DE102013200661B4 - NOZZLE AND HOLE PLATE FOR A UNDERWATER GRANULATOR - Google Patents

Abstract

Nozzle (4) for a granulating head (100) of an underwater granulator, comprising an axial bore (8) opening into an end face (10) of the nozzle (4) for the passage of plastic melt, characterized in that a radially inner contour of one in the direction of passage axially frontmost portion (12) of the end face (10) is spaced radially outward from the axial bore (8), the end face (10) having a conical recess (11) whose surface is parallel to the axial bore (8). vertical plane has an angle of less than or equal to 20 °.

Description

The invention relates to a nozzle for a granulating an underwater granulator according to the preamble of claim 1, a nozzle assembly with such a nozzle, a perforated plate for an underwater granulator, which is adapted for use with such a nozzle according to the preamble of patent claim 6, and an underwater granulator with such a nozzle and / or perforated plate.

Underwater granulators are used to produce plastic granules. For this purpose, the plastic is pressed through the perforated plate of a granulating head into a water chamber. By means of a rotating cutter head emerging from the through holes of the perforated plate plastic strands are severed, the resulting plastic granules is discharged with the cooling water flowing through the water chamber.

The temperature of the plastic melt at the outlet end of the passage openings is of particular importance, since the plastic melt may solidify only after it has emerged. A solidification of the melt already in the through holes of the perforated plate or arranged therein nozzles causes an uneven melt flow or even the interruption of the melt flow. Due to such disturbances, the entire granulating plant may need to be switched off. In particular, when starting the granulating this is also called "freezing" phenomenon to be avoided.

Clogging of individual nozzles during operation has the disadvantage that the granule length changes, uneven granules can arise and the pressure conditions in the granulating head change. The pressure increases due to the increased flow rate as well as the increasing viscosity of non-Newtonian fluids with a larger shear rate. If the contact pressure is generated by an extruder, the backflow length of the melt increases as the head pressure increases, and the product can be thermally damaged. The clogging of individual nozzles thus has a negative effect on the plastic melt and the granulation process.

In the prior art, different solutions are described to guide the plastic melt in the through holes of the perforated plate and in the nozzles so that their surface practically has up to the outlet melt temperature. The perforated plates are heated to the rule, but a strong heat gradient occurs at the outlet side of the perforated plate in contact with the cooling water.

In order to prevent heat flow from the nozzles to the water-contacting perforated plate, ie cooling of the nozzles by the adjacent cooling water, proposes the AT 505 845 B1 to store the nozzles without contact in the through holes of the perforated plate, wherein the direct contact of the nozzle with the perforated plate is avoided by an elastic sealing material. The sealing material rests on an end face of the nozzles and is supported in each case against a shoulder on the outlet-side end of the through-openings, which projects radially into the through-openings. In this way, the heat flow from the nozzles to the perforated plate can be reduced so that the above-mentioned problems are largely eliminated. However, the necessary elastic high-temperature seals are relatively expensive and limited in their thermal capacity. In addition, the seals must be removed, for example during maintenance and either re-used or possibly replaced by new seals.

A solution without such thermally sensitive, separately handled seals is in the DE 10 2010 030 614 A1 proposed. The nozzles are located with their respective exit-side end face on the shoulders of the through holes of the perforated plate directly. Since the nozzles in the outer cross section taper at its outlet end and are only in contact with the perforated plate in the direction of passage axially foremost part of their end faces, the contact area between the nozzles and the perforated plate is small, so that the heat flow between the nozzles and with the perforated plate in contact with the cooling water is small. The pressure of the pressed against the perforated plate nozzle against the free end of the shoulders, which results from the axial adjustment of the nozzle, may result in thinner hole plates that bulges the perforated plate in these relatively weak passage opening areas to the outside. The knife head then no longer runs on a flat surface, so that increases the wear of moving over the perforated plate surface cutting blade.

