DE2023216C3 - Method and device for the production of a continuously cast or injection-molded plastic strip - Google Patents

Description

30th

The invention relates to a method for the continuous production of a strip of plastic with a base part and projections protruding from this, which are connected in one piece with the base part, in particular for the production of a surface zipper, by extrusion or injection molding, in which in mold cavities that extend along a move endless closed conveying path ^,? Mouldable plastic is introduced under pressure, and in which, after the plastic has solidified in the mold cavities, the finished strip is demolded from the mold cavities, as well as on a device for carrying out such a method. Strips of this type are used, for example, in separable packaging devices such as those described in US Pat. No. 2,17,437.

U.S. Patent 3,196,490 describes an apparatus for making a similar cast or injection-molded one Strip. In this patent the base part is a reinforcing strip of fabric. That for Plastic material used in molds is pushed from side to side by the fabric! and educates then the pile-like formations or protrusions. The device according to this patent specification uses mold plates that are moved across their width. In the known device Furthermore, the mold plates during a considerable section of the circular path in which they move, separated from each other and during the remaining section of the circular path and during the Injection molding process brought into a tightly pressed position.

A disadvantage of the known machine is that it is permeable to the plastic used porous material must be used as the basis, and that because of the displacement of the plates in the direction of movement only a small part of the circumference of the machine drum for producing the hooks is available.

The invention is based on the object of a method and a device of the type mentioned at the beginning To create types in which it is possible to continuously have a one-piece plastic Manufacture strips of the type mentioned without using a porous base material must be, at the same time the device is simple and less prone to failure, and the active length of the conveying path of the device is increased, d. h- the area where the strip will be produced.

To solve this problem, the invention proposes a method of the type mentioned at the beginning the plastic through an opening first directly into the mold cavities to form the projections is introduced and in which before the solidification of this plastic in de mold cavities

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leads and applied to a mold surface connected to the mold cavities to form the base part will.

With the help of this embodiment of the method according to the invention, the need for use becomes a porous base material avoided.

The method according to the invention is further described in claims 2 to 4.

The invention also proposes a device according to claim 5.

According to this, and in particular according to the advantageous embodiment described below, the mold plates with edges similar to one another are arranged next to one another in groups and are held in this position in order to form a flush surface. The mold cavities for molding, extruding or injection molding the upright projections, which can be designed in the form of hooks, loops, button-shaped or the like, are provided in the surfaces of the mold plates in the region of their circumference. Each of the mold cavities is closed on one side by dip continuously flat surfaces of the adjacent plates. It is ensured that the plaits which close the mold cavities are displaced inwards at the right time in order to open the mold cavities and to expose the extruded or injection-molded upright parts. There are further provided to moldable or spritzgießfähiges plastic material under suitable pressure in the \ introduce nrmhohlräume means and thereby to extrude the projections to form or / u injection molding.

Such material is also applied to the continuous surface to form the base part or to form the strip with which the upright elements are integrally formed.

It is happily pointed out that, if in the following the term "hook" is used for the formation of the projections, this is only the simple description happens in context with the invention include hooks, loops, button-like designs and others in particular behind,; to understand cut types of protrusions.

The spacer plates are preferably arranged alternately with the mold plates. The spacer plates

serve to close the mold cavities. According to the advantageous embodiment mentioned in the description, groups of shaped plates are arranged in this way, the groups of plates being held in position laterally by the walls of a groove or recess running around the circumference of a disk-shaped part. The disk-shaped part carries the mold plates so that they form a continuous or aligned cylindrical surface. The head of an extruder or an injection device for plastic works together with the cylindrical surface of the forming wheel formed in this way. A molten plastic is pressed under pressure into the mold cavities by the extruder or the injection molding device and forms the projections. This material also forms the base part or the band on the surface of the forming wheel. The in the Formhnhlrätimpn uehilHptpn Vnrenriinop cinrl connected directly or in one piece with the base part or band. A suitable fusible material is, for example, polyamide.

The mold plates containing the mold cavities and the spacer plates are in groups or sets arranged with their ends substantially coincident and extending around the circumference around the circumferential recess of the support disc. The disc is integral with a heavy rotating one Shaft arranged, which is advantageously received in the frame of the machine and with a relatively small Speed of about 6 to 16 revolutions per minute is rotated.

