Centrifugal screw, and solid bowl screw centrifuge

Abstract

The invention relates to a centrifugal screw (10) comprising a screw hub (15) and a screw flight (20) connected to the screw hub (15), the screw hub (15) having, in the longitudinal direction (R), at least one cylindrical longitudinal portion (11) and a portion (12) at the solid-discharge end. According to the invention, an open wall structure (40) is formed only in some sections of the cylindrical longitudinal portion (11), said open wall structure (40) in the cylindrical longitudinal portion (11) extending at most over a length (LW) of 50% of the total length (GL) of the cylindrical longitudinal portion (11).

Description

[0001] The invention relates to a centrifuge screw with a screw hub and a screw helix connected to the screw hub, wherein the screw hub has a cylindrical longitudinal section and a solids discharge section in the longitudinal direction, according to the preamble of claim 1. Furthermore, the invention relates to a solid-jacket screw centrifuge according to claim 11.

[0002] Solid-jacket screw centrifuges are characterized by a drum with a closed or solid jacket. The drum is rotated at high speed, allowing a multiphase mixture inside to be separated into at least a heavy phase and a light phase. The heavy phase is typically a solid phase, which is conveyed out of the drum by a screw, i.e., a centrifuge screw. For this purpose, the screw is mounted so that it can rotate within the drum and has a helix. The helix is ​​arranged around a screw hub.

[0003] The screw helix travels along the inner surface of the drum, conveying the heavier phase material to an axial end of the drum. At the end of the drum, the heavier phase material is discharged. The multiphase mixture to be clarified is therefore located between the inner surface of the drum and the screw hub.

[0004] In certain solid-wall screw centrifuges, a large pond depth is desirable, particularly for clarification reasons. However, the pond depth is limited by the diameter of the screw hub and the resulting buoyancy and sedimentation effects of the mixture or light phase being clarified.

[0005] WO 2010 / 142300 A1 discloses a solid-bowl screw centrifuge with an inlet area on the solids discharge side. A feed accelerator is provided in the inlet area to accelerate the feed of the material to be processed into the separation chamber via the inlet area.

[0006] From EP 0 602 766 A2, a decanter centrifuge is known with a hub that is largely made of solid material, with support ribs located on the outer circumference of the hub. A screw helix is ​​attached to these support ribs. The inlet chamber is directly adjacent to the solids discharge side of the screw hub.

[0007] From DE 18 15 199 A1 and DE 10 20 575 B it is known to form only small circular openings in a tubular hub.

[0008] EP 2 551 020 A1 discloses a snail hub with rectangular passage openings.

[0009] WO 2016 / 019944 A1 discloses a solid-bowl screw centrifuge with a screw hub that has a cylindrical section with a lattice structure. The cylindrical section is formed entirely from the lattice structure. The lattice structure is essentially composed of longitudinal bars, allowing the medium to be clarified to flow through openings between the longitudinal bars into the drum chamber or separation chamber. Such a structure, consisting solely of longitudinal bars, has the disadvantage of insufficient torsional stiffness. Furthermore, high centrifugal forces act on the longitudinal bars during operation, negatively affecting the running behavior of the screw hub.

[0010] To increase the rigidity of the worm hub, stiffeners in the form of diagonal braces are used inside the cylindrical section. Such diagonal braces can only be installed with considerable straightening and welding effort, thus increasing the overall costs associated with the worm hub's design. Furthermore, because the diagonal braces are located inside the cylindrical section, the worm hub exhibits reduced material utilization.

[0011] The invention is therefore based on the objective of providing a centrifuge screw that, through an improved design, exhibits increased rigidity and simultaneously improved flow characteristics, and is also easier to manufacture. Furthermore, the invention is based on the objective of providing a solid-wall screw centrifuge.

[0012] According to the invention, this problem is solved with regard to the centrifuge screw by the subject matter of claim 1. With regard to the solid-wall screw centrifuge, the problem is solved by the subject matter of claim 11. The dependent claims include at least advantageous embodiments and further developments.

[0013] Specifically, the task is solved by a centrifuge screw with a screw hub and a screw helix connected to the screw hub, wherein the screw hub has at least one cylindrical longitudinal section and a solids discharge side section in the longitudinal direction.

[0014] The screw helix can be directly connected to the screw hub. This connection can be achieved, for example, through a material bond. Alternatively, the screw helix and hub can be formed as a single piece, with the connection occurring during the manufacturing process and the production of the individual components of the centrifuge screw.

[0015] According to the invention, an open wall structure is formed only in sections of the cylindrical longitudinal section, wherein the open wall structure extends over a length of at most 50% of the total length of the cylindrical longitudinal section.

[0016] This design of a cylindrical longitudinal section offers the advantage that, at least in certain sections, the screw hub can enter the material being clarified. This improves the flow characteristics within a solid-bowl screw centrifuge. Furthermore, it allows for a screw hub design with increased rigidity.

[0017] The longitudinal direction of the worm hub is essentially defined by its longitudinal axis. This direction runs parallel to the hub's longitudinal axis. The longitudinal axis of a worm hub is the axis around which it rotates during operation. It can also be referred to as the axis of rotation.

[0018] The longitudinal direction is preferably defined as the direction of transport of the solids discharge.

[0019] In the longitudinal direction, the screw hub of the centrifuge screw according to the invention has at least two distinct sections. A first section is the cylindrical longitudinal section. A further section is the solids discharge side section.

[0020] The solids discharge side section can form at least one end of the screw hub. It is also possible that the solids discharge side section encompasses one end of the screw hub.

