JPH0416255B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to a first idea, the mold cavity is injected via an inlet slit by a jerky suction method with at least one application of vacuum;
and relates to a method for producing, in particular, horizontal uncased molds or cores etc. from sand which is later compacted mechanically by moving at least the boundaries of the mold cavity, and according to the second idea. For example, it has an inlet slit connected to a mold plate and a sandbin to form a mold cavity that can be connected to a vacuum source and that can be moved like a stamp by a lifting mechanism. The present invention relates to an apparatus for carrying out the method, comprising at least one enclosing case capable of engaging with a pressing plate on the opposite side of the forming template.

Japanese Patent Application No. 61-035389 describes a method and apparatus for this design. The sand thereby introduced into the mold cavity is supplied with compressed air after the first vacuum application and is then simply mechanically compressed.
The inlet slit remains closed while compressed air is applied and mechanical post-compression takes place.
For this purpose, the inlet slit is located in a roller rotatably supported in the pressure plate and has a flat periphery. The disadvantage of this design is that, due to the application of vacuum and subsequent compressed air to the mold cavity, the mold cavity is depressurized and It must be sealed against overpressure, but this actually requires a reverse sealing direction and is therefore relatively expensive. If the seal is inaccurate, undesirable air suction will occur when a vacuum is applied, resulting in sand being released into the environment when compressed air is applied. This has negative effects on both efficiency and the environment. Special equipment suitable for the use of vacuum and compressed air requires additional costs. Furthermore, when the mold cavity is supplied with compressed air, it must be taken into account that the introduced air is discharged again via the mold plate. Therefore, Patent Specification of the Federal Republic of Germany no.
The method of No. 3507179 can only be used with hollow templates that have a special device for draining compressed air. In addition, the application of compressed air can only be carried out when the inlet slit is closed. A device in the form of a rotatable roller is therefore required for opening and closing the inlet slit, which is also more expensive. Such elements that are moved within the sand are easily worn, resulting in the prospect of reduced lifespan. Another drawback is that when compressed air is applied, air is introduced into the sand which is already pre-compacted by the application of the vacuum.
This results in a so-called springback effect.
This means that the enclosed air not only expands after the mechanical pressure, which has a disadvantageous effect on the accuracy to be achieved, but also causes smoking in the casting state, which is undesirable to create favorable working conditions.

In view of this prior art, the object of the present invention is therefore to provide not only a simplified method, but also a simple and easy-to-use method in which a simple and hardware arrangement is ensured and, nevertheless, a high-quality production is achieved. The object of the present invention is to improve the previously proposed methods and apparatus by economical means.

To achieve this purpose, the inlet slit for receiving the sand is kept open during the entire manufacturing process, including the mechanical post-compaction and the immediate subsequent application of vacuum. In this design, the inlet slit of the pressure plate cannot be moved and is defined by a solid wall.

With these measures, there is no need for a movable part to guide the entrance slit upwardly or downwardly. A very simple and economical design as well as high durability is thus obtained. Since no compressed air is used, there is no disadvantage in that the inlet slit remains open during the entire manufacturing process. The open inlet slits do not force sand out of the mold cavity or allow pressure to reach the sand bin and cause undesired compaction of the sand there. On the other hand, as much air as possible is removed from the sand so that there is no risk of mold smoking occurring in the casting condition. At the same time, the absence of air also ensures a high precision of the product being manufactured, since there is no or almost no spring back effect after the compression process. According to the invention, only a vacuum seal is required, which can be reliably achieved by relatively simple means. This prevents sand from leaking out of the mold cavity. In addition, it is also not necessary to evacuate compressed air, thus further simplifying the design and opening up new possibilities of construction and application. The invention not only no longer relies on hollow templates, but can also be applied to solid templates (match plates) used on one or both sides, for example. This shows that the object of the invention is achieved by simple and economical means.

According to yet another advantageous aspect of the invention, several, preferably two, vacuums can be applied in succession. This favors a particularly uniform compaction of the sand over the entire cross section of the mold, and is particularly because the sand actually supplied by the second and possibly subsequent additional vacuum application is This is due to the fact that less parts of the compression go through the application of vacuum at times. The result therefore is a sufficient filling of the mold cavity with sand and a substantially uniform compaction even if relatively deep molds are used.

