Apparatus for calibrating an extruded plastic profile piece that forms at least one longitudinal groove

An apparatus for calibrating an extruded plastic profile forming at least one longitudinal groove (5), comprises a calibrating body (1) receiving the profile (2). Body (2) comprises a form nose (6) with a cooling channel (9) engaging in the longitudinal groove (5) and extending in the direction of passage of the profile, and coolant bores (13, 14, 26) extending transversally to the form nose (6) and crossing its cooling channel (9). Cooling channel (9) which is open on both face sides is connected via a continuous slot (10) with a receiving recess (11) for sealing elements (12) which are inserted from the open face sides and form connecting openings (19) for the flow connection between the cooling channel (9) and the associated coolant bores (13, 26), which receiving recess penetrates the calibrating body (1) in the direction of passage and extends into the region of the coolant bores (13, 14, 26)

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of PCT/AT2004/000199, filed on Jun. 9, 2004, which claims the benefit of Austrian Patent Application No. A 897/2003, filed on Jun. 10, 2003.

FIELD OF THE INVENTION

The invention relates to an apparatus for calibrating an extruded plastic profile forming at least one longitudinal groove, comprising a calibrating body receiving the profile strand emerging from a shaping extrusion die for profiles, the body comprising a form nose with a cooling channel engaging in the longitudinal groove of the profile strand and extending in the direction of passage of the profile strand, and coolant bores extending transversally to the form nose and crossing its cooling channel.

DESCRIPTION OF THE PRIOR ART

During the extrusion of a plastic profile, the hot profile strand emerging from the shaping profile extrusion die is calibrated and cooled. This cooling is of especial importance in the inlet region of the calibrating apparatus because the friction between the hot profile strand and the calibrating body receiving this profile strand depends on the temperature of the calibrating body in the region of the calibrating surfaces resting against the profile strand. If this temperature rises beyond a critical value of usually 50 to 70° C., the frictional forces exceed the tensile strength of the not yet solidified profile strand, which can then no longer be withdrawn. The calibrating body receiving the hot profile strand must therefore be cooled especially well in the inlet region, which naturally causes problems at places where the cross section of the calibrating body does not allow any generously dimensioned cooling channels. This is always the case when the extruded plastic profile has longitudinal grooves with a comparatively small cross section in which a form nose of the calibrating body engages for calibration, which form nose extends in the direction of passage. These form noses need to be drilled laboriously for forming cooling channels and their connections. It is necessary to ensure a separate cooling circulation because the cooling channels cannot be configured to extend parallel to the usual coolant bores that have a larger cross section due to the small flow cross section without endangering the forced circular flow in the region of these cooling channels. The cooling channels in the region of the form noses of the calibrating body have a considerably larger flow resistance as a result of their small cross section than the usual coolant bores that have a larger cross section.

The cooling channels with their separate connections in the region of the form noses of the calibrating body are of a complex configuration not only concerning their construction but also concerning their maintenance. Due to unavoidable contamination of the coolant, which usually is caused by water, a constriction of the flow cross section can occur and thus to an insufficient cooling of the form noses. This means that the cooling channels need to be opened regularly in the region of the form noses, which is a complex matter in the provided face-side seals because these seals consist of pressed-in or glued-in sealing plugs which become useless after removal.

SUMMARY OF THE INVENTION

The invention is thus based on the object of providing an apparatus for calibrating an extruded plastic profile of the kind mentioned above in such away that the constructional effort required for providing cooling channels in the region of the form noses can be reduced to a considerable extent. Moreover, the maintenance of these cooling channels is to be simplified.

This object is achieved by the invention in such a way that the cooling channel which is open on both face sides is connected via a continuous slot with a receiving recess for sealing elements which can be inserted from the open face sides and form the connecting openings for the flow connection between the cooling channel and the associated coolant bores, which receiving recess penetrates the calibrating body in the direction of passage and extends into the region of the coolant bores.

