EP0330003B2 - Screw extruder - Google Patents

Abstract

Screw extruder comprising a screw (1) consisting of two sections (11, 12), the connection of which is provided by a surface-bearing coupling which is held under prestress using a safety device. The second screw part (12) at the free screw end consists of wear- resistant material, in which the dimensions of the screw core, screw thread and of the screw end are in conformity with the requirements of the material to be extruded. <IMAGE>

Description

The invention relates to a screw press with a cantilevered screw that can be driven into a conical press nozzle and is arranged in a screw trough with a feed opening.

Screw presses of this type are used to compact goods with a low bulk density or to mix and plasticize substances using a high compression pressure.

With these screw presses, due to the nature of the ingredients, particularly abrasive substances such as quartz or TiO2 etc. and due to the high pressing pressures to be applied, very high frictional forces on the conveying flank of the worm gear, which lead to very rapid removal of the worm gear, the zone of greatest wear, contrary to the flow of material, always detecting new areas of the worm until the entry of the press nozzle is reached.

To overcome this problem, in addition to the usual measures of surface treatment by applying layers of particularly wear-resistant material, more complex methods have also been proposed by dividing the screw into successive segments and producing them from cast hard material, which have been pushed onto a core piece. The main disadvantage of this arrangement is that the screw diameter had to be increased considerably if the load-bearing core had the required load capacity. Furthermore, with screws of larger construction length, difficulties arise in applying the necessary pretensioning forces, which are required for sealing against the penetration of material at the dividing points, and moreover the load limit for hollow screw pieces made of hard material is slightly exceeded and thus leads to the destruction of the screw and heavy ones Machine malfunctions.

In order to avoid these disadvantages, it has been proposed to provide a division on a screw and to provide the two screw parts with a threaded bore and screw them with a threaded bolt on both sides, an additional adjusting screw being provided to ensure that the screw turns of the two screw parts continuously, ie can be assembled without protruding joint.

In addition to the fact that this device requires extensive adjustment measures, a sufficiently large screw core diameter must be available so that the forces that occur can be transmitted. These cross-sections are available when using conical press nozzles because of the diameter of the screw core, which is to be reduced towards the free end of the screw, in the region of the free screw end, which is arranged within the conical press nozzle, which allows the transfer of the necessary force for those running there Mixing and compaction processes. From this division to the free end of the screw, the forces acting on the screw increase extremely. This is the area of the conical press nozzle in which the material is made strong and compressed or even plasticized.

When processing pressed goods, where the flowability at the end of the consistent press nozzle is not always sufficient, or if foreign bodies create particularly high resistance due to their position, it is particularly important to reverse the screw for the conveyance into the conical press nozzle, i.e. for conveying to drive at least briefly in the direction of the feed opening. available - an increase in the nozzle diameter would result in a disproportionate increase in the pressing forces, so that the problem cannot be solved thereby.

The object of the invention is to sustainably reduce the removal on the screw using a relatively simple design thereof in a screw press of the type mentioned at the outset and to enable simple replacement of the part of the screw located in the wear zone without disadvantageously shaping the screw winding to change.

This object is achieved on a screw press of the type mentioned by the means of claim 1.

Particularly advantageous embodiments of the invention are claimed in subclaims 2 to 28.

The use of a pressure-bearing coupling between the screw parts in connection with a fixed assignment of the screw parts in relation to their position in the direction of rotation enables a safe transmission of the large forces and ensures that there are no fluidically unfavorable transitions in the division area of the screw, which the removal and increase the frictional resistance.

It is particularly advantageous to divide either at the transition between the screw part with a constant core diameter and that with a decreasing diameter or at the transition between the high and low pitch of the

When processing pressed goods, in which material can penetrate into gaps in liquid or fine particles, the abutting surfaces in the division area of the screw must be processed particularly carefully and prestressed against each other. In both cases, a securing device is particularly advantageous, which secures the two assembled screw parts against axial glazing, wherein in the former case much greater forces have to be secured.

A particularly simple and effective securing is achieved with the aid of several setscrews which are screwed into the screw part with the polygonal bore and are brought into contact with the corresponding flanks of countersunk bores or bores on the polygonal pin of the other screw part with generation of a preload.

