EP0521361B1 - Sieve drum - Google Patents

Abstract

Sieve drum (2) for conditioning and classifying granular material, having a feed device (100) and inner annular sieve sections (NW32, NW25, NW10) in succession in the longitudinal direction of the drum. The mesh size of the annular sieve sections changes in such a manner that the section (NW10) with relatively small mesh size is the annular sieve section closest to the discharge (9) and the section (NW32) with the largest mesh size is the annular sieve section axially furthest removed from the discharge (9). Outer annular sieve sections (NW4, NW18) with different mesh sizes are arranged radially outside the inner annular sieve sections (NW10, NW25, NW32). The section (NW4) with the smallest mesh size is the annular sieve section axially closest to the discharge (9), section (NW18) with medium mesh size is axially furthest removed from the discharge (9). A catch region (4-10) for sieved material with a particle size between the smaller (NW10) and the smallest mesh size (NW4) is arranged axially between the outer annular sieve sections with the smallest and the medium mesh size (NW4, NW18). <IMAGE>

Description

The invention relates to a sieve drum for conditioning and classifying granular material with at least one input device at one end of the drum rotating about its longitudinal axis and an output of the conditioned material at the other drum end in a first annular space between the drum and successive in the longitudinal direction of the drum Inner ring screen sections concentrically surrounding the drum, the mesh size of the ring screen sections changing such that the section with the smaller mesh size is the axially closest to the output, the section with the largest mesh size is the most distant ring screen section, and with the underside of the drum arranged silos for receiving screenings of different particle sizes.

Such screening drums are used, for example, to process the material of road surfaces using bitumen or old asphalt and grit of different grain sizes. Coarse grit grit is used to build a support structure, smaller grit grit is used to partially fill the cavities of the support structure and the bitumen penetrating into the remaining cavities serves to bind the other covering components. A generic screening drum can be used to bring the individual components into the correct mixing ratio and, in particular, to prepare them by tempering in the heated mixing drum if the individual components of the road surface are to be applied to the road base at the same time.

In a known sieve drum dating back to the same inventor (German patent 38 01 383), ring sieve sections with three different mesh sizes are provided, and in this case the sieve with the smallest mesh size is loaded with the entire material to be sieved, i.e. this fine sieve is also loaded with the largest particles, which leads to rapid wear of the sieve with the smallest mesh size. In addition, the efficiency of the sieving process is not optimal, since, for example, the larger particles can take smaller particles with them, so that the smaller particles cannot fall through the sieve provided.

The object of the invention is to design a generic device such that the individual ring screen sections can be assigned to the drum in a particularly expedient manner. A "possible as possible" is understood in particular that the ring screen sections can be assembled and disassembled as quickly as possible and with a minimum of tooling, and that the assembled ring screens are reliably attached to the drum in the assembled state. Furthermore, this is to be understood to mean that the ring sieve sections are assigned to one another in such a way that the sieves are acted upon in accordance with their mesh size in accordance with the particle distribution in the sieved material.

This object is achieved by the features specified in the characterizing part of the patent claim.

In the present invention, in addition to radially inner ring sieve sections, outer ring sieve sections are used, the individual mesh sizes being different and being selected such that not the full amount of the sieved material is passed over the finest sieve, but in the range from 50 to 60% of the sieved material. This can be achieved by a pre-sieve with a larger mesh size arranged upstream of the ring screen cut with the smallest mesh size.

According to the invention, the outer ring screen sections are designed in the form of windows in which the individual screens are fastened. It is sufficient to simply place the sieves on the frame and fasten them to this frame, the frames additionally being provided with guide parts which project radially inwards when placed on the sieve drum and ensure that the material to be sieved is in the outer annular space performs the desired axial movement.

Fig. 1

ist eine schaubildliche Darstellung einer Trommel in Seitenansicht, wobei die äußeren Ringsiebabschnitte entfernt worden sind.

Fig. 2

ist eine der Figur 1 entsprechende Darstellung, jedoch mit den äußeren Ringsiebabschnitten.

Fig. 3

ist eine schematische Darstellung des Siebprinzipes, das der vorliegenden Erfindung zugrunde liegt.

The invention is explained below with reference to the drawing, for example.

Fig. 1

is a perspective view of a drum in side view with the outer ring screen sections removed.

Fig. 2

is a representation corresponding to Figure 1, but with the outer ring screen sections.

Fig. 3

is a schematic representation of the sieve principle on which the present invention is based.

In a fixed housing 1, a drum 2 is rotatably mounted about its longitudinal axis 3. A burner 40, whose longitudinal flame axis coincides with the longitudinal drum axis 3, projects into the drum 2 from the left end of the drum in the illustration. The burner 40 can be operated with gas or oil. The drum 2 is driven by a motor (not shown) via a gear unit which encloses a race 5 which surrounds the drum and is fixedly connected to it. On the underside of the housing 1, a number of so-called hot silos 6 are arranged in succession in the longitudinal direction of the drum. These hot silos are funnel-shaped containers that are largely insulated from temperature radiation and hold screenings or chippings of different particle sizes emerging from the drum 1.

