WO1994013412A1

WO1994013412A1 - Tension wave strainer

Info

Publication number: WO1994013412A1
Application number: PCT/AT1993/000189
Authority: WO
Inventors: Leander Ahorner
Original assignee: Ife Industrie-Einrichtungen Fertigungs-Aktiengesellschaft
Priority date: 1992-12-11
Filing date: 1993-12-09
Publication date: 1994-06-23
Also published as: EP0673287A1; FI952829A0; FI952829A; AT400533B; IL107986A0; ATA245392A; HUT72518A; CZ151695A3; HU9501678D0

Abstract

The invention relates to a tension wave strainer with a strainer lining secured to rods (3, 4) running across or along the direction of the strainer, wherein adjacent rods vibrate in relation to one another in such a way that the strainer lining is alternately relaxed and tensioned. According to the invention, a plastic fabric, e.g. polyamide (nylon), is used as is known for filtering liquids in process technology. In one embodiment, the tension wave strainer consists of two strainer frames (1, 2) and the rods (3, 4) are fitted alternately in the two frames (1, 2). To increase the vibration frequency of the rods (3, 4), the two frames (1, 2) are interconnected via springs (5) and the vibration exciter is an electromagnetic exciter (7) fitted between the two frames (1, 2).

Description

Tensioning screen machine

The invention relates to a tensioning shaft sieve with a sieve covering, which is fastened to bars running transversely or longitudinally to the sieving direction, adjacent bars executing vibrations relative to one another such that the sieve covering is loosened and tensioned alternately in time.

The bars are usually (alternately) grouped in at least two frames and the frames perform the relative movement. This movement between the two or more frames can take place by a forced movement, for example a crank mechanism, as disclosed in DE-PS 21 58 128 and EP-A2 0208 221, or, as is the case in, for example AT-PS 383 054 is disclosed, one of the two frames is mounted elastically and caused to vibrate by an unbalance drive.

By suitably arranging the second frame in the first and a corresponding resilient connection between the two frames, different forms of resonance vibrations can be achieved between the frames, which can vary from one end to the other from linear to circular even with one and the same sieve. This is also possible in the case of a tensioned shaft sieve machine excited by an eccentric according to DE-G 88 16 250.

A different system of screening machines that does not belong to the tensioning shaft screening machines is known, for example, from DE-OS 32 10 290: beating bars hit the prestressed screening surface from below in order to excite it directly. The blow bars sit on levers that are pivoted about pivot points, for example by a connecting rod of an eccentric drive common to all blow bars. Such a device with electromagnetic, linear excitation is known from DE-GM 83 24 012.

DE-PS 29 18 984 proposes an electromotive individual drive of the levers and is based on DE-OS 23 18 392, which discloses an unbalance drive.

A disadvantage of the operation of all directly excited sieves is the very incomplete cleaning of the covering, but above all the excessive stress on the underside of the covering in the area of the impact points of the blow bars. It has therefore already been proposed to strengthen these points, for example by vulcanizing on a rubber layer or by gluing a plastic cover in these areas.

A major disadvantage in the construction of such screens is the complicated fastening of the blow bars and their drive underneath the screen covering in the area of the worst dust nuisance, highest mechanical stress and poor accessibility.

In sieving there is generally a close connection between the particle size (mesh size), the oscillation frequency and the oscillation amplitude. With the same vertical acceleration and the same throwing angle, the height of the vertex of the throwing parabola is linearly proportional to the value of the vibration range; With a low number of vibrations and a large vibration range, the screenings are thrown higher and thus further than with a small vibration range and high frequency.

In order to achieve an optimal sieving effect, the particles to be sieved must be moved in the horizontal direction so far in the course of an oscillating movement relative to the sieve covering that they do not fall back into the same sieve opening, but also do not jump over too many sieve openings. It can also be deduced from this for tensioning shaft sieves that small mesh sizes require a small vibration width and a high frequency, so that small separating grain sizes quickly reach the limit of the feasibility of known tensioning shaft sieving machines for the following reasons.

Known strainer screening machines use linings made of polyurethane or rubber.

The polyurethane or rubber coverings have a thickness of a few millimeters, so that with mesh sizes (the openings are actually cut into the covering) in the range of one millimeter in diameter or one millimeter square, the openings mutate into tubes or hoses, which leads to the passage of the passage grain practically prevented. In addition to this problem, smaller sieve openings are also practically not feasible in terms of production technology.