WO 2010 / 049080A1 discloses a nozzle with an axial bore having a tapered inlet channel and a tapered outlet channel and optionally a cylindrical central region. The end face of the nozzle is flat and perpendicular to the longitudinal axis of the nozzle. The end face of the nozzle is bounded by the outer edge of the nozzle on the one hand and the outer edge of the bore on the other. The axially foremost part of the end face of the nozzle is directly adjacent to the bore. The construction of this nozzle should serve to avoid deposits in the nozzles. In other words, the flow through the nozzle, ie the rheological properties, should be improved.

DE 102 26 749 A1 discloses a nozzle plate having bores, each bore having a conical inlet and a cylindrical or conical outlet, and wherein the diameter of the bore at the inlet to be larger than at the outlet, in particular for influencing the granule size. The inner surface of the bore has an angle to the bore axis perpendicular to an angle of at least 45 °, preferably 67.5 to 82.5 ° on.

EP 0 566 276 A1 discloses a nozzle plate having enlarged diameter bores at the exit end to prevent accumulation of the plastic melt on the exit side of the nozzle plate.

The object of the present invention is therefore to provide a perforated plate for an underwater granulator and nozzles for such a perforated plate, wherein a deformation of the perforated plate is reduced or avoided due to the pressed against the perforated plate nozzles, while a minimum heat flow between the perforated plate and nozzles and a reliable sealing effect remain guaranteed.

This object is achieved by a perforated plate with nozzles for a granulating head of an underwater granulator according to the independent claims. Further developments and advantageous embodiments are specified in dependent claims.

According to the invention, it is provided that a radially inward contour of the axially foremost part of the end face of at least one and preferably all nozzles is spaced radially outwards from the axial passage bore of the nozzle, wherein the end face has a conical recess whose surface is in relation to a plane perpendicular to the axial bore has an angle of less than or equal to 20 °. This axially foremost part of the end face of the nozzle is located on a shoulder of the corresponding through hole of the perforated plate, d. H. this part of the end face forms a contact surface with the perforated plate. By placing this contact surface in a region of the nozzle end face which is radially spaced from the axial through hole of the nozzle, in other words displaced radially outwardly toward the outer periphery of the nozzle compared to known arrangements, the pressure load on the perforated plate is increased displaced radially further away from the passage opening region, which results when the nozzles are pressed from behind against the perforated plate. Due to the law of levers, the regions of the shoulders radially remote from the through-holes can absorb more force without deforming than the free ends of the shoulders facing the through-holes. A disadvantageous deformation of the perforated plate in the region of the passage openings can thus be avoided.

Advantageously, it can be provided that the axially foremost part of the end face comprises an annular surface in a plane perpendicular to the axial bore. It is thus a uniform contact between the nozzles and the perforated plate, in particular a good sealing effect achieved, since not only a linear, but a flat contact can be made. In addition, this is counteracted by deformation of the end faces of the nozzles when pressing the nozzles against the shoulders of the perforated plate. In order to keep the heat flow low, however, the annular surface should be as narrow as possible.

In the radial direction of the passage bore and the axially foremost part of the end face of the nozzle, the surface of the end face is concave, so that the axially foremost part of the end faces is spaced from the axial bore. According to the invention, the concave end face has a conical, in particular frusto-conical, recess, which is preferably arranged coaxially to the axial bore and extends to the axially foremost part of the end face. Particularly advantageously, the axially foremost part of the end face on the outer circumference of the nozzle to maximize the radial distance of the contact surface to the passage bore of the nozzle.

In order to prevent or at least reduce the occurrence of plastic melt between the end faces of the nozzles and the shoulders in the through holes of the perforated plate, it is advantageous if the axial distance between the outlet end of the axial bores of the nozzles and the shoulders of the through holes is minimized. The surface of the conical recess therefore preferably has an angle of less than 20 °, preferably less than 15 °, more preferably less than 10 °, with respect to a plane perpendicular to the axial bore. If necessary, a thin plastic film then forms between the nozzle and the perforated plate in this area. Plastic is a good insulator. The film is so thin that a growth into the through hole is excluded. Although the nozzle can stick in this way the front side with the perforated plate. However, this problem can be effectively dealt with in the below-described field.