Both the mold plates and the spacer plates of each set or group are arcuate outer surfaces. The mold plates are mounted in a fixed position in relation to the supporting disc, whereby their arcuate faces with the cylindrical edges of the disc on each side of the recess cursing.

The cooperating spacer plates of each set or group of mold plates are with their curved edges, as already mentioned, with aligned with the similar edges of the Formpiarten when they are in their outer position. In your In the retracted position, the edges of the spacer plates are located radially inside the mold cavities, so that the pole-like projections come out of these cavities easily. To that end is fine Device provided to move each set or group of spacer plates radially inward.

To carry out such a shift are Hydraulic devices are provided which keep each group of spacer plates radially outward seek to press. Furthermore, curves are provided with rollers on displacement elements for the spacer plates on opposite sides of the forming wheel cooperate to create the spacer plates to move inwards against the hydraulic pressure. In the interaction of the hydraulic Pressure medium and the curves, the spacer plates are brought into their outer position and during the Injection molding process, d. H. when each set of the mold and spacer plates passes the die head of the extruder, kept in this. The spacer plates are in the same way in their outer position for a sufficient period of time after passing through the die to allow the moldable, extrudable or to allow injection-mouldable material to harden. The shaped strip with the ones protruding from it pile-like projections is from the forming wheel approximately on the opposite side the Extruderspriizköpies led away.

Some embodiments of the invention are in the drawings and are explained in more detail below. It shows

Fig. 1 is a side view of the device, parts broken away for better illustration are,

FIG. 2 shows an enlarged longitudinal section through the forming wheel along the line 2-2 in FIG. 3, with likewise individual parts are broken away to show the different positions of the displacement device for the spacer plates to show

Fig. 3 is a section through the forming wheel along the line 3-3 in Fig. 2,

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Part of the forming wheel and the injection head of the extruder, Fig. 5 is a section along the line 5-5 in Fig. 4,

6 shows an illustration corresponding to FIG. 5 of a modified form of the extruder nozzle,

7 shows a greatly enlarged partial longitudinal section along the line 7-7 in FIG. 2, the spacer plates are in their outer position,

FIG. 8 shows an even further enlarged partial section along line 8-8 in FIG. 7,

9 shows a section along line 9-9 in FIG. 8, of the sections of the various spacer and shaped plates shows,

10 shows a greatly enlarged partial section according to the line 10-10 in Fig. 2 prior to the separation of the hooks from the mold plates, with the spacer plates retracted are,

Fig. 11 is a section along line 11-11 in Fig. 2, with the hooks partially extending from the cavities have loosened the mold plate,

12 is a perspective view of the product,

Figure 13 is a perspective view of a modified form of hook element and the adjacent one Section of the base on which it is attached is and

14 and 15 show two views of the modified hook element.

If one looks first at Fig. 12, there is shown a short section of a base part 20 in the form of a continuous strip of molded or injection-molded plastic Humps out. These hooks are integral with the base 20 and stand approximately _sixteen inches (1.56 mm) on the surface thereof.

The machine for making this molded plastic product is in the rest Figures of the drawings shown. The machine is built around a shaft 22 (Fig. 3). This main wave protrudes to the right from a roller support bearing 23, the outer bearing ring of which is mounted in a part 24 is, which protrudes from the main frame 25. The shaft 22 is also by a not shown Storage stored in the main frame 25. A suitable drive to Drenung the shaft 2i with the more desirable. Speed is in the same housing locked in.

A forming wheel 26 is on the protruding portion of the shaft 22, which extends from the bearing 23 to the right

extends, arranged, The supporting part of the various individual parts of the Fofmrades 26 is a thick circular disc 27 (Fig. 2 and 3), which is connected as a unit, for example by welding, with the shaft 22, The disc 27 has in the middle of its circumference a continuous groove or recess 28 to accommodate several (in the present case eight) groups of molded and spacer plates. A group of the mold plates 29 with spacer plates 30 which are arranged alternately between them is shown at the top in FIG. 3 and a similar group at the bottom. The eight groups of associated molding and spacer plates are designated by the letters A to H in FIG. 2 and are arranged around the circumference of the molding wheel 26 and the disk 27. The group of plates fills substantially the entire recess 28, with the cup-shaped surfaces Her Fnrm- and spacer plates forming a cylindrical surface which merges continuously with the cylindrical surfaces 39 of the disc 27 on either side of the recess.