[0021] In the cylindrical longitudinal section, an open wall structure is formed only in certain sections. This open wall structure extends over a maximum length of 50% of the total length of the cylindrical longitudinal section. In other words, at least 50% of the total length of the cylindrical longitudinal section is formed by a different, preferably substantially closed, wall structure. A closed wall structure is, for example, a tubular wall structure. The closed wall structure may have occasional openings. However, the proportion of occasional openings in the closed wall structure is not as high as in the area of ​​the open wall structure.

[0022] An open wall structure is defined in particular as one that has a large number of openings and / or a large total opening area in the relevant section of the cylindrical longitudinal segment. The opening area is understood to be the sum of all individual opening areas within the relevant segment. In other words, the opening area need not be a single, continuous opening area.

[0023] Preferably, the value of the opening area is greater than the value of the closed area. A closed area is defined as the portion of the wall structure that is sealed and does not allow any material to pass from the inside of the screw hub to the outside (or vice versa). More preferably, a closed area is defined as the sum of all individual closed areas in the relevant section.

[0024] An open wall structure is defined as a screw hub wall structure with a high proportion of openings in the radial direction. The proportion of openings is higher than the proportion of closed surfaces. The proportion of openings in the radial direction of the screw hub must be at least 65% of the total wall structure in the radial direction.

[0025] Particularly preferred is the described proportion of openings in the radial direction over the entire longitudinal extent of the open wall structure.

[0026] The section of the open wall structure preferably refers only to such a section of a snail hub that has at least one of the preceding parts of openings and / or closed surfaces.

[0027] For the purposes of the invention, longitudinal extent means an extent of a component, a section, etc., which runs essentially in the direction, preferably parallel, to the longitudinal axis of the centrifuge screw and / or the solid shell screw centrifuge.

[0028] In a preferred embodiment of the invention, the open wall structure in the cylindrical longitudinal section extends over a length of at most 45% of the total length of the cylindrical longitudinal section, in particular over a length of at most 35% of the total length of the cylindrical longitudinal section, and most preferably over a length of at most 25% of the total length of the cylindrical longitudinal section.

[0029] In other words, in the preferred embodiments, 55% of the total length of the cylindrical longitudinal section is formed as a closed wall structure, in particular 65% of the total length of the cylindrical longitudinal section, in particular 75% of the total length of the cylindrical longitudinal section, is formed as a closed wall structure.

[0030] The specified ratios regarding the proportion of an open wall structure on the cylindrical longitudinal section represent optimal conditions for achieving an improvement in flow characteristics and simultaneously improving the stiffness of the screw hub.

[0031] Preferably, the open wall structure in the cylindrical longitudinal section extends over a length of at least 10% of the total length of the cylindrical longitudinal section, in particular over a length of at least 15% of the total length of the cylindrical longitudinal section, and in particular over a length of at least 20% of the total length of the cylindrical longitudinal section.

[0032] Preferably, the open wall structure in the cylindrical longitudinal section extends over a length of 10% to 45% of the total length of the cylindrical longitudinal section, in particular over a length of 15% to 40% of the total length of the cylindrical longitudinal section, and more preferably over a length of 20% to 35% of the total length of the cylindrical longitudinal section.

[0033] The specified area values ​​regarding the extent of the proportion of an open wall structure on the cylindrical longitudinal section represent optimal extent proportions with regard to achieving an improvement in flow characteristics while simultaneously improving the stiffness of the screw hub.

[0034] In a preferred embodiment of the invention, the open wall structure is spaced apart from both ends of the screw hub. Particularly preferably, the open wall structure is designed as a central segment. In such an embodiment of the invention, the open wall structure is formed essentially between the solids discharge-side section of the screw hub and the end of the screw hub opposite the solids discharge-side section.

[0035] The open wall structure is designed to be spaced apart from the solids discharge side section. The open wall structure is formed in the cylindrical longitudinal section in such a way that the cylindrical longitudinal section itself has two sections with a closed wall structure, with the central segment being formed between the two sections that have a closed wall structure.

[0036] The open wall structure is formed between a first section of a closed wall structure and a second section of a closed wall structure. This enables, firstly, particularly high bending and torsional strength. Secondly, the screw hub can immerse itself in the material to be processed in the area of ​​the open wall structure. In such an embodiment of the invention, the section with a closed wall structure facing the solids discharge side of the screw hub is preferably shorter than the section of the screw hub with a closed wall structure facing the second end of the screw hub.

[0037] In a further embodiment of the invention, the open wall structure is possible to be designed as a central segment, which is arranged particularly in the region of the vertical line dividing the total length of the screw hub into two equal sections. In other words, this vertical line is located in the central segment of the screw hub.

[0038] The open wall structure has a larger outer diameter than adjacent sections of the screw hub. In particular, it is possible that the open wall structure has the largest outer diameter of the screw hub. In such an embodiment of the invention, the open wall structure can extend deeper into the medium to be clarified or separated in the drum chamber or separation chamber.

[0039] In other words, the open wall structure can extend beyond the outer diameter of the adjacent sections of the screw hub. In such an embodiment of the invention, the open wall structure is preferably formed from longitudinal bars, such that the longitudinal bars of this open wall structure extend beyond the wall structure of the adjacent sections. The adjacent sections of the screw hub can, in particular, be partial areas of a closed wall structure. Furthermore, it is possible that, in this embodiment, an adjacent section of the screw hub is the solids discharge side section of the screw hub.

[0040] The ratio of the outer diameter of the open wall structure to the outer diameter of the screw helix is ​​preferably 0.8–0.4, particularly 0.7–0.4, and most preferably 0.4. The outer diameter of the screw helix refers to the outer diameter of the centrifuge screw formed by the radially outer tip of the screw helix.

