EP0780204B1 - Process and apparatus for making moulded sleeve pipes - Google Patents

Abstract

A hollow space (12) for the mass to be pressed is provided between an inner core (13) withdrawable in an axial direction and a concentrically arranged rubber-elastic membrane (14), which on the face side is tensioned and with the pressure pot (11) limits a pressure chamber (16) fed from a hydraulic pressure source. The inner core is provided with a forming ring (20) forming the muff area of the muff tube (40), which has an end area (21) reduced in dia. for formation of two concentric, but axially spaced face surfaces. At least the face surface of the forming ring forming the muff area of the muff tube has a surface of elastic plastics.

Description

The invention relates to a method and an apparatus for manufacturing of socket pipe moldings from a ceramic molding compound by isostatic pressing, in which the mold to be pressed is within a hollow cylindrical pressure pot between an in Extendable axial core and one concentric to it arranged rubber-elastic membrane formed mold cavity is introduced, the rubber-elastic membrane is clamped on the face and one of the pressure pots a pressure chamber that can be acted upon by a hydraulic pressure source limited and the inner core with a the sleeve area of the socket pipe with two concentric, but in the axial direction provided spaced end faces forming ring is. Furthermore, the invention relates to a device for performing of such a process,

A method and a device of this type are from DE-AS 14 59 330 known. The device described in this document is used for isostatic pressing of socket pipe fittings. The well-known Device has a hollow cylindrical tubular body, one Mold cavity, a pressurizable rubber-elastic membrane and a steel insert at the end to form the socket area on. The socket area of the molding is defined by an annular Steel insert generated. In the socket area, especially on the shoulder of the socket area can be due to the large wall thickness differences microcracks occur during isostatic pressing.

DE 28 25 611 C2 describes a device for isostatic pressing known from tongue and groove tubes. This device has an inner core with a bottom ring on top and a pressurized one Membrane. To form the tongue and groove of the pipe moldings ring-shaped inserts made of rubber or plastic are provided. This ring-shaped inserts have the task of being elastic Diaphragm outgoing pressure into a wedge of the mold cavity transferred, which is not directly exposed to the elastic membrane is. This has the consequence that the molding compound, which is in the Inner core adjacent recess to form a spring, is sufficiently well compacted by the pressing process.

DE 44 07 299 C1 describes a further device for isostatic Pressing tongue and groove pipes is known. As shaping elements steel rings are provided in this device.

The object of the invention is based on this prior art to provide a method and an apparatus for no cracks in the socket area of the isostatically pressed molding occur.

To achieve this object, a method for the production of Socket pipe moldings proposed according to claim 1. At the method according to the invention is at least one of the end faces of the molded ring with a surface made of an elastic plastic Mistake. The elastic plastic, which is advantageous is a high-molecular plastic, works despite its elasticity shaping in isostatic pressing. Still sees that inventive method a venting of the mold cavity during of the pressing process. Here, depending on the baling pressure Annular gap released, which is connected to a vent hole. The method according to the invention eliminates the risk of cracking greatly reduced in the socket area of the molding. The invention The method is particularly suitable for the production of large format Socket pipe moldings from about 100 to 1,500 mm in diameter.

In a further embodiment of the method according to the invention proposed that the elastic end face of the form ring the sleeve area the sleeve pipe is supported elastically during the pressing process.

Furthermore, the invention relates to a device for producing Socket pipe moldings. The device according to the invention is thereby characterized in that at least the sleeve area of the sleeve pipe forming end face of the end portion of the mold ring a surface has an elastic plastic and the end region of the form ring with the inner core delimits an annular gap, which depends at least one of the pressing pressure provided on the inner core, releases vent hole communicating with the mold cavity or closes.

In an advantageous embodiment of the invention, the end region of the Formrings on a coating of an elastic plastic. By not only the end faces of the molded ring, but the entire one End area a coating made of an elastic plastic has, there is a risk of cracking in the socket pipe moldings further decreased.

In another advantageous embodiment of the invention, the end area of the molded ring with a sleeve made of an elastic plastic. In addition to reducing the risk of cracking, the End region of the form ring in this embodiment according to the invention by simply replacing the sleeve made of elastic plastic other shapes can be adapted. Also in case of possible wear the entire molded ring cannot be replaced, it is enough to just use a new sleeve.

In a further embodiment of the invention, the rubber elastic Membrane on an area adjacent to the mold ring.

