DK151372B - METHOD AND APPARATUS FOR CONTINUOUS PREPARATION OF BEETS FROM A COAT OF THERMOPLASTIC FOAM - Google Patents

Description

in 151372

BACKGROUND OF THE INVENTION 1. Field of the Invention soft PVC, cross-linked or non-cross-linked polyethylene foam, by continuously shaping the web across its longitudinal direction into a tubular cross-section and closing the shock joint, e.g. by welding or bonding and then briefly heating the outside of the pipe.

10 Thin or thick-walled foam pipes made of larger or smaller diameters are used in particular for heat or cold insulation purposes, e.g. throughout the area for sanitary installations, including hot and cold water lines, heating lines, coal lines, etc. Such tubes can be extruded directly from foam, but it is also possible to manufacture them from strips of foam, especially in cases where the foam cannot be extruded directly, e.g. applies to cross-linked polyethylene foam. In this case, the foam strips are produced in webs, either by extrusion and subsequent foaming, or by a stripping process, the latter process e.g. used for soft PVC foam.

It is known to produce tubes from webs of deformable thermoplastic foam fabrics by folding and folding the foam strip onto which the butt joint is welded or bonded. The product thus obtained with a hollow cross-section is then subjected to "printing". However, the pipe produced from the web in this way has no round cross section, but rather an oval one, which is a disadvantage, in particular, if the pipe is later slit to facilitate installation work and the slot below opens, ie that it is not mold resistant. Furthermore, there is also a risk that the internal stresses remaining in the formed tube 35 will cause the adhesive or the weld seam to re-open and not to be held together in a mold-resistant manner.

SUMMARY OF THE INVENTION It is an object of the invention to make it possible to continuously produce a tube from a web of thermoplastic foam, which, even after the final molding, is free of stresses, so that the tube's mold resistance can also be maintained by subsequent machining and use of the tube. .

According to the invention, this object is achieved by a method of the kind mentioned in the preamble, characterized in that the web before the molding on the side, which later forms the inner surface of the pipe, is briefly heated to the thermoelastic or thermoplastic state and then formed and before the connection. of the side edges are cooled.

These heat treatments, which correspond to an "annealing" or relaxation, are carried out in such a way that the heating penetrates only part of the thickness of the strip 20, the plasticization being carried only so that the structure of the foam material is not destroyed. The incremental heat treatment according to the invention makes it possible to produce a stress-free pipe, which, even after later cutting - for example longitudinal slitting - shows no tendency to return to the original web form. it is also possible, by the invention to perform the reshaping in the thermoelastic / thermoplastic state, to form relatively rigid foam materials for tubes having relatively small internal diameters or to obtain large wall thicknesses at small pipe diameters, respectively.

In one embodiment of the method according to the invention, it is stated that, after forming, the web is passed through a forming tube in which it is cooled. The proposed first heat treatment not only makes the side that later constitutes the inside of the pipe stress-free, but also facilitates the forming of the strip material into a tubular cross section. Thereafter, cooling is carried out at the same time so that the shaped tube can solidify as it passes through a mold and thereby become stable.

Further, it can be proceeded by clamping the shaped and re-stiffened tube to an oval cross-section, with the major axis of the ellipse lying horizontal, and the butt joint, which must be closed by welding or adhesive, located at the upper end of the short ellipse axis.

15 In this way, an impeccable abutment is achieved between the cooperating surfaces of the butt joint in the full width thereof and thereby a resistant joint.

Since the first heat treatment causes the web of thermoplastic plastic to be relatively soft, 20 can be further advanced in that the web before and during the closure of the butt joint is continuously conveyed by means of a roughened surface conveyor belt, which adheres to the rough surface. In this way it is avoided that the web of thermoplastic plastic is stretched or cracked, and a uniform feed is obtained.

As a further process step, the process of the invention may comprise cooling the welded or bonded tubes in or near the butt joint after the external heat treatment, after which it is slit longitudinally again, preferably outside the butt joint. The slit thus obtained can later be closed by applying a slide closure or adhesive tape with overlapping of the tube. A pipe made in this way is advantageously suitable for insulating purposes, the slot facilitating the mounting work and the attached closing means making it easy to close the pipe after its placement in place. The pipe made according to the invention in its final state 5 is free from stress and mold resistant.