[0041] In the embodiment of the invention, wherein the open wall structure has a larger outer diameter than adjacent sections of the screw hub, the ratio of the outer diameter of the open wall structure to the outer diameter of the screw helix can be 0.8 - 0.6, in particular 0.7 - 0.6, particularly preferably 0.6.

[0042] In particular, it is possible that the larger outer diameter described above is essentially only formed in the section of the cylindrical longitudinal section that has the open wall structure.

[0043] To fasten or connect the open wall structure with its enlarged or larger outer diameter to the adjacent sections of the cylindrical longitudinal section, the enlarged outer diameter is also formed at the respective adjacent ends of the neighboring sections of the cylindrical longitudinal section. However, these fastening or connection areas should be kept as small as possible.

[0044] The longitudinal extent of the respective (individual) fastening or connection areas is a maximum of 20% of the total longitudinal extent of the area with the enlarged or larger outer diameter.

[0045] The specified dimensions regarding the maximum longitudinal extent of the fastening or connection areas represent optimal longitudinal extent proportions with regard to achieving an improvement in flow characteristics and separation effect with respect to the area with an enlarged or larger outer diameter, while simultaneously enabling sufficient fastening of the open wall structure to the adjacent sections of the cylindrical longitudinal section.

[0046] The given ratios show that the open wall structure is positioned relatively close to the tip of the screw helix. With such a ratio of the outer diameter of the open wall structure to the outer diameter of the screw helix, the screw hub can be immersed particularly deeply in the mixture to be clarified or separated.

[0047] The open wall structure can be formed with several rods extending longitudinally along the screw hub. The longitudinally extending rods are preferably arranged on an imaginary circle. In one embodiment of the invention, the diameter of the imaginary circle corresponds to the diameter of the adjacent sections of the screw hub.

[0048] When forming such an open wall structure that has a larger outer diameter than adjacent sections of the screw hub, the imaginary circle can have a larger diameter than the outer diameter of the adjacent sections of the screw hub.

[0049] Such a section of an open wall structure can be designed such that the longitudinal bars are each attached at their ends to a kind of transverse plate. It is also possible that the longitudinal bars are attached at one end to a kind of transverse plate.

[0050] Furthermore, it is possible that the longitudinal rods are attached at their ends to adjacent sections of the worm gear hub. In this case, the transverse discs can provide a supporting end to the two adjacent sections of the worm gear hub.

[0051] It is possible that both transverse discs are designed as closed discs. Furthermore, it is possible that at least one transverse disc is designed as a closed transverse disc. This applies both to the case where the longitudinal bars are connected to a transverse disc at least on one side, and to the case where the longitudinal bars are attached to adjacent sections of the worm gear hub on both sides.

[0052] It is also possible that, if the wall structure is formed in an inlet area of ​​the centrifuge screw, a transverse disk has a through-hole. This through-hole can, for example, serve to guide an inlet tube.

[0053] It is possible that the open wall structure includes a transverse disk. Such a transverse disk can be designed in such a way that at least one opening is formed on at least 75% of all circles extending from the center to the circumference of the transverse disk. These circles are all circles that can extend radially from the center to the circumference of the transverse disk.

[0054] Preferably, in the theoretical or imagined embodiments, the distance between the circles is only 5 mm, in particular 2 mm, in particular 1 mm, in particular 0.5 mm. When considering the circles in this way, the distance between them is preferably the same.

[0055] A cross-disc of a centrifuge screw is a disc that is positioned perpendicular to the longitudinal axis of the screw hub. The cross-disc serves primarily to stabilize the screw hub or the part of the screw hub that has an open wall structure. A cross-disc can also be referred to as a support disc.

[0056] Starting from the center point and extending towards the circumference of the transverse disk, the transverse disk has imaginary circular lines. At least 75% of all imaginary circular lines have an opening or a segment of an opening, at least partially.

[0057] In other words, at least one opening or at least a partial opening is formed in at least 75% of the total diameter range of the transverse disk, at least partially across the respective diameter. In other words, at least one opening or at least a partial opening is formed on at least 75% of all diameters of the transverse disk, at least partially across the respective diameter.

[0058] In a further embodiment of the invention, at least one opening or at least a partial section of an opening is formed in at least 85% of the total diameter range of the transverse disk, at least partially across the respective diameter. In other words, at least one opening or at least a partial section of an opening is formed on at least 85% of all diameters of the transverse disk, at least partially across the respective diameter.

[0059] In a further embodiment of the invention, at least one opening or at least a partial section of an opening is formed in at least 90% of the total diameter range of the transverse disk, at least partially across the respective diameter. In other words, at least one opening or at least a partial section of an opening is formed on at least 90% of all diameters of the transverse disk, at least partially across the respective diameter.

[0060] In a further embodiment of the invention, at least one opening or at least a partial section of an opening is formed at least sectionally across the entire diameter range of the transverse disk. In other words, at least one opening or at least a partial section of an opening is formed at least sectionally across all diameters of the transverse disk.

[0061] Such a design of openings across a large portion of the diameter of the transverse disk allows for good flow of the liquid or centrate in the area of ​​the screw hubs. At the same time, such a transverse disk exhibits sufficient rigidity to continue to provide good stabilization of the screw hub.

[0062] In one embodiment of the invention, a diameter region of the transverse disk, which defines a central opening of the transverse disk, can in particular be designed without opening(s). Such an opening-free section can provide additional stability to the transverse disk.

