DE3510552A1 - Weldable plastics mouldings - Google Patents

Abstract

Plastics mouldings are proposed which, because of a special design of their leading edges (12, 20) to be welded, are provided with recesses (44, 46) and (48, 50) and welding faces (26) adapted thereto, on the surfaces (28, 36) of which there are attached beads (30, 38), adapted to the groove-like depressions (46, 50), with cross-sections (32, 40) which are adapted to the cross-section of the grooves (46, 50). Channels (34, 42) in the beads (30, 38) permit the plug projecting at the weld edges (12, 20) to flow to the side to a small extent during pressing of the plastics mouldings (12, 18) onto the welding face (26). The plug (12, 20) remaining next to the recesses (44, 46) and (48, 50) is first of all melted under pressure, followed by pressureless heating of the grooves (46, 50) before, after the removal of the weld face (26), the heated parts (10, 18) are pressed against one another and thus the welding takes place. According to the invention it is achieved that a relatively smooth weld seam which is only slightly raised, without the formation of a weld bead, forms in the region of the recesses (44, 46) and (48, 50) after completion of the welding operation. <IMAGE>

Description

Weldable plastic molded parts

The invention relates to molded plastic parts which can be welded by means of the action of heat with a welding edge.

Such molded parts made of plastic can be plates or any shape Be plastic molded parts, but in particular pipes or container sections, which Can be joined together by means of welding to create pipelines and pipe systems or to manufacture complete containers. The plastic from which the molded parts are made, softens under sufficient heat and begins to flow; it can therefore Such molded plastic parts are connected to one another in that two to be joined Parts heated and heated at the same time as possible at suitable corresponding points the heated areas are pressed together after removing the heat source until the plastic has solidified again.

In this context, pipe sections made of plastic have proven particularly useful Proven to be advantageous in a simple manner with pipes of any length to produce a specifiable course. Pipe sections to be connected are aligned axially and kept at a distance with their corresponding leading edges. A so-called welding mirror, a heated plate, usually made of metal, which is smooth on both sides, is placed between the brought to be connected edges and the pipe sections are on both sides against the Welding mirror pressed until the leading edges are heated enough that the plastic begins to flow. The pipes are then moved apart, the Welding mirror removed and immediately afterwards the still soft front edges pressed together, until the plastic has solidified.

Since the material must be flowable at the welding point, form when the parts to be connected are pressed against each other on both sides on the outside weld beads from the section of material to be connected. When a pipe arises in this way an outer bead and a along the outer diameter inner bead running along the inner diameter. Both have weld beads approximately the shape of a double bead, since both plastic molded parts to be connected Material is pushed away radially outwards or inwards (in the case of a pipe). It has it has now been found that these weld beads are partially sharp projections or May have cavities. Since the molded parts are only pressed axially against each other, the radial weld beads can be released during joining and spread out unaffected, so that apart from said sharp-edged projections and cavities all possible, not even necessarily in the case of a weld constant, forms of weld beads can occur.

This has led to incompatibilities related to that especially with pipes and containers for liquids, which food law Are subject to regulations, for example beverages such as beer, lemonades, milk, etc., cleaning such pipes or containers inside is difficult or even impossible is because there are residues of the liquids in the irregularly shaped inner weld bead sections can stay behind. A microbacterially satisfactory one cleaning is then not possible.

For containers and pipes for liquids loaded with solids, particularly in the sewage sector, it has also been found that such solids on the inner weld beads of a pipe, especially where they are sharp-edged are shaped or have cavities, can fix what within a short time Time due to the accumulation of further solid particles to a blockage, for example a sewer pipe leads.

Such inconveniences have therefore occurred in many in the past Cases led to the fact that either such pipe sections are not used for the construction of pipelines could be used for the liquids and containers mentioned or else, that complex machining measures to straighten internal weld beads on pipes or containers were required. If such measures are feasible at all were, for example peeling or grinding the internal weld beads, so were they are at least very costly and time consuming. the The present invention is therefore based on the task of providing molded plastic parts, which are designed in such a way that said bulging no longer occurs. Another object is to provide one for welding the invention Plastic moldings suitable welding mirror; another aspect of the invention relates to a new method for joining plastic molded parts.

