EP0480430B1 - Process and apparatus for making ceramic hollow articles with lateral appendix, in particular cups with handle - Google Patents

Description

The invention relates to a method according to the preamble of claim 1 and a device according to the preamble of claim 5.

From DE-A-33 04 576 a pressing tool is known with which a cup-shaped ceramic hollow body is to be pressed together with a side attachment in the form of a handle in one operation from free-flowing ceramic mass. The device has a lower molded part designed as a male part, over which a cup-shaped first membrane is placed, and two upper molded parts, which can be placed against one another in a meridian plane of the hollow body to be pressed and its handle-shaped attachment and together form a female part. A core can be displaced in the matrix transversely to this meridian plane, around which a tubular second membrane extends in the meridian plane for isostatic pressing of the handle-shaped attachment. Both membranes delimit the part of the mold cavity assigned to them from the inside. Above the cup-shaped first Membrane is a pressure ram which, in an upper position pulled out of the die, releases a filling channel for free-flowing ceramic mass and an evacuation channel. In each working cycle, the common mold cavity for the cup-shaped hollow body and its handle-shaped attachment are filled with ceramic mass from above. The plunger is then lowered into the die so that it closes off the mold cavity. Pressure oil is then introduced under the cup-shaped first membrane and into the tubular second membrane, so that the ceramic mass of both membranes is pressed isostatically against the cup-shaped or handle-shaped inner walls of the male part. After the isostatic pressing, the plunger is moved up a little, the core with the second membrane is pulled out of the associated part of the mold cavity and the two mold parts of the die are moved apart so that the hollow body pressed in one piece with its handle-shaped attachment is removed can.

As is known, isostatically pressed moldings expand as soon as they are relieved of the pressure. In the known pressing tool described above, this has the result that tensions arise between the outer walls of the hollow body and its handle-shaped extension and the complementary inner walls of the molded parts forming the die, so that the molded article is damaged as soon as it is removed from the molding tool or during subsequent firing Can get cracks.

These dangers are eliminated in another pressing tool known from DE-A-36 26 365 for isostatic pressing of cup-shaped ceramic hollow bodies with a lateral attachment, in particular handle cups, largely avoided. There, too, a lower molded part is designed as a male; however, a one-piece upper molded part, which is lined with a single membrane for isostatic pressing, serves as the die. The membrane forms the outer surface of the ceramic hollow body to be pressed as well as the inner surface and part of the outer contour of the associated handle-shaped extension. The remaining part of the contour of the approach is formed by a rigid support part which is inserted into the male. The result of this is that the handle-shaped attachment in the region of this part of the contour cannot be uniformly compressed isostatically, which can also result in malformations during pressing or cracks during the subsequent firing.

The invention is therefore based on the object to provide an isostatic pressing method and a device suitable for carrying out the method, with which ceramic hollow bodies with a lateral attachment, in particular handle cups, can be pressed in such a way that damage occurs during removal and also during subsequent firing of the pressed moldings can be avoided with greater certainty.

The object is, insofar as it relates to the method, according to the invention, based on a method according to the preamble of claim 1, achieved in that a hollow body is produced without an attachment in a first operation and the attachment is produced in a second operation and thereby by the isostatic pressing pressure with the Hollow body is connected.

Advantageous further developments of the method according to the invention result from claims 2 to 4.

• mindestens eines der gegeneinander beweglichen Formteile eine Anlagefläche für den gesondert hergestellten Hohlkörper aufweist,
• der Formhohlraum mindestens eine in dieser Anlagefläche liegende Mündung aufweist und
• zum Anlegen des Hohlkörpers an die Anlagefläche mindestens ein Stützkörper vorgesehen ist.

As far as the object relates to the device, it is achieved according to the invention based on a device according to the preamble of claim 5 in that

• at least one of the mutually movable molded parts has a contact surface for the separately produced hollow body,
• the mold cavity has at least one mouth lying in this contact surface and
• at least one support body is provided for placing the hollow body on the contact surface.

Advantageous further developments of the device according to the invention result from claims 6 to 9.

Fig. 1

einen Meridianschnitt eines Formwerkzeugs zum isostatischen Pressen becherförmiger Hohlkörper;

Fig. 2

einen entsprechenden Meridianschnitt eines Formwerkzeugs zum isostatischen Pressen henkelförmiger Ansätze;

Fig. 3

den Querschnitt III-III in Fig. 2;

Fig. 4

einen der Fig. 2 entsprechenden Meridianschnitt mit weiteren Einzelheiten;

Fig. 5

den Querschnitt V-V in Fig. 4 in einer Preßstellung;

Fig. 6

einen entsprechenden Querschnitt in einer Entnahmestellung.