In another advantageous embodiment of the invention, the application of the vacuum can be carried out by supplying the vacuum to at least one hollow press plate having a nozzle accessible from the mold cavity. The sand entering the mold cavity through the inlet slit in the pressure plate moves towards the mold plate and stops towards the mold, but this is due to its inertia, and the sand that enters the mold cavity Does not depend on suction. Thus, by applying a vacuum to the hollow pressure plate, it is ensured that sand accumulates in the suction opening leading to the mold cavity only when the mold cavity is practically completely filled.
The energy supplied in the form of a vacuum is thus advantageously utilized during the entire filling process. This means that a virtually uniform force is applied during the entire filling process, so that sufficient compaction is ensured even in the lower part of the mold.

The one or more applications of vacuum to the pressure plate can each be carried out alone or in combination with the application of vacuum to the template and/or the surrounding case. Such a combination makes it possible to delay the application of the vacuum to the pressure plate, which in effect results in a second vacuum application and therefore results in a particularly good filling of the mold cavity. When the vacuum is applied only to the pressure plate, no supply lines leading to the template and/or the surrounding case are needed. In that case, the template and the housing need not be hollow and can be in the form of solid components.

According to a further advantageous aspect of the invention, the inlet slit can have its smallest cross section at its opening towards the mold cavity. This results in sand with its maximum acceleration on entry into the mold cavity, which helps the filling of the mold cavity particularly well. A particular advantage of this design is the minimal cross-section at the entry; during mechanical post-compaction, only relatively little sand is forced into the open inlet slit;
and ensures that this sand is removed when the pressing plate returns. Since the fracture occurs outside the pressing plate, no raised portions will be formed on the surface of the finished mold. The finished molds can therefore be placed on pallets or loaded with respective weights without the risk of bumping.

Further advantageous effects and advantageous embodiments of the present invention will be understood from the following detailed description of embodiments with reference to the accompanying drawings.

The illustrated apparatus allows simultaneous production of the upper and lower bales of the mold. The device therefore accommodates a template 1 which is supplied with substrates in a manner not detailed here and is provided with models 2 on its upper and lower sides. Opposite each side of the template 1 with the model 2 there is a pressing plate 4 which is supported on the base plate and can be moved by a lifting mechanism in the form of one or several piston assemblies 3. The distance between each pressure plate 4 and the side of the template 1 facing it is bridged by a surrounding case 6, which can be slid perpendicularly to the respective plane of the substrate. supported on the substrate so that it can be Two mold cavities 7 are thus created, each of which is defined by a mold plate 1, a pressure plate 4 and a case 6 engaging therewith. The connection between the case 6 and the mold plate 1 or the respectively cooperating pressure plate 4 is such that no unwanted air is sucked into the mold cavity 7 when a vacuum is supplied to the mold cavity 7 from the outside. each sealed against air.

The pressure plates 4 are each symmetrical with respect to the central longitudinal direction and serve to fill the mold cavity with sand 1
It has two entrance slits 8. Each inlet slit 8 is molded directly into the cooperating pressure plate 4 and is defined by a rigid wall 9. There is no closing mechanism cooperating with the inlet slit which remains open at all times. Each inlet slit 8 cooperates with a sandbin 10 placed on a respective pressing plate 4 which is moved like a stamp in relation to the respective case 6 by a lifting mechanism 3. The upper and lower sand bins 10 are connected to each other by a lateral outflow pipe 11 that engages telescopically so that the sand bins 10 can be filled together.