[0063] In a particularly preferred embodiment of the invention, an opening or a section of an opening is formed at least partially on all imaginary circular lines of the transverse disk. In other words, it is particularly preferred that at least one opening or at least a partial section of an opening is formed over the entire diameter range of the transverse disk with respect to each diameter.

[0064] It is possible to construct the transverse disc in such a way that the liquid or centrate can flow out across the entire diameter range of the transverse disc.

[0065] Preferably, the openings of the transverse disk are designed such that these openings have different geometries and / or opening sizes and / or arrangement patterns.

[0066] The geometry of an opening refers to its shape. It is possible that the transverse disk has several openings with different geometries.

[0067] In other words, the opening size refers to the opening area. Liquid can flow through and / or out of the opening. It is possible for the openings to have different dimensions.

[0068] The arrangement pattern is understood to mean the arrangement of several openings, wherein at least two openings form an opening group, and wherein several opening groups can be arranged distributed across the transverse disk. Furthermore, it is possible for the transverse disk to have a group of openings that form several openings evenly distributed across the transverse disk. Preferably, a group of openings is formed from several similarly designed openings. Similar openings are understood to be openings that have the same geometry and the same cross-sectional area.

[0069] In one embodiment of the invention, the transverse disk has several openings that are cam-shaped, egg-shaped, or elliptical. Preferably, such openings are arranged in pairs. A pair of such openings thus forms an opening group. Several such opening groups can, in turn, be arranged evenly across the transverse disk.

[0070] A cam-shaped opening is understood to be an opening that essentially has the shape, particularly the cross-sectional shape, of a cam lobe on a camshaft. Specifically, such an opening has the shape of a steep cam. In other words, such an opening is formed from two circular segments whose centers of radius lie on a common axis of symmetry of the opening. The circular segments are, in turn, connected to each other segmentally by straight lines.

[0071] Furthermore, the openings can be egg-shaped or elliptical. In a particularly preferred embodiment of the invention, two such openings are arranged relative to each other to form an opening group.

[0072] In a particularly preferred embodiment of the invention, six openings are formed in a cam-shaped, egg-shaped, or elliptical form, with two openings forming an opening group. The three opening groups thus formed are arranged uniformly in the circumferential direction on the transverse disk.

[0073] Furthermore, the transverse disk can have several openings extending from its circumference, which are designed as recesses in the transverse disk's circumference.

[0074] These recesses are preferably U-shaped.

[0075] Preferably, such recesses, in particular U-shaped recesses, are arranged in pairs. In a particularly preferred embodiment, the transverse disk has six such recesses, in particular six such U-shaped recesses. Two of the recesses form an opening group. The three opening groups thus formed are arranged uniformly in the circumferential direction on the transverse disk. Preferably, in the circumferential direction, an opening group formed from U-shaped recesses alternates with an opening group formed from cam-shaped openings.

[0076] Preferably, the U-shaped recesses in the direction of the center of the transverse disk have a length such that, in a radial extension from the center to the circumference of the transverse disk, the U-shaped recesses lie at least partially on congruent circular lines to the openings, which are cam-shaped.

[0077] Furthermore, it is possible that the transverse disc has several openings that are circular in shape.

[0078] Preferably, the circular openings are arranged in pairs. In other words, two circular openings form a group of openings.

[0079] Preferably, six circular openings are formed. Six such openings can form three groups of circular openings. The opening groups are again arranged uniformly in the circumferential direction on the transverse disk.

[0080] Furthermore, it is possible that circular openings are arranged as individual openings, i.e., not grouped together. It is also possible that the transverse disk has several different configurations of circular openings. For example, a first type of circular opening may be arranged as groups of openings. A second type of circular opening may each be arranged as an individual opening.

[0081] In a further preferred embodiment of the invention, a group of openings consisting of circular openings and a group of openings consisting of U-shaped recesses are each formed in the same circular segment. The group of openings with circular openings is formed internally, i.e., internally in the direction of the center point.

[0082] In a preferred embodiment of the invention, the transverse disk is formed from six circular sectors, wherein three circular sectors each have opening groups with cam-shaped openings, and three circular sectors each have one opening group formed from U-shaped recesses and one opening group formed from circular openings. The circular sectors thus formed are arranged alternately.

[0083] The circumference of the transverse disk can be fitted with recesses, preferably essentially semicircular, which are evenly distributed. These recesses, particularly the semicircular ones, can serve especially to accommodate longitudinal bars that, for example, form sections of the worm gear hub structure or are part of a so-called central segment.

[0084] Furthermore, it is possible that the recesses formed on the circumference of the transverse disc have a shape such that web elements of the screw hub's wall structure engage or can engage in the recesses. It is also possible that the recesses formed on the circumference of the transverse disc have a shape such that sections of the screw hub's tube wall can engage in the recesses.

[0085] An opening may also be formed at the center of the transverse disk. This central opening may be circular with additional circular segment-like recesses, in particular three circular segment-like recesses. A circular segment-like recess is defined as a recess formed from a circular segment, where the circular segment is a portion of a circular area bounded by a circular arc and a circular chord.

[0086] Preferably, the circular segment-shaped recesses, in particular the three circular segment-shaped recesses, are formed uniformly in the circumferential direction around the circular shape of the central opening thus formed.

[0087] In a further embodiment of the invention, it is possible that the circular segment-like recesses, in particular the three circular segment-like recesses, are arranged in the transverse disk in such a way that in the circumferential direction, an opening group, which is formed from two circularly shaped openings, and a circular segment-like recess of the central opening alternate.

[0088] Preferably, three groups of openings, each consisting of two circular openings, and three circular segment-shaped recesses are formed. Preferably, at least one imaginary circular line of the transverse disk intersects both the circular segment-shaped recesses and the groups of openings, each consisting of two circular openings.