The invention also relates to an apparatus for practicing the method and having a circumferential belt for transporting the continuously applied web, a molding funnel, a device for closing the seam and a pressing device 10 as well as a heating device acting on the outside of the pipe, and this apparatus is peculiar in that the conveyor belt has a rough surface and that a heating device is arranged in front of the molding funnel and, after the molding funnel, a cooling pipe fitted with a cooling device. In this case, the apparatus may be arranged such that at least at the inlet and outlet a guide slot is formed at the upper side of the manifold, in which a guide rail can be inserted into the butt joint of the shaped pipe. In order to achieve an impeccable assembly in the butt joint, the machine may comprise .20 bodies, e.g. in the form of clamping plates, to form the tube into an oval cross-section in the region of the device for closing the shock joint. In this way, it is achieved that the interacting surfaces of the butt joint lie well against each other and that a lateral pressure is exerted on the butt joint.

Furthermore, the apparatus may have a longitudinal separating knife for slitting the heat-treated and cooled pipe.

The invention will now be explained in more detail with reference to the drawing, in which 1 schematically shows a machine for continuous production of pipes from a web of thermosetting plastic foam; FIG. 2 is a schematic cross section through the heating device along line A-A in FIG. 1, 5 FIG. 3 is a schematic section through the manifold along line B-B in FIG. 1, FIG. 4 is a schematic section through the joining device 5 along the line C-C in FIG. 1, and FIG. 5 is a schematic section through the pressing mechanism along line D-D of FIG. First

By means of the device shown in FIG. 1, webs 2 are made of thermoplastic and deformable material 10 wound on storage rollers 1 for pipes. The web 2 runs from the supply roll 1 over the guide roll 3 to the workbench 4, which may be provided with an adhesive device 5 for endless joining of the webs 2 when changing the supply roll.

From the workbench 4, the web 2 runs through a guide roller pair 15 6 where it is inserted on the endless belt 8. The belt 8 here takes over the conveying of the web 2, and for this purpose the belt 8 is formed with a very rough upper surface, e.g. as an arbitrary band of arbitrary grain size. The belt 8 has a very good mechanical adhesion to the web 2, which is of great importance as the subsequent heat treatment of the web results in a mechanical weakening thereof, so that there could be a risk that the web was not uniformly conveyed. or that it cracked. The endless belt 8 is passed along with the web 2 through the various devices of the machine, after which it is diverted at the end of the pressing mechanism 20 and returned to the guide rollers 6 over the tensioning roller 17. The belt 8 is driven by a drive roller 22.

After the web 2 has been placed on the belt 8 and fed 30 thereon, the web 2 is passed through the heating device 7, cf. also the FIG. 2 shows a schematic cross section. The heating device 7 can be operated with hot air, radiant heaters etc. During the passage, the web 2 is heated on one side, i.e. on the side which later forms the inside of the tube 35 and brought into the thermoplastic state, the heating penetrating only so far through the thickness of the web that the back, which later forms the outside of the tube, remains practically cold and unplasticized so that it 5 enables the mechanical transport and attachment to the belt 8. The heating temperature and time are according to the properties of the foam and the thickness of the strip.

In this way, it must be sought that a plasticization, i.e. a heating to the thermoelastic and 10 transition to the thermoplastic state, respectively, in about half the thickness of the strip, in which case the plasticization must not proceed so far as to destroy the structure of the foam. This heat treatment, which the web is subjected to as it passes through the heater 15 7, is approximately equivalent to a "annealing" or relaxation.

Below this, the conveyor belt 8 runs across a work place 13. The space in which the heating takes place is shielded to the sides by means of shielding plates 9, so that uniform heating of the web 2 in the edge areas is also achieved. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 When the partially heated web 2 for 2 leaves the heating device 7, it is led in an in 3 direction to form the web into a pipe. Below this, the web 2 runs into a mold funnel 10 in which it is formed into 5 tubular cross sections. Directly connected to the mold funnel 10 is the 6 pipe 14, the upper side of which, however, is formed at least 7 in the inlet area and also at the outlet 8 a guide slot 14a, as shown in the 9 schematic cross-section of FIG. 3. In this guide slot 14a 10, at least in the inlet region, a guide plate 12, 11 which immediately engages the butt joint in the web 2 formed by a pipe 2a 12 and marks this joint so that during the subsequent forward transport, it is prevented from the tube is turned.