In an advantageous embodiment of the invention, the inner core is tubular formed and has at least one with the mold cavity communicating vent hole. Through this invention Measure is a pressure equalization between the inner core and the mold cavity, which also leads to an improvement contributes to the pressing quality of the socket pipe molding.

Other advantageous embodiments of the invention are the others See subclaims.

Figur 1

eine auf die wesentlichen Bestandteile beschränkte Schnittdarstellung einer erfindungsgemäßen Preßvorrichtung;

Figur 2

eine Detailvergrößerung der Darstellung der Figur 1 mit einem ersten Ausführungsbeispiel eines erfindungsgemäßen Formrings;

Figur 2a

eine vergrößerte Darstellung der Einzelheit IIa gemäß Figur 2;

Figur 3

die schematische Schnittdarstellung eines zweiten Ausführungsbeispiels eines erfindungsgemäßen Formrings;

Figur 4

eine schematische Schnittdarstellung eines dritten Ausführungsbeispiels eines erfindungsgemäßen Formrings;

Figur 5

einen Schnitt durch ein viertes Ausführungsbeispiel eines erfindungsgemäßen Formrings; und

Figur 6

eine Ansicht des Formrings der Figur 5 gemäß der Schnittlinie VI-VI.

The invention is explained in more detail below with the aid of a number of exemplary embodiments which are shown in the drawing in a schematic manner. Here show:

Figure 1

a sectional view of a pressing device according to the invention limited to the essential components;

Figure 2

a detailed enlargement of the representation of Figure 1 with a first embodiment of a molded ring according to the invention;

Figure 2a

an enlarged view of detail IIa of Figure 2;

Figure 3

the schematic sectional view of a second embodiment of a molded ring according to the invention;

Figure 4

is a schematic sectional view of a third embodiment of a molded ring according to the invention;

Figure 5

a section through a fourth embodiment of a molded ring according to the invention; and

Figure 6

a view of the form ring of Figure 5 along the section line VI-VI.

Figure 1 shows a simplified representation of the device according to the invention for the production of a socket pipe molding. The device comprises a substantially hollow cylindrical pressure pot 11, the lower region 3 is widened and vertical bores 4 has, for example, to fix the device on a Serve under table (not shown). Inside the pressure pot 11 is An inner core 13 is provided coaxially, which can be pulled out in the axial direction is. In the embodiment shown in Figure 1 is the inner core 13 together with a lower stamp 5, on which it rests, lowerable. The lower punch 5 can be designed, for example, as a nut be in which the inner core 13 with one in its lower Area provided external thread can be screwed.

At the upper end of the cylindrical outer wall 2 is an upper punch 15 is provided, which can be lowered onto the pressure pot 11.

Between the pressure pot 11 and the inner core 13 is concentric a rubber-elastic membrane 14 arranged by means of membrane holders 7, 8 is held. Together with the inner core 13 the rubber-elastic membrane 14 includes a mold cavity 12, in the lower region of which a molding ring 20 is introduced, which over an interposed spacer 9 rests on the lower punch 5.

The shaped ring 20 has an end region with a reduced diameter 21, which lies in the illustration of Figure 1 above. This end area 21 is used to form two concentric, but in the axial direction spaced end faces 22a, 22b (see also Figures 2 to 4).

The rubber-elastic membrane 14 borders with the pressure pot 11 Pressure chamber 16 from. In this pressure chamber 16 there is a cylindrical one Insert 10 is provided, on which the rubber-elastic membrane 14th abuts and which has a plurality of radial bores 18. Means A hydraulic pressure source (not shown) becomes the pressure chamber 16 pressurized. For pressurizing the Pressure chamber 16, radial bores 19 are provided in the pressure pot 11, wherein the lower radial bore in the drawing of Figure 1 19a serves the oil supply, while the upper radial bore 19b Oil drain is used. About the radial bores 18 of the insert 10 the pressure on the rubber-elastic membrane 14 is directed towards of the inner core 13 is deflected and thereby into the mold cavity 12 filled molding compound compressed and compressed so that a Socket pipe molding 40 is formed.

The representation of Figures 1 and 2 shows the device according to the invention after isostatic pressing, i.e. the rubber-elastic membrane 14 is in its non-pressurized idle state and the socket pipe molding 40 located in the mold cavity 12 finished pressed. The socket pipe molding 40 becomes the hollow cylindrical Pressure pot 11 removed by the inner core 13 together with the Lower punch 5 and the ring 20 resting thereon lowered becomes.

