EP0405477B1 - Sieving device - Google Patents

Abstract

In a screening machine comprising two screening frames (13 and 31) each having mutual oppositely located feed and discharge ends on which there is arranged an elastic screening lining (54) and which are caused to oscillate by independent oscillating drives wherein the two screening frames (13 and 31) are associated with each other at different heights in such a way that the lower region of the upper screening frame (31) and the upper region of the lower screening frame (13) lie in a common plane, that the elastic screening lining (54) is secured to the two screening frame (13, 31) in the common plane thereof and that the upper screening frame (31) is independently driven in a circular configuration at the feed end and the lower screening frame (13) is indepndently driven in a circular configuration at the discharge end.

Description

The invention relates to a sieving machine with two sieve frames to be set in vibration, which are arranged one above the other, on which an elastic sieve covering divided into several sieve fields is arranged and which are to be set in vibration by at least one oscillating drive.

From German utility model 71 45 669 a screening machine is known which has two screen frames arranged at different heights, an upper frame being mounted on a lower frame by means of an elastic bearing. The upper sieve frame is therefore floating on the lower sieve frame. An elastic mounting in the form of a U-shaped profile made of plastic is provided between the upper sieve frame and the lower sieve frame and also serves as a seal. This means that the upper frame is removed from the lower frame by the height of the elastic mounting. In the lower area of the upper sieve frame, cross members are arranged, which extend to approximately the middle area of the upper sieve frame. Also arranged on the lower sieve frame are crossbeams which protrude from the lower sieve frame so far upwards and protrude into the upper sieve frame that they are flush with the crossbeams of the upper sieve frame. The upper areas of the cross members form a common plane approximately in the middle area of the upper sieve frame. The screen covering is arranged in this level and fastened to the cross members.

An eccentric bearing with a crankshaft is provided on the lower sieve frame. Two crank rods mounted on the crankshaft engage the upper sieve frame.

When the crankshaft is driven by a motor arranged on a foundation, the lower sieve frame and the upper sieve frame are set in precisely opposite vibrations at the same time, since the driving force acting on the upper sieve frame via the crank rod has the same, but 180 ° out of phase on the lower sieve frame acting reaction force.

This screening machine is a two-mass system in which the mass forces are always out of phase by an angle of 180 ° and are in equilibrium. In addition, the driving force on the upper frame and the reaction force on the lower frame always have the same frequency. The two sieve frames both swing against each other and only in the longitudinal direction.

Another known screening machine consists of two vibrating screen frames, each of which has a plurality of cross members to which an elastic screen pad is attached. Relative to the middle position of the screen frame to each other, the screen covering is longer than the length of the frame, so that the screen covering between loosely sags the individual cross beams. The entire screen surface therefore forms a plurality of screen tracks one behind the other, which run transverse to the longitudinal direction of the screening machine, each screen track being located between two adjacent cross members.

When the sieve frames are in the one reversal point, every next but one sieve path of the sieve covering is tensioned, while the other sieve paths located between the tensioned sieve paths hang loosely between two adjacent cross members. In the other reversal point of the sieve frame, the tension state of the sieve paths is reversed, so that the previously tensioned sieve paths now sag between two adjacent cross members and the previously loosened sieve paths located between them are now tensioned. Thus, the tensioned sieve paths and the sagging sieve paths alternate from reversal point to reversal point of the sieve frame or the oscillating drives of the sieving machine.

Both frames of the screening machine are set in vibration by mutually independent unbalance drives in such a way that the two frames swing 180 ° out of phase with each other so that they are in mass balance. The frames both swing in their longitudinal direction, i.e. one-dimensionally in the same direction and in a common plane.

The screening machine known from German Offenlegungsschrift 22 30 812 has only a single screen frame. This sieve frame is mounted on a swing arm at the end of the feed. Further towards the discharge end beyond the center of the sieve frame, it is supported on two pendulum supports and driven in a circular motion. This means that the screen has a circular movement in the area of the drive and a vertical movement at the feed end and at the discharge end executes. This known screening machine does not have a screen covering divided into several screen fields. This screening machine is therefore foreign to the genus, since it does not meet several features of the preamble of the new claim 1, especially not the features according to which two screen frames are provided, according to which the screen frames are arranged one above the other at different heights and according to which a screen covering divided into several screen fields is attached to the screen frame is arranged.

In another known sieving machine, only a single sieve box is provided, in which a plurality of cross members are arranged, to which the sieve covering is attached. An unbalance drive is provided on each of the crossbeams, by means of which the associated crossbeam moves back and forth in the longitudinal direction of the screen frame, that is to say is set in vibration. The excitation of the vibrations takes place in such a way that adjacent cross beams each swing 180 ° out of phase, so that these cross beams are also in mass balance. The unbalance drives for the cross beams are synchronized, either mechanically by a chain drive or electrically by a synchronization circuit. The screening machine is therefore in the mass balance and does not release any restoring forces to the installation site or to the foundation.