An exemplary embodiment of a device according to the invention is explained in more detail below with the aid of schematic drawings. Show it:

Fig. 1

a meridian section of a mold for isostatic pressing cup-shaped hollow body;

Fig. 2

a corresponding meridian section of a mold for isostatic pressing of handle-shaped approaches;

Fig. 3

the cross section III-III in Fig. 2;

Fig. 4

one of FIG. 2 corresponding meridian section with further details;

Fig. 5

the cross section VV in Figure 4 in a pressing position.

Fig. 6

a corresponding cross-section in a removal position.

The device shown is used for isostatic pressing of cups, each consisting of a cup-shaped hollow body 10 with, for example, a cylindrical outer wall 12 and a bottom 14 and a shoulder 16 fastened to the wall 12. The approach 16 has shown in the Example, the shape of a conventional cup handle with two connecting surfaces 18 with which it is attached to the wall 12.

The molding tool 20 shown in FIG. 1 is provided for isostatic pressing of the cup-shaped hollow body 10. Its main components are a plate 22 which is to be fastened in the usual way to a table (not shown) of a preferably lying press and has an essentially cylindrical recess 24 and a fluid channel 26 opening into it. In the recess 24, a shaped part 28 is received, in which an elastic membrane 30 is inserted. This is clamped on its outer edge between a support ring 32 and a clamping ring 34 which is fastened to the plate 22 with screws 36.

The membrane 30 has a substantially concave inner surface, which points to the left in FIG. 1, which is complementary to the outer surface of the hollow body 10 to be pressed, and a rear surface which rests on the molded part 28 when the membrane is at rest. The molded part 28 contains channels 38 which connect the fluid channel 26 to the rear of the membrane 30. The fluid channel 26 can, as usual, be connected alternately to a vacuum source and to a pressure oil source, so that the membrane 30 can be sucked into the molded part 28 during each operating cycle and then pressed away from it.

The molding tool 20 also has a plate 40 shown on the left in FIG. 1, which is to be fastened to a ram 42 of the press mentioned only and has on its side facing the molded part 28 a molded part 44 designed as a male part, the surface of which towards the inner surface of the pressing hollow body 10 is complementary.

Between the membrane 30 and the molded part 44, a mold cavity 46 is formed, which can be filled through a filling channel 48 with free-flowing ceramic mass of the usual grain size.

A further molding tool 50 is provided for isostatic pressing of the projection 16, which is shown individually in FIGS. 2 and 3. The main component of the molding tool 50 is a lower plate 52 in the example shown with a recess 54 into which a fluid channel 56 opens and in which a molding 58 designed as a die is received. On the molded part 58 there is a membrane 60, the outer edge of which is clamped between an annular shoulder 62 formed on the molded part 58 and a clamping ring 64. For this purpose, the clamping ring 64 is fastened to the plate 52 with screws 66.

The membrane 60 forms the entire outer surface of the projection 16 to be pressed and can be sucked into the molding 58 in each working cycle by channels 68 in the molded part 58, which communicate with the fluid channel 56, and then pressed away from it. In this respect, the molding tool 50 works in the usual way, as does the molding tool 20.

The mold 50 also includes two upper plates 70 and 70 ', which lie against one another in a common central plane of the cup-shaped hollow body 10 and its shoulder 16, which is referred to as the meridian plane M when the mold 50 is closed, as in FIGS. 2 and 3 and also shown in Figs. 4 and 5. The two plates 70 and 70 'are suspended from a common support body 72 and guided in such a way that they can be displaced towards and away from one another normal to the meridian plane M, symmetrical to the latter.

A molded part 74 and 74 'is formed on the underside of each of the two plates 70 and 70'; these two molded parts together form a male part which, together with the membrane 60, delimits a mold cavity 76 for the isostatic pressing of the handle-shaped extension 16. The mold cavity 76 has two openings 78 which lie in a hollow cylindrical contact surface 80, 80 'formed on the upper side of the two plates 70 and 70'.

Through the mouths 78, the mold cavity 76 can be filled with free-flowing ceramic mass. For this purpose, a filling device can be used, which can be placed on the contact surface 80, 80 'and has two outlets which can be brought into register with one of the two coins 78.

At least two vertical bolts 82 are fastened to the lower plate 52, which have a dimensionally ground surface and are each guided in a correspondingly machined bushing 84 in the plate 70 or 70 '. Thus, the plate 52 together with the molded part 58 and membrane 60 can be applied from below in a closing movement to the two plates 70 and 70 'if these have previously been brought into the position according to FIGS. 3 and 5, in which they are in the meridian plane M lie together. Appropriate but horizontal bolts 86 and bushings 88 are provided in the illustrated example as guides for the movements of the two plates 70 and 70 'normal to the meridian plane M.