The set screws can be inserted perpendicular to the longitudinal axis of the screw. If particularly high pre-tensioning forces are to be used, an attachment at an acute angle obliquely to the longitudinal axis in the direction of the pre-tensioning force is of particular advantage because of the longer available pin length and the stress from shear to pressure.

The setscrews can also be replaced by adapter sleeves that are lined out if a particularly simple construction is necessary.

For the load capacity of the coupling, it is favorable to arrange the grub screws in the central area of the polygon surfaces and to separate them particularly advantageously from the transmission surfaces in order to avoid areas of particularly high load and to increase the permanent load capacity of the worm, especially the free end.

The use of special material has proven to be particularly advantageous, as a result of which the free end of the screw can have a very high level of stability, while the less stressed screw part can be produced from a more easily produced, cheaper material.

Of particular importance is the design of the second screw part with the free screw end with regard to the flank angle of the conveying flank of the screw flight for the direction of action of the pressing force in the axial direction as possible and the opening angle of the screw flight for the conveyance of the pressed material and the low-loss compression of the same, these two having a flank angle Define the support flank of the worm gear, which is important for the resilience and stability of the worm.

With solid, little or not liquid pressed material, e.g. Pre-shredded waste paper, the formation of the area at the free screw end is of particular importance. It is particularly favorable to taper the screw flight and the screw core of the second screw part at an angle to the longitudinal axis of the screw in order to keep the friction work and thus the load on the screw within limits and to smooth the transition between compression and conveyance and advance of the compact shape.

By designing the free end of the second screw part as a spherical section that merges into the screw flight and the screw core, the screw is supported so that bending stresses are reduced and at the same time excessive hole formation and inadequate compression of the compact are prevented by the termination of the Press work is done gradually.

With regard to the dimensions of the screw core and ball section, certain conditions are particularly favorable for perfect pressing work and trouble-free operation.

The dividing surfaces between the first and second screw parts are of particular importance, whereby special training forms, such as particularly conical design, offer advantages for the transfer of the pressing forces and for the sealing against penetrating substances. The particularly careful finishing of the dividing surfaces is cheap, but also reduces bending loads on the first screw part, which is sensitive and made of special material.

The production of a corrosion protection coating on the first screw part, the material of which is less corrosion-resistant than that of the second screw part, which withstands the high pressure, is of great importance for the stability of the screw in a split version.

For the perfect production of compacts from solid, pre-shredded material such as waste paper in particular, it is important to move the free end of the screw to the end of the compression section in the conical press nozzle so that the pressing process results in a sufficiently uniform press material. For this material, an above-sized feed opening of sufficient size is particularly advantageous.

For the processing of pre-shredded waste paper, the establishment of a metered addition of water is of particular advantage because the mixing and pressing process is thereby facilitated and improved, while the water supplied, due to the energy also supplied, essentially evaporates after the compacts emerge from the press.

The invention is described with reference to the drawing of an embodiment according to the invention.

• Fig. 1 eine schematische Seitenansicht einer Schneckenpresse als Brikettiermaschine,
• Fig. 2 den vorderen Teil einer Schnecke mit deren geteiltem Aufbau, teilweise im Schnitt,
• Fig. 3 den vorderen Teil einer Schnecke mit einem abgeänderten Aufbau der Teilung, teilweise im Schnitt und
• Fig. 4 einen Querschnitt durch die Schnecke im Bereich der Teilung nach I-II.

It shows :

• 1 is a schematic side view of a screw press as a briquetting machine,
• 2 the front part of a snail with its divided structure, partly in section,
• Fig. 3 shows the front part of a snail with a modified structure of the division, partly in section and
• Fig. 4 shows a cross section through the screw in the area of the division according to I-II.

In a screw press, the screw 1 is arranged in a screw trough 2 which has an upper feed opening 3 through which the material to be pressed is fed.

The screw 1 is overhung and can be driven in both directions by means of a drive, not shown.

The screw 1 conveys the material to be pressed through a conical press nozzle 4, in which it is mixed and compressed, which exits through an outlet opening 5 as a strand between the jaws of a pliers press 34 in the form of compacts 35.