The side walls of the recess 28 align the groups A to H of the mold and spacer plates in the lateral direction. The depth of the recess 28 is dimensioned so that the spacer plates of each group are radially displaceable in relation to their associated mold plates, as will be described in detail below. The mold plates 29 of each of these groups are positioned in the circumferential direction by means of a pin 3i which is fitted into corresponding openings 32 in the mold plates (FIGS. 2 and 3). As shown in Fig. 2, the bottom surface of the recess 28 is octagonal and the groups A through H of the mold plates 29 are aligned in the radial direction through the corresponding bottom surfaces 32 'of the octagonal bottom.

The mold plates 29 of each of the groups of mold and spacer plates A through H have mold cavities on their opposite sides (Fig. 7). The cavities shown in Fig. 8 are in the form of hooks to the hook-shaped protrusionsC OuCi 1 luv-nci ^ i iiin.ll ng. l2 TO ΙΟΓΓΠβΠ.

The group A of the mold and spacer plates (Fig. 2) moves slowly counterclockwise and relative to the injection head 35 of an injection press or an extruder 36 for a suitable moldable, extrudable or injection-mouldable plastic. This material moves under pressure through the spray head 35 in two channels 37 and 38 (FIG. 4). The spacer plates 30 (Fig. 7) are in their outer position so that their arcuate outer surfaces are aligned with one another from group to group around the forming wheel and the spacer plates also with the arcuate surfaces of the forming plates 29 and with the cylindrical surfaces 39 of the disc 27 align the opposite sides of the recess 28 (Fig. 3).

In order to prevent burrs, ie the formation of thin plastic parts protruding from the surfaces of the molded projections 21, the eo mold and spacer plates are prevented from moving apart. An advantageous way of preventing the panels from moving apart is to provide a gap, chamber or recess 40 to the right of group B shown in FIG Mold cavities 33 and 34 extends. As each group of the mold and spacer plates moves towards the opening of the channels 37, plastic penetrates into the chamber or recess 40 and exerts a lateral pressure which prevents the plates in that group from moving apart. The pressure is relieved after the plastic has set or hardened. In a modified form of an extrusion head 4i (FIG. 6), an additional channel 42 for plastic is provided, which lies in front of the channel 37 and is aligned with the chamber or recess 40 (FIG. 7).

The arrangement of the two channels 37, 38 creates considerable adaptability. The channel 37 injected plastic material is a high pressure of a pump 37a, while passing through the distance of the channel 38 of the mold, which is formed by the cylindrical surface portion 43, it is possible Kt rta.s ^ ⁿ scratch äüs the Κξπη! 38 to be made by means of the pump 38a under a lower pressure and thus to extrude or injection-mold the base part 44 as a band.

It is possible to use a single extruder channel to create a moldable, extrudable or injection moldable The use of mass both to press the mold cavities and to form the strip However, having two extruder channels and separate pumps for each channel has considerable advantages themselves.

It is important that the extrusion head 35 be in an accurate radial position relative to the forming wheel 26, e.g. B. to the cylindrical surfaces 39 of the disc 27 is held. To that end is how can be seen from Fig. 1, a rigid cross member 45 transversely to the extruder cylinder 46 fixed, but adjustable attached near the spray head 35. The adjustment is made along the extruder barrel. To this The purpose is a part 47 which has a horizontal opening through which the extruder cylinder 46 extends, welded or otherwise permanently attached to the extruder barrel 46. Four screws 48 extend through openings in part 47 and are received in threaded bores in Uuerträger 45, so that the desired limited adjustment movement is made possible.

Near each end of the cross member 45, a roller 49 is rotatably mounted in a bearing block 50 which extends from the left side of the cross member 45. The rollers 49 run on the cylindrical surfaces 39 of the disc 27 of the forming wheel 26. In order to press the extrusion head 35 in the direction of the forming wheel 26, two rods 51 and 51a (FIG. 3), one on each side of the Forming wheel, arranged parallel to the axis of the extruder cylinder 46. At its left end, the rod 51 is in threaded engagement with an opening in the part 24 of the main frame 25 of the device. The rod 51a similarly engages a heavy pulley 24a carried by a roller bearing 24b on a stepped end portion of the shaft 22. This disk 24a is held in place by a base connection (not shown).

The rods 5l and 51a pass freely through openings which are provided in the cross member 45 on each side of the extruder. At the right end of each rod there is a compression spring 52 and a pair of adjusting nuts 53. These springs serve to keep the rollers 49 in constant engagement with the cylindrical

see surfaces 39 of the disk 27 to hold. If the Rollers are so engaged, the extrusion head 35 is at the correct distance from the forming wheel.