[0089] In a further embodiment of the invention, openings can also have a rhombus shape and / or a polygon shape and / or a pointed arch shape and / or a triangular or quadrilateral shape with at least partially curved sides.

[0090] The material of the transverse disk is formed between the individual openings of the transverse disk. This material is preferably made of metal.

[0091] In one possible embodiment of the invention, the openings are of such a size and arranged relative to one another that the material of the transverse disk is formed as ribs. The ribs can be straight and / or curved. Forming ribs creates a particularly advantageous ratio of opening sizes to the remaining material of the transverse disk.

[0092] In a further embodiment of the invention, the open wall structure is formed by a plurality of web elements that define a plurality of openings, wherein the web elements are arranged radially outside with respect to the longitudinal axis of the screw hub and form a circumference of the cylindrical longitudinal section, wherein two web elements each form a web pair that defines at least one opening, wherein both web elements of the web pair extend in the longitudinal direction and transversely to the longitudinal direction, or wherein a first web element of the web pair extends in the longitudinal direction and a second web element of the web pair extends transversely to the longitudinal direction.

[0093] An open wall structure, formed by numerous web elements, offers the advantage of exceptional stability. The bending and torsional strength of a centrifuge screw manufactured in this way is particularly high.

[0094] In a further embodiment of the invention, the open wall structure is formed at least partially by a tube in which a plurality of openings are formed for the passage of a medium, wherein the openings each have a longitudinal extent that is greater than the width of the respective opening.

[0095] One such embodiment of the invention has the advantage that the open wall structure does not exhibit significant structural differences compared to the closed wall structure. Such an open wall structure can be easily manufactured, since openings can be introduced into a previously completely closed wall structure to form a sectionally open wall structure.

[0096] The solids discharge section can be conical, frustoconical (double conical), cylindrical, or tubular. Depending on the material being processed, the solids discharge section can therefore have different shapes. A conical shape is a particularly common design, allowing for simple and standardized manufacturing of the solids discharge section.

[0097] It is possible that the solids discharge section is designed as a cylindrical section and / or a cylindrical pipe section. Such a cylindrical section and / or cylindrical pipe section is understood to mean, in particular, a section that includes a pipe, the pipe being attached to the cylindrical longitudinal section, for example, by means of a connecting flange. In the following, a pipe is defined as such a cylindrical section that is at least partially hollow.

[0098] By using such a design for the solids discharge side of the screw hub, a screw hub and thus a centrifuge screw of this type can be provided that is particularly advantageous for reducing constrictions in the direction of solids discharge. Such constrictions are known in solid-bowl screw centrifuges. These are known to occur in the area of ​​the transition from a cylindrical longitudinal section to a discharge section.

[0099] The drum of a solid-walled screw centrifuge typically has a conical shape in this section. By forming a cylindrical section and / or a cylindrical pipe section, an increased volume is provided in the area of ​​solid discharge or in the final residence path of the solid being transported within the drum. This results in a reduction of known bottlenecks. Consequently, high solids loads can be transported within a specific timeframe during the processing of a material or medium to be separated.

[0100] A further advantage of designing the solids discharge section as a cylindrical section and / or cylindrical pipe section is that the solid is in a relaxed state. This also applies to solids that may have already been compressed during processing. Such a relaxed solid is less likely to form lumps at the discharge point and is free-flowing. Due to the reduced forces acting on the solids discharge section, this design is particularly wear-resistant.

[0101] Furthermore, no sedimented particles adhere to the cylindrical longitudinal section of the screw hub, which would otherwise sink from the mixture to be clarified towards the inside of the drum. Instead, the sedimented particles flow outwards to the outside of the drum.

[0102] With the aid of the screw hub according to the invention, a large pond depth can be constructed in conjunction with a solid-jacket screw centrifuge, while at the same time improvements in the area of ​​solids discharge are achieved.

[0103] It is possible that the cylinder section and / or cylindrical pipe section is designed in such a stepped manner that the cylinder section and / or the cylindrical pipe section has at least two sections with different diameters in the longitudinal direction of the screw hub.

[0104] Using such a stepped design, a further reduction in the unwanted formation of bottlenecks can be achieved. At the same time, the solid material being transported and discharged can be further depressurized.

[0105] The at least two sections of the cylinder section and / or the cylindrical pipe section are preferably arranged such that the section with the smaller or smallest diameter is spaced further away from the cylindrical longitudinal section than the section of the cylinder section and / or the cylindrical pipe section with the larger or largest diameter. The stepped design of the cylinder section and / or the cylindrical pipe section preferably proceeds such that the diameters of the sections are reduced stepwise towards the end face of the screw hub belonging to the section on the solids discharge side.

[0106] In a further embodiment of the invention, the solids discharge side section may have a double truncated cone shape. The double truncated cone shape is preferably designed such that the imaginary bases of two truncated cones lie against each other.

[0107] The frustoconical shape is preferably designed such that the largest diameter of the frustoconical shape is neither formed on a connecting section to the cylindrical longitudinal section nor on an end face of the screw hub associated with the solids discharge side section.

[0108] A first cover surface of a first truncated cone of the double truncated cone shape is arranged in a connecting section and / or a transition area to the cylindrical longitudinal section of the screw hub.

[0109] A second cover surface of a second truncated cone of the double truncated cone shape is formed on the end face associated with the solids discharge side section or pointing in the direction of this end face.

[0110] It is possible that the truncated cones forming the double-truncated cone shape have the same height. In such an embodiment of the invention, the double-truncated cone shape is axially symmetrical. The axis of symmetry is formed in the region of the overlapping bases of the two truncated cones.

