RU2026508C1 - Flexible tubing; method of and device for manufacture of fluoroplastic tube - Google Patents

Abstract

FIELD: manufacture of flexible tubes. SUBSTANCE: flexible tubing has fluoroplastic tube, reinforcing braid, and metal ends. Fluoroplastic tube is multilayer structure built up of set of functional fluoroplastic layers; reinforcing braid is pre-braided closed sheath molded in functional fluoroplastic tubes. For manufacturing fluoroplastic tube, multiple extrusion is required. Axial feed of reinforcing member in the form of pre-braided closed sheath is first effected together with guide rod and then together with reinforced functional layer of fluoroplastic tube. This improves strength of flexible tubing due to its multilayer structure. Device for manufacturing fluoroplastic tube has barrel, drift with longitudinal space, and changeable extensions on drift and barrel. Device is also provided with movable guide rod that mounts reinforcing Member in the form of pre-braided closed sheath or fluoroplastic tube with pre-braided closed sheath molded in its inner space and pre-braided closed sheath fitted onto its outer surface, depending on sequence number of fluoroplastic tube and in a spaced relation to drift. EFFECT: improved stability of flexible tubing sectional area shape, improved quality of tubing. 3 cl, 4 dwg

Description

 The invention relates to methods for processing polytetrafluoroethylene (fluoroplast 4D) and can be used in the manufacture of flexible pipelines for both general and special purposes.

 Closest to the proposed technical solution according to the technical essence is a flexible pipe containing a fluoroplastic tube, metal endings and an external reinforcing braid (see Art. St. USSR No 2033971, class F 16 L 33/22, 1976).

 However, the fluoroplastic tube, which is part of the product, has a low bending stiffness and strength limited by working pressure.

 Known is the closest to the proposed method of manufacturing a flexible fluoroplastic tube, including the preparation of a homogeneous paste from a mixture of fluoropolymer powders with or without inert filler and organic lubricant, molding from a paste by pressing a tubular cylindrical tablet - blanks, production from a tablet blank by piston extrusion through concentric to the extrusion axis, forming a gap of the fluoroplastic tube, followed by drying, sintering, and axial during extrusion odachu cavity of the mandrel into the mold gap for forming the inner member fluoroplastic tube disposed on an inner surface of the inner member (sm.Goryainova AV Fluorines in mechanical engineering. M .: Mechanical Engineering 1971, s.73-74).

 This method does not allow to obtain fluoroplastic tubes with walls reinforced with a metal and non-metal mesh, which reduces the efficiency of use of the tubes due to their low bending stiffness.

 A device is known for manufacturing a flexible fluoroplastic tube, which is closest in technical essence to the proposed one and contains a cylinder and a piston and a mandrel located inside the cylinder, the cylinder being equipped with a replaceable end nozzle of arbitrary cross section located concentrically to the end nozzle of arbitrary cross section of the mandrel, which is made with a cavity for the passage of the inner element (see Goryainova A. V. Fluoroplastics in mechanical engineering. M: Mechanical Engineering, 1971, p. 73-74).

 The known device has a limited range of manufactured fluoropolymer tubes of sufficient bending stiffness and resistance.

 The technical result of the proposed inventions is to improve the quality of pipelines of arbitrary cross section by increasing the bending stiffness of the fluoroplastic tube and its resistance to cracking.

 The specified technical result is achieved due to the fact that in a flexible pipe containing a fluoroplastic tube, a reinforcing braid and metal endings, according to the invention, the fluoroplastic tube is made in the form of a set of functional layers, and the reinforcing braid is made in the form of pre-woven closed shells molded into the corresponding functional layers.

 The introduction of a pre-woven closed shell ensures the continuous formation of the inner surface of each tube layer by the reinforcing mesh during the manufacturing process (extrusion).

 The introduction of a pre-woven closed shell into the inner surface of each soybean tube by molding during piston extrusion provides reliable fastening of the reinforcing mesh inside the tube.

 The presence of functional fluoroplastic layers in the composition of the tube ensures the creation of an optimal flexible pipeline.

 The use of a fluoroplastic tube in a flexible conduit composed of functional layers and a pre-woven reinforcing shell molded into the corresponding functional layers improves the strength of the flexible conduit.

