DE827550C - Process for manufacturing non-metallic, thermoplastic inserts for steam condensing tubes - Google Patents

Description

(WiGBL p. 175)

ISSUED JANUARY 10, 1952

/ 631 XII139a

for steam condensation pipes

The invention relates to a method for manufacturing inserts for steam condenser tubes, d. H. Pipes for condensing and / or cooling vapors or liquids. Such missions exist from a tubular protective lining made of non-metallic, thermoplastic material, which is used at the inlet end of the tube.

It is known pumps for inflating pneumatic tires made of hard rubber or similar material Manufacture by first going through a spraying process ο. Like. A tubular body made of a hard rubber mixture generated, the body is placed on a mandrel and subjected to an external pressure, by placing a pressing tool over the body in the unvulcanized state pulls and then vulcanizes it. It has also been suggested to use hollow objects, such as flashlight parts, fabricate in a hollow preform from a vinyl resin composition by the preform is placed in a die and heat and liquid pressure are allowed to act on it, until it takes the shape of the die and becomes heat-resistant. It has also been suggested that to manufacture articles at least partially made of vinyl resin composition in such a way that that one produces a heat-resistant preformed body from the mass mentioned and subjecting it to such a heat treatment that it assumes its final shape and you makes it heat-resistant.

There is also already the use of various non-metallic materials for condenser tube inserts brought into proposal, e.g. B. soft rubber or rubber-like substances, thermoplastic Plastics, for example polyacrylic acid esters, materials that harden in the heat of the phenol formaldehyde and furfural formaldehyde types.

In addition to high resistance to erosion and corrosion, the inserts are required very thin walls in order to have a somewhat significant difference in size between the bore of the Avoid condensation pipe and the hole in the insert. Furthermore, the stakes should be tight in Pipes of not quite the same bore fit, for example in pipes whose bores are inside the permitted manufacturing tolerances may vary. In practice this means that the stakes must have a certain degree of inherent elasticity and are so sized are that they are tight in pipes of the greatest tolerance dimension and by compression also in pipes of the smallest tolerance dimension. The production of condenser tube inserts that meet these requirements correspond in terms of critical dimensions, wall thickness and inherent elasticity quite a trouble. To accomplish this task, one has to attach Proposed longitudinal slots or grooves in the inserts. However, they have slits or grooves Inserts have the disadvantage that a layer of water or skin remains on the slots or grooves that promotes local corrosion of the condensate pipes.

The invention relates to an improved method of manufacturing non-metallic, tubular Inserts for steam condensing tubes made of a tubular material by making a conventional Way made by injection molding thermoplastic plastic pipe by putting on brings a mandrel to size, pulls one or more pressure tools over it and the pipe section then subjected to finishing by partially converting it into a tubular shape Insert holder and set the holder in revolutions while following the protruding section of the workpiece is heated to a temperature at which it becomes plastic and by centrifugal force is driven outward so that a flange is formed at the outer end, whereupon the Bends the flange backwards at its periphery and creates an edge at the end of the tube.

According to the invention, the preferred thermoplastic material is polyethylene or other thermoplastic materials, such as polyvinyl chloride, are used. Preferably that will Injected polyethylene in the form of tubes, the inner diameter of which is slightly larger than that required inner finished diameter and with a slightly greater wall thickness than that of the Finished measure, because the pipes produced by injection molding are a drawing process or a subjected to another operation in which they are brought to the correct finished size.

A method for the production of condenser tube inserts according to the invention from not metallic material, such as polyethylene, is in one embodiment in the drawings illustrated in these is

Fig. Ι a longitudinal section of an injection molding process manufactured pipe, from which an insert is made by means of a tailor-made and finishing process shall be;

Fig. 2 shows in a partial longitudinal section the operation for producing the size measure;

Figures 3 and 4 illustrate some stages of finishing; Fig. 5 shows the finished condenser tube insert.