In certain circumstances it is desirable to relocate the spray head 35 from its operative position to move to the Förrfii'äd 26. This is going through causes a slide 54 which moves on a rail 55 and through an arm 56 with the cross member 45 is connected. The carriage 54 is in engagement with an elongated motor-driven one Spindle 57 which is driven by a motor 58.

This arrangement allows the extrusion head 35 to be displaced quickly away from the mold edge 26 and put back into position just as quickly. The rollers 49 cause an accurate Positioning of the surface of the spray head in relation to the surface of the forming wheel.

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stand plates 30 and the cohesion of these plates and the mold plates 29 in the eight groups A to H described. Although the pins 31 are fitted into the openings in the mold plates 29, the spacer plates 30 have openings 59 which surround the pins 31 and which are larger in diameter than the pins. Thereby they allow the desired radial movement of the spacer plates. The mold plates 29 of each of the groups A to H are, as already described, attached immovably, their arcuate edges being aligned with the cylindrical surfaces 39 of the disk 27 of the molding wheel 26.

The various spacer plates 30 of each of groups A through H are moved radially outward and inward by a pair of slide members 60 and 61 (Figures 2 and 3). These are identical guide plates of triangular shape with rounded corners, as can be seen from FIGS. 1 and 2. The displacement elements 60 and 61 are slidably guided on the opposing surfaces of the disk 27.

A shaft 62 is attached to the inner and narrow ends of each pair of guide plates 6 $ and 61, at the outer ends of which rollers 63 and 64 are attached, with inner cam surfaces 65 and 66 are engaged (Fig. 3). The cam surface 65 is a heavy circular one on the solid Part 24a internally formed curve, while the curve surface 66 is arranged on the inside of the part that protrudes from the main frame 25. The wave 62 extends through an opening 67 in the thick support disk 27. The opening is sufficiently large to the necessary radial movement of the shaft 62 to effect the displacement of the spacer plates 30 to enable. On the shaft 62 a sleeve 68 is mounted, the ends of which the inner portions of the Keep guide plates spaced apart to allow their sliding movement on the side surfaces of the disc 27 to enable.

At their outer ends, the guide plates 60 and 61 are connected by two shafts 69 (Fig. 2) which are equidistant from one another with respect to the arcuate length of the form and spacer plates 29 and 30 of each group A to H. The shafts 69 engage tightly on the opposite sides of rectangular openings 70 in the spacing sections 30. Thus, the spacer plates 30 are held in a fixed position with respect to the guide plates 60 and 61. When these are in their outer layer ¹ , the arcuate surfaces of the spacer plates are precisely aligned with the arcuate surfaces of the mold plates.

Each of the guide plates 60 and 61 of each pair

has printing elements 71, e.g. B. a hydraulic cylinder in a rectangular opening 72 in this Plates attached. The inner end of each hydraulic cylinder 71 is for feeding hydraulic fluid open and has a feed channel 73

Lö {Fig. 3) connected liquid-tight for this liquid, by means of a screw 74 at the outer end of the cylinder, which is inserted into an opening in the outer Part of the guide plate is screwed in.

The eight pairs of guide plates or sliding members 60, 61 for the spacer plates are held in its outer position in the radial direction. In the illustrated embodiment for this purpose in the hydraulic cylinders 71

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generated by hydraulic fluid in an accumulator or memory 75. The accumulator is mounted on a circular plate 76 (Fig. 1) which (not shown) is carried to the right of the heavy disk 24a (Fig. 3). The hydraulic fluid from the accumulator 75 is connected to the supply channel 73 of all hydraulic cylinders 71 of groups A to H by means of pipes 77 and 78 (FIG. 1). A pressure indicator 79 and a filling connection 80 are also connected to the pipeline system.

The shape or curve guidance of the two inner curved surfaces 65 and 66 is identical. One of you is shown in FIG. The purpose of the hydraulic cylinder 71 is to drive the pair of guide plates 60 and 61 can be moved outwards for each group

gen, before and during the time in which the groups of mold and spacer plates run past the extruder head 35. The spacer plates are through the one in the cylinders 71 acting hydraulic pressure, even after injection molding or molding, is still sufficient Time held in its outer position to the plastic of the base part. Ribbon or strip 20 and to give the projections or hooks 21 time to solidify or harden. Accordingly have the cam surfaces 65 and 66 within circular sections by two displacement surfaces 81 are connected to each other, which are diametrically opposed to each other, approximately in the angular position shown in FIG.