[0111] In a further embodiment of the invention, the truncated cones forming the double frustum shape have different heights. Preferably, the truncated cone adjacent to the cylindrical longitudinal section has a lower height than the second truncated cone, which points towards the end face of the worm hub.

[0112] By forming the solids discharge side section in the shape of a double truncated cone, fine particles can be separated even better from materials to be processed that are already separated in phases.

[0113] In a further embodiment of the invention, the open wall structure can be formed in an inlet area of ​​the centrifuge screw, wherein an inlet pipe opening of an inlet pipe opens into the inlet area, wherein a baffle element, in particular a baffle disc, with an acceleration element is formed opposite the inlet pipe opening, wherein the acceleration element is designed such that a medium impacting the acceleration element can be accelerated in the direction of openings of the open wall structure.

[0114] Since in this embodiment of the invention the inlet area is not designed as an inlet chamber with corresponding solid and largely closed walls as in the classical sense, but is itself formed, for example, from individual segments, in particular longitudinal bars, of a screw hub, the openings of the open wall structure can themselves serve as openings of the inlet chamber.

[0115] It is possible that the inlet pipe runs from the solids discharge side section of the screw hub towards the inlet area.

[0116] The acceleration element preferably has impact surfaces positioned at an angle to the axis of rotation of the centrifuge screw. Due to the design of the acceleration element, the medium impacting the impact element or the acceleration element can be pre-accelerated gently and with relatively low turbulence.

[0117] The acceleration occurs in the direction of the openings in the open wall structure. Only then, in the case of a rotating screw hub or a rotating centrifuge screw, does the medium pass through the openings into the drum interior or the separation chamber.

[0118] The accelerator element is essentially designed as a projection pointing towards the inlet pipe opening. This projection may be mounted on a disc or plate, which can be flat or curved.

[0119] The projection, together with the disc or plate, can form an independent component that can be manufactured separately from the impact element, in particular the impact disc. This facilitates, for example, the subsequent retrofitting of an impact element with the acceleration element.

[0120] In a further embodiment of the invention, the projection can be attached directly to the impact element, in particular the impact discs. This allows for material savings.

[0121] In one embodiment of the invention, the accelerator element has struts, which are arranged in a cross-like pattern relative to one another. It is also conceivable that several struts form a star shape in a top view of the accelerator element. In such an embodiment of the invention, the projection is formed by an arrangement of struts.

[0122] In one embodiment of the invention, the height of the struts increases towards a point where the struts intersect. The height of the struts is understood to be the relative distance to the impact element, in particular to the impact disc, or – if designed – the relative distance to the separate disc or plate.

[0123] Preferably, the accelerator element is arranged on the impact element such that an intersection point and / or a highest point of the accelerator element is aligned with the center point of the impact element, in particular the impact disk. In other words, the intersection point and / or the highest point of the accelerator element is arranged on the longitudinal axis of the centrifuge screw.

[0124] In a further or alternative embodiment of the invention, the accelerator element can be designed as a projection extending from the impact element and pointing towards the inlet pipe opening. This projection has several radial flanks. Radial flanks are defined as flanks that extend from a centrally located point towards the impact element. Preferably, the radial flanks are arranged uniformly or at uniform intervals around the circumference of the projection.

[0125] Furthermore, channels may be formed between the flanks, and these channels may have a swirling shape. When a medium encounters such an accelerating element, it is deflected and accelerated along the channels in the direction of the impact element and in the direction of the free spaces. In other words, the channels and / or flanks are uniformly distributed across the projection.

[0126] It is possible that the acceleration element is designed as a projection extending from the impact element and pointing towards the inlet tube opening, which has several, for example four, impact surfaces arranged obliquely to the longitudinal axis of the inlet area. The longitudinal axis of the inlet area is, in particular, the axis of rotation of the centrifuge screw.

[0127] The impact surfaces can, for example, be arranged in such a way that the projection has a pyramid-like shape. The pyramid's apex can be particularly flattened.

[0128] The screw helix of the centrifuge screw is preferably uniform along its entire cylindrical longitudinal section. This can apply to the thickness of the screw helix, its outer diameter, and its pitch.

[0129] Furthermore, it is possible that the screw helix is ​​conical in the area of ​​the solids discharge side section.

[0130] The helical spiral can be completely connected to the outer surface of the sections with a closed wall structure in the cylindrical longitudinal section.

[0131] In the area of ​​the open wall structure, the spiral helix is ​​only connected to the open wall structure in sections. This applies in particular to the parts of the wall that are formed between individual openings of the open wall structure.

[0132] The helical thread is preferably arranged circumferentially around the helical hub. Preferably, the helical thread extends over almost the entire or the entire longitudinal extent of the helical hub.

[0133] In other words, the screw helix is ​​preferably arranged both on the cylindrical longitudinal section of the screw hub and on the solids discharge side section of the screw hub.

[0134] Another subordinate aspect of the invention relates to a solid-jacket screw centrifuge comprising a centrifuge screw located in a drum, wherein the centrifuge screw is designed according to the invention.

[0135] With regard to the solid-jacket screw centrifuge, reference is made to the advantages explained in connection with the centrifuge screw.

[0136] Furthermore, the solid-jacket screw centrifuge may alternatively or additionally exhibit one or a combination of several of the features previously mentioned in relation to the centrifuge screw.

[0137] The invention is explained in more detail below with reference to the accompanying drawings.

[0138] The illustrated embodiments represent examples of how the centrifuge screw according to the invention can be designed.