The mold cavity 7 is filled by one or several applications of vacuum. In each case this means a jerky suction process.
For this purpose, each mold cavity 7 is connected to a vacuum source in the form of a tank 13, which can be evacuated by means of a pump. Therefore, the flow path from the mold cavity 7 to the tank 13 is connected to the mold plate 1 and/or the pressing plate 4 and/or
or extending through case 6. In the embodiment shown here, suction of the mold cavity 7 can be carried out via the mold plate 1 and the pressure plate 4.
For this reason, the template 1 has a hollow part 15, and this hollow part
The section 15 is sealed via a vacuum conduit 14 to the tank 13 and by a sand filter 16 and is connected to the mold cavity.
It is connected to the mold cavity 7 via a nozzle 17 arranged above at the edge of the mold cavity. In this embodiment, the pressure plate 4 has a cavity 19 which is connected via a respective vacuum line 18 to the tank 13 and here evenly distributed over the entire surface and in each case a sand filter. 20 is connected to the cooperating mold cavity 7 via a sealed nozzle 21. When suction takes place via the cases 6, these cases have the same shape and are connected to the tank 13. Here, the case 6 does not have an empty space because suction is not performed through the case. For simplicity, empty section 15 or 1
9 are each not subdivided in the example shown here. However, it is also possible to provide each of the cavities 15 or 19 with several chambers formed by vertical partition walls and to which vacuum is applied separately. The horizontal partitions also make it possible to subdivide the cavity 15 of the mold plate 1 into regions cooperating with the upper mold cavity 7 and regions cooperating with the lower mold cavity 7.

Within each vacuum conduit 14 or 18, respectively, there is a shutoff device 22, which shutoff device 22 is connected to the control mechanism 2.
3 to the disconnection device 22, each of which can be activated or deactivated by a control mechanism 23 as shown. In the illustrated embodiment, control mechanism 23 is programmed to select one or several subsequent applications of vacuum. The impulsive (pulsed) vacuum application to the mold cavity 7 not only transports the sand from each sand bin 10 via the cooperating inlet slit 8 to the mold cavity 7, but also simultaneously compacts the sand. also possible.
The sand substantially retains its direction of movement imparted in the inlet slit 8 and therefore accumulates in the model 2 opposite the inlet slit 8 and is compacted at the same time. In a simple, not very deep mold,
One vacuum application is sufficient to sufficiently and substantially uniformly compact the sand. In more complex, deeper molds, several vacuum applications can be applied in succession. Several successive applications of vacuum tend to shift the sand to areas where it was less compacted by the previous application of vacuum, eventually resulting in approximately uniform compaction over the entire cross section. . Vacuum can be supplied to each cavity 15 or 19 of the template 1 and the press plate 4 at the same time. In the illustrated embodiment, the disconnection device 22 connects the cavities 15 of the mold plate 1 first to the respective vacuum source and then, after a short delay, to the cavities 19 of the pressure plate 4;
It is controlled in such a way that the effect of two successive vacuum applications is effectively applied. The nozzles 21 of the pressure plate 4 or the cooperating sand filter 20 each remain free, i.e. not covered by sand, and are therefore not covered by sand until the cooperating mold cavity 7 is completely filled. Application of the vacuum via the pressure plate 4 can achieve a sufficient effect even if there is one or several previous applications of the vacuum via the mold plate 1 and/or the case 6.

The sand filling the mold cavity 7, which has already been homogeneously precompacted by the application of a vacuum, can be further compacted by a mechanical compaction step. This compression step is carried out immediately, i.e. without any intervening application of compressed air, following the application of vacuum to the mold cavity 7. To carry out the compression process, the lifting mechanism 3 cooperating with the pressure plate 4 is activated. This means that from the control mechanism 23 to the lifting mechanism 3
This is done by control mechanism 23 as shown by signal line 25 extending to . A lifting mechanism 3 in the form of a hydraulic or respectively pneumatic cylinder-piston assembly is used to move the pressure plate 4 into a cooperating case 6 like a stamp. By doing this, the template 1 is fixed to the substrate. Case 6 is template 1
Can be supported on top. At the end of the compression process, the pressure plate 4 is returned by applying the lifting mechanism 3 in reverse. The case 6 can then be removed. For this purpose, the case 6 is connected to a removal mechanism 26 in the form of a lifting cylinder or the like. The removal process is also controlled by a control mechanism 23. The mold bail released by the removal of the case 6 is placed with the two-part mold, the lower bail being carried by a cooperating upper bail which is housed on a pallet and can be loaded by a weight. Covered.