In these known screening machines, there is a particular problem in that the movable parts of the screening machine, in particular the screen covering, must be sealed against the stationary parts of the screening machine adjacent to it, in particular against the two side walls. This seal is difficult and gives rise to special wear and breakdowns.

The invention has for its object to provide a screening machine of the type mentioned in the the sealing problems in the area of the edge of the screen covering no longer exist and in which particularly good screening results can be achieved in the fine and ultra-fine area of the screen items and in particular in the case of difficult to screen items by shear forces in the level of the screen covering.

According to a first solution to this problem, the invention consists in that the two sieve frames with longitudinal walls are assigned to one another in such a way that the lower end of the upper sieve frame and the upper end of the lower sieve frame lie in a common plane, that the elastic sieve covering is in the common plane the two sieve frames are attached to them and that the upper sieve frame is driven in a circular manner on the feed side in a horizontal plane and the lower sieve frame on the discharge side in a vertical plane.

In this way, a sieving machine of the type mentioned above is obtained, in which the edge sealing problems between the sieve covering and the edge of the sieving machine no longer exist. In addition, particularly good sieving results can be achieved in the fine and ultra-fine range of the sieved material and particularly in the case of difficult-to-sieve materials. The separating cut is particularly good here. Since there are no relative movements between the screen covering and the side walls adjacent to it, the edge sealing problem no longer exists between the screen covering and the side walls of the screening machine.

Since the upper sieve frame and the lower sieve frame are arranged at different heights such that the lower region of the upper sieve frame and the upper region of the lower sieve frame lie in one plane, the lower region of the upper sieve frame and the upper region of the lower sieve frame can be used as a clamping region can be used for the screen covering. This means that it is still possible that the upper screen frame can be set in circular movements on the feed side in a horizontal plane and at the same time the lower screen frame can be set in circular movements on the discharge side in a vertical plane. This means that the upper frame and the lower frame swing in mutually perpendicular planes, namely the upper frame in a horizontal plane and the lower frame in a vertical plane. With the upper frame at the end of the feed, this leads to particularly strong shear forces on the screen covering, which means that particularly intensive sieving effects already exist at the end of the feed of the upper screen frame. At the discharge end of the upper sieve frame, the effect of the shear forces is negligible. Here the effect of the up and down movement of the lower sieve frame comes to the fore of the sieve effect.

According to a second solution to the problem, the invention is that the two sieve frames with longitudinal walls are assigned to each other such that the lower end of the upper sieve frame and the upper end of the lower sieve frame lie in a common plane, that the elastic sieve covering in the common plane the two sieve frames are attached to them and that the upper sieve frame is driven in a circular manner on the feed side in a vertical plane and the lower sieve frame on the discharge side in a horizontal plane.

Here, the swinging movements of the two swing frames are reversed to the first solution of the task described above, namely such that the lower swing frame swings in a horizontal plane, while the upper swing frame swings in a vertical plane.

Moreover, it is also ensured here that the previous edge sealing problems of the known vibrating machines no longer exist and that particularly good screening results can be achieved especially in the fine and ultra-fine range of the screenings and in difficult screenings.

According to a third solution to the problem, the invention is that the two sieve frames with longitudinal walls are assigned to each other such that the lower end of the upper sieve frame and the upper end of the lower sieve frame lie in a common plane, that the elastic sieve covering in the common plane the two sieve frames are attached to them and that the upper sieve frame is driven in a circular manner in the same horizontal plane on the feed side and the lower sieve frame on the discharge side.

This also ensures that the edge sealing problems no longer exist. In addition, particularly good sieving results are achieved in the fine and ultra-fine area of the sieved material.

The vibratory drive can be designed as an unbalance drive or as an eccentric drive.

Both screen frames are expediently set in vibration at such different frequencies that no beats occur. This means that the difference between the frequency of one frame and the frequency of the other frame must be sufficiently large.

The two sieve frames are expediently driven in such a way that the upper sieve frame with an oscillation number in the range of 500, 750, 1000 or 1500 oscillations per minute and the lower sieve frame accordingly with an oscillation number in the range of 750, 1000, 1500 or 3000 oscillations per minute is driven or vice versa.

For example, with a vibration number of 1000 vibrations An oscillation rate of 1500 vibrations per minute of the lower sieve frame is recommended per minute of the upper sieve frame. In this case, one is not exactly dependent on the vibration numbers given above, but deviations to both sides are also possible with these vibration numbers.

It is recommended that the lower sieve frame and the upper sieve frame are each mounted on the drive side on a spring, for example a screw or rubber spring, and on the end on a link, for example a link spring.