In an advantageous embodiment of the nozzle, the outer diameter of the nozzle is constant over the length of the nozzle. The manufacture and construction of the nozzle are so particularly simple and inexpensive. Accordingly, the receiving nozzle in the perforated plate for receiving the nozzles may have a constant inner diameter, which corresponds approximately to the outer diameter of the nozzles. However, the inner diameter of the through holes in the perforated plate is preferably larger than the outer diameter of the nozzles to be inserted into the through hole at least in parts of the through holes located near the perforated plate surface to thermally insulate the nozzles within the perforated plate.

It is advantageous if the perforated plate has a nozzle plate for receiving the nozzles and an outlet side mounted in front of the nozzle plate cutting plate, in which the shoulders of the through holes are formed. The cutting plate forms a wear plate, on which slides the knife head along. The inner diameters of the through openings are preferably larger than the outer diameters of the nozzles at least in the cutting plate. In this way, there is no contact between the cutting plate and the outer periphery of the nozzles. Only the axially foremost part of the end faces of the nozzles is in contact with the cutting plate. Since the cutting plate is in contact with the cooling water of the underwater granulator, so the heat flow between the cutting plate and the nozzle is kept low, which in turn reduces the risk of freezing of the plastic melt in the nozzle.

The nozzles are preferably mounted in the perforated plate such that they are axially adjustable with respect to the perforated plate. In particular, it is advantageous if the nozzles can be inserted into the perforated plate. This allows, in contrast to a screwing the nozzles, which are then provided in this case with an external thread for this purpose, a simpler insertion of the nozzle in the perforated plate. In addition, the manufacture and construction of the nozzles are simplified if they do not require external thread.

Advantageously, therefore, a nozzle assembly is provided for a granulating head of an underwater granulator, which comprises the previously described nozzle and an adjusting screw for axial adjustment of the nozzle in a granulating head of an underwater granulator. In particular, the adjusting screw may be formed as a threaded ring, which has an external thread and an axial bore. The axial bore of the adjusting screw may have the same or a larger diameter as the axial bore of the nozzle, so as not to hinder the passage of the plastic melt.

For axial adjustment of the nozzles in the perforated plate, which is particularly important for sealing the nozzle against the perforated plate and to compensate for manufacturing tolerances, the nozzles, which are preferably inserted into the perforated plate and not screwed, as described above, each axially by means of the adjusting screw to be adjusted. The adjusting screw acts together with the inlet-side end of the corresponding nozzle, preferably without transmitting the rotary motion to the nozzles. The adjusting screw may have a tool engagement surface, for example a hexagon socket, in its axial bore.

For axially adjusting and holding the nozzles, the adjusting screws are screwed into corresponding internal threads of the through holes of the perforated plate. As mentioned, the rotational movement is not transmitted to the nozzles, so that they are only axially displaced. Thus, the axially foremost part of the end faces of the nozzles, which is pressed against the shoulder of the respective passage opening, exposed to no shear forces. This is particularly advantageous if, as described below, an additional insulating layer is provided on the contact surfaces between the nozzles and the perforated plate. The wear of such a layer is reduced if it experiences no shear forces by a rotational movement of the nozzle, but only pressed axially. Also, the removal of the nozzles from the perforated plate, for example, for maintenance purposes is simplified if they are not screwed themselves, but are axially adjusted and held by means of an adjusting screw. The nozzles can, if they have been established, for example, due to occurred in the spaces between the nozzle and perforated plate plastic melt, are simply knocked out of the perforated plate.

Advantageously, a layer is provided between the shoulders of the passage openings and the axially foremost part of the end faces of the nozzles, which in particular serves as insulation in order to reduce the heat flow between the perforated plate and the nozzles. Also, to avoid penetration of plastic melt between the nozzles and the perforated plate, the additional sealing may be advantageous. However, insulation is not required in all cases. Due to the small contact area between the nozzles and the perforated plate, the heat flow is very low anyway, so that the risk of freezing of the plastic melt in the nozzles is correspondingly low. Also, a sufficient tightness can be achieved without additional sealing, when the axially foremost part of the end faces of the nozzle is pressed sufficiently against the shoulders of the perforated plate. The layer preferably comprises a non-sintered, inorganic, non-metallic, in particular mineral, preferably monomineralic material, for example an industrial mineral. The layer preferably consists entirely of such a material.

