Patent Grant
7392895
Applicants claim priority under 35 U.S.C. §119 of German Application No. 10 2005 052 621.7 filed Nov. 2, 2005.
The invention pertains to a method and a device for discharging poorly flowing bulk materials such as, in particular, sawdust, splinters and wood chips from a receptacle.
In order to store bulk materials, receptacles are usually filled from the top and emptied through an outlet opening at the receptacle bottom. Bulk materials that interlock or have a poor pourability for other reasons show a steep angles of repose. Consequently such materials tend to bridge over the outlet opening and cannot be discharged from the receptacle without additional measures.
As prior art DE 197 06 407 C 1 describes a metering and discharging device for bulk materials, in which a stirrup-shaped agitator is arranged on a metering tube with a metering aperture. The bulk material flows into the metering tube through the metering aperture and is discharged from an outlet at the lower end of the metering tube. When processing poorly pourable bulk materials, the metering tube is set in rotation about the longitudinal axis such that the agitator breaks up the bulk material and the bulk material can be discharged through the metering aperture.
In this case, it is disadvantageous that the agitator is unable to separate individual bulk material particles from one another if they are more substantially entangled or interlocked. In such instances, the rotation of the agitator merely leads to a uniform rotational movement of the entire “block” of bulk material particles such that no bulk material is discharged from the receptacle.
As a further disclosure of prior art DE 43 39 974 A 1 shows a device for metering powdery bulk materials, in which an agitating element in the form of a screw-shaft discharges the bulk material from a funnel shaped reservoir. The quantity of bulk material to be metered can be varied in dependence on the rotational speed and the rotating direction of the screw-shaft. When using a screw shaft with a right-handed thread, a clockwise rotation of the shaft results in a high metering accuracy at a low throughput and a counterclockwise rotation results in a lower metering accuracy at a higher throughput.
However, this device is only suitable for powdery bulk material because this type of bulk material cannot interlock and form clumps. Due to their rough and cleaved surfaces, poorly pourable materials such as, e.g., splinters and wood chips tend to interlock and form clumps such that the screw-shaft is blocked.
Consequently, the invention is based on the objective of making available a method and a device for the discharge of poorly pourable bulk materials from a receptacle, in which the disadvantages of the state of the art in this respect are avoided.
With respect to the method, this objective is attained, according to the invention, by rendering the bulk material free-flowing in the receptacle via a first agitating element and discharged from the receptacle via a second agitating element. With respect to the device, this objective is attained by realizing the first agitating element in the form of a worm conveyor that is fixed on a shaft and the rotation of which forces the bulk material situated between the turns of the worm conveyer upward to the bulk material surface and by realizing the second agitating element in the form of a spiral conveyor that is fixed on a shaft and the rotation of which causes the broken up bulk material situated at the bottom of the receptacle to be transported to the outlet opening.
FIG. A shows a perspective view of the invention.
FIG. B shows a side view of the invention.
Advantageous embodiments of the inventive method and device are discussed below.
According to the invention, a poorly pourable bulk material is rendered free-flowing by means of a first helical agitating element and discharged from the receptacle by means of a second helical agitating element. In this case, it is particularly advantageous to mechanically couple the first helical agitating element and the second helical agitating element to one another such that only one drive is required for both agitating elements.
The first agitating element consists of a shaft and a worm conveyor, and the second agitating element consists of a shaft and a spiral conveyor. The shafts of the first and the second agitating element in fact consist of the same shaft such that the worm conveyor and the spiral conveyor are fixed on only one shaft. In this case, it is particularly advantageous that only one shaft is required and that the space requirement can be reduced accordingly.
The spiral conveyor is fixed on the shaft in such a way that it is positioned above the bottom of the receptacle, particularly directly above the bottom. The worm conveyor also begins in the region of the receptacle bottom and ends, in particular, at a point above the highest possible product filling level, at which it is connected to the shaft.
The rotation of the worm conveyor causes the material situated between the turns of the worm conveyer upward to the bulk material surface. This breaks up the bulk material. The material brought up by the worm conveyer flows downward again due to the gravitational force, thus generating a circulating flow of the bulk material.
The rotation of the spiral conveyor causes the broken up bulk material to be transported to the outlet opening at the receptacle bottom, at which it is discharged from the receptacle. The inventive device is particularly suitable for emptying receptacles that are filled with sawdust and/or wood chips.
The invention is described in greater detail below with reference to an embodiment that is illustrated in figures A and B respectively. The figure schematically shows a specially shaped agitating element according to the invention.
According to figure A, the agitating element consists of a shaft 3, a worm conveyor 1 and a spiral conveyor 2. The spiral conveyor 2 is fixed on the shaft 3 in such a way 6 that it is positioned directly above the bottom of the receptacle 4 (See fig B) The worm conveyor 1 also begins at the receptacle bottom and ends at a point above the maximum product filling level, at which it is connected 8 to the shaft 3.
The rotation of the worm conveyor 1 causes the bulk material situated between the turns of the conveyer to be transported upward to the bulk material surface in the receptacle 4. This breaks up the bulk material. The material lifted up, flows back to the bottom of the receptacle due to the gravitational force and follows a path outside or inside the worm conveyer, respectively. Consequently, circuiting motions of the bulk material develop.
The rotation of the spiral 2 conveyor causes the broken up bulk material to be transported to the outlet opening 5 at the bottom of the receptacle, at which it is discharged from the receptacle.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 052 621 | Nov 2005 | DE | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 2751203 | Compton | Jun 1956 | A |
| 3685638 | Siwersson et al. | Aug 1972 | A |
| 3949863 | Lippi | Apr 1976 | A |
| 4275808 | Bullivant et al. | Jun 1981 | A |
| 4324495 | Martinez | Apr 1982 | A |
| 4351627 | Forsberg | Sep 1982 | A |
| 4441603 | Baumard | Apr 1984 | A |
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| 6679559 | Kelm | Jan 2004 | B2 |
| 7192094 | Kelm | Mar 2007 | B2 |
| Number | Date | Country |
|---|---|---|
| 43 39 974 | Jun 1995 | DE |
| 197 06 407 | Jun 1998 | DE |
| Number | Date | Country | |
|---|---|---|---|
| 20070095632 A1 | May 2007 | US |
