EP0317720B1 - Process for making sanitary articles, in particular wash stands, by moulding under pressure, and apparatus for performing the method - Google Patents

Description

The invention relates to a method for the production of sanitary articles, in particular washstands by die casting according to the preamble of claim 1 and a device for carrying out this method according to the preamble of claim 8.

Known presses used for the manufacture of washstands for toilets by die-casting ceramic slip have two mold halves delimiting a mold cavity between them, which can be moved together into their closed position by means of clamping plates.

For the production of ceramic articles by die casting, it is known (DE-A-33 19 012) to close two mold halves, for which purpose one of the mold halves is arranged on movable rods which can be moved in the direction of the other mold half held stationary. In the closed position of both mold halves, they are fixed by clamps which grip over the outer flanges provided on the outside of the mold halves. The mold halves are made of a special material so that drainage of the ceramic slip introduced into the mold cavity is possible when pressure is applied. The disadvantage of this known Device consists in that the slip within the mold cavity is displaced to the outside as a result of the casting pressure via the joint between the two mold halves, which is favored by a limited flexibility of the special material of the two mold halves designed as a filter element. This not only causes a corresponding burr on the ceramic articles produced, but, depending on the amount of ceramic slip displaced, there are thickness deviations in the end product itself, which very often results in a rejection of the articles produced.

In order to counter this disadvantage, presses have been developed for the manufacture of washstands for toilets by die-casting ceramic slip, in which the mold halves can be moved together into their closed position by means of clamping plates.

The two clamping plates carrying the mold halves are moved together hydraulically by means of corresponding column guides. In order to ensure the pressure casting of sanitary articles, such as in particular washstands, a special material is used for the mold halves (EP-A 0 089 317). This is a porous plastic, the porous areas of which are connected to one another in order to allow both pressure build-up and pressure relief during the production process, in particular to remove the residual water from the broken pieces. In particular, after closing the mold, slip is filled into the mold cavity under pressure, after which the pressure inside the mold is increased to a casting pressure in order to accelerate the formation of the body. At the same time, the water becomes solidification the body of the body is discharged to the outside. By supplying compressed air to the back of the mold, a water film forms between the cullet and the mold due to the residual water present in the mold, which enables the body to be detached from the mold.

Due to the special porous plastic material required for the formation of the mold halves during die casting, which can be deformed within limits, there are special features that must be observed for the procedure. Since the slip within the mold cavity due to the casting pressure tries to escape from the mold cavity via the joint between the two mold halves, which is favored by a limited flexibility of the material of the mold halves, both mold halves must be pressed together under great pressure. The closing pressure to be applied by the press must in each case be higher than the counter pressure building up within the mold in order to ensure that the mold is closed at all times. However, since the pressure conditions within the mold cavity change during the casting process, in the known presses a corresponding compensation is provided for by a complex position control via the hydraulic closing pressure of the clamping plates in order to ensure that both mold halves fit tightly at just enough high pressure at all times. The readjustment required for this primarily serves to protect the mold halves, since tolerance deviations that can never be completely avoided at high closing pressures can lead to high local peak loads, especially edge pressures above the sealing or separating surface of the two mold halves. For this reason, the aim is to keep the clamping force only as high as it is due to the back pressures building up in the mold is required to close the mold.

The object of the invention is a for the die casting of sanitary ware, in particular washstands and. To create a suitable method which can be carried out simply and without great expenditure on control technology, the device for carrying out this method being distinguished by an extremely simple, robust and easy-to-use structure.

In procedural terms, this object is achieved by the features contained in the characterizing part of patent claim 1.

In terms of device technology, this object is achieved by the features contained in the characterizing part of patent claim 8.

Appropriate further developments of the method and the press are characterized by the features contained in the subclaims.

According to the invention, a hydraulic feed and readjustment of the clamping plates is dispensed with because an air cushion is used for the infeed movement of the clamping plates that support the mold halves, which allows good adaptation to the geometry of the shape and the course of the separating surface and thus tolerances-related inaccuracies easily can compensate. In this respect, the mold is spared when carrying out the process, which ensures a long service life of the mold. Due to the delivery of the mold halves in the closed position of the Press elements are used to move the platen into the closed position of the press, which are suspended from a portal frame, and the simplest drives can be used to adjust the press elements relative to each other. In particular, the relative adjustment of the two press elements to one another can be carried out by means of a pneumatic piston / cylinder drive.