Sieve coverings made of steel mesh or perforated sheets are available with the smallest mesh sizes, but cannot be used with tensioned shaft sieves because they are not sufficiently elastic and cannot bear the bending changes that occur (flutter breaks).

The problem with small separating grain sizes on the side of the sieve coverings is the creation of small mesh sizes and the endurance of the increase in the oscillation frequency.

In addition, there is a problem with the drives of the sieving machines that frequencies which are far below the frequencies customary for unbalance, eccentric or crank drives are required for separating grain sizes which are noticeably less than one millimeter. The invention aims to provide a tensioning shaft sieve for small pieces, which is easy to clean, allows large mass throughputs and has a long service life.

This aim is achieved according to the invention in that a mesh made of plastic, for example polyamide (nylon) or polyester, as used in process engineering, e.g. is known for filtering liquids.

These plastic sieves are available in mesh sizes from a few millimeters down to a few micrometers. Their thickness is small, as is their bending resistance, which results in their excellent ability to endure high-frequency vibrations. In addition, there is a high level of abrasion resistance, which is particularly important for achieving long service lives with sharp-edged goods.

In a variant of the invention it is provided that the material of the screen covering is selected from the group consisting of Keflar, carbon fibers, polyethylene, polypropylene, polyvinylidene fluoride or a combination of these and / or the aforementioned materials.

For mesh widths in the range of one millimeter and below, these properties of the screen coverings used according to the invention are fully utilized in one embodiment of the invention by a drive which is able to deliver the required high oscillation frequencies.

This is an electromagnetic exciter known from vibration technology, which is arranged between the two resiliently connected screen frames, which thus form a dual-mass oscillator.

Such electromagnetic drives are robust and reliable, they are easy to encapsulate, because of what is generally dusty environment is favorable and they are easy and widely adjustable due to their operation by electronic controls. This makes it possible to set the vibration range, to keep it constant, or to adjust it for a short time to clean the screen surface.

According to a preferred variant of the invention, the excitation frequency is selected so that it lies in the subcritical range of the vibration system under consideration, consisting of the two sieve frames and the intermediary springs, the sieve bottom contributing practically nothing to the spring stiffness and the mass. This has the advantage that the natural frequency of the system is not traversed when the screening machine is switched on.

In the drawing, the invention is illustrated using an exemplary embodiment and is explained in more detail below.

1 shows a schematic diagram of the two sieve frames and the resonance drive provided between them, FIG. 2 shows a sieve according to the invention in plan view and side view,

3 shows a section through a drive that is particularly suitable for use with a screen according to the invention, FIG. 4 shows a screen according to the invention with two drives, FIGS. 5 and 6 each have a screen according to the invention with three frames,

7 shows a sieve according to the invention with an oscillation direction lying obliquely to the sieve surface in order to impart a directional movement component to the material to be sieved, and FIGS. 8 to 11 show different frame systems with individual or group drive of the rods. 1 schematically shows an example of a sieve according to the invention. It consists of a first frame 1, which has a row of first sieve bars 3. The first frame 1 is connected to a second frame 2 via a spring 5 and guide elements (not shown). The second frame 2 has a row of second sieve bars 4, which are arranged alternately with the first sieve bars 3. Between the sieve bars, a sieve covering according to the invention, not shown, is provided, which is stretched and relaxed in sections by the relative movement between the two frames. The electromagnetic excitation is indicated by the coils 7, which are fixedly mounted on the frame 1 and periodically attract the frame 2 against the force of the spring 5.

1 shows the movement s of the two frames with respect to a fixed reference system over time _^ t. The movement depends on the two masses and the rigidity of the spring 5 and the tensile force of the solenoid 7, also on the way in which the entire vibratory system is mounted.

1 shows the course of the supply voltage Uo, the supply current Jo and the power Fo before the control, and the current J and the power F after the control by the thyristor 15 over the time t.

2 shows an actual embodiment of a sieve according to the invention. A drive 6, in which the spring connecting the two frames is also accommodated, is connected on the one hand to the first frame 1 and on the other hand to the second frame 2. The first frame 1 is designed as a box frame and lies within the box frame, which is also designed second frame 2, which has a correspondingly larger cross section.

