DE20008762U1 - Screening machine with unbalance motors - Google Patents

Description

Screening machine with unbalance motors

The invention relates to a screening machine with at least one vibration drive in the form of an unbalanced motor, whereby the screening surface can be set into vibration directly by means of the vibration drive or the entire screening unit can be set into vibration.

Screening machines with unbalanced motors as vibration drives are widely known in the state of the art. In screening machines of this type, either the screen lining is directly excited or the entire screening unit is set in vibration. With these screens, the effect occurs that after a certain period of operation of the screening machine, the screen lining becomes clogged, so that it must be cleaned in order to achieve effective screening. Various methods are known in the state of the art for the purpose of cleaning.

-2-

For example, there are electromagnetic drives with different oscillation ranges, chains, brushes, tapping bodies, options for changing the frequency, phase shifting of several drives, switching on motors, changing the fabric tension, switching on and off while passing through the resonance frequency and discontinuous manual cleaning.

The problem with screening machines with unbalanced mass drives is that an increase in frequency has no influence on the oscillation range of the unit. Cleaning aids such as chains, balls and brushes therefore have no influence. Even with screens with direct excitation of the screen lining, it is only possible to change the speed during operation.

Based on this prior art, the invention is based on the object of creating a screening machine of the generic type in which the screening material can be cleaned in a simple manner.

To solve this problem, the invention proposes

-3-

that the unbalance mass of the unbalance motor is variable so that the oscillation range can be set to at least two different values, whereby a first oscillation range is set for the purpose of sieving and a second oscillation range is set for the purpose of cleaning the sieve lining.

The design according to the invention makes it possible to operate the screening machine at two different working moments, namely one for normal screening and one with maximum oscillation range for a short cleaning. The cleaning time should be kept as short as possible because screening is very poor during this time.

A possibly preferred further development is that the unbalance mass of the unbalance motor can be changed by changing the direction of rotation.

Unbalance motors that have different unbalance masses depending on the direction of rotation are known in the state of the art. They are used, for example, in bulk material compactors and bunkers as well as conveyor troughs with two speeds or with different

-4-

loading. For example, such a drive is described in DE 42 25 564 C 1.

With such designs it is possible to change the oscillation range in a simple manner.

Preferably, it can be provided that the unbalanced mass can be changed by means of an actuator.

Here, the change in the unbalanced mass is not achieved by changing the direction of rotation, but by a servomotor, by means of which the unbalanced masses are adjusted relative to each other.

An alternative development is seen in the fact that the unbalance mass has a cavity that can be filled with a liquid.

Here too, the change in the unbalanced mass is not caused by a change in the direction of rotation, but by filling the unbalanced mass, for example with liquid during operation, so that the mass is variable.

&idigr;&idigr;· Ii **i* it mV

-5-

A preferred further development is that the unbalance mass consists of two unbalance weights which are limited to one another and which can rotate the drive shaft of the unbalance motor.

Preferably, it is also provided that the screening machine has at least one oscillating axis passing through the screening frame in bearings, at each end of which an unbalance motor is fixed.

In addition, it is preferred that each unbalance motor has two unbalance masses.

It may also be preferred that the two unbalanced masses are arranged on the shaft of the motor rotated by 180° to each other.

In addition, it is preferred that the unbalanced masses have the same mass.

In the case of stable sieve fabrics or the like, it is preferably provided that the natural frequency of the sieve or the oscillation axis of the sieve is above the excitation frequency of the unbalance drive.

V 6 '-*

This means that with every change of direction the natural resonance is passed through and additional cleaning impulses occur.

Preferably for fine fabrics, the natural frequency of the sieve or the oscillating axis is below the excitation frequency of the unbalance drive.

This means that the natural resonance is not passed through with each change of direction and no uncontrollable vibrations can damage the screen fabric.

In addition, it can preferably be provided that the unbalance drive is coupled to an automatic, preferably adjustable switch.

This allows constant times to be set for the cleaning intervals. The cleaning intervals can be regulated depending on the product properties or mesh size.

-7-

The invention provides a screening machine with one or more drives with unbalanced motors, which have different unbalances depending on the direction of rotation, for example.

One or more motors can be provided for each drive or oscillating axis. The motors can be designed in such a way that the right and left masses are operated at the same or at different angles. Angles of 0° or 180° are preferred. It is also preferred to use motors whose right and left masses have the same or different masses, with the same masses being preferred. Unbalanced drives can also be operated with the same or different frequency or speed. One or more of these drives can be provided on a sieve, whereby a targeted increase and decrease of the frequency is possible when changing direction. In particular, a different frequency is provided for each direction of rotation. Targeted frequency adjustment can also be achieved through appropriate instructive design.