For plastic molded parts that can be welded by means of heat a weld-on edge, the object is achieved according to the invention in that the weld-on edge is provided on one side with a groove-like recess. These Recess is located on the inside of the front edge of pipe sections, for example. By this amazingly simple measure can be achieved that when joining Such plastic molded parts no longer occur inside weld bead formation, but a smooth course with only a slight elevation radially inward of the welded joint is accomplished. In particular, no post-processing is required, the The welding process itself lasts in practice with the plastic molded parts according to the invention just as long as with conventional molded parts.

According to an advantageous embodiment of the invention it is provided that the recess in the weld edge has a first free section and a having adjoining second groove-like section. Next to the free section a protrusion remains in the molded plastic part, which has partially melted away and there forms a weld bead as usual, where the other groove-like Section is provided, a space is created for flowing plastic material, which finally fills this second section and leads to none here outwardly directed weld bead formation occurs.

Should the bulge still occurring to a small extent at the location of the recess of the weld area are further reduced, according to a further advantageous embodiment of the invention proposed that the first section has a groove. Then there is even more free space for the flowable plastic created and thus achieved a further straightening of the welding area. the The shape of the second groove-like section can be designed in a variety of ways will, According to preferred embodiments of the invention, the groove is semicircular Cross-section, a rectangular cross-section, a trapezoidal cross-section, or a triangular cross-section is provided. Through these different embodiments can advantageously be adapted to different flow properties different plastic mixtures are made and so a particularly good match to the respective purpose.

According to the invention there is also a welding mirror for the Plastic molded parts proposed, which has a mirror plate on both sides each having a bead symmetrically to one another, one of which is to be received in the second groove-like section has adapted shape. The first free section of the invention Plastic molded parts here take on the bead of the welding mirror without the Bead initially comes into contact with the plastic. Rather, lies first the plastic section remaining next to the first free section in each case the mirror plate on. This section is therefore heated vigorously when pressed and pressed outward to form weld beading, until the on the Mirror plate arranged beads just full in the respective second groove-like Section. By mutually adapting the shape of the weld bead and the groove-like section becomes a uniform one as a result of the mere fitting without significant pressure gentle heating in this area accomplished what after removing the welding mirror and pressing the plastic parts to be joined together to a particularly smooth course of the inner weld seam in the area of the previous one second groove-like section leads.

According to a further advantageous embodiment of the invention is the bead of the welding mirror is fluted at its outer diameter. These constructive measure has the same beneficial effect as a groove in the first section in the plastic part.

It goes without saying that the plastic molded parts according to the invention a mirror plate that is matched to this in terms of shape and dimensions molded bead required. However, a welding mirror consists of several parts, of which the mostly electrical heating device accounts for a not inconsiderable share of the cost matters.

According to a further advantageous embodiment of the invention is it possible to present a mirror plate in which the electric heating device is attached, with several different beads for different plastic moldings to use, changing both the diameter and the shape of the bead can. This is achieved by having interchangeable panels on both sides of the mirror plate Intermediate plates are arranged with a bead attached.

According to a further advantageous embodiment of the invention a simple attachment of the most diverse intermediate plates with different Bead shapes achieved in that the mirror plate has a central opening, which protrudes from a fastening means extending from an intermediate plate which through a corresponding opening in the other intermediate plate can protrude and is fixed there. In the simplest case, this fastening means a Be a threaded bolt, which is set with a nut.

