Abstract:
A seal for use in an extrusion device for producing continuous profiles, in particular plastics pipes includes an elastic sealing disc, which is arranged in a plane approximately perpendicularly to the extrusion direction and has a through-passage opening letting through the continuous profile and having a sealing rim bearing against the continuous profile. Connection members are arranged along the sealing rim, and clamping elements are provided for exerting a force on the connection members, with the force acting radially with respect to the extrusion axis. The clamping elements are arranged in a plane parallel to the sealing disc, have a passage opening for the continuous profile and include connecting members for connecting the connection members to the clamping elements.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2013/064315, filed on Jul. 5, 2013, which designated the United States and has been published as International Publication No. WO 2014/006210 and which claims the priority of German Patent Application, Serial No. 10 2012 106 035.5, filed on Jul. 5, 2012 pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a seal for use in an extrusion device for producing continuous profiles, in particular plastics pipes. 
     Seals of this type are known in a variety of embodiments. An established sealing principle is applied for example in pipe extrusion systems with a changeable pipe diameter in operation at the outlet of the vacuum chamber, between the vacuum chamber and the downstream water tank in the extrusion direction. The so-called segment seal comprises radially movable segments arranged around the pipe and in extrusion direction before the segment arrangement a simple elastic sealing disc with a passage opening for the extruded pipe. This functions because the flow direction (also sealing direction or pressure drop direction) acts contrary to the extrusion direction owing to the negative pressure in the vacuum tank. However, this principle can not be readily transferred to other regions of the extrusion system, as soon as the sealing direction and the extrusion direction are aligned. The sealing disc is then destroyed, because for example it remains adhered to the pipe or is drawn into the segment arrangement. 
     For example in extrusion direction behind the water tank, where the extrusion direction and the sealing direction are aligned, therefore frequently funnel seals have been used. These are indeed not destroyed, but are only at all practicable with very small diameters (approx. up to 250 mm) (the pressure build-up by the water is too great in the case of large diameters, so that a sealing action is no longer achieved) and have the disadvantage, within the region which is changeable in diameter, of the deficient sealing action in the case of smaller pipe diameters or so-called chattering in the case of larger diameters. Furthermore, such seals are subject to a large amount of wear, should therefore be easily replacable and advantageously have a lower cost for materials. 
     SUMMARY OF THE INVENTION 
     The invention is therefore based on the problem of providing a seal for use in an extrusion device which overcomes the disadvantages of the prior art. 
     This problem is solved by a seal for use in an extrusion device for producing continuous profiles, in particular plastics pipes, and including an elastic sealing disc, which is arranged in a plane approximately perpendicularly to the extrusion direction and has a through-passage opening letting through the continuous profile and having a sealing rim bearing against the continuous profile, and also has connection means arranged along the sealing rim, and clamping means for exerting a force on the connection means, with the force acting radially with respect to the extrusion axis, wherein the clamping means are arranged in a plane parallel to the sealing disc, have a passage opening for the continuous profile and comprise connecting means for connecting the connection means (128, 328) to the clamping means. Advantageous further developments are indicated in the subclaims. 
     The invention is based here on the idea of providing a seal for use in an extrusion device for producing continuous profiles, in particular plastics pipes, which comprises an elastic sealing disc with a through-passage opening for the continuous profile, wherein the through-passage opening can be widened or constricted by the application of a radial force. For this, close to the sealing rim, which lies in a crease-free manner against the continuous profile, surrounding the through-passage opening, connection means, for example eyes, are arranged on or in the sealing disc, which are connected with clamping means via connecting means, for example hooks or pins, which engage into the eyes. The clamping means exert a radial force onto the connection means and therefore onto the sealing rim. Depending on the direction of the radial force, radially outwards or inwards with respect to the extrusion axis, the sealing rim is therefore widened or constricted. The clamping means are arranged here in a plane approximately parallel to the sealing disc and also have a passage opening for the continuous profile. 