The invention will now be described by way of example with reference to the accompanying drawings. Show:

1 a granulating head of an underwater granulator in plan view,

2 the granulating head off 1 on average,

3 Detailed views of a contact area between a nozzle and a shoulder in a passage opening in section,

4a an adjusting screw for axially adjusting a nozzle in a through hole, and

4b a nozzle according to the invention for a granulating head of an underwater granulator.

1 shows a granulating head 100 for an underwater granulator in top view. The illustrated side of the granulating head 100 During operation of the underwater granulator is in contact with cooling water, which removes the plastic granules. The perforated plate 1 . 2 is formed by a nozzle plate 2 and an insert 1 and is surrounded by a heating tape 16 which supplies heat energy to the perforated plate to keep the perforated plate at temperature. The use of a heating tape has the advantage over heating cartridges, that during maintenance work, which is a removal of the perforated plate 1 . 2 from the granulating head 100 require, is easy to remove.

The perforated plate 1 . 2 has outlet holes arranged in a circle 6 on, through which plastic melt in the (not shown) water chamber exits, in this embodiment 16 evenly distributed exit holes 6 , The exit holes 6 are here in particular by the cutting plate 1 formed on which a knife block (not shown) rotates to produce the granules. The cutting plate 1 consists of a material which is better protected against wear by the knife block sliding over it than the nozzle plate 2 and is therefore also referred to as wear plate. The cutting plate 1 is with the nozzle plate 2 connected, which in turn via connecting elements 19 , for example screws, with a (in 1 not shown) basic component of the granulating head is connected.

In 2 is the granulating head 100 out 1 shown in section. The plastic melt is initially on the inlet side of the granulating 100 by means of a cone 14 divided into several streams. The melt streams pass through channels 17 in the base member 18 to passage openings 3 in the perforated plate, which through the nozzle plate 2 and cutting plate 1 is formed. The basic component 18 is by means of heating cartridges 15 heated so that the plastic melt in the channels 17 not frozen.

The perforated plate 1 . 2 is on the base part 18 attached and - as already related to 1 described - from the heating tape 16 surround. To the perforated plate 1 . 2 To protect against wear is in the area of the exit holes 6 the cutting plate 1 appropriate. In the passages 3 , which in this embodiment through the nozzle plate 2 and the cutting plate 1 lead, are nozzles 4 arranged, through which the plastic melt is passed. The nozzles 4 be in the through holes 3 by means of adjusting screws 5 held in the axial direction in the form of threaded rings. In this way, every nozzle can 4 be adjusted individually, for example during maintenance or even when building a granulation, so that small tolerances, especially in the axial dimensions of the nozzle 4 overcome and the desired contact pressure between the nozzles 4 and the cutting plate 1 can be applied.

In 3 is a detail view of a contact area between a nozzle 4 and a shoulder 7 a passage opening 3 in the cutting plate 1 shown. The nozzle 4 has an end face at its exit end 10 on, in which an axial bore 8th the nozzle 4 empties. Through the axial bore 8th the plastic melt becomes the exit hole 6 transported, where the melt by means of a rotating cutter head (not shown) is separated. The face 10 the nozzle 4 has a frusto-conical recess 11 on to the contact area between the nozzle 4 and the cutting plate 1 to reduce and thereby the heat flow between the cutting plate 1 and the nozzle 4 to reduce. The axially foremost part in the direction of passage 12 the face 10 which is a contact surface to the shoulder 7 is is from the axial bore 8th the nozzle 4 spaced radially outwards. In this embodiment, the axially foremost part 12 the face 10 on the outer edge of the face 10 so that the nozzle 4 overall has a constant outer diameter along its length. The axially foremost part 12 the face 10 is preferably narrow in relation to the overall diameter of the nozzle 4 For example, the axially foremost part 12 the face 10 have a width of 0.5 to 1.0 mm with an outer diameter of the nozzle of about 8 mm.