Fig. 1

einen Längsschnitt durch eine erfindungsgemäß ausgebildete Siebmaschine längs des Schnittes I-I der Figur 3,

Fig. 2

einer Querschnitt durch die Siebmaschine längs des Schnittes II-II der Figur 1,

Fig. 3

eine Draufsicht auf die Siebmaschine gemäß Figur 1,

Fig. 4

ein Bewegungsdiagramm des oberen Siebrahmens der Siebmaschine,

Fig. 5

ein Bewegungsdiagramm des unteren Siebrahmens der Siebmaschine,

Fig. 6

einen schematischen Querschnitt durch die Siebmaschine in der Mittelstellung der Siebrahmen,

Fig. 7

eine Darstellung gemäß Figur 6 mit den Siebrahmen in der einen Endstellung und

Fig. 8

eine Darstellung gemäß Figur 6 mit den Siebrahmen in der anderen Endstellung.

The invention is explained below with reference to an embodiment shown in the drawing. It shows

Fig. 1

3 shows a longitudinal section through a screening machine designed according to the invention along section II of FIG. 3,

Fig. 2

3 shows a cross section through the screening machine along the section II-II of FIG. 1,

Fig. 3

2 shows a plan view of the screening machine according to FIG. 1,

Fig. 4

a movement diagram of the upper sieve frame of the sieving machine,

Fig. 5

a movement diagram of the lower sieve frame of the sieving machine,

Fig. 6

2 shows a schematic cross section through the screening machine in the middle position of the screening frame,

Fig. 7

a representation of Figure 6 with the screen frame in one end position and

Fig. 8

a representation of Figure 6 with the screen frame in the other end position.

A machine frame 1 is resiliently supported on springs 2, 4, 5 on a foundation 6. The machine frame 1 consists of two cheeks 7, 8 delimiting the machine frame 1, which are connected to one another by cross members 9, 10, 11, 12 and are held at a distance.

A lower sieve frame 13 is provided on the machine frame 1, which essentially consists of two side walls 14, 15, which are connected to one another at their task ends 16, 17 via an end wall 18. At the feed ends 16, 17 of the side walls 14, 15, link springs 19, 20 are provided with which the lower sieve frame 13 is resiliently mounted on the machine frame 1. At the discharge ends 21, 22 of the lower sieve frame 13, the latter is resiliently mounted on coil springs 23, 24.

At the discharge-side end of the lower sieve frame 13, an unbalance drive 25 is fastened, through which the lower sieve frame 13 is moved in such a way that it carries out circular movements in a vertical plane at its discharge-side end 21, 22.

The circular movements carried out by the lower sieve frames 13 are rotated in FIG. 5 by 90 ° in relation to the representation in FIG. 3, that is to say represented in a vertical plane. At the discharge-side ends 21, 22 of the lower sieve frame 13, the latter performs a circular movement according to the circle 26 and at the end on the feed side a translatory movement in the direction of the double arrow 27. In the areas between the feed end 16, 17 and the discharge end 21, 22, the lower sieve frame 13 executes approximately elliptical movements according to the elliptical curves 28, 29, 30.

An upper sieve frame 31 is provided on the machine frame 1 and consists of two frames 32, 33 arranged side by side.

The frame 32 is delimited by the longitudinal beams 34, 35 and the frame 33 by the longitudinal beams 35, 36. At the feed end 37 of the upper sieve frame 31, the latter is spring-mounted on coil springs 38, 39 on blocks 40, 41. The jacks 40, 41 are supported on the machine frame 1.

At the discharge-side end 42 of the upper sieve frame 31, the latter is supported on link springs 43, 44 which are supported on the machine frame 1.

An oscillating drive 46 is arranged on the end wall 45 at the end 37 of the upper sieve frame 31 on the feed side, by means of which the upper sieve frame 31 on the end 37 of the feed end is set in circular movements.

These movements are shown in Figure 4. The upper sieve frame 31 executes the circular movement 47 shown in FIG. 4 at the end 37 on the feed side, while the discharge end 42 of the upper sieve frame 31 moves in the direction of the double arrow 48 moved one dimension. The movements of the upper screen frame 31 in the areas between the feed end 37 and the discharge end 42 correspond to the ellipse-like curves 49, 50, 51 according to FIG. 4.

The upper sieve frame 31 and the lower sieve frame 13 are arranged at a height such that the lower region 52 of the upper sieve frame 31 and the upper region 53 of the lower sieve frame 13 lie in a common plane. In this common plane, an elastic screen covering 54 is fastened to the upper screen frame 31 and the lower screen frame 13. This results in four screen tracks 55, 56, 57, 58 between the longitudinal walls 14, 15 of the lower screen frame 13 and the longitudinal walls 34, 35, 36 of the upper screen frame 31.

