FI56788C - REFRIGERATING THERMAL PLASTIC MATERIAL AND THERMAL PLASTIC MATERIAL - Google Patents

Description

@ FINLAND —FINLAND patent publication — patentskrift 56788 ® Kv.lk ^ Int.CI.3 B 29 D 23 / 04- ® @ Patent application - Patentansöknlng 3678/73 φ (g) Application date - Ansökningsdag 29.11.73 • jijpifö (g) Start date - Glltlghetsdag 29.11.73 S @ Released to the public - Bllvit offentlig 02.06.7l * @ Date of publication and publication—

Ansökan utlagd och utl.skriften pubi ice rad 31.12.79

National Board of Patents and Registration © Patent granted - Patent meddelat 10.0U.80

Patents and registries Λ Λ Λ

Requested privilege - Begärd priority 01.12.72

Norway-Norway (NO) UU35 / 72 (73) Forenede Plast A / S R? Srfabrikk, Storgaten 70, N-3900 Porsgrunn,

Norway-Norway (NO) (72) Arnold Aalo, Porsgrunn, Norway-Norway (NO) (7U) Berggren Oy Ab (5U) Method and apparatus for making pipe bending from thermoplastic material -Frange and anordering for framstalling with thermoplastic material

The present invention relates to a method of manufacturing a pipe bend by extruding a thermoplastic having a constant wall thickness and a diameter considerable with respect to the radius of curvature of the bend, wherein the circumferential wall thickness of the pipe to be compressed varies and the pipe is compressed at a substantially constant discharge velocity. The invention also relates to an apparatus for carrying out said method.

There are several known methods for making a pipe bend and the most widely used method is based on welding the pipe bend into one of the segments. This method requires high labor costs because it is usually performed by hand, and it is difficult to achieve a reliable inspection of the welds. Another method starts from a straight tube which is bent while being heated. The disadvantages of the method are that additional stresses and uneven wall thickness are created in the bend.

A third known way to make pipe bends is to use mold casting. Pipe bends made by mold casting are generally small in diameter, and when the bends often have to be welded to extruded pipes, it is mandatory to use an extrusion-quality raw material. This makes manufacture cumbersome, and in practice it has been shown that the quality of pipe bends made by extruding plastic from mold-grade plastic to mold 2 56788 is too poor to be used in pressurized systems.

The object of the present invention is to overcome the above-mentioned problems and to provide a method for producing a thermoplastic pipe bend which is of good quality and which can be manufactured at a reasonable price in a device characterized by simplicity.

The method according to the invention is characterized in that the pipe is guided into a cooling matrix having the desired curvature so that the part of the pipe jacket with the largest wall thickness at the outlet is given the largest radius of curvature in the cooling matrix, after which the curved pipe exits the cooling matrix.

The invention also provides an apparatus for carrying out said method, which apparatus comprises a pipe extrusion head, the mandrel and die of which can be arranged eccentrically with respect to each other and which is characterized in that a curved cooling matrix is arranged in connection with the extrusion head. wall thickness, a maximum radius of curvature is given, and that a traction device for curved tubes is connected to the cooling matrix, the traction device having traction wheels whose circumferential speeds can be adapted to correspond to the radii of curvature and diameter of the curved tube.

German patent No. 529 5 ^ 8 discloses a method for producing curved hoses or pipes having a uniform wall thickness. According to this patent, an extrusion head is used, and the curvature of the compressed tube is achieved by braking or throttling the compressed material in certain circumferential portions. This is accomplished by constricting the substance passage gap prior to the outlet, and the variable velocity of the material thus causes the compressed tube to curve according to the velocity distribution after the outlet.

The method according to the German patent requires both an impractical and a complex device, because there must be special tools for each pipe dimension. In addition, for each tool type and each pipe dimension, it is necessary to perform a series of test runs and tool adjustments before achieving the desired curvature and material thickness for the product. This results in increasing costs for the parts of the device in addition to the very high labor costs during the test run of the device. In addition, it is questionable whether the device according to the patent can of course be used for the production of thermoplastic pipe bending, since the attenuation of thermoplastic products usually requires more specific conditions, e.g. as far as refrigeration technology is concerned.

Norwegian Patent No. 107,062 discloses a semi-finished product for plastic support rings for fishing gear, and the patent discloses that the product is in the form of a coiled extruded tube. However, the diameter of the tube is small here in relation to the diameter of the coil. There is no specific mention of how this semi-finished product is made, but since it is obvious that it is not essential in the invention to provide good curvature, desired diameter and wall thickness for the pipe, one skilled in the art will only refer to very simple known methods which are not suitable for pipe bending. .

Other features and advantages of the invention will now be described in more detail with reference to the accompanying drawing, in which Figure 1 is a longitudinal section of an apparatus for carrying out the method according to the invention, and Figure 2 shows a side view of the apparatus.

Figure 1 shows an extruder screw 1 which can rotate about its horizontal longitudinal axis in a cylinder 2 to which a pipe extrusion head 3 is connected. · There is an open plate 2 'between the cylinder 2 and the press head 3. The pressing head 3 consists of a fixed funnel-shaped tool holder 3 'and a torpedo-shaped mandrel 4 fixed to the tool holder 3' by fasteners 5, and a funnel-shaped tool matrix 8. The air duct 6 extends through the air intake 7 and one fastener 5 and further radially into the mandrel 4 4 out along its longitudinal axis.

