PRESSING METHOD AND APPARATUS

Abstract

A pressing apparatus having a strainer cage and at least two feeding screws, which are arranged one behind the other in the feeding direction on a common screw shaft, wherein a pressure zone with no screw helix is arranged between the feeding screws. In the region of the pressure zone, the pressing apparatus according to the invention has a plurality of scraper shells, and these provide for improved efficiency of the pressing operation.

Claims

1. A pressing apparatus comprising: a pressing chamber delimited by at least one strainer cage; at least two feeding screws arranged behind one another on a common screw shaft, each of the feeding screws having a screw helix, wherein a respective pressure zone is arranged between the feeding screws; and, in at least one of the pressure zones, at least one scraper shell arranged between cage bars of a cage zone, said scraper shell having at least one extension that projects into the pressing chamber.

2. The pressing apparatus according to claim 1, wherein at least two scraper shells are arranged in the cage zone or the cage zones of a respective segment of the strainer-cage.

3. The pressing apparatus according to claim 2, wherein the scraper shells are distributed uniformly in the respective strainer-cage segment.

4. The pressing apparatus according to claim 2, wherein the scraper shells have a base strip and an extension that projects out of the base strip.

5. The pressing apparatus according to claim 4, wherein the base strip has a contour adapted to a shape of the strainer cage.

6. The pressing apparatus according to claim 5, wherein the base strip is formed as a hollow-cylindrical segment.

7. The pressing apparatus according to claim 4, wherein the extension of at least one of the scraper shells has a contour adapted to a shape of a feed device in the respective strainer-cage segment.

8. The pressing apparatus according to claim 4, wherein the extension of at least one of the scraper shells has a height that increases or decreases in a longitudinal direction.

9. The pressing apparatus according to claim 1, wherein the at least one pressure zone is free of screw helixes.

10. A pressing method comprising the steps of: feeding a pressing material into a region of a pressure zone using a first feeding screw; mixing and/or guiding and/or holding the pressing material in the pressure zone using a plurality of scraper shells; and feeding the pressing material onwards in a feeding direction downstream of the pressure zone using a second feeding screw.

11. The method according to claim 10, including carrying out the pressing method using a pressing apparatus comprising: a pressing chamber delimited by at least one strainer cage; at least two feeding screws arranged behind one another on a common screw shaft, each of the feeding screws having a screw helix, wherein a respective pressure zone is arranged between the feeding screws; and, in at least one of the pressure zones, at least one scraper shell arranged between cage bars of a cage zone, said scraper shell having at least one extension that projects into the pressing chamber.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0051] In the drawing:

[0052] FIG. 1: shows a perspective illustration of a scraper shell of a pressing apparatus according to the invention,

[0053] FIG. 2: shows a perspective view of a cage zone according to the invention which comprises scraper shells,

[0054] FIG. 3: shows a perspective view of a detail of a pressing apparatus according to the invention in the region of one strainer-cage half,

[0055] FIG. 4: shows a view of a detail of an embodiment of a pressing apparatus according to the invention with its strainer cage open, in the region of a scraper shell,

[0056] FIG. 5: shows a cross section of an embodiment of a scraper shell according to the invention, and

[0057] FIG. 6: shows a section taken in the longitudinal direction of an embodiment of a scraper shell according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0058] FIG. 1 shows a perspective illustration of a scraper shell (10) of a pressing apparatus (1) according to the invention. The scraper shell (10) has a base strip (11), which is adapted to the contour of a strainer cage (2). For this purpose, the base strip (11) of the scraper shell (10) is curved in the transverse direction, and therefore it is designed for example in the form of a hollow-cylinder segment. An extension (12) is arranged approximately centrally on the inner side of the scraper shell (10) and projects out of the base strip (11). The extension (12) is designed in the manner of a crosspiece and the height of the extension (12) decreases o continuously in one direction.

[0059] FIG. 2 shows a perspective illustration of the cage zone of a strainer-cage portion (3) of a pressing apparatus (1) according to the invention. The cage zone has been divided into two cage-zone segments, which are each formed from a plurality of cage bars (5) arranged one beside the other. Gaps are formed in each case between the cage bars (5). Each of the cage-zone segments contains in each case three scraper shells (10), which are spaced apart uniformly from one another in the respective cage-zone segment. The extensions (12) of the scraper shells (10) project inward from the cage zone, which is formed by the cage bars (5) and the base strips (11) of the scraper shells (10), into the strainer-cage portion (3), which is formed from the cage-zone segments and the cage frame (6) (not shown in this illustration). The cage bars (5) have reinforcement plating (5a) on their inner side for wear-reducing purposes.

[0060] FIG. 3 illustrates a perspective view of a detail of an embodiment of a pressing apparatus (1) according to the invention in the region of the open, and only partially fitted-out, strainer cage (2). The strainer-cage segments (4) illustrated are arranged in a cage frame (6). Arranged alongside that strainer-cage segment (4) which is arranged on the right-hand side of the cage frame (6) is a split cage ring (7), which compensates for a change in diameter of the cage frame (6), and therefore, in the feeding direction, there is a continuous reduction in diameter of the pressing chambers in the region of the split cage ring (7). A strainer-cage segment (4) having three scraper shells (10) inserted into the cage zone is illustrated approximately in the centre of the cage frame (6). Arranged alongside the strainer-cage segments (4), in the cage frame (6), are fastening means (9) for fastening clamping bars (9) (not illustrated) for fixing the cage bars (5) and/or scraper shells (10) in the respective strainer-cage segment (4).

