DE3807688C2 - Method and device for producing a plastic pipe fitting - Google Patents

Description

The invention relates to a method for producing a Plastic pipe fitting with at least one sleeve, in particular of a pipe bend, from a straight piece of pipe according to the preamble of claim 1. The invention also relates to a device according to the preamble of claim 6 for performing this method.

Plastic pipe fittings with sleeves at their ends Larger sizes are welded to the sleeves Manufactured ends of a pipe section. Elbows are often made welded several sector-shaped pipe sections, wherein the sleeves must also be welded at both ends. The Her Position of such fittings is therefore particularly large Nominal sizes are very labor intensive and relatively expensive.

Plastic pipe fittings can also be sprayed pour be made. However, this method is only suitable for small nominal widths, as for fittings with larger nominal widths Molding and manufacturing costs for economical manufacturing are too high.

The production is from the patent abstract of Japan for JP 56-162 610 A2 known from pipe bends made of thermosetting synthetic resin. In doing so, a tube-shaped tube becomes into the uncured straight tube Hollow body used and in a first centrifuge shape, in which only the straight, unhardened pipe section is formed, inflated. The just unhardened piece of pipe on the inflated The hollow body is then removed from the mold, the hollow body prevents the uncured tube from collapsing. The hollow body  then with the straight pipe section on it used in a second centrifuge shape, in which the pipe section by the centrifugal force of the rotating mold curved mold wall. After removing the hose pipe the tube is then heated and hardened in the mold from the mold. Shaping and heating take place one after the other. The shape happens while reducing the internal pressure in the carrier hose by centrifugal force.

U.S. Patent 4,009,982 describes the formation of the sleeves the ends of a finished molding, in particular one Elbow. For shaping the sleeve on the preformed fitting becomes a cylinder with a pneumatically inflatable jacket retracted the end of the plastically softened fitting and then inflated, causing the end of the fitting to become a sleeve is expanded. The simultaneous shaping, especially the Curvature of the plastic pipe fitting and the formation of sleeves, is not possible after this.

CH-PS 558 248 only describes the formation of one Sleeving at the end of a pipe section using an inflatable sleeve. The deformation of the pipe part between the sleeves is over nothing known in this document. For the rest, the formation of a Sleeve described by an inflatable air bag as disadvantageous.

Finally, it is known from US Pat. No. 3,833,699, in one Form the ends of a thermoplastic pipe piece with socket formation expand and deform the pipe piece itself. In the shape is a rigid straight mandrel on which the plastic pipe section to be deformed is pulled up. In the mold, the ends of the pipe section are first inflated the sleeves on the mandrel ends on the mold wall brought to rest, with the middle area of the annulus  is shut off between the mandrel and the pipe section. Only after this seal is the middle part of the pipe section inside Air pressure set and thereby pressed against the mold wall. The work is therefore carried out in two stages: first the sleeves are formed; then the middle part of the pipe section can be deformed. Since the pipe section to be deformed is also on a rigid straight line Thorn sits, the possibility of deformation of the pipe section is limited. The pipe section can be expanded, but it must essentially stay straight. Incidentally, this procedure the formed piece uncured on a separate hardening mandrel transfer.

In contrast, the object of the invention based on a method and an apparatus for manufacturing Plastic pipe fittings with no weld seams at the ends to create trained sleeves, the sleeve formation and the shape of the pipe section between the sleeves simultaneously should be done in one operation. In particular, a procedure should and a device can be created with which plastic pipe Fittings with a non-linear axis, such as. B. pipe elbow, can be formed. There are further advantages from the following description.

Accordingly, the invention is based on a method for Production of a plastic pipe fitting with at least one Socket from a straight piece of pipe, in which the plastic deformable piece of pipe pulls on a hollow body whose diameter is smaller than that of the pipe section, the pipe section with the Insert the hollow body into a shape corresponding to the pipe fitting, the form closes, the pipe section by loading the hollow body with compressed air on the inside of the mold wall to the system brings, the hollow body relaxed again and the formed piece after opening the mold. The task is solved in this method according to the invention in that  the thermoplastic pipe piece to a temperature heated in the temperature range of plastic softening, the softened pipe section to an elastically expandable Hose piece pulls and after closing the form by inflating of the hose piece against the mold wall and the molding in the mold to a temperature below the Allows the softening area of the plastic to cool.