The solution to the problem posed by the method according to the invention, which was already indicated above, looks when joining plastic molded parts at their front edges with heating of the front edges by means of a temporary in between arranged welding mirror, after its removal the heated to flowability Front edges pressed against one another until the plastic has at least partially solidified are, according to the invention, the following steps: a) Provision of two to be joined Plastic molded parts, b) formation of a first free section in a partial area the leading edges along their entire course, c) formation of a groove-like Deepening of the first free section in a direction facing away from the front edge, d) aligning the two plastic molded parts, e) inserting the heated welding mirror between the two plastic molded parts, f) approaching the plastic molded parts on both sides to the welding mirror, g) applying the molded plastic parts with a Welding mirror directed pressure until the on the welding mirror attached beads lies in the groove-like depression, h) releasing the pressure and heating, i) removing the welding mirror, j) slowly moving molded parts to each other move towards and press against each other, k) hold pressure for a while until the temperature of the plastic at the welding point has dropped sufficiently.

In this process, previously known plastic molded parts can be used are used, in which according to steps b) and c) through suitable manufacturing measures, For example turning, milling or the like, cut the necessary recesses will. The method can therefore be used universally.

However, it is even simpler if steps b) and c) are used for welding the plastic moldings can be omitted, and that is in a simple manner according to a further advantageous embodiment of the method according to the invention thereby achieves that such measures are already constructive when manufacturing the plastic molded parts are provided. The plastic parts to be joined together on a construction site, for example are therefore already prepared accordingly.

According to a further advantageous embodiment of the invention is the temperature of the welding mirror 195 to 230 ° C. The exact temperature will be on the used Plastic or the granulate mixture used customized.

Here, in steps g) and / or i), there is an axial contact pressure the plastic molded parts of about 10 bar turned out to be particularly advantageous.

For cooling the weld of the joined plastic parts in step j) is according to a further advantageous variant of the invention Proposed method to wait for a temperature decrease to about 500C. at at this temperature, the so-called "thermoplastic reminder" is guaranteed, thus a partial depolymerization of the plastic is avoided.

The invention is described below with the aid of exemplary embodiments shown in the drawings explains in more detail from which further advantages and features emerge.

They show: FIG. 1 two joined pipe sections made of plastic, 2 shows a first preparatory stage for joining with pipe sections and Welding mirror, Fig. 3 a second stage with the start of heating under pressure, FIG. 4 shows a third stage with the end of the heating without pressure, FIG. 5 shows a different one Bead shape (not fluted) of the welding mirror, Fig. 6 is another Bead and correspondingly rectangular groove shape, FIG. 7 shows a representation as in FIG. 6, but with a fluted bead, FIG. 8 shows another bead and groove shape, the bead is trapezoidal, the groove beveled on one side, Fig. 9 shows an embodiment like Fig. 8, but with a scalloped bead, Fig. 10 another, namely triangular bead- and groove shape, Fig. 11 shows an embodiment like Fig. 10, but with a fluted bead, FIG. 12 shows an embodiment as in FIG. 5, but with a recessed groove, FIG. 13 shows an embodiment as in FIG. 12, but with a tube on the outside from the start attached thickening (pressure pipe), FIG. 14 shows a welding mirror according to the invention, 15 shows a section along XIV-XIV from FIG. 14, FIG. 16 shows a welding mirror with attached intermediate plate adapter for other groove or bead diameters.

In Figure 1 is a first pipe section with 10 and a second pipe section denoted by 18, which are joined together at their leading edges 12 and 20, respectively. Outer beads 14, 22 have formed on the outer sides, while according to the invention inside only a slight, smooth elevation 16,24, originating from the two sections 10 and 18, respectively. The shape of the plastic pipe parts according to the invention 10, 18 and the welding mirror can be seen particularly clearly from FIGS. 2 to 4 emerged.

FIG. 2 shows a wall of the front section shown in FIG of the tubes 10, 18 shown. The tube 10 has a leading edge 12 in which radially inwardly, a first free section 44 of the recess according to the invention is provided, on which a second groove-like section is axially inward 46, here with a semicircular cross-section, connects. Corresponding to this is the opposite tube 18 with a leading edge 20, a first free Section 48 and a second groove-like semicircular section 50 of the recess Mistake. Between the tubes 10, 18 there is a welding mirror 26, which on its one mirror surface 28 facing the tube 10 has a bead 30, which has an approximately semicircular cross-section 32, but in which a groove 34 is provided. Corresponding to this and to the pipe 18 is on the opposite mirror surface 36 has a bead 38 with a groove 42 provided in the otherwise semicircular cross-section 40.