For a more detailed explanation of the shaped ring 20 according to the invention, in Figure 2 shows an enlarged detail according to the dash-dotted section shown in Figure 1. There are the same elements with the provided with the same reference numerals.

In the enlarged illustration in FIG. 2, the diameter is clearly shown reduced end region 21 of the shaped ring 20 can be seen. By the reduction in the diameter of this end region 21 will be two concentric but axially spaced end faces 22a, 22b formed in the illustrated embodiment of the invention Device with a lowerable inner core 13 as standing surfaces serve for the socket pipe molding 40. According to the invention, at least the upper end face 22a of the shaped ring 20 in the region of the Shoulder 41 of the socket pipe molding 40 a surface 24 from a elastic plastic. In the embodiment shown in Figure 2 have both concentric end faces 22a, 22b Surfaces 24 made of elastic plastic.

With the elastic plastic for the end faces 22 of the molded ring 20 it is in particular a high-molecular plastic, for example polyamide 6.6.

The upper end region of the molding ring 20 is on the inner diameter of the molded ring 20 is provided with a stepped shoulder 23 which abuts an associated edge of the inner core 13. Paragraph 23 has a horizontal contact surface that is offset along the circumference arranged radial grooves 23a is provided. On par with the Radial grooves 23a, the inner core 13 has a radial vent hole 17 on.

As can be seen particularly clearly from FIG. 2a, is the elastic one Surface 24 of the upper end surface 22a of the mold ring 20 on the inside Diameter formed with a lip-shaped projection 24a. in the installed state delimits the upper end region of the molded ring 20 with the inner core 13, an annular gap 42, which with the radial vent hole 17 communicates. Here is the gap width of the annular gap 42 depends on the pressure prevailing in the mold cavity 12. Depending on the pressing pressure present in the mold cavity 12, the Annular gap 42 released or closed, so that the inner core side Pressure on the blank 40 can be compensated.

FIG. 3 shows a representation corresponding to FIG. 2 as a further one Embodiment of the invention a form ring 20, the im Diameter reduced end region 21 a coating 25 made of elastic Has plastic. Thus, the entire is the sleeve area of the socket pipe molding 40 forming end region 21 made of elastic Plastic, so that the risk of cracking is further reduced becomes. The elastic coating is also used in this variant 25 in the area of the upper end face 22a with a lip-shaped Approach 25a formed.

A third exemplary embodiment of a shaped ring 20 according to the invention is correspondingly shown in Figure 4, in this embodiment the end region 21 of the molded ring 20 with a sleeve 26 an elastic plastic is formed. The sleeve 26 can simply be placed on the end region 21 of the shaped ring 20 and advantageously if necessary, for example when the Sleeve 26 or other shape in the socket area, exchanged become.

Figure 5 shows a sectional view through a fourth embodiment a shaped ring 20 which according to the invention has a diameter reduced end portion 21 to form two concentric, however has axially spaced end faces 22a, 22b, wherein the entire form ring 20 consists of an elastic plastic. in the Area of the shoulder 23 are radial grooves 23a on the horizontal Support area provided. The radial grooves 23a are axial grooves 43 assigned, which run on the inner diameter of the mold ring 20. The axial grooves 43 go into radial grooves at the lower end of the form ring 20 44 over. In this exemplary embodiment, therefore, the ventilation takes place of the mold cavity 12 via the between the mold ring 20 and Inner core 13 present annular gap, the radial grooves 23a, the axial grooves 43 and the radial grooves 44.

FIG. 6 shows a top view of the form ring 20 according to FIG. 5 the section line VI-VI. To simplify the illustration, FIG only one half of the form ring 20 is shown. For further better ventilation of the mold cavity 12 has the mold ring 20 along its outer diameter axially extending ventilation grooves 27. At The ventilation grooves 27 are regularly along the Distributed axially extending flats of the ring circumferential surface. For a better illustration is the outer surface of the form ring 20 is dashed at the locations of the flats shown (see also Figure 5). Through the axially extending ventilation grooves 27 is the mold cavity 12 after isostatic pressing ventable.

In the embodiment shown in Figures 5 and 6 acts it is the preferred embodiment.