The outlet pipe section is expediently a cylindrical one Pipe piece which, after being heated to the required warmfor temperature on a hollow body, preferably in the form of a tube, is pulled, which brings about the desired shape. That on the Deformation temperature of the pipe section on the hose body is then caused in a mold by inflation and thereby Expansion of the tube body deformed until it is at the Form wall is present, through which the shape of the desired pipe Fitting is specified. After cooling to a temperature, where the fitting is essentially dimensionally stable, the Hollow body relaxes so that it no longer puts pressure on the formed Exercises shaped piece and removed from the formed piece can be. The dimensionally stable shaped piece is then removed from the mold. By the method according to the invention becomes generally linear Output pipe piece in one working process in the desired Shaped, d. H. the sleeves are formed, and that Pipe piece is z. B. curved to the desired extent.

According to the preferred embodiment of the invention The procedure removes the piece of tubing after relaxing from the formed piece and then opens the mold for removal of the fitting. Because the hollow body through the two openings protrude to the outside, it can be added after relaxing closed form can be removed from the fitting. The hollow body can therefore plastic for the next batch with a new one softened tube piece can be populated while the formed  Continue to cool the pipe fitting in the closed form can.

It is preferable to blow the tube piece before closing it the form partially and completely after closing the form on. In this way, uneven stretching will occur over the circumference of the plastic material and possibly wrinkles of the pipe section avoided when the hollow body in the closed Form is fully inflated.

Expediently you blow the piece of hose except for one Internal pressure in the range of 3 to 10 bar, preferably 4 to 8 bar on. A common pressure is e.g. B. at 6 bar. The expansion of the hollow body under this air flow causes sufficient pressure of the plastically softened pipe section on the mold wall and the safe formation of the fitting. When to open and Closing the mold a molded part can be pneumatically operated the existing compressed air source for feeding the Serve hollow body.

Preferably, a piece of pipe made of PVC, polyethylene, Polypropylene or flame retardant polypropylene to one temperature in the range of 110 to 190 ° C.

In terms of the device, the invention is based on a two-part, open at both ends with ring-shaped recesses on the inside for the shaping of the sleeves, the two molded parts are apart and collapsible, and a closed at both ends Hollow body with one guided on it, on one Compressed air source connectable line in which one is under the internal pressure closing of the hollow body, opening from the outside Valve is arranged, the hollow body having a smaller diameter than the pipe section has. This device is according to the invention characterized in that the hollow body as an elastic  expandable, up to the contact of the drawn pipe section with the Molded wall of inflatable tube piece is formed.

The two-part shape determines the Shape of the pipe fitting to be formed. For everyone by shape and size (nominal size) specific fitting is a separate shape required. The hollow body is used to hold the plastic soften pipe section and its introduction to the shape and Widening and pressing against the mold wall. The hollow body is not adapted to the shape. Because of the elasticity of his The material adapts when the shape of the mold wall is inflated at. In addition, a hollow body can vary within limits be inflated heavily so that he can use shapes for different Fittings can work together. The loading of the hollow body with compressed air takes place via a line in which a check valve is arranged. The valve allows inflow the compressed air in the hollow body, but prevents it from escaping the compressed air. The valve body can also through the outside Operator are operated so that the hollow body relaxes and its pressure on the formed piece can be released, when the fitting has become dimensionally stable due to its cooling. The hollow body in the normal state, i.e. H. in the absence of internal overpressure, has a smaller diameter than the soft piece of pipe. The plastically softened pipe section has a pipe circumference that is preferred is smaller than the circumference of the finished fitting. The plastically softened pipe piece experiences in the course of the expansion of the Hollow body a limited stretch in the circumferential direction. These Stretching is, of course, in the area of the ring-shaped recesses, in which the sleeves are formed, slightly larger than in the rest of the form.

The annular extensions are preferably through the molded parts attached headstock parts formed at closed form a larger clear diameter than that  Have shape yourself.