-8th-

A schematic embodiment of the invention is shown in the drawing and described in more detail below. It shows:

Figure 1

a section of a screening machine with vibration drive, partially cut away;

Figure 2 and
Figure 3

a part of an unbalance motor with two unbalance masses that can be changed by changing the direction of rotation;

Figure 4

a corresponding unbalance motor in view, partially broken open,

In the drawing figure 1, a screening machine 1 is shown with at least one vibration drive in the form of an unbalance motor 2. In the embodiment, the screen covering (screen fabric) is set into vibration directly by means of a vibration axis 4 by means of the vibration drive 2, with a seal 5 being provided above the screen covering on the side longitudinal edges.

is provided. The bearing for the oscillating axis is shown at 6. The unbalanced motor 2 has a housing 7 which is fixed to a plate at the end of the oscillating axis 4. A shaft 8 is mounted in the housing. Two unbalanced masses 9, 10 are arranged on the shaft 8, the unbalanced mass 9 being firmly connected to the shaft, while the unbalanced mass 10 can be rotated to a limited extent, so that it can either be brought into the congruent position with the unbalanced mass 9 when rotating anti-clockwise, for example, as can be seen from Figure 2, or it can be rotated relative to the unbalanced mass 9 when rotating clockwise, so that a different unbalanced mass is made available. The unbalanced motor 2 carries out a wobbling movement as shown by arrow 11 in Figure 4 while the unbalanced mass is rotating. The directions of rotation of the unbalanced motor are indicated by the movement arrows 12 for anti-clockwise rotation and 13 for clockwise rotation.

As can be seen from Figure 4, adjustable unbalance masses are provided at both ends of the shaft 8, which are rotated by 180 ° relative to each other.

The inventive design makes it possible to

-10-

Unbalance mass of the unbalance motor 2 so that in the exemplary embodiment, a first oscillation range is set for the purpose of sieving when rotating anti-clockwise and a different oscillation range is set for the purpose of cleaning (clockwise). In the exemplary embodiment, the change in the unbalance mass is achieved solely by changing the direction of rotation of the unbalance motor 2. The actual unbalance mass consists of two unbalance weights 9, 10 which can be rotated to a limited extent relative to one another. This design makes it easy to change the oscillation range simply by changing the direction of rotation in order to enable excellent sieving on the one hand and short-term cleaning of the sieve lining 3 on the other.

The invention is not limited to the embodiment, but is variable in many ways within the scope of the disclosure.

All new individual and combination features disclosed in the description and/or drawing are considered essential to the invention.

Claims (12)

1. Screening machine ( 1 ) with at least one vibration drive in the form of an unbalanced motor ( 2 ), whereby the screen lining ( 3 ) can be set into vibration directly by means of the vibration drive or the entire screening unit can be set into vibration, characterized in that the unbalanced mass of the unbalanced motor ( 2 ) can be changed so that the oscillation range can be set to at least two different values, whereby a first oscillation range is set for the purpose of screening and a second oscillation range is set for the purpose of cleaning the screen lining. 2. Screening machine according to claim 1, characterized in that the unbalanced mass of the unbalanced motor ( 2 ) can be changed by changing the direction of rotation. 3. Screening machine according to claim 1, characterized in that the unbalanced mass can be changed by means of an actuator. 4. Screening machine according to claim 1, characterized in that the unbalanced mass has a cavity that can be filled with a liquid. 5. Screening machine according to one of claims 1 to 3, characterized in that the unbalanced mass consists of two unbalanced weights ( 9 , 10 ) which can be rotated to a limited extent about the drive shaft of the unbalanced motor. 6. Screening machine according to one of claims 1 to 5, characterized in that the screening machine ( 1 ) has at least one oscillating axis ( 4 ) which passes through the screen frame in bearings ( 6 ), at each end of which an unbalance motor ( 2 ) is fixed. 7. Screening machine according to one of claims 1 to 6, characterized in that each unbalance motor ( 2 ) has two unbalance masses. 8. Screening machine according to claim 7, characterized in that the two unbalanced masses are arranged on the shaft of the motor ( 2 ) rotated by 180° to each other. 9. Screening machine according to claim 7 or 8, characterized in that the unbalanced masses have equal masses. 10. Screening machine according to one of claims 1 to 9, characterized in that the natural frequency of the screen or the oscillation axis of the screen is above the excitation frequency of the unbalance drive ( 2 ). 11. Screening machine according to one of claims 1 to 9, characterized in that the natural frequency of the screen or the oscillation axis is below the excitation frequency of the unbalance drive ( 2 ). 12. Screening machine according to one of claims 1 to 11, characterized in that the unbalance drive ( 2 ) is coupled to an automatic, preferably adjustable switch.