Since the cooling body does not require any complex connection bores for the cooling channel as a result of these measures (the connection between the cooling channel and the coolant bores crossing the cooling channel at a distance is achieved by separate sealing elements), a comparatively simple production of the cooling channel jointly with the connection slot for the receiving recess for the sealing elements is obtained as a result of the progress of these openings which continue in the direction of passage of the profile strand, which openings can thus be produced simultaneously with the calibrating surfaces and the form nose by wire erosion for example. The fact that the sealing elements extend into the region of the coolant bores provided for the supply and discharge of the coolant simplifies the connection of the cooling channel in the form nose of the calibrating body with the coolant bores via the sealing the elements because the sealing elements merely need to have respective connection openings for the flow connection between the cooling channel and the associated coolant bores. An additional factor is that the sealing elements are used for sealing off the open face sides of the pass-through opening of the calibrating body which is formed by the cooling channel, the connection slot and the receiving recess for the sealing elements, which provides advantageous mounting conditions.

In order to advantageously meet this closing function of the sealing elements, the sealing elements may comprise a molding body engaging in the receiving recess and comprising an outer face wall which outwardly seals the cooling channel, the receiving recess and the slot between the cooling channel and the receiving recess. If this face wall is provided with a circular boundary web which extends conically to the outside, a liquid-tight seal is obtained on pressing the face wall into the associated opening of the calibrating body without having to take any additional sealing measures.

If the coolant bores for the supply and discharge of the coolant to the cooling channel end in the region of the receiving recess for the sealing elements, a circular flow through the cooling channel is achieved via the connection openings of the sealing elements inserted into the receiving recess. This circular flow is endangered however when the coolant bore for the coolant supply penetrates the receiving recess in order to also supply other parts of the calibrating body with coolant. In this case there is a flow division according to the prevailing flow resistances, leading to an insufficient supply of the cooling channel with coolant in the form nose. For the purpose of adjusting the different flow resistances in the region of the coolant bores and the cooling channel, the molding bodies of the sealing elements can carry inserts in the pass-through region of coolant bores penetrating the receiving recess, which inserts control the flow rate through the coolant bores. With an insert forming a respective throttling position for the associated coolant bore it is thus possible to achieve an equalization of the flow resistances with the effect that the coolant flow is divided at a desired ration into the cooling channel and the continuing section of the coolant bore.

Such inserts for the sealing elements in the region of the penetration of the coolant bores through the receiving recesses of the calibrating body can also be used to additionally control an intermediate output of the connection openings of the sealing elements, so that the discharge of the cooling channel in the form nose of the calibrating body is connected with a coolant bore penetrating the receiving recess for the sealing elements or is blocked relative to this coolant bore in order to enable a connection to a further coolant bore.

A sufficient flow rate of the coolant through the cooling channel must be ensured for cooling the form nose of the calibrating body. Since the cooling channel is connected by a connecting slot with the receiving recess for the sealing elements, a coolant flow which is parallel to the cooling channel can form depending on the flow conditions within the connecting slot, which flow may under certain circumstances impair the cooling of the form nose. In order to suppress this parallel coolant flow through the connecting slot, the molding bodies of the sealing elements can comprise webs projecting into the connecting slot to the cooling channel. In the case of larger distances between the face-side sealing elements, a coolant flow which is parallel to the cooling channel can also form via the receiving recess for the sealing elements. In order to prevent this, a filling element can be inserted between the sealing elements in the receiving recess of the calibrating body.

As already explained, the respectively required connection between the coolant bores in the cooling body and the cooling channel in the form nose can be produced via the sealing elements and via inserts which may optionally be provided in the sealing elements and are preferably exchangeable without requiring any additional constructional effort in this respect. This also ensures joining the connection opening of the sealing element associated with the discharge end of the cooling channel with a separate coolant bore for coolant discharge in order to enable the monitoring of the proper flow of the coolant through the cooling channel on the basis of the coolant flowing from said coolant bore.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As is shown inFIG. 1, the calibrating apparatus comprises a calibrating body1which receives the profile strand2of a plastic profile emerging from the extrusion die for profiles. The pass-through opening for the profile strand2is delimited by calibrating surfaces3, towards which the profile strand2is pulled by suction in the conventional manner via vacuum slots which are not shown for reasons of clarity of the illustration. The extruded plastic profile comprises in the region of a leg4an undercut longitudinal groove5, into which engages a form nose6projecting beyond the adjacent calibrating surface3for calibration. The molding body1divided by separating surfaces7which extend in the direction of passage of the profile strand2in order to compose the profile cross section in a simple manner by the calibrating surfaces3from the individual molding strips8.