The sliding elements or guide plates 60 and 61 for the spacer plates are guided by the ends of the spacer plates attached to them during the radially inward and outward sliding movement. This can be seen from FIG. 2, group B , where the opposite end edges of the spacer plates 30 are denoted by the reference numeral 82. These edges are parallel to each other and to the radius through the pin 31. The end edges 82 rest against the same edges 83 (FIG. 9) of the adjacent mold plates 29. In order to enable the radial movement of the shafts 79 for the spacer plates 30 of each group, large circular openings 84 are provided in the mold plates 29.
The continuous or endless base H 44 with

_M the shaped projections 21 thereon is guided outwardly around a doffer rod or roller 85 (FIGS. 1 and 2) and wound onto a spool, not shown, or stored in some other way.

During the whole operation the different Parts of the device are kept at a suitable temperature, and for this purpose is a Hood 86 made of sheet metal, which encloses the device, arranged. A flap door 87 may be adjacent to the stripper roll 85 as an outlet for the Plastic product be arranged. The temperature in the hood 86 is controlled by a flow of air maintained at a controlled temperature through four inlet passages 88 (Fig. 2). The air flows through an annular opening 89 (FIG. 3) on the periphery of the part 24.

The mold cavities 33 and 34 create hooks or protrusions 21 which have rounded surfaces have, while Figs. 13, 14 and 15 show modified embodiments in which the hook "Eye" has an inclined surface 94 at its end which acts as a curved surface during extraction tics Hükci'is SUs dem Fürfniiuiiifüüm üiciii. If the Hooks are pulled from the strip or base 44 (Fig. 2) from the surface of the forming wheel and radially is pulled outwards, this cam surface will cause the hook to come out of the mold cavity is led out into the gap created by the displacement of the adjacent spacer plate. This clears the "eye" of the hook from the cavity.

In FIGS. 13, 14 and 15, the shaft portion 90 has two equally sized flat sides 91 and one slightly larger third side 92. The shaft portion 90 is larger in cross-section near the band or base portion 20 than at the tip of the hook, which makes it easier to fill the mold cavity. The three flat side sections facilitate demolding of the shaped hook from the cavity. The three flat side sections of the shaft go slightly curved into the Hook portion 93 over and over this. The shaft part of the third side 92 lies in the same continuous plane like the associated front side of the hook section 93, as can be seen from FIG. In addition, the hook portions 93 with the axis of the shaft part 90 form a smaller angle than

ίο in the case of the hook sections that are in the mold cavities 33 and 34 according to Fig. 8 are made.

It will be seen that articles having various shapes other than the specific ones shown in FIGS to 15 have shown hook parts, produced by the method and with the device described can be. It is, for example, the continuous production of a large number of objects possible, whereby each object is attached to a common strip, which acts as a carrier and dierit as a common connection of objects. It can also be seen that the described Apparatus is useful for making various types of shaped protrusions using the are designed in the manner of a pin and are integral with a reinforcement strip. Such protrusions can for example be a plurality of loops that form part of a fastener with hooks and Form loops, or can be hook elements which are shaped differently than those described.

Accordingly, it will be seen that only specific embodiments of the invention are described in the foregoing specification, of which are described numerous modifications are possible.

In addition 6 sheets of drawings

Claims (14)