The first sieve bars 3 are firmly connected to the first frame 1 and protrude through recesses 8 of the second frame 2, which have such a surface that the first sieve bars 3 do not abut the second frame 2 even when the greatest vibration amplitudes occur. In the example shown, the second sieve bars 4 simply consist of angle irons which are fastened on the inner surface of the second frame 2.

In this illustration, too, the screen covering is omitted; at the end on the feed side, a feed plate 9 is provided, which is attached to the second frame 2.

3 shows a drive which is particularly well suited for use with a sieve according to the invention and which is also shown in outline in the embodiment of FIG. 2.

A housing 10 serves to shield the drive and to connect to the first frame. The ends of a leaf spring assembly 11, which corresponds to the spring 5 of FIG. 1, are fixedly connected to the housing 10, with a magnet yoke 12 and a driver 13 connected to the center of the spring, which is flexibly guided through the housing 10.

Interacting with the magnet 12, which is movable relative to the housing, two magnet coils 14 are fixedly arranged with respect to the housing 10. They are attached to a magnetic yoke on the housing and thus connected to one another.

The invention is not limited to the exemplary embodiment shown, but can be modified in various ways. It is thus possible to place the spring or the spring package between the two frames at another location to arrange or to divide several springs into several locations, which then advantageously also form a bearing between the two frames. The guide for the movement between the two frames can be accomplished in a variety of ways, leaf springs which are stable and robust are preferred, but any other form of storage is also possible.

The drive used according to the invention suggests a linear relative movement between the two frames, but it is possible, for example, through an oblique arrangement of the drive to the main axis of the two frames, to superimpose a vertical movement component, whereby an additional conveying component is achieved, as shown in FIG. 7 is shown.

It is of course possible to arrange the drives differently, even if the positioning at the head of the system is advantageous because of the excellent accessibility and especially with... Dusty goods because of the higher position. However, it is possible, for example, to provide the electromagnets in the frame parts lying one inside the other or next to one another, between the cross bars. It is of course also possible to attach more than two magnetic coils.

4 to 6 show possible variants with two drives, which are each provided at the end:

Fig. 4 shows an embodiment for particularly heavy or long screening machines, in which two identical drives 15, 16 work in push-pull.

5 shows a screening machine with an inner frame 17 and two outer frames 18, 19, which can vibrate to each other with different vibration widths and / or frequencies, for example. Similar to FIG. 5, FIG. 6 shows a screening machine with two inner frames 20, 21 and one outer frame 22.

7 shows, as already mentioned above, a screening machine in which the direction of oscillation 23 between the inner frame 24 and the outer frame 25 does not coincide with the screening direction, so that a movement component is impressed on the material to be screened.

FIGS. 8 to 11 show screening machines according to the invention, in which every second rod is either provided with its own individual drive and thus corresponds to its own frame, or in which the frame common to these rods is degenerated into an actuating rod, and in one variant none fixed cross bars are provided with respect to the main frame. To a certain extent, these machines are derived from the screening machines with direct screening excitation mentioned at the beginning.

8 shows a screening machine, in which cross bars 26 are alternately provided, which are fixedly arranged in the base frame 27, and cross bars 28, which via (curved) swivel levers 29 and individual drives 30 approximately in the direction of the screen along a circular arc section 31 are moved. Here, the base frame 27 with the transverse rods 28 fixedly arranged in it corresponds to one of the frames and each of the movable transverse rods 26 together with the components 29, 30 which resonate with it corresponds to a further frame which carries out the vibration explained above with respect to the first frame.

Fig. 9 shows an arrangement similar to Fig. 8, but here adjacent sieve bars 28 are moved in relation to each other with respect to the base frame 27, whereby the vibration ranges can be reduced, whereby the vibration frequency can be increased. Here corresponds to the base frame 27, which does not have any transverse rods fixedly arranged in it (or only the initial and final attachment for the Screen covering) has, one of the frames and each of the movable cross bars 28 together with the components 29, 30 which resonate with it correspond to a further frame which carries out the above-described vibration with respect to the first frame.