Overall, this results in a simplification of the structure because, unlike in the case of a column guide, no large pressure force, which is introduced at certain points, has to be distributed onto a plate which carries the mold halves, which would lead to a correspondingly solid and rigid design.

The operability of the press is also simplified accordingly. For the operation of the press, only the two clamping plates are moved together in the closed position of the press, which can be done manually or automatically, after which the press elements carrying the two clamping plates are then mechanically locked relative to one another. The mold is then actually pretensioned via the air cushion, to which constant pressure is applied, so that there is no need to readjust the pressure applied to the air cushion. The simple feed movements mean that the column guides required in the presses previously used can be eliminated.

Expediently, only one of the clamping plates can be moved into the closed position of the press, whereas the other remains fixed on the associated press element. As a result, the feed movement for closing the press on a component, namely on one of the press elements, which holds the platen firmly.

The movable platen with the associated press element is expediently suspended on a slide which can be moved along simple guide rails by rolling on a portal of the press.

For the process control according to the invention, it is advantageous that the ceramic slip, after the mold has been filled, is kept at a pressure which is lower than the casting pressure, the so-called filling pressure, for a predetermined period of time. It has been shown that a first solidification of the body is achieved at this filling pressure, which is advantageous for sealing the separation gap between the two mold halves. This ensures that the mold material is protected since, when slurry penetrates into the area of the separating surface of the two mold halves, the mold material is gradually destroyed due to the abrasive slip particles. After the first solidification as a result of the filling pressure, the casting pressure is then gradually built up and held for a period of time dependent on the material used and the object to be produced.

The press is characterized by very simple components, since only a clamping plate which is firmly connected to a press element is moved on guide rails via a roller-guided slide, for which purpose hardened guide strips with a rectangular cross section can be used. The mechanical locking elements and the air cushion are also mechanically simple and therefore inexpensive components. Has proven to be advantageous as To use locking elements tabs that can be retracted into appropriately designed forks on the other press element and locked with the forks by the simplest locking bolts.

The air cushion is expediently arranged between the stationary press element and the clamping plate arranged thereon, because the slide structure and the weight of this additional component can then be reduced. Since the slide is guided on a portal-like frame, a self-contained structure results in connection with the lateral press elements and the press base, which is advantageous for absorbing the forces within the press.

Advantageously, the platen, which can be adjusted via the air cushion, is guided in parallel into the closed position of the mold by a parallelogram link. An additional articulated mounting of the platen on the parallelogram enables self-alignment of the mold half braced on the platen in the end position, that is, the closed position of the mold, so that a good possibility of adaptation is ensured. A spherical joint is used here as an articulated mounting, which enables the clamping plate to pivot out of a plane perpendicular to the direction of movement of the clamping plate guided in parallel.

• Fig. 1 eine Seitenansicht einer Ausführungsform einer Presse nach der Erfindung,
• Fig. 2 eine Ansicht entsprechend Schnitt nach Linie A-B in Fig. 1, sowie
• Fig. 3 eine Draufsicht auf die Presse nach Fig. 1.

An exemplary embodiment of the invention is described below with reference to the drawing. In it show:

• 1 is a side view of an embodiment of a press according to the invention,
• Fig. 2 is a view corresponding to section along line AB in Fig. 1, and
• 3 is a plan view of the press of FIG. 1st

According to Fig. 1, the press comprises two opposing press elements 3 and 3a, of which the press element 3 is arranged in a stationary manner and at the top through a portal-like structure 4 with a press stand 2 also arranged stationarily on the press base 1 to form a in the plane of the drawing according to Fig. 1 all-round closed press assembly is connected. In the interior of the press, which is completely freely accessible from the two broad sides (FIG. 1), two clamping plates 5 and 6 are arranged, which serve to accommodate the mold halves not shown in the drawing. For this purpose, the surfaces of the clamping plates 5 and 6 which are to face one another are provided with T-grooves which are continuous over the entire length, as can best be seen from the view in FIG. 2.