According to the preferred embodiment, the shape consists of two molded parts that are formed by one through the axis of the Form-guided cut are separated according to the Curvature of the fitting axis is curved. By the in the axis of the molding to be formed or the mold cavity Separating cut of the form there are two molded parts, according to their Moving apart allows for easy removal. The a molded part, in particular the lower mold can be stationary, and the other molded part, in particular the upper mold for opening and Slidable closing of the mold. The direction of displacement of the movable molded part is perpendicular to the parting plane. If the axis of the fitting is curved, the larger fitting is stationary and the smaller molding radially or vertically Slitting cut plane movable.

This embodiment is suitable for manifolds with a Elbow of 90 °. In another embodiment, the Shape for curved pipe pieces through a flat cut in two same mold halves must be separated. The split shape is suitable z. B. for elbows with an arc of 45 ° or less.

The plastic pipe fitting manufactured according to the invention has at least one end of the seamless pipe section over one Extension area a seamless molded sleeve. The fitting is therefore completely seamless, which means that on the one hand good durability and leak protection, on the other hand does not affect the appearance of the fitting is.

The invention will now be described with reference to the drawing described. It shows  

Fig. 1 is a schematic flow diagram of the individual process steps;

Fig. 2 shows the side view of an embodiment of the device according to the invention with the mold open and retracted hollow body;

Fig. 3 is a section along the line III-III of Fig. 2;

Fig. 4 is a section along the line IV-IV of Fig. 3;

Fig. 5 is a side view of the device of Figure 2 with the mold closed and the inflated hollow body.

Fig. 6 is a section along the line VI-VI of Fig. 5;

Fig. 7 is a section along the line VII-VII of Fig. 6;

8 shows the pipe bend in enlarged scale produced in the apparatus of Figures 2 to 7, partly in side view and partly in axial section..;

9 shows a connector having two protrusions for a throttle valve storage as a further embodiment of a pipe fitting OF INVENTION to the invention, partly in side view and partly in section. and

Fig. 10 shows the transition area between the pipe section and the sleeve in section in a schematic, greatly enlarged view.

Fig. 1 shows the sequence of the individual method steps, the sequence indicated by solid arrows representing the preferred embodiment. The process parts with dashed arrows show design variants.

First, the blank, e.g. B. a cylindrical tube cut, in an oven to the temperature of plastic expansion warmed. This temperature can vary depending on the material be different. With PVC it is e.g. B. at 160 ° C.

After the pipe piece is softened and there assumed a more or less flat, oval cross section it is removed from the oven and opened in this state an inflatable hollow body made of elastic material. This hollow body is generally in the form of a double end closed piece of hose. The outside diameter of this inflate The hose body is considerably smaller than the inside knife of the cylindrical plastic pipe section before heating, so that the plastically softened, oval-shaped blank also opens up the hollow body can be pulled up. Winding up the blank on the hollow body is done by hand, but can also be done by machine the hollow body can be retracted.

The tubular hollow body with the surrounding it soft piece of pipe is then inserted into the opened mold, whose inner contour corresponds to the pipe fitting to be formed. The plastically soft piece of pipe is not yet included touches the inside of the mold wall and, as a result of its compared to the inflatable hollow body of larger size this in the lower area distance. The shape and that softened Pipe piece with the hollow body are horizontal or arranged vertically.

Now the hollow body is attached to a compressed air source closed and inflated to the extent that the circumference of the hose shaped hollow body approximately equal to the circumference of the softened tube is piece, so that this of the hollow body surface essentially is applied on all sides. The partial inflation prevents the wall of the fitting when closing the form and open Blow the hollow body unevenly in all areas det or initially forms wrinkles in the finished product are recognizable and lead to rejects. The shape will then closed, and the hollow body is fully inflated, whereby the plastically softened pipe section on the inside to the shape wall is pressed. The fitting thus formed is then cooled under the pressure of the inflated hollow body until it is in has become substantially dimensionally stable. Because the heat to be dissipated is low, it is enough to form a good heat conductive Material, e.g. B. Al to make. However, it is also possible to change the shape to cool with a coolant.

