WO2004020184A1

WO2004020184A1 - Device and method for the production of blanks

Info

Publication number: WO2004020184A1
Application number: PCT/EP2002/009506
Authority: WO
Inventors: Robert Kremer; Stefan MÄHLER; Alfred Kaiser; Klaus Müller; Peter Morbach; Markus Pazen; Heiko Wegner; Elmar Betzler
Original assignee: Laeis Bucher Gmbh
Priority date: 2002-08-26
Filing date: 2002-08-26
Publication date: 2004-03-11
Also published as: AU2002333707A1

Abstract

The invention relates to a device for the production of blanks from flowable and/or pasty bulk material with a forming chamber (12) which is embodied in such a way that it can receive bulk material and compact bulk material received therein and which is defined at least during the compaction process by at least one forming frame provided with a forming hole and by at least one pressing tool extending from the stamping plate in the direction of at least one forming hole and which is preferably detachably fixed to a stamping plate, said tool resting upon the forming frame during the pressing process or being able to be inserted into at least one forming hole. A suctioning device, which can be operated in order to suction air from a suctioning chamber which includes said forming chamber, is also provided. Said suctioning chamber also comprises at least one sealing device which can be operated outside the forming chamber to seal the suction chamber and which is maintained on the forming frame and/or a connecting element arranged between the stamping element and a tool element of the pressing tool provided with at least one pressing surface located opposite the forming chamber.

Description

DEVICE AND METHOD FOR PRODUCING PRESSELINGS

The invention relates to a device for producing compacts from free-flowing and / or pasty bulk material with a shaping space designed for receiving the bulk material and for compressing the bulk material contained therein, which at least during the compression process has at least one mold frame having at least one mold hole and at least one in at least one a mold hole is retractable and / or is seated on the mold frame during the pressing process, is preferably releasably attached to a stamping plate and, starting from the stamping plate, is limited in the direction of at least one molding hole and a suction device operable to extract air from a suction chamber containing the shaping chamber and a shaping process that can be carried out with such a device. For the production of compacts, such as stones or plates, from free-flowing or pasty bulk material, stamp presses are usually used, in which the bulk material is compressed between two opposing sides in a mold hole of a lateral boundary surface of the shaping space forming mold or on the mold frame pressing tools becomes. The volume of the bulk material before the compression process can be 1.2 to 5 times the volume of the finished compact. The volume difference is taken up by gas stored between the individual particles of the bulk material before the compression process. During the compression process, most of this air can escape through a gap formed in conventional stamp presses between the press stamp and the mold frame. The air remaining in the compact is compressed during the compression process. As a result, there is on the one hand the risk that the compressed air will blow up the compact produced by the compression process due to a sudden decompression when stripping from the shaping tool and cause layer cracks. On the other hand, the air remaining in the compact prevents the individual particles of the bulk material from being optimally pushed into one another and clawed, and thus reduces the maximum density and strength of the compact which can be achieved by the compression process.

For the reasons mentioned, there are considerable quality defects and an increased scrap when using conventional stamp presses in the production of compacts.

To remedy these deficiencies, pressing devices have already been proposed in which the compression process is interrupted one or more times so that as much of the air as possible between the individual particles of the bulk material can escape from the shaping space during the compression process. A further improvement has been achieved if the press is reversed during the compression process so that it performs a short backward movement with which at least one of the rams is lifted off the compact.

However, these methods are very time-consuming, require a lot of circuitry for the control and drive of the press and ultimately do not lead to the desired qualities of the compacts in all material mixtures. In view of these shortcomings, methods have been proposed in which the air stored in the bulk material is sucked out of the shaping space with a suction device before the compression process is carried out.

A known stamp press which can be operated to carry out such methods has, in order to form vacuum chambers arranged above and below a lateral boundary surface of the shaping space, in each case a sealing cylinder which bears against the stamp plate bearing the upper stamp or the lower stamp plate and a subsequent, bowl-shaped, flexible border and a vertically movable sealing flange in connection therewith, the sealing flange attached to the upper stamp plate being able to be pressed in a sealing manner against the surface of the mold frame, and the sealing flange arranged on the lower stamping plate being able to be sealingly pressed onto the underside of a base or stand of the stamping plate is. The procedure for producing a shaped body using this known stamp press is as follows:

First, suitable press rams are attached to the upper and lower punch plates for the production of the shaped bodies. In a loading position, in which the upper stamp plate and the sealing flange arranged thereon and the upper press ram are pulled upwards, so that a large space is created under the upper press ram, the shaping space is opened by a freely accessible loading opening with bulk material in this position of the stamp press fed. The sealing flange arranged on the upper stamp plate and the sealing flange arranged on the lower stamp plate are then pressed in a sealing manner against the mold frame of the stamp press. In this state, the air can be sucked out of the vacuum chambers formed above and below the mold frame and the molding space connected to it through the loading opening. Then, while avoiding the formation of inclusions in the bulk material consisting of compressed air, the press die attached to the upper die plate is moved downward into the shaping space, so as to compress the bulk material in the shaping space closed at the bottom by the press die attached to the lower die plate ,

With the punch presses just explained and the shaping process that can be carried out with them, shaped articles can be produced of consistently high quality. However, it has been shown that the use of these stamp presses in a comparative low productivity is associated with high energy consumption. In addition, the known presses are also disadvantageous with regard to the high installation expenditure for forming the vacuum chambers. To solve these problems, a die press is proposed in DE 197 43 704, in which the shaping tool has at least one suction channel connecting the shaping space in the pressing position with a suction device.

In a preferred embodiment of such devices described in the cited document, the shaping space is sealed with the aid of a seal encircling the upper press ram, the suction channels being approximately perpendicular to the direction of insertion of the upper press ram and in the closed position in a between the boundary surface of the mold frame and the upper one Press die formed, the upper die running around the gap.

For the production of compacts with this stamp press, the molding space is first loaded with the bulk material. Then the upper press ram is inserted into the molding space until the seal attached to the upper ram rests on the lateral boundary surfaces of the molding space. The air still contained in the shaping space is then sucked off via the suction channels provided in the press ram and the bulk material is compressed. The time required to carry out this shaping process is significantly less than the time required to carry out the previously described processes because the volume to be evacuated is essentially restricted to the volume of the shaping space. Furthermore, the installation effort can be significantly reduced because only corresponding suction channels have to be provided in the shaping tool in order to extract air from the shaping space. However, it has been shown that the compacts produced with the devices known from DE 197 43 704 have considerable quality fluctuations.

In view of these problems in the prior art, the invention has for its object to provide a device for the production of moldings, which allows the production of moldings of consistently high quality with a high production speed while still acceptable energy consumption and installation effort, as well as a process for the production of them Specify moldings. In terms of the device, this object is achieved by a further development of the known devices, which is essentially characterized in that the suction device has at least one connecting element arranged on the molding frame and / or a connecting element of the pressing tool which has between the stamping plate and at least one pressing surface facing the shaping space held sealing device and operable to seal the suction space outside the shaping space.

This invention is based on the knowledge that the shortcomings observed when using the devices described in DE 197 43 704 are primarily due to the fact that the evacuation of the shaping space only after insertion of the upper ram into the shaping space and an associated pre-compression of the bulk material accommodated in the shaping space can be introduced. For this reason, it is no longer possible to remove all air pockets in the method described in DE 197 43 704. In the device according to the invention, on the other hand, a seal is effected outside the shaping space, so that suction of the air contained in the shaping space can be initiated before the upper punch is immersed in the shaping hole. This enables a free coordination (regulation) of air extraction on the one hand and pressure build-up / compression on the other hand. In addition, the sealing outside of the shaping space prevents excessive material stress on the sealing device, as occurs in the sliding contact of the sealing ring in DE 197 43 704 on the wall area of the shaping space to which the bulk material is applied. This means that no movement of the sealing element in the shaping space leading to wear is necessary. A considerably longer service life of the sealing device is thus achieved. A further increase in the service life is due to the fact that the sealing material is not attacked directly by aggressive components of the pressed material (for example solvents, binders, etc.).

The measures described above allow a largely free selection of the sealing material. The sealing material can therefore only be optimized with regard to the compression and springback behavior required to obtain a desired seal. An additional optimization for chemical resistance and abrasion resistance is not necessary. The advantages just described enable the production of compacts with consistent quality. On the other hand, the compacts with a device according to the invention can also be produced at a high production speed because the volume to be evacuated can be adapted particularly well to the shape of the compact by attaching the sealing device to the mold frame and / or the connecting element. It was recognized that the additional effort required by the provision of sealing devices for each connecting element required to establish a connection between the stamping plate and the tool element having the pressing surface with regard to the increase in production speed compared to the known devices in which a sealing device on the Stamp plate itself is set, can be accepted.