In order to be able to classify the material, inner ring sieve sections NW10, NW25 and NW32 built up successively from partial segments in the drum longitudinal direction are arranged on the drum 2 such that an inner annular space 8 exists between the casing of the drum 2 and the ring sieve sections. The ring screen sections have different mesh sizes, the ring screen sections 10 have a mesh size 10 and the ring screen sections 32 have a mesh size 32, for example. The annular space 8 communicates with the interior of the drum 2 via openings which are evenly distributed over the drum circumference at the drum end on the left in the drawing.

During operation of the system, different goods can now be input into the drum 2 at both drum ends via one feed device 100 and one each. Via the feed device 100 at the right end of the drum facing away from the burner 40, for example, new material in the cold state, in particular chippings of different grain sizes, is introduced into the drum and this material migrates to the flame of the burner 40 and is heated to the desired temperature. For example, old asphalt is fed into the drum via the feed device 11 at the end of the burner 40. The mixture of old asphalt and grit passes through the openings 9 into the annular space 8 and from there, classified according to the size of the grit, into the hot silos 6.

The dust and moisture are discharged through an exhaust stack 19 at the right-hand end of the drum.

2 not only shows the radially inner ring sieve sections NW10, NW25 and NW32, but also the outer ring sieve sections NW4, NW18 and NW25, which are also arranged at a greater radial distance. The outer ring screen sections are separated from the inner ring screen sections by an annular space 108.

The individual hot silos 6 are shown in FIG. 2, the numbers in the individual silos relating to the particle size. The hot silo 0 - 4 receives material with the smallest particle size, corresponding to the smallest mesh size NW4. NW10 corresponds to the smaller mesh size, NW18 the medium, NW25 the larger and NW 32 the largest mesh size. It can be seen that a collecting device G32 is provided at the right-hand end of the drum for the oversized grain, whereby the oversized grain can also be directed into the adjacent silo by a switching flap, which is in itself intended for the grain sizes between NW25 and NW32.

3 has been carried out schematically in order to better illustrate the idea on which the invention is based.

The individual ring screen sections are provided with the reference number which corresponds to the mesh size of the associated screen. The NW32 sieve therefore has a mesh size of 32, making it the sieve with the largest mesh size. The NW4 sieve is the sieve with the smallest mesh size and so on.

100% denotes the entire screenings that arrive at the left-hand end of the drum 2 and enter the radially inner annular space 8 through the openings 9.

The material to be sieved reaches the ring sieve section NW10 and all particles larger than the mesh size NW10 reach the sieves NW25 and NW32 in the axial direction.

The particles falling through the ring sieve sections 10 enter the outer annular space 108. The smaller particles fall through the ring sieve sections NW4. Experience has shown that the screenings in question here are at least 40% of the total screenings. Particles with a size between the mesh size 10 and 4 advance in the axial direction and are collected in an additional collecting section. This portion of the screenings has about 20% of the total screenings.

Material larger than NW10 reaches the ring screen sections NW32 in the axial direction. The larger particles go as quantity G32 into a separate collection container, which in turn is about 20% of the total quantity. The proportion of the amount of material to be screened which falls through the ring sieve sections 32 is divided into the ring sieve sections NW18 and NW25 into the quantities with grain sizes 18-10 and 25-18, experience having shown that the two proportions are each 10%.

With the selected sieve sizes and the ratios, it can be seen that the sensitive, finest ring sieve section NW4 is only acted upon with 60% of the total quantity of sieved material. The parts of the quantity of material to be screened which do not fall through the ring sieve sections NW4 are particles with only a slightly larger particle size than the mesh size of the ring sieve section NW4, i.e. the finest sieve is not particularly mechanically stressed by such particles.

It is additionally pointed out that with the sieve principle according to the present invention, four sieves are used to sieve out quantities which can be divided into five different particle sizes.

According to the invention, the screening drum 2 can also be operated with an inclined axis, both on the one hand and on the other end, so that the material to be screened remains correspondingly longer on the screens.

Claims (1)

1. A sieve drum (2) for conditioning and sorting granular materials having at least one input device (100) at one end of the drum rotating around its horizontal longitudinal axis (3) and an outlet (9) of the conditioned material at the other end of the drum into a first ring section (8) between the drum (2) and longitudinally consecutive inner ring sieve sections (NW32, NW25, NW10) surrounding the drum concentrically, with the meshes of the ring sieve sections changing so that the section (NW10) with the smaller mesh is the ring sieve section axially closest to the outlet means (9) and the section (NW32) with the largest mesh is the ring sieve section axially furthest from the outlet means (9), and with silos (6) arranged at the underside of the drum (2) to accept sifted material of different particle sizes, characterized in that radially outside to the inner ring sieve sections (NW10, NW25, NW32), outer ring sieve sections (NW4, NW18) with different meshes concentrically surrounding the drum (2) are arranged, with the section (NW4) with the smallest mesh being the axially closest ring sieve section to the outlet means (9), the section (NW18) with the middle mesh being the axially furthest ring sieve section from the outlet means (9), and a collecting section (4-10) for sifted materials with a particle size between the smaller mesh (NW10) and the smallest mesh (NW4) being arranged axially between the outer ring sieve sections with the smallest and the middle mesh (NW4, NW18), and with the outer ring sieve sections being designed in form of windows at which frames the sieves are fixed and that are designed with radially projecting conducting parts for the sifted materials.

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