DE3020793A1 - Two=part mould for thermoplastic foam - in which vacuum tightness is provided by peripheral double joint seals with vacuum between them - Google Patents

Abstract

A moulding is produced from foam thermoplastics or from a melt etc. using a vacuum for exhausting the mould, which is in two parts with sealed joint line, and feed for the material. The seal at the joint line is a vacuum seal connected to the vacuum source and extending along at least most of its lenqth. Suitable for e.g. expanded polystyrene, simple construction system which is efficient and reliable.

Description

Device for the production of a molding under vacuum

action The invention relates to a device for manufacturing a molding made of foamable, thermoplastic material, a melt or the like under vacuum to evacuate the mold, with at least two matching molded parts sealed in the region of the separating surface of the mold corresponding to the molding to be produced and a device for feeding the foamed or injection molded material to be deformed and a device for evacuating the Shape.

It is known devices for producing a molding from foamable, thermoplastic material, for example made of expandable polystyrene (EPS), which work according to the vacuum principle for the purpose of evacuating the mold, in the Form the separating surface with a (physical) seal that creates a vacuum during operation in the mold cavity. Vacuum training is sought, for example the compressed air used to introduce a granulated material from the mold cavity or the superheated steam fed into the mold cavity prefilled with foamable material suction again, which is used to expand the foamable material into the final Shape is needed. The quality of the vacuum in operation has a decisive influence the cycle time of manufacturing a molded article, especially when complicated External configurations of the molding are given. Knows as physical seals one according to the state of the art sealing elements made of various materials, like from rubber or from a rubber mixture, from Klingeritt or the like. Even Teflon connections should be mentioned in the case of tempered forms that are round or Flat seals of various hardness can be used. Disadvantage of the known Sealing elements is that these with constantly changing thermal and mechanical Stresses during a foaming process or during opening and closing the shape are exposed to loads that lead to premature wear. In order to create a good vacuum in operation, neatly prepared sealing surfaces must be used be incorporated into the parting surface of the mold. They also need for one satisfactory retention of the seal at the intended location grooves and / or an adhesive material can be provided for adhering the sealing material. Wear-prone Sealing elements lead in particular to moldings of reduced quality and of increased quality Cycle time in production and must when the tolerance limit is exceeded new sealing elements are replaced, with the result that the Production.

While avoiding the aforementioned disadvantages of the prior art, it is The object of the invention is to provide a device for manufacturing that works according to the vacuum principle to create a molding of the type mentioned, with a simple structure is very efficient and reliable in operation.

The object on which the invention is based is achieved in that the sealing between the molded parts by an integrated in the parting surface of the mold Va # rnnadichtung is formed, which is connected to a vacuum connection and at least for the most part encloses the mold cavity along the circumference of the parting surface.

The invention is in contrast to the known devices no separate sealing element is provided for producing a molding, but rather rather, it is the sealing point in the form of a vacuum seal in the race surface self integrated. Since no separate sealing element is provided, this results In a particularly advantageous manner, a practically wear-free, maintenance-free sealing option, the high thermal and mechanical stresses, and thereby Production disruptions as a result of defective seals as in the state of the art excluded are.

In an advantageous further development, the invention is characterized by that the vacuum connection of the vacuum seal and the evacuation connection of the mold are connected to the same vacuum source. This allows the operating system the vacuum seal integrated with the existing evacuation operating system so that no additional effort is required due to the vacuum seal of the invention arises.

The separating surface of the (mostly two) molded parts can be made with circumferential shoulders be provided, in which the vacuum seal is incorporated, in particular in the form a closed circumferential channel in the area of the shoulder, the channel walls determine outer and inner sealing edges that can be on the same circumference.

In particular, there can be two circumferential shoulders in the parting surface of the mold be provided, in the area of the (in relation to the atmosphere) outer paragraph the vacuum seal is provided, while the evacuation connection is in the area of the inner shoulder the shape is formed, which is similar in structure to the vacuum seal.