The worm 1 consists of a first worm part 13 with a first region 8 of the worm core 7 with a constant diameter and a first section 11 of the worm thread 10 with a large pitch and from a second worm part 14 adjoining it with a second region 9 of the worm core 7 for free Screw end 6 tapering diameter, which carries a second, tapering section 12 of the screw flight 10, which are detachably connected to one another by means of a surface-supporting coupling 15 with a polygonal profile. The conveyor flanks 16, 17 of the first and second screw parts 13, 14 are flush with one another at the dividing point 20.

The conveying flank 17 of the second screw part 14 can be offset in relation to the direction of rotation 18 of the screw 1 by a fraction of the winding thickness 19 of the screw flight 10, but the assignment of the two screw parts 13, 14 is unchangeable.

The pressing force is transmitted via a polygon pin 22 and a polygon bore 23, the length of the coupling being determined by the forces that occur.

To produce a contact pressure between the dividing surfaces 39, 39 'of the screw parts 13, 14 at the dividing point 20 and to protect them from being pulled out when the screw 1 returns in a circumferential direction 24, in which the conveyance away from the conical press nozzle 4 and towards the feed opening 3 is directed - if blockages are to be removed - the coupling 15 is provided with a securing device 25, which comprises three setscrews 26 which are screwed into threaded bores 27 perpendicular to the longitudinal axis 21 of the screw 1 and with their ends in each case against the facing flank 29 of the counterbore 28 come into contact in a cylindrical rotation 30, 30 'of the polygon pin 22. The position of the setscrews 26 in relation to the polygon profile is at the apex 36 of the polygon surface 40 of the polygon pin 22.

The two dividing surfaces 39, 39 'are perpendicular to the longitudinal axis 21 of the screw 1 in FIGS. 2 and 3.

These dividing surfaces 39, 39 'can form inclined conical surfaces at a larger transition angle 41, which result in larger coupling surfaces and a more favorable transition between the polygon pin 22 and dividing surface 39, 39'.

In the embodiment shown in FIG. 2, the conical press nozzle 4 extends over the area of the second screw part 14, so that the dividing point 20 is arranged at the end of the first section 11 of the screw flight 10 and the first area 8 of the screw core 7, and the second screw part 14 with the free screw end 6, the polygon pin 22 carries.

In the embodiment according to FIG. 2, the conical press nozzle 4 is pulled further to the rear and extends into the area 8 of the screw core 7 with a constant diameter and the first section 11 of the screw flight 10, with a dividing point 20 which is moved further away from the free screw end 6 is, whereby a larger diameter of the screw core 7 is available, so that here the first screw part 13 can carry the polygon pin 22.

Depending on the position at the base 31 or at the end 32 of the polygon pin 22, the cylindrical rotation 30, 30 'has a diameter which circumscribes or inscribes the polygon profile.

The conveying flank 17 of the second screw part 14 has a flank angle 37 of 75 ° approaching 90 °, through which the pressing pressure is directed sufficiently axially.

The opening angle 38 between the screw turns of the screw 10 is 30 degrees, with which the conveying of the pressed material is ensured.

The second screw part 14 has a second region 9 of the screw core 7, which tapers towards the free screw end 6 at an angle to the longitudinal axis 21 of the screw 1 of 5 angular degrees, while the second section 12 of the worm gear 10 counters at an angle of 20 angular degrees the free screw end 6 tapers.

The free screw end 6 is formed by a spherical section 42, the radius of which is large in comparison to the second region 9 of the screw core 7 and which causes the centering and the smooth transition from compression and conveyance to pure conveyance.

With an increase in the opening angle 38 between the screw turns, the support flank 44 is flattened, thereby strengthening the screw flight 10.

Reference numeral: EM 81 005

1

slug

2nd

Snail trough

3rd

Food opening

4th

conical press nozzle

5

Outlet opening

6

free screw end

7

Snail core

8th

first area of the screw core 7

9

second area of the screw core 7

10th

Snail gear

11

first section of the worm gear 10

12th

second section of the worm gear 10

13

first snail part

14

second snail part or snail head

15

clutch

16

Conveying flank of the first screw part 13

17th

Conveying flank of the second screw part 14

18th

Circulation direction for conveying into the press nozzle 4

19th

Winding strength of the worm gear 10

20th

Division of snail 1

21

Longitudinal axis of the worm 1

22

Polygon cones

23

Polygon drilling

24th

Direction of rotation for the promotion of the press nozzle 4 directed away

25th

Safety device

26

Grub screw

27

Tapped hole

28

Counterbore

29

Flank of the counterbore

30.30 '

cylindrical rotation

31

Bottom of the polygon pin 22

32

End of the polygon pin 22

33

Snail end

Claims (28)