     The sealing disc is advantageously configured in a single piece, advantageously with a seamless, circumferential sealing rim. The term “in a single piece” includes here also several layers of one or more materials which are vulcanized, glued or otherwise connected in a planar manner on one another. In an advantageous embodiment, the sealing disc is configured in two layers, therefore has two layers which are connected securely with one another, for example glued, vulcanized on one another. Provision can then be made that the connection means, connecting means and/or clamping means are arranged at least partially between the layers. The connection means, connecting means and/or clamping means can therefore be arranged completely between the layers; or, for example, the connection means, e.g. in the form of eyes, are arranged partly between the layers, whilst the connecting means, e.g. in the form of hooks, and the clamping means, e.g. in the form of wire cables, are arranged outside the layers; or, for example, the connection means and connecting means between the layers and the clamping means, e.g. in the form of wire cables, which run from the interior (between the layers) outwards (outside the layers). The sealing disc is so elastic that a radial widening of the sealing rim and restoring into the initial state is possible. In the unstressed initial state, the sealing disc is arranged almost flat in a plane approximately perpendicularly to the extrusion direction. It is also possible to arrange several sealing discs axially one behind the other. 
     On or in the sealing disc, connection means for example in the form of rings or eyes, pins, hooks, screws, nuts, loops, thimbles, etc. are securely connected, for example vulcanized in, glued, etc., therewith, and are distributed along the sealing rim so that the latter always lies in a reliably sealing manner against the continuous profile. The connection means must be arranged so close to the sealing rim that the latter can be widened and constricted by a radial application of force onto the connection means. 
     The connection means are connected with the clamping means via connecting means. The connecting means can be configured for example as pins, hooks, rings, eyes, screws, nuts, loops, thimbles etc., which are mounted on the clamping means. Connection means and connecting means are expediently configured in a complementary manner to one another—for example, eye and pin, hook and eye, screw and nut, loop and hook, etc. A detachable connection between connection means and connecting means, such as for example eyes, which can be fitted onto pins, has the advantage that the wearing-out sealing disc can be quickly replaced. It is also possible that the connection means are connected with the connecting means in another way, for example are vulcanized in, glued, welded, spliced, etc., depending on the configuration of the connection means and connecting means. The connection must hold reliably in a force transmission between clamping means and connection means. 
     The clamping means are arranged advantageously in a plane parallel to the sealing disc. In advantageous embodiments, the clamping means are arranged close to the sealing disc, lying against the latter or introduced, for example vulcanized-in, into it. When several sealing discs are arranged axially one behind the other, the clamping means can also be arranged between the sealing discs. 
     By means of the clamping means, a radially acting force is exerted onto the connection means via the connecting means, so that the diameter of the through-passage opening is changed. 
     The clamping means preferably have a passage opening which is changeable in diameter, wherein the connecting means are advantageously arranged along the circumference of the passage opening so that through a change in diameter of the passage opening a change in diameter of the through-passage opening of the sealing disc is also brought about. It can be expedient to arrange the connecting means close to the passage opening of the clamping means, in order to be able to widen the through-passage opening of the sealing disc to the greatest possible extent. When the clamping means are integrated into the sealing disc, the passage opening is, as it were, implicitly included. 
     In an advantageous embodiment, the clamping means are configured as wire cables (also designated as cables, for example of metal or synthetic fibres) running radially with respect to the extrusion axis. Advantageously, thimbles or loops are formed as connecting means at the end of the wire cables facing the extrusion axis. In this case, the clamping- and connecting means would therefore be configured in a single piece. Further advantageously, the wire cables, together with thimbles, are vulcanized into the sealing disc, for example between two layers, so that the thimbles are fixed in the sealing disc, whilst the wire cables are displaceable in the sealing disc, for instance such as in a guide channel. For fixing the thimbles in the sealing disc for example anchor discs, for example of the same material as the layers of the sealing disc, can be vulcanized in as connection means inside the thimbles. The connection means are then configured as it were in one piece with the sealing disc. The wire cables and/or thimbles can also be arranged outside the sealing disc. 