In an alternative embodiment, in the case of essentially no paragraphs flat parting surface of the mold, the vacuum seal through a circumferential groove in the parting surface be formed of a molded part.

Not only the vacuum seal, but also the evacuation connection can have a circumferential groove, which, based on the atmosphere, on radially inner Is located at the point of separation.

Both circumferential grooves are expediently incorporated in the same molded part, so that there is a simple production.

Circumferential channels and / or circumferential grooves are in an advantageous embodiment of the invention designed circular.

Vines of the vacuum seal can also be an additional seal in Be provided in the form of a rubber sleeve, which (in relation to the atmosphere) outer separation gap of the joint set molded parts circumferentially covers. The separation gap through which the rubber sleeve is not formed during operation The vacuum seal would cause air to flow from the outside to the inside, causing suction the rubber sleeve and thereby an increase in the sealing effect, the sealing effect the higher the vacuum, the higher it is.

In the invention are thus an outer vacuum ring according to a Vacuum seal and an inner vacuum ring corresponding to an evacuation connection provided, the latter primarily for evacuating the mold for the aforementioned Purposes acts. During operation, an after-flow of Air is prevented from entering the mold cavity when there is a vacuum through the inner vacuum ring is created. The invention is practically applicable to all forms of manufacture or processing of materials applicable in which the mold cavity with negative pressure is filled. The invention is particularly useful in molds for manufacture thin-walled EPS parts as well as molds for the production of thick-walled parts, with simple as well as complicated molding geometry.

Not only EPS, but also plastics or metal can be used as molded goods Can be used (e.g. injection molding or die casting), so a wide range can be used be manufactured on bricks by a device according to the invention, e.g. thin-walled Cups made of expandable polystyrene up to cast metal wheels.

The invention is explained below using exemplary embodiments Reference to the drawing explained in more detail without being limited thereto, wherein all of the details apparent from the drawing are part of the disclosure of the invention; it shows: Fig. 1 shows an axial section through a device according to of the invention, wherein a separating surface is provided with shoulders, Fig. 2 a Section similar to FIG. 1 through another embodiment according to the invention with a substantially planar parting surface of the mold, and FIG. 3 shows a plan view the lower mold half of the device according to FIG. 2.

In the drawing, the same lines are provided with the same reference numerals.

The figures denote: 1 upper mold part 2 lower mold part 3 molding / mold cavity 4 cover plate 5 inlet 6 evacuation gap outer sealing edge 8 inner sealing edge 9 Circumferential channel 10 vacuum seal 11 vacuum connection 12 evacuation connection 13 connection channel 14 connecting channel 15 outer separating gap 16 rubber sleeve 18 connecting channel 19 Circumferential channel 20 circumferential groove 21 inner circumferential groove 22 radial section According to Fig. 1 shows an apparatus for producing a molding from foamable, thermoplastic Plastic, for example made of expandable polystyrene, an upper molded part 1 and a lower mold part 2, which are positively fitted into one another to a to form inner mold cavity 3, which corresponds to a molding to be produced.

Both molded parts 1, 2 are radially symmetrical about the vertical axis and are covered by an upper cover plate 4.

The lower molded part has a central inlet 5 for feeding the Schäunguts to be deformed from below. The mold also has steam nozzles (not shown) as well as a cooling water inflow and outflow, which for the sake of clarity in are not shown in the drawing.

The interface between the upper mold part 1 and the lower mold part 2 According to the embodiment of FIG. 1, the shape has two paragraphs that are circular extend around the central axis over the entire circumference and in both radial and also fix both mold parts in their position with respect to one another in the axial direction and thereby determine the mold cavity 3.

The one circumferential shoulder of the parting surface of the form, the closer to the surrounding one Located in the atmosphere, essentially determines the vacuum seal according to the invention 10, while the other circumferential shoulder of the separating surface is the evacuation connection 12 the mold is assigned to the evacuation of the actual mold cavity 3 in the Operation of the device is provided.