Patent claims: 1. A method for the continuous production of a strip of plastic with a base part and from this protruding projections which are integral with the base part, especially for the production of a flat zipper, by extrusion or injection molding, in the case of the mold cavities that move along ι ο an endless closed conveying path, malleable plastic is introduced under pressure, and in which after solidification of the Plastic in the mold cavities, the finished strip is demolded from the mold cavities, i = characterized in that the plastic first enters directly through a first opening Mold cavities is introduced to form the projections and that before solidification of this Plastic introduced into the mold cavities further plastic through a second opening and applied to a mold surface connected to the mold cavities to form the base part will. 2. The method according to claim I, characterized in that that the projections as a hook of inverted J-shape integral with the Base part to be shaped. 3. The method according to claim 1 or 2, characterized in that the base part and the hook made of plastic of different composition. 4. The method nac '"one of claims 1 to 3, characterized in that the plastic for the hook is more flexible than ί / for the base part. 5. Device for the continuous production of a strip of plastic with protrusions, which protrude from a base part, in particular a flat zipper part, by extrusion or injection molding, in particular for carrying out the method according to claims 1 to 4, with a molding device which contains mold plates with mold cavities which have an end face penetrate at the edge and an end face of the mold plates, and with a feed device for supplying moldable plastic under pressure to the mold cavities for formation of the projections, with parts of the molding device for releasing the projections from the mold cavities after the plastic has hardened from a mold position to a relative release position are movable to one another, characterized in that that a) the mold plates (29) are arranged in groups (A to H) which are adjacent to one another with their ends. b) that the mold plates (29) of each group (A hi «. H) are separated from one another by flat spacer plates (30), the flat side surfaces of which each form a wall of the mold cavities (53, 34), C) that the groups (A to H) of plates (29, 30) are arranged in such a way that their edges lie in a continuous shaped surface which is formed from the end faces of the plates, d) that one of the edges of the spacer plates (30) connects in the molding position (29), e) that the spacer plates (30) of each group (A to H) are radially retractable into their release position relative to the mold plates (29) of the group, and f) that the feed device (36) for the application of moldable plastic to both the mold cavities (33, 34) to form four projections (21) as well as the continuous Forming surface for the formation of the base part (44) in the form of a with the projections , (21) one-piece plastic strip formed is. 6. Apparatus according to claim 5, characterized in that that the continuous shaped surface from the end faces of the plates (29, 30) forms a rotationally cylindrical surface. 7. Apparatus according to claim 5 or 6, characterized in that the forming device (26) is carried by a rotatable shaft (22), that a rigid circular component (27) is attached for rotating the shaft (22). that the component (27) "has a cylindrical surface (39) and a continuous circumferential recess (28), and that the groups (A to H) of the mold and spacer plates (29,30) in the circumferential recess (28) with their Ends are arranged adjacent to one another. 8. Device according to one of claims 5 to 7, characterized in that the feed device (36) has a spray head (35) with two channels (37, 3rd), one of which for Plastic feed to the mold cavities (33, 34) and the second to form the continuous Plastic strip of the base part (44) is formed. 9. Apparatus according to claim 8, characterized in that the spray head (35) has a cylindrical surface portion (43) which is arranged at a distance from and parallel to the cylindrical mold surface, which of the end faces of the groups (A to H) of the mold and the spacer plates (29, 30) is formed and forms a gap for receiving the plastic from the second channel (38) of the spray head (35). 10. Vorn · hut according to one of claims 5 to 9, characterized in that at least one of the plates of each of the groups of shaped and spacer plates (29, 30) has a circumferential recess (40) in one end face and that the recess (40) receives moldable plastic under injection pressure and holds the group (A to H) of the plates (29.30) in contact with one another to prevent burrs. 11. Device according to one of claims H to 10, characterized in that the spray head (41) has a third channel (42) which is arranged in front of the first and second channel (37,38) to inject plastic under fuel / pressure to press the circumferential recess (40). I 2 device according to one of claims 5 to 11, characterized in that a cross member (45) is attached adjacent to the extrusion head (35), on its cylindrical mold surface the molding device (26) projecting parts rollers (49) are attached, which with the cylindrical · see forming surface of the forming device cooperate, and that spring elements (52) are provided are the rollers (49) to the exact Positioning of the spray head (35) with respect to maintaining the mold surface of the mold device (26) in contact with the mold device (26). 13. Device according to one of claims 5 to 12, characterized in that for displacement of the spacer plates (30) a pair of sliding elements for each of the groups (4 to H) (60, 61) is provided that rt on the outer side surface the Formmejnrichtung (26) lie that the sliding elements (60,61) close to their äuße- '° Ren edges are connected to one another by two shafts (69), which are formed by matching openings (70) in the spacer plates (30) and into larger openings (84) in the mold plates (29) can move and that the sliding elements of each group at their inner Ends are connected to one another by a sleeve (68), which has a roller (63, 64) at each end. which are each assigned to a fixed cam track (65, 66), and that each group n ^ L ^ lpt / Tl \ inilArflnat oirt * 4 A \ * ± Ai *> \ 7 * a «- sliding elements (60, 61) against the effect push the cam outwards. 14. Apparatus according to claim 13, characterized in that the pressure elements (71) from a hydraulic pressure device exist.