Before an attachment 16 can be pressed in the molding tool 50 shown separately in FIGS. 2 and 3, the orifices 78 of the mold cavity 76 filled with ceramic granulate must be closed. This is done in that a cup-shaped hollow body 10 previously pressed in the mold 20 according to FIG. 1 with its cylindrical outer wall 12 is pressed tightly onto the mouths 78. For this purpose, the hollow body 10 is removed from the mold 20 and clamped between a support body 90 penetrating into it and a counter-holder 92 placed on its base 14 from the outside and then brought into the position according to FIGS. 4 and 5.

Support body 90 and counter-holder 92, both of which have a cylindrical outer surface, are displaceably guided in a piston-like manner in a cylinder bore 94 of the support body 72 and are each connected to a hydraulic or pneumatic piston-cylinder unit 96 or 98. These are controlled in such a way that the cup-shaped hollow body 10 remains firmly clamped between the support body 90 and the counter-holder 92 during the movement into the position according to FIGS. 4 and 5.

For the isostatic pressing of the attachment 16, pressure oil is passed through the fluid channel 56 and further through the channels 68 to the underside of the membrane 60, as is customary in isostatic pressing. A special feature of the device shown is that the projection 16, while it is pressed isostatically, is simultaneously pressed against the previously pressed hollow body 10 and connected to it to form a unit without the uniformity of the isostatic pressure being impaired thereby.

The space below the membrane 60 is then relieved of pressure oil and placed under vacuum. The plate 52 together with the molded part 58 and the membrane 60 is then pulled down, as a result of which the pressed attachment 16 is exposed in the region of its outer circumference up to two planes parallel to the meridian plane M. Then the two molded parts 74 and 74 'are moved apart transversely to the meridian plane M, so that the extension 16 also in the area of its inner circumference up to the two named planes parallel to the meridian plane M is exposed. Then support body 90 and counter-holder 92 are moved together out of the cylinder bore 94 of the support body 72 and finally moved apart, so that the cup-shaped hollow body 10 with a pressed handle-shaped extension 16, that is to say a complete handle cup, can be removed.

The approach 16 only needs to be deburred; for this purpose it is generally sufficient to pass it between two parallel grinding belts or the like in order to remove the burrs formed between the membrane 60 and the two shaped parts 74 and 74 '. The outer peripheral surface of the extension 16 does not require any post-processing, since it has only been formed by the membrane 60. On the inner circumferential surface of the extension 16 there is generally no disturbing burr if the two molded parts 74 and 74 ', as usual, are made of hard steel and therefore, even after prolonged use with the mold 50 closed, lie completely close together.

Claims (9)

1. A method of producing ceramic hollow bodies (10) with a lateral appendage (16), in particular cups with a handle, wherein the appendage is isostatically pressed from a pourable ceramic substance,
   characterized in that a hollow body (10) without appendage is produced in a first operating cycle and the appendage (16) is produced in a second operating cycle being thereby connected to the cup-shaped hollow body by isostatic pressure.
2. A method according to claim 1,
   characterized in that the hollow body (10) is also isostatically pressed in the first operating cycle.
3. A method according to claim 2,
   characterized in that during each respective pressing of a hollow body (10) in a first die (20), a second die (50) is prepared for pressing an appendage (16) by filling a mould cavity (76) of the second die (50) with a pourable ceramic substance.
4. A method according to any one of claims 1 to 3,
   characterized in that the hollow body (10) is supported at its inner surface while the ceramic substance forming the appendage (16) is subjected to isostatic pressure.
5. Apparatus for carrying out the method according to any one of claims 1 to 4, comprising mould parts (58, 74, 74') movable against each other and a membrane (60) capable of bearing fluid pressure for isostatic pressing of a pourable ceramic substance in a mould cavity (76) to form an appendage (16) of a hollow body (10),
   characterized in that

   - at least one of the mould parts (58, 74, 74') movable against each other comprises an abutting surface (80, 80') for the separately produced hollow body (10),

   - the mould cavity (76) comprises at least one opening (78) located on said abutting surface (80, 80'), and

   - at least one supporting body (90) is provided for applying the hollow body (10) to the abutting surface (80, 80').
6. Apparatus according to claim 5,
   characterized in that the supporting body (90) is adapted to fit the interior space of the hollow body (10).
7. Apparatus according to claim 6,
   characterized in that a hold-up means (92) is adapted to be applied to the hollow body (10) from the outside.
8. Apparatus according to any one of claims 5 to 7,
   characterized in that a die part (58), formed as a female die, is lined with the membrane (60) for isostatic pressing of the appendage (16).
9. Apparatus according to claim 8,
   characterized in that for pressing handle-shaped appendages (16), two die parts (74, 74'), together forming the male die, respectively comprise part of the abutting surface (80, 80') for the separately produced cup-shaped hollow body (10), the die parts being separated along a meridional plane (M) of the hollow body (10) and its appendage (16) and movable against each other normal to said meridional plane (M).

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