DE2424007A1 - Screening machine with flexible screen base - with two powered floor sections oscillating at varying frequencies - Google Patents

Abstract

Screening machine with flexible screen floor which includes at least one screen area with two drivable screen floor cross supports arranged in parallel to each other and self oscillating which are largely located vertical to the direction of conveyance of the material being screened. The screen floor cross supports of each screen area are attached to guides which permit only a drive movement directed at an incline to the screen field plane. The drive unit applied to one of the screen floor cross supports produces an oscillation frequency which varies from that produced by the drive unit in contact with the second cross support.

Description

Sieving machine The invention relates to a sieving machine with a flexible Sieve bottom, which comprises at least one sieve field, the two parallel to each other, Independently oscillating and essentially linearly drivable sieve bottom cross members shows between which the screen lining is clamped.

In a known screening machine of this type (see DT-AS 1 248 lot; 33) the sieve bottom vibrates directly via elastically mounted cross members offset in the normal to the sieve level.

When the sieve bottom cross members of a sieve field vibrate in phase are excited, the fundamental oscillation of the sieve bottom results in a parallel shift perpendicular to the sieve plane, while in antiphase excitation the Sieve bottom cross member of a sieve field a limited reciprocal rotary movement takes place around a line in the sieve level.

The invention is based on the object of a screening machine for screening of difficult to screen and moist screenings.

It is known that surface tensions occur when the material to be screened is moist. This surface tension (capillary constant) is caused by cohesive forces in the Moisture caused, causing single particles with a large surface area to form a lump of granules caking. Depending on the total size of the particle surface in a lump of granules aggregated particles is the surface energy corresponding to the capillary constant.

The grain lumps then show boundary conditions of plastic bodies, which move as a unit across the sieve bottom. The size of the energy pulse known screening machines is usually not sufficient, the surface energy of lumps of grain to be overcome, since with parallel fundamental vibrations of the sieve bottom the in the area of a grain lump acting impulse is also directed parallel. Through this there are almost no shear forces that initiate the disintegration of the lumps of grain can.

The object on which the invention is based is to develop a screening machine to create that is able to radiate pulses when the sieve bottom moves or spherically to a lump of grain or to the screenings, so that shear forces initiate the loosening of the lump of grain and thereby a sieving of moist, difficult to screen becomes possible.

The screening machine according to the invention is capable of solving this problem characterized in that the sieve bottom cross members of each sieve field in oblique to the sieve field plane lying directions can be driven with differing oscillation frequencies are-.

The screen lining is tension-free between two cross members built-in. The bottom cross member driven with the lowest frequency is generated one fundamental oscillation in the sieve field, and the one driven with the higher frequency Sieve bottom cross member creates an overhead in the sieve field. Depending on the vote of the two mutually independent oscillation systems to each other result in oscillation nodes and antinodes. The size of an antinode depends on the length of the Sieve field, from the top, the oscillation amplitude and the direction of oscillation of the individual sieve bottom cross member.

If there is a lump of grain on a swinging belly, then there is this emits a radial impulse, which creates shear forces in the lump of grain causing the lump to break up. The acceleration is proceeding thereby radiating from a minimum through a maximum to a minimum.

Their size depends on the vibration amplitude and frequency of the Swing belly abt whereby values of up to 50 g and more can be achieved.

According to the invention, the screening machine can have several consecutive Sieve fields include, each with different depending on the difficulty of the sieving Frequencies or harmonics can work, always with the sieve bottom cross member determines the fundamental oscillation with the lower frequency.

The oscillation frequency of the individual sieve bottom cross members can according to the invention controlled by a control circuit depending on the humidity.

Each sieve bottom cross member represents a closed oscillating system and is provided with a linear drive.

The elastic screen linings are preferably made of rubber bases or plastic-elastic sieve bottoms.

Embodiments of the invention are based on the Fig.

1 to 4 explained. 1 to 3 show schematic side views of a sieve field of a sieve bottom, and FIG. 4 shows a schematic side view of a from four sieve bottom assembled on another following sieve fields.

The sieve field which is shown in FIG. 1 and forms part of a sieve bottom comprises two sieve bottom cross members 5 and 8, between which the sieve lining 3 is clamped is. Each sieve bottom cross member 5 or 8 is attached to a parallel link system 6, so that the individual sieve bottom cross member can only be moved back and forth linearly. To the An eccentric drive 1 with a drive rod is used to drive the sieve bottom cross member 5 4. The second sieve bottom cross member 8 is driven by means of the eccentric drive 2, which acts on the sieve bottom cross member 8 via the drive rod tf.