In Figure 3, the first stage of the actual welding process is shown. The leading edge 12 of the tube 10 lies just like the leading edge 20 of the tube 18th on the smooth surface of the welding mirror 26.

The beads 32, 40 protrude into the free sections 44, 48.

FIG. 4 shows the pressing process at a pressure of about 10 bar clear. You can see how the respective pressing of the tubes 10 and 18 on the welding mirror 26 to the outside of the tubes 10, 18 an outer bead 14, 22 trains. In the area of the previous leading edges 12, 20, this is the case Material has been heated to flowability. The pressure is operated as far as to the cross sections 32, 40 of the beads 30, 38 in the respective groove-like recesses 46, 50 and heat them up without pressure. It is also clear from Figure 4, that due to the greater flowability of the material of the leading edges 12, 20 the Grooves 34, 42 of the beads 30, 38 are filled. In this one shown in FIG Position is after the formation of the bead parts 14, 22 of the contact pressure of the tubes 10, 18 removed and initiated a pressureless heating phase, in which the groove-like Sections 46, 50 are heated.

The tubes 10, 18 and the welding mirror are then moved apart 26 in between is removed, whereupon the tubes 10, 18 for the final Forming a welded joint are pressed together. Be in this position the parts are kept at about 50 ° C. until they cool, whereupon that shown in FIG Formation of the inner bead 16, 24 takes place, which in comparison to the outer bead 14, 22 can actually no longer be called a weld bead, but at most as a slight increase. In particular, the course of this internal elevation is 16, 24 of the weld smooth, so that neither parts adhere to it liquid residues can still adhere during cleaning or rinsing processes.

In Figure 5, a further embodiment of the invention is shown, in which the tubes 10, 18 and their structural design remained unchanged are, however, a welding mirror 52 is provided with beads 54, 58, which a each have semicircular cross-section 56, 60 without a groove.

Another embodiment of the invention is clear from Figure 6, in which pipe sections 62, 66 are designed differently and accordingly also the beads of the welding mirror; namely, the second groove-like section 64 in the tube 62 has a rectangular cross section, to which a bead 72 on the welding mirror 70 also corresponds to a rectangular shape. The opposite is analogous Tube 66 formed, in which the second section 68 is also rectangular as the associated bead 74 on the welding mirror 70.

A variant of the embodiment of Figure 6 is shown in Figure 7, the tubes 62, 66 with their groove-like sections 64, 68 are unchanged, however Another welding mirror 76 is provided, in which the grooves 78, 82 a Have recess 80 or 84.

The embodiment of the invention shown in FIG. 8 shows tubes 86, 90, in which the second groove-like sections 88, 92 have a trapezoidal shape have a beveled side edge. The associated beads 96, 98 of the welding mirror 94 are trapezoidal executed with two beveled side edges.

Figure 9 shows a variant of the embodiment according to Figure 8, at which the tubes 86, 90 with their groove-like sections 88, 92 remained unchanged however, the beads 102, 106 on the welding mirror 100 are fillets 104, 108 exhibit.

FIGS. 10 and 11 show further embodiments of the invention shown, which in turn is due to the formation of the beads of the welding mirror differentiate.

Pipe sections 110, 114 to be joined are triangular groove-like sections 112, 116 provided, triangular corresponding to their shape Beads 120, 122 of the welding mirror 118 correspond. Those shown in Figure 11 Tubes 124, 128 also have groove-like sections 126, 130 with approximately triangular Cross-section, in which, however, a leg opposite that shown in FIG Embodiment is shortened.

To this correspond beads 134, 138 on the welding mirror 132, which are also shortened on one side by recesses 136, 140.