[0139] These show: Fig. 1 shows a longitudinal section through a centrifuge screw according to a first non-inventive embodiment; and Fig. 2 shows a longitudinal section through a centrifuge screw according to a further inventive embodiment.

[0140] In the following, the same reference numbers are used for identical and equivalent parts.

[0141] In Fig. 1 A centrifuge screw 10 according to the invention is shown with a screw hub 15. The screw hub 15 has a cylindrical longitudinal section 11 in the longitudinal direction R and a solids discharge section 12.

[0142] The longitudinal direction R runs essentially parallel to the longitudinal axis L of the screw hub 15. In the following case, the longitudinal direction R is defined as the direction of solids transport. Solids transport occurs as shown in the diagram. Fig. 1 und 2 from right to left.

[0143] The centrifuge screw 80 also includes a screw helix 20.

[0144] The cylindrical longitudinal section 11 is longer than the solids discharge side section 12. The solids discharge side section 12 of the screw hub 15 is to be understood as such a functional section, which serves in particular to transport the solid separated from the material to be processed in the direction R of the solids discharge.

[0145] In the cylindrical longitudinal section 11, an open wall structure 40 is formed only in certain sections. The open wall structure 40 is formed by several rods 41.

[0146] As shown in the left sectional view of the Fig. 1 As shown in section AA, the rods 41 are arranged at regular intervals around the circumference of the screw hub 10 in its longitudinal direction R, i.e., parallel to the longitudinal axis L. In this case, the open wall structure 40 is formed from eight rods 41. The number of rods 41 can vary and may be designed differently, depending, among other things, on the diameter of the screw hub 15.

[0147] The open wall structure 40 can also be formed by web elements, specifically web pairs, as explained in the preceding description.

[0148] Alternatively, the open wall structure 40 is formed by a tube in which a multitude of openings are formed for the passage of a medium.

[0149] The cylindrical longitudinal section 11 extends from a second end face 32 of the screw hub 15 to the beginning of the solids discharge section 12.

[0150] In this case, the solids discharge section 12 is formed by a conical shape 18. The solids discharge section 12 also includes the first end face 31 of the screw hub 15.

[0151] Furthermore, bearing sections 35 and 35' are designed for the storage of the illustrated centrifuge screw 10 in a drum (not shown) of a solid shell screw centrifuge (also not shown).

[0152] The open wall structure 40 extends in the cylindrical longitudinal section 11 for a maximum length LW, where this length LW is at most 50% of the total length GL of the cylindrical longitudinal section 11.

[0153] In the illustrated example, the open wall structure 40 is formed between a first section 51 of a closed wall structure and a second section 52 of a closed wall structure. This embodiment enables, firstly, particularly high bending and torsional strength. Secondly, the screw hub 15 can immerse itself in the material to be machined in the area of ​​the open wall structure 40.

[0154] Embedding the open wall structure 40 between two sections 51 and 52 with a closed wall structure simplifies the fastening of the open wall structure 40 in the area of ​​the screw hub 15.

[0155] The open wall structure 40 is spaced from both ends, or rather both end faces 31 and 32, of the screw hub 15. The open wall structure 40 forms a kind of central segment 50, since the central segment 50 is formed both between two sections 51 and 52 of the cylindrical longitudinal section 11 and also surrounds a vertical line A. In other words, the vertical line A is formed in the region of the central segment 50. The vertical line A is the one that is perpendicular to the longitudinal axis L and bisects the screw hub 15 with respect to its length in the longitudinal direction R.

[0156] The rods 41 of the open wall structure 40 are attached to two transverse disks 61 and 62. The first transverse disk 61 is a completely closed disk. This prevents, among other things, material to be processed from penetrating the interior of the solids discharge-side section 12. Furthermore, it is possible for a type of acceleration element to be formed on the transverse disk 61. This is particularly advantageous if the open wall structure 40 also forms the inlet area of ​​a screw hub 15.

[0157] The second transverse disk 62 has an opening 63. An inlet pipe, for example, can be guided through this opening 63, so that the material to be processed can flow outwards through the open wall structure 40 into the interior of the drum.

[0158] In the present case, an inlet pipe (not shown) would extend from the second end face 32 towards the opening 63 of the second transverse disk 62.

[0159] Alternatively, an inlet pipe could extend from the first end face 31 towards the open wall structure 40. In such a case, the transverse disks 61 and 62 would each have to be oriented in the opposite direction to that shown in the diagram. Fig. 1 as shown, i.e., at the position of the first transverse disk 61 shown, such a transverse disk would have to be formed which has an opening.

[0160] According to the sectional view of the Fig. 1 It becomes clear that the outer diameter DW of the open wall structure 40 has a value that corresponds to the outer diameter DI of the adjacent sections 51 and 52 of the screw hub 15.

[0161] In Fig. 2 A further embodiment of a centrifuge screw 10 according to the invention is shown. The difference to the one described in Fig. 1 The embodiment shown relates to the specific design of the open wall structure 40.

[0162] The in Fig. 2 The depicted wall structure 40 consists essentially of rods 41, which in the illustrated example are attached to sections 51 and 52 with a closed wall structure. Alternatively, attachment to the transverse discs 61 and 62 is conceivable and possible.

[0163] Unlike the one in Fig. 1 In the illustrated embodiment, the open wall structure 40 has a larger outer diameter DW than the adjacent sections 51 and 52 of the screw hub 15. In other words, the outer diameter DI of the adjacent sections 51 and 52 of the screw hub is smaller than the outer diameter DW of the open wall structure 40.