[0061] FIG. 4 shows a view of a detail of an embodiment of a pressing apparatus (1) according to the invention with its strainer cage (2) open, in the region of a scraper shell (10). The strainer cage (2) contains two feeding screws (13a, 13b), which are arranged one behind the other on a common screw shaft. A cone element (15) is arranged between the first feeding screw (13a) and the second feeding screw (13b). The feeding screws (13a, 13b) each have a hollow-cylindrical main body, on which in each case at least one screw flight (14) is arranged. The at least one screw flight (14) delimits the screw helix of the respective feeding screw (13a, 13b). The main body of the first feeding screw (13a) has a smaller diameter than the main body of the second feeding screw (13b). The cone element (15) realizes an approximately continuous transition from the diameter of the main body of the first feeding screw (13a) to the diameter of the main body of the second feeding screw (13b). The screw flight (14), and therefore the screw helix, of the first feeding screw (13a) terminates at a small distance upstream of the extension (12) of the scraper shell (10), as seen in the feeding direction. There is no screw flight (14) arranged in the region of the cone element (15). The screw flight (14), and therefore the screw helix, of the second feeding screw (13b) begins at a distance downstream of the end of the extension (12) of the scraper shell (10), as seen in the feeding direction.

[0062] The cage bars (5) and scraper shells (10) of the strainer-cage segment (4) are fixed in the strainer-cage segment (4) with the aid of clamping bars (8).

[0063] A pressure region of the pressing apparatus (1), the scraper shells (10) also being arranged in said pressure region, is formed in the region of the cone element (15).

[0064] FIG. 5 illustrates a cross section of an embodiment of a scraper shell (10) according to the invention. The underside and the upper side of the base strip (11) of the scraper shell (10) are curved along segments of a circle. The underside of the base strip (11) of the scraper shell (10) is curved along a segment of a first circle, which has the diameter A, and the upper side of the base strip (11) of the scraper shell (10) is curved along a segment of a second circle, which has the diameter B. It is also the case that the upper side of the extension (12) of the scraper shell (10) is curved along a segment of a circle, use being made here of a segment of a third circle, which has the diameter C. As seen three-dimensionally with the corresponding lengths, the aforementioned sides are each designed in the manner of a segment of a cylinder wall.

[0065] The scraper shell (10) has a width a in the region of the upper side of the base strip (11) and a width b in the region of the upper side of the extension (12).

[0066] In relation to the centre axis X-X′, the base strip (11) of the scraper shell (10) extends, as seen in a first lateral direction along the segment of the first circle, in an angle range I and, in the opposite, second lateral direction, in an angle range II.

[0067] In one embodiment of the invention, the angle range I and the angle range II differ from one another. In one embodiment of the invention, one angle range is greater than the other angle range.

[0068] The scraper shell (10) has reinforcement plating (16) on the upper side of the extension (12).

[0069] FIG. 6 shows a section taken in the longitudinal direction of a scraper shell (10) according to the invention. The scraper shell (10) has the length c. On the upper side of the base strip (11), reinforcement plating (16) is arranged around the extension (12). The extension (12) has the length d and is arranged at the distance e from a first end of the scraper shell (10). The extension (12) has a height which decreases in the longitudinal direction of the scraper shell (10). The upper side of the extension (12) here is arranged at an angle III in relation to the continuation of the side wall of the extension (12). At the highest point, the scraper shell (10) has the height f.

[0070] The absolute dimensioning of the individual parameters of the scraper shells (10) depends on the design of the strainer cage as a whole. In particular, the desired number of gaps, and the width thereof, the throughput of pressing material through the press as a whole, the degree to which the liquid constituents are pressed out of the pressing material, and the amount of energy which is appropriate to use for the pressing operation, all play a role.

[0071] The following dimensions of embodiments of scraper shells (10) according to the invention relate not to individual exemplary embodiments amongst those mentioned above, but to all of the embodiments of the scraper shell (10) according to the invention.

[0072] In one embodiment of the invention, the width a of the scraper shell (10) is 30 mm to 80 mm. In a preferred embodiment, this width is 45 mm to 65 mm.

[0073] In one embodiment of the invention, the height f of the scraper shell (10) is 30 mm to 60 mm. In a preferred embodiment, this height is 40 mm to 50 mm.

[0074] In one embodiment of the invention, the width b of the extension (12) of the scraper shell (10) is 10 mm to 40 mm. In a preferred embodiment of the invention, this width is 20 mm to 30 mm.

[0075] In one embodiment of the invention, the length d of the extension (12) of the scraper shell (10) is 40 mm to 80 mm. In a preferred embodiment, this length is 50 mm to 70 mm.

[0076] In one embodiment of the invention, the angle range I and the angle range II are each between 5° and 15°.

[0077] The angle III is adapted to the contour of the cone segment in the respective pressure region of the pressing apparatus. In one embodiment of the invention, the angle III is 80° to 89°. In a preferred embodiment of the invention, the angle III is 84° to 88°.

[0078] While specific embodiments of the invention have been shown and described in detail to illustrate the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.