In the embodiments described so far, there were grooves, if any were provided, these attached in the beads on the welding mirror. It is however, a corresponding groove is also possible and in many cases advantageous to be provided in the respective first section of the recess of the tubes and one such an embodiment is shown in FIG. A tube 142 with a semicircular second groove-like section 144 has a groove 146 opposite it as a result of a recess the second section widened the first section 100 on. Of the Bead 54 on welding mirror 52 is semicircular in cross section 56. In analog Way is the opposite pipe part 48 with a semicircular second groove-like section 150 and a first section provided with a groove 152 and the cross section 60 of the bead 58 on the welding mirror 52 is also semicircular. Of course, a groove can also be made in the first sections the other groove-like second sections described above are provided will.

In the previously described embodiments of pipes according to the invention took place by forming the first and second sections of the recesses on the Leading edge a certain reduction in cross-section. For increased printing requirements In pipeline construction, the next larger pipe wall thickness could in principle simply be used which would then have to be provided with recesses accordingly. In the case of the figure 13 shown, advantageous embodiment of the invention is an increased Strength at the weld is achieved in that the tubes 154, 158 with second, groove-like sections 144, 150 of the recesses radially outwardly ring-like, projections 156 extending along the outer diameter of the tube 154 or 158, 160 are provided, which ensure that the wall thickness of the tubes 154, 158 is also retained in the grooved sections 144, 150.

A welding mirror according to the invention is shown in FIG. The plan view shows a welding mirror 162 with an annular one mounted thereon Bead 164 for welding pipes together. There is a hole in the center of the welding mirror 166 is provided, which is used to accommodate the in Figure 16 shown further embodiment is used.

A transition part extends from the actual welding mirror 162 168, in which the electrical connections for the mirror 162 are attached electric heaters are grouped together; the transition portion 168 is after Loosening of screws in holes 170, 172 to open to gain access to the Connection parts or an adjustment or control device attached there for the Maintain the temperature of the welding mirror. A mounting part goes from the transition part 168 164 from, with which the welding mirror 162 in a suitable trained holder can be included, through which he is to be connected, for example, between Pipes in and can be swiveled out again after they have been heated.

FIG. 15 shows a cross section along the lines XIV-XIV of FIG 14. The smooth welding mirror 162 with on opposite sides are clear arranged beads 164, 176 and the central hole 166 in the welding mirror 162 to recognize.

An adaptation to different diameters and / or bead shapes is with the embodiment of the inventive welding mirror shown in Figure 16 possible. The welding mirror 178 is covered on both sides with intermediate plates 182, 188, on which in turn, as previously on the welding mirror, beads 184, 182 are attached are. A threaded bolt 186 extends from one intermediate plate 182 through the hole 166 shown in FIG. 15 in the welding mirror 178. The threaded bolt 186 penetrates a further hole 190 in the intermediate plate 188, and via a washer 194 and a nut 196 on the threaded bolt 186 are the both Intermediate plates 182, 188 against one another and against the one arranged in their center Welding mirror 178 pressed. In such an embodiment, it must be ensured that the temperature required for welding the plastic molded parts is now no longer on the welding mirror 178, but on the intermediate plates 182, 188 must be reached. For this it may prove necessary to use the Set the heating device of the welding mirror 178 to a correspondingly higher output, so that the correct temperature on the intermediate plates 182, 188 is reached. Appropriately accordingly changed setting values for the heating device can be transferred to the intermediate plates 182, 188 stamped so that they can be read at any time.

Finally, some details of the invention Procedure are explained in more detail. In one embodiment of the invention with too connecting pipes with a diameter of 110 mm has in step g) a Applying a pressure of 10 bar to the pipes over a period of 5 seconds proved to be advantageous, the temperature of the welding mirror was about 210 ° C. Thereupon the pressure was released and depressurized for 45 seconds according to step h) heated, that is to say in the position shown in FIG. Thereupon the welding mirror became removed, step i) of the method according to the invention, and the tubes were with the same pressure of 10 bar and held for about 5 minutes (steps (j) and (k)) until the temperature of the heated plastic parts has decreased to about 50 ° C was.