After the pipe fitting has achieved dimensional stability, the hollow body relaxes. It detaches from the inner surface of the pipe fitting formed and can already by one of the Mold openings are removed from the mold. Then will then opened the mold and removed the molding from the mold.

From Fig. 1 it can also be seen that in special cases the partial inflation of the hollow body can be omitted before the mold is closed. The inflation then takes place only after the mold is closed. This embodiment will be chosen when there is no risk of wall irregularities or folds when closing and inflating because z. B. the plastically softened piece of pipe on the hollow body forms no or only a small hanging loop. Of course, it is also possible to first open the mold after the hollow body has been relaxed and to remove the hollow body from the mold together with the tube molding formed.

Figs. 2 to 4 show an apparatus for performing the method according to the invention for the preparation of 90 ° -pipe bend. The device consists of a molded part 1 and a molded part 2 . The molded part 1 is interchangeably mounted on the stationary platen 3 . The molded part 2 is in a similar way interchangeably attached under the movable platen 4 . The inflatable tube body 5 is shown in the position after insertion into the mold 1, 2 , but before the mold is closed. The axis of the hose body 5 lies in the same plane as the quarter-circular axis of the cavity of the form 1, 2nd The tubular body 5 was fitted with a piece of plastic softened by heating pipe 6 before entering the mold. As can be seen from FIGS. 2 to 4, the pipe section 6 has a longer circumference than the hose body 5 when its internal pressure is still equal to the external pressure. As a result, the plastically softened pipe section 6 lies in the upper longitudinal region of the outside of the hose body 5 , while it hangs down in the form of a loop in the lower longitudinal region and is at a distance from the outside of the hose body 5 , as can be seen particularly from FIGS. 3 and 4. The circumferential difference between the tube body 5 and the plastic-softened tube piece 6 is expedient in order to facilitate or enable the pulling on of the tube piece on the tube body 5 . At the hose body 5 , a line 7 is connected, in which an from the outside, for. B. is by an operator manually opening valve 8 . The hollow body 5 can be connected via the line 7 to a pressure medium source (not shown), so that the tubular body 5 under a desired internal pressure, for. B. 6 bar can be set on a z. B. arranged in line 7 manometer (not Darge provides) can be read. The tube body 5 is made of an elastic material so that it can expand under the internal pressure, ie its outside diameter increases.

As is apparent from FIGS. 2 and 4, 9 of the lower mold 1 top plate portions 10 are fitted interchangeably to the two output-side end faces, in particular screwed on. In the same way, on the output-side end faces 11 of the upper molded part 2 head plate parts 12 are exchangeable bar, in particular screwed on. The head plate parts 10, 12 have a semicircular recess, so that after closing the shape of each pair of head plate parts 10, 12 forms a flat cylindrical cavity, the clear diameter of which is slightly more than twice the wall thickness of the pipe material than the clear width of the subsequent pipe section. In the head plate part pairs 10, 12 , the sleeves of the pipe fitting, in the vorlie example of the 90 ° pipe elbow are formed. The head plate parts 10 and 12 are interchangeable.

Figs. 5 to 7 show the same device as FIG. 2 to 4 after closing the mold and inflating the tubular hollow body 5. Due to the excess air pressure in the hollow body, this has widened, and by closing the mold parts 1, 2 , the hollow body has fit into the mold cavity, the plastically softened pipe section 6 being pressed against the mold inner wall, as shown in FIGS . 6 and 7 can be seen. The length of the tube 6 is to be dimensioned such that after the deformation outside the head plate parts 10, 12 protrusions 6 a remain so that the sleeves 14 can be formed fully and without errors. The supernatants 6 a are separated after demolding. From Fig. 7 it can also be seen that in the area of the head plate parts 10, 12, the shape of the sleeve 14 is carried out.

After the shaping according to FIG. 7, the formed piece is cooled until it is dimensionally stable. Then the hose body 5 is relaxed by operating the valve 8 by the operator. The hose body 5 is already detached from the inner surface of the formed piece 16 to such an extent that it can be pulled out of the closed mold 1, 2 . When the molding 16 has the stability required for the demolding, the molding 1 or 2 is opened so that the molding can be removed.