The vacuum seal 10 has at the level of the outer peripheral shoulder of the Grenu area has a circumferential channel 9, the several axially distributed on the circumference up has extending connection channels 14, which through the upper cover plate 4 extend and are connected to the vacuum connection 11. The circumferential channel 9 is determined by the radially outermost boundary of its upper side wall one (in relation to the atmosphere) outer sealing edge 7 as well as through the radially outermost one Limiting its lower side wall an inner sealing edge 8, both on the same Perimeter are located. Circumferential channel 9 and connecting channels 14 extend in the upper Molded part 1.

The evacuation connection 12 for evacuating the mold cavity 3 is the same in its construction the vacuum connection 11 connected to the vacuum seal 10 is however, assigned to the other (radially inner) circumferential shoulder of the parting surface of the mold.

Accordingly, in the upper mold part 1 is a itself at the corresponding point Annular circumferential channel 19 extending over the entire circumference is provided, which is connected to axially extending connection channels 13 which are connected to the evacuation connection 12 related. The lowermost side wall of the circumferential channel according to FIG. 1 9 determines the width of a so-called evacuation gap by its outermost radial extension 6, which also extends annularly around the entire circumference of the mold and through which the actual evacuation of the mold interior is carried out. In the practical Embodiment according to FIG. 1, which is for foaming expandable polystyrene (EPS) is provided, the evacuation gap is 6 depending on the bead size of the polystyrene 0.2 to a maximum of approx. 1 mm.

Vacuum connection 11 and evacuation connection 12 are expedient connected to a common vacuum source (not shown), but separate controllable, for example in the form of a vacuum vessel with a vacuum pump can be designed that a constant vacuum of about 3 Torr in the vacuum vessel generated.

In operation of the device is for the purpose of producing a molding made of expandable polystyrene after assembling the two molded parts 1 and 2 and, if necessary, pre-expanded polystyrene after the parts have been locked in granulate form fed through the inlet 5 to the mold cavity 3 by means of compressed air and at the same time the air originally present in the mold cavity 3 and the air supplied Compressed air through the evacuation gap 6 when the evacuation connection is in operation 12 derived. The width of the evacuation gap 6 is chosen so that the granules cannot escape into the evacuation connection 12. To evacuate the form is it is necessary to close the vacuum connection 11 before, after or at the same time operate so that a subsequent flow of air from the atmosphere through the outer separation gap 15 along the interface of the two mold parts 1 and 2 to the mold cavity 3 reliably is prevented, rather the air entering the vacuum connection 11 from the outside is deducted.

The performance of the vacuum seal depends largely on the fit of the outer sealing edge 7 and the fit of the inner sealing edge 8.

It can be seen that the vacuum seal designed according to the invention has 10 does not have any discrete sealing elements that are in operation due to high thermal and mechanical stress can be worn. The evacuation port 12 and the vacuum connection 11 are also after the mold cavity 3 has been prefilled with foam in operation when the foam, such as polystyrene, on its final shape by heating, for example by means of supplied superheated steam, expanded is, then the supplied superheated steam through the evacuation gap 6 in the Evacuation connection 12 is derived.

In order to increase the sealing effect is according to the embodiment 1, a rubber sleeve 16 is provided, which when assembled the outer separating gap 15 covers the circumference and when the vacuum connection is in operation 11 is tightened to the separating gap 15 in a form-sealing manner.

The embodiment shown in Figs. 2 and 3 sees an upper one Molded part 1 as well as a lower molded part 2 with a substantially planar separating surface in front, which has no circumferential paragraphs. The vacuum seal 10 of this embodiment is essentially formed by a circumferential groove 20, practically over the entire Circumference in the lower molded part 2 incorporated radially symmetrically about the vertical central axis and with the eccentrically extending axially downward in the lower mold part 2 Vacuum connection 11 is connected.

* The inlet 5 for feeding the material into the mold cavity 3 takes place through the upper mold part 1 in the axial direction of the mold and through one in the parting surface formed radial channel which connects the inlet 5 with the mold cavity 3.

