Liquid purification or separation – Structural installation – Flume stream type
Reexamination Certificate
2002-01-24
2004-04-13
Upton, Christopher (Department: 1724)
Liquid purification or separation
Structural installation
Flume stream type
C210S160000, C210S161000, C210S328000, C210S391000, C210S400000
Reexamination Certificate
active
06719898
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a sieving device for mechanically separating and extracting solid elements, solid bodies, or solid matter from a liquid flowing in a sluice channel, in particular, to sieve or filter gratings for process, cooling water or effluent currents or for use in sewage treatment plants or hydroelectric power stations.
Such sieving devices are usually equipped with a number of sieving panels which are substantially arranged in a transverse direction to the direction of flow of the liquid current, said sieving devices normally being linked together and forming a revolving endless sieve belt immersing into the liquid current. The devices also comprise a drive for the endless sieve belt, which preferably enables continuous separation and extraction of the solid matter from the liquid current. Generally, in the so-called “transverse flow embodiment”, the endless sieve belt completely covers the cross-section of the liquid current. Therefore, the solid matter cannot pass through the sieving device, as long as its dimensions are no larger than the gap width or the mesh size of the sieving panels. It thus becomes deposited on the sieving panels.
The solid matter from the liquid current which has been deposited on the sieving panels is guided upward by the revolving motion of the endless sieve belt and discharged or removed at a discharge point located above the water level. By spraying off the sieving panels at the discharge point, the sieving panels can be thoroughly cleaned before they are re-submerged in the liquid current.
Such Sieving Devices Are Known in Various Embodiments:
One version comprises an endless sieve belt composed of rectangular sieving panels which are linked together by articulation. The individual sieving panels can be pivoted with respect to one another around a horizontal axis. The endless sieve belt is submerged in the liquid current, so that the liquid current flows through a section of the endless sieve belt that faces upstream and a section that faces downstream. The upstream-facing section and the downstream-facing section of the endless sieve belt are linked together by an upper and lower reversal device. A spraying device for the sieving panels is generally located at the upper reversal device.
One disadvantage of this state of the art, which is also called the “transverse flow” embodiment, is that the desired cleansing effect of the liquid current has already essentially been achieved when it flows through the upstream-facing section of the endless sieve belt, even though the liquid current must still also pass through the downstream-facing section of the endless sieve belt. This means that the inevitable pressure loss which occurs upon flowing through the endless sieve belt is doubled.
This pressure loss results in what is normally an undesired drop of the liquid level, which must be raised again to some extent by using pumps and similar devices.
This pressure loss is disadvantageous both for effluent plants, in which equalization must be achieved by pumps or other measures, and for cooling water plants, which are a preferred area of use for this invention. Large primary cooling water pumps are present in cooling water plants for the entire volume of water. This additional pressure loss results in a lower water level in the pump chamber, for which the cooling water pumps must compensate. This leads to significant excess energy costs and thus excess operating costs. The required length of construction may also be disadvantageous, especially for cost reasons.
In another version of known sieving devices, the liquid current is divided by structural means so that the inevitable pressure loss due to the cleansing effect only occurs in one permeated sieving panel, i.e. about half of the liquid current is deflected about ninety degrees to the left and to the right. In this case, the endless sieve belt is submerged in the liquid current in such a way that the sieving panels are arranged along the original direction of flow of the liquid current. Half of the divided liquid current is then guided to the left through the left section of the endless sieve belt, and the other half of the liquid current is guided to the right through the right section of the endless sieve belt. After they flow through the endless sieve belt, both halves of the liquid current are deflected again and reunited.
This second version may also be constructed in such a way that the liquid current flows outward through the endless sieve belt from the inside of the endless sieve belt, or vice versa. These embodiments are also designated as “from in to out” or “from out to in”, as appropriate. Of course, the advantage of the liquid current only flowing once through the endless sieve belt, which results in a smaller pressure loss, is countered by the disadvantage of expensive structural measures. Additionally, substantial reduction factors arise due to the means for changing the direction of flow of the current, which cause a reduced flow rate capacity or increased size of the equipment. Furthermore, the double deflection of the liquid current causes a disproportionately large assembly length in the direction of flow of the combined current. This is often either not an option at all, or it is only an option if one is willing to accept substantial additional costs.
In order to solve these problems, the applicant proposed in its application DE 19654132 A1 to equip a sieving device of the first kind described above with sieving panels which can be pivoted outward from the downstream-facing rear section of the endless sieve belt to free the sluice current in a substantially open position. Structural measures according to the second version described above are not necessary in this case. The current essentially only flows through the sieving panels once. Thus, the total loss of pressure remains conveniently small. This will, however, complicate the construction of the endless sieve belt, and some effort must be made to guarantee the water-tightness of the closed sieving panels in the forward section of the endless sieve belt.
Furthermore, this transverse flow embodiment also is disadvantageous in that a portion of the debris retained on the sieving panels that revolve from the wastewater side to the clean water side is conveyed from the wastewater side to the clean water side by the panels. This contaminates the clean water side.
Both the “in-out” and the “out-in”, and especially the “transverse flow” embodiments of the state of the art have the disadvantage that debris collects on the bottom in the area between the sieving panels due to sedimentation processes. In time, this can obstruct the course of the sieving panels. Furthermore, the construction of known devices is costly, since they all require two chain hoists (in/out or left/right) to transport the sieving panels.
SUMMARY OF THE INVENTION
Based on this state of the art, the object of the invention is to create a sieving device of the type described at the beginning of this text which combines the smallest possible loss of pressure in the liquid current with a small length of construction in the direction of the current flow of the device and a simple design for the endless sieve belt.
This problem has been solved by the invention of a sieving device with the features as described herein.
Preferred embodiments and additional improvements of the invention are shown in the following description with the corresponding figures.
A sieving device according to the invention for mechanically separating and extracting solid elements, solid bodies, or solid matter from a liquid flowing in a sluice channel comprises a number of sieving panels which are substantially arranged in a transverse direction to the direction of flow of the liquid current and form a revolving endless sieve belt immersing into the liquid current. The sieve belt comprises a plurality of sieving panels which are sequentially arranged adjacent to one another in the direction of motion of the endless sieve belt and form a common sieving su
Geiger International GmbH & Co. Technology KG
Kinberg Robert
Smith Stuart I.
Upton Christopher
Venable LLP
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