 In a method for manufacturing a flexible fluoroplastic tube, which consists in preparing a homogeneous paste from a mixture of fluoropolymer powder with an inert filler or without it and organic lubricant, molding from paste by pressing a tubular cylindrical tablet blank, producing a tablet from the blank by piston extrusion through a concentric axis of extrusion molding the gap of the fluoroplastic tube, followed by drying and sintering, and in each extrusion process, the axial feed from the cavity of the mandrel into the forming gap is carried out an internal element for forming a fluoroplastic tube with an internal element located on its inner surface to achieve the above technical result, the extrusion process is carried out repeatedly, while in the extrusion process, the axial feed from the mandrel cavity of the inner element, which is performed in the form of reinforcing pre-woven closed shells, is carried out first only with a guide rod, and then together with the functional layer of the fluoroplastic tube reinforced beforehand hydrochloric closed shell, forming a concentric gap of variable outer diameter to form a flow cross section of the multilayer pipe with functional layers.

 Implementation in the manufacturing process of a flexible fluoroplastic reinforced tube that differ from each other in characteristics and, therefore, in properties, multiple piston extrusion operations and axial feed of the reinforcing mesh together with either a guide rod, or in combination with a fluoroplastic tube from the longitudinal cavity of the mandrel to the forming slot allows you to get a multilayer tube with functional layers, which significantly expands the range and quality of products with minor refinement existing on equipment and enhances the performance of the hose.

 The specified technical result is achieved in that a device for manufacturing a fluoroplastic tube containing a cylinder and a piston and a mandrel placed inside the cylinder, the cylinder being equipped with a removable end nozzle of arbitrary cross section located concentrically to the end nozzle of arbitrary cross section of the mandrel, which is made with a cavity for passage of the inner element , according to the invention is equipped with a movable guide rod for placement on it with a gap to the inner surface of the mandrel, depending spacing from the serial number of the functional layer of the inner element in the form of a reinforcing pre-woven closed shell, or a functional layer of a fluoroplastic tube with a reinforcing pre-woven closed shell formed on its inner surface and put on a reinforcing pre-woven closed shell on the outer surface of the functional layer, the end nozzle of the mandrel also made interchangeable.

 The introduction of a hollow mandrel with a replaceable nozzle into the device ensures the placement of either a movable guide rod or a fluoroplastic tube with a molded mesh and a reinforcing braid on them.

 The use of a movable perforated guide rod ensures the installation of a pre-woven closed shell on it, as well as easy removal of the reinforced shell after heat treatment.

 The presence of interchangeable annular nozzles of the cylinder and the mandrel provides the manufacture of a multilayer tube with a reinforcing mesh.

 The use of a device for manufacturing a multilayer tube with functional layers of a hollow mandrel and a movable guide hollow core installed with a gap inside the mandrel, as well as a set of end nozzles of the cylinder and mandrel will expand the range of manufactured products and product quality.

 In FIG. 1 shows a sectional view of a flexible conduit; figure 2 - flexible pipe with an outer braid in a section; figure 3 is a flow chart of the implementation of the proposed method; figure 4 - a device for the manufacture of a flexible fluoroplastic tube with functional layers.

 The flexible pipeline (figure 1) contains metal endings - nipple 1, liner 2, the inner functional layer 3 of the fluoroplastic tube, the inner pre-woven closed shell 4, molded into the functional layer 3, the outer functional layer 5 of the fluoroplastic tube, the middle pre-woven closed shell 6 constituting a reinforcing braid of a flexible conduit molded into a functional layer 5. In addition, the flexible conduit (FIG. 2) may have an outer braid 7 and a sleeve 8.

 The technological sequence of the implementation of the proposed method (figure 3) includes the following basic operations.

 Operation 1 - preparation of a homogeneous paste from a mixture of fluoroplastic powders, an inert filler (if necessary, and organic lubricant.

 Step 2 - tabletting, which consists in molding a tablet blank fully or partially by successively growing cylindrical layers (or fragments thereof) from an uncompressed paste, accompanied by compaction of each layer (or its fragments) individually, mainly by isostatic or compression-isostatic pressing.