1. A screw extruder comprising an overhung screw drivable for conveyance into a conical extrusion die and arranged in a screw trough having a feed opening, adjoining which screw trough is an extrusion die tapering towards at least one outlet opening, said screw comprising a first region of the screw core having a substantially constant diameter and an adjoining second region with a core diameter narrowing towards the free screw end and the part of the screw provided with at least one screw thread and extending towards the free end comprising at least two successive sections with different screw windings, of which the second section arranged towards the free screw end has a smaller pitch than the first section arranged behind and the screw being enclosed at least in the second section by the conical extrusion die and being formed by two screw parts, of which the second screw part arranged towards the free end of the screw is connected with the first screw part by means of a coupling transmitting the generated torque, and in which the second screw part (14) and the first screw part (13) are disposed in a fixed arrangement relative to one another, so that the conveying flank (17) of the screw windings of the second screw part (14) adjoins the conveying flank (16) of the screw windings of the first screw part (13) in precise flush fashion, characterised in that the coupling is formed from a polygonal journal (22) on the one screw part (13,14) and from a polygonal bore (23) on an other screw part (13, 14) and that the second screw part (14) is manufactured from particularly wear-resistant material necessarily having a reduced loading capacity, of hot isostatically pressed steel having a high content of finely distributed vanadium carbides, and is preferably manufactured from an forged blank.
2. A screw extruder according to claim 1, characterised in that the axial extension of the polygonal journal (22) corresponds at least to the greatest diameter of the screw core (7).
3. A screw extruder according to claim 1, characterised in that the screw (1) is divided between the second screw part (14) and the first screw part (13) at the transition between the first region (8) of the screw core (7) with the constant diameter and the second region (9) of the screw core (7) with the tapering diameter.
4. A screw extruder according to claim 1, characterised in that the screw (1) is divided between the second screw part (14) and the first screw part (13) at the transition between the first section (11) of the screw thread (10) with the larger pitch and the second section (12) of the screw thread (10) with the smaller pitch.
5. A screw extruder according to claim 3 and 4, characterised in that the transitions between the first region (8) and the second region (9) of the screw core (7) and the first section (11) and the second section (12) of the screw thread (10) essentially coincide with the dividing site (20) of the screw (1).
6. A screw extruder according to claim 5, characterised in that the dividing site (20) forms a plane extending vertical to the longitudinal axis (21) of the screw (1).
7. A screw extruder according to one or more of the preceding claims, characterised in that the polygonal journal (22) is formed on the second screw part (14) and the polygonal bore (23) in the first screw part (13), when no more than the second region (9) of the crew core (7) with the tapering diameter and/or the second section (12) of the srew thread (10) is enclosed by the conical extrusion die (4).
8. A screw extruder according to one or more of the preceding claims, characterised in that the polygonal journal (22) is formed on the first screw part (13) and the polygonal bore (23) in the second screw part (14), when in addition to the second region (9) of the screw core (7) and/or the second section (12) of the screw thread (10), part of the first region (8) of the screw core (7 and/or of the first section (11) of the screw thread (10) is enclosed by the conical extrusion die (4).
9. A screw extruder according to one or more of the preceding claims, characterised in that the screw (1) is designed so that, in addition to the direction of rotation (18), it can also be driven at least temporarily in the opposite direction of rotation (24), during which time the conveyance is effected away from the conical extrusion die (4) towards the feed opening (3).
10. A screw extruder according to claim 9, characterized in that the screw (1) is provided in the region of the coupling (15) with a safety device (25), which secures the first screw part (13) and the second screw part (14) against axial displacement.
11. A screw extruder according to one or more of the preceding claims, characterized in that the safety device (25) comprises at least one, preferably more and in particular three threaded pin(s) (25), which is (are) inserted in (a) threaded bore(s) (27) in the part of the screw (1) comprising the polygonal bore (23).
12. A screw extruder according to claim 11, characterized in that the safety device (25) engages with each threaded pin (26) in a counterbore (28) or an internal turn of the polygonal journal (22), the threaded pin (26) coming to rest with its end face against the facing flank (29) of the counterbore (28) or internal turn, thereby exerting a pretensioning force acting between the screw parts (13, 14).