The inlet slit 8 of the pressing plate 4 is formed with its smallest cross section at the opening towards the cavity 7, giving it a large acceleration to the sand near the inlet. The entrance slit 8 always remains open. This also applies to the compression process carried out by the lifting mechanism 3. therefore,
When the compaction process is carried out, a small amount of sand is forced back into the inlet slit 8. This sand pushed back into the inlet slit 8 does not appear in the form of bulges or the like in the finished mold. When the pressure plate 4 is lifted out of the cooperating bail of the mold, the fracture occurs via the fracture line 27 outside the inlet slit 8.
Said break line 27 is either in line with the adjacent surface of the mold or somewhat low, but not so high that the lower bail of the mold can be placed on the pallet, and the upper bail can be weighted without problems. In the illustrated embodiment, the area of the solid side wall 9 of the inlet slit 8 located close to the opening is inclined at an angle of approximately 10 DEG to the central longitudinal plane. The side surfaces of the inlet slit 8 can be in the form of inclined flat planes, as in the inlet slit 8 cooperating with the lower mold cavity 7. However, it is also possible for the sides of the inlet slits 8 to be inclined further away from the cooperating mold cavity 7 and towards each other, as in the inlet slits 8 cooperating with the upper mold cavity. It is possible.

However, the aspects described so far are
It is intended to cover advantageous embodiments of the invention without limiting its use. On the contrary, there are many possibilities open to the expert to adapt the general outline of the invention to the requirements of a particular situation. for example,
It is also possible to have a template in the form of a so-called match plate and to connect only the pressure plate to the vacuum source.

[Brief explanation of drawings]

The drawing is a partial cross-sectional view schematically illustrating the invention. In the figure, 1 is a template, 2 is a model, 3 is a lifting mechanism, 4 is a pressing plate, 6 is a surrounding case, and 7 is a mold cavity.
8 is an inlet slit, 9 is a solid wall, 10 is a sand bin, 13 is a tank, 18 is a vacuum conduit, 20 is a sand filter, 22 is a shutoff device, and 23 is a control mechanism.

Claims (1)

[Scope of Claims] 1. Sand material is introduced into the mold cavity 7 from the side facing the mold plate 1 through the inlet slit 8 by an impact suction step by applying vacuum several times, and the final vacuum is applied to the mold cavity 7. In the method for manufacturing a caseless mold or core made of sand or the like, the mold or core is mechanically densified by the movement of at least one pressure plate 4 after the application of 1
The slits 8 are open during the entire process including the vacuum application process and the mechanical densification process, and the sand material is introduced into the mold cavity, and the vacuum application performed at least in the final stage only covers the pressing plate 4. carried out through
A method for manufacturing a mold or core, characterized in that a densification step is performed after this final application of vacuum. 2. It consists of a vacuum source 13, at least one surrounding case 6, a mold plate 1, a pressing plate 4 facing the mold plate and an inlet slit 8, the surrounding case, the mold plate and the pressing plate being connected to the vacuum source. A mold cavity 7 is formed, and the entrance slit is formed into a sand bin 1.
0 and moved like a stamp by the lifting mechanism 3, characterized in that the entrance slit of each pressure plate is designed to be immovable within the pressure plate and is defined by a solid wall. Equipment for manufacturing molds or cores. 3. Manufacturing device according to claim 2, characterized in that the inlet slits 8 have the smallest cross-sectional area at the opening cooperating with the respective mold cavity. 4 Make sure that the side of the inlet slit is at least as empty as possible in the mold.
3. Apparatus according to claim 2, characterized in that the inlet slit is inclined at an angle of about 10 DEG towards the longitudinal center plane of the inlet slit in the vicinity of the opening. 5. Any one of claims 2 to 4, characterized in that the mold cavity or cavities are exclusively sealed under pressure at the connection points between the mold plate, the surrounding case and the pressing plate. 2. The manufacturing device according to item 1. 6 Consists of a vacuum source 13, at least one enclosing case 6, a mold plate 1, a pressing plate 4 facing the mold plate and an inlet slit 8, the surrounding case, the mold plate and the pressing plate forming a mold connected to the vacuum source. A cavity 7 is formed, the inlet slit is connected to the sand bin 10 and moved like a stamp by a lifting mechanism, and the inlet slit of each pressure plate is designed so that it cannot be moved within the pressure plate and is rigid. 1. An apparatus for producing molds or cores, characterized in that the apparatus is defined by a wall and is provided with a control device capable of switching on and off the application of a vacuum to each mold cavity. 7. The manufacturing apparatus according to claim 6, characterized in that the control device applies vacuum to the mold cavities independently of each other.