[0164] Due to the increased outer diameter DW, the rods 41 of the open wall structure 40 can immerse themselves more effectively in the material contained in the drum or in the pond. The ratio of the outer diameter DW of the open wall structure 40 to the outer diameter DS of the screw helix 20 is preferably 0.8–0.4.

[0165] Finally, it should be noted that all features mentioned in the application documents and in particular in the dependent claims, despite the formal reference made to one or more specific claims, shall be afforded independent protection, whether individually or in any combination. Reference symbol list

[0166] 10 Centrifuge screw 11 Cylindrical longitudinal section 12 Solids discharge side section 15 Screw hub 18 Cone shape 20 Screw helix 31 First end face 32 Second end face 35, 35' Bearing section 40 Open wall structure 41 Longitudinal bar 50 Middle segment 51 First section Closed wall structure 52 Second section Closed wall structure 61 First transverse disc 62 Second transverse disc 63 Opening A Perpendicular DS Outer diameter screw helix DI Outer diameter sections cylindrical longitudinal section DW Outer diameter open wall structure GL Total length cylindrical longitudinal section L Longitudinal axis LWL Length open wall structure R Longitudinal direction

Claims

1. A centrifugal screw (10) having a screw hub (15) and a screw spiral (20) connected to the screw hub (15), wherein the screw hub (15) in the longitudinal direction (R) has at least one cylindrical longitudinal portion (11) and a portion (12) at the solid-discharge end, wherein an open wall structure (40) is configured merely in sections in the cylindrical longitudinal portion (11), wherein the open wall structure (40) extends in the cylindrical longitudinal portion (11) at most over a length (LW) of 50% of the total length (GL) of the cylindrical longitudinal portion (11), characterised in that the open wall structure (40) is configured so as to be spaced from the portion (12) at the solid-discharge end, wherein the open wall structure (40) is configured between a first portion (51) of a closed wall structure and a second portion (52) of a closed wall structure, wherein the open wall structure (40) has a larger outer diameter (DW) than neighbouring portions (51, 52) of the screw hub (15), wherein to fasten or connect the open wall structure (40) to the neighbouring portions (51, 52) of the cylindrical longitudinal portion (11), the increased outer diameter (DW) is also configured at the respective adjacent ends of the neighbouring portions (51, 52) of the cylindrical longitudinal portion (11), wherein the longitudinal extension of the respective individual fastening or connecting regions is a maximum of 20% of the total longitudinal extension of the region having a larger outer diameter (DW), wherein such a wall structure of the screw hub (15) which has a high proportion of openings in the radial direction is to be understood to be an open wall structure (40), wherein the proportion of openings in the radial direction of the screw hub is at least 65% of the total wall structure in the radial direction.

2. The centrifugal screw (10) according to Claim 1, characterised in that the open wall structure (40) in the cylindrical longitudinal portion (11) extends at most over a length (LW) of 45% of the total length (GL) of the cylindrical longitudinal portion (11), in particular at most over a length (LW) of 35% of the total length (GL) of the cylindrical longitudinal portion (11), particularly preferably at most over a length (LW) of 25% of the total length (GL) of the cylindrical longitudinal portion (11).

3. The centrifugal screw (10) according to Claim 1 or 2, characterised in that the open wall structure (40) is configured so as to be spaced from both ends, in particular from both front sides (31, 32) of the screw hub (15), in particular as a middle segment (50)4. The centrifugal screw (10) according to any one of the preceding claims, characterised in that a ratio of a / the outer diameter (DW) of the open wall structure (40) to the outer diameter (DS) of the screw spiral (20) is 0.8 - 0.4, in particular 0.7 - 0.4, particularly preferably 0.4.

5. The centrifugal screw (10) according to any one of the preceding claims, characterised in that the open wall structure (40) is formed with multiple rods (41) running in the longitudinal direction (R).

6. The centrifugal screw () according to any one of Claims 1 to 4, characterised in that the open wall structure (40) is formed by a plurality of web elements which delimit a plurality of openings, wherein the web elements are arranged radially outside with respect to the longitudinal axis (L) of the screw hub (15), and form a circumference of the cylindrical longitudinal portion (11), wherein two web elements respectively form a web pair which delimits at least one opening, wherein both web elements of the web pair extend in the longitudinal direction (R) and transversely to the longitudinal direction (R), or a first web element of the web pair respectively extends in the longitudinal direction (R), and a second web element of the web pair extends transversely to the longitudinal direction (R).

7. The centrifugal screw (10) according to any one of Claims 1 to 4, characterised in that the open wall structure (40) is formed at least in sections by a tube in which a plurality of openings is configured for the passage of a medium, wherein the openings each have a longitudinal extension which is larger than a width of the respective opening.

8. The centrifugal screw (10) according to any one of the preceding claims, characterised in that the portion (12) at the solid-discharge end has a cone shape or a double truncated cone shape or is configured as a cylindrical portion or as a cylindrical tube portion.

9. The centrifugal screw (10) according to any one of the preceding claims, characterised in that the open wall structure (40) is configured in an inflow region of the centrifugal screw (10), wherein an inflow tube opening of an inflow tube opens into the inflow region, wherein a baffle element, in particular a baffle disc, having an acceleration element is configured opposite the inflow tube opening, wherein the acceleration element is configured such that a medium impinging on the acceleration element can be accelerated in the direction of openings of the open wall structure (40).

10. The centrifugal screw (10) according to Claim 9, characterised in that the inflow tube runs starting from the portion (12) at the solid-discharge end in the direction of the inflow region.

11. A solid bowl screw centrifuge which comprises a centrifugal screw (10) located in a drum, wherein the centrifugal screw (10) is configured according to any one of Claims 1 to 10.

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