Classifying – separating – and assorting solids – Sifting – Drum sifters
Reexamination Certificate
1998-11-13
2001-02-27
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Sifting
Drum sifters
C209S284000, C209S285000, C209S240000, C209S262000, C209S263000
Reexamination Certificate
active
06193072
ABSTRACT:
This application claims Paris Convention Priory of German Patent application number 197 51 419.7 filed Nov. 20, 1997 the complete disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
The invention concerns a sifting machine having a stationary sifting basket, a rotor rotating in the sifting basket and a worm conveyor feeding into an end of the sifting basket for dosing and introducing a material to be sifted, wherein the rotor and the worm conveyor are driven for rotation.
In sifting machines having a stationary sifting basket disposed within a sifting machine housing and having a rotor rotating therein, the material to be sifted is normally introduced by means of a worm conveyor which projects into an end of the sifting basket and transfers the material. The material is engaged by the rotor in the sifting basket and accelerated in a centrifugal fashion against the sifting surface of the sifting basket. The sifted material falls into a receiving hopper and is passed out of the sifting machine housing, whereas the course product is transported out at the end of the sifting basket facing away from the worm conveyor. This is generally effected in that the rotor plates have a slight tilt in the axial direction.
In order to drive the worm conveyor and the rotor for rotation, both seat on a common shaft and one single drive motor is provided for which is disposed on the end of the worm conveyor facing away from the rotor. The amount of material fed to the rotor depends on the rate of revolution of the drive motor and may not exceed certain values to prevent unsifted material from being removed along with the course material discharge. The rate of revolution must also be chosen in such a fashion that a sufficient dwell time in the sifting basket is guaranteed for the material being sifted. The highest degree of sifting efficiency for a sifting machine thereby requires, on the one hand, an optimal rotor rate of revolution for the actual sifting process and, on the other hand, an optimized rate of revolution for the worm conveyor with regard to the introduction of material. Since both rates of revolution are not equal and also depend on the material, it is always necessary to strike a compromise for operation of the drive motor with regard to the rate of revolution.
Attempts have been made to dispose an additional independently driven dosing device above the inlet chute of the worm conveyor so that the amount of material introduced to the sifting basket is no longer dependent on the rate of revolution of the worm conveyor so that the sifting machine can be operated with the optimized rate of rotor revolution. The additional dosing device is however associated with significant additional constructional effort and also requires extra clearance height in the vicinity of the inlet chute. This is undesirable, since it makes the filling process more difficult.
Another possibility for avoiding the above mentioned disadvantages is to provide the worm conveyor, at least in its dosing region, with a larger core diameter or with a steeper conveyor screw pitch for reducing the amount transported. If appropriate, the worm conveyor can also be exchanged for a worm conveyor having differing geometry. All these measures, however, constitute unacceptable compromises in practical applications.
When the material being sifted by the sifting machine is changed, the sifting machine must normally be cleaned. Towards this end, the worm conveyor, the sifting basket and the rotor must be removed. This is also true when exchanging the sifting basket for a differing grain spectrum. Removal and exchange is however difficult and costly due to the relatively large axial constructional extent.
It is therefore the underlying purpose of the invention to create a sifting machine of the above mentioned kind with which the rotor and the worm conveyor can be operated at optimized rates of revolution and which facilitates a simplified cleaning and reconfiguration.
SUMMARY OF THE INVENTION
This purpose is achieved with a sifting machine of the above mentioned kind in that the worm conveyor and the rotor each have their own separate drive device.
Due to separation of the rotor drive from that of the worm conveyor, the rotor can be driven with a rate of revolution optimized for the material to be sifted and for the sifting action, whereas the input amount is adjustable by the worm conveyor drive device. In this manner, the additional clearance height for the dosing device disposed above the inlet chute is eliminated. In addition, the separate rotor and the worm conveyor drives facilitate directed removal of only those components necessary for reconfiguration or cleaning, wherein the axial constructional length of the individual components which are to be removed is reduced, since the shaft supporting the rotor is separate from the shaft bearing the worm conveyor.
A preferred configuration of the invention provides that the drive device for the rotor is disposed on that end thereof facing away from the worm conveyor. In this manner, the drive device installation is compact and coaxial configuration of the rotor and the worm conveyor is facilitated.
In order to remove the rotor as well as the sifting basket for cleaning or reconfiguration, a further improvement of the invention provides that the rotor, together with the sifting basket and its drive mechanism, can be axially pulled out of the sifting machine housing along a guiding mechanism. Towards this end, the rotor, the sifting basket, and the drive mechanism are conjoined, e.g. by means of an end lid of the sifting machine, into one single unit which, subsequent to release of appropriate locking mechanisms, can be pulled out of the housing by the axial extent of the sifting basket and the rotor so that the sifting basket and the rotor are freely accessible.
The guiding device preferentially includes at least one, preferentially however, two axis-parallel guiding rods introduced onto the unit comprising the rotor, the sifting basket and the drive mechanism, which are borne in a displaceable fashion in guides formed in the sifting machine housing.
In order to be able to more easily exchange the rotor and/or the sifting basket once they have been removed from the sifting machine housing, a preferred embodiment provides that the unit comprising the rotor, the sifting basket and the drive device is connected to the guide rods by means of a pivot bearing. After the sifting basket and the rotor have been pulled out of the sifting machine housing along their axial constructional length, the complete unit is pivoted about the pivot bearing to the side, so that the components are easily accessible. In particular, the rotor can be pulled axially out of the sifting basket and the sifting basket can be detached. In this manner, assembly space is reduced in the axial direction.
The pivot axis of the pivot bearing can be substantially perpendicular to the rotor axis and, in particular, extend in a vertical direction. It is, however, also possible for the pivot axis of the pivot bearing to coincide with the longitudinal axis of the guide rod.
The worm conveyor drive device is disposed on that end of the worm conveyor facing away from the rotor. This facilitates removal of the worm conveyor, extending within a worm conveyor housing, out of this housing together with the drive device to effect good accessibility for cleaning.
Further details and features of the invention can be extracted from the following description of embodiments with reference to the drawing.
REFERENCES:
patent: 4236676 (1980-12-01), Bialski et al.
Link Otmar
Schmitt Josef
AZO GmbH & Co.
Miller Jonathan R.
Vincent Paul
Walsh Donald P.
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