The screen lining 3 takes in its rest position essentially through the dashed line 3 'a position shown.

The attachment of the sieve bottom cross members 5 and 8 by means of the parallel link systems 6 is such that the oscillating derived from the eccentric drives 1 and 2 linear movement takes place in one direction, and at an angle OC 1 resp.

0t 2 obliquely to the sieve field plane determined by the dashed line 3 ' lies. The angles OC1 and C (2 have a size below 90, preferably about 75 - 89 The sieve bottom cross members 5 and 8 are driven by the eccentric drives 1 and 2 driven to linear oscillations with the amplitude a1 or a2. The drive of a sieve bottom cross member 5 takes place with the frequency fmin. Is the second Sieve bottom cross member 8 still, the elastic oscillating field leads one Fundamental oscillation with the frequency fmin and an oscillation belly.

When the sieve bottom cross member 8 closes at the frequency f1 and 2 x fmin an oscillating linear movement is driven, then it is in the oscillating field according to the illustration of FIG. 1, a first harmonic is forced.

The maximum deflection Hmax of the antinode depends on the direction of movement oC1 and 042 from and from the eccentricity al and a2 of the eccentric drives or the Amplitude of other linear actuators.

In Fig. 2 a state is shown in which the sieve bottom cross member 8 is driven with a frequency f2 = 3 x fmin, whereby the fundamental oscillation fmin of the first sieve bottom cross member 5, a second harmonic with the frequency f2 is superimposed.

In the illustration according to FIG. 3, the first sieve bottom cross member is driven 5 with the frequency imins while the second sieve bottom cross member 8 with one frequency 9 = 5 x fmin is driven. As a result, the fundamental fmin becomes harmonics superimposed with the frequency f4.

In the illustration according to FIG. 4, there are several sieve fields 11, 12, 13 and 14 attached one behind the other to sieve bottom cross members, which are driven by eccentric drives 15, 16, 17, 18 and 19 are driven. In the case of the one composed of several sieve fields Sieving machine 10 can be adjusted by tuning the vibration frequencies of the individual Sieve fields have different vibration patterns, for example in the one shown in FIG. 4 Generate kind.

Claims (7)

Claims 1. Sieving machine with a flexible sieve bottom, which is at least one Sieve field includes, the two arranged parallel to each other, oscillating independently and essentially linearly drivable sieve bottom cross members, between which the sieve lining is clamped, characterized in that the sieve bottom cross member (5, 8) of each sieve field in directions inclined to the sieve field plane with one another different oscillation frequencies can be driven. 2. Sieving machine according to claim 1, characterized in that the directions of vibration of the two sieve tray supports (5, 8) of a sieve field differ from one another. 3. Sieving machine according to claim 1 or 2, characterized in that the sieve tray supports (5, 8) can be driven with different amplitudes. 4. Sieving machine according to one of claims 1 to 3, characterized in that that for each sieve field the oscillation frequency of one sieve base support is the same an integral multiple of the oscillation frequency of the other Siebbodencluerträger is. 5. Sieving machine according to one of claims 1 to 4, characterized in that that the angle between the sieve field plane and the direction of oscillation of the sieve bottom cross member (5) is between 750 and 89. 6. Sieving machine with several successive sieve fields after one of claims 1 to 5, characterized in that the screen linings (3) are adjacent Sieve panels are attached to a common sieve bottom cross member. 7. Sieving machine according to one of claims 1 to 6, characterized in that that the drive frequencies and the vibration amplitude of the sieve bottom cross member (5, 8) are infinitely variable. P a t e n t a n s p r u c h 1 1st sieve machine with flexible sieve bottom, which comprises at least one sieve field, the two arranged parallel to each other, independently has oscillating and essentially linearly drivable sieve bottom cross members, which are essentially perpendicular to the conveying direction of the material to be screened, thereby marked, that the sieve bottom cross members (5, 8) of each sieve field are attached to links that only one drive movement of the sieve bottom cross member directed obliquely to the sieve field level (5, 8) allow, and that on the one sieve bottom cross member (5) a drive member (1) attacks whose drive or Vibration frequency from the drive or vibration frequency of the on the other sieve bottom cross member (8) acting drive member (2) deviates. L e r s e i t e