Fig. 8 shows the pipe bend 16 produced in the apparatus of FIGS. 2 to 7 in an enlarged scale. The sleeves 14 are integrally formed on the elbow 16 . The smoothness of the molding is much greater on the outside 16 a than on its inside 16 ^b .

Fig. 9 shows a rectilinear connector 17 with sleeves 14 at both ends. Approximately in the middle of the connecting piece in the wall are two diametrically opposite formations 18 , in which the bearings of a throttle valve (not shown) can be used. On the outside, the pipe fittings 16 and 17 carry two diametrically opposed impression marks 22 , which as a weak groove or step have a depth of the order of 10 to 100 microns, but with the great smoothness of the outer surfaces 16 a and 17 a are clearly recognizable.

Fig. 10 shows the transition area 19 of the tube section 16 or 17 to the sleeve 14. It is typical for the fittings according to the invention that the extension from the pipe section to the sleeve is not carried out by a perpendicular to the axis 20 , ie radial extension, but distributed over an extension area 19 of length a. The slope α on the outside of the wall is greatest at the beginning of the extension area 19 , ie at point 21, and decreases steadily towards the socket 14 down to zero. The length a of the expansion area 19 is greater than the dimension b of the radial expansion of the sleeve 14 with respect to the pipe section 16 or 17 . The ratio a / b is in the range from 1 to 12, preferably in the range from 1.4 to 8. In the case of fittings with larger nominal widths, the ratio a / b is generally greater than with fittings with smaller nominal widths.

Claims (8)

1. Process for the production of plastic pipe fittings with at least one sleeve, in particular a pipe bend, from a straight pipe section, in which
pulls the plastically deformable pipe section onto a hollow body, the diameter of which is smaller than that of the pipe section
insert the tube piece with the hollow body into a shape corresponding to the tube shape piece,
the form closes,
brings the pipe section into contact with compressed air on the inside of the mold wall by charging the hollow body,
relaxed the hollow body and
takes the formed piece after opening the form,
characterized in that one
the pipe section made of thermoplastic plastic is heated to a temperature in the temperature range of plastic softening,
pulls the softened tube piece onto an elastically expandable tube piece and, after closing the mold, inflates it against the mold wall by inflating the tube piece and
the mold in the mold to cool to a temperature below the softening range of the plastic. 2. The method according to claim 1, characterized in that one the hose piece after relaxing from the formed piece removes and then opens the mold for removing the fitting. 3. The method according to claim 1 or 2, characterized in that part of the hose piece before closing the mold and inflates completely after closing the mold.   4. The method according to any one of claims 1 to 3, characterized in that one in the hose piece to an internal pressure the range of 3 to 10 bar, preferably 4 to 8 bar. 5. The method according to any one of claims 1 to 4, characterized in that you have a piece of pipe made of PVC, polyethylene, polypropylene or flame retardant polypropylene to a temperature in the Heated from 110 to 190 ° C. 6. Device for performing the method according to one of claims 1 to 5 with a two-part, open at both ends form ( 1, 2 ) with internal annular recesses for the formation of the sleeves, the two molded parts ( 1, 2 ) can be moved apart and moved together , and a hollow body ( 5 ) which is closed at both ends and has a line ( 7 ) guided to it and connectable to a compressed air source, in which a valve ( 8 ) which closes under the internal pressure of the hollow body and can be opened from the outside is arranged, the hollow body ( 5 ) has a smaller diameter than the pipe section ( 6 ), characterized in that the hollow body ( 5 ) is designed as an elastically expandable hose section which can be inflated until the drawn pipe section ( 6 ) bears against the mold wall. 7. The device according to claim 6, characterized in that the annular recesses ( 13 ) by the molded parts ( 1, 2 ) head plate parts ( 10, 12 ) are formed, which have a larger clear diameter than the mold itself when the mold is closed. 8. Apparatus according to claim 6 or 7, characterized in that the shape consists of two molded parts ( 1 and 2 ) which are separated by a section through the axis of the molded piece to be formed ( 15 ) which is curved in accordance with the curvature of the molded article axis is.