the leg facing the front surface 12 being shorter than the rear leg, because it leaves the space for the passage 19.

In this recess 1 6 is the holding device, generally designated 20, for a metal heating tape 21. The holding device 20 has the shape of a bar and consists of a front support bar 22 and a rear or upper support bar 24 connected to this by means of a series of screws 23, both of which form a unit. To the front, both support strips 22, 24 are each provided with an extension 25 or 26, which leave an L-shaped gap 27 between them, in which the likewise L-shaped heating tape 21 is loosely inserted so that it extends forward from the extensions 25, 26, that is, protrudes forward from the holding device 20 over the entire width B of the contact plate 4. In normal and idle mode, however, it only protrudes so far that the right, narrow front end 28 shown in FIGS. 1 and 2 protrudes behind the plane into the passage 1 9 formed by the front surfaces of the contact plates 2 and 4, that is behind one by the level set in the front surface 1 2. This is not the state of the heating tape 21 shown in FIG. 1, which rather represents the separation welding position. The shorter, vertically upstanding leg of the L-shaped heating tape 21 prevents it from slipping out to the front, because it lies only loosely in the gap 27. The entire holding device 20 is also smaller in its outer contours than the recess 16, which is why it can be moved back and forth in the direction 29 (double arrow in FIG. 2) and perpendicular to the plane through the front surface 12 of the contact plate 4. When moving forward, the separation welding position of Figure 1 is reached.

This movement of the holding device 20 is carried out by a drive which is formed from a glass fiber reinforced silicone hose 30 as pressure medium 30 and an empty, elastic hose 31 as counter pressure medium 31. The silicone tube 30 is shown protruding on the left in FIG. 4, while it is closed at its right end. On the left at the other end, it is provided with a pneumatic nipple 32. Opposite this nipple 32, the electrical connection 33 for one side of the heating tape 21 is shown in FIG. The opposite side has a similar design, but is not shown here, because the person skilled in the art can connect the heating tape and control it with current pulses so that it reaches the desired temperature of, for example, 250 ° C.

The so-called first space behind the holding device 20 in the recess 16 is denoted by 34, while a second space 35 is provided in the direction of movement 29 of the holding device 20 at the front toward the front surface 12 of the contact plate 4. in this is the counter pressure medium 31, i.e. the elastic, empty hose 31, which is shown compressed in the separation welding position of Figures 1 and 2. It acts like a compression spring, against the force of which the expanding silicone hose 30 works as the first pressure medium 30.

On the side opposite the contact plates 2 and 4 with respect to the material web 1, there is the third contact plate 5 at the top. From FIGS. 1 and 2, it can be seen particularly clearly how their front flat end wall 9 to the flat front surface 1 2 of the second contact plate 4 under one Angle a of about 45 ° is set. FIG. 2 also shows the vacuum lines 36, via which vacuum is applied to the front surface 11 of the contact plate 5 for pulling up and holding the material web 1.

Downstream in the conveying direction 3, ie below the third contact plate 3, the molding tool 6 is arranged, which just presses the section 7, ie the front, lower part of the material web 1 against the contact plate 2. Here, in particular at the level of the movable heating tape 21, the elastically soft Teflon tape 37 as the aforementioned elastic insert 37 is held by the molding tool 6 so that the heating tape 21 presses against the Teflon tape as a cutting counter strip in its separating welding position according to FIGS. 1 and 2. The Teflon tape 37 is supported by the resilient plate 38 on the front of the molding Stuff 6 held, which is connected via screws 39 to the mold.

Coolant passes through the bores 40 into the body of the molding tool 6 in order to cool and harden the deep-drawn section 7 ′, which is shown in broken lines in FIG. 2, in this desired position. Via the vacuum or pressure bore 41, vacuum is brought via the straight intermediate line 42 to the lines 43 with a small diameter, which open onto the inner surface of the deep-drawing tool and evacuate the space during deep-drawing. Compressed air can be introduced here during demolding. Vacuum or compressed air is also applied through the tubes 44 on the opposite side.