In order to prevent any adherence of the profile strand on the calibrating surfaces3, which profile emerges in a molten state from the extrusion die, and in order to keep the take-off resistance of the profile strand2from the calibrating body1within permissible limits under the conditions of an immediately starting solidification of the melt, the calibrating body1needs to be cooled especially in the inlet region to a sub-critical temperature of less than 50 to 70° C. for example. For this purpose, the molding strips8of the calibrating body1are provided with coolant bores, through which coolant (which is generally water) is pumped in a circulation. Whereas the calibrating surfaces3can be cooled in a relatively simple manner by providing respective coolant bores, the cooling of the form noses6which are used for calibrating the longitudinal grooves5poses difficulties due to the small cross section of these form noses6. In order to avoid these difficulties, the form nose6is provided with a cooling channel9which extends in the pass-through direction of the profile strand2and which is connected by a slot10with a receiving recess11for the sealing elements12. The cooling channel9thus forms in combination with the connecting slot10and the receiving recess11a common pass-through opening in the molding strip8of the calibrating body1forming the form nose6(as shown inFIGS. 2 to 4), which opening continues in the direction of passage of the profile strand.

The molding strip8is provided with coolant bores13and14which extend transversally to the form nose6, penetrate the receiving recess11and open into a connecting bore15which is perpendicular to the same, so that the coolant entering through the coolant bore13is supplied via a bore15to the coolant bore14connected to a coolant discharge.

According toFIGS. 5 and 6, the sealing elements12comprise a molding body16engaging in the receiving recess11of the profile strip8, which body carries a face wall17on the respective outside which not only extends beyond the receiving recess11but also beyond the connecting slot10and the cooling channel9in order to seal off the entire pass-through opening on the face side. For the purpose of better sealing, the face wall17is provided with a circular boundary web18which extends conically towards the outside and which on engagement in the pass-through opening of the molding strip8is pressed in a sealing manner against the opening wall, as is shown inFIGS. 2 and 4.

For supplying coolant to the cooling channel9, the molding bodies16comprise after the face wall17a connecting opening19which extends transversally to the cooling channel9, starts out from a recess20on the circumferential side of the molding body16opposite of the cooling channel9and opens into the region of the slot10. Moreover, the molding bodies16of the sealing elements12are provided in the region of the coolant bores13and14with pass-through openings21which extend into the region of the connecting openings19, thus producing an intermediate output22for the connecting bores19, which output can be sealed optionally by inserts in the pass-through openings21. The inserts23are not only used for the optional connection of the connecting openings19with the associated coolant bore13or14, but also allow a throttling of the coolant flow through the coolant bores13and14in order to force a respective equalization of the flow resistances and thus a desired division of the coolant flow to the coolant bores and the cooling channel9. According toFIGS. 2 to 4, the insert23is provided in the region of the coolant bore13with a throttling bore24in the region of the coolant bore13. Since this insert is also provided with a conical configuration, a flow path to the intermediate output22of the connecting opening19remains between the insert23and the pass-through opening21, through which the connecting opening19is in connection with the coolant bore13. Since the recess20is covered by the wall of the receiving recess11on the circumferential side of the molding body16which is opposite of the cooling channel9, coolant thus flows from the coolant bore13through the connecting opening19and the connecting slot10into the cooling channel9, as is shown especially inFIGS. 2 and 4. In order to limit the coolant flow to cooling channel9, the molding bodies16of the sealing elements12are provided with webs25projecting into the connecting slot10, which webs are arranged adjacent to the orifice of the connecting opening19.

An insert23in the form of a cylindrical sleeve is inserted in the pass-through opening21of the sealing element12associated with the coolant bore14, which sleeve seals the intermediate output22of the connecting opening19relative to the coolant bore14, so that the coolant flows from the cooling channel9through the connecting opening19into the recess20where a separate coolant bore26ends, so that the coolant from cooling channel9flows off via this coolant bore26. This separate discharge of the coolant flow from the cooling channel9can be used advantageously for monitoring the transmissibility of the cooling channel9.

By providing sealing elements12which engage on the face side into the receiving recesses11and which comprise connecting openings19for connecting the cooling channel9with the coolant bores13,14,26crossing the cooling channel9it is possible to avoid otherwise required complex connecting bores for the cooling channel9through the off-set throat of the form nose6. In cooperation with respective inserts23, flow connections adjusted to different conditions can be achieved between the coolant bores and the cooling channel, this being with the help of constructionally predetermined, uniform sealing elements12, which as a result of their configuration which is symmetrical to a longitudinal plane can also be used on both face sides of the receiving recesses11.