Due to the displacement of the contact surface (part 12 the face 10 ) as far as possible from the axial bore 8th the nozzle 4 away, there is a risk of deforming the insert 1 reduced. In particular, the risk of buckling of the cutting plate 1 reduced to the outside. Such deformation may occur because of axial adjustment of the nozzles 4 this against the shoulder 7 the passage openings 3 be pressed to achieve a seal. However, the further the contact area between the nozzle 4 and the shoulder 7 from the axial bore 8th or the exit hole 6 the better the shoulder can be 7 which is, for example, only 1 mm thick (with a thickness of the insert 1 from about 7 to 9 mm), absorb these axial forces without deformation.

To prevent penetration of plastic melt into the conical part of the face 10 , in this embodiment, the frusto-conical recess 11 To keep it as low as possible, it is beneficial if the recess 11 as flat as possible. In this embodiment, the angle between a plane perpendicular to the axial bore 8th and the surface of the conical recess 11 about 15 °.

In addition, the outer diameter of the nozzle 4 smaller than the inner diameter of the through hole 3 in the cutting plate 1 , leaving a gap 20 is formed and no radial contact between the cutting plate 1 and the outer periphery of the nozzle 4 consists. For example, the nozzle 4 a diameter of about 7-8 mm and the passage opening 3 in the cutting plate 1 have a diameter of 10 mm, leaving a gap 20 of about 1 mm is formed. The gap 20 serves as insulation to prevent heat flow between the insert 1 and the nozzle 4 to prevent.

Furthermore, a layer 24 between the axially foremost part 12 the face 10 and the shoulder 7 provided, which serves as insulation and / or sealing. The layer 24 consists of an industrial mineral, in particular a monomineral material. The layer 24 is hardly flexible and in particular not plastically deformable even at high temperatures.

In 4a is an adjustment screw 5 represented in the form of a threaded ring. The adjusting screw 5 has an external thread 23 , an axial bore 21 and a tool engagement surface 22 in the form of a hexagon socket. The axial bore 21 the adjusting screw 5 has a sufficiently large diameter so as not to hinder the melt flow. In particular, the diameter of the axial bore 21 the adjusting screw 5 greater than or equal to the diameter of the axial bore 8th the nozzle 4 For example, 6 mm, wherein the maximum diameter of the axial bore of the nozzle, for example, 5.5 mm.

In 4b is the nozzle 4 shown. The axial bore 8th has three sections, which extend in the direction of the exit-side end face 10 Rejuvenate in their inner diameter. For example, the inlet-side portion of the axial bore 8th have a diameter of 5.5 mm, the middle section has a diameter of 4 mm and the outlet-side section has a diameter of about 3 mm, for example 2.9 mm. Preferably, the exit holes 6 the cutting plate 1 then a diameter of 3.0 to 3.2 mm. The constant outer diameter of the nozzle 4 is for example about 8 mm.

The nozzles 4 themselves have no thread. They are in the passageways 3 the perforated plate 1 . 2 plugged in. By means of adjusting screws 5 become the nozzles 4 against the appropriate shoulder 7 pressed and in the respective passage opening 3 held, with the contact pressure by means of adjusting screws 5 easy and can be adjusted separately for each nozzle. The adjusting screws 5 each act on the entrance end 13 the nozzles 4 without turning them over. Because the nozzles 4 even not be turned, no shear forces on the layer 24 exercised, which could otherwise be damaged. The nozzles 4 just be axial against the shoulders 7 and the layer 24 pressed to achieve a sufficient seal. To remove the nozzles 4 after removing the adjusting screws 5 simply pulled out or knocked out.