The first step in the manufacture of a condenser tube insert is that one Tube ι made of non-metallic, thermoplastic material, in the present embodiment Made of polyethylene, manufactured by the usual spraying process so that the bore of the pipe is flat is slightly larger than that of the finished insert. The tube is pulled over a mandrel 2, the Corresponds to the diameter of the bore of the finished insert. A drawing tool 3 is over the front end of the mandrel 3 and advanced far enough over the tube so that a second tool 4 can be placed on the mandrel and the tube. The front end of the mandrel is in slightly retracted its diameter 5, and the tool 4 has such dimensions that it The end of the tube is compressed and locked onto the taper of the mandrel.

The drawing tool 3, which is within the limits of g ₀ 0.0254 to 0.127 mm smaller than the diameter of the finished insert, is then carefully drawn along the pipe almost to its other end, where the tool is fixed by a device not shown to prevent it from receding towards the front end of the mandrel. In this process step, the thermoplastic pipe is heated to a temperature at which it becomes sufficiently plastic to relieve the stresses caused by the drawing process. When using polyethylene, this is successfully done by immersing the tube and mandrel assembly in boiling water for a few minutes. After heating, the whole is cooled to room temperature and the tube is pulled off the mandrel.

The polyethylene pipes made in the usual way by injection molding and made to measure are used then subjected to a finishing process in which one end of each tube extends over or over to the outside. bent over and thus a flange 6 is formed which is able to grasp the end of the Koiidensrolires. The flange is produced by inserting the dimensionally stable pipe into a metal pipe 8, whose bore corresponds to the outer diameter of the thermoplastic pipe and part of the Can protrude tube from the metal tube to the outside. The metal tube is then placed in a lathe chuck or clamped in another device, not shown, of known type, which at a monitored speed, namely at an initial speed of 50 to 60 revolutions per minute rotates, while the protruding thermoplastic material is moderate is heated until it takes on a consistently plastic consistency. When using poly

Then the temperature is between ι ίο and 130 ⁰ C. The speed of rotation is then increased to approximately 400 to 600 revolutions per minute until the softened plastic mass is driven evenly outward by the centrifugal force and a wide, flat flange 6 "is formed Rotation is then stopped and the flange is bent backwards by means of a heated tool 9, the beveled central pin of which is surrounded by an annular recess. The outer wall of the recess presses the plastic material around the end of the metal tube 8 and creates the rearwardly bent edge 6 at the end of the plastic tube to the correct external dimensions, while the beveled central pin is pressed into the mouth of the plastic tube and smooths out any internal inequalities. The tool 9 also cuts off any excess material .On request can n the inner end of the insert is fluted in a suitable manner, for example by turning. Flanges on cylindrical hollow bodies made of thermoplastic plastics have already been produced by centrifugal force and turning the cantilever end part (patent specification 711 567).

Claims (3)

PATENT CLAIMS: i. Method of making a non-metallic, thermoplastic tubular Insert for steam condensation pipes made from a tubular workpiece, characterized in that that the thermoplastic plastic pipe produced by conventional spraying is correct Measure is brought by placing the pipe section on a mandrel (2) and a Tool or tools (3) pulls over it, whereupon the dimensionally stable workpiece is partially in a tubular holder (8) is inserted and the holder is rotated while the section protruding therefrom is heated to a temperature at which it becomes plastic is and driven outwards by centrifugal force and so enters at its outer end Flange (6 ") is formed, whereupon the outer periphery of the flange is bent backwards and at the outer end of the tube produces an annular rim (6). 2. The method according to claim 1, characterized in that that the operation producing the size measure is carried out at normal temperature and the dimensionally stable workpiece in the desired dimensions during heat treatment for the purpose of elimination the material tension and a subsequent cooling is maintained. 3. The method according to claim 1 or 2, characterized in that polyethylene as thermoplastic material is used. Referred publications:
German patent specification No. 711 567. For this purpose ι sheet of drawings 2718 12.51