14

The forming tube 14 is furthermore equipped with a cooling device 15 11, by means of which cooling air is blown into the forming tube 14. In this way, it is ensured that the path formed for the tube 2a during passage through the forming tube 14 is again cooled to room temperature and solidified. Also, the conveyor belt 8 is introduced into the manifold 14 and adjusts to its rounding, thereby also exerting pressure on the conveyor belt 8 from the formed pipe 2a, so that the conveying is impeccable despite the friction in the manifold 14. The width of the belt 8 can be substantial. less than the width of the web 2, e.g. between a quarter and a third thereof. Also, at the end of the manifold 14, guide rollers 16 may be provided, but this is not necessarily necessary and depends on the foam tube to be manufactured. However, it is also convenient to place in the outlet area a guide plate 15 at the upper side, which guide plate 15 engages the butt joint in the formed tube 2a and 15 prevents a rotation of the tube. This is also important in that the pipe butt joint must always leave the pipe in the same orientation, so that in this orientation it can be introduced into the subsequent mechanism for closing the butt joint. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

The still open shaped tube 2a can now be subjected to 2 more equal treatments, e.g. welding of the butt joint, 3 adhesion of the butt joint, wrapping with a foil with 4 adhesive edges, welding of a guide closure, etc. In the illustrated embodiment 5, the shaped tube 2a passes through a 6 welding device 19 for welding the joint 7 of the tube, as is also shown in the cross-section of FIG. 4th

8

To achieve impeccable welding of the butt joint 9, the preformed tube 2a is passed between an upper and a lower 10 clamping plate 18a and 18b, respectively, which clamp the tube 11 to an oval cross section with the major axis 12 of the ellipse lying horizontally. The butt joint in the formed tube 2a is above the 13 side so that the heating knife 19 engages the butt joint and 14 plasticizes the surfaces so that they are welded together. With this squeezed oval cross-sectional shape, the tube 2b welded into the butt joint is inserted directly into the pressing mechanism 20 which, over a predetermined distance, holds the tube in the predetermined shape until the weld seam is stiffened. At the end of the pressing mechanism 20, the conveyor belt 8 is pulled free of the tube 2b and returned to the initial position, while the tube 2b is further conveyed by the feed rollers 23 to the subsequent heating device 24.

FIG. 5 shows a cross-section through the pressing mechanism 20, in which can be seen the oval cross-section of the tube 2b welded in the butt joint 35 10, which is controlled partly by laterally adjustable guide 21 and partly by the upper and lower band 20a and 20b respectively of the pressing mechanism 20.

The feed rollers 23 arranged after the pressing mechanism 20 can further perform the function of giving the oval tube its round shape by pressure from the sides. Then comes the second heating device 24 which performs the external tensioning of the tube 2b. When passing through the heating device 24, the outer surface of the tube is heated until the plasticization of the outer skin, but only for a short time, so that the structure of the foam is retained. By means of this heat treatment, the last remaining stresses in the outer layer of the pipe are relaxed so that there are no longer any stresses in the pipe which could bring this back to the flat web shape. Upon expiration of the heating device, the tube is cooled again, e.g. is passed through a cooling pipe 27, such as e.g. can be operated by cooling air supplied through an inlet 26. Conveniently disposed in front of the cooling tube 27 is a screen 25 which ensures an impeccable supply of cooling air 30. The cooling tube 27 may be interchangeable so that its diameter can be adjusted at any time to the tube to be manufactured. The further advance of the pipe is effected by the obliquely arranged pivoting rollers 28. In this area, e.g. For example, a separator 35 is arranged in the form of a rotary longitudinal knife 30 which slits the welded, heat-treated and stiffened pipe longitudinally outside the butt joint. The slotted tube 2c is passed through a guide 32, e.g. a guide bush to which 5 is connected a trimming knife 33. The cut tubes are removed by a tilting mechanism 34.

Claims (4)

151372 A method for continuous fabrication of tubes from a web of thermoplastic foam by molding the web across its longitudinal direction to cross-section and connecting the side edges and then briefly heating the outer surface of the tube, characterized in that the web prior to molding on the side later, the inner surface of the tube forms, briefly heated to the thermoelastic or thermoplastic state and then formed and before the connection of the side edges is cooled. A method according to claim 1, characterized in that the tube is cooled and re-slit preferably at a location outside the longitudinal seam after the external heat treatment. Apparatus for carrying out the method according to claim 1 or 2 and having a circumferential belt (8) for transporting the continuously applied web (2), a mold funnel (10), a device (19) for closing the shock seam and a pressing device (20) as well as a heating device (24) acting on the outside of the pipe, characterized in that the conveyor belt (8) has a rough surface and a heating device (7) is arranged in front of the molding funnel (10) and after the molding funnel (10) a with a cooling device (11) provided with pipe (14). Apparatus according to claim 3, characterized in that the guide tube (14) is formed at least at both ends on its upper side with a guide slot (14a) into which a guide rail (15) can be inserted which projects down between the 30 side edges. on the formed tube (2a).