Below is the operation of the above Device explained. First, with the upper stamp removed 15 the ceramic molding compound in the mold cavity 12 in a suitable Quantity introduced. Then the upper stamp 15 with the Pressure pot 11 reconnected. For isostatic pressing of the molding 40, the pressure chamber 16 is acted upon by hydraulic oil. Here the hydraulic oil passes through the radial bores 18 of the insert 10 on the rubber-elastic membrane 14. This is then in the direction of the inner core 13 deflected, thereby compressing the molding compound is so that the socket pipe molding 40 is formed.

In isostatic pressing, it is pressed against the elastic surface 24 pressed according to Figures 1, 2 and 2a. In the embodiments 3, 4 and 5, the pressing takes place as a whole Sleeve area against an elastic surface.

The mold cavity 12 is vented during the pressing process. Here the venting takes place via the annular gap 42, which is in the region of the Paragraph 23 of the end portion 21 of the mold ring 20 and the inner core 13 is limited. Via the annular gap 42 takes place depending on Pressing pressure to vent the mold cavity 12.

The measures listed above can in the area of Shoulder 41 of the socket pipe molding 40 micro cracks can be prevented. Such microcracks widen when the molding burns, which creates defective socket pipes.

Claims (10)

1. A method of manufacturing bell and spigot pipe moldings from a ceramic molding compound by isostatic pressing, in which the molding compound to be pressed is inserted into a molding cavity (12) within a hollow-cylindrical pressure pot (11), said molding cavity (12) being provided between an inner core (13) extractable axially and an elastomeric diaphragm (14) arranged concentrically to the latter, said elastomeric diaphragm (14) being clamped in place at the face end and defining by the pressure pot (11) a pressure chamber (16) exposed to a source of hydraulic pressure, said inner core (13) being provided with a molding ring (20) forming the bell region (41) of the bell and spigot pipe (40), said molding ring comprising two face end surface areas (22a, 22b) which are concentric but spaced away from each other axially, characterized in that the molding compound in the bell region (41) of said molding is pressed against a surface (24) of an elastic plastics material provided at least on the upper face surface area (22a) of said molding ring (20), the end region (21) of said molding ring (20) defining by the inner core (13) an annular gap (42) which during pressing releases or closes at least one vent port (17) communicating with said molding cavity (12), depending on the pressing force existing in said molding cavity (12).
2. A method as set forth in claim 1, characterized in that said elastic surface (22a) of said molding ring (20) elastically supports the bell region (41) of the bell and spigot pipe (40) during pressing.
3. An apparatus for manufacturing bell and spigot pipe moldings, particularly for performing a method as set forth in claim 1 or claim 2, in which within a hollow-cylindrical pressure pot (11) a molding cavity (12) for the molding compound to be pressed is provided between an inner core (13) extractable axially and an elastomeric diaphragm (14) arranged concentrically to the latter, said diaphragm being clamped in place at the face end and defining by the pressure pot (11) a pressure chamber (16) exposed to a source of hydraulic pressure, said inner core (13) being provided with a molding ring (20) forming the bell region (41) of the bell and spigot pipe (40), said molding ring (20) comprising an end region (21) reduced in diameter for forming two face end surface areas (22a, 22b) which are concentric but spaced away from each other axially, characterized in that at least said face surface area (22a) of said end region (21) of said molding ring (20) forming the bell region (41) comprises a surface (24) of an elastic plastics material and said end region (21) of said molding ring (20) defines by the inner core (13) an annular gap (42) which, depending on the pressing force releases or closes a vent port (17) provided on said inner core (30) communicating with said molding cavity (12).
4. The apparatus as set forth in claim 3, characterized in that said end region (21) of said molding ring (20) comprises a coating (25) of an elastic plastics material.
5. The apparatus as set forth in claim 3 or claim 4, characterized in that the complete molding ring (20) consists of an elastic plastics material.
6. The apparatus as set forth in claim 3 to 5, characterized in that said end region (21) of said molding ring (20) is configured by a sleeve (26) of an elastic plastics material.
7. The apparatus as set forth in claim 3 to 6, characterized in that said elastomeric diaphragm (14) features a region adjoining said molding ring (20).
8. The apparatus as set forth in any of the claims 3 to 7, characterized in that said inner core (13) is configured tubular.
9. The apparatus as set forth in any of the claims 3 to 8, characterized in that said molding ring (20) is provided with vent grooves (43) oriented axially.
10. The apparatus as set forth in any of the claims 3 to 9, characterized in that said elastic plastics material is a high-molecular plastics material, particularly polyamid 6.6.

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