By reducing the volume to be evacuated compared to the known devices in which the sealing device is attached to the stamp plate itself without adaptation to the shape of the compact, a faster build-up of the negative pressure required to produce high-quality compact is achieved. In addition, when using devices according to the invention, it is not necessary for the suction to take place via annular gaps formed between the press rams and the shaped hole. This results in a lower flow rate of the extracted air in the mold gaps. This reduction in the flow rate in turn leads to a reduction in the material entrainment at the corners and edges, which results in a higher edge strength of the finished compact.

The reduction in the volume to be evacuated further allows a reduction in the size of the vacuum reservoir, the use of smaller vacuum pumps and a lower energy consumption for evacuating the molding space. Therefore, the use of devices according to the invention is associated with lower investment and maintenance costs and a lower overall height and space requirement. Finally, a device according to the invention also allows a simpler design of the compact discharge device.

In a preferred embodiment of the invention, the connecting element is cylindrical, in particular circular-cylindrical, the sealing device having at least one sealing element that runs around the connecting element and is held thereon along the cylinder axis of the connecting element. At this Embodiment of the invention, a wall element abutting the connecting element via the sealing element when the pressing tool moves in the direction of the molding hole initially comes into contact with a boundary surface of the molding space before the molding tool plunges into the molding space. This favors the extraction of the air contained in the molding space. In the further course of the manufacturing process, the stamp plate and thus also the tool element connected to it via the connecting element and having the pressing surface are introduced into the shaping space, the wall element slidably held on the connecting element sliding along the connecting element, so that one also during the pressing process to enable reliable sealing of the molding space. Expediently, the wall element running around at least one pressing surface of the pressing tool also also has at least one sealing surface that can be placed on a boundary surface of the mold frame. This sealing surface can be designed as a wide strip, which leads to a particularly good sealing effect even at low contact pressure. It is particularly advantageous in this embodiment of the invention that a seal which can be placed on the mold frame and is not moved with respect to the mold frame is particularly dirt-tolerant. This means that any dirt lying on the sealing surface of the mold frame does not impair the sealing effect and does not cause increased wear, since there is no simultaneous sliding friction or shear stress. As already indicated above, in a particularly advantageous embodiment of the invention, the sealing surface assigned to the wall element is formed by a further sealing element, in particular fastened to the wall element.

To increase the flexibility of devices according to the invention, it has proven to be advantageous if the wall element is compressible in a direction running perpendicular to the boundary surface of the mold frame to which it can be placed. This enables flexible adjustment of the possible compression path of the seal. A high degree of flexibility with good dimensional stability can be achieved if the wall element of the sealing device surrounding the at least one sealing surface has a composite structure in which at least one the at least one pressing surface extends in a direction perpendicular to the boundary surface of the molding frame to which it can be attached circumferential frame element made of a rigid material, such as steel, and at least one layer of a resilient material, such as neoprene, are arranged one behind the other. This makes maintenance possible with particularly little effort, because in the event of a wear-related drop in the sealing performance, only that the mold frame facing layer must be replaced from a resilient material. Furthermore, the composite structure opens up the possibility of passing lines, cables and the like into the suction space. The compressibility of the wall element also allows the mold frame to be moved away when a certain compression is reached.

As can be seen from the above explanation, the mold frame of a device according to the invention can expediently be designed to be movable in the compression direction and / or an opposite direction. In this case, the shaping space is expediently delimited by at least one press die accommodated in the at least one shaping hole of the shaping frame. The shaping space is formed by moving the mold frame in a direction opposite the compression direction with respect to the press ram. On the other hand, the compacts can be removed particularly easily after the compaction process by moving the shaping frame in the compaction direction with respect to the press ram.

In particular, in the last-described embodiment of the invention, the shaping space is expediently delimited on at least one side by at least one press die received in a molding hole. In this case, the suction device can have a sealing ring which can be placed on a side of the press die facing away from the shaping space and is fastened to the molding frame. In this embodiment of the invention, the replacement of the sealing ring is associated with little effort because only the mold frame has to be moved to expose the sealing element. In addition, this embodiment enables a particularly compact and space-saving design, which is subject to only slight wear, since the sealing ring does not have to rest against the press ram at the moment of the movement of the mold frame with respect to the press ram.