The press element 3a shown on the left in FIG. 1, with which the clamping plate 5 is firmly connected and is arranged behind the stiffening struts 7 converging in a V-shape, is suspended on a carriage 8. The carriage 8 is guided by rollers 9 on two guide rails 10 and 11 arranged on the portal-like structure 4. To stabilize the carriage movement, laterally arranged rollers 12 are also provided. This ensures smooth guidance of the platen 5 or the corresponding press element 3a relative to the opposing platen 6, so that the feed movement of the platen 5 into the closed position of the press can even be carried out manually. In order to automate the Infeed movement, however, a pneumatic piston / cylinder unit 13 can be provided, which is fastened on one side to a frame 14 of the slide 8 and on the other hand to the opposite press element 3 with the other end.

The opposite clamping plate 6 is arranged on the stationary press element 3, but is movable relative to this press element 3. For this purpose, an air cushion 15, shown in dashed lines in FIG. 1, is arranged between the clamping plate 6 and the stationary press element 3, which is acted upon pneumatically and advances the clamping plate 6 relative to the opposite mold half to close the two mold halves after the press is closed. The maximum feed movement of the air cushion 16 is 20 mm. The parallel movement of the platen 6 in relation to the stationary press element 3 takes place via a parallelogram link 16, which can be seen in FIG. 1 and is suspended at the top of the portal structure 4. For safety reasons, the air cushion 16 is covered on the outside by a cover 17. As indicated in FIG. 1, the air cushion 15 extends essentially over the overlap area of the mold half and the associated clamping plate 6. Moreover, the stationary press element 3 is stiffened equally by struts 7 tapering in a V-shape. The platen 6 is finally articulated on the parallelogram guide 16, so that the platen 6 can be pivoted in the advanced end position from a plane perpendicular to the direction of movement of the platen. This results in an automatic alignment of the clamping plate 6, which is advanced parallel to the end position, as a result of which a uniform surface pressure is achieved over the entire sealing surface of the mold (parting line). The articulated storage takes place here via a pin 25 which has a ball or a spherical part to form a ball joint with the clamping plate at its lower end. The ball joint can also be replaced by another suitable universal joint.

A total of four return springs 18 arranged in the corner area are arranged for the return movement of the clamping plate 6.

Locking elements 19 are arranged between the two press elements 3 and 3a, namely forks 20 in the corners of the clamping plate 5 and tabs 21 which can be inserted into the forks in the corners of the press element 3. In the closed position of the press, that is to say when the mold halves are moved together on impact, the tabs are 21 fully retracted into the forks 20. Corresponding cross bores in the forks 20 and in the brackets are aligned with one another in such a way that corresponding locking bolts can be inserted laterally into the aligned cross bores and the two press elements 3, 3a are mechanically rigidly locked in their position. In Fig. 1, only the cross bores 22 are shown in the tabs, because the cross bores in the forks, the axis of which is identified by the axis cross 23, are not visible from the outside. This mechanical rigid locking of the two press elements is essential, because in this way the counterforce during the feed movement of the platen 6 is applied via the air cushion 15.

There are also suitable hydraulic shock absorbers on the press, which serve as a stop for the end positions of the clamping plates, only one of the shock absorbers 24 being shown in FIG. 1. The pump for the slip supply is shown on the right in FIG. 1, the various feed and return lines likewise being shown at the bottom right, but not are explained in more detail here. A double diaphragm pump is expediently used as the pump.

The operation of the press is as follows. To close the press, the platen 5 is advanced relative to the stationary press element 3. In this closed position of the press, the locking elements 19 have moved so far into one another that the transverse bores are aligned with one another. The mechanical locking then takes place by inserting locking bolts into the transverse bores, so that the press elements 3 and 3a are locked to one another in a fixed position.

Then the actual closing movement of the two mold halves takes place in order to close the mold, namely by appropriate pressurization of the air cushion, by means of which the clamping plate 6 is pressed away from the stationary press element 3 in the direction of the clamping plate 5 or the mold half arranged thereon, specifically with constant pressurization, the pressure being essentially dependent on the size of the mold, the sealing surface size of the mold and the component to be produced, but is approximately 5 to 9 bar. In the closed position of the two mold halves, the slip is then introduced, the slip is acted upon by the filling pressure, and after a predetermined holding time the pressure rises to the casting pressure, but the fixed pressure between the mounting plates is kept constant over the air cushion. A readjustment of the closing pressure of the mold halves depending on the pressure conditions of the slip within the mold is therefore not necessary.