In the idle state of the two screen frames 13 and 31 or in their central position, the four screen tracks 55, 56, 57, 58 hang loosely, as shown in FIG. FIGS. 6, 7 and 8 show the state of the four screen tracks 55, 56, 57, 58 at the input end 37 of the upper screen frame 31 and at the input side end 16, 17 of the lower screen frame 13.

FIG. 7 shows the situation in the one reversal point of the sieve frame 13, 31. The upper sieve frame 31 is deflected to the left relative to the lower sieve frame 13, so that the sieve tracks 55 and 57 are tensioned at this point of reversal, while the other sieve tracks 56, 58 sag more.

FIG. 8 shows the situation in the other reversal point of the sieve frames 13, 31, in which the upper sieve frame 31 is deflected to the right relative to the lower sieve frame 13, so that the sieve tracks 55, 57 which were previously tensioned sag during this reversal point, while the previously loose sieve tracks 56.58 are now tensioned.

The state of the wire webs 55, 56, 57, 58 changes from the state shown in FIG. 7 to the state illustrated in FIG. 8 and vice versa, the intermediate state shown in FIG. 6 being established between the two end states.

Claims (8)

1. A sieving machine comprising two sieve frames wich are to be displaced with an oscillating movement and wich are arranged one above the other and on wich is arranged an elastic sieve lining subdivided into a plurality of sieve areas and wich are to be displaced with an oscillating movement by at least one oscillating drive, characterised in that the two sieve frames (13, 31) with longitudinal walls (14, 15; 34, 35, 36) are associated with each other in such a way that the lower end of the upper sieve frame (31) and the upper end of the lower sieve frame (13) lie in a common plane, that the elastic sieve lining (54) is fixed to the two sieve frames (13, 31) in the common plane of the two sieve frames and that the upper sieve frame (31) is driven in a circular motion in a horizontal plane at the feed end and the lower sieve frame (13) is driven in a circular motion in a vertical plane at the discharge end.
2. A sieving machine comprising two sieve frames which are to be displaced with an oscillating movement and wich are arranged one above the other and on wich is arranged an elastic sieve lining subdivided into a plurality of sieve areas and wich are to be displaced with an oscillating movement by at least one oscillating drive, characterised in that the two sieve frames (13, 31) with longitudinal walls (14, 15; 34, 35, 36) are associated with each other in such a way that the lower end of the upper sieve frame (31) and the upper end of the lower sieve frame (13) lie in a common plane, that the elastic sieve lining (54) is fixed to the two sieve frames (13, 31) in the common plane of the two sieve frames, and that the upper sieve frame (31) is driven in a circular motion in a vertical plane at the feed end and the lower sieve frame (13) is driven in a circular motion in a horizontal plane at the discharge end.
3. A sieving machine comprising two sieve frames wich are to be displaced with an oscillating movement and wich are arranged one above the other and on wich is arranged an elastic sieve lining subdivided into a plurality of sieve areas and wich are to be displaced with an oscillating movement by at least one oscillating drive, characterised in that the two sieve frames (13, 31) with longitudinal walls (14, 15; 34, 35, 36) are associated with each other in such a way that the lower end of the upper sieve frame (31) and the upper end of the lower sieve frame (13) lie in a common plane, that the elastic sieve lining (54) is fixed to the two sieve frames (13, 31) in the common plane of the two sieve frames and that the upper sieve frame (31) is driven in a circular motion at the feed end and the lower sieve frame (13) is driven in a circular motion at the discharge end, each in the same horizontal plane.
4. A sieving machine according to claim 1, claim 2 or claim 3 characterised in that the oscillating drive (25, 46) is an unbalance drive.
5. A sieving machine according to claim 1, claim 2 or claim 3 characterised in that the oscillating drive (25, 46) is an eccentric drive.
6. A sieving machine according to at least one of the preceding claims characterised in that the two sieve frames (13, 31) are displaced and maintained with an oscillating movement at oscillation speeds wich are different such that no beat phenomena occur.
7. A sieving machine according to at least one of the preceding claims characterised in that the upper sieve frame (31) is driven at an oscillation speed in the range of 500, 750, 1000 or 1500 oscillations per minute and the lower sieve frame (13) is correspondingly driven at an oscillation speed in the range of 750, 1000, 1500 or 3000 oscillations per minute, or correspondingly vice-versa.
8. A sieving machine according to at least one of the preceding claims characterised in that the lower sieve frame (13) and the upper sieve frame (31) are each mounted at the drive end on a spring (23, 24, 38, 39), for example a coil or rubber spring, and at the terminal end on a guide member (19, 20, 43, 44), for example a guide spring.

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