In a particularly preferred embodiment, a device according to the invention has a control device for controlling the press pressure, the pressure build-up speed, the press force and / or the air suction, the control device expediently for controlling the press pressure, the pressure build-up speed and / or the press force as a function of that in the Forming space generated negative pressure is operable. A further improvement in the quality of compacts produced using the device according to the invention can be achieved if the device also has a vibration generating device for generating mechanical vibrations in the bulk material accommodated in the shaping space. By means of such a vibration compression, the bulk material can be pre-compressed and homogenized before the compression process is carried out.

As can be seen from the above explanation of devices according to the invention, a method for producing moldings with such a device is essentially characterized in that the compression process is only started after air has been extracted from a suction chamber containing the molding space, the compression process expediently depending is controlled by the negative pressure generated in the molding space. It is expedient to proceed in such a way that the tool element having the pressing surface only acts on the material to be pressed when a minimum vacuum of, for example, 100-200 mbar has been reached in the shaping space.

The invention is explained below with reference to the drawing, to which reference is expressly made with regard to all details which are essential to the invention and which are not detailed in the description. The drawing shows:

Fig. 1 is a schematic representation of a pressing device according to the invention and

Fig. 2 is a schematic representation of a wall element of the device shown in Fig. 1.

The device shown in FIG. 1 essentially comprises a mold frame, designated overall by 10, a plurality of pressing dies 22 fastened to a lower stamping plate 20 and a plurality of pressing tools fastened to an upper stamping plate 30. Each of the pressing tools attached to the upper stamping plate 30 comprises a plurality of tool elements 34 each having a pressing surface 35 and a cylindrical connecting element 32 for connecting the tooling elements 34 to the upper stamping plate 30. The mold frame 10 has a plurality of mold holes 12 into which the tool elements 34 are retracted from above that can. The lateral boundary surfaces of the shaped holes 12 are formed by material layers 14 made of a particularly abrasion-resistant material. The press punches 22 fastened to the lower die plate 20 are received in the shaped holes 12.

Sealing devices 40 are assigned to the connecting elements 32 fastened to the upper stamp plate 30. Each of these sealing devices has two sealing elements 42 bearing against a lateral surface of the connecting element 32 and a wall element 44 extending from these sealing elements 42 in the direction of the mold frame 10. A sealing strip 46 is arranged on the lower edge of the wall element 44.

A further sealing device 50 is assigned to the press punches 22 fastened to the lower die plate 20, which has a plurality of sealing rings 52 each surrounding the press punches 22, which are held on the molding frame 10 by means of retaining rings 54. In the operating position of the device according to the invention shown in FIG. 1, the sealing rings 52 rest against the boundary surface of the press die 22 facing away from the shaping space 12.

With the device shown in FIG. 1, a compression process is carried out as follows:

First, the device is brought into the operating position shown in FIG. 1. In this operating position, the bulk material to be compressed is filled into the form holes 12. The upper stamp plate 30 is then moved together with the tool elements 34 fastened to it via the connecting element 32 and the sealing device 40 in the direction indicated by the arrow P in the direction of the mold frame 10 until the sealing strips 46 bear against the upper boundary surface of the mold frame 10. In this position, a suction space having the shaped holes 12 is evacuated with the aid of a pump, not shown in the drawing, until a pressure of less than 200 mbar in the shaped holes 12 is reached. When this pressure is reached, the upper stamp plate 30 is lowered further. In the course of this lowering movement, the pressing surfaces 35 of the tool elements 34 come into contact with the bulk material received in the shaped holes 12. The lowering movement of the upper die plate 30 causes the bulk material to be compressed in the shaped holes 12. The compression process is carried out as a function of the pressure of the air still remaining in the molding holes 12. controls, wherein a compression pressure of more than 30 bar, for example, only at a pressure of the air remaining in the mold holes 12 of less than 80 mbar, for example. After the maximum pressing pressure has been reached, the shaping space 12 is ventilated to a predetermined absolute pressure. This can be done by natural pressure equalization or additional pressurized air.

After completion of the compression process, the mold frame 10 is lowered with the aid of hydraulic cylinders 60 in the direction indicated by the arrow P, the pressing surfaces 35 resting on the compacts.