     Alternatively, the connection means can be configured as eyes, for example sheet metal pieces with a hole, which are arranged completely or partially between the layers of the sealing disc and are securely connected therewith. The wire cables can have hooks at their ends facing the extrusion axis as connecting means which engage into the eyes. The eyes and wire cables can also be connected in another manner. A reverse connection is also conceivable, i.e. hooks as connection means and eyes as connecting means on the wire cables. 
     Drive means, for example a servomotor or pneumatic cylinder, can be provided for drawing in or paying out the wire cables. In an advantageous embodiment, a circumferential wheel can be provided as drive means, which is connected with the wire cables so that by turning the circumferential wheel the radial length of the wire cables is altered. This takes place for example by deflection of the wire cables on an outer diameter of the clamping means arrangement with respect to the passage opening from the radial course to a more circumferential course. This deflection can take place for example on a frame in which the sealing disc is fixed and is guided around the circumferential wheel. By turning the circumferential wheel, the sections of the wire cables running radially and running circumferentially are shortened or lengthened relative to one another. The circumferential wheel can be turned manually or again by means of a servomotor or similar. The frame can have a channel for the circumferentially running sections of the wire cables. 
     In another advantageous embodiment, the clamping means are configured as segments, for example of plastic or metal, aligned for instance radially with respect to the extrusion axis, distributed over the circumference, which enclose between them the passage opening on the extrusion axis. Advantageously, by radial moving of the segments, the diameter of the passage opening can be changed. The radial moving can take place by passive adapting to the pipe diameter, or actively with drive means, for example a servomotor or pneumatic cylinder. 
     In an advantageous embodiment, the segments are provided close to the passage opening with pins, running approximately axially, parallel to the extrusion axis, as connecting means, so that a sealing disc with correspondingly inlet eyes as connection means can be easily fitted. With the passive diameter adaptation, the segments are pushed radially outwards with an enlarging pipe diameter and entrain the sealing rim of the sealing disc owing to the connection by means of connecting means and connection means. When the pipe diameter becomes smaller again, the segments move radially inwards again, for example through the elastic effect of the sealing disc or additional elastic elements. With a passive adaptation of the through-passage opening to the cross-section of the continuous profile, in particular the pipe diameter, the restoring force of the sealing disc (owing to its elasticity) and, if present, the restoring force of the segments (for example through springs) must be configured so that with an increase in size of the pipe diameter the contact pressure by the sealing disc and/or the segments is not too high and the pipe is not damaged. The radial moving of the segments can, as mentioned, also be supported by the assistance of drive means. 
     In a further advantageous embodiment, the clamping means are configured as struts, distributed over the circumference, arranged in a plane approximately perpendicularly to the extrusion axis, which enclose the passage opening in their centre, on the extrusion axis. In an advantageous embodiment, the struts are mounted pivotably by their one end on an outer diameter of the clamping means arrangement with respect to the passage opening, whilst their opposite ends, facing the extrusion axis, engage displaceably into one another and run approximately tangentially to the passage opening, so that by pivoting the struts the diameter of the passage opening is changed. The change in diameter of the passage opening can again take place passively or actively, as already described above. 
     In an advantageous embodiment, at the ends of the struts facing the extrusion axis, pins running parallel to the extrusion axis are provided as connecting means, so that a sealing disc with correspondingly let-in eyes as connection means can be easily fitted. The longer the struts are, or respectively the further the pivot points lie from the extrusion axis, the more the curve described by the pins comes close to the radius course in the case of a change of diameter. It is therefore advantageous to select the distance between pivot points and extrusion axis to be as large as possible, in order to prevent a twisting of the sealing disc about the extrusion axis, or at least to keep it very small. 
     The clamping means, for example in their embodiment as segments or struts, can be configured as a support construction for the axial supporting of the sealing disc. The clamping means are then positioned with respect to the sealing disc so that an axial movement of the sealing rim along the continuous profile is largely prevented. This has the advantage, for example, that the sealing disc can be configured to be relatively thin, so that less material consumption is necessary for the wearing-out sealing disc. In addition, in this way the restoring force of the sealing disc can be kept relatively small, which enables a passive diameter adaptation of the clamping means which are configured as a support construction. 