 Operation 3 — obtaining from a cylindrical pellet blank by a piston extrusion method through a concentric axis of extrusion a forming slit of the first functional layer of an extrudate tube with a closed perforated guide rod reinforced by a closed braided shell.

 Operation 4 - heat treatment of a reinforced extrudate (drying, sintering, hardening).

 Operation 5 - obtaining from a tablet blank by piston extrusion through a modified concentric forming slit of the second functional layer of a reinforced extrudate tube with a first functional layer and a movable perforated guide rod.

 Operation 6 - heat treatment of the reinforced extrudate (drying, sintering, hardening).

 Operation 7 - removal of a movable perforated guide rod by supplying air to the cavity of the rod.

 T.O. in the proposed method, the extrusion process is carried out repeatedly, while in the extrusion process the axial feed from the cavity of the mandrel of the inner element, which is made in the form of reinforcing pre-woven closed shells, is carried out initially only with a guide rod, and then together with the functional layer of a fluoroplastic tube reinforced with pre-woven closed shell, in a concentric forming slot of variable outer diameter with the formation of the bore of a multilayer fluoroplastic tube with functional layers.

 A device for manufacturing a flexible PTFE tube for a flexible pipeline contains a cylinder 9 with an adjacent end nozzle 10, inside of which a piston 11, a mandrel 12 with a longitudinal cavity 13 and with replaceable end nozzles 14 are installed.

 The end nozzles 10, 14 may have an arbitrary cross section and are arranged concentrically to each other. The device is equipped with a movable guide rod 15 with a plug 16 and a hole 17 for supplying compressed air. Perforations are made in the guide rod 15 — openings 18 for the exit of compressed air. At the exit of the cylinder 9, a forming slit 19 is formed.

 The device operates as follows. A plastic tablet preform 20 is squeezed out by a piston 11 through an annular slot 19 and, interacting in a section 21 with an internal element, which is made in the form of a reinforcing pre-woven closed shell - mesh 22, carries out axial movement of the latter together with or with a perforated guide rod 15, or with a fluoroplastic tube with a molded mesh 22 from the cavity 13 of the mandrel 12 into the annular gap 19, with a variable outer diameter, forming a cross section of the multilayer tube. At the exit from the annular gap 19 receive a reinforced extrudate 23 with a perforated guide rod 15. After the first heat treatment, the extrudate 23 is sent to re-extrusion as a guide rod. After the final heat treatment, compressed air is fed into the internal cavity of the guide rod 15 through the hole 17, which, through the perforated holes 18, enters the joints of the rod 15 with a multilayer tube, providing the latter from the rod.

 An example implementation of the method. The manufacture of a multilayer tube 12, the thickness of the layers: outer 0.4 mm, inner 0.4 mm). The implementation of the method was carried out in the sequence above (see steps 1-7) on the device shown in Fig.4.

 Operation 1 - preparation of a homogeneous paste. The composition of the paste: fluoroplastic powder 4D grade III GOST 14906-77 (100 parts by weight), organic lubricant (18 parts by weight).

Operation 2 - tabletting. Equipment - tablet press 0-1387. The pressing pressure of the paste is 20 kgf / cm ² ).

Operation 3 - piston extrusion. Equipment - extrusion press UZSS-I. Pressing pressure 150 kgf / cm ² . The tablet 20 with the mandrel 12 obtained on the tablet press is installed in the cylinder 9 of the extrusion press, as shown in FIG. A guide perforated rod 15 is preliminarily placed in the inner cavity 13 of the mandrel 12, on top of which a reinforcing braid 22 is made of 0.1 mm diameter copper wire. The plastic tablet preform 20 is squeezed out through the annular gap 19 by compression of the piston 11. As a result of the interaction in the area 21, the material of the tablet preform 20 with a reinforcing mesh 23 and a perforated guide rod 15 provide axial feeding of the latter, from the inner cavity 13 of the mandrel 12 to the annular slot 19, at the exit of the annular gap 19 receive a reinforced extrudate 23 with a perforated guide rod 15.

Operation 4 - heat treatment. The resulting extrudate is reinforced with a perforated guide rod 15 is dried at a temperature of 40-100 ^{° C,} sintering at a temperature of 380-400 ^{° C} and subsequent tempering with heating to 345-378 ^C and cooled in a water bath.