In operation, the material web 1 is continuously conveyed from top to bottom by first heating it from the upper contact plate 5 to, for example, 1 30 ° and after transfer to the front first contact plate 2 to 1 85 °. When the material web 1 is at a standstill, the position of FIGS. 1 and 2 is set by the tool parts. Compressed air is applied to the silicone hose 30 acting as pressure medium 30, whereby the holding device 20 is moved in the direction of arrow 29 to the right perpendicular to the front surface 12 of the second contact plate 4 against the spring force of the empty hose 31 as counter pressure medium 31. At this moment, the front edge 28 of the heating tape 21 pierces the material web 1 until the front edge 28 abuts the Teflon tape 37 and the cut through the web 1 is made over its entire width (slightly smaller than the width B of the contact plates). Then - again using the nipple 32 - vacuum is applied to the silicone hose 30, as a result of which the restoring force of the empty hose 31 as counterpressure means 31 moves the holding device 20 back towards the first space 34. The heating tape 21 is thus withdrawn and the section 7 of the material web 1 is successfully cut off. At the same time or immediately after this separating cut has been made, the deep drawing into the mold according to FIG. 2 takes place, so that the half-shell of the pack is finished.

Claims

Patent claims

1 . Device for separating a section (7) of a material web (1) made of thermoformed plastic, which is transported intermittently in the conveying direction (3), with a front first contact plate (2), which heats the material web (1) by thermal contact, against which a molding tool (6) can be moved , and a second contact plate (4) arranged upstream and heating the material web (1) by thermal contact, relative to which a third contact plate (5) for clamping and heating the material web (1) can be moved therebetween, characterized in that in the region of the end walls (17, 18) of the contact plates (2, 4) lying against one another on these end walls (17, 18), a metal heating tape (21) is arranged, carried by a holding device (20) and from there in the direction (29) transverse to the front surface (1 2 ) of the contact plate (4) is movably driven to linearly touch the heated material web (1) that the heating tape (21) over the width (B) d he contact plate (4) extends and is provided at both ends for resistance heating with electrical connections (33).

2. Device according to claim 1, characterized in that the holding device (20) in a to the end wall (17) of the contact plate (4) opening recess (1 6) is arranged, which also to the front surface (1 2) of the contact plate (4th ) has a passage (19) extending across the width (B) of the contact plate (4), behind which the heating tape (21) stands back in the idle state and through which it is used to separate the section (7) of the material web (1) a drive (30, 31) moved out.

3. Device according to claim 1 or 2, characterized in that the holding device (20) has the shape of a bar extending over the width (B) of the contact plate (4) and a front (22) and a rear support bar attached to the latter ( 24), each of which is provided with an extension (25, 26) engaging in the passage (1 9) of the contact plate (4), between which a gap (27) with an L-shaped cross section is left, in which the cross section L-shaped heating tape (21) is loosely inserted.

4. Device according to one of claims 1 to 3, characterized in that the support strip (22, 24) of the holding device (20) surrounded by a hard anodizing layer and a Teflon layer is preferably applied over the hard anodizing layer.

5. Device according to one of claims 1 to 4, characterized in that the heating tape (21) together with the holding device (20) in the recess (1 6) of the contact plate (4) by the drive (30, 31) is movable.

6. Device according to one of claims 1 to 5, characterized in that the drive (30, 31) has a pressure medium (30) and a compressible counter-pressure means (31) which in a first space (34) behind or a second space (35) are arranged in front of the holding device (20) in the recess (1 6) of the contact plate (4).

7. Device according to one of claims 1 to 6, characterized in that the pressure medium (30) is a glass fiber reinforced silicone hose (30) which is closed at one end and provided with a pneumatic nipple (32) at the other end.

8. Device according to one of claims 1 to 7, characterized in that the counter-pressure means (31) is an empty, elastic hose (31).

9. Device according to one of claims 1 to 8, characterized in that on the passage (1 9) of the contact plate (4) opposite side at the level of the movable heating tape (21) an elastically soft insert (37), preferably a Teflon tape (37), is held by the mold (6).

10. Device according to one of claims 1 to 9, characterized in that the front flat end wall (9) of the third contact plate (5) to the flat front surface (1 2) of the second contact plate (4) at an angle (σ) of 40 ° - 70 °, preferably 45 °, is employed.