At the radially inner point 2 is concentric to the lower mold part Circumferential groove 20, a further inner circumferential groove 21 is provided, which is connected to the evacuation connection 12 is connected via a connecting channel 18. The connecting channel 18 is here diametrically to the inlet 5, and it is the inner circumferential groove 21 in the area of the inlet 5 interrupted, while the (outer) circumferential groove 20 in the area of the connecting channel 18 is interrupted. The inner circumferential groove 21 has radial cuts distributed around the circumference 22, which lead to the mold cavity 3. Four radial cuts are expedient to be provided that are equally distributed over the circumference.

* (can also be plastic or metal) Evacuation connection 12 and vacuum connection 11 can also be connected to a common in this exemplary embodiment Connected to the vacuum source.

Thus, in summary of the invention, there is an apparatus for manufacture a molding made of foamable, thermoplastic material, a metal melt or the like provided under vacuum for the purpose of evacuating the mold, the at least two matching molded parts corresponding to the molded part to be produced having. The molded parts are in the area of the interface by a vacuum seal sealed, incorporated in an integrated manner in the parting surface of the mold and extends along the perimeter of the parting surface of the mold for at least the greater part of the circumference, the vacuum seal being inserted into the interface of the one Molding can be incorporated circumferential channel, which is connected to an external vacuum source is connectable. Because of the integrated in the parting surface of the mold Vacuum seals are susceptible to wear and tear as in the prior art Avoided technology.

Claims (8)

Claims 1. Device for producing a molding from foamed thermoplastic plastic, a melt or the like under vacuum action for the purpose of evacuating the enormous with at least two matching in the area of the Parting surface of the mold sealed molded parts according to the molding to be produced and a device for supplying the shrinkable or injection molded material to be deformed as well a device for evacuating the port, thereby g e k e n n n z e 1 c h n e t, that the seal between the molded parts (1, 2) by one in the parting surface the mold integrated vacuum seal (10) is formed, which is connected to a vacuum connection (113 is connected and the mold cavity (3) along the B-catch of the parting surface at least for the most part encloses. 2. Apparatus according to claim 1, characterized in that g e k e n n -z e i c h n e t that the vacuum connection (11) of the vacuum seal (10) and the evacuation connection (12) The mold is connected to the same or a separate vacuum source. 3. Apparatus according to claim 1 or 2, characterized in that g e k e n u -z e i c h n e t that when provided with at least one peripheral shoulder the separating surface rorm the vacuum seal (10) through a closed circumferential channel (9) is formed in the area of the paragraph, the outer sealing edge (7) and the inner sealing edge (8) of the vacuum seal (10) lie on the same circumference (Fig. 1). 4. Apparatus according to claim 3, characterized in that g e k e n n z e i c hn e t, that the parting surface of the mold has one or two circumferential shoulders; being in the field of the outer paragraph the vacuum seal (10) is provided while in the area of the inner shoulder of the evacuation connection (12) of the mold is formed, the resembles the vacuum seal in its structure. 5. Porrichtung according to claim 1 or 2, characterized in that g e k e n u -z e i c h n e t that with a substantially stepless planar parting surface of the form the Vacuum seal (10) through a circumferential groove (20) in the trenu surface of one molded part (2) is formed (Figs. 2 and 3). 6. Apparatus according to claim 5, characterized in that g e k e n n -z e i c h n e t that the evacuation connection (12) of the mold essentially through an inner Circumferential groove (21) is formed similar to the circumferential groove (20) of the vacuum seal (10), with both circumferential grooves incorporated in the same or the opposite molded part (2) are. 7. Device according to claims 3 to 6, characterized g e -k e n n z e i c h n e t that the circumferential channels (9,19) andtor circumferential grooves (20, 21) accordingly the part geometry, for example round, angular or linear. 8. Device according to claims 1 to 7, characterized in that g e -k e n n z e i c h n e t that the outer separating gap (15) of the assembled molded parts (1, 2) is covered circumferentially by a rubber sleeve (16).