     The clamping means and connecting means can be configured in one piece with one another, for example wire cable as clamping means with formed loop or thimble as connecting means or segments formed in one piece with pins as clamping- and connecting means. 
     As already mentioned above, drive means, such as for example a servomotor or a pneumatic cylinder, can be provided in order to provide the clamping means with a radial traction- or thrust force. In the case of the configuration of the clamping means as wire cables running radially with respect to the extrusion axis, a circumferential wheel can be provided as drive means, as mentioned above, which is connected with the wire cables so that by turning the circumferential wheel the radial length of the wire cables is changed. Furthermore, control means can be provided for the automatic control or regulation of the drive means as a function of the cross-section of the continuous profile, in particular of the pipe diameter. 
     The seal according to the invention therefore has several advantages—it is able to be used flexibly, independently of the sealing direction, offers a reliable sealing action (also in the case of great changes in pipe diameter), whilst chattering or respectively stick-slip effects are avoided, is easily replacable and operable, is more favourably priced and in addition brings about a saving of space through smaller axial dimensions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention is explained in further detail below with the aid of example embodiments and with reference to the drawings. Further advantageous configurations can be seen from the example embodiments. 
         FIG. 1  shows a section of an extrusion line with a funnel seal and a segment seal according to the prior art. 
         FIG. 2  shows the section of an extrusion line illustrated in  FIG. 1  with a seal according to the invention, instead of the funnel seal. 
         FIG. 3  shows a portion of a seal according to the invention in accordance with a first example embodiment of the invention with radial segments as clamping means. 
         FIG. 4  shows a portion of a seal according to the invention in accordance with the first example embodiment of the invention with radial segments as clamping means and pins as connecting means. 
         FIG. 5  shows a sealing disc with vulcanized-in rings as connection means in accordance with the first example embodiment of the invention. 
         FIG. 6  shows an enlarged cut-out of  FIG. 5 . 
         FIG. 7  shows a section of a seal according to the invention in accordance with the first example embodiment of the invention, in operation. 
         FIG. 8  shows an enlarged cut-out of  FIG. 7 . 
         FIG. 9  shows a portion of a seal according to the invention in accordance with a second example embodiment of the invention with pivotable struts as clamping means. 
         FIG. 10  shows a seal according to the invention in accordance with a third example embodiment of the invention with vulcanized-in wire cables as clamping means. 
         FIG. 11  shows an enlarged sectional illustration of  FIG. 10  with wire cable mount in the circumferential wheel. 
         FIG. 12  shows an enlarged sectional illustration of  FIG. 10  with anchor discs in the thimbles. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a section of an extrusion line, here for the production of pipes, with a pipe  10  running through a vacuum tank  12  and a water collection container  14  and with a known segment seal  16  between vacuum tank  12  and water collection container  14  and a funnel seal  18  at the outlet of the water collection container  14 . 
     Therein, the segment seal  16  comprises only an elastic, approximately flat sealing disc arranged perpendicularly to the extrusion axis with a through-passage opening for the extrude pipe  10  and radially movable segments arranged in extrusion direction behind and parallel to the sealing disc. As the flow direction, owing to the negative pressure in the vacuum tank  12 , acts contrary to the extrusion direction, this principle functions without destroying the simple sealing disc. 
     At the outlet of the water collection container  14 , these forces which oppose one another do not exist; the extrusion direction and flow direction are aligned. Therefore, the segment seal can not be used at this point; it would be destroyed. Therefore, a funnel seal  18  has been used, as shown in  FIG. 1 . However, in the case of small pipe diameters, this has become leaky and, in the case of larger pipe diameters, caused so-called chattering. In addition, the funnel seal was no longer able to be used for very large pipe diameters (in the adjustment range 250 to 450 mm). 
       FIG. 2  now shows the section of an extrusion line illustrated in  FIG. 1  with vacuum tank  12  and water collection container  14  and with a segment seal  16  arranged between vacuum tank  12  and water collection container  14 . However, instead of the funnel seal at the outlet of the water collection container  14  a seal  100  according to the invention, in accordance with a first example embodiment, is arranged. 