Operation 5 - piston extrusion. Equipment - extrusion press UESS-I. The pressing pressure is 150 kgf / cm ² . The sequence of operations is similar to that described in the description of operation 3, with the exception of the following features. Tablet blank 20 differs from previous materials, in this case, fluoroplastic with filler (coke) was used. An extrudate 23 with a perforated guide rod 15 is pre-placed in the inner cavity 13 of the mandrel 12 with a pre-installed nozzle 14, over which a reinforcing braid 22 made of copper wires with a diameter of 0.1 mm is put on. The annular gap 19 is formed by a replaceable nozzle 10. As a result of the interaction of the material of the tablet preform 20 with the reinforcing mesh 22 and the extrudate 23 with the perforated guide rod 15 in section 21, the latter are axially fed to the inner cavity 13 of the mandrel 12 into the annular gap 19, which is resized by its size.

Step 6 - heat treatment. The resultant laminate extrudate is dried at a temperature of 40-100 ^{° C,} sintering at a temperature of 380-400 ^{° C} and subsequent tempering with heating to 345-378 ^C and cooled in a water bath.

 Operation 7 - removal of the guide perforated rod 15 from the multilayer extrudate 23 by supplying air from the factory network to the inner cavity of the rod 15.

 Fabrication according to the technology described above fluoroplastic tubes in the form of a set of functional layers with preformed woven shells are used to assemble flexible hoses, which are then subjected to laboratory bench tests. According to the test results, it was found that the strength of a flexible sleeve with a fluoroplastic tube made in the form of a set of functional layers with molded reinforcing shells made by the proposed method exceeds the strength of known flexible pipelines by more than 2 times.

 The use of the proposed device for the manufacture of a fluoroplastic tube with functional layers provides, in comparison with known devices, a significant expansion of the range and quality of products, achieved by increasing the overall strength of the flexible pipe and its corrosion resistance, as well as reducing the cost of the product by using any materials as a reinforced braid and increase resistance to cracking under conditions of alternating pulsating loads.

Claims (4)

 FLEXIBLE PIPELINE, METHOD FOR MANUFACTURING PTFE PIPE AND DEVICE FOR IMPLEMENTING THE METHOD.  1. A flexible pipeline containing a fluoroplastic tube, a reinforcing braid and metal endings, characterized in that the fluoroplastic tube is made in the form of a set of functional layers, and the reinforcing braid is made in the form of pre-woven closed shells molded into the corresponding functional layers.  2. A method of manufacturing a flexible fluoroplastic tube, which consists in preparing a homogeneous paste from a mixture of fluoropolymer powder with an inert filler or without it and organic lubricant, molding from a paste by pressing a tubular cylindrical tablet preform, receiving from a tablet preform by piston extrusion through a concentric axis of extrusion the forming gap of the fluoroplastic tube, followed by drying and sintering, moreover, during the extrusion process, the axial feed from the cavity of the mandrel into the forming gap of the inner its element for forming a fluoroplastic tube with an inner element placed on its inner surface, characterized in that the extrusion process is carried out repeatedly, while in the extrusion process, the axial feed from the mandrel cavity of the inner element, which is made in the form of reinforcing pre-woven closed shells, is initially carried out only with a guide rod, and then, together with the functional layer of the fluoroplastic tube reinforced with a pre-woven closed shell, in a concentric rmuyuschuyu gap variable outer diameter to form a flow cross section of the multilayer PTFE tube with functional layers.  3. A device for manufacturing a flexible fluoroplastic tube containing a cylinder and a piston and a mandrel placed inside the cylinder, the cylinder being equipped with a removable end nozzle of arbitrary cross section located concentrically to the end nozzle of an arbitrary cross section of the mandrel, which is made with a cavity for passage of the inner element, characterized in that it is equipped with a movable guide rod for placement on it with a gap to the inner surface of the mandrel, depending on the serial number layer of the inner element in the form of a reinforcing pre-braided closed shell or a functional layer of a fluoroplastic tube with a reinforcing pre-braided closed shell formed on its inner surface and put on a reinforcing pre-woven closed shell on the outer surface of the functional layer, while the end mandrel is also replaceable.

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