Claims (18)

1. Method for making sanitary articles, in particular washstands, consoles and the like, by pressure casting, by which ceramic slip is introduced under pressure into a mold cavity formed by in particular two mold parts made of porous plastic material, disposed on appropriate plate-like mounting means of a press, said mold parts being arranged on mounting plates of a press which are supported by press elements, the slip located in the mold cavity being brought to casting pressure after the mold is filled, so that the slip comes to lie against the inside of the mold to form a body, and water is removed from the body to the outside via the porous mold parts, the residual slip being displaced by supplying compressed air to the mold cavity, and the mold parts finally being detached from the body, characterized in that both mold parts together with the press elements are moved relative to each other to close the press, that the two press elements are locked together rigidly relative to each other in the closed position of the press and that thereafter the mold is biased by an air cushion.

2. Method according to claim 1, characterized in that to close the press one of the mold parts together with its press element is moved toward the other mounting plate disposed on a stationary press element.

3. Method according to claim 2, characterized in that the closing motion is effected pneumatically.

4. Method according to any of the preceding claims, characterized in that to close the mold one of the mold parts together with the corresponding mounting plate is pressed by the air cushion away from the press element bearing the mounting plate toward the other mold part which is held stationary in the closed position of the press.

5. Method according to any of the preceding claims, characterized in that the maximum feed motion caused by the air cushion is less than or equal to 20 mm.

6. Method according to any of the preceding claims, characterized in that after the mold has been filled, the slip is held for a predetermined time period at a pressure lower than the casting pressure (the so-called filling pressure) and thereafter the pressure is slowly increased to the casting pressure.

7. Method according to claim 6, characterized in that the filling pressure is held for a time span of 5 to 10 seconds and is about 3 to 5 bar, and that the pressure is increased over a time span of 10 to 30 seconds to the casting pressure of about 15 to 20 bar and the casting pressure is held for a time span of about 360 to 500 seconds.

8. Press for carrying out the method according to any of the preceding claims, comprising mounting plates disposed on press elements for taking up the mold parts which are movable relative to each other into the closed position of the press along a guide means, characterized in that one of the two press elements (3, 3a) is suspended on a slide (8) movable along guide rails (10, 11) and the other press element (3) is stationary, that one of the two mold parts is capable of being advanced relative to the associated press element (3) toward the other mold part by an air cushion (15) disposed between a mounting plate (6) and the associated press element (3) located therebehind, and in that the two press elements (3, 3a) have locking elements (19 to 23) engaging each other in the closed position of the press.

9. Press according to claim 8, characterized in that the air cushion (15) extends substantially over the entire area where the mold part and corresponding mounting plate (6) overlap.

10. Press according to claim 8 or 9, characterized in that the air cushion (15) is disposed between the stationary press element (3) and the mounting plate (6) disposed thereon.

11. Press according to any of claims 8 to 10, characterized in that the slide (8) is suspended on a horizontal, portal-like frame (4) of the press via rolls (9, 12).

12. Press according to any of claims 8 to 11, characterized in that the slide (8) is connected with the press element (3) bearing the opposite mounting plate (6) by at least one pneumatic piston/cylinder aggregate (13).

13. Press according to any of claims 8 to 12, characterized in that the locking elements (19 to 23) each have a fork (20) and a shackle (21) to be moved into the fork, which are both provided with transverse bores (22) aligned with each other in the closed position of the press to take up a lock bolt.

14. Press according to claim 13, characterized in that the four forks (20) and shackles (21) are arranged so as to point toward each other, the forks (20) being disposed on the mounting plate (5) movable with the slide (8), and the shackles (21) being disposed on a plate fixed with the press element (3).

15. Press according to claim 13 or 14, characterized in that the shackles (21) or forks (20) are adjustable relative to the press element (3).

16. Press according to any of the claims 8 to 15, characterized in that restoring springs (18) for the mounting plate (6) are disposed between the mounting plate (6) to be advanced by the air cushion (15) and the associated press element (3).

17. Press according to any of the claims 8 to 16, characterized in that the mounting plate (6) to be advanced by the air cushion (15) is moved parallel with regard to the associated press element (3) by a parallelogram linkage (16).

18. Press according to claim 17, characterized in that the mounting plate (6) is hinged to the parallel guide means in such a way as to be pivotable in the end position, for the purpose of self-alignment, out of a plane vertical to the moving direction of the mounting plate (6).

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