10 shows a variant in which cross bars 26 are provided alternately, which are fixedly arranged in the base frame 27, and cross bars 28, which extend approximately in the direction of sieving by means of (straight) swivel levers 32 and a common drive 33 via an actuating rod 34 a circular arc section 31 are moved. Here, the base frame 27 with the crossbars 26 fixedly arranged in it corresponds to one of the frames and the movable crossbars 28 together with the components 32 which vibrate with them, including the actuating rod 34, correspond to the second frame, which with respect to the performs the above-described vibration in the first frame,

Finally, FIG. 11 shows an embodiment which connects the drive according to FIG. 10 to the cross bar arrangement according to FIG. 9, two drives (one not being visible), one for each group of cross bars, being provided.

The suspension or assembly of the entire screening device is also possible in a variety of ways: it can be provided that both frames can be provided independently on a supporting frame, but one of the two frames is advantageously made by means of elastic elements such as rubber buffers, springs or the like. cantilevered in the desired inclined position. If, as in the embodiment shown in FIG. 2, one of the frames surrounds the other, this frame is of course preferably used for the assembly. If the two frames are arranged next to one another, there is a free one Choice possible. This applies mutatis mutandis to the embodiments with multiple frames.

The application of material, the side wall sealing and the final separation of the overflow from the passage can be carried out in the usual way.

It is of course possible to equip the tensioning shaft screening machines according to the invention with several, essentially parallel screening levels.

Finally, the measures according to the invention can also be applied to tensioning shaft screening machines with longitudinal bars.

Claims

Claims:

1. Span wave screening machine with a screen covering, which is fastened to bars running transversely or longitudinally to the direction of screening, adjacent bars executing vibrations relative to one another in such a way that the screen covering is loosened and tensioned alternately over time, characterized in that a mesh made of plastic is used as the screen covering , for example nylon or polyester, as is known in the process technology for filtering liquids, is used.

2. Span wave screening machine according to claim 1, characterized ge indicates that the screen covering has a mesh size of less than 3 mm.

3. Span wave screening machine according to claim 2, characterized ge indicates that the screen covering has a mesh size of less than 1 mm.

4. Tensioning screen machine according to one of claims 1 to 3, characterized in that the material of the Siebbela¬ ges from the group consisting of Keflar, carbon fibers, polyethylene, polypropylene, polyvinylidene fluoride or a combination of these and / or the materials mentioned in claim 1 is selected .

5. Tensioning sieve machine according to one of the preceding claims, which consists of at least two sieve frames, the parallel rods being mounted alternately in the sieve frame, characterized in that the two sieve frames (1, 2) are resiliently connected to one another and that as a vibration exciter an electromagnetic ¬ exciter (6) is arranged between the two sieve frames.

6. Spannwellensiebmaschine according to claim 5, characterized in that the excitation frequency of electromagnetic exciter (6) is smaller than the resonance frequency of the two-mass oscillator consisting of the spring-connected screen frames (1, 2) in the ready-to-operate state.

7. Tensioning shaft sieving machine according to claim 5 or 6, characterized in that the resilient connection between the two sieve frames (1, 2) and the electromagnetic exciter (6) are combined to form a structural unit which is arranged between the two sieve frames is.

8. Tensioning shaft screening machine according to claim 7, characterized in that the resilient connection consists of a leaf spring or a leaf spring assembly (11) which runs essentially parallel to the bars (2, 3), the ends of the leaf spring assembly with the one sieve frame ( 1) and the center of the leaf spring assembly is connected to the other sieve frame (2) and the electromagnetic exciter (6) acts on the middle of the leaf spring assembly (11) on the side opposite the connection (13) to the sieve frame (2) .

9. Tensioning sieve machine according to one of claims 5 to 8 with at least three frames, characterized in that in a frame (17, 22) the other frames (18, 19; 20, 21) in the sieving direction one after the other angeord¬ net and each with its own Drive are provided.

10. Tensioning screen machine according to claim 9, characterized in that the last frame seen in the direction of screening has a lower vibration amplitude than its direct neighboring frame.

11. Tensioning screen machine according to one of claims 1 to 4, characterized in that the cross bars (26, 28) are arranged in a base frame (27) and that at least every second cross bar (28) in the base frame (27) is linear or arcuate (31) Vibration accomplished.

12. Tensioning screen machine according to claim 11, characterized in that the oscillating cross bars (28) are individually driven.

13. Tensioning screen machine according to claim 11, characterized in that the oscillating cross bars (28) are driven together via an actuating rod (34).