Only when the lower edges of the compacts have passed the upper boundary surface of the mold frame 10 in the course of the lowering movement of the mold frame 10 are the press surfaces 35 lifted off the press surfaces so as to enable the compacts to be removed from the device. After the compacts have been removed, the mold frame is again moved into the starting position shown in FIG. 1, so that a new press cycle can begin.

According to FIG. 2, the wall elements 44 encircling the pressing surfaces 35 can have a sandwich structure in which a plurality of flexible neoprene layers 44a and steel frames 44b are arranged alternately one behind the other in the direction of compression indicated by the arrow P. Alternatively, the wall elements can also preferably be designed to be telescopically displaceable, as shown in FIG. 2 at 44c.

The invention is not limited to the exemplary embodiment explained with reference to the drawing. Rather, the use of devices is also contemplated in which only one tool element having a pressing surface is connected to the upper press die via a connecting element. Furthermore, devices according to the invention can also have immovable mold frames and lower press rams which can be moved back and forth. Furthermore, instead of the sealing device 50 shown in the drawing with a plurality of sealing elements 52 fastened to the molding frame 10, a sealing device corresponding to the sealing device 40 can also be provided in the region of the lower press rams 22.

Claims

EXPECTATIONS

1. Device for producing compacts from free-flowing and / or pasty bulk material with a shaping space (12) designed for receiving the bulk material and for compressing the bulk material contained therein, the at least during the compression process of at least one mold frame (10) having at least one mold hole and at least one a pressing tool which is retractable into at least one molding hole (12) and / or is seated on the molding frame during the pressing process, is preferably detachably fastened and extends from the stamping plate (30) in the direction of at least one molding hole (12) and a suction device operable to extract air from a suction space containing the shaping space, characterized in that the suction device has at least one pressing surface on the molding frame (10) and / or one between the stamping plate (30) and at least one pressing surface facing the shaping space (35) having tool element (34) of the pressing tool arranged connecting element (32) held and operable to seal the suction space outside the shaping space sealing device (40, 50).

2. Apparatus according to claim 1, characterized in that the connecting element (32) is cylindrical, in particular circular cylindrical, and the sealing device (40) at least one sealing element (32) encircling the connecting element (32) and slidably held along the cylinder axis of the connecting element (32) (40).

3. Apparatus according to claim 1 or 2, characterized in that the sealing device has at least one pressing surface (35) of the pressing tool encircling wall element (44) with a sealing surface (46) which can be placed on a boundary surface of the mold frame (10).

4. The device according to claim 3, characterized in that the sealing surface is formed by a further, in particular on the wall element (44) attached sealing element (46).

5. Apparatus according to claim 3 or 4, characterized in that the wall element (44) in a direction perpendicular to the boundary surface of the mold frame (10) to which it can be applied, compressible direction.

6. The device according to claim 5, characterized in that the wall element (44) has a composite structure in which in a direction perpendicular to the boundary surface of the mold frame (10) to which it can be applied, at least one of the at least one pressing surface (35 ) circumferential frame element (44b) made of a rigid material and at least one layer (44a) made of a flexible material, such as neoprene, are arranged one behind the other.

7. Device according to one of the preceding claims, characterized in that the shaping space is limited on one side by at least one press die (22) accommodated in a shaping hole (12) and the suction device has a side of the press die (12) facing away from the shaping space (12). 22) which can be applied and which is attached to the molding frame (10) and has a sealing ring (52).

8. Device according to one of the preceding claims, characterized in that the molding frame (10) in the compression direction (P) and / or an opposite direction can be moved and / or the at least one press ram (22) is arranged stationary.

9. Device according to one of the preceding claims, characterized by a control device for controlling the pressing pressure, the pressure build-up speed, the pressing force and / or the air suction.

10. The device according to claim 9, characterized in that the control device for controlling the pressing pressure, the pressure build-up speed and / or the pressing force as a function of the negative pressure generated in the molding space is operable.

11. Device according to one of the preceding claims, characterized by a vibration generating device for generating mechanical vibrations in the bulk material received in the shaping space.

12. A process for the production of moldings from free-flowing and / or pasty bulk material, in which a molding space is filled with the bulk material, air contained in the molding space is extracted and the bulk material received in the molding space is compressed, characterized in that the compression process, in particular the compression pressure, the pressing force and / or the pressure build-up speed is controlled as a function of the negative pressure generated in the molding space.