       FIG. 3  shows a portion of the seal  100  according to the invention in accordance with the first example embodiment with radially aligned clamping means, arranged circumferentially in a plane perpendicularly to the extrusion axis, in the form of segments  120 , which in their radial centre, on the extrusion axis, form a passage opening  122  for the extruded pipe which is not illustrated this figure. In this example embodiment, the segments  120  are made of plastic. The segments  120  have segment rolls  121  along the passage opening  122 , which lie against the pipe  10  and roll along its surface, in order to keep the friction as small as possible. The segments  120  are arranged so as to be radially moveable and in the case of an enlargement of diameter of the pipe  10  are pressed outwards by the pressure of the pipe  10 . This radial movement can be assisted in addition by drive means, for example servomotors or, as in this example embodiment, pneumatic cylinders  142 . 
       FIG. 4  shows a portion of the seal  100  according to the invention in accordance with the first example embodiment with the elements of  FIG. 3  and additionally with carrier pins  124 , mounted on the segments  120 , as connecting means. The carrier pins  124 , for example made of metal or plastic, are arranged circumferentially close to the passage opening  122  for the extruded pipe  10  and are aligned approximately parallel to the extrusion axis. 
       FIG. 5  shows a sealing disc  126  with a through-passage opening  132 , a sealing rim  130  surrounding the through-passage opening  132 , and carrier rings  128 , arranged close to the sealing rim  130 , as connection means.  FIG. 6  shows an enlarged cut-out of  FIG. 5 . As can be readily seen in these figures, the sealing disc  126  is substantially flat in the unclamped initial state. In this example embodiment, the sealing disc  126  is in addition in one piece and the sealing rim  130  is configured so as to be seamlessly circumferential. In this example embodiment, the carrier rings  128 , for example made of metal, are vulcanized on, and the sealing disc  126  is reinforced in the region of the carrier rings  128 , close to the sealing rim  130 . Of course, the carrier rings can also be mounted in a different way on or in the sealing disc, for example by stamping in or riveting in, or stabilizing elements can be dispensed with and, for example, merely holes can be stamped into the sealing disc. 
     The arrangement of the carrier pins  124  on the segments  120  and the arrangement of the carrier rings  128  on the sealing disc  126  are coordinated with one another, in a complementary manner to one another, so that when the carrier rings  128  are pushed over the carrier pins  124 , the sealing disc  126  is arranged approximately flat in front of the segments  120  and the sealing rim  130  lies against the pipe  10 . 
       FIG. 7  shows the seal  100  according to the invention in accordance with the first example embodiment, in operation.  FIG. 8  shows an enlarged cut-out of  FIG. 7 . The seal  100  comprises the segments  120  with the carrier pins  124  and the sealing disc  126  with the carrier rings  128 . Segment rolls  121 , arranged at the radially inner end of the segments  120 , are also illustrated, which lie against the pipe  10  and roll along its surface, in order to cause as little friction as possible. In this example embodiment, the segments  120  are configured as a support construction and support the sealing disc  126  axially against the water pressure, acting in extrusion direction, of the water in the water collection container  14 —in  FIG. 7  it can be seen how the sealing disc  126  lies against the segments  120 . 
     The carrier pins  124  are mounted close to the passage opening  122 , distributed over its circumference and aligned parallel to the extrusion axis on the segments  120 . In this example embodiment, the carrier pins  124  are anchored to the segments  120  by means of carrier pin anchors  125 , which penetrate the segments  120  and the carrier pins  124  axially. Of course, there are also several alternative fastening possibilities, for example by the carrier pins penetrating the segments directly or by segments being produced in one piece with carrier pins. 
     The carrier rings  128  are fitted onto the carrier pins  124 , so that the sealing disc  126  in its unstressed initial state is arranged approximately flat in extrusion direction in front of the segments  120 . Here, the sealing rim  130  lies against the pipe  10 . In this illustration, the sealing disc  126  is bulged somewhat in extrusion direction owing to the water pressure in the water collection container  14 . 