The die 8 is adjustably attached to the tool holder 3 'by a compression ring 9 which, by means of fastening means (not shown), presses against the outer stop 10 in the die 8 so that its leading end edge 11 is frictionally held against the inner stop in the tool holder 3'. In the illustrated embodiment, the mandrel 4 is held by fasteners 5, while the matrix 8 can be positioned eccentrically with respect to the mandrel 4. In this case, a gap 13 of circular cross-section is provided with a variable width between the mandrel 4 and the matrix 8. The wall thickness of the pipe profile coming from the pressing head 3 will thus vary according to the width of the gap 13.

Attached to the flanges 14 of the matrix 8 is a curved cooling matrix 15 which remains attached to the flanges 14 by means of its own flanges 16 4 56788 and fastening members (not shown). The cooling matrix 15 cools the flowable thermoplastic mass coming from the hole of the press 3 and gives the pipe bend the desired geometric shape. In the drawing, the cooling matrix 15 is made double-walled (17 and 18, respectively), between the walls of which cooling water is circulated, which enters through the inlet walls 19 and exits through the outlet nose 20. In the direction of movement of the pipe coming from the cooling matrix 15, a traction device 21 is arranged, which consists of a drive chain 22, a traction wheel 23 and other traction wheels 24.

Fig. 2 schematically shows the traction device 21 and the drive device of the traction wheels 23 and 24. The drive consists of a motor 25 with variables which, via a shaft 26, by means of a drive wheel 27, drives a chain 22 which in turn rotates the drive wheels 23 and 24 via the sprockets 23 * and 24 'and the shafts 23 "and 24".

The thermoplastic material, which may be e.g. HD (high density) polyethylene, is introduced into the cylinder 2 as a tough mass at a temperature of about 200 ° C. By means of the pressing screw 1, the mass is pressed through the apertured plate 2 'into the head 3 of the press. Further, the mass is compressed past the fasteners 5 from the gap 13 between the mandrel 4 and the tool matrix 8, and thus the compressed material has an annular profile as it enters the curved cooling matrix 15, which gives the fed pipe the desired curvature. During the supply, the inside of the pipe is 0.5-0.6 kp / cm under overpressure, which is provided via duct 6 by means of compressed air. To keep the tube tight during feeding, a plug is placed at its end.

During compression, the pre-compressed curved tube can be cut into finished bends according to the desired angle, e.g. 45 ° or 90 °. The tubes can also be deflected so that its turns will be side by side like a helix. When the pipe is cut, it is first compressed airtight so that its overpressure is not lost. After cutting, the plug is inserted at the end of the pipe fed forward while the pipe is still sealed.

In order to obtain a uniform wall thickness in the pipe bend, the mandrel 4 and the tool matrix 8 are placed eccentrically with respect to each other so that the gap 13 is at its largest where the material supply is greatest. Eccentricity can be calculated in advance, where in practice it can be adjusted afterwards depending on the prevailing production conditions. At high material thicknesses or high production rates, it may be necessary to carry out additional cooling in addition to the cooling in the cooling matrix, and this can be achieved, for example, by means of a water jet arranged between the cooling matrix 15 and the drive device 21.

During extrusion and feeding, the surface of the pipe bend against which the traction wheels 2 * 1 are always has a higher circumferential speed than the surface part of the pipe bend against which the traction wheel 23 is. In order to achieve a circumferential speed for the traction wheels corresponding to the radius of curvature of the jacket line of the tube against the wheel, the diameter of the traction wheels 24 can be made correspondingly larger than the diameter of the wheel 23, as shown in the drawing. Another possibility is to give the wheels different rotational speeds by changing the gear ratio with respect to the drive motor 25. Since the traction wheels 23 and 24 rest on the jacket lines of the pipe with the smallest radius of curvature, the ratio of the circumferential speeds of the traction wheels can be determined from the expression (Rm + 0,5D) / (Rm - 0,5D), where Rm is the radius of curvature of the pipe bend at the center line and D denotes the diameter of the pipe bend.

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Claims (4)

56788 6 A method of making a pipe bend by extruding a thermoplastic having a substantially constant wall thickness and a diameter considerable with respect to the radius of curvature of the bend, wherein the mandrel and die of the extrusion head are located eccentrically with respect to the tube at the outlet speed from the outlet slot of the press head, characterized in that the pipe is led directly to a cooling matrix having the desired curvature so that the jacket portion of the pipe with the largest wall thickness at the outlet is given the largest radius of curvature in the cooling matrix. Apparatus for carrying out the method according to claim 1, comprising an extrusion head (3) of a tube, the mandrel (4) and the die (8) of which are eccentrically relative to each other, characterized in that a curved cooling matrix (15) is arranged in connection with the extrusion head (3). so that the part of the pipe with the largest wall thickness at the extrusion head is given the largest radius of curvature and a drive device (21) for curved pipes is connected to the cooling matrix (15), the drive device (21) having traction wheels (23, 2k) with adjustable circumferential speeds to correspond to the radii of curvature and the diameter of the curved tube. 1. Extraction for the manufacture of extruded thermoplastics with a thermoplastic medium of constant weight and with a diameter of one or more of the extruders used in the extraction process, in which the extruders of the extruder en ikrttriktningen varierande väggtjocklek ocr röret extruderas med huvudsakligen ensartad utloppshastighet kring extruderhuvudets ut-paysspalt, kännetecknat av attörsten förres vektst directs in i en refrigeration with self-contained crankshaft , varefter det krökta röret som kommer ut frän kylmatrisen drages bort fran matrisen.