Claims (13)

Jet ( 4 ) for a granulating head ( 100 ) of an underwater granulator comprising one in an end face ( 10 ) of the nozzle ( 4 ) opening axial bore ( 8th ) for the passage of plastic melt, characterized in that a radially inner contour of an axially foremost part in the direction of passage ( 12 ) of the end face ( 10 ) from the axial bore ( 8th ) is spaced radially outwards, wherein the end face ( 10 ) a conical recess ( 11 ), the surface of which with respect to one of the axial bore ( 8th ) vertical plane has an angle of less than or equal to 20 °. Nozzle according to claim 1, wherein the axially foremost part ( 12 ) of the end face ( 10 ) an annular surface in a plane perpendicular to the axial bore ( 8th ). Nozzle according to claim 1 or 2, wherein the recess ( 11 ) coaxial with the axial bore ( 8th ) is arranged and extends from the axial bore radially outward to the axially foremost part ( 12 ) of the end face ( 10 ). Nozzle according to one of claims 1 to 3, wherein the surface of the conical recess ( 11 ) with respect to one to the axial bore ( 8th ) vertical plane at an angle of less than 15 °, preferably less than 10 °. Nozzle kit for a granulating head ( 100 ) of an underwater granulator comprising a nozzle ( 4 ) according to one of claims 1 to 4 and an adjusting screw ( 5 ), with the adjusting screw ( 5 ) an external thread ( 23 ) and an axial bore ( 21 ) whose diameter is greater than or equal to the diameter of the axial bore ( 8th ) of the nozzle ( 4 ). Perforated plate ( 1 . 2 ) for a granulating head ( 100 ) of an underwater granulator with passage openings ( 3 ) for the passage of plastic melt and into the passage openings ( 3 ) used nozzles ( 4 ), wherein at least one of the nozzles ( 4 ) one in an end face ( 10 ) of the nozzle ( 4 ) opening axial bore ( 8th ) to the passage of the plastic melt and having a in the direction of passage axially foremost part ( 12 ) of her face ( 10 ) on a shoulder ( 7 ) of the corresponding passage opening ( 3 ) is applied, characterized in that a radially inner contour of the axially foremost part ( 12 ) of the end face ( 10 ) from the axial bore ( 8th ) of the nozzle ( 4 ) is spaced radially outwards, wherein the end face ( 10 ) a conical recess ( 11 ), the surface of which with respect to one of the axial bore ( 8th ) vertical plane has an angle of less than or equal to 20 °. Perforated plate according to claim 6, wherein the axially foremost part ( 12 ) of the end face ( 10 ) an annular surface in a plane perpendicular to the axial bore ( 8th ) of the nozzle ( 4 ). Perforated plate according to claim 6 or 7, wherein the recess ( 11 ) coaxial with the axial bore ( 8th ) of the nozzle ( 4 ) and up to the axially foremost part ( 12 ) of the end face ( 10 ). Perforated plate according to one of claims 6 to 8, wherein the nozzle ( 4 ) in the perforated plate ( 1 . 2 ) is stored in such a way, in particular plugged in, that with respect to the perforated plate ( 1 . 2 ) is axially adjustable. Perforated plate according to claim 9, wherein the nozzle ( 4 ) by means of an adjusting screw ( 5 ), which have an entry-side end ( 13 ) of the nozzle cooperates, without rotational movement of the nozzle ( 4 ) is axially adjustable. Perforated plate according to one of claims 6 to 10, wherein at least between the shoulder ( 7 ) of the passage opening ( 3 ) and the axially foremost part ( 12 ) of the end face ( 10 ) of the nozzle ( 4 ) a layer ( 24 ), which comprises a mineral, preferably monomineralic material. Perforated plate according to one of claims 6 to 11, wherein the perforated plate ( 1 . 2 ) a nozzle plate ( 2 ) for receiving the nozzles ( 4 ) and one exit side in front of the nozzle plate ( 2 ) mounted cutting plate ( 1 ), in which the shoulders ( 7 ) of the passage openings ( 3 ) are formed, wherein the inner diameter of the passage openings ( 3 ) at least in the cutting plate ( 1 ) are larger than the outer diameter of the nozzles ( 4 ). Underwater granulator for granulating plastics, comprising at least one nozzle ( 4 ) according to one of claims 1 to 4 and / or at least one nozzle assembly according to claim 5 and / or a perforated plate ( 1 . 2 ) according to any one of claims 6 to 12.

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