       FIG. 9  shows the configuration of the clamping means as struts  220  in a seal  200  according to the invention in accordance with a second example embodiment of the invention. The struts  220  are arranged substantially in a plane perpendicularly to the extrusion direction and form in their centre, on the extrusion axis, a passage opening  222 . On an outer diameter with respect to the passage opening  222  with the extrusion axis as central point, a frame  240  is arranged. The struts  220  are mounted pivotably in the frame  240  by their ends facing away from the extrusion axis, whilst their ends facing the extrusion axis lie approximately tangentially against the passage opening  222  and are mounted so as to be displaceable into one another. In this example embodiment, for this displaceable connection of the ends of the struts  220  facing the extrusion axis a pin  224  running parallel to the extrusion axis and an elongated hole  225  in the strut, directed to the frame  240 , are provided at each of these ends. Each pin  224  engages into the elongated hole  225  of the adjacent strut  220  and is displaceable therein. By pivoting the struts  220  in the frame  240 , the pins  224  move in the elongated holes  225  so that the passage opening  222  is increased or decreased in size. The diameter of the frame  240  is selected here to be so large that the pins  224 , in the case of a change in diameter of the passage opening  222 , describe a path which lies almost on the radius of the frame  240 . 
     In this example embodiment, the pins  224  are lengthened so that, in an analogous manner to the first example embodiment, they constitute carrier pins onto which a sealing disc, not illustrated in this example embodiment, with carrier rings (analogous to the first example embodiment, see  FIGS. 5 and 6 ) can be fitted. The mode of operation in the case of a change of diameter is then likewise analogous to the first example embodiment. 
     The larger the diameter of the frame  240 , the more the curve of the pins  224  comes close to the radius line in the case of a change of diameter of the passage opening  222 . It is therefore advantageous to select as large a diameter as possible for the frame  240 , in order to prevent a twisting of the sealing disc about the extrusion axis. 
       FIG. 10  shows a seal  300  according to the invention in accordance with a third example embodiment of the invention. An elastic sealing disc  326 , for example made of rubber, is illustrated therein, with a through-passage opening  332  and a sealing rim  330  surrounding the through-passage opening. Wire cables  320  as clamping means and thimbles or respectively loops  324  as connecting means between two layers of the sealing disc  326 , for example made of rubber, are vulcanized in to the sealing disc  326 . The wire cables  320  are arranged radially with respect to the extrusion axis and form at their end facing the through-passage opening  332  the thimbles  324  in one piece. Within the thimbles  324 , anchor discs  328  ( FIG. 12 ), for example likewise made of rubber, are vulcanized in as connection means between the two layers of the sealing disc  326 . The thimbles  324  are therefore fixed in the sealing disc, whilst the wire cables  320  are displaceable in the sealing disc, so that by traction on the wire cables  320  the diameter of the through-passage opening  332  is enlarged. 
     The sealing disc  326  is enclosed in an approximately planar manner into a frame  340 . A circumferential wheel  342  is mounted rotatably around the frame  340 . The circumferential wheel  342  can be fixed in its rotation position by a retaining screw  344 . The wire cables  320  are fixed on the circumferential wheel  342  and are deflected by rotation of the circumferential wheel  342  on the frame  340 , so that their radial length is shortened and the sealing rim  330  is widened. 
       FIG. 11  shows an enlarged sectional illustration of  FIG. 10 . The fastening of the wire cables  320  on the circumferential wheel  342  in wire cable mounts  346  to receive the wire cables  320  by their end facing away from the through-passage opening  332  can be seen therein. A channel  348 , running in the frame  340 , in which the wire cables  320  run along when the circumferential wheel  342  is turned from the initial position and the radial sections of the wire cables  320  are shortened, can also be seen. 
       FIG. 12  also shows an enlarged sectional illustration of  FIG. 10 . Therein, the anchor discs  328 , vulcanized in within the thimbles  324 , which fix the thimbles  324  in the sealing disc, are emphasized. In this example embodiment, wire cables  320 , thimbles  324  and anchor discs  328  are vulcanized in between two layers of the sealing disc  326 .