With the method according to the invention as well as according to the invention designed plastic parts and corresponding Welding mirrors is therefore achieved in effect that at the moment in which the transition from pressing takes place in the thermoplastic, pressureless preheating time, the inner bead inserts into the corresponding recess and thereby the recesses through the bead be melted without pressure. So there is a curling of the pins in the recesses instead, which creates a smooth, just a little bit on the inside of the joined pipe parts excessive weld bead arises. This welding bead is easy to keep clean and there is no risk of substances getting stuck there.

- blank page -

Claims (16)

Claims "Weldable plastic molded parts" 1. By means of the action of heat weldable plastic molding with a welding edge, characterized in that that the welding edge has a groove-like recess on one side (44,46,48,50,64, 68,88,92,112,116,126, -130,144,150) is provided. 2. Plastic molding according to claim 1, characterized in that the recess has a first free section (44, 48) and an adjoining section second groove-like section (46,50,64,68,88,92,112,116,126, 130,144,150). 3. Plastic molding according to claim 2, characterized in that the first section (44,48) has a groove (146,152). 4. Plastic molding according to claim 2 or 3, characterized in that that the second section is a groove (46, 50) with a semicircular cross-section. 5. Plastic molding according to claim 2 or 3, characterized in that that the second section is a groove (64,68) with a rectangular cross-section. 6. Plastic molding according to claim 2 or 3, characterized in that that the second section is a groove (88,92) with a trapezoidal cross-section. 7. Plastic molding according to claim 2 or 3, characterized in that that the second section has a groove (112,116; 126,130) with a triangular cross-section is. 8. welding mirror for plastic molded parts according to claim 1 or one of the following claims, characterized in that on both sides of the mirror plate (26,52,70,76, -94,100,118,132) symmetrically to each other bulges (30,38,54,58,72,74, 78,82,96,98,102,106,1 20,122,134, -138,164) with one for inclusion in the second groove-like section adapted shape (32.40, 56.60, -72.74, 78, 82, 96, 98, 102, 106, 120, 122, 134, 138) are provided. 9. welding mirror according to claim 8, characterized in that the Bulges (30.38; 78.82; 102.106; 134.138) on their outer diameter with a groove (34.42; 80.84; -104.108; 136.140) are provided. 10. Welding mirror according to claim 8 or 9, characterized in that that on both sides of the mirror plate (178) an interchangeable intermediate plate (182,188) with the bead (184,192) attached thereon. 11. welding mirror according to claim 11, characterized in that the intermediate plates (182,188) by means of a central opening (166) in the mirror plate (178) protruding fastening means (186) can be fixed. 12. Method of joining plastic molded parts at their leading edges with heating of the leading edges by means of a temporarily interposed Welding mirror, after its removal the leading edges heated to flow are pressed together until the plastic has at least partially solidified, I do not have the following steps: (a) Provide two plastic molded parts to be joined (10,18) (b) formation of a first free Section (44,48) in a portion of the leading edges (12,20) along the same entire course (c) formation of a groove-like depression (46, 50) of the first free Align the section (44,48) in the direction (d) facing away from the front edge (12,20) of the two molded plastic parts (10, 18) (e) Insertion of the heated welding mirror (26) between the two plastic molded parts (10, 18) (f) Mutual Approach of the plastic molded parts (10, 18) to the welding mirror (26) (g) application of the plastic molded parts (10, 18) with one directed at the welding mirror (26) Pressure until the beads (30,38) on the welding mirror are in the groove-like indentation (46, 50) lie (h) releasing the pressure and heating (i) removing of the welding mirror (26) (j) slowly move the molded parts (10, 18) towards one another and press against each other (k) hold pressure for a while until the temperature of the plastic has sunk sufficiently at the welding point. 13. The method according to claim 12, characterized in that the cuts (b) and (c) already take place during the manufacture of the molded plastic parts. 14. The method according to claim 12 or 13, characterized in that the temperature of the welding mirror is 195 to 2300C. 15. The method according to claim 2 or one of the following claims, characterized in that with the cuts (g) and / or (i) a pressure of about 10 cash is exercised. 16. The method according to claim 12 or one of the following claims, characterized in that in the cut (j) a temperature decrease to about 500C is awaited.