13. A screw extruder according to claim 11 or 12, characterised in that the threaded pins (26) are arranged on the circumference of the screw core (7) in such a manner that, viewed in the cross section of the screw (1), they are arranged In the central region, preferably in the apex (36), of the polygonal surface (40).
14. A screw extruder according to one or more of claims 11 to 13, characterised in that the threaded pins (26) are screwed in vertical to the longitudinal axis (21) of the screw (1).
15. A screw extruder according to claim 14, characterized in that the threaded pins (26) are screwed in at an acute angle in the direction of the pretensioning force Inclined relative to the longitudinal axis (21) of the screw (1).
16. A screw extruder according to claims 11 to 15, characterized in that the threaded pins (26) are replaced by clamping sleeves.
17. A screw extruder according to one or more of the preceding claims, characterized in that the safety device (25) is arranged on a cylindrical internal turn (30, 30') at the base (31) or end (32) of the polygonal journal (22) and accordingly comprises a circumference circumscribing the polygonal cross section or inscribed therein.
18. A screw extruder according to one or more of the preceding claims, characterized in that the conveying flank (17) of the second screw part (14) has a flank angle (37) of between 60 and 90°, which is preferably closer to 90° and can be 75°.
19. A screw extruder according to one or more of the preceding claims, characterized in that an angle of opening (38) is formed between successive windings of the screw thread (10) of between 15 and 45°, preferably 30°.
20. A screw extruder according to one or more of the preceding claims, characterized in that, at least in the region of the free screw end (6), the second screw part (14) has a tapering of the screw thread (10) forming an angle with the longitudinal axis (21) of the screw (1) of between 15 and 30°, preferably 20°, measured at a tangent to the screw thread (10).
21. A screw extruder according to one or more of the preceding claims, characterised in that, at least in the region of the free screw end (6), the second screw part (14) has a tapering of the screw core (7) forming an angle with the longitudinal axis (21) of the screw (1) of between 2 and 10°, preferably 5°, measured at a generatrix (43) of the screw core (7).
22. A screw extruder according to one or more of the preceding claims, characterised in that the second screw part (14) ends at its free screw end (6) with a shape corresponding to a body of revolution having a constant curvature with its apex in the longitudinal axis (21) of the screw and which preferably forms a spherical segment (42), whose radius forms a ratio with the screw core diameter at the free screw end (6) of between 1 : 0.3 and 1 : 0.8, preferably 1 : 0.5.
23. A screw extruder according to one or more of the preceding claims, characterised in that the dividing surfaces (39, 39') of the screw parts (13, 14) are designed to extend at an angle to the longitudinal axis (21) of the screw (1) deviating from a right angle, so that a transition angle (41) greater than 90° is formed between the dividing surfaces and the polygonal surface (40) of the polygonal journal (22) at the base of said journal, the dividing surfaces (39, 39') having a conical or spherical shape or forming surfaces of a higher order.
24. A screw extruder according to one or more of the preceding claims, characterised in that the dividing surfaces (39, 39') of the screw parts (13, 14) are finely ground at the dividing site (20) of the screw (1).
25. A screw extruder according to one or more of the preceding claims, characterised in that the dividing surface (39) of the first screw part (13) of the screw (1), and the surface of the polygonal bore (23) and preferably the outer surface of the first screw part (13), at least in the region in which it is acted upon by extrusion material, is provided with a coating protecting against corrosion, which withstands the occuring pressing forces at the dividing surface (39) and is preferably obtained by gas nitration of the first screw part (13).
26. A screw extruder according to one or more of the preceding claims, characterised in that the second screw part (14) with the screw end (33) ends essentially at the site of the conical extrusion die (4) where the latter's tapering, i.e. having the smallest diameter, ceases.
27. A screw extruder according to one or more of the preceding claims, characterised in that the screw (1) is acted upon by extrusion material from a feed opening (3) arranged at the top and preferably essentially covers the first screw part (13).
28. A screw extruder according to one or more of the preceding claims, characterised in that, for manufacturing briquettes (35) from pre-pulverized waste paper, the screw (1) is provided in the region of the conical extrusion die (4) with a device for the addition of water during the mixing and compression process.

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